xvEPA
           United States
           Environmental Protection
           Agency
          Municipal Environmental Research
          Laboratory
          Cincinnati OH 45268
EPA-600/9-83-021
December 1983 ^
            Research and Development
Operation and
Maintenance of
Publicly-Owned
Treatment Works
(POTW's):

Proceedings of the
EPA National
Conference

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                                        EPA-600/9-83-021
                                        December 1983
        OPERATION AND MAINTENANCE OF

   PUBLICLY-OWNED TREATMENT WORKS (POTW's)
             PROCEEDINGS OF THE
           EPA NATIONAL CONFERENCE

              Chicago,  Illinois
             January 12-14, 1982
              Sponsored by the

 Municipal Environmental Research Laboratory
                     and
Center for Environmental Research Information
    U.S. Environmental Protection Agency
               Administered by

             Roy F.  Weston, Inc.
      West Chester,  Pennsylvania  19380
           Contract No. 68-03-3055
               Project Officer

                Gary R. Lubin
        Wastewater Research Division
 Municipal Environmental Research Laboratory
           Cincinnati, Ohio  45268
 MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
     OFFICE OF RESEARCH AND DEVELOPMENT
    U.S. ENVIRONMENTAL PROTECTION AGENCY
           CINCINNATI, OHIO  45268

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                                 DISCLAIMER
     Mention of trade names or commercial products does not  constitute
endorsement or recommendation for use by the U.S.  Environmental  Protection
Agency.
                                     ii

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                                  FOREWORD
     The Environmental Protection Agency was created because of  increasing
public and governmental concern about the dangers of pollution to  the  health
and welfare of the American people.   Noxious air,  foul water, and  spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of the environment and the interplay between its  components
require a concentrated and integrated attack on the problem.

     Research and development is the first necessary step in problem solution;
it involves defining the problem, measuring its impact,  and searching  for
solutions.  The Municipal Environmental Research Laboratory develops new and
Improved technology and systems to prevent, treat, and manage wastewater and
the solid and hazardous waste pollutant discharges from municipal  and  com-
munity sources; to preserve and treat public drinking water supplies,  and to
minimize the adverse economic, social, health and aesthetic effects of pollution.
This publication is one of the products of that research—a vital  communications
link between the researcher and the user community.

     These Proceedings present information on improved POTW operation, main-
tenance, design, performance and energy effectiveness.
                                      Francis T. Mayo
                                      Director
                                      Municipal Environmental
                                        Research Laboratory
                                     iii

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                                 PREFACE
     This proceedings is a compilation of the papers presented at EPA's
National Conference on the Operation and Maintenance of POTW's held in
Chicago, Illinois on January 12-14, 1982.  The purpose of the conference
was to present information on improved POTW operation, maintenance, design,
performance and energy effectiveness.  Most of the information presented
at this conference was based upon results from research funded through
the Plant Operation and Design Program of EPA's Municipal Environmental
Research Laboratory, Wastewater Research Division in Cincinnati, Ohio.

     This proceedings is intended to provide a permanent record of the
information presented at this conference and to make those involved in
POTW operation, maintenance, and design aware of the type of research
funded through EPA's Plant Operation and Design Program.  The conference
was organized into five different sessions corresponding to major areas
of program interest.

     All of the papers and final reports resulting from the research
funded by the Plant Operation and Design Program are listed in a separate
reference section of this proceedings.  Copies of the material listed in
the reference section are not generally available through the Environmental
Protection Agency.  Most of these references are only available through
the National Technical Information Service  (NTIS), 5285 Port Royal Road,
Springfield, VA  22161 unless they are part of a published periodical.
                                   IV

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                        TABLE OF CONTENTS
                              TITLE
Foreword
Preface

Session No. 1
     Paper No. 1
     Paper No. 2
     Paper No. 3
Session No. 2
     Paper No. 4
     Paper No. 5
     Paper No. 6
     Paper No. 7
O&M of Wastewater Treatment
Processes

"Results of National O&M Cause
and Effect Survey,"
Bob A. Hegg

"A Model Protocol for the
Comprehensive Evaluation
of POTW's,"
Albert C. Gray and Hugh D. Roberts

"Operation and Maintenance
Considerations of Land
Treatment Facilities,"
Kimm Perlin

Improving the Performance of
Conventional Wastewater
Treatment Processes

"Making-Do with Clarifier
Hydraulic Overload,"
Robert M. Crosby

"Minimizing Impact of Side Streams
on Total Plant Performance,"
Roy 0. Ball

"Composite Correction Program -
Concepts and Demonstration,"
Bob A. Hegg

"Application of Intrachannel
Clarifiers in the Oxidation
Ditch Process,"
Harold J. Beard
                                        PAGE

                                         iii
                                          iv
 14
 42
 63
 63
 78
 95
105

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                        TABLE OF CONTENTS
                           (Continued)
     Paper No. 8



Session No. 3

     Paper No. 9



     Paper No. 10
     Paper No. 11


Session No. 4

     Paper No. 12


     Paper No. 13




     Paper No. 14



Session No. 5


     Paper No. 15



     Paper No. 16
        TITLE                           PAGE

"Biological Fouling of Fine              119
Bubble Diffusers,"
William C. Boyle and David T. Redmon

Improving Process Reliability            136

"Stability and Reliability of            136
Biological Processes,"
Edward D. Schroeder and Salar Niku

"Evaluation and Documentation of         159
Mechanical Reliability of
Conventional Wastewater Treatment
Plant Components,"
David W. Shultz and Van B. Parr

"Fail Safe Design Concepts,"             171
Roy 0. Ball

Improving POTW Design                    176

"Design Deficiencies in POTW's,"         176
Roy 0. Ball

"Performance Capabilities and            182
Design of Oxidation Ditch
Processes,"
William F. Ettlich

"Performance and Design of               195
RBC Processes,"
Warren H. Chesner

Energy Conservation in Municipal         201
Wastewater Treatment

"Energy Conservation in Unit             201
Processes and Sludge Management,"
Daniel Cortinovis

"A Composite Approach to Energy          210
Conservation Through Process
Optimization - Some Case Studies,"
Ashok K.  Singhal,  Phillip N.  Loud
and Donald W.  Lystra
                               vi

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                        TABLE OF CONTENTS
                           (Continued)
                              TITLE                           PAGE

     Paper No.  17     "Alternative Energy Sources in           232
                      Municipal Wastewater Treatment:
                      the Wilton,  Maine Experience,"
                      David R. Fuller

Reference Section:     Plant Operation and Design Program -     255
                      Related Publications and Papers
                               vii

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SESSION NO. 1
   O&M of Wastewater Treatment Processes
                                PAPER NO.  1
                          RESULTS OF NATIONAL O&M

                            CAUSE AND EFFECT SURVEY
                                    by
                                Bob A. Hegg
                  Vice President Plant Operations  Division
                      M & I,  Inc., Consulting Engineers
                          4710  South College Avenue
                       Fort Collins, Colorado  80525

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RESULTS OF NATIONAL 0 & M CAUSE AND EFFECT SURVEY

Bob A. Hegg ,  Vice President Plant Operations Division
M & I, Inc., Consulting Engineers
INTRODUCTION

     The  Federal  Water Pollution  Control  Act with  Amendments established
goals for the quality of the nation's public waters.  A major aspect of the
act was  an  expanded construction grants activity  through which new waste-
water  treatment  facilities  were constructed  and  existing  facilities  up-
graded.   However, the U.S. Environmental Protection  Agency's  (EPA) annual
reports  to  Congress (1) have  indicated that  a  significant number  of  the
facilities constructed with  Federal  grant  assistance  have not  provided  the
desired effluent  quality.  Other reports and articles have supported these
conclusions (2, 3, 4).

     In  response  to these  findings, EPA1s  Office  of  Research  and Develop-
ment  initiated  a  three  and  one-half year  research  program  to  identify,
quantify  and rank the  factors  causing poor wastewater treatment plant per-
formance.  M &  I, Inc.,  Consulting Engineers  was  selected to  complete  the
two-phase project  in the Western United  States.  To accomplish  the research
objectives, comprehensive plant  evaluations were conducted in  facilities in
nine Western states.   Initially, 271 facilities  were considered for study.
Ninety-eight were visited and  fifty were selected  for comprehensive studies
(5, 6, 7).

RESEARCH APPROACH

     The major  objective of  the  project was to  identify  and rank the fac-
tors causing poor wastewater treatment plant performance.  Because a limit-
ed number of  facilities  were  studied,a  specialized  plant selection proce-
dure was  established.   The major  target of facility  selection was plants
that were supposedly developed to meet specific treatment requirements.   As
such, "operable plants" which were loaded within currently used design cri-
teria, which were operated using  reasonable  staffing levels  and  were  not
having major equipment problems  with critical  process units were  selected.
Additional selection  criteria  limited the  facilities  to biological waste-
water treatment plants with  flows  less  than 37,850 cum/day (10 mgd) and to
plants not involved in enforcement action.

     EPA  Regions   VII  and  VIII  and  nine   state  regulatory agencies  were
informed of the plant selection criteria.  These agencies suggested a total
of 271 facilities  for research.  Of the  facilities suggested, half-day site
visits were  conducted at 98  facilities.   Fifty of  these  facilities were
selected for the more comprehensive studies.  Both plants that  were meeting
treatment requirements and  plants  that did  not meet   requirements  were
selected.

     The comprehensive plant evaluations were  typically  conducted with  one
and one-half  to  two  man-weeks of  effort  over  a  four to  ten-day  period.

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Persons conducting the surveys were sanitary engineers with experience in
plant operations and in identifying and evaluating performance-limiting
problems.  During each evaluation the research team worked with plant per-
sonnel to eliminate any obvious and controllable performance-limiting prob-
lems.  This action-oriented, assistance approach to data gathering necessi-
tated open communication between plant personnel and research personnel.
As such, a service to the plant owner was provided while more accurate and
less apparent research information was collected.

     Each in-plant evaluation was followed by a written report which docu-
mented the problems identified.  Recommendations to the city or sanitation
district were offered, but implementation of these was voluntary.

     Problems limiting plant performance were evaluated using a list of 71
pre-defined factors.  Each factor was assigned from zero to three points  in
proportion to the adverse effects that factor had on an individual plant's
performance.  The results from all individual surveys were combined to
obtain an overall ranking of these factors.

PRESENTATION OF DATA

     Only 13 of 50 facilities surveyed consistently met minimum secondary
treatment standards as defined in CFR 38-159.  The mean hydraulic loading
on all plants surveyed was 66 percent of design flow.  The mean hydraulic
loading for the 37 facilities that violated standards was also 66 percent
of design flow.  These loadings were in line with plant selection criteria,
in that the plants studied were within design limits and supposedly were
capable of meeting required effluent standards.

     Table  1 shows the ranking of all 71 factors for the 50 facilities
evaluated.  The number of times each factor occurred is also shown.  An
average of  13 and a range of 4 to 30 performance-limiting factors were
documented at individual facilities.  Many different performance-limiting
factors were noted, and no two facilities had an identical combination of
factors.

     The two highest ranking factors were inadequate operator application
of concepts and testing to process control and inadequate sewage treatment
understanding.  These findings indicate that many operators were not ade-
quately trained.  It could be concluded that expanded training programs are
necessary, but it was observed that "trained" operators did not properly
apply concepts of operation to process control.  Therefore, expanded train-
ing  appears necessary, but modifications to existing programs are needed.
Any  attempt to modify and improve training must include a full awareness  of
the  number three ranked factor, improper technical guidance concerning
plant operations.  Improper technical guidance was documented from authori-
tative sources including design engineers, state and federal regulatory
personnel, operator training program staff, other plant operators and
equipment suppliers.

     These findings indicate that other sources have limited the capability
of operators:  first to attain adequate sewage treatment understanding and

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TABLE 1.  RANKING OF FACTORS LIMITING PERFORMANCE
£
8
i


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
31


32
33
34

35
36

M «
1


2
3

4
5

5
7
8

8

10
11
12

13


14
15
15
15
18


19
19
21
22
22
22
25
25
27

27
27

27
31


31
33
33

33
33

Factor
Limiting
Performance
Operator Application of Concepts
and Testing to Process Control

Sevage Treatment Understanding
Technical Guidance

Sludge Vasting Capability
Process Control Testing

Process Controllability
Process Flexibility
Aerator

Infilt ration/Inflow

Clarifier (Secondary)
Ultimate Sludge Disposal
Sludge Treatment

Familiarity with Plant Needs
(Adminstrators)

Performance Monitoring
Policies (Administrators)
Laboratory Space and Equipment
Disinfection
Plant Coverage


Unit Process Layout
Preliminary (Design)
forking Conditions
Equipment Malfunction
Alternate Power Source
Alarms Systems
Motivation (Operators)
Number (Staff)
Scheduling and Recording
(Maintenance)
Adequacy (0 & M Manual)
Productivity (Operators)

Aptitude (Operators)
Return Process Streams


Training Operators
Industrial (Loading)
Insufficient Funding

Housekeeping
Pay (Operators)

,. :s
O • O V*
O-«« « V
KHK.C5
48


28
25

26
32

32
24
17

24

16
19
19

11


16
10
16
11
15


7
15
12
8
13
13
12
11
11

10
9

8
7


9
6
9

8
7

A.
3
96


55
54

51
47

47
45
35

35

28
27
24

20


18
17
17
17
16


15
15
14
13
13
13
12
12
11

11
11

11
10


10
9
9

9
9

8
4J
37

38
39

40
41

42
43
44

45

46
47
48

49


50
51
52
53
54

55


56
57
58
50
60
61
62
63

64
65


66
67


68
69
70


71
m
MB.
e
37

38
38

38
41

41
41
41

41

46
46
46

49


49
51
52
52
52

52


52
52
58
58
58
58
58
63

63
63


63
63


63
63
63


63
Factor o
Limiting ^
Performance *
Plant Inoperability Due to Weather

Lack of Unit Bypass
Flow Proportioning to Units

Supervision


Equipment Age
Insufficient Time on Job
Lack of Program (Maintenance)

Manpower (Maintenance)

Unnecessary Expenditures

Flow Backup

Plant Management


Plant Location
Hydraulic (Loading)
Toxic (Loading)
8

Lack of Standby Units for Key
Equipment

Process Automation Control
0 & M Manual, Use by Operators
Quality of Equipment
Level of Education
Organic (Loading)
Submerged Heirs
Bond Indebtedness

References Available
Staff Expertise (Emergency
Maintenance)

Critical Parts Procurement
Technical Guidance (Emergency
Maintenance)

Unit Design Adequacy, Primary
Process Automation, Monitoring
Equipment Accessibility for
Maintenance)

Shift Staffing Adequacy
Times
Factors
Occurred II
6

7
6

5


6
5
5

5

5
5
3

2


3
3
2

2
2


2
2
1
1
1
1
1
0

0
0
0

0
0


0
0
0


0
£
g
8

7
7

7
£

6
6
6

6

5
5
5

4


4
3
2


2


2
2
1
1
1
1
1
0

0
0
0

0
0


0
0
0


0

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second to apply this understanding to process control.  Just as important,
the improper technical guidance and associated lack of understanding by
authoritative personnel has carried over into plant design.  Five of the
top ten factors limiting performance were process design oriented.  These
areas of inadequate design in order of severity were:  sludge wasting cap-
ability, process controllability, process flexibility, aerator and secon-
dary clarifier.  The inability of persons involved with plant design to
properly apply the technology necessary to develop adequate treatment
facilities, coupled with the improper operations technical guidance from
these and other sources, indicates that the plant performance problem is
widespread and not limited to strictly plant personnel.

     This analysis of the top ten performance-limiting factors indicates
that problems limiting facility performance are interrelated, and a
straight forward approach to improved performance by addressing these fac-
tors is not readily apparent.  Other evaluations of selected individual
factors support this conclusion.  The approach used to evaluate other fac-
tors was to relate the potential problem area to plant performance.  Sever-
al prominently discussed factors were evaluated using this approach:  plant
staffing, operator salaries, aerator size and operator certification.

     Figure 1 shows staff size plotted versus plant flow rate.  As shown by
the least squares line of best fit, staff size increased with plant flow.
The thirteen fully shaded dots represent the plants where secondary treat-
ment standards were met.  If a larger number of operations personnel was
                 100
              tL
              tu
              ta
              2
              u.
              u.
              <
              CO
              l-
              o
10
                  1.0
                 0.1
                     • STANDARDS MET
                     O STANDARDS NOT MET
                     M3/DAY ' MGD » 3785
                     O -
                   .01           0.1           1.0           10

                          PLANT FLOW  RATE -MGD
               Figure 1.   Staff Size versus Plant Flow Rate

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the  key  to  the  solution  of  the  plant performance  problem,  shaded  dots
representing plant where standards were met  would  tend to be located above
the  line of  best  fit.  Six  of  thirteen points  are  below the  line,  and a
correlation between plant staffing and performance could not be made.

     A similar  analysis was  performed for  staff  salaries.   As  shown  in
Figure 2, higher salaries  did not  appear  to  correlate directly with better
treatment.
      O
      O
      oc
      V)
      u.
      ML
      CO
20


18


16


14
          12
          10
             • STANDARDS MET
             O STANDARDS NOT MET
             M3/DAV - MOD x 3T8S
                                                        O

                                                        O  O
            .01
                  0.1              1.0
             PLANT  FLOW  RATE- M6D
10
            Figure 2.  Staff Salary versus Plant Flow Rate
      Aerator  loadines in  oounds  of ^005 per  day per 1000  cubic feet  are
 presented  in Figure  3.   As  used  here,  "aerator"  refers  to the  facility
 utilized  for  the conversion  of  soluble  organic  matter  into  settleable
 organic  matter.   Examples  of  aerators  are  trickling  filters,  activated
 sludge  aeration basins and  activated  bio-filters.   The extreme  scatter  of
 data  did  not lend itself  to a  line of best  fit; however, aerator  loading
 appears  to  increase  gradually as  plant  flow rate  increases.   Nine of  the
 thirteen plants that  met standards had  low aerator loadings, less  than  15
 Ib  BOD5/day/1000 cu ft.   A  premature  conclusion  could be that  low  aerator
 loadings are  a  key to improved performance,  and therefore  more  conservative
 design  criteria  are  needed.  However,  just  as  many  facilities with  low
 aerator  loadings  violated  secondary  effluent  standards.   A  conservative
 design  approach  may  help,  but  it  is not  reliable  in  achieving  desired
 performance.   It  is  also  suggested that improved performance through very
 conservative  design is not  the most cost  effective  alternative.

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"• 80
0
O
2 70
^.
< 60
O
o
r
.01 0.1 1.0 1<

                         PLANT  FLOW RATE - MGD
            Figure 3.  Aerator Loading versus Plant Flow Rate

     The relationship between operator certification and plant performance
is summarized in Table 2.  Only 40 percent of the facilities which had "A"
and "B" certified operators were found to be meeting effluent standards.

     This was a higher percentage than for the lower and noncertified
operator's facilities.  Certification of treatment plant operators seems  to
be a step in the right direction, but it too does not appear to be the
total answer.

TABLE 2.  EVALUATION OF OPERATOR CERTIFICATION VERSUS PLANT PERFORMANCE
Certification Class
         Of
                           Number of
Secondary Treatment Standards
Chief Operator*
"A"
"B"
"C"
"D"
None
Facilities Surveyed
15
10
9
9
7
Met
6
4
1
1
1
Violated
9
6
8
8
6
%Met
40
40
11
11
14

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     Evaluation of the data collected indicated  that each  facility was
typically limited from achieving good performance by a  combination of
factors unique to that facility.  Evaluations of high ranking  factors did
not lead to any positive conclusions regarding methods  to  improve indivi-
dual plant performance on a broad scale.

UNIFIED CONCEPT FOR ACHEIVING OPTIMUM PLANT PERFORMANCE

     Many programs and activities are available  that deal  with correcting
the performance limiting factors at wastewater treatment facilities.
Examples are operator training schools, operator certification programs,
the NPDES permit program, Federal and State construction grant programs,
design seminars, 0 & M manuals, and regulatory agency inspections.  All of
the facilities evaluated had participated  in one or more of  these activi-
ties; however, in most cases the implementation  of these programs did not
result in a particular plant achieving  a desired level  of  performance.
Apparently, the combinations of factors unique to each  facility were not
compatible with or were not adequately  addressed by the programs that had
been implemented, and several performance-limiting factors continued to
degrade plant effluent quality.

     The interrelationship between factors limiting performance and pos-
sible solutions was further defined for the research project in a "Unified
Concept for Achieving Optimum Plant Performance."  The  Concept is illus-
trated in Figure 4.  The goal is tc obtain an optimum performance level for

                                   GOAL
                            OPTIMUM  PERFORMANCE
                                            PLANT
                                            POSITION 2
/
                            T

\P
                                                    PLANT
                                                    POSITION i
                         FACTORS  LIMITING PERFORMANCE
                             • ADMINISTRATION
                             •MAINTENANCE
                             • OPERATION
                             •DESIGN
                        Figure 4.   Unified Concept

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a given treatment plant.  The horizontal line represents the position of a
treatment facility with respect to optimum performance.  The length of the
horizontal line represents the combined magnitude of all factors limiting
performance at that plant.  Administrative, maintenance, operation and/or
design factors that limit performance tend to increase the length of the
horizontal line and move a plant away from the goal  (Plant Position 1).
These factors are indicated by the number and length of arrows pointing
downward.

     Performance limiting factors are typically addressed through implemen-
tation of programs such as enforcement, a construction grant, an operator
training program, etc.  Correction of a factor or group fo factors moves a
plant's position closer toward the goal of optimum performance.  However,
if all the performance-limiting factors are not addressed, the plant will
only move to Position 2.  At Position 2 the length of the horizontal line
is shorter indicating fewer or less severe performance-limiting factors
remain, but optimum performance has not been achieved and effluent quality
may or may not meet requirements.

     The Concept can be illustrated with an example.  Assume that a plant's
performance was severely limited  (Position 1) by two factors:  a hydraulic
overload and poor process control.  If the plant's overload problem was
corrected through a plant modification supported by  a construction grant
but poor process control continued, the plant's position would improve
(Position 2) but the plant would not achieve optimum performance.  This
example illustrates why many programs have not been  able to achieve desired
performance at a particular facility:  all the factors significantly limit-
ing performance at that facility were not corrected.

COMPOSITE CORRECTION PROGRAM

     Ideally, optimum performance can be achieved only if all of the fac-
tors limiting performance are corrected.  This objective can be more
directly and positively addressed by implementing a  single comprehensive
program at each facility.  In such a manner, the comprehensive program can
address the factors limiting performance unique to that facility.  This
approach has been termed a Composite Correction Program (CCP) and is con-
ceptually illustrated in Figure 5.

     As illustrated, a CCP addresses all the performance-limiting factors
at a particular facility  (Plant Position 1), and can thus ideally achieve
optimum plant performance.  To demonstrate this approach, a CCP was imple-
mented at Havre, Montana, as a part of the research  project.  A separate
report was prepared describing the implementation and results  (6).  Plant
effluent BOD^ and TSS concentrations are shown in Figure 6, and are indi-
cative of the capability of the CCP approach to improve performance of an
individual facility plagued by  various  unique  combinations  of factors.

     A CCP could not be implemented  at  all  of the facilities  surveyed
because the combination of factors limiting performance was  not usually
amenable  to correction within  the budget  constraints of the  research
project.   However,  sufficient  data was  collected at  each research facility

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                         GOAL
                 OPTIMUM PERFORMANCE
                                 PLANT
                                 POSITION 2
                   COMPREHENSIVE
                      APPROACH

                       T
T
 PLANT
yosmoN 1
              FACTORS  LIMITING  PERFORMANCE
                  •ADMINISTRATION
                  •MAINTENANCE
                  • OPERATION
                  •DESIGN
Figure 5.  Unified Concept - Composite Correction Program
                                                1980
   Figure 6.   Results of CCP  approach - Havre, Montana
                           10

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to project the probable results of implementing a CCP.  A dramatic  improve-
ment in overall performance would occur.  Table 3 presents  a  summary of  the
performance  of the  fifty facilities  evaluated  in relation  to secondary
treatment standards.   CCP's without  major facility upgrades could  allow 27
additional plants to meet  secondary  treatment.   Ten plants would require a
major upgrade as part  of the CCP in  order to meet secondary standards.

              TABLE 3.  PERFORMANCE  OF FIFTY PLANTS EVALUATED
	VERSUS SECONDARY TREATMENT  STANDARDS	

                              Prior  to Research   Potential After CCP*

Standards Violated                   37                     10
Standards Met                        13                     40
*In this evaluation the option of a major facility upgrade was excluded as
 a portion of the CCP.

     An  evaluation  of all facilities  surveyed  showed  that  the performance
of 38 facilities could  be improved  using the CCP approach (excluding major
facility  modifications).    The projected  average improvement  in effluent
quality  was  25  mg/1  for  BOD^ (59  percent  decrease)  and 46 mg/1  for TSS
(63 percent decrease).

     The CCP approach provides a viable method  for improving plant perform-
ance  at individual  treatment facilities  and  should  be implemented  on  a
broad scale.  However,  incentives are  needed  to encourage the use of CCP's,
and qualified personnel are  required  to  implement CCP's (5,  6).  Personnel
who  implement  CCP's must   be  able   to  recognize  and  prioritize  actual
performance-limiting  factors  in  the  broad  areas  of  design,  operation,
maintenance and  administration.   These persons must then be  in a position
to implement recommendations  over a  long enough time period  to insure that
desired  performance is  achieved and maintained.  A properly implemented CCP
utilizes all available  resources to economically correct  the unique combin-
ation of factors limiting performance  at a particular  facility.

CONCLUSIONS AND RECOMMENDATIONS

     Conclusions of the research effort were  separated  into two categories:
conclusions on all  facilities  and conclusions concerning individual treat-
ment plants.  For all facilities, it was determined that  individual facili-
ties are hindered  from achieving desired  performance   by multiple  factors
unique to each facility.  As such, specific programs implemented to address
selected  factors at  all facilties will have  a limited correlation between
program  implementation  and improved performance at individual plants.  This
conclusion  is  significant   in  that   large   scale  programs  normally  are
assessed on  their  most  obvious  intended impact.   It   is  thus  conceivable
that programs could  be  excluded  from  development  or eliminated because of
their inability to show a direct correlation between program implementation
and improved plant  performance.   Yet  these programs may be  very necessary


                                    11

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to  address  the  high ranking and  frequently occurring  performance limiting
factors identified.

     For  individual  plants  it  was  concluded  that  multiple  and  unique
factors  limit  a  facility's  performance.    The scope of  these  factors  is
often  beyond  the plant operator's  control  (i.e.,  improper  technical  gui-
dance  and  design deficiencies).   To  achieve   a direct  correlation between
an  individual plant's  performance  and  program  implementation,  a comprehen-
sive site-specific effort is required.

     Based  on  the  above conclusion,  the  following  recommendations  were
developed.

     -All  Facilities  -  Implement  programs   to   address  identified  high
       priority  factors.    Implementation  must  be  achieved with a  full
       awareness  of the difficulty in directly assessing impact.

     - Individual Facilities -  Implement  programs  to  support initiation  of
       comprehensive  site-specific efforts  (CCP's)  at  individual facili-
       ties.  For example, enforcement for noncomplying facilities could  be
       used to encourage CCP activities.

ACKNOWLEDGEMENTS

     The data upon which this publication is based was compiled pursuant  to
Contract Nos.  68-03-2224 and  68-03-2572  with the Office of  Research  and
Development, U.S.   Environmental  Protection Agency,  Cincinnati, Ohio.   The
guidance  and  assistance  from  Mr.  John  M. Smith, who  served   as project
officer  for the  Environmental Protection  Agency,  is  gratefully acknow-
ledged.   The  cooperation  and  assistance  provided by  federal,  state  and
local water pollution  control agencies is also gratefully acknowledged.

REFERENCES

1.  "Clean  Water  Report to  Congress  - 1973,  1974,  1975  Annual  Reports",
    U.S. Environmental Protection  Agency, Washington, D.C.,  May 1973,  June
    1974, June 1975.

2.  Gilbert, Walter G.,"Relation  of Operation  and  Maintenance  to Treatment
    Plant Efficiency",  Journal  of Water  Pollution Control  Federation,  48,
    1822 (1976).

3.  "Continuing Need  for  Improved Operation  and  Maintenance of Municipal
    Waste  Treatment Plants",  Report  to  the   Congress  by  the  Comptroller
    General of the United States,  Washington,  D.C., (April 11,  1977).

4.  "Costly Wastewater Treatment  Plants  Fail to Perform  As  Expected",
    Report to the Congress by the Comptroller General of the United States,
    Washington, D.C.,  (November 14, 1980).

5.  Hegg, B.A., K.L.  Rakness and  J.R.  Schultz, "Evaluation of  Operation  and
    Maintenance  Factors  Limiting  Municipal   Wastewater  Treatment  Plant

                                    12

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    Performance",  EPA-600/2-79-034,  NTIS  No.  PB-300331,  U.S.  Environmental
    Protection Agency,  Cincinnati,  Ohio (1979).

6.  Hegg, B.A., K.L.  Rakness and J.R.  Schultz,  "A Demonstrated Approach for
    Improving Performance and Relaibility of  Biological  Wastewater Treat-
    ment Plants",  EPA-600/2-79-035,  NTIS  No.  PB-300476,  U.S.  Environmental
    Protection Agency,  Cincinnati,  Ohio (1979).

7.  Hegg, B.A., K.L.  Rakness and J.R.  Schultz,  "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, Cincinnati, Ohio (1980).
 "This paper has been reviewed in accordance with the U.S. Environmental
 Protection Agency's peer and administrative review  policies and approved
 for presentation and publication."
                                    13

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                PAPER NO.  2


           A MODEL PROTOCOL FOR

       THE COMPREHENSIVE EVALUATION

     OF PUBLICLY OWNED TREATMENT WORKS
                    by

                A. C.  GRAY
              Project  Manager

                    and

               H. D. ROBERTS
             Project Engineer
Gannett, Fleming, Corddry & Carpenter,  Inc.
               P.O. Box 1963
      Harrisburg, Pennsylvania  17105
                    14

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  A MODEL  PROTOCOL  FOR  COMPREHENSIVE  EVALUATION  OF  PUBLICLY  OWNED  TREATMENT
  WORKS

  Albert C.  Gray  and  Hugh  D.  Roberts  , Project Manager and Project Engineer
  Gannett, Fleming, Corddry  & Carpenter,  Inc.

INTRODUCTION

     Findings of EPA sponsored studies conducted during the 1970's indicate
that:  a)  at least 50 percent of the publicly owned treatment works (POTW's)
constructed under the federal construction grants program (PL 92-500)  are
not achieving permit  compliance (1); b)  poor plant performance is  usually
due to a combination  of inhibitory factors (2, 3); c) implementation of a
composite  correction  plan (CCP) could bring the great majority of these
plants into compliance without requiring major plant expansion or upgrading.
The key to developing an effective CCP is the performance of a comprehensive
plant evaluation which results in the identification of performance limiting
factors and an analysis of the degree to which each factor impacts treatment
efficiency.  An effective plant evaluation will provide the basis  for prior-
itization  of requisite corrective measures which then can be implemented to
bring about treatment performance improvements in a timely, cost effective
manner.  Conversely  an  improperly conducted evaluation can result in wasted
time and effort in implementing inappropriate corrective procedures.

     In the course of conducting research to determine factors limiting
performance of biological treatment plants in the eastern U.S., 53 detailed
plant evaluations were performed over a three year period.   Of necessity, to
promote efficiency and uniformity, an evaluation protocol to be followed by
the field research teams was developed.   This methodology and related exper-
ience have been incorporated in a model plant evaluation protocol  manual
which is  the subject of this paper.   The manual presents a systematic ap-
proach to conducting a comprehensive performance evaluation of a municipal
wastewater treatment plant.   The ultimate objective of the evaluation is to
identify  and rank causes of poor plant performance.  In the context of this
evaluation procedure plant performance is measured by the consistency with
which effluent quality meets the provisions of the NPDES permit.

     The manual breaks down  the evaluation into five major problem areas;
design, performance monitoring, operation, maintenance and administration.
In addition, the manual reviews the preparatory steps to be completed before
the actual plant visit.   Such preevaluation activities can be instrumental
in assuring that data collection will be productive, efficient, and complete.
A section on the preparation of the evaluation report is also included.

     The protocol manual has been designed for use by an evaluation team
that includes at least one individual with wastewater treatment engineering
expertise  and one individual with plant  operation training and experience.
In the case where a plant is small enough  to be evaluated by one  person,
that individual should be a  professional engineer who also holds operations
certification.   As noted above, this manual reviews the evaluation of  treat-
ment plant performance only  insofar as effluent quality is concerned.   Other
aspects of performance,  most notably energy utilization efficiency have not

                                     15

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been addressed.  Other references (4,5,6,7) have been, or are being, devel-
oped for that purpose.  Furthermore, the manual does not provide guidance
for in depth analysis of management issues or alternatives.  Rather, we are
concerned here with the "First Level" evaluation in which factors that di-
rectly impact effluent quality are investigated.  The findings of the EPA
biological plant performance surveys indicate that tangible performance im-
provements can be realized through implementation of programs on an oper-
ational  level without necessarily making major  management changes.  This is
not to minimize the significance of effective management to treatment plant
performance.  Over the long term good management practices will facilitate
continuous optimization of plant performance and certainly improve the cost
effectiveness  of treatment.  At least one  reference currently addresses
wastewater utility management in some detail (4).  Finally, while the eval-
uation protocol manual reviewed in the  following pages sets forth guidelines
for structuring and conducting an evaluation, it is not to be considered all
inclusive.   Each treatment plant will present the evaluator with certain
unique features and no single manual could cover all such contingencies.
Other available references can and should  be used to supplement the protocol
manual.  These include EPA published guidelines on NPDES compliance sampling,
(8), facility  staffing (9), methods for chemical analysis  (10), and detailed
evaluation of plant unit processes  (11).

PRELIMINARY  ACTIVITIES

     In  order  to minimize time in the field and to maximize the quality of
information  gained, the necessary preliminary procedures should include:

     1)  Contacting cognizant regulatory officials to
         obtain all existing relative data.

     2)  Contacting responsible treatment  authority or municipal
         officials to inform them of the proposed evaluation.

     5)  Contacting the treatment plant superintendent to inform him of
          the proposed evaluation, and  to  discuss the purpose and scope.

     4)  Estimation of time, manpower requirements, and
         materials needed to conduct the evaluation.

     5)  Formulation  of field sampling  and analytical program.

     Some comments regarding these preevaluation tasks are presented in the
following paragraphs.

REGULATORY AGENCY CONTACTS

     The leader of the evaluation team  should obtain all existing information
on subject plant that may be on file with  the EPA or state environmental con-
trol agency.   Data to be acquired from  the regional EPA office includes at
least the STORET records for the subject facility and the EPA Form  7500-5
 survey  form, If  one  has  been  completed.  The  State  Regulatory Agency should
 be assessed  to obtain copies  of  the NPDES  permit, monitoring  records and  any

                                      16

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design related information that may be on file.  These data are to be care-
fully reviewed to identify performance limiting problems that have been
previously noted, and to observe past trends in effluent quality.

NOTIFICATION OF POTW AUTHORITY AND MUNICIPAL OFFICIALS

     The chairman of the POTW owning authority and the head of the municipal
department responsible for plant operation must be notified of the planned
evaluation.   The responsible official is usually the head of the department
of public works or the municipal sanitation department.  The NPDES permit can
be checked to determine the responsible official.   These officials should be
notified in writing two weeks prior to the scheduled evaluation.  Written
notification should be followed with a telephone contact one week prior to
the evaluation.

     The written notification should indicate the reason for the evaluation;
for example, to determine what factors are responsible for the failure of the
treatment plant to meet its discharge permit.  The scope of the evaluation
should be briefly summarized, and  the dates on which field work will be per-
formed indicated.  The responsible official should be asked to have his plant
superintendent available throughout the field study period to respond to
questions raised by the evaluation team and to provide copies of operating
records.  Furthermore, the responsible official is to be notified that the
budgetary information for the most recent fiscal year is desired for review
by the evaluation team, and that an individual should be designated as a con-
tact for the evaluation team regarding budgetary and other administrative
information.  Names of the evaluation team personnel and the designated team
leader should be included in the  notification.

     The administrative officials  should be made aware of the positive aspect
and tangible benefit  that can result from the undertaking such as the identi-
fication of areas where 0 & M programs can be improved.  Such improvements
may involve minimal investment when compared to structural upgrading, but
significant performance improvement may be achieved.  The concept that should
be communicated  is  that the evaluation is the first step in maximizing the
return on the investment represented by the pollution control plant.  If
these idea's are  clearly communicated, negative attitudes will be reduced and
cooperation from the plant staff and administrators will facilitate the
evaluation process.

  NOTIFICATION OF THE POTW SUPERINTENDENT

     Contact with the plant superintendent should not be made until the re-
sponsible authority or municipal official has discussed the scope and pur-
pose of the evaluation with the plant superintendent.  Then the team leader
should call the  superintendent to  explain the nature of the evaluation to
the superintendent, inform him of how much of his or his staff's time may be
required, and  answer his questions concerning the type and extent of infor-
mation he will be asked to provide.  The team leader should indicate the
specific operating  records and technical references he will inspect during
the field investigation.  The intent of contacting the plant superintendent
is both to solicit his cooperation and to allow him some time to prepare so


                                     17

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that information retrieval is expedited.  No written contact need be made.
Again, the concept that the evaluation team's findings may benefit his
plant's performance is to be communicated to the superintendent.

CONTACTING CONSULTING ENGINEER OF RECORD

     When the plant administration is notified, the name and address of the
design engineering firm should be obtained.  The administrator may refer the
evaluation team leader to his consultant engineer to answer plant specific
questions.  In any case, the administrative official should be asked to give
clearance to his engineer to release information regarding plant design to
the evaluation team.  The team leader should then directly contact the con-
sultant and request to be given a copy of the basis of design, which may be
returned to the consultant at the conclusion of the evaluation.  Also, at
this time, the scope and purpose of the evaluation should be discussed with
the consultant.  He should be asked for his suggestions concerning areas or
facets of plant operation that should be specifically observed during the
evaluation.

ESTIMATION OF EVALUATION TIME

     Field time required for a comprehensive evaluation is a function of
size of plant, complexity of treatment process, and the amount of cooperation
provided by the plant operating staff.  A minimum of three days in the field
should be allowed for plants with design capacities of 11,355 cu m/d (3.0
mgd) or less and a minimum of five days field evaluation time should be al-
lowed for larger plants.  The cutoff point between three and five day field
studies is somewhat arbitrary and based on average conditions.  Judgment
must be exercised in making adjustment in time allotments for plants where
unusual or extenuating circumstances exist.  It is better to overestimate
the time required to conduct a comprehensive evaluation than plan for too
tight a schedule.  The slower pace will allow the evaluation team to better
observe plant operations and to converse at some length with the operators.
Such conversations can provide additional insight into problems which would
otherwise be missed in the rush of a tight schedule.  Also, the slower eval-
uation pace can result in an atmosphere in which the operating staff feels
the evaluation team is providing some technical assistance to them.  Under
such circumstances, a good attitude and the cooperation of the plant staff
increases the quality of the evaluation.

ESTIMATION OF REQUIRED MANPOWER

     The provision of proper staffing involves two considerations.  The
number of individuals required to accomplish all tasks within the three to
five day time frame must be determined. Just as important, however, is that
the evaluation team include individuals with appropriate training and ex-
perience to gather all performance, design, operational,  maintenance and
administrative information, and to perform necessary sampling and field
analysis.  The number of individuals required to perform these tasks is a
function of the size and complexity of the treatment plant.  Since com-
plexity of the treatment facility normally increases with design flow, man-
power requirement can be related to plant size.  Table 1 shows the recom-


                                     18

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mended number of staff for an evaluation team as a function of plant design
flow.  This staffing guide should be viewed as a minimal allocation of
manpower.
                                   TABLE 1

         GUIDE TO STAFFING REQUIREMENTS FOR COMPREHENSIVE EVALUATIONS

      Plant Design Flow                         No. of Investigators
     cu m/d         mgd

      11,355          3                                   1

  11,355-94,625     3-25                                  2

  94,625-227,100   25-60                                  3

     227,100         60                               3 or more

      Every evaluation team must include two categories of technical expertise;
 plant design and process operations.  In the case of small plant evaluations
 where only one individual is involved,  that individual must be an engineer
 who has had experience in treatment  plant design or review of such designs,
 and has been involved in facets of plant operations.  He should also be a
 registered professional engineer and hold state certification as an operator,
 in states where certification  programs exist.  Although an individual with
 this dual certification is not always available, experience and a working
 knowledge in both areas is absolutely necessary.  In the case where an
 evaluation team is comprised of two  or more individuals, at least one sani-
 tary engineer and one certified operator should be included.  Other indi-
 viduals on the team may be technicians familiar with sampling, analysis, and
 field measurement techniques.  These personnel would perform field data col-
 lection tasks under the supervision  of one of the senior team members.

      One of the senior team members  should be designated as the evaluation
 team leader.  The duties of the team leader include:   (1) making all pre-
 liminary contacts, (2) collecting and coordinating review of previously
 available data, (3) overseeing scheduling, transportation, and lodging ar-
 rangements, (4) reviewing and  approving of field sampling program, (5) co-
 ordinating field work, and (6) preparation of the evaluation  report.

 DETERMINATION OF REQUIRED EQUIPMENT  AND MATERIALS

      To enhance efficiency and organization of the field data collection
 effort, several forms have been developed for the protocol manual.  As part
 of the preliminary activities, copies of these forms should be reviewed so
 that the evaluation team understands the data requirements and format before
 proceeding into the field.  All available preevaluation information should
 be entered on the forms prior  to the field study and confirmed during the
 field investigation.
                                      19

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     The Field Analysis Requirement Form is a guide to be used to design the
sampling and analysis program portion of the evaluation.  It should be com-
pleted prior to the on-site work so that proper sample containers, reagents,
and instruments can be obtained.  However, a process flowsheet and some
plant  design  information  is  needed  to  complete  the  form.  If  this  information
is  not available,  then sampling program  decisions will  necessarily be made  in
the field,  in which  case  the team must be sure  to bring sufficient sample
containers  and  reagents to cover any contingency.

     The following items  are to be  obtained,  cleaned  and calibrated prior  to
conducting  the  field  study:

     1.  Sample Bottles - Approximately  1/2  liter capacity, sufficient
         number to sample plant influent,  effluent, and interprocess
         streams at  least daily during the 3-5  day  survey.  One hundred
         sample bottles will normally  be sufficient.

     2.  Automatic Composite Samplers  -  To be used  for  sampling all
         wastewater  flows including influent, primary effluent,
         secondary clarifier effluent, and final discharge.

     3.  Reagents  for  Sample Preservation -  Sulfuric  acid, nitric
         acid,  mercuric chloride.

     4.  50 Liter  Cooler  - For  sample  storage and transport.

     5.  Field  pH  Meter

     6.  Field  D.O. Meter

     7.  Tape Measure  - 30.5 m  (100 ft.)

     8.  Bucket and Rope

     9.  Stop Watch

    10.  Dye  Tablets

    11.  Protective clothing  including boots and wet weather gear

    12.  Calculator

    13.  Clipboards

LABORATORY ANALYSES

     The extent of laboratory analysis to be performed on collected samples
depends on  several factors.   Of  primary  importance are  the analyses for
parameters  required to quantify  the process control indicators, which will
vary with the treatment process  flowsheet.  Also, analyses for all discharge
permit parameters  should  be  performed on influent,  effluent, and unit pro-
cess flows  so that removal of these pollutants may be profiled through the


                                     20

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                                                                      TABLE 2.  SUGGESTED SAMPLING  AND ANALYSIS PROGRAM
     Analyses




BOD,- (total




BOD, (soluble)




Settleable sot ids




Suspended solids  (total)




Suspended solids  (volatile)




Dissolved oxygen




Phosphate"




Ammon i a nit rogen-'-




A\ka1in i ty




PH




Chlor i ne  res i dua1




Feca1 coliform




Me ta Is ••
  Where app1i cable

-------
facility.  Table 2 presents a general guideline indicating analyses to be
performed on samples obtained from various points in the treatment process.
Daily samples should be obtained at each indicated sampling point.  Where
possible, composite samples should be collected.  Whether these should be
time proportioned or flow proportioned, depends on the flow characteristics
at the particular sampling point.  Use of automatic samplers, wherever pos-
sible, is strongly recommended.  This will reduce manpower requirements
while improving sample integrity.  Samples for solids analysis must be col-
lected manually, but several samples per day should be combined into one
composite.  For all samples collected, careful judgment must be used in
determining the actual point where a unit process will be sampled to assure
that a timely representative sample is obtained.

     Table 3 shows recommended sampling locations for the various plant unit
processes.  In the case of multiple parallel units, each unit should be
individually sampled in order to isolate problems.  There are many unusual
or specialty processes that are not specifically covered in Table 3.  In
deciding where to sample such processes, the evaluator must exercise careful
judgment.  Every effort must be made to obtain the most representative sample
in light of the purpose ofr sampling at the point in question.  Additional
references (8,11) will be useful in establishing sampling details.

     Since no person is more familiar with access to the various plant units
than the operator, Table 3 should be reviewed with him at the start of the
field survey.  The operator will be able to indicate where sampling ports,
free discharges, or other appropriate sampling points can be found.  If
there is a serious problem with accessing a particular flow, and it is
critical to the evaluation, alterations such as inserting a valve or tap in
a line must be discussed with the supervisory operator.  The long-term
advantages of having complete sampling access for purposes of process con-
trol should be explained at that time.  It may be necessary to postpone the
evaluation for several days to allow any necessary modifications to be made.

                                   TABLE 3

                         RECOMMENDED SAMPLING POINTS

     Plant Influent                    Wet well, after bar screen,
                                       comminutor and raw sewage pumps

     Grit Removal                      Near effluent weirs, approximately
                                       2 feet beneath surface

     Primary Clarifier                 Free discharge into effluent
                                       launder (over weir)

     Trickling Filter                  Effluent junction box, beneath
                                       surface (or manhole if no junction
                                       box exists)
                                     22

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                                   TABLE 3
                                 (Continued)
     Aeration Tank



     Sludge Return



     Secondary Clarifier


     Disinfection Unit



     Plant Effluent

     Raw Sludge



     Primary Digester


     Secondary Digester
     Thickener


     Polishing Pond


     Polishing Filters


ESTIMATING THE COST OF AN EVALUATION
Near center of tank, 2 feet beneath
surface (D.O. should be run at
several depths)

Free discharge into aeration tank,
return sludge distribution box,
sampling valve on return pump

Free discharge at weir into
effluent launder

Near effluent weir  (if chlorine
residual is to be run, sample
should be fixed)

At outfall discharge

Sampling port on sludge transfer
line (or lines), free discharge
into aerobic digester

Tap on line between primary and
secondary digester

Supernatant - at collection sump
or port on recycle  line, free fall
discharge at plant headworks
Sludge - free discharge to drying
beds, influent line to thickener,
influent line to holding tank for
dewatering equipment

Dewatering holding  tank, influent
line to holding tank

Near effluent weir or other
discharge device

Tap on filter effluent line,
discharge to chlorine contact tank
     A budget for the comprehensive evaluation must be prepared during the
planning stage.  The variables that impact the cost of an evaluation include:
duration of the survey, number of team members, extent of sampling and
analysis program, and transportation, lodging and subsistence costs.  A guide
for estimating the funds to be budgeted for an evaluation is given in Table
4.  Experience indicates the costs of comprehensive evaluations typically
                                     23

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N)
                              Cost  Center
                                                                        TABLE 4

                                              A Cut tie To Estimating The Cost Of A  Comprehensive Evaluation

                                                     Variable No. 1        Variable  No.  2      Variable No. 3
                                                                                                Constant
                  A.  Pro-1C valuation  Act I vl l li'.s     No. roan-hours    x    Average  payroll
                       1.   Make  contacts ;m
-------
                                                                     TABLK  4  (Cont'd)
                             Cost C(nn t c t
                 c.
                           _
                      1 .   Diita Kcilucl. Ion iiiul
                          analys Is
                                                     Variable No. I
                                                                            Variable No. 2      Variable  No.  3    Constant
No. man-hours     x    Average payroll
                       rate (S/hr)
                                                                                                                                 Subtotal
N3
Ul
                      2.   Writ Inf, and edit I nf.
                          Typing and assi-mb 1 I nj;
                     'i.   I'r lilt I nj; and
                          dncLI on

                     Subtotal
No. man-lionrs     x    Average payroll
                       rate ($/hr)

No. man-hours     x    Average payroll
                       rate ($/hr)

No. of paf.oij
                                                            KeproductIon
                                                            rate ($/pagi?)
                     Total Evaluation Com

-------
fall in the range of $3,000 to $8,000, including all field work and the
preparation of an evaluation report.

MONITORING DATA COLLECTION

     Three potential sources of monitoring data exist by which the perform-
ance of a treatment plant and its individual unit processes should be evalu-
ated.  First, there are the plant operating reports that document all anal-
yses performed at the facility.  The results of analyses performed on samples
collected as part of the evaluation are the second source of monitoring data.
The third source is the sampling and analysis information maintained by the
regulatory agency in certain states.

PLANT MONITORING DATA

     A member of the survey team should obtain copies of all monitoring data
and reports maintained by the plant staff during the previous 12 months.
Such information would include overall plant performance data such as flow
records, influent and effluent 6005, suspended solids, phosphorus, nitrogen,
and pH analyses.  As a minimum, Such information should include results of
all tests performed in accordance with the NPDES monitoring requirements,
set forth in the plant's permit.  Other available monitoring data maintained
at  the plant may include:  primary effluent BOD^ and suspended solids, MLSS
MLVSS, and aeration basin dissolved oxygen (D.O.) and pH, and digester per-
formance indicators, including alkalinity, volatile acids, temperature, and
pH.  Results of analyses on side streams such as return sludge, digester
supernatant, thickener overflow, and dewatering filtrate should also be
requested.

EVALUATION MONITORING DATA

     One of the tasks performed by the evaluation team during a survey is the
collection of samples for the purpose of monitoring process performance.
Table 2 discussed earlier in this paper, indicates the inter-unit streams
and process contents which should be sampled during the evaluation.  The
typical analyses to be performed on these samples have also been indicated.
Sample volume requirements and preservation methods should be predetermined
before arrival in the field.

REGULATORY AGENCY DATA

     Certain state water pollution control agencies periodically conduct
sampling and analysis studies at treatment plants within their jurisdiction
as a check on performance.  By contacting the respective state agencies,
such data may be available for evaluation purposes or for confirming
evaluation monitoring data.

     Some general guidelines should be followed relative to samples col-
lected in the field.  Samples should be split and labeled aliquots pre-
served in accordance with intended analyses.  Samples should be delivered
as  expeditiously as possible to the designated laboratory.  Complete
written instructions should be left with the laboratory supervisor speci-

                                     26

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fying analytical parameters, suspected concentration ranges, reporting re-
quirements for results, and deadlines for reported results.  If the evalua-
tion team does not have prior knowledge of a lab oratory, a visit to review
items such as sample chain of custody, quality assurance, and record
keeping procedures is suggested.

DESIGN ANALYSIS

     An important part of the comprehensive evaluation  is to evaluate  the
basis of design and to compare  the plant  facilities  in  place with the  basis
of design.  The objectives of this portion of the  comprehensive evaluation
are  to (1) discern any design factors which may  limit the ability of the
plant to meet its permit conditions,  (2)  determine the  limitations on  oper-
ations imposed by design, and (3) identify minor design deficiencies that
may  be easily and inexpensively  corrected.  This analysis will include exam-
ination of process design parameters, such as detention times, hydraulic
and  organic loadings,  recirculation  rates, and sludge age.  Also, a visual
comparison of plans and specifications to existing equipment and layout must
be made to determine if changes  have been made either at the time of con-
struction or  thereafter.  The adverse impact of  some design errors or  omis-
sions, such as undersized unit  processes, is easily  perceived.  However,
the  evaluation team must also establish  the extent to which more subtle de-
sign problems adversely impact  the performance of  the treatment plant.
Examples  of such  problems could be inadequate sludge return or wasting
capacity, or  poor control over  recycle flows.  Inadequate process flexibility
is another potential design  problem   that may not  be readily apparent  on
initial review of the  basis  of  design.

     General  design  information can  be obtained  from several sources.  These
include:  the preliminary  engineering report or  201  Facilities Plan prepared
for  the  plant,  the plant basis  of design, the O&M  manual, as-built drawings
retained  by owner, design drawings retained by the consultant  engineer, and
permit applications  on file  with the state regulatory agency.  In addition
to all unit process  design  information,  Design wastewater  characteristics
and  flows must also  be determined.   As a  minimum the general background
information that  must  be obtained to evaluate the  treatment plant design
includes:

         Average  design flow
          Peak design flow  (rate)
          Design BOD5 and suspended solids loadings
          Design service population
          Design year
     —   Age  of existing facility
     —   Present  average flow
     —   Present  peak  flow  (rate)
          Present  BOD5  and suspended  solids loadings
     —  Present  service population
     —  Volume of industrial wastewater
     —   Character of  industrial wastewater  (6005,
          suspended solids, heavy metals,  toxics, etc.)
         Volume of infiltration/inflow

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     In addition, review of recent operating records, or regulatory agency
inspection records, must be conducted to obtain information on current waste-
water flows and characteristics.  Records of any infiltration/inflow analyses
that have been performed are available from the plant owner or the consulting
engineer.

     The major portion of the design evaluation phase is devoted to the
analysis of individual unit process designs.  This analysis consists of de-
termination of process design parameters and loadings, comparison of these
parameters with good engineering practice, and comparison of design para-
meters with values realized in the process under actual operating conditions.
Thorough evaluation of unit process design will provide the necessary infor-
mation to establish the existence and degree of the following potential
plant performance limiting conditions:

     1.  Poor process design which subverts the ability of a process
         to meet design intent.  For example:  .excessive solids loading
         on a secondary clarifier, inadequate detention time in an
         aeration tank, etc.

     2.  Construction or installation which does not conform to design.
         An example would be clarifier weirs installed out of level,
         causing short circuiting in the unit.

     3.  Inadequate process flexibility.  This situation interferes with
         the operator's ability to adjust the process to variations in
         wastewater conditions.  An example of this would be an activated
         sludge return line for which flow cannot be adjusted.

     4.  Poor process selection.  An example would be the use of the con-
         tact stabilization mode of the activated sludge process to treat
         wastewater which is highly variable in organic strength.

     5.  Incompatibility of unit process with the constituent removal re-
         quirements.  An example of this would be the use of a secondary
         clarifier to achieve effluent suspended solids concentrations of
         less than 20 mg/1.

     All unit process design evaluations must be conducted with the above
five potential problem areas being carefully considered.

     It can be expected that some of the following unit processes must be
evaluated at any biological treatment facility:

     Raw sewage pumping
     Screening
     Shredding
     Grit removal
     Flow measurement
     Primary sedimentation
     Trickling filters
     Aeration (Activated Sludge)

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     Rotating biological contactors (RBC)
     Secondary sedimentation
     Disinfection
     Filtration
     Microscreening
     Carbon adsorption
     Land application (wastewater)
     Thermal sludge conditioning
     Sludge thickening
     Anaerobic digestion
     Aerobic digestion
     Sludge dewatering
     Land application (sludges)

Design and current loading parameters must be obtained for each of these unit
processes.  A form is provided in the protocol manual to facilitate collec-
ting this data.  Though the collection of design data is a somewhat routine
undertaking, the evaluation team must be continually aware that the data
must be complete to definitely determine whether unit process design is in
any way placing limitations on the plant's performance.

     The protocol manual sets forth guidelines for the collection and manip-
ulation of data for each of the above listed unit processes, although
brevity precludes such detail in this paper.  Design parameters to be in-
vestigated and raw data needed to calculate them are specified for each unit
process.  Various references such as "UPCF Manual of Practice No. 8" (12),
the EPA Technology Transfer Series, and tests such as that edited by Metcalf
and Eddy  (13), can be used to establish ranges for design parameters
considered representative of good engineering practice.

     In conducting the design analysis the evaluation team must be aware
that all  potential design problems are not necessarily evident upon an
analysis  of  unit process loadings.  Factors such as process flexibility,
accessibility of sampling points for process control, capability to divert
and balance  flows, and calibration requirements for process control
instruments  should be evaluated.

OPERATIONAL  INVESTIGATIONS

     The  evaluation of operational capabilities and limitations comprises
an extremely important segment of a comprehensive evaluation of a treatment
facility.  This area historically has not been given adequate consideration
in plant  evaluations.  Operational factors affecting plant performance range
from qualitative factors such as the personal characteristics and traits of
operators  (e.g., process knowledge and general aptitude), to more quantita-
tive physical constraints placed on the staff, such as deficiencies in lab-
oratory equipment or a lack of reference materials.  The evaluation team
must be objective but diplomatic during all of its fact-finding activities,
out this  is  especially true in relation to operations.  The operators may be
very sensitive to question in this area, because they may interpret the
evaluator's  questions as an attempt to assess their job performance.  To
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some degree, operator job performance must be assessed in this section of the
comprehensive evaluation.

     In the evaluation protocol, plant operational practices are divided into
four major categories:  operating personnel, plant monitoring, process con-
trol, and operations references.  The information to be obtained for each
category is discussed.  Also, for comparison purposes, acceptable baseline
capabilities are given wherever possible which will assist the evaluator in
determining the adequacy or acceptability of plant operational procedures and
resources.  A form for the purpose of summarizing operational data is
included in the protocol manual.

