v>EPA
United States
Environmental Protection
Agency
Municipal Environmental
Research Laboratory
Cincinnati OH 45268
EPA-625/6-82-007
Technology Transfer
Handbook
Identification and
Correction of Typical
Design Deficiencies at
Municipal Wastewater
Treatment Facilities
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EPA-625/6-82-007
HANDBOOK FOR
IDENTIFICATION AND CORRECTION
OF TYPICAL DESIGN DEFICIENCIES
AT MUNICIPAL WASTEWATER
TREATMENT FACILITIES
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
U,S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590
April 1982
-..*
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NOTICE
The mention of trade names of commercial products in this
publication is for illustration purposes and does not constitute
endorsement of recommendation for use by the U.S. Environmental
Protection Agency.
11
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FOREWORD
The U.S. Environmental Protection Agency was created because
of increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimonies
to the deterioration of our natural environment. The complexity
of that environment and the interplay between its components re-
quire a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem solution; it involves defining the problem, measuring
its impact, and searching for solutions. The Municipal Environ-
mental Research Laboratory develops new and improved technology
and systems to prevent, treat, and manage wastewater and solid
and hazardous waste pollutant discharges from municipal and
community 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 and provides a most vital communi-
cations link between the researcher and the user community.
Since the passage of PL 92-500, the Construction Grants Pro-
gram has spent several billion dollars in government funds for
the design and construction of publicly-owned treatment works
(POTWs). As these facilities became operational, it soon was
apparent that 40 to 60 percent of all municipal facilities were
not meeting the effluent quality for which they were designed.
The Municipal Environmental Research Laboratory Plant Oper-
ation and Design Program funded a 3 1/2-year national survey of
the factors limiting the performance of POTWs. The survey found
that no one factor was limiting the performance at the 103
facilities surveyed, but that an interrelated unique combina-
tion of design, O&M, and management deficiencies was involved
at each facility. A major conclusion of this survey was that
errors in design were severely limiting the operator's ability
to achieve maximum performance from the facility.
This handbook represents an effort directed by the Plant
Operation and Design Program to identify and suggest corrections
for design deficiencies typically found in municipal wastewater
treatment facilities. The listing of deficiencies was prepared
from discussions with various engineers familiar with design
and operation of municipal wastewater treatment facilities. The
111
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deficiency listing does not represent all possible design defi-
ciencies, but represents the input from a number of engineers
who have observed that these deficiencies hinder operation
and/or limit process performance.
Design considerations are presented to prevent the occur-
rence of the design deficiencies in new facilities. Where feas-
ible, procedures for correcting deficiencies at existing facil-
ities are presented. In development of this document, it became
apparent that design deficiencies are best eliminated during
the original design of the facility. Correction of design defi-
ciencies at existing facilities is not always cost effective.
Francis T. Mayo
Director
Municipal Environmental Research
Laboratory
iv
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ACKNOWLEDGMENTS
This handbook was prepared for the United States Environmental
Protection Agency (EPA) by Roy F. Weston, Inc. under the
direction of Mr. James H. Dougherty.
Mr. Jon H. Bender, Program Manager for the Municipal
Environmental Research Laboratory's Plant Operation and Design
Program, was responsible for overall project direction in the
development of the design deficiencies matrix, and for the
direction of research studies providing supporting background
information.
Other contributing EPA employees were:
o Mr. John M. Smith, EPA Municipal Environmental
Research Laboratory
o Dr. Curtis Harlin, EPA Robert S. Kerr Environmental
Research Laboratory
o Mr. Lowell Leach, EPA Robert S. Kerr Environmental
Research Laboratory
v
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CONTENTS
Foreword iii
Acknowledgments v
INTRODUCTION 1
USER GUIDE 2
Report Format 2
Design Deficiencies Matrix 2
Design Consideration Modules for POTWs 3
Procedures for Using Document 4
DESIGN DEFICIENCIES MATRIX 7
1.0 General Plant Design 8
2.0 Preliminary Treatment 19
3.0 Primary Treatment 23
4.0 Air Activated Sludge 25
5.0 Oxygen Activated Sludge 30
6.0 Trickling Filter 31
7.0 Disinfection 33
8.0 Anaerobic Digestion 35
9.0 Aerobic Digestion 37
10.0 Sludge Dewatering 39
11.0 Lagoons 43
12.0 Land Application 45
13.0 Sludge Disposal 48
14.0 Sludge Reduction 50
15.0 Rotating Biological Contactors 53
DESIGN CONSIDERATIONS ' 54
1.0 General Plant Design 55
1.1 General 55
1.2 Preliminary 103
1.3 Primary 111
1.4 Secondary Treatment 116
1.5 Sludge Handling 125
Vll
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CONTENTS
(continued)
1.6 Sludge Digestion 132
1.7 Sludge Dewatering 136
1.8 Sludge Incineration 142
1.9 Sludge Disposal 144
1.10 Disinfection 146
1.11 Lagoons 150
1.12 Land Application 152
1.13 Small Package Plants 156
1.14 Energy Conservation 168
1.15 Laboratory 169
1.16 Chemical Handling 172
1.17 Control Building 175
1.18 Site Selection 177
2.0 Preliminary Treatment 178
2.1 Manual Bar Screens 178
2.2 Mechanical Bar Screens 182
2.3 Comminutor 183
2.4 Barminutor 187
2.5 Macerator 191
2.6 Manually Cleaned Grit Chambers 193
2.7 Mechanically Cleaned Grit Chambers 197
2.8 Aerated Grit Chambers 198
2.9 Degritter 199
2.10 Grit Pumps 200
2.11 Influent Flow Measurement 200
2.12 Raw Waste Pumping 203
2.13 In-Line Flow Equalization 207
2.14 Side-Line Flow Equalization 208
2.15 General 209
3.0 Primary Treatment 211
3.1 General 211
3.2 Primary Clarifier 212
3.3 Primary Sludge Removal 215
3.4 Primary Sludge Pumps 219
3.5 Scum Removal 220
4.0 Air Activated Sludge 222
4.1 Aeration Basin 222
4.2 Diffusers 235
Vlll
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CONTENTS
(continued)
4.3 Fixed Mechanical Aerators 237
4.4 Floating Aerators 240
4.5 Blowers 242
4.6 Air Distribution System 243
4.7 D.O. Control and Measurement 244
4.8 Return Sludge Pumping 246
4.9 Waste Sludge Pumping 250
4.10 Secondary Clarification 252
4.11 Oxidation Ditch 260
5.0 Oxygen Activated Sludge 264
5.1 Aeration Basin 264
5.2 Air Compressors 265
5.3 D.O. Measurement 265
5.4 D.O. Control 268
5.5 Pressure Swing Adsorption 268
5.6 Oxygen Gas Flow Control 269
5.7 Influent Flow Control 269
5.8 Sampling and Monitoring 269
6.0 Trickling Filter 270
6.1 Trickling Filter 270
6.2 Rock Media 274
6.3 Plastic Media 275
6.4 Flow Splitting to Filters 276
6.5 Distribution of Media 276
6.6 Flow Recirculation 277
6.7 Secondary Clarifier 279
6.8 Sludge Pumping 280
7.0 Disinfection 281
7.1 General 281
7.2 Chlorine Contact Chamber 283
7.3 Chlorinator 286
7.4 Chlorine Control 288
7.5 Dechlorinator 288
7.6 Ozone Contact Vessel 289
7.7 Ozone Generator 289
7.8 Ozone Controller 290
7.9 Safety 290
IX
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CONTENTS
(continued)
8.0 Anaerobic Digestion
8.1 General
8.2 Single-Stage Digester
8.3 Two-Stage Digester
8.4 Gas Collection
8.5 Gas Measurement
8.6 Supernatant Withdrawal
8.7 Supernatant Disposal
8.8 Heating
8.9 Maintenance
8.10 Safety
8.11 Sludge Withdrawal
8.12 Sludge Recirculation
8.13 Sludge Feed
9.0 Aerobic Digestion
9.1 General
9.2 Aerobic Digester
9.3 Decanting
9.4 Clarification
9.5 Diffused Aeration
9.6 Mechanical Aeration
9.7 Sludge Removal
10.0 Sludge Dewatering
10.1 General
10.2 Gravity Thickeners
10.3 DAF Thickeners
10.4 Vacuum Filters
10.5 Centrifuges
10.6 Filter Presses
10.7 Belt Filters
10.8 Sludge Drying Beds
10.9 Sludge Transfer
10.10 Sludge Conditioning
11.0 Lagoons
11.1 Facultative Ponds
11.2 Aerated Ponds
11.3 Aerobic Ponds
11.4 Polishing Ponds
x
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CONTENTS
(continued)
11.5 Anaerobic Ponds 351
11.6 Baffles 352
11.7 Recirculation Pumps 353
11.8 Pond Configuration 353
11.9 Aerators 354
11.10 Dikes 355
11.11 Primary Cell 356
11.12 General 356
12.0 Land Application 358
12.1 Overland Flow Slope Design 358
12.2 Buffer Zone 359
12.3 Cover Crop 360
12.4 Hydraulic Acceptance 361
12.5 Pretreatment 362
12.6 Storage 365
12.7 Crop Harvest 367
12.8 Surface Drainage 368
12.9 Soil Depth 369
12.10 Infiltration Beds 370
12.11 Subsurface Drainage 371
12.12 Odor Control 372
12.13 Center Pivot Sprinkler 373
12.14 Traveling Gun Sprinkler 375
12.15 Single Set Sprinkler 377
12.16 Lineal Travel Sprinkler 378
12.17 Grated Pipe Distribution 380
12.18 Ridge and Furrow 381
12.19 Spreading Basins 381
13.0 Sludge Disposal 382
13.1 General 382
13.2 Landfill 385
13.3 Spraying 388
13.4 Planning 389
14.0 Sludge Reduction 391
14.1 General 391
14.2 Multiple Hearth Incineration 395
14.3 Heat Treatment 399
14.4 Fluidized Bed 401
XI
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CONTENTS
(continued)
14.5 Flash Drying 404
14.6 Composting 406
14.7 Atomized Spray 407
14.8 Co-Incineration 408
15.0 Rotating Biological Contactors 412
15.1 General 412
15.2 RBC 414
15.3 Secondary Clarification 416
Xll
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INTRODUCTION
This handbook has been prepared for use by engineers in-
volved in the design and review of designs for POTWs. Its in-
tent is to identify design deficiencies found to limit the
performance of POTWs. Design considerations have been develop-
ed that will eliminate these deficiencies during the design
phases of the project. The document will prove useful to per-
sonnel involved in the operation and maintenance of POTWs since
procedures are presented, where feasible, for correction of de-
sign deficiencies at existing facilities. Use of the handbook
will assure that the design incorporates a maximum number of
operational conveniences.
Typical design deficiencies found in POTWs are identified
and associated methods to correct each of the deficiencies noted
are presented. The information is not intended for use as a
troubleshooting guide for process-oriented operational problems.
Reference should be made to other documents for assistance con-
cerning operational problems.
This handbook describes design deficiencies that contribute
to performance and reliability problems, poor safety practices,
and/or decreased flexibility of plant process control. The re-
sult of such deficiencies may be any combination of increased
plant operations and maintenance, cost, and energy requirements.
The handbook is intended to provide design engineers with guid-
ance that will make their designs more operable and maintainable
at less cost, as well as more flexible in providing adequate
performance during times of changing influent characteristics.
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USER GUIDE
The organization and format of this handbook have been
designed to facilitate the location of information concerning
typical design deficiencies found in various wastewater treat-
ment systems and, more specifically, individual unit operations,
and to reference the deficiencies noted with related solutions.
The document is divided into two main sections:
Design Deficiencies Matrix.
Design Consideration and Correction Modules for POTWs.
REPORT FORMAT
Design Deficiencies Matrix
Design deficiencies commonly found in the POTWs are categor-
ized 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:
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Layout, Arrangement, and Placement of Components
in Design of Plant.
Hydraulic Design Considerations.
Mechanical Design Considerations.
Electrical/Instrumentation Design Considerations.
Safety Considerations.
Environmental Considerations.
Design Consideration Modules for POTWs
The design deficiencies listed in the matrix are discussed
in "Design Consideration Modules" in terms of items that should
be reviewed by the engineer during design of a new or expansion
of an existing wastewater treatment plant. Features of the
module format are as follows:
The design consideration category and applicable
unit operation or component are indicated in the
upper left-hand corner.
A treatment plant block flow diagram is presented
in the upper right-hand corner for each category.
The deficiency category 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. The associated design con-
siderations are 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-
referencing with the Design Considerations table of
contents on page 54.
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Suggested methods to correct the design deficiencies, when
already present at an existing wastewater treatment facility,
are presented in the document. The correction procedure, where
applicable, may include the following items:
Method.
Materials.
Cost.
Sketch.
PROCEDURES FOR USING DOCUMENT
The format of the document allows the reader the flexibility
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 iden-
tify those items he should review during design of a specific
unit operation or component.
The correct procedure for using the design deficiency matrix
is as follows:
1
Select the appropriate design considerations
category (i.e., preliminary, primary, activated
sludge, etc.) and refer to that section of the
matrix at the top of the page.
2. Determine which general deficiency group (i.e.,
mechanical, hydraulic, safety, etc.) the problem
falls under and turn to that portion of the matrix
on the left hand side of the page.
3. Identify the applicable unit operation or component
under the design considerations category and move
down that column until the desired deficiency with-
in that deficiency group is located. (NOTE: If
the deficiency is not listed for the applicable
unit operation or component, refer to the remainder
of the deficiencies within the deficiency group and
determine if it is listed under another unit
operation.)
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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
DEFICIENCY
GROUP
1.0)- GENERAL PLANT DESIGN
DEFICIENCY
Lack of hoists over larger pieces of equip-
ment .
Lack of spare pumps.
Lack of walkways around tanks, limiting
operator access.
Tall above-ground tanks frequently require
operator to climb long stairways.
No provisions for moving equipment and
supplies from one building floor to another.
Use of a room as a 800 incubator is incon-
venient because in-and-out traffic makes it
difficult to maintain proper temperature.
Lab building air vents are located too close
to air conditioning air intakes.
Use of fixed louvers in buildings that
cannot be shut during winter weather
condIt Ions.
Deficiency Reference Number is: 1.1.4
5. Turn to the digit deficiency reference number
identified above by noting the reference numbers
at the bottom of the Design Considerations section
pages (just on top of the page numbers).
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.
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DESIGN DEFICIENCIES MATRIX
Category Page
1.0 General Plant Design 8
2.0 Preliminary Treatment 19
3.0 Primary Treatment 23
4.0 Air Activated Sludge 25
5.0 Oxygen Activated Sludge 30
6.0 Trickling Filter 31
7.0 Disinfection 33
8.0 Anaerobic Digestion 35
9.0 Aerobic Digestion 37
10.0 Sludge Dewatering 39
11.0 Lagoons 43
12.0 Land Application 45
13.0 Sludge Disposal 48
14.0 Sludge Reduction 50
15.0 Rotating Biological Contactors 53
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Mo rock trzps provided.
No access to raw wastewater flow for sam-
pling before sidestream addition occurs.
1 nadequate cons (deration of needs for odor
cont rol .
Inadequate consideration of increased O&M
and energy costs resulting from elimination
of grit removal process .
1 nadequate velocity through process due to
poor flow control .
Inad equate design of pumpi ng station, re-
sultlng In frequent cyclinq of units causing
f 1 ow surges in downst ream processes .
Measurement cont ro 1 sect ion not compa 1 1 b 1 e
with flow measurement device.
1 nadequate des i gn of downst ream channe 1 s lope
and geometry causes back-up in control
sect Ion .
Inadequate design of obstructions downstream
of cont rol section induces inaccuracies in
flow measurement.
1 nadequate design permits grit depos its in
control section of flow measurement device.
Inadequate consideration of debris in waste-
water in selection of float for flow measure-
ment.
Lack of emergency overflow.
Improper velocity in bar screen chamber
1 ead I ng to grit depos 1 1 i on .
Improper flow-through velocity In grit
chamber.
Difficulty in handling high peak flows.
Short-circuiting in grit chamber.
Imp roperl y s ! zed wet wel Is resulting in lone
detention times and odor problems, or too
short detention time and cycl ing of pumps.
Flow meters located such that backwater
elevation changes, due to clogging of bar
screen, affect accuracy of meter.
Inadequate consideration of diurnal flow
patterns in sizing of flow measurement
equ i pment resul ts in measurement equipment
being inaccurate at the high and/or low
flow ranges.
1 nadequate approach channel length re suits
In flow measurement Inaccuracies.
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Lack of depth gauges provided on basins that
operate at varying levels.
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systems.
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Weirs and gates are not watertight.
Inability to back-flush influent pumps for
c 1 ean i ng purposes .
Inadequate consideration of effect of waste
material on mechanical reliability.
Corrosive and/or explosive gases close to
electrical motors and equipment.
Wet wel 1 1 evel float cont rol s may becorng
greasy.
Inadequate consideration of humidity in
influent structure results in inaccuracies
to flow sensors.
Lack of proper ventilation at lift station.
Inadequate consideration of potential
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DEFICIENCY'
GROUP
C 4->
O
>> 4-
ro o
DEFICIENCY
Inadequate odor control where excess waste
activated sludge is received at primary
clari f ier.
Flushing and cleanout connections for sludge
line not provided.
Primary sludge pumps located too far away
from clarifiers.
Lack of screening and grit removal ahead of
primary sedimentation.
Poor flotation of grease.
Improper length to width ratios.
Inadequate provisions for preventing fre-
quent maintenance resulting from stringy
material in wastewater.
Improper placement of scum removal equipment
hinders clarifier performance.
Inadequate provisions for chain, flight, and
sproket repair and replacement.
Inadequate clarifier depth.
Improper sizing of increments on time clock
results in pumping of unnecessarily thin
sludge.
Design includes a common sludge removal pipe
for two or more clarifiers resulting in
unequal sludge removal from the clarifiers.
Inadequate provisions for sampling of raw
sludge.
Operator is not provided with the capability
to observe sludge while pumping.
Inadequate flexibility in sludge pumping
system.
3.0 - PRIMARY TREATMENT
1
5!
01
LU
z.
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2
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1
2
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7
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01
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DEFICIENCY
GROUP
i i
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ro a
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c E O ro
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DEFICIENCY
Scum is recycled through the plant and not
removed from the system.
Improper materials selection.
Improper selection of scum pumping facil-
ities results in excessive OSM.
Effluent weir not uniformly level.
Improper baffling resulting in short-circuit-
ing.
Short-circuiting causing poor solids removal.
Septic conditions resulting from overloading.
No provisions for measuring sludge flow.
Inadequate consideration of impact of waste
secondary sludge pumping on clarifier load-
ing.
Inadequate consideration of impact of various
trickling filter reci rculation rates and
strategies on clarifier loadings.
Inadequate consideration of clarifier inlet
design.
Inadequate consideration of character of
sludge in sizing and layout of sludge lines.
Inadequate sizing of torque requirement for
sludge removal mechanism.
Heavy wear on scrapers due to grit«
Inadequate freeze protection.
3.0 - PRIMARY TREATMENT
1
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DEFICIENCY
GROUP
c
C i/i
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C O
V CL
CTi (-) c
1- O 0.
4-
C O
* 11
w E C
O U
nj V
_J CL O
DEFICIENCY
Lack of flexibility to operate in different
modes (i.e., complete mix, plug flow, con-
tact-stabilization, etc.).
Aerator spacing not adequately considered.
No provision for addition of chemicals to
improve settling characteristics.
Improper type of sludge removal mechanism
sel ected.
No separate waste sludge pumps.
Inadequate consideration for alkalinity
adjustment.
Inadequate foam control.
Insufficient mixing to prevent solids de-
position and provide uniform SS and D.O.
concentrations In the basin.
Improper clarifier sidewater depth (SWD).
Inadequate aeration capacity.
Inadequate screening of raw wastes causes
plugging of aerators and return/waste sludge
pumping system.
Inadequate access to weirs for sampling and
mai ntenance.
Inability to adequately measure and adjust
air flow rates to control D.O. levels and
energy consumption.
Inflexible design does not permit isolation
of reactors and changes In flow schemes for
maintenance purposes and/or to adjust for
changes in waste characteristics.
Inadequate consideration of Impact and con-
trol of In-plant sidestreams.
Inadequate provisions for sampling and ob-
servation of return and waste activated
si udge.
Inadequate consideration of debris in
wastewater.
Inability to dewater tanks for repair.
Improper selection of valves for sludge
1 i nes.
Inadequate provision for by-passing aera-
tion basin.
Inadequate or no air cleaners provided on
b lowers.
*t.O -- AIR ACTIVATED SLUDGE
1
2
~
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4
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6
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6
7
8
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24
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DEFICIENCY
GROUP
DEFICIENCY
it.O -- AIR ACTIVATED SLUDGE
UJ <
X 2
U- <
O UJ
u or
13
(/)
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* UJ
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10
Improper return sludge flow splitting.
Overflow rate (OFR) of clarifiers too high
to meet effluent SS requirement limitation.
No provisions for flow diversion boxes.
Inadequate waste sludge pipe sizing for
"slip-stream" wasting.
Short-circuiting in clarifiers.
Lack of consideration of inlet-outlet losses
Improper or no use of a scale-down factor
to convert lab overflow rate (OFR) to design
OFR."
Improper weir placement (i.e., proper weir
length, but closely-placed troughs create
high localized upward velocities within
clarifiers).
Improper length-to-width rat 10.
Improper sldewater depth (SWD) and baffling
cause splashing problems in basin.
Inadequate sludge recycle/waste capacity.
Inadequate sludge flow measurement for
small plants using air lift pumps.
Inability to control and measure mixed
liquor flow distribution to multiple
secondary clarifiers.
I nab 11i ty to adj ust, measure, and control
return/waste sludge flows.
Inability to change placement of return
sludge in aeration basin.
Inadequate consideration of impact of
changing aeration basin levels on aerator
performance.
Improper installation of flow control walls
results in inadequate nixing.
12
13
15
10
10
10
13
Improper air piping material.
No provisions for removing air diffuser
drop pipes from aeration tanks.
Multicompartmental basins do not have reln-
force'd Inner walls; therefore, Individual
tanks cannot be dewatered.
Air valves not graduated to allow even dis-
tribution of air flow to diffusers.
16
25
-------
DEFICIENCY
GROUP
DEFICIENCY
AIR ACTIVATED SLUDGE
=: 2:
o uj
o a:
10
Inadequate or no provision for scum removal
from secondary clarifiers.
Inability to drain foam spray system re-
sults in freezi ng problems.
Supports for air drop pipes cannot be seen
when aeration basin is full, making it
difficult to reinstall the drop pipes.
Long scum lines frequently become clogged.
Scum will not flow from scum tanks once
subnatant is pumped out.
Sludge lines periodically clog with rags,
and no backflush facilities are provided.
Inability to conveniently dewater scum pits.
Floating aerators located too close to wall
or pontoons not aligned properly, causing
pontoons to strike the basin wall when
started up.
Lack of splash shields in front of effluent
gates.
Scum accumulation in flow splitter boxes.
Improper placement of gear box drains causes
oil to drain into aeration basin.
Diffusers plug due to dirty air supply.
Improper selection of bearings which are
not compatible with excessive moisture.
Improper support of aerators results in
misalignment and premature bearing failure.
17
18
12
Amp meters not provided at motor control
center so operator cannot tell if proper
anperage is be i ng drawn.
Quick disconnect plugs on aerators become
wet and short out.
Lack of instrumentation to totalize recycle/
waste s1udqe flows.
No time delay relays provided to 1imit stres
shock to aerat ion gears when sh i ft i ng from
high speed to low speed.
Improper design of 0.0. measuring i nst rumen-
tation does not allow easy removal of equip-
ment for rout i ne i nspection and ma i ntenanee.
13
12
26
-------
DEFICIENCY
GROUP
DEFICIENCY
>t.O AIR ACTIVATED SLUDGE
89 10 11
SIC
Spray from surface aerators makes wa1kways
sii ppery.
Blower silencers not provided.
10
17
-------
DEFICIENCY
GROUP
TJ
C (A
C.
4-» C
C O 4J
0) Q. C
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0) O
Ol O Q-
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c o
L±J CJ
DEFICIENCY
Inadequate access for maintenance to anti-
foam spray headers in covered tanks.
Inadequate access to D.O. measuring equip-
ment due to mounting in flanged portholes.
Inadequate forward flow control causing
ripples in reactor.
Overly sensitive instrumentation responding
to hydraulic ripples and cycling 0 gas
f 1 ow .
Inadequate turndown capauility due to
selection of rotary compressor.
Inadequate condensdte removal in reactor
gas sampl e 1 i nes.
Inadequate consideration for free/ing of
reactor gas sampler lines.
5.0 - OXYGEN ACTIVATED SLUDGE
1
2
CO
0
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to
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C£. ^
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DEFICIENCY
GROUP
(A
O
4J
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TJ
in
s
c
O1
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(0
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c
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SL
1
DEFICIENCY
Improper design and installation of dis-
tribution arms cause clogging and rotation
problems.
Side wall not high enough to prevent splash-
ing or aerosol drifting.
Inability to add flocculants to aid settling
Lack of flexibility to flood the filter.
Lack of flexibility to chlorinate the filter.
Poor ventilation of filter causes odor
problems.
Clogging of distributor orifices caused by
inadequate primary treatment.
Inflexibility related to isolation of re-
actors and changes in flow and/or recircu-
lation strategy.
Improper sizing of media.
Improper selection of media without good
weathering properties.
Inadequate air circulation provided during
periods of high flows.
Inadequate consideration of overspray on
filter walls and resulting fly problems.
Inability to adjust, measure, and control
reci rcul at ion rate.
Inadequate flow dosing equipment.
Inability to adjust and control flows to
clarif iers.
6.0 TRICKLING FILTER
1
UJ
u_
CD
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vx
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c£.
1-
1
2
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5
6
7
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DEFICIENCY
GROUP
in
c
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u
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c
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Efe
ui
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c o
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DEFICIENCY
Inadequate sizing of filter unit to meet
a more stringent effluent limitations
requirement.
Insufficient flow, particularly during low
flow conditions, to rotate the distribution
arm.
Lack of proper reci rcul at ion pumping capac-
ity.
Excessive sloughing from filter due to ex-
cessive organic loading.
Reci rculat ion of secondary clarifier efflu-
ent is causing high flows through the
clarifier, resulting in clarifier solids
carry-over.
No provision for flushing underdrains.
Inadequate consideration of clarifier inlet
and outlet structures to optimize hydraulic
characteristics.
Inadequate flow to filter causes media
plugging.
Inadequate consideration of effects of re-
circulation through primaries on clarifier
loadings.
Inadequate consideration of effects on the
sludge blanket of taking reci rcul at ion flow
from below weirs of clarifier.
Inadequate freeze protection.
Ice build-up on filter media.
6.0 TRICKLING FILTER
1
LU
(
ll
CD
^
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C£
1-
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13
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15
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DEFICIENCY
GROUP
4-1
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c en
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DEFICIENCY
Lack of adequate working space behind
chlorinators.
Lack of scum removal facilities.
Hoist rail does not extend beyond edge of
building, making cylinder unloading more
di ff icul t .
No provision for sampling at outfall.
Inadequate use of concrete coatings, which
slough off tank walls and plug pipes and
pumps .
Lack of stand-by equipment.
Lack of consideration of upstream NH, con-
central ion.
Improper location of chlorine diffuser.
Inadequate provision for sump to facilitate
sol ids removal .
Improper location of utility water suction
draws excess solids into system.
Lack of adequate mixing at Cl2 addition
point.
Insufficient contact time in outfall.
Inadequate consideration of possible short-
ci rcui ting.
Inadequate consideration of potential for
flooding baffles during high flows.
Inadequate consideration of present and
future flows in equipment sizing.
7.0 - DISINFECTION
1
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UJ
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DEFICIENCY
GROUP
c
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DEFICIENCY
Inadequate consideration of potential flow
ranges during selection of automatic control
equipment.
Inadequate feedback for control of chlorine/
ozone feed rate.
Inadequate consideration of emergency alarms,
controls, and ventilation.
Floor drains from chlorine room are connected
to floor drains from other rooms.
Inadequate safety equipment.
Improper temperature control in Cl2 tank
storage area.
Improper selection of construction materials
to minimize corrosion.
7.0 - DISINFECTION
1
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passage of concentrated si
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off pump too 1 ong , resu 1 1 i
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Sludge mete ring system inac
rel iab 1 e.
Individ ual gas measurement
mul t i pi e di gesters .
1 nadequdte provi s i on for h
pressure alarms.
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DEFICIENCY
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DEFICIENCY
9.0 - AEROBIC DIGESTION
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Lack of depth gauges provided on basins that
operate at varying liquid depths.
Lack of thickening ahead of digestion, and
no prov i s ion for decant i ng wi th i n the
digester.
Inadequate consideration of a decrease in
operating efficiency due to the temperature
drop in winter.
Inadequate consideration of denitrification-
induced sett 1 ing probi ems duri ng decant i ng.
Pressure relief valve not provided in area
with high groundwater which prohi bits batch
operat ion.
Inadequate supernatant f)exibi1i ty.
Inadequate air supply.
Inadequate flexibility in aeration equipment
prohibits operation of tank unless full.
Inadequate cons ideration of diffuser main-
tenance problems and clogging tendency.
Inadequate mixing to prevent solids
deposition and provide uniform D.O. concen-
trations.
Inadequate consideration of pH control.
Inadequate freeboard for foam contaInment and
spray control.
Inadequate ventilation in covered digesters.
Inadequate structural design in common wall
construetion, causing structural failure
dur i ng batch operat ion.
nj L.
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TD 4) -O
Lack of flexibility to dewater small above-
ground tanks by gravity.
Inability to visually observe the quality of
supernatant being drawn off.
Inadequate cons iderat ion of sIudge v iscos i ty
during pump selection.
Inability to draw supernatant off at deep
enough 1 eve!.
Lack of spare supernatant pump for both main-
tenance purposes and to allow rap i d dewa ter-
i ng of bas in.
Provisions provided to add defoamer to
aeration basin, but not to aerobic digester.
2 §
Inadequate freeze protection.
35
-------
DEFICIENCY
GROUP
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from freezing conditions.
Vacuum valves on equipment are inaccessible.
Inability to feed chemicals to both sides of
a tank that can be baffled into two separate
tanks .
Improper conveyor operating angle.
Excessive cake discharge height results in
severe sludge splashing.
f I 1 trate/centrate streams.
Improper placement of control panels in
spray/splash areas hampers clean-up and
results in abnormally high corrosion rates.
Lack of preliminary treatment prior to a
disc-nozzle centrifuge.
1 nad equate dra i nage system ,
No provisions for cake removal from sand bed.
Inadequate provisions for proper sludge
d istr ibut ion.
1 nadequate layout of underdrains.
Improper location of sand bed allows inflow
of surface drainage.
Inadequate consideration of potential flood-
ing of sand bed.
Lack of operational flexibility and considera-
tion of need for back-up unit during periods
of maintenance.
Insufficient provisions for storage of
chem ica 1 s .
dewatered sludge during inclement weather.
Elevated equipment such as conveyors and
chemical storage bins are inaccessible for
inspection and maintenance.
Sludge feed troughs from chemical condition
tank to vacuum filter frequently become
clogged.
demands in common air/water supplies results
in competition among multiple units.
Inadequate capability to handle peak loads.
Design specifies solids loading, but neglect
hydraulic loading requirements.
Insufficient effluent recycle capacity.
10.0 - SLUDGE DEWATERING PROCESSES
1
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36
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DEFICIENCY
GROUP
DEFICIENCY
lo.o - SLUDGE DEWATERING PROCESSES
8 9 10
Short-circuiting of flow through tank causes
poor solids removal.
Feed pumps run on an "on-off" cycle, causing
uneven feed to DAF unit.
Wide variations in feed solids concentrations
occur because DAF is fed directly from final
clarifier.
C C TJ
OJ 01
Lack of flow meters on sludge feed lines to
multiple pieces of dewatering equipment.
Top of sludge chute not large enough to
accept all the cake that comes off the
dewatering equipment, causing some sludge
cake'to fall on the floor.
Insufficient conveyor skirt length, resulting
in severe splashing.
No flushing facilities provided for sludge
transfer or feed pumps.
10
No drains provided on elevated sections of
conveyor drip pans.
No provision for dust collection when using
powdered conditionfng agents.
No provision for chemical addition.
Inadequate scum remova1.
Improper cleaning of filter cloth.
Improper sidewater depth (SWD).
Improper sand gradation.
Improper selection of filter media.
Inadequate sizing of dewatered sludge
conveyor.
Inadequate consideration of potential plugg-
i ng problems in s1udge p i p I ng.
Inadequate cons ideration of corros i ve na ture
of materials to be handled.
Wa 1 Is d iv id i ng sludge dry i ng beds are made
of untreated wood and warp rapidly.
Insufficient number of floor dra i ns around
dewatering equipment.
Drain lines from filter vats are too small
and become clogged.
Spray water systems exhibit clogging
problems.
Tank drain lines are located 2" to 3" off the
bottom of tanks, making it difficult to
dewater them.
Chemical feed line and pH probe are located
close together, causing erroneous and/or
cyclic read!ngs.
10
13
12
13
10
12
12
13
15
16
10
13
17
18
12
37
-------
DEFICIENCY
GROUP
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DEFICIENCY
Clogging problems in lime piping.
Excessive agitation in chemical conditioning
Poor cake release.
in sludge piping design.
Inadequate grit removal results in excess
cor ros ion.
Inadequate treatment of flushing water
results in plugged nozzles.
...
f i 1 1 rate/cent rate 1 i nes .
Inadequate removal of cake from filter media.
Filtrate pumps frequently become air bound.
Lack of moisture removal from instrument air
lines results in failure of control equipment
Improper use of needle valves in hydraulic
drives, resulting in overheating.
No ' ' f
sludge pumps, chemical pumps, vacuum filter
drive, etc., from a central location.
Sludge pumping and dewa taring area not
properly ventilated.
Inadequate provisions for lifting equipment
for repa i rs .
Inadequate freeze protection.
Inadequate consideration of impact of local
climate on dewateriog rate and size require-
ments for sand beds.
10,0 - SLUDGE DEWATERING PROCESSES
1
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Deficiency
Inability of process to meet effluent
requirements in winter.
Inadequate (or lack of) liner to meet
state requirements, and to prevent
groundwater pollution.
No provision to vary liquid depth
for mosquito control in lagoon.
Single point entry into pond
overloads pond in feed zone.
Pond located too close to residential
areas.
Lack of multiple cells for operating
flexibility.
Dike widths too small for maintenance
vehicles.
Control inflexibilities.
Inadequate D.O. control.
Anaerobic conditions due to organic
overloading.
Inadequate sludge storage.
Complete mixing problems.
Inability to control and adjust
recirculation rate.
Short circuiting.
Inadequate erosion control measures.
Improper seedling of dikes (long root
plants used that eventually damage
thew dike).
No drain plrovided in lagoon.
Water level gauges not provided.
Odor problems.
Rodent problems.
Improper depth between lagoon bottom
and groundwater table.
No groundwater monitoring wells
provided.
Inadequate freeze protection.
No fence or all-weather road
provided.
11.0 LAGOONS
1
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an tat ton in pi p i ng .
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Inadequate posting of signs identifying
hazards.
Inadequate perimeter fencing for public
safety.
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GROUP
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DEFICIENCY
Inadequate selection of disposal vehicle re-
sults in inability to maneuver in landfill.
Inadequate truck tire size for landfill
di sposal .
Inadequate consideration of sludge concentra-
tion/transportation tradeoffs.
Inadequate consideration of site geology/
topography and climate.
Inadequate consideration of hydraulic trans-
port reduction due to ion exchange.
Inadequate consideration of equipment
utility in all weather conditions.
Inadequate consideration of gas migration/
accumulation.
Lack of vector control .
Inadequate consideration of nutrients and
public health hazards (metals, bacteria)
transport in soi 1/groundwater .
Inadequate buffer zone at disposal site.
Lack of odor control/prevention.
Sludge loading delayed due to lack of truck
or container capacity.
13.0 - SLUDGE DISPOSAL
1
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DEFICIENCY
Inadequate consideration of equipment
arrangement in overall process flow.
Inadequate space for sludge staging and
preparation.
Inadequate sludge storage during maintenance
periods.
Inadequate consideration of feed solids
concentration .
Use of high volumes of city water for air
scrubbers instead of plant utility water.
No heat exchanger provided to make use of
waste heat.
Inadequate consideration of fresh air supply
and overall ventilation requirements.
Improper feed equipment selection.
Inadequate provisions for reliable auxiliary
fuel source.
Inadequate consideration of impact of recycle
streams on main stream processes.
Improper selection of materials of construc-
tion results in excessive corrosion.
Improper consideration of reliability of
mechanical components.
Inadequate consideration of back-up equipment
requi rements.
Inadequate consideration of Impact of excess
scale and ash on air pollution equipment and
ash removal facilities.
Improper selection of equipment drives for
service in high-temperature areas.
14.0 -- SLUDGE REDUCTION
1
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DEFICIENCY
No oxygen analyzing equipment provided to
moni tor burn.
No remote control capability provided for
burners to optimize burn.
to remote control capability provided for
shaft drive to optimize burn.
Improper use of mercury manometers for
scrubber water flow measurement causes loss
of mercury into system during system surges.
No remote control provided for natural draft
and induced draft flow control valves.
Inadequate instrument monitoring of process
flows (flue gas temperature, pressure) and
inadequate number of monitoring points (be-
fore and after scrubber).
No stack sampling ports provided.
Lack of protective insulation on exposed hot
pi pi ng.
Inadequate access to incinerator ash
container.
Inadequate consideration of ultimate residue
disposal .
Inadequate odor control.
Inadequate air pollution control.
14.0 -- SLUDGE REDUCTION
1
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15
16
17
18
19
20
21
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23
24
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11
12
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14
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17
18
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20
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15
16
17
18
19
20
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22
23
24
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45
-------
Deficiency
Group
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Deficiency
Bearings located below grade and
are susceptible to flooding.
Buildings not insulated and facil-
ity looses heat in winter causing
wastewater temperature to drop.
Primary clarifiers not provided
causing settling of dense material
in tankage and plugging of media.
No provision for addition of
chemicals to improve settling
characteristics.
No provision for measuring and
sampling waste sludge flow.
Excessive collection system
detention times promote
incoming septic waste.
Inadequate conf ideration of pos-
sible development of septic con-
ditions in channels.
Sidestreams not accounted for in
design of RBC units.
Insufficient tank mixing causes
dead spots and solids deposition
in RBC tank.
Improper design of overflow baffles
between stages, causes solids
deposition.
Inadequate screening of raw wastes
causes plugging of RBC media.
15.0 Rotating Biological Contactors
1
<
cc
w
z
K
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1
2
3
4
5
6
7
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46
-------
DESIGN CONSIDERATIONS
Category Page
1.0 General Plant Design 55
2.0 Preliminary Treatment 178
3.0 Primary Treatment 211
4.0 Air Activated Sludge 222
5.0 Oxygen Activated Sludge 264
6.0 Trickling Filter 270
7.0 Disinfection 281
8.0 Anaerobic Digestion 292
9.0 Aerobic Digestion 303
10.0 Sludge Dewatering 311
11.0 Lagoons 345
12.0 Land Application 358
13.0 Sludge Disposal 382
14.0 Sludge Reduction 391
15.0 Rotating Biological Contactors 412
47
-------
Design Considerations
Category J^JL Ge ne r a 1
Plant
Design
Unit Operation/Component:.
1.1 General
DEFICIENCY
1.1.1 Lack of hoists
over larger pieces
of equipment.
1.1.2 Lack of spare
pumps.
CONSIDERATIONS
New POTW's
Architectural and structural designs
should include necessary members for
hoists over larger pieces of equip-
ment (i.e., pumps, gates, filter
presses, etc.) to allow equipment
removal for maintenance purposes.
Existing POTW's
Method; Provide a hoist (pulley,
tackle, etc.) to move equipment ver-
tically, and an overhead rail to move
equipment horizontally. For small
plants, a portable hoist may be
appropriate.
Materials; A permanent installation
may require reinforcing the building
superstructure.
New PQTW's
Provide a spare pump(s) at every
pumping installation in the plant or
as a minimum spare pumps at all
major pumping stations (i.e., influ-
ent, sludge recycle/waste, interme-
diate lift, utility water, etc.) and
portable pump hook-ups at small pump-
ing stations (i.e., chemical feed,
spray water, etc.).
1.1.1 - 1.1.2
48
-------
DEFICIENCY
1.1.3 Lack of walk-
ways around tanks,
limiting operator
access.
Method:
CONSIDERATIONS
Existing POTWs
If space was provided for
future expansion in original design,
pour a pad for the pump (if neces-
sary) , mount the pump, and install
the required piping. Otherwise, it
will be necessary to tap into the
existing suction header or directly
into the wet well.
Materials: Concrete for pad (if
required), pump, piping, valves.
New POTW's
Provide adequate walkways and/or
stairways to allow operator access
to valve handles, gates, instrumenta-
tion, etc., and/or to equipment and
tank sidewalls for maintenance and
clean-up purposes.
Existing POTW's
Method; Add OSHA-approved walkways
constructed of weather-resistant
materials. Locate so that operator
will have access to tank for sam-
pling, for maintenance of instruments
and equipment, for cleaning tank
sidewalls, and for turning valve
stems.
Materials; Galvanized steel or alum-
inum.
Cost; Dependent on length of walk-
way(s) to be provided, as well as on
supporting structure(s) required.
1.1.2 - 1.1.3
49
-------
DEFICIENCY
1.1.4 Tall, above-
ground tanks fre-
quently require
operator to climb
long stairways.
1.1.5 No provisions
for moving equipment
and supplies from
one building floor
to another.
CONSIDERATIONS
New and Existing POTW's
If space is available, size tanks
with adequate width and length to
minimize height requirements, and/or
construct deep tanks at least par-
tially in ground, or as a minimum
provide hoists at the top of stair-
ways to eliminate need for operator
to carry equipment up long stairways.
New POTW's
Provide convenient means of moving
equipment and supplies from one
building floor to another through use
of ramps, hoists, and/or elevators.
In below-ground structures such as
pump stations, roof hatches with per-
manent or portable lifting frames can
be provided for equipment removal.
Care should be taken to ensure that
elevators and floor cut-outs for
hoists are large enough to allow pas-
sage of the largest pieces of equip-
ment anticipated to be used in the
building being designed.
Existing POTW's
Method; Install an elevator or a
hoist and overhead rail. If stair-
ways are too narrow to accommodate
larger pieces of equipment, add large
doorways on appropriate ends of
building, or provide floor hatchway
in line with hoist rail.
Materials; Pulley(s), chain(s),
rail(s), wheel(s), doorway(s) for
oversized equipment.
1.1.4 - 1.1.5
50
-------
DEFICIENCY
1.1.6 Use of fixed
louvers in buildings
that cannot be shut
during winter weather
conditions.
1.1.7 Inadequate
flexibility to by-
pass units.
CONSIDERATIONS
New POTW's
Where louvers are used, they should
be an adjustable type, so that they
can be closed during cold or wet
weather. This is particularly impor-
tant in buildings such as labs and
control rooms which contain people a
large percentage of the time.
Induced draft ventilation should be
considered in lieu of fixed louver
systems.
Existing POTW's
Method; Replace fixed louvers with
movable louvers that can be closed
in cold weather when not in use.
Induced draft louvers should also be
considered.
Materials; Use same materials as in
fixed louvers, or other weather-
resistant materials.
New POTW's
For preliminary treatment units (grit
chamber, bar screens, communitors,
etc.), provide by-pass channels. For
larger multi-unit systems (clari-
fiers, aeration tanks), tank piping
should include necessary valves to
allow the stoppage of flow to each
tank. For pretreatment units such as
equalization, oil and grease removal,
odor control, etc., by-pass piping
should also be provided.
Existing POTW's
Method; Design of by-pass structure
of piping dependent on individual
plant or unit process.
1.1.6 - 1.1.7
51
-------
DEFICIENCY
CONSIDERATIONS
1.1.8 Inadequate
consideration of
means to remove
equipment for
repair or replace-
ment.
1.1.9 Inadequate
valving for maxi-
mum flexibility and
proper maintenance.
1.1.10 Inadequate
consideration of
consequences of
rupture disc or
shear pin failure.
New POTW's
Provide doors large enough to permit
passage of any vehicles or tools
required to remove pieces of equip-
ment from a building, and also large
enough to permit passage of equip-
ment itself. Adequate passageways in
the building and around the equip-
ment should be provided to allow easy
access for both maintenance and
removal. A minimum working space of
four feet should be provided around
all equipment.
Existing POTW's
Method; Refer to 1.1.1 and 1.1.5.
New and Existing POTW's
Piping should be designed with enough
valves, long radius elbows, tees,
crosses, and clean-outs to provide
adequate maintenance and operational
flexibility. Sufficient valving
should be provided to allow bypass-
ing pieces of equipment for main-
tenance purposes.
New POTW's
When considering rupture discs for
piping systems (e.g., on discharge
side of a positive displacement
pump), specify disc to withstand
pressure below the maximum allowable
pressure for the piping system. In
addition, pipe the blow-off valve
(i.e., rupture disc, spring loaded
type, etc.) to discharge to a nearby
sump so that, in the event of a rup-
ture disc failure, clean-up of sludge
or other materials will be minimized.
1.1.8 - 1.1.10
52
-------
DEFICIENCY
1.1.11 Relative
layout of process
units and inter-
connecting piping
not optimized.
CONSIDERATIONS
When specifying shear pins (e.g., for
clarifier or thickener mechanisms),
also provide a high-torque switch
wired to: alarm at a high torque
prior to shut down; and to shut down
the mechanism at a predetermined
torque that is less than the shear
pin failure torque.
Existing POTW's
Method; If rupture disc is located
inside a building, pipe the blow-off
valve to a nearby floor drain, build-
ing sump, or wet well. If the disc
is located outside, pipe it to the
plant drainage system or nearby wet
well.
Install alarms that are energized at
a lower torque than that rated for
the shear pin; such alarms forewarn
the operator of a potential problem.
New POTW's
When laying out process units and
interconnecting piping, space the
units far enough apart so that main-
tenance equipment can have access to
units. In the case of common-wall
tanks (e.g., rectangular clarifiers),
provide access at both ends of the
battery of tanks to facilitate main-
tenance .
Provide sufficient clearance and
paved turnaround area for large
vehicles (e.g., tank trucks deliver-
ing chemicals) to facilitate maneu-
verability.
1.1.10 - 1.1.11
53
-------
DEFICIENCY
1.1.12 Excessive
length of chemical
feed lines, par-
ticularly lime
slurry recircula-
tion loops.
Method:
CONSIDERATIONS
Existing PQTWs
In an existing POTW, it is
difficult and costly to change the
location of tanks. However, some-
times the function of a tank can be
changed if necessary, e.g., an aero-
bic digester can be converted to an
aeration basin by changing valve
arrangements.
Piping runs can be optimized in order
to reduce pumping costs by eliminat-
ing unnecessary bends and lengths of
pipe.
New POTW's
Locate chemical feed equipment as
close as possible to point of appli-
cation. Minimize pipe length and
number of bends. In feed lines where
settling is possible (especially lime
slurry lines), add a clean-out plug
at each elbow to facilitate cleaning.
In most cases, lime systems should
include a continuous recirculation
loop with controlled draw-off at the
point(s) of application. The recir-
culation pump should provide a mini-
mum velocity of 5 feet/second in the
loop under all flow conditions.
Lime pumping should be installed with
quick-disconnect pipe joints and
flushing connection for ease of main-
tenance. Automatic line flushing
systems should be considered for use
with lime systems. Lime piping
should be accessible for flushing and
clean-out, and should not be install-
ed underground.
1.1.11 - 1.1.12
54
-------
DEFICIENCY
1.1.13 Inadequate
consideration of the
impact of major
industrial users.
CONSIDERATIONS
Avoid any low points in piping sys-
tems. Minimum pipe diameter for lime
slurry feed lines should be 1 1/2 to
2 inches.
Existing PQTW's
Method; Increase the pumping capac-
ity in slurry-conveying lines in
order to keep solids in suspension.
If possible, relocate chemical feed
facilities closer to point of appli-
cation.
Materials; Larger impeller in exist-
ing pump, or larger pump.
New POTW's
The impact of industrial users on a
POTW can be minimized by implementing
the following measures:
Enforce the local sewer ordi-
inance. If necessary, update
an existing ordinance to pro-
hibit the discharge of any
wastes that: create a fire or
explosion hazard; impair the
hydraulic capacity of the sewer
system; inhibit biological
treatment processes; and/or
create a hazard to people, the
the sewer system, the treatment
process, or the receiving
waters.
During the POTW design stages,
solicit maximum input from
contributing industries regard-
ing total flows, peak flows,
waste composition, etc. Encour-
age industries to conserve
water by installing such devices
as closed system recirculation
1.1.12 - 1.1.13
55
-------
DEFICIENCY
1.1.14 Inadequate
communication capa-
bilities between
buildings and
process areas.
1.1.15 Insufficient
color coding of pipes
and valves.
CONSIDERATIONS
loops and cooling towers. Pro-
hibit industries from diluting
their wastes with uncontaminated
water.
Method:
Existing POTW's
Enforce local sewer ordi-
nances regarding industrial users.
Require the industry to meet Federal
pretreatment standards for that
industry.
New POTW's
Provide adequate in-plant communi-
cation facilities by specifying an
intercom system for each building.
Outside speakers for paging person-
nel should also be provided.
Existing PQTW's
Method; Install an intercom system
between buildings and an outside pag-
ing (i.e., speakers) system.
New and Existing POTW's
All exposed pipes and valves should
be color-coded according to the
material carried. The color-coding
system can vary from plant-to-plant,
but the following is a suggested
system:
Potable water
Sealing water,
wash water,
plant effluent
Raw wastewater
Sludge
*Dark Blue
White
*Grey
*Dark Brown
1.1.13 - 1.1.15
56
-------
DEFICIENCY
CONSIDERATIONS
Equipment
drains
Sanitary
drains
Chemical feed
Process air,
compressed air,
blower inlet
and outlet
Orange
Orange with
tags
Aqua
*Dark Green
Chlorine *Light Yellow
Scum and grease Light Green
Domestic hot
water
Oil lines, gas
lines
Hoists and
trolleys
Fire protection
system, sprinkler
piping
Steam line
Vents
Water lines for
heating build-
ing or diges-
ters
Light Blue
*Brick Red
Safety Yellow
Safety Red
Tan
Ivory
Blue, with
6-in. bands
spaced 30-in.
apart.
*These colors are recommended as
standard by WPCF.
1.1.15
57
-------
DEFICIENCY
1.1.16 Inadequate
stand-by equipment,
1.1.17 Lack of
sampling taps
at pumping
stations.
CONSIDERATIONS
Include on each line an arrow indica-
ting the direction of flow. Prepare
the surface of the pipe or valve as
required by paint supplier.
New POTW's
Provide stand-by equipment per EPA
publication Design Criteria for
Mechanical, Electric and Fluid System
and Component Reliability (Publica-
tion No. EPA-430-99-74-001).
Existing PQTW's
Method; Maintain a complete inven-
tory of spare parts for larger pieces
of equipment, such as spare motors
and impellers for aerators. Provide
a spare pump at pumping stations, a
spare chlorinator, and an emergency
generator as a stand-by power source.
Refer to 1.1.2 and 1.1.95.
New POTW's
Provide sampling taps on the dis-
charge lines of major pumping sta-
tions such as raw wastewater, sludge,
and process sidestreams (i.e., fil-
trates, supernatants, underflows,
etc.).
Existing POTW's
Method; Add a sample tap of appro-
priate size to the discharge line of
a pump, downstream of the check
valve. Shut off valve downstream of
tap location in order to prevent
backflow during installation of tap.
1.1.15 - 1.1.17
58
-------
DEFICIENCY
1.1.18 Inadequate
process flexibility.
1.1.19 Lack of
all-weather roads
to pump stations.
1.1.20 Insufficient
number and poor
placement of high-
pressure hose
hydrants through-
out plant.
CONSIDERATIONS
Materials; Sample tap (plug valve)
on reducing tee, with two legs of tee
same diameter as a pump discharge
line, and a third leg of tee same
diameter as tap (1 1/2" to 3" for
sludge, 1/2" for relatively clear
water).
New and Existing POTW's
Provide necessary pumps, piping, and
valving to ensure each piece of major
mechanical equipment or unit opera-
tion can be isolated for routine
maintenance, repairs, and/or opera-
tional changes.
New POTW's
To ensure year-round, reliable acces-
sibility to pump stations, all-
weather access roads (i.e., gravel
or paved) should be provided.
Method:
Existing POTW's
Provide an all-weather road
to each pump station.
Materials/Cost;
Gravel road: $2/sq ft, depend-
ing on length of road.
Asphalt road: $4/sq ft, depend-
ing on length of road.
New POTW's
High-pressure hose hydrants should be
easily accessible throughout a POTW,
but not located in vehicle traffic
routes. Hydrants should be provided
both inside and outside plant build-
ings. \
1.1.17 - 1.1.20
59
-------
DEFICIENCY
1.1.21 Layout of
unit processes
does not allow
for future
expansion of
plant.
CONSIDERATIONS
Sufficient flushing hydrants should
be provided to allow clean-up at any
location on the plant grounds, par-
ticularly around major pieces of
equipment. This would include clar-
ifiers, aeration basins, scum pits,
bar screens, sludge handling areas,
chemical addition facilities, etc.
If the plant is located in a cold-
climate area, outside hydrants should
be anti-freeze type.
Existing POTWs
Method; Add flushing hydrants, as
needed, throughout the plant, both
inside and outside buildings. Out-
side hydrants should be anti-freeze
type if the plant is located in a
cold climate area. A minimum hydrant
pressure of 50 psi should be pro-
vided. An effluent sump and utility
water pump can be installed to recy-
cle treated effluent back to the
plant flushing hydrants.
New PQTW's
During the layout of a new POTW,
space should be dedicated for instal-
lation of equipment required for
future expansion. Such space alloca-
tion should be indicated on the site
plans and building layouts. Piping
as well as tankage arrangements
should allow for future expansion
needs.
1.1.20 - 1.1.21
60
-------
DEFICIENCY
CONSIDERATIONS
1.1.22 Use of
covered basins
inhibit access
to and observa-
tion of unit
processes.
1.1.23 All valves
not operable from
floor level.
1.1.24 Inadequate
clearance around
equipment for main-
tenance functions.
Existing POTW's
Method; Place new unit processes as
close as possible to existing units.
Allow for possible differences in
elevation when calculating flow dis-
tribution and sizing pumps. Consider
the use of multi-story structures.
New and Existing POTW's
Covered basins should only be uti-
lized to prevent freezing problems
at POTWs located in areas charac-
terized by several months of below-
freezing temperatures. At other
locations, the use of in-ground tanks
should be considered as an alter-
native approach. If covered basins
are warranted, covers with multiple
entrances and observation ports that
can be readily removed should be
specified.
New and Existing POTW's
For safety and convenience reasons,
all valves should be easily acces-
sible by POTW operators. Overhead
valves should be provided with chain
operators, and below grade valves
should be equipped with extended
valve stems. Wherever possible,
valves should be placed within reach
of an operator from floor level.
New and Existing PQTW's
For maintenance purposes, provide a
minimum of 4-foot clearances around
indoor equipment and allow room for
truck access around outdoor equip-
ment.
1.1.21 - 1.1.24
61
-------
DEFICIENCY
1.1.25 Inadequate
view of unit proc-
esses from control
building.
1.1.26 Inadequate
provisions for
draining tanks
and sumps.
CONSIDERATIONS
New POTW's
The plant control building should be
centrally located in order to offer a
view of the plant grounds which
encompasses as many of the unit oper-
ations as possible. Consideration
should also be given to an elevated
control room located on the second
story level of one of the plant
buildings. Outside lighting should
be adequate to offer night-time view
of the units.
Existing POTW's
Method; Install more process instru-
mentation to monitor treatment oper-
ation. Schedule operations personnel
for hourly tours through plant. Pro-
vide an observation station on the
control building roof.
New PQTW's
A plant drain system should be pro-
vided which is low enough to service
all tanks and buildings in the plant.
All tank and sump bottoms and build-
ing floors should be sloped to pro-
vide good drainage. Tanks should be
equipped with mud (drain) valves
and/or pump-out sumps. If possible,
tanks should be drained to the plant
drain system.
Existing POTW's
Method; Install mud valves, pump-out
sumps, and/or drains in the bottom
of wet wells and sumps. For small
sumps, the bottom should be grouted
to provide a sloped surface that
drains to the sump drain.
1.1.25 - 1.1.26
62
-------
DEFICIENCY
CONSIDERATIONS
1.1.27 Inadequate
provisions for
sampling of indi-
vidual processes.
1.1.28 Inadequate
consideration of
access require-
ments for large
equipment (cranes,
trucks, etc.)
required for
maintenance.
New POTW's
Sampling facilities should be pro-
vided throughout the POTW to allow
performance evaluations of the indi-
vidual unit operations. Such facil-
ities would include sample taps at
pumping stations, sample ports in
tanks, stairways and ladders that
allow access to sampling sites, etc.
Existing PQTWs
Method; Refer to 1.1.17.
New POTW's
A crane, monorail or a beam to which
a hoist can be attached should be
located above all major pieces of
equipment. The roof or floor above
the equipment should be designed for
the lifting load of the hoist. Build-
ings that contain large pieces of
equipment, (i.e., filter presses,
vacuum filters, pumps, etc.) should
have adequate ceiling heights and
floor loading capacities to allow
entrance of equipment removal
vehicles. The access area around
equipment should be adequate for its
removal. Access roads and access
areas should be provided around all
outdoor equipment.
Method:
Existing POTW's
Use portable hoisting frame
and hoist with hand truck to move
equipment to accessible area. Where
feasible, install larger overhead
doors to provide increased access
into a building.
1.1.27 - 1.1.28
63
-------
DEFICIENCY
1.1.29 Inadequate
scum handling and
disposal system.
1.1.30 Foam sprays
not concentrated in
basin corners where
foam build-up
occurs.
CONSIDERATIONS
New POTW's
Scum removal facilities should be
provided on all tanks (i.e., clar-
ifiers, chlorine contact tanks, wet
wells, splitter boxes, etc.) that
provide quiescent conditions. A
positive scum removal system consist-
ing of sumps and pumps should be
provided to transfer the scum from
various collection points in the
plant to a central holding site. The
collected scum should be hauled to a
final disposal site or incinerated
on-site along with plant sludge, and
not allowed to recirculate through
the treatment system.
Existing POTW's
Method; Add skimmer and scum sump
to tanks with scum accumulation prob-
lems, along with requisite scum
pump(s) and level controls. Pipe
scum removal equipment so that the
scum is removed from the system and
not allowed to recirculate through
the system.
New POTW's
Spray heads should be spaced one foot
apart in basin corners to minimize
foam build-ups. Foam sprays may also
be required in certain open channels,
such as aeration basin influent
and/or effluent channels.
Existing POTW's
Method; Install additional spray
nozzles (1-foot apart) along spray
water header in basin corners.
Materials; Non-clog spray nozzles.
1.1.29 - 1.1.30
64
-------
DEFICIENCY
CONSIDERATIONS
1.1.31 Control
panels not easily
accessible (i.e.,
too high off
ground or placed
in close quar-
ters) .
1.1.32 No pro-
vision for water
tap at top of
above-ground
package units.
1.1.33 Lack of
flexibility to
operate POTW at
low-flow start-
up conditions.
New POTW's
All field-mounted control panels
should be conveniently located for
operator access. The panel controls
should be within easy reach of an
operator, and a four-foot working
space should be provided around the
console.
Existing PQTWs
Method: Relocate panel to a position
that is within easy reach of an oper-
ator and provides at least 4 feet of
clearance around the console.
New POTW's
Provide water tap (i.e., hose bib) at
top of unit, using plant effluent as
utility water source.
Existing POTW's
Method; Add water tap at top of unit
by connecting into the plant utility
water system or by using plant eff-
luent as the water source.
Materials; Choose piping and valving
to be compatible with existing pip-
ing materials; a PVC system can be
installed as an expedient measure.
New POTW's
Utilization of parallel flow trains
should be considered during concep-
tual and preliminary engineering
design. This would allow use of
only the capacity required during
initial plant operations. Use of
multiple pumps versus single large
units is also advantageous for
handling initial small influent
flows.
1.1.31 - 1.1.33
65
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DEFICIENCY
CONSIDERATIONS
1.1.34 Floor drain
piping system under-
sized.
1.1.35 Drains from
buildings discharge
into basins with
normally (or peri-
odically) high-
water levels,
causing drains
to back-up.
Existing POTW's
Method; Install lift pumps properly
sized to handle initial flows; these
can be used as spare or back-up pumps
eventually. If necessary, construct
partitions in tanks in order to pro-
vide proper detention times.
New POTW's
Before sizing the floor drain piping
for a building, the flows that will
be discharged to the drain system
must be identified. This could
include relatively large flows such
as filtrates, supernatants, pump seal
water, etc.
While floor drains for lab or admin-
istrative buildings may only require
2- or 4-inch piping, sludge dewater-
ing may require 6- or 8-inch drain
lines.
Existing POTW's
Method; Install larger floor drain
piping or provide additional piping
to reduce the volume of flow dis-
charged to the existing drain piping.
Re-pipe certain nieces of equipment
to discharge directly to the plant
drain sewer rather than to a building
drain system.
New POTW's
Ensure the discharge elevation of the
plant drainage system is low enough
to always provide adequate gravity
flow to the system discharge point.
Tanks with varying water levels, such
as equalization basins, should not be
utilized as drain line discharge
points unless anticipated tank high-
water levels are still low enough to
prevent water backing up into build-
ing drains. The plant influent wet
well should be considered for use as
the discharge point.
