United States Off ice of February 1980
v Environmental Protection Water Program Operations (WH-547) 430/9-80-001
&.PA430/9-80-001 Agency Washington DC 20460 x
V
Water
vvEPA Evaluation of Sludge
Management Systems
Evaluation Checklist
and Supporting Commentary
MCD-61
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DISCLAIMER
This report has been reviewed by the Office of Water Programs Operations, U.S.
Environmental Protection Agency, and approved for publication. Approval does not
signify that the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
NOTES
To order this publication, MCD-61, Technical Bulletin, "Evaluation
of Sludge Management Systems: Evaluation Checklist and Supporting
Commentary" (430/9-80-001), write to:
General Services Administration (8FFS)
Centralized Mailing Lists Services
Building 41, Denver Federal Center
Denver, Colorado 80225
Please indicate the MCD number and title of publication.
Multiple copies may be purchased from:
National Technical Information Service
Springfield, Virginia 22151
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EPA 430/9-80-001
February 1980
EVALUATION OF SLUDGE MANAGEMENT SYSTEMS
Evaluation Checklist and Supporting Commentary
by
Gordon L. Gulp
Justine A. Faisst
Daniel J. Hinrichs
Bruce R. Winsor
Culp/Wesner/Culp
Consulting Engineers
El Dorado Hills, California 95630
Contract No. 68-01-4833
Project Officers
Sherwood C. Reed
and
Robert K. Bastian
Office of Water Programs Operations
Washington, D.C. 20460
OFFICE OF WATER PROGRAMS OPERATIONS
U. S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
MCD-61
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ABSTRACT
This Bulletin is intended to be an aid for review of facility plans,
designs, specifications, and O&M manuals which deal with sludge management
systems. The document is divided into three parts: Facility Planning
(Part I), Design and Specifications (Part II), and Operation and
Maintenance Manuals (Part III). Each part is complete and independent of
the others so it is only necessary to use those portions relevant to the
project under review.
Each Part contains a checklist of pertinent factors supported by
technical commentary. This technical discussion is sufficiently detailed
for an understanding of the concepts but not complete enough for design.
This document is not a design manual and should not be used as such. Those
readers interested in design should use the Process Design Manual for Sludge
Treatment and Disposal (EPA 625/1-79-011, September 1979).
At the facility planning stage the checklist can be used to assure that
all feasible sludge management alternatives were properly considered. At
the later stages of a project a particular concept has already been selected
so the reviewer only needs to be concerned with the relevant portions of
Parts II and III to insure that all critical aspects are covered.
11
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TABLE OF CONTENTS
Figures iv
Tables vi
Introduction 1
Purpose 1
Report Organization 1
Use 1
Scope 2
I. Facility Planning
Introduction 5
Checklist 7
A. Project Objectives 7
B. Characteristics of Sludge 7
C. Existing Facilities 7
D. Environmental Considerations 7
E. Sludge Transport 7
F. Land Application 8
G. Landfill 9
H. Combustion 10
I. Sludge For Off-Site Use by Others 11
J. Cost-Effectiveness Analysis 12
K. Reliability 14
L. Energy Analysis 14
M. Environmental Assessment 14
N. Implementation Program 15
Supporting Commentary 17
A. Project Objectives 17
B. Characteristics of Sludge 18
C. Existing Facilities 27
D. Environmental Considerations 27
E. Sludge Transport 30
F. Land Application 36
G. Landfill 52
H. Combustion 59
I. Sludge For Off-Site Use by Others 76
J. Cost-Effectiveness Analysis 87
K. Reliability 90
L. Energy Analysis 93
M. Environmental Assessment 94
N. Implementation Program 99
II. Design and Specifications
Introduction 103
Checklist 105
A. Agreement With Facilities Plan 105
B. Sludge Transport 105
C. Land Application 105
D. Landfill 107
E. Combustion 108
iii
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TABLE OF CONTENTS (Continued)
Page
F. Sludge For Off-Site Use by Others 112
Supporting Commentary
A. Agreement With Facilities Plan 115
B. Sludge Transport 115
C. Land Application 125
III. Operation and Maintenance Manual
Introduction 173
Checklist 175
A. Sludge Transport 175
B. Land Application 176
C. Landfill 177
D. Combustion 178
E. Process for Off-Site Use of Sludge By Others 179
Supporting Commentary 181
A. Sludge Transport 181
B. Land Application 186
C. Landfill 192
D. Combustion 200
E. Process for Off-Site Use of Sludge By Others 205
References 213
Bibliography 219
Appendices
A. Design of Land Application Systems For Agricultural Utilization
of Sewage Sludge
B. Landfill Design
iv
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TABLES
Number
1 Qualitative Comparison of Municipal Sludge With
Municipal Solid Waste 18
2 Normal Quantities of Sludge Produced by Different
Treatment Processes 20
3 Major Components of Stabilized Sludge 21
4 Typical Heat of Combustion of Sludge (Total Dry Solids Basis) 26
5 Pipeline Size and Flow Rates 31
6 Pipeline Sludge Pumping Characteristics 32
7 Pipeline Pumping Station Energy 32
8 Plant Nutrient Utilization by Various Crops 44
9 Suggested Total Amount of Sludge Metals Added to
Agricultural Land 46
10 Typical Sludge Dewatering Performance 59
11 Sludge and Site Conditions 134
12 Landfill Design Criteria 136
13 Landfill Equipment Performance Characteristics 139
14 Multiple Hearth Furnace Loading Rates 143
15 Typical Sizes of Multiple Hearth Furnace Units 145
16 Fluidized Bed Furnace Loading Rates 151
17 Typical Composting Design Criteria 159
18 Composting Equipment 162
19 Dry Bed Loading Rates 164
20 Drying Bed Design Parameters 165
21 Drying Lagoon Design Parameters 166
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FIGURES
Number Page
1 Facility planning decision making process 3
2 Basic sludge management alternatives 4
3 Theoretical heat required to sustain combustion of sludge 60
4 Cross section of a typical multiple hearth incinerator 62
5 Cross section of a fluid bed reactor 63
6 Wet air oxidation system schematic 67
7 Impact of excess air on the amount of auxiliary fuel for
sludge incineration 69
8 Potential heat recovery from incineration of sludge 72
9 Cage mill flash dryer system 81
10 Rotary kiln dryer 82
11 Static pile composting 85
12 Multiple hearth furnace area vs. design capacity 144
13 Multiple hearth air supply vs. design capacity 146
14 Multiple hearth furnace heatup and standby fuel consumption rate 147
15 Fluidized bed, bed area vs. capacity 150
16 Typical sludge dry bed construction 163
17 Typical multiple hearth furnace monitoring program 202
VI
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INTRODUCTION
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INTRODUCTION
PURPOSE
Evaluation of Sludge Management Systems is intended to be an aid for review of
facility plans, design and specifications, and operation and maintenance manuals
which deal with sludge management systems. While this document is primarily
intended for use by Environmental Protection Agency evaluators, it is anticipated
that it will also be of use to public officials, planners, and engineers.
The checklists and accompanying commentary included are to be used by the evalua-
tor to check the completeness of the work being reviewed. Data included are for
illustrative purposes to aid in assessing the reasonableness of a plan or design.
This document is not a design manual and should not be used as such. In the
reference section of this document and throughout the text are listed many
sources of additional information on the selection and design of sludge manage-
ment systems which should be consulted when more information is needed.
Specifically, the reader is referred to the latest edition of the EPA Process
Design Manual for Sludge Treatment and Disposal.
REPORT ORGANIZATION
This report is divided into three parts: Facility Planning (Part I), Design and
Specifications (Part II) and Operation and Maintenance Manuals (Part III). This
reflects the normal sequence in the planning and design of municipal facilities.
Each part is independent of the others. It is only necessary to use those por-
tions relevant to the project under review.
USE
When reviewing a plan or design the evaluator should mark off items on the check-
list as he comes across them. Items can be marked off for both presence and fea-
sibility as determined by the supporting commentary and referenced material. It
is not the intent of this report to limit alternatives to those discussed. If a
process is not included in the checklist, it does not mean it is unacceptable.
Conversely, there will be items so obviously inapplicable to the specific situa-
tion that no mention need be made in planning or design.
Under the authority of the Resource Conservation and Recovery Act (P.L. 94-580)
(2) the EPA is currently preparing proposed guidelines for the utilization and
disposal of sewage sludge. The requirements of these guidelines will affect the
selection, design and evaluation of all the sludge management systems discussed
herein. When available, these guidelines should be consulted by the evaluator,
planner, designer or operation and maintenance manual author in using this
publication. The information contained herein should be interpreted in light of
the proposed and final guidelines.
It should be kept in mind by the evaluator that facility planning and design of a
sludge management system are not conducted as straight line procedures, but
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instead involve several interlocking sets of decision loops, each of which
affects others. Figure 1 is a flowchart which illustrates the decision-making
process.
At all times during the facility planning, design and specifications preparation,
and operations and maintenance manual preparation stages it must be kept in mind
that the sludge management system is a part of the overall wastewater management
system.
SCOPE
With very few exceptions, alternatives for sewage sludge management result in the
ultimate disposal of the sludge in or on the land. Dumping of sludge in large
bodies of water, especially ocean dumping, is currently practiced but national
environmental policy calls for the cessation of water dumping in the near future.
Disposal of sludge by dumping in large bodies of water will, therefore, not be
considered in this report.
Sludge management systems consist of components which perform some combination of
the following functions:
Thickening
Digestion
Disinfection
Conditioning
Dewatering
Combustion
Drying
Composting
Land application
Landfilling
Off-site use
Storage
Transportation
Figure 2 illustrates the most common combinations of these elements. There are,
of course, many other possible combinations which may be applicable in a specific
situation, but the vast majority of plants will fit into one of the patterns in
Figure 2. Sludge transport and storage can occur at any point in the system and
are not shown. Sludge management systems are generally divided into sludge treat-
ment and sludge disposal stages. Sludge treatment includes thickening, digestion,
disinfection, conditioning and dewatering. Sludge disposal includes off-site use
by others, landfill, and land application. Combustion, composting, and drying,
are generally considered to be disposal processes although they are, strictly
speaking, treatment processes. This publication deals with evaluating the selec-
tion and design of the disposal method, and those processes generally considered
to be disposal methods; and sludge transport. It does not discuss in detail eval-
uating the selection and design of sludge treatment processes, except as they
relate directly to the selection of the disposal method. This report is aimed at
evaluating facility plans, designs and specifications, and operation and mainte-
nance manuals for medium-to-large sludge management systems. The evaluator should
use discretion in applying the checklists included herein to smaller systems.
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Definition of Project
Objectives
Evaluation of Sludge
Characteristics
Evaluation of Existing
Facilities
Evaluation of Environ-
mental Factors
Not suited to
Project Objectives
Selection of Technically
Feasible Alternatives
Cost—Effectiveness
Analysis
Feasibility Assessment
Reliability Assessment
1
Energy — Effectiveness
Analysis
Environmental Impact
Assessment
Selection of Sludge
Management System
Design of Implementation
Program
No Feasible
Alternatives
Design and Specification
Stage
Figure 1. Facility planning decision
maKing process.
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PART I
FACILITY
PLANNING
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FACILITY PLANNING
INTRODUCTION
The sludge management plan recommended in the facility plan must be the apparent
best alternative derived from detailed evaluation of the technically feasible
alternatives. Factors to be considered and weighed against each other in deter-
mining the best alternative are:
• Cost-effectiveness
• Energy-effectiveness
• Reliability
• Flexibility
• Environmental impacts
Part 1 emphasizes the careful preparation of a facility plan for sludge manage-
ment and a thorough evaluation of that plan. It must be used in conjunction with
Guidance for Preparing a Facility Plan (3). The facility plan should reflect a
careful analysis of the merits of the technically feasible alternatives as well
as the necessary tradeoffs among the goals of cost-effectiveness, energy-effec-
tiveness, high reliability, high flexibility and environmental acceptability. The
facility plan should present the final system selection in definitive form so
that design plans and specifications may easily follow.
It is not the intent of this document to favor one management approach over
another, as each system will have a combination of characteristics and criteria
which are unique to that system. Certain specific sludge management systems,
cyclonic incinerators for example, are not discussed in detail primarily because
they are not in common use for sewage sludge management in the United States.
Where such systems appear to have merit for the specific situation under consid-
erations, the facility planner and evaluator should explore them in greater
detail.
The decision-making process involved in the preparation of a facility plan does
not readily lend itself to evaluation by rigid adherence to a checklist due to
the many interlocking relationships among the decisions to be made. This check-
list can be of value, however, if the user recognizes the complexity of the
interrelationships among the steps in the decision-making process. It should also
be recognized by the evaluator that certain alternatives can frequently be elim-
inated from consideration without detailed engineering analysis due to their
obvious inapplicability to the case at hand. An example would be consideration of
sludge transport by barge where no navigable waterways exist. This obviously does
not merit evaluation and need not be considered.
There are 14 major categories in the Facility Plan Checklist:
A. Project Objectives
B. Characteristics of Sludge
C. Existing Facilities
D. Environmental Considerations
E. Sludge Transport
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F. Land Application
G. Landfill
H. Combustion
I. Off-Site Use of Sludge by Others
J. Cost-Effectiveness Analysis
K. Reliability
L. Energy Analysis
M. Environmental Assessment
N. Implementation Program
Within each category are numerous sub-elements. All of the major categories
should usually be included to insure selection of the most feasible alternative.
It is not necessary that all the sub-elements be included. Sufficient detail
should be provided to support the rejection of unfeasible alternatives and to
insure that all critical factors in the proposed method were considered.
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FACILITY PLANNING
CHECKLIST
A. PROJECT OBJECTIVES
1. ENVIRONMENTAL PROTECTION
2. SLUDGE UTILIZATION
3. SLUDGE DISPOSAL
4. CO-DISPOSAL WITH SOLID WASTE
B. CHARACTERISTICS OF SLUDGE
1. QUANTITY, PRESENT AND PROJECTED
a. Present, Projected, and Peak Flows
b. Sludge Concentration
c. Present, Projected, and Peak Solids
2. ANALYSIS, PRESENT AND PROJECTED
a. Physical Characteristics
b. Organic Matter (VS, BOD, COD, TOC)
c. Nutrients (Nitrogen, Phosphorus, Potassium)
d. Sulfur
e. Inorganic Ions, Heavy Metals
f. Pathogen Content
g. Heat Content
h. pH
i. Toxic Organic Compounds
3. INDUSTRIAL CONTRIBUTIONS
C. EXISTING FACILITIES
1. THICKENING
2. DEWATERING
3. STORAGE
4. STABILIZATION
5. COMBUSTION
6. TRANSPORT
7. DISPOSAL
D. ENVIRONMENTAL CONSIDERATIONS
1. CLIMATE
a. Precipitation Analysis
b. Evapo-transpiration Potential
c. Temperature Analysis
d. Wind Analysis
2. LAND CHARACTERISTICS
a. Topography
b. Soils
c. Geology
d. Groundwater
e. Surface Water
E. SLUDGE TRANSPORT
1. PIPELINE
a. Route
b. Size and Material
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c. Pumping Requirements
2. TRUCK
a. Route and Travel Time
b. Size and Number of Trucks
c. Fuel Requirements
d. Manpower Requirements
e. Loading, Unloading, and Vehicle Service Facilities
3. BARGE
a. Route and Travel Time
b. Size and Number of Barges
c. Fuel Requirements
d. Manpower Requirements
e. Loading, Unloading, and Vehicle Service Facilities
f. Tow Tariffs
4. RAILROAD
a. Route and Travel Time
b. Size and Number of Cars
c. Fuel Requirements
d. Manpower Requirements
e. Loading, Unloading, and Service Facilities
f. Tariffs
F. LAND APPLICATION
1. PURPOSE
a. Dedicated Disposal
b. Agricultural Utilization
c. Reclamation of Disturbed or Marginal Lands
d. Combinations
2. EVALUATION OF POTENTIAL SITES
a. Geographical Location
(Proximity to surface and groundwaters, distance
from treatment plant, proximity to transportation)
b. Compatibility with Land Use Plans
(Current and proposed future use, zoning and adjacent land
use, proximity to current or proposed developed areas,
room for future expansion)
c. Method of Land Acquisition
(Purchase, Lease, Purchase w/lease back, Contract
w/user, Combination aquisition-lease)
3. STABILIZATION PROCESS
a. Anaerobic Digestion
b. Aerobic Digestion
c. Heat Treatment
d. Chemical Stabilization
4. AGRICULTURAL MANAGEMENT PLAN
a. Crops to be Grown, Rotation Plan and Markets
b. Farming by Municipal Agency or Contract
c. Long Range Plan
5. NUTRIENT BALANCE
a. Nitrogen
(1) Forms of Nitrogen in the Sludge
(2) Mineralization Rate of Organic Nitrogen
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(3) Future Application Rate Adjustments for
Mineralized Organic Nitrogen
(4) Additional Nitrogen Needed for Crop (if any)
b. Phosphorus
c. Potassium
6. HEAVY METAL LOADINGS
a. Cation Exchange Capacity
b. Sludge and Soil pH
c. Cadmium
Annual rate and total projected accumulation (Ibs/acre)
d. Nickel
Annual rate and total projected accumulation (Ibs/acre)
e. Copper
Annual rate and total projected accumulation (Ibs/acre)
f. Molybdenum
Annual rate and total projected accumulation (Ibs/acre)
g. Zinc
Annual rate and total projected accumulation (Ibs/acre)
h. Lead
Annual rate and total projected accumulation (Ibs/acre)
7. SLUDGE APPLICATION RATES
(Maximum annual rate tons per acre wet or dry, limiting
factors, variations for crops, daily maximums)
8. SITE CONSIDERATIONS
a. Site Size
(1) Application Area
(2) Wet Weather Plan for Stockpile Storage or
Alternative Disposal
(3) Buffer Area
(4) Expansion or Replacement Area
b. Compatiblity with Future Expansion
(Future process changes, changes in constituent levels,
capacity increases.)
9. RUNOFF CONTROL
(Containment, recycle, or disposal)
10. STORAGE (Days of storage at design sludge production rate)
a. Capacity
b. Odor Control (Prior stabilization, mixing and/or
aeration)
c. Drainage or Leachate Control
11. MONITORING PROGRAM
a. Monitoring Wells and Tests (Type and frequency)
b. Soil Tests (Type and frequency)
c. Sludge Tests (Type and frequency)
d. Crop Tissue Analysis
G. LANDFILL
1. METHOD
a. Sludge Only Trench Fill
(1) Narrow Trench
(2) Wide Trench
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b. Sludge Only Area Fill
(1) Mound
(2) Layer
(3) Diked Containment
c. Co-disposal With Refuse
(1) Sludge refuse mixture
(2) Sludge soil mixture
2. SITE SELECTION
a. Identify Potential Sites
b. Public Participation Program
c. Technical Considerations
(1) Haul Distance
(2) Site Life and Size
(3) Topography
(4) Surface and Groundwater
(5) Soils and Geology
(6) Vegetation
(7) Environmentally Sensitive Areas
(8) Archaeological and Historical Significance
(9) Site Access
(10) Land Use
3. LEACHATE CONTROLS
a. Adequate Surface Drainage
b. Natural Attenuation
c. Containment
(Soil or membrane liner, leachate collection
and treatment)
4. GAS CONTROL
(Permeable or impermeable methods and/or extraction)
5. RUNOFF CONTROL
6. MONITORING
H. COMBUSTION
1. METHOD
a. Incineration
(1) Multiple Hearth
(2) Fluidized Bed
(3) Cyclonic Reactors, and Electric Incinerators
b. Pyrolysis
c. Wet Air Oxidation
d. Co-disposal with Solid Waste
(1) Total Co-disposal
(2) Refuse Derived Fuel
2. MASS BALANCE
a. Inputs
(1) Dry Solids and Moisture in Sludge
(2) Air Required for Combustion
(3) Other Factors
(auxiliary fuel, makeup sand, steam)
b. Outputs
(Ash, combustible gas, tar, char, water, C02> CO,
N, sand, excess air)
10
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3. ENERGY BALANCE
a. Inputs
(Solids heat of combustion, auxiliary fuel heat of com-
bustion including afterburner)
b. Outputs
(Latent heat of free moisture and moisture of combustion.
Sensible heat of gases of combustion, excess air, and mois-
ture. Sensible heat of ash, radiation and conduction, sen-
sible heat of shaft cooling air and recovered energy.)
4. USE OF RECOVERED ENERGY
a. On-site Use
(Combustion air preheating, space conditioning, sludge
thermal conditioning, sludge digester heating, steam tur-
bines, gas turbines, pyrolysis reactor heating.)
b. Off-site use
(Combustible gas, tar (oil), char, steam, electricity.)
5. ASH DISPOSAL
a. Transport
b. Dewatering
c. Land Application
d. Landfill
e. Off-site Use By Others
6. AIR QUALITY CONTROL
(Scrubbers, afterburners, electrostatic precipitators.)
7. FUELS
(Gas, oil, refuse derived fuel, powdered coal.)
I. SLUDGE FOR OFF-SITE USE BY OTHERS
1. MARKET ANALYSIS
a. Intended market
(1) Governmental Agencies
(Highway departments, municipal parks, golf courses,
and stadiums, forestry departments.)
(2) Wholesalers or processors
(3) Private users
(Golf courses and stadiums, nurseries, agriculture,
individuals.)
b. Capacity of Market to Absorb Product
c. Market Value of Product
d. Packaging Requirement
2. PROCESSING METHOD
a. Drying
(1) Drying beds
(2) Drying lagoons
(3) Heat drying
(a) Flash drying
(b) Rotary kiln drying
b. Composting
(1) Windrow
(2) Static Pile
11
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(3) Mechanical System
c. Co-disposal with Solid Waste
(1) Refuse as Bulking Agent
(2) Sludge as Nutrient and Moisture Source
d. Nutrient Enrichment Considered
3. PACKAGING AND DELIVERY
(Pick up by user, bulk delivery to user, bagged)
J. COST-EFFECTIVENESS ANALYSIS
1. GENERAL CONSIDERATIONS
a. Planning Period
b. Discount Rate
c. Construction or Other Cost Indices
d. Service Lives of Facility and Equipment
e. Capital Costs and Credits
f. Fixed Annual Costs
g. Variable Annual Costs and Credits
2. SLUDGE TREATMENT
a. Capital Costs
(1) Land Acquisition
(2) Facility Construction
(3) Filtrate, Centrate, or Supernatant Treatment
Facilities
(4) Impact of Chemical Addition on Other Treatment Process
b. Fixed annual costs
(1) Labor
(2) Maintenance
(3) Monitoring
(4) Supplies
c. Variable Annual Costs and Credits
(1) Power
(2) Auxiliary Fuel
(3) Chemicals
(4) Filtrate, Centrate, or Supernatant Treatment
(5) Impact of Chemical Addition on Other
Treatment Processes
(6) Value of Recovered Digester Gas
3. SLUDGE TRANSPORT
a. Capital Costs
(1) Right-of-way Acquisition
(2) Vehicle Purchase
(3) Pipeline Construction
(4) Facilities Construction
b. Fixed Annual Costs
(1) Labor
(2) Maintenance
(3) Vehicle Leasing
(4) Supplies
c. Variable Annual Costs
(1) Pumping Energy
(2) Vehicle Fuel
(3) Contract Haul Costs
12
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4. LAND APPLICATION
a. Capital Costs
(1) Land Acquisition
(2) Equipment Purchase
(3) Site Preparation
(4) Facilities Construction
(5) Value of Reclaimed Land
b. Fixed Annual Costs
(1) Land Leasing
(2) Labor
(3) Maintenance
(4) Equipment Leasing
(5) Monitoring
(6) Supplies
c. Variable Annual Cost or Credit
(1) Equipment Fuel
(2) Supplemental Fertilizer
(3) Credit for Sale or Cost for Disposal of Crop
5. LANDFILL
a. Capital Costs or Credits
(1) Land Acquisition
(2) Equipment Purchase
(3) Site Preparation
(4) Facilities Construction
(5) Runoff and Leachate Treatment Facilities
(6) Value of Reclaimed Land
b. Fixed Annual Costs
(1) Land Leasing
(2) Labor
(3) Maintenance
(4) Equipment Leasing
(5) Runoff Treatment
(6) Monitoring
(7) Supplies
c. Variable Annual Costs or Credits
(1) Equipment Fuel
(2) Leachate Treatment
(3) Value of Collected Gas
6. COMBUSTION
a. Capital Costs
(1) Reduction Facility Construction
(2) Scrubber Effluent Treatment Facilities
(3) Liquor Treatment Facilities
(4) Ash Disposal Facilities
b. Fixed Annual Costs
(1) Labor
(2) Maintenance
(3) Monitoring
(4) Supplies
c. Variable Annual Costs or Credits
(1) Auxiliary Fuel
(2) Power
13
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(3) Ash Handling and Disposal
(4) Value of Residues
(a) Gas
(b) Tar
(c) Char
(d) Ash
(5) Value of Energy Recovered
(6) Scrubber Effluent Treatment
(7) WAO Liquor Treatment
7. SLUDGE FOR OFF-SITE USES BY OTHERS
a. Capital Costs
(1) Land Acquisition
(2) Equipment Purchase
(3) Facility Construction
b. Fixed Annual Costs
(1) Labor
(2) Maintenance
(3) Monitoring
(4) Supplies
c. Variable Annual Cost or Credit
(1) Equipment Fuel
(2) Power
(3) Packaging
(4) Bulking Agent
(5) Value of Product
K. RELIABILITY
1. MECHANICAL DOWNTIME
a. Standby Power Supply
b. Standby Fuel Supply
c. Storage
d. Duplicate Equipment
e. Backup Equipment
(1) At Site
(2) At Other Sites
(3) Leaseable
f. Alternative Management Techniques
2. AVAILABILITY OF NEEDED RESOURCES
a. Electric Power
b. Fuel
c. Chemicals
d. Manpower
e. Replacement Parts
3. FACTORS OF SAFETY
L. ENERGY ANALYSIS
M. ENVIRONMENTAL ASSESSMENT
1. ENVIRONMENTAL IMPACTS
a. Soil and Vegetation
b. Groundwater
c. Surface Water
14
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d. Animal and Insect Life
e. Air Quality
f. Climate
2. PUBLIC HEALTH IMPACTS
a. Disease Vectors
b. Soil and Vegetation
c. Groundwater Quality
d. Surface Water Quality
e. Air Quality
3. SOCIAL IMPACTS
a. Relocation of Residents
b. Greenbelts and Open Spaces
c. Recreational Activity
d. Community Growth
e. Noise and Odor
4. ECONOMIC IMPACT
a. Property Values
b. Overall Local Economy
c. Taxation
d. Conservation of Resources and Energy
N. IMPLEMENTATION PROGRAM
1. PUBLIC PARTICIPATION PROGRAM
a. Planning Stage
b. Design Stage
c. Construction Stage
d. Operational Stage
2. POTENTIAL ROADBLOCKS
3. LAND ACQUISITION PROGRAM
a. Purchase
b. Lease
c. Condemnation
d. Land Dedication
4. IMPLEMENTATION SCHEDULE
a. Facility Plan Approval
b. Land Acquisition
c. Design
d. Design Approval
e. Construction
f. Operation
5. STAFFING PLAN
a. Operations
b. Maintenance
c. Supervisory
d. Laboratory
e. Administrative
6. COMPATIBILITY WITH REGULATIONS
a. Zoning and Land Use
b. Solid Waste Disposal
c. Air Pollution Control
d. Water Pollution Control
e. Public Health
15
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FACILITY PLANNING
SUPPORTING COMMENTARY
Section A - PROJECT OBJECTIVES
The basic project goal is to provide for sludge management in a cost-effective
and environmentally acceptable manner. In order to accomplish this goal, the
specific objectives and goals of the sludge management system must be clearly
defined in the facility plan. The successful implementation of the plan depends
primarily on the formulation and appropriateness of these goals. It is imperative
that the goals relative to sludge reuse and co-disposal with solid waste estab-
lished in the initial phase of facility planning be re-evaluated throughout the
planning process.
A.I. ENVIRONMENTAL PROTECTION
The facility plan should establish goals for the environmentally sound manage-
ment of sludge. These goals should take into account the following factors, which
are discussed in greater detail in the appropriate sections of this document.
• Groundwater protection
• Surface water protection
• Air quality protection
• Land protection
A. 2. SLUDGE UTILIZATION
The facility plan must establish goals for utilization or disposal of sludge.
In many, but not all instances, consideration of the sludge as a resource rather
than as a material to be disposed of can result in a more cost-effective solu-
tion to the sludge management problem. Among the utilization operations which
have been proposed or implemented are:
Use of sludge as a soil conditioner or fertilizer
Use of sludge as fill material for land reclamation
Use of sludge as an energy source
Use of sludge (ash) as a concrete or asphalt additive
Use of sludge as a raw material for manufacture of activated carbon
A.3. SLUDGE DISPOSAL
Where sludge utilization is not feasible, sludge disposal must be practiced.
Sludge disposal alternatives include landfill and lagoon operations and land
application of sludge to a dedicated site. Incinerator ash is most often disposed
of rather than utilized.
17
-------
A. 4. CO-DISPOSAL WITH SOLID WASTE
Consideration should be given (4) to co-disposal of sludge with solid wastes.
This may result in significant improvements in the cost-effectiveness of dis-
posal of both materials. In considering co-disposal alternatives, it is important
to remember the differences as well as the similarities between sludge and solid
waste. These differences are summarized in Table 1.
TABLE 1. QUALITATIVE COMPARISON OF MUNICIPAL SLUDGE WITH MUNICIPAL SOLID WASTE
Property Comparison
Volume The per capita volume of solid waste is much greater
than sludge (typically 5.72 Ib/cap/day vs 0.14
Ib/cap/day) (5, 6).
Moisture content The moisture content of sludge is typically higher
than that of solid waste.
Heat content Solid waste has a higher heat content than sludge
Homogeneity Sludge is much more homogeneous than solid waste.
Nutrient content Sludge has a higher concentration of the nutrients
required for biological growth than solid waste.
These differences present opportunities for improving disposal cost-effectiveness
as well as problems involved in combining the materials. Typical co-disposal
techniques include:
Co-incineration or co-pyrolysis
Co-disposal by landfill
Use of refuse as an auxiliary fuel in sludge incineration
Use of refuse as a bulking agent in sludge composting
Use of sludge as a moisture and nutrient source in solid waste
composting
• Use of sludge as a soil conditioner for solid waste landfill cover
Section B - CHARACTERISTICS OF SLUDGE
An evaluation of the characteristics of the sludge is an essential step in
selecting sludge management alternatives, and may provide a basis of preliminary
screening of methods. The best available data should be used in establishing the
sludge characteristics. Actual flow data and laboratory analyses are always pre-
ferrable, but it is often necessary to estimate sludge characteristics based
18
-------
on typical values or on the experiences of similar treatment plants. This is
always true in the case of a new or upgraded wastewater treatment facility.
B.I. QUANTITY, PRESENT AND PROJECTED
A detailed analysis of the future sludge flow is required on both liquid and dry
solids basis. The analysis should include data or estimates describing the
following:
• Initial sludge flow, concentration and dry solids production
• Future sludge flow, concentration and dry solids production
• Seasonal variations in sludge flow, concentration and dry solids
production
Future sludge quantities should be estimated from population and industrial
growth projections. Consideration should also be given to planned process
modifications that will affect sludge production.
It is generally possible to control short-term peaks in sludge and solids produc-
tion by storage within wastewater and sludge treatment process units, reducing
their effect on the sludge management system. Consideration should be given to
peaks which are in excess of those which can be successfully stored.
Table 2 is a summary of typical sludge production rates for various treatment
processes. The EPA Process Design Manual for Sludge Treatment and Disposal (1, 7)
contains additional information useful for estimating sludge production
quantities.
B.2. ANALYSIS, PRESENT AND PROJECTED
The analysis of the sludge will have as great an impact on the selection of
sludge management techniques as will the quantity. Sludge analysis varies widely
from plant-to-plant due to such factors as wastewater treatment processes,
industrial contributions, water supply quality, and the presence or absence of
storm water in the collection system. Table 3 summarizes typical chemical compon-
ents of sewage sludges in 150 treatment plants in the northcentral and eastern
United States.
B.2.a. Physical Characteristics
Because the nature of sludges resulting from the treatment of municipal waste-
waters varies so greatly from one locale to another, generalized statements about
their physical characteristics are of limited value. However, some observations
which are usually true follow.
19
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20
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TABLE 3. MAJOR COMPONENTS OF STABILIZED SLUDGE (8)*
Component
N03-N,
mg/1
NH4-N,
mg/1
Total N, %
Organic C,
7
/o
Total P,
%
Total S,
7
/o
K, %
Na, %
Ca, %
Mg, %
SampJ
Type
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Le
Number
35
8
3
45
67
33
3
103
85
38
68
191
31
31
60
101
86
38
65
189
19
9
—
28
86
37
69
192
73
36
67
176
87
37
69
193
87
37
65
189
Rz
2 -
1 -
—
2 -
120 -
30 -
5 -
5 -
0.5 -
0.5 -
0.1 -
0.1 -
18
27
6.5 -
6.5 -
0.5 -
1.1 -
0.1 -
0.1 -
0.8 -
0.6 -
—
0.6 -
0.02-
0.08-
0.02-
0.02-
0.01-
0.03-
0.01-
0.01-
1.9 -
0.6 -
0.1 -
0.1 -
0.03-
0.03-
0.03-
0.03-
inge
4,900
830
4,900
67,600
11,300
12,500
67,600
17.6
7.6
10.0
17.6
39
37
48
48
14.3
5.5
3.3
14.3
1.5
1.1
—
1.5
2.64
1.10
0.87
2.64
2.19
3.07
0.96
3.07
20.0
13.5
25.0
25.0
1.92
1.10
1.97
1.97
Median
-mg/1- —
79
180
140
1,600
400
80
920
4.2
4.8
1.8
3.3
26.8
29.5
32.5
30.4
3.0
2.7
1.0
2.3
1.1
0.8
—
1.1
0.30
0.38
0.17
0.30
0.73
0.77
0.11
0.24
4.9
3.0
3.4
3.9
0.48
0.41
0.43
0.45
Mean
520
300
780
490
9,400
950
4,200
6,540
5.0
4.9
1.9
3.9
27.6
31.7
32.6
31.0
3.3
2.9
1.3
2.5
1.2
0.8
—
1.1
0.52
0.46
0.20
0.40
0.70
1.11
0.13
0.57
5.8
3.3
4.6
4.9
0.58
0.52
0.50
0.54
(Continued)
21
-------
TABLE 3. (Continued)
Sample
Component
Ba, %
Fe, %
Al, %
Mn, mg/kg
B, mg/kg
As, mg/kg
Co, mg/kg
Mo, mg/kg
Hg, mg/kg
Pb, mg/kg
Type
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Number
27
10
23
60
96
38
31
165
73
37
23
133
81
38
24
143
62
29
18
109
3
—
7
10
4
—
9
13
9
3
17
29
35
20
23
78
98
57
34
189
Range
0.01-
0.01-
0.01-
0.01-
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
58 -
55 -
18 -
18 -
12 -
17 -
4 -
4 -
10 -
—
6 -
6 -
3 -
—
1 -
1 -
24 -
30 -
5 -
5 -
0.5 -
1.0
2.0 -
0.5 -
58 -
13 -
72 -
13 -
0.90
0.03
0.44
0.90
15.3
4.0
4.2
15.3
13.5
2.3
2.6
13.5
7,100
1,120
1,840
7,100
760
74
700
760
230
—
18
230
18
—
11
18
30
30
39
39
10,600
22
5,300
10,600
19,730
15,000
12,400
19,700
Median
/o
0.05
0.02
0.01
0.02
1.2
1.0
0.1
1.1
0.5
0.4
0.1
0.4
/«
—mg/kg
280
340
118
260
36
33
16
33
116
9
10
7.0
4.0
4.0
30
30
30
30
5
5
3
5
540
300
620
500
Mean
0.08
0.02
0.04
0.06
1.6
1.1
0.8
1.3
1.7
0.7
0.3
1.2
400
420
250
380
97
40
69
77
119
11
43
8.8
4.3
5.3
29
30
27
28
1,100
7
810
733
1,640
720
1,630
1,360
(Continued)
22
-------
TABLE 3. (Continued)
Component
Zn, rag/kg
Cu, mg/kg
Ni, mg/kg
Cd, mg/kg
Cr, mg/kg
Sample
Type
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
Anaerobic
Aerobic
Other
All
s
Number
108
58
42
208
108
58
39
205
85
46
34
165
98
57
34
189
94
53
33
180
Rz
108 -
109 -
101 -
101 -
85 -
85 -
84 -
84 -
2 -
2 -
15 -
2 -
3 -
c _
4 -
3 -
24 -
10 -
22 -
10 -
mge
- rag/
27,800
14,900
15,100
27,800
10,100
2,900
10,400
10,400
3,520
1,700
2,800
3,800
3,410
2,170
520
3,410
28,850
13,600
99,000
99,000
Median
tlr n _
Kg
1,890
1,800
1,100
1,740
1,000
970
390
850
85
31
118
82
16
16
14
16
1,350
260
640
890
Mean
3,380
2,170
2,140
2,790
1,420
940
1,020
1,210
400
150
360
320
106
135
70
110
2,070
1,270
6,390
2,620
*Dissolved substances reported as weight per unit volume of sludge of mg/1;
particulates are reported as weight per unit sludge either as a percent of
total solids for major constituents, or as mg per kg total solids for trace
constituents.
Raw primary sludges settle, thicken and dewater with relative ease compared to
secondary biological sludges due to their coarse, fibrous nature. Generally, at
least 30% of the solids are larger than 30 mesh in size. These coarse particles
permit rapid formation of a sludge cake with sufficient structural matrix to per-
mit good solids capture and rapid dewatering. Anaerobic digestion of primary
sludges frequently makes them more difficult to thicken and dewater. However, the
dewatering results attainable at relatively low costs are still generally good.
Activated sludges show much greater variation in dewatering characteristics than
do primary sludges. These variations may even be substantial from day-to-day at
the same plant. The sludges are much finer than primary sludges and are largely
cellular organic material with a density very nearly the same as water. They are
much more difficult to dewater than primary sludges.
23
-------
The nature of sludges resulting from chemical coagulation of sewage depends on
the nature of the coagulant used. Generally, alum and iron coagulants produce
gelatinous floe which is difficult to dewater. Lime coagulation produces a sludge
which readily thickens and dewaters in most cases. Estimates of sludge character-
istics from a variety of wastewater processes may be found in EPA's Process
Design Manual for Sludge Treatment and Disposal (1).
The physical characteristics of the sludge will affect the selection of sludge
treatment processes and ultimate disposal. The difficulty of dewatering waste
activated sludge, for example, may preclude the use of incineration because it
may not be possible to obtain a sludge cake capable of sustaining autogenous or
economical burning.
B.2.b. Organic Matter (VS, BOD, COD, TOC)
The organic content of sludge is expressed in terms of its Volatile Solids (VS),
biochemical oxygen demand (BOD), chemical oxygen demand (COD), or total organic
carbon (TOC). Methods for determining these values are given in Standard Methods
(9). Another measure of organic content which is useful in the evaluation and
design of combustion processes is the theoretical oxygen demand (THOD). This is
the oxygen required to completely oxidize the major constituents of the sludge,
based on stochiometric relationships. The organic content of sludge affects:
• Biological decomposition rate
• Heat value
• Potential for odor
• Value as a soil conditioner
B.2.c. Nutrients (Nitrogen, Phosphorus, Potassium)
Nitrogen is present in sludge in the form of organic nitrogen, ammonium ions,
nitrates and nitrites. The concentrations of all forms are customarily expressed
as equivalent nitrogen; that is, a sludge with an actual nitrate ion concentra-
tion of 2,000 mg/kg (ppm) would be said to have a concentration of 2,000 mg/kg
x 14 (molecular weight of N) t- 62 (molecular weight of NO^) = 452 mg/kg as N.
Nitrogen in the nitrate form is important because it is highly mobile and can
contaminate groundwater at land application and landfill sites. Nitrogen is an
essential nutrient for all forms of life and, as such, will affect the decomposi-
tion rate of sludge, its value as a fertilizer, and its potential for surface
water contamination.
Phosphorus is found in sludges in many forms, including the phosphate and ortho-
phosphate ions. Concentrations of phosphorus or any of its constituent ions are
normally expressed as phosphorus, although they may be expressed as phosphoric
acid, P2°5' which ls a method sometimes used in the fertilizer industry.
Phosphorus is an essential nutrient for bacterial decomposition and for plant
growth, and can affect both the rate of sludge decomposition and the value of the
sludge as fertilizer. Additionally, the nutrient value of the phosphorus affects
the potential for surface water pollution from sludge disposal or utilization.
Excess phosphorus applications can result in phytotoxicity in some plants.
24
-------
The potassium concentration is often expressed in terms of potash K^O rather
than potassium as that is a method often used by the fertilizer industry for
expressing potassium concentrations. Potassium is a vital plant nutrient, but is
rarely found in commercially usable concentrations in sludge.
B.2.d. Sulfur
Sulfur is present in sludge in the form of sulfates and sulfides, usually
expressed as sulfur. Sulfur is of importance because of its role in anaerobic
decomposition of sludge and in the production of odors (hydrogen sulfide). An
additional problem associated with sulfur is the possible formation of sulfuric
acid and resultant corrosion. If combustion of sludges with high sulfur content
is contemplated, the possibility of sulfur dioxide production should also be
explored.
B.2.e. Inorganic Ions, Heavy Metals
Inorganic ion concentrations are significant because of their potential for air,
land, and water pollution and their potentially toxic effect on plants, animals,
and humans. Not to be neglected, however, is the fact that most of the inorganic
ions which may be toxic in high concentrations are also essential micronutrients
required by plants and animals.
Among the possible deleterious effects of inorganic ions are:
• Increases in soil, groundwater, and surface water salinity.
• Toxic effects on crops from high concentrations of such heavy metals as
zinc, boron, copper, and nickel.
• Toxic effects on humans or animals due to excess plant uptake of such
heavy metals as cadmium, molybdenum, and zinc.
• Air pollution from volatilization of lead and mercury in combustion
processes.
• Groundwater pollution by leaching of heavy metals from sludge.
B.2.f. Pathogen Content
Pathogen content measured by the fecal coliform, salmonella, and ascaris egg
tests, is normally quite low in well stabilized sludges. Pathogen content of
sludge is of particular concern in any sludge management alternative involving
food chain crops, use of a sludge product by the public, or potential contamina-
tion of ground or surface waters.
B.2.g. Heat Content
The heat content (heat of combustion) of the sludge is of importance in evalua-
ting sludge combustion techniques. Typical values are shown in Table 4.
25
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TABLE 4. TYPICAL HEAT OF COMBUSTION OF SLUDGES (TOTAL DRY SOLIDS BASIS) (10)
Combustibles Ash Average
Material % U) BTU/ pound
Grease and scum 88.5 11.5 16,800
Raw sewage solids 74.0 26.0 10,300
Fine screenings 86.4 13.6 9,000
Ground garbage 84.8 15.2 8,200
Digested sewage solids
and ground garbage 49.6 50.4 8,000
Digested sludge 59.6 40.4 5,300
Grit 33.2 69.8 4,000
If the available heat of combustion from the sludge equals or exceeds the heat
required to dry and ignite the sludge and to compensate for heat losses from the
system, then the sludge incineration process is autogenous (self-burning), and
very little external energy is required, except for furnace start-up. If the heat
or moisture content of the sludge is such that autogenous burning is not pos-
sible, operating costs must include auxiliary fuel requirements for combustion
and for afterburning of stack gasses.
The heat content of the sludge can be approximated by the heat released in the
oxidation of the primary constituents of the sludge, given estimates of their
concentrations (11). Several other methods of calculation which have been pro-
posed give similar, but varying results (11-13). The accuracy of heat content
calculation is questionable, however, and actual calorimeter tests should be used
whenever possible (10).
B.2.h. pH
The pH of the sludge has an impact on the availability of heavy metals and the
pathogen concentration of the sludge. High pH (above 11), in general, promotes
the destruction of pathogens and inhibits the movement of heavy metals through
the soil and the uptake of heavy metals by plants.
B.2.i. Toxic Organic Compounds
Toxic organic compounds, which are persistent in the environment, such as pesti-
cides and polychlorinated biphenyls (PCB's), are of concern where the sludge man-
agement system may result in discharge of these substances to the atmosphere,
groundwater, or surface waters, or allow their entry into human or animal food
chains. Uptake by plants is unlikely. The pathways of major concern are
contamination of plant or soil surfaces.
26
-------
B.3. INDUSTRIAL CONTRIBUTIONS
The industrial contributions to the wastewater should be analyzed to determine
their effects on the sludge production rate (both average quantity and peak
quantities, especially seasonal peaks) and on the sludge analysis. Some indus-
tries are a major potential source of toxic substances such as heavy metals. The
facilities plan should evaluate whether pretreatment is required for industrial
wastes by the "Federal Pretreatment Standards" (40CFR128) (14) or any state or
local pretreatment standard for removal of toxic substances.
Section C - EXISTING FACILITIES
The existing sludge treatment and management facilities will be an important
factor in the economics of sludge management alternative selection. Extensive
existing facilities will, of course, tend to favor those alternatives which make
effective use of those facilities. Existing facilities must be evaluated as to
their reasonable future life and continued effectiveness. Sludge processing
facilities which perform some combination of the following functions may be
present:
Thickening
Dewatering
Storage
Stabilization
Combustion
Transport
Disposal
Section D - ENVIRONMENTAL CONSIDERATIONS
Environmental considerations are those features of the environment which affect
the selection of a sludge management system.
D.I. CLIMATE
A climatalogical analysis is important in the selection of most sludge manage-
ment alternatives. While certain factors are of more concern for some systems
than others, all factors should be considered to aid the decision-making process.
The possibility of climatalogical variations within the planning area should also
be considered. Sources of climatalogical data include (15):
• National Weather Service local offices
• Climatalogical Data, Published by the National Weather Service,
Department of Commerce
• Airports
• Universities
• Military installations
• Agricultural extension services
• Agricultural experiment stations
27
-------
• Agencies managing large reservoirs
• American Society of Heating and Refrigeration Engineers publications
D.I.a. Precipitation Analysis
The precipitation analysis will affect the choice of ultimate disposal method,
the selection of crops for land application, and the scheduling of land applica-
tion and landfill operations, as well as many other features of land application
and landfill systems. The precipitation analysis should include the following
minimum information:
• Mean annual rainfall
• Seasonal distribution
• Storm intensity
D.l.b. Evapotranspiration Potential
The evapotranspiration potential affects crop selection and application rates for
agricultural utilization of sludge. Evaporation rates effect sludge processing
methods such as composting, sandbed drying and lagoon drying. Analysis of evapo-
ration rates and evapotranspiration potentials should include:
• Mean annual rates
• Seasonal variations
D.l.c. Temperature Analysis
The temperature analysis is important in the selection of crops in land applica-
tion systems and in scheduling of landfill and land application operations. The
temperature analysis should include:
• Mean annual temperature
• Seasonal variations
• Number of frost-free days
• Number of freezing days
D.l.d. Wind Analysis
The wind analysis will affect the design of incinerator stacks and the siting
and design of landfill and land application sites. Wind data should include the
average and design maximum velocities, and the prevailing direction.
D.2. LAND CHARACTERISTICS
Land characteristics are of critical importance in the selection of the ultimate
disposal method.
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Sources of land characteristics data include (15):
U.S. Department of Agriculture - Commodity Stabilization Program
U.S. Department of Agriculture - Soil Conservation Service
U.S. Department of Agriculture - Extension Service
U.S. Geological Survey
U.S. Environmental Protection Agency (STORE!)
Local planning departments
U.S. Corps of Engineers offices
Private photogrammetry and mapping companies
State mine and geology agencies
State water resources agencies
Local water conservation districts
Groundwater users (municipalities, water companies, individuals, etc.)
D.2.a. Topography
The topography will, to a large extent, determine the design of the ultimate
disposal system and affects the potential of the site for runoff and subsequent
surface and groundwater pollution.
D.2.b. Soils
The data describing soils should include the following:
Depth
Texture
Structure
Bulk densities
Porosity
Permeability
Moisture
Ease of excavation
Stability
PH
Cation exchange capacity
D.2.c. Geology
The geologic data should include the following:
• Depth
• Type
• Fractures
• Surface outcrops
D.2.d. Groundwater
Groundwater data are important because of the necessity of protecting the
aquifers from leachate pollution. Groundwater data should include:
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Depth to groundwater
Depth of aquifer
Direction of flow
Hydraulic gradeline
Quality
Location of recharge zones
Present and future uses
D.2.e. Surface Water
Surface water data should include:
Location of surface waters
Direction of flow
Rate of flow
Quality
Present and intended uses
Section E - SLUDGE TRANSPORT
The evaluation of sludge transport systems requires the examination of several
factors. The quantity and type of sludge and degree of processing it receives
influence the means of transport as does the method of ultimate disposal.
