NATIONAL SANITATION FOONDATION
PACKAGE SEWAGE TREATMENT PLANTS
CRITERIA DEVELOPMENT
PART I: EXTENDED AERATION
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PACKAGE PLANT CRITERIA DEVELOPMENT
PART I: EXTENDED AERATION
NATIONAL SANITATION FOUNDATION
ANN ARBOR, MICHIGAN
Dr. Henry F. Vaughan, President
Mr. Robert M. Brown, Vice President
Mr. Charles A. Farish, Executive Director
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEMONSTRATION GRANT PROJECT
WPD • 74
BRIAN L. GOODMAN, Project Director
September, 1966
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FOREWORD
Package Sewage Treatment Plant Criteria Development - Part I: Extended Aeration summarizes
the research which was conducted to establish a means by which the performance of this type of
wastewater treatment device could be evaluated. This research effort resulted in the development of
The Standard Performance Evaluation Method which is presented here. The evaluation method is
based on the Performance Criteria which are also presented in this report.
At the present time the research required for the establishment of performance evaluation criteria
for contact stabilization package sewage treatment plants is being conducted. This research will be
summarized and the criteria developed will be presented in Part II of this report which will be
published in about a year.
It is the hope of the Foundation that the information contained in these reports will be used ex-
tensively by regulatory agencies, manufacturers, engineers, contractors, owners, operators, and all
others concerned in the design, application, and operation of package sewage treatment plants.
Further, it is hoped that such use of the findings presented here will result in a better understanding
of the capabilities of this type of wastewater treatment device.
NATIONAL SANITATION FOUNDATION
September, 1966
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INDEX
Page
Previous Studies 1
Project History 2
Project Methodology and Facilities 3
Executive Committee 3
Policy Committee 3
Technical Committee 4
Industry Committee 5
Extended Aeration Plants 16
Startup and Solids Accumulation 21
B.O.D. Removal 23
Oxygen Requirements. ................ 25
Nitrification 26
Solids Separation 27
Skimming 31
Temperature 31
Page
Optimum Mixed Liquor Solids 32
Solids Wasting . 32
Routine Operation and Maintenance 33
Bacteriological 35
Plant Size and Construction 35
Rapid Analytical Methods 35
Standard Analytical Methods and Samples. . . 37
Performance Criteria 38
Standard Performance Evaluation Method ... 38
Responsibilities 43
Summary 45
Acknowledgements 46
References 48
Tables (I through I-C) 50-53
TABLES AND
FIGURES
Table
Page
Figure
Page
I
Steady State Data, Fall and Winter
21-28
Extended Aeration Package
Studies
. . 50
Plant Photographs
17-18
I-A
Steady State Data, Spring and
29-33
Research Site Photographs
Summer Studies
. . 51
34
Subdivision Flow Pattern
I-B
Subdivision Flow Pattern Data . . .
35
School Flow Pattern
I-C
School Flow Pattern Data
36
Steady State Flow Pattern
II
Solids Buildup Rate
37
Solids Accumulation
m
Oxygen Uptake Rate
38
Mature Extended Aeration Process
. . 22
Figure
39
B.O.D. Removal
1
General Research Site Plan
40
B.O.D. Removal .
. . 23
2
Control Shelter and Piping, Typical
41
B.O.D. and Suspended Solids Removal 25
Section
42
Zone Settling Rate
. . 28
3
Research Site Flow Diagram ....
. . 9
43
Zone Settling Rate
4
Typical Flow Control Scheme ....
. . 10
44
Extended Aeration Package Plant,
5-14
Research Site Construction Photo-
Internal Flow Rates
. . 28
graphs
12-13
45
Sludge Density Index Values
. . 30
15-19
Ann Arbor Sewage Characteristics
14-15
46
Sludge Loading and Sludge Density
30
20
Simple Extended Aeration Package
Index
Plant
47
Nitrification
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PACKAGE PLANT CRITERIA DEVELOPMENT
Part I: Extended Aeration
I. GENERAL
Fifty years ago Americans lived, generally,
either on farms or in towns. Today, a third
major area has developed which we call suburbia.
During that fifty year period many other changes
in the American way of life have taken place.
The development of the automobile and the con-
struction of superhighways have added the di-
mension of mobility to the American way of life.
Tremendous population growth has taken place
and many businesses and industries have followed
the migration of a large segment of the popula-
tion into suburbia both to serve these new areas
and to escape the overcrowded cities. Further,
as the population grew so did the problem of
pollution until it became not only one of local
significance but of national significance as well.
Until the advent of suburbia and the era of mo-
bility the collection and treatment of sewage in-
volved either the use of conventional collection
and treatment systems in the towns and cities
or the use of individual disposal methods such as
privies, cesspools, and septic tanks in the rural
areas. Neither of these two basic methods were
well suited for suburbian use. Attempts to utilize
the existing individual disposal methods largely
were unsatisfactory in suburbia because of the
limited amount of land available to the individual
home owner and the variability of soil conditions.
Further, as mobility increased the use of highway
rest area facilities taxed the limited capabilities
of existing waste disposal methods. What was
clearly needed was a waste treatment and dispo-
sal system which was capable of achieving a
relatively high level of treatment in connection
with waste volumes intermediate between those
of the cities and the farms. The so-called package
treatment plant has been claimed by its developers
to be the answer to this dilemma.
PREVIOUS STUDIES
The forerunners of today's package sewage
treatment plants were in use in this country at
least as early as 1934.1 In 1947 aerobic diges-
tion as a complete treatment process was brought
to the attention of the Ohio Department of Health
through the reports of the East Palestine (Ohio)
Sewage Treatment Plant Superintendent.2 Porges,
Jasewicz, and Hoover proposed the total oxida-
tion of influent organic substrate in a treatment
system as a result of their study of dairy waste
treatment which was published in 1953.3 In 1958
McKinney etal reported on the design and opera-
tion of a completely mixed activated sludge system
having a high B.O.D. removal efficiency.4 During
the same year Tapleshay reported on the design
and efficiency of total oxidation package plants.5
He pointed out that the degree of treatment achieved
was a function of design. Also in 1958 Symons
and McKinney pointed out that not all organic
substrate entering the system was totally oxidized
but rather that a small residue of non-oxidizable
polysaccharide material remained.6 Kountz and
Forney (1959) using dry skim milk as feed for a
total oxidation treatment system found that residual
material accumulated in the system equivalent to
20-25 percent by weight of the new activated
sludge produced.7
During 1959 and 1960 the Ohio Department of
Health made extensive field studies of a number
of extended aeration package plants being operated
in that state and found that properly designed and
operated plants were capable of achieving a high
degree of treatment.2 Joplin (1960) reported on
a field study of ten extended aeration package
treatment plants in California and stressed the
relationship of routine operational and mainte-
nance attention to the degree of treatment achieved. 8
Kiker (1960) reported a field study of fourteen
extended aeration package plants in Florida which
also stressed the importance of operation and
maintenance.9 Porges and Morris (1960) pre-
sented a review of the information then available
on extended aeration package plants which pointed
out both their basic usefulness and limitations.10
One of the most thorough analysis of process
fundamentals was presented by Ludwig et al in
I960.1 This was followed by a somewhat con-
densed presentation of the material by Stewart
and Ludwig in 1962.11 •12 Shatto (1960) demon-
strated that a package plant effluent free of
detectable B.O.D. could be produced by using a
diatomite filter as the final treatment step.13 In
1961 Howe presented a discussion of package
plant operational problems.14 Ludzack, Schaffer,
and Ettinger (1961) demonstrated the importance
of temperature and feed as process variables, is
During 1961 a study of fourteen package plants in
1
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2
Massachusetts to determine how actual perfor-
mance and operation correlated with theoretical
concepts was reported.16 This study found that
with proper design and operation these plants
were capable of producing a satisfactory effluent.
Based on the information developed during the
study, an operating manual was developed.17
Baker (1962) following a study of package treat-
ment plants in Florida reported the belief that
such units were capable of achieving a better than
95 percent B.O.D. and suspended solids remo-
vals.18
Another thorough analysis of extended aeration
package plant fundamentals was presented by
McCarty and Brodersen in 1962.19 Porges and
Morris (1962) presented a discussion of the cri-
teria for utilization of extended aeration package
plants.20 Stewart, Ludwig, and Kearns (1962)
found that extended aeration plants were capable
of satisfactory performance under conditions of
constant or varying salinity over a relatively wide
range.21 Washington and Symons reported on the
accumulation of volatile solids in activated sludge
systems during 1962.22 An extensive review of
the mathematics of completely mixed activated
sludge systems was presented by McKinney in
1963.2:s Also in 1963, the effect of extended
aeration package plant effluent on intermittent
watercourses was detailed by Morris et al.~i
Sludge loading and dissolved oxygen as ac-
tivated sludge process variables were studied by
Orford, Heukelekian, and Isenberg, 1963.2S Pfeffer
(1963, 1966) has reviewed extended aeration de-
sign criteria.26-27 Additional studies and obser-
vations on package plants in Florida were re-
ported by Baker in 1964. 28 Lawton and Norman
(1964) detailed studies on aerobic digestion.29
Monn (1964) reviewed the design and maintenance
of extended aeration plants. 30 Schulze (1964, 1965)
presented a mathematical model for the activated
sludge process.^1'32 Ludzack reported on an
extensive bench-scale study of extended aeration
in 1965.33 Rao and Gaudy (1966) demonstrated
the importance of sludge concentration as a pro-
cess variable.34 Smith (1966) reported on homo-
geneous activated sludge studies.35
From the foregoing it is evident that much
knowledge has been gained and much development
has taken place in the package plant field during
the past twenty years. Further, many fundamen-
tal studies have been made which have an impact
on this field. In the sections which follow, this
information which has been developed will be re-
lated to the findings of the present study so that
as complete a picture as possible of our present
knowledge in this area can be presented.
Coincident with the studies reported above
was the commercial development of the extended
aeration package plant concept. In 1950 only
three such plants were reported while today many
thousands are in use. This rapid growth and
widespread application of a new concept in waste
treatment left many questions unanswered. One
of the prime unanswered questions was how to
evaluate the performance of extended aeration
package plants.
PROJECT HISTORY
In 1956 the Sewerage Committee, Engineering
Section, Michigan Public Health Association ex-
pressed an interest in packaged treatment plants
and a desire to explore on a national scale whether
agreement could be reached on how to evaluate
the performance of these plants. In 1957 this
committee called a meeting of interested public
health, sanitary engineering, user, manufacturer,
and other groups and agencies to examine this
question. The meeting was held at Michigan State
University on April 27th of that year. It was the
consensus of those attending this meeting that
there was a need for units possessing the char-
acteristics generally attributed to packaged plants,
that additional information was needed on per-
formance and control, and that some independent
testing agency such as the National Sanitation
Foundation would provide a valuable service if it
would make a study of these plants. This proposal
did not go forward because of the lack of financial
support.
In 1961 the Great Lakes Upper Mississippi
Board of State Sanitary Engineers requested its
Sewage Works Standards Committee to find a
means of developing performance evaluation cri-
teria for packaged treatment plants. During 1962
the Board on the recommendation of its committee
directed the committee chairman to explore
whether the National Sanitation Foundation would
undertake such a study.
Pursuant to the action of the Great Lakes
Upper Mississippi Board, above, and supported
strongly by the resolution adopted by the Board
recommending this course of action, the Founda-
tion appointed an interim Joint Industry-Public
Health Committee which developed through a num-
ber of work sessions a proposed methodology for
the study and an application seeking a U.S. Public
Health Service Demonstration Grant for the Finan-
cial support of the project. Additional support
for this course of action came from the Con-
ference of State Sanitary Engineers and the As-
sociation of State and Interstate Water Pollution
Control Administrators.
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3
The Foundation application was subsequently
approved and given high priority by the Demon-
stration Grants Committee (now a part of the
Federal Water Pollution Control Administration)
of the U.S. Public Health Service in 1964. This
grant which is known as WPD-74 was given an
effective data of January 1, 1965 and provided
$150,075.00 for the first year's work and contem-
plated at least two additional years of research
each with a total budget of $90,600.00
PROJECT METHODOLOGY AND FACILITIES
January 15, 1965 represented the ending of
one era and the beginning of another insofar as
this project is concerned for it was on that day
that the last meeting of the interim Joint Indus-
try-Public Health Committee was held and it was
at that meeting that the Foundation announced the
project as an official Foundation study. Imme-
diately following the meeting the Foundation ap-
pointed the following committees to serve through-
out the project:
EXECUTIVE COMMITTEE
Dr. B. A. Poole, Director - CHAIRMAN
Bureau of Environmental Sanitation
Indiana State Board of Health
Indianapolis, Indiana
Dr. Leon W. Weinberger
Chief, Basic and Applied Sciences Branch
Water Pollution Control Administration
Department of the Interior
Washington, D.C.
Mr. George H. Eagle
Chief Engineer
Division of Engineering
Ohio Department of Health
Columbus, Ohio
Mr. Ralph C. Pickard, Director
Division of Environmental Health
Kentucky Department of Health
Frankfort, Kentucky
Dr. Meredith H. Thompson
Assistant Commissioner
Division of Environmental Services
New York State Department of Health
Albany, New York
Dr. Gordon McCallum
Assistant to the President
INFILCO, Inc.
Tuscon, Arizona
Mr. Jasper Davis, President
DAVCO Manufacturing Company
Thomasville, Georgia
Mr. B. Alden Smith
President
Smith and Loveless
Division - Union Tank Car Company
Lenexa, Kansas
Mr. Milton Spiegel
Consultant
FMC Corporation
Panorama City, California
POLICY COMMITTEE
Dr. B. A. Poole, Director - CHAIRMAN
Bureau of Environmental Sanitation
Indiana State Board of Health
Indianapolis, Indiana
Dr. Leon W. Weinberger, Chief
Basic and Applied Sciences Branch
Water Pollution Control Administration
Department of the Interior
Washington, D. C.
Mr. George H. Eagle
Chief Engineer
Division of Engineering
Ohio Department of Health
Columbus, Ohio
Mr. Ralph C. Pickard, Director
Division of Environmental Health
Kentucky Department of Health
Frankfort, Kentucky
Mr. Kenneth H. Spies, Director
Division of Sanitation and Engineering
Oregon State Board of Health
Portland, Oregon
Dr. Meredith H. Thompson
Assistant Commissioner
Division of Environmental Services
New York State Department of Health
Albany, New York
Mr. Walter A. Lyon, Director
Division of Sanitary Engineering
Pennsylvania Department of Health
Harrisburg, Pennslyvania
Mr. John E. Trygg, Director
Division of Continued Public Health Engineering
Louisiana Board of Health
New Orleans, Louisiana
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4
Mr. Worthen H. Taylor, Chief
Bureau of Environmental Sanitation
Massachusetts Department of Public Heamh
Boston, Massachusetts
Dr. Gordon E. McCallum
Assistant to the President
INFILCO, Inc.
Tuscon, Arizona
Mr. Jasper Davis, President
DAVCO Manufacturing Company
Thomasville, Georgia
Mr. B. Alden Smith
President
Smith and Loveless
Division - Union Tank Car Co.
Lenexa, Kansas
Mr. J. D. Walker, President
Walker Process Equipment, Inc.
Aurora, Illinois
Mr. Milton Spiegel
Consultant
FMC Corporation
Panorama City, Californioa
Mr. Robert Gloppen, Manager
Water Treatment Division
Yeomans Brothers Company
Melrose Park, Illinois
Mr. C. M. Comstock
Dorr-Oliver, Inc.
Houston, Texas
Mr. Harry Lee, President
Defiance, Inc.
Bradenton, Florida
Mr. James E. Jump, President
Aer-O-Flo Corporation
Florence, Kentucky
Professor John B. Kiker
Department of Civil Engineering
University of Florida
Gainesville, Florida
Dr. Harvey F. Ludwig, President
Engineering-Science, Inc.
Arcadia, California
Dr. DeVere W. Ryckman
Director of Environmental and Sanitary
Engineering
Washington University
St. Louis, Missouri
TECHNICAL COMMITTEE
Mr. Donald M. Pierce - CHAIRMAN
Chief, Wastewater Section
Division of Engineering
Michigan Department of Health
Lansing, Michigan
Mr. George H. Eagle - VICE CHAIRMAN
Chief Engineer
Division of Engineering
Ohio Department of Health
Columbus, Ohio
Mr. David B. Lee
Director
Bureau of Sanitary Engineering
State Board of Health
Jacksonville, Florida
Mr. R. S. Nelle
Division of Sanitary Engineering
Illinois Department of Health
Springfield, Illinois
Mr. Ralph Porges
Head, Water Quality Branch
Delaware River Basin Commission
Trenton, New Jersey
Mr. R. J. Schliekelman
Division of Engineering
Iowa Department of Health
Des Moines, Iowa
Mr. Gerald E. Hauer
Manager of Engineering
Infilco, Inc.
Tucson, Arizona
Mr. Jack W. Pratt
Process Engineers
Division of the Eimco Corporation
Salt Lake City, Utah
Mr. M. L. Reed
General Manager
Tex-Vit Manufacturing Division
Can-Tex Industries, Inc.
Mineral Wells, Texas
Mr. Ray Golly
Chief Sanitary Engineer
Smith and Loveless
Division - Union Tank Car Co.
Lenexa, Kansas
Mr. Tom H. Forrest
Senior Product Manager
Chicago Pump Company
Chicago, Illinois
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ADVISORS
Mr. C. Preston Witcher
Superintendent
Ann Arbor Sewage Treatment Plant
Ann Arbor, Michigan
Mr. G. R. Herzik, Chief
Division of Environmental Sanitation Services
Texas Department of Health
Austin, Texas
Dr. J. A. Borchardt
Professor of Sanitary and Water Resources
Engineering
College of Engineering
University of Michigan
Ann Arbor, Michigan
Dr. G. M. Ridenour
Professor Emeritus
School of Public Health
University of Michigan
Ann Arbor, Michigan
INDUSTRY COMMITTEE
Mr. James E. Jump, President
Aer-O-Flo Corporation
Florence, Kentucky
Mr. Milton Spiegel, Consultant
FMC Corporation
Panorama City, California
Mr. Louis Sloan, Manager
Sewage and Waste Treatment Dept.
