vvEPA
United States ;
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati OH 45268
Technology Transfer
Handbook
Improving POTW
Performance Using the
Composite Correction
Program Approach
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EPA-625/6-84-008
HANDBOOK
IMPROVING POTW PERFORMANCE
USING THE
COMPOSITE CORRECTION PROGRAM APPROACH
U.S. ENVIRONMENTAL PROTECTION AGENCY
Center for Environmental Research Information
Cincinnati, Ohio 45268
October 1984
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NOTICE
This document has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
ii
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FOREWORD
The formation of the Environmental Protection Agency marked a new era of
environmental awareness in America. This Agency's goals are national in scope
and encompass broad responsibility in the areas of air and water pollution,
solid wastes, pesticides, hazardous wastes, and radiation. A vital part of
EPA's national pollution control effort is the constant development and
dissemination of new technology.
It is clear that only the most effective design and operation of pollution
control facilities will be adequate to ensure continued protection of this
Nation's natural resources. It is essential that we achieve the maximum
performance possible of existing Publicly Owned Treatment Works (POTWs) to
achieve maximum benefit from our expenditures.
The purpose of this Handbook is to provide POTW owners/administrators and the
engineering community with a new source of information to be used in improving
the performance of POTWs through application of the Composite Correction
Program (CCP) approach. It is the intent of the manual to supplement the
existing body of knowledge in this area.
This Handbook is one of several publications available from Technology
Transfer to describe technological advances and present new information.
i i i
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ACKNOWLEDGMENTS
Many individuals contributed to the preparation and review of this Handbook.
Contract administration was provided by the U.S. Environmental Protection
Agency (EPA), Center for Environmental Research Information, Cincinnati, Ohio.
CONTRACTOR-AUTHORS
Major Authors:
Bob A. Hegg, James R. Schultz, and Kerwin L. Rakness,
Process Applications Inc., Fort Collins, CO
CONTRACT SUPERVISORS
Project Officer:
Reviewers:
Denis J. Lussier, EPA-CERI, Cincinnati, OH
Jon H. Bender, EPA-MERL, Cincinnati, OH
Charles E. Gross, EPA-OWPO, Washington, DC
Torsten Rothman, Dynamac Corp., Rockville, MD
TECHNICAL PEER REVIEWERS
Thomas M. Rachford, Gannett Fleming Environmental Engineers,
Inc., Harrisburg, PA
Stephen Poloncsik, EPA Region 5, Chicago, IL
Walter G. Gilbert, EPA-OWPO, Washington, DC
IV
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CONTENTS
Chapter
Page
FOREWORD
ACKNOWLEDGMENTS
LIST OF FIGURES
LIST OF TABLES
INTRODUCTION ;
1.1 Purpose and Scope,
1.2 Background
1.3 Overview
1.4 References i
m
iv
vii
viii
1
2
3
3
APPROACH TO CONDUCTING COMPREHENSIVE PERFORMANCE EVALUATIONS
2.1 Objective
2.2 Methodol ogy
2.3 Personnel Capabilities for Conducting CPEs
2.4 Estimating CPE Costs
2.5 References
HOW TO CONDUCT COMPREHENSIVE PERFORMANCE EVALUATIONS
3.1 Introduction
3.2 Initial Activities
3.3 Data Collection
3.4 Evaluation of Major Unit Processes
3.5 .Evaluation of Performance-Limiting Factors
3.6 Performance Evaluation
3.7 Presentation to POTW Administrators and Staff
3.8 CPE Report
3.9 Example CPE
3.10 CPE Results
3.11 CPE Worksheets
3.12 References
APPROACH TO CONDUCTING COMPOSITE CORRECTION PROGRAMS
4.1 Objective
4.2 Methodology
4.3 Personnel Capabilities'for Conducting CCPs
4.4 Estimating CCP Costs
4.5 References
HOW TO CONDUCT COMPOSITE CORRECTION PROGRAMS
5.1 Introduction
5.2 CCP Activities
5
5
12
13
14
16
16
20
25
45
56
58
59
61
69
69
69
71
72
74
76
77
78
78
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CONTENTS (continued)
Chapter
5
APPENDIX
A
B
C
D
E
F
G
H
I
J
K
L
M
N
0
HOW TO CONDUCT COMPOSITE CORRECTION PROGRAMS (Cont.)
5.3 Initial Site Visit
5.4 Improving Design Performance-Limiting Factors
5.5 Improving Maintenance Performance-Limiting Factors
5.6 Improving Administrative Performance-Limiting Factors
5.7 Improving Operational Performance-Limiting Factors
5.8 Example CCP
5.9 CCP Results
5.10 References
CPE CLASSIFICATION SYSTEM, CHECKLIST AND GUIDELINES FOR
PERFORMANCE-LIMITING FACTORS
CPE SUMMARY SHEET FOR RANKING PERFORMANCE-LIMITING FACTORS
EXAMPLE CPE REPORT
DATA COLLECTION FORMS USED IN CONDUCTING CPEs
GUIDELINES FOR FIELD ESTIMATING EQUIPMENT POWER USAGE
PROCEDURE FOR CONVERTING STANDARD OXYGENATION RATES TO
ACTUAL OXYGENATION RATES
EXAMPLE FORMS FOR ESTABLISHING A PREVENTIVE MAINTENANCE
PROGRAM FOR SMALL POTWs
DESIGN RELATED PERFORMANCE-LIMITING FACTORS IDENTIFIED
IN ACTUAL CPEs
EXAMPLE PROCESS MONITORING SUMMARY FOR AN ACTIVATED
SLUDGE POTW
EXAMPLE PROCESS MONITORING SUMMARY FOR AN RBC POTW
PARAMETERS USED TO MONITOR THE ABF TREATMENT PROCESS
SUSPENDED GROWTH MAJOR UNIT PROCESS EVALUATION WORKSHEET
TRICKLING FILTER MAJOR UNIT PROCESS EVALUATION WORKSHEET
RBC MAJOR UNIT PROCESS EVALUATION WORKSHEET
ABF MAJOR UNIT PROCESS EVALUATION WORKSHEET
vi
Page
79
83
85
86
86
103
106
108
110
127
130
137
182
185
190
196
208
214
219
225
235
242
250
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LIST OF FIGURES
Number
2-1
3-1
3-2
3-3
4-1
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
F-l
CPE/CCP Schematic of Activities
Effect of Aeration Basin DO Concentrations on Sludge
Settling Characteristics
Typical Return Sludge Flow Rates with Various
Clarifier Surface Overflow Rates
Flow Diagram of POTW in Example CPE
Relationships of Performance-Limiting Factors to
Achieving a Performance Goal
Typical Scheduling of Onsite and Offsite Involvement
Sample Process Control and Performance Monitoring
Form for a Small POTW
Representations of Activated Sludge Floe
Activated Sludge Mass Control Using MCRT
Activated Sludge Mass Control Using Total Sludge Mass
Simplified Activated Sludge Process Diagram
Process Control Testing at a 950 m3/d Contact
Stabilization POTW ;
Graphical Representation of Improved Performance from
a Successful CCP
Atmospheric Pressure at Various Altitudes
Page
6
52
54
62
73
80
82
88
91
92
93
99
107
189
vii
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LIST OF TABLES
Number
Page
2-1
2-2
3-1
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
3-10
3-11
3-12
3-13
3-14
3-15
3-16
3-17
3-18
3-19
3-20
3-21
3-22
4-1
5-1
5-2
Classification System for Prioritizing Performance-Limiting
Factors 9
Typical Costs for Conducting CPEs 13
Preliminary Plant Information to Collect by Telephone 18
Parameters for Scoring Capability of Aeration Basins
in Suspended Growth POTWs 26
Typical Standard Oxygen Transfer Rates 27
Parameters for Scoring Capability of Clarifiers in
Suspended Growth POTWs 29
Typical Ranges for Return Activated Sludge Pumping
Capacities 30
Criteria for Scoring Sludge Handling Capability for
Suspended Growth POTWs 31
Typical Unit Sludge Production Values for Suspended
Growth POTWs 32
Typical Sludge Concentrations for Suspended Growth
POTWs 33
Guidelines for Evaluating Capacity of Existing Sludge
Handling Processes 34
Miscellaneous Unit Values Used in Evaluating Capacity
of Sludge Handling Capability 35
Suspended Growth Major Unit Process Capacity Evaluation 36
Parameters for Scoring Aerator Capability for Trickling
Filter POTWs 38
Parameters for Scoring Aerator Capability for RBC POTWs 39
Parameters for Scoring Aerator Capability for ABF POTWs 40
Parameters for Scoring Capability of Clarifiers in
Trickling Filters and RBCs 41
Criteria for Scoring Sludge Handling Capability for
Fixed Film POTWs 42
Typical Unit Sludge Production Values and Sludge
Concentrations for Fixed Film POTWs 43
Trickling Filter Major Unit Process .Capacity Evaluation 44
RBC Major Unit Process Capacity Evaluation 44
ABF Major Unit Process Capacity Evaluation 44
Typical Mean Cell Residence Times for Suspended Growth
POTWs ' 51
Suspended Growth Major Unit Process Capacity Evaluation
for Example CPE 67
Typical Costs for Conducting a CCP 76
Typical CCP Facilitator Involvement 80
Process Control Monitoring at a Small Activated
Sludge Plant 98
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Number
C-l
C-2
E-l
F-l
F-2
LIST OF TABLES (continued)
Springfield, KS POTW Major Unit Process Evaluation
Springfield, KS POTW Capacity Potential
Worksheet for Calculation of Power Factor
Typical Values of Alpha Used for Estimating AOR/SOR
Oxygen Saturation at Standard Pressure and Actual
Water Temperature
Page
132
133
183
187
188
ix
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CHAPTER 1
INTRODUCTION
1.1 Purpose and Scope
This Handbook provides information on methods to economically improve the
performance of existing publicly owned treatment works (POTWs). It is
"how-to" oriented and describes ;an approach that POTW owners can use to
achieve improvements in treatment without major capital expenditures. The
approach consists of an evaluation phase and a performance improvement phase.
The eyaluation phase is a thorough review and analysis of a POTW's design
capabilities andassociated administration, operation, and maintenance
practices. It is conducted to provide information for POTW administrators to
make decisions regarding efforts necessary to improve performance. The
primary objective is to determine if significant improvements in treatment can
be achieved without making major capital expenditures. This objective is
accomplished by assessing the capability of major unit processes and by
identifying and prioritizing those factors that limit performance and can be
corrected to improve performance. !
The performance improvement phase is a systematic approach to eliminating
those factors that limit performance in existing POTWs. Its major benefit is
that it optimizes the capability of existing facilities to perform better and/
or treat more wastewater.
This document has been prepared for the benefit of POTW owners and
administrators. It is expected that consultants for POTWs, regulatory
personnel, and administrators of privately owned treatment works will also
find the information useful. This Handbook focuses on POTWs treating typical
municipal wastewater compatible With common biological wastewater treatment
processes. It has been written mainly for POTWs with flows up to about 40,000
nr/d (10 mgd), which includes pver 95 percent of existing POTWs in the
United States (1). The scope of the Handbook is further focused on mechanical
plants using activated sludge (suspended growth), trickling filters (fixed
film), and variations of these prpcesses for secondary treatment. Variations
of suspended growth processes .included are:
Plug flow
Complete mix
Extended aeration
- Contact
- Tapered
stabilization
aeration
- Oxidation
- Step feed
ditches
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Fixed film processes included are:
- Conventional rock filters
- Plastic media filters
- Redwood media filters
- Activated biofilters (ABFs)
- Rotating biological contactors (RBCs)
1.2 Background
A 1980 General Accounting Office report indicated that 87 percent of 242 POTWs
surveyed were in violation of the effluent requirements in their discharge
permit (2). At 9 of the 15 POTWs studied further, operation and maintenance
problems were determined to be a significant cause of poor performance. A
comprehensive national study to identify and quantify the specific causes of
inadequate POTW performance was conducted in the late 1970s (3-6). This
study, involving site visits to 287 facilities and detailed evaluations of 103
of these facilities, identified the most predominant problems at POTWs. The
top factors identified included problems in all four major areas that affect
plant performance: design, administration, operation, and maintenance. A
major conclusion from this study is that each POTW usually has a number of
performance-limiting problems that are unique to that facility.
In response to these needs, a program that effectively eliminates all
performance-limiting factors at an individual POTW has been developed and
demonstrated. It is called the Composite Correction Program (CCP) because it
brings together the positive features of many individual programs to correct
all the specific performance-limiting problems identified at a subject plant.
CCPs have been successfully demonstrated at a number of facilities (6-8). The
most successful of these demonstrations have occurred in POTWs where a
combination of minor design changes, process adjustments, operator training,
and appropriate administrative actions led to improving plant performance to
the desired level.
Application of the CCP approach has been made more attractive by recent
congressional actions. In December 1981, the EPA Construction Grants Program
was changed to provide (starting October 1984) for 55 percent rather than 75
percent as the Federal funding share for POTW construction (9). In addition,
the Federal share of planning and design phases will not be paid until the
construction phase is approved and funded (10). These changes, and trends at
both the national and State levels, make it more important than ever to
achieve maximum utilization of existing facilities and to avoid or delay the
need for capital improvement projects.
It is apparent that improved performance is not achievable in some facilities
without making significant capital improvements. To identify facilities where
performance could be improved using a nonconstruction-oriented approach, a
Comprehensive Performance Evaluation (CPE) phase was developed. A CPE is
performed to determine if a CCP could result in significant improvement in
plant performance and/or capacity.
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The 1981 changes to the EPA Construction Grants Program also added the
requirement that, one year after being placed in operation, grantees either
certify that their facilities are capable of meeting the treatment levels for
which they were designed or propose a corrective course of action (10). A
CPE5 with its emphasis on identification of problems, and a CCP, with its
emphasis on making existing plants perform to their optimum level, can be
valuable tools for POTW owners to use in satisfying this grant requirement.
1.3 Overview
Many parties are involved in achieving optimum performance from wastewater
treatment facilities (11). The following discussion provides perspective to
the roles of these parties.
A recent project conducted to develop a strategy to improve POTW performance
and achieve compliance with effluent permit requirements concluded that local
owners and administrators of wastewater treatment facilities should be made
more aware that they are clearly responsible for their plant's performance
(8). Compliance with effluent permit requirements was found to be only a
secondary objective of many local administrators. Often their primary
concerns were obtaining facility' grants, avoiding problems with State and
Federal regulatory personnel, and providing safe working conditions for
employees. Although each of these concerns is important, local facility
administrators must recognize that their primary objective in treating
wastewater is to achieve the required effluent quality. Once local priorities
have been focused toward cost-effectively achieving adequate treatment, owners
can direct their technical staffs or consultants toward the ultimate goal.
Technical assistance is available from a variety of sources: engineers,
operators, suppliers, contractors, trainers, contract operators, and financial
consultants.
It is assumed that POTW owners and administrators have already recognized a
need to improve the performance of their wastewater treatment facilities and
will use this Handbook to economically accomplish the required wastewater
effluent quality.
1.4 References
When an NTIS number is cited in a 'reference, that reference is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
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1. The 1980 Needs Survey - Conveyance, Treatment and Control of Municipal
Wastewater, Combined Sewer Overflows, and Stormwater Runoffs, Summary of
Technical Data. EPA-430/9-81-008, NTIS No. PB-82-131533, U.S.
Environmental Protection Agency, Office of Water Program Operations,
Washington, DC, 1981.
2. Costly Wastewater Treatment Plants Fail to Perform as Expected.
CED-81-9, Report by the Comptroller General of the United States,
Washington, DC, 1980.
3. Hegg, B. A., K. L. .Rakness, and J. R. Schultz. Evaluation of Operation
and Maintenance Factors Limiting Municipal Wastewater Treatment Plant
Performance. EPA-600/2-79-034, NTIS No. PB-300331, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979.
4. Gray, A. C., Jr., P. E. Paul, and H. D. Roberts. Evaluation of Operation
and Maintenance Factors Limiting Biological Wastewater Treatment Plant
Performance. EPA-600/2-79-087, NTIS No. PB-297491, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979.
5. Hegg, B. A., K. L. Rakness, J. R. Schultz, and L. D. Demers. Evaluation
of Operation and. Maintenance Factors Limiting Municipal Wastewater
Treatment Plant Performance - Phase II. EPA-600/2-80-129, NTIS No.
PB-81-112864, U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, OH, 1980.
6.
7.
8.
9.
10.
11.
Hegg, B. A., K. L. Rakness, and J. R. Schultz. A Demonstrated Approach
for Improving Performance and Reliability of Biological Wastewater
Treatment Plants. EPA-600/2-79-035, NTIS No. PB-300476, U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, 1979.
Hegg, B. A., K. L.
Effluents. Water
1982.
Rakness, and J.
Engineering and
R. Schultz.
Management,
The CCP Way
12910 40-43,
to Better
September
Schultz, J. R., B. A. Hegg, and C. S. Zickefoose. Colorado CCP
Demonstration and Development of Areawide Compliance Strategy. Draft
report, U.S. Environmental Protection Agency, Municipal Environmental
Research Laboratory, Cincinnati, OH, 1983.
Municipal Wastewater Treatment Construction Grant Amendments of 1981.
Public Law 97-117, December 29, 1981.
Grants for Construction of Treatment Works; Interim and Proposed Rules.
40 CFR Part 35, Vol. 47, No. 92, May 12, 1982.
Hill, W. R., T. M. Regan, and C. S. Zickefoose. Operation and
Maintenance of Water Pollution Control Facilities - A WPCF White Paper.
JWPCF 51:899-906, 1979.
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. CHAPTER 2
APPROACH TO CONDUCTING COMPREHENSIVE PERFORMANCE EVALUATIONS
2.1 Objective
The objective of a Comprehensive Performance Evaluation (CPE) is to establish
whether a major facility upgrade is necessary or if a Composite Correction
Program (CCP) is capable of producing the desired effluent qu*1 '•*;-.
2.2 Methodology
A CPE achieves the above objective through several activities: evaluation of
the major unit processes; identification of all performance-limiting factors;
prioritization of performance-limiting factors; assessment of ability to
improve performance with a CCP; arid reporting CPE results. Although these are
distinct activities, some of them are conducted concurrently with others. For
example, evaluation of the major unit processes and identification of
performance-limiting factors are generally conducted at the same time.
Although this Handbook presents all the information required to conduct a CPE,
many references are available on techniques for evaluation of treatment plant
performance, reliability, etc. !(1-14). It is recommended that these
references be consulted for further specifics on the subject.
2.2.1 Evaluation of Major Unit Processes
Major unit processes are evaluated to assess the general ability of the CCP
approach, as opposed to a major construction approach, to achieve desired
performance levels. If the CPE indicates that the major unit processes are
adequate, a major plant expansion! or upgrade is not necessary and a properly
conducted CCP should achieve the desired performance. If, on the other hand,
the CPE shows that major unit processes are inadequate, owners should consider
the expansion of these processes as the focus for achieving desired
performance. '
Results of evaluation of major unit processes can be summarized by
categorization of plant type, as illustrated in Figure 2-1.
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Type 1 plants are those POTWs where a CPE shows that current performance
difficulties are not caused by limitations in the size or capabilities of the
existing major unit processes. In these cases, the major problems are related
to plant operation, maintenance, or administration, or to problems that can be
corrected with only minor facility modifications. POTWs that fall into this
category are most likely to achieve desired performance through the
implementation of a nonconstruction-oriented CCP.
Identification of a POTW as Type 2 represents a situation where the marginal
capacity of major unit processes will potentially prohibit the ability to
achieve the desired performance level. For Type 2 facilities, implementation
of a CCP will lead to improved performance but may not achieve required
performance levels without significant physical plant improvements.
A Type 3 plant is one in which the existing major unit processes are
inadequate. Although other limiting factors may exist, such as the operators'
process control capability, minor design features, or the administration's
unfamiliarity with plant needs, 'performance cannot be expected to improve
significantly until physical limitations of major unit processes are
eliminated. In this case, implementation of a nonconstruction-oriented CCP is
of limited value and is not recommended. Owners with a Type 3 facility would
best meet their needs by pursuing development of wastewater treatment
facilities suitable for handling! present and future waste loads as well as
addressing factors identified in the CPE. A more detailed study of treatment
alternatives and financing mechanisms would be warranted. CPEs that identify
Type 3 facilities are still of benefit to POTW administrators in that the need
for construction is clearly defined for facility owners. Additionally, the
CPE provides an understanding of|the capabilities and weaknesses of existing
operation and maintenance practices and administrative policies. POTW owners
can use this information to evaluate use of existing facilities as part of any
major plant upgrade and as a guideline for optimizing operation, maintenance,
and administration.
2.2.2 Identification of Performance-Limiting Factors
Whereas the evaluation of major unit processes in a plant is
categorize performance potential by assessing only 'physical
identification of performance-limiting factors focuses on one
factors unique to that facility.
used to broadly
facilities, the
facility and the
To assist in this identification, a list of 70 different factors that could
potentially limit a POTW's performance is provided in Appendix A (1). These
factors are divided into the ,categories of administration, maintenance,
design, and operation. Suggested definitions of each factor are also
provided. This list was developed as a result of many plant studies and is
provided for convenience and reference. If alternate names or definitions
provide a clearer understanding to those involved in conducting a CPE, they
should be used instead. If different terms are used, each factor should be
defined and these definitions should be readily available to those conducting
the CPE and those interpreting the results.
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Note that the list includes factors on capacity of major unit processes. If
the evaluation of major unit processes results in a Type 2 or Type 3
classification, these same limitations should be documented in the list of
factors limiting the POTW's performance. Completing the identification of
factors is difficult in that true problems in a POTW are often masked. This
concept is illustrated in the following discussion.
A contact stabilization plant was routinely losing sludge solids over
the final clarifier weirs, through the chlorine contact tank, and to the
receiving stream, resulting in noncompliance with the plant's permit.
Initial observations could lead to the conclusion that the plant had an
inadequately sized final clarifier. However, further investigation
indicated that the solids loss was a result of the operator's routinely
wasting less sludge than was produced. It was determined that, to
properly control the sludge mass, increased operator time and additional
equipment to adequately monitor and waste activated sludge to the
digester would be required. It was further determined that the digester
was undersized and would not provide adequate residence time for
complete digestion.
The most obvious problem is the operator's lack of knowledge of how to
apply the concept of sludge mass control. The needed laboratory
equipment was within the approved budget for the facility and therefore
was not assessed as a major problem. Plant administrators indicated
that they could not afford additional operator time. This
administrative policy was a significant factor limiting performance.
The undersized digester was not a significant problem in this case
because unlimited cropland for disposal of partially digested sludge was
available. (Note: Disposal of partially digested sludge on cropland can
no longer be considered a permanent solution since enactment of Federal
regulations for land disposal of POTW sludges). It was concluded that
four factors contributed to the solids loss that caused poor plant
effluent quality:
1. Inadequate operator knowledge to apply the concept of sludge
mass control.
2. Restrictive administrative policy that prohibited needed
operator time.
3. Inadequate test equipment.
4. Inadequate digester capacity.
The above discussion illustrates that a comprehensive analysis of a
performance problem is essential to identify the true performance-limiting
factors. If the initial obvious problem of lack of clarifier capacity had
improper corrective actions and unnecessary expenditures of
been identified,
funds would likely have occurred.
identified as limiting performance.
be listed without regard to order of
In almost all CPEs, several factors are
Initially, each factor identified should
severity.
8
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It is emphasized that the purpose pf identifying performance-limiting factors
is to identify, as accurately as possible, causes of poor performance unique
to a particular plant. Observation that a factor does not meet the "industry
standard" does not necessarily constitute cause for identifying that factor as
limiting the POTW's performance. An actual link between poor plant
performance and an identified factor must exist.
2.2.3 Prioritization of Performance-Limiting Factors
i
After the factors that limit performance have been identified, they are
prioritized as to their adverse effect on achieving desired plant performance.
The purposes of this prioritizatipn are to establish the type of followup
activities necessary to achieve compliance and the emphasis that would have to
be put on each factor. If the highest ranking factors, i.e., those having the
most negative impact on performance, are related to physical limitations in
unit process capacity, initial corrective actions are directed toward defining
plant modifications and obtaining Administrative funding and action for their
implementation. If the highest ranking factors are process control oriented,
the initial emphasis of fpllowup activities would be directed toward
plant-specific operator training.
The prioritization of factors is accomplished by a two-step process. First,
all factors that have been identified are individually assessed with regard to
adverse impact on plant performance (Table 2-1); second, those factors
receiving "A's" and "B's" are listed in order of priority.
TABLE 2-1
CLASSIFICATION;SYSTEM FOR PRIORITIZING
PERFORMANCE-LIMITING FACTORS
Rati ng
A
B
Adverse Effect of Factor
on Plant Performance
Major! effect on long-term repetitive basis
1
Minimum effect on routine basis or major
effect on a periodic basis
Minor effect
Each factor previously identified as limiting performance is now assigned an
"A," "B," or "C" rating. The checklist of factors in Appendix A includes a
column to enter this rating. |
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The factors that receive an "A" are the major problems that cause a
performance deficiency. They should be the central focus of any subsequent
program to improve plant performance. An example of an "A" factor would be
"ultimate sludge disposal" facilities, i.e., drying beds, that are too small
to allow routine wasting of sludge from an activated sludge POTW.
All "B" factors (as well as "A's") typically must be eliminated before a plant
will achieve consistent desired performance. Two categories of factors
receive a "B" rating:
1. Those that routinely contribute to poor plant performance but are
not the major problems. An example would be a shortage of
person-hours to complete required process control testing in a small
activated sludge plant where the underlying problem is that the
operator does not understand how to run or interpret the tests or
understand the need for a better testing program.
2. Those that.cause a major degradation of plant performance, but only
on a periodic basis. Typical examples are an inadequate spare parts
inventory that causes excessive process downtime once or twice a
year, or marginal oxygen transfer capacity that causes an oxygen
shortage only during the hottest month of the year. As a comparison,
the example "A" factor above ("ultimate sludge disposal") would
receive a "B" rating if adequate drying bed capacity were available
in the summer but winter weather inhibited drying bed use.
Factors that receive a "C" rating can be shown to contribute to a performance
problem but their effect is minor. They would likely be corrected with little
effort and/or time during followup activities. For example, if a critical
process stream were accessible, but difficult to sample, it could indirectly
contribute to poor performance by making process control less convenient and
more time consuming. The problem would not be a major focus of a subsequent
corrective program. As a further comparison, the example "A" factor above
("ultimate sludge disposal") would receive a "C"rating if adequate drying bed
capacity were available but cleaning the beds with a front loader has crushed
several underdrain tiles.
In the illustration presented in Section 2.2.2, "inadequate operator knowledge
to apply the concept of sludge mass control" is assigned an "A" because of its
continuous detrimental effect on plant performance; "administrative policy" a
"B" because of its routinet effect; and "testing equipment" a "C" because its
effect is only a minor contributing factor. "Inadequate digester size" is
given a "B" because it made proper sludge mass control more difficult and
labor intensive. It is not given an "A" because it did not limit performance
in a major way since adequate sludge disposal capacity is available by
utilizing nearby cropland.
Once each identified factor is assessed individually and assigned an "A," "B,"
or "C" classification, those receiving "A's" and "B's" are listed on a
one-page summary sheet in order of priority. This requires that the evaluator
assess all the "A's" and "B's" to determine the most serious cause of poor
performance, second most serious, etc. A summary sheet for ranking the
10
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prioritized factors limiting plant performance in order of severity is
presented in Appendix B. This process is effective in reducing the identified
factors to a one-page summary and serves as a valuable reference for the next
step of the CPE: assessing ability to improve plant performance.
2.2.4 Assessing Ability to Improve Performance
By definition of a CCP, all performance-limiting factors can theoretically be
eliminated. Nevertheless, it is necessary to specifically assess the ability
of a CCP to improve performance in each POTW. An effective approach is to
evaluate each identified factor individually to determine whether there are
any practical reasons a factor cannot be addressed. Examples of factors that
may not be feasible to address are replacement of key personnel, drastic
increases in funding, or extensive training of owners or administrators to
support POTW needs.
Some factors have a variety of potential solutions or combinations of
corrective actions that can effectively address the problem. For example, an
activated sludge clarifier may be improved by installing baffles to decrease
short-circuiting, by utilizing partial flow equalization to reduce hydraulic
peaks, or by switching to other activated sludge mass modes to better control
sludge settling characteristics and to reduce clarifier loading. Often a
combination of these corrective actions would be appropriate. The systematic
assessment of the prioritized factors helps assure that all factors can
realistically be addressed, thus providing the basis for the comprehensive
approach to improving performance.
It is the prioritization and assessment phase of a CPE that requires maximum
application of the evaluators1 judgment and experience. It should be noted
that it is often necessary to later modify the original corrective steps and
requirements as new or additional information becomes available during the
conduct of a CCP phase. This concept is illustrated by the following:
A CPE conducted at an activated sludge plant identified the major
performance-limiting factors as:
i
1. Inadequate operator understanding to make process adjustments
to control sludge settling characteristics.
2. Inadequate staffing to make operational adjustments.
3. Inadequate program to keep equipment functioning continuously.
Based on these factors, a CCP was implemented to improve performance of
the existing facilities. It was decided that this plant could perform
best when the activated sludge settling rate was relatively slow. The
plant operator's understanding was improved through training, and he
became capable of making process control adjustments to achieve the
desired slower sludge settlirig rate. Once the desired slower sludge
settling rate was achieved, poor clarifier performance was observed and
11
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effluent quality deteriorated. Further investigation indicated that
modifications made a year earlier to the clarifier inlet baffles were
allowing short-circuiting to occur. This short-circuiting only became
apparent after the slower settling had been achieved. These baffle
modifications were reassessed and changed to reduce short-circuiting and
effluent quality improved dramatically.
In this illustration, a minor design modification was determined to be a
performance-limiting factor. This factor was not identified in the original
CPE. An awareness that it may not be possible to identify all performance-
limiting factors in the CPE, as well as an awareness that the CCP approach
allows further definition and identification of factors during its
implementation, is an important aspect of assessing a POTW's capability to
achieve improved performance.
2.2.5 CPE Report
The results of a CPE should be summarized in a brief, written report to
provide guidance for facility owners and administrators. An example is
included in Appendix C. A typical CPE report is 8-12 pages in length and
includes the following topics:
- Facility background
- Major process evaluation
- Performance-limiting factors
- Projected impact of a CCP
- CCP costs
A CPE report should not provide a list of specific recommendations for
correcting individual performance-limiting factors. This often leads to a
piecemeal approach to corrective actions where the goal of improved
performance is not met. For Type 1 and Type 2 plants, the necessity of
comprehensively addressing the combination of factors identified by the CPE
through the implementation of a CCP should be stressed. For Type 3 plants, a
recommendation for more detailed study to support the anticipated upgrade may
be warranted.
2.3 Personnel Capabilities for Conducting CPEs
Persons responsible for conducting CPEs should have a knowledge of wastewater
treatment, including the following areas:
- Regulatory requirements
- Process control
- Process design
- Samp! ing
- Laboratory testing
- Microbiology
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- Hydraulic principles
- Operator training i
- Wastewater facility budgeting
- Safety
- Maintenance
- Management :
Consulting engineers who routinely work with POTW design and startup, and
regulatory agency personnel with experience in evaluating wastewater treatment
facilities, represent the types iof personnel with adequate backgrounds to
conduct CPEs. This Handbook is not intended as a guide to the design or
operation of POTWs.
2.4 Estimating CPE Costs ;
i
The cost of conducting a CPE depends on the size and type of facility.
Activated sludge plants tend to be more complex than trickling filter plants
or other fixed film facilities. Guidelines for estimating CPE costs and
person-days are presented in Table 2-2. These estimates are for contracting
with a consultant who normally performs this type of service. The cost to a
community for conducting a CPE with municipal employees would probably be less
than the amounts shown in Table 2-2. However, municipal employees may not
have the necessary qualifications or may be too close to the existing
operation to be able to perform a truly objective evaluation.
: TABLE 2-2
TYPICAL COSTS FOR CONDUCTING CPEsa
Type and Size of Facility ;
Suspended Growth r*5'0 |
<800 m3/d (0.2 mgd) !
800-8,000 m3/d0(0.2-2 mgd) |
8,000-38,000 m3/d (2.0-10 mgd)
Typical
Person-days
Onsite
2
5
7
Typical Cost
(1984 $)
1,500- 3,000
2,000-10,000
4,000-16,000
Fixed Film:d ;
<2,000 m3/d (0.5 mgd)
2,000-38,000 m3/d (0.5-10 mgd)
2
5
1,500- 4,000
3,000-12,000
aFor contract consultant. •
^Includes all variations of activated sludge.
CABF systems, which combine suspended and fixed growth, require an
effort similar to activated sludge.
^Includes trickling filters with both plastic and rock media and RBCs
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2.5 References
When an NTIS number is cited in a reference, that reference is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
1. Hegg, B. A., K. L. Rakness, J. R. Schultz, and L. D. Demers. Evaluation
of Operation and Maintenance Factors Limiting Municipal Wastewater
Treatment Plant Performance - Phase II. EPA-600/2-80-129, NTIS No.
PB-81-112864, U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, OH, 1980.
2. Gulp, G. L. and N. F. Helm. Field Manual for Performance Evaluation and
Troubleshooting at Municipal Wastewater Treatment Facilities.
EPA-430/9-78-001, NTIS No. PB-279448, U.S. Environmental Protection
Agency, Office of Water Program Operations, Washington, DC, 1978.
3. Process Design Manual: Wastewater Treatment Facilities for Sewered Small
Communities. EPA-625/1-77-009, U.S. Environmental Protection Agency,
Center for Environmental Research Information, Cincinnati, OH, 1977.
4.
Hinrichs, D. J. Inspectors Guide for Evaluation of Municipal Wastewater
Treatment Plants. EPA-430/9-7 9-010, NTIS No. PB-80-138605, U.S.
Environmental Protection Agency, Office of Water Program Operations,
Washington, DC, 1979.
Schultz, D,
Mechanical
Components.
Protection
Cincinnati,
W. and V. B. Parr. Evaluation and Documentation of
Reliability of Conventional Wastewater Treatment Plant
EPA-600/2-82-044, NTIS No. PB-82-227539, U.S. Environmental
Agency, Municipal Environmental Research Laboratory,
OH, 1982.
6. Niku, S., E. D. Schroeder, G. Tchobanoglous, and F. J. Samanieqo.
Performance of Activated Sludge Processes: Reliability, Stability arid
Variability. EPA-600/2-81-227, NTIS No. PB-82-108143, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1981.
7. Haugh, R., S. Niku, E. D. Schroder, and G. Tchobanoglous. Performance of
Trickling Filter Plants: Reliability, Stability and Variability.
EPA-600/2-81-228, NTIS No. PB 82-109174, U.S. Environmental Protection
Agency, Municipal Environmental Research Laboratory, Cincinnati, OH,
1981.
8. Handbook for Identification and Correction of Typical Design Deficiencies
at Municipal Wastewater Treatment Facilities. EPA-625/6-82-007. U.S.
Environmental Protection Agency, Center for Environmental Research
Information, Cincinnati, OH, 1982.
14
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9. Ball, R. 0., M. Harris, a;nd K. Deeny. Evaluation and Control of
Sidestreams Generated in Publicly Owned Treatment Works.
EPA-600/2-82-016, NTIS No. PB-82-195272, U.S. Environmental Protection
Agency, Municipal Environmental Research Laboratory, Cincinnati, OH,
1982. i
10. Energy Management Diagnostics. EPA-430/9-82-002, NTIS No. PB-82-198219,
U.S. Environmental Protection Agency, Office of Water Program Operations,
Washington, DC, 1982.
11. Comprehensive Diagnostic Evaluation and Selected Management Issues.
EPA-430/9-82-003, NTIS No. 'PB-82-212770, U.S. Environmental Protection
Agency, Office of Water Program Operations, Washington, DC, 1982.
12. Contract Operations. EPA-4 30/9-82-004, NTIS No. PB-82-197161, U.S.
Environmental Protection Agency, Office of Water Program Operations,
Washington, DC, 1982.
13. Wastewater Utility Recordkeeping, Reporting, and Management Information
Systems. EPA-430/9-82-006, NTIS No. PB-83-109348, U.S. Environmental
Protection Agency, Office of Water Program Operations, Washington, DC,
1983.
14. New England Wastewater Management Guide - Utility Management System.
Available from the New England Water Pollution Control Commission.
15
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CHAPTER 3
HOW TO CONDUCT COMPREHENSIVE PERFORMANCE EVALUATIONS
3.1 Introduction
This chapter provides guidance for persons conducting Comprehensive
Performance Evaluations (CPEs). If a person associated directly with the POTW
is the evaluator conducting the CPE, some of the steps may not be necessary.
3.2 Initial Activities
To determine the magnitude of the fieldwork required, and to make the onsite
activities most productive, as much initial information as possible should be
gathered by telephone. This information includes basic data on the POTW and
sources for any needed additional information.
3.2.1 Personnel
The evaluator should obtain the names of those persons associated with the
POTW who will be the primary sources of information for the CPE. The POTW
superintendent, manager, or other person in charge of the wastewater treatment
facility should be identified. If different persons are responsible for plant
maintenance and process control, they should also be identified.
The person most knowledgeable about the details of the POTW budget should be
identified by name, position, and physical location. A 1- to 2-hour meeting
with this person during the fieldwork will have to be scheduled to obtain a
copy of the budget and discuss it. In many small communities, this person is
most often the city clerk; in larger communities, the utilities director,
wastewater superintendent, or person of similar title can usually provide the
best information on the budget.
The key administrative person or persons should also be identified. In many
small communities or sanitation districts, an operator or plant superintendent
may report directly to the elected governing administrative body, usually the
city council or district board. In larger communities, the key administrative
person is often the director of public works, city manager, or other
nonelected administrator. In all cases, the administrator(s) who has the
authority to effect a change in policy or budget for the POTW should be
identified.
16
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If a consulting engineer is currently involved with the POTW, that individual
should be informed of the CPE and, be provided a copy of the final report for
comment. Normally, the consulting engineer will not be directly involved in
conduct of the CPE. An exception may occur if there is an area of the
evaluation that could be supplemented by the expertise available through the
consultant. !
3.2.2 Wastewater Treatment Plant
The initial information contained in Table 3-1 should be obtained by telephone
to estimate field time required. The plant superintendent and/or chief
operator should be the contact for this information. This information should
be collected bearing in mind that some of the data may later be found to be
inaccurate. Generally, the data that a chief operator can provide
extemporaneously or from a readily available reference is sufficient at this
time. j
Irregularities that may warrant special consideration when planning or
conducting the fieldwork shouldjbe identified, and more specific questions
should be asked to define the potential effect on the evaluation. Frequently
occurring irregularities include:, major process or pieces of equipment out of
service; key persons on vacation or scheduled for other priority work; and new
or uncommon treatment'processes. ;
The single trickling filter, aeration basin, or final clarifier being out of
service will probably necessitate postponing fieldwork in small plants. In
plants with two or more duplicate unit processes, a CPE can be conducted with
one unit out of service if the results of the evaluation are needed before
normal operation can be resumed. !
