v>EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-79-078
July 1979
Research and Development
Evaluation of
Operation and
Maintenance
Factors Limiting
Biological
Wastewater
Treatment Plant
Performance
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution-sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-79-078
July 1979
EVALUATION OF OPERATION AND MAINTENANCE FACTORS
LIMITING BIOLOGICAL WASTEWATER TREATMENT PLANT PERFORMANCE
by
Albert C. Gray, Jr.
Paul E. Paul
Hugh D. Roberts
Gannett Fleming Corddry and Carpenter,
Harrisburg, Pennsylvania 17105
Inc.
Contract No. 68-03-2223
Project Officer
John M. Smith
Benjamin W. Lykins
Wastewater Research Division
Municipal Environmental Research Laboratory
Ohio 45268
I
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
dFFlGE OF 'RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U. S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U. S. Environmental Protection Agency, nor does men-
tion of trade names or commercial products constitute endorsement or recom-
mendation for use.
11
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health and
welfare of.theAmerican people. Noxious air, foul water, and spoiled land are .
tragic testimony to the deterioration of our natural environment. The com- .
plexity of that environment and the interplay between its.components require
a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solution
and it involves defining the problem, measuring its impact and searching for
solutions. The Municipal Environmental Research Laboratory develops new and
improved technology and systems for the prevention, treatment, and management
of wastewater and solid and hazardous waste pollutant discharges from municipal
and community sources, for the preservation and treatment of public drinking
water supplies, and to minimize the adverse economic, social, health, and
aesthetic effects of pollution. This publication is one of the products of
that research; a most vital communications link between the researcher and
the user community.
In the report documentation from comprehensive biological treatment plant
evaluations establishes cause and effect relationships for poor plant perform-
ance and the top ten factors causing poor performance are identified. A proce-
dure, called a Composite Correction Program, was developed and implemented to
improve plant performance. Unlike existing programs, the CCP approach
identifies all factors limiting plant performance at individual facilities and
solutions to all the problems are implemented. Results show that many plants
formerly not in compliance are performing to meet their design standards and
permit requirements without the need for major construction.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
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PREFACE
This document sets forth findings, conclusions, and recommendations as a
result of a two-year examination of selected biological wastewater treatment
facilities. The purpose of this investigation is to evaluate operational and
maintenance programs at biological facilities, identify deficiencies in such
programs, and determine where improvements in operation and maintenance will
upgrade plant performance to the point that secondary treatment is consistently
achieved. Two separate contracts were awarded by the U. S. Environmental Pro-
tection Agency for performance of investigations in the eastern and western
sectors of the country, respectively. The contract for the eastern study area,
which included Pennsylvania, Maryland, Virginia, and West Virginia, was
awarded to Gannett Fleming Corddry and Carpenter, Inc., Harrisburg, Pennsyl-
vania. M§I, Inc., Fort Collins, Colorado, was responsible for performing
these investigations in Colorado, Iowa, Montana, Nebraska, South Dakota, Utah,
and Wyoming.
From the inception of the study, it was apparent that both contractors
would need to follow the same general guidelines if the findings and recommen-
dations resulting from the two studies were ultimately to be compared. Cri-
teria for selection of candidate plants, field investigative practices, data
compilation and analysis, and reporting procedures had to be as uniform as
possible. However, it was not the intent of EPA, nor the contractors, to
make one study a duplicate of the other. Region-specific conditions made com-
plete uniformity of plant selection criteria impractical. Although plant se-
lection guidelines with respect to type of treatment, plant capacity, and
plant upgrading or enlargement were relatively uniform for both regional
studies, the issue of infiltration/inflow was treated differently by each con-
tractor. As a result of geologic and climatic conditions in those states com-
prising the eastern contractor's study area, infiltration/inflow in varying
degree is a widely existent phenomenon. Exclusion of a candidate plant from
this study base for that reason alone was not felt to be in the best interests
of the study, since many plants in the eastern region must be operated, and
will continue to be operated, with infiltration/inflow in the plant influent.
This infiltration/inflow was a problem identified at several sites in the
eastern study area. Such was not the case for the studies performed in the
western region, where excessive infiltration/inflow was a criterion for re-
jection of a plant as a study site. The investigations under the two con-
tracts were performed independently; yet in some respects the conclusions de-
veloped from the two studies were similar. Both contractors reported that
operational problems had a greater adverse impact on plant performance than
did design deficiencies. Furthermore, lack of application of biological pro-
cess control principles, inadequate process monitoring, no technical guidance,
inadequate training, and lack of a comprehensive operations manual, were
found to be the principal causes of performance problems in both study regions.
iv
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Accordingly, corrective actions as recommended by both contractors address the
matter of improving process control through instruction and application of pro-
cess testing and control theory.
In summary, the objectives and methods of the eastern and western regional
studies were parallel to the extent possible under constraints imposed by lo-
cal physical conditions. Findings and conclusions presented in each contrac-
tor's report were arrived at independently. The similarity in conclusions of
both studies indicates that the nature of current operational problems is not
related to treatment plant locality. Rather, the problems are fundamental and
involve the biological principles governing wastewater treatment processes.
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EXECUTIVE SUMMARY
Previous surveys conducted by the U. S. Environmental Protection Agency
have demonstrated that over half of the secondary treatment plants in this
country are not producing an effluent in compliance with the definition of
secondary treatment. Since, on the surface, most of these plants appeared to
be adequately designed for their respective organic and hydraulic loadings,
these surveys led to the conclusion that the performance of many plants could
be upgraded through improvement of operation and maintenance techniques. In
July 1975, Gannett Fleming Corddry and Carpenter, Inc. (GFCC), was retained by
the EPA to study operation and maintenance programs at selected biological
treatment plants in the eastern United States. The overall objective of the
24-month study was to identify and evaluate factors adversely affecting treat-
ment plant performance. By so doing it was felt that correction programs,
specifically aimed at ameliorating the identified major problem conditions at
each plant could be developed and that plant performance could be upgraded
without the need for major capital improvements.
The scope of this investigation was limited to facilities under the juris-
diction of EPA Region III. GFCC (with the assistance of the Chief of the Mu-
nicipal Permit Programs Branch) contacted the various state agencies within
Region III responsible for water pollution control. These agencies were re-
quested to identify candidate treatment facilities, meeting the following
criteria:
1. Plants must incorporate a biological treatment process as the
basic method of wastewater treatment.
2. Plants should have a history of inadequate performance as
measured by effluent quality.
3. Hydraulic capacities of plants should range from 1 to 5 mgd.
4. Plants should not be hydraulically or organically overloaded
to any great extent.
5. No enforcement action should be presently under way against the
municipality or authority involved. :
The treatment plant lists as submitted by' the various state agencies were
then reviewed, and plants which did not conform to one or more of the selec-
tion criteria were deleted. For those that did meet criteria, arrangements were
made for study personnel to conduct a site visit. The maximum duration of such
Visits was one day. Such site visits were conducted at 120 facilities during
the course of the investigation. During each site visit, various data were ob-
tained including process flow sheets, influent and effluent wastewater
VI
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characteristics, staff size,, plant laboratory characteristics, condition of
equipment, discharge permit criteria, and other information made available by
the superintendent at the time of the site visit. In addition, the plant oper-
ating personnel were questioned relative to problems interfering with plant
operations.
From those plants visited, 30 were selected for more comprehensive "pre-
liminary evaluation" studies, generally ranging from 3 to 5 days per plant.
Generally, the basis,for selecting a plant for study under the preliminary
evaluation phase was the apparent predominance of operation and maintenance re-
lated problems, rather than design inadequacies. Evidence of inadequate staff-
ing, process control deficiencies, improper maintenance, and insufficient
funding w.as noted during the site visits. Also noted were major design de-
ficiencies that could interfere with plant operability. Occasionally, plants
wer^s selected for study under the preliminary evaluation phase on the basis of
employing^nontypical treatment processes, in order to cover as many biological
treatment processes as' possible undeftthe study. As originally envisioned,
the presence of infiltration/inflow problems at the facility was to be justi-
fication for eliminating a plant as a preliminary evaluation candidate. How-
ever, infiltration/inflow is a widespread problem in the geographical area ex-
amined under this contract, and exclusion of a candidate plant for this reason
alone.was found not to be practical since many plants with significant oper-
ating problems would not have been eligible for further study. During each
preliminary evaluation, the most recent year's operating records were obtained,
sampling and analysis of influent, effluent, and interprocess flows were con-
ducted, ' and detailed budgetary information was obtained. In addition, oper-
ating personnel were interviewed extensively concerning many aspects of oper-
ations. Reports covering findings and conclusions for each preliminary eval-
uation were prepared and submitted to EPA.
One treatment plant, a 4.0 mgd complete mix activated sludge facility,
was the subject of an in-depth special study of about 3 months duration. The
purpose of the special study was to develop a control strategy for the sludge
bulking problem at the plant. Sludge bulking, in varied degrees, had been
identified under the preliminary evaluation phase as a major problem at many
activated sludge plants. Very little success in long-term alleviation of the
problem has been reported. This appears to be due in large measure to the
fact that in most cases the specific cause of the problem was not identified.
The special study was designed to identify the cause of the bulking problem,
and determine a method, of eliminating the cause, and therefore, increase the
likelihood of a successful control program.
Data collected during each.of the 3 project phases (site visit, prelimin-
ary evaluation, and special study) resulted in conclusions as summarized in the
following paragraphs. The site visit phase included a wide data base with
limited depth of investigations. Conclusions, therefore, are of a broad and
general nature. Conclusions forthcoming;from the preliminary evaluation are
qonsiderably more detailed with^respect to specific process problems and 0§M
programs. Conclusions from the.special study relate specifically to the prob-
lem of sludge bulking. ;
VII
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The 120 site visits resulted in data that suggested several trends or re-
lationships between treatment plant size or process type and various opera-
tional or administrative characteristics. Observations from the site visit
phase included:
1.
2.
3.
4.
5.
7.
8.
9.
Treatment plants serving the smaller populations tend to em-
ploy extended aeration, contact-stabilization, or trickling
filter processes. Large populations tend to be served by
conventional activated sludge plants.
Sixteen percent of all plants studied handle a high indus-
trial waste load. Thirty percent of the larger (10 mgd or
larger) plants receive high industrial waste loads. High in-
dustrial waste loads normally resulted in a total plant over-
load and reduced plant efficiency. There is no apparent cor-
relation between size or type of facility and impact of in-
dustrial waste on operation.
Forty- three percent of plants studied experience operating
problems as a result of receiving excessive volumes of infil-
tration/inflow. There is no apparent correlation between
size or type of facility and impact of infiltration/inflow on
operation.
Plants of greater than 5.0 mgd design capacity make signifi-
cantly greater use of their laboratories through both process
control testing and performance testing than do those less
than 5.0 mgd. Generally, the laboratories in larger plants
are better equipped and staffed.
Greater degree of process control is exercised in larger plants
(>5.0 mgd) than in smaller plants. Although somewhat greater
controllability is built into these facilities, the presence
of knowledgeable operators is the principal reason for the de-
gree of control.
more
Inadequate process control impacts activated sludge plants
severely than trickling filter plants.
Adequacy of maintenance programs shows a positive correlation
with size of facility.
On the average, the large plants contain a greater percentage
of new equipment than do the smaller plants, since most large
facilities tend to be better maintained and have more flexible
operating budgets, thus permitting timely replacement of equip-
ment. Smaller plants are frequently required to "make do" when
equipment fails.
Larger plants have significantly greater unit process backup
capability. Process type does not affect backup capability.
Vlll
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10. Larger.plants have better preventive maintenance programs
than do the smaller facilities. The extent of preventive •
maintenance programs is not related to process type. '
11. Technical references are considerably more complete at the
larger plants. These include 0§M manuals and literature
related to specific items of equipment. , '
12. Seventy-one percent of plants greater than 5 mgd design •••;•
capacity have auxiliary power provisions, while only 40
percent of those less than 5 mgd capacity have such pro-
visions. •
In general the site visit data indicated that there is a large degree of
variation among treatment plants in such areas as level of staff training, pro-
cess control, age or condition of equipment, and maintenance or housekeeping
procedures.
During the preliminary evaluation phase, the degree of impact of identi-
fied problem areas on plant performance was assessed. In conducting each pre-
liminary evaluation, the major areas that were investigated in detail included:
unit process performance and design adequacy, operational procedures and sup-
port facilities (0§M manuals, laboratory, etc.), maintenance programs, and ad-
ministrative aspects (staffing and budget). A Weighting and Ranking Table was
prepared whereby deficiencies and problems at each of the 30 plants studied
under the preliminary evaluation phase were reported. This table permitted
quantitative weighing of the problems, followed by a ranking of thejhighest
weighted problems. In all, 70 potential problem areas were addressed at each
facility. The 10 most frequently encountered problems were identified, and
ranked and are listed in decreasing order of severity as follows:
1. Operator application of treatment concepts and testing
to process control.
2. Infiltration/inflow
3. Process control testing procedures
4. Adequacy of OiJM manual
5. Industrial loading
6. Training
7. Hydraulic loading -:
8. Treatment understanding
9. Process controllability
10. Sludge treatment "
IX
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As the above ranking list indicates, inadequate plant performance is a
function of both specific design problems (loadings and processes) and oper-
ational deficiencies. However, the major conclusion of the preliminary evalu-
ation phase is that proper biological process control is not being practiced
at most treatment plants. This situation is partially due to -inadequate oper-
ator training. In many cases, however, it was found that operators with a :
good knowledge of biological treatment concepts are not controlling theif sys-
tems according to those concepts, indicating that the importance of process
control is apparently not fully appreciated.
In looking into the administrative aspects of treatment plant operation,
it was found that a significant number of plants were understaffed. When com-
pared against EPA staffing guidelines, over 50 percent of the plants studied
had staffs smaller than the recommended number. In many cases the adverse im-
pact of the small staff is not readily apparent, since buildings, equipment,
and grounds appear to be generally well maintained. However, this may simply
mean that manpower that could be used for process control is being diverted to
maintenance duties. Also, an indication of understaffing on the basis of EPA
guidelines does not necessarily mean these plants are not staffed adequately.
Rather, the guidelines themselves may be inaccurate, or for a particular
facility a relationship between staffing and plant performance is not present-
ly identifiable. Examination of the 0§M budgets for the 30 treatment plants
indicated that the level of funding in most cases is comparable with the na-
tional average for treatment plants of similar type and size. However, there
is reason to believe that upgrading the staffing and salary segment of the
average wastewater treatment budget would result in improved plant performance.
This is especially true for the smaller (<5 mgd) treatment systems.
The final study phase of the project consisted of a detailed investiga-
tion to identify the cause of sludge bulking at a special study plant and to
recommend physical or operational changes to eliminate the problem. The study
site was an activated sludge plant with flexibility and process control designed
into the system. However, since start-up, process control was virtually im-
possible as a result of bulking sludge. The bulking problem has limited re-
turn and wasting rates due to the dispersed nature of the sludge in the sec-
ondary clarifier. Thus, these important operational parameters could not be
adjusted to control the process F/M ratio and mean cell residence time. Pre-
vious attempts to "operate out of bulking" by such methods as shifting from
complete mix to contact stabilization had met with temporary, or no, success.
The special study was designed to illustrate a more scientific approach
to be taken to solve the bulking problem. Using samples of the mixed liquor,
the specific filamentous bacteria causing the settling problem were isolated
and identified. Thiothrix was found to be the major problem organism. Know-
ing the environmental conditions favoring the proliferation of Thiothrix,
sources of high sulfide concentration were sought. It was found that design
deficiencies in the sludge removal equipment in the final clarifiers caused
excessive sludge detention in certain areas of the clarifier bottoms. Ex-
tremely high sulfide concentrations were measured in these areas. The propen-
sity for high sulfide concentrations to stimulate the growth of Thiothrix has
been documented in the literature. Consequently, recommendations were made to
alter the clarifier sludge removal systems.
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During the site visit and preliminary evaluation phases, it was observed
that bulking causes poor effluent quality in many activated sludge plants of
all types. The special study points out that the cause of the problem is site
specific: each instance must be studied, the cause identified, then solutions
to resolve the problem can be determined and implemented to correct the prob-
lem. Nonspecific approaches, such as additions of chemical oxidants to the
aeration system or the return sludge flow, often treat the effect, rather than
the cause, of the process problem. Hence, such methods are likely to provide
only temporary relief arid, furthermore, represent an operating cost that may
not be necessary.
This report was submitted in partial fulfillment of Contract No. 68-03-
2223 by Gannett Fleming Corddry and Carpenter, Inc., Harrisburg, Pennsylvania,
under the sponsorship of the Environmental Protection Agency. Work described
in this report was accomplished during the period from June, 1975 to December,
1977.
xx
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CONTENTS
Foreword ...... ......................... •
Preface ................................ -^
Executive Summary ......................... • • v*
Figures ................................. X1V
Tables ....................... • ......... *^.
Acknowledgment ... .......................... XV11
1. Introduction ......................... 1
2. Conclusions ......................... 3
3. Recommendations ....................... 6
4. Research Approach ...................... 9
Site Visits ....................... 9
Preliminary Evaluations ................. 11
5. Evaluation of Causes of Limited Plant Performance ...... 16
Administration ...................... 16
Design .......................... 23
Operation ...... . .................. 27
Maintenance ....................... 29
6. Priority Listing of Problems ................. 36
7. Other Investigations - Special Study ... .......... 44
8. Relationship Between 0§M Parameters and Size and
Type of Facility ...................... 64
9. Impact of Established Programs on Priority Problems ..... 86
10. Potential for Improved Plant Performance ........... 92
References ....... - .................. ..... 101
Appendices
A. Summary of Site Visit Data - General Information ....... 103
B. Plant Evaluation Summary ............. . ..... 115
C. List of Recommendations from Preliminary Evaluation Reports . . 145
Xlll
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FIGURES
Number
1 Relationship between operation and maintenance expenditures
and plant design flow . 17
2 Comparison of actual operation and maintenance costs with
average costs at similar plants 18
3 Relationship between plant capacity and staff size 19
4 Relationship between actual staff sizes and recommended
EPA staff levels 20
5 Overall staff capabilities at site visit plants ....<... 22
6 Present average flow as a function of design flow (site
visit phase) 24
7 Present average flow as a function of design flow (pre-
liminary evaluation phase) ..... 24
8 Operation and maintenance performance indicators - plant
laboratory 28
9 Operation and maintenance performance indicators - process
control procedures 30
10 Operation and maintenance performance indicators - oper-
ation and maintenance manual - 31
11 Operation and maintenance performance indicators - routine
maintenance » 33
12 Operation and maintenance performance indicators - emer-
gency maintenance „ 34
13 Schematic of wastewater treatment facility .......... 45
14 Recommended reactor concentrations and waste rates « 49
15 Effect of return sludge rate on blanket depth 50
16 Effect of influent clarifier flow on blanket depth - 51
17 Relationship of return sludge rate to clarifier solids
concentrations 52
18 Gravitational settling velocity as a function of suspended
solids concentration ... 54
19 Transport of solids due to gravity sedimentation 55
20 Transport of solids due to sludge withdrawal 56
21 Transport of solids due to gravity sedimentation and sludge
withdrawal 56
22 Profile of H2S concentrations in final clarifier bottom
sludge 60
23 Profile of H2S concentrations in final clarifier bottom
3ludge 61
24 Relative number of plants with respect to design capacity • • 65
25 Relative number of plants with respect to facility type .... 65
xiv
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Number Page
26 Relationship between staff capabilities for operation
and size and type of facility . 70
27 Relationship between use of laboratory and size and
type of facility 71
28 Relationship between process control and size and
type of facility 73
29 Quality evaluation of technical references for operation ... 74
30 Evaluation of use of consulting engineering services" ..... 74
31 Relationship between staffing capabilities for mainte-
nance and size and type of facility 75
32 Relationship between age of equipment and size and type
of facility ..... 76
33 Relationship between spare parts inventory and size and
type of facility 77
34 Relationship between preventive maintenance and size
and type of facility 79
35 Relationship between emergency provisions and size and
type of facility 80
36 Relationship between backup unit provisions and size
and type of facility 81
37 Relationship between technical references for maintenance
and size and type of facility 82
38 Relationship between housekeeping practices and size and
type of facility 83
39 Relationship between availability of auxiliary power and
size and type of facility 85
xv
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TABLES
Number
1 Impact of recommendations on frequently encountered
problems ...... 7
2 Actual and recommended labor effort distributions . . 21
3 Plant evaluation summary (ten problems most frequently
encountered) 37
4 Plant evaluation summary (other problems encountered) 38
5 Mixed liquor settling velocity and gravity flux ........ 53
6 Microbiological characteristics of filamentous cells
in sludge at special study plant 57
7 Hydrogen sulfide concentrations 59
8 Relationship between service population and type and
size of facility .....; 66
9 Relationship between type of wastewater collection
system and type and size of facility 66
10 Relationship between year of most recent upgrading and
type and size of facility 67
11 Relationship between wastewater characteristics and
type and size of facility 67
12 Relationship between industrial waste impact and type
and size of facility 68
13 Relationship between infiltration/inflow impact and
type and size of facility . 69
14 Distribution of plants with respect to noncompliance
with NPDES permit standards •. . . . 93
15 Current annual effluent characteristics of preliminary
evaluation plants . * 94
16 Discharge pollutant loads based on NPDES permit levels
and present average annual flow ..... 95
17 Effluent characteristics attainable through implemen-
tation of recommendations 97
18 Anticipated effluent characteristics with NPDES permit
limits as goal 98
19 Improved performance evaluation 99
xvi
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ACKNOWLEDGMENTS
, -. This project was conducted by Gannett Fleming Corddry and Carpenter, Inc.
the principal investigators received substantial technical project contribu-
tions from the following staff:
... Gerald P. Voegler
Thomas E. Whittle
',: , . Raymond H. Myers
'.•--. * Steven C. Huntzinger
•:•'., Dennis W. Po.ntius
•. '-. John L. Latsha
The efforts of Mrs. Jean P. Lippincott in preparation of the final report
manuscript and of Mr. Donald W. Deppen in preparation of graphics were also
gratefully acknowledged.
Appreciation is expressed to all managers, operators, and other personnel
of the various.wastewater treatment facilities who participated in the re-
search effort. Appreciation is also expressed to all state and EPA regulatory
agency personnel who developed the various lists of facilities as research
candidates, and who actively participated in various phases of the research
program.
';'•.,,..,
The direction provided and assistance given by Mr. John Smith, Mr. Ben
Lykins,,and Mr. John Sheehy, of the Environmental Protection Agency, Office of
Research and Development, Cincinnati, Ohio, were greatly appreciated.
xvi i
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SECTION 1
INTRODUCTION
The Federal Water Pollution Control Act Amendments of 1972 established
specific goals for controlling wastewater discharges to meet certain water
quality objectives. Achieving these goals will require significant capital ex-
penditures for construction of new wastewater treatment plants and will also
require all treatment plants, both new and existing, to be operated effi-
ciently and effectively. Proper operation of new and modified plants, and im-
proved operations of existing ones, are essential if water quality goals are
to be met. Optimization of operation is critical to realizing the maximum re-
turn on the sizable investment being made for sophisticated pollution control
systems.
Operation and maintenance surveys conducted in accordance with Section
210 of the Act are included in the annual Clean Water Report to Congress. In
1973 and 1974, the years preceding this study, these surveys showed that
about one-third of all treatment plants constructed with federal grant assis-
tance were not operating at the design efficiency level when the plants were
inspected. These surveys showed severe deficiencies in the areas of operation
and maintenance, manpower, hydraulic load, laboratory facilities, and testing
programs. As a result the plants failed to meet their permit requirements
for effluent loadings of biochemical oxygen demand (BODs), suspended solids,
and settleable solids. These same shortcomings were also perceived by the
national and regional offices of the EPA.
This study was conducted to identify and rank the causes of poor perfor-
mance in biological treatment plants. Performance problems were studied on
three levels. One-day site visits were used to screen 120 candidate plants.
