United States Office of Reprint of
Environmental Protection Water Program Operations Department of the Army
Agency (WH-595) EM 1110-2-501
Washington, D.C. 20460 September 1978
EPA/430/9-79-008
Water
>EPA Design of Wastewater
Treatment Facilities
Major Systems
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DEPARTMENT OF THE ARMY EM 1110-2-501
Office of the Chief of Engineers Part 1 of 3
DAEN-CWE-BU Washington, D.C. 20314
Engineer Manual 29 September 1978
No. 1110-2-501
ENGINEERING AND DESIGN
Design of Wastewater Treatment Facilities
Major Systems
1. Purpose. Part One of this manual provides guidance for the selection
of wastewater treatment systems and processes and criteria for the design
of wastewater treatment facilities.
2. Applicability. The provisions of this manual are applicable to Corps
of Engineers Divisions and Districts concerned with the planning, design,
and optimization of new and upgraded wastewater treatment facilities for
Civil Works, and for the preparation of documents for wastewater management
programs.
3. General. In 1972 the Corps of Engineers became a full partner, along
with other Federal agencies, in Urban Area Comprehensive Planning organized
by the state and local governments. The Corps of Engineers was given the
authority for studying water problems in urban areas in addition to its
traditional sanitary sciences role at recreation sites, and for providing
information valuable to state and local governments for making grant
applications. These governments have the responsibility for relating
urban water problems, such as flood control, water supply, and wastewater
management to other urban problems, such as neighborhood renewal, recreation,
and transportation. This new responsibility emphasizes the need for in-depth,
and sound plans and designs for wastewater treatment facilities. This
manual is intended to provide design and cost criteria on which logical
choices for urban wastewater treatment plants may be made.
FOR THE CHIEF OF ENGINEERS:
f
PETERSON
Colonel, Corps of Engineers
Executive Director, Engineer Staff
U.S. Environmental Protection Agency
Region V, Library
230 South Dearborn Street
Chicago, Illinois 60604
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U,C. Environmental Protection /.£-r,:r/
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DAEN-CWE-S
Engineer Manual
No. 1110-2-501
DEPARTMENT OF THE ARMY
Office of the Chief of Engineers
Washington, D. C. 20314
EM 1110-2-501
Part 1 of 3
29 September 1978
Engineering and Design
DESIGN OF WASTEWATER TREATMENT FACILITIES
MAJOR SYSTEMS
Table of Contents
Subject
Page
CHAPTER 1. INTRODUCTION 1-1
CHAPTER 2. CHARACTERIZATION OF WASTEWATER FOR URBAN
AREAS 2-1
CHAPTER 3. DESIGN CONSIDERATIONS 3-1
CHAPTER 4. DESIGN AND EVALUATION OF PROCESSES AND
SYSTEMS 4-1
CHAPTER 5- PHYSICAL UNIT PROCESSES
Section I. INTRODUCTION 5-1
Section II. GRIT REMOVAL 5-3
Section III. SCREENING 5-19
Section IV.' COMMINUTION 5-29
Section V. EQUALIZATION 5-33
Section VI. FLOTATION 5-41
Section VII. THICKENING jGravity) 5-57
Section VIII. SEDIMENTATION (Primary Clarifier) 5-6?
Section IX. SEDIMENTATION (Secondary Clarifier) 5-83
Section X. FILTRATION 5-93
Section XI. VACUUM FILTRATION 5-119
Section XII. CENTRIFUGATION 5-131
Section XIII. MICROSCREENING 5-139
Section XIV. DRYING BEDS 5-149
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Section XV.
Section XVI.
Section XVII.
Section XVIII.
CHAPTER 6.
Section I.
Section II.
Section III.
Section IV.
Section V.
Section VI.
Section VII.
Section VIII.
Section IX.
CHAPTER 7.
Section I.
Section II.
Section III.
Section IV.
Section V.
Section VI.
Section VII.
Section VIII.
Section IX.
Section X.
Section XI.
Subject
POSTAERATION ,
SLUDGE HAULING AND LANDFILLING
MULTIPLE HEARTH INCINERATION -
FLUIDIZED BED INCINERATION
CHEMICAL UNIT PROCESS
INTRODUCTION
CARBON ADSORPTION
CHEMICAL COAGULATION
AMMONIA STRIPPING
CHLORINATION
ION EXCHANGE
NEUTRALIZATION
RECARBONATION
TWO-STAGE LIME TREATMENT
BIOLOGICAL UNIT PROCESSES
INTRODUCTION
TRICKLING FILTERS
PLUG FLOW ACTIVATED SLUDGE
COMPLETE MIX ACTIVATED SLUDGE
STEP AERATION ACTIVATED SLUDGE
EXTENDED AERATION ACTIVATED SLUDGE
MODIFIED OR HIGH-RATE AERATION ACTIVATED
SLUDGE
CONTACT STABILIZATION ACTIVATED SLUDGE
PURE OXYGEN ACTIVATED SLUDGE
AERATED AEROBIC LAGOONS
AERATED FACULTATIVE LAGOONS
Page
- 5-159
- 5-169
- 5-177
- 5-189
6 1
- 6-3
- 6-17
- 6-25
- 6-35
- 6-^3
- 6-55
- 6-61
6 69
- 7-1
- 7-3 ^
- 7-13 "
- .7-37
- 7-69
- 7-95
- 7-129
- 7-151
- 7-171
- 7-205
- 7-223
11
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Subject
Page
Section XII. OXIDATION DITCH 7-235
Section XIII. NITRIFICATION-DENITRIFICATION 7-253
Section XIV. AEROBIC DIGESTION 7-277
Section XV. ANAEROBIC DIGESTION 7-291
Section XVI. STABILIZATION PONDS 7-307
CHAPTER 8. COST DATA AND ECONOMIC ANALYSIS
Section I. INTRODUCTION 8-1
Section II. PHYSICAL UNIT PROCESSES 8-5
Section III. CHEMICAL UNIT PROCESSES 8-13
Section IV. BIOLOGICAL UNIT PROCESSES 8-17
APPENDIX A. REFERENCES A-l
APPENDIX B. ABBREVIATIONS B-1
APPENDIX C. CONVERSION FACTORS FOR UNITS OF MEASUREMENT;
DISSOLVED-OXYGEN SOLUBILITY DATA; PHYSICAL
PROPERTIES OF WATER; CHEMICAL ELEMENTS AND
SUBSTANCES; SPECIFIC WEIGHT C-l
GLOSSARY Glossary 1
INDEX Index 1
111
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CHAPTER 1
INTRODUCTION
1-1. Purpose. Part One of this manual provides guidance for the selec-
tion of wastewater treatment systems and processes and criteria for the
design of wastewater treatment facilities.
1-2. Applicability. The provisions of this manual are applicable to
Corps of Engineers Districts and Divisions concerned with the planning,
design, and optimization of new and upgraded wastewater treatment facil-
ities for Civil Works, and for the preparation of documents for waste-
water management programs.
1-3. References. See Appendix A for a list of selected references.
1-4. General Considerations.
a. In 1972 the Corps of Engineers became a full partner, along with
other Federal agencies, in Urban Area Comprehensive Planning organized
by the state and local governments. The Corps of Engineers was given
the authority for studying water problems in urban areas in addition to
its traditional sanitary sciences role at recreation sites, and for pro-
viding information valuable to state and local governments for making
grant applications. These governments have the responsibility for re-
lating urban water problems, such as flood control, water supply, and
wastewater management to other urban problems, such as neighborhood
renewal, recreation, and transportation. This new responsibility empha-
sizes the need for in-depth, and sound plans and designs for wastewater
treatment facilities. This manual is intended to provide design and
cost criteria on which logical choices for urban wastewater treatment
plants may be made.
b. The Corps of Engineers executes the Urban Studies Program in a
manner consistent with two basic principles:
(1) The responsibility for, and leadership of, urban area compre-
hensive planning is vested in state and local governments; and
(2) Duplication or conflict among Federal, state, regional, and
local agencies participating in urban area comprehensive planning is to
be avoided.
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c. The Corps of Engineers' responsibility for planning, optimizing,
and integrating selected treatment plant designs with other regional
water resource priorities is directed toward meeting the goals set forth
in the 1972 Amendments to the Federal Water Pollution Control Act
(PL 92-500).
d. Wastewater composition in urban/regional areas includes wastes
that are: (l) domestic in nature; (2) generally domestic with some
industrial; (3) primarily industrial; (4) primarily agricultural runoff;
(5) urban storm water runoff; or (6) combinations of the above.
1-5- Problems. Some of the problems associated with designing adequate
wastewater treatment facilities for metropolitan areas are:
a. The composition and relative level of enforcement of wastewater
standards and criteria vary substantially from state to state and along
different waterways and may exceed the requirements of PL 92-500.
b. Appropriate technical design guidance either has not been avail-
able or is inadequate for certain systems or subsystems, and, in some
instances, existing guidance may contribute to operational problems.
c. Flow rates and composition of discharged waste vary widely.
d. Requirements demand aesthetic quality be considered in site se-
lection, design, construction, and operational practices.
e. A high degree of treatment is often required (up to and includ-
ing advanced wastewater treatment standards).
f. Characterization of raw, primary, and secondary waste treatment
systems in some areas is generally inadequate to support a comprehensive
planning process for the area.
g. Data from recent and current research activities and from spe-
cific design problems in the field have not yet been correlated to yield
the maximum benefit.
1-6. Use of the Manual.
a. This manual is arranged in three parts so that the planner or
designer will have quick access to data for many wastewater treatment
processes both for the design of new treatment facilities and for the
checking and optimization of existing facilities. Subsequent chapters
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of Part One of this manual include design equations for waste treatment
processes; systems for computing costs and estimating the overall effi-
ciency of selected processes for major waste-water treatment facilities.
Part Two addresses those problems unique to the recreation area planner
and provides characterization and designs for "Small Scale Wastewater
Treatment Systems." To further aid planners and designers, a computer
aided design program (CAPDET) is available incorporating the design
methodology encompassed by Parts One and Two of this manual plus land
treatment. This program is currently running on the Waterways Experi-
ment Station GE-600 computer. The user guide for the CAPDET program is
Part Three of this manual.
b. This part of the manual serves to familiarize the designer with
the practical and theoretical aspects of physical, chemical, and bio-
logical processes and process trains for urban-type facilities ranging
from simple to complex systems, including tertiary systems for nutrient
removal. A table of factors for converting U. S. customary units of
measurement to metric (Si) units, a chart containing the physical prop-
erties of water, and a glossary are appended hereto for the convenience
of the user.
c. It should be recognized that the effects of scale are severe
limitations when dealing with physical-biologic systems such as those
found in wastewater treatment. This is especially true when small
facilities are being considered such as those required for very small
communities or intermittent-use systems such as those found at Corps'
recreational sites. In these cases,.where physical units become very
small and operators are not on the plant site continuously, many of the
more sophisticated unit process designs described in this manual are not
applicable. The user is referred to Part Two of the manual which deals
with small-scale wastewater management when faced with problems of this
scope.
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CHAPTER 2
CHARACTERIZATION OF WASTEWATER FOR URBAN AREAS
2-1. General. Water usage rates, wastewater production rates, and
wastewater characterization data for domestic sewage have been docu-
mented for urban area design. These rates and qualities are representa-
tive of the "average" city and are subject to the engineer's knowledge
of the area for their intelligent application. Needless to say, no table
of statistical values is a good substitute for field data. However, the
information presented in this chapter will allow the engineer to prepare
a first-look design and obtain rudimentary cost data for the area. Sub-
sequent iterations in the planning process demand that these average
values be replaced with site-specific values.
2-2. Selection of Urban Area Flow Design Parameters.
a. Total Waste Flow.
(l) One- of the most important parameters required for the effective
and realistic planning of any community sanitary facility is flow. Flow
is the major determinant of size, location, and public acceptance of any
plant. Unfortunately, flow may frequently be the most elusive parameter
to forecast. Many factors dramatically affect the flow reading of a
waste treatment facility; among these are (a) geographical location,
(b) type of users (e.g., residential, industrial, agricultural, etc.),
(c) sewer inflow, infiltration, and exfiltration, (d) consumptive uses
(e.g., lawn watering, car washing, etc.), (e) storm event history, and
(f) precipitation and resulting runoff.
(2) Metcalf and Eddy have found that between 60 and 80 percent of
the per capita consumption of water will become sewage. Based on
studies by the U. S. Public Health Service for the Select Committee on
Natural Water Resources published in I960, the average water consumption
on a national basis was found to be approximately iVf gallons per capita
per day (gpcd). This therefore represents an average wastewater flow
from 88 to 118 gpcd or about the 100-gpcd figure so frequently reported
in the literature. It should again be emphasized that this value rep-
resents only an average value which must be used with caution. An in-
crease of only 1 gpcd in a city the size of Kansas City can amount to
over $500,000 in capital and $150,000/year in operation and maintenance
(O-M) costs.
b. Flow Variations. In addition to the average flow, the designer
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must be cognizant of the maximum and minimum flows. The design of many
unit processes is based on a knowledge of peak flows, while the design
of others is based on minimum flows. Table 2-1 provides some compari-
sons found by Clark and Viessman in their research on domestic flow
fluctuations. Additional references to flow variations are given in
sections 4-3, 4-4, 4-6, 9-c(l)(2), 9-b, 10-f(2), and Technical Manual
No. 5 - 814-3, "Domestic Wagtewater Treatment."
c. Inflow/Infiltration. The terms "inflow" and "infiltration" are
used to describe flows into the sanitary sewer system from sources other
than normal sewage connections. Inflow refers to connections of waste-
water to the system which may not be septic in the biologic sense of the
term. Such connections include roof drains, parking lot drains, miscon-
nected storm water laterals, etc. Most inflows provide low pollutant
levels with relatively high volume quantities. This water is exces-
sively expensive to reclaim in the sanitary system and normally is
better disposed of by other means. Frequently nonstructural solutions
(e.g., sewer ordinances) are required to deal with areas of excessive
inflows. On the other hand, infiltration refers to the inward seepage
of groundwater into the collection system. The volume of such infiltra-
tion is a direct function of the length, size, and condition of the col-
lection system as well as the depth of the groundwater. According to
Environmental Protection Agency (EPA) guidelines, inflow/infiltration
below 1000 gpd per inch diameter of pipe per mile is nonexcessive.
Current EPA procedure is to determine if inflow/infiltration is excessive
to a point where it is more cost-effective to replace and/or rehabilitate
than to continue to transport and treat.
2-3. .Selection of Urban Area Wastewater Quality. Like flow, the quality
of raw sewage fluctuates from region to region. Table 2-2 gives a set
of typical characteristics of domestic sewage representative of most
urban areas. It must likewise be realized that heavy industrial or
commercial loadings can have a dramatic effect on the values listed.
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Table 2-1. Residential Sewage Flows
as Ratios to the Average
Flow
Maximum daily
Maximum hourly
Minimum daily
Minimum hourly
Ratio
2.25 to 1
3.00 to 1
0.6T to 1
0.33 to 1
Table 2-2. Typical Characteristics of Domestic Sewage
(mg/Jl unless
Parameter
BOD
COD
TOC
pH (units)
Total solids
Suspended, total
Fixed
Volatile
Dissolved, total
Fixed
Volatile
Settleable solids (m£/£)
Total nitrogen (as N)
Free ammonia (as NE~)
Total phosphorus (as P)
Chlorides (as Cl)
Sulfates (as SO, )
Alkalinity (as CaCO,.)
Grease
noted
High
350
800
300
7.5
1200
350
100
250
850
500
350
20
60
30
20
150
kO
350
150
otherwise)
Amount
Average
200
Uoo
200
7.0
700
200
50
150
500
300
200
10
1*0
15
10
100
20
225
100
Low
100
200
100
6.5
Hoo
100
25
75
300
200
100
5
20
10
5
50
10
150
50
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CHAPTER 3
DESIGN CONSIDERATIONS
3-1. Design Factors. Factors that must "be considered in the prepara-
tion of a design of a waste-water treatment facility may be subdivided
into site and system selection factors.
a. Site Selection.
(l) Distribution of facilities.
(2) Topography.
(3) Vegetation.
(U) Soil type—permeability and chemical composition.
(5) Groundwater elevation and location of aquifers.
(6) Distance to and condition of bedrock.
(?) Proximity to surface vaters.
(8) Land availability and cost.
(9) Stream water quality designation.
(10) Sludge disposal opportunities.
(ll) Collection system accessibility.
(12) Proximity to human nabitation.
b. System Selection.
(l) Governing criteria—legal and political.
(2) Number and types of facilities to be served.
(3) Energy requirements and availability.
(h) Capital cost of system.
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(5) Operation and maintenance costs.
(6) Number and types of operating personnel required.
(?) Waste-water characteristics and flows.
(8) Level of odors, noise, and insects.
(9) Acceptability of aesthetics.
(10) Flexibility of system.
(ll) Aesthetic and social concerns.
(12) Climate—seasonal variation.
3-2. Design Steps. The principal phases of design can be subdivided
into four steps: site selection, determination of waste flows and
strengths, and system selection.
a« Site Selection. Site selection includes a review of the techni-
cal and aesthetic factors listed in paragraph 3-la.
"b- Calculation of Flows. The calculation of wastewater flows to a
treatment facility was discussed in Chapter 2.
c. Calculation of Waste Strength. The strength of waste from most
domestic sources is known (Table 2-2) and was discussed in Chapter 2.
d- System Selection. Once a site has been selected and waste flows
and strengths have been estimated, the process of selecting/designing
a treatment facility can begin. This process includes a review of the
system selection factors (para 3-lb) and a mathematical analysis of one
or more waste treatment systems. At this point, a computer-based design
procedure may be used to design a system or to review the feasibility of
one or more recommended systems. Otherwise, the designer may indepen-
dently design a system, exercising his professional judgment in the se-
lection of processes to be considered, and manually compute the size and
operational characteristics of the system.
3-2
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CHAPTER U
DESIGN AND EVALUATION OF PROCESSES AND SYSTEMS
^-1. Factors Determining Process Selection. Selection of a process
train (combination of processes) for vastevater treatment will depend on
a variety of factors including:
a. Stream standards and/or receiving water quality.
b. Federal, state, and local effluent criteria.
c. Wastewater characteristics.
d. Economics.
e. Availability of fuel and/or electric power.
f. Specific exclusions of certain processes.
g. Possible requirements for future expansion and/or upgrading.
^-2. Process Substitution Diagram. The process substitution diagram
(fig- ^-l) is useful in system design and evaluation. In practice, the
diagram is entered from the left and the designer may select processes
for preliminary, primary, secondary, tertiary, and/or sludge treatment
according to specific needs. For a given set of wastewater character-
istics, there may be 30 or more viable treatment processes; a complete
treatment system may employ from 1 to 10 processes. Thus, there are
literally thousands of possible combinations and it is virtually impos-
sible for an individual designer or design team to evaluate all viable
processes and combinations of processes without the aid of the computer.
To limit the amount of evaluation required, the designer must rely
heavily on experiences and examples set by others to select processes or
eliminate certain processes from consideration. This practice places a
great burden on the designer and occasionally results in designs that
are far from an economic optimum.
^-3- Process Design. Specific design equations and practices for Uo
chemical, physical, and biological unit processes are given in Chap-
ter 5. The coverage of each process includes the following:
a. Background data.
U-i
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ro
PRE- TREATMENT
0»
(D
*0
PRIMARY TREATMENT SECONDARY TREATMENT
CHEMICAL
ntYStCAL DISSOLVED ORGANICS
h»j i-
«
f*
' SCREENING AMD ._
• GRIT REMOVAL ,
. EQUALIZATION 1.
' AND STORAGE jT*
OIL ..
• SEPARATDN j
» AERATED L.
* LAGOOM1 4["
> PONDS ••
S
TRICKLING
• FILTERS t *
» DILUTION [-«
• Mrt- *
OH.ORIKATION ,
*
1^ NEUTRALIZATION ^
t
*
CHEMICAL
• ADDITION FOR «
COAGULATION 1*
[^ PHOSPHORUS L
I*1
\
SUSPENDED SOLIDS
TERTIARY
TREATMENT
fc SPRAT .
MITIGATION ,,
~ FLOTATION [-•
* ll|
• SCOMENTATION J
1}
ACTIVATED 4
• SLUDGE
PROCESSES U *
TRICKLING •<
' FR.TH 4 .
„ STABILIZATION ,
" PONDS (3 TYPtSl s
B AC RATED
* LAGOONS 4 4
FACULTATIVE
• LAGOONS ,5 "
LAW
TREATMENT ,,
^ PHOSPHORUS „
REMOVAL „-
T
* ^ SCOHENTAriOM ^J
. U— ^~~ 'n
u.
M-
K
•
»J
^ LAND _
"* TREATMENT „
«J NITRIFICATION ^J"*
£ COAGULATION
* SEDHENTATKW 17
J FILTRATION *
* EXCHANGE *
• CHLORtNATUN «
1
j. -L
LIQUID
^ RECEIVING
I _ 2J
. LAND DISPOSAL
* AND SEEPAGE j,
EVAPORATIVE
SYSTEMS w
11
• DIGESTION L. i" 1
»hi * 1
SUPERNATANT OR DECANT t »^ _J 4
LEGEND
LIQUID WASTE STREAM
SOLIDS WASTE STREAM
1] PRIMARY SLUDGC
13A ACTIVATED SLUDGE
• 'ROUGHMG" SYSTEMS FOR
HIGH BOD WASTE
•* MAT IE USED W SCRIES
K" VACUUM *1 * LANDFILL
1
£* CENTRIFUGATKM *
LAGOONS OR V*
^, MYING BFDS 1
** OTHERS ~
DIGESTION DEWATEMING | DISPOSAL
SOL IDS HANDLING
U) \J1
Figure U-l. Wastewater treatment sequence processes substitution diagram.
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b. Input data requirements.
c. Design parameters (normal operating ranges).
d. Design procedures.
e. Output data.
f. Example calculations.
g. Bibliography.
^-^' Economic Analysis. The user is referenced to Chapter 8 for a dis-
cussion on cost estimating and economic analysis of wastewater treatment
facilities.
^-5- Bibliography.
a. U. S. Environmental Protection Agency, "Guidance for Facilities
Planning," Jan 1971*, Washington, D. C.
b. Water Resources Council, "Water and Related Land Resources,
Establishment of Principles and Standards for Planning," Federal Regis-
ter, Vol 38, No. 1?H, Sep 1973, pp 2^778-2^869.
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CHAPTER 5
PHYSICAL UNIT PROCESSES
Section I. INTRODUCTION
5-1. _ Definition. Those wastevater treatment processes that employ
SSt™ tf0rCe8 (meC?anica1' gravimetric, etc.) as a principal means of
treatment are generally referred to as physical unit processes or unit
operations. The physical unit processes described in this chapter are:
a. Grit removal.
b. Screening.
c. Comminution.
d. Equalization.
e. Flotation.
f. Thickening (gravity).
g. Sedimentation (primary clarifier).
h. Sedimentation (secondary clarifier).
i. Filtration.
j- Vacuum filtration.
k. Centrifugation.
1. Microscreening.
m. Drying beds.
n. Postaeration.
o. Sludge hauling and landfilling.
p. Multiple-hearth incineration.
I- Fluidized bed incineration.
5"1 (next page is 5-3)
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Section II. GRIT REMOVAL
5-2. Background.
a. Grit removal is classified as a protective or a preventive
measure. The process does not contribute materially to the reduction
in the pollutional load applied to the wastewater treatment facility.
Grit chambers are designed to remove grit which may include sand,
gravel, cinder, and other inorganic abrasive matter. Grit causes wear
on pumps, fills pump sumps and sludge hoppers, clogs pipes and channels,
and occupies valuable space in sludge digestion tanks. Grit removal,
therefore, results in the reduction of maintenance costs of mechanical
equipment and the elimination of operational difficulties caused by
grit. Grit removal is recommended for small as well as large treatment
facilities and for those served by combined as well as separate sewer
systems. Bar screens are usually installed ahead of grit chambers to
remove large floating objects.
b. Grit removal is normally accomplished through control of veloc-
ity and settling time. The objective is to settle the grit particles
while keeping the putrescible matter in suspension. Theoretically, it
is desirable to remove all grit; however, experience indicates that re-
moving 65-mesh grit, i.e. grit that is retained on a 65-mesh screen,
provides sufficient protection to mechanical equipment and eliminates
the majority of operational troubles caused by the grit. To remove the
65-mesh grit with a minimum of putrescible matter, a flow-through veloc-
ity of 0.75-1.25 fps must be provided at all flows.
c. The type of settling that normally takes place in a grit chamber
is classified as discrete settling, since each particle retains its
identity while settling at a constant rate. The design of such a
chamber is usually based on an overflow rate that- exceeds the settling
velocity of the smallest particle desired to be removed. Smaller par-
ticles are removed in proportion, according to the ratio of their set-
tling velocities to the settling velocity of the smallest particle that
is, theoretically, 100 percent removed. The overflow rates selected in
the design of a grit chamber must, therefore, exceed the settling
velocity of the 65-mesh particle. Grit settling velocities are sum-
marized in Table 5-1.
d. Grit chambers may be classified generally as either horizontal
flow or aerated. In the horizontal flow type, the velocity is con-
trolled by the dimensions of the chamber or by the use of a proportional
weir or a Parshall flume at the effluent end of the chamber. Aerated
5-3
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grit chambers consist of a spiral flov aeration tank with the spiral
flow velocity controlled by the dimensions and 'the quantity of air sup-
plied to the chamber. These chambers are very efficient and the grit
will be washed and easy to handle. Aerated grit chambers provide a
detention time of 3 min at the maximum rate of flow. Mechanical grit
removal equipment is usually recommended.
e. In summary, the design of grit chambers depends on the type
selected, type of grit removal equipment, specification of the selected
grit removal equipment, and the quantity and quality of the grit to be
handled.
f. Extensive discussion of grit removal is presented in the bibli-
ography (para 5-9 below).
g. As the trend toward mechanization of wastewater treatment facil-
ities continues to increase at a rapid rate, it is becoming a common
practice to include grit removal facilities in the design of treatment
systems serving small, as well as large, communities. Picnickers and
campers in some recreation areas either maliciously or accidentally drop
cans, bags, bottles, sticks, and rocks into vault toilets, trailer dump
stations, and other facilities. Hence, wastewater characteristics
should be thoroughly examined to determine the need for grit removal
facilities in the design of systems for recreation areas. Figure 5-1
shows a typical aerated grit chamber. Figure 5-2 shows a typical hori-
zontal flow grit chamber.
5-3. Input Data.
a. Wastewater Flow.
(l) Minimum and peak flows, mgd.
(2) Average daily flow, mgd.
b. Wastewater Characteristics (not applicable).
5-1*. Design Parameters (Tables 5-1 and 5-2).
a. Horizontal Flow Grit Chamber.
(l) Particle size, mm.
(2) Specific gravity.
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
SWING DIFFUSER IN
RAISED POSITION
MONORAIL SUPPORT
ALUMINUM PIPE
RAILINGS
SWING
DIFFUSER
ASSEMBLY
DIFFUSER TUBE ASSEMBLY-*
HEADER /
STOp
x- CONCRETE SADDLE UNDER EACH TEE
f AND HALFWAY BETWEEN TEES
SWING JOINT
MAX WATER SURFACE
UPPER HANGER PIPE
KNEE JOINT
LOWER HANGER PIPE
/•Irom Metcalf and
Eddy, 1972
Figure 5-1. Schematic of a typical aerated grit chamber.
v_ .__
/^>>>> "^^^
^OOOO^^N^V^ V^^^v »^vvJ
. S. S Si V Vfo
s
S,
s
s
•s
s
y^^ W^
PLAN VIEW
^7
^ GRIT WEIR_^
^v;^^^^^^^'^^. . . •'•••'•
\
\
A.N
\
SIDE VIEW ^FLUSHING SUMP
Figure 5-2. Schematic of a typical horizontal flow grit chamber.
5-5
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
(3) Maximum and average velocities, fps.
(U) Current allowance (l.?)-
3
(5) Volume of grit, ft .
(6) Number of units.
b. Aerated Grit Chamber.
(l) Detention time, min.
(2) Air supply, cfm/ft.
(3) Maximum and average velocities, fps.
3
(k) Volume of grit, ft .
(5) Number of units.
5-5. Design Procedure.
a. Horizontal Flow Grit Chamber.
(1) Select the number of units and calculate flow per unit,
QT
Q/unit = —
where
0 = total flow to plant, mgd
N = number of units
(2) Select maximum controlled velocity, v « 1.25 fps.
(3) Calculate cross-sectional area.
v
max
where
2
A = cross-sectional area, ft
5-6
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
Q = maximum flow/unit, mgd
IHcljC
Vmax = maximum controlled velocity, fps
(k) Assume depth and calculate width or vice versa.
A = WD
where
W = channel width, ft
D = channel depth, ft
(5) Calculate settling velocity of the smallest particle desired
to be 100$ removed (according to Table 5-1 or calculations).
Size « 0.2 mm
Specific gravity « 2.65
V =
s
3.28 x io~3
1/2
where
vg = settling velocity of smallest particle that is
100$ removed, fps
r)
g = gravitational acceleration, 32.2 fps
c = drag coefficient
P = specific gravity of the particle
S
d = diameter of the particle, mm
5-7
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EM 1110-2-501
Part 1 of 3
29 Sep 78
R = Reynolds number = - £ - -
n v x 3.28 x lo"-3
v = kinematic viscosity of the liquid, ft /sec
_o
3.28 x 10 = conversion factor, mm to ft
(6) Calculate the length of each channel.
/v \
L=D /JE93L}(1.7)
max I v /
\ s /
where
L = length of the channel, ft
D = depth at maximum flow, ft
max
v = velocity at maximum discharge, fps
max
v = settling velocity of the smallest particle that is 100%
removed, fps
l.T = allowance for currents
(T) Calculate detention time.
Q x i.lt
where
t = detention time, sec
D = channel depth, ft
W = channel width, ft
L = length of channel, ft
Q = flow, mgd
1.5U = conversion factor, mgd to cfs
5-8
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(8) Calculate bottom slope of channel.
v
avg n
where
v = velocity at average discharge, fps
n = Manning's coefficient (a value of 0.03 may be used)
A
R = hydraulic radius of cross section = for rectangular
channel 2D W
S = slope
(9) Calculate approximate volume of grit. The volume of grit may
vary from less than 1 ft3 to more than 12 ft3 per million gal of waste-
water. It must also be noted that the grit collected from a horizontal
flow grit chamber will contain a high amount of putrescible matter and
should be washed before disposal.
o
Assume h ft /million gal (approximate)
V = UQ
g
where
o
V = volume of grit, ft /day
O
Q = flow, mgd
(10) Design control section at outlet.
b. Aerated Grit Chamber.
(1) Calculate the length of channel.
_ (t)(Q
L = -
where
5-9
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EM 1110-2-501
Part 1 of 3
'29 Sep 78
L = length of channel, ft
t = detention time, min
Q = peak flow, mgd
2
A = cross-sectional area, ft
(2) Calculate air requirements, cfm.
Total air = L x O^/ft
where
L = length of chamber
0 /ft = air supply per ft of length (Table 5-2)
5-6. Output Data.
a. Horizontal Flow Grit Chamber.
(l) Maximum flow, cfs.
(2) Average flow, cfs.
(3) Minimum flow, cfs.
(U) Temperature, °C.
(5) Maximum flow-through velocity, fps.
(6) Average flow-through velocity, fps.
(7) Size smallest particle 100% removed, mm.
(8) Specific gravity of particle.
(9) Number of units.
(10) Maximum flow/unit, cfs.
(11) Width of channel, ft.
5-10
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(12) Depth of channel, ft.
(13) Length of channel, ft.
(14) Settling velocity of particle, fps.
(15) Slope of channel bottom.
(16) Allowance for currents.
(17) Detention time, sec.
(18) Manning's coefficient.
(19) Volume of grit, ft3/day.
(20) Design outlet control section.
"b. Aerated Grit Chamber.
(l) Detention time, min.
(2) Air supply, cfm/ft.
(3) Length, ft.
(it) Total air requirement, cfm.
5-7. Example Calculations.
a. Horizontal Flow Grit Chamber.
(1) Select number of units and calculate flow per unit.
unit N
where
Q = total flow to plant = 1 mgd
N = number of units = 1
5-11
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EM 1110-2-501
Part 1 of 3
29 Sep 78
.'. Q/unit =
Q./unit = 1
(2) Select maximum controlled velocity, v « 1.25 fps,
(3) Calculate cross-sectional area.
V
max
where
2
A = cross-sectional area, ft
Q = maximum flow/unit, 1 mgd
max
v = maximum controlled velocity, 1.25
max
1.5U = conversion factor
" 1.25
A = 1.23 ft2
Assume depth and calculate width.
where
W = width, ft
2
A = cross-sectional area, 1.23 ft
5-12
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EM 1110-2-501
Part 1 of 3
29 Sep 78
D = assumed depth, 1 ft
. .. 1.23 ft2
.. W =
1 ft
W = 1.23 ft
(5) Calculate settling velocity of smallest particle desired to be
100% removed from Table 5-1.
Size w 0.2 mm
Specific gravity « 2.65
1/2
where
v =
s
(V3)(g/cd)(Ps -
3.28 x 10 3
c = + - (0.3U)
d VW
v = settling velocity of smallest particle that is 100%
o
removed, fps
2
g = gravitational acceleration, 32.2 fps
c = drag coefficient
P = specific gravity of particle, 2.65
S
d = diameter of particle, 0.2 mm
P
R = Reynolds number =
v x 3.28 x
5-13
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
v = kinematic viscosity of liquid (use 1.0 x io~5 ft2/sec)
3.28 x 10 = conversion factor, mm to ft
From Table 5-1 select v
s
v = 3.7 ft/min = 0.06 fps
S
(6) Calculate the length of each channel.
L = D
max \ v /
\ s '
where
L = length of channel, ft
D = depth at maximum flow, 1 ft
Vmax = velocity of maximum discharge, 1.25 fps
vg = settling velocity of smallest particle 100$ removed, 0.06 fps
1.7 = allowance for currents
L = x (m) ^
L = 35.^ ft
(7) Calculate detention time.
= (D)W(L)
Q x 1.5
where
t = detention time, sec
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
D = channel depth, 1 ft
W = channel width, 1.23 ft
L = channel length, 35-^ ft
Q = flow, 1 mgd
1.5^= conyersion factor, mgd to cfs
t = 1(1.23)35.**
t = 28.3 sec
(8) Calculate bottom slope of channel.
32/30l/2
q
V = ~~~~~^ K o
avg n
where
v = velocity at average discharge, 1.23 fps
avg
n = Manning's coefficient (use 0.03)
R = hydraulic radius = 2pA+ y for rectangular section
S = slope
R=
2D + W
where
A = area, 1.23 ft2
D = depth, 1.0 ft
W = width, 1.23 ft
5-15
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
R =
2 + 1.23
R = 0.38
(0.38)3/2S1/2
S = 0.01 ft/ft
(9) . Calculate approximate volume of grit assuming k ft3/million gal.
V = UQ
O
vhere
V = volume of grit, ft3/day
&
Q = flow, mgd
v = MD
o
V = U ft3/day
pi _______
5-8. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-9- Bibliography^
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
"b. Camp, T. R. , "Grit Chamber Design," Sewage Works Journal.
Vol Ik, No. 2, Mar 19^2, pp 368-381.
c. Fair, G. M. , Geyer, J. C. , and Okun, D. A., Water Purification
and Wastewater Treatment and Disposal; Water and Wastewater Engineering
Vol 2, Wiley, New York, 1968. ~~ -
5-16
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
d. FMC Corporation, "Link-Belt Wastewater Treatment Equipment
Design Catalogue," Binder 2650, Colmar, Pa.
e. Lee, M. L. and Babbitt, H. E. , "Constant Velocity Grit Chambers
with Parshall Flume Control," Sewage Works Journal, Vol 18, No. 4,
Jul
f. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
g Neighbor, J. B. and Cooper, T. W. , "Design and Operation
Criteria for Aerated Grit Chambers," Water and Sewage Works. Vol 112,
Dec 1965, PP
5-17
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Table 5-1. Grit Settling Velocities
Particle Size
Mesh
18
20
35
k&
65(a)
100
150
I „ ^
mm
0.833
0.595
0.1+17
0.295
0.208
0.1U7
0.105
Settling Velocity
ft/min
lit. 7
10.5
7.1*
5.2
3.7
2.6
1.8
gpd/ft2
160,000
114,500
80,100
56,700
Uo,ooo
28,200
20,200
mgd/ft2
0.1600
0.111*5
0.0801
0.0567
0.01*00
0.0282
0.0202
Area Required
2
ft /million gal
6.3
8.7
12.5
17-7
25.0
35.5
1*9.5
Minimum particle size desirable for removal. »<"» Met">>f'»* ™dy, 1972
Table 5-2. Design Parameters for Aerated Grit Chambers
1. Air supply - 3 cfm/ft of tank length
2. Air diffusers - located 2 to 3 ft above tank bottom on one side of
tank
3. Surface velocity - 1.5 to 2 fps
1*. Tank floor velocity - 1 to 1.5 fps
5. Grit collectors - air lift pumps to decanting channels, grit con-
veyors or grit pumps
6. Detention time - 2 to 3 min
7. Efficiency - 100$ removal of 65-mesh grit
From Metcalf and Eddy, 1972
5-18
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
Section III. SCREENING
5-10. Background.
a. Screening devices are used normally to remove large floating
objects that otherwise may damage pumps and other equipment, obstruct
pipelines, and interfere with the normal operation of the treatment
facilities. Screens used in wastewater treatment facilities or in pump-
ing stations are generally classified as fine screens or bar screens.
b. Fine screens are those with openings of less than lA in. These
screens have been used as a substitute for sedimentation tanks to remove
suspended solids prior to biological treatment. However, few plants
today use this concept of solids removal. Fine screens may be of the
disk, drum, or bar type. Bar-type screens are available with openings
of 0.005 to 0.10 in.
c. Bar screens are used mainly to protect pumps, valves, pipelines,
and other devices from being damaged or clogged by large floating ob-
jects. Bar screens are sometimes used in conjunction with comminuting
devices. Bar screens consist of vertical or inclined bars spaced at
equal intervals (usually 3A to 3 in.) across the channel where waste-
water flows. These devices may be cleaned manually or mechanically.
Bar screens with openings exceeding 2-1/2 in. are termed trashracks.
d. The quantity of screenings removed by bar screens usually de-
pends on the size of the bar spacings. Since the handling and disposal
of screenings is one of the most disagreeable jobs in wastewater treat-
ment, it is usually recommended that the quantity of screenings be kept
at a minimum. Amounts of screenings from normal domestic wastes have
been reported from 0.5 to 5 ft3/million gal of wastewater treated.
Screenings may be disposed of by burial, incineration, grinding, and
digestion.
e. Design of bar screens is based mainly on average and peak
wastewater flow. Normal design and operating parameters are usually
presented in the manufacturer's specifications. The bibliography
(para 5-17) presents a thorough discussion of the design, operation,
and maintenance of screening devices. General characteristics of bar
and fine screens are presented in Tables 5-3 and 5-l|, respectively.
Figure 5-3 shows a mechanically cleaned bar rack.
5-19
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EM 1110-2-501
Part 1 of 3
29 Sep 78
\"j'.':'.'-.'. ;•'•.'••.y':''•'•.'• W' From Air Force Manual 88-11
Figure 5-3. Schematic of a mechanically
cleaned bar rack.
5-11. Input Data.
a. Wastewater Flow.
(l) Average daily flow, mgd.
5-20
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
(2) Maximum daily flow, mgd.
(3) Peak wet weather flow, mgd.
b. Wastewater Characteristics (not applicable).
5-12. Design Parameters.
a. Type of bar screen.
(l) Manually cleaned.
(2) Mechanically cleaned.
b. Velocity through bar screen, fps (Table 5-3).
c. Approach velocity, fps (Table 5-3).
d. Maximum head loss through screen, in. (Table 5-3).
• e. Bar spacings, in. (Table 5-3).
f. Slope of bars, deg (Table 5-3).
g. Channel width, ft.
h. Width of bar, in.
i. Shape factor.
5-13. Design Procedure,.
a. Consult equipment manufacturer's specifications and select
a bar screen which meets design requirements.
b. Calculate head loss through the screen. It should be noted that
when screens start to become clogged between cleanings in manually
cleaned screens head loss will increase.
(w
\b
sin2
2g
5-21
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
h = head loss through the screen, ft
3 = bar shape factor
= 2.U2 for sharp-edged rectangular bars
=1.83 for rectangular bars with semicircular upstream faces
=1.79 for circular bars
=1.67 for rectangular bars with semicircular upstream and
downstream faces
=0.76 for rectangular bars with semicircular upstream faces
and tapering in a symmetrical curve to a small circular
downstream face (teardrop)
W = maximum width of bars facing the flow, in.
b = minimum width of the clear spacings between pairs of bars, in.
v = longitudinal approach velocity, fps
0 = angle of the rack with horizontal, deg
g = gravitational acceleration
c. Calculate average depth.
D " "(wc)Tv)
where
D = average depth, ft
Q = average flow, mgd
W = channel width, ft
c
V = average velocity, fps
5-22
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
d. Calculate maximum depth.
where
D = maximum depth, ft
max
D = average depth, ft
Q = peak flow, mgd
0 = average flow, mgd
avg
5-ll}. Output Data.
a. Bar size, in.
b. Bar spacing, in.
c. Slope of bars from horizontal, deg.
d. Head loss through screen, ft.
e. Approach velocity, fps.
f. Average flow-through velocity, fps.
g. Maximum flow-through velocity, fps.
h. Screen channel width, ft.
i. Channel depth, ft.
5-15. Example Calculations.
a. Select a mechanically cleaned bar screen from Table 5-3 with bar
screen size of width = 1/U in., depth = 1 in., spacing = 5/8 in., slope
= 10 deg, approach velocity = 2 fps, and allowable head loss = 6 in.
b. Calculate head loss through screen.
5-23
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
hg = head loss, ft
3 = "bar shape factor, 1.83
W = width = lA in.
b = spacing = 5/8 in.
v = approach velocity = 2 fps
0 = slope of rack = 10 deg
g = gravitational acceleration = 32.2 ft/sec2
|"22(sin210)"|
L 2(32.2) J
= 0.001 ft
c. Calculate the average depth.
(Q )(l.5lO
D = _aZS. _
Wc(v)
where
D = average depth, ft
Save = averaSe fl°w)
W = channel width, 1.23 ft
v = average velocity, 2 fps
5-21+
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
" 1.23(2)
D = 0.63 ft
d. Calculate maximum depth.
max \avg
where
D = maximum depth, ft
max
D = average depth, 0.63 ft
Q = peak flow, 2 mgd
Q = average flow, 1 mgd
avg
D = 0.63(f)
max \ 1 /
D = 1.26 ft
max _
5-16. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
5-17. Bibliography.
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Equipment Manufacturers' Catalogs.
c. Fair, G. M. , Geyer, J. C. , and Okun, D. A., Water Purifica-
tion and Wastewater Treatment and Disposal; Water and Wastewater Engi-
neering, Vol 2, Wiley, New York, 1968.
5-25
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
d. Goodman, B. L. , Design Handbook of Wastewater Systems-
Domestic, Industrial. Commercial. T*nV.n™n-,, , u^^^ !Lnn ^
_e. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, Recommended Standards for Sevage Works (Ten States Stan-
dards), 1971, Health Education Service, Albany, N. Y.
f. Metcalf and Eddy, Inc., Wastevater Engineering: Collection
ireatment, and Disposal. McGraw-Hill, New York, 1972. - ~~~^
5-26
-------
Table 5-3. General Characteristics of
Bar Screens
Table 5-*K General Characteristics of
Fine Screens
EM 1110-2-501
Part 1 of 3
29 Sep 78
Item
Bar screen size
Width, in.
Depth , in .
Spacing, in.
Slope from vertical, deg
Approach velocity, fps
Allowable head loss, in.
Hand Cleaned
lA to 5/8
1 to 3
1 to 2
30 to U5
1 to 2
6
Mechanically
Cleaned
lA to 5/8
1 to 3
5/8 to 3
0 to 30
2 to 3
6
Item
Disk Drum
Fine screen
Openings, in. 0.126 to 0.009 0.126 to 0.009
(6 to 60 mesh) (6 to 60 mesh)
Diameter, ft U to 18 3 to 5
Length, ft U to 12
rpm
5-27 (next page is 5-29)
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
Section IV. COMMINUTION
5-l8. Background.
a. Comminutors are screens equipped with a device that cuts and
shreds the screenings without removing them from the waste stream.
Thus, comminuting devices eliminate odors, flies, and other nuisances
associated with other screening devices. A variety of comminuting
devices are available commercially.
b. Comminutors are usually located behind grit removal facilities
in order to reduce wear on the cutting surfaces. They are frequently
installed in front of pumping stations to protect the pumps against
clogging by large floating objects.
c. The comminutor size is based usually on the volume of waste to
be treated. Treatment plants with a wastewater flow below 1 mgd
normally use one comminutor. Table 5-5 summarizes design characteris-
tics of comminutors.
d. In wastewater treatment facilities for recreation areas, one
comminutor may be installed in the wet well to protect the pump from
large floating objects. In the treatment of vault waste, a comminutor
may be included as an integral part of a vault waste holding station.
Figure 5-k shows a comminutor.
5-19. Input Data.
a. Wastewater flow, mgd.
(l) Average daily flow, mgd.
(2) Maximum flow, mgd.
b. Wastewater characteristics (not applicable).
5-20. Design Parameters. None.
5-21. Design Procedure. Select comminutor from equipment manufac-
turer's catalog to correspond to maximum wastewater flows.
5-22. Output Data.
a. Comminutor specifications.
5-29
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EM 1110-2-501
Part 1 of 3
29 Sep 78
BYPASS BAR
SCREEN
CLOCKWISE
* ROTATION
I CONDU/T'BOX
STOP GATES
COUNTERCLOCKWISE
ROTATION
PLAN
2-HP MOTOR AND
GEAR REDUCER
•36A COMMINUTOR
:«: :••»•• * ^-SiCi:
• .*'•'.'>.'•. r'. ' * •
3'-0" D/AWETER
*.
-VALVED DRA/N FOR DEWATERING
COMMINUTOR CHANNEL
From Metcalf and Eddy, 1972
SECTION A-A
Figure 5-i*. Schematic of a typical comminutor.
5-30
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EM 1110-2-501
Part 1 of 3
29 Sep 78
b. Number of commimrtors .
5-23. Example Calculations. None.
5-2it. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-25. Bibliography.
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Fair, G. M., Geyer, J. C., and Okun, D. A., Water Purifica-
tion and Wastewater Treatment and Disposal; Water and Wastewater Engi-
neeringy Vol 2, Wiley, New York, 1968.
c. Goodman, B. L., Design Handbook of Wastewater Systems: Do-
mestic, Industrial, Commercial, Technomic, Westport, Conn., 1971.
d. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
5-31
-------
Table 5-5- Comminutor Size Selection
Standard Sizes
Drum
Diameter
in.
4
7
7
10
15
ui 25
i
u>
25
36
Drum
rpm
56
56
56
45
37
25
25
15
Avg Slot
Width
in.
1/4
1/4
1/4
1/4
1/4
3/8
3/8
3/8
Horse-
power
1/4
1/4
1/4
1/2
3/4
1-1/2
1-1/2
2
Height
2 ft 3-1/4 in.
4 ft 3 in.
4 ft 3 in.
4 ft 5 in.
4 ft 11-1/2 in.
5 ft 9-1/2 in.
6 ft 11-1/2 in.
9 ft 4-1/2 in.
Net
Weight
Ib
175
450
450
650
1100
2100
3500
8500
Rates of
Flow
Avg 12 -hr Day
Time,
0 to
0.03 to
0.06 to
0.17 to
0.25 to
0.97 to
1.00 to
1.30 to
mgd
0.035
0.113
0.200
0.720
1.820
5.100
9.400
20.00
Maximum Hourly
Rates of Flow
mgd
0.09
0.24
0.36
1.08
2.40
6.10
11.10
24.00
TO p
^O »iii
- o ?
1
L>J\J]
From Goodman, 1971
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
Section V. EQUALIZATION
5-26. Background.
a. Equalization is a unit operation used for highly variable waste
flows or strengths to provide a uniform discharge and/or concentration
to a treatment facility or receiving streams. Experience has shown that
treatment processes (physical, chemical, or biological) perform better
if extreme load fluctuations enroute to the process can be settled.
Equalization before biological treatment prevents slugs of toxic sub-
stances and provides a uniform organic loading to the system. Equali-
zation may also follow chemical coagulation to facilitate the automatic
pH control schemes and chemical feeding.
b. Flow equalization tanks are usually aerated to prevent deposi-
tion of solids and/or the development of anaerobic conditions. Mixing
requirements for wastewaters having a suspended solids concentration of
approximately 200 mg/£ range from 0.02 to 0.0*1 hp/1000 gal of maximum
storage volume. Aeration (approximately 15 mg 02/&/hr) is recommended
to prevent septic odor problems. Airflow rates from 5 to 20 cfm/ft3 of
tank volume are common.
c. Design of equalization basins varies with the quantity of the
waste and the pattern of its discharge. Concentration time profiles
and the frequency flow fluctuations are normally used as a basis in the
design of these tanks. Supplying enough air to keep the basin aerobic
and providing adequate mixing to prevent solids deposition may be con-
sidered the major factors in equalization basin design.
5-27. Input Data.
a. Flow data.
(l) Peak daily flow, mgd.
(2) Average daily flow, mgd.
(3) Minimum daily flow, mgd.
b. Wastewater characteristics.
(l) Desired mean concentration, mg/£.
•
(2) Time variation in concentration, hr.
5-33
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EM 1110-2-501
Part 1 of 3
29 Sep 78
5-28. Design Parameters.
a. Detention time (dependent on the fluctuation cycle), days.
"b. Mixing requirements (0.02 to 0.04 hp/1000 gal).
c. Air requirements (5 to 20 cfm/ft ).
d. a (0.9).
e. 3 (0.9).
f. Standard transfer efficiency, STE, Ib 0 /hp/hr.
g. Oxygen requirements, mg/£/hr.
5-29. Design Procedure.
a. Select detention time based on the cycle of flow fluctuation.
b. Calculate volume of basin.
V = (Q)(t)
where
V = volume, million gal
Q = design flow, mgd
t = detention time, days
c. Assume horsepower requirements for mixing' (manufacturer's
requirements or 20 to UO hp/million gal) and calculate total horsepower
requirement.
hp = (hp/1000 gal) x (v) x (lOOO)
d. Check horsepower for oxygen requirement to maintain aerobic
conditions.
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(l) Calculate 0 required for aerobic conditions.
02(lb/hr) = (15 mg/A/hr) x (V) x 8.3^
where
V = volume of "basin, million gal
(2) Calculate 0 transfer at operating conditions.
(BCs - C) T 20
OTE = STE - — — x a x (1.02U)
where
OTE = operating transfer efficiency, Ib 09/hp/hr
STE = standard transfer efficiency at zero dissolved
oxygen (DO), tap water, and 20°C sw 3.8
Op saturation in waste
0.9
Op saturation in water
C = oxygen saturation at summer temperature
s
C = minimum DO concentration in tank as 2 mg/Jl
0 transfer in waste
0 transfer in water
T = temperature, °C
(3) Calculate horsepower required to supply 0~ for aerobic
conditions.
0 (Ib/hr)
hp =
OTE
(k) Compare horsepower calculated from (3) above with horsepower
calculated for mixing (c above), and select the larger of the two
horsepowers.
5-35
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EM 1110-2-501
Part 1 of 3
29 Sep 78
5-30. Output Data.
a. Detention time, days.
b. Desired concentration 0 , mg/£.
c. Mixing requirements, hp/1000 gal.
o
d. Air requirements, cfm/ft .
e. Volume, million gal.
f. Total power requirements, hp.
5-31. Example Calculations.
a. Select a detention time. It has been determined that a deten-
tion time of 1-1/2 days is necessary for flow equalization.
b. Calculate volume of basin.
V = Qt
where
V = volume, million gal
Q = average daily flow, 1 mgd
t = detention time, 1.5 days
V = 1(1.5)
V = 1.5 million gal
c. Assume horsepower requirements for mixing of 30 hp/million gal
and calculate total horsepower requirement.
hp = (hp/1,000,000 gal)(V)
5-36
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EM 1110-2-501
Part 1 of 3
29 Sep» 78
where
hp/1,000,000 gal = hp required for mixing, 30
V = volume, 1.5 million gal
hp = 30(1.5)
hp = k5
d. Check horsepower for oxygen requirement to maintain aerobic
conditions.
(l) Calculate 0 required for aerobic conditions.
0-(lb/hr) = (15 mg/4/hr)V(8.3M
where
0 (ib/hr) = oxygen requirement
V = volume of tank, 1.5 million gal
02(lb/hr) = (15)U.5)(8.3M
) = 187.65
(2) Calculate the 0 transfer at operating conditions,
(3C - C)
OTE = STE S a 1.02HT~20
where
OTE = operating transfer efficiency, Ib 0 /hp/hr
5-37
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EM 1110-2-501
Part 1 of 3
20 Sep 78
STE = standard transfer efficiency, 3.
C = oxygen saturation at temperature T, 7-63 mg/£
s
C = minimum oxygen concentration, 2.0 mg/£
a = 0.9
T - temperature, 30°C
9.17 = oxygen saturation at 20°C
OTE = 3.8 t°'9(T.63) - 2.0] (0<9)1.02U(30-20)
OTE = 2.3
(3) Calculate horsepower required to maintain aerobic conditions.
0 (lb/hr)
hp =
OTE
where
hp = required horsepower
0 (lb/hr) = oxygen requirement, 187.65
OTE = operating transfer efficiency, 2.3
hu = 187.65
hp 2.3
hp = 81.6
(U) Select larger horsepower requirement for mixing or for main-
taining aerobic conditions.
hp = 81.6 use 82
5-38
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EM 1110-2-501
Part 1 of 3
29 Scp 78
5-32. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-33. Bibliography.
a. Nemerow, N. L., Liquid Waste of Industry, Addison-Wesley,
Reading, Mass., 1971.
b. Reynolds, E., Gibbon, J. D., and Attwood, D., "Smoothing Quality
Variations in Storage Chests Holding Paper Stock," Transactions, Insti-
tution of Chemical Engineers, Vol k2, T13, 196*1.
c. Roy F. Weston, Inc., "Process Design Manual for Upgrading Exist-
ing Wastewater Treatment Plants," prepared for the U. S. Environmental
Protection Agency, Technology Transfer, Oct 1971, Washington, D. C.
d. Wallace, A. T., "Analysis or Equalization Basins," Journal,
Sanitary Engineering Division, American Society of Civil Engineers,
Vol 9k, SA6, 1968, pp 1161-117!^.
e. Wallace, A. T., "Equalization," Seminar on Process Design in
Water Quality Control, 9-13 Nov 1970, Vanderbilt University, Nashville,
Tenn.
° (next page is 5-
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section VI. FLOTATION
5-3^. Background.
a. Flotation is a solid-liquid separation process. Separation is
artificially induced by introducing fine gas "bubbles (usually air) into
the system. The gas bubbles become attached to the solid particulates,
forming a gas-solid aggregate with an overall bulk density less than
the density of the liquid; thus, these aggregates rise to the surface
of the fluid. Once the solid particles have been floated to the surface,
they can be collected by a skimming operation.
b. In wastewater treatment, flotation is used as a clarification
process to remove suspended solids and as a thickening process to con-
centrate various types of sludges. However, high operating costs of
the process generally limit its use to clarification of certain indus-
trial wastes and for concentration of waste-activated sludge.
c. Air flotation systems may be classified as dispersed air flota-
tion or dissolved air flotation. In dispersed air flotation, air bubbles
are generated by introducing air through a revolving impeller or porous
media. This type of flotation system is ineffective and finds very
limited application in wastewater treatment. Dissolved air flotation
may be subclassified as pressure flotation or vacuum flotation. Pres-
sure flotation involves air being dissolved in the wastewater under
elevated pressures and later released at atmospheric pressure. Vacuum
flotation, however, consists of applying a vacuum to wastewater aerated
at atmospheric pressure. Dissolved air-pressure flotation, considered
herein, is the most commonly used in wastewater treatment.
d. The principal components of a dissolved air-pressure flotation
system (fig. 5-5) are a pressurizing pump, air injection facilities,
a retention tank, a back pressure regulating device, and a flotation
unit. The primary variables for flotation design are pressure, recycle
ratio, feed solid concentration, detention period, air-to-solids ratio,
and solids and hydraulic loadings. Optimum design parameters must be
obtained from bench scale or pilot plant studies. Typical design param-
eters are listed in Table 5-6.
5-35. Input Data.
a. Wastewater (or sludge) flow, mgd.
b. Suspended solids concentration in the feed, mg/&.
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EM 1110-2-501
Part 1 of 3
29 Sep 78'
CHEMICALS
1
' I
T I
CHEMICAL
MIX TANK
PRESSURIZING /"
PUMP ( <
-1
f
THICKENED
Ql llpr^p
_
1 1
RETENTION!
1 SLUDGE COLLECTOR 7~\_ v'
^"•"^ 1 -1 — *~J~ I
5T 1 1
FLOTATION TANK •
BOTTOM SLUDGE COLLECTOR
OFTEN INCLUDED
^7 PRESSURE
)t| REDUCING
nr VALVE
.,.,, | From Metcalf a
BAFFLE
EFFLUENT
*
id Eddy, 1972
Figure 5-5. Schematic of a dissolved-air flotation tank
without recycle.
(l) Average concentration.
(2) Variation in concentration.
5-36. Design Parameters. From laboratory or pilot plant studies.
a. Air-to-solids ratio (A/S).
ID. Air pressure (P), psig.
c. Detention time in flotation tank (DTFT), hr.
d. Solids loading (ML), Ib/ft2/day.
f^
e. Hydraulic loading (HL), gpm/ft .
f. Detention time in pressure tank (DTPT), min.
g. Float concentration (CL,), percent.
r
5-37- Design Procedure.
a. No Recycle (Direct Pressurization).
5-U2
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(l) Select air-to-solids ratio (from laboratory or pilot plant
studies) (Table 5-6).
(2) Calculate the required pressure.-
1.3S (0.5P - 1)
A/S =
C
o
where
A/S = air-to-solids ratio, Ib air/lb solids
S = air solubility at standard conditions, cc/SL
£l
P = absolute pressure, in atmospheres = psig +
C = suspended solids concentration in the feed, mg/&
psig = gage pressure
(3) Select a mass loading rate (or hydraulic loading rate) and
calculate surface area.
(Q)(C
ML
(HL)(60)(2U)
where
2
SA = surface area, ft
Q = feed flow, mgd
C = suspended solids concentration in the feed, mg/£
2
ML = mass loading, Ib/ft /day
2
HL = hydraulic loading, gpm/ft
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Use the larger of the two areas calculated in (3).
(5) Select detention time and calculate volume of flotation tank,
VOLFT =
where
VOLFT = volume of flotation tank, ft3
Q = total flow, mgd
DTFT = detention time in flotation tank, hr
(6) Calculate volume of sludge produced.
(Q)(C )(%, removal)
VSP =
(CF)(specific gravity)
where
VSP = volume of sludge produced, gpd
Q = total flow, mgd
C = suspended solids concentration
C = solids concentration in float, %
"b. With Recycle.
(l) Select air-to-solids ratio.
(2) Assume pressure (ho to 60 psig).
(3) Calculate P in atmospheres = psig + lU.7/1^.7
Calculate recycle flow.
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EM 1110-2-501
Part 1 of 3
29 Sep 78
, 1.3S (0.5P - 1)R
— "•
S" ~ QC
o
vhere
A/S = air-to-solids ratio
S = air solubility at standard conditions, cc/£
a
P = absolute pressure, atmospheres
R = recycle flow, mgd
Q = feed flow, mgd
C = influent suspended solids concentration, mg/£
o
(5) Select a mass loading rate (for thickening) or hydraulic load-
ing rate (for clarification) and calculate surface area.
(Q)(C )(8.3lO
SA = —
ML
qfl - (Q + R)do6)
(HL)(60)(2iO
where
2
SR = surface area, ft
Q = feed flow, mgd
C = influent suspended solids concentration, mg/&
2
ML = mass loading rate, Ib/ft /day
R = recycle flow, mgd
2
HL = hydraulic loading rate, gpm/ft
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(6) Use the larger of the two areas calculated in (5).
(7) Select detention time in the flotation tank and calculate the
volume .
VOLFT = (Q + R) x _l_ (DTFT)(106)
where
VOLFT = volume of flotation tank, ft3
Q = total flow, mgd
R = recycle flow, mgd
DTFT = detention time in flotation tank, hr
(8) Select pressure tank detention time and calculate volume of
pressure tank.
VOLPT= (R) (^)(^-) (DTPT)(106)
where
o
VOLPT = volume of pressure tank, ft
R = recycle flow, mgd
DTPT = detention time in pressure tank, min
(9) Calculate volume of sludge.
(Q)(C }(% removal)
F
where
VS = volume of sludge , gpd
Q = feed flow, mgd
- - _
(C)( specific gravity)
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
C = influent suspended solids concentration, rng/H
o
C = solids concentration in float, percent
F
5-38. Output Data.
a. Suspended solids concentration, mg/£
b. Air-to-solids ratio.
c. Air pressure, psig.
d. Solids loading, Ib/ft /day.
2
e. Hydraulic loading, gpm/ft .
f. Recycle flow, mgd.
2
g. Surface area, ft .
h. Volume of pressure tank, ft .
i. Volume of flotation tank, ft .
j. Pressure tank detention time, min.
k. Flotation tank detention time, hr.
5-39- Example Calculations.
a. No Recycle.
(l) Select the air-to-solids ratio from Table 5-6. A/S = 0.003
(2) Calculate the required pressure
1.3S (0.5P - 1)
A/S =
C
o
where
A/S = air-to-solids ratio, 0.03
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EM 1110-2-501
Part 1 of 3
29 Sep 78
& = air solubility at standard conditions, 18.7 cc/£
P = absolute pressure, atmosphere
Q = suspended solids concentration, 200 mg/£
00-3 = 1-3(18. 7)(0.5P - 1)
' 200
P = 2.5
P =
area.
psig = 1U.7P - iU.7
psig = 1^.7(2.5) - 14.7
psig = 22
,3) Select a mass loading rate -(Table 5-6) and calculate surface
(Q)(C
SA = -
where
o
SA = surface area, ft
Q = average flow, 1 mgd
CQ = suspended solids concentration, 200 mg/£
ML = mass loading, 10 Ib/ft /day
q, _ 1(200)8.3*+
" 10
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EM 1110-2-501
Part 1 of 3
29 Sep 78
SA = 166.8 ft2
(U) Use SA = 167 ft2.
(5) Select a detention time and calculate volume of flotation tank
•where
VOUT = volume of flotation tank, ft
Q = average flow, 1 mgd
. DTFT = detention time, 3 hr
3
J.hQ = conversion, gal to ft
2k = conversion, day to hr
vnT™ - K3) x 106
VOLFT -
VOLFT = 16,711 ft3
(6) Calculate volume of sludge produced.
Q(C )(% removed)
VSP =
CL,( specific gravity)
r
where
VSP = volume of sludge produced, gpd
Q = average flow, 1 mgd
C = suspended solids concentration, 200 mg/£
o
5-U9
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EM 1110-2-501
Part 1 of 3
29 Sep 78
% removed = Q0%
CF = solids concentration in 'float,
Specific gravity =1.05
= 1(200)80
5(1.05)
VSP = 3.QU8 gpd
t. With Recycle.
(l) Select air-to-solids ratio, use 0.05.
(2) Assume pressure, use 50 psig.
(3) Calculate P in atmosphere.
P - psig + 111. 7
Ik. 7
P = 50 + lk.7
111. 7
P = k.k atm
(k) Calculate recycle flow.
1.3S (0.5P - 1)R
A/S =
a
where
A/S = air-to-solids ratio, 0.05
Sa = air solubility at standard conditions, 18.7 cc/S-
P = absolute pressure, k.k atm
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EM 1110-2-501
Part 1 of 3
29 Sep 78
R = recycle flow, mgd
Q = average flow, 1 mgd
C = suspended solids concentration, 200 mg/£
o
n n,; - ... 5(U. U) -
°'°5 ~
-
~ 1(200)
R = 0.3^3 mgd
(5) Select hydraulic loading and calculate surface area.
qA _ (Q + R)io6
bA ~ HL(60)2H
where
2
SA = surface area, ft
Q = average flow, 1 mgd
R = recycle flow, 0.3^2 mgd
2
HL = hydraulic loading, 1.5 gpm/ft
2k = hr/day
60 = min/hr
. _ (1 + 0.3U2)106
SA = 621.3 ft2
(6) Use SA = 622 ft2 .
(7) Select detention time in flotation tank and calculate volume.
5-51
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EM 1110-2-501
Part 1 of 3
29 Sep 78
VOLFT = (Q + R)DTFT x 1Q6
7.1*8(210
where
VOLFT = volume of flotation tank, ft3
Q = average flow, 1 mgd
DTFT = detention time in flotation tank, 0.5 hr
7.1*8 = conversion factor, gal to ft3
24 = hr/day
VOLFT = (1 + 0.3l*2)(0.5) x 1Q6
7.1*8(210
VOLFT = 3738 ft3
(8) Select pressure tank detention time and calculate volume of
pressure tank.
VOTPT = R(DTPT)106
where
VOLPT = volume of pressure tank, ft3
R = recycle flow, 0.342 mgd
DTPT = detention time in pressure tank, 3 min
7-1*8 = conversion factor, gal to ft3
2k = hr/day
60 = min/hr
5-52
-------
VOLPT _
VOLPT "
VOLPT = 95 ft3
(9) Calculate volume of sludge
Q(C )(% removed)
EM 1110-2-501
Part 1 of 3
29 Sep 78
_ 0.3H2(3)106
"
VS =
C_( specific gravity)
r
where
VS = volume of sludge, gpd
Q = average flow, 1 mgd
C = suspended solids concentration, 200 mg/£
o
% removed = 80$
C = solids concentration in float , 5$
F
Specific gravity = 1.05
VQ - 1(200)80
VS ' 5(1.05)
VS = 30H8 gpd
5-Uo. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-Ul. Bibliography.
a. Burd, R. S., "A Study of Sludge Handling and Disposal," Publica
tion WP-20-1*, May 1968, Federal Water Pollution Control Administration,
Washington, D. C.
b. Eckenfelder, W. W. , Jr., Industrial Water Pollution Control.
McGraw-Hill, New York, 1966.
5-53
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EM 1110-2-501
Part 1 of 3
29 Sep 78
c. Eckenfelder, W. W., Jr., Water Quality Engineering for Prac-
ticing Engineers, Barnes and Nobel, New York, 1970.
d. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970.
e. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
f. Roy F. Weston, Inc., "Process Design Manual for Upgrading Exist-
ing Wastewater Treatment Plants," prepared for the U. S. Environmental
Protection Agency, Technology Transfer, Oct 1971, Washington, D. C.
g. Stander, G. J. and Van Vuuren, L. R. J., "Flotation of Sewage
and Waste Solids," Advances in Water•Quality Improvements - Physical
and Chemical Processes, E. F. Gloyna and W. W. Eckenfelder, Jr., ed.,
University of Texas Press, Austin, 1970.
h. U. S. Environmental Protection Agency, Technology Transfer
Seminars, "Sludge Handling and Disposal," 11-12 Dec 1973, Washington,
D. C.
i. Van Vuuren, L. R. J. et al., "Dispersed Air Flocculation/
Flotation for Stripping of Organic Pollutants from Effluents," Water
Research, Vol 2, 1968, pp 177-183.
j. Vrablik, E. R., "Fundamental Principles of Dissolved-Air
Flotation of Industrial Wastes," Proceedings, lUth Industrial Waste
Conference, 1959, Purdue University, Lafayette, Ind.
5-51*
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Table 5-6. Air Flotation Parameters
Parameter
Air pressure, psig
Effluent recycle, %
Detention time, hr
Air-to-solids ratio
(lb air/lb solids)
Solid loading, Ib/ft2/day
Activated sludge
(mixed liquor)
Activated sludge
(settled)
Typical Value
Thickening Clarification
hO to JO itO to TO
130 to 150 30 to 120
3 0.25 to 0.5
(0.005 to 0.06)
5 to 15
10 to 20
Paragraph
(5-iti)
f
f
f,b
e,f
e
e
e
e
e
50% primary
+50$ activated 20 to UO e
Primary only To 55 e
r)
Hydraulic loading, gpm/ft 0.2 to it 1 to it b,e
Detention time, min
(pressurizing tank) 1 to 3 1 to 3 b,a
5-55 (next page is 5-5T)
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section VII. THICKENING (Gravity)
5-U2. Background.
a. General.
(l) Thickening reduces the moisture content of a slurry. Thick-
ening is used at most waste treatment plants, as an ecomomic measure,
to reduce the volume of sludge or for .greater efficiency in subsequent
processes. Thickening is normally accomplished by gravity or flotation
thickeners; centrifuges have also been used as sludge thickeners.
(2) Gravity thickening is discussed below; air flotation and
centrifugation are discussed under separate headings.
b. Gravity Thickening.
(1) Gravity thickening is the most common process currently used
for dewatering and for the concentration of sludge prior to digestion.
Gravity thickening is essentially a sedimentation process similar to
that which occurs in all settling tanks. The process is simple and is
the least expensive of the available thickening processes.
(2) Gravity thickening may be classified as plain settling and
mechanical thickening. Plain settling usually results in the formation
of scum at the surface and stratification of sludges near the bottom.
Sludges from secondary clarifiers usually cannot be concentrated by
plain settling. Gentle agitation is usually employed to stir the
sludge, thereby opening channels for water escape and promoting densi-
fication. A common mechanical thickener consists of a circular tank
equipped with a slowly revolving sludge collector. Primary and secon-
dary sludges are usually mixed prior to thickening. A ratio of secon-
dary sludge to primary sludge of 8 to 1 or greater is recommended to
assure aerobic conditions in the thickener. Chlorine has been used to
prevent sludge septicity and gasification which interfere with optimum
solids concentration of organic materials. A chlorine residual of
0.5 to 1.0 mg/£ in the thickening tank overhead prevents such problems.
Organic polyelectrolytes (anionic, nonionic, and cationic) have been
used successfully to increase the sludge settling rates, the overflow
clarity, and the allowable tank loading.
c. Design of Thickeners. In the design of thickeners, concen-
tration of the underflow and clarification of the overflow must be
achieved. Mechanical thickeners (fig. 5-6) are designed on the basis
5-57
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Part 1 of 3
29 Sep 78
CONDUIT TO MOTOR
A
INFLUENT PIPE
CONDUIT TO
OVERLOAD ALARM
EFFLUENT PIPE
COUNTERFLOW
INFLUENT WELL
OVERLOAD ALARM
EFFLUENT WEIR
DIRECTION OF ROTATION
EFFLUENT CHANNEL
PLAN
HANDRAIL
TURNTABLE BASE
DRIVE
INFLUENT PIPE
CENTER COLUMN
CENTER CAGE
WEIR
STILTS
CENTER SCRAPER
SQUEEGEES
SLUDGE PIPE
SECTION A-A
From Metcalf and Eddy, 1972
Figure 5-6. Schematic of a mechanical thickener.
of hydraulic surface loading and solid loading. These parameters are
normally obtained from laboratory batch settling tests. Procedures
for conducting the tests and evaluating the design parameters are well
documented in literature (para 5-^9c, d, e, f). In the absence of
laboratory data, Table 5-7 may be used as a guide for selecting solid
5-58
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Part 1 of 3
29 Sep 78
2
loading rates. Typical surface loading rates of 600 to 800 gpd/ft are
recommended for most thickeners. Hydraulic loading rates of less than
1*00 gpd/ft2 were reported to produce odor problems (para 5-^9 h).
Detention time of the thickener may range between 2 and h hr. Gravity
thickening is the most common method currently used at wastewater treat-
ment plants for concentrating sludges.
5-1*3. Input Data.
a. Sludge flow (Q), gpd.
(l) Average daily flow (Q ), gP
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EM 1110-2-501
Part 1 of 3
29 Sep 78
C. = solids concentration at settling velocity U. , percent
p TT 1
= (mg/£) x (HT4) - ° °
H.
(settling test, Fig. 5-j)
-L \
C = initial solids concentration, percent = (mg/Jl) x (lO~ )
H = initial height, ft
H = intercept of tangent to the settling curve, ft (Fig. 5-7)
C = underflow concentration, percent
U = settling velocity at the interface, ft/day (settling velocity,
Fig. 5-7)
UJ
U
<
U.
ir
u
h
Z
U.
o
H
I
O
U
I
Figure 5-7• Typical settling curve from laboratory test.
5-60
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Part 1 of 3
29 Sep~78
"b. Calculate mass loading.
where
2
ML = mass loading, Ib/ft /day
p
UA = unit area, ft /lb/day
c. If settling data are not available, select mass loading
from Table 5-7-
d. Calculate total surface area.
TSA ~
vhere
2
TSA = total surface area, ft
Q = average daily flow, gpd
avg
C = initial solids concentration, percent
o
2
ML = mass loading, Ib/ft /day
e. Check hydraulic loading.
HL =
Q
HL = -SSL (<_800
O^T.
where
2
HL = hydraulic loading, gpd/ft
Q = minimum flow , gpd
mm
Q, QY = maximum flow, gpd
iliCLA.
2
SA = surface area, ft
5-61
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Part 1 of 3
29 Sep 78
f . Select number of tanks and calculate surface area per tank.
TKA
SAPT = ±22-
N
where
SAPT = surface area per tank, ft
TSA = total surface area, ft2
N = number of tanks
g. Select a detention time (2 to 6 hr) and calculate tank volume.
where
V = volume, ft
Q = average daily flow, gpd
t = detention time, hr
h. Calculate depth.
D = -<-V->
(SAPT)
where
D = depth, ft
V = volume, ft
SAPT = surface area per tank, ft
i. Calculate volume of thickened sludge.
(Q)(C )(% recovery/100)
VTS = -, r-7^
(C )(specific gravity)
where
VTS = volume of thickened sludge, gpd
5-62
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Q = sludge flow, gpd
C = initial solid concentration, percent
o
C = desired underflow concentration, percent
u
5-1*6. Output Data.
a. Average sludge flow, mgd.
b. Initial concentration, percent.
c. Thickened concentration, percent
2
d. Mass loading, Ib/ft /day.
2
e. Hydraulic loading, gal/day/ft .
f. Detention time, hr.
g. Number of units.
h. Depth, ft.
3
i. Volume, ft .
2
j. Surface area per tank, ft .
k. Volume of thickened sludge, gpd.
5-1+7. Example Calculations. Design of a gravity thickener is dependent
on performing laboratory batch settling tests. Therefore, no example
calculations are presented here.
5-1*8. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-U9. Bibliography.
a. Burd, R. S., "A Study of Sludge Handling and Disposal," Publica-
tion WP-20-U, May 1968, Federal Water Pollution Control Administration,
Washington, D. C.
5-63
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Part 1 of 3
29 Sep 78
b. Dick, R. I., "Thickening," Seminar on Process Design in Water
Quality Engineering, 9-13 NOT 1970, Vanderbilt University, Nashville
Tenn.
c. Eckenfelder, ¥. ¥., Jr., Industrial Water Pollution Control.
McGraw-Hill, New York, 1966. ~~ ~~
d. Eckenfelder, W. W., Jr., Water Quality Engineering for
Practicing Engineers, Barnes and Nobel, New York, 1970.
e. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control. Pemberton Press, New York, 1970.
f. Edde, H. J. and Eckenfelder, W. W., Jr., "Theoretical Concept
of Gravity Sludge Thickening," Technical Report EHE-02-6701, CRWR-15,
1967, Center for Research in Water Resources, University of Texas,
Austin.
g. Metcalf and Eddy, Inc., Wastewater Engineering; Collection
Treatment, and Disposal, McGraw-Hill. New York, 1972.
h. Roy F. Weston, Inc., "Process Design Manual for Upgrading
Existing Wastewater Treatment Plants," prepared for the U. S. Environ-
mental Protection Agency, Technology Transfer, Oct 1971, Washington,
D • L- •
i. U. S. Environmental Protection Agency, Technology Transfer
Seminars, "Sludge Handling and Disposal," 11-12 Dec 1973, Washington,
-U • w •
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EM 1110-2-501
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29 Sep 78
Table 5-7- Concentrations of Unthickened and Thickened
Sludges and Solids Loadings for Mechanical Thickeners
Type of Sludge
Separate sludges
Primary
Trickling filter
Modified aeration
Activated
Combined sludges
Primary and trickling filter
Primary and modified aeration
Primary and activated
Sludge, Solid, percent
Unthickened Thickened
Solids
Loading for
Mechanical
Thickeners
Ib/ft2/day
2.5 to 5-5
h.O to 7.0
2.0 to k.O
0.5 to 1.2
8.0 to 10.0
7-0 to 9.0
it. 3 to 7-9
2.5 to 3.3
20 to 30
8 to 10
7 to 18
h to 18
3.0 to 6.0 7.0 to 9.0 12 to 20
3.0 to k.O 8.3 to 11.6 12 to 20
2.6 to k.Q k.6 to 9.0 8 to 16
5-65
From Metcalf and Eddy, 1972
(next page is 5-67)
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EM 1110-2-501
Part 1 of 3
*y Sep 78
Section VIII. SEDIMENTATION (Primary Clarifier)
5-50. Introduction. Sedimentation is a solid-liquid separation process
designed primarily to remove the suspended particles that are heavier
than water. This process is the most popular and the most widely used
process in waste treatment. Sedimentation removes grit, removes the
settleable fraction of the suspended solids from raw wastes in primary
clarifiers, separates the "biological floe from the mixed liquor in the
final clarifier of a biological treatment system, separates the chemical
floe from the supernatant in physical-chemical systems, and concentrates
sludges in thickeners.
5-51. Classification. Sedimentation may "be classified into four
categories, depending on the characteristics of the suspension.
a. Discrete Settling. Suspended solids in this case are discrete
particles which retain their identity, size, shape, and settling veloc-
ity during the settling process. The main factor influencing the effi-
ciency of the process is the overflow rate expressed as gal/ft2/day.
All particles with settling velocities greater than the design overflow
rate will be removed. Particles with settling velocities less than the
design overflow rate will be removed in proportion to the ratio of their
settling velocities to the design overflow rate. This type of settling
normally occurs in a grit chamber.
b. Flocculant Settling. In this type of settling, particles floc-
culate and agglomerate during settling with changes in size, shape, and
density. The settling velocity increases as the particles grow larger.
The settling characteristics of the flocculant suspension can be de-
termined through laboratory settling tests. Efficiency of removal is
influenced by both the overflow rate and the detention time. Flocculant
settling normally occurs in a primary clarifier.
c. Zone Settling. This type of settling normally occurs with acti-
vated sludge. Particles adhere to each other and settle as a blanket,
forming a distinct solid-liquid interface at the top of the settling
zone. Removal efficiency is influenced by mass loading, overflow rate,
and detention time. Batch sedimentation tests are usually performed to
evaluate these characteristics for industrial waste suspensions.
d. Compression Settling. In this case, the concentration of the
suspension is so great that the particles rest on each other at the bot-
tom of the sedimentation basin. This type of settling occurs in a
sludge thickener.
5-67
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Part 1 of 3
29 Sep 78
5-52. Background.
a. Primary clarifiers are normally used in conjunction with
biological waste treatment systems to remove the settleable solids and
a fraction of the BOD, thereby reducing the load on the biological
systems. Efficiently designed and operated, primary clarifiers can
remove 50 to 65 percent of the suspended solids and 25 to 35 percent
of the 5-day BOD.
b. Primary clarifiers are usually keyed to the overflow rates
(gal/day/ft2) and detention times. Detention times of 2 to 3 hr,
based on average flows, are recommended. Surface loading rates usually
depend on the characteristics of the suspension to be separated. Batch
laboratory studies may be used to determine the optimum design param-
eters for a specific suspension. Typical values for various suspensions
are reported in Table 5-8. Ten State Standards (para 5-59e) recommends
a surface loading not to exceed 600 gal/day/ft2 for small plants (l mgd
or less). Relationship of overflow rates, detention times, and tank
depths are presented in Table 5-9.
c. Outlet design and arrangement have been reported to affect
the efficiency of the primary clarifier. Weir loadings, defined in the
Ten State Standards, should not exceed 10,000 gpd/ft for small plants
(1 mgd or less) and 15,000 gpd/ft for larger plants.
d. Primary clarifiers, rectangular or circular (fig. 5-8), are
usually cleaned mechanically. Two tanks should be provided to allow
for maintenance and repair work.
e. The volume of sludge produced in primary settling tanks de-
pends on several factors which include the characteristics of the raw
waste, the design of the clarifier, the condition of the removed solids,
and the period between sludge removals (para 5-59a). Sludge should be
removed continuously or at least once per shift (more frequently in hot
weather) to avoid deterioration of the effluent quality. Specific
gravities of several types of sludge are shown in Table 5-10.
f. Primary sedimentation may be used in both biological treatment
systems and physical-chemical systems. Figure 5-8 shows typical pri-
mary sedimentation tanks.
5-53- Input Data.
a. Wastewater flow.
-------
L=LENGTH OF TANK
-DRIVE SPROCKETS WITH
RECESS FOR
DRIVE CHAIN
PIVOTING FLIGHT
2"X6" FLIGHTS SPACED APPROXIMATELY
JO'-O" CENTERS
V/l
I
a\
HANDRAILING •
DRIVE UNIT
TURNTABLE
BRIDGE
SCUM TROUGH
SWINGING SKIMMER
BLADE
SCUM BAFFLE
EFFLUENT WEIR
/•MAXIMUM WATER
SURFACE
PIER CAP WITH
OUTLET PORTS
EFFLUENT
LAUNDER
INFLUENT
BAFFLE
3 DIAM
SCUM PIPE
-SKIMMER
SUPPORTS*-
CENTER PIER AND
INFLUENT RISER PIPE
SIDE WATER
DEPTH
DRIVE CAGE
TRUSSED RAKE
1-1/2" BLADE
CLEARANCE
ADJUSTABLE
SQUEEGEES
2" GROUT
SLUDGE DRAW-OFF PIPE
TOP OF GROUT
AT WALL
INFLUENT PIPE
From Metcalf and Eddy, 1972
Figure 5-8. Schematics of typical primary sedimentation tank.
vod-
W H
"O O
00 U)
H
O
I
ro
I
vn
O
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(l) Average flow, mgd.
(2) Peak flow, mgd.
b. Suspended solids, mg/£.
c. Volatile suspended solids, percent.
d. BOD concentration, mg/£.
5-5^. Design Parameters.
2
a. Overflow rate, gpd/ft . See Tables 5-8 and 5-9.
b. Detention time, hr. See Table 5-9.
c. Specific gravity of sludge. See Table 5-10.
d. Solids content of underflow, percent (h to 6 percent).
e. Removal efficiencies.
(l) Suspended solids, percent. See Figure 5-9.
(2) BOD , percent. See Figure 5-10.
J
f. Weir loading, gpd/ft (10,000 to 15,000 gpd/ft).
5-55- Design. Procedure.
a. Select an overflow rate by using Table 5-8 or by laboratory
methods and calculate surface area.
SA =
x 106
OFR
where
2
SA = surface area, ft
Q = peak flow, mgd
OFR = overflow rate, gal/ft2/day
5-70
-------
I
—3
H1
H-
cw
I
VO
SUSPENDED SOLIDS REMOVAL. %
Ni i-j H
VO ct- M
(0 IX)
•u o i
*-b vn
^i o
00 U) H
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EM 1110-2-501
Part 1 of 3
29 Sep 78
60
40
J«
J
O
Ul
o:
Q
O
m
20
3000 ,000 500
SETTLING RATE, GPD/SQ FT TANK AREA (DESIGN FLOW)
Figure 5-10. BOD removal rate in primary clarifier.
t>. Select detention time and calculate volume (see Table 5-9).
400
= (Qavg)(t)
where
V = volume of tank, ft
Q = average flow, mgd
t = t iaie , hr
c. Calculate side water depth.
SWD =
JL
SA
5-72
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Part 1 of 3
29 Sep 78
vhere
SWD = side water depth, ft
V = volume, ft3
2
SA = surface area, ft
d. Check solid loading rate.
(Q J(SSI)(8.3M
(SA)
where
2
SLR = solid loading rate, lb/ft /day
Q = average flow, mgd
avg
SSI = influent solids concentration, mg/£
2
SA = surface area, ft
e. Select weir loading rate and calculate weir length.
WL = Ikx lo6
where
WL = weir length, ft
Q = peak flow, mgd
WLR = weir loading rate, gal/ft/day
f. Determine percentage of suspended solids removed from Figure 5-9•
g. Calculate amount of primary sludge produced.
5-73
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Part 1 of 3
29 Sep 78
PSP = (Q )(SSI)(SSR)(10~2)(8.3>0
where
PSP = primary sludge produced, Ib/day
Q = average flow, mgd
SSI = influent solids concentration, mg/£
SSR = suspended solids removed, percent (50 to 60 percent for
municipal systems)
h. Select underflow concentration (3 to 6 percent) and sludge
specific gravity (Table 5-10), and calculate the volume flow of primary
sludge produced.
VPSP = PSPUQO}
(specific gravity )(UC)(8. 3M
where
VPSP = volume flow of primary sludge produced, gal/day
PSP = primary sludge produced, gal/day
UC = underflow concentration (3 to 6 percent)
i. Determine BODR in primary clarifier (25 to 35 percent in mu-
nicipal systems), or select BODR from Figure 5-10, and calculate primary
effluent characteristics.
SSE = (SSI)II
SSR\
100 /
BODE = (BODl)l -
where
SSE = primary effluent suspended solids, mg/£
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EM 1110-2-501
Part 1 of 3
29 Sep 78
SSI = influent solids concentration, mg/£
BODE = primary effluent BOD, mg/£
BODI = influent BOD, mg/£
BODE = BOD removal in primary clarifier, percent
5-56. Output Data.
2
a. Overflow rate, gal/ft /day.
2
"b. Surface area, ft .
c. Side water depth, ft.
d. Detention time, hr.
2
e. Solid loading, It/ft /day.
f. Weir loading, gal/ft/day.
g. Weir length, ft
h. Volume of sludge produced, gal/day.
i. Suspended solids removal, percent.
3. BOD removal, percent.
k. COD removal, percent.
1. TKN removal, percent.
m. PO, removal, percent.
n. Effluent BOD, mg/&.
o. Effluent suspended solids, mg/£.
p. Effluent COD, mg/£.
q.. Effluent TKN, mg/£.
5-75
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29 Sep 78
5-57- Example Calculations.
a. Select an overflow rate and calculate surface area.
SA =
x 106
OFR
where
2
SA = surface area, ft
Q = peak flow, 2 mgd
OFR = overflow rate, 600 gpd/ft2
SA= 2 x
SA
600
SA = 3333 ft2
"b. Select detention time and calculate volume.
Q t x 10
v = ^yg
where
^
V = volume, ft
Q = average flow, 1 mgd
t = detention time, 2.4 hr
o
7.^8 = conversion factor, gal to ft
24 = hr/day
5-76
-------
V =
V = 13,369 ft3
c. Calculate side water depth.
where
SWD = side water depth, ft
V = volume, 13,369 ft3
2
SA = surface area, 3333 ft
_ 13,369
SWD = H.O ft
d. Check solids loading rate.
Q (SSI)8.3U
SA
where
2
SLR = solids loading rate, It/ft /day
0 = average flow, 1 mgd
avg
SSI = influent suspended solids, 200
8.3*1 = conversion factor, mg/£ to Ib/million gal
2
SA = surface area, 3333 ft
5-77
EM 1110-2-501
Part 1 of 3
29 Sep 78
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Part 1 of 3
29 Sep 78
gLR = 1(200)8.31+
SLR = 0.5 Ib/ft2/day
e. Select weir loading rate and calculate weir length.
WL = SL- x 106
where
WL = weir length, ft
Q = peak flow, 2 mgd
WLR = weir loading rate, 6000 gpd/ft
_ _2 6
6000 X 10
WL = 333 ft
f. Determine percentage of suspended solids removed. SSR = 60%.
g. Calculate amount of primary sludge produced.
PSP = Qavg(SSl)SSR(lO~2)8.3l+
where
PSP = primary sludge produced, Ib/day
Qavg = averaSe flov, 1 mgd
SSI = suspended solids concentration, 200 mg/i
SSR = suspended solids removed,
5-78
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EM 1110-2-501
Part 1 of 3
29 Sep 78
f^
10~ = conversion factor, % to decimal
8.3^ = conversion factor, mg/£ to Ib/million gal
PSP = 1(200)(60)10~2(8.3M
J1
FSP = 1000 Ib/day
h. Select underflow concentration and sludge specific gravity and
calculate the volume flow of primary sludge produced.
VPSP = PSP (IPO?
VFb^ (specific gravity)UC(8.3U)
where
VPSP = volume flow of primary sludge produced, gal/day
PSP = primary sludge produced, 1000 gpd
100 = conversion factor, % to decimal
Specific gravity =1.03
UC = underflow concentration, 3%
Q.3h = conversion factor, mg/£ to !b/million gal
VPSP = 1000(100)
1.03(3)8.3H
VPSP = 3880 gpd
i. Select BODR and calculate primary effluent characteristics.
SSE = SSI
_ / BODR}
BODE - BODI^l - 10Q J
5-79
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
SSE = effluent suspended solids, mg/£
SSI = influent suspended solids, 200 mg/H
SSE = percent removal suspended solids, 60$
BODE = effluent BOD, mg/2,
BODI = influent BOD, 200 mg/£
BODR = percent removal of BOD, 36%
SSE = 200
100 /
SSE = 80 mg/l,
BODE = 200 ll 36.]
BODE = 128 mg/A
5-58. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
5-59. Bibliography.
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Burns and Roe, Inc., "Process Design Manual for Suspended
Solids Removal," prepared for the U. S. Environmental Protection Agency,
Technology Transfer, Oct 1971, Washington, D. C.
c. Camp, T. R., "Sedimentation and the Design of Settling Tanks,"
Transactions, American Society of Civil Engineers, Vol 111 Part III
inl-6, pp 895-952.
d. Gulp, G. L., Hsuing, K., and Conley, W. R., "Tube Clarification
5-80
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Process, Operation Experience," Journal, Sanitary Engineering Division,
American Society of Civil Engineers, Vol 95, SA5, 1969, PP 829-8H8.
e. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works (Ten States Stan-
dards)," 1971, Health Education Service, Albany, N. Y.
f. Hansen, S. P., Gulp, G. L. , and Stukerberg, J. R. , "Practical
Application of Idealized Sedimentation Theory in Wastewater Treatment,"
Journal, Water Pollution Control Federation, Vol hi, Aug 1969, PP
g. McLaughlin, R. T. , "The Settling Properties of Suspensions,"
Journal, Hydraulic Division, American Society of Civil Engineers, Part I,
Paper No. 2311, Vol 85, No. HY12, 1959, PP 9-^1-
h. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
i. Wallace, A. T. , "Design and Analysis of Sedimentation Basins,"
Proceedings, Sixth Annual Sanitary and Water Resources Engineering
Conference, Technical Report No. 13, 1967, PP 119-128, Department of
Sanitary and Water Resources Engineering, Vanderbilt University, Nash-
ville, Tenn.