3.2.3 Performance
An indication of past plant overall performance should be obtained from plant
personnel. Most likely, a CPE will not be conducted unless a performance
problem is at least suspected. However, an evaluator should not expect to
learn on the telephone the exact details of a performance problem. That is,
after all, the purpose of the CPE.
3.2.4 Scheduling
The major criterion for scheduling the time for a CPE should be the ability to
get. commitment of local personnel availability. Usually, one-half to
two-thirds of the time scheduled' for fieldwork will require the availability
and help of these persons. !
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TABLE 3-1
PRELIMINARY PLANT INFORMATION TO COLLECT BY TELEPHONE
PI ant Name
Phone Contact
Position
Phone No.
Design Flow
Service Population
Year Plant Built
Directions to Plant
Date
Current Flow
Most Recent Upgrade
Major Processes (type and size):
Preliminary treatment
Primary treatment
Secondary treatment
Aeration basin
Trickling filter
Clarifier
Disinfection
SIudge treatment
Unusual processes or equipment
Any processes or major equipment currently not operational
18
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TABLE 3-1 (continued)
Who does performance monitoring tests?
Who does process control tests?
What process control test equipment is available?
Plant coverage (8 am-5 pm, 24 hr,1 etc.)
Work hours of key individuals
Known conflicts with scheduling fieldwork
I
Contact for scheduling fieldwork
Administrator or owner (responsible official)
Who has records on the budget?__;
Who is consultant?
Information resources (availability):
As-built construction plans _
O&M manual
Monitoring records
Equipment literature
19
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Scheduling should be coordinated with the availability of at least the major
process control decisionmaker, the major administrative decisionmaker, and the
person most knowledgeable of the plant budget. A commitment of time from
these key persons is essential to the successful conduct of a CPE. It may
also be beneficial to inform State and Federal regulatory personnel of the CPE
schedule to avoid possible interference with enforcement activities.
Responsibility for this task should be clearly identified between the
evaluator and local personnel during the scheduling of activities.
During the fieldwork, the process control decisionmaker should be prepared to
devote at least half of his/her time to the evaluation. The administrative
decisionmaker should be available for 1 hour for a kickoff meeting, several
hours for reviewing the budget, another several hours for talking about
general administration, and 1-2 hours for a summary meeting.
The persons required for the conduct of a CPE are often very busy; however,
the evaluator should make every effort to include all necessary individuals to
ensure success of the CPE.
3.3 Data Collection
Initial onsite CPE activities are largely devoted to collection of data
required for later evaluation of the POTW. As a courtesy, and to promote
efficient data collection, the fieldwork is initiated with a kickoff meeting
and a plant tour. These activities are followed by a period of time where a
large amount of detailed data on the POTW is gathered.
3.3.1 Kickoff Meeting
A short meeting of key POTW personnel (including key administrators) and the
evaluator should be held to initiate the fieldwork. The major purposes of
this meeting are to explain and gain support for the CPE effort, to coordinate
and establish the schedule, and to initiate the administrative evaluation
activities. The objectives of the CPE should be presented along with the
proposed activities. Specific meeting times with nonplant personnel should be
scheduled. Information, and resource requirements should be spelled out.
Specific items that are required and may not be readily available are: budget
information to provide a complete overview of costs associated with wastewater
treatment; schedule of sewer use and tap charges; discharge permit (NPDES) for
the POTW; historical monitoring data (2 years); utility bills (1 year); sewer
use ordinance (if applicable); and any facility plans or other engineering
studies completed on the existing facility. Administrative factors should be
noted during this meeting, such as the priority put on permit compliance,
familiarity with plant needs, and policies on increased funding. These
initial perceptions often prove valuable when formally evaluating
administrative factors later in the CPE effort.
20
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3.3.2 Plant Tour
A plant tour should follow the Mckoff meeting. The objectives of the tour
are to familiarize the evaluator with the physical 'plant, make a preliminary
assessment of design operational ^flexibility of the existing unit processes,
and provide an initial basis for discussions on performance, process control,
and maintenance. A walk-through! tour following the flow of wastewater is
suggested. It is then appropriate to tour the sludge treatment and disposal
facilities, followed by the support facilities such as maintenance areas and
laboratories. The evalua tor should note the sampling points established
throughout the plant for both process control and compliance monitoring.
Suggestions to Help the evaluator meet the objectives of the plant tour are
provided in the following sections.
3.3.2.1 Preliminary Treatment
Major components of preliminary treatment typically include
or comminution, grit removal, and;flow measurement.
coarse screening
Although inadequate screening rarely has a direct effect on plant performance,
if, for example, surface mechanical aerators must be shut down twice a day to
remove rags in an activated sludge plant with marginal oxygen transfer
capacity, it could become a ! significant performance-limiting factor^
Screening could be an identified area that could improve performance with
minor design improvements (at least in a small plant that could utilize hand-
cleaned bar screens). Indications of screening problems are:
- Plugging (with rags) of raw sewage or primary sludge pumps
- Plugging of trickling filter distributors
- Rag buildup on surface mechanical aerators
- Plugging of activated sludge return pumps where primary clarifiers
are not used 1
Grit removal generally only has an indirect effect on plant performance. For
example, inadequate grit removal ;can cause excessive wear on pumps or other
downstream equipment resulting irj excessive downtime, and replacement/repair
costs, and could deprive critical'processes of needed operator time.
Raw wastewater flow measurement facilities are important to accurately
establish plant loadings. The plant tour should be used to observe the
primary measuring device and to ask several questions regarding plant flows.
If flow is turbulent or nonsymmetrical through flumes and over weirs commonly
used as primary flow measurement devices, the flow records are immediately
questionable. If flow is nonturbulent and symmetrical, there is a good chance
the primary device is sufficiently accurate. The evaluator should always plan
to check the accuracy of flow measurement later during the fieldwork.
21
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3.3.2.2 Primary Clarification
The value of primary clarification in relation to overall plant performance is
in decreasing the load on subsequent secondary treatment processes. As such,
the evaluator should determine what performance monitoring of the primary
processes is conducted. As a minimum, sufficient data to calculate average
BODg loadings on the secondary portion of the plant should be available.
The areas of major concern that should be discussed during the tour are
flexibility available for changing operational functions and clarifier
performance.
The major operational variable that affects primary clarifier performance and
can be controlled in most plants is sludge removal. The evaluator should
discuss the process control method used to adjust sludge withdrawal. In
general, primary clarifiers work best with a minimum of sludge in the
clarifier (low sludge detention times and low blanket level). The practical
limit for minimizing the sludge in the clarifier is when the sludge becomes
too thin, i.e., too much water for the sludge handling facilities. A primary
sludge concentration of greater than 5 percent total solids is an indication
that primary clarifier performance may be improved by increased sludge pumping
and warrants further investigation. A primary sludge concentration of less
than 3 percent total solids indicates there is likely little opportunity to
improve performance with increased sludge pumping. The operational approach
used to improve primary clarifier performance must be weighed against the
impact on the sludge handling processes.
The surface overflow rate (SOR), which is the daily average flow divided by
clarifier surface area (CSA), can be a good indicator of the performance that
can be expected from a primary clarifier handling typical domestic wastewater.
A clarifier operating at. an SOR of less than 25 m3/m2/d (600 gpd/sq ft)
will typically remove 35-45 percent of the BODg in domestic wastewater. A
clarifier operating at an SOR of 25-40 m3/m2/d (600-1,000 gpd/sq ft) will
typically remove 25-35 percent of the
3.3.2.3 Aerator
The term "aerator" is used in this Handbook to describe the unit process that
provides the conversion of dissolved and suspended organic matter to
settleable microorganisms. Examples of an aerator are: aeration basin,
trickling filter, and rotating biological contactor (RBC). The aerator
represents a critical process in the wastewater flow stream in determining
overall, plant performance capability. Evaluation of POTW capability will
require careful analysis of the aerator unit in all plants. During the plant
tour, the evaluator should determine if current operating conditions represent
normal conditions and inquire about what operational flexibility is available.
For example: Can trickling filters be run in parallel as well as series? Can
recirculation be provided around the filter only? Can aeration basins be
operated in a contact stabilization mode as well as plug flow and complete
mi x?
22
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3.3.2.4 Secondary Clarification
In all biological wastewater treatment plants, the main function of secondary
clarification is to separate the; sludge solids from the treated wastewater.
Another purpose is to thicken the sludge before removal from the clarifier.
Characteristics that should be noted on the plant tour are configuration,
depth, and operational flexibility.
The evaluator should note the general configuration of the clarifier,
including shape, sludge removal mechanism, and weir and launder arrangement.
A circular clarifier with a "donut" launder located several feet from the
clarifier wall and a siphon-type,; rapid withdrawal sludge collector typically
provides optimum performance. A long, narrow, rectangular clarifier with
effluent weirs only at the end and countercurrent sludge removal should signal
an immediate concern about clarifier performance. Clarifiers with depth less
than 3 m (10 ft) provide limited sludge storage and thickening capability and
create concerns about capacity, especially in activated sludge plants.
i
The SOR caa be used to roughly estimate final clarifier capacity. An SOR less
than 25 nr/nr/d (600 gpd/sq ft) for a circular clarifier indicates good
clarifier capacity. A significantly higher SOR would mean that other
processes would have to be fairly conservative to make the system perform
adequately, and they should be evaluated with consideration of this higher
clarifier loading.
When touring activated sludge facilities, the evaluator should become familiar
with operation and flexibility of the return sludge scheme: how sludge is
withdrawn from the clarifier; ability to operate at higher or lower loadings;
availability of return sludge flow measurement; and flexibility to direct
return sludge to different aeration basins or points in the flow stream.
3.3.2.5 Disinfection
Disinfection facilities should be toured to become familiar with the process
and equipment available and because inspection of disinfection facilities
often provides insight into performance of the secondary treatment process.
Where disinfection is required, nearly all POTWs use chlorine as the
disinfectant and incorporate a Chlorine contact basin of sufficient size to
provide 10 minutes to 2 hours of contact time.
In biological wastewater treatment facilities that periodically lose sludge
solids over the final clarifier weirs., chlorine contact basins generally
contain a buildup of sludge solids. If more than 5-10 cm (2-4 in) of sludge
has built up on the bottom of the basin, there is a good chance that
significant solids loss is occurring from the secondary clarifier.
23
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3.3.2.6 Sludge Handling Capability
The evaluator's major concern with sludge handling facilities is in
identifying any potential "bottlenecks" and possible alternatives if capacity
problems are indicated. During the plant tour, the evaluator should become
familiar with the general flow pattern of sludge from the point at which it is
removed from the primary and secondary clarifiers to the point of final
disposal.
All return flow streams should be identified during the tour and the plant
personnel should be questioned regarding each stream's volume and strength and
the availability of data. Return supernatant streams from anaerobic digesters
are the most common return streams that cause performance problems.
Supernatant from aerobic digesters and filtrate from dewatering operations are
generally not a serious problem.
3.3.2.7 Laboratory
The laboratory should be included as part of the plant tour. Performance
monitoring and process control testing should be discussed with laboratory
personnel. Available analytical capability should also be determined.
Sampling and analytical support are often essential parts of the evaluation
effort and the evaluator should determine what level of support is available
from the laboratory for the CPE.
3.3.3 Detailed Data Gathering
Following the plant tour, a major effort is initiated to collect all data
necessary to assess the performance potential of the existing facilities.
This data collection effort may require two or three persons for 3-7 days in a
larger plant, and one or two persons for 1-2 days in a smaller plant.
Information is collected to document past performance, process design,
maintenance, management, budget, process control, and administrative policies.
Collecting information for many of these items requires the assistance of POTW
and other personnel. As such, the data gathering should be scheduled around
their availability. The time when key personnel are not available should be
used by the evaluator to initially review documents such as O&M manuals and
construction plans, to summarize notes and questions for POTW personnel, and
to check completeness of data collection.
The forms in Appendix D
data collection effort
below:
have proven to be
(1-2). The items
valuable working guidelines for the
covered by these forms are listed
- General POTW Information, Form D-l
- Administrative Data, Form D-2
24
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- Design Data, Form D-3
- Operations Data, Form D-4 j
- Maintenance Data, Form D-5 ,
- Performance Data, Form D-6 \
When collecting data using these forms, the evaluator should be aware that the
data are to be used to evaluate the performance capability of the existing
POTW. The evaluator should continuously be asking "How does this affect plant
performance?" If the area of; inquiry is directly related to plant
performance, such as a clarifier design or an administrative policy to cut
electrical costs to an unreasonable level, the evaluator should spend
sufficient time and effort to fully understand and define the effect on plant
performance. If the area of inquiry is not directly related to plant
performance, such as an operator's certification or the appearance of the
plant grounds, the condition should be noted and efforts directed toward areas
that specifically impact performance.
Completion of Form D-l requires that values be selected to represent current
plant hydraulic and organic loadings. Peak month loads should be used for
these calculations to be compatible with the definition of secondary treatment
requirements used as the basis for this Handbook. In POTWs where special
allowance has been made for high infiltration/inflow, such as permitted
bypassing above a selected flow, that flow at which secondary treatment is
required should be used.
3.4 Evaluation of Major Unit Processes
Once data collection has been substantially completed, data evaluation is
initiated. Initial focus is on evaluation of the POTW's major unit processes
to determine the general applicability of a CCP to improve performance, i.e.,
define the facility as Type 1, 2, or 3 as described in Chapter 2.
Performance cannot be improved to a desired level unless existing major
processes have adequate capacity to handle current loadings. The three basic
unit processes whose capacities most frequently affect biological wastewater
treatment plant performance are:! aerator (the unit that provides for the
conversion of nonsettleable prganics), the clarifier (solids/liquid
separator), and the sludge handling system (1-4).
A point system is used to quantify the evaluation of these three basic unit
processes. Key loading and process parameters are calculated and results for
each parameter assigned a score by comparison with standard tables.
Subsequently, each of the three major unit processes receives a total score by
adding together the points assigned the loading and process parameters. The
totals are then compared with standards to assess whether a Type 1, Type 2, or
Type 3 capability is indicated for that unit process. The overall plant type
is determined by the "weakest link" among the three major process areas. It
must be remembered in using this point system that this simplification can
provide valuable assistance but; cannot replace the overall judgment and
experience of the evaluator. i
25
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3.4.1 Suspended Growth Major Unit Processes
Suspended growth facilities include those plants using variations of the
activated sludge process. The three significant unit processes within these
types of facilities that determine capacity and performance are the aeration
basin, secondary clarifier, and sludge handling system.
3.4.1.1 Aeration Basin
Parameters that are used for scoring the capability of an aeration basin are:
hydraulic detention time, organic loading, and oxygen availability. The point
system for scoring these parameters is presented in Table 3-2. To obtain the
necessary parameters, information is required on wastewater flow to the
aeration basin, aeration basin BODs loading, aeration basin liquid volume,
and oxygen transfer capacity.
TABLE 3-2
PARAMETERS FOR SCORING CAPABILITY OF AERATION BASINS
IN SUSPENDED GROWTH POTWs*
Current Operating Condition
Hydraulic Detention Time, hr:
24
10
5
3
Organic Loading, kg BOD5/m3/(j| (ib/d/1,000 cu ft):
0.24 (15)
0.40 (25)
0.80 (50)
1.28 (80)
Oxygen Availability, kg 0£/kg BOD5 load:
2.5
1.5
1.2
1.0
0.8
Points
10 (max.)
6
0
-6
10 (max.)
6
0
-6
10 (max.)
5
0
-5
-10
Interpolate to nearest whole number between loadings listed.
26
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Oxygen transfer capacity is usually the most difficult information to obtain
if the original engineering data are not available or if there is some reason
to question the original design data based oh current conditions. Generally,
the evaluation proceeds by using .available data on oxygen transfer capacity
and assuming it is correct unless the transfer capacity appears to be
marginal. If oxygen transfer capacity appears marginal, further investigation
is warranted. Any of the following conditions would lead an evaluator to
suspect marginal oxygen transfer:;
- Difficulty in maintaining minimum DO
- Continuous operation of all blowers, or all aerators set at high
speed
- Design data showing less than 1.4 kg oxygen transfer capacity per
kg actual BOD5 load
If design oxygen transfer capacity is unavailable or is believed suspect,
oxygen transfer rates presented In Table 3-3 can be used to estimate oxygen
transfer capacities.
TABLE 3-3
TYPICAL STANDjURD OXYGEN TRANSFER RATES3
Aeration System
Coarse bubble diffusers^
Fine bubble diffusers0
Surface mechanical; aerators
Submerged turbine aerators^
Jet aerators6
Standard Oxygen
Transfer Rate
Ib 02/hp-hr
2.0
6.5
3.0
2.0
2.8
aGuidance for adjusting to field conditions is
presented in Appendix F.
bFor 2.7-3.6 m (9-;12 ft) submergence.
CFor 18-26 w/m3 (0.7-1.0 hp-hr/100 cu ft).
^Includes both blower and mixer horsepower.
elncludes both blower and pump horsepower.
27
-------
Additional data required to make the estimate are field measurements to
calculate wire horsepower and calculations to adjust oxygen transfer rates
from standard conditions to the local conditions of the subject plant. The
oxygen transfer capacity (kg/d) is equal to the wire horsepower (from Appendix
E) times the actual oxygen transfer rate (Ib/hp-hr, from Appendix F) times 24
hr/d times 0.454 kg/lb. When using Table 3-3 and Appendixes E and F, the
evaluator should remember that data obtained through these estimating
procedures are only approximate, but generally have the same degree of
accuracy with which oxygen demands can be predicted.
Once data are available on wastewater flows, 8005 of influent to the
aeration basin, aeration basin volume, and oxygen transfer capacity, the
following calculations should be completed by the evaluator:
Hydraulic Detention Time in Aerator =
Aeration Basin Volume
Average Daily Wastewater Flow
Organic Loading =
Loading
Aeration Basin Volume
Oxygen Availability =
Capac1ty
t>uL>5 Loading
When the above calculations have been completed for the subject POTW, the
results are compared to the values given in Table 3-2 and appropriate points
are assigned each parameter. If the parameters for the subject POTW fall
between the values listed, interpolation is used to assign appropriate points.
3.4.1.2 Secondary Clarifiers
return
is presented in Table
the weir location on
Parameters that are used for scoring the capability of suspended growth
secondary clarifiers are: configuration, SOR, depth, return sludge removal
mechanism, and return sludge control. The scoring system for these parameters
3-4. The configuration score addresses the influence of
the rise rate of the sludge blanket. A lower score is
assigned when the effective clarifier surface area is judged to be decreased
due to the location of effluent weirs and launders. For example, a clarifier
15 m long and 3 m wide (total surface area of 45 m2) with a two-sided 1-m
wide weir located 1 m from the end is judged to have 9m2 of launder
coverage [(3 m wide) x (1 m + 1 m + 1 m)], or only 20% of the surface area.
The parameter that needs to be determined to complete the clarifier1s
evaluation is SOR:
SOR = !l}ow.trom the Clarifier
Clarifier Surface Area
28
-------
TABLE 3-4
PARAMETERS FOR SCORING CAPABILITY OF CLARIFIERS
IN SUSPENDED GROWTH POTWs
Current Operating Condition j
Configuration: ;
Circular with "donut" or interior launders
Circular with weirs on walls
Rectangular with 33% covered with launders
Rectangular with 20% covered with launders
Rectangular with launder at or near end
Surface Overflow Rate, m3/m2/d (gpd/sq ft):
I
12 (300) ;
20 (500)
27 (650)
33 (800)
41 (1,000)
49 (1,200)
Depth at Weirs, m (ft): !
4.6
3.7
3.0
2.4
2.1
(15)
(12)
(10)
(8)
(7)
Return SIudge Removal:
Circular, rapid withdrawal
Circular, scraper to hopper1
Rectangular, cocurrent scraper
Rectangular, countercurrent scraper
No mechanical removal i
Return Activated Sludge Control:
Points
10
7
0
-5
-10
15
10
5
0
-10
-15
10
4
0
-5
-10
10
8
2
0
•• y
Actual RAS flow range completely within recommended RAS
flow range; capability to;mea§ure RAS flow 10
Actual RAS flow range completely within recommended RAS
flow range; no capability'to measure RAS flow 7
50% of recommended RAS flow range covered by actual RAS
flow range; capability to measure RA 5
50% of recommended RAS flow range covered by actual RAS
flow range; no capability to measure RAS flow 0
Actual RAS flow range completely outside recommended
RAS flow range -5
-------
Evaluation of return activated sludge control is based on the ability to
control the return activated sludge flow rate volume within the range normally
recommended for the particular type of activated sludge plant. Typical ranges
for return activated sludge pumping rates are presented in Table 3-5.
TABLE 3-5
TYPICAL RANGES FOR RETURN ACTIVATED
SLUDGE PUMPING CAPACITIES
Process Type
Return Activated Sludge
% of average daily wastewater flow
Conventional A.S. and ABF
(plug- flow or complete mix)
Extended Aeration
(including oxidation ditches)
Contact Stabilization
25-75
50-100
50-125
3.4.1.3 Sludge Handling Capability
The capability of sludge handling facilities associated with an activated
sludge plant is scored by the controllability of the wasting process and the
capability of the available sludge treatment and disposal facilities. Scoring
for sludge handling capability is not as straightforward as for the aerator or
clarifier. This is because the capacity of existing facilities cannot be
easily assessed due to the variability that exists in precalculated
"standards" for process or loading parameters. To evaluate the sludge
handling capacity, the evaluator must first calculate expected sludge
production based on current loadings to the wastewater treatment processes.
The evaluator then assesses the capability of the existing sludge facilities
to handle the calculated sludge production.
The criteria and point system for evaluating sludge handling capability are
presented in Table 3-6. As indicated by the lower points allocated,
controllability is much less important than capacity.
30
-------
;TABLE 3-6
CRITERIA FOR XORIN6 SLUDGE HANDLING CAPABILITY
FOR SUSPENDED GROWTH POTWs
Current Operating Condition Points
Controllability:
Automated sampling and volume control 5
Metered volume and hand sampling 3
Hand measured volume and hand sampling 2
Sampling or volume measurement by hand not practical 0
Capacity:
t
150% of calculated long-term average sludge production 25
125% of calculated long-term average sludge production 20
100% of calculated long-term average sludge production 15
75% of calculated long-term average sludge production 0
50% of calculated long-term average sludge production -10
Controllability of the wasting process is indicated by the type of waste
sludge volume measurement and th£ type of waste sludge sampling available.
The optimum control for an activated sludge wasting system includes automatic
volume control and automatic sampling. A positive displacement pump and
automatic sampler, both controlled by an accurate and precise clock, is an
example of this type of control. ;
Most small activated sludge plants can manually measure a wasted volume (rise
in holding tank or digester, or the number of tank trucks filled) and manually
sample (from a tap or the open end of the waste sludge line). Most larger
plants have flow measuring and totaling devices on waste sludge lines.
Capacity of existing sludge handling facilities is evaluated using the
following procedures: ;
- Calculate expected sludge production.
- Establish capacity of existing sludge handling unit processes.
- Determine percentage of the calculated sludge production each unit
process can handle.
- Identify the "weakest link" process as the overall capacity of the
existing sludge handling facilities and compare to scoring values
in Table 3-6. «
31
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Expected sludge production is calculated using current BODs loadings (unless.
believed inaccurate) and typical unit sludge production values for the
existing wastewater treatment processes (5). Typical unit sludge production
values for various processes are shown in Table 3-7. For example, an
oxidation ditch removing about 1,000 kg BOD5/d would be expected to have an
average sludge production of about 650 kg TSS/d (1,000 kg BOD5/d x 0.65 kg
TSS/kg BOD5 removed).
TABLE 3-7
TYPICAL UNIT SLUDGE PRODUCTION VALUES
FOR SUSPENDED GROWTH POTWs
Process Type kg TSS (sludge)/kg BODs removed
Primary Clarification 1.7
Activated Sludge w/Primary Clarification 0.7
Activated Sludge w/o Primary Clarification
Conventional5 0.85
Extended Aerationb 0.65
Contact Stabilization 1.0
alncludes tapered aeration, step feed, plug flow, and
complete mix with wastewater detention times <10 hours.
blncludes oxidation ditch.
If plant records include sludge production data, the actual unit sludge
production value should be compared to the typical value. If a discrepancy
greater than 15 percent exists between these values, further evaluation is
warranted. The most common causes of inaccurate recorded sludge production
are:
- Excessive solids loss over the final clarifier weirs
- Inaccurate waste volume measurement
- Insufficient waste sampling and concentration analyses
- Inaccurate determination of BOD removed
Using the determined unit sludge production values and actual BOD5 removals
for the subject plant, the expected mass of sludge produced per day can be
calculated. To complete the scoring of sludge handling capability, the
expected volume of sludge produced per day should also be calculated.
32
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Typical waste sludge concentrations for activated sludge plants are presented
in Table 3-8 and can be used to convert the expected mass of sludge produced
per day to the expected volume of sludge produced per day.
TABLE 3-8
I
TYPICAL SLUDGE CONCENTRATIONS
FOR SUSPENDED GROWTH POTWs
Sludge Type
Waste Concentration
Primary
Activated ;••
Return Sludge/Conventional
Return Sludge/Extended Aeration
Return Sludge/Contact Stabilization ^
Return Sludge/small plant with low SOR *
Separate waste hopper in secondary clarifier
mg/1
50,000
6,000
7,500
8,000
10,000
12,000
Returns can often be shut off for short periods to thicken
waste sludge in clarifiers with SORs less than 20 m3/mz/d
(500 gpd/sq ft). '.
The capacity of each of the components of the sludge handling process must be
evaluated with respect to its ability to handle the calculated long-term
average sludge production for current loadings. Any process that may become a
"bottleneck" should be considered critical. Typical components found in
activated sludge facilities are:\ thickening, digestion, dewatering, hauling,
and di sposal. j
Guidelines for the capacity evaluation of the components of the existing
sludge handling processes are provided in Tables 3-9 and 3-10. The guidelines
provided in Table 3-9 are used to. compare existing facility capacity to
expected sludge production. For example, an existing aerobic digester with a
volume of 380 m3 (100,000 gal) in a plant with a calculated waste sludge
volume of 19 m3/d (5,000 gal/d) would have a hydraulic detention time of 20
days. This is 133 percent of the guidelines provided for aerobic digesters in
Table 3-9. Thus, this component of the sludge handling process in this
particular POTW would have capacity for 133 percent of the long-term average
sludge production. If the aerobi|c digester proved to have the lowest capacity
to handle long-term average sludge production of all the components of the
sludge handling processes in this POTW, sludge handling capability would score
22 points (interpolated from Table 3-6). The sludge handling capability
evaluation is illustrated as part of the CPE example presented in Section 3.9.
33
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TABLE 3-9
GUIDELINES FOR EVALUATING CAPACITY OF
EXISTING SLUDGE HANDLING PROCESSES
Process
Gravity Thickeners
Primary Sludge
Activated Sludge
Primary + Activated
Fixed Film
Primary + Fixed Film
Dissolved Air Flotation
Primary SIudge
Activated Sludge
Primary + Activated
Fixed Film
Primary + Fixed Film
Digesters
Aerobic
Anaerobic
Single Stage
Two Stage
Drying Beds
Mechanical Dewatering
Single Unit
Multiple Units
Liquid Sludge Haul
Short Haul (<3 km)
Long Haul (>20 km)
Parameters That Can Be Used
to Represent 100% of Required
Sludge Handling Capacity9
125 kg/m2/d (25 Ib/d/sq ft)
20 kg/m2/d (4 Ib/d/sq ft)
50 kg/mf,/d (10 Ib/d/sq ft)
40 kg/nt/d (8 Ib/d/sq ft)
75 kg/m2/d (15 Ib/d/sq ft)
125 kg/m2/d (25 Ib/d/sq ft)
50 kg/m2/d (10 Ib/d/sq ft)
100 kg/m2/d (20 Ib/d/sq ft)
75 kg/m2/d (15 Ib/d/sq ft)
125 kg/nfVd (25 Ib/d/sq ft)
15 days' hydraulic detention timeb
40 days' hydraulic detention time
30 days' combined hydraulic detention time
Worst season turnover time
30 hours of operation/week
60 hours of operation/week (with one unit
out of service)
6 trips/day maximum
4 trips/day maximum
^Capacity of existing unit processes should not be downgraded to these
values if good operation and process performance are documented at
higher loadings. For example, if records appear accurate and show that
all sludge production has been successfully thickened in a gravity
activated sludge thickener for the past year at an average loading of
25 kg/nr/d (5 Ib/d/sq ft), the existing thickener should be considered
to have 100% of required capacity.
^Hydraulic detention time = Volume of digester/Volume of waste sludge
expected to be produced.
34
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TABLE 3-10
MISCELLANEOUS UNIT VALUES USED IN EVALUATING
CAPACITY OF SLUDGE HANDLING CAPABILITY9
Aerobic Digesters
Following Extended
Aeration (MCRT>20 days)
Aerobic Digesters
Following Conventional
A, S. (MCRT<12 days)
Anaerobic Digesters for
Activated + Primary, and
Fixed Film (Supernating
Capability Useable)
Digester13
IHDT
idays
J10
i!5
120
Total Solids
Reduction
10
;15
>20
i
J20
;30
40
Volatile Solids Content I
of Waste Activated Sludge, :
Conventional (MCRT<12 days) :
Extended Aeration (MCRT>20 days)
10
20
30
35
20
35
40
25
35
45
80%
70%
Output Solids
Concentration
mg/1
12,000
15,000
17,000
20,000
12,000
15,000
17,000
Equal to input
10% greater than input
20% greater than input
aValues in table are intended fori use in allowing an evaluation of sludge
handling capability to proceed in the absence of available plant data. Many
other variables can affect the vjalues of the parameters shown.
"Hydraulic detention time = Volumfe of digester/Volume of waste sludge
expected to be produced.
3.4.1.4 Suspended Growth Major Unit Process Analysis
Once individual major unit processes are evaluated and given a score, these
results should be recorded on a| summary sheet, as shown in Table 3-11, and
compared with standards for each major unit process and the total plant. This
analysis results in the subject iPOTW being rated a Type 1, Type 2, or Type 3
facility, as described in Chapter 2. The sum of the points scored for
aeration basin, secondary clarifiier, and sludge handling capability must be 60
or above for the subject POTW to be designated a Type 1 facility.
Furthermore, regardless of total points, the aerator must score at least 13
points, the secondary clarifier at least 25 points, and sludge handling
capability at least 10 points for the plant to be considered Type 1.
35
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TABLE 3-11
SUSPENDED GROWTH MAJOR UNIT PROCESS CAPACITY EVALUATION
Points Scored
Aeration Basin
Secondary Clarifier
Sludge Handling Capability
Total
Points Required
Type 1Type 2
13-30
25-55
10-30
60-115
0-12
0-24
0- 9
20-59
Type 3
<0
<0
<0
<20
*Each unit process as well as the overall total points must fall in the
designated range for the plant to achieve the Type 1 or Type 2 rating.
If the subject POTW meets the criteria for a Type 1 plant, the evaluation has
indicated that all major processes have adequate capacity for a CCP to be able
to bring the plant into compliance. If the total is less than 60 points, or
if any one major unit process scores less than its minimum, the facilities
must be designated as Type 2 or Type 3.
The minimum criteria for a Type 2 plant are 20 total points and zero for each
individual process. If the total is less than 20, or if any major process
scores a negative value, the POTW must be considered inadequate and the plant
designated as Type 3. Type 3 plants generally require major construction
before they can be expected to meet secondary treatment effluent limits.
A suspended growth POTW that scored the following during the evaluation of
major unit processes would meet the criteria for a Type 3 plant:
Aeration Basin 14 points
Secondary Clarifier -8 points
Sludge Handling Capability 10 points
Total 16 points
The point system in Table 3-11 has been developed to aid in assessing the
capability of a POTW's major physical facilities. It cannot replace the
overall judgment and experience of the evaluator, which is often the deciding
factor in determining the applicability of a CCP.
36
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3.4.2 Fixed Film Major Unit Processes
Fixed film facilities include those plants using rock or plastic media plus
those using the RBC or ABF variations of the basic'trickling filter process.
The unit process in fixed film wastewater treatment plants that most
significantly affects capacity and; performance is the "aerator" portion of the
plant, i.e., the amount and type of trickling filter media, RBC media, etc.
Other significant unit processes are the secondary clarifier and sludge
handling capability. i
3.4.2.1 Aerator
a. Trick! ing Filters
An approach to develop "equivale'ncy" is used to evaluate the
trickling filters of varying media types. The unit surface area
rock media is typically 43 m2/m? (13 sq ft/cu ft) (6). This
can be used to convert data from 'trickling filters with artifici
equivalent volumes of common rock media. For example, 1,000
ft) of a plastic media with a $pecific surface area of 89
ft/cu ft) is equivalent to (89/43) x (1,000 m3) or 2,070 m3 (7
of common rock media. Unit surface area information for various
is generally available in manufacturers' literature.
capacity of
for common
information
1 medi a to
3,500 cu
/nr* (27 sq
,300 cu ft)
media types
Using the equivalency calculation, organic loadings can be calculated for all
types of media. Despite fixed fijlm performance being a function of surface
area, loadings for trickling filters are typically expressed as mass of BOD5
per volume of media. The volumetric loading can be calculated using the
equivalency calculation presentee! above. Results can be compared with
criteria in Table 3-12 to compute a "score" for the trickling filter.
The capacity of a trickling filter! can be significantly decreased if the media
becomes plugged. Ponding on the filter is a common indicator of plugging and
is generally due to overgrowth of ^microorganism mass or disintegration of the
media. The evaluator should inspect the filter in several places by removing
media to a depth of at least 15 cm (6 in) to ensure that ponding or plugging
underneath the upper layer of rocks is not occuring.
b. RBCs
Parameters for scoring RBCs are presented in Table 3-13 (7). The key
parameters to be evaluated are: organic loading on the first stage and on the
entire system; number of stages provided; and whether or not sidestreams from
anaerobic" sludge treatment are received. Organic loading used for evaluating
RBCs is soluble BODs (SBOD5) |per unit of media. If data are not
available, SBOD5 is estimated for typical domestic wastewater as one-half
37
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TABLE 3-12
PARAMETERS FOR SCORING AERATOR CAPABILITY
FOR TRICKLING FILTER POTWs
Current Operating Condition
Organic Loading, kg BOD5/m3/d
(lb/d/1,000 cu ft):a
Points
Freezing
Temperatures^*
0.16 (10) 20
0.32 (20) 15
0.48 (30) 0
0.80 (50) -10
1.12 (70) -20
Recirculation, ratio to raw flow:
2:1
1:1
None
Anaerobic Sidestreams:c
Not returned ahead of the trickling filter
Returned to the wastewater stream
ahead of the trickling filter
Covered Filter
or Nonfreezing
Temperatures
20
10
-5
-10
3
2
0
0
-10
aBased on primary effluent and common rock media having a specific
surface area of about 43 mz/m3 (13 sq ft/cu ft).
"Temperatures below freezing for more than one month.
cSupernatant from anaerobic digesters or filtrate/concentrate from
the dewatering processes following anaerobic digesters.
the primary effluent total 6005. If significant industrial contributions
are present in the system, SBOD5 should be determined by testing.
Surface area data for RBCs are generally available in manufacturers'
literature or in plant O&M manuals. If these sources are unavailable or do
not contain the needed information, the manufacturer's representative or the
manufacturer should be contacted to obtain the data.
First-stage media loading is calculated by dividing the mass of SBODs going
to it by the total surface area of only the first-stage media. System media
loading is calculated by dividing the total SBODs load to the RBCs by the
total surface area of all RBC media. In most cases, the mass of SBOD5 will
be the same for these calculations. They should only be different in plants
where some of the SBOD5 load is bypassed around the first stage.
38
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. TABLE 3-13
PARAMETERS FOR SCORING AERATOR CAPABILITY
FOR RBC POTWsa (7)
Current Operating Condition
First-Stage Loading, g SBOD5/m2/d (lb/d/1,000 sq ft)
12 (2.5)
20 (4.0)
29 (6.0)
System Loading, g
2.9 (0.6)
4.9 (1.0)
7.3 (1.5)
Number of Stages:
4
3
2
Anaerobic Sidestreams:b ;
Not returned ahead of RBC
Returned to wastewater stream
ahead of RBC I
(lb/d/1,000 sq ft):
Points
10
0
-6
10
0
-6
10
7
4
0
10
alncludes mechanical and ^ir drive RBCs.
^Supernatant from anaerobic digesters or filtrate/concentrate
from the dewatering processes following anaerobic digesters.
c. ABFs
Parameters for evaluating ABF aerators are presented in Table 3-14 (8). The
key parameters are: biocell organic loading and aeration basin detention time.
A criterion of lesser importance! is recirculation directly around the biocell.
i
Organic loadings on the biocejll are calculated in a manner similar to
trickling filter loadings: primary effluent BOD5 is divided by the volume of
the biocell media. Aeration basin detention time is calculated in a manner
similar to activated sludge aeration basin hydraulic detention time: the
aeration basin liquid volume is [divided by the average daily wastewater flow.
Sludge recirculation is not included in the calculation.
39
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TABLE 3-14
PARAMETERS FOR SCORING AERATOR CAPABILITY
FOR ABF POTWs (8)
Current Operating Condition
Biocell Organic Loading, kg BOD5/m3/d (lb/d/1,000 cu ft):
1.6 (100)
2.4 (150)
2.8 (175)
3.2 (200)
4.0 (250)
4.8 (300)
Aeration Basin Detention Time, hours:
4
3
2
1
0.75
0.5
Points
15
10
5
0
-5
-10
20
15
12
5
0
-10
Oxygen Availability in Aeration Basin, kg 02/kg BOD5 to Biocell:
1.0 10
0.75 7
0.5 3
0.4 0
0.3 -15
Recirculation - Directly Around Biocell, ratio to raw flow:
1:1 3
None 0
Oxygen availability in the aeration basin of an ABF plant is calculated by
dividing mass of oxygen transfer capacity by the total mass of BOD5 applied
to the biocell. This is done because the removal attributed to the biocell
versus that occurring in the aeration basin is not easily distinguished. Most
ABF plants provide for recirculation directly around the biocell.
Recirculation is calculated as a ratio to raw flow.