Thirty of these plants were selected for three- to five-day preliminary eval-
uations in which various administrative, design, operational, and maintenance
factors were examined. At one plant, identified as having a severe filamen-
tous bulking problem, a three-month extended study was made to identify the
cause of the bulking and to recommend specific corrective measures. Based on
the detailed studies at the preliminary evaluation level, a priority listing
of causative factors was developed. These problems represented those areas
most frequently identified as requiring application of corrective measures (ex-
clusive of major expenditures for construction) to bring treatment plant per-
formance into compliance with design intent and permit criteria. At each of
the thirty plants that was the subject of a three-to-five day intensive study,
recommendations to improve performance were made. The impact of implementing
these recommendations in terms of reduced pollutant loadings to the environ-
ment was assessed.
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The project which is discussed in the following pages represents a sig-
nificant first step in maximizing the return of the national investment in pol-
lution control facilities. There are many well-designed wastewater treatment
plants capable of high degrees of pollutant removal now on line, and the num-
ber is^continually increasing. However, the evidence indicates construction
of facilities is only part of the solution. Good operation, maintenance, and
administrative programs must be in force or the best of facilities will pro-
duce unacceptable effluent. Through projects such as this, areas where oper-
ational programs and procedures are weak can be identified. In this manner,
programs may be developed to optimize the efficiency of treatment systems
which currently have a partially untapped potential.
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SECTION 2
CONCLUSIONS
On the basis of the 30 preliminary evaluations conducted in the eastern
U. S. study area, treatment plant performance appears to be more limited by
operational, maintenance, and administrative shortcomings than by design
deficiencies or errors. The more common operational causes of inadequate plant
performance were:
1. Wastewater treatment concepts and process testing results were
not applied by the operators to control the biological process.
2. To varying degrees, personnel staffing most treatment facilities
were familiar with conventional process control techniques, but
this knowledge was not effectively applied in practice.
3. At most plants process testing was not performed at a level re-
quired for proper monitoring and control. Basic process con-
trol parameters such as MLSS, MLVSS, SVI, and F/M were fre-
quently not monitored.
4. Plant laboratory capabilities, including equipment, test pro-
cedures, and record keeping, were marginally adequate or in-
adequate in many cases.
5. 0§M manuals were either nonexistent or not comprehensive enough
to be of benefit to the plant staff.
6. Most .operators ha.d received some sort of training in waste-
water treatment technology. However, training programs were
general in nature and did not address plant-specific process
control or "troubleshooting" techniques.
Design-related limitations on plant performance were also noted during
the study, although not be the degree that operational problems were observed.
The more frequently encountered design related problems were:
I. Periodic hydraulic overloading as a result of excessive in-
filtration/inflow was widespread among plants in the study
region.
2. Process overloading occurred as a result of industrial waste
discharges, typically received by the plant in "slug" loadings.
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3. Lack of built-in controllability or flexibility, especially
in small package systems, resulted in limited performance
potential.
4. Inadequate sludge treatment or disposal capabilities limited
the control of sludge wasting and return rates, thereby in-
terfering with the operator's implementation of sound process
control strategies.
Maintenance programs and practices were examined at each of the prelimin-
ary evaluation sites and findings were as follows:
1. With the exception of spare parts inventories and parts pro-
curement, routine maintenance practices were marginally ade-
quate or better.
2. Housekeeping practices were generally satisfactory. In fact,
in many cases it was apparent that greater effort was devoted
toward maintaining plant appearance than was expended for ob-
taining optimal facility performance.
3. Emergency maintenance capabilities, including manpower, parts,
and equipment, are adequate at most facilities. However, im-
proved alarm systems and auxiliary power sources are needed.
Administrative deficiencies were occasionally found to be causes of poor
plant performance. The following items were specifically noted:
1. Total operating budgets at most of the preliminary evaluation
plants were nearly equal to or exceeded a calculated average
expenditure for operation and maintenance of plants of similar
size and type. However, budgets were frequently too general and
disorganized, making it difficult to determine how funds were ap-
portioned.
2. Approximately one-third of the facilities were staffed at a level
at least 20 percent less than that recommended by EPA staffing
guidelines.
3. In terms of labor categories, the greatest manpower deficiency
apparently existed in the area of maintenance. The validity of
this observation, however, is dependent on the accuracy with
which employee job titles and descriptions at each plant reflect
the employee's actual duties.
Over the past few years operational problems have been increasingly
recognized as limiting factors to treatment plant performance. As a result
programs and literature have been developed to aid the operator in optimiz-
ing performance. However, this study indicated that, to date, these programs
have had minimal impact on plant operations. According to observations at the
study sites, reasons for this minimal impact are as follows:
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1. EPA Technology Transfer information and Operation Manuals,
while readily available, are not reaching a large percent-
age of the operators.
2. Process control information presented in training courses
and certification programs is not being carried over into
the field. It is apparent that operators find it difficult
to relate the theoretical information presented in such
courses to the specific operating problems at their plants.
3. Operations and troubleshooting seminars presented by EPA
are not widely attended by operators.
4. Technical assistance is available through operations con-
sultation groups in some consulting engineering firms, but
municipalities rarely take advantage of this on a continuous
or regular basis. This is undoubtedly due to cost of such
services.
5. OfJM manuals as currently prepared do, not reflect the input
of the plant operating staff, and operators, therefore, often
find these manuals difficult to follow. The manuals are sel-^
• dom used on a day-to-day basis.
As a part of each preliminary evaluation, specific recommendations were
set forth for improving plant performance. The primary intent of these recom-
mendations was to set forth nonstructural modifications, addressing areas such
as training, process monitoring and control, 0§M manual preparation, and
budgeting for plant operations. The actual impact of implementing these
recommendations is not known. However, on the basis of engineering judgement
an estimate of attainable wastewater quality at each plant was developed. On
the basis of these estimates, compliance with NPDES permit limitations by the
30 plants would improve from 79 percent to 90 percent for BODs and from 55
percent to 86 percent for suspended solids, strictly as a result of implement-
ing the recommended operational improvements.
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SECTION 3
RECOMMENDATIONS
The results of this study show that there is significant potential for im-
proving performance of biological treatment systems through upgrading opera-
tion and maintenace practices. The specific areas where operation, mainte-
nance, or administration of wastewater treatment facilities apparently fall
short have been discussed in detail. As a result of this study there is little
doubt that there are tangible benefits to the environment to be gained through
operationally improving the performance of biological treatment plants, and
closing the gap between design intent and current effluent quality. Eight
specific recommendations are offered toward the ultimate achievement of the
above objective.
1. Operator training programs should be expanded and improved
to address process control technology and to emphasize the
direct impact of continuous process control on effluent qual-
ity. Positive step-by-step control strategies should be pre-
sented and fully explained. This could be done at state
level and tied in with certification programs, or through
the federal government's training activities. Also, site-
specific training programs should be provided for large or
complex treatment systems to provide the operating staffs
with a hands-on knowledge of available process control tech-
niques .
2. Positive action should be taken to assure process control
is practiced at treatment facilities to optimize performance.
An example of such positive action would be regulatory agency
monitoring of process control by requiring various process
parameters be reported along with the effluent quality param-
eters now specified in discharge permits.
3. More involvement of consulting engineers and other recognized
experts in technical operations assistance should be encouraged
and, in some cases, possibly be made a grant eligible cost.
4. During the design stage, more attention should be directed to the
treatment plant laboratory, especially at smaller (<5 mgd) fa-
cilities. The intent would be to insure that adequate facil-
ities are provided for effluent process control testing and
thorough wastewater characterization.
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5. More comprehensive and understandable process control de-
scriptions should be provided to operators by design engi-
neers and technical assistance sources. Such information
should be included in the plant operation and maintenance
manual, which in turn should reference manuals provided
through state and federal government for augmentation and
clarification of theory as necessary.
6. Budgeting for operation and maintenance of wastewater treat-
ment facilities must become more organized and needs-
sensitive. This is especially true in the case of the smaller
(<5 mgd) treatment systems. Higher priority for wastewater
treatment in the municipal budget must be established.
7. Mechanisms to attract, and keep, high-caliber operators should
be identified and implemented. Included might be higher en-
try level educational background requirements, higher salaries,
increased opportunities for advanced training, and better de-
fined potential for advancement. The status of the treatment
plant superintendent as a key public works official must be es-
tablished.
8. Operability and flexibility should be carefully considered dur-
ing the design process. This, of course, will do little for
existing plants, but may significantly reduce future problems.
If possible, the principal operating personnel to be employed
at the plant should be retained during the final design stages.
Their comments, criticisms, and suggestions should be fully
evaluated by the design engineer. Significant future operating
problems might thereby be avoided.
The recommendations set forth above are designed to reduce or remove the
negative impacts of the priority problem areas identified by this study.
Table 1 shows the problem areas which each of the recommendations as offered
below will impact.
TABLE 1. IMPACT OP RECOMMENDATIONS ON FREQUENTLY ENCOUNTERED PROBLEMS
Problem
Operator application of concepts and
testing to process control
Infi1tration/inflow
Process control testing
0§M manual adequacy
Industrial loading
Training
x
x
X
X
Recommendation
x
x
x
x
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TABLE 1 (continued)
Recommendation
123456
7 8
Problem
Hydraulic loading
Treatment understanding
Process controllability
Sludge treatment
x
x
Finally, this study has answered some questions with regard to where op-
erational programs are weak, and what impact these deficiencies are having ori
treatment plant performance. However, some questions have not been fully
answered, and the advisability of further study is indicated. We, therefore,
recommend that the investigations discussed herein be continued to provide a
greater data base for further identification of operational, maintenance, and
administrative areas, where improvement could result in better levels of treat-
ment plant performance. It is also recommended that certain problems identi-
fied during this investigation be studied in greater depth, so that the most
effective remedial programs may be evolved. An example is operator training.
It has been concluded that the level of training, to which many supervisory
operators have been exposed, has not, to date, been implemented in plant oper-
ation. The question must be raised relative to why there exists a gap between
knowledge of biological treatment principles, and implementation of these
principles in process control. A more intensive study of training programs
and methods of transferring classroom theory to field application, than could
be conducted within the scope of the present investigation, should provide
insight into this problem. Another area where further study seems advisable
is adequacy of wastewater treatment plant operations funding. It is apparent
that some treatment plants are underfunded, and performance suffers as a di- :
rect result. However, it is difficult to determine the severity of budget
deficiencies, or the specific areas where increased funding would have the
greatest positive impact. No standards for comparison to determine budget
adequacy on a unit pollutant removal basis exist.
The above are but a few examples where continued and increased study is
likely to help in the effort to achieve greater levels of performance from
existing treatment facilities.' There is little question that much is to be
gained through concentrating on.improving operational or administrative pro-
grams at wastewater treatment facilities. The maximum return on the national
investment in pollution control equipment has not yet been realized. Increas-
ing this return requires improvement of operational programs. This objective
should be heavily emphasized in research activities for the immediate future.
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SECTION 4
RESEARCH APPROACH
In this section the research approach on which this two-year investiga-
tion was structured will be described. This discussion will be broken down
into two subsections, the first dealing with research approach employed for the
site visit phase, and the second dealing with research approach employed for
the preliminary evaluation phase. The special study research approach will be
presented in the section devoted to that study (Section 7). Research ap-
proaches for all study phases were evolved prior to initiation of field stud-
ies, but some minor changes in approach were made as the project proceeded,
in an effort to optimize efficiency of data aquisition.
SITE VISITS
Prior to conducting in-depth evaluations, wastewater treatment facilities
were subjected to a screening process, whereby plants experiencing problems of
an operational or maintenance nature were identified. Throughout the project,
this screening process has been referred to as the site visit phase. Gener-
ally, those plants which were reportedly experiencing operation and mainte-
nance problems were recommended as candidates for comprehensive study in the
preliminary evaluation phase.
The procedure for selecting treatment facilities to be examined in the
site visit phase was established early in the project. As the eastern con-
tractor, Gannett Fleming Corddry and Carpenter, Inc. (GFCC), contacted repre-
sentatives at the EPA Region III office in Philadelphia, Pennsylvania, and re-
quested assistance in obtaining information regarding candidate plants for
site visits. Through a combined effort between the Region III office and the
state regulatory agencies, plants were identified which appeared to comply with
selection criteria developed to assist in differentiating between operational
and nonoperational problems. Briefly, these selection criteria were:
1. The plant must incorporate some type of biological treatment
process as the major wastewater treatment system. The pro-
cesses considered include numerous activated sludge modes
(conventional, extended aeration, complete mix, contact stab-
ilization, step aeration, and pure oxygen), fixed film sys-
tems (trickling filter and rotating biological disc), and
aerated lagoons.
2. Although not restrictive, a significant number of candidate
plants should range in size from 3,785 to 18,925 m3/d (1.0
to 5.0 mgd).
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3. The plant should not be overloaded with respect to either
flow or pollutant load, or have other readily identifiable
design deficiencies.
4. The plant should not be in the process of designing or con-
structing additions to the facility for purposes of upgrad-
ing the degree of treatment.
5. The history of the facility should be such that the plant
has encountered difficulty in achieving discharge limita-
tions .
Utilizing data in their files, the Region III office compiled a preliminary-
list of candidate plants for site visits. Additions and comments were solic-
ited from the Pennsylvania Department of Environmental Resources, the Maryland
Department of Natural Resources, the Virginia State Water Control Board, and
the West Virginia Department of Natural Resources. Following review by the
state agencies, the lists of potential plants were reviewed by GFCC and plants
were selected for site visits.
Following the selection of plants for site visits, the state agencies
were requested to arrange the visits according to a schedule prepared by GFCC.
In those cases in which the agencies preferred not to conduct the scheduling,
GFCC personnel made arrangements directly with the facilities. Depending on
the size of the facility, the type of treatment process, and the location of
the plant, the duration of .the visit was either one-half day or one day. Be-
cause of the informal nature of the visit, arrangements were typically made
with the respective plant superintendents or chief operators.
Typically, the site visits consisted of a complete tour of each treatment
facility and an interview of the superintendent or chief operator. Informa-
tion gathered during the visits was divided into three major categories: gen-
eral information, operation, and maintenance. The nature and extent of infor-
mation collected under each of these categories is as follows:
General Information
Owner and operator of the treatment facilities, design flow, type of pro-
cess, year of original construction, year of most recent upgrading, service
population, raw wastewater characteristics (percentage of industrial waste),
type of sanitary wastewater collection system (separate or combined with storm-
water), name of receiving body of water, impact of infiltration/inflow, and
impact of industrial wastewater discharges.
Operation
Number of operators, operational scheduling (eight hours per day, round-
the-clock), staff certification (number of certified operators, levels of cer-
tification), operator training programs (i.e., Sacramento and Clemson series),
analytical capabilities (apparatus, sampling techniques, testing methods, and
records), process control testing, plant performance monitoring, process con-
trol techniques, technical references for operation (comprehensive operations
10
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manual, equipment manufacturer information), and use of consulting engineering
services.
Maintenance
Staff capabilities for maintaining facility, age of equipment, spare parts
inventory, preventive maintenance programs, emergency maintenance provisions,
"housekeeping" practices, backup unit capabilities, technical reference for
maintenance, and auxiliary power capability.
In addition to the foregoing, the plant superintendents were given the
opportunity to verbally provide information regarding specific problems of
both operational and design natures.
Following the visit, 2- to 3-page report was prepared which summarized
the information collected during the site visit, noted the problems as stated
by the superintendent, and recommended or rejected the facility for further
study in the preliminary evaluation phase. Although site visits were con-
ducted at 120 treatment facilities, formal reports, describing specific oper-
ational and maintenance programs, design criteria, and administrative prac-
tices were prepared for only 80 plants. In the early stages of the project,
the purpose of the site visits was simply to screen facilities for further
study. After completing about one-third of the visits, this phase of the proj-
ect was expanded in scope to include preparing and submitting reports to EPA.
Thus, the information reported for the plants varies with respect to the time
of the site visit. As a means of quantifying the data collected during the
site visits, each plant characteristic was assigned a numerical value from.
zero to three, having the following interpretations:
Rating
3 Plant is deficient in this area. Capability
is nonexistent. Considerable problems result.
2 Plant may be deficient in this area. Capa-
bility is inadequate. Some problems result.
1 Plant may be deficient in this area. Capa-
bility is marginally adequate. Little or
no problems result.
0 No apparent deficiencies exist. Capability
appears adequate. No problems are apparent.
Appendix A presents a tabulation of the data collected throughout the site
visit phase of the project.
PRELIMINARY EVALUATIONS
The purpose of the preliminary evaluation phase was to examine the per-
formance of the individual wastewater treatment facilities and the unit pro-
cesses comprising each facility, to evaluate existing operation, maintenance,
11
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and administrative programs and practices, to identify and rank problems caus-
ing poor plant performance and to make specific recommendations for improving
plant performance. In theory, the thirty plants chosen for preliminary eval-
uation were selected on the basis of experiencing operation and maintenance
related problems, as identified during the site visit phase. However, a few
plants were chosen as a result of employing relatively uncommon biological
treatment processes (i.e., pure oxygen activated sludge) rather than because
they were experiencing performance problems. This was done in an attempt to
have the biological study based on as complete a data base as possible. In
several cases, a problem which had been identified during the site visit as
operational in nature was later determined, as a result of more in-depth in-
formation subsequent from the preliminary evaluation, to be design oriented.
Consequently, not all the treatment facilities for which preliminary evalu-
ations were conducted fully met all of the previously designated criteria for
conducting such a study.
The original intent of the research approach was to exclude plants that
were experiencing significant infiltration/inflow (I/T) problems. However,
in the area designated for study under this contract, I/I was very widespread,
due to high yearly precipitation,, topography and geological conditions. There-
fore, it was found to be impractical to exclude a site from further study for
reasons of I/I alone, especially if the I/I problem was not causing severe
hydraulic overloading. It was further felt that exclusion of plants with I/I
present in their collection systems would bias the study results insofar as
identification of problems at typical plants in the study area was concerned.
For these reasons I/I alone was not considered a basis for rejection of a
plant for-continued study under the project scope. It might also be added
that the presence of I/I was not always detectable during the short site visit
due to the condition of flow monitoring devices, or the record keeping prac-
tices, at a given treatment plant.
As described above, plants,were selected as candidates for preliminary
evaluation from those to which site visits had been made. Because of the ex-
tensive scope of work required for the preliminary evaluation studies, three
entities were normally contacted in order to obtain permission to conduct the
survey; namely, the plant superintendent; municipal authority chairman,
borough manager, or director of public works; and the consulting engineer for
the facility. The scope and goals of the project were explained to each.
Since assurance was given that the project was for research purposes, and that
information obtained during the survey would not be used for purposes of en-
forcement, any misgivings were removed and permission to conduct the survey
was granted in all, cases.
The surveys were conducted at thirty biological wastewater treatment
plants continuously from December51975 to March 1977. Initially, five days
were required to obtain the necessary data for preparing the preliminary eval-
uation report. However, as the field personnel became more familiar with the
survey procedures, and more efficient data collection methods were developed,
the individual investigations were reduced to 3-day studies. Similarly, in
the early stages of the study, two or three field personnel, ranging from en-
vironmental technicians to registered professional engineers, were normally
involved in the performance of each survey, whereas a single investigator
12
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normally conducted a survey later in the project. To some extent, however,
the duration and manpower required for a preliminary evaluation study was a
function of the size and complexity of the plant.
During a typical preliminary evaluation survey, the field personnel per-
formed the following tasks:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Obtain plant monitoring records for year preceding site visit. .
Whenever possible, records included results of both process con-
trol and performance monitoring.
Conduct survey gaging, sampling, and analysis program, including
field tests (i.e., pH, dissolved oxygen, settleable solids),
major unit process influent and effluent monitoring, unit pro-
;ampling (i.e,,, mixed liquor), and sludge treatment proc
major f
cess sampling (i.e
testing.
mixed liquor), and sludge treatment process
Complete Plant Evaluation Summary (Weighting and Ranking Table).
This table provides the means for subjectively quantifying de-
sign, operation, maintenance, and administrative problems ex-
perienced at the treatment facility. Design factors, operation,
maintenance, and administrative programs and practices are as-
signed a value from 0 to 3 which corresponds to decreasing
degrees of quality and completeness.
Complete, or obtain previously completed, EPA Form 7500-5 (Report
on Operation of Wastewater Treatment Plant). When completed
previously by EPA personnel, this form contained usable infor-
mation regarding operation and maintenance practices.
Examine present plant staffing noting distribution of labor ef-
forts in the work categories of management, operation, mainte-
nance, arid laboratory.
Gather specific information on analytical capabilities includ-
ing available laboratory equipment, sampling techniques, test-
ing methods, test frequencies, and analytical records.
Observe process control techniques employed by operating staff.
Obtain basic design information for major unit treatment pro-
cesses, including tank sizes, detention times, overflow rates,
and loadings.
Obtain copies of National Pollutant Discharge Elimination Sys-
tem (NPDES) permit and state regulatory agency permit.
Secure copy of wastewater treatment budget or most recent
record of expenditures.
13
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11. Address specific questions to plant superintendent regarding
maintenance practices to supplement information obtained dur-
ing the site visit.
12. Review available operation and maintenance manual and similar
references for content, including equipment information, mainte-
nance schedules, laboratory and process control techniques,
parts procurement, and as-built plans.
Upon completion of the field investigations, a preliminary evaluation re-
port was prepared which set forth the findings of the survey, and evaluate the
plant in terms of performance, design adequacy, operation and maintenance,
and administrative procedures. The following items were included in the prep-
aration of each report:
1. Use of a computer program, developed specifically for this proj-
ect, for analyzing the plant performance data. The printout pro-
vided a mathematical interpretation of the plant influent and
effluent quality, as well as individual unit treatment process
loadings and operating parameters. Also, the plant effluent
data were computed in terms of 7- and 30-day average concentra-
tions for purposes of comparison with NPDES permit requirements.
2. Results of analyses at Gannett-McCreath Laboratories on waste-
water and sludge samples collected during the survey. Tests
typically conducted included BOD^, various solids examinations,
fecal coliform, nutrient analyses, and occasional metal deter-
minations .
3. Comparison of plant design information with conventional design
standards. Sources of such standards were the EPA process de-
sign manuals, the "Ten States Standards", and various waste-
water treatment technology texts.
4. Comparison of plant performance data, using both the plant oper-
ating records and the results of the evaluation survey tests,
with NPDES and state permit requirements.
5. Comparison of individual unit process performance parameters
with accepted operating standards (i.e., primary clarifier ef-
ficiencies, overflow rates, detention times, MLSS concentra-
tions, food-to-microorganism ratios, and mean cell residence
times) .
6. Use of a specially developed computer program for determining
optimum staffing levels in accordance with the EPA report,
"Estimating Staffing for Municipal Wastewater Treatment Facil-
ities." The actual staffing patterns were then examined in
light of the recommended levels.
14
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Development of a unit cost for treatment using unit costs
set forth in the EPA document "A Guide to the Selection
of Cost Effective Wastewater Treatment Systems" and com-
parison with actual unit costs of treatment. Based on GFCC
in-house experience and cost information, the unit costs
from the document were adjusted to correct for increased
labor and material costs. The adjusted values from the re-
port were then used to compare expenditures at the various
plants with average funding levels.
Conclusions and recommendations for improving performance.
Recommendations were made for optimizing operation and mainte-
nance practices, improving staffing and budgetary conditions,
and making minor physical modifications.
15
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SECTION 5
EVALUATION OF CAUSES OF
LIMITED PLANT PERFORMANCE
In this section the various factors found in this study to affect treat-
ment plant performance will be discussed in detail. The discussion will be
broken down according to the four categories of data collected during the
evaluations; administration, operation, maintenance, and design.
ADMINISTRATION
Traditionally, wastewater treatment has been a low priority item for many
municipalities. Even in those cases where authorities have been formed to meet
the needs of the community, the attitude that properly treating the sanitary
wastewaters is not as important as other municipal functions frequently pre-
vails. In many cases local governments and authorities are reluctant to in-
crease taxes or sewer use rentals to offset rising costs of treatment because
of the general attitude of the public toward waste treatment. It is somewhat
paradoxical that although public opinion has moved toward improving the en-
vironment in recent years, the need for improved performance of existing treat-
ment facilities is not often considered in the same context by the public. As
a result many treatment facilities are operated with inadequate budgets or
staffs. As an average, salaries of wastewater treatment plant personnel are be-
low the level for persons with similar technical responsibilities. Therefore,
the personnel employed generally require considerable on-the-job training to
compensate for a minimal technical background.
