4>EPA
United States
Environmental Protection
Agency
National Training
and Operational
Technology Center
Cincinnati, OH 45268
EPA-430/1-81-017
August 1981
Water
Instructional Resources
Monograph Series:
Anaerobic Digestion
IRIS
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Monograph Series:
ANAEROBIC DIGESTION
Selected Instructional Activities
and References
prepared by
EPA Information Dissemination Projec
SMEAC Information Reference Center
1200 Chambers Road, Third Floor
Columbus, Ohio 43212
Compiled by - Robert D. Townsend
as part of
Grant No. T-901184-01-0
National Training and Operational Technology Center
Office of Water Program Operations
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
August 1981
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ABOUT THE AUTHOR
Robert D. Townsend is the Instructional Resources Coordinator
for The Ohio State University's EPA Information Dissemination Project.
Since 1980, he has been assigned to the USEPA's National Training
and Operational Technology Center (NTOTC) in Cincinnati, Ohio. His
experience includes teaching and directing workshops aimed toward
the implementation and searching of IRIS, ERIC, and related pollution
control databases.
CREDITS
Mr. Lynn Marshall, Engineering Technician, Operational Technology
Branch, National Training and Operational Technology Center, United
States Environmental Protection Agency, Cincinnati, Ohio was particularly
helpful in identifying instructional materials and providing a technical
review of the introduction.
Ms. Thea Teich Townsend, Writer-Editor, Program Operations Branch,
National Training and Operational Technology Center, United States
Environmental Protection Agency, Cincinnati, Ohio was helpful in
providing editorial review of the manuscript.
Primary staff work for this publication was completed by
Mrs. Linda Shinn, Mrs. Janice Hingsbergen, Mrs. Sarah Pockras,
Dr. Robert W. Howe and several graduate student assistants.
This monograph has been reviewed by the U.S. Environmental Protection
Agency and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names of
commercial products constitute endorsement of recommendation for use.
This document has been financed (in part) with Federal funds from
the U.S. Environmental Protection Agency, Office of Water Program
Operations, National Training and Operational Technology Center,
Cincinnati, Ohio, under grant identification number T-901184-01-0.
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FOREWORD
The National Training and Operational Technology Center in
cooperation with The Ohio State University is developing an
Instructional Resources Monograph Series. The monograph series
is an extension of the information provided in the Instructional
Resources Information System (IRIS) for water quality.
This document is one in the Instructional Resources Monograph
Series. These documents will assist the professional in identifying
and locating instructional and reference materials related to
various technical aspects of water quality control. Emphasis
is given to items useful in the development and presentation of
wastewater treatment training programs.
Each monograph reviews an aspect of wastewater treatment,
provides representative examples of available instructional
materials, and includes an annotated bibliography plus additional
references.
Your comments and suggestions regarding these publications
are invited.
Walter G. Gilbert
Director
NTOTC, USEPA
Cincinnati, OH 45268
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INTRODUCTION
The purpose of this monograph is to identify instructional and
reference materials for use by professionals in the field in the
development and implementation of new programs or in the updating
of existing programs. The materials identified in this document are
specific to the wastewater treatment process of anaerobic digestion.
The monograph will be useful to trainers, plant operations, educators,
engineers, consultants, and students with the need to efficiently
identify and locate specific instructional materials.
To help meet this need, the monograph is organized into four parts:
Part I Anaerobic Digestion - The Process. This section
presents a brief discussion of the anaerobic
digestion process in wastewater treatment operations.
Part II Learning Resources. This section presents
selected portions of illustrative resource
materials taken from a chapter or section of a
publication or other instructional material.
These resources were identified by professionals
as being representative of the materials currently
available. A reference to the source where the
material may be found in more detail is included.
Bibliographic data regarding these resources are
found in Part III, Abstracted Reference Materials.
Part III Abstracted Reference Materials. This section
presents document resumes of pertinent instructional
materials that may be used to supplement those
identified in Part II - Learning Resources.
Instructions for interpreting a document resume
are found in Part V.
Part IV Reference Materials - Bibliographic Citations.
This section provides additional resources, mostly
from technical and scientific journals. Resources
identified in this section tend to be highly specific
and more technical in nature. Information provided
includes title, author, corporate author (if
applicable) and availability.
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PREFACE
The need for training in the water pollution control field
continues to grow. Gilbert (1981) states that, based on continuing
changes in current programs and activities, the training programs
provided by an institution or organization must be responsive to
the information, knowledge, or skill gap that exists between what
an individual already knows or can do and what the individual needs
to know or be able to do to accomplish a given task. Examples of
changing areas with training implications include wastewater
treatment technology and water quality assessment.
Recent USEPA reports Gray, et al., (1979) and Hegg, et al.,
(1979) suggest that training needs do exist in the areas of
wastewater treatment system management and process control.
Major reasons given for the fact that many wastewater treatment
plants currently in operation are not in compliance with their
NPDES permits include lack of understanding by operators of the
wastewater treatment process and the inability of operators to
apply process control knowledge to inplant conditions. The General
Accounting Office report (1980) showed 97 percent of the 242
treatment facilities surveyed to be in violation of their effluent
discharge permits.
As technology alone cannot solve the problems, it is important
to realize that a well-trained workforce is essential to clean up
and control our water pollution problems. Most practitioners agree
that training is critical to the improvement of performance of
personnel. With training comes the need for training materials and
it is the intent of this monograph to assist in identifying and
locating instructional and reference materials specific to the
wastewater treatment process of anaerobic digestion.
Learning resources and reference materials are assembled here
to assist trainers and instructors in the development of training
programs. The learning resources are often segments of illustrative
materials on anaerobic digestion taken from a chapter or section of
a publication or other learning resource that provides additional
information. These resources are to serve only as a guide in
selecting appropriate training materials and should not be considered
a fixed structure or total program.
For further information about these materials contact:
EPA Information Dissemination Project
1200 Chambers Road, 3rd Floor
Columbus, Ohio 43212
614-422-6717
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REFERENCES
American Academy of Environmental Engineers. An Analysis of the
Role of the U. S. Environmental Protection Agency in the
Development of Manpower for Water Pollution Control. P. 0. Box
1278, Rockville, Maryland, July 1980.
Gilbert, W. G. , Perspective on Training Needs. Paper presented
at National Conference on Meeting Environmental Workforce Needs,
Washington, D.C., February 1981.
Gray, A. C., Jr., et al. Evaluation of Operation and Maintenance
Factors Limiting Biological Wastewater Treatment Plant Performance,
Municipal Environmental Research Laboratory, U. S. Environmental
Protection Agency, Cincinnati, Ohio, EPA-600/2-79-078 (July 1979).
Hegg, B. A., et al. Evaluation of Operation and Maintenance Factors
Limiting Municipal Wastewater Treatment Plant Performance, Municipal
Environmental Research Laboratory, U. S. Environmental Protection
Agency, Cincinnati, Ohio, EPA-600/2-79-034 (June 1979).
U. S. General Accounting Office, Costly Wastewater Treatment Plants
Fail to Perform as Expected, CED-81-9, November 14, 1980.
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TABLE OF CONTENTS
Anaerobic Digestion
PART I - ANAEROBIC DIGESTION - THE PROCESS 1
PART II - LEARNING RESOURCES 11
Section I. Primary Treatment and Sludge Digestion Workshop . 13
Ontario Ministry of the Environment
Topic: Digester Operations
Section II. Sludge Treatment and Disposal: Course No. 166 29
Linn-Benton Community College
Topic: Digester Classification and Types
Section III. Wastewater Treatment Plant Operator Training Program ... 49
Water Pollution Control Federation
Topic: Anaerobic Digestion - Purpose and Methods
Section IV. Field Manual for Performance Evaluation and Troubleshooting
at Municipal Wastewater Treatment Facilities 73
Culp/Wesner/Culp, Clean Water Consultants
Topic: Troubleshooting
Section V. Criteria for the Establishment of Two-Year Post High-School
Wastewater Technology Programs (CEWT) 87
Charles County Community College and Others
Topic: Second Stage Digestion
Section VI. Anaerobic Digestion and Analytical Control (XT-34) .... 95
National Training and Operational Technology Center
Topic: Decomposition Processes
Section VII. Standard Operating Job Procedures for Wastewater Treatment
Plant Unit Operations SOJP 10 97
Charles County Community College
Topic: Job Procedures for the Digestion Process
Section VIII. Operation of Wastewater Treatment Plants: A Field Study
Training Program (Second Edition) Ill
California State University, Sacramento
Topic: Sludge Digestion and Solids Handling Checklist
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Section IX. Troubleshooting 0 & M Problems in Wastewater Treatment
Facilities - Course No. 179.2 121
National Training and Operational Technology Center
Topic: Troubleshooting Anaerobic Digestion Problems
Section X. Operations Manual: Anaerobic Sludge Digestion 143
USEPA - Office of Water Program Operations
Topic: Potpourri
Section XI. Anaerobic Digestion Analysis Training Module 161
Kirkwood Community College
Topic: Anaerobic Digester Test Procedures
PART III - ABSTRACTED REFERENCE MATERIALS 167
PART IV - REFERENCE MATERIALS (Bibliographic Citation Only) 191
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PART I
Anaerobic Digestion - The Process
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ANAEROBIC DIGESTION
Introduc t ion
One of the major problems resulting from the primary (settling)
and secondary (biological) treatment of wastewater concerns the fate
of the solids fraction. Watery and noxious, this "sludge" must
undergo further treatment to minimize a variety of disposal problems.
One of the most common treatments utilized is anaerobic digestion.
Anaerobic digestion stabilizes the organic solids in sludge.
Total solids can be subdivided into a "volatile solids" (organic)
fraction and an "ash" (inorganic) fraction. The sludge fed to the
digester should contain as high a volatile solids fraction as possible
because this portion can be treated by the digestion process. The
inorganic material simply takes up space in the digester. Indeed, a
high percentage of inert or inorganic matter in the sludge might
indicate that the screening and grit removal machinery of the plant
was not operating efficiently.
DIGESTION AS PROCESS STEP
PRIMARY PLANT
SECONDARY PLANT
Figure I
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Sludge contains not only the solids fraction of the wastewater
flow, but also a great quantity of water. Very often, sludges must
be "thickened" to assure the 4 to 8 percent solids concentration
needed for efficient digestion. More diluted sludges can cause pH
changes in the alkaline buffer in the digester, decreased bacterial
contact with the organics, and increased digester heat and space
requirements. After the digestion process, even more water is
separated from the sludge so that other processes can further the
dewatering.
Digestion can take place under aerobic (with oxygen) or anaerobic
(without oxygen) conditions. Anaerobic digestion effectively handles
primary sludge and results in the production of methane gas as a
by-product, which can be used as a fuel source. However, the
anaerobic process is more sensitive to environmental changes and can
be upset by loading problems.
Anaerobic digestion proceeds through the action of certain forms
of bacteria upon organic material. As a result, the unpleasant
smelling sludge is broken down to several components; i.e.,
(1) methane gas with a lower Btu content than natural
gas, but still high enough for use as a fuel;
(2) scum, consisting of lightweight sludge particles;
(3) supernatant, consisting mainly of water, which must
be withdrawn from the digestion tank and subjected
to secondary treatment before being released in the
effluent; and
(4) digested stabilized sludge, relatively free of
odor and pathogens, which can be landfilled,
incinerated or recycled through land treatment.
These products will be discussed in further detail later.
DIGESTION PRODUCTS
MICROOI?<3AMIS«$—>.COZ,4-12O. _„ OC6ANIC ACIP4,
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Figure II
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Process Components
Bacteria
Since the job of anaerobically digesting sludge is done by
certain forms of bacteria already present in wastewater, a major
objective of the process is to provide and maintain an environment
conducive to the growth of those organisms.
Anaerobic digestion occurs in two phases which proceed
concurrently. The first is the utilization of the sludge as
food by a group of saprophytic bacteria which convert the
volatile (organic) solids to organic acids. These bacteria are
termed "acid formers." The organic acids, in turn, become the
food for the second phase - which actually is the sludge stabilization
step - where extremely sensitive bacteria convert the organic acids
to methane gas and carbon dioxide. The bacteria involved in this
conversion are called "methane fermenters."
As mentioned previously, these two phases occur at the same
time except when the digester is just starting up or when the
digestive process is upset or "going sour." One of the major
reasons a digester goes sour is the high sensitivity of the methane
fermenters to environmental change.
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Environmental Conditions
The optimum conditions for anaerobic digestion call for
- a temperature of 80° to 100°F
(29° - 37°C),
- absolutely no oxygen present,
- a pH of 6.8 to 7.2 (neutral), and
- no toxic materials present.
If these conditions are not met, the activity of the methane
fermenters can decrease drastically. Unable to keep up with the
acids produced by the acid formers, the methane fermenters continue
to slow down because of the decreasing pH (or increasing acidity or
"sourness") of the digester. Only part of the digestion process
then occurs.
As noted earlier, an insufficiently thick sludge can also upset
the process by diluting the alkaline buffer added to the digester to
maintain a near-neutral pH. This dilution can lead to decreases in
pH which result in poor methane fermenter activity and a "sour"
digester. Such a digester may take 30 to 60 days to recover and
require additions of alkaline compounds or "seed sludge" before
returning to "normal." This will be discussed later.
The acid former and methane fermenter groups of bacteria can be
further classified according to the temperatures at which they thrive.
Psychrophilic bacteria thrive in temperatures below 68°F (20°C),
although their activity becomes almost negligible below 50°F (10°C).
Because sludge digestion in this temperature range takes 50 to 180
days, few digesters are designed today to operate in this range.
However, many unheated digesters are still in use, including Imhoff
tanks.
Mesophilic bacteria require higher temperatures, preferably
85° - 100°F (30° - 38°C). Thus, the digester must be heated. The
advantage here is the reduced time required for digestion—5 to 50
days, with the normal time being 25 to 30 days, depending upon the
adequacy of mixing.
Thermophilic bacteria prefer even higher temperatures; i.e.,
greater than 113°F (45°C). Digestion in this range is hastened, and
takes from 5 to 12 days. However, difficulties in maintaining high
temperature and the sensitivity of the bacteria to temperature changes
have prevented most plants from operating at this level.
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Contact
To utilize the volatile solids in the sludge as food, the bacteria
must come into physical contact with them. In many anaerobic
digestion tanks, the only mixing which occurs is that caused
naturally by the rising methane gas. If the sludge loading to the
digester can be maintained at 0.4 pounds of sludge/cu. ft. of digester
capacity/day, natural mixing may be all that is needed. Periods of
decreased loading can interrupt mixing and cause the formation of scum
blankets at the top of the digester, fouling machinery and clogging
valves. Increased loading can slow gas production. Thus, natural
mixing works to a certain extent but only when carefully controlled.
More recently designed digesters do not rely on natural mixing
alone, however.
Mechanical mixing devices such as diffusers, propellers,
impellers, and turbine wheels can keep sludge in motion. However,
here again, the efficiency of the screening and grit removal stages
of wastewater treatment must be high, otherwise, rotors, impellers,
and other mixing equipment can be heavily damaged or worn by grit
and debris. External pumped circulation of food to designated
peripheral ports, has also become popular in design, mostly as an
aid to gas mixing.
Food
The composition of the sludge itself obviously has a large
effect upon the ease and speed of the digestive process. The volatile
solids that are readily soluble in water will be easily broken down
by the acid formers. Insoluble organics, such as vegetable fats and
oils must first be converted to soluble forms by bacterial enzymes.
Enzymes are proteins which occur in all living organisms and are
necessary for biological functions. Mineral oils, such as fuel oils,
automotive oils and paraffins, can cause toxicity problems in the
digester. Large amounts are best handled by pretreatment.
As important as the composition of the sludge fed to the digester
is its consistency. These factors have been noted in previous sections
but are worth reviewing here:
Sludge must be sufficiently concentrated or "thick"
enough to prevent dilution of the digester alkaline
buffer and other problems, yet "thin" enough to pump.
Sludge must have a large enough concentration of
volatile solids (organics to meet the food needs of
the bacteria and prevent the digester capacity from
filling with inert material (grit, debris).
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Tanks
The digestion process has been improved over the years
through the addition of new equipment to increase efficiency and
prevent problems. The earliest digesters were simply open-top,
unheated tanks mixed only by the movement of gases. As the sludge was
digested, its various components would arrange themselves in the
tank according to density. Grit and other inert material would fill
in the bottom of the tank. Decomposed sludge solids would form the
next layer. A zone of bacterial activity on newly-fed sludge would
form next. Then would come the supernatant or water layer. On
top of that a scum layer of lighter sludge particles would form.
Gases produced during digestion would escape to the atmosphere.
After a few years, digester capacity would be severely reduced because
of growth in bottom deposits and the scum layer.
Placing a cover on the digester enables the operator to collect
the methane gas produced by the digester process. Fixed covers are
concrete or metal, and are bolted to the digester wall. They must
be equipped with pressure relief devices. If these fail, serious
damage can result since pressure changes inside the digester can
cause an explosion or implosion (in case of vacuum relief failure).
ROOF DESIGNS
Floating Roof Design
Fixed Roof Design
CONTROL:
• gas draw off
•liquid tevd
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Floating covers move up and down along cover guides in the
digester walls. The cover floats on the sludge at a level dependent
upon the amount of sludge added to or withdrawn from the digester.
The guides must be maintained in operating order for this cover to
work properly. The amount of sludge pumped into the digester must
also be carefully controlled in this variable capacity situation.
Floating covers have been lifted over the digester walls because of
high sludge levels.
An extension of the floating cover concept is the Gas Holder
Cover. With this mechanism, the cover can lift as much as six feet
above the minimum height because of gas pressure under its dome. Metal
guides and rollers attached to the digester wall superstructure
permit this movement. Problems arise when scum is allowed to
accumulate between the walls and the cover.
The addition of a heating mechanism and a pump to recirculate
deposited sludge back up into the active zone increases the contact
between the volatile solids and the bacteria and decreases the amount
of time required for digestion. Because the mixing activity prevents
the layering present in unmixed tanks, all mixing mechanisms must be
shut down and time allowed for the solids to settle before the
supernatant liquid can be withdrawn from the tank.
This last problem can be eliminated by connecting a second tank
to the process. Now, in one tank, active digestion takes place; in
the other, settling occurs. This eliminates the need to shut down
mixers before withdrawing supernatant or digested sludge. Futhermore,
the second tank also contains digested sludge and active bacteria
which can be added to the first tank to correct souring. The
two-tank system is often referred to as "two-stage" digestion,
just as one-tank systems are called "one-stage."
Anaerobic Digestion Products
Digestion products are gases (methane and carbon dioxide),
supernatant liquid, and digested sludge. A problem by-product can be
a blanket of scum which forms at the surface of the digester.
Composed of lightweight sludge particles carried upward by rising
gases, the scum, if not broken apart, can become 5 to 15 ft. thick.
Volatile solids can become concentrated in the scum layer, and unless
mixing occurs, digestion will be minimal.
The other nuisance by-product is excess alkalinity in the form of
ammonium ions (NH +1). Unless removed by a denitrification step
before digestion, this ammonium must be eliminated by elutriation
(washing) or some other method prior to the chemical conditioning step
for sludge dewatering. Otherwise, the ammonium would react with the
conditioning chemicals to form ammonia gas which would escape into
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the atmosphere of the dewatering area, causing a health hazard to
plant personnel.
The supernatant primarily consists of water removed from the
sludge. This liquid is removed regulary and is commonly recycled to
the headworks of the plant. Often high in solids and BODj, the
supernatant may cause a decrease in the quality of the treatment
plant's final effluent. Many operators increase the number of
supernatant discharges to secondary treatment but decrease the amount
released at each discharge. This can help prevent shocking the
system. The problem of solids in the supernatant is also alleviated
by ensuring good settling conditions.
The solids portion of the digestion products consists of
inorganics and volatile solids that were not easily digested.
Digested sludge:
(1) can drain or dewater easily;
(2) does not have a noxious odor;
(3) has a smaller volume than did the original
sludge entering the digester;
(4) is "lumpy" and black in color—grey streaks
indicate undigested sludge;
(5) should contain 40 to 60 percent less volatile
solids than the feed sludge.
This stabilized sludge can then be disposed of through land-
filling, land application, incineration, or other approved process.
10
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PART II
Learning Resources
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Presented are selected portions of existing training resources
which may be useful in developing a training program on anaerobic
digestion. Each resource has been selected for its representativeness
to training level, topic area or instructional approach. These
resources are to serve only as a guide in selecting appropriate training
resources and should not be considered a total training program.
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Learning Resource 1
Primary Treatment and Sludge Digestion Workshop.
Ontario Ministry of the Environment
Training and Certification Branch
Pollution Control Branch
Ministry of the Environment
135 St. Clair Avenue West
Toronto, Ontario M4V 1P5
Presented are selected parts of a training manual prepared as a
home study and reference manual for plant operators and as the text
for the related workshop. Lesson objectives are indicated at the
beginning of each topic. Hands-on participation is encouraged.
This lesson discusses digester theory and operation, mixing, heating
systems, and single- and two-stage digestion.
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Other manuals relating to the water and wastewater
treatment processes published by the Training and
Certification Section, Ministry of the Environment,
include:
Basic Sewage Treatment Operation
Basic Water Treatment Operation
Surface Water Treatment Workshop
Activated Sludge Process Workshop
Prevention Maintenance Workshop
Pump Operation Workshop
Basic Gas Chlorination Workshop
Copies may be purchased at:
Ontario Government Book Store
880 Bay Street
Toronto, Ontario M5S 1Z8
or may be ordered by mail by writing to:
Ministry of Government Services
Publications Centre
880 Bay Street
Toronto, Ontario M5S 1Z8
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SUBJECT: TOPIC: 4
Digester Operations Anaerobic Digestion
OBJECTIVES:
The trainee will be able to:
1. Recall the objectives of Sludge
Digestion.
2. Discuss the principles of the
Anaerobic Digestion Process.
3. List the parameters which must be
controlled for good digester
operation.
4. Show by a simple diagram the
Anaerobic Digestion Process.
5. Name five objectives which mixing
can attain in the Anaerobic
Digestion Process.
6. Name the three temperature ranges
at which a digester may be operated.
7. Name and discuss four means used to
heat a digester.
8. Understand and discuss single stage
and two-stage digester operation.
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ANAEROBIC
DIGESTION OF SLUDGE
OBJECTIVES OF SLUDGE DIGESTION
Settled solids and floating scum removed from the sedimentation
tanks and clarifiers consist of a watery, malodorous mixture called
raw sludge. In the majority of the plants this raw sludge is pumped
to a digester for treatment before disposal. The primary purpose of
sludge digestion is to reduce the complex organic matter present in
the raw sludge to a material that is relatively odor free, can be
readily dewatered, capable of being disposed of without causing
environmental problems, and which will undergo little or no further
decomposition. Digestion of sludge can be carried out either by
anaerobic or aerobic processes. Topic 8 deals with the aerobic
process.
ANAEROBIC DIGESTION PROCESS PRINCIPLES AND THEORY
In the anaerobic process the organic solids are liquified and
brought into solution by a catalyst called enzymes present in the
sludge. The organic material is then broken down by the action of
two different groups of bacteria living together in the same
environment. One group consists of microorganisms commonly referred
to as acid formers. The second group, which utilize the acid formed
by the acid formers are methane fermenters, commonly referred to as
methane formers.
The digestion process is normally described in three stages:
1. Acid fermentation stage
2. Acid regression stage
3. Alkaline fermentation stage
Acid Fermentation Stage
During the acid fermentation stage, the organic compounds,
principally carbohydrates, are broken down to volatile fatty acids,
primarily acetic, butyric and propionic acids. This production of
volatile acids results in a drop in pH and causes putrefactive odors.
The organisms primarily responsible for this stage of digestion are
the acid formers. This group encompasses a large number of bacteria
which are anaerobic or facultatively anaerobic. As a rule, the acid
formers are very vigorous reproducers and are less sensitive to
environmental factors than the methane formers.
16
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Acid Regression Stage
During the acid regression stage, decomposition of organic acids
(volatile acids) and soluble nitrogenous compounds occurs which
result in the formation of the following principal compounds:
1. ammonia
2. amines
3. acid carbonates
During this stage the pH will tend to increase.
Alkaline Fermentation Stage
During the alkaline fermentation stage, destruction of
nitrogenous compounds and cellulose occurs. The volatile organic
acids, produced during stage 1 of the process are broken down to
produce carbon-dioxide (CO,,), methane (CH, ) and water. The principal
organisms responsible for this process are the methane formers.
These organisms are strictly anaerobic, are a slower reproducing
bacteria, and are much more sensitive to their environment than the
acid formers. These organisms reproduce most effectively in the pH
range of 6.8 - 7.2 although experience has shown that satisfactory
digestion will continue at the pH range of 6.5 - 7.5.
These three stages occur continously and, for all practical
purposes, simultaneously.
DIGESTER OPERATION CRITERIA
The basic criterion for good digester operation is the maintenance
of a suitably balanced environment in the digester for the growing or
reproducing of both acid formers and methane formers. To maintain this
balance in the process the operator must exercise control over the
following parameters:
1. food supply (raw sludge loading rate)
2. volatile acids/alkalinity relationship
3. mixing of the digester contents
4. temperature
Generally, in an efficient digester operation the volatile solids
content of the sludge is reduced by 40 to 60 percent. The time
required to digest the sludge, may be from two weeks to four months
17
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duration and is dependent upon the above parameters. Figure 4-1
illustrates in simple equations what happens in the digester.
It is important to note that the methane forming organisms are
more sensitive to upset and reproduce at a slower rate than the
volatile acid formers. Every effort should be made to operate the
anaerobic digester in a manner whereby the rate of acid formation
is kept in balance with the production of methane. The most common
cause of digester upset that occurs in the process is that of the
methane gas formers failing to keep pace with the acid forming
organisms with the result that the digester becomes overly acidic.
When a buildup of this acid condition develops, the rate of the
digestion process will begin to slow, and if left unchecked will
result in serious inhibition or even complete failure of the digestion
process. As acid concentrations increase, pH levels drop. The optimum
range for a good digestion process is a pH value of 6.8 to 7.2. pH
values lower than 6.8 might indicate a process failure. However,
experience has shown that the digester process upset will be far
advanced before the reduction in pH will indicate a problem. The
volatile acids test and the alkalinity test have proven more useful
and effective in predicting and avoiding process failures. In
general, there is a relationship between acids and alkalinity which
will remain fairly constant during satisfactory digestion. The
alkalinity is always greater than the volatile acids concentration to
some degree. A fairly rapid increase in volatile acids with an
associated decrease in alkalinity indicates an impending process upset.
Should the alkalinity concentration be allowed to drop to a level
lower than that of the acids, all digester buffering capacity will be
lost, the pH will very rapidly drop to a level well below 7.0, and
the process could be considered as having failed. Such an upset is
usually accompanied by poor gas production and quality and perhaps
by foaming. Careful monitoring, therefore, of the alkalinity and
acids concentrations, will provide warning of an impending process
upset, as opposed to pH showing process upset after the fact, and
various measures can be taken to avert complete digestion failure.
Such measures are described in detail later in the text.
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REACTIONS IN DIGESTION PROCESS
Raw Sludge , Microorganisms —> CO- , H?0 Organic Acids
Complex "A" Intermediate Cellular & Other
Substrate Principally Degradation Intermediate
Carbohydrates Acid Formers Products Degradation
Fats (Saprophytic) Products
Proteins (Faculative)
Organic Acids + Microorganisms—> CH^ + C02 , Other End
Cellular & Other "B" Methane Carbon Products
Intermediate Principally Dioxide H20, H2S
Degradation Methane
Products Formers
(Anaerobes)
MIXING
Mixing is an important factor in the process and should
accomplish the following:
1. Utilize as much of the total volume of the
digester as possible.
2. Quickly distribute the raw sludge throughout
the digester and put the microorganisms in
rapid contact with fresh food sources.
3. Achieve good pH control by distributing buffering
alkalinity throughout the digestion tank.
4. Obtain the best possible distribution of heat
throughout the tank.
5. Minimize the deposition of grit and inert solids
on the bottom, or floating scum material to the top.
Mixing the tank contents completely, speeds the digestion process
greatly.
Mixing can be accomplished by various means:
1. By mechanical mixers.
2. By digester gas recirculation.
Some mixing action is also contributed by recirculating sludge
through the heat exchanger.
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Mechanical Mixing
The propeller-type mixers are found mainly on fixed-cover
digesters. Normally, two or three of these units are supported on
the roof of the tank. Electric motors drive the mixers. A typical
propeller-type mixer is shown in Figure 4-2. It is usual for
mixing action and control to be enhanced by the installation of draft
tubes to serve the mixers. The draft tubes are steel and range from
18 to 24 inches in diameter. The top of the draft tube has a rolled
lip and is located approximately 18 inches below the normal water
level in the tank. The bottom of the draft tube may be straight or
equipped with a 90-degree elbow. The 90-degree elbow type is placed
so that the discharge is along the outside wall of the tank to create
a vortex (whirlpool) action.
The mixer propeller is located about two feet below the top of
the draft tube. This type of unit usually has a reversible motor so
that the prop may be rotated in either direction. In one direction
the contents are pulled from the top of the digester and forced down
the draft tube to be discharged at the bottom. By operating the
motor in the opposite direction, the digested sludge is pulled from the
bottom of the tank and is then discharged over the top of the draft
tube near the surface. If the digester is equipped with two units,
an effective method in breaking up a scum blanket is by operating one
unit in one direction and the other unit in the opposite direction,
thereby creating a push-pull effect. Mechanical mixers are sometimes
subject to shaft-bearing failure due to the abrasiveness of the sludge,
and corrosion by hydrogen sulphide present in the digester gas.
Maintenance consists of lubrication and, if belt—driven, adjustment
of belt tension.
The drawback of a draft-tube-type mixer is related to the
digester sludge level. If the sludge level is maintained at a
constant elevation, a scum blanket may form on the surface. When the
scum blanket becomes thick the mixer will only pull the liquid sludge
from under the blanket and not disturb the scum itself. Lowering the
level of the digester to just 3 or 4 inches over the top of the draft
tube may help to force the scum to move over and down the draft tube.
This particularly applies to single direction mixers.
Pumps are sometimes used to mix digesters. This method is
common in smaller tanks. When external heat exchangers are utilized,
a larger centrifugal pump is used to recirculate the sludge and
discharge it back into the digester through one or two directional
nozzles at the rate of about 200 to 1000 gpm.
The tank may or may not be equipped with a draft tube such that
the pump suction can be from the top or the bottom of the digester.
Control of scum blankets with this method of mixing is dependant upon
how the operator maintains the sludge level and where the pump is
pulling from and discharging to the digester.
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Maintenance of the recirculating sludge pump requires normal
lubrication and a good pump-shaft water sealing system. The digested
sludge is abrasive and pump packing, shaft, wearing rings, and
impellers are rapidly worn. Another problem associated with pump
mixing is clogging of the pump impeller with rags, plastic materials,
rubber goods and other pieces of material which can wind around the
impeller causing it to plug.
It is very important to check pump operation several times
a day.
Pressure gauges should be installed on the pump suction and
discharge pipes. If a rapid increase in pressure differential is
seen, the operator has an indication that pump clogging has occurred.
Mixing by Digester Gas Recirculation
In these systems, the digester gas is collected and fed by
blowers to the bottom of the digester where it is exhausted through
diffusers or "bubble-guns." Mixing of the sludge is accomplished as
the gas rises to the surface. See Figure 4-2.
HEATING AND TEMPERATURE CONTROL
RANGES OF DIGESTION TEMPERATURES
A digester may be operated in one of three temperature zones or
ranges, each of which has its own particular type of bacteria. The
lowest range (in an unheated digester) utilized psychrophilic (cold
temperature loving) bacteria. Temperature of the sludge inside tends
to adjust to the outside temperature. However, below 10°C (50°F)
little or no bacterial activity occurs and the required reduction in
sludge volatile solids (organic matter) will not likely occur. When
the temperature rises above 50°F the bacterial activity increases
and the digestion process improves. The bacteria appear capable of
surviving temperatures well below freezing with little or no harm.
The psychrophilic digestion upper limit is around 20°C (68°F).
Digestion in this range requires from 50 to 180 days, depending upon
the degree of treatment required. Generally, these digesters are
not very effective in digesting sludge.
The middle range of organisms are called the mesophilic (medium
temperature loving) bacteria; they thrive between a temperature of
20°C and 45°C (68° and 113°F). This is the most common operational
range, with temperatures usually being maintained at about 35°C to
37°C (95° to 98°F). Digestion at that temperature may take from
about 25 to 30 days, depending upon the required degree of volatile
solids reduction and the adequacy of mixing. The high rate processes
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are usually operated in the mesophilic temperature range. The high
rate process is a procedure providing mixing so that the organisms
and the food source can be brought together to allow the digestion
process to proceed more rapidly.
The third range of organisms are called the thermophilic (high
temperature loving) bacteria and they thrive between 49°C and 60°C
(120°F and 140°F). The time required for digestion in this range may
be between five and twelve days, depending upon the operation and the
degree of volatile solids reduction required. However, few plants
have actually been operated in the thermophilic range of temperatures
and there is little documentation of results.
When operating a digestion system in any of these temperature
ranges, care must be taken to maintain a more or less constant
temperature.
HEATING SYSTEMS
Digester heating can be accomplished by the following means:
1. Hot-water coils within the digester.
2. Recirculating sludge through an external heat
exchanger.
3. Direct contact of hot gas with sludge.
4. Steam injection.
External Heat Exchanger
The most common of the four is the recirculation of sludge through
an external heat exchanger. Hot water is pumped from the boiler to
the heat exchanger where it passes through a jacket while the
recirculating sludge passes through an adjacent jacket, and receives
heat from the water. In some heating installations the boiler and
exchanger are combined in a single unit. There are some advantages
in using external heat exchangers. These are: they help to control
scum buildup and there is no hotwater piping within the digester
which can be corroded or caked up. The only disadvantage is that in
a single stage digester system it is essential to stop sludge
recirculation to allow the tank contents to stratify prior to the
discharge of supernatant. This can result in an increased tendency to
form a "cake" on the exchanger coils, or jackets due to localized
overheating of the sludge.
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Hot-Water Coil
Hot-water coils within the digester consisting of pipes either
horizontally or vertically attached to the inside wall of the digester
is another method of heating digesters, although not too common in
newer plants. This method tends to create a problem of sludge caking
on the pipes and thereby effectively insulating them, thus reducing
the amount of heat transferred. Where coils are used water
temperatures entering the coils are limited to a temperature of 49°
to 54°C with boiler temperatures held to no higher than 82°C to prevent
excessive corrosion or caking of the sludge on the coils.
Direct Contact and Steam Injection
Direct contact of hot gas with sludge and steam injection methods
have been used in the past with varying degrees of success. However,
these systems are rarely installed in current practice.
SINGLE-STAGE DIGESTION
For simplicity, single-stage digester operation will be covered
under four headings:
1. Loading
2. Process
3. Supernatant Selection
4. Digested Sludge Removal
LOADING
Ideal conditions would be met if the raw sludge could be pumped
continuously to the digester. In practice, however, for various
reasons, continuous loading is not possible. Some small plants,
receiving eight hours per day of operator's supervision, may load the
digester three times a day, say at about 8 o'clock in the morning,
12 noon, and 4 in the afternoon. When automatic pumping facilities
are provided, the other extreme may be reached with loading being
effected once each hour. Where supervision is provided on a 24-hour
basis, manual controls may dictate 6 to 8 pumping cycles per day.
Excess amounts of primary effluent may be directed to the digester if
too many pumping cycles are provided due to exhaustion of raw sludge
supply. In installations where raw sludge must be pumped long
distances to the digester, the sludge line must be filled with diluted
sludge before the pump is shut off, to prevent plugging. The next
pumping cycle will direct the diluted sludge to the digester.
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In a single stage operation, the raw sludge is directed to the
top half of the digester. As indicated in the Flow Diagram appended
as Figure 4-3, the raw sludge may be mixed with seed sludge leaving
the heat exchanger.
PROCESS CRITERIA
The same process parameters apply to single-stage digestion as
multi-stage digestion with the following operational techniques
being peculiar to the single-stage process:
1. Mixing
In a single stage unit, mixing facilities, if any,
are designed only to mix the material in the top
half of the tank. In practice, this type of a
design makes it almost impossible to operate an
efficient digestion system. Thus it is difficult
to obtain a concentrated sludge from a single-stage
digester operation.
In a single-stage digester an improper mixing program
could lead to the process failure. The active volume
for the digester process can be greatly reduced by:
a) The formation of scum or sludge blankets.
b) Foaming occurring when the scum blanket begins
to digest.
2. Temperature
The importance of temperature has been discussed in
Section (Digester Systems). The major objective
here is to maintain the sludge temperature to within,
say, +1°C (±33°F).
SUPERNATANT SELECTION
In a single stage digester it is difficult to obtain a good
supernatant. Nevertheless, an attempt should be made to remove any
excess liquid. Mixing devices should be shut off for a period of
time before the supernatant is withdrawn. Through experience, the
operator will learn the duration of the quiescent settling period
required to obtain an optimum supernatant.
In digesters where a variable level of supernatant selection is
provided, the supernatant is removed via the line proving to be the
most satisfactory. An example of a supernatant selector system is
appended in Figure 4-4. In simpler installations the withdrawal
control is maintained by a sleeve-height adjustment. Other installations
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use valves to control these withdrawal processes. It should be noted
that in all installations the safety overflow should be kept open at
all times. To check the efficiency of the supernatant withdrawal
process the operator should carry out a series of suspended solids
tests. For quick results, the test can be carried out by using a
centrifuge with the standard suspended solids test being used where
complete laboratory equipment is available. In a good supernatant
a suspended solids concentration of 3,000 to 10,000 mg/1 might be
seen, although many supernatants have solids levels far exceeding
these concentrations.
DIGESTED SLUDGE REMOVAL
In a single stage digestion system the accumulated sludge should
be removed as frequently as possible. It may be difficult to obtain
a good concentrated sludge from this type of system. A 3 to 4 percent
sludge may be considered good for the digested sludge obtained from an
activated sludge plant using a single-stage digestion process. In a
digester equipped with a fixed cover and from which digester gas is
used to operate other components of the treatment system, the
digested sludge is best removed when the raw sludge is being pumped
to the digester. This practice will assist in maintaining the gas
pressure in the tank, and will tend to avoid a vacuum being formed.
WARNING
The withdrawal rate of sludge from the digester with a fixed
roof should be no faster than the rate of input of raw sludge. If
the draw-off rate is too fast, the gas pressure drops due to volume
expansion. This practice may create an explosive hazard by drawing
air into the digester, through the pressure-vacuum relief valve.
TWO STAGE DIGESTION
GENERAL
Two stage digestion is covered under five headings:
1. Sludge Loading
2. Operating Criteria
3. Sludge Transfer
4. Supernatant Selection
5. Digested Sludge Removal
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SLUDGE LOADING
Where mixing is practiced the raw sludge may be directed to any
point in the first-stage tank. Ideally, as with most biological
systems, a constant sludge feed rate would be preferred. However,
in practice, sludge is fed on a cyclical basis, usually by timers,
although manual operation may be featured from place to place. The
feeding cycles should be frequent and preferably made over a 24-hour
period although in smaller plants, the feeding might be accomplished
over an 8-hour period. A good two-stage design will allow the use
of either tank for the first stage. An example of a Two-Stage
Digester is appended in Figure 4-5.