40
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3.4.2.2 Secondary Clarifier
Criteria for scoring the capability of secondary clarifiers in trickling
filter and RBC plants are presented in Table 3-15. The calculations require
that wastewater flow rate and the clarifier configuration, surface area, and
depth be known (see Section 3.4.1.2). For ABF plants, the criteria for
suspended growth secondary clafifiers presented in Table 3-4 are more
appropriate and should be used. <
;TABLE 3-15
PARAMETERS FOR SCORING CAPABILITY OF CLARIFIERS
IN TRICKLING FILTERS AND RBCs
Current Operating Condition
Configuration:
Circular with "donut" or interior launders
Circular with weirs on walls
Rectangular with 33% Covered with launders
Rectangular with 20% covered with launders
Rectangular with launder at or near end
Surface Overflow Rate, m3/m2/d (gpd/sq ft):
12 (300) i
20 (500) i
27 (650) :
33 (800) !
41 (1,000)
49 (1,200)
Depth at Weirs, m (ft):
i
3.7 (12)
3.0 (10) i
2.1 (7)
Points
10
7
0
-5
-10
15
10
5
0
-10
-15
5
3
0
For ABF plants, criteria for suspended growth clarifiers
(Table 3-4) should be used.
41
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3.4.2.3 Sludge Handling Capability
Criteria for scoring sludge handling capability associated with fixed film
plants are presented in Table 3-16. The criteria for controllability in Table
3-16 are self-explanatory. The capacity of sludge handling associated with
fixed film is evaluated using the same four-step approach presented in Section
3.4.1.3 for suspended growth POTWs.
TABLE 3-16
CRITERIA FOR SCORING SLUDGE HANDLING CAPABILITY
FOR FIXED FILM POTWs
Current Operating Condition Points
Controllability:
Automated sampling and volume control 5
Metered volume and hand sampling 3
Hand measured volume and hand sampling 2
Sampling or volume measurement by hand not practical 0
Capacity:
125% of calculated long-term average sludge production 25
100% of calculated long-term average sludge production 15
75% of calculated long-term average sludge production 5
50% of calculated long-term average sludge production -10
Different unit sludge production values are used in determining expected
sludge production from fixed film facilities. A summary of typical unit sludge
production values for the various types of fixed film plants is presented in
Table 3-17.
Frequently, secondary sludge from fixed film facilities is returned to the
primary clarifiers. Typical underflow concentrations of the combined sludge
from the primary clarifier are shown in Table 3-17 as well as sludge
concentrations from the individual fixed film processes.
The guidelines presented in Tables 3-9 and 3-10 can be used to help an
evaluator determine the capacity limits of existing sludge treatment and
disposal facilities.
42
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TABLE 3-17
I
TYPICAL UNIT SLUDGE PRODUCTION VALUES AND SLUDGE CONCENTRATIONS
FOR FIXED FILM POTWs
Process Type
Primary Clari fIcation
Trickling Filter
RBC
ABF
Sludge Type
Primary
Primary + Trickling Filter
Primary + RBC
Primary + ABF
Trickling Filter
RBC
ABF
kg TSS (sludge)/kg BODq removed
1.7
1.0
1.0
1.0
Waste Concentration, mg/1
50,000
45,000
45,000
35,000
30,000
30,000
12,000
3.4.2.4 Fixed Film Major' Unit Process Analysis
Once major fixed film processes are evaluated, they should be
compared to standards for each type of fixed film facility.
3-19, and 3-20 can be used for thi]s purpose.
summarized and
Tables 3-18,
The standards are arranged similar to .those for suspended growth facilities
presented in Table 3-11 and discussed in Section 3.4.1.4. This analysis
results in the subject POTW being rated Type 1, Type 2, or Type 3, as
described in Chapter 2. Using these tables, the subject plant must score the
minimum number of points listed for each individual process and the minimum
number total points for all processes for the plant to qualify for a specific
plant type. For example, a trickling filter plant scoring the following would
meet the criteria for a Type Ij facility for overall points, aerator, and
secondary clarifier, but would be; classified Type 2 because of its score for
sludge handling capability. . j
Trickling Filter 21 points
Secondary Clarifier ; 27 points
Sludge Handling Capability 6 points
Total 54 points
43
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TABLE 3-18
TRICKLING FILTER MAJOR UNIT PROCESS CAPACITY EVALUATION
Points Scored
Points Required
"Aerator"
Secondary Clarifier
Sludge Handling Capability
Total
Type l
17-23
17-30
10-30
45-83
Type z
0-11
0-16
0- 9
15-44
Type 6
<0
<0
<0
TABLE 3-19
RBC MAJOR UNIT PROCESS CAPACITY EVALUATION
Points Scored
Points Required
"Aerator"
Secondary Clarifier
Sludge Handling Capability
Total
Type 1
14-30
17-30
10-30
Type 2
0-13
0-16
0- 9
Type 3
<0
<0
<0
48-90
15-47
TABLE 3-20
ABF MAJOR UNIT PROCESS CAPACITY EVALUATION
Points Required
"Aerator"
Secondary Cl
Sludge Handl
Total
Points Scored
arifier
ing Capability
Type 1
15-48
20-55
10-30
50-133
Type 2
0-14
0-19
0- 9
15-49
HType 3
<0
<0
<0
<15
Each unit process as well as the overall total points must fall in the
designated range for the plant to achieve the Type 1 or Type 2 rating.
44
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3.5 Evaluation of Performance-Limiting Factors
The identification of performance-limiting factors .should be completed at a
location other than the POTW so that all potential factors can be discussed
objectively. The checklist of I performance-limiting factors presented in
Appendix A, as well as the guidelines for interpreting these factors, provide
the structure for an organized review of problems in the subject POTW. The
intent is to identify as clearly as possible the factors that most accurately
describe the causes of limited i performance. For example, poor activated
sludge operation may be causing poor plant performance because the operator is
improperly applying activated sludge concepts. If the operator is solely
responsible for process control ;decisions as well as for testing for these
decisions, the factor of improper application of concepts should be
identified.
Often, operator inability can bp traced to another source, such as an O&M
manual containing inaccurate information or a technical consultant who
provides routine assistance to the operator. In this case, improper
application of concepts plus the ;source of the problem (O&M manual or improper
technical guidance) should be jidentified as performance-limiting factors,
since both must be corrected in ai CCP to achieve desired plant performance.
Whereas the checklist and guidelines in Appendix A provide the structure for
the identification of- performance-limiting factors, notes taken during the
plant tour and detailed data-gathering activities (including the completed
forms from Appendix D) provide the technical resources for identifying these
factors. . i
Each factor identified as limiting performance should be weighed with respect
to impact on plant performance ;and assigned an "A," "B," or "C" rating as
discussed in Section 2.2.3. !Further priori tization is accomplished by
completing the summary sheet presented in Appendix B. Generally, only those
factors receiving either an "A" or "B" rating are prioritized on this sheet.
Additional guidance for identifying and prioritizing performance-limiting
factors is provided in the following sections for the general areas of
administration, design, operation, and maintenance.
3.5.1 Administration Factors
The budget is the mechanism whereby POTW owners/administrators generally
implement their objectives. therefore, evaluation and discussion of the
budget is an effective mechanism for identifying administrative
performance-limiting factors. j For this reason, early during the onsite
fieldwork the evaluator should schedule ,a meeting with the key POTW
decisionmaker and the "budget person." This meeting should be scheduled to
occur after the evaluator is technically familiar with the plant.
45
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Nearly every POTW budget is set up differently so it helps to review the
budget with the assistance of plant personnel to realistically rearrange the
budget line items into categories emphasizing various costs. Forms for
collecting budget data are presented in Appendix D. Analysis of these data
can be supported by comparison with typical values for wastewater treatment
plants (1)(4)(9)(10). POTWs larger than 8,000 m3/d (2 mgd) in size usually
have budgets that clearly describe wastewater treatment costs. Budgets for
smaller POTWs are often combined with budgets for other utilities, such as
wastewater collection, water treatment and distribution, or even street
repairs and maintenance. For this reason, it is often more difficult and time
consuming to establish realistic costs for small POTWs.
Key POTW administrators should be identified and interviews scheduled with
them as described in Section 3.2.1. As a general rule, the POTW operating
staff should not attend the interviews with POTW administrators because their
presence may inhibit open discussion.
The evaluation of administrative performance-limiting factors is by nature
subjective. Typically, all administrators verbally support goals of low
costs, safe working conditions, good treatment performance, high employee
morale, etc. An important question that the evaluator must ask is, "Where
does good treatment fit in?" Often this question can be answered by observing
the priority of items implemented or supported by administrators. The ideal
situation is one in which the administrators function with full awareness that
they want to achieve desired performance as an end product of their wastewater
treatment efforts. Improving working conditions, lowering possible costs, and
other similar goals would be pursued within the realm of first achieving
adequate performance.
At the other end of the spectrum is an
raised the monthly rates 100 percent last
dime on that plant." POTW administration
criteria:
administrative attitude that "we just
year; we aren't spending another
can be judged by the following
Excellent:
Normal:
Poor:
Reliably provides adequate wastewater treatment at
lowest reasonable cost.
Provides best possible treatment with the money
available.
Spends as little as possible with no correlation
to achieving adequate plant performance.
made
Administrators who fall into the "poor" category typically are identified as
contributing to inadequate performance during the factor identification
activities.
Technical problems identified by the plant staff or the CPE evaluator, and the
potential costs associated with correcting these problems, often serve as the
basis for assessing administrative factors limiting plant performance. For
example, the plant staff may have correctly identified needed minor
modifications for the facility and presented those needs to the POTW
46
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administrators, but had their request turned down. The evaluator should
solicit the other side of the story from the administrators to see if the
administrative policy is indeedj nonsupportive in correcting the problem.
There have been many instances in which operators or plant superintendents
have convinced administrators to spend money to "correct" problems that
resulted in no improvement in plant performance.
Another area in which administrators can significantly, even though
indirectly, affect plant performance is through personnel motivation. If
administrators encourage professional growth through support of training,
tangible awards for initial or upgrading certification, etc., a positive
influence exists. If, however, administrators eliminate or skimp on essential
operator training, downgrade operator positions through substandard salaries,
or otherwise provide a negative influence on operator morale, administrators
can have a significant detrimental! effect on overall plant performance.
!
3.5.2 Design Factors
Data gathered during the plant tour, completed Form D-3, and the previously
completed evaluation of major unit process capabilities provide the bulk of
the. information needed to complete the identification and prioritization of
design-related performance-limiting factors. However, to complete the
evaluation of design factors in; many CPEs, the evaluator must make field
investigation of the operational flexibility of the various unit processes.
Field investigations should be \ completed in cooperation with the POTW
operator. The evaluator must not make any changes unilaterally. Any field
testing desiredshould be discussed with the operator,whose cooperation
should be obtained in making any needed changes. This approach is essential
since the evaluator may wish to implement changes that, while improving plant
performance, could be detrimental to specific equipment at the plant. The
operator has worked with the equipment, repaired past failures, and read the
manufacturers' literature and is in the best position to evaluate any adverse
impact of proposed changes. I
Field investigation of process flexibility defines the limitations of the
equipment and processes and al so promotes a better understanding of the time
and difficulty required to implement better process control. This is
illustrated by the following discussion:
A 380 m3/d (0.1 mgd) extended aeration facility has airlift sludge
return pumps that have been operated to provide return rates of 200-300
percent of influent flow rates. The evaluator desired to know if
returns could be held under 100 percent since this would substantially
reduce solids loading on the: final clarifier and potentially improve
clarifier performance. i
Discussions with the plant operator revealed that he had previously
tried to reduce the return rate by reducing the air to the airlift
return pumps. The operator abandoned the ideas because the airlifts
47
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repeatedly plugged overnight when left at the low rates. The evaluator
convinced the operator to again try reducing returns so that the limits
of return sludge flow control available could be defined.
An airlift pump consists of a vertical pipe with one end submerged,
usually 2-3 m (6-10 ft), in the basin from which liquid is to be pumped
and an air supply that introduces air into the pipe near its lower end.
Air introduced into the pipe decreases the specific gravity of the pipe
contents (air bubble and liquid mixture), and the heavier liquid in the
surrounding basin forces the air/liquid mixture up the pipe. The
pumping force created is proportional to the differential weight inside
and outside the pipe. Increased flow is achieved by increasing the
amount of air introduced thus reducing the specific gravity of the
mixture further and increasing the driving force.
The air rate was initially reduced to produce a return flow rate of 100
percent of incoming wastewater flow as measured by a bucket and
stopwatch. The airlift return pumps plugged completely in less than 2
hours because, as the sludge thickened due to reduced flow, the specific
gravity increased. The air rate that produced the desired flow with
thinner sludge was no longer adequate. The flow was reset to 100
percent by increasing the airflow substantially above the previous
setting. An hour later the return flow rate was measured as 220
percent. Because the pumping rate affects specific gravity and specific
gravity, in turn, affects the pumping rate, a "snowballing" effect was
produced when the airlift pump was changed in either direction. These
results supported the operator's contention that return flow rates could
not be controlled at reasonable levels.
The air supply was again adjusted to provide a flow rate halfway between
the current and the desired rate. This setting allowed better control
to be exercised but plugging still occurred with existing sludge
characteristics at return sludge flows of less than about 125 percent.
It was concluded that this was the practical lower limit for return
sludge flow rate control with the existing facilities and sludge
character. To maintain a return sludge in the range of 125-150 percent
required fr.equent checking, including an evening check not before asked
of the operator. In this manner, part - but not all - of the design
limitation could be overcome with increased operator attention.
The areas in a POTW that frequently require field investigations to determine
process flexibility are:
1. Suspended Growth Systems
- Control of return sludge flow rate within the ranges presented
in Table 3-5
- Control of aeration basin DO within the ranges presented in
Figure 3-1
48
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- Sludge mass control by wasting expected sludge production
presented in Table 3-7, and actual waste concentrations or
representative waste concentrations shown in Table 3-8
- Flow splitting to prevent unnecessary overloading of individual
process units
1 i
- Available mode changes to provide maximum use of existing
facilities:
o Contact stabilization when the final clarifier appears to be
the most limiting process
o Plug flow when oxygen transfer is marginal
2. Trickling Filters ;
- Alternate disposal methods for anaerobic digester supernatant
- Ability to lower sludge levels in clarifiers without thinning
out sludge to concentrations that would cause sludge treatment
or handling problems
- Recirculation to the filter without excess hydraulic loads on
the primary -or secondary clarifiers
3. RBCs i
- Alternate disposal methods for anaerobic digester supernatant
- Ability to lower sludge levels in clarifiers without thinning
out sludge to concentrations that would cause sludge treatment
or handling problems :
- Ability to redistribute individual stage loadings to provide
unit loadings within the ranges shown in Table 3-13
i i
4. ABFs !
- Control of return sludge flow rates within 50-100 percent of
influent flow !
- Ability to waste a precise mass of sludge on a daily basis
- Ability to spread a day's sVudge wasting over a 24-hour period,
or at least an extended period of time
i
- Ability to provide recirculation directly around the biocell
- Ability to maintain aeration basin DO at 2-3 mg/1
49
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3.5.3 Operation Factors
Significant performance-limiting factors often exist in the process control
activities of POTW unit processes (4) (11). The approach and methods used in
maintaining process control can significantly affect the performance of plants
that have adequate physical facilities. This section provides guidance to
evaluators for identification and prioritization of operational factors that
limit plant performance.
The evaluator starts collecting data for the process control evaluation by
identifying the key POTW person for process control strategies implemented at
the plant. The plant tour and data-gathering phases also provide opportunity
to assess the process control applied. In addition, the process control
capability of an operator can be subjectively assessed during the process
capacity evaluation. If an operator recognizes the unit process functions arid
their relative influence on plant performance, a good grasp of process control
is indicated. An approach to evaluating process control is discussed in the
following sections.
3.5.3.1 Suspended Growth Facility Process Control
The process controls that should be available to an operator of an activated
sludge facility are: sludge mass control, aeration basin DO control, and
return sludge rate control. Techniques and approaches to improving these
controls are presented in Chapter 5.
a. Sludge Mass Control
The activated sludge process removes colloidal and dissolved organic matter
from wastewater resulting in a net increase in the sludge solids in the
system. Control of the amount of sludge maintained in the system by wasting
(removing) excess sludge is a key element in controlling plant performance.
All variations of the activated sludge process require sludge mass control and
periodic wasting. In line with this requirement, an operator who properly
understands activated sludge mass control should be able to show the evaluator
a recorded history of a controlled sludge mass, e.g., records of mean cell
residence time (MCRT), mixed liquor volatile suspended solids (MLVSS), plots
of aeration tank concentration in the aeration basin, total mass of sludge in
the pi ant, etc.
The following are common indicators that sludge mass control is not applied
adequately at an activated sludge plant:
- A sludge mass indicator parameter or calculation (MLVSS, MCRT,
total sludge units) is not run on a routine basis (12). Routine
would be daily for an 8,000 nr/d (2 mgd) or larger plant and 3
times a week for a 400 nr/d (0.1 mgd) plant.
50
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Only a settled sludge; test is used to determine wasting
requirements, e.g., waste, if the 30-minute settled sludge volume in
a graduated cylinder is greater than 600 mg/1.
The operator does not relate mass control to control of sludge
settling characteristics and sludge removal performance, i.e.,
sludge character. !
Significantly less mass is wasted than produced;
clarifiers lose solids ov£r the weirs routinely.
i.e., the
Poor performance persists and the mass of sludge maintained
provides an MCRT significantly out of the ranges in Table 3-21.
! TABLE 3-21
TYPICAL MEAN CELL RESIDENCE TIMES
FOR SUSPENDED GROWTH POTWs
Process Type
Conventional Aeration
Extended Aeration
Contact Stabilization
Typical MCRT
days
6-12
20-40
10-30
b. Aeration Basin D(3 Control
The aeration basin DO level is ai significant factor in promoting the growth of
either filamentous or zoogleal-type sludge organisms (13). Higher DO tends to
speed up or slow down the relative populations of these major organism types
toward primarily zoogleal. Conversely, lower DO encourages the growth of
filamentous organisms and a bulky, slow settling sludge.
i
A general guideline for relating' sludge characteristics to DO concentration in
an aeration basin is presented iji Figure 3-1. This information can be used to
evaluate the DO control approach1 at the POTW under study.
51
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FIGURE 3-1
EFFECT OF AERATION BASIN 00 'CONCENTRATIONS
ON SLUDGE SETTLING CHARACTERISTICS
4 -]
3 -
8 2
3
m
1 -
0
Tendency To Increase
Sludge Settling Rate
Tendency To Decrease
Sludge Settling Rate
10
20 30 40 50
Oxygen Uptake Rate, mg/l/hr
60
70
52
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The following are common indicators that aeration basin DO control is not
applied adequately at an activated! sludge plant:
- DO testing is not run on the aeration basin on a routine basis.
Routine ranges from daily' for an 8,000 nr/d (2 mgd) or larger
plant to weekly for a 400 m3/d (0.1 mgd) plant.
- The operator does not understand or use the relationship between DO
and sludge character; i.e.,' sludge settling is very slow and DO is
very low, or sludge settling is very fast, effluent is turbid, and
DO is very high.
c. Return Sludge Control
The objective of return sludge control is to optimize sludge distribution
between the aerator and secondary clarifier to achieve and maintain good
sludge character. The anoxic condition of the sludge in the secondary
clarifiers is usually not conducive .to producing desired sludge character.
Thus, return sludge flow rate control should be used to maximize the sludge
mass and sludge detention time in jthe aeration basins and minimize the sludge
mass and sludge detention time in jthe clarifiers.
The following are common indicators that return sludge flow rate control ^s_
not adequately applied at an activ;ated. sludge plant:
- Returns are operated outside the ranges
indicated in Table 3-5 and Figure 3-2.
(especially higher)
-The operator believes that a high sludge blanket condition in a
final clarifier can categorically be improved by increasing the
sludge return rate.
- MLSS concentrations fluctuate widely on a diurnal basis, but return
rates are not adjusted throughout the day to account for diurnal
flow variations. ] .
i
- The operator has not devised a method to estimate or measure the
return sludge flow rate if measurement was not provided for in the
original design.
-The operator does not realize that increasing the return sludge
flow rate increases the so(lids loading to the final clarifier and
decreases the settling time in the final clarifier.
3.5.3.2 Fixed Film Facility Process Control
There is a lesser amount of process control that can be applied to fixed film
facilities than to suspended growjth facilities. However, because fixed film
53
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FIGURE 3-2
TYPICAL RETURN SLUDGE FLOW RATES
WITH VARIOUS CLARIFIER SURFACE OVERFLOW RATES
CD
t3
I
•«-*
CO
CO
CD
O>
TJ
•a
Q)
•*-*
c.
I
DC
180 -
160 -
140 _
120 -
CD
§ 100
Q.
80 -
60
40 -
20 -
0
High Return Range
(Poor Process Control)
Normal
Operating Range
i
20
i
24
i
32
8 12 16 20 24 28 32 36
Secondary Clarifier Surface Overflow Rate, m3/m2/d
i
40
54
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facility performance is so dependent on media loading, process control, which
may at first seem unimportant, ;can make a significant difference in plant
performance. The following are(common indicators that process control at a
fixed film facility is not optimum.(1)(4):
- Sludge blankets in either the primary or secondary clarifiers are
maintained at a high level, i.e., >0.3 m (1 ft).
- Organic loads from return process streams are not minimized despite
poor plant performance. \
- Lack of good maintenance,|indicated by:
o Distributors on trickling filters are plugged, or leaky
distributor seals are not fixed.
o Filter media is partially plugged and measures such as
chlorination, flooding, and recirculation are not used to address
the problem.
o Trickling filter underdrain
air vents are plugged. ,
collector outlets are submerged or
High recirculation, which increases primary or secondary clarifier
overflow rates, is provided without regard to clarifier
overloading. Some trickling filter plants provide recirculation
that is directed to the raw wet-well and must pass through the
primary clarifier a secorid time as well as the trickling filter.
Likewise, some trickling rfilters provide recirculation through the
secondary clarifier sludge return to the head of the plant.
Recirculation provided by these methods should not be used.
3.5.4 Maintenance Factors ;
General information on POTW maintenance is gathered during the detailed data
collection phase and i's recorded on Form D-5. However, the evaluation of
maintenance performance-limiting factors is done throughout the CPE by
observation and questioning -concerning the reliability and service
requirements of pieces of equipment critical to process control and thus
performance. -If these units are out of service routinely or for extended
periods of time, maintenance practices may be a direct cause of, or a
significant contributing cause to, a performance problem. An adequate spare
parts inventory, to prevent undue 'delays in restoring critical process
functions while awaiting arrival of parts on order, is essential to the
conduct of a good maintenance program. Equipment breakdowns are often used as
excuses for process control problems. For example, one operator of an
activated sludge plant blamed jthe repeated loss of sludge over the final
clarifier weirs on the periodic; breakdown of one sludge return pump. Even
with one pump out of service, the return sludge capacity was over 200 percent
of influent flow. The real cause of the sludge loss was inadequate process
55
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control, including inadequate
sludge flow rates.
sludge mass control and excessively high return
Observation and documentation are necessary portions of the approach utilized
to evaluate emergency and preventive maintenance practices. Important aspects
are examination and verification of spare parts inventories and recordkeeping
systems. An example approach to a preventive maintenance scheduling system
that has been applied successfully at several plants is presented in Appendix
6. A good preventive maintenance program includes a schedule to distribute
the workload evenly. Evaluation of these items provides
discussion from which the specific results of maintenance,
maintenance, of the unit processes can be assessed. This
illustrated by the following:
a basis for
or lack of
approach is
A poorly performing trickling filter plant has acceptable organic
loadings to the filter and very capable secondary clarifiers, but also
has a large buildup of sludge in both the primary and secondary
clarifiers. The excessive amount of sludge in the clarifiers indicates
that inadequate process control by the operator might be contributing to
poor plant performance. However, if sludge is not removed adequately
because the heated anaerobic digesters are upset every time that more
than a normal amount of sludge is added, a digester operation or loading
problem could be suspected. Further investigation revealed that the
boiler is being operated manually and just during the day because the
operator had tried unsuccessfully to fix the automatic controls. Thus,
inadequate maintenance is in fact a cause of poor plant performance.
The above discussion illustrates how a maintenance-related problem can
initially be identified as something else and requires careful evaluation to
identify the true cause of poor plant performance. Often, investigation of
maintenance scheduling records, work order procedures, and spare parts
inventories provides an adequate assessment of maintenance problems limiting
performance. The evaluator must, therefore, evaluate maintenance during all
phases of the CPE and should not expect to identify these factors solely in a
formal evaluation of maintenance procedures.
3.6 Performance Evaluation
The plant performance evaluation is directed toward two goals: 1)
establishing, or verifying, the magnitude of a POTW's performance problem; and
2) projecting the level of improved treatment that can be expected as the
result of implementing a CCP.
3.6.1 Magnitude of the Performance Problem
During the CPE, the evaluator should develop a clear understanding of the
performance problem associated with the subject POTW. As a first step of this
assessment, recorded historical performance data can be used. These data are
56
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available from copies of NPDES permit reports in small POTWs and from monthly
monitoring summary sheets in larger POTWs.
Once historical data are reviewedi the evaluator should attempt to verify the
accuracy of the reported plant performance. It should be stressed that the
purpose is not to blame the individual responsible, but rather to assist in
identifying and substantiating the; true cause(s) of poor plant performance.
The evaluator can indirectly collect data to establish authenticity of the
monitoring results throughout the;CPE. For example, major unit processes are
assessed for their capability to; achieve desired performance. If a POTW is
rated a Type 3 plant (inadequate major process capability), recorded excellent
effluent quality should be suspect. If recorded performance is consistent
with the results of the overall evaluation., the validity and accuracy of the
data are reinforced. Limitations of these comparisons are their subjective
nature. !
Fortunately, recorded monitoring data accurately represent the true
performance in many plants. Small activated sludge plants have been shown to
have the most variance between historical records and actual performance.
In small activated sludge pi ants i- such as package extended aeration plants
and contact stabilization plants and oxidation ditches - several days' or even
an entire week's sludge production^ can be lost as the result of sludge bulking
in a single afternoon. Effluent SS may be less than 10 mg/1 before and after
bulking occurs, but may reach 1,000-2,000 mg/1 while bulking. Yet there is
sufficient time between bulking periods to collect more than enough samples to
meet permit monitoring requirements and show a good effluent quality. This
situation is frequently revealed during the evaluation of major unit processes
when expected sludge production is compared to actual sludge wasted or when
bulking is actually observed durirtg the CPE.
Another sampling procedure that can result in nonrepresentative monitoring is
sometimes seen in fixed film facilities where performance degrades
significantly during peak daytime loads. Samples collected from 6 a.m. to 10
a.m. may meet the required compositing criteria (e.g., three samples at 2-hour
increments"), but would probably indicate better than overall average effluent
quality. Likewise, samples collected from Noon to 4 p.m. may indicate worse
than actual average effluent quality.
Occasionally, errors in laboratory procedures will cause a discrepancy between
reported and actual effluent quality. A quick review by an evaluator
experienced in laboratory procedures may identify a problem and assist the
analyst as well as provide the evaluator insight into what the true analytical
results should be. Major test parameters critical for completion of the CPE
are influent BOOs and flow. The evaluator can roughly check both BODs and
flow data by calculating a per capita BOD5 contribution. Per capita BOD5
contributions are usually 0.07-OJ09 kg (0.15-0.20 lb)/d for typical domestic
wastewater. When estimating BODs loads to a plant without actual data, or
checking reasonableness of existing plant data, loads from significant
industrial contributors must be abided to the calculated per capita loads.
57
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3.6.2 Projected Improved Performance with a CCP
The plant performance that is achievable through implementation of a CCP is
initially estimated by evaluating the capability of major unit processes. If
major unit processes are deficient in capacity, secondary treatment cannot be
achieved with a CCP and the existing POTW is incapable of achieving the
desired performance; i.e., it is a Type 3 plant.
If the evaluation of major unit processes shows that the major facilities have
adequate capacity, the CCP approach is applicable and can likely be used to
achieve improved POTW performance; i.e., it is a Type 1 or Type 2 plant. For
plants of this type, all other performance-limiting factors are considered as
possible to correct with adequate training of the appropriate POTW personnel.
The training is addressed toward the operational staff for improvements in
plant process control and maintenance; toward the POTW administration for
improvements in administrative policies and budget limitations; and toward
both operators and administrators to achieve minor design modifications.
"Training" as used in this context describes activities whereby information is
provided to facilitate understanding and encourage implementation of the CCP
approach.
Once the plant's major unit process capability has been established and the
performance-limiting factors have been identified and prioritized, the
evaluator is in a position to assess the potential for improved performance
with implementation of a CCP. During, this effort, the evaluator must assess
the practicability and potential time frame necessary to address each
identified factor. Additionally, it is necessary to project levels of effort,
activities, time frame, and costs associated with the CCP implementation. On
occasion, for Type 1 and Type 2 plants, the approach to addressing a
performance-limiting factor may be so unreasonable as to discourage a
recommendation to implement a CCP; i.e., the number and/or magnitude of minor
modifications exceeds the POTW's funding capability.
3.7 Presentation to POTW Administrators and Staff
Once the evaluator has completed the fieldwork for the CPE, a meeting should
be held with the POTW administrators and staff. A presentation of preliminary
CPE results should include brief descriptions of the following:
- Evaluation of major unit processes (Type 1, 2, or 3)
- Prioritized performance-limiting factors
- Performance potential with a CCP
If a CCP appears warranted, the evaluator should discuss the specific
performance-limiting factors that the CCP will address and ask for local
officials' support on how the identified factors can be eliminated. The
attitude of the staff is critical to the success of the CCP, particularly in
borderline cases where the evaluator feels a CCP can definitely help.but where
process control has to be precise and requires full cooperation from the POTW
58
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operating staff. If the staff is not behind the CCP approach, the CCP will
take longer, require more qualified leadership, and may have to include some
POTW personnel changes to be successful. The administrators should realize
these requirements before deciding on a course of action.
i
In general , it is desirable to present all findings at the meeting with local
officials. This approach eliminates surprises when the CPE report is received
and begins the cooperative approach necessary for implementing a CCP. In
situations where administrative or; staff factors are difficult to present, the
evaluator must use good judgment ;in presenting the results. Throughout the
discussions, the evaluator must (remember that the purpose of the CPE is to
identify and describe facts to be, used to improve the current situation, not
to place blame for any past or current problems.
It should be made clear that, dijring conduct of the CCP, other factors are
often identified and must be addressed to achieve the desired performance.
The CCP approach targets plant performance as the end point, and any factors
that interfere with achieving this goal must be addressed whether they were
identified during the CPE or not. This understanding is often missed by local
officials, and efforts may be developed to address only the items prioritized
during the CPE. The evaluator should stress that a local commitment must be
made to achieving the desired -improved performance, not to addressing a
"laundry list" of currently identified problems.
3.8 CPE Report j
The objective of a CPE report is to summarize the CPE findings and
conclusions. It is particularly important that the report be kept brief so
that the maximum amount of resources are used for the evaluation rather than
for preparing an all-inclusive! report. The report should present the
important CPE conclusions necessary to allow the decisionmaking officials to
progress toward achieving desired performance from their facility. Eight to
twelve typed pages are generally isufficient for the text of a CPE report. An
example CPE report is presented in Appendix C. Typical contents are:
i
- Introduction j
- Facility background
- Major unit process evaluation
- Performance-limiting factors
- Projected impact of a CCP i
- CCP costs '
The CPE report should be distributed' to POTW administrators and key plant
personnel, as a minimum. Further distribution of the report, e.g., to the
design engineer or regulatory agencies, depends on the. circumstances of the
CPE but should be done at the ;direction, or with the awareness, of local
administrators. ,
59
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3.8.1 Introduction
The introduction of the CPE report should be brief and cover the following
topics:
- Reason(s) for the CPE
- Objectives of the CPE
- Plant effluent performance requirements
3.8.2 Facility Background
This section should include general information about the POTW that will serve
as the reference basis for the remainder of the report. The following
information should be included as a minimum:
- POTW description (oxidation ditch, RBC, etc.)
- Design and current flows
- Age of plant and dates of upgrades
- Service population
- Significant industrial wastes
- Significant infiltration/inflow
- Unit process and/or flow diagram
- Staff number and plant coverage
3.8.3 Major Unit Process Evaluation
This section should include a description of the plant type (Type 1, 2, or 3)
and a summary of data sources for calculating current loading. For example,
"current loadings were calculated using plant laboratory results for
concentrations and plant flow records lowered by 10 percent to adjust for high
calibration of flow recording equipment."
Results should be presented for each major unit process (aerator, secondary
clarifier, sludge handling capability). The evaluator may choose to present
capacities of other unit processes if these data are pertinent to assessing
the POTW's treatment capability.
3.8.4 Performance-Limiting Factors
Factors limiting performance that were identified during the CPE should be
listed. Generally, the more serious factors (those receiving "A" or "B"
ratings) are listed in order of priority and short, two- or three-sentence
explanations of each are included.
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3.8.5 Projected Impact of a
The expected impact of a CCP on
reference to treatment requirements
reduction in energy consumption
indicated.
CCP
plant performance is discussed briefly with
Any additional benefits, such as
improved safety, etc., should also be
3.8.6 CCP Costs
Costs associated with a CCP should be projected as accurately as possible.
Ranges of costs can be used if an evaluator does not feel comfortable
projecting specific dollar amounts. Each cost projected should be indicated
as a "one-time" or "annual" cost.I Costs for a CCP facilitator (consultant) or
for a piping modification are examples of "one-time" costs. Increased sludge
handling and electrical or chemical costs are examples of "annual" costs.
i
i
3.9 Example CPE I
A 4,500 m3/d (1.2 mgd) oxidation ditch serves a primarily residential
community with a population of 8,500. The wastewater is mainly domestic. The
city council was notified by the State health department that a district
engineer's field inspection report has confirmed data provided in the city's
self-monitoring reports that improved POTW performance is required to meet the
city's NPDES permit requirements of 30 mg/1 (30-day maximum) for BODs and
TSS. i
i
After researching several alternatives, the public works director recommended
to the city council that a CPE be conducted to determine the causes of their
performance problem and provide Direction in selecting corrective actions. A
consultant who specializes in conducting CPEs and CCPs was subsequently hired
to conduct the CPE. I
* 9.1 PI ant Data
A flow diagram is presented in Figure 3-3. The following data were extracted
from the completed data collection forms as presented in Appendix D.
DESIGN DATA
Design Flow:
Hydraulic Capacity:
Organic Loading:
4,500 m3/d (1.2 mgd)
11,300 m3/d (3.0 mgd)
900 l|g (2,000 Ib) BOD5/d
900 kg (2,000 Ib) TSS/d
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FIGURE 3-3
FLOW DIAGRAM OF POTW IN EXAMPLE CPE
Raw Wastewater
Mechanical Bar
Screen
Aerated Grit
Chamber
Waste
Return
Aerobic
Digester
Sludge Drying Beds
Oxidation
Ditch
V-Notch
Weir
C) OO
Sludge
Pumps
Dewatered Sludge
Haul to Landfill
T
Chlorine
Contact
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Preliminary Treatment:
Flow Measurement:
Oxidation Ditch:
Final Clarifiers:
Disinfection:
Sludge Return:
Aerobic Digester:
Sludge Drying Beds:
CURRENT LOADING
Flow:
Influent BOD5:
Influent TSS:
Mechanical Bar Screen, Aerated Grit Chamber
Parshall Flume, Sonic Level Sensor, Strip Chart
Recorder
Volume: - 4,500 m3 (160,000 cu ft)
02 Transfer - 1,800 kg (4,000 lb)/d
@ 36° C (100° F) with 2.0 mg/1 residual
DO brush rotors
Number of Clarifiers - 2
Diameter - 10.7 m (35.0 ft)
Area -i 90 nf (962 sq ft) each
Sidewajter Depth - 2.7 m (9.0 ft)
Center Depth - 3.1 m (10.5 ft)
Center Feed and Peripheral Weirs
Numberj of Chlorinators - 2
Capacity - 113 kg (250 lb)/d each
Contact Basin - 142 m3 (37,500 gal)
Clarifier Scraper to Center Hopper
Number of Vortex Pumps -2
Flow Control - 1.9-5.7 m6 (500-1,500 gal)/min
Measurement - 90° V-notch Weir w/o Recording
Sampling - Manual @ Weir
Volume - 680 m3 (180,000 gal)
Sludge Removal - Bottom Pipe to Drying Beds
Supernatant Removal - Mulipie-port Drawoff to
Oxidation Ditch
Number of Beds - 8
Size f 15.2 m x 45.0 m (50 ft x 150 ft)
Dried; Sludge Buried to 0.5 m (1.5 ft)
Summer Drying Time - 3 weeks
Winter Drying Eliminated December-March
Subnatant Returned to Head of Plant
(0.95 mgd)
190 mg/1 or 680 kg (1,500 lb)/d
i
205 mg/1 or 740 kg (1,600 lb)/d
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3.9.2 Major Unit Process Evaluation
AERATOR
Hydraulic Detention Time: [(160,000 cu ft x 7.5)7(950,000 gpd)] x 24 =30 hr
From Table 3-2, Score = 10 points
Organic Loading: [(1,500 lb/d)/(160,000 cu ft)] x 1,000 = 9.4 lb/d/1,000 cu ft
From Table 3-2. Score = 10 points
Oxygen Availability: (4,000 Ib 02/d)/(1,500 kg BOD5/d)
= 2.6 Ib Oa/lb BOD5
From Table 3-2, Score = 10 points
Aerator Subtotals 10 + 10 + 10 = 30 points
SECONDARY CLARIFIER
Configuration: Circular with Weirs on Wall
From Table 3-4, Score = 7 points
Surface Overflow Rate: (950,000 gpd)/(1924 sq ft) = 494 gpd/sq ft
From Table 3-4, Score = 10 points
Depth at Weirs: 9.0 ft
From Table 3-4, Score = -3 points
Return Sludge Removal: Scraped to Center Hopper
From Table 3-4, Score = 8 points
Return SIudge Control:
From Table 3-5, Typical Range is 50-100% of Raw Wastewater Flow.
Desired Range = (50% x 0.95 mgd) to (100% x 0.95 mgd)
= 0.47-0.95 mgd
Actual Range = (500 gpm x 1,440 x 10-6) to (1,500 gpm x 1,440 x 10~6)
= 0.72-2.16 mgd
Actual Return Sludge Control is 50% (0.72 to 0.95 mgd) of Desired Range.
-------
Return Sludge Measurement Provided.
From Table 3-4, Score = 5 points
[
Secondary Clarifier Subtotal = 7 + 10 - 3 + 8 + 5 = 27 points
SLUDGE HANDLING CAPABILITY
Controllability: Waste Volume Manually Calculated
Waste Stream Manually Sampled
From Table 3-6, Score = 2 points
i
Capacity: i
a. Expected Sludge Production . j
Unit Sludge Production, From Table 3-7: 0.65 Ib TSS/lb BOD5 removed
BOD5 Removed = (Influent 6005 - Effluent BOD5 Achievable*) x Flow
= (190 mg/1 -i 15 mg/1) x (0.95 mgd) x (8.34)
= 1,385 Ib/d!