During the preliminary evaluation phase, plant administration was ex-
amined with respect to expenditures, staffing, operator motivation, adminis-
trative policies, and morale. In particular, budgetary and staffing matters
were examined in detail. Areas such as operator salary scales, motivation,
and morale were rarely found to be primary sources of performance problems
in the thirty plants studied. Specifically, insufficient salary was identified
as a source of significant problems at only two treatment plants. Motivation
was identified as a minor problem at four installations. Our own previous
experience has indicated that treatment facilities can be operated to produce
an acceptable effluent (e.g., meets permit requirements) despite low salary
levels. However, we must be extremely careful when interpreting the findings
of this study relative to salaries, motivation and related areas. During an
evaluation of the type comprising this study, where the investigators are ex-
posed to the plant staff for only a short time, problems of low morale and
salary dissatisfaction can go undetected. Furthermore, the results of low
salary scales may be indirect. For example, high-priority primary performance-
limiting problems such as lack of implementation of process control techniques
or inadequate testing may be caused, in part, by the lack of incentive
16
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assocaited with low salary scales and unidentifiable opportunities for advance-
ment. Upgrading the salary level of the wastewater treatment plant operator
classification position should put the municipality in a position to compete
for more technically qualified individuals. This would, in turn, increase
professionalism in the treatment industry and result in more conscientious
operation of facilities.
Adequate funds are required to effectively operate and maintain treat-
ment facilities. The rising costs of labor, energy, chemicals, and equipment
parts should be met by the users of the treatment systems. During the pre-
liminary evaluation phase, the current budgets or actual expenditures, where
available, were examined. From this information, the unit cost of providing
wastewater treatment was determined for each facility using its design flow as
a base. The results are presented in Figure 1. The dispersion of the data
points result -from process variables such as the need for chemical addition,
use of additional unit treatment processes (primary clarification, filtration,
and effluent polishing), and methods of sludge treatment and disposal. Vari-
ations in quality and completeness of budgets submitted also contributed to
dispersion in the data. As indicated, unit costs of treatment ranged from 50
cents per 3.78 nrVd (1,000 gallons) for a small, package-type plant to less
than 15 cents per 3.78 rn^/d (1,000 gallons) for a large, activated sludge
facility. Although the data points are widely scattered, an economy of scale
is indicated by the regression line.
9 ACTIVATED SLUDGE
m TRICKLING FILTER
50
«> 40
O
O
O
£ 30
CL
8
20-
10
0.2 0.5 1.0 2.0 5.0
SIZE OF PLANT (MGD)
10.0 20.0
Figure 1. Relationship Between Operation and Maintenance Expenditures and
Design Plant Flow
17
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To roughly assess the adequacy of the funds allocated for wastewater
treatment at each of the plants studied, a common reference was needed to
serve as a basis for comparison. The EPA technical report entitled, "A Guide
to the Selection of Cost-Effective Wastewater Treatment Systems," was used as
a means for computing theoretical operation and maintenance cost requirements
for various sizes and types of treatment facilities, inasmuch as the EPA
document was developed to perform relative cost comparisons among process
trains and not for absolute cost estimation, adjustments to the factors set
forth in the publication were made based on GFCC experience. Adjustments to
the cost data were made to account for inflation and increased cost of power
and materials since those data were collected and published. Theoretical unit
costs were calculated for each preliminary evaluation plant and compared to
the unit operational costs, determined using the plant budget and records of
expenditures.
The comparison of the treatment costs incurred at 30 plants with the de-
rived costs (from EPA reports) of operation based on type and size of facil-
ity is shown in Figure 2. Actual expenditures at 18 of the plants surveyed
were equal to or exceeded by the respective derived costs and were within 10
percent of the derived costs at two additional plants. However, six plants
indicated expenditures at least 20 percent less than the derived amount for
operation and maintenance. As might be expected, those six plants found to be
significantly underbudgeted also were found to have other operation and main-
tenance shortcomings. Size and coverage of the plant staff and familiarity
of >the local administrative body with the needs of the plant were rated
Statistically poorer at the underfunded plants. Knowledge of wastewater
treatment theory and preventive maintenance practices also tended to be rated
lowest at those facilities.
20
is
16
14
-
10
'
6
4
2
0
< 70% 70-80% 80-90% 90-99% >IOO%
PERCENT OF AVERAGE COSTS
Figure 2. Comparison of Actual Operation and Maintenance Costs with Average
Costs at Similar Plants
18
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Proper staffing, with respect to both numbers and capabilities, is the key
to effective operation of any wastewater treatment plant. During both the
site visit and preliminary evaluation phases, considerable effort was devoted
to examining staff capabilities at each plant. Figure 3 shows the relation-
ship between plant capacity and staff size for the plants examined during the
site visit phase. The figure shows the number of staff per unit of treated
flow decreases as design capacity increases above 37,850 m3/d (10 mgd).
10 12 14 16 18
PLANT CAPACITY (MGD)
20 22 24 26
30
Figure 3. Relationship Between Plant Capacity and Staff Size
As with budgeting, a published document was used as a basis for compari-
son to evaluate staffing adequacy. The EPA document, "Estimating Staffing for
Municipal Wastewater Treatment Facilities," was used to determine a recommended
staffing requirement for each of the preliminary evaluation plants. Using the
procedures in this report, the levels of effort to be devoted to the six major
labor categories (supervisory, operation, maintenance, laboratory, yardwork,
and clerical) were determined for each plant, These requirements were then
compared with the actual labor distribution as given by the superintendent at
each facility. Figure 4 shows the comparison between actual and recommended
staff levels. As the figure indicates, nine of the 30 plants were staffed at
a level at least 20 percent less than the recommended number. This analysis
is necessarily quite crude and serves only as a "first cut" look at the plant
19
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I2T
10"
Q m p
< 6--
a!
<50% 50-80% 80-90% 90-99% > 100%
PERCENT OF RECOMMENDED STAFF SIZE
Figure 4.
Levels
Relationship Between Actual Staff Sizes and Recommended EPA Staff
staffing picture. Assumptions intrinsic to the estimating procedure, such as
the quantitative productivity of manpower, can significantly affect the re-
sults. On the basis of reasonable assumptions, however, it would appear that
about one-third of the preliminary evaluation plants were slightly under-
staffed. As was earlier discussed concerning the salary and motivation situ-
ation, undei'staffing, while not identified as a major primary problem, may
indirectly contribute to the plant performance deficiencies.
Table 2 presents a summary comparison of actual and recommended distribu-
tions of labor for the preliminary evaluation plants. Upon inspecting the
table, several points were noted:
1. With respect to supervision and operation, no discernable
pattern existed. The number of plants with inadequacies
(28) was approximately equal to the number with excessive
efforts (25) devoted to the two categories.
2. Overall, manpower allocated to laboratory functions exceeded
the recommended level. This is not consistent with the low
degree of process control testing observed at the study sites.
No relationship appeared to exist between the complexity of the
plant monitoring requirements and the laboratory manpower.
20
_
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3. Sufficient manpower was not devoted to maintenance. Of the
major labor categories, deficiencies in manpower were the
greatest for maintenance.
Adequate staff size alone is not sufficient. The personnel at the waste-
water treatment facility should be trained and appropriately certified, and
should have an understanding of basic treatment fundamentals. For this study
the use of training programs by treatment plant personnel was defined as the
operator's enrollment in relevant courses. The adequacy or inadequacy of
such courses has not been determined in this study. Similarly, certification
refers to the level and number of certified operators at a particular facil-
ity, irrespective of the requirements of the certification programs or their
effectiveness.
Information obtained from the treatment plant personnel during the site
visit phase has been interpreted to evaluate the basic capabilities of the
operating staff. The term "staff capabilities", is a composite of the numer-
ical values (see Section 4 - Research Approach) assigned to the staff-related
characteristics. To develop the composite characteristic> four primary factors
(staff size, training, certification, and treatment understanding) have been
weighted, according to their estimated impact on the overall capability of the
staff, and combined. According to the weighting system, both staff size and
treatment understanding have been weighted heavier than training and certifica-
tion, since in our experience the former two characteristics more directly im-
pact the performance of the plants. For purposes of graphical presentation,
the levels of quality of completeness corresponding to the numerical ratings
(0, 1, 2, e>r 3) have been shown as good, fair, poor, and critical. Figure 5
shows the relative number of plants having good, fair, poor, or critical staff
capabilities. As the figure indicates, staff capabilities at 69 percent (or
73^ of 106 plants so rated) were judged adequate. The reader is reminded that
this analysis includes all plants visited under the site visit phase. There-
fore, in many cases judgements concerning staff capabilities were the result
of observations over a period of less than one day.
Figure 5. Overall Staff Capabilities
at Site Visit Plants
22
_
-------
DESIGN . : . •
Each preliminary evaluation included the examination of plant design in-
formation. Included were the analyses of total plant hydraulic and organic
loadings, unit process designs, including sludge treatment processes, and
plant flexibility. Since the primary objective of the project was to identify
areas in which increased performance efficiency could result through improved
operation and maintenance practices, design-, limit ing factors had to be iden-
tified, before the potential of improved operation and maintenance .programs
could be evaluated.
As noted previously, the main purpose of conducting the site visits was
to screen out plants not suitable for the more extensive preliminary evalu-
ation. One of the criteria for selection as a preliminary evaluation plant
was that the facility should not be hydraulically or organically overloaded to
a significant extent. For this reason, only a few plants studied in that
phase were subjected to hydraulic and pollutant overloads as a result of non-
extraneous noninfiltration/inflow related discharges. For the most part, the
organic overloads were a result of industrial wastewaters containing high pol-
lutant concentrations. Of the 30 plants evaluated, five were reportedly ex-
periencing organic overloading. The nature of the overloads was such that
fluctuations in influent BODs levels, rather than a continuous overload, were
reported at the treatment plants, presumably the result of slug industrial dis-
charges.
Continuous hydraulic overloading did not occur at any preliminary evalu-
ation plants. The majority of the plants were experiencing excessive fluctu-
ations in hydraulic loadings, occasionally exceeding design capacities. This
situation was attributed to infiltration of groundwater and storm-water in-
flow, rather than legitimate discharges from sewered customers. Infiltration/
inflow is a widespread, almost universal, problem in treatment plant collec-
tion systems in the geographical area of this study, although the problem
varies in degree. In several instances the volume of infiltration/inflow was
sufficient to cause major treatment process upsets in suspended growth systems,
either by causing a "washout" of solids from the secondary clarifier or by
diluting the sanitary wastewater to the point that a reasonable biomass load-
ing could not be maintained.
Figures 6 and 7, respectively, show a distribution of plants with respect
to present average flow as a function of design capacity for the site visit
and preliminary evaluation phases. As Figure 6 indicates, recorded flows at
27 plants examined under the site visit phase exceeded the design hydraulic
capacity on an average daily basis. This was a surprisingly high number con-
sidering that the site visit plants were selected from lists supplied by state
environmental control agencies who were instructed to exclude hydraulically
overloaded plants from consideration. It appears there is some need for state
regulatory agencies to update their information relative to treatment plant
status. Figure 7 shows that investigations during the preliminary evaluation
phase showed two plants to be 25 to 50 percent hydraulically overloaded on an
average daily basis. Five plants were found to be hydraulically overloaded,
but at a level of less than 25 percent over design. As previously discussed
the two plants experiencing the higher overloads had major performance problems
23
-------
50T
4O •
30-•
o 2O
10
100-
124%
125-
149%
>I50%
PERCENT OF DESIGN FLOW
Figure 6. Present Average Flow as a Function of Design Flow (Site Visit Phase)
o 4.
100-
124%
125- >I50%
149%
PERCENT OF DESIGN FLOW
Figure 7. Present Average Flow as a Function of Design Flow (Preliminary
Evaluation Phase)
attributable to hydraulics. It was doubtful that operation and maintenance
techniques could overcome this design problem at those two facilities.
24
-------
A comparison of unit process design to actual operating conditions was
made on an individual unit basis at each preliminary evaluation site. Design
information was obtained from the plant basis of design and drawings where
available. These were supplemented by field measurements where necessary. De-
sign adequacy was judged on the basis of experience and recognized published
information including: various EPA process design manuals; the "Recommended
Standards for Sewage Works - Great Lakes-Upper Mississippi River Board of
Sanitary Engineers", commonly referred to as the Ten-States Standards; and
wastewater treatment technology texts. Since the design of nearly all exist-
ing secondary wastewater treatment plants was subject to the review of the re-
spective state environmental agencies, the unit process design of these facil-
ities would be expected to conform with the design criteria adopted by the in-
dividual states, such as the Ten-States Standards. Nevertheless, unit pro-
cesses at several plants were noted to be improperly designed. At several
plants, sufficient detention time was not provided as a result of inadequate
baffling in the chlorine contact tank, possibly resulting in incomplete disin-
fection. At Plant OS9, weir loadings in the primary clarification stage ex-
ceeded the recommended limit by 500 percent, causing solids carry-over to sub-
sequent unit processes. At one contact-stabilization facility, Plant 006, the
two discrete aeration stages were not separated as called for in the design,
although performance problems could not be directly identified as a result of
this deficiency.
A basic problem was noted in the design of the contact-stabilization pro-
cess at several plants. Specifically, excessive detention time was provided
in the contact aeration stage. These plants were designed in accordance with
appropriate state standards, but it is the design standards which erroneously
specified the extended contact detention time to provide a factor of safety.
In practice, the excessive contact times have been shown to result in pre-
mature stabilization in the contact zone and, subsequently, a near-endogenous
condition in the reaeration zone. As a result, the adsorptive properties of
the active biomass in the contact zone were not fully utilized and the bio-
logical process did not perform as intended. In effect, the factor of safety
subverted the biological theory on which the contact-stabilization process is
based.
As opposed to process design errors, a number of plants were found to have
other design deficiencies, such as the lack of grit removal or primary clarif-
ication units, resulting in excessive primary solids being conveyed to the bio-
logical units. Although the majority of the facilities designed without such
preliminary and primary units did not appear to be adversely affected on a
regular basis, according to the plant staffs, performance problems at those
plants periodically occurred as a result of the inability to keep inert solids
from entering the biological phase.
Process controllability was found to be a problem primarily with the
smaller package-type (contact-stabilization or extended aeration) treatment
facilities. Suspended growth systems sized less than 3,785 m3/d (1 mgd) often
lacked the capability to vary and monitor air supply and to control return
sludge rates. Similarly, many of the package-type facilities were outfitted
with air-lift pumps for returning activated sludge which have historically
limited the ability of the operators to control the process. Controllability
25
-------
at many plants was limited by sludge handling and disposal facilities.
will be discussed further below.
This
Built-in operating flexibility was reported to be a constraint in two
cases. Although a number of plants (predominantly the smaller facilities) did
not have multiple unit capabilities for the major unit processes, performance
problems were rarely associated with that deficiency. The majority of the
package-type activated sludge treatment plants could be operated in only a
single mode (e.g., complete mix, extended aeration, contact-stabilization).
However, in no cases did a preliminary evaluation conclude that performance
problems would be reduced or eliminated through changing modes of operation.
In addition, the inability to bypass individual treatment units frequently re-
sulted in difficulty in performing maintenance service on those units, al-
though performance was usually not adversely affected on a long-term basis.
Several plants studied during the preliminary evaluation phase were ex-
periencing performance problems as a result of design deficiencies (or errors)
relative to sludge treatment and disposal. At a number of activated sludge
facilities, inadequate sludge stabilization and dewatering capabilities re-
sulted in excessive solids being retained in the treatment system or dis-
charged in the final effluent. At Plant 005, the drying beds were critically
undersized, which prevented the operator from wasting sludge at proper inter-
vals. A problem at Plant Q9.3 was reported to be a combination of inadequate
sludge digestion and drying capacity, and insufficient sludge disposal sites.
As^a result of inadequate sludge thickening capacity at Plant 059, the wet
oxidation unit could not sustain itself at the sludge wasting level required
by process considerations without auxiliary fuel. Therefore, to save fuel
costs, sludge wasting was controlled by the capacity of the thickener to pro-
duce a suitably thickened sludge.
It should be noted that control of sludge wasting rate is the primary
mechanism for control of the activated sludge process, regardless of specific
control strategy used (e.g., F/M, SRT, or oxygen uptake control). But a major
finding of this study is that process control is not being applied by most
operators. Therefore, many may not even be aware of sludge handling inade-
quacies until they become severe enough to result in physical problems.
Performance problems at two facilities appeared to be related solely to
the poor performance of proprietary biological units in the process scheme,
rather than to system design errors. At Plant 0.48, a relatively uncommon pro-
prietary activated sludge unit called an Aero Accelator was cited as the
source of performance problems. The physical characteristics of the unit were
such that intermixing of the thickening zone in the clarification chamber and
the aeration zone existed, causing turbulence, thereby inhibiting settling and
limiting return sludge solids concentrations,. In the second situation, Plant
07.7, which uses a combination of trickling filters and rotating biological con-
tactors, was not obtaining the level of treatment from the bio-discs that was
guaranteed by the manufacturer. Attempts to improve performance through vary-
ing the mode of operation had met with little success.
In summary, the primary purpose of the preliminary evaluation phase was to
identify operation and maintenance related problems limiting plant performance
26
-------
and making recommendations for their alleviation, However, routine examina-
tion of design parameters showed many plants, previously thought to be ade-
quately designed, had design-related problems. Such design problems, if not
corrected, would, limit the degree to which improved operation and maintenance
programs could upgrade plant performance. Recommendations for corrective
operation and maintenance programs must be made within the constraints of de-
sign adequacy.
OPERATION
The third major category of factors affecting plant performance is that
of operation, which includes process control adequacy and capabilities, use
and adequacy of the plant laboratory, and technical guidance availability.
Assessing various aspects of plant operation was necessarily a subjective pro-
cedure based on the experience of the preliminary evaluation field personnel,
all of whom were engineers and licensed operators. Factors were rated as ade-
quate, marginal, inadequate, or nonexistent. Evaluation of specific practices
or capabilities took into account related factors such as plant size, process
type, and permit requirementsx In this sense the standards against which
operational factors were judged varied among plants. However, the meanings of
the four descriptive terms in all cases were the following:
1.
4.
Adequate - practice or capability was not limiting to plant
performance, and could not be substantially im-
proved.
Marginal - practice or capability was not normally limiting
to plant performance, but could be improved.
Inadequate - practice or capability was insufficient to the
extent that it inhibited plant performance.
Nonexistent - no provision existed at the plant for that
facet of operation.
Information concerning the laboratories at the preliminary evaluation
plants is graphically summarized in Figure 8, The laboratories of the plants
surveyed generally met the requirements for performance monitoring established
under federal and state agency permits. Three-fourths of the plants displayed
adequate or marginally adequate laboratory equipment and analytical capabil-
ities. Most plants followed approved procedures for sample .collection, pres-
ervation, and analysis, and kept records documenting the results. Several of
the smaller plants used an outside laboratory for monitoring.
Most plants possessed the equipment and capabilities to perform process
control testing. However, testing programs for this purpose were less satis-
factory than they were for performance monitoring. Many smaller facilities
did not monitor such important parameters as the mixed liquor suspended solids
and settleability in suspended growth systems. A surprising number of facil-
ities of all sizes had never determined any basic process control parameters
such as the F/M, MCRT, or SVI.
27
-------
30 T
30 T
UJ
EQUIPMENT
ANALYTICAL CAPABILITIES
30 T
1
<
d
30 T
20-
IO--
ui
RECORDS
SAMPLING PROCEDURES
Figure 8. Operation and Maintenance Performance Indicators - Plant
Laboratory
28
_
-------
In the area of process control procedures shown in Figure 9, staffs at 17
of the plants showed an adequate understanding of process control fundamentals,
based on personal interviews and assessment of training levels. However, few-
er than half of the staffs applied such knowledge to plant operation in an at-
tempt to exercise control and stabilize the process.
Preliminary reasons appeared to be the inabilities to interpret labora-
tory data, determine and implement operating changes, and evaluate the system
response. This was particularly true for suspended growth systems where pro-
cess control is most complex.
In varying degrees of completeness, the plant staffs had several re-
sources available for technical operating assistance, including consultant-
prepared 0§M manuals, manufacturers' equipment information, and operations
assistance from consulting engineers or other experts. Figure 10 presents a
graphical summary of various criteria used to evaluate plant operating manuals,
including completeness, clarity with which operating procedures are set forth,
information on key equipment (i.e., pumps and aerators), and level of use by
plant personnel. As the figure indicates, half of the plants surveyed lacked
a complete 0§M manual.. Even in plants where an 0§M manual was available, the
manual frequently contained no detailed operating procedures or ranges for key
process control parameters. The 0§M manuals examined relied heavily on the
equipment and maintenance information supplied by the manufacturers, but
lacked process control instructions. In some cases a binder of equipment in-
formation was all that was available. Also, the figure shows that operators
frequently did not make use of the manuals and were often unfamiliar with
ther content.
Manufacturers' equipment information is typically provided to plants.
Such literature usually contains satisfactory instructions for required main-
tenance and procurement of spare parts. It was found that plants having this
material used it often. However, such information was of no use as far as
operating procedures or process control parameters were concerned, and is not
considered a substitute for a comprehensive 0§M manual.
Another source of technical operating assistance is the consulting engi-
neer. Most of the treatment plants studied reported having occasional contact
with the design engineer, but had no formal arrangement with a consultant for
technical assistance. Operational and process expertise available through
consulting engineers and other experts remains a little-used resource at this
time.
MAINTENANCE
Treatment plant maintenance was evaluated in terms of preventive and
emergency capabilities, treatment reliability, and causes of inadequate main-
tenance .
Routine maintenance indicators, including intervals between preventive
maintenance on equipment, spare parts supplies stocked at the plant (bearings,
seals, etc.), treatment reliability or absence of downtime, and housekeeping
practices (laboratory orderliness, yard appearance, etc.) were evaluated
29
-------
H!
u.
o
30
20-
10-
LU
U.
O
30
20 +
10-
UJ
PROCESS UNDERSTANDING
PROCESS
CONTROL EXERCISED
30 T
INTERPRETATION OF
RESPONSE TO CONTROL
RECORDS
Figure 9. Operation and Maintenance Performance Indicators - Process Control
Procedures
30
-------
g
OL
U.
O
30T
20-
30 T
QUALITY AND COMPLETENESS
OPERATING PROCEDURES
30 T
EQUIPMENT INFORMATION
USE BY OPERATORS
Figure 10. Operation and Maintenance Performance Indicators - Operation and
Maintenance Manual
31
-------
individually. Also, emergency maintenance capabilities, such as backup units,
ease of procuring parts, records of repairs, and the presence of alarm systems
were evaluated. Figures 11. and 12 summarize the findings of the prelimianry
evaluation phase with respect to routine and emergency maintenance programs.
The majority of the plants surveyed performed an adequate amount of preventive
maintenance as determined by the observed condition of the equipment and
records of maintenance-related downtime. Housekeeping also was generally sat-
isfactory. ^Most plants kept records of repairs and major preventive mainte-
nance activities, including a description of the problem, parts repaired or
replaced, and the date of repair. Record keeping and scheduling were often
less organized than desirable, and could be improved. Parts accessibility and
procurement were not a frequent problem.
Both audio and visual alarm systems to major equipment failures, such as
failure of the influent wastewater pumps or power outages, were present in 67
percent of the treatment systems. These are designed to alert the operator (or
alert other individuals if plant is unattended) in the event of failure or ab-
normality. Failure of other motorized or electrical equipment was indicated
with warning lights on the control panels at each plant.
Nearly all facilities had portable pumps and equipment for emergency re-
covery, although there exists much variation in the amount of suitability of
such equipment. Additional manpower and equipment was normally available from
other municipal departments. Most plants, however, had not developed a
problem-specific response plan that could be implemented in the event of an
emergency.
As Figure 12 indicates, about 85 percent of the treatment plants surveyed
in the preliminary evaluation phase were judged to have at least marginal or
better backup unit availability. This was a natural consequence of the fact
that most treatment plants were designed with dual units in parallel for the
key unit processes. Only very small C<3,785 m3/d (1 mgd)] plants were the ex-
ception. Dual or multiple units allowed at least partial treatment to con-
tinue when a unit was down for maintenance. Partial treatment refers to the
fact that the unit remaining in service may have been overloaded and unable
to operate at design efficiency. Regular preventive maintenance coupled with
the backup unit availability resulted in over half of the plants studied be-
ing judged to have adequate treatment reliability. Treatment reliability in
this sense refers to the minimization of downtime due to mechanical failures,
not to effluent quality. Those plants that did demonstrate inadequate treat-
ment reliability were characterized by excessive delays in response to equip-
ment malfunctions. This was often due to difficulties in procuring replace-
ment parts.