OPERATING CRITERIA
Where mixing devices are available they are operated to control
the scum blankets and minimize inactive or dead spaces, and to bring
bacteria and fresh food sources rapidly together. Mixing is carried
out, in the first-stage digester, the mixing devices may be operated
either full-or part-time. When part-time operation is desired the
cycle is set up in relation to test and observation of scum blanket
formation and not on power saving. In some operations the mixers
may be operated only a few hours a day. It should be emphasized that
full-time mixing is, however, the preferred practice.
An improper mixing program could result in process failure. The
active volume available for the digestion process can be greatly
reduced by the formation of a scum blanket or formation of foam when
the scum blanket begins to digest. In two-stage digesters which are
not equipped with positive mixing devices, the scum blankets may be
partly controlled by the use of compressed air to mix the tank contents.
This control measure may be carried out two or three times a year,
depending on the need. Caution: when using air for mixing, great
care must be taken to ensure that the explosive air/gas mixture is not
ignited. Obtain the services of a qualified Safety Officer. Forbid
smoking in plant area, use rubber footwear, use no-sparking tools and
do not bang pipes so as to cause a spark at digester opening. Also,
open as many manholes as possible for ventilation.
Temperature in the secondary digester normally is from 3° to 5°
Centigrade below that of the primary unit. Under normal conditions,
this makes heating of the secondary digester unnecessary except during
the coldest part of the year. But if satisfactory digestion is not
obtained, it may be necessary to increase the temperature. It should
be remembered that the optimum mesophilic digestion is carried out at
between 33 and 35 degrees C. However, lower temperatures may be used
where excess digester capacity is available allowing long sludge
retention times.
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In digesters where heating is provided by external heat exchangers,
the operator should recirculate warm supernatant to the top of the scum
layer at the center of the tank and preferably at one or more additional
points. This procedure will not only increase the temperature of the
scum blanket, but will increase the moisture content of the blanket
thus aiding digestion and increasing its specific gravity causing it
to settle and mix with the rest of the materials in the digester.
Examples of Operating Criteria for Mesophilic Digestion
Loading - 0.05 - 0.15 lbs.vS/ft3/day
Temperature - 35° - 37° C (95 - 98°F)
Retention Time - 20 - 30 days
Volatile Acids - 50 - 250 mg/1
Alkalinity - 2000 - 3000 mg/1
pH - 6.5 - 7.5
SLUDGE TRANSFER
Sludge can be transferred from the first-stage digester to the
second-stage digester by a number of methods; three of which are as
follows:
1. Automatic transfer may be effected by using an
equalizing line, as shown on Diagram Figure 4-5.
2. Sludge may be transferred using the heat exchange
unit recirculating line.
3. Bottom sludge may be pumped to the second stage
unit directly.
Most of the sludge digestion is accomplished in the primary
digester and 90% of the gas production occurs there. The secondary
digester is used basically as a holding tank for separation of the
solids from the liquor and to allow some further digestion of the
volatile matter in the sludge. To accomplish this the secondary
digester must be quiescent or with as little mixing as experience
deems necessary. Therefore, on a normal operation process, when raw
sludge is pumped to the primary digester, an equal volume is transferred
to the secondary digester and settled supernatant from the secondary
digester is returned to the plant. Nevertheless, at least once a
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week, transfer of sludge must be made from the bottom of the first-
stage tank. If this is not done the bottom withdrawal line will
plug up with grit or heavy compacted solids.
SUPERNATANT SELECTION
In a two-stage digestion system the supernatant is obtained from
the second digester. The supernatant can be selected automatically
when a sludge transfer takes place or as a manual operating procedure
when the plant can best receive the extra BOD loading. In either
the fixed-cover or the floating-cover installations, the operater
should select the best quality supernatant for withdrawal. By
observing and sampling material from the various supernatant sampling
lines, the operator can determine the depth of the best material.
Automatic quality selectors are sometimes installed for this purpose.
They should be checked for effectiveness quite frequently and
backflushed when they become clogged.
DIGESTED SLUDGE REMOVAL
Digested sludge should be withdrawn as soon as it has reached
a reasonably good stage of digestion as determined from its volatile
content or at a rate commensurate with minimal supernatant discharges.
In a fixed-cover installation the sludge must be removed in small
batches. If this is not done the gas pressure will not be maintained.
On the other hand, in a digester equipped with a floating cover, the
sludge settled in a second-stage unit may be removed more or less as
convenience requires; moderately large withdrawals will not cause
process failure or loss of gas pressure.
SAFETY CONSIDERATIONS
When withdrawing sludge from a fixed-cover unit, air may be
drawn into the digester creating possible explosive gas mixtures
unless the rate of sludge replacement is equal to the rate of
withdrawl. Equal care must be exercised to keep the liquid level
above the stops of a floating cover if creation of a vacuum is to be
prevented in the tank. For most efficient operation of the digestion
system the withdrawal rate of the sludge from either digester should
be no faster than the rate at which the gas production from the
system is able to maintain a positive pressure in the digester (at
least two inches of water). If the draw operation is too fast the
gas pressure drops due to volume expansion. Some operators prefer
to pump raw sludge to the digester during digested sludge drawoff
to maintain the required positive pressure.
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Learning Resource 2
Sludge Treatment and Disposal
Course Number 166
Anaerobic Digestion II
prepared by Linn-Benton Community College
6500 SW Pacific Boulevard
Albany, OR 97321
prepared for United States Environmental Protection Agency
National Training and Operational Technology Center
26 West St. Clair
Cincinnati, OH 45268
Presented is the second part of a two-part series on Anaerobic
digestion. This lesson emphasizes the classification of digesters
by function, roof design and temperature range. Also discussed are
mixing systems, gas system components, operational control basics,
and safety. The lesson utilizes the audio-visual (slide-tape) format
with accompany printed student materials. The program is designed
for use with any standard 35mm slide projector and a cassettee tape
player. Trainee objectives lesson outline, slide narrative, references,
and student worksheet are included.
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ANAEROBIC DIGESTION II
CONTENTS
Subject Page
Lesson Description AO-1
Estimated Time AO-1
Instructional Materials List AO-1
Suggested Sequence of Presentation AO-1
Required Reading AO-1
Reference Reading AO-1
Objectives AO-2
Lecture Outline AO-3
Narrative AO-8
References AO-14
Answers to Worksheet W-AO-1
Student Materials S-AO-1 thru 16
SW-AO-1 thru 5
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ANAEROBIC DIGESTION II
Lesson Description
This lesson is Part II of a two-part series on Anaerobic Digestion.
Part I should be viewed before Part II. This lesson discusses the
classification of digester by function, roof design and temperature
range. The lesson also discusses mixing systems, gas system components,
operational control basics, and general safety.
Estimated Time
Student preview of objectives 5-10 minutes
Presentation of material 40-80 minutes
Worksheet 10-15 minutes
Correct worksheet and discussion 10 minutes
Instructional Materials List
1. Student text "Anaerobic Digestion Part II"
2. Slide Set "Anaerobic Digestion Part II"
3. Slide Projector
4. Screen
5. Examples of gas safety equipment
Suggested Sequence of Presentation
1. Assign Reading - emphasis on flow diagrams, glossary and
objectives.
2. Show slide tape programs, or lecture using the slides.
3. Open discussion - review plant flow diagrams, safety equipment,
sampling and use of moving averages on trend charts.
4. Assign worksheets.
5. Correct worksheets.
Required Reading
Lesson "Anaerobic Digestion, Part II"
Reference Reading
Operations Manual Anaerobic Sludge Digestion, pages 4-25 through
4-31, 4-16 through 4-18.
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Objectives
Upon completion of this lesson the student should be able to do
the following:
1. Recall the three digester classifications by function.
2. State which digester performs the majority of digestion.
3. Identify digesters by roof design.
4. Recall the name of the most common digestive operating range.
5. State the temperature range for the mesophilic temperature
range.
6. State the normal digestion time for the mesophilic range.
7. Recall the maximum temperature variation allowed for a properly
operated anaerobic digester.
8. State the three types of heat exchanges.
9. Recall which type of heat exchanger is the easiest to maintain.
10. Describe the purpose of mixing.
11. Identify basic gas components.
12. Describe the function of the gas components.
13. Recall the typical volatile slid/ft.3 loading.
14. Recall a typical volatile acid/alkalinity ratio.
15. Identify the five sample points on an anaerobic digester.
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ANAEROBIC DIGESTION II
LESSON OUTLINE
I. Preview
A. Classification by function
B. Classification by roof design
C. Effects of temperature
D. Mixer types
E. Gas system
F. Sample points
G. Testing
H. Safety
II. Classification
A. Function
1. Primary
a) Receive sludge first
b) Majority of digestion
2. Secondary
a) Follows primary
b) Sludge gas storage
c) Multiple digesters - operational flexibility
B. Roof design
1. Fixed
a) Primary
2. Floating roof
a) floats on sludge
b) level controlled by sludge draw off
c) secondary
d) corbels prevent roof from falling
3. Gas Holding
a) floats on gas
b) height controlled by gas and liquid draw off rates
C. Temperature Classification
a) temperature controls digestion time
b) normal mesophilic
c) 95-98°F
d) 20-30 days
e) not vary more than l°F/day
III. Boilers and Heat Exchangers
A. Boiler
1. low pressure
2. uses methane
3. alternate source
B. Heat exchanger
1. internal - coils
a) difficult to maintain temperature
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2. Steam injection
a) internal
b) both heating and mixing
c) boiler water treatment
d) adds extra water
e) maintenance
3. Direct gas
a) heats and mixes
b) danger
4. External
a) ease of maintenance
b) hot water
c) pre-heat sludge
d) circulate sludge next to hot water coils
e) mixing
f) regular cleaning
5. Temperature Control and Efficiency
a) rate of recirculation
b) efficiency of boiler
c) BTU value of gas
d) rate of flow
e) temperature of raw sludge
f) efficiency of heat exchanger
g) l°F/day
IV. Mixing System
A. Contact of sludge and micro-organisms
B. Mixer
1. compressed gas
2. mechanical
3. pumps
V. Gas System
A. Equipment
1. heat sensitive valve
2. flame arresters
3. pressure reducing valve
4. moisture - sedimentation traps
5. orifices - manometers
6. gas meters
B. Designed for safety and control
1. corrosive
2. explosive
VI. Operation Control
A. Major areas
1. bacteria
a) anaerobic
b) slow
c) ratio 20:1
2. Food
a) 5-8% solids
b) no toxic material
c) stable pH
d) constant feed rate
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3. Loading
a) F/M ratio
b) hydraulic loading
c) 0.03 to 0.1 Ibs VS/ft3
d) 20 days retentive time
4. Mixing
a) artificial best
b) loading 0.4 Ibs VS/ft gives natural loading
5. Environmental conditions
a) anaerobic
b) pH 6.8 - 7.2
c) VA 50-300
d) alk 3,000-600 mg/1
e) VA/Alk 0.25 or below
6. Time
a) controlled by loading and temperature
b) 95-98°F, 20-30 days
VII. Sampling and Texting
A. Sampling points
1. digested sludge
2. digesting sludge
a) thief hole
3. raw sludge
4. supernatant
5. gas
B. Typical test pH, %, moisture, temperature, alk, V.A.
C. pH and temperature
1. raw, digested, digesting, supernatant
D. Flow
1. all points
E. Efficiency
1. T.S., % moisture, VS compared between raw and digested
F. Gas
1. C02, Flow
G. Supernatant
1. BOD, S.S. and VSS
H. Control test
1. VA/Alk ratio
2. better than pH
I. Plot on 30-day moving averages
VIII. Safety
A. General
1) rubber-soled shoes
2) relight burner with caution
3) fix leaks ASAP
4) check for combustible gas and 02 in tanks
IX. A. Summary
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Narrative
Slide //
1. Anaerobic Digestion - This is Part II of a two-part series on the
basic theory and operation of anaerobic digesters. The two parts
should be viewed consecutively.
2. This program was written by Mr. E.E. "Skeet" Arasmith. The
instructional development was done by Priscilla Hardin. Mr. Paul
Klopping was the project manager.
3. During this lesson, we will deal with the classification of
digesters by function, roof design and temperature, the effects of
sludge temperature and ways to control that temperature,
4. We will discuss mixer types, the gas system components, specifically
the safety devices and the overall system operation. We will also
discuss six factors that affect operational control, some common
test points and typical tests and finally there will be an overview
of safety considerations.
5. Digesters may be classified by function as to primary, secondary, or
gas-holding.
6. Primary digesters are the units that first receive the sludge - it
is here that the majority of the digestion takes place.
7. Secondary digesters receive digested sludge from the primary
digester. They serve essentially as sludge and gas storage areas.
The third function which a digester may provide is that of gas
holding. Gas holding digesters usually would follow secondary
digesters and collect gas from both primary and secondary digesters.
Having multiple digesters provides an operational flexibility,
especially during start up and digester upset.
8. Primary and secondary digesters may be further classified by roof
design as to fixed or floating roof. The gas holder is a type of
floating roof.
9. With the fixed roof design, gas is stored in the upper portion of
the tank. Gas pressure in the tank is controlled by gas draw off
rate and liquid level.
10. On the other hand, with the floating roof design, the roof floats
on the sludge. With this design, the gas must be drawn off as it
Is produced. There is very little gas storage area.
11. Fixed roof digesters can be identified by the fact that the solid
concrete roof usually is flush with the top of the walls.
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12. On the floating roof digesters the roof may be below or above the
walls, and roof guides are visible around the top edge of the
digester.
13. Primary digesters are usually the fixed roof type, and secondary
digesters are usually the floating roof design.
14. The floating roof allows for unsteady sludge draw off rates so that
disposal maybe periodic rather than constant. To prevent the
roof from falling to the bottom of the digester, steel or concrete
corbels project from the wall of the digester.
15. Digesters that serve the third function, gas holding, require a
special roof design. The roof of this type of digester floats
high above the sludge and is totally supported by the gas pressure
in the digester. Since gas pressure holds up the roof, its
position is controlled by rates of gas produced and gas and/or
sludge draw off.
16. The dome shaped roof makes the gas-holding digester easy to
identify.
17. Besides classifying digesters as to function and roof design, they
may be classified by the operating temperature of the digesting
sludge. There are three typical temperature ranges: psychrophilic,
mesophilic, and thermophilic, the most common of which is the
mesophilic.
18. The length of time required for digestion to come to completion is
a function of the temperature range. Operating within the
mesophilic range at 95-98° F. will normally complete digestion in
20-30 days.
Boilers and Heat Exchangers
19. This temperature should not vary more than 1° F. per day. To
maintain this temperature, a boiler and heat exchanger of some
type are necessary.
20. The boiler is usually of the low pressure type (less than 300 psi)
and fired by the methane in the digester gas. Using the digester
gas to fire the boiler reduces overall energy requirements and
makes the anaerobic digestion process an energy producer rather
than a consumer.
21. Besides having the digester gas available, an alternative energy
source such as natural gas is usually required for start up and
as back up at times of digester upset. During these incidents,
the quality of the gas will deteriorate to the point that proper
temperature can no longer be maintained.
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22. Along with the boiler, there must be a heat exchanger. There are
three basic types: internal, direct gas and external.
23. Internal heat exchangers are usually the hot water type and consist
of a set of internal coils through which the hot water passes.
24. Internal heat exchangers are difficult to maintain and require
efficient mixing to prevent stratification of the sludge.
25. Another type of internal heat exchanger is the steam injection
type - with this style of heat exchange, live steam is bubbled
through the digesting sludge both heating and mixing.
26. This type of heating adds extra water to the sludge. Furthermore,
it requires special chemical treatment of the boiler make up water
and continuous maintenance of check valves to prevent back flow of
sludge into the boiler.
27. Direct gas systems consist of an open flame contained in a hollow
tube below the sludge surface. This type of heat exchanger both
heats and mixes.
28. This type of system offers an obvious safety problem; that is, if
the methane within the digester is ignited by the open flame, a
violent explosion will occur.
29. External heat exchangers are much easier to maintain than either
internal or direct flame and are, therefore, more common. So,
let's look at the process when one of the many external heat
exchangers is used.
30. Hot water from the boiler is passed through a set of tubes within
the heat exchanger. Partially digested sludge is mixed with raw
sludge by the sludge recirculation pump and then circulated through
the spaces between the hot water tubes and then to the digester.
31. The mixing of partially digested sludge with raw sludge improves
heat transfer efficiency. The recirculation pump helps with
mixing.
32. To maintain the heat exchanger efficiently, the tubes must be
cleaned on a regular basis.
33. Controlling the temperature of the sludge and the overall energy
efficiency of the system is primarily dependent upon the BTU value
of the gas and the efficiency of the boiler and heat exchanger.
The efficiency is also effected by the temperature and feed rate of
the raw sludge as well as the recirculation rate of the digested
sludge.
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34. Remember, the temperature must not vary more than IOF. per day.
Fluctuations of greater than one degree per day, even though
within acceptable temperature ranges, will cause digester upset.
Mixing Systems
35. As has been mentioned before, the digestion of raw sludge cannot
take place unless the microorganisms within the digester can come
in contact with the volatile solids within the sludge.
36. This contact is enhanced by continual mixing of the digesting
sludge. Several methods of mixing are used. They include:
37. Compressing the gas that is produced and forcing it back through
the digesting sludge, or one of several types of mechanical mixers,
or a combination of mechanical mixers and pumps, such as the heat
exchanger recirculation pumps.
Gas System
38. As has been mentioned previously, one of the major by-products of
the anaerobic digestion process is the production of digester gas,
which is mostly methane.
39. Because of the explosive nature of the gas, special equipment is
required for safe handling. This is true regardless of the major
use of the gas.
40. To prevent flash fires in the digester, flame arresters are
installed on the top of the digester as well as all other gas
exit points.
41. Heat sensitive valves are installed at various points in the gas
system to help prevent explosion as a result of a fire within the
gas system.
42. Pressure within the gas system is maintained by a compressor and
various pressure regulation valves.
43. The functional quality of the gas is improved by the reduction of
moisture and sediment by moisture and sediment traps.
44. The rate of gas flow is measured by sharp edged orifices and
indicated on manometers.
45. Gas consumption is measured by the typical gas meter.
46. When digester gas systems are properly designed they operate safely
while controlling a steady pressure and removing sedimentation and
moisture plus monitoring both gas flow and consumption.
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47. Digester gas is not easily stored in a typical gas container due
to its corrosive and explosive nature. Therefore, any excess that
is produced is consumed via a waste gas burner.
48. To obtain optimum digestion from the digester, six factors must be
controlled.
49. They are bacteria, food, loading, mixing, environmental conditions
and time.
50. The bacteria of major concern are the methane producers which are
strict anaerobes. To protect their environment, all air must be
prevented from entering the digester.
51. These organisms are rather slow in their digestion process;
therefore, a ratio of 20 times more seed organisms than food is
required. That is, each day, only one Ib. of food should be fed
for each 20 Ibs. of organisms in the digester. That is why it
normally takes 20 days or more to complete digestion.
52. The food should be of high quality.
53. To be high quality, the raw sludge should contain a low volume of
water. It should contain no toxic materials, and have a stable
pH. The rate and frequency of feed must be constant.
54. Loading refers to both the food to organisms ratio and the hydraulic
loading.
55. The food to organisms ratio for conventional operations will range
from 0.03 to 0.1 Ibs. of volatile solids per cubic foot of digester
sludge. Hydraulic loading affects detention time. The detention
time must be long enough to allow for complete digestion, which
may be 20 days or more.
56. The food must mix with the organisms. Mixing may be natural or
artifical. However, artifical mixing gives the best results and
reduces dead spots.
57. As mentioned before, the environmental conditions must be strictly
anaerobic, and a volatile acids to alkaline ratio of 0.25 or below
will maintain a steady pH.
58. Digestion time is relative to temperature and controlled by loading.
That is, at 95-98°F. a detention time of 20-30 days should be
maintained.
59. To control the digester, it is necessary to monitor regularly at
various points. Samples should be collected from raw sludge,
digester sludge, digested sludge, supernatant and gas. Digested
sludge is usually collected through special sampling holes called
thief holes.
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60. One or more of these thief holes are located on the roof of the
digester.
61. Samples collected from these points should be evaluated by
laboratory tests. Tests such as pH, percent of moisture, temperature,
alkalinity, and volatile acids are among the many required
monitoring tests.
62. Raw sludge, digesting sludge, digested sludge, and supernatant are
all checked for pH and temperature. These tests should be run and
compared at least daily.
63. Sludge and gas flow are measured at all entrance and exit points on
the digester.
64. To determine the efficiency of the digester, total solids, percent
moisture, and volatile solids tests are run on the raw sludge and compared
with digesting and digested sludge. These same tests are conducted
on the supernatant to determine its quality and ultimate effect on
the other treatment processes.
65. The percent of C02 in the digester gas as well as flame color
indicates gas quality and digester performance. To determine the
effect of supernatant on the other treatment processes, both BOD
and S.S. are monitored.
66. The ultimate control tests for digester operations are volatile
acids and alkalinity. This ratio indicates impending changes in
the pH of the digester and, thus, the health of the methane formers.
A change in VA/Alk ratios will indicate possible digester
problems long before a change in pH can be measured.
67. For best control, trend charts of all parameters should be
established with 30 day moving averages.
68. To prevent accidents with digesters, the following precautions
should be considered. Wear rubber soled shoes when walking on
the roof. Never smoke around the digester vents. Relight the
waste gas burner with caution.
69. Fix gas leaks ASAP. Never enter a partially full or empty
digester without checking for oxygen depletion and explosive gases.
70. During this lesson, we have seen that digesters are classified three
ways: by function, by roof design, and by operating temperature.
The mesophilic temperature classification is the most common.
71. We learned that digester temperature is controlled by a heat
exchanger and that the sludge temperature must be controlled within
1° F/day.
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72. We looked at several types of mixers and learned that mixing improves
digestion.
73. We previewed the basic components of the gas system and learned that
the system is designed to control the pressure of the gas, remove
sediment and moisture, measure flow and consumption and protect
the digester from fire and explosion.
74. We saw that for proper operational control, the digester must be
monitored and special control tests run on the samples collected.
75. And, finally, we discussed some general safety precautions that
should be considered when working in and around digesters.
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ANAEROBIC DIGESTERS II
References
"Operations Manual; Anaerobic Sludge Digestion," EPA, 430/9-76-001,
Cincinnati, OH, 1976.
"Manual of Practice #11 Operation of Wastewater Treatment Plants,"
WPCF, Lancaster Press, Lancaster, PA, 1976.
"Operation of Wastewater Treatment Plants," Kenneth D. Kerri,
Sacramento State College, Sacramento, CA, 1980.
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ANAEROBIC DIGESTION II
WORKSHEET
1. Digestion may be classified by function. On the list below, place
an "X" beside the three terms used to describe these three functions:
a. digestion
x b. primary
c. solids reduction
d. conditioning
X e. secondary
f. gas production
g. energy cost savings
h. gas producers
X i. gas holding
2. Find the correct name for this digester in the above list and write
the corresponding letter in the following blank: B .
3. Select the proper name for the most common digester operating range.
X a. mesophilic
b. psychrophilic
c. esophilic
d. thermophilic
e. none of the above
4. Select the temperature range for the most common digester operating
range.
a. 65-78° F
b. 79-95° F
X c. 95-98° F
d. 98-108° F
e. none of the above
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5. For a normally operated anaerobic digester operating within the
typical temperature range, complete sludge digestion should take
place in:
a. 10-20 days
_X b. 20-30 days
c. 30-35 days
d. 40-50 days
e. none of the above
6. Using the pictures below, identify each of the digesters by roof
design.
A. gas holding
B. fixed
C. floating
D. floating
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7. In order to maintain an anaerobic digester in optimum condition,
the digester siudge temperature should not change more than ^_^_
degrees F. per day.
a. 4
b. 3
c. 2
_X d. 1
e. none of the above
3. From the list below, select the three most common types of heat
exchangers.
a. internal combustion engine
X b. direct gas flame
c. low pressure
d. coil type
X e. internal
f. draft tube
X g. external
h. boiler
9. From the previous list, indicate the type of heat exchanger that
offers the easiest maintenance.
10. The major purpose for mixing is to : (select one)
X a. bring food and microorganisms into contact.
b. break up the scum blanket.
c. reduce energy requirements by circulation heated sludge.
d. release gas from the sludge particles.
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1 1 . Hatch the list of gas handling equipment on the left with the list
of functions on the right. (An answer may he used more than once.)
P ___ flame arresters a . improve gas quality
E waste gas burner b. measure gas consumption
B gas meter c. measure, gas flow
D heat sensitive valve d. safety
C sharp edged orifice e. disposal of excess gas
__A moisture traps
A _ sediment traps
12. Typical volatile solids/ft. loadings for an anerobic digester
might be:
a. 0.004 to 0.04 lbs./ft.3
b. 0.04 to 0.4 lbs./ft.3
x c. 0.03 to 0.1 lbs./ft.3
d. 0.03 to 1.0 lbs./ft.3
e. all of the above
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13. Using the drawing above, match the items indicated with the
description.
A flame arrester
F waste gas burner
E gas meter
D heat sensitive valve
B moisture and sediment traps
C manometers
14. The most common volatile acids to alkalinity ratio for an anaerobic-
digester would be:
a. 0.25
b. 150
c. 0.4
X d. 0.25
e. 0.4
15. Using the diagram below, indicate what material is being sampled at
each point.
D supernatant B gas
A raw sludge E digested sludge
C digesting sludge
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Learning Resource 3
"Anaerobic Digestion"
Wastewater Treatment Plant Operator Training Program
Intermediate Course - Volume B
Water Pollution Control Federation
2626 Pennsylvania Avenue, N.W.
Washington, DC 20037
Presented are selected parts of a training program designed for
those already employed as wastewater treatment plant operators. The
leral objective of the program is to prepare students for further
ids-on and skills training in unit process operation.
gen
hands
This part of the unit describes the purpose and the methods of
anaerobic digestion. Also examined is the activity that occurs in
the anaerobic digester. Performance objectives, unit objectives,
instructional resources, instructor activities, and discussion
questions are included.
The unit uses the audio-visual (slide-tape) formate with an
accompanying printed student workbook. The audio-visual portion of
the program is designed for use with any standard 35mm slide projector
and a cassette tape player. Pre- and post-tests are provided within
the student workbooks.
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UNIT 8B - PRE-TEST
NAME: DATE:
The following questions are designed to help you find out how much you
already know about what we are going to be talking about in the next
Unit. This will give you a better idea about how much you have learned
by going through the Unit. Answer each question carefully, and where
necessary in your own words. Don't worry if you can't answer some of
the questions — you're not expected to be able to.
1. Put an "X" beside each of the following statements that is a reason
for and result of anaerobic digestion:
a. ^_^__^ production of a sludge easier to dewater.
b. elimination of all odors.
c. __^__ lowering in the number of pathogens.
d. reduction in the volume of solids.
2. What are the two different kinds of bacteria involved in the
anaerobic digestion process?
b.
3. Briefly explain how these two different kinds of bacteria work
together.
4. Which of these two different kinds of bacteria is more sensitive?
5. a. If organic loadings are too high, what will happen to the
balance between the bacteria?
b. If organic loadings are too low, what will happen to the balance
between the bacteria?
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6. About what percentage of the gases produced in the digester is
methane?
7. Why is it important to provide mixing in the digester?
8. Sludge that is easily dewaterable, does not smell too bad, has a
lumpy black appearance, and does not have grey streaks in it is
(well/incompletely) digested sludge.
9. Give a brief description of a:
a. two-stage digestion set-up
b. one-stage digestion set-up
10. It is expected that the liquid level will vary greatly in a digester
with a fixed cover.
TRUE FALSE
11. The bottoms of digesters are cone-shaped. Why?
12. It is important that the temperature of the digester be kept at a
constant temperature, someplace in the range of 90 to 98°F. How
is this done?
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13. What important control do we have over gas pressure or vacuum build-
ups in the fixed-cover digester?
14. There is water vapor in the gas removed from the digester,. As the
gas cools in the pipes, this water vapor condenses and forms water,
Where is this water collected?
15. What are the two ways used to provided mixing in the digester?
a.
b.
16. In terms of good digester results, what are the two main things
that we are looking for?
a.
b.
17. What are the two main indicators that we can use to warn us about
possible digester problems?
a.
b.
18. If we are getting indications of digester problems, can you list
at least two things that should be checked?
b.
When you have completed your answers and are ready to check them, go on
to the next page.
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ANSWERS TO
UNIT 8B - PRE-TEST
Check over your answers, remembering that we are more concerned with
you having the right idea than the same words as given here. Points
allotted for each question are indicated in parentheses.
1. (four points)
a. X
b.
c. X
d. X
2. (two points)
a. acid-forming bacteria
b. methane-producing bacteria
3. (four points) The acid-forming bacteria digest the organics in the
sludge producing acid as they do so. Too much would upset the
process. The methane-producing bacteria eat the acid, and thus
keep the process going.
4. (one point) methane-producing bacteria
5. (four points)
a. Acid forming bacteria will multiply rapidly and produce too much
acid. The methane-producing bacteria will not be able to handle
it all, and the process will fail.
b. There will not be enough acids produced to keep enough methane
producers alive. This means that even a small increase in
loading will be too much for the methane producers to handle
and the process will fail.
6. (one point) 65%
7. (two points) Mixing helps prevent a scum blanket from forming at
the top of the digester. It also helps distribute heat, prevent
dead areas, and helps to mix microorganisms and sludge.
8. (one point) well
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9. (four points)
a. Two stage digestion involves two tanks. In the primary
digester, the sludge is heated, mixed and broken down. The
secondary digester is used as a holding tank (a secondary
clarifier), where the supernatant is separated from the
sludge.
b. The digestion process happens in one tank. Mixing has to be
stopped before supernatant is withdrawn.
10. (one point) FALSE
11. (one point) This helps the sludge settle, and allows the thickest
sludge to be removed from the digester.
12. (one point) A sludge recirculation system is used to pass sludge
through a heat exchanger to keep the temperature in the proper
range.
13. (one point) pressure vacuum relief valve
14. (one point) drip traps
15. (two points)
a. mechanical mixing
b. gas mixing
16. (two points)
a. reduction in the volume of organic solids
b. a good supernatant
17. (two points)
a. volatile acids level
b. gas production
18. (two points) Any two of the following:
a. temperature
b. mixing system
c. hydraulic overloading
How well did you make out? Mark your score here.
out of 36
Now let your program administrator know that you are ready to begin
studying Unit 8B. Do not go on to the next page until after you have
completed the Unit 8B Tape 1 audio-visual program.
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UNIT 8B - SUMMARY
TAPE 1
The following summarizes what has been talked about so far in Unit 8B,
Tape 1. Read this summary over carefully, making sure that you
understand each of the points mentioned.
Reasons for and results of sludge digestion:
- production of a sludge easier to dewater;
- reduction of odors;
- lowering in the number of pathogens; and
- reduction in the volume of solids.
Anaerobic digestion is a biological process that makes use of two
different kinds of bacteria.
- Acid forming bacteria: These bacteria form acids as they
digest organics in the sludge. They keep on growing and
reproducing as long as food is available. They also keep
on producing acid as they work.
- Methane producing bacteria: The methane producing bacteria
provide the balance to the acid forming bacteria. The
methane producing bacteria eat the acid produced by the
acid-producing bacteria, and keep the process working. If
there were too much acid, the digestion process would stop.
The acid formers will survive as long as there is food available. But
the methane producers are sensitive and can only operate under anaerobic
conditions. Even changes in loading, pH, or temperature will affect
methane producers. Methane producers work best at a constant
temperature someplace between 90 and 98°F. They don't like changes
of more than 1°F per day.
If the methane producers cannot work, there will soon be too much acid
in the digester. The color of the sludge will become dirty grey, and
there will be a strong sour smell. Once it starts, the situation will
get worse.
Acid-forming bacteria form volatile acids. These volatile acids are
eaten by the methane producing bacteria, which change the acid into
methane, carbon dioxide, and water.
There has to be a proper balance between the acid forming and methane
producing bacteria.
- If the organic loading is too high, then the acid forming
bacteria will multiply rapidly and produce a large amount
of acid. The methane producing bacteria will not be able
55
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to handle it all, and the extra acid will lower the pH in
the digester. The process will fail.
- If the organic loading is too low, there will not be
enough acids formed to keep a reasonable number of methane
producers alive. Even a small increase in loading will be
too much for the methane producers to handle. The process
will fall.
There are gases produced in the digester. About 65% is methane, 30%
carbon dioxide, and 5% other gases like nitrogen and hydrogen. (In the
Basic Course, we had lumped this 5% in with the methane.)
Mixing in the digester is important because it helps prevent a scum
blanket from forming at the top of the digester liquid. Mixing also
helps distribute heat, prevent dead areas, and helps to mix the
microorganisms and the sludge.
When mixing is stopped, a supernatant forms. It includes the water that
was formed during the digestion process. This supernatant is put back
through the plant because it is high in suspended solids and B.O.D.
Well digested sludge is easily dewaterable and does not smell too bad.
It has a lumpy black appearance.
Incompletely digested has an extremely strong sour smell, and has grey
streaks in it.
Properly digested sludge is dewatered, and then disposed of on approved
land or land fills.
We can talk about two different anaerobic digestion set-ups.
- Two-stage digestion: Two tanks are involved. The first is
called the primary digester. It is used to heat, mix, and
break down raw sludge. The second tank is called the
secondary digester. It is used as a holding tank and
essentially is a secondary clarifier. In the secondary
digester, the supernatant is separated from the sludge.
Most of the decomposition and gas production takes place in the primary
digester.
When raw sludge is pumped to the primary digester, about the same
amount of digested sludge is transferred to the secondary digester.
The one-stage digestion set-up is more difficult to operate because
everything has to happen in the same tank. Also, all mixing has to
stop for several hours before any supernatant can be drawn off.
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If a digester has a fixed cover, then every time raw sludge is added,
about the same amount of supernatant has to be displaced because the
liquid in the digester is kept at ahout the same level.
If the digester has a floating cover, the roof can move up and down.
This means that the liquid level in the digester can vary.
The bottoms of all digesters are cone-shaped so that the thickest sludge
can be removed from the digester.
The sludge recirculation system keeps the contents of the digester
at the proper temperature. This diagram shows how digester sludge
passes through the heat exchanger:
D—4 to digester
hot water inlet
from digester
HOT WATER BATH
recirculating
pump
water outlet
Supernatant drawoff lines are set up so that the operator can choose
where he will withdraw from.
Gas from the digester is drawn off and carried to the boiler if the
methane is being used as fuel, or to the waste gas burner.
It is important that a close watch be kept on the gas produced in the
digester. If there is too much gas in a fixed cover digester, there
will be a build-up of pressure. On the other hand, if there is a rapid
drop in the level of the liquid, a vacuum could develop. Either way,
the digester cover could be damaged.
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One of the safeguards against pressure or vacuum build-ups is the
pressure-vacuum relief valve. If the pressure is too great, gas is
released. If there is a vacuum, air will be sucked in. Often, water
seals can be used as well.
Even if there are water seals or pressure-vacuum relief valves, this
does not allow you to disregard what is happening to gas pressure, in
the digester. If the methane and air are allowed to mix, an
explosive combination could result.
Manometers outside the digester tell you what the pressure is inside
the digester. The actual control of the gas pressure takes place on
the waste gas burner line by the pressure regulating valve.
Pipes carrying digester gas have drip traps, where condensed water
vapor from the digester gas will collect. These drip traps have to be
drained regularly.
Mixing in the digester can be done either mechanically, or by gas.
- Mechanical mixing: A propeller is attached to a shaft
which goes through the cover. A motor turns the shaft
and creates mixing action in the digester.
- Gas mixing: Basically, some digester gas is taken from
the digester, passed through a compressor, then forced
back into the digester a few feet from the bottom of the
digester. The gas bubbling back to the surface causes
mixing of the sludge.
When you have completed this review and are sure of all the points, tell
your program administrator that you are ready to go on to Unit SB
Tape 2 audio-visual program.
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UNIT 8B - SUMMARY
TAPE 2
In this part of the summary we will review the main points about
anaerobic digester control. Be sure that you understand each of the
points mentioned.
In terms of digester control, what we are looking for is:
- a reduction in the volume of organic solids; and
- the production of a good quality supernatant.
Inorganic solids are not affected in the digestion process, but there
are changes in organic or volatile solids.
Some of the organic or volatile solids are changed to water and gas in
the digester. In a properly operated digester, there should he an
organic solids reduction of about 40 to 60%. That is, the digestion
process reduces the amount of organic solids by about one-half.
If the supernatant is not as good as it should be, you probably need a
longer settling time before any supernatant is withdrawn.
There are two indicators that warn us if we are running into digester
problems:
- Volatile acids level: If there is a drastic change from your
digester's usual volatile acids level, or if the volatile
acids level reaches 2000 mg/1, you can expect digester
problems.
- Gas production and quality: Normally the gas produced in the
digester is about 65% methane, 30% carbon dioxide, and 5%
other gases. Your warning sign is a drop in the methane
concentration, or an increase in the carbon dioxide
concentration. Normally the methane burn-off flame will be
blue with only a trace of yellow. It will be almost
invisible in sunlight. As the methane concentration drops,
the flame will become yellower. With less methane, red
tongues and a little black smoke may appear, or the flame
may go out.
If your indicators are showing that you might be running into problems,
here are the things you should check:
- temperature: The temperature of the digester should be kept
constant, someplace between 90 and 98°F. A temperature
change of more than a couple of degrees in the past week, or
more than one degree in any one day, could be the cause of
the problem.
-------
- mixing system: Is the mixing system working properly? If
the plant has an intermittent mixing system, increase how
often and how long mixing takes place.
- hydraulic loading: Hydraulic loading is the number of days
that the liquid stays in the digester. In a heated, mixed
digester, the detention time is 10 to 15 days. If the
detention time is too short, the digestion process will
probably not be complete. If you cannot increase the
detention time, try to feed a more concentrated sludge to
the digester. You always have to be careful that you are
not pumping too much water - or grit - to the digester. Try
shorter and more frequent pumping of sludge to the digester.
MORE POINTS ABOUT DIGESTER OPERATION
If you are already operating an anaerobic digester, these extra points
may help you out a bit, until you are able to take the skill training
program on the anaerobic digester.
Digester LoadjLng
It would be ideal if raw sludge could be pumped to the digester
continuously. But this is not possible. Smaller plants that are
supervised for only eight hours a day may only load the digester three
times a day (eight in the morning, noon, and three in the afternoon).
In larger plants where automatic pumping is possible, pumping may be
so frequent that it is almost continuous. If there is 24-hour
supervision of the plant, and pumping is manually controlled, there may
be six to eight pumping cycles every day.
If sludge is being pumped to the digester for too long a period it may
become too thin and there will be too much extra water being pumped to
the digester.
Sludge Transfer
Moving sludge from the primary to the secondary digester can be done from
the top or the bottom of the primary digester. It is a good idea,
though, to use the bottom lines at least one a week, so that they will
not plug up with grit and solids.