Expected Sludge Mass = (0.65 Ib TSS/lb BOD5) x (1,385 Ib BOD5/d)
= 900 Ib TSS/d
Expected Sludge Concentration, From Table 3-8: 7,500 .mg/1
Expected Sludge Volume = (900 lb/d)/(7,500 mg/1 x 8.34 x 10'6)
= 14,400 gpd
b. Percentage of Expected Sludge Production Each Process Can Handle
1. Aerobic Digester
From Table 3-9, standard for evaluating aerobic digesters is a
hydraulic detention time of 15 days.
Sludge Volume Existing Digester Can Handle = (180,000 gal)/{15 days)
= 12,000 gpd
Percentage of Expected Sludge Production = (12,000 gpd)/(14,4000 gpd)
= 83 percent
*Assumed value for a well operated oxidation ditch facility.
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2. Drying Beds
From Table 3-9, the standard for evaluating drying beds is the worst
season turnover time as demonstrated by past experience.
Essentially, no drying is experienced from December through March so
that beds operate only as storage during that period. Storage volume
required must first be calculated.
Digester Hydraulic Detention Time = Digester Volume/Sludge Volume
HOT = (180,000 gal)/(14,400 gpd)
= 12 days
From Table 3-10, for HOT = 12 days, total solids reduction of 14% and
output solids concentration of about 13,000 mg/1 is expected.
Sludge to Drying Beds = (900 Ib TSS/d) x (1.00 - 0.14) = 774 Ib/d
Sludge Volume = (774 lb/d)/(13sOOO mg/1 x 8.34 x 1Q-6) = 7,140 gpd
Storage Capacity of Existing Beds = (8) x (50 ft x 150 ft x 1.5 ft)
= 90,000 cu ft
Storage Capacity Available = (90,000 cu ft x 7.5)/(7,140 gpd)
= 94 days
Storage Capacity Required = 31 (December)
31 (January)
28 (February)
30 (March)
= Hi: days
Drying bed capacity is available for 8 months of the year, but only
78% (94/121) of required storage capacity is available during the
winter 4 months.
Existing Drying Bed Adequacy = [(4/12) x (78)] + [(8/12) x (100)]
= 26 + 67 = 93 percent
3. Hauling
From discussions with the POTW staff and administrators, "Hauling
dried sludge is not a problem. If we have to, we can get the street
crew down to the plant to help out."
Hauling Adequacy = 100 percent
4. Landfill
From discussions with the POTW staff and administrators, "If we can
get it through the beds, we can get rid of it at the landfill."
Landfill Adequacy = 100 percent
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From the capacity evaluation, the aerobic digester is the "weakest link" at 83
percent capacity. , ;
From Table 3-6, Score = 3 points
Sludge Handling Capability Subtotal =2+3=5 points ^
Scores for each major unit process are presented in Table 3-22.
i
| TABLE 3-22
SUSPENDED GROWTH MAJOR UNIT PROCESS CAPACITY EVALUATION
FOR EXAMPLE CPE
Aeration Basin
Secondary Clarifier
Sludge Handling Capability
Total
Points Scored
! 30
! 27
! ' 5
i 62
Points Required
Type 1Type 2Type 3
13-30
25-55
10-30
0-12
0-24
0- 9
60-115 20-59
<0
<0
<0
<20
The data in Table 3-22 indicate that the aerator, secondary clarifier, and
total points scored for the example POTW are sufficient to rate a Type 1
plant. However, the points scored for sludge handling capability are only
sufficient for a Type 2 rating, jherefore, the overall plant rating is Type 2.
This rating indicates that a CCP is generally applicable and that improvement
in plant performance is likely,1 but that improvement in performance to the
desired level without any upgrade of major processes cannot be determined
until a CCP is implemented. \
3.9.3 Performance-Limiting) Factors
The following performance-limitijng factors were identified during the CPE and
given rankings of "A" or "B." Further ranking of these identified factors was
also completed as indicated by the number assigned to each factor.
1. Operator Application of Concepts and Testing to Process Control ("A")
I
Less sludge was wasted than was produced on a routine basis. Excess
sludge periodically bulked! from the final clarifiers. Mixed liquor
concentrations were monitored routinely, but the concept of controlling
total sludge mass at a desired level was not implemented. Operation of
67
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return sludge flow rates at excessively high rates, typically 150-200
percent of wastewater flow, contributed to solids loss.
2. Sludge Wasting Capability ("B")
An undersized digester, and drying beds that do not provide adequate
sludge disposal capability during winter months result in inadequate
sludge wasting capacity.
3. Improper Technical Guidance ("B")
The above process control and inadequate sludge disposal situation
continued despite annual plant inspections by the State district
engineer. "Periodic solids loss" was given the same emphasis in the
annual inspection reports as plant housekeeping, timely submittal of
monitoring reports, leveling and cleaning of clarifier weirs, and other
items far removed from the true performance-limiting problems and
potential solutions.
4. Clarifier ("B")
The final clarifiers have sidewater depths of only 2.7 m (9.0 ft). This
shallow depth promises loss of sludge solids and makes precise sludge
mass and return control mandatory.
5. Performance Monitoring ("B")
Performance monitoring samples were collected only during periods when
clarifiers were not bulking sludge to conceal performance problems.
6. Familiarity with Plant Needs ("B")
Administrators were not familiar enough with the plant requirements for
performance and operations to recog'nize that a performance problem even
existed.
7. Process Controllability ("B")
Oversized return activated sludge pumps were provided in the plant
design. This promoted poor operation with excessively high return flows
and would require a modification to improve process control.
3.9.4 Potential Impact of a CCP
The most serious of the performance-limiting factors identified were process
control oriented. The evaluation of major unit processes resulted in a Type 2
rating because of marginal, but not drastically deficient, sludge handling
capability. The POTW appears to be a good candidate for a CCP. This
recommendation should be presented to the city council. Performance of the
POTW can be improved with a CCP. Continual compliance will depend on the
68
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ability to dispose of adequate quantities of waste sludge. Documentation of
improved performance may be difficult because existing monitoring data do not
reflect true past effluent quality:
3.10 CPE Results
The success of conducting CPE' activities can be measured by POTW
administrators selecting an approach and implementing activities to achieve
the required performance from their wastewater treatment facility. If
definite followup activities are not initiated within a reasonable time frame,
the objectives of conducting a CPE 'cannot be achieved.
3.11 CPE Worksheets
Worksheets that can be used for evaluating POTW capability are presented in
Appendices L through 0. These worksheets are used to evaluate the capacity of
existing major unit processes, i.ej., aerator, secondary clarifier, and sludge
handling system, and determine whether the POTW is a Type 1, Type 2, or Type 3
plant. :
3.12 References
When an NTIS number is cited in a rfeference, that reference is available from:
National Technical Information Service
5285 Port Royal Road ;
Springfield, VA 22161 j
(703) 487-4650 j
1. Hegg9 B. A., K. L. Rakness, and J. R. Schultz. Evaluation of Operation
and Maintenance Factors Limi'ting Municipal Wastewater Treatment Plant
Performance. EPA-600/2-79-034, NTIS No. PB-300331, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979.
2. Gray, A. C., Jr., P. E. Paul, and H. D. Roberts. Evaluation of Operation
and Maintenance Factors Limiting Biological Wastewater Treatment Plant
Performance. EPA-600/2-79-08;7, NTIS No. PB-297491, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979. J
3. Hegg, B. A., K. L. Rakness, afid J. R. Schultz. A Demonstrated Approach
for Improving Performance and Reliability of Biological Wastewater
Treatment Plants. EPA-600/2-79-035, NTIS No. PB-300476, U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, 1979.
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4.
5.
Hegg, B. A., K. L. Rakness, J. R. Schultz, and L. D. Demers. Evaluation
of Operation and Maintenance Factors Limiting Municipal Wastewater
Treatment Plant Performance - Phase II. EPA-600/2-80-129, NTIS No.
PB-81-112864, U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, OH, 1980.
Schultz, J. R., B. A. Hegg,
Production for Activated Sludge
54(10):1355-1360, 1982.
and K. L. Rakness.
Plants Without Primary
Realistic Sludge
Clarifiers. JWPCF
6. Process Design Manual, Wastewater Treatment Facilities for Sewered Small
Communities. EPA-625/I-77-009. U.S. Environmental Protection Agency,
Center for Environmental Research Information, Cincinnati, OH, 1977.
7. Brenner, R. C., J. A. Heidman, E. J. Opatken, and A. C. Petrasek, Jr.
Design Information on Rotating Biological Contactors. EPA-600/2-84-106,
NTIS No. PB-84-199561, U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, OH, 1984.
8. Rakness, K. L., J. R. Schultz, B. A. Hegg, "J. C. Cranor, and R. A.
Nisbet. Full Scale Evaluation of Activated Bio-Filter Wastewater
Treatment Process. EPA 600/2-82-057, NTIS No. PB-82-227505, U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, 1982.
9. A Guide to the Selection of Cost-Effective Wastewater Treatment Systems.
EPA-430/9-75-002, NTIS Report No. PB-244417, U.S. Environmental
Protection Agency, Office of Water Program Operations, Washington, DC,
1975.
10. Process Design Manual, Sludge Treatment and Disposal. EPA-625/1-79-011,
U.S. Environmental Protection Agency, Center for Environmental Research
Information, Cincinnati, OH, 1979.
11. Schultz, J. R. Activated Sludge - Troubleshooting Techniques. Presented
at Rocky Mountain Water and Wastewater Plant Operator's School, Boulder,
CO, 1983.
12. West, A. W. Operational Control Procedures for the Activated Sludge
Process - Part IIIA, Calculation Procedures. EPA-330/9-74-001C, NTIS No.
PB-231598, U.S. Environmental Protection Agency, Cincinnati, OH, 1973.
13. Palm, J. C., D. Jenkins, and D. S. Parker. The Relationship Betv/een
Organic Loading, Dissolved Oxygen Concentration, and Sludge Settleability
in the Completely-Mixed Activated Sludge Process. Presented at the 51st
Annual Conference, Water Pollution Control Federation, Anaheim, CA,
1978.
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CHAPTER 4
APPROACH TO CONDUCTING COMPOSITE CORRECTION PROGRAMS
4.1 Objective
The overall objective of a Composite Correction Program (CCP) is to improve
the performance of an existing POTW (1). If the results of a Comprehensive
Performance Evaluation (CPE) indicate a POTW is a Type 1 plant (see Figure
2-1), then the existing major ^init processes have been determined to be
adequate to meet current treatment requirements. For Type 1 facilities, the
CCP focuses on systematically eliminating performance-limiting factors to
achieve the desired effluent quality. This can be done without long-term
planning or major plant modifications (2).
i
For Type 2 plants, the existing major unit processes have been determined
be marginal but improved performance is likely through the use of a CCP and
the POTW may meet performance objectives without a major plant upgrade. For
these plants, the CCP focuses on clearly defining the optimum capability of
existing facilities. . i
to
and
For
A factor that influences the conduct of a CCP at Type 2 plants is the
projected future growth in the service area. In an area with little projected
growth, there is generally more incentive to make existing facilities perform
adequately to meet long-term needs. Also, implementation time is not as
important in low- or no-growth areas. A CCP of 12 months' duration that leads
to long-term adequate performance with existing facilities is generally well
worth the time. Even if
and some construction is
any such construction is
the CCP does not achieve the desired effluent quality
indicated, plant administrators can be confident that
indeed necessary.
In a growth situation, implementation of a CCP for a Type 2 plant should
closely parallel analysis of future treatment needs. The POTW should be
planning expansion while the existing plant capability is being verified by a
CCP. This parallel effort will allow administrators to make knowledgeable
short-term decisions that will be compatible with long-term needs.
For Type 3 plants, major construction is indicated and a more comprehensive
study is warranted rather than ja CCP.
long-term needs, treatment alternatives,
mechanisms, and other factors beyond the
A study of this type would look at
potential location changes, financing
scope of a CCP.
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4.2 Methodol ogy
The methodology for conducting a CCP is a combination of implementation of
activities that support process requirements and systematic training of the
staff and administrators responsible for wastewater treatment (2-4).
4.2.1 CPE Results
The basis for implementation and training efforts is the prioritized list of
performance-limiting factors that was developed during the CPE (see Section
2.2.3). For example, if all of the prioritized factors were process control
oriented (highly unlikely), the initial CCP effort would naturally be directed
toward operator training in process control. More commonly, a combination of
performance-limiting factors is identified during the CPE and a combination of
implementation/training activities is therefore required. In addition,
performance-limiting factors not identified in a CPE often become apparent
during conduct of the CCP and must be addressed to achieve the desired level
of treatment (3).
4.2.2 Process Control Basis
The areas in which performance-limiting factors have been broadly grouped
(administration, design, operation, and maintenance) are all important in that
a factor in any one of these areas can individually cause poor performance.
Although no one area is more important than any other, it helps when
implementing a CCP to understand the relationship of these areas to each other
and the the goal of achieving a good, economical effluent.
Administration, design, and maintenance activities all lead to a plant
physically capable of achieving desired performance. It is the operation, or
more specifically the process control, that takes a physically capable plant
and produces adequately treated wastewater, as indicated by Figure 4-1.
A CCP continually focuses toward the goal of achieving desired plant effluent
quality. It often becomes difficult to prioritize the changes needed to
achieve this performance level, -due to the typical multiple performance-
limiting factors that exist. However, by focusing on the needs of the
biological treatment process, as established through process control efforts,
priorities for changes to achieve improved performance can be developed.
For example, if good performance in an extended aeration activated sludge
plant cannot be maintained because bulky sludge has developed as a result of
inadequate oxygen transfer capability, better performance requires meeting the
oxygen .deficiency. Limitations in meeting process needs (inadequate DO)
establish the need for design changes. The plant must be improved to the
point where it is capable of providing an adequate level of DO to allow
desired performance to be achieved.
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FIGURE 4-1
RELATIONSHIP OF PERFORMANCE-LIMITING FACTORS
TO ACHIEVING A PERFORMANCE GOAL
Administration
Goojd, Economical
i Effluent
|Operation
(Process Control)
Capable Plant
Design
Maintenance
73
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On the other hand, a plant may exhibit extensive limitations in grounds
maintenance and housekeeping. If these limitations do not interfere with
meeting the needs of the biological treatment process, low priority for
addressing these limitations is indicated.
Figure 4-1 and the above example illustrate how the process control basis can
be used to prioritize improvements in physical facilities. Proposed
improvements must alleviate a deficiency in the existing "incapable plant," as
identified by process requirements, so that progress toward the performance
goal can be pursued. In this way the most direct approach to improved
performance is implemented. Nonperformance-related improvements can properly
be delayed until the plant has achieved the treatment objective for which it
is intended.
4.2.3 Long-Term Involvement
Implementation of a CCP is a long-term effort, typically involving one year,
for several reasons:
- Inherently long response times associated with making changes and
achieving stability in biological systems.Biologicalsystems
typically respond slowly to process control adjustments that affect
the environment in which the microorganism population lives. New
environmental conditions eventually result in changes in the
relative numbers of different microorganisms. Although some
changes can be accomplished for activated sludge systems in the
period of three to five MCRTs, it is not uncommon for some changes
to take weeks and even months before desired shifts in
microorganism populations are accomplished (6).
- Time required to make physical and procedural changes. This is
especially true for those changes requiring financial expenditures
where governing board or council approval is necessary.
- Greater effectiveness of
_ repetitive training techniques. Operator
and administrator training can be conducted under a variety of
actual operating and administrative experiences.
Time required for identification and elimination of any additional
performance-limiting factors that may befoundduringtfieCCP.
4.3 Personnel Capabilities for Conducting CCPs
Persons responsible for conducting a CCP must have a comprehensive
understanding of wastewater treatment (see Section 2.3) as well as extensive
hands-on experience in biological wastewater treatment operations and strong
capabilities in personnel motivation. Authoritative understanding of, and
experience in, biological wastewater processes are necessary because the
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current state-of-the-art in biological treatment leaves room for much
individual judgment in both design and process control. For example,
references can be found to support the use of a variety of activated sludge
process control strategies. Tho?e responsible for implementing a CCP must
have sufficient process experience to determine which of these is most
applicable to the POTW in questiojn. Leadership and motivational skills are
required to implement changes required. These individuals must implement
changes, direct activities, provide training, set priorities, exercise
judgment, and, in general, facilitate those functions that lead to improved
performance. The term "facilitator" will therefore be used to describe those
individuals responsible for implementing a CCP.
Individuals who routinely work in! the area of improving wastewater treatment
plant performance will likely be best qualified to be CCP facilitators. These
persons are, typically, engineersjo.r operators who have focused their careers
on wastewater treatment plant troubleshooting and have gained experience in
correcting deficiencies at severa) plants of various types. It is important
that CCP facilitators have experience in a variety of plants because the
ability to recognize true causes jof limited performance is a skill developed
only through experience. Similarly, the successful implementation of a
cost-effective CCP is greatly enhanced by experience.
i
By the very nature of the CCP approach, the CCP facilitator must often address
improved operation, maintenance, a|nd minor design modifications with personnel
already responsible for these wastewater treatment functions. A "worst case
situation" is one in which the j POTW staff is trying to prove that "the
facilitator can't make it work either." The CCP facilitator must be able to
get all parties involved to focus on the common goal of achieving desired
plant performance.
A CCP facilitator must be able to conduct training in both formal classroom
and on-the-job situations. Training capabilities must also be broadly based,
i.e., effective with both the ; operating as well as the administrative
personnel. When addressing process control limitations, training must be
geared to the specific process control decisionmakers. Some may be
inexperienced and uncertified; others may have considerable experience and
credentials. Administrative "training" is often a matter of clearly providing
information to justify or support CCP activities. Although many
administrators are competent, successful, and experienced, some may not know
what their facilities require inj terms of manpoweri minor modifications, or
specific funding needs. i
CCP facilitators can be either consultants or utility employees. When local
administrators decide to use a consultant to implement the CCP, they should
conduct interviews and check references thoroughly. Nearly every CCP involves
correction of some administrative; factors, actual expenses to the POTW, and
could involve a substantial construction cost if the CCP is not capable of
bringing the POTW to the des-jred level of treatment. As such, the
administrators should have complete confidence in the abilities of the CCP
facilitator. An important attribute of a consultant providing CCP services is
the ability to explain problems and potential solutions clearly to a variety
of audiences, both technical and hontechnical.
75
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When local administrators decide to conduct a CCP without the services of
outside personnel, they should recognize that some inherent problems may
exist. The individuals implementing the CCP, for example, often find it
difficult to provide an unbiased assessment of the area in which they normally
work: operating personnel tend to look at design and administration as
problem areas; administrators typically feel the operating personnel should be
able to do better with what they have; the engineer who designed a facility is
often reluctant to admit design limitations, etc. These biases should be
recognized and discussed before personnel closely associated with the POTW
initiate a CCP.
4.4 Estimating CCP Costs
CCP costs vary widely depending on the size and complexity of the facility,
who implements the CCP, the number and nature of performance-limiting factors,
and the capability and cooperation available from the POTW technical and
administrative staff. The cost of a CCP falls into two main areas: 1) cost of
a consultant to implement the CCP; and 2) cost of implementing activities to
support the CCP effort, such as minor plant modifications, additional
staffing, more testing equipment, and certain process changes. Estimated
costs for using a CCP consultant are presented in Table 4-1.
TABLE 4-1
TYPICAL COSTS FOR CONDUCTING A CCPa
Facility
Suspended Growth:b
<800 m3/d (0.2 mgd)
800-8,000 mV
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Wide ranges are presented in [Table 4-1 because the performance-limiting
factors generally vary widely frpm plant to plant and require different types
and amounts of training before they can be eliminated.
i
The costs of implementing activities to support the CCP effort and for
operating the POTW at a higher level of performance are difficult to
generalize. They must be developed on an individual POTW basis since they are
more dependent on the particular jperformance-limiting factors than the size or
type of facility. In most CCPs [these costs equal or exceed the typical costs
of a CCP consultant, as presented in Table 4-1.
4.5 References
When an NTIS number is cited in a reference, that reference is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
I
1. Hegg, B. A., K. L. Rakness,| and J. R. Schultz. Evaluation of Operation
and Maintenance Factors Limiting Municipal Wastewater Treatment Plant
Performance. EPA-600/2-79-j034, NTIS No. PB-300331, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979. j
i
2. Hegg, B. A., K. L. Rakness^ and J. R. Schultz. The CCP Way to Better
Effluents. Water Engineering and Management, 129(10):40-43, 1982.
i
3. Hegg, B. A., K. L. Raknessi and J. R. Schultz. A Demonstrated Approach
for Improving Performance, and Reliability of Biological Wastewater
Treatment Plants. EPA-600/2-7 9-035, NTIS No. PB-300476, U.S.
Environmental Protection !Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, j 1979.
4. Gray, A. C., Jr., P. E. Paul, and H. D. Roberts. Evaluation of Operation
and Maintenance Factors Limiting Biological Wastewater Treatment Plant
Performance. EPA-600/2-79f087, .NTIS No. PB-297491, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979. |
i
I
5. Palm, J. C., D. Jenkins, and D. S. Parker. The Relationship Between
Organic Loading, Dissolved Oxygen Concentration, and Sludge Settleability
in the Completely-Mixed Activated Sludge Process. Presented at the 51st
Annual Conference, Water Pollution Control Federation, Anaheim, CA,
1978. |
6. Jenkins, D. and W. E. Garrison. Control of Activated Sludge by Mean Cell
Residence Time. JWPCF 40 (ll): 1905-1919, 1968.
77
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CHAPTER 5
HOW TO CONDUCT COMPOSITE CORRECTION PROGRAMS
5.1 Introduction
This chapter presents techniques, schedules, and guidelines that have been
successfully used in implementing Composite Correction Programs (CCPs). The
methods presented should not be taken as the only workable methods, since
experience has shown that no single approach will work at every POTW (1).
When implementing a CCP, it must be remembered that the concept of correcting
performance-limiting factors until the desired POTW performance is achieved
must remain the controlling guidance, with the specifics left to the CCP
facilitator.
5.2 CCP Activities
A CCP facilitator should schedule periods of onsite involvement interspersed
with off site limited involvement. During the onsite periods, the facilitator
assumes a leadership role in making process control decisions, assigning
responsibilities, training POTW staff, and checking progress. When not
onsite, POTW personnel are responsible for this leadership and the CCP
facilitator monitors their progress as well as the process control arid
performance of the plant.
The CCP should be scheduled and implemented using the following tools, keeping
their advantages and limitations in mind:
- Telephone calls, because of convenience and low cost, for routine
monitoring 6T~ CCP progress. Use of the telephone promotes
acceptance by POTW personnel of responsibility for making critical
plant observations, interpreting data, and summarizing important
indicators and conclusions. The effectiveness of telephone calls
is limited in that the CCP facilitator must rely on observations of
the POTW personnel rather than his/her own. To ensure common
understanding of the telephone conversations, the CCP facilitator
should always summarize important points, decisions that have been
reached, and actions to be taken subsequent to the call. Both the
CCP facilitator and POTW personnel should keep written phone logs.
78
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- Site
visits to
control
verify or I clarify plant status, indicate major
process control changes, j:est completed facility modifications,
provide onsite operator training, and report progress to POTW
administrators. Specific, dates for site visits should be scheduled
as indicated by the plant status and training requirements.
i
Written reports to promote clarity and continuity. Because the
cost of written reports 'depletes funds available for action-
oriented work by both the POTW staff and the CCP facilitator, only
concise, quarterly status reports are recommended. Short (1-page)
written summaries should i also be prepared for each facility
modification. Initially,! these may be prepared by the CCP
facilitator, but
transferred to the
this responsibility should ultimately be
POTW staff.
- Final CCP report to
recommendations should
Current status of the
presented.
summarize activities, since all major
have been implemented during the CCP.
POTW performance and capacity should be
The approach of interspersing onsite with off site involvement is illustrated
in Figure 5-1. As the CCP progresses, fewer site visits and telephone calls
should be used. This is in linejwith the transfer of responsibility back to
the permanent POTW staff. Typical levels of effort required by CCP
facilitators are presented in Tab|le 5-1. For any particular POTW, the level
of effort is dependent on the specific performance-limiting factors.
5.3 Initial Site Visit
The initial site visit is used to establish the working relationship between
the CCP facilitator and the POTV^ staff and administration. A good working
relationship - based on mutual respect, communication, and understanding of
the CCP - greatly enhances the potential for a successful CCP.
5.3.1 CPE Results
CPE, 25-50 percent of
re-create or confirm
the
the
If the CCP facilitator was not; involved in the
initial site visit time may be required to
conclusions of the CPE. |
A CCP is often implemented by individuals more experienced in identifying and
correcting factors limiting POTW performance than those who conducted the CPE.
During the initial site visit, the CCP facilitator should schedule time with
key plant personnel and key administrators to discuss confirmation and/or
modification of the original performance-limiting factors identified in the
CPE. This discussion should also address the Type 1 or Type 2 status of the
POTW and the improvement in plant performance and/or capacity expected from
implementation of a CCP. j
79
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FIGURE 5-1
TYPICAL SCHEDULING OF OMSITE AND OFFSITE INVOLVEMENT
123456 7 8 9 10 11 12
Telephone
Consultation
Onsite
Consultation
D
D
Months of Involvement
:TABLE 5-1
TYPICAL CCP FACILITATOR INVOLVEMENT
Facility Size and Type*
Suspended Growth:
3,800 mf/d (1 mgd)
38,000 nrYd (10 mgd)
Fixed Film:
3,800 nwd (1 mgd)
38,000 m3/d (10 mgd)
Initial Site
Visit
days
3- 5
4-10
2- 5
4-10
Telephone
Consultation
no.
initial
2-6
3-8
1-3
2-3
/wk
end
2-4
2-4
1-4
1-4
Additional
Site Visits
no./yr
4-12
6-20
3- 8
5-12
Suspended growth facilities have greater process control flexibility
and typically require a greater level of effort by the CCP facilitator.
80
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The initial site visit should also be used to begin the elimination of all
major performance-limiting factors (rated "A" or "B" in the CPE) and as many
other factors as possible. It is usually most advantageous to first work on
improving process control. Existing process control testing should be
reviewed and modified so that all necessary process control elements are
adequately monitored. Sampling frequency and location, collection procedures,
and laboratory analyses should! be standardized so that subsequent data
collected by POTW personnel and reviewed by the CCP facilitator can be used to
evaluate the results of CCP activities and represent the complete process
control monitoring needs of the POTW. New or modified sampling or analyses
procedures should be demonstrated, by the CCP facilitator and then performed by
plant personnel under the supervision of the CCP facilitator.
5.3.2 Monitoring Equipment j
i
Any needed sampling or testing! equipment should be obtained. The CCP
facilitator should assist the j POTW personnel in obtaining any required
administrative approvals. |
I
i
5.3.3 Process Control Summaries
The CCP facilitator should, with the help of plant personnel, draft a precise
weekly summary form for process control parameters and performance monitoring
results. Monthly records are [often available, but monthly data are too
infrequent to allow timely process control adjustments. POTW personnel should
provide the weekly summaries to tihe CCP facilitator throughout the CCP.
In some small plants, process dontrol and monitoring results can often be
recorded on a single page. An example process control form used both for in-
plant records and as a summary sent to the CCP facilitator is shown in Figure
5-2. i
5.3.4 Process Control Adjustments
The CCP facilitator should, as! much as possible, initiate process control
adjustments during the initial site visit. Where process controls are grossly
out of line, e.g., 300 percent estimated return sludge flows, the CCP
facilitator should initiate adjustments toward more reasonable values at the
earliest possible time. Fine tjuning' of process control and training of the
POTW staff cannot legitimately progress until this first level of effort is
initiated. j
During major process control adjustments, every effort should be made to
minimize adverse impact on the iPOTW operators' morale. Recommendations for
process control changes should be explained in terms of attempting to optimize
plant capabilities through process adjustments with both the CCP facilitator
81
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I
*
>w
~ ~ !"• O O fl E O)
— L. I. (A
§§fefe§§w.2.25
-------
and POTW operators involved in all aspects. Even with this approach, a CCP
obtain
facilitator should not expect to
personnel on all changes. A response such as
see" is often the best that
only the degree of consensus
work, but we can try it."
can be expected.
expressed by the
immediate complete support from POTW
"well, let's try it then and
Some changes may be made with
statement: "I don't think it'll
5.3.5 Minor Design Changes !
Any minor design changes identifjed as necessary by the CPE and confirmed by
the CCP facilitator should be initiated during the initial site visit. Minor
design changes often require significant amounts of time for approvals,
delivery of parts or equipment, or construction. It is necessary, therefore,
to start the process as soon as needs are identified so that the effect of any
changes can be evaluated during the majority of the CCP.
5.4 Improving Design Performance-Limiting Factors
i
i - '
The performance of Type 1 and Type 2 POTWs can often be improved by making
minor modifications or additions! to the original design. Examples of design
limitations identified in a CPE are included in Appendix H. Examples of
common minor modifications implemented during CCPs are:
i I
- Return sludge flow measurement in small activated sludge POTWs
i
- Sample taps on sludge dratyoff lines
(
- Piping to operate in alternative activated sludge modes (plug flow,
contact stabilization, etc.)
- Piping to provide recircutation without overloading clarifiers
I
• i
- Time clocks on waste and Return sludge pumps
i
- Bypasses on "polishing" pqnds
- Supplemental air in aeration basins
- Supplemental sludge disposal - usually land application capability
I ;
5.4.1 Identification and Justification
i
The CCP facilitator and POTW personnel must be able to justify each proposed
modification based on the resulting increased capacity or operability the
modification will provide. The degree of justification required for each
modification usually varies witih the associated costs and specific plant
83
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circumstances. For example, little justification may be required to convince
a superintendent to add a sampling tap in a sludge line if the necessary staff
and tools to do the job are already available. The same tap would require
more justification if a part-time operator would have to buy or rent tools and
complete the installation on his/her own time or obtain authorization for
additional paid time.
5.4.2 Implementation
The CCP facilitator should ensure that each minor design modification or
addition is formally documented in writing. This documentation is more
valuable in terms of training and commitment if it is completed by POTW
personnel. It should include:
- Purpose of the proposed change
i
- Detailed description of the change
- Quantitative criteria for evaluating success or failure of the
change
- Individual(s) responsible for completing the change
- Cost estimate
- Anticipated improvement in plant performance
- Schedule
Another role of the CCP facilitator is to assist POTW personnel in
understanding and implementing their responsiblity in regard to the
modification. Ideally, the CCP facilitator should be a technical and
managerial reference throughout the implementation of the modification, and
the POTW staff should have, or develop, the technical expertise, available
time, and motivation to complete the modification. If there is a breakdown in
completing assigned responsibilities, the CCP facilitator must become more
aggressive in assuring completion of the modification.
5.4.3 Assessment
Following completion of a minor modification, the CCP facilitator should
perform an evaluation of the improved POTW capability. This assessment should
compare the quantitative criteria established for the project with the
capability of the actual modification. A one-page summary is often helpful in
informing, and maintaining support from, POTW personnel and administrators.
84
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5.5 Improving Maintenance Performance-Limiting Factors
Plant maintenance can generally bejimproved in nearly all POTWs, but it is a
serious performance-limiting factor in only a small percentage of them (2-4).
Nevertheless, adequate maintenance jis essential to achieve consistent effluent
quality. As such, a CCP facilitator may end up improving the maintenance
program during a CCP to ensure that' improved performance achieved during a CCP
is maintained afterwards. ;
The first step in addressing maintenance factors that limit plant performance
is to review any undesirable resuljts of the current maintenance effort. If
plant performance is degraded as a result of equipment breakdowns that could
have been avoided with better preventive maintenance, the problem is easily
documented. Likewise, if high jcost of major corrective maintenance is
experienced, a need for improved preventive maintenance is easily recognized.
should have been (identified during the CPE when filling out
form in Appendjix D and identifying and prioritizing
performance-limiting factors. However, many POTWs lacking good maintenance
programs do not have such obvjous evidence directly correlating poor
maintenance practices with poor performance. For these POTWs, maintenance
would not have been identified as a; significant factor limiting performance.
These situations
the appropriate
Once the need for improved preventive maintenance is established, the next
step is to gain the. commitment! of the plant operating staff. Simply
formalizing recordkeeping will generally improve maintenance practices to an
acceptable level in many POTWs, par|ticularly smaller ones.
I
A suggested four-step procedure f,or developing a maintenance recordkeeping
system is to: 1) list all equipment; 2) gather manufacturers' literature on
all equipment; 3) complete equipment information summary sheets for all
equipment; and 4) develop time-based preventive maintenance schedules.
A list of equipment can most easil^ be developed by touring the POTW. As new
equipment is purchased it can be added to the list. Existing manufacturers'
literature should be inventoried jto identify missing but needed materials.
Maintenance literature can be obtained from the factory (usually a source is
identified on the equipment ! nameplate) or from local equipment
representatives. j
An equipment information sheet isjpresented in Appendix G. Once sheets are
completed for each piece of equipment, a time-based schedule can be developed.
This schedule typically includes daily, weekly, monthly, quarterly,
semiannualj and annual checkoff lists of required maintenance tasks. An
example of this scheduling system is also presented in Appendix 6.
I
In many small POTWs, the number: of pieces of equipment is so small that
scheduling is not critical. ijn larger plants, preventive maintenance
activities should be spaced to provide an even workload throughout the year.
Similarly, all monthly maintenance activities should be scheduled for
accomplishment over the entire 4-week period.
85
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The above system for developing a maintenance recordkeeping system has worked
successfully at several small POTWs. However, there are many other good
maintenance references available for use by CCP facilitators and POTW staffs
(5-7).
5.6 Improving Administrative Performance-Limiting Factors
Frequently encountered administrative factors that limit plant performance are
administrators who are unfamiliar with plant needs and policies that conflict
with plant needs. For example, such items as minor modifications, testing
equipment, expanded operator coverage, or increased utility costs may be
recognized by plant operating personnel as performance-limiting factors but
changes cannot be pursued due to lack of appreciation of their importance by
nontechnical administrators. Nearly all POTW administrators want to provide
adequate treatment capacity and performance. Their support and understanding
is essential to the successful implementation of a CCP. The following
techniques have pr.oven useful in overcoming administrative limitations:
- Involve plant administrators from the start of the CCP. The
initial site visit should include time with key administrators at
the plant to increase their understanding of plant processes and
problems.
- Educate administrators in the fundamentals of biological wastewater
treatment and in the specific needs of the plant's processes.
AdministratorsmayBereluctanttopursuecorrective actions
because of lack of understanding of treatment processes and the
role the desired change plays in improving such processes.
- Listen carefully to the concerns of administrators so that they can
be addressed during the CCP. Some of their concerns or ideas may
be technically unimportant, but must be addressed to ensure
continued progress of the CCP.
- Use technical data based
on
__^ process needs to persuade
administrators55takeappropriateactions;do not rely on
"authority." Alternatives should be presented, when possible, and
the administrators left with the decision.
5.7 Improving Operational Performance-Limiting Factors
Improvement of POTW operations during a CCP is achieved by providing training
while improved process control procedures, tailored for the particular plant,
are developed and implemented. The initial training efforts should be
directed at the key process control decisionmakers. In most plants with flows
less than 1,900 nr/d (0.5 mgd), one person typically makes and implements
all major process control decisions. In these cases, on-the-job training is
usually more effective than classroom training and is recommended. As the
86
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number of operators to be trained Increases with plant size, the need for and
effectiveness of combining classroom training with on-the-job training also
increases. !
i
As discussed in Chapter 4, process control is the primary goal in implementing
a CCP because it represents the i essential step that enables a capable plant
to achieve the ultimate goal of cost-effectively producing a good quality
effluent. A detailed discussion^ of process control for suspended growth and
fixed film facilities is therefore presented.
5.7.1 Suspended Growth Process Control
Process control of suspended growth facilities can be achieved through control
of the following important parameters associated with the process:
i
- Activated sludge mass !
- Return sludge flow 1
- Aeration basin DO !
•These items can be utilized to apply "pressure" to the biological environment.
If a particular pressure is held for an adequate length of time to get
biological system response, ja desired change in activated sludge
characteristics - such as settling velocity - will result. The inter-
relationships between sludge | characteristics, pressure, and time for
biological system response to oi:cur relative to sludge mass control, return
sludge control, and DO control are discussed in the following sections.
5.7.1.1 Activated Sludge Characteristics
The primary objective of activated sludge process control is achieving good
performance by maintaining proper sludge character. Sludge character is
defined as those physical and [biological characteristics of a sludge that
determine its ability to remove prganic material from wastewater. Good sludge
character requires filamentous ajnd zoogleal bacteria to be in proper balance.
Enough filaments should be present to form a skeleton for the floe particles,
but the filaments should not extend significantly beyond the floe.
More filaments tend to produce ja slower settling, larger sludge floe that
produces a clearer supernatant. I Too many filaments, however, produce a sludge
that will not adequately settle and thicken in the final clarifier, often
causing sludge to be carried over the clarifier weirs. Having fewer filaments
produces a more rapid settling ;sludge but also leaves more turbidity. The
faster settling, small sludge floe exhibits discrete settling and produces
"pin floe" or "straggler floe" as well as higher turbidities.
A representation of a microscopic view of this desirable type of sludge is
shown in Figure 5-3. ]
87
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FIGURE 5-3
REPRESENTATIONS OF ACTIVATED SLUDGE FLOC
Desirable Activated Sludge Floe
Filament
Backbone
Undesirable Slow-Settling Activated Sludge Floe
Filament
Backbone
Extended
Filament
Undesirable Fast-Settling Activated Sludge Floe
Dispersed
Particle
88
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It is desirable to obtain good sol [ids/liquid and the good sludge thickening
characteristics of a faster settling sludge along with the high quality
effluent produced by a slower settling sludge. This is achieved by control of
the sludge character to obtain the
characteristics.
best balance of fast- and siow-settling
Settling tests can be used to moniftor the sludge conditions shown in Figure
5-3. !
5.7.1.2 Activated Sludge Mass Control
Activated sludge mass is controlled to achieve and maintain desired sludge
character and, .as such, represents a critical aspect of good process control.
There are several ways to control slludge mass in a POTW. These variations put
emphasis on different calculations or different control parameters, but the
basic objective of each is to obtain the desired mass of microorganisms in the
system. j
Some mass control techniques, are ba^ed on the assumption that sludge can best
handle diurnal and day-to-day variations in influent wastewater strength and
the cyclic nature of sludge growth' rates by maintaining relatively constant
MLVSS concentration. Another technique attempts to adjust sludge mass to
produce a desired food to microorganism ratio (F/M). Yet another attempts to
maintain a consistent average age ofi the activated sludge in the system, i.e.,
mean cell residence time (MCRT). 'l
Mass control by monitoring only the MLSS or MLVSS concentration in the
aeration basin and wasting sludge jto maintain a desired level assumes that
variations in the amount of sludge in the secondary clarifiers is
insignificant. A preferred approaph includes secondary sludge in the mass
control monitoring program.