In addition to the above discussed ratings assigned to various mainte-
nance factors, several additional observations should be noted. Maintenance
staffing was generally below levels recommended in EPA reports. This was
most noticeable in small plants. The degree of adverse impact on plant per-
formance due to maintenance inadequacies was greater for suspended growth sys-
tems than for trickling filter plants. This was a result of the greater com-
plexity and interdependency of unit processes at the former facilities.
Finally, while 75 percent of the plants carried at least a marginal supply of
32
-------
If)
3
Q_
O
O
30T
20--
10- •
O.
U.
O
O
30'
20+
10"
MAINTENANCE
INTERVALS
SPARE PARTS
INVENTORY
301
20
u.
o
g 10--
30 T
TREATMENT
RELIABILITY
HOUSEKEEPING
PRACTICES
Figure 11.
nance
Operation and Maintenance Performance Indicators - Routine Mainte-
33
-------
CO
z
-------
commonly used spare parts, or were able to obtain them locally, delivery on
major parts such as motors or impellers was often on the order of months.
Such parts do not fail frequently and are expensive; so storage on-site was
not "practical. Therefore, the prolonged delivery times have been responsible
for periods of poor plant performance.
35
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SECTION 6.
PRIORITY LISTING OF PROBLEMS '"'"
The ranking tables prepared for each of the preliminary evaluation plants,
included as Appendix B, set forth the major problems noted at each facil-
ity. Since the majority of the data were collected during the 30-plant pre-
liminary evaluation phase, these data form the basis for the major conclu-, '
sions. Table 3, Plant Evaluation Summary, presents a priority listing of ten
factors which most frequently and severely affect biological treatment plant
performance. The top ten causes have been taken from the earlier discussed
Weighting and Ranking tables prepared for each of the 30 preliminary evalu-
ation plants. The total number of points assigned to each of the problem
areas and the number of times that each factor was determined to be the most
critical cause of treatment problems is also indicated. . Other plant perfor-
mance limiting problems, which were not included among the ten major problems,
are set forth in Table 4. These are listed in order of .decreasing adverse im-
pact on performance according to the number of points accumulated for each
problem on the 30 weighting and ranking tables.
Table 3 shows that the most significant cause of performance problems was
the lack of application of treatment concepts and unit operation testing in
controlling the biological process. This factor was, ranked as the most severe
deficiency at four of the 30 plants investigated. The third-ranked cause of
performance problems, namely, the lack of an adequate process control testing
program, is closely related to the first-ranked problem. A significant number
of treatment facilities, especially those employing a suspended growth process,
did not employ a process testing program. Specifically, standard unit oper-
ation control tests, such as mixed liquor suspended solids, mixed liquor disT.Q
solved oxygen, mixed liquor settleable solids, and return sludge suspended
solids, were seldom or never conducted at plants studied. Furthermore, im-
portant operating parameters, including sludge volume index (SVI), food-to-
microorganism ratio (F/M) and mean cell residence time (MCRT), were usually
not determined. Without testing procedures as described above, effective pro-
cess control is not likely.
Of noteworthy importance is the fact that the level of knowledge of the
individual staffs at the various plants concerning wastewater treatment funda-
mentals was judged to be less of a problem than was the application of this
knowledge. This situation is illustrated by the eighth place ranking that
treatment understanding has been assigned. In many cases, the operators were
familiar with process control tests and the application of concepts to process
control, but exercised little or no process control in their operations. There-
fore, although two of the highest ranked problem areas were associated with
process control, it appears that the lack of unit operation testing and process
control are not necessarily a result of inadequate training or comprehension
36;
-------
TABLE 3. PLANT EVALUATION SUMMARY
(Ten Problems Most Frequently Encountered)
Nature of
Problem
Operation
Design
Operation
Operation
Design
Operation
Design
Operation
Design
Design
Cause
Operator application of concepts
and testing to process control
Infiltration/ inflow
Process control testing
0§M manual adequacy
Industrial loading
Training
Hydraulic loading
Treatment understanding
Process controllability
Sludge treatment
Total
Points
49
44
36
34
19
18
17
15
15
14
Times
Ranked No.
4
4
-
-
1
-
2
1
1
3
37
-------
TABLE 4. PLANT EVALUATION SUMMARY
(Other Problems Encountered)
Nature of
Problem
Operation
Design
Operation
Maintenance
Design
Admini strat ion
Design
Maintenance
Administration
Administration
Maintenance
Design
Design
Design
Maintenance
Design
(continued)
Cause
Process control technical
guidance
Unit design adequacy-aerator
Performance monitoring
Spare parts inventory
Organic loading
Plant staff - number
Unit design adequacy -
disinfection
Preventive maintenance -
lack of program
Plant administrators -
familiarity with plant needs
Plant staff - plant coverage
Maintenance - manpower
Unit design adequacy - primary
Sludge wasting and return
Flow proportioning to units
Critical parts procurement
Lack of standby units for
key equipment
Total
Points
14
14
14
13
12
11
11
10
10
10
10
10
9
9
8
8
Times
Ranked No. 1
4
2
38
-------
TABLE 4. (continued)
Nature of
Problem
Design
Administration
Operation
Maintenance
Design
Design
Maintenance
Maintenance
Design
Maintenance
Administration
Administration
Design
Design
Design
Maintenance
Administration
Design
Operation
Design
Design
(continued)
Cause
Plant inoperability due to weather
Insufficient funding
Equipment malfunction
Preventive maintenance -
references available
Unit design adequacy -
process flexibility
Submerged weirs
Equipment age
Housekeeping practices
Alternate power source
Maintenance scheduling
and recording
Plant staff - productivity
Plant staff - motivation
Plant location
Lack of unit bypass
Ultimate sludge disposal
Emergency maintenance -
technical guidance
Plant administrators -
policies
Return process stream loading
Shift staffing adequacy
Unit accessibility
Toxic loading
Total
Points
8
7
7
6
6
6
5
5
5
4
4
4
4
4
3
3
3
3
3
3
3
Times
Ranked No. 1
39
-------
TABLE 4. (continued)
Nature of
Problem
Admini st rat ion
Operation
Maintenance
Administration
Design
Design
Operation
Administration
Operation
Design
Design
Design
Administration
Cause
Plant staff - wages
0§M manual - use by operators
Emergency maintenance -
staff expertise
Plant staff - supervision
Alarm systems
Flow backup
Certification level of
operators
Personnel turnover
Education level of operators
Process automation - control
Process automation - monitoring
Seasonal variation in loading
Plant staff - working conditions
Total Times
Points Ranked No. 1
3
2
2
2 -
2
2
2
2
1
1
1
1
1
40
-------
in these areas, but rather the lack of -application of (or inability to apply)
learned techniques. Although the reasons for this condition have not been
identified, it is believed that a basic lack of interest in, or incentive for,
process, control underlies the problem. Perhaps a disbelief in the merits of
process control techniques by the operator contributes to the problem. Also,
treatment knowledge notwithstanding, the individuals operating the majority -,
of treatment plants studied in this project, especially the smaller ones,
were inclined to be maintenance oriented rather than process oriented. , In ;•
other words, the attention of the operator was directed at keeping the plant
operating, rather than keeping the process at high performance levels. "
The second most frequent cause of performance problems at the thirty pre-
liminary evaluation plants was determined to, be infiltration/inflow. Although
constant hydraulic overloading was considered to be justification for elimin-
ation of a plant from further study at the outset of-the project, periodic
surging as a result of excessive infiltration/inflowwas found to exist at a
majority of the facilities visited. The topographic and meteorological nature
of the four states surveyed make infiltration/inflow a widespread problem.
For this reason, preliminary evaluations were conducted at a number of plants,
which, although they were not constantly hydraulically overloaded, experienced
severe fluctuations in flow rate. (See "Research Approach Section"). The most
notable and significant process problem caused by these surges was "washout" •:
of the suspended growth systems as a result of a loss of solids from the final
clarification stage during high flow periods. Also, the increases in extrane-
ous water caused the raw wastewater. to become dilute and the biological pro-
cesses, both fixed and suspended, were loaded at much less than optimal levels.
Inadequacy of (or lack of) a ;comprehensive operations and maintenance
manual was ranked as the fourth most severe cause of plant performance prob-
lems. This condition existed at a large number of plants. However, the fact
that this particular item was never judged to be the most serious cause of
problems at any given plant indicates15that although, the situation is wide-
spread, the measurable adverse impact on plant performance often is moderate.
As noted previously, the weighting and ranking process is necessarily sub-
jective. With respect to operations and maintenance manuals, the observation
of the investigating team was generally that a competent plant staff could
overcome the inadequate manual through the use of available manufacturer's
equipment information, as-built plans, readily obtainable operations publica-
tions as provided by EPA, and wastewater treatment technology texts. However,
the poor quality of most plant 0§M manuals undoubtedly has contributed to the
general de-emphasis of process control.
The fifth most frequently observed cause of performance problems was in-
dustrial loading. It is noted that there is a significant break in total
points between the fourth and fifth problem. Although industrial loading was
ranked as the number one cause of performance problems at one facility, the
total number of assigned points indicates that a minority of plants were ad-
versely affected by industrial wastewaters. Generally, these industrial
wastewaters caused fluctuating flows and pollutant loads as a result of inter-
mittent discharges. In addition, the nature of the industrial wastewaters was
usually such that the problems resulted from excessive compatible pollutant
levels, rather than incompatible or toxic wastes. In this study, types of
41-
-------
industries responsible for process upsets and plant overloading included food
processing, dairy, and textile manufacturing and dyeing.
Inadequate training was determined to be the sixth ranked cause of per-
formance problems. At the plants, evaluated, most of the personnel had re-
ceived some form of training, such as the Sacramento or Clemson wastewater
treatment courses. In six cases (as determined by a weight of 2 or 3 in the
weighting and ranking process) inexperienced personnel with little or no train-
ing were responsible for the operation of primarily small (<1 mgd) but rela-
tively complex plants, most of which employed suspended growth systems. The
relatively low point total suggests that the cause was not widespread and also
supports the hypothesis that the problem of inadequate process control is re-
lated more to application of control concepts than to a lack of knowledge of
techniques.
Three causes of performance problems were found to be directly associated
with characteristics of the plant service area. Two of these factors, infil-
tration/inflow and industrial loading, were discussed previously. Hydraulic
loading, which refers to the relationship between actual plant flows and de-
sign flows, was the number one cause of performance problems at only two facil-
ities and accumulated a total of only seventeen points. Its overall impact
on plant performance was moderate. Although hydraulic loading and infiltration
/inflow are closely related, a facility may be adversely affected by infil-
tration/inflow although hydraulic overloading may not be a problem. Specifi-
cally, in some plants studied in this project infiltration/inflow resulted in
a dilute wastewater, causing the biological system to be underfed and un-
stable. Direct impacts of hydraulic overloading consisted primarily of ex-
cessive process overflow rates, weir loading rates, and/or inadequate unit
process detention times.
Process controllability and sludge treatment were ranked respectively as
the ninth and tenth most frequently encountered causes of performance problems.
Both of these factors are design related and indicate the need for improve-
ments in design at several facilities. Inadequate process controllability
included, as examples, the inability to vary rates of return sludge, recircu-
lation of trickling filter effluent, and air input. As a result, the operator
was unable to "tune" his treatment system to the varying demands which were
placed on it by hydraulic and organic loading fluctuations.
The tenth ranked problem, sludge treatment, was the number one cause of
performance problems at three of the preliminary evaluation plants. Those
plants lacked adequate waste sludge handling, dewatering, or ultimate dis-
posal facilities. All of the rational procedures for activated sludge pro-
cess control use sludge wasting to set the control parameters (F/M, SRT, 02
uptake). Therefore, if the operator's ability to waste sludge is determined
by available equipment rather than process consideration, proper process con-
trol is not possible. Under the most severe conditions, a buildup of sludge
in the system results in the loss of solids in the final effluent. It was
found during this study that the latter condition is often erroneously diag-
nosed as sludge bulking.
42
-------
In summary, the major factors found to inhibit treatment plant perfor-
mance could be divided into three categories; operator oriented, design ori-
ented, and service area oriented. Through the weighting and ranking procedure,
the most widespread deficiency at treatment plants studied was found to be
operator oriented. A sound process control program was notably absent at many
plants. The service area problem was infiltration/inflow, and this of course
could be corrected through inspection and repair of collection systems. Al-
though design deficiencies and problems from industrial wastes were found to
exist, in many cases the adverse effects could probably be minimized using
sound process control techniques.
43
-------
SECTION 7
OTHER INVESTIGATIONS - SPECIAL STUDY
Each preliminary evaluation was designed to identify various aspects of
plant design, operation, maintenance, and administration that were adversely
affecting plant performance. Data obtained during the studies indicate that
poor sludge settleability, or sludge bulking, is a common problem among the
various types of activated sludge processes. Bulking sludge interferes with
plant performance and effluent quality by hindering solids settling and allow-
ing excess solids to overflow the secondary clarifier weirs. It also subverts
the controllability of an activated sludge process: sludge age, biomass load-
ing, and mixed liquor concentrations cannot be directly controlled by sludge
wasting when uncontrolled amounts of solids are leaving the system in the
plant effluent.
Because of the direct adverse impact that sludge bulking has on treatment
plant performance, and the widespread occurrence of the problem, a special
study was conducted at a regional treatment facility, designated as Plant 32
in Appendix A. The plant had also been the subject of a preliminary evalu-
ation study. The principal conclusion of the preliminary evaluation was that
poor sludge settleability was limiting the performance of the system. Al-
though some possible contributing factors to this problem were set forth in
the preliminary evaluation report, the available data were not sufficient to
support definitive conclusions. The plant, therefore, was considered an ap-
propriate site to conduct an in-depth study of the bulking phenomenon. The
study was undertaken to identify the direct cause of poor sludge settleability
at this plant, and to recommend operational procedures for eliminating the
problem.
The scope of the special study included, as a first step, a look at the
conventional approaches to eliminating bulking. These included F/M control,
aeration control, and selection of the operating mode for the activated sludge
system (e.g., complete mix vs. contact stabilization). Secondly, the per-
formance characteristics of the secondary clarifiers and sludge return capa-
bilities were investigated in detail. Thirdly, microbiological studies were
performed to identify the dominant filamentous organisms in the bulking sludge.
By identifying these bacteria and determining the environmental conditions
that favor their growth, the operator can formulate and implement a rational
control strategy to eliminate them.
This study was performed over a period of about three months, from mid-
winter through early spring 1977. Historically, the winter months have been
the period of the most severe sludge bulking problems at this particular
facility. The time of year chosen for the study, therefore, allowed maximum
opportunity to observe and evaluate the problem.
44
-------
DESCRIPTION OF TREATMENT PLANT
The special study plant is a conventional activated sludge facility with
the flexibility to be operated as a complete mix or contact stabilization pro-
cess. It has an average design flow of 15,140 m3/d (12.0 mgd), A process
flow schematic is presented in Figure 13. The major treatment units are two
circular primary clarifiers, two rectangular aeration tanks, two rapid sludge
removal-type circular secondary clarifiers, four multi-media filter beds, a
chlorine contact tank, and a post aeration basin. The multi-media filters
were not in use during the study and, in fact, have not been used for any
significant length of time since plant start-up in 1973, This has been pri-
marily due to the high level of solids in the secondary clarifier effluent and
the resultant rapid plugging of the filters. Under such conditions, the cycle
time between backwashings becomes unreasonably short, and the filter system is
basically" inoperable.
INFLUENT
EFFLUENT
ASH
DISPOSAL
Figure 13. Schematic of Wastewater Treatment Facility
Primary sludge and waste activated sludge are handled by thickening, cen-
trifugation, and fluidized bed incineration. Centrifuge centrate, filter
backwash, and thickener overflow are returned to the head of the plant.
The treatment facility examined under the special study phase is not
automated. All significant process control parameters are set by the oper-
ator including aeration rates, sludge return rates, and sludge wasting rates.
The operator also controls the routing of flow through the plant such that :
45
-------
complete mix activated sludge or contact stabilization is the treatment mode.
A lighted graphic panel indicates important plant equipment and various inter-
connections. The status of operation of each item is indicated by signals at
a control console. All major plant equipment may be controlled through the
control panel or by localized control at each particular unit. Dissolved
oxygen and pH probes are located in each of the two aeration tanks and pro-
vide continuous readout at the control panel for mixed liquor D.O. and pH.
Totalizers indicate flows occurring in various components. All additional
sampling and analysis for process control is done manually. Samples are ob-
tained daily from the primary distribution chamber and secondary clarifiers
for BODs and suspended solids analyses. Daily samples are obtained from each
aeration tank and analyzed for suspended solids and volatile suspended solids.
Therefore, between the automatic sensing devices and the plant laboratory,
all information necessary for process control may be obtained.
From a review of the basis of design, the various treatment units at the
plant are considered adequately sized and equipped to handle the flows and
loadings. When properly operating, the process should be capable of providing
the degree of treatment required by the discharge permit. Flexibility is pro-
vided in that dissolved oxygen may be controlled via the variable speed
aerators, mixed liquor concentrations and sludge age may be controlled through
adjustment of sludge return and wasting rates, and the process flow configur-
ation may be varied between the complete mix and contact-stabilization modes.
With this amount of process flexibility, optimization of the process should
be possible. However, sludge bulking can subvert the entire process by thwart-
ing proper operation of the aeration tanks, secondary clarifiers, sludge re-
turn system, and multi-media filters.
PRELIMINARY EVALUATION CONCLUSIONS
A general conclusion of the referenced preliminary evaluation report was
that the problem of poor solids separation in the final clarifiers resulted in
a high concentration of suspended solids passing over, the weirs. The con-
dition was attributed to sludge bulking. Microscopic analysis of the mixed
liquors during the bulking period showed that a large percentage of the micro-
bial population were filamentous bacteria types which cause sludge settleabil-
ity problems. At the time of the preliminary evaluation, plant operating per-
sonnel had not been able to determine the cause of the sludge bulking, or to
successfully prevent the problem.
Possible causes for the sludge bulking problem as listed in the prelimin-
ary report included:
1. Large variations in influent organic strength.
2. Frequent change in process configuration.
3. Insufficient process control (F/M, sludge wasting,
sludge return).
46
-------
The report concluded that a more consistent level of- organic loading to
the aeration system should be achieved. Recommendations to accomplish this
stability included:
1. Development of a thorough knowledge of the contributing
industrial wastewater.
2. Establishment of a schedule of the variation in
industrial flows and strengths.
3. Installation of a holding system to equalize industrial
waste loadings.
4. Elimination of the sources of infiltration.
5. Addition of chemical flocculants, such as lime, to the
primary clarifier system to aid in settling during
periods of high pollutant loadings.
Also included in the preliminary report was the recommendation that the
media filtration system be operated according to the design intent. It was
recognized that this was not possible under the conditions created by sludge
bulking because of rapid clogging in the filter beds.
Bulking activated sludge is sludge that occupies excessive volume after
sufficient time has been allowed for settling. The effect of filamentous
bacteria in increasing the bulk of activated sludge is primarily mechanical;
that is, the filaments protrude from the sludge particles and physically hold
them apart.
Filamentous organisms are of two basic types: bacterial, which are most
prevalent in municipal sewages; and fungi, which are usually most prevalent in
industrial wastewaters. The more common bacteria are Sphaerotilus natans,
Bacilus cereus, Thiothrix and Beggiatoa, while the more common fungi are Geo-
trichum, Candida and Trichoderma.
There are many suggested causes for sludge bulking. Some of the commonly
cited causes are low dissolved oxygen concentrations in the aeration tanks,
excessively low or high food to microorganism ratios, high sulfide levels in
the wastewater (indicative of septic wastewater), and extensive variations- in
organic loadings to the system. Many industrial wastes also can stimulate
growth of filamentous organisms by causing fluctuating or excessively high or-
ganic concentrations, which result in low dissolved oxygen levels, creating
the ideal conditions for bulking sludge.
Many remedies have been proposed for controlling bulking sludge. Some of
these include mixed liquor chlorination and hydrogen peroxide treatment, in-
creasing the dissolved oxygen of the return sludge, adding flocculant aids,
and optimizing the sludge loading rate. All but the last of these treat the
effect rather than the cause and, as such, are only temporary. This has been
47
-------
demonstrated at numerous treatment plants where bulking problems have returned
after attenuation of the chemical additions. An approach more likely to meet
with long-term success would consist of isolating and identifying the fila-
mentous organisms and adjusting operating conditions to hinder their growth.
MAINTENANCE OF SLUDGE SETTLEABILITY BY F/M CONTROL
A major problem identified at the plant during the earlier preliminary
evaluation study was the fluctuating organic strength of the incoming waste-
waters. This condition was felt to be due to the operation of food processing
industries in the service area. Since there are no equalization facilities
at the plant, the organics pass on to the primary sedimentation and aeration
systems, the result being variations in the F/M ratio. From the microbiologi-
cal standpoint, this situation represents instability in the system, and can
provide an environment that favors the filamentous bacteria associated with
sludge bulking. A logical first step in a corrective program, therefore, was
to hold the F/M within a reasonable range to promote the growth of a good
floe-forming bacterial population.
Primary effluent BOD5 is normally not monitored at the facility. There-
fore, for purposes of this study, the plant superintendent was asked to start
monitoring that parameter on a daily basis. A program was started to maintain
the F/M in the aeration system at approximately 0.3 Kg BODs/day/Kg MLSS by
controlling MLSS through daily sludge wasting. Thus, for any given primary ef-
fluent BODs concentration, a corresponding MLSS concentration in the aeration
tanks and volume of sludge to be wasted on that day were set. The relation-
ship is shown graphically in Figure 14. Since the sludge volumes were to be
determined solely on the basis of primary effluent 6005, the blanket level in
the secondary clarifier was to be controlled by recirculation rate.
Attempts to control F/M met with immediate difficulty. The calculations
called for a lower sludge wasting rate than previously in effect at the plant.
However, attempts to decrease this rate resulted in rising sludge blankets in
the secondary clarifiers. If, during a bulking period, the sludge recircula-
tion rate was increased in order to lower the sludge level, the opposite ef-
fect was observed. Increasing the sludge recirculation rate actually re-
sulted in the sludge blanket moving closer to the clarifier surface and, ul-
timately, the loss of solids over the clarifier weirs. Plant operating per-
sonnel indicated that past attempts to control the aeration reactor environ-
ment by adjusting the return sludge flow had failed because of similar physi-
cal limitations imposed by the clarifiers.
This first phase of. the special study, therefore, led to the conclusion
that control of the organic loading on the aerated biomass could not be used
as a means to operate out of the bulking conditions. This is not to say, how-
ever, that F/M control would not be a viable control option when the activated
sludge exhibits good settling properties. Proper controls under that con-
dition could prevent the bulking. It should be noted that influent BODs
fluctuations observed during this investigation were of a much lesser magni-
tude than those observed during the earlier study. Thus, the problem of vary-
ing F/M in the aeration system was somewhat attenuated during the special
study. The operator indicated, however, that this was probably a temporary
48
-------
phenomenon as similar dampening of BODs fluctuation had occurred in the past.
700O -i
6000
120
140 160 180 200
PRIMARY EFFLUENT BOD5, mg/l
78
220
Figure 14. Recommended Reactor Concentrations and Waste Rates
49
-------
SECONDARY CLARIFIER CHARACTERIZATION
Since initial attempts at process control indicated that limitations were
imposed by the secondary clarification system, a decision was made to study
the settling and sludge removal characteristics of the clarifiers in greater
detail. In order to determine the effect of increased return sludge rates
and clarifier influent flow on the sludge blanket level, clarifier blanket
depths were measured while varying each of those parameters. Results of this
study are presented in Figures 15 and 16. Return rates of less than 30 per-
cent and clarifier influent rates of less than 18,925 m^/d (5.0 mgd) were
found to permit comfortable blanket depths which did not result in a notice-
able solids loss in the secondary effluent. Moderate solids losses were ex-
perienced at return rates of 40 to 60 percent and" flows of 18,925 to 24,602
m.3/d (5.0 to 6.5 mgd). Excessive solids losses occurred at return rates of
greater than 70 percent and flows greater than 30,280 m3/d (8.0 mgd). It was
found that when the sludge blanket depth reached 0.46 meters (1.5 feet) be-
neath the surface, excessive solids were carried over the weirs.
