NATIONAL FIELD INVESTIGATIONS CENTER
CINCINNATI
OPERATIONAL CONTROL PROCEDURES
for the
ACTIVATED SLUDGE PROCESS
STATUS
of the
NFIC-C PROCEDURES PAMPHLETS
and the
AUDIOVISUAL TRAINING AIDS
MAY 1974
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCE/WENT AND GENERAL COUNSEL
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Status of the
"NFIC-C Procedures" Pamphlets
and Audiovisual Training Aids
May 1974
NFICC PROCEDURE PAMPHLETS
Completion of the "Appendix" to the Operational Control
Procedures for the Activated Sludge Process ("NFIC-C
Procedures"), brought to five the total number of Parts to
this series that have been distributed by the National Field
Investigations Center - Cincinnati (NFIC-C). These five
pamphlets, describing the process control procedures that
have been developed by the Waste Treatment Branch of NFIC-C
to improve performance and effluent quality at activated
sludge plants, have been distributed to EPA Regions, States,
and other groups and individuals interested in wastewater
treatment.
A brief description of the Parts follows:
PART I - OBSERVATIONS - APRIL 1973
This Part describes readily observed indicator
characteristics, such as the type and color of foam on the
surface of the aeration tanks, degree of turbulent mixing,
sludge color and odor, and the presence or lack of scums and
floating floe particles on the surface of the final
clarifiers. These characteristics, when used in conjunction
with the results of the control tests described in Part II,
help the operator identify mixed liquor sludge quality and
process status.
PART II - CONTROL TESTS - APRIL 1973
This pamphlet describes in detail the simple though
highly informative tests, such as the use of a settlometer
to determine sludge settling and compaction characteristics,
a centrifuge to establish mixed liquor and return sludge
concentrations, a blanket finder to determine the depth of
the settled sludge blanket within the final clarifier, and
the turbidity test to determine final effluent quality.
Other important control testing duties, such as flow
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metering, sample collecting and dissolved oxygen testing are
also described.
PART III-A - CALCULATION PROCEDURES - DECEMBER 1973
This pamphlet spells out in detail how essential
process control parameters can be calculated from the
results of the control tests described in Part II. Part
III-A documents the relatively simple procedures applicable
to the commonly used plug-flow and complete-mix activated
sludge process modifications. The more complex formulas
needed to describe and evaluate process reactions for step-
flow and the contact-stabilization modifications of the
activated sludge process will be included in Part III-B.
RETURN SLUDGE FLOW CONTROL - SEPTEMBER 1973
This companion piece to the pamphlet series is a
preview of a portion of the proposed Part V - "Process
Control". It was developed to answer recurring questions
about this element of process control while awaiting
completion of the more comprehensive volume.
The narrative and diagrams demonstrate process
responses to return sludge flow adjustments. They show how
such response trends reveal process adjustment requirements.
The discussions lead the operator, in a step-by-step
sequence, from control testing, through the calculation of
control needs, to determination of the specific return
sludge flow adjustment that will maintain or restore
appropriate process balance.
APPENDIX - MARCH 1974
The Appendix includes examples of daily report forms,
process trend charts, procedures for determining moving
averages and probability plots, plus a list of the symbols
used in process control. Operators now have this background
information readily available for use with existing and
future issues of the pamphlet series.
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FUTURE PAMPHLETS
Other Parts nearing completion, under development, or
proposed for the future include:
Part III-B - "Calculation Procedures for Step-Aeration"
Part IV - "Sludge Quality"
Part V - "Process Control"
Plans also call for a compilation of Case Histories
that describe performance of plug-flow, complete-mix, step-
aeration and possibly pure oxygen activated sludge plants
that were controlled according to the principles described
in the NFIC-C Procedures pamphlet series.
Purpose
These pamphlets were developed primarily for trained or
experienced activated sludge plant operators. It was
possible, therefore, to by-pass discussions of many well-
known and widely recognized preliminaries, such as primary
sedimentation and sludge digestion and such monitoring
laboratory tests as BOD, COD etc. Furthermore, it was
possible to avoid discussions of sophisticated theoretical
concepts, that are either not needed or that cannot be used
directly by the operator, such as alpha and beta
coefficients or the relative worth of nitrosomonas versus
nitrobacter organisms, etc.
NFIC-C hopes that this series will help expand
operators' knowledge and increase their skills. Though not
written specifically for others, such as entrance level
plant personnel or design engineers, the pamphlets should
also prove useful to them and anyone who is seriously
interested in waste treatment plant operation.
Precautions
A few cautionary statements concerning organization and
suggested use of the pamphlets are appropriate.
First of all, developing the complete series remains a
continuing effort. It is intended that the full series will
ultimately describe most of the fundamental laws governing
the activated sludge process and will provide operators with
most of the information they need to control the processes
predictably and successfully. Even so, some problems and
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questions will probably not be solved nor answered
completely. The operator's intelligence, skill, ingenuity,
and dedication remain essential to proper plant operation.
Secondly, the overall process requirements usually
cannot be determined successfully from an independent
analysis of any single process characteristic, by any
isolated process response, or by referring to only one Part
of the series. Part I, for example, that was developed
specifically to tell operators what to look for, also
contains generalized supplementary comments on control
adjustments that have helped correct some observed
deficiencies. But additional informative test data,
described in subsequent Parts of the series, must be used
along with the physically observed indicators to determine
what specific control adjustments are actually needed.
USE OF THE INFORMATION DISTRIBUTED TO DATE
Though certain important concepts remain to be
described in future pamphlets, the Parts distributed to date
contain sufficient information to help operators start using
these operational control procedures immediately to improve
final effluent quality. When a new pamphlet is received it
should be studied and combined with the previous issues.