     The best engineered plant would not perform to its potential without the
management provided by a capable operator.  Conversely, many poorly designed
plants can and do perform satisfactorily with respect to effluent criteria
due to conscientious and capable operators.  Through discussions with the
plant superintendent the evaluation team must establish the abilities and
limitations of the operating staff.  At small plants this may involve in-
depth discussions with only one operator.  At larger facilities, the in-
vestigations should be directed toward the chief operator for each shift or
the individuals in charge of overall operations, those in charge of specific
process operations (i.e., digester control operator), and those responsible
for laboratory functions.

     The evaluator should determine the level of education of each of the
responsible operating personnel.  For individuals in supervisory positions
and in situations where there is only one operator the equivalent of a high
school graduate would be considered baseline.  The evaluation team must
assess the level of knowledge that the plant operators have regarding waste-
water treatment.  The aptitude of the operating personnel in this regard
must be assessed through question-and-answer sessions in which treatment
theory and process control techniques are discussed.  Careful analysis of
the operators responses is the best way to determine his ability to compre-
hend and apply the concepts of wastewater treatment.  Specific questions to
be asked depend on the type and complexity of treatment process involved.
For example, in the case of an activated sludge plant the operator might be
asked if he has ever encountered a bulking problem and, if so, what action
he took in response.  He might further be asked if he feels his process can
be controlled by F/M or mean cell residence time techniques and how this
might be accomplished.  The operator of a trickling filter plant might be
asked about his plant's recirculation control capabilities.  Questions con-
cerning sludge handling and disposal, and laboratory techniques should also
be posed.

     Operator attitude has an important bearing on the overall performance
of a plant.  A good attitude toward operating the plant is an indication
that the personnel are at least expending the effort to produce a high
quality effluent.  Evaluation of operator attitude is necessarily subjective.
Often a poor attitude is evidenced by excessive complaining about working
conditions; an antagonistic reaction to the evaluation; placing all culpa-
bility for performance problems on the engineer, plant administration, or
regulatory entities; an inability to get along with others; high rate of


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absenteeism;  or (of most importance) indifference toward the problems at the
plant.  This  last manifestation of poor attitude is usually accompanied by
poor records  keeping, poor condition of equipment, and inadequate laboratory
testing.   It  is recognized that in many instances operators complaints are
justified by  the circumstances.  The evaluator must judge the degree to which
the operator  is offering constructive criticism, and conversely, the degree
to which negativism and attitude problems prevail.

     Monitoring activities conducted at a treatment facility by the opera-
ting personnel are a good indication of the emphasis placed on operations,
and the operator's understanding of process control.  The evaluation team is
responsible for making value judgment relative to several types of monitoring
activities.  Firstly, the sampling program followed at a treatment plant must
be compared with recommended or required procedures.  Performance sampling
should conform with permit requirements.  Such requirements may include com-
posite sampling.  The frequency of sampling may also be specified.  If sam-
ples are going to be held for any period longer than a few hours before be-
ginning the laboratory analyses, preservation techniques should be routinely
employed.  Laboratory procedure should be evaluated by direct observation of
technicians,  or at least by means of detailed interview of technicians re-
garding their analytical methods and laboratory procedures.  A form has been
provided in the protocol manual for performing the laboratory evaluation.

     Process testing should be evaluated in a manner similar to performance
testing.  Although these tests are not required by permit, effective process
control of certain unit processes, such as the activated sludge system or the
anaerobic digester, requires such tests be conducted in order that appropri-
ate control adjustments may be made.  Unlike the  performance testing case,
process testing scope and frequency will not be set forth in regulatory per-
mits.  Therefore,  the evaluator must use judgment and references in setting
a framework of acceptable process testing at a given plant.  Table 5 pre-
sents a guide  for  evaluating the acceptability of process control testing
for various processes and interprocess streams, for plants in the small,
medium, and large  design categories.  The table may be used as a general
guide, but specific  conditions at each plant should be taken into
consideration when applying the table in the field.

     Maintaining adequate records of plant monitoring is an important aspect
of operations.  Records should include copies of  NPDES monitoring reports
dating back at least two years and  complete records of all process monitoring
for the current and previous year.  As a minimum, annual summary sheets of
all performance and process monitoring should be  filed at the plant for all
previous years.  Neatness and organization of monitoring records should be
assessed.

     An effective  process control program is essential if a biological
treatment  plant's  performance  is  to be optimized.  This is especially true
in the case of activated sludge systems.  However, process control is not
something  that will be  easily quantified by the evaluation team.  In most
cases, the evaluators will have to  rely on discussions with the plant
superintendent and/or operators to supplement available records and
observations.

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                                                 Table 5

                                 Guide for Evaluationg Process  Testing
PRIMARY EFFLUENT
Less than 1 mgd
1 to 5 mgd
Greater than 5 mgd
TRICKLING FILTER EFFLUENT
Less than 1 mgd
1 to 5 mgd
Greater than 5 mgd
MIXED LIQUOR
Less than 1 mgd
1 to 5 mgd
Greater than 5 mgd
RETURN SLUDGE
Lesi than 1 mgd
1 to 5 mgd
Greater than 5 mgd
THICKENED SLUDGE
Less than 1 mgd
1 to 5 mgd
Greater than 5 mgd
PRIMARY DIGESTER
Less than 1 mgd
1 to 5 mgd
Greater than 5 mgd
DIGESTED SLUDGE
(Aerobic and Anaerobic)
Less than 1 mgd
1 to 5 mgd
Greater than 5 mgd
Suspended
BOO, Solids
1 /wk 1 /wk
2/wk 2/wk
2/wk 2/wk
1 /wk 1 /wk
2/wk 2/wk
2/wk 2/wk

2/wk
Vwk
Daily
1/wk
2/wk
4/wk
1/wk
2/wk
2/wk
-

I/mo
1/wk
2/wk
Volatile
Suspended
Solids 0.0. pH
Da i } y
Daily
Daily
Daily
Daily
Daily

1/wk Daily Daily
2/wk 3/daY Daily
lt/wk 3/day Daily
1/wk
1/wk
2/wk
1/wk
2/wk
2/wk
1/wk - 2/wk
2/wk - Daily
2/wk - Daily

1/mo
1/wk
2/wk
Volatile
Alkalinity Acids
-
-

-
-
-
1/wk 1/wk
2/wk 2/wk
2/wk 2/wk

-
DEwrtTERED SLUDGE

Less  than  1 mgd                 "       l/m°
1  10  5 mgd                      "       '/wk
Greater  than 5 mgd              "       2/wk

RETURN STREAMS (Thickener
overflow, secondary digester
supernatant, filtrate)

 Less than 1 mgd               1/mo      I/mo
 I to 5 mgd                    >/wk      1/wk
 Greater than 5 mgd            2/wk      2/wk
1/mo
1/wk
2/wk
 I /mo
 1/wk
 2/wk
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     The evaluation team must determine how knowledgeable the operator is
with respect to process control methods.  Are the typical process control
parameters, such as food to microorganism ratio (F/M) and mean-cell resi-
dence time (MCRT),  familiar to the operator?  Does the operator understand
how to calculate these parameters and does he know what reasonable values
are?  Is he aware of the process control monitoring  (i.e., influent 8005,
MLSS, volume of sludge wasted, etc.) which must be performed to determine
such control parameters?  The evaluation team must determine if a rational
process control stategy exists and how thoroughly that strategy is
implemented.

     Previous plant performance surveys have shown that at some plants, the
operator performs the recommended process tests, but makes no effective use
of the information.  For example, MLSS levels may be monitored daily, al-
though no  attempt is ever made to adjust sludge wasting routines in order
to maintain an optimum MLSS concentration.  Through  discussions with the
operator and review of plant records the evaluation  team must determine
whether the process monitoring data is being used to control the
facility's performance or simply being compiled.

     Good  technical references are a significant asset to the operator with
respect to efficient plant operation.  The operations manual prepared
specifically for the plant is the most important reference.  Other reference
materials  relating to operations include manufacturer's literature, publica-
tions by professional organizations such as the Water Pollution Control
Federation, and EPA documents.

     The evaluation team should judge the adequacy of the operations manual
at each plant.  A comprehensive operations manual will address all aspects
of the plant including laboratory functions, testing, process control, and
safety.  Start-up and shutdown procedures for all equipment should be pre-
sented in  a stepwise fashion.  The  control center or panel should be des-
cribed in  detail with particular emphasis on the features of automatic con-
trol systems.  The manual should include detailed schematics of the plant
piping that show all pumps, valves, and similar control devices.  Trouble-
shooting procedures should be described in detail.   The manual should con-
tain a detailed  process control procedure.  This procedure should include
all  process testing requirements as well as centerlines and ranges for key
process control  parameters.  The evaluation team should discuss the adequacy
and  use of the manual with the operator.

     Operational literature is frequently supplied to the treatment plant by
equipment  manufacturers.  These references provide operators with specific
information on  equipment and unit processes that is  intended to supplement
the  comprehensive operations manual.  The evaluation team should first as-
sess  the availability and extent of such information at the plant itself.
The  evaluators  should also determine whether the manufacturer's information
fills any  voids  in  the comprehensive manual.

     Operations  publications from professional organizations include Manuals
of Practice (MOP) prepared by the WPCF and various state association hand-
books.  Such publications provide the operator with  additional insight

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regarding items such as process control techniques and troubleshooting.
Those reference materials are particularly important if the plant lacks a
detailed comprehensive manual.  The evaluation team should note the pre-
sence or absence of such publications.  Do the operators find these refer-
ences helpful?  Are these publications frequently consulted?  The contents
and scope of these references should be discussed with the operator.  An-
other reference source for treatment plant operations is made available by
EPA under the Technology Transfer Series.  The evaluation team should note
the availability of these references at the plant site, and should inquire
as to their value to the plant staff.  Do plant operators find these pub-
lications understandable?  Have the manuals been used or merely stored on
site.

     In summary, thorough evaluation of operational factors is critical to
the comprehensive evaluation.  Successful investigation of this area re-
quires in-depth conversations with the operating staff as well as careful
analysis of operating records and observed process control and testing
techniques.  The evaluation team should be prepared to devote at least 50
percent of its field time to this effort.

MAINTENANCE INVESTIGATIONS

     Maintenance of the treatment plant is a primary responsibility of the
staff.  Maintenance duties typically range from performing routine main-
tenance functions, such as lubrication, to on-site major repair of equipment.
The plant maintenance program and its degree of success are a function of
design and construction methods, as well as staff capabilities.  Various
aspects of plant maintenance must be examined by the evaluation team and are
discussed in the protocol manual.

     The evaluators are directed to note all process units or equipment which
are inoperable at the time of the evaluation.  Through discussions with the
operator, the team should determine the length of downtime for each unit,
the performance and maintenance history of the unit, and estimate the level
of effort that would be required to put the unit back in operation.  The
evaluation team must assess the impact of out of service units on plant
reliability and performance.   The evaluation team should also document which
major plant processes are provided with multiple units to provide backup
capabilities or partial treatment during maintenance periods.  The evaluators
must question, in depth,  the plant operators and maintenance staff with re-
spect to which processes or equipment are the major problems from the main-
tenance viewpoint and where they feel additional preventive procedures or
spare parts inventory are warranted.

     Any units in operation but in need of repair should be noted.  Symptoms
of such needed repairs are noisy bearings in motors, seal and gland water
leaking from pumps, oil leaking from mechanical parts (other than minor drip-
page), and excessive digester fuel consumption for heating purposes.  The
evaluation team should reveiw with the plant maintenance personnel each of
the units determined to be in need of repair or servicing; noting their com-
ments regarding the reasons for such conditions, any proposed repair schedules,
and any long-range programs for eliminating such conditions in the future.

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     Scheduling of routine or preventive maintenance is to be assessed.
Examples of such maintenance include:  lubrication, periodic draining and
cleaning of tanks, repairing sludge scraping and skimming mechanisms, re-
packing pumps, replacing bearings, cleaning diffusers on air headers and
nozzles on trickling filter distributors, and cleaning flow measuring devices
and monitoring equipment.  Is such maintenance performed on schedule or only
when time permits?  Records for each piece of equipment requiring maintenance
should include the date and cost of repairs, time to repair, manpower expen-
ditures, materials, and outside contractor costs.  Generally, the evaluation
team should determine whether the emphasis at the plant is placed on pre-
ventive or corrective maintenance.  The existing spare parts inventory and
procurement procedures should be carefully assessed.

     To effectively deal with emergency situations the plant must maintain
certain baseline capabilities or provisions.  An alternate power source
(i.e., gasoline- or diesel-powered generators, or a second power service
line from a separate substation) should be provided.  Audible alarms should
alert failures of major equipment items, such as pumps, chemical feeders,
mixers, or aerators.  Also, portable pumps should be readily available in
case of flooding.  The manpower resources available to the plant in times of
emergency must be assessed.  Such manpower includes permanent staff and
personnel from other departments or private contractors that may be brought
in on short notice.  Contingency plants and provisions for emergency
communications should be reviewed.

     In short, the evaluation of plant maintenance practices involves visual
observations  to assess housekeeping practices and equipment upkeep, careful
review of maintenance schedules and records, review of spare parts availa-
bility, and an evaluation  of the maintenance references available to the
operator.  The protocol manual includes a maintenance checklist to be
completed by  the evaluation team.

ADMINISTRATION

     A wastewater  treatement facility must obviously be operated within the
constraints of administrative policy and provisions.  In some cases blatant
administrative shortcomings such as severe understaffing or under budgeting
may directly  inhibit treatment plant performance.  In other cases, however,
administrative shortcomings of a more subtle nature may indirectly impact
effluent quality.  The latter condition may be difficult to discern by an
evaluation team.  Indeed a thorough management-administrative evaluation
could  constitute a separate study of greater scope than the entire evalua-
tion  covered  by  the manual discussed in this paper.  As indicated earlier,
in  depth analysis  of wastewater utility management is the subject of other
references.   However, the  protocol manual does present guidelines for a very
general assessment of administration which is designed to expose major plant
performance limiting problems.  Four key aspects of plant administration are
reviewed:  plant staffing, budeting, staff training, and use of outside
technical  experts.

      It is unrealistic to  expect any treatment facility to produce an efflu-
ent which  consistently meets permit requirements and design performance


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standards if the plant does not have a sufficient number of employees to pro-
vide needed operation and maintenance.  In an evaluation, plant staff respon-
sibilities are grouped according to the following classifications:   manage-
ment, operations, maintenance, laboratory, and clerical.  Unfortunately,
labor breakdown at treatment facilities is not always in accordance with
these classifications.  For example, at small plants, a single employee may
be responsible for all five labor categories.  Even at large plants, an in-
dividual may be called an operator, although his duties include laboratory
or clerical work.  If an employee's time is divided between two or  more
labor categories, an estimate of the fraction of total time devoted to each
category should be made.  This should be accomplished by discussing the re-
sponsibilities and duties of each plant employee with the superintendent,
and with his help, establishing the percentage of working time which each
employee devotes to each of the five categories.  The evaluation team should
also note the number and specific days of the week that the plant is atten-
ded, the number of shifts staffed and the duty hours, and the types of per-
sonnel staffing and the categories of activities undertaken during  the
various shifts.

     After the staffing information is gathered, the evaluation team must
assess the adequacy of:  1) the number of plant employees, 2) the distribu-
tion of manpower among the five labor categories, and 3) shift coverage.
Where deficiencies are noted, the team should discuss with the superintendent
the extent to which these deficiencies have affected the performance of the
plant.  Also, the evaluation team must determine how successfully the present
plant staff could respond to any noted deficiencies, and assess the need for
additional personnel.  For example, if a deficiency is evident in the area
of process control, the evaluator must determine (in this example)  whether
the currently employed personnel can handle the additional responsibilities
to correct the deficiency.

     One reference for estimating baseline staffing requirements is the EPA
technical report entitled, "Estimating Staffing for Municipal Wastewater
Treatment Facilities". (9)  Because all plant specific contingencies could
not possibly be covered, the staffing estimates prepared according to guide-
lines given in this document are not to be considered absolute requirements.
However, this reference provides the mechanics for making a first order
estimate of staffing heads for a given size and type of facility and should
be used as such.

     Budgeted funds for operation and maintenance are often cited as being
responsible for deficiencies in performance.  However, many facilities are
operated effectively on tight budgets and are able to meet performance stan-
dards.  The evaluator must discern when funding is used as an excuse for
poor performance when it is not the true cause.  Also, the team must deter-
mine not only the adequacy of the operating budget, but the impact that bud-
6et has on performance.  The evaluation team must renew and analyze plant
budget data.  The protocol manual includes a form for organizing such data.

     For reference purposes, the publication, "Analysis of Operation & Main-
tenance Costs for Municipal Wastewater Treatment Systems", (14) can be used.
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It presents the results of comprehensive cost surveys for plants of various
types,  sizes, and geographical locations and can be used to compare operating
costs at a particular facility with the costs at similar facilities within the
same  geographic area.  The drawback to using the document to develop stan-
dards of comparison is that it is not known how many plants included in the
data base may have been inadequately funded.

     If the adequacy of budgeting is suspect or the inadequacy is documented,
the evaluation team should identify the needed improvements in budget amounts
and categoreies.  Areas where budget shortfalls are perceived should be
scrutinized to determine how plant performance is being specifically impacted,
for example, low salaries may be responsible for operation being left to
incapable or poorly trained individuals.

     Level of staff training is considered to be an administrative matter,
because entry level requirements as well as the opportunity to participate in
training courses are determined by those individuals with administrative re-
sponsibility for the plant.  Discussions should be held with the plant oper-
ators to determine the extent of training received.  Completion of formal
courses should be noted.  Attendance at conferences and seminars should be
assessed.  The team should determine the number and level of certified
operators on the plant staff.  State certification is an indication of basic
background knowledge of waste treatment fundamentals.

     In some instances, plants have instituted relatively sophisticated on-
the-job training programs, in which the more experienced, better trained,
senior operators convey their knowledge to new or inexperienced employees
through formal hands-on training seminars or programs.  Also, in many cases,
consultants  are retained  to provide training during start-up of new or up-
graded facilities.  Whenever programs such as these are encountered, the
evaluators should determine their relative effectiveness.

     The extent to which  consultants or outside technical experts are em-
ployed is also  an administrative decision.  The evaluation team should dis-
cuss with the plant superintendent or appropriate administrative official the
extent of their use of consultants or other technical experts.  Is there an
on-going service agreement with a consultant or is technical assistance only
called upon when problems develop?  The evaluation team must also assess the
effectiveness of technical assistance that has been employed.

     Finally, evaluation  of plant administration involves some subjective
judgment  regarding attitudes and policies.  In some cases municipal officials
have considered treatment plant needs a low priority item relative to other
municipal services.  Such attitudes will be reflected in plant condition and
performance.  The evaluation team can only discover problem attitudes and/or
policies  through careful  interview of officials and plant staff.

REPORT PREPARTAION

     The plant  evaluation report must summarize data and present conclusions
resulting from  the on-site observations and analyses and related computations.
In addition, the report should make specific recommendations for improving the

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plants performance within the limitations of operational, maintenance, ad-
ministrative or minor structural changes.  The effectiveness of the evalua-
tion as a foundation for preparation of the CCP will be a function of the
quality of the report.

     Although rigid report guidelines cannot be followed in all situations,
certain components are essential to the evaluation report.  For this reason
the protocol manual presents a standardized report format indicating the
areas that should be covered in the report.  The suggested report structure
is as follows:

     Section 1.  Summary - This section of the report briefly summarizes
                 the performance of the facility and identifies the major
                 problems or deficiencies noted during the survey.

     Section 2.  Description of Plant - This section describes the plant's
                 location and presents a general description of the plant.
                 A process flow schematic should be included.  Permit
                 criteria should be recorded.  Additional information to
                 be presented includes:  age of facility, date of most
                 recent upgrading, and point of discharge.

     Section 3.  Design Evaluation - This section presents a unit-by-unit
                 analysis of the treatment facility, addressing all major
                 unit processes.  The process design evaluation should
                 include the completed "Design Evaluation Summary" form.
                 A discussion of design errors, deficiencies, and over-
                 loads should be included, along with their impact on
                 plant and process performance.

     Section 4.  Performance Evaluation - This section summarizes the
                 plant's actual performance as it relates to both design
                 intent and optimum capabilities.  Performance should also
                 be described statistically in terms of its compliance with
                 NPDES limitations over the 12-month period.  Annual average
                 flows, influent and effluent pollutant concentrations,
                 pollutant loadings, and percent removals should be documented.

     Section 5.  Operations Evaluation - This section summarizes the findings
                 based on investigations of plant operational practices.  The
                 completed  forms, "Laboratory Testing Capability  and Per-
                 formance" and "Summary of Operations Performance Indicators"
                 should be included in this section.  All observations with
                 respect to operating practices and procedures should be
                 reported.  This section should identify, in detail, poten-
                 tial operationally oriented causes of performance problems.
                 Where program improvements are necessary, such needs should
                 be treated.

     Section 6.  Maintenance Evaluation - This section summarizes the results
                 of maintenance investigations.  The completed form,
                 "Summary of Maintenance Performance Indicators" should be
                                     38

-------
            included.   The section should include observations made
            concerning maintenance programs.  Areas of plant mainten-
            ance that can be cited as potential causes of performance
            problems should be identified.  Additional maintenance
            needs should be noted.

Section 7.  Administration Evaluation - The completed forms, "Wastewater
            Treatment Facility Annual Operating Budget" and "Summary of
            Administrative Practices and Policies" should be included
            in this section.  Administrative shortcomings should be
            reported, as well as their apparent impact on other plant
            areas.  Needed improvements in plant administrative
            procedures are to be noted.

Section 8.  Plant Evaluation Summary - The "Plant Evaluation Summary"
            should be presented, including a brief discussion on how to
            interpret the information contained in the summary.
            Instructions for completing this document are included in
            the protocol manual.

Section 9.  Conclusions and Recommendations - This section presents all
            relevant conclusions regarding plant design, performance,
            operation, maintenance,  and administrative factors adversely
            affecting plant performance.  Causes of performance problems
            should be summarized. Actions to correct  shortcomings should
            be classified as either:

            1.   Improvements needed  to correct deficiencies  that
                 have been directly correlated with performance
                 problems  (first  priority),  or

            2.   Improvements needed  to correct deficiencies,
                 although  performance problems cannot  be  directly
                 correlated with  such deficiencies  (second priority).

            Each corrective action should also be  classified with
            respect  to being either:

            1.   A non-capital  expenditure improvement, which is any
                 action not  involving the  construction or modification
                 of major  physical facilities  (first priority), or

            2.   a capital expenditure  improvement, which is  any action
                 involving the  construction  or extensive  modification
                 of major  physical facilities  (second  priority).

            Wherever possible,  the costs  of implementing the corrective
            actions  should  be  estimated.  Specific recommendations
            should be presented.  With few  exceptions,  recommendations
            must be limited to those corrective actions  classified  as
            "first priority" in  both of  the categories  above.
                                 39

-------
 Exceptions would Include any improvement that would require no (or minimal)
 cost.   This section should also include a statement of the best effluent
 quality believed by the evaluator to be achievable if all non-capital
 intensive recommendations were to be implemented.
                               REFERENCES

1.   Gilbert, W.G., Relation of Operation and Maintenance to Treatment
     Plant Efficiency, Journal  Water Pollution Control Federation,
     48(7):  1822-1833, 1976.

2.   Gray, A.C., Roberts, H.D., and Paul, P.E., "Evaluation and
     Documentation of the Effects of Operation and Maintenance Practices
     on the Performance of Selected Biological Treatment Plants", Final
     Report, Municipal Environmental Research Laboratory, U.S.
     Environmental Protection Agency, Cincinnati, Ohio.

3.   Hegg, B.A., Rakness, K.L., and Schultz, J.R., "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, Cincinnati, Ohio
     (1979).

4.   Wastewater Utility Management Manual, prepared by Government
     Finance Research Center, July, 1981.

5.   Energy Conservation in the Design and Operation of Wastewater
     Treatment Facilities, Water Pollution Control Federation, 1981.

6.   Energy Conservation in Municipal Wastewater Treatment, EPA-430/9-
     77-011, U.S. Environmental Protection Agency, Washington, D.C.,
     March 1978.

7.   Energy Conservation at Wastewater Treatment Plants, Special
     Publication, Technical Practice Committee, WPCF.

8.   NPDES Compliance Sampling  Inspection Manual, NTIS No. PB-81-153211,
     U.S. Environmental Protection Agency, Washington, O.C.

9.   Estimating Staffing for Municipal Wastewater Treatment Facilities,
     MO-1, U.S. Environmental Protection Agency, Washington, D.C., 1973.

10.  Methods for the Chemical Analysis of Water and Wastes, EPA-600/4-
     79-020, U.S. Environmental Protection Agency, Cincinnati, Ohio 1979.
                                      40

-------
11.   Hinrichs,  D.J.,  "Inspectors Guide for Evaluation of Municipal
     Wastewater Treatment Plants", U.S. Environmental Protection Agency,
     Contract No.  68-014727, 1979.

12.   Miorin, A.F., ed., Wastewater Treatment Plant Design, WPCF Manual
     of Practice No.  8, 1977, 560 pp.

13.   Metcalf and Eddy, Inc., Wastewater Engineering, McGraw Hill Book
     Company, New York, N.Y., 1972, 734 pp.

14.   Analysis of Operations and Maintenance Costs for Municipal Waste-
     water Treatment  Systems, EPA-430/9-77-015, NTIS No. PB-283471,
     U.S.  Environmental Protection Agency, Washington, D.C., February
     1978.
  "This  paper  has  been  reviewed  in accordance with the U.S. Environmental
  Protection Agnecy's  peer  and administrative review  policies and approved
  for  presentation  and  publication."
                                     41

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               PAPER NO.  3


OPERATION AND MAINTENANCE CONSIDERATIONS

      OF LAND TREATMENT FACILITIES
                    by

               Kimm Perlin
            Project Engineer
Roy F. Weston, Inc., Designers-Consultants
    West Chester, Pennsylvania  19380
                    42

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OPERATION AND MAINTENANCE CONSIDERATIONS OF LAND TREATMENT
FACILITIES

Kimm Perlin, Project Engineer
WESTON, Designers-Consultants, West  Chester,  PA
INTRODUCTION

    Land treatment of municipal wastewater has been practiced
since 1840.  The use of land to treat domestic wastewater has
received major impetus recently with the passage of the 1972
Amendments  (PL 92-500) and the 1977 Amendments  (PL 95-217) to
the Federal Water Pollution Control Act.  The 1977 Amendments,
the Clean Water Act, provide certain incentives for funding land
treatment systems through the U.S. Environmental Protection
Agency  (EPA) Construction Grants  Program.

    Previous EPA research has focused on two aspects of the land
treatment of wastewater:  The long-term environmental effects of
land treatment, and  the design considerations for land treatment
systems.  None of this research adequately addresses the  issues
of operation and maintenance of land treatment  systems.   The
purpose of  the study described  in this  report was to provide  in-
formation on operation and maintenance, staffing, and costs.
Also, the study was  intended to describe problems currently
being experienced at land treatment  sites due to operator and/or
design  limitations.   The  study  was divided into two phases.

     In  the  first phase, a project team  visited  various sites
using land  treatment systems to collect information on practices
currently  in use.  The  information was  collected on several gen-
eral  areas.  One area was facility staffing.  The data collected
 included numbers and functions  of the people engaged  in operat-
 ing  and maintaining  the land treatment  system and other treat-
ment  systems at the  site.

     Other  types of data collected during  the  site visits  were in
 the  areas  of process control  and  operational  information.  In-
 formation  collected  included  the  operational  strategy  used  by
 the  operator to decide  where,  when,  and how  much wastewater
 should  be  applied.   A third  area  in  which  data  were gathered
 during  the site visits  was  operation and  maintenance  costs.   Da-
 ta on operation  and  maintenance costs  of  the  land treatment  sys-
 tem were  collected,  and if  possible, divided into  salaries,  en-
 ergy, chemicals,  materials,  and other  well-defined  categories.
                                 43

-------
    During the site visits, data were also collected on factors
that hinder the operation and maintenance of a land treatment
facility.  The adequacy of the groundwater monitoring practices
was also assessed during the site visits.  Neighbors whose prop-
erty was adjacent to or in the vicinity of the land treatment
system were interviewed to determine the impact of the land
treatment system on private individuals.

    The second phase of the study was the development of defini-
tive recommendations for procedures to improve the operation and
maintenance of land treatment systems.

    The recommendations were developed from two different view-
points.  The first viewpoint involved the type of land treatment
system.  Therefore, all three major types of land treatment sys-
tems were visited:  slow-rate (irrigation), rapid infiltration
(infiltration-percolation), and overland flow systems.  The sec-
ond viewpoint involved the degree of preapplication treatment
associated with the facility.  Therefore, facilities where pri-
mary-, secondary-, and tertiary-treated wastewater is applied
were visited.  In addition, facilities with different types of
treatment, e.g., trickling filter versus activated sludge secon-
dary treatment, were visited. The potential effects of climatic
conditions were also included.

    The overall goal of the research project was to make specif-
ic recommendations to improve and optimize the operation and
maintenance of land treatment systems.

BACKGROUND

    The evaluation of a land treatment system is different from
the evaluation of typical wastewatfr treatment process in that
there is little in the way of direct evidence as to the effec-
tiveness of the land treatment system.  Therefore, determination
of the adequacy of a land treatment system must rely on circum-
stantial evidence.

    The following data are needed to assess the adequacy of a
land treatment system:

    •   Design loadings as compared to typical design
        limitations.

    •   Compliance/noncompliance with applicable state
        and Federal regulations/guidelines.

    •   Visual observations (aesthetics,  plant health,
        soil condition,  etc.).
                               44

-------
    •   Maintenance practices.

    •   Operational practices.

    It is only through consideration of such parameters that the
performance of a land treatment system can be adequately as-
sessed.  In other words, a direct standard, such as effluent
quality, by which the system can be gauged is not available.
Therefore, adherence to reliable design, operation, and mainte-
nance practices are used to determine the presumptive adequacy
of a system.

    The sites visited were selected based on a variety of fac-
tors, including degree and type of preapplication treatment,
climatic conditions, and type of land application system.  Using
these guidelines, the selected sites have been plotted geograph-
ically, as shown in Figure 1.  The sites are clustered around
California, Michigan, and Texas since this is representative of
the geographical distribution of land treatment systems in the
United States.  Figure 1 also presents the five different cli-
matic zones in the United States, as presented by Sullivan, et
al (1973)  (1).  At least one site was visited in each of the
climatic zones.

    During the site visits, a trip questionnaire/checklist was
completed  for each location.  The types of data collected are
summarized in Table 1.  The majority of information learned dur-
ing the site visits is believed to be factual.  Certain ques-
tions, however, required estimation on the part of the treatment
plant personnel in order to supply the required information.  In
cases where the personnel were unable to provide the information
requested, the data were estimated, if possible, by the inter-
viewers.

    Of the questions posed, the budgetary questions proved to be
the most difficult to answer.  One question involved the budget
information for the operation and maintenance of the facility.
For the majority of the facilities visited  (26 out of 28), the
budget  information obtained applied to the entire treatment fa-
cility  as  the funds spent on land application were not separated
from  those for preapplication treatment.  This necessitated es-
timation  to ascertain how much money was spent in each area.
Furthermore, at some of the smaller facilities, collection and
treatment  costs were lumped together and had to be separated.

    The  budgetary problem is further complicated by the fact
that  it  is sometimes difficult to decide if equipment is part of
the preapplication treatment or the land application treatment
                                45

-------
                    A - Mediterranean Climate -
                       Dry Summer, Mild, Wet Winter
                    B - And Climate ~ Hot, Dry
                    C - Humid Subtropical -  Mild Winter,
                       Hot, Wet Summer (Washington. Oregon
                       Area Mild,  Moist Summer)
                    D - Humid Continental -  Short
                       Winter, Hot Summer
                    E - Humid Continental -  Long
                       Winter, Warm Summer

                   (Adapted from Sullivan, et al, 1973)
FIGURE  1.   GEOGRAPHICAL  AND CLIMATIC  LOCATIONS
            OF LAND TREATMENT SITES  VISITED.
                       46

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 TABLE  1.   SUMMARY OF DATA  COLLECTED  DURING  SITE  VISITS

Background Information

    - Contributory population, flows,  loadings
    - Final disposition of wastewater
    - Budget
    - Instrumentation, electrical consumption
    - Analytical data

Staffing

    - Certification
    - Background data
    - Preapplication and land application staffing

Maintenance

    - Preventative maintenance program
    - Operation and maintenance manual

Wastewater  Preapplication Treatment System

    - Physical facilities  (type and number)
    - Process flow diagram

Land Treatment System

    - Wastewater  storage
    - Wastewater  distribution
     - Buffer  zones,  site access
     - Application rates
     - Soils information
     - Groundwater monitoring

Facility Layout

     - Preapplication  treatment
     - Land  application  system

 Land Application  - Agricultural Viewpoint

     - Operational strategies  (wastewater applications,
      time  and  amount)
     - Operational problems
     - Crop  management

 Land Application  - A Neighbor's Viewpoint

     -  Problems
     -  Changes
                             47

-------
system.  For example, a holding pond following secondary treat-
ment may actually function as an oxidation pond, thereby appear-
ing to be part of the preapplication treatment system. One could
also consider the holding pond as nothing more than an effluent
holding pond, however, and therefore, part of the land applica-
tion system.

    The second problem question, closely related to the budgeta-
ry dilemma, involved staffing requirements for the preapplica-
tion treatment and the land treatment systems.  The problem  in-
volves dividing the hours which are  spent daily into preapplica-
tion and land application treatment.

    A further complication to both the budgetary and staffing
information is afforded by the different operational practices
at the treatment plants.  For example, at one location the pre-
application treatment and land treatment systems may be operated
and maintained by the same staff, whereas at another facility,
the duties at the land treatment facility may be shared by the
wastewater treatment facility personnel and/or farmer.  At a
third facility, however, the operation and maintenance of the
land application system may be performed entirely by a farmer.
Therefore, only costs incurred by the municipality during the
land treatment portion were included, and no attempt was made
to calculate costs incurred by the farmer in the operation of
the land application facility, as the majority of these costs
would be incurred during irrigation  of a normal farm.

    An additional problem question concerned determining the
land treatment operating strategy.   The problem, however, was
not how the facility was operated, but rather why the facility
was operated in the mode that it was.  Typically, it appeared
that operational practices were gained through experience, and
once practices were successful, no attempt was made to change
the operation of the facility.  Therefore, when questioned about
the operation of the facility, the operators could typically re-
spond about how something was done,  but not necessarily why  it
was done.

EVALUATION OF CURRENT OPERATION AND  MAINTENANCE PRACTICES

    This section presents a summary  of the information which was
collected during the site visits.  The 28 site visits included
18 slow rate, seven rapid infiltration, and four overland flow
systems (one system was both slow rate and rapid infiltration).
Table 2 presents background information on the land treatment
systems.   Similarly, Table 3 gives a description of the physical
facilities at each land treatment site.  Information relative to
the operation and maintenance of the land treatment systems  is
contained in Table 4, with Table 5 presenting land treatment
system loading rates.  Data on groundwater monitoring are pre-
sented in Table 6 along with monitoring parameters and frequen-
cy.

                                48

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                        TABLE  2.    LAND  TREATMENT   SYSTEMS,  BACKGROUND  INFORMATION
                                                                                                                         Weather Data"
    Fac H Uy Name
 Villaup of Lake (ieorqe. WWTP
 North Hr anrh Fire  District No.
 City of Hart WWTF
 Ci ty of Fremont WWTI'
 Village of Ravenna  STP
 City of Wayland WWI'P
 Font ana Reg ional  Plant No. '1
 Pomona Wat*>r Reclamation  Plant.

 Whitt ier Nar rows Water Heel amat
 Palmdale Water  Reclamation Plan
 Irvine Ranch Water  District
 City of Tulare  WPCF
 City of Kerman  WWTP
 City of Manteca WWQCF
 F,l Dort-ido Hills WWTP
 U.S. Army COK,  WES Overland Flo
 Fa Ikner WWTF
 F,a s 1 ey Comb i nfd Utilities Sys ttM
   Flow Project
 Town of Wareham WPCF
 Chatham WPCF
 Town of Barnstable WPCF
 Kendal/Crosslands  l.aqoon  System
 Land i s Sewaqf An t hority
 C'amphe 1 1  Soup  (Texa s) ,  Inc .
 City of Coleman WWTP
 City of Santa Anna WWTP
 City of Winters WWTP
 City of Sweetwater WPCP
Site
Number

001
002
00!
004
005
006
007
008

009
01 0
Oil
012
013
014
015
016
01 7
018
019
020
021
022
02 )
024
025
026
027
02 H
Type of Years in Adjacent
System Operation 1-and Use8

HI
SH
SR
SR
SH
SR
RI.SH
SR

HI
SR
SR
SR
SR
SR
SH
OF
OF
OF
HI
HI
HI
SH
RI
OF
SH
SH
SR
SR

41
5
6
5
1 1
9
27
50

18
23
11
35*
4
17
5
4
3
2
8
9
45
7
iO
16
50
1 4
56
22

R
R , C , A
A
A
R,A
A
I ,A,O
H , C , I , A , 0

H,C
A
R ,C,A,O
A
A, I
A
A,O
A
A,H
A, H
H
R
C, R
R
I
C , I , A
A
A
A
A
Preapplicat ion Water
Effluent to Source in
Land Treatment Vicinity

100
100
100
100
100
100
100
Winter 33
Summer 66
100
100
100
100
100
100
40
33
100
100
100
100
100
100
100
100
70
100
100
100

Public
Well
Well
Well
Well
Well
Public
Public

Publ ic
Publ ic
Public
Well
Well
Well
Public
Publ ic
Public
Pu b 1 i c
Pu h 1 i c
Well I Public
Public
Public
Public
Public
Publ ic
Public
Public
Publ ic
Average
Annual
Temperature
°C
6.2
7.8
8.3
8.9
6.5
8.8
1 7.6
16.7

1 6.7
16.4
16.6
17.4
16.8
15.9
13.1
18.8
15.9
15.4
11.1
9.7
11.1
11.9
12.2
1 7.3
18.6
18.6
18.2
17.4
Estimated
Average Mean Annual
Annual Class A
Precipitation Pan Evaporation
m
0.95
1.09
0.84
0.64
0.80
0.82
0.32
0.42

0.42
0. 20
0. 31
0.24
0.26
0.30
1.01
1.31
1.38
1.32
1.01
1.10
1.01
1.10
1. 02
1. 15
0.68
0.68
0.55
0.56
m
0 .84
0.89
0.94
1 . 02
0 . 99
1 . 02
1.75
1.65

1.65
1.78
1.52
2.29
2 . 29
2.03
1.65
1. 52
1 .40
1.30
0.86
0 . 81
0.86
1.19
1. 14
1.91
2.41
2.41
2.49
2: 54
   R = Residential
   C = Commercial
   I = Industr i a)
   A = Agricultural
   O = Other

   From nearpst weather station.
WWTP  -  Wastewat f r t reat merit  plant
WPCF  -  Water pollution control  facility
WWTF  -  Wastewater treatment  facility
STP   -  Sewage treatment  plant
WWQCF -  Wastewater quality  control facility
WPCP  -  Water pollution control  plant

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                          TABLE  3.     LAND  TREATMENT   SYSTEMS,  PHYSICAL  FACILITIES
Facility Nam*

Village of take George WWTP
North Branch Fire District
No. 1 WPCF
City of Hart WWTF
City of Fremont WWTP
Village of Ravenna STP
City of Wayland WWTP
Fontana Regional Plant No. 3
Pomona Water Reclamation Plant
whittier Narrows water
Reclamation Plant
Palmdale water Reclamation Plant
Irvine Ranch Water
District
City of Tulare WPCF
City of Herman WWTP
City of Manteca WWQCF
El Dorado Hills WWTP
U.S. Army COE, WES
Overland Flow Site
Falkner WWTF
Easley Combined Utilities Sys-
tem Overland Flow Project
Town of Wareham WPCF
Chatham WPCF
Town of Barnstable WPCF
Kendal/Crosslands Lagoon System
Land is Sewage Authority
Campbell Soup (Texas), Inc.
City of Coleman WWTP
City of Santa Anna WWTP
City of Winters WWTP
City of Sweetwater WPCP
alncludea potential storage, such
Type Instru-
of menta-
Site Sys- tlon
No. tern System

001

002
003
004
005
006
007
oo a

009
010
Oil

012
013
014
015

016
017
018
019
020
021
022
023
024
025
026
027
028
as

RI

SR
SR
SR
SR
SH
RI.SR
SR

RI
SR
SR

SR
SR
SR
SR

OF
OF
OF
RI
RI
RI
SR
RI
OF
SR
SR
SR
SR
var i able

No

Yes
No
No
No
NO
No
Yes

No
No
Yes

No
No
No
No

Yes
No
Yes
No
No
No
Yes
No
Yes
No
No
NO
No
levels
Waste-
Water Land
Stor- Area.
age* U»edb
days
0

162
102
472
297
258
0
nd

0
42
98

28
3
4
7

N/A
118
44
0
0
0
51
0
0
0
369
9
15
ha
2.

13.
34.
24.
8.
31.
20.
29.

405»
279

2

8
a
1
1
6
3
1



607-809
(Seaso
205
87.
106
8.

0.
1 .
1.
1.
0.
3.
3.
26.
na 1

8

1

50
06
9
6
38
2
2
3
235
23.1
10.9
10.5
115
in oxidation

Sand

Silt,
Sand,
Sand,
Sand,
Sand,
Sand,
Widely

Sand
Silt,
Silt,
)
Sand,
Sand,
Sand,
Silt,

Silt,
Silt,
[.oam,
Sand
Sand,
Sand,
Silt,
Sand
Clay
Clay,
Clay,
Silt,
Silt,
Soil 1



sand,
loam
loam
clay
loam,
loam
Vpe



loam



clay

vary i nq


sand,
sand ,

loam
Inam
loam
loam

1 oam
loam,
clay ,

loam
loam*"
loam

1 oam,
loam ,
sand,
loam,


loam
clay.







clay
sand





silt
silt
clay,
clay
ponds using 0.61 m (t



Slope
of
Land i
Flat
Steep
Moderate
Flat
Flat
Moder ate
Flat
Flat-steep
Flat
Flat
Number
of
Ground-
water
Monitor-
ng Wells
24
6
6
32
0
rj
(J
0
16<
4
Flat-moderate 0
Flat
Flat
Flat
Moderate
0
0
1
0
Fl at-moder at *• 0
Flat-moderate 0
Moderate
Flat
Flat
Flat
Mod e r a t e
Flat
Moderate
Flat
Flat
Flat
Flat
,,
0
0
0
11
3
0
0
0
0
0

waste-
water
Distri-
bution
System
G,P
p
p
G, P
G
P
G,P
G,P
G
P
P
G
G,P
G,P
P
P
P
p
G
G
G
P
G,P
P
G
P
G,P
G,P
                                                                                                                  n   Wg s t ewa t e r AjjpHca t i on System
                                                                                                                    Inf i Itrat ion beds

                                                                                                                    Fixed nozzles
                                                                                                                    Gated pipe,  ridge and furrow
                                                                                                                    Border  str i p
                                                                                                                    Border  st r ip
                                                                                                                    Center  p i vot,  big qun spiay
                                                                                                                    Inf iltration beds, ridge fc  fur row
                                                                                                                    Spr ay r  ridqe and  furruw

                                                                                                                    InliItration beds
                                                                                                                    Side-wheel  rol1 spray
                                                                                                                    Spray,  ridge and  furrow, drip

                                                                                                                    Border  strip,  ridge and furrow
                                                                                                                    Ridqe and  furrow
                                                                                                                    Border  str ip
                                                                                                                    Spray

                                                                                                                    Trouqh distr i but Jon
                                                                                                                    Spray

                                                                                                                    Fixed nozzle,  trough, op«;n pipe
                                                                                                                    InfiJ tration beds
                                                                                                                    Inli Itrat ion beds
                                                                                                                    Inf iItrat ion beds
                                                                                                                    Spray
                                                                                                                    Inf iItrat ion beds
                                                                                                                    Spray
                                                                                                                    Border str ip
                                                                                                                    Side-wheel  roll  spray
                                                                                                                    Border str ip
                                                                                                                    Border strip
 operated this way.  Based  on current flow rate, not including  precipitation or  evaporation effects.
blncludes only land area  in use, not land available for use.
Cflat  0-3«i moderate  3-81; steep  over  8».
dAn 11,356-m3 storage basin is currently  under  construction.
^Imported sand has been used for replacement.
WV1TP  - waatewater treatment  plant
WPCF  - Water pollution control  facility
WWTF  - Wastewater treatment  facility
STP   - Sewage  treatment plant
WWQCF - Wastewater quality control  facility
WPCP  - Water pollution control  plant

-------
                                    TABLE  4.    LAND TREATMENT  SYSTEMS  INFORMATION
Type
of

Facility Name
Village of Lake George WWTP
North Branch Fire District
No. 1 WPCF
City of Hart WWTF
City of Fremont WWTP
Village of Ravenna STP
City of Wayland WWTP
Fontana Reqional Plant No. 3
Pomona Water Reclamation Plant
Whittier Narrows Water
Palmdale Water Reclamation Plant
Irvine Ranch Water District
City of Tulare WPCF
City of Herman WWTP

City of Manteca WWQCF
El Dorado Hills WWTP
U.S. Army COE, WES
Overland Flow Site
Falkner WWTF
Easley Combined Utilities System
Overland Flow Project
Town of Wareham WPCF
Chatham WPCF
Town of Barnstahle WPCF
Kendal/Crosslands Lagoon System
Landis Sewage Authority
Campbell Soup (Texas), Inc.
City of Coleman WWTP
City of Santa Anna WWTP
City of Winters WWTP

aDoes not include electrical usa<
nOP - Operating permit
PTQ - Preappl icat ion treatment
Site Sys-
No. tern
001
002
003
004
005
006
007 RI
008
009
010
Oil
012
01 3

014
015
016
017
018
019
020
021
022
023
024
025
026
027
028
RI
SR
SR
SR
SR
SR
,SR
SH
RI
SR
SR
SR
SR

SR
SR
OF
OF
OF
RI
RI
HI
SR
RI
OF
SR
SR
SR
RH

0
0
0
0
0
0
0
Gravity-$12. 16/1 ,000 m3
Pressure-$48. 93/1 ,000 m3
$16.21/1 ,000 m3
$4.05/1 ,000 m3
S32.43-$64.86/l ,000 m3
City receives 25% of crop
$l,000/yr for water
$181/ha/yr for land
$10.71/ha/yr for land
$100/month*$31/l ,000 m3
0
0
0
0
0
0
0
Average
Elec-
OtM Manual
Type Which System
of Addresses Oper-
Regu- Land ated

trical latory. Application as Buffer
Usage Permit On Hand? Designed? Zone Size
kwh/mo
1,365
4,700
16,228
3,505
0
14,000
11,250
16,933
0
0
Not known
0
194

10,000
Not known
Not known
360
2,326
0
Q

Q
3,630
0 3,460
0 Not known
$129.87/ha/yr for land 0
Farmer pays pumping cost 727
$8.09/ha/yr for entire site 3,000
0 2,700
PTQ
OP
GWQ
GWQ
SWDQ
GWQ
PTU
PTQ
PTQ
PTQ, GWQ
PTQ
PTQ
PTQ

PTQ, GWQ
PTQ, SWDQ
None
SWDQ
None
SWDQ
OP
OP
PTQ
OP
SWDQ
SWDQ
OP
OP
OP
No
Yes
Yes
Yes
No
Yes
No
N/A
N/A
N/A
N/A
Yes
Yes

Yes
No
Yes
Yes
Yes
Yes
Yes
Ye s
Yes
No
No
Yes
Being written
No
N/A
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes

No
No
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
m
76
61
15
15
15
0
91 RI basins
6 Citrus grove
0
0
0
0
0
0

0
0
400
0
15
30
305
30
46
0
30 +
6
305
30
15


Public Access Controls
Woods
Fence
Fence
Fence
Fence
Fence
Fence
Signs-
None
Fence
Signs
None
Signs
None

None
None
Signs
Fence
Fence
Fence
None
Fence

and signs
and signs
and signs
and signs
ana signs
and signs--RI basins
-citrus grove

and signs




and signs
and signs

One field--fence and signs
Other field—none
None
Fence
Fence
Fence
Fence
Fence
and signs
and signs
;e by end users unless paid by authority.

gual ity
quality


















 GWQ  - Groundwater quality                                   ,
cCity of Pomort* Water Department purchases  water for $9.26/1,000 m->.
WWTP  - Wastewater  treatment plant
WPCF  - Water pollution control facility
WWTF  - Wastewater  treatment facility
STP  - sewage treatment plant
WWQCF - Waatewater  quality control  facility
WPCP  - Water pollution control plant

-------
                                     TABLE 4.    LAND  TREATMENT SYSTEMS  INFORMATION
Ul
rO
Facility Name
Vlllaqe of Uke George WWTI'
North Branch Flte District
No. 1 WPCF
City of Hart WWTF
City o( Fremont WWTP
Village of Ravenna STP
City of Way land wwn>
Fontana Regional Plant No. '»
Pomona Water Reclamation Plant
Whittler Narrows Water
Heclamat ion Plant
Palmdale Water Reclamation Plant
Irvine Ranch Water District
City ol Tulare WPCK
City of Kertnon WWTP
City of Manteca WWOCF
Kl Dorado Mil Is WWTP
U.S. Army COF. , WKS
Overland Flow Site
Falkner WWTF
Eaaley Combined Utilities sys-
Town of Wareham WPCF
Chatham WPCF
Town of Barnstable WPCF
Kendal/Crosslands Laqonn System
Landis Sewage Authority
Campbell Soup (Texas), Inc.
City of Coleman WWTP
City of Santa Anna WWTP
City of winters WWTP
City of Sweetwater WPCP
Site
_No.
001
002
003
004
005
006
007
008
009
010
01 1
012
01 i
01 4
01S
016
01 7
nin
019
020
021
022
023
024
02S
026
027
028
Kjy
WWTP - Waatewater treatment plant
STP - Sewage treatment plant
:ility
Typ
ol
Sys
tern
HI
SH
SH
SH
SH
S.H
HI
SH
SR
HI
SH
SH
SH
SH
SH
OK
tit
OK
HI
HI
HI
SH
HI
OF
SH
SH
SH
ty
Su
e La nd H
Treatment
Syitem le
Management Dl
Wastewater agency
waslewater aqency
Wastewater aqency
Wastewater aqency
Wastewater agency'1
Wantewater aqency
and farmer
City of Pomona and
enrt users
t.Al'FCU
Fa rmpr
owners ar,r.oc.
Farmer
Fa rmpr
Farmer
(iolf course
ICOF-)
Wastpwater agency
and ClPlflBOn Univ.
Wastewater agency
wautpwater agency
Wastewater agency
Camphel 1 Soup
and farmer
and farmer
Fa rmpr
Fa rmpr
Vi*ui
rr ace
unoff Months
Col- System
cted/ in
verteo t'se_
Ye -i 1-12
Yea 1-12
Yes 4-11
Yen 4-11
Yer. 4-11
Yes ',-»
YP-! HI 1-1?
S H 4-10
No 1-12
Yer. 1-12
No 2-10
No
Nn
Yes
No

Yen
Yer,
Yer,
No
Ypj;
Yes

Yes
Yes
1-12
1-12
1-12
1-12

1-1 i'
1-12
1 12
1 -1 2
1 -1 2
1-1 2
1-12
1-12
1-1 1
1-12
iu J.UUCTU;
TyjpgB o f_ _rr ops
Not appl icabl p
Maple:;, beech PS, h i rch«*s ,
white pine, spruce, f it
Pi HP, hardwood , uncu 1 1 i vated
Alfalfa, o»t s . r ye
Uncul t i vat pd
Allaltrt, timothy, qisRp, clover
Sft-qraf>pf mils, oranqor.

Not app) it-dbl f
AH a 1 f a, oatr.
t.roccol i , can I i flowr r , 1 jnd-
scapp
cor n
oat R, cot t on. a 1 dionds
Har 1 py , oat F , cor n
ryp , tier mud a
Her mud a, reed canary, 1 f?.ru*>
Fescue , ryp
Not appl icabl *•
Not appl icahl *>
Not appl icahl «•
Heechcr., maples, popl ut , o.tk-
Not appl 1 r-flt.l '•
rye
Alfalfa, Johnson qi ass
Coastal Bermuda, Sudan qrar.s
Coaata 1 Bermuda, Sudan,
Johnpon, and Mer.rue qrasses.

An-
Farm-
ing
Pr ac-
Who ticeB
Harvests Di f-
N/A
Not appl icabl e - N/A
Not appl icable - N/A
Not appl icable - N/A
Human con sump- Fa rmer Ves
t l on
m
-------
                                TABLE   5.     LAND  TREATMENT   SYSTEM  LOADING  RATES
  Faci1i ty  Name
North Branch  Fire District No.  1 WPCF
City of  Hart  WWTF
City of  Fremont WWTP
Villaqe  of  Ravenna STP
City of  Wayland WWTP
Fontana  Regional Plant No. 3
Pomona Water  Reel amat i on  Plant
PaImdale Water Reclamat ion PI ant
Irvine Ranch  Water District
City of  Tulare WPCF
City of  Kerman WWTP
City of  Manteca WWQCF
El Dorado Hills WWTP
Kendal/Crosslands Lagoon  System
City of  Coleman WWTP
City of  Santa Anna WWTP
City of  Winters WWTP
City of  Swpetwater WPCP
Villaqe  of  Lake Georqe WWTP
Fontana  Req ional PI ant No. 3
Whittier Nar rows Water Reclamation Plant
Town of  Wareham WPCF
Chatham  WPCF

Town of  Barnstahle WPCF
Land i s Sewage Au thor i ty
U.S. Army COF,, WES Overland Flow Site
Falkner  WWTF
Easley Combined Ut i 1 i t ier, System
  Overland  Flow Project
Campbell Soup (Texas), Inc.

Site
Number
002
003
004
005
006
007
008
010
Oil
012
013
014
015
022
025
026
027
028
001
007
009
019
020

021
023
016
017
018

024
Type
of
Suspended
Hydr aul ic
System mm/wk
ER
SR
SR
SR
SR
SR
SR
SR
SR
SR
SR
SN
SR
SR
SR
SR
SR
SH
RI
RI
RI
RI
RI

RI
RI
OF
OF
OF

OF
21.
69.
76.

42.
54.
33.
43.
1 7.
58.
40.
32.
18.
76.
45.
1,130
330

2,110
m/yr
8 1.1
5 2.4
2 2.6
1.2
2 1.1
6 1.6
0 1 .4
2 2.3
0 0.89
4 3.0
6 2.1
3 1.7
3 0.95
2 4.0
7 1.2
40.5
17.3
49. 7t>
27.1
Winter 380 28.8
Summer 72

400
6 i. 5-254
17.
Raw 1 19
Ponci 103-19
40.
0
12.0
21 .0
3.3-13.2
8C

3
6 2.1
Organic
kg BOD5/ha/yr
40.7
1,208
316

287
1,623
637
2,253
89
1 ,471
320
67.2
266
1,775
21 5
23,862
17,162

4,103
5,616



87.6-349

11,810
1 ,446-2,740
12,790
Nutrients

Solids
kg SS/ha/yr

2,



1,
1,
4,

1,



2,

8,
12,

5,
4,



1 J9-

10,
3, 098
5,
45.2
101
817


247
699
070
53
382
428
16.8
578
365
132
897
771

471
405



555
--
982
-5,871
595
kg NH3-N/ha/yr kg NOj-N/ha/yr
5.4 63.7

- _

__
472 5.9
99.1
" u 1 a t e d
454

445 16.9
219
-_

_ _
_ _

4,995 43.1
_ _

_ _


_ _
55.0-222
-_
944 79.9
42.8-80.7 28.0-52.8
370d
kg T-P/ha/yr
15.6a
49. 3a
87

-_
410
15?a
__

--
149a


_-


4, 335





__
39. 3-158

172
64.0-121
160
^Phosphorus  measured as PO^.
bBased on total  water infiltrati
cDesiqn application rate.
dTotal - N.
n,  not  only  recla imed water.
Key

WWTP  - Wastewater  treatment plant
WPCF  - Water  pollution control facility
WWTF  - Wastewater  treatment facility
STP   - Sewaqe treatment plant
WWQCF - Wastewater  quality control facility
WPCP  - Water  pollution control plant

-------
                          TABLE  6.     GROUNDWATER  MONITORING  DATA
    age of  L»k* Georqr
     HWTP
North Branch  Fir*
Distrlet  No.  1 WPCK
City of  Bart WWTK
City of  Fremont WWTP
           Type     Number
F«c i1i ty     of        of
Number     System    Welln

001       HI        24
City of Wayland WWTP
Heel a mat ion Plant
Palrodale Water
Reclamat ion Plant
City of Mantec* WWQCF
Easley Combined Utilities
System Overland Flow Project
Kenda I/ Cross lands Lagoon
OO1)
009

010
014
018
022
SH
RI

SH
SH
OF
SR
5
1 6

2
9
S
7
System
                                                              Groundwater
                                                              Monitor i nq
Wells installed by Rensselaer
Polytechnic  Institute for
research purposes only

pK,  alkalinity, hardness,
sulfate, chlori de, ammonia -N,
nitrate-N,  phosphate

Static water  elevation,
chlor ide,  specilie conductance,  pM
Hardness,  alkalinity, ammonia-N,
nitrate-N,  phosphorus, MBAS, COD

Static water  elevation,  chloride,
specific conductance
pH,  hardness,  alkalinity, ammonia-N,
nitrate-N,  nitrite-N, phosphorjs,  su 1 fate

No samples  are taken due to problems
with wells.   New wells are to be installed.