2.01
I I.5H
UJ
1,0-
0.5-
20
40
60
80
100
120
RETURN SLUDGE (% OF FLOW RATE)1
. PLANT INFLUENT FLOW RATE DURING STUDY= 15,140 m3/d (4.0mgd)
FLOW RANGE = 14,000 to 15,897 m3/d (3.7 to 4.2 mgd)
Figure 15. Effect of Return Sludge Rate on Blanket Depth
50
-------
2.0 -|
1.5-
UJ
^
<
m
p
o.
UJ
Q
1.0-
0.5-
0 7,570 15,140 22,710 30,280 37,850 45J420
FLOW TO CLARIFIER= MAIN FLOW + OVERFLOWS + RETURN SLUDGE (m3/d)
Figure 16. Effect of Influent Clarifier Flow on Blanket Depth
The sludge thickening characteristics of the clarifiers were also
analyzed. For this purpose, suspended solids concentrations for return sludge
flow and secondary clarifier influent were measured at various sludge return
rates. The results, as shown in Figure 17, indicate that return sludge con-
centrations were reduced as recirculation pumping rates increased from 30 to
70 percent. This was due to the physical removal of the lower blanket solids
and the fact that the upper solids flux was not adequate to transport solids
to the tank bottom at a rate equal to, or greater than, the removal rate. At
return rates of 70 percent or greater, the solids concentration of the clari-
fier underflow was not significantly greater than that of the clarifier feed.
In other words, no thickening function was being performed by the clarifier.
Final settling tanks have two basic functions:
1. To produce an effluent low in suspended solids, and
2. To thicken the sludge to be returned to the aeration tanks
so that a stable F/M ratio can be maintained.
Inadequate thickening can result in an excessive loss of suspended solids in
the final effluent and a loss of biological process control, since mean cell
residence time and aeration tank solids concentration cannot be effectively
controlled. This condition was found to exist at the special study plant.
Solids flux through the final clarifiers was determined in order to allow a
comparison to a well-operated clarification system. Solids flux refers to the
51
-------
rate of solids passage downward across a horizontal cross section of the clari-
fier. The flux is due to gravity settling and sludge withdrawal.
eooo n
5000-
.-.. 4000 -
CO
Q
o
to 3000
O
UJ
Q
IU
Q.
CO
w 2000 -
1000 -
-RETURN SLUDGE
0 20 40 60 . 80
RETURN SLUDGE (% OF FLOW RATE) '
'AVG. INFLUENT FLOW TO PLANT DURING STUDY = 15,140 m3/d (4.Omgd)
FLOW RANGE= I4.00O to 15,897 mVd (3.7 to 4.2 mgd)
100
120
Figure 17.
trations
Relationship of Return Sludge Rate to Clarifier Solids Concen-
52
-------
Solids flux due to gravity settling equals, the product of the downward
particle velocity and the concentration of solids at a given depth. It can
be determined in the laboratory by performing a Settling test on a represen-
tative sample of sludge. The results of a settling test using clarifier in-
fluent are shown in Table 5, Settling velocity and solids flux as a function
of sludge concentration as shown in Figures 18 and 19. A maximum settling
velocity of 0.40 cm/min (0.013 ft/min) was observed at a suspended solids
concentration of 3,200 mg/1. Maximum flux also occurred at a concentration
of 3,200 mg/1, with a secondary peak occurring at 6,000 mg/1. Maximum grav-
ity flux was 14.6 to 19.5 Kg/m2/d (3 to 4 Ib/ft2/day).
o
o
>
z
UJ
CO
4.3
3.7-
30-
2.4-
1.8-
1.2-
0.6-
0-
2,000
T
3,000
1
4,000
1
5,000
1
6,000
1
7,000
8.00O
9.0OO
CLARIFIER INFLUENT SUSPENDED SOLIDS CONCENTRATION (mg/1)
Figure 18. Gravitational Settling Velocity As a Function of Suspended Solids
Concentrat ion
Solids flux as a result of sludge removal from the clarifier is simply
a function of the surface area of the clarifier and the return rate, and
represents a draw .down of the sludge blanket due to physical removal of liquid
from the bottom of the clarifier.. This flux can be calculated for the clari-
fiers at various suspended solids concentrations. This relationship is shown
graphically in Figure 20. The total solids flux is the result of adding the
curves shown in Figures 19 and 20, Total solids flux as a function of sus-
pended solids concentration, then, is shown in Figure 21. The resultant flux
is observed to be only slightly greater than the flux due strictly to sludge
withdrawl. This indicates that the downward transport of solids due to sedi-
mentation was poor. In order to effect acceptable thickening, the flux due to
53
-------
TABLE 5. MIXED LIQUOR SETTLING VELOCITY AND GRAVITY FLUX
Time
Min.
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
Settled
Volume
ml/1
1000
990
975
960
900
810
740
660
620
580
540
500
460
420
390
370
350
340
340
MLSS
mg/1
2825
2850
2897
2943
3139
3488
3818
4280
4556
4870
5231
5650
5885
6570
7434
7847
8071
8309
8309
mm/niin.
0.44
0.67
0.67
2.67
3.96
3.05
3.56
1.78
1.78
1.78
1.78
1.78
1.78
1.34
0.89
0.89
0.44
0
0
Ft/min.
.0015
.0022
.0022
.0088
.013
.010
.012
.0058
.0058
.0058
.0058
.0058
.0058
.0044
.0029
.0029
.0015
0
0
Solids
Flux
Kg/m 2/d
1.95
2.93
2.93
11.23
18.07
15.63
19.53
10.74
11.72
12.70
13.18
14.65
15.14
12.70
9.77
10.25
5.37
0
0
Solids
Flux
Ib/ft2/day
0.4
0.6
0.6
2.3
3.7
3.2
4.0
2.2
2.4
2.6
2.7
3.0
3.1
2.6
2.0
2.1
1.1
0
0
54
-------
gravity (solids sedimentation) would have to be significantly increased.
I
I
X
20.0—
15.0 —
10.0-
5.0-
3,000 4,000 5,000 6jOOO 7,000 8,000 9,000
CLARIFIER INFLUENT SUSPENDED SOLIDS CONCENTRATION (mg/l)
Figure 19. Transport of Solids Due to Gravity Sedimentation
A summary of the final clarifier studies considers the following major
points:
1. Maintenance of a stable biological system depends upon the
ability to control MLSS in the aeration tanks through ap-
propriate adjustment of return sludge mass.
2. Sludge wasting and return rates were found to be limited by
sludge settleability and resultant clarifier performance.
Parameters calculated to achieve best performance in the
aeration system cannot be maintained without severe solids
losses over the clarifier weirs.
3. Solids flux values measured for the sludge were found to be
much less than those required for good thickening in the
clarifier.
4. Sludge return rates of 60 percent with corresponding clarifier
influent flow rates of 22,710 m3/d (6.0 mgd), or greater,
result in a severely expanded sludge blanket and excessive
solids carryover.
55
-------
100.0-
I
75.0-
X
50.0-
O
in
25.0-
o-
2,000
3,000 4,000 5,000 6,000 7,000 8,000'
CLARIFIER INFLUENT SUSPENDED SOLIDS CONCENTRATION (mg/l)
9,OOO
Figure 20. Transport of Solids Due to Sludge Withdrawal
100.0
75.0
X
-------
MICROBIOLOGICAL STUDIES
The previously discussed clarifier studies proved that sludge settle^
ability was the major obstacle to efficient process control at the plant.
Microscopic observations and discussions with the plant superintendent in-
dicated that filamentous bacteria were present in the sludge. The quantity
of these organisms had been observed to vary with the time of year, being the
most predominant during the winter. Unfortunately, the identification of a
filamentous bulking situation does not conclusively suggest a remedy. The
identification of the organism(s) responsible is the first step in curing
the bulking problem, followed by the identification of those factors in the
microbial environment that can stimulate or support their growth. If one or
more such factors exist in the treatment plant, the control or removal of
them can effect a permanent solution. A temporary control alternative is to
destroy the filamentous bacteria using oxidants such as hydrogen peroxide or
chlorine.
A program was undertaken to identify and isolate the filamentous bacteria
present in the sludge* Microscopic studies to determine the in-situ charac-
teristics of the filamentous cells were performed. Characteristics of the pre-
dominant filamentous organisms are listed in Table 6. A cross-check of these
characteristics with bacteriological keys indicated Thiothrix to be the pre-
dominant organism at the time of the study. Sphaerotilus were also identified
in significant numbers.
TABLE 6. MICROBIOLOGICAL CHARACTERISTICS OF FILAMENTOUS
CELLS IN SLUDGE AT SPECIAL STUDY PLANT
Characteristics of Predominant Organism:
1. Trichomes existing in lengths up to 700 u
2. Sheath apparent but not distinct
3f, Occasional but infrequent jerking motility
4. No branching, some attached unicellular organisms
5. Occasional rosette formation
6. Cylindrical cells,, 1 to 2 u wide by 2 u long
7. Many intracellular deposits; tests indicate sulfur
granules, no iron
8. Cell size differentiation between base and tip,
rod-shaped cells on tip of trichomes
Characteristics of Secondary Organisms:
1. Trichomes several hundred microns long, sometimes
curved on tip
2. Very distinct sheaths
3. Some deposition in sheath, not identified
57
-------
To further support the, findings that Thiothrix was the predominant organ-
isms and that Sphaerotilus was also present, attempts were made to isolate
these bacteria using selective nutrient agars as growth media. Colonies
characteristic of Sphaerotilus were readily grown on a combination of stan-
dard nutrient agar and trypticase soy (TCS) agar. These colonies were iden-
tified as Sphaerotilus according to the methods of Farquhar and Boyle (1971).
Thiothrix was not successfully isolated on this medium.
A second isolation procedure was also followed. This procedure, docu-
mented by Liu, Kwasniewska, and Cohen (1977), is based on research that has
shown filamentous organisms to be much more tolerant of certain toxic agents,
specifically, n-amyl alcohol in this case. Samples of aeration basin mixed
liquor were spiked with n-amyl alcohol and streaked on modified nutrient agar
plates, fortified with sodium acetate and glucose. Two distinct types of fil-
amentous colonies were isolated. When examined, one was found to be Sphaero-
tilus. The other appeared to be Thiothrix. Since intracellular sulfur de-
posits are characteristic of Thiothrix, tests were performed to detect their
presence. The results were positive, lending further evidence of the isola-
tion and identification of Thiothrix. The literature indicates that Thiothrix
has generally not been grown in pure culture. In light of the relative new-
ness of the n-amyl alcohol procedure, further study would be recommended to
prove conclusively the apparent isolation of Thiothrix seen in this study.
In summary, microbiological investigations of the bulking sludge during
February and March 1977 indicated Thiothrix to be the predominant filamentous
bacteria present. A second genus, Sphaerotilus, was also identified. The
microscopic identifications were based on morphological characteristics and
associated traits such as the degree of motility and the content of cell
vacuoles. This existence of Thiothrix and Sphaerotilus was further supported
by isolation and examination of the filamentous organisms in pure culture.
HYDROGEN SULFIDE STUDIES
Since the microbiological analyses indicated Thiothrix to be the pre-
dominant filamentous form during periods when bulking was most severe, the
next step was to determine those factors in the treatment plant environment
which were responsible for the selective proliferation of that organism.
Thiothrix oxidizes hydrogen sulfide to sulfur with subsequent intracellular
deposition of sulfur. The microorganisms use this oxidation as a source of
energy, and hydrogen sulfide concentrations of 0.5 mg/1, or even less, can
stimulate the growth of Thiothrix. Consequently, eliminating and preventing
the formation of hydrogen sulfide is the key to eliminating Thiothrix. This
organism has been observed to grow well in the F/M range of 0.2 to 0.4 Kg BODs
/day/Kg MLVSS (Farquhar and Boyle, 1971). Since this is the optimum range for
activated sludge operation, corrective action in addition to F/M control is
necessary for eliminating the Thiothrix population.
Hydrogen sulfide was found in varying concentrations at a number of points
in the treatment train. Table 7 summarizes the results. As indicated, no
detectable hydrogen sulfide concentration was found in the effluent from
either primary clarifier. The concentration in the raw sewage is probably de-
stroyed by the aerating effect of the lift pumps at the head of the plant.
58
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TABLE 7. HYDROGEN SULFIDE CONCENTRATIONS
Sample
Raw Influent
Primary Effluent Clarifier No. 1
Primary Effluent Clarifier No. 2
Secondary Effluent
Centrate
Sludge Thickener Overflow
* Limit of detection =0.1 mg/1
H2S (mg/1)*
0
,1
CO.l
CO.l
CO.l
0.9
0.3
Dissolved oxygen concentrations of greater than 5 mg/1 in the primary clari-
fier influent were commonly measured during the study. Thus, the hydrogen
sulfide supporting the growth of Thiothrix was apparently not associated with
the influent sewage. Hydrogen sulfide in the thickener overflow and centri-
fuge centrate, was diluted to legs than 0.1 mg/1 when these flows were re-
cycled to the head of the plant and combined with the raw wastewater.
The sludge samples taken from the secondary clarifiers were also analyzed
for hydrogen sulfide. Samples were taken from 15 cm (6 inches) above the
Clarifier bottom at approximately 1.2 meters (4-foot) intervals measured
radially from the center of the clarifier. A profile on sludge hydrogen sul-
fide concentrations from the center to the outer wall of one of the final
clarifiers is shown in Figure 22. The hydrogen sulfide concentrations at the
points of sludge withdrawal were generally lower than the concentrations found
between the sludge withdrawal ports. The average concentration measured was
16.8 mg/1 and concentrations as high as 34.6 mg/1 were measured between the
ports. Across the clarifier bottom all sulfide concentrations in the sludge
were above that level which can stimulate the growth of Thiothrix.
As the point of sampling was moved up from the clarifier bottom, the sul-
fide concentration rapidly fell off. At an elevation of 30 cm (1 foot) above
the clarifier bottom, the sludge concentration varied from <0.1 mg/1 (the
detention limit) to 0.5 mg/1.
For comparison, hydrogen sulfide concentrations were measured at the bot-
toms of secondary clarifiers at several other treatment plants. Figure 23
shows the results for a conventional activated sludge plant in Pennsylvania.
At this plant, no trend of sulfide concentrations as a function of position
with respect to sludge withdrawal ports could be identified. However, the
2 mg/1 average sulfide concentration was considerably lower than that ob-
served at the special study plant. Since design sludge detention times at
both plants were similar, this parameter could not account for the higher
sulfide concentrations in the special study plant sludge.
The only significant difference found between the special study plant
and the other activated sludge plants with similar clarifiers is related to the
sludge withdrawal mechanism. In the special study facility, V-ploughs
59
-------
34.6
WALL
25.8
7.0 8.0
9.0
10.0
DISTANCE FROM $. (METERS)
Figure 22. Profile of H2S Concentrations in Final Clarifier Bottom Sludge
attached to the rotating arms are used to channel the sludge into the with-
drawal tubes. The tank center hopper is used only for draining the clarifier.
The other plants observed utilize mechanisms which, in addition to channeling
sludge to the withdrawal tubes, also scrape bottom sludge to the tank hopper,
which is used for waste sludge withdrawal. Waste sludge removal at the special
study plant is accomplished through the return sludge system.
It is significant that the bottom sludge which is not removed by the
withdrawal tubes Cabout a 50 cm (2 inch) layer] stays in the clarifier until
the unit is drained. This prolonged detention time promotes septicity in the
bottom sludge and leads to the development of high concentrations of hydrogen
sulfide. Contact of the return sludge with the high sulfide levels at the
clarifier bottom may well provide the stimulation for the growth of the Thio-
thrix organism in the system.
60
-------
6.2
1.0
2.0
~3xT 40 5.0 6.0
DISTANCE FROM
-------
associated with good settling floe. As a result, in-
creasing the recirculation rates above 30 percent of
influent flow, which is required :to prevent excessive
solids release over the weirs, severely thins out the
concentration of the return sludge. It was found to
be impractical to operate at a desirable recirculation
ratio.
3. Microscopic studies showed the hindrance of settling
to be due to a large population of filamentous bacteria
in the activated sludge. Isolation and identification
indicated Thiothrix was the predominant organism.
Sphaerotilus in significant numbers are also present.
4. Hydrogen sulfide levels in the influent sewage are not
sufficient to stimulate Thiothrix growth.
5. Because of the nature of the sludge withdrawal mechanism,
sludge holding times at the clarifier bottoms are ex-
cessive. This is conducive to the development and
maintenance of high sulfide levels.
6. High levels of hydrogen sulfide were found in the bottom
sludge of the secondary clarifiers. These levels are
an order of magnitude higher than those found in clarifier
bottoms at similar treatment plants.
7. Contact of the settled sludge with the high sulfide level
at the clarifier bottoms is probably providing a stimulus
for the growth of Thiothrix.
The detailed investigation of process problems in the special study points
to one major recommendation. Hydrogen sulfide concentration in the bottom
portions of the final clarifiers must be reduced and, if possible, eliminated.
Specifically, provisions should be made to scrape the clarifier bottom con-
tinuously to insure that all settled material is rapidly removed for waste or
recirculation. Since no other significant sources of sulfide exist at the
plant, the above clarifier improvements should inhibit the further prolifer-
ation of Thiothrix, in that a favorable environment for that organism will no
longer exist.
In conjunction with the clarifier improvements and the elimination of
the filamentous bacteria, a comprehensive process control program should be
initiated. Primary effluent BODs, mixed liquor suspended solids, and aera-
tion tank dissolved oxygen should be monitored daily. The information is re-
quired to insure that the biological portion of the treatment plant is oper-
ated under conditions that favor the growth of a healthy biomass. The ten-
dency for influent organic concentration to fluctuate makes it especially
critical that parameters such as F/M ratio and sludge age be monitored and
maintained within desirable ranges.
62
-------
The recommendations proposed are intended to eliminate activated sludge
bulking by eliminating the environmental conditions that support the problem
organisms. The more traditional approach has been to treat the symptoms of
the problem by adding oxidizing agents such as chlorine or hydrogen peroxide
to the activated sludge. At best, this method may destroy the filamentous or-
ganisms and temporarily ameliorate the settling problem. Experience has shown
that the problem will reoccur soon after the oxidant addition is ceased.
For this reason, the chemical treatment approach is of limited utility and is
not recommended for this facility.
63
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SECTION 8
RELATIONSHIP BETWEEN 0£M PARAMETERS AND SIZE AND TYPE OF FACILITY
During the site visit phase,of the project, data were obtained from 120
treatment facilities. The primary purpose of the site visit phase was to
serve as a screening process for the selection of plants for the preliminary
evaluation phase. However, because of the number of plants visited, these
data are also useful for developing possible relationships between plant oper-
ation and maintenance practices, and the sizes and types of facilities examined.
In this section, such relationships as they were found to exist will be ex-
amined.
GENERAL INFORMATION
Relative Number of'Plants with Respect to Design Capacity (Figure 24)
A significant percentage (38%) of the plants visited were designed for
an average daily flow less than 1,890 m3/d (0-5 mgd). Furthermore, less than
one-half of the facilities (45%) exceeded 3,780 m^/d (1.0 mgd) in design ca-
pacity.
Relative Number of Plants with Respect to Facility Type (Figure 25)
Most of the currently employed biological processes were represented in
those plants to which site visits were made. About 65 percent of the plants
utilized a form of suspended growth process, including activated sludge in the
various operating modes. The remaining 35 percent were fixed-film systems in-
cluding one rotating bio-disc plant.
Relationship Between Service Population and Type and Size of Facility (Table 8)
Treatment processes serving small, populations tended to be extended
aeration, contact-stabilization, or trickling filter, with extended aeration
confined to populations of less than 10,000 for the most part. Larger popula-
tions tended to be served by activated sludge plants, particularly by the con-
ventional or complete mix mode.
Relationship Between Type of Wastewater Collection System and Type and Size
of Facility (Table 9)
Smaller .plants had the highest percentage of separate sewer systems.
Treatment method employed showed no correlation with the type of sewer system.
64
-------
50T
40- •
3O-
20-
10-
PLANT CAPACITY
.Eigure 24. Relative Number of Plants with Respect to Design Capacity
5OT
40-
30"
20- •
10-•
CONVENTIONAL CONTACT EXTENDED PURE TRICKUNS OTHER
ACTIVATED STABILIZATION AERATION OXYGEN FILTER
SLUDGE ACTIVATED
SLUDGE
TYPE OF FACILITY
Figure 25. Relative Number of Plants with Respect to Facility Type
65
-------
TABLE 8. RELATIONSHIP BETWEEN SERVICE POPULATION AND TYPE
AND SIZE OF FACILITY
NUMBER OF PLANTS
500-2,500
2,500-5,000
5,000-10,000
10,000-20,000
20,000-50,000
OVER 50,000
CONV.
ACT.
SLUDGE
5
0
6
2
6
4
TYPE
EXT.
AER.
ACT.
SLUDGE
8
3
2
0
1
0
OF FACILITY
CO NT-
STAB
ACT.
SLUDGE
8
6
2
0
1
3
TRICK.
FILTER
4
11
6
8
5
1
OTHER
0
1
0
1
1
1
LESS
THAN
0.5
MOD
17
12
1
0
0
0
SIZE OF FACILITY
0.5
TO
1.0
MOD
4
9
3
1
0
0
1.0
TO
5.0
MOD
0
0
10
9
4
0
5.0
TO
10.0
MOD
0
0
0
0
8
0
GREATER
THAN
10.0
MOD
0
0
0
0
1
8
TABLE 9. RELATIONSHIP BETWEEN TYPE OF WASTEWATER COLLECTION
SYSTEM AND TYPE AND SIZE OF FACILITY
CONV.
ACT.
SLUDGE
TYPE
EXT.
AER.
ACT.
SLUDGE
NUMBER OF
PLANTS
OF FACILITY
CONT-
STAB
ACT.
SLUDGE
TRICK. OTHER
FILTER
LESS
THAN
0.5
MOD
SIZE OF FACILITY
0.5
TO
1.0
MGD
1.0
TO
5.0
MOD
S.O
TO
10.0
MGD
GREATER
THAN
10.0
MGD
SEPARATE
12
18
15
29
36
14
18
COMBINED
10
Relationship Between Year of Most Recent Upgrading and Type and Size of
Facility (Table 10)
The tabulated results support the hypothesis that most upgradings and new
construction projects were motivated by the passage of water pollution legis-
lation in the late 1950's and the 1960's.
With the exception of those few plants greater than 37,850 m3/d CIO mgd)
design capacity, the highest percentage of upgrading occurred in the smallest
facilities, indicating either the construction of totally new plants or up-
grading to secondary treatment levels. The fact that all the facilities
having capacities greater than 37,850 m3/d (10 mgd) were upgraded since 1970
reflects either the recent trend toward regionalization or the longer time
span necessary to plan, design, and construct larger facilities.
66
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TABLE 10. RELATIONSHIP BETWEEN YEAR OF MOST RECENT UPGRADING
AND TYPE AND SIZE OF FACILITY
NUMBER OF PLANTS
BEFORE 1940
TYPI OF FACILITY
SIZE OF FACILITY
CONV. iXT. CONT- TRICK. OTHER LESS 0.5 1.0 5.0 GREATER
ACT. AER. STAB FILTER THAN TO TO TO THAN
SLUDOE ACT. ACT. 0.5 1.0 5.0 10.0 10.0
SLUDGE SLUDOE MOD MOD MOD MOD MOD
1
1
1940 TO 1950
1950 TO 1960
00 010 00100
1 1 070 31320
1960 TO 1970
SINCE 1970
8 11 6 19 1 19 11 96 0
10 3 10 7 3 10 5 8 1 9
Relationship Between Wastewater Characteristics and Type and Size of Facility
(Table 11)
Industrial wastewaters appear to be distributed among all process types,
except extended aeration facilities. The small size and limited service area
of most extended aeration plants probably explain the absence of significant
industrial wastewater volumes. Their service areas are generally not indus-
trial, and, therefore, smaller plants have the higher percentage of domestic
wastewaters. Conversely, the plants with capacities greater than 37,850 mr/d
(10 mgd) exhibited the greatest percentage of high industrial loadings.