The F/M method of sludge mass conjtrol is difficult to implement because a
method to quickly and accurately monitor the food portion of this parameter is
not commonly available. Typically,! BODs or chemical oxygen demand (COD) are
used to indicate the amount of food available. The 8005 test requires five
days to complete and is therefore unsatisfactory for process control purposes.
Although the COD test can be completed in only several hours, it requires
equipment and laboratory capabilities that are not usually available in
smaller plants.
1
Mass control using the MCRT approafch can be set up to include the mass of
sludge in the aeration basin and the secondary clarifier (10). A variation of
this technique is to select a desfired level of total mass for the system
(i.e., both the aeration basin and (secondary clarifier) and adjust the amount
of sludge wasted to approach the selected total mass. It is recommended that
one of these two strategies be selected for controlling sludge mass. The
following discussion identifies the |differences between the two strategies.
89
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Activated sludge mass control using the MCRT approach requires that the total
sludge mass be measured each day and that total be divided by the target MCRT.
This calculated mass is then attempted to be wasted. Actual MCRTs are
calculated by dividing the total sludge mass in the system by the actual
sludge mass wasted. Actual data for a 3-week perio'd of sludge mass control
using the MCRT approach are shown in Figure 5-4. During this period the
target MCRT was kept constant at 10 days. The data in Figure 5-4 show that
fairly constant MCRT can be maintained. An advantage of mass control by this
method is that it requires daily wasting.
Sludge mass control using the total mass in the system approach requires that
wasting be varied depending on increases or decreases in the total sludge
mass. For example, if the total sludge mass was increasing above the selected
target level, wasting would be increased until the desired sludge mass was
again achieved. Actual data for a 3-week period of sludge mass control using
the target total mass approach are shown in Figure 5-5. An important
observation from Figure 5-5 is that total mass was held relatively constant
despite individual MCRTs ranging from 10 to infinity (no wasting that day).
Control of total sludge mass can be a useful process control parameter,
especially in activated sludge plants where wasting is not done every day.
5.7.1.3 Return Sludge Flow Rate Control
The return sludge flow rate determines the distribution of sludge between the
aeration basin and secondary clarifier. In general, return sludge flow rate
control should be used to maximize the sludge mass and sludge detention time
in the aeration basin and minimize the sludge mass and sludge detention time
in the final clarifier. This represents the optimum condition for an aerobic
biological treatment system and can be summarized as maximizing the sludge
distribution ratio (aerator sludge mass divided by clarifier sludge mass).
A general misconception concerning the use of return sludge flow rates for
process control is that increasing the flow of return sludge decreases the
sludge blanket level in the secondary clarifier. This is not as
straightforward as it first appears. Within the normal range of operation for
sludge settling characteristics, increasing the return rate will remove the
sludge mass from the clarifier faster. However, the return sludge ultimately
contributes to the total hydraulic load to the clarifier and therefore to the
total solids load on the clarifier from the aeration basin (see Figure 5-6).
Depending on the sludge settling characteristics, increased solids loading on
the clarifier may or may not increase the solids mass in the clarifier in
conjunction with the faster solids removal rate. Although the sludge
detention time in1 the clarifier may go down, the sludge mass in the clarifier
may go up. When the mass of sludge in the clarifier is increased along with
the rate of sludge removal, the objective of maximizing the sludge
distribution ratio is obviously not achieved. The positive aspect of a
decreased detention time in the clarifier must be weighed against the negative
aspect of a decreased sludge ! distribution ratio and a decreased sludge
detention time in the aerator.
90
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;FIGURE 5-6
SIMPLIFIED ACTIVATED SLUDGE PROCESS DIAGRAM
Q
T
Aeration
Basin
Q+R
^j Clarifier
R
R
Q
R
Wastewater Flow j
Return Sludge Flow
Waste
Two levels of improved sludge return control are typically encountered when
implementing a CCP: gross adjustments to bring the operation into normal
operating ranges followed by fine tuning to optimize performance. Thus, a
grossly out of line return rate should first be adjusted to fall in the middle
of the appropriate range presented in Table 3-5.
Most activated sludge plants with flows less than 7,500 m3/d (2.0 mgd) are
designed conservatively enough that, at wastewater flows less than design,
gross adjustments to bring the sludge return rate within normal ranges often
provide sufficiently improved control. Furthermore, most plants that have
been determined to be Type 1 (major unit processes are adequate) are
conservatively enough loaded that such gross adjustments may be all that is
necessary for current loadings. The applicability and results of gross sludge
return adjustments are illustrated by the following discussion:
An activated s]udge plant wasi experiencing almost continuous problems
with sludge bulking in the final clarifier. This continued despite
repeated efforts by the plant ^superintendent to control the filamentous
nature of the sludge. The superintendent had chlorinated and dumped the
entire activated sludge massj to polishing ponds twice and was now
considering adding clay as a settling aid.
93
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Review of plant operation indicated that the return sludge flow rates
were about 150 percent of the raw wastewater flow rate. After a
discussion of the advantages of a lower return rate, the superintendent
reduced the return sludge rate to about 50 percent of the raw wastewater
flow. Solids loss from the clarifiers stopped in about 3 hours.
This gross return rate adjustment did not solve all of the plant
problems, but it did significantly improve process control and
performance. At the higher return rate, hydraulic loading to the final
clarifier had been 2.5 times the raw wastewater flow. After the
adjustment, the hydraulic loading was reduced to 1.5 times the raw
wastewater flow. Although overflow rates were not affected, detention
time in the clarifier for settling was increased by 67 percent and
solids loading to the clarifier was reduced by 40 percent. This greatly
enhanced the solids/liquid separation function of the clarifier.
Most Type 2 plants (major unit processes are marginal) or plants where gross
return sludge flow adjustments do not produce the desired results will require
a higher level of return sludge flow control, such as diurnal adjustments
based on variations in wastewater flow and sludge character that occurs due to
variations in POTW loadings over a 24-hour period.
Fine tuning return sludge flow rates is an area in which several differing
philosophies exist within the technical community. A complete explanation of
each is beyond the scope of this Handbook. The selection of a specific
technique, and evaluation of the results, is best left to the skill and
judgment of an experienced CCP facilitator.
5.7.1.4 Aeration Basin DO Control
Oxygen levels in an aeration basin can be used to promote or hinder the growth
rates of filamentous organisms in the activated sludge process (8-11). DO
control can therefore be used to promote the desired balance between
filamentous and zoogleal microorganisms, control sludge character, and improve
plant performance.
In most activated sludge plants, regardless of size,, the greatest single use
of energy is for aeration and mixing in the aeration basin. The desire to cut
energy and associated costs while maintaining good performance makes the
decision as to how much oxygen to use a critical one. Some guidelines and
tests that have been used to aid in making this decision in other plants are
presented below.
Oxygen supply in an aeration basin can be thought of as satisfying two needs:
oxygen demand and residual DO. Typically, these are satisfied without
differentiation, but an understanding of both may be helpful when evaluating
oxygen needs. Oxygen demand is the mass of oxygen required to meet BOD and
nitrification demand and maintain a viable microorganism population. The
required residual DO is that mass of oxygen needed to provide the environment
that produces good sludge character. The residual DO, which exists in an
94
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aeration basin when the oxygen demand is satisfied, varies with the type of
process. Generally, the higher the organic loading rate on the activated
sludge system, the higher the resiidual DO will be when the demand is met. A
general guideline for residual bulk DO is shown in Figure 3-1. Higher oxygen
rates are, in general, associated with activated sludge systems that have
higher organic loadings. :
i
i
Operating experience has shown th^t DO becomes a growth-limiting factor for
zoogleal-type microorganisms before becoming a limiting factor for filamentous
microorganisms. Do control at low; levels in an aeration basin can therefore
be used to apply pressure to shift sludge characteristics toward slower
settling. Conversely, higher DO levels can be used to apply pressure for
faster settling. !
If a decision is made to lower DO by reducing aeration, proper tesing is
essential as it is a necessity to |recognize when too little oxygen is being
transferred. Tests that will be mpst beneficial are residual DO measurements
and oxygen uptake rate tests (12).: Residual DO measurements should be taken
initially at several locations throughout the aeration basin and verified
periodically to determine a sample ipoint that can be considered "average."
When determining residual DO, it ;is important to take measurements several
times during the day to be coincident with diurnal flow variations, since
residual DO demand typically varies with loadings. Where 24-hour operator
coverage or in-basin DO meters: with recorders are available, diurnal
fluctuations should be obtainable as often as needed. In other plants, a few
"special DO tests" in the middle of the night may be sufficient. The
importance of getting DO readings for all major plant load conditions is that
anoxic, or DO-deficient, conditions promote the growth of filamentous
organisms leading to bulky sludge character.
In general,, plants operating at low DO levels during peak loading may still
provide good treatment if considerably higher DO residuals exist before the
day's peak loading is received, i For example, a plant may operate very
successfully with a DO of 0.4-0.6img/l during the day if the morning DO is
1.0-1.5 mg/1. This daily fluctuation in DO levels can produce the desired mix
of zoog'leal and filamentous organisms.
The oxygen uptake test can also bie used as a measure of adequacy of oxygen
transfer (13). For example, if the oxygen uptake test indicates an oxygen
demand significantly greater than; 0.65 kg 02/kg BOD5 removed plus 0.1 kg
02/kg total sludge in an activated'sludge system, the test may be indicative
of an inadequate oxygen supply.! This analysis is illustrated by the
following. j
An activated sludge facility was removing approximately 240 kg (530 Ib)
BODs/d with a total sludge mass in the aeration basin and secondary
clarifier of about 2,000 kg (4,5pO Ib). The calculated oxygen demand is
[(240 kg BOD5/d) x (0.65 kg , Oo/kg BOD5)] + [(2,000 kg sludge) x
(0.1 kg 02/kg sludge/d)], or 356 kg (783 Ib) 02/d. However, the
measured oxygen uptake in the 760 m3 (200,000 gal) aeration basin was
30 mg/l/hr, or 550 kg (1,200 Ib) 02/d, or 150 percent of calculated
95
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oxygen demand. This indicated that the realistic oxygen requirements
are not being met with the current residual DO of 0.5-0.8 mg/1. Oxygen
supply was increased, turbidity of the effluent dropped, and the oxygen
demand measured by the oxygen uptake rate decreased to 110 percent of
the calculated demand.
The above illustrates the use of a successful troubleshooting technique for
identifying and correcting a DO deficiency. Like return sludge control, the
capability to use DO control to fine tune activated sludge processes is a
function of the experience and technical judgment of the CCP facilitator.
5.7.1.5 Process Control Pressure
As discussed in Section 5.7.1.1, overall activated sludge plant treatment
performance is primarily a function of the sludge character. Process control
tests and adjustments should be made with the purpose of achieving changes in
the direction of desirable sludge character. The specific process controls
discussed earlier (sludge mass, sludge returns, and aeration basin DO) are
used to apply a "pressure" to change sludge character by changing the
environment for the sludge mass.
When a change in sludge character is desired, a combination of operational
adjustments may be necessary to provide enough pressure to achieve that
desired range. For example, if sludge settling has slowed to an undesirable
level and a wet weather season (which will cause higher average and peak
clarifier hydraulic loadings) is approaching, it would be advantageous to
expedite efforts to increase the settling rate. Simultaneous adjustments of
several process control parameters could provide more pressure in the desired
direction than making a change in only one control. In general, a raise in
the sludge inventory, a raise in aeration basin DO, and more frequent return
rate adjustments to minimize sludge mass and sludge detention time in the
clarifier would all be appropriate to achieve faster settling and better
clarifier performance in a minimal time under the higher hydraulic loading
conditions.
5.7.1.6 Time for Biological System Response
When adjusting process control at activated sludge plants, it is important to
realize that changes in sludge character develop slowly and time must be
allowed for the biological system to respond to the pressures applied.
Adjustments may change the environment of the activated sludge very quickly,
but a considerably longer period of time may be required before sludge
character changes to reflect the new environment. For example, if low DO in a
diffused air aeration basin is believed to be a cause of slow-settling sludge,
it would be appropriate to increase the oxygen transfer by increasing blower
output. Two changes should be monitored, one immediate and one long-term.
Mixed liquor DO measurements a few hours after the change as well as the next
96
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day should indicate whether the increased blower output selected was
sufficient to change the environment (DO level) in the aeration basin, but it
may take several weeks of sludge settling tests to determine if that new
environment applied enough pressure to cause the sludge to settle more
rapidly.
There is a tendency to return ito status quo if a desired result is not
achieved quickly. In the above | example, a person using a trial and error
approach may decide after 3 days f higher DO that additional aeration was the
wrong adjustment and a waste of jenergy. However, a person directing a CCP
must have enough experience and confidence to hold the changed environmental
conditions long enough to producej the desired result. If the desired change
in sludge character has not started to take place in a length of time equal to
two or three MCRTs, additional pressure should be applied. As a general
reference, a time equal to three to five MCRTs may be necessary to produce
changes in sludge character due tp process control adjustments.
An appreciation for the time required for a biological system to respond to
new pressures should be a major training objective of the CCP effort to
improve process control. Graphing monitoring results to produce trend charts
can enhance this appreciation. |
5.7.1.7 Activated Sludge Testing
Activated sludge plant monitoring for effective process control must include
sludge character, sludge mass, return sludge, and DO. Several references are
available for selecting tests and] their frequency for activated sludge plants
The tests and schedule shown in table 5-2, developed for a 190 m3/d (50,000
gpd) plant operating under highly} variable conditions due to drastic climate
changes and wide seasonal population fluctuations, are applicable to many
small activated sludge plants. I The concept of providing two different
frequency schedules is a compromise between the desirable higher frequencies
and the minimum operator time typically allocated to this function in small
facilities. Under normal operating conditions, with little stress on the
processes, the "routine" frequency is adequate. When the system is under
stress, the "critical" frequency is appropriate. This occurs during
transitions to higher loadings, j during peak seasonal populations, and can
occur unpredictably if bulky sludge character develops or equipment fails.
Even in small activated sludge plants a concentrated process control effort
based on reliable testing and . j understanding of process fundamentals is
necessary, as illustrated by the process control testing schedule and
recording sheet developed for aj950 nr/d (0.25 mgd) contact stabilization
plant and shown in Figure 5-7. (ijlote: When the CCP was initiated, monitoring
of aeration basin DO was not included because the testing capability was not
available at the time.)
97
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TABLE 5-2
PROCESS CONTROL MONITORING AT A
SMALL ACTIVATED SLUDGE PLANT
Frequency
Test, Parameter, or Evaluation Routine Critical
Flow Equalization:
Water Level Daily 2/day
Pump Setting vs. Daily Flow, DO 3/week Daily
Activated Sludge:
Control Tests 3/week Daily
Centrifuge Spins (Aeration Tank Cone./
Return Sludge Conc./Clarifier Core Sample
Cone.), Settleometer Test, Depth to Blanket,
Aeration Basin DO
Control Calculations 3/week Daily
Total Sludge Mass, Aerator Sludge Mass,
Clarifier Sludge Mass, Return Sludge
Percentage, Sludge Distribution Ratio,
Clarifier Solids Loading, MCRT
Control Plots 3/week Daily
Graph 1: Settling Results, Return Sludge
Cone., MCRT, DO, Aerator Cone.
Graph 2: Total Sludge Mass (Aerator and
Clarifier), Wasted Sludge Mass
Wasting 3/week Daily
Volume, Concentration, Mass
Digester:
DO, Concentration, Temperature, pH Weekly 2/week
Waste Activated Sludge, Digested Sludge Monthly 2/month
Volatile Solids Percentage, Volatile
Solids Reduction
Chlorine Residual: 5/week Daily
*"Critical" refers to periods of transition to higher loadings and
during peak loadings and periods of stressed operation, i.e., bulky
sludge, process out of service, or major change in process control.
98
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•FIGURE 5-7
PROCESS CONTROL TESTING AT A 950 m3/d
CONTACT STABILIZATION POTW*
Week of
through
MO/DAY/YR
DAY OF WEEK
CENTRIFUGE TEST
CTC
RTC
RSC
DC
DSU
SLUDGE BLANKET TEST
DTB
RSFP
SLUDGE INVENTORY
CTSU
RTSU
CSU
TSU
SLUDGE SETTLING TEST
0 min
5 min
30 min
60 min
SLUDGE WASTING
centimeters
cubic meters
WSC
WSU
SLUDGE HAULING
loads
cubic meters
SC
SU
l*=i
mg/l
Weekly
Average
SSV
TOCO
SSC SSV
TOQO
! SSC SSV
j TQOO
SSC SSV
TDDQ
SSC SSV
TOOK)
SSC
SSV
TOGO
SSC
Weekly
Total
WEEKLY CALCULATIONS
Avg. Waste = Total WSU
Sludge Age = Avg. TSU * Avg. Waste =
BODs
TSS
Avg. Flow
INFLUENT
m3/d
EFFLUENT
*Acronyms for test parameters are; defined on the following page.
99
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FIGURE 5-7 (continued)
ACRONYMS FOR TEST PARAMETERS
CTC Contact Tank Concentration
RTC Reaeration Tank Concentration
RSC Return Sludge Concentration
DC Digester Sludge Concentration
DSU= Digester Sludge Units (mass of sludge)
DTB Depth to (Sludge) Blanket (in final clarifier)
RSFP Return Sludge Flow Percentage (of wastewater flow)
CTSU Contact Tank Sludge Units (mass of sludge)
RTSU Reaeration Tank Sludge Units (mass of sludge)
CSU Clarifier Sludge Units (mass of sludge)
TSU Total Sludge Units (mass of sludge in contact tank, reaeration
tank, and clarifier)
SSV Settled Sludge Volume (volume of settled sludge in a settleometer
jar after the indicated number of minutes)
SSC Settled Sludge' Concentration (calculated concentration of sludge
in the settled sludge volume in the settleometer jar after
the indicated number of minutes)
WSC Waste Sludge Concentration
WSU Waste Sludge Units (mass of sludge wasted)
SC Sludge Concentration
SU Sludge Units (mass of digested sludge hauled out)
100
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Larger activated sludge POTWs require that the same parameters be monitored,
but these plants are often designed 'less conservatively and therefore require
more frequent monitoring and process adjustments. For example, at a 21,000
nr/d (5.5 mgd) activated sludge plant, settling and mass control tests were
conducted once per 8-hour shift,! 7 days per week. At the contact
stabilization plant mentioned abovej sludge settling and mass control tests
were conducted only once per day, 5 days per week.
To improve process control, all [activated
monitoring for at least the following:
SI udge sett! ing
Total sludge mass control
Sludge wasting
Return sludge concentration
Aeration basin DO control
sludge plants should include
and flow control
Appendix I contains an example process control daily data sheet that has
proven to be useful in monitoringj activated sludge POTWs. However, the
specific tests and sampling frequency must be selected for each individual
POTW. !
5.7.2 Fixed Film Process Control
The performance of fixed film (trickling filter and RBC) POTWs is not as
critically affected by process control adjustments as suspended growth
facilities (1)(3). There are only!a limited number of process controls in
fixed film systems that can be optimized by a CCP, and the resulting
improvement in effluent quality is accordingly less. Two areas of fixed film
process control that can be optimized are return process stream loadings and
clarifier performance.
5.7.2.1 Reducing Return Process Stream Loadings
The CCP facilitator should strive! to reduce the organic loading returned
through the plant from anaerobic! digestion and from sludge dewatering
operations. Disposal of all digested supernatant with the digested sludge can
significantly reduce plant organic loadings. This has been implemented most
frequently in smaller POTWs where sljudge disposal is by liquid haul to nearby
farmland. Another way to achieve organic load reduction is by filtering the
digester supernatant through a dryinq bed.
!
When dewatering digester sludge with a belt press, vacuum filter, or
centrifuge, chemical dosages are often optimized to lower costs. If a low, or
relatively low, solids capture is being accomplished, increased chemical usage
to increase capture and reduce return flow through the plant should be
considered.
101
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Since land disposal of anaerobic digester supernatant or increased chemical
usage to improve dewatering capture can result in significantly higher
operating costs, a short-term (e.g., one month) trial period should be
conducted before advocating a permanent change in these controls.
5.7.2.2 Optimizing Clarifier Operation
Optimizing primary clarifier process control will decrease organic loading on
subsequent fixed film processes. Optimizing secondary clarifier process
control will improve overall organic removal for any fixed film system.
Organic removals in both primary and secondary clarifiers can be optimized by
minimizing overflow rates and controlling sludge quantities in the clarifiers.
Overflow rates can be minimized by eliminating any unnecessary flow through
the clarifiers. The most common situation that can be addressed by process
control occurs when trickling filter recycle also goes through either the
primary or secondary clarifier. At normal organic loadings associated with
domestic secondary treatment facilities, recirculation does not provide
significantly improved organic removals in fixed film processes (16). This is
especially true if the recirculation results in increased clarifier overflow
rates. If recirculation does in fact increase soluble BOD removal in the
fixed film process and the existing recirculation flow pattern is through the
primary or secondary clarifier, a facility modification to provide
recirculation only through the fixed film process may be justified (see
Section 5.4).
Keeping sludge blankets and sludge detention times low in both primary and
secondary clarifiers also tends to optimize organic removals. This can often
be accomplished by increasing sludge pumping, but must not be carried to the
extreme that removed sludge is so thin that it adversely affects sludge
treatment processes. Experience; and judgment of the CCP facilitator must be
used to achieve the best compromise.
5.7.2.3 Fixed Film Testing
Process control monitoring for fixed film facilities is generally simpler than
for suspended growth systems. It is normally comprised of process loading and
performance monitoring. The performance of the primary clarifier, fixed film
reactor, and final clarifier should be monitored on a routine basis. Fixed
film reactor performance can best be monitored by measuring soluble BOD5
removals. The soluble BOD test more directly addresses the primary function
of the biological reactor, to convert dissolved and colloidal organics to
microorganism solids. Measuring soluble 6005 across the fixed film reactor
monitors this conversion process.
An example process control summary sheet developed for a 7,500 m3/d (2.0
mgd) RBC POTW during a CCP is presented in Appendix J.
102
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5o7.3 ABF Process Control
The ABF design contains elements of both suspended growth and fixed film
facilities as does ABF process control. Sludge character (settling rates,
compaction capability, appearance, etc.) is more like that of fixed film
sludge in that wide fluctuations fare not common and are not as dependent on
process control adjustments. Consequently, overall sludge return rates and
diurnal adjustments are not as critical in the ABF system as in activated
sludge. The same is true for aerajtion basin DO. DO must be provided to meet
the demand in an ABF system without special consideration for the residual DO
and its effect on sludge character! (17). A DO residual of 2-3 mg/1 is usually
sufficient. !
I
The process control in an ABF system that is similar to an activated sludge
system and slightly more susceptible to problems is suspended growth sludge
mass control. Mass control is vory critical in an ABF system because a large
fraction of the mass, usually onej-quarter to one-half, is wasted daily. Any
error in wasting has a significant effect because the MCRT is usually only 2-4
days. j
Process control parameters monitored in two ABF POTWs
Appendix K. |
are presented in
5.8 Example CCP
An example CCP is difficult to! present because many of the performance-
limiting factors are addressed through training, interpersonnel relationships,
weekly data review, phone consultations, and other activities conducted over a
long period of time. These activities do not lend themselves readily to an
abbreviated discussion (18). As such, an overview of a CCP is presented based
on the example CPE presented in Section 3.9.
5.8.1 Addressing Performance-Limiting Factors
The most serious performance-limiting factors identified in the CPE were
process control oriented. The jmajor emphasis, therefore, of the initial
portion of the CCP was directed at improving plant operations (process
control). i
1
1. Operation (Process Control)
i
- Process control testing to monitor sludge settling, sludge mass,
sludge wasting, sludge return concentration and flow, and aeration
basin DO was initiated using the guidelines in Table 5-2.
- A process control summajry was developed and process control
calculations were implemented as shown in Appendix I.
I '
103
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-Trend graphs were initiated to monitor activated sludge mass
inventory and wasting, and activated sludge character and return
concentrations.
- On-the-job training was provided in the areas of biological
treatment fundamentals and specific process control tasks and
monitoring requirements (see Section 5.7)
- Effluent TSS was monitored closely to detect excess sludge losses
and provide justification for adequate sludge disposal capability.
Results of the improved
sequence of events:
process control activities led to the following
Operational tests showed that actual sludge production averaged
0.81 kg TSS produced/kg BOD5 removed. It was estimated that the
amount of sludge produced that was discharged as effluent SS would
decrease from 40 percent to 10 percent if adequate sludge disposal
facilities were available and used properly. New sludge wasting
requirements were 0.73 kg TSS/kg BOD5 removed. This actual value
was higher than the projected sludge production of 0.65 kg TSS/kg
BOD5 removed used in the CPE example, further aggravating the
capacity limitation of the anaerobic digester.
POTW administrators were presented with the sludge production
values and existing plant capabilities by using the following
explanation: "Your POTW treats about 350 million gallons of
wastewater.a year which results in about 5.5 million gallons of
sludge. This sludge must be disposed of properly. The existing
aerobic digester' is too small to handle the total sludge produced.
This one deficiency negates a significant portion of the pollution
control already accomplished in the rest of the plant. If you want
to bring your plant into compliance and obtain full benefit from
the rest of .the plant, additional acceptable sludge handling
capacity will have to be provided."
After considering various options, including construction, it was
decided to utilize a contract hauler to dispose of liquid sludge in
a nearby large POTW at a charge of $15.85/m3 ($0.06/gal).
The first month of contract, hauling resulted in a
sludge disposal cost of $4,500 and all involved
significant effort to reduce this cost was
was made to increase the concentration of
digester by thickening the sludge in an old
the plant site. Polymer was used to aid in
After several trial tests, a polymer was found that"significantly
improved waste sludge concentrations from the "thickening tank."
The concentration fed to the digester was increased about 250
percent by adding 20-25 Ib polymer/ton sludge solids. The net
effect was to decrease supplemental sludge disposal cost by 56
percent from the $4,500/month initially incurred.
supplemental
believed a
justified. An effort
the sludge fed to the
clarifier available on
the sludge thickening.
104
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2. Design I
- Minor piping changes and a polymer feed system had to be provided
to use the available tankage|at the plant as a "thickener." Major
design changes, such as enlarging the aerobic digester, were
avoided as a result of the CCP efforts.
i
3. Maintenance j
i
- Suggested preventive maintenance forms (similar to those in
Appendix 6) were provided the plant superintendent during the CCP.
However, the lack of a documented preventive maintenance program
had not been a significant performance-limiting problem before the
CCP was implemented and did hot become significant during the CCP.
Consequently, emphasis was placed on factors more directly related
to performance. ;
4. Administration >
i
- Administrators' familiarity frith plant needs and their ability to
make appropriate decisions regarding the plant was increased during
the CCP by explaining procesjs fundamentals at the plant, providing
oral status reports., and involving them in correction of the sludge
capacity deficiency.
5.8.2 Plant Performance
Plant performance was improved dramatically by implementation of the CCP.
results are summarized below: J
i
Eff1uent
TSS
The
Before CCP
Reported
Estimated Actual
After CCP
Actual
14
44
14
mg/1
15
75
17
The reported values prior to the CCP were collected only during periods when
the clarifiers were not bulking sludge. The estimated actual effluent quality
was projected by comparing sludge wasted prior to the CCP with sludge wasted
after the CCP was initiated. The difference in these values was projected to
have been consistently lost from rthe system in the plant effluent during
periods of bulking sludge. Actual results are based on proper testing and
represent a true picture of plant performance after the CCP was initiated.
105
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5.8.3 CCP Costs
The costs for the example CPE and CCP described in Sections 3.9 and 5.8 are
summarized below:
CPE Consultant
CCP Consultant
Test Equipment
Polymer Addition Equipment
Sludge Disposal
Polymer
Total
$ 3,500 (one-time)
12,000 (one-time)
700 (one-time)
550 (one-time)
26,500 (annual)
2,500 (annual)
$45,750 (first year)
$29,000 (ongoing annual costs)
5.8.4 Summary
This example illustrates several important points of the CCP approach and
-includes several problems and associated solutions that occur frequently
during CCP implementation. These are:
- The primary objective of a CCP is attaining adequate performance.
The second is minimizing costs within the framework of adequate
treatment.
- Some potential performance-limiting factors identified during a CPE
are later found to be incorrect or less significant when actually
eliminating problems with a CCP. This was true of the digester
design limitations in this plant.
- The degree of administrative support is sometimes difficult to
assess during a CPE but often becomes a major concern during a CCP.
This was true when the administrators were faced with supporting
dramatically increased sludge handling costs in the example CCP.
A Type 2
upgrade.
POTW was brought into compliance without a major plant
5.9 CCP Results
i
The success of conducting CCP activities can often be measured by a variety of
parameters, such as improved operator capability, cost savings, improved
maintenance, etc. However, the true success of a CCP should be documented
improved performance to the degree that the plant has achieved compliance.
Given this measure, the results of a successful CCP effort should be easily
depicted in graphical form. Results from an actual CCP are presented in
Figure 5-8. It is desirable to present CCP results in this format.
106
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107
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5.10 References
When an NTIS number is cited in a reference, that reference is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
1. Schultz, J. R., B. A. Hegg, and C. S. Zickefoose. Colorado CCP
Demonstration and Development of Areawide Compliance Strategy. Draft
Report, U.S. Environmental Protection Agency, Municipal Environmental
Research Laboratory, Cincinnati, OH, 1984.
2. Hegg, B. A., K. L. Rakness, and J. R. Schultz. Evaluation of Operation
and Maintenance Factors Limiting Municipal Wastewater Treatment Plant
Performance. EPA-600/2-79-0.34, NTIS No. PB-300331, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979.
3. Hegg, B. A., K. L. Rakness, J. R. Schultz, and L. D. Demers. Evaluation
of Operation and Maintenance Factors Limiting Municipal Wastewater
Treatment Plant Performance - Phase II. EPA-600/2-80-129, NTIS No.
PB-81-112864, U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Cincinnati, OH, 1980.
4. Gray, A. C., Jr., P. E. Paul, and H. D. Roberts. Evaluation of Operation
and Maintenance Factors Limiting Biological Wastewater Treatment Plant
Performance. EPA-600/2-79-087, NTIS No. PB-297491, U.S. Environmental
Protection Agency, Municipal Environmental Research Laboratory,
Cincinnati, OH, 1979.
5. Maintenance Management Systems for Municipal Wastewater Facilities.
EPA-430/9-74-004, NTIS No. PB-256611, U.S.. Environmental Protection
Agency, Office of Water Program Operations, Washington, DC, 1973.
6. Plant Maintenance Program. Manual of Practice OM-3, Water Pollution
Control Federation, Washington, DC, 1982.
7. Roberts, H. D., A. C. Gray, Jr., and P. E. Paul. Model Protocol for the
Comprehensive Evaluation of Publicly Owned Treatment Works Performance
and Operation. EPA-600/2-82-015, NTIS No. PB-82-180480, U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, 1981.
8. Jenkins, D., M. Sezgin, and D0 S. Parker. A Unified Theory of
Filamentous Activated Sludge Bulking. Presented at the 49th Annual
Conference, Water Pollution Control Federation, Minneapolis, MN, 1976.
9. Updated Summary of the Operational Control Procedures for the Activated
Sludge Process. EW006973, U.S. Environmental Protection -Agency,
Instructional Resources Center, Columbus, OH.
108
-------
10. Jenkins, D. and W. E. Garrison. Control of Activated Sludge by Mean Cell
Residence Time. JWPCF 40(11)11905-1919, 1968.
11. Palm J. C., D. Jenkins, and D. S. Parker. The Relationship Between
Organic Loading, Dissolved Oxygen Concentration, and Sludge Settleabil ity
in the Completely-Mixed Activated Sludge Process. Paper presented at the
51st Annual Conference, Water Pollution Control Federation, Anaheim, CA,
1978. |
i
i
12. Wooley, J. F. Oxygen Uptake1: Operational Control Tests for Wastewater
Treatment Facilities. EW008446, U.S. Environmental Protection Agency,
Instructional Resources Center, Columbus, OH, 1981.
i i
13. McKinney, R. E. Testing Aeration Equipment in Conventional Activated
Sludge Plants. JWPCF 53(l):4p-58, 1981.
14. Process Control Manual forj Aerobic Biological Wastewater Treatment
Facilities. EPA-430/9-77-006, NTIS No. PB-279474, U.S. Environmental
Protection Agency, Office of| Water Program Operations, Washington, DC,
1977. i
i
15. Gulp, G. L..and N. F. Helm. [Field Manual for Performance Evaluation and
Troubleshooting at Municipal Wastewater Treatment Facilities.
EPA-430/9-78-001, NTIS No. PB-279448, U.S. Environmental Protection
Agency, Office of Water Program Operations, Washington, DC, 1978.
16. Germain, J. E. Economic Treatment of Domestic Waste by Plastic-Medium
Trickling Filters. JWPCF 38{£):192-203, 1966.
i
i
17. Rakness, K. L., J. R. Schultz, B. A. Hegg, J. C. Cranor, and R. A.
Nisbet. Full Scale Evaluation of Activated Bio-Filter Wastewater
Treatment Process. EPA 6J)0/2-82-057, NTIS No. PB-82-227505, U.S.
Environmental Protection Agency, Municipal Environmental Research
Laboratory, Cincinnati, OH, 1J382.
18. Hegg, B. A., K. L. Rakness, and J. R. Schultz. A Demonstrated Approach
for Improving Performance and Reliability of Biological Wastewater
Treatment Plants. EPA-600/2-79-035, NTIS No. PB-300476, U.S.
Environmental Protection Algency, Municipal Environmental Research
Laboratory, Cincinnati, OH, 1J979.
109
-------
APPENDIX A
CPE CLASSIFICATION SYSTEM, CHECKLIST, AND GUIDELINES
FOR PERFORMANCE-LIMITING FACTORS
no
-------
CLASSIFICATION SYSTEM FOR PRIORITIZING PERFORMANCE-LIMITING FACTORS
Rating
Adverse Effect of Factor on Plant Performance
A
' B
Major effect!on a long-term repetitive basis
Minimum effect on a routine basis or major effect on
a periodic basis
Minor effect!
Ill
-------
CHECKLIST OF PERFORMANCE-LIMITING FACTORS
Factor 1
A. ADMINISTRATION
1. Plant Administrators
a. Policies
b. Familiarity with
Plant Needs
2. Plant Staff
a. Manpower
1) Number
2) Plant Coverage
b. Morale i
1) Motivation
2) Pay
3) Supervision
4) Working Conditions
c. Productivity
d. Personnel Turnover
3. Financial
a. Insufficient Funding
b. Unnecessary Expenditures
c. Bond Indebtedness
B. MAINTENANCE
1. General
a. Housekeeping
b. Equipment Age >
Rating
Comments
112
-------
CHECKLIST OF PERFORMANCE-LIMITING FACTORS (continued)
Factor \
i
c. Scheduling & Recording
d. Manpower !
2. Preventive
a. Lack of Program
b. References Available
c. Spare Parts Inventory
d. Workload Distribution
3. Emergency
a. Staff Expertise
b. Critical Parts
Procurement
c. Technical Guidance
C. DESIGN
1. Plant Loading
a. Organic
b. Hydraulic
c. Industrial
d. Toxic i
e. Seasonal Variation
f. Infiltration/ Inflow
g. Return Process Streams
2. Unit Design Adequacy
a. Preliminary
i
b. Primary
c. Secondary
Rating
Comments
-
113
-------
CHECKLIST OF PERFORMANCE-LIMITING FACTORS (continued)
Factor
1) Process Flexibility
2) Process
Controllability
3) "Aerator"
4) Clarifier
d. Advanced Waste Treatment
1)
2)
3)
4)
e. Disinfection
f. Sludge Wasting
Capability
g. Sludge Treatment
h. Ultimate Sludge
Disposal
3. Miscellaneous
a. Plant Location
b. Unit Process Layout
c. Lack of Unit Bypass
d. Hydraulic Profile
1) Flow Backup
2) Submerged Weirs
3) Flow Proportioning
to Units
e. Alarm Systems
f. Alternate Power Source
g. Process Automation
Rating
-
Comments
114
-------
CHECKLIST OF PERFORMANCE-LIMITING FACTORS (continued)
Factor
1) Monitoring
2) Control
h. Lack of Standby Units
for Key Equipment •
i . Laboratory Space and
Equipment
j. Process Accessibility
for Samplinq
k. Equipment Accessibility
for Maintenance i
1. Plant Inoperability Due
To Weather 1
m.
i
n.
D. OPERATION
1. Staff Qualifications
i
a. Ability :
1) Aptitude
2) Level of Education i
b. Certification
1) Level of
Certification
2) Training
c. Sewage Treatment
Understanding '
d. Insufficient Time on
the Job (Green Crew)
2. Testing
i
a. Performance Monitoring
b. Process Control Testing
3. Process Control Adjustments
Rating
Comments
115
-------
CHECKLIST OF PERFORMANCE-LIMITING FACTORS (continued)
Factor
a. Operator Application of
Concepts and Testing to
Process Control
b. Technical Guidance
4. O&M Manual
a. Adequacy
b. Use by Operators
5. Miscellaneous ;
a. Equipment Malfunction
b. Shift Staffing Adequacy ;
(Operations)
c.
d.
e.
f.
g-
h.
i.
Rating
Comments
116
-------
GUIDELINES FOR INTERPRETING PERFORMANCE-LIMITING FACTORS
Category
Explanation
A. ADMINISTRATION
1. Plant Administrators
a. Policies
b. Familiarity with
Plant Needs
2. Plant Staff
a. Manpower
1) Number
2) Plant Coverage
jDo the appropriate staff members have
the authority to make required decisions
regarding operation (e.g., adjust valve),
.maintenance (e.g., hire electrician),
iand/or administration (e.g., purchase
;cr1t1cal piece of equipment) decisions,
or do the administration policies
require a strict adherence to a "chain
of command" (which has caused critical
decisions to be delayed and in turn has
[affected plant performance and
'reliability)? Does any established
jadminl strati ve policy limit plant
[performance?
JDo the administrators have a first-hand
(knowledge of plant needs through plant
jvisits, discussions with operators, etc.?
If not, has this been a cause of poor
jplant performance and reliability
•through poor budget decisions, poor staff
morale, poor operation and maintenance
procedures, poor design decisions, etc.?
i
;Does a limited number of people employed
have a detrimental effect on plant oper-
ations (e.g., not getting the necessary
Work done)?
'Does the time period of plant operation
icause unnecessary operational adjust-
ments to be made or inefficient use of
[the number of people on the staff (e.g.,
^operators getting in each other's way)?
117
-------
b. Morale
1) Motivation
2) Pay
3) Supervision
4) Working Conditions
c. Productivity
d. Personnel Turnover
3. Financial
a. Insufficient Funding
b. Unnecessary
Expenditures
c. Bond Indebtedness
Does the plant staff want to do a good
job because they are motivated by
self-satisfaction?