Crane Company
King of Prussia, Pennsylvania
Mr. Jasper C. Davis, President
DAVCO Mfg. Company
Thomasville, Georgia
Mr. Harry Lee, President
Defiance, Incorporated
Bradenton, Florida
Mr. Bernard S. MacCabe, Manager
Dravo Corporation
Pittsburgh, Pennsylvania
Mr. Jack W. Pratt
The Eimco Corporation
Process Engineers Division
Salt Lake City, Utah
Mr. Joseph N. Rizzi, Jr.
Chief Engineer
Gulfstan Corporation
Miami, Florida
5
Mr. Gerald E. Hauer
Manager of Engineering
INFILCO, Inc.
Tucson, Arizona
Mr, David S. MacLaren, President
Jet Aeration Company
Cleveland, Ohio
Mr. William L. Berk
Vice President Research and Development
Lakeside Engineering Corporation
Chicago, Illinois
Mr. J. J. Gilbert
Manager Sanitary Engineering
Link-Belt Company
Colmar, Pennsylvania
Mr. Richard Mack, President
Mack Vault Company
Valley City, Ohio
Mr. Roy L. Johnson
Sales Manager
Marolf Hygienic Equipment, Inc.
Toledo, Ohio
Mr. J. W. Bell, General Manager
Tank Division
Logemann Brothers Company
Milwaukee, Wisconsin
Mr. R. Edward Burton, President
Microphor, Inc.
Willits, California
Mr. Sidney Krakauer
Vice President, New Products
Pall Corporation
Glen Cove, L.I., New York
Mr. I. M. Lefton
Sales Manager
Suburbia Division
Pritchard Products Corporation
Kansas City, Missouri
Mr. J. F. Spade, President
Seco, Inc.
Ruskin, Florida
Mr. R. C. Blackburn
General Manager
The Security Sewage Equipment Co.
Cleveland, Ohio
Mr. M. L. Reed, General Manager
Tex-Vit Mfg. Division
Can-Tex Industries
Mineral Wells, Texas
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6
Mr. Jack Howells
Chief Engineer
TOPCO Company
Div. Sterling-Salem Co.
Salem, Ohio
Mr. Richard M. Brown, President
Water and Sewage, Inc.
Daytona Beach, Florida
Mr. Elmer R. Wood, President
Wood Sanitation and Equipment Co.
Cleveland, Ohio
Mr. William A. Jahn, President
Worden-Allen Company
Milwaukee, Wisconsin
Mr. J. B. Pflaum
Marketing Manager
Package Sewage Plants
Yeomans Brothers Company
Melrose Park, Illinois
Mr. B. Alden Smith, President
Smith and Loveless
Division - Union Tank Car Co.
Lenexa, Kansas
Mr. Gordon H. Miller
Applications Engineering
Wastewater Program
AVCO Corporation
Spencer Heating-Lycoming Division
Williamsport, Pennsylvania
Mr. C. M. Comstock
Dorr-Oliver, Inc.
Houston, Texas
Mr. J. D. Walker, President
Walker Process Equipment, Inc.
Aurora, Illinois
Mr. William H. Wagner, Director
Environmental Health Research
Cromaglass Division
The Cromar Company
Williamsport, Pennsylvania
The Technical Committee held a two day
meeting in Ann Arbor on March 11 and 12, 1965
at which time detailed plans were presented by
the committee's engineering consultant, Mr.
George Hubbell, Hubbell, Roth and Clark, for the
project's research site facilities. The committee
made the following sixteen (16) recommendations
to the Policy Committee:
1. The physical facilities to be constructed
for this project should be those outlined
by Hubbell, Roth and Clark, see Figures
No. 1, 2, 3, & 4.
2. Plants studied should be identified by
number only and all data held as confi-
dential under rules to be specified by
the Policy Committee.
3. During the first year the project should
be limited to extend aeration package
plants, in the broadest meaning of the
term, unless found possible to study other
types without detriment to the extended
aeration study.
4. At least nine package plants should be
utilized in the initial study and these
divided into three groups of three plants
each. Each group of plants to be operated
under a different hydraulic and organic
loading pattern.
5. Plants selected for use in this project
should be operated in all respects in ac-
cordance with the manufacturers' instruc-
tions with the exception of the variations
in flow, flow patterns, and organic loadings.
6. Each series of tests should include both
Summer and Winter operations.
7. During Winter operations the package
plants should be protected by wind breaks
and other devices to provide essentially
the same protection to the plants as that
afforded by below grade installation.
8. Plants should be given necessary opera-
tional and maintenance attention with the
nature and extent of this attention being
reported in detail.
9. Detailed operational records should be
kept including observed meter readings
and the like as well as the personal ob-
servations and comments of the operating
staff. Detailed maintenance records should
be kept in like manner.
10. Observations should be made and reported
on the effect of process interruptions.
Such interruptions to be either the natural
result of the hydraulic pattern in use at
the time or the intentional simulation of
power failure and other conditions as time
and opportunity permit.
11. Observations should be made on the effect
of the following and reported:
(a) Optimum aerator solids concen-
tration
(b) Need for solids wasting
(c) Optimum return sludge rates
(d) Effectiveness of aerator mixing
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s„
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Fig. 2. Control Shelter and Piping, Typical Section
TYPICAL SECTION
CONTROL
SHELTER
PACKAGE PLANT
PACKAGE PLANT
CROSSWALKS
WALKWAY a
K
©
A - FLOW SPLITTING DEVICE
F - MAGNETIC FLOW METER
B - PLANT AIR BLOWER
G - AIR HEADER
C - ELECTRIC DUCT 480 V.
H - WATER HEADER
D - ELECTRIC HEATER
1 - CONTROL PANEL
E - RAW SEWAGE HEADER
J - RAW SEWAGE PUMP
K - CONCRETE SLAB
L - EFFLUENT COLLECTION 8
DRAINS
-------
Fig. 3.
Research Site Flow Diagram
B
F
ha
h
-------
10
Fig. 4. Typical Flow Control Scheme
TYPICAL FLOW CONTROL SCHEME
AA AA
AIR SIGNAL
ELECTRIC SUPPLY
WATER SUPPLY _ „
MOW Xh- G
n6
Ch)—
3-15 PSI
AIR SIGNAL
ELECTRIC
SIGNAL
WASTE
, K
ELECTRIC SUPPLY
i „ FLOW TO
* PLANT
A - I: I AIR RELAY J
B - CONTROLLER K
C - FLOW INOICATOR,RECORDER, L
TOTALIZER 8 TRANSMITTER M
D - PROGRAM SET POINT TRANS. N
E - PULSE COUNTER AA
F - EFFLUENT SAMPLER
G - AIR WATER RELAY
H " RAW SEWAGE HEADER
I - GATE VALVE
- THROTTLING VALVE
- CONTROL VALVE
- MAGNETIC FLOW METER
- FILTER
- WATER HEADER
- FILTERED AIR SUPPLY
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11
12. The need for and effectiveness of methods
for foam control should be observed and
reported.
13. The normal operational reports should
include observations on: (a) foam (b) odor
(c) scum (d) noise (e) safety (f) color of
aerator contents (g) effluent turbidity
These reports should also include a rec-
ord of labor and supplies required by
each unit.
14. Detailed maintenance reports should con-
tain a record of labor, parts, and supplies
required by each unit and a report of
and down time.
15. Laboratory Analyses:
Standard BOD suspended and volatile
suspended solids tests should be run daily
on all composite samples. Other tests
should be run as frequently as possible.
The following tests should be made on
the samples as indicated:
A. RAW SEWAGE
(1) Measurement of flow to each
unit
(2) Temperature
(3) pH
(4) B.O.D. (including K rate, car-
bonaceous and nitrogenous,
soluble and total)
(5) C.O.D.
(6) Suspended and volatile sus-
pended solids
(7) Total and volatile total solids
(8) Organic nitrogen, ammonia
nitrogen, nitrite and nitrate
(9) Phosphates
(10) A.B.S./L.A.S.
B. PACKAGE PLANT EFFLUENTS
The same as in A. above, with
the exception of item (1) and the
addition of dissolved oxygen de-
terminations.
C. "IN-PLANT" SAMPLES
(1) Aeration Tank
(a) Dissolved oxygen
(b) Suspended and volatile sus-
pended solids
(c) Solids settling rate
(SVI-SDI)
(2) Return Sludge
(a) Volume (rate of flow)
(b) Suspended and volatile sus-
pended solids
(3) Waste Sludge
(a) Volume
(b) Suspended and volatile sus-
pended solids
16. One or more studies of the oxygen trans-
fer coefficient of Ann Arbor sewage should
be made.
On April 12, 1965 the Policy Committee met
in Chicago and considered the Technical Committee
recommendations in detail. The recommendations
were adopted by the Policy Committee at that
meeting without significant change.
Bids were immediately taken on the necessary
construction work and construction was begun on
April 28, 1965. Much of the material required
was on hand by the end of May 1965, site grading
was completed, and major construction was in
progress, by the low bidder, Midwest Mechanical
Contractors, see Figures No. 5 thru 14. Con-
current with the foregoing activities the Founda-
tion had conducted an extensive search of the
pertinent literature, studied the characteristics
of the Ann Arbor Sewage which would be utilized
in the project, see Figures No. 15 thru 19, and
secured the agreement of a number of manufac-
turers to supply packaged sewage treatment plants
for use in the project. Further, during construc-
tion, the project staff had grown to include, in
addition to the Project Director, Mr. Brian L.
Goodman, Mr. John G. Havens (Research Site
Manager), Mr. Robert S. Greathouse, Sr. (Project
Chemist), Mr. Wendell Birdsall (Research As-
sistant), and Mrs. Adeline Carter (Project Secre-
tary). Mr. Jonn Karr (Research Assistant) joined
the staff early in 1966.
The first package plant was delivered by its
manufacturer to the research site on June 23,
1965 and fourteen others have since been supplied.
The research site occupies two acres of land
immediately adjacent to the Ann Arbor Sewage
Treatment Plant at 49 S. Dixboro Road, Ann
Arbor, see Figure No. 1. This land was provided
under a license agreement by the U.S. Public
Health Service. The auxiliary site for the
U.S.P.H.S. Midwest Regional Laboratory occupies
three acres of land adjoining the NSF Research
site.
A ten inch tap has been made on the Ann
Arbor Sewage Treatment Plant 48 inch inlet force
main just ahead of the plant's screening and girt
removal facilities. From this point sewage flows
through a ten inch line to the research site where
it passes through a one-fourth inch slot comminu-
tor. The sewage is then pumped at the rate of
1,000 gallons per minute through a distribution
line running the length of the research site. The
package treatment plants are located along this
distribution line and are fed sewage from it. The
rate of flow to each unit is automatically con-
trolled and so programmed as to simulate various
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12
NATIONAL SANITATION FOUNDATION
PACKAGE SEWAGE TREATMENT PLANT RESEARCH SITE CONSTRUCTION
Fig. 5. April 28, 1965, Site Preparation Fig. 6. May 26, 1965, Control Shelter Sections
Fig. 7. June 21, 1965, Control
Shelter, Underdrains and Piping
Fig. 8. June 23, 1965, First Plant Arrives Fig. 9. June 28, 1965, Control Shelter Slab
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NATIONAL SANITATION FOUNDATION
13
PACKAGE SEWAGE TREATMENT PLANT RESEARCH SITE CONSTRUCTION
Fig. 10. June 30, 1965, Pouring Slab
for Plants.
Fig. 11. July 10, 1965, Installation of
Concrete Tank Plants.
Fig. 12. July 12, 1965, Installation of
Steel Tank Plants
Fig. 13. July 13, 1965, Erection of
Control Shelter
Fig. 14. July 15, 1965, Control Shelter
Erection & Distribution Header Sections
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14
PROBABILITY % EQUAL TO OR LESS THAN
Fig. 16. City of Arm Arbor, Michigan, Raw Waste
Temperature.
Fig. 15. City of Ann Arbor, Michigan, Raw Waste
FLOW
SUSPENOED SOLIOS
Fig. 17. City of Ann Arbor, Michigan, Monthly Raw Fig. 18. City of Ann Arbor, Michigan, Raw Waste
Waste Variation Mean Values Daily Variation
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15
BOO,
mg/|
350
0
12 6 12 6 12
NOON
Fig. It). City of Ann Arbor, Michigan, Hourly BODg
Concentration Curve Raw Waste.
typical applications such as subdivisions, schools,
and the like. Each flow control unit consisted of
a flushing connection, a manual throttling valve,
an air to hydraulic operated flow control valve,
a magnetic flow meter, a flow indicator, recorder,
totalizer with pneumatic transmitter, a flow con-
troller proportioning and reset, to operate by air
signal the air water relay to control the valve,
together with the necessary flexible pipe con-
nections to the treatment unit(s). In addition,
program set point transmitters were used to
enable any flow pattern to be set up. Each of
these units could be used to control any number
of control valves. The cam for the programming
transmitters were field cut to provide the desired
flow program. Each control unit was capable of
controlling the flow for up to four package treat-
ment plants through the use of a flow splitter
weir box.
Influent and effluent samples were collected
by automatic samplers and composited propro-
tional to flow. Hydraulic conditions were auto-
matically maintained in the distribution system
such that the deposition of solids was prevented.
Excess sewage was returned to the Ann Arbor
Sewage Treatment Plant inlet for treatment.
Following sampling, the effluent from the package
plants was likewise returned to the Ann Arbor
Plant inlet. All controls and samplers were con-
tained in the 140 foot long control shelter which
also housed the laboratory and field facilities,
see Figures No. 1, 2, 3, & 4.
Ten steel package plants were located on the
East side of the control shelter and set on a con-
tinuous 30 foot wide concrete pad. Two concrete
package plants were installed on the West side of
the control shelter below grade. Two additional
steel package plants were located on a 30 foot wide
concrete pad located along the West side of the
control shelter. The control shelter was 12 feet
high with a walkway along the top. Crosswalks
from this gave access to the top of these package
plants which were installed above grade.
In all, fourteen package sewage treatment
plants were loaned to the Foundation for use in
this phase of the research project by their res-
pective manufacturers. Additional plants for use
in subsequent phases of this study have also been
provided.
Beginning with the startup of the first plant
on September 14, 1965, a large number of different
package treatment plants were operated simulta-
neously at the research site under a variety of
loading levels and patterns as well as the various
conditions of weather. The information and ex-
perience thus gained formed the core data. This
core data was extended through the collection of
field data. This activity has been going forward
for the past year and a half through the coopera-
tion of many State, county, and local health de-
partments, together with the cooperation of the
various manufacturers of these units. This
methodology insured that the final criteria were
applicable to the widest possible range of plant
design, loading, and weather conditions.
It was the objective of this research project
to develop criteria for the performance evaluation
of package sewage treatment plants. It is im-
portant to note that the objective of this study
was not to develop design criteria. The perfor-
mance evaluation criteria are such that the eval-
uations can be made completely independent of
design considerations.
So as to conserve valuable time plants were
started and the laboratory was put into operation
while major construction was still in progress.
During 1965 it became obvious that in order
to carry out the intent of the Technical Committee's
recommendations it would be necessary to add to
the facilities constructed in 1965. Accordingly,
a supplemental demonstration grant application
prepared by the Executive Committee and the
Foundation Project Staff was submitted to the
Grants Committee, Federal Water Pollution Con-
trol Administration. This request for an additional
$37,122.00 was approved by the Demonstration
Grants Committee to be effective January 1, 1966.
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16
This supplemental grant provided for the con-
struction of additional concrete pad area along
the West side of the control building, the ac-
quisition of additional control system components,
and necessary equipment and supplies.
Among the questions about extended aeration
package treatment plants which this research pro-
ject has attempted to answer are:
1. What is the effect of load level on per-
formance and performance evaluation?
2. What is the effect of organic and hydraulic
loading pattern on performance and per-
mance evaluation?
3. What is the effect of climatic conditions
on performance and performance evalua-
tion?
4. What is the effect of design considera-
tions on performance and performance
evaluation?
5. Are performance evaluation criteria which
are valid for one plant size in a model
series applicable to other sizes of the
same series?
6. What is the effect of the type of organic
loading on performance and performance
evaluation?
7. If one desired to evaluate the performance
of a plant, what analytical procedures
would he use?
8. In the performance evaluation of a plant,
what period of time is required for the
evaluation?
9. What are the effects of operating and pro-
cess variables on performance and per-
formance evaluation?
10. What are the interrelationships, if any,
that exist between the above and other
factors?
The present project represents a more than
one half million dollar joint effort on the part of
the water pollution control profession, the federal
government, and the manufacturers of package
plants to answer these and similar questions in
seeking a means of plant performance evaluation.
In order to eliminate bias from the delibera-
tions of the various project committees the iden-
tities of the manufacturers of the various package
plants used in the research were not disclosed
to the committee members and all data was pre-
sented to them identified only by code numbers.
The project data is presented here in the same
manner.
During the first one and a half years of this
project which is covered by this report, some
several thousand persons have visited the Re-
search Site. The record number of visitors for
one day was over two hundred. Among these
visitors have been representatives of most state
water pollution control and public health agencies,
many federal departments and agencies, pro-
fessional societies, universities, and the like.
EXTENDED AERATION PLANTS
Before proceeding to a more detailed dis-
cussion of process fundamentals it would perhaps
be useful to consider for a moment the basic
features of extended aeration plants.