1.1.33 - 1.1.35
66
-------
DEFICIENCY
1.1.36 Inadequate
number of flow
meters throughout
the plant.
Method:
CONSIDERATIONS
Existing POTW's
Install flap valve at the
end of the drain line if there is
enough head in the drain line to
open the valve without back-up of
flow. As an alternative solution,
re-pipe the drains to a lower basin
or wet well in the plant.
New PQTW's
As a minimum, provide flow meters to
monitor the following streams:
Influent flow.
Recycle sludge flow.
Waste sludge flow.
Flow to sludge conditioning
units.
Effluent flow.
Various sidestreams (i.e., supernat-
ants, filtrates, centrates, etc.)
from other areas of the plant may
require flow measurement, depending
on the individual POTW, but the
above flows should be measured at
all plants.
Existing POTW's
Method; Where required, in-line mag-
netic flow meters can be installed
in existing piping, if appropriate;
weir boxes or parshall flumes can be
utilized.
Materials; Suggested methods of
flow measurement in each area are as
follows:
1.1.35 - 1.1.36
67
-------
DEFICIENCY
CONSIDERATIONS
1.1.37 Inadequate
consideration of
groundwater move-
ment into POTW
site through
sewer trenches.
1.1.38 Inadequate
consideration of
hydraulics during
design of a ven-
turi flow meter,
resulting in a
negative pressure
occurring in the
meter throat.
Influent and effluent flows:
magnetic flow meter, sonic
flow meters, venturi meter,
V-notch weir with float.
Sludge flow (recycle, waste,
conditioning unit): use
closed-pipe flow meters only
(magnetic, sonic, venturi).
New POTW's
Impermeable barriers (i.e., bento-
nite clay or concrete) should be
placed across sewer trenches leading
to a POTW site. The barriers should
extend between the trench walls and
from the bottom of the trench to
within one foot of the ground sur-
face.
Existing PQTW's
Method; Install impermeable barriers
in the sewer trench.
Materials; Concrete or clay.
New POTW's
Ensure that sufficient line pressure
is provided upstream of the venturi
meter or a negative pressure will
occur in the venturi throat. This
will cause air to be drawn into the
meter DP cell or out of solution in
the wastewater and cause erroneous
flow readings. If necessary, a
goose-neck venturi can be specified
or the DP cell can be located below
the venturi in order to ensure a pos-
itive throat pressure.
Existing POTW's
Method: Install a goose-neck venturi
meter and move the meter box below
the level of the venturi throat.
1.1.36 - 1.1.38
68
-------
DEFICIENCY
CONSIDERATIONS
1.1.39 Inadequate
consideration of
pumping system
design and/or
fluid character-
istics, resulting
in pump cavita-
tion.
1.1.40 Inadequate
location of thrust
blocks on pipe
lines, particu-
larly where
couplings are
involved or where
automatic valves
are located.
New POTW's
Avoid high suction lifts and specify
pumps that have low net positive suc-
tion head requirements when designing
pumping systems. This is particu-
larly important when the liquid to be
pumped has a low vapor pressure.
Existing POTW's
Method: Replace existing pumps with
new pumps having low net positive
suction head requirement. Shorten
suction line by relocating pump.
Increase size of suction piping.
Install suction assistant devices
(i.e., steam ejectors).
New POTW's
Thrust blocks should be provided at
each point of change in pipe direc-
tion. Specify control rods on piping
to prevent pipe from pulling out
of couplings. Thrust blocks should
support automatic valves that will
periodically close and cause piping
to vibrate.
Existing POTW's
Method; Install thrust blocks at
points where piping changes direc-
tion (i.e., pipe bends, control
valves, changes in elevation, etc.)
for support. Install control rod on
piping to prevent pipe from pulling
out of the couplings. Set the
closing time on automatic control
valves slow enough to prevent a
sudden thrust at the valve.
1.1.39 - 1.1.40
69
-------
DEFICIENCY
CONSIDERATIONS
1.1.41 Use of
single-speed
pumps where
variable speed
units are required.
1.1.42 POTW design
based on average
flow and BOD and SS
loadings with no
recognition of peak
conditions.
New POTW's
Consider the use of variable-speed
(or two-speed) pumps at the following
locations:
Influent pumping station.
Recycle pumps.
Chemical feed pumps.
Feed pumps to sludge dewater-
ing systems.
Existing POTW's
Method; Add variable-speed drive to
existing pumps where required. Var-
iable-speed pumps should be used at
the following locations:
Influent pumping station.
Recycle pumps.
Chemical feed pumps.
Feed pumps to sludge dewater-
ing systems.
New POTW's
Both maximum and minimum flows and
organic loadings should be consid-
ered during design of a POTW. It
is particularly important that
plant pumping stations and piping
be adequately sized to handle peak
flow rates. Sludge handling equip-
ment should also be sized to handle
projected maximum solids loadings.
Existing POTW's
Method; Install additional pumping
capacity as needed to handle peak
flows (influent and sludge flows).
If feasible, install an equaliza-
tion basin to dampen peak organic
loads.
1.1.41 - 1.1.42
70
-------
DEFICIENCY
CONSIDERATIONS
1.1.43 Undersized
scum pits.
1.1.44 Use of
city water rather
than plant efflu-
ent for use as
POTW utility
water.
1.1.45 Individual
flow measurement
not provided for
each piece of
parallel units.
1.1.46 Lack of
floor trenches
around pumps to
carry water
spills to sumps.
New POTW's
Scum pits should be sized to hold one
day of scum production, and should
be a minimum size of 41 x 41 x 4'.
Existing POTW's
Method; Increase the capacity of
the scum pump and/or enlarge the
scum pit.
New POTW's
Plant effluent in lieu of city water
should be considered as a source of
utility water in order to reduce
annual operating costs. An effluent
sump, utility water pump, flow con-
trol valves, and piping would be
required to supply clean-up water
throughout the plant.
Method:
Existing POTW's
Install effluent reuse
system, consisting of a wet well,
recycle pumps, flow control valves
and piping. An existing tank such
as the chlorine contact chamber or
post-aeration basin can be used as a
wet well for the recycle system.
New POTW's
Provide individual flow measurement
for parallel units. Flow meter (or
weir) readings should be totalized
so that the entire plant flow is
recorded.
Existing PQTW's
Method; Refer to 1.1.36.
New POTW's
Provide floor trenches around pump
bases to route water spills to a
sump. An alternative approach is
to provide a pipe that carries water
spills from pumps to a sump. How-
1.1.43 - 1.1.46
71
-------
DEFICIENCY
CONSIDERATIONS
1.1.47 Change in
baseline conditions
at a POTW between
time of design
and construction.
1.1.48 Lack of
flow metering
device on chem-
ical feed lines.
1.1.49 Chemical
feed line is con-
nected to more than
one basin at dif-
ferent elevations,
ever, the pipes should not run along
the floor (or ground) in areas that
would create safety hazards.
Existing PQTW's
Method; Provide a drain pipe and
route water spills to building sump,
or install floor trenches or curbing
in concrete floor that carry water
to a nearby sump.
New POTW's
Due to the extensive lag that gen-
erally occurs between the time a
plant is designed, the Federal con-
struction grants are received, and
the plant is actually constructed,
it is imperative that future waste
loads are considered. This includes
projecting municipal and industrial
waste flows. It is emphasized that
overestimating or underestimating
future flows can cause serious
operational problems.
Existing POTW's
Method; Refer to 1.1.13.
New POTW's
Provide flow meters on chemical feed
lines. The meters should be located
near the chemical feed pumps.
Existing POTW's
Method; Install flow meter, such as
rotameter, on each chemical line.
The meters should be located near
chemical feed pumps. Install chem-
ical metering pumps equipped with
built-in flow meters.
New PQTW's
When feeding a chemical to more than
one tank, use separate feed lines
and metering pumps. If feeding
chemical through a common header,
specify that discharge points in dif-
1.1.46 - 1.1.49
72
-------
DEFICIENCY
CONSIDERATIONS
causing line to
drain rapidly into
lower basin and
requiring time to
fill header before
the higher basin
can be fed.
1.1.50 Piping which
hangs under outside
edge of walkways in
clarifiers and
thickeners causes
the walkways to
tilt and mechanical
equipment to move
out of alignment.
1.1.51 No con-
venient means
provided to feed
dry chemicals
into top-loading
feeders.
ferent tanks must be at the same
elevation. If discharge points must
be at different elevations, provide
throttle valve at lower basin(s),
so that both (all) basins are fed
at same rate; also, provide a check
valve in the chemical feed lines to
prevent the back-flow of chemical
from one tank to the other.
Method:
Existing POTW's
Throttle valve to lower
basin(s), so that both (all) basins
are fed at the same rate; or use
spare pump, and arrange valving so
that lead pump feeds one basin and
spare pump feeds the other. Install
a check valve to prevent lines from
draining when pump is not operating.
New POTW's
Piping supported by walkways should
be placed beneath and run along the
middle of the walkways to avoid
twisting the unit and any other
equipment attached to the walkway.
As an alternative, if clarifiers or
thickeners are indoors, support pip-
ing from building ceilings or walls.
Otherwise, support piping from tank
walls.
Existing POTW's
Method; Relocate the piping to hang
directly beneath the middle of the
walkway to prevent an imbalance of
weight hanging under the walkway.
New POTW's
To avoid this problem: design chem-
ical feed facilities such that the
top of the mix tanks are at floor
level (i.e., provide a mezzanine);
specify mechanical, dry-chemical
feeder loading devices; provide a
stairway and platform that allows
operators to manually feed chemicals
to top-loading feeders.
1.1.49 - 1.1.51
73
-------
DEFICIENCY CONSIDERATIONS
For larger quantities of dry chem-
icals, use overhead cranes, fork-
lift trucks, etc., to load chemicals
into feeders.
Existing POTW's
Method; Install an elevated plat-
form that allows operator access to
the top of the chemical feeder. Dry
chemical feeder loading device can
be manual or mechanical:
Manual: Clamp 50-lb bag
onto a plywood plank. Tilt
plank over edge of tank,
slit bag, and empty bag
contents into feeder.
Mechanical; For larger
quantities of dry chemicals,
use overhead crane, fork-
lift trucks, etc., to load
chemicals into feeder.
1.1.52 Lack of New POTW's
drains on chem- Provide drain -valves in the bottom of
ical mix tanks. all above-ground chemical mix tanks.
Ensure that drains allow complete
drainage of tanks. Sumps should be
provided in the bottom of below-grade
tanks.
Existing PQTW's
Method; Add drain valve(s) to the
bottom of above-ground chemical mix
tank(s).
Materials; Drain valves and piping
should be compatible with tank mate-
rial.
Cost; Less than $100 per tank,
including labor.
1.1.51 - 1.1.52
74
-------
DEFICIENCY
CONSIDERATIONS
1.1.53 Lack of
seal water drip-
page drain lines.
1.1.54 Excessive
grouting cracks.
1.1.55 Samplers
frequently clog.
1.1.56 Pumps are
located above the
normal water level,
making them dif-
ficult to prime.
New and Existing POTW's
Refer to 1.1.46.
New POTW's
Specify the use of non-shrink grout
for plant construction.
Existing POTW's
Method; Chip out old grout and
replace it with new non-shrink grout,
New POTW's
Specify that 3/4 inch or larger sam-
ple lines be used with wastewater
samplers. In addition, clean-out
taps should be provided on sample
lines. For wastewaters with high
solids levels, automatic line flush-
ing systems (air or water) can be
used.
Existing POTW's
Method; Replace existing sampling
lines with 3/4-inch lines. Provide
means to periodically air or water
flush the sample lines.
New POTW's
Whenever possible, lay out pumping
systems such that the pump suction
line is flooded. If this is not
feasible, specify self-priming pumps.
Air bleed-off valves should also be
provided at high points in the pump
piping system to allow removal of
air locks and subsequent priming of
the pumps.
Existing POTW's
Method; Add self-priming feature to
existing pumps, or rearrange piping
so that suction is flooded.
1.1.53 - 1.1.56
75
-------
DEFICIENCY
CONSIDERATIONS
1.1.57 Pressure
gauges not located
on inlet side of
back-pressure
relief valves,
making it diffi-
cult to check
and/or adjust the
valve.
1.1.58 Chemical
feed pumps are too
small to allow
high dosages of
chemicals during
emergencies.
1.1.59 No ladders
provided in man-
holes.
1.1.60 Lack of air
bleed-off valves
at high points in
pump discharge lines,
1.1.61 Lack of
mud valves in
tanks.
New and Existing POTW's
Install pressure gauges on upstream
and downstream side of back pressure
valves and on pressure side of relief
valves.
New POTW's
Chemical feed pumps should be sized
to feed both maximum and minimum dos-
ages. The use of metering pumps with
variable stroke adjustment allows a
broad pumping capacity range. Multi-
ple pumps should also be specified;
this would allow the use of the
spare pump during emergency periods
when high chemical dosages are
required.
Existing POTW's
Method; Use spare pump; if spare
pump not available, use portable
pump, or make chemical batches with
higher dosages, if possible. If
warranted, install larger pumps.
New POTW's
All manholes should be equipped with
a ladder that is securely anchored to
the manhole wall.
Method:
Existing POTW's
Install steel or aluminum
ladders in manholes.
New and Existing POTW's
Provide air bleed-off valves at high
points in pump discharge lines to
allow removal of air-locks and sub-
sequent priming of pumps.
New and Existing POTW's
Provide mud valves or pump out sumps
at low point in tank bottoms. Refer
to 1.1.26.
1.1.57 - 1.1.61
76
-------
DEFICIENCY
CONSIDERATIONS
1.1.62 Lack of
water supply
near field
samplers.
1.1.63 Lack of
locally-mounted
gauges on field
instrumentation.
1.1.64 Lack of by-
passes around sole-
noid valves.
1.1.65 Lack of
sumps in dry wells,
1.1.66 Lack of
driers on instru-
ment air lines.
1.1.67 Lead-sealed
caps on clean-outs
in pressure lines
periodically blow
off.
1.1.68 Improper
water pressure
is supplied to
rotameters,
causing them
to burst.
New and Existing POTW's
Provide a hose bib or yard hydrant
near samplers for clean-up purposes.
New and Existing POTW's
Provide locally-mounted gauges on all
field-mounted flow meters, pH meters,
D.O. meters, etc. to allow instantan-
eous meter readings in the field by
POTW operators.
New and Existing POTW's
Provide by-pass piping around sole-
noid valves to facilitate cleaning
and repair.
New PQTW's
Provide pump-out sumps in all dry
wells to allow removal of rainwater
clean-up water, etc.
Existing POTW's
Method: Add sump to each dry well
for use with portable pump.
Materials; Compatible with exist-
ing dry well.
New and Existing POTW's
Provide air dryers on instrument air
system.
New and Existing POTW's
Clean-outs on pressure lines should
be equipped with clamp-on caps.
New POTW's
Ensure rotameters are rated for the
maximum line pressure that will be
achieved, particularly if rotameters
are used in lines carrying city
water since these lines may be under
very high pressure.
1.1.62 - 1.1.68
77
-------
DEFICIENCY
CONSIDERATIONS
1.1.69 Inadequate
provisions for
pressure relief
around positive-
displacement pumps.
1.1.70 Lack of pres-
sure gauges on plant
pumps.
1.1.71 Excess oil
from stationary
units not contained.
1.1.72 Lack of
influent composite
sampler.
Existing POTW's
Method; Install pressure-reducing
valves in front of rotameters, or
install new rotameters with a rated
maximum operating pressure that
exceeds the line pressure of the
water supply system.
New POTW's
Provide pressure-relief valves or
rupture discs in discharge lines from
positive-displacement pumps.
Existing POTW's
Method; Add pressure-relief valve
at discharge of each positive-dis-
placement pump.
Materials; Rupture discs rated for
pressure slightly less than rated
pressure of discharge piping system.
New and Existing POTW's
Provide pressure gauge on discharge
side of all pumps in plant.
New and Existing POTW's
Provide drip pans to collect oil
drippage from equipment (blowers,
pumps, clarifier/thickener mecha-
nisms, aerators, etc.).
New POTW's
Provide an influent composite sam-
pler. In some cases, two influent
samplers may be desirable to collect
raw wastewater samples and additional
samples downstream that include plant
side-streams routed back to the head-
end of the treatment plant.
Existing POTW's
Method; Provide refrigerated, heated
composite sampler for influent
stream.
1.1.68 - 1.1.72
78
-------
DEFICIENCY CONSIDERATIONS
Materials; Composite sampler, sample
pump, piping (3/4 inch or greater).
Cost; Composite sampler - $4,000.
1.1.73 Inadequate New and Existing POTW's
consideration of The following items should be kept in
the type of valve mind when specifying valves and
or gate used. gates:
If watertight conditions are
required, a sluice gate
rather than a slide gate should
be used.
Valve material must be com-
patible with the adjoining
piping material and with the
liquid to be carried.
Specification of a valve type for a
particular use should follow these
guidelines:
Globe valve; Used for
throttling or regulating
flow.
Gate valve; Used for
stopping flow completely.
Valve is used in fully-
open or fully-closed posi-
tion.
Check valve: Used to pre-
vent back flow through
equipment, i.e., to pre-
vent fluid from flowing
back through a pump.
Check valves with
obstruction in the flow
stream should not be used
for raw sewage, sludges,
slurries, or fluids
containing solids.
1.1.72 - 1.1.73
79
-------
DEFICIENCY CONSIDERATIONS
Piping pressure relief
valve; Used to relieve
excessive pressure, tem-
perature, or vacuum in a
piping system, e.g., on the
discharge side of positive
displacement pumps. Rupture
discs, instead of relief
valves, should be used when
handling fluids containing
solids or stringy fibers.
Plug valve: Used in
wastewater treatment plants
for flow shut-off in raw
sewage and sludge lines and
any other lines carrying
stringy matter. Valve should
be eccentric type to offer
full port opening.
Butterfly valve: Used where
low head loss, throttling
capabilities, small space
requirements, drip-tight
shut-off, etc., are required.
Ball valve; Use in chemical
feed lines, where throttling
capabilities and tight
shut-off are required. Full
port openings should be used.
Diaphragm valve: Used in
lines that carry corrosive
fluids, fibrous slurries,
sludges, solids in suspension,
etc., where material in pipe
should not contact any of the
operating parts of the valve.
Flap valve; Used in POTW's at
the effluent end of a pipe to
open when there is flow out of
the pipe and close to prevent
backflow into the pipe when
flow ceases. Flap valves are
also termed tide gates.
1.1.73
80
-------
DEFICIENCY
CONSIDERATIONS
Float valve; Used to
prevent overflow of liquid
from a tank, to control flow
rate from a tank, and/or to
maintain a predetermined
level of liquid in a tank
(e.g., chemical mix tank).
Mud valve; Used to drain
tanks (i.e., clarifiers,
aeration tanks, mix tanks,
etc.) with a valve oper-
ator at the top of the tank.
Tank pressure relief valve;
Used as tank groundwater
blowoff valve (i.e., lets
groundwater enter an empty
tank to prevent the tank
from floating out of the
ground).
1.1.74 Design does
not emphasize heating
conservation measures.
1.1.75 Inadequate
provisions for
manual valve
operation during
emergency con-
ditions.
New POTW's
Specify insulation be installed under
all roofs and in all walls and
thermopane and/or storm windows be
used in buildings containing labs
and control rooms. Utilize active
and/or passive solar designs where
possible. Add heat exchangers to
incineration systems for energy
recovery.
Method:
Existing POTW's
Add insulation wherever pos-
sible, especially under building
roofs. Add storm windows, or replace
existing single-pane windows with
thermopane windows. Replace exist-
ing heating systems with more effi-
cient units.
New and Existing PQTW's
All valves with automatic operators
should be equipped with manual, aux-
iliary operators or a piping by-pass
with manual-operated valves provided.
1.1.73 - 1.1.75
81
-------
DEFICIENCY
CONSIDERATIONS
1.1.76 Lack of
tank dewatering
systems to permit
rapid servicing
of submerged
equipment.
1.1.77 Lack of
wyes, tees, and
crosses to facil-
itate cleaning
of chemical
lines.
New and Existing PQTW's
Refer to 1.1.26.
1.1.78 Lack of
cathodic protection
for steel tanks.
1.1.79 Lack of
a foam control
system.
1.1.80 Absence of
electrical outlets
on top of treatment
units.
New POTW's
Ensure adequate clean-out taps (i.e.,
flushing valves) are provided on
chemical feed lines to allow removal
of pipe blockages. The clean-outs
should be installed at wyes, tees,
and crosses in the piping. Automa-
tic line flushing systems should be
considered for lime systems.
Existing POTW's
Method; Install flanged fitting with
flushing valve. If flushing does
not remove blockage, the clean-out
flange can be removed in order to rod
the pipe.
New and Existing POTW's
Provide corrosion protection for
steel tanks and pipes by means of
auxiliary anodes and/or protective
coatings.
New and Existing POTW's
Foam control systems should be pro-
vided for agitated tanks such as
aeration basins and aerobic diges-
ters. Foam control systems could
consist of spray-water or de-foamer
chemical feed systems.
New and Existing POTW's
Provide electrical outlets to serv-
ice each treatment area including
outlets on various pieces of equip-
ment such as clarifiers, aeration
basins, thickeners, etc.
1.1.76 - 1.1.80
82
-------
DEFICIENCY
CONSIDERATIONS
1.1.81 Electrical
cable trenches
have no provisions
for drainage.
1.1.82 Lab elec-
trical circuits on
same circuits as
POTW equipment,
causing inter-
ference with lab
instrumentation.
1.1.83 Lack of
electrical outlets
at field-mounted
instrumentation
for portable
calibration
equipment.
1.1.84 Drains in
electrical manholes
are not provided
with backflow
valves to prevent
flooding from
plant drain
system.
1.1.85 Inadequate
wiring, schematic,
and logic diagrams
including terminal
and wire number-
ing in field and
on drawings; no
standard adhered
to.
New and Existing POTW's
Provide trench drains that discharge
to the plant drain system.
New and Existing POTW's
Provide an isolation transformer to
separate lab electrical circuits from
POTW equipment circuits.
New and Existing POTW's
Electrical outlets (110 v) should be
located at field-mounted instrumen-
tation stations. This allows the
operator to use portable equipment
(without need for batteries) to cali-
brate field-mounted instrumention
or to utilize a temporary instrumen-
tation hook-up while permanent
equipment is out of service.
New and Existing POTW's
Provide backflow valves in all elec-
trical manhole drains.
New and Existing POTW's
Specify in contract documents that
as-built wiring drawings, schematics,
and logic diagrams must be prepared
by the contractor constructing the
treatment plant. Also, wiring in the
field must be numbered and wiring
identification lists provided at all
circuit breaker boxes.
1.1.81 - 1.1.85
83
-------
DEFICIENCY
CONSIDERATIONS
1.1.86 Improper
selection of type
timer relays,
making fine
adjustments
difficult.
1.1.87 Electrical
design does not
have a power
factor correc-
tion.
1.1.88 Infrequent
use of high effi-
ciency lighting
sources.
1.1.89 Stand-by
generator under-
sized to run all
essential equip-
ment.
1.1.90 Use of open
fluorescent lighting
in humid areas of
POTW.
1.1.91 Placement of
motor control cen-
ters too close
to wash-down
areas.
New and Existing PQTW's
Provide timer relays properly grad-
uated for the intended application.
For instance, a timer graduated by
hours shouldn't be specified if
control must be based on minutes.
New and Existing POTW's
Provide power factor correction
capacitor for entire plant electrical
system or at local high-use motors.
New and Existing POTW's
Specify high efficiency lighting sys-
tems such as high pressure sodium
or fluorescent units.
New and Existing POTW's
Stand-by generator capacity should be
sufficient to start and operate all
lighting, ventilation, controls,
instrumentation, and essential proc-
ess equipment (i.e., aerators, lift
pumps, etc.) needed to handle aver-
age flows.
New and Existing POTW's
Cover plant lighting fixtures to keep
moisture out, or specify fixtures
designed for outdoor use.
New POTW's
Motor control centers (MCC) should
not be placed in rooms with equip-
ment that requires routine wash-
down. MCC's should generally be
located in separate rooms or build-
ings.
Method:
Existing PQTW's
Construct an enclosure
around the motor control center to
keep the electrical equipment from
getting wet. A curb should also be
installed around the enclosure to
prevent wash-water flowing into the
room from equipment areas.
1.1.86 - 1.1.91
84
-------
DEFICIENCY
CONSIDERATIONS
1.1.92 Inadequate
electrical capacity
to permit stand-by
pumps and blowers
to operate in
parallel.
1.1.93 Lack of
ventilation pro-
motes corrosion
of electrical
components.
1.1.94 Electrical
control panels
located below
ground where
exposed to
flooding.
1.1.95 Lack of
auxiliary power.
1.1.96 Motors over-
sized for future
growth which never
materializes,
resulting in
motors operating
at less efficiency
with lower power
factors.
New and Existing POTW's
Electrical systems should be suffi-
ciently sized to allow the simul-
taneous use of designated operating
and stand-by equipment. This is
particularly important for pumping
and aeration systems.
New and Existing POTW's
Adequate room ventilation must be
provided to remove moisture and/or
gases such as chlorine or hydrogen
sulfide, and to prevent equipment
corrosion problems.
New and Existing POTW's
All electrical control panels should
be located in areas protected from
flooding.
New and Existing POTW's
All POTWs should include emergency
power for major process equipment.
This can be accomplished by use of
diesel fuel, gasoline, natural gas
or digester gas powered generators;
or provide dual power feed lines to
the plant site. The stand-by power
should be automatically activated
upon a plant electrical power
failure.
New and Existing POTW's
Provide power factor correction
capacitor for the entire plant
electrical system.
1.1.92 - 1.1.96
85
-------
DEFICIENCY
CONSIDERATIONS
1.1.97 Insufficient
use of high-effi-
ciency motors.
1.1.98 Electrical
quick-disconnect
plugs not provided
with submerged
pumps to facil-
itate rapid
replacement.
1.1.99 Inadequate
plant lighting.
1.1.100 Stairways
without non-skid
surfaces.
1.1.101 Inadequate
handrailing and
kick plates.
New POTW's
Specify high-efficiency motors in
lieu of standard "off-the-shelf"
units.
Existing POTW's
Method; As motors are replaced, spe-
cify high-efficiency motors in lieu
of standard "off-the-shelf" units.
New and Existing POTW's
Quick-disconnect electrical plugs
should be provided with submerged
equipment (pumps, samplers, etc.)
to allow rapid replacement with
stand-by units when maintenance is
required.
New and Existing POTW's
Provide sufficient lighting to ensure
safe operating conditions are
attained in all areas of the plant.
This is particularly important around
open tanks, aeration basins, below
grade tanks and sumps, stairways,
etc.
Design plant lighting system to con-
form to "Lighting and Thermal Oper-
ation Guidelines" published by the
Federal Energy Administration. Refer
to 1.1.88.
New POTW's
Specify non-skid surfaces for all
stairways.
Existing POTW's
Place non-skid strips on all
Method;
stairways,
New POTW1s
Provide handrailing and kick plates
on both sides of all stairways and
on all walkways around tanks and
equipment. Handrail and kick plates
should meet OSHA requirements.
1.1.97 - 1.1.101
86
-------
DEFICIENCY
CONSIDERATIONS
1.1.102 Inadequate
fencing around
site.
1.1.103 Use of air
headers as guard
railing at small
package-plant
type POTWs.
1.1.104 Stairs
inclined at too
steep an angle.
Existing POTW's
Method; Add handrailing on both
sides of all stairways and on all
walkways around tanks. Add kick
plates at all handrails.
Materials; Weather-resistant mate-
rial such as aluminum, galvanized
steel, etc.
New POTW's
Provide fencing (a minimum of 8 feet
high) around the entire site to make
it inaccessible to all unauthorized
personnel.
Existing POTW's
Method; Add fencing (approximately
8 feet high) around entire site to
make it inaccessible to all unauthor-
ized personnel.
Materials; Chain-link fence con-
structed of weather-resistant mate-
rial (aluminum, galvanized steel,
etc.)
Cost; Approximately $8-10/linear
foot.
New POTW's
Air headers can become very hot and
should not be used as guard railings.
Refer to 1.1.101.
Method:
Existing POTW's
Install insulation on air
headers that are used as guard rail-
ings. Add handrails as described in
1.1.101.
New and Existing POTW's
Design stairways to meet OSHA
requirements; specify a maximum
incline of 30 degrees.
1.1.101 - 1.1.104
87
-------
DEFICIENCY
CONSIDERATIONS
1.1.105 Guard
railing not
provided around
ground-level
tanks.
1.1.106 Guard
railing kick
plates bow with
change in
ambient tem-
perature.
1.1.107 Stairways
provided with
only one handrail.
1.1.108 Valve
handles located
in unsafe areas.
1.1.109 Inadequate
consideration of
state and OSHA
ventilation
requirements in
confined spaces.
1.1.110 Inadequate
consideration of
noise control.
New and Existing POTW's
Guard railing or fencing should be
provided around all tanks that have
open tops at ground-level. Refer to
1.1.101.
New and Existing POTW's
Specify that slotted kick plates be
attached to handrail posts with U-
bolts to allow for expansion.
New and Existing POTW's
Refer to 1.1.101.
New and Existing POTW's
Locate valves so that they are easily
accessible and can be operated
safely.
New and Existing POTW's
Review OSHA and state regulations
concerning design of ventilation
systems for wastewater treatment
plants and safety requirements for
confined space.
New POTW's
Specifications for mechanical equip-
ment and their associated electric
motors should have a noise emission
criteria section. Work areas should
also be designed to meet OSHA noise
criteria. Noise absorbing and/or
containing enclosures should be con-
sidered only when equipment cannot
be designed to meet the work place
noise criteria.
Existing POTW's
Method; All replacement mechanical
equipment and their associated
T.E.F.C. electrical motor specifica-
tions should have a noise emission
criteria section.
1.1.105 - 1.1.110
88
-------
DEFICIENCY
CONSIDERATIONS
1.1.111 Inadequate
separate access to
the influent wet
well, screening
or comminutor room,
and chlorine room.
1.1.112 Dangerous
chemicals not
stored in sepa-
rate areas.
1.1.113 Inadequate
security provisions,
1.1.114 Inadequate
provisions for
vehicle and asso-
ciated equipment
protection.
Work areas should be redesigned to
meet OSHA noise criteria. Refer to
the Institute on Noise Control Admin-
istration for specific equipment
and/or building noise abatement cor-
rections.
Noise absorbing and/or containing
enclosures should be considered only
when equipment cannot be designed to
meet the work place noise criteria.
New and Existing PQTW's
For safety reasons, separate access
should be provided to all individual
process areas. This is particularly
true for chlorine storage areas and
chlorinator rooms.
New and Existing POTW's
Provide separate, well-ventilated
areas for storage of hazardous chem-
icals. Ensure adequate clean-up
facilities are also provided.
New and Existing POTW's
Provide plant lighting per 1.1.99
and fencing per 1.1.102.
New POTW's
Specify fenced-in garages to house
plant vehicles and maintenance equip-
ment. This provides a secured area
to store parts and equipment, and a
work area to maintain vehicles. A
maintenance shop could be incorpo-
rated as part of the vehicle stor-
age complex.
Existing POTW's
Method; Store vehicles and asso-
ciated equipment in a fenced area or
in a locked garage when not in use.
1.1.110 - 1.1.114
89
-------
DEFICIENCY
CONSIDERATIONS
1.1.115 Hand rails
and grating not
secure.
1.1.116 Stairs not
painted bright
colors.
New POTW's
Secure hand rails and grating by
anchoring with bolts to concrete
or by welding to other metal, as
appropriate. Clip and/or bolt
grating. Refer to 1.1.106.
Existing PQTW's
Method; Secure hand rails and grat-
ing by anchoring with bolts to con-
crete or by welding to other metal,
as appropriate. Place hand rail
posts in shoes bolted to the floor
rather than on flat anchor plates.
Clip and/or bolt grating to concrete,
New POTW's
Indoor or outdoor stairs which
require painting should be painted
with bright colors for safety rea-
sons.
1.1.117 Wet floors
in some areas
(pump rooms and
pipe galleries)
are slippery.
Method:
Existing POTW's
Indoor or outdoor stairs
which require painting should be
painted with bright colors for safe-
ty reasons.
Material: Moisture-resistant paint.
Cost: Approximately $0.50 per
square foot.
New POTW's
Specify a non-slip surface for floors
in areas that will frequently be wet;
this would include pump rooms, sludge
handling areas, pipe galleries, etc.
Method:
Existing POTW's
Abrade surface of floor to
make rough, or add mats (metal or
plastic) to walkways to make walk-
ing safer.
1.1.115 - 1.1.117
90
-------
DEFICIENCY
CONSIDERATIONS
1.1.118 Electric
cut-off switches
not locally
mounted at indi-
vidual pieces of
equipment.
1.1.119 Ladders in
manholes and con-
crete tanks not
secure.
1.1.120 Hazardous
areas not well
defined.
1.1.121 Handling
facilities not
provided for
mechanical com-
ponents over 100
pounds.
1.1.122 Inadequate
consideration of
OSHA safety
requirements.
1.1.123 Permanent
access platforms
required for
New and Existing POTW's
Locally-mounted power cut-off
switches that override power
switches at motor control centers
should be provided at (within view
of) individual pieces of equipment.
This prevents a piece of equipment
being activated while it is being
serviced by an operator.
New and Existing POTW's
Specify galvanized steel (not plas-
tic) rungs for tanks and manholes.
The ladders should also be brightly
painted. Refer to 1.1.59.
New and Existing POTW's
Hazardous areas should be well
defined via use of signs and bright
colors (safety paints) and also be
restricted by means of fencing or
separate access (e.g., chlorine
room).
New and Existing PQTW's
Provide portable or fixed hoist sys-
tems to move large pieces of equip-
ment. Refer to 1.1,1 and 1.1.28.
New POTW's
Refer to OSHA safety requirements
during design of POTW.
Existing POTW's
Method t Conduct OSHA survey of
entire plant; make required changes
where necessary.
New and Existing POTW's
Provide permanent access platforms
for all equipment mounted on large
1.1.118 - 1.1.123
91
-------
DEFICIENCY
CONSIDERATIONS
maintenance not
provided.
1.1.124 Inadequate
noise abatement in
various plant areas
(i.e., blower, pump,
and dewatering
rooms, etc.) .
1.1.125 Plant located
in a flood plain.
1.1.126 Inadequate
buffer zone to
alleviate problems
due to noise, odor,
aerosol, fog, etc.
tanks (e.g., fixed aerators, clari-
fier mechanisms) and for all equip-
ment which is otherwise inaccessible
(e.g., elevated motors, valves,
mixers, etc.).
New POTW's
Consider noise abatement measures in
areas which house mechanical equip-
ment such as blowers, pumps, centri-
fuges, etc. Refer to 1.1.110.
Existing PQTW*s
Method; Provide noise abatement
measures per 1.1.110.
Conduct noise survey of entire plant
to identify problem areas. Install
vibration attenuating mounts on
motors and equipment. Install flex-
ible coupling between equipment and
pipes and conduit. Install vibration
alternating pipe hangers.
If above procedures fail to reduce
work area noise levels to acceptable
levels, install noise attenuating
enclosures. As a last resort, issue
personnel protective hearing equip-
ment.
New and Existing POTW's
Provide dikes and berms as required
to protect the plant from a 100-year
flood.
New and Existing POTW's
Locate plant in a relatively remote
area. Provide a visual buffer zone
by planting trees around the plant
site. Cover tanks if appropriate
to minimize fogging on adjacent
highways. Landscape area to
facilitate mowing and grooming
activities. Refer to 1.1.10 and
1.1.124 for noise abatement
procedures.
1.1.123 - 1.1.126
92
-------
DEFICIENCY
CONSIDERATIONS
1.1.127 Inadequate
consideration of any
potential freezing
problems of plant
components.
1.1.128 Inadequate
consideration of
odor development
and control.
New POTW's
Specify in-ground tanks in cold cli-
mate areas. Specify splash guards
around fixed aerators to decrease
freezing during winter months. Cover
tanks if required. Provide insula-
tion and/or heat tracing of exposed
pipes and valves. Refer to 1.1.22.
Method:
Existing POTW's
Add splash guards around
fixed aerators to decrease freezing
during winter months. Routinely
check surfaces of exposed tanks for
ice formation that interferes with
functioning of mechanisms such as
fixed aerators, clarifier mechanisms,
etc. Cover tanks if required. Pro-
vide insulation and/or heat tracing
of exposed pipes and valves.
New and ExistingPOTW's
Principal sources of odors in POTWs
include: septic raw wastewater;
industrial waste discharges; unwashed
grit; scum; organically overloaded
biological treatment processes; flue
gas from incinerators without after
burners; and sludge handling facil-
ities. Preventative odor control
measures that can be taken include:
the use of submerged inlets; proper
process design loadings; covered
tanks with gas treatment systems
such as activated carbon adsorbers;
air or oxygen additions to in-plant
wastewater transmission troughs;
combustion of off-gases at proper
temperatures; addition of chemicals
such as chlorine, hydrogen peroxide,
ozone, and lime to tanks, wet wells,
sewer lines, etc; and providing
facilities such as closed dumpsters,
ample yard hydrants, floor drains,
etc., that encourage good housekeep-
ing practices.
1.1.127 - 1.1.128
93
-------
DEFICIENCY
CONSIDERATIONS
1.1.129 Interior
building surfaces
not painted with
bright, easily-
cleaned paints.
1.1.130 Accumulation
of rags and debris
around plant site
due to inadequate
disposal facilities.
1.1.131 Inadequate
consideration of
local weather
conditions and
their impact on
the accessibility
of a plant site.
New POTW's
Paint interior building surfaces
with bright, easily-cleaned paints.
Rubber-based paints are superior
to water-based paints for concrete
surfaces, since they are easily
cleaned and more resistant to
corrosive gases.
Existing POTW's
Method; At next scheduled repaint-
ing, paint all interior surfaces of
the plant, especially surfaces from
the floor level to five feet above
the floor, with a gloss or semi-gloss
paint in a light or bright color.
New and Existing POTW's
Provide covered trash cans or dump-
sters at various places throughout
the plant (i.e., bar screens, grit
chambers, maintenance shops, sludge
handling areas, pumping stations,
etc.) and make rag and debris
clean-up a part of the regular
housekeeping routine.
New and Existing POTW's
During the site selection process,
consideration must be given to area
climatic conditions Areas that are
characterized by heavy rainfall will
require all-paved roads, consid-
eration of impact of local flooding
problems on plant accessibility,
provisions for adequate drainage,
etc. POTWs should not be located
at a remote site in areas that
experience heavy snow fall. Local
snow removal capabilities and emer-
gency snow routes should be iden-
tified. Refer to 1.1.19.
1.1.129 - 1.1.131
94
-------
DEFICIENCY
1.1.132 Inadequate
consideration of
spill prevention
plan.
CONSIDERATIONS
New PQTW's
In order to prevent spills of oil
and/or hazardous materials from con-
taminating surface or groundwaters,
the following measures should be
taken.
Provide dikes, berms,
retaining walls, etc.,
around above-ground
storage tanks with suffi-
ficient capacity to
retain the entire contents
of the largest tank.
Removal of the contents of
the diked area must be by
positive means, such as a
manually-operated valve or
pump, after an inspection
of the material has deter-
mined where it should be
directed.
Plant drainage systems from
undiked areas should flow,
if possible, into ponds,
lagoons, or catchment basins
if there is a possibility
that runoff could come in
contact with oil or hazardous
chemicals.
Existing POTW's
Method; Prepare a Spill Prevention
Control and Countermeasure (SPCC)
Plan and Pollution Intervention Pre-
vention Plan (PIPP) for the facility,
and follow through with implementa-
tion of spill containment measures
proposed therein. This could
include constructing dikes around
chemical storage tanks, routing
stormwater runoff from potentially-
contaminated areas to the plant
drain system, providing proper on-
site clean-up materials, etc.
1.1.132
95
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 1.2 Preliminary
1.2.1 Lack of
spare pumps.
1.2.2 Inadequate
consideration of
scum removal
from plant.
1.2.3 Inadequate
process flexibility,
New and Existing POTW's
Refer to 1.1.2.
New POTW's
Some type of scum removal mechanism,
such as a rotating scum trough,
should be provided to remove scum
from the influent wet well. The
material removed should be pumped to
the sludge handling facilities at the
plant, and not recycled back through
the plant.
Method:
Existing POTW's
Scum should be taken out of
the plant system and not allowed, for
example, to drain to the influent
pump station.
New POTW's
Provide necessary piping and valving
to ensure major pieces of mechanical
equipment, such as bar screens, grit
chambers, lift pumps, and comminu-
tors, can be isolated for maintenance
and repairs.
Method:
Existing POTW's
Add by-pass lines around
mechanical equipment (bar screen,
comminutor, grit chamber, etc.) for
servicing during repair.
The following provisions should be
made where applicable to enhance the
controllability of preliminary treat-
ment equipment:
1.2.1 - 1.2.3
96
-------
DEFICIENCY CONSIDERATIONS
Influent Pumping Station
- Racks or screens to protect
pumps from abrasive material and
objects that can plug the suc-
tion lines.
- Pump speed controllers and wet
well level controllers set to
minimize the number of pump
starts and stops.
- Influent flow meter.
Bar Screen
- Mechanical cleaner adjusted so
that screen face is cleaned
often enough to prevent back-
up of flow in influent channel.
Velocity-Controlled Chain-and-
Flight Grit Chamber
- Scrapers set to operate at low
speed to minimize collection of
organic matter along with grit.
- Bucket elevator set to operate
at a rate fast enough to remove
the grit collected.
Aerated Grit Chamber
- Adjustable air flow set low
enough to allow grit to settle,
but high enough to prevent
organic material from being
removed with the grit.
1.2.4 Lack of New and Existing POTW's
all-weather roads Refer to 1.1.19.
to pump stations.
1.2.3 - 1.2.4
97
-------
DEFICIENCY
CONSIDERATIONS
1.2.5 Insufficient
number and poor
placement of high-
pressure hose hy-
drants throughout
plant.
1.2.6 All valves
not operable from
floor level.
1.2.7 Inadequate
clearance around
equipment for main-
tenance functions.
1.2.8 Inadequate
provisions for
draining tanks and
sumps.
1.2.9 Inadequate
provisions for
sampling of in-
dividual processes.
New and Existing POTWs
Hose bibs should be provided at
wet wells, bar screens, grit
chambers, comminutors, clarifiers,
and pump stations.
New and Existing POTWs
Overhead valves should be provided
with chain operators, and valves
below grade should be provided with
extended stems.
New POTW's
Provide a minimum of 4 feet around
indoor equipment, such as pumps, and
allow truck access for outdoor equip-
ment such as screens, comminutors,
grit screw conveyors, etc.
Existing POTW's
Method; Where possible, relocate
equipment to a more accessible
position.
New "and Existing POTW's
Wet' well designs should consider dual
compartments to allow continued oper-
ation during cleanout or maintenance
periods, and should have bottom drain
valves or pump-out sumps. Sumps
should have sloped bottoms to facil-
itate dewatering.
New POTW's
Provide facilities for an influent
sampling station. This would include
an automatic composite sampler, elec-
trical outlet, hose bib, and a sam-
pling tap (or a submersible sampling
pump).
Existing POTW's
Method; Provide a composite sampler
per 1.1.72 for influent flow.
1.2.5 - 1.2.9
98
-------
DEFICIENCY
CONSIDERATIONS
1.2.10 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks,
etc.) required for
maintenance.
1.2.11 Inadequate
scum handling and
disposal system.
New and Existing POTW's
Refer to 1.1.28.
1.2.12 Lack of
flexibility to
operate POTW at
low flow start-
up conditions.
1.2.13 Inadequate
consideration of
pumping system de-
sign and/or fluid
characteristics,
resulting in pump
cavitation.
1.2.14 Use of
single-speed pumps
where variable-
speed units are
required.
1.2.15 Undersized
scum pits.
New and Existing POTW's
Provisions should be made to remove
scum from the influent wet well and
aerated grit chambers. This could
include skimmer underflow baffles, a
scum trough, scum pits, and pumps,
etc. Refer to 1.1.29.
New POTW's
Refer to 1.1.33.
Method:
Existing POTW's
Refer to 1.1.33.
Where
required, partitions may have to be
installed to narrow channels in order
to obtain proper liquid velocities.
New and Existing POTW's
Refer to 1.1.39.
New and Existing POTW's
Dual-speed or variable-speed pumps
should be considered for use at POTW
influent lift stations in order to
provide the necessary pumping
capacities and desired efficiencies
to handle both minimum and maximum
flows.
New and Existing POTW's
Refer to 1.1.43.
1.2.10 - 1.2.15
99
-------
DEFICIENCY
CONSIDERATIONS
1.2.16 No provisions
made to allow per-
iodic cleaning of
the influent wet
well.
1.2.17 Inadequate
consideration of
possible develop-
ment of septic
conditions in
channels and
splitter boxes.
1.2.18 Lack of
floor trenches
around pumps to
carry water spills
to sumps.
1.2.19 Lack of
seal water
drippage drain
lines.
New POTW's
The wet well design should include
dual compartments to allow continued
operation during maintenance periods,
and should have a bottom drain valve
or a pump-out sump.
Existing POTW's
Method; Construct partitions in the
wet well that will compartmentalize
it; the individual compartments can
be dewatered when required for clean-
ing purposes.
New PQTW's
Design channels for a flow velocity
of 2 ft/sec at design flow. Provide
means to clean out channels and
splitter boxes (i.e., to remove
settled solids and/or scum). Pro-
vide the flexibility to aerate
channels carrying raw wastewater.
Existing POTW's
Method; Inject air along the channel
or in the splitter boxes to maintain
aerobic conditions. The channels or
splitter boxes could also be par-
titioned off to reduce their volume
and, therefore, increase flow-thru
velocities and the time wastewater
or sludge is allowed to remain in
them.
New and Existing POTW's
Refer to 1.1.46.
New POTW's
Refer to 1.1.53.
Existing POTW's
Method: Refer to 1.1.46
1.2.16 - 1.2.19
100
-------
DEFICIENCY
1.2.20 Pumps are
located above the
normal water level,
making them diffi-
cult to prime.
1.2.21 Lack of
air bleed-off
valves at high
points in pump
discharge lines.
1.2.22 Lack of
mud valves in
tanks.
1.2.23 Lack of
sumps in dry wells.
1.2.24 Excess oil
from stationary
units not contained,
CONSIDERATIONS
New and Existing POTW's
Refer to 1.1.56.
New and Existing POTW's
Refer to 1.1.60.
New and Existing POTW's
Refer to 1.1.61 and 1.2.0.
New and Existing POTW's
Refer to 1.1.65.
New PQTW's
Refer to 1.1.71.
Existing POTW's
Method; Provide drip pans to collect
lubrication oil which drips from
pumps and similar equipment. The
drip pans can be emptied into a waste
oil collection tank. The waste oil
can then be reprocessed by a waste
oil reprocessor.
Materials; Metal or plastic drip
pans large enough to have to be
emptied only once every day or two.
A covered 55-gallon drum or similar
container for waste oil storage.
The drum should be located away from
storm drains and in an area where it
will not be affected by traffic
(vehicular or personnel) or by
weather.
Cost: Less than $100.
1.2.20 - 1.2.24
101
-------
DEFICIENCY
CONSIDERATIONS
1.2.25 Lack of
influent composite
sampler.
1.2.26 Lack of
flexibility in
disinfection systems
to permit prechlori-
nation for odor
control or return
sludge chlorination
for control of bulk-
ing.
1.2.27 Inadequate
electrical capacity
to permit stand-by
pumps and air
blowers to operate
in parallel.
1.2.28 Lack of
ventilation pro-
motes corrosion
of electrical
components.
New and Existing POTW's
Refer to 1.1.72.
New and Existing POTW's
Provide facilities necessary to
allow prechlorination of raw waste-
water to prevent odor problems at the
front-end of a POTW. This would in-
clude extra chlorinator capacity over
that required for just effluent dis-
infection, rotameters to control the
flow of chlorine solution to the in-
fluent wet well, a diffuser in the
wet well, wet well ventilation fans,
and required piping.
New POTW's
Electrical systems should be sized
to permit stand-by pumping equipment
to operate in parallel with normally
operating equipment. This may be
periodically required during high
influent flow periods.
Existing POTW's
Method; Refer to 1.1.92.
New POTW's
Provide adequate ventilation in bar
screen, comminutor, and pumping rooms
to prevent corrosion of electrical
components; in addition, specify
sealed electrical components.
Method:
Existing POTW's
Install ventilation fans and
associated duct work to continually
vent enclosed areas that have high
humidity or corrosive gases (i.e.,
chlorine, hydrogen peroxide, hydrogen
sulfide, etc.) present. The fans
should provide a room air change rate
of two times per hour. Provide
NEMA-4 boxes for electrical compo-
nents.
1.2.25 - 1.2.28
102
-------
DEFICIENCY
CONSIDERATIONS
1.2.29 High water
alarm systems not
provided.
1.2.30 Motors
oversized for
future growth
which never
materialized,
resulting in motors
operating at less
efficiency with
lower power
factors.
1.2.31 Electrical
quick-disconnect
plugs not provided
with submerged pumps
to facilitate rapid
replacement.
1.2.32 Inadequate
plant lighting.
1.2.33 Handling
facilities not
provided for
mechanical compo-
nents over 100
pounds.
1.2.34 Inadequate
consideration of
OSHA safety re-
quirements.
New and Existing POTW's
Specify high-level alarm systems
in wet wells, scum sumps, flow
channels, chemical mix tanks,
and similar unit operations.
Alarms should signal at the main
control panel as well as outside
alarm horns to indicate to the
operator the area of the plant
having problems.
New and Existing POTW's
Refer to 1.1.96.
New and Existing POTW's
Refer to 1.1.98.
New and Existing POTW's
Provide adequate lighting around unit
operations located outside (i.e., wet
wells, grit chambers, bar screens,
etc.). Refer to 1.1.99.
New and Existing POTW's
Refer to 1.1.121.
New and Existing POTW's
Refer to 1.1.122.
1.2.29 - 1.2.34
103
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DEFICIENCY
CONSIDERATIONS
1.2.35 Inadequate
consideration of
any potential
freezing problems
of plant components
induced by wind
and/or cold
temperatures.
New and Existing POTW's
In cold weather climates, considera-
tion should be given to placing pre-
liminary unit operations such as bar
screens, comminutors, and grit
chambers inside a protective struc-
ture. Provisions to cover wet wells
and splitter boxes should also be
made. Refer to 1.1.127.
Unit Operation/Component: 1.3 Primary
1.3.1 Inadequate
consideration of
scum removal from
plant.
1.3.2 Inadequate
process flexibility.
1.3.3 Insufficient
number and poor
placement of high-
pressure hose hy-
drants throughout
plant.
1.3.4 Use of
covered basins
inhibit access
to and observation
of unit processes.
New and Existing POTWs
Provide proper scum removal mech-
anism, such as chain-and-flight
collector or return sludge flight
collector, for rectangular tanks,
and transverse rotating helical
wiper attached to a shaft for cir-
cular tanks. Pumps should be
designed to transport the scum to
the solids handling facilities.
Scum should not be recycled back
through the plant.
New and Existing POTWs
Refer to 1.1.18.
New and Existing POTW's
Hose bibs should be provided at
primary clarifiers, scum troughs,
sumps, and pumping stations.
Refer to 1.1.20.
New and Existing POTW's
Refer to 1.1.22.
1.2.35 - 1.3.4
104
-------
DEFICIENCY
CONSIDERATIONS
1.3.5 All valves
not operable from
floor level.
1.3.6 Inadequate
clearance around
equipment for main-
tenance functions.
1.3.7 Inadequate
provisions for
draining tanks and
sumps.
1.3.8 Inadequate
provisions for
sampling of in-
dividual processes.
1.3.9 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks, etc.)
required for mainte-
nance.
1.3.10 Inadequate
scum handling and
disposal system.
1.3.11 Lack of
flexibility to
operate POTW at
low flow start-up
conditions.
New and Existing POTW's
Refer to 1.1.23.
New and Existing POTW's
Refer to 1.1.24.
New and Existing POTW's
Refer to 1.1.26.
New POTW's
Provide safe and convenient access
to primary clarifier effluent for
sample collection.
Existing POTW's
Method; Provide sampling taps (per
1.1.17) on discharge end of primary
sludge pumps.
New and Existing POTW's
Refer to 1.1.28.
New and Existing POTW's
Refer to 1.1.29.
New and Existing POTW's
Refer to 1.1.33.
1.3.5 - 1.3.11
105
-------
DEFICIENCY
CONSIDERATIONS
1.3.12 Poor
hydraulic and
solids distribu-
tion among
identical units
operating in
parallel.
1.3.13 Undersized
scum pits.
1.3.14 Individual
flow measurement
not provided for
each of parallel
units.
1.3.15 Inadequate
consideration of
possible develop-
ment of septic con-
ditions in channels
and splitter boxes.
1.3.16 Insufficient
or inflexible sludge
return and/or wasting
pumping capacity.
New and Existing POTW's
Provide a flow splitter box in
front of primary clarifiers. For
equal distribution, flow must have
free fall over weirs.
New and Existing POTW's
Refer to 1.1.43 and 1.2.15.
New and Existing POTW's
Provide means, such as weirs, to
measure the flow to individual units
(i.e., primary clarifiers) that oper-
ate in parallel in order to allow
adjustment of an equal flow rate to
each unit. Refer to 1.1.36, 1.1.45,
and 1.3.14.
New and Existing POTW's
Refer to 1.2.17.
1.3.17 Lack of flow
metering devices on
chemical feed lines.
New POTW's
Design pumping systems to include
spare pumps for increased flexi-
bility. Provide variable speed
drives on sludge pumps or install
multiple pumps so that additional
pumps can be operated to increase
system capacity when required.
Existing POTW's
Method: Add auxiliary sludge pumping
and piping or increase the impeller
and/or motor size of the existing
sludge pumps.
New and Existing POTW's
Refer to 1.1.48.
1.3.12 - 1.3.17
106
-------
DEFICIENCY
CONSIDERATIONS
1.3.18 Piping which
hangs under outside
edge of walkways in
clarifiers and thick-
eners causes the walk-
ways to tilt and
mechanical equipment
to move out of
alignment.
1.3.19 Lack of air
bleed-off valves at
high points in pump
discharge lines.
1.3.20 Lack of mud
valves in tanks.
1.3.21 No mixing
provided in scum
tank to keep scum
mixed during pumping.
1.3.22 Excess oil
from stationary units
not contained.
New and Existing POTW*s
Refer to 1.1.50.
1.3.23 No positive
method of removing
scum from center
well of clarifiers.
New and Existing POTW's
Refer to 1.1.60.
New and Existing POTW's
Refer to 1.1.61 and 1.2.22.
New and Existing POTW's
Mixers should be installed in scum
pits receiving large quantities of
scum to keep a crust from forming
in the pit, and the scum from coning
during pumping. Scum pit bottoms
should also be sloped.
New POTW's
Refer to 1.1.71.
Method:
Existing POTW's
Refer to 1.2.24.
New and Existing POTW's
Provide yard hydrants near clarifiers
to allow operators to periodically
clean out center wells.
If the wastewater contains high con-
centrations of oil and grease:
Provide additional scum slots in
center well wall.
Specify that a center well skimmer
is to be provided by the clarifier
supplier.
1.3.18 - 1.3.23
107
-------
DEFICIENCY
CONSIDERATIONS
1.3.24 Lack of tank
dewatering systems to
permit rapid servicing
of submerged equip-
ment.
Consider a spray water system that
forces scum through the slots in
the center well wall.
New POTW's
Refer to 1.1.76.
1.3.25 Absence of
electrical outlets
on top of treatment
units.
1.3.26 Inadequate
electrical capacity
to permit stand-by
pumps and air blowers
to operate in parallel,
1.3.27 High water
alarm systems not
provided.
1.3.28 Motors over-
sized for future
growth which never
materializes, re-
sulting in motors
operating at less
efficiency with lower
power factors.
1.3.29 Inadequate
plant lighting.
1.3.30 Handling
facilities not
provided for mechanical
components over 100
pounds.
Existing POTW's
Method; Refer to 1.1.26.
New and Existing POTW's
Refer to 1.1.80.
New and Existing POTW's
Refer to 1.1.92.
New and Existing POTW's
Refer to 1.2.29.
New and Existing POTW's
Refer to 1.1.96.
New and Existing POTW's
Provide lighting around open tanks
such as primary clarifiers. Refer
to 1.1.99.
New and Existing POTW's
Refer to 1.1.121.
1.3.23 - 1.3.30
108
-------
DEFICIENCY
CONSIDERATIONS
1.3.31 Inadequate
consideration of
OSHA safety require-
ments.
1.3.32 Inadequate
consideration of any
potential freezing
problems of plant
components.
New and Existing POTW's
Refer to 1.1.122.
New PQTW's
Refer to 1.1.127.
Existing POTW's
Method; If routine break-up of ice
on clarifier is insufficient to en-
sure proper functioning of clarifier
mechanism, add covers to primary
clarifiers.
Unit Operation/Component: 1.4 Secondary Treatment
1.4.1 Lack of walk-
ways around tanks,
limiting operator
access.
1.4.2 Inadequate
consideration of
scum removal from
plant.
New POTW's
Provide adequate walkways to allow
maximum operator access to valves,
tank sidewalls, gates, troughs, etc,
Method:
Existing POTW's
Refer to 1.1.3.
New and Existing POTW's
Provide proper scum removal mech-
anism, such as chain-and-flight col-
lector or return sludge flight col-
lector, for rectangular tanks, and
transverse rotating helical wiper
attached to a shaft for circular
tanks. Pumps should be designed to
transport the scum to the solids
handling facilities. Ensure the scum
is removed from the plant and not
merely recycled back into the treat-
ment system.
1.3.31 - 1.4.2
109
-------
DEFICIENCY
1.4.3 Inadequate
consideration of
consequences of
rupture disc or
shear pin failures.
1.4.4 Inadequate
process flexibility.
CONSIDERATIONS
New and Existing POTW's
Refer to 1.1.10.
New POTW's
Refer to 1.1.18.
Existing POTW's
Method; If plant layout warrants,
install piping and valving so that
multiple aeration basins can be oper-
ated in the complete mix mode, the
plug flow mode, or the contact-sta-
bilization mode (see sketches).
In addition:
Add piping necesssary to isolate
aeration basins, trickling
filters, and clarifiers.
Install variable-speed aerators
and/or blowers in aeration
basin (s).
Install variable-speed sludge
pumps for return and waste
sludge flow.
Provide for recirculation of
filter effluent at trickling
filter plants.
Provide chemical feed system
(capable of feeding at varying
rates), if necessary, to improve
settling characteristics.
Materials; Valving and piping should
be compatible with existing piping.
1.4.3 - 1.4.4
110
-------
DEFICIENCY
Influent
Influent
CONSIDERATIONS
Sketch; Activated sludge modes.
Complete Mix
Effluent
* Waste
Plug Flow
^ Waste
Effluent
Effluent
*- Waste
Contact Stabilization
Influent
Effluent
Waste
1.4.4
111
-------
DEFICIENCY
CONSIDERATIONS
1.4.5 Insufficient
number and poor
placement of high-
pressure hose hydrants
throughout plant.
1.4.6 Use of covered
basins inhibit access
to and observation of
unit processes.
1.4.7 All valves not
operable from floor
level.
1.4.8 Inadequate
clearance around
equipment for main-
tenance functions.
1.4.9 Inadequate
provisions for drain-
ing tanks and sumps.
1.4.10 Inadequate
provisions for
sampling of indi-
vidual processes.
New and Existing PQTW's
Yard hydrants should be available for
cleaning effluent weirs on tanks,
scum troughs in clarifiers, tank
sidewalls, and splitter boxes.
New POTW's
Refer to 1.1.22.
Method:
Existing POTW's
Remove the covers from the
basins unless the advantages of
observation and access are outweighed
by the freeze protection provided by
the covers. Refer to 1.1.22.
New and Existing POTW's
Refer to 1.1.23.
New and Existing POTW's
Refer to 1.1.24.
New and Existing POTW's
Refer to 1.1.26 and 1.2.22.
New POTW's
Provide sample taps on recycle/waste
pump discharge lines.
Method:
Existing POTW's
Provide D.O. probes for
aeration basins, sampling taps on
discharge side of sludge recycle/
waste pumps, and flow measurement
for sludge recycle stream and sludge
waste stream.
1.4.5 - 1.4.10
112
-------
DEFICIENCY
CONSIDERATIONS
1.4.11 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks, etc.)
required for main-
tenance.
1.4.12 Inadequate
scum handling and
disposal system.
1.4.13 Foam sprays
not concentrated in
basin corners where
foam buildup occurs.
1.4.14 Lack of
flexibility to
operate POTW at
low flow start-up
conditions.
1.4.15 Poor hydraulic
and solids distribu-
tion among identical
units operating in
parallel.
New and Existing POTW's
Refer to 1.1.28.
1.4.16 Undersized
scum pits.
New and Existing POTWs
Refer to 1.1.29.
New and Existing POTWs
Refer to 1.1.30.
New and Existing POTWs
Provide parallel secondary treatment
trains and the piping flexibility
needed to remove some of the units
from service when flow is low.
New POTWs
Provide a flow splitter box upstream
of both aeration basins and clar-
ifiers. For equal distribution, flow
must have free fall over weirs.
Existing POTWs
Method; Provide a splitter box, if
required, to divide flow and solids
evenly among aeration basins and sec-
ondary clarifiers. If necessary, add
valving to return sludge lines so
that sludge recycle from a given
clarifier will not be restricted to
one particular aeration basin.
New POTWs
Scum pits should be sized to accommo-
date one-day scum storage and be a
minimum size of 4" x 4' x 41.
1.4.11 - 1.4.16
113
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing POTWs
Refer to 1.1.43,
1.4.17 Individual
flow measurement not
provided for each
piece of parallel
units.