Supernatant Selection
It is hard to get a good supernatant from a single stage digester. Still,
you should try to remove excess liquid. Mixing devises should be shut
off for a while before supernatant is withdrawn. Experience will tell
you how long a settling time is needed to get a good supernatant. If
you have a number of supernatant draw-off lines, you should use the one
that gives the best supernatant.
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In two-stage digesters, the supernatant is drawn off from the secondary
digester. The supernatant might be selected automatically when a
sludge transfer takes place, or the supernatant might be withdrawn when
the plant can best take the extra B.O.D. loading. The equipment you
have available will determine how and when supernatnat is withdrawn.
You should carry out a suspended solids test on the supernatant. If the
suspended solids levels are more than 5000 to 7500 mg/1, you can
probably expect problems to develop in other parts of the plant.
Digested Sludge Removal
When you are taking out sludge from a fixed cover digester. This would
draw in air and create an explosive condition. Your best bet is to
pump only small amounts, and if possible, raw sludge should be added
at the same time so that the liquid level in the digester stays the same.
In single-stage digesters, sludge should be removed as often as possible.
It will be hard to get a concentrated sludge from the single-stage
digester. In fact, a 3 to 4% sludge is considered good for an activated
sludge plant using a single-stage digester. To judge the stability of
the sludge and its concentration, you should be using the total, and
the volatile solids tests.
A two-stage digester will produce a more concentrated sludge. If at
least one of the digesters has a floating cover, then you can remove
the sludge from the secondary digester whenever it is convenient.
Because the tanks are connected and at least one of the digesters has
a floating cover, taking out a lot of sludge at one time will not disturb
the process or cause a loss of gas pressure. Again, you should be
using the total, and the volatile solids tests to evaluate the stability
of the sludge and its concentration.
This is the end of the review for this Unit. Before going on to the
review exercise, however, you should check over the complete summary,
just to be sure that you have not missed any of the points.
When you are ready, go on to the review exercise on the next page.
61
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UNIT 8B - REVIEW EXERCISE
Answer the following questions as best you can, in your own words
where necessary.
1. We mentioned four results of the sludge process. Do you recall
what they are?
a.
b.
d.
2. There are two different kinds of bacteria involved in the anaerobic
digestion process. What are they? Briefly describe what each
kind does.
b.
3. These bacteria will survive as long as there is food available.
4. These bacteria are sensitive and can only operate under anaerobic
conditions.
5. There has to be a proper balance between these two different kinds
of bacteria.
a. What will happen if the organic loading is too high?
62
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b. What will happen if the organic loading is too low?
6. Normally about what percentage of the gases produced in the digester
is methane?
7. What are some of the reasons why it is important to have mixing in
the digester?
3. How would you describe:
a. a well-digested sludge?
b. an incompletely digested sludge?
9. Briefly describe the difference between two-stage and one-stage
operation.
10. Changes in gas pressure and liquid level are not as critical in the
cover digester.
11. Why are the bottoms of digesters cone-shaped?
63
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12. What is the purpose of the sludge recirculation system?
13. What is done with the gas that has been removed from the digester?
14. Briefly describe the double purpose of the pressure vacuum relief
valve.
15. What is the purpose of the drip traps?
16. What are the two ways in which mixing can be accomplished in the
digester?
a.
b.
17. In terms of digester control, what are the two things that we are
looking for?
a.
b.
18. What are the two indicators that we use to get warnings of digester
problems? Briefly describe each.
64
-------
b.
19. If you are getting warnings that there are digester problems, what
three things should you check?
a.
b.
When you have completed your answers and are ready to check them over,
go on to the next page.
65
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ANSWERS TO
UNIT 8B - REVIEW EXERCISE
In checking your answers, remember that we are more concerned that you
had the right idea rather than the exact words as given here.
Points are given for each question so that you can grade yourself.
1. (four points)
a. production of a sludge easier to dewater
b. reduction of odors
c. lowering in the number of pathogens
c. reduction in the volume of sludge
2. (four points)
a. Acid forming bacteria: These bacteria form acids as they digest
organics in the sludge. They keep on growing and reproducing
as long as there is food available.
b. Methane producing bacteria: These bacteria provide the balance
to the acid forming bacteria. They eat the acid produced by
the acid forming bacteria, and thus keep the process working.
(If there were too much acid, the digestion process would stop.)
3. (one point) acid forming bacteria
4. (one point) methane producing bacteria
5. (four points)
a. Acid forming bacteria will multiply rapidly and produce a large
amount of acid. The methane producing bacteria will not be
able to handle it all. The extra acid will lower the pH in the
digester, and the process will fail.
b. There will not be enough acid formed to keep a reasonable number
of methane producing bacteria alive. Even a small increase in
loading will be too much for the methane producers to handle,
and the process will fail.
6. (one point) 65%
7. (two points) Mixing helps prevent a scum blanket from forming at the
top of the digester liquid. It helps distribute heat, prevent
dead areas, and helps to mix the microorganisms and the sludge.
66
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8. (two points)
a. Well-digested sludge is easily dewaterable, and does not smell
too badly. It has a lumpy black appearance.
b. Incompletely digested sludge has a strong sour smell, and grey
streaks in it.
9. (three points) Two tanks are involved in two-stage digestion. The
primary digester is used to heat, mix and break down raw sludge.
The secondary digester acts as a holding tank, and essentially is
a secondary clarifier. Supernatant is separated from the sludge
in the secondary digester. In one-stage digestion, everything has
to happen in one tank.
10. (one point) floating cover
11. (one point) This allows the thickest sludge to be removed from the
digester.
12. (one point) The sludge recirculation system keeps the contents of
the digester at the proper temperature.
13. (two points) The gas is carried to the boiler if it is being used
as fuel, or to the waste gas burner *
14. (two points) The pressure-vacuum relief valve helps prevent gas
pressure or vacuum build-ups in the digester. Too much pressure
lifts the weights and allows the extra gas to escape. A vacuum
forces a valve open to let air into the digester.
15. (one point) The drip traps collect the water that is condensed
inside the pipes carrying the digester gas.
16. (two points)
a. mechanical mixing
b. gas mixing
17. (two points)
a. a reduction in the volume of organic solids
b. the production of a good quality supernatant
18. (four points)
a. Volatile acids level: The volatile acids level should be about
50 to 300 mg/1.At 1000 mg/1 there will be too much acid
produced and the process is likely to fail. At 2000 mg/1,
there is not much you can do to stop the digestion process
from failing.
67
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b. Gas production: Normally the methane burn-off flame is blue
with only a trace of yellow. As the methane production drops,
the flame will become yellower. Red flames and black smoke
may appear, or the flame may go out.
19. (three points)
a. temperature
b. mixing system
c. hydraulic loading
How well did you do? Mark your score here:
out of 41
If you score 33 or more points, you are doing fine. That is at least
On the other hand, if you scored less than 33 points, you should review
the points you had trouble with. If you want to go over this Unit
again, now is the time to do so.
When you are ready to try the final exercise for Unit 8B, see your
program administrator.
68
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UNIT SB - POST-TEST
NAME: DATE:
The following questions relate to the things you have studied in this
Unit. Answer each of the questions as best you can in your words.
1. Put an "X" beside each of the following statements that is a reason
for and result of anaerobic digestion:
a. production of a sludge easier to dewater.
b. elimination of all odors.
c. lowering in the number of pathogens.
d. reduction in the volume of solids.
2. What are the two different kinds of bacteria involved in the
anaerobic digestion process:
b.
3. Briefly explain how these two different kinds of bacteria work
together.
4. Which of these two different kinds of bacteria is more sensitive?
5. a. If organic loadings are too high, what will happen to the
balance between the bacteria?
b. If organic loadings are too low, what will happen to the balance
between the bacteria?
69
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6. About what percentage of the gases produced in the digester is
methane? ____ %
7. Why is it important to provide mixing in the digester?
8. Sludge that is easily dewaterable, does not smell too bad, has a
lumpy black appearance, and does not have grey streaks in it is
(well/incompletely) digested sludge.
9. Give a brief description of a.:
a. two-stage digestion set-up
b. one-stage digestion set-up
10. It is expected that the liquid level will vary greatly in
digester with a fixed cover.
TRUE FALSE
11. The bottoms of digesters are cone-shaped. Why?
12. It is important that the temperature of the digester be kept at a
constant temperature, someplace in the range of 90 to 98°F. How
is this done?
70
-------
13. What important control do we have over gas pressure or vacuum
build-ups the fixed-cover digester?
14. There is water vapor in the gas removed from the digester. As the
gas cools in the pipes, this water vapor condenses and forms
water. Where is this water collected?
15. What are the two ways used to provided mixing in the digester?
b.
16. In terms of good digester results, what are the two main things
we are looking for?
a.
b.
17. What are the two main indicators that we can use to warn us about
possible digester problems?
a.
b.
18. If we are getting indications of digester problems, can you list
at least two things that should be checked?
a.
b.
When you have completed your answers to this Post-Test, see your
program administrator.
71
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Learning Resource 4
Field Manual for Performance Evaluation and Troubleshooting at
Municipal Wastewater Treatment Facilities
prepared by Culp/Wesner/Culp
Clean Water Consultants
prepared for U.S. Environmental Protection Agency
Office of Water Program Operations
Washington, DC 20460
Presented is part of a manual designed to provide technical
guidance for persons conducting evaluations of wastewater treatment
plants and serve as a model which can be used by state regulatory
agencies. Common operating problems with anaerobic digesters are
identified by defining the indicators. Once the problem has been
identified, certain monitoring, analyses, and/or inspections that
must be performed prior to making a decision are discussed. Corrective
measures to be utilized are detailed.
73
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TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
1. A rise in the vola-
tile acid/alkalinity
(VA/Alk. ) ratio.
PROBABLE CAUSE
la. Hydraulic overload
caused by storm
infiltration, acci-
dental overpumping,
withdrawing too
much sludge.
Ib. Organic overload.
Ic. Discharge of toxic
materials to diges-
ters such as heavy
metals, sulfides,
ammonia.
CHECK OR MONITOR
la. Jtonitor the follow-
ing twice daily
until problem is
corrected :
- volatile acids
- alkalinity
- temperature
Ib. Monitor sludge pump-
ing volume, amount o:
volatile solids in
feed sludge; check
for increase in sep-
tic tank sludge dis-
charged to plant or
industrial wastes.
Ic. Volatile acids, pH,
gas production;
check industrial
wastes at source;
check for inadequate
sludge pumping gener-
ating sulfides.
SOLUTIONS
la. If ratio increases to 0.3:
(1) add seed sludge from
secondary digester (or)
(2) decrease sludge withdrawal
rate to keep seed sludge
in digester (and/or)
(3) extend mixing time.
(4) check sludge temperatures
closely and control heat-
ing if needed.
Ib. See la.
Ic. Use any or combination of the
following:
(1) solids recycle.
(2) liquid dilution.
(3) decrease feed concentraticr
(4) precipitate heavy metals
with sulfur compound. Be
sure pH in digester is
greater than 7.0.
(5) Use iron salts to pre-
cipitate sulfides.
(6) institute source control
program for industrial
wastes.
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
2. CC>2 in gas starts to
increase.
3. pH starts to drop
and CX>2 increases to
the point (42-45%)
that no burnable gas
is obtained.
4. The supernatant qual-
ity returning to
process is poor,
causing plant upsets.
PROBABLE CAUSE
2. VA/Alk. ratio has
increased to 0.5.
3a. VA/Alk. ratio has
increased to 0.8.
4a. Excessive mixing
and not enough
settling time .
4b. Supernatant draw-
off point not at
same level as super-
natant layer.
4c. Raw sludge feed
point too close to
supernatant draw-
off line.
4d. Not withdrawing
enough digested
sludge .
CHECK OR MONITOR
2a. Waste gas burner.
2b. Gas analyzer.
3a. Monitor as indicated
above .
3b . Hydrogen sul f ide
(rotten egg) odor.
3c. Rancid butter odor.
4a. Withdraw sample and
obse rve separ at ion
pattern.
4b. Locate depth of
supernatant by samp-
ling at different
depths.
4c. Determine volatile
solids content.
Should be close to
value found in well
mixed sludge and
much lower than raw
sludge.
4d. Compare feed and
withdrawal rates -
check volatile
solids to see if
sludge is well-digest
SOLUTIONS
2. See Item 1 and start adding
alkalinity using the volatile
acids to calculate the amount .
3a. Add alkalinity.
3b. Decrease loading to less than
0.01 Ib vol. solids/cu ft/day
until ratio drops to 0.5 or
below.
4a. Allow longer periods for
settling before withdrawing
supernatant.
4b. Adjust tank operating level or
draw-off pipe.
4c. Schedule pipe revision for
soonest possible time when
digester can be dewatered.
4d. Increase digested sludge with-
drawal rates. Withdrawal
should not exceed 5% of
digester volume per day.
ed.
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
5. Supernatant has a
sour odor from either
primary or secondary
digester.
6. Foam observed in
supernatant from
single stage or
primary tank.
7. Bottom sludge too
watery or disposal
point too thin .
PROBABLE CAUSE
5a. The pH of digester
is too low.
5b. Overloaded digester
("rotten egg odor"}-
5c. Toxic load (rancid
butter odor) .
6a. Scum blanket break-
ing up.
6b. Excessive gas
recirculation.
6c. Organic overload.
7a. Short-circuiting.
7b. Excessive mixing.
7c . Sludge coning , al low
ing lighter solids
to be pulled into
pump suction.
CHECK OR MONITOR
5a. See Item 3.
5b. See Item 3.
5c. See Item Ic.
6a. Check condition of
scum blanket.
6b. 20 CFM/1,000 cu ft
is adequate.
6c. Volatile solids
loading ratio.
7a. Draw-off line open
to Supernatant Zone .
7b. Take sample and ched<
how it concentrates
in setting vessel.
- 7c. Total solids test or
visual observation.
SOLUTIONS
4e . Review feasibility of adding
powdered carbon to digesters
with consultant or regulatory
agency.
5a. See Item 3.
5b. See Item 3.
5c. See Item Ic.
6a. Normal condition but should
stop withdrawing supernatant
if possible.
6b. Throttle compressor output.
6c. Reduce feeding rate.
7a. Change to bottom draw-off line.
7b. Shut off mixing for 24-48 hours
before drawing sludge.
7c. (1) "Bump" the pump 2 or 3 times
by starting and stopping.
(2) Use whatever means available
to pump digester contents
back through the withdrawal
line.
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
8. Sludge temperature
is falling and can
not be maintained at
normal level.
PROBABLE CAUSE
8a. Sludge is plugging
external heat
exchanger.
8b . S ludge reci rculat ion
line is partially or
completely plugged.
8c. Inadequate mixing.
8d. Hydraulic overload.
CHECK OR MONITOR
8a. Check inlet and out-
let pressure or
exchanger.
8b. Check pump inlet and
outlet pressure.
8c. Check temperature
pro fi le in dige ste r .
8d. Incoming sludge
concentration .
SOLUTIONS
7c, (continued)
(3) If available, attach a water
hose to the pump suction
line and force water through
it. (Water source must be
nonpotable.) Run for no mort
than 2 or 3 min to avoid
diluting the digester
8a. Open heat exchanger and clean.
8b. (1) Backflush the line with
heated digester sludge.
(2) Use mechanical cleaner.
(3) Apply water pressure. Do
not exceed working line
pressure .
(4) Add approx. 3 lb/100 gal
water of trisodium phos-
phate (TSP) or cornmerical
degreasers. (Most conven-
ient method is to fill scum
pit to a volume equal to
the line, add TSP or other
chemica 1 , then admit to the
line and let stand for an
hour. )
8c. Increase mixing.
8d. See Item la.
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TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
9 . S ludge temperature
is rising.
10. Recirculation pump
not running; power
circuits O.K.
11. Gas mixer feed lines
plugging.
PROBABLE CAUSE
8e. Low water feed rate
in internal coils
used for heat ex-
change .
8f. Boiler burner not
firing on digester
gas.
8g. Heating coils inside
digester have coat-
ing.
9. Temperature control-
ler is not working
properly.
10. Temperature override
in circuit to prevent
pumping too hot water
through tubes .
lla. Lack of flow
through gas line.
lib. Debris in gas lines.
CHECK OR MONITOR
8e. (1) Air lock in
line.
(2) Valve partially
closed.
8f. (1) Low gas pressure.
( 2 ) Unburnable gas
due to process
upset.
8g. Temperature of inlet
and outlet water is
about the same.
9. Check water tempera-
ture and controller
setting.
10. Visual check, no
pressure on sludge
line.
11. Identify low tempera-
ture of gas feed
pipes or low pressure
in the manometer.
SOLUTIONS
8e. (1) Bleed air relief valve.
(2) Upstream valve may be
partially closed.
8f . (1) Locate and repair leak.
(2) See Item 3.
8g, (1) Remove coating, may require
draining tank.
(2) Control water temperature to
130°F maximum.
9. If over 120°F, reduce tempera-
ture. Repair or replace
controller.
lOa. Allow system to cool off.
lOb. Check temperature control
circuits .
lla. Flush out with water.
lib. Clean feed lines and/or valves.
lie. Give thorough service when tank
is drained for inspection .
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TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICA TORS/OBSERV A TIONS
12. Gear reducer wear
on mechanical mixers.
13. Shaft seal leaking
on mechanical mixer.
14. Wear on internal
parts of mechanical
mixer.
15. Imbalance of internal
parts because of ac-
cumulation of debris
on the moving parts
of mechanical mixers
(large-diameter im-
pellers or turbines
would be affected
most) .
PROBABLE CAUSE
12a. Lack of proper
lubrication.
12b. Poor alignment of
equipment.
13. Packing dried out
or worn.
14. Grit or misalignment
15. Poor comminution
and/or screening.
CHECK OR MONITOR
12a. Excessive motor
amperage , excessive
noise and vibration,
evidence of shaft
wear .
12b. See Item 15
13. Evidence of gas leak-
age (evident odor of
gas) .
14. Visual observation
when tank is empty,
compare with manu-
facturer ' s drawings
for original size.
Motor amperage will
also go down as mov-
ing parts are worn
away and get smaller.
15 . Vibration , heating
of motor, excessive
amperage , noise .
SOLUTIONS
12a. Verify correct type and amount
of lubrication from manufac-
turer's literature .
12b. Correct imbalances caused by
accumulation of material on
the internal moving parts.
13a. Follow manufacturer's instruc-
tions for repacking.
13b. Replace packing any time the
tank is empty if it is not
possible when unit is operat-
ing.
14. Replace or rebuild - experience
will determine the frequency
of this operation.
15a. Reverse direction of mixer if
it has this feature.
15b. Stop and start alternately.
15c. Open inspection hole and
visually inspect.
15d. Draw down tank and clean mov-
ing parts.
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TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
16. Rolling movement of
scum blanket is
slight or absent.
17. Scum blanket is too
high.
18. Scum blanket is too
thick.
19. Draft tube mixers
not moving surface
adequately.
PROBABLE CAUSE
16a. Mixer is off.
16b. Inadequate mixing.
16c. Scum blanket is too
thick.
17. Supernatant overflow
is plugged.
18. Lack of mixing, high
grease content.
19. Scum blanket too high
and allowing thin
sludge to travel
under it.
CHECK OR MONITOR
16a. Mixer switch or
timer.
16c. Measure blanket
thickness.
17. Check gas pressure,
it may be above nor-
mal or relief valve
may be venting to
atmosphere .
18. Probe blanket for
thickness through
thief hole or in gap
beside floating covei
19. Rolling movement on
s ludge surface .
SOLUTIONS
16a. May be normal if mixers are
set on a timer. If not and
mixers should be operating,
check for malfunction.
16b. Increase mixing.
16c. See Items 18 and 19.
17- Lower contents through bottom
drawof f then rod supernatant
line to clear plugging.
18a. Break up blanket by using
mixers.
.18b. Use sludge recirculation pumps
and discharge above the
blanket.
18c. Use chemicals to soften
blanket.
18d. Break up blanket physically
with pole.
18e. Tank modification.
19a. Lower sludge level to 3-4"
above top of tube allowing
thick material to be pulled
into tube - continue for 24-
48 hours.
19b. Reverse direction (if possible)
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
20. Gas is leaking
through pressure re-
lief valve (PRV) on
roof.
21. Manometer shows
digester gas pressure
i s above no rma 1 .
22. Manometer shows
digester gas pres-
sure below normal.
23. Pressure regulating
valve not opening as
pressure increases.
PROBABLE CAUSE
20. Valve not seating
properly or is
stuck open.
21a. Obstruction or
water in main burner
gas line.
21b. Die,, ster PRV is
stuck shut.
21c. W^ gas burner
1 i . ! ) re s s ure con-
tr< ilve is closed
22a. Too fast withdrawal
causing a vacuum in-
side digester.
22b. Adding too much lime
23a. Inflexible diaphragm
23b. Ruptured diaphragm.
CHECK OR MONITOR
20. Check the manometer
to see if digester
gas pressure is
normal.
21a. If all use points
are operating and
normal, then check
for a waste gas line
restriction or a
plugged or stuck
safety device.
21b. Gas is not escaping
as it should.
21c. Gas meters show ex-
cess gas is being
produced, but not
going to waste gas
burner.
22a. Check vacuum breaker
to be sure it is
operating properly.
22b. Sudden increase in
CO in digester gas.
23a. Isolate valve and
open cover.
23b. Visual inspection .
SOLUTIONS
20. Remove PRV cover and move
weight holder until it seats
properly. Install new ring
if needed. Rotate a few times
for good seating.
21a. Purge with air, drain conden-
sate traps , check for low
spots. Care must be taken
not to force air into
digester.
21b. Remove PRV cover and manually
open valve, clean valve seat.
21c. Re level floating cover if gas
escapes around dome due to
tilting.
22a. Stop, supernatant discharge
and close off all gas outlets
from digester until pressure
returns to normal .
22b. Stop addition of lime and
increase mixing.
23a. If no leaks are found (using
soap solution) diaphragm may
be lubricated and softened
using neats-foot oil.
23b. Ruptured diaphragm would re-
quire replacement .
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICA TORS/OBSER VA TIONS
24. Yellow gas flame
from waste gas
burner.
{propeller or lobe
type) .
26. Gas meter failure
(bellows type) .
27. Gas pressure higher
than normal during
freezing weather.
PROBABLE CAUSE
24. Poor quality gas with
a high CO content.
25b. Mechanical failure.
26a. Inflexible diaphragm
26b. Ruptured diaphragm.
27a. Supernatant line
plugged.
2 7b . P re ssure re 1 ie f
stuck or closed.
CHECK OR MONITOR
24- Check CG>2, content
will be higher than
normal .
line.
25b. Fouled or worn
parts.
26a . Isolate valve and
open cover.
26b. Visual inspection.
27a. Supernatant over-
flow lines.
27b. Weights on pressure
relief valves.
SOLUTIONS
24. Check concentration of sludge
feed - may be too dilute. If
so, increase sludge concentra-
tion. See Items 2 and 3.
.
digester and working from
digester toward points of
usage.
25b. Wash with kerosene or replace
worn parts.
26a. If no leaks are ,found (using
soap solution) diaphragm may be
lubricated and softened using
neats-foot oil.
26b. Replace diaphragm.
26c. Metal guides may need to be
replaced if corroded.
27a. Check every two hours during
freezing conditions, inject
steam, protect line from
weather by covering and in-
sulating overflow box.
27b. If freezing is a problem, apply
light grease layer impregnated
with rock salt .
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICA TORS/OBSERVA TIONS
28. Gas pressure lower
than normal.
29. Leaks around metal
covers.
30. Suspected gas leaking
through concrete
cove r .
31. Floating cover tilt-
ing, little or no
scum around the edges
PROBABLE CAUSE
2Sa. Pressure relief
valve or other pres-
sure control devices
stuck, open.
28b. Gas line or hose
leaking.
29. Anchor bolts pulled
loose and/or sealing
material moved or
cracking.
30. Freezing and thawing
causing widening of
construction cracks.
31a. Weight distributed
unevenly.
CHECK OR MONITOR
28a. Pressure relief
valve and devices.
28b. Gas line and/or hose.
29. Concrete broken around
anchors , tie- downs
bent, sealing mater-
ials displaced.
30. Apply soap solutions
to suspected area and
check for bubbles.
31a. Location of weights.
SOLUTIONS
28a. Manually operate vacuum relief
and remove corrosion if present
and interferring with operation.
28b. Repair as needed.
29. Repair concrete with fast seal-
ing concrete repair material.
New tie- downs may have to be
welded onto old ones and re-
drilled. Tanks should be
drained and well ventilated for
this procedure. New sealant
material should be applied to
leaking area.
30. If this is a serious problem,
drain tank , clean cracks and
repair with concrete sealers.
Tanks should be drained and
well ventilated for this pro-
cedure .
31a. If moveable ballast or weights
are provided, move them around
un ti 1 the cove r is le ve 1 . If
no weights are provided, use
a minimal number of sand bags
to cause cover to level up.
(Note: pressure relief valves
may need to be reset if signi-
ficant amounts of weight are
added. )
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
32. Floating cover tilt-
ing, heavy thick scuir
accumulating around
edges.
33. Cover binding even
through rollers and
guides are free .
PROBABLE CAUSE
31b. Water from conden-
sation or rain water
collecting on top of
metal cover in one
location .
32a. Excess scum in one
area, causing excess
drag.
32b. Guides or rollers
out of adjustment.
32c. Rollers or guides
broken.
33. Internal guide or guy
wires are binding or
damaged (some covers
are built like umbrel-
las with guides
attached to the cen-
ter column ) .
CHECK OR MONITOR
31b. Check around the
edges of the metal
cove r . { Some cove rs
with insulating
wooden roo f s have
inspection holes for
this purpose . )
32a. Probe with a stick
or some other method
to de te rmi ne the con-
dition of the scum.
32b. Distance between
guides or rollers
and the wall.
32c. Determine the normal
position if the sus-
pected broken part
is covered by sludge
Verify correct loca-
tion using manufac-
turer' s information
and/or prints if
necessary.
33. Lower down to corbels
Open hatch and using
breathing apparatus &
explosionproof light,
if possible, inspect
from the top. If
cover will not go all
SOLUTIONS
31b. Use siphon or other means to
remove the water. Repair roof
i f leaks in the roof are con-
tributing to the water problem.
32a. Use chemicals or degreasing
agents such as Digest- aide or
San fax to soften the scum,
then hose down with water.
Co n t i n ue on re gular basis e ve r
two to three months or more
frequently if needed.
32b. Soften up the scum (as in 32a)
and readjust rollers for
guides so that skirt doesn't
rub on the walls.
32c. Drain tank if necessary taking
care as cover lowers to cor-
bels not to allow it to bind
or come down unevenly. It may
be necessary to use a crane or
jacks in order to prevent
structural damage with this
case .
33 . Drain and repair , holding the
cover in a fixed position if
necessary.
-------
TROUBLESHOOTING GUIDE
ANAEROBIC DIGESTION
INDICATORS/OBSERVATIONS
PROBABLE CAUSE
CHECK OR MONITOR
SOLUTIONS
33.(continued)
the way down, it may
be necessary to secure
in one position with a
crane or by other mean:
to prevent skirt dam-
age to sidewalls.
-------
-------
Learning Resource 5
"Second Stage Digestion"
Criteria for the Establishment of Two-Year Post High School
Wastewater Technology Programs (CEWT), Plant Operations for
Wastewater Facilities, Part C - September 1975
Charles County Community College
Greenville Technical College
Linn-Benton Community College
Clemson University
Clemson, SC
Presented is an excerpt from the instructor's guide for a
learning module on a floating-cover, second-stage digester unit with
gas storage. The module is organized around sixteen objectives common
to all processes. Each module is designed to help the instructor plan
a course of study for the operation of a treatment process using the
composite model plant process unit. Material in the module can be
adapted for courses which upgrade the training of operators in normal
operations procedures, abnormal operations procedures, preventive
maintenance procedures, or corrective maintenance procedures.
Each module begins with a statement of purpose that explains what
the student will be studying. Next, all the objectives of the module
and code numbers keyed to a computerized list of instructional
resources are listed. Also included are conditions of learning,
acceptable performance levels, instructor activity, and student
activity. Evaluation techniques are suggested. Examples for the
first five objectives are presented.
87
-------
MODULE 12
SECOND STAGE DIGESTION
A floating-cover unit
with gas storage
Composite Model Plant Unit L
PURPOSE: In this module the student will learn to perform all the
activities in the objectives as they apply to a floating-
cover unit with gas storage. READ PAGES 1 TO 11 BEFORE
USING THIS MODULE.
OBJECTIVES: 12.1 Identify the second stage digestion unit.
12.2 Describe the second stage digestion process in
technical and nontechnical terms.
12.3 Describe the safety procedures for the second
stage digestion unit and explain how the procedures
protect employees and visitors.
12.4 Identify the components of a second stage digestion
unit. Explain the purpose of each component, how
the component works and why it is important.
Describe the normal operation procedures for the
second stage digestion unit components.
Perform the normal operation procedures for the
second stage digestion unit.
Describe and perform the start-up and shut-down
procedures for the second stage digestion unit.
Describe the abnormal operation procedures for the
second stage digestion process.
Describe the preventive maintenance procedures for
the second stage digestion unit.
10 Perform the preventive maintenance procedures for
the second stage digestion unit.
12.11 Describe the corrective maintenance procedures for
the second stage digestion unit components.
12.12 Perform the corrective maintenance procedures for
the second stage digestion unit components.
12.13 Perform the safety procedures for the second stage
digestion unit and demonstrate how they protect
employees and visitors.
12.14 Compare other second stage digestion units to the
floating-cover unit with gas storage (composite
model plant unit L).
12.15 Name and locate the components of the second stage
digestion unit. Name and select reference
materials which explain the normal operation
procedures, the purpose of each component, how the
component works and why it is important.
12.5
12.6
12.7
12.8
12.9
12
-------
12.16 Perform the abnormal operation procedures for the
second stage digestion unit.
RESOURCES: 3 116 120 125 126 141 143 144 185 307 308
309 314 315 316 317 320 321 324 421 459 511
551 552 553 554 937 990 1033 1034 1399
OBJECTIVE 12.1 Identify the second stage digestion unit.
CONDITIONS: Given a unit, a model of a unit or a
photograph of a unit.
ACCEPTABLE PERFORMANCE: The student will:
Indicate whether the process unit is used
for second stage digestion.
INSTRUCTOR ACTIVITY: 1. Point out characteristics which
distinguish the second stage digestion
unit from other process units.
STUDENT ACTIVITY: 1. Develop a picture file of second stage
digestion units. Mark distinguishing
characteristics.
OBJECTIVE 12.2: Describe the second stage process in
technical and nontechnical terms.
CONDITIONS: Given photographs of the second stage
digestion unit.
ACCEPTABLE PERFORMANCE: The student will:
Describe the second stage digestion unit,
explaining the meaning of:
anaerobic digester
digester
digestion tank
sludge digester
Describe the purpose of second stage
digestion.
89
-------
INSTRUCTOR ACTIVITY:
STUDENT ACTIVITY:
OBJECTIVE 12.3
CONDITIONS:
Describe how second stage digestion
affects.
sludge conditioning
sludge dewatering
solids disposal
flow measurement
pumping and piping
1. Use diagrams, photographs and slides to
describe second stage digestion.
2. Describe the second stage digestion
process during a plant tour. React to
the student's description of the process.
1. Describe the second stage digestion
process while viewing photographs,
diagrams and slides.
2. Observe and describe the second digestion
process during a plant tour.
***** *****
Describe the safety procedures for the second
stage digestion unit and explain how the
procedures protect employees and visitors.
Given a list of operation and maintenance
procedures.
ACCEPTABLE PERFORMANCE: The student will:
Describe the safety procedures for the
second stage digestion unit, commenting
on:
High-risk activities
opening digester cover access hatches
removing debris from channels
working near sources of gas leakage
working with switches in automatic
position
Sources of danger
acid wastes
caustic wastes
deep wells
electrical equipment
explosive gases
90
-------
INSTRUCTOR ACTIVITY:
STUDENT ACTIVITY:
fire
moving parts
open doors and covers
slippery walks
toxic gases
welding torch
Safety equipment
explosion proof electrical fixtures
fire-fighting equipment
first aid kit
flame arrester
flame trap
gas masks
handrails
no smoking signs
nonsparking hand tools
pressure relief valve
protective clothing
safety treads on ladders and stairs
vacuum relief valve
vents
Explain how the procedures protect
employees and visitors.
1. Discuss treatment plant case histories.
2. Describe the conditions in a plant and
ask for evaluation.
3. Describe the safety procedures for each
operation and maintenance procedure
4. Prepare slides of sources of danger and
high-risk activities.
1. Read case histories and comment on
employee safety procedures.
2. Evaluate conditions which the instructor
has described. Suggest remedies.
3. Role play operation or maintenance
procedures. Select proper safety equipment
and name the sources of danger and high-
risk activities. Develop a manual of
safety procedures for the second
stage digestion unit.
4. Identify sources of danger and high-risk
activities pictured in slides.
***** *****
91
-------
OBJECTIVE 12.4:
CONDITIONS:
Identify the components of a second stage
digestion unit. Explain the purpose of each
component, how the component works and why it
is important.
Given a second stage digestion unit, unit
components or a diagram, model or photographs
of a unit and a list of components.
ACCEPTABLE PERFORMANCE: The student will:
INSTRUCTOR ACTIVITY:
Identify components of the second stage
digestion unit and associated equipment.
boiler
fire-fighting equipment
first-aid kit
floating cover
gas recirculation unit
compressor
oiler
pressure gage
valve
valve timer
manometer
meter
motor
piping
pressure relief valve
recirculation pump
sludge pump
switchgear
vacuum relief valve
water trap
Explain the purpose of each component, how
the component works and why it is
important.
Point out and name components in diagrams,
photographs or models.
Arrange photographs or models of
components in the workshop for student
identification.
Point out and name components during a
plant tour.
Question the students about the purpose
of each component, how the component
works and why it is important.
92
-------
STUDENT ACTIVITY:
OBJECTIVE 12.5:
CONDITIONS:
1. Identify the components which the
instructor names on diagrams, photographs
or models.
2. Identify the components at stations in
the workshop in writing.
3. Identify components during a plant tour.
4. Explain the purpose of each component,
how the component works and why it is
important.
***** *****
Describe the normal operation procedures for
the second stage digestion unit components
listed in Objective 12.4.
Given a second stage digestion unit or slides
or photographs of a second stage digestion
unit, a list of components of the unit, a
checklist of characterists and a normal
operation procedures manual.
ACCEPTABLE PERFORMANCE: The student will:
Describe the characteristics of each
component which the operator checks to
determine whether the component is
functioning normally, commenting on:
color
corrosion
motion
odor
position
pressure
sound
temperature
vacuum
vibration
Name the sense or indicator which monitor
each characteristic.
Explain how often the characteristics of
each component must be checked and why the
component indicate that it is not functioning
normally, including:
93
-------
INSTRUCTOR ACTIVITY:
STUDENT ACTIVITY:
making adjustments
deciding about corrective maintenance
reporting to supervisors
reporting in written records
Explain why a component's characteristics
must be returned to normal.
Describe routine sampling for the second
stage digestion process.
List routine calculations for the second
stage digestion process.
Describe routine procedures for recording
data.
Describe the characteristics of the
components of the second stage
digestion unit.
Describe the normal operation procedures
for the second stage digestion unit.
Use color pictures.
Describe the normal operation procedures
during a slide show of components of
the second stage digestion unit.
Describe and explain the"normal operation
procedures during a plant tour. Listen
to the student's description of the
procedures.
Develop a checklist, listing the
components of the second stage digestion
unit and their normal characteristics.
Develop a manual of normal operation
procedures.
Describe the normal operation procedures
during a slide show of components of the
second stage digestion unit.
Observe and describe the normal operation
procedures during a plant tour.
94
-------
Learning Resource 6
"Anaerobic Digestion and Analytical Control"
Slide Cassette XT-34 - 13 minutes
Available on loan from:
National Training and Operational Technology Center
26 West St. Clair
Cincinnati, OH 45268
Discussed are the anaerobic decomposition processes utilized to treat
organic materials in wastewater, the environmental conditions required
for the involved bacteria, and a description of the related process
control analyses. The program is designed for experienced wastewater
treatment plant operators who wish to upgrade plant performance and
to increase their own knowledge and skills. References and instructions
for the unit are provided.
Slide number Material presented in slide
1 Caption - Anaerobic Digestion and Analytical
Control
2 Three steps in treatment of organic wastes
3 Basic technology
4 Energy sources - organic materials
5 Bacteria
6 Anaerobic decompositions
7 Volatile organic matter
8 Digestion processes
9 Liquefaction
10 End products of liquefaction
11 End products of gasification
12 Balanced digestion processes
13 Stages of digestion
14 Graph
15 Acid fermentation stage
16 High acidity - low pH
17 Facultative organisms
18 Acid regression stage
19 Bicarbonate alkalinity
20 Alkaline fermentation state
21 Types of bacteria
22 Biological oxidation of organic wastes
23 Environmental characteristics of bacteria
24 Grow fast
25 pH independent
26 Temperature independent
27 Stimulated by oxygen
28 Characteristics of methane forming bacteria
29 Grow slow
30 Temperature dependent
31 Sudden temperature changes
32 pH dependent
33 Subject to oxygen toxicity
95
-------
Slide number Material presented in slide
34 Operation of an anaerobic digester
35 Analytical control
36 Analysis of sludge supernatant
37 Criteria for performance evaluation
38 Volatile acid to alkalinity ratio
39 Volatile acids determination in the
laboratory
40 Adding indicator
41 Adding sample to fritted glass crucible
42 Applying suction
43 Adding chloroform-butanol reagent
44 Titration
45 Column partition chromatography
46 Routine process control
47 Importance of volatile acid determination
48 Alkalinity
49 Test for alkalinity
50 Analyses of ammonia
51 Total organic nitrogen
52 Kjedahl nitrogen determination
53 Nitrogen content in sludge
54 COD test
55 COD criteria for a good supernatant
56 pH
57 Monitoring gas production
58 Environmental conditions
59 Need for analytical controls
60 Credits
61 Clean water
96
-------
Learning Resource 7
Standard Operating Job Procedures for Wastewater Treatment Plant
Unit Operations. SOJP 10-Digestion
Prepared by Charles Country Community College
Prepared for U.S. Environmental Protection Agency
Office of Water Program Operations
Manpower and Training Staff
Presented is a guide for the development of standard operating
job procedures for the digestion process. Following a brief
description of the process and equipment use, operating procedures
and step sequence are provided for safety inspection, tank and
structure inspection, equipment and electrical inspection, primary
digester start-up, continuous shift operation, shut-down procedures,
and equipment maintenance.
97
-------
STANDARD OPERATING JOB PROCEDURES
C.M. Schwing
SOJP NO 10 Prepared by T.T. Schwing Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES
A. I'RLSTART UP 11
1. Safety
Inspection
2. Tank and
Structure
Inspection
STEP SEQUENCE
SI'liCTION PROCliDURLS
1 . Make certain all
valves are closed.
2. Lock out all switch
gear.
I. Physically inspect the
interior of all tanks
for obstruction.
2. Replace and seal all
inspection parts.
3. Check all lines for
leaks .
4. Fill all digesters witl
water or raw sewage to
operating level in
primary digesters and
just enough to float
covers of secondary
digesters .
5. Close valves listed in
previous step.