Major minerals, nitrogen compound E, cot),
BOD, TDS,  electrical conductance,  pH,  odor
Trace metals,  chlorinated hydrocarbons

Va r lous wastewater pa rameter s measured  in
farmer ' s t wo  i rr i gat ion  wel]B

Static water  elevation,  ammonia-N,  nitrite-N,
nitrate-N

Groundwater moni tor ing lor research
purposes only

Static water  elevation,  pH, ammonia-N,
nitrite-N,  nitrate-N, phosphate,  fecal
col iforms
                                                                                                           Sam^l e
                                                                                                           Freguency
                                                                               I/month when not
                                                                               frozen
                                                                               1/month

                                                                               J/year


                                                                               •I/year

                                                                               1/year
                                                                                                           4/year

                                                                                                           I/year

                                                                                                           2/year


                                                                                                           4/year
                                                                                                           4/year
Land i s Sewaq e  Authority
                                                              Water table el vat ion
                                                                                                           L'ont i nuous
 Pour local  domestic wells aleo monitored.

-------
    Of the 28 sites visited, facility  002  (North Branch Fire
District No. 1, Dover, Vermont) was  located  in the coldest area,
with a mean annual temperature of  7.8°C  (46.0°F).  The Uti-
ca, Mississippi overland flow  site was located in the warmest
area, with a yearly average temperature  of 18.8°C (65.8°F).
Precipitation ranged from a high of  1.38 m/yr  (4.53 ft/yr) at
the Falkner, Mississippi facility  to a low of  0.20 m/yr (0.66
ft/yr) at the Palmdale, California Water Reclamation Plant.
Yearly annual estimated Class  A pan  evaporation ranged from a
high of 2.54 m  (8.3 ft) in Sweetwater, Texas,  to a low of 0.81 m
(2.7 ft)  in Chatham, Massachusetts.

    Wastewater  storage at the  facilities ranged from 0 to a high
of 472 days at  facility 004 (City  of Fremont, Michigan).  Stor-
age included any potential storage due to a  variable level in an
oxidation pond, plus storage in holding  basins.  Of interest, is
the fact that none of the seven rapid  infiltration systems visi-
ted had on-site storage.  The  overland flow  site at facility 024
(Campbell Soup, Paris, Texas)   had  no storage, whereas the other
overland flow sites had storage based  on a variable level in the
preapplication  treatment oxidation ponds.  There were only two
slow-rate systems which had no provisions for wastewater stor-
age; these were facilities 008 and 025 (Pomona, California Water
Reclamation Plant, and the Coleman,  Texas Wastewater Treatment
Plant).  In both of these plants,  however, provisions existed
for surface discharge.

    The land area receiving wastewater varied  from a low of 0.38
ha (0.94 acres) at the Chatham, Massachusetts  facility, to a
high of 809 ha  (2,000 acres)  associated  with the Irvine Ranch
Water District, California.  The land  area usage has been plot-
ted as a function of flow rate in  Figure 2.  As would be expect-
ed for the three different types of  systems, three distinct
areas on the graph are prevalent.  The lowest  land requirement
is for the rapid infiltration  systems.   The  highest land re-
quirement is for the slow-rate systems.  In  the middle area are
the four overland flow plants.  Facility 024 (Campbell Soup,
Paris, Texas)  appears slightly higher  on the curve than some of
the other overland flow systems.   This can be accounted for by a
recent expansion, and the fact that  the  facilities receive in-
dustrial wastewater with a high organic  loading.  Also plotted
in Figure 2 are the application land area requirements for mod-
erately-favorable conditions,   as taken from  "Water Reuse and Re-
cycling," Volume 2, OWRT/RU-79-2, U.S. Department of Interior,
1979 (2) .  Since the smallest  flow contained in this report is
0.044 m^/s (1.0 mgd), the plots are  extrapolated for lower
values.  The field data compare favorably with the OWRT data.
                                55

-------
EC
                                                            OWRT/RU-79/2 Data
                                                            Extrapolated
                                                                 A-SR
                                                                 • -RI
                                                                 • -OF
  0.1
   0.0004
    (0.01)
                           Land Treatment Row, m3/s (mgd)
            FIGURE 2.   LAND AREA  USED AS A FUNCTION  OF  FLOW RATE
                                      '

-------
    A wide variety of wastewater distribution equipment and ap-
plication system types were seen during the survey.  In addi-
tion, at nine of the 28 sites, wastewater was distributed by
both gravity and pumping.  At three of these sites, i.e., facil-
ities 001,007, and 023, the older portions of the systems re-
ceived gravity flow, while pumping was required for the newer
portions.

    A variety of contractual agreements exist, and typically
these agreements are for the slow-rate system, with the excep-
tion of facility 009  (Whittier Narrows Water Reclamation Plant,
California) where wastewater is purchased for groundwater re-
charge.  In the remaining facilities, the agreements typically
are for the purchase of wastewater or for rental of a portion of
the city-owned land, with the stipulation that the wastewater
will be utilized.  At facility 012  (Tulare, California), the
stipulation is that the city will receive 25 percent of the
crop-generated revenues.

    Of the sites visited, all of the rapid infiltration and ov-
erland flow systems were operated 12 months out of the year.  It
should be remembered, however, that the overland flow systems
were all located in mild climates.  Of the 18 slow-rate systems,
only six are operated less than 12 months of the year.  Of
these, the citrus crop irrigation at facility 007  (Fontana, Cal-
ifornia Regional Plant)  is included.  In this case, however, as
there is a rapid infiltration system also available, the slow-
rate system is not operated during the colder months.

    The types of crops grown and the ultimate use of the crops
are presented in Table 4 for the slow-rate and overland flow
sites.  Of the seven  rapid infiltration sites visited, only the
Chatham, Massachusetts facility had any major plant growth in
the basins.  This was just weed growth which had not been re-
moved.

    At the remaining  sites  (with the exception of Ravenna, Mich-
igan) , a wide range of crops are grown.  At three  sites, trees
are irrigated but not harvested.  At the Utica, Mississippi
overland flow site, the  vegetation was tested and discarded.  In
Falkner, Mississippi  the vegetation was cut and left in the
field.  At the Easley, South Carolina overland flow site, the
grass was  baled; it is currently used only for erosion control,
as permission has not yet  been granted for it to be used as ani-
mal feed.  At the remaining  sites, crops are grown and used for
either human or animal consumption.
                                57

-------
    At the 13 facilities where the major objective of the land
treatment system was crop production, the superintendent or
foreman involved was queried as to whether or not the farming
practices were different than at neighboring farms of equal soil
type growing the same crop.  At only three facilities were the
farming practices the same as practices at neighboring farms.


LAND TREATMENT SYSTEM STAFFING AND OPERATION AND MAINTENANCE

    The staffing requirements for both the preapplication and
land treatment systems were analyzed and then compared to num-
bers presented in the literature.  In addition, data pertaining
to the number of shifts per day and days per week that the sys-
tems are staffed were collected.  Utilizing these data, the in-
formation in Figure 3 was calculated, which presents the staff-
ing for the three land treatment systems (independent of preap-
plication treatment) as a function of facility size.  Staffing
requirements were also compared to OWRT data for the land treat-
ment portion of the facility.

    The slow rate staffing requirements were typically less than
reported in the OWRT report, whereas the rapid infiltration and
overland flow staffing requirements are in general agreement.

    Based on the limitations of the data collected and the
amount of data collected, the following conclusions can be
reached:  1) For the slow-rate land treatment system, the staff-
ing requirement is independent of the degree of preapplication
treatment; 2) For the rapid infiltration system, the labor re-
quired decreases as the degree of preapplication treatment in-
creases; 3)  No conclusions should be reached for the overland
flow systems due to the insufficiency of data; 4) For the same
degree of preapplication treatment, slow-rate land treatment
systems were less labor intensive than rapid infiltration sys-
tems.

    As was done with staffing, the operations and maintenance
costs were compared to the OWRT data, and the results are pre-
sented in Figure 4.  As was seen with the staffing requirements
(and also because of)  the slow-rate systems were typically less
expensive than OWRT data, whereas the rapid infiltration and
overland flow systems were in general agreement.  A major cause
of this apparent disparity for slow-rate staffing and operation
and maintenance costs being typically lower than OWRT data is
caused by the system being operated in conjunction with a local
farmer.  The farmer incurs a portion of the costs and therefore
the municipality need not incur the cost.  Furthermore, based on
the visits,  operations are improved by joint operation.
                                58

-------

0.01
0.0004
 (0.01)
0.0044
 (0.1)
                                                     0.044
                                                     (1.0)
                                                Flow, m3/s (mgd)
0.438
 (10)
4.38
(100)
                                   FIGURE 3-   LAND TREATMENT  STAFFING

-------
                      Updated
                   OWRT/RU-79/2
                        Data
        All Costs Second Quarter 1980
1,000
    0.0004
    (0.01)
0.0044
 (0.1)
    0.044
     (1.0)

Flow, m3/s (mgd)
       FIGURE  k.   LAND  TREATMENT OPERATIONS AND MAINTENANCE  COSTS
                                      60

-------
    Given the wide range of facilities which were visited, it is
not surprising that both preapplication and land application
treatment operation and maintenance unit costs vary greatly.
The least expensive preapplication treatment cost was $0.011/
m3 ($0.04/1,000 gal), whereas the most expensive preapplica-
tion treatment facility cost was $0.725/m3  ($2.74/1,000 gal).
The land treatment operation and maintenance costs also varied
widely, with the least expensive facility costing $0.0005/m3
($0.002/1,000 gal), whereas the most expensive facility cost
$0.207/m3 ($0.78/1,000 gal).  The total treatment operation
and maintenance cost, which is more than likely the most acc-
urate cost,  varied from a low of $0. 014/m3  ($0.05/1,000 gal)
to $0.744/m3 ($2.82/1,000 gal).

    Based on the small sample size and the various limitations
of the cost data collected, the following conclusions can be
made utilizing the cost data collected:  1)  The slow-rate land
treatment operation and maintenance costs are unaffected by de-
gree of preapplication treatment; 2) The rapid infiltration sys-
tem operation and maintenance costs decrease as the degree of
preapplication treatment increases.

EVALUATION OF OPERATION AND MAINTENANCE PRACTICES

    The equipment for any land treatment system consists basi-
cally of piping, pumps, controllers, and application equipment.
With the exception of the wastewater application equipment,
wastewater treatment plant maintenance personnel should be fa-
miliar with all of the equipment, and its operation should not
be a problem.  With minimal personnel training, the maintenance
of wastewater application equipment should pose no major prob-
lem.

    Although the performance of a land treatment system must be
based on circumstantial evidence (with the exception of the
overland flow system), it would appear that the majority of fa-
cilities are well run, and their performance is in line with
typical performance specifications.

    Based on operation of the land treatment system (without re-
gard to regulatory restraints), it is believed that a slow-rate
land treatment system can operate without major problems with a
minimum of primary preapplication treatment.  Similarly, a rapid
infiltration system can operate with a minimum of primary preap-
plication treatment if the required bed maintenance is prac-
ticed.  It appears that the overland flow system can operate
successfully with a minimum of preliminary  (screening and grit
removal)  treatment.
                                61

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DESIGN DEFICIENCIES

     The most  common  preapplication treatment design deficiency
involved preapplication  ponds which were unprotected from the
effects of erosion  caused by wind-induced waves.

     A wide  variety of design deficiencies were noted with
regard to the  land  treatment systems.  Only at one location were
the design deficiencies  severe enough to substantially hamper
facility operations.  The design deficiencies included:
unnecessary  pumping;  insufficient storage volume; improper nozzle
selection; lack of  consideration of the effect of soil type and
texture during selection of irrigation equipment; application
areas subject  to public  access; and improper grading causing
ponding.

REFERENCES

      1.   Sullivan,  R.H., et al. "Survey of Facilities Using Land
         Application  of  Wastewater".  EPA 430/9-73-006,
         NTIS  No. PB-227351, U.S. Environmental Protection
         Agency, Washington, D.C., July 1973.

      2.   U.S.  Department of the Interior, Office of Water
          Research and Technology.  "Water Reuse and Recycling",
          Volume 2,  Evaluation of Treatment Technology.
          OWRT/RU-79/2,  April 1979.
    "This paper has been reviewed in accordance with the U.S. Environmental
    Protection Agency's peer and administrative review policies and approved
    for presentation and publication."
                                 62

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SESSION NO. 2
   Improving the  Performance of Conventional Wastewater
   Treatment Processes
                                PAPER NO. 4
                 MAKING-DO WITH CLARIFIER HYDRAULIC OVERLOAD
                                    by

                             Robert M. Crosby
                                 President
                     Crosby,  Young and Associates, Inc.
                       1201 E.  15th Street, Suite  108
                             Piano, Texas  75074
                                     63

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MAKING-DO WITH CLARIFIER HYDRAULIC OVERLOAD

Robert M. Crosby, President
Crosby, Young and Associates, Inc.
INTRODUCTION

     In 1977, the engineering services firm: Crosby, Young  and
Associates, was organized with the specific purpose of  finding
ways of improving the hydraulic characteristics  and solids  sepa-
ration effectiveness of settling tanks.  The idea was born  during
a brief hydraulic study of the secondary clarifiers at  the
Trinity River Authority's 60 mgd Central Wastewater Treatment
Plant in Grand Prairie, Texas.  Naively, the writer had applied
open-water dye tracer techniques to a tank to  define the through-
flow route of the bulk  fluid, in the expectation that the fluid
path would also show the most likely route of  solids transport.
It  should be no surprise to anyone that the guess was a good  one.

     The general procedure was developed by physical oceano-
graphers to trace the route and ultimate fate  of pollutants dis-
charged to natural waters.  Usually, a boat was  steered over  a
defined course while towing sensors or taking  frequent  samples to
define the three-dimensional distribution of indicative parame-
ters such as temperature, dissolved oxygen, or the concentration
of  an injected tracer dye.  For the first clarifier flow pattern
study, we chose one of  these oceanographer's tools, continuously
injected Rhodamine WT,  a stable fluorescent dye. The test  clari-
fier is shown in cutaway, Figure 1.  We were interested in  flow
phenomena in a vertical longitudinal section,  between the inlet
and weir region, from top to bottom.  Our  "boat" was the travel-
ing bridge.  The resulting contours of equal dye concentration
for one sampling run are shown in Figure 2.  From this, we  were
able to estimate an excessively fast transport of fluid directly
from the bottom inlet ports to the overflow weirs, with a dead
region at the upper right.
                        Weirs
                                        Inlets
   Figure 1.   Cutaway view of a rectangular secondary clarifier.


                                64

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                                                   NLET
                                                   END
               100   90
                       80   70   60   50  40   30   20
                         LONGITUDINAL DISTANCE FROM ("LET ENO (PERCENT)
    Figure 2.  Isolines  of dye concentration in a rectangular
               secondary clarifier.

     To interrupt  the high velocity jets and provide better
vertical distribution of the incoming mixed liquor, the design
engineer simply placed half-cylinders of pipe on the clarifier
floor, 6 inches from the inlet wall, Figure 3.  Monthly average
effluent total suspended solids and associated BOD immediately
dropped dramatically, Table 1.  Using longer-term data, TSS
dropped from  84 to 17 mg/1, a reduction of 79%.  Material and
labor cost for modifications to the four secondary clarifiers
was $20,000.
Table  1.

 Month

 BOD
 TSS
 Figure 3.  Baffling for bottom  inlet ports.

Effluent  Quality  Before and After Baffling, TRA Central

 Jun      Jul      Aug      Sep     Oct     Nov     Dec
  64
  60
80
43
75
56
56
37
A
17
14
33
17
31
20
                             Baffle  installed
                                 65

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WHAT IS HYDRAULIC OVERLOAD?

      The "Ten State Standards"(1) place limits on overflow rate:
for a conventional activated sludge secondary, 1200 gpd/sq ft for
peak hourly effluent rate.  Most readers will recall that surface
area overflow rate is derived from Camp's(2) ideal geometric
derivation, Figure 4.  If fluid moves uniformly, horizontally in
any cross-section, vo is the minimum vertical velocity for all
particles which will settle out completely.  In this ideal case,
v0 is exactly equal to effluent rate divided by surface area.
Thus, surface area overflow rate.  Not everyone recognizes that
the same geometric model can be used to derive vo which does not
include surface area at all.
 However:
             V0 = m
                                where T = time
      Figure 4.
 VH
  L
Camp's geometric settling zone model
alternate derivations.
                                                       with
      But, by definition of nationally or locally accepted design
standards, a clarifier is hydraulically overloaded if the surface
area is too small for a given effluent rate.

REALITY

      Unfortunately, most real clarifiers don't behave much like
the ideal model.  Figure 5 contrasts an ideal flow pattern assumed
by Camp's model with the kind of pattern more commonly observed.
Note that the upflow occurs over a relatively small fraction of
the surface area.  Henceforward in this presentation, real flow
patterns will be described, with emphasis on simple modifications
which were successful in making the clarifiers behave more
ideally.
      I
           Figure 5.  Ideal versus real flow patterns.
                                66

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MAKING REAL CLARIFIERS WORK BETTER

      To date, we have conducted analyses of 13 full-scale operat-
ing clarifiers.  Of the 13, 12 were found to have either internal
or upstream problems which degraded their effectiveness in captur-
ing solids.  One of the most common problems, the subject of
considerable honest controversy, is the sludge blanket.

Importance of Blanket Control

      What is a sludge blanket?  Various optical and sonic sensors
are marketed which provide an indication of a change in some fuz-
zily defined property of the water column at a certain depth.  One
very simple device, called a Sludge Judge, lets the operator see
a sample of the fluid column and judge the depth of mostly-
compacted solids.  In the scientific literature one often finds a
fixed concentration, such as 2000 mg/1, defined as a blanket.  In
fact, we felt compelled to make up a new term:  Virtual Blanket,
to describe the depth above which horizontal flow occurs, usually
in a zone of fluidized solids.

      To illustrate this, Figure 6(a,b,c) is a series of snapshots
of dye concentrations in a radial section of a peripheral feed,
peripheral overflow secondary after 35, 70, and 105 min.
  Figure  6.  Peripheral  feed  clarifier  flow pattern time-series
             35,  70,  and 105  min,  65% of  design hydraulic load.
                                 67

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In all of these, it can be clearly seen that the most prominent
horizontal flow is occurring approximately 4 ft from the tank's
bottom, indicated by the lower portion of the 140 parts per
billion (ppb) dye contour in Figure 6c.  When we look at the
distribution of the square-root of solids concentrations in the
same radial section, Figure 7, we see that the still-fluid
 Figure  7.
Peripheral feed clarifier square-root of TSS distri-
bution, 65% of design hydraulic load.
part of the blanket falls between the 20 and 40 contours, which by
squaring, are translated to a range of 400-1600 mg/1.  All the
snapshots of this flow pattern test series were made at a con-
trolled overflow rate of 65% of the clarifier's design overflow
rate.

      At 100% of design hydraulic loading, the same clarifier pro-
duced a similar time series with a modest virtual blanket of 4 ft
thickness.  Figure 8a is the flow picture at 105 min.  The 160 ppb
contour is most representative of the horizontal flow depth, again
4 ft from the bottom.  Figure 8b shows the square-root of TSS dis-
tribution during this test series.  The 20 contour, representing
400 mg/1 of solids was somewhat deformed by the flow.
          -100-.
          -no...	
                                             	_	40	
                                                      I
 Figure 8.  Peripheral feed clarifier flow pattern after 105 min
            (a) and the square-root of TSS distribution (b), 100%
            design hydraulic load, 4 ft blanket.
                                68

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      At the same flow rate with a virtual blanket 7 ft from the
bottom, Figure 9a, the pattern of flow is disturbed; Figure 9b is
suggestive of turbulent eddies at the left-hand side.  From subse-
quent flow pattern tests elsewhere, these eddies seem to be char-
acteristic of flows in cases where the blanket is in close
proximity to the inlet baffle, resulting in a relatively small
cross-sectional area for initiation of horizontal flow.
 Figure  9.  Peripheral  feed  clarifier  square-root  of  TSS distri-
            bution  (a)  and disturbed flow pattern  (b),  100%
            design  hydraulic load,  7 ft  blanket.


     In an extreme  case, the blanket may  rise to a depth at which
the lower extremity of  the inlet baffle is actually covered by a
high blanket.  In the case shown in Figure lOa a bulking sludge
was the cause.  The upward curving contours just outside the feed-
well are suggestive of  a partial solids blowout at this location,
but Figure lOb shows that horizontal flows, Lest defined by the
80 ppb contour, were occurring  in a fluidized solids  zone of
between 1600 and 2500 mg/1 concentration.  Effluent quality based
on TSS was excellent at the  time.
Figure 10.
Centerfeed clarifier, bulking sludge distribution (a)
and resultant flow pattern in 19 min (b).
     One plant we  studied briefly, maintains consistently low
effluent TSS by means of a high  return  sludge rate which essen-
tially strips the  blanket, Figure  lla.  There is some tendency
for the throughflow  to  climb  up  the peripheral wall, Figure lib,
but the zero-blanket practice works for this plant.
                                69

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Figure 11.
Center feed clarifier with high underflow rate,
square-root of TSS distribution  (a) and flow pattern
in 16 min  (b).
     Holly Hill, Florida's small rectangular secondaries initial-
ly had a high velocity, sludge trough scouring throughflow, shown
in Figure 12a.  We balanced the inlet ports hydraulically with
concrete blocks in the mixed liquor channel and replaced the
side-to-side baffle structure with close-in reaction baffles,
with the apparent result of a more benign throughflow pattern,
Figure 12b.  It can be seen here that the blanket was fairly low.
However, when the solids rose to somewhere near mid-depth, Figure
13, the cross-sectional area available for horizontal throughflow
was reduced, and effluent TSS quality deteriorated seriously.
Figure 12.
Flow pattern after 15 min in a small rectangular
secondary before modification  (a), and after  (b).
Blanket was low in both cases.
Figure 13.
Flow pattern after 15 min in a small rectangular
secondary after modification, but with flow con-
stricted by a high blanket.
                                70

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     In general, what seems to happen with a virtual blanket too
near the feedwell is a turbulent, high velocity horizontal flow,
illustrated in Figure 14.  Figure 14 is a composite of numerous
samplings of suspended solids in a radial section of a blast
furnace scrubber thickener.  One such contour plot is shown in
Figure 15.
   Figure 14.  "Average" solids behavior in a center feed blast
               furnace thickener, high blanket.
  Figure  15.
Solids distribution in a blast furnace thickener,
high blanket.
     These examples were given  to  illustrate  the writer's belief
in the importance of controlling blanket depth with respect to
inlet baffling.  In rare cases  of  very  small  flow variability, a
blanket which resides above  the feedwell depth can result in very
low effluent suspended  solids,  probably through the simple physi-
cal means of filtration.   In the majority of  cases studied, there
seems to be a decided advantage in maintaining a blanket as far
from the lower extremity of  baffling as practicable.  (It is
recognized that a low blanket may  also  result in low  solids con-
centrations for wasting.)  The  worst cases of effluent quality
seem to be associated with a medium blanket height, especially
when there is little clearance  between  the compacted  sludge and
the bottom of a feedwell.
                                 71

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Upgrading Modifications

     In every case we have studied so far, the design standard
requiring inlets which distribute the flow equally, vertically,
has been ignored.  The common practice is to encourage immediate
downflow of the solids by inlet baffling.  There is a widely held
belief that the downflow feature of most inlets enhances solids
contact and flocculation.  Although this may be true, forced
downflow also abets development of a density flow which is, in
many cases, detrimental to effluent quality.  Earlier, it was
shown that a bottom-inlet clarifier was improved significantly by
encouraging inlet region upflow and breaking up inlet jets.  In
at least one case, the same effect was achieved by accident.


The Bubble-Curtain Phenomenon—
     In a large rectangular secondary in Central Florida,  the
traveling bridge sludge removal mechanism scraped and lifted
sludge only on movement from the effluent end toward the inlet.
The result was a resident deposit up to 4% solids concentration
on the tank floor near the inlet end.  The sludge was septic and
producing fine bubbles.  The flow pattern which resulted is shown
in Figure 16. The shape of the 20 and 25 ppb dye contours at

                             _  i	r _
                                         f JF

  Figure 16.  Large rectangular secondary's flow pattern with a
              methane "bubble curtain" causing vertical mixing
              near the inlet.


upper left  clearly shows the upward movement of fluid at the
quarter point,  just where bubbling could be seen at the surface.
The 5 and 10 ppb contours at the right are strongly suggestive of
a near-ideal plug flow condition.  The solids distribution near
the overflow weirs is shown  in Figure 17.  With the 10 mg/1 TSS
contour below the weir, effluent suspended solids were less than
10 mg/1, despite a hydraulic load 33% above design.  This is very
close to the ideal solids distribution one would expect from
Camp's geometric flow model  presented earlier.  Obviously, no
modifications were recommended for these clarifiers.
                                72

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 Figure 17.
Near-ideal solids distribution in a large rectangu-
lar secondary in which vertical mixing occurs near
the inlet.
The Stamford Baffle—
     Center feedwell, peripheral overflow clarifiers are the most
common secondaries in the United States today.  The initial flow
pattern tests at Stamford, CT, Figure 18a showed a relatively
rapid fluid transport in a zone about 12 feet deep, with a sharp
upturn at the periphery.  Not surprising was the tendency of the
solids to follow the flow, Figure 18b.  At this time, we felt
 Figure 18.
Center feed clarifier flow pattern  (a) and solids
distribution  (b) before baffling, Stamford, CT.
(Note:  Solids are not square-roots.)
that the expedient modification would be  a peripheral baffle to
interrupt the upflow.  Figure  19a  is the  initial  flow pattern
snapshot after baffle  installation.  The  baffle can be seen at
the right, roughly to  scale.   The  flow was turned back toward the
center as hoped.  The  solids were  also more  favorably distrib-
uted, Figure 19b.  Later, we recognized the  probable cause of
upflow in the flow pattern  radial  section.   The test radial sec-
tion was directly in line with one of four inlet  ports,  inside
the feedwell.  A plot  of the time  variation  of solids near the
second dot from the top in  the right-hand line of sample points
in Figure 19 before baffle  installation is shown  in Figure 20a.
The time between peaks was  exactly the period of  sludge  riser
pipe passage.  After baffle installation, we measured the weir-
wall solids plot shown in Figure  20b.  The variable solids
                                73

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Figure 19.
Center feed clarifier flow pattern (a) and square-
root of TSS distribution (b)  after peripheral baffle
installation.
                to
               Tint t
 Figure 20.
Time-variation of TSS near the weirs  at  Stamford
before baffling  (a) and after baffling  (b).
phenomenon was almost certainly caused by persistent jets from
the inlet ports, periodically interrupted by the rotating sludge
header riser pipes.  This was confirmed by a solids tracer study,
Figure 21.  Figure 21a shows the position of the sampling cross-
section, at mid-radius (shaded)  near the blanket.  Figure 21b
shows the concentration of sludge dye near the blanket interface,
20 min after dye release in the mixed liquor feed pipe.

     The result of the peripheral baffle at Stamford was a 38%
reduction in effluent TSS.  Material and labor cost was about
$3000 for the marine plywood prototype.
 Figure 21.
 Location of  the  mid-radius  sampling section (a)  for
 the sludge jet test.   Sludge dye concentrations are
 contoured at the right (b).
                                74

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The Morganton Baffle—
     The pre-modification flow pattern in a radial section of
Morganton's center feed circular secondary clarifiers is most
clearly illustrated in Figure 22.  The Morganton pure oxygen
   Figure 22.
                 I
Intense density-flow pattern before baffling,
Morganton, NC.
sludge apparently  developed  a  strong  density  flow which essen-
tially ignored the feedwell.    Near the  periphery, horizontal
flow was less than 1  ft  thick.   Flow  rebounded, or splashed on
the peripheral wall.  At this  plant,  we  also  believed we saw a
periodic disturbance  in  weir-wall  solids resulting from sludge
header rotation.   As  an  easy first modification, we therefore
slowed the header  rotation to  56%  of  the design speed at a cost
of $75.  The result was  an effluent TSS  reduction of 10.4%.  The
second modification at Morganton was  a ring baffle/flocculation
chamber at mid-radius, extending from the bottom of the tank
upward to mid-depth.  The baffle was  intended to interrupt the
forceful density flow which  was shown in Figure 22.  The flow
pattern after baffle  installation  is  shown in Figure 23a.  As
expected, the throughflow regime was  radically altered.  Fortu-
nately the solids  distribution was also  benign, Figure 23b.
   Figure 23.
Post-modification flow pattern  (a) and square-
root of TSS distribution  (b), Morganton, NC.
Material cost for this modification, installed by plant opera-
tors, was about $3000.  An additional 37.5% reduction in effluent
TSS was realized.  Thus, an overall effluent TSS reduction of
nearly 48% was accomplished at Morganton for a material cost of
only $3100 per clarifier.  At last report, the plant now meets
its permit requirements consistently by sending 60% of its flow
to the modified clarifier and 40% to a second, parallel unit
which has had only the header speed reduction modification.
                                75

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PITFALLS OF GENERALIZATION

     In the 13 clarifiers we've looked at to date, we have yet to
meet the same set of effluent degrading circumstances twice.  In
deciding on clarifier upgrading measures, there is no substitute
for careful observation, measurements, and the application of
common-sense.  The writer is frequently asked to analyze problems
by long-distance or on observation of surface phenomena alone.
The conclusions reached by this short cut method are almost
always wrong.  For example, surface observations in a chemical
plant's secondaries clearly showed a line of bubbles which fol-
lowed the single tube sludge header around the tank.  The first
guess was that the nominal 4 inch clearance of the header above
the tank floor was allowing septic sludge to accumulate below,
with the header disturbing this layer just enough to skim the
methane bubbles.  The clarifier had a very low overflow rate, but
about 200% underflow rate.  The flow pattern, Figure 24, gave an
entirely unexpected picture.  Instead of diving toward the suc-
tion header, the tracer dye avoided the header entirely.  The
header was completely inactive; all sludge was being returned by
way of a missing seal at the center of the tank.  The problem was
repaired within hours, with a new seal fabricated on-site.
  Figure 24.
Flow pattern in a center feed circular secondary
with an inactive sludge header.
     Generalizations must be possible, but this writer does not
know how to  make them, with the possible exception of those
comments already made regarding blanket control.  There is no
known substitute for the application of a sense of how fluid
behaves, backed by the kind of graphic data which has been pre-
sented in this paper.  Dispersion tests, long used as a measure
of hydraulic efficiency, are seen only as back up data; they do
not define the reasons for fluid problems.  On the other hand,
flow pattern tests, although considerably more complicated and
costly to perform, can clearly define hydraulic problems in such
a way that solutions become obvious.
                                76

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     This nation now has tens of thousands of municipal  and
industrial  clarifiers whose hydraulic characteristics will be
found to closely resemble the examples given here.   It seems a
reasonable  goal  to upgrade the "bad actors" to achieve more
nearly ideal performance before we proceed with major capital
expenditures to  provide additional hydraulic capacity in the
traditional, or  design standard dictated sense.  If  such design
standards are  to be applied, the design engineer and the regula-
tory agencies  should recognize their shortcomings in light of the
real clarifier hydraulic behavior which has been illustrated
REFERENCES
     1.  Great Lakes  -  Upper Mississippi Board of State Sanitary
         Engineers.   Recommended Standards for Sewage Works.
         Health Education Service, Inc., Albany, New York, 1978
         PP 60-1 to 60-3.

     2.  Camp, T.R. Sedimentation and the Design of Settling
         Tanks.  Transactions Am. Soc. C.E., No. 2285, 1946,
         pp 895-936.
  "This paper has been reviewed in  accordance with the U.S. Environmental
  Protection Agency's peer and administrative review policies and approved
  for presentation and publication."
                                77

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           PAPER NO. 5


MINIMIZING IMPACT OF SIDE STREAMS

     ON TOTAL PLANT PERFORMANCE
               by

     Roy 0. Ball, Ph.D.,  P.E.
             Principal
    ERM - North Central, Inc.
    200 South Prospect Avenue
   Park Ridge, Illinois  60068
                78

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MINIMIZING IMPACT  OF  SIDE STREAMS ON TOTAL PLANT PERFORMANCE

Roy O.  Ball,  Ph.D., P.E.
Principal
ERM-North Central,  Inc.


     The  objective  of this  conference is to provide technical
input  to operators  and designers of publicly owned treatment
plants with  the overall goal of improving POTW reliability and
performance.   The  objective  of  this  paper is  to  provide
information  on an  EPA technical report (soon to be available)
with  regard  to the  impact  of  side  streams on  main  stream
performance.^

     What  are side  streams?  Side streams are those hydraulic
flows  which  result  from sludge or waste stream treatment and
disposal activities.  For example, the supernatant flow from a
gravity thickener;  the filtrate  from a vacuum filter; the
supernatant  from a secondary  digester; and, the liquor from heat
treatment operation are all  examples of side streams.  If these
side  streams are returned  into the  main stream treatment
process,  then they  may  represent  an added  load  on  the
facilities.   This  added load may be purely hydraulic or it may
contain significant amounts of pollutants, such as BOD or TSS,
or  it  may  contain  acidity  and  alkalinity  which might
significantly vary the pH in the main stream.

     Bob  Hegg described many of the conditions that can effect
POTW  reliability and performance.  Although not  specifically
included  in  his  catalog, side streams are one of the  factors
that  can degrade POTW performance, both in theory  and in fact.
Must  the side streams degrade POTW performance?   Based on the
analysis described  in the Side Streams Report,  side streams do
not  have to degrade  POTW performance.  The fact that they do, or
appear to,  is related to the duration of the  return event.  If
the  side stream is returned evenly, then it would appear  to be a
rare  situation  at  which the  side  streams could  degrade main
stream performance, even if  those  side streams  had not been
included in the original design basis for the facilities.

     How  do  we determine if side streams are a  problem?   That is
one  of the  major objectives of the side stream's  report.  The
side  stream's report is composed of three major sections.  The
first section has to do with  the investigation  and  evaluation of
the  plant  to answer the question  "If  there are operational
problems,  can  they be attributed  to side streams?"   The
procedures  outlined in this  section will enable  a definitive
answer to  that  questions.   The second section  of the report
deals with  mitigation of the  impact of the side  streams.  The
remaining  sections of the report deal with handling the effect
of the side streams,  or mitigating them.  The side stream  effect

                               79

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can be mitigated in two ways:  by changing  the source of the
side stream, that is the fludge treatment or disposal facility
that is generating the flow; and by altering the operation of
the main stream process.

     In addition to these three major  sections, appendices are
included which provide information as  to the average quality
characteristics of side streams as reported in the literature,
and also the indexing procedure which  was followed to prioritize
the side stream matrix; that is which  side  streams from which
facilities being returned to which main stream processes are the
most important and worthy of discussion.

     The manual provides a user guide  with  information needed to
use the monitoring program, evaluation algorithm, control
algorithm, design modification matrix, and  design information.
Also included in the side stream manual is  a detailed example.
Three checklists are provided to help  the user work through the
algorithm.  In this paper, it is not possible to display the
full scope of the report, but only to  indicate the types of
material that can be found.
                                                 2
     Figure 1 shows the process matrix evaluated.  The selection
of side stream generator/treatment process  pairs was based on an
indexing procedure.  The procedure included factors for the
population served by POTW's with that  side  stream, the side
stream average quality and the cost of treating the side stream
pollutants.

     Table 1 shows literature references describing side stream
quality.  It can be seen that little agreement is evident
between references.  For many of the side streams, the refer-
enced quality differs by three or more orders of magnitude.

     Figure 2 shows a summary of the evaluation algorithm
process, while Figure 3 indicates where sampling would be
required in order to complete the evaluation algorithm.

     Figure 3 shows an example of one  of the algorithms; in this
case, for primary clarification.  It can be seen that even this
"simple" process requires 33 steps and may  refer the analyst to
one or more of three design methods for mitigation and one
method for operational control.

     Figure 4 shows a similar process  for activated sludge.
Here, 77 steps are required, up to 13  design mitigation methods
may be recommended, and up to 25 operation  methods may be
recommended.

     Figure 5 shows an example of an operational methods algo-
rithm for primary clarifiers, and Figure 6  shows a correspon-
ding algorighm for activated sludge.   In each case,


                               80

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once all the main stream changes that can  be  made have been
made, the user  is referred to side stream  operational control
algorithms; an  example of which  (in this case for gravity
thickeners) is  shown in Figure 7.

     After  all  operational methods have been  implemented, some
design modifications are described in the  manual.  Most of the
modifications deal with increasing the time span over which the
side stream is  returned.

     In summary,  the side streams manual represents a flexible
and powerful tool to diagnose and mitigate the impact of side
streams at  POTWs.
 Presentation  based on a study and report  by Roy F.  Weston, Inc
 for EPA MERL.
2
 The Figures and Tables used in this paper duplicate those
 used in the Side Streams Report.
   "This paper has been reviewed in accordance  with the U.S.  Environmental
   Protection Agency's peer and administrative review policies and approved
   for presentation and publication."
                                81

-------

Sidestream Generator
Gravity Thickener (GT)
Dissolved Air Flotation (DAF)
Anaerobic Digestion (AnD)
Aerobic Digestion (AeD)
Vacuum Filter (VF)
Centrifuge (C)
Belt Filter Press (BF)
Sand Drying Bed (SB)
Lagoon (LA)
Heat Treatment (HT)
Wet Air Oxidation (WAO)
Pressure Filter (Filter Press, FP)
Purifax(PX)
Treatment Process
Primary
(P)
o
o
•
0
•
•
•
•
o
•
•
6
•
Activated
Sludge
(AS)













Trickling
Filter
(TF)













Rotating
Biological
Contactor
(RBC)









•
•
e
•
No evaluation required
Evaluation required
          FIGURE  1.   PROCESS MATRIX
                        82

-------
                                                                                           Table 1

                                                                                 Summary of Literature Review
00
Sldestream Abbreviation
Generator
Gravity GT
Thickening
Dissolved Air DAF
Flotation
Anaerobic AnD
Digestion
Aerobic Digestion AeD
Vacuum Filtration VF
Numbers
In Use
940
3l"t
6.796
4,750
1,912
Solids Retention BOD.
% References mg/C
80-95 3, "12,49,59, 75 100-400
70-99.1 4,39,40,42,48,55, 50-3,950
59,60,64,75,121
2-11,014
5-6,350
80-99.5 33,65,70,75,94, 10-10,000
96,120
References
35,49,72,75
72,75
13.14,29,49,55,
56,57,72,75,76,
87,995,100,108,
121
1,21,52,55.75.121
14,55,75,108,122
ss
mg/L
98-2,500
20-2,440
100-32,400
10-41 ,800
160-20,000
References
3.7,25.35,42,49,
59,61.64,72,74,75,
77,81.10«-,118(120,
121
"t.25,39,40,42,49,
55,59,60,64,67,72,
75,76,87,94,95,100,
104,108,114,121
12,13,14,21,49,55,
56,57.62,72,75,76.
87,94,95.100,104,
108,114,121
1,4,52.55.64,75,
121
4,14,25,26,33,36,
42,47,55,65,70,72,
75,80,87,94,96,108,
114,120,121
     CentrifugalI on
368
30-98
3,4,6,21,33,40,    173-10,000   49,75,87,122
42,43,55,72,75,
83,87,94,96,98,
104,108,115,121
122
                                                                                                                                           100-20,000
                                                                                                     2,3,4,20,21,25,33,
                                                                                                     40.42,49,55.72,75,
                                                                                                     83,87,94,96,98,108,
                                                                                                     114,115,120,211,122
Belt Fl 1 ter Press
Sand Drying Beds
Lagoons
Heat Treatment
Wet Air Oxidation
Pressure Filter
Purl fax
BF
SB
LA
HT
WAD
FP
PX
132
10,939
797
170
13
157
69
22-99.8
85-100

90-99+
90-99+
96-100

"1,33.36,94,117,
122
33,108

49
49
18,33,75,96

46-146
6-6,000
150
1 ,600-15,000
3,000-10,000
1 ,000-6,500
100-350
122
14,
49
47,
42,
72,
14,
55,
25
14.

29

14
48
75
29
49

16

,55,

.29,
."•9.
,108
.32,
,72,

,108

72


,108

30,32,
50,55,
.121
37
75


.42,
,108





37.
56,
51,
,121


                                                                                                                                           30-3,400     4,9,16,33.36.55.94,
                                                                                                                                                        96,117.122

                                                                                                                                           20-800       14,33,54,72,104,112

                                                                                                                                           71           49

                                                                                                                                           50-11,400    14,25,32,42,48,49,50,
                                                                                                                                                        55,72,75.87,103,108,
                                                                                                                                                        112

                                                                                                                                           20-500       14,32,42,49,55,75,99
                                                                                                                                           100-1,926    4,25,26,33.42,55,75,
                                                                                                                                                        96.121

                                                                                                                                           50-150       14,16,112,121

-------
                                                                                                      Chlorination
       Influent  f

              \

              \

              i
              •
              i
oo
•e-
              u.
              i
Activated
 Sludge
                              Forward Flow--Wastewater
                              Forward Flow-Sludge
                              Sidestream Flow
                              Sample Point
                                        FIGURE  2 PROCESS
  MONITORING  PROGRAM
                                                                                  12
                                                       Effluent
                                                         To
                                                      Discharge
To Ultimate
 Disposal

-------
No
            Mainstream Treatment Process
                 Evaluation Algorithms
       Primary Treatment
          Evaluation
Secondary Treatment
     Evaluation
                  Evaluation Algorithm
                       Checklist
                Anything New Added?
                           Yes
         Operational
     Mitigation Algorithms
 Design Modification
       Matrix
      Operational Mitigation  I  Design Modification
       Algorithm Checklist   I    Matrix Checklist
                                    I
       -I Has Everything Been Implemented? I
                           Yes
                       Ranking
       J
                -I   Implementation  I
                         End of Evaluation
      FIGURE  3.   SUMMARY OF EVALUATION  PROCESS
                              85

-------
©
FIGURE k.   EVALUATION  OF  SIDESTREAM  IMPACT ON PRIMARY CLARIFICATION
                                 86

-------
                                                           Were Any
                                                           Implementation
                                                           Steps. Either
                                                           Operational Or
                                                           Design. Required
                                                           That Had Not
                                                           Previously Been
                                                           Implemented?
                                                           Possibilities Are
                                                                 No
FIGURE  A (CONTINUED).
EVALUATION  OF SIDESTREAM  IMPACT  ON

                 87
PRIMARY
CLARIFICATION

-------
  Is Secondary
  Effluent S S
  and/or BODs
  Concentration(s)
   ^ 35 mg/f
                   No
                                No Impact
          Yes
Measure/Calculate
Forward Flow (W.'O
Sidestream) To
Secondary Treatment.
i.e	Influent Q -
(Primary Sludge Q
 - Sidestream Q) =
Forward Flow
Is Fofward Flow
To Secondary-
Treatment Less
Than Design Forward
Flow'
                   No
Collection System
Enforcement Problems
and'or Secondary
Treatment Design
Deficiencies Exist
No Further Evaluation
of This Parameter is
Possible Go To,
               51
          Yes
Measure'Calculate
Forward Flow (With
Sidestream) To
Secondary Treatment.
i.e..  Influent Q -
Sidestream Q -
Primary Sludge Q
Forward Flow
 Is Forward Flow To
 Secondary
 Treatment Less
 Than Design
 Forward Fiovv9
                   Mo
Have Operational
Methods To Reduce
Impact Been
Implemented7
                                                 Yes
                                                       Implement
                                                       Design Methods [l(
                                                       and           L-
                                                       Continue
                                                       Algorithm
                                                       Evaluation
                                                       Go To
                                                         Implement Operational
                                                         Methods To Reduce
                                                         Sidestream
                                                         Hydraulics
                                                         Continue
                                                         Algorithm
                                                         Evaluation Go To
FIGURE
                  EVALUATION OF  SIDESTREAM  IMPACT  ON ACTIVATED  SLUDGE
                                             88

-------
    Measure pH of
    Forward Flow (W/O
    Sidestream) To
    Secondary Treatment
       Is pH Between
       6.5 and 8.5?
                       No
 Provide Collection
 System
 Enforcement
              Yes
     Measure pH of
     Forward Flow (With
     Sidestream) To
     Secondary
     Trealment
       Is pH Between
       65 and 8 5?
                        No
Have Operational
Methods To Reduce
Impact Been
Implemented9
                                                   Yes
                                                   No
              Yes
No Further Evaluation
of This Parameter
Is Possible  Go To
                           Implement
                           Design
                           Methods
                           and
                           Continue Algorithm
                           Evaluation      S  ,
                           GoTo         (60
                           Implement
                           Operational
                           Methods TO
                           Reduce
                           Sidestream pH
                           Possibilities Are:
                                                            Belt Filter
                                                            Press
                                                           Continue
                                                           Algorithm
                                    GoTc
FIGURE  S  (CONTINUED).   EVALUATION OF SIDESTREAM  IMPACT  ON  ACTIVATED  SLUDGE

                                                89

-------
 Measure Reactor
 D O Level (W O
 Sioesttearm Nnie
 Maintain D O
  Is the Secondary
  Influent Suspended
  Solids Concentration
  Less Than 100 mo/L?
                                                                                                 trnpleftient Operational
                        Collection System
                        Enforcement
                        Prootems and-or
                        Secondary
                        Treatment Design
                        Deficiencies Exist
Note Oo Not Change
                                                                                                 Implement •Opec ationai
During Measurement
                                                                                                 Evaluation. Go Tot 75
                                                 Were Any Implementation
                                                 Steps. Either Operational
                                                 Or Design. Required
                                                 That Had Not Previously
                                                 Been Implemented-'
                                                 Possibilities Are
          FIGURE  5  (CONTINUED).
EVALUATION  OF  SIDESTREAM  IMPACT  ON
ACTIVATED  SLUDGE
                                                      90

-------
Schedule Adjust
Sludge Removal
To Maintain A
Sludqi1 RlanHt-t ot
1  j leet iCircuiai
Fo' Hec'.anguia'
Oanhers  Maintai
;ne S'uage
inven!or>  in the
5unp Beiow the
C:anfie' F oor
  WAO
                       For Plants
                       Equipped With
                       Constant Rate
                       Sludge Removal.
                       Adjust Primary
                       Sludge Removal
                       To Occur More
                       Frequently, But
                       For A Shorter
                       Period of Time.
                       Allow Only 1 -2 foot
                       Change In the
                       Sludge Blanket
                       Depth
FIGURE 6.    OPERATIONAL  METHODS TO  REDUCE  THE
                                                  91
                IMPACT  OF  SIDESTREAMS  ON
                             PRIMARY  CLARIFIERS

-------
  Dampen Flo*
  Surges To the
  Basmis) By
  Limiting A Feed
  Valve or Gale
  Position Allow
  Level Changes To
  Occur In Feed
  Cnannefs or
  Piping Observe
  Each Shift to
  Prevent Overflow
                           Su'ges To me
                           Seconfla'y
                           Ciantiertst by
                           Limiting A Basin
                           Discharge Valve or
                           Gate Position
                           AIIOW Level
                           Changes To Occui
                           In ine Basin
                           Effluent Channels
                           Or Piping ODserve
                           Each Shift To
FIGURE 7.   OPERATIONAL  METHODS TO  REDUCE  SIDESTREAM   IMPACTS  ON  A.S.
                                                       92

-------
           &_t








O2>
X/ 1







Reduce the
Variability In the
Waste Sludge
Removal By
Wasting Sludge on
A More
Continuous Basis

1
y\
<34> '
For Plants
Equipped With
Variable Rate
Sludge Removal


/£\
X7 ,

V



'


For Plants
Equipped With
Constant
Rate
Sludge Removal


/£~
N/^ i

Adjust Waste
Sludge Rate To Be
Continuous The
Desired Waste
Rate Should Be
Based on
Controlling the
Activated Sludge
Process
Through
F M. MCRT Etc


1























Adjust Waste
Sludge Removal
To Occur More
Frequently. But
For Shorter
Periods of Time
The Desired
Waste Volume
Should Be Based
on Controlling the
Activated Sludge
Process
Through
P.M. MCRT. Etc
-













r


^36^
\/ i




















Go To

GT
DAF

AND

AED
VF

C

BF
SB

LA

HT






<110>
X
<130>
<<40>
x.
<160>
X
<180>
x
<200>
X
<210>
x
<220-
WAO \S



FIGURE  7  (CONTINUED).
OPERATIONAL METHODS TO  REDUCE
SIDESTREAM  IMPACTS ON A.S.
                        93

-------
<8>
Th'c^el
<8> ,
\\ -lie'

'^
M'li'T'.'e - se o*
NX 1


Wasie Actuated
Siudges
Separate
<«> ,
*es
i
Measure me
Suspended SaMs
Concentrations Jn
me Thtcke^^1
Overflows
 .

SS
^\s '
t




No

ves
F
Cons.de- 3'end.ng
Siudges To
increase Qv&an
Tnickenet
Performance
Perform Jar Tests
To Evaluate
Tmckener
Blended Sludges







\y^ 1


W-i- S;udye
Resu': tr A
Decrease tn ;ne
Overflow SOMQS
Bssi1-.: or jar
\/ l
>
Ope'^ie
ThtCKeners With
Btenaed Sfudges.



Chemica;
Facilities'1
\/
Yes
Evaluate
Thickener
Ftoccui^nt Aids By
Performing jar
Tests ana UM



No
— »
r
A'here Possible
Reduce ifie Solids
Retention Time in
the Tfucken«ns,y
To Minimize Septic
Cond'tions Take
Unneeded Units
Ouf ot Service jf
Required


r




<8> „
is The Piani
Equrppea Wdh An
Aeraied GM
Yfes
Where Possible.
Redirect the
Thickener
Overflow
Upstream of ;ne
Grrt ChaTiDef TO
Elevate the DO
Belore Entering
the Clanfier
i r


i
No



<93>


Minimize ir>e
Sludge Retention
Time In the
Primary C'anfiers
<8> .


Reduce me
Variability In the
Thickener
Overflow Rate By
Scheduling the
Pumping of
Primary and
Secondary
Sludges on A More
Conlmuous Basts
Likewise.
Schedule Sludge
Pumping From" the
Tntckener(s) on A
More Continuous
Basis
'
\^/ 1 '
For Plants
Equ pped With
Variable Rate
Sludge Pumping
*S ' '
Adjust Sludge
Pumping From Ifte
Thickener{s) To
Be Continuous
,.




<$>

'

For Plants
Equipped With
Constant Rate
Sludge Pumping:


Adjust Studge
Pumping From the
Thicneoerts) To
Occur More
Frequency But For
Shorter Periods of
Time.
'
r
Return To
Appropriate
Evaluation of
SKJestream Impact
Algorithm
Primary ( 1 )
Activated (*n\
Sludge \3/
Trtckling (gj)N


FIGURE 8.  OPERATIONAL METHODS TO REDUCE THE IMPACT  OF
           GRAVITY THICKENERS
                          94

-------
               PAPER NO. 6


      COMPOSITE CORRECTION PROGRAM-

       CONCEPTS AND DEMONSTRATION
                   by

               Bob A. Hegg
Vice President Plant Operations Division
    M & I, Inc., Consulting Engineers
        4710 South College Avenue
     Fort Collins, Colorado  80525
                    95

-------
COMPOSITE CORRECTION PROGRAM - CONCEPTS AND DEMONSTRATION

Bob A. Hegg, Vice President Plant Operations Division
M & I, Inc., Consulting Engineers

INTRODUCTION

     Non-compliance of wastewater treatment facilities has been the focus of
numerous  studies,  seminars,  and published articles  for a number  of  years.
Several of these studies were funded by EPA1s Office  of Research and  Devel-
opment and have been  collectively  referred to as the  "National  0  & M Cause
and Effect Survey" (1,2,3,4).

     Conclusions of these research efforts can be broadly summarized  in two
categories:    conclusions  on   all  facilities  and  conclusions  concerning
inidividual  treatment  plants.    For  all facilities  it was  determined  that
individual  facilities  are hindered  from  achieving  desired performance  by
multiple  factors unique to each facility.   As  such,  specific programs  imple-
mented to address  selected  factors at  all facilities  will  have  a  limited
correlation between program implementation and improved performance at indi-
vidual plants.  This conclusion  is significant in that broad scale programs
normally  are  assessed  on their  most  obvious  intended  impact.   It is  thus
conceivable that programs could be  excluded  from development  or eliminated
because  of their  inability  to  show  a direct  correlation between  program
implementation and  improved  plant  performance.   Yet  these programs  may be
very necessary to address the high  ranking and frequently occurring perform-
ance limiting factors indentified.

     For individual plants it  was concluded that  multiple and unique  factors
limit a facility's performance.  The scope of these  factors  is often  beyond
the plant  operator's  control  (i.e.,  improper  technical guidance and  design
deficiencies).   To  achieve  a  direct  correlation  between  an  individual
plant's performance and program  implementation, a comprehensive  site  speci-
fic  effort  is  required.    The comprehensive  site   specific  program  was
described in concept as  a Composite  Correction  Program (CCP).   The purpose
of such a program is to address the  multiple  and  unique factors that  limit a
facility's performance.

     An evaluation that was  completed for  the 50 plants  studied  in the  ori-
ginal EPA research is  shown in  Table  1.   At  the  start of  the  research  pro-
ject, 13  out of 50  facilities were consistently meeting secondary  treatment
standards.   In other  words,  37 facilities were frequently violating  secon-
dary treatment standards  which was defined  as  30  mg/1 8005  and  TSS.    By
looking at the factors limiting performance, an assessment was made that 40
of the 50 facilities  could  consistently meet  secondary  treatment  standards
without a  major  facility upgrade and  only ten  would  require  some kind  of
upgrade.    Nine  of those ten  that  would require an  upgrade were  trickling
filter facilities.   Most of the evaluations were done  at  plants  in northern
climates so there was a direct relation with climate and  the affect on  pro-
jected trickling filter performance.   The  potential  for broad scale improve-
ment without major upgrades represented an appealing  aspect  of the research
results.


                                     96

-------
TABLE 1.  PERFORMANCE OF 50 PLANTS VS. SECONDARY TREATMENT STANDARDS (4)
Prior to Evaluation

Potential Without Upgrade
      Standards
      Frequently
       Violated

          37

          10
 Standards
Consistently
    Met

     13

     40
CASE HISTORIES

     Case histories  demonstrating  the  Composite  Correction Program  (CCP)
approach for two facilities will be presented.
                           CASE HISTORY - PLANT A
A.   Description
     Plant A  is  a 1700  cum/day  (0.45)  mgd  contact-stabilization  activated
sludge plant.  Wastewater treatment processes include flow measurement,  con-
tact-stabilization activated  sludge,  secondary clarification,  and  chlorine
disinfection.  About 25 percent of the  influent wastewater  can   be  diverted
to sewage  lagoons  for  land application purposes.    Sludge  handling  includes
treatment in aerobic digesters and land application of liquid sludge.

B.   Current Process Loading

TABLE 2.  SUMMARY OF PROCESS LAODINGS FOR PLANT A
Parameter
Raw Sewage
Flow
BOD5
TSS
Units
cum/d (mgd)
mg/1
mg/1
Value
1070 (0.28)
210
209
Contact Stabilization
   Contact Basin Wastewater
     Dent ion Time
   *Reaeration Detention Time
   **0rganic Loading
Secondary Clarifier
   Surface Loading
          hrs                  2.1
          hrs                  13
    gm/day/cum (Ib            336 (21)
  BOD5/day/1000 cu  ft)
cum/day/sq m (gpd/sq ft)      23.7 (580)
 *Based on 100% return flow percentage

**Based on contact plus reaeration volume
                                      97

-------
D.
Factors Addressed During CCP

Administration:

1.  Modified  permit  to  allow  discharge  from  contact-stabilization
    plant and not "polishing pond".

2.  Emphasized  priority for  sludge disposal  and obtained  commitment
    for sufficient manpower and equipment to accomplish the task.

Operation:

1.  Implemented  improved  and  expanded  process  control  and  sludge
    wasting program.

2.  Developed  operator  skills  in  making  process control  adjustments
    based on proper interpretation of test results.

Design:

1.  Modified piping to direct raw sewage to ponds and/or to plant.

2.  Obtained  sludge  hauling  truck  and  "installed  sludge  measuring
    devices.

Maintenance:

1.  Repaired leak in  walls  between aerobic digester,  reaeration basin
    and contact basin.

2.  Repaired raw sewage flow meter and chlorine feed system.

Performance
               100
                    FIGURE 1.   Plant A Effluent Quality
                                     98

-------
E.   Discussion

     At the  start  of the CCP Plant A  was  rated as a 1140  cum/day (300,000
gpd) facility and had received a Cease and Desist Order from the state regu-
latory agency for  frequent  violations  of its effluent BOD5  and  TSS limita-
tions.  When the plant  consistently  achieved effluent compliance  at  flows
greater than 1140 cum/day  (300,000  gpd),  its  capacity  was  officially  up-
graded to 1700 cum/day (450,000 gpd).  As  such,  a threatened tap moratorium
by the State was avoided.   Over twelve months were required to obtain opti-
mum, stable  performance.  The impact of  improved process  control was  demon-
strated by the ability to avoid wide fluctuations in final effluent quality.
Improved  performance plus  a  dramatic  increase  in plant  capacity  were  the
major aspects of this CCP.

                           CASE HISTORY - PLANT E

A.   Description

     Plant E is a 5680 cum/day  (1.5 mgd)  activated sludge facility.  Waste-
water treatment processes include a flow diversion structure,  flow measure-
ment,  screening,  grit  removal, lift  station,   activated  sludge  aeration,
secondary clarification,  disinfection,  and a holding  pond.   Effluent  from
the ponds is discharged  to the river  and/or to  multi-media  filtration  and
land application  for reuse.  Sludge  is  wasted  to a  regional  facility  for
processing.