TABLE 11. RELATIONSHIP BETWEEN WASTEWATER CHARACTERISTICS
AND TYPE AND SIZE OF FACILITY
~ ~~~ ' ——— NUMBER OF PLANTS
TYPE OF FACILITY
SIZE OF FACILITY
CONV. EXT. CONT- TRICK. OTHER
ACT. AER. STAB FILTER
SLUDOE ACT. ACT.
SLUDOE SLUDOE
LESS 0.5 1-0 5.0 OREATER
THAN TO TO TO THAN
0.5 1,0 5.0 " 10.0 1O.O
MOD MOD MOD MOD MOD
DOMESTIC
12
16
13
21
32
14
15
LOW INDUSTRIAL
MODERATE
INDUSTRIAL
(10-20X)
HI6H INDUSTRIAL
(20-50%)
6 1
6 0
31321
32232
13822
67
-------
Relationship Between Industrial Waste Impact and Type and Size of Facility
CTable 12)
The impact of industrial wastewaters on the treatment facility did not
appear to vary with respect to the size or type of plant. This indicates that
while larger plants have the higher industrial loadings, they are also more
able to handle industrial wastes without experiencing process problems.
TABLE 12. RELATIONSHIP BETWEEN INDUSTRIAL WASTE IMPACT AND
TYPE AND SIZE OF FACILITY
NUMBER OF PLANTS
TYPE OF FACIUTY
SIZE OF FACIUTY
CONV. EXT. CONT- THICK. OTHEI LESS 0.5 1.0 5.0 CHEATER
ACT. AH. STAI FILTE* THAN TO TO TO THAN
SLUDOE ACT. ACT. 0.5 1.0 S.O 10.0 10.0
SLUDOE SLUDOE MOD MOD MOD MOD MOD
MINIMAL
17
17
26
35 16
20
LOW
MODERATE
22 1 30 22220
41472 33642
HIGH
1
00 10100
Relationship Between Infiltration/Inflow Impact and Type and Size of Facility
(Table 15)
Infiltration/Inflow (I/I) demonstrated a moderate to severe effect on 43
percent of all plants examined during the site visit phase. The trickling
filter plants as a group had the highest amounts of extraneous flows in their
collection systems, probably because the plants and their collection systems
tended to be older. However, the effect on performance at those plants re-
ceiving excessive volumes of I/I was greater at suspended growth facilities
for reasons discussed in Section 5, No correlation was seen between size of
plant and impact of I/I.
68
-------
TABLE 13. RELATIONSHIP BETWEEN INFILTRATION/INFLOW IMPACT
AND TYPE AND SIZE OF FACILITY
NUMBER OF PLANTS
TYPE OF FACILITY
SIZE OF FACILITY
CONV. EXT. CONT- TRICK. OTHER LESS 0.5 1.0 5.0 GREATER
ACT. AER. STAB FILTER THAN TO TO TO THAN
SLUDGE ACT. ACT. O.S 1.0 5.0 1O.O 10.0
SLUDGE SLUDGE MOD MOD MOD MOD MOD
MINIMAL
1
8
1
LOW
MODERATE
10 4 5 10 5 98935
5 6 S 20 0 16 795 2
HIGH
1
1
OPERATION
Each plant was rated on a scale of 0 - 3 as to its standing in various
operational categories. The best standing (0) is defined as good, next is
fair (1), then poor (2), and, finally, critical (3). The following figures
show the plant rating distribution for each category. The numbers in paren-
theses are the actual numbers of plants so rated.
Relationship Between Staff Capabilities for Operation and Size and Type of
Facility (Figure 26)
As previously noted, the term "staff capabilities",represents four
characteristics of the plant staff, Cl) staff size, (2) training, (3) cer-
tification, and (4) treatment understanding. For the most part, large plants
were capable of maintaining an adequately sized staff because of more flex-
ibility in budgetary matters, Similarly, large facilities were better equipped
to administer in-plant training programs and sufficiently flexible to accom-
modate personnel attending training and certification classes. Generally, the
trickling filter processes scored better than the activated sludge plants be-
cause operation of the trickling filter facility is usually less demanding
in terms of operational requirements and process knowledge. Greater training
and treatment understanding are required to control the more complex activated
sludge process
Relationship Between Use of Laboratory and Size and Type of Facility
(Figure 27) .
Larger plants made significantly greater use of the laboratory than did
the smaller facilities. Because of the larger staff sizes, a greater percent-
age of labor, and more specialized workers, could be devoted to laboratory-
related work. Regarding type of process, use of the laboratory appears to be
more effective at trickling filter plants, most likely as a result of fewer
69
-------
CRITICAL (4)
GOOD (57)
66%
(PLANT CAPACITY < 5 MOD)
(PLANT CAPACITY >5 MOD)
FAIR (14),
POORX 20%
(8) ll
CRITICAL (3)
4% GOOD (46)
65%
FAIR (2)
6%
CRITICAL(I)
3% GOOD (29)
82%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 26. Relationship Between Staff Capabilities for Operation and Size
and Type of Facility
70
-------
GOOD(I6)
% 80%
(PLANT CAPACITY< 5 MOD)
(PLANT CAPACITY > 5 MOD)
CRITICAL(2)
3%
GOOD (34)
^CRITICAL(4)
10% GOOD (23)
59%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 27. Relationship Between Use of Laboratory and Size and Type of
Facility
71
-------
process variables to monitor,
Relationship Between Process Control and Size and Type of Facility (Figure 28)
Larger plants exercised greater process control than smaller plants. Ad-
equately sized staffs, suitably trained laboratory personnel, and properly
equipped laboratories are all prerequisites to effective process control. As
previously noted these conditions are more likely to be found at the larger
plants. The fact that 83 percent of the trickling filter facilities were
rated fair or good in the area of process control actually reflects the fact
that few control options (other than recirculation ratio) are available to the
operator. Process control at a trickling filter plant, therefore, requires a
lower level of effort than is required for the activated sludge process.
Quality Evaluation of Technical References for Operation (Figure 29)
Less than one-third of the plants examined during the site visit phase
were judged to have adequate technical references for operation of the facil-
ity. For purposes of this study, adequate references would include a compre-
hensive operations manual, information provided by the equipment manufacturers,
and as-built drawings of the facilities.
Evaluation of Use of Consulting Engineering Services (Figure 50)
Based on the opinions of the operators, consulting services were utilized
adequately in a majority of cases. However, this assessment may be optimistic,
since the operators frequently felt little assistance of this nature was
necessary, even where serious performance problems have been documented.
MAINTENANCE
Relationship Between Staffing Capabilities for Maintenance and Size and Type
of Facility (Figure 51)
As experienced, larger plants had more adequate maintenance staffs, since
staff size was found to be a major factor in determining maintenance capa-
bilities for a given plant size. Trickling filter plant staffs were more
maintenance oriented than were those at activated sludge facilities.
Relationship Between Age of Equipment and Size and Type of Facility (Figure 52)
No correlation was found between size of plant and age of equipment.
The fact that treatment plant designs have trended toward activated sludge and
away from trickling filters in recent years is demonstrated by the higher pro-
portion of newer equipment in activated sludge facilities.
Relationship Between Spare Parts Inventory and Size and Type of Facility
(Figure 55)
Larger plants maintained a more complete inventory of spare parts. This
was probably due to better organization and greater administrative attention
given to larger facilities. However, the adequacy of such inventories was not
72
-------
CRITICA
(9) 11%
GOOD (20)
24%
(PLANT CAPACITY < 5 MOD)
FAIR (6)
POOR \ 30%
(4) 20%
GOOD (10)
50%
(PLANT CAPACITY > 5 MOD)
FAIR (16)
POOR \ 38o,
(5) **/
RITICAL(2)
5%
GOOD (19)
45%
POOR(24)
40%
CRITIC
(7) 12%
(TRICKLING FILTER)
(ACTIVATED SLUDGE)
Figure 28. Relationship Between Process Control and Size and Type of Facility
73
-------
40T
-J 30'
20-
10-
GOOD FAIR POOR CRITICAL
Figure 29. Quality Evaluation of Technical References for Operation
60
50
40
CL
u_ 30
o
a:
20
10-
GOOD FAIR
POOR CRITICAL
Figure 30. Evaluation of Use of Consulting Engineering Services
74
-------
FAIR (20)
POOR \ 23%
(13) 15%
CRITICAL(3 3%
(PLANT CAPACITY < 5 MOD)
(PLANT CAPACITY > 5 MOD)
FAIR07)
POOR\ 25%
(10) 15%
CRITICAL(2)3%
GOOD(38)
VLCRITICAL(I) 2%
GOOD(27)
73%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 31. Relationship Between Staffing Capabilities for Maintenance and
Size and Type of Facility
75
-------
-CRITICAL (3) 3%
GOOD(52)
61%
(PLANT CAPACITY< 5 MOD)
(PLANT CAPACITY > 5 MOD)
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 32. Relationship Between Age of Equipment and Size and Type of Facility
76
-------
POOR(22)
30%
/CRITICA
(8) 11%
(PLANT CAPACITY < 5 MOD)
(PLANT CAPACITY > 5 MOD)
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 33. Relationship Between Spare Parts Inventory and Size and Type of ,
Facility ' • .•-.,, .•-..••:;.
77
-------
related to process type.
Relationship Between Preventive Maintenance and Size and Type of Facility
(Figure 54)
Generally, plants with capacities greater than 18,920 m3/d (5 mgd) prac-
ticed preventive maintenance to a greater extent than did the smaller facil-
ities. This condition can be attributed to the better spare parts inventories
and staffing capabilities noted previously. Process type did not appear to
have any significant bearing on the adequacy of preventive maintenance prac-
tices.
Relationship Between Emergency Provisions and Size and Type of Facility
(Figure 55)
Larger facilities tended to be better prepared for emergency situations,
reflecting their greater resources. The larger plants were usually new, en-
larged, or upgraded plants having been constructed in a period when some
emergency provisions, such as emergency power supply and duplicate units, be-
came mandatory for design approval. The extent to which facilities were pre-
pared for emergencies did not appear to be related to process type.
Relationship Between Backup Unit -Provisions and Size and Type of Facility
(Figure 56)
As expected, larger plants had significantly greater backup capability
since all such plants had dual or multiple process units. No significant dif-
ference in backup provisions was seen between activated sludge and trickling
filter plants in the site visit phase.
Relationship Between Technical References for Maintenance and Size and Type
of Facility (Figure 57)
Comprehensive, organized technical references for maintenance purposes
were found at those plants which also had good operational references. The
adequacy of maintenance references showed a positive correlation with plant
size. There was no significant difference between the fraction of trickling
filter plants and activated sludge plants having adequate maintenance refer-
ences. The extent to which such references are required for trickling filter
plants would be less, again due to the lesser amount of mechanical equipment
involved.
Relationship Between Housekeeping Practices and Size and Type of Facility
(Figure 58)
Housekeeping practiced at larger wastewater treatment facilities was
found to be slightly more satisfactory than that practiced at smaller plants.
This was undoubtedly a result of a combination of factors related to plant
size, including availability of maintenance staff, age of equipment, and ad-
ministrative practices. No appreciable difference in quality of housekeeping
was observed between trickling filter and activated sludge processes.
78
-------
CRITICAL(7)
7% GOOD (45)
51%
(PLANT CAPACITY < 5 MOD)
(PLANT CAPACITY > 5 MOD)
POOR03)/ FA,R(,4)
18% / 20%
CRITICAL (5)
7%
GOOD(39)
55%
POOR(IO)/FA|R(4>
CRITICAL (2)
5% GOOD (22)
58%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 34.
Facility
Relationship Between Preventive Maintenance and Size and Type of
79
-------
-CRITICAL
0 6%
GOOD (15)
44%
GOOD(7)
78%
(PLANT CAPACITY< 5 MOD)
(PLANT CAPACITY > 5 MOD)
v FAIROI)
POOR(4)\ 32%
12%
CRITICAL (2)
GOOD (17)
50%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 35. Relationship Between Emergency Provisions and Size and Type of
Facility
80
-------
'CRITICAL
(14) 19%
POOR (I!),
15%
'FAIR(II)
15 %
GOOD (38)
51%
(PLANT CAPACITY < 5 MOD)
(PLANT CAPACITY >5 MOD)
CRITICAL
(85 13%
GOOD (38)
62%
CRITICAL
(6) 19%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 36.
Facility
Relationship Between Backup Unit Provisions and Size and Type of
81
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CRITICAL
(4) 11%
GOOD (14)
88%
(PLANT CAPACITY < 5 iWGD)
(PLANT CAPACITY > 5 MOD)
CRITICAL
(3) 7%
GOOD (18)
45%
FAIR (4)
29%
^CRITICAL (I)
7%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 37. Relationship Between Technical References for Maintenance and
Size and Type of Facility
82
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POOR
(12) 15%
FAIRG3)/
16%
CRITICAL (3)
3% GOOD (55)
66%
(PLANT CAPACITY < 5 MOD)
POOR(I)
5%
GOOD (15)
o
(PLANT CAPACITY > 5 MOD)
CRITICAL (2)
3o/0 GOQD(46)
69%
CRITICAL(I)
3% GOOD(24)
69%
(ACTIVATED SLUDGE)
(TRICKLING FILTER)
Figure 38.
Facility
Relationship Between Housekeeping Practices and Size and Type of
83
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Relationship Between Availability of Auxiliary Power and Size and Type of
Facility (Figure 59)
Approximately one-third of the plants less than 18,920 ra^/d (5 mgd) in
design capacity had auxiliary power capabilities. About two-thirds of those
plants larger than 18,920 m^/d (5 mgd) in design capacity were reported to
have such capability. The higher percentage of activated sludge facilities
having auxiliary power capacity reflected the fact that these plants were
generally newer and were subject to recently enacted state and federal re-
quirements on backup power systems.
84
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40T
40 T
CO
30-
20
Ul
m
10 +
YES
CAPACITY<5 MOD
YES NO
CAPACITY>5 AAGD
40 T
40-T
m
(O
<
D-
O 20' •
CC
Ul
CD
i 10
YES
ACTIVATED SLUDGE
YES NO
TRICKLING FILTER
Figure 39. Relationship Between Availability of Auxiliary Power and Size and
Type of Facility
85
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SECTION 9
f , • ,",•'*' ' ' • ' i
IMPACT OF ESTABLISHED PROGRAMS ON PRIORITY PROBLEMS
The causative factors of poor plant performance are not of recent origin.
Their presence has long been acknowledged, although their priority has been
more difficult to identify. Programs have been established by the federal and
state governments, operators' associations, manufacturers, and consultants to
resolve these problems. The extent of those efforts in correcting these prob-
lems is examined in the following discussion.
Since the inception of EPA, .the Agency has sponsored the preparation and
publication of a number of documents designed to convey state-of-the-art in-
formation on wastewater treatment design and operation to those employed in
this field. Process design manuals are published by the Government Printing
Office and made available through EPA Technology Transfer without fee. These
manuals are primarily directed toward those in the consulting engineering and
academic fields. Existing volumes address key design areas, such as sludge
treatment and disposal, suspended solids removal, upgrading existing treatment
plants, and tertiary treatment. These publications set forth specific design
parameters for individual unit processes, and are generally intended as a
guide to the preliminary design of wastewater treatment facilities. These
documents will contribute to the reduction of operational problems associated
with design, but few are applicable to the needs of a plant operator. Oper-
ations-related manuals are also available through EPA. Publications such as
"Anaerobic Sludge Digestion" and "Stabilization Ponds" outline procedures to
be followed in operating and controlling these biological processes. Sim- .
ilarly, the "Procedural Manual for Evaluating.the Performance of Wastewater
Treatment Plants" includes information, such as a section on common operating
problems and suggested solutions, that would be of value to the plant oper-
ator. The study reported here would indicate that a major difficulty with
both design and operations manuals is their dissemination to treatment plants.
Relatively few of the plants visited had copies on file of any EPA publica-
tions. Although this effort may benefit the operator indirectly through his
consultant, the information is not reaching the operator directly, where it
would be of greatest benefit.
Under the construction grants program established as a result of the
Water Pollution Control Act Amendments of 1972, federal funds are available to
municipalities seeking to reduce infiltration/inflow. In the design of new
facilities involving federal funds, a cost-effectiveness analysis must be per-
formed during the facilities planning step of the project. On the basis of
this study a sewer, rehabilitation program may be implemented to reduce infil-
tration/inflow to the cost-effective level. As new plants are constructed,
the I/I problem will diminish, but as sewer systems continue to age and de-
teriorate, new critical cases will develop. The federal program will help to
86
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reduce the overall magnitude of the adverse effects of I/I on sewage treat-
ment plant performance when one looks at the overall national picture. How-
ever, looking at specific cases, only those plants which become involved in
upgrading or expansion will be encouraged to address their I/I situation.
Therefore, many plants currently experiencing operational difficulties re-
sulting from excessive I/I will not be affected by existing federal programs.
Established programs to date have had little impact on the industrial
loadings to municipal treatment plants; Local programs have consisted of pro-
visions in municipal ordinances setting forth surcharges for discharge of
high concentration of certain pollutants to the collection system, and placing
limitations or tans on discharge of other pollutants. However, such ordinance
provisions have, in the past, been very poorly enforced for two reasons:
• •'!. Time and manpower are not available to: vigorously monitor •••
industrial wastes,,
2." Rigorous enforcement may have caused conflicts with major
employers in the community. ! '
Two recent programs should result in amelioration of some industrial
loading problems. First, the ICR-User Charge provisions of PL 92-500 have
caused,-and will continue to cause, industries to consider the economics of
pretreating their wastewaters. Sewer rental rates to' industry under ICR-User"
Charge regulations are directly proportional to wastewater flow and charac- '
teristics. Such rental rates can often be substantially reduced "by treat-'
ing to reduce pollutant concentrations* Of broader and more direct signifi-
cance, however, are the recently promulgated (June 26, 1978) industrial pre- ;
treatment regulations. These general regulations identify 21 industrial cate-
gories 'for which specific pretreatment guidelines'will be established within
the^next three years. Also, limits will be established for. 65 toxic pollu-
tants which all dischargers t.6 municipal treatment plants will be required to
meet. Administration of the pretreatment program will be the responsibility of
the municipality where the design'flow-of the plant is greater than 18,920
m3/d (5 mgd). In all other cases, the state agenc'y or EPA will be required to
accept this responsibility. As the pretreatment limits are set forth for each
industry, the incompatible pollutants and slug loadings currently reaching
municipal treatment plants will diminish. Of course, this prediction assumes
adequate administration of the program and compliance by industry;
As a requirement of the construction grants program, 0§M" manuals are now
being prepared for all federally funded wastewater collection and treatment
systems. The purpose of this requirement is to insure that all federally
funded treatment facilities being constructed have comprehensive plant-
specific manuals. Through adherence to the EPA document, "Consideration for
Preparation of Operation and Maintenance Manuals," and as a result of detailed
review by. EPA, these manuals should conform to EPA standards. As existing
plants are upgraded and new ones built, the problem of 0$M manual inadequacy
should greatly diminish. Also, many consulting firms are now involving the
plant operator in the preparation of the 0§M manual, and are using the manual
.as a training device. This will result in a manual that is more responsive
to the operators'needs, and use of the document should increase.
87
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All states now operate a mandatory or voluntary program of operator cer-
tification. Though all state programs have been developed and are adminis-
tered independently, they have had the effect of assuring some minimum com-
petence level for certified operators, based on the size and complexity of the
treatment plant. In the program's early years, certification was an effective
means of increasing the training level of operators. Currently, most plants
meet the requirements for certified operators, and enough additional operators
are being certified to meet the needs of newly-constructed facilities. Cer-
tification programs have their place in assuring minimum competency; however,
in their present form, they do not insure that learned principles and tech-
niques will be applied in on-site operational situations.
Training programs play a major part in providing basic wastewater treat-
ment knowledge to potential and practicing treatment plant operators. Ex-
amples of such programs include the Sacramento course and Clemson course, and
other courses sponsored by the state agencies, water pollution control organ-
izations, technical schools, and community colleges.
In Pennsylvania, the Sacramento course is offered through the Department
of Community Affairs. Operator training provides basic understanding of treat-
ment principles and fundamentals, training in laboratory procedures, and ex-
posure to process control technology. Originally, these courses were designed
to enable a plant operator to learn the material necessary to become certified.
A basic shortcoming of these courses is that they are designed for an individ-
ual with little or no wastewater background, and, hence, are limited in what
they offer to an experienced individual who seeks to upgrade his skills, A
few community colleges offer advanced courses or an associate degree program,
which are designed for experienced personnel interested in supervision of
operation and maintenance personnel. Enrollment in these programs requires
time and money, which makes them inaccessible to many operators. The courses
available to a majority of operators do not provide sufficient exposure to
convey the depth of understanding necessary for meaningful process control ap-
plication or testing. The findings of this study would indicate that class-
room training must be supplemented with on-site training to more effectively
convey process control concepts to the operator.
Equipment manufacturers typically provide excellent material on the
maintenance and operation of their products, particularly for equipment that
is standard or for which operating experience is available. For new products
or processes, less information is available, especially in the area of oper-
ations. The quality of assistance in the form of trained personnel available
varies among manufacturers and among individuals representing each manu-
facturer. Manufacturers' representatives are a potentially excellent source
of knowledge, if suitable contractural arrangements can be made for their
services. For small package plants, operators may possibly have access to the
manufacturer who could provide operating assistance. For large treatment sys-
tems, assistance with the biological process operation is not likely to come
from an equipment manufacturer. However, manufacturers of proprietary unit
processes, such as pure oxygen activated sludge, can usually provide operating
assistance. In general, the manufacturer must be considered a specialized
temporary source of technical assistance to the operator.
88
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Some consulting firms maintain a qualified staff to provide technical
and administrative assistance to municipal wastewater clients. Such a staff
typically includes personnel who are certified treatment plant operators with
a thorough knowledge of process theory or design concepts. An engineer without
first-hand operating experience is rarely as successful in providing opera-
tional assistance as an experienced operator. Plants evaluated in this study
reported a low level of consultant service. Those having consultants avail-
able usually did not use them for training or problem-solving. Those not re-
taining consultants felt that consultant services would not be beneficial.
Personnel at most plants seemed to feel that an engineer could not help with
operating problems. Most consulting firms at this time do not maintain the
type of staff necessary to offer technical assistance at the operating level,
nor do they indicate to their clients that such services are available else-
where. This area of service is growing, however, and will be offered by an
increasing number of engineering firms in the future.
Within the wastewater industry, associations have existed for a number of
years to foster professionalism, increase the technical knowledge of their
members, and to effectively represent the members' interest and opinions.
Some associations, such as the Water Pollution Control Federation, have de-
veloped or sponsored operator training courses. Additionally, they sponsor
seminars and workshops, and issue publications aimed at improving the knowl-
edge of plant operators. Such organizations provide the opportunity for oper-
ators to discuss problems with their colleagues and occasionally find solu-
tions. Overall, the associations provide some valuable training, but they
have a small to moderate effect on reducing the magnitude of problems as-
sociated with process control and understanding.
The problems of application of concepts, lack of adequate testing, in-
adequate training, and deficient understanding will not be fully resolved by
any of the established programs discussed above. To date, the programs di-
rected at these problems - 0§M manual preparation, operator training courses,
technology transfer publications, and testing for certification - are too gen-
eralized in content while the need is for specific on-site learning experi-
ence .
OfJM manuals are prepared by the consultant with little or no input from
the plant operators. Little opportunity is given the operator to come to an
understanding of the manual's contents or to be instructed on how they should
be used. Many 0§M manuals are ending up on the shelf, unused, for these
reasons. The organizational format of many 0§M manuals has been criticized
to the EPA in earlier comments by many groups. The accuracy of some 0§M man-
uals is also questionable, since they represent information derived during the
early design stages of a project and do not accurately reflect actual oper-
ation.
Operator training courses of all types - Sacramento, Clemson, corres-
pondence, association-sponsored, seminars, and workshops - do offer excellent
opportunities for textbook learning that can improve an operator's understand-
ing of treatment goals and methods,, But yery few programs bridge the gap be-
tween classroom learning and concept application with hands-on experience or
site specific, on-the-job training. This same difficulty is present in
89
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technology transfer publications, and in certification programs that rely
solely on (or include as a.criterion) the ability to score satisfactorily on a
written exam.