5-81
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Part 1 of 3
29 Sep 78
Table 5-8. Recommended Surface-Loading Rates
for Various Suspensions
Suspension
Untreated wastewater
Alum floca
Range
r
Loading Rate, gpd/ft'
Iron- floe'
Lime floe
a
600 to 1200
360 to 600
5kO to 800
5^0 to 1200
Peak Flow
1200
600
800
1200
Mixed with the settleable suspended solids in the untreated waste-
water and colloidal or other suspended solids swept out by the floe.
From Met calf and Eddy, Inc., 1971
Table 5-9. Detention Times for Various
Surface-Loading Rates and Tank Depths
Surface-Loading
o
Rate, gpd/ft
1*00
600
800
1000
7-ft
Depth
3.2
2.1
1.6
1.25
Detention
8- ft
Depth
3.6
2.U
1.8
1.1*
Time, hr
10-ft
Depth
U.5
3.0
2.25
1.8
12-ft
Depth
5.U
3.6
2.7
2.2
From Met calf and Eddy, Inc., 1971
Table 5-10. Specific Gravity of Raw Sludge
Produced from Various Types of Sewage
Type of
Sewerage System
Sanitary
Sanitary
Combined
Combined
Strength
of Sewage
Weak
Medium
Medium
Strong
Specific
Gravity
1.02
1.03
1.05
1.07
From Met calf and Eddy, Inc., 1971
5-82
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29 Sep 78
Section IX. SEDIMENTATION (Secondary Clarifier)
5-60. Background.
a. The final clarifier performs a vital role in a secondary waste
treatment system. In the activated sludge process, the final clarifier
must provide an effluent low in suspended solids and an underflow of
sufficient concentration to maintain a sufficient population of active
microbial mass in the aeration tank. Final clarifiers are, therefore,
designed to provide clarification, as well as thickening.
b. In addition to being governed by the overflow rate and detention
time, the design of final clarifiers must be based on solid loading
rates (ib solids/ft2/day). Surface overflow rates and detention times
recommended by the Ten State Standards (para 5-6?f) are presented in
Table 5-11. Typical values of overflow rates recommended for the design
of secondary clarifiers include 600 gal/ft2/day for smaller plants (up
to 1 mgd), and up to 800 gal/ft2/day for larger plants. The design
calculations should consider the peak incoming wastewater flow; the re-
turn sludge flow rate is not included since, in most secondary clari-
fiers, the return sludge withdrawal takes place at a point very near
the inlet to the tank. Solids loading rates for various mixed liquor
suspended solids are illustrated in Figure 5-11. Typical solids load-
ing rates reported range from 12 to 30 Ib/ft2/day. Solid concentration
of the underflow ranges from 0.8 to 1.20 percent, by weight.
c. The performance of the final clarifiers is also affected by the
method of sludge withdrawal. The preferred sludge collection mechanism
is a vacuum- or suction-type draw off (para 5-67b). The plow-type
collectors with the chain and flight mechanism in rectangular basins
or the bridge with attached plows in circular basins ineffectively con-
centrate the waste activated sludge.
d. The bibliography (para 5-67) contains excellent discussions on
the design and operation of final clarifiers.
5-6l. Input Data.
a. Wastewater flow.
(l) Average daily flow, mgd.
(2) Peak flow, mgd.
5-83
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EM 1110-2-501
Part 1 of 3
29 Sep 78
TE BASED ON MIXED-
OW, GPD/SQ FT
b b
< -1
> C 500
0°
ulO'
U-1
o
100
-LIMI
O
- - • — — ^__
TING PEAK OVERFLOV
N PLANT FLOW (1,200
-WITH 50 PERCENT RE
^
v
V
too
\\
-\-
^0 \
^ R/I
GPC
:CY
TE BA!
)/SQ FT
3LE)M
M
<^<£>f, ••%•
*«j£^
^
i
11
\
1.OOO
^S*
N s
V >
S,
V
S
s
>ED -
< - - •
31^
s S
•.
••
MIXED-LIQUOR SUSPENDED-SOLIDS
CONCENTRATION, MG/LITER
10,000
Figure 5-11. Solids loading rates for
various mixed liquor suspended solid
concentrations .
b.
Mixed liquor suspended solids, mg/£.
5-62. Design Parameters.
rate
(from Fig. 5-11)
b. Surface overflow rate.
(1) Small plants <_600 gal/ft2/day.
(2) Larger plants <800 gal/ft2/day.
c. Sludge specific gravity from Table 5-10.
d. Underflow concentration (UC), percent.
(1) For activated sludge UC = 0.8-1.2 percent.
(2) For trickling filter UC = 2-k percent.
5-84
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29 Sep 78
e. Weir overflow rate = 10,000-15,000 gpd/ft/day.
f. Detention time = 2-h hr.
5-63. Design Procedure.
a. Select a solids loading rate (fig. 5-11) and calculate the
surface area.
(Qav )(MLSS)(8.3U)
SA = ^ SLR
where
2
SA = surface area, ft
Q = average flow, mgd
avg
MLSS = mixed liquor suspended solids, mg/fc
2
SLR = solid loading rate, Ib/ft /day
t>. Check the maximum overflow rate.
Q^ x 106
OFR =
SA
where
2
OFR = maximum overflow rate, gal/ft /day
S= peak flow, mgd
2
SA = surface area, ft
If OFR is within range, proceed to next step; if OFR is outside
range, assume OFR and recalculate SA as follows.
Q x 10
SA = OFR
c. Assume detention time and calculate volume.
5-85
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Part 1 of 3
29 Sep 78
where
V = volume , ft
Sivg = averase daily flow, mgd
t = detention time, hr
d. Calculate side water depth.
where
SWD = side water depth, ft
V = volume, ft
p
SA = surface area, ft
e. Select weir overflow rate and calculate weir length.
Q x io6
WL = -£ -
WOFR
where
WL = weir length, ft
Q = peak flow, mgd
WOFR = weir overflow rate, gal/ft/day
5-6U. Output Data.
a. Solids loading rate, Ib/ft2/day.
o
b. Surface area, ft .
c. Overflow rate, gal/ft2/day.
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Part 1 of 3
29 Sep 78
d. Detention time, hr.
e. Weir overflov rate, gal/ft/day.
f. Tank side water depth, ft.
g. Weir length, ft.
h. Volume of wasted sludge, gal/ day.
i. Underflow concentration, percent.
j. Effluent total BOD, mg/fc.
5-65. Example Calculations.
a. Select a solids loading rate and calculate the surface area.
Q
SIK
where
2
SA = surface area, ft
0 = average flow, 1 mgd
avg
MLSS = mixed liquor suspended solids, 3000 mg/£
2
SIR = solids loading rate, 15 It/ft /day
8.3k - conversion factor, mg/& to lb /million gal.
OA 1(3000)8.3*+
SA = 1668 ft2
b. Check the maximum overflow rate.
Q x ic6
OFR = _£ _
SA
5-87
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
OFR = maximum overflow rate, gal/ft2/day
Q = peak flow, 2 mgd
SA = surface area, 1668 ft2
rwp - 2 x IP6
°FR - 1668
OFR = 1199 gal/ft2/day
This value is excess; therefore, redesign on OFR = 1000 gal/ft2/day.
Q x io6
SA = OFR
= 2 x lo6
1000
SA = 2000 ft2
Q
SLR =
SA
- 1(3,000)8.3^
-- -
SLR = 12.5 lWft2/day
c. Assume detention time and calculate volume.
Q (t)!06
V =
where
Q
V = volume of tank, ft
Q = average flow, 1 mgd
^ " o
t = detention time, 2.5 hr
5-88
-------
.U8 = conversion factor, gal to ft
2h = hr/day
v _ 1(2.3)10'
EM 1110-2-501
Part 1 of 3
29 Sep 78
3
V = 13,926 ft3
d. Calculate side water depth.
vhere
SWD = side water depth, ft
V = volume, 13,926 ft3
2
SA = surface area, 2,000 ft
SWD = T.O ft
e. Select weir overflow rate and calculate weir length.
Q^ x 10
WL =
WOFR
where
WL = weir length, ft
Q = peak flow, 2 mgd
WOFR = weir overflow rate, 10,000 gal/ft/day
WL -
10,000
WL = 200 ft
5-89
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EM 1110-2-501
Part 1 of 3
29 Sep 78
5-66. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-67. Bibliography.
a. Burns and Roe, Inc., "Process Design Manual for Suspended Solids
Removal, prepared for the U. S. Environmental Protection Agency Tech-
nology Transfer, Oct 1971, Washington, D. C.
b. City of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
c. Dick, R. I., "Fundamental Aspects of Sedimentation 2," Water and
Wastes Engineering. Vol 6, No. 3, 1969, pp kh-h^.
d. Dick, R. I., "Thickening," Advances in Water Quality Improve-
ments - Physical and^ Chemical Processes. B. F. fvinvr,.. an* T.T T/ F^n
felder, Jr., ed., University of Texas Press, Austin, Texas, 1970.
e. Eckenfelder, W. W., Jr., and O'Connor, 0. J., Biological Waste
Treatment, Pergamon Press, New York, 1961. ~~
f. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, Recommended Standards for Sewage Works (Ten States Stan-
dards;, 1971, Health Education Service, Albany, N. Y.
g. McLaughlin, R. T., "The Settling Properties of Suspensions "
Journal. Hydraulic Division. American Society of Civil Engineers Part I
Paper No. 2311, Vol 85, HY12, 1959, PP 9-1*1. " '
h. Metcalf and Eddy, Inc., Wastewater Engineering; Collection
Treatment, and Disposal. McGraw-Hill, New York, 1972. '
i. Rex Chainbelt, Inc., "A Mathematical Model of a Final Clari-
fier, Report No. 17090FJW, Feb 1972, U. S. Environmental Protection
Agency, Washington, D. C.
J. Wallace, A. T., "Design and Analysis of Sedimentation Basins,"
Proceedings, Sixth Annual Sanitary and Water Resources Engineering Con-
ference» Technical Report No. 13, 1967, pp 119-128, Department of Sani-
tary and Water Resources Engineering, Vanderbilt University, Nashville
Tenn. '
5-90
-------
Table 5-11. Design Requirements for Final Settling Tanks
v_n
VQ
Type of Process
Conventional, modified, or
"high rate" and step aeration
Contact
stabilization
Extended aeration
Average Design
Flow, mgd
To 0.5
0.5 to 1.5
1 . 5 and up
To 0.5
0.5 to 1.5
1.5 and up
To 0.05
0.05 to 0.15
0.15 and up
Detention
Time , hr
3.0
2.5
2.0
3.6
3.0
2.5
U.O
3.6
3.0
Surface
Settling Rates
gal/day/ft2
600
TOO
800
500
600
TOO
300
300
600
0>
X
ct-
p>
tw
vo
u>
Note: The inlets and sludge collection and withdrawal facilities shall be designed
to minimize density currents and assure rapid return of sludge to the aeration tanks.
Multiple units capable of independent operation are desirable and shall be provided in
all plants where design flows exceed 0.1 mgd unless other provision is made to assure
continuity of treatment.
The detention time, surface settling rate, and weir overflow rate should be adjusted
for the various processes to minimize the problems with sludge loadings, density cur-
rents inlet hydraulic turbulence, and occasional poor sludge settleability.
' From Ten States Standards, 1971
10
•g
E
M
'
O I
HI vn
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section X. FILTRATION
5-68. Background.
a. Filtration is the removal of suspended solids through a porous
medium. Until recently, filtration was used mainly in water treatment
to remove suspended solids and bacteria. However, the increasing con-
cern for abatement of water pollution and the requirements for high
quality effluents from wastewater treatment facilities have resulted in
the rapid, wide acceptance of filtration in wastewater treatment. Fil-
tration is "being used for the removal of biological floe from secondary
effluents, phosphate precipitates from phosphate removal processes, and
as a tertiary wastewater treatment operation to prepare effluents for
reuse in industry, agriculture, and recreation.
b. Granular media used in filtration include sand, coal, crushed
anthracite, diatomaceous. earth, perlite, and powdered activated carbon.
Sand filters have been mostly used in water treatment. These filters
are classified into slow sand filters and rapid sand filters.
c. Slow sand filters are normally 12-30 in. deep. The sand rests
on a layer of gravel which, in turn, rests on an underdrain system. The
filter is usually operated at a rate of 3 gal/ft2/hr. When the filter
becomes clogged, it is normally deactivated, drained, allowed to par-
tially dry, and the surface layer of sludge is manually removed. Since
slow sand filters require large space, have high maintenance costs, and
clog rapidly, their application to water treatment has been abandoned;
their application to wastewater treatment has been very limited. Design
and operational characteristics of slow sand filters are summarized in
Table 5-12.
d. Rapid sand filters consist of a layer of sand 18-30 in. thick
supported by a layer of gravel 6-l8 in. thick and an underdrain system.
The underdrain system not only supports the sand, but also collects the
filtered water and distributes the backwash water. The gravel aids in
the distribution of the wash water while preventing the loss of filter
media to the underdrain. Rapid sand filters are usually operated at a
rate of 2 gal/ft2/min. The filters are cleaned by backwashing. Nor-
mally, the filter is backwashed when the head loss increases to a value
approaching the actual head available or when the effluent•quality be-
gins to deteriorate. The length of time of filter runs normally depends
on the quality of the feed water. The common rate of backwashing is
2^-30 in./min (about 15 gal/ft2/min) for 3-10 min. This rate results in
about 30 percent expansion of the sand.
5-93
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29 Sep 78
e. Rapid sand filters (fig. 5-12) are usually constructed in dupli-
cate. The filters are commonly arranged in rows along one or both sides
of a pipe gallery. Total depths of filters from water surface to under-
drains range from 8 to 10 ft. A length-to-width ratio of the filter t>ox
of 3 to 6 has been found most economical. Wash water gutters must be
located so that they limit the horizontal travel of dirty water during
backwashing to 3 ft. As a safety factor, the top edge of the backwash
gutter is normally located 6-12 in. above the allowed expansion of the
sand (usually 50 percent). Backwash gutters must -be designed to carry
all backwash water with a minimum 3-in. free fall at the upper end. The
underdrain system must be designed to carry the backwash water and to
provide uniform distribution of backwash water. Some rules of thumb
that have been used in the design of pipe lateral underdrain systems are
shown in Table 5-13. Filter piping, design flows, and velocities are
presented in Table 5-lU. Design and operational characteristics of
rapid sand filters are shown in Table 5-12. Typical gravel bed for pipe
underdrain system is shown in Table 5-15.
f. The removal of surface material by sand filters leaves a heavy
residue of removed solids on the raw water side of the filter medium.
Surface filtration is extremely sensitive to suspended solids concentra-
tion in the feed water. Sand filters may quickly become clogged at the
surface, resulting in an extremely short filter run, thereby limiting
the practical application of sand filters in wastewater treatment.
g. One method used to increase the effective depth of filtration
involves the use of dual-media or multimedia beds. The filters are com-
posed of two or three materials of different specific gravities and
sizes. The coarsest and lightest materials are placed on top; the fin-
est and heaviest materials are on the bottom. An anthracite/sand filter
is an example of a dual-media filter. Typical anthracite/sand filters
may include from 12 to 2k in. of anthracite (specific gravity, l.U-1.6)
and 6 to 16 in. of sand (specific gravity, 2.65). Multimedia filters
normally consist of anthracite placed on top of sand which is placed on
top of garnet. Typical design data for dual-media and multimedia fil-
ters are presented in Table 5-l6.
h. Another innovation introduced into filtration is the mixed media
concept. For this process, the size distribution of the different media
is selected to ensure intermixing between the various media at the inter-
faces. This mixing will prevent the formation of an impervious layer at
the interface during filtration. A typical mixed dual-media filter may
consist of 12 in. of sand with an effective size of 0.5-0.55 mm and a
uniformity coefficient of less than 1.65, and 12 in. of crushed
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EM 1110-2-501
Part 1 of 3
29 Sep 78
LATERALS
FILTER TO WASTE
WASH OUTLET HEADER
WASH-WATER INLET HEADER
PIPE GALLERY FLOOR
CLEAR WELL
a.
WASH TROUGH
PERFORATED LATERALS
FILTER FLOOR
CAST IRON MANIFOLD
WITH STRAINERS IN TOP
FILTER TANK
b.
Figure 5-12. Schematics of typical rapid sand filters.
5-95
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Part 1 of 3
29 Sep 78
anthracite coal with an effective size of 0.9-1.0 nun and a uniformity
coefficient of less than 1.8. A typical mixed multimedia filter has a
particle size gradation that decreases from about 2-mm anthracite at the
top to about 0.15-mm garnet at the bottom. Information concerning vary-
ing mixed media designs for various types of floe removal is presented
in Table 5-17- The filter piping is usually designed for the flows and
velocities shown in Table 5-l8.
i. A mixed-media design typically used for removal of moderate
quantities of chemical floe requires a backwash rate of about 15 gpm/ft2.
The head loss through the expanded filter is 2-b ft. The required dura-'
tion for backwash water is typically 2-5 percent of the plant throughput.
Surface wash is also necessary to break up the clumps. Normally, sur-
face wash is initiated 1 min before the main backwash starts and is
stopped about 1 min prior to the end of the backwash.
J. In conclusion, the design of filters depends on the influent
wastewater characteristics, process and hydraulic loadings, method and
intensity of cleaning, nature, size, and depth of the filtering material,
and the required quality of the final effluent. In general, mixed dual-
media and multimedia filters are more effective and easier and less ex-
pensive to operate than sand filters for the treatment of wastewaters;
therefore, they are more widely accepted in wastewater treatment. The
design of a multimedia filter is illustrated below. However, the proce-
dure can be applied to the design of a rapid sand filter also.
5-69. Input Data.
a. Wastewater characteristics.
(l) Average daily flow, mgd.
(2) Peak flow, mgd.
b. Suspended solids, mg/£.
c. Suspended solids characteristics.
(l) Biological floe.
(2) Chemical floe.
(a) Alum dose.
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Part 1 of 3
29 Sep 78
(b) Lime dose.
(c) Ferric chloride.
d. Temperature, °F.
e. Alkalinity.
f. pH.
5-70. Design Parameters.
2
a. Rate of wastewater application, gal/min/ft .
b. Size distribution of filter media, mean diameter, mm.
c. Approach velocity, fps.
d. Number of layers.
e. Shape factor for each layer.
f. Porosity of unexpanded bed depth.
g. Specific gravities of filter medium and of water.
h. Depth of each filter medium, ft.
i. Permeability of each layer.
J. Size distribution of gravel.
k. Depth of gravel medium, ft.
1. Desired degree of bed expansion (20-50 percent).
m. Type of underdrain system.
n. Head loss in underdrain system, ft.
o. Diameter of 60 percentile particles, d,-_, mm.
2
p. Specific weight of sand, Ib/ft .
5-97
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Part 1 of 3
29 Sep 78
2 , k
q. Density of water, Ib-sec /ft .
r. Absolute viscosity of water, centipoises.
s. Porosity of expanded bed.
t. Number of troughs.
u. Width of trough, ft.
v. Depth of underdrain, ft.
w. Operating depth of water above sand, ft.
x. Freeboard, ft.
y. Time of backwash, min.
z. Distance from top of trough to underdrain, ft.
5-71- Design Procedure.
a. Select a loading rate (filtration rate) and calculate filter
surface area (Table 5-l6).
Q (106)
"" ~ LR(2U)(60)
where
2
SA = surface area, ft
Q = average flow, mgd
2
LR = loading rate, gal/min/ft
b. Select filter medium and evaluate size distribution and depth of
each layer (Tables 5-12 and 5-l6).
c. Calculate terminal head loss through filter using Kozeny
equation.
5-98
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Part 1 of 3
29 Sep 78
hf_ /v\
LI /
\ g /
(1 - £
:)2"
£3
(v/Sf/
ld jl
\P/ V
1
,3.28 x io~3x
where
h = loss of head in depth of "bed, ft
L = length, ft
K = coefficient of permeability, ^
2
v = kinematic viscosity, ft /sec
2
g = gravitational acceleration, ft/sec
£ = porosity of layer
v = approach velocity, fps
a = shape factor = (6 for spherical, 8.5 for crushed
granules)
d = mean particle size, mm
_o
3.28 x 10 = conversion factor, mm to ft
d. Calculate unit head loss through each expanded media.
Ap = D(l - e)(G - G )
s,m s,w
where
Ap = pressure drop across fluidized bed, ft
D = unexpanded bed depth, ft
e = porosity of unexpanded media
G = specific gravity of filter medium
s 9 in
5-99
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Part 1 of 3
29 Sep 78
G = specific gravity of water
e. Calculate total head loss through expanded media.
(Ap)T = EAp
where
(Ap) = total pressure drop across fluidized bed, ft
f. Calculate rate of filter backwashing for any desired expansion
using the Amirtharajah method (para 5-75a) as follows.
(l) Calculate minimum fluidization velocity.
) ' 2 fw (W - W )~|°'9
L s m s J
v
f 0.88
y
where
2
v_ = minimum fluidization velocity, gpm/ft
dg0 = 60 percent finer size of the sand, mm, s=0.75
W = specific weight of water, Ib/ft
s
o
W = specific weight of sand, Ib/ft
\i = absolute viscosity of water, centipoises
(2) Calculate Reynolds number corresponding to the minimum
fluidization velocity.
x 10"3)
1 y(T.^8)(6o)(2.09 x
where
5-100
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Part 1 of 3
29 Sep 78
\ = Reynolds number
2, 4
p = density of water, Ib-sec /ft
X»
2
v = minimum fluidization velocity, gpm/ft
d^ = 60 percent finer size of the sand, mm, *0.75
3.28 x 10 - conversion factor, mm to ft
y = absolute viscosity, centipoises
-3
7.U8 = conversion factor, ft to gal
60 = conversion factor, sec to min
2.09 x 10 = conversion factor, centipoises to Ib-sec/ft
(3) 'If (R ) > 10 , apply a correction factor to the calculated
n f
value of v as follows:
** = I
where
1C = correction factor
(k) Calculate the unhindered settling velocity as follows:
where
2
v = unhindered settling velocity, gpm/ft
s
2
v = minimum fluidization velocity, gpm/ft
(5) Calculate Reynolds number based on the unhindered settling
velocity.
\
n'
P.v dg (3.28 x icT3)
* s PU
y(7.U8)(60)(2.09 x 10~
5-101
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
(R \ = Reynolds number
11 S 2, k
p = density of water, lb-sec /ft
o
v = unhindered settling velocity, gpm/ft
S
d,- = percent of sand SS0.075 mm
y = absolute viscosity, centipoises
(6) Calculate expansion coefficient as follows.
n =
where
n = expansion coefficient
(T) Using v_ and n , calculate the constant K for the
system.
where
2
v_p = minimum fluidization velocity, gpm/ft
£ = porosity of unexpanded media
n = expansion coefficient
(8) Calculate the desired porosity at the desired bed expansion.
^ 1- E
D"l- I
where
D = depth of expanded bed, ft
5-102
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Part 1 of 3
29 Sep 78
D = depth of unexpanded ted, ft
e = porosity of unexpanded bed
e = porosity of expanded "bed
(9) Calculate the backwash rate.
n
BR = Ke(e) Q
where
2
BR = backwash rate, gpm/ft
K = system constant
e = porosity of expanded bed
n = expansion coefficient
g. Select wash water troughs arrangement and calculate depth of
wash water troughs.
Q = 2.U9bh3//2
where
Q = total trough flow, cfs
b = trough width, ft
h = trough minimum depth, ft
h. Select an underdrain system and calculate the minimum total
filter depth.
TD = UD + GD + MD + MOD + FB
where
TD = total filter depth, ft
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Part 1 of 3
29 Sep 78
UD = depth of underdrain, ft
GD = gravel depth, ft
MD = media depth, ft
MOD = maximum operating depth of water above sand, 3-5 ft
FB = freeboard, ft
i. Calculate total head necessary to backwash water.
TH = HLUD + HLG + HLM + DWT
where
TH = total head necessary for backwash
HLUD = head loss in underdrain (manufacturer's requirement)
HLG = head loss in gravel (c above)
HLM - head loss through fluidized bed (d above)
DWT - total depth from top of wash water trough to underdrain, ft
;j. Assume backwash time and calculate total backwash water
needed.
BWW = (BR)(BWT)(SA)'
where
BWW = total backwash water, gal
2
BR = backwash rate, gpm/ft
BWT = backwash time, min
2
SA = surface area, ft
5-
-------
5-72. Output Data.
EM 1110-2-501
Part 1 of 3
29 Sep 78
a.
b.
c.
d.
e.
f.
g-
h.
i .
J.
k.
5-73.
Depth Diameter Shape
Layer ft ft Factor
1 XX. X XX. X XX. X
2 xx. x xx. x xx. x
3 xx. x xx. x xx. x
k XX. X XX. X XX. X
2
Average loading rate, gpm/ft .
2
Surface area, ft .
Under drain head loss, ft.
Wash water gutter width, ft.
Wash water gutter depth, ft.
Terminal head loss through bed, ft.
Maximum head for "back-washing, ft.
Total filter depth, ft.
Wash water needed, gal.
2
Backwash rate, gpm/ft .
Example Calculations.
Specific
Gravity
XX. X
XX. X
XX. X
XX. X
a. Select a loading rate and calculate filter surface area.
SA =
Q 10
avg
LR(2U)(60)
where
SA = surface area, ft
Q = average flow, 1 mgd
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Part 1 of 3
29 Sep 78
2
LR = loading rate, 6 gal/min/ft
2h = hr/day
60 = min/hr
CA - 1 x 106
bA ~ 6(2M60
SA = 116 ft2
b. Select filter medium and evaluate size distribution and depth of
each layer.
Anthracite
Depth = 18 in.
Effective size = 1.2 mm
Uniformity coefficient =1.5
Sand
Depth = 12 in.
Effective size = 0.5 mm
Uniformity coefficient = l.U
c. Calculate terminal head loss through filter using Kozeny
equation.
h
f
d -
1
p/ \3.28 x 10"
vhere
h = head loss in depth of bed, ft
5-106
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Part 1 of 3
29 Sep 78
L = length, 1.5 ft anthracite, 1.0 ft sand
K = coefficient of permeability, 6
— 5 2
v = kinematic viscosity, 1.088 x 10 ft /sec
2
g = gravitational acceleration, 32.2 ft/sec
e = porosity, 0.50 anthracite, 0.^4-0 sand
v = approach velocity, O.OU fps
a = shape factor, 8.5
s
d = mean particle size, 1.2 mm anthracite, 0.5 mm sand
_'}
3.28 x 10 = conversion factor, mm to ft
for anthracite
5
1.088 x 10 5\
32.2 /
(1 - 0.5)2
L 0.53
o.oU
LI
1.2
1
3.28 x 10
-3
hf = 1.13 ft
for sand
hf = s 1.088 x 10 5
1.0
32.2
d - o.u;
o.ok
°'5/ V3.28 xio-3
hf = 5.^5 ft
Total hf = 6.58 ft
d. Calculate the unit head loss through each expanded media.
5-107
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Part 1 of 3
29 Sep 78
Ap = D(l - e) (G - G \
V s,m s,w,/
where
Ap = pressure drop across fluid!zed bed, ft
D = unexpanded bed depth, 1.5 ft anthracite, 1.0 ft sand
e = porosity of unexpanded media, 0.50 anthracite, O.kO sand
G = specific gravity media, 1.67 anthracite, 2.65 sand
s 5 in.
G = specific gravity water, 1.0
Ap anthracite = 1.5(1 - 0.5) (1.67 - 1.0)
Ap = 0.50 ft
Ap sand = 1.0(1 - O.U) (2.65 - 1.0)
Ap = 0.99 ft
e. Calculate total head loss through expanded media.
(Ap)T = EAp
(Ap)T = 0.50 + 0.99
(Ap)T = l.li9 ft
f. Calculate rate of filter backwashing.
(l) Calculate minimum fluidization velocity
1.82 r /T, „ N-,0.9U
0.00381(d,n)±lCV fw (V - W \~\
60 L sy m s/J
Vf 0.88
y
5-108
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Part 1 of 3
29 Sep 78
where
2
v = minimum fluidization velocity, gpm/ft
dx-n = 60 percent finer size of sand, 0.75 mm
W = specific weight of water, 62. U lb/ff
s
¥ = specific weight of sand, 165 Ib/ft
y = absolute viscosity of water, 1.009 centipoises
0.00381(0.75)1'82 {62.'U[2.65(62.U) - 62.1i]l°-9U
V™
n f\ I
f 1.0090'1
v = 8.68 gpm/ft2 = 0.0193 fps
(2) Calculate Reynolds number corresponding to the minimum fluidiza-
tion velocity.
y(7. U8)60(2. 09 x 10"5)
where
(E \
= Reynolds number
2 h
p = density of water, 1.9^ Ib-sec /ft
2
V- = minimum fluidization velocity, 8.68 gpm/ft
cL- = 60 percent finer size of sand, 0.75 mm
y = absolute viscosity, 1.009 centipoises
_0
3.28 x 10 = conversion factor, mm to ft
o
7.^8 = conversion factor, ft to gal
5-109
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Part 1 of 3
29 Sep 78
-5 ?
2.09 x 10 = conversion factor, centipoises to lb-sec/ft
60 = conversion factor, sec to min
(E\ = 1-9H(8.68)(0.75)(3.28 x
^ n'f 1.009(7.^8)60(2.09 * ]
(R ) = it.u
V n/f
(3) Because /R \ < 10 , no correction factor is needed.
\ 1+ -f
(k) Calculate the unhindered settling velocity as follows:
vs = 8.U5vf
where
2
v = unhindered settling velocity, gpm/ft
s
v = minimum fluidization velocity, 8.68 gpm/ft
v = 8.1+5(8.68)
S
v = 73.3 gpm/ft2
o
(5) Calculate Reynolds number based on the unhindered settling
velocity.
P.v d,n(3.28 x 10^)
(H ) = £ S 6° =-= 8.U5(R )
V n/ 9 x 10"5) V n/f
where
2
vs = unhindered settling velocity, 73.3 gpm/ft
: \ = Reynolds number for minimum fluidization velocity, UJ
/ -p
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29 Sep 78
(K \ = Reynolds number for unhindered settling velocity
v n;
(Hn)
s
. 37.2
(6) Calculate expansion coefficient.
where
n = expansion coefficient
e
/R \ = Reynolds number for unhindered settling velocity, 37-2
S
n = 1^5(37.2T0-1
n = 3.1
e
(7) Calculate K for the system.
where
2
v_p = minimum fluidization velocity, 8.68 gpm/ft
K = constant for system
e
e = porosity of unexpanded media, O.hd
n = expansion coefficient, 3.1
5-111
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29 Sep 78
8.68 = K (0.40)3'1
= 1U9 gpm/ft2
(8) Calculate the desired porosity at the desired bed expansion.
where
Dg = depth to expanded bed, 1.2 ft
D = depth of unexpanded bed, 1.0 ft
e = porosity of unexpanded bed, O.hO
e = porosity of expanded bed
1.2 _ 1 - Q.hO
1-°* i-r
r = 0.50
(9) Calculate the backwash rate.
BR = K (e) e
e
where
p
BR = backwash rate, gpm/ft
p
K = constant, 1^9 gpm/ft
e = porosity of expanded bed, 0.50
n = expansion coefficient, 3.1
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29 Sep 78
BR = lU9(0.50)3'1
BR = I'M gpm/ft
g, h, i, and j. Calculation of trough minimum depth (ho), total
filter depth (TD), total head for backwash (TH), and "backwash water
needed (BWW) are dependent upon the type of equipment selected for back-
washing the filter.
5-7l|. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-75. Bibliography.
a. Amirtharajah, A. and Cleasby, J. L., "Predicting Expansion of
Filters During Backwash," Journal, American Water Works Association.
Vol 6H, 19T2, pp 52-59-
b. Burns and Roe, Inc., "Process Design Manual for Suspended Solids
Removal," prepared for the U. S. Environmental Protection Agency, Tech-
nology Transfer, Oct 1971, Washington, D. C.
c. Camp, T. R., "Theory of Water Filtration," Journal, Sanitary En-
gineering Division, American Society of Civil Engineers, Vol 90, SAU,
196U, pp 1-30.
d. Cleasby, J. L., "Deep Granular Filters, Modeling and Simulation,"
Proceedings, Association of Environmental Engineers in Profession,
Eighth Annual Workshop, 18-22 Dec 1972, Nassau.
e. Cleasby, J. L. and Baumann, E. R., "Selection of Sand Filtration
Rates," Journal, American Waterworks Association, Vol 5^, 1962, pp
579-602.
f. Gulp, R. L. and Gulp, G. L., Advanced Wastewater Treatment, Van
Nostrand, New York, 1971.
g. Fair, G. M., Geyer, J. C., and Okun, D. A., Water Purification
and Wastewater Treatment and Disposal; Water and Wastewater Engineer-
ing, Vol 2, Wiley, New York, I960.
5-113
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h. Hsuing, K. and Cleasby, J. L., "Prediction of Filter Perfor-
mance," Journal, Sanitary Engineering Division, American Society of
Civil Engineers, Vol 9^, SA6, 1968, pp 10*13-1070.
i. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
j. O'Melia, C. R. and Stumm, ¥., "Theory of Water Filtration,"
Journal, American Water Works Association, Vol 59, Nov 1967 pp
1383-11*12.~~ ~ '
k. Tchobanoglous, F. and Elliassen, R., "Filtration of Treated
Sewage Effluents," Journal, Sanitary Engineering Division, American
Society of Civil Engineers, Vol 96, SA2, 1970.
1. "Water Treatment Plant Design," prepared by American Society of
Civil Engineers, American Water Works Association, Conference of State
Sanitary Engineers, 1969.
m. Weber, W. J., Jr., Physicochemical Processes for Water Quality
Control, Wiley-Interscience, New York, 1972.
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Table 5-12. General Features of Construction and Operation of Conventional
Slow and Rapid Sand Filters
Feature
Slow Sand Filters
Did Sand Filters
Rate of filtration
Size of bed
Depth of bed
Size of sand
1 to 3 to 10 mgad
Large, half acre
12 in. of gravel; 1*2 in. of sand,
usually reduced to no less than
21* in. by scraping
Effective size 0.25 to 0.3 to
0.35 mm; coefficient of nonuni-
formity 2 to 2.5 to 3
Grain size distribution Unstratified
of sand in filter
Underdrainage system
Loss of head
Length of run between
cleanings
Penetration of suspended
matter
Method of cleaning
Amount of wash water used
in cleaning sand
Preparatory treatment of
water
Supplementary treatment
of water
Cost of construction,
U. S.
Cost of operation
Depreciation cost
Split tile laterals laid in
coarse stone and discharging
into tile or concrete main
drains
0.2 ft initial to k ft final
20 to 30 to 60 days
Superficial
(1) Scraping off surface layer
of sand and washing and storing
cleaned sand for periodic re-
sanding of bed; (2) washing
surface sand and sand in place
by washer traveling over sand
bed
0.2 to 0.6 percent of water
filtered
Generally none
Chlorination
Relatively high
Relatively low where sand is
cleaned in place
Relatively low
100 to 125 to 300 mgad
Small, 1/100 to 1/10 acre
18 in. of gravel; 30 in. of sand
or less; not reduced by washing
O.U5 mm and higher; coefficient of
nonuniformity 1.5 and lower, de-
pending on underdrainage system
Stratified with smallest or light-
est grains at top and coarsest
or heaviest at bottom
(l) Perforated pipe laterals dis-
charging into pipe mains; (2) po-
rous plates above inlet box;
(3) porous blocks with included
channels
1 ft initial to 8 or 9 ft final
12 to 2U hr
Deep
Dislodging and removing suspended
matter by upward flow or back-
washing, which fluidizes the bed.
Possible use of water or air
Jets, or mechanical rakes to im-
prove scour
1 to 1* to 6 percent of water
filtered
Coagulation, flocculation, and
sedimentat ion
Chlorination
Relatively low
Relatively high
Relatively high
From Fair, Geyer, and Okun, 1968
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Table 5-13. Rules of Thumb for Underdrainage System
1. Ratio of area of orifice to
area of bed served
2. Ratio of area of lateral to
area of orifices served
3. Ratio of area of main to
area of laterals served
U. Diameter of orifices
5. Spacing of orifices
6. Spacing of laterals
[(1.5 to 5) x 10 3] to 1
(2 to h) to 1
(1.5 to 3) to 1
lA to 3A in.
3 to 12 in. on centers
Closely approximating
spacing of orifices
From Fair, Geyer, and Okun, 1968
Table 5-l4. Design Considerations for Various
Velocities and Flov Volumes
Piping
Influent
Effluent
Wash water supply
Wash vater drain
Filter to vaste
Velocity
fps
1 to U
3 to 6
5 to 10
3 to 8
6 to 12
Maximum Flow per
Filter Area Served
gpm/ft2
3 to 8
3 to 8
15 to 25
15 to 25
1 to 6
From American Water Works Association, 1969
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Table 5-15. Typical Gravel Bed for Pipe Underdrain System
No. of Layers
Description
Depth of layer, in.
Square mesh screen opening, in.
Passing
Retained
1
1
1
3A
2
3
3A
1/2
3
3
1/2
1/U
k
k
iA
1/8
5
U
1/8
1/16
NOTE: Bottom layer should extend to a point U in. above the highest outlet of
wash water. From Cuip and Culp, 1971
Table 5-l6. Typical Design Data for Dual-Media and Multimedia Filters
Characteristic
Anthracite
Depth, in.
Effective size, mm
Uniformity coefficient
Sand
Depth, in.
Effective size, mm
Uniformity coefficient
2
Filtration rate, gpm/ft
Anthracite
Depth, in.
Effective size, mm
Uniformity coefficient
Sand
Depth, in.
Effective size, mm
Uniformity coefficient
8.
Garnet
Depth, in.
Effective size, mm
Uniformity coefficient
2
Filtration rate, gpm/ft
Value
Range
Dual-Media
8 to 2U
0.8 to 2.0
l.U to 1.8
10 to 2k
0.3 to 0.8
1.2 to 1.6
2 to 10
Multimedia
8 to 20
1.0 to 2.0
l.U to 1.8
8 to 16
O.U to 0.8
1.2 to 1.6
2 to U
0.2 to 0.6
2 to 12
Typical
18.0
1.2
1.5
12.0
0.5
l.U
6.0
15.0
l.U
1.5
12.0
0.6
l.U
3.0
0.3
1.0
6.0
Garnet becomes intermixed with sand and anthracite.
From Met calf and Eddy, 1972
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Table 5-17- Typical Removals by Tahoe Mixed-Media Filters
Substance
Phosphorus, total
Pho sphorus , di s s olved
Phosphorus, particulate
COD
BOD
SS
Turbidity, JU
Typical
Influent
0.65
0.1*5
0.20
23.00
9.00
15-00
7.00
Concentrations
mg/£
Effluent
0.05
0.05
0.00
15.00
5.00
0.00
0.30
Range
% R emo val
70 to 95
65 to 90
100
20 to 1*5 '
1*0 to 70
100
60 to 95
From Gulp and Culp, 1971
Table 5-18. Flows and Velocities Determining
Filter Piping Design
Piping
Influent
Effluent
Wash water supply
Backwash waste
Filter to waste
Velocity
fps
1 to H
3 to 6
5 to 10
3 to 8
6 to 12
Maximum Flow per
Filter Area Served
gpm/ft2
8 to 12
8 to 12
15 to 25
15 to 25
It to 8
From Culp and Culp, 1971
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Section XI. VACUUM FILTRATION
5-76. Background.
a. Vacuum filtration is one of the most widely used methods for
mechanical dewatering of wastewater sludges. The process is carried out
using a slowly rotating drum, the outside of which is covered "by a fil-
ter medium. A portion (about 20-HO percent) of the drum is submerged
in sludge in the vat below the drum. Vacuum (10-26 in. of mercury)
is applied to the submerged portion of the trough. As a result, water
is drawn into the drum and a thin mat of sludge is formed on the filter
medium. As the filter rotates, the vacuum is continued, and further
moisture reduction occurs. In addition, the deposited cake is further
dried by air which rushes through the cake into the drum. Before the
filter cake reaches the sludge vat again, it passes over a roller and is
broken off onto a conveyor for ultimate disposal. The time the drum
spends submerged in the slurry is called the "filter time"; the time the
cake spends on the drum above the vat is called the "drying time.
b. Vacuum filtration facilities are generally sold as a package
by various filter manufacturers. In addition to the filter itself, the
package normally includes vacuum pumps, sludge feed pumps, filtrate
pumps, sludge conditioning tanks, chemical feed pumps, and belt con-
veyors that transport dewatered filter cake. Filter medium made of
cloth (cotton, wool, nylon, dacron, or other synthetic material), coil
springs, or a wire-mesh stainless steel fabric are available in various
weaves of different porosities.
c. Vacuum filter performance is measured by filtration rate and
dryness of the filter cake. Several factors affecting the performance
of a vacuum filter include:
(l) Vacuum — As the vacuum increases, the filtration rate and
the dryness of the cake also increase; this process is limited, ob-
viously, by capacity of the drum. An ideal filter design would incor-
porate two independent vacuum systems: one operating while the cake is
being formed, and the other after it comes out of submergence and is
being dried. A vacuum of at least 20 in. of mercury is desirable.
(2) . Feed Solid Concentration — In general, the sludge filtra-
tion rates increase directly in proportion to the increase in feed
sludge solids concentration; a smaller filtrate volume has to be removed
per pound of filter cake formed. The practical limit for optimum opera-
tion for sewage sludges is U-8 percent.
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(3) Drum Speed and Submergence — The drum speed influences the
cycle time and consequently influences filter yield and filter cake
moisture. A decrease in filter cycle time should increase the yield.
However, lower filter cake moisture will be obtained by increasing the
filter cycle, thereby extending the drying cycle. A submergence level
of 20-40 percent has been used. It is usually more economical to
run the filter at lower submergence since it will increase the ratio of
dewatering time to cake formation time, and will still allow a short
cycle for greater filtration rates.
(10 Chemical Conditioning of Sludge — Chemical conditioning of
sludge is usually a necessary step prior to sludge vacuum filtration.
Chemical conditioning agglomerates solids and causes a release of water,
thereby making the sludge easier to filter. A wide variety of chemicals
have been evaluated for conditioning sludges prior to vacuum filtration.
In general, lime and ferric chloride are the most commonly used condi-
tioners. Recently, some organic polyelectrolytes have become popular as
sludge conditioners. The amount and type of conditioning chemicals re-
quired depend on the physical and chemical characteristics of the sludge.
Tables 5-19 and 5-20 summarize chemical doses reported from the operat-
ing records of various treatment facilities (para 5-83b).
d. Vacuum filter systems are designed from data describing quanti-
ties of sludge to be filtered, sludge characteristics, filtration rates
cake moisture, and filter operation cycles. The data could be generated
from laboratory or pilot investigations of the sludge. The Buchner fun-
nel test and the filter leaf test are commonly used in laboratory test-
ing programs for estimating the filterability of sludges. The Buchner
funnel test evaluates the optimum chemical requirements and sludge
filtration characteristics measured in terms of specific resistance.
The filter leaf test determines the effect of different fabrics, fabric
forms, and drying times on filter yield. Table 5-21 summarizes specific
resistance; Table 5-22 presents filter yields recommended for various
sewage sludges.
e. Filter yield, or production rate, is the basic factor used in
determining the size of vacuum filter installations. A conservative de-
sign rate of 3-5 Ib/ft2/hr has been widely used. However, assuming the
yield to be equal to the solids concentration of the sludge to be fil-
tered is more accurate. Generally, the yield may vary from 2 to 10
lb/ft^/hr. The low values represent filtration of fresh and digested
activated sludge; the high values are typical for raw primary or primary
plus trickling filter humus sludge filtration.
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f. The bibliography (para 5-83) contains thorough discussions of
the theory and application of vacuum filtration and example problems.
g. Vacuum filtration is being widely used for devatering sewage
sludges in small treatment facilities because of its flexibility, small
space requirement, and the excellent characteristics of the cake. Thus,
vacuum filtration is a viable alternative for sludge dewatering in treat-
ment facilities serving recreation areas.
5-77. Input Data.
a. Volume of sludge to be dewatered, gpd.
b. Initial moisture content of sludge, percent.
5-78. Design Parameters.
a. Final moisture content of sludge, percent.
O
b. Specific resistance, sec /g (Buchner funnel test).
c. Applied vacuum, psi.
d. Fraction of cycle time for cake formation (formation time/cycle
time), depends on degree of submergence.
e. Cycle time, min (usually 1.5 to 5 min).
f. Filtrate viscosity, centipoises.
g. Chemical dose, percent of dry weight in solids fed to
filter.
h. Operation per week, days.
i. Operation per day, hr.
o
j. Loading rate, Ib/ft /hr.
k. Number of units.
5-79. Design Procedure.
a. Calculate filter loading rate.
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M'35-7
R = r(lO~7) = sec2/g
C =
C. Cf
100 - C± 100 - C
where
LR = filter loading rate, Ib/ft2/hr
X = form time/cycle time (0.1 to 0.6)
C = weight of dry solids in cake, g/m£
P = applied vacuum, psi (5 to 15 psi)
V = filtrate viscosity, centipoises
r = specific resistance (Buchner funnel test or Table 5-21),
secVg
t = cycle time (1.5 to 5 min), time of revolution of drum
C. = initial moisture content of sludge, percent
C~ = final moisture content of sludge, percent
b. If data are not available, select loading rate from Table 5-22
or use 3.5 Ib/ft2/hr.
c. Calculate required total filter area.
V(100 - C.)(8.3U)(7)2U
TFA =
LR(100)(HPD)(DP¥)
where
TFA = total filter area, ft2
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V = sludge volume, gal/day
C. = initial moisture content of sludge, percent
LR = filter loading rate, Ib/ft /hr
HPD = operation per day, hr
DPW = days/week
d. Calculate amount of chemicals required.
C,V (100 - C )
_ Cl /rrWO ->1, \ i_
CK —
(HPD) (DPW) (100) """'^' 100
where
CR = amount of chemicals required, Ib/hr
C = chemical dosage, percent of dry weight of solids fed to
filter
V = sludge volume, gal/day
HPD = operation per day, hr
DPW = days/week
C = initial moisture content of sludge, percent
i
e. Select number of filters and calculate area per filter.
NF
where
2
APF = area per filter, ft
2
TFA = total filter area, ft
NF = number of filters
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5-80. Output Data.
a. Loading rate, Ib/ft2/hr.
b. Total filter area, ft2.
c. Chemical requirements, Ib/hr.
d. Initial moisture content, percent.
e. Final moisture content, percent.
f. Cycle time, min.
g. Formation time, min.
h. Chemical dose, percent.
i. Applied vacuum, psi.
j. Operation per day, hr.
k. Operation per week, days.
5-8l. Example Calculations.
a. Calculate filter loading rate.
LE -
R = r(lO T) = sec2/gm
C =
100 - C± 100 - C
where
LR = filter loading rate, Ib/ft2/hr
X = form time/cycle time, 0.5
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C = weight of dry solids in cake, g/m£
P = applied vacuum, 10 psi
y = filtrate viscosity, 1.12 centipoises
R = specific resistance
t = cycle time, 3 min
7 2
r = specific resistance, 3.0 x 10 sec /g
C = initial moisture content, 97-5 percent
i
C = final moisture content, 75.0 percent
R = 3.0 x 10T (10 T)
2
R = 3.0 sec /g
C =
97.5 _ 75.0
100 - 97.5 100 - 75.0
C = 0.028 g/m£
LR _ o. o.5(0.028)lQ1/2
LR -
LR = U.2 rb/ft2/hr
b. Use LR = U.2 Ib/ft2/hr.
c. Calculate required total filter area.
V(lOO - C.
nrp/\ _
- ._ _________ , . . -------
LR(IOO)HPD(DPW)
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where
TFA =. total filter area, ft2
V = sludge volume, 7000 gpd
C^ = initial moisture content, 97.5 percent
LR = loading rate, lj.2 It>/ft2/hr
HPD = hours of operation per day, 16
DPW = days of operation per week, 5
7 = days/week
2k = hr/day
TFA = -7000(100 - 97.5)8.3Um2_U_
4.2(100)16(5)
TFA = 730 ft2
d. Calculate amount of chemicals required.
cdV24 100 - C.
CR = HPD(DPW)100 7(8'3^
where
CR = chemical requirement, Ib/hr
Cd = chemical dosage, 1 percent
V = sludge volume, 7000 gpd
HPD = hours of operation per day, 16
DPW = days of operation per week, 5
C± = initial moisture, content, 97.5 percent
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1(7000)(7) 8 ^ 100 - 97.5
16(5)100 °'^ 100
CR = 1.28 Ib/hr
e. Select number of filters and calculate area per filter.
APF =
NF
vhere
2
APF = area per filter, ft
TFA = total filter area, 730 ft2
NF = number of filters, 2
APF = 365 ft2
5-82. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-83. Bibliography.
a. American Society of Civil Engineers and the Water Pollution Con-
trol Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Burd, R. S., "A Study of Sludge Handling and Disposal," Publica-
tion WP-20-H, May 1968, Federal Water Pollution Control Administration,
Washington, D. C.
c. Eckenfelder, W. W., Jr., Water Quality Engineering for Practicing
Engineers, Barnes and Nobel, New York, 1970.
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d. Eckenf elder, W. W. , Jr., and Ford, D. L., Water Pollution Con-
trol, Pemberton Press, New York, 1970.
e. Jones, B. R. S., "Vacuum Sludge Filtration, II, Prediction of
Filter Performance," Sewage and Industrial Wastes, Vol 28, No. 9, Sep
1956, pp 1103-1115-
f. Malina, J. F. , "Sludge Filtration and Sludge Conditioning,"
Advances in Water Quality Improvements, University of Texas, Water Re-
sources Symposium No. 3, 1970, Austin, Tex.
g. Metcalf and Eddy, Inc., Wastewater Engineering; Collection.
Treatment, and Disposal, McGraw-Hill, New York, 1972.
h. Roy F. Weston, Inc., "Process Design Manual for Upgrading Exist-
ing Wastewater Treatment Plants," prepared for the U. S. Environmental
Protection Agency, Technology Transfer, Oct 1971, Washington, D. C.
i. Simpson, G. D. , "Operation of Vacuum Filters," Journal, Water
Pollution Control Federation, Vol 36, Dec 196^, pp
j. U. S. Environmental Protection Agency, Technology Transfer
Seminars, "Sludge Handling and Disposal," 11-12 Dec 1973, Washington,
D. C.
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Table 5-19- Average Chemical Doses for Vacuum Filtration
Chemical Dose
Rate, percent
Type of Sludge
Raw primary
Digested primary
Elutriated digested
primary
Raw primary plus filter
humus
Raw primary plus
activated
Raw activated
Digested primary plus
filter humus
Digested primary plus
activated
Elutriated digested pri-
mary plus activated:
Average without lime
Average with lime
Ferric
Chloride
2.1
3.8
3.U
2.6
2.6
7.5
5.3
5.6
8.U
2.5
Lime
8.8
12.1
0.0
11.0
10.1
0.0
15.0
18.6
0.0
6.2
Yield
Ib/fWhr
6.9
7.2
7.5
7.1
U.5
0.0
U.6
U.o
3.8
3.8
Cake
Moisture
percent
69.0
73.0
69.0
75.0
77.5
8U.O
77.5
78.5
79-0
T6.2
Table 5-20. Polyelectrolyte Doses (Usual Ranges)
Vacuum Filtration
From Burd, 1968
for
Type of Sludge
Raw primary or raw primary
plus filter humus
Digested primary
Dose Rate
percent
0.2 to 1.2
0.2 to 1.5
Yield
Ib/ft2/hr
6 to 20
h to 15
Cake
Moisture
percent
63 to 72
66 to 7^
Digested primary plus
activated
0.5 to 2.0
to 8
68 to 76
From Burd, 1968
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Table 5-21. Specific Resistance of Some Industrial
and Municipal Sludges
Type of Sludge
Neutralization of sulfuric acid with
lime slurry
Neutralization of sulfuric acid with
Specific
Resistance
sec2/g x ioT
at 500 g/cm^
1 to 2
Coefficient of
Compressibility
dolomitic lime slurry
Processing of aluminum
Paper industry
Neutralization of fatty acids with
sodium carbonate
Froth flotation of coal
Malt whisky distillery
Mixed chrome and vegetable tannery
Biological treatment of chemical
wastes
Activated (domestic)
Raw conditioned (domestic)
Digested conditioned (domestic)
Digested and activated (conditioned)
Raw (domestic)
3
3
6
T
80
200
300
300
2880
3.1
10.5
lU.6
UTO
0.77
O.UU
0.0
0.0
1.6
1.3
0.0
0.0
0.81
1.00
0.0
1.10
0.5^
From Eckenfelder, 1970
Table 5-22. Expected Performance of Vacuum Filters
Handling Properly Conditioned Sludge
Type of Sludge
Fresh solids
Primary
Primary plus trickling filter
Primary plus activated
Activated (alone)
Digested solids (with 01 without elutriation)
Primary
Primary plus trickling filter
Primary plus activated
Yield, Ib/ft2/hr
h to 12
U to 8
U to 5
2.5 to 3.5
U to 8
U to 5
U to 5
From Simpson, 1964
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Section XII. CENTRIFUGATION
5-81*. Background.
a. Centrifugation is a widely used process for concentrating and
dewatering sludge for final disposal. The process offers the following
advantages (para 5-91c ) '•
(l) Capital cost is low in comparison with other mechanical
equipment.
(2) Operating costs are moderate, provided flocculants are not
required.
(3) The unit is totally inclosed, thus odors are minimized.
(U) The unit is simple and will fit in a small place.
(5) Chemical conditioning of the sludge is often not required.
(6) The unit is flexible and can process a wide variety of solids.
(T) Minimum supervision is required.
"b. Disadvantages associated with centrifugation are:
(l) Without the use of chemicals, solids capture is often poor.
(2) Chemical costs can be substantial.
(3) Trash must often be removed from the centrifuge feed by
screening.
(U) The percentage of cake solids is often lower than that result-
ing from vacuum filtration.
(5) Maintenance costs are higher than vacuum filtration.
(6) Fine solids (in concentrate) that escape the centrifuge may
resist settling when recycled to the head of the treatment plant and
gradually build up in concentration, eventually raising effluent solids
level.
c. Centrifuges applicable to sludge thickening and dewatering
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fall into three general classifications: disc, basket, and the currently
popular solid-bowl. Basically, centrifuges separate solids from liquids
through sedimentation and centrifugal force. Process variables in cen-
trifugation include feed rates, sludge solids characteristics, feed
consistency, and chemical additives. Machine variables include bowl de-
sign, bowl speed, pool volume, and conveyor speed.
d. The main objectives in centrifuge design are cake dryness and
solids recovery. The effect of the various parameters on these two
factors are summarized in Table 5-23. Operating data reported in the
literature indicate that raw primary and digested primary sludges de-
water easily. With polymer addition, a centrifuge (fig. 5-13) can pro-
duce 25-^0 percent cake solids with better than 90 percent recovery.
SLURRY IN
LIQUIDS
DISCHARGE
SOLIDS
DISCHARGE
Figure 5-13. Schematic of a centrifuge.
Waste activated sludge, however, is difficult to thicken or dewater
with centrifugation. High polymer dosages will be required to produce
8-10 percent cake solids and 90 percent recovery.
e. Design criteria for centrifugation systems are scarce. One
criterion used in determining the size of centrifuge required is the
power requirement per gallon per minute of inflow (0.5-2.0 hp per gpm) .
Generally, a power requirement of 1.0 hp/gpm of inflow is applicable to
most centrifuges commercially manufactured.
5-132
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29 Sep 78
5-85. Input Data.
a. Sludge flow, gpd.
b. Sludge concentration, percent solids.
5-86. Design Parameters.
a. Centrifuges power requirement, hp/gpm (^.0).
b. Operation per day, hr.
c. Operation per week, days.
d. Number of units.
e. Excess capacity factor, 1.25.
f. Chemical dosage, percent of dry weight of solids.
5-87• Design Procedure.
a. Calculate total power required.
= (SF)(CPR)(7 DPW)(ECF)(2U HFD)
(2k HPD x 60 MPH)(DPW)(HPD)
where
THP = total power required, hp
SF = sludge flow, gpd
CPR = centrifuge power requirement, hp/gpm
DPW = operation per week, days
ECF = excess capacity factor, 1.25
HPD = operation per day, hr
HPH = minutes per hour
5-133
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29 Sep 78
b. Calculate power per unit. Use duplicate units
, / ., THP
hp/unit = ^j-
where
THP = total power required, hp
NU = number of units
c. Compare horsepower with manufacturer's specification and
select centrifuge that meets the requirements.
d. Calculate chemical requirements.
(SF)(T DPW)(Cj(8.3H Ib/gal) /100 - C.
j
_ _
(HPD)(DPW)(100) \ 100
where
CR = chemical requirements, Ib/hr
SF = sludge flow, gpd
C = chemical dosage, percent of dry weight of solids fed to
filter
HPD = operation per day, hr
DPW = operation per week, days
C. = initial moisture content of sludge, percent
5-88. Output Data.
a. Power required/unit.
b. Number of units.
c. Chemical requirements, Ib/hr.
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29 Sep 78
d. Sludge flow, gal/day.
e. Initial solid concentrate, percent.
f. Operation per day, hr.
g. Operation per week, days.
5-89. Example Calculations.
a. Calculate total power required.
Twp _ SF(CPR)7(ECF)2U
i±ir ~ 2M60)DPW(HPD)
where
THP = total power required, hp
SF = sludge flow, TOGO gpd
CPR = centrifuge power requirement, 1.0 hp/gpm
ECF = excess capacity factor, 1.25
DPW = days of operation per week, 5
HPD = hours of operation per day, 16
- 7000(7)2Ml.25)1.0
~ 2U(60)5(16)
THP = 12.8hp
b. Calculate power per unit.
hp/unit = ^
where
hp/unit = power per unit, hp
5-135
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Part 1 of 3
29 Sep 70
THP = total power required, 12.8 hp
NU = number of units, 2
, / .. 12.8
hp/unit = ——
hp/unit = 6.U hp
c. Compare horsepower with manufacturer's specification and select
centrifuge that meets the requirements.
d.. Calculate chemical requirements.
SF(7)(C,)8.3U AGO - C.
CR =
HPD(DPW)100 V 100
where
CR = chemical requirements, lb/hr
SF = sludge flow, TOOO gpd
C = chemical dose, 1 percent
HPD = hours of operation per day, l6
DPW = days of operation per week, 5
C. = initial moisture content of sludge, 97.5 percent
PR = TOOO(T)(1)8.3U /loo - 97.5\
16(5)100V 100 /
CR =1.28 Ib/hr
5-90. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-136
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Part 1 of 3
29 Sep 78
5-91. Bibliography»
a. Albertson, 0. E. and Guidi, E. E., Jr., "Centrifugation of Waste
Sludges," Journal, Water Pollution Control Federation, Vol Ul, Apr 1969,
pp 607-628.
b. Bernard, J., "Sludge Centrifugation," 1st Seminar on Process
Design for Water Quality Control, 1970, Vandertdlt University, Nashville,
Tenn.
c. Burd, R. S., "A Study of Sludge Handling and Disposal," Publi-
cation WP-20-^, May 1968, Federal Water Pollution Control Administration,
Washington, D. C.
d. Jenks, J. H., "Continuous Centrifuge Used to Dewater Variety of
Sludges," Waste Engineering, Jul 1958, pp 360-361.
e. Roy F. Weston, Inc., "Process Design Manual for Upgrading Exist-
ing Waste-water Treatment Plants," prepared for the U. S. Environmental
Protection Agency, Technology Transfer, Oct 1971, Washington, D. C.
f. U. S. Environmental Protection Agency, Technology Transfer
Seminars, "Sludge Handling and Disposal," 11-12 Dec 1973, Washington,
D. C.
g. White, W. F. and Burns, T. E., "Contiguous Centrifugal Treatment
of Sewage Sludge," Water and Sewage Works, Vol 109, Oct 1962, pp
38U-386.
5-137
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29 Sep 78
Table 5-23. Summary of the Effect of Various
Parameters on Centrifuge Performance
To Increase Cake Dryness
Increase "bowl speed
Decrease pool volume
Decrease conveyor speed
Increase feed rate
Decrease feed consistency
Increase temperature
Do not use flocculants
To Increase Solids Recovery
Increase bowl speed
Increase pool volume
Decrease conveyor speed
Decrease feed rate
Increase temperature
Use flocculants
Increase feed consistency
From Burd, 1968
5-138
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Section XIII. MICROSCREENING
5-92. Background.
a. Microscreening is a method of filtration which uses fabric as
the filtering medium. Microscreens usually consist of a special metal-
lic fabric mounted on the periphery of a revolving drum. The untreated
water flows into the drum and radiates outward through the microfabric,
leaving behind the suspended solids removed by the cloth. The solids
retained on the inside of the rotating screen are carried upward to a
row of backwash jets which flush them into a hopper, which is mounted on
a hollow axle of the drum, for return to the treatment plant.
b. Microscreens have been used as a tertiary treatment process for
filtering effluents from biological waste treatment systems. In a study
at Lebanon, Ohio (para 5-99a), suspended solids removals of 89 and
73 percent were obtained with 23- and 35-micron fabrics, respectively.
Backwash water averaged 5 percent of the throughput volume. Studies at
Chicago Sanitary District (para 5-99J) reported an effluent suspended
solids of 6-8 mg/H and a BOD of 3-5-5 mg/£ when applying a good Duality
(suspended solids = 20-25 mg/£ and BOD 15-20 mg/Jl) activated sludge ef-
fluent to a 23-micron screen. Microscreens were reported to be ineffec-
tive in the filtration of alum floes. Removal efficiencies as recommended
for secondary effluents are presented in Table 5-2^ (para 5-99d).
c. Operating problems that have been reported for microscreens in-
clude slime growths, grease accumulation, and the possible buildup of
iron and manganese on the screen. Ultraviolet lights placed in prox-
imity to the screen have been somewhat successful in controlling slime
growths. In general, however, units must be taken out of service on a
regular basis for screen cleaning. Chlorine solutions, acid solutions,
and hot water have been used as cleaners.
d. Currently, there is little information available on the design
of microscreening devices. Individual manufacturers have specific de-
signs and sizes for various types of installations, and much of this
design information is proprietary in nature. Design elements required
for microscreening include hydraulic loading, solids inputs, solids
character, microscreen fabric, backwash, and head loss.
e. The rate of flow through the screen is limited by the allowable
head loss and the character and concentration of the suspended solids
in the feed'. Typical loading rates of 2.5-10 gpm/ft2 of submerged drum
surface area have been reported. Studies at Chicago reported an upper
5-139
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29 Sep 78
limit on hydraulic loading of 6.5 gpm/ft2. The solid loading was the
limiting design factor with an upper limit of 0.88 Ib/ft2/day. Head
loss across the microscreening unit, including inlet and outlet struc-
tures, is limited to 12-18 in. for normal flows and to 6 in. for peak
flows.
f. The continuous backwashing jets require 3-5 percent of the total
throughput volume. In a recent study (para 5-991) the cleaning effi-
ciency depended on the fabric nominal size, screen speed, and backwash
pressure. Cleaning efficiency was found to increase with increasing
fabric nominal pore size to a maximum level of 0.90-0.95 at a pore size
of 16.5 microns and then to decrease slightly with increasing fabric
pore size. Screen speeds of 1*1.0-25.8 ft2/min were found to provide a
cleaning efficiency of 0.85. Cleaning efficiency was independent of
pressure in the range of 15-35 psig and of speed in the range of
14.0-25.8 ft2/min. The authors concluded that at no time should a
microscreen unit be specified for specific application in the absence
of pilot scale microscreen performance data developed with the water
under consideration. Tables 5-25 and 5-26 summarize the microscreen
sizes available from two manufacturers. A schematic of a microstrainer
appears in Figure 5-14.
From Metcalf and Eddy, 1972
Figure 5-14. Schematic of a microstrainer.
5-140
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29 Sep 78
5-93. Input Data.
a. Wastewater flow.
(l) Average flow, mgd.
(2) Peak flow, mgd.
b. Suspended solids concentration, mg/£.
c. Effluent requirements, mg/£.
5-9^- Design Parameters.
a. Head loss across microscreen, in. , ss6 in. water.
b. Initial resistance of clean filter fabric, in feet, at a given
temperature and standard flow conditions (manufacturer's requirements).
c. Filterability index of influent measured on fabric in use
(volume of water obtained per unit head loss when passed at a standard
rate through a unit area of standard filter). (From laboratory.)
d. Speed of strainer (number of square feet of effective fabric
entering water in given time), ft2/min (lit. 0-25. 8 ft2/min).
e. Constants: m = 0.0267; n = 0.1337
5-95- Design Procedure. Utilize the Boucher concept of filter-
ability index (para 5~99b).
a. Calculate the effective submerged area of the screen.
106
H(2it)60
where
2
A - effective submerged area, ft
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EM 1110-2-501
Part 1 of 3
29 Sep 78
m = 0.0267
Q = total rate of flow through unit, mgd.
Cf = initial resistance of clean filter fabric, feet, at a given
temperature and standard flow conditions (manufacturer's
requirements) (1.8 ft for 23-micron screen; 1.0 ft for
35-micron screen)
n = 0.1337
I = filterability index of influent measured on fabric in use
(laboratory) «0.5(SS)
eff
Q
S = speed of strainer, ft /min
H = head loss across microscreen, in. , ss6 in.
b. Calculate hydraulic rate of application.
HP = (Q)do6)
(A)(2lO(60)
where
r>
HR = hydraulic rate, gpm/ft
Q = total rate of flow through unit, mgd
t~)
A = effective submerged area, ft
c. Calculate solids rate of application.
(Q)(C.)(8.3U)
where
SR = solids loading rate, Ib/ft2/day
Q = total rate of flow through unit, mgd
C = influent SS , mg/£
-------
A = effective submerged area, ft
d. Calculate amount of backwash water.
BW = (3-6 percent)(Q)(lO )
where
BW = backwash rate, gpd
Q = total rate of flow through unit, mga
5-96. Output Data.
2
a. Effective submerged area, ft .
2
b. Hydraulic rate of application, gpm/ft .
2
c. Solids rate of application, Ib/ft /day.
5-97. Example Calculations.
a. Calculate effective submerged area of screen.
A "
EM 1110-2-501
Part 1 of 3
29 Sep 78
2
ff( 2)060
where
2
A = effective submerged area, ft
m = constant, 0.0267
Q = flow, 1 mgd
C = initial resistance, 1.8 ft (23-micron fabric)
n = 0.1337
I = filterability index, 0.5
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EM 1110-2-501
Part 1 of 3
29 Sep 78
2
S = speed of strainer, 20 ft /min
H = head loss across microscreen, 6 in.
.. 1Q6
A ~ 6(2*060
A = 56.7 ft2
"b. Calculate hydraulic rate of application.
A(2U)60
where
2
HR = hydraulic rate, gpm/ft
Q = flow, 1 mgd
2
A = effective submerged area, 56.7 ft
HR =
56.7(2*1)60
2
HR = 12.25 gpm/ft
led limit
culate area using HR = 6.5 gpm/ft2.
2
Note: HR exceeds recommended limit of 6.5 gpm/ft ; therefore, recal-
A =
A =
6.5(2^)60
2
A = 106.8 ft
c. Calculate solids rate of application.
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EM 1110-2-501
Part 1 of ^
29 Sep 78
Q(C.)8.3U
SR = —„
where
2
SR = solids rate of application, It /ft /day
Q = flow, 1 mgd
C. = influent suspended solids, 20 mg/A
o
A = area submerged, 106.8 ft
OR - 1(20)8.31*
SR ' 106.8
SR = 1.56 Ib/ft2/day
2
Note: SR exceeds reconmended limit of 0.88 lb/ft /day; therefore, recal-
culate area using SR = 0.88 Ib/ft2/day.
Q(C )8.3U
, _ 1(20)8. 3U
A 0.88
A = 189.3 ft2
d. Calculate amount of backwash water.
"/.i 11 i i i~*
BW =
100
where
BW = backwash rate, gpd
% = percent, U
Q = flow, 1 mgd
100
BW = 1^0,000 gpd
5-11*5
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EM 1110-2-501
Part 1 of 3
29 Sep 78
5-98. Cost Data. Appropriate cost data and economic evaluation may lie
found in Chapter 8.
5-99. Bibliography.
a. Bordien D. G. and Stenburg, R. L., "Microscreening Effectively
Polishes Activated Sludge Effluent," Water and Wastes Engineering
Vol 3, Sep 1966, pp 7^-77.
b. Boucher, P. L. , "A New Measure of the Filtrability of Fluids
with Application to Water Engineering," ICE Journal (British), Vol 27
No. k, 19U7, PP U15-UU6.
c. Burns and Roe, Inc., "Process Design Manual for Suspended Solids
Removal," prepared for the U. S. Environmental Protection Agency, Tech-
nology Transfer, Oct 1971, Washington, D. C.
d. Culp, R. L. and Gulp, G. L., Advanced Wastewater Treatment,
Van Nostrand, New York, 1971. ~~ ~
e. Engineering-Science, Inc., "State of the Art of the Micro-
screen Process," prepared for the Federal Water Quality Administration,
Contract No. 11+-12-819, Jul 1970, Washington, D. C.
f. Engineering-Science, Inc., "Theoretical Formulation of
Operational Model for Simulation of Microscreen Behavior, Report No.
B-l, Sep 1970, Federal Water Quality Administration, Washington, D. C.
g. Engineering-Science, Inc., "Current State of Operational Model
for Simulation of Microscreen Behavior," prepared for the Federal Water
Quality Administration, Contract No. ll*-12-8l9, Nov 1970, Washington,
D • 0 i
h. Engineering-Science, Inc., "Development of Field Data
Acquisition Program for Pilot-Scale Microscreens," prepared for the
Federal Water Quality Administration, Contract No. lU-12-819, Jan 1971,
Washington, D. C.
i. Engineering-Science, Inc., "investigation of Response Surfaces
of the Microscreen Process," Report No. 17090EEM, Dec 1971, U. S. En-
vironmental Protection Agency, Washington, D. C.
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EM 1110-2-501
Part 1 of 3
29 Sep 78;
j. Lyman, B. , Ettelt, G. , and McAloon," T. , "Tertiary Treatment at
Metro Chicago by Means of Rapid Sand Filtration and Microstrainers,"
Journal, Water Pollution Control Federation, Vol Ul, Feb 1969,
pp
k. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
1. Mixon, F. 0., "Filterability Index and Microscreener Design,"
Journal, Water Pollution Control Federation, Vol ^2, No. 11, Nov 1970,
pp 19^-1950.
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Table 5-24. Suggested Removals from Secondary
Effluents by Microscreens
Fabric Aperture
microns
23
35
Anticipated Removal, %
Suspended Solids
70 to 80
50 to 60
BOD
60 to 70
40 to 50
Flow, gpm/ft2
of Submerged Area
6.7
10.0
From Gulp and Gulp, 1971
Table 5-25. Microscreen Sizes Available from
Glenfield and Kennedy
Motors
Drum Sizes, ft
Diameter
5
5
7-1/2
10
Width
1
3
5
10
Drive
1/2
3A
2
h
, bhp
Wash
Approximate
Ranges
Pump Capacity
1
3
5
7-1/2
0.
0.
0.
05
3
8
3
to
to
to
to
of
, mgd
0.5
1.5
4
10
for
Recommended
Maximum Flow
Tertiary Sewage
Applications, mgd
23 microns
0.
0.
0.
2.
075
20
70
00
35 microns
0.
0.
1.
3.
11
30
00
00
From Culp and Gulp, 1971
Table 5-26. Microscreen-Sizes
(Zurn Industries)
Drum Sizes,
Diameter
k
U
6
6
6
10
ft
Width
2
U
k
6
8
10
Screen Area
ft2
2k
48
72
108
144
315
From Gulp and Culp, 1971
5-148
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EM 1110-2-501
Part 1 of 3
29 Sep 78>
Section XIV. DRYING BEDS
5-100. Background.
a.
c,. Sj-udge drying beds (fig. 5-15) are a common means of dewatering
digested sludges, particularly for small plants. Drying beds normally
consist of U-9 in. of sand over 8-18 in. of graded gravel or stone. The
beds are provided with underdrains spaced 9-20 ft apart. Underdrain
piping is often vitrified clay with open joints, having a minimum di-
ameter of U in. and a minimum slope of about 1 percent. Wet sludge is
usually applied to the drying beds in layers of 8-12 in.
b. Design and use of drying beds for sludge dewatering are affected
by weather conditions, sludge characteristics, land value, proximity of
residences, use of sludge conditioning aids, and subsoil permeability.
Sludge bed loadings can be computed on a per capita basis. Table 5-27
summarizes typical loading rates for various sludges. Drying beds may
be open to the atmosphere or covered with glass or clear plastic.
c.
.. Due to potential odor problems, sludge drying beds should be
covered. Bed inclosures protect the beds from rain, help control odors
and insects, reduce the drying period, reduce land requirements, and
improve the appearance of the waste treatment facility.
5-101. Input Data.
a. Sludge flow, gpd.
b. Solids in thickened sludge, percent.
c. Solids desired, percent.
5-102. Design Parameters.
a. Depth of sludge applied (8-12 in.).
b. Days (T) in which drainage is the primary drying mechanism
(1-8 days).
c. Solids after T days (15-25$).
d. Clearwater evaporation rate (available from the U. S. Weather
Bureau).
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EM 1110-2-501
Part 1 of 3
29 Sep 78
c
•-o o-.
Tf
II
II
II
H
1 II
i|
II
II
II
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M
ii
r-TJ — *-,
ir
ii
ii
ii
ii
ii
ii
|i
ii
!!
M
ii
6-iN. VITRIFIED' PIPE LAID \^
WITH PLASTIC JOINTS (
1 'I i"i ' }
'! r !
|l
ij
i'
]l
1 ''!
SH BOX\ !|
\
U
\i >
1 ' r
-!' 1
* — :Si_
t
f d kn
,r
,^^ i
1 1
J 1 C
Uj u,
Q- K 1
E S I
g^ II
£5 ii
£ o "
"* £ i '
2 g |
-A..JI
i
1 !
1
1
1
ll
Ii
.6-IN. FLANGED M
y SHEAR GATE ^
r-L
I
X!
•&
,T
i|
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H
l|
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ll
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ii
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"^
6-IN. CL PIPE
PLAN
,PIPE COLUMN FOR
CLASS-COVER
2-IN. PLANK
WALK
•6-IN. FINE SAND
3-IN. COARSE SAND
3-IN. FINE GRAVEL
.3-IN. MEDIUM GRAVEL
.3 TO 6-IN. COARSE GRAVEL
3-IN. MEDIUM GRAVEL
"2-IN. COARSE SAND
6-IN. UNDERDRAIN LAID\/
WITH OPEN JO/NTS f
SECTION A-A
Figure 5-15- Schematic of a typical sludge drying bed.
5-150
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EM 1110-2-501
Part 1 of 3
29 Sep 78
e. Correction of evaporation rate for1 sludge (^0.75).
f. Average rainfall in wet month (available from the U. S. Weather
Bureau).
g. Fraction of rainfall absorbed by the sludge (MD.57)-
h. Number of sections desired.
5-103. Design Procedure. Fill several columns with thickened/digested
sludge to desired application depth. The bottom of the column should
contain sand and gravel in similar depths to that expected in the bed.
Check the bed daily until drainage from the bottom has essentially
ceased*. Record the number of days of drainage (t ) and the percent
solids in the sludge(s).
a. Calculate the required drying time.
30 x H x so, ,
1 " aE - bR lsi S2 I ^d
where
T = total drying time, days
H = depth to which sludge is applied, in.
S = initial solids, percent
o
a = correction of evaporation rate for sludge, 2iO«75
E = clearwater evaporation rate, in./month
b = fraction of water absorbed by sludge, 2i°-57
R = rainfall during wet month, in./month
S = solids content after t days, percent
S = final solids content, percent
t,, = time during which drainage is significant, days
d
5-151
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EM 1110-2-501
Part 1 of 3
29 Sep 78
b. Calculate the surface area.
Q x T(12)
SA = -
where
2
SA = surface area required, ft
Q = volumetric sludge flow, gpd
S
The drying bed is divided into several sections which are filled in turn
so that one is always available to accept additional sludge.
where
N = number of sections
The area of each section can be given by
^ = r
where
AS = the area of each section, ft
c. Calculate the solids produced.
DTPY . Vo (365 days/yr)
where
DTPY = tons of dry solids per year
d. Calculate weight of solids removed.
DTPY
where
TPY =
S2
5-152
-------
TPY = total tons per year removed.
5-10H. Output Data.
2
a. Area required, ft
b. Depth of sludge application, in.
c. Number of sections.
2
d. Area of each section, ft
e. Drying time in bed, days
5-105. Example Calculations.
a. Calculate the required drying time.
30(H)S
m =
aE - bR
where
T = total drying time, days
H = depth of sludge applied, 12 in.
S = initial solids content, 2.5 percent
o
a = correction for evaporation, 0.75
E = clearwater evaporation rate, h in. /month
b = fraction of rainfall absorbed, 0.57
R = rainfall of wet month, 2 in. /month
S = solids content after t days, 20.0 percent
S = final solids content, 30 percent
t, = time in which drainage is significant, 6 days
EM 1110-2-501
Part 1 of 3
29 Sep 78
5-153
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EM 1110-2-501
Part 1 of 3
29 Sep 78
T _ 30(12)2.5 /]_ i_
0.75(4) - 0.57(2) \2Q ~ 30
T = Ik days
"b. Calculate the surface area.
(Q
QA = a
H(7.48)
where
SA = surface area, ft
Qg = sludge flow, 7000 gpd
H = depth of sludge applied, 12 in.
T = drying time, Ik days
oA = (7000)14(12)
12(7.48)
SA = 13,102 ft2
c. Calculate the solids produced.
QSSQ(8.34)(365)
(100)2000
where
DTPY = tons of dry solids, tons/year
Qg = sludge flow, 7,000 gpd
So = initial solids content, 2.5 percent
8.34 = conversion factor, lb to gal
365 = days per year
2000 = Ib/ton
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EM 1110-2-501
Part 1 of 3
29 Sep 78
TVTPY - 7000(2.5)8.3M 365)
DTPY " (100)2000
DTPY =266 tons/year
d. Calculate the weight of solids removed.
DTPY
TPY = =±£±
where
TPY = tons per year removed
DTPY = tons of dry solids per year, 266
S = final solids content, 0.30
TPY = 26°
0.30
TPY = 86? tons/year
5-106. Cost Data. Appropriate cost .data and economic evaluation may
be found in Chapter 8.
5-107. Bibliography.
a. American Society of Civil Engineers and-the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Bowers, M., "Tips on Sludge Drying Beds Care," Sewage and
Industrial Waters, Vol 29, No. 7, Jul 1957, PP 835-836.
c. Burd, R. S., "A Study of Sludge Handling and Disposal," Publi-
cation WP-20-**, May 1968, Federal Water Pollution Control Administration,
Washington, D. C.
d. Eckenfelder, W. W., Jr., Water Quality Engineering for Prac-
ticing Engineers, Barnes and Nobel, New York, 1970.
5-155
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e. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
f. Smith, R. , "Preliminary Design of Wastewater Treatment Systems,"
Journal, Sanitary Engineering Division, American Society of Civil
Engineers, Vol 95 SA1, 1969, pp 117-118.
g. Vesilind, P. A., Treatment of Wastewater Sludges, Ann Arbor
Science Publishers, Inc., 1975.
h. Walski, T. M., "Mathematical Model Simplifies Design of Sludge
Drying Beds," Water and Sewage Works, Vol 123, No. U, April 1976,
pp 6*1-65.
5-156
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Table 5-27
Area Required for Sludge Drying Beds
in the Northern United States
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29 Sep 78
Type of Sludge
Primary digested
Primary and humus digested
Primary and activated digested
Primary and chemically precip-
itated digested
Open Beds
2
ft /capita
1.0 to 1.5
1.25 to 1.75
1.75 to 2.5
2.0 to 2.5
Covered Beds
2
ft /capita
0.75 to 1.0
1.0 to 1.25
1.25 to 1.5
1.25 to 1.5
(next page is 5-159)
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Section XV. POSTAERATION
5-108. Background. Postaeration is increasingly required by many
state pollution control agencies for the purpose of maintaining certain
dissolved oxygen concentrations in wastewater treatment plant effluents.
Postaeration can be accomplished either in a separate aeration tank
equipped with a diffused or mechanical aeration system or by cascade
aeration.
5-109- Mechanical or Diffused Aeration.
a. Design of Aeration Tank.
(l) Input data.
(a) Average wastewater flow.
(b) Peak wastewater flow.
(2) Design parameter. Detention time (5-10 min).
(3) Design procedure. Calculate the volume of the aeration tank.
1
j
V =
where
V = volume of aeration tank, million gal
Q = peak daily flow, mgd
t = detention time, min (5-10 min)
b. Design of Diffused Aeration System.
(l) Design parameters.
(a) Standard transfer efficiency, percent, from manufacturer
(5-8 percent).
(b) 0 transfer in waste/0? transfer in water, 0.9.
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(c) 0 saturation in waste/0 saturation in water, 0.9.
(d) Correction factor for pressure, 1.0.
(2) Select summer operating temperature (25°-30°C) and determine
(from standard tables) 0 saturation.
(3) Adjust standard transfer efficiency to operating conditions:
(C ) (8)(p) - C
OTE = STE S 1 - ±1 a(l.02)T"20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(C ) = saturation at selected summer temperature T, °C, mg/&
i3 J-
3=0 saturation in waste/0 saturation in water, %0.9
p = correction factor for pressure, %1.0
C = minimum dissolved oxygen to be maintained in the basin,
2.0 mg/£
a = 0 transfer in waste/0? transfer in water, 0.9
T = temperature, °C
(U) Calculate required air flow:
R =
a Ib
(OTE)0.0176
0
ft3 air day
where
R = required air flow, 20 to 30 cfm/1000 ft3
9-
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0 = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(5) Check horsepower for complete mixing against horsepower required
for complete mixing >_0.1 hp/1000 gal; select the larger horsepower.
c . Design of Mechanical Aeration System.
(l) Design parameters.
(a) ' Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
(b) 0 transfer in waste/0 transfer in water, 0.9.
(c) 02 saturation in waste/0 saturation in water, 0.9.
(d) Correction factor for pressure, 1.0.
(2) Select summer operating temperature (5°-30°C), and determine
(from standard tables) 0 saturation.
(3) Adjust standard transfer efficiency to operating conditions.
where
(Cs) (0)(p) - C
OTE = STE - - - a(l.02r
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(Cs) = 0 saturation at selected summer temperature T, °C, mg/£
3=0 saturation in waste/0 saturation in water, 0.9
p = correction factor for pressure, 1.0
C = minimum dissolved oxygen to be maintained in the basin,
2.0 mg/Jl
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a = 0 transfer in waste/0 transfer in water, 0.9
T = temperature, °C
(k) Calculate horsepower requirement.
where
hp = horsepower, per 1000 gal
0 = oxygen required, Ib/day
OTE = operating transfer efficiency
V = volume of basin, gal
(5) Check horsepower for complete mixing against horsepower required
for complete mixing >0.1 hp/1000 gal; select the larger horsepower.
d. Output Data.
(l) Diffused aeration system.
(a) Standard transfer efficiency, percent.
(b) Operating transfer efficiency, percent.
o
(c) Required air flow, cfm/1000 ft .
(2) Mechanical aeration system.
(a) Standard transfer efficiency, Ib 0 /hp-hr.
(b) Operating transfer efficiency, Ib 0 /hp-hr.
(c) Horsepower required.
(3) Aeration equipment.
e. Example Calculations.
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(l) Design of aeration tank.
60(24)
where
V = volume of aeration tank, million gal
Q = peak flow, 2 mgd
t = detention time, 5 min
y-
60(2*0
V = 0.007 million gal = 7000 gal
(2) Design of diffused aeration system.
(a) Adjust standard transfer efficiency to operating conditions
(C ) g(p) - C
OTE = STE 5 1 - ± a(l.02)T~20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 8 percent
(C ) = saturation at temperature T, 8.2 mg/£
0 = 0.9
p = pressure correction factor, 1.0
a = 0.9
T = temperature, 25°C
C = minimum dissolved oxygen, 2 mg/SL
9.17 = saturation at 20°C
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OTE = 4.7$
(b) Calculate required air flow.
R =
02(105)7.48
'a lb 0
(OTE)0.01T6 d 1440 frf V
ftj air y
where
•3
R = required air flow for mixing, 25 cfm/1000 ft
a
Q = oxygen required, Ib/day
OTE = operating transfer efficiency, 4.7 percent
V = volume of basin, 7000 gal
25 =
4.7(0.0176)lU4o(2000)
0 required =2.79 Ib/day
(c) Check horsepower for mixing.
where
hp = horsepower required
0_ = oxygen required, 27-9 Ib/day
OTE = operating transfer efficiency, 4.7 percent
V = volume of tank, 2000 gal
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hp = 2T.9
* >*.7(2*07000
hp = 0.035 hp/1000 gal
Therefore, use hp required for mixing.
hp = 0.1 hp/1000 gal
(3) Design mechanical aeration system.
(a) OTE is same as for diffused aeration system = \.1%
(b) hp for oxygen requirements = 0.035 hp/1000 gal
(c) Use hp = 0.1 hp/1000 gal
5-110. Cascade Aeration. Cascade aeration takes advantage of the
principle that reaeration occurs when water flows over a dam or a weir
and turbulent flow takes place. Oxygen is transferred from the atmo-
sphere. Head requirement depends upon the initial dissolved oxygen and
the desired dissolved oxygen.
a. Input Data.
(l) Water temperature, °C.
(2) Initial dissolved oxygen concentration, mg/£.
b. Design Parameters.
(l) Desired oxygen concentration, mg/£.
(2) constants n and m
(a) n = water quality parameter =0.8 for wastewater treatment
plant effluent
(b) m = weir geometry parameter
1.0 for a free weir
1.3 for step weirs
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c. Design Procedures. Use equation developed "by Barrett et al.
(para 5-112a).
(l) Calculate oxygen saturation, C , at the selected design
temperature.
C = (lU.562 - 0.*a02T + O.OOT910T2)
s
where
C = dissolved oxygen saturation at the selected temperature, mg/£
O
T = temperature
(2) Calculate the deficit ratio, r.
C - C
r =
C - C^
s b
where
r = deficit ratio
C = oxygen concentration above the weir, mg/£
3>
C = oxygen concentration below the weir, mg/£
(3) Calculate the required head, h.
h=
0.11 n(m)(l + O.OU6T)
where
h = required head, ft
n = water quality parameter
= 0.8 for wastewater treatment plant effluent
m = weir geometry parameter
= 1.0 for free weir
=1.3 for step weirs
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T = temperature
d. Output Data.
(l) Initial dissolved oxygen concentration, C , mg/£.
3.
(2) Final dissolved oxygen concentration, C , mg/£.
(3) Design temperature, T , °C.
(1|) Required head, h , ft.
e. Example Calculations.
(l) Calculate oxygen saturation, C
S
C = (111. 562 - 0.4102T + 0.00791T2)
o
where
C = oxygen saturation, mg/£
S
T = temperature, 25°C
C = [iH.562 - O.lil02(25) + 0.00791(25)2]
S
c = 9.25
(2) Calculate deficit ratio.
C - C
C - C
where s D
r = deficit ratio
C = oxygen saturation, 9.25 mg/£
S
Ca = oxygen concentration above weir, 2.0 mg/£
C^ = oxygen concentration below weir, 5.0 mg/£
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= 9.25 - 2.0
9-25 - 5.0
r = 1.7
(3) Calculate required head.
O.OU6T)
where
h = required head, ft
r = deficit ratio, 1.7
n = water quality parameter, 0.8
m = weir geometry parameter, 1.3
T = temperature, 25°C
1.7 - 1
h 0.11(0.8)1.3[1 + O.OU6(25)]
h = 2.85 ft
5-111. Cost D_a_ta. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-112. Bibliography.
a. Barrett, M. J. et al., "Aeration Studies for Four Weir System,"
Water and Water Engineering, 6k, No. 9, I960, pp U07A13.
b. Roy F. Weston, Inc., "Upgrading Existing Wastewater Treatment
Plant," Process Design Manual for Environmental Protection Agency,
October 1971-
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Section XVI. SLUDGE HAULING AND LANDFILLING
5-113. Background.
a. General. Landfilling can provide an acceptable and inexpensive
method for ultimate sludge disposal, particularly for smaller facilities.
The method may be of special importance if it can be integrated with
solid waste disposal systems that have an operating sanitary landfill.
Other methods of sludge treatment, such as drying beds or incineration,
are considered to be methods of volume reduction that produce a residue
requiring ultimate disposal.
b. Principles of Operation.
(l) Sludge hauling and landfilling may be approached in a manner
similar to that for a typical solid waste disposal problem. Most solid
waste disposal systems have at least four definable components: storage,
collection, haul, and disposal. In addition, sludge disposal systems
usually require some form of pretreatment if associated costs are to be
minimized.
(2) Pretreatment of sludge is related to reducing the volume to a
minimum before transporting. Typical unit processes used for volume
reduction may include digestion, centrifugation, vacuum filtration, .and
sludge drying beds. Costs associated with these processes are not con-
sidered to be part of sludge hauling or landfilling but are very impor-
tant in the overall sludge handling train.
(3) Storage costs are site-specific and depend largely upon the
method selected in the sludge handling train. They may be simply the
costs associated with the purchase of bins for storage of waste acti-
vated or primary sludge, a dump truck for storage of digested sludge
solids that have been centrifuged or vacuum filtered, or the cost asso-
ciated with sludge drying beds.
Collection costs are dependent upon a time-labor relationship
to transfer the sludge from storage to the transporting vehicle, as a
dump or tank truck. There may not be a collection cost associated with
labor; however, a cost would be incurred to provide a vehicle during the
loading period. Larger facilities may require that a driver be assigned
to the vehicle during loading periods. Collection costs may be signifi-
cant when it is necessary to shovel sludge from drying beds into trucks
for transportation to the landfill. As indicated in the above paragraphs
collection costs are site and system specific.