Extended aeration package sewage treatment
plants consist of two main parts, the aeration
compartment and the final settling or clarification
compartment. Raw sewage flows directly into the
aeration compartment without having first been
subjected to primary sedimentation. A trash
trap, bar screen, and/or comminutor, however,
may sometimes be used ahead of the aeration
compartment. Within the aerator the raw sewage
is mixed with the return sludge to form the mixed
liquor which is aerated for from 18 to 30 (com-
monly 24) hours. At the end of the aeration
period, the mixed liquor flows into the sedimen-
tation or clarification compartment where the
suspended solids (MLSS) and liquid are separated
by gravity. The separated solids are returned
to the aeration compartment as the return sludge
(RSSS) while the liquid flows out of the plant as
the plant effluent. This effluent may or may not
be chlorinated prior to final disposal in a river
or lake. Sometimes a sand filter or lagoon is
used following the plant to further purify the plant
effluent prior to final disposal. Foam control
AIR SCUM RETURN 8 FOAM SPRAY
SEOtMENTATION
AERATION
EFFLUENT,
RETURN SLUDGE
Fig. 20. Simple Extended Aeration Plant
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17
TYPICAL PACKAGE SEWAGE TREATMENT PLANTS
CENTER
WEIL
Fig. 24
-------
18
Fig. 26
Fig. 25
Fig. 27 Fig. 28
'///////
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19
NATIONAL SANITATION FOUNDATION
PACKAGE SEWAGE TREATMENT PLANT RESEARCH SITE
Fig. 29. January, 1966, Overall View
Fig. 32. Access to Plants from Top of Control Shelter
Fig. 33, Walkway on Top of Control Shelter
Flow Control Panel
Fig. 30. Control Shelter Laboratory Section
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20
sprays and skimmers to remove floating material
from the surface of the clarification compartment
are also commonly included. Aeration of the mixed
liquor is by diffused aeration, mechanical aeration,
and variations and combinations of these methods.
Settled sludge and scum are returned to the aera-
tion compartment usually by the use of air lifts,
however, gravity and hydraulic methods are also
employed. Excess sludge is withdrawn from the
unit from time to time as needed. This waste
sludge is frequently disposed of through septic tank
cleaning companies or on sand beds adjacent to the
plant. Separate aerobic sludge digestion tanks are
often used prior to final disposal of the sludge to
further reduce the volume of sludge to be disposed
of. Figure 20 presents the main features of a typi-
cal, simple, extended aeration plant. Various types
of extended aeration package sewage treatment
plants are pictured in Figures 21 thru 28.
"Wherever in this section the words 'aeration
compartment' or 'clarification compartment' are
used it shall not be construed as restricting such
units to single compartments."
II. STUDIES AND FINDINGS
GENERAL
During the Fall and Winter of 1965-66 ten
extended aeration package sewage treatment plants
were operated at the National Sanitation Founda-
tion's Research Site in Ann Arbor. These plants
were operated and maintained in accordance with
the recommendations of their respective manu-
facturers at the design loading for each plant
applied steady state with respect to flow. This
resulted in organic loadings at, or just below,
design. The design daily hydraulic capacities
of these plants, based on a twenty-four hour
aeration period ranged from a low of 5,000 gpd
to a high of 16,000 gpd with intermediate capa-
cities of 7,500, 9,000, 10,000 and 12,000 gpd.
Two of these plants were constructed of concrete
and the remainder of steel. The concrete plants
were installed essentially below grade with the
steel tank plants being installed on a concrete
pad above grade. Pursuant to the instructions of
the Technical Committee, the above grade plants
were given winter protection.
The plants were operated by the Research
Site staff who made extensive reports on the
operating and maintenance time and materials re-
quired for each plant. In general, these plants
were operated continuously from Steptember 1965
until March 1966, when all but two of the plants
were drained and cleaned. During this period
1,830 plant days of operating time was logged.
For the Spring and Summer studies twelve
extended aeration package plants were operated
at the Research Site beginning in April 1966 and
ending in August 1966 for a total operating time
of 1,524 plant days. The plants utilized in this
portion of the studies were the same as were
used in the Fall and Winter studies with the ad-
dition of two steel tank plants. The range of
plant sizes in the Spring and Summer studies
were the same as were noted previously for the
Fall and Winter studies. All of the plants used
in both sets of studies employed diffused aeration
with the exception of one plant in the Spring and
Summer studies which employed mechanical aera-
tion. Additional views of various portions of the
Research Site are shown in Figures 29 thru 33.
During the Spring and Summer studies a num-
ber of different flow patterns were employed. The
plants were operated in pairs with the influent
flow to the various pairs being programmed as
follows:
PAIR FLOW PATTERN
A Steady State - Maximum Hydraulic Design
B Steady State - One Half Hydraulic Design
C Subdivision - Maximum Hydraulic Design
D Subdivision - One Half Hydraulic Design
E School - Maximum Hydraulic Design
F School - One half Hydraulic Design
These patterns are illustrated in Figures 34, 35,
and 36.
The performance of the plants during the
various phases of these studies is summarized
in Tables I through I-C.
All the plants selected for use in these studies
were standard models currently being offered for
sale by their respective manufacturers as attested
to by catalogs, brochures, and drawings filed with
the Foundation prior to acceptance of the plants.
* TOTAL DAILY VOLUME
7
6
S
4
3
2
0
.AM
6:00'
IZ'OO
Fig. 34. Subdivison Flow Patterns
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21
% TOTAL DAILY VOLUME
14
12
10
8
6
«
2
0 ~ —, , ,
12 00M 6 00AM 12 OO" 6 00PM I2:00M
Fig. 35. School Flow Pattern
* TOTAL DAILY FLOW
7
6
5
3
2
I
O 1 ¦ ¦ 1
I2 00M 600AM I200N 8:00P" I200M
Fig. 36. Steady State Flow Pattern
All analytical methods employed during these
studies, except as specifically noted, were those
set forth in the latest edition of Standard Methods
for the Examination of Water and Wastewater
available at the time.3'1'37
STARTUP AND SOLIDS ACCUMULATION
The startup period for extended aeration
package plants is defined as the time between the
placing of the plant in service and its attainment
of the required level of treatment of the applied
waste. Since, as it will be shown, treatment ef-
ficiency is, among other things, a function of the
active solids mass present in the system it follows
that the rate at which such solids accumulate
during startup is an important criterion of plant
performance.
Solids will accumulate in an extended aera-
tion system so long as the system is operating at
less than its equilibrium value or separate sludge
wasting is employed to maintain the system at a
solids level less than its equilibrium value. Other-
wise, once the system reaches equilibrium, solids
will be wasted from the system as they are formed.
The accumulation of solids can be expressed
as:
A = [(a F - b Md) + Si] - x M (1)
Where: A = Accumulation of solids
a = The fraction of F synthesized
per unit time
F = Foodstuff entering the system
b = The fraction of M oxidized
per unit time
Mci = The mass of degradeable solids
in the system
Sj = The inert solids entering the
system
x = Some fraction of M leaving the
system in unit time
M = The mass of solids in the sys-
tem
This can be illustrated by using the data from
plant F-l during its startup in the Spring and
Summer studies:
Where: a = 0.65
F = 5 lb. BOD /day
b = 0.18
Md = 12 lbs. (as MLVSS)
Si = 2.5 lbs ./day
xM = 1.25 lbs./day (as effluent sus-
pended solids)
A = [0.65 (5) - 0.18 (12)] + 2.5 - 1.25 = 2.2
lbs ./day (calculated)
A = 2.08 lbs ./day (observed, based on ob-
served MLSS increase of 50 mg/l/day)
As the food to microorganism ratio decreases
due to the increase of the active sludge mass
(some fraction of MLSS) and the fixed influent
BOD 5, the net sludge accumulation rate (a F -
b Mci) will decrease and will approach but not
reach zero, see Figure 37. This has been thor-
oughly demonstrated by Washington and Symons.22
The oxidation of 1 lb. of BOD results in an inert
residue of 0.12 lb. of solids, see Figure 38.
Based on the foregoing, it is clear that the
rate at which solids will accumulate in an ex-
tended aeration package plant beginning with the
placing of the plant in service is dependent on:
1. The rate at which foodstuff enters the
plant, therefore, longer startup periods are
to be expected in the case of under loaded
plants than those which receive their de-
sign load from the onset.
-------
(LB/LB BODb REMOVED)
1,000 2,000 3,000
MIXED LIQUOR SUSPENDED SOLIDS (mg/l)
Fig. 37. Solids Accumulation
LB. BOO.
+
BACTERIA
0.5 LB. Ot
SYNTHESIS
0.65 LB. CELLS
OXIDATION
0.12 LB. INERT
RESIDUE
ENERGY
Fig. 38. Mature Extended Aeration Process
2. The rate at which solids are lost from the
plant, therefore, plants with poorly designed
clarifiers or which are overloaded hy-
draulicly will have long startup periods.
3. The rate at which inert solids enter the
system.
4. The rate at which solids are being oxidized
in the system.
In order to determine the effect of loading
on solids buildup one half of the plants in the
Spring and Summer studies were started at design
load and one half at half design load. The re-
sults are given in Table II. Analysis of this data
reveals that for the loading levels, patterns, and
conditions studied the plants would achieve a
mixed liquor solids concentration of 2,500 mg/l
in from 36 to 49 days with the highest loadings
resulting in the lowest startup times.
TABLE II
Solids Buildup Kate
Spring - Summer Studios
Loading Pattern
Solids Buildup Rate
mg/l/day
1.
One Half Design Load,
Steady State
55
2.
Full Design Load, Steady
State
61
3.
One Half Design Load,
Subdivision
51
4.
Full Design Load, Sub-
division
G3
5.
One Half Design Load,
School
54
6.
Full Design Load, School
70
It is recognized that the achievement of mixed
liquor suspended solids concentrations sufficient
to yield consistently high treatment efficiency in
less than 36 to 49 days may be desirable in some
cases. In such cases seeding of the treatment
unit with activated sludge from a mature unit
treating a similar waste is recommended. A
second possible method of achieving a high treat-
ment efficiency within a relatively short time
was investigated during these studies. This method
involved allowing raw sewage to flow through the
treatment unit without aeration or sludge return
for a period of one week during which time the
package plant served in effect as a primary treat-
ment device. At the end of a week the plant is
placed into full operation. The use of this method
at one point during the studies resulted in a
mixed liquor suspended solids concentration of
980 mg/l at the beginning of the full startup
period and the achievement of 90% or better BOD5
removals by the end of the first week of full
operation. During the one week period of primary
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23
treatment BOD5 removals were 60% or better.
This method has been employed by at least one
manufacturer of package plants with equal success
and other sources report significantly reduced
startup times through the use of digested sludges
as seed material.
During the Fall-Winter studies the ten plants
had an average solids buildup rate of 42 mg/l/day
with a range of from 36 to 51 mg/l/day. In this
connection it should be noted that the mean sewage
strength was significantly lower in the Fall-Winter
studies than in the Spring-Summer studies and it
is believed that the lower buildup rate is consis-
tent with the characteristics of the sewage em-
ployed as feed.
BOD REMOVAL
For package sewage treatment plants of the
extended aeration type, the BOD removal from the
applied waste will depend on the mixed liquor
suspended solids (MLSS) concentration and the
time the organisms contained in the mixed liquor
suspended solids are in contact with the waste,
assuming that the concentration of oxygen in the
aerator is not a limiting factor. It is further
assumed here that the pH and temperature of the
aerator contents are sufficiently near optimum
values so as not to seriously impair biological
activity and that significant amounts of toxic sub-
stances are not present. It will be shown later,
however, that temperature is not as significant
a factor here as might otherwise be expected.
For a particular waste a relationship of
MLSS (Sa) times time (T) versus BOD removal
can be established which in general yields a curve
similar to that in Figure 39. This relationship
is further illustrated by Figure 40.
100
PER CENT
BOD
REMAINING
0
100
0
S0T .10*
Fig. 39. BOD Removal
% BOD REMAINING
90
80
70
60
50
40
30
20
10 -
70
80
40
50
60
0
10
20
30
S0T « 10s
•BASED ON MEAN INFLUENT a EFFLUENT B0Ds-PLANT A-l
Fig. 40. Mean BOD5 Removal
Conventional activated sludge systems utilizing
2,000 mg/1 MLSS and 6-8 hours aeration yield
Sa T values of from 12-16 x 103 which result in
BOD removals of 90% or greater. The typical
extended aeration package plant operates at MLSS
values near 5,000 mg/1 and mean aerator de-
tention times of 18-30 hours thus yielding Sa T
values of from 90 to 150 x 103. MLSS values
of up to 10,000 mg/1 are not altogether uncommon
in the field. Therefore, for extended aeration
plants it is not surprising that BOD removals of
greater than 90% are not only common but indeed
are to be expected. Substrate BOD is, for all
practical purposes, nearly entirely removed by
the system.
Since nearly all the BOD entering the system
is removed, the effluent BOD will be due almost
entirely to the endogenous respiration of the organ-
isms contained in the effluent suspended solids
and the effluent substrate concentration, which
approaches zero, can be neglected in routine
computations. Many researchers,including Ludwig
etal1, McCarty and Broderson19, and McKinney 23
have pointed this out. Therefore, effluent BOD5
values can be computed as follows:
Effluent BOD5 = S + C Es t (2)
0 = F
1 + Kbod t (3)
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24
Where: S = Organic (substrate) concentra-
tion, mg/1
C = Solids Degradation Rate (24%/day
for mature systems of 20° C,
12%/day at 10° C)
Es = Effluent degradable solids (some
fraction of effluent volatile sus-
pended solids), mg/1
t = Time (days)
Kbod = mg/l BOD removed per mg/1
BOD remaining per day (180/day
at 10° C, 360/day at 20° C)
F = Influent BOD 5, mg/1
The oxygen uptake or respiration rate of the
mixed liquor suspended solids can be easily
measured, Eckenfelder and O'Connor38, with a
value of approximately 5 mg O2 / gram MLSS
/ hour being a common one encountered during
these studies, see Table III. The effluent sus-
pended solids were shown to exhibit the same
oxygen uptake rate as the MLSS from the same
plant during these studies which is not surprising
since the effluent suspended solids represent
some fraction of the MLSS and, as can be seen
from the tables, both contain essentially the same
fraction of volatile matter. Therefore, knowing
the respiration rate of the MLSS will permit the
calculation of the effluent BOD5 with some ac-
curacy. If the specific oxygen uptake rate for
S =
198
0.55 mg/1
Effluent BOD;
Effluent BOD ]
Eff. SSx O2 uptake rate (mg/g/hr)
_ x 24 hr/day x 5 days
1,000 mg/g
Eff. SS x 5 x 24 x 5
1,000
= Eff. SS x 0.6 ....
(4)
the MLSS has been determined and is used in the
computation, the observed BOD5 value can be
closely approximated.
EXAMPLE
Data Source:
Subdivision Pattern - Full
Design Loading
Mean Influent BOD 5:
Mean Effluent BOD 5:
Mean Effluent SS :
O2 Uptake Rate :
198 mg/1
20 mg/1
36 mg/1
4.6 mg/g/hr
36 x 4.6 x 24 x 5 lr, or7
Effluent BOD5 = T~000 = mS/1
Effluent BOD. = 19.87 + S
1 + 360 (1)
Effluent BOD5 = 0.55 + 19.87 = 20.42 mg/1
TABLE III
Mean Mixed Liquor Oxygen Uptake Kates
Spring - Summer Studies
Loading Pattern Oxygen Uptake Rate
mg/g/hour
Aerator Influent Aerator Effluent
1. One Half Design
Load, Steady State
5.3
3.9
2. Full Design Load,
Steady State
5.6
4.6
3. One Half Design
Load, Subdivision
5.0
2.6
4. Full Design Load,
Subdivision
5.5
4.6
5. One Half Design
Load, School
6.9
3.5
6. Full Design Load,
School
7.7
4.8
It is, therefore, clear that the degradable
influent organic load is almost completely re-
moved by the extended aeration process and that
the effluent BOD5 is due almost entirely to the
solids present. This suggests that if Sa T is
great enough and the effluent suspended solids are
removed by some additional treatment step then
the overall process BOD5 removal efficiency would
be very nearly 100 percent. Shatto13, as noted
previously, found that when the effluent from an
extended aeration package sewage treatment plant
was passed through a diatomite filter the overall
process BOD 5 removal efficiency was 100 percent
for all practical purposes by virtue of the fact
that no detectable BOD5 remained in the effluent.
BOD5 removals of 90% or better, based on
mean influent and effluent values, .were observed
for all plants in this study for all levels and
patterns of loading employed except for the pair
of plants which received their total design daily
hydraulic load in an eight hour period (school
pattern). This sustained high hydraulic loading
resulted in the washout of sufficient solids to
significantly raise the effluent BOD5 concentra-
tion with the result that the mean BOD5 removal
fell to 82 percent. This result, however, was to
be expected as will be shown later in the section
on clarification.
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25
A mixed liquor suspended solids concentra-
tion of 2,500 mg/1 has been taken as evidence
of process maturity based on the performance of
the plants in this study during the time they were
being operated at maximum design loading applied
steady state with respect to flow. Figure 41
shows that beginning at approximately this point
sustained BOD.j removals of 90 percent or better
were achieved.
% REMOVED
100
900 1,000 I.S00 2,000 2,500
MIXED LIQUOR SUSPENDED SOLIDS
(mfl/l)
Fig. 41. Mean BOD5 & SS Removal, Ten Extended
Aeration Plants
OXYGEN REQUIREMENTS
Oxygen will be required for both synthesis
and oxidation:
BOD5 + X (02) -
b (VSS) + X' (02)
a (VSS) + C02 + H2O (5)
~ CO2 + H2O+NH3 (6)
Where: X = wt. of oxygen required per wt. of BOD5
removed
X = wt. of oxygen required per wt. of VSS
destroyed
Based on the formula C5H7NO2 for the bio-
logical VSS produced, X' can be evaluated as
equal to 1.415.
Recently Schultze31,32 working with a pure
culture and glucose found that 37 percent of the
glucose assimilated was oxidized and 63 percent
was synthesized. He also found that approxi-
mately 0.77 gram of oxygen was required per
gram of cellular material synthesized. This
represents a value of X = 0.485 and a = 0.63.
