EPA-43O-99-74-OOI

SUPPLIMENT TO FEDERAL GUIDELINES:  DESIGN, OPERATION, AND
MAINTENANCE OF WASTEWATER TREATMENT FACILITIES
    DESIGN CRITERIA FOR
    MECHANICAL, ELECTRIC,
    AND  FLUID SYSTEM AND
    COMPONENT RELIABILITY
        U.S. ENVIRONMENTAL PROTECTION AGENCY
           Office of Water Program Operations
               Washington, D.C. 20460

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                     TECHNICAL BULLETIN
   DESIGN CRITERIA FOR MECHANICAL,  ELECTRIC,
  AND FLUID SYSTEM AND COMPONENT RELIABILITY
        Supplement to Federal Guidelines for Design,
         Operation, and Maintenance of Waste Water
                     Treatment Facilities
             Office of Water Program Operations
           U. S. Environmental Protection Agency
                 Washington, D. C.  20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 85 cents

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                          FOREWORD
In response to the recent clean water legislation, this country
will undertake an unprecedented building program for new and
improved municipal wastewater treatment works.   It is the
responsibility of the EPA to ensure that the Federal funds
authorized under Title II of PL 92-500 for this program will
be justifiably spent.  Accordingly, we must ensure that these
works have been designed with a high degree of technical
excellence and will operate effectively day in and day out.
As a part of this effort, this Technical Bulletin provides
a national standard to help ensure that unacceptable degradation
of the works' effluent does not occur from time to time as
a result of periodic maintenance or the malfunctioning of
mechanical, electric, and fluid systems and components.

To assure a workable and effective document, we have involved
all sectors of the wastewater treatment industry in the develop-
ment and review of this Technical Bulletin.  In this regard,
I particularly wish to thank the EPA Technical Advisory Group
for Municipal Waste Water Systems for their advice and counsel.

The design criteria contained in this Technical Bulletin are
meant to be specific enough to have force and meaning, yet
have administrative flexibility so as to permit innovation as
to how the intent of the criteria will be met in each individual
case.  It is our intent to update and revise these criteria
as experience dictates.

I am confident that through the continued efforts and coopera-
tion of the engineering profession, the objective of improved
reliability of wastewater treatment works will be achieved.
                                        ^,~~k 	-^
                           Robert L.  Sansom
                        Assistant Administrator
                       for Air and Water Programs

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                         TABLE OF CONTENTS
Foreword                                                        i

Purpose                                                          1

Applicability of Technical Bulletin                                1

Definitions                                                      2

Terms  Used in Specifying Criteria                               4

Reliability Classification                                         5

100,    Works  Design Criteria                                    7

200.    System Design Criteria                                   14

   210.    Wastewater Treatment System                         15
   220.    Sludge Handling and Disposal System                  30
   230.    Electric Power System                                38
   240.    Instrumentation and Control Systems                  47
   250.    Auxiliary  Systems                                     49
                                  11

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                DESIGN CRITERIA FOR MECHANICAL,
                ELECTRIC, AND FLUID SYSTEM AND
                     COMPONENT RELIABILITY
Purpose

          The purpose of this Technical Bulletin is to amplify and

supplement the Federal Guidelines for Design,  Operation, and Mainte-

nance of Wastewater Treatment Facilities with regard to establishing

minimum standards of reliability for mechanical, electric, and fluid

systems and components.  This Technical Bulletin provides reliability

design criteria for wastewater treatment  works  projects seeking

Federal financial assistance under PL 92-500.


Applicability  of Technical Bulletin

          New treatment works and additions or  expansions to existing

treatment works shall comply with this Technical Bulletin.  Portions

of existing works,  for which the addition or expansion is  dependent for

reliable operation,  shall comply with this  Technical Bulletin to the

degree  practicable.   There may be some  treatment  works  for  which

fulfillment of some of the design criteria may not  be necessary or

appropriate.  There will be other cases in which these criteria are

insufficient, and additional  criteria will be identified by the Regional

Administrator.  It is  expected that additional criteria may be needed


                                   -1-

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for unusual environmental conditions and for new processes.  Within




this context, the design criteria should be used as a reference,  allowing




additions or deletions as an individual case may warrant.