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(5) Transportation costs are associated with such parameters as
truck cost, truck size, haul time, labor, and operating costs per unit
time for items such as depreciation, fuel, insurance, maintenance, etc.
Operating costs may "be estimated from manufacturer's rating information
and used in conjunction with estimates of sludge production from various
wastewater treatment processes.
(6) Disposal costs are related to the operation and management of
the final disposal facility. This cost should be minimal if the fa-
cility will integrate ultimate sludge disposal with the disposal of
refuse. When this is possible, the disposal costs may only include the
costs of unloading and a landfill fee. On the other hand, if the land-
fill is to receive only waste sludge; costs may be very significant as
other equipment for operation of the landfill will be required. The
equipment used for landfill operation may include units for excavation,
placing, covering, and compaction of fill.
(7) The lowest possible moisture content attainable at a reasonable
cost should be produced for economical sludge hauling and landfill
operations. A reduction of moisture content will produce a savings in
storage, initial equipment, operating, and labor costs.
5-II1*. Input Data.
a. Average wastewater flow, mgd.
b. Sludge volume, gal/million gal.
c. Raw sludge solids concentration, percent.
d. Dewatered sludge solids concentration, percent.
e. Vehicle loading time, hr.
f. Round-trip haul time, hr.
g. Vehicle capacity, yd .
h. Solids capture in dewatering process, percent.
i. Distance to disposal site, miles.
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5-115- Design Parameters.
a. Sludge volume per million gallons treated (Table 5-28).
b. Raw sludge solids concentration (Table 5-28), 1.5-15 percent.
c. Concentrated solids (Table 5-28), 6-60 percent.
o
d. Vehicle capacity, yd /truck.
e. Truck loading time, 0.5-2.0 hr.
f. Haul time, local conditions.
g. Daily work schedule, 6-8 hr.
h. Solids capture (Table 5-29), 70-99 percent.
5-116. Design Procedure.
a. Compute the sludge volume hauled, yd /day.
°v ~ (7A8)(27)(CSS)
where
o
SV = sludge volume hauled, yd /day
Q = average wastewater flow, mgd
SF = sludge flow, gal/million gal (Table 5-28)
SS = suspended solids in sludge flow, percent (Table 5-28)
CSS = concentrated suspended solids from final treatment process,
percent (Table 5-29)
b. Calculate the number of vehicles for collection and hauling of
the sludge.
= (SV)(LT + HT)
(HPD)(CAP)
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where
NTR = number of trucks required
LT = loading time, hr (0.5-2.0 hr)
HT = round-trip haul time, hr (local conditions)
HPD = work schedule, hr/day (6-8 hr)
3 3
CAP = vehicle capacity, yd /truck (3-12 yd )
c. Compute the tons of sludge hauled per day.
(Q )(SF)(SS)(SCAP)(8.3M
rncti = S
100(CSS)(2000)
where
TSH = tons of sludge hauled per day
SCAP = solids capture, percent (Table 5-29)
5-117. Output Data.
a. Volume of sludge to be dewatered, gpd.
b. Initial moisture content, percent.
c. Final moisture content, percent.
o
d. Volume of sludge hauled, yd /day.
3
e. Truck capacity, yd .
f. Time to make one load, hr.
g. Work schedule, hr/day.
h. Number of trucks required.
i. Tons of sludge hauled per day.
j. Distance to disposal site, miles.
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5-118. Example Calculations.
a. Compute the sludge volume hauled.
(Q )(SF)(-SS)
°v ~ 7.W(27)CSS
where
Q
SV = sludge volume hauled, yd /day
Q = average daily flow, 1.0 mgd
SF =' sludge flow, 2700 gal/million gal
SS = suspended solids in sludge flow, 6 percent
CSS = concentrated suspended solids from final treatment process,
12 percent
1.0(2700)6
bV 7-^8(27)12
SV = 6.7 yd /day
"b. Calculate number of vehicles required.
_ (SV)(LT + HT)
HPD(CAP)
where
NTR = number of trucks required
SV = sludge volume hauled, 6.7 yd /day
LT = loading t ime, 1.5 hr
HT = round-trip haul time, 2.5 hr
HPD = work schedule, 8 hr
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CAP = vehicle capacity, ^ yd/truck
+ 2.5)
8
NTR = 1 truck at 2 trips /day
c. Compute tons of sludge hauled per day.
QQir (SF)SS(SCAP)(8.3U)
TSH = "
100(CSS)2000
where
TSH = tons of sludge hauled per day
Qa = average flow, 1.0 mgd
SF = sludge flow, 2700 gal/million gal
SS = suspended solids in sludge flow, 6 percent
SCAP = solids capture, 95 percent
CSS = cake suspended solids, 12 percent
TSH = 1-°(2TOO)6(95)8.3^
100(12)2000
TSH =5.3 tons /day
5-119- Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-120. Bibliography.
a. Clark, R. M. and Helms, B. P., "Fleet Selection for Solid Waste
Collection Systems," Journal, Environmental Engineering Division,
American Society of Civil Engineers, Vol 98, No. 71, 1972.
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29 Sep 78
b. Clark, R. M. and Gillean, J. I., "Systems Analysis and Solid
Waste Planning," Journal, Environmental Engineering Division, American
Society of Civil Engineers, Vol 100, No. 7, 197*+.
c. Guarino, C. F. et al., "Land and Sea Solids Management Alter-
natives in Philadelphia," Journal, Water Pollution Control Federation,
Vol U7, No. 2551, 1975.
d. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
e. Parkhurst, J. D. et al., "Dewatering Digested Primary Sludge,"
Journal, Water Pollution Control Federation, Vol U6, No. U68, 197^.
f. U. S. Environmental Protection Agency, Technology Transfer,
Process Design Manual for Sludge Treatment and Disposal, October 197*+.
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Table 5-28. Normal Quantities of Sludge Produced by
Different Treatment Processes
Waste-water Treatment Process
Primary sedimentation
Undigested
Digested in separate tanks
Trickling filter
Chemical precipitation
Primary sedimentation and
activated sludge
Undigested
Digested in separate tanks
Activated sludge
Waste sludge
Septic tanks, digested
Imhoff tanks, digested
Gallons
Sludge/
mg
Treated
2,950
1,^50
7^5
5,120
6,900
2,700
19,^00
900
500
Solids
percent
5.0
6.0
7.5
7.5
k.O
6.0
1.5
10.0
15.0
Sludge
Specific
Gravity
1.02
1.03
1.025
1.03
1.02
1.03
1.005
1.0k
1.0k
Table 5-29- Process Efficiencies for Dewatering
of Wastevater Sludge
Unit Process
Centrifugation
Solid bowl
Disc-nozzle
Basket
Dissolved air flotation
Drying beds
Filter press
Gravity thickener
Vacuum filter
Solids Capture, percent
80-90
80-97
70-90
95
85-99
99
90-95
90+
Cake Solids, percent
5-13
5-7
9-10
k-6
8-25
kO-60
5-12
28-35
From EPA Process Design Manual for Sludge Treatment and Disposal
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Section XVII. MULTIPLE-HEARTH INCINERATION
5-121. Background. The multiple-hearth furnace is the most widely used
wastewater sludge incinerator in use today because it is simple to
operate, durable, and capable of burning a wide variety of materials.
Reasonable fluctuations in the feed rate may be accommodated without
interruption of the incineration process. Figure 5-l6 represents a
typical cross section of a multiple-hearth incinerator. Sludge from
water or wastewater treatment is normally thickened and dewatered by
vacuum filtration and/or centrifugation. The dewatered sludge enters
the multiple-hearth furnace at the top and is held first on the top
hearth. The sludge is stirred constantly to promote drying and burning
by rabble arms. These slow-moving arms move the sludge across the
hearths to the inner or outer edge where it drops to the hearth beneath.
This process continues until the sludge reaches the bottom of the fur-
nace as ash.
5-122. Input Data.
a. Average wastewater flow, mgd.
b. Sludge volume, gal/million gal.
c. Raw sludge concentration, percent solids.
d. Dewatered sludge concentration, percent solids.
2
e. Wet sludge loading rate, Ib/hr/ft .
5-123. Design Parameters.
a. Sludge volume per million gal treated (Table 5-30).
b. Raw sludge concentration, percent solids (Table 5-30), 1.5-
15 percent.
c. Dewatered sludge concentration, percent solids (Table 5-31),
U-60 percent.
d. Design multiple-hearth furnace wet sludge loading rate, 7-12 lb/
hr/ft2 at 20-25 percent total solids.
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COOLING AIR DISCHARGE
FLUE GASES OUT
DRYING ZONE
COMBUSTION ZONE
COOLING ZONE
ASH DISCHARGE
INLET
RABBLE ARM
AT EACH HEARTH
COMBUSTION
AIR RETURN
COOLING AIR FAN"
Figure 5-l6. Typical multiple-hearth furnace.
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Design Procedure.
a. Calculate the pounds of dry solids in sludge flow per day.
(Q )(SF)(SS)(SCAP)(8.3U)
Dr ~ (100)(100)
where
SP = dry solids produced per day, lb
Q = average wastewater flow, mgd
SF = sludge flow, gal/million gal (Table 5-30)
SS = suspended solids flow to dewatering process, percent
SCAP = solids capture, percent (Table 5-31)
b. Calculate the dry solids loading rate.
_ (WSLR)(PSTMHF)(2iQ
LR ~ 100
where
2
LR = dry solids loading rate, Ib/day/ft
2
WSLR = wet sludge loading rate, Ib/hr/ft
PSTMHF = percent solids in sludge to multiple-hearth furnace
c. Calculate total hearth area requirement.
LR
2
where SA = required total hearth area, ft
d. From Table 5-32, select the next larger standard size of
multiple-hearth furnace and enter data for final design.
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THA = xxxx.x ft2
O.D. = xx. xx ft
No. of hearths = xx
No. of furnaces = x
where THA = total hearth area furnished
e. Calculate combustion air blower horsepower required.
PRTTP - (0.15)(WSLR)(THA)2H
U3KP _
where
CBHP = combustion air blower horsepower required
0.15 = horsepower required per ton of wet sludge per day at 1-psig
pressure
f . Calculate combustion air blower SCFM supplied.
CBSCFM =
2000
where
CBSCFM = combustion air blower SCFM supplied
22.5 = SCFM required per ton of wet sludge per day at 1-psig
pressure
g. Calculate cooling air fan horsepower requirements.
PTHP - (0-08)(WSLR)(THA)2U
CLHP - 2000 -
where
CLHP = cooling air fan horsepower required
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0.08 = horsepower required per ton wet sludge per day at 8-in. water
static pressure
h. Calculate cooling air fan SCFM supplied.
- (36'.0)(WSLR)(THA)2H
where
CLSCFM = cooling air fan SCFM supplied
36.0 = SCFM required per wet ton sludge per day at 8-in. water
static pressure
5-125. Output Data.
a. Raw sludge concentration, percent solids.
b. Dewatered sludge concentration, percent solids.
c. Dry solids produced per day, l"b.
2
d. Dry solids loading rate, Ib/hr/ft .
2
e. Required total hearth area, ft .
2
f. Total hearth area furnished, ft .
g. Outside diameter, ft.
h. Number of hearths.
i. Number of furnaces.
J. Combustion air blower horsepower required, hp.
k. Combustion air blower SCFM supplied, SCFM.
1. Cooling air fan horsepower required, hp.
m. Cooling air fan SCFM supplied, SCFM.
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5-126. Example Calculations.
a. Calculate the pounds of dry solids produced per day.
Q (SF)SS(SCAP)8.3U
SP = • ° 7- —
100(100)
where
SP = dry solids produced per day, Ib
Q = average flow, 1.0 mgd
SF = sludge flow, 2700 gal/million gal
SS = suspended solids in sludge flow, 6 percent
SCAP = solids capture, 95 percent
SP = 1-0(6)2700(95)8.31*
100(100)
SP = 128U Ib/day
b. Calculate the dry solids loading rate.
Tn (WSLR)(PSTMHF)2U
LR 100
where
f-}
LR = dry solids loading rate, Ib/day/ft
WSLR = wet solids loading rate, 8.5 lb/hr/ft2
PSTMHF = percent solids to MHF, 12 percent
TR - 8.3(12)21;
LR loo—
5-182
-------
LR = 2U.5 Ib/day/ft
c. Calculate total hearth area required.
SA = LR
where
2
SA = required total hearth area, ft
SP = solids produced, 12.Bh Ib/day
LR = loading rate, 2U.5 Ib/day/ft
0/1 ~ 2^75
SA = 52.U ft2
d. Select next larger size hearth.
Use
TEA = 85 ft2
O.D. = 6.75 ft
Wo. of hearths = 6
Wo. of furnaces = 1
e. Calculate combustion air horsepower required.
rmui, - 0.15(WSLR)THA(2U)
CBHP - 2000
where
CBHP = combustion horsepower
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29 Sep 78
2
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29 Sep 78
0.15 = horsepower required per ton of wet sludge
WSLR = wet sludge loading rate, 8.5 lb/hr/ft2
THA = total hearth area, 85 ft2
CBHP = 0-15(8.5)85(21+)
2000
CBHP = 1.3 hp
f. Calculate combustion air blower SCFM.
CBSCFM = 22
2000
where
CBSCFM = combustion SCFM
22.5 = required SCFM per ton of wet sludge
WSLR = wet sludge loading rate, 8.5 lb/hr/ft2
THA = total hearth area, 85 ft2
CBSCFM = 22-5(8.5)85(2lQ
2000
CBSCFM = 195 cfm
g. Calculate cooling air fan horsepower requirements.
CLHP = °•°8(WSLR)(THA)2U
2000
5-1814
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EM 1110-2-501
Part 1 of 3
29 Sep 7d''
where
CLHP = cooling horsepower
0.08 = horsepower required per ton of wet sludge
WSLR = wet sludge loading rate, 8.5 lb/hr/ft2
THA = total hearth area, 85 ft2
PTHP - 0.08(8.5)85(2lQ
CLHP - —
CLHP = 0.7 hp
h. Calculate cooling air fan SCFM.
CLSCFM = 36(WSLR)THA(2U)
where
CLSCFM = cooling SCFM
36 = SCFM required per ton of wet sludge
WSLR = wet sludge loading rate, 8.5 lb/hr/ft2
2
THA = total hearth area, 85 ft
CLSCFM - 36(8.5)85(21+)
CLSCFM -
CLSCFM = 312 cfm
5-127. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
5-185
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29 Sep 78
5-128. Bibliography.
a. Burgess, J. V., "Comparison of Sludge Incineration Processes,"
Process Biochemistry, Vol 3, April 1968, p 27.
b. Gray, D. H. and Penessis, C., "Engineering Properties of Sludge
Ash," Journal. Water Pollution Control Federation. Vol Uk, May 1972,
P 8^7.
c. Helmenstein, S. and Martin, F., "Planning Criteria for Refuse
Incineration Systems," Combustion, Vol 1*5, May 197^, p 11.
d. Loran, B. I., "Burn That Sludge," Water and Wastes Engineering,
Vol 12, October 1975, p 65. ~~~ SL
e. Unterberg, ¥., Sherwood, R. J., and Schnerder, G. R., "Com-
puterized Design and Cost Estimation for Multiple Hearth Sludge Incin-
erators," Environmental Protection Agency Publication No. EP 1 16-17070
EBP 07/71, 1971.
5-186
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31 Jul 78
Table 5-30. Normal Quantities of Sludge Produced by-
Different Treatment Processes
Waste-water Treatment Process
Primary sedimentation
Undigested
Digested in separate tanks
Trickling filter
Chemical precipitation
Primary sedimentation and
activated sludge
Undigested
Digested in separate tanks
Activated sludge
Waste sludge
Septic tanks, digested
Imhoff tanks, digested
Gallons
Sludge/
mg
Treated
2,950
1,^50
7^5
5,120
6,900
2,700
19,kOO
900
500
Solids
percent
5.0
6.0
7.5
7.5
h.o
6.0
1.5
10.0
15.0
Sludge
Specific
Gravity
1.02
1.03
1.025
1.03
1.02
1.03
1.005
I. Ok
1.0k
Table 5-31. Process Efficiencies for Dewatering
of Wastewater Sludge
Unit Process
Centrifugation
Solid bowl
Disc-nozzle
Basket
Dissolved air flotation
Drying beds
Filter press
Gravity thickener
Vacuum filter
Solids Capture, percent
80-90
80-97
70-90
95
85-99
99
90-95
90+
Cake Solids, percent
5-13
5-7
9-10
U-6
8-25
1*0-60
5-12
28-35
From EPA Process Design Manual for Sludge Treatment and Disposal
5-187
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29 Sep 78
Table 5-32. Standard Sizes of Multiple-Hearth
Furnace Units
No. of Hearths 6 to 12
Wall Thickness, in. 13.5
Outer Diameter (O.D.), ft 6.75 to 22.25
Effective Hearth Area, ft2 85 to 3120
THA
ft
85
98
112
125
126
i4o
145
166
187
193
208
225
256
276
288
319
323
351
364
383
i
452
510
560
575
672
760
845
857
944
O.D.
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
No.
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
THA
ft2
988
io4i
1068
1117
1128
1249
1260
1268
l4oo
l4io
1483
1540
1580
1591
1660
1675
1752
1849
1875
1933
2060
2084
2090
2275
2350
2464
2600
2860
3120
O.D.
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
No.
Hearths
7
11
6
8
12
7
9
>
6
10
8
7
11
6
9
8
12
10
7
9
x
11
10
8
12
11
9
12
10
11
12
5-188
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section XVIII. FLUIDIZED BED INCINERATION
5-129. Background.
a. Fluidized bed incineration for waste-water sludges involves the
destruction of waste-water solids through combustion. Basically, de-
watered sludge is pumped into the incineration vessel containing a
heated catalytic bed. This bed is fluidized by a controlled upward air-
flow at pressures of 2.0 to 5.0 psig; this air also supplies oxygen for
combustion. Temperatures for combustion range from 1200° to l600°F.
Supplemental fuel may be added by burners to keep temperatures at opti-
mum levels if the sludge characteristics do not allow for autogenous
combustion. Burning of wastewater sludge produces ash and several gases
which are carried upward by the flow of air through an exhaust stack.
Figure 5-17 describes a typical material balance for incineration of
1 Ib of dry sludge. Normally, some type of air pollution equipment such
as scrubbers, electrostatic precipitators, and cyclones are connected to
process the incinerator byproducts. This exhaust may also pass through
other control devices if noxious odors are expected to result from
combustion.
AUXILIARY FUEL
(NO. 2 OIL)
0.4246 LB.
0.3706 LB. C
0.0533 LB. H
0.0008 LB. S
f 5.4625 LBS. O2] .
118.2875 LBS. N2J
SLUDGE ONE DRY POUND
0.4363 LB. C
0.0637 LB. H
0.0024 LB. S
0.1400 LB. ASH
0.3335 LB. O2
0.0241 LB. N
H20 2.984 LBS. —
"IN WETSLUDGE"
WHICH CONTAINS
ONE DRY POUND
SLUDGE
1 EXCESS AIR
T ?n 79«9 1 HC
FLUIDIZED
BED
INCINER-
ATOR
(SANDS)
f 2.7140 LBS. O2|
^18.3116 LBS. N2J
*• ASH 0.14 LB.
^- H2O 4.027 LB.
*> CO2 2.955 LB.
^- SO2 0.0064 LB.
^
^^^^ SAND GRANULES?
NOx?
Figure 5-17- Material balance for fluidized bed
sewage sludge incineration.
5-189
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29 Sep 78
"b. The fluidized bed. incinerator used for combustion of waste-water
sludge is a vertical cylinder with an air distributor plate containing
small openings near the bottom as seen in Figure 5-l8. The base plate
serves two functions: (l) allows air to pass into the media and (2)
supports the media. An external air source forces the air into the
bottom of the vessel where it is distributed in such a manner as to
fluidize the bed and supply oxygen for combustion.
c. The bed material is composed of graded silica sand with size
varying from ASTM No. 8 to No. 20. The normal operating temperatures
for these fluidized sand beds are between 1200° and l600°F, the maximum
being 2000°F. At this temperature, the sand approaches its melting
point which is detrimental to the incinerator process. Also, damage to
the incinerator vessel would be experienced in the heat exchanger and
flue piping.
d. There are two possible locations for the sludge feed inlet to
be placed on a fluidized bed incinerator vessel. One is positioned so
that the sludge is pumped (screw-type) directly into the fluidized bed.
The advantage of this configuration lies in the fact that complete com-
bustion is realized in a short time. Yet, problems can be incurred due
to clogging from dried sludge. The second location is above the fluid-
ized bed or the freeboard zone. Hot gases evaporate the water in the
sludge as the solids enter the vessel. This operation is more amenable
to combustion of solids with high moisture contents. However, combus-
tion time for the elevated configuration is increased.
e. Sludge combustion in an incinerator occurs in two zones: Zone 1
(bed) where the principal processes are pyrolysis and combustion and
Zone 2 (freeboard) where the principal processes are flame holding and
final burnup. Combustible elements contained in sludge are carbon,
hydrogen, nitrogen, and sulfur, which when completely burned with oxy-
gen, form the combustion products C02, 1^0, NOX, and S02, respectively.
Ash is also generated in the process of incinerating sludge. The NOX,
S02, and particulate ash can be classified as major air pollutants. In
order to prevent the release of these by-products into the atmosphere,
all fluidized bed incinerators are equipped with scrubbers of varying
efficiency. These units have been found to be quite effective.
f. In some cases, an air preheater or heat exchanger can be used
in conjunction with a fluidized bed as seen in Figure 5-18. The func-
tion of the preheater is to raise the temperature of the incoming air to
1000°F by mixing the cool air at 70°F with the exhaust gas at 1500°F.
5-190
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EM 1110-2-501
Part 1 of 3
29 Sep 78
SIGHT GLASS
EXHAUST
SAND FEED
PRESSURE
TAP
PREHEAT BURNER
ACCESS
DOORS
THERMOCOUPLE
--_ SLUDGE INLET
FLUIDIZING
AIR INLET
Figure 5-18. Cross section of a fluid bed reactor.
5-191
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Part 1 of 3
29 Sep 78
5-130. Input Data.
a. Average flow, Q , mgd.
b. Sludge volume, gal/million gal (Table 5-33).
c. Sludge solids concentration, percent (Table 5-33).
d. Moisture content of dewatered sludge, percent (Table 5-3*0
e. Work schedule, hr/day.
f. Sludge analysis.
(l) Carbon content, percent.
(2) Hydrogen content, percent.
(3) Oxygen content, percent.
(k) Sulfur content, percent.
g. Heat value of fuel.
h. Fuel analysis, for fuel oil.
(l) Carbon content, percent.
(2) Hydrogen content, percent.
(3) Oxygen content, percent.
(h) Sulfur content, percent.
i. Operating temperature of preheater, °F.
j. Ambient air temperature, °F.
k. Sand-to-sludge ratio.
1. Specific weight of sand, Ib/ft .
m. Volatile solid content of sludge, percent.
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29 Sep 78
n. Fuel cost, dollars per million Btu.
5-131. Design Parameters.
a. Sludge solids concentration, 1.5 to 5 percent.
b. Moisture content of dewatered sludge, liO to 96 percent.
c. Sludge analysis. Use laboratory values if known; otherwise use
the following.
(l) Carbon content, 1*3.6 percent.
(2) Hydrogen content, 6.k percent.
(3) Oxygen content, 33.^ percent.
(4) Sulfur content, 0.3 percent.
d. Heat value of fuel oil, 18,000 Btu/lb.
e. Fuel analysis. Use reported values, or for fuel oil use the
following.
(l) Carbon content, 87.3 percent.
(2) Hydrogen content, 12.6 percent.
(3) Oxygen content, 0 percent.
(k) Sulfur content, 1.0 percent.
f. Operating temperature of preheater, 1000° to 1200°F.
g. Incinerator retention time, 10 to 50 sec.
h. Ratio of incinerator height:diameter, lt:l to 6:1.
i. Heat release rate, <50,000 Btu/hr/ft.
j. Sand-to-sludge ratio, 3 to 8 Ib/lb/hr.
k. Specific weight of sand, 110
5-193
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Part 1 of 3
29 Sep 78
1. Grid jet velocity, >300 fps.
m. Volatile solids content of sludge, percent. Use reported values,
or ^0 to 60 percent volatile.
n. Fuel cost, dollars per million Btu.
5-132. Design Procedure.
a. Determine the amount of sludge to be incinerated, It/day.
(Q )(SF)(SS)(SCAP)(8.3^)
(100)(100)
where
SP = dry sludge produced per day, lb
Q = average waste-water flow, mgd
avg
SF = sludge flow, gal/million gal (Table 5-33)
SS = suspended solids in sludge, percent
SCAP = solids capture, percent (Table 5-3M
b. Calculate the sludge hourly loading rate.
TR - SP
LR ~ Ira
where
LR = dry sludge loading rate, Ib/hr
HPD = work schedule, hr/day
c. Calculate sludge heat value.
BS = 11*5^ + 620
where
BS = sludge heat value, Btu/lb
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EM 1110-2-501
Part 1 of 3
29 Sep 78
C = carbon in sludge, percent (if unknown, use k3.6)
R^ = hydrogen in sludge, percent (if unknown, use 6.k)
QI = oxygen in sludge, percent (if unknown, use 33.lt)
BI = sulfur in sludge, percent (if unknown, use 0.3)
d. Calculate sludge loading rate.
SL = 10(2-T-0.0222M)
where
SL = sludge loading rate, Ib/ft2/hr
M = moisture content of dewatered sludge, percent
e. Calculate cross-sectional area of incinerator.
A - ^
A~ SL
where A = area of incinerator, ft2
f. Calculate diameter of incinerator.
where D = diameter, ft
g. Compute auxiliary fuel supply.
(l) Calculate "burning rate.
BR = 10(5-9Vr-0.0096M)
where BR = burning rate, Btu/ft2/hr
(2) Compute total heat input rate.
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29 Sep 78
HIR = (BR)(A)
where HIR = total heat input rate, Btu/hr
(3) Calculate heat input from sludge.
HIS = (BS)(LR)
where HIS = heat input from sludge, Btu/hr
(U) Calculate auxiliary fuel supply.
AFS = HIR - HIS
where AFS = auxiliary fuel supply, Btu/hr
(5) Calculate fuel oil required.
HV
where
FO = fuel oil required, Ib/hr
HV = heat value of fuel
h. Compute air supply rate (20 percent excess air),
(l) Calculate air supply rate for sludge.
q, = 0.0127[(HR)(2.67Cn + 7.9UHn + Sn - 0.
1 111.
where q = air supply rate for sludge, scfm
(2) Calculate air supply rate for fuel.
q2 = 0.0127[(FO)(2.67C + 1
where
q = air supply rate for fuel, scfm
5-196
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Part 1 of 3
29 Sep 78
C2 = carbon in fuel, percent (if unknown, use 87.3)
E^ = hydrogen in fuel, percent (if unknown, use 12.6)
S2 = sulfur in fuel, percent (if unknown, use 1.0)
02 = oxygen in fuel, percent (if unknown, use 0.0)
(3) Calculate air supply rate.
d = qx + q2
where q. = total dry air supply, scfm
i. Calculate total gas flow (air plus water).
LE M
100 - M 3.01
where a = total gas flow, scfm
j. Calculate air preheater capacity.
(l) Calculate the air-to-sludge ratio.
where ASR = air-to-sludge ratio, Ib air/lb sludge
(2) Calculate air preheater capacity.
APHS = (0.2U)(ASR)(T2 - T )(LR)
where
APHS = air preheater capacity, Btu/hr
T2 = operating temperature, °F (1000° to 1200°F)
T.^ = incoming air temperature, °F
k. Assume a retention time for the incinerator. (See Table 5-35'
5-197
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29 Sep 78
10 <_ at <_ 50 sec
where dt = retention time, sec
1. Determine volume of reactor.
... dt
V= *t 60
3
where V = volume of reactor, ft
m. Calculate the height of the reactor. (U <_ H/D <_ 6)
H = -
where H = height of reactor, ft. (if H/D does not fall between 1* and
6, adjust dt and make a new determination of the volume, V .)
n. Check heat release rate. (Hr <_ 50,000 Btu/hr/ft)
HIR
Hr =
V
3
where Hr = heat release rate, Btu/hr/ft
o. Assume a sand-to-sludge ratio (Table 5-35). Use 3 to 8 Ib
sand/lb sludge/hr for ASTM No. 8 sand.
3 < Rss < 8 Ib/lb/hr
where Rss = ratio of sand to sludge
p. Calculate the depth of ASTM No. 8 silica sand required.
T _ (!2)(LR)(Rss)
(TS)(A)
where
L = depth of sand, in.
y^ = specific weight of sand, Ib/cu ft (approx 110)
o
5-198
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29 Sep 78
q.. Calculate the grid jet velocity (Table 5-35; V > 300 fps).
V. = 160 + 160 log L
J
where V. = grid jet velocity, fps
J
5-133. Output Data.
a. Dry sludge loading rate, lb/hr.
b. Sludge heat value, Btu/lb.
2
c. Sludge loading rate, Ib/ft /hr.
2
d. Cross-sectional area of incinerator, ft .
e. Diameter of incinerator, ft.
2
f. Burning rate, Btu/ft /hr.
g. Total heat input rate, Btu/hr.
h. Heat input from sludge, Btu/hr.
i. Auxiliary fuel supply, Btu/hr.
j. Fuel oil required, lb/hr.
k. Total dry air supply, scfm.
1. Total gas flow, scfm.
m. Air preheater capacity, Btu/hr.
3
n. Volume of reactor, ft .
o. Height of reactor, ft.
p. Heat release rate, Btu/ft/hr.
q.. Depth of sand, in.
r. Grid jet velocity, fps.
5-199
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EM 1110-2-501
Part I -of 3
29 Sep 78
. Example Calculations.
a. Determine the amount of sludge produced.
Q (SF)SS(SCAP)8.3U
SP =
100(100)
where
SP = sludge produced, Ib/day
Q = average daily flow, 1.0 mgd
avg
SF = sludge flow, 2700 gal/million gal
SS = suspended solids in sludge, 6 percent
SCAP = solids capture, 95 percent
1.0(2700)6(95)8.3if
100(100)
SP = 128J4 Ib/day
b. Calculate the sludge loading rate.
" HPD
where
LR = loading rate, Ib/hr
SP = sludge produced, 128U Ib/day
HPD = work schedule, 8 hr/day
TR -
LR -
LR = 160 Ib/hr
c. Calculate sludge heat value.
5-200
-------
BS =
where
BS = sludge heat value, Btu/lb
C = carbon in sludge, 1*3.6 percent
H = hydrogen in sludge, 6.1* percent
C^ = oxygen in sludge, 33.U percent
S = sulfur in sludge, 0.3 percent
BS = ll*5(U3.6) + 620 e.k - + 1*5(0.3)
EM 1110-2-501
Fart 1 of 3
29 Sep 78
BS = 7695 Btu/hr
d. Calculate the sludge loading rate.
SL= 10(2.7-0.022M)
where
SL = sludge loading rate, Ib/ft /hr
M = moisture content of dewatered sludge, 60 percent
SL = 10[2. 7-0. 022(60)]
SL = 2U Ib/ft2/hr
e. Calculate cross-sectional area of incinerator.
A = M
A SL
where
p
A = area, ft
5-201
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EM 1110-2-501
Part 1 of 3
29 Sep 78
LR = loading rate, 160 Ib/hr
Q
SL = sludge loading rate, 2h Ib/ft /hr
A - 16°
A ~ ~2U
A = 6.7 ft2
f. Calculate diameter of incinerator.
where
D = diameter, ft
A = area, 6.7 ft2
D = 2.92 ft
g. Compute auxiliary fuel supply.
(l) Calculate burning rate.
BR = 10(5.9U7-0.0096M)
where
2
BR = burning rate, Btu/ft /hr
M = moisture content of dewatered sludge, 60 percent
BR = 10t5.9^7-0.0096(60)]
BR = 23^,960 Btu/ft2/hr
(2) Compute total heat input rate.
5-202
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EM 1110-2-501
Part 1 of 3
29 Sep 78''
HIR = BR(A)
where
HIR = heat input rate, Btu/hr
A = area, 6.7 ft2
BR = burning rate, 23^,960 Btu/ft /hr
HIR = 231|,960(6.T)
HIR = 1,57*1,250 Btu/hr
(3) Calculate heat input from sludge.
HIS = BS(LR)
vhere
HIS = heat input, from sludge, Btu/hr
BS = sludge heat value, 7695 Btu/lb
LR = loading rate, l60 Ib/hr
HIS = 7695(160)
HIS = 1,231,200 Btu/hr
(U) Calculate auxiliary fuel supply.
AFS = HIR - HIS
where
AFS = auxiliary fuel supply, Btu/hr
HIR = heat input rate, 1,574,250 Btu/hr
HIS = heat input from sludge, 1,231,200 Btu/hr
5-203
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EM 1110-2-501
Part 1 nf 3
29 Sep 78
AFS = 1,57^,250 - 1,231,200
AFS = 3^3.050 Btu/hr
(5) Calculate fuel oil required.
HV
where
FO = fuel oil required, l"b/hr
AFS = auxiliary fuel supply, 3^3,050 Btu/hr
HV = heat value of fuel, 18,000 Btu/lb
-
" 18,000
FO = 19 Ib/hr
h. Compute air supply rate (20$ excess).
(l) Calculate air supply rate for sludge.
qx = 0.0127[LR(2.67C1 + 7-9^ + S^ - 0^)]
where
q. = air supply for sludge, scfm
LR = loading rate, 160 Ib/hr
C = carbon in sludge, U3.6 percent
H = hydrogen in sludge, 6.k percent
S = sulfur in sludge, 0.3 percent
0 = oxygen in sludge, 33.^ percent
q = 0.0127{l6o[(2.67)(^3.6) + 7- 9^(6. U) + 0.3 - 33-U]}
5-204
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Part 1 of ^
29 Sep 78
q = 272.5 scfm
(2) Calculate air supply rate for fuel.
q2 = 0.0127[FO(2.67C2 + 7-9^ + S2 - 0^)]
where
q = air supply rate for fuel, scfm
FO = fuel oil required, 19 lb/hr
C = carbon in fuel, 87-3 percent
H = hydrogen in fuel, 12.6 percent
S = sulfur in fuel, 1.0 percent
0 = oxygen in fuel, 0 percent
q2 = 0.0127[19(2.67)(87.3) + 7«9Ml2.6) + 1.0 - o)]
q = 80.6 scfm
(3) Calculate air supply rate.
where
q = total air supply, scfm
q = sludge air supply, 272.5 scfm
q = fuel air supply, 80.6 scfm
q = 272.5 + 80.6
q = 353.1
i. Calculate total gas flow.
5-205
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EM 1110-2-501
Part 1 of 3
29 Sep 78
t 100
where
q^ = total gas flov, scfm
q = air supply rate, 353.1 scfm
LR = loading rate, 160 Ib/hr
M = moisture content, 60 percent
/_M_\
- M \3.01/
ioo - 6o
q, = ^33 scfm
j. Calculate air preheater capacity.
(l) Calculate the air-to-sludge ratio.
60
where
ASR = air-to-sludge ratio, Ib air/lb sludge
q = air supply rate, 353.1 scfm
LR = loading rate, 160 Ib/hr
ASR = ^-
ASR = 9.9 Ib air/lb sludge
(2) Calculate air preheater capacity.
APHS = 0.2MASR)(T2 - T
where
5-206
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Part 1 of 3
29 Sep 79
APHS = air preheater capacity, Btu/hr
ASR = air-to-sludge ratio, 9-9 !b air/lb sludge
T = operating temperature , 1100°F
T = incoming air temperature, 72°F
LR = loading rate, l60 Ib/hr
APHS = 0.2U(9.9)(HOO - 72)160
APHS = 390. SOU Btu/hr
k. Assume a retention time for incinerator.
dt = 15 sec
1. Determine volume of reactor.
where
V = volume of reactor, ft
cr = total gas flow, U33 scfm
dt = detention time, 15 sec
V -
V = 108.3 ft3
m. Calculate height of reactor.
"-}
where
H = height of reactor, ft
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29 Sep 78
V = volume of reactor, 108.3 ft
p
A = area of reactor, 6.7 ft
108.3
H = 16.2 ft
|= |~= 5.5 (OK)
n. Check heat release rate (H _<_ 50,000 Btu/hr/ft)
n = HIR
r V
where
o
H = heat release rate, Btu/hr/ft
HIR = heat input rate, 1,57^,250 Btu/hr
V = volume, 108.3 ft3
H = 1,57^,250
r 108.3
= lH,536 Btu/hr/ft3 <_ 50,000 (OK)
o. Assume a sand-to-sludge ratio (Rss ) .
Ess = 5 Ib/lb/hr
p. Calculate depth of ASTM No. 8 silica sand.
(Y )A
S
12(LR)(Rss)
L =
where
L = depth of sand, in.
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LR = loading rate, 160 Ib/ft2/hr
Ess = ratio, sand to sludge, 5 lb/lb/hr
o
Y = specific weight of sand, 110 Ib/ft
s
2
A = area of reactor, 6.7 ft
T - 12(160)5
L " 110(6.7)
L = 13 in.
q. Calculate grid jet velocity.
V = 160 + 160 log L
cJ
where
V. = grid jet velocity, fps
J
L = depth of sand, 13 in.
V. = 160 + 160 log (13)
J
V = 338 fps > 300 fps (OK)
5-135. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
5-136. Bibliography.
a. "Air Pollution Aspects of Sludge Incineration," EPA Technology
Transfer, EQA 625A-75-009, June 1975-
b. Alford, J. M., "Sludge Disposal Experiences at North Little
Rock, Arkansas," Journal, Water Pollution Control Federation, Vol Ul,
No. 1, pp 175-183.
c. Balakrishnan, S., Williamson, D., and Odey, R., "State of the
Art Review on Sludge Incinerator Practices," FWQA. 17070 Div CA/70,
April 1970.
5-209
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29 Sep 78
d. Burgess, J. V., "Comparison of Sludge Incinerator Processes,"
Process Biochemistry, Vol 3, No. 7, 1968, pp 27-30.
e. Cardinal, P. J., "Advances in Multihearth Incineration," Process
Biochemistry, Vol 6, 1971, PP 27-31.
f. Copeland, C. G., "Design and Operation of Fluidized Bed Inciner-
ators," Water and Sewage Works, Vol 117, 1970, p R245-9.
g. Copeland, C. G., "The Copeland Process Fluid Bed System and
Pollution Control Worldwide," Proceedings, 19th Industrial Waste
Conference, Purdue University, Lafayette, Indiana, 1964.
h. Copeland, C. G. , "Water Reuse and Black Liquor Oxidation by the
Container-Copeland Process," Proceedings, 19th Industrial Waste
Conference, Purdue University, Indiana, 196k.
i. Fair, G. M. and Geyer, J. C. , Elements of Water Supply and Waste
Water Disposal, John Wiley and Sons, Inc., New York, 1955.
j. Fair, G. M., and Moore, E. W., "Sewage Sludge Fuel Value Related
to Volatile Matter," Eng. News Record, 1935, p 68l.
k. Gaillard, J. R., "Fluidized Bed Incineration of Sewage Sludge,"
Water Pollution Control, Vol 73, pp 190-192, 1973.
1. Hanway, J. E., "Fluidized-Bed Processes - A Solution for Indus-
trial Waste Problems," Proceedings,'21st Industrial Waste Conference,
Purdue University, Lafayette, Indiana, 1966.
m. Harkness, N. et al, "Some Observations on the Incineration of
Sewage Sludge," Water Pollution Control. Vol 71, No. 1, 1972, pp 16-33.
n. Liao, P. B., "Fluidized-Bed Sludge Incinerator Design," Journal,
Water Pollution Control Federation, Vol 1*6, No. 8, 1974, pp 1895-1913.
o. Liao, P. B. and Pilat, M. J., "Air Pollutant Emissions from
Fluidized Bed Sewage Sludge Incinerators," Water and Sewage Works
Vol 119, No. 2, pp 68-72.
p. Liptak, B. G., Environmental Engineers Handbook, Vol 1, Chilton
Book Company, Radnor, Pennsylvania, 1974.
5-210
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29 Sep 78
q.. Lor an, B. I. , "Burn That Sludge," Water and Wastes Engineering,
Vol 12, No. 10, 1975, PP 65-68.
r. Millward, R. S. and Booth, P. B. , "Incorporating Sludge Com-
bustion Into Sewage Treatment Plant," Water and Sewage Works, Vol 115,
No. R-169-171*, 1968.
s. Pavoni, J. L. et al, Handbook of Solid Waste Disposal, Van
Nostrand Reinhold Company, Nev York, 1975-
t. "Process Design Manual for Sludge Treatment and Disposal," EPA
Technology Transfer, EPA 625/11-7^-006, October 197^.
u. "Sludge Incineration Plant Uses Fluid-Bed Furnace," Chemical
and Process Engineering, April 1972, p 7.
v. Vesilind, P. A. , Treatment and Disposal of Waste-water Sludges,
Ann Arbor Science, Ann Arbor, Mich.,
5-211
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Table 5-33. Normal Quantities of Sludge Produced by
Different Treatment Processes
Wastewater Treatment Process
Primary sedimentation
Undigested
Digested in separate tanks
Trickling filter
Chemical precipitation
Primary sedimentation and
activated sludge
Undigested
Digested in separate tanks
Activated sludge
Waste sludge
Septic tanks, digested
Imhoff tanks , digested
Gallons
Sludge/
mg
Treated
2,950
1,1*50
7^5
5,120
6,900
2,700
19,^00
900
500
Solids
percent
5-0
6.0
7-5
7-5
h.O
6.0
1.5
10.0
15-0
Sludge
Specific
Gravity
1.02
1.03
1.025
1.03
1.02
1.03
1.005
I. Oh
l.Oh
Table 5-3^. Process Efficiencies for Dewatering
of Wastewater Sludge
Unit Process
Centrifugation
Solid bowl
Disc-nozzle
Basket
Dissolved air flotation
Drying beds
Filter press
Gravity thickener
Vacuum filter
Solids Capture, percent
80-90
80-97
70-90
95
85-99
99
90-95
90+
Cake Solids , percent
5-13
5-7
9-10
h-6
8-25
1|0-60
5-12
28-35
From EPA Process Design Manual for Sludge Treatment and Disposal
5-212
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Table 5-35. Recommended Fluidized Bed Sludge Incinerator
Design Criteria
Parameter
Sludge loading rate*
Burning rate
Heat release rate
Air:dry sludge ratio
Fuel:dry sludge ratio*
Combustion temperature
Retention time (at standard conditions)
Pressure drop
Height:diameter ratio
Grid jet velocity
Freeboard gas velocity
Stack gas velocity
Ratio of freeboard diameter:grid diameter
Ratio of No. 8 sand to sludge rate**
Magnitude
5 to UO Ib dry sludge/hr/ft'
Up to 300,000 Btu/hr/ft2
Up to 50,000 Btu/hr/ft3
6 to 50 Ib/lb
0 to 30,000 Btu/lb
1200 to lli000F
10 <_ time <_ 50 sec
50 to 100 in. of water
k to 6:1
Greater than 300 fps
5 to 10 fps
20 to 50 fps
1.5
3 to 8 Ib/hr/lb
* Sludge loading rates and air and fuel requirements depend on sludge
moisture content and the ratio of air and sludge.
** Sand to sludge ratios depend on sludge moisture content.
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CHAPTER 6
CHEMICAL UNIT PROCESSES
Section I. INTRODUCTION
6-1. Definition. Chemical processes may involve the addition of chemi-
cals, the use of chemical reaction columns, and the use of electrical
currents. In the process design procedure, although the fundamentals of
chemistry are not discussed, a basic knowledge cf chemistry is helpful
when assessing the applicability of such processes to a particular waste
treatment problem. The processes included in this section are:
a. Carbon adsorption.
b. Chemical coagulation.
c. Ammonia stripping.
d. Chlorination.
e. Ion exchange.
f. Neutralization.
g. Recarbonation.
h. Two-stage lime treatment.
(next page is 6-3)
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Section II. CABBON ADSORPTION
6-2. Background.
a. Adsorption is the process by which matter is extracted in a
first phase and concentrated at the surface in a second phase. Adsorp-
tion with activated carbon has long been used to remove taste and odor-
causing impurities from public water supplies. However, with the advent
of physicochemical systems, carbon adsorption has emerged as a practical,
reliable, and economically competitive process in wastewater treatment.
b. The most efficient and practical use of activated carbon in
wajtewater treatment has been in fixed beds of granular carbon in com-
bination with chemical coagulation and precipitation for the removal of
suspended impurities. In such systems, the wastewater is applied to the
bed at a rate ranging from U to 8 gpm/ft2. Contact times employed range
from 30 to 60 min. Provision must be made to regularly backwash packed
bed carbon systems to flush out accumulated suspended solids and biolog-
ical growth. A good design practice is to allow for a bed expansion of
from 10 to 15 percent. Flow rates during backwashing may range from
10 to 15 gpm/ft2. Biological growth can be controlled effectively by
chlorination of influent to the columns or by chlorination during the
regular backwash operation. Figure 6-1 shows a typical activated-carbon
adsorption column.
c. Packed beds of granular carbon are suitable only for wastewaters
containing low suspended solids. However, biological growth and an
accumulation of solids present in the waste have often presented prob-
lems in the use of packed bed adsorbers. To eliminate these problems,
expanded bed adsorbers have been recommended. This system passes the
waste upward through the bed at velocities sufficient to expand the bed
about 10 percent. Expanded beds require little or no cleaning or back-
washing and have low and constant feed pressure requirements.
d. The adsorption capacity of the activated carbon can be measured,
to a fair degree, by conducting isotherm studies in the laboratory.
Design data, however, must be evaluated from pilot plant carbon column
tests. These data will include the minimum contact time required to
produce the desired effluent quality, optimum flow rates, head loss at
various flows, backwash rate, and required carbon dosage. The effluent
resulting from physicochemical treatment systems has been reported to
6-3
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29 Sep 78
/• FULL OPEN COVER WITH
/ 15-IN. PORTHOLE
(20) 1-IN. HOLES
k-^-eOLT- RING
CHARGE
— CARBON BED SURFACE
16 FT
^_ CARBON
DISCHARGE
EFFLUENT
BACKWASH
Me teal f and Eddy, 1972
Figure 6-1. Typical activated-car"bon
adsorption column.
be crystal clear and suitable for many reuse aDplications. Carbon ad-
sorption should be considered in the design of physicochemical systems,
6-3. Input Data.
a. Wastewater flow, mgd.
(l) Average daily flow, mgd.
(2) Flow variations, mgd.
b. Wastewater characteristics.
(1) BOD, mg/£.
(2) Chemical oxygen demand (COD), mg/£.
(3) Suspended solids, mg/£.
6-k
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29 Sep"78
(10 PH.
(5) Total organic carton (TOG), mg/Jl.
6-H. Design Parameters.
a. Carbon requirements, rb/million gal (from pilot plant).
(l) Tertiary treatment (^50-350 Ib/million gal).
(2) Secondary treatment (^00-1800 It/million gal).
o
TD. Hydraulic loading (U-8 gpm/ft ).
c. Contact time (30-60 min).
2
d. Backwash rate (10-15 gpm/ft ).
e. Breakpoint concentration.
f. Backwash time, min.
g. Adsorption capacity, Ib/ft (from laboratory study).
h. Rate constant, ft /rb carbon/hr (from laboratory study).
6-5. Design Procedure.
a. Select a minimum contact time and calculate bed volume.
where
Vol = volume of bed, ft
MCT = minimum contact time, min
Q = peak waste flow, mgd
b. Select a minimum flow rate and calculate surface area.
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SA =
where
2
SA = surface area, ft
Q = peak waste flow, mgd
FR = flow rate, gpm/ft2
c. Calculate column depth.
where
CD = column depth, ft
-3
Vol = volume of bed, ft
2
SA = surface area, ft
d. Calculate total service time.
ST = —r
(0.621; x 10 )(60)C (FR)
(CD> - —15?— * c:
o
where
ST = total service time to breakthrough, hr
NQ = equilibrium adsorption capacity of carbon, lb
TOC/ft3_carbon (from pilot plant)
C = initial concentration, mg/£
FR = flow rate, gpm/ft2
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29 Sep 78
CD = column depth, ft
K = rate constant, ft /lb carbon/hr (from laboratory or
pilot plant)
In = natural log
C_ = concentration at break point, mg/£
o
0.62U x io~ = conversion factor, mg/£ to Ib/ft
e. Calculate total volume of waste treated before exhaustion.
TVWT = (ST)(Q )
avg
where
TVWT = total volume waste treated prior to exhaustion, million gal
ST = total service time, hr
Q = average waste flow, mgd
f. Calculate frequency of column regeneration per month.
(30) (106)
where
NCRM = frequency of column regeneration/month
Q = average waste flow, mgd
TVWT = total volume of waste treated per one regeneration
g. ' Calculate bed efficiency.
(TVWT)(C - c
<100)
6-7
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29 Sep 78
where
eff = bed efficiency, percent
TWT = total volume of vaste treated, million gal
C = initial concentration, mg/£
CL = breakpoint concentration, mg/£
•3
N = equilibrium adsorption capacity, Ib TOC/ft
3
Vol = volume of bed, ft
h. Select a flow rate for backwashing and calculate water
requirement.
WRBW = (RFR)(SA)
where
WRBW = water requirements for backwashing, gpm
2
RFR = backwashing flow rate, gpm/ft
2
SA = surface area of bed, ft
i. Select total time for backwashing and calculate total volume of
"backwash water.
VBWW = (WRBW)(BWT)
where
VBWW = total volume of backwash water, gal
WRBW = backwash water requirement, gpm
*
BWT = total backwash time, min
6-8
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29 Sep 78
6-6. Output Data.
a. Carbon requirements, lb/million gal.
b. Minimum contact time, min.
2
c. Flow rate, gpm/ft .
2
d. Backwash rate, gpm/ft .
e. Backwash time, min.
9
f. Bed volume, ft .
2
g. Surface area, ft .
h. Column depth, ft.
i. Service time prior to regeneration, hr.
j. Volume treated prior to regeneration, gal.
k. Frequency of regeneration/month.
1. Bed efficiency, percent.
m. Volume of backwash water, gal.
6-1. Example Calculations.
a. Select a minimum contact time and calculate bed volume.
where
Vol = volume of bed, ft
MCT = minimum contact time, ^5 min
Q = peak wastewater flow, 2 mgd
6-9
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Part 1 of 3
29 Sep 7&
Vol = 83^6 ft3
b. Select a minim-urn flow rate and calculate surface area.
SA = \FR
where
2
SA = surface area, ft
Q = peak wastewater flow, 2.0 mgd
FR = flow rate, U.O gpm/ft2
_ /2.0\ (106
SA = 3^7 ft2
c. Calculate column depth.
where
CD = column depth, ft
Vol = volume of column, 8356 ft
o
SA = surface area, 3^7 ft
6-10
-------
CD = 2k ft
d. Calculate total service time.
EM 1110-2-501
Part 1 of 3
29 Sep 78
ST =
)(FR)
<•»-
(FR)
where
ST = total service time to breakthrough, hr
N = equilibrium adsorption capacity of carbon,
° TOC/ft3
C = initial concentration, 100 mg/£
FR = flow rate, U.O gpm/ft2
CD = column depth, 2h ft
K = rate constant, 11.0
C_ = concentration at breakpoint, 20 mg/£
0.62*1 x io~ = conversion factor, mg/£ to lb/ft3
Ib
ST =
(U.UH7.U8)
In
ST = 507 hr
e. Calculate total volume of waste treated before exhaustion.
6-11
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29 Sep 78
TVWT =
where
TWT = total volume of waste treated before exhaustion, million gal
ST = total service time to breakthrough, 507 hr
Q = average flow, 1.0 mgd
TVWT = 507(1.0)
TVWT = 21.125 million gal
f. Calculate frequency of column regeneration per month.
Q
NCRM = T~£ (30)
where
NCRM = number of column regenerations per month
Q = average flow, 1.0 mgd
TVWT = total volume of waste treated before exhaustion, 21.125 mil-
lion gal
NCRM = 2I7I25 (30)
NCRM = 1.U2 regenerations/month
g. Calculate bed efficiency.
TVWT(C - C )(8.3U)
eff = o *> 10Q
N (Vol)
o
6-12
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29 Sep 78
where
eff = bed efficiency, percent
TVWT = total volume of waste treated, 21.125 million gal
CQ = initial concentration, 100 mg/£
CB = breakpoint concentration, 20 mg/£
NQ = equilibrium adsorption capacity, h.k Ib TOG /ft3
Vol = volume of bed, 8356 ft3
eff =
1
eff = 38 percent
h. Select a flow rate for backwashing and calculate water
requirement.
WRBW = RFR(SA)
where
WRBW = water requirements for backwashing, gpm
RFR = backwashing flow rate, 15 gpm/ft2
r)
SA = surface area, 3^7 ft
WRBW = 15(31*7)
WRBW = 5205 gpm
i. Select total time for backwashing and calculate total volume of
backwash water.
6-13
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29 Sep 78
VBWW = WRBW(BWT)
where
VBWW = total volume of backwash water, gal
WRBW = "backwash water requirement, 5205 gpm
BWT = total backwash time, 15 min
VBWW = 5,205(15)
VBWW = 78,075 gal
6-8. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-9- Bibliography.
a. Cover, A. E. and Pieron, L. J., "Appraisal of Granular Carbon
Contactors Phase I and II," Report No. TWRC-11, May 1969, Federal Water
Pollution Control Administration, Washington, D. C.
b. Cover, A. E. and Wood, C. E., "Appraisal of Granular Carbon Con-
tactors Phase III," Report No. TWRC-12, May 1969, Federal Water Pollu-
tion Control Administration, Washington, D. C.
c. Gulp, R. L. and Gulp, G. L., Advanced Wastewater Treatment, Van
Nostrand, New York, 19T1-
d. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
e. Metcalf and E.d.dy, Inc., Waabewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
f. Mine Safety Appliances Research Corporation, "Optimization of
the Regeneration Procedure for Granular Activated Carbon," Report
No. 1T020DAO, Jul 19TO, U. S. Environmental Protection Agency, Washing-
ton, D. C.
6-11*
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29 Sep 78
g. South Tahoe Public Utility District, "Advanced Wastewater
Treatment as Practiced at South Tahoe," Report Ho. 17010ELQ, Aug 1971
U. S. Environmental Protection Agency, Washington, D. C. '
h. Swindell-Dresser Company, "Process Design Manual for Carbon
Adsorption," Oct 1971, U. S. Environmental Technology Transfer Washing-
ton, D. C.
(i U. S. Environmental Protection Agency, Technology Transfer,
Process Design Manual for Upgrading Existing Wastewater Treatment
Plants," 1973, Washington, D. C.
J. Weber, W. J., Jr., "Principles and Applications of Adsorption,"
Manual of Treatment Processes. Environmental Science Services Inc
Briarcliff Manor, New York, 1969. ' ''
k. Weber, W. J., Jr., Physicochemical Processes for Water Quality
Control, Wiley-Interscience, New York, 1972. ~
(next page is 6-17)
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Section III. CHEMICAL COAGULATION
6-10. Background.
a. Chemical coagulation involves the aggregation of small particles
into large, more readily settleable conglomerates. Chemical coagulation
is a common process used in water treatment for the removal of turbidity
and color. In wastewater treatment, chemical coagulation has been used
to remove colloidal and suspended matter from raw wastes, remove phos-
phorus, remove algae from oxidation pond effluents, and enhance sludge
dewaterability.
b. Wastewater can be coagulated using any of the coagulants common
for water treatment. The most widely used chemicals include: iron
salts (ferric chloride, ferric sulfate, ferrous chloride, and ferrous
sulfate), aluminum salts (alum and sodium aluminate), lime, and syn-
thetic polymers. The choice of chemicals should be based on careful
evaluation of the wastewater characteristics, availability and cost of
the coagulant, and sludge handling and disposal characteristics. Jar
tests must be conducted to determine the coagulant dosage, the optimum
conditions for coagulation, the quality of the effluent, and the charac-
teristics of the chemical sludge.
c. Chemical coagulation systems normally consist of rapid mix
basins for dispersion of the coagulants, flocculation basins where the
coagulated solids agglomerate to form settleable solids, and settling
basins to separate the floe from the liquid. Rapid mix basins are
equipped with high-speed mixing devices designed to create velocity
gradients of 300 fps/ft or more with a detention time of 15-60 sec.
Power requirements for mechanical mixers range from 0.25 to 1 hp/mgd.
d. Flocculation may be accomplished in a separate basin or in an
integral part of the clarifier structure. The velocity in the conduits
conveying the floe to the clarifier should be 0.5-1.0 fps to prevent
shearing of the floe. Velocity gradients ranging from 30 to 100 fps/ft
may be induced by mechanical means (usually revolving paddles), or by
air diffusion. Flocculator detention times of 15-60 min have commonly
been used in water treatment plant design.
e. Clarifiers for the separation of the chemical floe are usually
designed on the basis of hydraulic loadings (chap 5, sec VIII). Typical
hydraulic loadings for clarifiers (sedimentation basins) processing
various types of chemical sludges are presented in Table 6-1. Detention
times ranging from 2 to 6 hr have been used (Table 6-2).
6-17
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29 Sep 78
f. Chemical coagulation may be used as a part of a physicochemical
treatment system or for phosphorus removal from wastewaters generated at
recreation areas.
6-11. Input Data.
a. Wastewater flow, mgd.
(l) Average daily flow, mgd.
(2) Variation in flow, mgd.
b. Wastewater characteristics.
(l) BOD, total and soluble, mg/£.
(2) COD, total and soluble, mg/£.
(3) Phosphorus, mg/£.
(U) Suspended solids, mg/£.
(5) pE.
(6) Alkalinity, mg/£.
6-12. Design Parameters.
a. Desired quality of treated effluent, mg/£.
b. Coagulant dosage, mg/£ (jar test).
c. Detention time of rapid mix basin (l-3 min).
d. Detention time of flocculator basin (15-60 min).
6-13. Design Procedure.
a. Calculate coagulant requirements.
CR = (CD)(Q
6-18
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29 Sep 78
vhere
CR = coagulant requirements, Ib/day
CD = coagulant dosage, mg/&
Q = average daily flow, mgd
b. Calculate volume of flash mixing basin.
VFM = (Qp)(DTFM)(l06)
where
VFM = volume of flash mix basin, gal
Q = peak flow, mgd
DTFM = detention time of flash mixer, min (l-3 min)
c. Calculate volume of flocculator basin.
VFL= (Qp)(DTFL)(l06) fa) fa)
where
VFL = volume of flocculator basin, gal
Q = peak flow, mgd
DTFL = detention time of flocculator basin, min (15-60 min)
d. Design clarifier as presented under the design of primary
sedimentation.
6-lU. Output Data.
a. Coagulation process.
(l) Coagulant dosage, mg/£.
(2) Optimum pH.
6-19
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29 Sep 78
(3) Rapid mix detention time, min.
(U) Flocculator detention time, min.
(5) Coagulant requirement, rb/day.
(6) Volume of flash mix "basin, gal.
(7) Volume of flocculator basin, gal.
"b. Clarifier.
(l) Overflow rate, gal/day/ft .
p
(2) Surface area, ft .
(3) Side water depth, ft.
(h) Detention time, hr.
(5) Solid loading, Ib/ft2/day.
(6) Weir loading, gal/ft/day.
(7) Weir length, ft.
(8) Volume of sludge produced, gal/day.
(9) Suspended solids removal, percent.
(10) BOD removal, percent.
(ll) COD removal, percent.
(12) Total Kjeldahl nitrogen (TKN) removal, percent,
(13) P0< removal, percent.
6-15. Example Calculations.
a. Calculate coagulant requirements.
CR = CD(Q )8.3^
avg
6-20
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Part 1 of 3
29 Sep 78
where
CR = coagulant requirements, Ib/day
CD = coagulant dosage, 20 mg/£
Q = average flow, 1.0 mgd
o» v^
CR = 20(1.0)8.3^
CR = 166.8 Ib/day
b. Calculate volume of flash mixing basin.
Q (DTFM)IO
VFM = 60(2*0
where
VFM = volume of flash mix basin, gal
Q = peak flow, 2.0 mgd
DTFM = detention time flash mixer, 1 min
(60) 2k
VFM = 1389 gal
c. Calculate volume of flocculator basin.
Q (DTFL)lO
VFL = 60(2*0
where
VFL = volume of flocculator basin, gal
6-21
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29 Sep 78
Q = peak flow, 2.0 mgd
DTFL = detention time flocculator, 30 min
- 2.0(30)106
*
VFL = Hi,667 gal
d. Design clarifier as presented under the design of primary
sedimentation.
6-1.6. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-17• Bibliography.
a. American Water Works Association, Water Quality and Treatment,
McGraw-Hill, New York, 1971.
b. Camp, T. R., "Flocculation and Flocculation Basins," Transac-
tions, American Society of Civil Engineers, Vol 120, 1955, PP 1-16.
c. Cohen, J. M. and Hannah, S. A., "Coagulation and Flocculation,"
Water Quality and Treatment, McGraw-Hill, New York, 1971.
d. Gulp, R. L. and Gulp, G. L., Advanced Wastewater Treatment,
Van Nostrand, New York, 1971.
e. Eckenfelder, W. W., Jr., and Cecil, L. K., Application of New
Concepts of Physical-Chemical Wastewater Treatment, Pergamon Press,
New York, 1972.
f. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
g. O'Melia, C. R., "Coagulation in Water and Wastewater Treat-
ment," Advances in Water Quality Improvements—Physical and Chemical
Processes, E. F. Gloyna and W. W. Eckenfelder, Jr., ed., University of
Texas Press, Austin, 1970.
6-22
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29 Sep 78
h. Sawyer, C. N. and McCarty, P. L., Chemistry for Sanitary Engi-
neers, McGraw-Hill, New York, 1967.
i. Stumm, W. and Morgan, J. J., Aguatic Chemistry, Wiley, New York,
1970.
j. Stumm, W. and O'Melia, C. R., "Stoichiometry of Coagulation,"
Journal, American Water Works Association, Vol 60, 1968, pp 51^-539.
k. Weber, W. J., Jr., Physiochemical Processes for Water Quality
Control, Wiley-Interscience, New York, 1972.
6-23
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29 Sep 78'
Table 6-1. Recommended Surface-Loading Rates
for Various Suspensions
Suspension
Loading Rate, gpd/ft?
Untreated wastewater
(a)
Range
Alum floe
Iron floe
Lime floe
(a)
600 to 1200
360 to 600
to 800
to 1200
Peak Flow
1200
600
800
1200
/ x From Gulp and Gulp, 1971
Mixed with the settleable suspended solids in the untreated waste-
water and colloidal or other suspended solids swept out by the floe.
Table 6-2. Detention Times for Various Surface-Loading
Rates and Tank Depths
Surface-Loading
Rate, gpd/ft2
Uoo
600
800
1000
7- ft
Depth
3.2
2.1
1.6
1.25
Detention
8- ft
Depth
3.6
2.U
1.8
I.k
Time , hr
10- ft
Depth
3.0
2.25
1.8
12- ft
Depth
3.6
2.7
2.2
From Gulp and Gulp, 1971
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section IV. AMMONIA STRIPPING
6-l8. Background.
a. The process of ammonia stripping converts ammonium ions in the
waste to ammonia gas and then strips off the ammonia gas by agitating
the waste in ammonia-free air. Ammonium ions in wastewater exist in
equilibrium with ammonia and hydrogen ions as follows:
NH^ j NH + H+
As shown in the equation above, raising the wastewater pH above 7 will
shift the equilibrium to the right, thus ammonia gas is formed. Raising
the pH beyond 11 will, therefore, convert most of the ammonium ions to
ammonia gas which can be liberated by agitation of the wastewater in a
stripping tower equipped with an air blower.
b. Ammonia stripping towers may be operated as crosscurrent or
countercurrent flow; most designers now seem to prefer the crosscurrent
design.
c. Limitations of ammonia stripping towers were first revealed
during the initial operation of the Lake Tahoe project, conducted during
the winter season. Some of these limitations are:
(l) The towers are inoperable at air temperature below 0°C due to
the freezing of water at the air inlet.
(2) Since ammonia solubility increases with decreasing temper-
atures, more air is required to remove it (800 ft^/gal at 0°C), result-
ing in increased cost of treatment.
(3) A mostly calcium carbonate scale forms in the tower.
d. Typical design parameters for various ammonia levels of removals
obtained during the Lake Tahoe tests are summarized in Table 6-3.
e. Figure 6-2 is a typical flow sheet for ammonia stripping of
raw wastewater. Figure 6-3 is a typical flow sheet for the stripping of
ammonia from digester supernatant.
6-25
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29 Sep 78
AIR, NH
SETTLING
TANK
TREATED
EFFLUENT
Figure 6-2. Typical flow sheet for ammonia
stripping of raw wastewater.
DIGESTER
SUPERNATANT
AIR. NH
STRIPPER
SLUDGE
SCRUBBER
CO
^_ ACID
(NH3)
(RECARBONATION OPTIONAL)
Figure 6-3- Typical flow sheet for the stripping of
ammonia from digester supernatant.
6-26
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29 Sep 78
6-19. Input Data.
a. Wastewater flow.
(l) Average flow, mgd.
(2) Peak flow, mgd.
b. Wastewater characteristics.
(l) Ammonia concentration, mg/£.
(2) pH.
(3) Temperature, °F.
(U) Air temperature, °F.
6-20. Design Parameters.
a. Desired effluent quality, mg/£.
b. Liquid loading rate, Ib water/hr/ft (500-1000).
p
c. Gas loading rate, Ib air/hr/ft .
d. Packing characteristics (from manufacturer).
e. Lime dose to pH 11-12, mg/£.
f. Height of transfer unit, ft (from manufacturer).
g. Ammonia concentration in liquid at bottom of tower, mg/fc.
h. Ammonia concentration in air at bottom of tower, mg/fc.
6-21. Design Procedure.
a. Select a liquid loading rate and calculate the surface area.
(Q )(8.3M(106)
SA = -2
(LLR)(2lO
6-27
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29 Sep 78
where
2
SA = surface area, ft
Q = peak flov, mgd
LLR = liquid loading rate, I"b/ft2/hr
"b. Calculate gas loading rate.
GLR = (2 - IO(LLR)
where
o
GLR = gas loading rate, lb air/ft /hr
LLR = liquid loading rate, Ib/ft2/hr
c. Calculate tower height.
(l) Four countercurrent towers.
z =
(ATT)
where
z = tower height, ft
(A - l! Xl + X2 - O ^
(A - 1} X2 + X2 - (L!)
HTU = height of transfer unit, ft (from manufacturer)
A =
_ (m) (GLR)/29
(LLR)/l8
0.026l2T
m = O.lllTe ' (Henry's law constant)
T = temperature, °F
6-28
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29 Sep 78
2
GLR = gas loading rate, Ib air/ft /hr
2
LLE = liquid loading rate, Ib/ft /hr
X = ammonia concentration in waste at top of tower, mg/£
X = ammonia concentration in waste at bottom of tower, mg/&
Y = ammonia concentration in air at bottom of tower, mg/£, *
Yp = ammonia concentration in air at top of tower, mg/£
(2) For crosscurrent''towers.
Y _ Y -m(GLR/LLR)(z/HTU)
A — A . e
i
where
X = ammonia concentration in waste at z ft down the tower, mg/&
X. = initial ammonia concentration at top of tower, mg/£
2
GLR = gas loading rate, Ib air/ft /hr
2
LLR = liquid loading rate, Ib/ft /hr
z = tower height, ft
HTU = height of transfer unit, ft (from manufacturer)
d. Calculate lime required to raise pH to 11:
LR = (Qavg)(LD)(8.3U)
where
LR = lime requirement, Ib/day
Q = average flow, mgd
avg
LD = lime dosage, mg/£
6-29
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29 Sep 78
6-22. Output Data.
2
a. Liquid loading rate, Ib/ft /hr.
2
b. Gas loading rate, Ib/ft /hr.
2
c. Tower surface area, ft .
d. Tower height, ft.
e. Effluent ammonia concentration, mg/£.
f. Wastewater flow, mgd.
g. Initial ammonia concentration, mg/£.
h. Lime requirements, Ib/day.
6-23. Example Calculations.
a. Select a liquid loading rate and calculate the surface area.
Q(8.3>0106
an = — E _
A LLR(2H)
where
o
SA = surface area, ft
Q = peak flow, 2.0 mgd
LLR = liquid loading rate, 600 Ib/ft2/hr
SA - 2-0(8. 3M106
A 600(210
SA = 1158 ft
b. Calculate gas loading rate.
6-30
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29 Sep 78
GLR = 3(LLR)
where
2
GLR = gas loading rate, Xb air/ft /hr
2
LLR = liquid loading rate, 600 It/ft /hr
GLR = 3(600)
GLR = 1600 Ib air/ft2/hr
c. Calculate tower height. Use crosscurrent tower.
v -m(GLR/LLR)(z/HTU)
X = A. e
i
where
X = ammonia concentration in waste at z ft down the tower
2.0 mg/£
X. = initial ammonia concentration at top of tower, 30 mg/£
0 026l2T
m = constant, O.lllTe ' where T = temperature 85°F,
m = 1.02866
2
GLR = gas loading rate, 1800 Xb air/ft /hr
LLR = liquid loading rate, 600 Ib/ft /hr
z = tower height, ft
HTU = height of transfer unit, IT ft
2 o = 30 0e-(1-02866)(i8oo/6oo)(z/iT)
z = 15 ft
6-31
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Part 1 of 3
29 Sep 78
d. Calculate lime required to raise pH to 11.
LR = Q^ (LD)8.3^
where
LR = lime required, Ib/day
QQirn. = average flov, 1.0 mgd
d Vg
LD = lime dosage (from laboratory experiments), 20 mg/£
LR = 1.0(20)8.3k
LR = 167 Ib/day
6-2U. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-25. Bibliography.
a. Gulp, R. L. and Gulp, G. L., Advanced Wastevater Treatment.
Van Nostrand, New York, 1971. " ~"
b. Roesler, J. F., Smith, R., and Eilers, R. G. , "Mathematical
Simulation of Ammonia Stripping Towers for Wastewater Treatment,"
Internal Report, Jan 1970, Advanced Waste Treatment Research Laboratory,
Cincinnati, Ohio.
c. Slechta, A. F. and Gulp, G. L., "Water Reclamation Studies at
the South Tahoe Public Utility District," Journal, Water Pollution
Control Federation, Vol 39, May 1967, pp 787-8lk.
d. Smith, R., "Design of Ammonia Stripping Towers for Wastewater
Treatment," Seminar on Process Design for Water Quality Control,
9-13 Nov 1970, Vanderbilt University, Nashville, Tenn.
e. Snow, R. H. and Wenk, W. J. , "Ammonia Stripping Mathematical
Model for Wastewater Treatment," Report No. IITRI-C6l52-6, Dec 1968,
Federal Water Pollution Control Administration, Washington, D. C.
6-32
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29 Sep 78
Table 6-3. Air and Surface-Loading Requirements for
20- and 2U-Ft Towers for Various Ammonia Removal
20-ft Depth
Surface
Loading
Percent Ammonia - N Removal ft air/gal gpm/ft2
80 230 3.6
85 2^0 3.2
90 280 2.5
95
2^-ft Depth
Surface
Loading
ft3 air/gal gpm/ft2
200
210
250
Uoo
800
3.9
3.55
3.0
2.0
0.8
From Gulp and Gulp, 1971
6-33
(next page is 6-35)
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section V. CHLORINATION
6-26. Background.
a. Disinfection is the selective destruction of pathogenic organ-
isms; sterilization is the complete destruction of all microorganisms.
Disinfection may be considered as one of the most important processes in
waste-water treatment. This practice used in wastewater treatment has
resulted in the virtual disappearance of waterborne diseases.
b. Disinfection may be accomplished through the use of chemical
agents, physical agents, mechanical means, and radiation. In wastewater
treatment, the most commonly used disinfectant is chlorine; however,
other halogens, ozone, and ultraviolet radiation have been used.
c. The rate of disinfection by chlorine depends on several factors,
including chlorine dosage, contact time, presence of organic matter,
pH, and temperature. The recommended chlorine dosage for disinfection
purposes is that which produces a chlorine residual of 0.5 to 1 mg/£
after a specified contact time. Effective contact time of not less than
15 min at peak flow is recommended. Typical chlorine dosages recommended
for disinfection and odor control are presented in Table 6-U.
d. The most common forms of chlorine used in wastewater treatment
plants are calcium and sodium hypochlorites and chlorine gas. Hypo-
chlorites are recommended for small treatment plants where simplicity
and safety are more important than cost. Chlorine gas may be applied as
a gas, or mixed with water to form a solution, a method used almost ex-
clusively in wastewater treatment.
e. The design of the chlorine contact tank plays an important role
in the degree of effectiveness produced from chlorination. Factors
which must be considered in the design include method of chlorine addi-
tion, degree of mixing, minimization of short circuiting, and elimina-
tion of solids settling. A recent study (para 6-33d) indicated that,
to minimize short-circuiting, the basin outlet may be designed as a
sharp-crested weir that spans the entire width of the basin outlet.
The longitudinal baffling of a serpentine flow basin was superior to
cross-baffling; a length-to-width ratio of Uo to 1 was necessary to
reach maximum plug flow performance regardless of the type of baffling.
6-21. Input Data.
a. Chlorine contact tank influent flow, mgd.
6-35
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Part 1 of 3
29 Sep 78
b. Peak flow, mgd.
c. Average flow, mgd.
6-28. Design Parameters.
a. Contact time at maximum flow, min.
b. Length-to-width ratio.
c. Number of tanks.
d. Chlorine dosage, mg/£.
6-29 • Design Procedure^.
a. Select contact time at peak flow and calculate volume of contact
tank.
Q (CT) x 10
VPT1 = P.
VC1 (210(60)
where
VCT = volume of contact tank, gal
Q = peak flow, mgd
CT = contact time at maximum flow, min
b. Select a side water depth and calculate surface area.
SA = ,
(7
where
2
SA = surface area, ft
VCT = volume of contact tank, gal
SWD = side water depth *8 ft
6-36
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Part 1 of 3
O
'
29 Sep 78
c. Select a length-to-width ratio and calculate dimensions.
CTW -
CTW ~
CTL = SA
CTW
where
CTW = contact tank width, ft
2
SA = surface area, ft
RLW = length-to-width ratio
CTL = contact tank length, ft
d. Select chlorine dosage (Table 6-*0 and calculate chlorine
requirements.
CR = (Q )(CD)(8.3U)
avg
where
CR = chlorine requirement, Ib/day
Q = average flow, mgd
avg
CD = chlorine dosage, mg/fc
e. Calculate peak chlorine requirements:
PCR = (CR)
w
avg
where
PCR = peak chlorine requirements, lt>/day
6-3T
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29 Sep 78
CR = chlorine requirements, It/day
Q = peak flow, mgd
Qavg = averaSe
6-30. Output Data.
a. Maximum flow, mgd.
"b. Average flow, mgd.
c. Contact time, min.
d. Volume of contact tank, gal.
e. Average chlorine requirement, Ib/day.
f. Peak chlorine requirement, Ib/day.
g. Tank dimensions.
6-31. Example Calculations.
a. Select contact time and calculate volume of contact tank.
Q (CT)106
•yPT1 _ P _
VCT ~ 2* (60)
where
VCT = volume of contact tank, gal
Qp = peak flow, 2.0 mgd
CT = contact time, 15 min
2M6o)
VCT = 20,833 pal
6-38
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EM 1110-2-501
Part 1 of 3
29 Sep 78
b. Select a side water depth and calculate surface area.
_ ,
7A8(SWD)
where
2
SA = surface area, ft
VCT = volume of contact tank, 20,833 gal
SWD = side water depth, 8 ft
_ 20.833
" 7.U8(8)
SA = 3^8 ft2
c. Select a length-to-width ratio and calculate dimensions,
CTW =
CTL =
where
CTW = contact tank width, ft
SA = surface a-rea, 3^8 ft
RLW = ratio, length to width, 1
CTL = contact tank length, ft
CTW =
6-39
CTW
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EM 1110-2-501
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29 Sep 78
CTW = 2.95 ft
CTT -
CTL ~
2.95
CTL = 118 ft
d. Select chlorine dosage and calculate chlorine requirements.
CR = Qavg(CD)8.3U
where
CR = chlorine requirements, Ib/day
Q = average flow, 1.0 mgd
CD = chlorine dosage, 8 mg/£
CR = 1. 0(8)8. 3^
CR = 66.7 Ib/day
e. Calculate peak chlorine requirements.
PCR = CR
where
PCR = peak chlorine requirements, Ib/day
CR = chlorine requirement, 66.7 Ib/day
= peak flow, 2.0 mgd
avg
P
= average flow, 1.0 mgd
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EM 1110-2-501
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29 Sep 78
PCB - 66.7(2$
PCR = 133.U Ib/day
6-32. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-33. Bibliography.
a. American Society of Civil Engineers and the Water Pollution Con-
trol Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. American Water Works Association, Water Quality and Treatment,
McGraw-Hill, New York, 1971.
c. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works (Ten States Stan-
dards)," 1971, Health Education Service, Albany, New York.
d. Marske, D. M. and Boyle, J. D., "Chlorine Contact Chamber
Design - A Field Evaluation," Water and Sewage Works, Vol 120, Jan 1973,
PP 70-77,
e. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
f. Ruben, A. J., "Chemistry of Water Supply Treatment and Dis-
tribution," Ann Arbor Science, Ann Arbor, Michigan, 197^.
g. Sawyer, C. N. and McCarty, P. L., Chemistry for Sanitary
Engineers, McGraw-Hill, New York, 1967.
h. Smith, R., "Preliminary Design of Wastewater Treatment Systems,"
Journal, Sanitary Engineering Division, American Society of Civil
Engineers, Vol 95, SA1, 1969, PP 117-118.
i. Water Pollution Control Federation, "Chlorination of Sewage and
Industrial Wastes," Manual of Practice, No. 4, 1951.
J. Weber, W. J., Jr., Physiochemical Processes for Water Quality
Control, Wiley-Interscience, 1972.
6-Ul
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29 Sep 78
Table 6-U. Typical Chlorine Dosages for
Disinfection and Odor Control
Dosage Range
Effluent from mg/Jl
Untreated waste-water (prechlorination) 6 to 25
Primary sedimentation 5 to 20
Chemical precipitation plant 2 to 6
Trickling filter plant 3 to 15
Activated sludge plant 2 to 8
Multimedia filter following activated sludge plant 1 to 5
From Water Pollution Control Federation, 1961
6-U2
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29 Sep 78
Section VI. ION EXCHANGE
6-3^. Background.
a. Ion exchange is the reversible interchange of ions between a
solid ion-exchange medium and a solution. Ion exchange has been used
extensively in the removal of hardness and iron and manganese from
ground-water supplies. In wastewater treatment, ion exchange has been
used mainly for the treatment of industrial wastes. Recently, however,
ion exchange was evaluated for the removal of nitrogen and phosphorus
from municipal wastes.
b. An ion-exchange system usually consists of the exchange resin
(cation or anion natural or synthetic), with provisions made for regen-
eration and rinsing. The most commonly used regenerants include sul-
fur ic acid and caustic soda. Prior to application to the ion-exchange
bed, wastewater may be subjected to pretreatment to remove certain con-
taminants which may hinder the performance of the exchange bed. Common
pretreatment requirements are listed in Table 6-5.
6-35. Input Data.
a. Wastewater flow.
(l) Average flow, mgd
(2) Minimum and maximum flows, mgd.
b. Cation and anion concentrations, mg/£.
c. Allowable effluent concentrations, mg/£.
6-36. Design Parameters.
a. Type of resin.
o
b. Resin exchange capacity, Ib/ft (manufacturer's specifications).
c. Regenerant dosage, Ib/ft (consult resin manufacturer's
specifications).
d. Flow rates.
(1) Treatment flow rate (2-5 gpm/ft3).
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EM 1110-2-501
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29.6ep 78
(2) Regenerant flov rate (1-2 gpm/ft ).
(3) Rinsing flow rate (0.5-1.5 gpm/ft ).
e. Amount of rinse water (30-120 gal/ft ).
f. Column depth (2*1-30 in. minimum).
g. Operation per day, hr.
3
h. Amount of backwash water, gal/ft .
i. Regenerant level, Ib/ft .
j. Regenerant concentration, percent.
k. Regenerant specific gravity.
2
1. Backwash water rate, gpm/ft .
6-37. Design Procedure.
a. Select an ion-exchange system (consult manufacturer's
specifications).
b. Select leakage, regenerant dosage, exchange capacities, and
flow rates (consult manufacturer's specifications).
c. Compute service volume and time.
"" IRC
where
IRC = (influent concentration - allowable effluent concentration)
SV = service volume, gal/ft
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29 Sep 78
REG = resin exchange capacity, Ib/ft
IRC = ion removal concentration, Ib/gal
orp _ _§V
ST " SFR
where
ST = service time, min
•3
SV = service volume, gal/ft
SFR = service flow rate, gpm/ft
d. Compute volume of resins.
Vol
where
= |IRC(Q)(106)1 f ST 1
L REG J L(60)(2MJ
•3
Vol = volume of resin, ft
IRC = ion removal concentration, l~b/gal
Q = total flow, mgd
Q
REG = resin exchange capacity, l"b/ft
ST = service time, min
e. Calculate volume of regenerant.
v = RL x Vol x (100)
R RC(8.3*0 (specific gravity)
where
V = volume of regenerant, gal
RL = regenerant level, Ib/ft
6-U5
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29 Sep 78
3
Vol = volume of resin, ft
RC = regenerant concentration, percent
f. Compute rinse requirements.
VRW = RW x Vol
where
VRW = volume of rinse water, gal
RW = rinse water, gal/ft
Vol = volume of resin, ft
g. Compute "backwash water requirements.
VBW = (BW)(Vol)
where
VBW = "backwater requirements, gal
BW = backwash water, gal/ft
3
Vol = volume of resin, ft
h. Compute exchange cycle time.
EC = ST + BT + RT + WT + OMT
where
EC = exchange cycle, min
ST = service time, min
BT = backwash time, min
RT = regeneration time, min
6-1*6
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29 Sep 78^
WT = rinse time, min
OMT = operation and maintenance time, hr
and
ST = service time, min
RT - M
BT ~ BR
o
BW = backwash water, gal/ ft
Q
BR = rate of backwashing, gpm/ft
V
prp _ _ £1 v -L
RT " RRF Vol
VR = volume of regenerant
•3
RRF = rate of regenerant flow, gpm/ft
3
Vol = volume of resin, ft
RRW
3
VRW = rinse water, gal/ ft
RRW = rate of rinse water flow, gpm/ft
OMT = 0.10(ST + BT + RT + WT)
i. Calculate number of cycles per day.
P i ix HPD(60)
Cycles /day = — - '-
where HPD = operation per day, hr
6-38. Output Data.
a. Average waste flow, mgd.
b. Effluent concentration, mg/&.
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29 Sep 78
2
c. Resin exchange capacity, l"b/ft .
2
d. Regenerant level, l"b/ft .
2
e. Treatment flow rate, gpm/ft .
2
f. Regenerant flow rate, gpm/ft .
2
g. Rinse flow rate, gpm/ft .
2
h. Backwash flow rate, gpm/ft .
i. Volume of regenerant, gal.
j. Volume of rinse water, gal.
k. Volume of "backwash water, gal.
2
1. Volume of resin, ft .
m. Service time, min.
n. Exchange cycle, min.
o. Cycles per day.
p. Service volume, gal/ft .
q. Backwash water, gal/ft .
2
r. Rinse water, gal/ft .
6-39- Example Calculations.
a. Select an ion exchange system from manufacturer's
specifications.
b. Select leakage, regenerant dosage, exchange capacities, and
flow rates from manufacturer's specifications.
c, Compute service volume and time.
REG
SV =
IRC
6-U8
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EM 1110-2-501
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29 Sep 78
where
o
SV = service volume, gal/ft
Q
REG = resin exchange capacity, 1| Ib/ft
IRC = ion removal concentration = (influent concentration - effluent
concentration) —-— ,Q
IRC = (200 mg/£ - 2 mg/£) °'62^ ^10
IRC = 1.6$ * 10 3 lb/gal
sv = u lb/ft3
1.65 x 10 3 lb/gal
SV = 21+24 gal/ft3
- SV
~ SFR
where
ST = service time, min
SV = service volume, 2^24 gal/ft
SFR = service flow rate, 3 gpm/ft
3
ST = 808 min
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29 Sep 78
d. Compute volume of resins.
Vol =
x r ST i
[60(2U)J
REC
where
Vol = volume of resin, ft
IRC = ion removal concentrate, 1.65 x 10 Ib/gal
Q = average flow, 1.0 mgd
o
REC = resin exchange capacity, U Ib/ft"
£T = service time,
Vol = [(1.65 x 10-3)(1.0)1061 x ffiOS
231.5 ft3
e. Calculate volume of regenerant.
= RL(Vol)lOO
R RC(8.3*0 (specific gravity)
where
VT, = volume of regenerant, gal
K
2
RL = regenerant level, 7-5 Ib/ft
Vol = volume of resin, 231.5 ft
RC = regenerant concentration, 7-5 percent
6-50
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29 Sep 78
specific gravity = specific gravity of regenerant, 1.0^
v = T.5(231.5)100
R 7.5(8.3U)1.0U
VR = 2668 gal
f. Compute rinse requirement.
VR¥ = RW(Vol)
where
VRW = volume of rinse water, gal
RW = rinse water, 60 gal/ft
Vol = volume of resin, 231.5 ft3
VRW = 60(231.5)
VRW = 13.890 gal
g. Compute backwash water requirements.
VBW = BW(Vol)
where
VBW = "backwash requirements, gal
BW = backwash water, 100 gal/ft
Vol = volume of resin, 231.5 ft3
VBW = 100(231.5)
VBW = 23.150
6-51
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Part 1 of 3
29 Sep 78
h. Compute exchange cycle time.
EC = ST + BT + RT + WT + OMT
where
EC = exchange cycle, min
ST = service time, oOo min
BT = backwash time = :r— = ——• = 6.7 mi
is K Lj
RT = regeneration time = RRF(*ol) = L5(^3?.5) = T-7 min
WT = rinse time = —— = -—- = 60 min
nnw -L.U
OMT = 0.10(ST + BT + RT + WT)
EC = 808 + 6.7 + 7-7 + 60 + 0.10(808 + 6.7 + 7.7 + 60)
EC = 970.6k min
i. Calculate number of cycles per day.
_ ., ,, HPD(60)
Cycles/day = —g£ -
where
HPD = operation per day, 16 hr
EC = exchange cycle time, 970.6h min
n l Ix 16(60)
Cycles/day = Q ^
Cycles/day =0.99
6-52
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29 Sep 78
6-UO. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-1*1. Bibliography.
a. Gulp, R. L. and Gulp, G. L., Advanced Wastevater Treatment,
Van Nostrand, New York, 1971.
b. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
c. Kunin, R., Ion Exchange Resins, 2d ed., Wiley, New York, 1958.
d. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
e. Sanks, R. L., "ion Exchange," Seminar on Process Design for
Water Quality Control, 9-13 Nov 1970, Vanderbilt University, Nashville,
Tenn.
f. Weber, W. J., Jr., Physiochemical Processes for Water Quality
Control, Wiley-Interscience, New York, 1972.
6-53
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29 Sep 78
Table 6-5. Common Pretreatment Requirements
Contaminant
Suspended solids
Organic
Oxidants
Iron and manganese
Effect
Bind resin particles
Large molecules foul
strong base resins
Slowly oxidize resins
Coat resin particles
Removal
Coagulation and
filtration
Carbon absorption or
weak base resins
only
Avoid prechlorination
Aeration.
6-5U
From Banks, 1970
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section VII. NEUTRALIZATION
6-U2. Background.
a. Neutralization is a unit operation in which pH adjustment of
highly acidic or highly alkaline wastewaters takes place. Neutrali-
zation of such wastes is necessary prior to:
(l) Biological waste treatment where the optimum pH for bacterial
activity (pH 6.5-8.5) must be maintained.
(2) Chemical treatment to provide an optimum pH for the reaction.
(3) Disposal to the receiving streams.
Neutralization is applied mainly to the treatment of industrial wastes.
b. There are many acceptable methods for the neutralization of
acidic and alkaline wastes. Acidic wastes may be neutralized by reac-
tion with caustic soda, lime, or by passing the wastewater through a
limestone bed. Neutralization through limestone beds may be accom-
plished through upflow or downflow systems. A maximum hydraulic rate
of 1 gpm/ft is recommended for downflow systems to ensure sufficient
retention time (para 6-^9a). Maximum acid concentration of 0.6 percent
HgSO^ is suggested to avoid coating the limestone with nonreactive cal-
cium sulfate and to prevent excessive evolution of carbon dioxide, both
of which limit complete neutralization. Higher hydraulic rates may be
used for upflow beds since the products are swept out before precipita-
tion. However, the disposal of exhausted limestone beds may be a seri-
ous drawback to this method of neutralization.
c. Mixing acid wastes with lime slurries is an effective means of
neutralization. The reaction is similar to that obtained with limestone
beds. Lime is relatively inexpensive and possesses a high neutralizing
power. Hydrated lime may produce a problem in handling since it has a
tendency to arch or bridge over the outlet in storage bins and has poor
flow characteristics. Both caustic soda and sodium carbonate are more
powerful than lime, and the reaction products are soluble and do not
increase the hardness of the receiving waters.
d. Alkaline wastes can be neutralized with acid (mostly sulfuric
or hydrochloric), with flue gas containing lU percent carbon dioxide,
or with bottled carbon dioxide. Carbon dioxide will form carbonic acid
when dissolved in water which will neutralize alkaline wastes. The
6-55'
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EM 1110-2-501
Part 1 of 3
29 Sep 78
reaction is slow, but sufficient, if the desired pH is near 7 or 8. The
use of acid to neutralize alkaline vastes is fairly common. The reac-
tion rate is almost instantaneous. A titration curve of the alkaline
waste neutralized with various amounts of acid is helpful to ascertain
the quantities of acid required for neutralization.
e. The selection of a pH control system may prove to be one of the
most troublesome tasks facing the design engineer because of the follow-
ing factors (para 6-h9h):
(l) The relation between the amount of reagent and pH is nonlinear.
(2) The input pH can vary rapidly over a range of several decades
in a short time.
(3) The flow can change while the pH is changing, and the two are
not related.
(h) The pH at neutrality is so sensitive to the addition of reagent
that a slight excess can cause large deviations from the setpoint.
(5) Measurement of the pH can be affected by materials which coat
the electrodes.
(6) The buffer capacity of the waste has a profound effect on the
relation between reagent feed and pH and may not remain constant.
f. Several types of pH control schemes have been applied in waste
neutralization systems, including manual control, open loop control,
closed loop systems, combined open and closed loop systems, feedback
control, and feed forward control.
g. Figure 6-h shows an acid-waste neutralization system.