INFORMATION/OPERATING GOALS/SPECIFICATIONS
1. If valves' operation is not proper-stop
1. Remove all foreign objects such as
containers, woodscraps, welding rods,
ladders , et c .
TRAINING
GUIDE NOTE
V.I
X 1 1 . 1
XII .2
V.8
XII. 3
SOJP NO
10
-------
STANDARD OPERATING JOB PROCEDURES
C.M. Schwing
SOJP NO 10 Prepared by T.T. Schwing Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES
3. iiquipment
Inspecti on
4 . Electrical
I nspect ion
STEP SEQUENCE
I. Check all manometers
for proper fluid.
2. Check all gas meters
for proper operation.
3. Check sludge recircu-
lation pumps for
proper operation.
4. Check sludge drawoff
pump for proper
operation .
5. Check heat exchangers
for proper operation.
6. Check pressure and
vacuum relief valves
for proper operation.
7. Check gas recirculatioi
unit for proper
operation.
1. Check electrical
switch gear for proper
nomenclature and make
certain explosion-
proof fixtures are
intact.
L. Unlock and activate
switch gear.
INFORMATION/OPERATING GOALS/ SPECIFICATIONS
1. Kefer to Manufacturers bulletin
1. Refer to Manufacturers bulletin
1. Refer to Manufacturers bulletin
1. Refer to Manufacturers bulletin
1. Kefer to Manufacturers bulletin
1. Refer to Manufacturers bulletin
1. Refer to Manufacturers bulletin
1. Refer to equipment maintenance records for
overload heater proper size.
1. Measure voltage at all points up to motor
disconnect .
TRAINING
GUIDE NOTE
V.3
V.4 , XI .1
V.5
V. £
V.b
V.7
Xll .4
V.8
XII .4
V.9
XII. 5
SOJP NO
11)
-------
STANDARD OPERATING JOB PROCEDURES
C.M. Scliwing
SOJP NO 10 Prepared by T.T. Schwinf> Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES
STEP SEQUENCE
3. Activate explosive
gas detector and
alarm system.
INFORMATION/OPERATING GOALS/SPECIFICATIONS
1. Refer to Manufacturers instructions.
TRAINING
GUIDE NOTE
V. 10, XI . 1
X11.6
SOJP no
10
-------
STANDARB OPERATING JOB PROCEDURES
C.M. Schwing
SOJP NO 10 Prepared by '[,'[, Schwim; Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES! STEP SEQUENCE
B. STARTU11 PUOC1-I
1. Primary
Digester
Startup
UUiiS
1. Heat »1 and 03
digesters to operating
temperature .
2. Maintain digester at
operating temperature.
3. Add seed sludge from
a well operated
digester .
4. Add sludge at the rate
of 5 pounds of volatile
solids per day/per
1000 cu.ft. of capacity
INFORMATION/OPERATING GOALS/SPECIFICATIONS
1. To achieve goal, start up heat exchangers
as outlined in 0 tj M manual for this unit
Open valves 4, 6, 7, 8, 9, and 10; start
recirculat ion pumps 1 and 2. Auxiliary
fuel will have to be used for this step.
1. To achieve this goal, by-pass heat
exchanger by opening valves 18, 19, 20,
and 21 and closing valves 7 and 8 until
temperature drops l°f and then go back to
normal valve arrangement. Continue to
recirculate the contents by the use of
the recirculat ion pumps.
1. Seed sludge should be about 201 of the
volume of the digester being started up.
1. Determine pll, total solids, volatile
total solids, alkalinity and volatile
acids on all sludge added to digesters.
TRAINING
GUIDE NOTE
1.2
V.5
1.2
1.2
III . 1
V11.3
X. 1
SO.IP NO
10
-------
STANDARD OPERATING JOB PROCEDURES
SOJP HO
PROCESS
10
Uigest ion
Prepared by
Approved by
C.M. Schwing
T.T. Schwing
Date 4-73
OPERATING PROCEDURES
STEP SEQUENCE
INFORMATION/OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
6 .
7.
If gas production, pll,
and alkalinity increase
increase the sludge
feed rate to 10 pounds
of volatile solids per
day/per 1000 cu.ft. of
capacity. This may
take 60 days. If
good digestion
operation continues,
increase sludge feed
at increments of 5
pounds of volatile
solids/per day/per
1000 cu.ft. of capacity
until a loading of
50 pounds of volatile
solids per day/per
1000 cu.ft. is
achieved.
When sufficient gas is
available, start up
gas recirculation unit
After initial digester
is in operation, make
all transfers to other
primary unit and
proceed through steps
B.I through 11.6 above.
The pll should rise to approximately
6.8-7.2; alkalinity should increase to
about 1800 ppro. SI'LC.IAL NOTU: In general
do not expect the volatile acids to drop
until organic feed rate is stabilized.
III.l
VI.1
VII.1
V11I .1
X.I
1. See manufacturers operations bulletin.
WARNING: Do not permit digester gas
pressure to fall below 0.5" W.C.
V.8,
VII. 1 i,
VIII.1
XII.7
SOJP NO 10
-------
STANDARD OPERATING JOB PROCEDURES
SOJP HO
10
PROCESS Digestion
Prepared by
Approved by
C.M. Schwing
T.T. Schwinfi
Date 4-73
OPERATING PROCEDURES
STEP SEQUENCE
INFORMATION/OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
After both primary
digesters are
successfully operating
make transfers to
secondary digesters.
-------
STANDARD OPERATING JOB PROCEDURES
SOJP NO
PROCESS
10
Digestion
C.M. Schwing
Prepared by T.T. Schwing
Approved by
Date 4-73
OPERATING PROCEDURES
INFORMATION/OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
STEP SEQUENCE
C. CONTINUOUS OPIRATING PROCEDURES
1.
Continuous
Shift
Operation
Pump raw sludge for
thickener or other
units on a continuous
basis if at all
possible.
2. Grab sample and
composite.
1. Raw sludge pumped
2. Transfer sludge
3. Digested sludge
4. Supernatant
5. Gas
3. Observe operation of
heat exchangers for
proper temperature.
1.
2.
Sample should be analyzed for pi
solids, volatile total solids.
total
Sample should be analyzed for pll, total
solids, volatile total solids.
3. Sample should be analyzed for pll, total
solids, volatile total solids.
4. ' Sample should be analyzed for pll, total
solids, volatile total solids.
5. Sample should be analyzed for methane
concentration.
1.2
III. 1
VIII. 1
X.I
VII.2
SOJP NO
10
-------
STANDABD OPERATING JOB PROCEDURES
C.M. Schwing
SOJP NO 10 Prepared by T.T. Schwing Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES
2. l:very 4 Hours
STEP SEQUENCE
4. Observe operation of
all pumps for proper
operation .
5. Observe operation of
gas reci rculat ion unit:
for proper operation.
I. Record the following
meter readings:
1. Volume of gas
from each
digester .
2. Volume of gas to
waste.
3. Volume of gas to
other process
units .
4. Volume of raw
sludge to digester
5. Volume of digested
sludge from
digester.
6. VoJuino of super-
natant .
INFORMATION/ OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
IV. 1, XI. 1
X I II . 1
SOJP NO
10
-------
STANDARD OPERATING JOB PROCEDURES
C.M. Schwing
SOJP NO 10 Prepared by T.T. Schwing Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES
3. livery Shift
4. Daily
STEP SEQUENCE
2. Record the following
manometer readings:
1. liach digester
2. Service line
3. Waste line
3. Record the elevation
of the floating
covers .
1. Place composite
samples in central
sample storage.
2. Complete shift report.
1 . Replace recorder
charts .
1. Carefully calculate
24 hour flows.
2. Check recorder pen
for proper inking.
2. Complete daily and
monthly log sheets.
INTORMATION/OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
IV. 1
X 1 1 1 . 1
IV. 1, X.I
IV. 1
X1I1 . 1
IV. 1, XI. 4
XI I . 1
IV. 1
XIII. 1
SOJP NO
10
-------
STANDARD OPERATING JOB PROCEDURES
SOJP HO
PROCESS
10
Digesti on
Prepared by
Approved by
C.M. Schwina
T.T. Schwing
Date 4-73
OPERATING PROCEDURES
INFORMATION/OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
STEP SEQUENCE
U. SHUT DOWN PIU
CCDURl-S
The Shut Down
Procedure is
for taking the
digester out
of service for
cleaning.
Stop feeding raw
sludge or transferring
sludge to the unit at
least one week prior
to expected shut down
date.
2. When gas production
has fallen off to a
minimum, close gas
valve.
3. Open hatches to
atmosphere.
4. If primary digester,
pump sludge to other
primary and/or
secondary digesters.
1. If secondary
digester, withdraw
as much superna-
tant as possible
back to plant.
SOJP NO
10
-------
SOJP NO
PROCESS
10
STANDARD OPERATING JOB PROCEDURES
Digestion
C.M. Schwing
Prepared by T.T. Schwing
Approved by
Date 4-73
OPERATING PROCEDURES
STEP SEQUENCE
INFORMATION/OPERATING GOALS/SPECIFICATIONS
TRAINING
GUIDE NOTE
5. Pump digested sludge
to disposal as long
as possible.
When sludge can no
longer be withdrawn
by normal pumping,
ventilate digester
space above liquid by
discharging fresh air
into digester.
7. Use Stang deluge
nozzle or fire hoses
to break up sludge,
scum, and grit
deposit.
8. Recirculate contents
with trash pump.
9. Pump homogenized
sludge to disposal.
10. When digester is empty
continue ventilation
and then do inspection
tor determining
maintenance required.
11. After required
maintenance, go back
to startup procedures.
WARNING: Uo Not enter digester unless
equipped with breathing apparatus.
30JP NO
10
-------
STANDARD OPERATING JOB PROCEDURES
C.M. Sell wing
SOJP NO 10 Prepared by -f.T, Schwina Date 4-73
PROCESS Digestion Approved by
OPERATING PROCEDURES
li. I'RliVliNTIVI: M.
1 . Equipment
Maintenance
STEP SEQUENCE
INTENANCE (MAY Bli DONE BY
1. Inspect pumps
2. Lubricate motors
3. Check motor
electrically
4. Inspect switch gear
annually.
5. Inspect pressure
relief valves
annually.
6. Inspect all flame
arresters annually.
7. Calibrate flow meters.
INFORMATION/OPERATING GOALS/SPECIFICATIONS
THE US)
1. See Manufacturers 0 fj M Manual
1. See lubrication schedule for proper
lubricant and interval.
1. Record:
1. Voltage
2 , Amperage
3. Insulation resistance
1. See Manufacturers 0 (, M Manual
••> ...
1. See Manufacturers 0 (, M Manual
1. See Manufacturers 0 (-; M Manual
TRAINING
GUIDE NOTE
IV. 1, V,
IX. 1
XIII. 1
IV. 1, V,
IX. 1
XIII. 1
IV. 1 , V,
IX. 1
XIII. 1
IV. 1, V
IX. 1
XIII. 1
IV. 1, V
IX. 1
XIII. 1
IV. 1, V
IX. 1
XIII. 1
IV. 1, V
IX. 1, XI. 1
XIII . 1
SOJP NO 10
-------
STANDARD OPERATING JOB PROCEDURES
SOJP HO
PROCESS
10
Digestion
C.M. Schwing
Prepared by T.T. Schwing
Approved by
Date 4-73
OPERATING PROCEDURES
STEP SEQUENCE
INFORMATION/OPERATING (XMLS/SPECIFICATIONS
TRAINING
GUIDE NOTE
8. Inspect heat
exchangers annually.
9. Paint floating covers
as necessary. «
1. See Manufacturers 0
7
M Manual
Notify fire underwriters inspector in
sufficient time for inspection of dewatere
uni t .
IV.1, V
IX.1
XI11.1
IV.1, V
IX.1
XIII.1
80JP NO
10
-------
Learning Resource 8
Operation of Wastewater Treatment Plants: A Field Study
Training Program
Second Edition
Prepared by California State University, Sacramento
Kenneth D. Kerri, Project Director
Prepared for U.S. Environmental Protection Agency
Office of Water Program Operations
Municipal Permits and Operations Division
This lesson stresses the importance of sound and thorough daily
operational checks in combination with adequate sampling and neat,
well-organized records of the resulting data to the successful
operation of a digestion system. Presented is a checklist intended
to belp the operator remain "on-top" of the system. The list is
general in nature and serves as a model for the preparation of a
similiar anaerobic sludge digestion checklist. Plotting certain
operational data in graphic form is stressed.
Ill
-------
CHAPTER 12. SLUDGE DIGESTION AND SOLIDS HANDLING
(Lesson 5 of 6 Lessons)
12.4 OPERATIONAL STRATEGY
AH previous discussions and problem assignments were in-
tended to provide you with the basic working principles of
anaerobic sludge digestion. Their successful application in the
operation of a digestion system requires sound and thorough
daily operational checks in combination with adequate sam-
pling and neat, well-organized records of the resulting data.
Many operators find that plotting certain operational data in a
graphical form is very helpful to recognize changes or trends in
digester performance. Informative operational data that could
be plotted against time include:
1. Digester loading
a. Volatile solids added, Ibs/day per cubic foot of digester
capacity
or b. Volatile solids added, Ibs/day per volatile solids under
digestion, Ibs
2. Volatile acids/alkalinity relationship
Volatile acids, mg/L per alkalinity, mg/L
3. Gas production
1000 cubic feet of gas produced per day
4. Carbon dioxide content of digester gas
Percent carbon dioxide
5. Temperature
Degrees Fahrenheit or Degrees Celsius
Successful plant operators use basic knowledge together
with the daily checks and data to remain alert to changes in the
system and to anticipate problems, rather than finding it nec-
essary to react to fully developed upsets.
12.40 Operation and Maintenance Checklist
The following checklist is intended to help the operator re-
main "on-top" of the system. This list is general in nature, and
does not cover all situations, but serves as an example of the
checklist that should be made for each plant. You should pre-
pare a similar checklist for the anaerobic sludge digesters at
your treatment plant. As you make your rounds inspecting
each item, be alert. Investigate and record anything that looks
different or unusual, smells different, feels different (hotter or
vibrating more) and sounds different. If problems appear to be
developing, correct them now or alert your supervisor of the
changes.
112
-------
Sludge Digestion
ITEM
A. Raw Sludge Pumping
1. Total sludge volume pumped in 24 hours or indi-
vidual feed periods. Record pump counter or meter
reading.
2. Proper operation of pump(s). Check oil level. While
operating check motor, pump, packing (teaks), suc-
tion and discharge pressure.
3. If density meter is used, check for proper operation
during pump run.
4. Instrumentation, especially pump time clock opera-
tion.
5. Sludge line valve positions.
6. Visual observation of raw sludge being pumped.
Note consistency (thick or thin), color and odor (sep-
tic).
7. Automatic sampler operation.
8. Exercise all sludge valves by opening and closing.
9. Lubricate all valve stems. Inspect and grease pump
motor bearings according to manufacturer's rec-
ommendations.
B. Boiler and Heat Exchanger
1. Temperature of the recirculated sludge.
2. Temperature of the recirculated hot water.
3. Boiler and heat exchanger temperature and pres-
sure.
4. Water level in sight glass of day-water tank.
5. Boiler and heat exchanger operation.
a. Gas pressure
b. Make-up water valve
c. Pressure relief (pop-off) valve
d. Power failure or low gas pressure shutdown
e. Safety devices
6. Boiler firing (flame-air mixture).
7. Hecirculated sludge pump operation. Check oil
level. While pump is operating check motor, pump,
packing (leaks), suction and discharge pressures.
8. Inspect and grease pump motor bearings according
to manufacturer's recommendations.
C. Digesters
1. Record gas meter reading.
2. Check gas manometers, (digester gas pressure)
3. Record digester gas pressure and/or floating cover
position and indicator level reading.
4. Drain gas line condensate traps and sedimentation
traps (from one to four times per day depending on
location of trap in gas system, temperature changes
and digester mixing systems).
5. Check liquid level in the digester.
6. Check supernatant tubes for operation and wash
down supernatant box.
7. Check digester gas safety analyzer (L.E.L.) and
recorder.
SCHEDULE
DAILY
X
X
X
X
X
X
X
WEEKLY
•."^WS^i-S^B-
X
MONTHLY
-iZi£.iftafr '
SEMI-
ANNUALLY
ws^f*fsyst
Li-«,vSsteft.
X
*v^m*&~&y&3^&&&3
X
X
X
X
X
X
X
X
X
X
X
X
x
X
X
X
X
X
&jr,~
X
^'p&f *
AS
REQUIRED
BEST'S ;VV«j:
afStt-.-J!:*
.'j^;*3
X
113
-------
Treatment Plants
8. Check and record level of water seal (located on
center dome of fixed cover digesters and between
tank wall and cover of floating cover digesters).
9. Check operation of mixing equipment.
GAS
a. Flow rate, cfm
b. Pressure, psi
c. Compressor operation
MECHANICAL
a. Motor operation
b. Drive belts or gear reducers
c. Vibrations
d. Direction of mixing (down-up)
10. Examine waste gas burner for proper operation.
a. Pilot on
b. Number of burners on
c. Digester gas pressure (wasting or excess)
11. Exercise all sludge and gas system valves by open-
ing and closing.
12. Check all supernatant tubes for operation and sam-
ple each for clearest liquor for supernatant removal
from digester.
13. Check digester for scum blanket buildup.
14. Examine the digester structure and piping system
for possible gas leaks. Examine the digester struc-
ture for cracks.
15. Clean, inspect and calibrate the digester gas safety
analyzer and recorder.
16. Lubricate all valve stems and rotating equipment as
required by the manufacturer.
17. Clean and refill gas manometers with proper fluids
to levels specified by manufacturers.
18. Flush and refill water seals (from 2 to 6 months).
Check weekly on fixed cover digester seals.
19. For floating cover digesters, inspect flotation com-
partment for leakage or excessive condensation
buildup (pump out) and look for corrosion of cover
interior.
20. Dswater digester and clean out, repair and paint.
Normal cleanout schedules are three (3) to eight (8)
years.
SCHEDULE
DAILY
X
X
X
X
X
X
X
X
X
X
WEEKLY
X
X
X
X
X
MONTHLY
X
X
SEMI-
ANNUALLY
X
X
X
AS
REQUIRED
X
X
12.41 Sampling and Data Checklist
Results and interpretation of lab tests tell you what you are
feeding a digester and how the digester is treating the sludge.
Graphically recording lab results helps to interpret what's hap-
pening in a digester. If undesirable trends start to develop,
refer to the appropriate section in this manual for the proper
corrective action.
114
-------
Sludge Digestion
ITEM
Raw Sludge
1. Composite raw sludge sample. If grab is taken instead,
then prepare a composite twice a week.
2. Total and volatile solids.
3. pH
Supernatant
1. Solids (total and volatile) and COD. Graphically record
the data and be alert to long-term decreasing quality
(increased levels of solids and COD) of supernatant
quality.
Digested Sludge
1. Grab sample
2. Temperature
3. pH
4. Cubic feet of total gas and CO2 content.
5. Calculate and graphically record gas production and
CO2 content.
6. Calculate and graphically record loading rate (solids
and hydraulic).
7. Volatile acids
8. Alkalinity
9. Calculate and graphically record volatile acid/alkalinity
relationship.
10. Digested sludge total solids and volatile solids.
11. Solids (total and volatile) and temperature profile at
five-foot (1.5m) intervals from the digester bottom up
to the surface. If scum blanket present, try to break it
up.
D. Solids Balance
1. Calculate the solids balance on the digesters (see Sec-
tion 12.3M. Solids Balance). This calculation helps in-
dicate to you how well you are controlling the digester
operation.
In Item 12.41, C-11, as regards the profile sampling of the
digester, the solids and temperature data should be carefully
examined for indications of poor mixing in the digester or grit
accumulation at the bottom of the digester. The operator
should use the data to calculate the useful volume of the diges-
ter (total volume minus the grit volume). Such data can be
graphically plotted against time to show the rate of grit buildup
and the date for digester cleaning. An example of such a plot is
illustrated in Figure 12.21, although actual data may not plot a
straight line.
SCHEDULE
DAILY
X
X
X
X
X
X
X
X
X
BI-
WEEKLY
(X)
(X)
X
X
X
X
WEEKLY
MONTHLY
X
j
" - -]
X
X
115
-------
Treatment Plants
TIME IN SERVICE (YEARS)
F/'g. 72.27 ^cf/Ve volume of a digester tank
(Permission ol Los Angelas County Sanitation Duma)
116
-------
Sludge Digestion
12.42 Normal Operation
In this chapter we have discussed the following important
topics regarding digester operation:
1. Section 12.1. Components in the Anaerobic Sludge Diges-
tion Process;
2. Section 12.2, Operation of Digesters; and
3. Section 12.3. Digester Controls and Test Interpretation.
This section combines the highlights of those portions of the
previous sections that are critical to the actual day-to-day op-
eration of an anaerobic sludge digester. For details, refer to the
actual section. The normal operation of a digester involves the
following activities:
1. Feeding Sludge to the Digester (Section 12.22, Feeding);
2. Maintaining the Proper Temperature (Section 12.14, Diges-
ter Heating);
3. Keeping the Contents of the Digester Mixed (Section 12.15,
Digester Mixing);
4. Removing Supernatant (Section 12.27, Supernatant and
Solids); and
5. Withdrawing Sludge (Section 12.28, Rate of Sludge With-
drawal).
Let's study each one of these activities.
1. Feeding Sludge to the Digester (See Section 12.41, A. Raw
Sludge)
a. Pump as thick a sludge as possible to the digester.
Watch sludge being pumped, listen to sound of sludge
pump, and observe any instruments that indicate thick-
ness of sludge.
b. Pump small amounts of sludge at regular intervals to
prevent adding too much raw sludge too fast for the
organisms or for the temperature controls to maintain a
constant temperature.
c. Calculations
(1) Try not to add more than one pound of volatile
matter per day for every ten pounds of digested
sludge in storage (1 kg V.M./day per 10 kg digested
sludge). This ratio may vary from digester to diges-
ter and from season to season.
(2) Calculate the volatile acid/alkalinity relationship
and plot the results. If the relationship starts to in-
crease, try to pump a thicker sludge or reduce the
amount of volatile matter added per day. Also re-
duce the pumping rate of digested sludge.
See Section 12.3. Digester Controls and Test Interpretation,
B. Volatile Acid/Alkalinity Relationship and K. Computing Di-
gester Loadings for details.
2. Maintaining the Proper Temperature (See Section 12.40, B.
Boiler and Heat Exchanger)
Record the temperature of the recirculated sludge every
day. If the temperature changes from the desired level, ad-
just the temperature controls. Do not allow the temperature
to change more than 1°F (0.5°C) per day. Determine the
temperature (usually between 95 and 98°F or 35 and 37°C)
that best suits your digester.
3. Keeping the Contents of the Digester Mixed
How a digester is mixed depends on the mixing equipment
and whether you have a single-stage or two-stage digestion
process. Digester contents must be well mixed to provide
an even distribution of food (raw sludge), organisms, alka-
linity, heat and waste bacterial products. Good mixing
should prevent the buildup of a scum blanket and the depo-
sition of grit on the bottom of the digester. If mixing is in-
adequate, try increasing the time of mixing and/or looking
for equipment problems.
4. Removing Supernatant
Supernatant should be removed from the digesters on a
daily basis. Whether you have a single-stage or two-stage
digestion process, mixing should be stopped for 6 to 12
hours before supernatant removal to allow the supernatant
to separate from the digested sludge. Adjust or select the
supernatant tube that produces the least solids to remove
supernatant from the digester. Carefully observe your other
treatment processes to be sure the supernatant does not
cause a solids or BOD overload on other treatment pro-
cesses. Remove supernatant and digested sludge until suf-
ficient space is obtained in the digesters for the incoming
raw sludge.
5. Withdrawing Sludge
Before withdrawing sludge, stop mixing for 6 to preferably
12 hours to allow the digested sludge to separate from the
supernatant. The digester contents must be well mixed be-
fore stopping mixing so a lot of raw sludge will not be re-
moved with the digested sludge. Good mixing also prevents
the buildup of a scum blanket and the development of con-
ing during the removal of digested sludge. The withdrawal
rate of sludge from either digester should be no faster than
a rate at which the gas production from the system is able to
maintain a positive pressure in the digester (at least two
inches (5 cm) of water column).
12.43 Troubleshooting
Using the information obtained from the analysis of the sam-
ples and the daily rounds, the knowledgeable and alert
operator can note changes from normal operation. The first
step is to realize that there is a problem, and the second step is
to take the appropriate corrective action. Table 12.2 is in-
tended to be an example of a logical sequence that can be
followed to identify and correct an impending or actual digester
upset. The four indicators of a problem tell you to look for one
or more of the problem areas listed that need correcting.
Toxicity can be a very difficult problem to identify and solve.
Heavy metals can gradually creep up in concentrations until
toxic levels are reached. Also as the pH decreases the concen-
trations of dissolved metals tend to increase and become toxic
to bacteria in the digester.
Possible methods of controlling toxic materials include:
1. Remove toxic material from waste,
2. Dilute toxic material below its toxic level,
3. Add a chemical that will neutralize the toxic material, and
4. Add a chemical that will cause the toxic material to precipi-
tate out of solution or form an insoluble compound.
If soluble toxic heavy metals are present, sodium sulfide
(Na2S) can be added which will cause the formation of non-
toxic insoluble heavy metal sulfide compounds. Digesters are
similar to people in many ways. A small amount of something
may be very good for a digester, but too much may be toxic as
shown in Table 12.3.
117
-------
Treatment Plants
TABLE 12.2 DIGESTER OPERATION TROUBLESHOOTING
INDICATION FROM DATA
PROBLEM AREA
POSSIBLE CAUSE
• Rise in V.A./Alk Ratio
• Gas Production Decrease
or Increase in CO2
• Decrease in V.S. Reduction
• High Solids in Supernatant
Toxicity -
Digester Loading -
Digester Heating -
Digester Mixing -
Gas System -
- 1. Slug of toxic material.
2. Constant feed that has reached toxic limit.
-1. Change in raw sludge pumping.
2. Raw sludge density or V.S. changed
3. Raw sludge pH change.
4. Decrease in effective volume of the
digester.
-1. Heat exchangers plugged.
2. Recirculated sludge pump not working.
3. Boiler malfunction.
4. Unsteady sludge temperatures — more than 1°R
day or 0.5°C/day.
-1. Fouled draft tube.
2. Mechanical or electrical failure.
3. In case of gas mixing, inadequate recirculation.
~ 1. Gas meter failure.
2. Leaking gas.
3. Abnormal pressure.
4. Plugged gas line.
118
-------
TABLE 12.3 BENEFICIAL AND TOXIC
CONCENTRATIONS OF MATERIALS ON DIGESTION
PROCESS
Material
Ammonia Nitrogen, mg/L
Calcium, mg/L
Magnesium, mg/L
Potassium, mg/L
Sodium, mg/L
Beneficial
50-200
100-200
75-150
200-400
100-200
Moderately
Inhibitory Toxic
1500-3000" 3,000
2500-4500 8,000
1000-1500 3.000
2500-4500 12.000
3500-5500 8.000
aToxic at higher pH values
12.44 Actual Digester Operation
By using the procedures outlined in this Section, digesters
can be operated successfully without any problems. The in-
formation plotted in Figure 12.22 shows some of the informa-
tion used by an operator to operate four digesters with a total
capacity of 6.9 million gallons (26,000 cu m). This activated
sludge plant treats an average daily flow of approximately 18
MOD (68,130 cu m/day) with flows averaging over 24 MGD
(90,840 cu m/day) during the canning season. Under adverse
conditions, the digesters have provided only 8 days of deten-
tion time, yet the digesters have never become upset.
Raw sludge from the primary clarifiers and gravity thickened
waste activated sludge are fed on a regular basis throughout
the day to each digester. Every 2 hours the operators read and
record the gages, pump meters and temperature readings.
Temperatures are controlled by adjusting the heat exchanger.
Digester contents are continuously mixed through draft
tubes. Every day the flows through the draft tubes are reversed
for two hours to knock off rags accumulated on the draft tubes.
Additional mixing is available using digested sludge recircula-
tion pumps, if necessary. The operator reviews the lab data
and if problems appear to be developing, additional mixing is
applied, if appropriate. If everything is satisfactory and mixing
is greater than usual, mixing is reduced.
The following information is recorded with regard to the di-
gesters:
1. Raw Sludge and Thickened Waste Activated Sludge to Di-
gesters
a. Volume, gallons per day
b. pH
c. Total solids. %
d. Volatile solids. %
2. Digester Gas
a. Total production, cubic feet per day
b. Carbon dioxide, %
3. Digested Sludge (mixed digester contents)
a. Volatile acids, mg/L
b. Alkalinity, mgIL
c. Total solids. %
d. Volatile acids, %
e. pH
4. Sludge removed (mixed digester contents)
a. Volume, gallons per day
b. Total solids. %
c. Volatile solids, %
Volatile acid/alkalinity relationship has been the key to suc-
cessful digester operation over the last nine years without any
of the five digesters becoming upset. Volatile acids and alkalin-
ity are normally run three times per week on each digester. If
Sludge Digestion
one high volatile acid reading is observed, the volatile acid test
is repeated the next day. Usually the volatile acid value is back
down to the normal range the next day. If the volatile acid value
is high, the raw sludge pumped to the digester is cut in half or
stopped until the volatile acid reading is normal again. Usually
this requires only one or two days.
These digesters are not used for liquid-solids separation.
Therefore, no information is collected on the supernatant.
119
-------
-------
Learning Resource 9
Troubleshooting O&M Problems in Hastewater Treatment Facilities
Course 179.2 - 1979
Environmental Protection Agency
National Training and Operational Technology Center
26 West St. Clair
Cincinnati, OH 45268
Presented is a learning activity that requires trainees to
practice applying the process of troubleshooting to anaerobic
digestion problems using a role-playing simulations exercise. The
exercise is conducted using the "fish bowl" technique in which second
four-person group observes the role-playing exercise and then
critiques the performance of the troubleshooters. This lesson
includes: trainee entry level behavior and learning objectives,
trainee and instructor materials used, classroom set-up lesson
outline, and trainee notebook contents.
121
-------
TROUBLESHOOTING 0 & M PROBLEMS IN
WASTEWATER TREATMENT FACILITIES
Unit ofa InAtiuc^tion 12: Sotidt> Handling
Lesson 2: Problem Solving in Anaerobic Digestion
Lesson 2 of 5 lessons Recommended Time: 110 minutes
Puipoie: This lesson requires the trainees to practice applying the
process of troubleshooting to anaerobic digestion problems using a role
playing simulation exercise. Three trainees from each four person work
group role play troubleshooters while the fourth member of the work group
role plays the operator. The exercise is conducted using a "fish bowl"
technique in which a second four person work group observes the role
playing exercise and then critiques the performance of the troubleshooters.
Two problems are solved so that each work group participates in both
observer and troubleshooter roles. The thrust of the exercise is to em-
phasize the importance of oral communication and attitude in troubleshoot-
ing. In this exercise proper application of the process of troubleshooting
and interpersonal communication skills are more important than is solution
of the technical problems provided.
T>iaA.niii En&iy Le.vei Bzhavioi: Trainees should have achieved the learn-
ing objectives specified for Unit 12, Lesson 1 before beginning this lesson.
Tnainee. Le.iLim.ng Ob]'e.c£i.veA: At the conclusion of this lesson the
trainee will be able to:
1. Demonstrate proper troubleshooter behavior and apply the
process of troubleshooting in an oral interview role playing
exercise.
2. Explain the importance of proper troubleshooter behavior by
observing and constructively critiquing other trainees' per-
formances during a role playing troubleshooting exercise.
3. Demonstrate his/her ability to organize and conduct an oral
interview to obtain essential technical data for trouble-
shooting an anaerobic digester problem and recognize how the
interview technique must be adapted to respond to the person-
ality and attitude of the plant operator.
4. Demonstrate his/her understanding of anaerobic digester
operations and troubleshooting by successfully solving the
problems presented.
122
-------
Approach: Trainee problem solving in a role playing
exercise using the "fishbowl" technique.
Fishbowl Technique. The approach to this lesson subdivision employs
two educational techniques that allow the trainees to participate in and
experience the process of troubleshooting.
1. One technique is "role playing." For each problem, a four-person
group is assigned, with one person playing the role of the operator - with
specific instructions, and the other three persons playing the role of
troubleshooters.
The second technique is the "fishbowl" technique, where one group ob-
serves the other group carrying out the role playing exercise in attempting
to solve the assigned problem. The observing group should take notes on
what they see and report back at the appropriate time.
The group involved in "role playing" to solve the assigned problem is
known as the "inner group" (inside the fishbowl) and is seated accordingly.
The group of observers is known as the "outer group."
Groups for this lesson subdivision must be pre-designated by the in-
structor and should be as balanced as possible in composition so that all
groups are roughly comparable.
2. The individual selected to play the role of "plant operator" from
each group should be a person who is relatively experienced in the inspec-
tion of treatment plants compared to his/her fellow trainees. The selected
individuals should also be chosen from among those who have personalities
which would make them not reticent to participate. The individuals who
are to be "plant operators" should be pre-selected and given their instruc-
tions in advance of this lesson subdivision.
3. It is very important that the observers be encouraged to give honest
feedback to the troubleshooters - after the 20 minute troubleshooting ex-
perience is completed. It is this feedback that provides much of the learn-
ing experience for this lesson.
4. After one problem has been analyzed and feedback provided, the
groups must switch so that the "inner" and "outer" groups change places.
A new "operator" and new troubleshooters then address the second problem
with the new observers taking notes.
5. After both problems have been analyzed and feedback i§ reported by
the observers, it is important for the instructor to bring the entire class
together to discuss the results and for the trainees to discuss their role
playing experiences. This overall comparison of what occurred in each
group is an essential conclusion to this exercise that allows the trainees
to compare notes and obtain an overall impression of the troubleshooter-
operator relationship.
123
-------
6. Some trainees may be very timid in their role playing involvement.
In trial presentations, a very small percentage (1%) were very negative
and even belligerent. The instructor must "cruise" from group to group
to see that people participate and to encourage them to do so. However,
if a trainee's attitude is so negative as to disrupt the others, he/she
should be excused from this portion of the lesson.
Details on administering the lesson are provided in the lesson plan
outline.
Sc.he.dule.: The 110 minutes allocated to this lesson should be
scheduled as follows:
TIME SUBJECT
0-10 minutes Instructor Introduces the Lesson, Sets
up Groups, Provides Instructions
10 - 30 minutes Groups Plan their Approach to the Problem
30 - 50 minutes Designated Groups Analyze and Troubleshoot
Problem 1
50 - 60 minutes Observers for Problem 1 Report Findings
60 - 80 minutes Designated Groups Analyze and Troubleshoot
Problem 2
80 - 90 minutes Observers for Problem 2 Report Findings
90 - 110 minutes Entire Class Convenes to Discuss Findings
and Experiences with the Instructor
Trainee MateAJ-otts U*,e.d In (.eiion:
1. Tlcune.e. Notebook, pages T12.2.1, "Instructions to Troubleshocters:
Problem 1.
2. Tiaine.e. notebook, pages T12.2.2, "Instructions to Troubleshooters:
Problem 2.
3. F-ce/d Ma.nu.ai ^01 PeA&onmance. tvaJiuation and Tnou-bteAhootinq at
Mu.nlcA.pa2
-------
McutMMttt, Recommended £01 Ve.vntopme.nt: None
AdcLLtionaf. In&&w.tito>i Re^e-tence*: None
SeX-Up: The classroom should be set up to accommodate
groups of eight (8) trainees. If possible, to avoid distraction from one
group to another, separate rooms should be used for each group of 8.
Each group of 8 consists of two (2) four-person groups, an "inner"
group who are actually participating in the role playing-problem solving
and an "outer" group who are observing.
Each "inner" group consists of three (3) troubleshooters and one (1)
trainee who is playing the operator's role.
Each group of 8 should be arranged as in this diagram.
Inner Group ylX I X / p—Outer Group
One Operator \ \ 71 X / J^~ 4 Observers
Three Troubleshooter
125
-------
I.
LESSON OUTLINE
Prior to Start of Lesson
A. Trainee groups should be designated by
Course Director or instructor.
B. Instructor should choose one member of
each group to play the role of "operator."
1. Distribute "Instructions to Operating
Personnel" to persons selected as
operators.
II. Introduction (10 minutes)
A. Introduce lesson
B. Announce group composition
C. Select groups to be "inner" or "outer"
groups.
D.
Emphasize to trainees playing the role of
troubleshooters that they should:
1. Work as a team in questioning the
"operator."
2. Use the "Process of Troubleshooting,"
i.e., be analytical.
3. Find the answer and solve the opera-
tor's problem in 20 minutes.
E. Emphasize to the "outer" group of obser-
vers to take notes and be prepared to
comment on how well the troubleshooters
perform.
F. Privately emphasize to the trainees acting
as operators for.Problem 1 that they are
to be cooperative, but i.nexpMinnc-e.d. In
response to any question that is not
covered in the operator's instruction
sheet they are to indicate that they don't
KEY POINTS &
INSTRUCTOR GUIDE
Guide: Instructions for operator
are available as part of IM&UUSJLQM.
Notebook, pages H12.2.1 - H12.2.5
They must be reproduced prior to
the lesson.
Instructions for troubleshooters
are included in the Pi.ox.nee Notebook,
pages T12.2.1 - T12.2.2
Refer to the "Instruction Approach"
section of the lesson plan for de-
tailed discussion of the approach.
Pairing Group 1 with Group 2,
Group 3 with Group 4, etc., is
probably the easiest approach. Odd
numbered groups solve problem 1 and
even numbered groups solve problem 2.
Use the 20 minutes allocated for
preparation below to brief the
"operators" while the troubleshooters
plan their approach.
126
-------
LESSON OUTLINE
know the answer. If the troubleshooters
give detailed instructions on how to ob-
tain the answer, the operator will agree
to get the answer and call the trouble-
shooter back tomorrow.
Privately emphasize to the students acting
as operators for Problem 2 that they are
to be inJLu.vtja.YVt and de^etw-ive to the. po-Lnt
0(5 tlu.nty v&ite.d kobtUUMj. In response
to any question that is not covered in
the operator's instruction sheet, they are
to indicate that they don't know the
answer. If the troubleshooters ask for
additional information or data, the
operator cannot, will not or does not
have time to furnish it.
G. Have student groups go to their assigned
places.
III. Prepara-tion (20 minutes)
A. Allow troubleshooting groups and opera-
tors 20 minutes to prepare their approaches
to Problem 1.
IV. Problem 1 (20 minutes)
A. Instructor should make sure "inner" and
"outer" groups go to their respective
seats.
B. Instructor should "cruise" from group to
group to oversee the exercise.
C. Call time after 20 minutes.
V. Feedback for Problem 1 (10 minutes)
A. Observers should report their findings on
how the troubleshooters performed.
B. After 10 minutes, have groups switch
places for Problem 2.
KEY POINTS &
INSTRUCTOR GUIDE
Use this time to brief "operators"
127
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LESSON OUTLINE
VI. Problem 2 (20 minutes)
A. Instructor should make sure "inner" and
"outer" groups go to their respective
seats.
B. Instructor should "cruise" from group to
group to oversee the exercise.