Wastewater treatment plants vary in size and complexity and in the qual-
ity of the operating personnel. It can safely be said that, in terms of total
number of plants, relatively few are large and complex; the majority are much
smaller but may involve some complex processes. Large plants with appropriate
budgets can attract qualified superintendents who can insure that lower level
personnel are properly trained for their work through both classroom and on-
the-job instruction. Smaller plants are less likely to have highly trained
superintendents, adequate budgets, and training capabilities, and therefore,
are more dependent on training achieved through programs such as certifica-
tion.
Effective training to produce qualified (not merely certified) operators
requires a bridge between the existing training programs and site-specific
training assistance in process control and laboratory testing in the plant.
A similar bridging mechanism must also provide additional knowledge to per-
sonnel at other plants experiencing problems which still may be beyond the
capabilities of the staff.
The bridging mechanism suggested is best provided by persons who are
knowledgeable and experienced in process theory, hands-on operation of equip-
ment and processes, and training techniques. These persons, working with the
plant operators over an extended time period, would be "outside experts" who
could both identify and solve ..problems, and teach the operators process con-
trol. In this manner, the operator supplements the knowledge he has gained
away from the plant, and is given the opportunity to exercise process control
while under the supervision of an experienced individual.
The EPA recognized the viability of such a concept by issuing under the
construction grants program its Program Requirements Memorandum (PRM) #77-2
in November 1976. This PRM authorized grant funding for up to 300 man-days
(an average of 90 man-days for most plants) of start-up services per plant for
the plant's first year of operation, to be rendered by the design engineer or
his designees. These covered services, applicable to new, expanded, or up-
graded plants include pre and post start-up on-site training, control adjust-
ments to optimize process performance, instruction in laboratory procedures,
maintenance and records management, and 0§M manual revision. Specifically,
nongrant fundable are routine, entry-level, or update operator training.
PRM #77-2 was established to fund start-up services to insure that:
"design operational efficiency is achieved as quickly as possible; process
control and related equipment problems are identified and resolved; on-site
instruction to personnel in details of the. process and equipment of each
particular plant is provided, and final revisions to the 0§M manual, based
upon actual operating experience, are made." Plants which have recently up-
graded or do not need to construct additional processes to handle their design
loadings will not be eligible for this assistance. Yet, as this study has
shown, plants in this category may also be experiencing severe problems pre-
venting their achieving permit compliance. The type of service detailed in
90
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PRM #77-2 should be available to all plants requiring assistance in problem-
solving regardless of the age of the facility, These services are available
to a varying degree from consulting firms, although they are not eligible for
federal funding. Making such'services eligible for federal funds would in-
crease the likelihood that municipalities would use them. Under the existing
statutes, EPA or the states cannot require a municipality to use such ser-
vices.
Currently, the key element of a compliance strategy is enforcement
through a penalty. There are no direct incentives for improving operation and
maintenance programs. A possible alternative to" noncompliance penalties is a
requirement that municipalities utilize operational assistance provided by
qualified experts, if their treatment plants are not performing satisfactor-
ily. Partial federal or state funding of such assistance would increase the
acceptance of this approach.
91
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SECTION 10
POTENTIAL FOR IMPROVED PLANT PERFORMANCE
As noted previously in this report, during each preliminary evaluation
performance data from available plant operating records were collected and
compiled. Complete performance records were not available for all 30 plants,
but whenever possible, performance data from the individual facilities were
analyzed in terms of 30-day average concentrations and compared with the limi-
tations set forth in the plant's NPDES permit. The number of times that the
30-day average concentrations of major constituents exceeded the permit re-
quirements was determined. Table 14 shows a distribution of the study plants
with respect to the percentage of time that the reported effluent parameters
were not in compliance with the permitted 30-day average concentrations. As
the table indicates, the 30-day average effluent concentrations at 8 plants
exceeded the BODs limit for the respective facility more than 60 percent of
the time. Four plants exceeded the BODs limit 40 percent to 60 percent of the
time. Also, more than half of the plants surveyed violated individual sus-
pended solids limits at least 40 percent of the time. Compliance with fecal
coliform limits was relatively good, with 75 percent of the plants for which
data were available showing noncompliance less than 20 percent of the time.
Table 15 presents a summary of effluent characteristics for the 30 plants
studied in the preliminary evaluation phase. The table summarizes the flow,
and effluent BODs and suspended solids data reported by the plants for the
year preceding the survey. Inasmuch as the BOD5 and. suspended solids tests
were frequently conducted improperly or with poor technique by the plant per-
sonnel, the reliability and/or representativeness of these data is question-
able. Although composite sampling was normally a provision of the NPDES per-
mit of each facility, compositing was rarely conducted. Improper sampling
techniques were frequently noted by study personnel with respect to BODs ex-
aminations. In addition, the analytical methods employed were often not those
approved by EPA. For these reasons, the information in Table 15> may not ac-
curately reflect actual conditions, but the table is based on the only data
available for each plant. The data suggest that the facilities examined dur-
ing the preliminary evaluation phase were discharging average daily BODs and
suspended solids loads of 7,290 Kg/d (16,080 Ib/d) and 8,720 Kg/d (19,235
Ib/d), respectively. Table 16 sets forth the allowable effluent BOD5 and sus-
pended solids loads based on the present average annual flow and NPDES permit
limitations. As the table indicates, at the present average flow an aggregate
total BOD5 and suspended solids load of 9,490 Kg/d (20,915 Ib/d) and (8,700
Kg/d (19,185 Ib/d), respectively, could be discharged by the plants while
still remaining within the permit limitations.
As a result of each preliminary evaluation, various recommendations were
made for improving the administration, operation, or maintenance of each
-92
-------
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wastewater treatment facility. Appendix C presents a summary of the major
specific recommendations set forth in each of the preliminary evaluation re-
ports. As indicated in the appendix, some of the more common recommendations
involved establishment of an effective process monitoring and process control
program, preparation of a comprehensive operations manual, improvement of
spare parts inventory and routine maintenance, or operator training in pro-
cess control. Other actions frequently recommended, including facility ex-
pansion or infiltration/inflow reduction, would require significant capital
expenditures and are, therefore, beyond the scope and intent of this study.
Presumably, if the 0§M related recommendations were properly implemented, im-
provements in plant performance would be realized. Accordingly, if these
recommendations were carried out, the plants would achieve their optimal de-
gree of performance, beyond which further improvement would not be feasible
without upgrading the existing facilities. Table 17 sets forth estimates of
effluent quality for each plant attainable through the implementation of all
administrative, operational, and maintenance-related modifications, presented
in each of the preliminary evaluations. These estimates of attainable ef-
fluent quality were developed with professional judgement on the basis of
knowledge of the systems evaluated and of accepted performance standards for
properly designed systems^ As shown in the table, total effluent BOD5 and
suspended solids loadings for the combined 30 plants could be reduced to
5,491 kg/d (12,105 Ib/d) and 6,053 Kg/d (13,345 Ib/d), respectively, thereby
reducing the present average effluent BOD5 and suspended solids loads to the
environment by 1,803 Kg/d (3,975 Ib/d) and 2,672 Kg/d (5,890 Ib/d), respec-
tively.
Realistically, the recommendations should not be expected to be imple-
mented by plant operating or administrative personnel to the extent that an
effluent of better quality than that called for by the permit would be con-
sistently produced. There is no incentive to produce an effluent of sig-
nificantly better quality than defined by effluent concentrations set forth
in the permit and, therefore, Table 17, may show an overestimate of reduction
in total pollutants discharged. With this fact in mind, in those cases
where implementation of the recommended operational changes could result in
an effluent quality exceeding that required by the permit, the NPDES permit
limits have been substituted as the characteristics of the effluent that are
likely to be attained. The results of this analysis are shown in Table 18.
As the table indicates, through implementation of the recommendations to the
point of achieving the NPDES limits (wherever possible), the BOD5 and sus-
pended solids loads currently discharged to the environment by the study
plants, could be reduced by 1,365 Kg/d (3,010 Ib/d) and 1,803 Kg/d (3,975
Ib/d), respectively. On an annual basis, the reductions would be approximate-
ly 0.5 million Kg (1.1 million pounds) of BOD5 and 0.635 million Kg (1.4
million pounds) of suspended solids
In terms of improving compliance with effluent limitations, it is esti-
mated that 26 of the preliminary evaluation plants would .be capable of meeting
their respective BODs limitations by implementing the recommendations to the
point of achieving NPDES permit standards. Similarly, 24 plants would meet
their suspended solids limitations. Therefore, 85 percent to 90 percent of
the plants studied would be in continuous compliance with their respective
NPDES permits. Table 19 summarizes the potential for improved performance at
96
-------
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the facilities studied under the preliminary evaluation phase, as well as the
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100
-------
REFERENCES
1. APHA, AWWA, WPCF. Standard Methods for the Examination of Water
and Wastewater. American Public Health Association, Inc., New
York, New York, 1975. 1193 pp.
2. Buchanan, R.E. and Gibbons, N. E. Bergey's Manual of Determinative
Bacteriology. The Williams and Wilkins Company, Baltimore,
Maryland, 1974.
3. Clark, J. W., Viessman, W., and Hammer, M. J. Water Supply and
Pollution Control. International Textbook Company, Scranton,
Pennsylvania, 1971. 646 pp.
4. Eikelboom, D. H. Filamentous Organisms Observed in Activated Sludge.
Water Research, 9, 365, 1975.
5. Fair, G. M., Geyer, J. C., and Okun, D. A. Elements of Water Supply
and Wastewater Disposal. John Wiley and Sons, Inc., New York, New
York, 1971. 687 pp.
6. Farquhar, G. J. and Boyle, W. C. Identification of Filamentous
Microorganisms in Activated Sludge. Journal Water Pollution Control
Federation, 43(4): 604-622, 1971.
7. Farquhar, G. J., and Boyle, W. C. Occurrence of Filamentous Micro-
organisms in Activated Sludge. Journal Water Pollution Control
Federation, 43(5): 779, 1971.
8. Gilbert, W. G. Relation of Operation and Maintenance to Treatment
Plant Efficiency. Journal Water Pollution Control Federation, 48(7) :
1822-1833, 1976.
9. Great Lakes - Upper Mississippi River Board of State Sanitary
Engineers. Recommended Standards for Sewage Works. Health
Education Service, Albany, New York, 1973. 150 pp.
10. Hegg, Bob A. Rakness, Kerwin L., and Schultz, James R., Evaluation
of Operation and Maintenance Factors Limiting Municipal Wastewater
Treatment Plant Performance, U. S. EPA, Contract'/No. 68-03-2224
Final Report 1978, 157 pp.
11. Lui, D., Kwasniewska, K.,and Cohen, D. B. Controlling Sludge Bulking.
Water and Sewage Works, March, 1977.
101
-------
12. Metcalf and Eddy, Inc. Wastewater Engineering. McGraw-Hill Book
Company, New York, New York, 1972. 734 pp.
13. U. S. Environmental Protection Agency. Estimating Staffing for
Municipal Wastewater Treatment Facilities. U. S. EPA Office of Water
Program Operations, Washington, D.C., 1973. 62 pp.
14. U. S. Environmental Protection Agency. Process Design Manual for
Sludge Treatment and Disposal. U. S. EPA National Environmental
Research Center, Cincinnati, Ohio, 1974. 368 pp.
15. U. S. Environmental Protection Agency. Process Design Manual for
Upgrading Existing Wastewater Treatment Plants. U. S. EPA National
Environmental Research Center, Cincinnati, Ohio, 1974. 366 pp.
16. U. S. Environmental Protection Agency. A Guide to the Selection of
Cost Effective Wastewater Treatment Systems. U. S. EPA Office of
Water Program Operations, Washington, D. C., 1975. 147 pp.
102
-------
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TABLE B-l. PLANT EVALUATION SUMMARY
PLANT NO.
042
PLANT TYPE: Aerated Lagoon
DESIGN FLOW: 0.55 MGD
ACTUAL FLOW: 0.40 MGD
YEAR PLANT BUILT: 1969
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design 2.e.
Design 4.b.3.
Operation 2.b.
Operation 4. a.
Operation 3. a
Design 4.f.
Design 2.c.2.
Design I.e.
Design l.b.
Administration 2. a.
CAUSE
Disinfection
Flow Proportioning to Units
Process Control Testing
0£M Manual - Adequacy
Operator Application of Concepts
and Testing to Process Control
Laboratory Space and Equipment
Process Controlability
Plant Loading - Industrial
Plant Loading - Hydraulic
2 Manpower - Plant Coverage
POINTS
3
3
3
2
2
2
2
2
2
2
115
-------
TABLE B-2. PLANT EVALUATION SUMMARY
PLANT NO.
037
PLANT TYPE: Extended Aeration
DESIGN FLOW: 0.5 MGD
ACTUAL FLOW: °-5 MGD
YEAR PLANT BUILT: 1965
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Operation 3. a.
Operation 3.b.
Operation 4. a.
Design 2.C.3.
Design 2.f.
Design l.b.
Design 2.C.2.
Design 2.e.
Operation l.b. 2.
Operation 2. a.
CAUSE
Operator Application of Concepts
and Testing to Process Control
Technical Guidance
0§M Manual Adequacy
Unit Design Adequacy-Secondary-Aerator
Sludge Wasting and Return
Plant Loading - Hydraulic
Process Controlability
Disinfection
Training
Performance Monitoring
POINTS
3
3
3
3
3.
2
2
2
2
2 -> (
116
-------
TABLE B-3. PLANT EVALUATION SUMMARY
PLANT NO.
102
PLANT TYPE: Contact-Stabilization
DESIGN FLOW: °-125 MGD
ACTUAL FLOW:
YEAR PLANT BUILT: 1969
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2 (
3 '
4
5
6
7
8
9
10
TABLE REFERENCE
idministration l.b.
)peration l.b. 2.
Jperation 2.b.
Operation 3. a.
Dperation I.e.
Operation 2. a.
Dperation l.b.l
Administration l.a.
Maintenance 2.b.
Design l.f.
CAUSE
Plant Administrators -
Familiarity with Plant Needs
, Training
Process Control Testing
Operator Application of Concepts
and Testing to Process Control
Sewase Treatment Understanding
Performance Monitoring
Level of Certification
Plant Administrators - Policies
References Available
Plant Loading - Infiltration/ Inflow
POINTS
3
3
3
•*
2
2
2
2
2
2
117
-------
TABLE B-4. PLANT EVALUATION SUMMARY
PLANT NO.
005
PLANT TYPE: Extended Aeration
DESIGN FLOW: 0.25 MGD
ACTUAL FLOW: °-15 MGD
YEAR PLANT BUILT: 197°
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design 2.g.
Operation 3. a.
Operation l.b.2.
Operation 2.b.
Operation i.e.
Administration 3. a.
Operation 4. a.
Administration l.b.
Design l.f.
Design 4.e.
CAUSE
Sludge Treatment
Operator Application of Concepts
and Testing to Process Control
Training
Process Control Testing
Sewage Treatment Understanding
Insufficient Funding
0§M Manual Adequacy
Plant Administrators - Familiarity
with Plant Needs
'Plant Loading - Infiltration/ Inflow
Lack of Standby Units For
Key Equipment
POINTS
3
3
2
2
2
2
2
2
2
2
118
-------
TABLE B-50 PLANT EVALUATION SUMMARY
PLANT NO.
086
PLANT TYPE: Contact-Stabilization
DESIGN FLOW: 0*5 mgd
ACTUAL FLOW: °-39 MGD
YEAR PLANT BUILT: 1963
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Maintenance 2. a.
Operation 3. a.
Administration 2 .a J
Operation 2.b.
Operation I.e.
Operation 4. a.
Maintenance 2.c.
Design 4.f.
Administration 2. a.
Design l.f.
CAUSE
Preventive Maintenance - Lack
of Program
Operator Application of Concepts
and Testing to Process Control
Manpower - Number
Process Control Testing
Sewage Treatment Understanding
0§M Manual Adequacy
Spare Parts Inventory.
Laboratory Space and Equipment
- Manpower - Plant Coverage
PI and Loading - Infiltration/Inflow
POINTS
3
3
3
2
2
2
2
2
2
2
119
-------
TABLE B-6. PLANT EVALUATION SUMMARY
PLANT NO.
032
PLANT TYPE: Conventional Activated Sludge
DESIGN FLOW: 4.0 MGD
ACTUAL FLOW: 3.1 MGD
YEAR PLANT BUILT: 1973
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.a.
Operation 3.b.
Operation 2.b.
Operation 3. a.
Operation I.e.
Design l.f.
Design I.e.
Maintenance l.d.
Operation 4.b.
Administration 2.b J
CAUSE
Plant Loading - Organic
Technical Guidance
Process Control Testing
Operator Application of Concepts
and Testing to Process Control
Sewage Treatment Understanding
Plant Loading - Infiltration/ Inflow
Plant Loading - Industrial
Manpower
0§M Manual - Use by Operators
Motivation
POINTS
2
2
2
2
1
1
1
1
1
1
120
-------
TABLE B-7. PLANT EVALUATION SUMMARY
PLANT NO.
059
PLANT TYPE: Contact-Stabilization
DESIGN FLOW: 12.0 MGD
ACTUAL FLOW: 9.2 MGD
YEAR PLANT BUILT: 1933
YEAR OF MOST RECENT UPGRADE: 197°
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design 2.g.
Design 2.b.
Design 4.b.2.
Operation 3. a.
Design 2.e.
Design 4'.b.l ,
Maintenance l.d.
Operation I.e.
Design l.f.
Design 3.b.
CAUSE
Sludge Treatment
Unit Design Adequacy - Primary
Submerged Weirs
Operator Application of Concepts
and Testing to Process Control
Disinfection
Flow Backup
Manpower .
Sewage Treatment Understanding
Plant Loading - Infiltration/ Inflow
Alternate Power Source
POINTS
3
3
3
2
2
2
1
1
1
1
121
-------
TABLE B-8. PLANT EVALUATION SUMMARY
PLANT NO.
024
PLANT TYPE- Conventional Activated Sludge
DESIGN FLOW: 1.30 MGD
ACTUAL FLOW: !-30 MGD
YEAR PLANT BUILT: 1952
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.a.
Design I.e.
Design l.f.
Design 2.C.3.
Operation 4. a.
Maintenance l.b.
Operation 2. a.
Operation 2.b.
Operation 3. a.
Design 4.£.
CAUSE
Plant Loading - Organic
Plant Loading - Industrial
Plant Loading - Infiltration/Inflow
Unit Design Adequacy -
Secondary - Aerator
0§M Manual Adequacy
Equipment Age
Performance Monitoring
Process Control Testing
Operator Application to Concepts
and Testing to Process Control
Laboratory Space and Equipment
POINTS
3
3
3
3
3-
2
2
2
2
2
122
-------
TABLE B-9. PLANT EVALUATION SUMMARY
PLANT NO.
038
PLANT TYPE: Trickling Filter
DESIGN FLOW: 7.0 MGD
ACTUAL FLOW: 4.6 MGD
YEAR PLANT BUILT: 1936
YEAR OF MOST RECENT UPGRADE: 1969
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.a.
Design I.e.
Design 3.c.
Design 2.c.2.
Dperation 4. a.
Operation 2.b.
Maintenance 2 . b . 1
Administration 2 .b . :
Administration 2.c.
Design 3.b.
CAUSE
Plant Loading - Organic
Plant Loading - Industrial
Plant Location
Process Control ability
0§M Manual Adequacy
Process Control Testing
References Available
Motivation
Productivity
Alternate Power Source
POINTS
2
2
2
1
1
1
1
1
1
1
123
-------
TABLE B-10. PLANT EVALUATION SUMMARY
PLANT NO.
093
PLANT TYPE: Conventional Activated Sludge § Contact Stabilizat:
DESIGN FLOW: 10'. 0 MGD —
ACTUAL FLOW: 5.9 MGD
YEAR PLANT BUILT: 1965
YEAR OF MOST RECENT UPGRADE: 1976
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
8
9
10
TABLE REFERENCE
Design 2.g.
Design 2.C.3.
Design 2.e.
Operation 3. a.
Maintenance 2.b.
Operation 4. a.
Operation l.b.2
Design l.£.
Operation 5.b.
Maintenance 2.c.
CAUSE
Sludge Treatment
Unit Design Adequacy - Aerator
Disinfection
Operator Application of Concepts
and Testing to Process Control
References Available
0§M Manual Adequacy
Training
Plant Loading - Infiltration/ Inflow
Shift Staffing Adequacy
Spare Parts Inventory
POINTS
2
2
2
2
2
2
1
1
1
1
on
124
-------
TABLE B-ll. PLANT EVALUATION SUMMARY
PLANT NO.
082
PLANT TYPE: Contact Stabilization
DESIGN FLOW: °-95 MGD
ACTUAL FLOW: 1*° MGD
YEAR PLANT BUILT: 1961
YEAR OF MOST RECENT UPGRADE: 1970
PLANT PERFORMANCE:
RANKING
,,1
2 ...
3
4,
5
6
7
8
9
10
TABLE REFERENCE
Design 2,f.
Design 2.b.
Operation 2.b.
Operation 4. a.
Design l.b.
Design I.e.
Design l.g.
Operation 3. a.
Operation 3.b.
Design 3. b.
CAUSE
Sludge Wasting and Return
Unit Design Adequacy - Primary
Process Control Testing
0§M Manual - Adequacy
Plant Loading - Hydraulic
Plant Loading - Industrial
Return Process Streams
Operator Application of Concepts
and Testing to Process Control
Technical Guidance
Alternate Power Source
POINTS
3
3
3
3
2
2
2
2
2
1
125
-------
TABLE B-12. PLANT EVALUATION SUMMARY
PLANT NO.
006
:
PLANT TYPE: Conventional Activated Sludge
DESIGN FLOW: 0.5 MGD
ACTUAL FLOW: °-55 MGD
YEAR PLANT BUILT: 1947
YEAR OF MOST RECENT UPGRADE: 1973
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Administrator 2 . a. 1
Maintenance l.d.
Operator 3. a.
Operation l.c
Administration l.b.
Operation 4. a.
Design 2.e.
Operation l.b. 2.
Design 4.e.
Design l.f.
CAUSE
Plant Staff - Number
Manpower
Operator Application of Concepts
and Testing to Process Control
Sewage Treatment Understanding
Plant Administrators -
Familiarity with Plant Needs
0£M Manual - Adequacy
Disinfection
Training
Lack of Standby Units
for Key Equipment
Plant Loading - Infiltration/ Inflow
POINTS
2
2
2
2
2
2
2
2
2
2
126
-------
TABLE B-13. PLANT EVALUATION SUMMARY
PLANT NO.
PLANT TYPE: Complete Mix Activated
Sludge
DESIGN FLOW: 3.0 MGD
ACTUAL FLOW: 4.0 MGD
YEAR PLANT BUILT: 1973
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.f
Design 2.c.2
Design 2.c.l
Design 2.f.
Operation 5. a.
Design 4.b.2
Design 2.c.4
Design 2.C.3
Design 4.c.
Maintenance 3.b.
CAUSE
Inf i 1 t r at ion/ Infl ow
Process Control ability
Secondary Process Flexibility
Sludge Wasting and Return
Equipment Malfunction
Submerged Weirs
Unit Design Adequacy -
Secondary-Clarifier
Unit Design Adequacy -
Secondary- Aerator
Unit Accessibility
Critical Parts Procurement
POINTS
3
3
2
2
2
2
2
2
1
1
127
-------
TABLE B-14. PLANT EVALUATION SUMMARY
PLANT NO.
089
.
PLANT TYPE: Contact-Stabilization
DESIGN FLOW: 0.6 MGD
ACTUAL FLOW: 0.37 MGD
YEAR PLANT BUILT: 1966
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Operation 3. a.
)peration l.b.2.
Design I.e.
Design l.f.
Operation 2.b.
Operation I.e.
Operation 2. a.
Operation 3.b.
Operation 4. a.
Design 2.c.l.