In the following discussion, the values used
will be:
X = 0.5
a = 0.65 (0.53 + 0.12)
b = 0.18
X' = 1.42
The maximum oxygen required in terms of
pounds of oxygen per pound of BOD5 removed will
be:
02 / BOD5 = 0.5 + 1.42 (0.53) = 1.2526
(7)
At an oxygen concentration of 0.0176 lbs.
oxygen per ft3 free air and a transfer rate of 5%
or 0.05, the free air requirement per pound of
BOD5 removed per day will be:
ft3 air / lb BOD5 =
1
0.0176 x 0.05
x 1.25 = 1416 (8)
But, alpha (the ratio of oxygen transferred in a
waste to oxygen transferred in water) is approxi-
mately 0.95 for domestic waste, therefore:
ft3 air / lb BOD5 = 1416 x
0.95
1490
(9)
It must, however, be remembered that BOD5
will not be entering the plant uniformly. From
a practical standpoint it is not correct to size
blower capacity as:
.. n . . 1490 ft3/lb BOD
Air Requirement = 144Q m//day
= 1.035 cfm / lb BOD.
(10)
In the case of a school for instance all the daily
load might enter the plant in eight (8) hours and
this fact would have to be taken into account if
satisfactory dissolved oxygen levels are to be
maintained throughout the day.
If nitrification is to be provided for additional
air will have to be supplied.
All of the plants used in this study proved
capable of maintaining a residual dissolved oxygen
concentration in their aeration compartments of
2.0 mg/1 or better, except immediately in the area
of raw waste introduction, at all times and under
all conditions of loading. All but one of the plants
in the study utilized diffused aeration with the
one exception being a plant employing mechanical
aeration. Judged on the basis of performance, the
method of aeration is unimportant so long as it
produces the required mixing effect and oxygen
transfer in the aeration compartment. While
there may very well be economic and other con-
siderations, the type of diffusers employed is
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26
unimportant so long as the required mixing and
transfer is achieved.
During the present studies several types of
testing were carried out on the plants being used
to determine if solids deposition was occurring
in their aeration compartments. All of these tests
were negative and it was concluded that within
normal mixed liquor suspended solids ranges,
BODr, loadings of from 50-100% of design, and
sufficient air being introduced into the aeration
compartment to maintain a residual dissolved
oxygen concentration of from 1-2 mg/1 this amount
of air was sufficient to provide adequate mixing
of the compartment's contents regardless of the
means of aeration utilized in these studies.
In some of the plants in these studies air
was introduced only at or near the center of the
aeration compartment, in some plants at the
effluent end, in others at the influent end, and in
still others air was introduced along one or both
sides of the aeration compartment. In the various
studies made, it appeared that the point of air
introduction was important only as it related to
the overall geometry of the particular aeration
compartment in question.
NITRIFICATION
When sufficient oxygen is supplied, extended
aeration package sewage treatment plants are
capable of a high degree of nitrification. Ammonia
nitrogen is a constituent of the waste fed these
treatment plants. Ammonia nitrogen is released
into solution within such treatment plants as the
result of the auto oxidation of cellular material:
C5H7N 02 + 5 02 — 5 C02+NH:j + 2 H20 (11)
1 lb. cell material + 1.42 lb. oxygen —~- 0.15 lb.
nh3
Ammonia nitrogen can be subsequently oxi-
dized to nitrite:
2NH3 + 3 02 — 2N02+2H++ 2H20 (12)
1 lb. ammonia + 2.8 lb. oxygen —•- 2.7 lb. nitrite
Nitrite can be further oxidized to nitrate:
2 N02 + 02 — 2 N03 (13)
1 lb. nitrite + 0.35 lb. oxygen —~- 1.35 lb. nitrate
Equations 12 and 13 can be combined:
NH 3+2 02 — N03+H20+H+ (14)
0.15 lb. ammonia + 0.56 lb. oxygen — 0.55 lb.
nitrate
Thus for the oxidation of one pound of de-
gradable cell material a total of 1.98 pounds of
oxygen are required if the oxidation is to be
carried completely through to nitrate.
During one portion of the present studies no
particular attempt was made to control aerator
dissolved oxygen levels except to maintain them
above 1.0 mg/1 with the result that levels of
5.0 mg/1 or greater became common. At these
dissolved oxygen levels a high degree of nitrifi-
cation was experienced with subsequent denitrifi-
cation in the settling portions of the plant and
nitrogen flotation of sludge solids resulting in an
impairment of effluent quality due to the presence
of increased amounts of solids and related BOD5.
All but two of the ten plants in operation at the
time were originally equipped with a baffle just
ahead of the effluent weir and in the case of those
plants so equipped the floated solids were largely
trapped by the weir and held in the plant, however,
since they were trapped at the surface of the
settling compartment they were not being returned
to the process and so the food to microorganism
ratio in the aerator rapidly changed and the pro-
cess began to fail due to the imbalance. An
attempt to combat this problem by the continuous
operation of the skimming mechanisms with which
all plants were equipped resulted in such high up-
flow rates in the settling compartment that in
many cases this upflow potential exceeded the
settling potential of the sludge and resulted in
additional losses of solids. When the skimming
mechanisms were not operated continuously the
floated solids became concentrated at the surface
of the settling compartments and in several severe
cases nearly all the sludge in the plant was thus
removed from the process. It was found that one
control method was to reduce the intensity of
aeration and to thus carry a lower aerator dis-
solved oxygen level. In the case of those plants
having a baffle ahead of the effluent weir, symp-
tomatic relief could be achieved by operating the
skimmers once or twice a day while hoseing down
the surface of the settling compartment. The
problem of denitrification can be illustrated by the
following equation:
2 NOs — 3 02+ N2f (15)
The reason for denitrification is the utilization of
nitrate by the respiring organisms as a secondary
source of oxygen in the absence of sufficient dis-
solved oxygen. This does not mean that during
denitrification low dissolved oxygen values would
occur in the plant effluent or the upper portions
of the plant's clarification compartment. Indeed,
during denitrification such dissolved oxygen values
were found to be only slightly lower than at other
times. Denitrification, therefore, is a function of
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27
the respiration rate of the organisms contained
in the settling sludge, the dissolved oxygen pre-
sent in the immediate vicinity of the organisms,
and the availability of nitrite and nitrate in the
liquor surrounding the organisms. For these
reasons another control method would be to re-
duce the residence time of the organisms in the
settling compartment so that they were being re-
turned to the aeration compartment while they
still had an adequate supply of dissolved oxygen
available in their vicinity. This method has cer-
tain distinct limitations as will be shown in the
section of this report on clarification. A third
method was also found to be helpful but since
this involved the maintenance of very high dis-
solved oxygen levels in the aeration compartment,
in the hope that such levels would be sufficient
to permit a more normal sludge residence time
in the clarification compartment, the economics
of the situation, however, would not seem to favor
such an approach.
The problem of nitrification-denitrification
becomes most acute when the pattern of unit
loading involves high and low or no flow periods
such as that which occurs with school installa-
tions. In such cases, unless steps are taken to
avoid it, nitrate builds up to high levels within
the system during low or no flow periods. During
high flow periods bacterial respiration may still
be somewhat elevated at the time the organisms
enter the clarification compartment resulting in
the rapid depletion of dissolved oxygen and the
breakdown of relatively large amounts of nitrate
with subsequent nitrogen flotation of solids. Under
such circumstances, flotation of solids occurred
during laboratory settling rate tests conducted on
the mixed liquor in less than thirty minutes. To
overcome this difficulty, many of the plants used
in this study were equipped with timers in the air
blower power circuit so that one or more blowers
could be automatically turned off or on at a pre-
determined time corresponding to the peaks and
valleys of the loading level pattern. The use of
such timers to adjust the air input more closely
to the loading of the treatment units proved most
beneficial in combating the nitrification-denitrifi-
cation problem.
The importance of aeration system flexibility
is also obvious during the startup period es-
pecially if the plant has not been seeded. During
the time the plant is building up mixed liquor
solids its oxygen demand is increasing due to the
increasing removal of BOD. Due to this more
air is required to keep the aerator solids in
suspension than is desired from a process stand-
point. As the process approaches maturity this
imbalance becomes somewhat less and more
easily controlled. However, during startup without
seeding nitrification-denitrification becomes a
problem unless oxygen transfer can be controlled
and unless some means of retaining solids in the
system is provided the loss of solids in the plant's
effluent will perpetuate the problem and result in
very long startup times. During the Fall-Winter
study two of the ten plants were not equipped with
a baffle ahead of their final effluent weir, nitri-
fication-denitrification became a problem during
startup, and large solids losses occurred. It was
only with considerable difficulty that these two
plants were nursed through this period, however,
like all the other plants, once they had achieved
mixed liquor solids levels of approximately 2,500
mg/1 the quality of their effluents became nearly
the same as those from the other plants. It is
therefore recommended that all plants be equipped
with weirs and/or other devices designed to con-
trol the loss of solids from the system during
periods of startup and/or denitrification.
SOLIDS SEPARATION
Nearly all applied BOD is removed from the
raw waste in the aeration compartment of a pack-
age sewage treatment plant of the extended aera-
tion type. The effluent BOD from such plants is
due, almost entirely, to the endogenous respira-
tion of the organisms in the effluent. Therefore,
the overall plant efficiency is dependent on the
efficiency of the plant's solid-liquid separation or
settling compartment. The efficiency of this com-
partment is, of course, design dependent.
Periodic losses of solids have frequently
been noted in connection with the operation of
package and conventional activated sludge plants
alike which result in significant reduction in over-
all process efficiency. Such losses are a func-
tion of the settling rate of the solids and the
hydraulic load applied to the settling compartment.
When mixed liquor is allowed to settle the
contained solids settling rate is at first constant
and uniform creating a rather discrete solids-
liquid interface, see Figure 42. If the height of
this interface is measured and plotted versus
time, the zone settling rate for the particular
activated sludge so tested can be computed. Ac-
tivated sludge from domestic waste treatment
plants commonly display zone settling rates of
from 20 to 30 ft/hr at a concentration of 1,000
mg/1 MLSS down to 5 to 6 ft/hr at a concentra-
tion of 4,000 mg/1 MLSS, see Figure 43. There-
fore, as the MLSS concentration increases the
zone settling rate decreases until a point is reached
where, for all practical purposes, no sedimenta-
tion occurs. Aside from the matter of concentra-
tion dependency, a particular sludge's zone settling
rate is further influenced by the biological and
physio-chemical characteristics of thi particular
system such as the food to microorganism ratio,
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28
intensity of aeration, period of aeration, and si-
milar factors.
INTERFACE HEIGHT
CLEAR WATER ZONE
HINOEREO SETTLING ZONE
TRANSITION ZONE
COMPRESSION ZONE
TIME
Fig. 42. Zone Settling Rate, Activated Sludge
20
a:
x
h-
u.
<
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29
Further, the influent applied flow tends to follow
a regular pattern for a siven application and in
the case of subdivisions peak flows of 3-4 times
the mean value occur with some frequency each
day. Since these peak flows are of the greatest
importance here, the equation for Qm needs to
be modified further as:
It is then obvious that the true flow rate to the
clarifier in this case is approximately 6 times the
theoretical value (based on mean influent flow,
above) and equally obvious is the fact that unless
sludge were wasted from this system, the situa-
tion would continue to deteriorate as the MLSS
concentration increased.
Q,
't
T X 0.66 x 0.33
(19)
For a 10,000 gpd plant the importance of these
factors can be seen from the following example:
Q,
Qi
10,000
1,440
7 gpm
10,000
1,440 X 0.66 X 0.33
= 32 gpm
Proper design of the clarifier portion of an
extended aeration package plant must, therefore,
take into consideration, among other things:
(a) The adjusted influent flow rate
(b) Peak flow rates expected
(c) MLSS concentration to be maintained
(d) Use of foam control and scum return
equipment
(e) Biological and physio-chemical character-
istics of the system expected
From the discussion of flow rates at various
points in a plant we can see that as far as the
final settling compartment is concerned this rate
of flow is further increased by the use of the
scum return and foam control equipment both
of which increase the surface overflow rate and
oppose the sludge settling rate. If the foam con-
trol and scum return equipment were operated
continuously this could easily add another ten
gallons/minute or more to the surface overflow.
For the purpose of illustration in the present
case we will assume that the total clarifier over-
flow is 45 gpm with some frequency during each
day. While clarifier surface areas vary from
manufacturer to manufacturer to a certain extent,
we will here assume a 10,000 gpd plant having a
clarifier surface area of 78.5 ft2. At 45 gpm
the surface overflow rate would be:
°r = 4%X8 5,44° = 825 gal/ft2/day
If the MLSS concentration for this plant is 5,000
mg/1 and the zone settling rate for this sludge
is 4 ft/hr, then the equivalent overflow rate
would be:
From an operational viewpoint, the zone
settling rate and the surface overflow rate can be
compared as follows:
Vs (ft/hr) x 7.5 gal/ft3 = Vs (gal/ftz/hr)
Q (gal/hr) O (gal/ft 2/hr)
SA (ft2) (20)
If Vs/Or is significantly greater than 1.0 excessive
amounts of solids will not be swept out of the
system, however, if it is significantly less than
1.0 loss of solids will occur.
EXAMPLE
Given: MLSS = 7,500 mg/1
Q = 24 hr mean = 10,000 gpd/24 hr
= 416 gph
SA = 78.5 ft2
Vs =2 ft/hr
2 x 7.5 = 15.0 = 2.83
416 5.3
78.5
Or = 180 x 4 = 720 gal/ft2/day
From the foregoing it is clear that solids would
likely be discharged from this plant during peak
daily flows. However, if we had only looked at
theoretical mean influent flow rates we would
have had:
If, however, the comparison is made on the
basis of the peak flow rate being three times the
average rate and all flow is received during an
18 hour period each day and, further, if the foam
sprays and skimmer are operated constantly, we
would have:
2 x 7.5 = IL _
(3 x 556) + 10 21 u
°r = 7 -8y40 = 129 gal/ft2/day 78.5
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30
For the preceeding example the maximum
allowable MLSS concentration would be less than:
7-5 (X)
21
.(21)
x = 2.8 ft/hr = 6,500 mg/1 approx.
McKinney has related the maximum MLSS
concentration that can be maintained in the aera-
tion tank to the sludge density index of the MLSS
as follows:
= (SDI) (10,000)
r + 1
Where: SDI = Sludge Density Index
r = Recirculation Ratio
EXAMPLES
SDI = 1.0
Mt = (1): (10>00Q) = 7,500 mg/1
3 + 1
SDI = 0.50
(0.50) (10,000)
• (22)
Mt =
1
3 + 1
3,750 mg/1
However, at high MLSS values the compression
zone represents a large percentage of the total
30 minutes settling time and the SDI derived
from the data is not reliable. It has been found
that if a high MLSS mixed liquor is diluted with
various amounts of clear effluent from the same
plant and the mixtures are allowed to settle for
30 minutes, the suspended solids concentrations
for the mixtures determined, and the SDI for
each mixture derived, the derived values may vary
over a fairly wide range, see Figure 45.
This difficulty was noted by Orford, Heuke-
lekian, and Isenberg25 who adjusted the solids
content of the sludges tested to 1,000-1,500 mg/1
to eliminate the effect of solids concentration on
the test result. The importance of making such
an adjustment in the test procedure can be seen
when one attempts to relate sludge density index
to sludge loading. In terms of the loadings en-
countered in conventional activated sludge plants
sludge density index decreases with increasing
loadings, however, as was shown by Orford et
al 25, below a loading of 0.17 lb. BOD/lb. ML VSS/day,
sludge density decreases with decreasing loadings.
But, at loadings below 0.05 lb. BOD/lb. MLVSS/day
the trend apparently again reverses unless the
solids concentration of the mixed liquor being
tested is adjusted prior to conducting the settling
test. In terms of mixed liquor suspended solids,
this second reversed occurs at about 4,500 mg/1.
When both adjusted and unadjusted data is plotted
two distinctly different curves are obtained as can
be seen in Figure 46.
1.2
i.i
1.0
0.9
0.8
0.7
C-l
SOI
10 t
0 1000 2000 3000 4000 SOOO 6000
MIXED LIQUOR SUSPENDED SOLIDS (mg/I) IN DILUTION
Fig. 45. SDI Values for Various Dilutions, Plant
>"
/
0.01
O ORFORD ET al"
X NSF UNA0JUSTE0
~ NSF ADJUSTED
LB BOD/LB MLVSS/DAY
Fig. 46. Sludge Loading and Sludge Density Index,
Fourteen Plants (1,526 Plant Days)
While the volume of return sludge, which is
withdrawn from the final clarifier at or near the
bottom of the compartment and which reappears
in the clarifier influent as an increased volume
of mixed liquor, cannot be considered as having
a direct upflow potential or be expressed as
equivalent overflow rate it does create turbulence
and movement in the clarifier which can, to some
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31
extent, act to offset a portion of the sludge settling
rate which might otherwise occur. This is es-
pecially true of very high sludge return rates.
Many manufacturers have combated this problem
by the use of baffles and stilling wells at the
point where the mixed liquor enters the clarifier.
Nevertheless, in general, it is well to operate with
as low a return sludge rate as practical consis-
tent with the other demands of the process and
system involved. This is perhaps the best argu-
ment against the use of high return sludge rates
to help combat the denitrification problem outlined
in a previous section of this report.
During these studies suspended solids re-
movals for all plants under all conditions of
loading, with but one exception, were 80 percent
or greater based on mean influent and effluent
values, see tables. The exception to this was the
pair of plants operated at maximum loading on a
school flow pattern during the Spring-Summer
studies. It is believed that this flow pattern
overtaxed the capabilities of these plants' solids
separation systems and that under such hydraulic
loading the solids separation systems became the
dominant process efficiency limiting factor.
SKIMMING
All of the plants ultilized in these studies
were equipped with skimming devices designed to
remove floatables from the surface of their cla-
rification or solids separation compartments.
During the early phases of the study these skim-
mers were operated continuously. As the mixed
liquor suspended solids concentration increased
in these plants the upflow potential created by the
continuous skimming began to assume the role
of an important process efficiency limiting factor.
Solids were pulled upward by the skimmers and
once resuspended in the upper portion of the
clarifier were being swept out of the plants in
their effluents.