B.   Current Process Loading

TABLE 3.  SUMMARY OF PROCESS LOADINGS FOR PLANT E	

    Parameter                              Units                  Value

Raw Sewage
    Flow                              cum/day (mgd)            5675 (1.50)
    BOD5                                   mg/1                    195
    TSS                                    mg/1                    160

Effluent
    BOD5                                   mg/1                    8
    TSS                                    mg/1                    14

Activated Sludge
    Wastewater Dentention Time             hrs                     11
    Organic Loading              gm/day/cum (Ib BOD^/day/
                                             1000 cu ft)         424 (26.5)

Secondary Clarifier
    Surface Loading             cum/day/sq m (gpd/sq ft)        24.4 (597)
                                      99

-------
D.
Factors Addressed During CCP

Administration:

1.  Improved  communication  between  laboratory  personnel  and  plant
    staff.

2.  Modified shift coverage to improve process control capability.

Operation:

1.  Implemented improved and expanded process control program.

2.  Changed the mode of operation from complete mix to plug flow.

3.  Adjusted return sludge, waste sludge and dissolved oxygen levels.

4.  Developed operator skills in making process control adjustments.

Design:

1.  Modified aeration basin discharge overflow weirs.

2.  Installed valve to control flow splitting to final clarifiers.

3.  Modified flow splitter to aeration basins.

4.  Changed the drive on aerators to increase speed.

Maintenance:

1.  No changes.

Performance

     i.e
          t.*
    01.(

    i O.fr
    u
    H..
         o
         u!o.2-
                                   •  »
                                   /  \ /AY - FLOW SOLO

                                  /   V  \
                                                           /\
            '	1	S—*

                                                     /
                                                                   K
                                                                   a
                                                                   9
                                                                   U
1
IU
                                                               o
           1978
                           J
                         1970
                                                  1080

                     FIGURE 2.  Plant E Wastewater Flow
                                    100

-------
E.  Discussion

    Plant E was located adjacent to a large interceptor and was capable of
treating selected amounts of sewage.  Remaining flow was treated by a down-
stream facility.  Increased treatment capacity meant decreased charges from
the downstream plant.  In addition, increased capacity made more water
available for reuse to irrigate a golf course.  A severe sludge bulking
problem had limited this facility's ability to treat increased flows.  Using
the CCP approach the plant flow capacity for 1979 was increased 90 percent
over 1978 values.  Flows for 1980 were increased by 350 percent.  Effluent
standards have consistently been met throughout these flow increases.  A
$55,000 annual cost savings for 1980 was projected, due to decreased charges
from the downstream facility.  An additional benefit was that water avail-
ability for reuse was no longer limited by plant capacity.  During this CCP
the benefits of optimizing process control to obtain maximum capacity from
existing facilities was clearly demonstrated.

COLORADO PROJECT

     The Environmental Protection Agency (EPA) gave a grant to the State of
Colorado to try and demonstrate the effectiveness of the CCP and how it
might be utilized to improve facility performance on an areawide basis.  The
project was enforcement related in that all of the activities in this pro-
ject were carried out under the Enforcement Division of the Colorado Depart-
ment of Health, and each plant evaluated was aware of the potential enforce-
ment action.  Three steps were involved in the project:

     1.  The State and EPA jointly identified poor performing facilities.
     2.  M & I, Inc. was to conduct comprehensive evaluations (3,4) at the
         identified plants.
     3.  M & I, Inc. was to implement CCP programs and achieve the desired
         performance.

     Some of the initial results will be summarized.  Many of the owners did
not realize their responsibility for achieving compliance at a wastewater
treatment facility.  In initial interviews with the facility owners, which
was part of the evaluation effort, many felt that the regulatory agency, the
design engineer, the operator, the equipment supplier and others were
responsible for the performance of their plant.  They were confused in sum-
marizing their particular responsibility in achieving compliance at their
facility.

     Another result was that much confusion was found to exist among plant
owners and personnel if the State or EPA focused on specifics like the need
for grounds maintenance or plant fencing during an evaluation.  It was
observed that recommendations made by a regulatory agency resulted in tre-
mendous effort and enthusiasm to address these suggestions often at the
expense of efforts to improve plant performance.  Plant owners place a pri-
ority on regulatory agency recommendations, often at the expense of focusing
efforts on plant performance as a goal.  In addition, many owners had imple-
mented specific recommendations from regulatory agencies only to find that
desired performance had not been achieved and the regulatory agency had

                                    101

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returned.  In one case, a  facility owner made  the  comment  that if the regu-
latory  agency  came back  one  more time,  they  would turn  the keys  for  the
plant over  to  them.   Another confusing aspect for owners was  their under-
standing of  the regulatory role.  Do they enforce or  do  they assist?   On
numerous occasions regulators had taken an active role in directing specific
aspects of a facility's operations.   By doing  so,  they  assumed a  portion of
the  responsibility for plant performance  in  the eyes of  the owner.   This
also has served to confuse the  owner as to what his  true  responsibility is
in achieving compliance.   The  important  aspect of these results  is  that it
indicates  that  the regulatory  agency may be  better  off  to  let  the  owner
develop their own  specific actions while emphasizing owner responsibility to
achieve plant performance.

     A  couple  of other results can be  placed  into the broad  categories of
political and training limitations.

     Political  Limitations - We found in  a  very real  sense  that the  con-
struction  grants program  is  rewarding  poor performance.   In our  original
research  study  we  always initiated efforts by holding discussions with  the
owners  and  explained  the possibility of  improving  performance.   At  an  un-
named  plant  in Wyoming one owner said, "We don't  want  your help.   We  just
got  high enough on the priority list  to get funding for  a  new facility,  and
if we improve performance, we could  lose our priority ranking."   As  such,  a
negative incentive has resulted to a degree from the grants program.

     Another key limitation in our  original  research and  in the State of
Colorado study  was identifying a poor performing plant.   Much  discussion has
centered on the definitions of  poor  performance, i.e., how many months  does
it take to be out of compliance, how may bad samples,  and what constitutes  a
good sampling program  to  document  poor  performance.   In the  Colorado study
we attempted to use  the NPDES  discharge monitoring reports.   This  approach
allowed identification of a few facilities but  does not  appear adequate  as  a
true indicator  of  a plant's performance.   Presently, the job  of identifying
a poor  performer often  falls upon regulatory agency field  personnel.   Prob-
lems that these regulatory people face  in  assuming  this  responsibility  will
be discussed later.

     Training  Limitations - The third  ranking  factor  limiting  wastewater
treatment  plant performance identified  in our  original  research  (4)  was
improper technical guidance.  This factor  still exists.   For example,  almost
each month  you can pick up a  technical   publication  and  find conflicting
reports.   Particular  topics especially subject  to  conflicting reports  are
causes  and cures for bulking sludge or the impact of side streams  on  process
performance.  Often, magnitudes of difference  may exist  in the descriptions
of an approach  to  take to correct these problems.   Other  claims  that have
remained flagrant are those describing activated sludge  processes  that never
require wasting of sludge  and that need  little or no attention to  operate.
Another training limitation that  also still exists is operator application
of concepts.  Many operators have had a great deal  of  classroom training  but
cannot apply this training to their particular  facility.  What has worked to
overcome  this   limitation  is  on-site  training  specific  to  a  particular
facility.

                                     102

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     A lack of authoritative understanding of process capability also repre-
sents a training limitation.  Authoritative understanding and specifics of
process capability for biological systems is admittedly a tough area to
quantify.  However, the continuing disagreement of "experts" has done little
to make the field more easily understood.  For example, if you put activated
sludge "experts" in one room, it would be difficult to conclude what consti-
tutes good settling sludge, what constitutes poor settling sludge, what
constitutes good return rates, etc.  As such, a lot of confusion exists as
to the exact capability that can be expected from the activated sludge pro-
cess.  Process understanding and capability are important to everyone that
is involved in evaluating wastewater treatment facilities.  It has been
documented that many factors limit a facility's performance (3,4).  These
factors can be administrative, design, operation or maintenance related.
They can all appear to have equal weight and importance especially if a
facility is out of compliance.  How then do you set priorities on what
should be addressed first?

     The necessary first step is process understanding.  With good process
understanding you can put priorities on maintenance, design or administra-
tion limitations to support the process needs.  Without process understand-
ing as a basis, priority setting becomes a maze of trial and error efforts.

     Several unresolved issues remain in trying to develop an areawide com-
pliance strategy for the Colorado CCP project.  A focus on performance can
be acnieved through enforcement.  Indeed many of the plants that we have
been able to go into and improve and directly address performance problems
have been because the owner's focus was brought to bear by an enforcement
activity.  However, there has been some reluctance to use enforcement as a
very strong tool to bring this focus about.  Should enforcement be stronger
to accelerate the understanding of the plant performance/owner responsibil-
ity relationship?

     A second step is identifying poor performance.  A regulatory agency is
in a tough role in making an initial assessment.  Ideally, they should not
make specific recommendations at a particular facility nor should they make
interim recommendations.  Yet they have to get the facility owner to focus
on performance.  To accomplish these objectives, the evaluator must have an
idea of the steps that are probably logical to get a plant from its present
state to compliance without dictating the steps to the owner.   Otherwise, he
will confuse and cloud the focus on performance.  Another unresolved issue
is who should conduct comprehensive evaluations or conduct CCP's.  Should
that De a role of the EPA or state agencies or should it be done privately?
Trie tools are available to improve performance.  The mechanisms to provide
impetus to using these tools are apparently lacking.
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REFERENCES

1.  Gannett, Fleming,  Cordry and  Carpenter,  Consulting Engineers,  Harris-
    burg,  Pennsylvania.    Evaluation  of Operation  and Maintenance  Factors
    Limiting Biological Wastewater Treatment Plant Performance.   Report  No.
    EPA-600/2-79-087 (July 1979).

2.  Hegg,  B. A., K.  L.  Rakness  and J.  R. Schultz.  A  Demonstrated  Approach
    for  Improving  Performance   and  Reliability  of  Biological  Wastewater
    Treatment  Plants.   M &  I,  Inc.,   Consulting  Engineers,  Fort  Collins,
    Colorado, Report No. EPA-6-00/2-79-035 (June 1979).

3.  Hegg,  B.  A.,  K. L.  Rakness and J.  R.  Schultz.   Evaluation of  Opera-
    tion  and Maintenance  Factors  Limiting Municipal  Wastewater Treatment
    Plant  Performance.   M & I, Inc.,  Consulting  Engineers,  Fort  Collins,
    Colorado, Report No. EPA-600/2-79-034 (June 1979).

4.  Hegg,  B. A., K.  L.  Rakness  and J.  R. Schultz.   Evaluation  of Operation
    and  Maintenance Factors Limiting Municipal  Wastewater Treatment  Plant
    Performance - Phase II, M & I,  Inc., Consulting Engineers,  Fort  Collins,
    Colorado, Report No. EPA-600/2-80-129 (August 1980).
   "This  paper  has  been reviewed  in  accordance  with  the  U.S.  Environmental
   Protection Agency's  peer and administrative review policies and approved
   for  presentation and publication."
                                     104

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              PAPER NO. 7


APPLICATION OF INTRACHANNEL CLARIFIERS

    IN THE OXIDATION DITCH PROCESS
                  by

            Harold J. Beard
               President
         Beard Engineering,  Inc.
              P.O.  Box 3838
   Baton Rouge, Louisiana  70821  3838
                  105

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.APPLICATION OF INTRACHANNEL CLARIFIERS IN THE OXIDATION DITCH PROCESS

Harold  J.  Beard,  President
Beard  Engineering,  Inc.
 INTRODUCTION

      Conventional  solutions to the wastewater enigma  faced  by many communi-
 ties today,  often  results in high capital  expenditure, as well as  increas-
 ing operation and  maintenance costs over  the  life  of  the project.  The
 increasing awareness of the need  for energy conservation has  led many
 EPA construction  grant applicants to the  EPA  Innovative/Alternative Program
 which Congress incorporated into  the Clean Water Act  of 1977.  The purpose
 of  the I/A program is to develop  new technologies  that will meet required
 effluent limits with a minimum amount of  resources.   Since  its introduction,
 communities have  had the incentive to utilize this program  because of
 the associated cost savings.  That is,  the federal government would pay
 for 85% of design  and construction of all  or  part  of  a treatment process
 determined  to meet the requirements of the  I/A program.  Even though
 communities and their consultants have been required  to look at alternatives
 for treatment  since the enactment of the  Federal Water Pollution Control
 Act Amendment  of 1972, it was not until  the introduction  of promised
 cost and energy savings that the  program was  vigorously embraced.  As
 a  result, consulting engineers have gone beyond the alternative technologies
 of  land treatment  and sludge composting to advance the state-of-the-art
 by  the introduction of innovative technology  to conventional treatment
 schemes.

      One of  the most common  conventional treatment schemes  utilized to
 meet effluent standards imposed as a  result of individual  discharge stream
 requirements is that of activated sludge treatment for biological oxidation
 of  organic material  present in influent wastewater.   The purpose of this
 paper is to describe the innovative technologies applied to the activated
 sludge treatment process found to be  most  suitable for the city of
 Winnfield,  Louisiana.

      The existing  Winnfield,  La.  wastewater treatment facility consisted
 of  a 1.2 - mgd  single  stage  high  rate  trickling filter system with an
 anaerobic single stage sludge  digester and drying beds.  The alternatives
 evaluated were  subject to a  detailed  analysis to determine  the one that
 would be  most cost-effective,  implementable,  environmentally sound and
 energy  efficient,  and  yet would be  simple  to  operate  and maintain.   A
 multi-screening process eliminated  those treatment schemes  that would
 not  satisfy  a majority of the  present  guidelines such as unavailability
 of  land,  resource  conservation  and  use of  existing structures.  The
 alternative  system that adequately  satisfied  the selection criteria and
 was  subsequently selected through a  detailed  analysis of effluent
 requirements, wastewater characteristics,  capital cost, operating cost,
 energy  consumption and sludge  handling and environmental  consideration
was  an  extended aeration  process  utilizing an oxidation ditch with
 intrachannel clarifiers.

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IMMEDIATE ADVANTAGES OF THE INTRACHANNEL CLARIFIER

     Design criteria for an oxidation ditch is based on the theoretical
destruction of all organic matter applied by using an extended aeration
period and increased aeration.  The raw wastewater flow is fed directly
to the ditch where the contents are aerated and kept in continual motion.
The aerated sewage is then passed to a final settling tank which utilizes
mechanical scraping devices to move settled active solids to a collection
point in the tank.  A portion of the collected sludge is then picked up
by return sludge pumping system and returned to the oxidation ditch in
order to maintain a desired mixed liquor suspended solids concentration.  (1)

     A most obvious advantage to the "intrachannel clarifier" system of
mixed liquor clarification is the significant savings associated with both
energy consumption and construction.  In contrast with the conventional
external clarifier which requires feed and/or return sludge pumping, once
the influent has been fed to the oxidation ditch, except for aeration
purposes, no further energy consumption is required for clarification
purposes.  Since no external  basin  is required, there is also a definite
savings  in construction costs.  Any treatment system selected should be
relatively simple and easily operable by an operator of medium skill and
training.  The process equipment and controls should not be highly
sophisticated.  An additional advantage to be realized of the "intrachannel
clarifier" is the possible reduction in plant operational  expertise required
with respect to sludge waste and return pumping associated with maintaining
optimum MLSS concentration.

     In June of 1981, a proposal was submitted by the city of Winnfield,
Louisiana to the EPA Municipal Environmental Research Laboratory for
the purpose of requesting a Research Cooperative Agreement for bench and
pilot scale testing of an intrachannel clarifier design.  Evaluation of
various clarifier designs would be  in conjunction with an anticipated EPA
Step 2 Construction Grant for proposed wastewater treatment facilities.

     Previous testing of an intrachannel final clarifier in the oxidation
ditch at the wastewater treatment facility located in Campbel1svi1le,
Kentucky led to the first generation development of a unique final
sedimentation process.  This intrachannel clarifier system was shown to
provide significant construction and energy cost savings as compared
to conventional final clarifiers.  However, the results of this testing  has
led the staff of Beard Engineering, Inc. to the identification of several
variables which when optimized, may significantly enhance the clarifier
performance, and result in additional cost savings.  Since the intrachannel
clarifier was shown to provide satisfactory clarification and sludge return
characteristics for a secondary treatment level, consideration has been
given to the possibility of improving the concept by eliminating the need
for sludge scraping mechanisms.  The first generation intrachannel system
utilized scraper mechanisms for both sludge and scum removal.

     It  is the intent of the research program to utilize developed math-
ematical models and calculations to successfully design and subsequently
construct an intrachannel clarifier which can substantially reduce the

                                     107

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capita] and OSM costs required for sewage treatment.

INTRACHANNEL CLARIFIER CONCEPT

     The boat shaped clarifier operates within the channel of an oxidation
ditch, thereby immediately returning sludge to the mixed  liquor stream.
With placement of the unit in the direct flow of the mixed liquor, the
stream flow is restricted to that channel area between the clarifier and
the bottom of the ditch and between the walls of the ditch and the unit.
In the area of the channel beneath the "boat clarifier" the velocity of
the stream is therefore increased and a net head difference is produced.
Because the bottom of the unit is open at various locations with variable
sludge ports, this head differential is sufficient to actually pull a
quantity of flow and therefore the settled sludge from the inside of the
clarifier and back into the mixed liquor stream.  It is for this reason
that no sludge pumping or scraping is required.

     The head differential created by the restriction of  the stream flow
will also result in a lowering of the channel depth along the sides of
the boat clarifier.(2,3)  This difference of water levels between the
inside and the outside of the clarifier will allow for the removal of
floating debris in the clarifier.  Surface baffles within the boat will
direct floatables towards several adjustable scum ports on both sides
of the unit.   The debris will be returned to the ditch through these scum
ports and will be continuously removed from the ditch surface with
additional baffling.

RESTRICTION OF FLOW

     As previously mentioned, the boat clarifier concept operates on
the principal  that as flow is restricted in a channel,  this transition
produces a net head difference less than that of the flow prior to this
transition.  So that  a minimum of loss occurs in the available head
difference produced,  the cross sectional surface area of  the boat and
its front end design  are critical to tranquil flow around and beneath
the clarifier.  A mathematical  analysis of eleven (11)  different cross
sectional shapes was  performed to determine which would achieve the maximum
velocity increase beneath the clarifier in a rectangular channel and yet
expose the smallest amount of surface area to the stream flow in order
to minimize frictional losses of energy.  In a rectangular open channel,
we know that flow is  equal to the velocity times the cross sectional area
of the channel.   With the flow remaining constant in the channel and
through the restricted area beneath the boat, the velocity in the
restricted area  would then be a function of the cross sectional  areas
as fol lows:

                             V2 * Vl
                                   A2
     Where A., and V. are associated with the channel upstream of the
clarifier and A«, and V_ are associated with the mixed liquor stream
beneath and around the clarifier.

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CHANNEL WATER LEVEL AND CRITICAL DEPTH

     Having determined the ideal clarifier cross section for a rectangular
channel, the proper operating depth of the clarifier can be established
considering the water level and velocity in the channel.  Clarifier depth
in the channel must produce a sufficiently large head differential  to
provide proper skimming and sludge return flows.  Therefore, there  is
a minimum clarifier depth required for proper operation.

     The maximum clarifier depth is that depth at which a hydraulic jump
will occur.   If this "critical depth" is exceeded, high velocity in the
restricted area beneath the clarifier will result in a hydraulic jump
where the channel flow exits the restricted area.  A hydraulic jump must
be avoided since its turbulence results in a large loss of energy.   (Figure 1)
     Therefore, for a given velocity and water level  in the channel  there
is a certain minimum and maximum clarifier depth.  Calculations were
performed using five different water levels, three clarifier depths, the
selected channel cross section, and a channel velocity of 1 ft/sec.
Similar calculations were performed using a velocity  of 1.5 ft/sec to
evaluate the clarifier depths required for the normal velocity range of
oxidation ditches.

     These calculations were used to plot curves of velocity beneath the
clarifier vs. water level in the channel at the three clarifier depths
and two channel velocities.  A critical depth curve was plotted using
the velocity at critical depth for each water level and each channel
velocity.  The  resulting plot  (Figure 2) can be used to find the maximum
clarifier depth for a given water level at a velocity  in the channel of
1 fps.  Similar curves can be developed for other stream velocities in
the channel .

     The calculations were also used to plot curves of head differential
vs. water  level in the channel at the three clarifier  depths and two
channel velocities.  Therefore, for a certain clarifier depth, channel
water  level, and channel velocity the curves can be used to find the head
differential.   If head differential  is  known then the  skimming and sludge
return  flows can be calculated.   (Figure 3)

      In summary, this clarifier design  involves developing a set of curves
of velocity beneath the clarifier vs. channel water  level.  These curves
are used to determine the maximum allowable clarifier  depth for a certain
water  level and velocity  in  the channel.  A  second set of curves of head
differential vs. channel water  level can be  used to calculate  skimming
and sludge  return flows for  a certain clarifier depth, channel water
 level,  and channel velocity.

SLUDGE  CHARACTERISTICS

      An evaluation of sludge settling characteristics  must be  included
 in order to properly design  the clarifier  internals.   For evaluation

                                      109

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purposes an artificial sludge was produced utilizing ferric chloride.
This sludge was prepared to have a Sludge Volume  Index of 73 at a solids
concentration of 3000 mg/1.  Thus, the settling characteristics of this
iron sludge were very similar to typical activated sludge in a domestic
wastewater treatment plant.

     Settling column tests were performed by  recording the  interface
height at regular time intervals as the sludge blanket settled in a one
liter graduated cylinder.  This data was then used to develop the settling
curve shown in Figure b.  Analysis of this curve  reveals that a compressive
settling zone is formed  in approximately nine minutes when  the sludge
blanket occupies A6% of  the volume of the cylinder.

     As shown in the lower portion of this curve, settling  of the sludge
blanket is considerably  slower once the compressive zone is formed.  This
type of settling occurs  in the bottom portion of  a conventional clarifier
where the sludge is collected and pumped from the clarifier basin.  Since
settling sludge  is rapidly returned to the mixed  liquor stream via ports
distributed over the entire floor of the boat clarifier, there will be
no  formation of a compressive zone.  For this reason the boat clarifier
operates more as a phase separator continuously drawing off sludge, rather
than a conventional and  somewhat quiescent settling basin which requires
bottom scraping.

     To dramatize the effects of continuous sludge draw off, a more
realistic settling test was developed utilizing a graduated cylinder from
which the artificial sludge was withdrawn from the bottom at various rates
of  millimeters/minute.

     This test data was used to develop the settling curves shown in
Figure 5-  These curves are a graphical presentation of a column of
influent water as it moves through the length of  the boat towards the
bow.  It is anticipated  that these curves will represent the actual shape
of  the sludge blanket which will form subsequent  to various adjustments
of  the sludge ports.

     From the previous settling column tests, it was determined that
ultimate settling would  result in a sludge blanket which would occupy
13% of the volume of the cylinder.  To represent  the effects of sludge
draw off on the volume of sludge per unit volume of the clarifier, the
initial settling curve in Figure 4 was converted  to the percentage curve
shown in Figure 6.  Analysis of this curve reveals that as  the total
volume of the cylinder decreases, a direct result of draw off, the
percentage of sludge in the remaining volume  increases.  For example,
in  18 minutes the sludge occupies k$% of the  remaining volume and at 28
minutes it occupies 5&% of the volume.
      In combining the results of the settling tests, it was concluded
that  the sludge blanket which will form in the boat clarifier will be
affected by the percentage of boat volume removed through the sludge ports
and the amount of time required for the flow to move the length of the
clarifier.


                                     110

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ANALYSIS OF CLARIFIER FLOWS

     In order to determine the optimum amount of clarifier volume which
should be removed through the sludge ports,  it was necessary  to perform
an analysis of all flows in the clarifier.

     Initially it must be recognized that the flow into the rear of the
clarifier is determined entirely by what  is  removed from the  effluent
launderers (0.), the surface skimmer (Q ), and the sludge return ports
(Q.) on the bottom.

     The value of Q, is determined by plant  capacity and is therefore
a constant.   The value of 0__ is such that movement of the surface water
is sufficient to remove floating debris through the skimming  ports.  For
the purpose of developing a mathematical model, it is assumed  that Q, = Q_
and therefore Q, can be varied to determine  its effect on the  sludge blanket
formation.  In the analysis it was assumed that the bottom of  the clarifier
was evenly spaced with the (10) sludge ports.  With the ultimate sludge
settling volume of 13% in mind, the percentage of sludge per  unit volume
of the clarifier was determined for 10 cummulative time intervals.  These
determinations were made for various Q_ values and resulting  total volumes
(0_) =0, + 0. + Q,•  The resulting percentages were then used to determine
approximately how much flow (Q,) was being removed in excess  to that which
would be required to remove the average volume of sludge.  These excess
amounts, or "safety factors" were then plotted against their  respective
Q- to 0_ ratios.

     To dramatize the effect of flow time in the clarifier, a  similar
curve was developed with effluent launders placed in the rear  of the boat
where the influent comes in.

     Mathematical models were also done on uneven flows on the ten port
openings with the greatest flow being from the rear of the boat clarifier
where the initial wastewater flows into the  clarifier and the  smallest
flow from the bow where the launders were located.  These results showed
an improvement in removal over the equal flows.   In these calculations
the same ratios of 0- to QT were utilized as with the ten even flows so
that relative data and effects could be established.

     The resulting Figure 7 reveals that the maximum efficiency of sludge
removal occurs when approximately 64% to 65% of 0- is removed  through
the sludge ports and the effluent launders are located in the  bow of the
boat.

SLUDGE FLOW FROM CLARIFIER BOTTOM

     The two determining factors which effect the flow from the sludge
ports on the bottom of the clarifier are the head differential produced
by the restriction of flow and the size of the ports themselves.

     For the purpose of this explanation, the following assumptions were
made:

                                     111

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     A)  The velocity in the channel is 1 ft/sec.

     B)  The cross sectional area of the channel is 11.52 ft^/linear foot.

     C)  The skimmer port is set at .5" below the water level when the
         channel  is not flowing.

     D)  The head loss under the clarifier is 1  inch.

     Assuming the bottom of the clarifier is -750 ft. from the bottom of
the channel and the water level is at 2.4 ft., the total head differential
is then 1.91 inches (head differential created by difference in velocity
based on Bernoulli).

     Therefore, the available head for sludge flow Q3 is:

                       1.91" - 1.0" - .5" = .41"

     The velocity exiting the bottom (less opening losses is determined
by the equation V =—» /2gh.  Therefore, the exit velocity is:
                                 x 32.2 x

                       V3 = 1.48 ft./sec.

     This velocity then allows the calculation of the total opened area  in
the bottom required to achieve a 0.3 of 64% to 65% of 0_j.

     Recognizing that there are numerous variables that effect the amount
of open area,  it is advisable to have the bottom of the clarifier designed
so that the sludge port opening can be varied.

     The proposed bench scale model will be built identical to the full
scale system with all influent ports, effluent weirs, and scum and sludge
removal ports  being operational and variable.

     Initial testing will involve determination of the most efficient
clarifier orientation with respect to the channel bottom and water depth.
In our mathematical development of the boat clarifier, headless beneath
the unit was determined for a wood structure.  However, since the bench
scale model is to be fabricated from fiberglass, it is believed that the
actual  velocities and head differentials produced by restriction of the
channel flow will approach and perhaps surpass those calculated in the
mathematical analysis.  Velocities and head differentials will be recorded
for what is hydraulicaly the most efficient boat configuration utilizing
various clarifier and channel  depths.  The approach channel velocity will
also be varied to collect similar data for the normal velocity range
common to oxidation ditch wastewater treatment systems.

     The next  portion of the testing procedure will involve the use of dye
or fine bubbles to video record the actual flows produced beneath, around
and within the clarifier.  This data will allow for actual refine-


                                    112

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merit of the clarifier shape both internally and externally.  Again, this
will include a variance in the channel and clarifier depths as well as
approach velocities.

     Finally, once the most efficient boat configuration and orientation
have been determined, the same artificial sludge used in the mathematical
development will be introduced into the oxidation ditch.  Also, sludge
and skimmer ports will be adjusted so that optimum flows are achieved
for both sludge blanket and floatable solids removal from the clarifier.

     At this time it  is most important to note the conservative assumptions
made during development of this concept.  The calculations for determining
the optimum Q_ to QT  ratio and subsequently the length of the boat clarifier,
were based on the assumption that there  is a specific amount of time required
for the sludge to attain the ultimate compressibility of 13% of total
volume.  However, since this concept  involves continuous removal of sludge
it  is anticipated that actual testing will result in a much shorter sludge
blanket.  Also, settling curves where developed for sludge which occupied
the entire depth of the settling columns.  When the artificial sludge
enters the rear of the clarifier, a  baffle will direct the flow down
towards the sludge removal ports.  Therefore, the solids particles will
actually start their descent to the bottom of the clarifier at or below
the mid-depth point.  Again  it is anticipated that this will result in
a shorter sludge blanket and subsequently quicker removal of all solids.

     Upon conclusion of the testing procedure, all pertinent data will
be utilized to modify the original mathematical model.  It is this resulting
configuration and channel requirements upon which design of a pilot model
will be based.

REFERENCES

     1.  John W. Clark et al., Water  Supply and Pollution Control,
         International Textbook Co., New York, 1971.

     2.  Victor L. Streeter and E. Benjamin Wylie,  Fluid Mechanics, 6th
         ed., McGraw-Hill Book Co., New York, 1975.

     3.  Calvin Victor Davis and Kenneth E. Sorensen, Handbook of Applied
         Hydraulics,  3rd ed., McGraw-Hill Book Co., New York, 1970.

     4.  Metcalf & Eddy,  Inc., Wastewater Engineering, McGraw-Hill Book
         Co., New York, 1972.
    "This  paper  has  been  reviewed in accordance with  the U.S.  Environmental
    Protection  Agency's  peer and  administrative review policies and approved
    for  presentation and  publication."
                                     113

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4.5-,
4.0.
                                                      Clarifier  .400  Ft.
                                                           From Bottom
                                                       .525  Ft.  From
                                                          Bottom
                                                       .650  Ft.  From
                                                          Bottom
                                                      .710?

                                                      Critical  Depth
                                                          Curve
                                             Channel  Velocity  1.0  Fps

                                             Note:   Critical  Depths
                                                    Are  Plotted
                                                    Re 1 a t i ve  To  Clarifier
                                                    Depths
    1.4
—T—
 1.9
     2.4
Depth (Feet)
2.9
3.4
        Figure  2.   Velocity  Beneath  Clarifier  vs.  Channel  Depth
                                 115

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                                          Clarifier  .^00  Ft.
                                              From Bottom
                                            525  Ft.  From
                                              Bottom
                                            650  Ft.  From
                                              Bottom
                             Channel  Velocity 1.0 Fps
                2.1*         2.9
             Channel  Depth (Feet)
Figure 3.  Head Differential vs. Channel Depth
                      116

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4-1
-C
Ol
QJ
:r
(0
j-j
o
 0)
3:
 0)
 o
 (0
100 ,

 90.

 80.


 .70.

 60.

 50.

 40-

 30.

 20 _

 10.

  0
                        i
                                            T
                                            T
T
T
T
                                                               .22
   T	1	1	T^T	1	1	1	r
0  2   k  6   8   10  12  14  16  18   20  22 2k  26 28  30 32
                          Time (Min.)

       Figure  4.   Settling Curve For  Artificial Sludge
                                  D i splacement
                                    Volume
                 SIudge
                  Blanket
                   Zone
                                                        Very Clear
                                                             Zone
                   i—T—i—r—T—i—i—i—i—r—r—i—i
                   8   10  12  14  16  18  20  22  24  26  28   30   32
                            Time  (Minutes)

        Figure 5-  Test  No.  5 Bottom Removal  Settling Curves
                                 117

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                                                            100%
                                              removal  of blanket
              Figure  6.
 T—i	1	r
12   ]k  16   18
   Time (Min.)
  % Of Maximum Settlement
                                                 Launder in  Front
                                              Maximum Efficiency
                                              Occurs at 6k to 65%
                                                 Launder in Back
                 50                6T
                      % Of Total  Flow

Figure 7.  Safety Factor vs. Flow From Bottom Clarifier
                           118

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                  PAPER NO.  8
  BIOLOGICAL FOULING OF FINE BUBBLE DIFFUSERS
                      by

               William C. Boyle
Professor of Civil & Environmental Engineering
           University of Wisconsin
              Madison, Wisconsin

                      and

                David T. Redmon
                   Engineer
           Ewing Engineering Company
             Milwaukee, Wisconsin
                      119

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BIOLOGICAL FOULING OF FINE BUBBLE DIFFUSERS

William C. Boyle, Professor of Civil & Environmental Engineering, University
of Wisconsin, Madison, WI
David T. Redmon, Engineer, Ewing Engineering Co., Milwaukee, WI


     Aerobic biological processes continue to be the most popular methods for
the treatment of municipal and industrial wastewaters.  The supply of oxygen
to the biomass in activated sludge and aerated lagoons represents the single
largest energy consumer in the treatment plant.  Recent studies indicate that
from 50 to 90 percent of the net power demand for a treatment plant lies
within the aeration system (1).  It is not surprising, therefore, that engi-
neers continue to seek the most efficient aeration systems for new and
existing wastewater treatment facilities in order to provide energy-
conserving operation.

     Although there is considerable controversy over which aeration system
provides the most favorable oxygen transfer efficiency, the fine bubble
diffusion of air has recently gained renewed popularity as a very competitive
high efficiency system.  Yet, considerable concern has been registered re-
garding the maintenance of fine bubble systems owing to their susceptibility
to clogging.  Diffuser clogging, if severe, may lead to deterioration of
aeration efficiency resulting in an escalation of power costs.  Furthermore,
troublesome maintenance of diffusers may consume a substantial amount of
operator time.

     Originally, oxygen was diffused into wastewater through perforated pipes
located at the bottom of the aeration tank.  The development of the porous
plate for aeration was considered an important advance in the diffused air
process because of the high transfer efficiency of this fine pore diffuser
(2).  Porous diffuser plates were used in activated sludge processes as early
as 1916 and they became the most popular method of aeration by the 1930's (3,
4).  Shortly after their installation, however, it became clear that clogging
could be a problem.  Early work by Bushee and Zack (5) at the Sanitary
District of Chicago from 1922 to 1924 prompted the use of coarser media to
avoid severe clogging problems.  Similar studies confirmed this at Milwaukee
in the early 1930's.  In a comprehensive review of fine bubble diffuser ser-
vicing, Roe  (2) outlined a number of causes of diffuser clogging.  This list
has been expanded over the years and is presented in Table I.

     It was clear even in the early years of fine bubble diffusion that
clogging was highly site specific and quite often difficult to forecast (4,
6).  Diffuser clogging was chronic at some plants after only a few months of
operation, yet, at others, virtually no difficulties with clogging arose.
Substantial effort was applied in the early years to reducing internal clog-
ging by means of efficient air cleaning (7,8,9), a practice still performed
today.  External clogging was not as easy to analyze or control, however, and
operations research concentrated primarily on treating the symptom rather
than the cause.
                                     120

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                   TABLE I.  CAUSES OF DIFFUSER CLOGGING


     Air Side
          •  Dust and dirt from unfiltered air
          •  Oil from compressors or viscous air filters
          •  Rust and scale from air pipe corrosion
          •  Construction debris due to poor clean up
          •  Wastewater solids entering through diffuser or pipe leaks

     Liquor Side
          •  Fibrous material attached to sharp edges
          •  Inorganic fines entering media at low or zero air pressure
          •  Organic solids entering media at low or zero air pressure
          •  Oils or greases in wastewater
          •  Precipitated deposits, including iron and carbonates
          •  Biological growths on diffuser media
TESTS FOR CLOGGING

     In 1934, Roe (2) indicated that clogging of air diffusers could best be
monitored by measuring air main pressure changes with time for each aeration
tank.  Further, he indicated that visual observation of the aeration tank
surface could often provide evidence of severe diffuser fouling.  Over the
years, little change has been made in this technique.  As indicated by Roe,
sequential readings of air main pressure, air flow and temperature are made
(Figure 1).  A plot of air pressure at a given standard air flow rate versus
time is subsequently used to detect fouling.  One of the major factors that
severely limits the precision of this method is that the differential pres-
sure across the diffusion element itself, which is the parameter of principal
interest, is very small relative to the pressure in the main.  Other factors
and variables that further limit the precision of the method include the
water surface elevation in the aeration tanks, water temperature, air flow
variation, and variable line losses.

     A method that measures the drop across selected diffusion elements at
measured flow rates is considered to be of far greater accuracy and preci-
sion.  An example of such a system is shown in the detail sketch on Fig. 1.
Flow may be determined by observation of manometer A which measures the dif-
ferential across the previously calibrated control orifice C.  Manometer B
measures the pressure drop across the diffusion element itself, or the
dynamic wet pressure (DWP).

Dynamic Wet Pressure

     The dynamic wet pressure, DWP, is the pressure differential across the
diffusion element alone when operating in a submerged condition and is ex-
pressed in terms of inches of water, at some specified flow rate.  It
differs substantially from the permeability test, where the specific air flow
rates are typically much higher and where surface tension of the submerging
liquid is not a factor.

                                     121

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                                        Valve
                            PLAN VIEW SCHEMATIC
                       DETAIL
                                            'See Detail

                                                Air Source
                                                  Air Flow Control
                                                     Orifice
                                   Header^7
          Figure  1.   Measurement of Air Line and Diffuser Pressure

     In the dynamic wet  pressure test,  most of the pressure differential is
due to the force  or pressure required to form bubbles against the force of
surface tension and only a small fraction of the total pressure  gradient is
required to overcome  frictional resistance.

     The DWP  is normally relatively insensitive to airflow rate.  This
results since the surface tension effect is not greatly influenced  by flow
rate in flow  ranges normally applied and the contribution of frictional re-
sistance is a small part of the total pressure gradient.

     That the frictional resistance is small with respect to the total,  can
be shown as follows:

     Assume the typical  airflow rate at average design conditions is
     about 2  SCFM per square foot of diffuser surface area.  Since  the
     frictional resistance is only 2.0 in. wg. at 25 SCFM Cspecific
                                     122

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     permeability of 25) and this unit is typically operated at 2 SCFM
     under average design conditions, its theoretical frictional
     resistance at this rate is roughly 2.0/25.0 of 2 in. wg. or
     about 0.2 in. wg.  The total DWP at 2.0 SCFM is about 6.9 in. wg.
     So the frictional resistance at this airflow rate is roughly 3%
     of the total resistance.

     The DWP test is of value in analyzing diffuser fouling in at least two
ways.  It is a much more sensitive indicator of fouling than air main pres-
sure readings and the analysis of the DWP vs. flow relationship gives some
indication of the nature and type of fouling.

Bubble Release Pressure

     The bubble release pressure (BRP) test provides a means of comparing the
relative effective pore diameter at any point on the surface of a ceramic
element to other point(s) on its surface.  Ewing Engineering Company develop-
ed this test procedure as a tool to assess the uniformity of pores on the
surfaces of ceramic diffusers.

     The bubble release pressure test, as indicated by the name, measures the
pressure in inches of water gauge required to emit bubbles from a localized
point on the surface of a submerged and thoroughly wetted porous diffuser
element.  This is accomplished by forcing air at a very low rate of flow into
the diffuser and measuring the pressure of the air when bubbles are released
from the diffuser at the point in question.

     The test procedure was developed from a similar test found in ASTM,
Part 41, under Standard Test Method E128-61.  This standard describes a
technique for measuring the maximum pore on a porous structure and uses the
force to make bubbles in a known fluid to calculate a capillary diameter
corresponding to this force or pressure.

     Ewing Engineering Company modified the hardware to suit their needs and
used BRP observations of a statistically significant number of points on the
element to ascertain the degree of uniformity.  After determining the air
flow distribution on several elements on which BRP data was available, it
became apparent that the BRP test data was a sensitive indicator of flow
distribution.

     This test has been applied to a variety of fine pore diffuser elements.
It has been found to be a sensitive indicator of the degree of fouling of
porous diffusers and provides a quantitative means of assessing the rate and
location of plugging.

     Furthermore, analysis of partially fouled diffusers have given indica-
tion that the BRP test is even more sensitive than the DWP test.  Conse-
quently, in diffuser fouling investigations, the use of these test methods
permits significant shortening of the test period required to obtain defini-
tive conclusions about diffuser clogging.
                                     123

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Air Profile Test

     The airflow profile test uses quantitative techniques to evaluate the
uniformity of air release across the surface of ceramic diffusers while
operating rather than appraising uniformity by visual means.  This  is accom-
plished by testing the element at an air rate which is approximately equal
to 2 SCFM/sq. ft., or at the recommended design rate, with anywhere from
2-8 inches of water over it.

     The rate of air release from small areas is measured by displacing water
from an inverted graduated  cylinder and recording the rate of displacement
of water with a stopwatch.  The same sites monitored in the BRP  test are
tested  in this procedure.   By combining the cylinder area and the rate of air
discharge, a flux rate, expressed as SCFM/sq. ft. or other convenient units,
can be  calculated.  By comparing the individual readings with one another,
a quantitative measure or graphical representation of the profile can be
generated.

      The  combination of DWP, BRP, and  flow profile tests applied to new
diffusers and at various stages in their operating history, provides a very
useful  diagnostic tool in evaluating the rate, the nature and the effect of
 fouling,  be  it organic or inorganic, on fine bubble porous diffusion ele-
ments.   It  is also effective in appraising the effectiveness of  various
 cleaning  procedures.

 BIOFOULING  OF DIFFUSERS

      The  occurrence of biological growths or slimes on  fine pore diffusers
was recognized early after  their application in activated  sludge.   Roe  (2)
 indicated that biological growths were found on the liquor side  of  most
 diffusers  in operation.  He attributed this growth primarily  to  the non-
uniformity  of the diffuser  medium.  There were very few published  reports  of
 serious diffuser clogging problems attributed to  biological  growths,
however.  Anderson  (9)  indicated that  fungal growths were  commonly  found  on
 diffusers at the Sanitary District of  Chicago Southwest Plant with  heaviest
 growths occurring  in  the  summer near the  influent end  of the  aeration  tanks.
 These growths produced  little measurable  effect on air line  pressure  loss
 except  during the  summer  of 1944 when  an  exceptionally heavy  growth of
 Saprolegnia s£ developed.   No  reason for  the unusual  growth  that year  was
 cited.   Beck (3) reported a severe  clogging of  diffuser plates  after  69  days
 at the  Chicago  North  Side Works where  return sludge was aerated.  The  plate
 surfaces,  clogged with approximately 1/8  inch of  biological  slime,  were
 refurbished by  aeration over  a  45  day  period without  addition of wastewater.
 Lamb (10)  referred  to  one or  two  cases where biological slimes  caused in-
 creased head loss  of  fine bubble  tube  diffusers  but no details  were given.

      In 1980,  Houck and Boon  (11)  carried out  an extensive survey of  19
 wastewater treatment  plants in the United Kingdom,  the Netherlands, and the
 U.S. that employed fine bubble dome diffuser  aeration devices.   The major
 objective of this  work was  to  assess  long term oxygen transfer performance
 and operation and  maintenance history  of dome  diffuser aerators.  As a part
 of this study,  the authors  reported that the major operational problem


                                     124

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associated with dome diffusers was the formation of biological slimes on
diffusers operating in zones of high volumetric loading and/or low dissolved
oxygen.  In only two cases, however, were domes observed to contain excessive
amounts of biological slime (Beddington, U.K., and Madison, WI).  All other
plants apparently exhibited signs of "coarse bubbling" which the authors
attributed to the development of biological slimes.  The authors further
cited pilot plant work at the Water Research Centre at Stevenage, U.K. which
verified the causes of diffuser sliming as the result of very high loading
rates (12).  No data was presented, however.

     Madison, Wisconsin observed a severe biological sliming problem in the
early part of 1980, about two years after installation (13).  Heavy infesta-
tions of stalked ciliates (predominantly Epistylis) were observed on the dome
surfaces and the plastic air piping.  Slime cover on the domes was not uni-
form, completely covering some domes while being almost absent on other
adjacent domes.  It appeared that slightly more growth occurred on domes in
the first pass and less in the third pass of this step aeration system.  This
plant experienced high BOD loading throughout the first half of 1980, the
predominant source being several dairies in the community.  Prior to this
heavy loading period no apparent heavy slime growth was noted on the dif-
fusers when the tanks were dewatered.  Following the high loading period in
early 1980, the domes were steam cleaned in-place and returned to service.
Since that time, the domes have been periodically checked.  Some slime growth
has reappeared but it contained few stalked ciliates and was more diverse in
biological population.  The slime was easily removed with high pressure water
hoses.  Since the high load incidence, in 1980, there has not been a recur-
rence of the heavy biological slime formation at the plant.

Biofouling Agents

     Over the years, several investigators have analyzed the biological
slime that developed on fine bubble diffusers.  A synopsis of these findings
appears in Table II.  In most cases when biological slimes were found, no
specific identification was provided but descriptions of color or consistency
were given.

                       TABLE II.  BIOFOULING AGENTS
     Worms - Tubifex, Aulophorus
     Iron bacteria - Crenothrix
     Stalked ciliates - Epistylis
     Filamentous bacteria
     Fungii - Saprolegnia
     "Biological slime"
                                                       Source
[Setter (7),
[Setter (7)]
[Setter (7),
[Setter (7)]
[Anderson (9)]
[Roe (2), Wisley
  Cont.(5),  Lamb
  & Boon (11)]
Madison (13)]
Madison (13)]
    (6), Op &
    (10), Houck
     The occurrence of Epistylis (species undetermined) as a predominant
organism in the biological slime on the domes at Madison, Wisconsin was
                                     125

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interesting.  Further investigation of the heavy plant loads during the
severe bioslime incidence, indicated that an unusually high amount of dairy
wastewater including whey was discharged during that period (13).  Metabolic
studies with Epistylis have indicated that this attached ciliate, unlike many
others, may feed on inert wastewater nutrients as well as bacteria (14).
Whether the presence of specific nutrients in the dairy waste promoted the
unusual bloom of Epistylis and subsequent formation of heavy slime growths
on the ceramic diffusers or whether the presence of this organism was inci-
dental to the real causative agent in the bioslime at Madison is uncertain.
The almost complete absence of Epistylis in subsequent biological slimes at
Madison suggests that the waste characteristic itself (rather than organic
load or low dissolved oxygen) may have played a predominant role in the
development of serious bioslimes on the diffusers at that plant.

Causes of Biofouling

     The published literature does not contain any report of a controlled
study on the causes of bioslime development in activated sludge diffused air
systems.  Most hypothesis have been based on observations at operating
plants.  The major causes of biofouling that have been proposed based on
field experience are presented in Table III.  Roe (2, 15) indicated that
quite often a film of biological growth appeared on the diffuser surface
and even grew into the pore structure of ceramic diffuser plates.  He indi-
cated that poor air distribution within the plate resulted in biological
growths along and within the quiescent pore spaces.  Lamb (10) speculated
that these slimes appeared after the pores of the diffuser had become clogged
by dirt from the inside or incrustation from the outside.  Setter (.7) pro-
posed that biological clogging became more severe as the BOD loading increas-
ed and as the permeability of the plates decreased.  He also suggested that
sufficient air flow rate per diffuser should be maintained in order to avoid
excessive biofouling.  Both Setter (7) and Anderson (9) suggested that bio-
logical clogging appeared to be seasonal.  Heaviest fungal growths were
found to occur during the summer months (9).

                      TABLE III.  CAUSES OF BIOFOULING


          Uneven air distribution in diffuser (2, 7, 10)
          Low air flow rate per diffuser (7)
          High organic loading (7, 11)
          High temperatures (7, 9)
          Low dissolved oxygen concentration (11)
          Low permeability of diffusers (6, 7)
          Waste characteristics
     The field study of 19 diffused air plants conducted by Houck & Boon
 (11) provided additional data on bioslime formation.  These investigators
 claimed that the formation of biological growths on dome diffusers was the
 result of high organic load and/or low dissolved oxygen.  They speculated
 that the growth was exacerbated by extreme plug flow aeration tank design.
 Boon and Burgess (12) also reported heavy slime growth development on dome
                                    126

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diffusers in pilot plant studies using organic loads to a first stage aera-
tion tank of up to 420 Ib BODc/1000 ft.3/day.

     Similar excessive slime growth problems reported for the activated
sludge plant at Madison occurred during high organic load conditions.  A
synopsis of the data collected at Madison prior to and following this bio-
fouling incident is presented in Table IV.  Several interesting points should
be emphasized regarding this and other studies.  The organic loads (expressed
as Ib BOD5/1000 cu ft/d) to the Madison plant prior to heavy biofouling
averaged about 20.  During the heavy load period, the average rose to about
35 and subsequently dropped after the first six months of 1980 to about 29
where it has remained.  Only during the heavy load period in the first six
months of 1980 did a severe slime development occur.  This was coincident
with heavy dairy waste loadings including whey which were discontinued by
mid year.  At the time of this heavy slime infestation, the plant was being
operated in a step aeration mode.

          TABLE IV.  DIFFUSER STUDIES - MADISON NINE SPRINGS PLANT
     Aeration Tank Information:
          Tanks 1-6 each 31' x 135' x 15.5' deep (2-3 pass tanks)
          Diffusers:  Ceramic Domes - Tapered Aeration
          In Service:  October, 1977
DATE
10/27-12/77
1/78-6/78

7/78-12/78
1/79-6/79
7/79-12/79
1/80-6/80

7/80-12/80
Mode of
Operation
CS
CS

CS
CS
S/CS
S

S
F/M
(LB/DLB)
0.27
0.29

0.25
0.23
0.37
0.34

0.34
BOD LOAD
(LB/1000 FT^/D)
20.3
22.3

17.2
19.2
25.5
34.6

29.2
OTE
_
14

18
-
-
7.5-8

8-10
NOTES

Dewater tanks -
diffusers OK



Dewater tanks -
heavy slime
Steam cleaned
                                                             diffusers
                                                            Dewatered - mod-
                                                             erate slime
                                                            Steam cleaned
                                                             diffusers
1/81-6/81

7/81-11/81
S

S
0.33

0.39
30.1

30.4
-

16
Dewatered - mod-
erate slime
OTE by off gas
      CS - Sludge Reaeration in First Pass
       S - Step Aeration
     In contrast to this, the slime infested aeration tanks at the Beddington,
U.K. works were only loaded at 11 Ib BOD5/1000 cu ft/day but the plant did
                                     127

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receive heavy industrial waste loadings.  Other plants surveyed by Houck &
Boon (11) experienced loadings ranging from about 10 to over 110 Ib BOD5/1000
cu ft/d.  Some of these plants experienced coarse bubbling, but no severe
sliming problem was reported (all diffusers likely were coated with some
biological material but the authors did not present quantitave evidence of
severe fouling).  A review of operating records at the Milwaukee Jones
Island West Plant during the years 1952-66 (16) indicated BOD loadings ave-
raging 60 Ib BOD5/1000 cu ft/d.  This plant received substantial amounts of
industrial waste.  No severe biofouling incidences have been reported for the
ceramic plates at this plant during that time although incrustations and rust
contributed to clogging problems.

     The point to be made from this scant information is that biofouling is
apparently highly plant and waste specific.  No generalizations may yet be
made in reference to specific causes of severe biofouling.  The Madison
experience strongly suggests that their problem was waste specific and inter-
mittent  (not unlike the problem of sludge bulking in many plants); the prob-
lem at Beddington, on the other hand, is endemic, but, again, is likely due
to plant and waste specific characteristics.

The Effects of Biofouling

     The development of a biological growth on diffuser media could have
several effects on diffuser performance.  One might develop the following
sequence of events that would occur as the biofilm developed.

          As air passes through the media, biological growths begin
     to develop along the media where little air passes (e.g., over
     the finer pores).  This mat continues to develop and begins to
     overlap regions where air is escaping.  The presence of the
     bioslime leads to bubble coalescence along the media.  The effect
     of this progressive clogging might produce little noticeable
     change in DWP unless the biological slime envelopes the entire
     media surface.  Under these conditions,  the uniformity of the
     air released from the diffuser may be detrimentally affected
     and poor distribution may result.  The OTE may decrease as
     bubble coalescence occurs and there could be visible changes
     in bubble patterns and the appearance of "coarse bubbling" at
     the surface.  This type of diffuser clogging may not be evident
     as routinely measured by air line pressure losses or demand for
     more air (as a result of some loss in transfer efficiency).
     The biological slime may fluctuate in thickness and extent with
     season.  Its net effect may not be serious depending upon the
     extent of slime development.

     Other mechanisms of biological clogging may also occur as well as the
one outlined above.  Several investigators have speculated that biofouling
occurs after or simultaneously with internal clogging or external encrusta-
tion.  For such a situation, the following scenario might take place.

          Since porous media represents a distribution of pore sizes,
     air will initially flow through the coarser pores first where

                                     128

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     resistance to flow is the lowest.  Particulates in the air or
     chemical encrustations could begin to lodge within the larger
     pores forcing air to the next smaller pore size.  This would
     result in the progressive utilization of the finer pores producing,
     perhaps, more uniform distribution and finer air bubbles.
     Increases in DWP could be small at this point.   As time progresses,
     the next size pores could begin to fill, eventually resulting in
     the utilization of the finest pore openings.  As the effective
     cross-section through which air passes is restricted, finer
     bubbles may form and dynamic wet pressures would increase to a
     point where significant air line losses would be detected.
     Heavier biological growth would begin to develop in the quiescent
     regions at the diffuser.  Eventually the biological mat may
     result in bubble entrapment and coalescence.  The net effect of
     this progressive clogging might be an increase in OTE up to a
     point (as air distribution improves and bubble size decreases)
     followed by a drop in OTE as coarser bubbles begin to form.
     Dynamic wet pressures would slowly rise to a point where only
     the finer pores are carrying air; after this, pressures would
     rapidly rise.  At this stage, depending upon diffuser shape and
     general design considerations, coarse bubbles may form or major
     short circuiting of air past gaskets or around bolts may occur.
     At these high air flow rates per unit area, a continuous stream
     of bubbles may be discharged from these locations and the diffuser
     would no longer behave as a fine pore device.  Surface tension
     would no longer be measureable and the area would act like a
     very large pore.  DWP would not change at this point and the major
     effect would be a substantial loss in OTE as the behavior of the
     device approached that of a coarse bubble diffuser.  In another
     case, where no outlet for air flow is available within the
     diffuser element, the extent of fouling could be such as to
     severely restrict flow to a point where DWP (and BRP) rapidly
     increased to a point where significant air line pressures would
     require diffuser cleaning.

     Presently, there is not a great deal of evidence to support either of
these hypotheses of progression of biological clogging.  Historically, the
literature indicated that biofouling normally produced little change in DWP.
Isolated incidences at Madison and Beddington, U.K.  suggested that severe
biological slime development produced dramatic changes in DWP and BRP.  An
example of the effects of heavy biofouling of a ceramic dome at Madison is
presented in Figures 2-5.  In this example, it is seen that the DWP at 0.75
SCFM increased from about 6 inches to about 18 inches after severe clogging
(Figure 2).  BRP values on the top side of the dome increased from about 6
inches of water to a range of 14 to 10 inches after bioslime development
(Figure 3).  There was a slight increase in BRP on the bottom side of the
dome increasing from about 6 inches to 7.5 inches (Figure 4).  It was clear
that in this case, the bioslime produced the major resistance to air flow.
Note in the air flow profiles of Figure 5, the majority of the air passed
out along the periphery of the center bolt washer and the edges of the dome
once a clogging mat had developed within the main body of the dome.  Even
when new, the air flow profile suggested that air distribution was not ideal

                                     129

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,*  60
g  50
 .  40
-  30

u  20
13
V)
LU
a:
Q.
i-
UJ

o
     8
     6
     5
     4
     3
     2
I   1
                                             FOULED
                                              CLEAN
                     I
                   I
                    0.5    1.0    1.5   2.0
                        AIR  RATE - SCFM
                                      2.5   3.0
     Figure 2.  Dynamic wet pressure for clean and clogged dome - Madison,WI.

but once clogging was initiated,  the biological slime  exacerbated the air
flow distribution producing excessively high rates in  very localized regions.
It is likely that this condition  Ipd to severe reductions  in  OTE,  but no data
is currently available to substantiate this  under properly controlled condi-
tions.

     Of significant interest in diffuser fouling phenomenon is  the impact of
the slime on OTE.  Results from Madison (Table IV) suggest that the severe
biofouling of the domes produced  dramatic reductions in  OTE.  Once cleansed,
these diffusers appeared to essentially return to their  original high level
of efficiency.  It should be carefully noted,  however, that the field OTE
measurements made at Madison were crude,  at  best.   Early measurements were
made during the sludge reaeration process whereas later  measurements were
made in the aeration tanks when operated as  a step aeration process.  Dif-
ferences in alpha could have strongly influenced the comparison of these
data.