Environmental considerations and the availability of transport facilities also
influence the decision-making process. Barging, for example, will be precluded
from consideration if there is no appropriate watercourse between the processing
and disposal sites. In the preliminary analysis of alternatives, it should be
readily apparent that certain transport modes are unsuitable for the particular
local conditions.
There are four basic methods of sludge transport-pipeline, truck, barge and rail-
road. In certain instances, the methods may be combined and in others they may
not be required at all. An example of the latter would be if local residents
hauled processed sludge from the treatment plant themselves. With the exception
of short loading and unloading pipelines in combination with truck, barge or
railroad transport, combined systems are rarely the best choice. The EPA publica-
tion Transport of Sewage Sludge (16) has a great deal of information on the plan-
ning of sludge transport systems.
E.I. PIPELINE
Headloss through a sludge pipeline is determined by the solids content of the
sludge. Sludges greater than 10 percent can be pumped, but it may not be econom-
ically feasible. In general, pipeline transport is appropriate for sludges 4 per-
cent or less (16). Liquid sludges with higher solids content can be diluted prior
to transport through pipeline.
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E.l.a. Route
Alternative pipeline routes must be evaluated. The terrain and distance between
the treatment and disposal sites for various routes will influence the facility
costs. Pipeline crossings such as highways, railroads and waterways may pose con-
struction and maintenance problems. Subsurface considerations such as soil types
and the locations of other utility lines must also be evaluated. Health consid-
erations may prevent routing sludge pipelines in the close proximity of domestic
water supply lines due to potential for cross-connections. The allowable distance
will vary from a requirement that pipes not be installed in the same trench to
requiring several feet of separation, depending on local regulations.
E.I.b. Size and Material
Preliminary sizing is required in the planning of pipelines. Table 5 gives pipe-
line sizes and flow rates for liquids. Typically, cement-lined cast iron or
ductile iron pipe is used for sludge pipelines. Depending on local conditions,
other materials may be more suitable.
TABLE 5. PIPELINE SIZE AND FLOW RATES
Pipeline
size, in.
4
6
8
10
12
14
16
18
20
Sludge flow rate
gpm @ 3 fps
velocity
120
280
500
800
1,100
1,400
2,000
2,500
3,000
Pipeline capacity
various daily hourly
4
0.03
0.06
0.11
0.18
0.25
0.35
0.45
0.57
0.70
8
0.06
0.13
0.24
0.38
0.53
0.67
0.96
1.20
1.44
at 3 fps velocity for
operating periods, mgd
12
0.09
0.20
0.36
0.58
0.79
1.01
1.44
1.80
2.16
20
0.14
0.34
0.60
0.96
1.32
1.68
2.40
3.00
3.60
E.l.c. Pumping Requirements
Pipeline pump station information is presented in Tables 6 and 7. The former
gives the sludge pumping characteristics and the latter, the energy required for
different operating times.
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TABLE 6. PIPELINE SLUDGE PUMPING CHARACTERISTICS (16)
Pipeline
size, in.
4
6
8
10
12
14
16
18
20
Flow,
gpm
120
280
500
800
1,100
1,400
2,000
2,500
3,000
Hydraulic
loss, ft/
100 ft (C=90)
2,10
1.40
1.02
0.82
0.61
0.45
0.45
0.39
0.33
available each
pumping station,
ft1
4002
4502 '
260
230
230
210
2103
2253
2003
Pump
efficiency,
percent
45
50
50
64
73
78
70
76
78
Pumping station
spacing-level
terrain, ft
19,048
32,143
25,490
28,049
37,705
46,667
46,667
57,179
60,606
* Based on non-clog, centrifugal, 1,780 rpm pumps.
2 Pumps in series for additional head.
Pumps in parallel for additional capacity.
TABLE 7. PIPELINE PUMPING STATION ENERGY (16)
Pipeline
size, in.
4
6
8
10
12
14
16
18
20
Power, kw/
1,000 gph
ft head
0.0078
0.0070
0.0070
0.0055
0.0048
0.0045
0.0050
0.0046
0.0045
Annual energy, kwh/ft head
for daily hours of operation shown*
Total station
4 8
90 180
378
675
0 843
1,016
1,211
1,927
2,219
2,594
12
270
567
1,012
1,265
1,525
1,816
2,891
3,328
3,891
20
450
944
1,686
2,108
2,541
3,027
4,818
5,547
6,486
^Motor efficiency = 90%; pump efficiency = 80%; kw/11,000 gph-ft head
0.00315
(pump eff) (Motor eff)
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E.2. TRUCK
Truck transport is appropriate for liquid sludge with at least four percent
solids and for dewatered sludge. Truck transport is normally feasible for one-way
haul distances up to 80 miles.
E.2.a. Route and Travel Time
Travel time can be determined from the transport distance and traffic patterns.
Average speeds of 25 mph for the first 20 miles and 35 mph for the remainder of
the trip can be used to approximate the total travel time per truck load of
sludge (16).
E.2.b. Size and Number of Trucks
The size and number of trucks can be determined from the type and quantity of
sludge to be transported and the distance between the treatment and disposal
sites. Local traffic regulations may govern the maximum size of trucks. Informa-
tion for determining truck requirements are given in reference 16. For example a
10 mgd secondary treatment plant with a 20 mile haul distance, with trucks opera-
ting 8 hours a day 360 days per year, would require a total of 6 2,500 gallon
trucks for liquid sludge or one 15 cubic yard truck for dewatered sludge.
E.2.C. Fuel Requirements
Unit fuel requirements for various types and sizes of sludge transport trucks
are given in reference 16. The fuel use for the trucks in the previously cited
example would be 4.5 miles per gallon.
E.2.d. Manpower Requirements
Manpower requirements for truck transport are given in reference 16 for liquid
and dewatered sludges. These are based on the truck operating hours plus ten per-
cent. For the 10 mgd example cited previously approximately 16,000 man-hours per
year of truck operator time would be required for liquid sludge and 2,600 man-
hours for dewatered sludge.
E.2.e. Loading, Unloading, and Vehicle Service Facilities
Auxiliary facilities for truck transport of sludge include elevated storage for
dewatered sludge, loading equipment and unloading equipment. These should be
planned in conjunction with the specific sludge processing systems they will
serve. Other facilities may be necessary, depending on local conditions.
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E.3. BARGE
Barging, although not a common method of sludge transport, is appropriate for
liquid sludge with four to ten percent solids. Practical transport distances
range from 20 to 320 miles and, of course, a suitable waterway must be available.
Conceivably, barging could be combined with other methods of transport; however,
it is generally preferable to use only one.
E.3.a. Route and Travel Time
The route for barging is confined to local waterways. It is unlikely that more
than one, or possibly two, alternatives for barging sludge will be available.
The average speed of barges is about 4 mph although speeds of up to 7 mph can be
achieved in open waterways. Transit times will be variable depending on traffic,
draw bridges, locks, tides, currents, and other factors (16). For the 10 mgd
plant cited in the earlier example, with a 80 mile barging distance approximately
2,600 hours of hauling time would be required for a 300,000 gallon barge, carry-
ing 4 percent solids sludge.
E.3.b. Size and Number of Barges
The barge requirements vary with the type of sludge produced and the processing
it receives prior to disposal. Barge requirements are given in reference 16. For
the example cited above one 300,000 capacity barge would suffice, assuming stor-
age at the plant is available while the barge is in transit.
E.3.c. Fuel Requirements
Fuel is required for operating the barge tow boat. Estimates for the tow boat
size and fuel consumption are given in reference 16. In general, larger barges
and tow boats are more efficient than smaller ones since fewer trips are needed
to transport the same quantity of sludge. For the 300,000 gallon barge cited
above, a tow boat of approximately 1,200 horsepower would be needed with a fuel
consumption of 2,000 gallons per day.
E.3.d. Manpower Requirements
The annual labor requirements for barging operations are approximately twelve
man-hours/barge load. Maintenance requirements are approximately 680 man-hours/
year for plants up to 10 mgd, 1,640 man-hours/year for plants up to 100 mgd, and
2,400 man-hours/year for plants up to 500 mgd (16). Towed barges are generally
unmanned during transit, therefore they have lower labor requirements than self-
propelled barges.
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E.3.e. Loading, Unloading, and Vehicle Service Facilities
Auxiliary facilities for barge transport include loading storage and equipment
(pumps and a pipeline), a dock and control building, and unloading equipment
(pipeline). Towing equipment servicing is the responsibility of the towing
company unless self-propelled barges are used, in which case a shop will be
needed.
E.3.f. Tow Tariffs
Tow charges are normally based on total tow boat billing times, including round
trips and idling time. Tow tariffs are a function of tow boat size rather than
barge size, so it is important to carefully match the two for maximum economy.
E.4. RAILROAD
Railroad transport is suitable for dewatered sludge and liquid sludge. Trans-
port distances generally range from 20 to 320 miles. Railroad transport is not a
common method of transporting sludge.
E.4.a. Route and Travel Time
Rail transport of sludge is constrained by the established rail lines and their
routes. It is unlikely that more than one or two options would be available in a
particular area. Transit times for transporting sludge by rail are usually on the
order of several days, even for relatively short haul distances. The possibility
of nuisance conditions arising because of putrifying sludge should be
considered.
E.4.b. Size and Number of Cars
Tank cars used for rail transport of liquid sludge must be supplied by the
shipper. These can be acquired from the manufacturer by purchase, lease, or con-
tract. The demand requirements are given in reference 16. Hopper or side dump
cars for dewatered sludge may be available from the railroad. A 20,000 gallon
capacity tank car is the normal capacity. For a 10 mgd secondary plant producing
15 mg of sludge per year approximately 13 tank cars would be required of 2 loads
per day. For dewatered sludge 50 cy hopper cars are used.
E.4.c. Fuel Requirements
While the fuel demands will be met by the rail company and will be included in
the tariffs, the fuel consumed in transporting the sludge should be estimated
for inclusion in the energy effectiveness analysis.
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E.A.d. Manpower Requirements
Typical labor requirements for loading and unloading the railroad cars and for
maintenance are given in reference 16. For the 10 mgd example cited above, O&M
labor would be approximately 4,400 man-hours per year for liquid sludge and 3,600
man-hours per year for dewatered sludge.
E.4.e. Loading, Unloading, and Service Facilities
Railroad transport of sludge typically requires loading storage and equipment
(pumps and piping for liquid sludge and hoppers for dewatered sludge), railroad
sidings and unloading equipment. Unloading is ordinarily accomplished by
gravity.
E.4.f. Tariffs
Costs for railroad transport vary widely and should be obtained as a result of
close consultation with the carrier in question. In addition to distance and
weight carried, the ownership of the cars, and regional variations will affect
the tariffs. If the cars are to be leased, consideration must be given to leasing
costs.
Section - F LAND APPLICATION
Land application includes those projects where sludge is applied to land for dis-
posal, crop utilization, or reclamation of spoiled areas. Land application does
not include trenching or landfill projects. Land application systems frequently
involve utilization of sludge for agricultural production.
The local farm advisor, i.e. the state agricultural extension service or county
agent, can be of tremendous help in the planning and evaluation of land applica-
tion systems involving sludge application to cropland and should be consulted
closely throughout the planning, design and operational stages of a land applica-
tion system. A typical land application design calculation is shown in Appendix
A.
F.I. PURPOSE
There are several possibilities for land application plans. In order to determine
the proper techniques and loading rates, the land use purpose must be defined.
The land may simply be a dedicated disposal site, utilized for agriculture, util-
ized for reclaiming marginal or disturbed soils or some combination of the above.
Although annual application on parks or forests is not commonly practiced appli-
cation prior to planting provides a good soil conditioner and a slow release
nitrogen source. Discussions related to reclaiming marginal land apply to these
special systems.
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F.I.a. Dedicated Disposal
A site may be used for dedicated disposal with no crop grown. This should be a
modification of a landfill system. Ultimate land use must be studied carefully
before creating a dedicated land disposal area to avoid pollution of underlying
groundwater or the buildup of excessive levels of heavy metals that could make
the land unfit for agriculture.
F.l.b. Agricultural Utilization
Sludge applied for agricultural utilization can be of real benefit to farmers
when applications are properly controlled. Agricultural use requires careful con-
trol of application rates to maximize the beneficial use of organic matter,
nitrogen, phosphorus, and desired trace elements (those elements which are
essential to plant growth but lacking in some soils, such as zinc and copper.)
to insure contaminants are controlled within limits. Application rate determina-
tions depend upon various factors such as soil type, crops to be grown, method of
application and regulatory constraints.
Throughout this section and in later sections agricultural utilization at maximum
rates on sites owned or controlled by the operating agency is emphasized. This
does not preclude utilization on privately owned land or utilization at lower
rates. It is common practice for farmers to use a combination of organic and
chemical fertilizers. For example, sludge could be sold to the farmer and he may
use it to meet half his nitrogen or phosphorus needs and supplement with chemical
fertilizer to meet the rest of his needs. For more information refer to the sec-
tion on off-site use by others.
F.l.c. Reclamation of Disturbed or Marginal Lands
Another purpose for utilizing sludge is reclaiming marginal or disturbed soils.
These projects are similar to agricultural utilization projects in terms of goals
and controls required. Higher application rates may be necessary to achieve the
desired results.
F.I.d. Combinations
There may be several purposes for an area where sludge is applied. Agricultural
operations or climatic constraints may result in an area being split such that
some acreage is used for crops and some is used for dedicated land disposal.
Reclamation sites may in some cases be converted to agricultural production
areas.
F.2. EVALUATION OF POTENTIAL SITES
Site evaluation should include a review of all potential sites. This review must
be through and timely since site acquisition or contractual agreements with pri-
vate landowners can be time-consuming and must begin well in advance of facility
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construction. Site acquisition evaluation items should be reviewed on a short-
term as well as long-term basis.
F.2.a. Geographical Location
The location of the site will affect economics of the land application system as
well as the type system to be used. The site must be located so that surface
water is not contaminated. The minimum distance between the site and surface
water is a function of the application method to be used, the type of soil, crop,
and slope of the land adjacent to the surface water. Intermittent or ephemeral
streams should be considered as surface water systems. A major cost item in land
application systems is transportation cost. This cost is a function of distance
to transport and method of transportation. Also, in a given locale, some modes of
transportation are more readily available than others. Condition and location of
the nearest highways should be determined. In some instances road building or
rebuilding may be required to bring roads up to standards required for heavy
truck traffic. If river transportation systems or barges are available, then
their proximity to proposed sites should be determined. In certain unusual situa-
tions a barge transportation system may be combined with another mode of trans-
portation. For example, sludge may be barged from the plant to a transfer area
and then trucked to the application area. Rail systems can often be found close
to a treatment plant. Railroad transport availability at the site should be
determined. As discussed above with barge systems, railroad transport may be
considered in conjunction with other modes of transportation.
F.2.b. Compatibility with Land Use Plans
Regional planners or the planning commission should be consulted to determine
land use plans for potential sites. The current use of the site should be deter-
mined by visiting each site. Variations during recent years should be noted, then
the compatibility of the current use with the land application project should be
determined. Regional plans, basic plans, and/or master plans should be consulted
to determine the proposed future use of potential sites. Potential for variation
in these plans should also be determined. Planners should be consulted for
insights regarding these questions.
Current site zoning and adjacent area zoning and use should be determined. Actual
zoning may be different from current use or from planned use. Adjacent land use
may limit use of a site or cause restrictive conditions to be placed on use of a
particular site. For example, if a nearby area is zoned for residential use,
spraying of sludge may not be allowed. Area plans or zoning will reflect general
planning intentions and can be changed with good justification. However, if
specific development projects have been approved or have been initiated, then
changes may not be accepted. Location of planned development projects should be
determined. Selected sites should be flexible so that there is room for future
expansion. This should be considered even for areas with growth controls since
sludge characteristics and quantities per capita can change. Also, the additional
space will allow room if application rates are lowered from those originally
proposed.
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F.2.C. Method of Land Acquisition
There are several means of acquiring the land for the application site. The best
method will depend upon the local agency constraints, local regulatory agency
requirements, and current ownership of the land.
Purchase of a site may take several years especially if the owners are not
anxious to sell or are asking a very high price for the property. Condemnation
proceedings may be required which cause further delay. Site purchase has the
major benefit of allowing maximum flexibility to the agency. Since there are no
arguments over operations with land owners and contract commitments are less.
Purchase price, as well as potential acquisition problems, should be determined
for potential sites.
Site lease agreements can be advantageous when a landowner does not want to perm-
anently give up his property or wants to take advantage of improved soil charac-
teristics resulting from the sludge addition. Lease agreements must be long-term
in nature (10-20 years) to insure that the agency will have time to find alter-
native sites earlier than necessary. Lease agreements should specify acreage, use
of land, and application procedures.
Some agencies may prefer to control the site but not have the responsibility for
farming. This can be accomplished by purchasing the property and then leasing the
site to a farmer, usually the previous owner. The farmer will then continue the
farming operation. This approach provides the flexibility for the agency to
change operators at a later date or to operate the system themselves.
Another approach to obtaining a site is to contract with a user. The advantages
of this approach are that land acquisition problems are eliminated and the agency
does not have to operate the farming system. Sludge application may be by the
user or by the agency. The agency should have contracts with users with 10- to
20-year terms unless adequate acreage and interest in the use of sludge assure
availability of alternate application sites.
Another possible alternative is a combination of land acquisition and lease
agreements. Application rates for crop growth will be lower than rates for dedi-
cated disposal without crops. With the combination approach, it may be advanta-
geous for an agency to purchase adequate area for dedicated land disposal and
still maintain leases with farmers to take sludge for soil conditioner. This pro-
vides maximum flexibility. The dedicated disposal area will provide the site for
disposing of sludge when farming operations are not favorable for sludge applica-
tion. Land leases are eligible for grant participation under certain conditions.
The land acquisition problem can be eliminated through direct sales of sludge to
farmers. The farmer could be charged for sludge delivered (price per ton) and/or
for sludge applied (price per acre). Sales should be through contract specifying
quantities, application rates, areas to be used, monitoring required, and price.
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F.3. STABILIZATION PROCESS
Under most circumstances before applying sludge to land the sludge should be
stabilized to reduce pathogenic organisms and minimize odors and vector breeding.
There are several alternative sludge stabilization processes discussed below.
Some treatment plants may have more than one type of stabilization process. A
major impact of variation in the sludge stabilization process used is the change
in the resulting nutrient forms and concentrations. The potential for public
access to a site is usually directly proportional to the degree of sludge stabil-
ization that may be required. The processes discussed below are anaerobic diges-
tion, aerobic digestion, composting, incineration, pasteurization, and chemical
stabilization. This discussion describes the expected results. Detailed discus-
sion of the process mechanisms is beyond the scope of this document.
Some stabilization occurs in storage lagoons. The stabilization rate and degree
of stabilization are unpredictable. Storage lagoons are normally designed to be
periodically drawn down. During this time, there would be no stabilization. The
design can utilize several parallel lagoons to provide continuous storage for
stabilization. The unpredictable lagoon performance and the potential for nui-
sance conditions with raw sludges are factors which must be thoroughly
considered.
F.3.a. Anaerobic Digestion
Anaerobic digestion reduces pathogen concentrations significantly. Nitrogen con-
centrations can also be greatly impacted. Typical nutrient concentrations in
anaerobically digested sludge are as follows:
COMPOSITION OF REPRESENTATIVE ANAEROBIC SEWAGE SLUDGES (17)
Component Range* Lb/Ton**
Total nitrogen 1-5 20 - 100
Ammonium nitrogen 1-3 20-60
Total phosphorus 1.5-3 30 - 60
Total potassium 0.27-0.8 4-16
* Percent of oven-dry solids
** Lb/ton dry sludge
F.3.b. Aerobic Digestion
Pathogen destruction by the aerobic digestion process is similar to that achieved
by anaerobic digestion. Aerobic digestion has been used extensively at small
activated sludge plants. Many extended aeration (including oxidation ditch)
plants dispose of sludge without further digestion. This sludge will be similar
to anaerobically digested sludge in terms of both nutrient content and degree of
stabilization (measured by reduction in volatile solids, which averages 40-55
percent). Typical nutrient concentrations in aerobically digested sludge are as
follows:
40
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COMPOSITION OF REPRESENTATIVE AEROBIC SEWAGE SLUDGES (8)
Component Range* Lb/Ton**
Total nitrogen 3-6 60-120
Ammonium nitrogen 1-3 20-60
Nitrate nitrogen 0.5-1.5 10-30
Total phosphorus 1.1-5.5 22-110
Total potassium 0.8-1.1 16-22
* Percent of oven-dry solids
** Lb/ton dry sludge
F.3.c. Heat Treatment
Pasteurization is generally accomplished by a heat treatment conditioning pro-
cess. Pathogens will be destroyed when the sludge is exposed to 159°F or 70°C
heat for 30 to 60 minutes. Higher temperatures require less time for pathogen
destruction. Nutrient concentrations in heat treated sludge are extremely vari-
able. One source (18) reports the following:
NUTRIENT CONTENTS OF HEAT TREATED SLUDGE CONCENTRATION, %
Total N 2.8
NH3-N 0.25
Total P 0.46
K 0.09
Generally, heat treatment processes reduce nitrogen contents while phosphorus and
potassium content remains unchanged from raw sludge values. Heat treatment pro-
cesses do not significantly reduce volatile organics or odors.
F.3.d. Chemical Stabilization
There are three main methods of chemical stabilization used at this time. They
are stabilization by lime or lime and ferric chloride addition and by chlorine
addition through the patented process "Purifax". All have been effective means of
pathogen destruction but information regarding nutrient contents and the poten-
tial for generating toxic organics is limited. Ammonia levels will be reduced by
either of these three processes. This reduction results from volatilization of
ammonia at high pH values with lime treatment or the combination with chlorine to
form chloramines. Lime stabilization can impact the phosphorus concentration (19)
by combining some of the phosphorus with calcium to form calcium phosphate. A
slight loss of total phosphorus is also likely.
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F.4. AGRICULTURAL MANAGEMENT PLAN
Agricultural management is an essential part of planning a land application pro-
ject. Selection of the crop(s) to be grown is necessary to determine loading
rates and timing of sludge applications. Coupled with these considerations is
planning the farming operation. Is the farming to be done by the agency or under
contract? Long range planning should provide a flexible system.
F.4.a. Crops to be Grown, Rotation Plan, and Markets
The choice of crops to be grown depends primarily on local considerations and
regulatory constraints. If locally grown crops are not suitable for sludge
amended soils, then crops should be chosen which would be adaptable to local
farming practices. Crop selection should be discussed with the local farm
advisor. The crops chosen should be high nutrient users and have a cash value so
sales can help offset operating costs. Field corn and forage crops are most fre-
quently used. Sod farms are also excellent for utilizing sludge.
In many areas it may be advantageous to develop a crop rotation plan where the
crop grown changes periodically. Crop rotation can be an important factor in the
area of nutrient utilization and soil fertility. The crop rotation plan (if
appropriate) should be developed before determining sludge application rates.
If cash sales are expected with crops grown on the land application site, then a
market analysis should be completed. This analysis may be very brief if the crops
grown are already common to the area. If a new crop(s) is to be brought into the
area, the marketing analysis may be more complex since new markets would have to
be developed. In either case some market analysis work is required.
F.A.b. Farming by Municipal Agency or Contract
If the agency or authority responsible for operating the sewage treatment plant
will also be responsible for the farming operation, then plans must include
hiring a staff and aquisition of equipment for farming. This staff should include
equipment operators, maintenance staff and possibly additional laboratory tech-
nicians. The type of farm equipment is determined by the crop grown and sludge
application techniques.
There are several options regarding contract farming. One would provide for all
farming to be done by contract. Another option is to contract for harvesting,
with the agency accomplishing all other farming operations. Other options include
variations of responsibilities accomplished by contract and by the agency.
Application to private land would eliminate this responsibility with the munici-
pality providing transport, application, both, or neither.
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F.4.c. Long Range PIan
Long range planning should include plans to cover the management of application
sites directly controlled by the municipality where recommended limitations for
heavy metal additions are exceeded. These plans may include non-agricultural
uses. For example, the application site may change from agricultural to forest
land use.
F.5. NUTRIENT BALANCE
The major nutrients of interest in municipal sludge from an agricultural stand-
point are macronutrients, or nitrogen, phosphorus, and potassium. Agricultural
fertilizer requirements are expressed in terms of nitrogen compounds as nitrogen
(%N), phosphorous compounds as phosphoric acid (%P20^) or phosphorus (%P),
and potassium compounds as potassium oxide or potash (l^O). Once the nutrient
contents in the sludge are determined and crops selected, nutrient balances and
corresponding application rates can be computed.
F. 5.a. Nitrogen
Nitrogen is the most complex of the three nutrients. Plants utilize nitrogen in
the ammonium and nitrate forms. Organic nitrogen in the soil must be converted or
mineralized to the nitrate form. The mineralization rates are specific to indi-
vidual areas and soil types. Nitrogen control is important since nitrates can
create a potential problem if excessive levels are allowed to build up in ground-
water supplies. Table 8 shows nitrogen requirements for various field crops.
These requirements will vary at different locations and with different yields.
Note that the values shown are pounds per acre utilized. This assumes that the
crop is harvested and not plowed back into the soil.
F.5.a.(1) Forms of Nitrogen - Most sludges have nitrogen present in the ammonium
and nitrate forms as well as organic nitrogen. Each nitrogen form must be
addressed when planning a land application system. Nitrate nitrogen is readily
usable by crops. If more nitrate is available than used by the crop, the excess
may leach into groundwater supplies, potentially causing problems for the future
use of this groundwater. Ammonia in sludge is found in the ammonium ion form.
Ammonium is usable by crops. Planning for the correct application rate should
take into account ammonia losses if sludge is applied and allowed to dry. If
sludge is applied and allowed to remain on the surface, some of the ammonium will
convert to ammonia, volatilize, and be lost to the atmosphere. These losses can
amount to 20 to 70 percent depending on site specific conditions and length of
time before the sludge is incorporated into the soil. The most complex nitrogen
form (in terms of planning a land application system) is organic nitrogen. Plants
cannot utilize organic nitrogen until it has converted or mineralized to the
plant available forms.
F.5.a.(2) Mineralization Rate of Organic Nitrogen - Organic nitrogen is
converted to usable forms at a variable rate, which depends on climate and soil
type. The mineralization rate should be estimated based on experiences at sites
with similar soil types in areas with similar climates. Usually, 15-25 percent
A3
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TABLE 8. PLANT NUTRIENT UTILIZATION BY VARIOUS CROPS (20)
Crop
Field crops
Barley
Corn (grain)
Corn (silage)
Cotton (lint)
Grain sorghum
Oats
Rice
Saf flower
Soybeans
Sugar beets
Wheat
Vegetable crops
Asparagus
Beans (snap)
Broccoli
Cabbage
Celery
Lettuce
Potatoes (Irish)
Squash
Sweet potatoes
Tomatoes
Fruit and nut crops
Almonds (in shell)
Apples
Cantaloupes
Grapes
Oranges
Peaches
Pears
Prunes
Forage crops
Alfalfa
Bromegrass
Clover-grass
Orchardgrass
Sorghum-sudan
Timothy
Vetch
Turf crops
Bentgrass
Bermudagrass
Yield
per acre
2 1/2 t
5 t
30 t
1,500 Ibs
4 t
3,200 Ibs
7,000 Ibs
4,000 Ibs
3,600 Ibs
30 t
3 t
3,000 Ibs
10,000 Ibs
18,000 Ibs
35 t
75 t
20 t
500 cwt
10 t
12 t
30 t
3,000 Ibs
15 t
30 t
15 t
30 t
15 t
15 t
15 t
8 t
5 t
6 t
6 t
8 t
4 t
7 t
2 1/2 t
4 t
N
175
240
200
210
250
115
110
200
335
275
175
95
175
80
230
280
95
250
85
115
250
200
100
190
105
120
95
85
90
450
165
300
300
325
150
390
225
225
Pounds per acre
P2°5
65
100
80
90
80
40
60
50
65
85
80
50
35
30
65
165
30
115
20
45
80
75
45
60
45
40
40
25
30
80
65
90
100
125
25
105
80
40
K20
175
230
245
150
200
145
170
150
145
550
140
120
200
75
250
750
200
355
120
230
480
250
180
340
125
175
120
95
130
480
255
360
375
475
250
320
160
160
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of the organic nitrogen is converted the first year of application. Lesser
amounts of the remaining organic nitrogen are converted during subsequent years.
These amounts range from 5-10 percent the second year and from 2-3 percent in
subsequent years (20, 21).
F.5.a.(3) Future Application Rate Adjustments for Mineralized Organic Nitrogen -
Each year the application rate should be adjusted to account for mineralization
of previous applications. This means that if sludge is being used on cropland and
the nitrogen balance is critical, then either acreages must be increased or an
alternative crop which uses higher nitrogen levels grown.
F.5.a.(4) Additional Nitrogen Needed for Crop (if any) - If application rates
are limited (by heavy metals, for example), crop nitrogen requirement may not be
met. There are two alternatives to solving this requirement. One is to switch to
a crop with a lower nitrogen requirement. The other is to provide supplemental
nitrogen. When needed supplemental nitrogen can be provided in several ways for
each of many forms. The best method depends on local supplies and types of
fertilization equipment available. Supplemental nitrogen would be provided only
where crops have a high market value and are critical in terms of offsetting
operating costs.
F.5.b. Phosphorus
For most crops phosphorus requirements are much lower than nitrogen requirements.
Nitrogen and phosphorus contents in sludge are nearly the same. Therefore, appli-
cation rates set for nitrogen utilization result in more phosphorus being added
to the soil than will be used by the crop. While there are no established limits
for phosphorus addition phytotoxic reactions can occur in plants if excessive
phosphorus is applied. Records keeping should include phosphorus additions. If
high levels of phosphorus are to be applied plans should be made for the future
management of the application site if excessive phosphorus creates a problem.
Actual phosphorus applications should be measured or expressed as ?2®5' Crop
utilization rates for phosphorus are shown on Table 8. These rates should be
verified by the local farm advisor before they are used.
F.5.C. Potassium
Potassium concentrations in sludges are usually much lower than nitrogen and
phosphorus concentrations. Crop potassium needs are generally higher than their
phosphorus needs, and often equal to nitrogen requirements. Therefore, supple-
mental potassium is frequently required to insure maximum crop production.
Typically it is supplied in the form of potash. Some areas having high background
levels of potash in the soil may not require additions of potassium. Crop potas-
sium utilization rates are shown on Table 8. When potash additions are required
the supplemental requirements are determined by subtracting that added by the
sludge and that amount available in the soil from the crop requirement.
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F.6. HEAVY METAL LOADINGS
There has been much controversy about heavy metal applications and their impact
on food chain crops. Essentially there are two criteria which minimize the
potential for excessive metal uptake by crops. They are cation exchange capacity
and maintenance of a soil pH greater than 6.5.
EPA, USDA, and a number of state agencies and land grant universities have issued
guidance documents to assist project planners in determining sludge application
rates. A number of these references cite guidelines or regulations which limit
heavy metal additions to cropland through sludge application (22 to 29). The most
current regulations are the EPA 40CFR257, "Criteria for Classification of Solid
Waste Disposal Facilities and Practices" (29). Local, state, and federal require-
ments should be determined for the particular area at the time the project is
planned.
F.6.a. Cation Exchange Capacity
The level of heavy metals in soils that begin to cause crop production problems
can vary due to a number of soil factors, such as organic matter and clay content
of the soil, which are reflected by the soil's cation exchange capacity (CEC).
Suggested total amounts of heavy metals added to agricultural land as provided in
EPA guidance documents published in 1978 are shown on Table 9. These suggested
values were based upon maintaining the soil pH at greater than 6.5.
TABLE 9. SUGGESTED TOTAL AMOUNT OF SLUDGE METALS ADDED TO
AGRICULTURAL LAND (30)
Soil cation exchange capacity (meq/100 g)
Metal
Pb
Zn
Cu
Ni
Cd
Determined by the
0-5
Maximum
500
250
125
125
5
pH 7 ammonium
5-15
Cumulative Amount of Metal
1,000
500
250
250
10
acetate procedure
15
(Ib/acre)
2,000
1,000
500
500
20
F.6.b. Sludge and Soil pH
The combined sludge-soil pH should be maintained above 6.5 and when lower pH
values are found, lime should be added to raise the pH. The metals concentrations
are cumulative so previous additions must be considered.
F. 6.c. Cadmium
Cadmium is generally the metal that causes the most concern for sludge applica-
tions to cropland. Both the soil and food chain crops can be adversely affected.
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The US EPA interim final guidelines provide for two approaches to controlling
land application of sludges containing cadmium. The first approach consists of
three requirements. First, the pH of the sludge and soil mixture is 6.5 or
greater at the time of application, except for sludge containing cadmium at con-
centrations of 2 mg/kg (dry weight) or less. Secondly, the annual application of
cadmium from sludge does not exceed 0.5 kg/ha on land used for the production of
tobacco, leafy vegetables, or root crops grown for human consumption. For other
food chain crops, the annual cadmium application rate does not exceed:
Annual Cd
Time period Application Rate
(kg/ha)
Present to June 30, 1984 2.0
July 1, 1984 to Dec. 31, 1986 1.25
Beginning Jan. 1, 1987 0.5
Thirdly, the cumulative application of cadmium from sludge does not exceed the
following levels:
Soil Cation Maximum Cumulative Application (kg/ha)
Exchange Capacity Background soil pH* Background soil pH
(meg/100 g) <6.5 >6.5
<5 55
5-15 5 10
>15 5 20
* If the pH of the sludge and soil mixture is adjusted to and maintained at 6.5
or greater whenever food chain crops are grown then the levels of the next
column are allowed.
The second approach consists of four requirements. These requirements are manage-
ment oriented rather than providing specific cadmium levels. The first require-
ment is that the only food-chain crop grown is animal feed. Secondly, the pH of
the sludge and soil mixture is 6.5 or greater and is maintained at this level
during periods when food-chain crops are grown. Thirdly, there must be a facility
operating plan which demonstrates how the animal feed will be distributed to pre-
clude ingestion by humans. Measures required to safeguard against possible health
hazards from cadmium entering the food chain should be included in the operating
plan. The fourth requirement consists of notification of future property owners
by a stipulation in land record or property deed that the property has received
sludge at high cadmium application rates and that food chain crops should not be
grown.
F.6.d. Nickel
Recommended maximum addition levels of nickel by sludge application to cropland
are shown in Table 9 section F.6.a. Presently, toxicity of nickel to plants has
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only been observed in acid soils. If nickel concentrations are excessive then pH
adjustment (upward) by lime addition should lessen the chances of plant damage.
F.6.e. Copper
Copper is useful to plants in small quantities but can be hazardous in excessive
amounts to grazing animals (especially sheep). Recommended maximum addition
levels by sludge application to cropland of copper are shown on Table 9.
F.6.f. Molybdenum
Very small amounts of molybdenum are necessary for crop growth. Plant damage is
not likely but grazing cattle and other animals are susceptible to molybdenum
toxicity. No limits have been established at this time. Areas near natural
molybdenum deposits should be aware of this potential problem.
F.6.g. Zinc
Small amounts of zinc are necessary for crop growth. Zinc toxicity in plants is
uncommon, occurring in acid soils. Sheep and cattle are susceptible to zinc
toxicity at high zinc concentrations. If pH levels are maintained at or above
6.5, zinc toxicity should not be a problem.
F.6.h. Lead
Maximum recommended addition levels of lead by sludge application to cropland are
shown in Table 9. Toxicity of lead to plants is likely only when the soil/sludge
mixture pH is less than 5.5. Plant uptake of lead is minimized by increased
soil/sludge pH, CEC, and available phosphorus (23).
F.7. SLUDGE APPLICATION RATES
The actual sludge application rate is determined based on the preceeding analy-
sis. This rate is expressed in terms of annual dry weight, annual and daily wet
weights. With the computed nitrogen additions and the known concentration con-
tained in the sludge a maximum annual dry application is determined. In some
instances this maximum will be limited by heavy metal limitations. The rate must
not exceed the evaporation/percolation capability of the site unless provisions
are made for control of surface runoff. To allow ease of acreage computations any
variations in crop nutrient requirements, the total sludge application rate
should be computed for each crop. Each application has a limiting factor. This
factor should be determined early in the planning phase so that process changes
affecting that factor can be determined. This can result in a major change in
site size requirements. The maximum daily application with liquid sludge is
usually determined by experience with a similar soil type.
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As discussed previously annual applications are usually limited by the nitrogen
balance. Nitrogen removal rates should be equal to or greater than application
rates. If the sludge application rate has been set by balancing nitrogen removal
with application and the maximum annual cadmium is exceeded with this rate, then
the rate must be reduced to that allowable by the cadmium limitation. Phosphorus
and heavy metals limitations discussed previously are generally maximum cumula-
tive application limits.
F.8. SITE CONSIDERATIONS
Potential sites should be reviewed for size and flexibility for expansion or
changing from one type of system to another. The following sections describe the
considerations to be included in the facilities plan.
F.S.a. Site Size
The site size is a function of the net application area plus buffer area, future
expansion, replacement area, and emergency sites for adverse weather conditions.
The site size can be as much as twice the net application area depending on the
specific circumstances.
F.8.a.(l) Application Area - The application area is determined as outlined in
later sections. This is the land that receives sludge. This area is sized without
buffer or replacement area considered and does not include standby disposal
areas. These items are added as described below.
F.S.a.(2) Wet Weather Plan For Stockpile Storage or Alternative Disposal - The
site area requirements should include space for stockpiling dewatered sludge,
lagooning liquid sludge or an alternative disposal system unless provided at an
alternative location. The alternative system might consist of a landfill, trench
disposal, or a composting operation. When field conditions do not permit land
application then the sludge can be stored or disposed of by an alternate method.
F.S.a.(3) Buffer Area - Some space may be required to separate the application
area from neighboring areas. This space or buffer helps limit public access and
minimizes the chances for nuisance conditions to develop. The space required is a
function of the application method, prevailing wind velocity, and topography of
the site. Application by spraying in a windy area in close proximity to resi-
dences might require a large buffer area. Sludge injection on level land should
require very little buffer. The amounts vary between these two extremes.
F.S.a.(4) Expansion or Replacement Area - If the treatment plant capacity or
treatment level increases, more sludge will be produced and must be managed. If
this increased volume is to be applied to the land then more land will be
required. An alternative to acquiring more land would be sizing the application
area for future quantities expected in the next 20 years and apply at lower load-
ing rates until the full capacity is reached. If application is accomplished on
privately owned land then landowner committments should be made with increased
quantities accounted for. When heavy metals limitations are reached on a particu-
lar site then an alternative application area must be found.
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F.S.b. Compatibility With Future Expansion
Land application areas must be compatible with projected future expansions. The
expansion may mean an increase in quantity due to increased population served by
the plant, process modifications or changes in constituent levels. Any of these
changes could cause a change in the area requirements or type of system to be
used.
Changes in unit processes used can result in larger quantities of sludge, dif-
ferent chemical makeup of the sludge, or a sludge with a different physical
nature or moisture content. Larger quantities of sludge or sludges of a different
physical or chemical nature can result from a variation in operation of existing
processes, replacement of a unit process with another type of process, or addi-
tion of new unit processes to meet more stringent discharge standards. Trans-
portation costs are sensitive to the degree of dewatering. Variations in dewater-
ing process operations may lower the volume to be hauled. This would also require
adjustments at the application area. As communities grow there can often be
significant changes in raw sewage constituent levels. This may be industrially
related or related to tourism increases or changes in life styles. Changes in raw
sewage constituent levels will result in a change in sludge constituent levels
thus requiring adjustments in land application procedures or sludge application
rates.
F.9. RUNOFF CONTROL
There are two sources of runoff. One is the liquid in the sludge and the other is
precipitation falling on a sludge application site. Runoff control consists of
containment and/or treatment of liquid from the site to prevent degradation of
nearby surface streams. One of the best approaches to control of liquid in the
sludge is rapid incorporation into the soil. Runoff from adjacent properties
should be diverted around the application site. On-site containment of liquid
from sludges or precipitation is normally provided by small impoundments placed
at needed locations on the site. The contained liquids can be recycled for
further treatment or can be reduced through evaporation and percolation or can be
discharged after sufficient detention time to meet regulatory standards.
F.10. STORAGE
Storage is critical for time periods when application operations are not pos-
sible. These time periods may be several months due to severe cold weather con-
ditions or they may be several days due to excessive precipitation. Storage
requirements should include provisions for agricultural operations. If the types
of crops grown preclude application for certain time periods, then storage will
be required. Storage is usually provided by lagoons. Storage systems must be
adequately sized and designed to minimize the possibility of nuisance conditions.
The storage requirement will vary somewhat depending on application method. For
example, dewatered sludge could be spread on frozen ground but liquid injection
would not be feasible.
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F.lO.a. Capacity
Land requirements are based on the type of land application system. Agricultural
utilization systems are sized based on application rate determinations described
previously. Dedicated disposal systems are sized by operation constraints, such
as weather limitations to operation, seasonal limits, and/or application equip-
ment limitations.
F.lO.b. Odor Control
Odor control is best achieved by adequate stabilization before storage. Odor con-
trol of partially stabilized sludge is extremely difficult. High dosages of
chlorine or lime may help temporarily but may not be allowed by regulatory
authorities. The best control method is backup stabilization processes and proper
operation of stabilization systems.
Mixing aids in odor control by preventing layers from developing in deep storage
systems which are subject to seasonal turnover which in turn causes odors. Mixing
can help maintain aerobic conditions throughout. Aeration systems are an excel-
lent means of providing odor control and additional stabilization of sludge.
These systems must be very flexible since storage lagoon levels may fluctuate
widely.
F.lO.c. Drainage or Leachate Control
Storage lagoons should be lined in areas where groundwater supplies are threat-
ened. More positive control can be provided by drainage ditches placed on the
outside of berms around the lagoons. If lining is inadequate, and groundwater
levels are high, the leachate may be captured by ditches for appropriate
treatment.
F. H. MONITORING PROGRAM
Monitoring of land application systems is usually required by local, state or
federal regulatory agencies. The monitoring program should meet these require-
ments and provide information feedback to assure proper system operation. The
degree of monitoring will vary depending on regulatory agency requirements, type
of crop grown, and sludge quality. Most land application monitoring programs are
primarily concerned with three areas - subsurface water, soil, and sludge. In
some instances monitoring of crop tissues may be included. These programs are
developed to prevent potential health hazards and assure the production of high
quality crops.
The entire monitoring program should be summarized in a tabulated form. This
allows easy estimating of staff and laboratory facility requirements. This also
provides a quick check on all monitoring results.
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F.ll.a. Monitoring Wells and Tests
Monitoring well requirements vary depending on local regulatory agency require-
ments and the depth to the water table. As a minimum wells should be 20 to 30
feet deep or to the first impermeable layer (if the layer is closer to the sur-
face). The number of wells varies with site size and proximity of groundwater
aquifers.
The tests normally taken at the wells are nitrate concentration, total coliform
and fecal coliform counts and TDS concentrations. Nitrate concentrations should
not exceed 10 mg/1. If background levels are found to increase significantly then
changes should be made in application rates or cropping methods before the maxi-
mum allowable levels are reached. If they do reach maximum allowable levels then
adjustments should be made to the application rates. If total coliforms, fecal
coliforms or other measures are excessive operations should be stopped or sharply
curtailed in the vicinity of the failing test until appropriate actions are taken
to lower these levels. These tests should be run in accordance with procedures
outlined in Standard Methods (9).
F.ll.b. Soil Tests
The most common soil tests are nitrogen (all forms), phosphorus, potassium, pH
and the heavy metals (Zn, Cn, Cd, Ni, Pb) listed previously. Significance of
these tests has been discussed (23). The primary purpose of these tests is to
check levels of each constituent in the soil as computed or predicted prior to
sludge application. These tests should be run in accordance with Methods of Soil
Analysis (31) or other standardized method.
F.ll.c. Sludge Tests
The most common sludge tests required are the same as the soil tests plus percent
solids and percent volatile solids. Their significance has been discussed in
earlier paragraphs. These tests should be run in accordance with Standard Methods
(9) and/or the Kansas State document (32).
F.ll.d. Crop Tissue Analysis
Some regulatory agencies may require a crop analysis of crops grown on sludge
amended soils. These tests are accomplished to determine plant uptake of heavy
metals. Test procedures are found in the Kansas manual (32) and the "Official
Methods of Analysis of the Association of Official Analytical Chemists, 1975
(33)
Section G - LANDFILL
Landfill is the planned burial of processed sludge at a site designated for this
purpose. The sludge is applied to the land and buried by applying a layer of
52
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cover soil over it. It differs from land-spreading in that to be defined as a
landfill, the soil cover should be thicker than the depth of the plow zone (34).
The following sections deal with various aspects of landfill planning. For more
detailed information, the reviewer is referred to Process Design Manual;
Municipal Sludge Landfills, EPA Technology Transfer, October 1978 (34).
G.I. METHOD
There are three basic methods of landfill disposal of sludge. Each has specific
conditions for application which will be discussed.
G.I.a. Sludge Only Trench Fill
The sludge only trench method involves excavating subsurface trenches so that
sludge may be buried entirely below the original ground surface. The soil
resulting from the trenching operation is used as cover and not mixed with the
sludge as a bulking agent. The sludge is dumped directly into the trench from the
haul vehicle and generally covered the day it is received. Trench disposal is
most appropriate for unstabilized or poorly stabilized sludges; the frequency of
cover reduces the odors generally associated with these types of sludge.
G.I.a.(1) Narrow Trench - Narrow trenches are defined as having widths of less
than 10 ft. This method is generally used for sludges with solids contents
ranging from 15 to 28 percent. The application rate is 1,200 to 5,600 cu yd
sludge/ac. Excavated material is usually used immediately to cover an adjacent
sludge-filled trench. The soil cover thickness is between 3 and 4 ft.
The main advantage of the narrow trench method is that it is suitable for sludge
with a relatively low solids content. The primary disadvantage of this method is
that it is land-intensive because of the low application rates.
G.I.a.(2) Wide Trench - Wide trenches used for sludge disposal have widths of
greater than 10 ft. Material which is excavated from the trenches is stockpiled
neatly and used as cover for that trench. The method is suitable for sludges with
solids contents of 20 percent or greater (34). The application rates range from
3,200 to 14,500 cu yd sludge/ac. The cover thickness depends on the type of
equipment used at the landfill. For land-based equipment, 3 to 4 ft of cover is
sufficient, however for sludge-based equipment, 4 to 5 ft of cover is required.
When compared to narrow trench operations, the wide trench method has two dis-
tinct advantages. It is less land-intensive, and liners can be used to contain
sludge moisture, thus protecting the groundwater from contamination, thereby per-
mitting deeper excavation. The primary disadvantage of the wide trench method is
the need for a sludge with a solids content greater than 20 percent. However, if
it is too high (greater than 32 percent) the sludge will not spread evenly.
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G.l.b. Sludge Only Area Fill
With sludge only area fill, sludge is usually mixed with soil and placed above
the original ground surface. It requires substantial amounts of imported soil,
but is suitable in areas where the groundwater is shallow or bedrock prevails.
This method is best suited for well stabilized sludge since daily cover is not
usually provided. Liners can be used to protect the groundwater, and adequate
drainage and run-off control are necessary to prevent contamination of nearby
surface waters.
G.l.b.(l) Mound - Area fill mound applications are generally suitable for
stabilized sludges with solids content greater than 20 percent. Soil is mixed
with the sludge to provide bulk and stability before it is hauled to the filling
area. At the filling area, the mixture is placed in 6 ft mounds and then covered
with 3 to 5 ft of soil. A level area is required for disposal, however the use of
earthen containment structures can permit disposal in hilly areas.
G. 1 .b. (2) Layer - Area fill layer applications are suitable for stabilized
sludge with solids as low as 15 percent. Soil is mixed with the sludge, either at
the filling area or at a special mixing area. The sludge/soil mixture is spread
in even layers 0.5 to 3.0 ft thick. Interim cover is 0.5 to 1 ft thick and final
cover 2 to 4 ft thick. Although level ground is preferred for this operation, it
is possible to execute it on mildly sloping terrain.