          A basic requirement specified in these criteria is component




backup.  However,  system reliability can also be attained  through




flexibility in the design and  operation of systems and components.  This





document does not attempt to define requirements for system flexibility.






Definitions




          The following definitions apply to the terms used in this




Technical Bulletin:




   Component  - A single piece of equipment which performs a specific




   function in the wastewater treatment works.  In this context a




   component may be an entire piece of process equipment (e.g.,




   sedimentation basin or vacuum filter) or may be a single piece of




   equipment (e0g. , a valve or a pump).




   Controlled Diversion - Diversion in a controlled manner  of




   inadequately treated wastewater around the  treatment works  to




   navigable waters.




   Design Flow - That flow used as the basis of design of a component




   and/or system.





   Design Period -  The period of time from first operation to the year





   at which  the treatment  works is expected to treat the design flow.
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Effluent Limitation - Any restriction established by a State or the





EPA Administrator on quantities, rates, and concentrations of





chemical,  physical,  biological, and other constituents which are





discharged from point  sources into navigable waters,  the waters of





the contiguous zone, or the ocean, including schedules of compliance.





Fluid System - A system within the treatment works which contains





liquid  or gaseous fluids.  This includes the main wastewater treat-





ment system,  parts  of the  sludge handling and disposal system,  and





auxiliary systems.





Hydraulic  Capacity - The maximum flow capacity of a component





which  does not result in flooding or overflowing.





Navigable  Waters - The waters of the United States,  including the





territorial seas, as  defined in PL 92-500.





Peak Wastewater Flow  - The  maximum wastewater  flow expected





during the design period of the treatment works.





Reliability - A measurement  of the ability of a component or system





to perform its designated function without failure.  In this Technical





Bulletin,  reliability  pertains to mechanical, electric,  and fluid





systems and components only and includes the maintainability of





those systems and components.  Reliability  of biological  processes,





operator training,  process design, or structural design is not within





the scope of this Technical Bulletin.   The reliability aspects related
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   to works'  influent from  combined  sewers  are not within the





   scope  of this Technical  Bulletin.





   Unit Operation - An operation involving a single physical or chemical





   process.  Examples of a unit operation are comminuting,  mixing,





   sedimentation, aeration,  and flocculation.





   Vital Component - A component whose operation or function is





   required to prevent a controlled diversion,  is required to meet





   effluent limitations, or is required to protect other vital components





   from damage.





   Wastewater Treatment Works - The works that treats the waste-





   water, including the associated wastewater pumping or  lift stations,





   whether or not the stations are physically a part of the works.





   Holding ponds or basins are considered included,  whether or not





   the ponds or basins are physically a part of the works.






Terms Used in Specifying Criteria





          The following are clarifications of terms used in specifying





criteria in this Technical Bulletin:





   °    Shall - Used to specify criteria which are  mandatory.  Depar-





       ture from these criteria requires  a Departure Request to be





       submitted by the Grant Applicant and approval of the request





       by the Regional Administrator.
                                 -4-

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   0   Permissible - Used to clarify the intent of mandatory criteria

       by giving examples of designs which are in conformance with

       the criteria.

   0   Consideration and Where Practicable  - Used to  specify criteria

       which shall be considered by the Grant Applicant,  but which are

       not mandatory.


Reliability Classification

          This  Technical Bulletin establishes minimum standards of

reliability for three classes of wastewater treatment works.   Unless

identified as applying to  a particular class, all criteria contained in

this document apply equally to all three classes.   The reliability  classi-

fication shall be selected and justified by the  Grant Applicant, subject

to the approval  of the Regional Administrator, and shall be based on

the consequences of degradation of the  effluent quality on  the receiving

navigable waters.  This  document does  not specify requirements for

classifying works; however,  suggested guidelines are:

Reliability
Class I         Works which discharge into navigable waters that could

                be permanently or unacceptably damaged by  effluent

                which was degraded in quality for only a few hours.