C. Call time after 20 minutes.
VII. Feedback for Problem 2 (10 minutes)
A. Observers should report their findings
on how the troubleshooters performed.
B. After 10 minutes, bring the entire class
back together to review the problems,
the observations and the results of the
exercise.
VIII. Discussion of Findings and Results (20 minutes)
A. Brief review of results of the trouble-
shooting problems.
1. Problem 1
If the troubleshooters follow proper
troubleshooting techniques, the most
obvious cause should become apparent.
The digester is organically and hydrau
lically overloaded because the weekend
operator pumped down the out of ser-
vice primary clarifier as quickly as
possible- The operator should re-
duce or cease pumping raw sludge to
the digester.
KEY POINTS &
INSTRUCTOR GUIDE
Key Point: The instructor should
cover the technical solutions as
quickly as possible. Focus dis-
cussion on the observed behavior
of the troubleshooters and operators.
Emphasize:
1. The importance of a systematic
approach
2. That the technique can be used
by peop.le other than operations
consultants
a. Senior operators
b. Department heads
c. Regulatory personnel
Clues:
1. Rapid temperature drop indicates
increased hydraulic load to
digester.
2. Foaming and froathing character-
istic of organic overload.
3. "Rotten egg" odor is typical of
organic overload problems.
128
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LESSON OUTLINE
He should add lime to raise the pH and
continuously recirculate the digester
contents via the heat exchanger to
gradually raise the temperature to
95°F.
The troubleshooter should have the
operator start the corrective program
immediately and then assure the opera-
tor that a continual follow-up will
be implemented to confirm and assist.
2. Problem 2
If the troubleshooters follow proper
troubleshooting procedures, the
problem and its cause can be deter-
mined.
The digesters have received a slug of
toxic material, maybe heavy metals.
The operator should isolate and hold
the waste if possible. (He tried to
do this.) If not, the operator should
reduce mixing to minimize contact of
the toxic sludge with the entire
digester contents.
KEY POINTS &
INSTRUCTOR GUIDE
Feeding Lime:
1. Must slurry lime before feeding.
2. Can estimate lime dose by drawing
a five gallon sample of digester
contents and adding lime to sam-
ple while monitoring the pH. Can
then estimate the total pounds of
lime needed to increase the diges-
ter pH.
3. Feed about half the total lime
dose the first day. Wait a day
and monitor pH. Add more lime
as needed on following days to
avoid overdosing the digester.
Clues:
1. Sudden loss of gas production and
rapid drop in pH indicates possi-
ble toxicity.
2. "Rancid butter" odor of digested
sludge indicates presence of
butyric acid. The methane form-
ers have been killed. This is
characteristic of toxic effects.
"Rotten egg" odor is character-
istic of organic overload.
3. Operator was treating the dairy
waste problem which he had be-
fore but the treatment is not
working this time.
129
-------
LESSON OUTLINE
The final solution will depend on the
type and amount of waste present. It
may be possible to dilute the waste
below toxic level using either seed
sludge from another digester or water
for the dilution.
Or you might:
1. Form an insoluble product. Remove
soluble sulfides by adding iron
salts causing iron sulfide to form.
Remove heavy metals by adding sul-
furic acid or a sulfide to cause
formation of metal sulfides.
2. Use another compound that will re-
act with the toxic compound to
form less harmful compounds. To
discover just what type of antago-
nistic element is needed, some
careful work will be needed.
3. Empty the digesters and start
all over again.
4. The best long-term solution is to
implement a good industrial pre-
treatment system to make sure that
this doesn't happen again.
KEY POINTS &
INSTRUCTOR GUIDE
The "rotten egg" odor came from
the raw sludge pumped to the
drying beds. Lime the sludge on
the beds to reduce odors and de-
composition.
"Bulking" in the activated
sludge units may be defloccula-
tion caused by toxic load to the
plant.
Note: This is especially true with
cyanide and chromium wastes.
Have class discuss how one might im-
plement a total digester dump if
this is needed.
130
-------
LESSON OUTLINE
B. Discuss with class whether or not the
troubleshooters approached the problem by
using the Process of Troubleshooting.
C. What aspects of troubleshooter-operator
behavior were observed in the exercise?
KEY POINTS 8,
JNSTRUCTOR GUIDE
Key Points: Discuss these key
points with the class and maximize
class input.
131
-------
Note on Distribution of Instructions
The following sets of instructions must be reproduced prior to this
lesson and distributed to trainees for the lesson.
Distribution
"Instructions to Troubleshooters" go to each troubleshooter
and each observer and are included in the Trainee Notebook as
pages T12.2.1 and T12.2.2.
"Instructions to Operators" go only to trainees playing the
role of "Operator" and to each observer. These are included in
the liut>iu.cto>i Notebook as pages H12.2.1 -H12.2.5. Troubleshooters
are not given the "Instructions to Operators" for the problem which
they must troubleshoot.
Troubleshooters may be given copies of the "Instructions to
Operators" after the problem has been completed.
The easiest way to handle distribution of the "Instructions to
Operators" is to give the trainee who role plays the operator eight
copies of the instructions. The operator can distribute copies to
the "observers" as the problem solving exercise begins and copies
to the "troubleshooters" when the exercise is completed.
132
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TROUBLESHOOTING 0 & M PROBLEMS IN
fc/ASTEWATER TREATMENT FACILITIES
Unit 0(5 Ittii.tuc-fcion 72: So£x.cii Handi-Lng
Lesson 2: Problem Solving in Anaerobic Digestion
Notebook Con-tetiti
Instructions to Troubleshooters
Problem Number 1 T12.2.1
Problem Number 2 T12.2.2
133
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Solids Handling
Problem Solving in Anaerobic Digestion
lni>tnu.c.ti.ont: to 7nou.bteAhoo£eAA
Problem Number 1
You are an operations consultant with Acne Environmental Associates.
It is early Monday morning and you receive a telephone call from an
operator that is a client of your firm.
He reports that foam is being discharged from the upper level super-
natent line and foam is visible through the sight glasses in the digester
roof.
The plant is a 1 MGD trickling filter unit with a fixed cover anaerobic
digester. The last time that you visited the plant was 6 months ago.
The operator is uncertified and has been on the job for about a year.
He is cooperative but relatively inexperienced. He is concerned and asking
for help.
You inform the operator that you expect to be in his vicinity later in
the morning and will be traveling with some of the other field staff per-
sons from your office, so you'll bring them along.
As you enter the plant you notice that the flame at the waste gas burner
has an orange color. You detect a septic sewage "rotten egg" odor. You
also notice that one of the two primary clarifiers is out of service.
When you arrive at the plant (after having reviewed all available records),
you begin your troubleshooting procedures.
134
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Solids Handling
Problem Solving in Anaerobic Digestion
iHA-ttucttOdi to JioubieAkooteAA
Problem Number 2
You are an operations consultant for Anderson Environmental Associates
(AEA). You have just received a telephone call from an irate municipal
official. He lives 600 yards downwind from a municipal wastewater treatment
plant that your firm designed. He states that the plant smells terrible and
that the odor is making him ill and the condition has existed for three days.
The official reminds you that AEA is on retainer to his city and demands
that you remedy the situation immediately.
He has already complained twice to the treatment plant operator. The
operator told the official that the odor wasn't his fault - he was doing all
that he could, but he had a "damn poor" engineering design to work with. He
suggested that the official talk with your firm since AEA designed and started
up the plant about seven years ago.
Before calling the plant, you pull the file and study the situation. The
plant is a 2 MGD activated sludge plant with two-stage anaerobic digesters.
The plant serves a community of 12,000 people and several small industries.
The industries consist of a poultry processing plant, a cheese and dairy pro-
ducts plant, a clothing manufacturer and a large metal office furniture
manufacturing and finishing operation.
All monthly operating records that you could obtain show good operating
results. You could find no operating records for the past 3 months however.
The operator is certified under the grandfather clause and has over 25 years
experience. The last AEA visit of the treatment plant site was about 7 months
ago. The operator has never called AEA to ask for assistance, so you assumed
that the operation was running smoothly.
You telephone the plant and offer to visit with the operator to assist in
solving the odor problem. The operator says that he is too busy to be visit-
ing with people because he's having digester problems and has had to dump
sludge to the drying beds. He agrees to spend a few minutes with you but lets
you know that he should be working on the digester problem and not wasting
time with a bunch of "f—ing engineers."
It sounds like an interesting problem, so you decide to take along several
work associates. As you enter the plant, you notice that there is no flame
at the waste gas burner. As you near the plant, you detect a strong septic
sewage "rotten egg" odor. The primary tanks which you pass look bad. They're
black and black sludge is floating on the surface.
135
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TROUBLESHOOTING 0 g M PROBLEMS IN
WASTEWATER TREATMENT FACILITIES
Unit o& Ini-fiuctum 12: SoLidb Handting
Lesson 2: Problem Solving in Anaerobic Digestion
lnit>t>iu.cto>i Handout Coyitin£t>
Instructions to Operating Personnel
Problem Number 1 H12.2.1
Problem Number 2 H12.2.3
136
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Solids Handling
Problem Solving in Anaerobic Digestion
InA&iuctionA to Operating Peuonn&t
Problem Number 1
1. You are the operator of a 1 MGD trickling filter plant with a single
fixed cover, heated anaerobic digester.
2. You are an uncertified operator and, in addition to the wastewater
treatment plant, you also operate the water plant, collection system
and water distribution system. You're still on probation with your
employer and are willing to do almost anything to solve the problem
quickly and demonstrate your competence as an operator.
3. On Monday morning when you arrive at the plant, you discover foam
being discharged from the upper level supernatant line and, when
you investigate the cover, you see foam through the sight glass.
4. Your anaerobic digester is a fixed cover unit with no mechanical or gas
mixing equipment. Total recirculation is possible and the unit is
heated by an external heat exchanger. Recirculation through the heat
exchanger provides the only mixing in the unit.
5. You immediately telephone your community's engineering firm and talk
with their operations consultant who promised to stop by later today.
The consultant has not been to your plant in 6 months.
6. In response to specific questions, you supply the following data. (If
you knew what data were important and how to properly interpret the data,
you would not have called for assistance.)
a. Operating Data on the Digester
Parameter Hon. Tues. Wed. Thurs. Fri. Sat. Sun. Hon.(today)
pH ? 7.0 7.0 7.0 7.0 - - 6.6
Temperature,
OF ? 95 95 95 95 - - 92
Volatile Acids,
mg/1 800 - - - - - ?
Alkalinity,
mg/1 2700 ... ?
Sludge Pumped
to Digester No Records
137
-------
b. You cannot perform solids analyses or gas analyses in your
laboratory because you don't have the equipment for these tests.
c. Digester gas has a "rotten egg" odor but is still burnable.
The waste gas burner flame is orange colored.
d. No sludge has been withdrawn from digester for over a month.
e. Nothing unusual occurred last week when you were on duty. The
only thing that you can remember is that a flight chain broke on
number one primary settling tank Friday.
f. You instructed the weekend operator to dewater number one pri-
mary settling tank on Saturday and Sunday so you could repair
the chain Monday. The tank was empty when you came to work this
morning.
g. There are no significant industries connected to the system.
h. Lime is available at the water plant.
7. Additional Data:
a. If the troubleshooters ask you to do so, you will run additional
tests. You will run these tests only if asked to do so.
Additional Data for Monday
Volatile Acids, mg/1 1600
Alkalinity, mg/1 1800
b. If the troubleshooters suggest that you "lime" the digester, make
sure that they tell you how to do it because you've never limed a
digester before. How do you add the lime? How much do you add?
Instructions on Operator Behavior
You are a cooperative but inexperienced operator. If you receive any
questions for which the answers are not provided in these instructions, indi-
cate that you do not know the answer. If the troubleshooter gives instruc-
tions on how to obtain the answer, agree to try to get it and indicate that
you will call him back tomorrow with the answer.
138
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Solids Handling
Problem Solving in Anaerobic Digestion
Ini.t'iuctconi to Operating PeMonnat
Problem Number 2
1. You are the operator of a 2 MGD activated sludge plant with two-stage
anaerobic digesters.
2. You are certified under the grandfather clause because you have
twenty-five years of experience and did not have to take a test de-
signed by some young engineer.
3. The anaerobic digesters are floating cover units of equal size with
gas mixing equipment and external heat exchangers. Digested sludge is
dewatered on sludge drying beds.
4. For the past week you have been working twelve hours a day with two
sick digesters and for the past three days people have been complaining
and demanding that you do something. To top off your day, some engineer
from AEA has decided to come over because of complaints by a city official.
5. The digesters were both full when you noticed the gas production and
pH drop. The last time that happened the cheese plant had slugged the
treatment plant. To cure the problem, you raised the pH with lime and
rested the digesters. This is what you are doing now, except you had
to fill two drying beds with sludge in order to have room to mix the
lime. The beds and what little gas is being produced have a "rancid
butter" odor.
6. You will answer questions from the troubleshooter but you will not offer
any additional information.
a. You have modified the digesters so that they operate as two single-
stage complete nixing digesters. Both digesters are sick.
b. pH: Today—6.1 on both digesters.
Prior to failure: pH varied between 7.1 and 7.2 on both digesters.
c. Volatile Acids: Today--4,000 mg/1
Prior to failure: 400 mg/1 on both digesters
d. Alkalinity: Today—1,200 mg/1
Prior to failure: 2,400 mg/1 on both digesters
139
-------
e. To date you have added 1,500 Ibs of lime to each of the digesters
and have succeeded in stopping the pH drop. The pH has not yet
begun to increase.
f. The temperature in each unit is 95°F and it has remained constant.
g. Prior to the failure the gas mixing system was operated on a daily
basis and scum is not a problem.
h. Total raw sludge solids content is between 6 and 8 percent.
1. Volatile solids content of sludge is approximately 60 percent.
j. The rate of feed to the digester has remained constant.
k. The digested sludge and what little gas is being produced does not
have a "rotten egg" odor. The odor is similar to the smell of
"rancid butter."
1. Since you have not been pumping raw sludge to the digesters
at a normal rate, there is'a sludge build-up in the primary
settling tank. The sludge is becoming septic and floating to the
top. You've had to pump some raw sludge to the drying beds and its
' beginning to smell.
m. The pH drop occurred overnight and the usable gas production ceased
overnight.
n. Your grit collector works well and there is no large accumulation
of grit in the digesters.
o. You have no laboratory capability to run exotic texts. The only
tests you can run are those required to operate the plant and comply
with NPDES reporting requirements.
p. To top things off, the activated sludge units started bulking about
the same time the digesters failed. You're having trouble getting
the activated sludge plant back in operation.
Instructions on Operator Behavior
You're getting near retirement and you don't really like other people
meddling around your plant. You are reluctant to provide information and
are defensive. You will answer specific questions reluctantly but you won't
volunteer any information.
You think you can solve your problem without any help if people will leave
you alone and let you do the job. You're upset because you're about to re-
ceive a 25 year award from the State Water Pollution Control Federation Chapter
and you don't want this incident to spoil it.
140
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You're upset with the city officials because they've asked the engineers
to come help you solve this problem. Your attitude about engineers is
negative because in your opinion you've never met one that knew anything
about operations and very few that knew anything about designing wastewater
treatment plants. You had some good ideas when the plant was being designed
but AEA chose to ignore them all.
You want to get rid of these AEA people as quickly as possible and get
back to work.
141
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Learning Resource 10
Operations Manual: Anaerobic Sludge Digestion - Part III, Potpourri.
U.S. Environmental Protection Agency
Office of Water Program Operations
Washington, DC 20460
Presented are selected parts of a manual designed to satisfy a
need for a guide to digester operation and maintenance for plant
operators. Topics include troubleshooting, general operation, safety,
start-up of units, basic theory, sampling, and laboratory testing.
The selections presented: discuss safety, present case history
examples of problem solving and operational experiences, and list
examples of gadgets devised by operators to assist in solving problems
around their plants.
143
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SAFETY
BASIC CAUTIONS
Sludge handling areas and equipment are
potentially among the most dangerous in a
wastewater treatment plant.
Plant operators should be thoroughly familiar
with the problem areas, the safety devices
that should be used, the precautions to take
and some general rules for working safely.
Pump rooms can accumulate combustible
gases, deplete oxygen in the air and be the site
of mechanical problems. Pump rooms should
be adequately ventilated and provided with
low-level oxygen alarms. Pumps should have
isolation valves on the suction and discharge
side for isolating the unit. Piping, connections
and equipment should be checked on a
frequent basis for leaks.
Dried sludge and powdered chemicals present
dust problems. Operators should wear goggles
and face-type breathing filters when working
with these compounds.
Methane gas is explosive when in contact with
air. Avoid mixing air with methane in the
range of from 20:1 to 5:1. Maintain a positive
pressure in all gas lines to prevent leakage of
air into the pipeline. Methane gas is also
produced from digested or partially digested
sludge, found in holding tanks. Therefore,
wherever gas may be present, there should be
no smoking, sparks or any open flame. Gas
detectors must always be used before entering
any empty digester.
Electrical installations, including light
switches, temporary devices or fixtures must
be of the explosionproof type.
Mechanical equipment should always have
machine guards in place. Operators must be
trained in their proper use and follow all
applicable safety rules.
MAINTENANCE SAFETY
The following rules apply at all times when-
ever working on equipment.
1. Lock out and tag main switch to prevent
accidental starting.
2. When working on pumps, be sure suction
and discharge valves are fully closed and
tagged. Be sure pump is vented and
drained.
3. Isolate fuel lines as applicable.
DANGER AREAS
Digester
When you must enter the digester, observe
the following basic rules for your protection.
1. Provide adequate ventilation to remove
gases and to supply oxygen. Be sure
exhaust fan is on.
2. Never enter the digester alone. Always
have someone to help in the event of
trouble.
3. Use safety harness equipped with safety
line.
4. Check for gases with explosimeter.
5. Be extremely careful about footing.
144
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6. Use bucket and rope to lower tools and
equipment.
Laboratory Safety
The handling of wastewater and numerous
chemicals creates a potential hazard to the
health and safety of individuals in the lab-
Danger originates when lab workers fail to use
caution in handling these materials, fail to
read labels or fail to follow directions as to
use and procedure. There always exists the
possibility of inadvertent or accidental spills
which wilt require immediate, specific and
correct action to minimize a potential hazard.
Inhalation of vapors must be avoided since
many chemicals or compounds are dangerous
in this respect. Most hazards caused in the lab
result from inattention, carelessness and poor
housekeeping. Some specific rules are listed
below:
1. Use chemicals with due respect. Know
their properties and how to use them.
2. Be sure each bottle or container is labeled
for contents, date, warnings, etc.
3. Read and follow directions carefully.
4. Arrange and store chemicals according to
poison, flammability, explosiveness, etc.,
and in proper areas.
5. Use existing ventilation.
6. Wear proper clothing; i.e., rubber gloves,
aprons, safety glasses, etc.
7. Know the antidote for poisonous
chemicals and keep these posted in lab.
8. When collecting samples, use appropriate
sample collecting devices.
9 Use the eye wash in the lab to flush
harmful chemicals accidently splashed on
the face and the emergency shower to
flush chemicals off other parts of the
body.
General Plant Safety
All personnel are to assume the responsibility
of keeping walking areas safe and free of
tools, debris, spills, grease, etc., checking to
see that guards are in place on operating
equipment, chain rails are in place and all
areas properly lighted.
Electrical Safety
1. Lock out and tag main switch of electrical
equipment before working on it.
2. Do not remove tag without first checking
with person who initialed the tag.
3. Notify plant superintendent in the event a
motor circuit breaker trips out.
4. Only trained plant personnel are to open
motor control center panels to perform
authorized work.
5. Report and log any unusual motor temp-
erature, noise, vibration, etc.
The safety material presented in this manual
is an incomplete summary of general safety
procedures. All plant operators should review
their practices from time to time. One of the
best manuals on plant safety for operators is
Safety in Wastewater Works MOP No. /, 1975
Edition published by the Water Pollution
Control Federation.
The following charts summarize details associ-
ated with devices and their function in
digester safety.
145
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DIGESTER SAFETY DEVICES
ITEMS
GAS
1. Methane-is explosive in
contact with air.
2. H2S (hydrogen sulfide)-can
be an odorless gas in lethal
concentrations.
3, General
DISEASE TRANSMISSION
Such as:
Skin diseases
Typhoid
Dysentery
SAFETY DEVICES
Flame Arrestors
Thermal Valves
Water Seal
Pressure Relief Valve
Vacuum Breaker Valve
Pressure Regulator
Automatic Gas Pilot Valves
Gas Detector
Self-Contained Air Pack
Good Ventilation
No smoking, sparks or open
ffarne.
Good inspection and
maintenance program on gas
system and safety devices.
Personal Hygiene
Wash basin
Showers
Rubber clothing
Boots, gloves & aprons
FUNCTION
Protect against flashback.
Shut off gas.
Vents excessive gas to atmosphere and
allows air into digester under vacuum.
Vents excessive gas pressure. v
Brings air into digester to break vacuum.
Controls gas pressure on system.
Controls gas burners.
To detect presence of H2$
To protect personnel
To remove gases from area.
To prevent explosion or fire.
To be sure they work when needed.
To prevent spread of diseases into body
MAINTENANCE
Inspect monthly dnd clejn every 6
months or as experience dictates
Inspect every 6 months or more
often for proper operation.
Inspect every 6 months or more
often for proper operation.
Check diaphragm every 6 months.
Check monthly.
Check monthly.
Service according to manufacturer's
instructions.
Check for corrosion and proper
water pressure. Operate showers
weekly. Check water flow rate
annually.
-------
DIGESTER SAFETY DEVICES (Cont.)
ITEMS
CHEMICALS
Danger from dust, inflammation
and burns.
PHYSICAL INJURY
Danger from falls and misuse
of equipment.
ELECTRICAL
Danger from shock and fire.
FIRE
SAFETY DEVICES
Self-contained air pack
Rubber gloves and aprons
Face dust masks
Eye wash
Showers
Machine guards
Railings and safety chains
Safety ladders
Safety harness
Housekeeping
Lighting
First aid kit
Electrical lock-out tags
Rubber mats
Maintenance program
Portable fire extinguishers
FUNCTION
To provide a noncontaminated source of
air for a limited period of time in
locations with deficient oxygen and/or
lethal gases.
To prevent physical injury.
To prevent accidental turning on of
equipment. To prevent electrical shock
by grounding through body. To keep
equipment clean.
To put out fires.
MAINTENANCE
Check air pack monthly. Chunk
duthiny each time it is worn
Check machine guards, safety
chains and lighting daily. Perform
housekeeping continually. Check
ladders and harness each time used.
Check first aid kit weekly.
Provide a sound maintenance
program.
Check monthly. Invite
representatives from fire
department to set up routine
for testing and checking fire
protection equipment.
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SAFETY RULES AND REGULATIONS
FOR THE PREVENTION OF ACCIDENTS
1 Protect your head! Wear a hard hat at all
times. Except in the office, lab or break
areas.
2. Prevent falling! Keep all areas clear and
clean.
o Pick up all loose objects, tools, trash,
ladders, hose, etc.
o Clean up all oil or grease spills
immediately.
3. Prevent body infections and disease!
o Do wash hands.
o Do wear gloves when working on or
with sewage equipment or collecting
samples.
o Do shower and change clothing
before going home.
4. Do use common sense when moving or
lifting heavy objects.
o Use proper equipment.
o Lift with your legs—not your back.
5 Do not RUN to answer the telephone!
6 Use handrails on stairways.
7 NEVER work on equipment without:
o Locking it out at push button or
circuit breaker.
o Tagging main circuit breaker.
8. Know where safety equipment is and
how to USE it!
9 Know locations of all fire extinguishers
and how to use them!
10 All injuries, even scratches or skin
abrasions, MUST be reported and first
aid given!
11 BE ALERT to safety conditions around
the plant!
If something is out of place or not work-
ing, fix it! Examples: light bulbs burned
out, safety chains not in place, padlocked
equipment not locked.
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CASE HISTORIES
LOADING
Controlling Waste Activated Sludge Load to a
Digester
A low solids concentration in the digester
feed caused detention time problems at a
5 mgd activated sludge plant treating wastes
from an industry producing corn chips. This
was a result of mixing waste activated with
the raw sludge. The problem was solved by
converting one of the two primary clarifiers
to a thickener. All of the waste activated
sludge was then diverted to the new thick-
ener. The thickened waste activated sludge is
then separately digested in one primary and
one secondary digester while raw sludge is
treated in another pair of digesters. By
prethickening, the waste activated sludge was
concentrated to approximately 3.3 percent
solids and with separate digestion the
digestion time was increased allowing both
systems to function efficiently.
Use of Soda Ash to Control Organic
Overloading
Vegetable processing plants seasonally cause
over 100 percent increase in the amount of
sludge handled at one plant. The operators
daily monitor the volatile acids and alkalinity
ratio for digester control during the pro-
cessing season. When the ratio climbs above
0.25, soda ash is added to bring it back into
control. As one example, when the ratio
reached 0.25, 500 pounds of soda ash were
added and then, seven days later when the
ratio again approached 0.25, 1,500 pounds
were added. Following these two additions,
the ratio dropped back down to less than .1
and gas production increased to its previous
level.
Hydraulic Overload Control by Using Polymer
A 10 mgd primary plant was hydraulically
overloaded and detention times were less than
design.
A program was implemented to decrease the
volume of sludge being fed to the digester.
This was accomplished by adding polymer to
the thickener at about 0.2 milligrams per liter
dosage to reduce the volume of sludge being
pumped. The polymer used was Zimmite
No. 651.
Grit Removal in a Single Stage Digester
In a plant that was handling twice its design
load, a single stage digester finally failed to
operate due to a thick scum blanket and
accumulation of grit. This plant operator
corrected the problem by opening all possible
openings, such as manhole covers and sample
vents, and allowing the digester to sit idle
with no recirculation. The scum blanket
formed a cover thick enough to prevent odors
in the area.
In order to move excess grit from the bottom,
an air compressor with a long pipe was
obtained and air was fed into the bottom of
the digester while sludge was being drawn off
to the beds. If tried in other locations, this
procedure might be safer using steam.
Breaking up a Scum Blanket with a Pump
How can a scum blanket be broken up
without emptying the digester? A plant in the
Northwest which had an eight-to-ten-foot
scum blanket in an existing digester, solved
the problem by inserting a large-capacity
149
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chopper type pump (Vaughan Scum Gun)
through a digester manhole. Several pre-
cautions were necessary in this operation.
1. Safety precautions were exercised to pre-
vent explosive situations during the
installation.
2. Very rapid breakup of the scum caused a
load on the digester because food, which
had been tied up in the scum, was released
into solution very rapidly. It was neces-
sary to monitor volatile acids and alka-
linity frequently, similar to any heavy
organic loading.
3. Floating covers must be balanced to
counter loads caused by placement of the
pump. This is particularly important if the
pump is placed off center.
MIXING
Use Motor Amperage Readings to Indicate
Impeller Wear
A plant in Washington noted progressively
worse mixing results in a digester with a draft
tube. This unit had a reversible propeller
mounted on it. When the unit was pulled for
inspection, the propeller which was originally
20 inches in diameter, had been worn to a
10-inch diameter. Amperage readings were
compared and it was noted that the amperage
had been getting progressively lower because a
smaller volume of sludge was being moved.
Regular monitoring of the motor's amperage
would have warned the operator about this
problem.
LINE PLUGGING
How to Unplug a Supernatant Line
Continuous plugging of supernatant lines by
scum can be a serious problem, particularly in
a fixed cover digester. In one plant, a one-inch
pipe was passed through a rubber plug. The
plug was fit tightly into the supernatant line
and high-pressure water discharged through
the pipeline into the digester, dislodging scum.
Freezing a Sludge Line to Install a Valve
During the remodeling construction at one
plant, it was necessary to break into a live
dram line that had no valve in it. This was
done by constructing a two-piece collar to fit
around the pipe. The collar was approxi-
mately four feet long and four inches larger in
diameter than the sludge line. A space was left
around the entire diameter of the pipe and
the length of the device. Liquid nitrogen was
fed into the space in the collar. This method
froze the sludge in the pipeline in about two
hours, blocking the line. The valve was
inserted in the line below the frozen section.
About eight hours later the frozen sludge had
thawed and began to flow through the newly
installed valve.
TOXICITY
For over a year a plant had had chronic
problems in starting the digester. The cause of
the problem was found to be outside the
plant. The digester would show signs of a
good startup with increasing acid production,
but every weekend the digester would quit
working and on Mondays the operator would
find no digestion taking place. This was
repeated week after week.
Because of the regular cycle of the problem, it
was thought that some industry might be
involved. The operator found that a furniture
factory was consistently dumping about
1,500 gallons of paint waste into the sewer
every Friday.
The problem was handled when the operator
reduced mixing to three hours a day, This
allowed the toxic sludge to stay on one side
of the tank and not become thoroughly and
immediately mixed with the digester
contents. The long-term solution for this
problem is to enforce the industrial waste
ordinance and prevent the paint dumps at the
source.
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COLD WEATHER PROBLEMS
How to Prevent Freezing of Digester Pressure
Relief Valves
Cold weather problems with gas pressure
relief valves are common and one operator
found the solution by placing a barrel over
the relief valve with a light bulb inside it. The
bulb produced enough heat to keep the valves
from freezing. This type of device should
contain an explosionproof cover over the
bulb.
Anothe nethod of solving freezing problems
in digester pressure relief valves is to put a
light grease mixed with salt on the mating
surfaces. This will prevent freezing. However,
it should be cleaned off in the summertime to
prevent corrosion.
DIGESTER DRAINING
Solving a Sludge Removal Problem
Plant operators in one plant needed to empty a
digester for routine cleaning. An area suitable
for sludge storage was found in a lagoon not
connected to the digester. Some method was
needed to transfer the sludge other than the
existing sludge drawoff line.
It was determined that the city personnel
could do the job less expensively than a
contractor if they had their own pump and
used their own personnel. A pump normally
used for emptying barnyard manure pits was
fitted with an explosionproof motor and
hoisted to the top of the digester.
A tripod was arranged over a large manhole
opening and the pump lowered into the
digester. A discharge hose was attached to an
irrigation pipe to carry the sludge to the
lagoon.
The pump had a cutter bar underneath the
impeller which chopped up thick scum, rags,
sticks, etc. When the thick scum was broken
up with high pressure water, it flowed quite
easily through the pump.
As the sludge level dropped, the pump was
lowered to keep it approximately 1 % to 2 feet
below the surface of the sludge.
About two digester volumes of water were
needed to liquify the sludge enough to pump.
A scum layer about three feet thick and a grit
layer about four feet deep were removed from
a 50-foot diameter digester in ten days.
How to Control Odors Using Hydrogen
Peroxide
When it was necessary to drain a digester
containing partially digested sludge, odors
were a problem. A line was tapped into the
sludge draw-off pipeline and hydrogen per-
oxide solution at 30 percent concentration
was added to the sludge. The concentration
was about one gallon for every 12,000 gallons
of sludge drawn to the beds.
PLANT STARTUP
A plant with two
secondary, found it
primary for repairs.
procedure was used.
Temp.
Day Deg. pH
69 6.7
75 6.1
7 82 5.4
8 92 5.5
9 93 5.6
10 97 5.9
digesters, primary and
necessary to empty the
The following startup
Tank being filled with
raw sewage.
Tank full.
Added 10,000 gallons
secondary sludge from
another plant.
Added 250 Ibs. of lime.
151
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11
12
13
19
20
25
35
79
97
97
98
97
98
98
98
98
5.7
5.7
5.7
5.7
5.8
5.9
6.0
7.1
Added 400 Ibs. of lime.
Added 200 Ibs. of lime.
Added 200 Ibs. of lime.
Added 300 Ibs. of lime.
Added 150 Ibs. of lime.
Added 1,000 Ibs. of lime
in last five days.
Added 1,000 Ibs. of lime
in last ten days.
Added 2,000 Ibs. of lime
in last 44 days in 100-lb.
or less increments.
Also added 2'/2 gat. de-
foaming agent about day
60 to prevent foaming
Sludge was being added at about 4,000 gpd at
3.3 percent solids and 77 percent volatile. At
the end of about 80 days, the volatile
reduction averaged about 51 percent.
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DIGESTER GADGETS
Operators have devised several gadgets that
assist in solving problems around their plants.
A few examples are listed on the following
pages showing what can be done with little
expense and some ingenuity.
DIGESTED SLUDGE SAMPLER—This "home-made" sampler is made from materials found
around the plant (some, such as the rubber balls, might even be retrieved off bar screens).
The lead can be poured around the inner can using a metal container approximately one inch
larger in diameter. The spring support and trip mechanism can be readily fashioned from scrap
materials. The spring is weak enough so that it trips without lifting the device.
A tripod with a reel for raising and lowering can be used to allow selecting samples at the desired
depths.
u
Rope or Cable
Calibrated @> 5 Feet
Trip Mechanism
Spring
Rubber Ball
Chain Attached To
Lifting Rope
FIGURE 3-1
DIGESTED SLUDGE SAMPLER
-------
GAS PRODUCTION ESTIMATOR-When the gas meter is not operating, the following system
may be used as a rough estimate of gas production.
1. Fill the carboy with sludge from the active zone.
2. Turn on heating pad and hold contents at same temperature as digester.
3. Fill a 500 ml graduated cylinder with water and invert it in a 2 liter beaker over the end of
the gas hose, being careful to keep the cylinder filled with water and not admit any air.
4. Allow gas to purge from the carboy for one hour, then set gas tube under lip of cylinder.
5.' Note length of time to displace 400-500 ml.
6. Repeat for several consecutive days to get trend of production.
Thermometer Q|ass Tube &
, Plastic Tubing
, 500 Ml Graduated
Cylinder
. 2 Liter Beaker
Electric Heating
Pad
FIGURE 3-2
GAS PRODUCTION ESTIMATOR
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SCUM BLANKET FINDER—One method for finding the depth of the scum blanket in a digester
is illustrated here.
A one inch pipe marked every foot is attached to a wooden paddle by a hinge. This can be
pushed between the digester wall and cover in the first position.
As the finder is raised after passing the bottom of the blanket, the paddle will straighten out and
lock under the scum blanket. The appropriate depth mark is noted, the paddle pulled back
parallel with the pole and lifted out of the digester.
Nylon Cord
VPipe
Mark Every Foot
Hinge
Lowering and
Raising Position
Push Down
Between
Wall and Cover
Wall-
Measuring
Position
Floating
Cover
Scum
Blanket
Measuring
Method
FIGURE 3-3
SCUM BLANKET FINDER
155
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SUPERNATANT LINE PURGE DEVICE-Plugged lines due to scum can cause severe problems
in fixed cover digesters, particularly in cold weather when pressure relief valves may freeze.
A two inch piece of rubber approximately the same size as the I.D. of the line can be fitted with
a piece of pipe through the center and secured for moving up and down in the line.
Either water or steam can be used to loosen the scum.
This may be used also in a chronically plugged sludge line if a tee or wye and valve are provided
for access.
Pipe Thread to Hose Thread
Adapter
2" x 6" Rubber Ring
FIGURE 3-4
SUPERNATANT LINE PURGE DEVICE
-------
AUTOMATIC PUMP SHUT-OFF CONTROL-To prevent damage to the piston pump, sludge
piping or valves, a pressure shut-off control can be added to existing systems with a minimum of
expense as described below.
An ad|ustable pressure switch to be used as a permissive interlock in the pump control circuit can
be installed. When pressures downstream from the pump exceed the switch setting, the pump
shuts off. This effectively prevents damage in the event a downstream valve is unintentionally
closed or if plugging develops in the discharge line.
The switch is available off the shelf at electrical or control supply firms.
Drive Motor
Positive Displacement
Sludge Pump
— O
L •
a
FIGURE 3-5
PRESSURE SHUT-OFF SYSTEM TO PREVENT DAMAGE TO PUMP
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RAW SLUDGE THICKNESS CONTROL-A rather simple control system was installed at one
plant to prevent pumping excess water to the digester by using the amperage from the piston
pump motor to sense changing sludge thickness.
Amperage readings were recorded at the same time that total solids samples were collected. It was
found that as the total solids decreased, amperage decreased and when the values for the two
were plotted on a graph, the minimum desirable solids content could be matched with an amper-
age reading (see Appendix G for information on graphing).
A load meter that sensed amperage of the motor was installed in conjunction with a one minute
time delay switch. When The pump came on automatically, sludge was cleared out of the line,
then the load switch sensed the sludge thickness and the pump shut off if the sludge thinned out
before the time clock timed out.
FIGURE 3-6
RAW SLUDGE THICKNESS CONTROL
158
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SUPERNATANT SELECTOR—An "operator-made" device was installed in an existing digester
while it was down for repairs that helped draw the best possible supernatant even though liquid
level varied.
A hoist was mounted on the tank wall and %" plastic coated boat control cable was attached to a
section of movable supernatant pipe. A swivel joint composed of an ell and street ell allowed the
draw-off point to be changed by operation of the hoist.
Hoist
FIGURE 3-7
SUPERNATANT SELECTOR BUILT BY OPERATORS
159
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Learning Resource 11
"Anaerobic Digestion Analysis Training Module" - 5.120.2.77
Kirkwood Community College
6301 Kirkwood Boulevard, S.W.
P.O. Box 2068
Cedar Rapids, IA 52406
Prepared for the:
Iowa Department of Environmental Quality
Wallace State Office Building
Des Moines, IA 50319
Presented are excerpts from an instructional module package for use
by an instructor familiar with alkalinity, volatile acids, and carbon
dioxide determinations for an anaerobic sludge digester. Included
in the package are handouts, instructor guides, student handouts, and
transparency masters. The learning activity detailed here describes
the determination of volatile acids by the silicic acid method.
161
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ANAEROBIC DIGESTER TEST PROCEDURES
Topics: Alkalinity
Alkalinity Testing
Determination of Alkalinity
Digester Gas Analysis
Volatile Acids
Volatile Acids Testing
Volatile Acids/Alkalinity Ratio
Determination of Volatile Acids by
Silicic Acid Method
Determination of Volatile Acids by
Rapid Distillation
Determination of Volatile Acids by Hach
Method
Selection of Method for Volatile Acids
Analysis
Objective: When the participants complete this module
they should be able to analyze anerobic
digester contents for alkalinity and
volatile acids and report the results as a
volatile acids/alkalinity ratio. The
participant should also be able to determine
the amount of C02 in digester gas upon
completion of this module.
References: Anaerobic Sludge Digestion Manual (EPA)
Operation of Wastewater Treatment Plants
(Kerri)
Standard Methods, 13th and 14th Eds.
Instructional Aids: EPA slide-tape is available from:
National Training and Operational
Technology Center
Audio-Visual Lending Library
26 West St. Glair
Cincinnati, Ohio 45268
Overheads
Typed overheads are example of overhead
layout and content. For classroom use,
the overhead should be constructed using
colored, % inch dry transfer letters.
Other overheads may be copied directly
162
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Submodule Title:
Topic:
Instructional Aids:
Instructional Approach:
References:
Class Assignments:
Instructor Notes:
Handout
Volatile Acids
Silicic Acid Method
Handouts
Handouts may be copied directly.
Laboratory supplies and apparatus
Supplies and apparatus should be supplied
per handouts so that participants may
work in groups of 2 or 3
Volatile Acids
Determination of Volatile Acids by Silicic
Acid Method
1. Identify proper apparatus and reagents
needed for the volatile acids test by
silicic acid method.
