PA
United States
Environmental Protection
Agency
Office of Water
(WH-546)
832R89001
Analysis of Performance
Limiting Factors (PLFs) at
Small Sewage Treatment
Plants
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This brochure was prepared by EPA's Office
of Municipal Pollution Control, Planning and
Analysis Division. EPA was assisted in the
preparation of this brochure by the staff of Roy
F. Weston, Inc.
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Analysis of Performance
Limiting Factors (PLFs) at
Small Sewage Treatment
Plants
-'" "•-••••) Agency
March 1989
Office of Municipal Pollution Control
Office of Water
U.S. Environmental Protection Agency
Washington, D.C. 20460
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Table of Contents
Page
Introduction: EPA is Transforming Data into Solutions 1
The Findings: Eight PLFs Topped the List 3
Some Factors Mainly Affect Plant Operation 5
Other Factors Relate to the Design of Small
Wastewater Treatment Plants 8
Certain Factors are Tied to Plant Administration 11
Conclusions and Recommendations 14
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EPA IS TRANSFORMING DATA INTO SOLUTIONS
The Environmental Protection Agency has long
been gathering data on the successes and prob-
lems of federally funded wastewater treatment
systems. Operational difficulties have been
carefully scrutinized, especially those leading
to permit violations. Small systems often suffer
most from frustrating operational problems.
Plants sized between 0.1 and 1.0 mgd are more
likely than larger plants to be underfunded,
understaffed, and not always reached by the
professional networks that can offer trou-
bleshooting advice.
Since 1982, the On-Site Operator Assistance
Program, created under Section 104(g) (1) of
the Clean Water Act, has been sending techni-
cal experts to small POTWs to help operators
and managers solve debilitating problems. The
program is hands-on, interactive, and very
successful. Its approaches are briefly described
in the accompanying sidebar.
Since the program's beginning, the "104" trou-
bleshooters have compiled operation and main-
tenance evaluations (OMEs) for the plants they
have visited. Each of these describes recom-
mendations and solutions prescribed for the
plant. It also records the plant's problems
using a checklist of 21 performance limiting
factors (PLFs). The PLFs are described in Table
1.1 on page 4. PLFs offer a consistent way to
categorize the factors that are frustrating good
performance at the treatment works.
This wealth of technical information has re-
cently been analyzed to discover what general-
ized practical advice it can offer about solving
operational problems at small POTWs.
THE STUDY APPROACH WAS
SHORT AND CLEAN
Analysts examined a cross-sample of small
plants that received "104" assistance, looking
closely at problems and solutions. This sample
of 150 POTWs was selected to be representa-
tive of all plants in the data base, not just nation-
ally, but within Regions. A checklist was de-
vised to assure that all participants would
compile data consistently when reviewing
OMEs.
Pilot reviews in two of the EPA Regions proved
the quality of the data in the OMEs and helped
refine the checklist. OMEs in the remaining
eight EPA Regions were then reviewed. The in-
formation was analyzed, and the preliminary
results discussed in a series of workshops in-
volving project staff. These discussions helped
reveal the root causes underlying each PLF, as
well as some creative solutions to the problem.
Recommendations and conclusions were dis-
tilled in the same way.
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In what follows you will find extracted the
main points from a technical report written for
EPA's Office of Municipal Pollution Control.
This brochure is primarily for the following
audiences:
• Local officials and treatment plant staff
ultimately responsible for facility design,
construction, and operation;
• State regulatory officials responsible for
approving design and assuring compli-
ance of individual treatment plants; and
• The design engineering community.
ABOUT THE SECTION 104
ON-SITE OPERATOR
ASSISTANCE PROGRAM
Statesrecei ve federal grants that support trou-
bleshooting at small plants experiencing per-
formance problems.
These technical experts typically:
• Visit the POTW. They perform a diag-
nostic evaluation by examining the plant;
reviewing performance records and
monitoring data; and talking over prob-
lems with plant managers and staff, as
well as community decisionmakers.
• Develop a training and assistance pro-
gram. This program is based on the pre-
liminary visit and may range from rec-
ommendationsonlytoanover-the-shoul-
der assistance and training course.
• Comp lete an OME for each facility. This
Operations and Maintenance Evaluation
recordseverything the troubleshooter ob-
served and did: the diagnosis, the prob-
lems, the training/troubleshooting ap-
proaches applied, and the outcome of ac-
tivities.
• Conduct Follow-up for Six Months.
Troubleshooters keep checking in with
plant staff for half a year to see that agreed-
upon activities are being continued.
To keep records consistent and cross-compa-
rable, each trouble shooter categorizes plant
problems using21 standardized PLFs—"per-
formance limiting factors."
While the "104 "programis managed by EPA's
OfficeofMunicipalPollutionControlin Wash-
ington, D.C., and coordinated by the Agency's
Regional Offices, the States direct the grants.