G.l.b. (3) Diked Containment - To be suitable for diked containment, sludge must
have a solids content of at least 20 percent. This method is suitable for either
stabilized or unstabilized sludge. If the disposal site is level, earthen dikes
are used on all four sides of the containment area. As an alternative to this, if
the site is at the toe of a hill, only a partial dike will be required. Depending
on the type of equipment being used, the interim cover will vary from 1 to 3 ft
and the final cover from 3 to 5 ft. Although diked containment is an efficient
disposal method from the point of view of land use, it does necessitate controls
to prevent localized contamination from leachates.
G.l.c. Co-disposal With Refuse
When sludge is disposed of at a refuse landfill, it is termed co-disposal.
There are distinct trade-offs in using this method rather than the sludge only
methods. These are presented in detail in reference 34.
The two techniques for disposing of sludge in this manner are to mix it with the
refuse or to mix it with soil.
G.l.c.(l) Sludge/Refuse Mixture - Stabilized and unstabilized sludges with a
solids content of 3 percent or greater have been mixed with refuse and land-
filled. The sludge is applied to the working face of the landfill on top of the
refuse. The two are thoroughly mixed before being spread, compacted and covered.
Interim cover is 0.5 to 1.0 ft and final cover, 2 ft. Application rates are low,
generally ranging from 500 to 4,200 cu yd sludge/ac. The appropriate regulatory
agencies should be consulted for their requirements on the disposal of unstabi-
lized sludge by this method.
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G.l.c.(2) Sludge/Soil Mixture- With this operation, sludge is mixed with soil
and used as cover for a refuse landfill. The procedure requires stabilized sludge
with at least 20 percent solids. One of the clear advantages of this method is
that it promotes growth of vegetation areas without the use of fertilizer. It
does, however, have the potential for causing odors since the sludge is not
completely huried.
G.2. SITE SELECTION
Site selection is a critical process in the planning of a sludge landfill. It is
directly related to the method of ultimate disposal. The site ultimately selected
must be suitable for the type of sludge to be disposed of and situated in a con-
venient, yet unobtrusive, location.
The first step in selecting a landfill site is to establish the study area. This
is most easily defined by determining a maximum economical haul distance.
Unsuitable locations such as populated or clearly inaccessible areas, can be
readily eliminated.
The site selection should be made by an iterative process in which numerous eval-
uation steps are made. The methodology for performing this analysis will vary
from project to project. Numerical rating systems can be helpful in assessing the
relative merits of prospective sites. A suggested procedure for assessment,
screening and final site selection is presented in reference 34.
G.2.a. Identify Potential Sites
The number of potential sites will depend on the local conditions, the method of
disposal, and the characteristics of the sludge being disposed of. Several
distinct options should be considered in the evaluation.
Given a variety of potential landfill sites, it may be possible to eliminate cer-
tain of them early in the planning process. Considerations such as size, terrain,
location, subsurface conditions and economics may be used in the initial screen-
ing process.
G.2.b. Public Participation Program
In the long run, active public participation will insure the ultimate acceptance
of the landfill program. Public participation in the decision-making process
should be initiated early in the planning stages to avoid unnecessary and costly
delays.
The public participation program must be tailored to suit the particular project
and the community which it is to serve. Public meetings, workshops, mass media
publicity, etc. all serve to increase the public's understanding of the proposed
project and provide the opportunity for people to contribute to the project.
55
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Chapter 2 of reference 34 addresses the objectives, formation and execution of
public participation programs for sludge landfill projects.
G.2.c. Technical Considerations
Numerous technical considerations must be reviewed as part of the final site
selection process. These are briefly discussed below. Additional information
regarding them can be found in reference 34.
G.2.c.(l) Haul Distance - The minimum distance over level terrain will be the
most favorable haul condition. Transport through areas with low populations is
preferable to transport through high density urban areas with congested
traffic.
G.2.c.(2) Site Life and Size - The site life and size are directly related to
the quantity and characteristics of the sludge and the method used for landfill-
ing. Since the entire site cannot be used as fill area, both the gross area and
the usable or fill area must be considered in determining the site size.
Initially, the life of the site can be roughly estimated. As the landfill is
used, the expected life should be re-evaluated to insure adequate capacity for
future operations.
G.2.c.(3) Topography - In general, sludge landfilling is limited to sites with
at least 1 percent slope and no more than 20 percent slope. Perfectly flat
terrain tends to result in ponding while fill on steep slopes can erode.
G.2.c.(4) Surface and Groundwater - The location and extent of surface waters in
the vicinity of the landfill can be a significant factor in the selection pro-
cess. Existing surface waters and drainage near proposed sites should be mapped
and their present and proposed uses outlined. Surface leachate control measures
(collection and treatment) may be required as part of the landfill design.
Data on the groundwaters in the vicinity of potential landfill sites is essential
in the selection process. Characteristics such as the depth to groundwater, the
hydraulic gradient, the quality and use of the groundwater and the location of
recharge zones are essential in determining the suitability of a landfill site.
Such information should be collected during the facility planning stage and in
advance of the final decision-making process.
G.2.c.(5) Soils and Geology - Soil plays an important role in sludge landfill-
ing. The properties of the soil such as texture, structure, permeability, pH and
cation exchange capacity, as well as the characteristics of its formation may
influence the selection of the landfill site. The geology of possible landfill
sites should be thoroughly examined to identify any faults, major fractures and
joint sets. The possibility of aquifer contamination through irregular formations
must be studied.
G.2.c.(6) Vegetation - The type and quantity of vegetation at and around the
proposed landfill sites should be considered in the evaluation. Vegetation can
serve as a natural buffer, reducing noise, odor and other nuisances. At the same
56
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time, clearing a site of timber or other heavy vegetation can add significantly
to the initial project costs.
G.2.c.(7) Environmentally Sensitive Areas - There are presently five environ-
mentally sensitive areas included in the "Classification Criteria for Solid Waste
Disposal Facilities." (34, 29) These include wetlands, flood plains, permafrost
areas, critical habitats of endangered species, and recharge zones of sole source
aquifers. These should be avoided if at all possible when a landfill site is
selected.
G.2.c.(8) Archaeological and Historical Significance - The archaeological and/
or historical significance of proposed sites should be determined early in the
evaluation process. Any finds of significance at the selected site must be accom-
modated prior to final approval and construction.
G.2.c.(9) Site Access - Haul routes should utilize major highways, preferably
those with a minimum of traffic during normal transport hours. Proposed routes
should be studied to determine impacts on local use and the potential effects of
possible accidents.
G.2.c.(10) Land Use - Zoning, restrictions and future development of potential
sites should be considered in the selection process. Ideally, the sludge landfill
should be located on land considered unsuitable for higher uses.
G.3. LEACHATE CONTROLS
It is essential that surface and groundwater supplies be protected from landfill
leachate. The primary sources of leachate are the moisture in the sludge itself
and storm water infiltration. Careful site selection is the first step in con-
trolling leachate; there are also design features which can reduce the potential
for contamination by leachates.
G.3.a. Adequate Surface Drainage
Providing adequate surface drainage is the first step in controlling leachate.
Ideally, the landfill site should be on slightly sloping land so there is
natural drainage. Storm water runoff should be diverted around the landfill.
G.3.b. Natural Attenuation
Contaminants in landfill leachate can naturally attenuate as they pass through
the soil. The mechanisms by which this occurs and the potential for natural
attenuation should be examined before artificial controls are planned or
designed.
57
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G.3.c. Containment
Clay soils can be used to provide an adequate barrier against leachate contami-
nation of groundwaters. In some cases enough of this material will be available
at the landfill site, while in other cases importation will be necessary. The use
of soils as landfill liners or additives is site-specific and must be evaluated
on an individual basis. Membrane liners may be useful at area fills and wide
trench application areas. Although soil liners are preferable, polymeric and
asphaltic materials have proven to be effective. The final selection of landfill
liners will depend on on the specific characteristics of the site. If leachate
containment is necessary at the landfill site, collection and treatment facili-
ties must be provided. An underdrain or tile collection system is effective in
routing the leachate to a sump or storage area. Several methods of treatment
should be evaluated. Alternatives include discharge to a local sewage treatment
plant, recycle through the landfill, evaporation of the leachate in collection
ponds or on-site treatment. The ultimate method chosen will depend on the indi-
vidual characteristics of the landfill method and site.
G.4 GAS CONTROL
Methane and carbon dioxide gas are products of the decomposition of organic
matter in sludge. The gas production depends on the type and quantity of sludge,
the type of landfill and the moisture present. Although both of these gases are
odorless, methane can be explosive in confined areas. Gas controls are not con-
sidered necessary in isolated areas or if the landfill is isolated from inhabited
areas. However, gas control measures will be necessary if the landfill is near
any populated area.
Possible gas control measures include permeable and impermeable methods and gas
extraction. Permeable methods involve installing a gravel-filled trench outside
the fill area. Migrating gas is intercepted and vented to the atmosphere. A bar-
rier of low permeability material can be used around the perimeter of the land-
fill to minimize lateral gas migration. A compacted clay layer about 2 ft thick
is adequate in most cases. Synthetic materials may also be considered as possible
barriers to migrating gas. Gas extraction, with or without methane recovery, has
been initiated at some refuse landfills. It is not suitable for sludge landfills
since they do not permit free movement of gas and are not ordinarily large enough
to make such systems economically justifiable.
G.5. RUNOFF CONTROL
Factors of concern are similar to those discussed in F.9.
G. 6. MONITORING
A preliminary monitoring schedule should be determined as part of the facility
planning process. This should include, but not necessarily be limited to, staff-
ing requirements, leachate, runoff, gas, and soil analyses, groundwater observa-
tion wells and general operational record keeping and reporting procedures.
58
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Once the landfill is operating, the monitoring program should be revised to
reflect changes in the original plan.
Section H - COMBUSTION
Combustion processes are not disposal methods but are volume and weight reduction
methods. A residue (ash) will remain which must be disposed of by one of the
three basic disposal techniques: land application, landfill, or off-site use by
others. The weight and volume reduction can be of great value where land is
scarce. In planning ultimate disposal methods for ashes, it must be kept in mind
that their physical and chemical characteristics differ substantially from those
of uncombusted sludge.
The efficiency of the sludge dewatering system (Table 10) is of key importance in
determining the feasibility of the incineration process. As can be seen from
Figure 3, the amount of heat (auxiliary fuel) required to sustain continuous com-
bustion is dependent on the solids content of the sludge entering the
incinerator.
TABLE 10. TYPICAL SLUDGE DEWATERING PERFORMANCES (7)
Sludge Cake Solids (%)
Bowl
Type of sludge Vacuum filter Filter press Centrifuge
Raw primary
Anaerobically digested primary
Primary & trickling filter humus
Primary & air activated
Primary & oxygen activated
Digested primary & air activated
25-38
25-32
20-30
16-25
20-28
14-22
45-50
45-50
45-50
35-45
35-45
45-50
23-35
28-35
20-30
15-30
-
15-30
H.I. METHOD
The basic methods of combusting sludge are described below.
H.I.a. Incineration
Incineration is the burning of the volatile fraction of the sludge in the pres-
ence of excess air. Incineration is a two-step process involving drying and com-
bustion. Adequate fuel, air, time, temperature, and turbulence are necessary for
a complete reaction. The drying step should not be confused with preliminary
dewatering, which is usually by mechanical means and precedes the incineration
process in most systems. When a sludge with a moisture content of about 65 per-
cent is delivered to the incinerators, the heat required to evaporate the water
nearly balances the available heat from combustion of the dry solids. Heat values
of sludges are summarized in Table 4.
59
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S2
s
*•
•^
a
m
Q
UJ
OC
O
Ul
OC
UJ
\
20
40
60
80
SLUDGE SOLIDS. % by weight
Figure 3. Theoretical heat required to sustain combustion of sludge
-------
Drying and combustion may be done in separate units or successively in the same
unit. Manufacturers have developed diversified types of equipment such as the
multiple hearth furnace and the fluidized bed incinerator.
H.l.a.(l) Multiple Hearth - A typical multiple hearth incinerator is shown in
Figure 4 and consists of a circular steel shell surrounding a number of solid
refractory hearths and a central rotating shaft to which rabble arms are
attached. The operating capacity of these furnaces is related to the total area
of the enclosed hearths. They are designed with diameters ranging from 54 inches
to 25 feet, 9 inches, with four to eleven hearths. The upper hearths are the dry-
ing zone where moisture is evaporated and driven off as steam, the middle hearths
are the combustion zone where the volatile portion of the sludge is burned, and
the lower hearths are the ash-cooling zone.
Sludge enters the incinerator at the top and is raked by the rabble arms alter-
nately outward and inward, as shown, to the entrance of the next hearth below.
The rabble arms serve the multiple functions of moving the sludge through the
furnace, forming furrows in the sludge layer on the hearth to maximize the
exposed surface area, breaking up the sludge, and agitating the sludge to insure
complete combustion.
Combustion air enters the incinerator at the bottom gaining heat from cooling
ash in the cooling zone and from burning sludge in the combustion zone, and giv-
ing up heat to evaporate water from sludge in the drying zone.
H.I.a.(2) Fluidized Bed - A typical fluidized bed incinerator is shown in Figure
5. The fluidized bed incinerator is a vertical cylindrical vessel with a grid in
the lower section to support a sandbed. Dewatered sludge is injected above the
grid and combustion air flows upward at a pressure of 3.5 to 5.0 psig and fluid-
izes the mixture of hot sand and sludge. Supplemental fuel can be supplied by
burners above or below the grid. In essence, the reactor is a single chamber unit
where both moisture evaporation and combustion occur at 1,400 to 1,500°F in the
sandbed. All the combustion gases pass through the 1,500°F combustion zone with
residence times of several seconds. Ash is carried out the top with combustion
exhaust and is removed by air pollution control devices. The heat reservoir pro-
vided by the sandbed enables reduced start-up times when the unit is shut down
for relatively short periods (overnight).
H.I.a.(3) Cyclonic Reactors and Electric Incinerators - Horizontal cyclonic
reactors are intended primarily for use at small wastewater treatment plants.
They are usually available as skid-mounted packaged systems, requiring a minimum
of field installation. High velocity air is preheated and introduced tangentially
into a Cylindrical combustion chamber, providing combustion air and heating the
reactor walls. Sludge is sprayed radially toward the heated walls and is immedi-
ately caught up in the rapid cyclonic flow. Combustion takes place before sludge
can adhere to the reactor walls. The ash is removed from the reactor by the
cyclonic flow of air and gases.
The vertical cyclonic reactor is more suited to larger plants. The vertical
cyclonic reactor has a rotating hearth and a single fixed plow. Preheated sludge
enters the reactor at the outer edge and is plowed toward the center where ash is
61
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COOLING AIR DISCHARGE
FLUE GASES OUT
SLUDGE INLET
RABBLE ARM AT
EACH HEARTH
DRYING ZONE
COMBUSTION ZONE
COOLING ZONE
ASH DISCHARGE
r*-COMBUSTION
AIR RETURN
RABBLE ARM
DRIVE
COOLING AIR FAN
Figure 4. Cross section of a typical multiple hearth incinerator.(7)
62
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Sight glass
Exhaust
Preheat burner
Thermocouple
Sludge Inlet
Access doors
Fluidizlng
afr inlet
Figure 5. Cross section of a fluid bed reactor. (7)
63
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removed. Combustion air is introduced tangentially at high velocity, which
results in a swirling motion over the top of the burning sludge. This provides
needed turbulence and, together with sludge agitation by plowing, promotes com-
plete combustion. Hot gases leave the cyclone through a top conical outlet in the
center. Neither type of reactor is in common use in the U.S.
The electric incinerator uses infrared heat to raise sludge temperatures to the
ignition point. Sludge is moved through the incinerator on a conveyor belt. It
passes through a drying zone in which hot gases from the combustion zone, flowing
countercurrent to the sludge, dry the sludge. The sludge then passes through a
combustion zone where a battery of infrared lamps heat it to ignition
temperatures. Combustion air enters in the combustion zone. Ash is discharged
into a hopper at the end of the conveyor.
H. l.b. Pyrolysis
Pyrolysis is a process in which organic material is decomposed at high tempera-
ture in an oxygen-deficient environment. The action, causing an irreversible
chemical change, produces three types of products: gas, tar (oil) and char (solid
residue). Water vapor is also produced, usually in relatively large amounts
depending on the initial moisture content of the materials being pyrolyzed.
Residence time, temperature and pressure in the reactor are controlled to produce
various combinations and compositions of the products. Two general types of
pyrolysis process may be used. The first, true pyrolysis, involves applying all
required heat externally to the reaction chamber. The other, sometimes called
partial combustion and gasification or starved air combustion, involves the addi-
tion of small amount of air or oxygen directly into the reactor. The oxygen sus-
tains combustion of a portion of the reactor contents which in turn produces the
heat required to dry and pyrolyze the remainder of the contents.
Pyrolysis of municipal refuse and of sewage sludge has been considered as a means
for ultimate disposal of wastes for several years (35, 36, 37, 38). The results
of various studies and pilot programs indicate that if the moisture content of a
sludge is below 70 to 75 percent, enough heat can be generated by combustion of
the oil and gases produced from the pyrolysis of sludge for the process to be
thermally sustaining. Pyrolysis of municipal refuse, and combinations of refuse
and wastewater sludges will provide energy in excess of that required in the
pyrolytic process (36, 37).
Laboratory, pilot and demonstration systems with wastewater sludges have been
tested but no full-scale systems are in operation. Therefore, data presented must
be considered preliminary. Pyrolysis systems are in the developmental stages and
additional information will become available as research and development work and
the operation of full-scale plants progresses.
Pyrolysis appears to have several advantages over incineration. For example, some
pyrolysis processes can convert wastes to storable, transportable fuels such as
fuel gas or oil while incineration only produces heat that must be converted to
steam. Pyrolysis can give a 50 percent greater reduction in volume of residue
over incineration and the residue is a more readily usable by-product. Air
64
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pollution is not as severe a problem in pyrolysis systems because the volume of
stack gases and the quantity of particulates in the stack gases are less.
On the other hand, pyrolysis is still in the developmental stage and, with few
exceptions, viable commercial systems are not readily available. Most of the
pyrolytic fuel gases have relatively low heat values and the pyrolytic oil is
corrosive, requiring it to be mixed with other fuel oil for best results.
The construction and operating costs for most pyrolysis systems are much more
uncertain than for incineration. Reliable cost data for pyrolysis systems will
not be available until significant operating experience is developed from the
ongoing and planned demonstration projects.
H.l.b.(l) Multiple Hearth - Research and development work has been conducted on
using multiple hearth furnaces, similar in design to conventional sludge incin-
erators, for pyrolysis of wastewater sludges mixed with municipal solid wastes
(39). Shredded and classified solid wastes and dewatered sludge are fed to the
furnace either in a mixture or separately, with the wetter sludge fed higher in
the furnace. Recirculated hot shaft cooling air and supplemental outside
combustion air are fed to the lower hearths to sustain partial combustion of the
wastes circulating down through the furnace. Fuel gas produced through the
pyrolysis reaction is then burned in a high temperature afterburner. The
resulting heat can be used in a waste heat boiler to produce high pressure steam.
It may also be possible to burn the fuel gases directly in a boiler. Char from
the process is not used, but because it has some fuel value it may be usable as
an industrial fuel.
The multiple hearth process offers the following advantages: (1) usable in much
smaller plants than most other pyrolysis systems, (2) employs modifications of
well developed sludge incineration equipment, (3) produces high temperature gases
without raising temperatures in the solid phase to the slagging point, and (4)
conversion from existing conventional sludge incineration systems is a relatively
simple procedure. Disadvantages include: (1) fuel value of the char is not used,
(2) high temperature fuel gases must be used on-site, and (3) incoming solid
wastes must be well classified.
H.l.b.(2) Other Processes - There are several proprietary processes for pyroly-
sis of solid wastes, including sewage sludge. Several of these processes are
listed below.
• Occidental Process - Occidental Research Corp.
• Purox - Union Carbide Corp.
• Torrax - Carborundum Environmental Systems, Inc.
H.l.c. Wet Air Oxidation
The wet air oxidation (WAO) process is based on the fact that any substance capa-
ble of burning can be oxidized in aqueous form at temperatures between 250°F and
700°F at elevated pressures. Wet air oxidation does not require preliminary
65
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dewatering or drying as required by conventional combustion processes. However,
the oxidized ash must be separated from the water by vacuum filtration, centrifu-
gation, or some other solids separation technique. Air pollution is minimized
because the oxidation takes place in water at low temperatures and no flyash,
dust, sulfur dioxide or nitrogen oxides are formed. A typical wet air oxidation
process is shown in Figure 6. Sludge is ground to a controlled particle size and
pumped to a pressure of 150-3,000 psig. Compressed air is added to the sludge,
the mixture is brought to a temperature of about 675°F by heat exchange with
treated sludge and direct steam injection, and then is processed (cooked) in the
reactor at the desired temperature and pressure. The hot oxidized sludge is
cooled by heat exchange with the incoming sludge. The treated sludge is settled
from the supernatant before the dewatering step. Gases released at the separation
step are passed through a catalytic afterburner at 650 to 750° or deodorized by
other means. In some cases these gases have been returned through the diffused
air system in the aeration basins for deodorization.
H. l.d. Co-Disposal with Solid Waste
Co-disposal of sludge with municipal solid waste has been proposed or practiced
for most incineration and pyrolysis techniques. Relative to combustion process,
co-disposal can take one of two forms:
• Combustion of the entire combined sludge and solid waste streams.
• Use of classified and shredded solid waste as a fuel to the extent
required to make difficult-to-burn sludges autogenous.
H.2. MASS BALANCE
The calculation of the expected flow of mass into and out of the combustion pro-
cess will aid in establishing its effectiveness and its economics. The mass
balance calculation must be performed in conjunction with the energy balance dis-
cussed later in this section. The mass of inputs to the combustion process must
equal the mass of outputs. (See Appendix C for sample calculation).
H.2.a. Inputs
• Dry Solids in Sludge - The mass of dry solids in sludge is usually
expressed as tons per day and may be estimated directly or calculated
from the wet sludge production and concentration.
• Moisture in Sludge - The mass of water in the sludge, usually expressed
as tons per day, may be calculated from estimated or actual sludge pro-
duction and concentration. The moisture will have a significant impact
on the energy balance due to the energy required to heat and vaporize
the water.
• Air - The quantity of air (or oxygen in some processes) introduced into
the combustion process is usually expressed in tons per day or scfm. In
combustion processes a certain theoretical (stoichiometric) oxygen
66
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o
•H
4J
o
CO
w
>.
co
§
•ri
4->
(0
T3
•H
X
o
-H
(0
g
•H
67
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demand (THOD) must be met for complete combustion. In actual incin-
erators, however, it is not possible to completely combine the avail-
able oxygen with the combustible materials. A certain quantity of air
in excess of the theoretical requirements must be provided to assure
complete combustion. It must also be kept in mind that oxygen is not
the only (or even the principle) constituent of air. The introduction
of excess air should be minimized as it has the effect of reducing the
burning temperature and increasing heat losses from the reactor. This
will have a great effect on the energy balances as shown in Figure 7.
The excess air requirements of the combustion process are empirically
derived values which vary from 20 to 200 percent, depending on the
installation. If a process has an approximate excess air requirement of
50 percent (typical for a fluidized bed reactor) and a theoretical oxy-
gen demand of 200 tons/day, the actual air requirement would be:
q = (200 tons 02/day) (1.5 total air )/(0.23 mass of oxygen)
theoretical air mass of air
= 1,300 tons air/day
or
24,125 scfm air
Pyrolysis processes are operated with deficient, rather than excess air. The cal-
culation of air requirements would be the same as above except the ratio of
actual to theoretical air would be less than one.
• Auxiliary Fuel - The mass of auxiliary fuel required will depend on the
energy calculation and on the auxiliary fuel selected.
• Makeup Sand - Makeup sand will be required to replace sand lost in
fluidized bed reactors.
• Steam - Steam is often injected into wet air oxidation reactors to
begin or sustain the reaction.
H.2.b. Outputs
• Ash - Ash is the non-combustible, sterile residue of the incineration
or wet air oxidation process.
• Combustible Gas - The principal product of pyrolysis is a combustible
gas containing several gaseous hydrocarbons and other gases.
• Tar - Tar, or oil, is the combustible liquid residue of a pyrolysis
process.
• Char - Char is the solid residue of the pyrolysis process.
• Water - Water is discharged from the process as water vapors in stack
gases, in the liquid effluent of the wet air oxidation process, and as
a contaminant in pyrolytic tar and combustible gas. The sources of
68
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10.0
8.0
m
•a
•
c
o
**x
3
m
c
o
6.0
Ul
o:
.J
X
4.0
2.0
0.0
20
40
60
80
100
EXCESS AIR, percent
Assumptions:
Solids. 30*A
Exhaust Temp: 1500°F
Volatiles: 70'/.
Figure 7. Impact of excess air on the amount of
auxiliary fuel for sludge incineration,
-------
water in the process discharge are, moisture in the incoming sludge,
the combination of the hydrogen fraction of sludge solids and auxiliary
fuel with oxygen, and steam supplied to the wet air oxidation process.
• Carbon Dioxide - Carbon dioxide is the result of the complete combus-
tion of the carbon fraction of sludge solids and auxiliary fuel.
• Carbon Monoxide - Carbon monoxide is a toxic product of incomplete com-
bustion. Its presence indicates insufficient excess air.
• Sulfur Dioxide - Sulfur dioxide is the combustion product of the sulfur
fraction of the sludge solids and auxiliary fuel.
• Nitrogen - Nitrogen consists of the combustion product of the nitrogen
fraction of the sludge solids and that portion of the theoretical com-
bustion air which is not involved in combustion (approximately 79
percent).
• Sand - In fluidized bed reactors a certain portion of the bed sand is
carried away with the fly ash.
• Excess Air - The excess air quantity discharged is the percent excess
air supplied to the process.
H.3. ENERGY BALANCE
The energy balance, together with the mass balance, provides the basic data for
determining the cost- and energy-effectiveness of the combustion process. The
total input and output of the combustion process must be equal.
H.3.a. Inputs
• Solids Heat of Combustion - The solids heat of combustion is the energy
released by the oxidation of the combustible fraction of the sludge.
• Auxiliary Fuel Heat of Combustion, Including Afterburner - The auxil-
iary fuel heat of combustion is the energy released by the burning of
auxiliary fuels in the reactor, in an afterburner, or in a wet air oxi-
dation steam generator.
H.3.b. Outputs
• Latent heat of moisture - That heat required to just vaporize the
moisture with no effect on its temperature.
• The sensible heat of the stack gases - That heat which is required to
raise those gases to respective temperatures at the point of exit from
the air pollution control equipment.
70
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• The sensible heat of the stack gases - That heat which is required to
raise those gases to respective temperatures at the point of exit from
the air pollution control equipment.
• Sensible heat of ash - Heat required to raise the ash or wet air oxida-
tion effluent, from the temperature at the sludge inlet to the tempera-
ture at the ash, or effluent, outlet.
• Radiation and conduction losses - The energy lost to the surrounding
air and objects by high temperature components of the combustion
system.
• ShajFt cooling air sensible heat: energy gained by the shaft cooling air
in a multiple hearth unit in protecting the center shaft and rabble
arms from heat damage.
• Recovered energy; that energy deliberately removed from the combustion
process for other uses.
H.4. USE OF RECOVERED ENERGY
The practice of energy recovery in the combustion process can significantly
affect the overall cost- and energy-effectiveness of a sludge management system.
The selection of energy recovery systems must be based on the cost- and energy-
effectiveness analyses, as in some instances the value of recovered energy may
not justify the capital expenditure required to recover that energy.
There are several heat losses from the combustion process which can, by proper
design, be intercepted so that a portion of the lost heat is recovered and put
to use.
• Sensible heat of gases of combustion, excess air, and moisture
• Radiation and conduction
• Sensible heat of shaft cooling air
• Sensible heat of wet air oxidation effluent
In addition, if pyrolysis is practiced, the products of pyrolysis can be expected
to have a fuel value apart from the heat recoverable from the process itself.
The exit gas sensible heat can be recovered by running the gases through a heat
exchanger to produce steam, or hot water; or to heat a heat exchange fluid. The
energy so recovered can then be used in any one of a number of ways. Figure 8
indicates the amount of energy recoverable from typical incinerator stack gases.
Radiation and conduction losses can be recovered by water jacketing the reactor
and using the steam produced as an energy source on-site or for sale to others.
The sensible heat of multiple hearth furnace shaft cooling air is most often
recovered by recycling it to the combustion process itself as preheated air.
71
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4500
a
UJ
c
LLI
>
o
o
HI
I
UJ
I
3730
2250
1500
750
H, 3000
f
?
1 i
PRIMARY* WAS
PRIMARY
500
1000 1500
INITIAL FLUE GAS TEMPERATURE.'F
Assumptions:
Final Stack Temp = 500° F
50% excess air
( To convert Btu to kwh: 1 kwh e 10,500 Btu)
Figure 8. Potential heat recovery from incineration of sludge
72
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The sensible heat of multiple hearth furnace shaft cooling air is most often
recovered by recycling it to the combustion process itself as preheated air.
The sensible heat of wet air oxidation effluent is normally recovered in the pro-
cess itself by preheating incoming sludge. Other uses may be feasible and should
be considered.
H.4.a. On-Site Use
Recovered energy from reduction processes can have a significant impact on the
overall energy consumption, and therefore the cost-effectiveness of the entire
wastewater and sludge treatment facility (40).
Combustion air preheating can significantly reduce auxiliary fuel requirements
and can be practiced by cooling air return or by heat exchange between exhaust
gases and combustion air. Steam, hot water, or heat exchange fluid could be used
as a building heat source either directly or utilizing heat pumps. Additionally,
the heat could be used as the heat input to absorption type cooling systems.
Recovered heat can be used as the heat source for sludge thermal conditioning,
improving the dewaterability of the sludge, which in turn improves its burning
characteristics. Heat recovered from combustion processes can be used to heat
anaerobic digesters, reducing the need for auxiliary fuel or eliminating the
diversion to sludge heating of the more easily transported and stored methane
gas. Steam generated by incinerator water jackets or by heat exchange with
exhaust gases can be used to drive steam turbines. The steam turbines could gen-
erate electricity or serve as prime movers for process equipment. Pyrolytic gas
may be burned in gas turbines for use in generating electricity or as prime
movers for process equipment or as a fuel source for the pyrolysis reactor.
H.4.b. Off-Site Use
Under certain conditions, energy produced by the combustion process may have a
market value which would justify its recovery. Facilities plans which anticipate
energy sales should realistically evaluate the market potential as well as the
value of the energy.
Combustible pyrolytic gas from sludge alone can be expected to have a heat con-
tent of 100-350 Btu/scf (35). By comparison, natural gas has a heat content of
approximately 1000 Btu/scf. Co-pyrolysis with solid waste may produce higher heat
values.
Pyrolytic tar, or oil, from sludge alone can be expected to have a heat content
of 78,000-117,000 Btu/gal (35). No. 6 fuel oil has a heat content of 148,840
Btu/gal. It has a lower sulfur content than most oils but has a great deal of
entrained moisture and is very corrosive. Co-pyrolysis with solid waste may
produce higher heat values.
Pyrolytic char from sludge alone has a heat content of 1,000-2,400 Btu/lb (35).
Pennsylvania anthracite coal has an approximate heat content of 13,900 Btu/lb.
Char could be useful as a raw material for adsorbent manufacture. Co-pyrolysis
with solid waste may produce higher heat values.
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Steam may be the most easily marketable of the energy forms available as
recovered energy. Many industrial processes use steam as an energy source. It is
not as readily transportable as the other forms, however. Therefore, a suitable
market must exist in the general vicinity of the combustion system. An additional
problem is assuring adequate reliability of supply to the purchaser, as an
unreliable supply of steam greatly diminishes its value.
Electricity is readily transportable and has the broadest potential market of the
forms of recovered energy. Marketing the electricity to an electric utility may
be feasible. The economics of electric power generation on the small scale pos-
sible at wastewater plants are, however, rarely favorable.
H.5. ASH DISPOSAL
Since the combustion process does not totally dispose of sludge, but merely
reduces its volume and weight, ultimate disposal of the ash or residue must be
considered.
H. 5. a. T r an sport
Transport of ash is usually by truck or pipeline, as the greatly-reduced volumes
usually preclude consideration of barges and rail. Incinerator ash can be pumped
in a slurry from the combustion site to the disposal site but may require
dewatering. Because of its finely divided nature, truck transport of dry ash can
present problems if adequate dust control measures are not taken.
H. 5 . b. Dewa t er ing
Wet air oxidation residual solids are easily dewatered for ultimate disposal on
vacuum filters. When pumped in slurry, incinerator ash is usually dewatered in
lagoons. Because of the relatively inert nature of ash, ash lagoons generally do
not present the odor and fly problems that are typical of sludge lagoons.
H.S.c. Land Application
Ash and wet air oxidation residue have very little value as nitrogen sources, but
their physical characteristics may make them useful as soil conditioners. In
addition, they can have high phosphorus contents. All types of land application
techniques are technically feasible, and several of the operational problems,
such as disease vectors, pathogens, odors, and nitrate pollution of groundwater,
are eliminated by the inert nature of the material.
H.S.d. Landfill
Landfilling of ash, including permanent lagooning, is the most common form of
ultimate disposal. Many of the problems associated with sludge, such as odors,
pathogens, disease vectors, gas production, and nitrate pollution of groundwater,
are not present with ash. Cover is, therefore, less critical but must be main-
tained in order to minimize dust and leachate problems.
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H.5.e. Off-Site Use by Others
Several off-site uses of combustion residues, other than the energy recovery dis-
cussed above, have been proposed or attempted. Incinerator ash has been tested
as a soil amendment to improve the freeze-thaw characteristics of road subgrades,
as a fine aggregate for building materials, as a soil conditioner, and as a
quasi-fertilizer for its phosphorus content (41). Dewatered wet air oxidation
residue has been tested with success as a soil conditioner and mulch and is valu-
able for its moisture-holding properties (42). Pyrolytic char has been suggested
as a raw material for activated carbon manufacture (35).
H.6. AIR QUALITY CONTROL
National air pollution standards for discharges from municipal sludge incinera-
tors have been promulgated which limit emissions of particulates (including visi-
ble emissions) from incinerators used to burn wastewater sludge as follows (43):
1. No more than 0.65 g/kg dry sludge input (1.30 Ib/ton dry sludge
input).
2. Less than 20 percent opacity.
For uncontrolled incineration of average municipal wastewater sludge, particu-
lates will be about 33 pounds of particulates per ton of sludge burned in a
multiple hearth (44), and about 45 pounds of particulates per ton of sludge
burned in a fluid bed incinerator (45). Particulate collection efficiencies of 96
to 97 percent are required to meet the standard, based on the above uncontrolled
emission rates. Impingement scrubbers, and Venturi scrubbers have demonstrated
the capability to meet the particulate discharge requirement (46). Other poten-
tially effective types include baffle, orifice and cyclone scrubbers. Wet scrub-
bing is normally required in conjunction with mechanical scrubbing. Most metals
present in municipal sludges are converted to oxides which appear in the particu-
lates removed by the scrubber or in the ash.
EPA has set a standard of 3,200 gms/day of mercury for discharge from a sewage
sludge incinerator reference (47). Metal discharges should not present a limita-
tion as properly designed and operated municipal systems have met all air pollu-
tion standards for metals.
Gaseous pollutants which could be released by sludge incineration are hydrogen
chloride, sulfur dioxide, oxides of nitrogen, and carbon monoxide. Carbon monox-
ide is no threat if the incinerator is properly designed and operated. Hydrogen
chloride, which would be generated by decomposition of certain plastics, is not a
significant problem at concentrations currently observed. Consideration of the
possibility of S02 and NOX pollution is aided by examination of the sulfur
and nitrogen content of sludges. Sulfur content is relatively low in most
sludges. In addition, much of this sulfur is in the form of sulfate, which
originated in the wastewater. Sulfur dioxide is not expected to be a serious
problem. NOX production from sludge incineration should be less than 100 ppm
from a properly operated incinerator. Considering this low concentration, the
production of oxides of nitrogen will probably not limit the use of incineration
for disposing of sludge in most cases.
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Toxic substances could be discharged from the organic substances such as pesti-
cides and PCB's - in the sludge. However, tests (48) have shown that total
destruction of PCB's was possible when oxidized in combination with sewage sludge
and with exhaust gas temperatures of 1100°F. Ninety-five percent destruction of
PCB's was achieved in a multiple hearth furnace with no afterburning at exhaust
temperatures of 700°F.
In all cases involving designated nonattainment areas the local regulatory agency
offset policy should be considered.
The principal methods of air pollution control are:
• Venturi scrubbers
• Afterburners
• Electrostatic precipitators
H.7. FUEL
There are a number of variables which influence the amount of fuel required and
the resulting cost for sludge incineration. Principal variables are the solids
and volatile solids content of the sludge. Their effect on the amount of heat
required for incineration is shown by Figure 3.
The principal sources of auxiliary fuel are:
• Natural gas
• Oil
• Refuse derived fuel
• Powdered coal (49)
Section I - SLUDGE FOR OFF-SITE USE BY OTHERS
The use of sludge as a fertilizer and soil conditioner under the direct control
of the wastewater treatment agency is discussed under the land application sec-
tion of this document. This section deals with sludge that is processed in-plant
and then given or sold to the public or private entrepreneurs. The processing
produces a dry, marketable product that is safe for limited applications as a
soil conditioner or fertilizer. This disposal scheme has several advantages over
other methods:
• Sludge is utilized rather than discarded
• Land purchase or lease requirements are reduced
• Part of the cost of processing may be recoverable through product sale
• Potential adverse environmental impacts are spread over a wider area,
minimizing their effect
The chief disadvantage to off-site use by others is the loss of agency control
over sludges which may be unsafe if improperly used.
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Sludge factors which affect acceptability and safety include:
• Degree of stabilization
• Heavy metals content
• Toxic organic compound content
• Pathogen content
The level of agricultural or horticultural sophistication of the intended users
should be kept in mind. Sludges which could be safely sold to professional nur-
serymen for use on ornamental plants only may not be suitable for sale in bagged
form to the general public. Local, state and federal agency regulations should be
consulted to determine if any restrictions on marketing exist.
I.I. MARKET ANALYSIS
A key step in evaluating potential off-site use alternatives is analyzing the
market for the product. This includes identifying the potential market, analyzing
the capacity of the market to absorb the product, determining the realistic
market value of the product, identifying the most desirable packaging for the
product, and establishing a brand name for the product. Data for the market anal-
ysis can be obtained by telephone or mail surveys of individuals, possibly sent
with their utility bills, and telephone or personal interviews with possible
large users, wholesalers, and processors. The EPA publication User Acceptance of
Wastewater Sludge Compost (50) contains considerable information on the market
for processed sewage sludge.
I.I.a. Intended Market
The first step in the market analysis is identifying the potential market and
market restrictions for the product. The potential users can be divided into
three broad categories:
• Government agencies
• Wholesalers and processors
• Private users
I.l.a.(l) Government Agencies - Government agencies offer what is potentially
the most advantageous of possible markets. Where sludge is used by government
agencies it is usually possible for the wastewater treatment agency to retain a
high degree of control over the final use of the product. There will usually,
however, be no direct cash return for the product, but an economic benefit may be
derived by the reduction in the cost of fertilizer use. The market analysis
should consider agencies at the local, state and federal level.
Highway departments often use fertilizers and soil amendments for plantings
alongside roadways. These plantings are not food chain crops and may present a
potential use for sludge not safe for use on food chain crops due to heavy metal
content. Care must be taken in sludge application, however, to avoid runoff. The
same advantages would apply to municipal recreation facilities such as parks and
golf courses, reforestation and tree or turf farming.
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I.I.a.(2) Wholesalers and Processors - Sewage sludge has been sold to fertilizer
wholesalersfordistributionthrough the normal fertilizer and soil conditioner
market place. Sludge has also been sold or given to fertilizer manufacturers for
use as a raw material in the manufacture of commercial fertilizers. These options
present a problem in that the end use of the sludge is nearly impossible to
control, limiting the market to those sludges which are safe for human food chain
crops.
I.I.a.(3) Private Users - The sale or distribution of sludge to private users
has also been utilized, especially by smaller communities when the sludge is safe
for food chain crops. Chief obstacles to be overcome include assuring the quality
of the sludge and the lack of control over the use of the sludge. While some
control can be exercised over large private users, it is virtually impossible to
control the use of sludge or sludge products by individuals. This is a major
factor being addressed by various agencies in updated guidance and regulations.
Nurseries of all types have the potential of using sewage sludge. In particular,
sludge would be useful in cultivating non-food chain ornamental plants for sale,
silviculture, and sod production. Agricultural uses of sludge are numerous
including all types of above ground crops. The use of most sludges on root crops
and leafy vegetables is generally not recommended (21). Sludge is also used in
many communities by home gardeners. This market is the most difficult to control
and requires the utmost care in assuring sludge quality and safe use. Sewage
sludges are most applicable to lawn and ornamental plant cultivation.
I.l.b. Capacity of Market to Absorb Product
The capacity of the intended market or markets to utilize the entire production
of the sludge management systems must be evaluated. In highly urbanized areas it
may not be possible to market the entire sludge production within an economical
transportation distance.
I.I.e. Market Value of Product
The potential market value of the product must be determined. The market value
is best approximated by the sale price of similar fertilizers and soil condi-
tioners similarly marketed. There are several complex factors which also enter
into the determination of the actual market value, such as public acceptance, but
their effects are difficult to quantify. Their effects can be explored through
surveys of public acceptance.
I.l.d. Packaging Requirements
Packaging and product delivery system requirements will vary with the intended
market. Large users will generally prefer delivery in bulk while smaller users,
such as individuals, may prefer a bagged product. In addition, a determination as
to whether the product must be delivered to the user or if the user is willing to
pick up the sludge.
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It has been found (50) that affixing a brand name to the sludge product greatly
enhances its marketability. Some typical brand names in use are:
• Nu-Earth (Chicago, IL)
• Hou-Actinite (Houston, TX)
• Zitrohumus (Los Angeles, CA)
• Philorganic (Philadelphia, PA)
1.2. PROCESSING METHOD
Biogrow (Salem, OR)
Metrogrow (Madison, Wl)
Milorganite (Milwaukee, Wl)
Largrow (Largo, FL)
Sludge suitable for use off-site by others is usually processed by drying or
composting.
I.2.a. Drying
Well stabilized sludges may be suitable for use off-site after drying.
I.2.a.(l) Drying Beds - The most widely used dewatering method in the United
States is drying of the sludge on open or covered sandbeds. They are especially
popular at small plants. Sandbeds possess the advantage of needing little opera-
tor skill. Air drying is normally restricted to well digested sludge, because raw
sludge is sometimes odorous, attracts insects, and does not dry satisfactorily
when applied at reasonable depths. The design and use of drying beds are affected
by many parameters. They include weather conditions, sludge characteristics, land
values and proximity of residences, and use of sludge conditioning aids.
Drying times typically range from 4 to 12 weeks, depending upon the weather.
Especially adverse weather can result in drying times as long as 6 months (51).
I.2.a.(2) Drying Lagoons - Lagoon drying is a low cost, simple system for sludge
dewatering that has been commonly used in the United States. Sludge is removed
periodically and the lagoon refilled. Sludge is stabiliEed to reduce odor prob-
lems prior to dewatering in a drying lagoon.
Most design factors include climate, subsoil permeability, lagoon depth, loading
rates, and sludge characteristics.
Sludge will generally not dewater in any reasonable period of time to the point
that it can be lifted by a fork except in an extremely hot, arid climate. If
sludge is placed in depths of 15 inches or less, it may be removed with a
front-end loader in 3 to 5 months. When sludge is to be used for soil condition-
ing, it may be desirable to stockpile it for added drying before use.
I.2.a.(3) Heat Drying - Heat drying raises the temperature of the incoming
sludge to 212°F (100 C) to remove moisture which reduces total volume, yet
retains the nutrient properties of the sludge. The end product is odor free, con-
tains no pathogenic organisms, and contains soil nutrients. Sludge has been heat
dried in flash drying equipment and rotary kilns. Heat dried sludge requires more
energy per unit of nutrient produced when compared to commercial fertilizers.
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I.2.a.(3) (a) Flash Drying - Flash drying is the instantaneous removal of
moisture from solids by introducing them into a hot gas stream. There are two
basic flash drying systems: cage mill dryers and jet mill dryers.
A flow diagram of the cage mill process is shown in Figure 9. The system is based
on three distinct cycles which can be combined in different arrangements. The
first cycle is the flash drying cycle, where wet filter cake is blended with some
previously dried sludge in a mixer to improve pneumatic conveyance. The blended
sludge and the hot gases from the furnace at 1,300°F are mixed ahead of the cage
mill and flashing of the water vapor begins. The cage mill mechanically agitates
the mixture of sludge and gas and the drying is virtually complete by the time
the sludge leaves the cage mill. The sludge, at this stage, is at a moisture con-
tent of 8 to 10 percent and dry sludge is separated from the spent drying gases
in a cyclone. The dried sludge can be sent either to fertilizer storage or to the
furnace for incineration. See F.3.c.(l), Part II for more detail.
1.2.a. (3) (b) Rotary Kiln Dryer - The rotary kiln is a cylindrical steel shell
mounted with its axis at a slight slope from the horizontal as shown in Figure
10. Dewatered sludge is fed continuously into the upper end. A portion of the
dried sludge is mixed with the feed sludge to reduce moisture and disperse the
cake. Vanes pick up the material, then steadily spill it off in the form of a
thin sheet of falling particles as the dryer rotates. This action is intended to
provide contact between sludge and gases to promote rapid drying. The dried
sludge from such a unit will consist of varied sizes of particles that may
require grinding before use. Deodorization of the exhaust gases by after burning
at approximately 1,200° to 1,400°F (650° to 760"C) is necessary if odors are to
be avoided. Also, scrubbers must be used to remove particulates from the exhaust
gases.
1.2.b. Composting
Composting is a method of biological oxidation of organic matter in sludge by
thermophilic organisms. Composting, properly carried out, will destroy objection-
able odor producing elements of sludge, destroy or reduce disease organisms
because of elevated temperature, and produce an aesthetic and useful organic
product.
Composting systems generally fall into three categories: (a) pile, (b) windrow,
and (c) mechanized or enclosed systems. The pile (static aerated pile) and
windrow systems have been used almost exclusively in composting sewage sludge
because of their low cost and demonstrated performance. Mechanized or enclosed
systems have not been used to any extent recently in the U.S. on sewage sludge.
The general composting method is very similar for all processes. The dewatered
sludge (typically 20 percent solids) is delivered to the site and is usually
mixed with a bulking agent. The purpose of the bulking agent is to increase the
porosity of the sludge to assure aerobic conditions during composting. If the
composting material is too dense or wet it may become anaerobic thus producing
odors or if it is too porous the temperature of the material will remain low. Low
temperatures will delay the completion of composting and reduce the kill of
disease organisms.
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, Rf Llf f VENT
CAGE MILL
HOT GAS DUCT
REFRACTORY
F?'/-/l HOT OAS TO DRYING SYSTEM
1 I OR ,'INC SYSTEM
SLUDGE
COMBUSTION AIR
DEODORIZED QAS
Figure 9. Cage mill flash dryer system. (52)
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'PUMP
WASTE
Ql\JW.JWW*A»JWMW
-------
Various bulking materials can be used and suitable low cost materials include,
previously composted sludge, wood chips, bark chips, rice hulls, and cubed solid
waste. Unscreened finished compost has also been used. Generally, one part sludge
(20 percent solids) is mixed with 2-3 parts bulking agent although this mixture
can be varied depending on moisture content of sludge, type of bulking agent, and
local conditions. The sludge-bulking agent mixture is then formed into the
windrow or static pile as applicable.
Following composting, the product is removed from the windrow or static pile and
cured in storage piles for 30 days or longer. This curing provides for further
stabilization and pathogen destruction. Prior to or following curing, the compost
may be screened to remove a portion of the bulking agent for reuse or for appli-
cations requiring a finer product. The compost can also be used without screen-
ing. Removal of the bulking agent also reduces the dilution of the nutrient value
of the compost.
I.2.b.(l) Windrow - The sludge-bulking agent mixture, (2-3 parts of bulking
agent by volume to one part of sludge) is spread in windrows with a triangular
cross section. The windrows are normally 10 to 16 feet wide and 3 to 5 feet high.