6-U3. Input Data.
a. Wastewater flow.
(l) Variations in waste flow (maximum and minimum), mgd.
(2) Average daily flow, mgd.
b. pH ranges at various waste flows.
6-56
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Part 1 of 3
29 Sep 78
QUICKLIME FEEDER
AND SLAKER
SLURRY STORAGE TANK
WASTE
AGIO
EQUALIZING
TANK OR
LAGOON
SOLENOID VALVE
AND pH CONTROL
MIXER
•PH CONTROLLER
ALKALINE WASTE
TO LAGOON
OR DISPOSAL
SYSTEM
From Eckenfelder, Jr., 1970
Figure 6-U. Schematic of acid-waste neutralization system.
c. Acidity or alkalinity, mg/Jl.
6-hh. Design Parameters.
a. Desired pH level and range-.
b. Buffer capacity.
(l) Pound reagent/gallon waste to neutralize to desired pH (from
titration curves).
(2) Flow rate, depth, and concentration of feed for limestone
neutralization (from laboratory investigation).
c. Residence time (depends on the degree of mixing).
d. Degree of mixing (hp/1000 gal) (manufacturer, 0.2-O.U hp/1000
gal).
6-57
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29 Sep 78
6-1*5- Design Procedure.
a. Select reagent.
(l) Acid waste (limestone bed or lime slurries or caustic soda).
(2) Alkaline wastes (sulfuric or hydrochloric acids, carbon dioxide
gas).
b. For limestone beds, select depth of bed and rate of flow (from
laboratory investigation) and calculate surface area.
Q x 106
=
(2U)(60)FR
where
o
SA = surface area, ft
Qavg = average flow, mgd
FR = flow rate, gpm/ft2
c. Calculate reagent feed using flow data and titration curves.
RF = (Q)(R)(106)
where
RF = reagent feed rate, Ib/day
Q = waste flow, mgd
R = buffer capacity, Ib reagent/gal waste to neutralize to desired
PH
d. Calculate volume of mixing tank.
Vol =
6-58
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Part 1 of ^
29 Sep 78
where
3
Vol = volume of mixing tank, ft
Q = waste flow, mgd
a = mixing time, min (from manufacturer, 5-10 min)
e. Calculate horsepower for mixing:
. _ (HPR)(Vol)(7.U8 gal/ft3)
np (1000)
where
hp = horsepower
HPR = horsepower for mixing per 1000 gal (0.2-O.U hp/1000 gal)
Vol = volume of mixing tank, ft
f. For feedback control, a may "be calculated "by equation pro-
posed by Greer (para 6-1*9d):
9A
AA = -3T
t\
-—I
a/
where
AA = allowable deviation in acidity or alkalinity from a given set
point in the effluent
— = maximum rate of acidity or alkalinity change in feed to the
unit
t = overall process lag time = reaction time + measurement and
transport lag («0.5 min)
a = minimum nominal residence time (time required for perfectly
mixed basin to give process controllability)
g. Calculate a and apply a factor of safety of 2-3.
6-59
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29 Sep 78
6-46. Output Data.
a. Buffer capacity, Ib/day.
•3
b. Volume of mixing tank, ft .
c. Detention time, min.
d. Horsepower.
6-1*7. Example Calculations. Design of a neutralization system is de-
pendent upon conducting a laboratory investigation; therefore, no design
example calculations will be presented in this section.
6-^8. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-^9. Bibliography.
a. Eckenfelder, W. W., Jr., Water Quality Engineering for Practic-
ing Engineers, Barnes and Nobel, New York, 1970.
b. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution Con-
trol, Pemberton Press, New York,- 1970.
c. Field, W. B., "Design of a pH Control System by Analog Simula-
tion," Instrument Society of American Journal, Vol 6, 1959, pp 42-50.
d. Greer, W. N., The Measurement and Control of pH. Leeds and
Northrup, Philadelphia, 1966.
e. Hoak, R. D., "Acid Iron Wastes Neutralization," Sewage and
Industrial Wastes, Vol 22, No. 2, 1950, pp 212-221.
f. Nemerow, N. L., Liquid Waste of Industry, Addison-Wesley,
Reading, Mass., 1971.
g. Shinskey, F. G., "Feed Forward Control of pH," Instrumentation
Technology, Vol 15, 1968.
h. Wallace, A. T., "Neutralization and pH Control," 1st Short
Course on Design of Wastewater Treatment, 1970, Vanderbilt ttoiversity,
Nashville, Tenn.
6-60
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Part 1 of 3
29 Sep 78
Section VIII. RECARBONATION
6-50. Background.
a. Recarbonation is a unit process that has long been used in lime-
softening water treatment plants. In water treatment, recarbonation is
usually practiced ahead of the filters to prevent calcium carbonate de-
position on the grains which will result in shortening of the filter
runs. Recarbonation is also used to lower the pH of the lime-treated
water to the point of calcium carbonate stability to avoid deposition of
calcium carbonate in pipelines.
b. More recently, with the increased use of lime treatment of
wastewaters, recarbonation has been more widely used in wastewater
treatment. Recarbonation, in wastewater treatment, is mainly used to
adjust the pH following lime treatment for such applications as phospho-
rus removal, ammonia stripping, or chemical clarification.
c. Recarbonation may be practiced as either a two-stage or a
single-stage system. Two-stage recarbonation consists of two separate
treatment steps. In the first stage, sufficient carbon dioxide is added
in the primary recarbonation stage to lower the pH of the wastewater to
pH = 9-3, which is near the minimum solubility of calcium carbonate.
The sludge produced, which is mainly calcium carbonate, is then removed
through settling and recalcined if recovery of the lime is desired. The
time required to complete the reaction is normally 15-30 min. In the
second stage, carbon dioxide is added to lower the pH to a value of
pH = 7. It is possible, however, to add sufficient carbon dioxide to
lower the pH from 11 to 7 in a single stage. Single-stage recarbonation
eliminates the need for an intermediate settling basin which is needed
in the two-stage system. However, single-stage recarbonation normally
results in an increase in the calcium hardness of the water.
d. The reactions involved in the recarbonation process may be
simplified as follows:
Ca(OH)2 + CO -> CaCO + HO
CaC03 + C02 + H20 -> Ca(HCO )2
e. The amount of C02 needed to complete the reactions, as calcu-
lated from the equations above is as follows:
6-61
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29 Sep 78
Calcium hydroxide to calcium carbonate
C02 (It/million gal) = 3.7 (OH~ alkalinity in mg/£, as CaCO )
Calcium carbonate to calcium bicarbonate
C02 (Ib/million gal) = 3.7 (CO^ alkalinity in mg/£ as CaCO ).
6-51. Input Data.
a. Wastewater flow.
(l) Average flow.
(2) Peak flow.
b. Wastewater characteristics.
(l) Alkalinity.
(2) Hydroxide alkalinity, mg/£ as CaCO .
(3) Carbonate alkalinity, mg/£ as CaCO_.
c. pH.
6-52. Design Parameters.
a. Contact time, min (15-30).
b. Carbon dioxide dose, lb/million gal.
c. Desired effluent pH.
6-53. Design Procedure.
a. Two-stage.
(l) Primary stage to pH = 9.3.
(a) Calculate tank volume, V = Q.lt)1P\
60(24)
6-62
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Part 1 of 3
29 Sep 78
where
V = tank volume, gal
Q = wastewater flow, mgd
t = contact time, min (15-30)
("b) Calculate CO requirement.
C00 = (3.7)(OH~(Q)/0.116/1UUO)
where
CO = carbon dioxide requirement, cfm/mgd
3.7 = stochiometric value to convert hydroxide to carbonate
OH~ = hydroxide alkalinity, in mg/£ as CaC03
Q = wastewater flow, mgd
0.116 = density of C00, Ib/ft
= min/day
(2) Secondary stage to pH = 7-
(a) Calculate tank volume, V = o
where
V = volume, gal
Q = wastewater flow, mgd
t = contact time, min (15-30 min)
("b) Calculate C0p requirement.
= 3.7(C03 + OH
6-63
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Part 1 of 3
29 Sep 78
where
C03 = carbonate alkalinity, mg/£ as CaCO
OH = hydroxide alkalinity, mg/£ as CaCO
Q = wastewater flow, mgd
"b. Single-stage recarbonation to pH = 7.
(l) Calculate volume of tank.
V = (Q)(t)/6o/lUo
where
V = volume, million gal
t = contact time, min (5-30 min)
(2) Calculate C0 requirements.
C02(cfm/mgd) = 7.MOH~) + 3.7 (CO^) (Q)/0. 116/1^0
where
OH = hydroxide alkalinity, mg/£ as CaCO
C03 = carbonate alkalinity, mg/£ as CaCO
6-5^. Output Data.
a. Volume of tank, million gal.
b. Carbon dioxide requirement, cfm/mgd.
c. Final pH.
d. Contact time, min.
6-6h
-------
6-55- Example Calculations.
a. Two-stage.
(l) Adjust primary stage to pH = 9-3.
(a) Calculate tank volume.
where
V = volume of tank, million gal
Q = average flow, 1.0 mgd
t = detention time, 15 min
EM 1110-2-501
Part 1 of 1
29 Sep 78
60(2U)
V = 10,^16 gal
(b) Calculate CO requirement.
= 3.7(OH")Q
OU2 0.1l6(lUUo)
where
CO = carbon dioxide requirement, cfm/mgd
3.7 = stochiometric value to convert hydroxide to carbonate
OH~ = hydroxide alkalinity, 50 mg/£
Q = average flow, 1.0 mgd
6-65
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Part 1 of 3
29 Sep 78
0.116 = density of CO , lb/ft3
= minutes per day
ro = 3.7(50)(i.Q)
2 0.116(]MO)"
CO = 1.1 cfm/mgd
(2) Adjust secondary stage to pH = 7.
(a) Calculate tank volume.
v -
~
2M6o)
where
V = volume of tank, gal
Q = average flow, 1.0 mgd
t = detention time, 15 min
v =
2k(60)
V = 10,Ul6 gal
(b) Calculate C02 requirement.
3.7(003 + OH~)Q
C°2 0.1l6(lltUo)
where
C02 = carbon dioxide requirement, cfm/mgd
6-66
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Part 1 of 3
29 Sep 78
3.7 = stochiometric value to convert C03 or OH to carbonate
C0~ = carbonate alkalinity, 150 mg/2.
OH~ = hydroxide alkalinity, 50 mg/£
Q = average flow, 1.0 mgd
= 3.7(150 + 50)1.0
UU2 0.1l6(lUUO)
CO = k.k cfm/mgd
6-56. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
6-57. Bibliography.
a. American Water Works Association, "Water Quality and Treatment,"
3rd edition, McGraw-Hill Book Co., 1971-
b. Gulp, R. L. and Gulp, G. L., "Advanced Wastewater Treatment,"
Van Nostrand Reinhold Company, 1971
c. Sawyer, C. N. and McCarty, P. L., "Chemistry for Sanitary Engi-
neers," McGraw-Hill Book Company, 2nd edition, 1967.
6-67 (next page is 6-69)
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Section IX. TWO-STAGE LIME TREATMENT
6-58. Background.
a. Two-stage treatment systems are used for phosphorus removal from
waste-waters. In principle, for a two-stage system, sufficient lime is
added to the waste-water in the first stage to raise the pH to above 11.
At this pH precipitation of hydroxy-apatite, calcium carbonate, and
magnesium hydroxide takes place. Carbon dioxide is then added following
the first-stage clarifier to reduce the pH to a value of 9-5-10, where
calcium carbonate precipitation results. The sludge, which is mainly
CaCOo, is then separated in a clarifier and the pH of the wastewater is
adjusted to around 7 for further treatment or final disposal. A flow
diagram of a two-stage lime treatment system is presented in Figure 6-5.
b. The design of a two-stage lime treatment system will be a com-
bination of (l) chemical coagulation-precipation basin using lime as a
coagulate; (2) a primary recarbonation stage; (3) a clarifier designed
as a primary clarifier; and (U) a secondary recarbonation stage.
6-59. Chemical Coagulation.
a. Input data.
(l) Wastewater flow, mgd.
(a') -Average daily flow, mgd.
(b) Variation in flow, mgd.
(2) Wastewater characteristics.
(a) BOD, total and soluble, mg/£.
(b) COD, total and soluble, mg/£.
(c) Phosphorus, mg/X,.
(d) Suspended solids, mg/Jl.
(e) pH.
(f) Alkalinity, mg/£.
6-69
-------
to
VO
P S
c+ H
WASTE
WASHWATER
cr\
WASHWATER
SLUDGE TO RECALCINATOR
OR DISPOSAL
00
O
O I
i-b ro
u) vn
o
LIME
Figure 6-5- Two-stage lime treatment syst
em,
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EM 1110-2-501
Part 1 of 3
29 Sep 78
b. Design parameters.
(l) Desired quality of treated effluent, mg/fc.
(2) Coagulant dosage, mg/£ (jar test).
(3) Detention time of rapid mix basin (1-3 min).
(U) Detention time of flocculator basin (15-60 min).
c. Design procedure.
(l) Calculate coagulant requirements.
CR = (CD)(Q )(8.3U)
avg
where
CR = coagulant requirements, Ib/day
CD = coagulant dosage, mg/&
Q = average daily flow, mgd
avg
(2) Calculate volume of flash mixing basin.
(Q )(DTFM)(10 )
T
where
VFM = volume of flash mix basin, gal
Q = peak flow, mgd
DTFM = detention time of flash mixer, min (l-3 min)
(3) Calculate volume of flocculator basin.
(Q )(DTFL)(10 )
VFL = —2-
6-71
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Part 1 of 3
29 Sep 78
where
VFL = volume of flocculator basin, gal
Q = peak flow, mgd
DTFL = detention time of flocculator basin, min (15-60 min)
6-60. Primary Clarifier.
a. Input data.
(l) Wastewater flow.
(a) Average flow, mgd.
(b) Peak flow, mgd.
(2) Wastewater characteristics.
(a) Suspended solids, mg/£.
(b) Volatile suspended solids, percent.
b. Design parameters.
Q
(l) Overflow rate, gpd/ft . (Tables 6-6 and 6-1.)
(2) Detention time, hr. (Table 6-7.)
(3) Specific gravity of sludge. (Table 6-8.)
(M Solids content of underflow, percent (h to 6 percent).
(5) Removal efficiency of suspended solids, percent. (Fig. 6-6.)
(6) Weir loading, gpd/ft (10,000 to 15,000 gpd/ft).
c. Design procedure.
(l) Select an overflow rate by using Table 6-6 or by laboratory
methods and calculate surface area:
6-J2
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EM 1110-2-501
Part 1 of 3
29 Sep 78
BO
70
J
SOLIDS REMOV
en
o
Q
Q 40
Z
UJ
a.
D
30
20
10C
O
0
. *
• 0
.
o MEDIAE
LESS T
RATES
O
0 •
0 0
\
\
0 \
°\ ,
^
o
/ LINE OMITTING
HAN 35% AND OVE
LESS THAN 300 G
,
.
O
o •
1 ° O
\
\
\
• o\
• >
REMOVALS") /
•RFLOW \^
PD/SO FT J
O
•
LEG
END
• RECTANGULAR TANKS
0 CIRCULA!
•
X
\
=i TANKS
^•^ •
• ^
) 500 1000 1500 2000 2500
OVERFLOW RATE, GPD/SQ FT
Figure 6-6. Suspended solids removal versus overflov rate
for secondary clarifiers.
6-73
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Part 1 of 3
29 Sep 78
where
2
SA = surface area, ft
Q = peak flow, mgd
o
OFR = overflow rate, gal/ft/day
(2) Select detention time and calculate volume (Table 6-7)
where
V = volume of tank, ft
Qavg = average flow, mgd
t = time, hr
(3) Calculate side water depth:
where
SWD = side water depth, ft
V = volume, ft
2
SA = surface area, ft
Check solids loading rate:
(Q0,,J(SSI)(8.3M
SLR = -
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
2
SLR = solids loading rate, Ib/ft /day
Q = average flow, mgd
SSI = influent solids concentration, mg/£
2
SA = surface area, ft
(5) Select weir loading rate and calculate weir length:
where
WL = weir length, ft
Q = peak flow, mgd
WLR = weir loading rate, gal/ft/day
(6) Determine percentage of suspended solids removed from Fig-
ure 6-6.
(T) Calculate amount of primary sludge produced.
PSP = (Qavg)(SSl)(SSR)(lO~2)(8.3^)
where
PSP = primary sludge produced, Ib/day
Q = average flow, mgd
SSI = influent solids concentration, mg/H (50 to 60 percent for
municipal systems)
SSR = suspended solids removed, percent
6-75
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Part 1 of 3
29 Sep 78
(8) Select underflow concentration (3 to 6 percent) and sludge
specific gravity (Table 6-8), and calculate the volume flow of primary
sludge produced:
VPSP = PSP(10D)
(specific gravity)(UC)(8.
where
VPSP = volume flow of primary sludge produced, gal/day
PSP = primary sludge produced, gal/day
UC = underflow concentration (3 to 6 percent)
6-6l. Recarbonat ion.
a. Input data.
(l) Wastewater flow.
(a) Average flow.
(b) Peak flow.
(2) Wastewater characteristics.
(a) Alkalinity.
(b) Hydroxide alkalinity, mg/£ as CaCO_.
(c) Carbonate alkalinity, mg/£ as CaCO_.
(3) pH.
b. Design parameters.
(l) Contact time, min (15-30).
(2) Carbon dioxide dose, Ib/million gal.
(3) Desired effluent pH.
6-76
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29 Sep 78
c. Design procedure for two-stage.
(l) Primary stage to pH = 9-3
(a) Calculate tank volume.
v - Q(t)io6
"
where
V = tank volume, gal
Q = wastewater flow, mgd
t = contact time, min (15-30)
(b) Calculate C0p requirement.
C02 = (3.7)(OH~)(Q)/0.1l6/lUUo
where
3.7 = stochiometric value to convert hydroxide to carbonate
OH = hydroxide alkalinity, mg/£ as
Q = wastewater flow, mgd
0.116 = density of C0 , lb/ft3
= min/day
(2) Secondary stage to pH = 7.
(a) Calculate tank volume.
2U(6o)
6-77
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29 Sep 78
where
V = volume, gal
Q = wastewater flow, mgd
t = contact time, min (15-30 min)
(b) Calculate C0_ requirement.
C02 = 3.7(CO:r + OH~)(Q)/O.H6/lMK)
6-62. Primary Clarifier.
a. Input data.
(l) Wastewater flow.
(a) Average flow, mgd.
(b) Peak hourly flow, mgd.
(2) Suspended solids, mg/£.
(3) Volatile suspended solids, percent.
b. Design parameters.
(1) Overflow rate, gpd/ft2. (Tables 6-6 and 6-7.)
(2) Detention time, hr. (Table 6-7.)
(3) Specific gravity of sludge. (Table 6-8.)
(k) Solids content of underflow, percent (k to 6 percent).
(5) Removal efficiency of suspended solids, percent. (Fig. 6-6.)
(6) Weir loading, gpd/ft (10,000 to 15,000 gpd/ft).
c. Design procedure.
6-78
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29 Sep 78
(l) Select an overflow rate "by using Table 6-6 or "by laboratory
methods and calculate surface area.
SA =
x 106
OFR
where
2
SA = surface area, ft
Q = peak flow, mgd
FR = overflow rate,
(2) Select detention time and calculate volume (Table 6-7),
OFR = overflow rate, gal/ft2/day
where
•3
V = volume of .tank, ft
Qavg = averaSe flow'' mSd
t = time, hr
(3) Calculate side water depth.
SWD = S
where
SWD = side water depth, ft
•3
V = volume, ft
p
SA = surface area, ft
(U) Check solid loading rate.
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(Qm )(SSI)(8.3U)
SLR = -
(SA)
where
o
SLR = solid loading rate, Tb/ft /day
Q = average flow, mgd
avg &
SSI = influent solids concentration, mg/£
o
SA = surface area, ft1"
(5) Select weir loading rate and calculate weir length.
where
WL = weir length, ft
Q = peak flow, mgd
P
WLR = weir loading rate, gal/ft/day
(6) Determine percentage of suspended solids removed from Table 6-6.
(7) Calculate amount of primary sludge produced.
PSP = (Qavg)(SSl)(SSR)(lO~2)(8.3M
where
PSP = primary sludge produced, Ib/day
Q = average flow, mgd
avg > &
SSI = influent solids concentration, mg/£ (50 to 60 percent for
municipal systems)
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SSR = suspended solids removed, percent
(8) Select underflow concentration (3 to 6 percent) and sludge
specific gravity (Table 6-8), and calculate the volume flow of primary
sludge produced.
VPSP =
(specific gravity) (UC)(8. 3M
where
VPSP = volume flow of primary sludge produced, gal/day
PSP = primary sludge produced, gal/day
UC = underflow concentration (3 to 6 percent)
6-63. Output Data.
a. Coagulation process.
(l) Coagulant dosage, mg/£.
(2) Optimum pH.
(3) Rapid mix detention time, min.
(H) Flocculator detention time, min.
(5) Coagulant requirement, Ib/day.
(6) Volume of flash mix basin, gal.
(7) Volume of flocculator basin, gal.
b. Clarifier.
(1) Overflow rate, gal/day ft2.
i")
(2) Surface area, ft .
(3) Side water depth, ft.
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(U) Detention time, hr.
(5) Solid loading, Ib/ft /day.
(6) Weir loading, gal/ft/day.
(7) Weir length, ft.
(8) Volume of sludge produced, gal/day.
(9) Suspended solids removal, percent.
c. Recarbonation unit.
(l) Volume of tank, million gal.
(2) Carbon dioxide requirement, cfm/mgd.
(3) Final pH.
(U) Contact time, min.
d. Clarifier.
2
(1) Overflow rate, gal/day ft .
2
(2) Surface area, ft .
(3) Side water depth, ft.
(U) Detention time, hr,
2
(5) Solid loading, Ib/.ft /day.
(6) Weir loading, gal/ft/day.
(7) Weir length, ft.
(8) Volume of sludge produced, gal/day.
(9) Suspended solids removal, percent.
e. Recarbonation unit.
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29 Sep 78
(l) Volume of tank, million gal.
(2) Carton dioxide requirement, cfm/mgd.
(3) Final pH.
(h) Contact time, min.
6-64. Example Calculations.
a. Chemical coagulation.
(l) Calculate coagulant requirements.
CR = CD(Qavg)8.3U
where
CR = coagulant requirements , Ib/day
CD = coagulant dosage, 100 mg/£
Q = average flow, 1.0 mgd
CR = 100(1. 0)8. 3^
CR = 83^ Ib/day
(2) Calculate volume of flash mixing basin.
Q (DTFM)IO
VFM = -£ — -
where
VFM = volume of flash mixing tank, gal
Q = peak flow, 2.0 mgd
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DTFM = detention time flash mixing tank, 5 min
1440 = min per day
= 694*+ gal
(3) Calculate volume of flocculator "basin.
Q (DTFL)IO
VFL = P -
where
VFL = volume of flocculator basin, gal
Q = peak flow, 2.0 mgd
DTFL = detention time flocculator basin, 30 min
VFL = Ul.667 gal
b. Primary clarifier.
(l) Select an overflow rate and calculate surface area.
SA=
x 106
6-8^
-------
where
2
SA = surface area, ft
Q = peak flow, 2.0 mgd
OFR = overflow rate, 600 gpd/ft
2
SA = —
600
SA = 3333 ft2
(2) Select detention time and calculate volume.
Q™ (t)io6
V =
where
V = volume, ft
Q = average flow, 1.0 mgd
t = detention time, 3 hr
v -
V ~
V = 16,711 ft2
(3) Calculate side water depth.
SWD = -v
SA
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where
S¥D = side water depth, ft
V = volume, l6,Tll ft3
2
SA = surface area, 3,333 ft
SWD = 5.0 ft
(U) Check solids loading rate.
SLR =
SA
where
2
SLR = solids loading rate, l"b/ft /day
Q = average flow, 1.0 mgd
SSI = influent suspended solids, 200 mg/fc
SA = surface area, 3333 ft2
QTP - 1.0(200)8.
SLR ~ 3333
SLR =0.5 Ib/ft2day
(5) Select weir loading rate and calculate weir length.
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where
WL = weir length, ft
Q = peak flow, 2.0 mgd
WLR = weir loading rate, 15,000 gpd/ft
WL -
15,000
WL = 133 ft
(6) Determine percentage of suspended solids removal. Percentage
suspended solids removed = 65 percent.
(7) Calculate amount of primary sludge produced.
PSP = Q (SSI)SSR(10~2)8.3U
avg
where
PSP = primary sludge produced, Ib/day
Q = average flow, 1.0 mgd
avg
SSI = influent suspended solids, 200 mg/£
SSR - suspended solids removed, 68 percent
PSP = 1.0(200)(68)10~2(8.3M
PSP = 113^ Ib/day
(8) Select underflow concentration and sludge specific gravity and
calculate the volume of primary sludge produced.
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. PSP(lOO)
" specific gravity(UC)8.
where
VPSP = volume of primary sludge produced, gal/day
PSP = primary sludge produced, 113U Ib/day
specific gravity = l.Oh
UC = underflow concentration, h percent
vpqp = 113M1QQ)
1.0M108.3U
VPSP = 3268 ffpd
c. Recarbonation.
(l) Primary stage pH = 9.3.
(a) Calculate tank volume.
v = Q(t)io6
2M6o)
where
V = volume, gal
Q = average flow, 1.0 mgd
t = detention time, 15 min
v =
2M60)
V = 10,ia7 gal
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(b) Calculate CO requirement.
where
CQ = carbon dioxide requirement, cfm/mgd
3,7 = conversion factor, by dioxide to carbonate
OH~ = hydroxide alkalinity, 50 mg/£
Q = average flow, 1.0 mgd
0.116 = density of C0, lb/ft3
3.7(50)1.0
0.1l6(iMo)
CO =1.1 cfm/mgd
(2) Secondary stage to pH = 7.
(a) Calculate tank volume.
v _ Q(t)io6
V " 2U(60)
where
V = volume of tank, gal
Q = average flow, 1.0 mgd
t = detention time, 15
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v _ 1.0(15)106
V ~ 2M60)
V = 10,1*17 gal
(b) Calculate C0? requirement.
3.7(00^ + OH~)Q
C°2 = 0.116(1UUO)
where
CO = carbon dioxide requirement, cfm/mgd
3.7 = stochiometric conversion factor CO-, and OH to carbonate
CO = carbonate alkalinity, 150 mg/£
OH~ = hydroxide alkalinity, 50 mg/£
Q = average flow, 1.0 mgd
0.116 = density of CO , lb/ft3
rn - 3.7(150+ 50)1-0
2 ~ 0.116(1UUO)
CO = k.k cfm/mgd
d. Primary clarifier. The primary clarifier for use after recar-
bonation is designed in the same manner as the clarifier for use after
the coagulation chamber.
6-65. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
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6 66 Bibliography. A bibliography for each unit process needed in
tvo-stage lime treatment is presented at the end of each of those sec-
tions; namely, chemical coagulation, primary clarification, and
recarbonation.
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Table 6-6. Recommended Surface-Loading Rates
for Various Suspensions
Loading Rate, gpd/ft2 ~~_
Suspension Range P_eak_Flow
Untreated wastewater 600 to 1200 1200
Q
Alum floe 360 to 600 600
Q
Iron floe 5^0 to 800 800
Lime floe 5^0 to 1200 1200
a !,»• = -j_, ., . , -, , , (From Metcalf and Eddy, Inc.. 1971
Mixed with the settleable suspended solids in the untreated waste-
water and colloidal or other suspended solids swept out by the floe.
Table 6-7. Detention Times for Various
Surface-Loading Rates and Tank Depths
Surface-Loading
Rate
, gpd/ft^
Uoo
600
800
1000
7-
De
3.
2.
1.
1.
ft
pth
2
1
6
25
Detention
8- ft
Depth
3.6
2.1*
1.8
1.1*
Time,
hr
10- ft
De
3.
2.
1.
pth
0
25
8
12
De
5
3
2
2
-f+
pth
)i
6
.7
. 2
(From Metcalf and Eddy, Inc., 1971)
Table 6-8. Specific Gravity of Raw Sludge
Produced from Various Types of Sewage
Type of
Sewerage System
Sanitary
Sanitary
Combined
Combined
Strength
of Sewage
Weak
Medium
Medium
Strong
Specific
Gravity
1.02
1.03
1.05
1.07
(From Metcalf and Eddy, Inc., 1971)
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CHAPTER 7
BIOLOGICAL UNIT PROCESSES
Section I. INTRODUCTION
7-1. Definition. Processes that employ biokinetic or biochemical
reactions as a principal means of treatment fall into the category
"biological unit processes." The following biological unit processes
are described in this section.
a. Trickling filters.
b. Plug flow activated sludge.
c. Complete mix activated sludge.
d. Step aeration activated sludge.
e. Extended aeration activated sludge.
f. Modified or high-rate aeration activated sludge.
g. Contact stabilization activated sludge.
h. Pure oxygen activated sludge.
i. Aerated aerobic lagoons.
j. Aerated facultative lagoons.
k. Oxidation ditch.
1. Nitrification-denitrification.
m. Aerobic digestion.
n. Anaerobic digestion.
o. Stabilization ponds.
(l) Aerobic.
(2) Anaerobic.
(3) Facultative.
7-1 (next page is 7-3)
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Section II. TRICKLING FILTERS
7-2. Background.
a. Trickling filters were one of the earliest forms of waste-water
treatment used in the United States. They are classified as low- or
high-rate filters, depending on the hydraulic loading (l-k mgad for low,
10-1*0 mgad for high). In the trickling filtration process wastewater
is distributed uniformly over the filter media "by a flow distributor.
The majority of such units use a reaction drive rotary distributor. A
large portion of the wastewater rapidly passes through the filter; the
remainder slowly trickles over the slime layer formed on the filter
surface. BOD removal is achieved by biosorption and coagulation from
the rapidly moving portion of the flow and by progressive removal of
soluble constituents from the more slowly moving portion of the flow.
b. The quantity of biological slime produced is controlled by the
available food; the growth will increase as the organic load increases
until a maximum effective thickness is reached. The maximum growth is
controlled by physical factors including hydraulic dosage rate, type
of media, type of organic matter, amount of essential nutrients present,
oxygen transfer, and nature of the particular biological growth
(para 7-9r). The microbiology of trickling filters can be found in
the bibliography (para 7-9k, p, and r). Various recirculation systems
used with trickling filters are shown in Figure 7-1.
c. The use of recently developed synthetic media has increased
the popularity as well as the capability of trickling filters in domes-
tic wastewater treatment. The granite stone medium is rarely used in
modern sewage treatment systems due to its higher capital costs (com-
pared with synthetic media) and other limitations such as growth of
filter flies, odor, and ponding problems (para 7-9c and o). Thus only
the synthetic medium filter tower will be designed here.
7-3. Input Data.
a. Wastewater flow.
(l) Average daily flow, mgd.
(2) Peak hourly flow, mgd.
b. Influent BOD, mg/£
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SINGLE-STAGE FILTERS
RECYCLE
TWO-STAGE FILTERS
FIRST-STAGE RECYCLE
SECOND-STAGE RECYCLE
From Clark and Viesmann, 1966
Figure 7-1. Various systems of recirculation used with trick-
ling filters.
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c. Desired effluent BOD, mg/£.
d. Temperature, °C.
e. Recirculation ratio.
7-l|. Design Parameters.
i. Reaction rate constant, k (0.0015-0.003) (from laboratory).
a.
b. Specific surface area of the media, ft2/ft3, from manufacturer
= Ap (9-35).
c. Media factor = n (from laboratory).
/~\
d. Hydraulic loading, gpm/ft = Q (from laboratory).
e. Sludge production factor = PF (0.1*2-0.65) lb solids/lb
7-5. Design Procedures.
a. Calculate the desired depth of the filter.
S
+ S(R) 1
+ S(R) J
D = depth of filter, ft
2
Q - hydraulic loading, gpm/ft
o
n = media factor
S = desired effluent BOD mg/£
R = recirculation ratio = Q /Q
3 = influent BOD^, mgA
o j
K = reaction rate constant
2
A = specific surface area of the media, ft /ft"
P
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Height must be checked against D < 30 ft. If D >_ 30 ft, select a
lower hydraulic loading (Q ) and recalculate D . ~
b. Calculate the surface area of the filter.
QilkkO]
SA = -S2&
where
2
SA = surface area, ft
Q& = average daily flow, mgd
QQ = hydraulic loading, gpm/ft
ikkO = min per day
c. Calculate the filter media volume.
V = SA(D)
where
o
V = volume of media, ft
2
SA = surface area, ft
D = filter depth, ft
d. Calculate sludge production.
SP = Q (S )PF(8.3M
avg o
where
SP = sludge produced, Ib/day
Qa = average daily flow, mgd
S = influent BODr, mg/H
o 5' e"
PF = sludge production factor, Ib solids/lb BOD
7-6
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29 Sep 78
7-6. Output Data.
a. Depth of filter, ft.
2
b. Surface area of filter, ft .
c. Volume of filter, ft .
2
d. Hydraulic loading, gpm/ft .
e. Recirculation ratio.
f. Sludge production, Ib/day.
7-7. Example Calculations.
a. Calculate desired depth of the filter.
+ S(R) 1
u KA
where
D = depth of filter, ft
2
Q = hydraulic loading to filter, 1.0 gpm/ft
o
n = 0.5
S = 15 i
S = 200
o
R = recirculation ratio, 100 percent, 1,0
K = reaction rate, 0.0022 ft/min
2 3
A = specific surface area, 30 ft /ft
P
n n^°-5 m f 15 + ^d-o)
(1.0) in [_ 20Q + 15(1.0)
D " 0.0022(30)
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D = 29.8 ft, say 30 ft
"b. Calculate surface area of filter.
Q
where
p
SA = surface area, ft
Q = average flow, 1.0 mgd
avg
Q
Q = hydraulic loading, 1.0 gpm/ft
SA = iMd ft
c. Calculate volume.
V = SA(D)
where
V = volume of filter, ft
SA = surface area, ih'kO ft2
D = depth, 30 ft
V = 1MK)(30)
V = J43,200 ft3
d. Calculate sludge produced.
SP = Q (S )PF(8.3U)
avg o
where
SP = sludge produced, Ib/day
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Q = average flow, 1.0 mgd
avg
S = influent BODC, 200 mg/A
o ?
PF = sludge production factor, O.H5 Ib solids/lb BOD
SP = 1.0(200)0.U5(8.3M
SP = 730 lb/day
7-8. Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
7-9. Bibliography.
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation, Wash-
ington, D. C.
b. Baker, J. M. and Graves, Q. B., "Recent Approaches for Trickling
Filter Design," Journal, Sanitary Engineering Division, American Society
of Civil Engineers, Vol 9^, SA1, Feb 1968, pp 65-8U.
c. Benjes, H. H., "Small Community Wastewater Treatment Facilities -
Biological Treatment Systems," prepared for the Environmental Protection
Agency, Technology Transfer National Seminar on Small Wastewater Treat-
ment Systems, March 1977-
d. Brown, J. C. et al., "Methods for Improvement of Trickling
Filter Plant Performance - Part I, Mechanical and Biological Optima,"
Report No. 670/2-73-OU7a, Aug 1973, U. S. Environmental Protection
Agency, Washington, D. C.
e. Clark, J. W. and Viessman, W., Jr., Water Supply and Protection
Control, International Textbook Co., Scranton, 1966.
f. Dow Chemical Company, "A Literature Search and Critical Anal-
ysis of Biological Trickling Filter Studies - Vols I and II," Report
No. 17050-DDY, Dec 1971, U. S. Environmental Protection Agency, Wash-
ington, D. C.
7-9
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29 Sep 78
g. Eckenfelder, W. W., Jr., "Trickling Filter Design and Perfor-
mance," Transactions, American Society of Civil Engineers Vol 128
Part III, 1963, pp 371-39**. '
h. Eckenfelder, W. W., Jr., Water Quality Engineering for Prac-
ticing Engineers, Barnes and Nobel, New York, 1970.
i. Eckenfelder, W. W., Jr., and Earnhardt, W., "Performance of a
High-Rate Trickling Filter Using Selected Media," Journal, Water Pollu-
tion Control^Federation, Vol 35, No. 12, 1963, 1535-1551.
J. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970.
k. Fair, G. M., Geyer, J. C., and Okun, D. A., Water Purification
and Wastewater Treatment and Disposal: Water and Wastewater Engineering
Vol 2, Wiley, New York, 1968.
_1. Galler, W. A. and Gotaas, H. B. , "Analysis of Biological Filter
Variables," Journal, Sanitary Engineering Division, American Society of
Civil Engineers, Vol 90, SA6, 196*1, pp 59-79.
m. Germain, J., "Economic Treatment of Domestic Waste by Plastic-
Medium Trickling Medium Filters," 38th Annual Conference, Water Pollu-
tion Control Federation, Oct 1965, Atlantic City, N. J.
n. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works (Ten State Stan-
dards)," 1971, Health Edi—^ -> Service. Albany, N v
o. Liptak, B. G., Environmental Engineers' Handbook, Volume I, Water
Pollution, Chiltori Book Co., 197*1, Radnor, Pa.
p. McKinney, R. E., Microbiology for Sanitary Engineers. McGraw-
Hill, New York, 1962.
q. National Research Council, "Trickling Filters (in Sewage Treat-
ment at Military Installations)," Sewage Works Journal. Vol 18, No. 5
19U6, PP 787-1028.
r. Roy F. Weston, Inc., "Process Design Manual for Upgrading Exist-
ing Wastewater Treatment Plants," prepared for the U. S. Environmental
Protection Agency, Technology Transfer, Oct 1971, Washington, D. C.
7-10
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s. Schulze, K. L., "Load and Efficiency of Trickling Filters,"
Journal, Water Pollution Control Federation, Vol 32, No. 3, PP 2^5-261.
t. Velz, C. J., "A Basic Law for the Performance of Biologic
Beds," Sewage Works Journal, Vol 20, No. 3, I960, pp 2U5-261.
(next page is 7-13)
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Section III. PLUG FLOW ACTIVATED SLUDGE
7-10. Background.
a. Activated sludge is definecf as "sludge floe produced in raw
or settled wastewater by the growth of zoogleal bacteria and other
organisms in the presence of dissolved oxygen and accumulated in suffi-
cient concentration by returning floe previously found." Similarly,
the activated-sludge process is defined as "a biological wastewater
treatment process in which a mixture of wastewater and activated sludge
is agitated and aerated." The activated sludge is subsequently sepa-
rated from the treated wastewater (mixed liquor) by sedimentation and
wasted or returned to the process as needed (para T-l8a).
b. In the past few decades, many modifications of this process have
been developed, although only two process variations are significant:
the conventional system, which achieves absorption, flocculation, and
synthesis in a single step; and contact stabilization during which oxi-
dation and synthesis of removed organics occur in a separate aeration
tank.
c. In the following paragraphs, seven activated sludge process mod-
ifications and variations will be considered: conventional plug flow,
complete mix, step aeration, modified-aeration or high-rate, contact
stabilization, extended aeration, and pure oxygen system. While other
modifications of the activated sludge process exist (namely tapered aera-
tion and the Kraus process) they will not be included in this chapter.
7-11. Plug Flow Activated Sludge.
a. The plug flow activated sludge process uses an aeration tank, a
settling tank, and a sludge return line to treat wastewater (fig. 7-2).
INFLUENT
AERATION TANK
SLUDGE RETURN
rSETTUNG\ EFFLUENT
TANK
WASTE
SLUDGE
Figure 7-2. Plug flow activated sludge.
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"b. Wastewater and returned sludge from the secondary clarifler
enter the head of the aeration tank to undergo a specified period of
aeration. Diffused or mechanical aeration is used to provide the
necessary oxygen and adequate mixing of the influent waste and recycled
sludge, the concentration of which is ^ligh at the head of the tank and
decreases with aeration time. Absorption, flocculation, and synthesis
of the organic matter take place during aeration. The mixed liquor
(sludge floe plus liquid in the aeration tank) is settled in the secon-
dary clarifier, and sludge is returned at a rate sufficient to maintain
the desired mixed liquor suspended solids in the aeration tank.
c. Process design parameters and design examples are found in para-
graph 7-l8c, h, o, and t.
1-12. Input Data.
a- Wastewater Flow (Average and Peak). In case of high variability,
a statistical distribution should be provided.
b. Wastewater Strength.
(1) BOD (soluble and total), mg/£.
(2) COD and/or TOC (maximum and minimum), mg/£.
(3) Suspended solids, mg/£.
(4) Volatile suspended solids (VSS), mg/£.
(5) Nonbiodegradable fraction of VSS, mg/£.
c. Other Characterization.
(1) pH.
(2) Acidity and/or alkalinity, mg/£.
(3) Nitrogen,1 mg/£.
(4) Phosphorus (total and soluble), mg/£.
The form of nitrogen should be specified as to its biological
availability (e.g., NH or Kjeldahl).
7-14
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(5) Oils and greases, mg/i.
(6) Heavy metals, mg/£.
(7) Toxic or special characteristics (e.g., phenols), mg/£.
(8) Temperature, °F or °C.
d. Effluent ^Quality Requirements^
(1) BOD , mg/£.
(2) SS, mg/£.
(3) TKN, mg/£.
(U) P, mg/fc.
(5) Total nitrogen (TKN + NO - N), rng/,'i.
(6) Settleable solids, ing/2/hr.
7-13. De_sig_n Parameters^
a. Reaction rate constants and coefficients (aveia^e values to be
used in absence of specific data).
Constants
k 0.0007 to 0.002 Jl/mg/hr
a 0.73
a' 0.52
b 0.075/day
f O.U
b1 0.15/day
f 0.53
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b. Organic leading, F/M ratio,
F/M = (0.2-0.4)
c. Volumetric loading (ib BOD /1000 ft3/day).
Range 20-140
d. Hydraulic detention time, t .
t - (4-8) hr
e. Solids retention time, t
J c;
t = (5-15) days
b
f. Mixed liquor suspended solids concentration, MLSS
MLSS = (1500-3000) mg/£
g. Mixed liquor volatile suspended solids, MLV3S.
MLVSS =0.7 MLSS
= (1050-2100) mg/£
h. Recycle ratio, Qr/0 .
Qr/Q = (0.25-0.5)
i. Oxygen requirements, Ib 0 /Ib BOD .
2 r
Ib 0 /Ib BOD > 1.25
2 r —
j. Sludge production, Ib solids/]b BOD .
r
Ib solids/lb BOD = 0.5-0.7
k. Temperature coefficient, 0 .
6 = 1.0-1.03
1. BOD removal efficiency (80-90 percent).
7-16
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29 Sep 78
m. Return sludge concentration.
7-lU. Design Procedure (Eckenfelder's Approach).
a. Assume the following design parameters from 7-13 when unknown.
(l) BOD removal rate constant (k).
(2) Fraction of BOD synthesized (a).
(3) Fraction of BOD oxidized for energy (a1).
(k) Endogenous respiration rate (b and b').
(5) Mixed liquor suspended solids (MLSS).
(6) Mixed liquor volatile suspended solids (MLVSS).
(7) Food-to-microorganism ratio (F/M).
(8) Nonbiodegradable fraction of VSS in influent (f).
(9) Degradable fraction of the MLVSS (f).
(10) Temperature correction coefficient (0).
"b. Adjust k for temperature.
fT-20)
KT = K20G
where
K = rate constant at desired temperature, °C
K = rate constant at 20°C
0 = temperature correction coefficient
T = temperature, °C
c. Determine the size of the aeration tank by first determining
the detention time.
7-17
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29 Sep 78
t =
(Xy)(F/M)
where
t = hydraulic detention time, hr
S = influent BOD, mg/l
Xy = MLVSS, mg/£
F/M = food-to-microorganism ratio
d. Check the detention time for treatability.
.
S = S e
e o
where
S = BOD (soluble) in effluent, mg/£
S = BOD in influent, mg/£
k = BOD removal rate constant , £/mg/hr
X^ = MLVSS, mg/£
t = detention time, hr
Solve for t and compare with t from above and select the larger.
e. Calculate the volume of aeration tank.
V = Q x ^~
^avg 2k
where
V = volume of tanks, million gal
Q = average -daily flow, mgd
avg
t - detention time, hr
7-18
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Part 1 of 3
29 Sep 78
f. Calculate oxygen requirements.
dt" ~ ~~t + bIXV
or
02 = a'(Sr)(Qavg')(8.3M + b'(Xy)(V)(8.3M
where
dO/dt = oxygen uptake rate, mg/£/hr
a' = fraction of BOD oxidized for energy
S = BOD removed (S - S ), mg/£
t = detention time, hr
b' = endogenous respiration rate,/hr
Xy = MLVSS, mg/£
0 = oxygen required, Ib/day
Q = average daily flow, mgd
V = volume of aeration tank, million gal
and check the oxygen supplied per pound of BOD removed >1.25.
CU
lb 0^/lb BOD =
where
0 = oxygen required, Ib/day
Q = flow, mgd
S = BOD removed, mg/£
g. Design aeration system.
7-19
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Part 1 of 3
29 Sep 78
(l) Diffused aeration system.
(a) Assume the following design parameters.
!_ Standard transfer efficiency (from manufacturer), 5-8 percent
(coarse bubble diffuser).
2. 02 transfer in waste/0 transfer *in water a£.9 = a .
3. 02 saturation in waste/0 saturation in water %0.9 = 3 .
k_ Correction factor for pressure ssL.O = p .
(b) Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
(c) Adjust standard transfer efficiency to operating conditions.
[(CS)T(8)(P) -C]
OTE = STE 4= i-£-^ ^ a(l.02)T~20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(cs)T = °2 saturation at selected summer temperature T , °C,
3 = 02 saturation in waste/0 saturation in water ;^0.9
p = correction factor for pressure s»1.0
C = minimum dissolved oxygen to be maintained in the basin
L >2.0 me '
02 transfer in waste/0 transfer in water %0.9
T = temperature, °C
(d) Calculate required air flow.
7-20
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Part 1 of 3
29 Sep 78
Pi ~
'a
(OTE %} (0.0176
ftj air
R - required air flow, cfm/1000 ft
a
V =•- volume of the basin, gal
(2) Mechanical aeration system.
(a) Assume the following design parameters.
1 Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C and tap water),
2 0 transfer in waste/0^ transfer in water ss£>.9.
~ 2 ^
3 0 saturation in waste/0,, saturation in water «£).9-
— 2 d
k Correction factor for pressure «sl.O.
(b) Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
(c) Adjust standard transfer efficiency to operating conditions,
[(Cs) (6)(P) - C ]
L. J J-l .J /-. s-\ f~* \ -1- t—vy
OTE = 3TE
where
OTE = operating transfer efficiency, Ib 00/hp-hr
STE = standard transfer efficiency, Ib 02/hp-hr
(Cs), = 0 saturation at selected summer temperature, mg/£
3=0^ saturation in waste/0 saturation in water «0.9
p = correction factor for pressure «1.0
T-21
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Part 1 of 3
29 Spp 78
T - miniiiiun Ussolved oxygen to be maintained in the basin
0
/o), W i r ~
^ 4 v'
x 1000
where
Q(SS -
".\ - r,].-f1^,e 11 educed, Ib/d&y
s. = ij'a/jiioK of liOD removed synthesized to cell material
? -: BOD r<--T^.Y< "• . n;~;'k.
b - endogenous respiration ra^e/day
V - volume of aeration tank, million gal
Q - flow, mgd
7SS = volatile suspended solid:-- in effluent,
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Part 1 of 3
29 Sep 78
f = non'biodegrada'ble fraction of VSS in influent
SS = suspended solids in effluent, mg/£
Check AX^ solids produced against pounds of BOD removed (0.5-0.7).
. AX.r
(Ib solids) = _ _V _
(Ib BOD ) S (Q)(8.3U)(# volatile)
r r
i. Determine nutrient requirements (ib/day)
for nitrogen
N = 0.123AXy
and phosphorus
P = 0.026AXy
and check against BOD:N:P = 100:5:1.
j. Calculate sludge recycle ratio.
X
a
Q X - X
avg u a
where
Q = volume of recycled sludge, mgd
r
Q = average flow, mgd
avg
X = MLSS, mg/£
a
X = SS concentration of returned sludge, mg/Ji
u
k. Calculate solids retention time.
(V)(X )(8.3U)
SRT = - a
AX
a
where
7-23
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Part 1 of 3
29 Sep 78
SRT = solids retention time, days
V = volume of aeration tank, million gal
X = MLSS, mg/£
—
a % volatile
1. Calculate effluent BOD .
BOD = S + (0.8M(V\ (f)
V v/
eff
where
S = effluent soluble BODC , mg/£
e 5
(Xy} „ , = volatile solids in effluent, mg/£
f = degradable fraction of the MLVSS
T-15. Output Data.
a. Aeration Tank.
(l) Reaction rate constant, £/mg/hr.
(2) Sludge produced per BOD removed.
(3) Endogenous respiration rate (b, b' )
(U) 0 utilized per BOD removed.
(5) Influent nonbiodegradable volatile suspended solids (VSS)(f)
(6) Effluent degradable volatile suspended solids (f1)-
(7) lb BOD/lb MLSS-day (F/M ratio).
(8) Mixed liquor suspended solids, mg/£ (MLSS).
(9) Mixed liquor volatile suspended solids, mg/£ (MLVSS ).
7-2U
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29 Sep 78
(10) Aeration time, hr.
(11) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
(13) Sludge produced, Ib/day.
(lU) Nitrogen requirement, Ib/day.
(15) Phophorus requirement, Ib/day.
(16) Sludge recycle ratio, percent.
(IT) Solids retention time, days.
b. Diffused Aeration System.
(l) Standard transfer efficiency, percent.
(2) Operating transfer efficiency, percent.
(3) Required air flow, cfm/1000 ft3.
c. Mechanical Aeration System.
(l) Standard transfer efficiency, Ib 0 /hp-hr.
(2) Operating transfer efficiency, Ib O^/hp-hr.
(3) Horsepower required.
d. Final Clarifier. Output (chap 5» sec IX).
7-l6. Example Calculations.
a. Assume the following design parameters.
(1) K = 0.0072 £/mg-hr at 20°C.
(2) a = 0.73.
(3) a' = 0.52
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29 Sep 78
(U) b = 0.075/day, V = 0.15/day.
(5^ MLSS = X = 3000 mg/£.
3.
(6) I4LVSS = Xy = 2kOO mg/£.
(7) F/M = O.UO It BOD/lb MLVSS-day.
(8) f = O.ItO.
(9) f = 0.53.
(10) 0 = 1.03.
"o. Adjust K for temperature.
K_ = Q(T-2°)
T 20"
where
K^ = rate constant at desired temperature
K = rate constant at 20°C, 0.0012
0 = temperature correction coefficient, 1.03
T = temperature, 15°C for winter conditions
Ky = 0.0012(1.03)15~2°
1C, = 0.0010£/mg-hr
c. Determine size of aeration tank by determining detention time.
t =
X^F/M)
where
t = hydraulic detention time, hr
S = influent BOD, 200 mg/£
7-26
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Part 1 of 3
29 Sep 78
Xy = MLVSS, 21*00 mg/£
F/M = food to microorganism ratio, 0.1*0 Ib BOD/lb MLVSS
_ 2l*(200)
21*00(0.1*0)
t = 5.0 hr
d. Check detention time for treatability.
S = S e
e o
where
S = BOD (soluble) in effluent, 10 mg/£
S = BOD in influent, 200 mg/£
k = BOD removal rate constant, 0.001 £/mg-hr
X = MLVSS, 2 1*00 mg/ 1
t = detention time, hr
10 = 200 e-(0.00l)2>+00(t)
t = 1.2^ hr
Therefore use t = 5 • 0 hr
e. Calculate volume of aeration tank.
V = Qavg + 2h
where
V = volume, million gal
Q = average flow, 1.0 mgd
avg
t = detention time, 5.0 hr
7-27
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Part 1 of 3
29 Sep 78
V =
V = 0.208 million pal
f. Calculate oxygen requirements.
where
0 = oxygen requirement, lb/day
a' = 0.52
S^ = BOD removed (S - S ) , 190 mg/£
Q = average flow, 1.0 mgd
V = 0.15/day
Xy = MLVSS, 21*00 mg/£
V = volume of aeration tank, 0.208 million gal
02 = 0.52(190)(1.0)8.3U + 0.15(2UOO)(0.208)8.3U
02 = lUUQ Ib/day
Check oxygen supplied per Ib BOD removed >1.25.
lb 0/lb
where
0 = oxygen required, ikkQ Ib/day
Q = flow, 1.0 mgd
s. = BOD removed, 190 mg/£
7-28
-------
ID 02/lb
Ib 0 /Ib BOD = 0.91 < 1.25
2 r
EM 1110-2-501
Part 1 of 3
29 Sep 78
1UU8
therefore
Ort = 1.25
= 1.25(Q)(Sr)8.3H
= 1.25(1.0)(190)8.3U
= 1980 Ib 02/day
g. Design aeration system (diffused).
(l) Assume following parameters.
STE =5.0 percent
a = 0.9
3 = 0.9
p = pressure correction factor, 1.0
(2) Select summer operating temperature and determine 0 saturation.
T = 25°C, (CS)T = 8.2 mg/£
(3) Determine operating transfer efficiency.
[(Cs) 3P - C ]
OTE = STE t - T9 1? LJ a(l.02)"~2°
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5 percent
7-29
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Part 1 of ^
29 Sep 78
(CS)T = 8.2 mg/Jl
6 = 0.9
p = 1.0
C = minimum dissolved oxygen, 2.0 mg/£
a = 0.9
T = 25°C
9-17 = 0 saturation at 20°C
OTE = 5 -2°^T- 2'01 0.9(1.02)25-20
OTE = 2.9 perdent
(4) Calculate required airflow.
0 (105)7.48
R =
a OTE(0.0176)l44o(V)
where
R = required air flow, cfm/1000 ft
cl
OTE = operating transfer efficiency, 2.9 percent
V = volume of basin, 208,000 gal
0.0176 = lb 02 per ft3 air
l44o = min per day
= lb 02/day - 1980
1980(10^)7.48
'— ' —
a 2.9(0.0176)1440(208,000)
R =96.9 cfm/1000 ft3
cL
7-30
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Part 1 of 3
29 Sep 78
h. Calculate sludge production.,
AXV = [a(Sr)Qavg - bXV(V) + Qavg(VSS)f + Qavg(SS ~ ™S)]Q.3±
where
a = 0.73
S = BOD removed, 190 mg/fc
Q = average flow, 1.0 mgd
avg
b = 0.075/day
Xy = MLVSS, 21*00 mg/£
V = volume of aeration tank, 0.208 million gal
VSS = volatile suspended solids in effluent, 150 mg/£
f = 0.1*0
SS = suspended solids, 200 mg/£
AX = [0.73(190)1.0 - 0.075(2l*00)(0.208)
+ 1.0(150)0.1*0 + 1.0(200 - 150)]8.31*
AXy = 1762 Ib/day
Check AX^ solids produced against pounds of BOD removed (0.5-0.7)-
Ib solids _ AXV
Ib BOD S (Q)8.31*(^ volatile)
r r
where
AX_ = sludge produced, 1762 Ib/day
7-31
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Part 1 of 3
29 Sep 78
S = S - S ,190 mg/£
Q = average flow , 1.0 mgd
volatile = 80 percent
Ib solids = _ 1762
Ib BOD 190(1.0)8.3^(0.8
i. Determine nutrient requirements
for nitrogen
N = 0.123 AX
for phosphorus
P = 0.026 AX
N = 0.123(1762) = 216 Ib/day
P = 0.02)46(1762) = U3.3 lb/day
N in influent = 30 mg/Jl (Q )8.3^
N in influent = 250.2 > 2l6 required
N needed to be added = none
P in influent = 15 mg/& (Q ) 8.31*
avg
P in influent = 125.1 > ^3-3 required
P to be added = none
j. Calculate sludge recycle ratio.
Q X
r a
I X - X
avg u a
7-32
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Part 1 of 3
29 Sep 78
where
Q = volume of recycle sludge, mgd
avg = average flow, 1.0 mgd
X = MLSS, 3000 mgM
a
X = solids concentration in recycled sludge, 10,000 mg/Ji
Qr 3,000
1.0 10,000 - 3,000
Q = O.U3 mgd
k. Calculate solids retention time.
V(X )8.3U
a
where
SET = solids retention time, days
V = volume of aeration tank, 0.208 million gal
X = MLSS, 3000 mg/£
3.
= 2202 Ib/day
a % volatile 0.8
m - 0.208(3000)8.:
SRT = 2.k days
1. Calculate effluent BOD .
where
7-33
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29 Sep 78
(BOD5)eff = effluent BOD , mg/£
S = soluble BODC, 10 mg/£
e j
(Xy)eff := volatile solids in effluent, 20 mg/£
f = 0.53
(BOD5)eff = 10 + 0.8>i(20)0.53
(BOD5)eff = 18.9 mg/£
7-17- Cost Data.. Appropriate cost data and economic evaluation may be
found in Chapter 8.
T-18. Bibliography.
a. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Wastevater Control Engineering," 1969.
b. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. S.
Environmental Protection Agency, Washington, D. C.
c. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, and 1968, Water Pollution Control Federation,
Washington, D. C.
d. Bargman, R. D. and Borgerding, J., "Characterization of the
Activated Sludge Process," Report No. R2-73-22H, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
e. Busch, A. W., Aerobic Biological Treatment of Wastewaters,
Oligodynamics Press, 1971.
f. Center for Research, Inc., University of Kansas, "Oxygen Con-
sumption in Continuous Biological Culture," Report No. 17050DJS, May
1971, U. S. Environmental Protection Agency, Washington, D. C.
g. City of Austin, Texas, "Design Guides for Biological Wastewater
7-3)4
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
h. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
i. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 19&9, Environmental Science
Services, Inc., Briarcliff Manor, New York.
j. Eckenfelder, W. W., Jr., Water Quality Engineering for Practic-
ing Engineers, Barnes and Nobel, New York, 1970.
k. Eckenfelder, W. W. Jr., "Activated Sludge and Extended Aera-
tion," Process Design in Water Quality Engineering - New Concepts and
Developments, Vanderbilt University, Nashville, Tenn. , 1971.
1. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970.
m. Eckenfelder, W. W., Jr., and O'Connor, 0. J. , Biological Waste
Treatment, Pergamon Press, New York, 1961.
n. Gaudy, A. G., Jr., and Gaudy, E. T., "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No. 17090-
FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington, D. C.
o. Goodman, B. L. , Design Handbook of Wastewater Systems: Domestic,
Industrial, Commercial, Technomic, Westport, Conn, 1971.
p. Goodman, B. L. and Englande, A. J., "A Consolidated Approach to
Activated Sludge Process Design," Conference on Toward a Unified Con-
cept of Biological Waste Treatment Design, 5-6 Oct 1972, Atlanta, Ga.
q. Lawarence, A. W. and McCarty, P. L., "Unified Basis for Biolog-
ical Treatment Design and Operation," Journal, Sanitary Engineering
Division, American Society of Civil Engineers, Vol 96, SA3, 1970.
r. Maier, W. J., "Biological Removal of Colloidal Matter from
Wastewater," Report No. R2-73-1^7, Jun 1973, U. S. Environmental Pro-
tection Agency, Washington, D. C.
s. McKinney, R. E., Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
7-35
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29 Sep 78
t. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
u. Okun, D. A., "System of Bio-Precipitation of Organic Matter
from Sewage," Sewage Works Journal. Vol 21, No. 5, 19^9, pp 763-79!+.
v. Smith, H. S., "Homogeneous Activated Sludge Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering
Vol h, Jul 1967, pp 1*6-50. ' *'
w. Smith, R. and Eilers, R. G., "A Generalized Computer Model for
Steady-State Performance of the Activated Sludge Process," F¥QA Report
No. TWRC-15, Oct 1969, Robert A. Taft Water Research Center, Cincinnati
Ohio.
x. Stensel, H. D. and Shell, G. L., "Two Methods of Biological
Treatment Design," Journal, Water Pollution Control Federation Vol U6
Feb 197l|, pp 271-281: ~ -'
y. Stewart, M. J. , "Activated Sludge System Variations - Specific
Applications," The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
z. Toerber, E. D., "Full Scale Parallel Activated Sludge Process
Evaluation," Report No. R2-72-065, Nov 1972, U. S. Environmental Protec-
tion Agency, Washington, D. C.
aa. Weston, R. F., "Design of Sludge Reaeration Activated Sludge
Systems," Journal, Water Pollution Control Federation Vol 33 No 7
1961, pp 7^8-757. ~ ' '
7-36
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" 29 Sep 78
Section IV. COMPLETE MIX ACTIVATED SLUDGE
7-19- Background.
a. There has "been much discussion and some confusion concerning
the definition of complete mix activated sludge. Nevertheless, any
definition will be arbitrary and many differences of opinion will be
aired. In this manual it will be assumed that a complete mix activated
sludge is achieved when the oxygen uptake rate is uniform throughout
all parts of the aeration tank and when sufficient mixing is provided
to maintain the solids in the aeration tank in suspension. In complete
mixing, the influent primary clarified wastewater and returned sludge
flow are distributed at various points in the aeration tank (fig. 7-3).
The tank serves to equalize or stabilize variations in flow and waste
strength; it also acts as a diluent for toxic materials.
INFLUENT
COMPLETE MIX
H=H
AERATION TANK
f
SLUDGE RETURN
EFFLUENT
WASTE
SLUDGE
Figure 7-3. Complete mix activated sludge.
b. Organic loading and oxygen demand are uniform throughout the
aeration tank, and mechanical or diffused aeration is used to completely
mix the mixed liquor.
c. References j, k, r, and y in paragraph 7-26 provide good dis-
cussions of the characteristics of this process and also contain con-
siderable data on design parameters and design examples.
7-20. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variabil-
ity, a statistical distribution should be provided.
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29 Sep 78
b. Wastevater Strength.
(l) BOD (soluble and total), mg/A.
(2) COD and/or TOG (maximum and minimum), mg/A.
(3) Suspended solids, mg/A.
(it) Volatile suspended solids (VSS), ing/A.
(5) Nonbiodegradable fraction of VSS, mg/A.
c. Other Characterization.
(1) PH.
(2) Acidity and/or alkalinity, mg/A.
(3) Nitrogen, mg/A.
(k) Phosphorus (total and soluble), mg/A.
(5) Oils and greases, mg/A.
(6) Heavy metals, mg/A.
(T) Toxic or special characteristics (e.g., phenols), mg/£.
(8) Temperature, °F or °C.
d. Effluent Quality Requirement's.
(1) BOD ing/A.
(2) SS, mg/A.
(3) TKN, mg/A.
(It) P, mg/A.
(5) Total nitrogen (TKN + NO - N), mg/A.
The form of nitrogen should be specified as to its biological
availability (e.g., NH or Kjeldahl).
7-38
-------
(6) Settleable solids, mg/i/hr.
7-21. Design Parameters.
a. Reaction rate constants and coefficients.
Constants
McKinney
K
m
K
s
K
e
Eckenfelder
k
a
a'
b
b1
f
f
Range
b. F/M = (0.3-0.6).
c. Volumetric loading = 50-120.
d. t = (3-6) hr.
e. t = (3-7) days.
s
f. MLSS = (3000-6000) mg/£.
g. MLVSS = 0.7 MLSS = (2100-1*200) mg/Jl.
EM 1110-2-501
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29 Sep 78
15 /hr at 20°C
lO.U/hr at 20°C
0.02/hr at 20°C
0.0007-0.002
0.73
0.52
0.075/day
0.15 /day
0.1*0
0.53
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h. Q./Q = (0.25-1.0).
r
i. lb 02/lb BOD ^1.25.
j. lb solids/lb BOD = (0.5-0.7).
k. 0 = (1.0-1.Oh).
1. Efficiency = (>90 percent).
7-22. Design Procedure.
a. McKinney's Approach.
(l) Assume the following design parameters from 7-21.
(a) Metabolism constant (K ).
m
(b) Synthesis factor (K ).
s
(c) Endogenous respiration factor (K )
e
(d) Temperature correction coefficient (0).
(e) Hydraulic detention time (t).
(f) Solids retention time (t ).
(2) Adjust metabolism constant, synthesis factor, and endogenous
respiration factor for temperature.
K 0(T-20)
"T 20
where
K^ = rate constant at desired temperature T , °C
K = rate constant at 20°C
0 = temperature coefficient
T = temperature, °C
(3) Determine size of the aeration tank.
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EM 1110-2-501
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29 Sep 78
V = Qavgt/2H
where
V = volume of tank, million gal
0 = average flov, mgd
avg
t = hydraulic detention time, hr
(U) Determine soluble effluent BOD^.
F.
Fe ' 1 + Kmt
where
F = soluble effluent BOD , mg/£
e ->
F. = influent BOD , mg/£
K = metabolism constant (15/hr at 20°C)
m
t = hydraulic detention time, hr
and check F < 10 mg/«- ; if Fp > 10 mgA , increase t and recalcu-
Q ~~ *~
late new F
(5) Calculate the MLSS concentration.
M. + M..
K F
M =
la K + l/2Ut
e s
M = 0.2K M t (2k)
e e a s
2kt
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M = SS.. x — + o.l(M + M
11 11 t a e'
where
M = total mass, mg/£
M = living, active mass,
3.
M = endogenous mass, mg/£
Mi = inert nonbiodegradable organic mass,
Mii = inert inorganic suspended solids, mg/£
KS = synthesis factor, 1/hr (lO.it/hr at 20°C)
Fg = effluent BOD , mg/£
Kg = endogenous respiration factor, 1/hr (0.02/hr at 20°C)
t = solids retention time, days
SS.^ = inert organic SS in influent, mg/£
= VSS x percent nonliodegradable (^D.h VSS for municipal waste)
SS^ = inert inorganic SS fraction in the influent
and check MT against 3000-6000 mg/£; vary t or t until M falls
within desired range. s ^
(6) Check organic loading against F/M = 0.3-0.6.
F/M = -
where
F/M = food to microorganism ratio
F = influent BOD , mg/£
M_ = total mass, mg/£
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Part 1 of 3
29 Sep 78
t = hydraulic detention time, hr
If F/M < lower limit, it is possible to reduce t and recalculate
If F/M > upper limit, increase t and recalculate MT .
(7) Calculate the oxygen requirements.
(a) Select the oxygen uptake rate. The average rate of oxygen
demand, if the waste load is uniform, is given by
1 5(F - F ) lA2(M + M )
dO _ i e . a e
dt t
o
where
dO/dt = average oxygen uptake under uniform flow conditions,
F = influent BODC, mgA
i ?
F = soluble effluent BOD , mg/£
e ?
t = hydraulic detention time, hr
M = living, active mass, mg/£
a
M = endogenous mass, mg/fc
e
t = solids retention time, days
s
Under conditions where the load varies, the oxygen uptake is equal to
the synthesis oxygen demand plus the endogenous respiration oxygen de-
mand or
e a
Ib 02/hr = ^ x V x 8.3^
where
= peak flow, mgd
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Qavg = avera§e flow, mgd
Ke = endogenous respiration factor, hr (0.02/hr at 20°C)
(b) Check oxygen supplied per pound of BOD removed >1.2|j.
lb 02 lb 02/hr
lb BOD Q(F. - F )B.3h
•i- -L G
(8) Design aeration system and check horsepower for complete mixing
against horsepower required for complete mixing _>0.1 hp/1000 gal;
select the larger horsepower.
(a) Diffused Aeration System.
!_ Assume the following design parameters.
^ Standard transfer efficiency, percent, from manufacturer
(5-8 percent ) .
b_ 02 transfer in waste/0 transfer in water «O.9.
_c 02 saturation in waste/Og saturation in water ssO.9.
d_ Correction factor for pressure asi.O.
2_ Select summer operating temperature (25-30°C) and determine (from
standard tables) 0 saturation.
3_ Adjust standard transfer efficiency to operating conditions.
[(CB)T(B)(p) - C ]
OTE = STE J= - ±j-^ - ^=1 a(l.02)T~2°
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(cs)T = 02 saturation at selected summer temperature T , °C, mg/H
3 = 02 saturation in waste/0 saturation in water «=0.9
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29 Sep 78
p = correction factor for pressure «1.0
C = minimum dissolved oxygen to be maintained in the basin
L > 2.0 mgA
a = 0 transfer in waste/02 transfer in water ^0.9
T = temperature, °C
lj_ Calculate required air flow.
02(105)(7A8)
\ ft" air/\
where
3
R = required air flow, cfm/1000 ft
a
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(b) Mechanical Aeration System.
!_ Assume the following design parameters.
a Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water)(5-8 percent).
b 0 transfer in waste/02 transfer in water «0.9-
c_ 0 saturation in waste/O^ saturation in water «O.9.
d Correction factor for pressure «1.0.
2 Select summer operating temperature (25-30°O, and determine
(from standard tables) 02 saturation.
3_ Adjust standard transfer efficiency to operating conditions.
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Part 1 of 3
29 Sep 78
[(cs) T(e)p - c
OTE = STE ±= - - - ^ a(l.02)T~2°
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(Cs),j, = ^2 saturation at selected summer temperature T , °C, mg/£
£ = 02 saturation in waste/0 saturation in water «0.9
p = correction factor for pressure ad.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 02 transfer in waste/0 transfer in water %0.9
T = temperature, °C
h_ Calculate horsepower requirement.
o2
hp = - - x 100°
where
hp = horsepower required/1000 gal
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, Ib 0 /hp-hr
V = volume of basin, gal
(9) Calculate sludge production and determine pounds of sludge
wasted per day.
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29 Sep 78
where
AIVL = sludge produced, Ib/day
1VL = total mass, mg/£
V = volume of aeration tank, million gal
t = solids retention time, days
s
(10) Check solids produced per pound of BOD removed.
AM
Ib solids T
Ib BODr ~ Q(F - Fe)8.3^
where
AM = sludge produced, Ib/day
Q = flow, mgd
F. = influent BOD , mg/£
F = effluent BOD.., mg/£
e 5
(ll) Calculate sludge recycle ratio.
Q M
where
Q = volume of recycled sludge, mgd
Q = flow, mgd
M_ = total mass, mg/£
solids concentration in return sludge, mg/£
Calculate total effluent BOD .
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EM 1110-2-501
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29 Sep 78
where
Sg = effluent soluble BOD, mg/£
(SS) = effluent suspended solids, mg/£
M = living mass, mg/£
3.
M = total mass, mg/£
(13) Determine nutrient requirements, Ib/day
for nitrogen
N = 0.123AMT(or
and phosphorus
P = 0.026AMT(or
where
AM = sludge produced, Ib/day
AX = sludge produced, Ib/day
and check against BOD:H:P = 100:5:1
b. Eckenfelder's Approach.
(l) Assume the following design parameters from paragraph 7-21 when
unknown.
(a) BOD removal rate constant (k).
(b) Fraction of BOD synthesized (a).
(c) Fraction of BOD oxidized for energy (a1).
(d) Endogenous respiration rate (b and b1).
(e) Mixed liquid suspended solids (MLSS).
(f) Mixed liquid volatile suspended solids (MLVSS).
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29 Sep 78
(g) Food-to-microorganism ratio (F/M) .
(h) NonModegradable fraction of VSS in influent (f).
(i) Degradable fraction of the MLVSS (f')-
(j) Temperature correction coefficient (0).
(2) Adjust rate constant for temperature.
(T-20)
KT ~ K200
where
1C, = rate constant at desired temperature, °C
K = rate constant at 20°C
0 = temperature correction coefficient
T = temperature, °C
(3) Determine the size of the aeration tank "by first determining
the detention time t .
t =
(XV)(F/M)
where
t = hydraulic time, hr
S = influent BOD , rngA
X^ = MLVSS, mg/£
F/M = food-to-microorganism ratio
(k) Check detention time for treatability
S
e _ 1
where
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Part 1 of 3
29 Sep 78
Sg = BOD (soluble) in effluent, mg/SL
S = BOD in influent, mg/£
k = BOD removal rate constant, £/mg/hr
Xy = MLVSS, mg/£
t = detention time, hr
Solve for t and compare with t above and select the larger,
(5) Calculate the volume of aeration tank.
V = Q x X-
avg 2k
where
V = volume, million gal
Q = average daily flow, mgd
a v g
t = detention time, hr
(6) Calculate oxygen requirements.
dO = a'Sr
dt t V
or
= a'(Sr)(Q )(8.3U) + b'(Xy)(V)(8.3M
r avg
where
dO/dt = oxygen uptake rate, mg/£/hr
a' = fraction of BOD oxidized for energy
S^ = BOD removed (S - S ), mg/£
t = detention time, hr
7-50
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Part 1 of 3
29 Sep 78
"b1 = endogenous respiration, 1/hr
Xy = MLVSS
0 = oxygen requirement , lb/day
Q = average flow rate , mgd
avg
V = volume of aeration tank, million gal
and check the oxygen supplied against paragraph 7-21 >1.25
where
0 = oxygen required, Ib/day
Q = flow, mgd
S - BOD removed, mg/£
(T) Design aeration system and check horsepower supply for mixing
against horsepower required for complete mixing _<0.1 hp/1000 gal.
(a) Diffused Aeration System.
JL Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer
(5-8 percent ) .
b_ 0 transfer in waste/0 transfer in water «=0.9.
c_ 0 saturation in waste/0 saturation in water «O.9-
d Correction factor for pressure «1.0.
2_ Select summer operating temperature (25-30°C) and determine
m standard tables) 0 saturation.
3 Adjust standard transfer efficiency to operating conditions.
7-51
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Part 1 of 3
29 Sep 78
[(Cs)T(3)(p) - C ]
OTE = STE - i- - ±- a(l.02)T-20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(cs)T ~ 02 saturation at selected summer temperature T, °C, mg/H
3 = 02 saturation in waste/0 saturation in water *0.9
p = correction factor for pressure ssd.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/J>
a = 02 transfer in waste/0 transfer in water =»0.9
T = temperature, °C
k_ Calculate required air flow.
R =
/ Ib 0- \ / .
(OTE) 0.0176 - —2- 141*0 ^ V
\ ft3 air/ V
where
R = required air flow, cfm/1000 ft
cl
02 = required oxygen, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(b) Mechanical Aeration System.
!_ Assume the following design parameters.
a Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen, 20°C,
and tap water) (5-8 percent).
7-52
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Part 1 of 3
29 Sep 78
"b 0 transfer in waste /O transfer in water *0.9-
d d
c 0^ saturation in waste/00 saturation in water «O.9.
— d d
d_ Correction factor for pressure ssl.O.
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
_3_ Adjust standard transfer efficiency to operating conditions.
[(CsU0)(p) -
OTE - STE - ±~~ - a(l.02)
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(Cs) = 0 saturation at selected summer temperature T , °C, mg/£
3=0 saturation in waste/0 saturation in water wO.9
p = correction factor for pressure «L.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a, = 0 transfer in waste/0 transfer in water
T = temperature , °C
k_ Calculate horsepower requirement.
hp = - 2 - x 100°
where
hp = horsepower required/1000 gal
0 = oxygen required, Ib/day
7-53
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Part 1 of 3
29 Sep 78
OTE = operating transfer efficiency, Ib 0 /hp-hr
V = volume of basin, gal
(8) Calculate sludge production.
bXyV + fQ(VSS) + Q(SS.-
where
AX = sludge produced, Ib/day
a = fraction of BOD removed synthesized to cell material
S = BOD removed, rag/ Si
Q = average flow, mgd
avg
b = endogenous respiration rate/day
Xy = MLVSS, mg/£
V = volume of basin, gal
f = noribiodegradable fraction of influent VSS
Q = flow, mgd
VSS = volatile suspended solids in effluent, mg/£
SS = suspended solids in influent, mg/£
(9) Calculate solids produced per pound of BOD removed and check
AX against value given in paragraph 7-21 .
V
AY
Ib solids V
(Ib BODr) Sr(Q)(8.3*0
where
AX = sludge produced, Ib/day
S = BOD removed, mg/&
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Q = flow, mgd
(10) Calculate sludge recycle ratio.
Q X
r a
Q X - X
u a
where
Q /Q = sludge recycle ratio
r
Q = volume of recycled sludge, mgd
Q = flow, mgd
X = MLSS, mg/Jl
a
X = solids concentration in return sludge, mg/&
(ll) Calculate solids retention time.
(V)X (8.310
SET = -
AX
where
SET = solids retention time, days
AX =
a % volatile
(12) Calculate effluent BOD .
eff -Se + 0.8MXv)
where
S = effluent soluble BOD, mg/£
e
(xv) ** - effluent volatile suspended solids, mg/£
v eff
f = degradable fraction of MLVSS
(13) Determine nutrient requirements, Ib/day
7-55
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EM 1110-2-501
Part 1 of 3
29 Sep 78
for nitrogen
N = 0.123AMT(or
and phosphorus
P = 0.026AMT(or
where
AM = sludge produced, lb/day
AX = sludge produced, lb/day
and check against BOD:N:P = 100:5:1.
7-23- Output Data.
a. Aeration Tank.
(l) Reaction rate constant, £/mg/hr.
(2) Sludge produced per BOD removed,
(3) Endogenous respiration rate ("b, b').
(k) Op utilized per BOD removed.
(5) Influent nonbiodegrada'ble VSS (f).
(6) Effluent degradable VSS (f').
(7) lb BCD/lb MLSS-day (F/M ratio).
(8) Mixed liquor SS, mg/Jl (MLSS).
(9) Mixed liquor VSS, mg/£ (MLVSS).
(10) Aeration time, hr.
(ll) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
7-56
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Part 1 of 3
29 Sep 78
(13) Sludge produced, Ib/day.
(ik) Nitrogen requirement, Ib/day.
(15) Phosphorus requirement, Ib/day.
(16) Sludge recycle ratio, percent.
(IT) Solids retention time, days.
b. Diffused Aeration System.
(l) Standard transfer efficiency, percent.
(2) Operating transfer efficiency, percent.
(3) Required air flow, cfm/1000 ft3.
c. Mechanical Aeration System.
(1) Standard transfer efficiency, Ib 02/hp-hr.
(2) Operating transfer efficiency, Ib 02/hp-hr.
(3) Horsepower required.
7-2U. Example Calculations, Eckenfelder's Approach.
a. Assume the following design parameters.
(1) k = 0.0012 £/mg-hr.
(2) a = 0.73.
(3) a' = 0.5-
(10 b = 0.075/day, b' = 0.15/day.
(5) MLSS = X = 3000 mg/A.
Si
(6) MLVSS = Xy = 2^00 mg/&.
(7) F/M = 0.1*0 Ib BOD/lb MLVSS-day.
7-57
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Part 1 of 3
29 Sep 78
(8) f = o.Uo.
(9) f = 0.53.
(10) 0 = 1.03.
b. Adjust the BOD removal rate constant for winter conditions,
T = 15°C.
K eT~20
T 20"
where
IL = rate constant at temperature T
Kg = rate constant at 20°C, 0.0012 £/mg-hr
T = temperature, 15°C
0 = temperature correction coefficient, 1.03
K.J, = 0.0012(1.03)15~2°
KL, = 0.0010 £/me-hr
c. Determine size of aeration tank by determining detention time.
24 S
t =
where
t = hydraulic detention time, hr
S = influent BOD, 200 mg/£
Xy = MLVSS, 2*100 mg/£
F/M = food-to-microorganism ratio, O.hO Ib BOD/lb MLVSS
= 2^(200)
2^00(0.
7-58
-------
t = 5.0 hr
d. Check detention time for treatability.
S
SQ 1 +
where
S = effluent BOD.- (soluble), 10 mg/£
e 5
S = influent BOD.., 200 mg/£
o P
K = BOD removal rate constant, 0.001 &/mg/hr
X = MLVSS, 2UOO mg/£
t = detention time, hr
10
200 1 + (O.OOl)2UOO(t)
t = 7.9 hr > 3.0 hr
e. Calculate the volume of the aeration tank.
V =
where
V = volume , million gal
Q = average flow, 1.0 mgd
avg
t = detention time, 7-9 hr
V = 0.329 million gal
f. Calculate oxygen requirements.
7-59
EM 1110-2-501
Part 1 of 3
29 Sep 78
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
°2 =
where
0 = oxygen required, Ib/day
a' = 0.52
Sr = BOD removed (S - S ) , 190 mg/&
Q = average flow , 1.0 mgd
b' = 0.15/day
Xy = MLVSS, 2UOO mg/£
V = volume of aeration tank, 0.329 million gal
02 = 0.52(190)1. 0(8. 3U) + 0.15(2UOO)0. 329(8. 3U)
02 = 1812 Ib/day
Check oxygen supplied per lb BOD removed >1.25.
"i T. TJ f~^Ti f*\ f o ^ Q
XD riUJJ wl D )o.
r r
where
0 = oxygen required, 1812 Ib/day
Q = average flow, 1.0 mgd
S = BOD removed, 190 mg/£
°2 1812
lb BOD 1.0(190)8.3^
lb 02/lb BOD = l.lU < 1.25
Therefore
T-60
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EM 1110-2-501
Part 1 of 3
29 Sep 78
0 = 1.25 BODr
= 1.25
L
= 1.25(1.0)190(8.3M
00 = 1980 Ib/day
g. Design aeration system (mechanical surface).
(l) Assume the following parameters,
STE =5.0 percent
a = 0.9
3 = 0.9
p = pressure correction factor, 1.0
(2) Select summer operating temperature and determine 0 saturation,
T = 25°C, (CS)T = 8.2 mg/£
(3) Determine operating transfer efficiency.
[(CsL(e)(p) - C ]
OTE = STE i1- a(l.02)
y • -L I
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5.0 percent
(CS)T = 8.2 mg/£
C = minimum dissolved oxygen, 2.0 mg/£
L
T = 25°C a = 0.9 3 = 0.9
7-61
9-17 = 0 saturation at 20°C
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EM 1110-2-501
Part 1 of 3
29 Sep 78 "
OTE = 5.0 [8.2(0.9)1 0 - 2.01 0.9(l.02)25-20
y • -i-1
OTE = 2,9% or Ib 02/hp-hr
(^) Calculate horsepower requirements.
hp ~ OTE(2MV
where
hp = horsepower requirements, hp/1000 gal
02 = oxygen required, 1980 Ib/day
OTE = operating transfer efficiency, 2.9 percent
V = volume of aeration tank, 0.329 million gal
, = 1980
P 2.9(2100. 329(1000)
hp = 0.09 hp/1000 gal < 0.1 hp/1000 gal
Therefore use hp = 0.1 hp/1000 gal
hp = 0.1(V)1000
hp = 0.1(0.329)1000
hp = 32.9 hp (use 35 hp)
h. Calculate sludge production.
avg
where
AX^ = sludge produced, Ib/day
a = 0.73
7-62
- bXy(V) + Qay(VSS)f + Qav(SS - VSS)]8.3U
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EM 1110-2-501
Part 1 of 3
29 Sep 78
S = BOD removed, 190 mg/£
r
=1.0 mgd
avg
b = 0.075 May
Xy = 2^00 mg/A
V = 0.329 million gal
VSS = effluent volatile suspended solids, 150 mg/£
f = O.UO
SS = suspended solids in influent, 200 mg/£
AX^ = [0.73(190)1.0 - 0. 075(2^00)0.329
+ 1. 0(150)0. UO + 1.0(200 - 150)]8.3U
AX = 1580 Ib/day (
i. Calculate solids produced per pound of BOD removed and check
> 0.5-0.7-
V
Ib solids _
Ib BOD SrQ8.3i
where
AX_ = solids produced, 1580 Ib/day
S = BOD removed (S - S ), 190 mg/i
r o e
Q = average flow, 1.0 mgd
Ib solids = 1580
Ib BOD 190(1. 0)8.
r
Ib solids/lb BOD = 1.0 > 0.5-0.7 (OK)
7-63
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Part 1 of 3
29 Sep 78
j. Calculate sludge recycle ratio.
X
a
Q X - X
u a
where
Qr = volume of recycled sludge, mgd
Q = average flow, 1.0 mgd
X = MLSS, 3000 mg/£
Si
X^ = return sludge concentration, 10,000 mg/£
Q
r _ 3,000
1.0 10,000-3,000
Qr = 0.^29 mgd
k. Calculate solids retention time.
V(X )8.
SRT = —
a
where
SRT = solids retention time, days
V = volume of aeration tank, 0.329 million gal
X = MLSS, 3000 mg/£
8-
volatile = 1580/0. 80 = 1975 Ib/day
_ 0.329(3000)8.3^
-- -
SRT = k.2 days
1. Calculate effluent BOD
7-6k
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(BOD5)eff = Se + 0.8MXV)efff
where
(BOD5) = effluent BOD , mg/£
S = effluent soluble BOD , 10 mg/&
e 5
(Xv) = effluent volatile suspended solids, 20 mg/SL
f = 0.53
(BOD5) = 10 + 0.8U(20)0.53
(BOD5)eff = 19 mg/£
m. Determine nutrient requirement
for nitrogen
N = 0.123AXV
N = 0.123(1580)
N = 19U lb/day
for phosphorus
P = 0.026AX
P = 0.026(1580)
P = ill Ib/day
N in influent = 30
av
= 30(1. 0)8. 3^
= 250 Ib/day > 19^ l"b/day required
N to be added = none
P in influent = 15 mg/2,(Qavg)8.
7-65
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Part 1 of 3
29 Sep 78
= 15(1.0)8.3U
= 125 Ib/day > kl Ib/day required
P_to_be_ added - _none_
7-25. Cpst Data. Appropriate cost data arid economic evaluation may be
found in Chapter 8.
7-26. Bibliography.
a. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Wastewater Control Engineering," 1969.
b. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. S.
Environmental Protection Agency, Washington, D. C.
c. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, and 1968, Water Pollution Control Federation
Washington, D. C.
d. Bargman, R. D. and Borgerding, J., "Characterization of the
Activated Sludge Process," Report No. R2-73-22U, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
e. Burkhead, C. E., "Evaluation,of CMAS Design Constants," Confer-
ence on Toward a Unified Concept of Biological Waste Treatment Design
5-6 Oct 1972, Atlanta, Ga.
f. Burkhead, C. E. and McKirmey, R. E., "Application of Complete-
Mixing Activated Sludge Design Equations to Industrial Wastes," Journal,
Water Pollution Control Federation. Vol 1*0, Apr -1968, pp 557-570~*"
g. Busch, A. W., Aerobic Biological Treatment of Wastewaters,
Oligodynamics Press, 1971.
h. Center for Research, Inc., University of Kansas, "Oxygen Con-
sumption in Continuous Biological Culture," Report No. 17050DJS, May
1971, U. S. Environmental Protection Agency, Washington, D. C.
i. City of Austin, Texas, "Design Guides for Biological Wastewater
7-66
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EM 1110-2-501
Part 1 of 3
29 Sep 78
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
j. "Design and Operation of Complete Mixing Activated Sludge
Systems," Environmental Pollution Control Service Reports, Vol 1, No 3,
Jul 1970.
k. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
1. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual^of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Briarcliff Manor, New York.
m. Eckenfelder, W. W., Jr., Water Quality Engineering for Practic-
ing Engineers, Barnes and Nobel, New York, 1970.
n. Eckenfelder, W. W., Jr., "Activated Sludge and Extended Aera-
tion," Process Design in Water Quality Engineering - New Concepts and
Developments, 1971, Vanderbilt University, Nashville, Tenn.
o. Eckenfelder, W. W., Jr., and Ford, D. L. , Water Pollution
Control, Pemberton Press, New York, 1970.
p. Eckenfelder, W. W., Jr., and O'Connor, 0. J. , Biological Waste
Treatment, Pergamon Press, New York, 1961.
q. Gaudy, A. G., Jr., and Gaudy, E. T. , "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No. 17090-
FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington, D. C.
r. Goodman, B. L. , Design Handbook of Wastewater Systems: Domestic,
Industrial, Commercial, Technomic, Westport, Conn., 1971.
s. Goodman, B. L. and Englande, A. J., Jr., "A Consolidated
Approach to Activated Sludge Process Design," Conference on Toward a
Unified Concept of Biological Waste Treatment Design, 5-6 Oct 1972,
Atlanta, Ga.
t. Lawrence, A. W. and McCarty, P. L., "Unified Basis for Biologi-
cal Treatment Design and Operation," Journal, Sanitary Engineering
Division, American Society of Civil Engineers, Vol 96, SA3, 1970.
u. Maier, W. J., "Biological Removal of Colloidal Matter from
7-67
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Part 1 of 3
29 Sep 78
Wastewater," Report No. R2-73-l>*7, Jun 1973, U. S. Environmental Protec-
tion Agency, Washington, D. C.
Q1 /' „ TMcKinney> R- E., "Mathematics of Complete-Mixing Activated
bludge, Journal, Sanitary Engineering Division, American Society of
Civil Engineers, SA3. Mav 1Q£P3 rr 87-113. ~*
w. McKinney, R. E., Microbiology for Sanitary Engineers McGraw-
Hill, New York, 1962.
x. McKinney, R. E. and Ooter, R. J., "Concepts of Complete Mixing
Activated Sludge," Bulletin No. 60, 1969, Transactions of the I9th
Annual Conference on Sanitary Engineering, University of Kansas Law-
rence, Kans. '
y. Metcalf and Eddy, Inc., Wastewater Engineering: Collection.
-treatment, and Disposal. McGraw-Hill, New York, 1972. "
z. Okun, D. A., "System of Bio-Precipitation of Organic Matter
from Sewage, Sewage Works Journal. Vol 21, No. 5, 191*9, pp 763-791*.
aa. Smith, H. S., "Homogeneous Activated Sludge and Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering.
\'ol U, Jul 1967, PP 1*6-50. ~~ "—' & fi-*
bb. Smith, R. and Eilers, R. G., "A Generalized Computer Model for
N^jifrep**6 n6^?™^0^ °f the Activated Sludge Process," FWQA Report
A- Taft Water Research Center, Cincinnati,
cc. Stensel, H. D. and Shell, G. L. , "Two Methods of Biological
Treatment Design, Journal, Water Pollution Control Federation Vol 1*6
Feb 197k, PP 271-283. ' ~ ~~
dd. Stewart, M. J., "Activated Sludge System Variations - Specific
Applications, The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
ee. Toerber, E. D., "Full Scale Parallel Activated Sludge Process
Evaluation,' Report No. R2-72-065, Nov 1972, U. S. Environmental
Protection Agency, Washington, D. C.
ff. Weston, R. F., "Design of Sludge Reaeration Activated Sludge
Systems," Journal, Water Pollution Control Federation Vol 33 No 7
1961, pp 748-757.~~~'
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29 Sep 78
Section V. STEP AERATION ACTIVATED SLUDGE
7-27- Background.
a. Step aeration is defined as "a procedure for adding increments
of settled wastewater along the line of flov in the aeration tanks of
an activated sludge plant" (para 7-3^a). It is a modification of the
activated sludge process in which an attempt is made to equalize the
food-to-microorganism ratio (F/M). The first application of this
process was at the Talljnans Island plant in New York City in 1939-
b. Baffles are used to split the aeration tank into four (or more)
parallel channels. Each of these channels is a separate step and all
channels are linked together in series (fig. 7-M •
INFLUENT
— fc
1
1
U
AERATION TANK
SL
.UDGE
RETURN
/C-TT, mr\ EFFLUENT
V TANK /
+ vyASTE
-*
Figure 7-U. Step aeration activated sludge.
c. Flexibility of operation is a prime factor to consider in the
design of the process. The oxygen demand is essentially uniform over
the length of the basin, resulting in more efficient utilization of the,
oxygen supplied. Introduction of influent waste at multiple locations
and return of a highly absorptive sludge floe permit this process to
remove soluble organics within a relatively short contact time; there-
fore, it is characterized by higher volumetric loadings than the con-
ventional plug flow activated sludge process.
d. References c, t, v, and y in paragraph 7-3^ discuss the step
aeration modification and enumerate the design parameters.