Some States choose to operate the program
themselves, but most conduct the "104 " assis-
tance program through State Training Cen-
ters established under Section 109(b) of the
Clean Water Act. These centers are frequently
associated with community colleges.
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THE FINDINGS: EIGHT PLFS TOPPED THE LIST
The eight PLFs described below are those most
frequently cited in the "104" data base. Al-
thoug h they often overlap categories, these PLFs
can be organized into three main areas:
• Factors Affecting Plant Operation;
• Factors Related to the Design of Small Waste-
water Treatment Plants;
• Factors Related to Plant Administration.
Many of the OMEs filed by "204" troubleshoot-
ers contained excellent solutions or constituted
effective case studies. Such information is in-
cluded here to add dimension to the study
findings and conclusions.
Because the formal titles used to identify PLFs
are not readily recognizable, PLF's will be itali-
cized in subsequent discussions to make them
easier to identify.
Q Operator's Understanding &
Application of Process Control
The operator either doesn't understand process
control theory, or is unable to apply practical
concepts related to it, or both. This PLF was the
one most frequently cited. Because it was so
broadly defined, it has been difficult to isolate
as a discrete issue. Indeed, it is often cited in
conjunction with other more specific factors
affecting plant performance, such as plant staff-
ing and process design errors.
Q Facility Staffing
Staffing problems most frequently identified in
the OME reports were: too few staff, staff with
many competing duties, or no staff at all. Exces-
sive turnover and lack of experienced staff were
also mentioned. '
Q Support from the
Municipality
This PLF covers unproductive municipal poli-
cies and actions concerning the day-to-day
operation of the treatment plant. Poor support
is often synonymous with inadequate funding.
"104" troubleshooters cited some specific prob-
lems:
• Plant staff were not empowered to make
decisions on operations, maintenance, and
administration;
• Administrative procedures were restrictive;
• Administrators were unfamiliar with plant
needs;
• There wasn't enough money to hire and
keep good staff and to perform basic O&M.
Q Infiltration/Inflow (I/I)
Excessive flows overwhelm the plant and/or
its operator. I/I is short- hand for the two main
extraneous flows entering the wastewater col-
lection system. Infiltration is groundwater
leaking into the system through cracks or breaks
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in pipes or structures. Inflow enters via sewer
system connections like roof leaders, basement
drains, land drains, and manhole covers.
Q Process Design Errors
These are mistakes made in the plant design.
Examples include improper sizing of process
units or selection of equipment and lack of op-
erational flexibility.
Q Solids Handling and Disposal
This PLF was the second most frequently cited.
It indicates that the plant's performance prob-
lems are due to faulty solids handling proce-
dures inside the treatment works and/or the
lack of an adequate sludge disposal system.
This PLF is often associated with operator's
understanding of and ability to apply process control.
Q Preventive Maintenance
Program
Preventive maintenance problems are logged
under this PLF. Plant staff are not regularly
inspecting, cleaning, and maintaining mechani-
cal hydraulic, electrical, and process equipment.
The result can be reduced service life of the
equipment and facilities, unexpected break-
downs, and higher operating costs.
Q Laboratory Capability for
Process Control and Discharge
Permit Monitoring
Either staff have not been trained in the correct
use of existing laboratory equipment, or the
proper hardware is lacking with which to collect
data for process control and discharge permit
compliance reporting. In half the cases where it
appeared, this PLF was the only one cited.
PLF Code
Table 1.1 Performance Limiting Factors (PLFs)
Description of Performance Limiting Factor
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
Poor Understanding and application of process control by operator
Staffing (too few staff, low pay, turnover, etc.)
Support from municipality (administrative and technical)
Operating budget and user charge system
Operability and maintainability considerations (process flexibility, automation,
standby units, etc.)
Infiltration/Inflow
Construction problems
Process design errors (clarifiers, aerators, disinfection, etc,.)
Over design
Under design
Solids handling and sludge disposal
Pretreatment, Industrial discharges, and toxics
Operation and maintenance manual
Preventive maintenance program
Spare parts inventory
Chemical inventory
Laboratory capability for process/NPDES testing
NPDES reporting
Equipment/Unit process broken down/inoperable
Hydraulic overload
Poor aeration system
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SOME FACTORS MAINLY AFFECT
PLANT OPERATION
Solid Operation is Built on Staff
Expertise
Successful day-to-day operation of a treatment
plant is perhaps most critically dependent on
the operator's understanding and ability to control
the treatment process. Troubleshooters cited
deficiencies in this area more frequently than in
any other.
Operators experienced difficulties in two main
areas: solids management and process moni-
toring (i.e., poor sampling protocol, analysis,
and/or data interpretation). While solids han-
dling and process monitoring are separate PLFs
in their own right, they overlap substantially
with the operator understanding and application
issue.