An alternative method of mixing the bulking agent and sludge and forming the win-
drow consists of laying the bulking agent out as a base for the windrow. The
sludge is dumped on top of the bulking agent and spread. A composting machine
(similar to a large rototiller) then mixes the sludge and bulking agent and forms
the mixture into a windrow. Several turnings about (4 to 6 times) are necessary
to adequately blend the two materials.
The windrow is normally turned daily using the compostor; however, during rainy
periods turning is suspended until the windrow surface layers dry out. Tempera-
tures in the windrow interior under proper composting conditions range from 55 to
65°C. Turning moves the surface material to the center of the windrow for expo-
sure to higher temperatures. The higher temperatures are needed for pasteuriza-
tion and kill off most pathogenic agents. Turning also aids in drying and
increases the porrosity for greater air movement and distribution.
The windrows are turned for a two week period or longer depending on the weather
and efficiency of composting. The compost windrow is then flattened for further
drying. The cmpost is moved to curing when the moisture content has decreased to
approximately 30 to 45 percent. Proper windrow composting should produce a rela-
tively stable product with moisture content of 30 to 45 percent which has been
exposed to temperatures of at least 50°C for a portion of time during the com-
posting process.
The composting process requires longer detention times in cold or wet weather,
therefore, climate is a significant factor with the windrow process in open
spaces. Covering the composting area would significantly reduce the effects of
cold weather and nearly eliminate the problems of wet weather. In any case, the
curing area should be covered if operations are to be carried out during
precipitation.
1^2.b.(2) Static Pile - The static pile composting method as applied to raw
sludge requires a forced ventilation system for control of the process. The pile
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then remains fixed, as opposed to the constant turning of the windrow, and the
forced ventilation system maintains aerobic conditions.
A base is prepared for the pile consisting of a 1 foot thick layer of bulking
agent or previously composted unscreened product. A 4-inch diameter performated
pipe is installed in the base as an aeration header. The base is constructed with
a typical plan dimension of approximately 40 by 20 feet. The sludge-bulking agent
mixture is piled on this base to a height of approximately 8 feet to form a tri-
angular cross section. The pile is capped with a 1 foot layer of screened compost
product. This top layer extends down the sides to help absorb odors and to act as
a shield or roof against penetration of precipitation. A typical static pile is
illustrated in Figure 11. An alternative configuration is the extended static
pile method where subsequent piles are "added" to the initial static pile. This
configuration saves space compared to a number of separate static piles.
The perforated underdrain pipe is attached to a blower by pipe and fittings. The
other side of the blower is piped to a smaller, adjacent pile of screened compost
product. Air and gases are drawn by the blower from the static compost pile and
discharged through the small pile of product compost. The small pile effectively
absorbs odors. The operating cycle of the blower is adjusted to maintain oxygen
levels in the exhausted gases and compost pile within a range of 5 to 15 percent.
Temperatures within the compost pile will vary somewhat with monitoring location
in the pile, but should reach 60-65°C. Normally the blower is operated on an
on-off cycle to maintain proper oxygen levels and temperatures within the pile.
After an average composting period of 3 weeks, the compost is moved to a curing
area.
Outdoor temperatures as low as -7°C and rain totaling 7 inches per week has not
interferred with the successful outdoor operation of exposed static pile com-
posting. Temperatures produced during static pile composting are generally above
55"C and often exceed 70 to 80°C.
I.2.b.(3) Mechanical Systems - There are several mechanical systems available
for composting. Most are designed for solid waste composting where the much
larger quantities of material to be composted make the reduction in land require-
ments due to mechanical compostors cost effective. The volume of sludge to be
composted at most operations is very small when compared to solid waste system
and mechanical compostors have not been found to be advantageous.
In general mechanical compostors consist of large vats or digesters with mechan-
ical equipment for aeration, mixing, and moving the compost through the digester.
Additional information on mechanical composting and European experience is given
in reference (53). These systems are proprietary.
I.2.c. Co-disposal with Solid Waste
Co-disposal of sludge and solid waste by composting usually takes one of two
forms:
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'/—• — —. — — —~ —• —>4
vS=s sx -a. -ru-ssmraZ:
LONGITUDINAL SECTION
FAN SCREENED
COMPOST
WOOD CHIPS AND SLUDGE
SCREENED COMPOST
UNSCREENED COMPOST
PERFORATED PIPE
EXTENDED PILES
CROSS SECTION
Figure 11. Static pile composting.
-------
• Use of shredded and classified solid waste as a bulking agent in sludge
composting
• Use of sludge as a nutrient source in solid composting
Sewage sludge has too high a moisture content for successful windrow or static
pile construction without the aid of a bulking agent. The cellulose (paper and
some garbage) fraction of solid waste may offer a suitable and economical bulking
agent. Solid waste on the other hand generally requires supplemental nitrogen
and moisture for successful composting. Sewage sludge has been suggested as an
economical source of additional nitrogen (54).
I.2.d. Nutrient Enrichment
It may prove cost-effective to increase the market value of the sludge product by
nutrient enrichment. While nitrogen and phosphorus contents can be increased with
a subsequent increase in value, the greatest nutrient shortcoming of most sewage
sludge products is the potassium (potash) content. Nutrient enrichment processes
may be part of the sludge management system or they may be practiced by fertili-
zer processors who purchase unenriched product from the wastewater agency.
1.3. PACKAGING AND DELIVERY
The facility plan must give adequate consideration to the methods of product
packaging and delivery, as they may determine the success or failure of the com-
posting system.
By far the most common system of delivery sludge for off-site use by others is to
allow or encourage individuals to pick up lagoon or bed dried sludge at the
treatment plant. Usually the sludge is given away, or a nominal price charged, if
it is loaded by the user. If the sludge is loaded by the utility a higher price
is often charged to off-set labor costs.
The same concept is sometimes applied to larger deliveries, with user owned
trucks loaded with sludge during regularly scheduled drying bed or lagoon
cleanings.
Sludge product is often delivered in bulk to the users. Trucks, railroads, and
barges have been used. The section on sludge transport has more information on
the selection of transportation modes.
Bagging of the sludge product is a costly process, but the bagged product can
usually be sold at a correspondingly higher price. Many urban and suburban indi-
vidual users will desire small quantities of sludge product and will not have the
means for transporting the unbagged product. This segment of the potential market
is accustomed to obtaining fertilizers and soil conditioners in bagged form and
is generally willing to pay a premium for the convenience. The bagged product can
be sold at the treatment plant site, although the visibility afforded by market-
ing through the usual outlets such as garden centers and nurseries can greatly
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improve sales. Regulatory agencies should be consulted to determine required
labeling.
Section J - COST EFFECTIVENESS ANALYSIS
In order to select the best sludge management alternative, a cost-effective anal-
ysis must be performed. The cost-effectiveness analysis may be on an amortized
annual basis or on a present worth basis, but all alternatives must be evaluated
in the same manner. Whether on an annual or present worth basis, the analysis
should include the costs of construction, operation, maintenance and supervision
for all components of the sludge management system, including sludge treatment
processes and any impacts on the wastewater treatment processes.
Cost-effectiveness analyses should be made in accordance with the Federal regula-
tions "Cost-Effectiveness Analysis Guidelines" (55).
In evaluating systems which involve co-disposal with solid waste, great care must
be exercised to insure that the costs used reflect the actual situation. Some
examples follow:
• When solid waste and sludge are to be managed in an all new facility,
the total cost of managing both waste streams together should be used.
In evaluating alternative sludge management systems not involving
co-disposal, the cost of separate solid waste management should be
included.
• Where sludge is to be added to an existing solid waste management sys-
tem, the incremental cost of the sludge management should be
evaluated.
• Where solid waste is added to a sludge management system as raw mate-
rial (refuse-derived fuel or bulking agent), the cost of separating
usable material from the overall solid waste stream and inserting it in
the sludge management stream should be treated as a variable annual
cost to the sludge management system for fuel or material. Credit for
an incremental reduction in the solid waste stream may be taken,
although the volumes involved may not justify this.
• Cost must be allocated between the sludge management system and the
solid waste management system according to EPA policy to determine
separate agency shares.
This section discusses only quantifiable costs. Such non-quantifiable costs as
social and environmental costs are discussed under the section on environmental
assessment; and the performance of a separate energy-effectiveness analysis is
discussed in the section on energy analysis.
Comparative cost information which may be useful may be obtained from the tech-
nical report, A Guide to the Selection of Cost-Effective Wastewater Treatment
Systems, (56) in conjunction with its supplement, An Analysis of Construction
Cost Experience for Wastewater Treatment Plants, (57).
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J.I. GENERAL CONSIDERATIONS
J.I.a. Planning Period
The planning period for cost-effectiveness analyses is 20 years.
J.l.b. Discount Rate
The discount, or interest rate to be used in cost-effectiveness analyses is the
rate established by the Water Resources Council for water resources projects.
Discount rates are normally revised on October 1 of each year.
J.l.c. Construction or Other Cost Indices
Cost vary with time and with geographical location. All usable cost data will be
referenced to a specific place and point in time. Cost indices must then be
applied to the data to adjust them to the conditions under consideration.
Adjustment is performed by multiplying the cost data by the ration of the current
cost index to the cost index for the place and time for which the data was com-
piled. The most useful indices (which are all published in Engineering
News-Record) are:
• The Engineering News-Record Construction Cost Index
• The EPA Sewage Treatment Plant Index
• The EPA Sewer Construction Cost Index
J.l.d. Service Lives of Facility and Equipment
The cost-effectiveness guidelines give service lives for various components of
the wastewater treatment system. These service lives are generally applicable to
sludge management systems. Many components of sludge management systems, however,
do not fit into the categories in the cost-effectiveness guidelines, and consid-
eration should be given to establishing more accurate service lives. Where the
sludge management system has a useful life less than the planning period, as is
often the case with landfills, the cost of sludge management for the remainder of
the planning period must be included in the analysis. In evaluating service lines
consideration must also be given to the salvage values of facilities and equip-
ment at the end of the project life.
J.l.e. Capital Costs and Credits
Capital costs and credits include such items as:
• Land or right-of-way purchase
• Facility construction including engineering, administration, construc-
tion cost, fixed equipment costs, start-up costs, and interest during
construction.
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• Mobile equipment costs including trucks, tractors, etc.
• The incremental cost of increasing wastewater treatment unit sizes to
accommodate sidestreams.
• Credit for salvage values of land and equipment if applicable.
In evaluating the cost of land acquisition, consideration should be given to any
losses in property tax revenues due to public ownership of the property.
J.l.f. Fixed Annual Costs
Fixed annual costs are those costs which are incurred regardless of the actual
flow to the sludge management system. These costs include operating labor, main-
tenance, supplies, monitoring, equipment leasing, and land leasing. Inflation of
material and wages should not be considered unless a change in the relative costs
of portions of the fixed annual costs can be anticipated.
J.l.g. Variable Annual Costs and Credits
Variable annual costs and credits are those which change with the sludge flow.
These costs and credits include:
Fuel
Electricity
Chemicals including supplemental fertilizer
Incremental operation and maintenance costs of sidestream treatment
Credits for energy recovery
Contract haul costs
Cost of product disposal or credit for product sale
Bulking agent costs
Product packaging costs
J. 2. SLUDGE TREATMENT
The cost of sludge treatment (thickening, stabilization, conditioning, dewater-
ing) is a major portion of any sludge management system. Detailed analysis of
sludge treatment costs must be made for each alternative under consideration. In
addition, possible alternative sludge treatment systems for each management
alternative should be analyzed for their effect on the overall cost. Sludge
treatment costs should not neglect the incremental addition to wastewater treat-
ment costs due to the return of sidestreams to the wastewater processes.
J.3. SLUDGE TRANSPORT
Each sludge transport system under consideration should be analyzed for its
cost-effectiveness. It should be recognized that each sludge management alterna-
tive will have a different set of sludge transport costs to evaluate. Data on
sludge transportation costs can be found in the EPA publication Transport of
Sewage Sludge (16).
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J.4. LAND APPLICATION
Cost-effectiveness analyses for land application systems should include credit
for the sale of any crop produced on land owned or leased by the wastewater
agency. The O&M costs for site preparation and sludge application can be
partially offset by a credit for the increased real value of the land (real
deflated value) resulting from the reclamation project. Land application systems
should be given 115 percent cost preference over other disposal systems in
accordance with EPA regulations on innovative/alternative systems. The credit for
the value of the reclaimed land should be based on the estimated market value of
the reclaimed land at the time the analysis is made. Conversely, if the intended
crop is unsalable, the cost of crop disposal should be included; and if land
application of sludge makes previously usable farm land permanently unsuitable
for food chain crops, consideration should be given to a possible loss in market
value. Area funding agencies should be contacted for their acceptance considering
these concepts.
J.5. LANDFILL
If the life of the landfill is less than the planning period, as is often the
case, the cost of sludge management through the remainder of the planning period
should be considered.
J.6. COMBUSTION
Analyses of combustion processes should consider the value of any energy
recovered in the form of waste heat or as pyrolysis products, the cost of residue
disposal, and the cost of sidestream treatment. It is possible that the combus-
tion process residue may have a market value, either as is, or after further
processing.
J.7. SLUDGE FOR OFF-SITE USE BY OTHERS
Analysis of off-site use alternative should include a realistic assessment of the
market value of the product. Considered in the evaluation of the product value
should be the cost of transporting it to the user.
Section K - RELIABILITY
The reliability of the sludge management alternative under consideration must be
evaluated. Sufficient reliability should be designed into the sludge management
system to prevent undesirable effects resulting from system interruptions. The
EPA technical bulletin Design Criteria for Mechanical, Electric, and Fluid System
and Component Reliability (58)should beconsultedin evaluatingthe reliability
of the proposed facility.
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K.I. MECHANICAL DOWNTIME
The sludge management system chosen should include features which minimize the
effects of mechanical downtime. Mechanical downtime usually occurs as a result
of:
• Scheduled maintenance
• Power failures
• Equipment failures
K.I.a. Standby Power Supply
In general, the nature of sludge management systems is such that power failures
of typical duration have no serious effects on the system operation. A notable
exception, however, is the multiple hearth incinerator. Loss of power to the rab-
ble arm drive and cooling air supply can result in serious damage to the rabble
arms and center shaft. Standby power should always be provided for at least the
rabble arm drive and cooling air fan. Whenever possible, standby power should
also be provided for the induced draft fan, as it is quite costly, and sometimes
damaging, to permit a multiple hearth furnace to cool and to subsequently reheat
it.
K.l.b. Standby Fuel Supply
It is sometimes desirable to have a standby source of fuel. This is particularly
true in the case of multiple hearth incinerators on interruptible natural gas
supplies. It is very costly to permit an operating multiple hearth incinerator to
cool down as a considerable amount of fuel is required to bring it back up to
operating temperature. In addition, uncontrolled cooling can result in refractory
damage.
K.I.e. Storage
Sludge storage is often the most economical way to provide adequate reliability.
Storage has the added benefit of providing operating flexibility at the sludge
disposal site, possibly allowing 8-hour, 5-day work schedules and shutdown during
inclement weather. Storage should be sized to accommodate the entire sludge pro-
duction from the wastewater treatment facility during the longest anticipated
outage due to mechanical downtime. Where operating flexibility is also a goal of
sludge storage, the sizing of the storage facility will often be governed by the
flexibility requirement.
K. 1.d. Duplicate Equipment
The provision of multiple process units can provide protection from mechanical
downtime for scheduled maintenance or equipment failure. This approach is most
often applicable to larger facilities which handle a quantity of sludge several
times the capacity of a typical sludge processing unit. An example would be a
sludge incinerator installation with four incinerators, three of which can, when
operating at peak capacity, handle the full sludge production of the wastewater
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treatment facility. Care should be taken to insure that duplicate items of equip-
ment are not subject to "common mode" failures, such as loss of a single gas line
which serves all incinerators. Storage can often be considered as an alternative
to duplicate equipment.
K. I.e. Backup Equipment
In the case of landfill and land application facilities, and some composting
operations, protection against mechanical failure can be provided by backup
equipment. Backup equipment can often be multi-purpose, such as a tractor with
dozer blade which can serve as a backup at a landfill site for more specialized
excavating, compacting, backfilling, and road grading equipment. Often it is not
necessary for the backup equipment to be dedicated to the sludge landfill site.
Backup equipment for a landfill might be obtainable by agreement from the local
solid waste landfill operation, the local public works department, or from other
utilities in the area. In many communities it may be possible to rent the neces-
sary backup equipment as needed from a local heavy equipment rental agency.
K.l.f. Alternative Management Techniques
The planning of an alternative sludge management technique can protect a facility
from mechanical downtime. An example would be an incineration facility with pro-
visions for hauling sludge to a solid waste landfill in the event of incinerator
failure. Care should be taken, however, that the alternative management system
is not subject to "common mode" failures with the principal management system.
K.2. AVAILABILITY OF NEEDED RESOURCES
A key factor in determining the reliability of the sludge management system is
the availability of the resources necessary to operate the system. An otherwise
well planned and designed system will not function reliably if these resources
are in short or unreliable supply.
K.2.a. Electric Power
The supply of power from the local electrical utility must be considered in the
early stages of facility planning. Frequently the electric utility will be forced
to construct new lines, the cost of which may be charged to the sludge management
operation. These costs should be included in the cost-effectiveness analysis in a
manner appropriate to the billing schedule.
K.2.b. Fuel
The supply of necessary fuels must be assured. If gas is required, the ability of
the local gas utility to provide service should be verified as service is often
on an interruptible basis. This will further affect fuel supply reliability.
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If liquid fuels are required, the local fuel marketing system's capability for
meeting the requirements of the sludge management system must be addressed.
Marketing capabilities must be matched to the system design (frequency of
delivery, size of delivery, etc.). Adequate on-site fuel storage should be
considered to allow for delivery delays.
K_._2. c_. Chemi cal s
The local availability of necessary chemicals must be considered. The ability of
the local chemical marketing system to reliably meet the facility's needs must be
assessed. The system design must be matchable to the marketing capabilities (fre-
quency of delivery, size of delivery, etc.). Sufficient on-site storage should be
considered to allow for delays in deliveries.
K. 2.d. Manpower
The ability of the local labor market to supply the needed qualified personnel
at the salary levels established for the sludge management operation must be
examined. Qualified maintenance personnel should be available in the local labor
market. In the case of agricultural operations, people with farming experience
must be available. If qualified heavy equipment operators are required, their
availability must be considered.
K.2.e. Replacement Parts
The availability of replacement parts for the sludge management system equipment
is critical to system reliability. In many small communities, spare parts for
even relatively common types of equipment may require long delivery times.
Machine shops may be locally available which could, in an emergency, fabricate
difficult-to-obtain parts.
K.3. FACTORS OF SAFETY
The design of the sludge management system should include factors of safety to
allow for abnormal sludge quantities and characteristics, unusual periods of
inclement weather, droughts, and other reasonably foreseeable occurrences.
Section L - ENERGY ANALYSIS
The energy-effectiveness of sludge management alternatives must be analyzed in
order to determine the effect of the facility on energy production and consump-
tion in the planning area. The EPA's "Grants Regulations and Procedures, Revision
of 40CFR30, 420-6" (59) requires all portions of the wastewater treatment system,
including sludge management systems, to be energy-efficient. The economics of
energy utilization are considered in the cost-effectiveness analysis.
Energy analyses must consider both the primary energy consumption (used in the
operation of the management system) and secondary energy consumption (used in
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the manufacture of consumables used by the management system). Energy analyses
should present all alternatives on a common basis. In the case of co-disposal
alternatives, the energy consumption of both solid waste and sludge management
should be considered for both the co-disposal alternative itself and alternatives
not involving co-disposal. Credits for energy recovery should be based on real-
istic estimates of the actual utilization of that energy. Credit for recovery of
steam from waste heat, for instance, should only be considered if a viable use
for the steam exists. Energy analyses should also include the energy consumed in
treating sidestreams.
Energy-effectiveness must be evaluated within the framework of cost-effective-
ness. Theoretically, the two should be similar, but for a variety of reasons this
may not be the case. For instance, the regional fuel price structure is variable
and will reflect the relative availability of a particular type of energy, such
as fuel oil, natural gas, coal, or nuclear. Thus, a particular sludge management
system might be energy- as well as cost-effective in one region, while only
energy-effective in another. Similarly, while the energy-effectiveness of a par-
ticular system might be high, the cost-effectiveness might not reflect this fact
if the system is labor intensive and labor costs are high for a particular
project.
The EPA publication Energy Conservation in Municipal Wastewater Treatment (40)
contains more detailed guidance on making energy-effectiveness analyses as well
as a great deal of primary and secondary energy consumption data.
Section M - ENVIRONMENTAL ASSESSMENT
An assessment of the impact of the sludge management system on the environment,
including public health, social, and economic impacts, is required for all fed-
erally funded projects. Similar assessments are required by many state and local
governments. The impact of each sludge management alternative under consideration
must be evaluated.
M.1 ENVIRONMENTAL IMPACT
Sludge management systems may affect the following components of the environ-
ment: (1) soil and vegetation, (2) groundwater, (3) surface water, (4) animal and
insect life, (5) air quality and (6) climate.
M.I.a. Soil and Vegetation
The effects of the deposition of sludge on the land may be adverse or beneficial,
or some combination of the two, depending on the character of the material
deposited, the manner in which it is deposited, and the character of the land.
(See Section F and I).
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M.l.b. Groundwater
Groundwater quality, level, and flow will normally be affected, to a minor
extent, by sludge management techniques which place sludge on or in the land.
Effects on groundwater quality is the most significant. Leachate moving from a
sludge land application or landfill site to groundwater by percolation can con-
tain significant concentrations of substances which are considered to be pollu-
tants. The sludge constituent typically of most concern is nitrate-nitrogen.
Other constituents which may leach from sludge into the groundwater include
phosphates, heavy metals, organics, dissolved solids, and others identified under
article B.2.
M.l.c. Surface Water
Surface water flow and quality can be affected by an improperly designed or
operated sludge management system. Flow can be increased or decreased by the
alteration of runoff patterns due to grading at a landfill or land application
site. Surface water quality can be adversely affected by allowing runoff from the
site to enter surface waters. Any of the constituents of the sludge could enter
surface water with the runoff.
When sludge is transported by barge, the additional possibility of surface water
pollution due to sludge spills must be evaluated.
M.l.d. Animal and Insect Life
The impact of sludge management systems on animal and insect life is normally
minimal. Where sludge is being deposited in or on previously unfarmed land, the
natural habitat of certain species may be disrupted. Conversely, the production
of crops on land with applied sludge may provide additional food sources for
wildlife. These and other effects must be evaluated for each species of concern.
M.l.e. Air Quality
Sludge incineration and heat drying processes may have a significant impact on
air quality. Among the air pollution components which may be produced by these
processes are:
Particulates
Sulfur dioxide
Oxides of nitrogen
Heavy metals
Toxic organic compounds
Hydrocarbons and carboxyls
The evaluation of the impact on air quality should consider each of these pollu-
tants as well as any other substances which may be formed in the atmosphere from
these pollutants, such as photochemicals.
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Sludge transport by truck, barge, or rail will have an impact on air quality due
to vehicle emissions. The nature and quantity of the pollutants from internal
combustion engines is well documented (60) and will not be discussed further
here. Land application systems which utilize spraying of sludge may lead to the
production of aerosols (finely divided airborne moisture). The chief concern with
aerosol production is the possibility of pathogens entering human or animal
respiratory systems.
All sludge management systems have the potential for odor production to some
degree or another. While odors are indicative of the presence of polluting
substances, primarily hydrocarbons and hydrogen sulfide, their primary adverse
effect is aesthetic. Odors will be discussed further under article M. 3. Social
Impacts.
M.l.f. Climate
The effects of sludge management systems on climate are minimal, generally lim-
ited to a small increase in humidity in the immediate vicinity of the project.
This increase may be due to evapotranspiration at land application sites or heat
evaporation at incineration or heat drying projects.
M.2 PUBLIC HEALTH IMPACTS
Public health impacts must receive careful attention in the facility plan. Most
public health effects of sludge management systems are the result of impacts on
animal and insect life, soils and vegetation, groundwater quality, surface water
quality, or air quality.
M.2.a. Disease Vectors
Several of the animals and insects which are known to thrive in certain sludge
management systems are also known to be vectors for several diseases of man and
animals. Of particular concern in this regard are rodents, notably rats and mice,
flies and mosquitoes.
Rodents are particularly troublesome on sites which employ the co-disposal of
sludge with solid waste by landfill or composting. The solid waste provides food
and harborage for the rodents, while the sludge may provide a source of patho-
genic organisms. The existence of large numbers of the rodents in a small area
such as a landfill can enhance the spread of the diseases from animal to animal
and thence to the human population. Proper operation of a landfill or composting
operation can minimize the rodent problem.
Flies are a potential problem with virtually all sludge management systems.
They find sludge storage and disposal sites to be very hospitable, feeding
directly on most sludges and laying their eggs within the sludge. Aside from the
aesthetic problems associated with flies, they are mechanical disease vectors,
carrying small particles of potentially pathogenic sludge on their bodies and
legs. Upon contacting human beings or human food, the pathogenic organisms may be
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transmitted to people. Fly control is primarily a matter of keeping the sludge
covered to prevent the emergence of larvae. Well-compacted, daily cover at
landfill sites will help control flies. Mosquitoes are known to transmit several
pathogenic organisms.
Mosquitoes breed in standing water. The most effective method of mosquito control
is proper grading of the site to prevent ponding of water.
M._2.b_. Soil and Vegetation
Soil and vegetation impacts are of concern to public health when crops grown on
land application or landfill sites or with the aid of sludge by-products may be
introduced into the human food chain. In this event, toxic substances deposited
in the soil with the sludge may be transferred to the crops, and thence to human
beings.
M.2.C. Groundwater Quality
The effects of sludge management or groundwater quality are a public health con-
cern whenever an aquifer is, or may be, used as a potable water supply. Leachate
capture and treatment may be required in order to protect the aquifer. Nitrate
pollution is the most common problem, but toxic organics, dissolved salts, trace
elements, and pathogens must be considered. Adequate leachate monitoring and con-
trol practices must be included in the facility plan.
M.2.d. Surface Water Quality
Surface water quality is a public health concern when runoff from a sludge man-
agement site enters a receiving water which is used as a potable water supply for
recreational activities involving bodily contact with the water, or for commer-
cial or recreational fishing. A properly planned landfill or land application
site will include grading to divert runoff around the site and/or to capture and
treat the runoff before it enters the receiving water.
M.2.e. Air Quality
Air quality is a public health concern from two standpoints: an increase in the
incidence of respiratory diseases from the increase in the general air pollution
level due to sludge combustion, heat drying or transport activities; and the pos-
sibility of aerosol-borne pathogens from spray-type land application sites.
Well-operated sludge incineration facilities with modern pollution control equip-
ment have a relatively low potential for air pollution when compared with, for
example, automobiles (61). The facility plan must define the operating parameters
for minimizing air pollution. The facility plan must take into account the cur-
rent federal, state, and local air quality regulations and policies. Other public
health effects of sludge combustion process pollutants and the resultant products
(photochemicals) must be evaluated in the facility plan.
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Aerosols are most successfully controlled by limiting their travel. This can be
done by use of buffer zones, vegetation, proper sprayer design, and scheduling of
spraying.
M.3. SOCIAL IMPACTS
The impact of sludge management on the sociological aspects of the community
must be evaluated.
M.3.a Relocation of Residents
Sludge management by land application or landfill often requires substantial
quantities of land. This may lead to relocation of residents. For projects
involving federal funds, land acquisition procedures must comply with the Uniform
Relocation Assistance and Land Acquisition Policies Act of 1970 (62). Inconven-
ience to residents must be weighed against the advantages of the sludge manage-
ment system.
M.3.b. Greenbelts and Open Spaces
Proposed sludge management systems should be evaluated with regard to their
effect on greenbelts and open spaces. While sludge management systems may dis-
rupt existing open space, existing damaged land, such as abandoned strip mines,
may be reclaimed for use as open space by land application and landfill
operations.
M.3.c. Recreational Activities
Sludge management systems may affect recreational activities by disruption of
existing parks or open space, by eventual creation of new parks or open space,
by improvement of existing parks where sludge is used off-site by the local
parks department, or by the deleterious effects of site run-off on recreational
waters.
M.3.d. Community Growth
Unless the sludge management system is the capacity-limiting element of the over-
all wastewater treatment system, the sludge management technique selected will
have only a minor effect on the rate of community growth. The overall wastewater
treatment system, of which the sludge management system is only one part, may
however, have a major effect on the rate of community growth.
The patterns of community growth may be greatly affected by the sludge manage-
ment system. Certain sludge management systems may deter residential growth in
the vicinity of the facility, while encouraging industrial growth. The availabil-
ity of recovered energy, for instance, will rarely be so significant as to affect
the decision of a new industry to move to a community, but it could conceivably
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be a factor in determining the exact site for the industrial development. The
effects of sludge management on the patterns of growth will affect the growth
patterns of other community services, which must be evaluated in the impact
assessment.
M.3.e. Noise and Odor
Noise and odor are primarily aesthetic concerns which affect the other sociolog-
ical aspects of the sludge management system. Nearly all sludge management sys-
tems must consider odor problems. Noise problems are normally associated with
sludge transport by truck and with landfill, land application and composting
operations. The facility plan should address these problems and formulate methods
of dealing with them. Appropriate scheduling of operations can be of great value
in minimizing noise problems. Adequate stabilization and prompt disposal of
sludge can be of value in reducing odor problems by eliminating septic conditions
in uncovered sludge.
M.4. ECONOMIC IMPACT
The facility plan should consider the effects of the sludge management system on
the economy. The effect of the system on the value of the site itself and of
adjacent property must be evaluated. The sludge management system may affect the
overall economy in terms of jobs created and land removed from agricultural
production. Public ownership of the sludge management system property may affect
the community tax base. The overall effect of the sludge management system on the
supply of resources and energy must be considered.
Section N - IMPLEMENTATION PROGRAM
Selection of the sludge management system is based on technical feasibility,
cost-effectiveness, flexibility, reliability, energy-effectiveness, and overall
impacts. At all stages of the planning processes the public must be involved in
order to aid the planner in selecting the most cost-effective system, especially
in considering non-monetary costs, and in assessing the impacts of the system.
N.I. PUBLIC PARTICIPATION PROGRAM
An appropriate, actively pursued public participation program can often make the
difference between a sludge management system which has the support of the major-
ity of the community and one which is unable to generate the support necessary
for successful completion. Public resistance to sludge management systems is an
almost universal phenomenon. This resistance is often rooted in misconceptions
and lack of understanding of the problems and the alternative solutions, and in a
feeling by the community that they have been excluded from the decision-making
process. The resistance may also be due to valid concerns of the community of
which the planner is not fully aware. A vigorous public participation program can
educate the community concerning the problems and solutions of sludge managment,
involve the public in a constructive manner in the planning process, and serve as
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a valuable information-gathering tool for the planner, assisting him in assessing
the impacts of the system on the community. The public participation plan must be
tailored to the scope of the project and to the potential for community concern.
Public involvement in the planning process can, of course, slow the process and
may result in additional cost. On the other hand, a lawsuit brought by uninformed
members of the community to halt a sludge management program in the final stages
of planning, or even during costruction, can be far more costly, and can delay
the project for a much longer period of time. While a public participation
program will not eliminate resistance to a proposed sludge management system, it
may be able to reduce that resistance to a manageable level. The EPA publication
Process Design Manual for Municipal Sludge Landfills (34) has a great deal of
information on the design of public participation programs which, while written
primarily for landfill systems, is generally applicable to all sludge management
systems.
N.2. POTENTIAL ROADBLOCKS
The facility plan should identify potential roadblocks to implmentation of the
plan. Typical items which may be considered are:
• Public resistance to the plan
• Inability to obtain necessary financing
• Difficulty in acquiring land
• Where the plan involves a contract with a private concern, such as use
of sludge as a raw material by a fertilizer manufacturer, failure to
execute the anticipated contract.
N.3. LAND ACQUISITION PROGRAM
The facility plan should include a proposal for land acquisition. If the required
land is not already owned by the authority operating the sludge management sys-
tem, it may be acquired by:
• Negotiated purchase of land or right-of-way
• Leasing of land
• Purchase by condemnation of land or right-of-way
• Dedication of land already owned by the sludge-managing authority or
another related authority to the sludge management system
N.4. IMPLEMENTATION SCHEDULE
The facility plan should include a schedule for project implementation. The
schedule should include anticipated start and stop dates for each major activity.
The schedule should take into account possible delays in implementation.
The schedule should be broken down to the level of detail justified by the scope
of the project. As a minimum, the following major tasks should be included:
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1. Facility plan approval
2. Land acquisition
3. Design
4. Design approval
5. Construction
6. Operation
Graphical presentation of the schedule is often useful as an aid to
understanding.
N.5. STAFFING PLAN
A preliminary project staffing plan should be included to permit the operating
authority to begin the process of hiring and training personnel at the most
appropriate time. The staffing plan should consider needs in the following gen-
eral categories:
Operations
Maintenance
Supervisory
Laboratory
Administrative
The staffing plan should be developed to a level of detail justified by the pro-
ject scope.
N.6. COMPATIBILITY WITH REGULATIONS
The facility plan must include an evaluation of the proposed sludge management
system compatibility with the applicable federal, state and local laws and
regulations.
N.6.a. Zoning and Land Use
The plan must take into consideration local and regional zoning ordinances and
land use plans. The proposed sludge management system must be compatible with the
planned growth patterns of the community.
N.6.b. Solid Waste Disposal
The management of sludge is governed by the Resource Conservation and Recovery
Act (2), the Toxic Substances Control Act (63) and federal regulations pertaining
to the disposal of solid waste as well as those pertaining to wastewater treat-
ment. In addition, many states regulate sludge disposal under their solid waste
regulations whenever the material is removed from the treatment plant site, as
for land application or landfill.
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N.6.c. Air Pollution Control
Sludge incinerators must comply with the "New Source Performance Standards for
Sludge Incinerators" (43, 47, 64), the applicable provisions of the Toxic
Substances Control Act (63) and any applicable federal regulations. In addition,
sludge incinerators and dryers must comply with the mercury limitations of the
"Amendments to the National Emission Standards". Many state, regional, and local
governments have air pollution control requirements which are more stringent than
the federal requirements, all of which must be met.
N.6.d. Water Pollution Control
The sludge management system must comply with the Clean Water Act (65), Federal
Water Polution Control Act (4), the Resource Conservation and Recovery Act (2),
and the Toxic Substances Control Act (53), and all applicable federal regula-
tions. Any applicable state or regional laws and regulations must also be met.
Until groundwater protection criteria are developed under the Resource Conserva-
tion and Recovery Act, the groundwater protection criteria in the EPA publication
Alternative Waste Management Techniques for Best Practicable Waste Treatment (66)
shall be used.
N.6.e. Public Health
Applicable state and local regulations regarding pathogen destruction must be
complied with. These regulations often deal specifically with hospital wastes,
and sludge to which public access is permitted or encouraged.
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PART II
DESIGN AND
SPECIFICATIONS
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DESIGN AND SPECIFICATIONS
INTRODUCTION
The design and specifications package should be a logical extension of the facil-
ity plan. The design and specifications are for the purpose of implementation and
construction of the sludge management system detailed in the facility plan. As an
aid to the evaluator, basic design criteria should be included with the package.
The format of this checklist has been selected to enable the reviewer to enter a
checkmark or comment to the right of each item. There are 6 major categories:
A. Agreement with Facilities Plan
B. Sludge Transport
C. Land Application
D. Landfill
E. Combustion
F. Off-Site Use of Sludge by Others
Within each category are numerous sub-elements. All the major categories should
usually be included. It is not necessary that all the sub-elements be included.
References are given for more detailed information and design criteria. In par-
ticular, the EPA Process Design Manual for Sludge Treatment and Disposal (1)
should be consulted for specific design information. It is not the intent of the
supporting commentary to limit alternatives to just those discussed. A particular
technique or process may be described as "best" or as "typical" but this does not
mean that other procedures are unacceptable.
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DESIGN AND SPECIFICATIONS
CHECKLIST
A. AGREEMENT WITH FACILITIES PLAN
1. MODIFICATIONS
2. CHANGES IN REGULATIONS AND POLICIES CONSIDERED
(In Federal, State, and Local regulations; in local or
regional land use plans.)
B. SLUDGE TRANSPORT
1. SLUDGE CHARACTERISTICS
a. Quantity: Maximum, Average, Minimum
b. Solids Content
c. Odor Potential
2. PIPELINE
a. Alternate Routes Considered
b. Distance
c. Elevation Changes
(Air relief, vacuum relief)
d. Operating Program
e. Pipe Selection
(Velocity, maximum and minimum, size, material,
friction losses, corrosion control)
f. Pumping Facilities
(Number and location of pumping stations, number and
type of pumps, pumping energy, station structure, station
utilities, controls.)
g. Pipeline Cleaning Provisions
h. Emergency Operation
(Storage, standby power.)
i. Excavation Conditions Verified
(Soil conditions, other underground utilities, highways,
rail crossings.)
j. Methods of Right-Of-Way Acquisition
(Existing utility easements, negotiation with landowners,
condemnation.)
3. TRUCKS
a. Alternate Routes Considered
b. Haul Distance, Speed and Travel Time
c. Compatability of Proposed Route with Existing
Road and Traffic
(Weight and height limits, turns required, speed
limits, traffic congestion, road width, elevation changes,
traffic control (stops, etc.).)
d. Operating Schedule
(Loading time, haul time, unloading time, return time
fueling and daily maintenance.)
e. Fuel Consumption
f. Manpower Requirements
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g. Truck Selection and Acquisition
(Size, type, quantity, useful life, purchase lease.)
h. Contract Haul Considered
i. Facilities Required
(Loading, unloading, vehicle maintenance, fueling,
parking, washdown, sludge storage)
4. BARGE
a. Haul Distance
b. Barge Speed and Travel Time
(Traffic, drawbridges, locks, tides, currents, and height
limitations.)
c. Operating Schedule
(Loading time, haul time, unloading time, return time.)
d. Barge Selection, Acquisition, and/or Tow Boat Acquisition
(Towed or self-propelled, type, size, quantity, useful
life, purchase, lease)
e. Contract Haul Considered
(Towing or complete operation.)
f. Manpower Requirements
g. Fuel Consumption
h. Facilities Required
(Loading, unloading, barge and tow-boat maintaenance,
fueling, docking, and wash-down, sludge storage
5. RAILROAD
a. Distance
b. Speed, Load-Limiting Factors, and Travel Time
(Clearance limitations, track conditions, traffic
schedule)
c. Operating Schedule
(Loading, haul, unloading and return times)
d. Car Selection and Acquisition
(Type, size, quantity, useful life, purchase, lease,
or railroad owned)
e. Fuel Consumption
f. Manpower Requirements
g. Facilities Required
(Loading, unloading, tank car maintenance, storage,
and cleaning, sludge storage, siding extensions.)
6. ENVIRONMENTAL IMPACT
(Air, land, surface water, groundwater, social, health,
economic, historical, archaelogical impacts, and environmen-
tally sensitive areas.)
7. REGULATIONS AND STANDARDS
a. Surface Water Protection
b. Sludge Loading and Unloading
c. Construction Within Navigable Waterways
d. Building Codes
e. Reporting Spills
f. Permits
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C. LAND APPLICATION
1. SLUDGE CHARACTERISTICS
a. Type of Processing at Treatment Plant _
b. Quantity: Maximum, Average, Minimum
c. Analysis
(Concentration, particle characteristics, volatile, content
nitrogen, phosphorus, potassium, heavy metals, pathogen
content, pH
2. TYPE
a. Crop Utilization _
(Crop(s) chosen, tillage requirements, application/
crop growth timing, application method.)
b. Dedicated Disposal _
(Application method, tillage requirement.)
c. Land Reclamation _
(Present condition of site, soil-sludge reactions,
application methods, tillage, requirements)
3. SITE CHARACTERISTICS
a. Topography _
(Limitations on application methods, erosion potential,
crop compatibility.)
b. Runoff Control
(From adjacent areas, on-site, storm flow added to liquid
sludge quantity, cut-off trenches, embankments for runoff
diversion.)
c. Soil _
(Soil Conservation Service soil maps; soil profiles:
Location, physical properties, pH, CEC, heavy metals.)
d. Geohydrology _
(Map of geologic formations and discontinuities;
groundwater: location, extent, use.)
4. DESIGN CRITERIA
a. Climatic Factors
(Rainfall: quantity, duration, seasonal variation; wind
velocity and direction, temperature variation)
b. Loading Rates
(1) Metals _
(Background level in soil, cation exchange capacity
limits, projected from industrial changes or pre-
treatment programs.)
(2) Nitrogen _
(Forms of nitrogen present, mineralization rate.)
c. Crops
(1) Nutrient uptake
(Nitrogen, phosphorus, potassium, micronutrients.)
(2) Compatibility With Applications
(Tillage requirements, timing of planting and harvesting,
can application be made on growing crop, forage, have
leaves been washed by rain or irrigation.)
(3) Harvesting requirement
(Single harvest each year, multiple harvest each
year, continual or intermittent harvest (grazing).)
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5. SYSTEM COMPONENTS
a. Dewatering
(Percent solids achieved, chemicals used)
b. Field Equipment
(Compatibility with crops, compatibility with sludge,
moisture content, compatibility with climatic factors.)
c. Storage
(Open, or covered; capacity to match non-operating
periods, nuisance condition prevention methods.)
d. Buffer Zones
(Size, vegetation provided, fencing.)
6. MONITORING
a. Land
(pH, pathogens, available nutrients, heavy metals.)
b. Crops
(Yield, tissue analysis, disease control.)
c. Water Quality
(BOD, suspended solids, nutrients, coliforms, etc.)
7. RELIABILITY AND FLEXIBILITY
(Expandability, storage, alternate sludge management
techniques.)
D. LANDFILL
1. SLUDGE CHARACTERISTICS
a. Type of Processing at Treatment Plant
b. Quantity: Maximum, Average, Minimum
c. Analysis
(Concentration, particle characteristics, volatile
content, nitrogen, inorganic ions, pathogen content, toxic
organic compounds, pH.)
2. REGULATIONS AND STANDARDS
(Sludge stabilization, sludge loading rates, frequency
and depth of cover, distances to road, residences and
surface water, monitoring, roads, building codes, permits.)
3. SITE CHARACTERISTICS
a. Site Plan
b. Soils
(Depth, texture, structure, bulk density, porosity,
permeability, moisture, ease of excavation, stability,
pH, cation exchange capacity.)
c. Geohydrology
(Groundwater: Location, extent, use, geologic formations,
discontinuities, surface outcrops.)
d. Climate
(Precipitation, evaportranspiration, temperatures,
number of freezing days, wind direction.)
e. Land Use
(Present, final, adjacent property.)
4. LANDFILL TYPE
a. Sludge Only Trench Fill
(1) Narrow trench
(2) Wide trench
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b. Sludge Only Area Fill
(1) Mound
(2) Layer
(3) Diked contaminent
c. Co-Disposal With Refuse
(1) Sludge-refuse mixture
(2) Sludge-soil mixture
5. LANDFILL DESIGNS
a. Trench or Area Dimensions
(1) Length
(2) Width
(3) Depth
b. Berm Dimensions
c. Trench or Area Spacing
d. Sludge Depth
e. Intermediate Cover Depth
f. Final Cover Depth
g. Bulking Agent
h. Bulking Ratio
i. Soil Importation
6. FACILITIES
a. Leachate Controls
(Adequate surface drainage, natural attenuation,
soil liners, membrane liners, collection and treatment.)
b. Gas Control
(Permeable methods, impermeable methods, gas extraction.)
c. Roads
d. Soil Stockpiles
e. Inclement Weather Areas
f. Minor Facilities
(Structures, utilities, fencing, lighting, washbacks,
monitoring wells, landscaping, equipment fueling,
storage and maintenance)
7. LANDFILL EQUIPMENT
(Excavation, sludge handling, backfilling, grading, road
construction.)
8. MANPOWER REQUIREMENTS
9. FLEXIBILITY AND RELIABILITY
(Expansion potential, modification for change in sludge
volume or type, equipment failure locally, storage.)
10. ENVIRONMENTAL IMPACTS
(Air, land, surface water, groundwater, social, health,
economic, historical, archeological impacts, and
environmentally sensitive areas.)
E. COMBUSTION
1. SLUDGE CHARACTERISTICS
a. Type of Processing at Treatment Plant
b. Quantity: Maximum, Average, Minimum
c. Analysis
(Moisture, heat value, nitrogen, sulfur, heavy
metals, toxic organic compound.)
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2. REGULATIONS AND STANDARDS
a. Air Quality Requirements
(Particulates, opacity, oxides of nitrogen, sulfur
dioxide, carbon monoxide, heavy metals, toxic organic
compounds, hydrocarbons and carbonyls, odors.)
b. Permits
3. MULTIPLE HEARTH INCINERATION OR PYROLYSIS
a. Operating Schedule
b. Reactor Design
(1) Hearth loading rate
(2) Hearth area
(3) Number of hearths
(4) Reactor dimensions
(5) Rabble speed
(6) Rabble drive cooling air requirements
(7) Sludge feed system
c. Auxiliary Fuel System
(1) Start-up
(2) Continuous operation
(3) Standby
d. Combustion and Excess Air Requirements
(1) Incineration
(2) Pyrolysis
e. Incineration Ash Systems
(1) Handling
(a) Truck
(b) Slurry pipeline
(2) Disposal
(a) Landfill
(b) Lagoon
(c) Land application
(d) Off-site use by others
f. Pyrolysis Residue Systems
(1) Gas
(2) Tar
(3) Char
g. Air Quality Control
(1) Afterburners
(2) Scrubbers
(3) Electrostatic Precipitators
4. FLUIDIZED BED INCINERATION
a. Operating Schedule
b. Reactor Design
(1) Bed loading rate
(2) Bed area and diameter
(3) Reactor volume and height
(4) Sand bed volume
(5) Fluidizing air requirement
(6) Sludge feed system
c. Auxiliary Fuel Systems
(1) Start-up
(2) Continuous operation
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(3) Standby
d. Combustion and Excess Air Requirements
e. Incineration Ash Systems
(1) Handling
(2) Disposal
(Landfill, lagoon, land application, reuse off-site
by others)
f. Air Quality Control
(1) Afterburners
(2) Scrubbers
(3) Electrostatic precipitators
5. WET AIR OXIDATION
6. OTHER PROCESSES
a. Cyclonic Reactors
b. Electric Incinerators
c. Proprietary Process
7. CO-DISPOSAL
a. Refuse Disposal
b. Refuse Derived Fuel
8. AUXILIARY FUEL SELECTION
(Gas, oil, powdered coal, refuse derived fuel, electricity.)
9. RELIABILITY AND FLEXIBILITY
(Expandable facilities, multiple units, alternative
reduction and/or disposal methods, storage, standby power,
standby fuel.)
10. MASS BALANCE
a. Inputs
(Dry solids in sludge, moisture in sludge, air, auxiliary
fuel, make-up sand, and steam.)
b. Outputs
(Ash, combustible gas, tar, char, water, carbon dioxide,
carbon monoxide, sulfur dioxide, nitrogen, sand,
excess air.)
11. ENERGY BALANCE
a. Inputs
(Solids heat of combustion, and auxiliary fuel heat
of combustion, including after-burner.)
b. Outputs
(Latent heat of free moisture and moisture of combustion,
sensible heat of gases of combustion, excess air, and
moisture, sensible heat of ash, radiation, sensible heat
of shaft cooling air, recovered energy for other plant
other plant processes.)
12. ENERGY RECOVERY SYSTEMS
a. Shaft Cooling Air Recycle
b. Stack Gas Heat Exchange
c. Reactor Water Jacket
d. Wet Air Oxidation Effluent Heat Exchange
e. Pyrolysis Product Recovery
13. ENVIRONMENTAL IMPACTS
(Air, land, surface water, groundwater, social, health,
economic impacts.)
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F. SLUDGE FOR OFF-SITE USE BY OTHERS
1. SLUDGE CHARACTERISTICS
a. Type of Processing At Treatment Plant
b. Quantity: Maximum, Average, Minimum
c. Analysis
(Moisture, nitrogen, phosphorous, potassium,
heavy metals, toxic organic compound content,
pathogens, heat content.