At first attempts were made to reduce this
effect by reducing the skimming rate and by ad-
justing the tops of the skimmers to as near the
surface of the water as practical. These adjust-
ments reduced the problem for a time but did not
entirely eliminate it. As the solids concentra-
tion in the units continued to increase, it became
more difficult to so adjust the skimmers so as to
avoid the problem and it was finally decided to
try operating them only once or twice a day. This
periodic operation of the skimmers virtually ended
the problem of solids losses from the system due
to the skimmers but it also resulted in the ac-
cumulation of floatables on the surface of the
clarifiers between skimmings in those plants
equipped with a baffle ahead of their effluent weir,
(see the section of this report on nitrification).
While the presence of floatables on the sur-
face of the clarifiers between skimmings may
render the plants loss ascetically pleasing than
otherwise, it was concluded that process efficiency
must be given precedence in this case. It is
recommended that all plants be designed to retain
floatables within the system and that clarifier
skimming be provided for with such flexibility as
to permit the plant operator to adjust the rate of
skimming or to shut it off entirely as required.
TEMPERATURE
During these studies package sewage treat-
ment plants of the extended aeration type were
operated during both Summer and Winter to deter-
mine, among other things, the effect of tempera-
ture on process efficiency.
During the Fall-Winter studies the mean
aerator contents temperature for all plants was
11.40C while during the Spring-Summer studies the
mean aerator contents temperature for all plants
was 18.0°C or above, see tables. Since some
plant pairs in the Spring-Summer studies were
started later in the season than others, a range
of mean temperatures from 18.0 to 23.3°C was
encountered.
At one point in the Fall-Winter studies the
aerator contents temperature of several plants
fell to low values of 3-4°C for some days due to
the long (twenty-four hour) aeration period in-
volved and the temperature of the air being blown
through the aerator contents. During this period
no significant loss of BOD5 removal efficiency was
experienced. The plants had been operating with
mixedliquor solids concentrations above 2,500 mg/1
for some time prior to the onset of very cold
weather (ambient temperatures of 0°C or less)
and it will be recalled from the preceding dis-
cussion of BOD5 removal that such combinations
of solids and time is equivalent to an Sa T value
of 60 x 103 or greater. Further, for a 10°C
decrease in process temperature the oxidation rate
of the organisms involved would be reduced by
half which is the same as having one half as many
organisms operating at the former rate or Sa T
values of 30 x 103 or more which is more than
adequate for a 90 percent BOD5 removal. Indeed,
far fewer organisms or a much lower rate of
activity would still be expected to produce a 90
percent removal. Therefore, it is not surprising
that the BOD5 removal efficiency of the systems
did not suffer significantly during periods of low
process temperature.
It was noted, however, that in the case of
those plants which reached low process tempera-
tures nitrification was reduced and in the most
severe cases of low temperature nitrification
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32
ceased altogether, see Figure 47. This occurred
despite the fact that residual dissolved oxygen
values in the aeration compartment of the plants
was at least as high, and in most cases higher,
than during periods of higher process tempera-
tures.
AERATOR CONTENTS
TEMPERATURE
S
0
0
24
PLANT EFFLUENT NH,-N (mj/l]
Fig. 47. Nitrification-Plant A-I, Fall-Winter Studies
During the Spring-Summer studies effluent
ammonia-nitrogen values for mature plants having
an aerator contents residual dissolved oxygen
value of 1-2 mg/1 were zero.
In order to provide at least some weather
protection for the steel tank package plants used
during the Fall-Winter studies bales of hay and
straw were piled around the hopper portion of
each plant. While this did not result in the same
degree of protection as that afforded by below
grade installation, it did, under the operating pro-
tocol employed, prevent any interruptions in plant
operations due to freezing.
OPTIMUM MIXED LIQUOR SOLIDS
As was pointed out previously, sustained
BOD5 removals of 90 percent or better were not
found to be generally associated with mixed liquor
suspended solids levels much below 2,500 mg/1.
While it is true that for aeration periods of twenty-
four hours mixed liquor solids concentrations of
considerably less than 2,500 mg/1 should suffice
to remove substantially more than 90 percent of
the applied BOD5, we are not concerned here
with specifically the removal of substrate in the
aeration compartment of package plants but rather
the overall apparent BODf, and suspended solids
removal of the plants.
The reason for the apparent difference be-
tween the theoretical removals and the observed
removals is, of course, that, as has been shown,
the influent solids and BOD are not strictly speaking
the same thing as those in the effluent of the
plant. The overall or apparent removals, es-
pecially during the plant startup period, are a
function of the rapidly changing food to micro-
organism ratio which affects the settling rate of
the solids and the rapidly changing solids concen-
tration itself which, as was noted earlier in this
report, affects the settling rate. At high food to
microorganism ratios solids flocculation is not as
pronounced as at somewhat lower values and res-
piration rates are higher. Further, at solids con-
centrations much below 1,000 mg/1 the activated
sludge particles do not settle as a mass (zone
settling) but rather as discrete particles with each
settling at its own rate essentially independent of
the other particles around it. All of these things
combine during startup to result in apparently
lower than theoretical removals of solids and DOD.
From an overall viewpoint, then, it is not
desirable to operate extended aeration package
sewage treatment plants at less than 2,500 mg/1
mixed liquor suspended solids. This is not to
say that any solids concentration value above this
level is desirable. It has been shown that zone
settling rate is dependent on, among other things,
the concentration of solids and that relatively small
increases in solids concentration can significantly
lower the settling rate. Since there is a mini-
mum permissible settling rate for any given plant
below which apparent overall process efficiency
is impaired then there is a corresponding upper
limit on the mixed liquor suspended solids con-
centration which should be carried in the plant in
order to achieve maximum efficiency. In general,
it does not appear desirable to maintain a mixed
liquor suspended solids concentration much in
excess of 6,000 mg/1. Indeed, a solids concen-
tration of 4,000 mg/1 would appear to be an ideal
target from an operational viewpoint. This opera-
tional target would give sufficient leeway on both
the higher and lower sides to admit of sustained
removal efficiencies of the desired magnitude.
SOLIDS WASTING
It has been shown in other portions of this
report that solids accumulate in extended aeration
package sewage treatment plants. This accumu-
lation is the result of the retention of inert solids
entering the plant in the raw waste, and the ac-
cumulation and retention of the inert solid and
products of endogenous respiration together with
the synthesis of new biological solids. This
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33
accumulation will continue until the plant's capacity
for solids retention is reached after which the
excess solids will be discharged in the effluent.
Where an intermediate level of treatment is de-
sired the excess solids may be allowed to dis-
pose of themselves in the effluent, however, if
sustained high level treatment is desired then
solids wasting must be practiced.
For extended aeration plants being fed do-
mestic wastes at or below design level and main-
taining a mixed liquor suspended solids level be-
tween 2,500 and 6,000 mg/1, the problem of
solids wasting would not appear to be a particu-
larly great one. During the Fall-Winter studies
which lasted about seven months, it was not
necessary to waste sludge from any of the plants
in order to maintain sustained high process ef-
ficiency. At the end of the Fall-Winter studies
all but two of the ten plants were drained and
cleaned. The other two plants were continued
in operation mainly to determine at what point
it would be necessary to waste solids in order
to maintain high process efficiency. After ap-
proximately ten months of continuous operation
at design load it became necessary to waste
solids from one of the two plants which had by
that time attained a mixed liquor suspended solids
concentration of 9,840 mg/1. During these ten
months this plant had been operated steady state
with respect to flow which permitted a buildup of
solids to this level without impairing process ef-
ficiency. After reducing the mixed liquor sus-
pended solids level to nearly 4,000 mg/1 this
plant was again allowed to accumulate solids
while being operated on a subdivision flow pattern
at design loading. On this flow pattern it was
necessary to waste solids at a mixed liquor
solids concentration of 7,480 mg/1 in order to
maintain treatment efficiency.
Frequent sludge wasting is not desirable
from several standpoints. First, the solids ac-
cumulation (lb/lb BOD Removed) is less at higher
solids levels, see Figure 37. Second, sludge
wasting creates an ultimate disposal problem in
that it must either be trucked to a suitable dis-
posal site or applied to sand beds which must
eventually be raked and otherwise cared for. In
the case of plants treating domestic waste at or
below design load it would not appear that wasting
would be required more than two or three times
a year. For domestic wastes containing unusual
amounts of inert solids and for certain commercial
or industrial wastes more frequent wasting will
be required.
ROUTINE OPERATION AND MAINTENANCE
Much has been said and written about the im-
portance of maintenance and operation in connec-
tion with package treatment plants. The experience
gained during the present studies points up the
importance of this but perhaps in a different way
than is generally thought. Manufacturers of ex-
tended aeration package plants commonly advocate
a minimum of one hour per day for combined
maintenance and operation. An analysis of the
research site records indicates that this amount
of time should be adequate in most cases. It was
the opinion of the staff members who operated
these plants that it is not a matter of the time
involved per se, but rather the degree of con-
scientiousness displayed by the operator during
that time. Further, it is obvious that conscien-
tiousness alone is not enough but rather that this
trait must be combined with a reasonable know-
ledge of the mechanics of the process and at
least some appreciation of the capabilities and
limitations of the organisms involved.
The foregoing can be taken as evidence that
the process efficiency of an extended aeration
package plant which receives an hour of con-
scientious attention every day should not be limited
by this factor.
As a check list for normal maintenance and
operations the following is suggested:
CHECK LIST FOR ROUTINE MAINTENANCE AND
OPERATIONS EXTENDED AERATION PACKAGE
SEWAGE TREATMENT PLANTS
1. Determine that power is being supplied the unit
and that all pumps and motors are operating
or operational as required.
2. Grease and oil equipment, clean air filters,
check pressure relief valves, and perform
related work as recommended by the manu-
facturer.
3. Hose down walkways, sideboard, and splash-
spray zones as needed.
4. Check air lifts and return lines for clogging.
5. Operate skimming device(s) as needed.
6. Perform recommended simple laboratory an-
alytical procedures and adjust operating vari-
ables as indicated. The recommended or
required analytical procedures for a given
plant may include but are not necessarily
limited to, any or all of the following depen-
ing on the requirements of the particular
regulatory agency having jurisdiction and the
needs of the installation:
a. Influent, effluent, mixed liquor, and return
sludge suspended and volatile suspended
solids. (Rapid photometric methods for the
determination of suspended solids have been
found to be reliable.)
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34
b. Influent and effluent five day biochemical
oxygen demand. Effluent BOD5 values can
be approximated through correlation with
suspended solids values if the oxygen up-
take rate of the solids is known. A modi-
fied chemical oxygen demand test has also
been shown to closely approximate these
values.)
c. Mixed liquor and effluent dissolved oxygen
concentration.
d. Influent, mixed liquor, and effluent pH and
temperature values.
e. Mixed liquor thirty minute settled volume
determination (SV30).
f. Mixed liquor oxygen uptake rate.
7. If effluent disinfection is required, insure that
an adequate supply of disinfectant is available
and that the feed device is operating properly.
8. Scrape down the insides of clarifier hopper at
least daily and/or determine that sludge col-
lection mechanisms are operating properly
depending on the design of the plant.
9. Remove litter from the plant area and per-
form grounds keeping operations as required.
10. Repaint exposed painted surfaces as needed.
11. Inspect aeration equipment thoroughly including
diffusers, impellers, and the like which may
be submerged. While this may not need to be
done as frequently as some other items of
maintenance, it should not be overlooked and
the manufacturer's recommendations should
be carefully followed.
12. Remove and dispose of in a sanitary manner
any material that may accumulate on inlet
bar screens and the like. Check and clean the
comminutor if one is a part of the plant.
13. Check, clean, and maintain any such plant
support units such as a sand bed, sludge
holding tank, trash trap, and the like.
14. Replace worn parts and/or equipment as
needed. Pay particular attention to pulley
belts and the like which may require rela-
tively frequent replacement. Maintain a
small stock of such items including belts,
fuses, heaters, and similar items which are
essential to plant operation.
15. Waste solids from the system as required to
maintain the solids within the desired range.
It should be emphasized that daily and con-
scientious maintenance and operational attention
is required in order to achieve the certified level
of performance.
During these studies the operating staff found
that some maintenance time could be saved by
having at least two air filters on hand for each
plant. This permitted the replacement of a dirty
filter with a clean one on a regular basis and the
cleaning of the dirty filter at a time when other
duties were less pressing. Further, the dirty
filters could be soaked in cleaning solvent for
some time thus rendering the job less difficult.
When the operator first went on a plant each
day during this work he would turn on the skim-
ming device and allow it to operate during the
time he was working on the plant. Other opera-
tional and maintenance items were performed in
sequence according to a regular routine which in
itself saves time through the efficient organiza-
tion of the work to be performed. The last item
of the daily routine was to turn off the skimming
device.
It was not found necessary to hose down the
plant each day especially after the plant's mixed
liquor suspended solids concentration reached
1,700 mg/1 since at about this point foaming of
the aerator contents was suppressed. It was
found that after the startup period a complete
cleanup of the plants once each week was sufficient
especially if a partial cleanup was performed
daily as required.
After the mixed liquor solids reach 2,500
mg/1 it was found that it was not necessary to
scrape the hopper portion of the clarifiers as
frequently as during the startup period. In general,
daily scraping was required during startup with
the necessity for this decreasing as the process
approached maturity. After the aerator solids
concentration reached 2,500 mg/1 it was necessary
to scrape the hoppers only about once a week.
Very little problem was encountered during
these studies with diffuser clogging.
No process support equipment such as blowers,
pumps, air lifts, or the like failed during the
course of this work. It was found that even under
the somewhat adverse conditions of above grade
operation during the Michigan winter, a regular
program of cleaning, greasing, oiling, and checking
sufficied to enable relatively trouble free opera-
tion of the plant involved.
During several periods the plants were neg-
lected and this resulted in significant efficiency
losses. Routine, conscientious, and knowledgeable
operation and maintenance is, therefore, strongly
recommended to achieve maximum efficiency.
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35
One major problem which was encountered
during this work resulted from momentary power
interruptions such as occur from time to time
during thunderstorms. When such momentary
interruptions occurred the electrical circuit with-
in the plants would be broken and the plants
would have to be manually restarted. This was
no problem so long as the plants were attended
at the time of the interruption, however, when
this occurred at night or other times when the
plants were not attended a considerable amount
of time elapsed before the plants were restarted.
Of course, during such periods treatment effici-
ency fell markedly. This problem was also noted
by Schwing:!!) in connection with his supervision
of a number of package plants in the field.
BACTERIOLOGICAL
At one point in these studies effluent samples
from two of the plants were examined bacterio-
logically for a total of 45 days. All determina-
tions were by membrane filter techniques. Both
plants were loaded at design levels during this
period. The average results obtained were as
follows:
Plant A-2
Organisms/100 ml.
1. Enterococci 8,000
2. Coliforms 97,250
3. Total Count 850,000
Plant C-l
1. Enterococci 1,360
2. Coliforms 45,500
3. Total Count 161,000
It was found that both the total and enter-
ococci count varied directly with the effluent sus-
pended solids. The coliform count followed es-
sentially this pattern but was more variable in
this respect. No difficulty would be anticipated
in reducing these bacterial numbers to desirable
levels through the use of appropriate bactericidal
agents and dependable application devices.
PLANT SIZE AND CONSTRUCTION
In order to determine the effect of plant size
and materials of construction on performance ten
package sewage treatment plants of the extended
aeration type were operated at maximum design
load, steady state hydraulic conditions, on the
same domestic waste feed, under the same con-
ditions of temperature and operation, at the same
time. The results of this study indicate that where
size is the only variable and when there is an
observed difference in performance the lowest ef-
ficiency will be associated with the smallest size
plant. Under the conditions of the test described
above the following results were obtained based
on mean values for all plants of a given size
range:
SIZE (gpd)
BOD REMOVAL (%)
5,000 - 7,000
88
7,500 - 9,000
89
10,000 - 14,000
91
15,000 - 20,000
94
Plants constructed of steel and concrete were
both utilized in these studies. A comparison of
overall process efficiency by both types of plants
of the same daily waste treatment capacity under
identical conditions of loading and operation failed
to disclose any significant differences in the re-
sults obtained. It was, therefore, concluded that
the material of construction is not of itself a
factor limiting overall process efficiency so long
as the unit is structurally sound.
RAPID ANALYTICAL METHODS
Throughout these studies an attempt was
made to find relatively quick, simple, and mean-
ingful test methods which could be used both to
operate and to determine the performance of ex-
tended aeration package plants. Once it became
clear that the concentration of BOD5 in the ef-
fluent of these plants was due almost entirely to
the respiration rate of the organisms contained
in the effluent solids it became equally clear that
the plant's performance could be judged on the
basis of effluent quality in terms of suspended
solids. What was then needed in the field was
some rapid and reliable method of determining
the suspended solids present in the plant effluent.
An additional need was the ability to determine
the respiration rate of those solids.
At least as early as 1940 a relationship had
been noted between turbidity and BOD 5 values for
several wastes 40. Eckenfelder 4i advocated the
use of photometric methods for the rapid estima-
tion of process efficiency in 1952. Krawcyzk and
Gonglewski42 described an accurate and rapid
suspended solids determination method using a
spectrophotometer in 1959. McTavish43 published
a similar method in 1965. The information con-
tained in these papers was studied and the methods
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36
advocated were investigated by the Foundation's
Research Site Staff who found as follows:
1. Samples containing readily settleable solids
should be blended at high speed for two
minutes prior to testing.
2. After blending, if needed, the sample's
absorbence or transmittance should be
read in a spectrophotometer using a one
inch sample container against a distilled
water blank, at 950 millimicrons.
3. A calibration curve for the particular in-
strument and sample containers employed
should be made by plotting STANDARD
METHODS1*7 and corresponding spectro-
photometer data for a number of samples.
4. The relationship of solids concentration
to absorbancy was found to be lineal thus
obeying the Lambert-Beer law over the
range of zero to three hundred fifty mg/1
suspended solids.
5. Samples having a suspended solids content
in excess of 350 mg/1 should be diluted
prior to blending so that the solids con-
tent of the sample read in the instrument
falls within the range investigated.