Proper Solids Handling is Vital
Overall operation was limited at many plants
where solids handling equipment was not
properly operated. The incorrect use of sand
drying beds was particularly prevalent. Fail-
ure to clean beds of dried sludge and reload
them with sludge from the clarifiers boosts the
solids inventory and undermines plant opera-
tions. Inappropriate operation and poor main-
tenance of solids handling equipment were
cited in several OME reports as the primary
cause of poor plant operation.
Savvy Lab Control Keeps
Operations on an Even Keel
The operation of a treatment plant is dependent
on complex biological and chemical reactions.
Data from process control monitoring provide
a type of "biofeedback" on the whole system,
identifying needs for adjustment and control.
If the process test results are incorrect or no
testing is being done, it becomes virtually
impossible for the operator to run the plant as
designed. Some specific process control-re-
lated problems were:
• The operator lacks the knowledge of how to
run basic laboratory procedures necessary
for process control and NPDES reporting.
• The operator is conducting the required
tests, but lacks the knowledge to interpret
the data and apply them to the operation of
the plant.
• The plant was constructed with a well-
equipped laboratory, but it is not being
used.
• The operator is using inadequate sampling
techniques and/or is miscalculating proc-
ess control set points. The incorrect results
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Solutions
Poor operator understanding of basic treatment
plant operation is focused on a lack of under-
standing and application of solids inventory con-
trol and improper monitoring. 104(g) trouble
shooters typically approached these basic skill
deficiencies by providing guidance in techniques
for keeping daily plant operating records, calcu-
lating wasting rates, and properly wasting sludge
from the final clarifiers. Trainers have also rec-
ommended that operators attend training and
certification courses sponsored by the state water
quality agency or the regional or state operator's
associations.
The facility O&M manual should also include a
detailed discussion of sludge facility operation.
Operational checklists for sand drying beds
should be included in the O&M manual to direct
and operator in a step-wise fashion on how to
load and unload sand drying beds.
that arise are generating false and often mis-
leading information about plant perform-
ance.
• Because of problems with hardware or staff
expertise, the treatment plant is using off-
site labs to conduct NPDES testing. This
approach has distinct disadvantages: it
diverts funds needed at the plant and it fails
to provide the process control information
that is needed regularly.
Operators Must Be Flexible in
Responding to Variable Loads
Many small treatment plants experience diffi-
culty in adjusting to changes in the strength and
volume of sewage entering the plant. This
problem was cited frequently in OME files,
particularly in the Midwestern regions and older
areas with combined sewers. Yet the operator's
ability to adjust process control to accommo-
date variable organic and hydraulic loads is
crucial to the plant's ability to meet its dis-
charge limitations.
Very small treatment plants can be upset eas-
ily—overloads can be caused by just one in-
dustrial user on the system, or by wet- weather
flow conditions. The most frequent opera-
tional problem resulting from J/7 was solids
washout during high flow events. This typi-
cally resulted from the combination of excessive
III flows to the plant and poor solids manage-
ment.
Since high-inflow events are ephemeral by na-
ture, they probably occur more often than they
are observed or revealed through data analy-
sis. While a thorough understanding of the
treatment process can help an operator handle
such problems, even experienced operators
were often unable to cope with particularly
high loadings.
Table 1.2 Five Most Frequently Occurring
PLFs* bv Region
Region I
Region II
Region III
Region IV
Region V
Region VI
Region VII
Region VIII
Region IX
Region X
A"
A
Q
A
A
A
A
A
A
A
K
K
A
K
K
C
Q
N
N
C
C
F
K
F
F
K
K
C
K
Q
B
H
F
Q
Q
B
B
H
Q
F
F
N
B
B
B
F
F
K
H
H
•As identified in the 104 data base
"See Table 1 for a listing of the PLF codes.
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Design Errors Can Frustrate
Operations
The POTW's design can exacerbate the impact
of other factors limiting plant performance by
being inflexible, unreliable, or only marginally
capable of meeting its own operating parame-
ters. On the other hand, top-notch operation
can be used to overcome design deficiencies.
Maintenance is the "Flip Side"
of Operations
Operations also suffered where the preventive
maintenance system was inadequate or nonex-
istent. The plant operator is generally respon-
sible for running this program; thus, its absence
or ineffectiveness can be seen as a result of op-
erator inexperience.
Although design errors were generally not iden-
tified as the primary factor undermining plant
performance, 27 percent of the OME reports
stated that they contributed to poor perform-
ance.
An effective preventive maintenance program
will reduce the cost of operating the facility
over time by increasing the service life of many
of the plants' major components. The lack of
such a program leads to crisis management,
inefficient operation, and unreliable perform-
ance.