2. Obtain and prepare a proper sample for
the volatile acids test.
3. Conduct a volatile acids test using the
silicic acid method given proper test
equipment, reagents, procedures sheet
and sample.
4. Translate the raw data from the volatile
acids test into proper units of
expression given appropriate conversion
factors and equations.
Handout Silicic Acid Method
Laboratory apparatus and reagents per handout
Overhead sample calculation
Laboratory
Standard Methods, 14th Ed.
Kerri
Perform analysis
Instructor Outline:
1. List the apparatus and reagents needed
for silicic acid method.
Demonstrate the makeup of reagents and
setup of apparatus.
2. Discuss sample collection and if possible
demonstrate sample collection.
163
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3.
Demonstrate the silicic acid method for
volatile acids.
Overhead
Sample Calculations
Example
Apparatus:
Have participant perform the test.
4. Work a sample calculation
Have participant work calcualtions
1. Centrifuge or filtering apparatus
2. Two 50 ml graduated cylinders
3. Two medicine droppers
4. Crucibles, Gooch or fritted glass
5. Filter flask
6. Vacuum source
7. One 50 ral beaker
8. Two 5 ml pipettes
9. Buret
1. Silicic Acid, solids, 100-mesh. Remove
fines from solid portion of acid by
slurrying the acid in distilled water and
removing the supernatant after allowing
settling for 15 minutes. Repeat the
process several times. Dry the washed
acid solids in an oven at 103°C. and then
store in a desiccator.
2. Chloroform - butanol reagent. Mix 300 ml
chloroform, 100 ml N-butanol, and 80 ml
0.5 HnSO^ in separatory funnel and allow
the water and organic layers to separate.
Drain off the lower organic layer through
filter paper into a dry bottle.
3. Thymol blue indicator solution. Dissolve
80 mg thymol blue in 100 ml absolute
methanol.
4. Phenolphthalein indicator solution.
Dissolve 80 mg phenolphtahlein
in 100 ml absolute methanol.
5. Sulfuric acid, 10 N.
6. Standard sodium hydroxide reagent, 0.02 N
Prepare in absolute methanol from cone.
NaOH stock solution in water.
164
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Procedure:
Precautions:
1. Centrifuge or filter enough sludge to
obtain a sample of 10 to 15 ml. This
same sample and filtrate should be used
for both the volatile acids test and
the total alkalinity test .
2. Measure volume (10 to 15 ml) of sample
and place in a beaker.
3. Add a few drops of thymol blue indicator
solution.
4. Add 10 N H2S04, dropwise, until thymol
blue color just turns to red.
5. Place 10 grams of silicic acid (solid
acid) in crucible and apply suction.
6. With a pipette, distribute 5.0 ml
acidified sample (from step 4) as
uniformly as possible over the column.
Apply suction briefly to draw the
acidified sample into the silicic acid
column. Release the vacuum as soon as
the sample enters the column.
7. Quickly add 50 ml chloroform-butanol
reagent to the column.
8. Apply suction and stop just before the
last of the reagent enters the column.
9. Remove the filter flask from the crucible.
10. Add a few drops of phenolphthalein
indicator solution to the liquid in the
filter flask.
11. Titrate with 0.02 N NaOH titrant in
absolute methanol, taking care to avoid
aerating the sample. Nitrogen gas of
C02 - free air delivered through a small
glass tube may be used both to mix the
sample and to prevent contact with
atmospheric C02 during titration
(C02 - free air may be obtained by
passing air through ascarite or
equivalent). Volume of NaOH used in
sample titration, a = _ ml.
12. Repeat the above procedure using a blank
of distilled water. Volume of NaOH used
in blank titration, b = _ ml.
1. The sludge sample must be representative
of digester. The sample line should be
allowed to run for a few minutes before
the sample is taken. The sample
temperature should be as warm as the
digester itself.
165
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2. The sample for the volatile acids test
should not be taken immediately after
charging the digester with raw sludge.
Should this be done, the raw sludge may
short-circuit to the withdrawal point
and result in the withdrawal of raw sludge
rather than digester sludge. Therefore,
after the raw sludge has been fed into
the tank, the tank should be well mixed
by recirculation or other means before
a sample is taken.
3. If a digester is performing well with low
volatile acids and then if one sample
should unexpectedly and suddenly give a
high value, say over 1000 mg/1 of
volatile acids, do not become alarmed.
The high result may be caused by a poor,
nonrepresentative sample of raw sludge
instead of digested sludge. Resample and
retest. The second test may give a more
typical value. When increasing volatile
acids and decreasing alkalinity are
observed, this is a definite warning of
approaching control problems.
Corrective action should be taken
immediately, such as reducing the feed
rate, reseeding from another digester,
maintaining optimum temperatures,
improving digester mixing, decreasing
sludge withdrawal rate, or cleaning the
tank of grit and scum.
Example: Equivalent Weight of Acetic Acid, A = 60 mg/ml
Volume of Sample, B = 10 ml
Normality of NaOH titrant, N = 0.02 N
Volume of NaOH used in sample titration,
a _ 2.3 ml
Volume of NaOH used in blank titration,
b = 0.5 ml
Calculation: Volatile Acids, mg/1 = A x 1000 ml/1 x N(a-b)
= 60 mg/ml x 1000 ml/1 x 0.02 (2.3 ml - 0.5 ml)
10 ml
= 216 mg/1
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PART III
Abstracted Reference Materials
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TITLE ACCELERATED DIGESTION OF CONCENTRATED SLUDGE.
AUTHOR SHINDALA, A.; DUST, J. V.; CHAMPION, A. L.
CORP AUTH MISSISSIPPI STATE UNIV., STATE COLLEGE. DEPT. OF SANITARY EN-
GINEERING.
AVAIL WATER AND SEWAGE WORKS, VOL. 117 NO. 9, SEPTEMBER, 1970, P
329-332, 2 FIG, 4 TAB, 16 REF
DESC *ANAEROBIC DIGESTION; *SLUDGE TREATMENT; *DOMESTIC WASTES;
ALKALINITY; HYDROGEN ION CONCENTRATION; PERFORMANCE;
*WASTEWATER TREATMENT; SOLIDS CONCENTRATION; VOLATILE ACIDS;
GAS PRODUCTION; LOADING RATE; VOLATILE MATTER REDUCTION.
ABSTRACT A LABORATORY STUDY WAS CONDUCTED TO DETERMINE THE EFFECT OF
CONCENTRATION OF SLUDGE ON THE ANAEROBIC DIGESTION OF A
DOMESTIC SLUDGE. SLUDGE CONCENTRATIONS OF 5, 15, 25, AND 35
PERCENT WERE USED AND A DIGESTION TEMPERATURE OF 92 TO 95F WAS
MAINTAINED. LOADING PERIODS OF 10, 15, 20, AND 30 DAYS WERE
USED. GAS PRODUCTION OF ALL DIGESTERS WAS RECORDED AND
CHANGES IN PH, ALKALINITY, VOLATILE ACIDS, AND REDUCTION IN
VOLATILE MATTER ADDED TO THE DIGESTERS WERE OBSERVED EVERY
FOUR DAYS. RESULTS SHOWED THAT SOLIDS CONCENTRATION HAD A DE-
FINITE EFFECT UPON DIGESTION AS THE PERCENT REDUCTION IN
VOLATILE MATTER DECREASED WITH INCREASED SOLIDS CONCENTRATION
FOR ALL LOADINGS. ALSO, THE VOLATILE ACIDS AND ALKALINITY IN
GENERAL INCREASED WITH THE INCREASE IN SOLIDS CONCENTRATION,
HOWEVER, THE PH REMAINED NEARLY CONSTANT. THE MAXIMUM AMOUNT
OF GAS PER LITER OF SLUDGE WAS PRODUCED AT THE 15 PERCENT
SOLIDS LEVEL WHILE THE 5 PERCENT SOLIDS LEVEL PRODUCED THE
MOST GAS PER UNIT OF DRY SOLIDS. LOADINGS OF CONCENTRATED
SLUDGES UP TO 10 MG/L PER DAY PRODUCED AN ACCEPTABLE VOLATILE
SOLIDS REDUCTION. (GALWARDI-TEXAS)
TITLE ALBUQUERQUE PLANT DESIGNED WITH COMPUTER IN MIND.
AUTHOR RICOY, J. L.; MOTOTAN, W. I.
CORP AUTH WILLIAM MATOTAN AND ASSOCIATES, ALBUQUERQUE, NEW MEXICO.
AVAIL WATER AND WASTES ENGINEERING, VOL. 13, NO. 1, P 32-35, 37,
JANUARY, 1976.
DESC *TREATMENT FACILITIES; *WASTEWATER TREATMENT; NEW MEXICO;
ACTIVATED SLUDGE; TRICKLING FILTERS; *AERATION; COMPUTERS;
EQUIPMENT; SETTLEMENT BASINS; ANAEROBIC DIGESTION; *SEWAGE
TREATMENT; WASTE DISPOSAL; PROCESS CONTROL; ALBUQUERQUE (NM);
SCREW PUMPS.
ABSTRACT A NEW SECONDARY TREATMENT PLANT IN ALBUQUERQUE IS DESCRIBED.
THE NEW ACTIVATED SLUDGE WASTE WATER TREATMENT PLANT INCLUDES
A PROCESS CONTROL COMPUTER SYSTEM, NEW LABORATORY TESTING
EQUIPMENT, AND MONITOR SENSORS. THE TWO EXISTING PLANTS
169
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INCORPORATE TRICKLING FILTERS. IN THE NEW SCHEME, EFFLUENTS
FROM THE TWO OLD PLANTS COMBINE AND PASS THROUGH A SERIES OF
SCREW PUMPS TO THE AERATION TANKS, THE FINAL SETTLING TANKS,
AND THEN TO THE RIO GRANDE RIVER FOR DISPOSAL. AERATION
FACILITIES WERE DESIGNED SO THAT THE PLANT CAN OPERATE AS
EITHER CONVENTIONAL TAPED AERATION, STEP AERATION, OR CONTACT
STABILIZATION. DIFFUSED AIR IS USED FOR MIXING AND OXYGEN
NEEDS. FINAL SETTLING TANKS ARE OF RAPID SLUDGE REMOVAL TYPE.
ANAEROBIC DIGESTION HANDLES SLUDGE SOLIDS, AND THE RESULTING
GAS IS USED TO GENERATE ELECTRICITY THROUGH THE SYSTEM. PUMPS
AND BLOWERS ARE CONTROLLED BY THE COMPUTER ON THE BASIS OF A
RUNNING TIME INVENTORY. THIS IS ALSO USED AS AN AID IN DE-
TERMINING MAINTENANCE AND OVERHAUL SCHEDULES. DISSOLVED OXY-
GEN LEVELS IN THE AERATION TANKS ARE CONTINUOUSLY MONITORED
BY THE COMPUTER. ALGORITHMS ARE PROVIDED IN THE SYSTEM FOR A
WIDE VARIETY OF CONTROLS AND SAMPLINGS. THE COMPUTER HAS A
FIXED HEAD MASS MEMORY OF 246K AND A CORE MEMORY OF 24K, BOTH
EXPANDABLE. (PINTO-FIRL)
TITLE ANAEROBIC DIGESTION AND ANALYTICAL CONTROL (XT-34).
AVAIL NATIONAL TRAINING AND OPERATIONAL TECHNOLOGY CENTER, 26 W. ST.
CLAIR, CINCINNATI, OH 45268.
DESC AUDIOVISUAL AIDS; INSTRUCTIONAL MATERIALS; LABORATORY PRO-
CEDURES; MICROBIOLOGY; POST-SECONDARY EDUCATION; ANAEROBIC DE-
COMPOSITION; SLUDGE STABILIZATION; WASTEWATER TREATMENT; POL-
LUTION; WATER POLLUTION CONTROL.
DESC NOTE 13 MINUTE TAPE, 62 SLIDES, AND A SCRIPT.
ABSTRACT THIS MODULE IS DESIGNED FOR EXPERIENCED WASTEWATER TREATMENT
PLANT OPERATORS WHO WISH TO UPGRADE PLANT PERFORMANCE AND TO
INCREASE THEIR OWN KNOWLEDGE AND SKILLS. IT PRESENTS A DIS-
CUSSION OF THE ANAEROBIC DECOMPOSITION PROCESS UTILIZED TO
TREAT ORGANIC MATERIALS IN WASTES, AND THE ENVIRONMENTAL CON-
DITIONS REQUIRED FOR THE INVOLVED BACTERIA. IT ALSO CON-
TAINS A DESCRIPTION OF THE RELATED PROCESS CONTROL ANALYSIS,
VOLATILE ACIDS (STEPWISE PROCEDURE GIVEN), ALKALINITY, TOTAL
ORGANIC NITROGEN CONTENT, TOTAL ORGANIC LOAD, PH, AND GAS PRO-
DUCTION.
TITLE ANAEROBIC DIGESTION ANALYSIS. TRAINING MODULE 5.120.2.77.
PUB DATE 77
AVAIL ERIC DOCUMENT REPRODUCTION SERVICE, P.O. BOX 190, ARLINGTON, VA
22210.
DESC CHEMISTRY; INSTRUCTIONAL MATERIALS; LABORATORY PROCEDURES;
POST-SECONDARY EDUCATION; CARBON DIOXIDE; WASTEWATER TREATMENT
SECONDARY EDUCATION; UNITS OF STUDY; WATER POLLUTION CONTROL;
SLUDGE DIGESTION.
170
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DESC NOTE 44P.
ABSTRACT THIS DOCUMENT IS AN INSTRUCTIONAL MODULE PACKAGE PREPARED IN
OBJECTIVE FORM FOR USE BY AN INSTRUCTOR FAMILIAR WITH ALKALIN-
ITY, VOLATILE ACIDS AND CARBON DIOXIDE DETERMINATIONS
FOR AN ANAEROBIC SLUDGE DIGESTER. INCLUDED ARE OBJECTIVES,
INSTRUCTOR GUIDES, STUDENT HANDOUTS AND TRANSPARENCY MASTERS.
THIS MODULE CONSIDERS TOTAL AND BICARBONATE ALKALINITY TITRA-
TION, PERCENT CARBON DIOXIDE AND DIGESTER GAS BY THE CAR-
BON DIOXIDE ABSORPTION METHODS AND VOLATILE ACIDS CON-
CENTRATION IN DIGESTER SLUDGE. THE RAPID DISTILLATION, THE
SILICIC ACID, AND THE "HACK" ESTERIFICATION METHODS ARE ALSO
DETAILED.
TITLE ANAEROBIC SLUDGE DIGESTION.
PUB DATE 68
AVAIL WATER POLLUTION CONTROL FEDERATION PUBLICATIONS DEFT., 3900
WISCONSIN AVE. N.W., WASHINGTON, DC 20016.
DESC ANAEROBIC DIGESTION; INSTRUCTIONAL MATERIALS; OPERATIONS
WASTEWATER; SLUDGE DIGESTION; SLUDGE; WASTEWATER TREATMENT;
POST SECONDARY EDUCATION; WASTEWATER SLUDGE.
DESC NOTE PRICE: $3.50-MEMBERS, $7.00-NONMEMBERS.
ABSTRACT DESIGNED TO PROVIDE TREATMENT PLANT OPERATORS WITH THE
FUNDAMENTAL THEORY OF ANAEROBIC SLUDGE DIGESTION AS IT CAN BE
APPLIED TO SOLVING PLANT OPERATION PROCEDURES AND PROBLEMS.
TITLE ANAEROBIC SLUDGE DIGESTION: OPERATIONS MANUAL.
AUTHOR ZICKEFOSSE, C.; HAYES, R. B.
AVAIL SUPERINTENDENT OF DOCUMENTS, U.S. GOVERNMENT PRINTING OFFICE,
WASHINGTON, DC 20402, PRICE: $9.95
DESC *ANAEROBIC DIGESTION; INSTRUCTIONAL MATERIALS; *MANUALS;
LABORATORY PROCEDURES; MAINTENANCE; *OPERATIONS (WASTEWATER);
SAFETY; SAMPLING; *SLUDGE; *SLUDGE TREATMENT; *WASTEWATER
TREATMENT.
DESC NOTE 189P
ABSTRACT COVERS TROUBLESHOOTING, GENERAL OPERATION, SAFETY, START-UP OF
UNITS, BASIC THEORY, SAMPLING, AND LABORATORY TESTING. MANUAL
DESIGNED FOR OPERATORS. FORMAT ALLOWS PORTION OF MANUAL OF
MOST INTEREST TO BE USED DIRECTLY.
TITLE ANAEROBIC WASTE TREATMENT FACILITY.
AUTHOR GARROTT, W. A. , JR.
AVAIL UNITED STATES PATENT 4,040,963. ISSUED AUGUST 9, 1977. OF-
FICIAL GAZETTE OF THE UNITED STATES PATENT OFFICE, VOL. 961.
NO. 2, P 759, AUGUST, 1977.
DESC *ANAEROBIC DIGESTION; *SLUDGE DIGESTION; *PATENTS; *DIGESTION
TANKS; *MIXING; DESIGN DATA; SLUDGE TREATMENT; WASTEWATER
TREATMENT.
171
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ABSTRACT AN ANAEROBIC DIGESTER WHICH CONTAINS A MIXING ZONE, A QUIESCENT
ZONE, A CLEAR ZONE, AND AN INLET AND OUTLET FOR THE MOVEMENT OF
WASTE WATER HAS BEEN PATENTED. THE SYSTEM CAN PREVENT THE EN-
TRY OF LARGE PARTICLES FROM THE QUIESCENT ZONE INTO THE CLEAR
ZONE, AND SELECTIVELY CIRCULATE MATERIAL BETWEEN THE MIXING AND
CLEAR ZONES WITH A ROTOR BELOW THE LIQUID LEVEL IN THE
DIGESTER. ROTARY CIRCULATION IS ACCOMPLISHED BY A STATIONARY
CONDUIT ROTOR AND A SECOND CONDUIT MEMBER WHICH IS
VERTICALLY MOVEABLE WITH RESPECT TO THE FIRST ROTOR. VERTICAL
MOTION OF THE SECOND ROTOR IS LIMITED SO THAT IT IS ALSO CON-
FINED BELOW THE LIQUID LEVEL IN THE SLUDGE DIGESTER. THE
DIGESTER ITSELF IS A FLAT-BOTTOMED TANK WITH OUTWARDLY SLOP-
ING SIDE WALLS AND A COVER. (SCHULZ-FIRL)
TITLE ANALYSIS AND OPTIMIZATION OF TWO-STATE DIGESTION.
AUTHOR FAN, L. T.; ERICKSON, L. E.; BALTES, J. C.; SHAH, P. S.
CORP AUTH KANSAS STATE UNIV., MANHATTAN. DEPT OF CHEMICAL ENGINEERING.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL. 45 NO. 4,
P 591-610, APRIL, 1973. 11 FIG. 77 EQU, 28 REF.
DESC *ANAEROBIC CONTACT PROCESS; TWO-STAGE DIGESTION; STEADY STATE
ANALYSIS; WASHOUT ANALYSIS; RECYCLE RATIO; ECONOMIC ANALYSIS;
ANAEROBIC PROCESSES.
ABSTRACT A MATHEMATICAL FORMULATION EMPLOYING THE KINETIC MODEL OF WIL-
LIMON AND ANDREWS IS USED TO SIMULATE CONVENTIONAL AND CON-
TACT ANAEROBIC DIGESTION PROCESSES CONSISTING OF TWO
STAGES. PRESENTED IS A SYSTEM OF TWO COMPLETELY MIXED
DIGESTERS IN WHICH THE PROCESS IS CARRIED OUT WITHOUT RECYCLE
(CONVENTIONAL) AND WITH RECYCLE (CONTACT). PERFORMANCE
EQUATIONS OF THE SYSTEM ARE DEVELOPED BY MEANS OF MASS BALANCE.
A UNIFIED ANALYSIS OF THE STEADY STATES OF THE SYSTEM IS MADE
BECAUSE OF THE POSSIBLE EXISTENCE OF MULTIPLE STEADY STATES.
TWO SPECIFIC STEADY-STATE OPERATIONS—NORMAL STEADY-STATE AND
WASHOUT STEADY-STATE—ARE CONSIDERED IN DETAIL. THE CRITICAL
FLOW RATES THAT CAUSE WASHOUT OF SOME OR ALL SPECIES ARE
INVESTIGATED. TO FURTHER CLARIFY THE RESULTS OF THE STEADY-
STATE AND WASHOUT ANALYSES, NUMERICAL SIMULATIONS ARE CAR-
RIED OUT. FINALLY, THE OPTIMAL DESIGN POLICY FOR A TWO-
STAGE CONTINUOUS ANAEROBIC DIGESTER SYSTEM IS DETERMINED BY
JOINING AN ECONOMIC MODEL TO THE PROCESS MODEL. THE OP-
TIMIZATION PROBLEM IS NONLINEAR AND IS PERFORMED USING THE
SIMPLEX SEARCH TECHNIQUE.
TITLE ANNUAL DIGESTER UPSET CORRECTED.
AUTHOR LEE, JOHN P.
CORP AUTH SAN MATED WASTE WATER TREATMENT PLANT, CALIF.
172
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*VOLATILE ACIDS; CARBON DIOXIDE; GAS PRODUCTION; SAN MATEO
(CAL); *ANAEROBIC DIGESTION; *OPERATION AND MAINTENANCE; *WASTE
WATER TREATMENT; HYDROGEN ION CONCENTRATION; LIME; CALIFORNIA;
ACTIVATED SLUDGE; SLUDGE DIGESTION.
ABSTRACT SAN MATEO, CALIFORNIA HAS EXPERIENCED THREE IDENTICAL PRIMARY
SEWAGE DIGESTER UPSETS IN THE PAST THREE YEARS AT ITS MUNICIPAL
WASTE WATER TREATMENT PLANT. THE PRIMARY DIGESTER HANDLES AP-
PROXIMATELY 20,000 GALLONS OF THICKENED SLUDGE PER DAY. THE
UPSETS WERE CHARACTERIZED BY (1) AN INCREASE IN THE VOLATILE
ACID CONTENT OF THE DIGESTER, (2) AN INCREASE IN THE CARBON
DIOXIDE FRACTION OF THE GAS PRODUCED, AND (3) A DRAMATIC DE-
CREASE IN GAS. PRODUCTION-OPERATIONAL DATA WERE PRESENTED FOR
THE PERIODS JUST BEFORE, DURING AND AFTER CORRECTION OF THE UP-
SETS FOR EACH OF THE THREE YEARS. FOR INSTANCE, VOLATILE
ACID CONTENT INCREASED FROM 108 TO 2070 MG/L WHILE C02
INCREASED FROM 27 TO 43 AND GAS PRODUCTION DECREASED FROM
91,600 TO 47,200 CU. FT. DURING THE UPSET OF 1966. THE BREAK-
ING UP OF THE GREASE BLANKET ON THE TOP OF THE DIGESTER
AT THE START OF WARM WEATHER INCREASED THE ACTIVITY OF THE
ACID-FORMING BACTERIA. CONTROL OF THE UPSETS WAS OBTAINED BY
THE ADDITION OF UP TO 600 POUNDS OF LIME AND THE DIVERSION OF
THE RAW SLUDGE TO THE SECONDARY DIGESTER. (GALWARDI-TEXAS)
TITLE ASSESSMENT OF THE MAXIMUM CONCENTRATION OF HEAVY METALS IN
CRUDE SEWAGE WHICH WILL NOT INHIBIT THE ANAEROBIC DIGESTION OF
SLUDGE.
AUTHOR MOSEY, F. E.
CORP AUTH WATER POLLUTION RESEARCH LAB., STEVENAGE (ENGLAND).
AVAIL WATER POLLUTION CONTROL, VOL. 75, NO. 1, P 10-20, 1976. 2 FIG,
7 TAB, 24 REF.
DESC *HEAVY METALS; *ANAEROBIC DIGESTION; *EQUATIONS; SOLIDS RE-
MOVAL; SLUDGE DISPOSAL; *WASTEWATER TREATMENT; SLUDGE TREAT-
MENT.
ABSTRACT A METHOD WAS DEVELOPED TO PREDICT THE EFFECT OF MIXTURES OF
HEAVY METALS ON THE ANAEROBIC DIGESTION PROCESS. TWO EQUATIONS
OF SIMILAR FORM WERE OBTAINED, ONE INDICATING CONDITIONS UNDER
WHICH INHIBITION IS EXPECTED, AND THE OTHER INDICATING CON-
DITIONS UNDER WHICH THE PROBABILITY THAT DIGESTION WILL NOT BE
INHIBITED IS AT LEAST 90%. BOTH EQUATIONS INCLUDE THE CON-
TENT OF ZINC, NICKEL, LEAD, CADMIUM, COPPER, AND SOLIDS AR-
RIVING IN DIGESTING SLUDGE. DIGESTION IS ALSO SAFEGUARDED FROM
HEAVY METAL INHIBITION WHEN THE TOTAL WEIGHT OF THESE HEAVY
METALS IN GRAMS ARRIVING DAILY IN THE CRUDE SEWAGE DOES
173
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NOT EXCEED 4939 TIMES THE AVERAGE DAILY DRY WEIGHT IN TONS OF
SOLIDS FED TO THE DIGESTER. INHIBITION OF OTHER STAGES OF
TREATMENT OCCURS AT HEAVY METAL CONCENTRATIONS SIMILAR TO THOSE
THAT INHIBIT ANAEROBIC DIGESTION. THE EFFECTS ON THE RECEIVING
STREAM AND LAND ON WHICH THE SLUDGE IS SPREAD MUST ALSO BE CON-
SIDERED WHEN FORMULATING SUITABLE CONDITIONS. (SNYDER-FIRL)
TITLE AN ASSESSMENT OF THE MIXING PERFORMANCE OF SEVERAL ANAEROBIC
DIGESTERS USING TRACER RESPONSE TECHNIQUES.
AUTHOR SMART, J.
CORP AUTH ONTARIO MINISTRY OF THE ENVIRONMENT, TORONTO. POLLUTION CON-
TROL BRANCH.
PUB DESC RESEARCH PUBLICATION NO. 72, 1978, 68 P, 17 FIG, 4 TAB, 29
REF, 2 APPEND.
DESC *ANAEROBIC DIGESTION; *MECHANICAL EQUIPMENT; *EVALUATION; *DE-
SIGN CRITERIA; PERFORMANCE; MIXING; WASTEWATER TREATMENT.
ABSTRACT THE MIXING CHARACTERISTIC OF A TYPICAL MODERN ANAEROBIC
DIGESTER WERE ASSESSED BY EVALUATING TEN DIFFERENT DIGESTERS.
THE DIGESTERS STUDIED REPRESENTED EXTREMES IN PHYSICAL SIZE,
AGE, AND CONDITION, AND INCLUDED MOST EQUIPMENT TYPES CURRENTLY
IN USE. DIGESTERS TESTED RANGED IN SIZE FROM 754 CU M TO 7667
CU M AND IN SPECIFIC NAMEPLATE POWER FROM 654 W/1000 CU M TO
6561 W/1000 CU M. DIGESTER MIXING RANGED FROM 10% TO 89% DEAD
SPACE AND AVERAGED ABOUT 45% DEAD SPACE. FOUR OF THE SEVEN
DIGESTERS EXPERIENCED SUBSTRATE SHORT-CIRCUITING RANGING FROM
18 TO 72% OF THE SLUDGE SUBSTRATE INPUT. FOR ALL TEN
DIGESTERS, OBSERVED HYDRAULIC RETENTION TIMES RANGED FROM 18 TO
72% OF THE SLUDGE SUBSTRATE INPUT. NO RELATIONSHIPS WERE SEEN
BETWEEN MIXING EFFICIENCIES AND DIGESTER SIZES, AGES AND
GENERAL CONDITIONS, TYPES OF MIXING EQUIPMENT INSTALLED, AND
SPECIFIC APPLIED NAMEPLATE POWER. A REVIEW OF LITERATURE DATA
SUGGESTED THAT DIGESTERS WERE GENERALLY OVERDESIGNED AND
INDICATED THAT MAXIMUM DIGESTER VOLUME UTILIZATION AND
ELIMINATION OF SUBSTRATE SHORT-CIRCUITING BY IMPROVED DESIGN
AND MIXING EFFICIENCIES WOULD PERMIT HIGHER APPLIED ORGANIC AND
HYDRAULIC LOADINGS. (SMALL-FRC)
TITLE DIGESTION FUNDAMENTALS APPLIED TO DIGESTER RECOVERY—TWO CASE
STUDIES.
AUTHOR DAGUE, RICHARD; HOPKINS, ROBERT L. ; TONN, ROBERT W.
CORP AUTH IOWA UNIV., IOWA CITY. DEPT. OF CIVIL ENGINEERING.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL 42, NO 9, P
1666-1675, SEPTEMBER 1970. 2 FIG, 2 TAB, 16 REF.
174
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DESC *CASE STUDIES; *UPSET RECOVERY; VOLATILE ACIDS; GAS PRODUCTION;
*CONTROL; *DIGESTION; *ANAEROBIC DIGESTION; HYDROGEN ION CON-
CENTRATION; ALKALINITY; AMMONIA; INDUSTRIAL WASTES; WASTE
WATER TREATMENT; METHANE
ABSTRACT THE ANAEROBIC DIGESTION SYSTEMS OF CONCERN ARE LOCATED AT
CLINTON AND KEOKUK, IOWA. BOTH SYSTEMS RECEIVED SIGNIFICANT
SOLIDS FROM GRAIN AND PROCESSING INDUSTRIES. INITIAL CON-
DITIONS AT CLINTON WERE PH 5.5 TO 6.0, VOLATILE ACIDS 4,000
TO 5,000 MG/L, ALKALINITY 2,000 MG/L, GAS PRODUCTION 0. AT
KEOKUK INITIAL CONDITIONS WERE PH 6.0 TO 6.3, VOLATILE ACIDS,
8,000 MG/L, ALKALINITY 3,000 MG/L, GAS PRODUCTION 0. ALKALI WAS
ADDED TO RAISE THE PH TO ABOUT 6.8. THE RECOVERY AT CLINTON
SHOWED SIGNIFICANT GAINS ONLY WHEN THE PH WAS GREATER THAN 6.5.
PART WAY THROUGH THE RECOVERY PERIOD AT KEOKUK THE ADDITION OF
LIME WAS HALTED IN FAVOR OF AQUEOUS AMMONIA. THE USE OF AM-
MONIA TO NEUTRALIZE 10,000 MG/L OF VOLATILE ACIDS RESULTED
IN AMMONIA TOXICITY AND CESSATION OF GAS PRODUCTION. AT THIS
TIME THE CONCENTRATION OF AMMONIA IN THE SYSTEM WAS 2,500 MG/L
AS NH3. THERE IS NO APPARENT RELATIONSHIP BETWEEN THE CON-
CENTRATION OF VOLATILE ACIDS IN THE DIGESTER AND THE RANGES
OF GAS PRODUCTION. A DEFINITE RELATIONSHIP BETWEEN PH AND THE
RATE OF GAS PRODUCTION IS APPARENT; THE MINIMUM PH INDICATED IS
6.5. (HANCUFF-TEXAS)
TITLE THE DISTRIBUTION OF HEAVY METALS IN ANAEROBIC DIGESTION.
AUTHOR HAYES, T. D.
CORP AUTH CORNELL UNIV., ITHACA, NY. DEPT. OF ARGICULTURAL ENGINEERING.
PUB DESC JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL 50, NO 1,
P61-72, JANUARY, 1978. 15 FIG, 5 TAB, 21 REF.
DESC *HEAVY METALS; *ANAEROBIC DIGESTION; *TOXICITY; *SEWERAGE
SLUDGE; *MODEL STUDIES; BIOMASS; NICKEL; COPPER; LEAD; CHRO-
MIUM; ZINC; CADMIUM; SOLUBILITY; DISTILLATION; WASTE WATER
TREATMENT; MUNICIPAL WASTES
ABSTRACT THE DISTRIBUTION OF HEAVY METALS IN ANAEROBIC DIGESTERS HAS
INVESTIGATED USING THREE BENCH-SCALE ANAEROBIC DIGESTERS FED
WITH SEWAGE CONTAINING VARYING CONCENTRATIONS OF HEAVY METALS.
NITRATE SALTS OF CHROMIUM, COPPER, NICKEL, ZINC, CADMIUM, AND
LEAD AND DICHROMATE WERE FED TO THE DIGESTERS IN CONCENTRATIONS
RANGING FROM 5-15,000 MG/LITER BY STEP OR PULSE FEED AP-
PLICATIONS OVER A PERIOD OF 10 DAYS. SLUDGE SAMPLES TAKEN DUR-
ING THE DIGESTION PROCESS WERE SEPARATED INTO SOLUBLE, PRE-
CIPITATED, EXTRACELLULAR, AND INTRACELLULAR FRACTIONS FOR
HEAVY METAL ANALYSIS. DECREASING GAS GENERATION, METHANE CON-
CENTRATIONS, AND ORGANIC ACIDS ACCUMULATION WERE MONITORED
AS INDICATORS OF ANAEROBIC DIGESTION DISRUPTION BY HEAVY
175
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METALS. THE TOXICITY IMPACT OF THE HEAVY METALS ON ANAEROBIC
DIGESTION FOLLOWED THE RELATIONSHIPS: NICKEL, COPPER, LEAD,
CHROMIUM ZINC, WITH NO TOXIC IMPACT OBSERVED FOR THE CADMIUM
DOSES. HEAVY METAL CONCENTRATIONS IN THE DIGESTER WERE DIS-
TRIBUTED BETWEEN THE INSOLUBLE OR PRECIPITATED FRACTION AND THE
INTRACELLULAR OR BIOMASS FRACTION, WITH LITTLE OF THE METALS
EVIDENT IN THE EXTRACELLULAR FRACTION. LEVELS OF HEAVY METALS
WHICH WOULD PRODUCE INHIBITION AND TOXICITY DURING ANAEROBIC
DIGESTION WERE CALCULATED. (LISK-FIRL)
TITLE FIELD MANUAL FOR PERFORMANCE EVALUATION AND TROUBLESHOOTING AT
MUNICIPAL WASTEWATER TREATMENT FACILITIES.
AUTHOR CULP, GORDON L.; HEIM, NANCY FOLKS.
PUB DATE 78
AVAIL SUPERINTENDENT OF DOCUMENTS, U. S. GOVERNMENT PRINTING OFFICE,
WASHINGTON, DC 20402.
DESC EQUIPMENT; EVALUATION; FACILITIES; MANAGMENT; MANUALS; OPER-
ATIONS (WASTEWATER); WASTEWATER TREATMENT; WATER ANALYSIS;
WATER POLLUTION; WATER QUALITY.
DESC NOTE 397P, STOCK NO. 055-001-010-01078-8, PRICE: $5.50.
ABSTRACT THIS MANUAL IS A TECHNICAL FIELD GUIDE AND REFERENCE DOCUMENT
FOR IMPROVING THE PERFORMANCE OF MUNICIPAL WASTEWATER TREATMENT
PLANTS. IT DESCRIBES GENERAL PROCEDURES FOR EVALUATING THE
PERFORMANCE OF TREATMENT PROCESSES AND EQUIPMENT COMMONLY USED
IN MUNICIPAL WASTEWATER FACILITIES. THE MANUAL IS ORGANIZED
INTO FOUR SECTIONS. THE FIRST SECTION IS AN INTRODUCTION. THE
SECOND CONTAINS A STEP-BY-STEP PROCEDURE FOR ORGANIZING AND
CONDUCTING A PLANT VISIT AND EVALUATION. THE THIRD SECTION
DISCUSSES VARIOUS UNIT PROCESSES AND HOW THEY AFFECT ONE AN-
OTHER. IT ALSO PRESENTS INFORMATION ON SAFETY, STAFFING, MON-
ITORING, EMERGENCY PROCEDURES, AND MAINTENANCE. THE FOURTH
PART GIVES DESCRIPTIONS, DESIGN CRITERIA AND SHORTCOMINGS, CON-
TROL CONSIDERATIONS, AND A TROUBLESHOOTING GUIDE FOR EACH
UNIT PROCESS.
TITLE FULL SCALE STUDIES ON THE THERMOPHILIC ANAEROBIC DIGESTION PRO-
CESS.
AUTHOR SMART, J.; BOYKO, B. I.
CORP AUTH ONTARIO MINISTRY OF THE ENVIRONMENT, TORONTO.
AVAIL CANADA-ONTARIO AGREEMENT OF GREAT LAKES WATER QUALITY, RESEARCH
REPORT NO. 59, 1977. ENVIRONMENTAL PROTECTION SERVICE, EN-
VIRONMENT CANADA, OTTAWA, CANADA, 79 P, 7 FIG, 12 TAB, 20
REF, 4 APPEND. 73-1-20.
DESC *THERMOPHILIC SYSTEM; *MESOPHILIC SYSTEM; *ANAEROBIC DIGESTION;
*THERMOPHILIC BACTERIA; *MICROORGANISMS; HEATING; HEAT RE-
SISTANCE; SLUDGE DIGESTION; *WASTE WATER TREATMENT
176
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ABSTRACT A PLANT SCALE THERMOPHILIC ANAEROBIC DIGESTION STUDY WAS CON-
DUCTED TO ASSESS THE FEASIBILITY AND PERFORMANCE AND TO PRO-
VIDE ECONOMIC GUIDELINES FOR THE PROCESS AS COMPARED WITH
THE CONVENTIONAL MESOPHILIC SYSTEM. THE STUDY WAS CONDUCTED IN
FOUR DISTINCT PHASES; THE FIRST THREE AT SPECIFIC APPLIED
DIGESTER LOADINGS. A FULL SCALE MESOPHILIC SYSTEM, OPERATING
ON THE SAME RAW SLUDGE FEED, WAS USED AS A COMPARISON. THE
STUDY PROVED FULL SCALE THERMOPHILIC DIGESTION TO BE
FEASIBLE AND CAPABLE OF SLUDGE STABILIZATION PERFORMANCE
SIMILAR TO THE MESOPHILIC CONTROL UNIT, BUT AT MORE RIGOROUS
APPLIED DIGESTER LOADING LEVELS. THE FINAL PHASE OF THE STUDY
SHOWED THAT WIDELY AND FREQUENTLY VARYING APPLIED DIGESTER
LOADINGS HAD LITTLE EFFECT UPON THE THERMOPHILIC PROCESS,
WHICH PROVED TO BE VERY FLEXIBLE IN PRODUCING A GOOD ALL AROUND
PERFORMANCE UNDER THE RANGE OF SHOCK LOADINGS APPLIED. WHILE
NO ACTUAL OPERATING COST COMPARISON WAS MADE BETWEEN THE TWO
DIGESTION SYSTEMS, ESTIMATES OF ENERGY REQUIREMENTS BASED ON
THE DATA OBTAINED SHOWED THAT REQUIREMENTS WOULD BE SLIGHTLY
GREATER FOR THE THERMOPHILIC PROCESS. HOWEVER, THE MAGNITUDE
OF THE INCREASE WAS SUCH THAT CONVERSION OF EXISTING OVERLOAD
MESOPHILIC SYSTEMS TO THERMOPHILIC OPERATION WOULD BE FEASIBLE
AND ACCEPTABLE IN VIEW OF THE LIKELY BENEFITS TO BE OBTAINED.