     The phenomenon referred to as "coarse bubbling" has been used as a
visual indicator of diffuser biofouling (11).   In some instances,  this de-
duction has been shown to be correct.  There are other cases, however, where
the incidence of "coarse bubbling" may be due to other factors.  These
authors have had the opportunity  to visit several plants where  "coarse
bubbling" occurred intermittently.  The coarse bubbles were most noticeable
at the influent end of the aeration tanks and would appear and  disappear
                                    130

-------
                  CD
                  LU
                  o:
                  co
                  CO
                  LU
                  cc.
                  CL
                  LU
                  CO
                  <
                  LJ
                  _l
                  UJ
                  cc
                  u
                  _1
                  CD
                  00
                  r>
                  m
                     18-
                     16
12
10
8
     Figure 3.  Bubble release pressures for the top of a  clean  and
                clogged dome - Madison, WI.

throughout the day.  No diffuser sliming was noted at these plants.  Cur-
rently, it is believed that coarse bubbles may occur as the result of  the
presence of high surfactant concentrations.  Poorly mixed  influent with
mixed liquor may produce zones of high surfactant concentration  with concomi-
tant low surface tension.  These zones may fluctuate as waste  flow and
characteristic change, but would be most noticeable at points  of waste
influent flow.

     The response of different types of diffuser materials and shapes  to
biofouling is not well documented.  At Madison, those aeration tanks equipped
with ceramic and plastic tube diffusers did not experience the severe  bio-
fouling problem that was prevalent in the ceramic dome aeration  tanks.  The
waste load to all the tanks was similar and tank geometry  was  approximately
the same.  Presently no explanation is available for these observed differ-
ences.

Design for Biofouling Control

     Until better information is available on the causes of biofouling of
fine bubble diffusers, it is difficult to delineate specific design criteria
to control the process of biological fouling.
                                     131

-------
 I
UJ
cc
g  8
CO
UJ
tr  ,
UJ
CO
<  4
UJ
_J
LU
                                                          BOTTOM
                                                          FOULED
                           BOTTOM
                           CLEAN
             UJ
             _j
             GQ
             m
             Z>
             GQ

     Figure 4.   Bubble release  pressures for the bottom of a clean and
                clogged dome  -  Madison, WI.

     There is a certain amount  of  field evidence that suggests that the
design of the diffuser element  itself  is important in preventing extreme
fouling problems.   Uniform distribution of air throughout the media would
seem to be of paramount importance.  Furthermore, it is quite likely that
there is a minimum air flow rate per diffuser that is required to prevent
encroachment of bioslimes  on  the diffuser surface.  Herein lies one dilemma
with diffuser design since low  air flow rates normally produce higher OTE
and there is a temptation  to  size  aeration facilities to favor better trans-
fer efficiencies.   Unfortunately,  the  placement of high diffuser densities
(and concomitant reduced air  flow  rates per diffuser) in an aeration tank to
take advantage of  the more favorable transfer efficiencies may eventually
lead to maintenance problems  and eventual loss of efficiency due to bio-
fouling.  More data needs  to  be collected to corroborate this reasoning,
however.

     The clean water testing  of fine bubble diffusers is most often used by
engineers to size  aeration systems for dirty water testing.  Although engi-
neers attempt to account for  this  translation through the use of an alpha
correction, little thought has  been given to changes that may occur in dif-
fuser properties once placed  in the dirty water over a period of time.  BRP
measurements made  on selected diffusers removed from operating plants suggest
that air flow distributions may be significantly changed.  This may produce
substantial changes in OTE, not accounted for in the clean to dirty water
                                    132

-------
                 u_
                 o
                 CO
                 o
                 CO
                  I
                 LJ
                 !5
                 cc.
                 X
                 :D
                 _J
                 u_
                 cr
                     6-
     5-
     2

     I
                                                FOULED
                                         CLEAN
     Figure 5.
translation.
Air flux rate for a clean and clogged dome - Madison, WI.
(Average flux rates for concentric circles.)
     Houck and Boon (11) recommended that aeration tanks be designed to
avoid excessively high localized organic loading which might lead to fine
bubble diffuser clogging.  They recommended the use of low length to width
ratios, step feeding and tapered aeration as means to reduce potential clog-
ging problems.  Another approach would be to employ a coarse bubble or
mechanical aeration system at the influent end of plug flow systems.  The
loss in efficiency may be well worth the decrease in diffuser maintenance.

     There has been considerable interest generated recently in the in situ
cleaning of fine bubble diffusers including internal gas cleaning as well as
mechanical jetting, steaming or brushing.  In any event, aeration tanks
employing full floor coverage units should employ some type of rapid tank
draining facility.

     If biological fouling is considered to be primarily the result of the
wastewater characteristics, pretesting of selected diffusers in that waste-
water may be highly desirable.  The installation of a test fixture employing
two or more diffusers within an existing aeration tank has provided very
useful information on diffuser clogging potential of selected wastewaters
(17).  A test fixture instrumented in a fashion similar to that in Figure 1
was used.  DWP measurements made over a two to three month period provided
                                     133

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useful data on clogging potential.  Laboratory follow up analyses on  indivi-
dual diffusers provided additional data on air flow distribution and  BRP
thereby providing a sensitive indicator of the relative degree and progres-
sion of clogging.

B10FOULING - FUTURE RESEARCH

     The impact of long-term fine bubble diffuser operation in wastewater
with respect to maintenance requirements and OTE is still poorly documented.
It is clear that some biological growth will develop on diffuser surfaces but
the impact of that growth on performance is unclear.  Research should be
directed under controlled experimental conditions toward measuring the pro-
gression of biological fouling employing sensitive BRP and air flow distribu-
tion techniques.  These studies should include a variety of diffuser  mat-
erials and geometry.  The selection of diffuser systems is often predicated
on the performance of clean diffusers in clean water.  The long term  changes
in OTE during diffuser operation in wastewater should be more clearly deli-
neated in order to provide the engineer with a clearer picture of what
happens to OTE over the design life of the diffuser.

     As energy costs continue to escalate, engineers will seek more effective
energy conserving systems for the transfer of oxygen to wastewater.   Until a
better understanding of the behavior of fine bubble diffusers under long-
term field conditions can be delineated, doubts will continue to be raised
regarding the effectiveness of the fine bubble system.  Furthermore,  mis-
application of these systems in certain situations may result in a greater
expenditure of manpower and energy than would be estimated.

ACKNOWLEDGEMENTS

     The authors wish to acknowledge the cooperation and assistance of
Mr. Paul Nehm and Mr. Tim Weir of the Madison Metropolitan Sewerage Commis-
sion.  Their contributions to a better understanding of biofouling are
greatly appreciated.  We also acknowledge the assistance and counsel  of
Mr. Jerry Wren, of Sanitaire-Water Pollution Control Corp, Milwaukee.

REFERENCES

1.  Wesner, G. M., et al.  Energy Conservation in Municipal Wastewater
    Treatment.  EPA 430/9-77-011; Office of Water Program Operations; U.S.
    EPA; March, 1978.
2.  Roe, F. C.  The Installation and Servicing of Air Diffuser Mediums,
    Water and Sew. Wks, 81:115, 1934.
3.  Beck, A. J.  Diffuser Plate Studies, Sew. Wks. Jour., 8:22, 1936.
4.  Committee on Sewage Disposal.  The Operation and Control of Activated
    Sludge Sewage Treatment Works, Sew. Wks. Jour., 14:3, 1942.
5.  Bushee, R. J. and Zack, S. 1.  Test on Pressure Loss in Activated Sludge
    Plants, Eng. News Record, 93:21, 1924.
6.  Wisley, W. H.  Summary of Experience in Diffused Air Activated Sludge
    Plant Operation, Sew. Wks. Jour., 15:909, 1945.
7.  Setter, L. R.  Air Diffusion Problems at Activated Sludge Plants, Water
    & Sew. Wks., 95:450, 1948.

                                     134

-------
 8.  Setter, L.  R.  and  Edwards,  G.  P.   Experimental Laundering of  Air
     Diffuser Plates, Sew.  Wks.  Jour.,  17:867,  1945.
 9.  Anderson, N. E.  Tests and  Studies on  Air  Diffusers  for Activated
     Sludge, Sew. and Ind.  Wastes,  22:461,  1950.
10.  Lamb, M.  Designing  and Maintaining Porous Tube  Diffusers  Wastes
     Engineering, 25:405, 1954.
11.  Houck, D. H. and Boon,  A. G.   Survey and Evaluation  of  Fine Bubble  Dome
     Diffuser Aeration  Equipment.   EPA  600/S2-81-222;  Municipal Environ.
     Research Lab;  U.S. EPA; Oct. 1981.
12.  Boon, A. G. and Burgess, D. R.  Treatment  of  Crude Sewage in  Two High
     Rate Activated Sludge  Plants Operated  in Series,  Water  Poll.  Control
     73:382, 1974.
13.  Nehm, P.  History  of Norton Dome Fine  Bubble  Diffused Aeration at MMSD.
     An Internal Report to  MMSD, July 1981.
14.  Pillai, S. C.  and  Subrahmangan, V.   The Role  of  Protozoa  in Aerobic
    Purification of Sewage,  Nature  (London), 154:179,  1944.

15'  1933 F' C'  SeWage Aeration by Diffused Air,  Sew. Wks.  Jour., 5:813,

16.  Leary, R.  D.,  Ernest,  L. A. and Katz,  W. J.   Effect  of  Oxygen Transfer
     Capabilities on Wastewater Treatment Plant Performance, Jour. Water
     Poll. Cont. Fed., 40:1298, 1968.
17.  Wren, Jerome; Personal  Communication;  Sanitaire-Water Pollution  Control
     Corp., Milwaukee, WI,  1981.
  "This paper has been reviewed in accordance with the U.S. Environmental
  Protection Agency's peer and administrative review policies  and approved
  for presentation and publication."
                                    135

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SESSION NO. 3
    Improving Process Reliability
                                PAPER NO. 9
              STABILITY AND RELIABILITY OF BIOLOGICAL PROCESSES
                                     by

                              E. D. Schroeder

                                    and

                                Salar Niku
                      Department of Civil Engineering
                      University of California,  Davis
                         Davis, California  95616
                                     136

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STABILITY  AND RELIABILITY  OF BIOLOGICAL PROCESSES

E.D. Schroeder  and Salar Niku
Department of  Civil Engineering
University of  California, Davis
Davis, CA  95616

       Biological wastewater treatment processes are treated  by  designers, operators
and  regulators  as  steady  state  processes  that do  not fail.  The  same  designers,
operators and regulators fully recognize  that  these  systems experience wide  ranges
of loading, and environmental parameters, and that the systems often  do fail. Despite
this knowledge process design is  based on  steady state assumptions, whether a kinetic
or a loading factor  approach is  used,  and operation  is based  on  the  same approach.
It  is an accepted fact that biological  treatment processes  are not completely stable
or reliable  but  present deterministic and conceptual  models  so  not come close  to
providing adequate descriptions  of process behavior.  The  principle factors that  are
missing are satisfactory dynamic models that incorporate hydrodynamic  coupling and
knowledge of actual stochastic  variation in process performance.   The  purpose  of
this  paper is  to discuss results of  a study in  which  daily data from  43 activated
sludge and 11 trickling filter plants  was analyzed.  Previous reports  based upon this
study will be summarized  and the work  will be extended to applications  in design,
operation and regulation (1, 2,  3, 4,  5).

Probabilistic Approaches To Process  Analysis

       Statistical methods  have  been  used to correlate process variables  for a very
long time.  An early example  is the NRC  report (6).   In this study mean effluent
BOD_  and  suspended  solids  values  from  trickling  filter   plants  at  34 military
installations were used to develop removal efficiency relationships  (the NRC formulas).
The  mean values used  were based  on monthly  values  and  for periods varying up  to
20 months.  The relationships  developed were  statistically  weak, even assuming that
comparison  of the  data populations  was appropriate (7).  Other  studies of one or  a
few plants have resulted in expressions for predicting  process performance (8,9)  but
the expressions  have not been  widely accepted.

       More recently work has been directed at determining the variation  in effluent
quality  and process performance (10,11,12,13,14,15).  With the  exception of  Hovey
et al. work (15) the previous studies  were based upon a large amount of  data from
one or  a few plants within a  limited geographical  region.  Hovey et al.  considered
annual data for  a one year  period from 28 plants some  of which  are  included in this
study.   Most  of Hovey  et  al's  plants were  in  California,  but a  few were from  the
Midwest.  A general conclusion  of these  workers was  that a  log-normal distribution
provided the best fit to  the data.  Hovey et al.  did  not find  a generally satisfactory
probability density function but  did find  excellent  correlation between  the effluent
characteristics percentile (i.e.  the  percentile  value  of a given concentration  value)
and the annual mean for  individual  plants.   A similar result had  previously been
reported by Townshend  (16).

       Considering  the  number  of physical and environmental  variables affecting
wastewater  treatment  plant  performance  it  is unlikely  that a  particular model,
deterministic  or stochastic, will fit  every  situation.   Variation  in  effluent quality
would  be expected  to  have a log-normal  component because the effects of many

                                        137

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variables are linked together multiplicatively.   Thus it is not surprising that previous
workers  have found good  log-normal fits  to  their  data and  that  in  this  study  the
log-normal distribution could  be rejected  in only  13 of the 43 cases.

Use of Distributions

       When  a  distribution  has been established a  number of useful relationships  can
be developed.  These include determination of  the probability  that  a given  plant  can
meet a particular discharge standard (reliability), the relative range  of product quality
with respect to  discharge standards and/or the  mean value from the  process  (stability)
and  the  effect  of selected variables  (eg. temperature) and process parameters (eg.
overflow  rate/design overflow rate) on  process performance.   These  determinations
were done for  the  plants studied and the results  are summarized  below:

Process Reliability

       In considering the reliability relationships developed  it  should be remembered
that  the  plants used in this  study were  chosen because they were believed to be
well  operated  and  sources of good  data.   Thus  the reliability  relations  should be
appropriate  for  use in design  and as measures of  expectation.   As stated above
reliability  is the  probability that a chosen  standard (eg. 30  d average BOD-  _< 30
g/m ) will be met.

       Construction of reliability model requires that a distribution function be chosen.
Because it provided the best  overall fit the log-normal distribution was chosen.   It
is also desirable  to have  a model stated  in arithmetic rather than log terms.  For
this reason the  effects of the  log-normal distribution  were incorporated into a single
parameter, the  coefficient  of  reliability (COR) that relates  the chosen standard,  X ,
to the mean effluent value, m  ,  required to meet the standard a  given fraction of
the  time.
                                m  =(COR)X                                   (1)
                                  A           O


       That is if  the standard  X  is to be  met  a given fraction of the  time the
actual process  mean effluent value  must be m  .   The  theoretical  COR  value  is
derived from  the  log-normal distribution probability density function.
                                                               I]54}              (2)
                              In
                                        138

-------
             where        V     =      coefficient of variation = a /m
                            X                                      XX

                           Z,    =      standard normal  variate

                           a      =      arthmetic standard deviation
                           A.

       Values of the COR are given in Table 1  for selected values of V   and  percent
reliability, and the relationship is  presented in graphical form  in Figure  1.

       Use of equation (1) for design, operation  or regulation requires some knowledge
of  "reasonable expectations."   The  first  step  is  to  verify that the  COR  values
developed  from the log-normal  distribution can be used  to predict  actual  process
performance.  Verification requires comparison of  the  predicted reliability based  on
measured  values  and  Table  1  or  Figure  1 with  calculated reliability from  data.
Results are  given  in  Tables  2 and  3  for activated  sludge  and trickling filter plants
respectively.

Process Stability

       Stability is  often used in a  qualitative  sense or  with respect to a particular
situation.  A quantitative definition  of stability  must reflect the commonly understood
definition to be accepted and useful.   Two  general approaches might be used.  First
the occurrence of upsets might be cataloged and stability defined in terms of  number
of upsets per  year or the ratio of upset days to non-upset  days.  This approach is
only quasi-quantitative because the definition  of "upset"  is  qualitative.  Additional
problems  result from  the  facts that  activated  sludge  plants are generally  termed
upset only when effluent  suspended solids  are high, a  visually observable situation
and  attached  growth  process  behavior is  quite  different  than suspended  growth
systems.   A  second approach is  to define a  parameter as  a measure of stability.
Suggested parameters include the  standard deviation, S , coefficient of  variation,  V
(ratio  of  standard  deviation to mean) and coefficient  of stability,  COS (ratio  01
variance to mean).  Both ratios  suffer from  the fact that processes with a low  mean
value can  have the same  coefficient as ones  with  high  mean values.   For example
a  plant with  mean  effluent  mean  and standard deviation values  of  6 and  3  g/m
respectively, will have the same  coefficient of variation as  a plant with mean and
standard deviations of 50  and 25 g/m .

       Standard deviation was chosen as the basic stability  parameter  in this  study
because a  definite, unnormalized measure of  dispersion is provided  and  because it
is  a widely  understood term.  Further support for the choice was  provided  when
strong correlations  between  the standard deviation and  the  mean annual maximum
value  and  the  COS were  found  (Table 4).   By itself  stability  is only a relative
parameter,  that is  the larger S  the  less  stable the plant.   A reference value  or
cut off point  is needed that divides plants into unstable and  stable  groups.   This
was  done arbitrarily  after plotting mean and  range vs  standard deviation  (Figures
2-5).   Both  range  and mean lend  to have  higher  values  for plants  with standard
deviations greater than 10 g/m  as either BOD5 or SS.  The  effect is quite pronounced
with activated sludge plants (Figure  2 and 3) and less so with  trickling filters (Figures
ft and  5).

Outliers:   Inclusion  of range (or maximum  value) as a factor in defining stability
forces consideration of outliers:  single points  that greatly deviate from the  general


                                        139

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TABLE  1.  COEFFICIENT OF RELIABILITY3 AS A FUNCTION
  OF Vx AND RELIABILITY FROM POOLED PLANT DATA


             Row 1 for BOD, Row 2 for SS
Reliability
VX
0.3
0.*
0.5
0.6
0.7
0.8
0.9
1.0
50%

1.08
1.08
1.11
1.11
1.1*
1.15
1.17
1.18
1.20
1.22
1.2*
1.26
1.28
1.30
1.32
1.35
80%

0.85
0.87
0.80
0.8*
0.77
0.80
0.73
0.77
0.70
0.7*
0.67
0.72
0.65
0.69
0.62
0.67
90%

0.7*
0.75
0.68
0.70
0.63
0.65
0.58
0.61
0.55
0.57
0.51
0.5*
0.*8
0.51
0.*6
0.*8
95%

0.6*
0.66
0.57
0.59
0.51
0.53
0.*6
0.*9
0.*3
0.*5
0.39
0.*2
0.37
0.39
0.3*
0.36
99%

0.50
0.*9
0.*3
0.*2
0.38
0.36
0.3*
0.32
0.30
0.29
0.28
0.26
0.25
0.2*
0.23
0.22
100%

0.39
0.3*
0.32
0.27
0.27
0.23
0.2*
0.20
0.21
0.17
0.19
0.15
0.17
0.1*
0.16
0.13
                      140

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0.1    02   0.3   0.4   0.5    0.6   0.7   0.3    0.9   1.0   U   12    U   1.4    1.5

                             NORMALIZED  MEAN , mx/Xs

    Figure 1.  Reliability  versus normalized mean for different
                coefficients of variations.
                                   141

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                   TABLE 2.  COMPARISON OF PREDICTED AND MEASURED PERFORMANCE
                       OF ACTIVATED SLUDGE PLANTS ACROSS THE UNITED STATES
to
Plant
Number
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

VX
0.75
0.52
0.67
0.62
0.57
0.56
0.54
0.99
0.91
0.38
0.90
0.43
0.87
0.95
0.86
0.51
0.72
0.34
0.42
0.49
0.56
0.48
0.58
1.11
0.70

X/30a
0.33
0.28
0.33
0.61
0.54
0.55
0.71
0.55
0.83
1.01
0.62
0.55
0.55
0.77
0.89
0.16
0.06
0.08
0.16
0.26
0.14
0.14
0.10
0.81
0.43
BOD
%time <
Predicted
97.10
99.80
98.30
87.50
92.30
92.60
82.40
87.20
73.50
56.30
84.30
95.10
88.00
76.60
70.20
99.99
99.99
99.99
99.99
99.90
99.99
99.99
99.99
75.30
95.10

30 R/m3
Measured
99.1
100.0
97.8
87.9
91.2
91.4
86.5
91.5
70.3
60.1
90.4
95.0
88.6
77.9
68.8
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
73.7
95.2

vx
1.17
0.43
0.32
0.83
0.74
0.73
1.27
1.26
0.98
0.32
1.70
0.79
1.13
1.37
1.21
0.55
1.13
0.47
0.48
0.64
0.58
0.53
0.56
1.33
1.07

X/30
0.37
0.21
0.48
0.87
0.71
0.73
0.56
0.70
1.48
1.96
0.34
0.49
0.49
1.16
0.94
0.18
0.09
0.15
0.27
0.23
0.21
0.19
0.12
0.63
0.40
ss
%time <
Predicted
93.80
> 99.99
99.40
71.10
80.20
78.10
86.00
80.40
52.70
2.30
93.40
91.50
89.20
64.40
70.50
> 99.99
> 99.99
> 99.99
> 99.99
99.70
99.90
> 99.99
> 99.99
83.20
93.10

30 R/m3
Measured
96.2
100.0
100.0
75.5
85.5
83.3
89.9
86.1
58.0
3.1
94.2
94.3
89.0
67.9
70.6
100.0
100.0
100.0
100.0
99.5
99.5
100.0
100.0
81.9
97.0
          a_
           X is the actual arithmetic mean value of the data  (BOD or SS) in the plants.

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TABLE 2 (continued)
Plant
Number
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43

VX
0.48
0.51
0.48
0.89
0.95
0.78
0.41
0.90
0.60
0.86
0.70
0.61
1.20
0.68
0.37
0.43
0.68
1.27

X/30
0.30
0.42
0.46
0.14
0.20
0.36
0.80
0.60
0.29
1.05
0.22
0.70
0.55
2.85
0.48
0.30
0.69
0.71
BOD
%time <
Predicted
99.80
97.90
97.30
99.80
99.20
96.60
77.80
85.20
99.40
62.00
99.70
82.00
86.50
8.20
98.70
99.90
81.90
79.90

30 R/m3
Measured
100.0
98.3
99.2
100.0
100.0
95.3
72.5
84.2
99.7
64.8
100.0
84.3
86.5
12.1
98.8
100.0
85.8
84.2

VX
0.66
0.62
0.80
0.58
0.70
0.44
0.38
0.75
0.52
1.07
0.53
0.76
1.37
0.93
0.60
0.69
1.30
1.68

X/30
0.32
0.30
0.30
0.33
0.34
0.36
0.80
0.73
0.49
1.18
0.24
0.64
2.17
2.67
0.29
0.33
0.95
1.41
SS
%time <
Predicted
98.60
99.20
98.10
99.00
97.90
99.60
78.60
73.10
95.60
59.80
99.90
84.10
40.50
19.80
99.40
98.20
70.80
61.10

30 R/m3
Measured
98.9
100.0
98.1
99.5
98.9
98.9
80.0
80.9
97.3
64.9
100.0
76.0
51.1
21.9
99.6
97.7
77.8
71.6

-------
                                        TABLE 3

                       COMPARISON OF PREDICTED AND MEASURED
                     PERFORMANCE OF TRICKLING FILTER PROCESSES


Plant
Number
1
2
3
4
5
6
7
8
9
10
11


VX
0.46
0.67
0.75
0.36
0.38
0.25
0.73
0.15
0.39
0.30
0.65


X/30
1.11
0.36
0.34
1.94
0.94
0.90
0.77
1.44
1.70
0.70
0.61
BOD
%time <
Predicted
49.3
97.6
97.4
4.3
63.8
70.9
76.6
2.1
11.1
91.4
87.1

30 g/m3
Measured
49.6
97.5
98.3
8.0
57.9
72.6
75.5
1.1
17.8
97.6
88.2


VX
0.59
0.62
0.79
0.27
0.48
0.40
0.63
0.40
0.43
0.61
0.55


X/30
1.75
0.72
0.70
1.83
0.61
0.50
0.80
1.13
1.37
0.79
0.54
55
%time <
Predicted
22.6
80.6
80.5
1.6
90.5
97.7
75.0
45.0
28.8
75.8
92.7

30 g/m3
Measured
19.4
78.1
76.2
5.6
93.1
98.1
70.7
45.8
28.5
72.8
93.4
Predicted percentages represent areas under the normal probability  curve F(Zi_^),  where
                                                                              j.-, is
                  In
equal  to:

                             1)'
                                           See Reference 5 for details,

-------
             TABLE 4.  PEARSON CORRELATION  COEFFICIENTS3, r, OF ANNUAL
                  DATA FOR H3 ACTIVATED SLUDGE TREATMENT PLANTS0


x sx vx
X 1.00 0.92 0.19
S 1.00 0.53
V 1.00
Max
COS
X
S
V
Max
COS
BOD

Max COS
0.80 0.74
0.9* 0.94
0.61 0.74
1.00 0.93
1.00






Antilog
(LnSx)
0.17
0.43
0.78
0.36
0.58







X
0.81
0.82
0.38
0.80
0.75
1.00






SX
0.67
0.82
0.64
0.87
0.87
0.88
1.00





VX
0.30
0.54
0.71
0.64
0.68
0.34
0.65
1.00


ss

Max
0.56
0.74
0.66
0.82
0.83
0.81
0.97
0.71
1.00



COS
0.50
0.72
0.71
0.81
0.84
0.75
0.97
0.74
0.98
1.00

Antilog
(Ln5x)
0.34
0.60
0.72
0.63
0.72
0.34
0.58
0.80
0.57
0.61
a  The Pearson  correlation coefficient, r, for  variables X and Y is defined as:


                       1
                                                                    g
                       n  X. - X   Y.  - Y
                Y = —   7  — - _   — - __ j  giving the  cross correlation between any two
                   n  i=l    x        y    chosen plant  variables, such as X = BOD and
                                           Y = SS
All  measurements  are at 0.001 significance level

-------
iUU
ISO


160




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-

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120


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SO



60




40



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-

i i











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i i i

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ei "2
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STABLE










UNSTABLE







t
-
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— S'andaid deviation
— Ranje
-



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-

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Plant





-r
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"i
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Ill
4






Numbers x



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j-


-

•>
4>
1 1
12 16 20 24 28
                          Standaid deviation (t/m )
Figwe 2.  Mean, standard deviation, and range of  effluent BOD
           concentration in different treatment plants.
                             146

-------
                2CC
                180
                160
             -  120
                ICO
                8G
                SO
                40
                20
                                  STABLE  UNSTABLE
                          Vejn

                          SSanaard deviation
                              Plan! Nu.T.im
                                            12   '     16

                                         Standard deviition d
                                                             20
                                                                       J   J
                                                                        I
                                                                      2<
2S
Figure 3.   Mean,  standard  deviation,  and  range  of effluent  suspended  solids
             concentration in different treatment plants.
                                           147

-------
 CD
 CXO
 cz
-o

ro

cr
o

ra
TJ
cr
CO
ro
O)
160



140



120



100



 80



 60



 40



 20


  0

                    STABLE

                      -^-
                                  UNSTABLE

                                 	^-
              —— Standard Deviation   ^

              	 Range

               •   Mean
              Plant Number
                        7
              1    1
                           1    1
          0       4        8       12      16       20       24

                                               T
                      Standard  Deviation  (g/tn  )
       Figure  4.   Variability  of effluent BOD as a
                   function of standard deviation.
                               148

-------
cu
00
-a
 c:
 o


 —

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Q


•o

 ra
 c:
 ra
 cu
200
180
160
140
120

100

80
50
40
20
0


/I
iii 11111 iiiyii
STABLE UNSTABLE ~
*•
••
M
- 	 St.
D-
• We
-
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indard Deviation
nge
an




Plant Number.
-
-
-
. u
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1 1
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-
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-
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-
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V
•* r\ tf f^ A "<^i"\ *^
                                  12      16       20      28      32
                          Standard  Deviation  (g/m  )
      Figure 5.   Variability of effluent suspended solids concentration

                  as a function of standard deviation.
                                 149

-------
trend.  These  points often greatly effect or even  dominate the standard deviation.
For example a number of extreme values occur  in the effluent BOD,- data  for both
of the plants of Figure 6. Possible causes of the extreme  values include mechanical
failure, measurement error,  introduction of toxicants, unusual weather and natural
stochastic variation.  If the  cause is  other  than stochastic variation the  points  are
true  outliers  and  may  be disregarded  in  determining the  process  characteristics.
Removing the upper one-percent of data resulted  in decreasing the standard deviations
of the BOD- and  suspended  solids concentrations by an average of 1.6 and 3.6 g/m
respectively, but the relative stability ranking of the 43 activated sludge  plants  did
not change.

Cyclic Patterns: It is well known that flow rates to municipal wastewater treatment
plants tend to  have weekly  and seasonal  cycles.   Thoman (8), Adams and  Gemmel
(9) and Lin and Heinke (17) used spectral and harmonic analysis to remove non-random
components from  effluent data.  They found significant weekly, seasonal and  annual
cycles.   Similar cycles can be seen in Figure 6 for plant  10.   In the 43 plants used
in this study seven (10,14,15,24,29,30,  and 35)  were  found  to  have significant cyclic
patterns. Five of the eleven  trickling filter plants exhibited significant weekly cycles
and overall  the BOD- and suspended solids concentrations tended to be below average
on Sundays.  Seasonal  patterns  were evident at  all 11 trickling  filter plants with
improved performance  in the summer.

Plant Configuration and Size: Seven types of activated sludge process were  included
in the study although  most  were either conventional  or stepfeed  systems.   Results
of considering  annual statistics of each process type as a  data population are given
in Table 5.   The  results are  interesting  because  for the four configurations with
more than one  representative there is a clear order of performance.

       Plant size  is also of  interest because of  trends toward construction  of large
regional  facilities.   The  results of this  study,  which included plants with average
flows ranging from less than 3000  to more than 750,000 m /d (0.8 to 200 mgd)  are
similar  to  those  of Hovey  et  al. (12).   No correlation between  plant size  and
performance could  be  found.  Thus improved  performance does not  appear to be a
valid reason for regionalization.

Process  Parameters and Variables

       A  number  of  parameters  and  variables   were   correlated with   process
performance  using  multiple  regression  analysis.    These  included  wastewater
temperature,  time  lag,  flow, sludge volume index  (SVI),  mean cell residence time
(MCRT),  food  to  microorganisms ratio (F/M)   mixed liquor suspended solids (MLSS),
recycle  solids  concentration (X ), recycle rate  (Q ),  influent  BOD and  influent
suspended solids.   Twenty one of the  43 activated plants  and all  11  trickling filter
plants had sufficient data to  allow evaluation of these parameters.   Lag time refers
to  lagging  input  and output values in  time to  determine if processing  time is a
factor.  Variation  in a number of the variables  and parameter  correlated significantly
with  variation  in effluent BOD5 and suspended solids  concentration  but the  pattern
was  not  consistent.   That  is  in  some plants  wastewater temperature  was most
important, in others influent  BOD and in others flow rate was the principle factor.
In general less than half the  variation in effluent quality could be explained  by  the
conbined  effects of the  process  parameters and variables.
                                        150

-------
                         (29   164   ZOI    Z37   2T*   311    547
                       "I	1	1	1	1	1	1	1	1	1	1	1	1	1
     -  T
     n   I
            i  >   i  i  i   i	i   |  |  'i	|	|	1	1	1	|	1	1	1	1
              36    7 5   tO9   >46    195    2'9   2*6   29?   529   366

                              Time (days)

            Plant No 10
            IB    S4    Bl   128   1««   201   J37   27<    311   347
            T	1	1	T










                                                        J


      E
      _  B3 -

      O
      o







        3d -



        27 *







         Bh  !  . i  i  i  .  ' .  i   i.i   i	1
          C    3fl    73   109   146    133   2
                              Time (day*)
Figure  6.  Typical time-series plots of  effluent BOD
             and  SS  concentrations.
                              151

-------
                             TABLE 5.  STATISTICS OF THE ANNUAL EFFLUENT  BOD AND
                             SS CONCENTRATION  DATA FOR DIFFERENT  PROCESS TYPES
Ui
N5
Process type
No. of
plants
Mean Standard
deviation
* Sx * Sx
Coef. of
variation
V^ Q
A 3x
Conventional
Complete-mix
Step-Feed/Aeration
Contact Stabilization
Extended Aeration
Kraus
Aerated Lagoon

All  Plants
18
 5
13
 4
 1
 1
 1

43
12.80
16.82
10.84
38.38
14.41
24.02
30.35

15.76
                                                                    BOD
                                                               6.85
                                                               6.67
                                                               7.68
                                                              32.08
                                                              13.43
 9.54
13.24
 8.28
28.17
 5.31
 9.85
11.61

11.28
 7.99
 6.51
 7.56
20.92
10.49
0.69
0.77
0.68
0.76
0.37
0.41
0.38

0.70
0.25
0.13
0.25
0.14
0.23
                                                                     SS
         Conventional
         Complete-Mix
         Step-Feed/Aeration
         Contact-Stabilization
         Extended-Aeration
         Kraus
         Aerated Lagoon

         All Plants
                              18
                               5
                              13
                               4
                               1
                               1
                               1

                              43
           14.92
           19.88
           16.23
           40.88
            8.82
           24.12
           58.79

           19.40
            10.53
            14.19
            16.65
            26.75
            17.03
16.02
19.65
16.83
37.66
 5.28
 9.26
18.71

18.35
18.61
16.92
23.89
26.18
20.60
0.86
1.00
0.83
0.90
0.60
0.38
0.32

0.84
0.38
0.51
0.34
0.14
0.37
            Average values from  all plants, not calculated  from parameter averages

-------
Design and  Operation Applications

      The results  of this study  provide  useful tools for both design and  operation
of biological wastewater treatment plants.  The  key relationships are Equation (1),
Table 1  and Figure  1.  It is important  to  recognize that  a desired  reliability must
be chosen and  that 100  percent reliability is impossible. Thus choosing a reliability
value is  the  first  step  in  application.   The second step is consideration  of the
coefficient  of  variation (Vx).   In general the higher the mean va^ue the lower the
estimated V .   Because ensuring stability requires QX =  <_ 10 g/m  the value of V
is partially  constrained.  For example if a standard of 30 g/m  (BOD or suspended
solids) is to be  met 99% of the time  and  a  is to be  maintained below  10  g/m  or
                                           x
less, the  mean  design  (or  operating) value is determined  from a  modified form  of
Table  1.   As can be seen  in Table  6 setting a reliability  constraint of 99% results
in required m  and a  values that will be  extremely difficult to  meet.
              X       X
       Discharge standards now in general use are  considerably less  stringent than
those of the above example because they  are  based on weekly and monthly averages.
For  a  log-normally distributed  population  if  the distribution of the means (weekly
or monthly)  has the same arithmetic mean and variance as the total  population the
geometric distribution  of the means is also log-normal with  a  mean (m]nQM^  equal
to  the log  of  the  population  mean (m. y)  and a variance,  Oi^r-i^  equal to the
population variance, o.  x, divided  by the  averaging period,  n  (1). Although discharge
standards would be better  stated  in  geometric terms (3)  they are in  fact stated  as
arithmetic averages. These can be related to the geometric  values through Equation
(«) and (5)


                    "inx - ln   -2 + '
                    mlnx -  in "\ -   °lnx
       A population having an arithmetic mean and  standard  deviation of 30 and  10
 g/m3 respectively will have a log mean of 3.35 and a log standard deviation of 0.32.
 The 30 day log goemetric  mean value  and log geometric standard deviation values
 are then 3.35 and  0.058.   These values can  be  used with Equations  (6) and (7)  to
 obtain the  geometric mean and  standard  deviation.
 Thus  the  population will  have, a geometric  mean of  28.6  g/m   and a  geometric
 standard deviation of 1.65 g/m .   To have a 99 percent probability  that the  30 day
                                        153

-------
TABLE 6:  DESIGN WL and a  FOR X = 30 g/m3
                   X      A       »>
Vx
0.3
0.*
0.5
0.6
0.7
0.8
0.9
1.0
1.2
1.5
99th
Percentile
COR
0.53
0.44
0.37
0.32
0.28
0.25
0.22
0.20
0.17
0.14
mx
15.9
13.2
1.1
9.6
8.4
7.5
6.6
6.0
5.1
4.2
ax
4.8
5.28
5.6
5.8
5.9
6.0
6.0
6.0
6.1
6.3
                      154

-------
arithmetic mean value  of 30 g/m   will not be  exceeded the combination of design
geometric  means and standard deviation shown  in Table  6  is necessary.

       The rn_., values  of Table 7  are reasonable and attainable  in activated sludge
processes.  Aftnough apparently quite small the standard deviations are  also reasonable
and  attainable.   The  key factor is that 30 day a values are related to single  day
value,  by lA^O~.  A second problem  results from  the  fact  that a method of designing
for a standard deviation  does not exist.  In practice it must be assumed that standard
deviations  attainable in  other plants are possible  in the  one  being  designed.

Recommended  Design Values

       In  conventional  process  design  procedures average  and  peak  loadings  are
incorporated into steady state models.  In essence the 7 and 30 day averages  used
by  regulating agencies  is ignored and an  attempt is  made to design a system  that
will  meet the  requirements  everyday.   The  general  procedure  of  applying  the
log-normal distribution  to  design value selection  was given above.   Comparison of
process by  process  configuration  and  setting a  stability criteria of a   =10 g/m
resulted  in  the  values given in Table 8.  The recommended  effluent 5b values  are
difficult  if not impossible to incorporate directly into a design.  Obtaining these  low
values  will require conservative overflow  rates, however.

Operation

       Application of statistical  procedures  to process operation  provides a method
of assessment and trend  for  a particular plant.  Plants incorporating computer control
can  be provided with programs for the necessary calculations.   Most plants  do  not
have this capacity  but  the calculations are  quite simple  and once  set  up  do  not
require more than a  few minutes a week  to update.   Correlation with  these  results
requires  a years data and there  is an advantage in having  a  complete  seasonal cycle.
If desired  a  longer  period at a  given plant would be useful, also.   At a particular
installation  monthly  values  could be used and compared  to the  same periods on an
annual basis.

       When the time period has been  chosen it  would  be  advisable to determine  the
most appropriate statistical distribution  to  use.   In most cases  this  will be  the
log-normal distribution  but there  is  no reason  to assume  it  to  be the  best in  all
cases.    For  the first period the  log  mean  and  log  standard deviation  values  are
calculated in  the normal manner.   The process of subtracting out the initial value
and adding a new one is very straight forward and can be taught to  operating staff
without a background in statistics as  a series  of steps on a pocket  calculator.  One
approximation must  be made in  determining the  standard  deviation because the mean
value changes on a daily basis.  It  would be unusual for the mean to  change enough
in one  or  two  days  to effect the  standard  deviation  significantly  however.   An
alternative  is  to  maintain  a running  years  data  on a cassette  for  a desk  top
minicomputer.  The actual mean value could then be used  in  determining the standard
deviation.

       Knowledge of  the statistical  parameters associated  with performance is useful
in comparing a  given  plant  to  others and  in  assessing  performance  trends.   For
example  it is useful to know if an apparently increasing mean value is within expected
normal variation or  if  performance is  actually  decreasing.   Detecting  what plant

                                        155

-------
     TABLE 7:  GEOMETRIC MEAN AND STANDARD
DEVIATION FOR 99th PERCENTILE AND 30 g/ni - 30  DAY
               ARITHMETIC AVERAGE
       VGM       MGM        °GM











Step

0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
TABLE 8:
PROCESS
Process Type
feed/aeration
Conventional
Complete Mix
Contact Stabilization
g/m3
27.9
27.2
26.6
26.0
25.4
24.8
24.3
23.7
23.2
22.7
RECOMMENDED
CONFIGURATION
Number
Plants
13
18
5
4
g/m3
0.3
0.5
0.8
1.0
1.3
1.5
1.7
2.0
2.1
2.3
DESIGN VALUES BY
(Niku et al, 1981b)
of BOD _< SS _<
g/m3 g/m3
15 12
15 12
13 10
13 11
                      156

-------
component is failing is beyond the scope of the simple statistical methods  used  here,
but in large plants more sophisticated analysis may  be useful.   An example would
be estimating the  effects of industrial spills.

       As noted above weekly and seasonal cycles exist at many plants.  Knowledge
of these cycles  can be used in operation.   In  many plants maintenance is scheduled
for low flow seasons,  already, but operational  response could include temporary unit
shut down over weekends, modifying aeration  rates during  periods of known low or
high organic loading rates and changing  process parameters in advance of  influent
characteristics changes.

Regulation Applications

       Regulatory agencies typically evaluate performance on the  basis  of  violations.
While  this is  a  reasonable  method  considerable knowledge is  added if it is known
that violations  should be  considered  characteristic  of  a given  plant  because the
average  and standard deviations  are high.  Response to  violations  will undoubtably
be  different for plants  having a high  probability of   repeatedly  violating standards
than for those with good reliability and stability.

       Simple,  standardized programs can be  used  with minicomputers  in  making
statistical  evaluations.   In evaluating single plants manipulation  of a  years  data  is
not time consuming and  the information provided is far more useful than  reports of
particular violations.

REFERENCES

1.  Niku, S., E.D.  Schroeder  and  FJ. Samaniego (1979).   "Performance of Activated
    Sludge Processes and Reliability Based  Design" Journal of Water Pollution Control
    Federation,  5J., 2841.

2.  Niku, S. and E.D.  Schroeder  (198la).   "Stability  of Activated Sludge Processes
    Based  on  Statistical Measures" Journal Water Pollution  Control Federation, 53,
    457.

3.  Niku, S.,  F.J., Samaniego and  E.D.   Schroeder (1981b).   "Discharge Standards
    Based on Geometric  Mean" Journal Water  Pollution Control Federation 53,  471.

4.  Niku, S. and E.D. Schroeder (1981c)  "Factors Affecting Effluent  Variability  From
    Activated Sludge Processes, Journal Water  Pollution Control Federation, 53,  546.

5.  Niku, S.,  R.S. Haugh and  E.D. Schroeder (198Id).   "Performance  of Trickling
    Filter  Plants"  in press Journal Water  Pollution  Control Federation.

6.  National Research  Council (1946).  "Sewage Treatment  at  Military Installations"
    Sewage Works  Journal, _18, 789.

7.  Schroeder,  E.D.  and G.  T. Tchobanoglous  (1975).  "Another  Look  at The  NRC
    Formula: Water and  Sewage  Works,  122, No. 7, 58.
                                        157

-------
8.  Fair, G.M. and H.A. Thomas (1950).  "The Concept of Interface and  Loading in
    Submerged,  Aerobic, Biological  Sewage  -  Treatment  Systems,"  Journal and
    Proceedings, Institute of Sewage Purification,  pt. 3, 235.

9.  Caller, W.S. and H.B. Gotaas  (1964).   "Analysis  of  Biological Filter Variables"
    Journal Sanitary Engineering Division, ASCE 90, SAG, 59.

10. Adams B.3. and R.S.  Gemmel  (1973).   "Performance  of Regionally Related
    Wastewater  Treatment  Plants," Journal  Water  Pollution Control Federation,  45,
    2088.

11. Thoman R.V. (1970). "Variability of Waste Treatment Plant  Performance" Journal
    Sanitary Engineering Division,  ASCE, 96, 819.

12. Hann, R.W.  et al.  (1972).   "Evaluation  of Factors  Affecting  Discharge  Quality
    Variation" Texas Water Quality  Board, Environmental Engineering Division, Austin,
    TX.

13. Bertheoux P.M. (1974).  "Some Historical Statistics Related to Future Standards
    Journal Environmental Engineering  Division,  ASCE,  100,  443.

14. Popel,  H.J.  (1976).   "A Concept for  Realistic Effluent Standards"  Progress  in
    Water Technology,  8, 1, 69.

15. Hovey, W.H.,  E.D.  Schroeder  and  G.  Tchobanoglous (1979).   "Activated Sludge
    Effluent Quality Distribution" Journal Environmental Engineering Division, ASCE,
    105, 819.

16. Townshend, A.R. (1968).  "Statistical Analysis of the Effluent Quality of Biological
    Sewage Treatment Processes,"  Proceedings, Third  Canadian Symposium on Water
    Pollution Research, Toronto, 272.

17. Lin, K.C. and G.W. Heinke (1977). "Variability of Temperature  and Other Process
    Parameters, A Time Series Analysis of Activated Sludge Data" Progress in Water
    Technology,  9,  2, 347.
   "This paper has  been  reviewed in accordance with the U.S.  Environmental
   Protection Agency's peer and administrative review  policies and approved
   for presentation  and  publication."
                                       158

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                     PAPER NO. 10


EVALUATION AND DOCUMENTATION OF MECHANICAL RELIABILITY

 OF CONVENTIONAL WASTEWATER TREATMENT PLANT COMPONENTS
                          by

                    David W. Shultz
                Senior Research Engineer

                          and

                      Van B. Parr
                    Staff Scientist
             Southwest Research Institute
               San Antonio, Texas  78284
                          159

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EVALUATION AND DOCUMENTATION OF MECHANICAL RELIABILITY OF CONVENTIONAL
WASTEWATER TREATMENT PLANT COMPONENTS

David W. Shultz, Senior Research Engineer
Van B. Parr, Staff Scientist
Southwest Research Institute

INTRODUCTION

     There are approximately 21,000 publicly owned municipal treatment
plants (POTWs) operating in the U.S. at the present time, with 1000-1200
new plants being constructed each year (1)(2). Since 1957, Federal grants
exceeding $20 billion have been awarded to help state and local governments
construct these treatment plants. Once constructed, local governments become
responsible for plant operation in accordance with effluent discharge permit
requirements established by the National Pollutant Discharge Elimination
System (NPDES).

     Many POTWs are apparently not meeting NPDES permit requirements. The
General Accounting Office (GAO) concluded in 1970 that operation and
maintenance problems with POTWs had been widespread for many years and
had resulted in inefficient plant operations (3). A 1975 EPA analysis of
954 POTW inspections showed 386 plants had sufficient design and operational
performance data to determine whether the plant was meeting design criteria
for biochemical oxygen demand (BOD) removal. 40 percent of 305 plants were
operating below design criteria for suspended solids removal. Other studies
have indicated significant problems of non-compliance by POTWs with NPDES
permits (4)(5)(6).

     In recognition of these operational and maintenance problems, the
U.S. EPA initiated a national research program dealing with performance
and reliability of POTWs. A significant part of the effort involves
determining the reliability of various mechanical components used at POTWs.

     This study was conducted by Southwest Research Institute (SwRI) to
quantify the In-service reliability of critical mechanical components found
in four types of secondary wastewater treatment plants. The four types of
plants Included in this study were air activated sludge, oxygen activated
sludge, trickling filter, and rotating biological contactor. The reliability
statistics determined included mean time between failure (MTBF), mean time
to repair (MTTR), and availability as a percent of scheduled operating
time.

     The technical approach, results, and conclusions are discussed in
the following sections.

TECHNICAL APPROACH

Criticality Analysis

     To determine the In-service reliability of critical mechanical
components, the first step was to identify the critical components. The

                                     160

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following components were identified as  critical  (i.e.,  failure would have
an immediate impact on effluent quality);  pumps,  power transmissions, motors,
compressors, diffusers, valves, controls,  and  conveyors.

     A criticality analysis was then conducted to determine  the component-
application combinations to be included  in the study.

     A failure mode, effects, and criticality  analysis was then performed
for each of the four types of plants. In performing  the  analysis, it was
assumed that there was no equipment duplication and  that  the plant was
operating at the design condition. The resulting  criticality rating for
each component-application combination reflected  the degree  of impact on
the effluent quality (significant, minimal,  or no impact) as a function
of time after failure (0-4 hours, 4-12 hours,  or  24  hours).

     From this analysis, the components  selected  for inclusion in the data
collection effort were:

      (1) Raw and intermediate wastewater  pumps,  power transmission and
          motors for all plant types,

      (2) Return activated sludge pumps, power transmission  and motors
          for air and oxygen activated sludge,

      (3) Recirculation pump, power transmission  and motors  for trickling
          filter and rotating biological contactors,

      (4) Motors and power transmission  for final clarifiers for all plant
          types,

      (5) Motors, power transmission, compressors, valves, controls and
          diffusers used in dissolved air  production application and
          mechanical aerators in air activated sludge plants,

      (6) Motors, power transmission, recirculation  pumps, controls,
          diffusers and valves used in oxygen  generation, application and
          recirculation in oxygen activated sludge plants,

      (7) Liquid application systems for trickling filter plants,

      (8) Compressors, motors, power transmission and controls used in
          primary clarifiers and primary sludge pumping  in trickling filter
          and RBC plants,

      (9) Recirculation pump controls used in  secondary  treatment in RBC
          plants,

     (10) Raw and intermediate wastewater  pump controls  used in all plant
          types and valves used in raw and intermediate  pumps in trickling
          filter plants,
                                     161

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     (11) Controls used in dosing siphon in secondary treatment in  trickling
          filter plants,

     (12) Controls used in final clarifiers for all plant types, and

     (13) Pumps, motors, power transmission and pressure vessels used  in
          disinfection for all plant types.

     Having defined the data collection requirements, the next  step involved
the selection of treatment plants having adequate records from  which these
data could be collected.

Data Source Selection

     The data source selection process involved the following tasks: develop
a list of candidate plants, select plants for one-day screening visits,
conduct the one-day visits, and select study plants.

     A candidate list of approximately 200 treatment plants was developed
utilizing information from the U.S. EPA staff, equipment manufacturers
and sales representatives, SwRI and subcontractor contacts, treatment  plant
operators and the literature. The criteria used to develop this list were
primarily (1) that the plants satisfied the plant type requirements (i.e.,
air or oxygen activated sludge, RBC, or trickling filter);  (2)  there was
an indication these plants would be willing to participate in the study;
and (3) maintenance records were available.

     Using information about these plants, forty-two plants were selected
for direct contact by telephone. As a result, seventeen plants  were
identified for further consideration. One-day screening visits  were then
scheduled for each plant. The one-day visits were made to discuss the  project
with plant personnel and verify the suitability of plant records for the
study.

     Following the one-day visits, the treatment plants to be included in
the data acquisition effort were selected. Criteria used to make the
selection were as follows:

     (1)  Existence of adequate and complete preventative and corrective
          maintenance records for all major equipment components at each
          plant,

     (2)  Existence of plant equipment typical of the generic equipment
          found in the four types of treatment plants under consideration,
          and

     (3)  An indication that plant operations and maintenance personnel
          were willing to cooperate in the data collection effort.

Data Acquisition

     A schedule was developed for visiting the various plants.

                                      162

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     Upon arrival at each plant, the data collection  team  (engineer/operator
and engineering technician) met with the plant  staff  involved. This meeting
provided an opportunity for the data collection team  to  further  explain
the project and discuss possible uses of the project  results.

     At this point, data collection was started.  Maintenance records for
each critical component were reviewed.  Data collection forms were used to
code all data. An example is shown in Figure 1.  Required data elements
are shown at the top of this form. All data collected in the field were
encoded using a numbering system which was developed  to  allow analysis of
the data using a computer program. These codes  are  shown in the  appropriate
columns in Figure 1. For example, column one contains the  code number 04-
8731. The first two digits, 04, identify the plant  location. The second
four digit number represents a record number used to  identify that specific
piece of equipment. Column two, plant type, shows the number 05, which
identifies this plant as a combination air/oxygen activated sludge plant.
Codes for each of the remaining 23 columns are  shown, with a description
of what each code means shown below the code. Column  23  was for  recording
actual down time of sludge processing systems.  Data for  the sludge processing
systems at each facility visited were recorded  as shown  at the bottom of
Figure 1. These data allowed calculation of the mean  time  between failure
and availability of the system.

     The data collection from plant records often required a degree of
judgment and interpretation. This was especially true when deciding when
equipment had actually failed. A failure was defined  as  when the mechanical
component no longer performed its intended function due  to a failure of
that component's subcomponent(s). In contrast,  an equipment malfunction
was defined as situations where the equipment could be placed back into
service by minor cleaning and/or adjustments. Only  data  for down time
considered to be caused by failure were recorded. Malfunctions including
pump blockages, reduction in blower capacities  due  to dirty air  filters,
and plugging of air diffusers were not recorded.  If interpretation of
maintenance records was questionable, the data  collection  team conferred
with plant maintenance staff to decide whether  a failure had occurred.

Data Analysis

     A computer program entitled "Wastewater Reliability Analysis
Program—WRAP" was written to handle the sorting and  analysis of the data
base. Reliability, maintainability, maintenance and availability statistics
were calculated from the data base across all plants  for:

     (1)  Components,

     (2)  Components by application,

     (3)  Components by size,

     (4)  Components by generic group,

     (5)  Components by generic group by application, and

                                      163

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-------
     (6)  Components by generic group by size.

     In addition, failure distribution information by subcomponent type
for the first four categories listed above were also calculated.  Also,
reliability and availability statistics were calculated for sludge processes,

     The statistics calculated from the data serve as the best summary of
the data base in terms of the reliability, maintainability, maintenance,
availability and subcomponent failure distribution parameters for the nine
wastewater treatment plants.  This information should be useful to other
plant owners and operators, equipment manufacturers, and plant designers.

RESULTS

Component Performance Statistics

     The performance statistics on critical components and sludge processes
which were calculated from the data gathered at nine wastewater treatment
plants are as follows:

     Reliability Statistics—
        Overall mean time between failures (Overall MTBF)
        Maximum mean time between failures (Max MTBF)
        Minimum mean time between failures (Min MTBF)
        Lower limit 90% confidence level for the mean time between failure
          point estimate  (overall 90% CL)

     Maintainability and Maintenanct Statistics—
        Mean time to repair (MTXR)
        Preventative maintenance man hours per unit per year  (PM-HRS/
          Unit/YR)
        Corrective maintenance man hours per unit per year (CM-HRS/
          Unit/YR)

     Availability Statistics—
        Inherent availability (AVI)
        Operating availability (AVO)
        Where AVI =    MTBF     . Total Hrs (TH) - TH Down Time (THU)=
                    MTBF + MTTR '           Total Hrs (TH)

     These statistics have been grouped as follows:

        (1)  By component,
        (2)  By component by generic group,
        (3)  By component by application,
        (4)  By component by size/capacity,
        (5)  By component by generic group by application, and
        (6)  By component by generic group by size/capacity.
                                    165

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                           TABLE  1.  RELIABILITY AND MAINTENANCE  DATA FOR PUMPS—OPEN
                                       IMPELLER  CENTRIFUGAL BY APPLICATION
                               Operating  Overall   Min.    Max.   Overall
                                  Hrs      MTBFl    MTBF    MTBF   90% CL   PM-Hrs 2 CM-Hrs/3
               No.  of   No.  of    (x 106    (x 106   (x 106  (x 106  (x 106   Unit/    Unit/   MTTR4      _
  Application   Units  Failures    Hra)	Hrs)     Hrs)    Hrs)    Hrs)     Year     Year    (Hrs)    AVI    AV
                                                                                                   o6
Raw Waste-
 water Pumping   34       60

Intermediate
 Wastewater
 Pumping         9        9

Return Acti-
 vated Sludge
   Handling     27       28

TOTAL           70       97
                       .9277     .01530
                       .1669



                      1.0230

                      2.1176
.01727
                        .01303   .009442  .317900   8.483  .99400  .98450
.01175   .107900  .787100  6.667  .99960  .95480
.03569    -       -      .02835   .001745  .102800   6.786  .99980  .99980

.02166   .01530  .03569   .01911   .003428  .094773   7.825  .99962  .98955
    3CM
    4MTTR
    5AVI
    6AVO
«" Mean Time  Between Failures
= Preventive Maintenance
= Corrective Maintenance
= Mean Time  to Repair
= Inherent Availability
= Operating  Availability

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     An example of the type of reliability, maintainability, maintenance,
and availability statistics which were calculated from the data is shown
in Table 1, data for pumps by application.

     Table 2 is an example of data on subcomponent failures by component
type.

     Table 3 is an example of the "by component" grouping showing reli-
ability statistics for the eight components included in the data base,
across all plants.

                TABLE 2.  PUMPS—OPEN IMPELLER CENTRIFUGAL

Rank
1
2

3
4
5
No. of
Subcomponent Type Failures
Impeller Wear Ring or Plate
Seal, Packed, Water, Oil, Grease
Lubricated
Solenoid Valve
Bearing, Ball, Double Row
Bearing, Cast, Pillow
15

14
14
6
5
Relative
Frequency
.197

.184
.184
.079
.066
         TABLE 3.  MEAN TIME BETWEEN FAILURE (MTBF) FOR COMPONENTS

Component
Pumps
Power Transmissions
Motors
Compressors
Diffusers, air /water
Valves
Controls
Conveyor (unconfined
materials handling)
Overall
MTBF
(x 106 Hrs)
.032066
.035620
.066700
.007140
.018130
.014440
.083580

.148480
Min.
MTBF
(x 106 Hrs)
.021662
.017850
.010880
.005620
.012630
.008930
.003930

.061750
Max.
MTBF
(x 106 Hrs)
.074191
.710910
.114820
.083920
1.834000
.032590
.100640

.358560
Overall
90% CL
(x 106 Hrs)
.028630
.033170
.061220
.006310
.016670
.010400
.075690

.116900
     Table 4 presents the maintainability, maintenance, and availability
statistics for eight components across all plants.
                                    167

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               TABLE 4.  MAINTENANCE STATISTICS FOR COMPONENTS
Components
Pumps
Power Transmissions
Motors
Compressors
Diff users, air/water
Valves
Controls
Conveyor (unconfined
materials handling)
PM-Hrs/
Unit/Yr
.00227
.00032
.00098
.03399
.00065
.00684
.00025

.00055
CM-Hrs/
Unit/Yr
.05177
.00469
.00660
.17843
.04664
.73845
.00261

. 10086
MTTR
(Hrs)
9.541
2.273
6.854
0.960
8.305
11.615
3.696

4.768
AVI
.99968
.99994
.99989
.99987
.99951
.99879
.99996

.99996
AVO
.99116
.99898
.99816
.99306
.99875
.96446
.99870

.99980
Sludge Process Performance Statistics

    As previously indicated, failure data for sludge processes were
collected at the nine treatment plants.  Table 5 presents the results of
the data analysis for five processes.