' , Case Study
A 0.3 mgd trickling filter plant located in the
Mid-Atlantic region was experiencing frequent
violations of its fecal coliform limits. The OME
reported that operators were not using the
correct sampling and test procedures for pH,
chlorine residual, and fecal coliform, and were
not correctly recording what monitoring data
was being gathered.
The correct sampling, testing and record
keeping procedures were presented to the plant
operators and to plant administrators. Particular
' attention was given to making sure that the
operators understood the correct method for
conducting the fecal coliform test. The plant was
then monitored for 12 months, during which
, time the plant experienced no violations of its
NPDES limits.
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OTHER FACTORS RELATE TO THE DESIGN
OF SMALL WASTEWATER TREATMENT
PLANTS
Poor Design Can Exacerbate
Problems Caused by Inexpert
Operators
Poorly designed treatment plants compound
the problems resulting from inadequate opera-
tor expertise. Design deficiencies were cited as
contributing to poor performance at nearly 18
percent of the plants whose OME files were
reviewed. Furthermore, they were discovered
in 30 percent of the cases where the operator's lack
of knowledge and application was cited.
Too frequently, plant designers have appeared
to disregard the realities of small plant opera-
tion. The simplest, most flexible approach is
often overlooked in favor of a scaled-down
design more appropriate for a larger plant. A
simple design with some redundant unit proc-
esses built in can do much to overcome imper-
fect expertise and still achieve acceptable per-
formance.
Some Wastewater Designs
May Be Too Complex for
Small Communities
Certain wastewater treatment processes are just
more difficult to run than others. Indeed, an
underlying cause of problems related to the
operator's understanding of the treatment process
may be the prevalence of activated sludge
plants, even in the smallest plant-size category.
These plants are much more complex than la-
goon and fixed-media processes, and may not
be appropriate where staff skill levels are likely
to be low.
Small Towns Can Be
Unpleasantly Surprised By
Plant Staffing Needs
The design of a small wastewater treatment
plant can aggravate staffing or other administra-
tive problems. "204" troubleshooters inter-
viewed several town administrators who said
that they were not made aware of (or perhaps
just didn't "hear") the plant's full staffing re-
quirements during either the planning or de-
sign phases. Officials also failed to realize how
difficult it would be to obtain staff with the skills
or talents necessary to run their plant. Many
small community budgets can't absorb the cost
of hiring the full complement of staff demanded
by the facility's design. The result: the plant
ends up operating with fewer—or less quali-
fied—staff.
The Case of the Disappearing
Flow Capacity
Design was also observed to play a supporting
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role in the I/I problems identified at some plants.
While it is easy to say that the plant was not
designed to handle peak flows, there is another
side to the story. Engineers may design a treat-
ment works with a certain maximum capacity
in good faith, after the municipality assures
them that it will fix the existing I/I problem to
save money on plant size. "Design problems"
arise when the I/I "fix" is never carried out.
Sometimes Designers Just
Make Mistakes
The basic design process for sewage treatment
works is well developed for the types of facili-
ties found in the OME reports reviewed. None-
theless, in numerous instances, designers had
plainly made errors in planning specific unit
processes. These are summarized below on
Table 2.1. Design errors seem to be most preva-
lent in the inlet works and the sludge dewater-
ing equipment. At the headworks of the plant,
engineers often failed to install adequate bar
screens, comminutor, or similar devices. The
sludge dewatering equipment was frequently
undersized for the amount of sludge the plant
produced.
j Case Study-
Poor performance at a 0.75 mgd rotating biologi-
' * cal contactor facility in Georgia was attributed to
^4 a lack of operator skills, an undersized secondary
•• ^ clarifier, and an inadequate sludge drying bed
/ j area. The 104(g) trainer worked with the operator
to develop skill in process control and to specifi-
4 cally overcome design deficiencies that were con-
tributing to the poor performance. The operator
learned how to control the solids inventory and
to monitor the process. Alum was added to
/ f mitigate the effect of the undersized clarifier.
Solids Handling: A Design
Issue?
More than 75 percent of the plants with solids
handlingand disposal problems identified under-
sized dewatering facilities, especially sand
drying beds, as being responsible. Several
"104 " troubleshooters reported treatment works
that were designed with no solids handling
facilities at all! These cases were usually ex-
tended aeration plants. One Regional "104"
coordinator believes that consulting engineers
have somehow misrepresented the process,
implying that it would produce little or no
sludge.