(WATDOC)
TITLE A GUIDE FOR DEVELOPING STANDARD OPERATING JOB PROCEDURES FOR
THE DIGESTION PROCESS WASTEWATER TREATMENT FACILITY. SOJP NO.
10.
AUTHOR SCHWING, CARL M.
PUB DATE 73
AVAIL ERIC DOCUMENT REPRODUCTION SERVICE, P. 0.
VA 22210.
DESC GUIDES; INSTRUCTIONAL MATERIALS; JOB TRAINING; WASTE
WATER POLLUTION CONTROL; SLUDGE DIGESTION; WASTEWATER TREAT-
MENT; INDUSTRIAL TRAINING; POST SECONDARY EDUCATION; SAFETY;
UTILITIES; WATER RESOURCES.
DESC NOTE 49P
ABSTRACT THIS GUIDE DESCRIBED STANDARD OPERATING JOB PROCEDURES FOR THE
DIGESTION PROCESS OF WASTEWATER TREATMENT FACILITIES. THIS
PROCESS IS FOR REDUCING THE VOLUME OF SLUDGE TO BE TREATED IN
SUBSEQUENT UNITS AND TO REDUCE THE VOLATILE CONTENT OF SLUDGE.
THE GUIDE GIVES STEP-BY-STEP INSTRUCTIONS FOR PRE-STARTUP,
STARTUP, CONTINUOUS OPERATING, SHUTDOWN, AND PREVENTIVE MAINTE-
NANCE PROCEDURES.
BOX 190, ARLINGTON,
DISPOSAL;
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TITLE HOW TO KEEP AN OLD PLANT RUNNING.
AVAIL WATER AND SEWAGE WORKS, VOL. 123, NO. 12, P 12, DECEMBER, 1976.
DESC DIGESTER SOURING; TONAWANDA (NY); SODIUM BICARBONATE
ABSTRACT A TWO-YEAR SOURING CYCLE IN THE ANAEROBIC SLUDGE DIGESTER WAS
RECENTLY BROKEN AT THE TONAWANDA, NEW YORK, SEWERAGE TREATMENT
PLANT. A SODIUM BICARBONATE TREATMENT CONSISTING OF A 500
POUND/WEEK SPRING DOSAGE AND THE USE OF A COMBINATION OF NAHC03
AND SODA ASH OR CONTINUED SODIUM BICARBONATE DOSING ON A YEAR-
ROUND BASIS WERE INSTRUMENTAL IN DISCONTINUING THE SOUR-
ING. A STABLE PH OF 7 HAS BEEN MAINTAINED. A DROP IN
METHANE PRODUCTION WAS THE FIRST INDICATION OF SOURING AND
CAUSED INCREASED ACID FORMATION AND A DROP IN PH. THE EFFECT
SNOWBALLED UNTIL PH REACHED 6.5 OR LOWER WHERE METHANE FORMA-
TION IS IMPOSSIBLE. TO A PLANT WHERE METHANE GAS FUELS
THE DIGESTER, THIS WAS A MAJOR PROBLEM. THE POOR SOLUBILITY OF
LIME AND THE LENGTHLY PERIOD IT TOOK TO RAISE PH, AS WELL AS A
STABILIZATION PROBLEM MADE IT A POOR SOLUTION. IT WAS ES-
TIMATED THAT 15 TONS OF SODIUM BICARBONATE ARE USED YEARLY.
TEMPERATURE DROPS DO NOT AFFECT BICARBONATE AND IT PERFORMS
WELL WHERE LIME WAS POOR. (COLLINS-FIRL)
TITLE KEEP YOUR DIGESTER IN GOOD SHAPE.
AUTHOR BARBER, N. R.
CORP AUTH CHURCH AND DWIGHT CO., INC., PISCATAWAY, NJ
AVAIL WATER AND WASTE ENGINEERING, VOL 14, NO 9, P 55, 59, SEPTEMBER,
1977. 1 FIG
DESC *ANAEROBIC DIGESTION; *CHEMICAL REACTIONS; *CHEMICAL PRE-
CIPITATION; *SLUDGE TREATMENT; LIME; HYDROGEN ION CON-
CENTRATION; ALKALINITY; TOXICITY; SLUDGE DIGESTION; WASTE
WATER TREATMENT
ABSTRACT SODIUM BICARBONATE HAS BEEN USED TO SAFEGUARD AGAINST CHEMICAL
MALFUNCTION OF ANAEROBIC DIGESTION CAUSED BY THE ACCUMULATION
OF VOLATILE ACIDS AND CARBON DIOXIDE. SINCE NAHC03 CAN
DIRECTLY SHIFT THE EQUILIBRIUM TO ANY DESIRED VALUE WITHOUT
FIRST REACTING WITH SOLUBLE C02, IT HAS BEEN USED AS AN
ALTERNATIVE TO LIME, WHICH CAN PRODUCE UNDESIRABLE SIDE EFFECTS
SUCH AS VACUUM AND/OR PRECIPITATION. WITH LIME ADDITION, THE
REMOVAL OF C02 FROM THE DIGESTER HEAD ROOM TO REPLENISH THE C02
TAKEN OUT OF THE SOLUTION CAN CREATE AN INSTATANEOUS VACUUM
WHICH PLACES STRESSES ON TANK STRUCTURES. THIS MAY, IN TURN,
ALLOW OXYGEN TO ENTER THE SYSTEM WITH RESULTING TOXICITY TO THE
ANAEROBIC ORGANISMS IN THE DIGESTER. SCALE FORMATION DUE TO
THE PRECIPITATION OF CAC03 AFTER IT REACHES ITS SOLUBILITY
LIMIT CAN ALSO PRESENT PROBLEMS. AN EQUATION REPRESENTING THE
INCREASE IN BICARBONATE ALKALINITY CAUSED BY THE REACTION OF
178
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LIME WITH SOLUBLE C02 IS PRESENTED. CALCULATIONS INDICATED
THAT SCALE FORMATION IS LIKELY AT CAC03 CONCENTRATIONS GREATER
THAN 500 MG/LITER OR AT LIME CONCENTRATIONS GREATER THAN 370
MG/LITER. AN EQUATION TO ESTIMATE THE REQUIRED ALKALINITY FOR
BUFFERING THE PH AT DIFFERENT LEVELS OF C02 PARTIAL PRESSURE IS
PRESENTED. NAHC03, A NATURAL PH CONTROL BUFFER IN ALL AQUEOUS
SYSTEMS, HAS A TOXICITY LEVEL IN ANAEROBIC DIGESTION SYSTEMS OF
0.2 MOLES NA/LITER FOR SLUG WASTES WHEN OTHER IONS ARE AT CON-
CENTRATIONS BELOW 10 MG/LITER. THE PRESENCE OF ANTAGONISTIC
IONS SUCH AS K AND CA MAY INCREASE THE TOLERABLE LEVEL OF NA TO
DIGESTER ORGANISMS. (SCHULZ-FIRL)
TITLE LIME/SODIUM BICARBONATE TREATMENT INCREASES SLUDGE DIGESTER EF-
FICIENCY.
AUTHOR BARBER, N. R.
CORP AUTH CHURCH AND DWIGHT CO., INC., PISCATAWAY, NJ
PUB DESC JOURNAL OF ENVIRONMENTAL SCIENCES, VOL. 21 NO. 2, P 28-30,
1978. 2 FIG, 1 TAB, 4 REF.
DESC *ANAEROBIC DIGESTION; *LIME; *SODIUM COMPOUNDS; *METHANE BAC-
TERIA: *ALKALINITY; CARBON DIOXIDE; CATIONS: METHANE; SEWAGE
SLUDGE; MICROBIAL DEGRADATION; WASTEWATER TREATMENT; CALCIUM
CARBONATE; MUNICIPAL WASTES; ACID BACTERIA
ABSTRACT COMBINED LIME AND SODIUM BICARBONATE TREATMENT OF SEWAGE SLUDGE
DURING ANAEROBIC DIGESTION IS EVALUATED. METHANE-FORMING BAC-
TERIA REQUIRE A PH OF 6.8-7.2 FOR OPTIMUM METHANE GENERATION;
NEUTRALITY IS MAINTAINED BY CHEMICAL TREATMENT OF THE SLUDGE TO
COUNTERACT THE EFFECT OF ACID-FORMING BACTERIA. WHEN ADDED TO
THE DIGESTER TO RAISE THE PH, LIME REACTS WITH C02 AND CAN
CAUSE A VACUUM TO FORM AT DIFFERENT CO2 PARTIAL PRESSURES. IN
IMBALANCED DIGESTERS, THE VACUUM POTENTIAL INCREASES AND AIR
MAY FLOW INTO THE DIGESTER WITH TOXIC EFFECTS ON THE METHANE-
FORMING BACTERIA. EXCESS LIME ADDITION IN THE PRESENCE OF C02
CAN FORM INSOLUBLE CALCIUM CARBONATE WHICH WILL NOT INCREASE
ALKALINITY. THE USE OF LIME AND SODIUM CARBONATE IN ANAEROBIC
DIGESTION REDUCES THE TOXICITY OF DIVALENT CATIONS. THE
COMBINED TREATMENT ALSO REDUCES THE PRESENCE OF HIGH PH PATCHES
IN THE SLUDGE LIQUOR. IT IS RECOMMENDED THAT LIME BE ADDED
INITIALLY TO INCREASE THE PH TO 6.3-6.5, FOLLOWED BY SODIUM
BICARBONATE TO INCREASE PH TO THE OPTIMUM 6.5-7.2. THE CHEMI-
CALS ARE ADDED TO MAINTAIN A DIGESTER ALKALINITY OF 2,500-5,000
MG/LITER AS CAC03 AND A VOLATILE ACID CONCENTRATION OF 300-500
MG/LITER AS ACETIC ACID. SODIUM BICARBONATE ADDITIONS OF 500
MG/LITER/DAY WILL MAINTAIN A SODIUM CONCENTRATION OF 137 MG/
LITER; ADDITIONS OF 1,500 LB SODIUM BICARBONATE/1 MILLION GAL
INFLUENT SLUDGE WILL INCREASE BICARBONATE ALKALINITY BY 180
MG/LITER WHEN DIGESTER ALKALINITY FALLS BELOW 2,500 MG/LITER.
(LISK-FIRL)
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TITLE LIME/NA2C03 TREATMENT IMPROVES SLUDGE DIGESTION.
AUTHOR JACOBSON, A. R.
CORP AUTH ILLINOIS STATE UNIV., NORMAL, COLL. OF APPLIED SCIENCE AND
TECHNOLOGY.
PUB DESC PUBLIC WORKS, VOL. 109, NO. 7, P 94, JULY, 1978.
DESC *SODIUM COMPOUNDS; *LIME; *ANAEROBIC DIGESTION; *METHANE BAC-
TERIA; *METHANE; ALKALINITY; AMMONIA; CARBON DIOXIDE; SLUDGE
DIGESTION; WASTEWATER TREATMENT; SLUDGE TREATMENT; MUNICIPAL
WASTES
ABSTRACT LIME AND SODIUM BICARBONATE TREATMENT OF ANAEROBICALLY DIGESTED
SLUDGE PROVIDES THE OPTIMUM PH FOR METHANE-FORMING BACTERIA. A
NATURAL BUFFER SYSTEM ESTABLISHED BY DIGESTERS IS BASED ON
BICARBONATE ALKALINITY FROM THE REACTION OF AMMONIA AND CARBON
DIOXIDE TO FORM AMMONIUM BICARBONATE. THE OPTIMUM PH FOR
GROWTH OF METHANE-PRODUCING BACTERIA IS IN THE RANGE OF PH 7.0.
LIME WILL ADJUST THE PH OF THE DIGESTER TO 6.3-6.5. SODIUM
BICARBONATE FURTHER INCREASES THE PH TO 7.0-7.4. WHEN DIGESTER
BICARBONATE ALKALINITY FALLS BELOW 2,500 MG/LITER, A 1,500
LB/MILLION GAL SODIUM BICARBONATE ADDITION WILL INCREASE THE
ALKALINITY BY 180 MG/LITER. TREATMENT WITH SODIUM BICARBONATE
IN ADDITION TO LIME PREVENTS LIME OVERDOSE OR LOCALIZED PH
VARIATIONS. (LISK-FIRL)
TITLE NEW PROBLEMS CAN OCCUR WITH ANAEROBIC DIGESTION.
AUTHOR TAVERY, MARY ANN; NELSON, JOHN
PUB DATE 79
AVAIL WATER AND WASTES ENGINEERING; V16 N12
DESC *WASTEWATER TREATMENT; WATER POLLUTION CONTROL; *OPERATIONS
(WASTEWATER); RESEARCH; *ANAEROBIC DIGESTION; *SLUDGE; MAINTE-
NANCE; FACILITY GUIDELINES: ENVIRONMENTAL INFLUENCES; RE-
CYCLING
DESC NOTE 14-15 & 47P
ABSTRACT THIS ARTICLE DISCUSSES THE PROBLEMS ENCOUNTERED BY THE DENVER
SEWAGE DISPOSAL DISTRICT IN ATTEMPTING TO STOP SLUDGE FOAMING
AND INCREASE SOLIDS/LIQUIDS SEPARATION IN ITS ANAEROBIC
DIGESTERS.
TITLE OPERATIONAL CHARACTERISTICS OF ANAEROBIC DIGESTERS AT SELECTED
MUNICIPAL WASTEWATER TREATMENT FACILITIES IN THE UNITED STATES.
AUTHOR SPENCER, R. R.; AND OTHERS
PUB DATE DEC 78
AVAIL NATIONAL TECHNICAL INFORMATION SERVICE,
SPRINGFIELD, VA 22161. PRICE: $6.00
DESC *ANAEROBIC DIGESTERS; ACTIVATED CARBON;
GAS; *ENERGY; *FACILITIES; *MUNICIPALITIES; METHANE; OPERATIONS
(WASTEWATER); *RESEARCH; SLUDGE; *WASTEWATER TREATMENT.
OPERATIONS DIVISION,
*ECONOMICS; DIGESTER
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DESC NOTE 36P
ABSTRACT ANALYZED ARE THE OPERATION CHARACTERISTICS OF A REPRESENTATIVE
SAMPLE OF 60 AMERICAN ANAEROBIC DIGESTERS. EXAMINED ARE GAS
PRODUCTION, SOLID RESIDENCE TIME, SLUDGE FLOW AND VOLATILE
SOLIDS DESTRUCTION. INCLUDED IS IDENTIFICATION OF DIGESTERS
OPERATING AT LESS THAN EXPECTED EFFICIENCY. THE ADDITION OF
CARBON TO THESE STRESSED DIGESTERS WILL IMPROVE VOLATILE SOLIDS
DESTRUCTION AND GAS PRODUCTION. THE CURRENT AND FUTURE ENERGY
VALUE AND USAGE (OR MONOSAGE) IS EVALUATED. DISCUSSED IS THE
DESIRABILITY OF USING AND INCREASING WASTE GAS.
TITLE OPERATION OF WASTEWATER TREATMENT PLANTS: A HOME STUDY TRAIN-
ING PROGRAM.
PUB DATE 70
AVAIL ERIC DOCUMENT REPRODUCTION SERVICE, P. 0. BOX 190, ARLINGTON,
VA 22210.
DESC ENVIRONMENTAL EDUCATION; ENVIRONMENTAL TECHNICIANS; INDEPENDENT
STUDY; INSTRUCTIONAL MATERIALS; SANITATION; WATER POLLUTION
CONTROL; EMPLOYMENT QUALIFICATIONS; EQUIPMENT MAINTENANCE; POL-
LUTION; PUBLIC HEALTH; SAFETY; WASTEWATER TREATMENT.
DESC NOTE 1.317P
ABSTRACT THIS MANUAL WAS PREPARED BY EXPERIENCED WASTEWATER TREATMENT
PLANT OPERATORS TO PROVIDE A HOME STUDY COURSE TO DEVELOP NEW
QUALIFIED WORKERS AND EXPAND THE ABILITIES OF EXISTING WORKERS.
THE OBJECTIVE OF THIS MANUAL IS TO PROVIDE THE KNOWLEDGE AND
SKILLS NECESSARY FOR CERTIFICATION. PARTICIPANTS LEARN THE
BASIC OPERATIONAL ASPECTS OF TREATMENT PLANTS AND THE INFORMA-
TION NECESSARY TO ANALYZE AND SOLVE OPERATIONAL PRO-
BLEMS. EACH OF THE CHAPTERS BEGINS WITH AN INTRODUCTION AND
THEN DISCUSSES START-UP, DAILY OPERATION AND INTERPRETATION OF
LAB RESULTS. TOPICS DISCUSSED INCLUDE MAINTENANCE, SAFETY,
SAMPLING, LABORATORY PROCEDURES, HYDRAULICS, RECORDS, ANALYSIS
AND PRESENTATION OF DATA, AND REPORT WRITING. EACH LESSON CON-
TAINS DISCUSSION AND REVIEW QUESTIONS AND IS COMPLETED WITH
AN OBJECTIVE TEST.
TITLE OPERATION OF WASTEWATER TREATMENT PLANTS: A HOME STUDY TRAIN-
ING PROGRAM (SECOND EDITION).
PUB DATE 80
AVAIL ERIC DOCUMENT REPRODUCTION SERVICE, P. 0. BOX 190, ARLINGTON,
VA 22210.
DESC ENVIRONMENTAL EDUCATION; ENVIRONMENTAL TECHNICIANS; INDEPENDENT
STUDY; INSTRUCTIONAL MATERIALS; SANITATION; WATER POLLUTION
CONTROL; WASTEWATER TREATMENT; EMPLOYMENT QUALIFICATIONS;
EQUIPMENT MAINTENANCE; POLLUTION; PUBLIC HEALTH; SAFETY.
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DESC NOTE HC - MANUALS ONLY $70.00 (3 VOLUMES) - PLUS POSTAGE.
ABSTRACT PRESENTED IS THE SECOND EDITION OF A MANUAL PREPARED BY EX-
PERIENCED WASTEWATER TREATMENT PLANT OPERATORS TO PROVIDE A
HOME STUDY COURSE TO DEVELOP NEW QUALIFIED WORKERS AND EXPAND
THE ABILITIES OF EXISTING WORKERS. THE OBJECTIVE OF THESE MAN-
UALS IS TO PROVIDE THE KNOWLEDGE AND SKILLS NECESSARY FOR
CERTIFICATION. PARTICIPANTS LEARN THE BASIC OPERATIONAL
ASPECTS OF TREATMENT PLANTS AND THE INFORMATION NECESSARY TO
ANALYZE AND SOLVE OPERATIONAL PROBLEMS. EACH OF THE CHAPTERS
BEGIN WITH AN INTRODUCTION AND THEN DISCUSSES START-UP, DAILY
OPERATION AND INTERPRETATION OF LAB RESULTS. TOPICS DISCUSSED
INCLUDE MAINTENANCE, SAFETY, SAMPLING, LABORATORY PROCEDURES,
HYDRAULICS, RECORDS, ANALYSIS AND PRESENTATION OF DATA, AND RE-
PORT WRITING. EACH LESSON CONTAINS DISCUSSION AND REVIEW
QUESTIONS AND IS COMPLETED WITH AN OBJECTIVE TEST.
TITLE OPERATION OF WASTEWATER TREATMENT PLANTS, MANUAL OF PRACTICE
NO. 11.
AUTHOR ALBERTSON, ORRIE E.; AND OTHERS.
PUB DATE 76
AVAIL WATER POLLUTION CONTROL FEDERATION, 2626 PENNSYLVANIA AVE.,
N.W., WASHINGTON, DC 20037.
DESC INSTRUCTIONAL MATERIALS; POST SECONDARY EDUCATION; SANITATION;
WASTE DISPOSAL; WATER POLLUTION CONTROL; WASTEWATER TREATMENT;
ENVIRONMENT; POLLUTION; PUBLIC HEALTH; TECHNICAL REPORTS;
UTILITIES; WATER RESOURCES.
DESC NOTE 536P
ABSTRACT THIS BOOK IS INTENDED TO BE A REFERENCE OR TEXTBOOK ON THE
OPERATION OF WASTEWATER TREATMENT PLANTS. THE BOOK CONTAINS
THIRTY-ONE CHAPTERS AND THREE APPENDICES AND INCLUDES THE DE-
SCRIPTION, REQUIREMENTS, AND LATEST TECHNIQUES OF CON-
VENTIONAL UNITS PROCESS OPERATION, AS WELL AS THE SYMPTOMS
AND CORRECTIVE MEASURES REGARDING PROCESS PROBLEMS. PROCESS
SUBJECTS DISCUSSED INCLUDE ROTATING BIOLOGICAL REACTORS, OXYGEN
ACTIVATED SLUDGE SYSTEMS, STABILIZATION LAGOONS, AND PHYSICAL-
CHEMICAL TREATMENT. MANAGEMENT TOPICS INCLUDED ARE EF-
FLUENT DISPOSAL, BY-PRODUCTS SOLIDS DISPOSAL, PROCESS MAN-
AGMENT AND CONTROL, ODOR CONTROL, AND ENERGY CONVERSION.
THE APPENDICES INCLUDE AN ABBREVIATED GLOSSARY, LABORATORY PRO-
CEDURES, AND UNITS OF MEASUREMENT.
TITLE PLANT OPERATIONS FOR WASTEWATER FACILITIES, VOL. II, PART C.
AN INSTRUCTOR'S GUIDE FOR USE OF INSTRUCTIONAL MATERIAL IN
WASTEWATER TECHNOLOGY TRAINING PROGRAMS.
AUTHOR STOAKES, K. C.; AND OTHERS.
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PUB DATE 75
AVAIL ERIC DOCUMENT REPRODUCTION SERVICE, P. 0. BOX 190, ARLINGTON,
VA 22210.
DESC POST SECONDARY EDUCATION; TEACHING GUIDES; TECHNOLOGY; WASTE
DISPOSAL; WATER POLLUTION CONTROL; SEWAGE TREATMENT; OPERATIONS
(WASTEWATER); WASTEWATER TREATMENT; EDUCATIONAL OBJECTIVES; EN-
VIRONMENTAL EDUCATION; TECHNICAL EDUCATION; VOCATIONAL EDUCA-
TION; WASTES.
DESC NOTE 92P
ABSTRACT THIS INSTRUCTOR'S GUIDE, DESIGNED FOR USE WITH THE CURRICULUM,
PLANT OPERATIONS FOR WASTEWATER FACILITIES, REPRESENTS A TWO-
YEAR WASTEWATER TECHNOLOGY INSTRUCTIONAL PROGRAM BASED ON PER-
FORMANCE OBJECTIVES DESIGNED TO PREPARE UNDERGRADUATE
STUDENTS TO ENTER OCCUPATIONS IN WATER AND WASTEWATER TREATMENT
PLANT OPERATIONS AND MAINTENANCE. THIS DOCUMENT, PART C OF
FIVE PARTS, COVERS THE TOPICS OF THICKENING, FIRST STAGE DIGES-
TION, SECOND STAGE DIGESTION AND SLUDGE CONDITIONING. IN
THIS GUIDE, THE TOPICS AND IDEAS ARE PRESENTED AS A SERIES OF
MODULES, ORGANIZED AROUND 16 GENERAL OBJECTIVES COMMON TO ALL
PROCESSES. THE MODULE BEGINS WITH A STATEMENT OF PURPOSE WHICH
EXPLAINS WHAT THE STUDENT WILL BE STUDYING. NEXT, ALL THE OB-
JECTIVES OF THE MODULE AND CODE NUMBERS KEYED TO A COM-
PUTERIZED LIST OF INSTRUCTIONAL RESOURCES ARE LISTED. ALSO
INCLUDED IN EACH MODULE ARE A GLOSSARY OF VERBS AND SECTIONS ON
LEARNING AND TESTING CONDITIONS, ACCEPTABLE PERFORMANCE,
INSTRUCTOR ACTIVITY AND STUDENT ACTIVITY. RECOMMENDATIONS ON
EVALUATION TECHNIQUES ARE INCLUDED.
TITLE PRIMARY TREATMENT AND SLUDGE DIGESTION WORKSHOP.
PUB DATE 77
AVAIL PUBLICATIONS CENTRE, ONTARIO MINISTRY OF GOVERNMENT SERVICES,
880 BAY ST., 5TH FLOOR, TORONTO, ONTARIO, CANADA M7A 1N8.
DESC BEHAVIORAL OBJECTIVES; ENVIRONMENTAL EDUCATION; POLLUTION;
WATER POLLUTION CONTROL; WORKSHOPS; SLUDGE; WASTEWATER TREAT-
MENT; ENVIRONMENTAL TECHNICIANS; EQUIPMENT; JOB-SKILLS; SAM-
PLING; WASTE DISPOSAL; ONTARIO.
DESC NOTE 289P, PRICE: $2.00, ORDERS MUST BE ACCOMPANIED BY CHECK OR
MONEY ORDER PAYABLE TO THE TREASURER OF ONTARIO.
ABSTRACT THIS MANUAL WAS DEVELOPED FOR USE AT WORKSHOPS DESIGNED TO UP-
GRADE THE KNOWLEDGE OF EXPERIENCED WASTEWATER TREATMENT PLANT
OPERATORS. EACH OF THE SIXTEEN LESSONS HAS CLEARLY STATED BE-
HAVIORAL OBJECTIVES TO TELL THE TRAINEE WHAT HE SHOULD KNOW
OR DO AFTER COMPLETING THAT TOPIC. AREAS COVERED IN THIS MAN-
UAL INCLUDE: SEWAGE CHARACTERISTICS, COLLECTION, TREATMENT,
AND SEDIMENTATION, AEROBIC AND ANAEROBIC DIGESTION, SAMPLING
AND INTERPRETATION, MONITORING AND CONTROL, AND SELECTED TESTS.
183
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TITLE RESURRECTING THE DEAD ANAEROBIC DIGESTER.
AUTHOR SNELLING, DONALD P.
PUB DATE AUG 79
AVAIL WATER AND SEWAGE WORKS: VI26 N8
DESC *WASTEWATER TREATMENT; *OPERATIONS (WASTEWATER); *EQUIPMENT;
WATER POLLUTION CONTROL; *CHEMICAL REACTIONS; UTILITIES;
*ANAEROBIC DIGESTERS
DESC NOTE 66-67P
ABSTRACT DISCUSSED ARE THE CAUSES AND REMEDIES FOR IMBALANCED ANAEROBIC
DIGESTERS. THE INFORMATION OUTLINES TESTS, PARAMETERS, AND
CORRECTIVE ACTIONS.
TITLE SODIUM BICARBONATE CAN SETTLE MANY WASTE WATER PROBLEM UPSETS.
AUTHOR BARBER, N.
CORP AUTH CHURCH AND DWIGHT CO., INC., PISCATAUAY, NJ
AVAIL POLLUTION ENGINEERING, VOL. 9, NO. 4, P 57-59, APRIL, 1977. 1
FIG.
DESC *SODIUM BICARBONATE; *BICARBONATES; *ANAEROBIC DIGESTION; *AER-
OBIC TREATMENT; TREATMENT FACILITIES; HYDROGEN ION CON-
CENTRATION; METHANE; CARBON DIOXIDE; MICROORGANISMS; EQUIP-
MENT; ALKALINITY; NITRIFICATION; SEDIMENTATION; PHYSICAL PRO-
PERTIES; CHEMICAL PROPERTIES; BIOCHEMICAL OXYGEN DEMAND;
ODOR; *WASTEWATER TREATMENT
ABSTRACT SODIUM BICARBONATE HAS BEEN USED BY ENGINEERS TO PREVENT
EQUILIBRIUM DISTURBANCES IN SEWAGE TREATMENT PLANTS. IT WAS
USED AS A BUFFER TO MAINTAIN THE DESIRED ACID/ALKALI RATIO FOR
MAINTENANCE OF AN OPTIMUM ENVIRONMENT FOR MICROBIAL GROWTH.
IN ANAEROBIC SYSTEMS, SODIUM BICARBONATE CAN CONTROL PH,
INCREASE METHANE PRODUCTION, INCREASE BIODEGRADATION RATES,
PRECIPITATE TOXIC METALS, AND AID SOLIDS CONCENTRATION. IT WAS
ALSO SUBSTITUTED FOR LIME AND OTHER ALKALIS IN AEROBIC PROCES-
SES, WHERE IT WAS ABLE TO CONTROL PH AND ALKALINITY, ENHANCE
NITRIFICATION, IMPROVE BOD REDUCTION, REDUCE OR ELIMINATE
ODORS, ENHANCE SETTLING CHARACTERISTICS, AND PRETREAT
INDUSTRIAL WASTES. (COLLINS-FIRL)
TITLE STABILITY AND CONTROL OF ANAEROBIC DIGESTION.
AUTHOR GRAEF, S. P.; ANDREWS, J. F.
CORP AUTH METROPOLITAN SANITARY DISTRICT OF GREATER CHICAGO, IL
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATIN, VOL 46, NO 4, P
666-683, APRIL, 1974. 14 FIG, 24 REF
DESC *OVERLOADS; HYDROCARBONS; CONTROL STRATEGIES; STABILITY;
PROCESS CONTROL; *SLUDGE DIGESTION; *ANAEROBIC DIGESTION;
CONTROL; *WASTE TREATMENT; *COMPUTER STUDIES; *MODEL STUDIES;
184
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DESC ORGANIC LOADING; TOXINS; DESIGN STANDARDS; OPERATION AND
MAINTENANCE; SLUDGE TREATMENT; METHANE; SLUDGE; ALKALINITY;
CARBON DIOXIDE; DIGESTION; CONTROL SYSTEMS
ABSTRACT THE DYNAMIC RESPONSE OF THE ANAEROBIC DIGESTER TO ORGANIC,
TOXIC, AND HYDRAULIC OVERLOADING WAS SIMULATED WITH A HYBRID
COMPUTER TO EVALUATE PROCESS STABILITY INDICATORS, DESIGN AND
OPERATION FACTORS INFLUENCING PROCESS STABILITY, AND CONTROL
STRATEGIES. THE RATE OF METHANE PRODUCTION WAS ONE OF THE BEST
INDICATORS FOR DETECTING IMPENDING FAILURE CAUSED BY TOXIC
COMPOUNDS. IMPROVED PROCESS STABILITY WITH RESPECT TO ORGANIC
OVERLOADING CAN BE ACHIEVED BY INCREASING THE RESIDENCE TIME,
ALKALINITY, INFLUENT SLUDGE CONCENTRATION, AND DIGESTED SLUDGE
RECYCLE. THREE CONTROL STRATEGIES (SCRUBBING OF CARBON DIOXIDE
FROM THE GAS PHASE WITH SUBSEQUENT GAS RECYCLE, ADDITION OF A
BASE, AND DIGESTED SLUDGE RECYCLE) WERE INVESTIGATED.
CONSIDERATION OF PROCESS STABILITY AND IMPLEMENTATION OF
CONTROL STRATEGIES COULD IMPROVE DIGESTER OPERATION, PERMIT
INCREASED LOADINGS ON EXISTING DIGESTERS, AND DECREASE THE
REQUIRED VOLUMES OF NEW DIGESTERS. (WITT-IPC)
TITLE START-UP OF MUNICIPAL WASTEWATER TREATMENT FACILITIES.
AUTHOR RADER, R. D.; GREEN, R. L.; PAGE, G. L., JR.
CORP AUTH WILEY AND WILSON, INC., LYNCHBURG, VA
AVAIL FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, U.S. GOVERNMENT
PRINTING OFFICE, WASHINGTON, DC 20402. PRICE: $1.40.
ENVIRONMENTAL PROTECTION AGENCY, WASHINGTON, DC. OFFICE OF
WATER PROGRAM OPERATION REPORT EPA-43019-74-008, DECEMBER,
1973. 92P, 3 FIG, 2 TAB, 42 REF. EPA CONTRACT 68-01-0341
DESC PROCEDURES; PROCESS; SEED SLUDGE; STAFFING; STANDARD OPERATING
PROCEDURES; SITE MEETINGS; INVENTORY; *ADMINISTRATIVE
DECISIONS; *TREATMENT FACILITIES; *WASTEWATER TREATMENT;
*OPERATIONS; LABORATORY TESTS; *SAMPLING; TESTING; ANALYSIS;
CONTROLS; ACTIVATED SLUDGE; TRICKLING FILTER; OXIDATION
LAGOON; ANAEROBIC DIGESTION; SAFETY; CHLORINATION; SUSPENDED
SOLIDS; HYDROGEN ION CONCENTRATION; ALKALINITY; BIOCHEMICAL
OXYGEN DEMAND; CHEMICAL OXYGEN DEMAND; PRE-TREATMENT (WATER);
SEWAGE TREATMENT
ABSTRACT THIS MANUAL PROVIDES GUIDANCE FOR PUTTING INTO INITIAL
OPERATION A MUNICIPAL WASTEWATER TREATMENT PLANT, A NEW
ADDITION TO AN EXISTING TREATMENT PLANT, OR A CHANGE IN THE
MODE OF THE TREATMENT PLANT'S OPERATION SO THAT THE TREATMENT
PLANT OR PROCESS WILL EFFECTIVELY TREAT THE WASTEWATER IN
COMPLIANCE WITH THE SPECIFIC CONDITIONS AND LIMITATIONS
ESTABLISHED FOR THE TREATMENT FACILITY. THE MANUAL WAS
DEVELOPED AND PREPARED WITH THE AID AND COOPERATION OF
WASTEWATER TREATMENT PLANT OPERATORS AND SUPERINTENDENTS,
185
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START-UP EXPERTS, THE ACADEMIC COMMUNITY, MANUFACTURERS AND
SUPPLIERS OF WASTEWATER TREATMENT PLANT EQUIPMENT, AND
LITERATURE REVIEW OF WASTEWATER TREATMENT PLANT OPERATIONS AND
RECOGNIZED START-UP TECHNIQUES. INFORMATION IS PROVIDED ON
PREPARING FOR ACTUAL TREATMENT PLANT START-UP. PREPARATIONS
FOR START-UP INCLUDE: STAFFING THE PLANT, DEVELOPING STANDARD
OPERATING PROCEDURES, DRY- AND WET-RUN TESTING OF EQUIPMENT,
ON-SITE OPERATOR TRAINING, SAFETY , AND ESTABLISHING PROCEDURES
WHEN CONSTRUCTION IS CONTINUING DURING START-UP. THIS MANUAL
DESCRIBES START-UP PROCEDURES FOR SOME OF THE MORE COMMON
PRETREATMENT AND PRIMARY TREATMENT UNITS; FOR THE SPECIFIC
SECONDARY TREATMENT PROCESSES OF ACTIVATED SLUDGE, TRICKLING
FILTERS, STABILIZATION PONDS AND AERATED LAGOONS; AND FOR THE
SLUDGE HANDLING UNITS AND THE ANAEROBIC DIGESTION PROCESS. THE
START-UP PROCEDURES FOR ADVANCED WASTEWATER TREATMENT UNITS AND
PROCESSES ARE NOT CONSIDERED IN THIS MANUAL. (EPA)
TITLE A SURVEY OF THE PERFORMANCE OF SEWAGE SLUDGE DIGESTERS IN GREAT
BRITAIN.
AUTHOR SWANWICK, J. D.; SHURBEN; D. G.; JACKSON; S.
CORP AUTH WATER POLLUTION RESEARCH LAB., STEVENAGE (ENGLAND)
AVAIL WATER POLLUTION CONTROL, VOL 68, NO 6, P 639-647, NOV-DEC,
1969. 13 TAB, 4 REF.
DESC *UNHEATED: *MESOPHILIC; OVERLOADING; ANIONIC DETERGENTS: GREAT
BRITAIN; *ANAEROBIC DIGESTION; *SEWAGE TREATMENT; *PERFORMANCE;
FACILITIES; RETENTION; OPERATION; DESIGN; TEMPERATURE; DE-
TERGENTS; INDUSTRIAL WASTES
ABSTRACT DURING THE LAST FOUR YEARS THE WATER POLLUTION RESEARCH
LABORATORY HAS BEEN ASKED TO INVESTIGATE AN INCREASING NUMBER
OF DIFFICULTIES WITH ANAEROBIC SLUDGE DIGESTION. A SURVEY HAS
MADE IT POSSIBLE TO ACCESS THE TOTAL POPULATION SERVED BY THE
ANAEROBIC PROCESS. THIS REPORT IS A FIRST ASSESSMENT OF THE
INFORMATION OBTAINED FROM 1400 QUESTIONNAIRES WHICH WERE
CIRCULATED TO ALL LOCAL AUTHORITIES AND MAIN DRAINAGE
AUTHORITIES. HEATED AND UNHEATED DIGESTERS WERE TREATED
SEPARATELY AND ALL PLANTS HAVE BEEN CLASSIFIED ACCORDING TO
DIGESTER PERFORMANCE. RETURNS WERE RECEIVED FROM 142 PLANTS
WITH HEATED DIGESTERS, SERVING POPULATIONS AMOUNTING TO A TOTAL
OF OVER 18 MILLION PEOPLE. THE CAUSES OF 92 CASES OF
DIFFICULTY AT 63 SEWAGE PLANTS WERE CLASSIFIED AS: TRADE
WASTES 37.2 PERCENT, INADEQUATE DESIGN OR OPERATION 56.2
PERCENT, AND ANIONIC DETERGENTS 6.5 PERCENT. THE CHIEF CAUSE
OF DIFFICULTIES ATTRIBUTED TO INADEQUATE DESIGN OR OPERATION
RESULTED FROM STRATIFICATION AND LOSS OF SOLIDS FROM THE
DIGESTION TANK. OVERLOADING WAS ALSO REPORTED AS THE MAIN
186
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CAUSE FOR DIFFICULTIES AT A NUMBER OF TREATMENT PLANTS.
LOADING RATES OF PRIMARY DIGESTERS WERE ANALYZED AND TABULATED.
HOWEVER, NO CORRELATION BETWEEN LOADING AND DIGESTER
PERFORMANCE WAS FOUND. RETURNS HERE RECEIVED FROM 104 PLANTS
WITH UNHEATED DIGESTERS, SERVING POPULATIONS AMOUNTING TO A
TOTAL OF 1.7 MILLION PEOPLE. TWENTY-FOUR WORKS REPORTED
DIFFICULTIES CAUSED MAINLY BY OVERLOADING AND LOW WINTER
TEMPERATURES. DUE TO THE FREQUENCY OF SHORT RETENTION PERIODS
REPORTED, A DETAILED ANALYSIS WAS MADE OF THIS PARAMETER AND
THE RESULTS FROM 83 WORKS WERE TABULATED. ALSO, IT WAS NOTED
THAT THE ABSENCE OF LABORATORY CONTROL WAS MORE PREVALENT AT
SMALLER WORKS. (GALWARDI-TEXAS)
TITLE TROUBLESHOOTING 0 & M PROBLEMS IN WASTEWATER TREATMENT AMERICAN
INST NAME PUBLIC WORKS ASSOCIATION
FACILITIES. INSTRUCTION NOTEBOOK.