1.4.18 Inadequate
consideration of
possible development
of septic conditions
in channels and
splitter boxes.
1.4.19 Insufficient
or inflexible sludge
return and/or wasting
pumping capacity.
1.4.20 Lack of flow
metering device on
chemical feed lines.
1.4.21 Piping which
hangs under outside
edge of walkways in
clarifiers and thick-
eners causes the walk-
ways to tilt and mech-
anical equipment to
move out of alignment.
1.4.22 No convenient
means provided to
feed dry chemicals
into top-loading
feeders.
1.4.23 Lack of drains
on chemical mix tanks.
New and Existing POTWs
Provide means/ such as weirs, to
measure the flow to individual units,
such as aeration basins and clar-
ifiers that operate in parallel in
order to allow adjustment of an equal
flow rate to each unit. Refer to
1.1.45.
New and Existing POTW's
Refer to 1.2.17.
New and Existing POTW's
Refer to 1.3.16.
New and Existing POTW's
Provide flow meters, such as rota-
meters, on chemical feed lines to
allow accurate determination of
chemical feed rates.
New and Existing POTW's
Refer to 1.1.50
New and Existing POTW's
Refer to 1.1.51.
New POTW's
Refer to 1.1.52.
1.4.16 - 1.4.23
114
-------
DEFICIENCY
1.4.24 Pumps are
located above the
normal water level,
making them difficult
to prime.
1.4.25 Chemical feed
pumps are too small
to allow high
dosages of chemicals
during emergencies.
1.4.26 Lack of
air bleed-off
valves at high
points in pump
discharge lines.
1.4.27 Lack of mud
valves in tanks.
1.4.28 No mixing
provided in scum
tanks to keep
scum mixed during
pumping.
1.4.29 Excess oil
from stationary units
not contained.
CONSIDERATIONS
Existing POTW's
Method; Add drain valves(s) to the
bottom of above-ground chemical mix
tank (s) .
Materials; Drain valves and piping
should be compatible with tank mate-
rial.
Cost; Less than $100 per tank, in-
cluding labor.
New and Existing POTW's
Refer to 1.1.56.
New and Existing POTW's
Refer to 1.1.58.
New and Existing POTW's
Refer to 1.1.60.
New and Existing POTW's
Refer to 1.1.61 and 1.2.8.
New and Existing POTW's
Refer to 1.3.21.
New POTW's
Refer to 1.1.71.
Existing POTW's
Method: Refer to 1.2.24.
1.4.23 - 1.4.29
115
-------
DEFICIENCY
CONSIDERATIONS
1.4.30 No positive
method of removing
scum from center
well of clarifiers.
1.4.31 Lack of tank
dewatering systems
to permit rapid
servicing of sub-
merged equipment.
1.4.32 Lack of
flexibility in dis-
infection systems
to permit prechlori-
nation for odor
nontrol or return
sludge chlorination
for control of
bulking.
1.4.33 Lack of
wyes, tees, and
crosses to facilitate
cleaning chemical
lines.
1.4.34 Lack of a
foam control system.
1.4.35 Absence of
electrical outlets
on top of treatment
units.
1.4.36 Lack of
electrical outlets
at field-mounted
instrumentation for
portable calibration
equipment.
New and Existing POTW's
Refer to 1.3.23.
New and Existing POTW's
Refer to 1.1.26.
New and Existing POTW's
Provide facilities necessary to allow
chlorination of return activated
sludge to alleviate bulking problems.
A chlorine addition line should be
tapped into the sludge return line.
Additional chlorinator capacity above
that required for effluent disin-
fection and a rotameter to control
the chlorine solution feed rate would
be required.
New and Existing POTW's
Refer to 1.1.77.
New and Existing POTW's
Refer to 1.1.79.
New and Existing POTW's
Electrical outlets should be provided
at all sluice gate locations on aera-
tion tanks to operate portable gate
cranks and at the center well on all
clarifiers for power tools. Refer to
1.1.80.
New and Existing POTW's
Electrical outlets should be pro-
vided at pH and D.O. monitoring
stations to allow calibration of the
equipment with portable equipment or
for temporary hook-up of equipment.
Refer to 1.1.83.
1.4.30 - 1.4.36
116
-------
DEFICIENCY
CONSIDERATIONS
1.4.37 Inadequate
electrical capacity
to permit stand-by
pumps and air blowers
to operate in parallel,
1.4.38 High water
alarm systems not
provided.
1.4.39 Motors over-
sized for future
growth which never
materializes, re-
sulting in motors
operating at less
efficiency with lower
power factors.
1.4.40 Inadequate
plant lighting.
1.4.41 Use of air
headers as guard
railing at small
package-plant type
POTWs.
1.4.42 Handling
facilities not pro-
vided for mechanical
components over 100
pounds.
1.4.43 Inadequate
consideration of
OSHA safety require-
ments.
1.4.44 Inadequate
noise abatement in
various plant areas
(i.e., blower, pump
and dewatering rooms,
etc.).
New and Existing POTW's
Refer to 1.1.92.
New and Existing POTW's
Refer to 1.2.29.
New and Existing POTW's
Refer to 1.1.96.
New and Existing POTW's
Provide lighting around aeration
tanks, clarifiers, walkways and
stairways. Refer to 1.1.99.
New and Existing POTW's
Refer to 1.1.103.
New and Existing POTW's
Refer to 1.1.121.
New and Existing POTW's
Refer to 1.1.122.
New POTW's
Aeration blowers should be specified
with noise reduction accessories such
as inlet and outlet silencers and
sound enclosures.
1.4.37 - 1.4.44
117
-------
DEFICIENCY
CONSIDERATIONS
1.4.45 Inadequate
consideration of
potential freezing
problem of plant
components.
Existing POTW's
Method; Provide noise abatement
measures per 1.1.124.
New POTW's
Refer to 1.1.127.
Method:
Existing POTW's
Provide splash guards around
fixed aerators to decrease freezing
during winter months. Cover aeration
basins/trickling filters and/or clar-
ifiers, if necessary. Provide in-
sulation and/or heat tracing of ex-
posed pipes and valves.
Unit Operation/Component: 1.5 Sludge Handling
1.5.1 No provisions
for moving equipment
and supplies from
one building floor
to another.
1.5.2 Inadequate
consideration of
scum removal from
plant.
New POTW's
Provide adequate means of moving
equipment and supplies from one
building floor to another through
the use of ramps, hoists, and/or
elevators. Care should be taken to
assure that elevators and floor cut-
outs for hoists are large enough to
allow passage of the largest pieces
of equipment in use, or anticipated
to be used, in the building being
designed.
Existing POTW's
Method; Refer to 1.1.5.
New and Existing POTW's
Refer to 1.4.2.
1.4.44 - 1.5.2
118
-------
DEFICIENCY
1.5.3 Inadequate
consideration of
consequences of rup-
ture disc or shear
pin failures.
1.5.4 Lack of
sampling taps at
pumping stations.
CONSIDERATIONS
New and Existing POTW's
Refer to 1.1.10.
New and Existing POTW's
Provide sampling taps in the dis-
charge lines from sludge pumping
stations. Refer to 1.1.17.
1.5.5 Inadequate
process flexibility.
New POTW's
Refer to 1.1.18.
Existing POTW's
Method; Add piping and valving so
that each thickener, sludge pump, and
sludge holding tank can be isolated
for routine maintenance and needed
repairs.
In the case where the sludge pumps
and the scum pumps are similar
models, provide valving and piping
(as' shown in the sketch) to allow
the scum pumps to be used as sludge
pumps whenever the sludge pumps have
to be serviced. If only sludge pumps
are available, provide valving and
piping to allow the sludge pumps to
serve any of the clarifiers. Pro-
vide valving at both the suction
and discharge sides of the pump so
that the pump can be removed for
repairs.
Materials; Piping and valving to be
compatible with existing piping.
1.5.3 - 1.5.5
119
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
Scum to Disposal
Sludge from
Clarifier No.
-=»
Scum from
Clarifier No. 1
Sludge from
Clarifier No. 2
Scum from
Clarifier No. 2
Normal
Sludge Pump
Scum Pump
-t*H
[Sludge Pump
I Scum Pump |
1
al
f*
i*u-i i rwA
$~"
X
r-,^uijsi-i
IVl-If^
i
^
!
i fc
; ;
Re
i
(
fccycle to Aeration
Basin No. 1
Re<
i
k
zycle to Aeration
Basin No. 2
Waste Sludge
1.5.5
120
-------
DEFICIENCY
CONSIDERATIONS
1.5.6 Insufficient
number and poor
placement of high-
pressure hose hydrants
throughout the plant.
1.5.7 All valves
not operable from
floor level.
1.5.8 Inadequate
clearance around
equipment for main-
tenance functions.
1.5.9 Inadequate
provisions for
draining tanks and
sumps.
1.5.10 Inadequate
provisions for sampling
of individual proc-
esses.
1.5.11 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks, etc.)
required for main-
tenance.
1.5.12 Lack of
flexibility to
operate POTW at
low flow start-
up conditions.
New and Existing POTW's
Provide hose bibs near all sludge
handling equipment such as pumps,
thickeners, dewatering units, etc,
New and Existing POTW's
Refer to 1.1.23.
New and Existing POTW's
Refer to 1.1.24.
New and Existing POTW's
Refer to 1.1.26.
New and Existing POTW's
Sample taps should be provided on
the piping connecting unit processes
and on sludge pump discharge lines.
Refer to 1.1.17 and 1.1.27.
New and Existing POTW's
Refer to 1.1.28.
New and Existing POTW's
Provide dual systems and stand-by
equipment (i.e., pumps) to allow
operation of single units during
low-flow periods. In addition,
rather than operating sludge
handling facilities on a continuous
basis, operate them only when suf-
ficient quantity of sludge is avail-
able.
1.5.6 - 1.5.12
121
-------
DEFICIENCY
CONSIDERATIONS
1.5.13 Floor drain
piping system under-
sized.
1.5.14 Use of single-
speed pumps where
variable-speed units
are required.
1.5.15 Poor hydraulic
and solids distribu-
tion among identical
units operating in
parallel.
1.5.16 Undersized
scum pits.
New and Existing POTW*s
Floor drain piping for sludge
handling facilities should be
specified at 6-inch diameter min-
imum. Refer to 1.1.34.
New POTW's
Specify sludge pumps that are two-
speed or variable-speed drive units,
Existing POTW's
Method; Add variable-speed device to
existing pumps or a pump recycle
line with a flow control valve (FCV)
that operates according to the liquid
level in the wet well (i.e., as the
level increases, the FCV closes and
vice versa).
New and Existing POTW's
Refer to 1.3.12 and 1.4.15.
New and Existing POTW's
Refer to 1.1.43 and 1.4.16.
1.5.17 Inadequate
consideration of
possible development
of septic conditions
in channels and
splitter boxes.
1.5.18 Lack of
floor trenches
around pumps to
carry water spills
to sumps.
1.5.19 Insufficient
or inflexible sludge
return and/or wasting
pumping capacity.
New and Existing POTW's
Refer to 1.2.17.
New and Existing POTW's
Refer to 1.1.46.
New and Existing POTW's
Refer to 1.3.16.
1.5.13 - 1.5.19
122
-------
DEFICIENCY
CONSIDERATIONS
1.5.20 Lack of flow
metering device on
chemical feed lines.
1.5.21 Piping which
hangs under outside
edge of walkways in
clarifiers and thick-
eners causes the walk-
way to tilt and
mechanical equipment
to move out of align-
ment.
1.5.22 No convenient
means provided to
feed dry chemical
into top-loading
feeders.
1.5.23 Lack of
drains on chemical
mix tanks.
1.5.24 Lack of seal
water drippage drain
lines.
1.5.25 Chemical feed
pumps are too small
to allow high dosages
of chemicals during
emergencies.
New and Existing POTW's
Refer to 1.1.48.
New and Existing POTW's
Refer to 1.1.50.
New and Existing POTW's
Refer to 1.1.51.
New POTW's
Refer to 1.1.52.
Existing POTW's
Method; Add drain valve(s) to the
bottom of above-ground chemical mix
tank(s).
Materials; Drain valves and piping
should be compatible with tank mate-
rial.
Cost; Less than $100 per tank, in-
cluding labor.
New and Existing POTW's
Pipe pump drain lip to sump or
floor drain. Refer to 1.1.46.
New and Existing POTW's
Refer to 1.1.58.
1.5.20 - 1.5.25
123
-------
DEFICIENCY
CONSIDERATIONS
1.5.26 Lack of air
bleed-off valves at
high points in pump
discharge lines.
1.5.27 Excess oil
from stationary units
not contained.
1.5.28 Lack of tank
dewatering systems to
permit rapid servicing
of submerged equip-
ment.
1.5.29 Inadequate
electrical capacity
to permit standby
pumps and air blowers
to operate in parallel.
1.5.30 Motors over-
sized for future
growth which never
materializes, re-
sulting in motors
operating at less
efficiency with
lower power factors.
1.5.31 Handling
facilities not
provided for mech-
anical components
over 100 pounds.
1.5.32 Inadequate
consideration of
OSHA requirements.
1.5.33 Inadequate
noise abatement in
various plant areas
(i.e., blower, pumps,
and dewatering rooms,
etc.).
New and Existing POTW's
Refer to 1.1.60.
New and Existing POTW's
Refer to 1.1.71.
New and Existing POTW's
Refer to 1.1.26.
New and Existing POTW's
Refer to 1.1.92.
New and Existing POTW's
Refer to 1.1.96.
New and Existing POTW's
Refer to 1.1.1, 1.1.28, and 1.1.121,
New and Existing POTW's
Refer to 1.1.122.
New POTW's
Refer to 1.1.110 and 1.1.124.
1.5.26 - 1.5.33
124
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing POTW's
1. Install silencers for T.E.F.C.
electric motor air inlets.
2. Install vibration damping motor
and pump mountings.
3. Replace existing pumps and
motors with ones that meet a
lower noise level specification.
4. Enclose electric motors and pumps
with noise attenuating enclosure
if above procedures do not reduce
work place noise level suffi-
ciently.
5. Install vibration attenuating
pipe supports or hangers, and/or
flexible couplings between pumps
and piping system.
6. As a last resort, issue personal
hearing protective equipment.
Unit Operation/Component: 1.6 Sludge Digestion
1.6.1 Inadequate con-
sideration of scum
removal from plant.
1.6.2 Inadequate proc-
ess flexibility.
New POTW's
Scum troughs, telescopic valves,
swing valves, or draw-off ports
should be provided to remove scum
from aerobic and anaerobic digesters,
The collected scum should be removed
from the plant and not recycled back
through it.
Existing POTW's
Method; Refer to 1.2.2.
New POTW's
Refer to 1.1.18.
1.5.33 - 1.6.2
125
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing POTW's
Add piping and valving to
1.6.3 Insufficient
number and poor place-
ment of high-pressure
hose hydrants through-
out plant.
1.6.4 All valves not
operable from floor
level.
1.6.5 Inadequate
clearance around
equipment for main-
tenance functions.
1.6.6 Inadequate pro-
visions for draining
tanks and sumps.
1.6.7 Inadequate pro-
visions for sampling
of individual process-
es.
1.6.8 Inadequate con-
sideration of access
requirements for large
equipment (cranes,
trucks, etc.) required
for maintenance.
isolate each digester (aerobic or
anaerobic) during maintenance.
Materials: Piping and valving to be
compatible with existing piping.
New and Existing POTW's
Provide yard hydrants near sludge
digesters and flushing connections to
digester piping.
New and Existing POTW's
Refer to 1.1.23.
New and Existing POTW's
Refer to 1.1.24.
New and Existing POTW's
Refer to 1.1.26.
New POTW's
Provisions should be made to allow
sampling of the digester influent and
effluent flows. Sample taps should
be installed on piping connecting
unit processes and on sludge pump
discharge lines.
Method:
Existing POTW's
Provide sampling taps at
discharge of sludge transfer pumps,
Provide sampling taps at multiple
levels in anaerobic digester.
New and Existing POTW's
Refer to 1.1.28.
1.6.2 - 1.6.8
126
-------
DEFICIENCY
CONSIDERATIONS
1.6.9 Inadequate scum
handling and disposal
system.
1.6.10 Foam sprays
not concentrated in
basin corners where
foam build-up occurs.
1.6.11 Floor drain
system undersized.
1.6.12 Poor hydraulic
and solids distribution
among identical units
operating in parallel.
1.6.13
pits.
Undersized scum
1.6.14 Individual flow
measurement not provid-
ed for each piece of
parallel units.
1.6.15 Inadequate con-
sideration of possible
development of septic
conditions in channels
and splitter boxes.
1.6.16 No conven-
ient means provided to
feed dry chemicals into
top-loading feeders.
New and Existing PQTW's
Scum collected from digesters should
be transported to the sludge handling
area and removed from the plant, not
recycled back through the plant.
Refer to 1.2.2.
New and Existing POTW's
Refer to 1.1.30.
New and Existing POTW's
All drain piping in the digester area
should be a minimum of 6 inches in
diameter. Refer to 1.1.34.
New and Existing POTW's
Provide a flow splitter box upstream
of digester units. Provisions to
allow stopping of the flow to each
unit must also be provided. For
equal distribution, flow must have
free fall over the weirs.
New and Existing POTW's
Refer to 1.1.43.
New and Existing POTW's
Provide means such as weirs to meas-
ure the flow to individual units,
such as digesters, that operate in
parallel in order to allow adjust-
ment of an equal flow rate to each
unit. Refer to 1.1.45.
New and Existing POTW's
Refer to 1.2.17.
New and Existing POTW's
Refer to 1.1.51.
1.6.9 - 1.6.16
127
-------
DEFICIENCY
1.6.17 Lack of drains
on chemical mix tanks.
CONSIDERATIONS
New POTW's
Refer to 1.1.52.
1.6.18 Lack of air
bleed-off valves at
high points in pump
discharge lines.
1.6.19 Lack of mud
valves in tanks.
1.6.20 Excess oil
from stationary units
not contained.
1.6.21 Design does
not emphasize heating
conservation measures,
1.6.22 Lack of tank
dewatering systems to
permit rapid servicing
of submerged equipment.
1.6.23 Lack of a foam
control system.
Existing POTW's
Method: Add drain valve(s) to the
bottom of above-ground chemical mix
tank(s).
Materials: Drain valves and piping
should be compatible with tank
material.
Cost; Less than $100 per tank,
including labor.
New and Existing POTW's
Refer to 1.1.60.
New and Existing POTW's
Refer to 1.1.61.
New and Existing POTW's
Refer to 1.1.71.
New and Existing POTW's
Off-gases (i.e., methane) from anaer-
obic digestion units should be used
as a fuel source for plant heating
systems (i.e., buildings and digest-
ers) and fuel-driven engines and
generators.
New and Existing POTW's
Refer to 1.1.26.
New and Existing POTW's
Refer to 1.1.79.
1.6.17 - 1.6.23
128
-------
DEFICIENCY
CONSIDERATIONS
1.6.24 Inadequate
electrical capacity to
permit standby pumps
and air blowers to
operate in parallel.
1.6.25 High water
alarm systems not
provided.
1.6.26 Motors over-
sized for future growth
which never material-
izes, resulting in
motors operating at
less efficiency with
lower power factors.
1.6.27 Handling facil-
ities not provided for
mechanical components
over 100 pounds.
1.6.28 Inadequate con-
sideration of OSHA
safety requirements.
New and Existing POTW's
Refer to 1.1.92.
New and Existing POTW's
Refer to 1.2.29.
New and Existing POTW's
Refer to 1.1.96.
New and Existing POTW's
Refer to 1.1.121.
New and Existing POTW's
Refer to 1.1.122.
Unit Operation/Component: 1.7 Sludge Dewatering
1.7.1 Lack of hoists
over larger pieces of
equipment.
1.7.2 No provisions
for moving equipment
and supplies from one
building floor to
another.
1.7.3 Inadequate proc-
ess flexibility.
New and Existing POTW's
Refer to 1.1.1.
New and Existing POTW's
An overhead crane or monorail should
be provided over each piece of
dewatering equipment. Refer to
1.1.5.
New POTW's
Refer to 1.1.18.
1.6.24 - 1.7.3
129
-------
DEFICIENCY
CONSIDERATIONS
1.7.4 Insufficient
number and poor place-
ment of high-pressure
hose hydrants through-
out plant.
1.7.5 All valves not
operable from floor
level.
1.7.6 Inadequate
clearance around equip-
ment for maintenance
functions.
1.7.7 Inadequate pro-
visions for draining
tanks and sumps.
1.7.8 Inadequate pro-
visions for sampling of
individual processes.
Existing POTW's
Method; Provide piping and valving
necessary to isolate dual units. If
warranted, install additional
dewatering equipment of the same type
as existing equipment.
New and Existing POTW's
Provide a hose bib at each piece of
dewatering equipment. Provide floor
drains around and under dewatering
equipment.
New and Existing PQTW's
Refer to 1.1.23.
New and Existing POTW's
Ensure ample room (4-ft minimum) is
provided around sludge dewatering
equipment to allow access by opera-
tors and equipment. Provide ample
overhead clearances as well.
New and Existing POTW's
Refer to 1.1.26.
New POTW's
Provide sample tapsTn sludge lines
to allow determination of feed solids
concentrations to sludge dewatering
equipment.
Method:
Existing POTW's
Provide sampling tap in
sludge feed line to measure solids
concentration in feed.
1.7.3 - 1.7.8
130
-------
DEFICIENCY
CONSIDERATIONS
Provide for process sampling as fol-
lows :
Centrifugation - Provide sam-
pling taps in centrate dis-
charge line to measure turbid-
ity or suspended solids of cen-
trate.
1.7.9 Inadequate con-
sideration of access
requirements for large
equipment (cranes,
trucks, etc.) required
for maintenance.
1.7.10 Lack of flexi-
bility to operate POTW
at low flow, start-up
conditions.
1.7.11 Floor drain
piping system under-
sized.
1.7.12 Drains from
buildings discharge
into basins with nor-
mally (or periodically)
high-water levels, caus-
ing drains to back-up.
Vacuum and Pressure Filtration
Provide sampling taps in fil-
trate discharge line to measure
filtrate suspended solids.
Sludge Drying Beds - Provide
access to allow operator to
measure sludge dryness at sev-
eral locations in the bed as
well as underflow from the bed.
New and Existing POTW's
Refer to 1.1.28.
New and Existing POTW's
Refer to 1.5.12.
New and Existing POTW's
All drain piping in sludge dewatering
areas should be a minimum of 6 inches
in diameter. Refer to 1.1.34.
New and Existing POTW's
Refer to 1.1.35.
1.7.8 - 1.7.12
131
-------
DEFICIENCY
CONSIDERATIONS
1.7.13 Poor hydraulic
and solids distribution
among identical units
operating in parallel.
1.7.14
pits.
Undersized scum
1.7.15 Individual flow
measurement not provided
for each piece of paral-
lel units.
1.7.16 Inadequate con-
sideration of possible
development of septic
conditions in channels
and splitter boxes.
1.7.17 Lack of flow
metering device on
chemical feed lines.
1.7.18 Piping which
hangs under outside
edge of walkways in
clarifiers and thick-
eners causes the walk-
ways to tilt and
mechanical equipment to
move out of alignment.
1.7.19 Chemical feed
pumps are too small to
allow high dosages of
chemicals during emer-
gencies.
New and Existing POTW's
Specifv feed tanks for sludge
dewatering equipment be mixed to pre-
vent solids settling and ensure equal
solids distribution to dewatering
equipment.
New and Existing POTW's
Refer to 1.1.43.
New and Existing POTW's
Provide flow measuring (and adjust-
ment) equipment to allow determina-
tion of flows to sludge dewatering
equipment, especially units such as
vacuum filters that operate continu-
ously. Refer to 1.6.14.
New and Existing POTW's
Refer to 1.2.17.
New and Existing POTW's
Refer to 1.1.48.
New and Existing POTW's
Refer to 1.1.50.
New and Existing POTW's
Refer to 1.1.58.
1.7.13 - 1.7.19
132
-------
DEFICIENCY
1.7.20 No mixing pro-
vided in scum tank to
keep scum mixed during
pumping.
1.7.21 Excess oil from
stationary units not
contained.
1.7.22 No positive
method of removing
scum from center well
of clarifiers.
1.7.23 Lack of wyes,
tees, and crosses to
facilitate cleaning of
chemical lines.
CONSIDERATIONS
New and Existing POTW's
Refer to 1.3.21.
New POTW's
Refer to 1.1.71.
Existing POTW's
Method; Refer to 1.2.24.
New and Existing POTW's
Refer to 1.3.23.
New and Existing POTW's
Refer to 1.1.77.
1.7.24 Absence of
electrical outlets on
top of treatment units.
1.7.25 Use of open
fluorescent lighting in
humid areas (i.e.,
dewatering building)
of POTW.
1.7.26 Placement of
motor control centers
too close to washdown
areas.
New and Existing POTW's
Provide electrical outlets on top of
thickeners and nearby dewatering
equipment.
New and Existing PQTW's
Refer to 1.1.90.
New POTW's
Since sludge dewatering areas are
subject to washdown, motor controls
should be housed in separate rooms.
Existing POTW's
Method: Refer to 1.1.91.
1.7.20 - 1.7.26
133
-------
DEFICIENCY
CONSIDERATIONS
1.7.27 Inadequate
electrical capacity to
permit standby pumps
and air blowers to
operate in parallel.
1.7.28 Lack of venti-
lation promotes corro-
sion of electrical com-
ponents.
New and Existing POTW's
Refer to 1.1.92.
1.7.29 Motors over-
sized for future growth
which never material-
izes, resulting in
motors operating at
less efficiency with
lower power factors.
1.7.30 Handling facil-
ities not provided for
mechanical components
over 100 pounds.
1.7.31 Inadequate con-
sideration of OSHA
safety requirements.
1.7.32 Inadequate
noise abatement in
various plant areas
(i.e., blower, pump,
and dewatering rooms,
etc.).
New POTW's
Adequate ventilation must be provided
to remove moisture and control humid-
ity levels to prevent instrumentation"
corrosion problems.
Method:
Existing POTW's
Refer to 1.2.28.
New and Existing POTW's
Refer to 1.1.96.
New and Existing POTW's
Refer to 1.1.121.
New and Existing POTW's
Refer to 1.1.122.
New POTW's
Refer to 1.1.124.
Existing POTW's
Method; The following steps are rec-
ommended :
1. Conduct noise survey to iden-
tify problem areas.
.21 - 1.7.32
134
-------
DEFICIENCY CONSIDERATIONS
2. Install vibration-attenuating
mounts on motors and equip-
ment.
3. Install flexible couplings
between equipment and piping,
i.e., fluid and electrical or
vibration-attenuating pipe
hangers.
4. Install air inlet and exhaust
silencers on compressors and
vacuum pumps.
5. If above procedures fail to
reduce work area noise levels
to acceptable levels, install
noise-attenuating enclosures.
6. As a last resort, issue per-
sonnel hearing protective
equipment.
1.7.33 Inadequate con- New and Existing POTW's
sideration of any poten- Trucks and dumpsters which receive
tial freezing problems dewatered sludge cake should be
of plant components. housed inside to prevent the cake
from freezing to the unit and making
it difficult to remove.
Unit Operation/Component: 1.8 Sludge Incineration
1.8.1 Inadequate proc- New POTW's
ess flexibility. Provide variable speed control on
incinerator feed conveyors. Provide
an alternate means to dispose of
sludge, such as a landfill, if the
incinerator is taken out of service.
1.7.32 - 1.8.1
135
-------
DEFICIENCY
CONSIDERATIONS
1.8.2 Insufficient
number and poor place-
ment of high-pressure
hose hydrants through-
out plant.
1.8.3 All valves not
operable from floor
level.
1.8.4 Inadequate
clearance around equip-
ment for maintenance
functions.
1.8.5 Inadequate pro-
visions for sampling of
individual processes.
Existing PQTW's
Method: Provide multiple incinera-
tion units sized such that if one
unit is taken out of service, the
remaining units can handle the entire
sludge feed; or provide a landfill so
that sludge can be disposed of when
the incinerator system is shut down
for repairs.
New and Existing POTW's
Provide hose bibs at each floor level
in the incinerator building. Refer
to 1.1.20.
New and Existing POTWs
Refer to 1.1.23.
Newand Existing POTW's
Refer to 1.7.6.
New POTW's
Provide sample ports in the incinera-
tor .
Existing POTW's
Method; Provide facilities (sample
taps, instrumentation, etc.) to per-
form the following tests for multiple
hearth or fluidized bed incineration
systems:
Measurement of sludge feed
solids concentration.
Measurement of excess air flow.
Measurement of oxygen, carbon
dioxide, and carbon monoxide in
the stack gases.
1.8.1 - 1.8.5
136
-------
DEFICIENCY
CONSIDERATIONS
1.8.6 Inadequate con-
sideration of access
requirements for large
equipment (cranes,
trucks, etc.) required
for maintenance.
1.8.7 Excess oil from
stationery units not
contained.
1.8.8 Lack of ventila-
tion promotes corrosion
of electrical components,
1.8.9 Handling facil-
ities not provided for
mechanical components
over 100 pounds.
1.8.10 Inadequate con-
sideration of OSHA
safety requirements.
New and Existing POTW's
Refer to 1.1.28.
New and Existing POTW's
Refer to 1.1.71 and 1.2.24.
New and Existing POTW's
Refer to 1.2.28 and 1.7.28.
New and Existing POTW's
Refer to 1.1.121.
New and Existing POTW's
Refer to 1.1.122.
Unit Operation/Component: 1.9 Sludge Disposal
1.9.1 Inadequate proc-
ess flexibility.
New POTW's
Provide an alternate disposal mode to
the primary method utilized. Alter-
natives could include landfilling,
storage lagoon, composting, etc.
Existing POTW's
Method; The following are sugges-
tions to increase the process flexi-
bility of the sludge disposal method
currently used at a given plant.
Add piping and valving to
isolate each unit in the
sludge disposal system (for
maintenance purposes).
1.8.6 - 1.9.1
137
-------
DEFICIENCY
CONSIDERATIONS
Provide adequate capacity to
store sludge or dewatered
cake prior to transporting to
landfill.
1.9.2 Insufficient
number and poor place-
ment of high-pressure
hose hydrants through-
out plant.
1.9.3 Inadequate con-
sideration of access
requirements for large
equipment (cranes,
trucks, etc.) required
for maintenance.
1.9.4 Inadequate con-
sideration of OSHA
safety requirements.
1.9.5 Inadequate con-
sideration of any
potential freezing
problems of plant com-
ponents.
1.9.6 Inadequate con-
sideration of local
weather conditions and
their impact on the
accessibility of a
plant site.
Provide an alternative dis-
posal mode to the primary
method utilized. Alterna-
tives could include landfill-
ing, storage lagoon, compost-
ing, and incineration.
New and Existing POTW's
Provide utility water hydrants near
all sludge handling areas.
New and Existing POTW's
Refer to 1.1.28 and 1.7.9.
New and Existing PQTW*s
Refer to 1.1.122.
New and Existing POTW's
Refer to 1.7.33.
New and Existing POTW's
Temporary sludge storage facilities
(or extra capacity in on-line units)
should be provided to hold sludge
during wet-weather conditions when
landfilling or land application are
the primary sludge disposal methods
utilized by a POTW.
1.9.1 - 1.9.6
138
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 1.10 Disinfection
1.10.1 Inadequate
valving for maximum
flexibility and proper
maintenance.
1.10.2 Inadequate proc-
ess flexibility.
New POTW's
Each chlorinator should be valved so
that it can be taken out of service
without shutting down the entire sys-
tem.
Method:
Existing POTW's
Add piping and valving to
isolate each chlorinator/ozonator and
each contact tank during maintenance.
If necessary, add provisions for
chlorination for odor control and/or
bulking control per 1.10.2.
Materials; Piping and valving to be
compatible with existing piping.
New POTW's
Process piping should be designed to
allow application of chlorine solu-
tions to various points in the POTW.
Each chlorine solution feed point
should be provided with a separate
feed line, and each feed line should
have flow measuring and control
devices. Refer to 1.2.26 and 1.4.32.
Existing POTW's
Method; The following applies to
both chlorination and ozonation sys-
tems:
Provide duplicate contact
chambers and chlorine/ozone
addition systems, as well as
piping and valving necessary
to isolate a contact chamber
and/or chlorinator/ozonator
for maintenance purposes.
1.10.1 - 1.10.2
139
-------
DEFICIENCY
CONSIDERATIONS
1.10.3 Insufficient
number and poor place-
ment of high-pressure
hose hydrants through-
out plant.
1.10.4 Inadequate
clearance around equip-
ment for maintenance
functions.
1.10.5 Inadequate pro-
visions for draining
tanks and sumps.
1.10.6 Inadequate pro-
visions for sampling of
individual processes.
1.10.7 Inadequate con-
sideration of access
requirements for large
equipment (cranes,
trucks, etc.) required
for maintenance.
1.10.8 Inadequate scum
handling and disposal
system.
Provide valving and piping
per 1.10.10 to facilitate
prechlorination/pre-ozonation
for odor control, control of
filter flies, control of
bulking by return sludge
chlorination/ozonation, etc.
New and Existing POTWs
Utility water hydrants should be pro-
vided near chlorine contact chambers
and hose bibs near chlorination
rooms.
New and Existing POTW's
A minimum clearance of 4 feet should
be provided around chlorinators and
disinfection equipment for mainte-
nance purposes.
New and Existing POTW's
Refer to 1.1.26.
New and Existing POTW's
Provision should be made for sample
collection at the effluent end of
chlorine contact tanks (even if it is
not the final plant discharge point).
New and Existing POTW's
Provide monorail for unloading and
moving chlorine cylinders. Refer to
1.1.28.
New and Existing POTW's
Scum removal facilities, such as a
scum trough, should be provided as
part of the chlorine contact chamber.
Scum should be removed from the plant
and not recycled through it.
1.10.2 - 1.10.8
140
-------
DEFICIENCY
1.10.9 Inadequate con-
sideration of possible
development of septic
conditions in channels
and splitter boxes.
1.10.10 Lack of flex-
ibility in disinfection
systems to permit pre-
chlorination for odor
control or return
sludge chlorination for
control of bulking.
CONSIDERATIONS
New and Existing POTW's
Refer to 1.2.17.
New POTW's
The chlorination system should be
designed to feed chlorine to both the
influent pumping and sludge areas.
Refer to 1.2.26 and 1.4.32.
Existing POTW's
Method; Provide valving and piping
to facilitate chlorine addition as
follows:
Prechlorination for odor control
1. Add to influent pump dis-
charge line.
2. Provide eductor or other in-
line mixing device. Typical
prechlorination dosages for
odor control range from 10
to 20 mg/L.
Control of bulking by return
sludge chlorination
(Chlorination is effective only
in controlling bulking caused by
filamentous growths.)
1. Add chlorine to discharge
line of return sludge pumps.
2. Provide eductor or other in-
line mixing device. Chlori-
nation of return sludge
should be based on the dry
1.10.9 - 1.10.10
141
-------
DEFICIENCY
1.10.11 Lack of venti-
lation promotes corro-
sion of electrical com-
ponents.
1.10.12 Inadequate
consideration of OSHA
safety requirements.
CONSIDERATIONS
sludge solids concentration.
A reasonable range is
between 0.2 and 1.0 percent
by weight.
Control of bulking by return
sludge chlorination has the
disadvantages of returning a
less viable and potentially
toxic sludge to biological
treatment systems and of
increased chlorine require-
ments. Careful considera-
tion must be given to the
advantages and disadvantages
before providing return
sludge chlorination.
Materials; Piping and valving to be
compatible with existing influent
piping and/or return sludge piping
and to be suitable for service with
chlorine.
New POTW's
Chlorination facilities should be
placed in separate, ventilated rooms
for safety reasons and to help pre-
vent chlorine gas from corroding
equipment and instrumentation.
Existing POTW's
Method; Refer to 1.2.28.
New POTW's
Chlorine leak detection equipment
should be available, and the chlori-
nator room should be ventilated at a
rate of one air change every three
minutes. Ventilation fans should be
located near the floor.
Existing POTW's
Method: Refer to 1.1.122.
1.10.10 - 1.10.12
142
-------
DEFICIENCY
CONSIDERATIONS
1.10.13 Inadequate
consideration of any
potential freezing
problems of plant com-
ponents.
New and Existing POTW's
Refer to 1.1.127.
Unit Operation/Component: 1.11 Lagoons
1.11.1 Inadequate
valving for maximum
flexibility and
proper maintenance.
New POTW's
Piping and valving should be pro-
vided between lagoons (or lagoon
sections) to allow isolation and
dewatering of individual units for
maintenance.
Existing POTW's
Method; Install piping and valving
so that each lagoon can be isolated
for maintenance and so that multiple
lagoons can be used in parallel or in
series.
Materials; Piping and valving to be
compatible with existing piping.
Sketch;
Isolate one lagoon
O
Influent
Lagoon
$c
Lagoon
O
JVJ k
1
c
* tTTIUGru
Parallel operation
O
Influent
Lagoon
-JX3-*
Lagoon
O
Effluent
1.10.13 - 1.11.1
143
-------
DEFICIENCY
CONSIDERATIONS
Series operation
1.11.2 Inadequate
process flexibility,
1.11.3 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks, etc.)
required for main-
tenance.
1
Influent
O
r 00-*-
k
C
Lagoon
X°
Lagoon
Effluent
New POTW's
Lagoon systems should be designed
such that the lagoons can be operated
in series or parallel. Refer to
1.11.1.
Existing POTW1s
Method: Provide piping and valving
per 1.11.1 so that the lagoons can be
operated in parallel during the
summer months and in series during
the winter months. This method of
operation conserves heat. The aera-
tors in both lagoons are operated un-
til ice formation forces the shut-
down of the aerator(s) in the second
lagoon. The second lagoon functions
as an anaerobic pond during the win-
ter months, but because the lagoon is
covered with ice, odor problems are
minimized. When the ice melts in
the spring, the lagoons can be oper-
ated in parallel. In addition, pro-
vide capability to recycle a portion
of the solids removed by settling.
New and Existing POTW's
Berms around and between lagoons
should be designed to allow vehicles
to travel along the top of the berm.
1.11.1 - 1.11.3
144
-------
DEFICIENCY
CONSIDERATIONS
1.11.4 Individual
flow measurement
not provided for each
piece of parallel
units.
1.11.5 Inadequate
consideration of
possible development
of septic conditions
in channels and
splitter boxes.
1.11.6 Inadequate
provisions for manual
valve operation during
emergency conditions.
1.11.7 Inadequate
consideration of OSHA
safety requirements.
New and Existing POTWs
Refer to 1.4.17.
New and Existing POTW's
Refer to 1.2.17.
New and Existing POTW's
Refer to 1.1.75.
New and Existing POTW's
Refer to 1.1.122.
Unit Operation/Component: 1.12 Land Application
1.12.1 Inadequate
valving for maximum
flexibility and proper
maintenance.
New POTW's
Refer to 1.1.9.
Method:
Existing POTW's
Provide valves and blind
flanges on each pipe run to facil-
itate cleaning, as shown in the
sketch below.
Materials: Valves and flanges to be
compatible with existing piping.
Sketch;
- Sprinkler or Spray Head
i
-oo«-
-oo«-
1.11.4 - 1.12.1
145
-------
DEFICIENCY
CONSIDERATIONS
1.12.2 Inadequate
process flexibility,
1.12.3 Insufficient
number and poor
placement of high-
pressure hose hy-
drants throughout
plant.
1.12.4 All valves
not operable from
floor level.
1.12.5 Inadequate
clearance around
equipment for main-
tenance functions.
1.12.6 Inadequate
provisions for
draining tanks and
sumps.
Cost; Under $50 for each flange,
under $100 for each valve. Cost
depends on pipe size and material.
New POTW's
Provide storage facilities or alter-
nate treatment approach for use dur-
ing inclement weather conditions
(i.e., rain, freezing temperatures).
Refer to 1.1.18.
Existing PQTW*s
Method; Provide piping and valving
per 1.12.1 to allow independent oper-
ation of each section of the applica-
tion system. Provide interim storage
facilities.
New and Existing POTW's
Provide yard hydrants around prelim-
inary treatment and any sludge
handling equipment.
New and Existing POTW's
Refer to 1.1.23.
New and Existing POTW's
Refer to 1.1.24.
New POTW's
Refer to 1.1.26.
Method:
Existing POTW's
Provide a frost-free valve
at the low point of each run of
distribution pipe.
1.12.1 - 1.12.6
146
-------
DEFICIENCY
CONSIDERATIONS
1.12.7 Inadequate
provisions for
sampling of in-
dividual processes,
1.12.8 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks, etc.)
required for mainte-
nance .
1.12.9 Individual
flow measurement
not provided for each
piece of parallel
units.
1.12.10 Inadequate
consideration of
possible development
of septic conditions
in channels and
splitter boxes.
1.12.11 Handling
facilities not pro-
vided for mechanical
components over 100
pounds.
Materials; Frost-free valves to be
of material compatible with existing
piping.
Cost; Under $150 for each line.
New POTWs
Provide capabilities to sample the
effluent from preliminary treatment
units. Refer to 1.1.27.
Existing POTW's
Method; Provide composite sampler or
other means of sampling effluent from
the leachate collection and treatment
system. Provide capabilities to sam-
ple the effluent from preliminary
treatment units. Refer to 1.1.27.
New and Existing POTW's
Refer to 1.1.28.
New and Existing POTW's
Refer to 1.1.45 and 1.3.14.
New and Existing POTW's
Refer to 1.2.17 and 1.3.15.
New and Existing POTW's
Refer to 1.1.121.
1.12.6 - 1.12.11
147
-------
DEFICIENCY
CONSIDERATIONS
1.12.12 Inadequate
consideration of OSHA
safety requirements.
1.12.13 Inadequate
consideration of
any potential
freezing problems
of plant components.
1.12.14 Inadequate
consideration of
local weather con-
ditions and their
impact on the
accessibility of
a plant site.
New and Existing POTW's
Refer to 1.1.122.
New POTW's
Refer to 1.1.127 and 1.12.2.
Method:
Existing POTW's
Provide cover material such
that distribution piping is buried a
minimum of 4 to 5 feet below ground.
Provide frost-free drain valves at
low point of each leg of the distri-
bution header. All exposed piping
and valves to be heat-traced (steam
or electric).
New POTW's
Rainfall and seasonal temperature
ranges must be considered when
selecting land application sites.
Optimum application techniques can
vary according to whether the site is
located in an arid or cold weather
area. Refer to 1.1.131.
Method:
Existing POTW's
Provide an all-weather
road
to the plant site, and add all-
weather roads within plant site as
required for equipment access. Refer
to 1.1.131.
Materials: Asphalt or gravel.
Cost; Gravel - $2 per sq ft
Asphalt - $4 per sq ft
1.12.12 - 1.12.14
148
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 1.13 Small Package Plants
1.13.1 Lack of
spare pumps.
1.13.2 Lack of
walkways around
tanks, limiting
operator access.
1.13.3 Tall, above-
ground tanks fre-
quently require
operator to climb
long stairways.
1.13.4 Inadequate
flexibility to by-
pass units.
New POTW's
Provide a spare pump(s) at every
pumping installation in the plant
or, as a minimum, spare pumps at
major pumping stations (i.e., in-
fluent, sludge recycle/waste, in-
termediate lift, utility water,
etc.) and portable pump hookups at
small pumping stations (i.e., chem-
ical feed, spray water, etc.).
Existing PQTW's
Method; Refer to 1.1.2.
New POTW's
Provide adequate walkways and/or
stairways to allow operator access
to valve handles, gates, instrumen-
tation, etc., and/or to equipment
and tank sidewalls for maintenance
and clean-up purposes.
Method:
Existing POTW's
Refer to 1.1.3.
New and Existing PQTW's
If space is available, size tanks
with adequate width and length to
minimize height requirements, and/or
construct deep tanks at least par-
tially in ground, or, as a minimum,
provide hoists at the top of stair-
ways to eliminate need for operator
to carry equipment up long stairways.
New POTW's
For preliminary treatment units
(grit chamber, bar screens, comminu-
tors, etc.), provide by-pass chan-
nels. For large multi-unit systems
(clarifiers, aeration tanks), tank
piping should include necessary
valves to allow the stoppage of flow
1.13.1 - 1.13.4
149
-------
DEFICIENCY
CONSIDERATIONS
1.13.5 Inadequate
consideration of
means to remove
equipment for repair
or replacement.
1.13.6 Inadequate
consideration of
scum removal from
plant.
1.13.7 Inadequate
valving for maximum
flexibility and
proper maintenance.
1.13.8 Inadequate
consideration of
consequences of
rupture disc or
shear pin failures.
to each tank. For pretreatment units
such as equalization, oil and grease
removal, odor control, etc., by-pass
piping should also be provided.
Method:
Existing POTW's
Refer to 1.1.7.
New and Existing POTW's
Provide doors large enough to permit
passage of any vehicles or tools re-
quired to remove pieces of equipment
from a building, and also large
enough to permit passage of the
equipment itself. Adequate passage-
ways in the building and around the
equipment should be provided to allow
easy access for both maintenance and
removal. A minimum working space of
four feet should be provided around
all equipment. Refer to 1.1.1 and
1.1.5.
New and Existing POTW's
Refer to 1.2.2, 1.3.1, 1.4.2, and
1.6.1.
New and Existing POTW|s
Piping should be designed with enough
valves, long radius elbows, tees,
crosses, and cleanouts to provide for
adequate maintenance and flexibility.
Sufficient valving should be provided
to allow by-passing pieces of equip-
ment for maintenance purposes.
New POTW's
When considering rupture discs for
piping systems (e.g., on discharge
side of a positive displacement
pump), specify disc to withstand
pressure below the maximum allow-
able pressure for the piping sys-
1.13.4 - 1.13.8
150
-------
DEFICIENCY
1.13.9 Inadequate
laboratory facilities
for process control.
1.13.10 Inadequate
stand-by equipment.
1.13.11 Inadequate
provisions for drain-
ing tanks and sumps.
CONSIDERATIONS
tern. In addition, pipe the blow-
off valve (i.e., rupture disc, spring
loaded type, etc.) to discharge to
a nearby sump so that, in the event
of a rupture disc failure, clean-up
of sludge or other material will be
minimized.
When specifying shear pins (e.g., for
clarifier or thickener mechanisms),
also provide a high-torque switch
wired to both alarm at a high torque
prior to shut-down and to shut down
the mechanism at a predetermined
torque that is less than the shear
pin failure torque.
Existing POTW's
Method; Refer to 1.1.10.
New and Existing POTW's
Provide laboratory facilities per EPA
publication Estimating Laboratory
Needs for Municipal Wastewater Treat-
ment Facilities (Publication No.
EPA-430/9-74-002). Refer to 1.15.6.
New POTW|s
Provide stand-by equipment per EPA
publication Design Criteria for Mech-
anical, Electric and Fluid System and
Component Reliability (Publication
No. EPA-430-99-74-001).
Method:
Existing POTW's
Refer to 1.1.16.
New and Existing POTW's
A plant drain system should be pro-
vided which is low enough to service
all tankage and buildings in the
plant. All tank and sump bottoms
and building floors should be sloped
to provide good drainage. Tanks
1.13.8 - 1.13.11
151
-------
DEFICIENCY
CONSIDERATIONS
1.13.12 Inadequate
provisions for
sampling of indi-
vidual processes.
1.13.13 Inadequate
consideration of
access requirements
for large equipment
(cranes, trucks, etc.)
required for mainte-
nance.
1.13.14 Inadequate
scum handling and
disposal system.
should be equipped with mud (drain)
valves and/or pump-out sumps. If
possible, tanks should be drained
to the plant drain system.
New and Existing POTW's
Sampling facilities should be pro-
vided throughout the POTW to allow
performance evaluations of individual
unit operations. Such facilities
would include sample taps at pump-
ing stations, sample ports in tanks,
stairways and ladders that allow
access to sampling sites, etc.
New and Existing POTW's
A crane, monorail or a support to
which a hoist can be attached should
be located above all major pieces of
equipment. The roof or floor above
the equipment should be designed for
the lifting load of the hoist.
Buildings that contain large pieces
of equipment (i.e., filter presses,
vacuum filters, pumps, etc.) should
have adequate'ceiling heights and
flobr loading capacities to allow en-
trance of equipment removal vehicles.
The access area around equipment
should be adequate for its removal.
Access roads and access areas should
be provided around all outdoor equip-
ment .
New and Existing POTW's
Scum removal facilities should be
provided on all tanks (i.e., clar-
ifiers, chlorine contact tanks, wet
wells, splitter boxes, etc.) that
provide quiescent conditions. A
positive scum removal system con-
sisting of sumps and pumps should be
provided to transfer the scum from
various collection points in the
plant to a central holding site.
1.13.11 - 1.13.14
152
-------
DEFICIENCY
CONSIDERATIONS
1.13.15 Foam
sprays not concen-
trated in basin
corners where foam
build-up occurs.
1.13.16 No provision
for water tap at
top of above-ground
package units.
1.13.17 Inadequate
consideration of
groundwater move-
ment into POTW
site through
sewer trenches.
1.13.18 Use of
single-speed pumps
where variable-
speed units are
required.
The collected scum should be hauled
to a final disposal site or be incin-
erated on-site along with plant
sludge, and not allowed to recir-
culate through the treatment system.
New and Existing POTW's
Spray heads should be spaced one foot
apart in basin corners to minimize
foam buildups. Foam sprays may also
be required in certain open channels,
such as aeration basin influent and/
or effluent channels.
New and Existing POTW's
Provide water tap (i.e., hose bib)
at top of unit, using plant effluent
as utility water source. If city
water is used, provide an air break
(or back-flow preventer).
New and Existing POTW's
Impermeable barriers (i.e., bentonite
clay or concrete) should be placed
across sewer trenches leading to a
POTW site. The barriers should ex-
tend between the trench walls and
from the bottom of the trench to
within one foot of the ground sur-
face.
New and Existing POTW's
Consider the use of variable-speed
(or two-speed) pumps at the following
locations:
Influent pumping station.
Recycle pumps.
Chemical feed pumps.
Feed pumps to sludge dewatering
systems.
1.13.14 - 1.13.18
153
-------
DEFICIENCY
CONSIDERATIONS
1.13.19 No provisions
made to allow periodic
cleaning of the in-
fluent wet well.
1.13.20 Use of city
water rather than
plant effluent for
use as POTW utility
water.
1.13.21 Inadequate
consideration of
possible develop-
ment of septic
conditions in
channels and splitter
boxes.
1.13.22 Change in
baseline conditions
at a POTW between
time of design and
construction.
1.13.23 Samplers
frequently clog.
New and Existing POTW's
Refer to 1.2.16.
New and Existing PQTW's
Plant effluent in lieu of city water
should be considered as a source of
utility water in order to reduce
annual operating costs. An effluent
sump, utility water pump, flow con-
trol valves, and piping would be re-
quired to supply clean-up water
throughout the plant. Refer to
1.1.44.
New and Existing POTW's
Refer to 1.2.17, 1.3.15, 1.4.18,
and 1.6.15.
New and Existing POTW's
Due to the extensive lag that gen-
erally occurs between the time a
plant is designed, the Federal con-
struction grants are received, and
the plant is actually constructed, it
is imperative that future waste loads
are considered. This includes pro-
jecting municipal and industrial
waste flows. It is emphasized that
over-estimating or under-estimating
future flows can cause serious oper-
ational problems. Refer to 1.1.13
and 1.1.47.
New and Existing POTW's
Specify that 3/4 inch or larger
sample lines be used with wa.stewater
samplers. In addition, clean-out
1.13.19 - 1.13.23
154
-------
DEFICIENCY
CONSIDERATIONS
1.13.24 Pumps are
located above the
normal water level,
making them diffi-
cult to prime.
1.13.25 Lack of
mud valves in tanks,
1.13.26 Lack of
water supply near
samplers.
1.13.27 Lack of
sumps in dry wells,
1.13.28 No mixing
provided in scum
tank to keep scum
mixed during pump-
ing.
1.13.29 No positive
method of removing
scum from center well
of clarifiers.
taps should be provided on sample
lines. For wastewaters with high
solids levels, automatic line flush-
ing systems (air or water) can be
used.
New and Existing POTW's
Whenever possible, lay out pumping
systems such that the pump suction
line is flooded. If this is not
feasible, specify self-priming pumps,
Air bleed-off valves should also be
provided at high points in the pump
piping system to allow removal of
airlocks and subsequent priming of
the pumps.
New and Existing POTW's
Provide mud valves or pump-out sumps
at low point in tank bottoms. Refer
to 1.1.26.
New and Existing POTW's
Provide a hose bib or yard hydrant
near samplers for clean-up purposes.
New POTW's
Provide pump-out sumps in all dry
wells to allow removal of rainwater,
clean-up water, etc.
Method:
Existing POTW's
Refer to 1.1.65.
New and Existing POTW's
Refer to 1.3.21.
New and Existing POTW's
Refer to 1.3.23.
1.13.23 - 1.13.29
155
-------
DEFICIENCY
CONSIDERATIONS
1.13.30 Lack of
tank dewatering
systems to permit
rapid servicing of
submerged equipment.
1.13.31 Lack of
flexibility in
disinfection systems
to permit prechlorina-
tion for odor control
or return sludge
chlorination for
control of bulking.
1.13.32 Lack of
a foam control
system.
New and Existing POTW's
Refer to 1.1.26.
1.13.33 Absence of
electrical outlets
on top of treatment
units.
1.13.34 Placement
of motor control
centers too close
to wash-down areas.
1.13.35 Inadequate
electrical capacity
to permit stand-by
pumps and blowers
to operate in parallel,
New and Existing POTW's
Refer to 1.2.26.
New and Existing POTW's
Foam control systems should be
provided for agitated tanks such
as aeration basins and aerobic
digesters. Foam control systems
could consist of spray-water or de-
foamer chemical feed systems.
New and Existing POTW's
Provide electrical outlets to serv-
ice each treatment area including
outlets on various pieces of equip-
ment such as clarifiers, aeration
basins, thickeners, etc.
New POTW's
Motor control centers (MCC) should
not be placed in rooms with equip-
ment that requires routine wash-
down. MCC's should generally be
located in separate rooms or build-
ings.
Method:
Existing POTW's
Refer to 1.1.91.
New and Existing POTW's
Electrical systems should be suf-
ficiently sized to allow the simul-
taneous use of designated operating
and stand-by equipment. This is par-
ticularly important for pumping and
aeration systems.
1.13.30 - 1.13.35
156
-------
DEFICIENCY
CONSIDERATIONS
1.13.36 High water
alarm systems not
provided.
1.13.37 Electrical
control panels lo-
cated below ground
and exposed to po-
tential flooding.
1.13.38 Lack of
auxiliary power.
1.13.39 Electrical
quick-disconnect
plugs not provided
with submerged pumps
to facilitate rapid
replacement.
1.13.40 Inadequate
plant lighting.
1.13.41 Stairways
without non-skid
surfaces.
New and Existing POTW's
Refer to 1.2.29.
New and Existing POTW's
All electrical control panels should
be located in areas protected from
flooding.
New and Existing POTW's
All POTW's should include emergency
power for major process equipment.
This can be accomplished by use of
diesel fuel, gasoline, natural gas
or digester gas powered generators;
or provide dual power feed lines to
the plant site. The stand-by power
could be automatically activated upon
a plant electric power failure.
New and Existing POTW's
Quick-disconnect electrical plugs
should be provided with submerged
equipment (pumps, samplers, etc.)
to allow rapid replacement with
stand-by units when maintenance is
required.
New and Existing POTW's
Provide sufficient lighting to ensure
safe operating conditions are
attained in all areas of the plant.
This is particularly important around
open tanks, aeration basins, below
grade tanks and sumps, stairways,
etc.
Design plant lighting system to
conform to "lighting and thermal
operation guidelines" published by
the Federal Energy Administration.
Refer to 1.1.88.
New POTW's
Specify non-skid surfaces for all
stairways.
1.13.36 - 1.13.41
157
-------
DEFICIENCY
CONSIDERATIONS
1.13.42 Inadequate
handrailing and kick
plates.
1.13.43 Inadequate
fencing around site.
1.13.44 Use of air
headers as guard
railing at small
package-plant type
POTWs.
1.13.45 Stairs
inclined at too
steep an angle.
1.13.46 Guard
railing not pro-
vided around ground-
level tanks.
1.13.47 Stairways
provided with only
one handrail.
Existing POTW's
Method: Refer to 1.1.100.
New POTW's
Provide handrailing and kick plates
on both sides of all stairways and
on all walkways around tanks and
equipment. Handrails and kick plates
should meet OSHA requirements.
Existing PQTW's
Method; Refer to 1.1.101.
New POTW's
Provide fencing (a minimum of 8 feet
high) around the entire site to make
it inaccessible to all unauthorized
personnel.
Existing PQTW's
Method: Refer to 1.1.102.
New POTW's
Air headers can become very hot
and should not be used as guard
railings. Refer to 1.1.101.
Existing POTW's
Method: Refer to 1.1.103.
New and Existing POTW's
Design stairways to meet OSHA re-
quirements; specify a maximum
incline of 30 degrees.
New and Existing POTW's
Guard railing or fencing should be
provided around all tanks that have
open tops at ground-level. Refer to
1.1.101.
New and Existing PQTW's
Refer to 1.1.101.
1.13.41 - 1.13.47
158
-------
DEFICIENCY
CONSIDERATIONS
1.13.48 Inadequate
consideration of noise
control.
1.13.49 Dangerous
chemicals not stored
in separate area.
1.13.50 Inadequate
security provisions.
1.13.51 Handling
facilities not pro-
vided for mechanical
components over 100
pounds.
1.13.52 Inadequate
consideration of
OSHA safety require-
ments.
New POTW's
Specifications for mechanical equip-
ment and their associated electric
motors should have a noise emission
criteria section. Work areas should
also be designed to meet OSHA noise
criteria. Noise absorbing and/or
containing enclosures should be
considered only when equipment cannot
be designed to meet the work place
noise criteria.
Method:
Existing POTW's
Refer to 1.1.110.
New and Existing POTW's
Provide separate, well-ventilated
areas for storage of hazardous
chemicals. Ensure adequate clean-
up facilities are also provided.
New and Existing POTW's
Provide plant lighting per 1.1.99
and fencing per 1.1.102.
New and Existing POTW's
Provide portable or fixed hoist
systems to move large pieces of
equipment. Refer to 1.1.1 and
1.1.28.
New POTW's
Refer to OSHA safety requirements
during design of POTW.
Existing POTW's
Method; Conduct OSHA survey of the
entire plant; make the required
changes where necessary.
1.13.48 - 1.13.52
159
-------
DEFICIENCY CONSIDERATIONS
1.13.53 Inadequate New and Existing POTW's
consideration of Specify in-ground tanks in cold
potential freezing climate areas. Specify splash guards
problems of plant around fixed aerators to decrease
components. freezing during winter months. Cover
tanks if required. Provide in-
sulation and/or heat tracing of
exposed pipes and valves. Refer
to 1.1.22 and 1.1.127.
1.13.54 Inadequate New PQTW's
consideration of In order to prevent spills of oil
spill prevention and/or hazardous materials from con-
plan, taminating surface or groundwaters,
the following measures should be
taken:
Provide dikes, berms, retain-
ing walls, etc., around above-
ground storage tanks with suf-
ficient capacity to retain the
entire contents of the largest
tank.
Removal of the contents of the
diked area must be by positive
means, such as a manually-oper-
ated valve or pump, after an
inspection of the material has
determined where it should be
directed.
Plant drainage systems from un-
diked areas should flow, if
possible, into ponds, lagoons,
or catchment basins if there is
a possibility that runoff could
come in contact with oil or
hazardous chemicals.
Existing PQTWs
Method: Refer to 1.1.132.
1.13.53 - 1.13.54
160
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 1.14 Energy Conservation
1.14.1 Use of a
room as a BOD
incubator is in-
convenient because
in-and-out traffic
makes it difficult
to maintain proper
temperature.
1.14.2 Use of fixed
louvers in buildings
that cannot be shut
during winter weather
conditions.
1.14.3 Use of single-
pane glass windows.
New POTW's
Large incubators should be used since
they are more energy efficient than a
room and would not be subject to the
access door being frequently opened.
Existing POTW's
Method; Provide a large incubator
since it is more efficient than a
room and would not be subject to the
access door being frequently opened.
Cost; Under $4,000; actual price
depends on size and controls.
New and Existing POTW's
Louvers should be specified as ad-
justable so that they can be closed
during cold weather.
New POTW's
Use double- or triple-paned glass
for windows.
1.14.4 Design does
not emphasize heating
conservation measures.
1.14.5 Motors over-
sized for future
growth which never
materializes, result-
ing in motors operating
at less efficiency with
lower power factors.
Method:
Existing POTW's
Add storm windows to all
windows, or replace single-pane
glass with thermal glass.
New and Existing POTW's
Refer to 1.1.74.
New and Existing POTW's
Refer to 1.1.96.
1.14.1 - 1.14.5
161
-------
DEFICIENCY
CONSIDERATIONS
1.14.6 Insufficient
use of high-efficiency
motors.
New and Existing POTW's
Refer to 1.1.97.
Unit Operation/Component: 1.15 Laboratory
1.15.1 Use of a room
as a BOD incubator is
inconvenient because
in-and-out traffic
makes it difficult
to maintain proper
temperature.
1.15.2 Lab building
air vents are located
too close to air con-
ditioning air intakes,
1.15.3 Use of fixed
louvers in buildings
that cannot be shut
during winter weather
conditions.
1.15.4 Lack of vents
in laboratory sink
drain lines.
New and Existing POTW's
Refer to 1.14.1.
New POTW's
To prevent vented laboratory fumes
re-entering the building, locate
air conditioning intakes on the
opposite side of the building from
any lab vents.
Method:
Existing POTW's
Relocate vents, or lengthen
and/or reposition vents so that lab
exhaust does not enter air intakes.