Table 2.1 Categorization of Design Problems by Unit Process
Item
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
Type of
Process Unit
Inlet Works
Primary Clarifier
Aeration Basins
RBC or Trickling Filter
Lagoon
Secondary Clarifier
Disinfection
Sludge Transport
Sludge Dewatering
Sludge Digesters
Primary or Secondary
Performance Limitation
Secondary
Primary
Secondary
Secondary
Secondary
Secondary
Primary
Secondary
Secondary
Secondary
Primary
Secondary
Number of
Times Cited*
13
2
6
10
3
5
2
8
2
15
2
3
* Number of times a design problem was cited for a particular unit process in the OMEs reviewed during the study
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Poorly Designed Laboratories
Undermine Plant Performance
Two design-related issues contributed to labo-
ratory problems and their related effects. First,
engineers failed to design a laboratory into the
plant (although this was reported in only two of
theOME files reviewed). The more widespread
deficiency was design of an inadequately sup-
plied laboratory. This design limitation was
observed in more than half of the OME files
reviewed where laboratory capability was cited
as the dominant PLF. Centrifuges and settle-
ometers were identifed as the equipment most
frequently missing.
Solutions
Laboratory capability was a frequently cited
problem at many of the treatment plants assisted
by the program. If no lab was present the 104(g)
trainers assisted plant staff in identifying other
laboratory facilities which could perform the
necessary analyses. If equipment was missing
from an existing laboratory then trouble shooters
identified what equipment the town needed to
purchase. In cases where limited funds pre-
vented the town from purchasing the equipment,
a financial plan was developed that identified the
source of the funds in future budget cycles.
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CERTAIN FACTORS ARE TIED TO PLANT
ADMINISTRATION
It can be claimed that lack of municipal support is at
the root of nearly all of the other PLFs, since it was
found to contribute to operational and even to
design problems.
Administrative Apathy Can
Debilitate Operations
No treatment plant can operate successfully
without good staff. And at the plants where
staffing was identified as the dominant factor
frustrating plant performance, administrative
issues were blamed in one-third of the cases re-
viewed. These issues included lack of adminis-
trative support or funding for training, and fail-
ure to fund the hiring and retention of good
staff.
Another one-third indicated that the staffing
problem was aggravated by a user charge that
was set too low to cover the costs of plant
operation. This is an example of the overlap
that occurs between PLFs. While the visible
problem is staffing, the root cause is a lack of
support from the municipality.
Town Managers Who Ignore
Staff Needs Find that
Turnover is High
In more than 30 percent of the OMEs that named
staffing as the dominant PLF, turnover was
cited as a problem. It is not surprising that staff
turnover is high at small treatment plants. Some
small towns do not offer adequate salary levels.
The position often has a low job prestige level.
Low operator morale is the general rule, and
was implied as an aggravating factor in many
OMEs. Most capable people stay only long
enough to get some experience and then move
up to a larger town where the pay is better.
Naturally, plant performance suffers as each
new recruit learns the ropes.
Operations Deteriorate When
Officials Ignore Training
One-third of the OME files listing storing as the
dominant PLF cited operators and staff with
insufficient experience and training. Often,
plants were being operated by personnel whose
State-required certification was below the level
specified in the plant's O&M manual, or who
had no certification at all. Small communities
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Case Study -
A 0.22 mgd aerated lagoon in the northeast was
experiencing frequent violations of its discharge
permit. 104(g) experts identified insufficient and
inappropriate use of staff as the problems afflict-
ing the plant.
The Village Administrator was the only certified
operator, but had so many other duties that he
was only able to attend to the plant sporadically.
The plant was also staffed by a part-time labora-
tory technician. The lack of adequate staffing re-
sulted in many problems at the plant, including a
build up of sludge in the lagoon and numerous
maintenance deficiencies. It was determined
during the OME that sludge had never been
wasted from the lagoons since the plant went on-
line.
The recommended solutions consisted of hiring a
full time certified operator for the plant and hav-
ing the Village Administrator provide a limited
amount of assistance. It was also recommended
that the part time laboratory technician position
be increased to full time. The village followed
through on these recommendations and plant
performance improved significantly.
A person with too many jobs will perform none
of them well, and will probably be too busy to
train thoroughly on the technical aspects of
wastewater management.
Authority Struggles Can Lead
to Poor Operations
Lack of municipal support can also mean a poor
relationship between the municipal adminis-
trator and the wastewater treatment plant
manager/operator. A balance of power must
be achieved between these two if the facility is
to operate well. This balance is difficult to
achieve if the plant staff is constantly turning
over. Issues in this area centered around poor
delegation of authority. In some cases, the
plant operator was prevented from ordering
even basic equipment and supplies. In others,
the plant manager was not permitted to hire or
fire staff at the facility.
often withhold municipal support by failing to
include any money for staff training in their
wastewater budgets. This prevents the opera-
tor from attaining the proper level of certifica-
tion.
Some Municipal
Administrators Stretch Staff
Too Far
Small-town treatment plant operators are com-
monly assigned to other public works duties
that restrict the amount of time they spend at the
plant. In this case, poor municipal support means
assigning too low a priority to the physical and
technical needs of the sewage treatment plant.