7-28. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variability,
a statistical distribution should be provided.
7-69
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"b- Wastewater Strength.
(1) BOD^ (soluble and total), rng/fc.
(2) COD and/or TOC (maximum and minimum), mg/£.
(3) Suspended solids, mg/H.
(k) Volatile suspended solids (VSS), mg/£.
(5) Nonbiodegradable fraction of VSS, mg/Ji.
c. Other Characterization.
(1) pH.
(2) Acidity and/or alkalinity, mg/£.
(3) Nitrogen, mg/£.
(^) Phosphorus (total and soluble), mg/£.
(5) Oils and greases, mg/£.
(6) Heavy rnetals , mg/£.
(7) Toxic or special characteristics (e.g., phenols), mg/£.
(8) Temperature, °F or °C.
d. Effluent Quality Requirements.
(1) BOD5, mg/4.
(2) SS, ing/A.
(3) TKN, mg/A.
(U) P, mg/Jl.
The form of nitrogen should be specified as to its biological
availability (e.g., NH or Kjeldahl).
7-TO
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29 Sep 78
(5) Total nitrogen (TKN + NO^N), mg/£.
(6) Settleable solids, mg/A/hr.
7_29. Design Parameters.
a. Reaction Rate Constants and Coefficients.
Constants .
Range
McKinney
K
m
K
s
K
e
Eckenfelder
k
a
a'
b
V
f
f
to. F/M = (0.2-0.10.
c. Volumetric loading = 40-60.
d. t = (3-5) hr.
e. t = (3-7) days.
s
f. MLSS = (2000-3500)
15/hr at 20°C
lO.U/hr at 20°C
0.02/hr at 20°C
0.0007-0.002 Jl/mg/hr
0.73
0.52
0.075/day
0.15/day
O.i*0
0.53
7-71
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Part 1 of •=!
29 Sep 78
g. MLVSS = (1400-2450)
h. Qr/Q - (0.25-0.75).
i. Ib 00/lb BOD >_ 1.25.
j. Ib solids/lb BOD = (0.5-0,7).
k. 0 = (1.0-1.04).
1. Efficiency = (>90 percent).
7-30. Design Procedure.
a. McKinney's Approach.
(l) Assume the following design parameters.
(a) Metabolism constant (K ).
m
(b) Synthesis factor (K ).
o
(c) Endogenous respiration factor (K ).
e
(d) Temperature correction coefficient (0).
(e) Hydraulic detention time (t).
(2) Adjust the metabolism constant, the synthesis factor, and the
endogenous rate of respiration for temperature.
K Q(T-2°)
T 20"
where
K^ = rate constant at desired temperature, T , °C
K = rate constant at 20°C
0 = temperature coefficient
T = temperature, °C.
7-72
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29 Sep 78
(3) Determine size of the aeration tank.
/t \
V = Q (•^Tj
where
V = volume of tank, million gal
Q = average flow, mgd
avg
t = hydraulic detention time, hr
(1+) Determine soluble effluent BOD .
F.
Fe = 1 + Kmt
where
F = soluble effluent BOD-, mg/X,
e ?
F. = influent BOD5, mg/X,
K = metabolism constant (15/hr at 20°C)
m
t = hydraulic detention time, hr
and check F £ 10 mg/X, . If F > 10 , increase t and calculate
new F
(5) Calculate the MLSS concentration and check total mass against
2000-3500 mg/£.
M. + M..
K F
M =
a " K + I/2h t
M = 0.2K M t (2k)
e e a sv '
7-73
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Part 1 of 3
29 Sep 78
M. = SS. — s
i i\. t
2kt
Mii = SSii X— T
vhere
Hp = total mass, mg/£
M = living active mass, mg/£
QI
Mg = endogenous mass, mg/£
IYL = inert nonbiodegradable organic mass, mg/£
M^^^^ = inert inorganic suspended solids, mg/£
Kg = synthesis factor, 1/hr (10 - Vhr at 20°C)
Kg = endogenous respiration factor, 1/hr (0.02/hr at 20°c)
"t = solids retention time, days
SS^ = inert organic SS in influent, mg/Ji
= VSS x percent nonbiodegradable
SSii = inert inorganic SS fraction in the influent
(6) Check organic loading against 0.2-0.4.
where
F/M = food-to-microorganism ratio
F± = influent BOD , mg/£
I^L = total mass, mg/£
t = detention time, hr
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m 1110-2-501
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29 Sep 78
If F/M < lower limit, it is possible to reduce t and recalculate MT .
If F/M > upper limit, increase t and recalculate MT .
(7) Calculate the oxygen requirements.
(a) Select oxygen uptake rate. The average rate of oxygen demand,
if the waste load is uniform, is given by
dO
dt
~1.5(Fi - Fe)~
t
-
"i.U;
a
M )"
e
2H
s
where
dO
dt
= average oxygen uptake rate, mg/£/hr, under uniform flow
conditions
F. = influent BOD , mg/£
F = effluent BOD,-, mg/£
t = detention time, hr
M = living mass, mg/£
a
M = endogenous mass, mg/£
t = solids retention time, hr
s
Under conditions where the load varies, the oxygen uptake is equal to
the synthesis oxygen demand plus the endogenous respiration oxygen
demand or
dO
dt
"0.5(F. - F
avg,
+ l.lUK M
e a
where
P
= peak flow, mgd
- average flow, mgd
K = endogenous respiration factor/hr
7-75
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29 Sep 78
(b) Supply oxygen for peak hourly load.
where
02 = oxygen required, Ib/hr
dO _
dt - average oxygen uptake rate, mg/£/hr, under uniform flow
conditions
V = volume of the tank, gal
and check oxygen supplied per Ib of BOD removed >1.25
lb 0
Ib
where
02 = oxygen required, Ib/hr
Q = flow, mgd
FI = influent BOD , mg/£
Fg = effluent BOD , mg/£
(8) Design aeration system and check horsepower supply for mixing
against horsepower required for mixing >0.1 hp/1000 gal.
(a) Diffused Aeration System.
!_ Assume the following design parameters.
_a Standard transfer efficiency, percent, from manufacturer
(5-8 percent).
b_ 02 transfer in waste/02 transfer in water ^0.9.
£ 02 saturation in waste/02 saturation in water 3=0.9.
1-16
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29 Sep 78
d_ Correction factor for pressure «1.0.
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0^ saturation.
3_ Adjust standard transfer efficiency to operating conditions.
s) (6)(p) -
OTE = STE -- - ^- - ad.02)
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(C ) =0 saturation at selected summer temperature T , °C,
3=0 saturation in waste/0 saturation in water ssO.9
p = correction factor for pressure szL.O
C = minimum dissolved oxygen to be maintained in the basin
L > 2.0 mg/£
a = 0 transfer in waste/0 transfer in water «£>.9
T = temperature, °C
h Calculate required air flow.
0
R =
a
(OTE)0.0176 -uUo V
\ft air/ v
where
•?
R = required air flow, cfm/1000 ft
a
0 = oxygen required, Ib/day
7-77
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29 Sep 78
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(b) Mechanical Aeration System.
!_ Assume the following design parameters.
a. Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
b_ 0_ transfer in waste/0? transfer in water «s0.9.
c_ Qg saturation in waste/0 saturation in water «0.9.
d_ Correction factor for pressure al.O.
_2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0? saturation.
3_ Adjust standard transfer efficiency to operating conditions
OTE = STE = - - i a(l.02)i~c:U
y • -L I
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
\ = 0 saturation at selected summer temperature T , °C, mg/£
3 = 0 saturation in waste/0 saturation in water a=o.9
p = correction factor for pressure «1.0
C = minimum dissolved oxygen to be maintained in the basin
> 2.0
a = 02 transfer in waste/0 transfer in water ssO.9
T-T8
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29 Sep 78
T = temperature, °C
k_ Calculate horsepower requirement.
- x 100°
where
hp = horsepower req.uired/1000 gal
Op = oxygen required, l"b/day
OTE = operating transfer efficiency, l"b 0 /hp-hr
V = volume of basin, gal
(9) Calculate sludge production and determine amount of sludge
wasted per day.
where
AM^ = sludge produced, Ib/day
ML = total mass, mg/£
V = volume of aeration tank, million gal
t = solids retention time, days
S
(10) Check solids produced per pound of BOD removed.
f'lb solids\ AMT
Ib BOD I Q(F. - F
1C / 1 t
where
AM_ = sludge produced, Ib/day
1-19
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Part 1 of 3
29 Sep 78
Q = flow, mgd
F. = influent BOD , mg/J,
F = effluent BODC, mg/Jl
e p
(ll) Calculate sludge recycle ratio.
Qr__ HT
ii "^^
where
Q = volume of recycled sludge, mgd
Q = flow, mgd
M = total mass, mg/£
M = solids concentration in return sludge, mg/£
u
(12) Calculate total effluent BOD.
(BOD^
'M \
~^ (0.76)
'eff "
where
S = effluent soluble BODC, mg/«,
e p
SS = suspended solids in effluent,
M = living mass, mg/£
3,
IVL = total mass, mg/£
(13) Determine nutrient requirements for nitrogen
N = 0.123AMT(or
and phosphorus
7-80
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Part 1 of 3
29 Sep 78
P = 0.026AMT(or M^)
where
AM^ = sludge produced, Ib/day
AM = sludge produced, Ib/day
and check against BOD:N:P = 100:5:1.
b. Eckenfelder's Approach.
(l) Assume the following design parameters when unknown.
(a) BOD removal rate constant (k).
(b) Fraction of BOD synthesized (a).
(c) Fraction of BOD oxidized for energy (a1).
(d) Endogenous respiration rate (b and b')«
(e) Mixed liquor suspended solids (MLSS).
(f) Mixed liquor volatile suspended solids (MLVSS).
(g) Food-to-microorganism ratio (F/M).
(h) Temperature correction coefficient (0).
(i) Nonbiodegradable fraction of VSS in influent (f).
(j) Degradable fraction of the MLVSS (f).
(2) Adjust BOD removal rate constant for temperature.
(T-20)
KT - K209
where
K = rate constant for desired temperature, °C
K = rate constant at 20°C
7-81
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29 Sep 78
Q = temperature correction coefficient
T = temperature, °C
(3) Determine size of the aeration tank by first determining the
detention time.
t =
(XV)(F/M)
where
t = detention time, hr
S = influent BOD, mg/£
Xy = MLVSS, mg/£
F/M = food-to-microorganism ratio
(M Check detention time for treatability.
S
e _ 1
S 1 + kX.rt
o v
where
Sg = BOD soluble in effluent, mg/£
SQ = BOD in influent, mg/£
k = BOD removal rate constant, £/mg/hr
Xy = MLVSS, mg/£
t = detention time, hr
and solve for t and compare with t in (3) above and select the
larger.
(5) Calculate the volume of aeration tank.
7-82
-------
v =
where
V = volume, million gal
Q = average daily flow, mgd
t = detention time, hr
(6) Calculate oxygen requirements.
dt
= a'(Sr)(Qavg)(8.3lO
or
where
-r— = oxygen uptake rate, mg/£/hr
dt
a1 = fraction of BOD oxidized for energy
S = BOD removed (S - S )
r o e
t = detention time, hr
V = endogenous respiration rate, £/hr
Xy = MLVSS
Op = oxygen requirement, lb/day
Q = average flow rate, mgd
avg
V = volume of aeration tank, million gal
and check the oxygen supplied against 5*L.25.
0^
EM 1110-2-501
Part 1 of 3
29 Sep 78
7-83
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EM 1110-2-501
Part 1 of ^
29 Sep 78
where
0 = oxygen required, l"b/day
Q = flow, mgd
S = BOD removed, mg/£
(7) Design aeration system.
(a) Diffused Aeration System.
_L Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer
(5-8 percent ) ,
b_ 0 transfer in waste/0 transfer in water %0.9.
c_ 0 saturation in waste/0 saturation in water ȣ).9.
d_ Correction factor for pressure sal.O.
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
J3 Adjust standard transfer efficiency to operating conditions.
|~(CS) (B)(p) - C "I
•*= - ^ - ^
OTE = STE .
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(Cs) = Op saturation at selected summer temperature T, °C , mg/£
B = 00 saturation in waste/0? saturation in water ssO.9
p = correction factor for pressure ^L.O
7-81+
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Part 1 of 3
29 Sep 78
C = minimum dissolved oxygen to be maintained in the basin
L' > 2.0 mg/A
T = temperature, °C
a = 0 transfer in waste/0 transfer in water «0.9
U Calculate required air flow.
R =
a
(OTE)0.0176ft3
where
R = required air flow, cfm/1000 ft
9,
Op = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(b) Mechanical Aeration System.
I_ Assume the following design parameters.
a. Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
b Q0 transfer in waste/0 transfer in water ssO.9.
c 0 saturation in waste/0 saturation in water «0.9-
d_ Correction factor for pressure «1.0.
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
3 Adjust standard transfer efficiency to operating conditions.
7-85
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EM 1110-2-501
Part 1 of 3
29 Sep 78
|~(cs) (e)(P) - c "I
OTE = STE L T 1T i* a(l.02)T~20
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(Cs) = 0^ saturation at selected summer temperature T, °C, mg/Jl
3 = 0 saturation in waste/0 saturation in water «0.9
p = correction factor for pressure «1.0
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 0,3 transfer in waste/0 transfer in water ssO.9
T = temperature, °C
*4 Calculate horsepower requirement.
hp = - - -- - x 1000
where
hp = horsepower required/1000 gal
0 = oxgen required, Ib/day
OTE = operating transfer efficiency, Ib 0 /hp-hr
V = volume of basin, gal
(8) Calculate sludge production.
- bXy(v) + fQ(VSS) + Q(SS -
where
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EM 1110-2-501
Part 1 of 3
29 Sep 78
AX^ = sludge produced, Ib/day
a = fraction of BOD removed synthesized to cell material
S = BOD removed, mg/£
Q = average flow, mgd
avg
b = endogenous respiration rate, I/day
Xy. = volatile solids in raw waste, mg/£
V = volume of tank, gal
f = nonbiodegradable fraction of influent VSS
Q = flow, mgd
VSS = volatile suspended solids in effluent, mg/fc
SS = suspended solids in influent, mg/£
(9) Check AX against 0.5-0.7.
Ib/solids AXV
where
(Ib BODr)
AX^ = sludge produced, Ib/day
S = BOD removed, mg/£
Q = flow, mgd
(10) Calculate sludge recycle ratio.
Xa
Q X - X
u a
where
Q = volume of recycled sludge, mgd
Q = flow, mgd
7-87
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Part 1 of 3
29 Sep 78
X = MLSS, mg/£
cl
Xu = susPend-e(i solids concentration in returned sludge, mg/£
(ll) Calculate solids retention time.
(V)(X X8.310
SET = — a
AX
a
where
SRT = solids retention time, days
V = volume of basin, gal
X = MLSS, mg/£
€L
AX = T^
a % volatile
AX = sludge produced, Ib/day
a
AXy = sludge produced, Ib/day
(12) Calculate effluent BOD .
/BOD,.\ = S^ + 0.8MVSS)^(f)
where
S = effluent soluble BOD , mg/£
VSS = effluent volatile suspended solids, mg/£
f ' = degradable fraction of MLVSS
(13) Determine nutrient requirements
for nitrogen
N = 0.123AMT (or
T-88
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EM 1110-2-501
Part 1 of 3
29 Sep 78
and phosphorus
P = 0.026AMT (or
where
= sludge produced, Ib/day
= sludge produced, It/day
and check against BOD:N:P = 100:5:1.
7-31. Output Data.
a. Aeration Tank.
(l) Reaction rate constant, Jl/mg/hr.
(2) Sludge produced per BOD removed.
(3) Endogenous respiration rate (b, b').
(10 0 utilized per BOD removed.
(5) Influent nonbiodegradable BSS (f).
(6) Effluent degradable VSS (f1).
(7) Ib BOD/lb MLSS-day (F/M ratio).
(8) Mixed liquor SS, mg/£ (MLSS).
(9) Mixed liquor VSS, mg/£ (MLVSS).
(10) Aeration time, hr.
(11) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
(13) Sludge produced, Ib/day.
Nitrogen requirement, Ib/day.
7-89
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29 Sep 78
(15) Phosphorus requirement, Ib/day.
(l6) Sludge recycle ratio, percent.
(IT) Solids retention time, days.
b. Diffused Aeration System.
(l) Standard transfer efficiency, percent.
(2) Operating transfer efficiency, percent.
(3) Required air flow, cfm/1000 ft .
c . Mechanical Aeration System.
(l) Standard transfer efficiency, Ib 0?/hp-hr.
(2) Operating transfer efficiency, Ib 0 /hp-hr.
(3) Horsepower required.
7-32. Example Calculations. The design procedure for a step aeration
activated sludge system is the same as that for a complete mix activated
sludge system. Example calculations are shown in paragraph 7-2^, and
therefore will not be repeated here.
7-33- Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
7-3^- Bibliography.
a. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Wastewater Control Engineering,"
b. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report lo. 17090DOY, Dec 1970, U. S.
Environmental Protection Agency, Washington, D. C.
c. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
Wo. 8, 1959, 1961, 1967, and 1968, Water Pollution Control Federation,
Washington, D. C.
7-90
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29 Sep 78
d. Bargman, R. D. and Borgerding, J., "Characterization of the
Activated Sludge Process," Report No. R2-T3-22^, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
e. Busch, A. W., Aerobic Biological Treatment of Waste-waters,
Oligodynamics Press, 1971-
f. Center for Research, Inc., University of Kansas, "Oxygen
Consumption in Continuous Biological Culture," Report No. 17050DJS,
May 1971, U. S. Environmental Protection Agency, Washington, D. C.
g. City of Austin, Texas, "Design Guides for Biological Waste-water
Treatment Processes," Report No. 1101OESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
h. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
i. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Briarcliff Manor, New York.
j. Eckenfelder, W. W., Jr., Water Quality Engineering for Practicing
Engineers, Barnes and Nobel, New York, 1970.
k. Eckenfelder, W. W., Jr., "Activated Sludge and Extended Aeration,"
Process Design in Water Quality Engineering - New Concepts and Develop-
ments, 1971, Vanderldlt University, Nashville, Tenn.
1. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution Control,
Pemberton Press, New York, 1970.
m. Eckenfelder, W. W., Jr., and O'Connor, 0. J., Biological Waste
Treatment, Pergamon Press, New York, 1961.
n. Gaudy, A. G., Jr., and Gaudy, E. T., "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No.
17090-FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington,
D. C.
o. Goodman, B. L. , Design Handbook of Wastewater Systems: Domestic,
Industrial, Commerical, Technomic, Westport, Conn., 1971•
7-91
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29 Sep 78
p. Goodman, B. L. and Englande, A. J., Jr., "A Consolidated
Approach to Activated Sludge Process Design," Conference on Toward a
Unified Concept of Biological Waste Treatment Design, 5-6 Oct 1972,
Atlanta, Ga.
q. Lawrence, A. W. and McCarty, P. L. , "Unified Basis for Bio-
logical Treatment Design and Operation," Journal. Sanitary Engineering
Division, American Society of Civil Engineers. Vol 96. SA3. 1970'.
r. Maier, W. J., "Biological Removal of Colloidal Matter from
Wastewater," Report No. R2-73-lVf, Jun 1973, U. S. Environmental
Protection Agency, Washington, D. C.
s. McKinney, R. E., Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
t. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal^ McGraw-Hill, New York, 1972.
u. Okun, D. A., "System of Bio-Precipitation of Organic Matter
from Sewage," Sewage Works Journal» Vol 21, No. 5, 19^9, pp 763-79^.
v. Smith, H. S., "Homogeneous Activated Sludge and Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering
Vol k, Jul 1967, pp >*6-50. "
w. Smith, R. and Eilers, R. G. , "A Generalized Computer Model for
Steady-State Performance of the Activated Sludge Process," FWQA Report
No. TWRC-15, Oct 1969, Robert A. Taft Water Research Center, Cincinnati,
Ohio.
x. Stensel, H. D. and Shell, G. L., "Two Methods of Biological
Treatment Design," Journal, Water Pollution Control Federation, Vol U6,
Feb 197^, PP 271-283"]
y. Stewart, M. J., "Activated Sludge System Variations - Specific
Applications," The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
z. Toerber, E. D., "Full Scale Parallel Activated Sludge Process
Evaluation," Report No. R2-72-065, Nov 1972, U. S. Environmental Pro-
tection Agency, Washington, D. C.
7-92
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EM 1110-2-501
Part 1 of 3
29 Sep 78
aa. Weston, R. F., "Design of Sludge Reaeration Activated Sludge
Systems," Journal, Water Pollution Control Federation, Vol 33, No. 7,
1961, pp 7W-757-
7-93 (next page is 7-95.
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29 Sep 78
Section VI. EXTENDED AERATION ACTIVATED SLUDGE
7-35. Background.
a. The extended aeration process is defined as "a modification of
the activated sludge process which provides for aerobic sludge digestion
within the aeration system. The concept envisages the stabilization of
organic matter under aerobic conditions and disposal of the end products
into the air as gases and with the plant effluent as finely divided sus-
pended matter and soluble matter" (para 7-li2a). The process operates
in the endogenous respiration phase which requires a relatively small
F/M ratio and long detention time. In the process, the aeration deten-
tion time is determined by the time required to oxidize the solids pro-
duced by synthesis from the BOD removed. The accumulation of volatile
solids is very low and approaches the theoretical minimum; however,
since some of the biological solids are inert, an accumulation of solids
occurs in the system. Sludge storage facilities should be provided;
most states make it a requirement. The flow chart for the extended
aeration process is identical to that for plug flow (fig. 7-5)-
INFLUENT ^
A
— w
L
AERATION TANK
SLUDGE RETURN
[SETTLING^ EFFLUENT ^
\ TANK J
^T
T WASTE ^
SLUDGE '
Figure 7-5- Plug flow activated sludge.
b. Process design parameters and excellent design examples are
found in References c, h, o, u, w, and z in paragraph 7-U2.
7-36. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variability.
a statistical distribution should be provided.
b. Wastewater Strength.
(1) BOD (soluble and total), mg/£.
(2) COD and/or TOG (maximum and minimum), mg/£.
7-95
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29 Sep 78
(3) Suspended solids, mg/£.
(h) Volatile suspended solids (VSS), ing/8,.
(5) Nonbiodegradable fraction of VSS, mg/£.
c. Other Characterization.
(1) PH.
(2) Acidity and/or alkalinity, mg/Jl.
(3) Nitrogen, mg/Jl.
(H) Phosphorus (total and soluble), mg/Jl.
(5) Oils and greases, mg/Jl.
(6) Heavy metals, mg/£.
(T) Toxic or special characteristics (e.g., phenols), mg/Jl.
(8) Temperature, °F or °C.
d. Effluent Quality Requirements.
(1) BOD5, mg/A.
(2) SS, ng/A.
(3) TKN, ing/£.
(U) P, mg/Jl.
T-37. Design Parameters.
a. Reaction rate constants.
The form of nitrogen should be specified as to its biological
availability (e.g., NH or KJeldahl).
7-96
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29 Sep 78
Constants
McKinney
K
m
K
s
K
e
Eckenfelder
k
a
a'
b
b'
ao
f
f'
b. F/M = (0.05-0.15).
c. Volumetric loading = 10-25,
d. t - (18-36) hr.
e. t = (20-30) days.
S
f. MLSS = (3000-6000) mg/£.
g. MLVSS = (2100-U200) mg/£.
h. Qr/Q = (0.75-1.5).
i. Ib 0 /ITa BOD >_ 1.5.
Range
15/hr at 20°C
10A/hr at 20°C
0.02/hr at 20°C
0.0007-0.002 £/mg/hr
0.73
0.52
0.075/day
0.15/day
0.77a = 0.56
0.1+0
0.53
7-97
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29 Sep 78
j. Ib solids/lb BOD < 0.2.
r —
k. 0 = (1.0-1.03).
1. Efficiency = (>90 percent).
7-38. Design Procedure.
a. McKinney's Approach.
(l) Assume the following design parameters.
(a) Metabolism constant (K ).
m
(b) Synthesis factor (K ).
s
(c) Endogenous respiration factor (K ).
e
(d) Temperature correction coefficient (0).
(e) Hydraulic detention time (t), min.
(f) Solids retention time (t ), days.
S
(2) Adjust the metobolism constant, synthesis factor, and endog-
enous rate of respiration for temperature.
K = K e^T~2°)
where
K^ = rate constant at desired temperature
K = rate constant at 20°C
6 = temperature coefficient
T = temperature, °C
(3) Determine the size of the aeration tank.
V = 0
7-
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Part 1 of 3
29 Sep 78
where
V = volume of tank, million gal
Q . = average flow, mgd
avg
t = hydraulic detention time, hr
Determine soluble effluent BOD .
F.
F = ±
e 1 + K t
m
where
F = soluble effluent BOD , mg/£
F. = influent BOD mg/£
K = metabolism constant, 15/hr at 20°C
and check F >_ 10 mg/£ ; if F > 10 mg/£ increase t and calculate
new F . e
e
(5) Calculate the MLSS concentration and check M against
3000-6000 mg/£. T
Mm=M +M + M. + M..
I1 a e i ii
11
K F
M = *-£
M = 0.2K'M t (2i|)
e e a s
M. = SS. x
. .
lit
M. . = SS. . x —-S- + o.l (M + M )
11 11 t x a e'
1-99
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29 Sep 78
where
M_ = total mass, mg/£
M = living active mass, mg/£
cl
M = endogenous mass, mg/Jl
1YL = inert nonModegradable organic mass, mg/£
M = inert inorganic suspended solids, mg/£
K = synthesis factor, 1/hr (lO.U/hr at 20°C)
s
K^ = endogenous respiration factor, 1/hr (0.02/hr at 20°C)
t = solids retention time, days
S
SS^ = inert organic suspended solids in influent
= VSS x % nonModegradable (O.h x VSS for municipal waste)
SSii = inert inorganic suspended solids fraction in the influent
(6) Check organic loading against 0.05-0.15.
where
F/M = food-to-microorganism ratio
Fi = influent BOD , mg/£
M™ = total mass, mg/£
t = retention time, min
If F/M < lower limit, it is possible to reduce t and recalculate
MT .
If F/M > upper limit, increase t and recalculate M
(T) Calculate the oxygen requirements.
T-100
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Part 1 of 3
29 Sep 78
(a) Select the oxygen uptake rate. The average rate of oxygen
demand, if the waste load is uniform, is given "by
dO ^(Fi - Fe} 1A2(\ + V
dt t 2kt
s
where
dO/dt = average oxygen uptake rate, mg/£/hr, under uniform flow
conditions
F. = influent BOD , mg/£
F = effluent BOD._, mg/£
e 5
t = detention time, days
M = living mass, mg/£
El
M = endogenous mass, mg/£
t = solids retention time, days
s
Under conditions where the load varies, the oxygen uptake is equal to
the synthesis oxygen demand plus the endogenous respiration oxygen
demand or
dt * VW
°2 = dt X V X 8'3k
where
Q = peak flow, mgd
Q = average flow, mgd
avg
K = endogenous respiration factor, 1/hr
e
GO = oxygen required, Ib/hr
V = volume of "basin, gal
7-101
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(b) Check oxygen supplied per pound of BOD removed >_ 1.5.
i - Fe)(8.3U)
(8) Design aeration system and check horsepower supply for
complete mixing against horsepower required for complete mixing
>_ 0.1 hp/1000 gal.
(a) Diffused aeration system.
!_ Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer
(5-8 percent).
b_ 02 transfer in waste/0 transfer in water asO.9.
c_ 02 saturation in waste/02 saturation in water s£>.9.
d_ Correction factor for pressure sal.O.
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
3_ Adjust standard transfer efficiency to operating conditions.
- Cl
OTE - STE ^y^ =± a(l.02)T-20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(Cs) = °2 saturation at selected summer temperature T , °C , mg/£
3 = 02 saturation in waste/02 saturation in water «£.9.
p = correction factor for pressure saL.O.
7-102
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29 Sep 78
C = minimum dissolved oxygen to be maintained in the basin
L > 2.0 mgA
a = 0 transfer in waste/0 saturation in water «€>.9
T = temperature, °C
Calculate required air flow.
R =
a
\ ftj air/x
where
R = required air flow, cfm/1000 ft
a
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(b) Mechanical aeration system.
!_ Assume the following design parameters.
a Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
b_ 0 transfer in waste/02 transfer in water «0.9-
c_ 0 saturation in waste/Og saturation in water aO.9.
d_ Correction factor for pressure «1.0.
2_ Select summer operating temperature (25-30°O and determine
(from standard tables) 02 saturation.
3 Adjust standard transfer efficiency to operating conditions.
7-103
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29 Sep 78
F(cs) (B)(p) - CL!
± - *_ -
OTE = STE ± - *_ - - a(l.02)T-2°
y • J- 1
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(Cs) = °2 saturati°n at selected summer temperature T, °C, mg/£
3 = 02 saturation in waste/02 saturation in water «0.9
p = correction factor for pressure ssl.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 02 transfer in waste/Og transfer in water ^0.9
T = temperature, °C
k_ Calculate horsepower requirement.
Op
hp = - - x 100°
where
hp = horsepower required/1000 gal
02 = oxygen required, Ib/day
OTE = operating transfer efficiency, Ib 0 /hp-hr
V = volume of basin, gal
(9) Calculate sludge production and determine pounds of sludge
wasted per day.
MV(8.3M
AMm = x
T t
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EM 1110-2-501
Part 1 of 3
29 Sep 78
where
AMj^ = sludge produced, Ib/day
Mr^ = total mass, mg/£
V = volume of aeration tank, million gal
t = solids retention time, days
s
(10) Check solids produced per pounds of BOD removed.
Ib solids _ _T
Ib BOD Q(F. - F )(8.3^)
r i e
(11) Calculate sludge recycle ratio.
Q M,,
T
where
M = solids concentration in return sludge, mg/A
u
(12) Calculate total effluent BOD .
/M
(BOD5) = Se + (0.8U)(SS)eff I ^(0.76)
where
S = effluent soluble BOD^, mg/H
e 5
(SS) = suspended solids in effluent, mg/£
M = living mass, mg/&
a
MT = MLSS, mg/£
b. Eckenfelder's Approach.
(l) Assume the following design parameters when known.
7-105
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(a) Fraction of BOD synthesized (a).
(b) Fraction of BOD oxidized for energy (a1).
(c) Endogenous respiration rate (b and b1).
(d) Fraction of BOD synthesized to degradable solids (a ).
2 o
(e) Nonbiodegradable fraction to VSS in influent (f).
(f) Mixed liquor suspended solids (MLSS).
(g) Volatile solids in mixed liquor suspended solids (MLVSS)
(h) Temperature correction coefficient (0).
(i) Degradable fraction of the MLVSS (f).
(j) Food-to-microorganism ratio (F/M).
(k) Effluent soluble BODr (S ).
5 e
(2) Adjust the BOD removal rate constant for temperature.
K = K 0(T~20)
where
KT = rate constant for desired temperature
K = rate constant at 20°C
0 - temperature correction coefficient
T = temperature, °C
(3) Determine the size of the aeration tank.
a (S - S )Q
V = ^
(xv)(f)(b)
7-106
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29 Sep 78
where
V = aeration tank volume, million gal
a = fraction of BOD.- synthesized to degradable solids
o 5
S = influent BOD , mg/£
S = effluent soluble BOD , mg/£
e 5
Q = waste flow, mgd
avg
Xy = MLVSS, mg/£
f = degradable fraction of the MLVSS
b - endogenous respiration rate, I/day
(h) Calculate the detention time.
where
t = detention time, hr
V = volume, million gal
Q = flow, mgd
(5) Assume the organic loading and calculate detention time.
T M
where
t = detention time, days
S = influent BOD , mg/£
7-107
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29 Sep 78
Xy = volatile solids in raw sludge, mg/£
F/M = organic loading (food-to-microorganism ratio)
and select the larger of two detention times from (It) or (5).
(6) Determine the oxygen requirements allowing 60 percent for
nitrification during summer.
° = a'S8'l + b'l + 0.6(1*.
2
where
0 = oxygen required, Ib/day
a' = fraction of BOD oxidized for energy
S^ = BOD removed, mg/£
Q = average waste flow, mgd
"b1 = endogenous respiration rate, I/day
Xy = MLVSS, mg/£
V = aeration tank volume, million gal
TKN = total Kjeldahl nitrogen, mg/&
and calculate oxygen requirement (>1.5)
lb 0 0
where
0 = oxygen, required, Ib/day
Q = waste flow, mgd
S = BOD removed, mg/£
7-108
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(7) Design aeration system and check horsepower supply for complete
mixing against horsepower required for complete mixing >_0.1 hp/1000 gal.
(a) Diffused aeration system.
!_ Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer
(5-8 percent).
b 0^ transfer in waste/00 transfer in water «O.9-
— 2 c.
c_ 0 saturation in waste/0 saturation in water =0.9-
d Correction factor for pressure %1.0.
2 Select summer operating temperature (25-30°C) and determine
m standard tables) 0 saturation.
3_ Adjust standard transfer efficiency to operating conditions.
OTE = STE J- * . .„ - a(l.02)T 2°
y« ->-1
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(C \ =0 saturation at selected summer temperature T, °C, mg/£
V S/rj-i 2
B = 0 saturation in waste/0 saturation in water =^0.9
p = correction factor for pressure a£L.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/H
a = 0 transfer in waste/0 transfer in water «O.9
T = temperature, °C
k_ Calculate required air flow.
7-109
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29 Sep 78
R =
a / Ib 0 \ . . .
(OTE) [0.0176 —-—— \llkhO ^-JV
\ .pj.3 . A day/
\ ft air/
where
R = required air flow, cfm/1000 ft
Q,
0 = oxygen required, lb/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(b) Mechanical aeration system.
!_ Assume the following design parameters.
a_ Standard transfer efficiency, lb/hp-hr (0 dissolved oxygen, 20°C,
and tap water).
b 0 transfer in waste/0 transfer in water asO.9-
d d
c 00 saturation in waste/00 saturation in water «=0.9.
— c. c.
d_ Correction factor for pressure »1.0.
2_ Select summer operating temperature (25-30°C) and determine (from
standard tables) 0^ saturation.
3_ Adjust standard transfer efficiency to operating conditions.
|7c ) (e)(P) - c I
T1 I T—PD
OTE = STE „ .^ a(l.02)
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
\ = 0 saturation at selected summer temperature T, °C, mg/£
/'ri C-
S/rji
T-110
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29 Sep 78
g = 0 saturation in waste/0 saturation in water =0.9
p = correction factor for pressure ssl.O
C = minimum dissolved oxygen to be maintained in the basin
L
> 2.0 mg/£
a = 0 transfer in waste/0? transfer in water ==0.9
T = temperature, °C
Calculate horsepower requirement.
hp =
OTEhFh?
where
hp = horsepower required/1000 gal
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, Ib 02/hp-hr
V = volume of basin, gal
5_ Calculate sludge production.
AXy = 8.3Ma(Sr)(Q) - (b)(Xv)(V) - Q(SSeff) + Q(VSS)f + Q(SS - VSS)]
where
A)L = volatile sludge produced, Ib/day
a = fraction of BOD synthesized
S = BOD removed, mg/£
Q = waste flow, mgd
b = endogenous respiration rate, I/day
7-111
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Xy = volatile solids in raw sludge, mg/£
V = aeration tank volume, million gal
SSeff = effluent suspended solids, ing/i
VSS = volatile suspended solids in influent, mg/£
f' = degradable fraction of the MLVSS
VSS = volatile suspended solids, mg/£
6_ Calculate solids produced per pound of BOD removed.
Ib solids AXV
Ib BODr Q(S - S
where
AX^ = volatile sludge produced, Ib/day
Q = waste flow, mgd
SQ = influent BOD mg/£
S = effluent soluble BODC, mg/£
e j
7. Calculate the solids retention time.
XB(V)(8.3U)
t = a
AXy
where
t = solids retention time, days
S
X = MLSS, mg/£
a
V = volume of aeration tank, million gal
AXV = volatile sludge produced, Ib/day
7-112
-------
8 Determine the effluent soluble BOD,..
~~ 5
S 1 + kXt
o V
where
S = soluble effluent BOD, mg/£
S = influent BOD, mg/£
k = rate constant, 1/mg/hr
Xy = MLVSS, mg/£
t = aeration time, hr
9. Calculate sludge recycle ratio.
3 X
r a
Q X - X
avg u a
vhere
Q = volume of recycled sludge, mgd
^ = average flow, mgd
EM 1110-2-501
Part 1 of 3
29 Sep 78
X = MLSS, mg/£
Qu
X = suspended solids concentration in returned sludge, mg/l
10 Calculate the nutrient requirements for nitrogen
N = 0.123AX^
and phosphorus
P = 0.026AX
where
AX^ = sludge produced, Ib/day
7-H3
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29 Sep 78
7-39- Output Data.
a. Aeration Tank.
(1) Reaction rate constant, 1/mg/hr.
(2) Sludge produced per BOD removed.
(3) Endogenous respiration rate (b, b').
(M 0 utilized per BOD removed.
(5) Influent nonbiodegradable VSS, mg/£.
(6) Effluent degradable VSS, mg/£.
(7) lb BOD/lb MLSS-day (F/M).
(8) Mixed liquor SS, mg/£ (MLSS).
(9) Mixed liquor VSS, mgA (MLVSS).
(10) Aeration time, hr,
(11) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
(13) Sludge produced, Ib/day.
(ih) Nitrogen requirement, Ib/day.
(15) Phosphorus requirement, Ib/day.
(16) Sludge recycle ratio, percent.
(17) Solids retention time, days.
"b. Diffused Aeration System
(l) Standard transfer efficiency, percent.
(2) Operating transfer efficiency, percent.
(3) Required air flow, cfm/1000 ft3
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29 Sep 78
c. Mechanical Aer'ation System.
(l) Standard transfer efficiency, Ib 0 /hp-hr.
(2) Operating transfer efficiency, Ib 0 /hp-hr.
(3) Horsepower required.
7-^0. Example Calculations (Eckenfelder's Approach).
a. Assume the following design parameters.
(1) a - 0.73
(2) a' = 0.52
(3) b = 0.075/day, V = 0.15/day
(If) a = 0.56
o
(5) f = 0.140
(6) MLSS = X = ^000 mg/£
£t
(7) MLVSS = Xy = 2800 mg/£
(8) 0 = 1.02
(9) f = 0.53
(10) F/M = 0.10
(11) Sg = 10 mg/£
b. Adjust the BOD removal rate constant for temperature.
where
= removal rate constant at desired temperature, °C
= removal rate constant at 20°C, 0.0010
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29 Sep 78
e = 1,02
T = 15°C
KT = 0.001(1.02)15~2°
Km = 0.0009
c. Determine the size of the aeration tank.
a (S - S )Q
v - '^
v"
where
V = volume of aeration tank, million gal
a = 0.56
o
S = influent BOD , 200 mg/£
Sg = effluent soluble BOD 10 mg/£
Qa = average flow, 1.0 mg/£
Xy = MLVSS, 2800
f = 0.53
"b = 0.075/day
0.56(200 - 10)1.0
2800(0.53)0.075
V = 0.96 million gallons
d. Calculate detention time
24
7-116
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29 Sep $8
where
t = detention time, hr
V = volume, 0.96 million gal
Q = average flow, 1.0 mgd
t = 23 hr
e. Assume organic loading and calculate detention time.
u ~ yF/M)
where
t = detention time, hr
S = influent BOD_, 200 mg/£
o 5
X = MLVSS, 2800 mg/£
F/M =0.10
- 2M200)
2800(0.10)
t = 17 hr
Select longer detention time, t = 23 hr
f. Determine oxygen requirements allowing 60 percent for nitrifi-
cation during summer.
7-117
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29 Sep 78
where
00 = oxygen required, lb/day
a' = 0.56
s = s - s = 190 vis/a
r c e
Q = average flow, 1.0 mgd
"• * o
b1 = 0.15/day
Xy = MLVSS, 2800 mg/£
V = voluiae of aeration tank, 0.96 million gal
^•57 ~ parts oxygen required per part TKW
TKN = total Kjeldahl nitrogen, 30 mg/£
0^ = [C.5^(190)1-0 + 0.15(2800)0.96 + 0.6(It. 57)30(1. 0)]8.
0,,; = 4936 lb/day
Calculate oxygen required per pound of BOD removed.
Q (S
avg r
where
0 = oxygen required, kyz6 lb/day
Q = average flow, 1.0 mgd
avg &
S = BOD removed, 190 mg/£
lb 0
2_ _ ^936
lb BODr 190(1.0)8.
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29 Sep 78
Ib 00
*- = 3.0 > 1.5 (OK)
Ib BOD
r
h. Design aeration system (diffused).
(l) Assume the following design parameters.
(a) STE =5.0$
(b) a = 0.9
(c) 3 = 0.9
(d) p = 1.0
(2) Select summer operating temperature and determine oxygen
saturation (C), T = 25°C , and cs =8.2 mg/A .
g
(3) Determine operating transfer efficiency.
[(ca)
UXp> -
' m ^ I ft! op,
OTE = STE ~-^ —-=*• a (1.0?)J U
where
OTE = operating transfer efficiency, percent
STE = standard operating efficiency, 5.0 percent
(C \ =8.2 mg/£
V S/T
e = 0.9
P = i.o
9.17 = 0,. saturation at 20°V
C = minimum dissolved oxygen concentration, 2.0 mg/£
a = 0.9
T = 25°C
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29 Sep 78
= 5.0 [8.2(0.9)1.0 - 2.01 0.9(1.02)25-20
y •->-1
OTE = 2.'
Calculate the required air flow.
00(io)57.W
R =
OTE(0.0176)1UUO(V)106
where
o
R = required air flow, cfm/1000 ft
a
0 = oxygen required, ^936 Ib/day
OTE = operating transfer efficiency, 2.9%
0.0176 = Ib 0 /ft3 air
V = volume of aeration tank, 0.96 million gal
a 2. 9(0. 0176)1^0(0. 96)106
R = 52.3 cfm/1000 ft3
a
(5) Calculate horsepower required.
0^(1000)
hp =
OTE(2lOV(lO )
where
0 = oxygen required, ^936 Ib/day
OTE = operating transfer efficiency, 2.9%
V = volume of aeration tank, 0.96 million gal
7-120
-------
hp =
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U936(1000)
2.9(2*00.96(106)
hp = 0.07U hp/1000 gal < 0.1 hp/1000 gal
Use 0.1 hp/1000 gal
Total hp = 0.1(V)1000
hp = 0.1(0.96)1000
hp = 96 hp; use 100 hp
i. Calculate sludge production.
AXy = [a(Sr)(Q) - (b)(Xy)(V) - Q(SSeff) + Q(VSS)f + Q(SS -
where
AX^ = sludge produced, Ib/day
a = 0.73
S = BOD removed, S - S = 190 mg/£
Q = average flow, 1.0 mgd
t = 0.075/day
Xy = MLVSS, 2800 mg/£
V = volume of aeration tank, 0.96 million gal
SS = solids in effluent, 20 mg/£
VSS = volatile solids in influent, 150 mg/£
f = 0.53
SS = solids in influent, 200 mg/Jl
7-121
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= [0.73(190)1.0 - 0.075(2800)0.96 - 1.0(20)
+ 1.0(150)0.53 + 1.0(200 - 150)]8.3U
AX = 389 Ib/day
. Calculate solids produced per pound of BOD removed.
113 solids _ AXV _
lb BOD
where
AX^ = sludge produced, 389 Ib/day
Q = average flow, 1.0 mgd
S = influent BOD, 200 mg/£
o
S = effluent BOD, 10 mg/£
e
solids _ _ 389
_
lb BOD 1.0(200 - 10)8.3^
k. Calculate solids retention time.
X V8.3H
. a
vhere
t = solids retention time, days
s
X = MLSS, >*000 mg/£
a
V = volume of aeration tank, 0.96 million gal
AX^ = solids produced, 389 Ib/day
7-122
-------
_ ^000(0.96)8.:
s " 389
t = 82 days
1. Determine effluent soluble BOD .
S ..
e 1
SQ 1
vhere
S = soluble effluent BOD, mg/£
e
S = influent BOD, 200 mg/H
o
k = reaction rate constant, 0.0009
X = MLVSS, 2800 mg/£
t = detention time, 23 hr
S
200 1 + (0.0009)2800(23)
S =3.^ mg/£
m. Calculate sludge recycle ratio.
X
a
} X - X
avg u a
where
Q = recycle flow, mgd
1 = average flow, 1.0 mgd
avg
X = MLSS, 1^000 mg/i
a
X = underflow concentration, 10,000 rag/a
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1.0 10,000 - 1+,000
Q =0.67 mgd
n. Calculate nutrient requirements for nitrogen.
N = 0.123AX^
N = 0.123(389)
N = hQ It/day
for phosphorus
P = 0.026AX
v
P = 0.026(389)
P = 10 Ib/day
N in influent = 30 mg/«,(Q)8.3l*
= 30(1.0)8.3^
= 250 lt>/day > U8 It/day
N to "be added = none
P in influent = 15 mg/£(Q)8.3It
= 15(1.0)8.3^
= 125 Ib/day > 10 Ib/day
P to be added = none
7-^1. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
7-121*
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7-U2. Bibliography.
a. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Wastewater Control Engineering," 1969.
b. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. S.
Environmental Projection Agency, Washington, D. C.
c. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, and 1968, Water Pollution Control Federation,
Washington, D. C.
d. Bargman, R. D. and Borgerding, J.. , "Characterization of the
Activated Sludge Process," Report No. R2-73-22U, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
e. Busch, A. W., Aerobic Biological Treatment of Wastewaters,
Oligodynamics Press, 1971-
f. Center for Research, Inc., University of Kansas, "Oxygen Con-
sumption in Continuous Biological Culture," Report No. 17050DJS, May
1971, U. S. Environmental Protection Agency, Washington, D. C.
g. City of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
V
h. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
i. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Briarcliff Manor, New York.
j. Eckenfelder, W. W., Jr., Water Quality Engineering for
Practicing Engineers, Barnes and Nobel, New York, 1970.
k. Eckenfelder, W. W., Jr., "Activated Sludge and Extended
Aeration," Process Design in Water Quality Engineering - New Concepts
and Developments, 1971, Vanderbilt University, Nashville, Tenn.
7-125
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Part 1 of 3
29 Sep 78
1. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970. '
m. Eckenfelder, W. W., Jr., and O'Connor, 0. J., Biological Waste
Treatment, Pergamon Press, New York, 1961.
n. Gaudy, A. G., Jr., and Gaudy, E. T., "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No. 17090-
FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington, D. C.
o. Goodman, B. L. , Design Handbook of Wastewater Systems: Domestic.
Industrial, Commercial, Technomic, Westport, Conn., 1971.
p. Goodman, B. L. and Englande, A. J., Jr., "A Consolidated Approach
to Activated Sludge Process Design," Conference on Toward a Unified Con-
cept of Biological Waste Treatment Design, 5-6 Oct 1972, Atlanta, Ga.
q. Lawrence, A. W. and McCarty, P. L., "Unified Basis for Biolog-
ical Treatment Design and Operation," Journal, Sanitary Engineering
Division, American Society of Civil Engineers, Vol 96. SA.VT 1Q707
r. Maier, W. J., "Biological Removal of Colloidal Matter from
Wastewater," Report No. R2-73-1V7, Jun 1973, U. S. Environmental Pro-
tection Agency, Washington, D. C.
s. McCarty, P. L., and Brodersen, C. F., "Theory of Extended
Aeration Activated Sludge," Journal, Water Pollution Control Federation.
Vol 3!*, 1962, pp 1095-1103. ' ~ ~~
t. McKinney, E. E., Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
u. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
v. Okun, D. A., "System of Bio-Precipitation of Organic Matter
from Sewage," Sewage Works Journal, Vol 21, No. 5, 19^9, pp 763-79!*.
w. Smith, H. S., "Homogeneous Activated Sludge Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering,
Vol h, Jul 1967, pp 1+6-50. ~~
7-126
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29 Sep 78
x. Smith, R., and Eilers, R. G., "A Generalized Computer Model for
Steady-State Performance of the Activated Sludge Process," FWQA Report
No. TWRC-15, Oct 1969, Robert A. Taft Water Research Center, Cincinnati,
Ohio.
y. Stensel, H. D. and Shell, G. L., "Two Methods of Biological
Treatment Design," Journal, Water Pollution Control Federation, Vol 1*6,
Feb 197U, pp 2T1-283.
z. Stewart, M. J., "Activated Sludge System Variations - Specific
Applications," The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
aa. Toerber, E. D., "Full Scale Parallel Activated Sludge Process
Evaluation," Report No. R2-72-065, Nov 1972, U. S. Environmental Protec-
tion Agency, Washington, D. C.
bb. Weston, R. F., "Design of Sludge Reaeration Activated Sludge
Systems," Journal, Water Pollution Control Federation, Vol 33, No. 7,
1961, pp 7^8-757-
7-127 (next page is 7-129)
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Section VII. MODIFIED OR HIGH-RATE AERATION ACTIVATED SLUDGE
T-U3. Background.
a. Modified or high-rate aeration activated sludge is defined as
"a modification of the activated sludge process in which a shortened
period of aeration is used with a reduced quantity of suspended solids
in the mixed liquor," (para T-50a). The flow diagram is the same as
that for the plug-flow process (fig. 7-6); the difference in the process
INFLUENT
AERATION TANK
SLUDGE RETURN
EFFLUENT
WASTE
SLUDGE
Figure 7-6. Plug flow activated sludge.
design parameters (shorter detention time and lower mixed liquid sus-
pended solids) results in less air requirements and, hence, less power
consumption. Modified aeration is also characterized by a poor settling
sludge and low BOD removal efficiencies.
b. Process design parameters and discussion of applications are
given in References c, t, and y in paragraph 7-50 below.
1-kh. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variabil-
ity, a statistical distribution should be provided.
b. Wastewater Strength.
(l) BOD (soluble and total), mg/£.
(2) COD and/or TOC (maximum and minimum), mg/JU
(3) Suspended solids, mg/£.
(h) Volatile suspended solids (VSS), mg/Jl.
7-129
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29 Sep 78
(5) Nonbiodegradable fraction of VSS, mg/£.
c. Other Characterization.
(1) PH.
(2) Acidity and/or alkalinity, mg/£.
(3) Nitrogen,1 mg/£.
(h) Phosphorus (total and soluble), mg/£.
(5) Oils and greases, mg/£.
(6) Heavy metals, mg/£.
(7) Toxic or special characteristics (e.g., phenols), mg/£.
(8) Temperature, °F or °C.
d. Effluent Quality Requirements.
(1) BOD mg/£.
(2) SS, mg/£.
(3) TO, mg/£.
P, mg/£.
(5) Total nitrogen (TKN + NO -W) , mg/£.
(6) Settleable solids, mg/£.
5. Design Parameters.
a. Reaction rate constants and coefficients.
The form of nitrogen should be specified as to its biological
availability (e.g., KH or Kjeldahl).
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Eckenfelder
k 0.0007-0.002 £/mg/hr
a 0.73
a' 0.52
b 0.075/day
b' 0.15/day
f O.UO
f 0.53
b. F/M = (1.5-5.0).
c. Volumetric loading = 100-250.
d. t = (1.5-3-0) hr.
e. t = (0.2-0.5) days.
s
f. MLSS = (200-1000) mg/a.
g. MLVSS = (lllO-TOO) mg/Si.
h. Qr/Q = (0.05-0.15).
i. Ib 02/lb BODr = (0.5-0.75).
j. Ib solids/lb BOD = (0.65-0.85).
k. Efficiency = (50-60 percent).
5. Design Procedure (Eckenfelder's Approach).
a. Assume the following design parameters when unknown.
(l) Fraction of BOD synthesized (a).
(2) Fraction of BOD oxidized for energy (a1).
7-131
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(3) Endogenous respiration rate (b and b')
(U) Mixed liquor suspended solids (MLSS).
(5) Mixed liquor volatile suspended solids (MLVSS).
(6) Food-to-microorganism ratio (F/M).
(T) Temperature correction coefficient (Q}.
(8) Wonbiodegradable fraction of VSS in influent (f).
(9) Degradable fraction of the MLVSS (f).
b. Determine the size of the aeration tank by first determining
the detention time.
2kS
t =
where
t = detention time, hr
SQ = influent BOD, mg/£
Xy = MLVSS, mg/l
F/M = food-to-microorganism ratio
c. Calculate the volume of aeration tank.
v = Qavg(
where
V = volume of aeration tank, million gal
Qavg = average daily flow, mgd
t = detention time, hr
d. Calculate oxygen requirements.
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29 Sep 78
at
or
00 = a'(S )(Q ) (8.310
2 r avg
where
ao/at = oxygen uptake rate, mg/£/hr
a* = fraction of BOD oxidized for energy
S = BOD removed (S - S ), mg/£
t = detention time, hr
0 = oxygen uptake rate , l"b/aay
Q = average flow rate, mga
avg
e. Check the oxygen supplied against pounds of BOD removed
(0.5-0.7).
o2/ib
where
0 = oxygen required, Ib/day
Q = flow, mgd
S = BOD removed, mg/£
f. Design Aeration System.
(l) Diffused aeration system.
(a) Assume the following design parameters.
!_ Standard transfer efficiency, percent, from manufacturer
5-8 percent) .
7-133
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2_ 0 transfer in waste/0? transfer in water «0.9.
_3_ 00 saturation in waste/0^ saturation in water aO.9.
k_ Correction factor for pressure s»1.0.
(b) Select summer operating temperature (25-30°C) and determine
(from standard tables) 0^ saturation.
CL
(c) Adjust standard transfer efficiency to operating conditions.
[(Cs)
B) 2,0 mg/£
a = 0 transfer in waste/0 transfer in water »<3.9
T = temperature, °C
(d) Calculate required air flow.
0
R =
a / Ib 0
I
(OTE) 0.0176 -rr—MpMo
V ft3 air/V
day I
\ X O t-liJ-J. / > '
where
R = required air flow, cfm/1000 ft3
3-
7-13U
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0? = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
(2) Mechanical aeration system.
(a) Assume the following design parameters.
JL Standard transfer efficiency, lb/hp-hr (0 dissolved oxygen,
20°C, and tap water).
2_ Q transfer in waste/0p transfer in water ssO.9.
3. Og saturation in waste/0? saturation in water »0.9.
h_ Correction factor for pressure ad.O.
(b) Select summer operating temperature (25-30°C) and determine
m standard tables) 0 saturation.
(c) Adjust standard transfer efficiency to operating conditions.
- CLI
OTE = STE x =J- a(l.02)T 2°
-J
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(Cs) = 0 saturation at selected summer temperature T, °C, mg/£
3=0 saturation in waste/0_ saturation in water a^O.Q
d. cL
p = correction factor for pressure sd..O
C = minimum dissolved oxygen to be maintained in the basin
L >2.0 '
7-135
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a = 0 transfer in waste/0 transfer in water
T = temperature, °C
(d) Calculate horsepower requirement.
°2
hp = — - x 100°
where
hp = horsepower required/1000 gal
0 = oxygen required, Ib/day
GTE = operating transfer efficiency
V = volume of basin, gal
(e) Calculate sludge production.
AXy = [aSrQavg + fQ(VSS) + Q(SS - VSS)] 8.3^
where
AT = sludge produced, Ib/day
a = fraction of BOD removed synthesized to cell material
S = BOD removed, mg/£
Q = average flow, mgd
f = nonbiodegradable fraction of VSS in influent
Q = flow, mgd
VSS = volatile suspended solids, mg/£
SS = suspended solids in influent, mg/Jt
7-136
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(f) Check AX against 0.65-0.85 lb solids/lb
AXV
Ib solids _
(lb BOD ) S
where
AX^ = sludge produced, Ib/day
S = BOD removed, mg/£
Q = flow, mgd
(g) Calculate sludge recycle ratio.
Q X
^r a
Q X - X
u a
where
Q = volume of recycled sludge, mgd
Q = flow, mgd
X = MLSS
a
X = suspended solids concentration in returned sludge,
u
(h) Calculate solids retention time.
V(X )8.31t
SET = ^ (% volatile)
where
SRT = solids retention time, days
V = volume of basin, million gal
7-137
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X = MLSS
a
AX = sludge produced, Ib/day
a
(i) Estimate effluent BOD .
BOD)
BOD
5eff
where
S = influent BOD , mg/£
BOD = BOD removed, percent
(j) Determine nutrient requirements for nitrogen
N = O.iaSAX^
and phosphorus
P = 0.026AXy
where
AX = sludge produced, Ib/day
and check against BOD:W:P = 100:5:1.
T-Vf. Output Data.
a. Aeration Tank.
(l) Reaction rate constant, 1/mg/hr.
(2) Sludge produced per BOD removed.
(3) Endogenous respiration rate (t>, b1).
(^) 0 utilized per BOD removed.
(5) Influent nonbiodegradable VSS, mg/SL.
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(6) Effluent degradable VSS,
(T) lb BOD/lb MLSS-day (F/M ratio).
(8) Mixed liquor SS, mg/£ (MLSS).
(9) Mixed liquor VSS, rngA (MLVSS).
(10) Aeration time, hr.
(11) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
(13) Sludge produced, Ib/day.
(lU) Nitrogen requirement, Ib/day.
(15) Phosphorus requirement, Ib/day.
(16) Sludge recycle ratio, percent.
(IT) Solids retention time, days.
3
(18) Volumetric loading, lb BOD/1000 ft .
b. Diffused Aeration System.
(l) Standard transfer efficiency, percent.
(2) Operating transfer efficiency, percent.
(3) Required air flow, cfm/1000 ft .
c. Mechanical Aeration System.
(1) Standard transfer efficiency, lb 02/hp-hr.
(2) Operating transfer efficiency, lb 02/hp-hr.
(3) Horsepower required, hp.
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T-^8. Example Calculations.
a. Assume the following design parameters,
(1) a = 0.73
(2) a' = 0.52
(3) b = 0.075/day, V = 0.15/day
(1*) MLSS = X =600 mg/£
3,
(5) MLVSS = Xy = 1*20 mg/£
(6) F/M = 3.0
(7) 9 = 1.02
(8) f = 0.1*0
(9) f = 0.53
b. Calculate the detention time.
2US
t =
X^F/M)
where
t = detention time, hr
S = influent BOD, 200 mg/Z
Xy = MLVSS, 1*20 mg/£
F/M = food to microorganism, 3.0
- 2M200)
t ~ 1*20(3.0)
t = 3.8 hr
c. Calculate the volume of the aeration tank.
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29 Sep 78
V = Qavg 2?
where
V = volume of aeration tank, million gal
0 = average flow, 1.0 mgd
avg
t = detention time, 3-8 hr
V = 1.
V = 0.158 million gal
d. Calculate the oxygen requirements.
where
0 = oxygen requirements, It/day
a1 = 0.52
S = BOD removed (S - S ) = 200 - 100 = 100 mg/A
Q = average flow, 1.0 mgd
avg
0 = 0.52(100)1.0(8.
0 = 1*31* It/day
e. Check oxygen supplied against pounds of BOD removed (0.5-0.7)
°2
It 0/1* BODr = Q(s )8>3U
r
where
0 = oxygen required, ^3^ Ib/day
7-lUl
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29 Sep 78
Q = average flow, 1.0 mgd
^ = BOD removed, 100 mg/£
lb O./lb BOD -
2'- ^ r 1.0(100)8.3U
lb 02/lb BODr = 0.52 (OK)
f. Design aeration system.
(l) Assume the following parameters.
(a) STE = 5.0$
(b) a = 0.9
(c) 3 = 0.9
(d) p = l.o
(2) Select summer operating temperature and determine 0 saturation
I - 25 C, 02 = 8.2 mg/£. 2
(3) Adjust standard transfer efficiency to operating conditions.
[(C } 0p - CT~]
I \ s y ]_j i
OTE = STE != ±j-^ =! a(l.02)T-20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5.0 percent
(Cs) = °2 saturatlon at summer temperature, 8.2 mg/£
3 = 0.9
P = 1.0
C = minimum dissolved oxygen, 2.0 mg/£
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29 Sep 78
a = 0.9
T = summer temperature, 25°C
OTE = 5>0 [8.2(0.9)1.0 - 2.0] (0.9)1.0225-20
OTE =2.9%
(k) Calculate horsepower requirement.
0- 1000
hp = T
OTE(2U)V(10
where
hp = horsepower required/1000 gal
0 = oxygen required, ^3^ Ib/day
OTE = operating transfer efficiency, 2.9%
7 = volume of aeration tank, 0.158 million gal
hP = — f.
2.9(2^)0.158(10°)
hp = 0.01+ hp/1000 gal < 0.1 hp/1000 gal required for mixing.
Therefore
hp - 0.1 hp/1000 gal
hp = 0.1(7)1000
hp = 0.1(0.158)1000
hp = 15.8 hp, use 20 hp
g. Calculate sludge production.
H f(Q)VSS + Q(SS -
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29 Sep 78
where
AXy = sludge production, Ib/day
a = 0.73
S^ = BOD removed, 100 mg/£
Qavg = average flov, 1.0 mgd
f = O.hO
VSS = volatile suspended solids in effluent, 150 mg/Ji
SS = suspended solids influent, 200 mg/£
AXy = [0.73(100)1.0 + 0.1*0(1.0)150 + 1.0(200 - 150)]8.3U
AXy = 1526 Ib/day
h. Check AX. against 0.65-0.55 lb solids/lb BOD .
v r
lb solids _ AXy
Ib BODr ~ Sr(Q)8.3^
where
AXy = sludge produced, 1526 Ib/day
S^ = BOD removed, 100 mg/£
Q = average flow, 1.0 mgd
lb solids _ 1526
lb BOD^ 100(1.0)8.34
lb solids _
lb BOD ~ '
r
i. Calculate sludge recycle ratio.
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29 Sep 78
X
a
- Xa
where
Q = volume of recycled sludge, mgd
Q = average flow, mgd
X = MLSS, 600 mg/£
a
X = suspended solids in returned sludge, 10,000 mg/£
600
1.0 10,000 - 600
Q =0.06 mgd
j. Calculate solids retention time.
V(X )8.3M$ volatile)
SRT = —
AX
a
where
SRT = solids retention time, days
V = volume of aeration tank, 0.158 million gal
X = MLSS, 600 mg/£
Q,
AX = sludge produced, 1526 Ib/day
cl
volatile = 10%
vw - 0.158(600)6.3MO.7)
SRT
SRT =0.36 days
k. Estimate effluent BOD .
7-1*15
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29 Sep 78
BOD
BOD, = S 1 -
5 o\^ 100
vhere
S0 ~ influent BOD, 200 mg/£
BOD^ = BOD removed, 50$
= 100 mg/SL
1. Determine nutrient requirements for nitrogen
N = 0.123 AXy
N = 0.123(2180)
N = 268 Ib/day
for phosphorus
P = 0.026 AXy
P = 0.026(2180)
P = 57 Ib/day
N in influent = 30 mg/£ Q 8.3^
avg
= 30(1.0)8.34
= 250 Ib/day < 268 Ib/day
N to be added = 18 lb/day
P in influent = 15 mg/£ Q 8.3^
avg
= 15(1.0)8.34
= 125 Ib/day > 57 Ib/day
P to be added = none
7-11*6
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7-^9- Cost'Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
7-50. Bibliography.
a. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Wastewater Control Engineering," 1969.
b. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. S.
Environmental Protection Agency, Washington, D. C.
c. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sevage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, and 1968, Water Pollution Control Federation,
Washington, D. C.
d. Bargman, R. D. and Borgerding, J., "Characterization of the
Activated Sludge Process," Report No. R2-73-22^, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
e. Busch, A. W., Aerobic Biological Treatment of Wastewaters,
Oligodynamics Press, 1971-
f. Center for Research, Inc., University of Kansas, "Oxygen Con-
sumption in Continuous Biological Culture," Report No. 17050DJS, May
1971, U. S. Environmental Protection Agency, Washington, D. C.
g. dity of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report Wo. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
h. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
i. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 19&9* Environmental Science
Services, Inc., Briarcliff Manor, New York.
j. Eckenfelder, W. W., Jr., Water Quality Engineering for Practicing
Engineers, Barnes and Nobel, New York, 1970.
7-1^7
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Part 1 of 3
29 Sep 78
k. Eckenfelder, W. W., Jr., "Activated Sludge and Extended Aera-
tion," Process Design in Water Quality Engineering - New Concepts and
Developments, 1971, Vanderbilt University, Nashville, Tenn.
1. Eckerif elder, W. W. , Jr., and Ford, D. L. , Water Pollution
Control, Pemberton Press, New York, 1970.
m. Eckenfelder, W. W., Jr., and O'Connor, 0. J. , Biological
Waste Treatment, Pergamon Press, New York, 1961.
n. Gaudy, A. G., Jr., and Gaudy, E. T., "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No. 17090-
FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington, D. C.
o. Goodman, B. L., Design Handbook of Wastewater Systems: Domestic,
Industrial, Commercial, Technomic, Westport, Conn., 1971.
p. Goodman, B. L. and Englande, A. J., Jr., "A Consolidated Ap-
proach to Activated Sludge Process Design," Conference on Toward a
Unified Concept of Biological Waste Treatment Design, 5-6 Oct 1972,
Atlanta, Ga.
q. Lawrence, A. W. and McCarty, P. L., "Unified Basis for Biolog-
ical Treatment Design and Operation," Journal, Sanitary Engineering
Division, American Society of Civil Engineers, Vol 96, SA3, 1970.
r. Maier, W. J., "Biological Removal of Colloidal Matter from
Wastewater," Report No. R2-73-l1i7, Jun 1973, U. S. Environmental Pro-
tection Agency, Washington, D. C.
s. McKinney, R. E. , Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
t. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
u. Okun, D. A., "System of Bio-Precipitation of Organic Matter
from Sewage," Sewage Works Journal, Vol 21, No. 5, 19^9, pp 763-79^.
v. Smith, H. S., "Homogeneous Activated Sludge Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering,
Vol U, Jul 1967, pp 46-50.
7-1U8
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29 Sep 78
w. Smith, R. and Eilers, R. G., "A Generalized Computer Model for
Steady-State Performance of the Activated Sludge Process," FWQA Report
Mo. TWRC-15, Oct 1969, Robert A. Taft Water Research Center, Cincinnati,
Ohio.
x. Stansel, H. D. and Shell, G. L., "Two Methods of Biological
Treatment Design," Journal, Water Pollution Control Federation, Vol ^6,
Feb 197*1, PP 271-283.
y. Stewart, M. J., "Activated Sludge System Variations - Specific
Applications," The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
z. Toerber, E. D.., "Full Scale Parallel Activated Sludge Process
Evaluation," Report No. R2-72-065, Nov 1972, U. S. Environmental Pro-
tection Agency, Washington, D. C.
aa. Weston, R. F., "Design of Sludge Reaeration Activated Sludge
Systems," Journal, Water Pollution Control Federation, Vol 33, No. 7,
1961, pp 7^8-757-
7-1)49 (next page is 7-151)
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Section VIII. CONTACT STABILIZATION ACTIVATED SLUDGE
7-51- Background.
a. The contact stabilization process (fig. 7-7) is defined as "a
modification of the activated sludge process in which raw wastewater is
aerated with a high concentration of activated sludge for a short period,
usually less than 60 min to obtain BOD removal by absorption. The
solids are subsequently removed by sedimentation and transferred to a
stabilization tank where aeration is continued further to oxidize and
condition them before their reintroduction to the raw wastewater flow"
(para 7-58a).
INFLUENT
ALTERNATE
WASTE
SLUDGE
CONTACT TANK
EFFLUENT
STABILIZATION
TANK
SLUDGE RETURN
WASTE SLUDGE
Figure 7-7. Contact stabilization activated sludge.
b. Contact stabilization was developed to take advantage of the
absorptive properties of the sludge floe. Contact stabilization
achieves absorption in the contact tank, and oxidation and synthesis
of removed organics occur in a separate aeration tank.
c. The volume requirement for aeration is approximately one-half
of that of a conventional plug-flow unit. Therefore, it is often
possible to double the capacity of an existing plug-flow plant by simply
repiping or making minor changes in aeration equipment.
d. References h, o, t, v, and y in paragraph 7-58, discuss the
contact stabilization variation and suggest rules of thumb for the
design parameters.
7-52. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variability,
a statistical distribution should be provided.
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b. Wastevater Strength.
(1) BOD (soluble and total), mg/S..
(2) COD and/or TOG (maximum and minimum), mg/S,.
(3) Suspended solids, mg/S,.
(4) Volatile suspended solids (VSS), mg/S,.
(5) Nonbiodegradable fraction of VSS, mg/S,.
c. Other Characterization.
(1) PH.
(2) Acidity and/or alkalinity, mg/S,.
(3) Nitrogen, mg/S,.
(4) Phosphorus (total and soluble), mg/S,.
(5) Oils and greases, mg/S,.
(6) Heavy metals, mg/S,.
(7) Toxic or special characteristics (e.g., phenols), mg/S,.
(8) Temperature, °F or °C.
d. Effluent Quality Requirements.
(1) BOD5, mg/A.
(2) SS, mg/£.
(3) TKM, mg/£.
(4) P, mg/Jl.
(5) Total nitrogen (TKW + No - N), mg/S,.
The form of nitrogen should be specified as to its biological
availability (e.g., NH or Kjeldahl).
7-152
-------
(6) Settleatile solids, mg/£.
7.53. Design Parameters.
a. Contact tank detention time, t^ .
t1 = (0.5-1-0) hr
b. System organic loading (F/M).
F/M = (0.2-0.6).
c. Volumetric loading = 60-75-
d. Stabilization tank detention time,
t = (2-U) hr
e. Contact tank MLSS, X .
CtL.
X = (2500-3500) mgA
ac
f . Contact tank .MLVSS, Xvc .
X = O.TX = (1750-2^50) mg/£
vc ac
a;. Stabilization tank MLSS, X .
•-> do
X = (itOOO-8000) mg/A
as
h. Stabilization tank MLVSS, X^s .
X = (2800-5600) mg/fc
vs
i. Air requirement (lb 02/lb BODr).
Ib 02/lb BODr = 1.25-1-5
j. lb solids/lb BODr = (0.2-O.U).
k. Recycle ratio,
Qr/Q = (0.25-1.0)
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1. Efficiency = (>90 percent).
7-5^- Design Procedure.
a. Assume the following design parameters.
(l) Aeration time in contact tank, hr.
(2) Aeration time in stabilization tank, hr.
(3) MLSS in contact tank, mg/£.
(4) MLSS in stabilization tank, mg/£.
(5) MLVSS in contact tank, mg/£.
(6) MLVSS in stabilization tank, mg/£.
(7) 0 requirements, Ib/day.
(8) Sludge produced, Ib/day.
b. Determine contact tank volume.
Vc =
where
V = volume of contact tank, million gal
Q = average flow, mgd
t = detention time in contact tank, hr
c. Determine stabilization tank volume.
V =
s
where
V = volume of stabilization tank, million gal
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Q = average flow, mgd
avg
t = detention time in stabilization tank, hr
d. Calculate system organic loading and check against desired
loading .
Q (S )
(F/M) = _ ayg o
^/M;system V (X ) + V (X )
c vc s vs
where
F/M = food-to-microorganism ratio
Q = average flow, mgd
avg
S = influent BOD , mg/£
V = volume of contact tank, million gal
X = MLVSS in contact tank, mg/£
V = volume of stabilization tank, million gal
S
X = MLVSS in stabilization tank, mg/£
e. Calculate volumetric loading and check against desired loading.
, Q (S )(62.10
ib/iooo ft3 =
(v + v )
c s
where
Q = average flow, mgd
S = influent BOD , mg/£
V = contact tank volume, million gal
V = stabilization tank volume, million gal
o
7-155
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f. Calculate the system oxygen required and select 1.25-1 5 lb
0 /lb BOD .
0 = (1.25-1.5)QflTO x S (8.3k)
£• avg r
where
02 = required oxygen, Ib/day
Sivg = averaSe flow, mgd
S^ = BOD removed (S - S ), mg/£
Supply approximately one-half of 0 for contact tank and one-half for
stabilization tank.
g. Design aeration system.
(l) Diffused aeration system.
(a) Assume the following design parameters.
1_ Standard transfer efficiency, percent, from manufacturer
(5-8 percent).
2_ 0 transfer in waste/00 transfer in water s£ 9
<- d.
3_ 02 saturation in waste/0 saturation in water «0.9.
h_ Correction factor for pressure «1.0.
(b) Select summer operating temperature (25-30°C) and determine
m standard tables) 0 saturation.
(c) Adjust standard transfer efficiency to operating conditions.
OTE = STE t T 17 i a(l.02)T"20
where
OTE = operating transfer efficiency, percent
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STE = standard transfer efficiency, percent
(C \ =0 saturation at selected summer temperature T, °C, mg/£
V S/rji '-
3=0 saturation in waste/0 saturation in water x£).9
p = correction factor for pressure sJ_.0
C = minimum dissolved oxygen to be maintained in the basin
L > 2.0 mg/£
a = 0 transfer in waste/0 transfer in water stO.9
T = temperature, °C
(d) Calculate required air flow.
a / It 0 '
(OTE)lo.0176 —
\ ft air,
where
R = required air flow, cfm/1000 ft
a
0 = required oxygen, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin (V + V ), gal
S »—
(2) Mechanical aeration system.
(a) Assume the following design parameters.
!_ Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
2_ 0 transfer in waste/0 transfer in water ssO.9-
3_ 0 saturation in waste/0 saturation in water ssO.9.
k_ Correction factor for pressure sal.O.
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(b) Select simmer operating temperature (25-30°C) and determine
m standard tables) 0 saturation.
(c) Adjust standard transfer efficiency to operating conditions.
OTE = STE i - 9~rf - a(l.02)T~20
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
= 02 saturation at selected summer temperature T, °C, mg/£
3 = 0 saturation in waste/0 saturation in water ssO.9
p = correction factor for pressure «i.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 02 transfer in waste/0 transfer in water *Q.9
T = temperature, °C
(d) Calculate horsepower requirement.
°
X 100°
where
hp = horsepower required/lOOO gal
0 = oxygen required, Ib/day
OTE = operating transfer efficiency
V = volume of basin (V + V ) , gal
o C
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h. Determine sludge production. Select 0.2-0. U Ib solids/lb
= (0.2-O.U)Q(Sr)8.3U
where
AX_ = sludge produced, lb/day
Q = flow, mgd
S = BOD removed, mgA
r
i. Estimate effluent BOD .
/ BOD
= s i- r
ff 100
eff \
where
S = influent BOD , mg/£
o 5
BOD = BOD removed, percent
r
j. Determine nutrient requirements for nitrogen
N = 0.123AX^
and phosphorus
P = 0.026AXy
where
AX^ = sludge produced, Ib/day
and check against rule of thumb BOD:N:P = 100:5:1-
k. Determine recycle ratio required and check against 0.25-1.0.
X
ac
X - X
as ac
7-159
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29 Sep 78
where
Qp = volume of recycled sludge, mgd
Q = total flow, mgd
Xac = MLSS in contact tank, mg/£
Xas = MLSS in stabilization tank, mg/£
7-55. Output Data.
a. Aeration Tank.
(1) Ib BOD/lb MLSS-day.
(2) Mixed liquor SS contact tank, mg/£ (MLSS).
(3) Mixed liquor SS stabilization tank, mg/£ (MLSS)
(k) Aeration time contact tank, hr (t ).
c
(5) Aeration time stabilization tank, hr (t ).
s
(6) Volume of contact tank, million gal (V ).
(7) Volume of stabilization tank, million gal (V ).
(8) Oxygen required, Ib/day.
(9) Sludge produced, Ib/day.
(10) Nitrogen requirement, Ib/day.
(11) Phosphorus requirement, Ib/day.
(12) Sludge recycle ratio, percent.
(13) Volumetric loading, Ib BOD/million ft3
to. Diffused Aeration System.
(1) Standard transfer efficiency, percent.
7-160
s
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29 Sep 78
(2) Operating efficiency, percent.
(3) Required air flow, cfm/1000 ft .
c. Mechanical Aeration System.
(1) Standard transfer efficiency, lb 02/hp-hr.
(2) Operating transfer efficiency, l"b Og/hp-hr.
(3) Horsepower required.
7-56. Example Calculations.
a. Assume the following design parameters.
(l) Aeration time in contact tank, t.^ = 0.6 hr.
(2) Aeration time in stabilization tank, t^ = 3.0 hr.
(3) MLSS in stabilization tank, X = 6000 mg/£.
£lS
(U) MLSS in contact tank, X = 3000 mg/&.
Q,C
(5) MLVSS in contact tank, X^ = O.TXac = 2100 mg/fc.
(6) MLVSS in stabilization tank, Xys = 0.7X&s = ^200 mg/A.
(7) 0 requirements, 1.3 lb 02/lb BODr.
(8) Sludge produced, 0.3 lb solids/lb
b. Determine contact tank volume.
Vc = QavgV2T
where
V = volume contact tank, million gal
c
= average flow, 1.0 mgd
avg
t = detention time, 0.6 hr
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29 Sep ~78
v =
c
= 0.025 million gal
c. Determine stabilization tank volume.
v = Q ( -
s ^avg \ 2
where
Vs = volume stabilization tank, million gal
Q = average flow, 1.0 mgd
t = detention time, 3.0 hr
V =0.125 million gal
S
d. Calculate system organic loading (F/M = 0.2-0.6).
Q (S )
(F/M)
'
system V (X ) + V (X )
c vc' sv vsy
where
= system organic loading
a = average flow, 1.0 mgd
SQ = influent BOD , 200 mg/£
VG = volume of contact tank, 0.025 million gal
XTC = MLVSS in contact tank, 2100 mg/£
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29 Sep 78
V = volume of stabilization tank, 0.125 millron gal
s
X = MLVSS in stabilization tank, 1+200 mg/Ji
(F/M) - 1^(200
system 0.025(2100) + 0.125(^200)
(F/M)system= °-3^6 (°K)
e. Calculate volumetric loading and check against 60-75 lb/
1000 ft3.
, Q (S )(62.U)
lb/1000 ft3 = avg °
(vc + vs)io3
where
Q = average flow, 1.0 mgd
S = influent BOD, 200 mg/&
V = volume of contact tank, 0.025 million gal
V = volume of stabilization tank, 0.125 million gal
S
lb/1000 ft3 = 1.0(200)(62.10
(0.025 + 0.125)103
lb/1000 ft3 = 83.2, slightly high but OK
f. Calculate system oxygen required and select 1.25-1.5 lb 00/
I
r
lb BOD . 2
02 = (1.25 to 1-5)Q (Sr)8.3U
where
0 = oxygen required, Ib/day
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29 Sep 78
Qa = average flow, 1.0 mgd
S^ = BOD removed (200 - 10), 190 mg/£
02 = 1.3(1. 0)190(8. 3U)
0 = 2060 Ib/day
g. Design aeration system (diffused).
(l) Assume the following parameters.
(a) STE =5.0 percent
(b) a = 0.9
(c) 3 = 0.9
(d) p = l.O
(2) Select summer operating conditions (T = 25°C) and determine 0
saturation.
(cj = 8.2 mg/£
(3) Adjust standard transfer efficiency to operating conditions.
OTE = STE
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5 percent
(Cs) = °o saturation at T = 25°C, 8.2 mg/Jl
T
3 = 0.9
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29 Sep 78
p = 1.0
C = minimum dissolved oxygen concentration, 2.0 mg/£
L
9.17 = 0 saturation at 20°C
a = 0.9
T = 25°C
OTE = 5.0 [8.2(0.9)1.0-2.0] 0.9(1.02)25-20
y • •>-1
OTE = 2.9$
(4) Calculate required airflow.
0?(105)7.48
R =
a OTE(0.0176)l440(V)lO
vhere _
R = required airflow, cfm/1000 ft
El
0 = oxygen required, 2060 Ib/day
OTE = operating transfer efficiency, 2.9 percent
0.0176 = Ib 02/ft3 air
V = (V + V ) = 0.15 million gal
s c
_ _ 2060(10^)7.48
n —
a 2.9(0.0176)1440(0.15)106
R = 140 cfm/1000 ft3
a
h. Determine sludge production. Select (0.2-0.4) Ib solids/
Ib BOD
r'
= (0.2-0.4)Q(Sr)8.34
7-165
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where
AXV = sludSe Production, Ib/day
Q = average flov, 1.0 mgd
Sr = BOD removed, 190 mg/£
= 0.3(1.0)(190)(8.34)
AXy = U75 Ib/day
i. Estimate effluent BOD .
/ \ / BOD
(BOD ) = S (l 2
V 5/eff °\ 100
where
(BOD ) = effluent BOD
eff 5
So = influent BOD^, 200 mg/H
= BOD removed,
(BOD ) = 10 mg/£
v •''eff
J. Determine nutrient requirements for nitrogen
N = 0.123AX
N = 0.123(475 Ib/day)
N = 58.4 Ib/day
for phosphorus
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29 Sep 78
P = 0.026 AXy
P = 0.026(475 Ib/day)
P = 12.4 Ib/day
N in influent = 30 mg/£(Q )8.3^
£LV£>
= 30(1.0)8.31*
= 250 Ib/day >58.U
H to be added = none
P in influent = 15 mg/Jl(Q )8.3^
= 15(1.0)8.3*t
= 125 Ib/day >12.H
P to be added = none
k. Determine recycle ratio and check against (0.25-1.0).
Q X
r ac
X - X
as ac
where
Q = sludge recycle, mgd
Q = average flow, 1.0 mgd
X = MLSS in contact tank, 3000 mg/£
ac
X = MLSS in stabilization tank, 6000 mg/£
as
3000
_
1.0 6000 - 3000
Qr = 1.0
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T-57- Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
7-58. Bibliography.
a. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Waste-water Control Engineering," 1969.
b. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. S.
Environmental Protection Agency, Washington, D. C.
c. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, and 1968, Water Pollution Control Federation,
Washington, D. C.
d. Bargman, R. D. and Borgerding, J., "Characterization of the
Activated Sludge Process," Report No. R2-73-22^, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
e. Busch, A. W., Aerobic Biological Treatment of Wastewaters,
Oligodynamics Press, 1971.
f. Center for Research, Inc., University of Kansas, "Oxygen Con-
sumption in Continuous Biological Culture," Report No. 17050DJS, May
1971, U. S. Environmental Protection Agency, Washington, D. C.
g. City of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
h. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966. ~~~
i. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Briarcliff Manor, New York.
j. Eckenfelder, W. W., Jr., Water Quality Engineering for Prac-
ticing Engineers, Barnes and Nobel, New York, 1970.
7-168
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29 Sep 78
k. Eckenfelder, W. W. , Jr., "Activated Sludge and Extended Aera-
tion," Process Design in Water Quality Engineering - New Concepts and
Developments, 1971, VanderMlt University, Nashville, Tenn.
1. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton'Press, New York, 1970.
m. Eckenfelder, W. W., Jr., and O'Connor, 0. J., Biological Waste
Treatment, Pergamon Press, New York, 1961.
n. Gaudy, A. G., Jr., and Gaudy, E. T., "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No. 17090-
FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington, D. C.
o. Goodman, B. L. , Design Handbook of Wastewater Systems:
Domestic, Industrial, Commercial, Technomic, Westport, Conn., 1971.
p. Goodman, B. L. and Englande, A. J., Jr., "A Consolidated
Approach to Activated Sludge Process Design," Conference on Toward a
Unified Concept of Biological Waste Treatment Design, 5-6 Oct 1972,
Atlanta, Ga.
q.. Lawrence, A. W. and McCarty, P. L. , "Unified Basis for Biolog-
ical Treatment Design and Operation," Journal, Sanitary Engineering
Division, American Society of Civil Engineers, Vol 96, SA3, 1970.
r. Maier, W. J., "Biological Removal of Colloidal Matter from
Wastewater," Report No. R2-73-1^7, Jun 1973, U. S. Environmental Pro-
tection Agency, Washington, D. C.
s. McKinney, R. E., Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
t. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
u. Okun, D. A., "System of Bio-Precipitation of Organic Matter from
Sewage," Sewage Works Journal, Vol 21, No. 5, 19^9, PP 763-79^-
v. Smith, H. S., "Homogeneous Activated Sludge Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering,
Vol k, Jul 1967, PP 1*6-50.
7-169
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29 Sep 78
w. Smith, R. and Eilers, R. G., "A Generalized Computer Model for
bteady-State Performance of the Activated Sludge Process " FWQA Re-
port No. TWRC-15, Oct 1969, Robert A. Taft Water Research Center, Cin-
cinnati, Ohio.
x. Stensel, H. D. and Shell, G. L., "Two Methods of Biological
Treatment Design," Journal, Water Pollution Control Federation Vol U6
Feb 1974, PP 271-283. ~ '
y. Stewart, M. J., "Activated Sludge System Variations - Specific
Applications, The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
z. Toerber, E. D., "Full Scale Parallel Activated Sludge Process
Evaluation," Report No. R2-72-065, Nov 1972, U. S. Environmental Pro-
tection Agency, Washington, D. C.
aa. Weston, R. P., "Design of Sludge Reaeration Activated Sludge
Systems, Journal, Water Pollution Control Federation. Vol 33 No 7
1961, pp 748-757. " ' ~ ' ' ' '
7-170
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Section IX. PURE OXYGEN ACTIVATED SLUDGE
7-59. Background.
a.
As early as 19^9, Okun (para 7-66w) reported the results of
tests using pure oxygen as a substitute for air in the activated sludge
process.
"b. The pure oxygen system may "be used for aeration in activated
sludge systems that operate in either the plug flow or complete mix
hydraulic regimes. It is readily adaptable to new or existing complete
mix systems and can be used to upgrade and extend the life of over-
loaded plug-flow systems. To use the pure oxygen system, the aeration
tanks must be covered and the oxygen introduced should be recirculated
(para 7-66a). The amount of oxygen that can be injected into the liquid
(for a specific set of conditions) is approximately four times the
amount that could be injected with an air system. Adjustment of pH may
be necessary to maintain a proper balance between the C02 removed and
buffer capacity of the wastewater.
c. Several advantages, such as increased bacterial activity, re-
duced aeration tank volume, decreased sludge volume, and better settling
sludge have been cited for pure oxygen aeration (para 7-66a). To sub-
stantiate these findings, however, further testing of this process in
a number of varying applications will be necessary. Several references
(o, u, and w, para 7-66) discuss the characteristics and application of
pure oxygen aeration.
7-60. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variability,
a statistical distribution should be provided.
b. Wastewater Strength.
(l) BOD (soluble and total), mg/£.
(2) COD and/or TOC (maximum and minimum), mg/£.
(3) Suspended solids, mg/£.
(k) Volatile suspended solids (VSS), mg/£.
(5) Nonbiodegradable fraction of VSS, mg/£.
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c. Other Characterization.
(1) PH.
(2) Acidity and/or alkalinity, mg/£.
(3) Nitrogen, mg/£.
(*0 Phosphorus (total and soluble), mg/2,.
(5) Oils and greases, mg/£.
(6) Heavy metals, mg/£.
(T) Toxic or special characteristics (e.g., phenols), mg/£,
(8) Temperature, °F or °C.
d. Effluent Quality Requirements.
(1) BOD5, mg/£.
(2) SS, mg/£.
(3) TO, mg/£.
(4) P, mg/£.
(5) Total nitrogen (TKN + NO -N), mg/X,.
(6) Settleable solids, mg/£.
T-6l. Design Parameters.
a. Reaction rate constants and coefficients.
The form of nitrogen should be specified as to its biological
availability (e.g., NH or Kjeldahl).
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Constants _ Range _
McKinney
K 15/hr at 20°C
m
K lO.U/hr at 20°C
s
K 0-.02/hr at 20°C
e
Eckenfelder
k O.OOOT-0.002 £/mg/hr
a 0.73
a1 0.52
b • 0.075/day
b' 0.15/day
f 0.1*0
f 0.53
b. F/M = (0.25-1.0).
c. Volumetric loading = 150-200.
d. t = (2-1*) hr.
e. t = (3-20) days, depending on application.
s
f. MLSS = (1*000-7000) mg/£, mean 5000 mg/i.
g. MLVSS = (3200-5600) mg/A.
h. Q /Q = (0.25-0.5) = recycle ratio.
i. Ib 0 /l"b BOD^ = 1.0-1.5 lb.
J. lb solids/lb BOD = (0.3-0.1*5).
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k. 9 = (1.0-1.03).
1. Efficiency = (>90 percent).
7-62. Design Procedure.
a. McKinney's Approach.
(l) Assume the following design parameters.
(a) Metabolism constant (K ).
m
(b) Synthesis factor (K ).
s
(c) Endogenous respiration factor (K ).
(d) Temperature correction coefficient (0).
(e) Hydraulic detention time (t).
(f) Solids retention time (t ).
s
(2) Adjust metabolism constant, synthesis factor, and endogenous
respiration factor for temperature.
KT - K20
0(T-20)
where
K = rate constant at desired temperature T, °C
K = rate constant at 20°C
0 = temperature coefficient
T = temperature, °C
(3) Determine size of the aeration tank.
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29 Sep 78
where
V = volume of tank, million gal
Q = average flow, mgd
avg
t = hydraulic detention tine, hr
(h) Determine soluble effluent BOD .
F.
Fe ~ 1 + K t
m
where
F = soluble effluent BOD , mg/fc
e 5
F. = influent BODC, mg/£
i 5
K = metabolism constant (15/hr at 20°C)
m
t = hydraulic detention time, hr
and check F < 10 mg/£ ; if F > 10 mg/Jl , increase t and recalcu-
6 — G
late new F
e
(5) Calculate the MLSS concentration.