New and Existing POTW's
Refer to 1.1.6 and 1.14.2.
New POTW's
Provide vents at each lab sink to
prevent air locks and resultant
drain back-ups.
Existing POTW's
Method; Provide vent in each lab-
oratory sink drain line which vents
to atmosphere above roof. This is
required by most local plumbing
codes.
1.14.6 - 1.15.4
162
-------
DEFICIENCY
1.15.5 Hoods not
provided in labs.
1.15.6 Inadequate
laboratory facilities
for process control.
CONSIDERATIONS
Materials; PVC or any material com-
patible with existing piping.
New POTW's
Each lab should be provided with a
fume hood for refluxing apparatus.
Method:
Existing POTW's
Provide exhaust hood(s)
in labs wherever heating operations
are conducted and fumes are emitted
(i.e., over hot plates, ovens, re-
flux apparatus, etc.). Vent the
hoods to the outside.
Cost; Approximately $500 to $3,000,
depending on size and accessories.
New POTW's
Refer to 1.13.9.
Existing POTW's
Method; NPDES permit limitations are
generally based on BOD, pH, suspended
solids, and fecal coliform, as a min-
imum. The following equipment is re-
quired for each of the determinations
(refer to "Standard Methods" for ad-
ditional equipment requirements):
BOD; Incubator, BOD bottles,
D.O. meter, distilled water.
pH; pH meter with probe,
buffer solutions to stan-
dardize probe, wash bottle,
beaker.
Suspended solids; Glass fiber
filter discs, filter holder,
Gooch crucibles, suction flask,
vacuum pump, drying oven, des-
iccator, analytical balance.
1.15.4 - 1.15.6
163
-------
DEFICIENCY
CONSIDERATIONS
1.15.7 Laboratory
vacuum system has
insufficient capacity.
1.15.8 Use of
single-pane glass
windows.
Fecal coliform: Culture
medium, culture dishes, incu-
bator, vacuum filter, filter
holder, membranes, pipets.
If storage space is limited, add
shelves (open or in cabinets) above
and below the work bench to store
glassware and reagents. Most fre-
quently-used items should be easily
accessible and supplies which are
spare or used infrequently can be
stored further away. If counter
space is limited, perhaps storing
easily-moved equipment (such as mag-
netic stirrers, small hot plates,
etc.) can be stored under the
counter, providing more working
space. However, instruments such as
pH meters should be moved as little
as possible. Other steps, such as
placing the incubator in a room ad-
jacent to the lab, can give more
working space in the lab. If all
of the steps above do not provide
sufficient laboratory space, inves-
tigate enlarging the existing lab.
New POTW's
The vacuum system should be adequate-
ly sized to handle all laboratory
equipment plus an additional 20 per-
cent.
Method
Existing POTW's
Provide additional lab-
oratory vacuum pump(s).
Cost; $100 to 3,000, depending on
size and service requirements.
New and Existing PQTW's
Refer to 1.14.3.
1.15.6 - 1.15.8
164
-------
DEFICIENCY
CONSIDERATIONS
1.15.9 Design does
not emphasize heating
conservation measures.
1.15.10 Lab elec-
trical circuits on
same circuits as POTW
equipment, causing
interference with
lab instrumentation.
1.15.11 Lack of
both 110V and 220V
electrical service
to labs.
New and Existing PQTW's
Refer to 1.1.74.
New and Existing POTW's
The lab electrical system should be
on a separate circuit. Refer to
1.1.82.
New and Existing POTW's
Provide both 110V and 220V electrical
service to laboratories since some
equipment, such as muffle furnaces,
require 220V service.
Unit Operation/Component: 1.16 Chemical Handling
1.16.1 No provisions
for moving equipment
and supplies from one
building floor to
another.
1.16.2 Excessive
length of chemical
feed lines, par-
ticularly lime slurry
recirculation loops.
1.16.3 Inadequate
provisions for drain-
ing tanks and sumps.
1.16.4 Lack of floor
trenches around pumps
to carry water spills
to sumps.
1.16.5 Lack of
flow metering
device on chemical
feed lines.
New and Existing POTW's
Refer to 1.1.5.
New and Existing POTW's
Chemical feed facilities should be
located as close as possible to
points of application. Refer to
1.1.12.
New and Existing POTW's
Refer to 1.1.26.
New and Existing POTW's
Refer to 1.1.46.
New and Existing POTW's
Refer to 1.1.48.
1.15.9 - 1.16.5
165
-------
DEFICIENCY
CONSIDERATIONS
1.16.6 Chemical
feed line is
connected to more
than one basin at
different elevations,
causing line to drain
rapidly into lower
basin and requiring
time to fill header
before the higher
basin can be fed.
1.16.7 No con-
venient means
provided to feed
dry chemicals into
top-loading
feeders.
1.16.8 Lack of
drains on chemical
mix tanks.
1.16.9 Pressure
gauges not located
on inlet side of
back-pressure relief
valves, making it
difficult to check
and/or adjust the
valve.
1.16.10 Chemical
feed pumps are too
small to allow high
dosages of chemical
during emergencies.
New and Existing POTW's
When feeding a chemical to more than
one tank, use separate feed lines and
metering pumps. If feeding chemical
through a common header, specify that
discharge points in different tanks
be at the same elevation. If dis-
charge points must be at different
elevations, provide throttle valve at
lower basins, so that both (all)
basins are fed at same rate; also,
provide a check valve in the chemical
feed lines to prevent the back flow
of chemical from one tank to the
other.
New and Existing POTW's
Refer to 1.1.51.
New and Existing POTW's
Refer to 1.1.52.
New and Existing POTW's
Provide pressure gauges on upstream
and down stream side of back pressure
valves and on pressure side of relief
valves.
New POTW's
Chemical feed pumps should be sized
to feed both maximum and minimum
dosages. The use of metering pumps
with variable stroke adjustment
allows a broad pumping capacity
range. Multiple pumps should also
be specified; this would allow the
use of the spare pump during emer-
gency periods when high chemical
dosages are required.
1.16.6 - 1.16.10
166
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing POTW's
Refer to 1.1.58.
1.16.11 Improper
water pressure is
supplied to rota-
meters, causing
them to burst.
1.16.12 Lack of
wyes, tees, and
crosses to facil-
itate cleaning
chemical lines.
1.16.13 Placement
of motor control
centers too close
to wash-down areas.
1.16.14 Lack of
ventilation promotes
corrosion of elec-
trical components.
1.16.15 High water
alarm systems not pro-
vided.
1.16.16 Dangerous
chemicals not stored
in separate areas.
1.16.17 Inadequate
consideration of
spill prevention
plan.
New and Existing POTW's
Refer to 1.1.68.
New POTW's
All chemical lines, particularly lime
slurry, should be specified with wyes
and tees for cleaning. Flushing
water should be provided near the
cleanouts.
Existing POTW's
Method; Refer to 1.1.77.
New and Existing POTW's
Refer to 1.1.91.
New and Existing POTW's
Refer to 1.1.93.
New and Existing POTW's
Provide high water alarms in chemical
mix and day tanks.
New and Existing POTW's
Chemicals should be stored in sep-
arate rooms with adequate ventila-
tion and safety showers.
New and Existing POTW's
All chemical tanks should be provided
with a dike around the storage area.
Refer to 1.1.132.
1.16.10 - 1.16.17
167
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 1.17 Control Building
1.17.1 No provisions
for moving equipment
and supplies from one
building floor to
another.
1.17.2 Lab building
air vents are located
too close to air con-
ditioning air intakes.
1.17.3 Use of fixed
louvers in buildings
that cannot be shut
during winter weather
conditions.
1.17.4 Lack of
vents in laboratory
sink drain lines.
1.17.5 Hoods not
provided in labs.
1.17.6 Inadequate
communication capa-
bilities between
buildings and
process areas.
1.17.7 Inadequate
laboratory facilities
for process control.
1.17.8 Inadequate
view of unit processes
from control building.
1.17.9 Control
panels not easily
accessible (i.e.,
too high off ground
or placed in close
quarters).
New and Existing POTWs
Refer to 1.1.5.
New and Existing POTW's
Refer to 1.15.2.
New and Existing POTW's
Refer to 1.1.6.
New and Existing POTW's
Refer to 1.15.4.
New and'Existing POTW's
Refer to 1.15.5.
New and Existing POTW's
Refer to 1.1.14.
New and Existing POTW's
Refer to 1.15.6.
New and Existing PQTW's
Refer to 1.1.25.
New and Existing PQTW's
Refer to 1.1.31.
1.17.1 - 1.17.9
168
-------
DEFICIENCY
CONSIDERATIONS
1.17.10 Floor
drain piping system
undersized.
1.17.11 Drains
from buildings
discharge into basins
with normally (or
periodically) high-
water levels, causing
drains to back-up.
1.17.12 Use of
single-pane glass
windows.
1.17.13 Design
does not emphasize
heating conservation
measures.
1.17.14 Lab elec-
trical circuits on
same circuits as POTW
equipment, causing
interferences with
lab instrumentation.
1.17.15 Lack of both
110 v and 220 v elec-
trical service in labs.
1.17.16 Placement
of motor control
enters too close
to wash-down areas.
1.17.17 Lack of
ventilation pro-
motes corrosion of
electrical components.
1.17.18 Handling
facilities not
provided for mech-
anical components
over 100 pounds.
New and Existing POTW's
Refer to 1.1.34 and 1.5.13.
New and Existing POTW's
Refer to 1.1.35.
New and Existing POTW's
Refer to 1.14.3.
New and Existing POTW's
Refer to 1.1.74.
New and Existing POTW's
Refer to 1.1.82.
New and Existing POTW's
Refer to 1.15.11.
New and Existing POTW's
Refer to 1.1.91.
New and Existing POTW's
Refer to 1.1.93.
New and Existing POTW's
Refer to 1.1.121.
1.17.10 - 1.17.18
169
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 1.18 Site Selection
1.18.1 Lack of
all-weather roads
to pump stations.
1.18.2 Electrical
control panels
located below ground
where exposed to
flooding.
1.18.3 Plant located
in flood plain.
New and Existing POTW's
Refer to 1.1.19.
New and Existing POTW's
Refer to 1.1.94.
1.18.4 Inadequate
buffer zone to
alleviate problems
due to noise, odor,
aerosol, fog, etc.
1.18.5 Inadequate
consideration of any
potential freezing
problems of plant
components.
1.18.6 Inadequate
consideration of
odor development
and control.
1.18.7 Inadequate
consideration of
local weather con-
ditions and their
impact on the
accessibility of
a plant site.
New and Existing POTW's
Elevate plant site during con-
struction above the plain level
or build a dike around the plant
to protect it against flooding.
Refer to 1.1.125.
New and Existing POTW's
Refer to 1.1.126.
New and Existing POTW's
Refer to 1.1.127.
New and Existing POTW's
Plants should be isolated from high-
populated areas. Refer to 1.1.126
and 1.1.128.
New and Existing POTW's
Refer to 1.1.131.
1.18.1 - 1.18.7
170
-------
Design Considerations
Category:2.0 Preliminary
Treatment
-------
DEFICIENCY
CONSIDERATIONS
Existing POTW's
Method: Construct a scum pit and
install an adjustable overflow trough
or plate immediately upstream of bar
screen.
Materials; Concrete to form pit, and
plastic or metal overflow trough.
Sketch:
L-MVCiaiUI 1 1
Gate >J
^^
Flow *^*
r-t;
Overflow Y
Trough or /\
Plate / i--
»
i*L, .1
^x
^JU
\ ""
Scurr
^-Existing Bar .Screen
Sump
i Pit
2.1.3 Not locating
grit removal and/or
screening devices
ahead of influent
pumps to protect pumps
from clogging or
excessive abrasion.
New POTW's
Locate bar screens and grit removal
facilities upstream of influent
pumps.
2.1.4 Inadequate con-
sideration of proper
disposal of coarse
screenings and grit.
Method:
Existing POTW's
Construct bar screen with
by-pass and floating material removal
facilities upstream of influent
pumps.
Materials: Concrete to form chamber,
by-pass, and scum pit, and a metal
bar screen.
New POTW's
Provide proper facilities, such as a
covered dumpster, to store screenings
and subsequently dispose of the mate-
rial at regular intervals.
2.1.2 - 2.1.4
172
-------
DEFICIENCY
2.1.5 Improper spac-
ing of bars on bar
screens.
2.1.6 No provision
for bypassing flow
during maintenance.
Method:
CONSIDERATIONS
Existing POTW's
Provide a covered dumpster
or wheeled container to store screen-
ings and dispose of the collected
material at regular intervals (mini-
mum of once per day) along with plant
sludges.
Materials; A covered dumpster or
container.
New POTW's
Provide bar screens with the proper
bar spacing that matches bar screen
cleaning equipment and complies with
state design requirements.
Existing POTW's
Method: Remove existing screen and
replace with one that has bars spaced
1 and 2 inches apart.
Materials: New bar screen and appur-
tenances.
New POTW's
Provide a second bar screen or sec-
ondary flow channel around the bar
screen. Bar screens should be able
to be completely isolated by diver-
sion plates, valves, etc. to allow
complete dewatering of the bar screen
chamber.
Existing PQTW's
Method: Construct a screen by-pass.
Materials; Concrete to form by-pass
channel, and valves or diversion
plates to divert flow around the bar
screen.
2.1.4 - 2.1.6
173
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
Diversion
Gates
Flow
Diversion
Gates or
Valve;
Bar Screen
i
By-Pass Channel
2.1.7 Improper veloc-
ity in bar screen
chamber leading to
grit deposition.
New POTW's
Design bar screen chambers to pro-
vide an average cross-sectonal veloc-
ity between 2 and 5 feet per second.
Existing POTW's
Method: Decrease width of chamber
and provide new screen.
Materials; Concrete to fill in cham-
ber walls and new bar screen.
Sketch:
Chamber Wall
Concrete-RH
New Bar Screen
2.1.8 Inadequate con-
sideration of potential
freezing.
New POTW's
In climates where freezing is possi-
ble, provide a weather-proof, heated
enclosure around the bar screen.
2.1.6 - 2.1.8
174
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing POTW's
Construct heated enclosure
around bar screen chamber.
Materials; Wood, masonry, or metal
building materials and adequate
building heating equipment (such as
space heaters).
Unit Operation/Component: 2.2 Mechanical Bar Screens
2.2.1 Lack of addi-
tional coarse screen
for combined sewers.
2.2.2 Lack of pro-
vision to remove
floating material.
2.2.3 Not locating
grit removal and/or
screening devices
ahead of influent pumps
to protect pumps from
clogging or excessive
abrasion.
2.2.4 Inadequate con-
sideration of proper
disposal of coarse
screenings and grit.
2.2.5 Improper spacing
of bars on bar screens.
2.2.6 No provision
for by-passing flow
during maintenance.
New and Existing POTW's
Refer to 2.1.1.
New and Existing POTW's
Refer to 2.1.2.
New and Existing POTW's
Refer to 2.1.3.
New and Existing POTW's
Refer to 2.1.4.
New and Existing POTW's
Refer to 2.1.5.
New and Existing POTW's
Refer to 2.1.6.
2.1.8 - 2.2.6
175
-------
DEFICIENCY
CONSIDERATIONS
2.2.7 Improper veloc-
ity in bar screen
chamber leading to
grit deposition.
2.2.8 Inadequate con-
sideration of effect of
waste material on
mechanical reliability.
2.2.9 Inadequate con-
sideration of potential
freezing.
New and Existing POTW's
Refer to 2.1.7.
New POTW's
Provide mechanical scraper mechanism
which is proven to be reliable and
durable enough for the intended
application. Ensure the character-
istics of any industrial wastewaters
that will be present have been con-
sidered. Provide manually-cleaned
bar screen as a stand-by.
Existing POTW's
Method; Replace scraper unit with a
more durable and reliable unit, and
provide a stand-by manual bar screen.
Materials; Replacement scraper unit.
New and Existing PQTW's
Refer to 2.1.8.
Unit Operation/Component: 2.3 Comminutor
2.3.1 Not locating grit
removal and/or screening
devices ahead of influ-
ent pumps to protect
pumps from clogging or
excessive abrasion.
New POTW's
Provide comminutor upstream of influ-
ent pumps.
Method:
Existing POTW's
Install a comminutor
upstream of influent pumps.
Materials; Concrete to form the com-
minutor chamber and new comminutor.
2.2.7 - 2.3.1
176
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
By-Pass Channel
r ~ ~
A=s£l
RO /JQ
"* To Influent
/ / ' \ ' "'"(-'^
'Diversion / / \Comminutor
Gates or//
Valves '
2.3.2 Comrainutors not
located downstream of
grit removal equipment
resulting in excessive
wear.
2.3.3 No bar screen
provided for protec-
tion of mechanical
components.
New and Existing POTWs
Provide grit removal equipment
upstream of comminutor. Refer to
2.1.3.
New PQTW's
Provide bar screen upstream of com
minutor. Refer to 2.1.3.
Method:
Existing POTWs
Install bar screen upstream
of comminutor.
Materials; Concrete to form bar
screen chamber with by-pass and scum
pit, and bar screen and related
appurtenances for floating solids and
screenings removal.
2.3.2 - 2.3.3
177
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
_ By-Pass
r ~] ., Diversion
1-f 1e-*P Gate
Flow _».
i
lyLj _
:
/ O
\^ r^ ~ -«"
Sump
2.3.4 No provision
for by-passing flow
during maintenance.
New POTW's
Provide by-pass for comminutor.
Existing POTW's
Method; Construct by-pass for
diverting flow around comminutor.
Materials; Concrete to form by-pass
channel or chamber and metal diver-
sion gates or valves to divert flow
and to isolate comminutor.
Sketch:
By-Pass Channel
1
1
Flow _». / >*
»>
"T-
Q
n
i
4-
-
Diversion// Comminutor
Gates ^
2.3.5 No rock traps
provided.
New POTW's
Provide rock traps upstream of com-
minutor.
2.3.3 - 2.3.5
178
-------
DEFICIENCY
2.3.6 Inadequate
design of obstructions
downstream of control
section induces inac-
curacies in flow
measurement.
CONSIDERATIONS
Existing POTW's
Method; Construct rock traps
upstream of comminutor.
Materials; Concrete to form trap.
Sketch: Xomminutor
\-X~ J
* Rock Trap
New POTW's
Provide comminutor which does not
affect flow characteristics at flow
measurement device or provide ade-
quate distance between comminutor and
flow measurement device to prevent
influence of backwater effects.
Existing POTW's
Method: Replace comminutor with
larger model.
Materials; Concrete to form larger
chamber and new comminutor.
Sketch:
,; New Chamber
Wall
, Existing Chamber
Wall
Flow
New Comminutor
'Comminutor
2.3.5 - 2.3.6
179
-------
DEFICIENCY CONSIDERATIONS
2.3.7 Inadequate New POTW's
design permits grit Provide larger capacity comminutor
deposits in control capable of passing grit.
section of flow meas-
urement device.
Existing POTW's
Method; Install larger capacity com-
minutor.
Materials; Concrete to form new
chamber for comminutor and new com-
minutor .
Sketch:
Chamber
yiNew onan
_/_ Wall^
Existing Chamber
/ Wall
Nv
sv
Flow
/
' * 1
\
\ V
;Q -
^s ,' ^Existing
, ' Comminutor
New Comminutor/
2.3.8 Inadequate con- New and Existing POTW's
sideration of effect of Provide a comminutor which is ade-
waste material on quately sized and which is designed
mechanical reliability. to handle wastes of the character
anticipated. Particular attention
should be given to industrial waste-
water discharges.
Unit Operation/Component: 2.4 Barminutor
2.4.1 Not locating New POTW's
grit removal and/or Provide barminutor upstream of influ-
screening devices ent pumps. Refer to 2.1.3.
ahead of influent pumps
to protect pumps from
clogging or excessive
abrasion.
2.3.7 - 2.4.1
180
-------
DEFICIENCY
CONSIDERATIONS
Existing POTW's
Method; Install barminutor upstream
of influent pumps.
Materials: Concrete to form bar-
minutor chamber and new barminutor.
Sketch:
By-Pass Channel
* ..Diversion
| ' ' " 1 M y Gale
low *
HHHIH
^HMH
o
/
\
Barminutor
2.4.2 No bar screens
provided for protec-
tion of mechanical
components.
New POTW's
Provide bar screen upstream of bar-
minutor .
Existing POTW's
Method: Install bar rack upstream of
barminutor.
Materials; Concrete to form bar rack
chamber and by-pass, and bar rack.
Sketch:
By-Pass Channel
Flow
Diversion
Gate
New
Bar Rack
o _»
^Existing
Barminutor
2.4.1 - 2.4.2
181
-------
DEFICIENCY
2.4.3 No provision
for by-passing flow
during maintenance.
CONSIDERATIONS
New POTW's
Provide by-pass for barminutor.
Existing POTWs
Method; Construct by-pass for
diverting flow around barminutor.
Materials; Concrete to form by-pass
channel, and metal diversion gates or
valves to divert flow and isolate
barminutor.
Sketch:
By-Pass Channel
1 » 1
1 1
ry 1 > i
Flow * / ,
^^H
^
0
Diversion// N Barminutor
Gate ^
2.4.4 No rock traps
provided.
New POTW's
Provide rock traps upstream of bar-
minutor.
Existing POTW's
Method: Construct rock trap upstream
of barminutor.
Materials; Concrete to form trap.
Sketch:
Barminutor
V
Rock Trap
2.4.3 - 2.4.4
182
-------
DEFICIENCY
2.4.5 Inadequate
design of obstructions
downstream of control
section induces inac-
curacies in flow
measurement.
CONSIDERATIONS
New POTW's
Provide barminutor which does not
affect flow characteristics at flow
measurement device or provide ade-
quate distance between barminutor and
flow measurement device to prevent
influence of backwater effects.
Existing POTW's
Method: Replace barminutor with
larger model.
Materials; Concrete to form larger
chamber and new barminutor.
Sketch:
>
X
X
Flow -*
.,New Channel
>f Wall
-- VTI ~^
j s
1 ^v x
U(
/
Existing Channel
Wall
X ~*
New Barminutor
2.4.6 Inadequate
design permits grit
deposits in control
section of flow
measurement device.
New POTW's
Provide larger capacity barminutor
capable of passing grit.
Method:
minutor.
Existing POTW's
Install larger capacity bar-
Materials; Concrete to form new
chamber for barminutor and new bar-
minutor .
2.4.5 - 2.4.6
183
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
New Channel
Wall
x Existing Channel
S Wall
>' ' V
>w * \ i (
v i ;v
\
j "^
-v
New Barminutor
^Existing Barminutor
2.4.7 Improper bar
spacing.
2.4.8 Inadequate
consideration of effect
of waste material on
mechanical reliability.
New POTW's
Refer to 2.1.5.
Existing POTW's
Method; Replace bars with 1 to 2
inch bar spacing.
Materials; New bar screen.
New and Existing POTW's
Refer to 2.3.8.
Unit Operation/Component: 2.5 Macerator
2.5.1 Not locating
grit removal and/or
screening devices ahead
of influent pumps to
protect pumps from
clogging or excessive
abrasion.
2.5.2 No bar screen
provided for protec-
tion of mechanical
components.
New and Existing POTW's
Provide macerators upstream of pump-
ing stations.
New POTW's
Provide bar screen upstream of
macerator.
2.4.6 - 2.5.2
184
-------
DEFICIENCY
CONSIDERATIONS
2.5.3 No provision
for by-passing flow
during maintenance.
Existing POTWs
Method; Install bar screen upstream
of macerator. Refer to 2.4.2.
Materials: Concrete to form bar
screen chamber with by-pass and scum
pit, and bar screen and related
appurtenances for floating solids and
screenings removal.
New POTW's
Provide by-pass for macerator
upstream of macerator.
Existing POTW's
Method: Construct by-pass for
diverting flow around macerator.
Materials; Piping and valves to con-
struct by-pass and to isolate
macerator.
Sketch:
. By-Pass Line
-txi-
Macerator
Flow
2.5.4 No rock traps
provided.
New POTW's
Provide rock traps.
2.5.5 Inadequate
design of obstructions
downstream of control
section induces inac-
curacies in flow meas-
urement.
Existing POTW's
Method; Construct rock trap upstream
of macerator. Refer to 2.3.5.
New POTW's
Provide macerator which does not
affect flow characteristics at flow
measurement device or provide ade-
quate distance between macerator and
flow measurement device to prevent
influence of backwater effects.
2.5.2 - 2.5.5
185
-------
DEFICIENCY
CONSIDERATIONS
2.5.6 Inadequate
design permits grit
deposits in control
section of flow meas-
urement device.
2.5.7 Inadequate con-
sideration of effect of
waste material on
mechanical reliability.
Existing POTW's
Method: Replace macerator with larg-
er model or move flow meter upstream.
Materials; Piping and electrical to
relocate meter.
New POTW's
Provide larger capacity macerator
capable of passing grit.
Existing POTW's
Method: Install larger capacity
macerator capable of passing grit or
move macerator further upstream of
flow meter.
Materials: New macerator and/or
piping.
New and Existing POTW's
Provide macerator which is adequately
sized and which is designed to handle
wastes of the character anticipated.
Particular attention should be given
to the potential effects of industri-
al wastes that will be present in the
wastewater. Refer to 2.3.8.
Unit
Operation/Component :
2.
6
Manually
Chambers
Cleaned
Gr
it
2.6.1 Not locating
grit removal and/or
screening devices ahead
of influent pumps to
protect pumps from
clogging or excessive
abrasion.
New POTW's
Provide grit chamber upstream of
influent pumps.
Existing POTW's
Method; Construct grit chamber
upstream of influent pumps.
2.5.5 - 2.6.1
186
-------
DEFICIENCY
CONSIDERATIONS
Materials; Concrete to form chamber
and necessary appurtenances.
Sketch:
Flow
Diversion
Gate
i A
i 1
Grit Char ,ber
By-Pass Channel
2.6.2 Comminutors not
located downstream of
grit removal equipment
resulting in excessive
wear.
New PQTW's
Provide grit chamber upstream of com-
minutor. Refer to 2.1.3 and 2.3.2.
Method:
Existing POTW's
Reinstall comminutor down-
stream of grit chamber.
Materials; Concrete to form com-
minutor chamber.
Sketch:
Flow
-o
Existing
Comminutor
Location
Grit
Removal
System
u -
Relocated
Comminutor
2.6.1 - 2.6.2
187
-------
DEFICIENCY
CONSIDERATIONS
2.6.3 Inadequate con-
sideration of proper
disposal of coarse
screenings and grit.
2.6.4 No provision
for by-passing flow
during maintenance.
New and Existing POTWs
Provide a covered dumpster to tempo-
rarily store collected grit and peri-
odically haul the grit to an approved
landfill.
New PQTW's
Provide a by-pass around the grit
chamber.
Existing POTW's
Method; Construct by-pass.
Materials: Concrete to form channel
and diversion gates or valves to
divert flow and isolate chamber.
Sketch:
*
I I
I l
1 l
I L_
I
1
Grit
Chamber
»
1^
1 1
1 1
J 1
1
1
*
^Diversion
Gate
By-Pass Channel
2.6.5 Inadequate con-
sideration of increased
O&M and energy costs
resulting from elimina-
tion of grit removal
process.
New POTW's
Lack of grit removal at the head end
of the POTW would result in increased
wear on pumps, accumulation of grit
deposits in tanks, wear and extra
loads on clarifications mechanisms,
etc. The obvious result would be
increased O&M costs.
Existing POTW's
Method; Construct grit chamber or
degritter.
Materials; Concrete to form chamber
or channel, and related equipment.
2.6.3 - 2.6.5
188
-------
DEFICIENCY
2.6.6 Inadequate veloc-
ity through process due
to poor flow control.
2.6.7 Improper flow-
through velocity in
grit chamber.
2.6.8 Short-circuiting
in grit chamber.
CONSIDERATIONS
New and Existing POTW's
Utilize a twin-compartment grit cham-
ber with weir control, a proportional
weir, or a vertical throat to
maintain a constant flow velocity
through the grit chamber with chang-
ing influent flow rate.
New POTW s
Design cross-sectional area of cham-
ber to provide velocity of 1.0 foot/
second at design flow.
Method:
Existing POTW's
Reduce width of chamber if
velocity is low; increase width of
chamber if velocity is high.
Materials; Concrete to form new
walls.
New POTW's
Provide baffles in the grit chamber.
2.6.9 Inadequate con-
sideration of potential
freezing.
Method:
Existing POTW's
Construct baffles to
increase distance of flow-through
chamber.
Materials; Metal or plastic baffles.
New and Existing POTW's
Provide heated enclosure around grit
removal and storage area. Design
chamber sides and inlet/outlet appur-
tenances to withstand ice build-up
and/or to allow ice removal.
2.6.6 - 2.6.9
189
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 2.7 Mechanically Cleaned Grit
Chambers
2.7.1 Not locating
grit removal and/or
screening devices ahead
of influent pumps to
protect pumps from
clogging or excessive
abrasion.
2.7.2 Comminutor not
located downstream of
grit removal equipment
resulting in excessive
wear.
2.7.3 Inadequate con-
sideration of proper
disposal of coarse
screenings and grit.
2.7.4 No provision for
by-passing flow during
maintenance.
2.7.5 Inadequate con-
sideration of increased
O&M and energy costs
resulting from elimina-
tion of grit removal
process.
2.7.6 Inadequate veloc-
ity through process due
to poor flow control.
2.7.7 Improper flow-
through velocity in
grit chamber.
2.7.8 Short-circuiting
in grit chamber.
New and Existing POTWs
Provide grit chamber upstream of
influent pumps. Refer to 2.6.1.
New and Existing POTW's
Provide grit chamber upstream of
comminutor. Refer to 2.6.2.
New and Existing POTW's
Refer to 2.6.3.
New and Existing POTW's
Provide a by-pass around the grit
chamber. Refer to 2.6.4.
New and Existing POTW's
Refer to 2.6.5.
New and Existing POTW's
Refer to 2.6.6.
New and Existing POTW's
Design cross-sectional area of cham-
ber to provide velocity of 1.0 foot/
second at design flow. Refer to
2.6.7.
New and Existing POTW's
Provide baffles in chamber. Refer to
2.6.8.
2.7.1 - 2.7.8
190
-------
DEFICIENCY
CONSIDERATIONS
2.7.9 Inadequate con-
sideration of effect of
waste material on
mechanical reliability.
New POTW s
Provide grit collector which is
designed for the waste material to be
handled. Particular attention should
be given to the characteristics of
any industrial wastes present in the
wastewater.
Existing POTW's
Method
Replace mechanical grit col-
lector with more-reliable unit.
Materials;
lector and
New mechanical
appurtenances.
grit col-
Unit
Operation/Component :
20
. o
Aerated
Grit
Chambers
2.8.1 Not locating grit
removal and/or screening
devices ahead of influ-
ent pumps to protect
pumps from clogging or
excessive abrasion.
2.8.2 Comminutors not
located downstream of
grit removal equipment
resulting in excessive
wear.
2.8.3 Inadequate con-
sideration of proper
disposal of coarse
screenings and grit.
2.8.4 No provision for
by-passing flow during
maintenance.
2.8.5 Inadequate con-
sideration of increased
O&M and energy costs
resulting from elimina-
tion of grit removal
process.
New and Existing POTW's
Provide grit chamber upstream of
influent pumps. Refer to 2.6.1.
New and Existing POTW's
Provide grit chamber upstream of com-
minutor. Refer to 2.6.2.
New and Existing POTW's
Refer to 2.6.3.
New and Existing POTW's
Provide a by-pass around the grit
chamber. Refer to 2.6.4.
New and Existing POTW's
Refer to 2.6.5.
2.7.9 - 2.8.5
191
-------
DEFICIENCY
CONSIDERATIONS
2.8.6 Improper flow-
through velocity in
grit chamber.
2.8.7 Short-circuiting
in grit chamber.
New and Existing POTWs
Design cross-sectional area of cham-
ber to provide velocity of 1.0 foot/
second at design flow. Refer to
2.6.7.
New and Existing POTW's
Provide baffles in chamber. Refer
2.6.8.
to
Unit Operation/Component: 2.9 Degritter
2.9.1 Not locating grit
removal and/or screening
devices ahead of influ-
ent pumps to protect
pumps from clogging or
excessive abrasion.
2.9.2 Comminutors not
located downstream of
grit removal equipment
resulting in excessive
wear.
2.9.3 Inadequate con-
sideration of proper
disposal of coarse
screenings and grit.
2.9.4 No provision for
by-passing flow during
maintenance.
2.9.5 Inadequate con-
sideration of increased
O&M and energy costs
resulting from elimina-
tion of grit removal
process.
New and Existing PQTWs
Provide grit chamber upstream of
influent pumps. Refer to 2.6.1.
New and Existing POTW's
Provide grit chamber upstream of com-
minutor. Refer to 2.6.2.
New and Existing PQTW's
Refer to 2.6.3.
New and Existing POTW's
Provide a by-pass around the degrit-
ter. Refer to 2.6.4.
New and Existing PQTW's
Refer to 2.6.5.
2.8.6 - 2.9.5
192
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 2.10 Grit Pumps
2.10.1 Not locating
grit removal and/or
screening devices ahead
of influent pumps to
protect pumps from
clogging or excessive
abrasion.
2.10.2 Inadequate con-
sideration of increased
O&M and energy costs
resulting from elimina-
tion of grit removal
process.
2.10.3 Inadequate con-
sideration of effect of
waste material on
mechanical reliability.
New and Existing POTW's
Provide grit chamber upstream of
influent pumps. Refer to 2.6.1.
New and Existing POTW's
Refer to 2.6.5.
New POTW's
Provide pumps which are adequately
sized, and which are specifically
designed to handle abrasive material.
Existing POTW's
Method; Replace grit pumps with new
units designed for the waste materi-
al. Refer to 2.7.9.
Materials; New grit pump and related
appurtenances.
Unit Operation/Component: 2.11 Influent Flow Measurement
2.11.1 Measurement
control section not
compatible with flow
measurement device.
2.11.2 Inadequate
design of downstream
channel slope and
geometry causes back-
up in control section,
New and Existing POTW's
Check with manufacturers of the type
of flow measurement device desired to
determine the proper control section
required.
New POTW's
Provide adequate slope and geometry
(i.e., no quick change in channel
direction) in the downstream channel
to prevent back-up.
2.10.1 - 2.11.2
193
-------
DEFICIENCY
2.11.3 Inadequate
design of obstructions
downstream of control
section induces inac-
curacies in flow meas-
urement.
CONSIDERATIONS
Existing PQTW's
Method: Reinstall flow measurement
device further upstream or provide a
new type measurement device which is
not affected by back-up.
Materials; Hardware or appurtenances
for reinstallation of new measurement
device.
New POTW's
Consider effect of obstructions
located downstream on flow conditions
at flow measurement device.
2.11.4 Inadequate con-
sideration of debris in
wastewater in selection
of float for flow meas-
urement.
Method:
Existing POTW's
Reinstall flow measurement
device further upstream or provide a
new type measurement device which is
not affected by back-up.
Materials; Hardware or appurtenances
for reinstallation of new measurement
device.
New POTW s
Provide type of float which is self-
cleaning or which inhibits debris
build-up. Consider using a stilling
well.
Method:
Existing POTW's
Install a self-cleaning
float and a stilling well, or, if
necessary, replace existing level
measurement with a sonic unit.
Materials: New float or new level
measurement device.
2.11.2 - 2.11.4
194
-------
DEFICIENCY
CONSIDERATIONS
2.11.5 Flow meters
located such that
backwater elevation
changes, due to clog-
ging of bar screen,
affect accuracy of
meter.
New POTW's
Provide bar screen upstream of flow
meter.
Method:
Existing POTW's
Reinstall flow meters down-
2.11.6 Inadequate con-
sideration of diurnal
flow patterns in sizing
of flow measurement
equipment results in
measurement equipment
being inaccurate at the
high and/or low flow
ranges.
2.11.7 Inadequate
approach channel length
results in flow meas-
urement inaccuracies.
stream of bar screen.
Materials; Concrete to form meter
chamber and necessary appurtenances.
New and Existing POTW's
Equipment specifications should
include expected maximum and minimum
flows to ensure the selected manu-
facturer will provide equipment which
will accurately measure flows over
the entire flow range anticipated.
New POTW's
Determine from equipment manufactur-
ers the length of approach channel
required to allow flow measurement
equipment to operate accurately.
Method:
Existing POTW's
Reinstall flow meter down-
stream where approach channel length
is sufficient to provide laminar
flow; a rule-of-thumb is that the
approach channel length should be 10
times the channel diameter.
Materials; Concrete to form new
meter chamber and necessary appur-
tenances.
2.11.5 - 2.11.7
195
-------
DEFICIENCY
CONSIDERATIONS
2.11.8 Inadequate con-
sideration of humidity
in influent structure
results in inaccuracies
to flow sensor.
2.11.9 Inadequate con-
sideration of potential
freezing.
New POTW's
Provide flow sensors and associated
metering equipment which are suitable
for continuous use in humid condi-
tions.
Existing POTWs
Method: Install dehumidifier or
replace sensor with one which is
affected by humidity.
not
Materials: New sensor or dehumidi-
f ier.
New and Existing POTWs
Provide flow measurement equipment
which is designed for operation in
cold weather conditions. Also con-
sider covering the flow measurement
station to prevent freezing problems
Unit Operation/Component: 2.12 Raw Waste Pumping
2.12.1 Inadequate
selection of the num-
ber, size, and type
of pumps.
New POTWs
Select proper number, size, and type
of pumps for the peak flow rate,
wastewater characteristics, and dis-
charge conditions anticipated. Spare
pumps should be provided and pump
vendor manuals utilized in selecting
the type of pump required.
Existing POTWs
Method; Install additional pumping
capacity needed to handle low and/or
peak flows; provide a spare unit.
Materials; New pumps and necessary
appurtenances.
2.11.8 - 2.12.1
196
-------
DEFICIENCY
CONSIDERATIONS
2.12.2 Inadequate pro-
visions for removing
scum from wet well.
2.12.3 No provisions
for odor control in
wet well.
2.12.4 Not locating
grit removal and/or
screening devices ahead
of influent pumps to
protect pumps from
clogging or excessive
abrasion.
2.12.5 No provisions
to periodically clean
the wet well.
2.12.6 No bar screens
provided for protection
of mechanical compo-
nents.
2.12.7 Inadequate
design of pumping sta-
tion results in fre-
quent cycling of units
causing flow surges in
downstream processes.
New POTW's
Provide scum removal facilities (such
as a swing pipe or telescopic valve)
in wet well.
Existing POTW's
Method; Construct scum pit or access
for scum pump suction.
Materials; Concrete for scum pit and
metal for overflow control, or addi-
tional manhole for suction hose.
New and Existing POTW's
Provide adequate ventilation and, if
necessary, aeration, chlorination, or
hydrogen peroxide dosing facilities.
New and Existing POTW's
Provide grit removal and/or screening
device upstream of influent pumps.
Refer to 2.1.13, 2.3.1, and 2.6.1.
New and Existing POTW's
Provide facilities to either tempo-
rarily stop influent to the wet well,
divert flow to an alternate wet well
or other storage facility, or provide
a compartmentalized wet well that
allows partial dewatering of the
well.
New and Existing POTW's
Provide bar screen upstream of influ-
ent pumps. Refer to 2.1.3.
New POTW's
Provide an adequately sized wet well
and lift pumps to prevent a rapid
drop in the water depth in the wet
well and a resultant on-off cycling
of the pumps.
2.12.2 - 2.12.7
197
-------
DEFICIENCY
CONSIDERATIONS
2.12.8 Lack of emer-
gency overflow.
Method:
Existing PQTWs
Increase wet well storage
volume by changing level controls and
throttle pumps with valves, or
install variable-speed pumps.
Materials ; Variable-speed pumps and
necessary controls.
New POTW's
Provide emergency overflow from wet
well.
Method:
Existing POTW's
Construct overflow.
Materials; Pipe and flap valve.
Sketch:
Flap Valve
Pipe
^Stream
Wet
Well
2.12.9 Improperly
sized wet wells result-
ing in long detention
times and odor prob-
lems, or too short
detention time and
cycling of pumps.
New POTW's
Provide wet well with an average
detention time of 10 minutes during
average flow conditions.
Existing POTW's
Method; Adjust wet well level con-
trols to decrease or increase storage
volume or construct additional wet
wells.
2.12.7 - 2.12.9
198
-------
DEFICIENCY
CONSIDERATIONS
2.12.10 Lack of spare
air compressor for
bubbler system.
2.12.11 Inability to
back-flush influent
pumps for cleaning pur-
poses.
Materials; Concrete to form new wet
wells, and piping and valves for
interconnection.
New POTW's
Provide spare-air compressor.
Existing POTW's
Method; Install stand-by air com-
pressor or large in-storage tank.
Materials; New air compressor or air
storage tank.
New POTW's
Provide back-flush facilities.
Method:
Existing POTW's
Install tee and valves in
pump discharge piping.
Materials; Tee and valves.
Sketch:
Wot
Well
V
Dry
WA!|-
j
JXH
bd-0
\?*f \^/
1
Pipe
Valves and Tee
For Back-Flushing
2.12.12 Corrosive and/
or explosive gases
close to electrical
motors and equipment.
New and Existing POTW's
Provide adequate ventilation and
specify explosion-proof motors and
equipment.
2.12.9 - 2.12.12
199
-------
DEFICIENCY
CONSIDERATIONS
2.12.13 Wet well level
float controls may
become greasy.
2.12.14 Lack of prop-
er ventilation at lift
station.
New PQTW's
Provide a stilling well or a sheath
around floats and facilities for
periodically cleaning float controls.
Existing PQTW's
Method; Clean floats periodically
with detergent, or replace floats
with bubbler system.
Materials; Bubbler system.
New and Existing POTW's
Provide continuous or intermittent
ventilation of both wet and dry
wells. Refer to the applicable state
guidelines for ventilation require-
ments.
Unit Operation/Component: 2.13 In-Line Flow Equalization
2.13.1 Surface float-
ing aerators do not
allow basin to be
dewatered.
2.13.2 Inadequate or
lack of facilities to
flush solids and grease
accumulations from the
basin walls.
2.13.3 Lack of facil-
ities for withdrawing
floating material and
foam.
New POTW's
Provide access for removal of aera-
tors before dewatering, or consider
use of fixed turbine aerators, a
diffused aeration system, or static
mixers/aerators.
Existing POTW's
Method; Install pulleys at the aera-
tor cable support posts that allow
the cable to be released and the
floating aerator lowered as the basin
liquid level drops.
New and Existing POTW's
Provide high pressure water at basin
for connection of hoses for cleaning.
Also ensure safe access is provided
around the basin. Refer to 1.1.20.
New and Existing POTW's
Provide a scum collection device such
as a swing pipe, a scum pit, and
pump.
2.12.13 - 2.13.3
200
-------
DEFICIENCY
CONSIDERATIONS
2.13.4 Lack of emer-
gency overflow.
2.13.5 Lack of depth
gauges provided on
basins that operate at
varying levels.
New POTW's
Provide emergency overflow back to
head end of the plant.
Method;
channel.
Existing POTW's
Install overflow pipe or
Materials: Pipe and valves, concrete
to form channel, and metal diversion
gates.
New POTW's
Provide depth gauges which are capa-
ble of indicating all depths antici-
pated.
Method:
Existing POTW's
Install float or capacitance
probe gauges which indicate basin
depth.
Materials; New gauges.
Unit Operation/Component: 2.14 Side-Line Flow Equalization
2.14.1 Surface float-
ing aerators do not
allow basin to be
dewatered.
New and Existing POTW's
Refer to 2.13.1.
2.14.2 Inadequate or
lack of facilities to
flush solids and grease
accumulations from the
basin walls.
2.14.3 Lack of facil-
ities for withdrawing
floating material and
foam.
2.14.4 Lack of emer-
gency overflow.
New and Existing POTW's
Refer to 2.13.2.
New and Existing POTW's
Refer to 2.13.3.
New and Existing POTW's
Refer to 2.13.4.
2.13.4 - 2.14.4
201
-------
DEFICIENCY
CONSIDERATIONS
2.14.5 Lack of depth
gauges provided on
basins that operate
at varying levels.
New and Existing POTW's
Refer to 2.13.5.
Unit Operation/Component: 2.15 General
2.15.1 No access to
raw wastewater flow for
sampling before side-
stream addition occurs.
New POTW's
Provide access for sampling before
sidestream addition.
Existing POTW's
Method: Construct new manhole or
access chamber upstream of where
sidestream enters.
2.15.2 Inadequate con-
sideration of needs for
odor control.
2.15.3 Difficulty in
handling high peak
flows.
Materials; Concrete to form manhole
or chamber and manhole frame and
cover or access hatch.
New POTW's
Provide covered dumpsters for storing
screenings and grit, and, if neces-
sary, a deodorant distribution system
around the site.
Existing POTW's
Method; Install covers over screen-
ings, scum and grit storage facili-
ties, and/or construct deodorant sys-
tem around site.
Materials; Covers and necessary ven-
tilation equipment and/or piping,
valves, etc. for deodorant system.
New POTW's
Design facilities for peak flows and/
or provide for emergency storage of
wastewater.
Existing POTW's
Method; Construct flow equalization
or storage facilities.
2.14.5 - 2.15.3
202
-------
DEFICIENCY CONSIDERATIONS
Materials; Concrete or earth embank-
ments and impermeable liner to form
basin, and necessary pumps, piping,
valves, etc.
2.15.4 Weirs and gates New POTW's
are not watertight. Specify watertight weirs and gates
wh*ar*a nAr-p«?c;a ru _
where necessary.
Existing POTW's
Method; Clean scaling surface and
install flexible gasket material to
allow better sealing.
Materials; Flexible gasket material,
2.15.3 - 2.15.4
203
-------
Design Considerations
Category:3.0 Primary
Treatment
Unit Operation/Component:.
3.1 General
DEFICIENCY
CONSIDERATIONS
3.1.1 Inadequate
odor control where
excess waste
activated sludge
is received at
primary clarifier.
New POTW's
Provide for complete mixing of excess
sludge and influent wastewater below
water surface.
Existing POTW's
Method: Reroute piping to allow
excess sludge discharge sufficiently
below water level.
Materials: Pipe and related appur-
tenances.
Sketch:
Clarifier
1 Existing Sludge
Discharge Line
-J Rerouted Line
3.1.1
204
-------
DEFICIENCY
CONSIDERATIONS
3.1.2 Lack of
screening and grit
removal ahead of
primary sedimentation.
3.1.3 Inadequate
provisions for
sampling of raw
sludge.
New POTW's
Provide screening and grit removal
facilities upstream of primary
sedimentation.
Existing POTW's
Method: Construct bar screen and/or
grit chamber upstream of primary
clarifier.
Materials; Concrete to form chamber,
and screen and mechanical cleaning
equipment.
New POTW's
Provide sampling point in raw sludge
withdrawal line.
Existing POTW's
Method; Install sampling tap in
sludge withdrawal line before sludge
treatment units.
Materials; Tap, valve, piping, and
related appurtenances.
Unit Operation/Component: 3.2 Primary Clarifier
3.2.1 Improper
length to width
ratios.
3.2.2 Inadequate
clarifier depth.
New and Existing POTW's
Provide clarifier with a length to
width ratio of at least 3 to 1, and
a minimum length of 10 feet.
New PQTW's
Provide at least 7-foot side water
depth, and up to a minimum of 14 feet
for large clarifiers.
Existing POTW's
Method; Construct parallel clarifier
and thereby reduce weir overflow rate
in existing unit.
3.1.2 - 3.2.2
205
-------
DEFICIENCY
CONSIDERATIONS
3.2.3 Design includes
a common sludge
removal pipe for
two or more clarifiers
resulting in unequal
sludge removal from
the clarifiers.
3.2.4 Effluent weir
not uniformlylevel.
Materials: Concrete to form new
clarifier and necessary sludge
removal equipment.
New and Existing POTW's
Provide separate sludge removal
pipes to each clarifier, or provide
valves on each clarifier outlet when
using a common removal pipe.
Specify that
be level.
New POTW's
the effluent weir must
3.2.5 Improper
baffling resulting
in short-circuiting.
3.2.6 Short-circuiting
causing poor solids
removal.
Existing POTW's
Method; Level weir.
New POTW's
Provide adequate baffling to pre-
vent short-circuiting.
Existing POTW's
Method: Rearrange baffles so that
length of flow through clarifier
is at least 10 feet and length
to width ratio of tank is at least
3 to 1.
New POTW's
Provide baffling to prevent short-
circuiting .
Method
Existing POTW's
Construct baffles in tank to
increase flow length through tank (to
at least 10 feet).
Materials; Baffles and related
installation hardware.
3.2.2 - 3.2.6
206
-------
DEFICIENCY
CONSIDERATIONS
3.2.7 Septic con-
ditions resulting
from overloading.
3.2.8 Inadequate
consideration of
impact of waste
secondary sludge
pumping on clarifier
loading.
3.2.9 Inadequate
consideration of
impact of various
trickling filter
recirculation rates
and strategies on
clarifier loadings.
New POTW's
Provide clarifier with adequate sur-
face area less than 600 gallons per
square foot for normal domestic sew-
age and sufficient sludge withdrawal
capacity.
Method:
Existing POTW's
Increase sludge withdrawal
pumping capacity.
Materials; Mechanical equipment for
sludge removal, and all necessary
appurtenances.
New POTW's
Size clarifier with adequate volume
and surface area to handle both
influent and any waste sludge flows.
Method:
Existing POTW's
Construct additional primary
clarification units or discontinue
sludge pumping to clarifier.
Materials; Concrete to form tank and
sludge removal equipment and neces-
sary appurtenances.
New POTW's
Provide adequately sized clarifier
for influent, recirculation, and
waste sludge flows.
Method:
Existing POTW's
Reroute recirculation water
downstream of clarifier.
Materials; Piping and necessary
appurtenances.
3.2.7 - 3.2.9
207
-------
DEFICIENCY
CONSIDERATIONS
3.2.10 Inadequate
consideration of
clarifier inlet
design.
3.2.11 Inadequate
sizing of torque
requirement for
sludge removal
mechanism.
New POTW's
Provide inlet which will dampen the
inlet velocity and distribute flow
equally across the width of the
clarifier.
Existing POTWs
Method: Construct baffles and flow
deflectors to obtain equal flow dis-
tribution across the width of the
clarifier.
Materials; Baffles, plates, and nec-
essary appurtenances.
New POTW s
Specify that the sludge removal mech-
anism must have adequate torque to
collect the sludge. Refer to manu-
facturers' specifications for torque
ratings provided for various applica-
tions.
Existing POTWs
Method: Install larger motor and/or
stronger removal mechanisms.
Materials; New motor and/or mech-
anism and related appurtenances.
3.2.12 Heavy wear
on scrapers due to
grit.
New and Existing POTWs
Provide grit removal facilities
upstream of clarifier. Refer to
2.1.3.
Unit Operation/Component: 3.3 Primary Sludge Removal
3.3.1 Flushing and
cleanout connections
for sludge line not
provided.
New POTW s
Provide sufficient number of clean-
outs or flushing connections to clean
all lines between tanks and equip-
ment.
3.2.10 - 3.3.1
208
-------
DEFICIENCY
CONSIDERATIONS
3.3.2 Primary sludge
pumps located too
far away from clar-
ifiers.
3.3.3 Inadequate
provisions for pre-
venting frequent main-
tenance resulting from
stringy material in
wastewater.
3.3.4 Inadequate
provisions for chain,
flight, and sprocket
repair and replacement,
Existing POTW's
Method: Install flushing and
cleanout connections at both ends
of sludge lines.
Materials; Tees or wyes and related
appurtenances.
New POTW's
Provide pumps as close as possible to
clarifiers.
Existing POTW's
Method; Relocate pumps closer to
clarifiers.
Materials; Materials for housing
pumps and required piping materials.
New POTW's
Provide cutter mechanism in sludge
line upstream of pump, or provide
pump which can handle stringy mate-
rial.
Method:
Existing POTW's
Install cutter mechanism
upstream of pumps or easily opened
hatch in pump volute for stringy
material removal.
Materials; Cutter mechanism or new
pumps and necessary appurtenances.
New POTW's
Provide duplex primary clarifiers so
that dewatering, repair, and replace-
ment can be done.
Existing POTW's
Method; Install new type of scraper
mechanism which has critical moving
parts above the water level, or con-
struct another clarifier so that one
can be taken off-line for repairs.
3.3.1 - 3.3.4
209
-------
DEFICIENCY
3.3.5 Design includes
a common sludge removal
pipe for two or more
clarifiers resulting
in unequal sludge
removal from the
clarifiers.
CONSIDERATIONS
Materials; New scraper mechanism or
concrete to form new clarifier and
scraper, pumps, piping, and related
appurtenances.
New POTW's
Provide separate sludge removal pipes
and pumps to each clarifier, or pro-
vide valves on each clarifier outlet
when using a common removal pipe.
Method:
Existing POTW's
Install control valves on
lines from each clarifier.
Materials: Valves and necessary
appurtenances.
Sketch:
3.3.6 Inadequate
provisions for
sampling of raw
sludge.
New POTW's
Provide sampling facilities for raw
sludge at each clarifier or raw
sludge pump.
3.3.4 - 3.3.6
210
-------
DEFICIENCY
CONSIDERATIONS
3.3.7 Operator is
not provided with
the capability to
observe sludge while
pumping.
3.3.8 Inadequate
flexibility in
sludge pumping system.
3.3.9 Improper mate-
rials selection.
3.3.10 No provisions
for measuring sludge
flow.
3.3.11 Inadequate
consideration of
character of sludge
in sizing and layout
of sludge lines.
Existing POTW's
Method: Install sampling tap on
line from each clarifier.
Materials; Tapping tee, piping, and
necessary appurtenances.
New and Existing POTW's
Provide sight-glass or sludge density
meter on suction side of sludge
pumps.
New and Existing POTW's
Provide spare pumps at each pumping
station and the flexibility to pump
from the clarifier desired if more
than one clarifier is provided.
New and Existing PQTW's
Provide sludge removal equipment
constructed from materials which
are compatible with the wastewater
anticipated. Particular attention
should be given to any industrial
wastes that will be in the POTW
wastewater.
New and Existing POTW's
Provide flow meter on withdrawal line
from each clarifier.
New POTW's
Sludge lines should be a minimum of 4
inches in diameter, and long runs and
sharp turns should be avoided when-
ever possible.
Existing POTW's
Method; Constrictions in piping
should be eliminated by replacement
of small pipes (less than 4 inches)
or sharp bends, etc.
Materials; New piping, fittings,
etc.
3.3.6 - 3.3.11
211
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 3.4 Primary Sludge Pumps
3.4.1 Flushing and
cleanout connections
for sludge line
not provided.
3.4.2 Primary sludge
pumps located too
far away from clar-
ifiers.
3.4.3 Inadequate
provisions for pre-
venting frequent
maintenance resulting
from stringy material
in wastewater.
3.4.4 Improper sizing
of increments on time
clock results in pump-
ing of unnecessarily
thin sludge.
3.4.5 Operator is
not provided with
the capability to
observe sludge while
pumping.
3.4.6 Inadequate
flexibility in sludge
pumping system.
New POTW's
Provide flushing connections and
cleanouts at the ends of sludge lines
and at other critical areas (such as
elbows and tees).
Existing POTW's
Method; Install flushing and clean-
out connections at both ends of
sludge lines and at all pumps,
meters, etc.
Materials; Tees or wyes and related
appurtenances.
New and Existing POTW's
Provide sludge pump as close as
possible to clarifiers.
New and Existing POTW's
Provide cutte'r mechanism upstream of
pumps or provide cutter pumps. Refer
to 3.3.3.
New and Existing POTW's
Provide time clock with 1/2 hour time
increments.
New and Existing POTW's
Refer to 3.3.7.
New and Existing POTW's
Refer to 3.3.8.
3.4.1 - 3.4.6
212
-------
DEFICIENCY
3.4.7 Improper
materials selection.
3.4.8 No provisions
for measuring sludge
flow.
3.4.9 Inadequate con-
sideration of character
of sludge in sizing and
layout of sludge lines.
CONSIDERATIONS
New and Existing PQTWs
Refer to 3.3.9.
New and Existing POTW's
Provide flow meters on all sludge
lines.
New and Existing POTW's
Refer to 3.3.11.
Unit Operation/Component: 3.5 Scum Removal
3.5.1 Poor flotation
of grease.
3.5.2 Inadequate
provisions for pre-
venting frequent main-
tenance resulting from
stringy material in
wastewater.
New POTW's
Provide pre-aeration and skimming.
Existing POTW's
Method; Install pre-aeration tank
with scum skimmer or install aera-
tion equipment feed channel to
primary clarifiers.
Materials: Concrete to form tank,
aeration, and skimming equipment and
necessary appurtenances.
New POTW's
Refer to 3.3.3 and 3.4.3.
Method:
Existing POTW's
Install alternative scum
removal equipment and cutter in
withdrawal line.
Materials; New scum removal equip-
ment, cutter, and necessary appur-
tenances.
3.4.7 - 3.5.2
213
-------
DEFICIENCY
3.5.3 Improper place-
ment of scum removal
equipment hinders
clarifier performance,
3.5.4 Scum is
recycled through
the plant and not
removed from the
system.
3.5.5 Improper
selection of scum
pumping facilities
results in excessive
O&M-
3.5.6 Inadequate
freeze protection.
CONSIDERATIONS
New PQTW's
Provide scum removal equipment near
clarifier outlet.
Existing POTW's
Method; Relocate or replace scum
removal equipment.
Materials; New scum removal equip-
ment and necessary appurtenances.
New and Existing POTW's
Provide facilities for wasting the
scum out of the plant along with the
waste sludge.
New POTW's
Provide scum pumping facilities which
are compatible with scum handled
(i.e., pumps that can handle a thick
liquid with large solids).
Existing POTW's
Method; Install new scum pumps or
new cutter mechanism upstream of
pumps.
Materials; New pumps, cutters,
piping, valves, etc.
New and Existing POTW's
Provide heated enclosure over tank
or provide type of removal mechanism
not subject to freezing.
3.5.3 - 3.5.6
214
-------
Design Considerations
Category: 4.0 Air
Activated
Sludge
<*-*.*.
Unit Operation/Component:.
4.1 Aeration Basin
DEFICIENCY
4.1.1 Lack of flexi-
bility to operate
in different modes
(i.e., complete
mix, plug flow,
contact-stabili-
zation, etc.).
CONSIDERATIONS
New POTW's
Provide piping and valving so that
multiple aeration basins can be
operated in the complete mix mode,
the plug-flow mode, or the contact-
stabilization mode, as shown in the
sketches below.
Method:
Existing POTW's
If plant layout warrants,
install piping and valving so that
multiple aeration basins can be
operated in the complete-mix mode,
the plug-flow mode, or the contact-
stabilization mode.
Materials: Valving and piping to be
compatible with existing piping.
Sketch:
Complete Mix
Influent
Effluent
Effluent
Waste
4.1.1
215
-------
DEFICIENCY
CONSIDERATIONS
Plug Flow
Influent
Effluent
Effluent
Recycle .
« I** Waste
Contact Stabilization
Influent
Effluent
Effluent
*» Waste
4.1.2 Aerator spacing
not adequately consid-
ered.
New POTW's
To ensure adequate mixing in an aera-
tion basin and the prevention of
"dead zones", the influence zones of
the aerators in a basin must
slightly overlap. Spacing of mechan-
ical aerators depends on the type of
aerator utilized, depth of the
basin, size of aerator, etc. Vendor
literature should be referred to in
order to identify proper spacing
between aerators and between aera-
tors and basin sidewalls. General-
ly, diffusers should be spaced more
than 6 inches and less than 24
inches on center. The spacing of
4.1.1 - 4.1.2
216
-------
DEFICIENCY
4.1.3 Inadequate
consideration for
alkalinity adjust-
ment.
CONSIDERATIONS
static mixers is dependent on the
design mixed liquor suspended solids
concentration and can vary from 5 to
30 feet.
Method:
Existing POTWs
If a fixed aerator is too
close to the wall of an aeration
basin which causes splashing prob-
lems, add splash shields under the
aerator platform or along the top of
the aeration basin wall.
If there is low D.O. and/or inade-
quate mixing within the aeration
basin, add baffling between aerator
zones of influence or add diffused
aeration or floating aerators to
supplement the aeration capability
of the existing aerators.
New POTW's
Alkalinity control is especially
important in activated sludge sys-
tems designed for nitrification.
During the conversion of ammonia to
nitrate, mineral acidity is pro-
duced. If insufficient alkalinity
is present in the wastewater, the pH
of the system will drop, and nitri-
fication may be inhibited. Approxi-
mately 7.1 mg of alkalinity as
CaC03 is destroyed per mg of
ammonia nitrogen oxidized, and,
depending on buffering capacity of
the wastewater, approximately 5.4 kg
of hydrated lime is required per kg
of ammonia nitrogen oxidized if a
constant pH must be maintained. In
order to maintain a constant pH
during nitrification, practice has
shown that a residual alkalinity of
50 mg/L for aeration and at least
150 mg/L for high-purity oxygen
systems is considered desirable.
4.1.2 - 4.1.3
217
-------
DEFICIENCY CONSIDERATIONS
Provide for lime addition facilities
for alkalinity control, including
(as required) lime storage, lime
slurry mixing equipment, chemical
feed pump(s), and pH monitoring.
Size the lime storage for at least a
one-month supply, and size the lime
slurry mixing and/or storage tanks
such that the slurry will have to be
made up no more frequently than once
per shift.
Existing POTW's
Method: Install an alkalinity
adjustment system.
Materials; Storage silo, mixing
tank, feed pumps, pH controller;
piping with victaulic couplings or
heavy-duty flexible rubber hoses and
appurtenances.
Cost:
Lime = $35/ton.