All Parts of the pamphlet series should be maintained in a
three-ring binder located in the control room or laboratory
available for ready reference and use by plant personnel.
The completed pamphlets represent a useful intermediate
plateau of accumulated information, even though the pamphlet
discussing excess sludge wasting control has not yet been
completed. The following outline describes how an operator
can make best use of the information distributed to date.
If the operatori
1. Maintains adequate dissolved oxygen with thorough
mixing (usually 1 to 3 mg/1 with exceptions noted
in Part I);
2. Remains aware of long-term process requirements
indicated by observation of the process (Part I);
3. Runs control tests (Part II);
U. Calculates process relationships (Part III-A)>
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5. Adjusts return sludge flow to satisfy calculated
demands (Return Sludge Flow Control preview);
6. Maintains trend charts and process characteristic
status (Appendix).
He will:
Most probably have satisfied process demands,
with the possible exception of sludge wasting, both of
which can be subject to restrictions imposed by
inadequate plant capacity or control inflexibility.
He can then:
1. Observe final effluent quality and study the
trend charts for process changes that may have
caused improvements (a) or degradation (b).
a. Continue control policy if the effluent is
improving or remains excellent.
b. Try to identify the other characteristics
whose trend line changes corresponded with
the changes in the effluent quality trend
line if effluent is unsatisfactory, or is
degrading.
2. Concentrate attention on sludge quality, pro-
cess balance, and effluent quality responses to
his established sludge wasting control, since
other process controls will most probably have
been correct.
He will then be able to:
1. Correct his wasting procedures if the cause of
the degradation has been recognized;
2. Alter, possibly reverse, the previously imposed
sludge wasting policy if the cause of effluent
deterioration has not been recognized;
3. Observe the subsequent trend curve changes and
correlations that occurred after the wasting
rate had been changed and then maintain the re-
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vised wasting policy if the sludge and final
effluent quality improve.
Judicious use of information in the pamphlets published
can eliminate many of the uncertainties confronting some
operators whose plants periodically swerve off-course
because they were unaware of fundamental factors that govern
the interrelated and interdependent cause - effect process
relationships. Guided by the NFIC-C Procedures completed to
date, operators may still be confronted with uncertainty
about one remaining significant control process variable -
sludge wasting. Even here, they have been presented with
some generalized guidance on long-term wasting requirements
in Part I of the series.
Additional information that will appear in future Parts
of this series will hopefully describe total process control
and continue to shift the balance in plant control still
further from an art towards a more predictable science.
Where to Order
Requests for pamphlets in the NFIC-C Procedures series
should be addressed to:
Waste Treatment Branch
National Field Investigations Center-Cincinnati
5555 Ridge Avenue
Cincinnati, Ohio U5268
AUDIOVISUAL INSTRUCTION UNITS
Parts of the audiovisual training material on activated
sludge plant operations, developed jointly by the Waste
Treatment Branch and the National Training Center, are also
available on a short term loan basis for group presentation.
Agencies wishing to keep their own series can have them
produced at cost by the Training Center. Reproducing the
loaned prints is discouraged because quality is lost in
copying a copy.
This audiovisual series is also developed primarily for
trained or experienced activated sludge plant operators and
the following parts are presently available.
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UPGRADING BIOLOGICAL TREATMENT
XT-25 (28-minute tape and 63 slides)
This introductory material describes the results of two
waste treatment plant upgrading projects in generalities and
in terms of final effluent quality improvements. Its
principal objectives are to document and emphasize the fact
that excellent final effluent quality can be achieved and
should be expected at properly operated activated sludge
plants. It also attempts to stimulate and support operators
in their continued efforts to achieve the highest possible
performance levels.
It is not a "how to do" presentation, since such
discussions are proposed for future parts of the series.
OPERATIONAL CONTROL TESTS FOR THE ACTIVATED SLUDGE PROCESS
XT-UO (16-minute tape and 51 slides)
XT-m (17-minute tape and HI slides)
XT-42 (22-minute tape and 67 slides)
This three-part series covers Observations and Control
Tests to illustrate the information contained in Parts I and
II of the pamphlet series. It is a self-contained lecture
and can be used effectively with or without the other
audiovisual materials.
PROCESS CONTROL DEMANDS
XT-60 (10-minute tape and 19 slides)
XT-61 (15-minute tape and 37 slides)
Since this intended subseries has not been completed,
it describes only two features that are either introductory
or supplementary to the proposed complete "Process Control
Demands" subseries. As such, the series does not as yet
tell the whole story nor show the operator how to fully
evaluate process requirements and make appropriate control
adjustments.
XT-60, an introduction to this subseries, presents the
effects of return sludge flow adjustment on sludge concen-
trations sludge detention times, process equilibrium, sludge
characteristics, and final effluent quality.
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XT-61 presents the derivation of mixing formulas that
will be used in subsequent sections to develop the return
sludge flow demand formula for use in operational control of
the activated sludge process.
Planned Additions t.o the Audiovisual Materials
Work continues on development of additional parts of
the "Process Control Demands" to complete this subseries.
Other features of activated sludge process control, such as
sludge quality and informative case histories, will be
developed in the future. When completed, the audiovisual
series will parallel and supplement the envisioned complete
pamphlet series described earlier.
Where to Order
Requests for a catalogue describing these and other
instructional aids or for the loan of the audiovisual units
described above should be addressed to:
Ms Eileen Hopewell
EPA - Water Programs Operations
National Training Center
Cincinnati, Ohio 45268
U.S. GOVERNMENT PRINTING OFFICE 1974- 758-495/1223
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