Does a low payscale discourage more
highly qualified persons from applying
for operator positions or cause
operators to leave after they are
trained?
Does the working relationship of the
plant superintendent and operator or
supervisor and operator cause adverse
operator incentive?
Does a poor working environment create a
condition for more "sloppy work habits"
and lower operator morale?
Does the plant staff conduct the daily
operation and maintenance tasks in an
efficient manner? Is time used effi-
ciently?
Does a high personnel turnover rate
cause operation and/or maintenance
problems that affect process performance
or reliability?
Does the lack of available funds cause
poor salary schedules, insufficient
stock of spare parts that results in
delays 1n equipment repair, insufficient
capital outlay for improvements, etc.?
Does the manner in which available funds
are dispersed cause problems in obtaining
needed equipment, staff, etc.? Are funds
spent on lower priority items while
needed, higher priority items are
unfunded?
Does the annual bond debt payment limit
the amount of funds available for other
needed items such as equipment, staff,
etc.?
118
-------
B. MAINTENANCE
1. General
a. Housekeeping
b. Equipment Age
c. Scheduling and
Recording
d. Manpower
2. Preventive
a. Lack of Program
b. References Available
c. Spare Parts Inventory
d. Workload Distribution
Does a lack of good housekeeping
procedures (e.g., grit channel cleaning;
bar screen cleaning; unkempt, untidy, or
cluttered working environment) cause an
excessive equipment failure rate?
Does the age or outdatedness of critical
pieces of equipment cause excessive
equipment downtime and/or Inefficient
process performance and reliability (due
to unavailability of replacement parts)?
Does the absence or lack of an effective
maintenance scheduling and recording
procedure create a condition for an
erratic preventive maintenance program
that results in unnecessary equipment
failure?
Does the lack of adequate maintenance
manpower result in preventive main-
tenance functions (to prevent equipment
breakdown) not being completed or in
emergency equipment repairs being
delayed?
Does the absence or lack of an effective
maintenance program cause unnecessary
equipment failures or excessive downtime
that results in plant performance or
reliability?
Does the absence or lack of good equip-
ment reference sources cause unnecessary
equipment failure and/or downtime for
repairs (includes maintenance portion of
O&M manual)?
Does a critically low or nonexistent
spare parts Inventory cause unnecessary
long delays 1n equipment repairs that
result 1n degraded process performance?
Does uneven distribution of preventive
maintenance tasks cause neglect of other
important duties at certain times of the
month or year?
119
-------
3. Emergency
a. Staff Expertise
b. Critical Parts
Procurement
c. Technical Guidance
C. DESIGN
1. Plant Loading
a. Organic
b. Hydraulic
c. Industrial
d. Toxic
e. Seasonal Variation
f. Infiltration/Inflow
g. Return Process
Streams
2. Unit Design Adequacy
a. Preliminary
Does the plant staff have the necessary
expertise to keep the equipment
operating and to make smaller equipment
repairs when necessary?
Do delays 1n getting replacement parts
cause extended periods of equipment
downtime?
If technical guidance for repairing or
Installing equipment is necessary to
decrease equipment downtime, is it
^available and retained?
iDoes the presence of "shock" loading
^characteristics over and above what the
iplant was designed for, or over and
above what 1s thought to be tolerable,
cause degraded process performance by
one or more of the loadings (a-e) listed
below?
IDoes excessive infiltration or inflow
cause degraded process performance
because the plant cannot handle the
extra flow?
Does excessive volume and/or a highly
iorganic or toxic return process flow
stream cause adverse effects on process
performance,.equipment problems, etc.?
Do the design features of any prelim-
inary treatment unit cause upsets in
downstream equipment wear and tear that
has led to degraded plant performance?
120
-------
b. Primary
c. Secondary
1) Process
Flexibility
2) Process
Controllability
3) "Aerator"
4) Clarifier
d. Advanced Waste
Treatment
Does the shape or location of the unit
contribute to its accomplishing the task
;of primary treatment? Does the unit
ihave any design problem area within it
that has caused it to perform poorly?
jDoes the unavailability of adequate
valves, piping, etc., limit plant
performance and reliability when other
modes of operation of the existing plant
ican be utilized to improve performance
;(e.g., operate activated sludge plant in
jplug, step, or contact stabilization
imode; operate trickling filter with
constant hydraulic loading or recir-
culation ratio; discharge good secondary
i treatment effluent as opposed to a
degraded "polishing pond" effluent)?
iDo the existing process control features
Iprovide adequate adjustment and measure-
!ment over the appropriate flows (e.g.,
jreturn sludge) in the range necessary to
(optimize process performance, or 1s the
iflow difficult to adjust, variable once
adjusted, not measured and recorded, not
jeasily measurable, etc.?
jDoes the type, size, shape, or location
of the "aerator" (aeration basin,
'trickling filter, RBC, etc.) hinder its
'ability to adequately treat the sewage
and provide for stable operation? Is
I oxygen transfer capacity inadequate?
Does a deficient design cause poor
; sedimentation due to the size, type, or
|depth of the clarifier; placement or
length of the weirs; or other
'miscellaneous problems?
I
! Advanced waste treatment is any process
;of wastewater treatment that upgrades
water quality to meet specific effluent
i limits that cannot be met by conven-
|tional primary and secondary treatment
jprocesses (I.e., nitrification towers,
'chemical treatment, multimedia
,f liters). (Space 1s available in the
'Checklist to accommodate advanced
processes encountered during the CPE.)
121
-------
e. Disinfection
f. Sludge Wasting
Capability
g. Sludge Treatment
h. Ultimate Sludge
Disposal
3. Miscellaneous
a. Plant Location
b. Unit Process Layout
Does the shape or location of the unit
contribute to its accomplishing disin-
fection of the wastewater (i.e., proper
mixing, detention time, feed rates,
feeding rates proportional to flow,
etc.)?
Does the plant have sludge wasting facil-
ities? If so, can desired volume of
sludge be wasted? Can sludge wasting be
adequately controlled? Can sludge
wasted be sampled without extreme
difficulty?
Does the type or size of the sludge
treatment process hinder sludge
stabilization (once sludge has been
removed from the wastewater treatment
system), thereby causing process
operation problems (e.g., odors, limited
sludge wasting, etc.)?
Is the ultimate sludge disposal program,
including facilities and disposal area,
of sufficient size and type to adequately
handle the sludge production from the
plant? Are there any specific areas
that limit ultimate sludge disposal such
as seasonal weather variations or crop
harvesting?
The design "miscellaneous" category
covers areas of design inadequacy not
specified in the previous design
categories. (Space is available in the
Checklist to accommodate additional
items not listed.)
Does a poor plant location or poor roads
leading into the plant cause it to be
inaccessible during certain periods of
the year (e.g., winter) for chemical or
equipment delivery or for routine
operation?
Does the arrangement of the unit pro-
cesses cause inefficient utilization of
operator's time for checking various
processes, collecting samples, making
adjustments, etc.?
122
-------
r
c. Lack of Unit Bypass
d. Hydraulic Profile
1) Flow Backup
2) Submerged Weirs
3) Flow Proportioning
to Units
e. Alarm Systems
f. Alternate Power
Source
g. Process Automation
1) Monitoring
i Does the lack of a unit bypass 1) cause
I plant upset and long-term poor treatment
iwhen a short-term bypass could have
jminimized pollutional load to the
i receiving waters; 2) cause necessary
j preventive or emergency maintenance
I items to be cancelled or delayed; or 3)
I cause more than one unit to be out of
i service when maintaining only one unit?
Does an insufficient hydraulic profile
cause ground flooding or flooding of
upstream units, except clarifiers? Does
periodic release of backed-up flow cause
hydraulic surge?
Does an insufficient hydraulic profile
cause flooding of clarifiers and sub-
merged clarifier weirs?
Does inadequate flow proportioning or
flow splitting to duplicate units cause
problems or partial unit overloads that
degrade effluent quality or hinder
achievement of optimum process
performance?
Does the absence or inadequacy of a good
alarm system for critical pieces of
equipment cause unnecessary equipment
failure or in any way cause degraded
process performance?
Does the absence of an alternate power
source cause problems in plant operation
leading to degraded plant performance?
i Does the lack of needed automatic
i monitoring devices (DO meter, pH meter,
etc.) cause excessive operator time to
i watch for slug loads or process upset to
occur because of slug loads? Does the
i breakdown or improper workings of
, automated process monitoring features
i cause disruption of automated control
features and subsequent degradation of
process performance?
123
-------
2) Control
h. Lack of Standby
Units for Key
Equipment
1. Laboratory Space
and Equipment
j. Process
Accessibility
for Sampling
k. Equipment
Accessibility
for Maintenance
1. Plant InoperabiHty
Due To Weather
D. OPERATION
1. Staff Qualifications
a. Ability
1) Aptitude
Does the lack of a needed automatic
control device (time clock, flow
activated controls, etc.) cause
excessive operator time, to make process
control changes or necessary changes to
be cancelled or delayed? Does the
breakdown or the improper workings of
automatic control features cause
degradation of process performance?
Does the lack of standby units for key
equipment cause degraded process per-
formance during breakdown or necessary
preventive maintenance items to be
cancelled or delayed?
Does the absence of an adequately
equipped laboratory limit plant
performance by the lack of operational
testing and performance monitoring?
Does the inaccessibility of various
process flow streams (e.g., recycle
streams) for sampling prevent needed
information from being obtained?
Does the inaccessibility of various
pieces of equipment cause extensive
downtime or difficulty in making needed
repairs or adjustments?
Are certain units in the plant extremely
vulnerable to weather changes (e.g.,
cold temperatures) and, as such, do not
operate at all or do not operate as
efficiently as necessary to achieve the
required performance?
Does the lack of capacity for learning
or understanding new ideas by critical
staff members cause poor O&M decisions
leading to poor plant performance or
reliability?
124
-------
2) Level of
Education
b. Certification
1) Level of
Certification
2) Training
c. Sewage Treatment
Understanding
d. Insufficient Time
on Job (Green Crew)
2. Testing
a. Performance
Monitoring
b. Process Control
Testing
3. Process Control
Adjustments
a. Operator Application
of Concepts and
Testing to Process
Control
Does a low level of education cause poor
O&M decisions? Does a high level of
education or a lack of process
understanding cause needed training to
be overlooked?
! Does the lack of adequately certified
i operators cause poor process control
| decisions?
i
i
, Does the operator's inattendance at
; available training programs cause poor
i process control decisions?
Is the operator's lack of understanding
of sewage treatment, in general, a
factor in poor operational decisions and
poor plant performance or reliability?
Does the short time on the job cause
improper process control adjustments to
be made (e.g., opening or closing a
wrong valve, turning on or off a wrong
pump, etc.)?
Are the required monitoring tests being
completed in compliance with the
discharge permit and are they truly
representative of plant performance?
Does the absence or wrong type of pro-
cess control testing cause improper
operational control decisions to be made?
Is the operator deficient in the applica-
tion of his/her knowledge of sewage
treatment and interpretation of process
control testing to process control
adjustments?
125
-------
b. Technical Guidance
4. O&M Manual
a. Adequacy
b. Use by the Operator
5. Miscellaneous
a. Equipment
Malfunction
b. Shift Staffing
Adequacy (Operations)
Does false operational information
'received from a technical consultant
cause improper operational decisions to
;be continued? Does a technical person
(e.g., design engineer, equipment
representative, State trainer or
inspector) fail to address obvious
operational deficiencies while being in
:a position to correct the problem?
Does a poor O&M manual used by the
operator result in poor or improper
operational decisions?
Does a good O&M manual not used by the
operator cause poor process control and
poor treatment that could have been
avoided?
The operation "miscellaneous" category
deals with any pertinent operational
information not covered in the previous
operational sections. (Space is
available in the Checklist to accom-
modate additional items not listed.)
Does malfunctioning equipment cause de-
teriorated process performance?
Does the improper distribution of ade-
quate manpower prevent process controls
from being made or made at inappropriate
times, resulting in poor plant per-
formance?
126
-------
APPENDIX B
CPE SUMMARY SHEET FOR RANKING PERFORMANCE-LIMITING FACTORS
127
-------
CPE SUMMARY SHEET FOR RANKING PERFORMANCE-LIMITING FACTORS
Plant Name/Location
CPE Performed by
Date
Plant Type:
Design Flow:
Actual Flow:
Year Plant Built:
Year of Most Recent Upgrade:
Plant Performance Summary:
RANKING TABLE
Ranking
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Performance-Limiting Factors
I
1
i
!
t
128
-------
CPE SUMMARY SHEET TERMS
PLANT TYPE
DESIGN FLOW
ACTUAL FLOW
YEAR PLANT BUILT
YEAR OF MOST RECENT UPGRADE
PLANT PERFORMANCE SUMMARY
RANKING TABLE
RANKING
PERFORMANCE-LIMITING FACTORS
Brief but specific description of type
of plant (e.g., two-stage trickling
filter with anaerobic digester or
extended aeration activated sludge with
polishing pond and without sludge
digestion).
Plant design flow rate as of most recent
upgrade.
Wastewater flow rate for current
operating condition (e.g., for past
I year). Also, significant seasonal
variation in flows should be noted.
Year initial
operation.
units were put into
Year last additional major units were
put into operation (e.g., digester,
chlorine contact chamber, etc.).
Brief description of plant performance
as related to present and anticipated
treatment requirements.
In descending order, a list of the major
causes of decreased plant performance
and reliability.
Causes of decreased plant performance
and reliability, with the most critical
ones listed first.
Categories listed
(Appendix A).
the Checklist
129
-------
APPENDIX C
EXAMPLE CPE REPORT
130
-------
RESULTS OF A CPE |AT THE SPRINGFIELD, KS, POTW
FACILITY BACKGROUND j
i
The Springfield POTW is a rotating biological contactor (RBC) type of
treatment plant designed for an average daily wastewater flow of 7,600
mVd (2.0 mgd). The plant j was originally completed as a primary
treatment plant in 1965 and upgraded for secondary treatment in 1980. The
plant serves the City of Springfield with an estimated population of
9,000. A railcar washing operation is thought to be the source of the
only significant industrial waste, but sampling has not confirmed this.
i i
Plant records indicated that wa;stewater flows had been averaging close to
design flow; however, flow calibration during the CPE indicated that flow
was actually about 4,500 m3/d (1.2 mgd), or only 60 percent of design
flow. Current organic loading iwas estimated to also be about 60 percent
of design. j
The Springfield plant consists of the following unit processes:
- Vortex grit chamber
- Mechanical bar screen
- 23-cm (9-in) Parshall flume
- Lift station j
- One 18-m (60-ft) diameter primary clarifier
- Four-stage RBCs (12 shafts)
- Two 6 x 33 m (20 x 110 ft) secondary clarifiers
- Two-cell chlorine contact chamber
- Two 11-m (35-ft) diameter! anaerobic digesters (Note; During
the CPE, the second-stage digester was not in service.)
- 2,800 m2 (30,000 sq ft) drying beds
The Springfield plant is required to meet standard secondary treatment
effluent requirements with 20,!000/40,000 fecal coliform limits. NPDES
monitoring data indicate performance of the plant has generally been
within standards;, but individual analyses indicate erratic performance.
During the CPE, sludge was bulking from both the primary and secondary
clarifiers.
MAJOR UNIT PROCESS EVALUATION i
Major plant processes were evaluated for their capacity to adequately
treat current loadings and the (general applicability of a CCP to improve
performance. Current hydraulic loadings were estimated with flow data
measured during the CPE. Organic loading on the RBC as measured by
•soluble BODs was estimated usftng 30 percent total BOD removal in the
primary clarifier and 50 percent of the primary effluent total BOD as
soluble BOD. !
131
-------
The ability to handle current loads was assessed using a numerical point
system, which resulted in the plant's being categorized Type 1, 2, or 3 as
described below: ;
i
- Type 1. Loadings are conservatively low, but performance problems
could be alleviated with training and/or minor facility
modifications.
- Type 2. Loadings are not conservatively low but also not so high
as to preclude improved performance from existing facilities.
- Type 3. Loadings are so high in relation to capacity that it is
not considered reasonably possible to consistently meet effluent
requirements without a major facility upgrade.
!
The results of the major process evaluation are shown in Table C-l.
TABLE C-l
SPRINGFIELD, KS, POTW MAJOR UNIT PROCESS EVALUATION
Points Assessed Type
Aerator
Secondary Clar1f1er
Sludge Handling Capability
Total of Major Processes
26
18
_5
49
1
1
2
1
As shown 1n Table C-l, the aerator, secondary clarifier, and the total of
major processes all received sufficient points to receive a Type 1
classification. Sludge handling capability received a Type 2
classification. The major limitation regarding sludge handling was
ultimate sludge disposal capability in winter.
The evaluation of major unit processes indicates that sludge handling will
likely require supplemental capacity, but the other major processes have
adequate capacity. In general,! the CCP approach appears applicable if
additional ultimate sludge disposal capacity can be provided.
The potential capacity of major unit processes in the Springfield plant is
Illustrated 1n Table C-2. The horizontal bar graph associated with each
major process depicts the potential capacity of that process.
Primary clarlflers, secondary clarlflers, and anaerobic digesters are all
believed to have capacities a little greater than design capacities. The
chlorine contact basin has capacity sufficient for design flows; however,
132
-------
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1t appears that the RBCs may not have quite enough capacity to adequately
treat design loadings. RBC capacity should be evaluated as flows approach
design.
The ultimate sludge disposal capability as represented by the sludge
drying beds appears to be the only major process that will be limiting at
current flows. The limitation 1n ultimate sludge disposal 1s during the
winter when the drying beds freeze and do not dry.
PERFORMANCE-LIMITING FACTORS :
During the CPE, the plant's performance-limiting factors In the areas of
design, administration, operation, and maintenance were Identified. These
factors are listed below and the most significant ones briefly discussed.
1. Sewage Treatment Understanding (Operation). A lack of
understanding of biological treatment process fundamentals and
operational requirements and goals significantly limit plant
performance. This limitation could be addressed with onsite
training over a .period of months or by periodic attendance at
seminars, schools, etc., over a period of many years.
2. Process Control Testing (Operation). An almost complete lack of
process control testing existed prior to the CPE. Base-level
testing was initiated during the CPE. Onsite training is
required to optimize process control testing and to teach the
operational staff to properly apply the test results to process
controls.
3. Return Process Streams (Design). Secondary sludge being returned
to the primary clarifier was causing primary clarifier "bulking,,"
Anaerobic digester supernatant return will also adversely impact
plant performance. The capability to minimize the adverse impact
of return process streams can be acquired through long-term,
onsite training.
4. Equipment Malfunction (Maintenance). The waste gas burner, the
digester gas mixing system, the heat exchanger temperature
control system, and the primary sludge pump were all out of
service during the CPE. A significant safety problem, as well as
operational problems, had developed. Administrative and operator
training are needed.
5. Improper Training Guidance (Operation). Current operation and
equipment problems have been existing for years despite formal
grant-supported startup of the expanded facilities and periodic
State inspections.
6. Administrative Familiarity With Plant Needs (Administration).
Through past poor communication and improper operation, the plant
administrators have been misled regarding plant needs. Increased
134
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9.
familiarity in the areas of treatment fundamentals, operation and
maintenance requirements, funding needs, and safety concerns is
needed. i
I
Process Controllability (Design). Existing flow-splitting
capability to the RBCs is inadequate. Correction of this
deficiency will likely'require minor design modifications.
i
Ultimate Sludge Disposal (Design). Existing drying beds are
inadequate for needed year-round sludge disposal. Additional
beds may be a long-term solution. Liquid sludge haul to farmland
may be a workable interim solution. Documentation for the need
and administrative trajning are necessary.
Performance Monitoring (Operation). Improved sampling to
represent actual performance and flow discharge is needed.
Onsite training coupled with administrative support to eliminate
problems are required.:
10. Insufficient
Funding
(Administration).
Administrative
unfamiliarity with plant needs, inadequate technical guidance,
and improper past operation and maintenance have all led to
insufficient funding, jAdministrative training is needed.
• i
Other factors that contribute^! to limited performance, but in a less
significant way, include: an !inadequate spare parts inventory, limited
staff expertise in handling emergency maintenance, a lack of an alternate
power source, a marginally equipped laboratory, poor accessibility for
maintenance in part .of the pl|ant, a lack of needed sample taps, and a
relatively "green" staff. I
PROJECTED IMPACT OF A CCP
Improved effluent quality, toj within NPDES permit limits, and overall
operational stability, safety, I and administrative ability to protect the
existing capital investment and provide for future wastewater treatment
needs, are expected if a CCP is|implemented.
CCP COSTS
Costs associated with a
facilitator and for
12-monlth CCP at Springfield would be for the CCP
equipment repairs, minor modifications, and
135
-------
supplemental winter sludge disposal
at Springfield are listed below:
estimated costs for conducting a CCP
CCP Facilitator
City Costs
Minor Modifications
Lab Equipment
Supplemental Sludge Disposal
Total CCP Costs
$ 9,500 (one-time)
1,000 (one-time)
400 (one-time)
18.000 (annual)
$19,400
$28.900
-------
APPENDIX 0
DATA COLLECTION FORMS USED IN CONDUCTING CPEs
Form
D-l
D-2
0-3
D-4
D-5
D-6
: Title
i
general POTW Information
Administration Data
Design Data
Operations Data
Maintenance Data
Performance Data
137
-------
FORM D-1
GENERAL POTW INFORMATION
A, NAME AND LOCATION:
Name of Facility
Type of Facility
Owner
Administrative Office:
Mailing Address
Primary Contact
Title
Telephone No.
Treatment Plant:
Mailing Address
Primary Contact
Title
Telephone No.
Directions to Plant
B. RECEIVING STREAM AND CLASSIFICATION:
Receiving Water
Tributary to
Major River Basin
Comments:
138
-------
FORM D-l (continued)
GENERAL IPOTW INFORMATION
C. PERMIT INFORMATION:
Plant Classification Assigned |by State.
Discharge Permit Requirements,from Permit Number
Date Permit Issued i
Date Permit Expires |
Effluent Limits and Monitoring Requirements:
Parameter
Flow, mgd
BODs, mg/1
TSS, mg/1
Fecal Coliform,
no./100 ml
Chlorine Residual,
mg/1
pH, units
Ammonia, mg/T
Oil & Grease, mg/1
Others
Maximum
Monthly
Average
Maximum
Weekly
Average
Monitoring Sample
Frequency Type
Required Required
Compliance Schedule:
139
-------
FORM D-l (continued)
GENERAL POTW INFORMATION
D. MAJOR PROCESS TYPE
E. DESIGN FLOW:
Present Design Flow
mgd x 3,785 =
m3/d
F. UPGRADING AND/OR EXPANSION HISTORY (original construction, date
completed, plant upgrade, date completed):
G. PROPOSED UPGRADES:
H. SERVICE AREA:
Number of Taps
General Description (residential, approximate commercial and/or
industrial contribution, etc.):
140
-------
FORM D-1 (continued)
GENERAL POTW INFORMATION
I. PLANT FLOW DIAGRAM:
141
-------
FORM 0-2
ADMINISTRATION DATA
A. ORGANIZATION:
Governing Body !
Scheduled Meeting Dates and Times
Authority and Responsibility:
Members' Names (notes on leadership, funding preferences, knowledge
of plant needs, etc.)-
Chain of Command (from governing body through major in-plant
decisionmakers):
142
-------
FORM D-2 (continued)
ADMINISTRATION DATA
B. PLANT PERSONNEL:
Personnel Classification
No. Title
Certification Pay Scale
C. PLANT COVERAGE:
Weekdays
Weekends & Holidays
Fraction of Time Spent
with Mastewater Treatment
143
-------
FORM D-2 (continued)
ADMINISTRATION DATA
D. PLANT BUDGET (Attach copy of actual budget if available)
(Budget Year )
144
-------
FORM D-2 (continued)
ADMINISTRATION DATA
E. BOND RETIREMENT:
Bond Type . Year Issued Duration
Interest
Rate
Project Financed
Comments:
145
-------
FORM D-2 (continued)
ADMINISTRATION DATA
F. REVENUE:
Type of Tap
Tap Fee
User Fee
Other Sources of Revenue:
Comments:
-------
FORM D-2 (continued)
ADMINISTRATION DATA
G. DISCUSSION OF EXPENDITURES:!
i
Budget for:
Salaries (incl. fringes)
Utilities j . •
I
Training !
Other ;
Operations Subtbtal
Capital Outlay ;
(incl. bond debt ;
retirement and
capital replacement)
Total ;
Dollar Amount
Percent of Total
100
Operational Cost Per Thousand Gallons (Operations Subtotal $ * Yearly Flow)
$.
Mgal/yr * 10 h
tf/1,000 gal x 0.264
Approximate Annual Cost Per Tap (Total $ -5- No. of Taps)
i
I
$ * taps = $ /tap
Comments:
147
-------
FORM D-2 (continued)
ADMINISTRATION DATA
H. POLICY, SUPPORT, AND ATTITUDE:
Owner Responsibility:
- Attitude toward staff? f
- Attitude toward regulatory agency?
- Self-sustaining facility attitude?
- Attitude toward consultants?
- Future plans? ;
- Policies?
Performance Goal: !
- Is plant 1n compliance? '
o If yes, what's making 1t that way?
o If no, why not? ;
- Is regulatory pressure felt for performance?
- What are performance requirements?
Administrative Support:
- Budget
o Within range of other plants?
o Covers capital Improvements?
o "Drained" to general fund?
o Unnecessary expenditures?
o Sufficient?
148
-------
FORM 0-2 (continued)
ADMINISTRATION"DATA
Personnel
o Within range of othei" plants?
o Allows adequate time?
o Motivation, pay, supervision, working conditions?
o Productivity? !
o Turnover? r ai
Involvement |
o Visits to treatment plant?
o Awareness of facility performance?
o Request status reports (performance and cost-related)?
o Familiarity with plajit needs?
Attitude Assessment:
Excellent:
Normal:
Poor:
Reliability provides adequate treatment at lowest
reasonable cost.
Provide as [good a treatment as possible with the
money available.
Spend as little as possible with no correlation made
to achieving plant performance.
149
-------
I. ENERGY CONSUMPTION:
FORM D-2 (continued)
ADMINISTRATION DATA
Electricity
Source of Information
Base Cost
£/kWh (Attach rate schedule If available)
Days in Energy Energy
Month/ Billing Usage Demand ECA* Base Total Flow
Year Period (kWh) Cost Cost Cost Cost (Hgal)
Total
Total Flow (Mgal)
kWh/d
kWh/1,000 gal x 0.264 =
$/d
rf/1,000 gal x 0.264 = _
kWh/m3
*ECA » Energy Cost Adjustment, which is the pass-through cost allowed to
public service companies for increased fuel cost to generate electricity.
150
-------
FORM;0-2 (continued)
I
ADMINISTRATION DATA
0. ENERGY CONSUMPTION:
Natural Gas
Source of Information
Unit Cost
(Attach rate schedule 1f available)
Month/Year
Total
Average
Days 1n Billing!
Period I
Usage
(cu ft)
Cost
Miscellaneous (Fuel 011. Digester Gas, etc.)
151
-------
FORM D-3
DESIGN DATA
A. INFLUENT CHARACTERISTICS:
Average Daily Flow:
Maximum Monthly Flow:
Maximum Hourly Flow:
Average Dally BOD5:
Average Dally TSS:
Infiltration/Inflow:
Seasonal Variations:
Major Industrial Wastes:
Collection System:
Deslqn
Current
Desiqn
Current
Deslqn
Current
i
Deslqn
Current
i
Deslqn
Current
mqd x 3.785 =
mqd x 3.785 =
mqd x 3.785 =
mqd x 3.785 =
mqd x 3.785 =
mqd x 3.785 =
Ib x 0.454 =
Ib X 0.454 =
Ib x 0.454 =
Ib x 0.454 =
m3/d
m37d
m3/d
m3/d
m3/d
m3/d
kg
kq
kq
kq
Comments:
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES:
Flow Measurement
(Form for eachjflow measuring device)
Flow Stream Measured
Control Section:
Type and Size
Location
Comments (operational problems, maintenance problems, unique
features, preventive maintenance procedures, etc.):
Recorder:
Name
Model
Range ',
bration Frequency
of Last Calibration
tion
i
lizer i
Comments (operation and design problems, unique features, etc.)
Accuracy Check During CPE:
Method of Check:
Results:
153
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES:
Pumping
(Complete as many forms as necessary)
Flow Stream
Pumped Type
No. of
Pumps Name
Model HP Capacity Head
Comments (flow control, suitability of installed equipment, results of
capacity check during CPE, etc.):
Comments:
Comments:
154
-------
8. UNIT PROCESSES:
FORM j)-3 (continued)
DESIGN DATA
Pre 11 mil nary Treatment
Mechanical Bar Screen:
Name
Model '
Bar Screen Width
Bar Spacing
Horsepower
Inch x 2.54
Within Building? _!
Description of Operation:;
inch, O.C. x 2.54
Heated?
cm
cm, O.C.
Hand-Cleaned Bar Screen:
Bar Screen Width
Bar Spacing
Cleaning Frequency
Within Building?
Screenings Volume:
Normal
Peak
Screening Disposal:
Comments:
inch x 2.54 =
inch, O.C. x 2.54 =
Heated?
cu yd/d x 0.75
cu yd/d x 0.75
cm
cm, O.C.
m3/d
m3/d
155
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES:
Preliminary Treatment
Comminutor:
Name
Model
Within Building?.
Maintenance:
Horsepower,
Heated?
Comments:
Grit Removal:
Description of Unit:
Grit Volume:
Normal _
Peak
cu yd/d x 0.75
cu yd/d x 0.75
_m3/d
m3/d
Disposal of Grit:
Comments:
56
-------
B. UNIT PROCESSES:
FORM D-3 (continued)
DESIGN DATA
Primary Treatment
Primary Clarifier(s):
Number
Water Depth (Shallowest)
Water Depth (Deepest) ,
Weir Location
Weir Length ;
Total Surface Area
Total Volume
Flow (Design)
(Operating)
Weir Overflow Rate
(Design)
(Operating)
Surface Settling Rate
(Design)
(Operating)
Surface Dimensions
ft x 0.3 =
ft x 0.3 =
ft x 0.3 =
sq ft x 0.093 =
cu ft x 0.028 =
_ mgd x 3,785 =
_ mgd x 3,785 =
gpd/ft x 0.012 =
gpd/ft x 0.012 =
_gpd/sq ft x 0.04 =
gpd/sq ft x 0.04 =
Hydraulic Detention Time (Design)
Collector Mechanism Name
Model , Horsepower
Scum Collection and Treatment:
Scum Volume: \
Normal: :
Peak: '
hr (Operating)
cu ft/d x 0.028 =
cu ft/d x 0.028 =
m
m
m
m
m
m3/d
m3/d
m /m/d
m3/m/d
m3/m2/d
m3/m2/d
hr
m3/d
m3/d
157
-------
B. UNIT PROCESSES
FORM D-3 (continued)
DESIGN DATA
Secondary Treatment
Aeration Bas1n(s):
No. of Basins
Surface Dimensions
Water Death
Total Volume
Flow (Design)
(Operating)
Sewage Detention Time
BODgLoading
(Design)
(Operating)
Covered?
Type of Aeration
Name
ft x 0.3 =
cu ft x 0.028 =
mgd x 3.785 =
mqd x 3.785 =
(Design
(Operating)
lb/d/1,000 cu ft x 0.16 =
lb/d/1.000 cu ft x 0.16 =
No. of Aerators
Model Horsepower
m
m3
m3/d
m3/d
hr
hr
kg/m3/d
kg/m3/d
Modes of Operation (Current and Other Options):
Types of Diffusers
Model
Manufacturer
_D.epth
ft x 0.3 =
No. of Blowers
Model
Name
Air Capacity (cfm)
Horsepower
Location
Oxygen Transfer Capacity
Ib/d x 0.454 =
m
kg/d
Comments:
158
-------
B. UNIT PROCESSES:
FORM D-3 (continued)
DESIGN DATA
Secondary Treatment
Contact Basin:
Surface Dimension
Water Depth
Volume
Flow (Design)
(Operating)
Sewage Detention Time (Design)
Covered? i
ft x 0.3 =
_cu ft x 0.028 =
_ mgd x 3,785 =
_ mgd x 3,785 =
_min (Operating)
m
3
m
m3/d
m3/d
min
Comments:
Reaeration Basin:
Surface Dimensions
Water Depth
Volume
ft x 0.3 =
m
cu ft x 0.028 =
Hydraulic Detention Time: at 100% Return
(Design) _j hr (Operating)
Flexibility to Operate a$ Conventional or Step Feed:
m
hr
Covered?
Comments:
159
-------
B. UNIT PROCESSES:
FORM D-3 (continued)
DESIGN DATA
Secondary Treatment
Oxygen Transfer:
Type of Aeration
Model
Capacity
No. of Blowers
Horsepower
Location
Type of D1ffusers
Model
No. of Aerators
Horsepower
cfm x 0.028 =
Ib/d x 0.454 =
Name
Capacity
Depth
Model
Name
cfm x 0.028 =
Manufacturer
m /min
_ kg/d
3
m /m1n
ft x 0.3 =
Comments:
160
-------
B. UNIT PROCESSES:
, FORM D-3
DESIGN'DATA
Secondary Treatment
Trickling Filter:
No. of Filters
Covered?
Surface Dimensions
Media Type
Specific Surface
Media Depth -
Surface Area .
Media Volume
sq ft/cu ft x 32.8 =_
_ ft x 0.3 =
ft x 0.093 =
Flow (Design)
(Operating)
Organic Loading
(Design)
cu ft x 0.028 =
_ mgd x 3,785 =
_ mgd x 3,785 =
(Operating).
Hydraulic Loading
(Design)
(Operating).
lb/d/1,000 cu ft x 0.016 =
lb/d/1,000 cu ft x 0.016 =
gpd/sq ft x 0.04 =
gpd/sq ft x 0.04 =
Recirculation (description, ranges, current operation):
Mode of Operation:.
Comments:
m2/m3
m
m
m3/d
m3/d
_kg/m3/d
_kg/m3/d
m3/m2/d
nr/nr/d
161
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES:
Secondary Treatment
Rotating Biological Contactor (RBC):
No. of Shafts Length of Shafts
ft x 0.3 =
m
No. of Cells Cell
Volume
cu ft x 0.028 =
m3
Name
Disc Diameter
ft x 0.
3 =
m
RPM
Peripheral Velocity
Total Surface Area
Percent Submergence
Flow (Design)
(Operating)
Hydraulic Loading:
(Design)
(Operating)
Temperature (Design)
Organic Loading (Design)
ft/sec
sa ft
mad
mad
gpd/sq ft
gpd/sq ft
°C
x 0.3 =
x 0.093 =
x 3.785 =
x 3,785 =
x 0.04 =
x 0.04 =
(Operating)
Ib SBOD/d/1,000
=
m/sec
m2
m3/d
m3/d
m3/m2/d
3.2..
m /m /d
°C
sq ft x 4.88
g SBOD/m2/d
(Operating).
Total Detention Time (Design)
Covered? Heated?
Ib SBOD/d/1,000 sq ft x 4.88
= g SBOD/m2/d
. hr (Operating) hr
Flexibility to Distribute Load to Stages;
Comments:
162
-------
B. UNIT PROCESSES
FORM| D-3 (continued)
'DESIGN DATA
Secondary Treatment
Activated Biofilter (ABF)
Biocell: Model
No. of Cells
Surface Dimensions
Total Surface Area
Media Depth
sq ft x 0.093
ft x 0.3 =
Total Media Volume
Media Type
cu ft x 0,028 =
m
m
m
Specific Surface
_sq ft/cu ft x 32.8
m2/m3
Loading
(Design)
_ lb/1,000 cu ft/d x 0.016 = _
j_ lb/1,000 cu ft/d x 0.016 = _
Recirculation Tank: Dimensions (LxWxD) _ ft =
(Operating)
Volume
cu ft x 0.028 =
Aeration Basin: Surface;Dimensions
Total Surface Area !
Depth •
Volume
sq ft x 0.093 =
ft x 0.3 =
!cu ft x 0.028 =
Hydraulic Detention Time (Design).
_min (Operating)
_kg/m3/d
_kg/m3/d
m
m
m
m
m
Comments:
163
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES
Secondary Treatment
Secondary Clarlfier(s):
No. of Clarifiers
Dimension(s)
Water Depth (Shallowest)
(Deepest)
Weir Location
ft x 0.3 =
ft x 0.3 =
Percent of Clarification Developed by Launders
Weir Length ' ft x 0.3
(Operating)
god/sa ft x 0.04
Hydraulic Detention Time
(Design)
hr
(Operating)
m
m
m
Surface Area
Vol ume
Flow (Design)
(Operating)
Weir Overflow Rate
(Design)
(Operating)
Surface Settling Rate
(Design)
! so: ft x 0.093 =
i cu ft x 0.028 =
mgd x 3.785
mgd x 3.785
i
1 god/ft x 0.012 =
god/ft x 0.012 =
god/so ft x 0,04 =
m2
m3
m3/d
m3/d
m3/m/d
m /m/d
m3/m2/d
nr/nT/d
hr
Collector Mechanism Name
Model
Horsepower
Return Sludge Collector Mechanism Type
Scum Collection and Removal:
Scum Volume: (Normal) ! gpd x 0.028 =
(Peak) ! gpd x 0.028 =
Comments:
_m3/d
m3/d
164
-------
FORM D-3 (continued)
i
DESIGN DATA
B. UNIT PROCESSES:
Return Sludge
Description of Sludge Movement (i.e., scrap to clarifier hopper, pump
to aeration basin inlet channel):
Controllable Capacity Range:
(Low)
(High)
mgd x 3,785
mgd x 3,785
_m3/d
m3/d
Method of Control:
Sampling Location:
Comments:
Waste Sludge
Description of Waste Procedure (i.e., variable-speed pump wastes
from separate clarifier hopper, continuous or by timeclock):
Method of Waste Volume Measurement:
Sampling Location: i
Comments: !
165
-------
B. UNIT PROCESSES:
FORM D-3 (continued)
DESIGN DATA
Disinfection
Contact Basln(s):
No. of Separate Basins
Surface Dlmenslon(s) _
Channel Length-to-Width Ratio
Water Depth
Total Volume
Detention Time (Design)_
Drain Capability:
Scum Removal Capability:
Comments:
ft x 0.3 =
No. of Bends
cu ft x 0.028
min (Operating)
m
_m3
min
Chlorinator(s):
Name
Capacity
Type of Injection
Feed Rate (Operating).
Dosage (Operating)
Chlorine Diffusion
Comments:
No. of Chlorinators
'L lb/d x 0.454
kg/d
Flow Proportioned?.