Sodium bicarbonate =» $220/ton
4.1.4 Inadequate New POTW's
foam control. Provide foam control facilities if
foaming may be a problem, such as
when high organic loadings or high
oil-and-grease concentrations are
expected. Facilities for foam con-
trol include:
Foam spray water system.
Defoaming agent addition
facility.
Yard hydrants to allow
periodic cleaning of
aeration basin sidewalls.
4.1.3 - 4.1.4
218
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing POTWs
Install a defoaming agent
addition system to include a spray
water system in the aeration basin.
As a minimum, acquire a metering
pump and 55-gallon drums of defoamer
agent. The defoamer addition system
should be located close to the appli-
tion point(s).
Materials; Spray headers, pipe and
related appurtenances, defoamer
metering pumps, and spray water
pumps. Piping should be insulated
in cold-weather regions.
Sketch:
Antifoam
/"Nin
H^tT"1
ci
Base Pump
Influent -^rr;
Legend
i;
Knockdown Showers
Aeration Basin
Knockdown Showers
: Effluent
4.1.5 Insufficient
mixing to prevent
solids deposition
and provide uni-
form SS and D.O.
concentrations in
the basin.
New PQTW's
Aeration systems should be sized
(i.e., horsepower specified) based
on both mixing and oxygen require-
ments. Factors to be considered
include basin depth, aerator spacing
baffles, system horsepower, and
4.1.4 - 4.1.5
219
-------
DEFICIENCY
CONSIDERATIONS
basin geometry. Rule of thumb for
mixing in diffused aeration systems
is 20 to 30 scfm/1,000 cu ft; for
surface aerators, it is 0.50 to 1.0
hp/1,000 cu ft.
4.1.6 Inadequate
screening of raw
wastes causes
plugging of aera-
tors and return/
waste sludge
pumping system.
4.1.7 Inflexible
design does not
permit isolation
of reactors and
changes in flow
schemes for main-
tenance purposes
and/or to adjust
for changes in
wastewater charac-
teristics.
4.1.8 Inadequate
consideration of
impact and control
of in-plant side-
streams.
Existing PQTW's
Method: Refer to 4.1.2.
New POTW's
Provide preliminary treatment via
comminutors and bar screens. Remove
rags and screenings from system
rather than grinding them up and
putting them back into the system.
Existing POTW's
Method: Construct grit removal and
screening devices upstream of influ-
ent wet well. Refer to 2.1.3, 2.3.1
and 2.6.1.
Materials; Concrete to form grit
removal and screening chamber, and
necessary equipment.
New and Existing POTW's
Provide parallel treatment tanks to
permit changes in operational mode
and for one tank to be dewatered for
maintenance while the remaining
tank(s) continue in service. Refer
to 4.1.1.
New POTW's
When sizing aeration basins, the BOD
and SS loadings from various plant
sidestreams (i.e., thickener over-
flows, filtrates, centrates, digester
supernatants, etc.) must be consid-
ered. The aeration basin must have
4.1.5 - 4.1.8
220
-------
DEFICIENCY
4.1.9 Inability to
dewater tanks for
repair.
4.1.10 Inadequate
provisions for
by-passing aera-
tion basin.
4.1.11 No provi-
sions for flow
division boxes.
CONSIDERATIONS
sufficient volume and aeration
capacity to treat the additional
sidestream loadings. Pretreatment
of sidestreams may be warranted to
reduce pollutant loadings and/or to
equalize flows.
Method:
Existing POTW's
Implement pretreatment and/
or equalization of sidestreams prior
to discharge to the POTW aeration
basin.
New and Existing POTW's
Provide mud valves in aeration basins
that allow the basins to be drained
to the plant drain system. Sumps
should also be provided in the tank
bottoms to allow complete dewatering.
Refer to 1.1.26 and 1.2.8.
New POTW's
Refer to 4.1.7.
Existing POTW's
Method: Install by-passes around
basins that preferably discharge to
other aeration basins. Refer to
4.1.1.
Materials; Piping, valves, and rela-
ted appurtenances.
New and Existing POTW's
Provide a flow division box to
equally split, regulate, and/or shut
off flow to the individual units that
make up a parallel treatment train.
4.1.8 - 4.1.11
221
-------
DEFICIENCY
CONSIDERATIONS
4.1.12 Improper
sidewater (SWD) and
baffling cause
splashing prob-
lems in basin.
4.1.13 Inability
to control and
measure mixed
liquor flow dis-
tribution to mul-
tiple secondary
clarifiers.
4.1.14 Inability
to change placement
of return sludge
in aeration basins.
New POTW's
Provide a minimum SWD of 2 ft in
aeration basins. When surface
aerators are utilized, splash shields
should be installed on top of basin
walls closest to the aerators. For
small tanks, splash shields should
be used to protect walkways from
water spray generated by surface
aerators.
Existing POTW's
Method; Construct splash shields
along base of walkway. Refer to
4.1.2.
Materials; Stainless steel, fiber-
glass, or reinforced plastic.
New and Existing POTW's
Provide necessary piping, valving,
and flow measuring facilities (i.e.,
in-line magnetic meters, V-notch
weirs, etc.) to allow operator to
route, adjust, and measure flow from
the aeration basin to any group of
multiple secondary clarifiers.
New POTW's
Design return sludge piping with the
flexibility to direct sludge to mul-
tiple points (i.e., at basin influent
gates, at surface aerators, etc.) in
aeration basins. The recycle sludge
discharge flexibility should be com-
patible with the treatment mode
options listed in 4.1.1, i.e., com-
plete mix, step aeration, plug flow,
and contact stabilization.
Examples of piping and flow options
are shown in the following sketches:
4.1.12 - 4.1.14
222
-------
DEFICIENCY
CONSIDERATIONS
Complete Mix
Return Activated Sludge
Influent
J
1
1
i
\
1
> i ;
t :
i
i /
i
\
t i
k i
r i
r 1
4
i i
F 1
3 ,
1 2
i i
:i ;
> t
\ t
< \
i
k
i ,
' i
r i
i
k
r
^. Effluent
Step Aeration
Return Activated Sludge
Influent
:in:n
Effluent
1 Pass Step Aeration
Return Activated Sludge
Influent
Ct t tU t
Effluent
Effluent
2 Pass Step Aeration
Return Activated Sludge
44
Effluent
4 Pass Step Aeration
4.1.14
223
-------
DEFICIENCY
CONSIDERATIONS
Plug Flow
Return Activated Sludge
Influent
ft
II
M
II
Effluent
1 Pass Conventional
Return Activated Sludge
Influent
-»
-»
lib ^
11 v i
(*
xr * i
Effluent
Effluent
2 Pass Conventional
Effluent
Influent
.(T
X -s
^ V
'C r * *
^
4 Pass Conventional
4.1.14
224
-------
DEFICIENCY
CONSIDERATIONS
Contact Stabilization
Effluent
Influent
R.A.S.
4.1.15 Inadequate
consideration of
impact of changing
aeration basin
levels on aerator
performance.
Existing POTW's
Method; Install additional piping
required to direct sludge to multiple
points in the aeration basin.
Materials; Piping, valves, and rela-
ted appurtenances.
New POTW's
Changing the submergence (i.e., the
aeration basin level) of fixed sur-
face aerators by just a few inches
can greatly affect their performance.
Diffuser aeration or turbine aerators
should be used in basins that will
operate at varying levels. Adjust-
able effluent gates should be pro-
vided to allow setting the proper
liquid level in the aeration basin.
In small aeration basins, signifi-
cant changes in forward flow could
change the operating level (i.e.,
the level over the effluent gates)
in the basin, and, consequently, the
performance of surface aerators.
Maximum flows must be considered,
therefore, in sizing the aeration
basins.
4.1.14 - 4.1.15
225
-------
DEFICIENCY
CONSIDERATIONS
4.1.16 Multicom-
partmental basins
do not have rein-
forced inner walls;
therefore, indi-
vidual tanks
cannot be dewa-
tered.
4.1.17 Inability to
drain foam spray
system results in
freezing problems.
For floating aerators, snubbers
should be provided at each mooring
to allow adjustment of the support
cables with changes in basin opera-
ting levels.
Existing PQTW's
Method; For fixed surface aerators,
install adjustable effluent weirs/
gates to allow adjustment of the
aeration basin liquid level. Install
snubbers on mooring cables to float-
ing surface aerators.
Materials; Concrete to form new
weir base; adjustable weirs and
related appurtenances for fixed
surface aerators; snubbers for
floating aerators.
New and Existing POTW's
Specify reinforced common walls
inside multicompartmental basins to
allow draining of individual tanks.
Also, specify drain valves in each
tank.
New POTW's
Design foam spray water systems with
pumps with casing drain plugs, or
piping systems with drain valves at
all low points. If portions of
exposed piping cannot be drained by
gravity via removal of a plug, pro-
vide taps to allow for an air purge.
Method:
Existing POTW's
Install drain valves/plugs
at low points in piping system and
on pumps. If necessary, install
taps to allow air purging the lines,
Materials ; One-inch drain plugs/
valves.
4.1.15 - 4.1.17
226
-------
DEFICIENCY
CONSIDERATIONS
4.1.18 Supports for
air drop pipes can-
not be seen when
aeration basin is
full, making it
difficult to re-in-
stall the drop
pipes.
4.1.19 Lack of
splash shields in
front of effluent
gates.
4.1.20 Quick dis-
connect plugs on
aerators become
wet and short out.
4.1.21 Inadequate
consideration of
freezing problems
and effect of
cold temperatures
on efficiency of
biological treat-
ment.
New and Existing POTW's
Provide top guides to bottom air drop
pipe supports that are located above
the highest operating level in the
aeration basin. Provide means, such
as a clasp, to secure pipe to top
guide.
New and Existing POTW's
Provide splash shields in front of
effluent gates in order to allow
accurate setting of the gates and a
relatively-constant flow from the
basin. Splash shields will also
help minimize foam build-up in
effluent troughs.
New and Existing POTW's
Locate quick disconnect plugs out of
the splashing range of aerators and
specify weather-proof plugs. Specify
the use of moisture/explosion proof
electrical couplings that include
locking collars, screws, or latches
to prevent the unintentional loosen-
ing of the coupling.
New POTW's
As wastewater temperature drops, the
efficiency of biological treatment
systems will also drop (unless oper-
ational adjustments are made). To
minimize this potential problem in
areas characterized by low seasonal
temperatures, consideration must be
given to:
Diffused aeration versus
mechanical aerators.
Below-grade versus above-
ground tank installation
for improved insulation.
Covered tanks.
4.1.18 - 4.1.21
227
-------
DEFICIENCY CONSIDERATIONS
Sludge recycle systems with
a capacity equal to 100
percent of forward flow.
Existing PQTW's
Method; Construct an earthen berm
around above-ground tanks to insu-
late the tank; install wind shields
around tank perimeter; supplement
surface aerators with diffused aera-
tion system; and/or provide covers
over open tanks.
Materials; Commercially-available
tank covers; stainless steel or
fiberglass windshields; diffused
aeration system.
Unit Operation/Component:
4.2
Diff users
4.2.1 Insufficient New POTW's
mixing to prevent A rule of thumb for mixing require-
solids deposition ments for diffused aeration systems
and provide uniform is 20 to 30 scfm/1,000 cu ft. Oxy-
SS and D.O. con- gen requirements must also be con-
centrations in the sidered. Refer to 4.1.5.
basin.
Existing POTW's
Method; Increase the horsepower of
existing blowers. Install baffles
to improve basin mixing patterns.
Supplement aeration systems with
additional diffusers. Refer to
4.1.2.
4.2.2 Inadequate New and Existing POTW's
aeration capacity. When sizing aeration systems, both
mixing and oxygen requirements must
be considered. Refer to WPCF MOP
No. 5, Ten States Standards, and
local standards for aeration capac-
ity guidelines. Refer to 4.1.2 and
4.2.1.
4.1.21 - 4.2.2
228
-------
DEFICIENCY
CONSIDERATIONS
4.2.3 Inadequate
screening of raw
wastes causes
plugging of
aerators and
return/waste
sludge pumping
systems.
4.2.4 Inadequate or
no air cleaners
provided on blowers.
4.2.5 No provisions
for removing air
diffuser drop
pipes from aera-
tion tanks.
4.2.6 Air valves
not graduated to
allow even dis-
tribution of air
flow to diffusers.
New and Existing POTWs
Provide bar screens, grit chambers,
and primary sedimentation facilities
prior to aeration in order to mini-
mize plugging of aerators and return
sludge systems. Effective prelim-
inary treatment is particularly
important for contact-stabilization
processes. Refer to 2.1.3, 2.3.1,
2.6.1, and 4.1.6.
New and Existing POTW's
Provide air filters on intake side
of blowers to minimize clogging of
diffusers. Refer to blower manufac-
turer recommendations.
New POTW's
Provide necessary equipment (hoists,
fittings, flexible joints, etc.) to
facilitate the removal of air diffu-
ser drop pipes for inspection and
maintenance. For small, package-
type treatment plants, specify lift-
ing rings be placed at the top of
drop pipes to allow the operator to
tie-off the pipe before disconnect-
ing it from the header. This will
prevent the pipe from accidentally
falling into the aeration basin.
Existing POTW's
Method: Install mobile gantry-type
hoist on aeration basin. For small,
package type plants, weld lifting
rings at the top of each drop pipe.
Materials; Commercially available
hoists.
New POTW's
Specify for each drop pipe (i.e.,
diffuser) air valves that have posi-
tion indicators (fully open, half
open, fully closed, etc.).
4.2.3 - 4.2.6
229
-------
DEFICIENCY
CONSIDERATIONS
4.2.7 Supports for
air drop pipes
cannot be seen when
aeration basin is
full, making it
difficult to re-in-
stall drop pipes.
4.2.8 Diffusers
plug due to dirty
air supply.
Existing POTW's
Method; Replace existing valves in
air lines to individual diffuser
heads with graduated butterfly
valves.
Materials; Butterfly valves with
position indicators.
New and Existing POTW's
Refer to 4.1.18.
New and Existing POTW's
Provide air filters on intake side of
blowers. Refer to 4.2.4.
Unit Operation/Component: 4.3 Fixed Mechanical Aerators
4.3.1 Aerator spac-
ing not adequately
considered.
4.3.2 Insufficient
mixing to prevent
solids deposition
and provide uniform
SS and D.O. concen-
trations in the
basin.
New POTW's
The zone of influence for surface
aerators is dependent on horsepower
and must be considered during design
to determine proper spacing between
aerators and between aerator and
basin sidewalls. Aeration basin
geometry may be dictated by aerator
spacing requirements. Vendor speci-
fications should be referred to for
spacing information.
Existing PQTW's
Method; Refer to 4.1.2.
New POTW's
Refer to 4.1.5.
4.2.6 - 4.3.2
230
-------
DEFICIENCY
CONSIDERATIONS
4.3.3 Inadequate
aeration capacity.
4.3.4 Inadequate
consideration of
debris in waste-
water .
Existing POTW's
Method; Increase the horsepower of
existing aerators. Install baffles
to improve basin mixing patterns.
Supplement existing surface aera-
tion system with diffused aeration
or a pure oxygen system. Refer to
4.1.2.
New and Existing POTW's
Refer to 4.2.2.
New POTW's
Provisions should be made for screen-
ing devices upstream of aeration
tanks. Refer to 4.1.6.
Method:
Existing POTW's
Refer to 4.2.3.
4.3.5 Inadequate
consideration of
impact of changing
aeration basin
levels on aerator
performance.
4.3.6 Improper place-
ment of gear box
drains causes oil
to drain into aera-
tion basin.
New and Existing POTW's
Refer to 4.1.15.
New PQTW's
Specify aerators with gear boxes that
can be easily drained, and minimize
the possibility of oil spilling into
the aeration basin. The drains
should be placed such that a contain-
er can be placed under the drain to
collect waste oil. The operator
should not be required to install or
modify the equipment with additional
drain pipes, valves, or fittings
after construction.
Method:
Existing POTW's
Use hand drill attached
pump and pump waste oil into suit-
able container. If possible,
install a pipe from the drain plug
to a position that provides conven-
ient access by the operator.
4.3.2 - 4.3.6
231
-------
DEFICIENCY
CONSIDERATIONS
4.3.7 Amp meters not
provided at motor
control center so
operators cannot
tell if proper
amperage is being
drawn.
4.3.8 No time delay
relays provided to
limit stress shock
to aerator gears
when shifting from
high speed to
low speed.
Materials: Drill pump, 1/4" O.D.
tubing.
Cost; $5 to $10 for drill pump.
New POTW's
Amp meters should be specified for
installation at aerator circuit
breakers to allow the operator to
determine if aerators are drawing
the proper amperage. If the aera-
tor blade is submerged too much,
this can cause the aerator to draw
too many amps and damage the aera-
tor. This is particularly helpful
during POTW start-ups.
Existing POTW's
Method; Install amp meters at MCC
circuit breakers.
Materials ; Electrical wire and
suitable connectors.
Cost; Approximately $500 per unit.
New POTW's
Specify time delay relays be provided
on aerator motors that will allow the
aerator blade to slow down before the
motor shifts into low speed in order
to minimize stress shocks when
switching aerators from high speed
to low speed.
Method:
Existing POTW's
Install time delay relays
in aerator controllers.
Materials; Electrical wire and
suitable connectors.
Cost; Approximately $250 per unit.
4.3.6 - 4.3.8
232
-------
DEFICIENCY
4.3.9 Spray from
surface aerators
makes walkways
slippery.
CONSIDERATIONS
New POTW's
Specify splash shields for aerators
that are placed in small tanks and
are located adjacent to walkways.
Spray shields can also be mounted
along the outside edge of walkways
to prevent spray water collecting on
walkways.
Method:
Existing POTW's
Install spray shields along
outside edge of walkways to prevent
spray water collecting on walkways.
Install aerator spray shields.
Materials; Stainless steel or
fiberglass walkway spray shields.
Refer to aerator manufacturer for
recommendations concerning aerator
splash plates.
Unit Operation/Component: 4.4 Floating Aerators
4.4.1 Aerator spac-
ing not adequately
considered.
4.4.2 Insufficient
mixing to prevent
solids deposition
and provide uniform
SS and D.O. concen-
trations in the basin,
4.4.3 Inadequate
aeration capacity.
New and Existing POTW's
Refer to 4.1.2 and 4.3.1.
New POTW's
Refer to 4.1.5.
Existing POTW's
Method; Refer to 4.1.3 and 4.3.2.
New POTW's
Refer to 4.2.2.
Existing POTW's
Method: Refer to 4.1.2 and 4.3.2.
4.3.9 - 4.4.3
233
-------
DEFICIENCY
CONSIDERATIONS
4.4.4 Inadequate
consideration of
debris in waste-
water .
New POTW's
4.4.5 Floating aera-
tors located too
close to wall or
pontoons not aligned
properly, causing
pontoons to
strike the basin
wall when starting
up.
4.4.6 Improper
placement of gear
box drains causes
oil to drain into
aeration basin.
4.4.7 Amp meters not
provided at motor
control center so
operator cannot tell
if proper amperage
is being drawn.
Refer to 4.3.4.
Existing POTW's
Method; Refer to 4.1.6 and 4.2.3,
New and Existing POTW's
Provide for safe installation of
floating aerators by:
Specifying use of low
voltage starters to
minimize initial
torque levels and
lateral .movement.
Minimizing slack in
mooring cables by
using "snubbers".
Assuring pontoons are
properly aligned
according to manufac-
turers' specifications.
Locating aerators a
safe distance from the
nearest wall.
New and Existing PQTW's
Refer to 4.3.6.
New and Existing POTW's
Refer to 4.3.7.
4.4.4 - 4.4.7
234
-------
DEFICIENCY
CONSIDERATIONS
4.4.8 Quick dis-
connect plugs on
aerators become
wet and short out.
4.4.9 No time delay
relays provided to
limit stress shock
to aerator gears
when shifting from
high speed to low
speed.
4.4.10 Spray from sur-
face aerators makes
walkways slippery.
New and Existing POTW's
Refer to 4.1.20.
New and Existing POTW's
Refer to 4.3.8.
New and Existing POTW's
Refer to 4.1.2 and 4.3.9.
Unit Operation/Component: 4.5 Blowers
4.5.1 Inadequate
aeration capacity.
4.5.2 Inadequate or
no air cleaners
provided on blowers.
4.5.3 Blower silen-
cers not provided.
New and Existing POTW's
Provide blowers with sufficient
capacity and discharge pressure to
both thoroughly mix and provide
oxygen to the entire contents of the
aeration basin. Provide a stand-by
blower for use during unusually high
oxygen demand periods and/or when
another unit is out of service.
Refer to 4.2.2.
New and Existing POTW's
Provide air cleaners (filters) on the
intake side of each blower. This
will help prevent damage to blowers
and clogging in fine bubble dif-
fusers. Refer to 4.2.4.
New and Existing POTW's
Provide silencers on both the intake
and discharge side of blowers. Refer
to blower manufacturers' recommenda-
tions.
4.4.8 - 4.5.3
235
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 4.6 Air Distribution System
4.6.1 Inability to
adequately measure
and adjust air flow
rates to control
D.O. levels and
energy consump-
tion.
New POTW's
Provide flow meters on all main air
headers to aeration tanks. Provide
graduated valves in each drop pipe
to diffusers to allow air flow regu-
lation.
4.6.2 Improper air
piping material.
4.6.3 No provisions
for removing air
diffuser drop pipes
from aeration tanks.
Method:
Existing POTW's
Install annubar flow ele-
ment in air supply pipe to each
basin. Install butterfly control
valves with indicator markings for
throttling on individual assembly
units of diffusers.
Materials: Flow elements and grad-
uated butterfly valves.
New POTW's
Specify non-scaling material for air
piping systems. Avoid organic coat-
ings such as coal tar dips which may
deteriorate with time and cause fine
particles to dislodge and clog air
diffusers.
Method:
Existing POTW's
To intercept piping scale,
install fine mesh strainer in dif-
fuser drop-leg.
Material: Basket-type strainer.
New POTW's
Refer to 4.2.5.
Existing POTW's
Method: Install adjustable gantry
on aeration basin. Weld lifting
rings to top of air drop pipes.
4.6.1 - 4.6.3
236
-------
DEFICIENCY
CONSIDERATIONS
4.6.4 Air valves not
graduated to allow
even distribution
of air flow to
diff users.
4.6.5 Supports for
air drop pipes can-
not be seen when
aeration basin is
full, making it
difficult to re-in-
stall the drop
pipes.
Materials ; Commercially available,
New and Existing POTW's
Refer to 4.2.6.
New and Existing POTW's
Refer to 4.1.18.
Unit Operation/Component: 4.7 D.O. Control and Measurement
4.7.1 Inability to
adequately measure
and adjust air
flow rates to
control D.O. levels
and energy consump-
tion.
New POTW's
Where varying organic loads are
applied to aeration basins, provi-
sions are needed to constantly
monitor and control dissolved oxy-
gen levels in the basins. As a
minimum, D.O. probes should be speci-
fied to monitor D.O. levels. For
large plants, an automatic D.O.
analyzer and a D.O. controller
should be considered to automatically
control the "ON-OFF-SPEED" setting
on plant aerators/blowers. Refer to
4.6.1.
Method:
Existing POTW's
Install automatic D.O. sys-
tern to vary air input, by control-
ling the "ON-OFF-SPEED" setting of
the blowers according to the basin
D.O. level.
Materials; Dissolved oxygen monitor-
ing system and related automatic
control systems.
4.6.4 - 4.7.1
237
-------
DEFICIENCY
CONSIDERATIONS
Cost; Approximately $20,000 to
$30,000.
Sketch:
D.O. Analyzer
Logic Panel
i
i
i r
er :
D.O. Probe
i
i
B--!
1X1
IXI
1
n
1
1
1
1 i
1
Blowers
As D.O. level decreases
below set-point, blower
speeds are increased and
more blowers are started
As D.O. level increases
above set-point, blower
speeds are decreased and
some blowers are stopped
Air
x^~v fi r\
^y ^
v^S "7;%.
vV1 5 ^~f
|
D O. Analyzer
and
Logic Panel
]
As D.O. level decreases
below set-point, 2-speed
aerator shifts from low
to high speed.
As D.O. level increases
above set-point, 2-speed
aerator shifts from high
to low speed.
4.7.1
238
-------
DEFICIENCY
CONSIDERATIONS
4.7.2 Inadequate
consideration of
impact and control
of in-plant side-
streams.
4.7.3 Air valves not
graduated to allow
even distribution
of air flow to
diffusers.
4.7.4 Improper
design of D.O.
measuring instru-
mentation does
not allow easy
removal of
equipment for
routine inspec-
tion and main-
tenance.
New and Existing POTW's
Refer to 4.1.8.
New and Existing POTW's
Refer to 4.2.6.
New POTW's
Specify D.O. measuring instrumenta-
tion that can be conveniently removed
for cleaning the probe, calibration,
and for general maintenance purposes.
Existing POTW's
Method; Install swivel-type support
to handrail to permit easy removal
from basin.
Materials; 1-1/2" swivel joint.
Unit Operation/Component: 4.8 Return Sludge Pumping
4.8.1 Inadequate
screening of raw
wastes causes
plugging of aera-
tors and return/
waste sludge
pumping system.
New and Existing POTW's
Specify sludge piping with a minimum
diameter of four inches. Pump impel-
lers should be non-clog type, able to
easily handle heavy solids that may
accumulate in the secondary clari-
fier. Provide capability to flush
out (back-flush) pumps and lines with
high pressure water. Consideration
should be given to using progressive
cavity pumps in lieu of centrifugal
pumps. Refer to 4.1.6.
4.7.2 - 4.8.1
239
-------
DEFICIENCY
CONSIDERATIONS
4.8.2 Inflexible
design does not
permit isolation
of reactors and
changes in flow
schemes for main-
tenance purposes
and/or to adjust
for changes in
waste character-
istics.
4.8.3 Inadequate
consideration of
impact and con-
trol of in-plant
sidestreams.
4.8.4 Inadequate
provisions for
sampling and
observation of
return and waste
activated sludge.
4.8.5 Inadequate
consideration of
debris in waste-
water .
4.8.6 Improper
selection of
valves for sludge
lines.
New and Existing POTW's
Return sludge pumps and piping should
be designed to allow the isolation of
aeration basins. The return sludge
system should include: common pump
suction line from clarifiers to allow
switching pumps; common discharge
header; valving system that allows
diverting sludge flow in order to
isolate a basin; one recycle pump for
each basin; plus a common spare.
Refer to 4.1.1 and 4.1.14.
New and Existing PQTW1s
Provide sufficient recycle capacity
to make adjustments in the aeration
basin mixed liquor to compensate for
increased loads from in-plant side-
streams. Refer to 4.1.8.
New and Existing POTW's
Provide sampling taps on recycle and
waste sludge discharge lines. Sam-
pling taps should have a minimum di-
ameter of two inches. Consideration
should also be given to specifying
in-line sludge density meters. In
addition, when possible, provide a
"free fall" discharge of return
sludge flow to aeration basins and
waste sludge to aerobic digesters,
holding tanks, etc. Refer to 1.1.17.
New and Existing POTW's
Refer to 4.1.6 and 4.8.1.
New POTW's
Provide valves that will minimize the
possibility of solids getting jammed
into the moving and projecting parts.
Avoid; spring-loaded vertical-lift-
disk check valves and solid wedge or
single-gate valves. Provide; plug
valves, knife gate valves, or pinch
valves.
4.8.2 - 4.8.6
240
-------
DEFICIENCY
4.8.7 Improper
return sludge
flow splitting.
4.8.8 Inadequate
sludge recycle/
waste capacity.
Method:
CONSIDERATIONS
Existing POTW's
Replace existing valves
with proper type.
Materials: Plug valves, knife gate
valves, or pinch valves.
New POTW's
Provide positive control of return
sludge distribution. Do not rely
entirely on piping wyes and tees to
split flow evenly. Valving should
be provided to adjust flows to dif-
ferent points within an aeration
basin, and separate recycle pumps
should be used to distribute flow to
multiple aeration tanks.
Existing POTW's
Method; Install a flow splitter box
to ensure even distribution of recy-
cled sludge to multiple aeration
basins and/or application points.
Install valves in existing recycle
lines to provide better flow con-
trol. Provide overflow weirs and/or
in-line magnetic flow meters to meas-
ure sludge flow rates. Refer to
4.8.6.
New POTW's
Provide sufficient sludge recycle
pumping and piping capacity to allow
the operator to recycle 100 percent
of the forward flow. As a minimum,
one stand-by pump should be supplied.
Existing POTW's
Method: Install additional recycle/
waste sludge pump or increase the
impeller and/or motor size of the
existing sludge pumps. Refer to
1.3.16.
4.8.6 - 4.8.8
241
-------
DEFICIENCY
CONSIDERATIONS
4.8.9 Inadequate
sludge flow meas-
urement for small
plants using air
lift pumps.
4.8.10 Inability
to adjust, measure,
and control return/
waste sludge flows.
Materials: Concrete to form pump
pad, motor controls, piping, valves,
and related appurtenances.
New and Existing POTW's
Provide magnetic flow meters with
flow indication in gpm as part of
each sludge return (and waste) sys-
tem. As a minimum, provide a flow
box equipped with a V-notch weir to
allow the operator to manually deter-
mine sludge flow rates.
New POTW's
Refer to 1.3.16, 4.1.1, 4.8.2,
4.8.6, 4.8.7, 4.8.8, and 4.8.9.
4.8.11 Inability to
change placement
of return sludge
in aeration basin.
4.8.12 Scum accu-
mulation in flow
splitter boxes.
Existing POTW's
Method: Install an automatic flow
control valve, and a flow meter in
the return sludge line.
Materials; Flow meters, control
valve, and related appurtenances.
New and Existing POTW's
Refer to 4.1.14.
New POTW's
Design flow splitter boxes such that
flow is distributed from the top of
the box rather than at the bottom;
the constant overflow will prevent
sludge from accumulating in the box.
If an underflow splitter box is
required, provide means, such as a
scum trough, to remove scum from the
box.
Existing POTW's
Method; For splitter boxes with
distribution pipes at the bottom of
the box:
4.8.8 - 4.8.12
242
-------
DEFICIENCY CONSIDERATIONS
Relocate the discharge
pipes to the top of the
box.
Install an overflow weir
inside the box so that
water must flow over the
weir and drop down to the
bottom discharge pipes.
Install a scum trough and
scum collection pit.
4.8.13 Lack of New and Existing POTW's
instrumentation Provide flow meters on sludge recy-
to totalize cle and waste lines and specify a
recycle/waste flow totalizer as part of the instru-
sludge flows. mentation package. This allows the
POTW operator to compute a solids
balance for solids handling purposes,
Refer to 4.8.10.
Unit Operation/Component: 4.9 Waste Sludge Pumping
4.9.1 No separate New POTW's
waste sludge pumps. For large plants (greater than 5
mgd), provide separate waste sludge
pumps.
Existing POTW's
Method; Install separate waste
sludge pumps.
Materials; Concrete to form pump
pad, starter/control panel, pip-
ing, magnetic flow meter and related
instrumentation and valves.
4.9.2 Inadequate New and Existing POTW's
screening of raw Refer to 4.1.6 and 4.8.1.
wastes causes
plugging of aera-
tors and return/
waste sludge pump-
ing system.
4.8.12 - 4.9.2
243
-------
DEFICIENCY
CONSIDERATIONS
4.9.3 Inadequate
consideration of
impact and control
of in-plant side-
streams.
4.9.4 Inadequate
provisions for
sampling and obser-
vation of return
and waste activa-
ted sludge.
4.9.5 Inadequate
considerations of
debris in waste-
water.
4.9.6 Improper
selection of
valves for sludge
lines.
4.9.7 Inadequate
waste sludge pipe
sizing for "slip-
stream" wasting.
New POTW's
Provide sufficient sludge wasting
capacity to handle increased sludge
loadings generated by in-plant side-
streams.
Method:
Existing POTW's
Provide increased sludge
wasting capacity to handle increased
sludge loadings generated by in-
plant sidestreams.
Materials; New wasting pump and/or
larger pump motor and/or pump impel-
ler.
New and Existing POTW's
Refer to 4.8.4.
New and Existing POTW's
Refer to 4.1.6 and 4.8.1.
New and Existing POTW's
Refer to 4.8.6.
New POTW's
Design sludge piping to allow simul-
taneous maximum wasting and recycling
flow rates. For large plants, pro-
vide separate wasting pumps in lieu
of a "slip-stream" wasting scheme.
Existing POTW's
Method; Install separate waste
sludge pumps.
4.9.3 - 4.9.7
244
-------
DEFICIENCY
CONSIDERATIONS
4.9.8 Inadequate
sludge recycle/
waste capacity.
4.9.9 Inadequate
sludge flow meas-
urement for small
plants using air
lift pumps.
4.9.10 Inability to
adjust, measure,
and control return/
waste sludge flows.
4.9.11 Scum accu-
mulation in flow
splitter boxes.
4.9.12 Lack of
instrumentation
to totalize
recycle/waste
sludge flows.
New POTW's
Provide waste pumping capacity to
handle expected peak flows. Sludge
generation from in-plant sidestreams
should be considered. A spare pump
should be provided to help handle
peak flows and for use when another
pump is out of service.
Existing POTW's
Method; Refer to 4.8.8.
New and Existing POTW's
Refer to 4.8.9.
New and Existing POTW's
Refer to 4.8.10, 4.9.7, 4.9.8 and
4.9.9.
New and Existing POTW's
Refer to 4.8.12.
New and Existing POTW's
Refer to 4.8.10 and 4.8.13.
Unit Operation/Component: 4.10 Secondary Clarification
4.10.1 No provision
for addition of chem-
icals to improve
settling character-
istics.
New POTW's
Provide a chemical addition system to
enable the operator to feed settling
aids such as alum or polymer to
secondary clarifiers. Specify floc-
culator-clarifiers for the secondary
treatment system, particularly if
the design overflow rate (OFR) is
less than 500 gpd/sq ft.
4.9.8 - 4.10.1
245
-------
DEFICIENCY
4.10.2 Improper type
of sludge removal
mechanism selected.
4.10.3 Improper
clarifier side-
water depth (SWD).
Method:
CONSIDERATIONS
Existing POTW's
Install chemical addition
system near effluent trough of
aeration basin. Allow in-line
mixing between effluent trough and
center well of clarifier.
Materials: Chemical make-up and
storage system, piping, and related
appurtenances. Building to house
equipment and chemicals.
New and Existing POTW's
Ensure the sludge removal mechanism
selected is compatible with the
clarifier geometry. Traveling bridge
mechanisms are suitable for rectan-
gular clarifiers, while circular
plow type units (with or without
positive sludge withdrawal through
the rake arms) are designed for use
with circular clarifiers. Plow type
mechanisms are suitable for heavy
sludges such as primary or some
chemical sludges. Positive with-
drawal mechanisms are suitable for
lighter sludges such as secondary
sludges from an activated sludge
POTW.
New PQTW's
Provide a minimum clarifier side-
water depth of 10 feet for clarifiers
up to 40 feet in diameter. This
depth should increase proportionally
by 1 foot of SWD for each additional
20 feet of diameter up to a 15-foot
SWD for tank diameters 140 feet and
over. Another rule of thumb is to
increase the SWD by 1 foot for each
1,000 mg/L increase in MLSS. To
compensate for depth limitations,
reduce the overflow rate 100 gpd/sq
ft for each lost foot of sidewater
depth.
4.10.1 - 4.10.3
246
-------
DEFICIENCY
CONSIDERATIONS
Method:
Existing PQTW's
If hydraulically feasible,
4.10.4 Inadequate
access to weirs for
sampling and main-
tenance.
4.10.5 Inflexible
design does not
permit isolation
of reactors and
changes in flow
schemes for main-
tenance purposes
and/or to adjust
for changes in
waste characteris-
tics.
raise the height of the clarifier
effluent troughs (this may require
an intermediate pumping station).
Install additional effluent troughs
to reduce weir overflow rates, and
reduce upward velocities in the
clarifier. Construct additional
clarifier to reduce system overflow
rates.
New POTW's
Provide clarifiers that permit opera-
tor easy and safe access to weirs for
sampling and maintenance. Clarifiers
should have effluent troughs of suf-
ficient width to permit operator to
walk along the trough. Hand rail-
ings should be provided around the
outside perimeter of the clarifier.
Existing POTW's
Method; Bridgeway of clarifier is
used to obtain sample from effluent
trough. For those clarifiers built
above-grade, operator may walk inside
effluent launder with attached
safety line. Where this is not
feasible, construct access walkway
around periphery of tank. Refer to
1.1.3.
Materials; Handrail, grating, sup-
ports, and related appurtenances.
New POTW's
Provide necessary piping and valving
to allow recycle of sludge from each
clarifier to any one of the POTW's
aeration basins.
4.10.3 - 4.10.5
247
-------
DEFICIENCY
CONSIDERATIONS
4.10.6 Inadequate
consideration of
impact and control
of in-plant side-
streams.
4.10.7 Overflow rate
(OFR) of clarifiers
too high to meet
effluent SS limita-
tions.
4.10.8 No provisions
for flow division
boxes.
4.10.9 Short-cir-
cuiting in clarifiers,
Existing POTW's
Method; Refer to 4.1.1.
New PQTW's
When sizing clarifiers, include the
in-plant sidestream flows that will
be generated and ultimately dis-
charged to the clarifiers. Peak
flows that could occur should be con-
sidered. The effects of sidestreams
on the settling characteristics of
the waste should also be evaluated
prior to sizing any units since
settling aids may be required.
Existing POTW's
Method; Refer to 4.1.8 and 4.10.1.
New POTW's
Conduct pilot and/orlaboratory set-
tling tests to identify design over-
flow rates. Normally, the range will
be 400 to 600 gpd/sq ft. If the
design OFR is less than 500 gpd/sq
ft, consideration should be given to
providing a flocculator-clarifier
and a polymer addition system.
Existing POTW's
Method; Install a polymer addition
system to enhance settling. Install
additional effluent troughs to
reduce upward velocities in the
clarifier. Refer to 4.10.12.
New and Existing POTW's
Provide flow division boxes that per-
mit operator to control flow distri-
bution to multiple final clarifiers.
New POTW's
Provide inlet design to achieve hori-
zontal and vertical distribution
of the incoming flow across the
entire cross-sectional flow-through
area, while minimizing short circuit-
ing and turbulence factors.
4.10.5 - 4.10.9
248
-------
DEFICIENCY
4.10.10 Lack of con-
sideration of inlet-
outlet losses.
CONSIDERATIONS
The inlet in a rectangular clari-
fier should consist of a baffle
placed in front of the influent
point(s) to distribute the flow
laterally and vertically and to
minimize short circuiting. Baf-
fles are usually installed 2 to 3
feet in front of the inlets, sub-
merged 18 to 24 inches, with the top
of the baffle 2 inches below the
water surface.
In circular clarifiers with center
feed, uniform distribution of the
influent is accomplished by a con-
centric influent baffle to reduce
velocity and to distribute the flow
uniformly towards the outlet. With
100-percent recirculation, circular
tank inlet wells should not be less
than 20 percent of the tank diameter
and have a depth of 55 to 65 percent
of the SWD.
Outlet devices are commonly "V"-notch
weirs. A weir loading of 15,000 gpd/
ft is necessary to prevent excessive
upflow currents. In order to main-
tain an adequate weir overflow rate,
multiple weirs may be necessary.
Outlet velocity should be reduced to
less than 10,000 gpd/ft for sus-
pensions with poor settling
characteristics.
Existing POTW's
Method; Install additional baffles
in rectangular clarifiers. Refer to
3.2.5 and 3.2.6.
New POTW's
When sizing clarfiers, the clarifi-
cation area losses due to inlet and
outlet structures must be considered
in order to ensure that the actual
"effective area" of the clarifier is
4.10.9 - 4.10.10
249
-------
DEFICIENCY
CONSIDERATIONS
4.10.11 Improper or
no use of a scale-
down factor to con-
vert lab overflow
rate (OFR) to design
OFR.
4.10.12 Improper weir
placement (i.e., prop-
er weir length but
closely placed
troughs create
high, localized
upward velocities
within clarifier).
4.10.13 Improper
length-to-width
ratio.
sufficient. For small clarifiers,
loss in the clarification area can
be as high as 40 percent.
Existing POTW's
Method; Refer to 4.10.9.
New PQTW's
Overflow rates identified during
laboratory treatability studies
must be scaled down for design use
due to losses (i.e., inlet, outlet,
density currents, etc.) in the
clarifier.
The lab OFR's are generally reduced
by 40 to 50 percent up to an OFR of
800 gpd/sq ft. A design overflow
rate above this value is not
recommended for secondary clarifiers.
Existing POTW's
Method; Refer to 4.10.7.
New POTW's
If multiple weir troughs are required
in a clarifier, space the troughs far
enough apart to prevent high, local-
ized upward velocities within the
unit and resultant solids carry-over.
The weirs should also be distributed
over the entire effluent end (or
perimeter) of the clarifier to pre-
vent high rising velocities in iso-
lated sections of the clarifier.
The upflow velocity in the immediate
vicinity of weirs should be limited
to approximately 18 fph.
Existing POTW's
Method; Separate effluent troughs.
New POTW's
Common geometrical configurations for
rectangular clarifiers are:
Length-width of 3:1 to 4:1.
Width-depth of 1:1 to 2:1.
4.10.10 - 4.10.13
250
-------
DEFICIENCY
CONSIDERATIONS
4.10.14 Inadequate
or no provisions
for scum removal
from secondary
clarifiers.
4.10.15 Long scum
lines frequently
become clogged.
4.10.16 Scum will not
flow from scum tanks
once subnatant is
pumped out.
Existing POTW's
Method: Provide polymer addition
system to enhance settling. Upgrade
the clarifier (s) to attain proper
geometrical configuration.
New POTW's
Provide a scum removal system which
discharges scum to a separate hold-
ing tank and does not recycle scum
back into the treatment system.
The scum should be disposed of sepa-
rately along with sludge hauled from
the plant.
Existing POTW's
Method; Install a scum trough that
discharges to a scum collection pit.
Install a skimmer on circular clari-
fiers.
New POTW's
Eliminate long scum lines from POTW
designs. If required, provide facil-
ities to flush scum pumps after they
have shut off in order to clear the
pumps and scum lines of residual
material. Also, provide clean-outs
along entire length of scum piping.
Existing PQTW's
Method; Install macerator upstream
of scum pumps. Install pump flushing
system to flush lines after each
pumping cycle. Install clean-outs
along the length of the scum lines
and hose bibs to allow manual flush-
ing.
Materials: Piping, solenoid valves,
timer, and related appurtenances.
New and Existing POTW's
Provide sloped bottoms in scum tanks
to enhance scum removal. In addi-
tion, provide a water tap at the scum
tanks to allow the operator to peri-
4.10.13 - 4.10.16
251
-------
DEFICIENCY
CONSIDERATIONS
4.10.17 Sludge lines
periodically clog
with rags, and no
back-flush facil-
ities are provided.
4.10.18 Inability to
conveniently dewater
scum pits.
4.10.19 Inadequate
consideration of
freezing problems
and effect of cold
temperatures on
efficiency of
biological
treatment.
odically flush out excess scum and
prevent scum build-ups.
New and Existing POTW's
Provide bolted flanges and flexible
couplings in exposed sludge piping
to facilitate pipe dismantling and
the insertion of cleaning equipment.
Tees with 1.5- to 2.5-inch hose con-
nections should be placed at the
ends of long pipe runs to allow
rodding and flushing of the sludge
piping.
New and Existing POTW's
Scum pits should be provided with
permanent scum pumps orf as a mini-
mum, a sump into which a portable
pump can be lowered. The floor of
the scum pit should slope toward the
pump-out sump. Refer to 4.10.16.
New POTW's
In cold weather regions, considera-
tion should be given to using in-
ground tanks and also providing
covers over clarifiers. Piping,
such as chemical addition and util-
ity water lines, to clarifiers should
be heat traced. Input from operators
at existing POTWs in the area should
be solicited in order to identify
the need to cover equipment.
Method:
Existing POTW's
Construct an earthern berm
around above-ground tanks to insu-
late the tank, install wind shields
around the tank perimeter, and
provide covers over open tanks.
Piping (such as chemical addition
and utility water lines) to clari-
fiers should be heat traced.
Materials; Commercially-available
tank covers, stainless steel or
fiberglass windshields.
4.10.16 - 4.10.19
252
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 4.11 Oxidation Ditch
4.11.1 Inadequate
consideration for
alkalinity adjust-
ment.
4.11.2 Insufficient
mixing to prevent
solids deposition
and provide uniform
SS and D.O. concen-
trations in the
basin.
4.11.3 Inadequate
aeration capacity.
New and Existing POTW's
Refer to 4.1.3.
New POTW's
Design channel flow velocities of 1
to 2 feet per second to ensure thor-
ough mixing and to prevent solids
settling. Normally, for a standard
27.5-inch rotor, 16,000 gallons of
ditch volume per foot of rotor
length will provide a channel veloc-
ity sufficient to maintain solids in
suspension. Refer to 4.1.5.
Existing POTW's
Method; Increase speed of rotor or
depth of rotor submergence. Consult
the equipment manufacturer: if the
rotor speed exceeds 90 rpm and a 6-
inch depth of immersion for
27-1/2-inch rotors; if the rotor
speed exceeds 60 rpm and a 10-inch
immersion for a 42-inch rotor
installation. If sufficient mixing
continues to be a problem, add
another rotor to the channel.
Install baffles in the channel to
improve mixing patterns.
New PQTW's
Consult manufacturer's design cri-
teria for oxygenation capacity ver-
sus rotor speed and depth of submer-
gence. Provide adjustable effluent
weir to allow varying the liquid
level in the channel in order to
regulate the amount of oxygen
transfer. Refer to 4.2.2.
4.11.1 - 4.11.3
253
-------
DEFICIENCY
CONSIDERATIONS
4.11.4 Inadequate
screening of raw wastes
causes plugging of aera-
tors and return/ waste
sludge pumping system.
4.11.5 Inflexible
design does not permit
isolation of reactors
and changes in flow
schemes for maintenance
purposes and/or to ad-
just for changes in
waste characteristics.
Existing PQTW's
Method; Increase rotor speed and/or
depth of rotor immersion. Consult
equipment manufacturer's design
curves for rotor speed and depth of
immersion versus oxidation
capacity. Refer to 4.11.2.
New and Existing POTWs
Refer to 4.1.6 and 4.8.1.
New POTW's
For those installations which have a
varied usage (loading) over the year
(roadside rest areas, amusement
parks, etc.), it is desirable to use
the following layout. During the
winter the outer ditch would normally
be out of operation.
Bar
Screen
Settled Sludge
Refcjm
-Rotors
r
I
»> ^
Ditch No. 1
Ditch No. 2
-------
DEFICIENCY
CONSIDERATIONS
and observation of
return and waste
activated sludge.
4.11.8 Inadequate
consideration of
debris in wastewater,
4.11.9 Inadequate
provision for by-
passing aeration
basin.
4.11.10 Improper
sidewater depth
(SWD) and baf-
fling cause
splashing prob-
lems in basin.
4.11.11 Inability
to control and
measure mixed
liquor flow dis-
tribution to multiple
secondary clarifiers.
4.11.12 Inadequate
consideration of
impact of changing
aeration basin
levels on aerator
performance.
New and Existing POTW's
Refer to 4.1.6.
New and Existing PQTW's
Refer to 4.1.7 and 4.11.5.
New and Existing POTW's
Provide splash shields adjacent to
rotor installation on each side of
ditch. Consult manufacturer's
design data for rotor size; too large
a rotor will cause excessive splash-
ing (and velocity through ditch).
Refer to 4.1.12.
New and Existing POTW's
Refer to 4.1.13 and 4.10.8.
New POTW's
The depth the rotor is submerged
affects the aeration capacity of the
units; therefore, the oxidation
ditch design should include provi-
sions for adjusting the liquid level
in the channel.
Method:
Existing POTW's
Install an adjustable
4.11.13 Improper
installation of
flow control walls
effluent gate in the channel to
allow the operator to change the
rotor submergence.
New POTW's
The ends of the oxidation ditch
must be rounded to prevent eddying
4.11.7 - 4.11.13
255
-------
DEFICIENCY
CONSIDERATIONS
results in inade-
quate mixing.
4.11.14 Improper place-
ment of gear box drains
causes oil to drain
into aeration basin.
4.11.15 Improper selec-
tion of bearings which
are not compatible
with excessive moisture,
4.11.16 Improper
support of rotors
results in mis-
alignment and
premature bearing
failure.
4.11.17 Spray from
surface aerators
makes walkways
slippery.
4.11.18 Inadequate
consideration of
freezing problems
and effect of cold
temperatures on
efficiency of bio-
logical treatment.
and dead areas, and the outside
edges of the curves must always be
given erosion protection.
Existing POTW's
Method; Install baffles or guide
vanes to prevent eddying and dead
areas.
New and Existing POTW's
Refer to 4.3.6.
New POTW's
Provide sealed bearings or bearing
closures; use pre-mounted bearings or
pillow blocks with labyrinth seals.
Existing POTW's
Method; Replace bearings with seal-
ed-type bearings.
New POTW1s
Properly mount rotors according to
manufacturer's specifications. Shaft
deflection should be held to no more
than 0.0002 inch per inch.
Method:
Existing PQTW's
Properly support and (shim)
align rotors according to manufac-
turer's specifications.
New and Existing POTW's
Refer to 4.3.9.
New and Existing POTW's
In cold weather regions, provide
protective housings over rotors
to avoid damage or inoperability due
to ice build-up. Rotors should be
sized to handle MLSS concentrations
up to 10,000 mg/L for winter opera-
tion. Refer to 4.1.21.
4.11.13 - 4.11.18
256
-------
Design Considerations
Category: 5.0 Oxygen
Activated
Sludge
Unit Operation/Component:.
5.1 Aeration Basin
DEFICIENCY
5.1.1 Inadequate
access for maintenance
to antifoam spray head-
ers in covered tanks.
CONSIDERATIONS
New POTWs
Lay out spray headers longitudinally
along the covered basin (reactor).
Install spray header into hangers
suspended from cover. The connection
between the feeder and each header
should be a quick disconnect type.
Provide access ports on reactor
sidewall in line with each spray
header. The header can then be
removed for maintenance by removing
the access port, disconnecting the
header from the feeder, rotating the
header 180°, and sliding the header
out of the reactor on the suspended
hangers. Refer to sketch.
Plan View
Spray
Feeder
Section View
5.1.1
257
-------
DEFICIENCY
CONSIDERATIONS
Existing POTW's
Method: Install strainers on spray
water supply line to minimize clog-
ging of spray nozzles. At next
scheduled dewatering of reactor,
install accessible flushing taps to
backflush spray headers and feed
lines.
Unit
Operation/Component :
5.
2
Air
Compressors
5.2.1 Inadequate turn-
down capability due to
selection of rotary
compressor.
New POTW's
Evaluate the use and efficiency of
reciprocating and centrifugal com-
pressors to supply air to the pres-
sure swing adsorption oxygen supply
system. The compressor should be
able to be turned down or idled dur-
ing periods of low demand to conserve
energy.
Existing POTW's
Method; Replace existing rotary com-
pressor with a centrifugal or recip-
rocating compressor. Modify control
equipment to vary the loading of the
compressor as a function of oxygen
(pressure) requirement.
Unit Operation/Component: 5.3 D.O. Measurement
5.3.1 Inadequate access
to D.O. measuring equip-
ment due to mounting in
flanged portholes.
New POTW's
Provide for mounting the probes
through access ports as shown in the
sketch. This will allow convenient
removal of probes for maintenance/
calibration. Note: Tap through dust
cover should be of adequate size to
pass end coupler. Utilize a split
grommet for penetration through
cover.
5.1.1 - 5.3.1
258
-------
DEFICIENCY
CONSIDERATIONS
Existing POTWs
Method 1; Replace the existing
flange nuts and bolts with locking
latches as shown in the sketch for
Method 1. This will facilitate
removal of the D.O. probe for cali-
bration and/or maintenance. Note;
Maintain existing gasketing and seals
around flange penetration.
5.3.1
259
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
Replace Flange Nut &
Bolts With Locking
Latches
Existing POTWs
Method 2; Modify the top portion of
the flange to accept the addition of
piping and dust cover as shown in the
sketch for Method 2. Extend the pipe
penetration below the water surface
as per the sample port.
Materials; Materials used must be
suitable for oxygen service.
5.3.1
260
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
Modify Flange & Add
Access As Per Sample
Port
Extend Pipe Penetration
Below Water Surface
As Per Sample Port
Unit Operation/Component: 5.4 D.O. Control
5.4.1 Inadequate access
to D.O. measuring equip-
ment due to mounting in
flanged portholes.
New and Existing POTW's
Refer to 5.3.1.
Unit Operation/Component: 5.5 Pressure Swing Absorption
5.5.1 Inadequate turn-
down capability due to
selection of rotary com-
pressor .
New and Existing POTW's
Refer to 5.2.1.
5.3.1 - 5.5.1
261
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 5.6 Oxygen Gas Flow Control
5.6.1 Overly sensitive
instrumentation respond-
ing to hydraulic ripples
and cycling 02 gas flow.
New POTW's
Provide reactor pressure measurement
instrumentation with signal dampening
capability.
Existing PQTW's
Method; Modify pressure measurement
instrumentation to dampen reactor
pressure signals. This may include
replacement of the differential pres-
sure transmitter or modification of
the existing unit.
Unit Operation/Component: 5.7 Influent Flow Control
5.7.1 Inadequate for-
ward flow control caus-
ing ripples in reactor.
New and Existing POTW's
Provide an accessible stilling well
around level probe/bubbler tube in
forward flow 'wet well. Locate probe
in calm area of wet well.
Unit Operation/Component: 5.8 Sampling and Monitoring
5.8.1 Inadequate con-
densate removal in reac-
tor gas sample lines.
5.8.2 Inadequate con-
sideration for freezing
of reactor gas sample
lines.
New and Existing POTW's
Provide condensate removal traps and
moisture indicator/detectors down-
stream of the traps. This will serve
to protect the oxygen and lower
explosive limit analyzers from mois-
ture damage.
New and Existing POTW's
The humid air space in the oxygen
reactor is sampled for oxygen and
lower explosive limit analysis;
therefore, the exposed sample lines
upstream of the condensate trap
should be heat traced to prevent
freezing.
5.6.1 - 5.8.2
262
-------
Design Considerations
Category: 6.0 Trickling
Filter
V-a-^-
Unit Operation/Component:.
6.1 Trickling Filter
DEFICIENCY
6.1.1 Improper design
and installation of
distribution arms
cause clogging and
rotation problems.
CONSIDERATIONS
To preclude
problems:
New POTW's
distribution arm clogging
1. Provide a minimum 2" diameter
port size.
2. Provide "quick opening" gates
at the end of each arm to
permit easy flushing.
3. Provide preliminary grit and
rag removal. Shredding or
grinding of rags is insuffi-
cient; they should be
removed.
To prevent rotary reaction distribu-
tion arm moving too slowly for ade-
quate distribution:
1. Provide for adequate flow
recirculation during periods
of low flow.
2. Assure filter feed pumps have
sufficient discharge head to
drive rotary distributor.
Existing POTW's
Method; To minimize clogging prob-
lems in the distribution arms because
port sizes are too small, provide
preliminary screening to remove large
solids. (Remove rags rather than
just grinding them.)
6.1.1
263
-------
DEFICIENCY
CONSIDERATIONS
6.1.2 Side wall not
high enough to prevent
splashing or aerosol
drifting.
6.1.3 Lack of flexibil-
ity to flood the filter,
6.1.4 Lack of flexibil-
ity to chlorinate the
filter.
If the rotary reaction distributor
arm moves too slowly for adequate
distribution, provide larger pumps
for higher head and/or provide a
motor drive for the existing distrib-
utor arm.
New POTW's
Assure side wall is at least 2 feet
above top of distributor arm. Pro-
vide 3-foot wide concrete walks
around filter to eliminate fly prob-
lems.
Existing POTW's
Method; Provide splash plates along
the top of the side wall.
Materials; Choose weather-resistant
materials such as galvanized steel,
aluminum, treated wood.
Cost; $10-$25 per linear foot,
depending on material.
New PQTW's
Provide valving and/or slide gates on
inlet and discharge end of filter to
permit flooding.
Existing POTW's
Method; Provide a slide gate in the
effluent pipe of the filter. The
gate can be completely or partially
closed to control flies, snails,
odors, etc.
Materials: Stainless or galvanized
steel, aluminum, etc.
Cost: $3,000 per filter, installed.
New POTW's
Provide separate chlorine solution
line from the influent line to each
filter.
6.1.1 - 6.1.4
264
-------
DEFICIENCY
CONSIDERATIONS
6.1.5 Poor ventilation
of filter causes odor
problems.
6.1.6 Clogging of dis-
tributor orifices caused
by inadequate primary
treatment.
6.1.7 Inflexibility
related to isolation
of reactors and changes
in flow and/or recircu-
lation strategy.
6.1.8 Inadequate con-
sideration of overspray
on filter walls and
resulting fly problems.
Existing POTW's
Method; Tap into the chlorine solu-
tion manifold and run a separate sup-
ply to the filter influent line.
New POTW's
Provide aeration chamber before inlet
to filter to raise D.O. to filter.
Avoid excessive bed depth which may
promote anaerobic conditions. Pro-
vide forced air ventilation. Pre-
chlorinate the filter influent.
Method:
Existing POTW's
Install additional vents
(4"-dia. vertical risers); install
continuous duty blower on vents;
cover filter and deodorize the off
gas; install an aeration chamber
prior to the inlet of the filter to
raise the influent D.O.
New and Existing POTW's
Assure primary treatment is adequate
to remove grease as well as settle-
able solids.
1. Provide "quick opening" gates
at end of distributor arms to
permit easy flushing.
2. Provide for removal of rags
rather than just grinding
them.
New and Existing POTW's
Provide necessary pumps and piping to
permit operator to place reactors in
series or parallel, flood the filter,
take the filter out of service, and
recirculate flow.
New POTW's
Provide side wall height which is a
minimum of 2 feet above the top of
the distributor arm.
6.1.4 - 6.1.8
265
-------
DEFICIENCY
CONSIDERATIONS
6.1.9 Inadequate sizing
of filter unit to meet a
more stringent effluent
limitations requirement.
6.1.10 Insufficient
flow, particularly dur-
ing low flow conditions,
to rotate the distribu-
tion arm.
6.1.11 Excessive slough-
ing from filter due to
excessive organic load-
ing.
6.1.12 Recirculation
of secondary clarifier
effluent causes high
flows through the clari-
fier, resulting in
clarifier solids
carry-over.
6.1.13 No provision for
flushing underdrains.
Existing POTW's
Method; Install splash shields along
the top of the filter wall or build
up the wall to a height 2 feet above
the distributor arm.
New and Existing PQTW's
Provide chemical feed systems (ferric
chloride, alum, etc.) for nutrients
removal and anticipate larger sludge
volumes.
1. Set up for series versus par-
allel operation.
2. Provide for phosphorus and
nitrogen removal.
3. Consider use of plastic media
packed towers.
New and Existing POTW's
Provide recirculation system to
divert effluent from the secondary
clarifier back to the influent of
the secondary' trickling filter.
New and Existing PQTW's
Provide recirculation system to di-
lute influent flow. Provide equali-
zation to dampen anticipated shock
loads.
New and Existing POTW's
Consider recirculation flow during
clarifier design. Specify variable-
speed recirculation pumps. Provide
baffles in clarifier to avoid short
circuiting.
New and Existing POTW's
Provide for flushing underdrains via
peripheral head channel with vertical
vents. Inspection facilities should
also be provided.
6.1.8 - 6.1.13
266
-------
DEFICIENCY
CONSIDERATIONS
6.1.14 Inadequate flow
to filter causes media
plugging.
6.1.15 Inadequate freeze
protection.
6.1.16 Ice build-up on
filter media.
New and Existing POTWs
Provide for recirculation system and
assure media is properly and uniform-
ly sized.
New and Existing POTW's
Provide piping flexibility that will
permit series and parallel operation,
Provide sidewalls 2 feet higher than
top of distribution arm to provide a
wind break. Insulate and heat trace
exposed piping. If warranted, pro-
vide a filter cover.
New and Existing POTW's
Provide adjustable splash plates to
minimize spraying during excessive
cold weather. Provide cover for fil-
ter in extreme cold weather loca-
tions. Provide wind barriers.
Unit Operation/Component: 6.2 Rock Media
6.2.1 Poor ventilation
of filter causes odor
problems.
6.2.2 Improper sizing
of media.
New and Existing POTW's
Assure media is uniform in size.
Provide vents around periphery of
filter. Provide large enough
underdrain system so that conduits
do not exceed 50 percent of capacity
during peak flows. Refer to 6.1.5.
New POTW's
Select media of a uniform size,
between 2" and 4" in diameter.
(Avoid nonuniform media since the
smaller pieces fit between the larger
ones, and thus make it easier for the
slimes to plug the filter.)
Select plastic media which provides a
large surface area per unit and is
uniform in size.
6.1.14 - 6.2.2
267
-------
DEFICIENCY
CONSIDERATIONS
6.2.3 Improper selec-
tion of media without
good weathering proper-
ties.
6.2.4 Inadequate air
circulation provided
during periods of high
flows.
6.2.5 Inadequate flow
to filter causes media
plugging.
6.2.6 Ice build-up on
filter media.
Existing POTW's
Method; Remove existing media and
replace with proper size, or use
plastic media.
New POTW's
Refer to ASCE Manual 13, Filtering
Materials for Sewage Treatment
Plants, prior to selection of filter
media.
Existing POTW's
Method: Replace media.
New and Existing POTW's
Size underdrain system so that it
does not exceed 50 percent full dur-
ing peak flows. Provide vents (ver-
tical risers) around the periphery of
the filter. Provide mechanical ven-
tilating system. Refer to 6.1.5.
New and Existing POTW's
Refer to 6.1.13 and 6.1.14.