2. COMPOSTING
a. Bulking Agents
(1) Finished compost
(2) Refuse
(3) Wood products wastes
(4) Other wastes
b. Sludge Receiving and Mixing
c. Windrow composting
(1) Windrow construction
(2) Windrow mixing and turning
d. Static Pile Composting
(1) Pile construction
(2) Aeration system
(3) Recycle of air for pile heating
e. Mechanical Composting Systems
f. Curing
g. Screening
h. Facilities
(Bulking agent storage area, curing area, screening,
packaging, equipment storage, maintenance, and
fueling areas, structures, utilities, fencing.)
i. Equipment
(1) Front end loader
(2) Windrow turner
(3) Aeration blowers and piping
(4) Mechanical composter
(5) Screens
(6) Dump trucks
3. DRYING
a. Drying Beds
(1) Surface area
(2) Sludge loading depth
(3) Base design
(4) Underdrain design
(5) Wall design
(6) Sludge removal
b. Drying Lagoons
(1) Surface area
(2) Lagoon depth
(3) Surface water control
(4) Berm design
(5) Decanting system
(6) Sludge removal
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c. Heat Drying
(1) Flash dryers
(Flash drying cycle, incineration cycle, effluent
gas cycle, product handling cycle.)
(2) Rotary kiln dryers
(Rotary kiln, sludge feed system, effluent gas
system, product handling system.)
(3) Air pollution control
(Scrubber, filters, electrostatic precipitators.)
(4) Auxiliary fuel
(Gas, oil, coal, dried sludge, electricity.)
4. COMPOSTING WITH REFUSE
(Refuse as a bulking agent or sludge as a nutrient source.)
5. NUTRIENT ENRICHMENT
6. PACKAGING
a. Pick Up By User
(User loads, utility loads.)
b. Bulk Delivery To User
(Truck, rail, barge.)
c. Bagged
(Sold at site, or sold through usual fertilizer
outlets.)
d. Instructions and Guidelines For Use
e. Brand Name
7. ENVIRONMENTAL IMPACTS
(Air, land, surface water, groundwater, social, health,
and economic impacts.)
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DESIGN AND SPECIFICATIONS
SUPPORTING COMMENTARY
Section A - AGREEMENT WITH FACILITIES PLAN
When reviewing the design plans and specifications, the evaluator must have a
clear understanding of the facility plan and its relationship to the design.
The design should conform as closely as possible to the facility plan. It is
often necessary or desirable, however, to deviate from the facility plan as the
project progresses. Deviation from the facility plan may be due to new infor-
mation or to changes in regulatory requirements. The design and specifications
package submitted for review should include a statement regarding agreement with
the facility plan with emphasis given to those areas where the design deviates
from the facility plan. When deviations from the facility plan are substantial, a
re-evaluation of the plan, in whole or part, may be required.
A.I. MODIFICATIONS
Modifications to facility plans are often necessary, and may be the result of
new information from pilot studies, detailed site investigations, or any one of
a number of other sources. Changes in regulations, policies, and project goals
between the time of facility plan preparation and the completion of design plans
and specifications may also necessitate revision of the facility plan. When the
facility plan is modified during the design process, the design engineer should
prepare a full explanation and justification of the changes. This explanation and
justification may take the form of a supplement to the facility plan or may be
submitted as supporting material with the design plans and specifications.
Any modification to the facility plan must be evaluated to assess its effect on
other criteria of the facility plan and on other treatment processes within the
overall wastewater treatment-sludge management system. Particular care should be
taken to insure that any effects on the wastewater treatment system are taken
into account.
A.2. CHANGES IN REGULATIONS AND POLICIES CONSIDERED
In preparing the design plans and specifications, the design engineer should
review the regulations and official policies relating to the sludge management
project to determine if any changes since the preparation of the facility plan
affect the design to the extent that modification of the facility plan is
required. This review should cover, as a minimum, federal, state and local laws
and regulations and local or regional land use plans.
Section B - SLUDGE TRANSPORT
Transport facilities must be designed to be compatible with the type and quan-
tity of sludge produced at the treatment plant. The degree of processing prior
to disposal will also affect the design of transport facilities. The mode of
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transport must be appropriate for the type of sludge and the ultimate disposal
method. Local conditions and environmental features may play an important role
in the design of sludge transport facilities and the selection of equipment.
B.I. SLUDGE CHARACTERISTICS
B.I.a. Quantity; Maximum, Average, Minimum
The quantity of sludge produced will determine the size of transport facilities.
If equalization is included, the average quantity produced by the final unit
process (dewatering, incineration, etc.) will be the determining factor in trans-
port sizing; if not the peak quantity should be used. Staged items may be appro-
priate depending on the method of transport since some equipment is permanent and
other equipment has a short service life.
B.l.b. Solids Content
The solids content is important in the design of auxiliary equipment as well as
the details of the transfer equipment. It may be necessary to dilute very thick
sludge for pipeline transport.
B.I.e. Odor Potential
Odorous or highly putrescible sludge can be a nuisance, particularly in cases
where the transport distances or the transit times are long. Delays in trans-
port of partially stabilized or conditioned sludge can create significant,
highly objectional odor problems.
B.2. PIPELINE
Design of pipelines for transport of 0-4 percent sludge solids is essentially the
same as for water or sewerage facilities(16). The key factors in pipeline design
and providing adequate appurtenant facilities are described in the following
sections.
B.2.a. Alternate Routes Considered
Preliminary design is used to reduce the number of potential pipeline routes.
Generally, one route will be clearly favorable over the others, however, due to
unknown or hidden conditions, a certain amount of flexibility should be main-
tained until final design is begun. Crossings can add significantly to the cost
of the pipeline and to the complexity of construction
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B.2.b. Distance
The length of the sludge pipeline can have a significant bearing on costs of the
pipeline itself, on the pump station costs, and on the annual O&M costs. Sludge
pipelines can be feasible for relatively short distances (approximately 5 miles)
up to fairly long distances (100 miles).
B.2.c. Elevation Changes
In order to protect the pipeline from air binding due to entrapped air or from
collapse due to vacuums which develop when pumps are stopped, air and vacuum
relief valves should be provided at critical high points in the line.
B.2.d. Operating Program
A comparison use of constant versus variable speed pumps is important in deter-
mining the design flow through the pipeline. Variable speed pumps allow for con-
tinuous operation and lower storage requirements. Constant speed pumping will
require more storage, for peak flow dampening by equalization, but is usually
more efficient. The maximum and minimum velocities are an important consideration
in pipeline design. For sludge transport 3 fps is a satisfactory value (16);
slower rates can promote solids settling and decomposition, while higher rates
cause scouring and increase head loss. Since pipelines represent a significant
investment and have long service lives, they should be sized to permit efficient
operation under existing conditions yet provide adequate capacity for future
growth.
B.2.e. Pipe Selection
Sludge pipelines are generally cement-lined cast-iron or ductile iron pipe.
Friction losses should be minimized since they can contribute significantly to
the pumping requirements. Abrupt changes in slope and direction should be mini-
mized as they introduce headless for in excess of the loss through straight
pipe. Depending on the nature of the sludge and the characteristics of the soil,
corrosion-control features should be incorporated in the pipeline design.
B.2.f. Pumping Facilities
More than one pump station may be needed if the piping distance is long. The
number of pump stations should be balanced with the size and number of pumps
required for the most cost effective combination. Pumps should be appropriate for
the type of sludge to be pumped and standby units must be provided.
B.2.g. Pipeline Cleaning Provisions
Pigging facilities, or an appropriate alternative, should be provided to allow
for cleaning the sludge pipelines on a regular basis.
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B.2.h. Emergency Operation
Storage for several days should be provided in case of equipment failure. Diges-
ters can be used for this purpose if available. Standby power should be provided
if there are not two independent sources of electricity to the pump stations.
Additional storage may be substituted for standby power under certain conditions,
although continuous operation is preferable.
B.2.J. Excavation Conditions Verified
Field tests should be used to establish or verify the subsurface soil condi-
tions. Borings should be taken after the pipeline route has been established but
prior to final design. The report should be used to isolate areas where special
design considerations are needed. If highly unusual localized conditions exist,
they should be avoided, if possible, or additional field tests made.
Existing or other planned underground utilities should be located and field ver-
ified if possible. If exact locations cannot be established, the contractor may
be held responsible for locating them during design.
B.2.J. Methods of Right-of-Way Acquisition
Rights-of-way must be acquired for all pipelines. This process should be init-
iated in the early stages of the project. The preferable method is to obtain
access rights on easements owned or controlled by other utilities or to negotiate
with landowners. Condemnation is a lengthy, complex procedure which should be
used only after all other methods fail.
B.3. TRUCKS
B.3.a. Alternate Routes Considered
It is often the case that several possible truck routes exist. The advantages and
disadvantages of these must be examined before the final route is established. An
alternative route should be planned to insure uninterrupted transport of sludge.
B.3.b. Haul Distance, Speed and Travel Time
The haul distance should be minimized to reduce travel time and the potential
for accidents enroute to the disposal site. Topographic features may influence
routing such that the shortest haul distance is not the most favorable. The prac-
tical limit is about 10 to 20 miles one-way, although in some special cases,
hauls of up to 80 miles may be cost-effective.
Effective speed and travel time can be estimated from the haul instance, allow-
able speed of various segments of the route and the anticipated traffic condi-
tions. In scheduling sludge hauling, activities during the day may affect the
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travel time; periods of heavy traffic should be avoided both from a safety
standpoint and for efficiency of operation.
B.3.C. Compatibility of Proposed Route with Existing Road and Traffic
The existing conditions must be considered 'in the evaluation of truck transport.
Physical constraints such as weight, height and speed limits may preclude truck
transport and will definitely influence vehicle and route selection. Local traf-
fic congestion and traffic controls will not only influence routing but should
also be considered in determining the transport operation schedule. Public
opinion on the use of local roadway, particularly residential streets may have a
significant effect on truck transport operation.
B.3.d. Operating Schedule
An operating program must be outlined to insure efficient operation and adequacy
of facilities. Realistic estimates of loading, unloading and round-trip haul
times should be made. Daily maintenance of the trucks and other facilities must
also be included in the working schedule. The trade-offs between longer working
hours and more hauling equipment should be considered when scheduling sludge
hauling.
B.3.e. Fuel Consumption
Fuel availability and costs can have a profound impact on the future of sludge
hauling activities. Larger trucks tend to be more fuel efficient than smaller
ones. Also, short haul distances over flat terrain will have lower fuel require-
ments than long distances and hills.
B.3.f. Manpower Requirements
Manpower requirements can be determined from the operating schedule. Truck
drivers and mechanics as well as loading and unloading personnel will be
required for an efficient sludge hauling operation (16).
B.3.g. Truck Selection and Acquisition
Truck selection is based on sludge type and quantity. The size, type and number
of trucks must be specified. The useful life and long-term maintenance require-
ments of the vehicles should be considered in the selection of sludge transport
trucks (16).
The trade-offs between purchase and lease should be evaluated before the method
of acquisition is determined.
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B.3.h. Contract Haul Considered
For small plants in particular, the possibility of contracting for periodic
sludge hauling may be feasible. If such a program is undertaken, a contract and
guarantee of reliable service will be required.
B.3.J. Facilities Required
Plant-site loading facilities should be accessible and in a convenient location.
Depending on the type of sludge being hauled, hoppers or pipelines will be
needed to load the trucks. Unloading is generally by gravity, either at a trans-
fer station or directly on the land application site. Vehicle storage and a main-
tenance/repair shop should be located at the plant site. Washdown equipment and
parking should be nearby.
Sludge storage facilities will be needed at the plant site. The capacity of these
facilities will be influenced by the sludge unit processes and the reliability of
the transfer system.
B.4. BARGE
The characteristics of a barge transport system are described in the following
sections. These have been generalized and may not pertain to all barging
operations.
B.4.a Haul Distance
The haul distance is an important parameter since it affects several aspects of
operation.
B.4.b. Barge Speed and Travel Time
In planning a barge transport system, speed factors can play an important role.
The traffic on the waterway; physical features, such as drawbridges, locks and
height limitations; and natural characteristics such as currents and tides will
all affect the speed of barge operation. Certain delays may be hard to judge,
therefore travel time estimates should include a conservative safety factor.
B.4.c. Operating Schedule
An operating schedule should be developed taking the loading, unloading and
round-trip travel times into consideration. This is critical when contracting for
towing service.
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B.4.d. Barge Selection, Acquisition and/or Tow Boat Acquisition
A major consideration in barge selection is the choice between towed or self-
propelled. Other factors such as the size and number are related to the plant
size and specific sludge processing system (16). The useful life of equipment
will have a significant influence of the overall economics of the transport
operation. The trade-offs between purchasing and leasing barges must be weighed.
The final selection will depend on the size of the barges, use demands and
service life. Depending on the frequency of barge towing, economics may favor
purchase over lease of a tow boat. This is likely not warranted except for
sizeable facilities with large quantities of sludge to be transported.
B.4.e. Contract Haul Considered
For moderate-sized operation, contract towing will most likely be the favored
method of barge transport. For small operations with intermittent transport
requirements, contracting for complete transport service may prove the most
practical, efficient and economical. Contractual agreements should clearly define
all services to be provided and include a barging schedule.
B.4.f. Manpower Requirements
The manpower requirements should be determined so that there is an adequate staff
of properly trained individuals to carry out the sludge transfer and transport
services.
B.4.g. Fuel Consumption
Unless self-propelled barges are used, the fuel use will be the responsibility
of the towing company. In general, larger barges are more fuel efficient than
smaller ones.
B.4.h. Facilities Required
Sludge loading and unloading will require pumping facilities and relatively
short pipeline. Maintenance, fueling and cleaning facilities should be located
near the loading dock. Storage requirements at the docking site will depend on
the amount of storage at the processing site and on the reliability of the
process and transport systems.
B.5. RAILROAD
Railroad transport is not common, therefore examples of existing systems are
scarce. The following general guidelines should be modified to fit the partic-
ulars of the proposed railroad transport system.
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B.5.a. Pis tance
The feasible haul distance for rail transport is dependent on the quantity of
sludge transported, the cost of transportation and the value of sludge at the
receiving end. Haul distance usually range from 50 to 150 miles.
B.5.b. Speed and Load-Limiting Factors and Travel Time
The speed of railroad transport will depend on the track conditions and traffic
schedule. The limits on loads will determine the size and type of cars to be
used. If the shipper is supplying cars, they will be required to meet the rail-
road's clearance limitations. The effective speed and travel time will depend on
the railroad's operating schedule. Realistic estimates of travel time will be
necessary to assess the suitability of the system for meeting transport needs.
B.5.C. Operating Schedule
An operating schedule based on loading time requirements and on the railroad's
required travel time should be outlined during design to insure adequate trans-
fer, transport and storage facilities.
B.5.d. Car Selection and Acquisition
The type, size and number of cars selected will depend on the type and quantity
of sludge being transported and on the transport distance. The useful life of the
cars and the frequency of maintenance will have an impact on the economics of the
operation.
Tank cars are ordinarily supplied by the shipper. If liquid sludge is to be
transported by rail, cars can either be purchased or leased from the manufac-
turer. Dump cars which would be needed for dewatered sludge are often owned by
the railroad and available on a rental or fee basis.
B.S.e. Fuel Consumption
Fuel supply will be the responsibility of the railroad. Costs will be included in
the transport charges.
B. 5.f. Manpower Requirements
Staff will be required for loading and unloading the railroad cars and for a
varying amount of maintenance, depending on type and ownership of the cars.
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B.5.g. Facilities Required
Railroad sidings will be necessary at both the treatment facility and the dis-
posal site. At the treatment plant, the siding could be designed in conjunction
with the chemical delivery facilities. Loading and unloading facilities will
depend on the type of sludge being transported and the ultimate disposal method.
Car maintenance storage and cleaning will depend on the type and ownership of the
cars.
B.6. ENVIRONMENTAL IMPACTS
The environmental impacts of the transport system should be clearly identified
and mitigating measures designed to lessen any negative impacts. A certain amount
of air pollution is associated with vehicular transport of sludge. Emission con-
trols will minimize this potential. The impact of transport facilities on land
use is minimal. Disruption from pipeline construction is short-term. Most routes
can be restored to near their original condition in a relatively short time. A
small amount of land will be dedicated to permanent use for transfer facilities.
The impact of this is usually minor due to the remote location of most facili-
ties. Of the methods available for sludge transport, barging has the greatest
potential for having adverse effects on surface water. Accidental sludge spills
which would cause surface water pollution should be guarded against. There is
little danger that a groundwater supply would be adversely impacted by sludge
transport.
Public acceptability of the transport method and route can have a profound
effects on system operation. Safety features are important, particularly in con-
gested areas where accidents are more likely to occur. The handling, transfer and
transport of sludge can represent a certain health hazard; however, with adequate
precautionary measures taken, this can be minimized. Sludge spills and the
resultant human contact can be a health problem if not quickly attended to.
The financial impacts of sludge transport should be fully analyzed. Possible
measures for reducing costs should be explored and implemented as practical. In
the long run, a comprehensive maintenance program will reduce the general
operating costs of the transport system and minimize unnecessary and expensive
emergencies. Local historical and archaeological sites of significance identified
in the facility plan should be protected. Care should be taken to minimize
disruption of environmentally sensitive areas identified in the facility plan and
to protect any endangered species in the vicinity. Such impacts are not usually
significant in predisturbed areas such as treatment plant sites or pipeline
rights-of-way.
B.7. REGULATIONS AND STANDARDS
The engineer must be cognizant of the regulations governing design and other
local, state and federal standards which must be met. These must be followed
throughout design and construction, and any conflicts resulting from overlapping
jurisdictions must be resolved.
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B.7.a. Surface Water Protection
Surface water quality must be maintained during construction and operation of
all facilities. Federal standards have been set in P.L.92-500 and its amendments;
local water quality standards may, however, be more rigorous and must be
followed.
B.7.b. Sludge Loading and Unloading
Certain local regulations may govern the methods used for sludge transfer.
Clean-up will be essential and there may be restrictions on the disposal of
spilled sludge.
B.7.c. Construction Within Navigable Waterways
There are strict regulations regarding construction in navigable waters. These
should be thoroughly examined during the preliminary stages of design. Often the
waters are multi-jurisdictional, therefore, more than one agency will be
approving plans and specifications and monitoring construction.
B.7.d. Building Codes
All local building codes and applicable employee health and safety requirements
must be met by new construction projects. In addition, it may be required that
existing facilities being modified comply fully to current codes.
B.7.e. Reporting Spills
Depending on local and state regulations, the reporting of sludge spills may be
required. This is particularly important if such spills result in the violation
of surface discharge regulations. The operating agency should be informed of the
procedures for filing such a report.
B.7.f. Permits
All necessary permits for field studies, construction and operation should be
identified early in the design stages. Procurement procedures should be initiated
in sufficient time so that progress is not delayed because of the lack of proper
permits and approvals.
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Section C - LAND APPLICATION
C.I SLUDGE CHARACTERISTICS
C.l.a. Type of Processing at Treatment Plant
Stabilization and dewatering processes impact the type of land application and
equipment used as different equipment is used for liquid and dewatered sludges.
C.l.b. Quantity: Maximum, Average, Minimum
The average sludge quantity is necessary to determine the land application area
requirements and in estimating the useful life of the site. Maximum quantities
are required to determine equipment and storage facility capacities and to
estimate daily operating schedules.
C. I.e. Analysis
The solids concentration affects the application equipment type and capacity.
Particle or physical characteristics impact the soil conditioning value of the
sludge. Volatile content is important for estimating the potential for developing
odors while being stored or surface applied. The importance of heavy metals, pH,
and nutrient content monitoring has been discussed in the facility planning
section.
C.2. TYPE
The types of systems included below are crop utilization, dedicated disposal and
land reclamation. Some areas may include a combination of two or three of these
types of systems. A typical design for crop utilization is presented in Appendix
A.
C.2.a. Crop Utilization
Crop utilization systems are designed to take advantage of the nutrient contents
as well as the soil conditioning properties of the sludge. In the facilities plan
a crop or crops were selected for utilization of sludge. These crops were
selected for either their cash value, nitrogen or phosphoruous utilization rate,
or their tolerance of heavy metals. This selection should be reviewed at the
beginning of the design phase and adjusted if necessary. Along with the crop
selection, individual tillage requirments should be determined. Grain crops such
as corn require annual tillage. Other crops such as forages require tillage only
when a new stand is desired (several years). The significance of determining
tillage requirements is for costs and coordination with application operations so
sludge incorporation can be completed simultaneously. In the case of a forage
crop, incorporation is not possible except by an injector system. Therefore,
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applications on forage crops will usually be by surface systems unless an injec-
tion system can be used. The design should specify the application cycle in
detail. Some crops such as forages can receive applications during the growth
phase with a rest period just prior to harvest or grazing by animals. The rest
period time depends on the frequency of rainfall or irrigation.
Liquid sludge is applied by spraying from a modified irrigation system, spraying
from a truck, injection by tractor-towed system, injection by a truck mounted
system or by a surface irrigation type system such as ridge and furrow or
flooding. Dewatered sludge is usually applied by trucks with moving beds and
spreading mechanisms or conventional agricultural manure spreaders.
C.2.b. Dedicated Disposal
Land application for disposal or dedicated disposal systems are similar to crop
utilization systems except application rates exceed agronomic rates. Crops will
not always grow well in these conditions and are generally not of major impor-
tance to system design. Application methods and tillage requirements are similar
to those described above.
C.2.c. Land Reclamation
Land reclamation systems may be designed for future agricultural use, park land,
residential development or commercial use. The design of the reclamation project
will depend on the future use and conditions of land being reclaimed. If the
site's future planned use is agricultural or residential, then heavy metal addi-
tions are a factor to be observed (Part I, Section F.6). Nitrate contamination of
groundwater should be avoided. Surface application of dewatered-stabilized sludge
can be left without incorporation allowing more of the ammonia to volatilize
rather than nitrify, thus allowing somewhat higher application rates. The cumula-
tive contaminant levels should be monitored if the site is to be used for
agriculture, residential development, or parks.
The site should be analyzed to determine whether the soil is in poor condition
due to natural causes or as a result of strip mining or some other man-made
activity. Naturally occurring poor soils usually require more organic material
and nutrients. Disturbed soils resulting from mining activities usually have low
pH values and higher than normal concentrations of trace elements or heavy
metals. Each site analysis should include these items. The analyses should also
consider potential reactions of constituents in the ludge with constituents in
the soil. The same application methods can be used for reclamation projects as
used for crop utilization projects. Tillage requirements are the same as the
other systems except possibly where loading rates are significantly higher than
agronomic rates. In some instances deep plowing may be necessary instead of
disking.
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C 3. SITE CHARACTERISTICS
C.3.a. Topography
Extremely hilly areas may limit application equipment operation. Proper design
should include slope determination to check if the application method will be
operable. Site ground slopes should be determined and reviewed to develop erosion
control practices. Even row crops such as corn may not be feasible on certain
soils with high slopes. This problem can be minimized somewhat by contour
planting or terracing.
C.3.b. Runoff Control
The design should include runoff control facilities containing or rerouting run-
off from adjacent areas. These facilities may consist of small basins where run-
off can be contained and allowed to percolate or evaporate. Another option would
be to place a ditch along the affected area in order to route runoff elsewhere. A
third option provides for use of existing drainways. The design should allow for
buffer areas between application areas and drainways in order to minimize the
possible contamination of drainage water. Provisions made for control of run off
from liquid sludge applications should be designed for an emergency situation.
Generally, if the system is being properly operated there should be no runoff
created by liquid in the sludge. Runoff resulting from rainfall on the applica-
tion site must be contained or controlled so that this runoff does not contam-
inate nearby surface water.
C.3.c. Soil
The soil characteristics at the proposed land application site should be typed
and mapped. The pH and cation exchange capacity should be determined for each
soil type. As discussed earlier these parameters impact the movement and possible
plant uptake of heavy metals. Other parameters that are important to design are
water intake rate, permeability, heavy metal concentrations, and texture.
C.3.d. Geohydrology
The groundwater aquifers underlying the land application site need to be delin-
eated. The depth of the aquifer under varying conditions should be determined at
several locations. Other characteristics such as the direction and rate of flow,
the hydraulic gradient, the quality, and present and planned uses should also be
established. The location of the primary recharge zones is critical in protecting
quality.
The geologic formations underlying the land application site are important in
establishing the design parameters. The type of bedrock; its depth, fractures,
and surface outcroppings; and any faults are critical design factors.
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C.4. DESIGN CRITERIA
C.4.a. Climate Factors
In order to determine application equipment sizing the designer should have
included an estimate of the number of days when operations are not possible due
to rainfall. Twenty-year records are preferred for analysis of rainfall data
concerning agricultural operations. Wind velocity and direction is important in
minimizing movement of aerosols and development of buffer areas to minimize the
possibility of aerosols reaching neighboring property. This is a concern with
spray type systems. Temperature variation is critical mainly with surface
application during freezing weather when the ground is frozen or covered with
snow. Unless special procedures are taken to avoid water pollution problems,
surface application should be halted during these periods.
C.4.b. Loading Rates
C.4.b.(l) Metals - Design of crop utilization or reclamation systems should
include a determination to prevent possible heavy metal buildup. The design
should include the following items: background level of heavy metals (Pb, Zn,
Cu, Ni, Cd); soil cation exchange capacity limits (see Table 9)
C.4.b.(2) Nitrogen - Crop utilization systems should include a determination of
nitrogen forms present and an estimate of the mineralization rate. Additionally,
the designer should have specified a procedure for confirming the actual mineral-
ization rate (see Table 8 and Appendix A).
C.4.c. Crops
C.4.c.(l) Nutrient Uptake - The crop or crops chosen should be listed along with
nitrogen, phosphorus, potassium, and micronutrient requirements for each. The
table used for planning purposes should have been reviewed with the local farm
advisor to see if local conditions will cause variations in the recommended
quantities. (See Table 8 for typical values).
C.4.c.(2) Compatibility with Applications - Different crops are harvested in
different ways at different times of the year. Land application systems must be
designed with this in mind. Tillage requirements for incorporating surface
applied sludge would interfer with growing a forage crop. Application schedules
must be timed so as not to interfer with planting and harvesting. Each crop
should be reviewed to determine if application can be made on the growing crop.
C.4.c.(3) Harvesting Requirement - Critical to both the application procedures
and harvest operations is the timing and frequency of harvest. Some crops are
harvested once a year with the plant removed completely or destroyed. Forage
crops such as alfalfa are harvested several times a year with the plant base and
root system left intact.
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C.5. SYSTEM COMPONENTS
Within the treatment plant there are system components which impact application
procedures or methods. These are discussed in the following sections. The design
reviewer should be sure that the designer has developed compatible systems
throughout (e.g. dewatered sludge can't be injected).
C.S.a. Dewatering
Dewatering designs or systems should be reviewed to determine percent solids
achieved or expected and the chemicals used. Solids content will impact trans-
port and application methods and costs.
C.5.b. Field Equipment
Field equipment should be designed to be compatible with crops. Any type of
application equipment can be used for annual crops if the application is accom-
plished between harvest and planting. Spray injection systems are limited with
forage crops. Also capacities must be designed for the expected number of days
each year when application can actually take place. The field equipment design
should be compatible with the moisture content of the sludge. Variation in mois-
ture content can limit the type of equipment and impact costs of alternative
types of equipment. Equipment should also be designed to acclimate to field con-
ditions caused by climatic conditions. High flotation tires or tracked vehicles
are often necessary to insure mobility.
C.5.c. Storage
Lagoon or pond storage systems are very economical to construct and maintain.
The reviewer should analyze designs of these systems for adequate embankment pro-
tection. Covered storage is less common than open storage due to the higher cost.
Covered storage or tank storage is preferred when storage areas are near residen-
tial areas. There are several potential nuisance conditions. They are odors,
insect breeding, excessive weed growths on embankments, or vector breeding. Pre-
ventive methods should be included in the design. These include chemical addition
facilities or aeration for odor control and proper design of embankment slopes
and liquid depths to minimize the others.
C.5.d. Buffer Zones
Buffer zone size should be justified in the design. Applicable regulatory agency
requirements should be reviewed. Spray systems require the largest buffer area
(especially in windy areas) and injection systems the least. The designer should
provide rationale for selection of the type of vegetation in the buffer zone. The
type depends on the needs of the buffer area. Examples are shrubs for aesthetics,
grass for erosion control, and trees for wind breaks. Fencing requirements depend
on the surrounding land use. If the site is rural with privately owned land then
a simple animal detainment fence may be sufficient. In an area near public acces-
sible lands a chain link fence may be necessary.
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C.6. MONITORING
C. 6.a. Land
Soils monitoring may include pH, CEC, nitrogen, phosphorus, potassium, and heavy
metals (Cd, Cu, Zn, Pb, Ni). The nutrient analyses are useful for good crop
growth and for preventing excessive amounts of nitrogen or phosphorus in
suceeding applications or for determining additional nutrient needs. Potassium is
not normally a problem but monitoring is necessary to determine additional needs
for good crop growth. The pH, CEC and metals determinations are useful for pre-
venting metals accumulations in soils or crops. Pathogen monitoring should be as
specified by the regulatory agency.
C.6.b. Crops
Crop monitoring should include yield, crop disease, and crop pest evaluations.
Tissue analysis may be required periodically for food-chain crops. Crops destined
for human consumption should be monitored for pathogens.
C.6.C. Water Quality
Surface waters and intermittent streams (when flowing) should be monitored as
required by the appropriate regulatory agencies. Monitoring points should include
at least one sampling station upstream of the application area and one downstream
from the application area. Frequencies depend on circumstances of each site.
Minimum parameters include 8005, suspended solids, nutrients, and coliforms.
Nearby domestic wells should be tested prior to project startup and then moni-
tored periodically. On-site monitoring wells should be placed and sampled as
required by the appropriate regulatory agency. At a minimum, tests should include
nitrates, total dissolved solids and coliforms.
C.7. RELIABILITY AND FLEXIBILITY
Reliability is normally provided by extra storage facilities. Some systems may
have standby equipment and/or a good spare parts inventory. Designs should iden-
tify potential application areas for future expansion, and operational flexi-
bility. Flexibility may be attained by converting a crop growing area to a dis-
posal area or switching to a different type of crop. This may allow greater
loading rates. The design should consider this option. The decision for deter-
mining the proper amount of standby equipment should be justified in the design.
Standby tractor or trucks can be very costly and may not be necessary if the
right spare parts inventory is maintained.
Section D - LANDFILL
The design of a sludge landfill depends on many interrelated factors. These will
be addressed in the following sections. For more detail regarding these areas,
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the evaluator is referred to Process Design Manual for Municipal Sludge Landfills
(34). An example landfill design calculation is given in Appendix B.
D.I. SLUDGE CHARACTERISTICS
The first step in landfill design is to clearly define certain sludge
characteristics.
D.l.a. Type of Processing at Treatment Plant
Stabilization and dewatering processes effect the type oflandfill and the daily
quantity of sludge that can be accepted.
D.1.b. Quantity; Maximum, Average, Minimum
The sludge quantity is necessary in establishing the landfill area requirements
and in estimating the useful life of the site. The average quantity will prove
most useful for this purpose. Maximum sludge quantities will be needed to size
equipment and storage facilities and for determining daily operating schedules.
D.I.e. Analysis
The solids content or concentration of sludge is related to the nature of waste-
water treatment and to the sludge processing steps. The type and operation of
dewatering equipment has, perhaps, the most significant effect on the sludge con-
centration. A certain degree of flexibility should be incorporated in the design
of landfills to compensate for the variability in dewatered sludge. Volatile
solids content of the sludge determines the gas produced and the long term volume
reduction of solids. Typically the volatile portion of sludge ranges from 30 to
80 percent. Gas is generated at 16 to 18 ft-^/lb volatile solids destroyed(34).
Almost all the volatile solids will eventually be destroyed. The nitrogen found
in sludge represents a potential source of groundwater pollution. The total
quantity of nitrogen as well as the species present are of importance. Nitrate
is the principal species of concern and is relatively mobile in soil. It is con-
servative to assume that all of the nitrogen forms present will eventually be
oxidized to nitrate. Inorganic ions such as heavy metals are found in most munic-
ipal sludge. These can be leached if soil and sludge are acidic. If near neutral
conditions can be maintained, the metals will not be as readily leached from the
sludge. Most sludge treatment processes reduce the number of pathogens and the
possibility of pathogenic contamination associated with sludge landfilling (34),
but do not provide a sterile product. Toxic organic compounds can present a
potential contamination problem. These should be identified and dealt with
according to their nature and the disposal methods employed.
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D.2. REGULATIONS AND STANDARDS
Consideration must be given to requirements governing the degree of sludge sta-
bilization, the loading rates, the frequency and depth of cover, monitoring and
reporting. The design should conform to all building codes and should include
adequate buffer zones to protect public roads, private structures and surface
waters.
Obtaining permits for construction and operation of sludge landfills can be a
long and costly process. The following is a partial list of the permits which may
be required:
• NPDES permit-if landfill is in wetlands
• Army Corps of Engineers permit-for construction of levee, dike or con-
tainment structure to be placed in the water in a wetlands area
• Office of Endangered Species permit-if landfill is located in critical
habitual of an endangered species
• Solid Waste Management permit
• Special Use permit
• Sedimentation Control permit
• NPDES permit-if landfill is in wetlands
• Army Corps of Engineers permit-for construction of levee, dike or con-
tainment structure to be placed in the water in a wetlands area
• Office of Endangered Species permit-if landfill is located in critical
habitual of an endangered species
• Solid Waste Management permit
• Special Use permit
• Sedimentation Control permit
• Highway Department permit
• Construction permit
• Building permit
D.3. SITE CHARACTERISTICS
The definition of site characteristics is essential to the design of the land-
fill. These should be clearly described and analyzed to insure the suitability of
the site and the method of landfilling.
D.3.a Site Plan
The site plan should contain the following information as a minimum:
• Boundaries of fill area and buffer zones
• Topographic features and slopes of fill area and buffer zones
• Location of surface water, roads, and utilities
• Existing and proposed structures and access roads
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• Existing vegetation to remain and to be removed; areas to be
re-vegetated.
D.3.b. Soils
The soil characteristics at the landfill site should be thoroughly catalogued
and mapped. The information of most importance to the design and operation of the
landfill includes depth, texture, structure, bulk density, porosity, permea-
bility, moisture, stability, and ease of excavation. The pH and cation capacity
have a direct bearing on heavy metal transport through the soil; these must be
considered to insure protection of surface and groundwater supplies.
D.3.c. Geohydrology
The groundwater aquifers underlying the landfill site need to be delineated.
The depth of the aquifer under varying conditions should be determined at sev-
eral locations. Other characteristics such as the direction and rate of flow, the
hydraulic gradient, the quality, and present and planned uses should also be
established. The location of the primary recharge zones is critical in protecting
quality.
The geologic formations underlying the landfill are important in establishing the
design parameters. The type of bedrock; its depth, fractures, and surface
outcroppings; and any faults are critical design features.
D.3.d. Climate
The climate influences many factors in the design of landfills. It plays a part
in the rate of organic decomposition, the composition and quantity of leachate
and runoff and the day-to-day fill operations. Information such as seasonal
temperature, precipitation, evapotranspiration, number of freezing days, and wind
direction and speed can be obtained from a local weather station.
D.3.e. Land Use
The present and proposed use of the landfill site and adjacent properties will
have a decisive influence on the mitigating measures taken to reduce any adverse
impacts of the project. If the site is already dedicated to refuse or sludge dis-
posal it is unlikely that expanding it will result in adverse impacts. However,
if it is located in or near a populated area, extensive measures may be needed to
justify the proposed use and maintain the value of adjacent properties.
D.4. LANDFILL TYPE
There are three basic types of landfill for sludge. These are sludge only trench
fill, sludge only-area fill and co-disposal with refuse. The conditions for which
each are best suited are given in Table 11.
133
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D.5. LANDFILL DESIGN
Typical design criteria for the three methods of landfill disposal are given in
Table 12.
D.6. FACILITIES
Various ancillary facilities will be needed at the landfill site. These are
described in the following sections. It should be noted that all of these may not
be needed at every site.
D.6.a. Leachate Controls
Leachate from the landfill must be contained and disposed of if it poses a
threat to public health or represents a potential source of water pollution.
Numerous methods are available for controlling leachate including drainage,
natural attenuation, soil or membrane liners, or collection and treatment. The
method chosen and the design features are specific for each project.
D.6.b. Gas Control
Gas produced by the decomposition of organic matter can present a potential
danger, particularly if the landfill is located near a populated area. Methane
gas, in particular, is highly explosive if confined in an enclosed area.
Some method for venting the gases produced at the landfill must be provided.
The two types widely accepted are the permeable and impermeable. Permeable
methods usually consist of a gravel filled trench around the fill area to inter-
cept migrating gas and vent it to the atmosphere. Impermeable methods consist of
placing a barrier of low permeability material, such as compacted clay, around
the fill area to minimize lateral movement of gas. In general, methane recovery
is not economically cost-effective at sludge only or small co-disposal sites.
Additional information dealing with the design of gas controls is presented in
reference 34.
D.6.C. Roads
Access and on-site roads are necessary at the landfill site. Access roads and
permanent on-site roads should be paved; temporary roads may be constructed of
well compacted natural soil. For loaded vehicles uphill grades should be less
than 7 percent and downhill grades less than 10 percent. Radii should be suitable
for the trucks which are to use the roads.
135
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D.6.d. Soil Stockpiles
If insufficient or inappropriate soil at the landfill site warrants importation
of soil, a storage place should be located on-site. The quantity and type of soil
to be stockpiled will depend on the individual demands of the landfill. Stock-
piles nay also be desirable for winter operations in cold climates where frozen
ground may limit excavation of cover or bulking materials.
D.6.e. Inclement Weather Areas
Special work areas should be provided so that landfilling operations may be con-
tinued even during inclement weather. It is most convenient to locate these near
the entrance to the site and to provide paved or all-weather roads around them.
D.6.f. Minor Facilities
An office and other employee facilities should be provided at the landfill site.
For larger operations a permanent structure should be provided, while at smaller
sites a trailer might suffice. An equipment barn and shop may be desirable in
areas where weather is inclement.
Larger landfills should have electrical, water, communication and sanitary ser-
vices; for remote facilities, this may mean extending existing utilities. Chem-
ical toilets, bottled water and on-site electrical generation may reduce the cost
of obtaining services from the utility companies.
To protect the landfill site and the general public, the site should be fenced.
Access should be limited to one or two entrances secured with gates. The height
and type of fence provided should be chosen to suit local conditions. A 6-ft
chain link fence topped with barbed wire will restrict trespassers; a wood fence
or hedge is effective in screening the operation from view; and a 4-ft barbed
wire fence will keep livestock from the site. Portable lighting is effective if
landfill operations are carried out at night. Permanent lights should be provided
for all structures and heavily used access roads. A cleaning program will be
necessary for equipment in frequent contact with sludge. A curbed wash pad and
collection basin should be provided to contain the contaminated wash water so
that it can be treated. Groundwater monitoring is crucial and should not be over-
looked. The number, type and location of monitoring wells must be suited to the
specific conditions associated with the landfill. Depending on the size and loca-
tion of the landfill, landscaping may be an important design factor. The aes-
thetic acceptability of the landfill is critical if it is in or near an urban or
densely populated area. In general, plants should be low maintenance types which
will quickly become an effective visual barrier.
Depending on the size and location of the landfill, on-site equipment facilities
may be warranted.
137
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D.7. LANDFILL EQUIPMENT
A wide variety of equipment is required for a sludge landfill. The type of equip-
ment depends on the landfill method employed and on the quantity of sludge to be
disposed of. Equipment will be needed for sludge handling, excavation, back-
filling, grading and road construction. Table 13 presents typical equipment
performance characteristics for various methods of sludge landfilling.
D.8. MANPOWER REQUIREMENTS
For effective operation, landfill operations must be staffed by well-trained,
qualified personnel. Typical positions include equipment operators, a superin-
tendent/foreman/supervisor, mechanics and laborers. The size of the staff will
depend on the type of landfill and the operating schedule.
D.9. FLEXIBILITY AND RELIABILITY
Due to the possibility of changes in sludge characteristics and quantities, a
landfill site should be designed with a maximum degree of flexibility. Since the
life of a landfill is difficult to predict accurately expansion may be needed
sooner than originally planned or it be delayed for various reasons. Any change
in wastewater treatment or sludge handling may affect the nature and quantity of
sludge produced. If this is drastic, operational modifications may be needed.
The landfill should be designed so that such changes can be made without major
disruption to operations.
Reliability is also an important factor in designing a landfill operation. Con-
tinunity of operation should not be stopped because of inclement weather unless
absolutely necessary. In such cases, special work areas and storage facilities
should be available. Adequate back-up equipment should be available on-site or
nearby for emergency operations or unexpected equipment failures.
D.10. ENVIRONMENTAL IMPACTS
The specific areas of environmental impact will vary among landfill locations.
However, crucial impact areas normally include land use; air, surface water and
groundwater quality; social, health and economics; historical and archaeological
sites and habitats of endangered species. Adverse impacts should be mitigated by
the measures suggested in the facilities plan. These mitigating measures should
be definitive and included as features of the design.
Section E - COMBUSTION
Combustion systems are usually designed with the close cooperation and assist-
ance of one or more manufacturer of combustion equipment. Most design criteria
and procedures available relate specifically to one manufacturer of the type of
equipment in question. The similarities between manufacturers are such that
138
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generalities can be drawn which will aid the evaluator in determining the reason-
ableness of a particular design.
E.I. SLUDGE CHARACTERISTICS
The characteristics of the sludge which have the greatest impact on the design
of combustion systems are the quantity, moisture content, and heat value. Other
characteristics which will have an effect on the potential for air pollution are
the nitrogen, sulfur, heavy metals (lead and mercury) and toxic organic
compounds.
E.I.a. Type of Processing at Treatment Plant
The type of prior processing at the plant will determine the sludge character-
istics to the combustion process. The stabilization process, if any, will
influence the volatile solids/heat content. The dewatering process will determine
the solids content of the sludge. If pressure filters or vacuum filters are used
for dewatering large quantities of non-volatile inorganic chemicals may be added.
The design of the prior processing deserves as much consideration as the design
of the combustion process. Any failure of the prior processing to provide the
design sludge characteristics will also cause failure of the combustion process.
E.l.b. Quantity; Maximum, Average, Minimum
The quantity of sludge produced will determine size of the combustion process
equipment. Typically, the combustion process will not be designed for peak sludge
production, but for some quantity between peak and average production, with
storage provided to make up the difference. A portion of this storage may be in
the sludge process unit processes. Care must be taken that any septic conditions
which may occur in sludge storage are adequately considered. Sludge quantity
estimates must take into account the mass of chemicals added in the conditioning
and dewatering processes.
E.l.c. Analysis
The sludge solids and heat content will, together with sludge quantities, deter-
mine the size and fuel and air requirements of the combustion process. The solids
and heat contents should be experimentally determined, whenever possible, but
where necessary there have been several formulae, with varying accuracies,
developed for heat content estimates (10, 12, 13). In making heat content esti-
mates, the masses and heats of the reactions of the conditioning chemicals must
be considered.
Sulfur affects the heat content of the sludge, and is also important in
determining the sludge's potential for air pollution. Additional possible air
pollutants are heavy metals, especially mercury and lead, and persistent toxic
organic compounds such as pesticides and polychlorinated biphenyls.
140
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E.2. REGULATIONS AND STANDARDS
Federal, state and local air quality requirements must be met by the combustion
process design. Permits and standards relating to ash disposal will be discussed
under the sections for the respective disposal methods.
E.2.a. Air Quality Requirements
The federal "New Source Performance Standards for Sewage Sludge Incinerators"
(64) establishes the following limitations for particulate emissions:
1. No more than 0.65 g/kg dry sludge input 1.30 Ib/ton dry sludge input
2. Less than 20 percent opacity, except where opacity is due to uncombined
water
The EPA has also established a limitation of 3,200 g/day for mercury emissions
in the Amendments to the National Emission Standards (47).
If PCS's exceed 25 mg/kg dry sludge, 95 percent destruction must be assured by
the design of the incinerators. Additional regulations are being developed under
the Toxic Substances Control Act (63) and the Resource Conservation and Recovery
Act (2) which should be consulted in designing the sludge incineration system.
Many states, regional authorities, and local governments have established emis-
sion limitations more stringent than the federal regulations. In addition to more
restrictive particulate, opacity, mercury, and PCB requirements, other limita-
tions may be imposed on emissions, such as:
Oxides of nitrogen
Sulfur dioxide
Carbon monoxide
Heavy metals, especially lead
Persistent organic compounds, such as pesticides
Hydrocarbons and carbonyls
In general, a properly designed and operated sludge combustion process will have
little difficulty in meeting emission standards.
E.2.b. Permits
All appropriate federal, state, regional and local permits, licenses and approv-
als should have been identified and obtained or applied for by the time of
design review. The ambient air standards in the vicinity of the combustion sytem
must also be considered.
141
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E.3. MULTIPLE HEARTH INCINERATION OR PYROLYSIS
A description of these processes is given in Part I, Section H.I.
E.3.a. Operating Schedule
The operating schedule will affect the sizing of all components after the final
sludge storage tank. Eight-hour-a-day, five-day-a-week operations are possible
but not practical because they require three to four times the equipment of con-
tinuous operations and are also costly to maintain at operating temperature with
no sludge feed (67).
E.3.b. Reactor Design
In designing the reactor, the key parameter is hearth loading rate. Values of 6
to 12 Ibs/sq ft/hr on a total wet sludge basis (68) and 1.47 to 3.32 Ib/sq ft/hr
on dry solids basis (67). Table 14 illustrates several typical wet sludge loading
rates and Figure 12 is a plot of hearth area vs. design capacity on a dry solids
basis for several actual installations.
The number of hearths, reactor dimensions, and rabble speed will be established
from the incinerator manufacturer's data. Table 15 is a summary of the standard
furnace dimensions available from one of the major manufacturers. Current prac-
tice favors 5 to 12 hearths for sewage sludge incineration (67). In addition, the
heaviest wall thickness available is generally recommended (69).
Typical center shaft and rabble arm cooling air flows as function of wet sludge
flow for several operating incinerators are shown in Figure 13.
The sludge feed system should be designed for the maximum anticipated charging
rate and should include a sludge weighing or metering device. Where pyrolysis is
to be practiced, the sludge feed system should be designed to minimize the entry
of air through the charging port.
E.3.c. Auxiliary Fuel System
The auxiliary fuel requirements fall into three categories: start-up, continu-
ous operation and standby. The fuel supply system must have sufficient capacity
at the greatest of those three rates. Substantial quantities of auxiliary fuel
are always required to bring a multiple hearth furnace up to the required temper-
atures for sludge ignition. In addition, these heat-ups, and cool-downs, must be
at very slow rates, typically 20 to 25 F°/hr for large incinerators, 150 F°/hr
for very small incinerators, for temperature changes from 70°F to 1500°F. Figure
14 illustrates typical heat-up and standby fuel consumption rates as a function
of hearth area. The fuel consumption rate for continuous operation will be estab-
lished by the mass and energy balance calculations. Standby fuel is that fuel
required to maintain the furnace at a constant, slightly reduced, temperature
during periods in which no sludge is fed.
142
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TABLE 14. MULTIPLE HEARTH FURNACE LOADING RATES
Type
1.
2.
3.
4.
5.
of sludge
Primary
Primary + Fed
Primary + low lime
Primary + WAS
Primary + (WAS +
FeCl3)
Solids
%
30
16
35
16
20
Volatile
solids,
%
60
47
45
69
54
Chemical
concentration, *
mg/1
N/A
20
298
N/A
20
Typical
wet sludge
loading rate,**
Ib/hr/sq ft
7.0-12.0
6.0-10.0
8.0-12.0
6.0-10.0
6.5-11.0
6. (Primary + FeCl )
+ WAS 16
7. WAS 16
8. WAS + FeCl 16
9. Digested primary 30
53
80
50
43
20
N/A
20
N/A
6.0-10.0
6.0-10.0
6.0-10.0
7.0-12.0
* Assumes no dewatering chemicals.
** Low number is applicable to small plants, high number is applicable to
large plants.
The data in this table developed from manufacturers' information.
143
-------
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DESIGN (AVERAGE) DRY SOLIDS FLOW PER MULTIPLE HEARTH FURNACE, Ib/hr
Figure 12. Multiple hearth furnace hearth area vs. design capacity.