CAUSE
Operator Application of Concepts
and Testing to Process Control
Training
Plant Loading - Industrial
Plant Loading - Infiltration/ Inflow
Process Control Testing
Sewage Treatment Understanding
Performance Monitoring
Technical Guidance
0(|M Manual - Adequacy
Secondary Process Flexibility
POINTS
2
2
2
2
1
1
1
1
1
1
128
-------
TABLE B-15. PLANT EVALUATION SUMMARY
PLANT NO.
095
. . . . .
PLANT TYPE: Contact > Stabilization
DESIGN FLOW: O-35 MGD
ACTUAL FLOW: 0.30 MGD
YEAR PLANT BUILT: 1964 '
YEAR OF MOST RECENT UPGRADE: -
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design 2.C.3. -
Design l.f.
Design 2.c.l
Design 4.a.
Operation 4. a.
Design I.e.
Design 4.d.l.
Design 4.d.2.
Administration 2. a.
>•
CAUSE i
Unit Design Adequacy -
Secondary - Aerator •
Plant Loading - Infiltration/ Inflow
Secondary Process' Flexibility
Lack of Unit Bypass
0§M Manual Adequacy
Plant Loading - Industrial •
Process Automation - Monitoring
Process Automation - Control
2 Manpower - Plant Coverage
POINTS
.: 2 '•
2 t
, 2
2
1
1
1
1
1
; •
129
-------
TABLE B-16. PLANT EVALUATION SUMMARY
PLANT NO.
120
PLANT TYPE: Conventional Activated Sludge (w/Roughing Filter)
DESIGN FLOW: 3.0 MGD
ACTUAL FLOW: 2.7 MGD
YEAR PLANT BUILT:
YEAR OF MOST RECENT UPGRADE: 197°
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
)esign I.e.
Design l.a.
Administration 2.c.
Operation 3. a.
\dministration 2. a.
Dperation l.b.2.
Design l.f.
Dperation 2.b.
Plaint enance 1 . d .
Administration 2.b.
CAUSE
Plant Loading - Industrial
Plant Loading - Organic
Productivity
Operator Application of Concepts
And Testing to Process Control
! Manpower - Plant Coverage
Training
Infiltration/ Inflow
Process Control Testing
Manpower
. Motivation
POINTS
2
2
2
2
1
1
1
1
1
1
130
-------
TABLE B-17. PLANT EVALUATION SUMMARY
PLANT NO.
034
PLANT TYPE: Extended Aeration
DESIGN FLOW: °*25 MGD
ACTUAL FLOW: 0.40 MGD
YEAR PLANT BUILT: 1963
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
/
9
10/
TABLE REFERENCE
Design l.b.
/
Operation 3. a.
/
Design l.f.
Operation 2.b/.
/
Administration 2. a.
/
Operation 2. a.
Design 4.£.
Operation l.b. 2.
Operation 3.b.
Administration 2.d.
CAUSE
/ Hydraulic
Operator Application of Concepts
And Testing to Process Control
Infiltration/ Inflow
Process Control Testing
2 Manpower - Plant Coverage
Performance Monitoring
Laboratory Space and Equipment
Training
Technical Guidance
Personnel Turnover
POINTS
3
2
2
2
2
/
2
1
1
1
1
131
-------
TABLE B-18. PLANT EVALUATION SUMMARY
PLANT NO.
PLANT TYPE: Activated Sludge - Aerator/Clarifier ,/
DESIGN FLOW: 0.5 MGD
ACTUAL FLOW: 0.49
YEAR PLANT BUILT: 1949
YEAR OF MOST RECENT UPGRADE: 1969
PLANT PERFORMANCE:
RANKING
1
2
3
4
'5
6
7
8
9
10
TABLE REFERENCE
Operation I.e.
Operation 2.b.
Operation 3. a.
Design 4.c.
Administration 3. a.
Operation 2. a.
Design l.f.
Operation 4. a.
Maintenance 2. a.
Maintenance I.e.
CAUSE
Sewage Treatment Understand n g-
Process Control Testing
Operator Application of Concepts
And Testing to Process Control
Unit Accessibility
Insufficient Funding
Performance Monitoring
Plant Loading - Infiltration/ Inflow
0§M Manual - Adequacy
Lack -of Program
Scheduling and Recording
POINTS
••?,
2
2
2
2
2
2
2
1
1
132
-------
TABLE B-19. PLANT EVALUATION SUMMARY
PLANT NO.
071
PLANT TYPE: Trickling Filter
DESIGN FLOW: 1.25 MGD
ACTUAL FLOW: 1.15 MGD
YEAR PLANT BUILT: 1961
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.d.
Design l.f.
Design 4.£.
Operation 3. a.
Operation l.b.2.
Design 4.e.
Maintenance l.b.
Maintenance 2.c.
Design 3.f.
CAUSE
Plant Loading - Toxic
Plant Loading - Infiltration/ Inflow
Laboratory Space and
Equipment
Operator Application o± concepts
And Testing to Process Control
Training
Lack of Stand-by Units
For Key Equipment
Equipment Age
Spare Parts Inventory
Plant Inoperability Due to Weather
POINTS
3
2
2
1
1
1
1
1
1
133
-------
TABLE B-20. PLANT EVALUATION SUMMARY
PLANT NO.
077
PLANT TYPE:
Trickling Filter/Bio-Discs
DESIGN FLOW:
1.75 MGD
ACTUAL FLOW:
1.2 MGD
YEAR PLANT BUILT:
1969
YEAR OF MOST RECENT UPGRADE: 1975
PLANT PERFORMANCE:
RANKING
TABLE REFERENCE
CAUSE
POINTS
Design 2.C.2.
Secondary Process Controlability
Design l.f.
Infiltrat ion/Inflow
10
Design 3.b.
Alternate Power Source
134
-------
TABLE B-21. PLANT EVALUATION SUMMARY
PLANT NO.
021
PLANT TYPE: Rvt.«nH«H Aivral-imi
DESIGN FLOW: 1.25 MGD
ACTUAL FLOW: 0.88 MGD
YEAR PLANT BUILT: 1970
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Operation 3. a.
Design 4.f.
Design 2.g.
Operation 4. a.
Operation I.e.
Design l.b.
Design I.e.
CAUSE
Operator Application of Concepts
and Testing to Process Control
Laboratory Space and Equipment
Sludge Treatment
0§M Manual - Adequacy
Sewage Treatment Understanding
Plant Loading - Hydraulic
Plant Loading - Infiltration/ Inflow
POINTS
-)
2
2
2
1
1
1
135
-------
TABLE B-22. PLANT EVALUATION SUMMARY
PLANT NO.
026
PLANT TYPE: Activated Sludge
DESIGN FLOW: 8-5 MGD
ACTUAL FLOW: 7'5 MGD
YEAR PLANT BUILT: 1957
YEAR OF MOST RECENT UPGRADE: 1969
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.b.
Design l.f.
Operation 2.b.
Operation 3. a.
Operation 4. a.
Design 2.b.
Operation 3.b.
Administration l.a.
Maintenance 2.c.
Administration 2.c.
CAUSE
Plant Loading - Hydraulic
Plant Loading - Infiltration/ Inflow
Process Control Testing
operator Application of Concepts
and Testing to Process Control
0§M. Manual - Adequacy
Unit Design Adequacy - Primary
Technical Guidance
Policies
Spare Parts Inventory
Productivity
POINTS
3
2
2
2
2
2
1
1
1
1
136
-------
TABLE B-23. PLANT EVALUATION SUMMARY
PLANT NO.
046
. . . . ... • . . ,- .• - . ..,,„•....•- ..,.,..
PLANT TYPE: Extended Aeration . , .... . ; •
DESIGN FLOW: ., 0.21 MGD .......;.:..-' * ,,
ACTUAL FLOW: 0.24 MGD ;
YEAR PLANT BUILT: 197°
,YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
<
RANKING
1
,. -.„ 2
3
4
5
6
. 7 .,„ .
8
9
10
TABLE REFERENCE
Administration 2,. aJ.
Design 4.e.
Maintenance 2. a
Maintenance l.d.
Maintenance 2.c.
Maintenance I.e.,
Maintenance l.a.
Dperation 2.b.
Design l.f.
Dperation 4. a.
CAUSE
Plant Staff -.: Number, „ ., ...;.
Lack of Standby Units
for Key Equipment /
Preventive - Lack of Program
Manpower
Spare, Parts Inventory
; - ' ~- - . - - .
Scheduling and Recording
Housekeeping ,
Process Control Testing
Plant Loading - Infiltration/Inflow
0£M Manual - Adequacy
POINTS
, , 3 , , :
. .. ?,.• , :.
2
2 .;
2 ......
2
2 ... :
2 ,. . .;
2
1
137
-------
TABLE B-24. PLANT EVALUATION SUMMARY
PLANT NO.
114
PLANT TYPE:
Oxygen Activated Sludge
DESIGN FLOW:
14.0 MGD
ACTUAL FLOW:
10.7 MGD
YEAR PLANT BUILT:
1954
YEAR OF MOST RECENT UPGRADE: 197°
PLANT PERFORMANCE:
RANKING
TABLE REFERENCE
CAUSE
POINTS
Design 2.h.
Ultimate Sludge Disposal
Design 4.b.2
Submerged Weirs
10
Design l.f.
Infiltration/Inflow
138
-------
TABLE B-25. PLANT EVALUATION SUMMARY
PLANT NO.
106
PLANT TYPE: Extended Aeration
DESIGN FLOW: 7-° MGD
ACTUAL FLOW: Z'1 MGD
YEAR PLANT BUILT: 1965
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.f.
Dperation 3. a.
Dperation 2.b.
Design 4.b.3
CAUSE
Infiltration/ Inflow
Operator Application of Concepts
and Testing to Process Control
Process Control Testing
Flow Proportioning to Units
POINTS
2
1
1
1
139
-------
TABLE B-26. PLANT EVALUATION SUMMARY
PLANT NO.
053
PLANT TYPE: Conventional Activated Sludge
DESIGN FLOW: 3.0 MGD
ACTUAL FLOW: 2'2 MGD
YEAR PLANT BUILT: 1971
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.f.
Design 4.b.3.
Operation 4. a.
Operation 3. a.
Operation 2.b.
Design 2.g.
Maintenance 2.c.
Maintenance 3.b.
Design 4.f.
CAUSE
Plant Loading - Infiltration/ Inflow
Flow Proportioning to Units
0§M Manual - Adequacy
operator Application or Concepts
and Testing to Process Control
Process Control Testing
Sludge Treatment
Spare Parts Inventory
Critical Parts Procurement
Laboratory Space and Equipment
POINTS
3
3
3
2
2
2
2
2
1
140
-------
TABLE B-27. PLANT EVALUATION SUMMARY
PLANT NO.
074
PLANT TYPE: Trickling Filter
DESIGN FLOW: °-89 MGD
ACTUAL FLOW: °'7 MGD
YEAR PLANT BUILT:
YEAR OF MOST RECENT UPGRADE: 1959
PLANT PERFORMANCE:
RANKING
1
2
3
4
. .. .5.
6
... 7 - •
a
9
~ 10
TABLE .REFERENCE
Design l.a.
Design I.e.
Design 4.b.3
Operation 5. a.
Maintenance l.b.
Maintenance 2. a.
Operation 4. a.
Maintenance l.a.
CAUSE
Plant Loading - Organic
Plant Loading - Industrial
Flow Proportioning to Units
Equipment Malfunction
Equipment Age
Preventive Maintenance, -
Lack of Program
0§M Manual - Adequacy
Housekeeping
POINTS
2
2
2
1
1
1
1
1
141
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TABLE B-28. PLANT EVALUATION SUMMARY
PLANT NO.
083
PLANT TYPE: Activated Sludge
DESIGN FLOW: 15 MGD
ACTUAL FLOW: 8'8 MGD
YEAR PLANT BUILT: 1956
1 Q74
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Operation 3. a.
Maintenance 2.c.
Maintenance 2. a.
Administration 2 .b .
Administration 2.d.
Design 4. a.
Design I.e.
Maintenance 3.b.
Design 2.c.2
CAUSE
Operator Application of Concepts
and Testing to Process Control
Spare Parts Inventory
Preventive Maintenance- Lack of Program
! Pay
Personnel Turnover
Lack of Unit Bypass
Plant Loading - Industrial
Critical Parts Procurement
Secondary Process Controlability
POINTS
2
2
1
1
1
1
1
1
1
142
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TABLE B-29. PLANT EVALUATION SUMMARY
PLANT NO.
066
PLANT TYPE: Contact-Stabilization
DESIGN FLOW: 1.0 MGD
ACTUAL FLOW: 0.33 MGD
YEAR PLANT BUILT: 1969
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Design l.f.
Design l.a.
Design 2.C.2.
Design 2.g.
Design I.e.
Operation 2.b.
Operation 3. a.
Operation 5. a.
Maintenance 3.b.
Design 2.h.
CAUSE
Plant Loading - Infiltration/ Inflow
Plant Loading - Organic
Secondary Process Control ability
Sludge Treatment
Plant Loading - Seasonal Variation
Process Control Testing
Operator Application of Concepts
and Testing to Process Control
Equipment Malfunction
Critical Parts Procurement
Ultimate Sludge Disposal
POINTS
2
2
1
1
1
1
1
1
1
1
143
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TABLE B-30. PLANT EVALUATION SUMMARY
PLANT NO.
078
PLANT TYPE: Extended Aeration (Oxidation Ditch)
DESIGN FLOW: 0.21 MGD
ACTUAL FLOW: °'24 MGD
YEAR PLANT BUILT: 197°
YEAR OF MOST RECENT UPGRADE:
PLANT PERFORMANCE:
RANKING
1
2
3
4
5
6
7
8
9
10
TABLE REFERENCE
Administration 3. a.
Maintenance l.d.
kdmini s trat ion 2 . a . ]
Design 3.f.
Dperation 3. a.
Design 2.c.4.
Maintenance 2. a.
Maintenance l.a.
Operation l.b.2.
Maintenance 2.c.
CAUSE
Insufficient Funding
Manpower
Plant Staff - Number
Plant Inoperability Due to Weather
operator Application of Concepts
and Testing to Process Control
Unit Design Adequacy
Clarifier
Preventive - Lack of
Housekeeping
- secondary
Program
Training
Spare Parts Inventory
POINTS
3
3
3
3
2
2
2
2
2
2
144 ;
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TABLE C-l. LIST OF RECOMMENDATIONS FROM PRELIMINARY EVALUATION REPORTS
Plant Number
034
048
068
114
037
086
Recommendat ions
1. Upgrade sampling and analysis techniques.
2. Prepare comprehensive 0 § M manual.
3. Provide plant specific training for operating
staff.
1. Upgrade plant capacity or reduce infiltration/
inflow.
1. Improve chlorination of effluent.
2. Reduce infiltration/inflow.
3. Upgrade sampling and analysis techniques.
4. Discontinue addition of lime to aeration tanks.
5. Employ process control/laboratory technician.
6. Prepare comprehensive 0 § M manual.
7. Install auxiliary power supply and alarm system.
1. Prepare daily cleanup schedule.
2. Modify analytical program to put more emphasis
on process control.
1. Upgrade laboratory facilities.
2. Upgrade training of personnel regarding
analytical function.
3. Expand wastewater parameters tested and process
control.
1. Repair grit chamber and comminutor.
2. Repair or replace sludge collection mechanism.
3. Increase return sludge volume.
4. Operate aeration stage blowers continuously.
5. Establish systematic routine maintenance program.
6. Improve quality control of laboratory work.
7. Hire supervisory and maintenance personnel.
8. Increase budget 20 percent.
(continued)
145
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Plant Number
Recommendations
042
021
046
006
005
093
(continued)
1. Increase substantially the operation and
routine maintenance manpower.
2. Implement preventive maintenance program.
3. Prepare comprehensive 0 § M manual.
4. Upgrade laboratory program for adequate process
control.
1. Prepare comprehensive 0 § M manual and train
personnel in accordance with manual.
2. Upgrade laboratory capabilities for process
control and performance monitoring using EPA
approved procedures.
3. Conduct performance testing as required by
NPDES permit.
4. Eliminate filamentous growth in activated
sludge system.
1. Reduce infiltration/inflow.
2. Improve sampling procedures in accordance with
provisions of NPDES permit.
3. Submit quarterly NPDES reports as required by
regulatory agency.
4. Maintain full-time operating personnel.
5. Train plant staff in process control techniques.
6. Modify 0 § M manual to address unit processes
and equipment not covered in present manual.
7. Maintain adequate spare parts inventory.
8. Increase budget to provide for a full-time
plant operator.
1. Reduce floating material on final clarifier.
2. Repair chlorinators
3. Utilize lab data to optimize operating
parameters.
4. Prepare comprehensive 0 § M manual.
5. Provide auxiliary power source and alarm system.
6. Employ a full-time superintendent.
1. Improve process control.
2. Upgrade training of staff.
3. Modify plant 0 § M manual.
4. Utilize one of two aeration tanks as an
aerobic digester.
1. Reduce suspended solids in effluent through
increased sludge wasting.
2. Decrease chlorine feed concentrations and
improve mixing of chlorine and wastewater.
3. Hire two additional personnel and implement
staffing schedule.
146
-------
Plant Number
Recommendations
083
066
071
053
095
024
078
1. Continue to optimize centrifuge performance.
2. Upgrade vacuum filter.
3. Expand spare parts inventory.
4. Increase and improve control of sludge wasting
rate.
1. Optimize use of contact and stabilization tanks.
2. Improve control of F/M.
3. Provide additional sludge dewatering capacity.
4. Use approved chlorine residual test method.
5. Prepare comprehensive 0 § M manual.
1. Use BODg method approved by EPA.
2. Install a standby power source.
1. Modify or replace grit chamber screw pumps.
2. Initiate process control testing.
3. Purchase apparatus for daily analysis of MLSS
concentration.
4. Prepare comprehensive 0 f| M manual.
5. Establish maintenance schedule.
6. Establish spare parts inventory.
7. Sewer Authority should develop separate budget
for each plant under its control.
1. Keep F/M between 0.2 and 0.5 Kg BOD5/day/KgMLSS.
2. Reduce infiltration/inflow in collection system.
3. Upgrade sampling and analysis procedures.
4. Determine cause of excessive coliform counts.
5. Prepare comprehensive 0 § M manual.
1. Conduct industrial waste survey.
2. Establish controlled discharge or pretreatment
program for industries.
3. Prepare comprehensive 0 § M manual and train
workers in accordance wiith manual.
4. Expand laboratory capabilities.
5. Perform regular process control analyses.
1. Modernize equipment.
2. Increase MLVSS until F/M is reduced to about
0.30 Kg BOD5/d/Kg MLSS.
3. Upgrade process control by monitoring DO, SVI,
F/M, MCRT, MLSS, and MLVSS.
4. Prepare comprehensive 0 § M manual.
5. Hire individual with treatment plant maintenance
experience.
(continued)
147
-------
Plant Number
077
082
089
074
120
102
Recommendat ions
1. Revise sampling according to NPDES permit
requirements.
2. Operate biological facilities in series.
1. Improve sludge handling.
2. Remove sludge directly from aerobic digester
to tank truck.
3. Prepare comprehensive 0 § M manual.
4. Sample effluent in accordance with provisions
of NPDES permit.
5. Monitor process control parameters.
6. Initiate part-time non-daylight shift coverage.
1. Enforce pretreatment ordinance.
2. Submit quarterly monitoring reports to regulatory
agency.
3. Adhere to NPDES sampling and analysis procedures.
4. Increase sludge wasting rate.
5. Train plant staff in theory of contact-
stabilization system and process control
techniques.
6. Initiate process control monitoring program.
7. Prepare supplement to 0 § M manual.
1. Improve routine maintenance procedures.
2. Increase staff size.
3. Prepare comprehensive 0 § M manual.
4. Add ferric chloride and polymer to effluent
only when needed.
1. Collect final effluent BODs samples prior to
disinfection.
2. Monitor F/M and MCRT regularly for control of
activated sludge system.
3. Improve final clarifier efficiency through
maintaining increased MLSS levels, thus,
enhancing flocculation and settling
qualities.
4. Provide third shift operator.
5. Prepare for removal of NH3-N at plant as
required by NPDES permit after July 1, 1977.
1. Inform responsible officials of plant conditions
and consequences if conditions are not improved.
2. Employ full-time operator, experienced in both
operations and maintenance.
3. Provide additional training of present operator.
4. Prepare comprehensive 0 § M manual.
(continued)
148
-------
Plant Number
Recommendat ions
102 (Cont'd)
106
026
032
038
059
6.
7.
8.
9.
1.
2.
3.
4.
5.
6.
1.
2.
3.
1.
2.
3.
2.
3.
4.
Retain consultant to evaluate performance and
process monitoring needs, laboratory equipment
needs, and maintenance program needs.
Establish adequate spare parts inventory.
Improve "housekeeping" practices.
Obtain emergency maintenance equipment.
Establish a workable budget.
Select biological process control method and
operate under conventional parameters.
Enclose thickener as planned to prevent freezing
problems in winter.
Prepare a comprehensive 0 § M manual.
Prepare supplement to 0 § M manual.
Utilize F/M or MCRT techniques to control
operation.
Employ two additional maintenance personnel.
Increase supplies of spare parts and hand tools.
Improve "housekeeping" practices.
Increase budget to offset increased costs.
Equalize loadings on treatment plant.
Eliminate infiltration sources.
Increase primary clarifier efficiency through
chemical addition.
Operate tertiary filtration system according to
design intent.
Enforce provisions of local pretreatment ordinance.
Prepare comprehensive 0 § M manual.
Revise sampling techniques to conform to NPDES
permit.
Increase sludge wasting rate to achieve lower
MLSS concentrations and F/M more in line with
conventional parameters.
Provide additional weir length in primary
clarifiers to reduce weir loadings.
improve removal of skimmings from primary
clarifiers.
Remove sludge collection mechanism from chlorine
contact tank and install baffles to eliminate
short-circuiting.
Examine methods of increasing capacity of sludge
thickening stage.
149
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-79-078
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
EVALUATION OF OPERATION AND MAINTENANCE FACTORS LIMIT-
ING BIOLOGICAL WASTEWATER TREATMENT PLANT PERFORMANCE
5. REPORT DATE
July 1979 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Albert C. Gray, Jr., Paul E. Paul, and Hugh D. Roberts
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Gannett Fleming Corddry and Carpenter, Inc.
P. 0. Box 1963
Harrisburg, Pennsylvania 17105
10. PROGRAM ELEMENT NO.
1BC821; SOS 2; Task Al
11. CONTRACT/aassajffl- NO.
68-03-2223
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES See also EPA-600/2-79-034, Evaluation of Operation and Maintenance
Factors Limiting Municipal Wastewater Treatment Plant Performance" and EPA-600/2-79-035,
"A Demonstrated Approach for Improving the Performance and Reliability of Biological
TJflgf-p>TJflt-«ar- T-roaf-Tnonf- P1gni-g"' f.on^ar-t-• TT-ranm'a T. Tirana TTT
16. ABSTRACT
The purposes of this research study were to evaluate operational and maintenance
programs at municipal biological wastewater treatment facilities; identify all the
deficiencies in the areas of design, operation, maintenance and administration; and to
determine how the deficiencies could be overcome and operations could be improved in
order to upgrade plant performance to meet standards. Conclusions and recommendations
are based on 1/2-to-l-day site visits made to 120 facilities and 3-to5-day comprehensive
evaluations conducted at 30 facilities. Of 70 potential problem areas evaluated, the
ten highest ranked, based on frequency of occurrence and severity of impact were opera-
tor application of treatment concepts and testing to process control, infiltration/
inflow, process control testing procedures, adequacy of O&M manual, industrial loading,
training, hydraulic loading, treatment understanding, process controllability, and
sludge treatment.
This report was submitted in partial fulfillment of Control No. 68-03-2223 by
Gannett Fleming Corddry and Carpenter, Inc., under the sponsorship of the U.S. Envir-
onmental Protection Agency. This report covers the period June 25, 1975 to July
1977, and work was completed July 1978.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPERl ENDED TERMS
c. COSATI Field/Group
Waste treatment, Activated sludge process,
Trickling filtration, Settling basins,
Wastewater—water pollution
Freatment plant performance
Emproving plant performance
Poor plant performance fac
tors, Composite correction
program (CCP), Wastewater
treatment plant—operation
naintenance, design,
idministration
13B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
168
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rov. 4-77)
150
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