New and Existing POTW's
Refer to 6.1.15 and 6.1.16.
Unit Operation/Component: 6.3 Plastic Media
6.3.1 Poor ventilation
of filter causes odor
problems.
6.3.2 Inadequate air
circulation provided
during periods of high
flows.
6.3.3 Inadequate flow
to filter causes media
plugging.
6.3.4 Ice build-up on
filter media.
New and Existing POTW's
Refer to 6.1.5 and 6.2.1.
New and Existing POTW's
Refer to 6.1.5 and 6.2.4.
New and Existing POTW's
Refer to 6.1.13 and 6.1.14.
New and Existing POTW's
Refer to 6.1.15 and 6.1.16.
6.2.2 - 6.3.4
268
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 6.4 Flow Splitting to Filters
6.4.1 Lack of flexi-
bility to flood the
filter.
New and Existing POTW's
Refer to 6.1.3.
6.4.2 Poor ventilation
of filter causes odor
problems.
6.4.3 Inflexibility
related to isolation of
reactors and changes in
flow and/or recircula-
tion strategy.
6.4.4 Inability to
adjust, measure, and
control recirculation
rate.
6.4.5 Insufficient
flow, particularly dur-
ing low flow conditions,
to rotate the distribu-
tion arm.
New and Existing POTWs
Refer to 6.1.5 and 6.2.1.
New and Existing POTWs
Refer to 6.1.7.
New and Existing POTW's
Provide for controls to measure and
adjust recirculation rate (flow
meter, throttling valve, speed con-
trols, etc.).
New and Existing POTW's
Refer to 6.1.10.
Unit Operation/Component: 6.5 Distribution of Media
6.5.1 Improper design
and installation of
distribution arms cause
clogging and rotation
problems.
6.5.2 Lack of flexi-
bility to flood the
filter.
New and Existing POTW's
Refer to 6.1.1.
New and Existing POTW's
Refer to 6.1.3.
6.4.1 - 6.5.2
269
-------
DEFICIENCY
CONSIDERATIONS
6.5.3 Poor ventilation
of filter causes odor
problems.
6.5.4 Clogginq of dis-
tributor orifices caused
by inadequate primary
treatment.
6.5.5 Inadequate air
circulation provided
during periods of high
flows.
6.5.6 Inadequate flow
dosing equipment.
6.5.7 Insufficient
flow, particularly dur-
ing low flow conditions,
to rotate the distribu-
tion arm.
6.5.8 Inadequate freeze
protection.
New and Existing PQTW's
Assure media is of uniform diameter
(sizing) so that smaller size stones
will not fill the voids. Refer to
6.1.5 and 6.2.1.
New and Existing POTW's
Refer to 6.1.6.
New and Existing POTW's
Refer to 6.1.5 and 6.2.4.
New and Existing POTW's
Provide for twin dosing tanks to
ensure that flow is sufficient to
discharge from all nozzles.
New and Existing POTW's
Refer to 6.1.10.
New and Existing POTW's
Refer to 6.1.15 and 6.1.16.
Unit Operation/Component: 6.6 Flow Recirculation
6.6.1 Inflexibility
related to isolation of
reactors and changes in
flow and/or recircula-
tion strategy.
6.6.2 Inadequate con-
sideration of overspray
on filter walls and
resulting fly problems.
New and Existing POTW's
Refer to 6.1.7.
New POTW's
Refer to 6.1.2 and 6.1.8.
6.5.3 - 6.6.2
270
-------
DEFICIENCY
CONSIDERATIONS
6.6.3 Inability to
adjust, measure, and
control recirculation
rate.
6.6.4 Lack of proper
recirculation pumping
capacity.
6.6.5 Recirculation of
secondary clarifier
effluent causes high
flows through the clar-
ifier, resulting in
clarifier solids carry-
over.
6.6.6 Inadequate con-
sideration of effects
of recirculation through
primaries on clarifier
loadings.
6.6.7 Inadequate con-
sideration of effects
on the sludge blanket
of taking recirculation
flow from below weirs of
clarifier.
Existing POTW's
Method: Raise the filter walls and/
or install deflectors on distributor
arms.
New and Existing POTW's
Refer to 6.4.4.
New POTW's
Provide pumps of sufficient discharge
volume and head to rotate distributor
arms and keep media wet.
Existing POTW's
Method: Install larger impeller and/
or horsepower on existing pumps. Use
speed controls, auxiliary pump, or
replacement pump.
New and Existing POTW's
Refer to 6.1.12.
New and Existing POTW's
Conside.r recirculation flows when
sizing clarifiers. Refer to 6.1.12,
New and Existing PQTW's
Take recirculation flow from the
clarifier effluent pipe.
6.6.2 - 6.6.7
271
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 6.7 Secondary Clarifier
6.7.1 Inability to add
flocculants to aid set-
tling.
6.7.2 Inability to
adjust and control flows
to clarifiers.
6.7.3 Recirculation of
secondary clarifier
effluent causes high
flows through the clar-
ifier, resulting in
clarifier solids carry-
over .
6.7.4 Inadequate con-
sideration of clarifier
inlet and outlet struc-
tures to optimize
hydraulic characteris-
tics.
New POTW's
Provide chemical addition facilities
and specify floe clarifiers.
Existing PQTW's
Method; Replace section of existing
piping with mixing chamber. Excavate
and connect chemical feed line to
existing piping at a point to provide
sufficient mixing before next treat-
ment unit.
New and Existing POTW's
Provide piping and throttling valves
necessary to control flow to individ-
ual clarifiers. Also, provide flow
measuring facilities (i.e., weirs,
flow meters, etc.).
New and Existing POTW's
Refer to 6.1.12.
New POTW's
Consider inlet and outlet losses dur-
ing clarifier sizing. Provide inlet
and outlet baffles to minimize turbu-
lence in the clarifier.
Existing POTW's
Method; Inlet baffles should be
installed to dissipate the inlet
velocity, distribute the flow
evenly, and prevent short-circuiting,
Scum baffles should be installed
ahead of overflow weirs. Use mechan-
ical scum skimmers on circular clari-
fiers.
6.7.1 - 6.7.4
272
-------
DEFICIENCY CONSIDERATIONS
6.7.5 Inadequate con- New and Existing POTW's
sideration of effects Refer to 6.6.7.
on the sludge blanket of
taking recirculation
flow from below weirs of
clarifier.
Unit Operation/Component: 6.8 Sludge Pumping
6.8.1 Lack of proper New and Existing POTW's
recirculation pumping Refer to 6.6.4.
capacity.
6.7.5 - 6.8.1
273
-------
Design Considerations
Category: 7.0 Disinfect ion
Unit Operation/Component:.
7.1 General
DEFICIENCY
7.1.1 Hoist rail does
not extend beyond edge
of building, making
cylinder unloading
more difficult.
7.1.2 No provision for
sampling at outfall.
7.1.3 Lack of con-
sideration of upstream
NH3 concentration.
CONSIDERATIONS
New and Existing POTW's
Provide hoist rail which extends
beyond edge of building to facilitate
unloading chlorine cylinders from
truck or rail car. Hoist rail should
be high enough to pick up a cylinder
off the truck, and have sufficient
clearance to lift one cylinder over
another.
New and Existing POTW's
Provide access to outfall for manual
sampling, or provide automatic com-
posite sampler with sample transfer
pump.
New POTW's
Since NH3 exerts a chlorine demand,
the upstream NH3 concentration must
be considered. NH3 monitoring
(occasional or routine) should be
provided, and the pH should be con-
trolled to prevent the formation of
noxious products during the reaction
of Cl2 and NH3.
Method:
Existing POTW's
Knowledge of the upstream
NH3 concentration is important
because NH3 in the waste stream
combines with the Cl2. The NH3
concentration can be determined
7.1.1 - 7.1.3
274
-------
DEFICIENCY
CONSIDERATIONS
7.1.4 Improper loca-
tion of utility water
suction draws excess
solids into system.
7.1.5 Inadequate con-
sideration of present
and future flows in
equipment sizing.
quickly by means of a specific ion
electrode, and the Cl2 feed rate
can be adjusted as required.
New POTW's
Locate the utility water suction a
minimum of 2 feet from the bottom of
the chlorine contact chamber.
Existing POTW's
Method; Relocate the utility water
suction line to a higher elevation
(i.e., 2-ft minimum from tank
bottom), or construct an overflow
baffle around the utility water
intake to prevent solids from
entering the system.
New POTW's
Both present and future maximum and
minimum flows must be considered when
sizing disinfection systems. The
chlorine contact tank should be sized
to provide a contact time of 30
minutes at average flow, and not less
than 15 minutes contact time at peak
flow. Local standards should be used
during design.
Chlorination equipment should be
sized to feed approximately 50-100
Ibs Cl2/million gallons treated.
To provide for future flow increases,
equipment can be specified to feed a
range of dosages, and/or dual units
can be installed.
Existing POTW's
Method; I~£ forward flow through the
POTW has increased significantly over
that expected in the original design,
increasing the capacity of the exist-
ing chlorinator or installation of an
additional chlorination/ozonation
system may be required.
7.1.3 - 7.1.5
275
-------
DEFICIENCY
CONSIDERATIONS
7.1.6 Inadequate
safety equipment.
New and Existing POTW's
Adequate safety features and equip-
ment must be included as part of the
chlorination system design. These
requirements are stipulated in each
state's individual design standards
for municipal wastewater works. Two
additional references are the follow-
ing Water Pollution Control Federa-
tion (WPCF) manuals of practice
(MOP) :
MOP No. 1 -- Safety in Waste-
water Works
MOP No. 4 --
Wastewater
Chlorination of
Unit Operation/Component: 7.2 Chlorine Contact Chamber
7.2.1 Lack of scum
removal facilities.
7.2.2 Inadequate use
of concrete coatings,
which slough off tank
walls and plug pipes
and pumps.
New and Existing PQTW's
Provide baffles in the chlorine con-
tact chamber to prevent the dis-
charge of floating solids. Provide a
scum collecting device, such as a
trough, and pump the scum to the col-
lection point for scum from other
sources in the treatment plant or
remove the scum directly from the
POTW.
New POTW's
Epoxy coatings should be used to pro-
tect contact chamber tank walls.
Suggested materials of construction
for handling various disinfection
components are presented in the Water
Pollution Federation Manual of Prac-
tice No. 4.
Method:
Existing POTW's
Drain the existing chlorine
contact tank, scrape off the remain-
ing coating, and apply a new coating
following the guidelines presented.
7.1.6 - 7.2.2
276
-------
DEFICIENCY
CONSIDERATIONS
7.2.3 Improper loca-
tion of chlorine dif-
f user.
7.2.4 Inadequate pro-
vision for sump to
facilitate solids
removal.
7.2.5 Lack of ade-
quate mixing at
addition point.
New POTW's
Locate the chlorine diffuser at the
influent end of the contact chamber
and at the point of maximum turbu-
lence to ensure adequate mixing.
Provide a mixing chamber prior to
the contact tank.
Method:
Existing POTW's
Relocate the chlorine dif-
fuser at the point of maximum turbu-
lence to ensure adequate mixing. If
relocation is not possible, add a
mechanical mixing device just down-
stream of the diffuser. If neces-
sary, relocate the chlorine residual
analyzer so that it is 30 to 45 sec-
onds downstream of the chlorine dif-
fuser .
New PQTW's
Provide a sump and drainline in the
chlorine contact chamber so that
solids can be hosed to the sump dur-
ing periodic tank clean-out.
Existing POTW's
Method: Construct a sump in the con-
tact chamber; a portable pump can be
used to dewater the sump during cham-
ber cleaning operations.
New POTW's
Chlorine should be added at the point
of maximum turbulence immediately
upstream of the chlorine contact
tank. The best mixing can be
obtained by diffusing the chlorine
solution in a hydraulic pump or in a
conduit or channel that has been
designed to provide turbulent flow.
If high-velocity flows cannot be pro-
vided by hydraulic pumps, use mechan-
ical mixers, and apply the chlorine
solution upstream of the mixer.
7.2.3 - 7.2.5
277
-------
DEFICIENCY
CONSIDERATIONS
7.2.6 Insufficient
contact time in out-
fall.
7.2.7 Inadequate con-
sideration of possible
short-circuiting.
7.2.8 Inadequate con-
sideration of potential
for flooding baffles
during high flows.
Existing POTW's
Method; Refer to 7.2.3.
New POTW's
Size the chlorine contact chamber to
provide a minimum contact time of 15
minutes at peak flow and 30 minutes
at average flow. Refer to local
standards during design of the
chlorination system.
Method:
Existing POTW's
The chlorine contact chamber
should provide a minimum contact time
of 15 minutes at peak flows and 30
minutes at average flow. If these
times are not being achieved, an
addition to the contact chamber may
be required. Installation of a mixer
should also be utilized to achieve
proper Cl2 residuals.
New POTW's
Design the chlorine contact chamber
to approximate plug flow. Design
long, narrow sections with length-to-
width ratios of at least 10:1.
Existing POTW's
Method: Provide baffling in the
channels to ensure complete mixing
and a sufficient contact time.
New POTW's
During the design phase, a hydraulic
profile should be formulated for all
units in the treatment plant, con-
sidering both average and peak flow.
In this way, the proper elevations
for the baffles in the chlorine con-
tact chamber can be determined, and
baffle flooding during peak flows
can be avoided.
7. 2.5 - 7.2.8
278
-------
DEFICIENCY
CONSIDERATIONS
7.2.9 Inadequate con-
sideration of present
and future flows in
equipment sizing.
7.2.10 Inadequate
safety equipment.
7.2.11 Improper selec-
tion of construction
materials to minimize
corrosion.
Existing POTW's
Method: If possible, raise the
height of the baffles; otherwise,
install an additional chlorine
contact chamber.
New and Existing POTW's
Refer to 7.1.5.
New and Existing PQTW's
Refer to 7.1.6.
New and Existing POTW's
Refer to Water Pollution Control
Federation Manual of Practice No. 4
(Chlorination of Wastewater), Chapter
6, Table X, for suggested materials
of construction for use in chlorina-
tion facilities. Refer to 7.2.2.
Unit Operation/Component: 7.3 Chlorinator
7.3.1 Lack of adequate
working space behind
chlorinators.
New POTW's
For maintenance purposes, it is
important to provide adequate working
space behind each chlorinator when
sizing the chlorine room. It is
recommended that a minimum of 4 feet
be allowed between the wall and the
back of each chlorinator.
Existing POTW's
Method: Move the chlorinator a mini-
mum of 4 feet from the chlorine room
wall.
Materials; Concrete to enlarge the
chlorinator base and PVC pipe to
lengthen water and chlorine gas
lines.
Cost; If accomplished by the POTW
staff, less than $100 per
chlorinator.
7.2.8 - 7.3.1
279
-------
DEFICIENCY
CONSIDERATIONS
Sketch:
New Position ~ ~
Expanded
Base
"\i L
' ,^ 4' j»
Ch
lorinator
^
Wall
Old Position
7.3.2 Lack of stand-
by equipment.
7.3.3 Inadequate con-
sideration of present
and future flows in
equipment sizing.
7.3.4 Inadequate feed-
back for control of
chlorine/ozone feed
rate.
7.3.5 Inadequate
safety equipment.
New and Existing POTW's
To ensure reliable disinfection of
the POTW effluent, it is imperative
that a stand-by chlorinator be pro-
vided.
New and Existing POTW's
Refer to 7.1.5.
New and Existing POTW's
For POTWs with a capacity greater
than 1 mgd, the utilization of an on-
line chlorine analyzer should be con-
sidered. This would allow the plant
operator to continuously monitor the
chlorine residual in the plant efflu-
ent and help minimize both over- and
under-dosing chlorine. The flexibil-
ity to pace the plant chlorinators
based on effluent flow and/or chlor-
ine residual should also be provided.
New and Existing POTW's
Refer to 7.1.6.
7.3.1- 7.3.5
280
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 7.4 Chlorine Control
7.4.1 Inadequate con-
sideration of potential
flow ranges during
selection of automatic
control equipment.
7.4.2 Inadequate feed-
back for control of
chlorine/ozone feed
rate.
New and Existing POTW's
The most effective method of chlorin-
ation control is the compound loop
system. This arrangement uses two
separate and independent signals to
the chlorination device: a flow-
proportional signal to the chlorine
metering orifice, and a chlorine
residual signal to the vacuum regu-
lating valve (the dosage control
device). The chlorination mechanism
compounds these two signals to
achieve a wide range of operation in
excess of 100 to 1.
New and Existing POTW's
Refer to 7.3.4.
Unit Operation/Component: 7.5 Dechlorinator
7.5.1 Lack of stand-
by equipment.
7.5.2 Inadequate con-
sideration of present
and future flows in
equipment sizing.
New and Exi s t ing POTW's
To ensure reliable dechlorination of
the POTW effluent, it is imperative
that a stand-by dechlorinator be
provided.
New and Existing POTW's
Both present and future maximum and
minimum flows must be considered when
sizing equipment.
If dechlorination is accomplished by
means of sulfur dioxide (S02), the
equipment should be sized to feed 1
mg/L S02 to dechlorinate 1 mg/L of
chlorine residual (free or combined)
based on the expected range of chlor-
7.4.1 - 7.5.2
281
-------
DEFICIENCY CONSIDERATIONS
ine residuals. The SO2 feed rate
can be paced on the basis of chlorine
residual. S02 can be added by
means of a diffuser, and, since the
dechlor ination reaction is instantan-
eous, no S02 contact chamber is
required.
If sodium metabisulf ate (Na2S2°5) is
used for dechlor ination, the equip-
ment should be sized to feed 1.5
parts metabisulf ite per part
chlor ine .
Size activated carbon dechlorination
beds for a wastewater application
rate of 3 gpm/sq ft and contact time
of 15 to 20 minutes.
Unit Operation/Component: 7.6 Ozone Contact Vessel
7.6.1 Inadequate con- New and Existing PQTW's
sideration of present The ozone contact vessel should be
and future flows in sized to provide 10 minutes contact
equipment sizing. time at peak flows.
7.6.2 Inadequate New and Existing POTW's
safety equipment. Refer to 7.1.6.
Unit Operation/Component: 7.7 Ozone Generator
7.7.1 Inadequate con- New POTW's
sideration of present Ozone dosage equipment sizing should
and future flows in be based on ozone demand tests for
equipment sizing. the wastewater. The range of dosages
should be based on the expected flow
rate range and on the range of ozone
demands expected.
Existing PQTW's
Method; Modify or replace the exist-
ing unit(s) to ensure adequate ozone
generation capacity is available.
Refer to 7.1.5.
7.5.2 - 7.7.1
282
-------
DEFICIENCY
CONSIDERATIONS
7.7.2 Inadequate feed-
back for control of
chlorine/ozone feed
rate.
7.7.3 Inadequate
safety equipment.
New and Existing POTW's
The ozone feed rate can be controlled
by the output signal from the efflu-
ent flow meter. Ozone feed rate con-
trol by an on-line ozone residual
meter is technically feasible, but
not widely used.
New and Existing PQTW's
Refer to 7.1.6.
Unit Operation/Component: 7.8 Ozone Controller
7.8.1 Inadequate feed-
back for control of
chlorine/ozone feed
rate.
New and Existing POTW's
Refer to 7.7.2.
Unit Operation/Component: 7.9 Safety
7.9.1 Inadequate con-
sideration of emergency
alarms, controls, and
ventilation.
7.9.2 Floor drains
from chlorine room are
connected to floor
drains from other
rooms.
New and Existing POTW's
For detailed guidelines on safety in
disinfection systems, consult the
following:
WPCF MOP No. 1 (Safety in
Wastewater Works) -- Sections
3.28 and 6.15.
WPCF MOP No. 4 (Chlorination
of Wastewater) -- Chapter 6
(Chlorination Safety).
New and Existing POTW's
In order to prevent chlorine leaks
from penetrating other areas through
the floor drains, the chlorine room
floor drains should not be connected
to any other floor drains in the
plant.
7.7.2 - 7.9.2
283
-------
DEFICIENCY CONSIDERATIONS
7.9.3 Inadequate New and Existing POTW's
safety equipment. Refer to 7.1.6.
7.9.4 Improper temper- New POTW's
ature control in chlor- The chlorine storage area temperature
ine tank storage area. should not be allowed to drop below
10°C (50°F) to prevent liquefaction
of chlorine gas in the header. The
temperature should be kept below
70°C (158°F) in the storage area
to keep the tank from bursting.
Existing POTW's
Method: Space heaters and ventila-
tion fans should be installed in
chlorine tank storage area to main-
tain room temperature between 60°F
and 8QOF.
7.9.3 - 7.9.4
284
-------
Design Considerations
Category:8.0 Anaerobic
Digestion
Unit Operation/Component:
8.1 General
DEFICIENCY
8.1.1 Inadequate con-
sideration of the impact
of the supernatant side-
stream on other unit
operations.
8.1.2 Inadequate pro-
vision for sampling.
8.1.3 Inadequate treat-
ment of digester gas
before utilization in
plant.
CONSIDERATIONS
New PQTW'5
Consider the additional pollutant
loading due to sidestream return.
The major pollutants to be considered
are BOD and suspended solids, with
pH and odor problems also of concern.
Method:
Existing POTW's
Provide pumps and piping
necessary to route digester superna-
tant to multiple points in the plant.
New and Existing POTW's
Provide sampling locations such that
samples can be obtained from:
Raw sludge.
Digester (active)
Digested sludge.
Supernatant.
Digester gas.
sludge.
New and Existing POTW's
If gas is to be burned as a fuel,
install a wet or dry gas scrubber to
remove impurities (mainly hydrogen
sulfide).
8.1.1 - 8.1.3
285
-------
DEFICIENCY
CONSIDERATIONS
8.1.4 Inadequate pro-
vision for digester
cleaning.
8.1.5 Insufficient
capacity at peak loads.
8.1.6 No provision for
cleaning sludge heating
lines.
8.1.7 Lack of pH and
temperature control
facilities.
8.1.8 Pressure relief
valves are exposed to
cold weather, resulting
in freezing.
New and Existing POTW's
Provide facilities for grit and
debris collection and removal from
the digester tank. Provide an access
way and high pressure water supply as
a minimum. Considerations include
grit and debris disposal, sludge
storage during cleaning, tank drain-
ing, and disposal of rinse waters.
New and Existing POTW's
Ensure digester pumps and pipes are
sized for both maximum expected
sludge production rate and maximum
sludge removal rate.
New POTW's
Ensure that access for cleaning of
the heat exchange equipment is pro-
vided.
Method:
Existing POTW's
Install flushing taps in
heating lines to allow proper clean-
ing.
New POTW's
Provide pH and temperature probes
within the active portion of the
digester.
Method:
Existing PQTW's
Retrofit digester with pH
and temperature probes within the
active portion of the digester.
New and Existing PQTW's
Provide insulation, heat tracing,
and/or a shelter for pressure relief
valves to minimize environmental
effects.
8.1.4 - 8.1.8
286
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 8.2 Single-stage Digester
8.2.1 Inadequate con-
sideration of the impact
of the supernatant side-
stream on other unit
operations.
8.2.2 Lack of sludge
thickening ahead of
digester.
8.2.3 Inadequate loca-
tion of supernatant
withdrawal.
8.2.4 Inadequate pro-
vision for sampling.
8.2.5 Inability to
feed chemicals during
process upset.
New and Existing POTW's
Refer to 8.1.1.
New and Existing POTW's
During the design phase, the econom-
ics of feeding a concentrated sludge
versus a diluted sludge to the diges-
ter should be evaluated. Generally,
sludge thickening prior to digestion
is desirable.
New POTW's
Provide the flexibility for superna-
tant removal at various levels in the
upper portion of the digester. This
may be extremely important at small
plants with variable operating sched-
ules.
Method:
Existing POTW's
Install a telescopic swing
valve to allow draw-off of superna-
tant at varying levels.
New and Existing PQTW's
Refer to 8.1.2.
New POTW's
Provide the capability to add chemi-
cals to the digester, including
facilities to mix the digester con-
tents and chemicals following addi-
tion.
Method:
Existing POTW's
Install a hatch in the
digester cover to allow chemical
addition.
8.2.1 - 8.2.5
287
-------
DEFICIENCY
CONSIDERATIONS
8.2.6 Inadequate
treatment of digester
gas before utilization
in plant.
8.2.7 Inadequate pro-
vision for digester
cleaning.
8.2.8 Pressure relief
valves are exposed to
cold weather, resulting
in freezing.
New and Existing POTW's
Refer to 8.1.3.
New and Existing POTW's
Refer to 8.1.4.
New and Existing POTW's
Refer to 8.1.8.
Unit Operation/Component: 8.3 Two-Stage Digester
8.3.1 Inadequate con-
sideration of the
impact of the superna-
tant sidestream on
other unit operations.
8.3.2 Lack of sludge
thickening ahead of
digester.
8.3.3 Inadequate loca-
tion of supernatant
withdrawal.
8.3.4. Inability to
isolate and feed sludge
to all digesters.
New and Existing POTW's
Refer to 8.1.1.
Method; Refer to 8.1.1.
New and Existing POTW's
Refer to 8.2.2.
New and Existing POTW's
Refer to 8.2.3.
New POTW's
Provide pumps and piping arrangements
such that sludge can be fed to all
digesters, both first- and second-
stage.
Existing POTW's
Method: Provide piping and valves
necessary to route raw sludge to any
one of multiple digesters.
8.2.6 - 8.3.4
288
-------
DEFICIENCY
CONSIDERATIONS
8.3.5 Inadequate pro-
vision for sampling.
8.3.6. Inability to
feed chemicals during
process upset.
8.3.7
ing.
Inadequate mix-
8.3.8 Inadequate treat-
ment of digester gas
before utilization in
plant.
8.3.9 Inadequate pro-
vision for digester
cleaning.
8.3.10 Pressure relief
valves are exposed to
cold weather, resulting
in freezing.
New and Existing POTW's
Refer to 8.1.2.
New and Existing POTW's
Refer to 8.2.5.
New and Existing POTW's
Provide external (i.e., mechanical)
mixers or internal (gas circulation)
mixers to agitate the digester con-
tents. Select the proper velocity
gradient for design (typically 50 to
80 sec"-'-) . Take into consideration
the temperature, solids concentra-
tion, and volatile content of the
sludge at which the digester is to be
operated.
New and Existing POTW's
Refer to 8.1.3.
New and Existing PQTW's
Refer to 8.1.4.
New and Existing POTW's
Refer to 8.1.8.
Unit Operation/Component: 8.4 Gas Collection
8.4.1 Inadequate pro-
vision for sampling.
8.4.2 Inadequate place-
ment of condensate traps
on gas lines.
New and Existing POTW's
Provide sampling ports to allow for
sampling of digester gas. Refer to
8.1.2.
New and Existing POTW's
Ensure that traps are placed at the
lowest points in the gas collection
system.
8.3.5 - 8.4.2
289
-------
DEFICIENCY
CONSIDERATIONS
8.4.3 Inadequate treat-
ment of digester gas
before utilization in
plant.
8.4.4 Inadequate pro-
vision for high/low gas
pressure alarms.
8.4.5 Lack of conden-
sate and flame traps in
lines.
8.4.6 Pressure relief
valves are exposed to
cold weather, resulting
in freezing.
New and Existing POTW's
Refer to 8.1.3.
New and Existing POTW's
Provide high/low pressure alarms in
the digesters, the gas collection/
cleaning equipment, and the gas stor-
age facilities.
New and Existing POTW's
Provide condensate and flame traps in
gas lines and at pressure relief
valves. Install flame traps as close
as possible upstream of all sources
of ignition.
New and Existing PQTW's
Refer to 8.1.8.
Unit Operation/Component: 8.5 Gas Measurement
8.5.1 Individual gas
measurement not pro-
vided on multiple
digesters.
8.5.2 Pressure relief
valves are exposed to
cold weather, result-
ing in freezing.
New and Existing POTW's
Provide gas measurement equipment
(such as rotometers, venturi meters,
or rotary displacement type meters)
on all digesters.
New and Existing POTW's
Refer to 8.1.8.
Unit Operation/Component: 8.6 Supernatant Withdrawal
8.6.1 No provision for
changing supernatant
withdrawal point within
tank.
New and Existing POTW's
Provide digester with variable level
supernatant removal mechanism such as
a telescopic valve or floating mech-
anism. Refer to 8.2.3.
8.4.3 - 8.6.1
290
-------
DEFICIENCY
CONSIDERATIONS
8.6.2 Inadequate con-
sideration of the
impact of the superna-
tant sidestream on
other unit operations.
8.6.3 Inadequate loca-
tion of supernatant
withdrawal.
8.6.4 Inadequate pro-
vision for sampling.
8.6.5 Improper use of
water seals on pumps.
New and Existing PQTW's
Refer to 8.1.1.
New and Existing POTWs
Refer to 8.2.3.
New and Existing POTW's
Refer to 8.1.2.
New and Existing POTW's
Utilize mechanical seals on digester
pumps. Provide an air break in seal
water lines if potable water is used.
Specify proper seal water pressure to
minimize pumpage and excessive loss
of seal water.
Unit Operation/Component: 8.7 Supernatant Disposal
8.7.1 No provision for
changing supernatant
disposal point within
plant.
8.7.2 Inadequate con-
sideration of the impact
of the supernatant side-
streams on other unit
operations.
New and Existing POTW's
Provide piping to allow disposal of
supernatant liquor at a minimum of
two points in the plant (i.e., thick-
ener and primary tanks) to provide
operational flexibility.
New and Existing POTW's
Refer to 8.1.1.
Unit Operation/Component: 8.8 Heating
8.8.1 Inadequate insu-
lation of heating pipes.
New and Existing POTW's
Provide insulation on all pipes
exposed to the environment to prevent
heat loss.
8.6.2 - 8.8.1
291
-------
DEFICIENCY
CONSIDERATIONS
8.8.2 Inadequate siz-
ing of heat exchanger.
8.8.3 No provision for
cleaning sludge heating
lines.
8.8.4 Improper use of
water seals on pumps
around digester.
New PQTW's
When sizing heat exchangers, heat
losses through the top, bottom, and
sides of the digester must be con-
sidered. It is noted that the heat
transfer coefficients for the three
are different.
Existing POTW's
Method; If exchanger is undersized,
try insulating system to minimize
losses and retain heat within system,
If this fails, replace exchanger.
New and Existing POTW's
Refer to 8.1.6.
New and Existing POTW's
Refer to 8.6.5.
Unit Operation/Component: 8.9 Maintenance
8.9.1 Inadequate pro-
vision for digester
cleaning.
New and Existing POTW's
Refer to 8.1.4.
Unit Operation/Component: 8.10 Safety
8.10.1 Inadequate pro-
vision for digester
cleaning.
8.10.2 Inadequate pro-
vision for high/low gas
pressure alarms.
8.10.3 Lack of conden-
sate and flame traps in
gas lines.
New and Existing POTW's
Refer to 8.1.4.
New and Existing POTW's
Refer to 8.4.4.
New and Existing POTW's
Refer to 8.4.5.
8.8.2 - 8.10.3
292
-------
DEFICIENCY
CONSIDERATIONS
8.10.4 Pressure relief
valves are exposed to
cold weather, resulting
in freezing.
New and Existing POTW's
Refer to 8.1.8.
Unit Operation/Component: 8.11 Sludge Withdrawal
8.11.1 Inadequate pro-
vision for sampling.
8.11.2 Inadequate siz-
ing of sludge lines pre-
vents passage of concen-
trated sludge.
8.11.3 Sludge line
from digester to sludge
draw-off pump too long,
resulting in plugging
problems.
8.11.4 Lack of multi-
ple sludge withdrawal
and return points.
8.11.5 Improper use of
water seals on pumps
around digester.
8.11.6 Sludge metering
system inaccurate or
unreliable.
New and Existing POTW's
Refer to 8.1.2.
New and Existing POTW's
As a minimum, provide 4-inch diameter
sludge lines. Install flush-out con-
nections in the sludge piping.
New and Existing POTW's
Minimize distance between digester
and sludge draw-off pump as much as
possible.
New and Existing POTW's
It is particularly desirable for
unmixed digesters to provide multi-
ple sludge withdrawal and return
points. Arrange pumps and piping
such that both the sludge removal
pipe at the bottom of the tank and
the sludge recirculation line can be
utilized for either task.
New and Existing POTW's
Refer to 8.6.5.
New and Existing POTW's
Utilize non-constructing, non-contact
flowmeters (i.e., magnetic, ultrason-
ic) .
8.10.4 - 8.11.6
293
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 8.12 Sludge Recirculation
8.12.1 Inadequate siz-
ing of sludge lines pre-
vents passage of concen-
trated sludge.
8.12.2 Lack of multi-
ple sludge withdrawal
and return points.
8.12.3 Improper use of
water seals on pumps
around digester.
8.12.4 Sludge metering
system inaccurate or
unreliable.
New and Existing POTW's
Refer to 8.11.2.
New and Existing POTWs
Refer to 8.11.4.
New and Existing POTW's
Refer to 8.6.5.
New and Existing POTW's
Refer to 8.11.6.
Unit Operation/Component: 8.13 Sludge Feed
8.13.1 Lack of sludge
thickening ahead of
digester.
8.13.2 Inability to
isolate and feed sludge
to all digesters.
8.13.3 Inadequate num-
ber of sludge feed lines
hinder operation.
8.13.4 Inadequate flow
measurement.
New and'Existing POTW's
Refer to 8.2.2.
New and Existing POTW's
Refer to 8.3.4.
New and Existing POTW's
Provide multiple feed lines (4-inch
minimum diameter) to all digesters.
Specify flushing connections on all
sludge lines.
New and Existing POTW's
Provide non-contract, non-restricting
flow measurement devices on sludge
feed lines such that flow rates to
all digesters can be measured.
8.12.1 - 8.13.4
294
-------
DEFICIENCY
8.13.5 Inadequate siz-
ing of sludge lines pre-
vents passage of concen-
trated sludge.
8.13.6 Improper use of
water seals on pumps
around digester.
8.13.7 Sludge metering
system inaccurate or
unreliable.
CONSIDERATIONS
New and Existing POTW's
Refer to 8.11.2.
New and Existing POTW's
Refer to 8.6.5.
New and Existing PQTW's
Refer to 8.11.6.
8.13.5 - 8.13.7
295
-------
Design Considerations
Category:9.0 Aerobic
Digestion
Unit Operation Component:
9.1 General
DEFICIENCY
9.1.1 Lack of depth
gauges provided on
basins that operate
at varying liquid
depths.
9.1.2 Lack of
thickening ahead
of digestion, and
no provision for
decanting within
the digester.
CONSIDERATIONS
New POTW's
Provide level meters on digestion
tanks, particularly if they are
to be operated via the fill and
draw method, or if the tanks are
covered.
Method:
digester
Existing POTW's
Install
tanks.
level meters on the
Materials; Utilize a level meter
such as a float, bubbler, capaci-
tance probe, or ultrasonic probe.
New POTW's
Compare economics and operational
flexibility of providing a thick-
ener prior to digestion versus a
larger aeration basin and batch
operation of the digester with
periodic decanting.
Existing POTW's
Method: Install a swing valve or
a telescopic valve to allow super-
nating the digester (i.e., period-
ically turn the aeration system off,
allow solids to settle, and then
supernate.
9.1.1 - 9.1.2
296
-------
DEFICIENCY
CONSIDERATIONS
9.1.3 Inadequate con-
sideration of a decrease
in operating efficiency
due to the temperature
drop in winter.
9.1.4 Pressure
relief valve not
provided in area
with high ground-
water, which pro-
hibits batch oper-
ation.
9.1.5 Inadequate con-
sideration of pH con-
trol.
9.1.6 Inadequate
structural design in
common wall construc-
tion, causing struc-
tural failure during
batch operation.
New POTW's
Design the digester for operation
at the lowest predicted winter tem-
perature. Consider diffused aera-
tion rather than surface aerators.
Consider a covered tank or insula-
tion of above-ground tanks.
Existing POTW's
Method; Insulate existing tank if
above ground. Consider replacement
of surface aerators with diffused
aeration.
New and Existing PQTW's
Install pressure relief valves in
tanks constructed in high groundwater
areas to allow emptying tanks without
resultant foundation problems.
New POTW's
If POTW receives industrial wastes
high in Kjeldahl nitrogen, consider
need for addition of alkalinity due
to pH depression during nitrifica-
tion.
Existing PQTW's
Method; If pH control is required,
install a lime feed system (i.e.,
slurry tank, mixer, feed pump,
etc.) .
New POTW's
Ensure that common wall tankage is
capable of maintaining structural in-
tegrity when one side of the tank is
empty.
9.1.3 - 9.1.6
297
-------
DEFICIENCY
CONSIDERATIONS
9.1.7 Lack of flex-
ibility to dewater
small above-ground
tanks by gravity.
9.1.8 Inability to
draw supernatant
off at deep enough
level.
9.1.9 Provisions pro-
vided to add defoamer
to aeration basin, but
not to aerobic digester
Existing PQTW's
Method; Brace the existing common
wall to allow batch operation (i.e.,
allow the tank on one side of the
wall to be full while the adjacent
tank is empty).
New POTW s
If hydraulics permit, make provisions
for gravity dewatering of digestion
tanks.
Existing POTW's
Method: Install a sump in the lowest
portion of the tank. If hydraulics
dictate that gravity flow is not
possible, install a lift pump to
drain the sump.
New POTW's
Provide variable level supernatant
removal mechanism with ability to
withdraw liquid from entire depth of
tank, thereby allowing back-up for
sludge removal and tank dewatering.
Existing PQTW's
Method: Install a telescopic valve
or a swing pipe (with a float) to
provide variable-level supernatant
removal.
New POTW's
Provide a water spray system, as a
minimum, or a defoamer addition
system for the digester to provide
foam control.
Method:
Existing POTW's
Tap into the existing de-
foamer system and install an addi-
tional line and pump (if required)
to feed defoamer to the digester.
9.1.6 - 9.1.9
298
-------
DEFICIENCY
CONSIDERATIONS
9.1.10
freeze
Inadequate
protection.
New POTW's
If climate dictates, ensure that all
above-ground piping and pumping is
insulated and/or heat traced. Con-
sider covering tanks and insulating
above-ground tanks. Utilize diffused
aeration rather than surface aer-
ators.
Existing POTW's
Install insulation and/or
Method; Install insulation and/or
heat tracing around all exposed pipes
where freezing is a problem. If an
above-ground tank is being used,
insulate it by constructing 3r>
earthern berm around the
an
tank walls.
Unit Operation/Component: 9.2 Aerobic Digester
9.2.1 Inadequate con-
sideration of de-
nitrification-induced
settling problems dur-
ing decanting.
9.2.2 Pressure relief
valve not provided in
area with high ground-
water, which prohibits
batch operation.
9.2.3 Inadequate mixing
to prevent solids deposi-
tion and provide uniform
D.O. concentrations.
New POTW's
Minimize time required to decant
digester by proper sizing of decant
pump and/or lines.
Method:
Existing POTW's
Install additional or larger
decant pumps and lines to minimize
time required to decant.
New and Existing POTW's
Refer to 9.1.4.
New POTW's
Ensure that sufficient energy is
supplied to the digester to main-
tain sludge particles in suspension
at the design suspended solids level.
9.1.10 - 9.2.3
299
-------
DEFICIENCY
CONSIDERATIONS
9.2.4 Inadequate free-
board for foam contain-
ment and spray control.
9.2.5 Inadequate ven-
tilation in covered
digesters.
9.2.6 Inadequate
structural design
in common wall con-
struction, causing
structural failure
during batch opera-
tion.
9.2.7 Inadequate
freeze protection.
Existing POTW's
Method; Install an additional sur-
face aerator or upgrade horsepower
of existing aerator. If diffused
aeration is being used, increase
blower capacity.
New and Existing POTW's
As a minimum, supply a 3-ft free-
board around digester tanks.
New POTW's
Review OSHA and state regulations
concerning design of ventilation
systems for wastewater treatment
plants and safety requirements for
confined spaces.
Method:
Existing PQTW's
Provide a ventilation sys-
(i.e., blower, vents, ducts,
or increase the capacity of the
tern
etc.)
existing system.
New and Existing POTW's
Refer to 9.1.6.
New and Existing POTW's
Refer to 9.1.10.
Unit Operation/Component: 9.3 Decanting
9.3.1 Inadequate
consideration of deni-
trification-induced
settling problems dur-
ing decanting.
New and Existing POTW's
Refer to 9.2.1.
9.2.3 - 9.3.1
300
-------
DEFICIENCY
CONSIDERATIONS
9.3.2 Inadequate
supernatant flex-
ibility.
9.3.3 Inability to
visually observe the
quality of supernatant
being drawn off.
9.3.4 Inability to
draw supernatant off
at deep enough level.
9.3.5 Lack of spare
supernatant pump for
both maintenance
purposes and to allow
rapid dewatering of
basin.
9.3.6 Inadequate
freeze protection.
New POTW's
Provide capability to supernate at
varying levels.
Existing POTW's
Method: Replace existing supernatant
withdrawal equipment with variable
level equipment.
Materials; Utilize either a swing
arm or floating decant removal mech-
anism.
New and Existing PQTW's
Provide bleed-off valve on super-
natant line to allow for supernatant
quality inspection.
New and Existing POTW's
Refer to 9.1.8.
New and Existing POTW's
If supernatant is pumped from diges-
ter, provide spare pump or arrange
piping so that an alternate pump can
be used.
New and Existing POTW's
If climate dictates, ensure that
all above-ground piping and pumping
is insulated and/or heat traced.
Refer to 9.1.10.
Unit Operation/Component: 9.4 Clarification
9.4.1 Inadequate con-
sideration of deni-
trification-induced
settling problems dur-
ing decanting.
New and Existing POTW's
Refer to 9.2.1.
9.3.2 - 9.4.1
301
-------
DEFICIENCY
CONSIDERATIONS
9.4.2 Inadequate
supernatant flexibility.
9.4.3 Inability to
visually observe the
quality of supernatant
being drawn off.
New and Existing PQTW's
Refer to 9.1.8 and 9.3.2.
New and Existing PQTW's
Refer to 9.3.3.
Unit Operation/Component: 9.5 Diffused Aeration
9.5.1 Inadequate
air supply.
9.5.2 Inadequate
consideration of
diffuser maintenance
problems and clogging
tendency.
9.5.3 Inadequate
mixing to prevent
solids deposition and
provide uniform D.O.
concentrations.
New PQTW's
Ensure that sufficient oxygen is
supplied to meet oxygen demand
(including nitrification), and that
diffuser spacing will allow
adequate mixing.
Method:
Existing POTW's
Determine whether the limit-
ing variable is air suoply or number
of air diffusers, and then supplement
the air supply by increasing blower
horsepower or the number of dif-
fusers.
Materials; Consistent with existing
equipment.
New and Existing POTW's
Provide couplings or swing pipes to
allow removal of diffusers from the
aeration basin for routine mainte-
nance. For fixed diffusers, pro-
visions must be made for emptying
the basin and subsequent diffuser
maintenance.
New and Existing POTW's
Refer to 9.2.3.
9.4.2 - 9.5.3
302
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 9.6 Mechanical Aeration
9.6.1 Inadequate air
supply.
9.6.2 Inadequate
flexibility in aera-
tion equipment pro-
hibits operation of
tank unless full.
9.6.3 Inadequate
mixing to prevent solids
deposition and provide
uniform D.O. concentra-
tions.
New POTW's
Supply sufficient horsepower to
meet oxygen demand and to maintain
suspended solids in suspension.
Method:
Existing POTW's
Install additional mechan-
ical aerators, or replace exist-
ing aerators with larger units.
Install a diffused aeration system
to supplement the existing system.
Convert to a pure oxygen system.
New and Existing POTW's
Install floating rather than
fixed aerators if tank is to be
operated partially full.
New and Existing POTW's
Refer to 9.2.3.
Unit Operation/Component: 9.7 Sludge Removal
9.7.1 Inadequate
consideration of sludge
viscosity during pump
selection.
New POTW's
Consider sludge solids concentration
and temperature when selecting sludge
pumps.
Existing POTW's
Method: Replace centrifugal pump
with a plunger-type pump to handle
concentrated sludge.
9.6.1 - 9.7.1
303
-------
Design Considerations
Category: 10.0 Sludge
Dewatering
Unit Operation/Component:.
10.1 General
DEFICIENCY
10.1.1 Truck loading
areas not covered or
protected from freezing
conditions.
10.1.2 Inability to
feed chemicals to both
sides of a tank that
can be baffled into two
separate tanks.
CONSIDERATIONS
New and Existing POTW's
In cold-weather regions, trucks and
dumpsters which receive sludges from
dewatering equipment should be parked
inside a building to prevent the
sludge from freezing to the sides
and bottom of the transfer vehicle,
making it difficult to unload the
sludge cake at the final disposal
site. In warm-weather regions, the
sludge transfer vehicle should be
parked under cover to keep the cake
dry during wet-weather conditions.
New PQTW's
Chemical feed lines into splitter
boxes and/or chemical mix tanks that
can be divided into multiple compart-
ments should be designed to discharge
into each compartment rather than in-
to just one side of the tank in case
a portion of the tank must be taken
out of service or different chemical
dosages are required in various com-
partments.
Method:
Existing POTW's
3Provide a central pivot-
ing chute that can be manually
rotated to provide discharge into
one portion of the tank or the other;
or (2) Repipe and valve chemical feed
lines to discharge into either side
of the tank.
10.1.1 - 10.1.2
304
-------
DEFICIENCY
CONSIDERATIONS
Materials; One-eighth inch or
greater thickness steel plate and
common welding.
Cost: Less than $500.
Chute
Sketch;
Inlet Pipe
10.1.3 Excessive cake
discharge height results
in severe sludge splash-
ing.
10.1.4 Inadequate
access provided to
sample filtrate/cen-
trate streams.
Tank
Tank
New POTW's
Old Line
*{XH- Chemical
New Line
Cake discharge heights greater than
15 feet should be avoided if possi-
ble. If a long drop from the dewa-
tering unit to the collection vehicle
is necessary, consideration should
be given to providing portable splash
shields that can be set around the
vehicle or specify a pliable curtain
that hangs from the discharge chute
down to the collection vehicle.
Existing POTW's
Method; Provide portable splash
shields that can be set
around the receiving truck or dump-
ster, or hang a pliable curtain from
the discharge chute down to the
collection vehicle.
Materials; Rubber-coated canvas
or neoprene.
Cost; Less than $500.
New POTW's
Sample taps should be specified for
the filtrate/centrate lines from each
piece of dewatering equipment. The
sample taps should be located in a
position that allows sufficient room
10.1.2 - 10.1.4
305
-------
DEFICIENCY
CONSIDERATIONS
10.1.5 Improper place-
ment of control panels
in spray/splash areas
hampers clean-up and
results in abnormally
high corrosion rates.
10.1.6 Lack of oper-
ational flexibility
and consideration of
need for back-up unit
during periods of main-
tenance.
for a sample container to collect
samples from the tap.
Existing POTW's
Method; Install sample taps in con-
veniently accessible locations.
Materials; One-half inch diameter
nipple and one-half inch gate valve.
Cost: Less than $100.
Filtrate/Centrate Pipe
Sketch:
IVN
Gate Valve
New and Existing POTW's
Motor control centers for sludge
dewatering equipment should be
located in a separate room to pre-
vent clean-up water from damaging
electrical equipment. The room
should have a curb around it to
prevent water"flowing over the floor
and into the room. Local control
panels for equipment should be
located far enough from the units
to allow the operator to hose down
the equipment without getting the
panels wet. Water-proof (i.e.,
Nema-4) enclosures should be spec-
ified for localized control panels.
New POTW's
When multiple dewatering units are
required, size the units such that,
with one out of service, the remain-
ing unit(s) can process the sludge
by operating an extra shift or at an
increased loading rate. If only one
unit is warranted, provide temporary
sludge holding capacity (i.e., thick-
ener, digester, holding tank, etc.)
in the plant for use when the unit
is out-of-service.
10.1.4 - 10.1.6
306
-------
DEFICIENCY
CONSIDERATIONS
10.1.7 Insufficient
provisions for storage
of chemicals.
10.1.8 Inadequate
consideration of stor-
age of dewatered sludge
during inclement weather
10.1.9 Elevated
equipment such as
conveyors and chemical
Existing POTW's
Method; Install a sludge holding
tank to temporarily store sludge
while the dewatering unit is out-of-
service. The tank should have a
mixer and a supernatant line to
allow periodic settling (i.e., con-
centration) of the sludge.
New and Existing POTW's
When bagged (versus bulk storage)
chemicals such as lime and polymer
are used, dry storage space must be
provided. The space should be suf-
ficient to store one month's supply
of chemicals and be close to the
point of use. The storage area
should be protected from clean-up
waters and high-humidity conditions.
Consideration should be given to
storage of chemicals on a mezzanine
above chemical mix tanks and feeding
chemicals to the tanks from the ele-
vated mezzanine rather than storing
chemicals on the same floor level as
the mix tanks which would require
lifting the bags up over the edge of
the mix tanks in order to feed chem-
icals.
New and Existing POTW's
Incorporate into the facility's
design extra trucks or dumpsters
to provide temporary sludge storage
capacity during periods of inclement
weather when access to the final dis-
posal site is limited (i.e., due to
heavy snows) or when the receiving
landfill is closed (i.e., due to
heavy rainfall). Refer to 10.1.6.
New and Existing POTW's
Elevated conveyors should be a min-
imum of five feet below building
10.1.6 - 10.1.9
307
-------
DEFICIENCY
CONSIDERATIONS
storage bins are
inaccessible for
inspection and main-
tenance.
10.1.10 Inadequate
consideration of cyclic
peak demands in common
air/water supplies
results in competition
among multiple units.
10.1.11 Inadequate
capability to handle
peak loads.
10.1.12 Lack of flow
meters on sludge feed
lines to multiple pieces
of dewatering equipment.
ceilings to allow operator access
and maintenance work. Stairs and
platforms which allow access to
equipment (such as blowers, agi-
tators, and instrumentation mounted
on the top of chemical storage bins)
should be incorporated into the chem-
ical system design.
New and Existing POTW's
Peak demands on each unit serv-
iced by a common air/water
supply must be considered when sizing
utilities and/or auxiliary equipment.
Either sufficient capacity to meet
equipment peak demands must be pro-
vided, or periodic staggered oper-
ation of the equipment must be in-
corporated into planned operating
procedures.
New POTW's
Dewatering equipment should be sized
to handle peak loads or sufficient
storage capacity should be provided
in upstream units to equalize peak
loadings. This storage capacity
could be provided via extra side-
water depth (i.e., sludge holding
capacity) in thickeners, aerobic
digesters that operate at varying
depths, sludge holding tanks, extra
capacity in two-stage anaerobic
digesters, etc.
Existing POTW's
Method: Refer to 10.1.6.
New POTW's
In-line flow meters or overflow
weirs out of flow splitter boxes
should be provided to allow measure-
ment of sludge flow to individual
pieces of dewatering equipment in
order to: properly balance flow
10.1.9 - 10.1.12
308
-------
DEFICIENCY
10.1.13 Inadequate scum
removal.
10.1.14 Inadequate
consideration of poten-
tial plugging problems
in sludge piping.
CONSIDERATIONS
between multiple units, identify
loading rates, and/or determine
required chemical conditioning feed
rates.
Existing PQTW's
Method; For dewatering units fed
by gravity flow, provide overflow
weirs out of flow splitter boxes;
for pressure flow to dewatering
equipment, install in-line mag-
netic flow meters and control
valves.
Materials: Weirs for gravity flow;
magnetic flow meters and pinch valves
for pressure flow.
New and Existing POTW's
Scum removed from clarifiers and
thickeners should not be recycled
back into the plant treatment system
or mixed with waste sludge prior to
dewatering, but should be collected
and removed separately from the
plant. Scum removal capabilities
should be provided in all tanks or
flow splitter boxes that handle
wastewater prior to secondary clar-
ification or that handle sludges.
New and Existing POTW's
The minimum size pipe that should
be used for sludge handling is four
inches. In addition, sludge piping
should be equipped with hose bibs to
allow flushing the lines to break-up
plugs in the lines. Consideration
should also be given to periodically
using couplings in sludge piping to
allow operators to break into lines
to fix a plugging problem.
10.1.12 - 10.1.14
309
-------
DEFICIENCY
CONSIDERATIONS
10.1.15 Inadequate
consideration of
corrosive nature of
materials to be handled.
10.1.16 Insufficient
number of floor drains
around dewatering equip-
ment .
10.1.17 Tank drain
lines are located 2
to 3 inches off the
bottom of tanks, mak-
ing it difficult to
dewater them.
10.1.18 Chemical feed
line and pH probe are
located close together,
causing erroneous and/or
cyclic reading.
New POTW's
When selecting piping materials, con-
sideration must be given to the cor-
rosive nature of any sludge condi-
tioning chemicals (i.e., ferric
chloride, alum, lime, etc.) that will
be utilized. Stainless steel or PVC
piping (and tanks) will be required
for handling most chemicals.
Existing POTW s
Method; Replace existing piping with
proper type of pipe needed to carry
corrosive material.
New and Existing PQTW's
Provide floor drains on all four
sides and underneath dewatering
equipment.
New PQTW's
Specify that drains on tanks are
installed at the very bottom to
allow complete dewatering of the
tank.
Method:
Existing POTW's
Relocate tank drains to the
bottom of the tank to allow complete
dewatering.
New POTW's
The pH probe in a complete mix,
chemical addition (i.e., pH adjust-
ment) tank should be installed at the
opposite end from where chemicals are
added. This will ensure the probe is
measuring the pH of a completely-
mixed solution. This is particularly
important when pH readouts are used
to control chemical feed rates.
Method:
Existing POTW's
Relocate chemical feed lines
to discharge into mixing equipment
vortices. Ensure that the pH probe
is located at the opposite side of
the tank from the chemical inlet.
10.1.15 - 10.1.18
310
-------
DEFICIENCY CONSIDERATIONS
10.1.19 Clogging prob- New and Existing POTW's
lems in lime piping. Design techniques that can be em-
ployed to minimize clogging prob-
lems in lime piping include the fol-
lowing:
Locate lime feeder within
a few feet of application
point.
Utilize open channel (i.e.,
gravity) flow in lieu of pump-
ing the lime slurry.
Pre-soften the dilution water
with sodium hexametaphosphate.
Discharge the slurry through
an air gap into the open pH
adjustment tank.
Utilize supernatant from lime
slurry settling tanks as dilu-
tion water.
Specify heavy-duty flexible
rubber hoses or heavy, plastic
pipe in lieu of metal pipe;
this allows flexing the pipe
to break up any scaling inside
the pipe.
Provide clean-out/flushing
taps on lime piping.
Provide quick-disconnect coup-
lings that allow lime piping
to be taken apart for cleaning.
10.1.20 Excessive New POTW's
agitation in chemical For sludge conditioning tanks,
conditioning tanks utilize turbine impellers that
causes floe to shear. rotate at approximately 150 rpm.
If paddle-type mixers are used, the
paddles should rotate at 2 to 3 fps.
10.1.19 - 10.1.20
311
-------
DEFICIENCY
CONSIDERATIONS
10.1.21 Inadequate
provisions for vibra-
tion control in sludge
piping design.
10.1.22 Lack of
moisture removal from
instrument air lines
results in failure of
control equipment.
10.1.23 Sludge pump-
ing and dewatering
areas not properly
ventilated.
Existing POTW's
Method; Do not provide slow-speed
mixing by installing oversized im-
pellers or paddles; rather, consult
the manufacturer with regard to the
use of a step-down transformer to
provide slower rotations without
damaging the electrical motors.
New and Existing PQTW's
Discharge piping from piston pumps
should be securely anchored to pre-
vent excessive vibration. Long runs
of unbraced piping should be avoided,
and thrust blocks should be installed
at points where sludge piping changes
direction. Piping braces or racks
should be specified in lieu of
hangers to support elevated runs of
sludge piping from plunger pumps.
New POTW's
Provide air driers to remove moisture
from instrument air supplies since
water can collect in automatic con-
trol instrumentation and impair
operation. The air should be dried
to a minus 40°F dew point. Con-
sideration should also be given to
insulating the air lines.
Existing POTW's
Method: Install an air dryer in the
instrument air line.
Cost: Less than $5,000.
New and Existing POTW's
Sludge handling areas should be well
ventilated to prevent accumulation
of gases (i.e., H2S, ammonia).
Approximately 12 room air changes per
hour should be provided.
10.1.20 - 10.1.23
312
-------
DEFICIENCY
CONSIDERATIONS
10.1.24 Inadequate
provisions for lifting
equipment for repairs.
New PQTW's
Architectural and structural designs
should include necessary support
members for hoists over larger pieces
of equipment (i.e., pumps, gates, de-
watering equipment, etc.) to allow
removal for maintenance purposes.
Method:
Existing PQTW's
Consider the use of port-
able-type gantry cranes
Cost: For portable gantry cranes
with up to 2-ton capacity, the cost
would be less than $500.
Unit Operation/Component: 10.2 Gravity Thickeners
10.2.1 Design satis-
fies solids loading,
but neglects hydraulic
loading requirements.
10.2.2 Short-cir-
cuiting of flow
through tank causes
poor solids removal.
New POTW's
Thickeners are generally designed for
hydraulic overflow rates of 400 to
800 gpd/sq ft. Overflow rates are a
particularly-important consideration
if dilution water is to be added to
the thickener.
Existing POTW's
Method; Sample waste sludge concen-
tration to thickener to ensure that
excessive pumping is not being per-
formed. Also, reduce or eliminate
the use of dilution water to the
thickener.
New and Existing POTW's
Ensure the thickener is properly
baffled to prevent short-circuit-
ing across the thickener. Influent
and effluent baffles should be used
to ensure influent is evenly dis-
tributed across the thickener.
10.1.24 - 10.2.2
313
-------
DEFICIENCY
CONSIDERATIONS
10.2.3 No provision
for chemical addition.
10.2.4 Inadequate scum
removal.
10.2.5 Improper side-
water depth (SWD).
10.2.6 Inadequate
freeze protection.
New POTW's
Provide flexibility to add a set-
tling aid, such as polymer, to the
thickener to enhance performance or
for use during up-set periods.
Method:
Existing POTW's
Provide chemical addition
facilities.
Mater ials; 55-gallon drum of pre-
mixed chemical and metering pump
for controlled addition.
Cost; Less than $1,000.
New and Existing POTW's
Provide.a scum skimmer with thick-
eners; the scum should be removed
from the plant and not recycled
back into the treatment system.
.New POTW's
Thickeners are generally designed
with a SWD depth of 10 to 12 feet.
Existing POTW's
Method; If hydraulically possible,
raise the effluent weirs. Operate
thickeners in batch mode. Minimize
or eliminate the addition of dilu-
tion water, and remove sludge as soon
as it has attained a satisfactory
concentration in the bottom.
New POTW's
In cold-weather climates, in-ground
tanks should be used and/or covers
should be specified. Operating expe-
rience gained at other plants in the
vicinity can be used to determine if
covers are warranted. Another alter-
native is to place the units inside
buildings.
10.2.3 - 10.2.6
314
-------
DEFICIENCY
CONSIDERATIONS
Existing POTW's
Method; Construct an insulating
earthen berm around above-ground
tanks. Install wind breakers around
the tank. Insulate and heat trace
exposed piping.
Unit Operation/Component: 10.3 DAP Thickeners
10.3.1 Inadequate con-
sideration of cyclic
peak demands in common
air/water supplies
results in competition
among multiple units.
10.3.2 Design satis-
fies solids loading,
but neglects hydraulic
loading requirements.
New POTW's
If common air compressors are used
for multiple DAF units, the com-
pressors must be designed to supply
peak demands for all the DAF units.
This could be accomplished by pro-
viding a stand-by unit that could be
used during peak periods (also when
one of the other compressors is out-
of-service).
Method:
Existing POTW's
Eliminate other air uses
during peak DAF demands, or supply
an additional stand-by unit for
use during peak periods.
New POTW's
Dissolved air flotation units are
generally designed for overflow rates
of 0.5 to 2 gpm/sq ft. Pilot-plant
or laboratory testing should be con-
ducted to develop specific design
parameters.
Existing POTW's
Method; Supply hydraulic load to
DAF thickeners as uniformly as
possible. Install a sludge holding
tank upstream of the DAF units to
equalize flows to the thickeners.
10.2.6 - 10.3.2
315
-------
DEFICIENCY
CONSIDERATIONS
10.3.3 Insufficient
effluent recycle
capacity.
10.3.4 Feed pumps
run on an "on-off"
cycle, causing uneven
feed to DAF unit.
10.3.5 Wide variations
in feed solids concen-
trations occur because
DAF is fed directly
from final clarifier.
10.3.6 No provision
for chemical addition.
10.3.7 Improper side-
water depth (SWD).
New POTW's
A maximum recycle capacity of 150 to
200 percent of the influent flow
should be provided. However, recycle
pumping systems should be designed to
allow minimum recycle flows of 30 to
50 percent.
Method:
Existing POTW's
Since effluent is used to
convey dissolved air into the sys-
tem, add air diffusers into the air
dissolution tank. If air is pulled
into recycle lines through a metered
suction, do not exceed four percent
by volume to avoid cavitation.
New and Ex isting POTW s
A sludge holding tank (equipped with
a mixer) should be provided upstream
of DAF thickeners. DAF units should
have a continuous and constant influ-
ent flow rate with a constant solids
concentration in order to consis-
tently maintain an optimum air-to-
solids ratio within the unit.
New and Existing PQTW's
Refer to 10.3.4.
New PQTW's
Refer to 10.2.3.
Existing POTW's
Method: Provide space for a
55-
gallon drum for batch or contin-
uous feed. Provide metering into
the feed lines following the dis-
solved air release.
New POTW's
DAF units are generally designed with
SWD's from 3 to 10 feet.
10.3.3 - 10.3.7
316
-------
DEFICIENCY
CONSIDERATIONS
10.3.8 Lack of mois-
ture removal from
instrument air lines
results in failure
of control equipment,
10.3.9 Inadequate
freeze protection.