            TABLE 5.  WWTP REPORT-RELIABILITY OF SLUDGE PROCESSES
Operating No. of
Hours Failures
Process (x 106 Hrs)
Sludge Process External
to WW Treat, Process
Anaerobic Digestion
Incineration
Sludge Thickening DAF
Vacuum Filter

.780 400
.678 40
.374 454
.406 702
.697 1150
MTBF
(x 106 Hrs)

.195
.167
.824
.577
.606
90% CL AVO
(x 106 Hrs)

.183
.137
.776
.550
.583

.997
.100
.723
.994
.931
CONCLUSIONS

     Based upon the results of the performance data collection and analysis
effort conducted during this project, the following general conclusions
are made:

     (1)  Three types of performance statistics (reliability,
          maintainability, and availability) have been determined for
          selected critical mechanical components of wastewater treatment
          plants.
                                    168

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     (2)   These statistics  were  not  available elsewhere in the literature,
          from manufacturers  or  owners of  equipment.

     (3)   These performance statistics can be used by design engineers as
          a tool to (a)  compare  and  predict performance of generic equipment
          in various applications, and (b) design reliability into new
          treatment plants.

     (4)   These data can be used by  operators of wastewater treatment plants
          to develop spare  parts inventories for new equipment and establish
          preventative maintenance programs.

     (5)   In spite of the significant number of operating hours included
          in this study, this data base  does not cover all the size ranges
          or types of equipment  found in the 20,000 treatment plants
          operating in the  U.S.  Lacking  are data for many small size range
          components. It was  found that  these records are not routinely
          kept by the smaller plants surveyed during this study.

     (6)   The quality of data obtained from the nine treatment plants was
          good. The form of record keeping sometimes required judgments
          as to appropriateness  with respect to project data requirements.

     (7)   Effluent quality from  wastewater treatment plants can be expected
          to improve (to the  extent  that equipment failure causes decreases
          in quality) over  the long  term by use of performance statistics
          by design engineers and operators. Training will be required to
          help these people know how to  utilize such data. For example,
          design engineers  can utilize these data as an additional tool
          to be used for the selection of equipment, determination of the
          reliability and availability of unit operations as well as entire
          treatment systems,  and the prediction of operational performance
          of equipment in various applications. Plant owners/operators
          can utilize preventative and corrective maintenance data to help
          refine overall future  maintenance budget and staffing projections.
          Knowledge of equipment failure rates and subcomponent failures
          can provide input into determining spare parts inventories.
REFERENCES
     1.   Smith, J.  M., F. L. Evans,  and J.  H.  Bender.  Improved Operation
          and Maintenance Opportunities at Municipal  Treatment Facilities.
          Wastewater Research Division, MERL, EPA,  Cincinnati, Ohio, 1980.
          45 pp.

     2.   U.S. EPA,  Clean Water Report to Congress, Washington, B.C., 1975-
          1976.

     3.   Comptroller General of the  United  States. Continuing Need for
          Operation and Maintenance of Municipal Waste  Treatment Plants.
          Report to Congress, Washington, D.C., CED-77-46, April 1977.
                                     169

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   4.  Hegg, G.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/AS, June 1979.

   5.  Gray, A.C., P.E. Paul, and H.D. Roberts.  Evaluation of Operation
       and Maintenance Factors Limiting Biological Wastewater Treatment
       Plant Performance.  EPA 600/2-79-078, NTIS No. PB-80-108947,
       July 1979.

   6.  Weston, R.F., Inc.  Manual for Identification and Correction of
       Typical Design Deficiencies at Municipal Wastewater Treatment
       Facilities.  Draft Report, Municipal Environmental Research
       Laboratory, U.S. Environmental Protection Agency, Cincinnati,
       Ohio, October 1981.
"This paper has been reviewed in  accordance with  the U.S.  Environmental
Protection Agency's peer and  administrative review policies and approved
for presentation and publication."
                                  170

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       PAPER  NO.  11
 FAIL  SAFE  DESIGN  CONCEPTS
            by

  Roy 0.  Ball,  Ph.D.,  P.E.
         Principal
 ERM - North Central, Inc.
 200 South Prospect Avenue
Park Ridge, Illinois  60068


            171

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FAIL SAFE  DESIGN CONCEPTS

Roy 0.  Ball,  Ph.D., P.E.
Principal
ERM-North  Central, Inc.


     The  objective  of this investigation on "fail safe"  was to
evaluate  the  potential application of fail safe concepts  to the
design and/or operation  of POTW's.l  If application  of the
concept appears  promising, then  EPA would consider an expanded
R&D investigation of fail safe POTW design and operation.

     The  first question we had to answer in this investigation
is, "what  is  fail safe?"  It is easier to say what fail safe is
not  then  what it is.  The objective of investigating fail safe
operations  is to improve POTW reliability without reliance on
sophisticated operation, mechanical redundancy, or elaborate
instrumentation.   As  you can  see,  the term fail  safe  is
different  from that  used in  other  fields. Based on the
exclusionary  criteria  above, there appear to be three major
concepts  that  can  be considered  fail safe:  mechanical
interlock, mechanical simplicity, and latent energy.

     Mechanical  interlock are those processes  in  which
performing  action A  insures  that action B is also performed,
generally through direct mechanical linkage.  An  example
(unrelated  to POTW operation)  is providing that the only key
that can  lock a  car  is  the ignition key.  In POTW's,  a  simple
example is  a center pivoted chute  to divide waste sludge flow to
one  of two  tanks.   If  the chute  is  pivoted to one tank, it
necessarily excludes the other.

     The  second concept is mechanical simplicity, the ultimate
of  which  is  no  moving parts. Other speakers of this conference
are  addressing  the subject of mechanical reliability;  that is,
extending the mean time between failures, failure being defined
as  an  operation  that  reduces the  effluent  quality from the
facility.  Mechanical simplicity,  for the purposes of fail safe,
is  defined  as being  fewer failure modes of equal probability;
that is to  say if the facilities  in any two plants are compared
one  to one,  and  one  plant contains fewer items having equally
probable  failure modes,  then one  plant  is  said  to be more
mechanically  simple  compared to the other.  A common example
would  be  a  plant in which there is an influent lift station and
also a lift  station  between  primary and secondary treatment.
Elimination  of  one of the lift  stations provides a more
mechanically  simple plant.

     The  third concept is  that of latent energy.  Four separate
categories of latent forces  have been identified.
                              172

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     The first is  gravity,  which  would include hydraulic  head
and density related  phenomena.

     The  second  latent  energy source is  electromagnetic
radiation which  would  include  incident  solar radiation.
Wherever  there   is  a  naturally  generated source of
electromagnetic  radiation,  then  there  is  an opportunity to
capture  that  radiation  as  a  free energy  source  or,  more
realistically,  a reliable energy  source.

     The  third  type can  be generally referred to  as  the
teleonomic behavior of bacteria and plants.  By teleonomic, we
mean  that  for  reasons  of their own,  bacteria and plants exist
and  grow wherever  it is possible to do  so.  By virture of their
existence  and  growth,  they necessarily create gradients, and
thereby the opportunity  for  transport of materials  and their
subsequent oxidation  or  alteration.  Although we may provide
conditions where  such  bacteria  or plants can flourish, we in
fact  are not  tampering  with  their intent or desire to grow,
reproduce,  and  multiply.

     The fourth type of latent  energy  includes molecular forces
which would include such things as forces described by Hamaker
constants  and viscosity.

     Why are these  fail safe operations  attractive?  In general,
they  replace  operation  skills  with  maintenance skills and in
many  conditions,   it  is  more  practical to provide consistent,
reliable maintenance than it is consistent, reliable operation.

     The next  step in this evaluation  was to provide  a list of
examples  of   fail  safe operations that  achieve  certain
objectives.   For  example,  if  the objective is liquid/solid
separation, such  devices as  gravity sedimentation, swirl
concentrators  (which trade inertia for separation energy), and
hydros ieves are processes which seem to embody one or  more  fail
safe  principals.   A  fourth  example  is the enhancement of
coagulation and  flocculation by ion addition.

     Examples  of fail safe  operations  which accomplish  flow
regulation are  side leaping weirs (frequently used in stormwater
management )  ,  proportional  weirs (often  used to  control
velocities in  grit chambers),  siphons,  and other  hydraulic
structures.

     In addition to defining fail safe  devices, it was  necessary
to  determine  the  objectives  of main  stream treatment.
Approximately  35  objectives  within five major categories;  flow
control,  pretreatment, primary treatment, secondary treatment,
and  post-treatment were  defined.  As an  example,  secondary
treatment  frequently consists of two parts:  a bioreactor and  a
clarifier.   The  objectives of the clarifier are fivefold:


                              173

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     1.  to remove particulate BOD;

     2.  to  return  biosolids to  the reactor (with the  objective
        of reducing its size);

     3.  concentrate waste activated sludge;

     4.  store the concentrated  waste activated sludge;  and

     5.  remove suspended solids from the effluent stream.

     Therefore,  when  we consider the application of  fail safe
operations,  we  do  not  need  to  replace  all  five objectives
(conventionally achieved  with  some degree  of success) of a
secondary clarifier with  a  single  device.   We can,  rather,
improve  or satisfy some  of the objectives by fail safe means.
For  example, two of the fail  safe devices which were  discussed
in this evaluation were in-channel clarification and porous wall
reactors.  For  in-channel  aeration,  the objective of  returning
biosolids to the raactor is now  achieved in a fail safe  way, as
the  solids are  never removed in  the first place.  In the porous
wall  reactors,  several  of the  objectives are achieved.  The
biosolids return is achieved  because, again, they  are never
removed  from the reactor.   In  addition, because very high mixed
liquors  can be  maintained, the removal of particulate  BOD and
the  concentration and storage of  waste activated sludge are also
accomplished using fail safe  concepts.  Due to the build-up of
microbial growth in the pores of the walls, the removal of TSS
from the  effluent  stream  is also  achieved  with very  high
efficiency.   In fact,  the reactors must be cycled to allow
digestion of this film or the head difference between the inside
of the reactor and the exterior  will become too great.

     In this investigation,  therefore, we ended up with a matrix
which  compared  treatment  objectives such as those  described
above,  with fail safe operations.  In each block of the  matrix,
the  type of  fail safe concept was identified;  that  is,
mechanical interlock, mechanical simplicity,  or latent  energy.
It was  also indicated  whether  or not that operation  was fully
applicable to that objective, inapplicable to that objective, or
partially applicable.  Where  it was partially applicable, it
could  be  either based  on  climate,  topography (for example,
available hydraulic head) or  other factors.  It  was  also
indicated whether  or  not  the  fail  safe  operation could be
applied  on both a  new  and a retrofitted basis or only new or
only retrofitted.

     In summary, the  major benefit  of fail safe operations is
that  they require  maintenance  and  not operation.   The major
problem  with  fail safe  operations is  that they require
maintenance and not operation.   Once the fail safe devices are
installed,  there is little active control, in many cases, that


                              174

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can be exerted.   For  these reasons, a fail safe installation
generally needs  steady flow and good administration.

     Where can fail  safe be applied?  Small plants without
fulltime operators would appear to be a natural application.
Also, remote  sites where several plants are supervised by one
person would  seem to  be candidates.  The Department of Defense
installations, which  frequently have excellent maintenance  but
transient operation,  would appear to be another place where
these concepts can be applied.  Because of the problems  of
steady flows,  it is  possible that some of these concepts are
applicable at very  large facilities as well.

     In  summary, as  stated before, the objective of this study
was to. determine the  potential for application of  fail safe
principals to POTW's.  Based on the review described above, we
believe  that  the potential is significant.
 Presentation based on a study by Roy F. Weston,  Inc.  for
 EPA MERL.
  "This  paper has been  reviewed in accordance with the U.S. Environmental
  Protection Agency's peer and administrative review policies and approved
  for presentation and  publication."
                                175

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SESSION NO. 4
    Improving POTW Design
                               PAPER NO. 12
                        DESIGN  DEFICIENCIES IN POTWs
                                    by

                          Roy 0.  Ball, Ph.D., P.E.
                                  Principal
                          ERM - North  Central, Inc.
                          200 South  Prospect Avenue
                         Park Ridge, Illinois  60068
                                    176

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DESIGN DEFICIENCIES IN POTWs

Roy 0. Ball, Ph.D., P.E.
Principal
ERM-North Central, Inc.

     So far in this symposium, you have heard a number of pre-
sentations describing EPA funded reports, all of which have the
objective of describing factors which can prevent POTWs from
proper operation and attaining their design effluent quality.
Bob Hegg has discussed his survey of facilities and identifi-
cation of any such factors.  Kimm Perlin described factors
involved in the operation and maintenance of land treatment
facilities which can impact performance.  Bob Crosby has
described his measurements of the flow and secondary clarifiers.
I presented a description of the report on side streams which
can, in some cases, have very serious effects on plant per-
formance.  Professor Boyle has described biofouling of aerators.
Dave Schultz has discussed the mechanical reliability of
facilities and how to prevent treatment plant failures due to
mechanical problems.  Ed Schroeder has provided statistical
information on the overall performance and reliability of
plants.  With regard to new concepts for facilities or rather
the reapplications of old concepts, this morning I described
the fail safe feasibility investigation and Jon Bender discussed,
as part of the design information series, the effect of hydrau-
lic variation on treatment performance.

     The design deficiencies report I wish to now describe is
a catalog of factors or actions  that either did or did not
occur during the design process  that could impact the perfor-
mance or operability of the POTW.  The report is in 14 major
sections by process area.  For each section, the deficiencies
are grouped as being either general, hydraulic, structural,
electrical, mechanical, or instrument related.  The deficien-
cies  each carry a  number,  and on the matrices at the front of
the report, it is  possible to rapidly locate any particular
deficiency  by using the matrix numbers as indicated in this
example.  Alternatively, the operator designer can turn to the
section  on  a particular process  and rapidly  leaf through  all of
the identified deficiencies of the mechanical type to  insure
that  his design has  included  and dealt with  any such potential
problems.

      I will now describe the  organization and format of the
design deficiencies  report  in more detail.   The report was
designed to facilitate the  location of  information concerning
typical  design  deficiencies  found in various wastewater
treatment  systems  and,  more  specifically,  individual unit
operations,  and  to reference  the deficiencies noted with  re-
lated solutions.   The  report  is  divided  into two main  sections:
                               177

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     •  Design Deficiencies Matrix

     •  Design Consideration and Correction Modules for POTWs.

     Design deficiencies commonly found in the POTWs are cate-
gorized in a matrix format.  The 15 categories utilized are
listed below:

            Number          Category

            1.0            General Plant Design
            2.0            Preliminary Treatment
            3.0            Primary Treatment
            4.0            Air Activated Sludge
            5.0            Oxygen Activated Sludge
            6.0            Trickling Filter
            7.0            Disinfection
            8.0            Anaerobic Digestion
            9.0            Aerobic Digestion
            10.0           Sludge Dewatering
            11.0           Lagoons
            12.0           Land Application
            13.0           Sludge Disposal
            14.0           Sludge Reduction
            15.0           Rotating Biological Contactors

     The deficiencies within each category are further grouped
according to type and then numerically referenced to unit opera-
tions and components specific to the category.  The deficiency
groups used include:

     •  Layout, Arrangement, and Placement of Components in
        Design of Plant.

     •  Hydraulic Design Considerations.

     •  Mechanical Design Considerations.

     •  Electrical/Instrumentation Design Considerations.

     •  Safety Considerations.

     •  Environmental Considerations.

     The design deficiencies listed in the matrix are discussed
in  "Design Consideration Modules" in terms of items that should
be  reviewed by the engineer furing design of a new or expansion
of  an existing wastewater treatment plant.  Features of the
module format are as follows:

     •  The report section, design consideration category, and
        applicable unit operation or component are indicated in

                               178

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        the upper left-hand corner.

     •  A treatment plant block flow diagram is presented
        in the upper right-hand corner.  The deficiency cate-
        gory represented by the module is shaded to allow the
        reader to visually identify the portion of the plant
        discussed.

     •  The design deficiencies, including reference number
        and description, are presented in a column on the left
        side of the page and the associated design considera-
        tion discussed in a column opposite the deficiency.

     •  The reference numbers for the deficiencies discussed
        in each module are summarized at the bottom of the
        page.  This facilitates locating specific deficien-
        cies when referring to the modules.

     •  The modules are sequentially numbered for cross-refer-
        encing with the module table of contents.

     Suggested methods to correct the design deficiencies,
when already present at an existing wastewater treatment
facility, are presented in the document.  The correction pro-
cedure, where applicable, includes the following items:

     •  Method.
     •  Materials.
     •  Cost.
     •  Sketch.

     The  format of the document allows the reader the flexi-
bility to obtain  information either through the deficiency
matrix or the design consideration/correction modules.  A POTW
operator  experiencing a specific problem at his plant should
first refer  to the deficiency matrix  in order to identify the
appropriate  module(s) that describes methods that can be used
to correct the problem.  On the other hand, an engineer may
wish to proceed directly to the design consideration modules
in order  to  identify those items he should review during de-
sign of a specific unit operation  or  component.

     The  correct  procedure for  using  the design deficiency
matrix is  as follows  (see Figure I for illustration):

      1.   Select  the appropriate matrix category  (i.e., pre-
          liminary, primary, activated sludge, etc.)  and
          refer to that  section  of  the  matrix.

      2.   Determine which deficiency group  (i.e., mechanical,
          hydraulic, safety, etc.)  the  problem falls  under
          and turn to that portion  of  the matrix.


                             179

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    3.  Identify the applicable unit  operation or  component
        and move down that column until  the desired defi-
        ciency is located.   (NOTE:  If the deficiency  is not
        listed, refer to  the deficiency  list  and determine
        if it is listed under  another unit operation.)

    4.  Use the three digit deficiency reference number to
        identify the related deficiency/correction module as
        follows:

                1st Digit — Category Number

                2nd Digit — Unit Operation/Component
                             number  (i.e., column  number)

                3rd Digit -- Deficiency  Number

     5.  Turn  to the deficiency/correction module that  has
        has the same category  and unit operation/component
        number.

     6.  Read  down the  left-hand  column to the applicable
        deficiency  reference number.

     7.  The suggested  correction method  is  described in the
        opposite  right-hand  column.

     8.  Related considerations aimed  toward  preventing the
        deficiencies  during  design  are  also  discussed  in
        the opposite  right-hand  column.

     In many examples,  the deficiency  correction at existing
POTWs was  a reiteration of the  design  consideration.   To
avoid repetition,  only  the design consideration is  presented.

     All the  deficiencies described  in this report  seem to
persist in the design  field.   Perhaps  the reason is that the
person who performs  the conceptual design of the plant, al-
though he  may  have in  mind many of these  difficulties,  does
not fully  communicate  his concerns to the people preparing
the plans  and  specifications.   Frequently, too, the plans
and specifications are not reviewed by someone knowledgeable
and experienced in the operation and maintenance of treatment
plant facilities.   Also,  if there are such deficiencies, many
times they are of  a positional nature and may not be readily
corrected without redoing much of the final design.  Whatever
the reason, it appears that few,  if any,  firms have attempted
to make such a comprehensive catalog  of problems that can
occur.  The intent of this catalog is not to  substitute our
judgment or discretion for the designers, but rather to pro-
vide an indication of problems that have arisen at other treat-
ment facilities and have  been considered serious enough to


                             180

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 impact the performance or  operability of the facility.

      At this point, I would  like to ask members of the  audience
 to  provide us with examples  of design deficiencies that they
 have  noted.   For my part,  I  will point out whether or not
 these are included in the  catalog or what other allied  defi-
 ciencies are also included,  if any.

      Based on the degree of  participation here, it is evident
 that  this subject is of some general interest to members of
 our profession.  It is EPA's hope,  and mine, that this  docu-
 ment  will serve as a valuable starting point for the contin-
 ued cataloging of such deficiencies, with the ultimate  objec-
 tive  of improving the operability and reliability of POTWs.


DEFICIENCY







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    Deficiency Reference Number is:
                         FIGURE 1
 Presentation based on  an  investigation and report
 by Roy F. Weston, Inc.  for EPA MERL

"This paper has been reviewed in accordance with the U.S. Environmental
Protection  Agency's peer and administrative review  policies and approved
for presentation and publication."
                              181

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           PAPER NO. 13


PERFORMANCE CAPABILITIES AND DESIGN

   OF OXIDATION DITCH PROCESSES
                by

        William F. Ettlich
          Vice President
         Culp/Wesner/Culp
 El Dorado Hill, California  95630
                182

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PERFORMANCE CAPABILITIES AND DESIGN OF OXIDATION DITCH PROCESSES

William F. Ettlich, Vice President
Gulp/Wesner/Gulp

DESIGN FEATURES OF OXIDATION DITCH PLANTS

     An oxidation ditch plant is typically an extended aeration type of
activated sludge process that uses a continuously recirculating closed loop
channel or channels as an aeration basin.  The aeration basin is normally
sized for a 24-hour hydraulic retention time, but may be designed for any
other detention time.  Mechanical aerators are commonly used for mixing,
oxygen supply, and for circulation of mixed liquor.  Generally, these are
horizontal brush, cage, or disc-type aerators designed specifically for
oxidation ditch plants.  Secondary clarifiers similar to those used in
other activated sludge processes are normally provided.  Primary clarifica-
tion is not usually included in oxidation ditch plant design.

     The typical oxidation ditch aeration basin is a single channel or
multiple interconnected concentric channels.  An oxidation ditch plant
normally consists of one or more basins of either type operated in parallel
depending on  the flow and operation mode required.  Channel geometry can
vary to include many possible configurations, however, the single oval
configuration is the most common.  The multiple concentric channel basin
can have any number of interconnected channels with three to five being
typical and provides some process flexibility since it can be changed to
other activated sludge modes with minor modification.  Typically, the outer
channel is used for aerobic digestion of the waste activated sludge.  Shallow
channels are  typically four to six feet deep with 45 degree sloping side
walls.  Deep  channels have vertical side walls and are normally 10-12 feet
deep.  The channels are usually lined to prevent erosion and leakage.  Ditch
lining can be reinforced concrete, gunite, asphalt, or thin membranes.
Typically, shallow channels with sloped side walls are constructed of con-
crete poured  against earth backing with welded wire mesh reinforcing.  Deep
vertical wall channels require reinforced concrete walls.

     Several  manufacturers supply oxidation ditch brush or disc type
mechanical aerators.  These units may be either fixed or floating.  The
aerators normally span the channel width and may be installed in one or
more locations around the channel.  The aerators must supply the required
oxygen to the channel and impart a sufficient velocity in the channel
(>1.0 FPS) to keep the channel contents in suspension.  Oxygen transfer
capabilities  of an aerator will vary depending on the particular design,
rotational speed and submergence.  Most units operate in the range of 60 RPM
to 110 RPM with a submergence of 2 to 12 inches and produce oxygen transfer
rates of  from 3 to 5 Ibs of oxygen per hour.  The number of aerators pro-
vided depends on the size, configuration and oxygen requirements of the
plant.  A minimum of two aerators should be installed so that at least
partial aeration can be maintained with one unit out of service.
                                     183

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     There are many available configurations of plants and aerators and it
is recommended that care be taken to select the most energy efficient con-
figuration because aerator energy is a major operating expense for oxidation
ditch plants.  There should be little actual difference between manufacturers
aerator power requirements for given size plants.

     The real problems (and differences) in rotor configurations are mechani-
cal; the drive unit, line bearings, seals, aerator torque tube, materials of
construction and similar considerations.  These are the features that will
have the greatest impact on long term operation and maintenance of the plant.

     The mechanical features should receive careful consideration in design
and preparation of specifications.  Most of the bearings associated with
aerators are of the ball or roller type; grease lubricated with seals.
Therefore, bearings and drive units should be protected from splashing water
both to keep the water off and to provide convenient access for maintenance
personnel.  Extension of bearing  grease fittings up to convenient locations
on catwalks or easily accessible locations will certainly contribute to more
satisfactory maintenance.  Means for field alignment of bearings should be
provided and bearings should be carefully aligned prior to operation.  The
bearing supports for horizontal aerators may be up to 30 feet apart and
differential settling with eventual loss of alignment may occur if this is
not considered in the structural design of the aerator support foundation.
Generally, bearings with some self alignment capability will provide more
satisfactory long term service, but this feature does not reduce the need
for proper structural design and initial alignment.

     Some means must be provided for removal of the aerator; either a per-
manently installed lifting mechanism, a portable lifting mechanism, or
access for mobile lifting equipment.

     Many problems were caused by the aerator "slinging" mixed liquor onto
adjacent structures and onto aerator bearings, couplings, seals, and drive
units.  Most aerators have "slingers" at each end, but they only compound
the problem when the wind is blowing as liquid flying off the "slinger" is
blown by the wind.  Mixed liquor which lands on adjacent walkways causes
ice formation when it is cold and algal growths cause slippery conditions
at other times.  Bearings and drive units should be adequately shielded from
the inevitable liquid spray.

     The long narrow aeration channel of the oxidation ditch plant provides
a complete mix activated sludge process.  Even though a plug flow mode would
seem to be applicable, the minimum velocity of 1.0 fps results in a cycle
time of less than 15 minutes in the longest channels used.  Compared to the
typical 8 to 24 hour detention time design, the channel circuit time becomes
insignificant.  Therefore, the oxidation ditch may be considered a completely
mixed activated sludge process (CMAS) with respect to organic load.  It is
not completely mixed with respect to dissolved oxygen profile because this
profile can vary significantly around the channel and vertically within the
channel.  The mixed liquor can pass through varying oxygen rich or deficient
zones as it passes around the channel.
                                    184

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     The procedure for design of an oxidation ditch plant is basically the
same as used for an extended aeration process with emphasis given to the
hydraulic considerations imposed by the basin geometry.  The manufacturers
can provide assistance in design for specific applications.

     Some low alkalinity wastewaters may require pH adjustment when subjected
to extended aeration because of nitrification.

     Oxidation ditch plants are designed for long sludge retention times
and nitrification will occur if sufficient oxygen is provided.  Usually, suf-
ficient oxygen should be provided for complete nitrification in addition to
satisfying the carbonaceous BOD requirements.  Complete mix activated sludge
plant design procedures have been described by McKinney(l), Eckenfelder^),
and Monod'-^, and presented in a unified model by Goodman(^,5) .   j{- ^_s
frivolous and time consuming to compare the nuances of these various models;
proper use of any of these models results in sufficiently accurate results
for design purposes.

     Screening seems to be the single most important pretreatment step.  If
rags, boards, and other similar objects are not removed prior to the ditch
they will cause trouble with the aerators and will, in most cases, plug
sludge control valves (telescoping valves), sludge lines, sludge pumps, and
weirs.  Few problems have been observed or reported directly related to
inadequate grit removal although it is certain that this grit accumulates in
the ditch and will have to be removed at some time.

     Generally, final clarifier design is consistent with other activated
sludge processes.  A surface overflow rate of 400 to 500 gpd/sq ft is recom-
mended for average daily flows and 1,000 to 1,200 gpd/sq ft at peak flows.
Many plants are constructed with 8 foot deep clarifiers, but depths of 10
to 14 feet provide greater process reliability.

     Any biological plant design must consider the quantity of sludge pro-
duced, the nature and stability of the sludge, and suitable disposal pro-
cedures.  An oxidation ditch plant, operated in the extended aeration mode,
has certain inherent advantages relative to sludge handling and disposal.
Oxidation ditch plants can be operated at a 20 to 30 day SRT resulting in a
sludge having characteristics similar to a well stabilized aerobically
digested sludge.  A conventional activated sludge plant operated at a 4 to
10 day SRT will produce a sludge with high residual biodegradable organic
content.  If placed on drying beds or on the land, it will become odorous
and objectionable.  Aerobic digestion of this sludge for 7 to 15 days is
normally required to produce a stable product suitable for disposal on
drying beds or the land.  For a properly operated conventional activated
sludge plant plus aerobic digestion the total SRT prior to disposal will be
15 to 20 days.  In effect, the oxidation ditch extended aeration process
provides sludge stabilization equivalent to conventional activated sludge
plus aerobic digestion.

     In most oxidation ditch plants where the extended aeration process is
used (16 to 24 hours aeration detention) sludge is wasted directly to open
                                    185

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drying beds.  In a few cases sludge is wasted directly to tank trucks which
spread the liquid sludge on the plant grounds or on adjacent land.  Field
inspections of oxidation ditch plants revealed no odor problems at plants
using either method.  The field inspections consistently confirmed the lack
of odor problems with sludge from the extended aeration oxidation ditch
plants.  Several plants complained of insufficient drying bed capacity
because of poor dewaterability especially during periods of cold or wet
weather.  Adequate drying bed capacity must be considered carefully in design.

     Some design engineers and regulatory authorities may require additional
sludge stabilization for oxidation ditch plants operated in the extended
aeration mode.  Part of the consideration may be the possibility of periodic
poor operation of the process.  Also, future flow increases may force opera-
tion of the plant at shorter SRT's to the point where additional sludge
stabilization is required.

     The quantity of sludge produced is related to the characteristics of
the incoming wastewater solids.  Normally, wastewater solids contain frac-
tions  that  are inert, volatile and nonbiodegradable, and volatile and bio-
degradable.  The inert  (nonvolatile) and volatile/nonbiodegradable fractions
will accumulate in the  system solids inventory in proportion to the SRT.
Normally 20 to 25 percent of the raw waste suspended solids are inert.  The
remaining 75 to 80 percent are volatile solids with, typically, 30 to 40 per-
cent nonbiodegradable.  Therefore, about half of the incoming suspended
solids  are  not subject  to biological action and will accumulate in the mixed
liquor  in proportion to the SRT.  Proper sludge wasting is absolutely neces-
sary in extended aeration plants as with conventional activated sludge plants
or the  excess solids will be automatically wasted periodically in the
secondary clarifier effluent.

COMPARATIVE PERFORMANCE & RELIABILITY

     Performance and reliability data for oxidation ditch plants  were
developed from actual plant operating records,  obtained from published
literature,  telephone and letter contact with operating plants,  visits to
operating plants,  EPA records,  special studies,  and engineer's files.   There
were very few plants where complete data could  be obtained for all desired
parameters.   In addition, reliance had to be placed  on the sampling and
analysis methods used by various plant personnel.   It is recognized that these
procedures are not consistent from plant to plant  and therefore,  not always
directly comparable.  Nevertheless,  the results represent the data as obtained
without modification.   Inordinately high or low readings were not removed
from the data during compilation because most plants experience these varia-
tions at one time or another.  It is felt that  these variations do occur in
oxidation ditch plants as in most other activated sludge plants.

     Oxidation ditch plant performance was developed primarily from monthly
average data.   Generally, the data from a plant were not used unless several
data points were available.   Plant daily performance data, when available,
were converted to monthly averages,  which were then analyzed for each plant.
                                      186

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     Where possible, the performance is calculated for both summer and
winter.  Winter is arbitrarily determined to be the months of November
through March.  The "average" performance was determined by averaging the
performance of all of the individual plants.  The high and low individual
plant performance is shown to establish the range limits of individual plants.

     Based on an analysis of available data it was found that both BOD5 and
suspended solids removal appear to be relatively independent of plant
capacity.

     Performance data from 29 oxidation ditch plants from various United
States and Canadian locations are summarized as follows:
             SUMMARY PERFORMANCE OF 29 OXIDATION DITCH PLANTS
                            Effluent, mg/L
                                        Removal
BOD
     High plant
     Average
     Low plant

Suspended solids
     High plant
     Average
     Low plant
Winter

 55
 15.2
  1.9
 26.6
 13.6
  3.1
Summer

 34
 11.2
  1.0
 19.4
  9.3
  1.9
Average
annual

 41
.12.3
  1.5
 22.4
 10.5
  2.4
                                                   Winter   Summer
37
92
99
81
93
98
86
94
99
82
94
98
Average
annual

  87
  93
  99
  82
  94
  98
     The performance  of  competing biological treatment processes was also
evaluated and the  data are  summarized as  follows:

                PERFORMANCE - COMPETING BIOLOGICAL PROCESSES
            Activated  sludge
              (1.0 mgd)
            Activated  sludge
              (Package  Plants)
            Trickling  filters
            Rotating biological
              contactor
                                    Effluent, mg/L
                                    TSS
                 31

                 28
                 26

                 23
               26

               18
               42

               25
                                  Removal,  %
                                  TSS   BOD5
               81


               82

               79
        84


        79

        78
      Analysis  of data from 12  operating oxidation  ditch plants showed the
 reliability for meeting various  BOD5  and TSS  effluent  standards as follows:
                                     187

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                     RELIABILITY - OXIDATION DITCH PLANTS

               % of time effluent concentration (mg/L) less than
                        10 mg/L      20 mg/L      30 mg/L
                      TSS   8005   TSS   6005   TSS   6005

     Best plant       99     99    99     99    99     99
     Average all
      plants          65     65    85     90    94     96
     Worst plant      25     20    55     55    80     72


     Of the plants analyzed, the effluent BOD^ and TSS seldom exceeded a
maximum of 60 mg/L.

     The reliability of competing biological treatment processes was
evaluated on the same basis and is summarized as follows:


          AVERAGE RELIABILITY - COMPETING BIOLOGICAL PROCESSES

                    % of time effluent concentration (mg/L) less than
                             10 mg/L      20 mg/L      30 mg/L
                           TSS   BOD5   TSS   BOD5   TSS   BOD5

     Activated sludge
      (1.0 mgd)            40     25    75     70    90     85
     Activated sludge
      (Package Plants)     15     39    35     65    50     80
     Trickling filters      -      2     -      3-15
     Rotating biological
      contactor            22     30    45     60    70     90


     An oxidation ditch plant is capable of 95% to 99% nitrification without
design modifications.  This high degree of nitrification even at wastewater
temperatures approaching 0°C is possible due to the 24-hour hydraulic reten-
tion time in the channel(s) and the capability of operating at a high solids
retention time (SRT)  of 10 to greater than 50 days.

     Nitrogen removal by single-stage biological nitrification-denitrifica-
tion has also been achieved at properly designed and well operated oxida-
tion ditch plants.  Nitrogen removal is achieved by producing both aerobic
and anoxic zones within the same channel.   These zones are created by
controlling the aerator oxygen transfer rate so that mixed liquor dissolved
oxygen is depleted within a portion of the aeration channel.

     The carbon source for the anoxic zone (denitrification) is provided by
feeding the raw sewage into the channel upstream of the anoxic zone.  With
careful operation, 80% nitrogen removal has been achieved in a single
channel oxidation ditch plant.
                                    188

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OXIDATION DITCH PLANT OPERATION

     As a group, oxidation ditch plants appear to perform consistently well
in spite of limited operation and maintenance in a number of cases.  All
plants visited appeared to have adequate aeration capacity, adequate
velocity in the ditch, an acceptable mixed liquor and a lack of odor or
other nuisance.  In general, the operators were able to obtain good treat-
ment results in almost all cases.  Sludge handling and disposal was
relatively simple and trouble free, however, in some cases operators re-
ported difficulties in dewatering the sludges on open drying beds due to
lack of proper bed area or due to slow dewatering of the sludge.  The plants
were easy to keep in service and would operate for long periods of time
with very little operation and maintenance.  Many plants operated for periods
of time unattended (evenings and weekends) without significant problems.
No particular type of oxidation ditch plant seemed to stand out as superior
or substandard; the relative performance depended on many more factors such
as original design criteria (clarifier surface overflow rate for instance)
and operational procedures.  There are some exceptions to these comments
and a few oxidation ditch plants have been removed from service because of
operational problems.  These cases are the exception.

     The most serious process operation difficulties resulted from equip-
ment related problems.

     Many of the plants visited were manned only during a single shift and,
in many cases, for only a portion of a single shift.  A number of plants
received little or no  attention during weekends.  Assuming no mechanical
malfunctions, the plants perform well for long periods (days to weeks at
a time) with little or no operator attention.  Most plants practiced regular
or periodic sludge wasting.  In some cases sludge wasting was not practiced,
but this caused eventual or regular carryover of excess solids in the
effluent.

     Almost without exception, operators and administrative personnel were
well satisfied with the plants.  In most cases the plants were meeting state
discharge requirements.

     A study of EPA Region VII    of winter performance of secondary waste-
water treatment facilities concluded "...in general, the facilities were
not meeting the secondary treatment effluent definition on the average
except for the oxidation ditch subset".

     All plants visited exhibited good mixed liquor characteristics (by
visual observations).  Some plants reported more than desired carryover of
solids in the effluent and it is believed that the cause was either ex-
cessive oxygenation of poor management of sludge return wasting.

     Many plants could reduce the level of oxygenation in the aeration basin
without detrimental effect and reduce energy cost.  There were no signs of
lack of oxygen.  One plant was cycling the aerator one hour on and one hour
off and reported excellent results for over a year.  Several other plants
                                     189

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were considering this scheme to lower operating costs and reduce oxygen
levels.

     When screening or comminution is not regularly and properly carried
out, rags and debris tend to cause problems in the plant expecially in the
return sludge system.

     One deep type (10 feet) single channel plant reported poor mixing in
the ditch.

     A number of plants lacked sufficient drying bed capacity which may
have led to erratic sludge wasting practices.  This problem was also re-
ported by EPA Region VIII personnel.

     A number of plants lacked proper laboratory facilities and equipment.
Some even lacked a building.  These facilities are necessary for proper
operation and maintenance of a wastewater treatment plant.

     As with any plant containing mechanical equipment, oxidation ditch
plant equipment was subject to problems, malfunctions, and failures.  As
a general observation, oxidation ditch plants are capable of long periods
of operation without mechanical problems and appear to operate with a very
high mean time between equipment failures, particularly with proper pre-
ventative maintenance and inspection programs.

     The following is a general summary of mechanical problems as related
by plant personnel.

     1.   Some plant personnel reported that drives trip out on momentary
          electrical failures and do not restart upon restoration of power.
          This causes problems with unattended operation and consideration
          should be given to maintained-contact type electrical control
          for drives such as lift pumps, aerators, sludge return pumps,
          and other items in cases where plants operate unattended.  Time
          delays can be provided so all drives do not restart at the same
          time.

     2.   Some troubles were reported with return sludge pumping.  In
          general, centrifugal, non-clog pumps seemed to give good service
          especially when a separate potable grade seal water source was
          used.  Air lift pumps were not common as would be expected at
          plants with mechanical aeration.  A number of plants returned
          sludge by gravity to the raw sewage lift station and pumped it
          to the ditch with the raw sewage.  This increased the size of
          the lift pumps, but eliminated one set of pumping.

     3.   Comminutors were a continuing maintenance problem.  They required
          regular cleaning and care.  Some operators had so many problems
          they stopped using the comminutor and allowed unscreened sewage
          to flow into the ditch.  Almost without exception this caused
          problems in the return sludge system by clogging the sludge
          return rate adjustment valve (generally a telescoping valve)


                                    190

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     or pumps.  This altered the sludge return rate and caused process
     problems if not detected early.  Oscillating type comminutors
     appear to give best service, but still require regular maintenance.

4.   Access walks should be designed to avoid receiving spray from
     aerators even under various wind conditions.  This spray creates
     hazardous conditions because of algal growths and freezing.
     This oversight created continuing maintenance problems and
     should be considered in all designs.

5.   Sludge reportedly settled in channels at some plants where flow
     control walls were not installed as recommended by manufacturers.

6.   There are some reported corrosion in final clarifiers which re-
     sulted in materials failures (bolts in particular).   These units
     should be drained and inspected annually.  Any corrosion should
     be removed and the area recoated.

7.   Weirs are a maintenance problem and must be cleaned frequently;
     in some cases as often as daily.

8.   Aerators and aerator drives account for a major portion of the
     mechanical problems.  Most plants experienced the following
     aerator related problems every two to five years per aerator unit.

     a.   Loss of some "teeth" from brush type aerators due to cor-
          rosion of bolts or damage sustained while handling the
          aerators is a common occurance.  This generally is not a
          serious problem and can be repaired during periodic shut-
          downs.  Some manufacturers have redesigned their aerators to
          minimize this problem.

     b.   Bearing problems were reported in gear drives, line shafts,
          and aerator shafts.  Experience whould seem to indicate a
          bearing problem every 2 to 5 years per aerator.  These
          problems result from poor selection of bearings, constant
          splashing of water onto the bearing, improper initial align-
          ment, differential settlement of bearing support structures
          and similar problems.  Some manufacturers have taken steps
          to reduce bearing problems by using self aligning bearings,
          double seals, and by providing water shields, but bearing
          problems can still be expected.  The magnitude of the bear-
          ing problem is not excessive and normal plant maintenance
          programs can handle this  problem.

     c.   Flexible couplings between line shafts caused problems on
          multiple concentric ring  type plants.

     d.   At one plant some of the  disc aerators loosened from the
          shaft and had to be shimmed and reclamped.
                               191

-------
          e.   Gear reducer output shaft seals need replacing about once a
               year at some plants.

          f.   There are a number of plants where gear reducer failure was
               experienced within a year of plant startup.  This was
               probably due to improper initial alignment or differential
               settling of the aerator support structure.

          g.   A couple of plants have experienced aerator torque tube
               failure or excessive deflection with very long aerators.  At
               one plant the tube failed, collapsing in the middle.  One
               consultant not requires solid shafts on all aerators rather
               than hollow torque tubes.  It may be well to avoid the use
               of very long aerators.  If a wide ditch is necessary, the
             ,  width can be spanned using two shorter aerators driven by
               a common drive.

          h.   Protective covers around bearings, couplings and drive units
               are not provided at most installations.  Spray from the
               aerators keeps these components wet and possibly contributes
               to short life.  The "slingers" at each end of the aerator
               are ineffective because wind blows this "tail" of water
               sideways onto adjacent components such as bearing and drive
               units.  Corrosion and grit on shafts probably contributes
               to short seal life.  For maximum service life and minimum
               maintenance these components should be shielded from water
               spray.  Some manufacturers are taking steps to modify their
               standard designs to provide spray baffles and shields.

          i.   Some drive configurations require the aerator to be lifted
               out of position to remove the gear drive.  This is a diffi-
               cult operation requiring a crane.  Access for a mobile crane
               should be provided to all aerators or other lifting pro-
               visions designed into the plant.

     Cold weather problems related to oxidation ditch plants appear to be
minimal except in severe climates.  Those which have been identified are
listed.  These comments are based on visits and literature.

     1.   Final clarifiers should be covered where this is typical practice
          for other types of plants.

     2.   In moderately cold areas the spray from aerators will freeze on
          adjacent structures, bearings, gear reducers, and like equipment
          making maintenance difficult.  Drive components should be covered
          to provide shielding from spray or these drives mounted in
          isolated compartments.

     3.   In moderately cold areas some problems were reported from ice
          build-up on clarifier scum collection boxes and eventual jamming
          of skimmer mechanisms.
                                   192

-------
     4.   Problems were reported with freezing of spray around aerators.
          The problem is solved by covering aerators in moderately cold
          areas, providing heated covers in very cold areas, and providing
          heated buildings over the aerators or over the whole ditch in
          extremely cold areas.  When installed inside buildings, a shield
          should be provided over aerators to control spray.

     5.   In areas with periods of very cold weather all equipment requir-
          ing regular maintenance or service should be housed.

     6.   Poor mixed liquor settling was experienced during winter months
          at several plants in cold weather locations.  This was probably
          due to filamentous growths resulting from the low winter loadings.

     Waste activated sludge handling requirements depend on the plant de-
sign and operation.  Plants operated with a 24-hour channel hydraulic
retention time at 20 to 30 day SRT produce a biologically stable waste
sludge that can be handled without causing significant odor problems.
Plants operated with 6 to 8 hour channel hydraulic retention time and less
than 10 day SRT require additional sludge treatment, typically aerobic
digestion.  Some problems have been noted in dewatering activated sludge
directly on sand beds from plants operated at a 24-hour hydraulic retention
time.  These sludges tend to dewater very slowly requiring significantly
increased sludge drying bed area.  In areas where wet and cold weather are
common, sludge drying bed area should be even larger.  Some plants are
operated indefinitely without formal sludge wasting allowing solids to build
up in the aeration channel.  This type of operation is considered marginal
because the plant is prone to periodic clarifier upsets resulting in high
final effluent solids.

CONCLUSIONS

     Oxidation ditch plants are capable of consistently achieving high
levels of BOD,- and TSS removals with minimum operation.  High levels of
nitrification (95%-99%) are possible with proper operation.  Nitrogen
removals as high as 80% can be achieved in a single channel plant with
careful operation of the aeration equipment to produce aerobic and anoxic
zones within the channel.  Increased operator attention is required to
produce the high levels of nitrogen removal.
                                    193

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REFERENCES
     1.  McKinney, R.E.  Mathematics of Complete Mixing Activated Sludge.
         Trans. Amer. Soc. Civil Eng. , 128, Part III, Paper No. 3516 (1963).

     2.  Eckenfelder, W.W.,  Jr.; O'Connor, D.J.  Biological Waste Treatment.
         Pergamon Press, Oxford, England (1961).

     3.  Monod, J.  Research on Growth of Bacertia Cultures.  Herman et Cie
         Paris (1942).

     4.  Goodman, B.L.; Englande, A.J.   A Unified Model of the Activated
         Sludge Process.  Journal Water Pollution Control Federation,  46, 2,
         p. 312,  February, 1974.

     5.  Goodman, B.L.  Monod Type Relationships Applied to Complete Mixing
         Activated Sludge.  Unpublished,  January 25,  1973.

     6.  Draft Report.  Winter Performance of Secondary Wastewater Treatment
         Facilities.   EPA Region VII.
 "This paper has been reviewed in accordance with the U.S. Environmental
 Protection Agency's peer and administrative review  policies and approved
 for presentation and publication."
                                   194

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             PAPER NO. 14
PERFORMANCE AND DESIGN OF RBC PROCESSES
                  by

           Warren H. Chesner
                Partner
 Engineering Consultants & Associates
      Fort Lee, New Jersey  07024
                  195

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PERFORMANCE AND DESIGN OF RBC PROCESSES1

Warren H. Chesner, Partner
Engineering Consultants & Associates
Fort Lee, New Jersey

INTRODUCTION

     Rotating Biological Contactor  (RBC) Systems have been in operation in
this country treating municipal wastewaters for more than ten years.  Over
260 municipal wastewater installations were in operation as of 1979 with
design flowrates ranging from 0.01 mgd to 5^* mgd.

     RBC performance in terms of treatment efficiency, power requirements
and equipment have been almost exclusively defined by equipment vendors.
Vendors have provided design curves for both carbonaceous and nitrogenous
removal, recommendations for stagina and flow distribution, projected power
consumption and media, shaft and drive requirements.

     During the operating history of RBC's in this country, additional  in-
formation has become available through the literature and through the
collection of plant data from which to evaluate RBC performance and design.
This historical record has revealed relevant information which should as-
sist the designer, operator and vendor in evaluating, designing and opera-
ting RBC systems.

CARBONACEOUS BOD PROCESS PERFORMANCE AND DESIGN

     A comparison of cumulative performance versus vendor design guidelines
for sixteen RBC facilities approaching design flow revealed that RBC per-
formance was less than that predicted by vendor design recommendation for
average influent municipal  wastewater concentrations ranging from 97 to
21^ mg/1 BOD, with hydraulic loadings in the range of approximately 0.5 to
3.0 gpd/sf (1).

           1.  The absolute value of the vendor curves are based
               upon field data accumulated at specific locations
               which may not reflect RBC performance elsewhere.

           2.  Plant performance is the result of a series of
               unit processes.  Poor secondary clarifier per-
               formance would adversely effect recorded RBC
               performance.

           3.  Operation and maintenance practices at specific
               plants influence overall  plant performance
               which would reflect upon RBC performance.
1 Presentation based on a study by Roy F. Weston, Inc. for EPA MERL.


                                   196

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     Some of the specific process problems the facilities encountered were
the result of one or more of the following:

           1.  Unanticipated sidestream loadings

           2.  Low influent concentrations

           3.  High organic loadings

     Unanticipated sidestream loadings such as return supernatant from
sludge treatment processes or septage disposal can result in organic over-
loads to the RBC system.  These can be corrected by planning for the addi-
tional load by either increasing the RBC treatment capacity or better
equalizing the sidestream flow to the system.

     Low influent concentrations (less than 100 mg/1  raw BOD) are common in
sewerage systems with inflow/infiltration problems.  Lower organic concen-
trations with altered wastewater characteristics and treatability result
in reduced performance.   The solution to these problems again rests with
proper facility planning with respect to anticipated wastewater conditions.

     High organic overloads is a problem resulting from oxygen deficiency
within the biofilm.  This condition can result in the competitive growth
of nuisance organisms and reduced organic removal rates.  The condition
which results in an organic overload is dependent upon many factors.  For
a given media, these include rotational speed, influent flow distribution,
organic concentration, and flowrate.

     Rotational speed influences the film thickness,  the aeration of the
reactor liquid as well as the residence time per rotational cycle that the
biofilm is exposed to thp atmosphere and the reactor liquid.  Too slow a
speed can result in excessive residence time in the liquid, with little
oxygen ava i1able.

     Proper  influent flow distribution is necessary to evenly distribute
the influent flow and loading to all parts of the media, and to avoid over-
loading individual shafts or portions or shafts.

     Organic concentration and flowrate jointly determine the organic load.
Individually organic concentration determines the mass transfer driving
force, and flowrate the reactor or treatment retention time.  The greater
the organic concentration, the greater the demand for oxygen.  The greater
the flowrate, the shorter the retention and the higher the reactor organic
concentration adjacent to the biofilm.

     Organic overloads typically occur in the initial stages of RBC systems,
One vendor  (2) presently recommends a maximum first stage organic loading
of k.O pounds of soluble BOD per day per 1000 sf of media to avoid over-
loading in mechanically driven systems.  A review of twenty-three facili-
ties around  the country with and without the reported presence of organic
overloads for 12-foot diameter discs operating at rotational speeds of
approximately 1.6 rpm revealed a first stage loading of 6.4 pounds of BOD


                                    197

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(total) per day per 1000 sf as the first stage loading beyond which organic
overloads were reported (1).

EQUIPMENT AND MAINTENANCE

     RBC equipment can be subdivided into various components:  media, shaft,
bearings, drive and media supports (radial arms).

     Each vendor offers media with their own unique configuration.  In
general, there are two types of media:  standard and high density.  Stan-
dard density contains approximately 100,000 sf per 25-foot shafe, and high
density which is packed more tightly contains 150,000 sf per 25-foot shaft.
Disc media is constructed by extruding high density polyethylene  into in-
dividual sheets which are subsequently formed into the desired surface con-
figuration.  These individual sheets are cut into pre-shaped segments each
representing one-eighth of the total  circular disc.  Some manufacturers
group the pre-shaped slices together to form a wedge of media held in place
by penetrating rods or straps.  The wedges are supported by steel arms
radiating from the shaft.  As the shaft rotates, the steel arms  in turn
rotate the media.  A second method of construction is a unitized  self
fupporting plastic disc, mounted on and driven by a square shaft.  In this
case, the pre-shaped pieces are connected to form circular plates that are
welded together and mounted in the shaft.  A reinforced hub provides the
transfer of drive from the shaft to the media.  A third type recently in-
troduced consists of strips of high density polyethylene which are vacuum
formed, spirally wound and heat welded in a continuous wrapping  process on
a ci rcular shaft.

     The RBC shaft and media can be driven directly by motor (most commonly
rated at 7-5 hp) or by recently introduced air drive systems which make use
of the buoyant force of compressed air released into the reactor  to drive
the disc.

     A survey of equipment history in RBC facilities (1) revealed signifi-
cant problems with respect to the reliability of certain components of the
system.  A summary of the results of this survey are presented in Table 1.

     The results indicate an unusually high percentage of shaft  failures
(8.5%), with almost all occurring in the first stage where higher loadings
and heavier growth occur.  Bearing problems were not significant, but re-
ported radial arm problems (30%) were high.  Reported medial problems were
most commonly reported in radial arm facilities (80%), the result of a
shifting of the media, relative to the radial arm.  Drive problems were not
major.  The average years of operation prior to reported problems were low
in all cases, which is indicative of design deficiencies as opposed to
normal equipment wear.

     Solutions to equipment problems rests with both the vendor  and the
engineer to insure that the equipment is specified properly and  utilized
within its design limitations.
                                   198

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      A survey  of maintenance requirements,  presented  in  Table 2,  revealed
little manpower requirements directly attributable  to  RBC maintenance or
process control.
   Equipment
   Shaft
                       TABLE 1.    RBC  EQUIPMENT  SURVEY
No. of             Percent
Facilities  Reported  Reporting
Surveyed    Fa!lures  Failure

  17
                                         No. of
                                         Shafts
                                                          Percent
                                                  Shaft     Shaft
                                                  Failures  Failures
                                                   12*
                                                           8.5
                                                          Percent
                                         No. of   Bearing   Bearing
                                         Bearings Failures  Failures
                                        Average Years
                                        Of Operation
                                        At Failure

                                             1.9
   Bearing
   Radial Arm
                17
                                 18
                                 50
                282
               No. of
               Shafts
                 23
                                             3.3
                                                 Radial
                                                 Arm
                                                 Fa i1ures
                                            Percent
                                            Radial Arm
                                            Failures

                                              30
   Media
   Drive
                17
                17
5-**
                    29
                                 18
                                                          Percent
                                         No. of    Chain    Chain
                                         Shafts    Failures  Failures
                                           1M       8       6
                                             2.3
    * Of the 12 reported shaft failures, 11 occurred in the first stage.
   ** Of 5 facilities with media problems, k were radial arm type.

                        TABLE 2,  MAINTENANCE  REVIEW
No

. of Plants
Surveyed
20
k
No. of
Shafts
2-8
10-*<8
Equipment Maintenance
Man-Hours Per Week
0.25-7
3-13
POWER  PERFORMANCE
      Energy utilization  is rapidly  becoming  the major  O&M item  in  many
wastewater treatment facilities.   Selection  of  processes  with low  energy
requirements  is  a major  priority.   A power survey of seven mechanically
driven  systems  revealed  an average  power requirement of approximately 3-^
for  a  25-foot  shaft with standard  density media and 3-8 kw for a 25-foot
shaft with high  density  media.  Table 3 presents the results relative to
reported vendor  values.
                                                                                 kw
                                      199

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       TABLE 3.  MANUFACTURER POWER ESTIMATES AND FIELD OBSERVATIONS
Manufacturer
Autotrol
Clow
Hormel
Walker
Average Field
Power Requi
Standard Media
2
2.k
2.3
2.5
3.*»
rements (kw)
Hi -Den si ty Med i a
3
2.6
2.6
3.1
3.8
             Observat ions

     Energy utilization will vary from stage to stage in RBC facilities
with the initial stages utilizing more energy than the latter stages.  This
was judged to be due to the greater friction resulting from heavier growth
on the media.  Power requirements were also found to be proportional to
the third power of the rotational velocity, which limits the cost effec-
tiveness of increased rotational speed to enhance treatment performance.

CONCLUSIONS

     The operating history of RBC facilities has revealed design limitations
with respect to organic overload, a suspect record with respect to equip-
ment problems and higher than anticipated power requirements.  Additional
care is warranted in the selection and the design of the RBC process for
municipal wastewater treatment.  Sufficient facility information is avail-
able for designers to assess the loading requirements, equipment history,
and power requirements of the process.  Vendors must address equipment
deficiencies which should not be limiting to RBC performance.

REFERENCES

     1.  Review of Current RBC Performance and Design Procedures;
         EPA-MERL; to be published in 1982

     2.  Autotrol Design Manual; 1979
  "This  paper has  been  reviewed in  accordance with the U.S.  Environmental
  Protection Agency's peer and  administrative review policies and approved
  for  presentation and  publication."
                                   200

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SESSION NO. 5
   Energy Conservation in Municipal Wastewater Treatment
                                PAPER NO. 15



                    ENERGY CONSERVATION  IN UNIT PROCESSES


                            AND SLUDGE MANAGEMENT
                                     by


                              Daniel Cortinovis
                        Operating Services  Department
                              Brown  and Caldwell
                        Walnut Creek,  California  94596
                                     201

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ENERGY CONSERVATION IN UNIT PROCESSES AND SLUDGE MANAGEMENT

DANIEL CORTINOVIS,  OPERATING SERVICES DEPARTMENT
BROWN AND CALDWELL
INTRODUCTION

     The  key link  between  a valid  design  concept  for energy-efficient
wastewater treatment and the  realization of that  goal  is  the  treatment plant
operator.  His  understanding  of  the processes and  equipment  systems  and  his
ingenuity  in dealing with changing  conditions  make energy conservation  and
recovery  possible.    He needs  a  grasp  of the  interrelations  between unit
processes and their costs in dollars and energy so he can  fine-tune the plant
to optimize  the use of our resources.

     All of  the wastewater treatment plants in the United  States consume only
about 0.25 percent  of  the nation's electricity, but that  amounts  to  several
hundred million dollars worth of  energy.  As this  figure increases  and energy
supplies  continue to  dwindle,  more emphasis is being  directed  toward energy
conservation in plant design and  operation.

     Since most  treatment  facilities  depend largely on electricity as their
source of energy, this paper will begin by defining in  general how  power rate
schedules  are  set  up.   Treatment plant  operators need  to  understand  the
methods used to  compute  the plant's power  bill  so that they can direct their
energy-saving efforts toward cost-saving as well.

     Examples of energy-conservation  techniques  used  in  various  plants  are
described using generalized case  examples.   The operator's role  in  optimizing
the use  of  energy is the focus  of  these discussions,  with emphasis on areas
such  as  biological  treatment,  solids handling,  and  energy  recovery.   The
intent of  this  presentation  is that operators will  relate these examples  to
situations  in   their  own  plants  to aid  them  in devising  programs  for
conserving energy.