Ib/d x 0.454 =
kg/d
_mg/l
166
-------
Form D-3 (continued)
!DESIGN DATA
B. UNIT PROCESSES:
Aerobic Digestion;
No. of Basins
Water Depth _
Volume
Sludge Handling
Surface Dimension(s)
ft x 0.3 = L_
m
Covered?
Type of Aeration
cu ft x 0.028 =
Heated?
Supernatant Capability
No. of Aerators
Model
Name
Horsepower
Type of Diffusers
Model .
. Depth
Manufacturer
ft x 0.3
m
No. of Blowers
Model
Name
Air Capacity •
Oxygen Transfer Capacity
Location j_
Horsepower
cfm x 0.47
Ib/d x 0.454 =
_kg/d
Mode of Operation:
Comments:
167
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES:
Sludge Handling
Anaerobic Digestion:
No. of Digesters
Sidewall Depth
Center Depth
Total Volume
Floating Cover?
Flow (Design)
(Operating)
Detention Time (Design)
Diameter ft x 0.3 =
ft x 0.3 =
ft x 0.3 =
cu ft x 0.028 =
i
mgd x 3.785 =
mgd x 3.785 =
days (Operating)
m
m
m
m3
m3/d
m3/d
days
Heating:
Mixing:
Sampling Ports:
Mode of Operation:
Comments:
168
-------
B. UNIT PROCESSES:
Sludge Drying Beds:
No. of Beds
Covered?
FORM D-3 (continued)
DESIGN INFORMATION
Sludge Handling
Size of Beds
Subnatant Drain To
Dewatered Sludge Removal:
i
Mode of Operation: ,
Comments: i
Other Dewatering Unlt(s):
No. of Units Type/of Unit(s) Manufacturer.
Model
Horsepower
Hr/Wk
Loading Rate
Polymer Used
Ib/dry ton
Cake Solids k Sol Ids
I
i
Comments: !
Ib/hr x 0.454 =
_kg/h
x 0.5 =
_g/kg
169
-------
FORM D-3 (continued)
DESIGN DATA
B. UNIT PROCESSES:
Item
Summary of Plant Horsepower
HP Usage (%)
Weighted HP
170
-------
FORM 0-3 (continued)
DESIGN DATA
C. OTHER DESIGN INFORMATION: ;
Standby Power (description of unit; automatic activation? capacity
for which processes? frequendy of use, etc.):
Alarm Systems (description of system, units covered, etc.):
Miscellaneous:
171
-------
FORM D-3 (continued)
DESIGN DATA
D. PLANT AUTOMATION (description of any plant automation not covered
under more specific topics):
E. LABORATORY CAPABILITY:
Location
Floor Dimensions
ft x 0.3 =
m Hot Water?
Desk?
Counter Space
File Cabinet?
Tests Performed by Whom?
Monitoring Tests Conducted (TSS, BOD, pH, Fecal Coliform, Others)
According to Permit
Tests Conducted More Frequently
Tests Conducted Less Frequently
Tests with Suspected or Known Analytical Problems
Operational Test Capability (Equipment/Chemicals)
(Check if available)
DO meter
BOD5
Mallory-type settleometer
Graduated cylinder
Imhoff cone
Turbidity
Ammonia
Nitrate
172
-------
FORM 0-3 (continued)
DESIGN DATA
E. LABORATORY CAPABILITY:
f
Operational Test Capability: (Check 1f available)
Total Kjeldahl nitrogen
Suspended solids
Volatile suspended solids
Sludge blanket depth measurement
Core sample; taker
Alkalinity
Volatile adds
pH meter
Centrifuge jsollds concentrations
Oxygen uptake rates
173
-------
FORM D-4
OPERATIONS DATA
A. PROCESS CONTROLS:
Who sets major process control strategies and decisions?
Where is help sought when desired performance is not achieved?
Are staff members asked their opinions?
B. SPECIFIC PROCESS CONTROLS:
Primary Clarification
1. Sludge Removal:
2. Performance Monitoring:
3. Other:
Suspended Growth POTW Secondary Systems
1. Sludge Mass Control:
2. Return Sludge Control:
3. DO Control:
4. Clarifier Solids Loading:
i
5. Other:
174
-------
FORM D-4 (continued)
OPERATIONS DATA
Fixed Film POTW Secondary
1. Secondary Clarifier Sludge Removal
2. Anaerobic Sidestream Returns:
3. Other:
Sludge Handling
1. Purpose Relative
Systems
to Other Processes;
2. Sludge Stabilization:
3. Sludge Disposal:
*
i
4. Other: :
C. PROCESS CONTROL REFERENCES USED (Specifically note references that
are the source of poor process control decisions or strategies,
suspected or definitely identified):
175
-------
FORM D-5
MAINTENANCE DATA
A. EQUIPMENT OR PROCESSES OUT OF SERVICE DUE TO BREAKDOWNS (Identify
equipment or process, description of problem, length of time out of
service, what has been done, what remains to be done, estimated time
before repair, how 1t affects performance):
DURING THE CPE (List and explain)
DURING THE LAST 24 MONTHS (11st and explain):
176
-------
FORM :D~5 (continued)
MAINTENANCE DATA
8,. PREVENTIVE MAINTENANCE PROGRAM: ;
J
Method of Scheduling: ;
Method of Documenting Work Completed:
, i
Adequacy of Resources Available:
Lubricants:
I
i
I
Tools:: i
Others: i
C. EMERGENCY MAINTENANCE PROGRAM:
i
Small Spare Parts (fuse?, belts, bearing, packing dlffusers, etc):
Major Spare Parts (largj* motors, gear boxes, blowers, flowmeter, etc,,
Manpower: j
Expertise: ;
i
References: |
i
i '
O&M Manual:
Accurate As-Bullts:,
Manufacturer's Literature:
177
-------
FORM D-5
MAINTENANCE DATA
D. 6ENERAL HOUSEKEEPING:
178
-------
i FORM D-6
PERFORMANCE DATA
A. SOURCE OF DATA:
B. REPORTED MONITORING DATA FpR PREVIOUS 12 MONTHS (flows In mgd; others
in mg/1, except as noted): :
Raw
Primary Effluent
Mo/Yr Flow BODC TSS
o
TSS
AVG
179
-------
FORM D-6 (continued)
PERFORMANCE DATA
B. REPORTED MONITORING DATA FOR PREVIOUS 12 MONTHS (cont.)
Final Effluent Other
Mo/Yr Flow BOD& TSS
BOD> TSS
o
AVG
180
-------
FORM D-6 (continued!)
PERFORMANCE DATA
C. PERMIT PERFORMANCE VIOLATIONS WITHIN LAST 12 MONTHS (30-day averages,,,
7-day averages, Instantaneous violations, effluent mass violations,
percent removal violations^
No. of Mdnths Without a Violation
No. of Months With a Violation
D. REASONS (if any) REPORTED MONITORING DATA ARE NOT BELIEVED TO
REPRESENT ACTUAL EFFLUENT QUALITY (unrepresentative sampling,
improper lab analyses, 'unaccounted-for sludge loss, selective
reporting, etc.):
181
-------
APPENDIX E
GUIDELINES FOR FIELD ESTIMATING
EQUIPMENT POWER USAGE
182
-------
FIELD ESTIMATING EQUIPMENT POWER USAGE
The power a particular piece of equipment 1s drawing can be estimated In
the field by measuring the current being drawn by the motor. The measured
power being drawn by a motor (Inductive user) 1s "apparent power" and must
be multiplied by the power factor (PF) to calculate actual power. Four
methods are available to arrive 'at a suitable power factor:
1. Assume a power factor: ',
Use 0.9 for recently constructed plants that likely included use
of capacitors to adjust the power factor toward 1.0. Use 0.75
for old and small pla;nts where it is unlikely that capacitors
have been added.
j
2. Measure the "plant power factor" using an ammeter and the plant
kilbwatttiour meter and|assume the power factor applies for larger
pieces of equipment. !See Table E-l for calculation worksheet.
(WARNING: DO NOT USE THIS METHOD UNLESS QUALIFIED.)
3. Ask the electric company to measure the power factor or actual
power usage of specific! equipment.
4. Rent an appropriate Instrument and measure power factor or actual
power usage. (WARNING:; DO NOT USE THIS METHOD UNLESS QUALIFIED.)
Once the PF has been determined> the following calculations can be used to
estimate power drawn by a particular piece of equipment:
Measure: '
Average Voltage (line-to-line) =
\ ' i
Average Amperage = •
Calculate: ,
Volts
Amps
kVA =
V x A x
1000
kW = kVA x PF
(3-phase power)
whp =
kW
0.746
183
-------
TABLE E-l
WORKSHEET FOR CALCULATION OF POWER FACTOR
Apparent Power
L1ne-to-L1ne Voltage on Incoming Power:
vl-2
avg
Volts
Volts
Volts
Volts
Amperage for Each Phase on Incoming Power:
I-j = Amps
I_ = Amps
I3 = ' Amps
Amps
avg
kVA =
'x
1000
Actual Power
CTR
watthours/revolution (from meter)
,b
PTR
TR = CTR x PTR =
Disc Speed =
Seconds/
Revolution(s)
kW = Kn x TR x
Power Factor
Dlscev; 3600ec
1 kW
Sec
Hour
1000 Watts
PF
kW_
KVA
aCTR (Current Transformer Ratio) - ratio of primary to secondary current.
For current transformer rated 200:5, ratio is 200/5 or 40/1.
bPTR (Potential Transformer Ratio) - ratio of primary to secondary volt-
age. For potential transformer rated 480:120, ratio is 480/120 or 4/1.
CTR (Transformer Ratio) - total ratio of current and potential trans-
formers. For CTR = 200:5 and PTR = 480:120, TR = 40 x 4 = 160.
184
-------
APPENDIX F
PROCEDURE FOR CONVERTING STANDARD OXYGENATION
RATES TO ACTUAL OXYGENATION RATES
185
-------
PROCEDURE FOR CONVERTING STANDARD OXY6ENATION
RATES (SORs) TO ACTUAL OXYGENATION RATES (AORs)
AOR = SOR (a)
[ BCSW - CL1
- CL~I (T-20)
e
Where:
AOR
SOR
a
e
= actual oxygen transfer rate, Ib 02/hp-hr
standard oxygen transfer rate, Ib Op/hp-hr (from Table
3-3)
relative rate of oxygen transfer in wastewater compared to
water. Estimate from Table F-l.
= relative to oxygen saturation value in wastewater compared
to water. Estimate fj = 0.95 for mixed liquor.
temperature correction constant, e = 1.024
= oxygen saturation value of clean water at standard
conditions, Cs = 9.17 mg/1
= oxygen saturation value of clean water at site conditions
of temperature and pressure, mg/1
'SW
CL
T
C14.7
mixed liquor DO concentrations, mg/1
temperature of the liquid, °C
oxygen saturation value of clean water at standard pressure
of 14.7 psi and actual water temperature (see Table F-2).
actual pressure at oxygen transfer point
a) For surface aerators, use atmospheric pressure (see
Figure F-l).
b) For others, use atmospheric pressure from Figure F-l,
plus the pressure at mid-depth of the tank from the
surface to the diffusers (i.e., diffuser depth in'feet
x 0.5 x 0.434 psi/ft).
186
-------
iTABLE F-l
i
TYPICAL VALUES OF ALPHA (a) USED FOR,ESTIMATING AOR/SOR
Aeration Device
Course Bubble Diffusers
Fine Bubble Diffusers
Jet Aeration
Surface Mechanical Aerators
Submerged Turbines
Typical
0.85
0.50
0.75
0.90
0.85
187
-------
TABLE F-2
OXYGEN SATURATION AT STANDARD PRESSURE AND ACTUAL WATER TEMPERATURE
Temperature
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Dissolved Oxygen
Saturation Level
(mg/1)
14.62
14.23
13.84
13.48
13.13
12.80
12.48
12.17
11.87
11.59
11.33
11.09
10.83
10.60
10.37
10.15
9.95
9.74
9.54
9.35
9.17
8.99
8.83
8.68
8.53
8.38
8.22
8.07
7.92
7.77
7.63
11)8
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189
-------
APPENDIX G
EXAMPLE FORMS FOR ESTABLISHING A PREVENTIVE
MAINTENANCE PROGRAM FOR SMALL POTWs
Form
G-l
G-2
6-3
G-4
Title
Equipment Information Sheet
Daljly Preventive Maintenance
Weekly Preventive Maintenance
Monthly Preventive Maintenance
190
-------
1 FORM 6-1
EQUIPMENT INFORMATION SHEET
Plant Equipment Number.
[EQUIPMENT!
Location
Model
Manufacturer
Type R'ated Capacity _]
Additional Data _ i
_0riginal Installation Date
i Serial No;
Rated Pressure or Head
DRIVE Type
Description
Manufacturer
I MOTOR| Manufacturer
Frame
Type ^___
Rated Voltage
SUPPLIER(S):
Company Name & Address
HP
Enclosure Type
Rated Amperage
Contact Person
RPM
S.F.
Telephone No.
Additional Information and Comments:
191
-------
FORM 6-1 (continued)
EQUIPMENT INFORMATION SHEET
RECOMMENDED PREVENTIVE MAINTENANCE:
Frequency
RECOMMENDED LUBRICANTS:
Part Lubricant Name & Description Source
RECOMMENDED SPARE PARTS:
Part Description
Number
Quantity
192
-------
! FORM G-2
j
DAILY PREVENTIVE MAINTENANCE
Inlet Building
Check operation of grit pump, cyclone, a.m..
grit bin, pump seal water pressure p.m..
(psi), leakage _(drops/m1n).
Check grit collector for unusual noise a.m..
or torque. ; p.m..
- Check flow meter operation, chain, float, a.m..
stilling well. p.m/
Check auto sampler operation and bottle a.m..
installation. p.m..
i
Grit Separator #2 Building '
\
Check for unusual noise or vibration a.m..
1n collector or conveyor. , p.m..
j
Primary Clarifier ;
Check for unusual noise or vibration a.m..
in drive unit. p.m..
Aeration Building
Check blowers for unusual nbise or a.m..
vibration. p.m..
TIME
INITIALS
Temperature:
#1 Inlet
#2 Inlet
#3 Inlet
°C
~
Outlet
Outlet
Outlet
Check auto sampler operation and bottle
installation. !
a.m..
p.m..
(Form continued to include all process units and buildings requiring daily
maintenance.)
193
-------
FORM 6-3
WEEKLY PREVENTIVE MAINTENANCE
DATE
INITIALS
Inlet Building
Grit #1 Collector Drive: Apply grease to upper
and lower bearings 1n worm gear housing.
Grit #1 Collector Drive: Check oil level in
gear housing; remove condensate in gear drive.
Grit #1 Collector Drive: Lubricate chain
between drive unit and motor gear.
Grit #1 Collector Drive: Check torque ^
overload alarm for proper operation.
Communitor: Check oil level in main gear
box (lower).
Communitor: Check oil level in motor gear unit.
Automatic Sampler: Remove and clean sampling
tube and strainer.
Grit Separator #2 Building
- Grit #2 Drive Unit: Check oil level in
Philadelphia gear reducer.
Grit #2 Conveyor Unit: Apply grease to all
bearings of chain drive and support sprockets.
Grit #2 Conveyor Unit: Check oil level in '
conveyor drive reducer.
Aeration Building
Automatic Sampler: Remove and clean sampling
tube and strainer.
Aeration Blowers: Check oil level - 3 points
(gears, two bearings)
Aeration Blowers: Operate blower(s) (10 min
each) not in service. Check oil level and
temperature.
(Form continued to include all process units and buildings requiring
weekly maintenance.)
194
-------
FORM G-4
MONTHLY PREVENTIVE MAINTENANCE
Inlet Building
Automatic Sampler: Check pump tubing for
signs of failure. Remove from pump housing
to Inspect. I
Grit Separator #2 Building ,
Gear Reducer: Apply grease to upper and
lower bearings. j
Primary Clarlfler '
Drive Mechanism: Check gear lubrication
(dipstick). Check base plate lubrication
(oil cap) |
Gear Reducer: Apply grease to upper, lower,
and two side bearings. :
DATE
INITIALS
(Form continued to Include all process units and buildings requiring
monthly maintenance.)
Porvlde Similar Forms For: ;
QUARTERLY PREVENTIVE MAINTENANCE
SEMIANNUAL PREVENTIVE MAINTENANCE
ANNUAL PREVENTIVE MAINTENANCE
195
-------
APPENDIX H
DESIGN-RELATED PERFORMANCE-LIMITING
FACTORS IDENTIFIED IN ACTUAL CPEs
196
-------
DESIGN-RELATED PERFORMANCE-LIMITING FACTORS
The design problems listed 1n this appendix were Identified during actual
comprehensive performance evaluations. Most of these problems have
resulted 1n unnecessary or excessive maintenance, difficult process
control, Inaccurate or excessive!sampling, and poor POTW performance.
These design-related problems i are discussed
following categories:
1n the -context of the
Plant Layout
Flow Measurement
Bar Screens
Comminutors
Grit Removal
Primary Clarlfiers
Aeration Basins
Aerators
Trickling Filters
ABF Towers
RBCs
Secondary Clarifiers
Return Sludge Flows
Polishing Ponds
Chlorination
Wasting Capability
Sludge Holding Facilities
Aerobic Digesters
Anaerobic Digesters
Sludge Dewatering & Ultimate Disposal
Laboratory Facilities
Miscellaneous
197
-------
Plant Layout
- Individual process trains, without interconnection, require
operation of units as if three separate activated sludge plants
exist at one POTW rather than just one
- Covered basins without adequate observation access prevent
observation of processes
- Return sludge air compressors are located outside and repeatedly
break down
- No flow splitting flexibility to parallel units
- Bar screen located downstream from comminutor
- Freezing of influent sampler located outside
- Plant location inaccessible during Inclement weather
- Excessive compressor noise
- Disinfection before polishing pond
- Parallel secondary treatment units not capable of being operated
as one facility
- Inadequate piping flexibility requires shutdown of one trickling
filter if one clarifier is down
- One scraper drive for primary and final clariflers requires
shutdown of both for maintenance on either
- Lack of bypasses on individual treatment units such as aeration
basins, trickling filters, chlorine contact basins, etc.
- Use of a septic tank for inplant domestic and laboratory wastes
and overflow from the septic tank to the plant effluent
- Both trickling filter and activated sludge processes in very
small plant causes excessive operational requirements
Flow Measurement
- Discharge through a pipe rather than the control section for
which the recorder is appropriate
- Downstream channel slope and geometry causes backup in P.arshall
flume throat
198
-------
- Parshall flume oversized
- Flow measurement inaccurate due to upstream barminutor placement
- No flow recorder j
- Excessive upstream velocity causes turbulent flow through
Parshall flume
i
- Control section not accessible for inspection and maintenance
- Level transmitting instrumentation not compatible with level
receiving instrumentation
- Parshall flume on POTW Affluent submerged during high river flows
- Recycle flows (cooling water) included in plant flow measurement
- Roll up flow chart requires removal to observe flow for more than
the preceding 4 hours
- Wires crossed in totalizer, resulting in wrong reading
- Humid influent structure causes problem with moisture-sensitive
level sensor i
- Flow velocity too highiin Kennison nozzle
- Liquid level sensing float freezes
- Downstream bar screen backs flow into flume throat as screen plugs
Bar Screens :
i . • -
- Bar spacing too narrowband causes excessive blinding
- Backed-up flow released after cleaning causes hydraulic surges
through aeration basinjand into clarifier
- Freezing problems with(mechanical bar screen located outside
Comminutors '
- Repeated mechanical failure of hydraulic drive-type comminutor
199
-------
Grit Removal ', '
- Excess wear on grit screw center bearing because of exposure to
grit
- Odors from organics settling out in oversized grit channel
- Pump discharge to grit chamber directed at grit buckets, and
washes grit from buckets
- Grit auger not functional
- Grit auger discharges too low for disposal in truck
Primary Clarifiers '
- Overloaded by excessively large trickling filter humus return pump
!" '
- Overload due to trickling filter recirculation designed to route
through primary clarifier
- Improper placement of valve limits scum pumping
- Short-circuiting due to inlet baffle construction
- Preaeration in center tof clarifier reduces effective clarifi-
cation area
Aeration Basins
- Pipe outlet plugs with rags
- Lack of piping to operate as conventional as well as step-load or
contact-stabilization activated sludge
- Receives hydraulic surges when the bar screen is cleaned and from
oversized return pump on timeclock
- Loss of solids caused by flooding due to aeration basin design
elevation and lack of drainage control
- Action of aeration rotors and revolving bridge and configuration
of basin creates swells and voids that result in wavelike
stresses on bridge
- Leakage between contact and reaeration basins of contact
stabilization plant due to movable wall design
- No wall between contact and reaeration areas of contact
stabilization plant
200
-------
Aerators
- Inadequate capacity for oxygen transfer
- Surface mechanical aerators overheat and shut off under increased
flows due to infiltration/inflow
- Inadequate DO control because blowers provided are too large
- With floating aerators, repeated breaking of cables when operated
on intermittent basis
•I
- With submerged turbine aerators, repeated downtime due to bearing
and shaft failure
- Surface aerators that do not provide adequate bottom mixing in a
deep oxidation ditch \
- Inadequate freeboard for splashing with surface mechanical
aerators i
- Brush aerators provided in cold climate without ice protection
- Icing problems with surface mechanical aerators
- Rag accumulation on surface mechanical aerators
- Inadequate 00 control i
Trickling Filters |
i
- Recirculation only through primary clarifier
- Inadequate capacity of irickling filter arms
- Poor flow splitting to trickling filters
I
ABF Tower :
- Inadequately sized for prganic load
i
- Undersized pipe carrying tower underflow back to recirculation tank
i
- No flexibility to vary percent tower underflow returned to
recirculation tank
- Sludge return and tower recycle flow are directed into the same
pipe, which limits thelj" volume recycled
I
- No flow measurement on direct recycle flow around tower
201
-------
RBCs
- No positive flow splitting to various trains
- No access provided through covers to take dissolved oxygen
measurements
- Inadequate shaft design causes excessive downtime
Secondary Clariflers
- Poor flow splitting to clarifiers
- Poor development of surface area with weirs
- Sludge scraper mechanism directing contercurrent to wastewater
flow
- Hydraullcally connected clarifiers not of the same elevation
causes unequal flow splitting
- Freezing during cold weather
- Inlet and outlet on circumference, a large diameter, a large
design overflow rate, and failure to consider process recycle
flows cause problems with hydraulic washout of solids
- Scum returned to aeration basin; no ultimate disposal of scum
- Combined primary and final clarifler unit allows mixing of two
with scraper mechanism
- Hydraulic restriction causes submerged overflow weirs
- Short-circuiting due to inlet baffle construction
- Placement of trickling filter redrculation drawoff overloads
final clarlfier
- Weirs on single launder not balanced to pull evenly from each side
- No skimming device
- Shallow depth promotes thin underflow concentrations and solids
washout
202
-------
Return Sludge Flows
- Constant-speed centrifugal pumps make it d-ifficult to adjust flow
- Oversized constant-speed!pumps provided
- Return sludge flow not visible at any point
- No measurement j
- Single pump returning from multiple clarifiers; balancing return
flow difficult I
- Variable-speed return pumps too large even at lowest setting
- Plugging of telescoping valves at lower flows
- Sludge returned to a point near the outlet of the aeration basin
i
- Not accessible for sampling
- Piping prohibits return sludge flow for several hours while
sludge is being removed from the aerobic digester
- Measurement with 90° V-notch weir not sensitive enough for
needed flow adjustments
- Oversized pump on timeclock draws down final clarifier, then
hydraulically overloads aeration basin
- Waste piping and appurtenances require excess return rate to
accomplish wasting
i
- Stilling box ahead of V-notch weir too small
i
- Location of return measurement requires operator to walk out on
narrow wall over basins, resulting in unsafe working conditions
- Sludge return from clarifiers controlled by plug valve into wet
well> Excess operator time required to match variable-speed pump
with valve-controlled rate
- Return adjustment requires alternate operation of pump from first
clarifier, second clarifier, and both clarifiers to set desired
total return
- Partial plugging with
sludge flow control
rags of butterfly valve used for return
- Rapid withdrawal sludge removal designed without sampling or
adjustment capability from various ports
203
-------
Polishing Ponds
- No pond bypass
- Sludge wasted to polishing pond ',
- Pond located after disinfection
Chlorination !
- Chlorine diffuser located at center of contact tank rather than
at inlet
- Chlorine diffuser located at outlet of contact tank
- Single contact tank prohibits disinfection during cleaning and
discourages cleaning of contact basin
- Rotometer on chlorinator too large for present application
- Poor mixing
- Chlorine dosage paced by effluent flow, but filter backwash water
removed from combined contact-backwash storage tank shuts off
chlorination until it is again filled and discharging
- Inadequate chlorine contact time in outfall pipe
- No depth control device on contact tank results in inadequate
contact time and short-circuiting
- Short-circuiting over baffles during high flows
- Short-circuiting due to inlet design
Wasting Capability
- No digester or sludge holding facility; inadequate drying beds
- Downtime of exotic sludge treatment facility causes inadequate
wasting
- Wasting capability only from mixed liquor requires excessive
waste volume
- Insufficient wasting capacity
- Sludge lagoons undersized
204
-------
- No waste flow measurement
- Partial plugging of waste pump prevents use of pumping rate to
calculate waste volume
- Valve choice for directing return sludge to waste requires excess
operator time
- Undersized waste pump
Sludge Holding Facilities
- Odors from unaerated, uncovered sludge storage
- Undersized storage capacity given ultimate sludge disposal
limitations
- Potential gas buildup problem with covered, unaerated sludge
storage '
Aerobic Digesters '
- High groundwater and pressure relief valve prevents batch
operation
- Inadequate air supply !
- Inadequate supernating capability
- Undersized
- Pump used for sludge removal prevents thickening of sludge
- Small digesters and minimum freeboard make foam containment
difficult !
- Freezing problems J
j
- Common wall with aeration basin structurally insufficient to
allow batch operation
- Provided with "automatic" supernating device that cannot work
I
Anaerobic Digesters
I
- Inadequate supernatant drawoffs
- With multiple units, Inflexibility to waste to desired primary
digester !
205
-------
- Plugging problem between bottom of primary digester and
second-stage digester
- Water seal on sludge recirculation pump loads digester with cold
water
- Sludge pumping line from clarifier plugs prevents digester
loading at concentrations above about 6 percent
,-•
- No gas meters
- No mixing
- Cold digester produces poor supernatant quality and poor digestion
- Single gas meter for two digesters
- Uninsulated heating pipes outside
Sludge Dewatering & Ultimate Disposal
- Truck ramp too steep for use during winter
- Excessive maintenance on sludge incineration facilities
- Insufficient sludge drying lagoons
*
- Disposal of sludge in polishing lagoon
- Truck capacity too small for sludge produced
- Insufficient drying beds for wet or cold weather operation
- Land application not possible during certain times of the year;
no alternate disposal or storage
Laboratory Facilities
- Vibrations prevent use of scale
- Inadequately equipped
- Humidity difficult to work in and hard on equipment
- Noise from blowers limits usability
- Poor lighting
- Insufficient floor space
206
-------
Miscellaneous
- Stabilization of sludge with chlorine releases heavy metals to
recycled supernatant \
- Wooden gates 1n flow diversion structure swell and cannot be
removed ;
- No automatic restart afiter power outage
- Butterfly valve used Ibetween mixed liquor and final effluent
leaks mixed liquor into; effluent
- Undersized raw lift pumps
207
-------
APPENDIX I
EXAMPLE PROCESS MONITORING SUMMARY
FOR AN ACTIVATED SLUDGE POTW
208
-------
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209
-------
COLUMN INFORMATION FOR DAILY CONTROL CALCULATION SHEET
Column Symbol
Symbol Meaning
Explanation
I DATE Self-Explanatory
2 ATC Aeration Tank Concentration
3 RSC Return Sludge Concentration
4 CSC Clarifier Sludge Concentration
DTB
TURB
FLOW
RSF
RFP
Average of values recorded during the day
on the Daily Data Sheet.
Average of values recorded during the day
on the Daily Data Sheet.
Average concentration of sludge within the
clarifier as determined from a core sample
(Method I) or by calculation (Method 2).
Method I. Core Sample - average of values
recorded during the day on the Daily Data
Sheet.
Method 2. Calculation - average of ATC
and RSC.
CSC =
ATC + RSC
Depth to (Sludge) Blanket
Turbidity
Daily Wastewater Flow
Return Sludge Flow
Return Sludge Flow Percentage
Average of values recorded during the day
on the Daily Data Sheet.
Average of values recorded during the day
on the Daily Data Sheet.
Total wastewater flow for a given 24-hour
time period (e.g., 8:00 a.m. to 8:00 a.m.).
Total daily return sludge flow. (Note:
Time period for determining this rate
should be the same as the time period used
for determining daily wastewater flow rate
[e.g., 8:00 a.m. to 8 :00 a.m.])
Return sludge flow divided by average
daily wastewater flow.
RFP = — x 100%
FLOW
!210
-------
COLUMN INFORMATION FOR DAILY CONTROL CALCULATION SHEET (continued)
Column Symbol
Symbol Meaning
Explanation
10 RSP Return Sludge Percentage
II ASU Aerator Sludge Units
12 CSU Clarifier Sludge Units
13 SDR Sludge Distribution Ratio
14 TSU Total Sludge Units
15 ESU Effluent Sludge Units
Return sludge flow percentage based on
mass balance.
RSP =
I
RSC
ATC
x 100%
Total aeration tank volume CAV) times ATC.
ASU = (AV)(ATC)
Method I. Core Sample - clarifier sludge
concentration times the clarifier volume
(CV).
CSU = (CSCXCV)
Method 2. Calculation - clarifier sludge
concentration times the fraction of the
clarifier filled with sludge, times the
clarifier volume (CV).
CSU = (CSC)
CD - DTB
CD
(CV)
Ratio of the quantity of solids under
aeration vs the quantity of solids in the
clarifier.
SDR =
ASU
CSU
TSU = ASU + CSU
Quantity of sludge lost in the effluent
each day.
ESU = Effluent suspended solids (TSS)
times FLOW divided by ratio of MLSS to
percent solids by centrifuge (e.g., ratio
= MLSS divided by ATC).
ESU =
(TSS)(FLOW)
Ratio
211
-------
COLUMN INFORMATION FOR DAILY CONTROL CALCULATION SHEEt (continued)
Column Symbol
Symbol Meaning
Explanation
16 XSU Intentionally Wasted Sludge
Units
Quantity of Sludge intentionally wasted
from the system each day = average
concentration of wasted sludge times the
volume of sludge wasted (from the Daily
Data Sheet).
17 WSU Total Waste Sludge Units
18 MCRT Mean Cell Residence Time
19 RSU Return Sludge Units
20 SDTA Sludge Detention Time in
the Aerator
WSU = ESU + XSU
Average of number of days a given quantity
of sludge remains in the system.
MCRT =
TSU
WSU
Return sludge flow rate times the return
sludge concentration.
RSU = (RSF)(RSC)
Average number of hours a given quantity
of sludge ramain in the aerator.
21 SDTC Sludge Detention Time in
the Clarifier
22 SDT/\ x See meanings above j
ATC
23 CSL Clarifier Solids Loading
SDTA
(AV) (24 hr/d)
FLOW + RSF
Average length of time a given quantity of
sludge remains in the clarifier.
SDTC =
(CSU)(24 hr/d)
RSU
Indication of the treatment: pressure in the
system.
Average daily mass of sludge to the
clarifier divided by the clarifier surface
area (CSA).
CSL =
(FLOW + RSF)(ATC)
CSA
212
-------
COLUMN INFORMATION FOR DAILY CONTROL CALCULATION SHEET (continued)
Column Symbol
24
OFR
25
26
SSC5
SSCgg
Symbol Meaning'
Clarifier Surface Overflow
Rate
Settled Sludge Concentration
in 5 minutes'
Settled Sludge Concentration
in 60 minutes
Explanation
Upward velocity of the treated wastewater
in the secondary clarifiar.
OFR =
FLOW
CSA~
Average of values recorded during the day
on the Daily Data Sheet.
Average of values recorded during the day
on the Daily Data Sheet.
213
-------
APPENDIX J
EXAMPLE PROCESS MONITORING SUMMARY
FOR AN RBC POTW
214
-------
EXAMPLE RBC PROCESS MONITORING SUMMARY*
Week of
19
Date
Day Sun Mon Tues Wed Thurs Fr1
Flow, mqd
INFLUENT
BOD. mq/1
SBOD. mq/1
TSSf mq/1 ;
pH. units !
Temp . . °C
j
.WET WELL j
SBOD- mq/1
PRIMARY CLARIFIER j
DTB.* m i
BODg. mq/1 i
SBOD... mq/1
5
TSS. mq/1
pH. units
Temp . . C
SECONDARY CLARIFIERS
DTB, . m
1 - ;
DTB-. m
2 : ;
BODg. mq/1
SBODC. mq/1
5 !
l
'1
Sat
AVQ
Ava
Ava
Ava
Avg
Avg
Ava
Avq
*Explanat1on provided at the end of Appendix J
215
-------
EXAMPLE RBC PROCESS MONITORING SUMMARY (continued)
Week of
19
Date
Day
Sun
Mon
Tues Wed Thurs Fri
Sat
CHLORINE CONTACT EFFLUENT
C12 Res. mg/1
Fecal CoHform,
MPN/1
pH, units
TSS. mg/1
O&G,* mg/1
Avg
GM*
Avg
Avg
SECONDARY SLUDGE
m1n/d pumped
1/s
m3/d
spin.* %
ratio*
mg/1
kg/d
Avg
Avg
PRIMARY SLUDGE
Start Time
End Time
Minutes
m3/d
m3
spin. %
ratio
mg/1
kg/d
Avg
Avg
216
-------
EXAMPLE RBC PROCESS MONITORING SUMMARY (continued)
Stage 1
Stage 2
Stage 3
Stage 4
RBC DISSOLVED OXYGEN
(Date Time )
Train 1 Train 2 ;Train 3
RBC TRAIN PERFORMANCE
(Date _ Time _ )
SBOO
Train 1
Train 2
Train 3
_mg/l
_mg/l
_mg/1
DO
jng/1
TSS
RBC EFFLUENT
(Date J Time )
mg/1 pH.
Temp
20
18
16
si12
B! 10
si —
C
-------
EXAMPLE RBC PROCESS MONITORING SUMMARY (continued)
Term
Explanation
DTB
GM
O&G
SPIN
RATIO
Depth to (Sludge) Blanket
Geometric Mean
Oil and Grease
Concentration; percent of sample volume the
compacted sludge occupies after a 15-minute
laboratory centrifuge spin
MLSS divided by ATC (see Appendix I, Column
Information for Daily Control Calculation
Sheet)
218
-------
APPENDIX K
PARAMETERS USED TO MONITOR THE
ABF TREATMENT PROCESS
219
-------
PARAMETERS USED TO MONITOR
THE ABF TREATMENT PROCESS
>lumn Symbol
Symbol Meaning
Explanation
I
2
10
DATE
ATC
RSC
CSC
DTB
TURB
FLOW
RSF
RFP
BCRF
SeIf-ExpIanatory
Aeration Tank Concentration
Return Sludge Concentration
Average of values recorded during the day
on the Daily Data Sheet.
Average of values recorded during the day
on the Daily Data Sheet.
Clarifier Sludge Concentration Average concentration of sludge within the
clarifier. Average of values recorded
during the day on the Daily Data Sheet.
Depth to (Sludge) Blanket
Turbidity
Daily Wastewater Flow
Return Sludge Flow
Average of values recorded during the day
on the Daily Data Sheet.
Average of values recorded during the day
on the Daily Data Sheet.
Wastewater flow for a given 24-hour time
period (e.g., 8:00 a.m. to 8:00 a.m.)..
Total daily return sludge flow. (Note:
Time period for determining this rate
should be the same as the time period used
for determining daily Wastewater flow rate
[e.g., 8:00 a.m. to 8:00 a.m.])
Return Sludge Flow Percentage Return sludge flow divided by average
daily wastewater flow.
RFP
RSF
FLOW
x 100*
Biocell Direct Recirculation
Flow
Daily total flow from the biocelI under
drain directly to the recirculatiori wet
well. (Note: Time period for determining
this flow should be the same as for
determining the average daily wastewater
flow.)
*A Dally Control Calculation Sheet similar to the one presented for ac-
tivated sludge 1n Appendix I can be used to present these parameters in
tabular form.
220
-------
PARAMETERS USED TO MONITOR
THE ABF TREATMENT PROCESS (continued)
Column Symbol
11 BCRFP
12
13
14
15
16
17
18
19
TFBC
BCHL
ASU
CSU
TVBC
BCSU
TSU
SDR
Symbol Meaning i
Biocell Direct Recirculation
Flow Percentage '
Total Flow to the Biocel I
Biocell Hydraul ic Load
Aerator Sludge Units
Clarifier Sludge Units
Total Volume in thai Biocel I
Biocell Sludge Units
1
Total Sludge Units
Sludge Distribution Ratio
Explanation
Percentage expression of the ratio of the
volume of direct biocell recirculation to
the volume of raw wastewater.
BCRFP =
FLOW
x 100*
Total volume of liquid pumped to the
biocel I .
TFBC = FLOW + RSF + BCRF
Volume of liquid pumped to the biocell per
unit area of biocell in operation.
TFBC x 695
Biocell Surface Area
Total aerator volume (AV) times ATC.
ASU = AV x ATC
Clarifier volume. (CV) times clarifier
sludge concentration.
CSU = CV x CSC
Volume of mixed liquor in the biocell and
associated appurtenances. TVBC = volume
in tower, volume in underdrain, volume in
recirculation, and volume in tower piping.
BCSU = TVBC x ATC
TSU = ASU + BCSU + CSU
Ratio of the mass of solids in the
aeration tank + mass of sludge in the
biocell to the mass of sludge in the final
clarifier.
SDR =
ASU + BCSU
CSU
221
-------
PARAMETERS USED TO MONITOR
THE ABF TREATMENT PROCESS (continued)
Column Symbol Symbol Meaning
20 ESU Effluent Sludge Units
21
XSU
22
23
WSU
MCRT
24
25
RSU
SDTA
26
Intentionally Wasted Sludge
Units
Total Waste Sludge Units
Mean Cell Residence Time
Return Sludge Units
Sludge Detention Time in
the Aerator
Sludge Detention Time in
the Biocel I
Explanation
Quantity of sludge lost in the effluent
each day.
ESU =
(TSS)(FLOW)
Ratio =
Ratio
MLSS
ATC
Quantity of SIudge intent!ona11y wasted
from the system each day = average
concentration of wasted sludge times the
volume of sludge wasted (from the Daily
Data Sheet).
WSU = ESU + XSU
Indication of sludge age or the "mean time
an average sludge cell is in residence in
the system."