Existing POTW1s
Method; Feed DAF unit as uniformly
as possible. Remove float as rapid-
ly as possible, consistent with
attainment of design concentration.
Ensure that settled solids are fre-
quently (at least weekly) drawn off
the DAF unit bottoms.
New and Existing POTW's
Refer to 10.1.22.
New and Existing POTW's
Refer to 10.2.6.
Unit Operation/Component: 10.4 Vacuum Filters
10.4.1 Truck loading
areas not covered or
protected from freezing
conditions.
10.4.2 Vacuum valves
on equipment are in-
accessible.
10.4.3 Excessive
cake discharge height
results in severe
splashing.
New and Existing POTW's
Refer to 10.1.1.
New and Existing POTW's
Avoid unsafe practices such as climb-
ing on equipment to reach valves. If
valves are not within reach from
floor level, chain-operated valves
should be specified and/or stairways
and platforms provided.
New and Existing POTW's
Refer to 10.1.3.
10.4.4 Inadequate
access provided to
sample filtrate/cen-
trate streams.
New and Existing POTW's
Refer to 10.1.4.
10.3.7 - 10.4.4
317
-------
DEFICIENCY
CONSIDERATIONS
10.4.5 Improper place-
ment of control panels
in spray/splash areas
hampers clean-up and
results in abnormally
high corrosion rates.
10.4.6 Lack of oper-
ational flexibility
and consideration of
need for back-up unit
durinq periods of main-
tenance.
10.4.7 Elevated equip-
ment such as conveyors
and chemical storage
bins are inaccessible
for inspection and main-
tenance .
10.4.8 Sludge feed
troughs from chemical
conditioning tank to
vacuum filter frequent-
ly become clogged.
10.4.9 Lack of flow
meters on sludge feed
lines to multiple
pieces of dewatering
equipment.
New and Existing POTW's
Refer to 10.1.5.
New and Existing POTW's
Refer to 10.1.6.
New and Existing POTW's
Refer to 10.1.9.
New POTW's
Provide troughs that are a minimum
of 1 foot wide and sloped at a min-
imum angle of 30 degrees.
Method:
Existing POTW's
Provide troughs that are a
minimum of 1 foot wide and sloped at
a minimum angle of 30 degrees.
Materials; 1/8 inch steel plate and
common welding.
Cost; Less than $500 per unit.
New and Existing POTW's
Refer to 10.1.12.
10.4.5 - 10.4.9
318
-------
DEFICIENCY
CONSIDERATIONS
10.4.10 Top of sludge
chute not large enough
to accept all the cake
that comes off the de-
watering equipment,
causing some sludge
cake to fall on the
floor.
10.4.11 No provision
for chemical addition.
10.4.12 Improper
cleaning of filter
cloth.
New PQTW's
Provide flared tops on sludge chutes
that are approximately 1 foot longer
than the dewatering unit and are as a
minimum 1 foot wide.
Existing POTW's
Method; Provide flared tops on
sludge chutes that are approximately
one foot longer than the dewatering
unit and are as a minimum 1 foot
wide.
Materials: 1/8 inch steel plate
and common welding.
Cost; Less than $10,000 per unit.
New and Existing POTW's
Facilities for conditioning sludge
prior to dewatering should be pro-
vided. This would include chemical
storage, mixing and feeding facil-
ities, and a sludge blending (con-
ditioning) tank. A common chemical
feed system can often be used to
supply sludge conditioning chemicals
to multiple application points (i.e.,
clarifiers, dewatering equipment) in
the POTW. Refer to 10.3.6.
New POTW's
Specify that spray nozzles be sup-
plied with equipment to wash the
filter cloth after the sludge cake
has been discharged. The spray
nozzles should be located within 1/2
inch of the cloth to ensure adequate
cleaning with a minimum nozzle
pressure of 50 psig.
10.4.10 - 10.4.12
319
-------
DEFICIENCY
CONSIDERATIONS
Ensure that heavy water use in other
parts of the plant will not come off
the same main that feeds the spray
nozzles. If municipal water is used,
provide booster pumping if necessary
to ensure a delivery pressure of at
least 50 psig at the spray nozzle.
Existing POTW's
Method: Provide spray nozzles to
wash off the filter cloth after the
sludge cake has been discharged.
Locate the spray nozzles within 1/2
inch of the cloth to ensure adequate
cleaning with a minimum nozzle pres-
sure of 50 psig.
Materials: Nozzles, 1/2-in. pipe.
Cost: Less than $500 per unit.
Sketch;
Filter Cloth
Cake Discharge Point
Roller
Nozzle and Pipe
10.4.13 Improper
selection of filter
media.
10.4.14 Inadequate
sizing of dewatered
sludge conveyor.
New and Existing POTW's
Conduct laboratory testing to deter-
mine the solids retention charac-
teristics of various filter media.
Select equipment that allows for
simple replacement of filter media
in the event that sludge properties
and/or conditioning chemicals are
changed during operation.
New and Existing POTW's
There are three considerations for
design of sludge conveyors. The
first is that conveyor capacity
10.4.12 - 10.4.14
320
-------
DEFICIENCY
CONSIDERATIONS
10.4.15 Insufficient
number of floor drains
around dewatering
equipment.
10.4.16 Drain lines
from filter vats are
too small and become
clogged.
10.4.17 Spray water
systems exhibit clog-
ging problems.
must be adequate to transport the
mass flow of sludge which will be
produced by the dewatering
equipment. Second, the conveyor
system must provide adequate
freeboard to prevent spillage from
uneven placement of the sludge on
the conveyor. Third, the conveyor
must provide for adequate entrapment
of the material as it is released
from the dewatering equipment. The
latter considerations are best
served by making sectional drawings
of the relative placement of the
dewatering equipment and the
conveyor to ensure that adequate
freeboard and entrapment are
available. Refer to 10.4.3.
New and Existing POTW's
Locate floor drains such that, in
the event of an overflow of the con-
ditioning tank or vacuum filter feed
tank, the flow will be directed to
a nearby floor drain. Refer to
10.1.16.
New and Existing PQTW's
Specify all floor drains and drains
from filter vats are a minimum of 4
inches in diameter and contain as
few bends and connections as pos-
sible. Provide clean-outs and
flushing taps in the drain lines.
New and Existing POTW's
If the spray water source is
municipal water, measure alkalinity,
calcium, and pH to ensure the water
is stable. If the water is
unstable, recarbonate prior to use
to prevent calcium carbonate
deposition in the spray water system.
10.4.14 - 10.4.17
321
-------
DEFICIENCY
CONSIDERATIONS
10.4.18 Poor cake
release.
10.4.19 Inadequate
provisions for clean-
ing of filtrate/cen-
trate lines.
10.4.20 Inadequate
removal of cake from
filter media.
10.4.21 Filtrate pumps
frequently become
air bound.
10.4.22 Improper
use of needle valves
in hydraulic drives,
resulting in over-
heatings.
If treatment plant effluent is used
for spray water, provide a cartridge
filtration system ahead of the spray
water system.
New and Existing POTW's
Poor cake release is usually due
to an improper choice of filter media
or inadequate sludge conditioning.
Refer to 10.4.11 and 10.4.13.
New and Existing PQTW's
Provide for clean-up or access to
all parts of filtrate lines and
provide for valved crossed con-
nection between spray water sys-
tem and filtrate lines to allow
for high-pressure cleaning of lines
when the equipment is not in use.
New and Existing POTW's
Specify that the doctor blade be
easily adjustable to the surface
of the filter media. Refer to
10.4.12.
New and Existing POTW's
Provide for recirculation of pump
discharge to the filtrate tank to
maintain a sufficient level to pre-
clude air binding.
New POTW's
Do not specify needle valves or
hydraulic drives.
Existing PQTW's
Method: Replace needle valves or
hydraulic drives with ball valves.
10.4.17 - 10.4.22
322
-------
DEFICIENCY
CONSIDERATIONS
10.4.23 No provision
for remote speed con-
trol on sludge pumps,
chemical pumps, vacuum
filter drive, etc.,
from a central loca-
tion.
10.4.24 Inadequate
provisions for lift-
ing equipment for
repairs.
New and Existing POTW's
Consider providing a dewatering
equipment layout, such that a single
operator may operate and control all
components of the dewatering system
from one location. Give special con-
sideration to sludge feed pumps from
remote thickeners and/or wasting
lines.
New POTW's
Provide sufficient overhead clear-
ance (at least 20 feet) and suffi-
cient lifting capacity hoists (at
least 4 tons) to remove any motors,
pumps, and drives that may become
damaged and require replacement.
Method:
Existing POTW's
Lease or buy portable gan-
try equipment.
Unit Operation/Component: 10.5 Centrifuges
10.5.1 Truck loading
areas not covered or
protected from freez-
ing conditions.
10.5.2 Inadequate
access provided to
sample filtrate/cen-
trate streams.
10.5.3 Improper
placement of control
panels in spray/splash
areas hampers clean-up
and results in abnormally
high corrosion rates.
10.5.4 Lack of pre-
liminary treatment
prior to a disc-nozzle
centrifuge.
New and Existing POTW's
Refer to 10.1.1.
New and Existing POTW's
Refer to 10.1.4.
New and Existing POTW's
Refer to 10.1.5.
New and Existing PQTW's
Abrasive solids such as grit and sand
must be removed from the sludge
generating stream prior to a nozzle
10.4.23 - 10.5.4
323
-------
DEFICIENCY
CONSIDERATIONS
10.5.5 Lack of oper-
ational flexibility
and consideration of
need for back-up unit
during periods of
maintenance.
10.5.6 Elevated
equipment such as
conveyors and chemical
storage bins are
inaccessible for
inspection and main-
tenance.
10.5.7 Lack of flow
meters on sludge feed
lines to multiple
pieces of equipment.
10.5.8 No provision
for chemical addition.
10.5.9 Inadequate
sizing of dewatered
sludge conveyor.
10.5.10 Inadequate
consideration of cor-
rosive nature of mate-
rials to be handled.
10.5.11 Insufficient
number of floor drains
around dewatering
equipment.
centrifuge to prevent frequent
replacement of nozzles. Nozzle
centrifuges in general are not
suitable for primary sludges nor for
secondary sludge unless influent
screening, aerated grit removal, and
primary sedimentation are provided.
New and Existing POTW's
Refer to 10.1.6.
New and Existing POTW's
Refer to 10.1.9.
New and Existing PQTW's
Refer to 10.1.12.
New and Existing POTW's
Refer to 10.4.11.
New and Existing POTW's
Refer to 10.4.14.
New and Existing POTW's
Refer to 10.1.15.
New and Existing POTW's
Refer to 10.4.15.
10.5.4 - 10.5.11
324
-------
DEFICIENCY
CONSIDERATIONS
10.5.12 Inadequate
provisions for vibra-
tion control in sludge
piping design.
10.5.13 Inadequate
grit removal results
in excess corrosion.
10.5.14 Inadequate
treatment of flushing
water results in plugged
nozzles.
10.5.15 Inadequate
provisions for clean-
ing the filtrate/cen-
trate lines.
10.5.16 No provisions
for remote speed con-
trol on sludge pumps,
chemical pumps, vacuum
filter drive, etc., from
a central location.
10.5.17 Inadequate
provisions for lifting
equipment for repairs.
New and Existing PQTW's
Isolate centrifuges from rigid
piping by a flexible connector to en-
sure that centrifuge vibration does
not cause damage to the pipes.
Ensure that the flexible connectors
are compatible with the abrasive
and corrosive properties of the
material to be handled. Refer to
10.1.21.
New and Existing POTW's
Refer to 10.5.4.
New and Existing POTW's
Refer to 10.4.17.
New and Existing POTW's
Refer to 10.4.19.
New and Existing PQTW's
Refer to 10.4.23.
New and Existing POTW's
Refer to 10.4.24.
Unit Operation/Component: 10.6 Filter Presses
10.6.1 Truck loading
area not covered or
protected from freezing
conditions.
New POTW's
Refer to 10.1.1.
10.5.12 - 10.6.1
325
-------
DEFICIENCY
CONSIDERATIONS
10.6.2 Excessive cake
discharge height
results in severe
sludge splashing.
10.6.3 Inadequate
access provided to
sample filtrate/cen-
trate streams.
Existing POTW's
Method; Refer to 10.4.1.
New POTW's
Refer to 10.1.3.
Method:
Existing POTW's
Refer to 10.4.3.
New and Existing POTW's
Refer to 10.1.4.
10.6.4 Improper place-
ment of control panels
in spray/splash areas
hampers clean-up and
results in abnormally
high corrosive rates.
10.6.5 Lack of oper-
ational flexibility and
consideration of need
for back-up unit
during periods of
maintenance.
10.6.6 Elevated equip-
ment such as conveyors
and chemical storage
bins are inaccessible
for inspection and
maintenance.
10.6.7 Lack of flow
meters on sludge feed
lines to multiple
pieces of dewatering
equipment.
New and Existing POTW's
Refer to 10.1.5.
New and Existing POTW's
Refer to 10.1.6.
New and Existing POTW's
Refer to 10.1.9.
New and Existing POTW's
Refer to 10.1.12.
10.6.1 - 10.6.7
326
-------
DEFICIENCY
CONSIDERATIONS
10.6.8 Top of sludge
chute not large enough
to accept all the cake
that comes off the
dewatering equipment,
causing some sludge
cake to fall to the
floor.
10.6.9 No provision
for chemical addition.
New and Existing POTW's
Refer to 10.4.10.
New and Existing POTW's
Refer to 10.4.11.
10.6.10 Improper
cleaning of filter
cloth.
New and Existing POTW's
Refer to 10.4.12.
10.6.11 Improper
selection of filter
media.
10.6.12 Inadequate
sizing of dewatered
sludge conveyor.
10.6.13 Insufficient
number of floor drains
around dewatering
equipment.
10.6.14 Spray water
systems exhibit clog-
ging problems.
10.6.15 Poor cake
release.
10.6.16 Inadequate
provisions for clean-
ing of filtrate/cen-
trate lines.
New and Existing POTW's
Refer to 10.4.13.
New and Existing POTW's
Refer to 10.4.14.
New and Existing POTW's
Refer to 10.1.16.
New and Existing POTW's
Refer to 10.4.17.
New POTW's
Refer to 10.4.18.
Existing POTW's
Method; Increase mechanical vibra-
tion. Manually clear each filter
cell as it opens. Refer to 10.4.18.
New and Existing POTW's
Refer to 10.4.19.
10.6.8 - 10.6.16
327
-------
DEFICIENCY
CONSIDERATIONS
10.6.17 Inadequate
removal of cake from
filter media.
10.6.18 No provision
for remote speed con-
trol on sludge pumps,
chemical pumps, vacuum
filter drives, etc.,
from a central loca-
tion.
10.6.19 Inadequate
provisions for lift-
ing equipment for
repairs.
New POTW's
Provide a safety (electric-eye)
curtain to allow operator to
manually clean plates with a
paddle during the press cake-
release cycle. Refer to 10.4.18.
Existing POTW's
Method; Provide wash water
connections to filter feed line
and run filter through a cleaning
cycle. Manually backwash each cell
with high-pressure water. Refer to
10.6.15.
New and Existing POTW's
Refer to 10.4.23.
New and Existing POTW's
Refer to 10.4.24.
Unit Operation/Component: 10.7 Belt Filters
10.7.1 Truck loading
areas not covered or
protected from freezing
conditions.
10.7.2 Vacuum valves
on equipment are
inaccessible.
10.7.3 Excessive
cake discharge height
results in severe
sludge splashing.
New and Existing POTW's
Refer to 10.1.1.
New and Existing POTW's
Refer to 10.4.2.
New and Existing POTW's
Refer to 10.1.3.
10.6.17 - 10.7.3
328
-------
DEFICIENCY
CONSIDERATIONS
10.7.4 Inadequate
access provided to
sample filtrate/cen-
trate streams.
10.7.5 Improper
placement of control
panels in spray/splash
areas hampers clean-up
and results in
abnormally high
corrosion rates.
New and Existing POTW's
Refer to 10.1.4.
New and Existing POTW's
Refer to 10.1.5.
10.7.6 Lack of oper-
ational flexibility
and consideration of
need for back-up unit
during periods of
maintenance.
10.7.7 Elevated
equipment such as
conveyors and chemical
storage bins are
inaccessible for
inspection and main-
tenance.
10.7.8 Lack of flow
meters on sludge feed
lines to multiple
pieces of dewatering
equipment.
10.7.9 Top of sludge
chute not large enough
to accept all cake that
comes off the dewater-
ing equipment, causing
some sludge cake to
fall on the floor.
10.7.10 No provision
for chemical addition.
New and Existing POTW's
Refer to 10.1.6.
New and Existing POTW's
Refer to 10.1.9.
New and Existing POTW's
Refer to 10.1.12.
New and Existing PQTW's
Refer to 10.4.10.
New and Existing POTW's
Refer to 10.4.11.
10.7.4 - 10.7.10
329
-------
DEFICIENCY
CONSIDERATIONS
10.7.11 Improper
cleaning of filter
cloth.
New and Existing PQTW's
Refer to 10.4.12.
10.7.12 Improper
selection of filter
media.
10.7.13 Inadequate
sizing of dewatered
sludge conveyor.
10.7.14 Insufficient
number of floor drains
around dewatering
equipment.
10.7.15 Drain lines
from filter vats are
too small and become
clogged.
10.7.16 Spray water
systems exhibit clog-
ging problems.
10.7.17 Poor cake
release.
10.7.18 Inadequate
provisions for clean-
ing of filtrate/cen-
trate lines.
10.7.19 Inadequate
removal of cake from
filter media.
10.7.20 Filtrate
pumps frequently become
air bound.
10.7.21 No provisions
for remote speed con-
trol on sludge pumps,
chemical pumps, vacuum
filter drives, etc.,
from a central location,
New and Existing POTW's
Refer to 10.4.13.
New and Existing PQTWs
Refer to 10.4.14.
New and Existing POTW's
Refer to 10.1.16 and 10.4.15.
New and Existing POTW's
Refer to 10.4.16.
New and Existing POTW's
Refer to 10.4.17.
New and Existing POTW's
Refer to 10.4.18.
New and Existing POTW's
Refer to 10.4.19.
New and Existing POTW's
Refer to 10.4.20.
New and Existing POTW's
Refer to 10.4.21.
New and Existing POTW's
Refer to 10.4.23.
10.7.11 - 10.7.21
330
-------
DEFICIENCY
CONSIDERATIONS
10.7.22 Inadequate
provisions for lifting
equipment for repairs.
New and Existing POTW's
Refer to 10.4.24.
Unit Operation/Component: 10.8 Sludge Drying Beds
10.8.1 Inadequate
drainage system.
10.8.2 No provisions
for cake removal from
sand bed.
10.8.3 Inadequate
provisions for proper
sludge distribution.
New and Existing POTW's
Provide for minimum of 4-inch
diameter drain piping laid at a
minimum slope of 1 percent with a
maximum spacing of 20 feet between
underdrains.
New and Existing POTW's
Provide roadway access along at
least one edge of all beds. Also,
provide concrete truck tracks at
20-foot centers in all beds.
New POTW's
Specify that bed surfaces are to be
level. The influent pipe should ter-
minate at least 1 foot above the sur-
face, and one influent pipe should
feed no more than 1,000 square feed
of bed.
Method:
Existing PQTW's
Level bed surfaces.
Terminate the influent pipe one
foot above the bed surface. Use
one influent pipe per 1,000 square
feet of bed. Use concrete splash
pads under pipe.
Sketch:
Sludge
1' Minimum
Concrete Pad
(2 ft x 2 ft x 4 in. thick)
L"
Sand Bed
10.7.22 - 10.8.3
331
-------
DEFICIENCY
CONSIDERATIONS
10.8.4 Inadequate
layout of underdrains.
10.8.5 Improper
location of sand bed
allows inflow of sur-
face drainage.
10.8.6 Inadequate
consideration of
potential flooding
of sand bed.
10.8.7 Lack of oper-
ational flexibility and
consideration of need
for back-up unit dur-
ing periods of mainte-
nance .
10.8.8 Improper sand
gradation.
New and Existing POTW's
Refer to 10.8.1.
New PQTW's
Outer walls of sand bed should be
curbed to prevent soil from wash-
ing onto the beds and to divert
runoff away from the sand bed area,
Method:
Existing POTW's
Raise the outer walls
of the sand bed to prevent soil
from washing onto the beds and to
divert runoff away from the sand
bed area.
New and Existing POTW's
Ensure that no portion of the sand
bed is within the 100-yr flood plain
of nearby waterways. As a minimum,
provide adequate diversion channels
to prevent bed flooding during the
1-hr, 10-yr storm event.
New and Existing PQTW's
Refer to 10.1.6.
New POTW's
The bed should consist of 6 to 9
inches of sand which has an effec-
tive size of 0.3 to 1.2 mil and a
uniformity coefficient of less than
0.5. The sand should be placed over
12 to 18 inches of gravel. The top
three inches shall consist of 1/8 to
1/4 inch gravel. The gravel shall
extend at least 6 inches above the
top of the underdrain and be at least
12 inches deep.
10.8.4 - 10.8.8
332
-------
DEFICIENCY
CONSIDERATIONS
Existing POTW's
Method; Replace existing sand with
9 inches of sand which has an effec-
tive size of 0.3 to 1.2 mil and a
uniformity coefficient of less than
0.5. Place the sand over 12 to 18
inches of gravel. The top three
inches shall consist of 1/8 to 1/4
inch gravel. The gravel shall extend
at least six inches above the top of
the underdrain and be at least 12
inches deep. Use 1/8 to 1/4 inch
gravel.
Sketch:
Sand
6" Min.
Gravel
9" Min.
12" Min.
/ ~
Underdrain
10.8.9 Walls dividing
sludge drying beds
are made of untreated
wood and warp rapidly.
10.8.10 Inadequate
freeze protection.
New and Existing POTW's
Require pressure-treated lumber
for sand drying bed separation
barriers.
New POTW's
In cold-weather climates, covers
should be specified and/or sea-
sonal sludge drying should be con-
sidered. In the event seasonal
sludge drying is selected, provide
adequate sludge storage for at least
the 10-yr freezing weather events.
Existing POTW's
Method: Either install a sludge
storage facility for seasonal dry-
ing or cover beds.
10.8.8 - 10.8.10
333
-------
DEFICIENCY
CONSIDERATIONS
10.8.11 Inadequate
consideration of local
climate on dewatering
rate and size require-
ments for sand beds.
Materials: Glass, framing members.
New POTW's
Approximately 50 percent of pre-
cipitation evaporates from open sand
drying beds with the remainder adding
to the hydraulic load to the sand
bed. The design load to the bed
should include consideration of max-
imum monthly rainfall as an added
load.
Existing POTW's
Method; Expand the bed to include
50 percent of the expected precip-
itation in design load.
Unit Operation/Component: 10.9 Sludge Transfer
10.9.1 Truck loading
areas not covered or
protected from freez-
ing conditions.
10.9.2 Improper con-
veyor operating angle,
10.9.3 Excessive cake
discharge height results
in severe sludge splash-
ing.
10.9.4 Inadequate
consideration of stor-
age of dewatered sludge
during inclement
weather.
New and Existing POTW's
Refer to 10.1.1.
New POTW's
To prevent rolling of the sludge
along the conveyor during transfer,
ensure that no conveyor angle is
greater than 30°.
Existing POTW's
Method; Reduce the conveyor angle
to 30 percent or install a flighted
conveyor.
New and Existing POTW's
Refer to 10.1.3.
New and Existing POTW's
Refer to 10.1.8.
10.8.11 - 10.9.4
334
-------
DEFICIENCY
CONSIDERATIONS
10.9.5 Elevated
equipment such as con-
veyors and chemical
storage bins are
inaccessible for inspec-
tion and maintenance.
10.9.6 Lack of flow
meters on sludge feed
lines to multiple pieces
of dewatering equipment.
10.9.7 Top of sludge
chute not large enough
to accept all the cake
that comes off the dewa-
tering equipment, causing
some sludge cake to fall
on the floor.
10.9.8 Insufficient
conveyor skirt length,
resulting in severe
splashing.
10.9.9 No flushing
facilities provided for
sludge transfer or feed
pumps.
10.9.10 No drains
provided on elevated
sections of conveyor
drip pans.
10.9.11 Inadequate
sizing of dewatered
sludge conveyor.
10.9.12 Inadequate
consideration of poten-
tial plugging problems
in sludge piping.
New and Existing PQTW's
Refer to 10.1.9.
New and Existing POTW's
Refer to 10.1.12.
New and Existing POTW's
Refer to 10.4.10.
New and Existing PQTW's
Provide a minimum of one foot of
freeboard above the maximum expected
sludge level on the conveyor. Refer
to 10.1.3 and 10.1.14.
New and Existing POTW's
Refer to 10.1.14 and 10.4.19.
New and Ex ist ing POTW's
Ensure that all sections of con-
veyors have drip pans with a min-
imum of 4-inch drain lines to floor
drains.
New and Existing POTW's
Refer to 10.4.14.
New and Existing POTW's
Refer to 10.1.14.
10.9.5 - 10.9.12
335
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 10.10 Sludge Conditioning
10.10.1 Inability to
feed chemicals to both
sides of a tank that
can be baffled into two
separate tanks.
10.10.2 Insufficient
provisions for storage
of chemicals.
10.10.3 No provision
for dust collection
when using powdered
conditioning agents.
10.10.4 No provision
for chemical addition.
10.10.5 Tank drain
lines are located 2"
to 3" off bottom of
tanks, making it diffi-
cult to dewater them.
10.10.6 Chemical feed
line and pH probe are
located close together,
causing erroneous and/or
cyclic readings.
10.10.7 Clogging prob-
lems in lime piping.
10.10.8 Excessive
agitation in chemical
conditioning tanks
causes floe to shear.
New and Existing POTW's
Refer to 10.1.2.
New and Existing PQTWs
Refer to 10.1.7.
New and Existing POTW's
Enclose the conditioning system and
provide forced ventilation to an air
filtering system with a minimum of
six air changes per hour to the con-
ditioning system.
New and Existing POTW's
Refer to 10.2.3 and 10.4.11.
New and Existing POTW's
Refer to 10.1.17.
New and Existing POTW's
Refer to 10.1.18.
New and Existing PQTW's
Refer to 10.1.19.
New and Existing POTW's
Refer to 10.1.20.
10.10.1 - 10.10.8
336
-------
DEFICIENCY CONSIDERATIONS
10.10.9 No provision New and Existing POTW's
for remote speed con- Refer to 10.4.23.
trol on sludge pumps,
chemical pumps, vacuum
filter drivers, etc.,
from a central location.
10.10.9
337
-------
Design Considerations
Category:!!. 0 Lagoons
Unit Operation/Component: -
11.1 Facultative Ponds
DEFICIENCY
11.1.1 Inability
of process to meet
effluent require-
ments in winter.
11.1.2 Inadequate
(or lack of) liner
to meet state
requirements, and
to prevent ground-
water pollution.
CONSIDERATIONS
New POTW's
During design, use lagoon temperature
prediction techniques to ensure that
system is designed to meet effluent
requirements at lowest predicted win-
ter temperatures.
Method
Existing POTW's
Provide additional detention
time in lagoons by either increasing
depth in pond by raising embankment
height and/or raising effluent dis-
charge structure, or installing an
additional cell.
Materials; Consistent with existing
structure.
New POTW's
Provide lagoon liner that complies
with local code regulations, ensuring
that the liner can withstand the
expected environmental conditions.
Consider the potential effects of
industrial wastes discharged to the
POTW.
Existing POTW's
Method: Install (or replace exist-
ing) liner with one that complies
with state requirements.
Materials; Based on local require-
ments, install synthetic, clay, or
pavement liner as required.
11.1.1 - 11.1.2
338
-------
DEFICIENCY
CONSIDERATIONS
11.1.3 No provision
to vary liquid depth
for mosquito control
in lagoon.
11.1.4 Single point
entry into pond over-
loads pond in feed zone,
11.1.5 Lack of multi-
ple cells for operating
flexibility.
11.1.6 Anaerobic con-
ditions due to organic
overloading.
New POTW's
Specify a variable height discharge
structure to allow depth adjustments.
Existing POTW's
Method; Install an adjustable efflu-
ent weir to allow control of the pond
liquid depth.
New and Existing POTW's
Provide multiple entry points into
pond to reduce the potential for
organic overloading in isolated zones
of the pond.
New POTW's
Provide two or more ponds rather than
one large pond to allow the opera-
tional flexibility of series versus
parallel operation.
Existing POTW's
Method; Divide existing cell into
two basins if construction of earthen
dike will not reduce usable lagoon
below that required for efficient
operation. Alternately, install
bulkhead wall or construct an addi-
tional cell, particularly if effluent
quality is unacceptable or marginally
acceptable.
New POTW's
Consider the potential effects (i.e.,
oxygen demand, pH, toxicity, etc.) of
industrial discharges to the POTW.
Ensure that sufficient oxygen is
available from algal production and
oxygen transfer at the water surface
to sustain aerobic conditions in
surface portions.
Existing POTW's
Method; Enlarge pond volume to
reduce organic loading rate.
11.1.3 - 11.1.6
339
-------
DEFICIENCY
CONSIDERATIONS
11.1.7 No drain pro-
vided in lagoon.
11.1.8 Water level
gauges not provided.
11.1.9 Improper depth
between lagoon bottom
and groundwater table.
11.1.10 No groundwater
monitoring wells pro-
vided.
Materials ; Consistent with existing
construction.
New PQTW's
Specify a drain to allow emptying of
the pond. Alternately, construct an
effluent control mechanism to permit
pond dewatering.
Existing POTW's
Method; Install drain in lagoon.
Alternately, install siphon to allow
drainage of pond.
New and Existing PQTW's
Provide either float level gauges or
noncontact (i.e., ultrasonic) level
gauges.
New and Existing POTW's
Ensure that an unlined lagoon bottom
is above the seasonal high ground-
water table; utilize above-ground
dikes, if necessary. For a lined
lagoon, provide a groundwater inter-
ception and collection system.
New and Existing POTW's
Specify groundwater monitoring wells
be located around the pond.
Unit Operation/Component: 11.2 Aerated Ponds
11.2.1 Inability of
process to meet efflu-
ent requirements in
winter.
11.2.2 Inadequate (or
lack of) liner to meet
state requirements, and
to prevent groundwater
pollution.
New and Existing POTW's
Refer to 11.1.1.
New and Existing POTW's
Refer to 11.1.2.
11.1.6 - 11.2.2
340
-------
DEFICIENCY
CONSIDERATIONS
11.2.3 No provision to
vary liquid depth for
mosquito control in
lagoon.
11.2.4 Single-point
entry pond overloads
pond in feed zone.
11.2.5 Lack of multi-
ple cells for operating
flexibility.
11.2.6 Anaerobic con-
ditions due to organic
overloading.
New and Existing POTW's
11.2.7 Complete mixing
problems.
11.2.8 No drain pro-
vided in lagoon.
Refer to 11.1.3.
New and Existing POTW's
Refer to 11.1.4.
New and Existing POTW's
Refer to 11.1.5.
New PQTW' s
Ensure that sufficient oxygen is pro-
vided (typically 0.8 to 1.2 Ib 02/
Ib BOD5). Refer to 11.1.6.
Existing PQTW's
Method; Increase the capacity (i.e.,
horsepower) of the existing aeration
system. If industrial discharges are
contributing to organic overload con-
ditions, formulate pretreatment regu-
lations and implement them.
New POTW's
When sizing aerators, consider the
horsepower requirements to keep sus-
pended solids from settling. Also,
consider the horsepower requirements
for oxygen demand.
Existing POTW's
Method; For surface mechanical aera-
tors, increase the size of existing
units or install additional aerators.
For diffused aeration, first deter-
mine whether sufficient air supply
exists. If so, install additional
diffusers. If sufficient air supply
does not exist, increase the size or
number of blowers.
New and Existing POTW's
Refer to 11.1.7.
11.2.3 - 11.2.8
341
-------
DEFICIENCY
CONSIDERATIONS
11.2.9 Water level
gauges not provided.
11.2.10 Improper depth
between lagoon bottom
and groundwater table.
11.2.11 No groundwater
monitoring wells pro-
vided.
New and Existing POTW's
Refer to 11.1.8.
New and Existing POTW's
Refer to 11.1.9.
New and Existing POTW's
Refer to 11.1.10.
Unit Operation/Component: 11.3 Aerobic Ponds
11.3.1 Inability of
process to meet efflu-
ent requirements in
winter.
11.3.2 Inadequate (or
lack of) liner to meet
state requirements, and
to prevent groundwater
pollution.
11.3.3 No provision to
vary liquid depth for
mosquito control in
lagoon.
11.3.4 Single-point
entry into pond over-
loads pond in feed zone,
11.3.5 Lack of multi-
ple cells for operating
flexibility.
11.3.6 Anaerobic con-
ditions due to organic
overloading.
New and Existing POTW's
Refer to 11.1.1.
New and Existing POTW's
Refer to 11.1.2.
New and Existing POTW's
Refer to 11.1.3.
New and Existing POTW's
Refer to 11.1.4.
New and Existing POTW's
Refer to 11.1.5.
New POTW's
Consider the potential effects (i.e.,
oxygen demand, pH, toxicity, etc.) of
industrial waste discharges. Ensure
that sufficient oxygen is available
from algal production and oxygen
transfer at the water surface to
sustain aerobic conditions
throughout the water column.
11.2.9 - 11.3.6
342
-------
DEFICIENCY
CONSIDERATIONS
11.3.7 No drain pro-
vided in lagoon.
11.3.8 Water level
gauges not provided.
11.3.9 Improper depth
between lagoon bottom
and groundwater table.
11.3.10 No groundwater
monitoring wells pro-
vided .
Existing POTW's
Method; Increase usable volume of
pond by increasing height of embank-
ments and/or increasing discharge
structure height. Alternately, con-
sider addition of increasing oxygen-
ation capacity through pumpage or
installation of an aeration system.
New and Existing POTW's
Refer to 11.1.7.
New and Existing POTW's
Refer to 11.1.8.
New and Existing POTW's
Refer to 11.1.9.
New and Existing POTW's
Refer to 11.1.10.
Unit Operation/Component: 11.4 Polishing Ponds
11.4.1 Inability of
process to meet efflu-
ent requirements in
winter.
11.4.2 Inadequate (or
lack of) liner to meet
state requirements,
and to prevent ground-
water pollution.
11.4.3 No provision to
vary liquid depth for
mosquito control in
lagoon.
11.4.4 Single-point
entry into pond over-
loads pond in feed zone.
New and Existing POTW's
Refer to 11.1.1.
New and Existing POTW's
Refer to 11.1.2.
New and Existing POTW's
Refer to 11.1.3.
New and Existing POTW's
Refer to 11.1.4.
11.3.6 - 11.4.4
343
-------
DEFICIENCY
CONSIDERATIONS
11.4.5 Lack of multi-
ple cells for operating
flexibility.
11.4.6 Anaerobic con-
ditions due to organic
overloading.
11.4.7 No drain pro-
vided in lagoon.
11.4.8 Water level
gauges not provided.
11.4.9 Improper depth
between lagoon bottom
and groundwater table.
11.4.10 No groundwater
monitoring wells pro-
vided.
New and Existing POTW's
Refer to 11.1.5.
New and Existing POTW's
Refer to 11.1.6.
New and Existing PQTW's
Refer to 11.1.7.
New and Existing POTW's
Refer to 11.1.8.
New and Existing POTW's
Refer to 11.1.9.
New and Existing POTW's
Refer to 11.1.10.
Unit Operation/Component: 11.5 Anaerobic Ponds
11.5.1 Inability of
process to meet efflu-
ent requirements in
winter.
11.5.2 Inadequate (or
lack of) liner to meet
state requirements, and
to prevent groundwater
pollution.
11.5.3 No provision to
vary liquid depth for
mosquito control in
lagoon.
11.5.4 Single-point
entry into pond over-
loads pond in feed zone.
New and Existing PQTW's
Refer to 11.1.1.
New and Existing POTW's
Refer to 11.1.2.
New and Existing POTW's
Refer to 11.1.3.
New and Existing POTW's
Refer to 11.1.4.
11.4.5 - 11.5.4
344
-------
DEFICIENCY
CONSIDERATIONS
11.5.5 Lack of multi-
ple cells for operating
flexibility.
11.5.6 No drain pro-
vided in lagoon.
11.5.7 Water level
gauges not provided.
11.5.8 Improper depth
between lagoon bottom
and groundwater table.
11.5.9 No groundwater
monitoring wells pro-
vided.
New and Existing POTW's
Refer to 11.1.5.
New and Existing PQTW's
Refer to 11.1.7.
New and Existing POTW's
Refer to 11.1.8.
New and Existing POTW's
Refer to 11.1.9.
New and Existing POTW's
Refer to 11.1.10.
Unit Operation/Component: 11.6 Baffles
11.6.1 No provision to
vary liquid depth for
mosquito control in
lagoon.
11.6.2
ing.
Short circuit-
11.6.3 Inadequate ero-
sion control measures.
New and Existing POTW's
Ensure that baffles will be effective
regardless of liquid level. Refer to
11.1.3.
New POTW's
In small unmixed ponds, consider bar-
rier walls with orifices. In larger
unmixed tanks, consider parallel
baffles for end-around (plug) flow.
Existing PQTW's
Method: Perform dye tests to first
determine type of short circuiting
present. Next, install baffles in
proper locations to minimize short
circuiting.
New and Existing POTW's
Consider installation of baffles near
dikes to dissipate wave energy and to
minimize erosion.
11.5.5 - 11.6.3
345
-------
DEFICIENCY
CONSIDERATIONS
11.6.4 Inadequate
freeze protection.
New and Existing POTW's
Provide removable or floating baffles
to minimize damage caused by ice
cover.
Unit
Operation/Component :
11.
7
Recirculation
Pumps
11.7.1 Control inflex-
ibilities.
11.7.2 Inadequate dis-
solved oxygen control.
11.7.3 Anaerobic con-
ditions due to organic
overloading.
11.7.4 Complete mixing
problems.
11.7.5 Inability to
control and adjust
recirculation rate.
New and Existing POTW's
Make provisions for parallel and ser-
ies operation for both intercellular
recirculation for maximum operator
flexibility.
New and Existing POTW's
Connect recirculation pumps to dis-
solved oxygen meter/controller to
allow automatic cycling of pump.
New and Existing POTW's
Provide intercellular recirculation
to reduce organic overloading in the
overloaded cell.
New and' Existing PQTW's
Provide a recirculation rate up to
eight times the forward flow.
New and Existing POTW's
Where possible, install flow control
valves on discharge side of recircu-
lation pump to allow decreased flow.
Alternately, install a time system
to allow automatic on/off operation
or provide variable speed pumps.
Unit Operation/Component: 11.8 Pond Configuration
11.8.1 Lack of multi-
ple cells for operating
flexibility.
New and Existing POTW's
Refer to 11.1.5.
11.6.4 - 11.8.1
346
-------
DEFICIENCY
CONSIDERATIONS
11.8.2 Control inflex-
ibilities.
11.8.3 Anaerobic con-
ditions due to organic
overloading.
11.8.4 Inadequate
sludge storage.
New and Existing POTWs
Provide multiple cells with provi-
sions for depth control and recircu-
lation control. Refer to 11.7.1.
New and Existing PQTW's
Provide sufficient area, multiple
cells, and intercellular recircula-
tion to minimize anaerobic condi-
tions.
New and Existing POTWs
Include provisions for periodic
sludge removal in facultative and
anaerobic ponds. In aerated ponds,
provide additional sludge storage if
adequate storage is not provided in
clarifier.
11.8.5 Short circuit-
ing.
11.8.6 Odor problems,
11.8.7 Inadequate
freeze protection.
New and Existing POTWs
Refer to 11.6.2.
New and Existing POTWs
Provide grass sod or asphalt slope
protection. Ease of cleaning will
lower odor potential. Provide round-
ed corners to minimize scum and
grease accumulation.
New and Existing PQTW's
For aerated ponds, increase depth to
minimize heat loss. Provide at least
a 3-ft freeboard to act as a wind
barrier.
Unit Operation/Component: 11.9 Aerators
11.9.1 Inadequate D.O.
control.
11.9.2 Complete mixing
problems.
New and Existing POTWs
Utilize D.O.meter/controlIer in con-
junction with aerators to maximize
aerator and removal efficiencies.
New POTWs
Refer to 11.2.7.
11.8.2 - 11.9.2
347
-------
DEFICIENCY
CONSIDERATIONS
11.9.3 Inadequate
freeze protection.
Existing POTW's
Method: First, perform dye tests to
isolate dead zones. Then, install
additional aerators in dead spots in
tanks to ensure complete mixing.
Refer to 11.2.7.
New and Existing POTW's
For floating aerators, specify aera-
tors with ice shields. For fixed
aerators, specify spray shields and
ensure that support structures can
withstand ice-induced loads.
Unit Operation/Component: 11.10 Dikes
11.10.1 Dike widths
too small for mainte-
nance vehicles.
11.10.2 Inadequate ero-
sion control measures.
11.10.3 Improper seed-
ing of dikes (long root
plants used that eventu-
ally damage the dike).
11.10.4
lems.
Rodent prob-
New and Existing POTW's
Size dike roads according to the
maintenance requirements expected.
For pickups, trucks, backhoes, bucket
cranes, tank/pump trucks, etc., a
10-ft minimum width is recommended.
New and Existing POTW's
Utilize 4 to 5:1 grassed outer
embankment slopes. Utilize 2 to 3:1
inner dike slopes. For side slopes,
utilize rip-rap, lining, or pavement
to minimize erosion. If the pond is
aerated, provide concrete pads or
crushed stone beneath aerators to
minimize erosion. Make provisions
for erosion control at influent and
effluent ends of ponds.
New and Existing POTW's
Plant perennial grasses on the dike
embankments. Ensure that grasses
selected are not deep-rooted to mini-
mize root damage to the embankment.
New and Existing POTW's
Provide means for altering lagoon
level rapidly and long term to dis-
courage muskrat tunneling. Provide
11.9.2 - 11.10.4
348
-------
DEFICIENCY
CONSIDERATIONS
4 to 5:1 outer embankment slopes to
allow for mowing.
Unit Operation/Component: 11.11 Primary Cell
11.11.1 No provision
to vary liquid depth
for mosquito control
in lagoon.
11.11.2 Anaerobic con-
ditions due to organic
overloading.
11.11.3 Inadequate
sludge storage.
New and Existing POTW's
Refer to 11.1.3.
New and Existing POTW's
Consider potential effects (i.e.,
oxygen demand, pH, toxicity, etc.) of
industrial waste discharge. Ensure
that oxygen generated by algae and
oxygen transferred at the surface are
sufficient to supply oxygen to bacte-
ria degrading wastes and to supply
oxygen caused by degrading sludge on
tank bottom. Refer to 11.1.6.
New and Existing POTW's
Provide adjustable discharge weir and
sufficient pond depth to increase
water level and, hence, sludge stor-
age capacity. Refer to 11.8.4.
Unit Operation/Component: 11.12 General
11.12.1 Pond located
too close to residen-
tial areas.
New POTW's
Review site plan for a location bet-
ter situated in relation to residen-
tial areas. Consider distance, wind
direction, groundwater flow direc-
tion, altitude, etc.
Existing POTW's
Method; Make the following provi-
sions in design to overcome nuisance
factors:
Install yard hydrants to
increase clean-up capability.
11.10.4 - 11.12.1
349
-------
DEFICIENCY
11.12.2 Inadequate ero-
sion control measures.
11.12.3 Water level
gauges not provided.
11.12.4 No groundwater
monitoring wells pro-
vided.
11.12.5 No fence or
all-weather road pro-
vided.
CONSIDERATIONS
Increase aeration if anaerobic
conditions are a problem.
Install/upgrade recirculation
pumps.
Provide additional cell volume.
Provide odor masking agent.
New and Existing POTW's
Refer to 11.10.2.
New and Existing POTW's
Refer to 11.1.8.
New and Existing POTW's
Refer to 11.1.10.
New and Existing POTW's
Unless plant is inaccessible, provide
fencing. Provide all-weather road
capable of supporting the largest
vehicle expected at the site.
11.12.1 - 11.12.5
350
-------
Design Considerations
Category: 12. 0 Land
Application
Unit
12.1 Overland Flow Slope Design
DEFICIENCY
12.1.1 Improper slope
construction.
12.1.2 Inadequate
detention time on
slope to achieve
desired level of
treatment.
12.1.3 Inappropriate
location of land
treatment plots.
12.1.4 Inadequate
soil depth for suit-
able land treatment.
CONSIDERATIONS
New POTW's
Specify slopes be within the range of
2 to 8 percent, with 2 to 6 percent
the preferred range.
Existing POTW's
Method; Regrade slope to within 2
to 6 pecent of grade if the existing
grade does not allow for suitable
operation.
New and Existing POTW's
Provide 150- to 300-foot long slopes
to allow for sufficient detention
time. In addition, make provisions
for series operation of slopes.
New POTW's
Overland flow technique requires
slowly-permeable soils, such as clays
and clay loams.
Existing POTW's
Method: If soil types are
excavation and/or
consider
importation.
incorrect,
soil
New POTW's
Although soil depth is not an
extremely-important variable in over-
land flow design, ensure a minimum
2-foot depth to groundwater level so
12.1.1 - 12.1.4
351
-------
DEFICIENCY
CONSIDERATIONS
that the root zone is not water-
logged.
12.1.5 Inadequate
site loading for
optimum treatment.
12.1.6 Inadequate
shaping of drainage
channels for efficient
system operation.
12.1.7 Improper
selection of main-
tenance equipment to
minimize soil com-
paction.
Existing
Method
POTW ' s
If more soil
quired, bring soil
permit) or consider
site.
New and Exist
depth is re
in (if hydraul
underdraining
ing POTW s
ics
of
Ensure that sufficient organic load-
ing is imparted to the site to main-
tain a healthy, biological community,
A loading range from 14 to 100 lb
BOD5/acre/day is typically used.
New and Existing POTW's
Shape drainage channels to provide
sufficient velocity (1 to 2 fps) to
maintain solids in suspension under
normal operation, but do not impart
excessive velocity that causes scour
and erosion problems during rainfall
runoff events.
New POTW's
Select maintenance equipment with
flotation tires to minimize soil
compaction.
Existing POTW's
Mejhod; If existing equipment does
not have flotation tires, install
flotation tires. Alternatively,
consider utilizing dual wheels on
equipment.
Unit Operation/Component: 12.2 Buffer Zone
12.2.1 Inadequate
location of service
roads.
New and Existing POTW's
Consider installation of all-weather
service roads within the buffer zone,
thereby reducing the entire land area
requirement.
12.1.4 - 12.2.1
352
-------
DEFICIENCY
CONSIDERATIONS
12.2.2 Inadequate
perimeter fencing
for public safety.
12.2.3 Inadequate
posting of signs
identifying hazards,
12.2.4 Aerosol drift
to neighboring land.
New and Existing POTWs
Unless the land application site is
located in a remote area away from
population centers, provide perimeter
fencing to limit access to site.
New and Existing POTWs
Place signs along perimeter of site
to notify the public of hazards asso-
ciated with entry into the site.
New and Existing POTWs
Aerosols may drift 100 to 600 feet
off the site. Minimize health risks
by:
Limiting public
site.
access to a
Properly sizing the irrigated
area in relation to surrounding
communities and lands.
Providing buffer
plantings around
zones and/or
the site.
Considering local climatic con-
ditions such as prevailing wind
directions when siting a land
application facility.
Unit Operation/Component: 12.3 Cover Crop
12.3.1 Inadequate
detention time on
slope to achieve
desired level
of treatment.
12.3.2 Inadequate
site loading for
optimum treatment.
New and Existing PQTWs
Refer to 12.1.2.
New and Existing POTWs
Liquid loading rates for the overland
flow method vary from 2 to 9 inches
per week. Liquid loading rates for
12.2.2 - 12.3.2
353
-------
DEFICIENCY
CONSIDERATIONS
12.3.3 Improper
selection of main-
tenance equipment to
minimize soil com-
paction.
the irrigation method vary from 0.5
to 4.0 inches per week. Refer to
12.1.5.
New and Existing POTWs
Refer to 12.1.7.
Unit Operation/Component: 12.4 Hydraulic Acceptance
12.4.1 Improper slope
construction.
12.4.2 Inadequate
soil depth for suitable
land treatment.
12.4.3 Inadequate
site loading for
optimum treatment.
New POTW's
Consider both the vertical and hor-
izontal permeability to ensure that,
at the given slope (i.e., detention
time), the soil can infiltrate the
desired volume.
Existing POTWs
Method; If the soil cannot accept
the applied water, consider enlarging
the site.
New POTW's
For slow rate infiltration systems,
provide a minimum 2 to 3 foot soil
depth to the water table. For rapid
infiltration, allow 10 feet (lesser
depths acceptable if underdrains are
provided).
Method:
Existing PQTW's
Refer to 12.1.4.
New and Existing POTW's
Ensure that percolation rates are
great enough to supply sufficient
organic carbon to the soil micro-
organism to maintain healthy pop-
ulations.
Typical organic loading rates
(Ib BOD5/acre-day) are as follows:
12.3.2 - 12.4.3
354
-------
DEFICIENCY
CONSIDERATIONS
12.4.4 Inadequate
knowledge of subsurface
drainage alternatives
to alleviate drainage
problems.
12.4.5 Improper
selection of main-
tenance equipment to
minimize soil compac-
tion.
12.4.6 Inadequate
use of data telemetry
for efficient operation
of the treatment system.
12,4.7 Inadequate
type and inter-
action of soil con-
sideration given to
soil with sodium in
the wastewater.
Slow rate - 10 to 25.
Rapid infiltration - 9 to 57.
Overland flow systems - 14 to
20.
New and Existing POTW's
For infiltration systems, ensure
that the lower soil horizons have
a permeability equal to or greater
than the surface horizon. Alter-
nately, install an underdrain col-
lection system.
New and Existing POTW's
Refer to 12.1.7.
New and Existing POTW's
Install instrumentation to monitor
liquid levels throughout the land
treatment system.
New POTW's
To minimize clay-bearing soils from
dispersing, apply wastewaters with
sodium adsorption ratios (SAR) of
less than 9 to fine-textured soils.
Existing PQTW's
Method: Have soil and wastewater
analyzed for sodium, magnesium, and
calcium to determine if sodium is
causing problems.
Unit Operation/Component: 12.5 Pretreatment
12.5.1 Spray nozzles
plug due to solids
in wastewater.
New POTW's
Provide for a pretreatment system
that will minimize the problem of
solids plugging the spray nozzles.
The required minimum nozzle size
12.4.3 - 12.5.1
355
-------
DEFICIENCY
CONSIDERATIONS
12.5.2 Excessive wear
on pumps due to sand
in wastewater.
12.5.3 Inappropriate
location of storage
facilities for optimum
energy utilization.
12.5.4 Inadequate
provisions for by-
passing flow during
maintenance.
12.5.5 Inadequate
construction of lagoons
for maintenance and
sludge removal.
should be a function of the degree
of pretreatment, with increasing
treatment for smaller nozzles, if
desired.
Existing POTW's
Method; Replace nozzles with larger
diameter nozzles able to pass largest
solids found in treated wastewater.
Ensure that sufficient pressure is
available in the system to utilize
larger nozzle and still get good
wastewater distribution.
New and Existing POTW's
Provide for degritting as a minimum
and possibly primary clarification as
part of the pretreatment process.
New POTW's
If possible, storage facilities
should be located down-gradient from
the pretreatment system to eliminate
any unnecessary pumping.
Existing POTW's
Method; If any subsequent expansion
of land application site or storage
lagoons is required, consider the
possibility of gravity flow.
New and Existing PQTW's
Provide for parallel treatment units
so that flow can be temporarily
diverted to one while the other is
down for maintenance.
New POTW's
As a minimum, provide an eight-foot
wide embankment for maintenance
vehicles. Provide inner slopes of
4 or 5:1 for accessibility by main-
tenance vehicles and sludge removal
equipment. If a steeper grade is
used, provide an access ramp.
12.5.1 - 12.5.5
356
-------
DEFICIENCY
CONSIDERATIONS
Method:
Ex is t ing PQTW's
Consider installation of an
12.5.6 Inadequate
storage for local
weather and its
impact on the func-
tioning of the system.
12.5.7 Inadequate
pumping facilities
for control of sed-
imentation in piping.
12.5.8 Inadequate
selection of protective
coatings to minimize
corrosion.
12.5.9 Insufficient
ventilation of pump
houses to minimize
corrosion potential.
access ramp to the lagoon to facil-
itate sludge removal.
New POTW s
Provide adequate storage,
in cold northern states,
water used for irrigation
crops. This may require
4 to 7 months of storage.
consideration the annual
peratures, rainfall, and
especially
for waste-
of annual
as much as
Take into
average tern-
evaporation.
Existing POTW's
Method; If existing storage is
inadequate, install additional lagoon
capacity. Alternately, if hydraulics
permit, decrease lagoon freeboard by
piping changes and, subsequently,
increase sidewater depth.
New and Existing POTWs
Provide pumping facilities for a min-
imum velocity of 2 fps. Avoid sharp
bends and unnecessary valves and
fittings. Eliminate low points in
system.
New and Existing POTWs
When specifying paint, be sure to
include surface preparation, a good
primer coat, and a top coat to be
compatible with the primer coat.
Consider the use of stainless steel,
aluminum, zinc, and plastics. Also,
consider a sacrificial anode for
cathodic protection.
New and Existing POTWs
Provide sufficient ventilation to
purge wet wells and dry wells of
the accumulation of hydrogen sul-
fide gas and water vapor. Use forced
air ventilation for systems over 30
feet below ground.
12.5.5 - 12.5.9
357
-------
DEFICIENCY
CONSIDERATIONS
12.5.10 Inadequate
methods for servicing
lagoon aerators.
12.5.11 Inadequate
design for back-up
pumping equipment.
12.5.12 Improper
selection of elec-
trical contacts and
machinery for corrosive
environments.
12.5.13 Inadequate
construction of under-
ground wiring.
12.5.14 Inadequate
protection of elec-
trical hardware from
voltage surges.
12.5.15 Inadequate
posting of signs
identifying hazards.
New and Existing POTW's
Provide cable clamps on mooring lines
that can be easily removed. The aer-
ator should be pulled to the near
shore, and serviced at that location.
New and Exist ing POTW's
Provide a minimum of one spare pump
at all essential pumping locations
within the plant.
New and Existing POTWs
Provide an enclosure that is her-
metically sealed or continuously
purged to keep corrosive gases from
reaching electrical contacts.
New and Existing PQTW's
Provide separate conduits for power
and signal wiring. Prevent water
from entering electrical manholes
entering into conduits.
New and ExistingPOTW's
Provide surge protectors.
New and Existing POTW's
Provide signs around perimeter of
plant to identify the area as a
wastewater treatment plant. In addi-
tion, place signs near all poten-
tially-dangerous equipment and
potentially-dangerous chemical han-
dling areas (e.g., chlorine, ferric
chloride, etc). Place "no smoking"
signs in areas where explosive gases
may accumulate.
or
Unit Operation/Component: 12.6 Storage
12.6.1 Inappropriate
location of storage
facilities for optimum
energy utilization.
New and Existing POTW's
Refer to 12.5.3.
12.5.10 - 12.6.1
358
-------
DEFICIENCY
CONSIDERATIONS
12.6.2 Inadequate
consideration for
needs of pre-chlor-
ination or preaera-
tion.
12.6.3 Inadequate
construction of lagoons
for maintenance and
sludge removal.
12.6.4 Inadequate
protection of equip-
ment from freezing
conditions.
12.6.5 Inadequate
storage for local
weather and its
impact on the func-
tioning of the sys-
tem.
12.6.6 Inadequate
pumping facilities for
control of sedimenta-
tion in piping.
12.6.7 Inadequate
methods for servicing
lagoon aerators.
12.6.8 Inadequate
design for back-up
pumping equipment.
New and Existing POTWs
Where long detention times and/or
high temperatures are expected, pre-
chlorination and/or aeration should
be used to minimize odor problems
and algae growth.
New and Existing POTW's
Refer to 12.5.5.
New POTW's
During design, ensure that provisions
have been made for protection of
pumps, aerators, gates, etc. due to
freezing and ice accumulation.
Existing POTW's
Method: Isolate equipment which is
subject to damage by freezing. Next,
provide either shelter or, if pos-
sible, reinstall equipment so as to
make it removable during the cold
months of the year.
New and Existing POTW's
Refer to 12.5.6.
New and Existing POTW's
Refer to 12.5.7.
New and Existing POTW's
Refer to 12.5.10.
New and Existing POTW's
Refer to 12.5.11.
12.6.2 - 12.6.8
359
-------
DEFICIENCY
CONSIDERATIONS
12.6.9 Inadequate use
of data telemetry for
efficient operation of
the treatment system.
12.6.10 Inadequate
perimeter fencing for
public safety.
New PQTW's
Install level probe on all storage
ponds, with a meter/recorder in the
control room as a minimum. Consider
installation of D.O. and pH probes
and recorders.
Existing POTW's
Method; Following consultation with
plant operators, install the desired
instrumentation.
New and Existing POTW's
Fence the perimeter of storage
lagoons, especially if the entire
perimeter of the treatment plant is
not fenced in. Specify 6-ft high
chain-link fence with three-strand
barbwire top if the plant is in an
area easily accessed by the public.
Unit Operation/Component: 12.7 Crop Harvest
12.7.1 Improper slope
construction.
12.7.2 Inadequate site
loading for optimum
treatment.
New PQTW's
Limit slopes to 20 percent as a max-
imum to allow for access by farm
machinery and eventual harvesting.
Existing POTW's
Method; If the slope is too steep to
permit access by farm and harvest
equipment, regrade and terrace site.
New and Existing POTW's
Provide for optimum liquid loading,
especially on irrigation systems
where crops are utilized extensively.
The range should be 0.5 to 4.0 inches
per week with 1.5 inches as the
average. Nitrogen, phosphorus, and
organic matter must also be con-
trolled. Stop irrigation prior to
harvesting to allow for farm machin-
ery access and traction.
12.6.9 - 12.7.2
360
-------
DEFICIENCY
CONSIDERATIONS
12.7.3 Inadequate
knowledge of sub-
surface drainage
alternatives to
alleviate drainage
problems.
12.7.4 Improper
selection of main-
tenance equipment to
minimize soil com-
paction.
New and Existing POTW's
Install subsurface drainage in poor-
ly-drained soils or when the ground-
water level affects water renovation
or crop growth. Design the under-
drain system after investigating to-
pography of land and the position,
level, and annual fluctuation of the
groundwater table. Conduct detailed
field investigations prior to final
design. Space underdrains based on
soil permeability and depth to
groundwater.
New and Existing POTW's
Refer to 12.1.7.
Unit
Operation/Component :
12.
8
Surface
Drainage
12.8.1 Spray nozzles
plug due to solids
in wastewater.
12.8.2 Improper slope
construction.
12.8.3 Inappropriate
location of storage
facilities for optimum
energy utilization.
12.8.4 Inadequate
location of service
roads.
New and ExistingPOTW's
Solids in wastewater can cause soil
sealing and undesirable runoff char-
acteristics. Refer to 12.5.1.
New PQTW's
For overland flow, refer to 12.1.1.
For a slow-rate system, use 20 per-
cent as a maximum slope. Although
not critical for rapid infiltration
systems, water must be evenly dis-
tributed.
Existing PQTW's
Method; Regrade site if necessary.
New and Existing PQTW's
If surface drainage is collected and
stored for future re-application,
design a gravity collection system.
New and Existing POTW's
Locate service roads so that they do
not interfere with surface drainage.
12.7.3 - 12.8.4
361
-------
DEFICIENCY
CONSIDERATIONS
12.8.5 Inadequate
storage for local
weather and its
impact on the func-
tioning of the system.
New POTW s
When designing storage facilities,
ensure sufficient storage capacity
exists, not only for wastewater, but
also for any runoff which is expected
to be generated from the application
site.
12.8.6 Inadequate
shaping of drainage
channels for efficient
system operation.
12.8.7 Improper
selection of main-
tenance equipment to
minimize soil com-
paction.
12.8.8 Inadequate
use of data telemetry
for efficient oper-
ation of the treatment
system.
Existing POTWs
Method; If the system is a collect-
ing site for non-contaminated storm-
water, divert this flow away from
the storage pond. If this is not
the case, refer to 12.5.6.
New and Existing POTWs
Refer to 12.1.6.
New and Existing POTWs
Refer to 12.1.7.
New POTW s
Consider the installation of soil
moisture measurement equipment to
maximize system operation and to
minimize the production of surface
runoff.
Existing POTW s
Method: Refer to 12.6.9.
Unit Operation/Component: 12.9 Soil Depth
12.9.1 Inadequate
soil depth for suit-
able land treatment.
New POTW's
Provide a minimum soil depth of
approximately 3 ft for slow-rate
systems, and 10 ft for rapid-infil-
tration systems (unless underdrains
are provided). Although not as im-
portant, allow 2 ft minimum depth
for overland flow systems.
12.8.5 - 12.9.1
362
-------
DEFICIENCY
CONSIDERATIONS
12.9.2 Inadequate
site loading for
optimum treatment.
12.9.3 Inadequate
consideration given
to soil type and the
interaction of soil
with sodium in the
wastewater.
Existing POTW's
Method; Refer to 12.1.4.
New and Existing POTW's
Refer to 12.7.2.
New POTW's
The sodium adsorption ratio (SAR)
should not exceed 9. Values higher
than this may adversely affect the
permeability of fine-textured soils
and be toxic to plants. For a SAR
greater than 9, consider chemical
addition to adjust the ratio.
Existing POTW's
Method: Refer to 12.4.7.
Unit Operation/Component: 12.10 Infiltration Beds
12.10.1 Improper
slope construction.