POWER RATE SCHEDULES


     In past years, before there  was commonly  thought to be an energy  crisis,
large  users  of  electrical  power  received  discounts   as their consumption
increased.   This  encouraged industrial  growth  and increased power  generation
by the utilities.   Because of regulatory pressure and  the increased emphasis
on conservation, rate schedule structures have not been drastically revised.

     A.  Energy and Demand

     Energy  is defined as the  quantity  of  power used per  unit time, measured
as kilowatt-hours (kWh).  Demand  is an instantaneous measurement of the power
being used at any particular  time.   It  is measured in kilowatts (kW), which
can be related  to the effective  horsepower of  the  equipment  in operation at
the time.

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     An energy charge is  made for  each kWh  used to pay  the utility's
operating  costs for  generating the  power.  A demand  surcharge may  also
be assessed each billing period,  based on the maximum  demand sustained
throughout  a specified time  interval such as 30 minutes.  This surcharge pays
the  capital costs  for having generating capacity  available to meet  the
demand.

     B.  Time-of-Day Demand

     In areas where the demand threatens  to exceed  power production capacity
at certain  times,  a  sliding scale  is  being  used to adjust the  demand
surcharge to the time  of day and the season.  This  is intended to discourage
large customers from creating  a high demand during peak times, such as summer
afternoons  when a  large number of air conditioners are running.

     Some  manufacturing  operations  are  probably  able  to  adjust  their
production schedules to  avoid peak  demand periods, but doing this  in a
wastewater  treatment plant requires a lot of ingenuity because of the lack of
control over incoming  flow and loadings.  However, some possibilities are:

     1.  Flow storage  prior  to treatment.

     2.  Shutting  down  solids processing during demand peaks  and  catching
         up later.

     3.  Storing digester  gas  or other fuel and  generating power during peak
         demand periods.

     An example of  a peak-period demand surcharge schedule  for a plant with a
monthly demand greater than  4,000 kW is shown below.
          Demand charge per  kW                Summer

     On peak (early summer and  late
     winter afternoons)                      $4.20

     Partial peak (mornings  and evenings)      0.35

     Off peak (nights,  Sundays,  holidays)      None

     C.  Other Charges
Winter


$2.80

 0.35

 None
     Several  other  factors which  affect  the dollar amount  of  the monthly
power bill are:

          Customer  charge—A  flat rate  service  charge for each  metered
          connection as assessed.

          Voltage adjustment—Customers  taking  delivery  at  voltage higher
          than 2 kV  may get a demand charge discount.

          Power  factor—The  ratio  of lagging  kilovolt  ampere  hours  to
          kilowatt  hours  consumed  increases  or  decreases the  total  bill,
          depending  on how much it  deviates  from a specified ratio  (usually
          about 0.85).
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          Facility  charge—If the  utility  spends more  constructing  service
          facilities  for  a customer  than they  receive  in  revenue, an
          additional  charge may be made  as a percent of the excess.

          Energy cost adjustment—A  variable  charge  per  kWh  is made  to  cover
          changes in  the  cost of  fuel used to generate power.


ENERGY-SAVING TECHNIQUES


     Specific methods  for  trimming energy  costs  are outlined  below,  using
generalized case  examples based  on  actual operating plants.  With  some
techniques,  the cost  savings  result  from reduction  in demand peaks.   In most
cases,  an overall  reduction  in  energy consumption is the primary method of
saving money.  The  most  important aspect of an energy conservation program is
a  total  system  approach.   For  each  operational  change  initiated  to  save
energy, the whole facility  must  be  considered to ensure  that a corresponding
increase does not occur  in  another area.

     A.  Power Monitoring

     Relatively  inexpensive  instrumentation  is now  available  for  constant
monitoring of  both  energy  use  and  demand.   Installation  of monitoring
equipment at the plant's incoming substation and at individual motor control
centers  supplies  on-line  information to  the operations  staff,  telling
them how much  power is being used in which  areas.  This  information is
essential, especially if time-of-day  demand peaks  are being  shaved  through
operational modifications.    Where   digital  computer  systems (or even  small
microprocessors) are  available,  the  data can be trended  and  totalized to aid
in interpretation and record keeping.

     B.  Unit Capacity Optimization

     Plant managers should  carefully evaluate process operations  to determine
when treatment  units  should  go  in  and out of  service,  especially in plants
where  the load  changes  seasonally.    Although  short-term  fluctuations in
loading may  not dictate changes, anticipation  of  and response   to  seasonal
variations can  save  significant  amounts of  energy while still  maintaining
effluent  quality.   Accurate judgments  are  required—for instance,   cutting
back on  anaerobic  sludge digester  mixing may  save only minimal amounts of
energy while causing  a  disastrous  upset.   In  contrast,  secondary treatment
units  such  as  activated  sludge aeration  tanks  and high-head oxidation
towers  are very energy intensive  and should  not be  operated  far  below design
capacity.   Clarifiers,  on  the other  hand,  require  a very  small amount of
power and may enhance treatment  efficiency when multiple units  are  operated
at low overflow rates.

     A municipal secondary  treatment plant using high purity  oxygen activated
sludge  was designed for  120  million  gallons  per day  (mgd).  The   flow
configuration uses  8  biological  reactor trains and 12 clarifiers.   Although
the  nominal design  flow  for  each reactor train  is  15  mgd,  the oxygen

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dissolution capacity  is  adequate  for at least twice that  to handle seasonal
load increases  and  a possible  future  requirement  for  nitrification.   Since
each of  the  eight trains uses  400  horsepower (hp) of mixers,  a  significant
energy savings  is realized  by  operating only three or  four  trains  for the
actual average  dry-weather  flow  of 80  mgd.   All available  clarifiers  are
used, since  they  have only  1-hp  drive motors.   During low loading periods,
mixers on some stages can be shut down, saving up to $5.00  per hour each.

     C.   Aeration Blower Control

     In most  conventional  activated sludge plants, the largest consumers of
energy  are the blowers or  mechanical  devices used  to supply  air  to the
aeration tanks.   Many plants in past years  were designed with strictly manual
control of the aeration system,  due  to the  following factors:

     1.   Reliable  on-line   instruments  for measuring  the  dissolved  oxygen
         (DO) level  of  the mixed liquor in the  aeration tanks  were not yet
         available.

     2.   The  cost of energy was much  lower  than now,  as compared  to the
         relative cost of instrumentation systems.

     3.   The  state  of the  art  of activated sludge process control was  less
         advanced.

     Now that energy  costs  are  high and DO control  systems fairly reliable,
the majority of new plants  are  being designed with these  control  systems and
many agencies are adding them to  their existing  plants.   Although there  have
been some  attempts  to control  mechanical  aerators by  DO level,  most of the
current  systems  use  diffused  aeration with suction-throttled   centrifugal
blowers.    An electrical signal  from the DO  probes  in the tanks is usually
converted  to  a pneumatic  signal which  controls  automatic air  distribution
valves on  the headers to each  aeration tank  pass.  A  pressure sensor on the
blower  discharge manifold  upstream  of the  distribution valves  controls
the  inlet  guide vanes on the blowers  to maintain  a constant pressure in the
manifold.  Analog or digital control loops  can be used.

     The energy  consumption is  reduced  with  DO control because  centrifugal
blowers use  less  power  when the suction  is  throttled.   The turndown limit
(surge point)  is usually  about  50 percent  of  design capacity,  so several
blowers  of different sizes may be used  to  provide  a better  coverage of
operating ranges.   The activated sludge process is subject  to upset at low DO
levels,  so controlling  the  DO at higher levels  for higher  loadings protects
effluent quality.

     Many oil refineries have activated sludge systems  for treatment of their
process  wastewater.    For  two   systems  which  originally  used  single-speed
mechanical aerators with no control  systems, studies showed that  installation
of  completely  new aeration  systems using   DO control  with diffused  air and
centrifugal  blowers  could  save enough  in power  costs  to pay  for  the new
equipment in several years.  Some particular considerations which  contributed
to this analysis were:


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     1.  Due  to the  cyclic nature of  refinery  processes,  the incoming
         waste load varies  widely  over periods of short duration.

     2.  The temperature of the wastewater is unusually high  which cuts into
         aeration  efficiency and  makes   a  more  efficient system  more  cost-
         effective.

     D.  On-Site Power Generation

     The current emphasis on the environment  and energy has focused attention
on  the  production of  "bio-gas"  from digesting  organic  matter.   Municipal
waste  treatment  plants  have used  the  anaerobic  digestion process for  over
50  years to  stabilize sludge before  utilization  or disposal.  The  gas
produced, containing about  65  percent methane,  has been  used  in  boilers to
produce  heat  for  the  digesters and plant site  buildings.   In some  larger
plants, the excess gas  is used  to  generate  power.

     One problem  with  using digester gas  for power generation is the  high
initial  capital cost  and   high  maintenance   costs  for  large  reciprocating
engines.   Another  problem,  particularly  with primary plants, has  been  that
the greatest excess of  gas  is available in  the summer, when heat requirements
are  less  and  power requirements  lower  due to decreased  flows.   Experience
with engine-generator design and the development  of gas turbines have  helped
to minimize maintenance costs.   Some plants  expanded  to  secondary treatment
have found a drastic  shift  in their  seasonal  energy requirements, with  summer
peaks  occurring  for  biological treatment  of food  processing  wastes.    The
advent of  cogeneration, where  induction  generators  are  operated in parallel
with  utility  power,  will  also contribute   to  the  cost effectiveness  of
installing on-site power generation  systems.

     A 55-mgd primary and  secondary plant  located  in  a largely agricultural
area  treats  a  mixture of  domestic sewage   and  seasonal cannery wastes.
Methane gas  from anaerobic digesters is  used to fuel three piston engines
driving variable-frequency  generators.  Two generators power the effluent and
effluent pumps  using  the  variable-frequency  feature  to  control  pump  motor
speed.   The  third unit powers other  plant equipment when  extra  gas  is
available.   In  1980,  36 percent of the  power used in the entire plant  was
generated on-site at  a  savings  of  over $150,000.  Hot water from the engines'
cooling system  is  circulated through a  reservoir  loop  to heat  the digesters
and plant buildings.

     E.  Heat Reclamation Systems

     Heat is produced in some treatment  plant processes while being required
in others.   Waste heat  can  be recovered in  large quantities from incinerators
boilers, and  engines.   It  is  transferred  in  water  to  heat  sludge digesters
and  plant  buildings  or  in steam to power turbines driving mechanical
equipment.   Operational  control  is critical  because  the systems   are  often
complex,  with  the balance between heat requirements and  availability
constantly  changing as  changes occur in  plant  load,  flow,  and ambient  air
temperature.

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     One type  of  system uses a  hot  water reservoir loop to circulate waste
heat  from  digester  gas-powered  engines  to  digester and  building  heating
systems.   Thermostatically  controlled  valves  and  pumps regulate  the flow
of water  to  the  various  units.    A  balance in  the  system  is  maintained  by
disposing of  excess heat in exchangers located  in the  wastewater flow stream.
In emergencies,  heat  from  auxiliary boilers  or resistance-type  electrical
heaters  is  added.   Because no  automatic system can  anticipate  changes  in
variables such as digester  gas  availability  and  ambient  temperatures,  the
experience of  the  operators  is  relied upon for  judgments as to when engines
should be started or control set points  changed.

     F.  Solids Handling Trade-Offs

     The push  for  secondary  treatment expansions mandated  by the  1972 Water
Pollution Control  Act  often resulted  in  a decrease  in  emphasis  on  solids
handling and disposal.   Now that many  new secondary plants are on line,  the
full impact of increased sludge production and  changes in  its characteristics
are  being  realized.   Processing  and  disposal  or  utilization  of  solids  is
rapidly  becoming  the  most  cost-  and  energy-intensive aspect  of  wastewater
treatment,   especially  as  urban sprawl increases  the  distance  between
treatment plants and land areas available for disposal.

     The operator's success in reducing the overall  amount of energy consumed
in  solids  handling  processes  will  depend  on  his recognition of  the
relationships between trade-offs in which he can make  choices.   Some examples
of these follow:

     1.  Vacuum or  belt  filters are  very  energy-efficient devices  for
         dewatering some types of  sludges.   Correct  chemical conditioning of
         the sludge  is  critical  and relates  to energy  use  because  higher
         production and  lower moisture  content mean  shorter running time for
         equipment and lower offhaul costs.

     2.  The use of centrifuges for dewatering digested primary  and secondary
         sludges   is  becoming  more  common because  of  the difficulty  in
         thickening  these  sludges.  When  centrifuges  are  operated  at  a low
         capture,  the  operator may have the illusion  that he is producing  a
         lot of  cake at a  low  chemical dosage.   He should realize that the
         cost  and  energy penalty  is high for  this because solids recycled
         through the plant have to be retreated and  reheated in  the digesters
         before  he gets  another  chance  to remove  them.    In-plant  solids
         recycle is also a major cause of effluent quality degradation.

     3.  When  sludge  is to  be  incinerated,  dryness is usually of paramount
         importance  because  large amounts of  supplemental  fuel are  required
         when  excess water is fed  to the furnaces.  Most dewatering equipment
         will  produce  a drier  cake  at  lower  throughput,  so it becomes the
         responsibility  of the  operations  staff to  operate more  dewatering
         units on  a longer schedule  if  the trade-off is favorable.

     4.  The difference  between  being able  to  use a low-energy  land disposal
         or  composting operation  or  a  higher technology,  more  energy-
         intensive alternative often depends on  the  operator.  He  can  ensure


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         adequate  sludge stabilization  through  efficient  process  operation
         and develop favorable  public  relations  by taking prompt  action  on
         odor and  nuisance problems.

     G.   Pumping and Hydraulics

     Operators  cannot  be  expected to  redesign  the hydraulic  profile of  a
treatment  plant,  but  they  can often  save energy by making  some  simple
adjustments.  The approach of the  design  engineer  is  usually  to conserve  as
much pumping head as possible in equipment and structure design, since it  is
estimated that  each  foot  of  head will  cost  about  $500 per year per  mgd  in
energy.   However,  the  design must  allow  operational   flexibility  and leave
room for possible future expansion, so pumps are sometimes oversized and head
losses designed in.

     Treatment units  such  as  synthetic  media oxidation towers (modern
version of the "trickling  filter")  depend  on  recirculat ion  pumping for
aeration and  contact  between  waste  and microorganisms.  Using frequent
loading  rate  calculations, the  operator can adjust the  recycle  rate  to  the
minimum  necessary to maintain process  efficiency.   Excess recirculation only
wastes  energy  and  will not   increase removals.  This  also applies  to  return
activated sludge  pumping.   It may be easier  to  crank the pumps up  to high
speed  and   forget  about  them,  but  careful  sludge  blanket monitoring  will
result  in an increase in solids  concentration, which will  allow lower pumping
rates.
SUMMARY


     1.  Wastewater treatment plants  in the United  States  depend  primarily
         on  electrical  power  as  a  source  of  energy,  consuming  about
         0.25 percent of  the nation's  total.

     2.  The size  of  the monthly  power bill  depends  on the  amount  of energy
         used  and  the magnitude  of  the  demand,  as  well  as  several  other
         factors.

     3.  Plant  operators  need  to understand  the  energy  interrelationships
         and individual impact of variables under  their control so  that they
         can fine-tune the  treatment  processes  to reduce energy consumption.

     4.  Some energy saving programs  and techniques currently in use are:

         A.  Shaving demand peaks  by  careful  operations scheduling.

         B.  Optimizing process units  to  reduce the amount  of equipment  in
             service.

         C.  Aeration equipment  control automation by dissolved oxygen level.

         D.  Power generation using gas from  sludge digesters.
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    E.  Reclaiming  excess heat  from mechanical systems, such as
        engines  and incinerators.

    F.  Evaluation  of  solids handling  energy trade-offs.

    G.  Conservation of  hydraulic  head.
views of the

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               PAPER NO. 16


A COMPOSITE APPROACH TO ENERGY CONSERVATION

       THROUGH PROCESS OPTIMIZATION


             SOME CASE STUDIES
                    by

          Ashok K. Singhal, P.E.
         Vice President/Treasurer

                    and

              Phillip N. Loud
                 Engineer

                    and

          Donald W. Lystra, P.E.
              Vice President
     Ayres, Lewis, Norris & May, Inc.
        Ann Arbor, Michigan  49481
                    210

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A COMPOSITE APPROACH TO ENERGY CONSERVATION
THROUGH PROCESS OPTIMIZATION
Some Case Studies

Ashok K.  Singhal,  P.E.,  Vice  President/Treasurer; Phillip N.  Loud, engineer;
and Donald W. Lystra,  P.E., Vice President
Ayres, Lewis, Norris & May, Inc.,  Ann  Arbor, MI


INTRODUCTION

    Municipal wastewater systems are heavy  users of  energy, not only directly
through the  use  of electricity, natural gas,  and  other fuels but indirectly
through the  use  of large quantities of chemicals produced by energy-intensive
manufacturing  processes.   Table  1   summarizes  energy  consumption for  the
manufacturing of the various chemicals used  for wastewater treatment.  A recent
study by  the U.S.  Office  of  Water Research and Technology  showed water and
wastewater systems to  be the largest single component of energy consumption by
local units  of government,  averaging  about 25 percent of the total municipal
energy  use (1).    Moreover, recent utility rate studies have shown that the
direct energy costs of wastewater systems account for fully 20  percent of their
total operating  budgets  (2).

    During the past three  years, Ayres, Lewis, Norris &  May, Inc., (ALNM) has
performed energy audits for eight wastewater treatment facilities  in Michigan.
This paper summarizes  the  findings of  the energy audits.  The main objectives
of these  audits  have been  threefold:

    —   to establish  energy  consumption profiles  of the buildings  and the
        treatment  processes;
    —   to identify,  analyze,  and rank cost-effective  retrofit measures and
        operational and  maintenance strategies which will conserve energy;
    —   to develop an  on-going  energy  management program.

ENERGY AUDIT METHODOLOGY

    An energy audit is defined as a critical examination of an energy-consuming
facility  for the  purpose of identifying  energy conservation opportunities.
Because of the  overall  complexity of  wastewater facilities  and the various
technical specialties  represented  by their processes and equipment, the audits
were  broken  down  into smaller  components.   This made  it possible to create
specialized  audit  packages  that  could be addressed  by  team  members  from
appropriate  technical  fields.   The following subsystems  were identified.

    Treatment System:     all  processes and  equipment used to treat wastewater
    and render it  suitable for  discharge into  the receiving stream.

    Capacity Control  System:    equipment  used for  pumping wastewater  at
    various  points in  a  treatment  process.

    Heating,  Ventilating,  and  Air Conditioning  System (HVAC):    equipment
    that  provides  the  control for  the  internal environment  of buildings,
    including the  building envelope itself.

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    Electrical  Systems:     equipment that  distributes electricity  to plant
    loads and provides artificial illumination for the interior and exterior of
    the facility.

    An auditing team of technical specialists in civil, sanitary,  mechanical,
and electrical engineering,  as well as architecture, was created to perform the
energy audits at each of the study sites.  The auditing procedures involved a
review of  existing  documents and records, site  visits,  operator  interviews,
identification of energy conservation opportunities  (ECOs), analysis of ECOs,
and reporting.

    Audit  team members  were instructed  to look  for ECOs in the following
general areas:  changes to operational and  maintenance strategies; equipment
changes  (i.e.,  same function,  different  device);  design  changes  (i.e., dif-
ferent function, different  device);  and  relaxation or modification of design
standards.

DESCRIPTION OF STODI SITES

    Table 2 summarizes design capacity, service area population and the  type of
treatment  for the  eight  sites studied.   All  facilities rely  primarily on
electricity  and natural gas for  their  energy requirements except Ann Arbor
which also uses fuel oil.   Electricity is typically  used as the energy source
for motor  drives and  illumination,  whereas  natural gas is used as the energy
source for  building heat,  water heating, digester  heating,  sludge incinera-
tion, and chemical  pretreatment.

    The breakdown by  energy source  of total energy consumption at each study
site is given in Table 3.   The  breakdown of energy consumption for each site
within the  four functional  subsystems is shown in Table 4.  In general, more
than half  of the energy used by  the wastewater facilities is for treatment
equipment and relatively little for pumping.   The total energy  consumption and
energy cost per cubic  meter  of water treated at each of the  facilities is given
in Table 5.  As shown in the table,  these  costs vary from $57 per million gallon
at Wyoming, Michigan,  to $133 per million gallon at  E. Lansing, Michigan.

PROCESS OPTIMIZATION

    In the process of identifying energy conservation opportunities  at the
wastewater treatment plant sites,  it was  recognized that the treatment  systems
account  for  50 percent or  more of  the  total energy consumed at  a wastewater
plant.   As shown in Table  4,  at  the eight  sites  studied, treatment  systems
accounted for 44 percent of the total energy consumed at Wyoming,  Michigan, to
75 percent at Ann Arbor, Michigan.  In addition,  treatment systems  also  utilize
considerable  amount of  chemicals  which  have an  indirect impact on  energy
consumption through manufacturing and transportation. Therefore, it was recog-
nized that  process  optimization should be a very integral part  of an energy
audit plan at a wastewater treatment plant.  Process optimization would  serve a
dual purpose of conserving  energy, as well as chemicals.

    A six-step model for treatment process optimization used during the energy
audits is  summarized  in  Table 6.   The  first  step  is to review historical

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records from a  treatment plant to establish the present plant performance in
terms  of  influent  water  quality  parameters,  chemicals  used,   and process
performance parameters  for each of  the  unit  processes.   This information is
generally obtained from the monthly operational summary sheets submitted  to the
State  regulatory  agencies.   The  data is  summarized both graphically and in
tabular form to establish  trends and history.  Figure  1 provides  a summary of
operational records for the Cadillac, Michigan, Wastewater Plant as an example.

    The second  step is  to  compare the plant  performance parameters with the
expected  design  performance  for  each  unit  process.    In  this process,  a
comparison of the actual plant efficiencies is made with the expected  design
efficiencies.   In addition, during  this stage,  marginal  utilities   of adding
various chemicals in the processes are also established.  Marginal utility is
defined by the following equation  in reference to  Figure 2:

                                        Ay
                 Marginal Utility   =
                                        A
                     where   £> y  =   increm ental removal of a pollutant
                            ^x  =   incremental cost of the chemical to
                                    remove a pollutant

    In general,  the idea is  to  add a chemical to a point where the marginal
utility is one,  or more than one.  If from reviewing the historical  records, it
is found  that the marginal  utility for some of the  chemicals  is considerably
less than one in  actual plant performance, it  would  be an indication of gross
process inefficiencies and  deficiencies.   Thus,  Step  2, would generally pro-
vide a fairly good  idea regarding  the  processes that are performing less than
optimally.

    The third step  in the  process optimization is to  review the physical and
chemical parameters effecting each unit process.   The  purpose  of this step is
to identify and pinpoint the reasons for poor performance of the unit processes
identified in Step  2.  As an  example,  at one of the treatment sites studied,
ferric chloride was being added in the aeration system for phosphorus removal.
Considerable amount of chemical  was being  used without achieving the desired 80
percent  phosphorus  removals.    After  reviewing  the  physical  and chemical
parameters associated with mixing and flocculation of the  chemical,  it was
discovered that the aeration system was resulting, in excessive shear velocities
(G) resulting  in G values of  130 to  150 sec— ,  thus  breaking  up the floe
particles.   As  a result  of the investigations,  the chemical feed point was
moved  toward  the tail-end  of the aeration system and the  amount of air was
reduced to provide  a shear velocity (G) of 60  to 65.  This change resulted in a
considerable  improvement in  phosphorus  removals  as  well  as the amount  of
chemicals used for phosphorus removal.  Prior to initiating this change, 80 mg/1
of ferric chloride  was being  used  along with 0.5 mg/1  polymer.  Subsequently,
ferric chloride  dosage was  reduced to 50 mg/1 and the polymer was eliminated
completely.   In another  instance,  the  chemical percipitation  process was
resulting in a poor floe formation during the  winter months of operation.  It
was noted that  fine pinpoint floe was being formed  which was  not  coagulating
properly.  Investigations of the parameters effecting the flocculation process
indicated  that   the plant  had  a  fixed  speed floe  mixer  providing adequate


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flocculation energy during the warmer months but was not capable of providing
the necessary energy for flocculation during the colder months.  It was noted
that with the falling water temperatures,  the viscosity of  the wastewater went
up by approximately  50 percent resulting in  a similar increase in the power
requirements for flocculation as shown by the  following formula.  A change in
the flocculation process improved the results  considerably.

                  G =~yP/u.V where G=mean velocity gradient (sec^) ,
                                                  P=power required (ft-lb/sec)
                  jaat 20 C (58 F)  =   1.009    >i=absolute fluid  viscosity
                  juat 5°C  (1M°F)  =   1.519
                                                  V=f locculator volume  (cu ft)
    The  fourth  step in the  process optimization is to review alternate ap-
proaches for achieving process results in order to conserve energy as well as
chemicals.  The purpose of this step is to see if a particular process  can be
changed or altered to achieve the  desired results at a lower overall cost.  An
example of this would be changing  a chemical  feed point in the process  or using
alternate chemicals.  At one  of the treatment sites,  lime was being used for
phosphorus  removal.   Because  of  the  high  hardness   of the  wastewater,  a
considerable amount of lime was being added to achieve desired 80 percent re-
movals.  Lime also produced large quantities  of sludges.  Replacement of lime
with ferric chloride resulted in considerable energy and  cost savings.

    Once an  alternate  approach has been identified  for a process, the fifth
step  is to conduct  lab scale  studies  using alternate  chemicals or process
parameters for achieving the desired results.   The purpose of the  lab tests is
to  provide  adequate data for evaluating  cost effectiveness  of a particular
change  being contemplated.    It should be  noted that  the lab  tests  should
reflect  the actual operating  conditions as closely as possible.   For example,
if a given treatment process is operating under low temperature conditions, the
lab  tests should  also  be  performed  under   similar temperature conditions.
Following the lab scale studies and a cost effectiveness analysis  of alternate
approaches being  considered,  a decision should  be  made regarding conducting
full plant scale studies which is  the sixth and final step.  In conducting full
plant scale studies, it is very important that process parameters  be monitored
very closely and be evaluated  in terms of the  changes that  are being made. As a
result of the full  plant scale studies,  if the proposed  changes are found to be
cost effective, they should be implemented.

IDENTIFICATION OP ENERGY CONSERVATION OPPORTUNITIES

    In  order  to identify the energy conservation  opportunities at the study
sites, the following conceptual model of energy consumption was utilized:
     Energy Source In       Conversion System          Function Out
 (e.g.,  electricity,  gas)    (e.g.,  light bulb,      (e.g., light, motion,
                           motor,  boiler, etc.)           heat)

                           Energy Consumption Model
                                     214

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    As the model illustrates,  energy  enters  a  conversion  system and is trans-
formed  into  a  useful  function.   Therefore,  there  are three basic  ways to
conserve energy and/or cost which  correspond to  each phase  of the model.

    1.  Use a Less  Expensive Source:
            —   change fuel
            —   use off-peak electricity
            —   use waste energy
            —   use renewable  source  (solar, wind, etc.)

    2.  Increase System  Efficiency:
            —   improve  performance
            —   improve  maintenance
            —   change equipment

    3.  Modify Functions:
            —   eliminate unnecessary functions
            —   retain function but use less
            —   substitute less expensive  function

    Based  on the   above  conceptual  model as a guide,  energy  conservation
opportunities were identified at each  of the study sites.  These can be divided
into  low  cost  or  no cost  energy conservation  measures  and those requiring
capital  investment  for  implementation.   Low  cost  measures are  typically
operational measures which cost less  than $500 to implement  and have a payback
period of less than one month.  The most commonly  encountered low cost measures
in each of the four functional areas  are discussed below:

Architectural

    Low  cost architectural  measures   typically  involve insulating,  weather-
stripping, caulking, and repointing.  These measures  generally serve to reduce
infiltration or slow the rate  of heat transfer through  a  structural membrane.
These measures can  be implemented  by  plant staff and  result  in savings in the
annual heating  load.   Implementation  costs for most  facilities are generally
$100 or less.

Heating, Ventnating and Air Conditioning

    Three major low cost energy conservation  measures  in the  HVAC subsystem are
identified in almost every  wastewater treatment  facility.   These  measures
include dialing down temperature settings,  reducing outside  air flow, and fine
tuning boiler burners.

    Dialing  down  plant  thermostat settings  plantwide  from 72° to  68° will
effectively reduce  the  plant  heating  load  by approximately 9-10 percent.  In
many cases, certain areas  can be  heated to even lower  temperatures providing
even greater savings without any implementation  cost.

    Reductions  in  outside  air quantities of 10-50  percent  are  typically
proposed in wastewater  plants  equipped with  heating  systems utilizing mixing
air boxes.  These changes have resulted in heating load reductions of up to 20
percent.
                                     215

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    Fossil fueled boilers are typically operated with too much excess air and
potentially dirty heat exchangers.  Inexpensive flue gas testing kits costing
around $200 have been utilized to  fine tune boiler operations to improve burner
efficiencies by 2-4 percent.   A plant with a $10,000/yr boiler fuel cost would
pay for the test kit in one year with a 2 percent increase  in efficiency.

Treatnent Process Systems

    Low cost operational changes to the  treatment  process systems which result
in energy savings typically involve the  operation  of more efficient pumps, the
reduction in chemicals fed through process optimization as  discussed earlier,
or a reduction in total aeration requirements.

    Variances in operating efficiency of redundant pumps, identified  during an
energy  audit,  often  result  in a  low  cost  measure  recommending increased
operation  of  the most efficient  pump.   Similar  pump  efficiencies may often
differ  by  3-7 percent  depending on age  and  utilization.   A  three percent
difference  in  efficiency  for a 50 hp pump  running continuously represents a
potential savings of $960 annually ($0.05/kwh).

    Reductions in quantities of chemical fed does not typically result in large
direct energy savings.  However, the secondary impacts on sludge production and
process efficiency  can potentially result in  large  energy savings.

    Aeration systems in wastewater plants typically represent 30-60 percent of
total plant electrical energy consumption.  An analysis  of the air requirements
for  several activated  sludge  plants has resulted in an  identification of
potential reductions  in aeration  levels of 12-27  percent  at cost savings of
approximately $3,000-$3i*,000 annually.   Figure 3 shows  an example of potential
for reducing air at a wastewater  treatment plant.

Elfictrical/niunlnatlon Systems

    The  most  common  low  cost  energy  conservation  measures  applicable to
electrical/ illumination systems fall into the categories of lamp replacement,
delamping, and fixture cleaning.

    Many wastewater plants utilize standard  fluorescent  lamps for operating
areas,  as  well  as  pipe galleries.   Reduced  wattage  fluorescents typically
consume  20 percent  less  power and  cost  approximately 33  percent more  than
standard bulbs.  A  program of replacing standard fluorescents when they burn
out  with reduced wattage  bulbs  provides  energy savings  capable  of 6-month
paybacks for each bulb.

    Regular  cleaning of fixture  housings,  reflectors,  and diffusers can im-
prove lamp efficiencies by as much as 35 percent.   Clean fixtures operate at a
lower  temperature  which can  typically  lengthen the life  of a lamp by 25-30
percent.

    Another  potentially significant  area of electrical  cost  savings  is in
electric billing structures.   Communities  who are currently  on "flat rate"
electric structures may qualify  for "variable" rate electric contracts with

                                     216

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their utility.  Wastewater facilities often benefit from variable rate struc-
tures due to their inherent diurnally and seasonally varying electric demands.
Cost savings  ranging from  15-25  percent have been seen  in  our studies from
simple contractual changes to variable rate structures incorporating on-peak,
off-peak, and kw demand components into  the billing.

    Tables 7 through 10 summarize capital cost energy conservation measures for
four of the treatment plant sites studied.  In general, capital cost measures
dealing with  HVAC and illumination  systems have the  fastest  payback period
while the  architectural  items  have  the slowest payback.   Treatment systems
offering the greatest potential  for conservation are related to sludge handling
and disposal and aeration system modifications.

    Based  on  the  energy  audit  studies,   the  following  is  a checklist  of
potential energy conservation opportunities (ECOs)  at a wastewater treatment
plant.

    Ventilation and  Cooling System ECOs

        —   Close off unoccupied areas by blocking supply  register
        —   Shut off system and open windows
        —   Raise cooling temperatures to 78   (non-reheat)
        —   Install  ventilating equipment timeclocks
        —   Install  ceiling fans in  high bays
        —   Install  local switches for exhaust fans
        —   Install  economizer/enthalpy  control
        —   Close air dampers during morning warm-up
        —   Install  attic ventilation
        —   Use window fans
        —   Redirect air diffuser in non-cooling seasons
        —   Maintain filters monthly
        —   Check damper operations  monthly
        —   Check belt tension  monthly
        —   Post and use operational and schedule sheet

    Heating System ECOs
        —   Reduce outside air
        —   Waste heat utilization
        —   Tune-up  boilers
        —   Repair and/or replace steam  traps
        —   Repair hot water and  steam  leaks
        —   Reduce boiler pressure in response to load
        —   Fire one boiler at  full  load rather than  two  at part load
        —   Maintain boiler instruments
        —   Reduce space temperatures to 65
        —   Reset space temperature  during  off hours

    Hot Water  System ECOs

        —   Repair leaks
        -   Reduce water temp.  -  105 F  (handwashing only),  120  F (showers)
        —   Install  water  flow  restrictors/flush dams


                                      217

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    —   Install timers on hot water heaters and circulating pumps
    —   Insulate hot water tank
    —   Turn off hot water in summer
    —   Flush system annually

Illumination System ECOS

    —   Use higher efficiency fixtures and lamps
    —   Clean fixture lenses and reflectors
    —   Remove lights (and disconnect ballasts) where not needed
    —   Install time-out switches
    —   Use photocells/timeclocks on exterior lights
    —   Install multi-level brightness controls
    —   Use high reflectance paint on interior surfaces
    —   Install night-lighting system

Electrical System ECOs

    —   Install electric metering and sub-metering
    —   Clean or replace contact surfaces on motor starters
    —   Increase conductor size on large motors
    —   Use high efficiency motors and transformers for replacement
    —   Correct low power factor
    —   Install load warning or load shedding devices
    —   Keep electric motors in good condition
            (lubricate,  replace worn  bearings,  check  alignment,  clean,
            tighten belts and pulleys)

Aeration System ECOs

    —   Change fuel source (utilize digester gas-driven engine)
    —   Improve oxygen transfer efficiency
            (change  header  placement geometry,  optimize  mixing pattern,
            retrofit coarse  bubble with fine  bubble  diffusers, increase
            operating depth)
    —   Modify blower function
            (variable speed drives, throttling blower suction for hp sav-
            ings, automatic control based on D.O., adjusting volume based
            in  diurnal/seasonal variations, meet  mixing  requirements at
            low loadings)

Sludge Handling System ECOs

    —   Digester gas utilization
            (electric generation  with heat recovery,  blower drive, pump
            drive, boiler fuel)
    —   Waste heat recovery from incineration
                                 218

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CONCLUSIONS

    Based on the information acquired from the study of the energy conservation
opportunities available at  the various treatment sites, the following conclu-
sions have been identified:

    (1) Municipal  wastewater  systems in Michigan  rely  almost  entirely  on
        electricity  and  natural  gas  for  their  energy  requirements.    The
        reliance on each  of these two energy sources  is roughly equal.

    (2) The major  components of energy consumption in wastewater systems are
        electricity  for aeration blower  drives and  natural  gas  for sludge
        heating and  incineration.   Therefore,  these areas offer the greatest
        opportunity for conservation.

    (3) The six-step process optimization model presented in this  paper can be
        quite successfully  used  in  identifying energy and chemical conserva-
        tion opportunities  related  to treatment processes.

    (H) No  obvious  relationship exists  between  the  size of  a wastewater
        facility and the  efficiency with  which it  consumes  energy.

    (5) It  is  projected  that municipal wastewater systems in Michigan could
        reduce  their  electricity consumption  by  about 15  percent  and their
        natural gas consumption by about 20  to 25 percent through the implemen-
        tation of  cost-effective energy conservation  measures.

    (6) Approximately  15  to 20 percent of  the total  identified energy-saving
        potential  in a wastewater  system can be achieved through operational
        and maintenance changes costing less than $500 and having an average
        simple payback period of less than  one month.

    (7) Significant  energy  conservation  opportunities relating  to  HVAC and
        illumination systems exist  in municipal wastewater  facilities because
        of  the unusual occupancy pattern  in many  areas of the facility.

    (8) Municipal  wastewater facilities  have significant  indirect energy im-
        pacts as a result of their consumption of large quantities  of chemicals
        produced by  energy-intensive manufacturing processes.
 REFERENCES

 1.   An  Explanatory  Study of  Possible Energy  Savings as  a  Result of  Water
     Conservation Practices.  NTIS No. PB-260 490.  Prepared  for the Ofce.  Water
     Res.  and  Technol.,  Washington,  D.C. (Jul.  1976).

 2.   In-house  rate  studies:   Ayres,  Lewis,  Norris &  May,  Inc.,  Engineers  -
      Architects  -Planners,  Ann Arbor,  Michigan.
   "The  work described  in this  paper was not  funded  by the U.S. Environ-
   mental  Protection Agency.  The contents do  not necessarily reflect the
   views of the  Agency  and  no  official endorsement  should be inferred."

                                     219

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                              TABLE 1

            ENERGY REQUIREMENTS FOR CHEMICAL PRODUCTION

Chemical
Activated Carbon
Alum
Ammonium Hydroxide
Carbon Dioxide
Chlorine
Ferric Chloride
Lime (Calcium Oxide)
Methanol
Oxygen
Polymer
Salt (Sodium chloride)
Evaporated
Rock and Solar
Sodium Hydroxide
Sulfur Dioxide
Sulfuric Acid
Fuel ,
(Btu/ton) x 10
102. Oa
2.0a
41. Oa
2.0
42.0
10.0
5.5a
36. Oa
5.3
3-0

4.0a
0.5
37.0
0.5
1.5
Power
(kwh/lb)
4.9
0.1
2.0
0.1a
2.0a
0.5a
0.3
1.7
0.25a
0.1

0.2
a
0.024a
1.8a
0.0243
0.1

 Source:   "Energy  Conservation in  Municipal  Wastewater  Treatment,"
 U.S. EPA., March, 1978.

alndicates  principal  type  of energy  used in  production.    Does not
 include energy for transportation.
                                220

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                             TABLE 2

                          SITES STUDIED



Study Site
E. Lansing, MI
Big Rapids, MI
Alma, MI
Wyoming, MI
Cadillac, MI
Ann Arbor, MI
Saline, MI
Greenville, MI

Design
ML/d
68
9
9
72
8
30
7
5

Capacity
mgd
18.0
2.4
2.5
19.0
2.0
8.0
1-9
1.3
Service
Area
Population
105,000
16,500
9,700
59,600
10,200
104,000
6,500
8,000

Type of
Treatment3
T/AS/POjj/NH
S/AS/PO,
S/AS/POjj/NH
S/TF/AS/POjj
T/AS/RBC/PCL/NH
S/AS/PO^/NH
T/TF/PO^
S/TF/PO,
Sludge
Handling
Facilities
SD/SI
AN
CSS
CSS
AN/SD
AN/SD/SI
AN/SD
AN/SD

Primary - P
Secondary - S
Tertiary - T
Activated Sludge
- AS
Trickling Filter - TF
Rotating Biological Contactor - RBC
Phosphorus Removal - PCv
Ammonia Removal - NH_
Anaerobic Digestion - AN
Aerobic Digestion - AE
               Sludge Dewatering - SD
               Sludge Incineration - SI
               Chemical Sludge Stabilization - CSS
                                221

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                         TABLE 3
   ENERGY CONSUMPTION BY FUEL TYPE AT EACH STUDY SITE
                      (in percent)

Study Site
East Lansing, MI
Big Rapids, MI
Alma, MI
Wyoming, MI
Cadillac, MI
Ann Arbor, MI
Saline, MI
Greenville, MI
Electricity
47
46
82
60
52
25
44
81
Natural Gas
53
54
18
40
48
60
56
19
Fuel Oil
0
0
0
0
0
15
0
0

                         TABLE 4
BREAKDOWN OF ENERGY CONSUMPTION BY FUNCTIONAL SUB-SYSTEMS
                      (in percent)


Study Site
East Lansing, MI
Big Rapids, MI
Alma, MI
Wyoming, MI
Cadillac, MI
Ann Arbor, MI
Saline, MI
Greenville, MI
Capacity
Control
System
10
5
9
11
11
4
26
26
Treatment
System
72
58
70
44
49
74
57
54
HVAC
System
14
31
18
41
36
14
15
18
Illumination
System
4
6
3
4
4
8
2
2
                          222

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                   TABLE 5
  ENERGY  CONSUMPTION AND ENERGY COST
OF  WASTEWATER TREATED  AT EACH FACILITY
              Energy  C onsu m ption
                   per m
Energy C ost
Study Site
East Lansing, MI
Big Rapids, MI
Alma, MI
Wyoming, MI
Cadillac, MI
Ann Arbor, MI
Saline, MI
Greenville, MI
kj/m3x103
6.1
3.9
1.8
2.6
4.2
4.7
2.2
5.8
Btu/milgalxlO6
21.9
14.0
6.6
9.2
14.9
16.9
7-8
20.9
per m
$0.035
0.026
0.017
0.015
0.034
0.023
0.016
0.028
per mil gal
$133
98
63
57
131
89
59
105
                    223

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                                                     TABLE 6
                                    A MODEL FOR TREATMENT PROCESS OPTIMIZATION

      (1) REVIEW OF HISTORICAL RECORDS                    (H) REVIEW ALTERNATE APPROACHES FOR
              -   chemicals used/mg                           ACHIEVING PROCESS RESULTS
              -   influent water quality                          ~   changing chemical feed point
              -   effluent water quality (NPDES Permit)           ~   ^circulation of solids
              -   process performance parameters                  ~   alternate chemicals
      (2) PLANT PERFORMANCE VS. EXPECTED                          ~   varying treatment needs
          DESIGN PERFORMANCE                                          (winter VS" SUmmer)
              -   theoretical vs. actual performance      <5> CONDUCT LAB SCALE STUDIES
£                 from (1) above                                  -   run jar tests with different chemicals
              -   establish efficiencies of various unit              and chemical do3aees
                  processes                                       -   evaluate results
              -   establish marginal utility of adding    (6) CONDUCT PLANT SCALE STUDIES
                  chemicals                                            ,                .
                                                                  —   change one parameter at a time
          REVIEW PARAMETERS AFFECTING THE                                ,  ..      ,
          UNIT PROCESSES                                          ~   evaluate results
                  grit removal                                    "   ^P^ent plant changes
                  rapid mixing
                  flocculation
                  settling
                  aeration

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                                           TABLET
                       LIST OF ENERGY CONSERVATION OPPORTUNITIES
                             ANN ARBOR WASTEWATER  TREATMENT  PLANT

Description
Reduce Heat Recovery
Unit Capacities
Power Factor Correction
Digester Gas Utilization
(Blower Engine)
(Heating)
Activated Sludge Aeration
Lab Exhaust Hood Makeup
Insulate Digester Covers
Install (1) Boiler Economizer
Insulate Blank Walls
Roof Insulation
Install (2) Boiler Economizers
Replace Overhead Doors
Annual Energy
Savings
76,800 kwh
2,500 ccf
	
248,330 kwh
44,896 ccf
486,850 kwh
2,845 ccf
2,290 kwh
110,500 kwh
5,000 ccf
4,550 ccf
2,156 kwh
941 ccf
6,100 ccf
747 ccf
Annual
Cost
Savings
$ 3,455
1,000
2,592
11,170
17,958
21,910
1,138
103
4,972
2,000
1,820
97
376
2,440
299
Implementation
Cost
$ 3,000
4,880
25,935
62,000
4,500
26,180
20,000
24,600
6,505
25,000
4,465
Payback
Period
(yrs)
0.7
1-9
2.2
2.8
3.6
5.3
10.0
13-5
13-7
14.3
14.9

 Base  Costs:
Electricity = $.045/kwh;
Natural Gas = $.40/ccf , where ccf=100 cubic feet
 No  direct  energy savings associated with this ECO.
^Digester heating equipment purchased separately.

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                                                    TABLE 8

                               LIST OF ENERGY CONSERVATION OPPORTUNITIES
                               EAST LANSING WASTEWATER TREATMENT PLANT
 Energy Conservation Opportunities
          Projected Annual Energy & Cost Saving	
     Electricity           Natural Gat           Total
 Amount    Cost      Amount     Cast   Amount     Cost
 (kwhr)      (S)       (cuft)       ($)   tatuxlO')    ($)
                                             Impiemen-  Simple
                                               t of ion   PoyoocK
                                                Cost     Period
                                                ($)     (years)
 Installation of More Efficient
 Variable-Speed Drives

 Preferential Operation of Most
 Efficient Row Sewage Pumps

 Monitoring of Pump Efficiency1

 Reduction of Fuel Requirements
 Far Sludge Incineration

 Recovery of Incinerator
 Exhaust Heat'

 Bypassing of Tertiary Filters '

 Modification of Aeration System

 Lowering of Water Level in
 Equalization Basin

 Cleaning of Boiler

 Reduction of MV-2 Use

 Reduction of Outside Air

 Recovery of Waste Heat
 from Aeration  Blowers

 Installation of Water Source
 Heat Pumps*

 Installation of Insulated Glass

 Recovery of Waste Meal from
 Transformers

 Increase in  Conductor  Size'

 Correction of  Motor Circuit
 Power  Factor1

 Reptocement af Standard
 Fluorescent Fixtures with
 low-Wattage Fluorescent
 Fixtures


Replacement of Incandescent
Lamps  with Self-Sal las ted Metal
Halide  Fixtures

Replacement of Mercury Vapor
Fixtures with High-Pressure
Sodium Fixtures

Replacement of Manual Switches
with Time-Out Switches


TOTALS
  SS.SOO     1,780       --        --        189.4    1,780       27,000  15.2


   4,000       200       »        »         20.5      200         -0-    -0-




               -   29,200,000  87,400   29,200    87,400    1,200,000  13.7
 3K.OOO    12,700


 Ml,iOO    20,500
 25,200
114,000
                            1,351.5   12,700
                            2,189.8   20,500

      1,450,000   4,350     1,450      4,350

910     473,000   1,420      559      2,230

      4,527,000   13,580     4,527     13,580
                       148,000     440
                                            148
                        91,200
                                          2,971.4

                                   273       91.2
                                       4*0


                                       300

                                       273
            3.713
                                            395.9   3.713
70,800    5.4


  -0-     -0-

   800    0.18

  -0-     -0-

 7,700    0.57


  -0-     .0-


75,000  250

11,195  41


37,000  10
 40,200      1,290




 97,900     3,130



 48.500      1,550


108.500     3.470
                             137.2   1,290       3,240    2.5




                             334.1   3,130       3,370    I.I



                             iSS.S   1,550       2,520    1.4


                             370.3   3,470       l,7«0   0.5
                                 1,535.400    49,143  35,889,200 107.443   44,101    157,I0(    1,440,385
   1This ECO is unquontif ioble within the scope of this study so no values are given far costs or savingx.

   >Th*_*"*fQ>' savings associated with  mis ECO are estimated in Section  2.2.4.  It was beyond the scape of mis study to
    estimate the implementation costs,  therefore, all values for mis ECO were omitted rather man inflate the totol energy
    savings far all ECOs relative to implementation costs.

   •Annual totals cannot be estimated for this ECO because it  applies to only certain  periods of the year. Weekly  savings
    estimates are given in Section 2-2.4.
           i mis ECO involves changing from one heating source to another, only the total savings in Stu was given.
   'The energy which could be saved through mis ECO and me cost to implement the ECO are both dependent on the extent
    of implementation, therefore these estimates ware not included.
                                                     226

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                                                   TABLE 9
                              LIST OF ENERGY CONSERVATION OPPORTUNITIES
                               BIG RAPIDS WASTEWATER  TREATMENT PLANT
Energy Conservation Opportunities
Reduction of Lift Pump Speed
Reduction of Blower Operation
Use of Fine Bubble Aeration
Oiffusers
Increased Uxe of Digester Gas
Solar Heating of Digester]
Reduction of Sludge Trucking '
Modification of Final Effluent
Supply Pumping
Cleaning of Boiler
Installation of Nighttime
Setback Controls
Reduction of Temperature in
Storage Room
Modification of Gravity Turbines
Reduction of Outside Air
Us* of Waste Digester Gas
Weatherstripping of Double-
Door Astragals
Enclosure of Existing Main
Entrance
Recovery of Waste Heat
from Transformers
Projected Annual Energy & Cost Savings
Electricity Natural Gas Total
Amount Cost Amount Cost Amount
(kwhr) ($) (cuft) ($) (BtuxlO1)
4,000 160 » — 13.6
30,700 1,228 -- -- 104.8
111,300 4,500 -- — 379.8
£00,000 1,800 £00
1,845,000 5,535 1,845
130.5
154,000 6,160 -- -- 525.6
42,000 126 42
370,000 1,110 370
136,000 410 136
93,500 280 93.5
704,000 2,120 704
270,000 810 270
18,500 55 18.5
6,600 20 6.6
12,300 492 -- -- 41.9

Cost
($)
160
1,228
4,500
1,300
5,535
1,175
6,160
126
1,110
410
280
2,120
810
55
20
492
nplemen- Simple
tation Payback
Cost Period
($) (years)
100
-0-
10,000
-0-
150,000
-0-
2,670
600
5,000
200
320
4,600
9,000
70
1,020
4,920
0.625
-0-
2.22
-0-
27.1
-0-
0.43
4.3
4.5
0.49
1.14
2.2
II. 1
1.3
51
10
Increase in Conductor Size :

Replacement of Incandescent
Fixtures with Low-Wattage
Fluorescent Fixtures

Replacement of Incandescent
Lamps with Self-Ballasted
Metal Halide Fixture)

Replacement of Mercury Vapor
Fixtures with High-Pressure
Sodium Fixtures

Replacement of Manual Switches
with Time-Out"Switches
TOTALS
                                   40,200      1,610



                                   48,127      1,930



                                    6,131       245


                                   20,150       300
                                          137.2    1,610
                                          164.3    1,930
2,940   1.8
  490  0.25
                                           20.9      245        770   3.1


                                           68.8      300        230   0.35
426,908    17,075   4,085,600   12,266    5,673     26,066     192,980
   The energy saving associated with thii ECO is 1022 gallons of gasoline, worth
   The energy which could be saved through rhis ECO and the cost to implement
    of implementation, therefore these estimates were not included.
                                     $1,175 assuming a cost of $1.15/gal.
                                     the ECO are both dependent on the extent
                                                   227

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                           TABLE  10
           LIST OF ENERGY CONSERVATION OPPORTUNITIES
               SALINE HASTEtfATER TREATMENT PLANT

Description
Destratifier Fans
Digester Gas Utilization
Replace Electric Unit
Heaters
Timer Light Switches
Outside Lighting Lamps
Incandescent Replacement
Lower Wattage Lamps
Insulate Digester Roof
Insulate Bldg Roofs
Storm Windows
Variable Frequency Drive
Annual
Energy
Savings
195 ccf
12,180 ccf
706 kwh
795 kwh
1,446 kwh
6,495 kwh
844 kwh
4,060 ccf
590 ccf
78 ccf
70,000 kwh
Annual
Cost
Savings
$ 22
4,139
240
40
72
325
42
1,421
206
27
3,500
Implemen-
tation
Costa
$ 240
7,300
600
120
339
2,030
194
1,800
3,050
250
12,800
Payback
Period
(yrs)
10.9
1.7
2.5
3.0
4.7
6.2
3.5
1.3
14.8
9.3
3.7
Based on $.05/kwh and $.35/ccf
ccf = 100 cu ft natural gas
kwh = kilowatt hours electricity
                              228

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                            FIGURE 1
                  SUMMARY  OF OPERATING DATA
WASTE WATER TREATMENT PLANT, CACHLLAC, MICHIGAN (MARCH 76-SEPT. 78!
                              229

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                       FIGURE 2.

    MARGINAL  UTlL\T>f  OF  C*EM\GAL ADDITION
           1
    REMOVALS
          COST OF CHEMICAL USAGE
MARGINAL  UTILITY = INCREMENT*!
                    INCREMENTAL COST OF
                    CHEMICAL
                          230

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                                      FIGURE   3

                      EXCESS AIR USED  FOR

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                                                                   417
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                                   231

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                   PAPER NO.  17


ALTERNATIVE ENERGY SOURCES IN MUNICIPAL WASTEWATER

     TREATMENT:  THE WILTON,  MAINE EXPERIENCE
                        by
                  David R. Fuller
         Director of Technical  Services
     Wright - Pierce Architects and Engineers
               Topsham, Maine  04086
                        232

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ALTERNATIVE ENERGY SOURCES IN MUNICIPAL WASTEWATER TREATMENT:
THE WILTON, MAINE EXPERIENCE

David R. Fuller ,  Director  of  Technical  Services
Wright-Pierce Architects and Engineers
INTRODUCTION

     The Municipal Wastewater Treatment Plant at Wilton, Maine was designed
to incorporate  energy conservation and alternative energy features such as
active and passive solar space and process heating, effluent heat recovery,
digester gas generation and utilization, ventilation air heat recovery, and
electricity  generation using  digester gas.   Designed  in 1975  by Wright-
Pierce Architects  and Engineers  of Topsham,  Maine  and Douglas  A.  Wilke,
Architect  and  Solar  Consultant  of Glen Head,  New York,  the plant became
operational  in  September,  1978.   Wright-Pierce received  a  grant from the
U.S.  Environmental  Protection  Agency to monitor the plant's energy systems
from May,  1979  to  March, 1981.   This  paper  discusses  the  design of the
Wilton facility; the  results of the monitoring  program; and recommendations
for design improvement, with emphasis on the solar heating systems.
                                    233

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DESCRIPTION OF TKEATMENT PLANT

     The Wilton  Wastewater  Treatment Plant was designed to provide second-
ary  treatment of  the wastewater  generated  by the  Town's  population of
4,200,  with  the  added  requirement  that  there be  zero discharge  to the
receiving stream at streamflows less than 0.12 m /d the seven-day, ten-year
draught flow  (7/Q/10).

     Figure  1 is a  process flow  diagram.   Wastewater is  lifted into the
plant  by screw  pumps.   Preliminary treatment  consists  of  grit removal,
comminution,  flow measuring, sampling, and screening.  Secondary biological
treatment consists of  rotating biological contactors (RBC).  Final clarifi-
cation takes  place in  two peripheral feed clarifiers.  The effluent is  then
disinfected and discharged.

     To meet  the 7/Q/10  streamflow  limitations, a  4.5  ha  spray irrigation
plot directly north  of the treatment facility is utilized.  This system is
designed  for  10  continuous  days'  operation  during  drought  conditions.

     Sludge,  consisting  of screenings  from the  preliminary  screens and
sludge  from  the final clarifiers,  is combined  and mixed  in a raw sludge
holding  tank, then pumped to anaerobic sludge digesters for stabilization.
High-rate two-stage  mesophilic  digestion is used.  Following digestion the
sludge  is  pumped  to  the  dewatering area,  then  conveyed  to  the disposal
vehicle and trucked to a local farm  for spreading on fields.

     Architecture is a key element in any project where energy  conservation
and the use of alternative energy  sources are prime objectives.

     Due  to  Wilton's  cold climate,  the entire plant  is  enclosed  in two
structures  with  all  the  processes placed close together to keep the struc-
tures  as small  as  practicable  and  reduce hydraulic  runs,  while providing
for future expansion.  Gravity is  used to avoid unnecessary pumping.

     The  building  is shaped to hold snow on the roof and collect drifts of
snow  against  walls  for increased  natural  insulation  during  the  colder
months.  Projections past the wall lines adjacent to glazed surfaces reduce
surface wind  velocity and cut heat  loss, as do recessed windows and doors.

     Basic  concrete  materials were chosen for walls and  roofs, because of
heat  retention potential and low  maintenance factors.   Insulated glass is
used in all windows.

     The  building interior  spaces  are  partitioned to separate  areas re-
quiring  different  temperatures  and  different air  changes  for maximum  con-
trol of  heat  loss.   Partitions and  doors between spaces with a temperature
differential  of more  than 6°C  are  insulated.   Wherever  possible,  trans-
lucent  fiberglass  partitions  are used so lighting from adjacent spaces can
be shared  .   Natural ventilation  and air flow is controlled by louvers and
windows.