^T ~ a e i ii
K F
M =
a K + l/2Ut
e s
M = 0.2K M t (2U)
e e a s
M. = SS. x
. .
i it
M.. = SS. . x —-§. + o.l(M + M )
11 11 t a e
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where
M = total mass, mg/£
M = living, active mass, mg/£
cL
M = endogenous mass, mg/£
M. = inert nonbiodegradable organic mass, mg/X,
M.. = inert inorganic suspended solids, mg/X,
KS = synthesis factor, 1/hr (lO.Vhr at 20°C)
Fg = effluent BOD , mg/X,
Kg = endogenous respiration factor, 1/hr (0.02/hr at 20°C)
t = solids retention time, days
S
SS.^ = inert organic SS in influent, mg/£
= VSS x percent nonbiodegradable (f*Q.h VSS for municipal waste)
SSi:L = inert inorganic SS fraction in the influent
and check MT against 4000-7000 mg/£; vary t or t until M falls
within desired range. s
(6) Check organic loading against 0.25-1.0.
F/M = —r-
where
F/M = food-to-microorganism ratio
F± = influent BOD , mg/£
M = total mass, mg/£
t = hydraulic detention time, hr
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If F/M < lower limit, it is possible to reduce t and recalculate
MT •
If F/M > upper limit, increase t and recalculate M .
(7) Calculate the oxygen requirements.
(a) Select the oxygen uptake rate. The average rate of oxygen
demand, if the waste load is uniform, is given by
dO
dt
where
dO/dt = average oxygen uptake rate under uniform flow
conditions, mg/£
F = influent BOD , mg/£
F = soluble effluent BOD , mg/£
t = hydraulic detention time, hr
M = living, active mass, mg/£
3d
M = endogenous mass, mg/£
t = solids retention time, days
S
Under conditions where the load varies, the oxygen uptake is equal to
the synthesis oxygen demand plus the endogenous respiration oxygen
demand or
dO
— = I ::— I —£:— +1 i UK M
-ii I i l^-i i _L » _L H- IV 1¥1
dt L t J Q e a
avg
Ib 0_/hr = x v
i— ClO
where
Q = peak flow, mgd
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Q = average flow, mgd
K = endogenous respiration factor, hr (0.02/hr at 20°C)
(b) Check oxygen supplied per pound of BOD removed >1.25.
Ib 02/hr (2k)
Q(F. - F )8.3U
(8) Design aeration system and check horsepower for complete mix-
ing against horsepower required for complete mixing >_0.1 hp/1000 gal;
select the larger horsepower.
(a) Diffused Aeration System.
!_ Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer.
b_ 0 transfer in waste/09 transfer in water asO.9.
c_ 0 saturation in waste/0 saturation in water asO.9-
d_ Correction factor for pressure %L.O.
2_ Select summer operating temperature (25-30°C) and determine (from
.dard tables) 0 saturation.
3_ Adjust standard transfer efficiency to operating conditions.
OTE = STE ^ x - a(l.02)T 2°
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(C \ = 0 saturation at selected summer temperature T, °C, mg/£
V s /_ c.
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3=0 saturation in waste/0? saturation in water ssO.9
p = correction factor for pressure ^L.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/H
a = 0 transfer in waste/0 transfer in water asO.9
T = temperature, °C
^_ Calculate required air flow.
R =
where
R = required air flow, cfm/1000 ft
cl
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
CF = correction factor, Ib 0 /ft air
(b) Mechanical Aeration System.
1_ Assume the following design parameters.
a_ Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen, 20°C,
and tap water).
b_ 0 transfer in waste/0 transfer in water 5*0.9.
c_ Og saturation in waste/0 saturation in water «s0.9.
cl Correction factor for pressure «1.0.
2_ Select summer operating temperature (25-30°C), and determine
(from standard tables) 0 saturation.
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3. Adjust standard transfer efficiency to operating conditions.
I \ / rn -"I m on
OTE - STE a(l.02r~dU
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
„) = 0 saturation at selected summer temperature T, °C, mg/£
g = 00 saturation in waste/0 saturation in water adO.9
p = correction factor for pressure sal.O
C - minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 0 transfer in waste/0p transfer in water ssO.9
T = temperature, °C
Calculate horsepower requirement.
°2
hp = TT-^ x 1000
where
hp = horsepower required/1000 gal
0_ = oxygen required, Ib/day
OTE = operating transfer efficiency, Ib 0 /hp-hr
V = volume of "basin, gal
(9) Calculate sludge production and determine pounds of sludge
wasted per day.
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where
AM = sludge produced, Ib/day
1VL - total mass, mg/£
V = volume of aeration tank, million gal
t = solids retention time, days
(10) Check solids produced per pound of BOD removed.
Ib solids _ AMT
Ib BOD Q(F. - F )Q.3k
r i e
where
AM = sludge produced, Ib/day
Q = flow, mgd
F. = influent BOD , mg/Jl
F = effluent BOD , mg/£
(ll) Calculate sludge recycle ratio.
5r
Q
where
Q = volume of recycled sludge, mgd
Q = flow, mgd
M = total mass, mg/£
M = solids concentration in return sludge, mg/£
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(12) Calculate total effluent BOD .
/M \
,eff - °e * °-*
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29 Sep 78
(e) Mixed liquor suspended solids (MLSS).
(f) Mixed liquor volatile suspended solids (MLVSS).
(g) Food-to-microorganism ratio (F/M).
(h) Nonbiodegradable fraction of VSS in influent (f).
(i) Degradable fraction of the MLVSS (f).
(j ) Temperature correction coefficient (0).
(2) Adjust rate constant for temperature.
K Q(T-20)
where
K = rate constant at desired temperature, °C
K = rate constant at 20°C
0 = temperature correction coefficient
T = temperature, °C
(3) Determine the size of the aeration tank by first determining
the detention time t .
t =
(XV)(F/M)
where
t = detention time, hr
S = influent BOD, mg/'£
Xy = MLVSS, mg/£
F/M = food-to-microorganism ratio
(h) Check detention time for treatability.
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fe
So
vhere
S = BOD (soluble) in effluent, mg/£
S = BOD in influent, mg/fc
k = BOD removal rate constant, 1/mg/hr
Xy = MLVSS, mg/H
t = detention time, hr
Solve for t and compare with t 'above and select the larger.
(5) Calculate the volume of aeration tank.
t
^avg 2^
vhere
V = volume, million gal
Q = average daily flow, mgd
t = detention time, hr
(6) Calculate oxygen requirements.
dt t
or
°2= a'(Sr)(Qavg)(8-3l° H
where
dO/dt = oxygen uptake rate, mg/£/hr
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29 Sep 78
a' = fraction of BOD oxidized for energy
S = BOD removed (S - S ), mg/Jl
t = detention time, hr
b' = endogenous respiration rate, 1/hr
Xy = MLVSS
0 = oxygen requirement, Ib/day
Q = average flov rate, mgd
avg
V = volume of aeration tank, million gal
and check the oxygen supplied against >_1.25
°2
Ib 00/lb BOD =
r ~ Q(Sr) x 8.3^
where
0 = oxygen required, Ib/day
Q = flow, mgd
S = BOD removed, mg/£
(T) Design aeration system and check horsepower supply for mixing
against horsepower required for complete mixing <_0.1 hp/1000 gal.
(a) Diffused Aeration System.
~L_ Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer.
b_ 0 transfer in waste/0? transfer in water ssO.9.
£ 0 saturation in waste/0 saturation in water «0.9.
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29 Sep 78
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) Q saturation.
3_ Adjust standard transfer efficiency to operating conditions.
[(c.)
OTE = STE i—— a(l.02)T~2°
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
(C ) = 0 saturation at selected summer temperature T, °C, mg/£
3 = 0 saturation in waste/0 saturation in water ssO.9
p = correction factor for pressure sj_.0
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 0 transfer in waste/0 transfer in water saO.9
T = temperature, °C
H_ Calculate required air flow.
0
R =
,
(OTE)fl^O
where
R = required air flow, cfm/1000 ft
3*
0 = required oxygen, Ib/day
OTE = operating transfer efficiency, percent
V = volume of basin, gal
OF = correction factor, Ib 0 /ft air
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(b) Mechanical Aeration System.
1_ Assume the following design parameters.
a_ Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen, 20°C,
and tap water.
b_ 0 transfer in waste/0 transfer in water ajO.9-
c_ 0 saturation in waste/0 saturation in water stQ.9-
d_ Correction factor for pressure %1.0.
2_ Select summer operating temperature (25°C-30°C) and determine
(from standard tables) 0 saturation.
3_ Adjust standard transfer efficiency to operating conditions.
1
- CT
where
L
OTE = STE *-' T =1 a(l.02)T~2°
y • -L /
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
/C ^ = 0_ saturation at selected summer temperature T, °C, mg/£
\ S/T 2
3=0 saturation in waste/0 saturation in water «O.9
p = correction factor for pressure a=1.0
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 0 transfer in waste/0 transfer in water
T = temperature, °C
h Calculate horsepower requirement.
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29 Sep 78
100°
where
hp = horsepower required/1000 gal
0 = oxygen required, l"b/day
OTE = operating transfer efficiency, Ib 02/hp-hr
V = volume of basin, gal
(8) Calculate sludge production.
AX, = [aS Q - bX V + fQ(VSS) + Q(SS - VSS)]8.3^
T L r avg v
where
AX = sludge produced, Ib/day
a = fraction of BOD removed synthesized to cell material
S = BOD removed, mg/£
r
0 = average flow, mgd
avg
b = endogenous respiration rate/day
X^ = volatile solids in raw sludge, mg/X,
V = volume of basin, gal
f = nonbiodegradable fraction of influent VSS
Q = flow, mgd
VSS = volatile suspended solids in effluent, mg/£
SS = suspended solids in influent, mg/£
(9) Check AX.^ against 0.3-0.1+5.
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29 Sep 78
Ib solids = AXV
BODr) Sr(Q)(8.3M
where
AX^ = sludge produced, Ib/day
S = BOD removed, mg/'H
r
Q = flow, mgd
(10) Calculate sludge recycle ratio.
Q X
r a
X - X
u a
where
Q /Q = sludge recycle ratio
Q = volume of recycled sludge, mgd
Q = flow, mgd
X = MLSS, mg/H
a
X = solids concentration in return sludge, mg/£
u
(11) Calculate solids retention time.
(V)X (8.310
SRT = -
AX
a
where
SRT = solids retention time, days
AX
AX =
a % volatile
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(12) Calculate effluent BOD .
BOD = S + 0.81*
where
Sg = effluent soluble BOD, mg/£
(\ ) = effluent volatile suspended solids, mg/£
x v/eff
f ' = degradable fraction of MLVSS
(13) Determine nutrient requirements for nitrogen
N =
and phosphorus
P = 0.026AMT(or
where
AM = sludge produced, l"b/day
AX^ = sludge produced, l"b/day
and check against BOD:N:P = 100:5:1.
7-63. Output Data.
a. Aeration Tank.
(l) Reaction rate constant, 1/mg/hr.
(2) Sludge produced per BOD removed.
(3) Endogenous respiration rate (b, b').
(k) 0 = utilized per BOD removed.
( 5 ) Influent nonbiodegradable VSS ( f ) .
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(6) Effluent degradable VSS (f).
(7) Ib BOD/lb MLVSS-day (F/M ratio).
(8) Mixed liquor SS, mg/£ (MLSS).
(9) Mixed liquor VSS, mg/£ (MLVSS).
(10) Aeration time, hr.
(11) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
(13) Sludge produced, Ib/day.
(lU) Nitrogen requirement, Ib/day.
(15) Phosphorus requirement, Ib/day.
(l6) Sludge recycle ratio, percent.
(IT) Solids retention time, days.
b. Diffused Aeration System.
(l) Standard transfer efficiency, percent.
(2) Operating transfer efficiency, percent.
(3) Required air flow, cfm/1000 ft3.
c. Mechanical Aeration System.
(1) Standard transfer efficiency, Ib 0 /hp-hr.
(2) Operating transfer efficiency, Ib 0 /hp-hr.
(3) Horsepower required.
k. Ey Jiple Calculations. Eckenfelder's Approach.
a. Assume the following design parameters.
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(1) K = 0.0012 £/mg-hr
(2) a = 0.73
(3) a' = 0.5
(1+) b = 0.075/day, b1 = 0.15/day
(5) MLSS = X = 3000 mg/£
cl
(6) MLVSS = Xy = 21+00 mg/£
(7) F/M = 0.1+0 lb BOD/lb MLVSS-day
(8) f = 0.1+0
(9) f = 0.53
(10) 0 = 1.03
b. Adjust the BOD removal rate constant for winter conditions,
T = 15°C.
„ _ „ 0T-20
T1 20
where
K = rate constant at temperature T
K = rate constant at 20°C, 0.0012 £/mg-hr
T = temperature, 15°C
6 = temperature correction coefficient, 1.03
K^, = 0.0012(1.03)15~2°
K = 0.0010 £/mg-hr
c. Determine size of aeration tank by determining detention time.
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29 Sep 78
t =
X^F/M)
where
t = hydraulic detention time, hr
S = influent BOD, 200 mg/£
o
= MLVSS, 2UOO mgA
F/M = food-to-microorganism ratio, 0.^0 l"b BOD/lb MLVSS
2U(200)
2UOO(O.UO)
t = 5.0 hr
d. Check detention for treatability.
S .
e 1
S 1 +
where
S = effluent BOD ..(soluble), 10 mg/£
e 5
S = influent BOD , 200 mg/&
K = BOD removal rate constant, 0.001 £/mg/hr
Xy = MLVSS, 2UOO mg/&
t = detention time, hr
10
200 1 + (O.OOl)2UOQ(t)
t=T.9hr>5.0hr
e. Calculate the volume of the aeration tank,
7-193
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29 Sep 78
V =
where
V = volume, million gal
Q& = average flow, 1.0 mgd
t = detention time, 7.9 hr
V = 1.
V = Q.329 million gal
f. Calculate oxygen requirements.
°2 = a'SAvg(8-3l° +
where
0 = oxygen required, Ib/day
a' = 0.52
S^ = BOD removed (S - S ), 190 mg/£
Q& = average flow, 1.0 mgd
V = 0.15/day
Xy. = MLVSS, 2^00 mg/£
V = volume of aeration tank, 0.329 million gal
o2 = 0.52(190)1.0(8.3^) + 0.15(21+00)0.329(8.310
02 = 1812 lt>/day
Check oxygen supplied per Ib BOD removed >1.25.
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29 Sep 78
• °2
Ib 00/lb —
2 r - Q(s )8>
r'
where
0 = oxygen required, 1812 Ib/day
Q = average flow, 1.0 mgd
S = BOD removed, 190 mg/£
Ib 02/lb
Ib 0Jib BOD = I.Ik < 1.25
Therefore
0 =1.25 BOD
P y1
0 = 1.25Q(Sr)8.3^
02 = 1.25(1.0)190(8.3U)
0 = 1980 Ib/day
g. Design aeration system (mechanical surface).
(l) Assume the following parameters
STE = 5.0 percent
a = 0.9
3 = 0.9
p = pressure correction factor, 1.0
(2) Select summer operating temperature and determine 0 saturation.
T = 25°C, (CS)T = 8.2 mg/A.
(3) Determine operating transfer efficiency.
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[(CB)T*».-CL]
OTE = STE —• al.02T~20
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5.0 percent
(c \ =8.2 mg/£
CL = minimum dissolved oxygen, 2.0 mg/£
T = 25°C, a = 0.9, B = 0.9
9-17 = 0 saturation at 20°C
OTE = 5.0 [8.2(0.9)1.0 - 2.01 0.9(1.02)25-20
y • -L I
OTE = 2.9% or Ib 0 /hp-hr
(4) Calculate horsepower requirements.
hp = ^2
OTE(24)V
where
hp = horsepower requirements, hp/1000 gal
02 = oxygen required, 1980 Ib/day
OTE = operating transfer efficiency, 2.9 percent
V = volume of aeration tank, 0.329 million gal
h _ 1980
2.9(2100.329(1000)
hp = 0.09 hp/1000 gal < 0.1 hp/1000 gal
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29 Sep 78
Therefore, use hp = 0.1 hp/1000 gal
hp = 0.1(V)1000
hp = 0.1(0.329)1000
hp = 32.9 hP (use 35
h. Calculate sludge production'
- bXy(V) + Qavg(VSS)f + Qayg(SS - VSS)]8.3U
avg
vhere
AX = sludge produced, Ib/day
a = 0.73
S = BOD removed, 190 mg/Jl
Q =1.0 mgd
avg
ID = 0.075/day
X_^ = 2UOO mgA
V = 0.329 million gal
VSS = effluent volatile suspended solids, 150 mg/£
f = 0.^0
SS = suspended solids in influent, 200 mg/&
AX^ = [0.73(190)1.0 - 0.075(2UOO)0.329
+ 1. 0(150)0. UO + 1.0(200 - 150)]8.3U
AX = 1580 Ib/day
i. Calculate solids produced per pound of BOD removed and check
> 0.5-0.7-
7-197
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Ib solids _ AXV
Ib BOD ~ S
EM 1110-2-501
Part 1 of 3
29 Sep 78
r
where
AX = solids produced, 1580 Ib/day
S^ = BOD removed (S - S ), 190 mg/£
Q = average flow, 1.0 mgd
Ib solids _ 1580
Ib BOD 1.90(1.0)8.3lt
r
0.5-0.7 (OK)
j. Calculate sludge recycle ratio
Q X
r a
Q X - X
u a
where
Q = volume of recycled sludge, mgd
Q = average flow, 1.0 mgd
X = MLSS, 3000 mg/£
a
X = return sludge concentration, 10,000 mg/£
3,000
1.0 10,000 - 3,000
Qr = O.U29 mgd
k. Calculate solids retention time.
V(X )8.
SRT = a
AX
a
7-198
-------
where
SRT = solids retention time, days
V = volume of aeration tank, 0.329 million gal
X = MLSS, 3000 mg/£
a
AX = AXy/^ volatile = 1580/0.80 = 1975 It/day
_ 0.329(3000)8.3^
SRT = k.2 days
1. Calculate effluent BOD .
\ = S + 0.8U(X ) f
5/eff e eff
where
(BOD = effluent BOD , mg/£
^
5'
ii J.
S = effluent soluble BOD^, 10 mg/£
e 5
(x. ) = effluent volatile suspended solids, 20
P"f>"P
f = 0.53
(BOD ) = 10 + 0.8^(20)0.53
^ 5/^eff
(B°D5)
= 19
eff
m. Determine nutrient requirements for nitrogen
N = 0.123AXy.
N = 0.123(1580)
N = 19k Ib/day
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for phosphorus
P = 0.026A3C.
P = 0.026(1580)
P = hi Ib/day
N in influent = 30 mg/£(Q )Q.3k
= 30(1.0)8.3U
= 250 Ib/day > igb Ib/day required
N to be added = none
P in influent = 15 mg/£(Q )8.3^
- 15(1.0)8.3U
= 125 Ib/day > la Ib/day required
P to be added = none
7-65- Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8.
7-66. Bibliography.
a. Albertsson, G. G. et al., "Investigation of the Use of High
Purity Oxygen Aeration in the Conventional Activated Sludge Process,"
Water Pollution Control Research Series Report No. 17050DNW, May 1970,
Federal Water Quality Administration, Washington, D. C.
b. American Public Health Association, American Society of Civil
Engineers, American Water Works Association, and Water Pollution Control
Federation, "Glossary, Water and Wastewater Control Engineering," 1969.
c. American Public Works Association, "Feasibility of Computer
Control of Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. S.
Environmental Protection Agency, Washington, D. C.
7-200
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29 Sep 78
d. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 196T, and 1968, Water Pollution Control Federation,
Washington, D. C.
e Bargman, R. D. and Borgerding, J., "Characterization of the
Activated Sludge Process," Report No. R2-73-22U, Apr 1973, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
f. Busch, A. W., Aerobic Biological Treatment of Wastewaters,
Oligodynamics Press, 1971-
g. Center for Research, Inc., University of Kansas, "Oxygen Con-
sumption in Continuous Biological Culture," Report No. 17050DJS, May
1971, U. S. Environmental Protection Agency, Washington, D. C.
h. City of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
i. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
j. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Briarcliff Manor, New York.
k. Eckenfelder, W. W., Jr., Water Quality Engineering for
Practicing Engineers, Barnes and Nobel, New York, 1970.
1. Eckenfelder, W. W., Jr., "Activated Sludge and Extended Aera-
tion," Process Design in Water Quality Engineering - New Concepts and
Developments, 1971, Vanderbilt University, Nashville, Tenn.
m. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970.
n. Eckenfelder, W. W., Jr., and O'Connor, 0. J., Biological Waste
Treatment, Pergamon Press, New York, 1961.
o. Gaudy, A. G., Jr., and Gaudy, E. T., "Biological Concepts for
Design and Operation of the Activated Sludge Process," Report No. 17090-
FQJ, Sep 1971, U. S. Environmental Protection Agency, Washington, D. C.
7-201
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29 Sep 78
p. Goodman, B. L. , Design Handbook of Wastewater Systems: Domestic
Industrial, Commercial, Technomic, Westport, Conn., 1971.
q.. Goodman, B. L. and Englande, A. J., Jr., "A Consolidated
Approach to Activated Sludge Process Design," Conference on Toward a
Unified Concept of Biological Waste Treatment Design, 5-6 Oct 1972,
Atlanta, Ga.
r. Lawrence, A. W. and McCarty, P. L., "Unified Basis for Biologi-
cal Treatment Design and Operation," Journal, Sanitary Engineering
Division, American Society of Civil Engineers, Vol 96, SA3, 1970.
s. Maier, W. J., "Biological Removal of Colloidal Matter from
Wastewater," Report Wo. R2-73-1^7, Jun 1973, U. S. Environmental Protec-
tion Agency, Washington, D. C.
t. McKinney, R. E., Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
u. McKinney, R. E. and Pfeffer, J. T., "Oxygen-Enriched Air for
Biological Waste Treatment," Water and Sewage Works, Vol 112, Oct 1965
PP 381-381*.
v. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
w. Okun, D. A., "System of Bio-Precipitation of Organic Matter
from Sewage," Sewage Works Journal, Vol 21, No. 5, 19^9, pp 763-79^.
x. Smith, H. S., "Homogeneous Activated Sludge Principles and
Features of the Activated Sludge Process," Water and Wastes Engineering,
Vol k, Jul 1967, pp 46-50.
y. Smith, R. and Eilers, R. G., "A Generalized Computer Model for
Steady-State Performance of the Activated Sludge Process," FWQA Report
No. TWRC-15, Oct 1969, Robert A. Taft Water Research Center, Cincinnati,
Ohio.
z. Stensel, H. D. and Shell, G. L., "Two Methods of Biological
Treatment Design," Journal, Water Pollution Control Federation, Vol h6,
Feb 197^» PP 271-283.
7-202
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29 Sep 78
aa. Stewart, M. J., "Activated Sludge System Variations - Specific,
Applications," The 15th Ontario Industrial Waste Conference, 9-12 Jun
1968, Niagara Falls, Ontario.
bb. Toerber, E. D., "Full Scale Parallel Activated Sludge Process
Evaluation," Report Wo. R2-72-065, Nov 1972, U. S. Environmental Pro-
tection Agency, Washington, D. C.
cc. Union Carbide Corporation, "Continued Evaluation of Oxygen Use
in Conventional Activated Sludge Processing," Report No. 17050DNW, Feb
1972, U. S. Environmental Protection Agency, Washington, D. C.
dd. Union Carbide Corporation, "Unox System Wastewater Treatment,"
Report of Pilot Study at Hooker's Point Treatment Plant, Tampa, Fla.
ee. Weston, R. F., "Design of Sludge Reaeration Activated Sludge
Systems," Journal, Water Pollution Control Federation, Vol 33, No. '7,
1961, pp 7^8-757-
7-203 (next page is 7-205)
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Section X. AERATED AEROBIC LAGOONS
T-6T- Background.
The contents of an aerated aerobic lagoon must be completely mixed
so that the incoming solids and the biological solids produced in the
lagoon do not settle. Effluent quality is a function of the detention
time and will normally have a BOD ranging from one-third to one-half
of the influent value. This BOD is due to the endogenous respiration
of the biological solids escaping in the effluent. Before the effluent
is discharged, the solids may be removed by settling. Where sedimenta-
tion is used, it may be advantageous to provide for recycle. A schema-
tic of aerated lagoons is shown in Figure 7-8.
AEROBIC
ANAEROBIC
SLUDGE
DEPOSITS
b.
From Metcalfand Eddy, 1972
Figure 7-8. Schematic of (a) an aerated lagoon
and (b) an aerobic-anaerobic lagoon.
7-68. Input Data.
a. Wastewater Flow.
(l) Average daily, mgd.
(2) Peak (hourly), mgd.
b. Wastewater Characteristics.
(l) BOD influent, mg/£.
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(2) Influent SS, mg/£.
(3) Influent VSS, mg/SL.
(h) Nitrogen, mg/H.
(5) Phosphorus, mg/£.
(6) Nonbiodegradable fraction of VSS.
c. Desired degree of treatment, percent.
d. Temperature, °F or °C (summer and winter).
7-69. Design Parameters.
a. McKinney's Approach.
(1) . Reaction rates: K , 15/hr at 20°C; K , lO.Vhr at 20°C-
and K , 0.02/hr at 20°C. s
e
(2) Hydraulic detention time, 2-k days.
(3) Solids retention time, 3-7 days.
(M MLSS under aeration, 200-500 mg/£.
(5) Temperature coefficient, 1.035.
(6) Depth, 6-12 ft.
b. Eckenfelder's Approach.
(1) Reaction rate constant, 0.0007-0.002 1/mg-hr.
(2) MLSS, 200-500 mg/A.
(3) MLVSS, 1140-350 mg/Ji,.
(h) Fraction of BOD synthesized, 0.73.
(5) Fraction of BOD oxidized for energy, 0.52.
(6) Endogenous respiration rate per day (b = 0.075/dav
b' = 0.15/day).
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(T) Temperature coefficient, 1.035.
(8) Hydraulic detention time, 2-k days.
(9) Depth, 6-12 ft.
7-70. Design Procedure. Most designers choose to treat this type of
lagoon as a variation of an activated sludge process. Two well-known
systems for design are as'follows.
a. McKinney's Approach.
(l) Determine size of lagoon. Select the metabolism constant,
K , and the detention time, t .
V = Qt
where
V = volume, million gal
Q = flow, mgd
t = detention time, days
(2) Adjust the metabolism constant for temperature. Select
temperature correction coefficient.
_ fl(T-20)
mT " Km(20)0
where
K = metabolism constant
K , , = rate constant at 20°C
Q = temperature correction coefficient
T = temperature, °C
(3) Calculate the effluent BOD for both winter and summer,
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F.
F =
e 1 + K t
m
where
F. = influent BOD , mg/£
F = effluent BOD,., mg/£
e 5
Calculate the total mass; select the synthesis factor, K ,
and the endogenous respiration factor, K
Mm = M +M + M. + M. .
TO a e i 11
K K
s e
a K + 1/2H
e s
M = 0.2K M t (2M
e e a s
M. = SS.
. .
i it
2Ut
M. . = SS. . x — — £- + 0.1(M + M )
11 11 t a e
where
M = total mass, mg/fc
M = living active mass, mg/£
£L
M = endogenous mass, mg/£
M. = inert nonbiodegradable organic mass, mg/H
M.. = inert inorganic suspended solids, mg/£
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K •= synthesis factor, hr (lO.U/hr at 20°C)
s
K = endogenous respiration factor, hr (0.02/hr at 20°C)
e
t = solids retention time, days
s
SS. = inert organic SS in influent, mg/£
= VSS x nonbiodegradable (ssO.it VSS for municipal waste)
SS.. = inert inorganic SS fraction in the influent
(5) Substitute Fe for winter and summer conditions into equation
below and check against allowable winter and summer BOD,_ effluent. In
this equation M (eff) = M in lagoon.
8>
(BOD \ = F +
(6) Determine oxygen uptake rate.
dt
and calculate oxygen for peak load
0. 5(F. - F ) Q
0 _ J - i - g_ x — -E- + 1.U2K M (O.T6)
2 t Q e a
avg
where
dO/dt = oxygen uptake rate, mg/A/hr
F. = influent BOD , mg/£
F = effluent BODr, mg/£
e ?
t = detention time, days
M = total mass, mg/£
a
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M = endogenous mass, mg/£
Q = peak flow, mgd
Q = average flow, mgd
K = endogenous respiration rate/hr
(7) Design mechanical aeration system and check horsepower supply
to keep all solids in suspension; horsepower required to keep solids in
suspension _>0.06 hp/1000 gal.
(a) Assume the following design parameters.
1_ Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,.20°C,
and tap water).
2 0 transfer in waste/00 transfer in water saO.9.
d. cL
_3_ 0 saturation in waste/0 saturation in water «0.9«
k_ Correction factor for pressure «1.0.
(b) Select summer operating temperature (25-30°C) and determine
m standard tables) 0Q saturation.
(c) Adjust standard transfer efficiency to operating conditions.
[(C.) (
OTE = STE x - a(l.02)T~2°
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
J = 0 saturation at the selected summer temperature T, °C,
T in mg/£
3=0 saturation in waste/0 saturation in water «0.9
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p = correction factor for pressure si.O
C = minimum dissolved oxygen to be maintained in the "basin
> 2.0 mg/£
a = 0 transfer in waste/0 transfer in water «0.9
T = temperature, °C
(d) Calculate horsepower requirement.
hp - - - - - -x 1000
where
hp = horsepower required/lOQjp gal
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, Ib 02/hp-hr
V = volume cf basin, gal
(8) Determine nutrient requirements.
BOD: Nitrogen: Phosphorus = 100:5:1
b. Eckenf elder ' s Approach.
(1) Determine size of lagoon.
(a) Select the BOD removal rate constant, the endogenous respira
tion rate, the fraction of BOD synthesized, and temperature (summer,
winter) S
(b) Adjust the BOD removal rate constant for winter and summer.
(T-20)
KT = K208
where
K = BOD removal rate constant, 1/mg/hr
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K = rate constant at 20°C
6 = temperature correction coefficient
T = temperature, °C
(c) Solve following equation for t to satisfy winter conditions
and desired treatment.
"k = ±
24aKS - b
e
where
t = detention, days
a = fraction of BOD synthesized
K = BOD removal rate constant, £/mg/hr
Sg = effluent soluble BOD mg/£
b = endogenous respiration rate, I/day
(d) Solve equation above for t to satisfy summer conditions and
desired treatment.
(e) Select larger t calculated above.
(f) Calculate volume of pond.
V = Qt
where
V = volume of pond, million gal
Q = flow, mgd
t = detention time, days
(2) Determine MLVSS; substitute value of t (determined above) into
X + aS
1 + bt
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where
X. = MLVSS, mg/£
X = suspended solids in influent, mg/£
a = fraction of BOD synthesized
S = BOD removed, mg/£
b = endogenous respiration rate, 1/mg/hr
t = detention time, days
(3) Calculate oxygen requirements.
02 = (a')(Sr)(Q)(8.3U) + (b
where
Op = oxygen required, Ib/day
a' = fraction of BOD oxidized for energy
S = BOD removed, mg/£
Q = flow, mgd
b' = endogenous respiration rate, 1/hr
Xy = MLVSS, mg/£
V = volume of the pond, million gal
(k) Design mechanical aeration system and check horsepower supply
to keep all solids in suspension: horsepower required to keep all
solids in suspension >_0.06 hp/1000 gal.
(a) Assume the following design parameters.
!_ Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
2_ 0 transfer in waste/0 transfer in water wO.9-
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3. 0 saturation in waste/0 saturation in water «s0.9.
U_ Correction factor for pressure ssl.O.
(b) Select slimmer operating temperature (25-30°C) and determine
n standard tables) 0 saturation.
(c) Adjust standard transfer efficiency to operating conditions.
]
- CL
OTE - STE " ± a(l.02)T~2°
where
OTFJ = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, Ib 0 /hp-hr
(C ) =0.2 saturation at selected summer temperature T, °G, mg/&
j
6 - 00 saturation in waste/0 saturation in water s=0.9
p "- -jc/yeoticri factor for pressure «1.0
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a, = 0,. transfer in waste/00 transfer in water «O.O
^' ^
T = temperature, °C
(d) Calculate horsepower requirement.
hp = - — - - x 1000
where
hp = horsepower required/1000 gal
0 = oxygen required, it/day
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OTE =• operating transfer efficiency, Ib 0 /hp-hr
V = volume of the pond, gal
(e) Calculate nutrient requirements.
BOD:Nitrogen:Phosphorus = 100:5:1
(f) Determine effluent BOD.
BODeff - Se +
where
BODeff = effluent BOD, mg/£
Sg = effluent soluble BOD , mg/£
Xy = MLVSS, mg/H
T-71. Output Data.
a. Lagoon.
(l) Summer temperature, °C.
(2) Winter temperature, °C.
(3) Effluent BOD, mg/£.
(4) Fraction BOD synthesized.
(5) Fraction BOD oxidized.
(6) Endogenous rate (b, b1).
(7) Temperature coefficient.
(8) Detention time, days.
(9) MLVSS, mg/£.
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(10) Volume, million gal.
(11) Oxygen requirement, Ib/day.
(12) Nitrogen requirement, Ib/day.
(13) Phosphorus requirement, Ib/day.
(iH) Total effluent BOD, mg/£..
b. Mechanical Aeration System.
(l) Standard transfer efficiency, Ib 0_/hp-hr.
(2) Operating transfer efficiency, Ib 0 /hp-hr.
(3) Horsepower required/1000 gal.
7-72. Example Calculations (Eckenfelder's Approach).
a. Determine size of lagoon.
(l) Select design parameters.
(a) k = 0.001
(b) a = 0.73
(c) b = 0.075/day
(d) T = 25°C summer, 15°C winter
(2) Adjust K for winter and summer conditions.
T-20
T 20
where
K = removal rate constant at T, £/mg/hr
KgQ = removal rate constant at 20°C, 0.001 &/mg/hr
6 = temperature correction coefficient, 1.035
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T = temperature, 15°C winter, 25°C summer.
K15 = 0.001(1.035)15~2°
K = 0.00084 £/mg/hr winter
K25 = 0.001(1.035)25"2°
K = 0.00119 £/mg/hr summer
(3) Under winter conditions determine detention time for desired
treatment.
t = 24aKS ^b
e
where
t = detention time, days
a = 0.73
K = K^ = 0.00084
S = effluent BODC = 15 mg/£
e :>
b = 0.075/day
t =
24(0.73)0.00084(15) - 0.075
t = 6.9 days, say 7 days
(4) Solve for summer conditions.
1
t =
24(0.73)(0.00119)15 - 0.075
t = 4.2 days, say 4 days
(5) Select larger t . t = 7-0 days
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(6) Calculate volume of the pond.
V = Qt
where
V = volume, million gal
Q = flow, 1.0 mgd
t = detention time, 7 days
V = 1.0(7)
V = 7 million gal
b. Determine MLVSS.
X + aS
T 1 + bt
where
X = MLVSS, mg/£
X = influent suspended solids, 200 mg/£
a = 0.73
S = S - S = 200 - 15 = 185 mg/£
roe
b = 0.075/day
t = 7 days
= 200 + 0.73(185)
\ 1 + 0.075(7)
Xy = 220 mg/£
c. Calculate oxygen requirements.
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29 Sep 78
= (a')Sr(Q)8.3U
where
0 = oxygen required, lb/day
a' = 0.52
S = 185
Q = average flow, 1.0 mgd
To' = 0.15/day
X = MLVSS, 220 mg/£
V = volume of basin, 7 million gal
02 = 0.52(185)1.0(8.3*0 + 0.15(220)7(8.
02 = 2729 lb/day
d. Design mechanical aeration system and check horsepower supply to
keep all solids in suspension: horsepower >0.06 hp/1000 gal.
(l) Assume the following parameters.
(a) STE = 5 percent
(b) a = 0.9
(c) 3 = 0.9
(d) p = 1.0
(2) Select summer operating temperature and determine 0 saturation.
Temperature = 25°C. (cs)2£r = 8-2 mg/£.
(3) Adjust the standard transfer efficiency to operating conditions.
]
3p - CL
OTE = STE ±—; a(l.02)T~2°
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where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5 percent
(C ) =8.2 mg/£
V s/T
e = 0.9
P = i.o
C = minimum dissolved oxygen, 1.0 mg/&
J_i
9.17 = 0^ saturation at 20°C
c.
a = 0.9
T = 25°C
OTE = 5 [8.2(0.9)1.0-1.03 0.9(1.02)25-20
y • -L i
OTE =3.5 percent
(it) Calculate horsepower requirement.
°2 1000
~ OTE(24)V 1Q6
where
hp = horsepower required per 1000 gal
0 = oxygen required, 2729 Ib/day
OTE = operating transfer efficiency, 3-5 percent
V = volume of "basin, 7 million gal
hp = 2729(1000)
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hp = 0.005 hp/1000 gal < 0.06 required to keep solids in suspension.
Therefore use hp = 0.06 hp/1000 gal.
Total hp = 0.06> - U20hp
(5) Calculate nutrient requirements.
BOD.-W.-P = 100:5:1
BOD =200 mg/£
N required = 10 mg/£
P required = 2 mg/£
(6) Determine effluent BOD.
BOD _ = S. + 0.3Xy
eff e
where
BOD „„ = effluent BOD, mg/£
eri
S = effluent soluble BOD, 15
X = MLVSS, 220 mg/£
BODeff = 15 + 0.3(220)
BODeff = 8l/mg/A
T-T3. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
7-7^. Bibliography.
a. Barnhart, E. L. and Eckenfelder, W. W., Jr., "Theoretical Aspects
of Aerated Lagoon Design," Symposium on Wastewater Treatment for Small
Municipalities, 1965» Ecole Polytechnique, Montreal, Quebec, Canada.
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b. Bishop, N. E., Malina, J. F., Jr., and Eckenfelder, W. W., Jr.,
"Studies on Mixing And Heat Exchange in Aerated Lagoons," Technical Re-
port EHE-70-21, CRWR-70, 1970, Center for Research in Water Resources,
University of Texas at Austin.
c. City of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
d. Eckenfelder, W. W., Jr., Industrial Water Pollution Control
McGraw-Hill, New York, 1966.
e. Eckenfelder, W. W., Jr., "Aerated Lagoons," Manual of Treatment
Processes. Vol I, 1969, Environmental Science Services, Inc., Briar-
cliff Manor, New York.
f. Eckenfelder, W. W., Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Brlarcliff Manor, New York.
g. Eckenfelder, W. W., Jr., Water Quality Engineering for Practicing
Engineers, Barries and Nobel, New York, 1970.
h. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970.
1. McKinney, R. E., Microbiology for Sanitary Engineers, McGraw-
Hill, New York, 1962.
j. McKinney, R. E., "Design and Operation of Complete Mixing
Activated Sludge Systems," Environmental Pollution Control Services
Reports, Vol 1, No. 3, Jul 1970, pp 1-3^.
k. McKinney, R. E. and Benjes, H. H., "Design and Operation of
Aerated Lagoons," Paper No. 3P2-1, Jul 1965, National Symposium on
Sanitary Engineering Research, Development and Design.
1. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
m. Sawyer, C. N., "New Concepts in Aerated Lagoon Design and
Operation," Advances in Water Quality Improvements - Physical and
Chemical Processes, E. F. Gloyna and W. W. Eckenfelder, Jr., ed. ,
University of Texas Press, Austin, 1970.
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Section XI. AERATED FACULTATIVE LAGOONS
7-75' Background.
a. The contents of this type of lagoon are not completely mixed.
Thus, portions of the incoming solids and the biologically produced
solids settle out and undergo anaerobic decomposition. As a result, '
the facultative lagoon produces a higher quality effluent than does the
aerobic one.
b. This type of lagoon may be useful in warm and arid climates, par-
ticularly in those areas requiring total retention, i.e. a facultative-
evaporative lagoon.
7-76. Input Data.
a. Wastewater flov.
(l) Average daily, mgd.
(2) Peak (hourly), mgd.
b. Wastewater characteristics.
(1) BOD influent, mg/£.
(2) Suspended solids, mg/£.
(3) Volatile suspended solids (VSS), mg/£
(k) Nitrogen, mg/£.
(5) Phosphorus, mg/£.
(6) Nonbiodegradable fraction of VSS.
c. Desired degree of treatment.
d. Temperature, °F or °C (summer and winter).
7-77- Design Parameters.
a. Reaction rate constant/day (0.5-1-0, avg 0.75).
b. Temperature correction coefficient «1.075.
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c. Fraction BOD removed for respiration (0.9-1.4).
d. BOD feedback from bottom or sediment (summer = 20 percent;
winter = 5 percent).
e. MLVSS, mg/£ (50-150) average 100.
7-78- Design Procedure.
a. Select the rate constant, K . Adjust K for summer and winter
temperatures.
K = K 0(T~2°)
where
K^ = rate constant for desired temperature, °C
K = rate constant at 20°C
6 = temperature correction coefficient
T = temperature, °C
b. For summer and winter efficiencies, calculate detention times to
meet winter efficiency.
Se
S^= 1 + Kt (1<05)
where
S = effluent soluble BOD,-, mg/£
e 5
S = influent BOD , mg/£
K = reaction rate constant
t = detention time, days
and summer efficiency
S
e 1
S 1 + Kt
7-22^
-------
Select the larger of the detention times.
c. Calculate volume.
V = Q t
avg
where
V = volume, million gal
Q = average daily flow, mgd
avg
t = detention time, days
d. Determine oxygen requirements. Assume a'
= a'SrQ(8.
where
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29 Sep 78
0 = oxygen required, Ib/day
a1 = fraction of BOD oxidized for energy
S = BOD removed, mg/£
Q = flow, mgd
e. Determine amount of effluent solids (50-150) mg/£.
f. Design mechanical aeration system and check horsepower supply
to allow solids to settle: horsepower required to allow solids to
settle (0.01-0.02 hp/1000 gal).
(l) Assume the following design parameters.
(a) Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen,
20°C, and tap water).
(~b) 02 transfer in waste/02 transfer in water asO.9.
(c) 0 saturation in waste/0 saturation in water «£).9-
7-225
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29 Sep 78
(d) Correction factor for pressure
(2) Select summer operating temperature (25-30°C) and determine
m standard tables) 0 saturation.
(3) Adjust standard transfer efficiency to operating conditions.
I T1—90
OTE = STE - —— (a) (1.02)
where
OTE = operating transfer efficiency, Ib 0 /hp-hr
STE = standard transfer efficiency, l"b 0 /hp-hr
(c \ = Q saturation at selected summer temperature, mg/£
^ S' m <-
3=0 saturation in waste/0 saturation in water aaO.9
p = correction factor for pressure ssiL.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 0 transfer in waste/0 transfer in water ;*0.9
T = temperature, °C
(k} Calculate horsepower requirement.
1000
i OTE
where
hp = horsepower required/1000 gal
®2 = oxygen required, Ib/day
OTE = operating transfer efficiency, Ib 0 /hp-hr
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V = volume of the basin, gal
. Calculate BOD in effluent.
(BOD)eff = Se + 0.3(VSS)eff
where
(BOD) = BOD in effluent, mg/£
S = effluent soluble BOD , mg/£
(VSS) = effluent volatile suspended solids, mg/£
h. Determine nutrient requirements.
BOD: Nitrogen-.Phosphorus = 100:5:1
7-79. Output Data.
a. Lagoon.
(l) Summer temperature, °C.
(2) Winter temperature, °C.
(3) Effluent BOD, mg/£.
(U) Reaction rate constant, I/day.
(5) Temperature correction coefficient.
(6) Detention time, days.
(7) MLVSS, mg/£
(8) Volume, million gal.
(9) Oxygen requirement, Ib/day.
(10) Nitrogen requirement, Ib/day.
(11) Phosphorus requirement, Ib/day.
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(12) Total effluent BOD, Ib/day.
b. Mechanical Aeration System.
(l) Standard transfer efficiency, Ib 0 /hp-hr.
(2) Operating transfer efficiency, Ib 0 /hp-hr.
(3) Horsepower required, hp.
7-80. Example Calculations.
a. Select reaction rate constant K and adjust for temperature
(25°C).
(T-20)
K25 ' K206
where
K = reaction rate at 25°C, rate/day
K = reaction rate at 20°C, 0.75/day
6 = temperature correction coefficient, 1.075
T = temperature, 25°C
K = 0.75(1.075)25~2°
K2Q = 1.077/day
b. Calculate detention times for winter and summer efficiencies,
For winter
S
S 1 + Kt
o
1 (1-05)
where
S = effluent soluble BOD 15 mg/£
7-228
-------
S = influent BODC, 200 mg/£
o 5
K = reaction rate constant, 1.077/day
t = detention time, days
1.05 = BOD feedback from sediment in winter
15 _
200 1 + 1.077(t)
t - 12 days
For summer
S
(1.05)
—
S ~ 1 + K(t) '
o
where
1.2 = BOD feedback from sediment in summer
(1.2)
200 1 + l.OTT(t)
t = lU-9 avg 15 days
Select larger detention time, t = 15 days
c. Calculate volume of lagoon.
V = Q t
avg
where
V = volume of lagoon, million gal
Q = average daily flow, 1.0 mgd
avg
t = detention time, 15 days
7-229
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v = 1.0(15)
V = 15 million gal
d. Determine oxygen requirements.
02 = a'SrQ(8.3H)l.2
where
Op = oxygen required, Ib/day
a' = 1,1
Sr = SQ - Se = 185 mg/£
Q = flow, 1.0 mgd
1.2 = Ib 0 required per Ib BOD removed
o2 = 1.1(185)1.0(8.3^)1.2
0 = 203T Ib/day
e. Determine effluent solids.
Assume (SS)eff = 100 mg/Jl.
f. Design mechanical aeration system.
(l) Assume the following parameters.
(a) STE =5.0 percent
(b) a = 0.9
(c) g = 0.9
(d) p = 1.0
(2) Select summer temperature (25°C) and determine 0 saturation.
(Cs)25 = 8.2 mg/£ . 2
7-230
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29 Sep 78
(3) Adjust STE to operating conditions.
61 TV P
II> ~ ^T
I T_?n
OTE = STE " - al.02
}
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 5-0 percent
(C ) =8.2 mg/H
^ rp
3 = 0.9
p = 1.0
CT = minimum dissolved oxygen, 0 mg/£
LJ
a = 0.9
9.17 = 0 saturation at 20°C
T = 25°C
OTE = 5.0 E8.2(0.9)l..O - 0] 0.9(1.02)25-20
y • -L i *
OTE = k.Q%
(k) Calculate horsepower required
00(1000)
hp
OTE 2it(V)(lO
where
hp = horsepower required, hp/1000 gal
Og = oxygen required, 2037 Ib/day
7-231
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OTE = operating transfer efficiency, k.O percent
V = volume of basin, 15 million gal
hp = 2037(1000)
1|.0(2M15(106)
hp = O.QCXU hp/1000 gal
g. Calculate BOD in effluent.
(BOD)eff = Se + °'3(VSS)eff
where
(BOD)eff = BOD in effluent, mg/£
Sg = soluble BOD in effluent, 15 mg/£
= -volatile suspended solids in effluent
= 0.8(SS)eff = 0.8(100) = 80 mg/£
(BOD)eff = 15 + 0.3(80)
(BOD)eff = 39 mg/Jl
h. Determine nutrient requirements.
BOD:N:P = 100:5:1
BOD =200 mg/£
N = 10 mg/£ required
P = 2 mg/Jl required
7-81. Cost Data. Appropriate cost data and economic evaluation
may be found in Chapter 8.
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T-82. Bibliography.
a. Barnhart, E. L. and Eckenfelder, W. W., Jr., "Theoretical
Aspects of Aerated Lagoon Design," Symposium on Wastevater Treatment
for Small Municipalities, 1965, Ecole Polytechnique, Montreal, Quebec,
Canada.
"b. Bishop, N. E. , Malina, J. F., Jr., and Eckenf elder, W. W. , Jr.,
"Studies on Mixing and Heat Exchange in Aerated Lagoons," Technical Re-
port EHE-70-21, CRWR-70, 1970, Center for Research in Water Resources,
University of Texas at Austin.
c. City of Austin, Texas, "Design Guides for Biological Waste-water
Treatment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
d. Eckenfelder, W. W., Jr., Industrial Water Pollution Control,
McGraw-Hill, New York, 1966.
e. Eckenfelder, W. W., Jr., "Aerated Lagoons," Manual of Treatment
Processes, Vol I, 1969» Environmental Science Services, Inc., Briarcliff
Manor, New York.
f. Eckenfelder, W. W. , Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 19&9, Environmental Science
Services, Inc., Briarcliff Manor, New York.
g. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution Control,
Pemberton Press, New York, 1970.
h. Goodman, B. L., Design Handbook of Wastewater Systems: Domestic,
Industrial, Commercial, Technomic, Westport, Conn., 1971-
i. McKinney, R. E., "Design and Operation of Complete Mixing
Activated Sludge Systems," Environmental Pollution Control Services
Reports, Vol 1, No. 3, Jul 1970, pp 1-3^.
j. McKinney, R. E. and Benjes, H. H., "Design and Operation of
Aerated Lagoons," Paper No. 3P2-1, Jul 1965, National Symposium on
Sanitary Engineering Research, Development and Design.
k. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
7-233
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1. Sawyer, C. W., "Mew Concepts in Aerated Lagoon Design and. Opera-
tion," Advances in Water Quality Improvements - Physical and Chemical
Processes, E. F. Gloyna and W. W. Eckenfelder, Jr., ed., University of
Texas Press, Austin, 1970.
T-23H
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Section XII. OXIDATION DITCH
7-83. Background. The oxidation ditch, developed in the Netherlands,
is a variation of the extended aeration process that has "been used in
small towns, isolated communities, and institutions in Europe and the
United States. The typical oxidation ditch (Fig. 7-9) is equipped with
aeration rotors or brushes that provide aeration and circulation. The
sewage moves through the ditch at 1 to 2 fps. The ditch may be designed
for continuous or intermittent operation. Because of this feature, this
process may be adaptable to the fluctuations in flows and loadings
associated with recreation area wastewater production.
O—:
•ROTOR
BAR
SCREEN
OXIDATION DITCH
FINAL
SETTLING
TANK
Figure 7-9- Typical oxidation ditch.
7-84. Input Data.
a. Wastewater Flow (Average and Peak). In case of high variability,
a statistical distribution should be provided.
b. Wastewater Strength.
(1) BOD (soluble and total), mg/£.
(2) COD and/or TOG (maximum and minimum), mg/£.
(3) Suspended solids, mg/£.
(M Volatile suspended solids (VSS), mg/fc.
(5) Nonbiodegradable fraction of VSS, mg/£.
c. Other Characterization.
7-235
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(1) PH..
(2) Acidity and/or alkalinity, mg/Jl.
(3) Nitrogen, mg/£.
Phosphorus (total and soluble), rng/A.
(5) Oils and greases, mg/£.
(6) Heavy metals, mg/&.
(7) Toxic or special characteristics (e.g., phenols), mg/£.
(8) Temperature, °F or °C.
d. Effluent Quality Requirements.
(1) BOD5, nig/ A.
(2) SS, mg/Jl.
(3) TKN, ing/ A.
(It) P, mg/Jl.
7-85- Design Parameters.
a. Reaction rate constants and coefficients.
Eckenf elder
k 0.0007-0.002 A/mg/hr
a 0.73
a' 0.52
b 0.075/day
The form of nitrogen should be specified as to its biological
availability (e.g., NH or Kjeldahl).
7-236
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29 Sep 78
bf 0.15/day
a O.TTa = 0.56
f O.UO
f 0.53
b. F/M = 0.03-0.1.
c. Volumetric loading = 10-HO.
d. t = 18-36 hr.
e. t = 20-30 days.
s
f. MLSS = ^000-8000 mg/A; mean, 6000 mg/£.
g. MLVSS = 2800-5600 mg/X..
h. Qr/Q = 0.5-1.0.
i. Ib 02/Xb BODr >. 1.5-
j. Ib solids/lb BOD <_ 0.2.
k. 6 = 1.0-1.03.
1. Efficiency = >90 percent.
7-86. Design Procedure.
a. Assume the following design parameters vhen known.
(l) Fraction of BOD synthesized (a).
(2) Fraction of BOD oxidized for energy (a1)-
(3) Endogenous respiration rate (b and b').
(h) Fraction of BOD synthesized to degradable solids (a ).
(5) Nonbiodegradable fraction of VSS in influent (f).
7-237
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(6) Mixed liquor suspended solids (MLSS).
(7) Volatile solids in mixed liquor suspended solids (MLVSS)
(8) Temperature correction coefficient (0).
(9) Degradable fraction of the MLVSS (f).
(10) Food-to-microorganism ratio (F/M).
(11) Effluent soluble BOD (S ).
b. Adjust the BOD removal rate constant for temperature.
K fl(T-20)
T 20
where
K_ = rate constant for desired temperature
K = rate constant at 20°C
6 = temperature correction coefficient
T = temperature, °C
c. Determine the size of the aeration tank.
a (S - S )Q
O O f*
TT _ *-* W *~
(xv)(f)(b)
where
V = aeration tank volume, million gal
a = fraction of BOD synthesized to degradable solids
S = influent BOD , mg/£
o 2
S = effluent soluble BOD , mg/£
= waste flow, mgd
T-238
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29 Sep 78
X^ = MLVSS,
f' = degradable fraction of the MLVSS
b = endogenous respiration rate, I/day
d. Calculate the detention time.
where
t = detention time, hr
V = volume, million gal
Q = flow, mgd
e. Assume the organic loading and calculate detention time.
2l|S
t _ o
•^V M
where
t = detention time, days
S = influent BOD.., mg/£
o ?
X = volatile solids in raw sludge, mg/fc
F/M = organic loading (food-to-microorganism ratio)
and select the larger of two detention times from d. or e.
f. Determine the oxygen requirements allowing 60 percent for
nitrification during summer.
°2 = a'SQ(8-3M + fc'XtS.aU) + °'6^-57) (
7-239
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29 Sep 78
where
0 = oxygen required, Ib/day
a1 = fraction of BOD oxidized for energy
Sr = BOD removed, mg/£
Q = average waste flow, mgd
b' = endogenous respiration rate, I/day
Xy = MLVSS, mg/H
V = aeration tank volume, million gal
TKN = total Kjeldahl nitrogen, mg/£
and calculate oxygen requirement (>1.5).
Ib BODr (Q)(Sr)(8.3U)
where
0 = oxygen required, Ib/day
Q = waste flow, mgd
S = BOD removed, mg/£
g. Calculate sludge production.
AXy = 8.3^[a(Sr)(Q) - (b)(Xy)(V) - Q(SS)eff + Q(VSS)f + Q(SS - VSS)]
t
where
AX^. = volatile sludge produced, Ib/day
a = fraction of BOD synthesized
= BOD removed, mg/£
T-2UO
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29 Sep 78
Q, = waste flow, mgd
to = endogenous respiration rate, I/day
X = volatile solids in raw sludge,
V = aeration tank volume, million gal
(SS) „ = effluent suspended solids, mg/fc
VSS = volatile suspended solids in influent, mg/£
f' = degradatole fraction of the MLVSS
(VSS) „_ = effluent volatile suspended solids, mg/£
efi
h. Calculate solids produced per pound of BOD removed.
Ib solids AXV
Ib BOD Q(S - S )8.
where
AX = volatile sludge produced, Ib/day
Q = waste flow, mgd
S = influent BOD , mg/£
o p
S = effluent soluble BOD^, mg/£
e 5
i. Calculate the solids retention time.
X (V)(8.3U)
t = a
AXv
where
t = solids retention time, days
S
X = MLSS, mg/£
3,
V = volume of aeration tank, million gal
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29 Sep 78
AX^ = volatile sludge produced, Ib/day
j. Determine the effluent soluble BOD ,
S
e _
S ~ 1
o
where
S = soluble effluent BOD, mg/£
G
S = influent BOD, mg/£
k = rate constant, 1/mg/hr
X^ = MLVSS, mg/£
t = aeration time, hr
k. Calculate sludge recycle ratio.
Q X - X
avg u a
where
Q = volume of recycled sludge, mgd
Q = average flow, mgd
X = MLSS, mg/£
cl
X = suspended solids concentration in returned sludge, mg/£
1. Calculate the nutrient requirements for nitrogen
N = 0.123AXy
and phosphorus
P = 0.026AXV
T-2U2
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29 Sep 78
where
AX = sludge produced, Ib/day
7-87. Output Data.
a. Aeration Tank.
(l) Reaction rate constant, 1/mg/hr.
(2) Sludge produced per BOD removed.
(3) Endogenous respiration rate (b, ~b').
(k) 0 utilized per BOD removed.
(5) Influent nonbiodegradable VSS.
(6) Effluent degradable VSS.
(7) lb BOD/lb MLSS-day (F/M).
(8) Mixed liquor suspended solids, mg/& (MLSS).
(9) Mixed liquor volatile suspended solids, mg/£ (MLVSS).
(10) Aeration time, hr.
(ll) Volume of aeration tank, million gal.
(12) Oxygen required, Ib/day.
(13) Sludge produced, Ib/day.
(Ik) Nitrogen requirement, Ib/day.
(15) Phosphorus requirement, Ib/day.
(16) Sludge recycle ratio, Ib/day.
(17) Solids retention time, days.
b. Mechanical Aeration System.
(l) Standard transfer efficiency, lb 0 /hp-hr.
7-21*3
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29 Sep 78
(2) Operating transfer efficiency, l"b 0 /hp-hr.
(3) Horsepower required, hp.
c. Diffused Aeration System.
(l) Standard transfer efficiency, percent.
(2) Operating efficiency, percent.
(3) Required air flow, cfm/1000 ft3.
7-88. Example Calculations (Eckenfelder's Approach).
a. Assume the following design parameters.
(1) a - 0.73
(2) a' = 0.52
(3) b - 0.075/day, V = 0.15/day
(U) a = 0.56
o
(5) f = 0.1+0
(6) MLSS = X = 6000 mg/H
Si
(7) MLVSS = Xy = 1*200 mg/£
(8) e = 1.02
(9) f - 0.53
(10) F/M = 0.06
(11) S =10 mg/£
"b. Adjust the BOD removal rate constant for temperature.
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29 Sep 78
where
K™ = removal rate constant at T°C
K = removal rate constant at 20°C, 0.0010
0 = 1.02
T = 1S°C
KT = 0. 001(1. 02)15~2°
K.J, = 0.0009
c. Determine the size of the aeration tank.
a (S - S )Q
v - oo ex avg
where
V = volume of aeration tank, million gal
ao = 0.56
S = influent BOD , 200 mg/£
S = effluent soluble BOD , 10 mg/l
Qa = average flow, 1.0 mgd
Xy = MLVSS, 4200 rng/A
f = 0.53
b = 0.075/day
V = 0-56(200 - 10)1.0
4200(0.53)0.075
V = 0.64 million gal
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d. Calculate detention time.
where
t = detention time, hr
V = volume, 0.6U million gal
Q = average flow, 1.0 mgd
t = 15 hr
e. Assume organic loading and calculate detention time.
2k(S )
t =
where
t = detention time, hr
S = influent BOD , 200 mg/£
Xy = MLVSS, U200 mg/fc
F/M =0.06
= 2U(200)
U200(0.06
t = 19 hr
Select larger detention time, t = 19 hr
f. Determine oxygen requirements allowing 60 percent for nitrifica-
tion during summer.
00 = [a'S Q + b'XV + 0.6(4.5T)TKN(Q)]8.31+
2 r avg v
T-2H6
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where
0 = oxygen required, Ib/day
a1 = 0.56
S = S - S = 190 mg/£
Q = average flow, 1.0 mgd
b' = 0.15/day
Xy = MLVSS, 4200 mg/£
V = volume of aeration tank, 0.6h million gal
4.57 - parts oxygen required per part TKN
TKN = total Kjeldahl nitrogen, 30 mg/£
02 = [0.56(190)1.0 + 0.15(4200)0.64 + 0.6(4. 57)30(1.
O = 4936 Ib/day
g. Calculate oxygen required per pound of BOD removed.
lb BOD Q (S )8.34
r avg r
where
0 = oxygen required, 4936 Ib/day
!J = average flow, 1.0 mgd
S = BOD removed, 190 mg/£
lb °2 4936
lb BOD 190(1.0)8.34
lb 0
= 3.0 > 1.5 (OK)
lb BOD
r
7-247
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h. Calculate sludge production.
AXy = [aSrQ - bXyV - Q(SS)eff + Q(VSS)f + Q(SS - VSS)]8.3U
where
A3C. = sludge produced, Ib/day
a = 0.73
S = BOD removed, S - S = 190 mg/£
Q = average flow , 1.0 mgd
b = 0.075/day
Xy = MLVSS 1*200 mg/A
V = volume of aeration tank, 0.6k million gal
(SS)eff = solids in effluent, 20 mg/£
VSS = volatile solids in, influent, 150 mg/Jl
f = 0.53
SS = solids in influent, 200 mg/£
AXy = [0.73(190)1.0 - 0.075(^200)0.61+
- 1.0(20) + 1.0(150)0.53 + 1.0(200 - 150)]8.3U
A = 389 Ib/day
i. Calculate solids produced per pound of BOD removed.
113 solids _ Axy
where
AXy = sludge produced, 389 Ib/day
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= average flow, 1.0 mgd
S = influent BOD, 200 mg/£
o
S = effluent BOD, 10 mg/£
Ib solids _ 389
It BOD ~ 1.0(200 - 10)8.31*
(OK)
j. Calculate solids retention time.
X V8.31*
where
t = solids retention time, days
o
X = MLSS, 6000 mg/SL
El
V = volume of aeration tank, 0.61* million gal
AX^ = solids produced, 389 Ib/day
_ 6000(0.6l*)8.31*
s 389
t = 82 days
S
k. Determine effluent soluble BOD .
fe
so
7-21*9
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29 Sep 78
where
S = soluble effluent BOD, mg/£
S = influent BOD, 200 mg/£
o
K = reaction rate constant, 0.0009
Xy = MLVSS, 4200 mg/£
t = detention time, 19 hr
S
e
200 1 + (0.0009)^200(19)
S =2.7 mg/£
1. Calculate sludge recycle ratio.
Q X
r a
X - X
avg u a
where
Q = recycle flow, mgd
= average flow, 1.0 mgd
avg
X = MLSS, 6000 mg/£
a
X = underflow concentration, 10,000 mg/£
Qr = 6,000
1.0 10,000 - 6,000
= 1.5
m. Calculate nutrient requirements for nitrogen.
7-250
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29 Sep 78
N = O.
N = 0.123(389)
N = 1*8 Ib/day
for phosphorus
P = 0.026AX
P = 0.026(389)
P = 10 Ib/day
N in influent = 30
= 30(1. 0)8. 3U
=250 Ib/day > hQ Ib/day
H to be added = none
P in influent = 15 mg/&(Q)8. 3^
= 15(1.0)8. 3U
= 125 Ib/day > 10 Ib/day
P to be added = none
7-89. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
7-90. Bibliography.
a. Guillaume, F. P., "Evaluation of the Oxidation Ditch as a Means
of Waste-water Treatment in Ontario," Research Publication Wo. 6, Jul
196U, The Ontario Wastewater Commission, Ontario, Canada.
b. Lakeside Engineering Corporation, "Rotor Aeration," Apr I960.
c. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
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29 Sep 78
d. Nesbitt, J. B., "Removal of Phosphorous from Municipal Sewage
Plant Effluents," Engineering Research Bulletin B-93, 1966, College of
Engineering, Pennsylvania State University, University Park, Pa.
e. Prather, B. F., "Wastewater Aeration," The Oil and Gas Journal,
Vol 57, No. U9, 1959, pp 78-80, 8U, 86-91.
f. U. S. Department of Transportation, "Oxidation Ditch Sewage
Waste Treatment Process," Water Supply and Waste Disposal Series, Vol 6,
Apr 1972, U. S. Department of Transportation, Washington, D. C.
g. Zeper, J. and DeMan, A., "New Developments in the Design of
Activated Sludge Tanks with Low BOD Loadings," 5th International Water
Pollution Research Conference, Jul-Aug 1971, San Francisco, Calif.
h. Parker, H. W., "Water Supply and Waste Disposal Series, Oxida-
tion Ditch Sewage Treatment Process," Apr 1972, U. S. Department of
Transportation, Federal Highway Administration.
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Section XIII. NITRIFICATION-DENITRIFICATION
7-91. Background.
a. General. Nitrogen exerts an oxygen demand in the unoxidized
state (NH3-N) and also contributes to eutrophication of natural waters.
Hence, nitrogen is considered a pollutant and, in many cases, removal
is required. Several methods have been developed for nitrogen removal;
perhaps the most promising biological process is the nitrification-
denitrification process. Depending on the forms of nitrogen present in
the waste-water, biological nitrogen removal can be accomplished in one
or more stages (fig. 7-10). When the ammonia form is present, two
stages are required. The initial stage involves the conversion of am-
monium to nitrates (called nitrification) by the aerobic bacteria (nitro-
somonas and nitrobacter). The second stage (denitrification) consists
of the anaerobic conversion of nitrate to nitrogen gas. If the nitro-
gen is already in the form of nitrate, as in the case of irrigation
return water, only the second stage (or denitrification) is required.
CHEM
ADDI
LETE\
* }— *
CTOR I
SLUDGE
CAL
TION
H TANK 1 1
RETURN
f
HASTE
SLUDGE
ORGANIC
CARBON
ptt ADJUSTMENT »«TE
(IF REQUIRED] SLUDGE
FACILITIES FOR REDUCED
VOLUME OPERATIC*
t f
1 1
r "-"S C|-
_ /SETTLMcX
* 1 TANK J
y
SLUDGE RETURN R
INTERCONNECTED SLUDGE RETURN \ /
N CASE NITR1FICAT ON SLUDGE Y
IS WASHED OUT OR LOST 1
INTERCONNECTED FOR STARTUP,
RESEEDING AND TO AID IN OPEftAT ON
OF NITRIFICATION SYSTEM
NITRIFICATION
CHEMICAL
ADDITION
5(E 3J2
SI ||
|j3 3S FACILITIES FOR REDUCED
£§ *u- VOLUME OPERATION
11 f f ' ^
1
R SLUDGE RETURN (
WASTE
SLUDGE
DENITRIF CATION
CONVERSION (AEROBIC'
From Metcalf and Eddy, 1972
Figure 7-10. Flow sheet for a three-stage biological
treatment process for nitrogen removal.
7-253
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EM 1110-2-501
Part 1 of 3
29 Sep 78
b. Nitrification. Nitrification can be accomplished in conventional
activated sludge reactors by increasing the solids retention time such
that it is greater than the growth rate of the nitrifier (nitrosomonas ) .
Nitrifying bacteria can exert a considerable oxygen demand; therefore,
sufficient air must be provided to the system. However, nitrification
is usually carried out in a separate reactor, which allows better flex-
ibility and optimum performance of both the carbonaceous oxidation and
nitrification.
c- Denitrification. Denitrification results from the utilization
of chemically bound oxygen (N03) by facultative organisms in the absence
of dissolved oxygen. Since denitrification takes place after the aero-
bic removal of carbon it may be necessary to add some carbon source in
the denitrification tank for use by the denitrifying bacteria in cell
synthesis. A number of studies have been conducted to evaluate the
denitrification process (d, f, g, h, and i, para 7-98).
7-92. Input Data.
a< Nitrification (following first stage complete mix).
(l) Wastevater flow (average and peak hourly), mgd.
(2) Wastevater characteristics.
(a) BOD , mg/£.
(b) NH -N (average and peak), mg/£.
(c) Temperature, °C.
(d) pH.
(3) Degree of nitrification desired, percent.
b. Denitrification (following nitrification).
(l) Wastewater flow (average and peak), mgd.
(2) Effluent quality from nitrification stage.
(a) N0, N0
7-25^4
2,
(b) Dissolved oxygen, mg/£.
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(c) Temperature, °C.
(a) PH.
(3) Degree of nitrification desired, percent.
7-93. Design Parameters.
a. Nitrification.
(l) NH loading versus temperature and MLVSS curve (fig. 7-ll)-
(2) Correction factor of loading for pH (fig. 7-12).
(3) MLSS, range 1500-2500 mg/SL.
(U) MLVSS as 0.8 MLSS.
(5) Percent nitrification, range 60-70 percent.
b. Denitrification.
o
(l) NO lb/day/1000 ft versus temperature and MLVSS (figs. 7-13
and 1-lk). 3
(2) MLSS as 1500-2500 mg/£.
(3) MLVSS as 0.8 MLSS.
Methanol requirements (3-3-5 lb/lb M).
7-9^. Design Procedure. The design procedures for nitrification and
denitrification are based on empirical relationships developed by
Sawyer (para 7-98h).
a. Nitrification.
(1) Select a MLVSS.
(2) Calculate the ammonia (NH ) load, Ib/day.
= (Q )(8.3U)(NH3-N)
avg
7-255
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EM 1110-2-501
Part 1 of 3
29 Sep 78
20
25
0 5 10 15
TEMPERATURE , °C
Figure 7-U- Permissible nitrification tank loadings.
7-256
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100
EM 1110-2-501
Part 1 of 3
29 Sep 78
80
60
O
I- 40
o
cc
111
0.
20
AT 20"C
I I I
I I I I
8
pH
Figure 7-12. Percent of maximum rate of nitrification
at constant temperature versus pH.
7-257
-------
I
IX)
Co
DENITRIFICATION RATE , LB OXIDIZED NITROGEN REMOVED/DAY/LB MLVSS
O P O O O o
i . v . ..,.>•'£?
J-J. O — W C*J ^ O< 0> -J QD
(g
4
fD
-0
1
H
U)
Oi
0 M
Hj H,
Hj
PJ 0)
(DO ,
-^ i5
^ 1
H- x
Ht> rt >
H- rt> H
00 C
{D W 3J
d- tD m
H- i-J -
0 P3 o"1
» ^ 0
' n
m
£
*5
o w
x ^
3 >J] °
4 1
P ^
<^ &
^ £,
% w
\
\
ss^
^^^
\t^
•a
m
-n
2
C
r— ...
CD
>
3)
^^^^^^
^^-^
•a
i
ro
i —
CD
^-^
^_
— • —
™l f — '
'
-------
ISO
EM 1110-2-501
Part 1 of 3
29 Sep 78
160
140
120
D
U
100
80
n
o
z
0)
60
40
20
3000
10
15
20
TEMPERATURE ; C
MLVSS
2500
2000
1500
1000
25
30
From Mulbarger
Figure 7-1^-• Permissible denitrification tank loadings.
7-259
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Part 1 of 3
29 Sep 78
fm -N\ = /NH-N)
^ 'p \ 'avg
where
NH-N = ammonia, mg/£
= peak NH , Ib/day
/ P
(NH -NJ = average NH , Ib/day
\ ' avg -*
Q = peak flow, mgd
Q = average flow, mgd
o,Vg
(3) Turn to Figure 7-U; for winter temperature, °C, and MLVSS
selected, determine the allowable loading of ammonia, lb/1000 ft3/day
at the optimum pH (8.4).
Then turn to Figure 1-12; adjust loading for operating pH (see
Input Data).
(5) Calculate volume of tank required.
V (HH ) adjusted X 100°
where
o
V = volume of the tank, ft
fNH_j = average ammonia load, Ib/day
* avg
(NH ) adjusted = allowable loading adjusted, lb/1000 ft3/day
(6) Determine oxygen requirements: total oxygen = (o ) +
(a) For nitrification.
(OP) = (4.57) (% nitrification). v
V 24 '*' \ 100 / V 3J
T-260
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Part 1 of 3
29 Sep 78
where
10 J = oxygen, Ib/day
N
/NH_\ = peak NH , Ib/day
^ 'P
(b) For BOD removal.
= (1.5)(BODC)(Q_J(8.34)
v ^BOD
where
= oxygen, Ib/day
BOD ^ avg'
BOD
BOD = influent BOD to nitrification tank, mg/£
Q = average flow, mgd
avg
(T) Design aeration systems.
(a) Diffused Aeration System.
!_ Assume the following design parameters.
a_ Standard transfer efficiency, percent, from manufacturer
(5-8 percent).
b_ 0 transfer in waste/0 transfer in water «0.9.
c_ 0 saturation in waste/0 saturation in water aO.9.
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29 Sep 78
vhere
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent
\ s) = ^2 saturati°n at selected summer temperature, mg/£
3 = 02 saturation in waste/0? saturation in water «0.9
p = correction factor for pressure si.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0 mg/£
a = 02 transfer in waste/0 transfer in water asO.9
T = temperature, °C
U_ Calculate required air flow.
0
R =
'a / lb °o \ / -
(OTE) 0.0176 , 2 UlUtO
V ft3 air/V
where
R = required air flow, cfm/1000 ft3
a,
0 = oxygen required, Ib/day
OTE = operating transfer efficiency, percent
V = volume of the basin, gal
(b) Mechanical Aeration System.
!_ Assume the following design parameters.
a. Standard transfer efficiency, Ib/hp-hr (0 dissolved oxygen, 20°C,
and tap water).
b_ 0 transfer in waste/0 transfer in water *0.9.
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29 Sep 78
c_ Correction factor for pressure si.O.
d_ 0 = saturation in waste/0 saturation in water asO.p-
2_ Select summer operating temperature (25-30°C) and determine
(from standard tables) 0 saturation.
3. Adjust standard transfer efficiency to operating conditions.
(e)(p) - c
where
OTE = STE " ' '* 17 ^ a(l.02)T~20
OTE = operating transfer efficiency, Ib 0^/hp-hr
STE = standard transfer efficiency, Ib 0?/hp-hr
[C ) = 00 saturation at selected summer temperature, mg/£
\ S/T
3 = 0 saturation in waste/0 saturation in water «0.9
p = correction factor for pressure asL.O
C = minimum dissolved oxygen to be maintained in the basin
> 2.0
a = 0 transfer in waste/0 transfer in water saO:9
T = temperature, °C
Calculate horsepower reguirement.
0
hp = .. . x x 1000
where
hp = horsepower required per 1000 gal
Op = oxygen required, Ib/day
7-263
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Part 1 of 3
29 Sep 78
OTE = operating transfer efficiency, Ib 0 /hp-hr
V = volume of the basin, gal
(8) Determine sludge production.
0.1 lb/(lb-NH \
\ /removed
= (0.1)/NH \ (% nitrification }
a V 3/avg V 100 /
where
(NH j
V '
A = sludge produced, Ib/day
A
a
= average NH loading, Ib/day
avg
(9) Determine lime requirements; for winter conditions add
of hydrated lime per pound of KH removed to maintain desired pH.
b. Denitrif ication.
(1) Calculate NO loading.
avg
= (NO ) (yQavg)
'p V /avg ^
where
/NO \
\ /
= average NO loading, Ib/day
avg
Q = average flow, mgd
avg
(NO \
V /
= peak NO loading, Ib/day
p
Q
= peak flow, mgd
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EM 1110-2-501
Part 1 of 3
29 Sep 78
(2) Turn to Figure 7-1^; for winter temperature and MLVSS determine
NO loading (ib NO /1000 ft3/day) at optimum pH.
(3) Adjust loading for operating pH (Table 7-1)-
Calculate volume of denitrification tank.
V = —— §_ (1000)
NO loading
where
3
V = volume of the denitrification tank, ft
= peak NO loading, Ib/day
NO loading = lb/1000 ft3/day
(5) Calculate methanol requirements.
Methanol (ib/day) = 2.Vf(NO ) + 1.53(W02) + 0.87(Dissolved Oxygen)
Or from rule of thumb
Methanol (ib/day) = (2.5) Ib/lb NO reduced
= (2.5)(NO \ (% NO reduced)
V /avg
(6) Determine sludge production.
A =0.2 Ib/lb methanol added
X
a
or
A =0.7 Ib/lb NO reduced
Xa 3
where
A = sludge produced, Ib/day
A
a
7-265
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29 Sep 78
7-95. Output Data.
a. Nitrification.
(l) Winter temperature, °C.
(2) pH.
(3) Effluent ammonia, mg/£.
(it) Mixed liquor volatile solids, mg/£ (MLVSS).
(5) Ammonia loading, lb/1000 ft /day.
(6) Volume, ft3.
(7) Oxygen required, lb/day.
(8) Sludge produced, lb/day.
(9) Lime required, lb/day.
(10) Mechanical aeration system.
(a) Standard transfer efficiency, Ib 0 /hp-hr.
(b) Operating transfer efficiency, Ib 0 /hp-hr.
(c) Horsepower required/1000 gal.
(ll) Diffused aeration system.
(a) Standard transfer efficiency, percent.
(b) Operating transfer efficiency, percent.
(c) Required air flow, cfm/1000 ft3.
"b- Intermediate Clarifier. (See chap. 5, sec IX, Sedimentation
(Secondary Clarifier).)
c. Denitrification.
(l) Winter temperature, °C.
7-266
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Part 1 of 3
29 Sep 78
(2) PH.
(3) Influent dissolved oxygen, mg/£.
(H) Nitrate loading, mg/£.
(5) Mixed liquor volatile solids, mg/£ (MLVSS).
(6) Volume, ft3.
(7) Sludge produced, Ib/day.
(8) Methanol required, Ib/day.
d. Final Clarifier. (See chap. 5, sec IX, Sedimentation (Secondary
Clarifier) . )
7-96. Example Calculations.
a. Nitrification.
(1) Select MLVSS =0.8 MLSS.
MLVSS = 0.8(2000)
MLVSS = 1600 mg/£
(2) Calculate NH3 load.
(NH -N)
^ -' '
(NH -N) = (NH -N)
V J /p V /
p(8.3U)(HH -N)
avg °
)
avg \ "avg /
where
= average NH load, Ib/day
avg
0 = average flow, 1.0 mgd
avg
NH -N = ammonia concentration, 30 mg/£
T-267
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29 Sep 78
= peak NH3 load, Ib/day
Q = peak flow, 2.0 mgd
(NH -N) = 1.0(8.3^)30
\ ' avg
-N\ =250 lb/day
/
3 'avg
/NH -N\ = 500 lb/day
^ 'P _
(3) Select winter temperature (lO°C) and MLVSS (1600 mg/£) and
determine allowable ammonia loading from Figure 7-10 at pH = 8.U.
NH = 8 lb/day /1000 ft3
Adjust NH loading to operating pH from Figure 7-11 (pH =7.8)
/NH \ = 87^(8 lb/day/1000 ft3)
V 'adjusted
'adjusted
adjusted
/^NlA = 7 lb/day/1000 ft3
Calculate volume of tank required.
(M3)
(1000)
3
/adjusted
where
•3
V = volume of tank, ft
7-268
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Part 1 of 3
29 Sep 78
/NH \
\ 3/
H ) = ammonia load, 250 lb/day
'avg -
= plant loading, 7 lV day/1000 ft
adjusted
V = (1000)
V = 35,700 ft3
(6) Determine the oxygen requirements.
(a) For nitrification
where
= oxygen required for nitrification, Ib/day
= peak ammonia load, 500 Ib/day
(0 ) =
2^N
/NH -N^
V 3 /
p
Percent nitrification = 60 percent
A
(b) For BOD-removal
= 1371 Ib/day
= 1.5(BODC)Q (8.3*0
BOD 5 aVg
where
= oxygen required for BOD removal, l"b/day
/O \
V /
BOD
BOD = influent BOD from secondary treatment, 30 mg/£
Q = average flow, 1.0 mgd
a. V Q
7-269
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Part 1 of 3
29 Sep 78
= 1.5(30)1.0(8.3U)
(0 )
V /BOD
= 375- 3 Ib/day
BOD
(c) 0 =
= (0 ) + (0 )
V ^/N V VBOD
02 = 1371 + 375
02 = 17U6 Ib/day
(7) Design aeration system (diffused).
(a) Assume the following design parameters
!_ STE = 7 percent
2_ a = 0.9
1 3 = 0.9
h_ p = 1.0
(b) Select summer operating temperature and determine 0 satura-
tion (C \ = 8.2 mg/£ . 2
PS
(c) Adjust standard transfer efficiency to operating conditions.
L V / T ^ I T1 on
OTE = STE —— al.02
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 7 percent
-s) =8.2 mg/£
e = 0.9
7-270
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29 Sep 78
p = 1.0
C = minimum dissolved oxygen, 0 mg/£
L
a = 0.9
T = 25°C
OTE = T>0 [8.2(0.9)1.0 - 0.0] 0.9(1.02)25-20
OTE = 5.6%
(d) Calculate required air flow.
Ra OTE(0.
where
R = required air flow, cfm/1000 ft
cL
0 = oxygen required, 17^6 l"b/day
OTE = 5.6 percent
V = volume of tank, 35,700 gal
R =
a 5.6(0.0176)1^0(35,700)
R = 258 cfm/1000 ft3
a
(8) Determine sludge production.
nitrification A
100 /
avg
7-271
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Part 1 of 3
29 Sep 78
where
A = sludge produced, Ib/day
a
/NH -U\ = average ammonia load, 250 Ib/day
V /avg
% nitrification = 60%
A = 0.1(250) •$-
xa 100
AX = 15 Ib/day
a
(9) Determine lime requirements for winter
Lime = 5.UHH -N) (* nitrification\
avg '
Lime = 5-M250) ~
Lime = 810 Ib/day
"b. Denitrification.
(1) Calculate WO loading.
= /NO
(NO \ = /
\ 3/p \
where
V °3) = avera§e N0^ loading, Ib/day
^ /avg -^
Q = average flow, 1.0 mgd
7-272
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Part 1 of 3
29 Sep 78
\ = peak'NO loading, Ib/day
Q = peak flow, 2.0 mgd
(NO \ = 30(1.0)8.sU
\ /avg
(NO \ = 250 It/day
\ /avg
=500 Ib/day
£
(2) Determine NO loading from Table 7-13.
NO = 18 lb/day/1000 ft3
(3) Adjust pH to operating conditions. Assume pH = 7-0, therefore,
optimum conditions.
(k) Calculate volume of denitrification tank.
Ib NO /day
V = ————: 1000
NO loading
where
V = volume of denitrification tank, ft
Ib NO /day = (NO \ = 500 Ib/day
p ^
NO loading = 18 lb/day/1000 ff3
v = (100Q)
V ^ 27,778 ft3
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29 Sep 78
(5) Calculate methanol (carbon) requirements.
Methanol (ib/day) = 2.5 Ib/lb NO reduced,
=2.5 (NO \ (% NO reduced)
V -Vavg J
= 2.5(250)
Methanol = 625 Ib/day
(6) Determine sludge production
A =0.2 Ib/lb methanol added
A
a
or
A =0.7 Ib/lb N0_ reduced
Xa 3
AX = 0.2(625)
a
AX = 125 Ib/day
a
7-97- Cost Data. Appropriate cost data and economic evaluation may be
found in Chapter 8 .
T-98. Bibliography.
a. Borchardt , J. A., "Nitrification in the Activated Sludge
Process," The Activated Sludge Process, Bulletin, University of
Michigan, Ann Arbor, Mich.
b. Brown and Caldwell, Engineers for EPA, "Nitrification and De-
nitrification Facilities," May 7-9, 197^, U. S. Environmental Protection
Agency Technology Transfer, Orlando, Fla.
c. Eckenf elder, W. W. , Jr., "General Concepts of Biological Treat-
ment," Manual of Treatment Processes, Vol 1, 1969, Environmental Science
Services, Inc., Briarcliff Manor, New York.
d. McCarty, P. L. , "Biological Processes for Nitrogen Removal:
Theory and Application," Proceedings, Twelfth Sanitary Engineering
Conference, 1970, University of Illinois, Urbana, 111.
7-27^
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EM 1110-2-501
Part 1 of 3
29 Sep 78
e. Mechalas, B. J., Allen, P. M., III, and Matyskiela, W. W., "A
Study of Nitrification and Denitrification," Report No. 17010DRD,
Jul 19TO, U. S. Environmental Protection Agency, Washington, D. C.
f. Metcalf and Eddy, Inc., Waste-water Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
g. Moore, S. F. and Schroeder, E. D., "An Investigation of the
Effects of Residence Time on Anaerobic Bacterial Denitrification,"
Water Research, Vol h, No. 10, 1970, pp 685-69^.
h. Mulbarger, M. C., "Nitrification and Denitrification in Acti-
vated Sludge Systems," Journal, Water Pollution Control Federation,
Vol 43, Oct 1971, PP 2059-2070.
i. Sawyer, C. N., "Nitrification and Denitrification Facilities,"
Aug 1973, U. S. Environmental Protection Agency, Technology Transfer,
Washington, D. C.
j. Seedel, D. F. and Criter, R. W., "Evaluation of Anaerobic De-
nitrification Processes," Journal, Sanitary Engineering Division,
American Society of Civil Engineers, Vol 96, No. SA2, 1970.
7-275
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29 Sep 78
Table 7-1. Effect of pH on Denitrification
p_H Condition
At 6.5 <_ pH <_ 7-5 Optimum
At 6.3 1 PH 1 6.5)
;. 6 <_ pH <_ 6.3 }
' -1 1 PH 1 8-6/
of optimum
At 7-5 < PH < 7.7)
At 5-6 <_ pH <_ 6.3'
50^ of optimum
, \
At 1.
7-276
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29 Sep 78
Section XIV. AEBOBIC DIGESTION
7-99- Introduction.
a. Both aerobic and anaerobic digesters are being used in new de-
signs for activated sludge systems; there are advantages and disadvan-
tages to both systems. Before a specific choice can be made, waste
characteristics, general climatic conditions, type of sludge handling
equipment, and the capacity of the facility must be considered. In a
large facility, it may be feasible or desirable to digest primary sludge
anaerobically, and secondary sludge aerobically.
b. Aerobic digestion is relatively new, and reliable information
on process kinetics and economics is scarce.
c. The aerobic combustion of the sludges is usually depicted as
follows .
The NH in the presence of oxygen can be further oxidized to NO to NO
d. Advantages claimed for aerobic as compared with anaerobic
digestion are listed below.
(l) VSS is reduced to 40-50 percent — nearly equivalent to that
for anaerobic .
(2) Supernatant has lower BOD.
(3) A relatively stable humuslike end product is produced.
(U) More basic fertilizer values are recovered.
(5) Operation is relatively simple.
(6) Capital cost is lower.
( 7 ) Odor i s minimal .
(8) Sludges dewater well (this is a controversial statement).
e. The major disadvantages appear to be:
7-277
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29 Sep 78
(1) A higher operating cost associated with 0 supply.
(2) The lack of a useful by-product (no CH, ).
7-100. Background.
a. This -nethod of digestion is capable of handling waste activated,
trickling filter, or primary sludges as well as mixtures of the same.
The aerobic digester operates on the same principles as the activated
sludge process. As food is depleted, the microbes enter the endogenous
phase and the cell tissue is aerobically oxidized to CO , HO, NH NO ,
and NO . ^ ^ 32
b. Up to 80 percent of the cell tissue may be oxidized in this
manner; the remaining fractions contain inert and nonbiodegradable mate-
rials. Factors to be considered during the design process are character-
istics (orig.in(s)) of the sludge hydraulic residence, true solids load-
ing criteria, energy requirement for mixing, environmental conditions,
and process operation.
7-101.
Sludge production.
(, 1) Pr i nary, Ib / day.
(2) Secondary, Ib/day.
b. Solids contents (percent solids).
(1) Primary, percent.
(2) Secondary, percent.
c. Specific gravity.
d. Volatile solids content, percent.
7-102. Design Parameters (Table J-2).
7-103- Design Procedure.
a. Calculate total quantity of raw sludge.
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29 Sep 78
Q = _ SP(IOO) _
s (specific gravity ) (percent solids) (8. 3^)
vhere
Q = volume of raw sludge to digester, gal/day
S
SP = sludge produced, Ib/day
b. Select hydraulic detention time and calculate digesters' volume.
V = (t)(Q )
S
where
V = volume of digester, gal
t = hydraulic detention time, days
Q = volume of raw sludge to digester, gal/day
S
c. Check volatile solids loading.
VS£ = VS (7.U8) < (0.1-0.2)
where
VS£ = volatile solids loading, Ib VS/ft3/day
V = volume of digester, gal
d. Calculate solids retention time.
(l) Assume percent destruction of volatile solids: Uo percent is
common but it increases with temperature and retention time from approxi
mately 33 to JO percent.
(2) Calculate solids accumulation per day.
S - qp qp (f> volatile W^ destroyed \ , ,
Sac - SP - SP ^ 10£) ^ 100 ) (0'T5)
7-279
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29 Sep 78
where
S = solids accumulated per day
3,C
SP = sludge produced
(3) Assume MLSS in digester and calculate total capacity of sludge
digester.
DC = (V)(MLSS)(8.3^)(10~6)
where
DC = digester capacity, It
V = volume of digester, gal
MLSS = mixed liquor SS in digester, mg/&
(4) Calculate solids retention time.
ac
where
SRT = solids retention time, days
DC = digester capacity, Ib
S = total solids accumulated, lb/day
£LC
e. Calculate sludge wasting schedule. Assume solids content in
digested sludge is approximately 2.5 percent.
„-, -,-,-, , , . , total sludge in digester (lb)(lOO)
Volume of sludge to be wasted = -, - — - fi - — — ff~s - TTT — WQ _< \
(specific gravity )(% solids )( 8. 34)
This volume must be wasted each SRT.
f. Calculate oxygen requirements.
(l) 0 required for bacterial growth. Assume 0 required per
pound of volatile solids destroyed.
7-280
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29 Sep 78
n - fn IQP (% volatile\{% destroyed *
°2 ~ (VSP V100A100
V
where
0 = total oxygen required, lb/day
OT = oxygen required/lb of volatile solids destroyed =a 2.0 Ib
SP = sludge produced, lb/day
(2) Energy for mixing.
(a) Assume standard transfer efficiency, percent.
(b) Assume constants a , 3 , and p .
(c) Select summer temperature T.
(d) Calculate operating transfer efficiency.
OTE = STE
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, percent (5-
= 02 saturation at the summer temperature
3 = (C waste/C water) wO.9
s s
p = correction for altitude ad.O
C = minimum oxygen to be maintained in the digester, mg/£
a = (1C. waste/K water) sdO.9
J_jcl lj£L
K_ = oxygen transfer coefficient
Ijcl
T = temperature, °C
7-281
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29 Sep 78
(e) Calculate air supply; check against a minimum of
20 cfm/1000 ft3.
0 (
S / Ib Or
(OTE %) I 0.0176 —-—-
\ ft air/
-where
R = air supply, cfm/1000 ft'3
S
02 = oxygen supply, Ib/day
OTE = operating transfer efficiency, percent
V = volume of the basin, gal
7-10H. Output Data.
a. Raw sludge specific gravity.
b. Detention time, days.
c. Volatile solids destroyed, percent.
d. Mixed liquor solids, mg/£.
e. Solids in digested sludge, percent.
f. Rate constant, BOD applied to filter.
g. Coefficient of 0 saturation in waste/0p saturation in water.
h. Standard transfer efficiency, percent.
i. Digester volume, gal.
j. Volatile solids loading, Ib VS/ft3/day.
k. Solids accummulated, Ib/day.