12.10.2 Inappropriate
location of storage
facilities for optimum
energy utilization.
12.10.3 Inadequate
soil depth for suit-
able land treatment.
12.10.4 Inadequate
construction of lagoons
for maintenance and
sludge removal.
New and Existing POTW's
The slope should be essentially flat
to allow for an even distribution of
water within the bed; however, sloped
land may be acceptable.
New and Ex isting POTW's
Where possible, storage facilities
should be down-gradient from the pre-
treatment system, and the infiltra-
tion beds should be down-gradient
from the storage facilities. This
minimizes the need for pumping
facilities.
New and Existing POTW's
Provide approximately 10 ft of soil
in the bed to allow for sufficient
treatment.
New and Existing POTW's
Refer to 12.5.5.
12.9.1 - 12.10.4
363
-------
DEFICIENCY
CONSIDERATIONS
12.10.5 Inadequate
site loading for
optimum treatment.
12.10.6 Improper
selection of main-
tenance equipment to
minimize soil compac-
tion.
12.10.7 Inadequate
use of data telemetry
for efficient operation
of the treatment sys-
tem.
New and Existing POTW's
Utilize a liquid loading rate of
4 inches to 7 ft/week with the rate
based on the saturated hydraulic
conductivity of the least permeable
layer. Allow sufficient resting
between application to restore aer-
obic conditions. Current systems
are loaded at a 8005 rate of from
9 to 57 Ib/acre-day.
New and Existing POTW's
Refer to 12.1.7.
New and Existing PQTW's
If desired, provide liquid level sen-
sors and flow controllers.
Unit Operation/Component: 12.11 Subsurface Drainage
12.11.1 Inappropriate
location of storage
facilities for optimum
energy utilization.
12.11.2 Inadequate
soil depth for
suitable land treat-
ment.
12.11.3 Inadequate
storage for local
weather and its
impact on the func-
tioning of the system.
New and Existing POTW's
If a subsurface underdrain system is
utilized, provide for gravity collec-
tion of reclaimed water.
New and Exist ing POTW's
When groundwater levels affect
wastewater renovation or crop growth,
underdrains will be required.
New and Existing POTW's
If subsurface drainage is collected
for future reuse, release or reappli-
cation, ensure sufficient storage is
available, considering groundwater,
wastewater applied, and precipita-
tion.
12.10.5 - 12.11.3
364
-------
DEFICIENCY
CONSIDERATIONS
12.11.4 Inadequate
knowledge of sub-
surface drainage
alternatives to
alleviate drainage
problems.
New and Existing POTW's
Refer to 12.7.3.
Unit Operation/Component: 12.12 Odor Control
12.12.1 Improper
slope construction.
12.12.2 Inadequate
detention time on slope
to achieve desired level
of treatment.
12.12.3 Inadequate
consideration for
needs of pre-chlor-
ination or pre-aeration,
12.12.4 Inadequate
construction of lagoons
for maintenance and
sludge removal.
12.12.5 Inadequate
protection of equipment
for freezing conditions,
12.12.6 Inadequate
pumping facilities
for control of sedi-
mentation in piping.
New and Existing POTW's
For overland and slow rate systems,
minimize local surface depressions
where wastewater may accumulate and
precipitate anaerobic conditions and
odors.
New and Existing POTW's
Ensure that the hydraulic and organic
loadings are proper. Minimize the
odor associated with the anaerobic
conditions caused by overloading.
New and Existing POTW's
Refer to 12.6.2.
New and Existing PQTWJ s
Provide access to all lagoons to
allow for sludge collection and
removal, thereby minimizing odor
potential. In addition, construct
side slopes to allow for access by
machinery, especially for grass
cutting. Refer to 12.5.5.
New and Existing POTW's
Refer to 12.6.4.
New and Existing POTW's
Refer to 12.5.7.
12.11.4 - 12.12.6
365
-------
DEFICIENCY
CONSIDERATIONS
12.12.7 Inadequate
knowledge of subsurface
drainage alternatives
to alleviate drainage
problems.
12.12.8 Inadequate
methods for servicing
lagoon aerators.
New and Existing POTW's
Avert anaerobic conditions by uti-
lizing subsurface drainage where
required. Refer to 12.7.3.
New and Existing POTW's
Negate odor potential by keeping aer-
ators operational. Refer to 12.5.10,
Unit Operation/Component: 12.13 Center Pivot Sprinkler
12.13.1 Spray
nozzles plug due
to solids in waste-
water.
12.13.2 Inadequate
protection of equip-
ment for freezing
conditions.
12.13.3 Inadequate
pumping facilities
for control of sedi-
mentation in piping.
12.13.4 Inadequate
facilities provided
for flushing of lateral
lines.
12.13.5 Inadequate
sprinkler head design
to minimize abrasion
and aerosolization.
New and Existing POTW's
Provide 50- to 65-psi water pressure
at the nozzles. Refer to 12.5.1.
New and Existing POTW's
Where freezing problems are possible,
utilize down nozzles which will drain
the sprinkler system, or provide
drain plugs. In addition, provide
drain plugs for the center pivot
section.
New and Existing PQTW's
Provide a minimum velocity of two
ft/sec in the distribution system.
New and Existing POTW's
Provide sufficient, high-pressure
water to flush lateral lines.
New and Existing POTW's
Choose a nozzle with the proper
pressure and diameter. For a spe-
cific nozzle size, a pressure too
high will cause mist and aerosol
production. A nozzle too small will
easily plug and abrade. Space
sprinklers closer together to
decrease the required arc of the
water, and thereby minimize aer-
osol production.
12.12.7 - 12.13.5
366
-------
DEFICIENCY
CONSIDERATIONS
12.13.6 Inadequate
selection of pro-
tective coatings to
minimize corrosion.
12.13.7 Improper
selection of elec-
trical contacts and
machinery for corrosive
environments.
12.13.8 Inadequate
construction of under-
ground wiring.
12.13.9 Inadequate
protection of elec-
trical hardware from
voltage surges.
12.13.10 Inadequate
use of data telemetry
for efficient operation
of the treatment system.
12.13.11 Inadequate
posting of signs
identifying hazards.
12.13.12 Plastic
laterals installed
above-ground are
breaking because of
cold weather.
New POTW's
Specify the main line and supply line
be cast iron, asbestos, cement, plas-
tic, or other corrosive-resistant
material. Specify either an aluminum
or galvanized steel sprinkler system.
Existing POTWs
Method; Replace highly-corroded
equipment with corrosion-resistant
materials. Alternately, apply
corrosion-resistant surface finishes.
New and Existing POTW's
Refer to 12.5.12.
New andExisting POTW's
Refer to 12.5.13.
New and Existing PQTW's
Refer to 12.5.14.
New and Existing POTW's
Refer to 12.8.8.
New and Existing POTW's
Post signs at 100-ft intervals along
the perimeter of the site that state
wastewater is being used for crop
irrigation.
New and Existing POTW's
Refer to 12.13.2.
12.13.6 - 12.13.12
367
-------
DEFICIENCY
CONSIDERATIONS
12.13.13 Aerosol
drift to neighboring
land.
New and Existing POTW's
Install properly-designed windbreaks
and buffer zones. The design of
these control devices is based upon
wind speed, spray height, and spray
pressure. Also, consideration to
neighboring land usage must be
given.
Unit Operation/Component: 12.14 Traveling Gun Sprinkler
12.14.1 Spray nozzles
plug due to solids in
wastewater.
12.14.2 Improper
slope construction.
12.14.3 Inadequate
protection of equip-
ment from freezing
conditions.
12.14.4 Inadequate
pumping facilities
for control of
sedimentation in
piping.
12.14.5 Inadequate
facilities provided
for flushing of
lateral lines.
New and Existing POTW's
Provide a spray nozzle on the gun
that has a large-enough bore to mini-
mize clogging. Refer to 12.5.1.
New POTW's
The traveling gun should not be lim-
ited by the slope of the terrain.
Method:
Existing POTW's
If the traveling gun cannot
move within the site due to terrain
restrictions, earthwork will be
required.
New and Existing POTW's
Provide drain plugs on both the
sprinkler and the supply piping.
New and Existing POTW's
Refer to 12.13.3.
New and Existing POTW's
Refer to 12.13.4.
12.13.13 - 12.14.5
368
-------
DEFICIENCY
CONSIDERATIONS
12.14.6 Inadequate
sprinkler head
design to minimize
aerosolization.
12.14.7 Inadequate
selection of pro-
tective coatings to
minimize corrosion.
12.14.8 Improper
selection of elec-
trical contacts and
machinery for corro-
sive environments.
New and Existing POTW's
Refer to 12.13.5.
New and Existing POTW's
Refer to 12.13.6.
New and Existing POTW's
Refer to 12.5.12.
12.14.9 Inadequate
construction of
underground wiring.
12.14.10 Inadequate
protection of elec-
trical hardware from
voltage surges.
12.14.11 Inadequate
use of data telemetry
for efficient opera-
tion of the treatment
system.
12.14.12 Inadequate
posting of signs
identifying hazards.
12.14.13 Plastic
laterals installed
above-ground are
breaking because
of cold weather.
12.14.14 Aerosol
drift to neighboring
land.
New and Existing POTW's
Refer to 12.5.13.
New and Existing POTW's
Refer to 12.5.14.
New and Ex i s ting POTW's
Refer to 12.8.8.
New and ExistingPOTW's
Refer to 12.13.11.
New and Existing POTW's
Refer to 12.13.12.
New and Existing POTW's
Refer to 12.13.13.
12.14.6 - 12.14.14
369
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 12.15 Single Set Sprinkler
12.15.1 Spray nozzles
plug due to solids in
wastewater.
12.15.2 Inadequate
protection of equip-
ment from freezing
conditions.
12.15.3 Inadequate
pumping facilities
for control of
sedimentation in
piping.
12.15.4 Inadequate
facilities provided
for flushing of
lateral lines.
12.15.5 Inadequate
sprinkler head
design to minimize
aerosolization.
12.15.6 Inadequate
selection of pro-
tective coatings to
minimize corrosion.
12.15.7 Improper
selection of elec-
trical contacts and
machinery for corro-
sive environments.
12.15.8 Inadequate
construction of
underground wiring.
12.15.9 Inadequate
protection of elec-
trical hardware from
voltage surges.
New and Existing POTW's
Refer to 12.14.1.
New and Existing POTW's
Provide drain plugs on both the
sprinkler and the distribution
system.
New and Existing POTW's
Refer to 12.13.3.
New and Existing POTW's
Refer to 12.13.4.
New and Existing POTW's
Refer to 12.13.5.
New and Existing POTW's
Refer to 12.13.6.
New and Existing POTW's
Refer to 12.5.12.
New and Existing POTW's
Refer to 12.5.13.
New and Existing POTW's
Refer to 12.5.14.
12.15.1 - 12.15.9
370
-------
DEFICIENCY
CONSIDERATIONS
12.15.10 Inadequate
use of data telemetry
for efficient opera-
tion of the treatment
system.
12.15.11 Inadequate
posting of signs
identifying hazards.
12.15.12 Plastic
laterals installed
above-ground are
breaking because
of cold weather.
12.15.13 Aerosol
drift to neighboring
land.
New and Existing POTW's
Refer to 12.8.8.
New and Existing POTW's
Refer to 12.13.11.
New and Existing POTW's
Refer to 12.13.2.
New and Existing POTW's
Refer to 12.13.13.
Unit Operation/Component: 12.16 Lineal Travel Sprinkler
12.16.1 Spray nozzles
plug due to solids in
wastewater.
12.16.2 Improper
slope construction.
12.16.3 Inadequate
protection of equip-
ment from freezing
conditions.
New and Existing POTW's
Refer to 12.14.1.
New PQTW's
Slope must be such that the traveling
sprinkler can negotiate the terrain.
Existing POTW's
Initiate slope regrading if
Method;
necessary,
New and Existing POTW's
Provide drain plugs on the lineal
section to allow for drainage.
12.16.4 Inadequate
pumping facilities
for control of
sedimentation in
piping.
New and Existing POTW's
Refer to 12.13.3.
12.15.10 - 12.16.4
371
-------
DEFICIENCY
CONSIDERATIONS
12.16.5 Inadequate
facilities provided
for flushing of
lateral lines.
12.16.6 Inadequate
sprinkler head
design to minimize
aerosolization.
12.16.7 Inadequate
selection of pro-
tective coatings to
minimize corrosion.
12.16.8 Improper
selection of elec-
trical contacts and
machinery for corro-
sive environments.
12.16.9 Inadequate
construction of
underground wiring.
12.16.10 Inadequate
protection of elec-
trical hardware from
voltage surges.
12.16.11 Inadequate
use of data telemetry
for efficient opera-
tion of the treatment
system.
12.16.12 Inadequate
posting of signs
identifying hazards.
12.16.13 Plastic
laterals installed
above-ground are
breaking because
of cold weather.
New and Existing POTW's
Refer to 12.13.4.
New and Existing POTW's
Refer to 12.13.5.
New and Existing POTW's
Refer to 12.13.6.
New and Existing POTW's
Refer to 12.5.12.
New and Existing POTW's
Refer to 12.5.13.
New and Existing POTW's
Refer to 12.5.14.
New and Existing POTW's
Refer to 12.8.8.
New and Existing POTW's
Refer to 12.13.11.
New and Existing POTW's
Refer to 12.13.12.
12.16.5 - 12.16.13
372
-------
DEFICIENCY
CONSIDERATIONS
12.16.14 Aerosol
drift to neighboring
land.
New and Existing POTW's
Refer to 12.13.13.
Unit Operation/Component: 12.17 Grated Pipe Distribution
12.17.1 Improper
slope construction.
12.17.2 Inappropriate
location of storage
facilities for
optimum energy util-
ization.
12.17.3 Inadequate
protection of equip-
ment for freezing
conditions.
New and Existing PQTWs
Refer to 12.8.2.
New and Existing POTW's
Refer to 12.10.2.
New and Existing POTWs
Design in-ground pipe distribution
system to allow for draining water
from low points of the system.
12.17.4 Inadequate
pumping facilities
for control of
sedimentation in
piping.
12.17.5 Inadequate
facilities provided
for flushing of
lateral lines.
12.17.6 Inadequate
selection of protec-
tive coatings to
minimize corrosion.
New and Existing POTW's
Refer to 12.5.7.
New and Existing POTW's
Refer to 12.13.4.
New and Existing PQTW's
Specify that the main line and supply
line be cast iron, asbestos, cement,
plastic, or other corrosive-resistant
material. Specify an aluminum-grated
pipe distribution system.
12.16.14 - 12.17.6
373
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 12.18 Ridge and Furrow
12.18.1 Improper
slope construction.
12.18.2 Inappropriate
location of storage
facilities for
optimum energy util-
ization.
12.18.3 Inadequate
pumping facilities
for control of
sedimentation in
piping.
New and Existing POTW's
Refer to 12.8.2.
New and Existing POTW's
Refer to 12.10.2.
New and Existing PQTWs
Refer to 12.5.7.
Unit Operation/Component: 12.19 Spreading Basins
12.19.1 Improper
slope construction.
12.19.2 Inappropriate
location of storage
facilities for
optimum energy util-
ization.
12.19.3 Inadequate
pumping facilities
for control of
sedimentation in
piping.
12.19.4 Inadequate
facilities provided
for flushing of
lines.
New and Existing POTW's
Refer to 12.8.2.
New and Existing POTW's
Refer to 12.10.2.
New and Existing POTW's
Refer to 12.5.7.
New and Existing PQTW's
Refer to 12.13.4.
12.18.1 - 12.19.4
374
-------
Design Considerations
Category:13. 0 Sludge
Disposal
Y_Q_>$,
Unit Operation/Component:,
13.1 General
DEFICIENCY
CONSIDERATIONS
13.1.1 Inadequate
truck tire size for
landfill disposal.
13.1.2 Inadequate con-
sideration of sludge
concentration/trans-
portation tradeoffs.
New and Existing POTW's
Replace tires with 10.00 x 20, 14 ply
or equal. Run at 80 Ibs. Cost
between $120 and $150 each, plus
tube.
New and Existing POTW's
Haulage costs/ton of solids decrease
as concentration increases.
,o
o
g
I
3
T
50.00
40.00
30.00
20.00
10.Q&
8.00
6.00
4.00
1.00
10 15 20 25
Percent Sotids In Sludge
30
13.1.1 - 13.1.2
375
-------
DEFICIENCY
CONSIDERATIONS
13.1.3 Inadequate con-
sideration of site
geology/topography and
climate.
13.1.4 Inadequate con-
sideration of equipment
utility in all-weather
conditions.
13.1.5 Lack of vector
control.
New PQTW's
Generally, application of sludge
should not be made within 100 ft of
streams, 300 ft of water supplies,
25 ft of bedrock outcrops, 50 ft of
property lines, and 300 ft of occu-
pied dwellings. Refer to local ordi-
nances for site-specific require-
ments.
Soil characteristics should be sandy
loam, loam, sandy clay loam, silty
clay, or silt loam, and have a well-
developed solum with at least 20 in.
to bedrock. Slopes should not exceed
30 percent and have no closed depres-
sions on-site. There should be a
minimum of 4.5 ft to the groundwater
table.
Method:
Existing POTW's
Grade the site to allow
rainfall runoff and prevent water
infiltrating into the landfill.
Provide all-weather roads for wet-
weather operation. Install imper-
meable barriers and/or leachate
collection system to prevent ground-
water contamination.
New PQTW's
Make provisions for temporary storage
of sludge during wet weather or
freezing conditions. Provide special
area near entrance for sludge dispos-
al during inclement weather. Provide
lighting (portable or permanent) for
night operation.
Method:
Existing POTW's
Refer to 13.2.1.
New and Existing POTW's
Cover sludge daily with a minimum of
6 inches of cover material.
13.1.3 - 13.1.5
376
-------
DEFICIENCY
CONSIDERATIONS
13.1.6 Inadequate con-
sideration of nutrients
and public health haz-
ards (metals, bacteria)
transport in soil/
groundwater.
13.1.7 Inadequate buf-
fer zone at disposal
site.
13.1.8 Lack of odor
control/prevention.
13.1.9 Sludge loading
delayed due to lack of
truck or container
capacity.
New POTW's
Specify sludge stabilization via
digestion or chemical treatment and
and sludge dewatering prior to final
disposal.
Provide collection lines beneath
landfills, leachate collection facil-
ities, and/or impermeable barriers to
prevent migration of leachate.
Existing POTWs
Method: Decrease the sludge loading
rate, install a leachate collection
system, and provide sludge dewatering
prior to disposal.
New and Existing POTW's
A buffer zone of 40 feet should be
provided as a minimum. Local ordi-
nances should also be referred to for
buffer zone requirements. Refer to
13.1.3.
New PQTW's
Specify a daily sludge cover of 6
inches or more. Provide facilities
for adding lime to the sludge, when
needed, to reduce the potential for
odors. Develop a grading plan that
prevents ponding.
Method;
mixture.
Existing POTW's
Add lime to the sludge soil
New POTW's
Incorporate into the facility's
design provisions for temporary stor-
age (i.e., extra trucks or contain-
ers) to provide temporary sludge
storage during periods of truck
breakdowns or landfill closure.
Existing POTW's
Method; Purchase an extra truck(s)
or container(s) to temporarily store
13.1.6 - 13.1.9
377
-------
DEFICIENCY
CONSIDERATIONS
sludge during periods of equipment
breakdown or landfill closure.
Unit Operation/Component: 13.2 Landfill
13.2.1 Inadequate
selection of disposal
vehicle results in
inability to maneuver
in landfill.
Vehicles
or equal
New POTW's
should have the
specifications:
following
Chassis; A 50,000 gross vehicle
weight rating (GVWR) chassis to
meet GVWR requirements, reinforced
high tensile steel frame (1/4-in.)
inside channel, heavy duty steel
front bumper with dual hooks, 10-
wheel tandem rear with 10.00 x 20,
14-ply tires with tubes at 80-lb
pressure, hydraulic power steer-
ing, full air brakes, front axle
14,000-lb cap. with 14,000-lb
aux. springs rear axle 36,000-lb
cap. with 4,000-lb aux. springs.
Power; A 200-hp (minimum) diesel
with vertical exhaust.
Transmission; An automatic or
standard heavy duty rear matched
to highway/off-road performance
requirements.
Body: Bulk carrier for 20 percent
solids; tank for 3 to 5 percent
solids.
Method:
Existing POTW's
Contract with private hauler
13.2.2 Inadequate con-
sideration of sludge
concentration/trans-
portation tradeoffs.
having the proper vehicles and/or
upgrade the existing equipment per
the specifications presented in
13.1.1.
New and Existing POTW's
Refer to 13.1.2.
13.1.9 - 13.2.2
378
-------
DEFICIENCY
13.2.3 Inadequate con-
sideration of site
geology/topography
and climate.
13.2.4 Inadequate con-
sideration of equipment
utility in all weather
conditions.
13.2.5 Inadequate con-
sideration of gas
migration/accumulation.
CONSIDERATIONS
New and Existing POTW's
Refer to 13.1.3.
New and Existing POTW's
Make provisions for temporary stor-
age of sludge during wet weather or
freezing conditions.
Provide special area near landfill
entrance for waste disposal during
inclement weather.
Provide tracked equipment (front-end
loaders, bulldozers, backhoes, etc.).
Provide paved or all-weather roads
at the site.
Transfer sludge from haulage vehicles
to super-flotation equipment at site.
Provide an enclosed truck (or con-
tainer) in the sludge loading area
to prevent the sludge from freezing
in the transportation vehicle.
New POTW's
Provide gas venting and migration
control at periphery of fill:
1. Place a barrier of low permea-
bility material, such as com-
pacted clay, around the fill
area.
2. Provide a gravel-filled trench
outside the clay barrier to
intercept migrating gas, and to
vent it to the atmosphere.
3. Place vertical perforated pipes
into each cell and/or lift to
vent each to the atmosphere.
13.2.3 - 13.2.5
379
-------
DEFICIENCY
CONSIDERATIONS
13.2.6 Lack of vector
control.
13.2.7 Inadequate con-
sideration of nutrients
and public health haz-
ards (metals, bacteria)
transport in soil/
groundwater.
13.2.8 Inadequate buf-
fer zone at disposal
site.
13.2.9 Lack of odor
control/prevention.
13.2.10 Sludge loading
ing delayed due to lack
of truck or container
capacity.
Existing POTW's
Method; Vent each lift to the next
higher lift:
1. By removing 2 to 5 sq ft of low
permeability cover material per
cell before applying new lift of
solid waste/sludge.
2. Vent final lift with vertical
perforated pipes (one per cell)
before placing final cover.
3. Place a barrier of low permea-
bility material, such as com-
pacted clay, around perimeter of
fill area.
New and Existing PQTW's
Personnel should be trained in con-
trolling vectors. Cover sludge daily
with a minimum of 6 inches of cover
material.
New and Existing POTWs
Refer to 13.1.6.
New and Existing POTWs
Refer to 13.1.7.
New and Existing POTWs
Refer to 13.1.8.
New and Existing POTW's
Refer to 13.1.9.
13.2.5 - 13.2.10
380
-------
DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 13.3 Spraying
13.3.1 Inadequate con-
sideration of sludge
concentration/trans-
portation/trade-offs.
13.3.2 Inadequate con-
sideration of site
geology/topography and
climate.
13.3.3 Inadequate con-
sideration of hydrau-
lic transport reduction
due to ion exchange.
13.3.4 Inadequate con-
sideration of equipment
utility in all weather
conditions.
New and Existing POTW's
Refer to 13.1.2.
New and Existing POTW's
Refer to 13.1.3.
New POTW's
High sodium concentrations in clay-
bearing soils disperse soil par-
ticles and decrease soil permeability
which can cause ponding.
Existing POTW's
Method; High sodium concentrations
in clay-bearing soils disperse soil
particles and decrease soil perme-
ability which can cause ponding.
Wastes with high sodium concentra-
tions should be segregated and dis-
posed of separately when possible.
In addition, add dolomitic lime to
the soil to displace Na with Mg and
Ca.
New and Existing PQTW's
Make provisions for temporary storage
of sludge during wet weather or
freezing conditions.
Provide flexibility to change from
subsurface to surface application
during wet or frozen ground condi-
tions.
Provide flexibility to transfer
sludge from haulage vehicle to super-
flotation equipment.
13.3.1 - 13.3.4
381
-------
DEFICIENCY
CONSIDERATIONS
13.3.5 Lack of vector
control.
13.3.6 Inadequate con-
sideration of nutrients
and public health haz-
ards (metals, bacteria)
transport in soil/
groundwater.
13.3.7 Inadequate buf-
fer zone at disposal
site.
13.3.8 Lack of odor
control/prevention.
New and Existing POTW's
Provide facilities to apply lime to
site after spraying.
Provide flexibility to use subsoil
injection in lieu of surface spray-
ing.
New POTW's
Refer to 13.1.6.
Existing POTW's
Method; Decrease the sludge appli-
cation rate to reduce nutrients and
metals loadings. Refer to 13.1.6.
New and Existing POTW's
Refer to 13.1.7.
New PQTW's
Refer to 13.1.8.
Existing POTW's
Method; Improve the site grading
plan to eliminte any ponding of pre-
cipitation; however, do not allow
direct runoff of sludge into surface
waters. Refer to 13.3.5.
Unit Operation/Component: 13.4 Planning
13.4.1 Inadequate con-
sideration of sludge
concentration/transpor-
tation trade-offs.
13.4.2 Inadequate con-
sideration of site
geology/topography and
climate.
New and Existing PQTW's
Refer to 13.1.2.
New and Existing PQTW's
Refer to 13.1.3.
13.3.5 - 13.4.2
382
-------
DEFICIENCY
CONSIDERATIONS
13.4.3 Inadequate con-
sideration of hydraulic
transport reduction due
to ion exchange.
13.4.4 Inadequate con-
sideration of equipment
utility in all weather
conditions.
New and Existing POTW's
Refer to 13.3.3.
New and Existing POTW's
Make provisions for temporary storage
of sludge during wet weather or
freezing conditions.
Provide special area near entrance
for sludge disposal during inclement
weather disposal. Provide tracked
equipment (front-end loaders,
bulldozers, backhoe, etc.).
Provide flexibility to convert from
subsurface application during wet or
frozen ground conditions.
Provide paved or all-weather roads at
site.
13.4.5 Lack of vector
control.
13.4.6 Inadequate con-
sideration of nutrients
and public health haz-
ards (metals, bacteria)
transport in soil/
groundwater.
13.4.7 Inadequate buf-
fer zone at disposal
site.
13.4.8 Lack of odor
control/prevention.
13.4.9 Sludge loading
delayed due to lack of
truck or container
capacity.
New and Existing POTW's
Cover sludge daily with a minimum of
6 inches of cover material.
Provide flexibility to utilize soil
injection in lieu of surface spray-
ing, if required.
New and Existing POTW's
Refer to 13.1.6.
New and Existing POTW's
Refer to 13.1.7.
New and Existing POTW's
Refer to 13.1.8 and 13.3.8.
New and Existing POTW's
Refer to 13.1.9.
13.4.3 - 13.4.9
383
-------
Design Considerations
Category:14. 0 Sludge
Reduction
Unit Operation/Component:.
14.1 General
DEFICIENCY
14.1.1 Inadequate con-
sideration of equipment
arrangement in overall
process flow.
14.1.2 Inadequate
sludge storage during
maintenance periods.
14.1.3 Use of high
volumes of city water
for air scrubbers
instead of plant util-
ity water.
CONSIDERATIONS
New and Existing POTW's
All sludge reduction devices require
the use of energy to attain and main-
tain an operating temperature. Any
handling of solids prior to sludge
reduction which involve dilution or
the addition of water should be
eliminated; rather, the material
should be dried as much as possible
prior to sludge reduction.
New and Existing POTW's
Provision must be made to store the
sludge in its least putrescible form
between the point of wasting and
prior to sludge reduction. The
storage capacity provided must be
compatible with the downtime which
is typically reported for the sludge
reduction operation to be utilized
at the POTW.
New POTW's
Provide scrubber water pumps that
utilize final effluent for air pollu-
tion control uses.
14.1.1 - 14.1.3
384
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DEFICIENCY
CONSIDERATIONS
14.1.4 Inadequate con-
sideration of fresh air
supply and overall ven-
tilation requirements.
14.1.5 Improper feed
equipment selection.
14.1.6 Inadequate con-
sideration of impact of
recycle streams on main
stream processes.
Existing POTW's
Method; Install scrubber water
pumps and a sump (if necessary) that
utilize POTW effluent for the
scrubber. Consider installing
larger utility water pumps (or pump
impellers, if applicable) and tie
the scrubber water system into the
plant utility water system.
New POTW's
For all sludge reduction units that
operate at elevated temperatures,
ensure that adequate fresh air supply
and ventilation are provided for
operator safety in the vicinity of
the unit, and to meet current OSHA
requirements for maximum tempera-
tures for shift operation.
Existing POTW's
Method; Refer to OSHA requirements
and install appropriately-sized ven-
tilation fans in sludge dewatering
area.
New and Existing POTW's
The two major characteristics of feed
equipment that must be considered for
sludge reduction are the ability to
deliver the required mass flow of
material working against the back
pressure of the sludge reduction
equipment and the ability to provide
a suitably steady flow to the reduc-
tion operation. Belt or screw con-
veyors are typically used to carry
sludge into incinerators and for ash
handling.
New POTW's
Waste streams generated by sludge
reduction processes are generally
recycled back to the head end of the
14.1.3 - 14.1.6
385
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DEFICIENCY
CONSIDERATIONS
14.1.7 Improper selec-
tion of materials of
construction results in
excessive corrosion.
14.1.8 Improper con-
sideration of reliabil-
ity of mechanical com-
ponents .
14.1.9 Inadequate con-
sideration of back-up
equipment requirements.
POTW. These waste streams can
significantly add to both the
organic and hydraulic loading to the
POTW and must be considered when
sizing main stream unit operations.
Existing PQTW's
Method: Provide pretreatment of
sidestreams prior to discharge to
head-end of plant. This could
include flow equalization and/or
solids removal.
New and Existing POTW's
In oxidative treatment processes that
operate at elevated temperatures,
sulfides (which may be oxidized to
sulfuric acids) and chlorides provide
special concerns for corrosion.
Equipment specifications should
involve consulting the manufacturer
as to corrosion resistance under
operating conditions.
New and Existing POTW's
Minimizing system down-time and pro-
viding consistent operation requires
consideration of two aspects: provi-
sion for adequate sludge storage, and
provision for back-up units to main-
tain reliable operation during equip-
ment maintenance periods. Refer to
14.1.2 and 14.1.9.
New and Existing POTW's
In general, the degree of duplication
of facilities must be proportional to
the complexity of the unit operation.
For large expensive operations, it
is generally more economical to pro-
vide greater sludge storage with a
single large unit than the duplica-
tion of smaller auxiliary equipment.
14.1.6 - 14.1.9
386
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DEFICIENCY
CONSIDERATIONS
14.1.10 Inadequate
instrument monitoring
of process flows (flue-
gas temperature, pres-
sure) and inadequate
number of monitoring
points (before and
after scrubber) .
14.1.11 No stack sam-
pling ports provided.
14.1.12 Lack of pro-
tective insulation on
exposed hot piping.
14.1.13 Inadequate
consideration of ulti-
mate residue disposal,
New and Existing PQTW's
Spot sampling analysis at elevated
temperatures is extremely difficult
and represents a safety problem;
therefore, great care must be taken
to ensure that maintainable, accessi-
ble sample points and instrument
locations are provided which fully
characterize the design and control
parameters for the unit.
New POTW's
Stack sampling ports should be
included as part of the original POTW
design. Local ordinances should be
referred to in order to determine
sampling requirements.
Existing POTW's
Method; Install stack sampling ports
before and after air pollution
control equipment. Refer to EPA
guide-lines "Methods for Air
Sampling, Volumes I and II" for
sampling port specifications. Refer
to OSHA regulations for construction
specifications related to safety
scaffolding and walkways.
New and Existing POTW's
For operator protection, insulation
should be wrapped around all exposed
hot piping, particularly along walk-
ways and other areas characterized by
high operator activity.
New and Existing POTW's
The flow balance for the sludge
reduction unit should include all
input streams (that is, fuel, air,
water, and residue) and ensure that
a proper (i.e., closed) balance is
drawn around the sludge reduction
system. In particular, ensure that
14.1.10 - 14.1.13
387
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DEFICIENCY
CONSIDERATIONS
the ash content of the material going
to sludge reduction has been ade-
quately characterized. The flow bal-
ance can then be used to identify the
characteristics and the quantity of
residue that must be ultimately dis-
posed of in some manner. This could
include landfilling, reuse as a
sludge conditioner prior to dewater-
ing, an additive for concrete, ground
cover, etc.
Unit Operation/Component: 14.2
Multiple Hearth
Incineration
14.2.1 Inadequate
sludge storage during
maintenance periods.
14.2.2 Inadequate
consideration of feed
solids concentration.
14.2.3 Use of high
volumes of city water
for air scrubbers
instead of plant util-
ity water.
14.2.4 No heat
exchanger provided to
make use of waste heat.
14.2.5 Inadequate con-
sideration of fresh air
supply and overall ven-
tilation requirements.
New and Existing POTW's
Provide a minimum sludge storage
capacity of 30 days.
New and Existing PQTW's
Ensure that the solids loading per
unit of hearth area falls within the
manufacturer's recommendations.
New and Existing PQTW's
To reduce POTW operating costs, plant
effluent should be used as the scrub-
bet water source. Refer to 14.1.3.
New and Existing POTW's
Provide heat exchangers in equipment
exhaust air ducts and/or residue
quenching exhaust ducts to collect
waste heat to the degree economically
possible.
New and Existing POTW's
Consider locating the incinerator
outdoors with the control room in an
enclosed and suitably-ventilated
building; or, if the incinerator is
located within the building, close
off or provide sufficient ventilation
14.1.13 - 14.2.5
388
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DEFICIENCY
CONSIDERATIONS
14.2.6 Improper feed
equipment selection.
14.2.7 Inadequate pro-
visions for reliable
auxiliary fuel source.
14.2.8 Inadequate con-
sideration of impact of
recycle streams on main
stream processes.
14.2.9 Improper selec-
tion of materials of
construction results in
excessive corrosion.
14.2.10 Improper con-
sideration of reliabil-
ity of mechanical com-
ponents.
14.2.11 Inadequate
consideration of back-
up equipment require-
ments .
14.2.12 Inadequate
consideration of impact
of excess scale and ash
on air pollution equip-
ment and ash removal
facilities.
to maintain acceptable operating tem-
peratures for the operators in the
working area. Refer to 14.1.4.
New and Existing POTW's
Refer to 14.1.5.
New and Existing PQTW's
Provide on-site storage of either
natural gas or fuel oil with a mini-
mum supply of 60 days.
New and Existing PQTW's
Refer to 14.1.6.
New and Existing POTW's
Incinerated materials must be able to
resist the reducing environment in
the upper portion of the incinerator,
as well as high temperature chloride
corrosion and sulfuric acid produc-
tion. Refer to 14.1.7.
New and Existing POTW's
Consider the need for spare rabble
arms and teeth, which represent the
highest wear points. Refer to
14.1.8.
New and Existing POTW's
It is seldom practicable to provide
dual units; therefore, a minimum
sludge storage capacity of 60 days is
recommended.
New POTW's
In order to properly size air pollu-
tion control equipment, sufficient
testing must be performed prior to
design to ensure that the ash content
of the feed material has been ade-
quately characterized so that realis-
tic ash quantities can be predicted.
14.2.5 - 14.2.12
389
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DEFICIENCY
CONSIDERATIONS
14.2.13 Improper
selection of equipment
drives for service in
high-temperature areas.
14.2.14 No oxygen
analyzing equipment
provided to monitor
burn.
14.2.15 No remote
control capability
provided for burners
to optimize burn.
14.2.16 No remote
control capability
provided for shaft
drive to optimize burn.
14.2.17 Improper use
of mercury manometers
for scrubber water flow
measurement causes loss
of mercury into system
during system surges.
14.2.18 No remote
control provided for
natural draft and
induced draft flow
control valves.
14.2.19 Inadequate
instrument monitoring
of process flows (flue
gas temperature, pres-
Existing POTW's
Method; Upgrade the air pollution
control system to handle increased
quantities of ash.
New and Existing POTW's
Temperature controls and cooling air
controls must be provided to ensure
that equipment drive temperatures do
not exceed the manufacturer's
requirements.
New and Existing POTW's
Ensure that oxygen analyzing equip-
ment is provided on intake air and
exhaust streams so that ventilation
controls may be tied into the oxygen
analyzer equipment.
New and Existing POTW's
Provide, where possible, integrated
control equipment to analyze and con-
trol oxygen, burn temperatures, and
fuel supplies.
New and Existing POTW's
Provide remote controls to allow
operator to adjust shaft rotation
speed (usually 0.5 to 1.5 rpm).
New and Existing POTW's
Specify closed manometer systems
that do not use mercury.
New and Existing POTW's
Refer to 14.2.14.
New and Existing PQTW's
Numerous parameters should be mon-
itored to properly control the incin-
eration process. These would include
14.2.12 - 14.2.19
390
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DEFICIENCY
CONSIDERATIONS
sure) and inadequate
number of monitoring
points (before and
after scrubber).
14.2.20 No stack
sampling ports pro-
vided.
14.2.21 Lack of pro-
tective insulation on
exposed hot piping.
14.2.22 Inadequate
access to incinerator
ash container.
14.2.23 Inadequate
consideration of ulti-
mate residue disposal,
14.2.24 Inadequate
odor control.
oxygen, carbon dioxide, carbon mon-
oxide, temperature, pressure, etc. of
the stack gas. The temperature of
the individual hearths must also be
monitored. Refer to 14.1.10.
New and Existing POTW's
Refer to 14.1.11 and 14.2.19.
New and Existing PQTW's
Refer to 14.1.12.
New and Existing POTW's
Provide sufficient and convenient
operator access to the ash container
at the bottom of the incinerator.
New and Existing POTW1s
The residue from the sludge reduc-
tion operation may have a high heavy-
metal content. Also, the material
may be susceptible to leaching and
may well be deemed hazardous under
current or future regulations; there-
fore, care should be taken to ensure
that the characteristics of the mate-
rial to be handled have been accu-
rately identified and that the dis-
posal facility is licensed for han-
dling potentially hazardous material.
Refer to 14.1.13.
New and Existing POTWs
For excess-air multiple hearth incin-
eration, either water scrubbing or
after burning is necessary in many
areas for odor control. For starved-
air multiple hearth incineration,
pyrolysis or ignition of the fuel gas
produced during pyrolysis provides
acceptable odor control for most
areas.
14.2.19 - 14.2.24
391
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DEFICIENCY
CONSIDERATIONS
14.2.25 Inadequate
air pollution control.
New and Existing POTW's
Prior to specification of air pollu-
tion control equipment, care must be
taken to determine the regulatory
requirements for air pollution con-
trol which are highly site-specific,
and require careful investigation.
Scrubbers and electrostatic precip-
itators are commonly-used air pollu-
tion control devices.
Unit Operation/Component: 14.3 Heat Treatment
14.3.1 Inadequate
sludge storage during
maintenance periods.
14.3.2 Inadequate
consideration of feed
solids concentration.
14.3.3 Use of high
volumes of city water
for air scrubbers instead
of plant utility water.
14.3.4 No heat
exchanger provided
to make use of waste
heat.
14.3.5 Inadequate
consideration of
fresh air supply
and overall ventila-
tion requirements.
14.3.6 Improper feed
equipment selection.
New and Existing POTW's
Provide a minimum of 60 days sludge
storage.
New and Existing POTW's
Ensure that feed pumps are capable
of handling the high viscosity mate-
rial to be fed to the sludge reduc-
tion unit.
New and Existing PQTW's
Refer to 14.1.3.
New and Existing POTW's
Provide a heat exchanger in the
equipment exhaust stream if it is
not provided as part of the manu-
facturer's equipment.
New and Existing POTW's
Refer to 14.1.4.
New and Existing POTW's
Refer to 14.1.5.
14.2.25 - 14.3.6
392
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DEFICIENCY
CONSIDERATIONS
14.3.7 Inadequate
consideration of
impact of recycle
streams on main
stream processes.
14.3.8 Improper
selection of mate-
rials of construc-
tion results in
excessive corrosion.
14.3.9 Improper con-
sideration of relia-
bility of mechanical
components.
14.3.10 Inadequate
consideration of back-
up equipment require-
ments.
14.3.11 Improper use
of mercury manometers
for scrubber water
flow measurement causes
loss of mercury into
system during system
surges.
New POTW's
The return stream from a heat treat-
ment operation may amount to 30 per-
cent of the design organic load of
the main stream treatment plant.
Failure to include this in the mate-
rial balance will have a significant
effect upon the operational stabil-
ity of the plant. Also, where pos-
sible, the return stream to the main
stream plant should be as constant
as possible and should be discharged
upstream of the plant grit chambers
in order to allow removal of as much
solid material as possible prior to
providing secondary treatment.
Method:
Existing POTW's
Refer to 14.1.6.
New and Existing POTW's
Ensure that piping used to transfer
material to and from the heat treat-
ment area is compatible with the
materials of construction in the unit
to prevent dissimilar metals corro-
sion or corrosion due to the mate-
rials being handled.
New and Existing PQTW's
It is seldom practical to provide
two heat treatment units; there-
fore, a minimum sludge storage
capacity of 60 days is recommended
to allow for equipment downtime.
New and Existing POTW's
Refer to 14.1.9 and 14.3.9.
New and Existing POTW's
Refer to 14.2.17.
14.3.7 - 14.3.11
393
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DEFICIENCY
CONSIDERATIONS
14.3.12 Inadequate
instrument monitoring
of process flows (flue
gas temperature, pres-
sure) and inadequate
number of monitoring
points (before and
after scrubber).
14.3.13 Lack of pro-
tective insulation on
exposed hot piping.
14.3.14 Inadequate
consideration of ulti-
mate residue disposal.
New and Existing POTW's
Refer to 14.1.10 and 14.2.19.
14.3.15 Inadequate
odor control.
14.3.16 Inadequate
air pollution control,
New and Existing POTW's
Refer to 14.1.12.
New and Existing POTW's
The return stream from heat treat-
ment may amount to 30 percent of the
designed organic load to the waste
treatment plant and, therefore,
greatly influence the quantity of
solids generated and which must
ultimately be disposed of in some
manner. Refer to 14.2.23.
New and Existing PQTW's
Where possible, provide heat treat-
ment in an enclosed area with forced
ventilation exiting through either
an activated carbon or ozone odor
control system in order to elim-
inate the characteristic odor gen-
erated by heat treatment units.
New and Existing POTW's
Refer to 14.3.15.
Unit Operation/Component: 14.4 Fluidized Bed
14.4.1 Inadequate
sludge storage during
maintenance periods.
New and Existing POTW's
It is seldom practical to provide
duplicate equipment for this oper-
ation; therefore, a minimum sludge
storage capacity of 60 days is rec-
ommended.
14.3.12 - 14.4.1
394
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DEFICIENCY
CONSIDERATIONS
14.4.2 Inadequate
consideration of feed
solids concentration.
14.4.3 Use of high
volumes of city water
for air scrubbers
instead of plant
utility water.
14.4.4 No heat
exchanger provided
to make use of waste
heat.
14.4.5 Inadequate
consideration of fresh
air supply and overall
ventilation requirements,
14.4.6 Improper feed
equipment selection.
14.4.7 Inadequate
provisions for
reliable auxiliary
fuel source.
14.4.8 Inadequate
consideration of impact
of recycle streams on
main stream processes.
14.4.9 Improper
selection of materials
of construction results
in excessive corrosion.
14.4.10 Improper
consideration of
reliability of mechan-
ical components.
New and Existing POTW's
Ensure that the pumping equipment
is capable of pumping high viscous
material through the fluidized bed,
New and Existing POTW's
Refer to 14.1.3.
New and Existing POTW's
Refer to 14.2.4.
New and Existing POTW's
Refer to 14.1.4.
New and Existing POTW's
Refer to 14.1.5.
New and Existing POTW's
Provide a minimum of 60 days storage
of either fuel oil or natural gas.
New and Existing POTW's
Refer to 14.1.6.
New and Existing POTW's
Refer to 14.1.7 and 14.2.9.
New and Existing POTW's
Refer to 14.2.10.
14.4.2 - 14.4.10
395
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DEFICIENCY
CONSIDERATIONS
14.4.11 Inadequate
consideration of
back-up equipment
requirements.
14.4.12 Inadequate
consideration of impact
of excess scale and
ash on air pollution
equipment and ash
removal facilities.
New and Existing POTW's
Refer to 14.2.11.
New and Existing PQTW's
Refer to 14.2.12.
14.4.13 Improper
selection of equip-
ment drives for serv-
ice in high-temper-
ature areas.
14.4.14 No oxygen
analyzing equipment
provided to monitor
burn.
New and Existing PQTW's
Refer to 14.2.13.
New and Existing POTW's
Refer to 14.2.14.
14.4.15 No remote
control capability
provided for burners
to optimize burn.
14.4.16 Improper use
of mercury manometers
for scrubber water flow
measurements causes loss
of mercury into system
during system surges.
14.4.17 Inadequate
instrument monitoring
of process flows (flue
gas temperature, pres-
sure) and inadequate
number of monitoring
points (before and
after scrubber).
14.4.18 Lack of
protective insula-
tion on exposed hot
piping.
New and Existing POTW's
Refer to 14.2.15.
New and Existing POTW's
Refer to 14.2.17.
New and Existing POTW's
Refer to 14.1.10.
New and Existing POTW's
Refer to 14.1.12.
14.4.11 - 14.4.18
396
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DEFICIENCY
CONSIDERATIONS
14.4.19 Inadequate
consideration of
ultimate residue
disposal.
14.4.20 Inadequate
odor control.
14.4.21 Inadequate
air pollution control,
New and Existing POTW's
Refer to 14.2.23.
New and Existing POTW's
Refer to 14.2.24.
New and Existing POTW's
Refer to 14.2.25.
Unit Operation/Component: 14.5 Flash Drying
14.5.1 Inadequate
sludge storage dur-
ing maintenance
periods.
14.5.2 Inadequate
consideration of feed
solids concentration.
14.5.3 Use of high
volumes of city water
for air scrubbers
instead of plant
utility water.
14.5.4 No heat
exchanger provided
to make use of waste
heat.
14.5.5 Improper feed
equipment selection.
14.5.6 Inadequate
provisions for reli-
able auxiliary fuel
source.
New and Existing POTW's
Refer to 14.3.1.
New and Existing PQTW's
Refer to 14.2.2.
New and Existing POTW's
Refer to 14.1.3.
New and Existing POTW's
Refer to 14.3.4.
New and Existing POTW's
Refer to 14.1.5.
New and Existing POTW's
Provide 60 days storage capacity for
either fuel oil or natural gas.
14.4.19 - 14.5.6
397
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DEFICIENCY
CONSIDERATIONS
14.5.7 Inadequate
consideration of
impact of recycle
streams on main
stream processes.
14.5.8 Improper
selection of mate-
rials of construction
results in excessive
corrosion.
14.5.9 Improper con-
sideration of relia-
bility of mechanical
components.
14.5.10 Improper use
of mercury manometers
for scrubber water flow
measurement causes loss
of mercury into system
during system surges.
14.5.11 Inadequate
instrument monitoring
of process flows (flue
gas temperature, pres-
sure) and inadequate
number of monitoring
points (before and after
scrubber).
14.5.12 Lack of pro-
tective insulation on
exposed hot piping.
14.5.13 Inadequate
odor control.
14.5.14 Inadequate
air pollution control.
New and Existing POTW's
Refer to 14.1.6.
New and Existing POTW's
Refer to 14.1.7 and 14.2.9.
New and Existing POTW's
Provide a back-up piece of equipment
as well as a minimum of 30 days of
sludge storage capacity.
New and Existing POTW's
Refer to 14.2.17.
New and Existing PQTW's
Refer to 14.1-.10.
New and Existing POTW's
Refer to 14.1.12.
New and Existing POTW's
Refer to 14.3.15.
New and Existing POTW's
Refer to 14.2.25 and 14.3.16.
14.5.7 - 14.5.14
398
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DEFICIENCY
CONSIDERATIONS
Unit Operation/Component:
14.6
Composting
14.6.1 Inadequate
space for sludge
staging and prep-
aration.
14.6.2 Inadequate
sludge storage during
maintenance periods.
14.6.3 Inadequate con-
sideration of feed
solids concentration.
14.6.4 Inadequate
consideration of fresh
air supply and overall
ventilation requirements,
New and Existing POTW's
Provide a minimum of 10 acres per ton
of dry sludge to be handled.
New and Existing PQTW's
Maintenance will be required when
the operating area becomes inacces-
sible due to inclement weather,
during personnel strikes, or if
filler material becomes unavailable.
Provide for a minimum sludge storage
capacity of 60 days.
New PQTW's
Ensure that the feed stream pretreat-
ment provides an acceptable material
with regard to moisture content and
solids concentration.
Method:
Existing POTW's
Ensure that the feed stream
pretreatment provides an acceptable
material with regard to moisture con-
tent and solids concentration. Pro-
vide a chemical conditioning system
to improve upstream dewatering opera-
tion.
New POTW's
Provide for positive control of the
air volume entering the composting
pile.
Method:
Existing PQTW's
Provide for positive control
of the air volume entering the com-
posting pile. Install air flow
meters and flow control valves.
14.6.1 - 14.6.4
399
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DEFICIENCY
CONSIDERATIONS
14.6.5 Inadequate pro-
visions for reliable
auxiliary fuel source.
14.6.6 Improper
selection of mate-
rials of construction
results in excessive
corrosion.
14.6.7 Improper con-
sideration of reli-
ability of mechanical
components.
14.6.8 Inadequate
consideration of
ultimate residue
disposal.
14.6.9 Inadequate
odor control.
New and Existing PQTW's
Ensure that contracts are available
for a minimum of four suppliers of
the filler material in the event it
becomes unavailable from the pre-
ferred supplier.
New and Existing POTW's
Refer to 14.1.7.
New and Existing POTW's
Provide back-up equipment for turn-
ing the composting pile. Specify
that a minimum of 50-percent excess
compost handling equipment is avail-
able.
New and Existing POTW's
Care must be taken in drawing up the
material balance to ensure that the
filler material (for example, wood
chips) has been included in the mate-
rial balance. Refer to 14.2.23.
New and Existing POTW's
Provide for back-up equipment to turn
and repress the pile in the event of
severe odor problems. Refer to
14.6.4.
Unit Operation/Component: 14.7 Atomized Spray
14.7.1 Inadequate
sludge storage
during maintenance
periods.
14.7.2 Inadequate con-
sideration of feed
solids concentration.
New and Existing POTW's
Provide a minimum of 30 days sludge
storage.
New and Existing POTW's
Provide sludge density meters to
ensure that the feed solids concen-
tration is not excessively high,
preferably less than 8 percent for
waste activated sludge.
14.6.5 - 14.7.2
400
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DEFICIENCY
CONSIDERATIONS
14.7.3 Improper con-
sideration of reli-
ability of mechanical
components.
14.7.4 Inadequate
consideration of impact
of excess scale and
ash on air pollution
equipment and ash
removal facilities.
14.7.5 Inadequate
consideration of ulti-
mate residue disposal.
14.7.6 Inadequate
air pollution control.
New and Existing POTW's
The impact of the added ash load to
the ash removing equipment must be
considered in determining the size
and type of equipment to be used.
Refer to 14.1.8 and 14.2.10.
New and Existing PQTW's
Refer to 14.2.12.
New and Existing PQTW's
The ash produced by burning the
atomized spray material must be
included in the plant residue han-
dling system. Refer to 14.2.23.
New and Existing POTW's
Ensure that consideration of the com-
ponents of the sludge, notably chlor-
inated hydrocarbons and metals, has
been included in the air pollution
control considerations for the burn-
ing equipment. Air pollution control
requirements are very site specific;
therefore, ensure that injection of
these materials is an acceptable
alternative.
Unit Operation/Component: 14.8 Co-Incineration
14.8.1 Inadequate
sludge storage during
maintenance periods.
14.8.2 Inadequate
consideration of feed
solids concentration.
New and Existing POTW's
Refer to 14.2.1.
New and Existing POTW's
Refer to 14.2.2.
14.7.3 - 14.8.2
401
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DEFICIENCY
CONSIDERATIONS
14.8.3 Use of high
volumes of city water
for air scrubbers
instead of plant
utility water.
14.8.4 No heat
exchanger provided
to make use of waste
heat.
14.8.5 Inadequate con-
sideration of fresh
air supply and overall
ventilation requirements,
14.8.6 Improper feed
equipment selection.
14.8.7 Inadequate pro*-
visions for reliable
auxiliary fuel source.
14.8.8 Inadequate con-
sideration of impact
of recycle streams on
main stream processes.
14.8.9 Improper
selection of mate-
rials of construction
results in excessive
corrosion.
14.8.10 Improper con-
sideration of reli-
ability of mechanical
components.
14.8.11 Inadequate
consideration of
back-up equipment
requirements.
New and Existing POTW's
Refer to 14.2.3.
New and Existing POTW's
Refer to 14.2.4.
New and Existing POTW's
Refer to 14.2.5.
New and Existing POTW's
Refer to 14.1.5.
New and Existing POTW's
Refer to 14.2.7.
New and Existing POTW's
Refer to 14.1.6.
New and Existing POTW's
Refer to 14.2.9.
New and Existing POTW's
Refer to 14.2.10.
New and Existing POTW's
Refer to 14.2.11.
14.8.3 - 14.8.11
402
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DEFICIENCY
CONSIDERATIONS
14.8.12 Inadequate
consideration of
impact of excess scale
and ash on air pollu-
tion equipment and ash
removal facilities.
14.8.13 Improper
selection of equip-
ment drives for service
in high-temperature
areas.
14.8.14 No oxygen
analyzing equipment
provided to monitor
burn.
New and Existing POTW's
Refer to 14.2.12.
New and Existing POTW's
Refer to 14.2.13.
New and Existing POTW's
Refer to 14.2.14.
14.8.15 No remote
control capability
provided for burners
to optimize burn.
14.8.16 No remote
control capability
provided for shaft
drive to optimize
burn.
14.8.17 Improper use
of mercury manometers
for scrubber water flow
measurement causes loss
of mercury into system
during system surges.
14.8.18 No remote
control provided for
natural draft and
induced draft flow
control valves.
New and Existing POTW's
Refer to 14.2.15.
New and Existing PQTW's
Refer to 14.2.16.
New and Existing POTW's
Refer to 14.2.17.
New and Existing POTW's
Refer to 14.2.14.
14.8.12 - 14.8.18
403
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DEFICIENCY
14.8.19 Inadequate
instrument monitoring
of process flows (flue
gas temperature, pres-
sure) and inadequate
number of monitoring
points (before and
after scrubber).
14.8.20 No stack
sampling ports pro-
vided.
14.8.21 Lack of pro-
tective insulation on
exposed hot piping.
14.8.22 Inadequate
access to incinerator
ash container.
14.8.23 Inadequate
consideration of ulti-
mate residue disposal.
CONSIDERATIONS
New and Existing POTW's
Refer to 14.2.19.
14.8.24 Inadequate
odor control.
New and Existing POTW's
Refer to 14.1.11 and 14.2.19.
New and Existing POTW's
Refer to 14.1.12.
New and Existing POTW's
Refer to 14.2.22.
New and Existing PQTW's
The addition of sludges to municipal
solid waste may well provide an ulti-
mate residue with a higher ash and
metal content than the solid waste
by itself. Care must be taken to
ensure that the ultimate disposal
facility can accept these materials.
New and Existing POTW's
Refer to 14.2.24.
14.8.25 Inadequate
air pollution control.
New and Existing POTW's
Refer to 14.2.25.
14.8.19 - 14.8.25
404
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Design Considerations
Category:15. 0 Rotating
Biological
Contactors
Unit Operation/Component:.
l-J.l i^ene
DEFICIENCY
15.1.1 Bearings locat-
ed below grade and are
susceptible to flood-
ing .
CONSIDERATIONS
New POTW's
Locate RBC unit so that the bearing
assembly is out of the tank and at
grade level.
15.1.2 Buildings not
insulated and facility
loses heat in winter,
causing wastewater
temperature to drop.
15.1.3 Primary clari-
fiers not provided,
causing settling and
plugging of media.
Existing POTW's
Method; Provide pressure lubrication
system to minimize effects of flood-
ing on bearings.
New POTW's
Provide insulated housing which is
designed for the lowest ambient
temperature to maintain the waste-
water at a minimum of 55°F.
Existing PQTW's
Method; Provide weather stripping,
gaskets, and insulation. Supplemen-
tal heat input may be required in the
form of portable heaters or perma-
nently-mounted electric heaters.
New and Existing POTW's
Provide for primary sedimentation
facilities upstream of RBC units.
15.1.1 - 15.1.3
405
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DEFICIENCY
CONSIDERATIONS
15,1.4 Excessive
collection system
detention times
promote incoming
peptic waste.
15.1.5 Inadequate
consideration of
possible develop-
ment of septic
conditions in
channels.
15.1.6 Sidestreams not
accounted for in design
of RBC units.
New POTW's
The design of the collection system
should provide for a minimum waste-
water velocity of 2 fps. The effec-
tive detention time of the pump sta-
tion wet well should not exceed 10
minutes for the design average 24-
hour flow.
Existing POTW's
Method: Provide aeration of pump
station wet well by use of spargers
or diffusers. The detention time
should be maximized by setting the
controls on the pumps so that the
well is not pumped down very far.
Materials; Compressor, piping.
New POTW's
Design channels for a flow velocity
of 2 ft/sec at design flow. Provide
means to clean out channels (i.e.,
to remove settled solids and/or
scum). Provide the flexibility to
aerate channels carrying raw waste-
water .
Existing PQTW's
Method; Inject air along the chan-
nels to maintain aerobic conditions.
The channels could also be parti-
tioned off to reduce their volume
and, therefore, increase flow-thru
velocities and the time wastewater
or sludge is allowed to remain in
them.
New POTW's
Since the RBC units exhibit first-
order kinetics at a specific hydrau-
lic loading, a specific percentage
removal of BOD will occur independent
of the organic loading. The primary
design criterion is hydraulic loading
15.1.4 - 15.1.6
406
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DEFICIENCY
CONSIDERATIONS
15.1.7 Inadequate
screening of raw wastes
causes plugging of RBC
media.
which must include the sidestream
from other unit processes.
Existing POTW's
Method: If sidestream is producing
an organic overload in the first
stage, remove baffle between first
and second stage to increase avail-
able surface area for first-stage
treatment.
Implement pretreatment and/or equal-
ization of sidestreams prior to dis-
charge to the RBC system.
New PQTW' s
Provide preliminary treatment via
comminutors and bar screens. Remove
rags and screenings from system
rather than grinding them up and
putting them back into the system.
Existing POTW's
Method; Construct grit removal and
screening devices upstream of influ-
ent wet well. Refer to 2.1.3,
2.3.1, and 2.6.1.
Unit Operation/Component: 15.2 RBC
15.2.1 Bearings locat-
ed below grade and are
susceptible to flooding.
15.2.2 Buildings not
insulated and facility
loses heat in winter,
causing wastewater
temperatures to drop.
15.2.3 Insufficient
tank mixing causes
dead spots and solids
deposition in RBC
tank.
New and Existing POTW's
Refer to 15.1.1.
New and Existing POTW's
Refer to 15.1.2.
New POTW's
Rotational velocity affects waste-
water treatment in several ways:
it provides contact between the bio-
mass and the wastewater, it shears
15.1.6 - 15.2.3
407
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DEFICIENCY
15.2.4 Improper design
of overflow baffles
between stages causes
solids deposition.
15.2.5 Inadequate
screening of raw wastes
causes plugging of RBC
media.
CONSIDERATIONS
excess biomass, it aerates the waste-
water, and it provides the necessary
mixing velocity in each stage.
Increasing the rotational velocity
increases the effect of each of these
factors.
The optimum peripheral velocity for
domestic wastewater is 60 ft/min.
This corresponds to a rotational
speed varying from 1.6 to 2.9 rpm,
depending on the media size.
Method:
Existing PQTVTs
Increase sheave size to
increase rotational speed of RBC
unit.
Provide supplemental air for mixing.
New PQTW's
Specify underflow baffle to minimize
solids deposition.
Method:
Existing POTW's
Construct wooden baffles
with underflow design.
New PQTW' s
Provide preliminary treatment via
comminutors and bar screens. Remove
rags and screenings from system
rather than grinding them up and
putting them back into the system.
Existing POTW's
Method; Refer to 2.1.3, 2.3.1,
2.6.1, and 15.1.7.
lb.2.3 - 15.2.5
408
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DEFICIENCY
CONSIDERATIONS
Unit Operation/Component: 15.3 Secondary Clarification
15.3.1 No provision
for addition of chemi-
cals to improve set-
tling characteristics,
15.3.2 No provision
for measuring and sam-
pling waste sludge
flow.
New POTW's
Provide a chemical addition system
to enable the operator to feed set-
tling aids, such as alum or polymer,
to secondary clarifiers.
Method:
Existing POTW's
Install chemical addition
system near effluent trough of RBC
system. Allow in-line mixing between
effluent trough and center well of
clarifier.
Materials; Chemical make-up and
storage system, piping, and related
appurtenances. Building to house
equipment and chemicals.
New POTW's
Provide flow meters on sludge waste
lines and specify a flow totalizer as
part of the instrumentation package.
This allows the POTW operator to com-
pute a solids balance for solids
handling purposes.
Existing POTW's
Method; Install a flow meter in the
waste sludge line. Install 1 1/2 to
3 inch sample tees on sludge pump
discharge line.
Materials; Flow meter, pipe valves,
and related appurtenances.
15.3.1 - 15.3.2
409
i U S GOVERNMENT PRINTING OFFICE 1962 -559-09Z/0427
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