(from data in Reference 67)
144
-------
TABLE 15. TYPICAL SIZES OF MULTIPLE HEARTH FURNACE UNITS (67)
Effective
hearth
area,
sq ft
85
98
112
125
126
140
145
166
187
193
208
225
256
276
288
319
323
351
364
383
411
452
510
560
575
672
760
845
857
944
Outer
diameter,
ft
6.75
6.75
6.75
7.75
6.75
6.75
7.75
7.75
7.75
9.25
7.75
9.25
9.25
10.75
9.25
9.25
10.75
9.25
10.75
9.25
10.75
10.75
10.75
10.75
14.25
14.25
14.25
16.75
14.25
14.25
Number
hearths
6
7
8
6
9
10
7
8
9
6
10
7
8
6
9
10
7
11
8
12
9
10
11
12
6
7
8
6
9
10
Effective
hearth
area,
sq ft
988
1041
1068
1117
1128
1249
1260
1268
1400
1410
1483
1540
1580
1591
1660
1675
1752
1849
1875
1933
2060
2084
2090
2275
2350
2464
2600
2860
3120
Outer
diameter,
ft
16.75
14.25
18.75
16.75
14.25
18.75
16.75
20.25
16.75
18.75
20.25
16.75
22.25
18.75
20.25
16.75
18.75
22.25
20.25
18.75
20.25
22.25
18.75
20.25
22.25
20.25
22.25
22.25
22.25
Number
hearths
7
11
6
8
12
7
9
6
10
8
7
11
6
9
8
12
10
7
9
11
10
8
12
11
9
12
10
11
12
145
-------
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6000
o
(ft
O
Li-
z
o
o
s
o
o
cc
o
(3
O
o
o
4000
2000
•COOLING AIR
COMBUSTION AIR
(INCLUDING
EXCESS)
50
100
150
200
DESIGN (AVERAGE) WET SLUDGE FLOW PER MULTIPLE HEARTH FURNACE, Ib/hr
Figure 13. Multiple hearth air supply vs. design capacity.
(From data in reference 67)
146
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147
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E.3.d. Combustion and Excess Air Requirements
E.3.d.(l) Incineration - The exact combustion air requirement is determined
from the theoretical oxygen demand (THOD) of the sludge and auxiliary fuel. Air
is approximately 21 percent oxygen, so the actual air requirement would be (100/
21) (THOD). Operating experience has shown that excess air is required for
complete combustion, usually on the order of 75 to 200 percent of the theoretical
requirement. Assuming 100 percent excess air, then, the actual air requirement
would be (200/21)(THOD) . Figure 13 illustrates typical combustion air supplies as
a function of dry solids feed.
E.3.d.(2) Pyrolysis - True pyrolysis is fractional distillation where all heat
is applied externally to the reactor and no oxygen is introduced. Pyrolysis, as
proposed for multiple hearth reactors, is starved oxygen combustion, wherein a
portion of the pyrolysis products are burned within the reactor as the heat
source for the reaction.
E.3.e. Incineration Ash Systems
The design of incinerators must include adequate facilities for handling and dis-
posing of incinerator ash. Ash handling and disposal systems should be sized for
the maximum anticipated ash flow, or sufficient storage provided to permit lesser
capacities. The design of the ash handling and disposal systems should take into
account the potential for dust problems which ash disposal presents.
E.3.e.(l) Handling - Ash is usually transported by truck or by slurry pipeline
to the disposal site. The slurry operation is often combined with a quenching
operation to cool ash discharged from the incinerator. Dewatering requirements
should be considered for any ash transported in a slurry form, either by truck or
pipeline.
E.3.e.(2) Disposal - Ash is usually disposed of by landfilling or lagooning of
a slurry. Land application is technically feasible but is not being practiced as
it is not generally considered to offer any advantages. Ash has been used as an
amendment for road subgrades to improve freeze-thaw characteristics, as a
building material additive, and as a quasi-fertilizer for its phosphate content.
E.3.f. Pyrolysis Residue Systems
Where pyrolysis is practiced, the design of the combustion process must include
systems for handling and utilizing or disposing of residues. All of the residues
may have value as fuels, and if their use or sale is contemplated, the handling
system should maximize their recovery. Pyrolysis char is of dubious value as a
fuel, and may lend itself best to disposal by landfill. Handling systems and
utilization should take into account the corrosive natures of the gases and tars,
as well as their relatively low rank as fuels.
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E.3.g. Air Quality Control
After-burners are used for odor control, hydrocarbon and carbonyl destruction,
and for persistent toxic organic compound destruction. Scrubbers of various
types and electrostatic precipitators are used for particulate removal. The elec-
trostatic precipitator is more efficient, but is more costly. The design of air
quality control equipment should be based on the actual volume of gases expected
to pass through the stack at the actual stack exhaust temperature. Equipment
design should consider the corrosive nature of stack gases.
Wet Venturi scrubbers are the most common type. The stack gases are passed
through a reduced cross sectional area throat where the gas velocity is raised to
200 to 600 feet per second. Water spray is introduced into the throat from above.
The water droplets contact and adhere to particulates increasing their mass. This
caused the particles to move downward for collection in a gas liquid separator.
Typical pressure drops across a Venturi scrubber range from 20 to 30 inches of
water column and typical water consumption rates range from 5 to 10 gallons per
1000 cubic feet of stack gas.
E.4. FLUIDIZED BED
A typical fluidized bed incinerator is shown in Figure 5, and desribed in para-
graph H.I. of the facility planning section.
E.4.a. Operating Schedule
Because of the heat reservoir afforded by the sandbed, fluidized bed incinera-
tors are well suited to intermittent or batch operations. While the equipment
required for 8-hour, 5-day operations is three to four times that for continuous
operation, the fuel required to maintain the incinerator near operating tempera-
tures overnight is minimal.
E.4.b. Reactor Des ign
Fluidized bed reactor loading rates for sewage sludge are typically in the range
of 10 to 20 Ibs/hr/sf on a dry solids basis with 12.7 Ibs/hr/sf being the average
for eleven installations by one manufacturer (68). The bed area and diameter are
determined from the sludge flow and the loading rate. Figure 15 is a plot of
sludge loading rates vs. bed area for the installations of one manufacturer of
fluidized bed furnaces. Table 16 is a tabulation of typical loading rates on a
wet sludge basis.
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200
100
90
~ 80
<
LU
tt
60
50
40
30
20
10 12
14 16
CAPACITY, Ib/day dry solids
Figure 15. Fluidized bed, bed area vs. capacity.
(From data in reference 68)
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TABLE 16. FLUIDIZED BED FURNACE LOADING RATES
Type of sludge
Primary
Primary + FeCl3
Primary + low lime
Primary + WAS
Primary + WAS + FeCl3
Primary + FeCl3 + WAS
WAS
WAS + FeCl3
Digested primary
Solids,
%
30
16
35
16
20
16
16
16
30
Vol.
solids ,
%
60
47
45
69
54
53
80
50
43
Chemical
concentration,*
mg/1
N/A
20
298
N/A
20
20
N/A
20
N/A
Wet sludge
loading
rate,
Ib/sq ft/hr
14
6.8
18
6.8
8.4
6.8
6.8
6.8
14
*Assumes no dewatering chemicals.
The required reactor volume, and thus its height, are determined by the burning
rate and detention time needed for satisfactory combustion of gases. The exact
reactor dimensions would then be determined by consulting a manufacturer's table
of standard dimensions.
The sandbed acts as the heat transfer medium and also serves to hold organic par-
ticles until combustion is complete and to grind ash particles, preventing the
formation of clinkers. Fluidizing air is the air flow required to maintain the
sand in a fluid state without excess carry-over of sand in the exhaust gases.
Fluidizing air also supplies the combustion air. Air supplied to the reactor
increases heat losses. Preheating of fluidizing and combustion air can, however,
minimize those losses.
The sludge feed system should be designed for uniform distribution of sludge
over the top of the bed. Where the supply of air to the process must be limited
the sludge feed system should be designed to minimize the entry of air.
E.4.C. Auxiliary Fuel System
The design of the auxiliary fuel system should take into account the rate of
fuel consumption for start-up (and shut-down), continuous operation and standby
operation.
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E.4.d. Combustion and Excess Air Components
E.4.d.(l) Incineration - The exact combustion air requirement is determined
from the theoretical oxygen demand (THOD) of the sludge and auxiliary fuel. Air
is approximately 21 percent oxygen, so the actual air requirement would be (100/
21)(THOD). Operating experience has shown that excess air is required for com-
plete combustion, usually on the order of 20 to 60 percent of the theoretical
requirement. Assuming 50 percent excess air, then, the actual air requirement
would be (150/21KTHOD).
E.4.d.(2) Pyrolysis - Pyrolysis, as proposed for sewage sludge reactors, is
starved air combustion, wherein a portion of the pyrolysis products are burned
within the reactor as the heat source for the reaction. Air supply requirements
will be less than the theoretical oxygen demand. The exact air supply requirement
would be determined empirically for optimum performance. One possible design
approach would be to size the air supply system for incineration and provide
controls to permit cutting back the supply to the level required for pyrolysis.
E.4.e. Incineration Ash Systems
Ash handling and disposal systems should be sized for the maximum anticipated
ash flow, or sufficient storage provided to permit lesser capacities. All flui-
dized bed incinerator ash is carried from the reactor in the exhaust gases and
collected by the air pollution control equipment.
The details of ash handling systems for fluidized bed incineration are similar
to those for multiple hearth incineration which are discussed in paragraphs
E.3.e, E.3.e.(l) and E.3.e.(2).
E.4.f. Air Quality Control
After-burners are not generally required for fluidized bed reactors. Scrubbers of
various types and electrostatic precipitators are used for particulate removal,
with the electrostatic precipitator being more efficacious, but more capital
intensive. The design of air quality control equipment should be based on the
actual volume of gases expected to pass through the stack at the actual stack
exhaust temperature. Equipment design should consider the corrosive nature of
stack gases.
The design of the air pollution control system should take into account the fact
that all the ash from the process will be carried from the reactor in the exhaust
gases together with a quantity of fine sand particles from the incinerator bed.
E.5. WET AIR OXIDATION
The wet air oxidation process is described in Part 1, paragraph H.l.c.
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Wet air oxidation is a proprietary process and should be designed with the close
cooperation of the manufacturer. While no specific parameters are listed here,
the following components of the system must be considered in the design.
Sludge grinder
Sludge storage
Sludge pumping
Air compressor
Heat exchanger
Steam generator
Gas/liquid separator
Auxiliary fuel system
Air quality control
Residue treatment
Dewatering
Handling
Disposal
Liquor treatment
E.6. OTHER PROCESSES
There are several other processes, most of them proprietary, which have been
used or proposed for the combustion of sludge. While the discussions included
herein do not cover the design of these processes, the basic elements of their
design are similar to those for multiple hearth and fluidized bed reactors.
E.6.a. Cyclonic Reactors
Horizontal cyclonic reactors are described in paragraph H.I.a.(3) of the facility
planning section.
E.6.b. Electric Incinerators
Electric Incinerators are described in paragraph H.I.a.(3) of the facility
planning section.
E.6.C. Proprietary Pyrolysis
Proprietary pyrolysis processes are described in paragraph H.l.b. of the facility
planning section.
E. 7. CO-DISPOSAL
The co-combustion of sludge with solid waste generally takes one of two forms:
• Incineration or pyrolysis of sludge with the solid waste stream in a
solid waste incinerator
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• Use of shredded and classified solid waste as an auxiliary stream in a
sludge incinerator
The co-disposal facility design should take into account the different handling
equipment required for solid waste and wastewater sludge. For refuse derived
fuel systems shredding and classification equipment should be included in the
design. The use of unclassified solid waste could lead to a slag production as
well as increased ash production.
E.8. AUXILIARY FUEL SELECTION
The term auxiliary fuel means the source of additional heat required, above the
heat content of the sludge, to bring the incinerator to operating temperature,
to begin sludge burning, to maintain sludge burning for non-autogenous sludges,
to hold the incinerator at or near operating temperature during standby periods,
and to control incinerator cooling rates during shut-down. The auxiliary fuels
presently in use are:
Gases natural gas, propane, liquified petroleum gas
Fuel oils
Powdered coal
Refuse derived fuel
Electricity
Electricity is used as an auxiliary fuel only in electric incinerators, and will
not be discussed further.
The value of powdered coal and refuse derived fuel is strictly as a source of
additional heat for burning of non-autogenous sludges, and either a gas or fuel
oil system must be provided for the other auxiliary fuel functions. The use of
coal or refuse as auxiliary fuel should not be overlooked, however, because of
their potentially low cost per Btu. In addition, refuse and powdered coal may
have value as sludge conditioners, improving the yield of dewatering processes.
Gases and fuel oils are the most common auxiliary fuels, being usable for all
the auxiliary fuel requirements. If natural gas is elected as the auxiliary
fuel source, it may be an interruptible service, in which case measures should
be taken to protect the incinerator from damage from an uncontrolled shutdown.
This will most often take the form of a gas, such as propane, stored on the site
in at least sufficient quantity to control temperature changes during shut-down.
Additional qualities may be provided for some fixed period of continuous opera-
tion. Backup sources of fuel may be advisable for other types of gas or oil
supplies, depending on the circumstances.
E.9. RELIABILITY AND FLEXIBILITY
The combustion process must be designed with reliability, operating flexibility
and future design flexibility in mind. Facilities must be designed in accordance
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with the EPA Technical bulletin Design Criteria for Mechanical, Electric, - and
Fluid System and Component Reliability (58).
E.9.a. Expandable Facilities
When future increases in sludge production beyond the capacity of the equipment
installed are anticipated by the facility plan, the process should be designed
with expansion in mind. Provisions for future expansions may include space allo-
cations for future equipment, blind flanges for future piping corrections and
provisions for structural extensions.
E.9.b. Multiple Units
The provision of multiple process units can enhance a combustion system's reli-
ability by making it less vulnerable to complete shut-down due to mechanical
failure or routine maintenance.
E.9.c. Alternative Reduction and/or Disposal Methods
It may be necessary to provide an alternative means of disposing of sludge in
the event of a failure of the combustion process. A common example is providing a
means of loading unincinerated sludge into trucks for transportation to a land-
fill. The alternative disposal or combustion method should not be subject to
common mode failures with the principal method.
E.9.d. Storage
Storage is often used to provide both reliability and operating flexibility for
the sludge management system. Storage can permit scheduling of operations as
desired, can permit the system to be out of service for a predetermined period of
time, and can increase the effective capacity of the combustion system by
smoothing the sludge and solids flow rate variations.
E.9.e. Standby Power
Standby power should be provided when required to prevent damage to equipment or
to maintain operation. Examples of the former condition are multiple hearth fur-
nace shaft cooling air fans, which should always be provided with a standby
source of power.
E.9.f. Standby Fuel
Standby fuel supplies should be provided where required to prevent refractory
damage or to maintain continuous operation.
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E. 10. MASS BALANCE
The calculation of the expected flow of mass into and out of the combustion pro-
cess will aid in establishing its design parameters. The mass balance calculation
must be performed in conjunction with the energy balance discussed later in this
section. The mass of inputs to the combustion process must equal the mass of out-
puts. See Appendix C for sample calculation.
E.10.a. Inputs
See part H.2.a. in the facility planning section.
E.lO.b. Outputs
See part H.2.b. of the facility planning section.
E.ll. ENERGY BALANCE
The energy balance, together with the mass balance, provides the basic data for
establishing the design parameters of the combustion process. The total input and
output of the combustion process must be equal.
E.ll.a. Inputs
See part H.S.a. of the facility planning section.
E.ll.b. Outputs
See part H.S.b. of the facility planning section.
E.12. ENERGY RECOVERY SYSTEMS
If energy recovery is planned as a part of the combustion process, the energy
recovery system design should be closely coordinated with the combustion system
design. The design of energy recovery systems should take into account the
degree of reliability of the energy source. It may be necessary to provide back-
up energy sources for critical uses, such as digester heating. Where pyrolysis
products are to be used as energy sources on or off-site conditioning systems may
be required to make the product usable. Energy recovery systems will be of the
following types:
• Multiple hearth furnace center shaft cooling air recycle
• Stack gas heat exchange
• Reactor water jacket
• Wet air oxidation effluent heat exchanger
• Pyrolysis product recovery
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E.13. ENVIRONMENTAL IMPACTS
The design of the sludge combustion system should consider the impact on the
environment, minimizing any deleterious effects. Air impacts are minimized by
properly designed air pollution control equipment. Land, surface water, and
groundwater impacts are a function of the ultimate disposal systems and are
discussed under the appropriate sections. The social and health impacts are
closely tied to the air impacts and are minimized by designing for minimum air
pollution. The economic impact of the system design is related to the proper
design of the reactor, selection of the auxiliary fuel, and design of the energy
recovery systems.
Section F - SLUDGE FOR OFF-SITE USE BY OTHERS
Systems which process sludge for off-site use by others are of widely varying
types. The principle processes which produced usable products are:
• Drying
Flash drying
Drying beds
Drying lagoons
• Composting
Windrow composting
Static pile composting
• Combustion
Incineration ash
Wet air oxidation residue
Pyrolysis process residues
Combustion processes are discussed in detail in the preceeding section and will
not be discussed further herein, except to mention that many of the product
safety and packaging design features discussed also apply to combustion process
residues.
The processes discussed in this section are all intended to produce a sludge
product which is useful as a soil conditioner or fertilizer.
F.I. SLUDGE CHARACTERISTICS
The characteristics of the sludge which have the greatest impact on the design
of the sludge processing are moisture content and sludge flow. Nutrient (nitro-
gen, phosphorus, potassium) content will affect the values of the final product
as a fertilizer while heavy metal, toxic organic compound and pathogen contents
will affect its safety and the suitable markets.
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F.I.a. Type of Processing at Treatment Plant
The degree of stabilization may be specified by local regulatory agencies to pre-
vent potential health hazards. The degree of dewatering will determine the size
and type of processing facilities.
F.l.b. Quantity: Maximum, Average, Minimum
The quantity of sludge produced will determine the size of the processing units,
the amount of land required for lagoon, drying bed, and composting operations
and the quantity of bulking agent required for composting operations. Sludge
quantities must take into account chemicals added to the sludge in conditioning
and dewatering steps.
F.l.c. Analysis
The solids content of the sludge will be an important factor in sizing drying
processes, in determining bulking agent requirements for composting, and in
assessing the sludge's value as a supplemental solids source for solid waste com-
posting. Dewatered sludge moisture content of 20 percent are typical for sludge
to be composted, while sludge flow to drying beds and lagoons is typically
undewatered anaerobically digested sludge with a solids content of 2-6 percent.
Sludges to be heat dryed should be dewatered to the highest cost-effective solids
content, 20 percent being typical.
F.2. COMPOSTING
Composting processes are described in Part I.2.b. of the facility planning sec-
tion. Typical design criteria for composting operations are summarized in Table
17.
F.2.a. Bulking Agents
The dewatered sludge (typically 20 percent) solids is delivered to the site and
is usually mixed with a bulking agent. The purpose of the bulking agent is to
increase the porosity of the sludge to assure aerobic conditions during com-
posting. If the composting material is too dense or wet it may become anaerobic
thus producing odors; or if it is too porous the temperature of the material will
remain low. Low temperatures will delay the completion of composting and reduce
the kill of pathogens.
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TABLE 17. TYPICAL COMPOSTING DESIGN CRITERIA
Loading Rates
Dewatered sludge
Sludge - Bulking agent
Mix ratio
Bulking agent
Composting period
Curing period
Expected Performance
Compost production
Unscreened
Screened 1/2 inch
screen)
Minimum composting
temperature
Finished compost
Moisture content
Volatile solids
Bulking agent recovery
Sidestream (Runoff water)
20 to 25 percent solids 1 dry ton
solids is equal to approximately 7
cubic yards of dewatered sludge
2.5 to 3.0 parts bulking agent to 1
part dewatered sludge by volume
Requires 17 to 21 cubic yard per
dry ton of sludge.
14 to 21 days
30 days
26 cubic yard per dry ton sludge
7 to 9 cubic yard per dry ton sludge
55 to 60°C - Forced air static pile;
50 to 55°C - Windrow
40 to 50 percent
40 percent
Variable depending on type of agent,
degree of screening, but in range of
60 to 80 percent following screening.
Data are not available on runoff water characteristics except that
the quantity may vary from 6 to 20 gallons per day per pile containing 50
cubic yards of sludge during dry weather.
159
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Various bulking agents have been used and several typical agents are:
• Unscreened finished compost
• Shredded and classified solid waste
• Wood products wastes
Wood chips
Bark chips
• Other wastes
Rice hulls
Licorice roots
Peanut shells
Generally, one part sludge 20 percent solids is mixed with three parts bulking
agent although this mixture can be varied depending on solids content of sludge,
type of bulking agent, and local conditions.
F.2.b. Sludge Receiving and Mixing
The design of the sludge receiving and mixing area should include facilities for
sludge storage, bulking agent storage, a mixing area, and sufficient maneuvering
space for the mixing equipment. At very large plants mixing may be performed by a
composting auger, but the majority of facilities will use a front end loader.
Surface area requirements for sludge mixing piles are typically 30 to 60 square
feet per cubic yard of sludge to be mixed. To this must be added the area
required for sludge and bulking agent storage and equipment maneuvering. Mixing
pile dimensions should be suited to the mixing equipment to be used. Concrete
pads are typical.
F.2.C. Windrow
This method is described in Part I.2.b.(l) of the facility planning section.
For composting periods of 14 to 21 days areas of 500 to 1500 sq ft wet basins,
are required for each cubic yard per day wet sludge flow. Approximately 100 per-
cent additional area is required for maneuvering of equipment. In locations that
receive substantial rain, windrow areas should be paved to facilitate operation,
F.2.d. Static Pile
This process is described in Part I.2.b.(2) of the facility planning section.
Static piles typically require areas of 8 sq ft/cu yd of mixture or 28 to 33 sq
ft/cu yd of sludge. For composting periods of 14 to 21 days, area requirements
are 390 to 690 sq ft/cu yd/day on a wet sludge flow basis. Approximately 100 per-
cent additional area should be allowed for pile construction equipment maneuver-
ing and aeration equipment. Composting areas should be paved to facilitate
operation.
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F.2.e. Mechanical Systems
Mechanical systems are described in Part I.2.b.(3) of the facility planning
section.
Mechanical composting systems are proprietary and should be designed in close
cooperation with the equipment manufacturers.
F.2.f. Curing
Following composting, the product is removed from the windrow or static pile and
cured in storage piles for 30 days or longer. Curing may be performed before or
after screening. Curing piles should be as large as possible to minimize space
requirements. Heights of 10 feet and widths of 20 feet are the maximum dimensions
practical with a typical front end loader. Large operations with more sophisti-
cated equipment can build more space efficient curing piles. For 30 days curing
pile areas of 170 sq ft/cu yd of curing compost are typical. Approximately 100
percent additional space should be allowed for equipment maneuvering. Screening
of compost prior to curing can significantly reduce curing area requirements.
The curing area need not be paved for ease of handling, but should be accessible
for movement of the product to the screening or packing stage.
F.2.g. Screening
Compost is typically screened with a horizontal rotary type screen with 1/4 to
one inch openings. Vibratory screens have also been successful. Bulking agents
retained by the screen is recycled to the mixing stage. Screening may be per-
formed before or after curing.
F.2.h. Facilities
The bulking agent storage areas should be adjacent to the receiving and mixing
area and should be accessible for new bulking agent deliveries and movement of
recycled bulking agent from the screening area. Screening should not be conducted
during heavy rainfall or high wind in an uncovered area. Consideration should be
given to equipment parking, maintenance and fuel needs. Covered storage may be
advantageous. Maintenance will usually be performed off-site. On-site fueling
facilities should be provided for all but the smallest facilities. In addition to
possible covered equipment storage, a small building with office space, and a
locker room with showers should be provided. The building should also include a
lunch room, which may be combined with the office space. Fencing around the
entire site is advisable. Eight foot high chain link fences with three top
strands of barbed wire are usually satisfactory, although the fencing may be
reduced in areas where the potential for vandalism is low.
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F.2.I. Equipment
Table 18 lists the equipment requirements for typical windrow and forced air sta-
tic pile operations. Actual equipment requirements will vary widely with the
equipment available, the size of the operation, and possible alternate uses of
the equipment at other sites.
TABLE 18. COMPOSTING EQUIPMENT
Windrow
Forced air static pile
Specialized windrow turner
Dump truck (*)
Rubber tired front loader,
4 cu yd
Drum screen
Rubber tired front loader, 4 cu yd
Dump truck (*)
Aeration blower assemblies and pipe
Drum screen
Composting machine (**)
* Requirement will depend on site and operation
* May be helpful for mixing on larger applications
F.3. DRYING
F.3.a. Drying Beds
Drying beds are generally used for dewatering of well digested sludges.
Attempts to air dry raw sludge usually result in odor problems.
The drying of sludge on sand beds is accomplished by allowing water to drain
from the sludge mass through a base of supporting sand to drainage piping and
natural evaporation to the air. As the sludge dries, cracks develop in the sur-
face allowing evaporation to occur from the lower layers which accelerates the
drying process.
Drying beds are generally open to the weather but may be covered with ventilated
green-house type of enclosures where it is necessary to dewater sludge in wet or
cold climates.
Figure 16 is a cross-section of a typical sludge drying bed.
The required surface area for sludge drying beds is dependent on such climatic
factors as air temperature, relative humidity, amount and rate of precipitation,
percentage of sunshine, and wind velocity.
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SLUDGE
COLLECTION
SYSTEM A
DRAINAGE
-*-fJ—
SLAB
o° „ GRAVEL. o»
. • »0 t> 00 »~0»»0
I
Figure 16. Typical sludge drying bed construction.
163
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Table 19 is useful in evaluating the adequacy of the total surface area. Sludge
beds consist of perforated or open joint drainage pipe laid within a gravel base.
The gravel is covered with a layer of sand. Partitions around and between the
drying beds may be of concrete, wood or earthen embankment.
TABLE 19. DRYING BED LOADING RATES
Condition
Open beds
Covered beds
Primary digested sludge,
sq ft/cap
Primary and humus
digested sludge,
sq ft/cap
Primary and activated
digested sludge,
sq ft/cap
Primary and chemically
precipitated digested
sludge, sq ft/cap
Solids loading rate,
Ib/yr/sq ft
Moisture content of dried
sludge, percent
1.0 - 1.6
1.25 - 1.75
1.75 - 2.5
2.0 - 2.5
up to 25
50 - 60
0.75 - 1.0
1.0 - 1.25
1.25 - 1.5
1.25 - 1.5
up to 40
50 - 60
Table 20 is useful in evaluating sludge loading depth, base design, wall design
and underdrain design.
Many design variations are used for sludge drying beds including the layout of
the drainage piping, thickness and type of materials in the gravel and sand
layers, and construction materials used for the partitions. The major variation
is whether or not the beds are covered. Any covering structure must be well
ventilated. In the past, some beds were constructed with flat concrete bottoms
for drainage without pipes, but this construction has not been very
satisfactory.
Consideration must be given to sludge removal. Hand removal by shoveling sludge
into trucks is typical for small plants. Mechanical removal of sludge from drying
beds has been practiced for many years at some large treatment plants, but now it
is receiving more attention because of the need to minimize labor costs. Mechan-
ical devices can remove sludges of 20 to 30 percent solids while cakes of 30 to
40 percent are generally required for hand removal. Small utility tractors with
modified front end loaders are often used for removal.
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TABLE 20. DRYING BED DESIGN PARAMETERS
Design parameter Typical design values
Sludge depth, inches 8-12
Gravel layer depth, inches, 12 - 18
typically 3-inch layers
graded from coarse at
bottom to fine at top
Sand layer depth, inches, 6-12
typically 0.55 mm size
Drainage pipe spacing, 8-20
feet typically 6-inch
diameter
Typical module size, feet:
Length 20 - 100
Width 20 - 25
Most removal systems, either hand or mechanical, benefit by the provision of con-
crete treadways in the drying bed for mechanical equipment or trucks. Beds can
also be designed with flexible plastic drainage pipe to allow tractors with
floatation tires directly on the beds.
In some instances drainage of the sludge can be speeded up or increased by
adding chemicals. Where it is known that a sludge is relatively difficult to
dewater by mechanical methods, it will most likely be difficult to dewater by
sandbeds, drain poorly and dry slowly. Addition of conditioning chemical facili-
ties should be provided in these cases.
F.4.b. Drying Lagoons
Sludge is periodically drawn from a digester, placed in the lagoon, removed
after a period of drying, and the cycle repeated. Drying lagoons are not typi-
cally provided with an underdrain system as most of the drying is accomplished by
decanting supernatant liquor and by evaporation. Plastic or rubber fabrics may
be used as a bottom lining, or they may be natural earth basins. Supernatant
liquor and rainwater drain off points can be provided, with the drained off
liquid returned to the plant for further processing.
Table 21 presents some typical parameters for the design of drying lagoons.
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TABLE 21. DRYING LAGOON DESIGN PARAMETERS (7)
Design parameter Range of design values
Solids loading rate 2.2 - 2.4 Ib/yr/cu ft of lagoon capacity
Area required:
Examples:
Dry climate, primary sludge 1 sq ft/capita
Wet climate, activated sludge 3-4 sq ft/capita
Dike height 2 ft
Sludge depth after decanting 15 in
(depths of 2-4 ft have been
used in very warm climates)
Drying time for depth of 15 in 3-5 months
or less
The design of the drying lagoons must also include adequate provisions for
decanting the lagoon and for removal of sludge. Methods for decanting the lagoons
include overflow weirs, partially or completely along one end of the lagoons and
stand pipes. For shallow lagoons sludge can be removed by front end loader and
truck. Deep lagoons (>4' deep) may require a dragline or clamshell. Lagoons
should be ramped for equipment access and, if permanent, berms should be designed
to support the constant use of heavy equipment. Temporary berms can be rebuilt
after every use.
F.3.c. Heat Drying
Flash dryers and rotary kilns are sized on the basis of the solids loading rate
and heating requirements. The principles that apply are similar to those used in
designing sludge incinerators. Flash dryers and rotary kilns are usually avail-
able in several module sizes with sludge drying capacities typically ranging from
40 pounds per hour to 2,400 pounds per hour of sludge feed. The expected perfor-
mance from a flash dryer or rotary kiln is a dried sludge with a solids content
ranging from 90 to 98 percent. Heat dryers are usually designed with the close
cooperation of one or more manufacturer of drying equipment and specific design
factors such as loading rates are functions of the equipment used. There are two
basic types of heat dryers, flash dryers and rotary kilns.
F.3.c.(l) Flash Dryers - Before introduction into the flash dryer, the sludge
must undergo thickening and dewatering. The incoming dewatered sludge is blended
with a portion of the previously heat dried sludge in a mixer. (See Figure 9).
Hot gases from the furnace at approximately 1,200° to 1,300°F (650° to 700°C)
then are mixed with the blended sludge before drying in the cage mill. Agitation
in the cage or jet mill dries the sludge to approximately 2 to 10 percent mois-
ture and reduces the temperature to approximately 300°F (150°C) before cyclone
separation of the solids from the gases. A portion of the dried solids are
recycled to the mill and the rest are stored for use or incinerated. The gases
from the cyclone separators are conveyed by the vapor fan to the deodorization
preheater in the furnace where the temperature is raised to approximately 1,200°
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to 1,400°F (650° to 760°C). The deodorized gases release a portion of the heat to
the incoming gases and release more heat in the combustion air preheater. The
temperature is reduced to approximately 500°F (260°C) before the gas is scrubbed
for particulate removal and conveyed to the stack by the induced draft fan. If
the dried solids are not used in the furnace as a fuel, then auxiliary fuel such
as gas, oil, or coal is necessary.
The design of flash drying systems must take into account the following major
subsystems:
• Flash drying cycle
Wet sludge conveyor
Sludge dry product mixer
Cage or jet mill
Cyclone
• Incineration cycle
Combustion air fan
Furnace
Combustion air preheater
• Effluent gas cycle
Deoderizing air preheater
Combustion air preheater
Dust collector
Induced draft fan
• Product handling cycle
Dry product conveying
Product storage
Product loading or packaging
Dust control must be given careful consideration in flash drying systems. The
product is a light, finely divided, combustible, abrasive material which presents
serious safety, maintenance, and housekeeping problems if not properly con-
trolled. When mixed with air the dust can be highly explosive and when inhaled
could aggravate respiratory problems. The dust is a major cause of mechanical
equipment failures at existing plants due to its action on bearings and other
moving parts. Adequate measures must be included in the project design to reduce
airborne dust to a minimum and to prevent conditions conducive to explosions.
F.3.c.(2)_ Rotary Kiln Dryers - Rotary kiln dryers are described in Part
I.2.a.(3)(b) of the facility planning section.
The design should consider the following major components of the system:
• Rotary kiln
• Sludge feed system
• Effluent gas system
• Product handling system
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While dust is not as severe a problem as with flash dryers, its control must be
considered in the project design.
F.3.c.(3) Air Pollution Control - Heat drying in general, produces an exhaust
that contains unacceptable quantities of air pollutants. Therefore, the system
design usually includes equipment necessary to reduce the emissions to acceptable
levels. This may require particulate collection efficiencies as high as 96 to 97
percent. Air pollution control requirements for heat drying are very similar to
those for sludge incineration and the reduction section of this manual shall be
consulted. In addition to cyclonic and wet scrubber and electrostatic precipita-
tors, dust filters are sometimes used for heat drying systems.
F.3.c.(4) Auxiliary Fuel - Substantial quantities of auxiliary fuel are
required for heat drying systems. The fuels most often used are:
• Gas
• Oil
• Coal
• Dried sludge
Gas, oil, and coal are used for cage mill flash dryers. Dried sludge is also
sometimes used, but an additional supply of gas or oil must be provided for sys-
tem startup and sludge ignition in that event. Gas and oil are suitable fuels for
both jet mill flash dryers and rotary kilns.
F.4. COMPOSTING WITH REFUSE
Co-composting of sludge with refuse generally falls into one of two categories:
• Use of refuse as a bulking agent in sludge composting
• Use of sludge as a nutrient and moisture source in solid waste
composting
The design of co-composting systems must take into account the differing require-
ments for sludge and solid waste composting.
F.4.a. Refuse As a Bulking Agent
Sewage sludge has too high a moisture content for successful windrow or static
pile construction without the aid of a bulking agent. The cellulose (paper and
some garbage) fraction of solid waste may offer a suitable and economical bulk-
ing agent. Design of systems for using refuse as a bulking agent should include
adequate shredding and classifying facilities. If the product is to be screened
with a finer screen that the typical shredded refuse partical size, classifi-
cation facilities may be unnecessary.
F.4.b. Sludge As a Nutrient Source
Solid waste generally requires supplemental nitrogen and moisture for successful
composting. Sewage sludge has been suggested as an economical source of the
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additional nitrogen (54). Composting facilities to use sludge for supplemental
nitrogen should provide facilities for distributing sludge and mixing it with the
solid waste. It should be recognized that sludge generally has a higher pathogen
content than solid waste, and great care must be taken in its handling.
F.5. NUTRIENT ENRICHMENT
It may prove cost-effective to increase the market value of the sludge product
by nutrient enrichment. While nitrogen and phosphorus (phosphoric acid) contents
can be increased with a subsequent increase in value, the greatest nutrient
shortcoming of most sewage sludge products is the potassium (potash) content.
Nutrient enrichment processes may be part of the sludge management system or they
may be practiced by fertilizer processors who purchase the unenriched product
from the wastewater agency.
Nutrient enrichment is a fertilizer manufacturing process and the design of
nutrient enrichment facilities should involve the close cooperation of a pro-
ducer or producers of fertilizer manufacturing equipment.
F.6. PACKAGING
The project design must provide facilities for some combination of product pack-
aging, loading, and transportation. The design of these systems will depend
heavily on the end use of the product.
F.6.a. Pick-up By User
By far the most common system of delivering sludge for off-site use by others is
to allow or encourage individuals to pick up lagoon or bed dried sludge at the
treatment plant. In this event, provisions should be made to avoid disrupting
other plant operations. Sludge may be loaded by the user or by utility personnel.
If it is planned for the user to remove dried sludge directly from drying beds,
provisions should be included in the design to prevent damage to sand layers and
underdrain systems caused by untrained personnel removing sludge from bed. The
same concept is sometimes applied to larger deliveries, with user owned trucks
loaded with sludge during regularly scheduled drying bed or lagoon cleanings.
_F._6.b._ __ Bulk_ Delivery to User
Sludge products are often delivered in bulk to the users. Trucks, railroads and
barges have been used. The section on sludge transport has more information on
the design of sludge transportation facilities.
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F.6.c. Bagged
Bagging facilities should be designed in close cooperation with manufacturers of
suitable bagging equipment. If the bagged product is to be sold on-site a sepa-
rate covered storage and marketing area should be provided and located so as to
avoid interference with other plant operations.
If the bagged product is to be sold off-site suitable loading and transportation
facilities must be provided.
F.6.d. Instructions and Guidelines for Use
Each bulk pick-up or delivery and each bag of sludge should be accompanied by
detailed instructions and guidelines for use, explaining the following:
• The exact nature of the material
• The guaranteed nutrient analysis
• Any limitation on its use, such as application to food chain crops
• Other suggestions and pointers on its use
In the case of bagged product, it is usually convenient to print the suggestions
and guidelines directly on the bag.
F.6.e. Brand Name
The selected brand name should be prominently displayed on bags and instruction
sheets, and in other appropriate ways.
F.7. ENVIRONMENTAL IMPACTS
The design of the sludge processing system should minimize any deleterious envi-
ronmental impacts.
The only system considered which has a significant impact on air quality is heat
drying. Air impacts, especially airborne dust can be minimized by adequately
designed emission control equipment and by including dust control measures in the
project design. The impacts of the system on the land are a function of the pro-
duct quality. Impacts are both positive, improved moisture holding character-
istics and nutrient levels, and negative, heavy metals, toxic organics, an patho-
gens. In most cases, the wide dispersion of the sludge product will minimize
deleterious effects. Adequate warning should accompany any product, indicating
recommendations for restricted use when distributed to the public. Runoff from
drying beds, drying lagoons, and composting operations can affect surface water
quality if not collected and treated. Provisions should be made in the project
design for collecting and treating the runoff. In most cases this will be by
returning the runoff to the wastewater treatment process, although separate
treatment facilities may sometimes be more cost-effective. Surface water impacts
due to product use will generally be minimal due to the wide dispersion of the
product. Groundwater impacts of sludge processing systems are due to infiltration
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composting operations. Groundwater impacts from product use are generally mini-
mal, but may be significant in exceptional cases. Infiltration and percolation
can be minimized by proper design of sludge lagoons, including impermeable liners
when necessary.
Social impacts of all sludge processing systems include odors and noise. Odors
are a particular problem with lagoons and drying beds and are best minimized by
only drying well stabilized sludges. Composting operations present potential odor
and noise problems. Odors can be reduced by proper composting procedures. In sta-
tic pile composting the provision of a small deodorizing pile of finished compost
on the blower discharge has been found helpful. Heat drying systems may require
deodorizing burners or heaters to control odors from volatile hydrocarbons vapor-
izing in the process.
The safety of the product is a primary concern in sludge processing systems.
While little can be done within the processing system to control heavy metals
and toxic organics contents, the system must provide adequate pathogen reduction
for the end use. Lagoon and drying bed sludges may require disinfection. Properly
operated composting and heat drying operations will generally provide adequate
pathogen reduction. Control of disease vectors, such as flys, mosquitos, and
rodents, must be given adequate consideration. Flys are a problem with all sludge
processing systems, but particularly with sludge drying beds.
Mosquitoes are best controlled by design of the site grading so that potential
breeding spots, such as standing pools of water, are eliminated.
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PART III
OPERATION AND
MAINTENANCE MANUAL
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OPERATIONS AND MAINTENANCE MANUAL
INTRODUCTION
The operation and maintenance manual is the key to a successful sludge manage-
ment system. An inadequate manual can doom the best planned and designed system
to failure, while a good manual can enable the plant personnel to operate and
maintain the plant at an optimum effectiveness level. The operation and mainte-
nance manual should be prepared in accordance with Considerations for Preparation
of Operation and Maintenance Manuals (70). The design concepts should be clearly
explained and procedures for operating and maintaining the facilities must be
delineated. The manual is intended to be a guide for the operators of the treat-
ment facilities and will help to ensure that they understand the key design
features and the objectives for which the system was designed. The manual should
include maintenance schedules, monitoring programs, and recommendations for man-
power utilization. Additionally, potential problem areas, symptoms of process
malfunction, and methods of control of adverse impacts should be described.
Special considerations, such as agricultural practices for land application sys-
tems, should also be included.
The format of this checklist has been selected to enable the reviewer to enter a
checkmark or comment to the right of each item. There are 5 major categories:
A. Sludge Transport
B. Land Application
C. Landfill
D. Combustion
E. Sludge Products for Off-Site Use by Others
Within each category are numerous sub-elements. Consideration of one or two of
the major categories may be required for a particular review.
It is not necessary to include all the sub-elements. Only those concerned with
the operation and maintenance of the selected sludge management system should be
considered.
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OPERATION AND MAINTENANCE MANUAL
CHECKLIST
A. SLUDGE TRANSPORT
1. PIPELINE
2. TRUCK
a. Description of Equipment
(Number and type of trucks, capacity of trucks.)
b. Description of Facilities
(Loading, unloading, washdown, fueling, and maintenance)
c. Normal Operation
(Operating schedule: Loading, time, travel time, unloading
time, return time, fueling and daily maintenance time;
route: normal and alternate; loading and unloading
procedures)
d. Emergency Procedures
(Vehicle breakdown, sludge spill)
e. Vehicle Safety Rules
f. Impact Control
(Environmental: air pollution, health disease vector
control; Social: Noise, odor, traffic.)
g. Personnel
3. BARGE
a. Description of Equipment
(Number and type of barges, capacity of barges.)
b. Description of Towing Arrangements
(Tow contractor, operating hours, haul distance and route,
barges per tow.)
c. Description of Facilities
(Loading, unloading, washdown and maintenance.)
d. Normal operation
(Operating schedule: loading time, travel time, unloading
time, return time; route: loading procedures, unloading
procedures.)
e. Emergency Procedures
(Tow vessel breakdown, sludge spill.)
f. Safety
g. Impact Control
(Environmental: air pollution, surface water pollution;
health: disease vector control; social: noise, odor.)
h. Personnel
4. RAILROAD
a. Description of Equipment
(Number and type of cars, capacity, ownership)
b. Description of Facilities
(Loading, unloading, washdown and maintenance.)
c. Description of Haul Contract
(Pick-up and set-out points and times)
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d. Normal Operation
(Operating schedule: loading time, haul time, unloading
time, return time; loading procedures, unloading procedures,
pick-up and set-out procedures, moving cars on-site.)
e. Safety
f. Impact Control
(Environmental: air pollution; health: disease vector
control; social: noise, odor.)
g. Personnel
B. LAND APPLICATION
1. PERMITS AND STANDARDS
a. Solid Waste Disposal _
(Permit number, renewal date, if applicable, permit
requirements, permit application guidelines, applicable
Federal/State laws and agency regulations.)
b. Discharge Permits for Runoff and Leachate
(Permit number, renewal date, if applicable, permit
requirements, permit application guidelines, Federal/State
laws and agency regulations.)
c. Crop marketing
2. APPLICATION EQUIPMENT
a. Description of Equipment
(Number and type of application vehicles and capacities.)
b. Description of Facilities
(Washdown, fueling, maintenance, records and
administration.)
c. Startup Procedures
(Equipment check, application schedule for the day.)
d. Normal Operation
(Field pattern, log sheet, applicator speed.)
e. Shutdown
(Equipment cleanup, completion and filing of log.)
f. Emergency Procedures
(Vehicle breakdown, sludge spills, injector clogging.)
g. Safety - Vehicle Safety Rules
h. Impact Control
(Environmental: soil pH, etc.; health: disease vectors;
social: odor, noise )
i. Personnel
(Number, qualifications or training required)
3. FARM MANAGEMENT
a. Description of Equipment
(Tillage equipment, harvest equipment, other equipment.)
b. Description of Facilities
(Maintenance shops, crop storage, seed storage.)
c. Crop Management
(Crops grown, rotation schedule, consultants used,
custom harvesting contracts.)
d. Contingency Procedures
(Equipment breakdown, crop problem identification
[e.g. disease].)
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e. Emergency Procedures
(Unacceptable increase in heavy metals or a toxic element,
extreme or unusual weather conditions)
f. Personnel
(Number, qualifications.)
4. MONITORING
a. Parameters to be Measured
b. Procedures
c. How to Use Results
d. Reporting Procedures
C. LANDFILL
1. PERMITS AND STANDARDS
a. Solid Waste Disposal
(Permit number, renewal date, if applicable, permit
requirements, permit application guidelines, Federal/State
laws and agency regulations pertaining to sanitary landfills.)
b. Discharge Permits For Runoff and Leachate
(Permit number, renewal date, if applicable, permit
requirements, permit application guidelines, Federal/State
laws and agency regulations.)
c. Reporting Procedure for Spills of Raw or Inadequately
Treated Wastewater
(Federal/State laws and/or agency regulations requiring
reporting of bypass/spill conditions; owner's responsi-
bilities, penalties; reporting procedure including telephone
numbers and sample report format.)
d. Water Quality Standards
(Runoff receiving stream, adjacent streams where there is
a potential of a spill, state stream classification system.)
2. DESCRIPTION OF LANDFILL
a. Definition of Sanitary Landfill
b. Design Criteria
(Trench fill or berm dimensions, cover dimensions,
site life.)
c. Description of Site
d. Generalized Description of Operations
3. RELATIONSHIP TO OTHER UNIT PROCESSES
a, Pretreatment Processes
b. Sludge Transport
c. Runoff and Leachate Treatment
d. Co-disposal With Refuse
4. MAJOR COMPONENTS
a. Facilities
(Leachate control, gas control, runoff control, roads,
soil stockpiles, inclement weather areas, structures,
utilities, washracks, monitoring wells, equipment fueling
and maintenance.)
b. Equipment
(Excavating, sludge handling, backfilling, mixing,
compacting, grading, road construction.)
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5. MONITORING
a. Parameters to be Measured
(Sludge, leachate, runoff, gas.)
b. Procedures
c. How To Use Results
d. Reporting Procedures
(Regulatory agencies, sample record and reporting forms.)
6. STARTUP PROCEDURES
(Monitoring background conditions, initial trench, fill, or
berm location, initial trench dimension, soil stockpile
locations, liners, if any.)
7. NORMAL OPERATION
a. Trench, Fill or Berm Locations
b. Trench, Fill or Berm Dimensions
c. Handling of Soil Removed From Trench
d. Imported Soil
e. Co-disposal Procedures
f. Liners
8. EMERGENCY OPERATION AND FAIL-SAFE FEATURES
a. Inclement Weather Operations
(All weather roads, minimum on-site haul distance.)
b. Gas Control
(Permeable methods, impermeable methods, monitoring.)
9. LANDFILL COMPLETION
a. Ultimate Use
b. Grading at Completion of Filling
c. Final Grading
d. Landscaping
e. Continued Leachate and Gas Control
10. SAFETY
a. Soil Stability
b. Equipment Operation
c. Gas Control
11. IMPACT CONTROL
(Environmental: Leachate, runoff; health: vectors, gas
control, attractive nuisance; social: odors, noise.)
12. PERSONNEL
D. COMBUSTION
1. PERMITS AND STANDARDS - AIR DISCHARGE PERMITS AND PERMIT
REQUIREMENTS
(Permit number, renewal date, if applicable, permit
requirements, permit application guidelines, Federal/State/
Local laws or agency regulations dealing with incinerator
discharge permits.)
2, DESCRIPTION OF FACILITY
a. Design Criteria
(Sludge loading rate, sludge characteristics, air
pollution criteria, energy recovery.)
b. Process Description
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3. RELATIONSHIP TO OTHER UNIT PROCESSES
(Pre-treatment process, sidestream treatment, ash disposal,
co-disposal with refuse.)
4. MAJOR COMPONENTS
a. Sludge Charging
b. Reactor
c. Auxiliary fuel
d. Air Supply
e. Steam Supply
f. Energy Recovery
g. Air Pollution Control
h. Ash Handling
5. MONITORING
a. Parameters
(Sludge, stack emissions, temperatures, air flows,
fuel consumption.)
b. Procedures
c. Using Results
d. Reporting Procedures
(Regulatory agencies, sample record and reporting forms.)
6. STARTUP
7. NORMAL OPERATION
8. EMERGENCY OPERATION AND FAILSAFE FEATURES
(Unit process downtime procedures, flame safety system.)
9. SHUTDOWN
10. SAFETY
(Flame safety system, auxiliary fuel safety, reactor safety.)
11. IMPACT CONTROLS
(Environmental: air; social: odors.)
12. PERSONNEL
E. PROCESS FOR OFF-SITE USE BY OTHERS
1. PERMITS AND STANDARDS
(Air discharge permits and permit requirements, Federal/State/
Local requirements for sale of fertilizers.)