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Inadequate User Charges Set
the Stage for Troubled
Performance
Inadequate user charges were identified in more
than a third of the OME files where a lack of
municipal support was cited as the dominant
limiting factor. In many cases, the user charge
system hadn't been evaluated since the plant
went on line. While costs steadily rose, the
budget either shrunk or remained constant.
Many user charge systems provided only
enough money to pay staff and meet the basic
requirements for utilities and expendable sup-
plies. Such systems failed to include funds for
proper parts, maintenance, and capital replace-
ment (i.e., a sinking fund for purchasing major
components). Aging treatment plants without
Solutions -
The solutions identified for dealing with staffing
issues generally require additional funds.
Among the solutions recommended by the 104(g)
trainers were:
• Performance of staffing evaluations to
determine the real number of staff and level
of skills needed to run the plant well;
• Hiring additional staff to bring the plant up
to the level identified in the O&M manual as
necessary for its operation;
• Assigning staff full-time to the treatment
plant;
• Providing funding so that the operator of
the plant is able to receive training and
attain the certification level necessary to run
the plant; and
• Using temporary work crews for non-
technical maintenance tasks such as
painting and lawn mowing.
the resources for refurbishing equipment are
headed for permit violations sooner rather than
later.
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CONCLUSIONS &
RECOMMENDATIONS
Diagnostic evaluations and on-site troubleshooting are, by definition, reactions to existing
problems. The conclusions and recommendations that follow are aimed at heading off such
problems before they arise.
The information is organized for two audiences: The section on "Plant Design and Startup"
is for the engineering design community; "Management and Regulation" is for those state
and local officials ultimately responsible for plant compliance. Both engineers and officials
should find all the material of interest, however.
HPLANT DESIGN & STARTUP
CONCLUSION 1: ACTIVATED
SLUDGE MAY NOT BE A GOOD
DESIGN CHOICE FOR MANY
SMALL PLANTS
The OMEs suggest that many plant designers
are not considering the unique needs of small
rural communities when selecting plant proc-
esses.
Activated sludge plants make up more than 60
percent of the plants included in the "204" data
base. Yet report after report cited operators
who did not adequately understand the acti-
vated sludge process or were not removing and
disposing of solids properly. It is a fact that the
activated sludge process requires more opera-
tor training and experience than fixed media or
lagoon processes, and that process monitoring
and laboratory knowledge (either at the plant or
from a contract lab) are critical to proper process
control. Small communities are the least likely
to be able to provide such expertise.
RECOMMENDATIONS
1. Design engineers should recognize that small
rural plants are not often able to keep highly
skilled operators. They ought to give fuller
consideration to simpler treatment processes
such as fixed media or lagoons. Only where
these techniques are unfeasible due to land
limitations, climate, or other constraints should
the activated sludge process be considered.
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2. The many alternative/innovative, low-tech-
nology systems that are easy to operate and
maintain should be given increased consid-
eration in the facility planning process. They
include facultative ponds, constructed wetlands,
intermittent sand filters, communal leach fields,
and other variations on land treatment.
3. The final selection of a treatment technol-
ogy should be based on a complete net present
worth analysis including all annual costs—
staff salary, equipment maintenance, periodic
recruitment of operators, staff training, moni-
toring, power equipment replacement, adminis-
trative costs, and full costs for sludge treatment
and disposal. The cost of sludge treatment and
disposal should be based on a conservative
estimate of sludge quantity and solids content.
Many of these costs are not considered or only
liberally considered in most cost effectiveness
analyses, biasing these assessments toward
selection of conventional treatment technolo-
gies.
CONCLUSION 2: PLANT
INFLEXIBILITY UNDERMINES
OPERABILITY
While lack of plant flexibility was not a
specific PLF, it was an underlying cause of
difficulties at plants where poor operator
understanding of process control was cited.
Such plants often lacked the redundancy in
unit processes that will permit a clarifier or
aeration basin to be taken off-line for repairs
or cleaning. This problem even exists in
lagoon systems: two of the OMEs reviewed
cited single lagoons and inflexible piping.
Plant inflexibility is also an issue relative to I/I.
Many of the troubleshooters who identified
I/I as the main PLF noted that the plant did not
have sufficient capacity to accommodate higher
flows during wet weather. Even a skilled,
knowledgeable operator can do little to im-
prove performance under such rigid circum-
stances.
RECOMMENDATION
4. Designers should conscientiously build
flexibility into small systems. Rather than
scaling one or two large clarifiers down to one
medium or small clarifier, two small clarifiers
should be specified. This recommendation
applies not just to piping configurations and
redundant unit processes, but to the use of
variable speed pumps for sludge wasting and
return and the application of flexibility in aera-
tion. Overall, it is recommended that small
plants be designed to accommodate a variation
in flow of +/- 30 percent. Equilization tanks
could also be considered to handle I/I flow
extremes.