1. Volume of wasted sludge, gal.
m. Solids retention time, days.
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n. Oxygen requirement, Ib/day.
o. Air supply, cfm/1000 ft3.
7-105. Example Calculations.
a. Calculate total quantity of raw sludge.
SP(IOO)
s (specific gravity)(percent solids)8.:
where
Q = volume of raw sludge, gpd
s
SP = sludge produced, 2191 It/day
Specific gravity =1.05
Percent solids =1.0
n _ 2191(100)
^s 1.05(1.0)8.3U
Qn = 25,020 gpd
S
b. Select detention time and calculate digester volume.
V= Qst
where
V = volume of digester, gal
Q = quantity of raw sludge, 25,020 gpd
S
t = detention time, 15 days
V = 25,020(15)
V = 375,300 gal
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c. Check volatile solids loading.
where
VS^ = volatile solids loading, Ib VS/ft3/day
VS = SP($ volatile) = 2191 (0.80) = 1753 Ib/day
V = volume of digester
VS^ = 0.035 < 0.1 (OK)
d. Calculate solids retention time.
(1) Assume percent reduction = 50 percent
(2) Calculate solids accumulation per day
S = SP - SF ft volatile)(# destroyed)
ac \ 100 'V 100 '
where
S = solids accumulation, l"b/day
SP = sludge produced, 2191 Ib/day
% volatile = 80$
% destroyed =50$
S = 153^ Ib/day
cLL-
(3) Assume MLSS in digester and calculate total capacity of
digester.
DC = V(MLSS)(8.3^ x io~6)
7-28^
-------
where
DC = digester capacity, Ib
V = volume of digester, 375,300 gal
MLSS = 12,000 mg/£
DC = 375,300(12,000)(8.3^ x io~6;
DC = 37,560 Ibs
(4) Calculate solids retention time
DC
SRT =
S
ac
EM 1110-2-501
Part 1 of 3
29 Sep 78
where
SRT = solids retention time, days
DC = digester capacity, 37,560 Ib
S = solids accumulation, 1,534 Ib/day
ac
qRm _ 37,560
SRT " 1,534
SET = 24.5 days
e. Calculate the sludge wasting schedule.
Volume of sludge to be wasted = 7 — —.-. > ,a TTT—r 8.34
to (specific gravity)(% solids)
where
DC = digester capacity = 37,560 Ib
Specific gravity =1.05
% solids =2.5%
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29 Sep 78
Volume of sludge to be wasted = .3,7,560(100)
1.05(2. 5)8. 31*
Volume of sludge to be wasted = 171,566 gal
Waste every SRT =2^.5 days
f. Calculate oxygen requirements.
(1) 02 required for bacterial growth. Assume 0 required/lb VS
destroyed =2.0. 2
Total 02 required = 2.0(SP)(* Y°oQtile)(* destroyed)
Total 02 required = 2 . 0 ( 2191 )
Total 0 required = 1753 Ib/day
(2) 0 required for mixing (diffused aeration).
OTE = STE
where
OTE = operating transfer efficiency, percent
STE = standard transfer efficiency, 8 percent
e = 0.9
P = i.o
:L = 2<0
a = 0.9
T = 25°C
7-286
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29 Sep 78
[8.2(0.9)1.0 - 2.0] lr
OTE = 8
"•-L l
OTE =
Check for mixing >_ 20 cfm/1000 ft3
- °2 required
~
s ~ OTE(0.01T6)lUUo(V)
where
R = air supply, cfm/1000 ft3
S
0 required = 1753 lb/day
V = volume of digester, 375,300 gal
OTE = \,1%
1,753(7.^8 x io5)
R =
s 1^7(0.0176)1^0(375,300)
R =29-3 cfm/1000 ft2 > 20 (OK)
s_
7-106. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
7-107. Bibliography.
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Burd, R. S., "A Study of Sludge Handling and Disposal," Publi-
cation WP-20-it, May 1968, Federal Water Pollution Control Administration,
Washington, D. C.
c. College of Engineering, Oklahoma State University, "Aerobic
Digestion of Organic Wastes," Report No. 17070DAU, Dec 1971, U. S.
Environmental Protection Agency, Washington, D. C.
7-287
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29 Sep 78
d. Dick, R. I., "Sludge Treatment, Disposal, and Utilization /
Literature Review," Journal, Water Pollution Control Federation, Vol 1*3,
Jun 1971, PP 113U-11U9.
e. Drier, D. E., "Aerobic Digestion of Solids," Proceedings of l8th
Purdue Industrial Waste Conference, 1963, Purdue University, Lafayette,
Ind.
f. Drier, D. E., "Aerobic Digestion of Sludge," paper presented
at Sanitary Engineering Institute,. Mar 1965, University of Wisconsin,
Madison, Wis.
g. Eckenfelder, W. W., Jr., Water Quality Engineering for Practic-
ing Engineers, Barnes and Nobel, New York, 1970.
h. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works (Ten States
Standards)," 1971, Health Education Service, Albany, N. Y.
i. Jaworski, N., Lawton, G. W., and Rohlich, G. A., "Aerobic Sludge
Digestion," International Journal of Air and Water Pollution, Vol k,
1961, pp 106-llU.
j . Loner, R. C., "Aerobic Digestion-Factors Affecting Design," 9th
Great Plains Sewage Works Design Conference, Mar 1965.
k. Lynam, B., McDonnell, G., and Krup, M., "Start-up and Operation
of Two New High-Rate Digestion Systems," Journal, Water Pollution Con-
trol Federation, Vol 39, Apr 1967, pp 518-535.
1. Malina, F. J., "Aerobic Sludge Stabilization," Manual of Treat-
ment Processes, Vol 1, Environmental Science Services, Inc., Briarcliff
Manor, New York, 1969.
m. McKinney, R. E. and O'Brien, W. J., "Activated Sludge - Basic
Design Concepts," Journal, Water Pollution Control Federation, Vol ho,
Nov 1968, pp 1831-181+3.
n. Metcalf and Eddy, Inc. , Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
o. Pohland, F. G. and Kang, J. J., "Anaerobic Processes," Journal,
Water Pollution Control Federation, Vol U6, No. 6, 1971, pp 1129-1133.
7-288
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29 Sep 78
p. Sawyer, C. N. and Grubling, J. S., "Fundamental Considerations
in High Rate Digestion," Journal, Sanitary Engineering Division, Ameri-
can Society of Civil Engineers, Vol 86, Mar I960, pp 49-63.
q.. Shindala, A. and Bryme, W. J., "Anaerobic Digestion of Thickened
Sludge," Public Works, Vol 101, Feb 1970, pp 73-76.
r. Shindala, A., Dust, J. V., and Champion, A. L., "Accelerated
Digestion of Concentrated Sludge," Water'and Sewage Works, Vol 117,
Sep 1970, pp 329-332.
7-289
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Table 7-2. Aerobic Digestion Design Parameters
ParameterValue
Hydraulic detention time, days at 20°C
Activated sludge only 12 to l6
Activated sludge from plant operated without
primary settling 16 to 18
Primary plus activated or trickling-filter sludge 18 to 22
Solids loading, Ib volatile solids/ft /day 0.1 to 0.2
Oxygen requirements
BOD in primary sludge, Ib/lb cell tissue =2
Energy requirements for mixing
Mechanical aerators, hp/1000 ft 0.5 to 1.0
Air mixing, cfm/1000 ft^ 20 to 30
Dissolved oxygen level in liquid, mg/H 1 to 2
Q
Detention times should be increased for temperature below 20°C. If
sludge cannot be withdrawn during certain periods (e.g. weekends,
rainy weather), additional storage capacity should be provided. Am-
monia produced during carbonaceous oxidation is oxidized to nitrate.
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Section XV. ANAEROBIC DIGESTION
7-108. Background.
a. This type of digestion can be traced back to the l850's. The
mechanics involved in the process are summarized in Figure 7-15. Anaer-
obic digestion may be adapted to both stationary and mobile systems for
handling solids from waste treatment systems, trailer dump stations,
marine dump stations, and vault toilets.
SLUDGE
INSOLUBLE ORGANIC MATERIAL
SOLUBLE ORGANIC MATERIAL
EXTRACELLULAR
ENZYMES
ACID-PRODUCING
BACTERIA
. OTHER .
' PRODUCTS "*
BACTERIAL
CELLS
ENDOGENOUS
METABOLISM
TO END PRODUCTS
Figure 7-15- Mechanism of anaerobic sludge
digestion (Eckenfelder).
b. There are conventional and high-rate digesters; the conventional
design uses the one- or two-stage process. In any of these systems,
provisions are normally made for sludge heating. The principal differ-
ence in the one- and two-stage systems is that, in the two-stage systems,
digestion is accomplished in the first tank. Figures 7-l6 and 7-17 con-
tain a pictorial explanation of the system.
c. The advantages of anaerobic as compared with aerobic digestion
include:
7-291
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29 Sep 78
SLUDGE
INLETS
GAS STORAGE
~ SCUM LAYER!_
SUPERNATANT
LAYER
ACTIVELY
DIGESTING
SLUDGE
GAS REMOVAL
SUPERNATANT
OUTLETS
From Metcalf and Eddy
Figure 1-1.6. Schematic of conventional
digester used in the one-stage process.
FIXED COVER
SLUC
INL
SLUDGE
HEATER
GE ^
ET ~*~
MIXER
_(
^ V
— * —
r ^
DIGESTER GAS OUTLET
FLOATING COVER
(OFTEN UNCOVERED)
^
••*-
SCUM LAYER
SUPERNATANT
LAYER
DIGESTED
SLI I nr;P
"^SUPERNATANT
"*"j OUTLETS
I SLUDGE
| OUTLETS
FIRST STAGE
(COMPLETELY MIXED)
SECOND STAGE
(STRATIFIED)
From Metcalf and Eddy
Figure 7-17. Schematic of two-stage
digestion process.
(l) Higher organic loading, i.e. rates of treatment not limited
"by 0 transfer.
(2) Minimal need for biological nutrients '(N and P) and for further
treatment .
(3) Lover energy requirement.
Production of a useful by-product (CH, ) which has a low heat
value compared to natural gas.
d. The disadvantages are as follows:
7-292
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29 Sep 78 '
(l) Digesters must be heated to 85-90°F for optimum operation.
(2) Molecular oxygen is toxic to the system and must be excluded.
(3) Fundamental knowledge concerning the process is sparce.
(h) Highly skilled operation is required.
(5) Anaerobic digesters are easily upset by unusual conditions and
are slow to recover.
(6) Recycled supernatant liquor tends to "shock" wastewater treat-
ment facilities.
(7) The fact that a closed vessel is required complicates the
inevitable cleaning necessary.
(8) The recovered gas, while useful, increases initial costs
because of the necessity of providing explosion-proof appurtenant
equipment.
(9) Digested sludge tends to be high in alkalinity. Where vacuum
filtration preceded by chemical coagulation with the usual inorganic
chemicals is practiced, increased chemical costs are inevitable.
7-109. Input Data.
a. Sludge production, Ib/day.
(l) Primary.
(2) Secondary.
b. Volatile solids in raw sludge, percent.
c. Solids content in raw sludge, percent.
(1) Primary.
(2) Secondary.
d. Volatile solids destroyed during digestion, percent
60 percent).
7-293
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29 Sep 78
e. Fixed solids produced from destruction of volatile solids,
' \:
percent (s£.25(X ) destroyed).
f. Solids concentration in digester, percent («3-7 percent).
7-110. Design Parameters.
a. Desired digester temperature, °F.
b. Temperature of fresh sludge, °F.
c. Digestion time, days.
d. Gas production per pound of volatile solids destroyed, ft /lb
e. Heat value of gas produced, BTU/ft («61|0).
7-111. Design Procedure.
a. Calculate total volume of raw sludge to digester.
v = SP(IOO)
f (% solids)(62.b)(specific gravity)
where
o
V = volume of raw sludge to digester, ft /day
SP = sludge produced, Ib/day
b. Calculate total quantity of solids accumulated after digestion.
Sac = SP - BP(% volatile)($ VS destroyed)(0.75)(10"^)
where
S = solids accumulated, Ib/day
Q.C
SP = sludge produced, Ib/day
c. Calculate total volume of digested sludge; assume solids con-
centration in digester.
7-29U
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EM 1110-2-501
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29 Sep 78
V, =
Sac(l°°;
solids)(62.U)(specific gravity)
where
V, = volume of digested sludge, ft"/day
d
S = solids accumulated, Ib/day
ac
d. Select the detention time for destruction of volatile solids
at a temperature of 95°F (fig. 7-18).
e. Calculate the average volume in the digester.
Vf + Vd
avg
10 20 30 40 SO 60 70
DETENTION, DAYS, BASED ON RAW SLUDGE FEED
Figure 7-l8. Reduction in volatile solids
in raw sludge, for detentions from 15 to
70 days, T = 85 to 95°F.
7-295
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29 Sep 78
where
Va = average volume in digester, ft /day
Vf = volume of fresh sludge added, ft^/day
Vd = volume of accumulated sludge after digestion, ft3/day
f. Calculate volume of digester.
V = V (t,)
avg d
where
V = volume in digester, ft
a
Va = average volume in digester, ft /day
t^ = digestion time, days
g. Calculate heat requirements.
(1) Heat supplied must be sufficient to raise the temperature of
the incoming sludge to 95°F.
Qs = (SP/Ps) x (c) x (Td - Tg)(1/210(100)
where
Q = BTU/hr required
s
SP = sludge added per day, l~b
P0 = solids in fresh sludge, percent
S
C = 1.0 BTQ/ft2/day/°F
T = temperature of sludge in digester = 95°F
Ts = temperature of incoming sludge, °F
(2) Heat losses are as follows.
7-296
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29 Sep 78
(a) Heat loss through the walls of digester.
Ov = UA(T2 - TI)
where
Q = heat loss, BTU/hr
U = heat loss coefficient, BTU/hr/ft2/°F (*0.l8)
2
A = surface area involved, ft
T = temperature within digester, °F
T = average temperature of coldest 2 weeks of a given year, °F
(t>) Heat losses through the floor.
Qf = UA(T2 - TX)
(c) Heat losses through the digester cover.
Qc = UA(T2 - Tx)
Heat requirements = (l_ + 2_) BTU/hr.
h. Calculate daily gas production. Assume volume of gas produced
per pound of volatile solids destroyed (12-18 ft3/lt>).
DGP = (SP)($ volatile)($ destroyed)(10~ )(ft3/rb gas production)
where
2
DGP = daily gas produced, ft /day
SP = sludge produced, Ib/day
i. Calculate daily gas requirement. Assume heat value of gas:
600 BTU/ft3 for digester gas; 1000 BTU/ft3 for natural gas.
7-297
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29 Sep 78
_ heat requirement (BTU/hr)
heat value of gas (BTU/ft3)
where DGR = daily gas requirement, ft /hr
7-112. Output Data.
a. VS destroyed, percent
"b. Solids concentration in digester, percent.
c. Raw sludge temperature, °F.
d. Digester temperature, °F.
e. Detention time, days.
f. Volume, ft3.
g. Gas produced, ft /day.
h. Heat requirement, ft /hr.
O
i. Digester gas requirement, ft /hr.
7-113. Example Calculations.
a. Calculate total volume of raw sludge to digester.
v = SP(IOO)
f (% solids)(62.4)specific gravity
where
V = volume of sludge, ft /day
SP = sludge produced, 2191 Ib/day
% solids = 1 percent
Specific gravity =1.05
7-298
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29 Sep 78
V - 2191(100)
f ~ 1(62.101.05
Vf = 33hU ft3/day
b. Calculate total volume of solids accumulated after digestion.
S = SP - SP(% volatile)(% VS destroyed)0.75 x 10
where
S = solids accumulated, l"b/day
£LC
SP = solids produced, 2191 Ib/day
% volatile = 80
VS destroyed = 60
S = 2191 - 2191(80)(60)(0.75 x 10
£LC
S = 1)402 Ib/day
ac
c. Calculate total volume of digested sludge.
S (100)
V, =
d % solids(62.U)specific gravity
where
•3
V = volume of digested sludge, ft /day
S = solids accumulated, 1^02 Ib/day
ac
% solids = 5 percent
specific gravity = 1.05
7-299
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29 Sep 78
V = 1402(100)
a 5(62.4)1.05
V = 428 ft3/day
d. Select the detention time for destruction of volatile solids at
a temperature of 95°F. Detention time = 28 days = t .
d
e. Calculate the average volume in the digester.
V + V
V = -£ I*
avg 2
where
o
V = average volume, ft /day
V = volume of raw sludge to digester, 3344 ft /day
V = volume of digested sludge, 428 ft /day
v 3344 + 428
V =
avg 2
= 1886 ft3/day
f. Calculate volume of digester.
V = V (t,)
avg d
where
•3
V = volume of digester, ft
V = daily volume in digester, 1886 ft /day
t = detention time, 28 days
V = 1886(28)
V = 52,808 ft3
7-300
-------
g. Calculate heat requirement.
(l) Heat required
where
Q = BTU/hr required
S
SP = sludge added per day, 2191 Ib
P = solids in fresh sludge, 1%
S
C = constant, 1.0 BTU/ft2/day/°F
T = temperature of sludge in digester, 95°F
T = temperature of incoming sludge, 70°F
S
Qs = d.o) (100)
Q = 228,230 BTU/hr
S
(2) Calculate heat losses.
(a) Losses through walls
^ = UA(T2 - T^
where
Q = heat loss through walls, BTU/hr
U = heat loss coefficient, 0.18 BTU/hr/ft2/°F
A = area of walls, h$2k ft2
T = temperature in digester, 95°F
7-301
EM 1110-2-501
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29 Sep 78
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29 Sep 78
T = average temperature of coldest 2 weeks of the year, 10°F
^ = (0.18)4524(95 - 10)
0 = 69,217 BTU/hr
("b) Losses through floor.
Qf = U(Af)(T2 - Tx
where
A = area of floor, l8lO ft2
Qf = (O.l8)(l8l0)(95 - 10)
Qf = 27,693 BTU/hr
(c) Losses through cover.
= U(Ac)(T2 -
where
o
A = area cf cover, l8lO ft
= (0.18)(1810)(95 - 10)
Qc = 27,693 BTU/hr
(d) Total heat losses.
Qf + Qc
where
Q = total heat losses, BTU/hr
"C
7-302
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29 Sep 78
Qt = 69,217 + 27,693 + 27,686
Q, = 12^,603 BTU/hr
Total heat requirement = Q + Q
u S
= 12*1,589 + 228,230
Total heat requirement = 352,819 BTU/hr
h. Calculate daily gas production.
Assume volume of gas produced per pound of volatile solids destroyed =
15 ft3/ib.
DGP = (SP)($ volatile}(% destroyed)15 x 10 ft3/lb
where
o
DGP = daily gas produced, ft /day
SP = sludge produced, 2191 Ib/day
% volatile = Q0%
% destroyed = 60%
DGP = 2191(80) (60) (15 x 10'14)
DGP = 15,775 ft3/day
At 600 BTU/ft3
DGP = 15,775(600)
DGP = 9,^65,000
i. Calculate daily gas requirement.
heat requirement (BTU/hr)
= * • —
heat value of gas (BTU/ft3
where
p
DGR = daily gas requirement, ft /hr
- 352,819
- 600
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29 Sep 78
DGR = 588 ft3/hr
where DGP or daily gas produced =
ft3/day
2U hr/day
DGP = 657 ft3/hr
There is sufficient gas produced to heat the digester.
7-111*. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
7-115. Bibliography.
a. American Society of Civil Engineers and the Water Pollution
Control Federation, "Sewage Treatment Plant Design," Manual of Practice
No. 8, 1959, 1961, 1967, 1968, Water Pollution Control Federation,
Washington, D. C.
b. Burd, R. S. , "A Study of Sludge Handling and Disposal," Publi-
cation WP-20-U, May 1968, Federal Water Pollution Control Administration
Washington, D. C.
c. College of Engineering, Oklahoma State University, "Aerobic
Digestion of Organic Wastes," Report No. 17070DAU, Dec 1971, U. S.
Environmental Protection Agency, Washington, D. C.
d. Dick, R. I., "Sludge Treatment, Disposal, and Utilization
Literature Review, Journal, Water Pollution Control Federation, Vol k3,
Jun 1971, pp
e. Drier, D. E. , "Aerobic Digestion of Solids," Proceedings of l8th
Purdue Industrial Waste Conference, 1963, Purdue University, Lafayette,
Ind.
f. Drier, D. E., "Aerobic Digestion of Sludge," paper presented at
Sanitary Engineering Institute, Mar 1965 s University of Wisconsin,
Madison, Wis.
g. Eckenf elder, W. W. , Jr., Water Quality Engineering for
Practicing Engineers, Barnes and Nobel, New York, 1970.
7-30U
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EM 1110-2-501
Part 1 of 3
29 Sep 78
h. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works (Ten States
Standards)," 1971, Health Education Service, Albany, N. Y.
i. Jaworski, N. , Lawton, G. W., and Rohlich, G. A., "Aerobic Sludge
Digestion," International Journal of Air and Water Pollution, Vol k,
1961, pp 106-111*.
j. Loner, R. C., "Aerobic Digestion-Factors Affecting Design,"
9th Great Plains Sewage Works Design Conference, Mar 1965.
k. Lynam, B., McDonnell, G., and Krup, M., "Start-up and Operation
of Two New High-Rate Digestion Systems," Journal, Water Pollution Con-
trol Federation, Vol 39, Apr 1967, PP 518-535-
1. Malina, F. J., "Aerobic Sludge Stabilization," Manual of Treat-
ment Processes, Vol 1, Environmental Science Services, Inc., Briarcliff
Manor, New York, 1969.
m. McKinney, R. E. and O'Brien, W. J., "Activated Sludge - Basic
Design Concepts," Journal, Water Pollution Control Federation, Vol ho,
Nov 1968, pp 1831-181*3.
n. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
o. Pohland, F. G. and Kang, J. J., "Anaerobic Processes," Journal,
Water Pollution Control Federation, Vol 1*6, No. 6, 1971, pp 1129-1133.
p. Sawyer, C. N. and Grubling, J. S., "Fundamental Considerations
in High Rate Digestion," Journal, Sanitary Engineering Division, Ameri-
can Society of Civil Engineers, Vol 86, Mar I960, pp 1*9763.
q. Shindala, A. and Bryme, W. J., "Anaerobic Digestion of Thickened
Sludge," Public Works, Vol 101, Feb 1970, pp 73-76.
r. Shindala, A., Dust, J. V., and Champion, A. L., "Accelerated
Digestion of Concentrated Sludge," Water and Sewage Works, Vol 117,
Sep 1970, pp 329-332.
7-305 (next page is 7-307)
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29 Sep 78
Section XVI. STABILIZATION PONDS
7-116. Background.
a- General. Waste stabilization ponds have been used extensively
for the treatment of organic and industrial wastes where sufficient land
area is available. Other reasons for its wide usage include fluctuating
organic loadings, shortage of trained operators for other, more complex
systems, and monetary currency restrictions. Ponds may be used for a
variety of different applications. Usually stabilization ponds are de-
signed to receive untreated waste; however, they may also be designed
to treat primary or secondary effluents, excess activated sludge, or
even vault wastes. Multiple stabilization ponds may be designed for
series or parallel use. Pretreatment by waste stabilization ponds is
used primarily to reduce BOD loadings and to reduce the concentration
of disease-causing agents (para 7-123f). For this manual, waste sta-
bilization ponds will be considered as three types: aerobic, faculta-
tive, and anaerobic.
b- Aerobic. An aerobic stabilization pond is one in which aerobic
bacteria and algae coexist in an aerobic environment (fig. 7-19). The
From Clark and Viessman, 1965
Figure 7-19- Schematic diagram of facultative oxidation
pond symbiosis between bacteria and algae.
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aerobic stabilization pond depends on algae photosynthesis and atmo-
spheric reaeration to supply the oxygen used by bacteria to stabilize
the organic matter. Because algae photosynthesis is directly dependent
upon sunlight, pond operating depths are normally limited to 3 feet. To
maintain aerobic conditions in the settled materials and good oxygen dis-
tribution, the contents of the pond should be mixed periodically. Solu-
ble BOD<5 removal in aerobic ponds is high (up to 95 percent)-, however,
separation of the algae from the effluent is necessary to obtain a true
BOD5 removal. The use of aerobic stabilization ponds should be avoided
where the waste to be treated contains materials toxic to algae growth.
c. Facultative. A facultative stabilization pond is characterized
by an upper aerobic layer or zone and an anaerobic bottom. It is possi-
.ble to find aerobic, facultative, and anaerobic organisms in this type
of pond. Variation of oxygen content in the aerobic zone is diurnal,
increasing during the daylight hours and decreasing during the night.
The settled sludge undergoes anaerobic decomposition, thus releasing
methane and other gases. In turn, the aerobic organisms utilize these
gases; therefore, maintaining an aerobic upper zone is essential in
minimizing odor problems. Normal operating depths range from 3 to 8 ft.
d. Anaerobic. Ana.erobic stabilization ponds are essentially un-
heated digesters. Loadings induce anaerobic conditions throughout the
pond and the conversion of organic matter is the same as in anaerobic
digestion. The acid-forming bacteria convert the organic matter to
organic acids which are further converted to methane gas by the methane
formers. Pond depths in the range of 8 to 15 ft are used to maintain
anaerobic conditions and to provide maximum heat retention.
7-117• Input_ Data.
a. Wastewater flow.
(l) Average daily, mgd.
(2) Peak hourly, mgd.
b. Wastewater strength, BOD mg/&.
c. Other characterizations.
(1) pH.
(2) Temperature (maximum and minimum).
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7-118. Design Parameters. (See Table 7-3).
7-119- Design Procedure. The biochemical relationships existing in
vaste stabilization ponds are very complex. Several attempts have been
made to develop a completely analytical rationale for the design of
ponds. However, the complexity has resulted in a design procedure based
on a load per unit area concept. Experience has shown this to be accept-
able design practice, one often specified by state regulatory agencies.
The following procedure is applicable to all three types of ponds:
aerobic, facultative, and anaerobic.
a. Calculate BOD present in the waste.
BOD5 = (Qavg)
where
BOD = BOD in the waste, Ib/day
Q = average flow, mgd
avg
(BOD J = influent BOD , mg/£
b. From the design parameters given in Table 7-3, select a BOD;.
loading.
c. Calculate the surface area required based on the Ib/day of
BOD and BOD loading.
BOD,.
SA =
BOD loading
where
SA = surface area, acres
BOD loading = Ib/acre/day
d. Select a pond operating depth from Table 7-3 and calculate the
pond volume.
V = (SA)(D)(0.32585)
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where
V = pond volume, million gal
SA = surface area, acres
D = pond depth, ft
0.32585 = conversion factor, acre-ft to mg
e. Check en the detention time.
,. _ V
avg
where
t = detention time, days
V = volume, million gal
Check t against the range of values given in Ta~ble 7-3.
-"". Sinre design equations are not available, the effluent soluble
BODr is estimated according to the following.
where
/'BOD \ = effluent BODr., mg/£
'eff
= decimal BOD conversion (from Table 7-3)
= influent BOD , mg/£
7-120. Output Data.
a. BOD loading, lb/acre/day.
b. Surface area, acres.
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c. Depth, ft.
d. Volume, acre-ft.
e. Detention time, days.
7-121. Example Calculations (Facultative).
a. Calculate BOD present in waste.
BOD5 =
where
BOD = BOD in waste, Ib/day
Q = average flow, 1.0 mgd
(BOD \ = influent BOD , 200 mg/I
BOD = 1.0(200)8.3^
BOD = 1668 Ib/day
b. Select a BOD loading = 50 Ib/acre/day
c. Calculate surface area.
BOD
GA = 2
BOD loading
where
SA = surface area, acres
BOD = BOD in waste, 1668 Ib/day
BOD loading = 50 Ib/acre/day
1668
" 50
SA = 33.it acres
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d. Select a pond operating depth and calculate the pond volume.
V = SA(D)0.32585
where
V = pond volume, million gal
SA = surface area, 33 A acres
D = pond depth, 6 ft
0.32585 = converts acre-ft to million gal
v = 33.^(6)0.32585
V = 65.3 million gal
e. Check detention time.
v
t =
where
t = detention time, days
V = volume of pond, 65-3 mg
Qavg
Q = average flow, 1.0 mgd
t _
t 1.0
t = 65.3 days
f. Determine effluent BOD .
(BOD ) = [i -
V -Veff L
where
(BOD ) = effluent BOD , mg/A
V -> A-pf ?
eff
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>M30D J = decimal BOD conversion, 0.65
= influent BOD 200 mg/£
(B°D5)
= (1 - 0.65)200
eff
(B°D5)
= TO mg/£
eff
7-122. Cost Data. Appropriate cost data and economic evaluation may
be found in Chapter 8.
7-123. Bibliography.
a. Barsom, G., "Lagoon Performance and the State of Lagoon Tech-
nology," Report Wo. R2-73-l^, Jun 1973, U. S. Environmental Protection
Agency, Washington, D. C.
b. City of Austin, Texas, "Design Guides for Biological Wastewater
Treatment Processes," Report Wo. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
c. Clark, J. W. and Viessman, W., Jr., Water Supply and Pollution
Control, International Textbook Co., Scranton, 1966.
d. Eckenfelder, W. W., Jr., and Ford, D. L., Water Pollution
Control, Pemberton Press, New York, 1970.
e. Gloyna, E. F. , "Basis for Waste Stabilization Pond Design,"
Advances in Water Quality Improvements - Physical and Chemical Processes,
E. F. Gloyna and W. W. Eckenfelder, Jr., ed., University of Texas Press,
Austin, 1970.
f. Gloyna, E. F., "Waste Stabilization Ponds," World Health Organi-
zation, Geneva, Switzerland, 1971.
g. Great Lakes-Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works (Ten States Stan-
dards)," 1971, Health Education Service, Albany, W. I.
h. Herman, E. R. and Gloyna, E. F., "Waste Stabilization Ponds,
III, Formulation of Design Equations," Sewage and Industrial Wastes,
Vol 30, No. 8, Aug 1958, pp 963-975.
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i. Marais, G. V. R., "New Factors in the Design, Operation and
Performance of Waste Stabilization Ponds with Special Reference to
Health," Expert Committee Meeting on Environmental Change and Resulting
Impact on Health Organization,
j. McKinney, R. E. , "Overloaded Oxidation Ponds -, Two Case Studies,"
Journal, Water Pollution Control Federation, Vol HO, Jan 1968, pp H9-56.
k. Metcalf and Eddy, Inc., Wastewater Engineering; Collection,
Treatment, and Disposal, McGraw-Hill, New York, 1972.
1. Oswald, ¥. J., "Rational Design of Waste Ponds," Proceedings ,
Symposium on Waste Treatment by Oxidation Ponds , Nagpur, India, 1963.
m. Oswald, W. J., "Quality Management by Engineered Ponds," Engi-
neering Management of Water Quality, McGraw-Hill, New York, 1968.
n. University of Kansas, "Waste Treatment Lagoons," 2d International
Conference on Lagoon Technology, 1970, Lawrence, Kans.
-------
Table 7-3. Design Parameters for Stabilization Ponds
Type of Pond
Parameter Aerobic
Flow regime Intermittently mixed
Pond size, acres <10 multiples
Operation Series or parallel
Detention time, days 10 to 1*0
Depth, ft 3 to U
pH 6.5 to 10.5
Temperature range, °C 0 to 1*0
Optimum temperature, °C 20
^ BODS loading, Ib/acre/day 60 to 120^d'
H ?
VJ1 BOD,, conversion 60 to 70
Principal conversion products Algae, C02> bacterial
cell tissue
Algal concentration, mg/JJ. 80 to 200
Effluent suspended solids,
mg/2>e' ll*0 to 3l*0
Facultative
—
2 to 10 multiples
Series or parallel
7 to 30
3 to 6
6.5 to 9.0
0 to 50
20
15 to 50
60 to TO
Algae, C02, CH^,
bacterial cell
tissue
1*0 to 160
160 to 1»00
Facultative
Mixed surface layer
2 to 10 multiples
Series or parallel
7 to 20
3 to 8
6.5 to 8.5
0 to 50
20
30 to 100
60 to 70
C02, CHjj, bacterial
cell tissue
10 to 1*0
110 to 3l*0
Anaerobic
~
0.5 to 2.0 multiples
Series
20 to 50
8 to 15
6.8 to 7-2
6 to 50
30
200 to 500
50 to 70
C02, CHjj, bacterial
cell tissue
—
80 to 160
v Conventional aerobic ponds designed to maximize the amount of oxygen produced rather than the amount of algae
produced.
Depends on climatic conditions.
Typical values (much higher values have been applied at various loadings). Loading values are often specified
by state control agencies.
Some states limit this figure to 50 or less.
Includes algae, microorganisms, and residual influent suspended solids. Values are based on an influent solu-
ble BODg of 200 mg/fc and, with the exception of the aerobic ponds, an influent suspended-solids concentration
of 200 mg/a. prom Metcalf and Eddy, 1972
'Tl
M 3- H
O
C/5 H 1
•S %^
^J °
oo >> I-1
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CHAPTER 8
COST DATA AND ECONOMIC ANALYSIS
Section I. INTRODUCTION
8-1. Economic Analysis.
a. As noted previously, cost data are available on the physical-
chemical -biological unit processes which allow the design engineer to
estimate the average capital and operating and maintenance costs for
each process and for a specific design train. Many alternative treat-
ment processes and treatment systems can be screened according to cost-
effectiveness analysis procedures with these cost estimates. Those
systems which meet discharge requirements and are most cost-effective
can be examined in depth with more exact cost estimates reflecting local
variation.
b. The cost estimates for the unit processes were obtained from
the most recent sources available. These sources are noted in each unit
process cost section ana are referenced at the end of each process.
Some unit processes have no cost data, hence the design team must use
its own judgement in evaluating the costs. No overall cost estimates
were available for these unit processes. As revised cost estimates for
known cost information are made available they will be furnished to the
user in the form of changes. At present, the designers must update the
cost information according to the year it was published. In this manner
all processes may be judged on the same basis or for the costs for the
same year. At present all cost data included in this manual have as
their base the year 1971•
c. The cost estimates are broken down into two areas:(l) capital
costs and (2) operating and maintenance costs. Capital cost reflects
all initial construction costs for each unit process. Estimated costs
of engineering, legal, fiscal, and administrative services, land, and
interest during construction are not included in the capital cost
estimate. These costs must be estimated separately and added to the
treatment process costs to reflect total system costs. The operating
and maintenance costs are all labor, materials, and supply costs nec-
essary to operate the processes after construction.
d. Most of the cost estimates were obtained by a statistical re-
gression analysis of the cost data from numerous treatment facilities.
Cost equations were formed which related an appropriate physical
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parameter to the cost. These equations give estimates of the capital
costs, number of man-hours of labor for operation per year, number of
man-hours of labor for maintenance per year, and a materials and supply
cost per year. The physical parameter inputs necessary for the design
of the unit process are used in the cost equations. The appropriate
parameter for each cost equation is noted in each cost section. The
man-hours of labor required per year for both operation and maintenance
must be multiplied by the average labor wage rate to obtain an estimate
of operating and maintenance costs.
e. After the design engineer performs the initial calculation out-
lined herein, estimates of the capital and operating and maintenance
costs for each unit process in the treatment train will be available.
Environmental Protection Agency (EPA) guidelines for waste-wafer treat-
ment plants state that a cost-effectiveness analysis must be performed
on alternative wastewater treatment systems. Before a comparison of
treatment systems with different capital and operation and maintenance
costs can be made, an economic analysis recognizing the time value of
money is required. The present worth method or the equivalent annual
cost method may be used in this analysis. The Federal discount (in-
terest) rate will be used for evaluation of water and related land re-
sources projects as published in the Federal Register.
f. The present worth method determines the sum which represents
capital cost and the present monetary value of the time stream of opera-
tion and maintenance costs for a given interest rate. On the other
hand, the equivalent annual cost method amortises the capital expendi-
tures at a given interest rate over the design life of the project.
This cost is added to the yearly operation and maintenance costs to
obtain an equivalent uniform yearly cost for the plant. Once a method
is chosen the design engineer uses the capital operating and maintenance
costs calculated for each alternative wastewater treatment system as
input into the analysis. Both methods give a true indication of the
total project costs for differing alternative wastewater treatment
systems. A discussion of both methods as they relate to cost effective-
ness analysis Ls provided by the EPA.
g. As part of the overall selection process, the design engineer
will want to consider as many viable treatment alternatives as possible.
However, the number of possible combinations of treatment processes
which make up a treatment system prevent manual consideration of all
possible systems. A way to screen alternatives according to their
ability to meet effluent standards and their cost is needed. The com-
puterized design process outlined in Part 3 gives the design engineer
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this capability. For any number of treatment system alternatives, the
computerized design process will screen alternatives to determine which
meet desired effluent criteria and which are the most cost-effective in
relation to monetary costs. The entire process for the manual calcula-
tion of unit process costs and economic analysis is provided by the
computer. The alternative treatment trains are presently compared by
the equivalent annual cost method in the computerized design process.
When used to examine all the feasible wastewater treatment plant designs
in the initial planning stages of a wastewater study the computerized
design process is a powerful tool.
8-3 (next page is 8-5)
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Section II. PHYSICAL UNIT PROCESSES
8-2. Grit Removal.
a. Most available data on cost of waste-water treatment facilities
combine the cost of screening, grit removal, and flow measuring devices
into one cost, referred to as "preliminary treatment." In this manual,
the cost of grit removal is combined with the cost of screening as well
as flow measuring devices. The following cost formulations are those
developed by Patterson and Banker and formulated by Eilers and Smith.
b. Cost formulations for preliminary treatment are:
CC= 27,500X0'606
OHR = 530X°'68U
XHR = 301X0'6011
su = i,o6ox°'6lU
where
CC = capital cost, dollars
X = Q = average daily flow, mgd
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
SU = materials and supplies cost
8-3- Screening.
a. Most available data on costs of wastewater treatment facilities
combine the cost of screening devices, comminutors, and grit removal and
flow measuring equipment under one heading usually referred to as "pre-
liminary treatment." No separate cost data are currently available.
Equipment manufacturers may be consulted with regard to capital and
operating costs of screening devices.
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b. In this manual, the cost of screening is included, along with
costs for grit removal and flow measuring equipment, and is referred
to as "preliminary treatment." Cost equations for screening are the
same as those listed under grit removal.
8-4. Comminution.
a. Since the size of the commiriutor is determined on the basis of
wastewater flow, cost formulations for the comminutor are also based on
wastewater flow. Capital cost of equipment only, not including special
housing or concrete structures, has been formulated as follows.
b. Cost formulations for comminution are:
CC = 580X0'114
where
CC = capital cost, dollars
X = Q = average daily flow, mgd
c. Cost data available for wastewater treatment facilities combine
the operating and maintenance costs of screening, comminution, and grit
removal and flow measuring devices under one item normally referred to
as "preliminary treatment." Currently, no data are available on opera-
tion and maintenance costs of comminuting devices.
8-5- Egualiz_ation_. Cost formulations for equalization basins are as
follows:
CC - 82X°'61|(lOOO)
OHR = 0
XHR = 0
SU = 3650(0.13^)3(0.02) + 0.035 CC
where
CC = capital cost, dollars
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X = V = volume of tank, million gal
SU = materials and supply cost, dollars
B = hp = horsepower required
8-6. Flotation. Cost formulations for flotation tanks are as follows:
CC = 17,U32X°'5TT3
OHR = 0
XHR = 0
SU = 0.02 CC
where
CC = capital cost dollars
X = V = volume of flotation tank, million gal
SU = materials and supply costs, dollars
8-7. Thickening (gravity). Cost formulations for gravity thickening
units are as follows:
CC = 3
OHR = ,
XHR = 161X°'602
SU = U8UX°-U16
where
CC = capital cost , dollars
X = TSA = total surface area, sq. ft
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
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8-8. Sedimentation (Primary Clarifier). Cost formulations for primary
clarifiers are as follows:
CC = 26,120X°'7611
OHR = 3UOX°'53
XHR = 1T7X°'52
SU = 293X°'Tla
where
CC = capital cost, dollars
SA
X = -, = surface area, sq ft
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
8-9. Sedimentation (Secondary Clarifier). Cost formulations for sec-
ondary clarifiers are as follows:
CC = 11,680X°'6523
OHR=
XHR = 301X0'60U
where
CC = capital cost, dollars
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
SA
1000
QTT _ SA
- -, nnn = surface area, sq ft
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8-10. Filtration. Cost formulations for filtration units are as
follows:
CC = 100,OOOX 519
OHR = 0
XHR = 0
SU = 365(U5)X°'6373
where
CC = capital cost, dollars
X = Q = average flow, mgd
avg
SU = Q = average flow, mgd
avg
8-11. Vacuum Filtration. Cost formulations for vacuum filtration units
are as follows:
CC = 38l6A°'T313
OHR = 30.5TPY°'6U63
XHR = 1K15TPY0'668
SU=M*.5TPY°-7139+30.3TPY°-8365
where
CC = capital cost, dollars
A = filter area, sq ft
OHR = annual operating labor, man-hours
B(C)8.3M365)
100(2000)
B = sludge volume, gpd
C = solids, percent
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XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
8-12. Centrifugation. Cost formulations for centrifugation units are
as follows :
CC = 32,92TA°'52''ri
OHR =
SU = 17.3B0'884 + 51.7B0'713
where
CC = capital cost, dollars
sludge flow (2U)
A =
hours per day of operation
OHR = annual operating labor, man-hours
B = sludge volume (% solidsj 8.3M365)
100(2000)
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
C = total horsepower required, hp
8-13- Microscreening. Cost formulations for microscreening units are
as follows:
CC = 0.031^6X°-8893(1,000,000)
OHR = 0
XHR = 0
su = 6.o(365)x0'96011
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where
CC = capital cost, dollars
X = Q = average flow, mgd
avg
SU = materials and supply cost, dollars
8-lU. Drying Beds. Cost formulations for drying beds are as follows:
cc =
OHR = 17.1B°'T395
XHR = 2.93B0'913
°'9W9
SU = 2.
where
CC = capital cost, dollars
X = SA = surface area, sq ft
OHR = annual operating labor, man-hours
B = TPY = tons sludge per year
XHR = annual maintenance labor, man-hours
SU = materials and supply costs, dollars
8-15. Postaeration. Cost formulations for postaeration chambers
equipped with mechanical or diffused aerators are as follows:
CC = 2,6l6.8x + 19,5^7.6
where
CC = capital cost, dollars
X = Q = maximum flow, mgd
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8-l6. Cascade Aeration. No cost formulations are available, at present,
for cascade aeration units.
8-17. Sludge Hauling and Land Filling. To be furnished.
8-l8. Multiple Hearth Incineration. To be furnished.
8-19. Fluid!zed Bed Incineration. To be furnished.
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Section III. CHEMICAL UNIT PROCESSES
8-20. Carbon Adsorption. Cost formulations for carbon adsorption units
are as follows:
CC = 566,856 + 8l,61*7X
OHR = 0
XHR = 1,1*UOX
su =
0.000112U5 + 0.00000014X
where
CC = capital cost, dollars
X = Q = average daily flow, mgd
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
8-21. Chemical Coagulation. Cost formulations for chemical coagulation
units are as follows:
CC = 15,028X0<1*2T
OHR = 0
XHR = 0
SU = 27X°'599
where
CC = capital cost, dollars
_ VFL _ volume of flocculator, gal
T.W(IOOO) = 7. ^8(1000)
SU = materials and supply cost, dollars
See Section 8-8 for cost of clarifier coagulation unit.
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8-22. Ammonia Stripping. Cost formulations for both crosscurrent and
counter cur rent ammonia stripping towers are as follows :
CC = 0.095X°'9(1,000,000)
OHR = 0
XHR = 0
SU = U
where
CC = capital cost, dollar
X = Q = average flow, mgd
avg
SU = materials and supply cost, dollars
8-23. Ghlorination. Cost formulations for chlorine contact tanks are
as follows :
CC = 6917X0'611 + 3.89B°^18
OHR = 8
XHR = 7.57TPY0'801
0'88
SU = 447TPY '^ + 273TPY
where
CC = capital cost, dollars
VCT _ volume of contact tank, gal
X ~ 7.48(1000) ~ 7.48(1000)
B = CR = chlorine requirement, Ib/day
OHR = annual operating labor, man-hours
TPY = ^yy^- = tons per year
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
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8-2U. Ion Exchange. Cost formulations for both anionic and cationic
exchange columns are as follows:
CC = ll*6,9H3X°'88
OHR = 0
XHR = 0
0 7?
SU = 3,371X
where
CC = capital cost, dollars
X = Q = average flow, mgd
avg
SU = materials and supply cost, dollars
8-25. Neutralization. Cost formulations for neutralization units are
as follows:
CC = 0.06X°-7(1,000,000)
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
X = Q = average flow, mgd
8-26. Recarbonation: At present no cost data are available for re-
carbonation units. As costs are made available they will be included
in this section.
8-27- Two-Stage Lime Treatment. At present, prices are available only
for the first stage of a two-stage lime treatment unit. Cost formula-
tions for this first stage unit are as follows:
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CC = 29U.U57 + 30.075X
OHR = 0
XHR = 2,683X°'U6
SU = 1,82UX°'65
where
CC = capital cost, dollars
X = Q = average flow, mgd
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
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Section IV. BIOLOGICAL UNIT PROCESSES
8-28. Trickling Filters. Cost formulations for trickling filters are
as follows:
CC = 5877X0'729
OHR = 57.9SA0'636
XHR = 51.3SA0'562
SU = 163.3SA°A65
where
CC = capital cost, dollars
2 0
Y = avg _ 2 average flow (mgd)
7.U8(1000) " 7-^8(1000)
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
SU = materials and supply cost, dollars
SA = surface area, sq. ft
8-29. Plug Flow Activated Sludge. Cost formulations for plug flow
activated sludge units are as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
X = Qavg^100°) = 0.5 (average flow) 1000
77^87.U8
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8-30. Complete Mix Activated Sludge. Cost formulations for complete
mix activated sludge units are as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
Qavg^1000^ _ average flow (mgd)(lOOO)
X~ jTW ~ T.kB
8-31. Step Aeration Activated Sludge. Cost formulations for step
aeration sludge units are as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
^Wr000^ _ average flow (mgd)lOOO
X - ^-£g 7.U8
8-32. Extended Aeration Activated Sludge. Cost formulations for ex-
tended aeration activated sludge are as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
3-18
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where
CC = capital cost, dollars
_ (l-5)Qavg(l°00) _ 1.5 average flow (mgd) 1000
A ~ 7A8 " 7-^8
8-33. Modified or High-Rate Aeration Activated Sludge. Cost formula-
tions for high-rate aeration activated sludge are as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
v - (0'2^)Qavg(l000) _ 0.25 average flow (mgd) 1000
* ~ 7.^8 ~ 7.1*8
8-3^. Contact Stabilization Activated Sludge. Cost formulations for
contact stabilization activated sludge units are as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
_ average flow (mgd) 1000
~
8-19
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8-35. Pure Oxygen Activated Sludge. Cost formulations for pure oxygen
activated sludge units are as follows:
•*_
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
_ (°-3)Qavg(l0°0) _ 0.5 average flow (mgd) 1000
X~ fTtS ~ 7.^8
8-36. Aerated Aerobic Lagoons. Cost formulations for aerated aerobic
lagoons are as follows:
CC = 23,222X0'6311
OHR = TUX0'361
0 ?QQ
XHR = 125X ^
SU = 0
where
CC = capital cost, dollars
X = V = volume of lagoon, million gal
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
8-37. Aerated Facultative Lagoon. Cost formulations for aerated
facultative lagoons are as follows:
CC = 23,222X°'6311
8-20
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OHR = 711X°'361
0 "3QQ
XHR = 125X 0>y
SU = 0
where
CC = capital cost, dollars
X = V = volume of lagoon, million gal
OHR = annual operating la"bor, man-hours
XHR = annual maintenance labor, man-hours
8-38. Oxidation Ditch. Cost formulations for oxidation ditches are
as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
_ 1.5 average flow (mgd) 1000
7758
8-39. Nitrification-Denitrif ication. Cost formulations for
nitrification-denitrification units are as follows:
a. Nitrification.
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
8-21
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where
CC = capital cost, dollars
QaYg(l°°0) _ average flow (lOQO)
X ~ 7.U8 7.U8
b. Denitrif icat ion.
cc =
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
_ average flow (mgd) 1000
X "
7.1*8 "
c. Mechanical aeration.
CC = 2911A0'788
A liQ
OHR = 150A y
XHR=
where
CC = capital cost, dollars
OHR = annual operating labor, man-hours
1 Mechanical or diffused aeration is used with processes described in
paragraphs 8-30 through 8-HO.
8-22
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XHR = annual maintenence labor, man-hours
SU = materials and supply cost, dollars
A = hp = horsepower required
d. Diffused Aeration.
CC = 78230X0'6627
OHR = 937X°-Wl8
XHR = i,63X°- ^6l
SU = 0
where
CC = capital cost, dollars
X = required air flow, 1000 cfm
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
8-40. Aerobic Digestion. Cost formulations for aerobic digesters are
as follows:
CC = 5658X0'6627
OHR = 0
XHR = 0
SU = 0
where
CC = capital cost, dollars
Mechanical or diffused aeration is used with processes described
in paragraphs 8-30 through 8-kO.
8-23
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_ vol _ volume (million gal)
~ 7.1*8(1000) ~ 7.^8(1000)
8-1*1. Anaerobic Digestion. Cost formulations for anaerobic digesters
are as follows:
CC = 17,1*32X°'5TT3
OHR = 88.8X0'6132
XHR = 56.7X0'596
su = i9ix°-6058
where
CC = capital cost, dollars
_ vol _ volume (million gal)
~ 1000 " 1000
OHR = annual operating labor, man-hours
XHR = annual maintenance labor, man-hours
SU = materials and supply costs, dollars
8-1*2. Stabilization Ponds. Cost formulations for stabilization ponds
are as follows:
CC = 20,180X°-58314
OHR = 58X°'55T
° "
XHR = 10UX
SU-1U2X0'513
where
CC = capital cost, dollars
X = SA = surface area, sq ft
OHR = annual operation labor, man-hours
8-2H
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XHR = annual maintenance labor, man-hours
SU = materials and supply costs, dollars
8-25
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APPENDIX A
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Sludges," Journal, Water Pollution Control Federation, Vol 1*1, Apr 1969,
pp 607-628.
ATbertsson, T. G. et al., "Investigation of the Use of High Purity
Oxygen Aeration in the Conventional Activated Sludge Process," Water
Pollution Control Research Series Report No. 17050DNW, May 1970, Federal
Water Quality Administration, Washington, D. C.
Alford, J. M., "Sludge Disposal Experiences at North Little Rock,
Arkansas," Journal, Water Pollution Control Federation, Vol 1*1, No. 1,
pp 175-183.
American Public Health Association, American Society of Civil Engineers,
American Water Works Association, and Water Pollution Control Federa-
tion, "Glossary, Water and Wastewater Control Engineering," 1969.
American Public Works Association, "Feasibility of Computer Control of
Wastewater Treatment," Report No. 17090DOY, Dec 1970, U. G, Environ-
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American Society of Civil Engineers and the Water Pollution Control
Federation, "Sewage Treatment Plant Design," Manual of Practice No. 8,
1959, 1961, 1967, 1968, Water Pollution Control Federation, Washington,
D. C.
American Water Works Association, Water Quality and Treatment, McGraw-
Hill, New York, 1971.
Amirtharajah, A. and Cleasby, J. L., "Predicting Expansion of Filters
During Backwash," Journal, American Water Works Association, Vol 61*,
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Anderson, C. V., "Zero Discharge Sanitation System," 53rd Annual Wash-
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Portland, Oreg.
Baker, J. M. and Graves, Q. B., "Recent Approaches for Trickling Filter
Design," Journal, Sanitary Engineering Division, American Society of
Civil Engineers, Vol 9^, SA1, Feb 1968, pp 65-81*.
A-l
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29 Sep 78
Balakrishnan, S., Williamson, D., and Odey, R., "State of the Art
Review on Sludge Incinerator Practices," Report No. 17070 Div 0^/70,
Apr 1970, Federal Water Quality Administration, Washington, D. C.
Bargman, R. D. and Borgerding, J., "Characterization of the Activated
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ships for Organic Industrial Wastes," 5th International Water Pollution
Research Conference, Jul-Aug 1970.
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Environmental and Water Resources Engineering, Vanderbilt University,
Nashville, Term.
Barnhart, E. L. and Eckenfelder, W. W., Jr., "Theoretical Aspects of
Aerated Lagoon Design," Symposium on Wastewater Treatment for Small
Municipalities, 1965, Ecole Polytechnique, Montreal, Quebec, Canada.
Barsom, G., "Lagoon Performance and the State of Lagoon Technology,"
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Washington, D. C.
Bennett, E. R., Rein, D. A., and Linstedt, K. D., "Economic Aspects of
Sludge Dewatering and Disposal," Journal of Environmental Division^
American Society of Civil Engineers,,, Vol 99 > 1973, P 55-
Bernard, J., "Sludge Centrifugation," 1st Seminar on Process Design for
Water Quality Control, 1970, Vanderbilt University, Nashville, Tenn.
Bishop, N. E., Malina, J. F., Jr., and Eckenfelder, W. W., Jr., "Studies
on Mixing and Heat Exchange in Aerated Lagoons," Technical Report
EHE-70-21, CRWR-70, 1970, Center for Research in Water Resources,
University of Texas at Austin.
Blecker, H. G. and Cadman, T. W., "Capital and Operating Costs of
Pollution Control Equipment Modules - Vol I," Report No. R5-73-023a,
Jul 1973, U. S. Environmental Protection Agency, Washington, D. C.
Blecker, H. G. and Nichols, T. M., "Capital and Operating Costs of
Pollution Control Equipment Modules - Vol II," Report No. R5-73-023t>,
Jul 1973, U. S. Environmental Protection Agency, Washington, D. C.
A-2
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29 Sep 78
Borchardt, J. A., "Nitrification in the Activated Sludge Process,"
The Activated Sludge Process, Bulletin, University of Michigan, Ann
Arbor, Mich.
Bordien, D. G. and Stenburg, R. L. , "Microscreening Effectively Polishes
Activated Sludge Effluent," Water and Wastes Engineering, Vol 3,
Sep 1966, pp 7^-77.
Boucher, P. L. , "A New Measure of the Filtrability of Fluids with Appli-
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Bouwer, H. , "High Rate Land Treatment," Water Spectrum, Vol 6, No. 1,
, PP 18-25.
Bowers, M. , "Tips on Sludge Drying Beds Care," Sewage and Industrial
Waters, Vol 29, No. 7, Jul 1957, PP 835-836.
Brown and Caldwell, Engineers for EPA, "Nitrification and Denitrification
Facilities," May 7-9, 197^, U. S. Environmental Protection Agency Tech-
nology Transfer, Orlando, Fla.
Brown, J. C. et al., "Methods for Improvement of Trickling Filter Plant
Performance - Part I, Mechanical and Biological Optima," Report No. 670/
2-73-OH7a, Aug 1973, U. S. Environmental Protection Agency, Washington,
D. C.
Burd, R. S., "A Study of Sludge Handling and Disposal," Publication
WP-20-1+, May 1968, Federal Water Pollution Control Administration, Wash-
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Burgess, J. V., "Comparison of Sludge Incineration Processes," Process
Biochemistry, Vol 3, Apr 1968, p 27.
Burkhead, C. E. , "Evaluation of CMAS Design Constants," Conference on
Toward a Unified Concept of Biological Waste Treatment Design, 5-6 Oct
1972, Atlanta, Ga.
Burkhead, C. E. and McKinney, R. E., "Application of Complete-Mixing
Activated Sludge Design Equations to Industrial Wastes," Journal, Water
Pollution Control Federation, Vol kO, Apr 1968, pp 557-570.
A-3
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29 Sep 78
Burns and Roe, Inc., "Process Design Manual for Suspended Solids
Removal," prepared for the U. S. Environmental Protection Agency Tech-
nology, Transfer, Oct 1971, Washington, D. C.
Busch, A. ¥., Aerobic Biological Treatment of Wastewaters, Oligodynamics
Press, 1971-
Camp, T. R., "Grit Chamber Design," Sewage Works Journal, Vol 1^, No. 2,
Mar 19^2, pp 368-381.
Camp, T. R., "Sedimentation and the Design of Settling Tanks," Transac-
tions, American Society of Civil Engineers, Vol 111, Part III, 19^6",
pp 895-952.
Camp, T. R., "Flocculation and Flocculation Basins," Transactions,
American Society of Civil Engineers, Yol 120, 1955, PP l-l6.
Camp, T. R., "Theory of Water Filtration," Journal, Sanitary Engineer-
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pp 1-30.
Cardile, R. P. and Verhoff, F. H., "Economical Refuse Truck Size
Determination," Journal, Environmental Engineering Division, American
Society of Civil Engineers, Vol 90, SAU, 196^, pp 1-30.
Cardinal, P. J., "Advances in Multihearth Incineration," Process Bio-
chemistry, Vol 6, 1971, PP 27-31.
Carlson, C. A., Hunt, P. G., and Delaney, T. B., Jr., "Overland Flow
Treatment of Wastewater," Miscellaneous Paper Y-TU-3, Aug 197^, U. S.
Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss.
Center for Research, Inc., University of Kansas, "Oxygen Consumption in
Continuous Biological Culture," Report Number 17050DJS, May 1971, U. S.
Environmental Protection Agency, Washington, D. C.
Center for the Study of Federalism, "Green Land - Clean Streams: The
Beneficial Use of Wastewater Through Land Treatment," 1972, Center for
the Study of Federalism, Temple University, Philadelphia, Pa.
City of Austin, Texas, "Design Guides for Biological Wastewater Treat-
ment Processes," Report No. 11010ESQ, Aug 1971, U. S. Environmental
Protection Agency, Washington, D. C.
A-U
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29 Sep 78
Clark, B. D. , "Basic Characteristics at Winter Recreational Areas."
PR-T, Aug 1968, Federal Water Quality Administration, Washington, D. C.
Clark, J. W. and Viessman, W. , Jr., Water Supply and Pollution Control.
International Textbook Co., Scranton, 1966.
Clark, R. M. and Gillean, J. I., "Systems Analysis and Solid Waste
Planning," Journal., Environmental Engineering Division, American
Society of Civil Engineers^ Vol 100, 1974, p 7.
Clark, R. M. and Helms, B. P., "Fleet Selection for Solid Waste Collec-
tion Systems," Journal, Environmental Engineering Divisip]n.J,__Ameri£an
Society of Civil Engineers, Vol 98, 1972, p 71.
Cleasby, J. L. , "Deep Granular Filters, Modeling and Simulation," Pro-
ceeding, Association of Environmental Engineers in Profession, Eighth
Annual Workshop, 18-22 Dec 1972, Nassau.
Cleasby, J. L. and Baumann, E. R., "Selection of Sand Filtration Rates,"
Journal, American Waterworks Association, Vol $k, 1962, pp 579-602.
Cohen, J. M. and Hannah, S. A., "Coagulation and Flocculation," Water
Quality and Treatment^ McGraw-Hill, New York, 1971.
College of Engineering, Oklahoma State University, "Aerobic Digestion
of Organic Wastes," Report No. 17070DAU, Dec 1971, U. S. Environmental
Protection Agency, Washington, D. C.
Copeland, C. G. , "Water Reuse and Black Liquor Oxidation by the Container -
Copeland Process," Proceedings, 19th Industrial Waste Conference, Purdue
University, Lafayette, Ind. , 1969.
Copeland, C. G. , "The Copeland Process Fluid Bed System and Pollution
Control Worldwide," Proceedings, 2Uth Industrial Waste Conference.
Perdue University, Lafayette, Ind., 1969.
Copeland, C. G. , "Design and Operation of Fluidized Bed Incinerators,"
Water and Sewage Works, Vol 117, 1970, p
Cotteral, J. A., Jr., and Norris, D. P., "Septic Tank Systems," Journal .
Sanitary Engineering Division, American Society of Civil Engineers
Vol 95, SA4,"l969, pp 715-746. *"
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29 Sep 78
Cover, A. E. and Pieron, L. J. , "Appraisal of Granular Carbon Contactors
Phase I and II," Report No. TWRC-11, May 1969, Federal Water Pollution
Control Administration, Washington, D. C.
Cover, A. E. and Wood, C. E. , "Appraisal of Granular Carbon Contactors
Phase III," Report No. TWRC-12, May 1969, Federal Water Pollution Con-
trol Administration, Washington, D. C.
Gulp, G. L., Hsuing, K. , and Conley, W. R., "Tube Clarification Process,
Operation Experience," Journal, Sanitary Engineering Division, American
Society of Civil Engineers, Vol 95, SA5, 19o9, PP 829-8U8.
Gulp, R. L. and Gulp, G. L. , Advanced Wastewater Treatment, Van Nostrand,
New York, 1971.
Daniels, S. L. , "Phosphorus Removal from Wastewater by Chemical Precip-
itation and Flocculation," The American Oil Chemists' Society, 1971,
Short Course, Update on Detergents and Raw Materials, Jun 1971, Lake
Placid, N. Y.
"Design and Operation of Complete Mixing Activated Sludge Systems,"
Environmental Pollution Control Service Reports, Vol 1, No. 3, Jul 1970.
Dick, R. I., "Fundamental Aspects of Sedimentation 2," Water and Wastes
Engineering, Vol 6, No. 3, 1969, PP ^-^5.
Dick, R. I., "Thickening," Advances in Water Quality Improvements -
Physical and Chemical Processes,, E. F. Gloyna and W. W. Eckenf elder, Jr.,
ed. , University of Texas Press, Austin, 1970.
Dick, R. I., "Thickening," Seminar on Process Design in Water Quality
Engineering, 9-13 Nov 1970, Vanderbilt University, Nashville, Tenn.
Dick, R. I., "Sludge Treatment, Disposal, and Utilization Literature
Review," Journal, Water Pollution Control Federation, Vol 1*3, Jun 1971,
pp "
Door-Oliver, Incorporated, "Cost of Wastewater Treatment Processes,"
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Dow Chemical Company, "A Literature Search and Critical Analysis of Bio-
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Dec 1971, U. S. Environmental Protection Agency, Washington, D. C.
A-6
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29 Sep 78
Drier, D. E. , "Aerobic Digestion of Solids," Proceedings of l8th Purdue
Industrial Waste Conference, 1963, Purdue University, Lafayette, Ind.
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Eckenfelder, W. W., Jr., Industrial Water Pollution Control, McGraw-
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Eckenfelder, W. W., Jr., and O'Connor, 0. J., Biological Waste Treatment,
Pergamon Press, New York, 1961.
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Eilers, R. G. and Smith, R., "Wastewater Treatment Plant Cost Estimating
Program," Apr 1971, Environmental Protection Agency, Water Quality
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Engineering-Science, Inc., "State of the Art of the Microscreen Process,"
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29 Sep 78
Field, W. B., "Design of a pH Control System by Analog Simulation,"
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FMC Corporation, "Link-Belt Wastewater Treatment Equipment Design Cata-
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29 Sep 78
Great Lakes-Upper Mississippi River Board of State Sanitary Engineers,
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Health Education Service, Albany, N. Y.
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Wastewater Treatment in Ontario," Research Publication No. 6, Jul 196k,
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tion of Idealized Sedimentation Theory in Wastewater Treatment," Journal ,
Water Pollution Control Federation, Vol Hi, Aug 1969, pp
Hanway, J. E. , "Fluidi zed-Bed Processes - A Solution for Industrial
Waste Problems," Proceedings, 21st Industrial Waste Conference, Purdue
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"Domestic Wastewater Treatment," Technical Manual TM 5-8lH-3/AFM 88-11,
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Helmenstein, S., and Martin, F., "Planning Criteria for Refuse Incinera-
tion Systems," Combustion, Vol ^5, May 197^, p 11.
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lation of Design Equations," Sewage and Industrial Wastes, Vol 30, No. 8,
Aug 1958, pp 963-975.
Hinsely, T. D. , "Sludge Recycling: The Most Reasonable Choice?" Water
Spectrum, Vol 5, 1973, pp 1-8.
Hinsely, T. D., "Water Renovation for Unrestricted Re-Use," Water
Spectrum, Vol 5, No. 2, 1973, pp 1-8.
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29 Sep 78
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A-11
-------
EM 1110-2-501
Part 1 of 3
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-------
EM 1110.-2-5 01
Part 1 of 3
29 Sep 78
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A-13
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EM 1110-2-501
Part 1 of 3
29 Sep 78
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EM 1110-2-501
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29 Sep 78
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A-15
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29 Sep 78
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A-16
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EM 1110-2-501
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29 Sep 78
Sawyer, C. N., "New Concepts in Aerated Lagoon Design and Operation,"
Advances in Water Quality Improvements - Physical and Chemical
Processes, E. F. Gloyna and W. W. Eckenfelder, Jr., ed., Univeraity of
Texas Press, Austin, 1970.
Sawyer, C. N., "Nitrification and Denitrification Facilities," Aug 1973,
U. S. Environmental Protection Agency, Technology Transfer, Washington,
D. C.
Sawyer, C. N. and Grubling, J. S., "Fundamental Considerations in High
Rate Digestion," Journal, Sanitary Engineering Division, American
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Sawyer, C. N. and McCarty, P. L., Chemistry for Sanitary Engineers,
McGraw-Hill, New York, 1967.
Schuessler, R. G., "Phosphorus Removal - A Controllable Process,"
Chemical Engineering Progress Symposium Series, Vol 67, No. 107, 1971-
Schulze, K. L., "Load and Efficiency of Trickling Filters," Journala
Water Pollution Control Federation, Vol 32, Wo. 3, I960, pp 245-261.
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Vol k, No. 3, 1972, pp 15-21.
Seedel, D. F. and Criter, R. W., "Evaluation of Anaerobic Denitrifica-
tion Processes," Journal, Sanitary Engineering Division, American
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Disposal Costs," 1975, Office of Water Program Operations, U. S. Environ-
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Public Works, Vol 101, Feb 1970, pp 73-76.
Shindala, A., Dust, J. V., and Champion, A. L., "Accelerated Digestion
of Concentrated Sludge," Water and Sewage Works, Vol 117, Sep 1970,
pp 329-332.
Shinskey, F. G., "Feed Forward Control of pH," Instrumentation Tech-
nology, Vol 15, 1968.
A-17
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EM 1110-2-501
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29 Sep 78
Simpson, G. D., "Operation of Vacuum Filters," Journal, Water Pollution
Control Federation, Vol 36, Dec 1961*, pp ll*60-J*67.
Slechta, A. F. and Culp, G. L. , "Water Reclamation Studies at the South
Tahoe Public Utility District," Journal, Water Pollution Control Federa-
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"Sludge Incineration Plant Uses Fluid-Bed Furnace," Chemical and Process
Engineering, Apr 1972, p 7-
Smith, H. S., "Homogeneous Activated Sludge/1 Principles and Features
of the Activated Sludge Process," Water and Wastes Engineering, Vol h,
Jul 1967, pp i*6-50.
Smith, R. , "Cost of Conventional and Advanced Treatment of Waste Water,"
Journal, Water Pollution Control Federation, Vol 1*0, Sep 1968, pp 15^*6-
__
Smith, R. , "Preliminary Design of Wastewater Treatment Systems," Journal ,
Sanitary Engineering Division, American Society of Civil Engineers,
Vol 95, No. SA1, 1969, PP 117-118.
Smith, R. , "Design of Ammonia Stripping Towers for Wastewater Treat-
ment," Seminar on Process Design for Water Quality Control, 9-13 Nov
1970, Vanderbilt University, Nashville, Term.
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Ohio .
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Cincinnati, Ohio.
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Tertiary Wastewater Treating Processes," PB 189 953, Jun 1969, Federal
Water Pollution Control Administration, Cincinnati, Ohio.
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Wastewater Treatment Plants," Technical Report No. AFWL-TR-72-l*5, Jul
1972, Air Force Weapons Laboratory, Kirtland Air Force Base, Albuquerque,
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29 Sep 78
Snow, R. H. and ¥enk, W. J., "Ammonia Stripping Mathematical Model for
Wastewater Treatment," Report No. IITRI-C6152-6, Dec 1968, Federal Water
Pollution Control Administration, Washington, D. C.
South Tahoe Public Utility District, "Advanced Wastewater Treatment as
Practiced at South Tahoe," Report No. 1T010ELQ, Aug 1971, U. S. Envi-
ronmental Protection Agency, Washington, D. C.
Stander, G. J. and Van Vuuren, L. R. J., "Flotation of Sewage and Waste
Solids," Advances in Water Quality Improvements - Physical and Chemical
Processes, E. F. Gloyna and W. W. Eckenfelder, Jr., ed., University of
Texas Press, Austin, 1970.
Stanley Consultants, Inc., "Sludge Handling and Disposal, Phase I, State
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Stensel, H. D. and Shell, G. L., "Two Methods of Biological Treatment
Design," Journal, Water Pollution Control Federation, Vol 1*6, Feb 197**,
pp 271-283.
Stewart, M. J. , "Activated Sludge System Variations - Specific Applica-
tions," The 15th Ontario Industrial Waste Conference, 9-12 Jun 1968,
Niagara Falls, Ontario.
Stumm, W. and Morgan, J. J., Aquatic Chemistry, Wiley, New York, 1970.
Stumm, W. and O'Melia, C. R., "Stoichiometry of Coagulation," Journal,
American Water Works Association, Vol 60, 1968, pp 51^-539-
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Using Land Application of Wastewater," Report No. 1*30/9-73-006, Jul 1973,
U. S. Environmental Protection Agency, Washington, D. C.
Swindell-Dresser Company, "Process Design Manual for Carbon Adsorption,"
Oct 1971, U. S. Environmental Technology Transfer, Washington, D. C.
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fluents," Journal, Sanitary Engineering Division, American Society of
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29 Sep 78
Toerber, E. D., "Full Scale Parallel Activated Sludge Process Evalua-
tion," Report No. R2-72-065, Nov 1972, U. S. Environmental Protection
Agency, Washington, D. C.
Union Carbide Coporation, "Continued Evaluation of Oxygen Use in Con-
ventional Activated Sludge Processing," Report No. 17050DNW, Feb 1972,
U. S. Environmental Protection Agency, Washington, D. C.
Union Carbide Corporation, "Unox System Wastewater Treatment," Report of
Pilot Study at Hooker's Point Treatment Plant, Tampa, Fla.
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Design and Cost Estimation for Multiple Hearth Sludge Incinerators,"
Report No. EP 17070EBP, Jul 1971, Environmental Protection Agency,
Washington, D. C.
U. S. Department of Health, Education and Welfare, "Manual of Septic-
Tank Practice," Publication No. (HSM) 72-10020 (formerly Public Health
Service Publication No. 526), 1972, Rockville, Md.
U. S. Department of Transportation, "Oxidation Ditch Sewage Waste Treat-
ment Process," Water Supply and Waste Disposal Series, Vol 6, Apr 1972,
U. S. Department of Transportation, Washington, D. C.
U. S. Environmental Protection Agency, "Process Design Manual for
Phosphorus Removal," Oct 1971, Washington, D. C.
U. S. Environmental Protection Agency, Technology Transfer, "Process
Design Manual for Upgrading Existing Wastewater Treatment Plants,"
1973, Washington, D. C.
U. S. Environmental Protection Agency, Technology Transfer Seminars,
"Sludge Handling and Disposal," 11-12 Dec 1973, Washington, D. C.
U. S. Environmental Protection Agency, "Guidance for Facilities Plan-
ning," Jan 197^, Washington, D. C.
U. S. Environmental Protection Agency, Technology Transfer, "Process
Design Manual for Sludge Treatment and Disposal," Oct 197^.
U. S. Environmental Protection Agency, Technology Transfer, "Air Pollu-
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1975, Washington, D. C.
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University
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Weber, W. J. , Jr., "Principles and Applications of Adsorption," Manual
of Treatment Processes. Environmental Science Services, Inc., Briarcliff
Manor, New York, 1969.
Weber, W. J., Jr., Physicochemical Processes for Water Quality Control,
Wiley-Interscience, New York, 1972.
Weston, R. F., "Design of Sludge Reaeration Activated Sludge Systems,"
Journal, Water Pollution Control Federation, Vol 33. No. 1 196l
pp 748-757-'' '
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Sewage Sludge," Water and Sewage Works. Vol 109, Oct 1962, pp 38^-386.
Wukasch, R. F. , "The Dow Process for Phosphorus Removal," Paper pre-
sented at the Federal Water Pollution Control Association Phosphorus
Removal Symposium, Jun 1968, Chicago, 111.
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Sludge Tanks with Low BOD Loadings," 5th International Water Pollution
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APPENDIX B
ABBREVIATIONS
atm atmosphere
av average
avg average
"bhp brake horsepower
Btu British Thermal Unit
cal calorie
cfs cubic feet per second
cm centimeter
cu ft cubic foot
fpm feet per minute
fps feet per second
ft foot
ft-lb foot-pound
g gram
gal gallon
gpad gallons per acre per day
gpcd gallons per capita per day
gpd gallons per day
gpm gallons per minute
hp horsepower
hr hour
in. inch
mgad million gallons per acre per day
mgd million gallons per day
mg milligram
mg/1 milligrams per liter
min minute
ml milliliter
mm millimeter
ppm parts per million
psi pounds per square inch
psia pounds per square inch absolute
psig pounds per square inch gage
rpm revolutions per minute
rps revolutions per second
cfm standard cubic feet per minute
sec second
sq ft square foot
vol volume
B-l
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APPENDIX C
CONVERSION FACTORS FOR UNITS OF MEASUREMENT; DISSOLVED-OXYGEN
SOLUBILITY DATA; PHYSICAL PROPERTIES OF WATER; CHEMICAL
ELEMENTS AND SUBSTANCES; SPECIFIC WEIGHT
C-l. Conversion Factors. U. S. customary to metric (Si) and metric
(Si) to U. S. customary units of measurement.
Length
1 inch = 2.5^ cm
1 foot = 0.30U8 m
1 yard = 0.915 m
1 mile (U. S. statute) = 1.6093 km
1 micron = 39-37 microinches
1 millimeter = 0.039^ in.
1 centimeter = 0.39^- in.
1 meter = 1.093 yd
1 kilometer = 0.621U mile
Area
1 square inch = 6.^516 cm
1 square foot = 0.0929 m
2
1 square yard = 0.836l m
2
1 square mile (U. S. statute) = 2.59 km
2
1 acre = k0^6.8 m
2
1 square centimeter = 0.155 in.
2
1 square meter = 1.196 yd
C-l
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1 hectare = 2.1*71 acres
P
1 square kilometer = 0.386 mile
Volume
cuMc inch = 16.39 cm
cuMc foot = 0.0283 m3
o
cubic yard = 0.76^5 m
acre-ft = 1233.5 m3
U. S. gal = 3.79 I
U. K. gal = It. 55 i
o
cubic centimeter = 0.06l in.
,3
cubic meter = 1.307 yd"
liter = 0.26 U. S. gal = 0.22 U. K. gal
Mass
ounce (avoirdupois) = 28.35 g
pound (avoirdupois) = 0.^536 kg
ton (short, 2000 Ib) = 907.185 kg
ton (long, 22^0 Ib) = 1016.05 kg
gram = 0.0352 oz
kilogram = 2.2 Ib
Pressure
pound per square inch = 689^.757 Pa
pound per square foot = ^7.88026 Pa
2
atmosphere = 1 kg/cm
kilogram per square centimeter = lU.697 psi
C-2
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Velocity
inch per second = 2.5^ cm/sec
foot per second = 0.30^8 m/sec
centimeter per second = 0.39^ in./sec
meter per second = 1.093 yd/sec
Power
1 horsepower = 0.7^57 kw
1 Btu (Int. Table) = 1055.056 joules
1 kilowatt = 1.3^1 hp
Miscellaneous
1 cubic foot per second = 28.3 I/sec
1 mgd (U. S.) = 3780 m3/day
1 mgd (U. K. ) = 1+550 m3/day
o
pound per cubic foot = 16.0185 kg/m
milligram per liter = 0.000138 oz/gal (U. S.)
centipoise = 0.001 Pa-sec
pound BOD/acre/day = 1.12 kg BOD/ha/day
degree Fahrenheit = 5/9 degree Celsius*
* To obtain Celsius (c) temperature readings
from Fahrenheit (F) readings, use the follow-
ing equation: C = (5/9)(F - 32).
C-3
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C-2. Physical Properties of Water.
Specific
fT . , , _ ., Viscosity
m Weight, Density,
Temper- & ' •" _, - 5
, Y, 0. u x 10 .
ture
°F lb/ftj slug/ft^ Ib-sec/ft
32 62.1*2
1*0 62.1*3
50 62.1*1
60 62.37
70 62.30
80 62.22
90 62.11
100 62.00
1.
1.
1.
1.
1.
1.
1.
1.
C-3. Dissolved-Oxygen
9l*0
91*0
9l*0
938
936
931*
931
927
3.
3.
2.
2.
2.
1.
1.
1.
Solubility
71*6
229
735
359
050
799
595
421*
Data.
Kinematic
, Viscosity,
v x 10~5.
2
Dissolved Oxygen
Tempera-
ture
°C
0
1
2
3
1*
5
6
7
8
9
10
11
12
13
ll*
ft /sec
1.
1.
1.
1.
1.
0.
0.
0.
931
661*
1*10
217
059
930
826
739
Surface
Tension,
a,
Ib/ft
0.00518
0.00511*
0.00509
0.00501*
0.001*98
0.001*92
0.001*86
o.ooi*8o
Vapor
Pressure,
pu,
psia
0.09
0.12
0.18
0.26
0.36
0.51
0.70
0.95
, mg/£
Chloride Concentration, mg/£
0
UK 62
ll*.23
13. 8U
13.1*8
13.13
12.80
12.1*8
12.17
11.87
11.59
11.33
11.08
10.83
10.60
10.37
5,000
13.79
13.1*1
13.05
12.72
12.1*1
12.09
11.79
11.51
11.21*
10.97
10.73
10.1*9
10.28
10.05
9.85
10,
12.
12.
12.
11.
11.
11.
11.
10.
10.
10.
10.
9.
9.
9.
9.
000
97
61
28
98
69
39
12
85
61
36
13
92
72
52
32
15
12
11
11
11
10
10
10
10
9
9
9
9
9
8
8
,000
.11*
.82
.52
.21*
.97
.70
.U5
.21
.98
.76
.55
.35
.17
• 98
.80
20
11
11
10
10
10
10
9
9
9
9
8
8
8
8
8
,000
.32
.03
• 76
.50
.25
.01
.78
.57
.36
.17
• 98
.80
.62
.1*6
.30
(Continued)
c-U
-------
EM 1110-2-501
Part 1 of 3
29 Sep 78
Tempera-
ture
°C
15
16
17
18
19
20
21
22
23
21*
25
26
27
28
29
30
C-l*. Chemical
Element
Aluminum
Bromine
Calcium
Carbon
Chlorine
Chromium
Cobalt
Copper
Fluorine
Hydrogen
Iodine
Iron (Ferrum)
Chloride Concentration, mg/fl.
0
10.15
9-95
9.7^
9-51*
9.35
9.17
8.99
8,83
8.68
8.53
8.38
8.22
8.07
7-92
7.77
7-63
Elements
5 , OOP
9-65
9.1*6
9.26
9-07
8.89
8.73
8.57
8.1*2
8.27
8.12
7.96
7.81
7-67
7.53
7.39
7-25
and Substances
Symbol
Al
Br
Ca
C
Cl
Cr
Co
Cu
F
H
I
Fe
10,000
9. 11!
8.96
8.78
8.62
8.^5
8.30
Q.Ik
7.99
7.85
7-71
7.56
7.1+2
7.28
7.H*
7.00
6.86
Atomic
Number
13
35
20
6
17
2k
27
29
9
1
53
26
15,000
8.63
8.^7
8.30
8.15
8.00
7.86
7.71
7.57
7.^3
7.30
7.15
7.02
6.88
6.75
6.62
6.1*9
Atomic
Weight
26.98
79.92
ho. 08
12.01
35.^6
52.01
58.91*
63.5^
19-00
1.008
126.92
55.85
20,000
8. Ill
7.99
7.81*
7.70
7-56
7.1*2
7.28
7.11+
7.00
6.87
6.71+
6.6l
6.1*9
6.37
6.25
6.13
Valence
3
1,3,5,7
2
2,1*
1,3,5,7
2,3,6
2,3
1,2
1
1
1,3,5,7
2,3
(Continued)
C-5
-------
EM 1110-2-510
Part 1 of 3
29 Sep 78
Element
Lead ( Plumbum )
Magnesium
Manganese
Mercury (Hydragyrum)
Nickel
Nitrogen
Oxygen
Phosphorus
Platinum
Potassium (Kalium)
Silicon
Silver (Argentum)
Sodium (Natrium)
Strontium
Sulfur
Tin (Stannum)
Zinc
Symbol
Pb
Mg
Mn
Hg
Ni
N
0
P
Pt
K
Si
Ag
Na
Sr
S
Sn
Zn
C-5. Specific Weight (at Standard
Atomic
Number
82
12
25
80
28
7
8
15
78
19
lU
kl
11
38
16
50
30
Temperature
Atomic
Weight
207-
2k.
5>i.
200.
58.
1U.
16.
30.
195.
39.
28.
107.
23.
87-
32.
118.
65.
21
32
93
61
69
01
00
98
23
10
09
88
00
63
07
70
38
Valence
2,U
2
2,3,M,7
1,2
2,3
3,5
2
3,5
2,U
1
k
1
1
2
2,1*, 6
2,1*
2
and Pressure).
Specific
Substance
Water
Salt water
Ice
Snow
Gasoline
Diesel oil
Wood
Feces
Dust
Earth
Sand
(loose).
(loose)
Weight
1.
1.
0.
0.
0.
0.
0.
1.
1.
1.
2.
00
02
91
UO
70
90
68
02
20
60
80
Density
62
6k
57
25
hh
56
h2
6k
75
100
175
A3
.5
1 cu ft of water = 62.1*3 lb
1 gal of water (U. S.) = 8.3U lb
1 m3 of air = 1.2 kg
1 kg/a = 62. it3 Ibs/cu ft
1 Ib/cu ft = 16.02 kg/m3
= 0.012 tons long/cu yd
C-6
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EM 1110-2-501
Part 1 of 3
29 Sep 78
GLOSSARY
absorption — The taking up of one substance into the body of another.
acid — (l) A substance that tends to lose a proton. (2) A substance
that dissolves in water with the formation of hydrogen ions. (3) A
substance containing hydrogen which may be replaced by metals to form
salts.
acidity — The quantitative capacity of aqueous solutions to react with
hydroxyl ions. It is measured by titration with a standard solution
of a base to a specified end point. Usually expressed as milligrams
per liter of calcium carbonate.
activated carbon — Carbon particles usually obtained by carbonization
of cellulosic material in the absence of air and possessing a high
adsorptive capacity.
activated sludge — Sludge floe produced in raw or settled wastewater
by the growth of zoogleal bacteria and other organisms in the pres-
ence of dissolved oxygen and accumulated in sufficient concentration
by returning floe previously formed.
activated sludge loading — The pounds of biochemical oxygen demand
(BOD) in the applied liquid per unit volume of aeration capacity or
per pound of activated sludge per day.
activated sludge process — A biological wastewater treatment process in
which a mixture of wastewater and activated sludge is agitated and
aerated. The activated sludge is subsequently separated from the
treated wastewater (mixed liquor) by sedimentation and wasted or
returned to the process as needed.
adsorption — (l) The adherence of a gas, liquid, or dissolved material
on the surface of a solid. (2) A change in concentration of gas or
solute at the interface of a two-phase system. Should not be confused
with absorption.
advanced wastewater treatment — Those processes that achieve pollutant
reductions by methods other than those used in conventional treatment
(sedimentation, activated sludge, trickling filter, etc). It employs
a number of different unit operations, including lagoons, post-
aeration, microstraining, filtration, carbon adsorption, membrane
solids separation, phosphorus removal, and nitrogen removal..
Glossary 1
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EM 1110-2-501
Part 1 of 3
29 Sep 78
aerated contact bed — A biological unit consisting of stone, cement-
asbestos, or other surfaces supported in an aeration tank, in which
air is diffused up and around the surfaces and settled wastewater
flows through the tank. Also called contact aerator.
aerated pond — A natural or artificial wastewater treatment pond in
which mechanical or diffused-air aeration is used to supplement the
oxygen supply. See oxidation pond.
aeration — (l) The bringing about of intimate contact between air and
a liquid by one or more of the following methods: (a) spraying the
liquid in the air, (b) bubbling air through the liquid, (c) agitating
the liquid to promote surface absorption of air. See following terms
modifying aeration: diffused-air, mechanical, modified, spiral-flow,
step.
aeration period — (l) The theoretical time, usually expressed in hours,
during which, mixed liquor is subjected to aeration in an aeration tank
while undergoing activated sludge treatment. It is equal to the vol-
ume of the tank divided by the volumetric rate of flow of the waste-
water and return sludge. (2) The theoretical time during which water
is subjected to aeration.
aeration tank — A tank in which sludge, wastewater, or other liquid is
aerated.
aerator — A device that promotes aeration.
aerobic — Requiring, or not destroyed by, the presence of free ele-
ment al oxy gen.
aerobic bacteria — Bacteria that require free elemental oxygen for their
growth.
aerobic digestion — Digestion of suspended organic matter by means of
aeration. See digestion.
agglomeration — The coalescence of dispersed suspended matter into
larger floes or particles which settle rapidly.
agitator — (l) Mechanical apparatus for mixing and/or aerating. (2) A
device for creating turbulence.
air —• The mixture of gases that surrounds the earth and forms its
Glossary 2
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EM 1110-2-501
Part 1 of 3
29 Sep 78
atmosphere, composed primarily of oxygen and nitrogen. It also con-
tains carbon dioxide, some water vapor, argon, and traces of other
gases.
algae — Primitive plants, one- or many-celled, usually aquatic, and
capable of elaborating their foodstuffs by photosynthesis.
alkali — Any of certain soluble salts, principally sodium, potassium,
magnesium, and calcium, that have the property of combining with acids
to form neutral salts and may be used in chemical processes such as
water or wastewater treatment.
alkaline — The condition of water, wastewater, or soil which contains a
sufficient amount of alkali substances to raise the pH above 7.0.
alkalinity — The capacity of water to neutralize acids, a property
imparted by the water's content of carbonates, bicarbonates, hydrox-
ides, and occasionally borates, silicates, and phosphates. It is
expressed in milligrams per liter of equivalent calcium carbonate.
alum — A common name, in the water and wastewater treatment field, for
commercial-grade aluminum sulfate.
aluminum sulfate — A chemical, formerly sometimes called "waterworks
alum" in water or wastewater treatment, prepared by combining a min-
eral known as bauxite with sulfuric acid.
ammonia — A chemical combination of hydrogen (H) and nitrogen (N)
occurring extensively in nature. The combination used in water and
wastewater engineering is expressed as NH .
ammonia stripping — A modification of the aeration process for removing
gases in water. Ammonium ions in wastewater exist in equilibrium
with ammonia and hydrogen ions. As pH increases, the equilibrium
shifts to the right, and above pH 9 ammonia may be liberated as a
gas by agitating the wastewater in the presence of air. This is usu-
ally done in a packed tower with an air blower.
ammonification — Bacterial decomposition of organic nitrogen to
ammonia.
anaerobic — Requiring, or not destroyed by, the absence of air or free
elemental oxygen.
Glossary 3
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EM 1110-2-501
Part 1 of 3
29 Sep 78
anaerobic bacteria — Bacteria that grow only in the absence of free
elemental oxygen.
anaerobic contact process — An anaerobic waste treatment process in
which the microorganisms responsible for waste stabilization are re-
moved from the treated effluent stream by sedimentation or other
means and held in or returned to the process to enhance the rate of
treatment.
anaerobic denitrification — A means to remove nitrates from wastewaters,
especially irrigation return waters that may be high in nitrates and
low in organics. In this method, an organic chemical such as meth-
anol, ethanol, acetone, or acetic acid is added as a carbon source
and the waste is placed in an anaerobic environment. Under these
conditions, nitrate will be reduced by denitrifying bacteria to nitro-
gen gas and some nitrous oxide, which escapes to the atmosphere. With
methanol, the chemistry can be represented as:
6H+ + 6NO~ + 5CH3OH 5C02 + 3N2 + ISHgO
anaerobic digestion — The degradation of organic matter brought about
through the action of microorganisms in the absence of elemental oxy-
gen.
anaerobic digestion of sewage solids — The first stage of the digestion
is characterized by the production of organic acids. Proteins, carbo-
hydrates, and fats are decomposed by the anaerobic bacteria, and the
products of the decomposition are organic acids. This digestion stage
is evident in sludge by a lowering of the pH and the presence of a
disagreeable sour odor. Unless the amount of acid produced is exces-
sive, the digestion will normally proceed to the second stage. With
excess acidity, such as is obtained when the addition of fresh solids
is too rapid, the bacteria will be destroyed and the process will end
with the first stage. The second stage is characterized by lique-
faction of sewage solids under mildly acid conditions. The bacteria,
by enzyme action, convert the insoluble solids material to the soluble
form. This is in accordance with the requirements of the bacterial
cells that all food material must be in solution before it can pass
through the cell wall. The third stage of digestion is characterized
by production of gases, carbon dioxide, methane, and hydrogen sulfide,
as well as an increase of pH and the production of carbonate salts.
anaerobic waste treatment — Waste stabilization brought about through
Glossary k
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EM 1110-2-501
Part 1 of 3
29 Sep 78
the action of microorganisms in the absence of air or elemental
oxygen. Usually refers to waste treatment by methane fermentation.
anion — A negatively charged ion in an electrolyte solution, attracted
to the anode under the influence of electric potential.
anthracite — Coal
available dilution — The ratio of the quantity of untreated wastewater
or partly or completely treated effluent to the average quantity of
diluting water available, effective at the point of disposal or at
any point under consideration; usually expressed in percentage. Also
called dilution factor.
average daily flow — The total quantity of liquid tributary to a point
divided by the number of days of flow measurement.
average flow — Arithmetic average of flows measured at a given point.
backwash — The reversal of flow through a rapid sand filter to wash
clogging material out of the filtering medium and reduce conditions
causing loss of head.
backwash bed expansion — The expansion that occurs when a filter bed
is being backwashed, usually expressed as a percentage of the back-
washed and settled bed.
backwashing — The operation of cleaning a filter by reversing the flow
of liquid through it and washing out matter previously captured in it.