2. DESCRIPTION OF FACILITY
a. Design Criteria
(Sludge loading rate, sludge characteristics, bulking
agents, product production rate, product quality.)
b. Process Description
3. RELATIONSHIP TO OTHER UNIT PROCESSES
(Pretreatment processes, sludge transport, sidestream
control and treatment, ash disposal, co-disposal with refuse.)
4. MAJOR COMPONENTS
a. Mixing
b. Aerating
c. Handling
d. Screening
e. Drying Beds or Lagoons
f. Ash Disposal
g. Auxiliary Fuel
h. Air Supply
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i. Air Pollution Control
j. Nutrient Enrichment
5. MONITORING
a. Parameters
(Sludge, product, stack emissions, temperatures, oxygen
air flows, fuel consumption.)
b. Procedures
c. How to Use Results
d. Reporting Procedures
(Regulatory agencies, sample record and reporting forms.)
6. STARTUP
7. NORMAL OPERATION
8. EMERGENCY OPERATION
9. SHUTDOWN
10. SAFETY
(Flame safety system, auxiliary fuel system, equipment
operation safety, dust control.)
11. IMPACT CONTROL
(Environmental: air, runoff; health: finished product,
disease vectors; social: odors, noise, dust.)
12. PERSONNEL
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OPERATION AND MAINTENANCE MANUAL
SUPPORTING COMMENTARY
The EPA publication Considerations for Preparation of Operation and Maintenance
Manuals (70), referred to as Considerations in this publication, includes a
detailed checklist and accompanying text describing the information to be
included in a comprehensive operation and maintenance manual.
Considerations and the information included herein are intended to be flexible
guidelines for the operation and maintenance manual evaluator and author and
must be tailored for the individual facility. It may be desireable, for
example, to prepare a separate manual for the sludge disposal site if it is
remote from the wastewater treatment facility. In that case, the chapter on
wastewater treatment facilities could be eliminated.
Section A - SLUDGE TRANSPORT
Manuals for sludge transport systems can generally follow the format listed in
Considerations for pumping stations and pipelines, with modifications to suit the
sludge transport system used.
The following discussion highlights the factors which are pertinent to the
efficient operation and proper maintenance of sludge transport. It is by no
means intended to be all-inclusive or to deal with every topic in great detail.
A.I. PIPELINE
The format and requirements for manuals for pumping stations and pipelines are
described in great detail in Considerations and will not be repeated herein.
A.2. TRUCK
Truck transport equipment and facilities will require regular maintenance
checks. A schedule of routine maintenance should be followed to insure trouble-
free operation of the transport trucks and avoid untimely emergencies.
A.2.a. Description of Equipment
A full description of the type and number of trucks should be available to the
drivers and other plant personnel. Maintenance manuals must be readily acces-
sible so that routine and emergency repairs can be made quickly and correctly.
Proper operation of the truck transport system depends on maximum utilization of
the trucks without exceeding safe-load capacities.
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A.2.b. Description of Facilities
A complete description of all transfer facilities should be available to the
operating staff. Procedures for loading and unloading sludge should be clearly
described and the staff given instruction on the function and proper operation
of all components. A maintenance schedule should be established and followed to
insure efficient operation and maximum performance of the equipment.
A. 2.c. Normal Operation
Records of normal operation should be kept and periodically reviewed as a check
of the efficiency of operations. The operating schedule and time spent perform-
ing each function (loading, unloading, haul, etc.) should be monitored. It can
provide useful information for improving current operations and planning future
changes. A map of the normal route and alternate routes should be available at
all times. The drivers (regular and substitute) should be familiar with the
various routes between the treatment plant and disposal site.
The operating staff must be familiar with the procedures for safe handling of
the sludge. These should be as simple as possible so the operation is efficient
and the potential for accidents is minimized.
A.2.d. Emergency Procedures
Emergencies are inevitable in this type of operation; however, their effects can
be minimized if the operators are trained and prepared for them. Procedures for
dealing with various types of emergencies, both general and specific, should be
clear, concise and readily available.
Perhaps the two most obvious emergencies would be vehicle breakdown and sludge
spills. The former will be minimized with regular maintenance. However, an
adequate supply of spare parts, particularly those which commonly fail or are
difficult to replace, should be stored at the treatment plant. A maintenance/
repair manual should contain all the information necessary for repairing dis-
abled transport vehicles. Sludge spills at the plant site can be avoided to
some degree if the transfer equipment is easy to operate and the staff properly
trained. Spills resulting from accidents involving the transport vehicle can
result in unsafe road conditions and present a threat to public health. These
should be cleaned up as quickly and thoroughly as possible to minimize the
inconvenience they cause.
The manual should outline spill notification procedures identifying the agencies
to be notified, such as the state health, highway and pollution control agen-
cies, give the telephone numbers for such notification, and include copies of the
reporting forms for the subsequent written report of the spill.
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A.2.e. Vehicle Safety Rules
Only qualified personnel or supervised trainees should be operating the transfer
and transport equipment. Safety rules should be posted and all drivers aware of
highway rules and other considerations which will make their jobs safer.
A.2.f. Impact Control
Although mitigating measures to reduce adverse environmental impacts are con-
sidered during design, impact control should be practiced on a day-to-day basis.
Air pollution equipment on the transport vehicles should be functioning prop-
erly. The exposure of the operation and general public to sludge should be
minimized. Transport activities should be carried out with the least amount of
disruption to public activities; this involves minimizing noise, odor and traffic
congestion.
A.2.g. Personnel
Plant personnel should be adequate in number and experience to operate the
transport facilities efficiently. They should be specially trained for the
functions they perform, familiar with the duties of other operators, and pre-
pared to handle any emergencies which may arise.
A. 3. BARGE
As with truck transport, barging facilities require regular maintenance. The
following discussion describes the general requirements for operating an effic-
ient barging system.
A. 3. a. Description of Equipment
All barging equipment should be fully described. The number, type and capacity
of the barges are important information for the operators to have.
A.3.b. Description of Towing Arrangements
The towing arrangements should be clearly spelled out for the operating staff.
The tow contractor, operating hours and phone number should be clearly posted in
an obvious location. The route, haul distance and travel time should be
recorded so that present operations can be monitored and future activities plan-
ned. A record of the number of barges towed per trip and the amount of sludge
transported should also be kept.
A.3.c. Description of Facilities
A complete description of all transfer facilities should be available to the
operating staff. Procedures for loading and unloading sludge should be clearly
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described and the staff given instruction on the function and proper operation of
all components. A maintenance schedule should be established and followed to
ensure efficient operation and maximum performance of the equipment.
A.3.d. Normal Operation
Records of normal operation should be kept and periodically reviewed as a check
of the efficiency of operations. The operating schedule and time spent perform-
ing each function (loading, unloading, etc.) should be monitored. It can provide
useful information for improving current operations and planning future changes.
A map of the barge route should be available for tracking and emergencies.
The operating staff must be familiar with the procedures for safe handling of
the sludge. These should be as simple as possible so the operation is efficient
and the potential for accidents is minimized.
A. 3.e. Emergency Procedures
Emergencies are inevitable with this type of operation, however, their effects
can be minimized if the operators are trained and prepared for them. Procedures
for dealing with various types of emergencies, both general and specific, should
be clear, concise and readily available.
Perhaps the two most obvious emergencies would be the towing vessel breaking
down and accidental sludge spills. The former is the responsibility of the tow-
ing company unless self-propelled barges are used, in which case regular mainte-
nance practices will minimize equipment failures. Sludge spills at the plant
site can be avoided to some degree if the transfer equipment is easy to operate
and the staff properly trained. Spills resulting from accidents during transport
can result in serious water pollution and associated health problems. Sludge
should be contained as well as possible and transferred to another barge as
quickly as possible to reduce risks.
The manual should outline spill notification procedures, identifying the agen-
cies to be notified, such as the state health and pollution control agencies,
give the telephone numbers for each notification and include copies of the
reporting forms for the subsequent written report of the spill.
A. 3.f. Safety
Only qualified personnel or supervised trainees should be operating the transfer
and transport equipment. Safety rules should be posted and strictly enforced.
A.3.g. Impact Control
Although mitigating measures to reduce adverse environmental impacts are con-
sidered during design, impact control should be practiced on a day-to-day basis.
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Air pollution equipment on the towing vessels should be functioning properly and
measures must be taken to avoid surface water pollution. The exposure of the
operators and the general public to sludge should be minimized. Transport activ-
ities should be carried out with the least amount of disruption to public activi-
ties; this involves minimizing noise, odor and other nuisances associated with
the barging activities.
A.3.h. Personnel
Plant personnel should be adequate in number and experience to operate the
transfer facilities efficiently. They should be specially trained for the
functions they perform, familiar with the duties of other operators and prepared
to handle any emergencies which may arise.
A.4. RAILROAD
Railroad transport of sludge is not common; however, it can be economically
competitive with other methods (16.) The following sections briefly describe
general considerations for operating rail transport facilities.
A. 4.a. Description of Equipment
The railroad cars, whether leased or purchased, should be described in detail.
The description should include the number and type, the capacity and ownership
status of all cars. Operation and maintenance procedures should be described
and available for use by the plant operators.
A.4.b. Description of Facilities
Sludge transfer facilities should be described in detail along with operating
procedures for loading, unloading and general maintenance.
A.4.c. Description of Haul Contract
The details of the transport arrangement pertinent to the efficient operation of
the system should be readily available to the plant operators. The pick-up and
delivery schedule of the railroad should be posted and any modifications to the
regular schedule clearly noted.
A.4.d. Normal Operation
A complete, detailed description of normal operations should be available to the
plant operators. Records of the time required for various functions should be
kept for historical purposes and to provide information for estimating future
operations. All procedures for loading and unloading the cars and moving them
about at the plant site should be outlined and reviewed periodically by the plant
staff.
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A.4.e. Safety
Only qualified personnel or supervised trainees should be operating the transfer
or transport equipment. Safety rules should be posted and strictly enforced.
A. 4.f. Impact Control
Although mitigating measures to reduce adverse environmental impacts are consid-
ered during design, impact control should be practiced on a day-to-day basis.
Air pollution controls are the responsibility of the railroad. The exposure of
the operators and the general public to sludge should be minimized. Transport
activities should be carried out with the least amount of disruption to public
activities; this involves minimizing noise, odor and other nuisances associated
with rail transport.
A. 4.g. Personnel
Plant personnel should be adequate in number and experience to operate the trans-
fer facilities efficiently. They should be specially trained for the functions
they perform, familiar with the duties of other operators and prepared to handle
any emergencies which may arise.
Section B - LAND APPLICATION
The land application system should be operated and maintained in such a way that
sludge is applied to the land without creating a nuisance or causing environ-
mental degradation. Accurate record keeping is essential to safe operation.
The operation and maintenance manual should be written with these concerns in
mind. Loading rate determination is presented in Appendix A.
B.I PERMITS AND STANDARDS
Numerous permits are required to operate a land application system. As well, cer-
tain standards must be upheld and reporting procedures for non-compliance clearly
specified. Land application systems are often considered solid waste disposal
systems from a regulatory agency viewpoint.
B.I.a Solid Waste Disposal
The information pertinent to operating the system which is specified in the
solids waste disposal permit should be readily available. The operators should be
familiar with specific information such as the issuing agency, permit number,
renewal date and specific requirements. In addition, they should be aware of more
general information such as permit application guidelines and laws and regula-
tions pertaining to land application systems.
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B.l.b. Discharge Permits for Runoff and Leachate
Permits will be required for the discharge of all uncontained and treated runoff
and leachate. The operators should be familiar with the permit, including such
information as the number, renewal date and specific requirements contained in
it. Copies of all permits should be readily available for reference. Information
such as application guidelines and general requirements should be available to
operators.
B. 1. c. Crop Marketing
Regulations concerning crop marketing or future crop production on the site must
be followed. There may be restrictions on the ultimate use of crops grown on
sludge-amended soils.
B.2. APPLICATION EQUIPMENT
Application equipment for injection of sludge can be attached to the back of a
tank truck or pulled by a farm tractor usually, the track-laying type. Surface
spreading can be accomplished by trucks or conventional farm manure spreading
equipment.If the sludge is in liquid form, spraying may be accomplished by large
nozzle sprinkler.
B.2.a. Description of Equipment
The O&M manual should contain a complete description of the equipment including
number, type, and capacities of all application vehicles.
B.2.b. Description of Facilities
The site facilities or those related to application will usually consist of wash-
down, fueling and maintenance facilities and an office or area for records
keeping and administration. These facilities along with equipment within them
should be described in the O&M manual.
B.2.c. Startup Procedures
Startup procedures can be divided into those required for daily or intermittent
startup and those required for seasonal startup. Daily procedures include lub-
rication and liquid level checks as well as usual checks on all equipment. The
seasonal checks consist mainly of preventive maintenance and cleaning. The
daily startup includes provision of a drawing or map telling the operator which
areas are to be covered and what quantities are to be applied.
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B.2.d. Normal Operation
Normal operation procedures should be very specific with step-by-step instruc-
tions included. The operating instructions should include a field pattern for the
application plan. This should show the areas to be covered and the order of
application. At the end of the day the operator should file a log sheet showing
areas and quantities applied. A sample log sheet should be included in the O&M
manual. The O&M manual should provide a nomograph or tables to correlate applica-
tor speed with amount applied (wet tons/acre). This correlation is specific to
the type of sludge and equipment used.
B.2.e. Shutdown
Specific procedures need to be provided to insure equipment readiness for the
following day. Injectors should be flushed with water to remove residual solids.
These instructions should be included in the manual. The O&M manual should pro-
vide instructions on completion and filing of the log sheet mentioned
previously.
B.2.f. Emergency Procedures
Emergency procedures should be provided with the O&M manual. They should include
the following items. The manual should provide instructions concerning what
action to take when a vehicle breaks down. This should include options for
removing sludge before it goes septic. Cleanup, containment and reporting
instructions for sludge spills should be included in the manual. Injector clogg-
ing can be caused by a minor obstruction or by faulty or damaged equipment. A
troubleshooting table should be provided on how to correct this problem.
B.2.g. Safety - Vehicle Safety Rules
Safety rules specific to the injection operation should be provided.
B.2.h. Impact Control
There are several environmental problems that should be prevented. Specific
instructions on control measures should be included in the manual. Prevention
programs for disease vector or rodent breeding areas should be provided as part
of the O&M manual. Odor control measures should be explained even if proper
stabilization processes and application procedures have been provided. Noise con-
trol measures are generally not a problem in rural areas. In exceptional cases,
however, noise control programs should be provided.
B.2.J. Personnel
The manual should include a recommended staffing level and a description of the
qualifications required and/or specialized training needs. There are no
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established manpower requirements because of variation in application time
periods, loading rates, sludge solids concentrations, and type of application
equipment. Personnel requirements must be considered on a case-by-case basis.
B.3. FARM MANAGEMENT
This section is required for those agencies who wish to conduct the farming
operation with their own staffs and equipment.
B.3.a. Description of Equipment
The farming equipment including tractors, trucks, tillage equipment and harvest-
ing equipment should be described and manufacturers operating and maintenance
schedules included. Lubrication schedules should be part of the maintenance
schedule.
B.3.b. Description of Facilities
The O&M manual should provide a complete description of the farm facilities
including the equipment within each facility. One of the most important areas of
a farming operation is the maintenance shop. There will be a large inventory of
specialized equipment within this shop. Complete operation and maintenance
instructions for this equipment should be included in the manual. Crop storage
facilities generally consist of bins or buildings with little mechanical equip-
ment other than the loading and unloading facilities. Maintenance instructions
plus rodent control procedures should be provided.
These facilities are similar to crop storage except more specialized handling
procedures must be delineated.
B.3.c. Crop Management
Instructions should be provided for each crop grown specifying planting and har-
vesting schedules. Recommended methods of tillage, weed control, and pest control
should also be included. Crop marketing practices should also be discussed. Sup-
plemental fertilizer computation procedures should be delineated. Methods for
adjusting pH should be shown.
Each item in the above section should be discussed for each crop grown. Recom-
mended crop rotation schedules should be provided along with a discussion of
changes in application procedures necessary to adjust to different crops. Recom-
mended areas requiring specialized expertise should be outlined. The agency can
then be prepared to obtain consulting services as recommended. The O&M manual
should provide guidance on how to obtain custom or contract harvesting. A sample
contract or contract format should be provided with the manual.
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B.3.d. Contingency Procedures
There are two areas where emergency procedures or contingency plans are
required. They are related to equipment operation and crop disease control.
Farm equipment breakdown can be considered an emergency if this breakdown occurs
at planting time or at harvest. The O&M manual should provide guidance on how to
continue or modify operations with alternate equipment. Unusual problems will
require a specialist but there are many problems that can be identified with min-
imal training. These problems include pests, weeds, nutrient deficiencies, and
poor drainage. This information should be included in a troubleshooting format.
B.3.e. Emergency Procedures
The two major emergency conditions that can develop with the farming operation
(not related to equipment) are discovery of excessive contaminants and extremely
cold or wet weather.
If sludge or soil monitoring shows unacceptable levels of heavy metals or other
contaminants, then the sludge must be applied at a lower rate or application site
shifted to another area. Changes may also be made at the treatment plant to
modify these concentrations. Plans for operating under these circumstances should
be included in the O&M manual.
Some climate extremes such as cold or wet weather can result in operational
problems or a major crop loss. For example, when faced with late spring, it may
be useful to switch from corn to soybeans or sorghum to make use of the shorter
season. These circumstances and the solutions to minimize losses should be
discussed in the manual.
B.3.f. Personnel
Personnel requirements are somewhat complicated due to the seasonal nature of
farming. The manual should show the number of personnel required for each farming
task. Along with this the timing of each task should be provided. This should be
shown in such a manner that seasonal variations can be easily recognized. Along
with the personnel requirements listed above, individual qualifications should be
shown. If special training is required, this should be shown also.
B.4. MONITORING
A complete monitoring program should be established. Background conditions should
be determined so that the effects of land application can be assessed.
B.4.a. Parameters to be Measured
Soils monitoring may include pH, CEC, nitrogen, phosphorus, potassium, and heavy
metals (Cd, Cu, Zn, Pb, Ni). The nutrient analyses are useful for good crop
growth and for preventing excessive amounts of nitrogen or phosphorus in
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succeeding applications or for determining additional nutrient needs. Potassium
is not normally a problem but monitoring is necessary to determine additional
needs for good crop growth. The pH, CEC and metals determinations are useful for
preventing metals accumulations in soils or crops. Pathogen monitoring should be
as specified by the regulatory agency.
Crop monitoring should include yield, crop disease, and crop pest evaluations.
Tissue analysis may be required periodically for food-chain crops. Crops destined
for human consumption should be monitored for pathogens.
Surface waters and intermittent streams (when flowing) should be monitored as
required by the appropriate regulatory agencies. Monitoring points should include
at least one sampling station upstream of the application area and one downstream
from the application area. Frequencies depend on circumstances of each site.
Minimum parameters include BODr , suspended solids, nutrients, and coliforms.
Nearby domestic wells should be tested prior to project startup and then moni-
tored periodically. On-site monitoring wells should be placed and sampled as
required by the appropriate regulatory agency. At a minimum, tests should include
nitrates, total dissolved solids and coliforms.
B.4.b. Procedures
The procedures for sample collection and analysis should be clearly outlined in
the operations guide. These will vary depending on the specific chracteristics of
the site, but for any site, they should be closely followed.
B.4.c. How to Use Results
The results of the monitoring and sampling program will be used to assess the
operation. The interpretation of the data collected can indicate the success of
the current operation, may lead to develop procedural changes to improve or
streamline activities, suggest design modifications and provide a useful tool in
planning future expansions. Based on the monitoring reports, a complete and
through assessment of operations should be made periodically.
B.4.d. Reporting Procedures
The operators should be familiar with the reporting requirements and procedures
outlined in the operating permits. Submitting regular reports to the various
agencies having jurisdiction over the operation is important. The operators
should be fully aware of the penalties involved in failure to do so.
Sample reports and record-keeping practices should be available to the operators.
All data, logs and reports should be kept in an orderly manner in a safe place.
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Section C - LANDFILL
The successful operation of a sludge landfill is a relatively straightforward
task although it requires attentive surveillance. The following sections describe
the information and procedures necessary to operate and properly maintain a
sludge landfill.
C.I. PERMITS AND STANDARDS
Numerous permits are required to operate a landfill. As well, certain standards
must be upheld and reporting procedures for non-compliance are clearly
specified.
C.I.a. Solid Waste Disposal
The information pertinent to operating the landfill which is specified in the
solid waste disposal permit should be readily available. The operators should be
familiar with specific information such as the issuing agency, permit number,
renewal date and specific requirements. In addition, they should be aware of
more general information such as permit application guidelines and laws and regu-
lations pertaining to sanitary landfill operations.
C.l.b. Discharge Permits for Runoff and Leachate
Permits will be required for the discharge of all uncontained and treated runoff
and leachate. The operators should be familiar with the permit, including such
information as the number, renewal date and specific requirements contained in
it. Copies of all permits should be readily available for reference. Information
such as application guidelines and general requirements should be available to
operators.
C.l.c. Reporting Procedure for Spills of Raw or Inadequately Treated Wastewater
All violations of discharge requirements must be reported to the jurisdictional
agency. The reporting procedures and emergency phone number should be clearly
posted and the operators familiar with them. A sample report format should be
available. The owner and operators should be informed of their responsibilities
for violating the discharge standards and the possible penalties which could be
levied.
C.l.d. Water Quality Standards
It is the responsibility of the operating agency to conform to the quality stan-
dards of any waters affected by the landfill operation. The operators should be
aware of local streams receiving runoff from the landfill and of their classifi-
cations and beneficial uses. Particular care should be taken to prevent the
accidential pollution of quality sensitive streams or water supplies near the
landfill.
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C.2. DESCRIPTION OF LANDFILL
A detailed description of the landfill will be useful to the regular operators,
new or substitute operators, owners, jurisdictional officers and consultants.
This should include narrative and graphical information defining the method land-
fill operations, the design criteria, the site and unusual or outstanding
features. A general description of the normal and emergency operating procedures
should be included. The description of the landfill should be simple and clear
enough for a non-technical audience yet comprehensive enough for those more
familiar with such systems.
C.3. RELATIONSHIP TO OTHER UNIT PROCESSES
Landfill is the last step in an often complex chain of wastewater and sludge
treatment processes. In order to fully understand its function and operation, the
operators should be aware of its relationship with these other processes.
C.3.a. Pretreatment Processes
The processes upstream of landfilling will determine the nature and quantity of
sludge to be disposed of. The operators should be aware of what these processes
are and how their operation or elimination will affect the sludge characteristics
and landfill operations.
C.3.b. Sludge Transport
The sludge transport operations directly influence the landfill operations.
Ideally, a more-or-less continuous or at least regularly scheduled delivery of
sludge should be expected at the landfill. The landfill operators should be
informed of any variations in the transport schedule and alerted to any emergen-
cies so their operations can be modified accordingly.
C.3.c. Runoff and Leachate Treatment
If runoff and leachate treatment facilities are located at the landfill site,
the operators should be familiar with them. If these flows are pumped or trucked
to an off-site location for treatment the operators should be familiar with the
transport system.
C.3.d. Co-disposal With Refuse
If sludge is to be included in a refuse landfill, close coordination will be
necessary. A clearly defined disposal plan and a regular transport schedule will
simplify operation and reduce the potential problems associated with combining
the two operations.
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C.4. MAJOR COMPONENTS
The successful operation of a sludge landfill depends, in part, on the under-
standing and operation of ancillary facilities and equipment. These must be main-
tained to insure reliable operations.
C.4.a. Facilities
The operating staff should be familiar with the operation and maintenance of all
facilities at the landfill site. In addition to the manufacturer's O&M instruc-
tions, an operations manual should be available and reviewed periodically. It
should include such information as a regular maintenance checklist, a trouble-
shooting guide, an emergency operation plan and safety guidelines. Features such
as leachate, runoff and gas controls, roads, soil stockpiles and inclement
weather areas are essential to the day-to-day operation of the landfill. Other
facilities such as offices, utilities and equipment yards are provided for the
operators' comfort and convenience; these must be maintained in the interest of
safety and aesthetics. Monitoring wells and equipment are to safeguard the
public health, protect against adverse environmental impacts and to aid in future
operations planning; these should be maintained and operational at all times.
C.4.b. Equipment
The mechanical equipment for periodic and day-to-day operations such as excava-
tion, sludge handling, and processing, filling and cover must be operational at
all times. Daily maintenance checks and preventive repairs are a necessity.
Periodic troubleshooting can reduce the unscheduled downtime of this equipment
and minimize costly work stoppages. Maintenance and operations schedules should
be carefully planned, clearly posted and followed as closely as possible.
C.5. MONITORING
A complete monitoring program should be established prior to the startup of a
sludge landfill. Background conditions should be determined so that the operation
and effects of the landfill can be assessed.
C.S.a. Parameters to be Measured
It is possible to measure numerous parameters at a landfill site, however, only
those features yielding useful information should be studied. The characteristics
of the sludge such as source, solids content, quantity application, location,
etc. should be recorded daily. The quantity and quality of leachate and runoff
should also be measured. Climatic conditions should also be noted.
The number and type of monitoring wells is highly site-specific. It is essential
that these wells be sampled according to the specified schedule. Maintaining sur-
face and groundwater quality is an essential task associated with landfill
operations.
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C. 5. b. Procedures
The procedures for sample collection and analysis should be clearly outlined in
the operations guide. These will vary depending on the specific characteristics
of the landfill, but for any site, they should be closely followed.
C.S.c* How to Use Results
The results of the monitoring and sampling program will be used to assess the
landfill operation. The interpretation of the data collected can indicate the
success of the current operation, may lead to develop procedural changes to
improve or streamline activities, suggest design modifications and provide a use-
ful tool in planning future expansions. Based on the monitoring reports, a com-
plete and through assessment of operations should be made periodically.
C.5.d. ^Reporting Procedures
The operators should be familiar with the reporting requirements and procedures
outlined in the operating permits. Submitting regular reports to the various
agencies having jurisdiction over the landfill is important. The operators should
be fully aware of the penalties involved in failure to do so.
Sample reports and record-keeping practices should be available to the opera-
tors. All data, logs and reports should be kept in an orderly manner in a safe
place.
C.6. STARTUP PROCEDURES
Several steps are necessary in starting up a sludge landfill. These will vary
with the site and type of fill operation, however certain basic practices should
be followed. During operation it would be prudent to check nearby aquifers and
surface waters against the original background conditions to be sure that opera-
tions have not adversely affected their quality. The initial work site must be
prepared according to the landfill plan. This work will depend on the method of
fill to be used and the measures designed for environment impact mitigation. The
initial trench dimension should be in accordance with the filling plan. Depending
on the degree of success of the startup operations, the trench size may be kept
the same or modified somewhat. A soil stockpile should be established at the
landfill site. Depending on the method of operation, the stockpile will be com-
posed of native soil excavated during initial trenching, imported soil to be used
as a bulking agent or cover, or a combination of the two. The stockpile should be
in a convenient location for both normal and inclement operations. Trench liners
may be an essential element in the landfill design. Whether constructed of soil,
or natural or artificial material they must be carefully placed prior to filling.
The liner specifications should be followed and an inspection made before any
lined trenches are used.
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C.7. NORMAL OPERATION
After initial startup, normal operations should follow a simple, routine set of
procedures. These will vary depending on the method of filling and may need to be
modified periodically. The operators should be informed of any modifications and
instructed on operational changes.
C.I.a. Trench, Fill, or Berm Locations
After the initial startup the landfill operation should follow a logical fill
sequence. The operators should be instructed on the location of subsequent fill
areas. A plan of these areas should be included in the O&M instruction manual and
periodically reviewed by the operators.
C.7.b. Trench, Fill, or Berm Dimensions
The size of the fill areas should roughly duplicate those initially created;
they may, however, vary depending on the terrain. The filling plan included in
the operators' manual should clearly specify any deviation in the established
operating scheme.
C.7.C. Handling of Soil Removed from the Trench
Native material excavated during trenching should be stockpiled for future use
as a bulking agent or cover material. The stockpile location should be convenient
and near the area where it is to be used. The methods for removing, placing, and
storing this material should be described in the O&M manual.
C.7.d. Imported Soil
The type and quantity of imported soil, if any, should be described in the opera-
tions guide. If more than one type of soil is to be used at the landfill, the
stockpiles should be clearly identifiable and separate.
C.7.e. Co-disposal Procedures
The procedures for co-disposal of sludge and refuse, if practiced, should be
clearly delineated in the operating instructions. The operators should be
instructed on the procedures for mixing the sludge and refuse as well as for the
actual filling operations.
C.7.f. Liners
Since liners are critical to the long-term operation of a landfill, if they are
required at all, their placement and maintenance is an important operational
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item. The materials and procedures for constructing liners should be clearly
described in the O&M manual; the operators should be made familiar with this
information.
C.8. EMERGENCY OPERATION AND FAIL-SAFE FEATURES
A contingency plan for emergency operation should be included in a separate sec-
tion of the O&M manual.
C.S.a. Inclement Weather Operations
In general, the procedures for operation in inclement weather should follow the
same basic steps as normal operation. The difference in the operation is the
location of the fill. A separate fill area with paved or all-weather roads is
designated for use during inclement weather. This area is generally located near
the main entrance to the landfill to minimize the sludge haul distance. Any
special procedures for using this portion of the site or for filling when the
weather is bad should be identified and easily found in the O&M manual.
C.S.b. Gas Control
The accumulation of gas produced during filled sludge decomposition can present
a hazard at the fill site. Methane is particularly dangerous since it is explo-
sive under certain conditions.
The gas control systems should be completely described in the O&M manual. Emer-
gency operations should be reviewed periodically so the operating staff is
familiar with them. Regular maintenance and monitoring will reduce the potential
for emergency operations. This cannot be overstressed in the operation and main-
tenance manual, in operator training sessions, or on the job.
C.9. LANDFILL COMPLETION
In completing a sludge landfill, a certain set of criteria must be met to make
it publically acceptable. These criteria will be established according to the
type of landfill and the location, size and ultimate use of the site. The proce-
dures for site closure should be included in the operations manual and updated or
modified if the original landfill plan is not followed.
C.9.a. Ultimate Use
The ultimate use of the site should be described and illustrated in the O&M man-
ual or a separate document which describes the completion of the site. The actual
work involved in completing the site will depend on its ultimate use and on the
care taken in day-to-day fill operations.
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C.9.b. Grading at Completion of Filling
When each section of the landfill is complete, the final cover should be graded
according to a pre-determined plan. It is imperative that no sludge become or
remain exposed after the grading has been completed.
C.9.c. Final Grading
The final grading is to be performed after a sufficient period of time has
passed for initial settlement to have occurred. The final grading plan will be
designed according to the ultimate intended use of the landfill site. It is
important that all sludge be completely covered with the prescribed depth of
cover material.
C.9.d. Landscaping
The landscaping plan should reflect the intended ultimate use of the landfill
site. Where practical, landscaping may be done on completed sections prior to the
completion of the entire fill project.
C.9.e. Continued Leachate and Gas Control
Since decomposition of the organics in the sludge may continue even after the
landfill has been completed, an ongoing monitoring and control program must be
maintained. Leachate and gas must be controlled even after the filling operations
have stopped. A program for doing this should be clearly outlined in the
completion plan.
C.10. SAFETY
Providing a safe working environment at the landfill should be a part of the gen-
eral O&M of the site. Certain safety features will be a part of the design, how-
ever, day-to-day practices to provide safe working conditions must also be
followed. The O&M manual should have a separate safety section as well as spe-
cific safety guidelines for each operation and feature of the landfill.
C.lO.a. Soil Stability
The stability of the soil at the fill site, particularly near the work areas can
present a critical safety problem, particularly with the use of large equipment.
The bearing strength of all disturbed areas should be checked prior to moving
fill equipment on them. Caution should be used when approaching muddy areas or
those subject to erosion.
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C.lO.b. Equipment Operation
The operation of large earth moving equipment presents the potential for numer-
ous minor and major accidents. Only fully trained operators should be allowed to
operate such equipment. Regular maintenance and safety checks can greatly reduce
the number of accidents associated with equipment failure.
C.10.C. Gas Control
Caution must be practiced when dealing with gas control equipment. Methane gas
can be highly explosive. The O&M manual should contain a complete set of
instructions on the safe servicing of gas control and monitoring equipment. Ver-
bal instruction on the operation of this equipment should be given periodically
at operation and safety training sessions.
C.ll. IMPACT CONTROL
The protection of the environment and of the public health are important aspects
of the landfill operation which cannot be overlooked. The O&M manual should con-
tain guidelines for providing this protection and the actual operation should
reflect these practices.
Environmental protection is generally focused on leachate and runoff controls to
prevent surface and groundwater contamination. Trench liners must be kept intact
during and after filling operations. Drainage systems should be checked to see
that they are functioning as designed. If monitoring shows that adverse
environmental impacts have occurred or pose a threat, immediate action should be
taken to mitigate them.
Protection of public health should be a foremost concern in the operation of
sludge landfills. Protection of water supplies and sole source aquifers is an
obvious responsibility. In addition, the control of disease by the reduction of
vectors such as flies, the adequate venting of explosive or toxic gases, and the
restriction of access to the landfill site are the responsibility of the
operators.
Minimizing the aesthetic impacts of a sludge landfill can greatly increase the
public acceptability of such a project. The control of odors, noise and other
nuisances is generally straightforward and can be accomplished as part of the
daily operating routine. All efforts should be made,to reduce the social impacts
of the fill operation particularly if the site is located in an accessible or
populated area.
C.12. PERSONNEL
The personnel requirements will vary depending on the specific features and size
of the landfill operation. Adequate personnel should be maintained to fill all
functions of the operation and allow for vacation relief and emergencies. The
staff should be properly trained to perform their primary duties and should be
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familiar with the other operations at the site. Regular training sessions and
safety incentive programs will encourage efficient landfill operations.
Section D - COMBUSTION
D.I. PERMITS AND STANDARDS - AIR DISCHARGE PERMITS AND PERMIT REQUIREMENTS
All applicable federal, state and local emission limitations and permit require-
ments should be fully explained in the operation and maintenance manual. Included
should be permit numbers, renewal dates, permit requirements and instructions for
making renewal applications and a summary of all federal, state, local, or
regional laws and regulations pertaining to the operation of incinerators.
D.2. DESCRIPTION OF FACILITY
D.2.a. Design Criteria
The facility description must include a summary of the system design criteria:
• Anticipated minimum, maximum, and average sludge loading rates
• Anticipated sludge characteristics, especially moisture and heat
contents
• Design criteria which relate to air pollution, such as temperatures and
detention times
• Design criteria for the energy recovery systems, including operating
temperatures, uses, and anticipated yields
D.2.b. Process Description
The facility description should include a description of the combustion process
used. The process description should follow the sludge through the combustion
process, explaining the reactions that take place. For example, a multiple hearth
incinerator description would describe the drying, combustion and cooling zones;
the action of the rabble arms; and the flow of sludge and air through the
reactor.
D.3. RELATIONSHIP TO OTHER PROCESSES
The relationships of the combustion process to the other wastewater and sludge
treatment processes must be explained. Included in the explanation should be
parameters for optimizing the relationships between the combustion process and
the related unit processes.
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D.3.a. Fretreatment Processes
The relationship of the sludge pretreatment processes to the combustion process
must be outlined. Typical relationships which should be discussed are:
• The effects of thickening and dewatering system efficiency on moisture
content and fuel consumption
• The effects of chemical addition on moisture content, heat content,
fuel consumption, and ash volume
• The effects of wastewater treatment process operation on sludge volumes
and characteristics
The combustion system sidestreams such as wet-air oxidation liquor and scrubber
effluent water on wastewater treatment processes should be explained.
Consideration should be given to the effects of the rest of the unit processes on
the ash disposal system, including:
• Sludge production from wastewater treatment processes
• Increases in ash quantities from chemical conditioning processes
• Effects on ash quantity and quality of combustion process operation
Where co-disposal with municipal refuse is to be practiced, the operating param-
eters of the refuse processing system must be explained. Data concerning the
approximate ratio of solid waste to sludge expected or desired, and the composi-
tion and quality (i.e., degree of classification, particle size, moisture content
and heat content) of the refuse should be identified.
D.4. MAJOR COMPONENTS
Each of the major components of the combustion process should be described in
detail, identifying the design criteria and critical operating parameters of each
item or system. The major items or systems which should be included are:
Sludge charging system, including pumps, grinders, and conveyors
Process reactor or furnace
Auxiliary fuel supply and control systems
Combustion, cooling, fluidizing and wet-air oxidation air supply
systems
Wet—air oxidation steam supply systems
Energy recovery systems, including heat exchangers, turbines, etc.
Air pollution control equipment
Ash handling and disposal systems
D.5. MONITORING
The operation and maintenance manual should include a detailed program for the
combustion process. The monitoring program should cover those parameters which
affect compliance with federal, state, regional and local air quality require-
ments as well as those which pertain to incinerator operation. Figure 17 illus-
trates a typical monitoring program for a multiple hearth incinerator.
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S
z
o
UJ
t-
U)
UJ
(9
(9
O
K
a
o
TEMPERATURE
TOTAL
VOLATILE
SOLIDS
TOTAL SOLIDS
STACK GAS
COMPOSITION
PLANT SIZE
( MGD;
Z
TEST
FREQUENCY
Mn
I/o1
1/D1
z
LOCATION OF
SAMPLE
A
F
P
F
P
S
METHOD OF
SAMPLE
Mn
G
G
Z
REASON
FOR TEST
P
P
P
R
ESTIMATED UNIT PROCESS SAMPLING AND
TESTING NEEDS
INCINERATION
(MULTIPLE HEARTH)
FEED
1
1
A
A
A
r1
>i
A
A
| "" ST^
S
v^
•-*• HEARTHS
PRODUCT
r
p
STACK GASES
A. TEST FREQUENCY
H =» HOUR M - MONTH
D - DAY R - RECORD CONTINUOUSLY
W=. WEEK Mn- MONITOR CONTINUOUSLY
B. LOCATION OF SAMPLE
I = INFLUENT
E = EFFLUENT
S= STACK GASES
C. METHOD OF SAMPLE
24C-24 HOUR COMPOSITE
G = GRAB SAMPLE
R = RECORD CONTINUOUSLY
Mn= MONITOR CONTINUOUSLY
D. REASON FOR TEST
H - HISTORICAL KNOWLEDGE
P = PROCESS CONTROL
C - COST CONTROL
R = TO MEET REGULATIONS
E. FOOTNOTES:
1. THESE TESTS SHOULD ALSO BE RUN ON RECEIVING
WATER, ABOVE AND BELOW OUTFALL. ON A
PERIODIC BASIS, DEPENDING ON LOCAL CONDITIONS.
2. AS REQUIRED TO MEET AIR QUALITY STANDARDS
Figure 17. Typical multiple hearth furnace monitoring program.
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D.5.a. Parameters
Sludge monitoring should include total sludge flow, total solids, and total vola-
tile solids. Additional monitoring may be required by air quality regulations,
such as mercury or PCB content. Stack emission monitoring should be in accordance
with air quality regulations. In addition to the data required by air quality
authorities, such information as carbon monoxide and hydrocarbon content are
often useful in analyzing reactor performance. Temperatures are the critical
parameters in reduction system operation. Temperature is usually monitored con-
tinuously at several points in the process. These monitoring points should be in
accordance with the combustion process manufacturer's recommendations. Monitoring
of combustion air, cooling, air, fluidizing air, or wet-air oxidation air flows
is often useful and should be included in the monitoring program if recommended
by the manufacturer. Fuel consumption records are valuable in optimizing the
operation of the combustion and dewatering processes.
D.5.b. Procedures
The manual should explain all monitoring and record-keeping procedures, includ-
ing sampling frequencies, methods, and locations. Laboratory procedures should
include step-by-step instructions together with reference to the appropriate
chapters in Standard Methods for the Analysis of Water and Wastewater (9) or
other laboratory desk reference.
D.5.C. Using Results
The operation and maintenance manual should explain the purpose and use of each
test. Where monitoring is for operational parameters, explanation should be
included as to the control actions which should be taken in response to the
measurements.
D.5.d. Reporting Procedures
The manual should include detailed instructions for reporting required data to
regulatory agencies. The agency, required parameters and reporting frequency
should be identified. Sample record and reporting forms are valuable aids to the
operator and should be included.
D.6. STARTUP
The startup procedures should include a sequence of operations for starting the
combustion system, maximum safe heating rates for reactors, expected auxiliary
fuel consumption and operating temperatures which must be attained before opera-
tion can begin.
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D.7. NORMAL OPERATION
Normal operating procedures should include the economical range of sludge feed
rates, the range of air supply rates, the range of auxiliary fuel consumption
rates, normal operating temperatures, and operating parameters for putting the
reactor on standby status during periods of low sludge flows, or at night for
daytime-only operations.
D.8. EMERGENCY OPERATION AND FAIL-SAFE FEATURES
A description of emergency procedures should be included, including the actions
to be taken in the event any component of the combustion system experience a
mechanical failure. The emergency procedures should identify the amount of time
expected to be available for corrective action and advise the operator of any
consequential problems which may result. This section of the manual is the appro-
priate place to describe facilities for improving reliabilities such as:
• Standby power
• Standby fuel
• Duplicate process units
• Alternative sludge management systems
D.9. SHUTDOWN
Shutdown procedures should include a detailed sequence of operations for shut-
ting down the combustion system, maximum safe cooling rates for reactors and
expected auxiliary fuel consumption during cooling.
D.10. SAFETY
Detailed safety procedures should be described for the combustion system. Most
safety requirements are those generally applicable to wastewater treatment
plants, but certain additional safety factors should be called to the operator's
attention. The flame safety system's purpose, operation and features should be
called to the operator's attention. Special instructions should be included for
the safe use of the auxiliary fuel and associated equipment.
Safety rules for the reactor should be outlined, including such things as the
use of air masks within the reactor and viewing burning sludge only through
smoked glass.
D.ll. IMPACT CONTROL
The manual must identify for the operator those operating parameters which are
vital to minimizing deleterious environmental impacts. Most of these parameters
relate to air quality or odor control and include such things as maintaining
adequate excess air supply, insuring adequate incineration temperatures and gas
detention times, and adequate maintenance of air pollution control equipment.
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D.12. PERSONNEL
The manual should outline operating and maintenance personnel requirements for
the combustion and energy recovery systems. Manpower requirements for incinera-
tion are given in reference 71. Emphasis should be given to any special qualifi-
cations or training recommended by the equipment manufacturers. Certain energy
recovery equipment may require a qualified stationary engineer, for instance.
Section E - PROCESS FOR OFF-SITE USE OF SLUDGE BY OTHERS
E.1. PERMITS AND STANDARDS
All applicable federal, state and local emission limitations and permit require-
ments should be fully explained in the operation and maintenance manual. Included
should be permit numbers, renewal dates, permit requirements and instructions for
making renewal applications and a summary of all federal, state, local, or
regional laws and regulations pertaining to the operation of flash dryers or
incinerators.
The manual should include a summary of all federal, state and local requirements
concerning the sale or use of sewage sludge as fertilizer. Some states restrict
the use of sludge to certain applications. Other states establish minimum
nutrient levels for a product to be termed "fertilizer". Sludge products not
meeting the minimum requirements may be required to be labeled as "soil condi-
tioner". Requirements for labeling of bagged product should be summarized, and
any necessary warning labels identified. The requirements for establishing the
nutrient analysis of the product (nitrogen, phosphorus and potassium) should be
presented together with the labeling requirements.
E.2. DESCRIPTION OF FACILITY
E.2.a. Design Criteria
The facility description should include a summary of the design criteria for the
system. The summary should include, as a minimum, the following information:
• Anticipated minimum, average, and maximum sludge loading rates
• Anticipated sludge characteristics including moisture, nitrogen, phos-
phorus, potassium, heavy metals, toxic organic compounds, and
pathogens
• Bulking agent description and anticipated consumption rate
(composting)
• Anticipated product production rate
• Anticipated product characteristics, including those items listed for
sludge.
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E.2.b. Process Description
The facility description should include a detailed description of the process.
The description should follow the sludge through the process, describing the
reactions that take place. A windrow composting process description, for example,
would describe mixing with the bulking agent, construction of windrows, the aero-
bic digestion process known as composting, windrow turning, curing and
screening.
E.3. RELATIONSHIP TO OTHER UNIT PROCESSES
The relationship of the sludge processing system to other wastewater and sludge
treatment processes must be explained in detail. Included in the description
should be parameters and procedures for optimizing the relationships among the
processes.
The effects of the operation of the wastewater treatment system on the quantity
and quality of product should be discussed in detail.
The relationship of the sludge and product transport systems to the process
should be explained, together with information on optimizing the delivery and
removal time for sludge and product.
The effects on the wastewater treatment process of the return or sidestreams
should be explained. Among the sidestreams of concern are:
• Composting process runoff
• Flash dryer scrubber effluent
• Lagoon supernatant
• Drying bed underflow
For flash drying using dried sludge as fuel systems the effects on ash produc-
tion of various production rates and operating modes should be explained. If ash
is returned to the wastewater treatment process, the effects of the increased
load on the treatment process should be explained.
Where co-composting with municipal refuse is practiced, the operating parameters
of the refuse processing system must be explained. Data concerning the approxi-
mate ratio of sludge to solid waste expected or desired, the composition and
quality (i.e. degree of classification, particle size and moisture content of
(i.e. moisture content and nutrient analysis) of the sludge should be
identified.
E.4. MAJOR COMPONENTS
The major components of the system should be described in detail, identifying
the design criteria and critical operating parameters of each item or system.
Major items and systems which should be included are:
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Mixing (composting)
Aerating (composting)
Handling
Screening (composting)
Drying beds or lagoons
Ash disposal (flash drying)
Auxiliary fuel (flash drying)
Air supply (flash drying)
Air pollution control (flash drying)
Nutrient enrichment
E.5. MONITORING
The operation and maintenance manual should include a detailed monitoring pro-
gram for the process. The program should include those parameters which affect
compliance with federal, state, regional and local air quality requirements,
those which pertain to the safety and utility of the final product, and those
which pertain to system operation.
E.5.a. Parameters
Sludge monitoring should include:
Total sludge flow
Total solids
Total volatile solids
Monitoring required to assure safety such as heavy metals, PCB's and
pathogens
Additional monitoring required by air quality requirements
Nutrient content including nitrogen, phosphorus and potassium
Product parameters which should be monitored include:
Production
Bulk density
Moisture content
Nutrient content including nitrogen, phosphorus and potassium
Monitoring required to assure safety such as heavy metals, PCB's and
pathogens
Stack emission monitoring should be in accordance with air quality regulations.
In addition to the data required by air quality authorities, such information as
carbon monoxide and hydrocarbon content are often useful in analyzing flash dryer
performance.
Compost pile temperatures should be monitored to assure a proper rate of
stabilization. Temperatures should be taken at the inside of the compost pile.
207
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Temperatures are the critical parameters in flash dryer system operation.
Temperature is usually monitored continuously at several points in the process.
These monitoring points should be in accordance with the dryer manufacturer's
recommendations.
Oxygen readings indicate the performance of the composting operation and serve as
the basis for turning windrows and adjusting aeration blowers for static pile
composting.
In static pile composting, monitoring of air flows may be useful in assessing
system performance. This can be most easily accomplished by monitoring blower
running time.
Monitoring of combustion air flows is often useful and should be included in the
monitoring program if recommended by the dryer manfacturer.
Fuel consumption records are valuable in optimizing the operation of the flash
drying processes.
E.5.b. Procedures
The manual should explain all monitoring and record-keeping procedures, includ-
ing sampling frequencies, methods, and locations. Laboratory procedures should
include step-by-step instructions together with references to the appropriate
chapters in Standard Methods for the Analysis of Water and Wastewater (9) or
other laboratory desk reference.
E.5.c. Using Results
The operation and maintenance manual should explain the purpose and use of each
test. Where monitoring is for operational parameters, explanation should be
included as to the control actions which should be taken in response to the
measurements.
E.5.d. Reporting Procedures
The manual should include detailed instructions for reporting required data to
regulatory agencies. The agency, required parameters and reporting frequency
should be identified. Sample record and reporting forms are valuable aids to the
operator and should be included.
E.6. STARTUP
The startup procedures should include a sequence of operations for starting the
process. This is particularly true for flash drying systems which should include
such data as maximum safe heating rates for reactors, expected auxiliary fuel
consumption and operating temperatures which must be attained before operation
can begin.