6. Suspended solids in samples of mixed
liquor, return sludge, and plant effluent
can be determined with equal accuracy.
7. Small, battery operated instruments which
are presently available can be used with-
out blending the samples in the field with
sufficient accuracy to determine the quality
of package plant effluents and to deter-
mine the level of solids at various points
in the process as an aid to plant opera-
tion and supervision. When samples are
not blended a separate calibration curve
will be required for them and such sam-
ples should be read as soon as they are
placed in the instrument. Of course,
thorough mixing of the sample just before
placing it in the instrument is required.
Dissolved oxygen levels at various points in
the process can be determined with high precision
and accuracy by any one of several battery powered
dissolved oxygen analyzers which are available.
These same instruments can be used in the field
to determine the oxygen uptake rate of the mixed
liquor solids according to the methods of Ecken-
felder and O'Connor 38.
The total cost of the two battery powered
instruments (spectrophotometer and dissolved
oxygen analyzer) is presently about $500.00 which
would appear to make this a reasonable invest-
ment for anyone who supervises or operates
several package plants or perhaps even one plant
of relatively large size.
Since it had been found that effluent suspended
solids could be determined with considerable ac-
curacy using photometric methods it seemed
reasonable to assume that one of the presently
available flow through turbidity meters could be
used to continuously monitor and record plant
effluent suspended solids. Such a unit was in-
stalled on one of the plants and operated for a
period of some months. For suspended solids
concentrations above 20 mg/1 reasonably good
correlation with STANDARD METHODS 37 solids
determinations was obtained. Below a solids
concentration of 20 mg/1 considerable variation
was encountered probably due to entrained air in
the sample registering on the instrument and the
decreasing precision and accuracy of the standard
method with decreasing solids concentrations.
It was assumed that a somewhat less sensitive
instrument might have yielded a better correlation
with the standard method.
Nevertheless, it was obvious that since little
adverse sanitary significance would likely be at-
tached to an effluent having a suspended solids
concentration of 20 mg/1 even the instrument
used would have value in monitoring the perfor-
mance of package plants in remote locations. By
utilizing a hookup to the telephone line system
such units could be readout by supervising per-
sonnel at some central office or the instrument
could transmit an alarm signal when the effluent
suspended solids reached some predetermined
upper limit. Such readout and alarm systems
could be readily assembled using standard parts
and equipment presently available.
Another interesting rapid analytical procedure
is the Oxygen Demand Index method developed by
Westerhold44. This method is a rapid chemical
oxygen demand test which can be completed in
about thirty five minutes and which yields a value
for ordinary domestic wastes and plant effluents
which closely approximates the BOD5 value. Any-
one equipped with a spectrophotometer, either
line operated or battery powered, could make this
determination. Actually, the person conducting the
test would only be involved about five minutes out
of the total of thirty five since most of the re-
quired time is for heating the sample.
Many workers in this field have advocated
the use of a thirty minute settling test as a prime
operational guide. Such a test is often used both
to judge the volume of solids in the aeration sys-
tem and the quality of the plant's effluent. In the
latter case, this method is, in the final analysis,
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37
based on the same reasoning as the photometric
method advocated earlier in this section. It
should be borne in mind, however, that it was
shown in another section of this report that the
sludge volume index is not strictly reliable at the
relatively high mixed liquor suspended solids
levels generally associated with extended aera-
tion plants. The thirty minute settling test or
Sludge Volume Thirty (SV 30) as it was named
during these studies is dependent to a certain
extent on the size and configuration of the vessel
in which it is conducted. If portions of a mixed
liquor having a suspended solids concentration of
4,000-5,000 mg/1 are settled for thirty minutes
in a 500 ml. graduated cylinder, a 1,000 ml.
graduated cylinder, a quart jar, and a three liter
battery jar a series of results will be obtained
which illustrate a portion of the problem and
which explain why such laboratory tests some-
times indicate that a certain state of affairs exists
within the plant which the observed plant opera-
tion fails to bear out. It can be said that, in
general, the closer the proportions of the test
vessel with respect to surface area and depth
ratio approaches the proportions of the settling
compartment of the plant the greater will be the
direct correlation between the two. Of the la-
boratory equipment readily available, the three
liter battery jar is perhaps the best choice for
SV30 determinations.
STANDARD ANALYTICAL METHODS AND SAM-
PLES
In a study such as the present one which in-
volves the monitoring of a large number of plants
being operated under a variety of carefully con-
trolled conditions and which utilizes nearly all of
the important sanitary chemistry standard methods
it is possible to make some judgements as to the
importance of various types and classes of data
in the performance evaluation of those plants.
Such judgements have been made in the present
case and are embodied in the following items:
1. Influent and effluent BOD5 tests serve as
the basic performance evaluation tech-
nique and should be conducted frequently
during the evaluation.
2. Influent and effluent COD test values serve
as a good basic check on the BOD5 de-
terminations since the removal of COD
has been observed to vary with the re-
moval of BODg.
3. Influent and effluent suspended and vola-
tile suspended solids should be deter-
mined frequently during the period of plant
evaluation since these tests serve as
another basic performance evaluation
technique and since effluent solids values
have been shown to be directly related to
effluent BOD values.
4. Influent and effluent pH values should be
determined during plant evaluation since
the change in pH values through the plant
serves to assist in defining the state of
the process and the influent value serves
to assist in defining the waste being treated.
5. Influent and effluent alkalinity values should
be determined frequently during the eval-
uation period since the change in this
value is related to the degree of nitrifi-
cation and thus serves as a check on ni-
trogen changes through the plant.
6. Influent and effluent ammonia-nitrogen
data should be frequently collected during
the evaluation since the change in this
value through the plant is related to,
among other things, the net state of the
process and especially to the time and
intensity of aeration.
7. For plants being evaluated on domestic
wastes the influent nitrate and nitrite-
nitrogen levels are of doubtful value in
performance evaluation since such values
are generally quite low if indeed any ni-
trogen is present in this form. However,
effluent nitrate values are most impor-
tant both as they relate to the net change
in ammonia-nitrogen values and the fac-
tors affecting those values but also as
they assist in assessing the potential im-
pact of the plant effluent on the receiving
waters. Effluent nitrite values are con-
sidered of minor significance since nitrite
exists as an intermediate form between
ammonia and nitrate-nitrogen and generally
is present in the plant effluent in small
amounts.
8. Influent and effluent phosphate values are
important in evaluating the removal of
this important nutrient from the waste feed
and in assessing the potential impact of
the plant effluent on the receiving waters.
9. Influent dissolved oxygen values are not
considered of significance in performance
evaluation since the weight of oxygen in
the raw waste feed is too small to have
any significant effect on plant operations
or performance. Effluent dissolved oxygen
values are important in assessing the po-
tential impact of the treated wastes on
the receiving waters and as a guide to the
state of the process embodied in the plant.
10. Influent and effluent methylene blue active
substance (MBAS) serve as the best routine
guide to the plant's detergent removal
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38
efficiency and, therefore, are important
in an evaluation of plant performance.
11. In order to correlate the observed plant
efficiency with the state of the plant pro-
cess the following mixed liquor deter-
minations are recommended:
a. suspended and volatile suspended solids
b. residual dissolved oxygen
c. pH
d. temperature (it is interesting to note
here that the temperature of the raw
waste feed is of minor importance
because of the relationship of feed
volume to aerator contents volume
and the temperature of the aerator
contents at or below design loading
levels approaches the ambient tem-
perature due to the aeration period
and quantity of air blown into the
aerator contents. The temperature of
the effluent is also of minor impor-
tance since at design loading efflu-
ent temperature and aerator contents
temperature will be nearly the same
even at relatively low ambient tem-
peratures).
e. Thirty minute settled volume (it should
be noted again here that the results of
the SV3y test must be interpreted with
caution at relatively high mixed liquor
suspended solids values unless the
solids contents of the sample being
tested is adjusted to approximately
1,500 mg/1 in the event of MLSS val-
ues significantly above this level).
f. oxygen uptake rate
12. For the purpose of plant performance
evaluation, return sludge tests should be
limited to the following:
a. suspended and volatile suspended solids
(these determinations should be con-
ducted with sufficient frequency to
fairly evaluate the concentration of
solids achieved in the settling com-
partment. The concentration of solids
in the return will be dependent on,
among other things, the rate of re-
turn).
b. rate of return (volume/unit time).
c. thirty minute settled volume (Caution!
dilute as required).
13. Both a continuous record of the rate of
raw waste application and the total daily
application are required to properly eval-
uate and interpret observed plant perfor-
mance.
14. Such other tests should be carried out
from time to time as may be necessary
to evaluate and interpret observed pro-
cess and performance phenomena.
Both samples composited strictly according
to applied waste feed rates and grab samples will
be required. All composites should be twenty-
four hour samples. For patterned flows both
maximum and minimum flow grab samples will
be required in some cases. All samples should
be handled, preserved, and tested STRICTLY in
accordance with the provisions of the latest edition
of Standard Methods for the Examination of Water
and Wastewater 37.
For routine operation and supervision of ex-
tended aeration package sewage treatment plants
the methods outlined in the preceding section may
be found useful and can be employed if proper
calibration is employed to take into account the
characteristics of the specific process and waste.
III. PERFORMANCE CRITERIA
AND
THE STANDARD PERFORMANCE EVALUATION METHOD
The findings detailed in Section II have been
translated into performance evaluation criteria
for extended aeration package sewage treatment
plants. These criteria are as follows:
1. The plant shall display a sustained mixed liquor
suspended solids buildup during the start up period.
2. The plant, when its design loading is not ex-
ceeded, shall achieve a sustained design BOD5
removal after the process reaches maturity.
3. The aeration system shall be capable of trans-
ferring sufficient oxygen to meet peak design
loads in addition to any other demands made on
the system such as maintaining the contents of
the aeration compartment completely in suspen-
sion, operation of air lifts, and the like.
4. The aeration system, when operating at the
midpoint of its rated capacity, shall have such
flexibility or admit of such adjustment as to not
adversely affect process efficiency.
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39
5. The solids separation system shall be capable
of separating and retaining within the plant suf-
ficient solids so as not to adversely affect over-
all process efficiency.
6. The floatable solids retention and skimming
system shall be capable of retaining and return-
ing to the aeration compartment sufficient float-
ables in such a way as not to adversely affect
over-all process efficiency.
7. When subjected to cold weather operating con-
ditions after reaching process maturity the plant
shall achieve essentially the same degree of pro-
cess efficiency as at other times of the year pro-
viding that it and its process support equipment
are protected from freezing.
8. The plant shall have such flexibility as to
readily permit maintenance of the desired range
of mixed liquor suspended solids concentrations.
Based on the fundamentals of the processes
involved, the findings of these studies, the in-
vestigations of others as cited, and the perfor-
mance criteria developed, the following method
for the evaluation of the performance of extended
aeration package sewage treatment plants has been
devised:
A. PREQUALIFICATION
1. Prior to the performance evaluation of
any extended aeration package sewage
treatment plant, the manufacturer of such
plant shall supply to the testing agency,
group, or organization sufficient evidence
to establish to the satisfaction of such
agency, group, or organization the basic
feasibility of the plant with respect to its
intended service.
2. As a part of his application for perfor-
mance evaluation of a particular plant
model or model series the manufacturer
shall set forth the basic description of
the plant or model series and design data
including complete drawings and specifica-
tions for the plant and all of its equip-
ment and appurtenances. The application
shall be accompanied by a complete in-
stallation, operation, and maintenance
manual which includes a thorough dis-
cussion of the process fundamentals in-
volved.
B. GENERAL TEST CONDITIONS AND REPORT-
ING
1. The waste utilized as feed for the unit
during these evaluations shall be a com-
minuted domestic waste free of any in-
dustrial waste which in any way might
affect the performance of the plant being
tested. Stale or septic sewages shall not
be utilized. The sewage utilized as feed
for the plant shall be sampled and tested
daily during the test period. The samples
shall be twenty-four hour samples com-
posited strictly according to the plant in-
fluent flow pattern in use at the time of
sampling. Analysis of these samples must
establish that the characteristics of the
waste utilized as feed during the test con-
formed to the following:
a. Five Day Biochemical Oxygen Demand
(BOD5) - a mean concentration based
on all data of 200 mg/1 plus or minus
30 percent, provided further that none
of the samples yield a BODs value of
less than 50 mg/1 or more than 400
mg/1.
b. Suspended Solids (SS) - a mean concen-
tration based on all data of 220 mg/1
plus or minus 30 percent provided,
further that none of the samples yield
an SS value of less than 55 mg/1 or
more than 440 mg/1.
c. Percent Volatile Suspended Solids - no
values less than 65 or more than 85
percent.
d. Temperature - no values less than ten
degrees or more than twenty-five de-
grees centigrade.
e. pH - no values less than pH 6.0 or
greater than pH 8.0.
2. All samples shall be strictly taken and pre-
served as provided in the latest edition of
Standard Methods for the Examination of
Water and Wastewater 37 except as amy be
otherwise provided herein.
3. All anlaytical methods employed shall be
those set forth in the latest edition of
STANDARD METHODS 37 except as may be
otherwise provided herein.
4. During the test period the plant shall be
operated and maintained according to the
manufacturer's instructions except as these
may in any way be in conflict with the
provisions of the Standard Performance
Evaluation Method in which case the pro-
visions of the Method shall be complied
with.
5. The Standard Evaluation Method can be
carried out at any time of the year pro-
vided that the plant being tested has reached
process maturity as evidenced by a mixed
liquor suspended solids concentration of
2,500 mg/1 prior to the time that the tem-
perature of the aerator contents falls to
8.0 °C and provided, further, that during
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40
the test period the temperature at no time
falls below 5 °C if the test is conducted
during cold weather and that the plant and
its equipment is protected from freezing.
If the test is conducted under warm
weather conditions the temperature of the
aerator contents shall at no time during
the test period exceed 30.0 °C.
6. The performance evaluation of a plant
shall be independent of its design and con-
struction except that structural weakness
and/or defects and failures of its process
support equipment noted during the test
shall be reported as a part of the test
results.
7. For a series of plants of the same model
which vary essentially only in capacity,
the results achieved by the smallest plant
in the model series shall be taken as in-
dicative of the capabilities of all other
plants in the series. In the event that the
manufacturer of the model series sub-
mits more than one plant in the series for
testing, the results achieved by each plant
tested shall be taken as indicative of the
capabilities of all other larger plants in
the model series up to the next larger
size tested.
8. The Standard Performance Evaluation
Method shall consist of three main parts:
a. Startup Performance Evaluation (The
period between actual startup of the
plant and its achievement of a mixed
liquor suspended solids concentration
of 2,500 mg/1).
b. Subdivision Flow Pattern Performance
Evaluation (A period of thirty days be-
ginning with the plant's achievement of
a mixed liquor suspended concentration
of approximately 2,500 mg/1).
c. School Flow Pattern Performance Eval-
uation (A period of thirty days following
the adjustment of the mixed liquor sus-
pended solids concentration to approxi-
mately 2,500 mg/1 at the end of the
subdivision pattern evaluation period).
9. During the performance evaluation phases
the plant shall be hydraulically loaded at
its rated daily capacity with the pattern
of hydraulic loading depending on the re-
quirement set forth for each phase.
10. The information and data developed during
each phase will be reported and sum-
marized separately in the certified per-
formance evaluation report.
11. The certified performance evaluation re-
port shall be signed by both the chief ad-
ministrative officer of the testing organi-
zation and the official of the organization
in direct responsible charge of the evalu-
ation. The report shall contain but not
necessarily be strictly limited to the fol-
lowing:
a. A copy of the Standard Performance
Evaluation Method.
b. All data and information developed
during the evaluation in detail. "Sum-
mary Data", "Typical Data", and the
like shall not be used. This informa-
tion and data shall be grouped accord-
ing to the three main parts of the eval-
uation and used only in the calculation
of the results of section to which the
data pertains.
c. A summary statement of the evaluation
results.
d. A certification statement signed by the
testing organization officials and/or
officers specified above which states
that the Standard Performance Evalua-
tion Method was used in the testing of
the plant, that no deviations from this
method were made during the test, and
that the results reported are true to
the best of their information and belief.
C. STARTUP PERFORMANCE EVALUATION
1. The plant shall be completely assembled
according to the manufacturers' directions
and all of its equipment checked to deter-
mine that it is free of mechanical defects
and operable. The plant shall be exa-
mined to determine that it is structurally
sound. All defects noted shall be reported.
If no defects are detected this fact shall
be reported.
2. If no defects are detected and the plant
is judged to be structurally sound it shall
be filled with domestic waste (previously
defined under B-l) as rapidly as possible
and immediately placed into full operation.
Sampling and testing shall begin as soon
as the plant is filled and placed into opera-
tion and shall continue without interrup-
tion until the end of the first two of the
three parts of the Standard Performance
Evaluation Method.
3. Aerator contents residual dissolved oxygen
levels shall be maintained between 1.0 and
2.0 mg/1 as nearly as possible. In no
case shall the residual dissolved oxygen
-------
41
level be permitted to fall below 1.0 mg/1
except in the immediate vicinity of raw
waste introduction where it shall not be
permitted to fall below 0.5 mg/1 at any
time. In the event these minimum dis-
solved oxygen levels cannot be maintained
the test shall be terminated.
4. The raw domestic waste utilized as feed
for the unit shall have been passed through
a 1/4 inch slot comminutor prior to entering
the unit and during this phase of the test
it shall be applied in a subdivision pattern
as defined elsewhere in this method.
5. Daily twenty-four hour influent and effluent
samples composited strictly according to
the influent flow pattern shall be collected.
The frequency of sampling to make up the
required daily composites shall be at least
once hourly.
6. The rate of flow applied to the unit under
test shall be measured and recorded con-
tinuously and the volume of waste applied
daily shall be totalized and reported. The
total volume of waste applied to the unit
daily shall be the rated capacity of the
unit plus or minus five percent.