PUB DATE AUG 76
AVAIL NATIONAL TECHNICAL INFORMATION SYSTEM, 5285 PORT ROYAL ROAD,
SPRINGFIELD, VA 22161. PRICE: $19.00
DESC BEHAVIORAL OBJECTIVES; BIOLOGICAL TREATMENT; *ENVIRONMENTAL
TECHNICIANS; EQUIPMENT; *INSTRUCTIONAL MATERIALS; JOB SKILLS;
*MAINTENANCE; *OPERATIONS (WASTEWATER); *POST SECONDARY
EDUCATION; SEDIMENTATION BASINS; SLUDGE; STAFFING; WASTE DIS-
POSAL; *WASTEWATER TREATMENT; WATER POLLUTION CONTROL
DESC NOTE 672P
ABSTRACT THIS DOCUMENT CONTAINS THE INSTRUCTOR GUIDELINES FOR A COURSE
ON OPERATION AND MAINTENANCE PROBLEMS IN WASTEUATER TREATMENT
PLANTS. EACH LESSON PLAN MODULE CONTAINS: (1) A SET OF
INSTRUCTIONS; (2) LESSON OUTLINE; (3) VISUAL AIDS; (4) NOTEBOOK
MATERIALS; (5) HANDOUT; AND (6) GUIDELINES ON THE APPROACH TO
THE LESSON. FOR EACH LESSON THE INSTRUCTOR IS PROVIDED WITH A
SET OF BEHAVIORAL OBJECTIVES, PRESENTATION OPTIONS, AND SUG-
GESTED JEST QUESTIONS. LESSON TOPICS INCLUDE: (1) SCREEN-
ING AND COMMUNICATION; (2) SEDIMENTATION BASINS; (3) BIOLOGI-
CAL TREATMENT UNITS; (4) SLUDGE CONDITIONING, DEWATERING, AND
DISPOSAL; (5) EQUIPMENT; AND (6) STAFFING.
TITLE TROUBLESHOOTING 0 & M PROBLEMS IN WASTEWATER TREATMENT PLANTS.
INSTRUCTOR MANUAL.
INST NAME SOUTHERN ILLINOIS UNIVERSITY AT EDWARDSVILLE, ENVIRONMENTAL
RESOURCES TRAINING CENTER, ENVIRONMENTAL PROTECTION AGENCY,
CINCINNATI, OH.
PUB DATE 80
AVAIL NATIONAL TECHNICAL INFORMATION SERVICE, 5285 PORT ROYAL ROAD,
SPRINGFIELD, VA 22161.
DESC SEWAGE TREATMENT; HANDBOOKS; ACTIVATED SLUDGE PROCESS;
ANAEROBIC PROCESSES; DISINFECTION; PERFORMANCE EVALUATION;
MAINTENANCE; LIQUID WASTES; SOLID WASTES.
187
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DESC NOTE PB81-142325.
ABSTRACT THE INSTRUCTOR NOTEBOOK IS DESIGNED FOR USE BY INSTRUCTORS WHO
WISH TO TEACH A SHORT-TERM EDUCATION/TRAINING COURSE ON THE
PROCESS OF TROUBLESHOOTING OPERATION AND MAINTENANCE PROBLEMS
IN WASTEWATER TREATMENT FACILITIES. THE MATERIALS ARE GEARED
TOWARD PROCEDURES FOR IDENTIFYING AND ISOLATING A PROBLEM,
FORMULTATING ALTERNATIVE ACTIONS AND SOLUTIONS, AND COMBINING
CORRECTIVE ACTION WITH SHORT AND LONG-RANGE FOLLOWUP. BOTH
INTERPERSONAL AND TECHNICAL SKILLS ARE STRESSED IN THIS 15 UNIT
COURSE WHICH INCLUDES BOTH INSTRUCTOR AND TRAINEE MATERIALS.
THE UNITS COVER THE MAJORITY OF LIQUID AND SOLID WASTE
TREATMENT PROCESSES AND OPERATIONS COMMONLY ENCOUNTERED IN
MUNICIPAL WASTEWATER TREATMENT FACILITIES.
TITLE WPCF WASTEWATER TREATMENT PLANT OPERATOR TRAINING PROGRAM:
BASIC COURSE.
PUB DATE 76
AVAIL WATER POLLUTION CONTROL FEDERATION, 2626 PENNSYLVANIA AVENUE,
WASHINGTON, DC 20037.
DESC AUDIOVISUAL AIDS; INSTRUCTIONAL MATERIALS; POLLUTION;
POST-SECONDARY EDUCATION; WATER POLLUTION CONTROL; OPERATIONS
WASTEWATER; WASTEWATER TREATMENT; BEHAVIORAL OBJECTIVES;
ENVIRONMENT; ENVIRONMENTAL TECHNICANS; JOB SKILLS; PUBLIC
HEALTH.
DESC NOTE INCLUDES 287 35MM SLIDES, 10 AUDIO CASSETTES, AND MODERATOR
WORKBOOKS - ORDER NO. E0100, $300.00; STUDENT MATERIALS ONLY -
ORDER NO. E0010, $7.00.
ABSTRACT THIS TRAINING PROGRAM IS DESIGNED FOR THOSE INDIVIDUALS ALREADY
EMPLOYED AS WASTEWATER TREATMENT PLANT OPERATORS AS WELL AS
THOSE NEW TO THE FIELD. THE COURSE SERVES AS A BASIC
INTRODUCTION AND UTILIZES A SYNCHRONIZED PRESENTATION
INCORPORATING SLIDES AND AUDIO CASSETTES. THIS PROGRAM MAY BE
USED INDIVIDUALLY OR WITH GROUPS. THE UNITS ARE CONCERNED WITH
SEWAGE CHARACTERISTICS, TREATMENT METHODS, TESTS AND SAMPLING,
RECORD KEEPING , MAINTENANCE AND SAFETY. AT THE END OF EACH
UNIT THE STUDENT IS PROVIDED WITH A SUMMARY AND REVIEW
EXERCISE. PRE- AND POST-TRAINING EVALUATION MECHANISMS ARE
PROVIDED. A PROGRAM GLOSSARY IS INCLUDED FOR REFERENCE.
TITLE WPCF WASTEWATER TREATMENT PLANT OPERATOR TRAINING PROGRAM,
INTERMEDIATE COURSE: STUDENT WORKBOOK, VOL B.
PUB DATE 78
AVAIL WATER POLLUTION CONTROL FEDERATION, 2626 PENNSYLVANIA AVENUE,
WASHINGTON, DC 20037.
DESC ENVIRONMENTAL TECHNICIANS; INSTRUCTIONAL MATERIALS; OPERATIONS
WASTEWATER; POST-SECONDARY EDUCATION; SLUDGE; TRICKLING
FILTERS; WASTE STABILIZATION PONDS; WASTEWATER TREATMENT;
AUDIOVISUAL AIDS; CERTIFICATION; JOB SKILLS; POLLUTION; WATER
POLLUTION CONTROL.
188
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DESC NOTE 144 P. COURSE MATERIALS: 35MM SLIDES (APPROX. 230), 7 TAPE
CASSETTES, ADMINISTRATOR HANDBOOK, CARRYING CASE, AND STUDENT
WORKBOOK - ORDER NO. E0293, $300.00; STUDENT WORKBOOK ONLY -
ORDER NO. E0294, $3.50.
ABSTRACT THIS DOCUMENT IS ONE IN A SERIES OF SELF-INSTRUCTIONAL
WORKBOOKS FOR TRAINING WASTEWATER TREATMENT PLANT OPERATORS IN
THE BASIC FUNCTIONS OF FACILITY OPERATION. THE WORKBOOK
CONTAINS A PRE- AND POST-TEST QUESTIONNAIRE FOR EACH UNIT AS
WELL AS SELF-TESTS AND INTERIM GUIDES. THE UNITS DISCUSSED IN
THIS VOLUME ARE WASTE STABILIZATION PONDS, TRICKLING FILTERS,
AND SLUDGE HANDLING AND DIGESTION.
189
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-------
PART IV
Reference Materials
(Bibliographic Citation Only)
191
-------
-------
A bibliographic citation includes only title, author, avail-
ability, and corporate author where applicable. All citations in
Part IV are arranged alphabetically, by title.
193
-------
194
-------
TITLE AGRICULTURAL AMMONIA FOR STUCK DIGESTERS.
AUTHOR COOPER, FRED; HINDEN, ERVIN; DUNSTAN, GILBERT H.
CORP AUTH WASHINGTON STATE UNIVERSITY, PULLMAN. DIVISION OF
INDUSTRIAL RESEARCH.
AVAIL PROCEEDINGS, INDUSTRIAL WASTE CONFERENCE, 20TH, MAY 4,
5, 6, 1965, ENGINEERING BULLETIN OF PURDUE UNIVERSITY,
VOL XLIX, NO. 4, JULY 1965, P. 126-130.
TITLE ANAEROBIC ACIDOGENESIS OF WASTEWATER SLUDGE.
AUTHOR GHOSH, S., J. R. CONRAD, AND D. L. KLASS.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION.
VOL. 47, P. 30, 1975.
TITLE ANAEROBIC DIGESTER OPERATION AT THE METROPOLITAN
SANITARY DISTRICTS OF GREATER CHICAGO.
AUTHOR ' GRAEF, S. P.
CORP AUTH PROCEEDINGS OF THE NATIONAL CONFERENCE OF MUNICIPAL
SLUDGE MANAGEMENT.
AVAIL INFORMATION TRANSFER, INC., ROCKVILLE, MARYLAND 20852.
JUNE 1974.
TITLE ANAEROBIC DIGESTER SUPERNATANT DOES NOT HAVE TO BE A
PROBLEM.
AUTHOR MIGNONE, N. A.
AVAIL WATER AND SEWAGE WORKS. DECEMBER 1976.
TITLE ANAEROBIC DIGESTION - CHARACTERISTICS AND CONTROL OF
ANAEROBIC DIGESTION.
AUTHOR KOTZE, J. P.
AVAIL WATER RESEARCH. VOL. 3, P. 459, 1969.
TITLE ANAEROBIC DIGESTION FAILURES.
AUTHOR ZABLATZKY, H. R. AND S. A. PETERSON.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL 40, P. 581,
1968.
TITLE ANAEROBIC DIGESTION IN BIOLOGICAL WASTE TREATMENT.
AUTHOR KIRSCH, E. J. AND R. M. SYKES.
AVAIL PROGRESS IN INDUSTRIAL MICROBIOLOGY. VOL. 9, P. 155, 1971.
TITLE ANAEROBIC DIGESTION - KINETICS OF ANAEROBIC FERMENTATION.
AUTHOR PRETORIUS, W. A.
AVAIL WATER RESEARCH. VOL. 3, P. 545, 1969.
TITLE ANAEROBIC DIGESTION - THE MICROBIOLOGY OF ANAEROBIC DIGESTION.
AUTHOR TOERIEN, D. F.
AVAIL WATER RESEARCH. VOL. 3, P. 385, 1969.
TITLE ANAEROBIC WASTE TREATMENT FUNDAMENTALS - PART 1.
AUTHOR MCCARTY, p. L.
AVAIL PUBLIC WORKS. P. 107. SEPTEMBER 1964.
195
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TITLE ANAEROBIC WASTE TREATMENT FUNDAMENTALS - PART 2 -
ENVIRONMENTAL REQUIREMENTS AND CONTROL.
AUTHOR MCCARTY, p. L.
AVAIL PUBLIC WORKS. P. 123. OCTOBER 1964.
TITLE ANAEROBIC WASTE TREATMENT FUNDAMENTALS - PART 3 -
TOXIC MATERIALS AND THEIR CONTROL.
AUTHOR MCCARTY, p. L.
AVAIL PUBLIC WORKS. P. 91. NOVEMBER 1964.
TITLE ANAEROBIC WASTE TREATMENT FUNDAMENTALS - PART 4 -
PROCESS DESIGN.
AUTHOR MCCARTY, p. L.
AVAIL PUBLIC WORKS. DECEMBER 1964.
TITLE APPLICATION OF DIGESTION THEORY TO DIGESTION CONTROL.
AUTHOR DAGUE, R. R.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 40,
P. 2021, 1968.
TITLE APPLICATION OF PROCESS KINETICS TO DESIGN OF ANAEROBIC
PROCESSES.
AUTHOR LAWRENCE, A. W.
AVAIL ANAEROBIC BIOLOGICAL TREATMENT PROCESSES, ADVANCES IN
CHEMISTRY. SERIES 105. AMERICAN CHEMICAL SOCIETY,
WASHINGTON, D.C. 20036. 1971.
TITLE ASSESSMENT OF THE MAXIMUM CONCENTRATION OF HEAVY METALS
IN CRUDE SLUDGE WHICH HILL NOT INHIBIT THE ANAEROBIC
DIGESTION OF SLUDGE.
AUTHOR MOSEY, F. E.
AVAIL WATER POLLUTION CONTROL. VOL 75, P. 10, 1976.
TITLE AUTOTHERMAL THERMOPHILIC AEROBIC DIGESTION.
AUTHOR GOULD, M. 5. AND DRNEVICH, R. R.
AVAIL JOURNAL ENVIRONMENTAL ENGINEERING DIVISION - ASCE.
VOL. 104. NO. EE2, p. 259, 1978.
TITLE CATION TOXICITY AND STIMULATION IN ANAEROBIC WASTE
TREATMENT, PART I - SLUG FEED STUDIES.
AUTHOR KUGELMAN, I. J. AND P. L. McCARTY.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 37,
P. 97, 1965.
TITLE CATION TOXICITY AND STIMULATION IN ANAEROBIC WASTE WATER,
PART II - DAILY FEED STUDIES.
AUTHOR KUGELMAN, I. J. AND P. L. McCARTY
AVAIL PROCEEDINGS 19TH PURDUE INDUSTRIAL WASTE CONFERENCE.
PURDUE UNIVERSITY, LAFAYETTE, INDIANA 47907. P. 667,
1965.
196
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TITLE CONTROL OF ANAEROBIC DIGESTION PROCESS.
AUTHOR COLLINS, A. S. AND B. E. GILLILAND.
AVAIL JOURNAL ENVIRONMENTAL ENGINEERING DIVISION -
ASCE. VOL. 100, EE2, P. 487, 1974.
TITLE CONTROLLING SULFIDES IN ANAEROBIC DIGESTERS WITH
FERROUS CHLORIDE.
AUTHOR TALTY, R. D.
AVAIL WPCF HIGHLIGHTS, NOVEMBER 1978.
TITLE DEMONSTRATION OF ANAEROBIC DIGESTERS IN DEVELOPING
COUNTRIES - PART II.
AUTHOR SIMPSON, M. H.
AVAIL JOURNAL ENVIRONMENTAL SCIENCES, 22, 3, 16 (1979).
TITLE DIGESTER GAS HELPS MEET ENERGY NEEDS.
AUTHOR WARD, R. S.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 46,
P. 620, 1974.
TITLE DIGESTER SUPERNATANT: PROBLEMS, CHARACTERISTICS, AND
TREATMENT.
AUTHOR KAPPE, S. E.
AVAIL SEWAGE IND. WASTES, 30, 937 (1958).
TITLE DIGESTION: CONCENTRATION - LOADING - TIME LIMITS.
AUTHOR CLARK, R. H. AND V. D. ORR.
AVAIL JOURNAL SANITARY ENGINEERING DIVISION - ASCE. VOL. 98,
SA5, P. 809, 1972.
TITLE DESIGN AND COST CONSIDERATIONS IN HIGH RATE SLUDGE DIGESTION.
AUTHOR ESTRADA, A. A.
AVAIL JOURNAL SANITARY ENGINEERING DIVISION - ASCE. VOL. 86, SA3,
P. Ill, 1960.
TITLE DESIGN CONSIDERATIONS FOR ANAEROBIC CONTACT SYSTEMS.
AUTHOR DIETZ, J. C., P. W. CLINEBELL, AND A. L. STRUB.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 38, P. 517,
1966.
TITLE DYNAMIC MODELING AND SIMULATION OF THE ANAEROBIC DIGESTION
PROCESS.
AUTHOR ANDREWS, J. F. AND S. P. GRAEF.
AVAIL AMERICAN CHEMICAL SOCIETY. 1971.
TITLE DYNAMIC MODELING OF THE ANAEROBIC DIGESTION PROCESS.
AUTHOR ANDREWS, J. F.
AVAIL JOURNAL SANITARY ENGINEERING DIVISION - ASCE. VOL. 95,
SA1. P. 95, 1969.
TITLE EFFECT OF ACRYLONITRILE ON ANAEROBIC DIGESTION OF DOMESTIC
SLUDGE.
197
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AUTHOR LANK, J. C. , JR.
CORP AUTH IDAHO UNIVERSITY, MOSCOW.
AVAIL MASTER'S THESIS, MARCH 1970, 63, P. 13.
TITLE EFFECT OF DETENTION TIME ON ANAEROBIC DIGESTION.
AUTHOR HINDIN, E. AND G. H. DUNSTAN.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 32,
P. 930, 1960.
TITLE THE EFFECT OF TEMPERATURE ON ANAEROBIC DIGESTION.
AUTHOR SCHWERIN, D. J.
AVAIL UNPUBLISHED MASTER'S THESIS. MARQUETTE UNIVERSITY,
MILWAUKEE, WISCONSIN 53233. JUNE 1976.
TITLE EFFECT OF THERMAL PRETREATMENT ON DIGESTIBILITY AND
DEWATERIBILITY OF ORGANIC SLUDGES.
AUTHOR HAUG, R. T., D. C. STUCKEY, J. M. GOSSETT,
p. L. MCCARTY.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 50,
P. 73, 1978.
TITLE EFFECTS OF ANAEROBICALLY DIGESTED MUNICIPAL SEWAGE SLUDGE
APPLICATION ON CHEMICAL PROPERTIES OF SELECTED SOILS WITH
EMPHASIS ON DISTRIBUTION OF ZINC AND CADMIUM FORMS
AUTHOR KOENIG, A.
CORP AUTH CORNELL UNIVERSITY, ITHACA, NY.
AVAIL UNIVERSITY MICROFILMS INTERNATIONAL, ANN ARBOR, MICHIGAN
48106; ORDER NO. 77-18, 175. PHD THESIS, 1976, P. 369.
TITLE EFFECTS OF SULFIDES ON ANAEROBIC TREATMENT.
AUTHOR LAWRENCE, A. W. AND P. L. McCARTY.
AVAIL PROCEEDINGS 19TH PURDUE IND. WASTE CONFERENCE. PURDUE UNIVER-
SITY, LAFAYETTE, INDIANA 47907. 1964.
TITLE ELECTRODE POTENTIALS AND ELECTROLYTIC CONTROL IN THE ANAEROBIC
DIGESTION PROCESS.
AUTHOR BLANC, F. C.; MOLOF, A. H.
CORP AUTH NORTHEASTERN UNIVERSITY, BOSTON, MASS.
AVAIL PROCEEDINGS, INDUSTRIAL WASTE CONFERENCE, 24TH, MAY 6, 7, AND
8, 1969, P. 1040-1059.
TITLE ELIMINATION OF ANAEROBIC DIGESTER SUPERNATANT.
AUTHOR MIGNONE, N. A.
AVAIL WATER AND SEWAGE WORKS. P. 48, FEBRUARY 1977.
TITLE ENERGY CONSERVATION IN MUNICIPAL WASTEWATER TREATMENT.
AUTHOR USEPA.
AVAIL OFFICE OF WATER PROGRAM OPERATIONS. WASHINGTON, D.C.
20460. EPA-430/9-77-011. MARCH 1978.
TITLE ENERGY REQUIREMENTS FOR MUNICIPAL POLLUTION CONTROL
FACILITIES.
198
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AUTHOR USEPA.
AVAIL ENVIRONMENTAL PROTECTION TECHNOLOGY SERIES. CINCINNATI,
OHIO 45268. EPA-600/2-77-214. NOVEMBER 1977.
TITLE ESTIMATING COSTS AND MANPOWER REQUIREMENTS FOR CON-
VENTIONAL WASTEWATER TREATMENT FACILITIES.
AUTHOR USEPA.
AVAIL OFFICE OF RESEARCH AND DEVELOPMENT. CINCINNATI, OHIO
45268. 17090 DAN 10/71. 1971.
TITLE FULL SCALE STUDIES ON THE THERMOPHILIC ANAEROBIC
DIGESTION PROCESS.
AUTHOR SMART, J. AND B. I. BOYKO.
AVAIL RESEARCH REPORT NO. 59. ONTARIO MINISTRY OF THE ENVIRONMENT.
TORONTO, ONTARIO. 1977.
TITLE HEAVY METAL REMOVAL WITH COMPLETELY MIXED ANAEROBIC FILTER.
AUTHOR DeWALLE, F. B., E. S. K. CHIAN, J. BRUSH.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 51, P. 22,
1979.
TITLE HEAVY METALS IN DIGESTERS: FAILURE AND CURE.
AUTHOR REGAN, T. M. AND M. M. PETERS.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 42, P. 1832,
1970.
TITLE HIGH-RATE DIGESTER LOADINGS.
AUTHOR ZABLATZKY, A. R. AND BAER, G. T.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL 43, P268,
1971.
TITLE HIGH-RATE DIGESTER MIXING STUDY USING RADIOISOTOPE TRACER.
AUTHOR ZOLTAK, J. AND A. L. GRAM.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 47, P. 79,
1975.
TITLE IDENTIFICATION OF THE VIRUCIDAL AGENT IN WASTE WATER SLUDGE.
AUTHOR WARD, R. L.; ASHLEY, C. S.
CORP AUTH SANDIA LABS., ALBUQUERQUE, N. MEXICO.
AVAIL APPLIED AND ENVIRONMENTAL MICROBIOLOGY, VOL. 33, NO. 4,
P. 860-864, APRIL 1977,
TITLE IMPROVING ANAEROBIC DIGESTER OPERATION WITH POWDERED
ACTIVATED CARBON.
AUTHOR VENTETUOLO, T. AND ADAMS, A. D.
AVAIL DEEDS AND DATA-WATER POLLUTION CONTROL FEDERATION, JULY, 1976.
TITLE INACTIVATION OF VIRUSES DURING ANAEROBIC SLUDGE DIGESTION
AUTHOR BERTUCCI, et al.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 49, P. 1645,
1977.
199
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TITLE INCREASED LOADINGS ON DIGESTERS WITH RECYCLE OF DIGESTED
SOLIDS.
AUTHOR PFEFFER, JOHN T.
CORP AUTH ILLINOIS UNIVERSITY, URBANA.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL. 40, NO. 11,
PART 1, P. 1920-1933, NOVEMBER 1968.
TITLE INDIVIDUAL VOLATILE ACIDS IN ANAEROBIC TREATMENT.
AUTHOR McCARTY, P. L., et al.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL. 35 P. 1501
1963.
TITLE INFLUENCE OF PARTICLE SIZE ON SLUDGE DEWATERABILITY.
AUTHOR KARR, P. R. AND T. M. KEINATH.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 50,
P. 1911, 1978.
TITLE INTERACTION OF HEAVY METALS IN THE ANAEROBIC SLUDGE
DIGESTION SYSTEM.
AUTHOR HAD, S. S.
AVAIL DISSERTATION ABSTRACTS. , 39, 6085 (1979).
TITLE ION EFFECTS IN ANAEROBIC DIGESTION.
AUTHOR LAWRENCE, A. W. , KUGELMAN, I. J., AND McCARTY, P. L.
AVAIL TECHNICAL REPORT NO. 33, DEPARTMENT OF CIVIL ENGINEERING,
STANFORD UNIVERSITY (MARCH 1964).
TITLE KINETIC AND ACTIVITY PARAMETERS OF ANAEROBIC FERMENTATION
SYSTEMS.
AUTHOR AGARDY, F. J., et al.
AVAIL SERL REPORT 63-2, UNIVERSITY OF CALIFORNIA, BERKELEY (1963).
TITLE KINETICS OF ANAEROBIC TREATMENT AT REDUCED TEMPERATURES.
AUTHOR O'ROURKE, J. T.
AVAIL UNPUBLISHED DOCTORAL DISSERTATION, STANFORD UNIVERSITY.
PALO ALTO, CALIFORNIA 94305. 1968.
TITLE KINETICS OF METHANE FERMENTATION IN ANAEROBIC TREATMENT.
AUTHOR LAWRENCE, A. W. AND P. L. McCARTY.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION RESEARCH
SUPPLEMENT. P. Rl. FEBRUARY 1969.
TITLE MANUAL OF PRACTICE NO. 8.
AUTHOR WATER POLLUTION CONTROL FEDERATION.
AVAIL WASTEWATER TREATMENT PLANT DESIGN WATER POLLUTION
CONTROL FEDERATION. WASHINGTON, D.C., 1977.
TITLE MIXING IN ANAEROBIC DIGESTERS—TONAWANDA, NEW YORK.
AUTHOR OLDSHUE, J. Y.
AVAIL AMERICAN CITY (FEB. 1974), P. 80.
TITLE MIXING IN ANAEROBIC DIGESTION.
AUTHOR VERHOFF, F. H., M. W. TENNEY, AND W. F. ECHELBERGER.
AVAIL BIOTECHNOLOGY AND BIOENGINEERING. VOL XVI, P. 757, 1974.
200
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TITLE A MULTI-STAGE FERMENTATION SYSTEM FOR FUNDAMENTAL ANAEROBIC
DIGESTION RESEARCH.
AUTHOR SCHAMBURG, FRANK D., KIRSCH, EDWIN J.
CORP AUTH BRITISH COLUMBIA RESEARCH COUNCIL, VANCOUVER.
AVAIL PROCEEDINGS, INDUSTRIAL WASTE CONFERENCE, 21ST, MAY 3, 4, 5,
1966, PURDUE UNIVERSITY, VOL. 1, NO. 2, MARCH 1966,
P. 368-380. PUBLIC HEALTH SERVICE GRANT WP00760-01, PUBLIC
HEALTH SERVICE FELLOWSHIP 5-F1-WP-22, 348-01.
TITLE NEW DIRECTIONS IN ANAEROBIC DIGESTION OF SLUDGES.
AUTHOR MALINA, J. F. AND E. M. MIHOLITS.
AVAIL ADVANCES IN WATER QUALITY IMPROVEMENT. GLOYNA, E. F.,
AND ECKENFELDER, W. W., EDS. UNIVERSITY OF TEXAS
PRESS. AUSTIN, TEXAS. 1968.
TITLE A NEW SLUDGE DIGESTION PROCESS.
AUTHOR DRNEVICH, R. F. AND L. C. MATCH.
AVAIL PROCEEDINGS OF THE 5TH NATIONAL CONFERENCE ON ACCEPTABLE
SLUDGE DISPOSAL TECHNIQUES, ORLANDO, FLORIDA. JANUARY 31-
FEBRUARY 2, 1978. INFORMATION TRANSFER INC., ROCKVILLE,
MARYLAND 20852.
TITLE NEW TWIST IN DIGESTER DESIGN.
AUTHOR DAVIS, G. H.
AVAIL AMERICAN CITY AND COUNTY. P. 68, MAY 1976.
TITLE NUTRIENT REQUIREMENTS AND BIOLOGICAL SOLIDS ACCUMULATION IN
ANAEROBIC DIGESTION
AUTHOR SPEECE, R. E. AND McCARTY, P. L.
AVAIL ADVANCES IN WATER POLLUTION RESEARCH, VOL. II, ED. BY
W. W. ECKENFELDER, PERGAMON PRESS (1964).
TITLE OPTIMIZING GAS PRODUCTION, METHANE CONTENT AND BUFFER
CAPACITY IN DIGESTER OPERATION.
AUTHOR BROVKO, N. AND K. Y. CHEN.
AVAIL WATER AND SEWAGE WORKS. P. 54, JULY 1977.
TITLE OXYGEN TOXICITY IN DIGESTERS.
AUTHOR FIELDS, M., AND F. J. AGARDY.
AVAIL PROCEEDINGS 26TH PURDUE INDUSTRIAL WASTE CONFERENCE.
PURDUE UNIVERSITY. P. 284, 1971.
TITLE THE pH TOLERANCE OF ANAEROBIC DIGESTION.
AUTHOR CLARK, R. H. AND R. F. SPEECE.
AVAIL ADVANCES IN WATER POLLUTION RESEARCH. VOL. I. S. H. JENKINS,
ED. PERGAMON PRESS, OXFORD, ENGLAND. 1970.
TITLE PERIPHERAL MIXING TURNS SLUDGE INTO FUEL GAS.
AVAIL THE AMERICAN CITY AND COUNTY. P. 58, JULY 1977.
TITLE POPULATION DYNAMICS IN ANAEROBIC DIGESTION.
AUTHOR PFEFFER, J. T., M. LEITER, AND J. R. WORLUND.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 39, P. 1305,
1967.
201
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TITLE POWDERED ACTIVATED CARBON IMPROVES ANAEROBIC DIGESTION
AUTHOR HUNSICKER, M., AND ALMEIDA, T.
AVAIL WATER AND SEWAGE WORKS, P. 62, JULY (1976).
TITLE PRINCIPLES OF ANAEROBIC DIGESTION.
AUTHOR PRETORIUS, W. A.
AVAIL WATER POLLUTION CONTROL (1973), PP. 202-204.
TITLE PROCESS DESIGN MANUAL FOR SLUDGE TREATMENT AND DISPOSAL.
AUTHOR USEPA.
AVAIL EPA TECHNOLOGY TRANSFER, EPA-625/l-79-011(1979). CHAPTER 6.
TITLE PROCESSING OF COMBINED PHYSICAL-CHEMICAL BIOLOGICAL SLUDGE.
AUTHOR PARKER, D. S., D. G. NILES, AND F. J. ZUDICK.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 46, P. 2281,
1974.
TITLE PUMPING SLUDGE LONG DISTANCES.
AUTHOR SPARR, ANTON E.
CORP AUTH POTTER (ALEXANDER) ASSOCIATION, NEW YORK.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL. 43, NO. 8,
AUGUST, 1971, P. 1702-1711.
TITLE REDUCTION OF BACTERIA IN SLUDGE TREATMENT.
AUTHOR KAMPELMACHER, E. H. AND N. VAN NOORLE, JANSEN, L. M.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 44,
P. 309, 1972.
TITLE REDUCTION OF DIGESTED SLUDGE VOLUME BY CONTROLLED RECIRCU-
LATION.
AUTHOR TORPEY, W. N. AND N. R. MELBINGER.
AVAIL JOURNAL WATER POLLUTION FEDERATION. VOL. 39, P. 1464, 1967.
TITLE REVIEW PAPER: THE THERMOPHILIC ANAEROBIC DIGESTION PROCESS.
AUTHOR BUHR, H. 0. AND ANDREWS, J. F.
AVAIL WATER RES. VOL. 11, P. 129, 1977.
TITLE THE ROLE OF SULFIDE IN PREVENTING HEAVY METAL TOXICITY IN
ANAEROBIC TREATMENT.
AUTHOR LAWRENCE, A. W. AND P. L. McCARTY.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 37, P. 392,
1965.
TITLE SLUDGE DIGESTION OF MUNICIPAL WASTEWATER SLUDGES, SLUDGE
TREATMENT AND DISPOSAL.
AUTHOR USEPA.
AVAIL VOL. 1. USEPA ENVIRONMENT RESEARCH INFORMATION CENTER.
CINCINNATI, OHIO 45268. EPA-625/4-78-012. OCTOBER 1978.
TITLE SLUDGE HANDLING AND CONDITIONING.
AUTHOR USEPA.
202
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AVAIL OFFICE OF WATER PROGRAM OPERATIONS. WASHINGTON, D.C. 20460.
EPA 430/9-78-002. FEBRUARY 1978.
TITLE SLUDGE HANDLING AND DISPOSAL PRACTICES AT SELECTED MUNICIPAL
WASTEWATER TREATMENT PLANTS.
AUTHOR SVERDRUP AND PARCEL AND ASSOCIATES, INC.
AVAIL REPORT SUBMITTED TO MUNICIPAL CONSTRUCTION DIV., OFF. WATER
PROGRAMS OPERATIONS, U. S. ENVIRONMENTAL PROTECTION AGENCY,
WASHINGTON, D.C., EPA-430/9-77-007 (1977).
TITLE SLUDGE HANDLING AND DISPOSAL PRACTICES AT SELECTED MUNICIPAL
WASTEWATER TREATMENT PLANTS.
AUTHOR USEPA.
AVAIL OFFICE OF WATER PROGRAM OPERATIONS. WASHINGTON, D.C. 20460.
MCD 36, APRIL 1977.
TITLE SLUDGE PROCESSING FOR COMBINED PHYSICAL-CHEMICAL-BIOLOGICAL
SLUDGES.
AUTHOR USEPA.
AVAIL ENVIRONMENTAL PROTECTION TECHNOLOGY SERIES. CINCINNATI, OHIO
45268. EPA-R2, 73 - 250. JULY 1973.
TITLE SLUDGE TREATMENT: PROBLEMS AND SOLUTIONS, PART 1.
AUTHOR SMITH, J. E., JR.
CORP AUTH NATIONAL ENVIRONMENTAL RESEARCH CENTER, CINCINNATI, OHIO.
ADVANCED WASTE TREATMENT RESEARCH LAB.
AVAIL WATER AND SEWAGE WORKS, VOL. 124, NO. 4, P. 80-83,
APRIL 1977.
TITLE SLUDGE TREATMENT PROCESS OFFERS FLEXIBILITY, LOW COST.
AUTHOR EVANS, R. R.
AVAIL CHEMICAL ENGINEERING, P. 86, DECEMBER 5 (1977).
TITLE SODIUM BICARBONATE PROVIDES PH RELIEF FOR DIGESTER.
AVAIL WATER AND WASTES ENGINEERING, VOL. 14, NO. 5, P. 57, MAY
1977.
TITLE STAGE DIGESTION OF WASTEWATER SLUDGE.
AUTHOR WOODS, C. E. AND V. F. MALINA.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 37, P. 1495,
1965.
TITLE STANDARD METHODS FOR THE EXAMINATION OF WATER AND WASTEWATER.
AUTHOR AMERICAN PUBLIC HEALTH ASSOCIATION.
AVAIL 15TH EDITION. AMERICAN PUBLIC HEALTH ASSOCIATION,
WASHINGTON, D.C. 1980.
TITLE START-UP AND OPERATION OF TWO NEW HIGH-RATE DIGESTION SYSTEMS.
AUTHOR LYNAM, B., G. McDONNELL, AND M. KRUP.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION. VOL. 39, P. 518,
1967.
203
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TITLE STUDIES ON THE OXIDATION KINETICS OF BIOLOGICAL SLUDGES.
AUTHOR ECKENFELDER, W. W., JR.
AVAIL SEWAGE AND INDUSTRIAL WASTES. VOL. 28, 8, P. 983, 1956.
TITLE A STUDY OF SLUDGE HANDLING AND DISPOSAL.
AUTHOR U. S. DEPARTMENT OF INTERIOR.
AVAIL FEDERAL WATER POLLUTION CONTROL ADMINISTRATION, OFFICE OF
RESEARCH. NO. WP-20-4. MAY 1968.
TITLE A SUMMARY OF OBSERVATIONS ON THERMOPHILIC DIGESTER OPERATIONS.
AUTHOR OHARA, G. T., AND COLBAUGH, J. E.
AVAIL PROCEEDINGS OF THE NATIONAL CONFERENCE OF MUNICIPAL SLUDGE
MANAGEMENT AND DISPOSAL. INFORMATION TRANSFER, INC.,
ROCKVILLE, MARYLAND 20852. AUGUST 1975.
TITLE SURVEY OF ANAEROBIC DIGESTION SUPERNATANT TREATMENT
ALTERNATIVES.
AUTHOR MIGNONE, N. A.
AVAIL WATER AND SEWAGE WORKS. JAN. 1977.
TITLE TEMPERATURE EFFECTS ON ANAEROBIC DIGESTION OF RAW SEWAGE
SLUDGE.
AUTHOR GOLVEKE, C. G.
AVAIL SEWAGE AND INDUSTRIAL WASTES. VOL. 30, P. 1225, 1958.
TITLE THERMAL EFFECTS ON COMPLETELY MIXED ANAEROBIC DIGESTION.
AUTHOR MALINA, J. F.
AVAIL WATER AND SEWAGE WORKS. P. 52, JANUARY 1964.
TITLE THERMOPHILIC DIGESTION AT THE HYPERION TREATMENT PLANT.
AUTHOR CAREER, W. F., et al.
AVAIL JOURNAL WATER POLLUTION CONTROL FEDERATION, VOL. 47, P. 950,
1975.
TITLE THERMOPHILIC PROCESSING OF MUNICIPAL WASTE.
AUTHOR COULTHARD, T. L. AND P. M. TOWNSLEY.
AVAIL PAPER NO. 74.219, CANADIAN SOCIETY OF AGRICULTURAL
ENGINEERS. 1974.
TITLE THE TOXICITY OF CADMIUM TO ANAEROBIC DIGESTION: ITS
MODIFICATION BY INORGANIC ANIONS.
AUTHOR MOSEY, F. E.
CORP AUTH WATER POLLUTION RESEARCH LAB., STEVENAGE (ENGLAND).
AVAIL WATER POLLUTION CONTROL, VOL. 70, 1971, P. 584-598.
TITLE TOXICITY, SYNERGISM AND ANTAGONISM IN ANAEROBIC WASTE
TREATMENT PROCESS.
AUTHOR KUGELMAN, I. J. AND K. K. CHIN.
AVAIL ANAEROBIC BIOLOGICAL TREATMENT PROCESSES. ADVANCES IN
CHEMISTRY SERIES, NO. 105. AMER. CHEM. SOC. 1971.
TITLE TREATMENT AND DISPOSAL OF WASTEWATER SLUDGES.
AUTHOR VESILIND, P. A.
AVAIL ANN ARBOR PRESS. ANN ARBOR, MICHIGAN 48106. 1974.
204
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TITLE TREATMENT OF SUPERNATANTS AND LIQUIDS ASSOCIATED WITH
SLUDGE TREATMENT.
AUTHOR MALINA, J. F., JR. AND DiFILIPPO, J.
AVAIL WATER SEWAGE WORKS (1971), R-30.
TITLE UNIFIED BASIS FOR BIOLOGICAL TREATMENT DESIGN AND OPERATION.
AUTHOR LAWRENCE, A. W. AND McCARTY, P. L.
AVAIL J. SANIT. ENG. DIV., A.S.C.E., 96 (SA3), 757-778 (1970).
TITLE UTILIZATION OF METHANE FROM SLUDGE DIGESTION.
AUTHOR KAPOOR, S. K. AND NEWTON, D.
AVAIL MUNICIPAL SLUDGE MANAGEMENT AND DISPOSAL PUBLISHED BY
INFORMATION TRANSFER INC., AUGUST (1975).
TITLE USE OF SOLAR ENERGY TO HEAT ANAEROBIC DIGESTERS.
AUTHOR USEPA.
AVAIL MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY. CINCINNATI,
OHIO 45268. EPA 600/2-78-114. JULY 1978.
TITLE WASTEWATER ENGINEERING: COLLECTION, TREATMENT, DISPOSAL.
AUTHOR METCALF AND EDDY, INC.
AVAIL McGRAW-HILL BOOK CO., NEW YORK, N.Y. (1972).
TITLE WATER AND WASTEWATER TREATMENT.
AUTHOR SCHROEDER, E. D.
CORP AUTH CALIFORNIA UNIVERSITY, DAVIS. DEPARTMENT OF CIVIL ENGINEERING.
AVAIL McGRAW-HILL, NEW YORK, N.Y. 1977. P. 370.
205
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