Filters would include true filters such as sand and diatomaceous-
earth types but not other treatment units such as trickling filters.
bacteria — A group of universally distributed, rigid, essentially uni-
cellular microscopic organisms lacking chlorophyll. Bacteria usually
appear as spheroid, rodlike, or curved entities, but occasionally
appear as sheets, chains, or branched filaments. Bacteria are usually
regarded as plants.
bacteria — See following terms modifying bacteria: aerobic, anaerobic,
facultative anaerobic.
baffles — Deflector vanes, guides, grids, gratings, or similar devices
constructed or placed in flowing water, wastewater, or slurry systems
to check or effect a more uniform distribution of velocities; absorb
energy; divert, guide, or agitate the liquids; and check eddies.
Glossary 5
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EM 1110-2-501
Part 1 of 3
29 Sep 78
bar screen — In a waste-treatment plant, a screen that removes large
suspended solids.
basin — (l) A natural or artificially created space or structure, sur-
face or underground, which has a shape and character of confining
material that enable it to hold water. The term is sometimes used for
a receptacle midway in size between a reservoir and a tank. (2) The
surface area within a given drainage system. (3) A small area in an
irrigated field or plot surrounded by low earth ridges and designed to
hold irrigation water. (k) An area upstream from a subsurface or
surface obstruction to the flow of water. (5) A shallow tank or de-
pression through which liquids may be passed or in which they are
detained for treatment or storage. Also see tank.
bed — The bottom of a watercourse or any body of water.
bed density, backwashed and drained (granular carbon adsorption) —
The weight per unit volume on a dry basis of a bed of activated
carbon that has been backwashed and drained. This value is usually
lower than the corresponding apparent density due to the classifi-
cation according to size of the carbon granules during backwashing.
bed depth (height) — (l) The depth of carbon, expressed in length units,
which is parallel to the flow of the stream and through which the
stream must pass. (2) The depth of the ion exchange resin in an ion
exchange column.
bed diameter — The diameter of a cylindrical carbon column or ion ex-
change column, measured perpendicular to the stream flow.
bed expansion — The separation and rise of ion exchange resin particles
in an ion exchange column during backwashing.
biochemical action — Chemical change resulting from the metabolism of
living organisms.
biochemical oxygen demand — A standard test used in assessing waste-
water strength. See BOD.
biodegradation (biodegradability) — The destruction or mineralization
of either natural or synthetic organic materials by the microorganisms
populating soils, natural bodies of water, or wastewater treatment
systems.
biological filter — A bed of sand, gravel, broken stone, or other
Glossary 6
-------
EM 1110-2-501
Part 1 of ^
29 Sep 78
medium through which waste-water flows or trickles that depends on bio-
logical action for its effectiveness.
biological filtration — The process of passing a liquid through the
medium of a biological filter, thus permitting contact with attached
zoogleal films that adsorb and absorb fine suspended, colloidal, and
dissolved solids and release end products of biochemical action.
biologically active floe — Floe formed by the action of biological
agencies; for example, activated sludge.
biological oxidation — The process whereby living organisms in the
presence of oxygen convert the organic matter contained in wastewater
into a more stable or a mineral form.
biological process — (l) The process by which the life activities of
bacteria and other microorganisms, in the search for food, break down
complex organic materials into simple, more stable substances. Self-
purification of polluted streams, sludge digestion, and all the so-
called secondary wastewater treatments result from this process.
(2) Process involving living organisms and their life activities.
Also called biochemical process.
biological purification — The process whereby living organisms convert
the organic matter contained in wastewater into a more stable or a
mineral form.
biological slime — The gelatinous film of zoogleal growths covering the
medium or spanning the interstices of a biological bed. Also called
microbial film.
biological treatment systems — "Living" systems which rely on mixed
biological cultures to break down waste organics and remove organic
matter from solution.
biological wastewater treatment — Forms of wastewater treatment in
which bacterial or biochemical action is intensified to stabilize,
oxidize, and nitrify the unstable organic matter present. Intermittent
sand filters, contact beds, trickling filters, and activated sludge
processes are examples.
BOD — (1) Abbreviation for biochemical oxygen demand. The quantity of
oxygen used in the biochemical oxidation of organic matter in. a
specified time, at a specified temperature, and under specified
conditions. (2) A standard test used in assessing wastewater strength.
Glossary 7
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EM 1110-2-501
Part 1 of 3
29 Sep 78
BOD load — The BOD content of vastevater passing into a waste treatment
system or to a body of water, usually expressed in pounds per unit of
time.
breakpoint chlorination — Addition of chlorine to water or wastewater
until the chlorine demand has been satisfied and further additions
result in a residual that is directly proportional to the amount
added beyond the breakpoint.
buffer — Any of certain combinations of chemicals used to stabilize
the pH values or alkalinities of solutions.
cake — Solids deposited on the filter medium.
cake compressibility factor — Also known as the coefficient of com-
pressibility. An empirically derived factor relating specific resis-
tance of sludge cake to filtering pressure (dimensionless).
cake solids -- Percent dry solids in wet cake discharged from a de-
watering device. As commonly reported, this includes the weight of
sludge conditioning chemicals which may comprise 5 to 15 percent of
the dry sludge solids.
calcium hypocnlorite — A dry powder consisting of lime and chlorine
combined in such a way that, when dissolved in water, it releases
active chlorine.
carbonate hardness — Hardness caused by the presence of carbonates and
bicarbonates of calcium and magnesium in water. Such hardness may be
removed to the limit of solubility by boiling the water. When the
hardness is numerically greater than the sum of the carbonate alka-
linity and the bicarbonate alkalinity, that amount of hardness which
is equivalent to the total alkalinity is called carbonate hardness.
See hardness.
cation — The ion in an electrolyte which carries the positive charge
and which migrates toward the cathode under the influence of a poten-
tial difference.
centrate — The effluent or liquid portion of a sludge removed by or
discharged1from a centrifuge.
centrifugal dewatering of sludge — The partial removal of water from
wastewater sludge by centrifugal action.
Glossary 8
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EM 1110-2-501
Part 1 of ^
29 Sep 78
centrifugal drying — The partial drying of industrial waste sludge or
waste-water by centrifugal action.
centrifuge — A mechanical device in which centrifugal force is used to
separate solids from liquids and/or to separate liquids of different
densities.
channel — A perceptible natural or artificial waterway which period-
ically or continuously contains moving water or which forms a con-
necting link between two bodies of water. It has a definite bed and
banks which confine the water.
chemical coagulation — The destabilization and initial aggregation of
colloidal and finely divided suspended matter by the addition of a
floe-forming chemical. See flocculation.
chemical dose — The application of a specific quantity of chemical to
a specific quantity of fluid for a specific purpose. See dose.
chemical feeder — A device for dispensing a chemical at a predetermined
rate for the treatment of water or wastewater. Change in rate of feed
may be affected manually or automatically by flow-rate changes.
Feeders are designed for solids, liquids, or gases.
chemical oxygen demand (COD) — A measure of the oxygen-consuming capac-
ity of inorganic and organic matter present in water or wastewater.
It is expressed as the amount of oxygen consumed from a chemical oxi-
dant in a specific test. It does not differentiate between stable and
unstable organic matter and thus does not necessarily correlate with
biochemical oxygen demand. Also known as OC and DOC, oxygen consumed
and dichromate oxygen consumed, respectively.
chemical precipitation — (l) Precipitation induced by addition of
chemicals. (2) The process of softening water by the addition of lime
or lime and soda ash as the precipitants.
chemical sludge — Sludge obtained by treatment of wastewater with
chemicals.
chemical toilet — (l) A commode chair in which a pail containing a
chemical solution for deodorizing and liquefying fecal matter is
placed immediately beneath the seat. (2) A nonwater-carriage toilet
arranged to discharge fecal matter directly into a deodorizing and
liquefying chemical solution contained in a watertight tank.
Glossary 9
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EM 1110-2-501
Part 1 of 3
29 Sep 78
chemical treatment — Any process involving the addition of chemicals
to obtain a desired result.
chlorination — The application of chlorine to water or waste-water,
generally for the purpose -of disinfection, but frequently for accom-
plishing other biological or chemical results.
chlorination chamber — A detention basin provided primarily to secure
the diffusion of chlorine through the liquid. Also called chlorine
contact chamber.
chlorine — An element ordinarily existing as a greenish-yellow gas
about 2.5 times as heavy as air. At atmospheric pressure and a tem-
perature of -30.1°F, the gas becomes an amber liquid about 1.5 times
as heavy as water. The chemical symbol of chlorine is Cl, its atomic
weight is 35.^57, and its molecular weight is JO.91^-
chlorine contact chamber — A detention basin provided primarily to
secure the diffusion of chlorine through the liquid. Also called
chlorination chamber.
chlorine demand — The difference between the amount of chlorine added
to the wastewater and the amount of residual chlorine remaining at
the end of a specific contact time. The chlorine demand for given
water varies with the amount of chlorine applied, time of contact,
temperature, pH, nature, and amount of impurities in the water.
chlorine residual — The total amount of chlorine (combined and free
available chlorine) remaining in water, sewage, or industrial wastes
at the end of a specified contact period following chlorination.
clarification •— Any process or combination of processes which reduce
the concentration of suspended matter in a liquid.
clarified wastewater — Wastewater from which most of the settleable
solids have been removed by sedimentation. Also called settled
wastewater.
clarifier — A unit which secures clarification. Usually applied to
sedimentation tanks or basins. See sedimentation tank.
coagulant — A chemical added to wastewater or sludge to promote agglom-
eration and flocculation of suspended solids to induce faster
Glossary 10
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EM 1110-2-501
Part 1 of 3
29 Sep 78
settling or more efficient filtration. Typical coagulants are poly-
electrolytes, alum, and ferric chloride.
coagulation — In water and waste-water treatment, the destabilization
and initial aggregation of colloidal and finely divided suspended
matter by the addition of a floe-forming chemical or by biological
processes.
coagulation basin — A basin used for the coagulation of suspended or
colloidal matter, with or without the addition of a coagulant, in
which the liquid is mixed gently to induce agglomeration with a
consequent increase in settling velocity of particulates.
coarse screen — Coarse or large screens have openings that range from
1.5 to 6 inches. They protect pumps, tanks, automatic dosing de-
vices, conduits, and valves from large objects such as pieces of
timber.
COD — Symbol for chemical oxygen demand. See chemical oxygen demand.
colloidal matter — Finely divided solids which will not settle but may
be removed by coagulation or biochemical action or membrane filtration.
See colloids.
colloids — (l) Finely divided solids which will not settle but may be
removed by coagulation or biochemical action or membrane filtration;
they are intermediate between true solutions and suspensions. (2) In
soil physics, discrete mineral particles less than 2 microns (y) in
diameter. (3) Finely divided dispersions of one material, called the
dispersed phase; with another, called the dispersion medium. (h) In
general, particles of colloidal dimensions are approximately 10 A to
1 M in size. Colloidal particles are distinguished from ordinary
molecules by their inability to diffuse through membranes that allow
ordinary molecules and ions to pass freely.
color — Colors in water are usually due to decomposition of organic
matter of vegetable or soil origin. Color caused by suspended matter
is referred to as "apparent color"; color due to colloid vegetable
or organic extracts is called "true color."
combined residual chlorination — The application of chlorine to water
or wastewater to produce, with the natural or added ammonia or with
certain organic nitrogen compounds, a combined chlorine residual.
Glossary 11
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EM 1110-2-501
Part 1 of 3
29 Sep 78
combined wastewater — A mixture of surface runoff and other waste-
water such as domestic or industrial wastewater.
comminuted solids — Solids which have been divided into fine particles.
comminuting screen — A mechanically operated device for screening waste-
water and cutting the screenings into particles sufficiently fine to
pass through the screen openings.
comminution — The process of cutting and screening solids contained in
wastewater flow before it enters the flow pumps or other units in the
treatment plant.
comminutor — A device for catching and shredding heavy solid matter in
the primary stage of waste treatment.
concentrate — To increase the proportion of solids in a sludge or
wastewater.
concentration — (l) The amount of a given substance dissolved in a unit
volume of solution. (2) The process of increasing the dissolved solids
per unit volume of solution, usually by evaporation of the liquid.
concentration tank — A settling tank of relatively short detention
period in which sludge is concentrated by sedimentation or flo-
tation before treatment, dewatering, or disposal. See sedimentation
tank.
concentrator — A solids contact unit used to decrease water content of
sludge or slurry.
conduit — Any artificial or natural duct, either open or closed, for
conveying liquids or possibly other fluids.
contact aerator — A biological unit consisting of stone, cement-
asbestos, or other surfaces supported in an aeration tank, in which
air is diffused up and around the surfaces and settled wastewater
flows through the tank.
contact bed — (l) An artificial bed of coarse material providing
extensive surface area for biological growth in a watertight basin.
Wastewater exposure to the surface may be accomplished by cycling
or by continuous flow through controlled inlet and outlet. (2) An
early type of wastewater filter consisting of a bed of coarse broken
Glossary 12
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EM 1110-2-501
Part 1 of 3
29 Sep 78
stone or similar inert material placed in a watertight tank or basin
which can "be completely filled with wastewater and then emptied.
Operation consists of filling, allowing the contents to remain for
a short time, draining, and then allowing the bed to rest. The cycle
is then repeated. A precursor to the trickling filter.
contact stabilization process — A modification of the activated sludge
process in which raw wastewater is aerated with a high concentration
of activated sludge for a short period, usually less than 60 min, to
obtain BOD removal by absorption. The solids are subsequently removed
by sedimentation and transferred to a stabilization tank where aera-
tion is continued further to oxidize and condition them before their
reintroduction to the raw wastewater flow.
contact tank — A tank used in water or wastewater treatment to promote
contact between treatment chemicals or other materials and the body of
liquid treated.
current — (l) The flowing of water or other fluid. (2) That portion
of a stream of water which is moving with a velocity much greater than
the average or in which the progress of the water is principally
concentrated.
cycle — Filtration interval: length of time filter operates before
cleaning.
dechlorination — The partial or complete reduction of residual chlorine
in a liquid by any chemical or physical process.
decomposition — The breakdown of complex material into simpler sub-
stances by chemical or biological means.
decomposition of wastewater — (l) The breakdown of organic matter in
wastewater by bacterial action, either aerobic or anaerobic.
(2) Transformation of organic or inorganic materials contained in
wastewater through the action of chemical or biological processes.
defoamant — A material having low compatibility with foam and a low
surface tension. Defoamants are used to control, prevent, or destroy
various types of foam, the most widely used being silicone defoamers.
A droplet of silicone defoamant which contacts a bubble of foam will
cause the bubble to undergo a local and drastic reduction in film
strength, thereby breaking the film. Unchanged, the defoamant con-
tinues to contact other bubbles, thus breaking up the foam. 'A val-
uable property of most defoamants is their effectiveness in extremely
Glossary 13
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low concentration. In addition to silicones, defoamants for special
purposes are based on polyamides, vegetable oils, and stearic acid.
defoaming agent — A material having low compatibility with foam and
a low surface tension. See defoamant.
denitrification — (l) Chemically bound oxygen in the form of either
nitrates or nitrites is stripped away for use by microorganisms. This
produces nitrogen gas which can bring up floe in the final sedimen-
tation process. It is an effective method of removing nitrogen from
wastewater. (2) A biological process in which gaseous nitrogen is
produced from nitrite and nitrate.
depth of side water — The depth of a liquid measured along the inside
of the vertical exterior wall of a tank.
detention time — The theoretical time required to displace the contents
of a tank or unit at a given rate of discharge (volume divided by
rate of discharge).
dewatering — Any process of water removal or concentration of a sludge
slurry, as by filtration, centrifugation, or drying. (A dewatering
method is any process which will concentrate the sludge solids to at
least 15 percent solids by weight.)
diatomaceous earth — A fine, siliceous earth consisting mainly of the
skeletal remains of diatoms (unicellular organisms).
diatomaceous-earth filter — A filter used in water treatment in which
a built-up layer of diatomaceous earth serves as the filtering medium.
diffused air — A technique by which air under pressure is forced into
sewage in an aeration tank. The air is pumped down into the sewage
through a pipe and escapes out through holes in the side of the pipe.
diffused-air aeration — Aeration produced in a liquid by air passed
through a diffuser.
diffusion aerator — An aerator that blows air under low pressure through
submerged porous plates, perforated pipes, or other devices so that
small air bubbles rise through the water or wastewater continuously.
digested sludge — Sludge digested under either aerobic or anaerobic
conditions until the volatile content has been reduced to the point at
which the solids are relatively nonputrescible and inoffensive.
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digester — A tank in which sludge is placed to permit digestion to
occur. Also called sludge digestion tank. See sludge digestion.
digestion — (l) The biological decomposition of organic matter in
sludge, resulting in partial gasification, liquefaction, and mineral-
ization. (2) The process carried out in a digester. See sludge
digestion.
digestion chamber — A sludge-digestion tank. Frequently refers specif-
ically to the lower or sludge-digestion compartment of an Imhoff tank.
digestion of sludge — Takes place in heated tanks where the material
can decompose naturally and the odors can be controlled.
digestion tank — A tank in which sludge is placed to permit digestion
to occur. See sludge digestion.
diluent — A diluting agent.
dilution — Disposal of wastewater or treated effluent by discharging
it into a stream or body of water.
discharge — (l) As applied to a stream or conduit, the rate of flow or
volume of water flowing in the stream or conduit at a given place and
within a given period of time. (2) The passing of water or other
liquid through an opening or along a conduit or channel. (3) The
rate of flow of water, silt, or other mobile substance which emerges
from an opening, pump, or turbine, or passes along a conduit or chan-
nel, usually expressed as cubic feet per second, gallons per minute,
or million gallons per day.
disinfectant — A substance used for disinfection.
disinfected wastewater — Wastewater to which chlorine or other disin-
fecting agents has been added, during or after treatment, to destroy
pathogenic organisms.
disinfection — The killing of the larger portion of microorganisms in
or on a substance with the probability that all pathogenic bacteria
are killed by the agent used.
disk screen — A screen in the form of a circular disk which rotates
about a central axis perpendicular to its plane.
dissolved air flotation — A process that adds energy in the form of air
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bubbles, which become attached to suspended sludge particles,
increasing the buoyancy of the particles and producing more positive
flotation.
dissolved oxygen (DO) — The oxygen dissolved in water, wastewater, or
other liquid, usually expressed in milligrams per liter, parts per
million, or percent of saturation.
dissolved solids — Theoretically, the anhydrous residues of the dis-
solved constituents in water. Actually, the term is defined by the
method used in determination. In water and wastewater treatment the
Standard Methods tests are used.
ditch — A small artificial open channel or waterway constructed through
earth or rock to convey water.
ditch oxidation — A modification of the activated sludge process or the
aerated pond, in which the mixture under treatment is circulated in
an endless ditch and aeration and circulation are produced by a me-
chanical device such as a Kessener brush.
domestic wastewater — Wastewater derived principally from dwellings,
business buildings, institutions, and the like. It may or may not
contain groundwater, surface water, or storm water.
dose — (l) The quantity of substance applied to a unit quantity of
liquid for treatment purposes. It can be expressed in terms of either
volume or weight, e.g., pounds per million gallons, parts per million,
grains per gallon, milligrams per liter, or grams per cubic meter.
(2) Generally, a quantity of material applied to obtain a specific
effect.
drum screen — A screen in the form of a cylinder or truncated cone which
rotates on its axis.
drying bed — A wastewater treatment unit usually containing a bed of
sand on which sludge is placed to dry by evaporation and drainage.
dumping — A method for solid waste disposal.
effective size — The diameter of the particles, spherical in shape,
equal in size, and arranged in a given manner, of a hypothetical
sample of granular material that would have the same transmission
constant as the actual material under consideration.
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efficiency — (l) The relative results obtained in any operation in rela-
tion to the energy or effort required to achieve such results. (2) The
ratio of the total output to the total input, expressed as a
percentage.
effluent — (l) A liquid which flows out of a containing space.
(2) Wastewater or other liquid, partially or completely treated, or
in its natural state, flowing out of a reservoir, basin, treatment
plant, or industrial treatment plant, or part thereof.
effluent stream — A stream or stretch of stream which receives water
from groundwater in the zone of saturation. The water surface of such
a stream stands at a lower level than the water table or piezometric
surface of the groundwater body from which it receives water.
endogenous respiration — An auto-oxidation of cellular material,
which takes place in the absence of assimilable organic material, to
furnish energy required for the replacement of protoplasm.
environment — The physical environment of the world consisting of the
atmosphere, the hydrosphere, and the lithosphere.
environmental pollution — The presence of any foreign substance or
interference (organic, inorganic, radiological, acoustic, or bio-
logical) in the environment (water, air, or land) which tends to
degrade its quality so as to constitute a hazard or impair the use-
fulness of environmental resources.
equalization — A process by which variations in flow and composition of
a waste stream are averaged in an equalizing unit.
equalizing basin — A holding basin in which variations in flow and
composition of a liquid are averaged. Also called balancing
reservoir.
eutrophication — (l) The normally slow aging process by which a lake
evolves into marsh and ultimately becomes completely filled with
detritus and disappears. (2) The intentional or unintentional en-
richment of water.
evaporation — (l) The process by which water becomes a vapor at a
temperature below the boiling point. (2) The quantity of water that
is evaporated; the rate is expressed in depth of water, measured as
liquid water, removed from a specified surface per unit of time,
generally in inches or centimeters per day, month, or year.
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evaporation rate — The quantity of water, expressed in terms of depth
of liquid water, evaporated from a given water surface per unit of
time. It is usually expressed in inches depth per day, month, or
year,
evapotranspiration — Water withdrawn from soil by evaporation and/or
plant transpiration. Considered synonymous with consumptive use.
evapotranspiration potential — Water loss that would occur if there
never was a deficiency oi water in the soil ±or use by vegetation.
evapotranspiration tank —• A tank, filled with soil and provided with a
water supply, in which representative plants are grown to determine
the amount of water transpired and evaporated from the soil under
observed climatic conditions. Sometimes improperly referred to as
lysimeter.
excess sludge — The sludge produced in an activated sludge treatment
plant that is not needed to maintain the process and is withdrawn
from circulation.
extended aeration — A modification of the activated sludge process
which provides for aerobic sludge digestion within the aeration sys-
tem. The concept envisages the stabilization of organic matter under
aerobic conditions, disposal of the end products into the air as gases,
with the plant effluent in the form of finely divided suspended and
soluble matter.
facultative anaerobic bacteria — Bacteria which can adapt to growth in
the presence., as well as in the absence, of oxygen. May be referred
to as facultative bacteria.
ferric chloride — A chemical (Fed ) often used for sludge conditioning.
filter — A device or structure for removing solid or colloidal material,
usually of a type that cannot be removed by sedimentation, from water,
wastewater, or other liquid. The liquid is passed through a filtering
medium, usually a granular material but sometimes finely woven cloth,
unglazed porcelain, or specially prepared paper. There are many types
of filters used in water or wastewater treatment. See trickling
filter.
filter bed — (l) A type of bank revetment consisting of layers of fil-
tering medium of which the particles gradually increase in size from
Glossary 18
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the "bottom upward. Such a filter allows the groundwater to flow
freely, "but it prevents even the smallest soil particles from being
washed out. (2) A tank for water filtration having a false bottom
covered with sand, as a rapid sand filter. (3) A pond with sand bed-
ding, as a sand filter or slow sand filter.
filter cake — The dewatered sludge discharged from the filter, contain-
ing 65 to 80 percent moisture, depending upon the type of sludge, the
type of dewatering equipment, and the conditioning of the sludge.
filter cloth — A fabric stretched around the drum of a vacuum filter.
filtered wastewater — Wastewater that has passed through a mechanical
filtering process but not through a trickling filter bed.
filter efficiency — The operating results from a filter as measured by
various criteria such as percentage reduction in suspended matter,
total solids, biochemical oxygen demand, bacteria, color.
filtering medium — (l) Any material through which water, wastewater, or
other liquid is passed for the purpose of purification, treatment, or
conditioning. (2) A cloth or metal material of some appropriate de-
sign used to intercept sludge solids in sludge filtration.
filter leaf — A laboratory device for testing potential performance of
a vacuum filter on a sludge.
filter loading — Organically, the pounds of biochemical oxygen demand
(BOD) in the applied liquid per unit of filter bed area or volume per
day. Hydraulically, the quantity of liquid applied per unit of 'filter
bed area or volume per day.
filter rate ~- The rate of application of material to some process
involving filtration, for example, application of wastewater sludge to
a vacuum filter, wastewater flow to a. trickling filter, water flow to
a rapid sand filter.
filter run — (l) The interval between the cleaning and washing oper-
ations of a rapid sand filter. (2) The interval between the changes
of the filter medium on a sludge-dewatering filter.
filter underdrains — A system of underdraining for collecting water
that has passed through a sand filter or biological bed.
filter wash — The reversal of flow through a rapid sand filter to wash
Glossary 19
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clogging material out of the filtering medium and reduce conditions
causing loss of head. See backwash.
filtrate ~ The liquid which has passed through a filter.
filtration — The process of passing a liquid through a filtering medium
(which may consist of granular material, such as sand, magnetite, or
diatomaceous earth, finely woven cloth, unglazed porcelain, or spe-
cially prepared paper) for the removal of suspended or collodial
matter.
filtration rate — The rate of application of wastewater to a filter,
usually expressed in million gallons per acre per day or gallons per
minute per square foot.
final effluent — The effluent from the final treatment unit of a waste-
water treatment plant.
final sedimentation — The separation of solids from wastewater in a
final settling tank.
final sedimentation tank — A tank through which the effluent from a
trickling filter or an aeration or contact-aeration tank is passed to
remove the settleable solids. Also called final settling basin. See
sedimentation tank.
final settling tank — A tank through which the effluent from a trick-
ling filter or an aeration or contact-aeration tank is passed to
remove the settleable solids. Also called final settling basin. See
sedimentation tank.
fine screen — A relative term, usually applied to screens with openings
of less than 1 in., but in wastewater treatment often reserved for
openings that may be 1/16 in.
five-day BOD — That part of oxygen demand associated with biochemical
oxidation of carbonaceous, as distinct from nitrogeneous, material.
It is determined by allowing biochemical oxidation to proceed, under
conditions specified in Standard Methods, for 5 days.
flash dryer — A device for vaporizing water from partly dewatered and
finely divided sludge through contact with a current of hot gas or
superheated vapor. It includes a squirrel-cage mill for separating
the sludge cake into fine particles.
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flash mixer — A device for quickly dispersing chemicals uniformly
throughout a liquid.
floe — Small gelatinous masses formed in a liquid by the reaction of a
coagulant added thereto, through biochemical processes, or by
agglomeration.
flocculating tank — A tank used for the formation of floe by the gentle
agitation of liquid suspensions, with or without the aid of chemicals.
flocculation — In water and wastewater treatment, the agglomeration of
colloidal and finely divided suspended matter after coagulation by
gentle stirring by either mechanical or hydraulic means. In biologi-
cal wastewater treatment where coagulation is not used, agglomeration
may be accomplished biologically.
flocculation agent — A coagulating substance which, when added to
water, forms a flocculent precipitate which will entrain suspended
matter and expedite sedimentation; examples are alum, ferrous sulfate,
and lime.
flocculator — (l) A mechanical device to enhance the formation of floe
in a liquid. (2) An apparatus for the formation of floe in water and
wastewater.
flotation — The raising of suspended matter to the surface of the
liquid in a tank as scum—by aeration, the evolution of gas, chemi-
cals, electrolysis, heat, or bacterial decomposition—and the sub-
sequent removal of the scum by skimming.
flowing-through time — (l) The time required for a volume of liquid to
pass through a basin, identified in terms of the characteristic being
measured, such as mean time, modal time, minimum time. (2) The aver-
age time required for a small volume of liquid to pass through a basin
from inlet to outlet.
flow rate — The rate at which a substance is passed through a system.
flow regulator — A structure installed in a canal, conduit, or channel
to control the flow of water or wastewater at intake or to control the
water level in a canal, channel, or treatment unit.
flume — (l) An open conduit of wood, masonry, or metal constructed on a
grade and sometimes elevated. Sometimes called aqueduct. (2) A
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ravine or gorge with a stream running through it. (3) To transport in
a flume, as logs.
foam — (l) A collection of minute bubbles formed on the surface of a
liquid by agitation, fermentation, etc. (2) The frothy substance com-
posed of an aggregation of bubbles on the surface of liquids by vio-
lent agitation or by the admission of air bubbles to liquid containing
surface-active materials, solid particles, or both.
foam separation — The planned frothing of waste-water or wastewater ef-
fluent as a means of removing excessive amounts of detergent materials,
through the introduction of air in the form of fine bubbles. Also
called form fractionation.
food-to-microorganism ratio — An aeration tank loading parameter.
gravity filter — A rapid sand filter of the open type, the operating
level of which is placed near the hydraulic grade line of the influent
and through which the water flows by gravity.
grease — In wastewater, a group of substances including fats, waxes,
free fatty acids, calcium and magnesium soaps, mineral oils, and
certain other nonfatty materials. The type of solvent and method used
for extraction should be stated for quantitation.
grinding — A process for solid waste handling and disposal by which
refuse is reduced to less than 2 in. by a shredder. Also called
shredding.
grit — The heavy suspended mineral matter present in water or waste-
water, such as sand, gravel, cinders.
grit chamber — A detention chamber or an enlargement of a sewer de-
signed to reduce the velocity of flow of the liquid to permit the
separation of mineral from organic solids by differential
s e diment at i on.
grit collector — A device placed in a grit chamber to convey deposited
grit to a point of collection.
groundwater — Subsurface water occupying the saturation zone, from
which wells and springs are fed. In a strict sense the term applies
only to water below the water table. Also called phreatic water,
plerotic water.
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gutter — An artifically surfaced, and generally shallow, waterway pro-
vided at the margin of a roadway for surface drainage.
halogen — Any one of the chemically related elements—fluorine, chlo-
rine, "bromine, iodine, and astatine.
hardness — A characteristic of water, imparted by salts of calcium,
magnesium, and iron such as bicarbonates, carbonates, sulfates,
chlorides, and nitrates, that causes curdling of soap and increased
consumption of soap, deposition of scale in boilers, damage in some
industrial processes, and sometimes objectionable taste. See
carbonate hardness.
head loss — The loss in liquid pressure resulting from the passage of
the solution through a pipe, a channel, or a treatment unit.
heavy metals — Metals that can be precipitated by hydrogen sulfide in
acid solution, for example, lead, silver, gold, mercury, bismuth,
copper.
high-rate digestion — Accelerated anaerobic digestion resulting pri-
marily from thorough mixing of digester contents. May be enhanced by
thermophilic digestion.
high-rate filter — A trickling filter operated at a high average daily
dosing rate, usually between 10 and hd mgd/acre including any recir-
culation of effluent.
horizontal-flow tank — A tank or basin, with or without baffles, in
which the direction of flow is horizontal.
humus sludge — (l) Sludge deposited in final or secondary settling
tanks following trickling filters or contact beds. (2) Sludge re-
sembling humus in appearance.
hydraulic loading — The flow (volume per unit time) applied to the sur-
face area of the clarification or biological reactor units (where
applicable).
hydraulic loss — The loss of head attributable to obstructions, fric-
tion, changes in velocity, and changes in the form of the conduit.
hydraulic radius — The right cross-sectional area of a stream of water
divided by the length of that part of its periphery in contact with
Glossary 23
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its containing conduit; the ratio of area to wetted perimeter. Also
called hydraulic mean depth.
hydraulic surface loading influent — (l) The flow (volume per unit
time) applied to a unit of surface area (square ft), applicable to
trickling filter and filtration processes. (2) Wastewater or other
liquid—raw or partially treated—flowing into a reservoir, basin,
treatment process, or treatment plant.
impeller — A rotating set of vanes designed to impel rotation of a mass
of fluid.
impervious — Not allowing, or allowing only with great difficulty, the
movement of water; impermeable.
incineration — Burning sludge to remove the water and reduce the re-
maining residues to a safe, nonburnable ash. The ash can then be
disposed of safely on land, in some waters, or into caves or other
underground locations.
industrial wastes — The liquid wastes from industrial processes, as
distinct from domestic or sanitary wastes.
industrial wastewater — Wastewater in which industrial wastes pre-
dominate. See domestic wastewater, industrial wastes.
infiltrate — (l) To filter into. (2) The penetration by a liquid or
gas of the pores or interstices.
infiltration — (l) The flow or movement of water through the inter-
stices or pores of a soil or other porous medium. (2) The quantity
of groundwater that leaks into a pipe through joints, porous walls,
or breaks. (3) The entrance of water from the ground into a gal-
lery. (10 The absorption of liquid by the soil, either as it falls
as precipitation or from a stream flowing over the surface. See
percolation.
influent — Water, wastewater, or other liquid flowing into a reservoir,
basin, or treatment plant, or any unit thereof.
inhibitory toxicity — Any demonstrable inhibitory action of a substance
on the rate of general metabolism (including rate of reproduction) of
living organisms.
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inorganic matter — Chemical substances of mineral origin, or more cor-
rectly, not of "basically carbon structure.
intake — (l) The works or structures at the head of a conduit into
which water is diverted. (2) The process or operation by which water
is absorbed into the ground and added to the saturation zone.
interface — (l) A stratum of water of varying thickness lying between
the fresh water above and ocean water below in certain estuaries.
(2) A boundary layer between two fluids such as liquid-liquid or
liquid-gas.
intermediate screen — A screen, with openings from 0.25 to 1.5 in.,
which prepares the waste flow for passage through grit chambers, pri-
mary sedimentation tanks, and reciprocating pumps.
intermediate treatment — Wastewater-treatment such as aeration or
chemical treatment, supplementary to primary treatment.
ion — (l) A charged atom, molecule, or radical, the migration of which
affects the transport of electricity through an electrolyte or, to a
certain extent through a gas. (2) An atom or molecule that has lost
or gained one or more electrons. By such ionization it becomes electri-
cally charged. An example is the alpha particle.
ion exchange — (l) A chemical process involving reversible interchange
of ions between a liquid and a solid but no radical change in struc-
ture of the solid. (2) A chemical process in which ions from two
different molecules are exchanged.
ion-exchange treatment — The use of ion-exchange materials such as
resin or zeolites to remove undesirable ions from a liquid and sub-
stitute acceptable ions.
irrigation — The artificial application of water to lands to meet the
water needs of growing plants not met by rainfall.
isotherm — A line drawn through all points having the same temperature.
kinematic viscosity — Ratio of absolute viscosity, expressed in poises
(grams per centimeter second), to the density, in grams per cubic
centimeter, at room temperature.
lagoon — A pond containing raw or partially treated wastewater in which
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aerobic or anaerobic stabilization occurs.
land disposal — Disposal of waste-water onto land.
lime — Any of a family of chemicals consisting essentially of calcium
hydroxide made from limestone (calcite) which is composed almost
wholly of calcium carbonate or a mixture of calcium and magnesium
carbonate.
liquid — A substance that flows freely. Characterized by free movement
of the constituent molecules among themselves, but without the ten-
dency to separate from one another characteristic of gases. Liquid
and fluid are often used synonymously, but fluid has the broader sig-
nificance, including both liquids and gases.
liquid sludge — Sludge containing sufficient water (ordinarily more
than 85 percent) to permit flow by gravity or pumping.
liquor — Water, wastewater, or any combination; commonly used to desig-
nate liquid phase when other phases are present.
load -- See following terms modifying load: BOD, peak, pollutional.
loading — The time rate at which material is applied to a treatment de-
vice involving length, area, or volume, or other design factor.
mechanical aeration — (l) The mixing, by mechanical means, of wastewater
and activated sludge in the aeration tank of the activated sludge
process to bring fresh surfaces of liquid into contact with the atmo-
sphere. (2) The introduction of atmospheric oxygen into a liquid by
the mechanical action of paddle, paddle wheel, spray, or turbine
mechanisms.
mechanical aerator — A mechanical device for the introduction of atmo-
spheric oxygen into a liquid. See mechanical aeration.
mechanical agitation — The introduction of atmospheric oxygen into a
liquid by the mechanical action of paddle, paddle wheel, spray, or
turbine mechanisms. Also see mechanical aeration.
mechanically cleaned screen — A screen equipped with mechanical clean-
ing apparatus for removal of retained solids.
membrane filtration — A method of quantitative or qualitative analysis
of bacterial or particulate matter in a water sample by filtration
Glossary 26
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through a membrane capable of retaining bacteria.
mesh screen — A screen composed of woven fabric of any of various
materials.
methane fermentation — Fermentation resulting in conversion of organic
matter into methane gas.
microbial activity — Chemical changes resulting from the metabolism of
living organisms. Biochemical action.
microbial film — A gelatinous film of microbial growth attached to or
spanning the interstices of a support medium. Also called biological
slime.
microbiology — Study of very small units of living matter and their
processes.
micron — Unit of length: 10 meters; 39 x 10 j_n.
microorganism — Minute organism, either plant or animal, invisible or
barely visible to the naked eye.
milligrams per liter — A unit of the concentration of water or waste-
water constituent. It is 0.001 g of the constituent in 1,000 ml of
water. It has replaced the unit formerly used commonly, parts per
million, to which it is approximately equivalent, in reporting the
results of water and wastewater analysis.
minimum flow — The flow occurring in a stream during the driest period
of the year. Also called low flow.
mixed liquor — A mixture of activated sludge and organic matter under-
going activated sludge treatment in the aeration tank.
mixed-liquor volatile suspended solids (MLVSS) — The concentration of
volatile suspended solids in an aeration basin. It is commonly as-
sumed to equal the biological solids concentration in the basin.
mixing basin — (l) A basin or tank wherein agitation is applied to wa-
ter, wastewater, or sludge to increase the dispersion rate of applied
chemicals. (2) A tank used for general mixing purposes.
mixing tank — A tank designed to provide a thorough mixing of chemicals
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introduced into liquids or of two or more liquids of different
characteristics.
modified aeration — A modification of the activated sludge process in
which a shortened period of aeration is used with a reduced quantity
of suspended solids in the mixed liquor.
moisture — Condensed or diffused liquid, especially water.
moisture content — The quantity of water present in soil, wastewater
sludge, industrial waste sludge, and screenings, usually expressed in
percentage of wet weight.
municipal waste — The combined residential and commercial waste mate-
rials generated in a given municipal area.
natural water — Water as it occurs in its natural state, usually con-
taining other solid, liquid, or gaseous materials in solution or
suspension.
neutralization — Reaction of acid or alkali with the opposite reagent
until the concentrations of hydrogen and hydroxyl ions in the solution
are approximately equal.
nitrification — (l) The conversion of nitrogenous matter into nitrates
"by "bacteria. (2) The treatment of a material with nitric acid.
Nitrosomonas — A genus of bacteria that oxidize ammonia to nitrite.
nonbiodegradable — Incapable of being broken down into innocuous prod-
ucts by the actions of living beings (especially microorganisms).
nonpotable water — Water which is unsatisfactory for consumption.
nonsettleable matter — That suspended matter which does not settle nor
float to the surface of water in a period of 1 hr.
nonsettleable solids — Wastewater matter that will stay in suspension
for an extended period of time. Such period may be arbitrarily taken
for testing purposes as 1 hr. See suspended solids.
nutrient — (l) Any substance assimilated by organisms which promotes
growth and replacement of cellular constituents. (2) A chemical sub-
stance (an element or an inorganic compound, e.g., nitrogen or phos-
phate) absorbed by a green plant and used in organic synthesis.
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odor control — (l) In water treatment, the elimination or reduction of
odors in a water supply by aeration, algae elimination, superchlorina-
tion, activated carbon treatment, and other methods. (2) In waste-
water treatment, the prevention or reduction of objectionable odors by
chlorination, aeration, or other processes or by masking with chemical
aerosols.
organic loading — Pounds of BOD applied per day to a biological reactor.
organic matter — Chemical substances of animal or vegetable origin, or
more correctly, of basically carbon structure, comprising compounds
consisting of hydrocarbons and their derivatives.
organic-matter degradation — The conversion of organic matter to inor-
ganic forms by biological action.
orthophosphate — An acid or salt containing phosphorus as PO,.
overflow — (l) The excess water that overflows the ordinary limits such
as the streambanks, the spillway crest, or the ordinary level of a
container. (2) To cover or inundate with water or other fluid.
overflow rate — One of the criteria for the design of settling tanks in
treatment plants; expressed in gallons per day per square foot of sur-
face area in the settling tank.
overland runoff — Water flowing over the land surface before it reaches
a definite stream channel or body of water.
oxidation — The addition of oxygen to a compound. More generally, any
reaction which involves the loss of electrons from an atom.
oxidation pond — A basin used for retention of wastewater before final
disposal, in which biological oxidation of organic material is ef-
fected by natural or artificially accelerated transfer of oxygen to
the water from air.
oxidation process — Any method of wastewater treatment for the oxi-
dation of the putrescible organic matter. The usual methods are
biological filtration and the activated sludge process.
oxidation rate — The rate at which the organic matter in wastewater is
stabilized.
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oxidized sludge — The liquid and solid product of the wet air oxidation
of wastewater sludge.
oxidized waste-water — Wastewater in which the organic matter has been
stabilized.
oxygen demand — (l) The quantity of oxygen utilized in the biochemical
oxidation of organic matter in a specified time, at a specified tem-
perature, and under specified conditions. See BOD.
oxygen saturation — The maximum quantity of dissolved oxygen that
liquid of given chemical characteristics, in equilibrium with the
atmosphere, can contain at a given temperature and pressure.
ozone — Oxygen in molecular form with three atoms of oxygen forming
each molecule (0 ).
Parshall flume — A calibrated device developed by Parshall for meas-
uring the flow of liquid in an open conduit. It consists essentially
of a contracting length, a throat, and an expanding length. At the
throat is a sill over which the flow passes at Belanger's critical
depth. The upper and lower heads are each measured at a definite
distance from the sill. The lower head need not be measured unless
the sill is submerged more than about 67 percent.
particle — Any dispersed matter, solid or liquid, in which the indi-
vidual aggregates are larger than single small molecules (about
0.0002 mm in diameter), but smaller than about 500 um in diameter.
particle size — (l) An expression for the size of liquid or solid
particles expressed as the average or equivalent diameter. (2) The
sizes of the two screens, either in the U.S. Sieve Series or the Tyler
Series between which the bulk of a carbon sample falls, e.g., 8 x 30
means most of the carbon passes a No. 8 screen but is retained on a
Wo. 30 screen.
parts per million — The number of weight or volume units of a minor
constituent present with each one million units of the major con-
stituent of a solution or mixture. Formerly used to express the
results of most water and wastewater analyses, but more recently
replaced by the ratio milligrams per liter.
pathogens — Pathogenic or disease-producing organisms.
peak demand — The maximum momentary load placed on a water or wastewater
•
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plant or pumping station or on an electric generating plant or
system. This is usually the maximum average load in 1 hr or less,
but may be specified as instantaneous or with some other short time
period.
peak load — (l) The maximum average load carried by an electric gener-
ating plant or system for a short time period such as 1 hr or less.
See peak. (2) The maximum demand for water placed on a pumping
station, treatment plant, or distribution system, expressed as a rate.
(3) The maximum rate of flow of wastewater to a pumping station or
treatment plant. Also called peak demand.
percolating filter — A type of trickling filter.
percolation — (l) The flow or trickling of a liquid downward through a
contact or filtering medium. The liquid may or may not fill the pores
of the medium. Also called filtration. (2) The movement or flow of
water through the interstices or the pores of a soil or other porous
medium.
pH — The reciprocal of the logarithm of the hydrogen-ion concentration.
The concentration is the weight of hydrogen ions, in grams, per liter
of solution. Neutral water, for example, has a pH value of 7 and a
hydrogen-ion concentration of 10~7.
phosphate — A salt or ester of phosphoric acid.
pipe gallery — (l) Any conduit for pipe, usually of a size to allow a
man to walk through. (2) A gallery provided in a treatment plant for
the installation of the conduits and valves and for a passageway to
provide access to them.
pit privy — A privy placed directly over an excavation in the ground.
pollution — A condition created by the presence of harmful or object-
ionable material in water.
pollutional load — (l) The quantity of material in a waste stream that
requires treatment or exerts an adverse effect on the receiving system.
(2) The quantity of material carried in a body of water that exerts a
detrimental effect on some subsequent use of that water.
polyelectrolytes — Long-chained, ionic, high molecular weight,
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synthetic, water soluble, organic coagulants. Also referred to as
polymers.
polymers — Long-chained, high molecular weight, synthetic, water sol-
uble, organic coagulants. Polymers can "be classified as nonionic,
cationic, and anionic.
porous — Having small passages; permeable by fluids.
postchlorination — The application of chlorine to water or wastewater
subsequent to any treatment, including prechlorination.
potable water — Water that does not contain objectional pollution, con-
tamination, minerals, or infective agents and is considered satis-
factory for domestic consumption.
preaeration — A preparatory treatment of wastewater consisting of aera-
tion to reirove gases, add oxygen, promote flotation of grease, and aid
coagulation.
prechlorination — The application of chlorine to water or wastewater
prior to any treatment.
precipitation — (l) The total measurable supply of water received
directly from clouds as rain, snow, hail, or sleet; usually expressed
as depth in a day, month, or year, and designated as daily, monthly,
or annual precipitation. (2) The process by which atmospheric mois-
ture is discharged onto a land or water surface. (3) The phenomenon
that occurs when a substance held in solution in a liquid passes out
of solution into solid form.
preliminary filter — A filter used in a water treatment plant for the
partial removal of turbidity before final filtration. Such filters
are usually of the rapid type, and their use allows final filtration
at a more rapid rate or reduces or removes the necessity of other
preliminary treatment of the water. Also called contact filter, con-
tact roughing filte-r, roughing filter.
preliminary treatment — (l) The conditioning of a waste at its source
before discharge, to remove or to neutralize substances injurious to
sewers and treatment processes or to effect a partial reduction in
load on the treatment process. (2) In the treatment process, unit
operations, such as screening and comminution, that prepare the liquor
for subsequent major operations.
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presettling — The process of sedimentation applied to a liquid before
subsequent treatment.
pressure regulator — A device for controlling pressure in a pipeline
or pressurized tank, such as a pressure-regulating valve or a pump
drive-speed controller.
primary settling tank — The first settling tank for the removal of
settleable soils through which wastewater is passed in a treatment
works.
primary sludge — Sludge obtained from a primary settling tank.
primary treatment — (l) The first major (sometimes the only) treatment
in a wastewater treatment works, usually sedimentation. (2) The
removal of a substantial amount of suspended matter but little or no
colloidal and dissolved matter.
privy — A building, either portable or fixed directly to a pit or
vault, equipped with seating and used for excretion of bodily wastes.
privy vault — A concrete or masonry vault that is provided with a
cleanout opening and over which is placed a privy building containing
seats.
proportional weir — A special type of weir in which the discharge
through the weir is directly proportional to the head.
public water supply — A water supply from which water is available to
the people at large or to any considerable number of members of the
public indiscriminately.
pumping station — A station housing relatively large pumps and their
accessories. Pump house is the usual term for shelters for small
water pumps.
purification — The removal of objectionable matter from water by
natural or artificial methods.
putrefaction — Biological decomposition of organic matter with the
production of ill-smelling products associated with anaerobic
conditions.
radiation — The emission and propagation of energy through space or
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through a material medium; also, the energy so propagated.
rakings — The screenings or trash removed from bar screens cleaned man-
ually or by mechanical rakes.
rapid filter — A rapid sand filter or pressure filter.
rapid sand filter — A filter for the purification of water, in which
water that has been previously treated, usually by coagulation and
sedimentation, is passed downward through a filtering medium. The
medium consists of a layer of sand, prepared anthracite coal, or other
suitable material, usually 2^-30 in. thick, resting on a supporting
bed of gravel or a porous medium such as carborundum. It is char-
acterized by a rapid rate of filtration, commonly from two to three
gallons per minute per square foot of filter area.
raw sludge — Settled sludge promptly removed from sedimentation tanks
before decomposition has much advanced. Frequently referred to as
undigested sludge.
raw wastewater — Wastewater before it receives any treatment.
receiving body of water — A natural watercourse, lake, or ocean into
which treated or untreated wastewater is discharged.
recycling — An operation in which a substance is passed through the
same series of processes, pipes, or vessels more than once.
regeneration — (l) In ion exchange, the process of restoring an ion-
exchange material to the state employed for adsorption. (2) The
periodic restoration of exchange capacity of ion-exchange media used
in water treatment.
regeneration efficiency — In ion exchange, regeneration level divided
by breakthrough capacity.
resinous anion exchangers — Organic polymers consisting of amines and
quaternary ammonium compounds. They may be regenerated by any
caustic.
resinous cation exchangers — Synthetic organic polymers generally of
the sulfonated polystyrene type produced in a granular or beadlike
form and in an effective size and uniformity coefficient comparable
to that specified for filter sand.
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retention — That part of the precipitation falling on a drainage area
which does not escape as surface streamflow, during a given period,
It is the difference between total precipitation and total runoff
during the period, and represents evaporation, transpiration, sub-
surface leakage, infiltration, and, when short periods are consid-
ered, temporary surface or underground storage on the area.
returned sludge — Settled activated sludge returned to mix with in-
coming raw or primary settled wastewater.
Reynolds' number — A numerical quantity used to characterize the type
of flow in a hydraulic structure where resistance to motion depends
on the viscosity of the liquid in conjunction with the resisting force
of inertia. It is equal to the ratio of inertia forces to viscous
forces. It is equal to the product of a characteristic velocity of
the system (it may be the mean, surface, or maximum velocity) and a
characteristic linear dimension, such as diameter or depth, divided
by the kinematic viscosity of the liquid; all expressed in consistent
units in order that the combinations will be dimensionless. The
number is chiefly applicable to closed systems of flow, such as pipes
or conduits where there is no free water surface, or to bodies fully
immersed in the fluid so the free surface need not be considered.
rotary distributor — A movable distributor made up of horizontal arms
that extend to the edge of the circular trickling filter bed, revolve
about a central post, and distribute liquid over the bed through
orifices in the arms. The jet action of the discharging liquid nor-
mally supplies the motive power.
rotary dryer — A long steel cylinder, slowly revolving, with its long
axis slightly inclined; through which passes the material to be dried
in hot air. The material passes through from inlet to outlet, tum-
bling about.
runoff — (l) That portion of the earth's available water supply that
is transmitted through natural surface channels. (2) Total quantity
of runoff water during a specified time. (3) In the general sense,
that portion of the precipitation which is not absorbed by the deep
strata, but finds its way into the streams after meeting the per-
sistent demands of evapotranspiration, including interception and
other losses. (h) The discharge of water in surface streams, usu-
ally expressed in inches depth on the drainage area, or as volume
in such terms as cubic feet or acre-feet. (5) That part of the
precipitation which runs off the surface of a drainage area and
reaches a stream or other body of water or a drain or sewer.
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sand filter — A filter in which sand is used as a filtering medium.
Also see rapid sand filter, slow sand filter.
scale — An accumulation of solid material precipitated out of
waters containing certain mineral salts in solution and formed on
interior surfaces, such as those of pipelines, tanks, "boilers, under
certain physical conditions. May also "be formed from interaction of
water with metallic pipe.
screen — A device with openings, generally of uniform size, used
to retain or remove suspended or floating solids in flowing water or
wastewater and to prevent them from entering an intake or passing a
given point in a conduit. The screening element may consist of
parallel bars, rods, wires, grating, wire mesh, or perforated plate,
and the openings may be of any shape, although they are usually cir-
cular or rectangular.
screening — The removal of relatively coarse floating and suspended
solids by straining through racks or screens.
screenings — Material removed from liquids by screens.
screenings dewatering — The removal of a large part of the water con-
tent of waste screenings by draining or by mechanical means.
screenings grinder — A device for grinding, shredding, or macerating
material removed from wastewater by screens.
screenings shredder — A device that disintegrates screenings.
screw-feed pump — A pump with either horizontal or vertical cylindri-
cal casing, in which operates a runner with radial blades like those
of a ship's propeller.
scum — (l) The layer or film of extraneous or foreign matter that rises
to the surface of a liquid and is formed there. (2) A residue de-
posited on a container or channel at the water surface. (3) A mass
of solid matter that floats on the surface.
secondary settling tank — A tank through which effluent from some
prior treatment process flows for the purpose of removing settleable
solids. See sedimentation tank.
secondary wastewater treatment — The treatment of wastewater by bio-
logical methods after primary treatment by sedimentation.
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sedimentation — The process of subsidence and deposition of sus-
pended matter carried by water, waste-water, or other liquids, by
gravity. It is usually accomplished by reducing the velocity of the
liquid below the point at which it can transport the suspended ma-
terial. Also called settling. See chemical precipitation.
sedimentation basin — A basin or tank in which water or wastewater con-
taining settleable solids is retained to remove by gravity a part of
the suspended matter. Also called sedimentation tank, settling basin,
settling tank.
sedimentation tank — A basin or tank in which water or wastewater con-
taining settleable solids is retained to remove by gravity a part of
the suspended matter. Also called sedimentation basin, settling
basin, settling tank.
septicity — A condition produced by growth of anaerobic organisms.
septicization -- In anaerobic decomposition, the process whereby in-
tensive growths of bacteria with the enzymes secreted by them liquify
and gasify solid organic matter.
septic sludge — Sludge from a septic tank or partially digested sludge
from an Imhoff tank or sludge-digestion tank.
septic tank — A settling tank in which settled sludge is in immediate
contact with the wastewater flowing through the tank and the organic
solids are decomposed by anaerobic bacterial action.
septic wastewater — Wastewater undergoing putrefaction under anaerobic
conditions.
settleability test — A determination of the settleability of solids in
a suspension by measuring the volume of solids settled out of a
measured volume of sample in a specified interval of time, usually
reported in milliliters per liter. Sometimes identified as the Imhoff
cone test.
settleable solids — (l) That matter in wastewater which will not stay
in suspension during a preselected settling period, such as 1 hr,
but either settles to the bottom or floats to the top. (2) In the
Imhoff cone test, the volume of matter that settles to the bottom of
the cone in 1 hr.
settled wastewater — Wastewater from which most of the settleable
Glossary 37
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solids have been removed by sedimentation. Also called clarified
wastewater.
settling — The process of subsidence and deposition of suspended matter
carried by water, wastewater, or other liquids, by gravity. It is
usually accomplished by reducing the velocity of the liquid below the
point at which it can transport the suspended material. Also called
sedimentation. See chemical precipitation.
settling basin — A basin or tank in which water or wastewater contain-
ing settleable solids is retained to remove by gravity a part of the
suspended matter. Also called sedimentation basin, sedimentation
tank, settling tank.
settling solids — Solids that are settling in sedimentation tanks or
sedimentation chambers and other such tanks that are constructed for
the purpose of removing this fraction of suspended solids. See
settleable s_olids.
settling tank -- A basin or bank in which water or wastewater containing
settleable solids is retained to remove by gravity a part of the sus-
pended matter. Also called sedimentation basin, sedimentation tank,
settling basin.
settling velocity — The velocity at which subsidence and deposition of
the settleable suspended solids in water and wastewater will occur.
sewage — The spent water of a community. Term now being replaced in
technical usage by preferable term wastewater.. See wastewater.
sewer — A pipe or conduit that carries wastewater or drainage water.
sewer gas — Gas evolved in sewers that results from the decomposi-
tion of the organic matter in the wastewater.
sharp-crested weir — A weir having a crest, usually consisting of a
thin plate (generally of metal), so sharp that'the water in passing
over it touches only a line.
short-circuiting — A hydraulic condition occurring in parts of a tank
where the time of travel is less than the flowing-through time.
shredder — A device for size reduction.
shredding — A process for the treatment and handling of solid wastes.
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The refuse is reduced to particles having no greater dimension than
2 in. "by a shredder. Also called grinding.
side water depth — The depth of water measured along a vertical ex-
terior wall.
skimming — The process of removing floating grease or scum from the
surface of wastewater in a tank.
skimmings — Grease, solids, liquids, and scum skimmed from wastewater
settling tanks.
skimming tank — A tank so designed that floating matter will rise arid
remain on the surface of the wastewater until removed, while the liq-
uid discharges continuously under curtain walls or scum "boards.
slimes — Substances of viscous organic nature, usually formed from
microbiological growth.
slow sand filter — A filter for the purification of water in which
water without previous treatment is passed downward through a filter-
ing medium consisting of a layer of sand or other suitable material,
usually finer than for a rapid sand filter and from 2h to hO in.
thick. It is characterized by a slow rate of filtration, commonly
3-6 mgd/acre of filter area.
sludge — (l) The accumulated solids separated from liquids, such as
water or wastewater, during processing, or deposits on bottoms of
streams or other bodies of water. (2) The precipitate resulting from
chemical treatment, coagulation, or sedimentation of water or
wastewater.
sludge bed — An area comprising natural or artificial layers of porous
material on which digested wastewater sludge is dried by drainage and
evaporation. A sludge bed may be open to the atmosphere or covered,
usually with a greenhouse-type superstructure. Also called sludge
drying bed.
sludge blanket — Accumulation of sludge hydrodynamically suspended
within an enclosed body of water or wastewater.
sludge cake — The sludge that has been dewatered by a treatment process
to a moisture content of 60-85 percent, depending on type of sludge
and manner of treatment.
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sludge circulation — The overturning of sludge in sludge-digestion
tanks by mechanical or hydraulic means or by use of gas recirculation
to disperse scum layers and to promote digestion.
sludge collector — A mechanical device for scraping the sludge on the
bottom of a settling tank to a sump from which it can be drawn.
sludge concentration — Any process of reducing the water content of
sludge that leaves the sludge in a fluid condition.
sludge conditioning — Treatment of liquid sludge before dewatering to
facilitate dewatering and enhance drainability, usually by the addi-
tion of chemicals.
sludge density index — The reciprocal of the sludge volume index multi-
plied by 100.
sludge dewatering — The process of removing a part of the water in
sludge by any method such as draining, evaporation, pressing, vacuum
filtration, centrifuging, exhausting, passing between rollers, acid
flotation, or dissolved-air flotation with or without heat. It in-
volves reducing from a liquid to a spadable condition rather than
merely changing the density of the liquid (concentration) on the one
hand or drying (as in a kiln) on the other.
sludge digestion — The process by which organic or volatile matter in
sludge is gasified, liquified, mineralized, or converted into more
stable organic matter through the activities of either anaerobic or
aerobic organisms.
sludge-digestion gas — Gas resulting from the decomposition of organic
matter in sludge removed from wastewater and placed in a tank to
decompose under anaerobic conditions. Also see sewage gas, sludge
digestion.
sludge-digestion tank — A tank in which sludge is placed for the pur-
pose of permitting digestion to occur. See sludge digestion.
sludge dryer — A device for removal of a large percentage of moisture
from sludge or screenings by heat.
sludge drying — The process of removing a large percentage of moisture
from sludge by drainage or evaporation by any method.
sludge filter — A device in which wet sludge, usually conditioned by
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a coagulant, is partly dewatered by vacuum or pressure.
sludge foaming — An increase in the gas in sludge in Imhoff and sepa-
rate digestion tanks, causing large quantities of froth, scum, and
sludge to rise and overflow from openings at or near the top of the
tanks.
sludge lagoon — A basin used for the storage, digestion, or dewatering
of sludge.
sludge reaeration — The continuous aeration of sludge after its ini-
tial aeration for the purpose of improving or maintaining its
condition.
sludge reduction — The reduction in quantity and change in character
of sludge as the result of digestion.
sludge solids — Dissolved and suspended solids in sludge.
sludge thickener — A tank or other equipment designed to concentrate
wastewater sludges.
sludge thickening — The increase in solids concentration of sludge in
a sedimentation or digestion tank. See sludge concentration.
sludge treatment — The processing of wastewater sludges to render them
innocuous. This may be done by aerobic or anaerobic digestion fol-
lowed by drying on sand beds, filtering, and incineration, filtering
and drying, or wet air oxidation.
sludge utilization — The use of wastewater sludges as soil builders
and fertilizer admixtures. Sludges produced by aerobic and anaerobic
digestion and activated sludge are used for these purposes.
sludge volume index (SVI) — The ratio of the volume in milliliters of
sludge settled from a 1,000-ml sample in 30 min to the concentration
of mixed liquor in milligrams per liter multiplied by 1,000.
slurry — A thin watery mud, or any substance resembling it, such as
a lime slurry.
sodium carbonate — A salt used in water treatment to increase the
alkalinity or pH value of water or to neutralize acidity. Chemical
symbol is Na -CO . Also called soda ash.
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solids-retention time — The average residence time of suspended soils
in a biological waste treatment system, equal to the total weight of
suspended solids in the system divided "by the total weight of sus-
pended solids leaving the system per unit of time (usually per
day).
specific gravity — The ratio of the mass of a body to the mass of an
equal volume of water.
specific resistance — A sludge filterability index, generally ex-
pressed as sec^/g.
spiral air-flow diffusion — A method of diffusing air in an aeration
tank of the activated sludge process where, by means of properly de-
signed baffles and the proper location of diffusers, a spiral or heli-
cal movement is given to the air and the tank liquor.
spiral-flow aeration — A method of diffusing air in an aeration tank
of the activated sludge process, See spiral air-flow diffusion.
spiral-flow tank — An aeration tank or channel in which a spiral or
helicoidal motion is given to the liquid in its flow through the tank
by the introduction of air through a line of diffusers placed en one
side of the bottom of each channel, by longitudinally revolving pad-
dles, or by other means.
spray irrigation — A method for disposing of some organic wastewaters
by spraying them on land, usually from pipes equipped with spray
nozzles. This has proved to be an effective way to dispose of wastes
from the canning, meat-packing, and sulfite-pulp industries where
suitable land is available.
stabilization — (l) Maintenance at a relatively nonfluctuating level,
quantity, flow, or condition. (2) In lime-soda water softening, any
process that will minimize or eliminate scale-forming tendencies.
(3) In waste treatment, a process used to equalize wastewater flow
composition prior to regulated discharge.
stabilization lagoon — A shallow pond for storage of wastewater before
discharge. Such lagoons may serve only to detain and equalize waste-
water composition before regulated discharge to a stream, but often
they are used for biological oxidation. See stabilization pond.
stabilization pond — A type of oxidation pond in which biological
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oxidation of organic matter is affected by natural or artificially ac-
celerated transfer of oxygen to the vater from air.
step aeration — A procedure for adding increments of settled -waste-
water along the line of flow in the aeration tanks of an acti-
vated sludge plant.
sterilization — The destruction of all living microorganisms, as patho-
genic or saprophytic bacteria, vegetative forms, and spores.
sterilized wastewater — An effluent from a wastewater treatment plant
in which all microorganisms have been destroyed by sterilization.
subsoil — That portion of a normal soil profile underlying the surface.
In humid climates it is lower in content of organic matter, lighter
in color, usually of finer particles, of denser, structure, and of
lower fertility than the surface soil. Its depth and physical prop-
erties control to a considerable degree the movement of soil mois-
ture. In arid climates there is less difference between surface and
subsoil.
sump — (l) A tank or pit that receives drainage and stores it tempo-
rarily, and from which the drainage is pumped or ejected. (2) A
tank or pit that receives liquids,
supernatant — The liquid standing above a sediment or precipitate,
surface evaporation — Evaporation from the surface of a body of water,
moist soil, snow, or ice. Also see evapotranspiration.
sui-face wash — (l) A supplementary method of washing the filtering
medium of a rapid sand filter by applying water under pressure at or
near the surface of the sand by means of a system of stationary or
rotating jets. (2) The surface runoff draining into a ditch or drain.
suspended solids — Solids that either float on the surface of, or
are in suspension in, water, wastewater, or other liquids, and which
are largely removable by laboratory filtering.
tank — Any artificial receptacle through which liquids pass or in
which they are held in reserve or detained for any purpose.
temperature — (l) The thermal state of a substance with respect to its
ability to communicate heat to its environment. (2) The measure of
the thermal state on some arbitrarily chosen numerical scale.
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tertiary treatment — A method used to refine the effluents from sec-
ondary treatment systems or otherwise increase the removal of
pollutants.
thickened sludge — A sludge concentrated to a higher solids content by
gentle mixing, gravimetric settling, centrifugation, or air flotation.
thickener, sludge — A type of sedimentation tank in which sludge is
permitted to settle, usually equipped with scrapers traveling along
or around the bottom of the tank to push the settled sludge to a
sump.
thickening tank — A sedimentation tank for concentrated suspensions.
total Kjeldahl nitrogen — The sum of free ammonia and of organic com-
pounds which are converted to (NH, ) SO, under the conditions of
digestion.
total organic carbon (TOG) — A measure of the amount of organic mate-
rial in a water sample expressed in milligrams of carbon per liter of
solution.
toxin — Poisonous compounds produced by the metabolic activity or
death and disintegration of microorganisms.
trash — Floating debris that may be removed from reservoirs, combined
sewers, and storm-water sewers by coarse racks.
trash rack — A grid or screen placed across a waterway to catch float-
ing debris.
trash screen — A screen installed or constructed in a waterway to col-
lect and prevent the passage of trash.
treated sewage — Wastewater that has received partial or complete
treatment .
treatment — See following terms modifying treatment : anaerobic waste ,
biological wastewater, chemical, intermediate, ion-exchange , prelim-
inary , primary , secondary wastewater, sludge , waste, wastewater , water.
trickling filter — A treatment unit consisting of a material such as
broken stone, clinkers, slate, slats, or brush, over which sewage is
distributed and applied in drops, films, or spray, from troughs,
drippers, moving distributors, or fixed nozzles, and through which
Glossary
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it trickles to the underdrains, giving opportunity for the formation
of zoological slimes which clarify and oxidize the sewage.
trickling filter humus — The sludge removed from clarifiers following
biological stabilization in trickling filter units.
trickling filter ponding — A condition occurring when voids in filter
media become clogged with excessive growth of organisms, preventing
the free flow of the wastewater.
trickling-filter process — In wastewater treatment, a process in which
the liquid from a primary clarifier is distributed on a bed of stones.
As the wastewater trickles through to drains underneath, it comes
in contact with slime on the stones, by which organic material in
the water is oxidized and impurities are reduced.
turbidity — (l) A condition in water or wastewater caused by the pres-
ence of suspended matter, resulting in the scattering and absorption
of light rays. (2) A measure of fine suspended matter in liquids.
(3) An analytical quantity usually reported in arbitrary turbidity
units determined by measurements of light diffraction.
ultraviolet radiation — Light waves shorter than visible blue-violet
waves of the spectrum, having wave lengths of less than 3,900 A.
ultraviolet rays — Those invisible light rays beyond the violet of the
spectrum.
underdrain — A drain that carries away groundwater or the drainage
from prepared beds to which water or wastewater has been applied.
underflow — (l) The movement of water through a given cross section
of permeable rock or earth, possibly under the bed of a stream or a
structure. (2) The flow of water under a structure.
undigested sludge — Settled sludge promptly removed from sedimentation
tanks before decomposition has much advanced. Also called raw sludge.
vacuum filter — A filter consisting of a cylindrical drum mounted on
a horizontal axis, covered with a filter cloth, and revolving with
a partial submergence in liquid. A vacuum is maintained under the
cloth for the larger part of a revolution to extract moisture. The
cake is scraped off continuously.
velocity — See settling velocity.
Glossary 45
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viscosity — The cohesive force existing "between particles of a fluid
which causes the fluid to offer resistance to a relative sliding
motion between particles.
volatile — Capable of being evaporated at relatively low temperatures.
volatile solids — The quantity of solids in water, wastewater, or other
liquids, lost on ignition of the dry solids at 600°C.
wash water — Water used to wash filter beds in a rapid sand filter.
wash-water gutter — A trough or gutter used to carry away the water
that has washed the sand in a rapid sand filter. Also called wash-
water trough.
wash-water rate — The rate at which wash water is applied to a rapid
sand filter during the washing process. Usually expressed as the.
rise of water in the filter in inches per minute or gallons per min-
ute per square foot.
waste — Something that is superfluous or rejected; something that can
no longer be used for its originally intended purpose.
wasted sludge — The portion of settled solids from the final clarifier
that was removed from the wastewater treatment processes and trans-
ferred to the solids handling facilities for ultimate disposal.
waste(s) — See following terms modifying waste(s): industrial,
municipal.
waste treatment — Any process to which wastewater or industrial waste
is subjected to make it suitable for subsequent use.
waste water — In a legal sense, water that is not needed or that has
been used and is permitted to escape, or that unavoidably escapes
from ditches, canals, or other conduits, or reservoirs of the lawful
owners of such structures. See wastewater.
wastewater — The spent water of a community. From the standpoint of
source, it may be a combination of the liquid and water-carried
wastes from residences, commercial buildings, industrial plants, and
institutions, together with any ground-water, surface water, and storm
water that may be present. Also referred to as sewage.
wastewater decomposition — Transformations of organic or inorganic
Glossary h6
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materials contained in waste-water through the action of chemical or
biological processes. Also see decomposition of wastewater.
waste-water disposal — The act of disposing of wastewater by any method
(not synonymous with wastewater treatment). Common methods of disposal
are: dispersion, dilution, broad irrigation, privy, cesspool.
wastewater facilities — The structures, equipment, and processes
required to collect, carry away, and treat domestic and industrial
wastes, and dispose of the effluent.
wastewater lagoon — An impoundment into which wastewater is discharged
at a rate low enough to permit oxidation to occur without substantial
nuisance.
wastewater treatment — Any process to which wastewater is subjected in
order to remove or alter its objectional constituents and thus render
it less offensive or dangerous. See intermediate treatment, primary
treatment.
wastewater treatment works — (l) An arrangement of devices and struc-
tures for treating wastewater, industrial wastes, and sludge. Some-
times used as synonymous with waste treatment plant or wastewater
treatment plant. (2) A water pollution control plant.
water — A transparent, odorless, tasteless liquid, a compound of hydro-
gen and oxygen, H20, freezing at 32°F or 0°C and boiling at 212°F or
100°C, which, in more or less impure state, constitutes rain, oceans,
lakes, rivers, and other such bodies; it contains 11.188 percent
hydrogen and 88.812 percent oxygen, by weight. It may exist as a
solid, liquid, or gas and, as normally found in the lithosphere, hy-
drosphere, and atmosphere, may have other solid, gaseous, or liquid
materials in solution or suspension.
water-borne disease — A disease caused by organisms or toxic substances
carried by water, the most common of which diseases are typhoid fever,
Asiatic cholera, dysentery, and other intestinal disturbances.
water closet — A plumbing fixture, usually a toilet bowl, seat, and
water tank, or valved pressure water connection, for carrying off
excreta and liquid wastes to a drain pipe connected below, by the
agency of flushing water.
water conditioning — Treatments, exclusive of disinfection, intended
Glossary ^7
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to produce a water free of taste, odor, and other undesirable
qualities.
water treatment — The filtration or conditioning of water to render it
acceptable for a specific use.
water treatment plant — That portion of water treatment works intended
specifically for water treatment; may include, among other operations,
sedimentation, chemical coagulation, filtration, and chlorination.
See water treatment works.
water treatment works — A group or assemblage of processes, devices,
and structures used for the treatment or conditioning of water.
weir — (1) A diversion dam. (2) A device that has a crest and some
side containment of known geometric shape, such as a V, trapezoid, or
rectangle, and is used to measure flow of liquid. The liquid surface
is exposed to the atmosphere. Flow is related to upstream height of
water above the crest, to position of crest with respect to down-
stream water surface, and to geometry of the weir opening.
weir loading — In a solids-contact or sedimentation unit, the rate in
gallons per minute per foot of weir length at which clarified or
treated liquid is leaving the unit. Also see overflow rate.
wet well — A compartment in which a liquid is collected, and to which
the suction pipe of a pump is connected.
zooglea — A jelly-like matrix developed by bacteria, associated with
growths in oxidizing beds.
zoogleal matrix — The floe formed primarily by slime-producing bacteria
in the activated sludge process or in biological beds.
Glossary k8
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INDEX
_Faragraph Page
Activated sludge (See Biological unit processes
and Cost data and economic analysis)
Adsorption (See Chemical unit processes and Cost
data and economic analysis)
Aeration (See Biological unit processes and Cost
data and economic analysis)
Ammonia (See Chemical unit processes and Cost
data and economic analysis)
Backwashing (See Filtration and Microscreening)
Biological unit processes:
Activated sludge:
Complete mix:
Background 7-19 7-37
Bibliography 7_26 7-66
Cost data 7-25 7-66
Design parameters 7-21 7-39
Design procedure:
Eckenfelder's approach .... 7-22b 7-48
McKinney's approach 7-22a 7-40
Example calculations
(Eckenf elder) 7-24 7-57
Input data 7-20 7-37
Output data 7-23 7-56
Contact stabilization:
Background 7-51 7-151
Bibliography 7.58 7-168
Cost data 7.57 7-168
Design parameters '7-53 7-153
Design procedure 7-54 7-154
Example calculations 7-56 7-l6l
Input data 7-52 7-151
Output data 7-55 7-l60
Extended aeration:
Background 7-35 7-95
Bibliography 7_l+2 7-125
Cost data 7-4l 7-124
Design parameters 7-37 7-96
Design procedure:
Eckenfelder's approach .... 7-38b 7-105
McKinney's approach 7-38a 7-98
Index 1
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Paragraph Page
Example calculations
(Eckenf elder) 7,-hO 7-115
Input data 7-36 7-95
Output data 7-39 7-llU
Modified or high-rate:
Background 7-^3 7-129
Bibliography 7-50 7-1^7
Cost data 7-^9 7-1^-7
Design parameters 7-^5 7-130
Design procedure (Eckenfelder) . . J-h6 7-131
Example calculations 7-U8 7-lUo
Input data 7-U4 7-129
Output data 7-^7 7-138
Plug flow:
Background 7-10 7-13
Bibliography 7-l8 7-3)1
Cost data 7-17 7-3^
Example calculations 7-l6 7-25
Design parameters 7-13 7-15
Design procedure (Eckenfelder) . . 7-Ik 7-17
Input data 7-12 7-lU
Output data 7-15 7-2^
Pure oxygen:
Background ..... 7-59 7-171
Bibliography 7-66 7-200
Cost data 7-65 7-200
Design parameters 7-6l 7-172
Design procedure:
Eckenfelder's approach .... 7-62b 7-182
McKinney's approach 7-62a 7-17U
Example calculations . 7-6U 7-191
Input data 7-bO 7-171
Output data 7-63 7-190
Step aeration:
Background ..... 7-27 7-69
Bibliography . 7-34 7-90
Cost data 7-33 7-90
Design parameters 7-29 7-71
Design procedure:
Eckenfelder's approach .... 7-30b 7-8l
McKinney's approach ..... 7-30a 7-72
Example calculations 7-32 7-90
Index 2
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Paragraph Page
Input data 7-28 7-69
Output data 7-31 7-89
Digestion:
Aerobic:
Background 7-100 7-278
Bibliography 7-107 7-287
Cost data 7-106 7-287
Design parameters 7-102 7-278
Design procedure 7-103 7-278
Example calculations 7-105 7-283
Input data 7-101 7-278
Introduction 7-99 7-277
Output data 7-104 7-282
Anaerobic:
Background 7-108 7-291
Bibliography 7-115 7-304
Cost data 7-111) 7-304
Design parameters "7-110 7-29^
Design procedure 7-111 7-294
Example calculations 7-113 7-298
Input data 7-109 7-293
Output data 7-112 7-298
Lagoons:
Aearated aerobic:
Background 7-67 7-205
Bibliography 1-lk 7-221
Cost data 7-73 7-221
Design parameters:
Eckenfelder's approach .... 7-69b 7-206
McKinney's approach 7-69a 7-206
Example calculations
(Eckenf elder) 7-72 7-216
Input data 7-68 7-205
Output data 7-71 7-215
Aerated facultative:
Background 7-75 7-223
Bibliography 7-82 7-233
Cost data 7-8l 7-232
Design parameters 7-77 7-223
Design procedure 7-78 7-224
Example calculations 7-80 7-228
Input data 7-76 7-223
Index 3
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Part 1 of 3
29 Sep 78
Paragraph Page
Output data 7-79 7-227
litrification-denitrification:
Background 7-91 7-253
Bibliography 7.98 7-27^
Cost data 7-97 7-271!
Design parameters 7-93 7-255
Design procedure 7-9^ 7-255
Example calculations 7-96 7-267
Input data 7-92 7-25*1
Output data 7-95 7-266
Oxidation ditch:
Background 7-83 7-235
Bibliography 7-90 7-251
Cost data 7-89 7-251
Design parameters 7-85 7-236
Example calculations (Eckenfelder) . . 7-88 7-2^4
Input data 7-84 7-235
Output data 7-87 7-2^3
Stabilization ponds:
Background 7-ll6 7-307
Bibliography 7-123 7-313
Cost data 7-122 7-313
Design parameters 7-118 7-309
Design procedure 7-119 7-309
Example calculations 7-121 7-311
Input data 7-117 7-308
Output data 7-120 7-310
Trickling filters:
Background 7-2 7-3
Bibliography 7-9 7-9
Cost data 7-8 7-9
Design parameters 7-^ 7-5
Design procedures 7-5 7-5
Example calculations 7-7 7-7
Input data ' 7-3 7-3
Output data 7-6 7-7
Centrifugation (See Cost data and economic
analysis and Physical unit processes)
Centrifuge (See Centrifugation)
Chemical coagulation (See Chemical unit
processes and Cost data and economic
analysis)
Index H
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29 Sep 78
Paragraph Page
Chemical unit processes:
Ammonia stripping:
Background 6-l8 6-25
Bibliography 6-25 6-32
Cost data 6-24 6-32
Design parameters 6-20 6-27
Design procedure 6-21 6-27
Example calculations 6-23 6-30
Input data 6-19 6-27
Output data 6-22 6-30
Carbon adsorption:
Background 6-2 6-3
Bibliography 6-9 6-14
Cost data 6-8 6-14
Design parameters 6-4 6-5
Design procedure 6-5 6-5
Example calculations 6-7 6-9
Input data 6-3 6-4
Output data 6-6 6-9
Chemical coagulation:
Background 6-10 6-17
Bibliography 6-17 6-22
Cost data 6-l6 6-22
Design parameters 6-12 6-l8
Design procedure 6-13 6-l8
Example calculations 6-15 6-20
Input data 6-11 6-18
Output data 6-14 6-19
Chlorination:
Background 6-26 6-35
Bibliography 6-33 6-41
Cost data 6-32 6-41
Design parameters 6-28 6-36
Design procedure 6-29 6-36
Example calculations 6-31 6-38
Input data 6-27 6-35
Output data 6-30 6-38
Ion exchange:
Background 6-34 6-43
Bibliography 6-41 6-53
Cost data 6-40 6-53
Design parameters 6-36 6-43
Index 5
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29 Sep 78
Paragraph Page
Design procedure 6-37 6-1*1*
Example calculations 6-39 6-U8
Input data 6-35 6-1*3
Output data 6-38 6-1*7
Neutralization:
Background 6-1*2 6-55
Bibliography 6-57 6-67
Cost data 6-56 6-67
Design parameters 6-52 6-62
Design procedure 6-53 6-62
Example calculations 6-55 6-65
Input data 6-51 6-62
Output data 6-5!* 6-61*
Recarbonaiiion:
Background 6-50 6-6l
Bibliography 6-57 6-67
Cost data 6-56 6-67
Design parameters 6-52 6-62
Design procedure 6-53 6-62
Example calculations 6-55 6-65
Input data 6-51 6-62
Output data 6-5^ 6-61*
Two-stage lime treatment:
Background 6-58 6-69
Bibliography 6-66 6-91
Chemical coagulation 6-59 6-69
Cost data 6-65 6-90
Example calculations 6-61* 6-83
Output data 6-63 6-8l
Primary clarifier 6-60;6-62 6-72;6-78
Recarbonation 6-6l 6-76
Chlorination (See Chemical unit processes and
Cost data and economic analysis)
Chlorine (See Chlorination)
Clarification (See Cost data and economic
analysis and Physical unit processes)
Clarifiers (See Clarification and'
Sedimentation)
Comminution (See Cost data and economic
analysis and Physical unit processes)
Index 6
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Part 1 of 3
29 Sep 78
Paragraph
Complete mix activated sludge (See Biological
unit processes and Cost data and economic
analysis)
Contact stabilization activated sludge (See
Biological unit processes and Cost data
and economic analysis)
Cost data and economic analysis:
Biological unit processes:
Activated Sludge:
Complete mix 8-30
Contact stabilization 8-34
Extended aeration 8-32
Modified or high-rate aeration . . 8-33
Plug flow 8-29
Pure oxygen 8-35
Step aeration 8-31
Digestion:
Aerobic 8-40
Anaerobic 8-4l
Lagoons, aerated:
Aerobic 8-36
Facultative 8-37
Nitrification-denitrification .... 8-39
Oxidation ditch 8-38
Stabilization ponds 8-1*2
Trickling filters 8-28
Chemical unit processes:
Ammonia stripping 8-22
Carbon adsorption 8-20
Chemical coagulation 8-21
Chlorination 8-23
Ion exchange 8-24
Neutralization 8-25
Recarbonation 8-26
Two-stage lime treatment 8-27
Physical unit processes:
Cascade aeration 8-l6
Centrifugation 8-12
Comminution 8-4
Drying beds 8-l4
Equalization 8-5
Filtration 8-10
Page
8-18
8-19
8-18
8-19
8-17
8-20
8-18
8-23
8-24
8-20
8-20
8-21
8-21
8-24
8-17
8-14
8-13
8-13
8-l4
8-15
8-15
8-15
8-15
8-12
8-10
8-6
8-11
8-6
8-9
Index 7
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29 Sep 78
Paragraph Page
Flotation 8-6 ^
Grit removal 8-2 8-5
Incineration:
Fluidized bed 8-19 8-12
Multiple-hearth 8-l8 8-12
o -i o $ "i n
Microscreening o-±j p
Postaeration 8-15 8-11
Screening 8-3 8-5
Sedimentation:
Primary clarifier 8-8 8-8
Secondary clarifier 8-9 8-8
Sludge hauling and land filling . . . 8-17 8-12
Thickening (gravity) 8-7 8-7
Vacuum infiltration 8-11 8-9
Denitrification (See Biological unit processes
and Cost data and economic analysis)
Digestion (See Biological unit processes and
Cost data and economic analysis)
Drying beds (See Cost data and economic
analysis and Physical unit processes)
Equalization (See Cost data and economic
analysis and Physical unit processes)
Filter (See Filtration)
Filtration (See Cost data and economic
analysis and Physical unit processes)
Floe (See Sedimentation)
Flotation (See Cost data and economic
analysis and Physical unit processes)
Grit (See Cost data and economic analysis and
Physical xmit processes)
Lagoons (See Biological unit processes and
Cost data and economic analysis)
Microscreening (See Cost data and economic
analysis and Physical unit processes)
Microscreens (See Microscreening)
neutralization (See Chemical unit processes and
Cost data and economic analysis)
Nitrification (See Biological unit processes
and Cost data arid economic analysis)
Physical unit processes:
Centrif-ugation:
Background 5-o4
Index 8
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29 Sep 78
Paragraph
Page
Bibliography 5-91 5-137
Cost data 5-90 5-136
Design parameters 5-86 5-133
Example calculations 5-89 5-135
Design procedure 5-87 5-131
Input data 5-85 5-133
Output data 5-88 5-13^
Comminution:
Background 5_l8 5-29
Bibliography 5-25 5-31
Cost data 5-2U 5-31
Design parameters 5-20 5-29
Design procedure 5-21 5-29
Example calculations 5-23 5-31
Input data 5-19 5-29
Output data 5-22 5-29
Drying Beds:
Area required in Northern U. S. ... Table 5-27 5-157
Background 5-100 5-1^9
Bibliography 5-107 5-156
Cost data 5-106 5-155
Design parameters 5-102 5-1^9
Design procedure 5-103 5-151
Example calculations 5-105 5-153
Input data 5-101 5-1^9
Output data 5-101* 5-153
Equalization:
Background 5-26 5-33
Bibliography 5-33 5-39
Cost data 5-32 5-39
Design parameters 5-28 5-3^
Design procedure 5-29 5-3^
Example calculations 5-31 5-36
Input data 5-27 5-33
Output data 5-30 5-36
Filtration:
Background 5-68 5-93
Bibliography 5-75 5-113
Cost data 5-7^ 5-113
Design parameters 5-70 5-97
Design procedure 5-71 5-98
Example calculations 5-73 5-105
Index 9
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29 Sep 78
Paragraph Page
Input data
Output data
Flotation:
Background
Bib-tiography
Cost data
Design parameters .
Design procedure
Exariple calculations
Input data .....
Grit removal:
Background.
Chairber
Aerated
y. terete settling
Horizontal flow
Particle size
Settling velocities
L;ibL:ic(-:r-a.ph;y
Cost ua~ca
Design procedure
Example calculations .
Input data .......
Output data
Incineration:
Fluid! zed bed:
Background .
5-69
5-72
5-34
5-41
5-1*0
5-36
5-37
5-39
5-35
5-38
5-2a,c,d
5-2d
5-2g
Figure 5-1
Table 5-2
5-2a,b,e
5-2f,g
5-2c
5-2d
5-2g
Figure 5-2
5-2b,c
5-2c
Table 5-1
5-9
5-8
5-4
5-5
5-7
5-3
5-6
5-129
5-96
5-105
5_Ui
5-53
5-53
5-42
5-42
5-47
5-^1
5-47
5-3
5-3
5-4
5-5
5-18
5-3-1*
5-4
5-3
5-3
5-4
5-5
5-3
5-3
5-18
5-16
5-16
5-4
5-6
5-11
5-4
5-10
5-189
Bibliography 5-136 5-209
Cost data 5-135 5-209
Design parameters 5-131 5-193
Design procedure 5-132 5-194
Example calculations 5-134 5-200
Index 10
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29 Sep 78
Paragraph Page
Input data 3-130 5-192
Output data 5-133 5-199
Multiple-hearth:
Background 5-121 5-177
Bibliography 5-128 5-186
Cost data 5-127 5-185
Design parameters 5-123 5-177
Design procedure 5-121* 5-179
Example calculations 5-126 5-182
Input data 5-122 5-177
Output data 5_125 5-l8l
Microscreening:
Bibliography 5.99 5-146
Cost data 5.98 5-146
Definition 5-92a 5-139
Design parameters 5-9^ t;--lU•
Design procedure 5.95 5-141
Example calculations 5-97 5-l!3
Input data 5-9^ 5-141
Output data 5-06 5-1^
Postaeration:
Background 5-108 5-159
Cascade aeration 5-110 5-lb5
Design parameters 5-110b 5-165
Design procedure 5-110c 5-l66
Example calculations 5-110e 5-167
Input data 5-110a 5-165
Output data 5-11 Of! 5-167
Mechanical or diffused aeration . . . 5-109 5-159
Bibliography . 5-112 5-l68
Cost data 5_111 5_l68
Screening:
Background 5_10 5-19
Bibliography 5-17 5-25
Cost data 5-l6 5-25
Design parameters 5-12 5-21
Design procedure 5-13 5-21
Example calculations 5-15 5-23
Input data 5-11 5-20
Output data 5-14 5-23
Sedimentation:
Primary clarifier:
Index 11
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29 Sep 78
Paragraph __ Page
Background 5-52 5-68
Bibliography 5-59 5-80
Categories 5-51 5-6?
Cost data 5-58 5-80
Definition 5-50 5-6?
Design parameters 5-54 5-70
Design procedure 5-55 5-70
Example calculations 5-57 5-76
Input data 5-53 5-68
Output data 5-56 5-75
Sedimentation tank Figure 5-8 5-69
Secondary clarifier:
Background 5-60 5-83
Bibliography 5-67 5-90
Cost data 5-66 5-90
Design parameters 5-62 5-84
Design procedure 5-63 ^~«
Example calculations 5-65 5-87
Input data 5-6l 5-83
Output data 5-64 5-86
Settling tanks Table 5-11 5-91
Sludge hauling and landfilling:
Background 5-113 5-169
Bibliography 5-120 5-17^
Cost data 5-119 5-174
Design parameters 5-H5 5-171
Design procedure 5-Ho 5-171
Example calculations 5-H8 5-173
Input data 5-114 5-170
Output data 5-H7 5-172
Thickening (gravity):
Background 5-42 (•
Bibliography 5-49 5-63
Cost data 5-U8 5-63
Design parameters 5-44 5-59
Design procedure 5-45 ^
Example calculations 5-47 5-63
Input data 5-43 5-59
Output data 5-46 5-63
Vacuum filtration:
Average chemical doses for Table 5-19 5-129
Background 5-76 5-119
Index 12
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29 Sep 78
Bibliography
Centrifuge performance
Cost data . .
Design parameters
Design procedure
Example calculations
Expected performance
Input data
Output data
Polyelectrolyte doses for
Plug flow activated sludge (See Biological
unit processes and Cost data and
analysis)
Polyelectrolytes (See Physical unit processes)
Screening (See Cost data and economic
analysis and Physical unit processes)
Screens (See Screening)
Sedimentation (See Cost data and economic
analysis and Physical unit processes)
Sludge (See Biological unit processes and
Cost data and economic analysis)
Step aeration (See Biological unit processes
and Cost data and economic analysis)
Thickeners (See Thickening)
Thickening (See Cost data and economic
analysis and Physical unit processes)
Trickling filters (See Biological unit
processes and Cost data and economic
analysis)
Urban Studies Program:
Area planning:
Duplication of effort
Responsibility .
Leadership
Vacuum filtration (See Cost data and economic
analysis and Physical unit processes)
Waste:
Flow:
Average
Calculations
Domestic
Paragraph
5-83
Table 5-23
5-82
5-78
5-79
5-81
Table 5-22
5-77
5-80
Table 5-20
l-ltb(l)
2-2a,b
2-2a(2)
Table 2-2
3-2c
Page
5-127
5-138
5-127
5-121
5-121
5-130
5-121
5-129
1-1
1-1
1-1
2-1
2-1
2-3
3-2
Index 13
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Paragraph Page
Factors affecting reading 2-2a(l) 2-1
Maximum reading 2-2b 2-2
Minimum reading 2-2b 2-2
Peak reading 2-2b 2-2
Residential Table 2-1 2-3
Wastewater:
Composition 1-Ud 1-2
Infiltration 2-2c 2-2
Inflow 2-2c 2-2
Quality 2-3 2-2
Systems:
Bibliography U-5 U-3
Design criteria 1-1 1-1
Design equations and practices .... U-3a-g U-l
Design factors 3-1 3-1
Economic analysis U-U U-3
Phases of design 3-2 3-2
Physical unit processes 5-la-q 5-1
Planning U-5a,b k-3
Problems of design l-5a-g 1-2
Selection of 1-1 1-1
3-lb(l)-(l2) 3-1
3-2d 3-2
Site selection 3-la(l)-(l2) 3-1
Wastewater treatment:
Process selection U-la-g U-l
Process substitution diagram U-2 U-l
Water consumption, average 2-2a,b 2-1
Index Ik
*U.S. GOVERSMENT PRINTING OFFICE : 1979 0-620-007/3776
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