7. The daily influent and effluent composites
shall be subjected to laboratory analysis
to determine the following:
a. Five Day Biochemical Oxygen Demand
(mg/1).
b. Suspended and volatile suspended solids
(mg/1).
c. pH
The temperature of the influent and effluent
shall be determined for both maximum and
minimum flow periods.
8. At the midpoint of the maximum flow
period a grab sample of the mixed liquor
shall be taken as near the center of the
aeration compartment as possible. A re-
turn sludge grab sample shall be taken
daily at the same time, if possible. Also,
at the same time the dissolved oxygen con-
tent and temperature of the aeration com-
partment contents in the immediate vici-
nity of the raw waste introduction point,
middle of the compartment, and the im-
mediate vicinity of the compartment exit
shall be determined.
Both the mixed liquor and return sludge
grab samples (see C-8) shall be subjected
to laboratory analysis to determine the
following:
a. Suspended and volatile suspended solids
(mg/1).
b. pH
c. Thirty minute settled volume (SV30, ml.)
(sludge volume index computed for mixed
liquor samples only).
9. As soon as the mixed liquor suspended
solids value reaches 2,500 mg/1 plus or
minus ten percent the Startup Performance
Evaluation shall be terminated and the Sub-
division Flow Pattern Evaluation shall start
at once without any interruption of feed to
the unit or lapse of time.
D. SUBDIVISION FLOW PATTERN PERFOR-
MANCE EVALUATION
1. The provisions of Section C, subsection 3,
4, 5, 6, and 8, shall be complied with
during this phase of the evaluation.
2. The period of Subdivision Flow Pattern
Performance Evaluation shall be the next
consecutive thirty days following the Start-
up Performance Evaluation period.
3. The daily influent and effluent composite
samples (see C-5) shall be subjected to
laboratory analysis to determine the fol-
lowing:
a. Five Day Biochemical Oxygen Demand
(mg/1, BOD5)
b. Suspended and volatile suspended solids
(mg/1)
c. pH
d. Methyl Orange Alkalinity (mg/1)
e. Ammonia-nitrogen (mg/1, NH3-N)
f. Total Soluble Phosphate (mg/1, PO4-P)
g. Methylene Blue Active Substance (mg/1,
MBAS)
h. Chemical Oxygen Demand (mg/1, COD)
In addition to the above, the daily effluent
composite shall also be subjected to the
following analyses:
a. Nitrate-nitrogen (mg/1, NO3-N)
b. Dissolved Oxygen (mg/1)
4. The temperature of the plant influent and
the effluent shall be determined during both
the maximum and minimum flow periods.
E. FLOW PATTERN CHANGE AND SOLIDS AD-
JUSTMENT PERIOD
1. At the end of the thirty day Subdivision
Performance Evaluation period and while
still maintaining the conditions of loading
required during that period, the mixed
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42
liquor suspended solids shall be adjusted
to 2,500 mg/1 plus or minus ten percent
by wasting solids from the plant. Such
wasting is to be carried out in as short
a time as possible not to exceed one day.
2. Immediately following the adjustment of the
mixed liquor suspended solids concentra-
tion the influent flow pattern shall be
changed to that of a school as defined else-
where in this method. The total volume
of waste applied to the unit daily shall be
the rated capacity of the plant plus or
minus five percent.
3. Sampling shall be suspended for a period
of one week during this period to permit
the adjustment of solids, change of flow
pattern, and the adjustment of the plant
to the new conditions.
F. SCHOOL FLOW PATTERN PERFORMANCE
EVALUATION
1. The provisions of Section C, subsections
3, 4, 5, 6, and 8, shall be complied with
during this phase of the evaluation.
2. The provisions of Section D, subsections
3, and 4, shall also be complied with during
this phase.
3. The period of School Flow Pattern Per-
formance Evaluation shall be the next con-
secutive thirty days following the Flow
Pattern Change and Solids Adjustment
Period. The school flow pattern shall be
on the basis of a five day week.
G. DEVIATIONS FROM STANDARD METHODS
1. The following deviations from the pro-
visions of Standard Methods for the Exa-
mination of Water and Wastewater37 are
permitted:
a. The thirty minute settled volume (SV3(I)
test shall be conducted by settling a
one liter volume of mixed liquor di-
luted with plant effluent to a suspended
solids concentration of approximately
1,500 mg/1.. The actual suspended
solids concentration shall be deter-
mined and used in computing the sludge
volume index value. A recommended
alternate is the use of a larger dilute
sample and a properly calibrated three
liter battery jar. These deviations
apply only to Section D and F tests.
b. Glass fiber filter mats may be used in
connection with the Gooch Crucible
Method for the determination of sus-
pended solids. The use of such mats
is recommended.
H. FLOW PATTERNS
The percentage of the total daily flow applied
during each hour of the day shall be as fol-
lows:
Hour
Subdivision
Pattern
School
Pattern
12:OOM -
1:00 AM
1.5
0
1:00AM -
2:00 AM
1.5
0
2:00AM -
3:00 AM
1.5
0
3:00AM -
4:00 AM
1.5
0
4:00AM -
5:00 AM
2.5
0
5:00AM -
6:00 AM
2.5
0
6:00AM -
7:00 AM
3.0
0
7:00AM -
8:00 AM
3.0
0
8:00AM -
9:00 AM
4.0
12.5
9:00AM -
10:00 AM
4.5
12.5
10:00 AM
- 11:00 AM
6.5
12.5
11:00 AM
- 12:00N
6.5
12.5
12:00N -
1:00 PM
6.5
12.5
1:00 PM -
2:00 PM
6.5
12.5
2:00 PM -
3:00 PM
4.5
12.5
3:00 PM -
4:00 PM
4.5
12.5
4:00 PM -
5:00PM
4.5
0
5:00 PM -
6:00 PM
4.5
0
6:00PM -
7:00 PM
5.0
0
7:00PM -
8:00PM
5.0
0
8:00PM -
9:00 PM
5.0
0
9:00 PM -
10:00 PM
5.5
0
10:00 PM
- 11:00PM
5.0
0
11:00 PM
- 12:00M
5.0
0
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43
IV. RESPONSIBILITIES
During the course of these studies the pro-
ject committees have given considerable thought
to the matter of the responsibilities of the several
parties to the manufacture and use of extended
aeration package sewage treatment plants. This
matter of responsibilities is so intimately a part
of the entire question of the use and performance
of package plants that it injects itself into any
serious discussion of such plants. The follow-
ing are offered in an attempt to define, at least
to some extent, the logical responsibilities of
those involved in the design, manufacture, appli-
cation, use, and supervision of package sewage
treatment plants.
A. THE MANUFACTURER-SUPPLIER
1. It is the responsibility of those who man-
ufacture, and supply package sewage treat-
ment plants to insure the durability and
workability of the plants' structure and pro-
cess support equipment. It is further their
responsibility to guarantee such durability
and workability to the buyer-owner.
2. It is the responsibility of the manufacturer-
supplier to define and warrant the overall
process efficiency to be expected in con-
nection with the treatment of a stated waste
having specified characteristics excepting
that such warranty is valid only so long as
the responsibilities of the other parties are
met by them.
3. The manufacturer-supplier should provide
the services of a qualified technician who
is thoroughly knowledgeable concerning the
equipment and processes involved to check
the installation of the plant, supervise the
startup of the plant, and to instruct the
buyer-owner's operator in the proper opera-
tion and maintenance of the plant. Such a
qualified individual should also be supplied
for a recheck of the plant after process
maturity has been achieved as evidenced
by a mixed liquor suspended solids concen-
tration of 2,500 mg/1 both to insure that
the plant is operating properly and to fur-
ther instruct the buyer-owner's operator.
Technical service in addition to the above
should also be provided at the owner's re-
quest and at his expense, except as any
guarantee or warranty between the parties
may apply.
4. If the plant is installed by the manufacturer-
supplier he should guarantee such installa-
tion. If the plant is installed by others
than the manufacturer-supplier he should
supply the installer with adequate installa-
tion instructions.
5. The manufacturer-supplier should provide
the buyer-owner at the time of plant start-
up with a complete manual outlining the pro-
per operation and maintenance procedures
and including adequate drawings and des-
criptive literature so as to render these
matters understandable to a qualified opera-
tor of such plants. This manual should also
include a complete but readily understood
discussion of the principles involved in the
processes employed by the plant as well as
a thorough description and discussion of the
test methods required for the intelligent
operation of such processes.
6. Also at the time of startup of the plant, the
manufacturer should supply the owner with
a complete replacement parts list for the
plant and all of its equipment including up-
to-date information on the availability of
replacement parts, parts suppliers, and any
known applicable substitute parts. Further,
such parts list should contain a recommen-
dation concerning the types and quantities
of spare parts which the buyer-owner should
maintain on hand to facilitate emergency
repairs. Any unusual tools that might be
required for the proper repair or mainte-
nance of the plant and its equipment should
also be brought to the owner's attention by
suitable mention in the parts list or main-
tenance manual. The availability of re-
placement parts for a specified period of
time should be a part of the manufacturer-
supplier's warranty to the buyer-owner.
7. It should be the responsibility of the manu-
facturer-supplier to furnish certified copies
of The Standard Performance Evaluation
Method results available pertaining to the
particular plant model series involved as
a part of any submission of plants and/or
specifications to a reviewing regulatory
agency or official that may be required by
law or regulation. It should be his further
responsibility to provide the same infor-
mation to the buyer- owner and his engineering
consultant.
B. THE BUYER-OWNER
1. It is the responsibility of those who buy,
own, and operate package sewage treatment
plants to secure or provide the services of
a competent engineer to set up specified
critical flow ranges and loadings for sizing
the plant within the general or specific re-
quirements of the regulatory agencies or
officials having jurisdiction, to determine
plant location, and to perform related en-
gineering services as outlined herein.
-------
2. The owner of a package sewage treatment
plant has the responsibility of providing as
the plant operator a person who is con-
scientious, of adequate intelligence, and in
good physical condition and who, therefore,
is capable of learning to operate and main-
tain the plant within a reasonably short
period of time given adequate instruction.
3. In the event the original plant operator
leaves the employ of the owner it is the
owner's responsibility to immediately se-
cure a replacement for him who has the
same attributes as set forth for the origi-
nal operator and to provide the new opera-
tor with suitable training for the job.
4. It is the responsibility of the buyer-owner,
through his engineering consultant, to se-
cure from the agencies or officials having
jurisdiction the approvals, permits, or
licenses required by law or regulation for
the construction and operation of the plant
unless this is specifically delegated by con-
tract to another of the parties
5. It is also the responsibility of the owner
to give general supervision to his operator
and to provide the operator with all neces-
sary tools, materials, parts, and the like
required for the proper operation and main-
tenance of the plant. It should be noted in
this connection that the owner himself is
ultimately responsible for the performance
of the plant.
6. The owner of a package sewage treatment
plant is responsible for any failure of the
plant to perform as set forth in the manu-
facturer-supplier's warranty and/or as re-
quired by law or regulation when such
failure is the result of organic and/or
hydraulic loadings or waste characteristics
which differ from those in the warranty.
It should be further noted that the owner
is, in most jurisdictions, solely responsible
for any failure of the plant to perform as
required by law or regulation regardless of
cause.
THE CONSULTING-SUPERVISING ENGINEER
1. The owner's engineer is responsible for the
setting of organic and hydraulic load levels
to be applied to the plant and for selecting
the plant(s) which in his best judgement are
capable of reliably treating the waste at
these loadings in such a manner as to con-
form with all applicable laws and regula-
tions.
2. Not only is the engineer responsible for
defining the load levels to be treated but
he is further responsible for defining both
the organic and hydraulic pattern of loading
and the specific characteristics of the waste
to be treated. It is the additional respon-
sibility of the engineer to fully disclose all
of these characteristics, loadings, and con-
ditions to the manufacturer-supplier and the
buyer-owner as well as the regulatory
agencies and officials having jurisdiction.
3. The engineer is responsible for determining
the location of the plant, the design of ade-
quate inlet and outlet sewers, the design of
required auxiliary structures and appurte-
nances as required as well as necessary
power lines and the like.
4. It is ordinarily the responsibility of the
engineer to represent the buyer-owner in
securing the required permits and licenses
or to delegate this by contract or agreement
to another of the parties.
5. It is the responsibility of the engineer to
generally oversee and inspect the installa-
tion and/or construction of the plant and its
appurtenances specified in the contract
drawings and to require such corrections
to be made by the manufacturer-supplier/
installer as may be necessary in order to
conform to the approved drawings and spe-
cifications.
D. THE INSTALLER-CONTRACTOR
1. In the event that an installer-contractor
rather than the manufacturer-supplier in-
stalls the package sewage treatment plant,
it is the responsibility of such installer-
contractor to make the installation in ac-
cordance with the manufacturer-supplier's
instructions.
2. It is the further responsibility of the in-
staller-contractor to insure that good work-
manship standards are maintained and that
the overall process efficiency is not limited
by any defect in installation.
E. THE REGULATORY AGENCY-OFFICIAL
1. In the course of the normal discharge of
their duties regulatory agencies and officials
having jurisdiction would carefully review
all of the available information concerning
the package sewage treatment plant pro-
posed fur use in each particular case. This
review would include The Standard Perfor-
mance Evaluation Method results which per-
tain to the particular plant model or model
series which is being proposed. After such
review it would finally be the responsibility
of the agency-official to make a value judge-
ment as to the capability of the proposed
plant to treat the specific waste, in view of
-------
45
the loadings and loading pattern, to the de-
gree required in each case.
2. Following the installation of the plant the
regulatory agency-official would normally
make an inspection of the plant. The agency-
official would require the owner to submit
for review certain test results and operating
reports and/or would conduct such tests and
inspections as required to insure that the
performance of the plant met the waste
treatment requirements in each case.
3. In the event that the agency-official deter-
mined that the plant was not meeting the
waste treatment requirements the owner
would be required to take the necessary
steps to insure the required level of treat-
ment.
F. THE PLANT OPERATOR
1. The plant operator is responsible for the
conscientious and proper operation and
maintenance of the plant under the overall
responsibility of the owner.
2. It is also the responsibility of the operator
to make such observations and to conduct
such tests as may be required for the proper
operation of the processes involved in the
plant, to record the results of such obser-
vations and tests, and to make these re-
sults known to the owner who, further, may
be required to make then known to the
regulatory agency-official.
3. The operator has the responsibility of ad-
vising the owner as to the tools, supplies,
and parts which amy be required from time
to time for the proper operation and main-
tenance of the plant and to do so in suf-
ficient time to insure that such items are
available when needed.
4. It is a prime responsibility of the operator
to become fully acquainted with the plant
and all of its appurtenances especially in-
cluding the processes involved in the treat-
ment system and to take full advantage of
all training offered by the manufacturer-
supplier, owner, and regulatory agency-
official.
5. The operator is responsible for informing
the owner at once of any process inter-
ruptions or observed losses of efficiency of
such a nature or extent as to render the
waste treatment level less than that required
by law or regulation.
G. THE PERFORMANCE EVALUATION
ORGANIZATION
1. It is the responsibility of the agency, group,
or organization which conducts plant per-
formance evaluations to do so strictly in
accordance with the Standard Performance
Evaluation Method and to certify the re-
sults of such testing to the manufacturer
of the plant. In addition to the detailed
test results a data summation shall be sup-
plied.
2. Standard Performance Evaluation method
data should be used by a recognized testing
organization in a certification program.
Such a program would make standard per-
formance information readily available for
use by those concerned in making judge-
ment decisions regarding package sewage
treatment plants.
From the foregoing seven sections on the
roles and responsibilities of the various parties
concerned in the design, manufacture, testing,
use, and supervision of package sewage treatment
plants it is clear that each of these parties in-
fluences and contributes to the final overall plant
performance actually observed in the field. This
is also clear from the studies and findings re-
ported here for these findings have shown that
defects in design, manufacture, application, and
operation greatly influence the observed overall
plant performance. In the final analysis, no one
of these factors can be said to be truly more
important than any other for it requires the best
efforts of all concerned to achieve the desired
result.
V. SUMMARY
The work reported here represents a joint
effort on the part of many persons, agencies,
companies, and organizations to find a means of
fairly evaluating the performance of package
sewage treatment plants. A large number of such
plants were operated under closely controlled
conditions so that those factors which influence
their overall efficiency could be identified and an
assessment made of the importance of each. In
brief, it can be said that the overall efficiency of
extended aeration package sewage treatment plants
depends upon their design, application, and opera-
tion. No one of these factors can be said to be,
in the final analysis, more important than the
others for it is only when a plant is designed,
applied, and operated properly that the desired
results are achieved.
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46
A standard method has been presented which
will give detailed information about package sewage
treatment plants under conditions of startup, aver-
age loading, and severe loading. It is felt that
these three conditions fairly bracket the range of
conditions under which the vast majority of pack-
age sewage treatment plants must operate and
that the operation of these plants under these
three conditions yields data which can be used
in making value judgements as to their likely
performance under specific conditions. Thus, a
method is provided which will assist water pol-
lution control regulatory officials, engineers, and
others concerned in the performance evaluation
of extended aeration package sewage treatment
plants.
It has also been shown through this study of
a representative cross section of the presently
available extended aeration package plants that
these plants are capable of sustained, high re-
moval of applied biochemical oxygen demand when
properly operated and maintained. The fundamen-
tals of the processes and factors involved have
been illustrated and discussed in detail. Rapid
analytical methods have been described which
have proven useful in the operation and perfor-
mance evaluation of package plants and which can
be used in the field by both those who operate
and who supervise the operation of extended aera-
tion plants.
Perhaps the most important contribution of
all, in the final analysis, has been the demonstra-
tion of cooperative problem solving in the waste-
water treatment field by all the parties who are
concerned with that problem. It is believed that
the same methodology which was demonstrated by
the present study could well be applied in the
search for answers to many other problems in
this field.
VI. ACKNOWLEGEMENTS
This project was supported in part by a
Demonstration Grant, number WPD-74, from the
Research and Training Grant Program, Federal
Water Pollution Control Administration. Grate-
ful acknowledgement is also made for permission
to utilize a portion of the Federal Water Pollu-
tion Control Administration's Midwest Regional
Laboratory Auxiliary Site at Ann Arbor, Michi-
gan as the research site for these studies.