     The  building  is  built  into  a  hillside,  with little  exposure to the
north,  to minimize  the  exterior  surface.   Shrubs  and trees  provide wind

                                    234

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 FIGURE 1
TREATMENT  PROCESS DIAGRAM

 1  SCREW PUMPS
 2  GRIT CHAMBER
 3  COMMINUTOR
 4  BAR SCREEN BY-PASS
 5  FLOW MEASURING  &  SAMPLING
 6  PRIMARY SCREENS
 7  ROTATING BIO-CONTACTORS
 8  SECONDARY CLARIFIERS
 9  FLOW MEASURING  &  SAMPLING
10  CHLORINE CONTACT  CHAMBER
11  PLANT EFFLUENT
12  SPRAY IRRIGATION
13  PRIMARY SLUDGE
14  SECONDARY SLUDGE
15  SECONDARY SKIMMINGS
16  SLUDGE HOLDING
17  SLUDGE TRANSFER
18  SLUDGE HEATER
19  SLUDGE RECYCLE PUMPS
20  ANAEROBIC SLUDGE DIGESTERS
21  SLUDGE HOLDING
22  SLUDGE DEWATERING PUMP
23  DEWATERING UNIT
24  DEWATERED SLUDGE
25  HYPOCHLORITE GENERATION
26  HYPOCHLORITE STORAGE
27  METERING PUMPS
DESIGN CRITERIA

Quantity of sewage
0.02 m3/s
Influent BOD
200mg/i (340 kg/d)
Influent suspended solids
200mg/1 (340 kg/d)
Effluent BOD
20 mg /1 (34 kg / d) •• 90% removal
Effluent suspended solids
20mg/l  (34 kg/d): 90% removal
Sludge quantity to digesters
9.5 mVd at 3.5% solids
Methane yield
HO to I25 m3/d
Methane heat value
22,400 kJ/m3or 2.4 to 2.7 GJ/d
RAW SEWAGE
               3CZ
        13
                                  235

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breaks.  Reflection off snow in front of the building and on an earth mound
to the west  supplements  solar energy collection.  The enclosing structures
are  oriented  southward  to  achieve  maximum  value from  the  sun's  direct
energy through both passive and hydronic  solar  energy  collection devices.

     Insulated translucent fiberglass panels are oriented to the south at a
60 d£gree  tilt  for  passive collection of solar  energy.   The  panels cover
89 m , have   a  light  transmission factor  of 45% and  a  0.29 "U" factor.
                                                              2
     Flat plate hydronic solar collector panels covering 130 m  set at a 60
degree slope form the  south roof of  the treatment  plant.   The collector
consists of  an extruded  aluminum plate and  frame, copper  tubing to trans-
port the collector fluid, and two panes of low iron content tempered glass.
The  backs  of  the  collectors are  insulated  with  114 mm of  rigid polyiso-
cyanurate  foam  board  insulation.   An  ethylene  glycol  solution  is  pumped
through these panels and heated to 50°- 60°C by the sun.

     Although  solar energy  is used  for  space  heating  and  domestic  hot
water, its primary purpose is to provide heat for the anaerobic digesters.
The  methane  gas produced  in the  digestion process can be stored  and used
not only in  the methane boiler for heating purposes, but to run the plant's
emergency generator.  This application of solar energy attempts to overcome
two  of the  main  constraints on its  widespread  acceptability,  namely  its
traditional  seasonal  use and  the  difficulty of  storing solar energy.   By
using  solar  to heat the digesters, the solar equipment is  used year round,
significantly decreasing the pay-back period.  By producing methane as part
of  the anaerobic  sludge  digestion  process,  solar energy  is effectively
stored  in the  form  of a  compressible,  combustible gas,  a  much  more  ef-
ficient storage medium than the usual hot air or water.

     A sophisticated heating and  ventilating design had to  be achieved in
order  to accomplish  the  energy goals.   Because the main component is solar
energy using flat plate collectors in a cold climate,  a  basic constraint on
the  heating  system design  was  the use  of  relatively  low temperature  hot
water  (50°C.)  instead  of  the conventional 90°C water.   Energy conservation
practices become extremely  important  when dealing with such  low tempera-
tures.  The  thermal  zoning of rooms to allow  for individual room tempera-
ture  control is very  important.   The  office,  locker room  and  laboratory
which  are clustered  at the northeast end of the building can be maintained
at 20°C  for  the  operator's  comfort.    The  rest  of the areas  in the plant
will experience  seasonal  and diurnal  temperature  fluctuations, dropping to
as cold as  7°C in winter and perhaps  approaching 30°C  on  warm,  sunny days
in  the summer.   The  operators  are normally not  in these  areas for  any
extended period of time.   It also should be kept in mind that most of these
areas  contain processes  which  normally are not  housed.   The operator is
very important to the success of the energy conservation effort,  in that he
must  see  to  it  that temperature  controls are properly set, the doors  are
kept closed and that temperatures are set back at night.

     The heating  system  is  designed  for cascading the  heating loads.   The
digesters  can be  heated with  49°C  water,  building  space heating  can be
                                    236

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accomplished  with 38°C water  and ventilation  units  use 32°C  water.   The
water which heats the digesters can, in turn, be used to supply heat to the
building's  heating  system and ventilation  units  without requiring supple-
mental heat between steps.  The system maintains the flexibility of supply-
ing heat directly to one specific load as required.

     Ventilation  is  a  major problem in energy efficient heating design for
wastewater treatment plants, in that many of the process areas require many
air changes.  In order to avoid throwing heat away, the plant makeup air is
conditioned with the exhaust air before it  is vented.

     Solar  energy  is  the  prime source of  heat,  both for the sludge diges-
tion process  and  the building.  A  secondary  source  of heat is the methane
gas produced  in the anaerobic digesters, and its availability is intimately
dependent upon  the  success of solar heating.  Another source of heat is an
electric heat pump  which  utilizes the heat energy available in the plant's
effluent.   This  heat  pump  is  approximately  three  times  as  efficient as
electric  resistance  heat,  and  its use  in wastewater treatment facilities
can be very cost-effective.

     Figure 2 represents  the inter-relationships among the heating sources
and heating  loads.  Heat  from the  solar   collectors  can  either be trans-
mitted directly to the heat distribution system or can be sent to the solar
energy  storage  tank, which  is  a  7.5 m  water  tank.   Which route it takes
depends  on  the relative  temperatures  of the  solar  collector  loop and the
solar storage tank and on the needs of the  system for heat.

     Fueled by  digester  gas produced in the anaerobic digesters, the meth-
ane  boiler  comes  on only  when there is  a call  for heat that  cannot be
satisified  either by direct input of solar  energy or by hot water stored in
the  solar  storage  tank.   The  heat  pump operates only  when solar  is un-
available either directly or indirectly and methane is unavailable.

     Backing  up  the  three primary heat  sources  are  some secondary sources
which  can  be significant.   Methane is  used  as  the prime  fuel  for the
plant's  55  KW electric generator  in addition to fueling the methane boiler.
Propane  is  stored  on  site in  case of  prolonged power outages  when the
supply  of methane is exhausted, but is not normally used as a fuel for the
generator.  When the  generator is operating it gives off  a  great deal of
heat.   It  is  cooled by water  from the  solar storage  tank, thus becoming a
usable  source of  heat.

     The solar storage tank can be considered a  heat source.   It is used
for  short-term storage of excess  energy which is  not directly usable.  By
utilizing  the  storage capacity,  the  operator does  not  waste potentially
usable  energy from  the  solar  collectors  or  the electric generator.  Heat
from  the solar  storage  tank can either be put into the heat distribution
system  or go  directly to  heating domestic  hot  water.  The  hot water heater
can  be  heated  electrically, but  it is unlikely  that this will  often be
required.
                                    237

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                                               FIGURE 2

                                    ENERGY  SYSTEMS  CONCEPTUAL DIAGRAM
U>
oo
                      1   PROPANE
                      |   (STANDBYf
                                                     PLANT
                                                     EFFLUENT
                                      HYDRO NIC
                                       SOLAR
                                     COLLECTORS
                                                                               METHANE
                                                                                BOILER
 SOLAR
STORAGE
                                        HEAT
                                     EXCHANGER
 ELECTRIC
GENERATOR
                                                   L-ELECTRIC
                                                      POWER
ELECTRICJ
POWER ^
                                                                         HEAT
                                                                      DISTRIBUTION
                                                                        SYSTEM
                          ELECTRC POWER
                          (SUPPLEMENTARY)
                                             HEAT RECOVERY
                                                                        PASSIVE
                                                                        SOLAR

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     Passive solar  energy is provided by translucent fiberglass panels for
direct  heating and  lighting.   Finally,  building ventilation air  is  con-
ditioned by exhaust air through the use of a heat exchanger.

     To accomplish the objectives of the digester gas system, two levels of
storage are  used.  J5hort duration storage  is  accomplished by compressing
the gas to  138 KN/m .   This is  a  conditioning storage mode used to insure
steady flow of methane for digester mixing and to prevent too rapid cycling
of  the  high pressure methane  storage  compressor.   Longer duration storage
is  accomplished  through  the high pressure methane storage system, in which
methane is  compressed to 1,380 KN/m  .   It  is  from  the  high pressure gas
storage tank that the boiler and generator are supplied.
ENERGY MONITORING OBJECTIVES AND DESCRIPTION

     The  objectives  of the energy systems  monitoring  program  were  to pre-
dict, verify, and summarize the performance of the building thermal systems
on  a totally  integrated  basis  that  is not available  through predictive
analysis  of individual components.

     These objectives  are tied very closely to  the basic energy conserving
design of the  plant.  Each subsystem  is not especially unique in design by
itself;  however, the  integrated subsystems  pose complex problems  in the
interaction  of  process variables.  This  is especially prevalent in inter-
action between energy  sources, i.e. solar input,  methane boiler, heat pump;
and energy users, i.e. digesters, building  heating and ventilation.

     The  integration  of  these  subsystems  is  unique;  and the  design was
based, in part,  on data  provided by solar, emergency generator, boiler and
digester  manufacturers who have detailed knowledge  of their  equipment but
limited  knowledge  of  the  total system.   It is in these areas  that the
system was monitored to determine how  the components interface.

Active Solar

     In  the  active  solar subsystem an  ethylene glycol water  solution is
circulated through  collector plates which  are  heated  from the sun's rays.
This  energy  is  then exchanged to the plant  circulating water system.  An
underlying design premise is to use solar  energy whenever it is available,
with the  use as  a function of exchanged  temperature.  The total performance
of  this  subsystem needed  to be determined.

     Solar  insolation was measured  (for (1)  direct, diffuse  and reflected
and (2)  direct and  diffuse only) and continuously recorded on a strip chart
with an  integrated  digital output as well.   Solar plate  temperature and
glycol  flows and temperatures were also recorded.   A hydronic BTU computer
monitored the  total heat  from the solar heat exchanger  for both analog and
digital   recording.   Electrical  input  to  solar  pumps  was  also monitored.
                                    239

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Digester

     The digester  subsystem again is not especially unique in its function
and design;  however,  the  integration with the total system and its part in
the  energy  conserving  nature of  the  plant  is  unique.   The  digester gas
released becomes  an  important part  of  the total operation, as  it was de-
signed to  be used in the gas boiler "in normal operation and the emergency
generator when excess gas is available.

     A determination  was  made to the quality  and  quantity  of  gas produced
and where  it is used.  The properties and quantities of the sludge flow in
and  out  of  the  digester,  the  sludge  and  digester temperatures  and the
heating and  electrical requirements were monitored.

Effluent Heat Pump

     The heat pump extracts  heat  from  the effluent for use in  the heated
water system.

     Electrical  input and heating output were monitored  continuously with
digital  outputs.   Additionally,  temperature and pressure drops  across the
evaporator  and  condenser  and  the  auxiliary pump  electrical usage  were
monitored.    The  unit  coefficient of performance was determined for various
conditions.

Passive Solar

     Light/heat  transmitting panels  are  employed  in  this plant.   Their
contribution  to  the  total plant  energy provides  useful  design  data for
scaled-up plants.

     Solar  insolation  and solar  transmissivity  were measured  and  con-
tinuously  recorded.   Space temperature and heating  requirements  were also
monitored  to give an indication of  the heat storage effect of  the struc-
tural mass of the building.

Weather Data

     All design  calculations  for this  plant were  based  on  weather data
provided by  the  National  Weather  Bureau.   Environmental  conditions  were
monitored  using a small  weather station located  at the Wilton  treatment
plant.  The  data  can  be used as a correlation for actual  plant performance
especially  in  solar  input as  a  function of  ambient  temperature,  wind
velocity, season, etc.

Electrical/Fuel Consumption

     This  plant's equipment was  designed  for high  efficiency,  high power
factor  and  low  energy  consumption.   High pressure  sodium  lighting was
employed where possible with selective switching and task  lighting.  Equip-
ment  was  arranged for  selective running from the  emergency generator de-
pending on gas production.


                                   240

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     All significant electrical usage was monitored and audited by function
so the total energy requirements for systems such as solar can be determin-
ed.

     Digester gas production and propane usage were recorded.

Ventilation Air Heat Recovery

     An  air-to-air  heat exchanger  is used to recover heat  from plant ex-
hausts.  The  efficiencies  for  varying conditions  were  determined  and the
increased fan power pressure drops were recorded.

Domestic Hot Water System  (DHW)

     The DHW  system  is  designed to  recover  heat  from  either the  storage
tank or  the system return  water whenever possible.  A hydronic BTU computer
monitored  its  output  along with the  electrical  input.   System losses and
the recovery pump requirements were determined.

Process  Flow

     Temperatures  were  recorded  at  various  points to  determine the  heat
transfer between the  process flow and the plant.
RESULTS

      The  monitoring system was designed  and  installed based on anticipated
results.   Generally,  the equipment was  of  sufficient sensitivity and range
to provide valid results.   With the available data,  each major component of
the  heating  system was  analyzed and  evaluated for its  energy  and cost-
effectiveness .

      From Table 1 it  can be seen  that each  of the  energy subsystems, except
for  Digester Gas  Production,  was  a net energy producer and net cost saver.
However,  the pay-back periods  generally  were greater than are economically
justifiable.
                                     241

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                                   TABLE 1

                   ENERGY AND COST-EFFECTIVENESS SUMMARY
Component

Active Solar

Passive Solar

Heat Pump

Generator Heat
Recovery

Air-to-Air Heat
Exchanger

Digester Gas
Production
Energy Output/
 Input Ratio
                                  (1)
Value Output/,-,
 Input Ratio ('
   113
   9.0
   0.59
     86
     6.1
     0.72
Cost-Effective
11.5
32%(3)
2.9
3.5
N/A
1.5
No
No
Yes
      No
                                                 (4)
      Yes
      No
1
 The Energy ratio  is  the total energy produced divided by the energy input
 required.
2
 The Value  Ratio  is  the dollar value  of the  energy produced divided  by
 input energy cost.

 Actual  average  monthly  solar radiation  transmitted through panels  from
 June 1,  1979 to April 1, 1980.
\
 Due to low usage;  if used more,  it could be  cost-effective.
                                   242

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Active Solar

     Table 2 summarizes the active solar system data between June, 1979 and
April, 1980, as follows:

     1.   Recorded  clear  day  insolation   levels  were  consistently  above
          ASHRAE  estimates with  an  average difference  of  13.8% (Item 9).

     2.   The  recorded  percent  of  possible  sunshine  was  60%  versus  an
          average of  52% predicted (Item 5).  This  is consistent with the
          unusually low precipitation levels experienced.

     3.   The  average incident solar radiation was  37.3% above that esti-
          mated (Item 11).

     4.   The  total  solar energy collected was 122  GJ (Item 16) which was
          64% of that estimated.

     5.   The  overall  solar   system  efficiency,  being  the  net  energy
          collected divided  by the total incident available, was 23% (Item
          15).

     An  overall efficiency  of  23%  is  significantly  lower than  that  an-
ticipated.  A  great deal  of effort was  spent  in  investigating the reasons
which were presumed to be  one  or more of the following:

     1.   Data/Instrumentation error.

     2.   Collector Heat Loss  Factor
          a.   Inadequate  thermal isolation.
          b.   Possible  convective losses  between  the  absorber  plate  and
               the rigid insulation.

     3.   Collector Heat Transfer Losses
          a.   Air within  the  fluid loop.
          b.   Effect of the glycol solution.

     4.   Control sequencing and response.

     5.   Collector response sensivity.

     6.   Collector  efficiency losses due  to  dirt  accumulated during con-
          struction.

     While  all of these factors  (excluding the first) certainly contribute
to  the solar  system  performance, the  overriding  cause appears  to  be  the
combination  of all of  them  coupled  with and the lack of  an accurate cal-
culation procedure to simulate this interaction.

     There  is  obviously  a  significant  difference between  instantaneous
collector efficiency  and day-long or, more importantly, year-long collector
efficiency.  Instantaneous  efficiencies are  useful  in  comparing  various
                                    243

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                                                                                      Table Z
N)
                                                            HOHTII1.T  SUMMARY  UiO SOLAR  UTILIZATION

 I   Month
 2   Hays in Month
 3   A5HRAE Clear Day Insolation  (W/m»)  (A)
 It   r.riimmaii Clear Day Insolation (W/m«) (Bl
 5   (Iran Percent of Possible  Sunshine (Cl
 6   Probable Available (4  x 5)
 7   Recorded Averaxe. Insolation  (W/m1 Day)
 8   Recorded Cleat Day Insolation (W/m*  Day)  (D)
 9   Recorded l/ASIIRAE I  (g /  3)  (E>
10   Recorded Clearness (7  / 8) (N)
11   Recorded I/Probable  I  (7  / 6) 
IB   Percent Solar (16 /  17 x  100) (Ml
19   Average Daily Temperature (°C)

     A    Solar insolation  for the 21sl of each month,  44° latitude., 59" tilt from the horizontal,  fscing due south.
     B.    Solar insolation  for the 15th of each month,  44" latitude, 60" tilt from the horizontal facing 2° west  of south.
          O.ita used in original projections.
     C.    Tabulation derived from "Normals, Means,  and  Extremes" table in U.S.  Weather Bureau publication, Local  ClImatological
          Data.  53 percent average using Albany,  New York.
     D.    Actual clear day  data  recorded  for each  month.
     E.    13.8 percent over ASIIRAE clear  day data.
     F.    37.3 percent over probable available insolation.
     G.    Probable net collected  6x collector  efficiency factors.
     H.    Net collected (water side of solar heat  exchanger).
     I.    64.2 percent of that estimated.
     J.    23 percent of recorded  incident solar collected.
     K.    For 119.5 m   collector surface, 122.9GJ/10 months.
     L.    Healing load includes process,  transmission and ventilation loads.
     M.    23 percent overall being supplied by solar.
     N.    Actual average  percent  of possible sunshine - 60 percent.
Jan
31
229
217
43
93
149
277
1.21
0.54
1.60
41
23
0.56
IS. 5
7.45
101.63
7
-7
Feh
29
276
263
51
134
198
300
1.09
0.66
1.48
63
44
0.71
22.4
13.25
92.16
14
-8
Mar
31
266
273
53
145
172
338
1.18
0.51
1.19
71
44
0.62
25.4
14.06
91.54
15
-1
Apr
30
267
Z57
53
136

..
..
..
..
65

..
__
_.
—
..
9
May
31
248
234
57
133
..
—
--
..
..
61
..
..
—
..
..
--
II
Jun
30
238
220
62
136
191
?64
1.11
0.72
1.40
62
33
0.54
17.4
10.31
16.96
61
ir
Jui
31
243
722
63
140
198
237
0.9;
0.84
1.42
69
28
O.'il
14.1
8.93
9.99
89
22
Aug
31
259
239
61
146
172
309
1.19
0.56
1.18
78
402
0.54
24.5
12.90
17.16
75
17
Sep
30
272
257
58
149
228
304
1.12
0.75
1.53
83
79
0.95
34.5
13 16
29.33
88
12
Oct
31
260
260
54
140
123
301
1.16
0.41
0.88
77
3.3
0.43
27.2
10.67
46.58
23
8
Nov
30
221
2J2
39
9O
112
262
1.16
0.43
1.24
46
27
0.58
21.6
8.22
47.24
17
4
Dec
31
205
199
38
76
137
245
1.19
0.56
1.81
33
35
I.OB
25.9
11 33
8.7.44
13
— 4
See N(

A
B
C


D
E
N
r'
G
II
I
J
K
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H


-------
types  of  collectors under  similar  steady  state  conditions,  but  tend to
create  a  misleading picture  of  the  efficiency  of  water heating  systems
operating  over  long periods.

     In  the  month  of March,  for example,  approximately 1/3 of the incident
radiation  was  of too low an intensity to collect.   In many cases the col-
lector plate temperature never reached  a  usable or threshold level although
considerable  insolation was available.  An  illustration of these losses in
long  term efficiency  is  shown  in Figure 3  for a clear  day.   The  corres-
ponding  losses  for  a cloudy day are obviously greater, particularly if the
solar  radiation  intensity  equals  the  critical,  or  threshold  intensity.
                             - '/COLLECTED. V
                             •;.-( USABLE)-'.'.
                             •SOLAR ENERGY;'
                                            TOTAL SOLAR
                                            RADIATION
                       -PERIOD OF COLLECTOR OPERATION'>\'.'.'X

                       CRITICAL OR THRESHOLD' INTENSITY^t^i',_
                              LOSSES DURING
                            COLLECTOR OPERATION
                             ( IF TEMPERATURE
                           DIFFERENCE 6 CONSTANT)
        SUNRISE |                    NOON                   I SUNSET
        SOLAR ENERGY TOO LOW IN INTENSITY TO COLLECT, TYPICAL FOR SUNRISE a SUNSET CONDITIONS
        FIGURE  3  COLLECTION  OF SOLAR RADIATION THROUGHOUT THE DAY
      The dominant factor in  establishing the  threshold  intensity level  is
 the temperature  difference between  the absorber plate and the ambient  air.
 If this difference is minimized by either a warmer climate or a  cooler  col-
 lector  fluid,  as in the  case of a heat pump assisted system, or both;  then
 this threshold level would be  reduced and  the long term system efficiency
 improved.   For  example,  in  the  case  of  a heat  pump/solar system with  an
 average  collector fluid  temperature of 10°C and  an ambient temperature  of
 24°C,  the  threshold  intensity  level would  actually be negative, enabling
 the system  to  collect heat without solar radiation.

      As  indicated,  the  causes  were  investigated  for  the  lower overall
 efficiency  based  on the assumption that  the estimating  procedures  were
 accurate.   Numerous alternative procedures  were  studied  with  similar in-
 flated  results.   In the  course of  the  investigation several publications
 were discovered which  included test data for actual  solar systems  monitored
 for  a   one  year period.   The  results of these studies  are similar  to the
 findings to date at the  Wilton plant.   Each of the  systems monitored  con-
                                      245

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sisLeu  of  flat  plate collectors,  non-selective  coating,  with  two glass
covers.  The tirst  involved  a  50 m2 solar  system  located in Morton Grove,
Illinois (1).    This system was  monitored in  1975 by  the  Fluid Handling
Division of  ITT and  had  an  overall efficiency of  21%.   The  second system
was located  in  Fort Collins,  Colorado (2).  It was monitored for one year
by  the Solar Energy  Applications  Laboratory at Colorado State University
and had an overall efficiency of 19%.

Passive Solar

     The passive  solar array  is built into the wall at two levels.  Solar
radiation passes  through  the  array providing both  heating and  lighting in
the  Clarifier  Room.  Each bank of  panels  has an  overhang which  tends to
shade  them during the summer months when heating is not required.  Operable
windows cool the  space  when the temperatures become excessive.   The energy
collected during these times is lost and, therefore, not considered useful.

     Increasing  the transmissivity and/or decreasing  the  "U"  factor would
increase the net quantity of collected solar radiation.  More would be pro-
vided  as useful during  the winter but more would  have to be dumped during
the summer.  For the panels, varying the ratio of transmissivity/"U" factor
and estimating  the net energy collected would provide an indication of what
a  change  in  that  ratio  would do  to  the  system.   Other factors  such as
overhangs,  the  blocking  effect  of the  internal  panel spacers,  and vari-
ations  in  trar.saiissivity with incident  angle  also  need be  considered.

     For this  installation,  the  variation in overall  performance appears
adequate,  transmissivity  increasing during  the winter,  decreasing during
the  summer.  The  overhang is responsible for a decrease  in transmissivity
during  the summer up to a daily average of 14 percent.

Heat Pump

     The heat pump  operating  time was greater than anticipated during this
period.  The Coefficient  of  Performance (COP) was  a  quite  acceptable 2.9
during  the heading season.  The generation of the heating energy gave a net
cost savings and  the payback period was reasonable (11.4 years).  Had the
heat pump operating time  equaled the projected operating time,  the payback
period  would have  been  closer to  i'.5 years,  which  is  still  reasonable.

     The  actual  and  projected  hours  of  operation are  based   on present
operating conditions.   As the  plant flow  increases and  digester gas pro-
duction increases,  the  heat pump may be used  less with an increasing pay-
back period due to less operating time.

     To date, the operation and maintenance problems encountered have been
relatively small.  A good deal of time, however, has been spent in cleaning
the effluent strainers.   Records should be kept for several years to deter-
mine realistic  O&M costs  for the system.
                                    246

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Generator Heat Recovery

     The generator  heat  recovery loop operated approximately one half hour
per week during  the generator exercise  period.   During  part of that time,
the recovery loop  was  not used  because the  storage  tank temperature was
warmer  than  the  maximum generator  cooling heat  exchanger  allowed.   Town
water  was   then  used  to cool  the  generator.   This  condition  will  arise
regularly during  the  summer when there  is  a limited heating demand and the
active solar  system is able to provide most of the heating required.

     The generator  could be exercised for longer periods of time during the
heating season when digester gas  is  available.

     The generator  heat recovery loop has  the highest energy output/input
ratio, but  the payback period is  the worst.  This  is due to the low periods
of  use  being   experienced.    Increased   usage  would   increase  cost-
effectiveness .

Digester Gas  Generation

     The digester  gas generation system is,  from Table  1,  an energy and
value  loser.   However,  process  requirements must  also  be considered when
evaluating  this system.

Reflected Solar Radiation

     The attempt to measure  the magnitude of the ground  reflected  solar
radiation component met  with limited success.  The reflected component for
peak  nonclear days was  within the  experimental  accuracy  of the equipment
being  used.  The average  daily  reflected  component  consists of  both re-
flected  and some diffuse solar insolation.  Thus  no meaningful data on the
magnitude  of the reflected componenet  were  gathered.   Part  of the reason
for  this  was  the  minimal  snow cover  experienced during  the winter  of
1979-80.

Electrical  Usage

      Even  with the heat pump operating more and  the generator operating
less  than  anticipated,  the total electrical  usage has been  12.5 percent
less  than projected.
                                    247

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ENGINEERING EVALUATION

     Several  areas  have been  recognized where  design modifications might
significantly improve the performance of the energy system.

Hydronic Solar System

     The solar  heating  system  should be designed  to  supply thermal energy
to  heat the  digester  only,  not  be part  of an  integrated space/process
heating  system.   While  theoretically  more  efficient, the  operating  dif-
ficulties associated  with  a highly integrated system result in significant
system losses.  The following guidelines apply:

     a.   The  solar  system should  be  designed  to  service the  digester
          directly  with a   glycol  loop  through  the  sludge heat exchanger.

     b.   The  solar system should  be designed  to "dump"  excess  heat  into
          the  secondary digester and/or a storage tank.   A heat  exchanger
          should  be provided  to recover heat  from sludge  transferred  from
          the primary digester to the secondary digester and/or from sludge
          wasted  from the secondary digester.

     c.   The  solar/sludge heat  exchange   system  should  be  designed  to
          operate  with  service  fluid  temperature  of 43°  to  46°C.   The
          effectiveness  of solar  thermal  energy  collection  improves  sig-
          nificantly with lower operating temperatures.

     d.   The ratio of solar collector surface area in m2 to sludge flow in
          m3/d  should be  approximately 25:1 (i.e.,  10 m3/d of sludge  re-
          quires  250 m2  of solar collector  surface), assuming  climatic
          conditions  similar  to  Wilson and digester  insulation  of R-20.

     e.   A conservative evaluation  of  expected sludge flow should be  used
          in sizing the solar collector array.  Generally,  sizing should be
          based on  average  flow over the design life, or less.

     f.   Solar heating system design details:

          1.   The  collector should be a flat plate design.

          2.   The  collector  tilt  angle should be  optimized  for maximum
               yield  approximately 4:S  days  prior  to  and  following winter
               solstice.

          3.   Systems  capable  of digester  heating  with  fluid  temperature
               of 43° to 46°C should use single glazing.

          4.   Systems   requiring  digester  heating   fluid  temperatures
               greater  than  48°C  should  use  double  glazed  collectors.

          5.   The  solar  collector  must  be  a  low  mass,  quick  response
               collector  with  a  selective  surface  of  a/e = 0.95/0.10,
               where  a/e  is   the ratio  of  absorptivity  to emissivity.

                                    248

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         6.   The  associated  hydronic system instrumentation and controls
              must be designed  to  respond more  quickly to the availability
              of  useable  solar energy.  Generally  this  requires a  simpler
              system design.

         7.   The  solar collector  array  should  be designed  for  thirty year
              operation  without  significant maintenance and  no replace-
              ment.

    g.   The  solar collector  may form  a  roof  under the following  guide-
         lines :

         1.   The  collector  absorber plate must  be thoroughly thermally
              isolated  from the building support structure.

         2.   All  seals must  be high temperature  silicone or  equivalent.

         3.   All  metals  must be  compatible  or dielectrically isolated.

         4.   The collector  glazing  elements  must  be  capable of  simple
               replacement.

         5.    The rear of the  collector  array should be within a  heated
               space  and be accessible from the  interior.

         6.    The rear  of the  collector  should   have R-20  insulation.

          1.    The tilt angle should be a minimum of 45 degrees.

     h.  Domestic hot  water required for  plant personnel should  be  sup-
          plied through a  takeoff heat exchanger on the main system.

     As discussed  below,   it  is doubtful that  solar heating of anaerobic
digester can be  shown  to  be cost-effective under current accepted  economic
projections,  or  under  any  conceivable  circumstances except  for   a  small
range  of treatment plant  sizes, perhaps 0.04 m3/s  to 0.10  m3/s.   However,
if  other   factors  (socio-political,  regulatory,  etc.)  dictate, the  above
guidelines will  assure  the most cost-effective use of solar thermal energy
for digester  heating.   It  should be noted that advances in solar collector
technology  since  1975  have  incorporated  many of  the  above  guidelines.

Passive Solar Heating

1.   Passive  heating should  be  applied to "occupied"  areas   such  as  the
     office and laboratory.  It is less  effective in areas exposed  to water
     surface  such as  Wilton's  clarifier  room, but may be desirable  for
     natural  lighting purposes.   Such  areas  should be  heated minimally,
     with  thermostats set at  5°C.   The movement  of wastewater in these
     areas will largely maintain temperatures greater than 5°C.

2.   In  areas to  be  heated to  20°C±,  passive  solar  collectors  should be
     fitted with manually  operated insulated shutters.


                                    249

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Heat Pump

     The  effluent pick  up  tank should be  sized to minimize drawdown pro-
blems  associated  with  plant  flow variations  and  designed to  facilitate
maintenance of  intake screens.

Instrumentation

     Keep instrumentation as simple as possible.  The  instrumentation tends
to  become complicated when integrating solar  and other alternative energy
systems with  the  heating, ventilating and processes  of the treatment plant.

Digester  Gas  System Design

     The  Wilton  wastewater treatment  plant's  energy systems  design  has
received  a great deal  of  attention.   Since  the inception  of  the energy
systems  monitoring project, reports have been  written concerning the eco-
nomic  feasibility of solar-assisted anaerobic  sludge  digestion  (3,4).   It
is  the author's  opinion that  some of these  reports are overly  optimistic
and  that the  operating results  at Wilton  do  not  justify  this optimism.

     The basis  for the Wilton design is that the  use of flat plate hydronic
solar  collectors  in concert with  anaerobic  sludge  digestion is  symbiotic,
that  the low temperature  thermal  energy produced  by  the solar  collectors
can be used to  heat the digesters, replacing a portion of the digester gas
produced  which  would  have  to be burned to heat a similar nonsolar-assisted
digester.   The  gas thus replaced  can be  stored for use as  a fuel  for the
production  of  direct thermal  energy  (boiler),  electrical  energy (engine-
generator) , or  mechanical energy (engine-drive).  The cost-effectiveness of
active  solar  energy production  is strengthened  when  so  combined with an-
aerobic  digestion.   Its payback  is quicker because the  thermal energy is
needed year-round to heat the sludge.   Storage of solar energy is much more
efficient in  the  form of the compressible,  combustible,  gas produced as a
byproduct of  digestion  than as  hot water  or air.  This  is the rationale
advanced  to support the Wilton  design and used  to  substantiate claims of
widescale cost-effective applicability in other reports.

     The  problem  with  the  solar  digester  scenario  is  in   its  cost-
effectiveness;  Wilton successfully  demonstrates its  technological  feasi-
bility.   The  evidence from Wilton and elsewhere indicates, however,  that
the payback  on active  solar  systems  is  longer  than anticipated  due  to
actual operating efficiencies being significantly lower than projected from
instantaneous design data efficiencies.

     The other  major  flaw  in the solar digester scheme is that heat can be
recovered,  directly  or  indirectly,   from  the  digester  gas  more  cost-
effectively than  by  using solar.  A  study done by Wright-Pierce  (5)  to
determine possible innovative and alternative  technologies  for use at  a
wastewater treatment plant  being designed for Caribou,  Maine indicates that
if there  is sufficient  sludge  to justify anaerobic digestion as a stabili-
zation process,  then  it  is  more cost-effective  to  1)  burn the gas  to heat
the digesters;  2) use the  gas  to  fuel an engine-generator  set  to  produce


                                    250

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electricity  and  recover  the heat  given  off  by  the  engine  to  provide
digester  heating;  or  3)  fuel  an  engine-drive  set to  operate equipment
(replacing electricity), with engine tieat recovery.  If sludge digestion is
justified,  then the heat  recovered  from any of  the above systems  will be
much  more significant  than  any  feasible solar contribution.   If there is
not  sufficient  sludge  to  make  anaerobic  digestion  cost-effective,  then
adding solar will not make it so  (this  is Wilton's  situation).

      Wright-Pierce's  report  to  EPA on  the Wilton Energy Monitoring project
evaluated the  cost-effectiveness of solar heated anaerobic digestion for a
range of treatment plant sizes  (6).  The conclusions  from this  analysis of
anaerobic digestion,  with and  without solar  heating,  compared with lime
stabilization  for  sludge processing were:

      1.    For  wastewater treatment plants the  size  of  Wilton's  (1730 m3/d),
           anaerobic  digestion is not  cost-effective and  adding solar heat
           make:; it even less  so.

      2.    For  a 3785  m3/d wastewater  treatment  plant, anaerobic digestion
           is  marginally cost-effective, but   adding  solar  heat  does  not
           improve  its cost-effectiveness and  in  fact  makes lime stabiliza-
           tion more cost-effective.

      3.    For   larger  plants  (37,850  m3/d),  anaerobic digestion is  clearly
           cost-effective;  and there  is no  use  for solar heating,  because
           all  heating requirements  caa  be met  with  waste  heat  recovery from
           the  use  of digester gas.

      It appears that there is no role  for  solar heating in association with
 anaerobic digestion.  Based on work done by others  (4),  if solar heating  is
 not cost-effec-cive when applied to  anaerobic digestion,  it is  doubtful that
 it is cost-effective  with  any  wastewater treatment process.   It should  be
 noted that  no attempt  has  been made  here to  consider  climatic conditions
 other than  those  encountered in Wilton, Maine,  or  other  treatment  proces-
 ses.   However, it is doubtful that solar heating of anaerobic  digestion can
 be shown to be cost-effective  in any climate,  regardless  of  primary and
 secondary treatment processes used.

      The  analysis  indicates that  the  price  of conventional energy  (oil,
 electricity)  will  have to  increase  substantially  more  than  projected and
 the  cost of  solar  heating  substantially decrease  before solar heating  of
 anaerobic  digestion  can  become  cost-effective,   and  then  only  for   a
 relatively insignificant number  of small wastewater treatment plants;  those
 large enough for anaerobic digestion to be cost-effective compared  to  other
 sludge  stabilization methods,  but too  small for  the  gas  produced to  be
 sufficient to  render the plant thermally self-sufficient.

      Non-economic   (socio-political,   regulatory)   factors  may  mandate   a
 greater  use  of  solar thermal  energy,  in  which case  solar heating  of
 anaerobic  digesters  may be  justifiable for small facilities.   The  argument
 has  been made that solar should be incorporated into wastewater treatment
                                     251

-------
plants, because  it is  an environmentally  compatible  "soft" energy source
and  is independent  of factors  which might  interrupt the  supply  of con-
ventional fuels.  The reasoning is that if there is a  sudden curtailment of
conventional  energy  supplies, public facilities  such  as  wastewater treat-
ment plants  probably would be  among the first to  be  cut off.   Therefore,
incorporation  of  solar energy  and other alternative  energy sources safe-
guards the operation  of the treatment facility and the resultant environ-
mental protection.

     By  far   the  most  energy used  in  wastewater  treatment  is  electrical
energy to  run equipment.   Even if solar heating could be shown to be cost-
effective,  the impact  on total  energy  use  in  treatment plants would  be
relatively insignificant.
CONCLUSIONS

     The results of the monitoring data analysis and engineering evaluation
of the  energy  systems  at the Wilton, Maine wastewater treatment plant have
led to the following conclusions:

1.   Wastewater treatment plant  effluent  heat recovery, through the use of
     a  water-to-water  heat  pump is  cost-effective  under  relatively severe
     temperature conditions.

2.   Ventilation air heat recovery is cost-effective.

3.   Generator  cooling loop  heat recovery  may be cost-effective  if  in-
     creased use of the generator is  warranted.

4.   Passive solar heating,  although  not cost-effective as analyzed for the
     Wilton plant,  can be  made  cost-effective  with  design  modifications.

5-   Solar  system  instantaneous  efficiencies,  when  applied to  clear  day
     insolation levels and  the  mean  expected percent sunshine,  may lead to
     an overly  optimistic evaluation of the  actual long-term  performance.
     These losses are  related  to the system threshold insolation intensity
     and  the  random weather  patterns.   It  would,  therefore,   appear  that
     computer  simulation,  using  averaged  hourly weather data  and  system
     performance criteria, is required to  accurately estimate the long-term
     efficiencies.   Moreover,  since  the threshold  intensity level  is  pre-
     dominantly affected  by the  difference in the  average collector fluid
     and  ambient  temperatures,  the   long-term  efficiency may  be  signifi-
     cantly reduced in northern climates.

6.   Solar thermal energy collection for  the purpose  of  producing supple-
     mental  heat  for  anaerobic  sludge digesters  is  probably not  cost-
     effective  under currently accepted economic projections, regardless of
     size or location of the facility.
                                   252

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RECOMMENDATIONS

     Based  on  the work done on  the  Wilton Treatment Plant monitoring pro-
     ject,  the following are recommended:

     1.   A more  realistic  procedure  must  be  developed  for accurately
          estimating  active solar heating system performance for the pur-
          pose  of designing solar installations  for  space or process heat-
          ing.    Computer   simulation models,  taking  into   account site-
          specific  hourly  weather  data,  solar  collector  system response
          time,   and  inherent  system  losses should  be developed  to   ac-
          curately    evaluate    alternative   solar   designs    for   cost-
          effectiveness  during  the  preliminary  design  of  a project.   On-
          site weather data should  be collected prior to the  design phase
          to take into account site-specific microclimatology.

      2.   Although the  it was  concluded that  solar heating  of  anaerobic
           digesters  is  probably not  cost-effective,  guidelines have  been
           developed (see ENGINEERING EVALUATION) which should,  if  followed,
           significantly  increase   the   efficiency  of   solar   heating  of
           digesters.

      3.    Passive solar heating  of  treatment plant structures  can be cost-
           effective  if  applied  to "occupied" areas such as  the office  and
            laboratory if good energy conservation principles  are followed in
            the design of such areas.    It is less cost-effective  when applied
            to process  areas exposed  to water surfaces.  In the  latter case,
            it  is important that  room thermostats be  set at  5°C,  a  temper-
            ature  which  can  largely  be   maintained  by  the  water  passing
            through  these areas.  Combined with  task  heating  (if necessary)
            and proper energy  conservation design, passive solar heating and
            lighting can be  cost-effective  in  process areas.

      4.    Effluent heat recovery through the use of a  heat pump  is cost-
            effective.  Operational problems  can be minimized by properly de-
            signing  the effluent sump  from which  the heat pump  draws to pro-
            vide  sufficient  capacity  at minimum plant  effluent flows.

      5.    Instrumentation  and  controls  should  be  simplified as  much as
            possible.   The  theoretical advantages of integrated energy  sys-
            tems  can be offset by  complicated trouble-prone instrumentation.

      6.    The available evidence indicates  that  solar  heating of anaerobic
            digesters  is probably  not cost-effective  in accordance with the
            EPA  guidelines,  regardless  of size  of  the  treatment facility.
            There has  been significant  interest  expressed  throughout the
            United  States   in  pursuing  this  concept under  widely varying
            conditions of climate,  process,  size,  etc.   It  is  recommended,
            therefore,  that EPA  undertake modeling  of   the  application of
            solar heating   of  anaerobic   digesters  to  determine  its  cost-
            effectiveness   under  different  conditions  to determine if the
            conclusions  drawn  from  the  Wilton  project  can  be  generalized.


                                      253

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           In the meantime, it is recommended that EPA not promote solar
           heating of anaerobic digesters and require detailed supporting
           documentation for any grantee requesting EPA Construction Grant
           Program funds for the design and construction of such facilities,
REFERENCES
     1.    Solar Heating Systems Design Manual.  Training and Education
           Department, Fluids Handling Division, ITT Bulletin TESE-576.

     2.    Solar Heating and Cooling of Residential Buildings - Sizing,
           Installation and Operation of Systems.  U.S. Department of
           Commerce, Economic Development Administration,   Stock No.
           003-011-00085-2.

     3.    Use of Solar Energy to Heat Anaerobic Digesters.
           EPA 600/2-78-114, NTIS No. PB 286940, U.S. Environmental
           Protection Agency, Cincinnati, Ohio, 1978.

     4.    Overly, P., and C. Franklin (Acurex Corp.)  Solar Energy for
           Pollution Control.  EPA Contract No. 68-03-2567, 1978.

     5.    Wright-Pierce.  Conceptual Design Report, Grimes Mill Waste-water
           Treatment Plant, Caribou, Maine.  1979.

     6.    Fuller, D.R., D.A. Wilke, P.L. Thomas and A.J. Lisa (Wright-
           Pierce) .  Integrated Energy Systems Monitoring of Municipal
           Wastewater Treatment Plant in Wilton, Maine.  EPA Contract No.
           68-03-2587, 1981.
 "This paper has been reviewed in accordance with the U.S. Environmental
 Protection Agency's peer and administrative review policies and approved
 for presentation and publication."
                                   254

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                    PLANT OPERATION AND DESIGN PROGRAM
                     Related Publications and Papers

                              December 1981
Areawide Assessment  Procedures Manual.   July  1976.   EPA-600/9-76-014,
U.S.EnvironmentalProtectionAgency,  Cincinnati,  OH.    Order  No.
PB-271863/AS* (Set--3 Volumes)

Bender, J. H,   March  1978.   Parallel Evaluation of Constant and Diurnal
Flow Treatment Systems.  EPA-600/Z-78-034, U.S. Environmental Protection
Agency, Cincinnati, OH.  Order No. PB-281401/AS*

Bender, J.  H.    January  1979.   "The Oxidation  Ditch  Process:   Superior
Performance and  Reliability  at Low Cost," Environmental  Research Brief.
U.S. Environmental Protection Agency, Cincinnati, OH.

Benjes, H.  J.    December 1976.  Cost Estimating Manual - Combined Sewer
Overflow  Storage and  Treatment.EPA-600/Z-76-286,  U.S.Environmental
Protection Agency, Cincinnati, OH.   Order No. PB-266359/AS*

Benjes, H.  H.,  J. A.  Faisst,  and T.  S.  Lineck.   Capital  and O&M Cost
Estimates  for  Biological VJastewater Treatment  Processes.August 1979.
DraftReport,MunicipalEnvironmentalResearchLaboratory,  U.  S.
Environmental  Protection Agency, Cincinnati, OH.

Chesner, W.  H.,  and  J. J.  lannone.  February  1980.   "Current Status of
Municipal  Wastewater  Treatment  with RBC Technology  in  the  U.S.," In:
Proceedings:   First National  Symposium/Workshop  on Rotating Biological
Contactor  Techno!ogyTVolume  I,  EPA-600/9-80-046a,  U.S. Environmental
Protection  Agency, Cincinnati, OH.   Order No. PB-81-124539*

Collins,  M. A., and  R.  M.  Crosby.    October  1980.    "Impact  of  Flow
Variation  on Secondary Clarifier Performance," Presented at 53rd Annual
Conference  WPCF, Las Vegas,  NV.

Construction   Costs  and Operation  and  Maintenance  Requirements  for
Vlastewater  Fi1tration.  Draft  Report,   Municipal  Environmental  Research
Laboratory,  U.S. Environmental Protection Agency, Cincinnati, OH.

Costs  of  Chemical Clarification of Wastewater.   Draft Report, Municipal
Environmental  Research Laboratory, U.S. Environmental Protection Agency,
Cincinnati,  OH.

Crosby, R.  M.   Evaluation  of the Hydraulic Characteristics of Activated
Sludge Secondary ClarifieTs"^   November  1981.   Draft Report, Municipal
Environmental   ResearchCaBoratory,   U.   S.   Environmental  Protection
Agency, Cincinnati, OH.
                                   255

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Crosby, R. M., and J. H. Bender.  March 1980.   "Hydraulic Considerations
That Affect Secondary Clarlfler Performance," Technology Transfer.  U.S.
Environmental Protection Agency, Cincinnati, QW.              ~~

Efficient  Treatment  of Small  Municipal  Flows  at  Dawson,  Minnesota.
October1977.EPA-625/Z-77-015,075^EnvironmentalProtection
Agency, Cincinnati, OH.

Ettllch,  W.   F.     December   1977.     Transport   of  Sewage  Sludge.
EPA-600/2-77-216, U.S.  Environmental  Protection Agency, Cincinnati,  OH.
Order No. PB-278195/AS*

Ettllch,  W.  F.   March 1978.  A Comparison of Oxidation Ditch Plants to
Competing Processes  for Secondary  and  Advanced Treatment  of Municipal
Wastes.      EPA-600/2-78-051,CmEnvironmental    Protection Agency,
Cincinnati, OH.  Order No.  PB-281380/AS*

Ettlich,  W.  F., and  A.  E.  Lewis.    August  1977.    User Acceptance  of
Wastewater   Sludge   Compost.     EPA-600/2-77-096,   ti7*T.  Environmental
Protection Agency, Cincinnati, OH.  Order No. PB-272095/AS*

Ettlich, W. F., and A. E. Lewis.  June 1978.  A Study  of Forced Aeration
Composting of  Wastewater Sludges.  EPA-600/2-78-057,  U.S. Environmental
Protection Agency, Cincinnati, OH.  Order No. PB-285232/5BE*

Evaluation  and Control  of  Sidestreams  in    Publicly  Owned Treatment
Works.July1981.DraftReport,MunicipalEnvironmentalResearch
Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH.

Evaluation and  Documentation of Mechanical  Reliability of  Conventional
Plant Components.December  1980.Draft Report, Municipal Environmental
Research  Laboratory,  U.S.  Environmental  Protection Agency,  Cincinnati,
OH.

Evans,  F.  L.    July  1979.   "Summary   of  National   Operational  and
Maintenance  Cause  and  Effect  Survey,"   Technology  Transfer.   U.S.
Environmental Protection Agency, Cincinnati, OH.

Ewing,  L. J.,  Jr.,  H. H. Almgren,  and R.  L. Culp.   June 1978.  Effects
of Thermal Treatment  of Sludge  on Municipal  Wastewater Treatment~Costs.
EPA-600/2-78-073, U.S.  Environmental  Protection Agency, Cincinnati,  OH.
Order No. PB-285707/AS*

Foess,  G. W.,  J.  G.  Meenahan,  and D.  Blough.   August 1977.   Effects of
Flow  Equalization  °_"  the  Operation *"d  Performance of an Activated
Sludge  Plant.EPA-600/Z-77-138,  U.S. Environmental  Protection Agency,
Cincinnati, OH.  Order No.  PB-272656/AS*
                                  256

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Foess,  G.  VI.,  J.   G.  Meenahan,  and  J.  M.  Harju.    December  1976.
Evaluation of  Flow  Equalization  at a Small Wastewater  Treatment Plant.
EPA-600/2-76-181, U.S.  Environmental  Protection Agency, Cincinnati,  OH.
Order No. PB-260375/AS*

Gray, A. C., P. E. Paul, and  H.  D.  Roberts.   October 1980. "Operational
Factors Affecting Biological  Treatment  Plant Performance," JWPCF, 52:7,
pp 1880-1892.                                               	

Gray, A. C., P. E. Paul, and H.  D. Roberts.   July   1979.   Evaluation of
Operation   and  Maintenance  Factors   Limiting  BiologicalWastewater
Treatment  Plant  Performance.    EPA-600/2-79-078,  OT  Environmental
Protection Agency, Cinclnatl, OH.  Order No. PB-80-108947*

Gray, A. C., P. E. Paul, and H.  D. Roberts. Evaluation and Documentation
of Operation  and  Maintenance Factors Limiting  Biological  Treatment  and
Plant  Performance,   Phase  IT.FinalReport,MunicipalEnvironmental
Research  Laboratory,  U.S.  Environmental Protection  Agency,  Cincinnati,
OH.

Grover,  K.   October  1979.    "Don't  Blame the  Operator,"  American City
and County.

Handbook   for   Identification    and   Correction   of   Typical   Design
Deficiencies  of  Municipal  Wastewater  Treatment  Facilities.October
1981.Draft  Final  Report,  Municipal  Environmental Research Laboratory,
U.S. Environmental Protection Agency, Cincinnati,  OH.

Harber, A.  F.,  and  R.  C.  Bain.   July 1979.  Novel Methods and Materials
of Construction. EPA-600/2-79-079, U.S. Environmental Protection Agency,
Cincinnati, OH.  Order No. PB-80-113681*

Hegg,   B.  A.,  K.  L.  Rakness,   and J.   R.   Schultz.     October  1977.
"Evaluation  of  Operation  and  Maintenance  Factors Limiting  Municipal
Wastewater  Treatment  Plant  Performance,"  Presented at  Rocky  Mountain
Water Pollution Control Association, Albuquerque,  NM.

Hegg, B.  A., K. L. Rakness, and  J. R. Schultz.  March 1978.  "Evaluation
of  Operation  and  Maintenance  Factors  Limiting  Municipal  Wastewater
Treatment Plant Performance," JWPCF. 50:3 pp. 419-426.

Hegg, B.  A., K. L. Rakness,  and  J.  R.  Schultz.   March  1978.   "Summary -
O&M  Factors Limiting Wastewater Treatment Plant Performance," Presented
at  O&M Workshop  -  Steering  Committee  for the Joint  U.S./Canada Great
Lakes Commission.

Hegg,   B.   A.,  K.  L.  Rakness,   and  J.   R.   Schultz.     October  1978.
"Evaluation  of  Operation  and  Maintenance  Factors Limiting  Municipal
Wastewater  Plant  Performance - Phase  II,"  Presented  at  51st Annual
Conference  WPCF, Anaheim, CA.
                                  257

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Hegg,  B.  A.,  K.  L.  Rakness,  and  J.   R.   Schultz.    June  1979.    A
Demonstrated  Approach  for  Improving  Performance  and  Reliability oT
Biological  Uastewater  Treatment  Plants.    LPA-600/2-79-035, - ITST
Environmental   Protection   Agency,   Cincinnati,    OH.      Order   No.
PB-300476/AS*

Hegg, B.  A.,  K. L. Rakness, and J.  R.  Schultz.   June 1979.  Evaluation
of  Operation  and Maintenance Factors   Limiting  Municipal  Wastewater
Treatment  Plant   Performance.    EPA -600/2- 79-034, — tiTST. — Environmental
Protection Agency, Cincinnati, OH.  Order No. PB-300331/AS*

Hegg, B. A., K. L. Rakness, and J. R. Schultz.  March 1980.  "Evaluation
of   O&M   Factors   Limiting  Wastewater   Plant  Performance,"  Pollution
Engineering.

Hegg, B.  A.,  K.  L.  Rakness, and  J.  R.  Schultz.    October  1980.  "Case
Histories - Improving Wastewater Treatment Plant Performance," Presented
at 53rd Annual Conference WPCF, Las Vegas, NV.

Hegg, B.  A.,  K. L. Rakness,  J.  R. Schultz,  and L.  D.  DeMers.   August
1980.     Evaluation   of   Operation  and  Maintenance  Factors  Limiting
^u^-lP8! __Wa!5ewa.ter   Treatment    Plant    Performance,    Phase   II.'
EPA-600/2-80-129,  UTs"!  Environmental  Protection   Agency,  Cincinnati,
OH.  Order No. PB-81-112864*

Hourly  Diurnal  Variations  in  P"blic1y  Owned  Wastewater  Treatment
Facilities"     September   H58T7   EPA-bOO/2-81-218,   [TTST  Envi ronmental
Protection Agency, Cincinnati, OH.  Order No. PB-107954/AS*

Lykins, B. W.,  Jr., and J.  M.  Smith.   January 1976.   Interim  Report on
the  Impact of  PL  92-500  on  Municipal  Pollution   Control  Technology.'
EPA-60U/Z-76-018, U.S. Environmental  Protection  Agency,  Cincinnati,  OH.
Order No. PB-248212/AS*

McMahon,  R.   F.    Socioeconomic  Impacts  of  Water   Quality  Strategies.
Final  Report,  Municipal   Environmental  Research   Laboratory,   01   5".
Environmental Protection Agency, Cincinnati, OH.

Niehus,  D.  C.   Incentives  for  Improved Operation  and Maintenance  of
Municipal Treatment Plant.   Unpublished Report,  Municipal  Environmental
Research  Laboratory,  ll.S.  Environmental  Protection  Agency,  Cincinnati,
OH.

Niehus, D. C.,  G. A.  Brown,  and  J.  M. Houthoofd. August 1981.   "Survey
of Private  Sector Provision of Operation  and Maintenance  Services  to
Publicly  Owned   Treatment   Works,"   Newsbrief.  U.   S.   Environmental
Protection Agency, Cincinnati, OH.
N1ku,  S. ,  E.   0.  Schroeder,  and  F.  J.   Samaniego.    December  1979.
"Performance  of  Activated  Sludge   Processes   and  Reliability  Based
Design," JWPCF, 51:12, pp 2841-2857.
                                 258

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N1ku,  S.  and E.  D.  Schroeder.   April  1981.    "Stability  of Activated
Sludge  Processes  Based  on  Statistical  Measures,"  JWPCF,  53:4,  pp
457-470.                                               -           H

Niku,  S.  and E. 0.  Schroeder.   May  1981.   "Factors Affecting Effluent
Variability from Activated Sludge Processes," JWPCF, 53:5, pp 546-559.

Nitrogen  Removal  In a  Flow Modulated,  Single State Oxidation   Ditch.
Draft   Report,   Municipal   Environmental   Research   Laboratory,   UTS".
Environmental Protection Agency, Cincinnati, OH.

Ongerth, J. E.  May  1979.   Evaluation of Flow Equalization 1n Municipal
Wastewater Treatment.   EPA-6UU/2-/9-096,  U.S.  Environmental  Protection
Agency, Cincinnati, OH.  Order No. PB-80-139835*

Operation  and  Maintenance  Considerations  of  Land Treatment  Systems.
July   1981.     Draft  Final  Report,  Municipal  Environmental  Research
Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH.

Performance of  Activated  Sludge Processes:  Reliability,  Stability, and
               September  1981.   EPA-600/2-81-227,    U.S. Environmental
Protection Agency, Cincinnati, OH. Order No.  PB-109604/AS*

Performance of Biological  Wastewater Treatment Plants:  Effects of Toxic
Pollutants.    September  1980.    Draft  Report,  Municipal Environmental
Research  Laboratory,  U.S.  Environmental  Protection Agency,  Cincinnati,
OH.

Performance  of  Trickling  Filter PJants:  Reliability,  Stability,  and
Variability!    September  1981.    EPA-600/2-81-228,  U7T.  Environmental
Protection Agency, Cincinnati, OH. Order No.  PB-108143/AS*

Review  of RBC Design Procedures, and  Process,  O&M, Equipment and Power
Performance.   September  1980.    Draft Report,  Municipal Environmental
Research  Laboratory,  U.S.  Environmental  Protection Agency,  Cincinnati,
OH.

Roberts,  H.  D.,  A.  C.   Gray,  and P.  E.  Paul.  Model  Protocol  for  the
Comprehensive  Evaluation of Publicly  Owned Treatment Works Performance
 and  Operation.  May 1982, EPA 600/2-82-015,  NTIS  No. PB  82-180 480, U.S.
 Environmental Protection Agency,  Cincinnati, Ohio.

Schultz,  J. R.,  B. A. Hegg,  and  K. L.  Rakness.   October 1980. "Realistic
Sludge    Production   for   Activated   Sludge   Plants   Without Primary
Clarifiers,"  Presented  at  53rd Annual  Conference WPCF,  Las Vegas, NV.

Smith,  J. M., F. L. Evans  III,  and  J. H.  Bender.   May 1980.  "Improved
Operation  and   Maintenance  Opportunities   at   Municipal   Treatment
Facilities,"  Presented  at 7th U.S. /Japan Conference on Sewage Treatment
Technology.
                                  259

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Vlesner,  G.   M.    November  1977.    Energy  Requirements  for  Municipal
Pollution  Control   Facilities.    EPA-600/Z-77-Z14,OuEnvironmental
Protection Agency, Cincinnati, OH.  Order No. PB-276989/AS*

Wesner, G. M., G. L. Gulp, T. S. Uneck, and D. J. Hlnrlchs.  June  1978.
Energy Conservation In Municipal Wastewater Treatment.   EPA-430/9-77-011
(MCD-32), U.S.  Environmental  Protection Agency,  Washington,  DC.   Order
No. PB-81-165391*
*Ava11able from:  National Technical Information Service
                  5285 Port Royal Road
                  Springfield, VA 22161
                  Telephone:  703-487-4650
                                   260
                                                        OUSGPO: 1983— 759-102/0788

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