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CONCLUSION 3: SMALL PLANTS
HAVE FRONT- AND BACK-END
PROBLEMS WITH PROCESS
DESIGN
The OME files revealed O&M problems arising
from certain unit processes, chiefly plant head-
works/grit removal and sludge dewatering and
disposal.
Many small plants were designed with inade-
quate screening and, in some cases, no primary
clarifiers. Grit, rags, and solids were building
up in the rest of the plant. Difficulties with the
solids processing train led many "204" trainers
to recommend abandoning sludge dewatering
systems and moving to land application of
liquid sludge.
RECOMMENDATIONS
5. Although it may be cost effective to design
plants with no primary clarif ier and easier to
dewater secondary sludge only, the entire plant
should reflect these design approaches.
Pumps, piping, and aeration systems should all
be designed to accommodate increased solids
and rags in the system.
6. Operators should be made fully aware of
the need for removal of floating debris that
passes primary screening.
7. Small plant operators have widespread prob-
lems with solids handling. Thus, it is strongly
recommended that engineers designing for them
always consider the feasibility of liquid sludge
disposal. Rural communities typically have
relatively easy access to agricultural land and
other areas suitable for disposal of liquid sludge*.
In most cases, this will be found to be a cost-
effective technique that also lessens the de-
mand for technical expertise on the part of the
plant operator.
* EPA and most state regulations do require
that sludge be stabilized properly prior to dis-
posal.
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CONCLUSION 4: HEAVY LOADS
CAN CONFOUND UNDERSKILLED
OPERATORS
Hydraulic and organic overloading of small
treatment plants was another common occur-
rence underlying many of the operational prob-
lems. Typical in cases where /// was cited as the
PLF, overloading was also identified in several
OME reports as operators' inability to maintain
process control. Small treatment plants are
clearly susceptible to problems resulting from
excess loading, particularly where the operator
has limited experience.
The basics of wastewater design prescribe that
the plant should have the capacity to handle the
anticipated hydraulic and organic loading.
Unfortunately, this is not always a simple mat-
ter, given the economic conditions in small
towns. During facility planning the design en-
gineer may duly discuss the need for hydraulic
capacity to accommodate I/I. And to econo-
mize on plant costs, the town in good faith
promises to fix the I/I problem. However,
what often happens is that the plant goes on
line without the capacity to accommodate wet
weather peak flows.
Furthermore, small communities tend to see
increased organic and industrial loads as a
boon, not a problem. Small rural communities
may often look past wastewater capacity prob-
lems in efforts to secure employment opportu-
nities. Many communities are reluctant to bring
stringent requirements to bear on an existing
industry, including pretreatment requirements,
even if the municipality's treatment plant can-
not accept the load. Side-stepping of such
constraints is even more common when a new
industry proposes moving into the commu-
nity.
RECOMMENDATION
8. It is recommended that design engineers
and community administrators carry out frank
discussions during the planning process and
agree on realistic loading levels for the facility.
It is incumbent on the design engineering com-
munity to take a conservative, if not skeptical,
approach to the design of small plants and to
take steps that accommodate I/I and industrial
loadings realistically.
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CD KiAN A GEMENT AND Professionalism—Reasonable opportuni-
I?Tf^l TJ A TTO7V7 t*es ^or s*a^ training and certification.
These minimum requirements are a quantum
CONCLUSIONS: STAFFING leap forward for many small communities. Such
DIFFICULTIES AGGRAVATE POOR a substantial shift will call for a change in atti.
PERFORMANCE tude and the money to underwrite improve-
ments.
Clearly, small communities have a great deal of
difficulty attracting and keeping trained waste- 10. Seek to Attract Better Staff.
water treatment plant staff. Analysts saw diffi-
culty with staffing—which includes inadequate Incentive-based pay levels for plant superin-
staff size, deficiently trained staff, and high tendents and operators would be one way of
staff turnover—reported very frequently, ei- increasing compensation, while at the same time
ther as a PLF in its own right or as a contributing improving plant performance and the likeli-
factor to other PLFs. hood that the community is receiving a benefit
equal to or greater than its increased outlays.
RECOMMENDATIONS Pay increases, even performance bonus pay
structures, are feasible only where the munici-
Because staffing is a pervasive problem, solu- pality can afford the salary levels.
tions must be broad-based.
One radical approach to the staffing problem
9. Increase operator status and visibility. would be for states to require certain minimum
"critical mass" for the areas served by new rural
Even small rural treatment plants need a strat- treatment plants. This could be accomplished
egy for finding and keeping good operators, by providing service through regional waste-
Components should include: water management districts serving, say, no
fewer than 5,000 residents. These larger dis-
Full-Time Position—At least one full-time tricts would be more able to afford realistic
(or nearly so) opera tor/superintendent. salaries and attract capable staff. A practical
constraint on this approach can be excessive
Adequate Fay — Salary that is competi- sewering costs which may be necessary to cre-
tive with other critical municipal func- ate such a district.
tions like police chief.