The National Sanitation Foundation would like
to express its appreciation to and acknowledge
the support of this project by the following manu-
facturers who provided the extended aeration
package sewage treatment plants used in these
studies.
Aer-O-Flo Corporation
Florence, Kentucky
Can-Tex Industries, Inc.
Mineral Wells, Texas
Chicago Pump
Hydrodynamics Division
FMC Corporation
Chicago, Illinois
Davco Manufacturing Company
Thomasville, Georgia
Defiance, Incorporated
Bradenton, Florida
Dravo Corporation
Pittsburgh, Pennslyvania
The Eimco Corporation
Salt Lake City, Utah
Infilco Division
General American Transportation Corporation
Tucson, Arizona
Logemann Brothers Company
Milwaukee, Wisconsin
Mack Vault Company
Valley City, Ohio
Smith and Loveless Division
Union Tank Car Company
Lenexa, Kansas
Topco Company Division
Sterling-Salem Corporation
Salem, Ohio
Worden-Allen Company
Milwaukee, Wisconsin
Yeomans Brothers Company
Melrose Park, Illinois
The Foundation would like to thank The Soap
and Detergent Association for its support of a
portion of the work reported. Acknowledgment
is also made to the continued support of and
copperation with the project and staff by the City
of Ann Arbor, Michigan and Mr. C. Preston
Witcher, Superintendent, Ann Arbor, Wastewater
Treatment Plant to whom particular appreciation
is expressed.
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47
The author would like to express his apprecia-
tion to the Project Staff without whose devoted
efforts this project would have not been possible.
Special acknowledgement is made of the out-
standing contribution to this work made by the
chairmen and members of the several project
committees. These committees designed the pro-
ject facilities and methodology, met frequently
with the Foundation Staff throughout the project,
and reviewed the results of the work at each
stage of the project. The sincere interest of the
committee members in this project and their
continued advice and council as the project pro-
gressed has been deeply appreciated.
Acknowledgement is further made of the con-
tribution to the success of the project which was
made by Mr. George E. Hubbell, Hubbell, Roth
and Clark, Inc., and Mr. R. S. Gabrielse, Midwest
Mechanical Contractors, Inc., who, respectively,
designed and constructed the physical facilities
required for the project.
-------
VII. REFERENCES
1. Ludwig, Harvey F. et al, Theory, Design, and Opera-
tion of the Rated Aeration Waste-Water Treatment
Process, Chicago Pump: 1960, p. 3.
2. Ohio Department of Health, A shuly of Aerobic Diges-
tion Plants in Ohio 1959-1960, p. 1.
3. Porges, N.eta!, "Aerobic Treatment of Dairy Wastes,"
Applied Microbiology 1:262 (1953).
4. McKinney, Ross E. el al, "Design and Operation of a
Complete Mixing Activated Sludge System", Seioage and
Industrial Wastes 30:3:287 (March, 1958).
5. Tapleshay, John A., "Total Oxidation Treatment of Or-
ganic Wastes", Sewage and Industrial Wastes 30:5:652
(May, 1958).
6. Symons, James M. and McKinney, Ross E., "The Bio-
chemistry of Nitrogen in the Synthesis of Activated
Sludge", Seimge and Industrial Wastes 30:7:874 (July,
1958).
7. Kountz, Rupert R. and Forney, Charles Jr., "Metabolic
Energy Balances in a Total Oxidation Activated Sludge
System", Sewage and Itulustrial Wastes 31:7:819 (July,
1959).
8 . Joplin, William F., A Shuly of "Hated Aeration: Sewage
Treatment Plants in Northern California, Wastes Sec-
tion, Bureau of Sanitary Engineering, California State
Department of Public Health: 1960.
9 . Kiker, John E. Jr., "Package and Subdivision Sewage
Treatment Plants", Journal WPCF 32:2:878 (August,
1960).
10. Porges Ralph and Morris, Grover L., Extended-Aera-
tion Sewage Treatment Robert A. Taft Sanitary Engi-
neering Center Technical Report W60-6, U. S. Depart-
ment of Health, Education, and Welfare, Public Health
Service, 1960.
11. Stewart, Mervin J. and Ludwig, Harvey F., "Theory of
the MAS Waste-Water Treatment Process-Part I",
Water & Sewage Works 109:2:53 (February, 1962).
12. Stewart, Mervin J. and Ludwig, Harvey F., "Theory of
the MAS Waste-Water Treatment Process-Part II",
Water & Sewage Works 109:3:97 (March, 1962).
13. Shatto, Harry, "Aerobic Digestion + Diatomite Filter",
Public Works (December, 1960) p. 82.
14. Howe, Richard S., "Operational Problems of Package
Activated Sludge Plants", Journal WPCF 33:11:1166
(November, 1961).
15. Ludzack, F. J. et al, "Temperature and Feed as Varia-
bles in Activated Sludge Performance", Journal WPCF
33:2:141 (February, 1961).
16. Massachusetts Health Research Institute, Inc., A Study
of Small, Complete Mixing, Extended Aeration, Activated
Sliulge Plants in Massachusetts, New England Interstate
Water Pollution Control Commission: Boston, 1961.
17. Massachusetts Health Research Institute, Inc., Operating
Manual for Small, Extended Aeration, Activated Sludge
Treatment Plants, New England Interstate Water Pollu-
tion Control Commission: Boston, 1961.
18. Baker, Ralph H., "Package Aeration Plants in Florida",
Journal Sanitary Engineering Division - ASCE (Novem-
ber, 1962), p. 75.
19. McCarty, Perry L. and Brodersen, C. F., "Theory of
Extended Aeration Activated Sludge", Journal WPCF
34:11:1095 (November, 1962).
20. Porges, Ralph and Morris, Grover L., "Criteria for
Utilization of Package Plants", Proceedings, 11th.
Southern Municipal and Industrial Waste Conference,
(April, 1962).
21. Stewart, Mervin J. et al, "Effect of Varying Salinity on
the Extended Aeration Process", Journal WPCF 34:11:
1161 (November, 1962).
22. Washington, Donald R. and Symons, James M., "Volatile
Sludge Accumulation in Activated Sludge Systems",
Journal WPCF 34:8:767 (August, 1962).
23. McKinney, Ross E., "Mathematics of Complete-Mixing
Activated Sludge", Transactions, ASCE, Vol. 128, 1963,
Part III, Paper No. 3516, page 497.
24. Morris, Grover, L. et al. Extended-Aeration Plants ami
Intermittent Watercourses, U. S. Department of Health,
Education, and Welfare, Public Health Service, Cincin-
nati: 1963.
25 Orford, H. E. et al, "Effect of Sludge Loading and Dis-
solved Oxygen on the Performance of the Activated
Sludge Process", Advances in Biological Waste Treat-
ment, Eckenfelder, W. W. and McCabe, Brother Joseph
eds., MacMillan Company, New York: 1963.
26. Pfeffer, John T., "Design Criteria for Extended Aera-
tion", Transactions, Thirteenth Annual Conference on
Sanitary Engineering, Bulletin of Engineering and Ar-
chitecture No. 51, University of Kansas Publications,
Lawrence: 1963.
27. Pfeffer, John T., "Extended Aeration", Water and Sewage
Works 113:6:207 (June, 1966).
28. Baker, Ralph H. Jr., "Current Use of Small Activated
Sludge Plants in Florida", presented at WPCF Conven-
tion, Bal Harbour (September, 1964) in manuscript.
29. Lawton, G. W. and Norman, J. D., "Aerobic Sludge Di-
gestion Studies", Journal WPCF 36:4:459 (April, 1964).
48
-------
49
30. Monn, Edgar P., "Design and Maintenance of Extended
Aeration Sewage Treatment Plants", - Public Works
(January, 1964) p. 70.
31. Schulze, K. L., "The Activated Sludge Process As A
Continuous Flow Culture", Water and Sewage Works
111:12:526 (December, 1964)
32. Schulze, K. L., "A Mathematical Model of the Activated
Sludge Process", Development in Industrial Microbiol-
ogy, Vol. 5, American Institute of Biological Sciences,
Washington: 1964 (p. 258).
33. Ludzack, F. J., "Observations on Beach-Scale Extended
Aeration Sewage Treatment", Journal WPCF 37:8:1092
(August, 1965).
34. Rao, B. S. and Gaudy, A. F. Jr., "Effect of Sludge Con-
centration on Various Aspects of Biological Activity in
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35. Smith, H. S. and Paulson, W. L., "Homogeneous Acti-
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Wastewater, 11 ed., American Public Health Associa-
tion, New York: 1960.
37. Standard Methods for the Examination of Water and
Wastewater, 12 ed., American Public Health Associa-
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Waste Treatment, Pergamon Press, New York: 1961
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trict, Personal Communication, July 14, 1966.
40. Bell, E. A., Water IVorfcs and Sewage 87:163 (1940).
41. Eckenfelder, W. W. Jr., "Rapid Photometric Estima-
tion of Process Efficiency", Water and Sewage Works
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42. Krawezyk, Daniel and Gonglewski, Norbert, "Deter-
mining Suspended Solids Using a Spectrophotometer",
Sewage and Imlustrial Wastes 31:10:1159 (October, 1959).
43. McTavish, D. A., "Spectrophotometer Determines Sus-
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NSF Note to the Tables, pp. 50-53
The data in the tables on the following four pages con-
stitute an appendix to the report on criteria development.
The figures presented represent values determined not neces-
sarily with all plants operated in conformance with normal
loading patterns. Tables I-A, I-B and I-C present mean
figures sometimes determined from a series of values too
few in number to be regarded as statistically significant.
Upon reexamination of influent data for the latter three
tables, it is questionable whether single values should be
offered or whether a range of values would give the reader
a better appreciation of plant loadings. On the other hand,
effluent values are based upon a much more significant num-
ber of determinations and appear to reflect quite fairly the
level of discharges obtained from the plants under the pat-
terns of operation prevailing.
It is urged that readers of (he report exercise consid-
erable restraint in using the data in the tables as a point
of reference in judging the performance of any individual
plant which may later be evaluated independently or by NSF.
In its testing and certification program, NSF proposes
to use the following procedure to provide, on the one hand,
data which will represent the performance of a given plant
under test and, on the other hand, valid point of reference
data which will be useful to any interested party for com-
parative purposes. In any given round of testing (until a
substantial body of testing experience is obtained) perform-
ance data will be determined for each individual plant under
test in the group, and also for the group of plants as a
whole. The mean performance of each individual plant may
then be validly compared, if desired, with the mean per-
formance ol the group as a whole.
NSF believes it to be important that the reader of the
report clearly appreciate that the data in the tables reflects
the analytical determinations carried out in the course of
establishing the criteria for performance evaluation and does
not in any way represent standards of performance to be
attained by plants under test.
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50
TABLE I
FALL AND WINTER STUDIES
TEN EXTENDED AERATION PACKAGE SEWAGE TREATMENT PLANTS
FULL DESIGN LOADING - STEADY STATE FLOW PATTERN
(Mean Values)
ITEM PLANT INFLUENT PLANT EFFLUENT
1. BOD s (mg/1) 175 17
2. SS (mg/1) 190 35
3. VS (mg/1) 1G5 28
4. % Volatile 82 80
5. pH 7.7 7.0
6. Alkalinity (mg/1) 98 28
7. NH3-N (mg/1) 18.7 6.0
8. NO3-N (mg/1) 9.2
9. PO4-P (Total Soluble) (mg/1) 12.0 12.0
10. Dissolved Oxygen (mg/1) 2.5
11. Methylene Blue Active Substance (mg/1) 5.0 1.2
12. % Reduction (Total Plant)
a. BOD5 90
b. SS 82
c. VS 83
d. Alkalinity 71
e. NH3-N 68
f. P04-P 0
g. M.B.A.S. 76
13. MLSS (mg/1) 3,100
14. MLVSS (mg/1) 2,450
15. % Volatile MLSS 79
16. pH, mixed liquor 7.0
17. SV30 (ml), mixed liquor 347
18. Temperature, mixed liquor (°C) 11.4
19. Dissolved Oxygen, mixed liquor 3.5
20. Sludge Density Index 0.9
21. BOD/SS 0.92 0.49
22. BOD/VS 1.06 0.61
23. lb. BODs/lb. MLSS 0.06
24. lb. BODs/lb. MLVSS 0.07
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51
TABLE I-A
SPRING AND SUMMER STUDIES
FOUR EXTENDED AERATION PACKAGE SEWAGE TREATMENT PLANTS
STEADY STATE FLOW PATTERN
(mean values)
ITEM
INFLUENT
FULL LOAD
EFFLUENT
HALF LOAD
1. BOD 5 (mg/1)
186
16
14
2. SS (mg/1)
216
29
30
3. VS (mg/1)
180
21
20
4. COD (mg/1)
210
32
25
5. % Volatile
83
72
67
6. pH
7.5
7.2
7.2
7. Alkalinity (mg/1)
47.0
17.8
14.5
8. NH3-N (mg/1)
16.2
0
0
9. N03-N (mg/1)
14.5
17.5
10. P04-P (Total Soluble) (mg/1)
14.0
14.0
13.3
11. Dissolved Oxygen (mg/1)
2.1
2.2
12. M.B.A.S. (mg/1)
5.5
0.9
1.0
13. BOD/SS
0.86
0.54
0.47
14. BOD/VS
1.03
0.74
0.70
15. BOD/COD
0.89
0.50
0.56
16. % Reduction
a. BODs
92
92
b. SS
87
86
c. VS
89
89
d. COD
85
88
e. Alkalinity
63
69
f. NH3-N
100
100
g. P04-P
0
5.0
h. M.B.A.S.
84
82
MIXED LIQUOR
Full Load
Half Load
17. MLSS (mg/1)
3,250
2,100
18. MLVSS (mg/1)
2,375
1,450
19. % Volatile
73
69
20. pH
7.1
7.1
21. SV30 (ml)
225
160
22. Sludge Density Index
1.49
1.32
23. Temperature (°C)
18.4
18.0
24. Dissolved Oxygen (mg/1)
3.3
2.1
25. lb. BOD/lb. MLSS
0.06
0.04
26. lb. BOD/lb. MLVSS
0.08
0.07
-------
TABLE I-B
SPRING AND SUMMER STUDIES
FOUR EXTENDED AERATION PACKAGE SEWAGE TREATMENT PLANTS
SUBDIVISION FLOW PATTERN
(mean values)
ITEM
INFLUENT
FULL LOAD
EFFLUENT
HALF LOAD
1.
BOD 5 (mg/1)
198
20
10
2.
SS (mg/1)
234
36
32
3.
VS (mg/1)
192
26
22
4.
COD (mg'/l)
220
32
18
5.
% Volatile
82
72
69
6.
pH
7.5
7.1
7.2
7.
Alkalinity (mg/1)
48.0
19.5
14.2
8.
NHj-N (mg/1)
17.4
0
0
9.
N03-N (mg/1)
15.3
20.0
10.
PO4-P (Total Soluble) (mg/1)
11.3
11.3
10.3
11.
Dissolved Oxygen (mg/1)
1.6
2.2
12.
M.B.A.S. (mg/1)
6.1
0.8
0.9
13.
BOD/SS
0.85
0.56
0.31
14.
BOD/VS
1.03
0.77
0.45
15.
BOD/COD
0.90
0.63
0..56
16.
% Reduction
a. BODs
90
95
b. SS
85
86
c. VS
86
89
d. COD
85
92
e. Alkalinity
59
71
f. NH3-N
100
100
g. po4-p
0
8.8
h. M.B.A.S.
87
85
Mixed Liquor
Full Load
Half Load
17.
MLSS (mg/1)
4,330
3,050
18.
MLVSS (mg/1)
3,120
2,130
19.
% Volatile
72
70
20.
pH
7.3
6.9
21.
SV30 (ml)
650
285
22.
Sludge Density Index
0.67
1.07
23.
Temperature (°C)
18.6
18.2
24.
Dissolved Oxygen (mg/1)
2.0
3.0
25.
lb. BOD 5/lb. MLSS
0.05
0.03
26.
lb. BOD5/lb. MLVSS
0.06
0.05
-------
53
TABLE I-C
SPRING AND SUMMER STUDIES
FOUR EXTENDED AERATION PACKAGE SEWAGE TREATMENT PLANTS
SCHOOL FLOW PATTERN
(mean values)
ITEM
INFLUENT
EFFLUENT
FULL LOAD
HALF LOAD
1. BOD 5 (mg/1)
210
38
20
2. SS (mg/1)
240
63
48
3. VS (mg/1)
198
44
30
4. COD (mg/1)
243
53
40
5. % Volatile
83
70
62
6. pH
7.5
7.3
7.3
7. Alkalinity (mg/1)
50.0
26.0
16.0
8. NH3-N (mg/1)
18.6
3.6
0.5
9. N03-N (mg/1)
8.0
20.8
10. P04-P (Total Soluble) (mg/1)
12.3
11.7
11.7
11. Dissolved Oxygen (mg/1)
1.1
2.2
12. M.B.A.S. (mg/1)
6.8
1.2
1.0
13. BOD/SS
0.87
0.60
0.42
14. BOD/VS
1.06
0.86
0.67
15. BOD/COD
0.86
0.72
0.50
16. % Reduction
a. BOD5
82
90
b. SS
74
80
c. VS
78
85
d. COD
78
84
e. Alkalinity
48
68
f. NHj-N
81
98
g. po4-p
4.9
4.9
h. M.B.A.S.
82
85
Mixed Liquor
Full Load
Half Load
17. MLSS (mg/1)
2,450
2,080
18. MLVSS (mg/1)
1,750
1,290
19. % Volatile
71
62
20. pH
7.2
7.3
21. SV30 (ml)
124
' 150
22. Sludge Density Index
1.97
1.39
23. Temperature (°C)
21.0
23.3
24. Dissolved Oxygen (mg/1)
1.0
2.4
25. lb. BOD/lb. MLSS
0.09
0.05
26. lb. BOD/lb. MLVSS
0.12
0.08
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