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Manuals for composting and bed and lagoon drying systems may be able to omit
separate startup instructions as the startup of these systems may be indistin-
guishable from normal operation.
E.7. NORMAL OPERATION
Normal operating instructions for sludge processing systems should identify the
economical range of sludge feed rates and product packaging and loading instruc-
tions. Composting system descriptions should also include:
Mixing instructions, including sludge-to-bulking agent ratios
Windrow or static pile construction instructions, including dimensions
Windrow turning instructions and frequency
Static pile aeration schedules
Normal range of pile temperatures
Composting time
Windrow or static pile removal instructions
Curing instructions
Curing time
Screening instructions
Bulking agent recycle instructions
Flash drying systems should include the following instructions:
• The normal range of air supply rates
• The normal range of auxiliary fuel consumption
• Normal operating temperatures
• Instructions for putting the system on standby status
Lagoon and bed drying system instructions should include expected drying times
and sludge removal procedures.
E.8. EMERGENCY OPERATION AND FAIL-SAFE FEATURES
A description of emergency procedures should be included, including the actions
to be taken in the event any component of the processing system experiences a
mechanical failure. The emergency procedures should identify the amount of time
expected to be available for corrective action and advise the operator of any
consequential problems which may result. This section of the manual is the
appropriate place to describe facilities for improving reliabilities such as:
Standby power
Standby fuel
Duplicate process units
Alternative sludge management systems
Availability of back-up equipment from other sites or agencies, or from
rental agencies.
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E.9. SHUTDOWN
The shutdown procedures should include a sequence of operations for shutting
down the process. This is particularly true for flash drying systems which should
include such data as maximum safe cooling rates for reactors, expected auxiliary
fuel consumption during cooling.
Manuals for composting and bed and lagoon drying systems may be able to omit
separate shutdown instructions as the shutdown of these systems may be indistin-
guishable from normal operation.
E. 10. SAFETY
Detailed safety procedures should be described for the processing system. Most
safety requirements are those generally applicable to wastewater treatment
plants, but certain additional safety factors should be called to the operator's
attention.
A flash dryers flame safety system's purpose, operation and features should be
called to the operator's attention. Special instructions should be included for
the safe use of the auxiliary fuel and associated equipment. Safety rules for the
reactor should be outlined, including such things as the use of air masks within
the reactor and viewing burning only through smoked glass. Dust is a particular
safety and maintenance problem for flash drying systems. The process product is a
very dry, finely divided, light, abrasive, combustible dust. The dust can be
highly explosive and can also cause equipment failures due to its abrasive
nature. Adequate measures must be detailed in the manual to insure control of the
dust.
Manuals for composting operations should include safety rules for the operation
of heavy construction equipment.
E.ll. IMPACT CONTROL
The manual must identify for the operator those operating parameters which are
vital to minimizing deleterious environmental impacts.
Environmental impact control relates primarily to air quality control from flash
drying processes and runoff control from composting operations. Air quality con-
trol can be enhanced by the operator by maintaining an adequate excess air supply
to the dryer furnace, insuring adequate burning temperatures and detention times,
adequate maintenance or air pollution control equipment, and proper dust control
procedures. Health impacts of sludge processing systems include the safety of the
finished product and control of disease vectors at the site. The safety of the
finished product is to a large degree, a function of the composition of the
sludge entering the process. The pathogen component can, however, be greatly
affected by the operation of the process. Proper composting and flash drying
operation can greatly enhance product safety. Disease vectors are potentially
troublesome in drying bed, drying lagoon and composting operations and detailed
measures for their control should be included in the operation and maintenance
manual.
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Social impacts such as odors, noise and dust are potential problems for sludge
processing systems, and adequate measures for their control should be identified.
Odors are usually minimized by proper operation of the process while the effects
of noise can often be minimized by scheduling of operations.
Dust is a particular problem in flash drying systems and its control is essen-
tial to successful operation.
E.12. PERSONNEL
The manual should outline operating and maintenance personnel requirements for
the sludge processing system (See references 71 and 72 for personnel requirements
for composting, sandbeds and sludge lagoons). Emphasis should be given to any
special qualifications or training recommended by equipment manufacturers.
Composting operations, for instance, will require a qualified heavy equipment
operator.
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REFERENCES
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REFERENCES
1. Process Design Manual for Sludge Treatment and Disposal EPA-625/1-79-011,
(September, 1979).
2. "Resource Conservation and Recovery Act," P.L. 94-580.
3. "Guidance for Preparing Facility Plans," EPA Office of Water Program Opera-
tions, (May, 1975).
4. "Federal Water Pollution Control Act Amendments of 1972," P.L. 92-500.
5. Metcalf and Eddy, Inc., Wastewater Engineering - Collection Treatment and
Disposal, McGraw-Hill, Inc., (1971).
6. 1968 National Survey of Community Solid Waste Practices, USEPA, USPHS,
(1968).
7. Process Design Manual for Sludge Treatment and Disposal, EPA-625/1-74-006
(October, 1974). [also note reference no.i]
8. Sommers, L.E., "Chemical Composition of Sewage Sludges and Analysis of Their
Potential Use as Fertilizers," Purdue University Agricultural Experiment
Station, Journal Paper 6420.
9. Standard Methods for the Examination of Water and Wastewater, APHA-AWWA-
WPCF, 14th Edition, (1975).
10. Owen, M.B., "Sludge Incineration," Journal of the Sanitary Engineering
Division, Proceedings of the ASCE, Vol 83, No. SA-1, (February, 1957).
11. Liao, Paul B. , "Fluidized-Bed Sludge Incinerator Design," Journal of the
Water Pollution Control Federation, Vol. 46, No. 8. pg. 1895C, (1974).
12. Fair, B.M., and Moore, E.W., "Sewage Sludge Fuel Value Related to Volatile
Matter," Engineering New-Record, p. 681, (1935).
13. Fair, G.M., and Geyer, J.C., Elements of Water Supply and Wastewater
Disposal.
14. "Federal Pretreatment Standards", (40 CFR 128).
15. Evaluation of Land Application Systems. EPA-430/9-75-001, (March, 1975).
16. Transport of Sewage Sludge, EPA-600/2-77-216, (December, 1977).
17. Knezek, B.D. and Miller, R.H. (ed.), "Application of Sludges and Wastewaters
on Agricultural Land: A Planning and Educational Guide" Ohio Agricultural
Research and Development Center, Wooster, Ohio, Research Bulletin 1090,
(October, 1970).
213
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18. Brough, Kerry, "Some Hot News About Sludge," Water & Wastes Engineering,
(August, 1977) pp.22-26.
19. Counts, C.A. and Shuckrow, A. J. , Lime Stabilized Sludge; It's Stability and
Effect on Agricultural Land, EPA-670/2-75-012, (April, 1975).
20. California Fertilizer Association, Western Fertilizer Handbook, The
Interstate Printers and Publishers, Inc., Danielle, 111., (1975).
21. Sommers, L.E. et al, "Principals and Design Criteria for Sewage Sludge
Application on Land" USEPA Sludge Treatment and Disposal, EPA-625/4-78-012,
(October, 1978).
22. Proceeding, Recycling Municipal Sludges and Effluents on Land, USEPA, USDA,
National Association of State Universities and Land-Grant Colleges, (July
9-13, 1973).
23. Council for Agricultural Science and Technology, Application of Sewage
Sludge to Cropland: Appraisal of Potential Hazards of the Heavy Metals to
Plants and Animals, EPA-430/9-76-013, (November, 1976).
24. Weber, B.A. et al, Land Application of Treated Sewage Sludge: Guidelines for
Communities and Farm Operators, Oregon State University Extension Service,
Corvallis, Oregon, (February, 1978).
25. State of Colorado, Department of Health, Guidelines for Sludge Utilization
on Land, (1976).
26. Keeney, D.R. et al, Guidelines For the Application of Wastewater Sludge To
Agricultural Land in Wisconsin, State of Wisconsin Department of Natural
Resources, Technical Bulletin #88, Madison, WI, (1975).
27. Life Sciences and Agricultural Experiment Station, Maine Guidelines For
Municipal Sewage Treatment Plant Sludge Disposal on the Land, Report No. 175
University of Maine, Orono, Maine, (November, 1975).
28. Ohio Agricultural Research and Development Center, Ohio Guide for Land
Application of Sewage Sludge, Ohio State University, Columbus, Ohio, (May,
1976).
29. "Criteria for the Classification of Solid Waste Disposal Facilities and
Practices (40 CFR 257), Federal Register, (September 13, 1979).
30. Knezek, B.D. and Miller, R.H. (ed.), Application of Sludges and Wastewaters
on Agricultural Land: A Planning and Educational Guide, MCD-35, reprinted
by EPA (March, 1978).
31. Black, C.A. ed., Methods of Soil Analysis, American Society of Agronomy,
Inc., Madison, Wise., (1965).
214
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32. Ellis R., et al, "Sampling and Analysis of Soils, Plants, Wastewaters, and
Sludge, Suggested Standardization and Methodology," Kansas State Experiment
Station, Research Publication No. 170, Manhatten, Kansas.
33. Official Methods of Analysis, Association of Official Analytic Chemists,
12th Edition, (1975).
34. Process Design Manual for Municipal Sludge Landfills, EPA-625/1-78-010, SW-
705, (October, 1978).
35. Folks, N.E., "Pyrolysis as a Means of Sewage Sludge Disposal," ASCE Journal
of Environmental Engineering Division, (August 1975).
36. Lewis, F.M., "Thermodynamic Fundamentals for the Pyrolysis of Refuse,"
Stanford Research Institute, (May, 1976).
37. Schultz, Dr. H.W. , "Energy from Municipal Refuse: A Comparison of Ten Pro-
cesses," Professional Engineer, (November, 1975).
38. Weinstein, N.J. and Toro, R.F., "Thermal Processing of Municipal Solid Waste
for Resource and Energy Recovery," Ann Arbor Science, Michigan, (1976).
39. Sieger, R. B., and Bracken, B.D., "Sludge, Garbage May Fuel California Sewage
Plant," American City and County, p. 37, (January, 1977).
40. Energy Conservation in Municipal Wastewater Treatment, Gulp, Wesner, Gulp,
EPA-430/9-77-011, Task 9, (1976).
41. Sebastian, Frank P., "Fertilizer Manufactures - Multiple Hearth Incinera-
tion," Environmental Engineering Handbook, Chilton Book Co.
42. Blattler, Paul X., "Wet Air Oxidation at Levittown," Water and Sewage Works,
(February, 1970).
43. "Background Information for New Source Performance Standards" (Vol.3), EPA-
450/2-74-003, APTD-1352C, (February, 1974).
44. Balakrishman, S., Williamson, D.E., and Okey, R.W., "State of the Art Review
on Sludge Incineration Practice," Federal Water Quality Administration
Report, 17070-DIV 04/70, (1970).
45. Burd, R.S., "A Study of Sludge Handling and Disposal," Federal Water Pollu-
tion Control Administration Publication WP-20-4, (1968).
46. Jones, J.L., Bomberger, D.C., Jr., and Lewis, F.M., "The Economics of Energy
Usage and Recovery in Sludge Disposal," presented at the 49th WPCF Confer-
ence, (October, 1976).
47. "Amendments to the National Emission Standards" (40CFR61.52).
48. "Air Pollution Aspects of Sludge Incineration," Technology Transfer, EPA-
625/4-75-009, (June, 1975).
215
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49. Hathaway, Steven W., and Olexsey, Robert A., "Improving Sludge Incineration
and Filtration Requirements With Pulverized Coal" Journal of the Water
Pollution Control Federation, p.2420, (December, 1977).
50. "User Acceptance of Wastewater Sludge Compost," EPA-600/2-096, (August,
1977).
51. Burd, R.S., A Study of Sludge Handling and Disposal, Federal Water Pollution
Control Administration Publication WP-20-4, (1968).
52. Bryan, A. C. and Gannett, M. T. Jr., "What Do You Do With Sludge? Houston Has
An Answer," Public Works, p.44, (December, 1972).
53. "Sludge Treatment and Disposal, Volume 1, "EPA-625/4-78-012, (October
1978).
54. Wiley, John S., "A Discussion of Composting of Refuse With Sewage Sludge,"
Presented at the 1966 APWA Public Works Congress, Chicago, Illinois,
(September 13, 1966).
55. "Cost Effectiveness Guidelines," Federal Register (40CFR35-Appendix A).
56. A Guide to the Selection of Cost Effective Wastewater Treatment Systems,
EPA-430/9-75-002, (July, 1975).
57. An Analysis of Construction Cost Experience for Wastewater Treatment Plants,
EPA-430/9-76-002, MCD-22, (February, 1976).
58. Design Criteria for Mechanical, Electric, and Fluid System and Component
Reliability, EPA-430/99-74-001, (1974).
59. "Grants Regulations and Procedures Revision of 40CFR30,420-6," Federal
Register, (May 8, 1975).
60. Patterson, Donald J. and Heiner, N.A., Emissions from Combustion Engines and
Their Control, Ann Arbor Science, (1972).
61. Sebastian, Frank P., Allen, Terry D., and Laughlin, William C. Jr., "Think
Thermal," Water and Wastes Engineering, p.47, (September, 1974).
62. "Uniform Relocation Assistance and Land Acquisition Policies Act of 1970."
63. "Toxic Substances Control Act" (P.L. 94-469).
64. "New Source Performance Standards for Sludge Incinerators" (40CFR60-15,
Appendix IV.).
65. "Clean Water Act" (P.L. 95-217).
66. Alternate Waste Management Techniques for Best Practicable Waste Treatment,
EPA-430/9-75-014.
216
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67. Sebastian, Frank P., "Advances In Incineration and Thermal Processes,"
University of California at Berkeley Short Courses on the Theory and Design
of Advanced Waste Treatment Processes.
68. Mayrose, D.P., "Fluidized Bed Reactor Ease Problems," Water and Wastes
Engineering, (October, 1976).
69. Unterberg, W., Sherwood, R. J. and Schnecters, G.R. , Computerized Design and
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70. Considerations for Preparation of Operation and Maintenance Manuals,
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71. Gulp, Gordon L., Handbook of Sludge Handling Processes, Garland, New York,
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72. "Estimating Staffing for Municipal Wastewater Treatment Facilities," EPA
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217
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BIBLIOGRAPHY
-------
BIBLIOGRAPHY
This Bibliography is a list of several representative works on sludge management
published over a five year period. It is not comprehensive as over 1500 books,
papers, articles and patents relating to sludge management were published during
that period. An extensive literature review is published annually in the June
issue of the Journal of the Water Pollution Control Federation. This is an
excellent source of additional Bibliographic information regarding all aspects of
water pollution control including the treatment, utilization and disposal of
wastewater sludges.
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Treatment—A Comparison of Alternatives." Rept. prepared for Council on Environ.
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Design." Water & Sew. Works, 122, 8, 52 and 122, 9, 100 (1975).
Bergstedt, D.C., "Energy Conservation and Recycling Program of the Metropolitan
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219
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Carroll, I.E., et al., "Review of Landspreading of Municipal Sewage Sludge." EPA.
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Claydon, M.B., et al., "Disposal of Municipal Sludges to Agriculture." Proc.
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Council for Agricultural Science and Technology, "Application of Sewage Sludge to
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(1976).
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220
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Ehreth, D.J., "Municipal Sludge Management: Problems and Research and
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Ember, L.R., "Ocean Dumping: Philadelphia's Story." Environ. Sci. & Technol., 9,
916 (1975).
Epstein, E., and Wilson, G.B., "Composting Sewage Sludge." Proc. Natl. Conf. on
Municipal Sludge Management, Information Transfer, Inc., Washington, B.C. 123
(1974).
Ettlich, W.F. "Economics of Transport Methods of Sludge." Proc. 3rd Natl. Conf.
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Ettlich, W.F., "Whats's Best for Sludge Tranport?" Water & Wastes Eng., 13, 10,
20 (1976).
Ettlich, W.F., and Lewis, A. K., "Is There a 'Sludge Market'?" Water & Wastes
Eng., 13, 12, 40 (1976).
Farrell, J.B., "Design Information of Dewatering Properties of Wastewater
Sludges." Sludge Handling and Disposal Seminar Conf. Proc. No, 2,269 (1974);
Water Res. Abs., 8, 23, W75-11722 (1975).
Farrell, J.B., "Overview of Sludge Handling and Disposal." Proc. Natl. Conf. on
Municipal Sludge Management, Information Transfer, Inc., Washington, D.C., 5
(1974).
Garber, W.F., et al., "Energy-Wastewater Treatment and Solids Disposal." Jour.
Environ. Eng. Div., Amer. Soc. Civil Engr., 101, 319 (1975).
Gates, D.W., "Incinerator is Part of Integrated Waste Disposal System." Public
Works, 105, 5, 64 (1974).
Grandt, A.F., "Use of Sewage Sludge for Land Reclamation—A Coal Company's Point
of View." Proc. 3rd Natl. Conf. on Sludge Management Disposal & Utilization,
Information Transfer, Inc., Rockville, Md., 46 (1977).
Hall, G.W., "Public Relations Aspects of the Prairie Plan: A Sewage Sludge on
Land Project." Proc. 3rd Natl. Conf. on Sludge Management Disposal & Utilization,
Information Transfer, Inc., Rockville, Md. , 54 (1977).
Hays, B.D., "Is There a Potential for Parasitic Disease Transmission From Land
Application of Sewage Effluents and Sludges?" Jour. Environ. Health, 39, 424
(1977); Water Res. Abs., 10, 23, W77-11750 (1977).
Hecht, N.L., et al, "Charaterization and Utilization of Municipal and Utility
Sludges and Ashes, Summary." EPA Technol. Series, EPA-670/2-75-033 (1975).
221
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Helle, S.C., "Estimating Costs of Wastewater Sludge Disposal." Public Works, 108,
3, 56 (1977).
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108, 9, 110 (1977).
Hinesly, T.D., "Sludge Recycling—The Most Reasonable Choice?" Water Spectrum, 5,
1, 1 (1973).
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Jour. Water Poll. Control Fed., 48, 77 (1976).
Jones, J.L., et al., "Municipal Sludge Disposal Economics." Environ. Sci. &
Technol., 11, 968 (1977).
Jorgensen, S.E., "Do Heavy Metals Prevent the Agricultural Use of Minicipal
Sludges." Water Res. (G.B.), 9, 2, 163 (1975).
Kalinske, A. A. "All Cost Must be Counted." Water & Wastes Eng., 11, 3, 49
(1974).
Kalinske, A.A. et al., "Sludge Disposal Alternatives." Water & Sew. Works 122,
11, 61 (1975).
Kelling, K.A. , et al., "The Effect of Wastewater Sludge on Soil Moisture
Relationships and Surface Runoff." Jour. Water Poll. Control Fed., 49, 1698
(1977).
Kellogg, C., "The Business of Processing and Marketing Wastes as Fertilizer and
Soil Conditioner." Compost Sci., 16, 3, 25 (1975).
Kirkham, M.B., "Disposal of Sludge on Land: Effect on Soil, Plants, and Ground
Water." Compost Sci., 15, 2, 6 (1974).
Kirkham, M.B., and Dotson, G.K., "Growth of Barley Irrigated With Wastewater
Sludge Containing Phosphate Precipitants." Proc. Natl. Conf. on Municipal Sludge
Management, Information Transfer, Inc., Washington, D.C., 97 (1974),
Knapp, I.M., "City Reaps Income from Sludge Processing System." Public Works,
108, 10, 103 (1977).
Kostolich, M.S., "Hauling Digested Sludge in Tank Cars." Proc. Natl. Symp. on
Ultimate Disposal of Wastewaters and Their Residuals, Water Resources Res. Inst.,
North Carolina State Univ., Raleigh, 178 (1974).
"Land as a Waste Management Alternative." R.C. Lehr [Ed.], Ann Arbor Publ., Inc.,
Ann Arbor, Mich. (1977).
Larger, D., "Sludge Drying and Incineration." Prog. Water Tech., 7, 161 (1975).
Lund, E., "Disposal of Sludges." Viruses in Water, Amer. Pub. Health Assn., Inc.,
Washington, D.C., 196 (1976).
222
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Lund, L.J. , et al., "Nitrogen & Phosphorus Levels in Soil Beneath Sewage Disposal
Ponds." Jour. Environmental Quality, 5, 1, 26 (1976).
Lynam, B.T., et al. , "Automation of Sludge Processing, Transport and Disposal."
In Research Needs for Automation of Wastewater Treatment Systems, H. 0. Buhr, et
al. [Eds.], Clemson Univ., Clemson, S.C., 70 (1975).
Hears, D.R., et al., "Thermal and Physical Properties of Compost." In Energy,
Agriculture, and Waste Management, W.J. Jewell [Ed.], Ann Arbor Sci. Publishers,
Inc., Ann Arbor, Mich., 515 (1975).
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(1975).
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226
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APPENDICES
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APPENDIX A
DESIGN OF LAND APPLICATION SYSTEMS
FOR AGRICULTURAL UTILIZATION OF SEWAGE SLUDGE
INTRODUCTION
Utilization of sludge as a soil amendment can be very beneficial to crop growth
or, if mismanaged, can have disastrous results. Benefits include the addition of
nitrogen, phosphorus, and organic matter. Nitrogen and phosphorus are necessary
plant nutrients. Organic matter improves drainage of clay soils and moisture
holding capacities of sandy soils. Tillage characteristics of soils are also
improved. Generally, the soil conditioning properties of sludge are more
significant than the nutrient additions. Mismanagement of a land application
system can result in public health problems, odor nuisances, and/or soil
destruction from excessive heavy metal buildup. A land application system must be
designed to provide maximum benefits from the sludge without creating problems.
The design should therefore include rate determination schedules and methods to
be used by operators. Monitoring requirements should also be specified to help
prevent nuisance conditions from developing. This appendix has been developed
with emphasis on the agricultural management aspects rather than the public
health. The procedure used is similar to one in Reference 21.
Sludge Analysis
Prior to applying sludge to cropland, the following tests should be run:
Sludge Analyses
Nitrogen content and forms
Organic nitrogen
Ammonia
Nitrates
Phosphorus
Potassium
Heavy metals
Cadmium
Lead
Copper
Zinc
Nickel
Percent solids
Tests required by local health agencies
These tests should be run monthly for three to six months prior to starting the
land application system so that averages can be computed. After the system has
begun operation, annual monitoring should be continued so that changes in
constituent levels can be detected and application rates adjusted.
A-l
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Site Preparation
Prior to applying sludge to a particular site, the soil should be tested for pH,
cation exchange capacity, and phosporus and potassium availability. The existing
crops grown should be reviewed for adaptability to sludge amended soils. If an
unacceptable crop is being grown (e.g., a raw vegetable), then another crop would
be required. Crop selection would have to be consistent with local farming
practices and locally marketable.
Futher site preparation can then be done after a crop or crops have been chosen.
Site work includes drainage control, monitoring wells, pH adjustment by lime
addition (if necessary), and field preparation fot eh crop to be grown. Drainage
control is essential for good agricultural practice as well as protection of
downstream water quality. In general, natural drainage courses should be left
undisturbed. If a drainage course passes through a site, field runoff should be
diverted but the drainage course left in place. Runoff from adjacent areas should
be diverted around the land application site.
Monitoring wells should be placed throughout the site. Depth of well would be
based on ground water location. Location of well is usually based on site layout
and groundwater flow direction. Diameters should be large enought to provide easy
sampling.
pH adjustment is generally necessary for those soils with pH values less than
6.5. The adjustment is usually accomplished by lime addition.
Field preparation is the tillage required for crop planting. If sludge is surface
spread, then field preparation will usually follow immediately so that the sludge
is tilled into the soil.
Application Rate Calculation
The application rate calculation is frequently based mainly on the nitrogen
requirements of the crop to be grown. The computed rate is then adjusted, if
necessary, to prevent excessive heavy metal or phosphorus buildups. A
step-by—step procedure follows:
Step 1 Determine Application Rate by Nitrogen Balance
a. Analyze sludge nitrogen content. Determine organic nitrogen, ammonium
nitrogen and nitrate nitrogen (if aerobically digested) concentrations.
Typical nutrient contents for anaerobic sewage sludges are shown on
Table A-l.
For this example, assume the organic nitrogen is 80 Ib/ton and ammonium
nitrogen is 30 Ib/ton.
b. Determine nitrogen requirement of the crop from Table A-2. For this
example assume corn is grown ( expected yield of 180 bu/acre). The
nitrogen requirment is 240 Ib/ac.
A-2
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TABLE A-l. COMPOSITION OF REPRESENTATIVE ANAEROBIC SEWAGE SLUDGES (8)
Component
Range
Lb/ton**
Organic nitrogen
Ammonium nitrogen
Total phosphorus
Total potassium
1%
1%
1.5%
0.27%
- 5%
- 3%
- 3%
- 0.8%
20 -
20 -
30 -
4 -
100
60
60
16
*Percent of oven-dry solids
**Lb/ton dry sludge
TABLE A-2. ANNUAL NITROGEN, PHOSPHORUS, AND POTASSIUM UTILIZATION
BY SELECTED CROPS*
Crop
Yield
Nitrogen
Phosphorus
Lbs. per Acre
Potassium
Corn
Corn silage
Soybeans
Grain sorghum
Wheat
Oats
Barley
Alfalfa
Orchard grass
Brome grass
Tall fescue
Bluegrass
150 bu
180 bu
32 tons
50 bu
60 bu
8,000 Ib
60 bu
80 bu
100 bu
100 bu
8 tons
6 tons
5 tons
3.5 tons
3 tons
185
240
200
257
336
250
125
186
150
150
450
300
166
135
200
35
44
35
21
29
40
22
24
24
24
35
44
29
29
24
178
199
203
100
120
166
91
134
125
125
398
311
211
154
149
* Note that this hypothetical illustrated case does not agree with Table 8
values. Values will vary with yield and regional crop practices.
c. Determine the amount of nitrogen available from mineralization of pre-
viously applied organic nitrogen and the amount that will be available
from present application. Crops utilize nitrogen when it is in the
ammonium or nitrate forms. Organic nitrogen must be converted to the
ammonium ion before it can be utilized by the plant. The conversion or
mineralization rate varies with climate and soil type, but a typical
mineralization rate would be 20 percent the first year and 3 percent of
the remaining organic nitrogen each year for subsequent years. The
release rates of nitrogen by this process are shown on Table A-3 for
different sludges.
A-3
-------
TABLE A-3. RELEASE OF RESIDUAL NITROGEN DURING SLUDGE DECOMPOSITION IN SOIL
Year after Organic N content of sludge, %
sludge application 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Lb. N Released per Ton or Sludge Added
1
2
3
1.0
0.9
0.9
1.2
1.2
1.1
1.4
1.4
1.3
1.7
1.6
1.5
1.9
1.8
1.7
2.2
2.1
2.0
2.4
2.3
2.2
The example sludge has 80 Ib/ton organic nitrogen. Assume this is the
fourth year of land application. The previous applications were at 10
tons/acre with sludge having an 80 Ib/ton or 4 percent organic nitrogen
content. The amount of available nitrogen is computed as follows:
Previous Year: 1.9(10) + 1.8(10) = 1.7(10) = 54 Ib/acre
This Year: 30 Ib/ton + 80 Ib/ton x .20(% available) = 46 Ib/ton
d. Compute Application Rate
Nitrogen Required - Nitrogen Available = Nitrogen to be applied
240 Ib/acre - 54 Ib/acre = 186 Ib/acre
Tons sludge required: 186 Ib/acre ^ 46 Ib/ton = 4 tons/acre
Step 2 Check Metals Accumulation
The maximum tolerable heavy metals accumulations depend on the soil cation
exchange capacity (CEC). These maximums are shown on Table A-4. These are valid
as long as the soil pH is maintained greater than 6.5. At lower pH values the
metals are taken up by the crops, resulting in plant damage or possible injury to
crop consumers. The metals concentrations are cumulative so previous additions
must be considered. Table A-5 shows heavy metal concentrations assumed for this
example.
TABLE A-4. TOTAL AMOUNT OF SLUDGE METALS ALLOWED ON AGRICULTURE LAND
Soil cation exchange capacity (Meq/100 g )
Metal 0-5 5-15 15
Maximum amount of metal (Ib/acre)
Pb 500 1,000 2,000
Zn 250 500 1,000
Cu 125 250 500
Ni 50 100 200
Cd 5 10 20
Determined by the pH 7 ammonium acetate procedure
A-4
-------
Table A-5. EXAMPLE HEAVY METAL CONCENTRATIONS
Concentration
Metal
Ib/ton
Pb
Zn
Cu
Ni
Cd
500
750
1,000
500
75
1.0
1.5
2.0
1.0
0.15
The cumulative metal additions are shown on Table A-6.
TABLE A-6. METALS ADDITIONS (Ib/acre)
Metal
Year 1
Year 2
Year 3
This Year
Total
Pb
Zn
Cu
Ni
Cd
10 (1.0)
10(1.5)
10(2.0)
10(1.0)
10(0.15)
10(1.0)
10(1.5)
10(2.)
10(1.0)
10(0.15)
10(1.0)
10(1.5)
10(2.0
10(1.0)
10(0.15
4(1.0)
4(1.5)
4(2.0)
4(1.0)
4(0.15)
34
51
68
34
5.1
-tons/acre of dry sludge
Ib/ton of dry sludge
The totals in the last column of Table 6 are then compared with the values in
Table 4. For this example the tons/acre application rate results in a cadmium
total addition greater than 5 Ib/ac. If the cation exchange capacity is less than
5 meq/100 grams, the safe cadmium level has been exceeded. The application rate
would then be lowered for this year and no futher application allowed in
subsequent years. The allowable cadmium concentration is 5 Ib/acre. Previous
applications resulted in 4.5 Ib/acre. The allowable application rate is
determined as follows: 5 lb/ac-4.5 Ib/ac = 3.33 tons/acre
.15 Ib/ton
The nitrogen balance would be recalculated and supplemental nitrogen added or a
decreased yield accepted.
For this example assume the CEC is greater than 5 so sludge application can
continue.
A-5
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Step 3 Determine Supplemental Nutrient Requirements
Phosphorus and potassium balances are checked. For this example, assume a
phosphorus content of 40 Ib/ton and a potassium for corn growth are 44 and 199
Ib/ac/yr, respectively. At 10 tons/acre for three years, the phosphorus addition
has been 1,200 Ib/ac with only 132 Ib/ac being utilized. Therefore, no additional
phosphorus is required.
Potassium additions have been 100 Ib/ac/yr at the 10 ton/ac application rate,
while crop requirements have been 199 Ib/ac/yr. At the 4 ton/ac application rate,
the potassium added is 40 Ib/ac. Therefore, 159 Ib/ac supplemental potassium (or
potash) is required.
Step 4 Determine Wet Application Rate
All calculations above were based on a sludge dry weight. The operator will be
applying sludge with varying concentrations of water. For subsurface injection or
spray systems, the liquid sludge will generally be less than 10 percent solids.
The dry weight used above of 4 tons/acre is 40 wet tons/ac or 9,592 gal/ac.
Assuming a spreading width of 9 feet and an application flow of 800 gpm, the
necessary application vehicle speed is calculated as follows:
9,592 gal/ac x 9 feet - 1.98 gal/ft
43,560 sq ft/ac
800 gpm x 60 min/hr = 4.59 mph
1.98 gal/ft x 5,280 ft/mile
or developing a conversion factor for this equipment, the speed is computed as
follows:
800 x 60 x 43,560 = 44,000 (conversion factor)
9 x 5,280
1 x (44,000) = 4.59 mpg
9,592
Once the equipment has been selected, the appropriate conversion factor can be
computed by the approach shown above.
SUMMARY
Essentially, as shown by the preceding example, the correct sludge application
rate depends on the constituent concentration of the sludge and the composition
of the soil receiving the sludge. A sludge application rate may be safe at one
site but hazardous at another site. The preceding information was developed for
agricultural purposes only. Local health officials and regulatory agencies should
be contacted for pretreatment requirements and application technique restraints.
A-6
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APPENDIX B
LANDFILL DESIGN
SLUDGE-ONLY LANDFILL AT A PRESELECTED SITE
TREATMENT PLANT CHARACTERISTICS
• Service Population = 150,000.
• Average Flow = 15 mgd.
• Liquid processes include preliminary screening and grit removal and primary
treatment followed by activated sludge, secondary sedimentation and
chlorination.
• Solids processes include gravity thickening, mixing, anaerobic digestion,
and vacuum filtration.
SLUDGE CHARACTERISTICS
• Solids content is 20 percent.
• Quantity on a dry weight basis = 10 ton/day.
• Quantity on a wet weight basis = 50 ton/day.
• Density = 1700 Ib/cu yd
• Quantity on a wet volume basis =
50 ton/day x 2000 Ib/ton = 58.8 cu yd/day
1700 Ib/cu yd
CLIMATE FACTORS
• Precipitation = 30 in/yr
* Evaporation = 25 in/yr
• Number of days min temperature freezing or below = 55 days
• Precipitation exceeds evaporation by 5 in/yr
SITE
• Size of property = 280 ac.
• Uniform slope of approximately 5 percent.
• Site currently covered with native grasses.
B-l
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• No surface water on site.
• Groundwater at a depth of 12 ft; soil moderate to slow permeability.
EVALUATION
• From the characteristics listed in Table 12, the narrow trench method is
suitable.
• From the design criteria listed in Table 13, the trench width should be 2-3
ft and the final cover 3-4 ft. There is no bulking agent required and no
important soil. The application rate should be 1,200 to 5,600 cu yd/acre.
DESIGN FEATURES
• Excavation - allow 4 ft separation between trench bottom and groundwater;
therefore, excavation will be 8 ft.
• Spacing - for stable soil, allow 1 ft for each foot of depth; therefore,
spacing between trenches will be 8 ft.
• Width - trench width should be 2 ft (dug with backhoe).
• Length - trench length to prevent solids flow to one end of trench is 200
ft; 5 ft should be provided between trenches for containment.
• Orientation - trenches should be parallel to each other.
• Fill depth - because of the depth of the trench, sludge should not be
filled closer than 1.5 ft to top of trench; therefore, depth is 6.5 ft and
the usual range is 1 to 2 ft.
• Cover thickness - cover should be 3 ft because of the depth of fill; the
usual range is 2 to 3 ft.
SITE DEVELOPMENT
• The site should be divided into fill areas depending on the shape of the
area. A wet weather fill area near the entrance to the site should be pro-
vided with a paved access road. Adequate buffer around the site would
include trees and a chain link fence. Access to the fill areas should be
gravel roads leading from the paved wet weather access road. About 50 per-
cent of the site is actually usable fill area.
TRENCH UTILIZATION RATE
• Trench Utilization Rate = sludge volume/day
cross-sectional area of sludge in trench
= 58.8 cu yd/day x 27 cu ft/cu yd = 122 ft/day
6.5 ft x 2 ft
B-2
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Sludge Application Rate
sludge application rate = cross-section area of sludge in trench
width of trench + spacing
= 6.5 ft x 25 = 13 sq ft or 13 cu ft
2 ft + 8 ft 10 ft 10 sq ft
= 13 cu ft x 1 cu yd/27 cu ft = 2097 cu yd/ac
10 sq ft x 1 ac/43,560 sq ft
Land Utilization Rate
land utilization rate = sludge volume/day
sludge application rate
= 58.8 cu yd/day = 0.028 ac/day
22097 cu yd/ac
Site Life
site life = usable fill area
land utilization rate
= .5 x 280 acres = 5000 days = 13.7 yr
0.028 ac/day 365 days/yr
B-3
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APPENDIX C
EXAMPLE COMBUSTION MASS AND ENERGY BALANCE CALCULATION
This example is based on a methodology presented in a paper in the Proceed-
ings of the American Society of Civil Engineers, Journal of the Sanitary
Engineering Division, by Mark B. Owen entitled "Sludge Incineration". (10)
This example is for a multiple hearth furnace with no energy recovery.
Sludge Feed
2500 Ib/day liquid sludge
80% moisture content
60% of solids are combustible
Chemical analysis of combustible solids:
C - 59.8%, H - 8.5%, O - 27.5%
N - 4.2%, P - negligible
Heat Content of Combustible Solids
Q = 14,600C + 62,000 (H = £•)
Q = heat value, Btu/lb
C = fraction of carbon in fuel (sludge)
H = fraction of hydrogen in fuel
O = fraction of oxygen in fuel
Q = 14,600 (0.598) + 62,000 (0.085 - °'^75)
= 11,870 Btu/lb
Note: Use actual calorimeter test results whenever possible.
Auxiliary Fuel
Fuel oil with a chemical analysis:
C - 85%, H - 12%, S - 1.5%, Ash - 1.5%
Heat content: 148,000 Btu/gal or 19,000 Btu/lb
Specific Heats
C02
H2°
H2O
N2
so2
Air
Ash
(vapor)
(liquid)
Latent Heat of Water
0.244
0.472
1.00
0.256
0.174
0.250
0.20
Btu/lb/F
Btu/lb/F
Btu/lb/F
Btu/lb/F
Btu/lb/F
Btu/lb/F
Btu/lb/F
Vaporization (1
o
0
0
o
0
0
0
atm, 212 °F
970 Btu/lb
Incinerator Operating Conditions
Inlet temperature of all inputs - 60°F
Outlet temperature of stack gas - 900°F
Outlet temperature of ash - 700°F
Excess air - 50%
C-l
-------
Dry Solids in Sludge
M (sludge solids) = 2500 Ib/day (1-0.80)
= 500 Ib/day
Moisture in Sludge
M (sludge moisture) = 2500 Ib/day (0.80)
= 2000 Ib/day
Combustibles in Sludge
M (sludge combustibles) = 500 Ib/day (0.60)
= 300 Ib/day
Ash Generated by Sludge
M (sludge ash) = 500 Ib/day (1-0.60)
=200 Ib/day
Sludge Heat of Combustion
H(sludge) = 300 Ib/day (11,870 Btu/lb)
= 3,561,000 Btu/day
Sludge Combustion Reactions
C + O2 = C02
2H + 02 = 2H20
2N = N2
M(C in sludge) = 300 Ib/day (0.598)
=179 Ib/day
M(H in sludge) = 300 Ib/day (0.085)
=25.5 Ib/day
M(O in sludge) = 300 Ib/day (0.275)
=82.5 Ib/day
M(N in sludge) = 300 Ib/day (0.042)
=12.6 Ib/day
,.,~^ -, -,* -, ™ -,1- ,j (44 mol. wt. C
M (C02 produced) = 179 Ib/day (12 mol. wt. c
= 658 Ib/day
,,/TT ~ j, J,^ ^C r- i^ ,= (18 mol. wt. H0O)
M(H20 produced) = 25.5 Ib/day
2 mol. wt. }
= 229.5 Ib/day
M(N2 produced) =12.6 Ib/day
„._ ,. ,_„ .. ., ,32 mol. wt. O9. ,1,/j ,32 mol. wt. Oo
M(O? required) = 179 Ib/day (— - -, - —zr~) +25.5 Ib/day (— - ; - ^-.
•* 12 mol. wt. C ' * 2(2 mol. wt. H2)
- 82.5 Ib/day
=599 Ib/day
Air Requirements (w/o auxiliary fuel)
u • ^ 599 Ib/day O?
M (combustion air) = - • - *-
U • 2. j
= 2604 Ib/day
M (excess air) = 2604 Ib/day (0.50 excess)
= 1302 Ib/day
C-2
-------
Air Requirements (w/o auxiliary fuel) cont.
M(air supplied) = 2604 Ib/day + 1302 Ib/day
= 3906 Ib/day
M(N2 in combustion air) = (2604 Ib/day - 599 Ib/day)
= 2005 Ib/day
Moisture in Outlet
M(H20 in outlet) = 2000 Ib/day + 230 Ib/day
=2230 Ib/day
Latent and Sensible Heat of Free Moisture
H(Free H2O) = 2000 Ib/day ((212°F - 60°F) (1.0 Btu/lb/F°) + (970 Btu/lb)
+ (900°F - 212°F) (0.472 Btu/lb/F0))
= 2,893,500 Btu/day
Latent and Sensible Heat of Combustion Products of Sludge
H(H20 produced) = 230 Ib/day ((212°F - 60°F) (1.0 Btu/lb/F0) + 970 Btu/lb
+ (900°F - 212°F) (0.472 Btu/lb/F0))
= 332,700 Btu/day
H(C02 produced) = 658 Ib/day (0.244 Btu/lb/F0) (900°F - 60°F)
= 134,900 Btu/day
H(N2 produced) = 12.6 Ib/day (0.256 Btu/lb/F0) (900°F - 60°F)
= 2,700 Btu/day
H(sludge combus-
tion products) = 69,400
Sensible Heat of Excess Air and Nitrogen
H(excess air) = 1302 Ib/day (900°F - 60°F)(0.250 Btu/lb/F0)
= 273,400 Btu/day
H(N2 in combustion air) = 2005 Ib/day (900°F - 60°F)(0.256 Btu/lb/F0)
= 431,200 Btu/day
Sensible Heat of Ash
H(Ash) = 200 Ib/day (700°F - 60°F)(0.200 Btu/lb/F0)
= 25,600 Btu/day
Radiation and Conduction
Determination of Radiation and Conduction losses requires a detailed
analysis of the actual construction and installation of the proposed
incinerator. For the purpose of this example the losses are assumed
to be 2% of the total heat evolved from combustion processes.
H(radiation and conduction) = 3,561,000 Btu/day (0.02)
= 71,200 Btu/day
Sensible Heat of Shaft Cooling Air
Determination of shaft cooling air sensible heat and the heat availa-
ble from recycle of cooling air required a detailed analysis of the
actual construction and installation of the propsoed incinerator. For
the purposes of this example, it is assumed that 10% of the heat
evolved from combustion is lost to shaft cooling air and that 90% of
C-3
-------
this loss Is recoverable by recycling the shaft cooling air to the
process.
H(cooling air) = 3,561,000 Btu/day (0.10)
= 356,000 Btu/day
H(recycle) = 356,100 Btu/day (0.90)
= 320,500
Mass Balance (w/o auxiliary fuel)
I: puts Ib/day
Dry solids in sludge 500
Moisture in sludge 2000
Air 3906
Auxiliary Fuel -
Total Inputs 6406
Outputs
Ash 200
Water 2230
Carbon Dioxide 658
Sulfur Dioxide
Nitrogen 2018
Excess Air 1302
Total Outputs 6408
Latent and Sensible Heat of Combustion Products of Fuel (per Ib of fuel)
h(H O produced) = 1.08 Ib ((212°F - 60°F)(Btu/lb/F°)
+ 970 Btu/lb + (900°F - 212°F)(0.472 Btu/lb/F°)
= 1560 Btu
h(CO produced) = 3.12 Ib (900°F - 60°F)(0.744 Btu/lb/F°)
= 639 Btu
h(SO produced) = 0.030 Ib (900°F - 60°F)(0.174 Btu/lb/F°)
=4.38 Btu
h(final combustion
product) = 1560 Btu + 639 Btu +4.38 Btu
= 2203 Btu
Sensible Heat of Excess Air and Nitrogen (per Ib of fuel)
h(excess air) = 7.0 Ib (900 F°- 60°F)(0.250 Btu/lb/F°)
= 1470 Btu
h(nitrogen in
excess air) = 10.7 Ib (900°F - 60°F)(0.256 Btu/lb/F°)
= 2340
Sensible Heat of Ash (per Ib of fuel)
h(Ash) = 0.015 Ib (900 F°- 60°F)(0.20 Btu/lb/F°)
=2.52 Btu
Radiation and Conduction (per Ib of fuel)
h(radiation and conduction) = (19,000 Btu)(0.02)
= 380 Btu
04
-------
Sensible Heat of Shaft Cooling Air (per Ib of fuel)
h(cooling air = (19,000 Btu)(0.10)
= 1900 Btu
h(recycle) = 1900 Btu (0.90)
= 1710 Btu
Auxiliary Fuel Heat Available for Sludge Incineration (per Ib of fuel)
h(available) = 19,000 Btu - 1560 Btu - 639 Btu - 4.38 Btu - 1470 Btu
- 2340 Btu - 2.52 Btu - 380 Btu - 1900 Btu + 1710 Btu
= 12,400 Btu/lb
The mass balance agrees within the accuracy of the assumptions.
Energy Balance (w/o auxiliary fuel)
Inputs Btu/day
Solids Heat of Combustion 3,561,000
Auxiliary Fuel Heat of Combustion
Shaft Cooling Air Recycle 320,500
Total Inputs 3,881,500
Outputs
Latent and Sensible Heat of Free Moisture 2,893,500
Latent and Sensible Heat of Sludge
Combustion Products 469,400
Latent and Sensible Heat of Auxiliary
Fuel Combustion Products
Sensible Heat of Excess Air 273,400
Sensible Heat of Nitrogen in Combustion
Air 431,200
Sensible Heat of Ash 25,600
Radiation and Conduction 71,200
Sensible Heat of Shaft Cooling Air 356,100
Total Outputs 4,520,400
The outputs exceed the inputs by 638,900 Btu/day. In order to maintain
the operating conditions specified for the incinerator auxiliary fuel
will be required. Had the inputs exceeded the outputs, it would have
indicated higher operating temperatures than specified. In order to
balance the energy balance equations, new higher outlet temperatures
would have to be specified and the energy balance recalculated.
Since in our example, auxiliary fuel is required to maintain the specified
conditions, the mass and energy balance must be recalculated to take into
consideration the effects of the auxiliary fuel added.
Ash Produced by Fuel (per Ib of fuel)
m(Ash) = 0.015 Ib
Fuel Combustion Reactions (per Ib of fuel)
C + O2 = C02
C-5
-------
2H2 + 02 = 2H20
S + 02 = S02
m(C in fuel) = 0.850 Ib
m(H in fuel) = 0.120 Ib
m(S in fuel) = 0.015 Ib,,,, ,
/™ ^ JN oc^ -IT. (44 mol. wt.
m(C02 produced) = 0.850 l*l
= 3.12 Ib
, , ~ -, -,« ~ ,^(18 mol. wt.
m(H2O produced) = 0.120 — - - - - -
z (2 mol. wt. H2)
= 1.08 Ib
/r.^ j j\ ^-i c (64 mol. wt. SO?)
m(SO_ produced) = 0.015,— - = - r*-
2 * (32 mol. wt. S)
= 0.030 Ib
,,. ,. __. ., (32 mol. wt. Oo) „-,„-., (32 mol. wt.
m(0 produced) = 0.850 Ib ;— - - - - — -f- + 0.120 Ib '-— - - - - — —-.
2 e (12 mol. wt. C) 2(2 mol. wt. H )
+ 0.015 Ib (32 mol. wt. O2)
(32 mol. wt. S)
= 3.24 Ib
Air Required by Auxiliary Fuel (per Ib of fuel)
, -x 3.24 Ib 02
m (combustion air) = - — —
U • 2. j
= 14.1 Ib
m(excess air) = (14.1 lb)(0.50 excess)
= 7.0 Ib
m(air required) = 14.1 Ib + 7.0 Ib
= 21.1 Ib
m(N in combustion air) = 14.1 Ib - 3.24 Ib
= 10.9 Ib
Auxiliary Fuel Required
«/* ^ 638,900 Btu/day
M(fuel) = 12,400 Btu/lb
=52 Ib/day
The mass and energy balances are rewritten adjusting the figures for the
addition of 52 Ib/day of auxiliary fuel.
Mass Balance (final)
Inputs Ib/day
Dry solids in sludge 500
Moisture in sludge 2000
Air 5003
Auxiliary Fuel 52
Total Inputs 7555
C-6
-------
Mass Balance (final) cont.
Outputs Ib/day
Ash 201
Water 2286
Carbon Dioxide 820
Sulfur Dioxide 2
Nitrogen 2585
Excess Air 1666
Total Ouputs 7560
This agrees within the accuracy of the assumptions made.
Energy Balance (final)
Inputs Btu/day
Solids Heat of Combustion 3,561,000
Auxiliary Fuel Heat of Combustion (Total) 988,000
Shaft Cooling Air Recycle 409,400
Total Inputs 4,958,400
Outputs
Latent and Sensible Heat of Free Moisture 2,893,000
Latent and Sensible Heat of Sludge
Combustion Products 469,400
Latent and Sensible Heat of Auxiliary Fuel
Combustion Products 114,600
Sensible Heat of Excess Air 349,800
Sensible Heat of Nitrogen in Combustion Air 552,900
Sensible Heat of Ash 25,700
Radiation and Conduction 91,000
Sensible Heat of Shaft Cooling Air 455,000
Total Outputs 4,951,900
This agrees within the accuracy of the assumptions made.
C-7
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