MCRT =
TSU
xiu
Return sludge flow rate times the return
sludge concentration.
RSU = CRSFMRSC)
Average length of time in hours a given
quantity of sludge remains in the aerator.
SDTA =
AV x 24 hr/d
TFBC - BCRF
Indication of the length of the time in
hours the suspended growth sludge spends
in the biocell and associated
appurtenances, equaI to the hydrauIi c
detention time.
TVBC
TFBC
222
-------
PARAMETERS USED TO MONITOR
THE ABF TREATMENT PROCESS (continued)
Column Symbol
27 SDTC
28
29
30
31
33
34
35
36
TOT
CYCLES
SDTAx
ATC
CSL
32 OFR
SSC5
SSC3Q
SSC60
SVI
Symbol Meaning
Sludge Detention Time in
the Clarifiers
Total Detention Time
Sludge Cycles per Day
See meanings above
Clarifier Solids Loading
Clarifier Overflow Rate
Settled Sludge Concentration
in 5 minutes !
Settled Sludge Concentration
in 30 minutes
Settled Sludge Concentration
in 60 minutes
Sludge Volume Index
Explanation
Average length of time the sludge remains
in the clarifiers during each pass around
the system.
SDTC =
CSU
RSU
TOT = SDTA
SDTC
Number of times the sludge cycles through
the entire system during the day.
CYCLES =
24 hr/d
TOT
Indication of the treatment pressure in the
system.
Indicates the mass loading of solids on
the final clarifiers.
CSL =
ATC
- BCRF)
CSA
Indication of the hydraulic upflow rate in
the final clarifiers.
OFR =
FLOW
CSA~
Average of values from the Daily Data
Sheet.
Average of values from the Daily Data
Sheet.
Average of values from the Daily Data
Sheet.
1.000.000
) (MLSS/ATC)
223
-------
PARAMETERS USED TO MONITOR
THE ABF TREATMENT PROCESS (continued)
Column Symbol Symbol Meaning
37 RSP Return Sludge Percentage
38 OUR Oxygen Uptake Rate
39 WASTE Waste Volume
40 RECIRC Recirculation Power
41 AERATION Aeration Blower Power
42 WASTE Waste Power
ExpIanati on
Indication of return flow percentage that
is based on a solids balance. i
RSP =
ATC x 100
RSC - ATC
Average of values from the Daily Data
Sheet.
Average of values from the Daily Data
Sheet.
Average of values from the Daily Data
Sheet.
Average of values from the Daily Data
Sheet.
Average of values from the Daily Data
Sheet.
224
-------
; Appendix L
Suspended Growth Major Unit Process Evaluation Worksheet
This worksheet is used to evaluate the capacity of existing major unit processes, i.e., aerator, secondary clarifier, and
sludge handling system. Key loading and process parameters are compared with standard values and point scores are
assigned. These points are subsequently compared with expected point scores for Type 1, Type 2, and Type 3 facilities
and a determination of the plant Type is made.
Instructions for Use: !
• Proceed through the steps contained in this worksheet in order.
• Use actual values in lieu of calculations if such data are collected and available, e.g., waste sludge volume.
• When assigning points, interpolate and use the nearest whole number:
• Minimum and maximum point values are indicated—do not exceed the range illustrated.
Aeration
Basin
Calculate Hydraulic Detention Time (HOT):
HOT =
Aeration Basin Volume
Average Daily Wast^water Flow
cuft> x (180) =
hr
gpd)
Determine HOT Point Score:
HDT(hr)
I , I
J I(J 1 K
I I
I I I I I 1 1 I I I I I
20 *
I I I I I II I
-6
0
I I I I I
Points
1 I I
10
HOT Point Score =
Calculate Organic Loading:
Organic Loading = BOD. Loading
Aeration Basin Volume
225
Suspended Growth
-------
Organic Loading
cu ft)
lbBOD5/d/1,OOOcuft
lb/d> x (1,000)
Determine Organic Loading Point Score:
80
I
Organic Loading (Ib BOD5/d/1,000 cu ft)
50 25
l" I . I
15
i r
I
i i
Points
' I
10
Organic Loading Point Score =
Calculate Oxygen Availability
If data are not available on oxygen transfer capacity, calculate it as Wire Horsepower (Appendix E)
times actual Oxygen Transfer Rate (Appendix F).
-hp) x (_
_lb/hp-hr) x (24) =
Ib/d
Oxygen Availability = Oxygen Transfer Capacity
Ib/d)
02/Ib BOD5
Determine Oxygen Availability Point Score:
0.8
I
Oxygen Availability (Ib O2/lb BOD5)
1.0 1.2 1.5 2:5
I i I _i l I l I I I I I I I I I
IIII\ T I I 1 I I I I I I I- I
-10 -5 0 5 10
Points
Oxygen Availability Point Score =
Suspended Growth
Add Scores 1, 2, and 3 to Obtain Subtotal for Aeration Basin:
Aeration Basin Subtotal =
©
226
-------
Secondary
Clarifier
Determine Clarifier Configuration Point Score:
Configuration
Points
Circular with "donut" or interior launders
Circular with weirs on walls
Rectangular with 33% covered with launders
Rectangular with 20% covered with launders
Rectangular with launder at or near end
10
7
-5
-5
-10
Clarifier Configuration Point Score =
Calculate Clarifier Surface Overflow Rate (SOR):
_ Clarifier Effluent Flow
Clarifier Surface Area
gpd) =
sqft)
_gpd/sq ft
Determine SOR Point Score:
1,200
I
I '
-15
Surface Overflow Rate (gpd/sq ft)
1,000 800 650
I I I . I ,
500
300
I
i i TITiTTT ill | i rn I
-10 0
Points
I I I I I I I I I
10 15
SOR Point Score =
Determine Depth at Weirs Point Score:
7
I
i Depth at Weirs (ft)
8 10
I , I
12 1!
I , , I
I '
10
1 1 1 I 1 I 1 I I 1 1
-5 0
1 I 1 1 1 1 1 1
4 1(
Points
Depth at Weirs Point Score =
227
Suspended Growth
-------
Determine Return Activated Sludge (RAS) Removal Point Score:
RAS Removal
Points
Circular, rapid withdrawal
Circular, scraper to hoper
Rectangular, co-current scraper
Rectangular, counter-current scraper
No mechanical removal
10
8
2
0
-5
RAS Removal Score =
Determine Typical RAS Rate from Following:
Process Type
Conventional
(plug flow or complete mix)
Extended Aeration
(including oxidation ditches)
Contact Stabilization
Minimum Typical RAS Rate = .
Maximum Typical RAS Rate =
Return Activated Sludge Rate
Minimum
Maximum'
% of average daily wastewater flow
25
50
50
-percent
75
100
125
-percent
Calculate Recommended RAS Flow Range:
Min. Typical Typical RAS Rate x POTW Flow = Min. Recommended RAS Flow
%)
gpd) x (0.01) =
-9Pd
Max. Typical Typical RAS Rate x POTW Flow = Min. Recommended RAS Flow
%) x
gpd) x (0.01) =
-gpd
®
Determine Actual RAS Flow Range:
Minimum Actual RAS Flow = J gpd
Maximum Actual RAS Flow = i gpd
Suspended Growth
228
-------
Determine RAS Control Point Score:
RAS Control
Points
The actual RAS flow range is completely within the recommended
RAS flow range and the capability to measure RAS flow exists 10
The actual RAS flow range is completely within the recommended
RAS flow range but the capability to measure RAS flow does not exist 7
50% of the recommended RAS flow range is covered by the actual
RAS flow range and the capability to measure RAS flow exists 5
50% of the recommended RAS flow range is covered by the actual
RASflowrangebutthecapabilitytomeasureRASflowdoesnot exist 0
The actual RAS flow range is completely outside the recommended
RAS flow range I -5
RAS Control Point Score =
Sludge Handling
Capability
Add Scores 5, 6, 7, 8, and 9 to Obtain Subtotal for Secondary Clarifier:
Secondary Clarifier Subtotal =
Determine Sludge Controllability Point Score:
Controllability
Points
Automated sampling and volume control 5
Metered volume and hand sampling 3
Hand measured volume and hand sampling 2
Sampling or volume measurement by hand not practical 0
Sludge Controllability Point Score =
Calculate BOD$ Mass Removed:
POTW w/Primary Clarification:
Prim. BODsm - Prim. BODSOut= Prim. BOD5 Cone. Removed
mg/l) - {
mg/l) =
-mg/l
Prim. BODsout- POTW Eff.!BOD5= Sec. BOD5 Cone. Removed
mg/l) - (
mg/l) =
mg/l
229
Suspended Growth
-------
Prim. BODS Cone. Removed x POTW Flow = Prim. BOD5 Mass Removed
( mg/l) x ( gpd) x (8.34 x 1CT6) = Ib/d
Sec. BOD5 Cone. Removed x POTW Flow = Sec. BOD5 Mass Removed
( mg/l) x ( gpd) x (8.34 x 10'6) = Ib/d
POTW w/o Primary Clarification:
BODsin - POTW Eff. BOD5 = Total BOD5 Cone. Removed
mg/l) - (_
mg/l) =
_mg/l
Total BOD5 Cone. Removed x POTW Flow = Total BOD5 Mass Removed
( mg/l) x ( gpd) x (8.34 x 10~6) = Ib/d
Determine Typical Unit Sludge Production from Following:
Process Type
Ib TSS (sludge)/lb
BOD5 Removed
Primary Clarification
Activated Sludge w/Primary Clarification
Activated Sludge w/o Primary Clarification
Conventional0
Extended Aeration"
Contact Stabilization
1.7
0.7
0.85
0.65
1.0
"Includes tapered aeration, step feed, plug flow, and complete mix with wastewater detention times
<10 hours.
Includes oxidation ditch.
If plant records include actual sludge production data, the actual unit sludge production value
should be compared to the typical value. If a discrepancy of more than 15 percent exists between
the two values, further evaluation is needed. If not, use the actual unit sludge production value.
Calculate Expected Sludge Mass:
POTW w/Primary Clarification:
Unit Sludge Prod, x Prim. BOD5 Mass Removed = Prim Sludge Mass
Ib/lb) x (
Ib/d) =
Ib/d
Suspended Growth
230
-------
Unit Sludge Prod, x Sec. BODs Mass Removed = Sec. Sludge Mass
Ib/lb) x (
Ib/d) =
Ib/d
Total Sludge Mass =
Ib/d
POTWw/o Primary Clarification:
Unit Sludge Mass x Total BOD5 Mass Removed = Total -Sludge Mass
Ib/lb) x
Ib/d) =
Ib/d
Determine Sludge Concentration from Following:
Sludge Type
Waste Concentration
Primary
Activated
Return Sludge/Conventional
Return Sludge/Extended Aeration
Return Sludge/Contact Stabilization
Return Sludge/small plant with low SORa
Separate waste hopper in secondary clarifier
mg/l
50,000
6,000
7,500
8,000
10,000
12,000
"Returns can often be shut off for short periods to thicken waste sludge in clarifiers with surface
overflow rates less than 500 gpd/sq ft.
Calculate Expected Sludge Volume:
POTW w/Primary Clarification:
Sludge Volume = Prim. Sludge Mass
Prim. Sludge Cone.
50,000
lb/d) x (120,000) =
mg/l)
-gpd
Sludge Volume = fee. Sludge Mass
Sec. Sludge Cone.
lb/d> x (120,000) =
mg/l)
-gpd
Total Sludge Volume =.
-gpd
231
Suspended Growth
-------
POTWw/o Primary Clarification:
Total Sludge Volume = Total Sludge Mass
Total Sludge Cone.
mg/l)
x (120,000) =
-gpd
Calculate Capacity of Sludge Handling Unit Processes:
1. Establish capacity of each existing sludge handling process (treatment and disposal). The
most common unit processes for which this calculation will have to be performed are:
Aerobic digestion
Anaerobic digestion
Gravity thickening
Mechanical dewatering
Drying beds
Liquid haul
For example, the capacity of a gravity thickener is the maximum sludge loading it can handle:
_.. , , .. Total Sludge Mass
Thickener Loadmg = Thickener Suyrface Area
Ib/d) _
sqft)
Jb/d/sq ft
2. Determine percentage of the expected sludge production that each process can handle.
_ .
Process Capac.ty =
Typical Process Loading
=
Process Loading
Assume the sludge being thickened by the gravity thickener above is mixed primary and
activated. From Table 3-9, 10 Ib/d/sq ft is considered typical loading for the thickener. Its
capacity would therefore be calculated as:
10
Ib/d/sq ft)
Ib/d/sq ft)
x (100) =
.percent
Suspended Growth
232
-------
List Each Process and Its Associated Sludge Handling Capacity and Identify the Lowest
Percentage Capacity:
Process
Percentage
Lowest Capacity =
percent
Determine Sludge Handling Capacity Point Score:
50
% of Calculated Long-Term Average Sludge Production
75 100 125
150
I I
-10
15
Points
20
Sludge Handling Capacity Point Score = _
Add Scores 11 and 12 to Obtain Subtotal for Sludge Handling Capability:
Sludge Handling Capability Subtotal =
25
233
Suspended Growth
-------
Compare Subtotals and Total Score with Following to Determine Whether POTWis Type 1,
Type 2, or Type 3:
Aeration Basin
Secondary Clarifier
Sludge Handling Capability
Total
Aeration Basin
Secondary Clarifier
Sludge Handling Capability
Total
Select the Worst Case: POTW is Type.
Score
(4)
(1D)
(13)
Type
s Typp
Points Required
Type 1 Type 2 Type 3
13-30 0-12 <0
25-55 0-24 <0
10-30 0-9 <0
60-115 20-59 <20
Suspended Growth
234
-------
Appendix M
Trickling Filter Major Unit Process Evaluation Worksheet
This worksheet is used to evaluate the capacity of existing major unit processes, i.e., aerator, secondary clarifier, and
sludge handling system. Key loading and process parameters are compared with standard values and point scores are
assigned. These points are subsequently compared with expected point scores for Type 1, Type 2, and Type 3 facilities
and a determination of the plant Type is made.
Instructions for Use:
• Proceed through the steps contained in this worksheet in order.
• Use actual values in lieu of calculations if such data are collected and available, e.g., waste sludge volume.
• When assigning points, interpolate and use the nearest whole number.
• Minimum and maximum point values are indicated—do not exceed the range illustrated.
"Aerator" Calculate Equivalent Filter Media Volume:
Equivalent Filter _ Actual Filter Media Specific Surface Area x Actual Media Volume
Media Volume ~ Rock Filter Media Specific Surface Area
sq ft/cu ft)
43
sq ft/cu ft)
x (
.cu ft) =
_cuft
Calculate Organic Loading:
_ ••_,•_ Primary Effluent BOD5
Organ.c Loading = Equjvalent Fjlter Media Vo|ume
Ib/d)
cuft)
Jb BOD5/d/1,000 cu ft
x (1,000)
Determine Organic Loading Point Score:
Organic Loading (Ib BODs/d/1',000 cu ft)
70 50 ; 30 20 10
I I I l I I 1 I I I I I I I I I I
I ' ' ' ' I
-20 -10
I I I i I l l l l l l i I I I I I I I I I I
0 15 20
Freezing Temperatures
I I I I I l i i i l i 11 « i i i i i i i i i i i | | i i i i
-10 -5 10 20
Covered Filter/Nonfreezing Temperatures
Points
Organic Loading Point Score =
235
Trickling Filter
-------
Calculate Recirculation Ratio:
Recirculation Ratio =
Return Flow
Average Daily Wastewater Flow
gpd) _
gpd)
Determine Recirculation Ratio Point Score:
None
1
Ftecirculation
1:1
I
2:1
J
1
0
I
2
i Points
I
3
Recirculation Ratio Point Score =
Determine Anaerobic Side Streams Point Score:
Anaerobic Side Streams*
Points
Not returned ahead of trickling filter
Returned to the wastewater stream ahead
of the trickling filter
-10
'Supernatant from anaerobic digesters or filtrate/concentrate from the dewatering
processes following anaerobic digesters.
Anaerobic Side Streams Point Score =
Add Scores 1, 2, and 3 to Obtain Subtotal for "Aerator":
Secondary
Clarifier
Determine,Clarifier Configuration Point Score:
Configuration
Circular with "donut" or interior launders
Circular with weirs on walls
Rectangular with 33% covered with launders
Rectangular with 20% covered with launders
Rectangular with launder at or near end
'Aerator" Subtotal =
Points
10
7
0
-5
-10
©
Trickling Filter
Clarifier Configuration Point Score =_
236
0
-------
Calculate Clarifier Surface Overflow Rate (SOP):
SOR = Clarifier Effluent Flow
Clarifier Surface Area
gpd) _
sqft)
_gpd/sq ft
Determine SOR Point Score:
, Surface Overflow Rate (gpd/sq ft)"
1,200 1,000 800 650 500 300
I , III . I . I.I
I I | I I I I I I I I I I I I I T I I I I11 III I I
-15 -10 0 5 10
Points
15
SOR Point Score =
Determine Depth at Weirs Point Score:
Depth at Weirs (ft)
10
12
I
D
I
3
Points
I
t
Depth at Weirs Score =
Add Scores 5, 6, and 7 fo Obtain Subtotal for Secondary Clarifier:
Secondary Clarifier Subtotal =
237
Trickling Filter
-------
Sludge Handling
Capability
Determine Sludge Controllability Point Score:
Controllability
Points
Automated sampling and volume control 5
Metered volume and hand sampling 3
Hand measured volume and hand sampling 2
Sampling or volume measurement by hand not practical 0
Sludge Controllability Point Score =
Calculate BOD5 Mass Removed:
Prim. BODsm - Prim. BODsout= Prim. BODS Cone. Removed
mg/l) - (
mg/l) =
_mg/l
Prim. BODsout- POTW Eff. BODS= Sec. BOD5 Cone. Removed
mg/l) - (
mg/l) =
mg/l
Prim. BOD5 Cone. Removed x POTW Flow= Prim. BODS Mass Removed
{ mg/l) x ( gpd) x (8.34 x 10~6) = |b/d
Sec. BODS Cone. Removed x POTW Flow = Sec. BOD5 Mass Removed
( mg/l) x ( gpd) x (8.34 x 1CT8) = Ib/d
Determine Typical Unit Sludge Production from Following:
Process Type
Ib TSS (sludge)/lb
BOD5 Removed
Primary Clarification
Trickling Filter
1.7
1.0
If plant records include actual sludge production data, the actual unit sludge production value
should be compared to the typical value: If a discrepancy of more than 15 percent exists between
the two values, further evaluation is needed. If not, use the actual unit sludge production value.
Trickling Filter
238
-------
Calculate Expected Sludge Mass:
Unit Sludge Prod, x PrimJ BODs Mass Removed = Prim Sludge Mass
( Ib/lb) x ( Ib/d) = Ib/d
Unit Sludge Prod, x Sec. BOD5 Mass Removed = Sec. Sludge Mass
( Ib/lb) x ( i Ib/d) = Ib/d
Total Sludge Mass =
Ib/d
Calculate Expected Sludge Volume:
Method 1
_. . ... Prim. Sludge Mass
Sudge Volume = =-r—„, .? „
a Prim. Sludge Cone.
Ib/d)
( ,50,000 mg/l)
_. . ... Sec. Sludge Mass
Sludge Volume = Sec Sludge Conc.
x (120,000) =
Ib/d)
x (120,000) =
130,000 mg/l)
Total Sludge Volume =
Method 2
Total Sludge Volume
Total Sludge Mass
Total Sludge Conc.
Ib/d)
( 45,000 mg/l)
x (120,000) =
-gpd
-gpd
-gpd
-gpd
239
Trickling Filter
-------
Calculate Capacity of Sludge Handling Unit Processes:
1. Establish capacity of each existing sludge handling process (treatment and disposal). The
most common unit processes for which this calculation will have to be performed are:
Aerobic digestion
Anaerobic digestion
Gravity thickening
Mechanical dewatering
Drying beds
Liquid haul
For example, the capacity of a gravity thickener is the maximum sludge loading it can handle:
Thickener Loading = Total Sludge Mass
Thickener Surface Area
Ib/d) _
sqft)
Jb/d/sq ft
2. Determine percentage of the expected sludge production that each process can handle.
Process Capacity = Typical Process Loading
Actual Process Loading
Assume the sludge being thickened by the gravity thickener above is trickling filter. From
Table 3-9, 8 Ib/d/sq ft is considered typical loading for the thickener. Its capacity would
therefore be calculated as:
Ib/d/sq ft)
Ib/d/sq ft)
x ,(100) =
-percent
List Each Process and Its Associated Sludge Hand/ing Capacity and Identify the Lowest
Percentage Capacity:
Process
Percentage
Lowest Capacity =
percent
Trickling Filter
240
-------
Determine Sludge Handling Capacity Point Score:
50
% of Calculated Long-Term Average Sludge Production
75 100
I I
125
-10
I
I
I
15
Points
Sludge Handling Capacity Point Score
20
Add Scores 9 and 10 to Obtain Subtotal for Sludge Handling Capability:
Sludge Handling Capability Subtotal =
Compare Subtotals and Total Score with Following to Determine Whether POTWis Type 1,
Type 2, or Type 3:
"Aerator"
Secondary Clarifier |
Sludge Handling Capability
Total
"Aerator"
Secondary Clarifier !
Sludge Handling Capability
Total
Score
Points Required
Type 1 Type 2 Type 3
- (4)
- (8)
-(11)
17-23
17-30
0-11
0-16
0- 9
1 5-44
Type
Select the Worst Case: POTW is Type_
<0
<0
<0
<1 5
241
Trickling Filter
-------
Appendix N
RBC Major Unit Evaluation Worksheet
This worksheet is used to evaluate the capacity of existing major unit processes, i.e., aerator, secondary clarifier, and
sludge handling system. Key loading and process parameters are compared with standard values and point scores are
assigned. These points are subsequently compared with expected point scores for Type 1, Type 2, and Type 3 facilities
and a determination of the plant Type is made.
Instructions for Use:
• Proceed through the steps contained in this worksheet in order.
• Use actual values in lieu of calculations if such data are collected and available, e.g., waste sludge volume.
• When assigning points, interpolate and use the nearest whole number.
• Minimum and maximum point values'are indicated—do not exceed the range illustrated.
'Aerator'
Calculate First-Stage Loading:
_ .... First-Stage Soluble BOD5 Loading
Organic Loading - First.Stage Media Surface Area
or
_ . . .. (0.5) x (First-Stage BOD5 Loading)
Organic Loading - First.Stage Medja Surface Area
Ib/d)
sqft)
x (1,000) =
JbSBOD/d/1,000 sqft
Determine First-Stage Loading Point Score:
6.0
I
-6
' '
First-Stage Loading (Ib SBOD/d/1,000 sq ft)
4.0
L .
I '
0
Points
2.5
10
RBC
First-Stage Loading Point Score =_
242
-------
Calculate System Loading:
Organic Loading =
_ Total Soluble BODS Loading
Total Media Surface Area
or
Organic Loading =
(0.5) x (Total BOD5 Loading)
First-Stage Media Surface Area
Ib/d)
sqft)
x (1,000) =
JbSBOD/d/1,000 sqft
Determine System Loading Point Score:
1.5
System Loading (Ib SBOD/d/1,000 sq ft)
: 1.0
J I I I
I
I
0.6
I I II
-6
1 I r r
0
Points
r r \ \ \ \
10
System Loading Point Score =
Determine Number of Stages Point Score:
No. Stages
3
7
Points
10
Number of Stages Point Score =_
243
RBC
-------
Determine Anaerobic Side Streams Point Score:
Anaerobic Side Streams'*
Points
Not returned ahead of RBC 0
Returned to the wastewater stream ahead of the RBC -10
'Supernatant from anaerobic digesters or filtrate/concentrate from the dewatering
processes following anaerobic digesters.
Anaerobic Side Streams Point Score =
Add Scores 1, 2, 3, and 4 to Obtain Subtotal for "Aerator":
'Aerator" Subtotal =
©
Secondary
Clarifier
Determine Clarifier Configuration Point Score:
Configuration
Circular with "donut" or interior launders
Circular with weirs on walls
Rectangular with 33% covered with launders
Rectangular with 20% covered with launders
Rectangular with launder at or near end
Points
10
7
0
,-5
-10
Clarifier Configuration Point Score =_
Calculate Clarifier Surface Overflow Rate (SOR):
SOR =
Clarifier Effluent Flow
Clarifier Surface Area
gpd) _
sqft)
_gpd/sq ft
Determine SOR Point Score:
1,200
Surface Overflow Rate (gpd/sq ft)
1,000 800 650
I.I . I .
500
300
I
I
-15
i i i 11 i 11 i i rrrj i i i I I i i rn i i r r
-10 0 5 10
Points
15
SOR Point Score =
RBC
244
-------
Determine Depth at Weirs Point Score:
Depth at Weirs (ft)
7
1
! 10
I'-:'-! I
12
I
1
0
' ' I
3
; Points
I
5
Depth at Weirs Score =
®
Sludge Handling
Capability
Add Scores 5, 6, and 7 to Obtain Subtotal for Secondary Clarifier:
Secondary Clarifier Subtotal =
Determine Sludge Controllability Point Score:
Controllability ; !
Points
Automated sampling and volume control 5
Metered volume and hand sampling 3
Hand measured volume and hand sampling 2
Sampling or volume measurement by hand not practical 0
Sludge Controllability Point Score =
Calculate BOD5 Mass Removed:
Prim. BODsin - Prim. BOD5put = Prim. BOD5 Cone. Removed
mg/l) -|
mg/l) =
-mg/l
Prim. BODsout- POTW Eff. BOD5= Sec. BOD5 Cone. Removed
mg/l) -;
mg/l) =
mg/l
245
RBC
-------
Prim. BOD5 Cone. Removed x POTW Flow = Prim. BOD5 Mass Removed
mg/l) x (
gpd) x (8.34 x1CT6) =
Ib/d
Sec. BOD5 Cone. Removed x POTW Flow= Sec. BOD6 Mass Removed
{ mg/l) x ( gpd) x (8.34 x 1(T6) = Ib/d
Determine Typical Unit Sludge Production from Following:
Process Type
Ib TSS (sludge)/lb
BODs Removed
Primary Clarification
Trickling Filter
1.7
1.0
If plant records include actual sludge production data, the actual unit sludge production value
should be compared to the typical value. If a discrepancy of more than 15 percent exists between
the two values, further evaluation is needed. If not, use the actual unit sludge production value.
Calculate Expected Sludge Mass:
Unit Sludge Prod, x Prim. BOD5 Mass Removed = Prim Sludge Mass
( Ib/lb) x ( : Ib/d) = Ib/d
Unit Sludge Prod, x Sec. BOD5 Mass Removed = Sec. Sludge Mass
{ Ib/lb) x ( Ib/d) = Ib/d
Total Sludge Mass =
Ib/d
Calculate Expected Sludge Volume:
Method 1
„. . ... Prim. Sludge Mass
S udgeVo ume = ^-.—-„, ,9 ^
a Prim. S udge Cone.
Ib/d)
( 50,000 mg/l)
x (120,000) =
-gpd
RBC
246
-------
_, Sec. Sludge Mass
Sludge Volume = Sec. s,Udge Conc.
Ib/d)
x (120,000) =
( 30,000 mg/l)
Total Sludge Volume =
-gpd
-gpd
Method 2
._, . .. . Total Sludge Mass
Total Sludge Volume = Total S|udge Conc.
Ib/d)
45,000 mg/l)
x (1.20,000) =
-gpd
Calculate Capacity of Sludge Handling Unit Processes:
1. Establish capacity oi each existing sludge handling process (treatment and disposal). The
most common unit processes for which this calculation will have to be performed are:
Aerobic digestion
Anaerobic digestion
Gravity thickening!
Mechanical dewatering
Drying beds , :
Liquid haul
For example, the capacity of a gravity thickener is the maximum sludge loading it can handle:
Thickener Loading =\
Total Sludge Mass
Thickener Surface Area
Ib/d) _
sqft)
Jb/d/sq ft
2. Determine percentage of the expected sludge production that each process can handle.
Typical Process Loading
Process Capac.ty = Actual Process Loading
Assume the sludge being thickened by the gravity thickener above is mixed primary and RBC.
From Table 3-9, 15 Ib/d/sq ft is considered typical loading for the thickener. Its capacity
would therefore be calculated as:
15
Ib/d/sq ft)
Ib/d/sq ft)
247
x (100) =
.percent
RBC
-------
List Each Process and Its Associated Sludge Handling Capacity and identify the Lowest
Percentage Capacity:
Process
Percentage
Lowest Capacity =
percent
Determine Sludge Handling Capacity Point Score:
50
% of Calculated Long-Term Average Sludge Production
75 100
I
-10
15
Points
Sludge Handling Capacity Point Score =
125
20
Add Scores 10 and 11 to Obtain Subtotal for Sludge Handling Capability:
Sludge Handling Capability Subtotal =
RBC
248
-------
Compare Subtotals and Total Score with Following to Determine Whether POTWis Type 1,
Type 2, or Type 3:
"Aerator"
Secondary Clarifier
Sludge Handling Capability
Total ;
"Aerator"
i
Secondary Clarifier j
Sludge Handling Capability
Total
Points Required
Score
Type 1
(5)
-(12)
14-30
17-30
10-30
48-90
Type
Type 2
Type 3
0-13
,- 0-16
0-9
1 5-47
<0
<0 ,
<0
<1 5
Select the Worst Case: POTW is Type_
249
RBC
-------
Appendix O
ABF Major Unit Evaluation Worksheet
This worksheet is used to evaluate the capacity of existing major unit processes, i.e., aerator, secondary clarifier, and
sludge handling system. Key loading and process parameters are compared with standard values and point scores are
assigned. These points are subsequently compared with expected point scores for Type 1, Type 2, and Type 3 facilities
and a determination of the plant Type is made.
Instructions for Use:
• Proceed through the steps contained in this worksheet in order.
• Use actual values in lieu of calculations if such data are collected and available, e.g., waste sludge volume.
• When assigning points, interpolate and use the nearest whole number.
• Minimum and maximum point values are indicated—do not exceed the range illustrated.
'Aerator"
Calculate Biocell Organic Loading:
Organic Loading =
BODs Loading
Biocell Media Volume
Ib/d)
cuft)
x (1,000)
JbBODs/d/1,000 cuft
Determine Biocell Organic Loading Point Score:
Organic Loading (Ib BOD5/d/1,000 cu ft)
300 250 200 175 150
I I I I. I I I I I I I I I I I | I
100
I I I
I ' '
-10
-5
I I I I
0
Points
I I I I
5
I 1 1 T
10
15
ABF
Organic Loading Point Score =
250
-------
Calculate Aeration Basin Detention Time:
Aeration Basin Aeration Basin Volume
Detention Time Average Daily Wastewater Flow
cuft)
gpd)
x (180) =
_hr
Determine Aeration Basin Detention Point Score:
Aeration Basin Detention Time (hr)
0.5 0.75 , 1 2
I I I I I I I I I
I
-10
I I I I I I I
5 12
Points
' '
15
20
Aeration Basin Detention Point Score =
Calculate Oxygen Availability:
If data are not available oh oxygen transfer capacity, calculate it as Wire Horsepower (Appendix E)
times actual Oxygen Transfer Rate (Appendix F).
_hp) x
Jb/hp-hr) x (24) =
Jb/d
Oxygen Availability =
Transfer Capacity
Biocell BODS Loading
Ib/d) _
Ib/d)
O2/lb BOD5
Determine Oxygen Availability Point Score:
0.3
Oxygen Availability (Ib O2/lb BOD5)
0.4 0.5 0.75
r i , i i ,
1.0
I I I I I I I I I I I I 1 I I I I I
-15 0
| I I I |
3 7
Points
\ I
10
Oxygen Availability Point Score =
251
ABF
-------
Calculate Recirculation Ratio:
Recirculation Ratio =
Return Flow
Average Daily Wastewater Flow
gpd) _
gpd)
:1
Determine Recirculation Ratio Point Score:
None
I
Recirculation
0.5:1
I 1 1
1:1
I
I
0
1 2
I
3
Points
Recirculation Ratio Point Score =
Secondary
Clarifier
Add Scores 1,2,3, and 4 to Obtain Subtotal for "Aerator":
Determine Clarifier Configuration Point Score:
Configuration
Circular with "donut" or interior launders
Circular with weirs on walls
Rectangular with 33% covered with launders
Rectangular with 20% covered with launders
Rectangular with launder at or near end
'Aerator" Subtotal =
Points
10
7
0
-5
-10
Clarifier Configuration Point Score =_
Calculate Clarifier Surface Overflow Rate (SOR):
SOR =
Clarifier Effluent Flow
Clarifier Surface Area
gpd) _
sqft)
_gpd/s$ ft
ABF
252
-------
Determine SOR Point Score:
1,200
I
l^
-15
Surface Overflow Rate (gpd/sq ft)
1,000 800 650
I.I . I .
1 1
-10
500
300
1
1 I I
7 I I
Points
10
T T r-j
15
SOR Point Score =
Determine Depth at Wefrs Point Score:
Depth at Weirs (ft)
10
12
1
II 1
1 1
1
0
1
3
i Points
1
£
Depth at Weirs Score =
Calculate Recommended PAS Flow Range:
Min. Typical Typical RAS Rate x POTW Flow = Min. Recommended RAS Flow
( 25 %) x (
gpd) x (0.01) =
-gpd
Max. Typical Typical RAS Rate x POTW Flow = Min. Recommended RAS Flow
( 75 %) x (
gpd) x (0.01) =
-gpd
Determine Actual RAS Flow Range:
Minimum Actual RAS Flow =
-gpd
Maximum Actual RAS Flow =
-gpd
253
ABF
-------
Determine HAS Control Point Score:
RAS Control
Points
The actual RAS flow range is completely within the recommended
RAS flow range and the capability to measure RAS flow exists
The actual RAS flow range is completely within the recommended
RAS flow range but the capability to measure RAS flow does not exist
50% of the recommended RAS flow range is covered by the actual
RAS flow range and the capability to measure RAS flow exists
50% of the recommended RAS flow range is covered by the actual
RAS flow range but the capability to measure RAS flowdoes not exist
The actual RAS flow range is completely outside the recommended
RAS flow range
10
7
5
0
-5
RAS Control Point Score =
Add Scores 5,, 6. 7. 8, and 9 to Obtain Subtotal for Secondary Clarifier:
Secondary Clarifier Subtotal =
Sludge Handling
Capability
Determine Sludge Controllability Point Score:
Controllability
Points
Automated sampling and volume control 5
Metered volume and hand sampling 3
Hand measured volume and hand sampling 2
Sampling or volume measurement by hand not practical 0
Sludge Controllability Point Score =
Calculate BOD5 Mass Removed:
Prim. BODsin- Prim. BOD5out= Prim. BODS Cone. Removed
mg/l) - (
mg/l) =
-mg/l
Prim. BODsout - POTW Eff. BOD5 = Sec. BOD5 Cone. Removed
mg/l) - (
mg/l) =
.mg/l
ABF
254
-------
Prim. BODs Cone. Removed x POTW Flow = Prim. BODS Mass Removed
( mg/l) x { gpd) x (8.34 x 1CT6) = Ib/d
Sec. BODs Cone. Removed x POTW Flow = Sec. BOD5 Mass Removed
mg/l) x (
-61 _
gpd) x (8.34x10-°) =
.Ib/d
Determine Typical Unit Sludge Production from Following:
Process Type
Ib TSS (sludge)/lb
BOD5 Removed
Primary Clarification
Trickling Filter
1.7
1.0
If plant records include actual sludge production data, the actual unit sludge production value
should be compared to the typical value. If a discrepancy of more than 15 percent exists between
the two values, further evaluation is needed. If not, use the actual unit sludge production value.
Calculate Expected Sludge Mass:
Unit Sludge Prod, x PrimJ BODs Mass Removed = Prim Sludge Mass
( Ib/lb) x (_ Ib/d) = Ib/d
I
Unit Sludge Prod, x Sec. BOD5 Mass Removed = Sec. Sludge Mass
( Ib/lb) x (_ Ib/d) = Ib/d
Tptal Sludge Mass
Calculate Expected Sludge Volume:
Method 1 l
Jb/d
„. . ... Prim. Sludge Mass
Sludge Volume = Prjm Slud*e Conc.
Ib/d)
50,000
mg/l)
x (120,000) =
-gpd
255
ABF
-------
„. . ... Sec. Sludge Mass
Sludge Volume = Sec. S|udg9e Conc.
Ib/d)
12,000
mg/l)
x (120,000) =
-9Pd
Total Sludge Volume =
-gpd
Method 2
-r ,^, j w i Tota Sludge Mass
Tota S udgeVo ume = T x , „, *—^
Tota Sludge Conc.
Ib/d)
( 35,000 mg/l)
x (120,000) =
-gpd
Calculate Capacity of Sludge Handling Unit Processes:
1. Establish capacity of each existing sludge handling process (treatment and disposal). The
most common unit processes for which this calculation will have to be performed are:
Aerobic digestion
Anaerobic digestion
Gravity thickening
Mechanical dewatering
Drying beds
Liquid haul
For example, the capacity of a gravity thickener is the maximum sludge loading it can handle:
,.. . . . .. Total Sludge Mass
Th,ckenerLoadmg = Tnickener Su*face Area
Ib/d) _
sqft)
Jb/d/sq ft
2. Determine percentage of the expected sludge production that each process can handle.
„ _ . Typical Process Loading
Process Capacity = -^r—T~E i—?~~^
Actual Process Loading
Assume the sludge being thickened by the gravity thickener above is ABF. From Table 3-9,4
Ib/d/sq ft is considered typical loading for the thickener. Its capacity would therefore be
calculated as:
Ib/d/sq ft)
Ib/d/sq ft)
x (100) =
-percent
ABF
256
-------
List Each Process and Its Associated Sludge Handling Capacity and Identify the Lowest
Percentage Capacity:
Process
Percentage
Lowest Capacity =
percent
Determine Sludge Handling Capacity Point Score:
% of Calculated Long-Term Average Sludge Production
50 75 100 125
I I \ I
I
-10
15
Points
Sludge Handling Capacity Point Score =
I
20
Add Scores 11 and 12 to Obtain Subtotal for Sludge Handling Capability:
Sludge Handling Capability Subtotal =
257
ABF
-------
Compare Subtotals and Total Score with Following to Determine Whether POTW is Type 1,
Type 2, or Type 3:
"Aerator"
Secondary Clarifier
Sludge Handling Capability
Total
"Aerator"
Secondary Clarifier
Sludge Handling Capability
Total
Select the Worst Case: POTW is Type.
Score
(K)
(in)
(13)
Type
5 Typp
Points Required
Type 1 Type 2 Type 3
15-48 0-14 <0
20-55 0-19 <0
10-30 0- 9 <0
50-133 15-49 <15
ABF
258
• Ua. flOVtflNMENTJWmNO OFFICE; 1M4- 759-102/10645
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