It is becoming more apparent that one of the
Reasonable Authority — For budgeting, biggest short falls in the industry is day-to-day
purchasing, hiring, and firing. operational expertise. This shortfall could be
met by using circuit riders to supervise a num-
ber of small rural treatment plants. Several
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small towns could pool resources to offer an
adequate salary. Pooling also affords econo-
mies of scale in purchasing supplies and secur-
ing laboratory support.
11. Strive to Keep Good Staff.
Other measures will be needed to develop and
advance staff so that turnover is minimized and
capable people stay. One recommendation is
that training outreach efforts be increased in
rural areas. While low population density can
make personalized outreach costly, computer-
ized technical assistance and training may be
the wave of the future. Many small communi-
ties now own personal computers, at City Hall
if not at the treatment plant. Electronic bulletin
boards and on-line training programs are prom-
ising methods for creating real wastewater
professionals in small towns.
A second recommendation is that states be-
come more active in verifying the certification
of POTW operators. While certification is re-
quired in every state, the OMEs revealed wide-
spread disregard for adequate certification.
Serious regulatory attention to this important
issue may affect plant performance positively.
CONCLUSION 6: PLANT
BUDGETS AND USER CHARGES
MAY BE TOO LOW
While insufficient funding was cited in fewer of
the OME reports than was expected, this may be
because only a limited number of the OMEs as-
sessed finances in detail. Discussion of under-
lying problems related to staff pay, sinking
funds, preventive maintenance, and operating
revenues made it clear that plant budgets and
user charges were often too low to meet the
facility's current and long term needs. In too
many cases, plants were run on general munici-
pal revenues. Salaries were low, plants under-
equipped, and sinking funds and preventive
maintenance funds nonexistent.
RECOMMENDATIONS
12. Better fiscal management must start with
a separate budget for the treatment plant. This
tool will make it possibl e to determine if the user
charges are adequate to support the facility, and
where they are not—to revise those charges.
The plant budget should be developed annu-
ally to reflect changing cost levels and new re-
quirements for plant upgrading or expansion as
well as operations, repair and replacement
needs.
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13. It is imperative that the budget provide for
a sinking fund to cover replacement of major
equipment.
14. The budget must also support adequate
staff salaries as well as training and required
certification courses.
CONCLUSION?: MUNICIPAL
SUPPORT IS A SUBTLE BUT VITAL
NEED
One very successful approach to this issue has
been to make the treatment plant into a multi-
use facility. The plant and grounds can often
accommodate recreational facilities. Offices
can be shared with other community agencies
or organizations. Rooms can be made available
for meetings. One very effective technique is to
have monthly town council meetings at the
treatment plant.
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13. It is imperative that the budget provide for
a sinking fund to cover replacement of major
equipment.
14. The budget must also support adequate
staff salaries as well as training and required
certification courses.
CONCLUSION?: MUNICIPAL
SUPPORT IS A SUBTLE BUT VITAL
NEED
Although lack of municipal support was not
often cited as a problem per se, close reading of
the OMEs indicates that it aggravated other
PLFs. A community's attitude toward its
wastewater treatment function affects many
aspects of plant life: morale and turnover;
funding and pay; disposal options; facility ap-
pearance and maintenance; and even opera-
tions. It is doubtful that the foregoing conclu-
sions and recommendations will be adequately
addressed unless general awareness and sup-
port for the wastewater treatment facility is
generated within the community.
RECOMMENDATIONS
15. Outreach and information transfer must
be applied to increasing community support.
American attitudes have historically regarded
sewage treatment as an unpleasantness best
kept out of sight and out of mind. Wastewater
specialists and technologies perform a com-
mendable ecological service for both the hu-
man and natural communities. This service
needs to be brought closer to the focus of
municipal attention.
One very successful approach to this issue has
been to make the treatment plant into a multi-
use facility. The plant and grounds can often
accommodate recreational facilities. Offices
can be shared with other community agencies
or organizations. Rooms can be made available
for meetings. One very effective technique is to
have monthly town council meetings at the
treatment plant.
O OVERALL CONCLUSIONS
The Section 104(g)(l) program has been very
successful in identifying the factors that have
typically limited performance of small treat-
ment plants and in providing solutions to these
problems. While the program is a cost-effec-
tive approach to meeting these needs, it is, by
design, an after-the-fact approach. As the fore-
going conclusions and recommendations dem-
onstrate, there are many actions—mostly
simple, straightforward, and inexpensive—that
can be taken right from the beginning to fore-
stall the problems that can limit small plant
performance.
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