                Examples of Reliability Class I works might be those

                discharging near drinking water  reservoirs, into

                shellfish waters, or in close proximity to areas used

                for water contact sports.

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Reliability
Class II
Reliability
Class III
Works which discharge into navigable waters that would

not be permanently or unacceptably damaged by short-

term effluent quality degradations,  but could be damaged

by continued (on the order of several days) effluent

quality degradation.  An example of a Reliability Class II

works might be one which discharges into recreational

waters.


Works not otherwise  classified as Reliability Class I

or Class II.

Note:  Pumping stations associated with,  but physically
removed from,  the actual treatment works could have
a different classification from the works  itself,,
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                                                Works Design Criteria
             100.	WORKS DESIGN CRITERIA





                                                             Page





110.    Works Location                                         8





120.    Provisions for Works Expansion and/or Upgrading        9





130.    Piping Requirements                                    9





   131.    Pipes Subject to Clogging                             9





   132.    Provisions for Draining Pipes                        10





   133.    Maintenance and Repair of Feed Lines                10





140.    Component Maintenance and Repair Requirements        11





   141.    Component Repair                                   11





   142.    Component Access Space                             12





   143.    Component Handling                                 12





   144.    Essential Services                                   13





150.    Isolation of Hazardous Equipment                        13
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                                                 Works Design Criteria
                100.     WORKS DESIGN CRITERIA
110.    WORKS LOCATION
       The potential for damage or interruption of operation due to




       flooding shall be considered when siting the treatment works.




       The treatment works'  structures and electrical and mechanical




       equipment shall be protected from physical damage by the




       maximum expected one hundred (100) year flood.   The treatment




       works shall remain fully operational during the twenty-five  (25)




       year flood, if practicable; lesser flood levels may be permitted




       dependent on local situations, but in no case shall less than a




       ten (10)  year flood be used.  Works  located in  coastal areas




       subject to flooding by wave action shall be similarly protected




       from the maximum expected twenty-five (25) and one hundred




       (100) year wave actions.







       Existing works being expanded,  modified, upgraded  or rehabili-




       tated shall comply with these criteria  to the degree practicable.







       The flood and wave action  elevations used to implement these




       criteria shall be determined and justified by the Grant Applicant,




       using available data sources  where appropriate.  Elevations for

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                                                  Works Design Criteria


       a specific location may be available from local or state studies

       as well as  studies by the following Federal organizations: U.S.

       Army Corps of Engineers,  U.S. Geological Survey, U.S. Soil

       Conservation Service, National Oceanic and Atmospheric

       Administration, and Tennessee Valley Authority.

       The works shall be accessible in all normal seasonal conditions,

       including the expected annual floods.


120.    PROVISIONS FOR WORKS EXPANSION AND/OR UPGRADING

       All new works and expansions to existing  works shall be designed

       for further expansion except where circumstances  preclude  the

       probability of expansion. During a works1 upgrading or expansion

       the interruption of normal operation shall be minimized and

       shall be subject to the approval of the Regional Administrator.


130.    PIPING REQUIREMENTS
   131.    Pipes Subject to Clogging

   131. 1     Provisions for Flushing of Pipes

             The works shall have provisions for flushing with water

             and/or air all scum lines, sludge lines,  lime feed and

             lime sludge lines, and all other lines which are subject to

             clogging.   The design shall be such that flushing can be

             accomplished without causing violation of effluent limita-

             tions or without cross-connections to the potable water

             system.
                                 -9-

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                                                Works  Design Criteria










131.2     Provisions for Mechanical Cleaning of Pipes





          All piping subject to accumulation of solids over a long





          period of time shall have sufficient connections and shall





          be arranged in a manner to facilitate mechanical cleaning.





          This may include the main wastewater treatment process





          piping,  service water system piping,  and sludge process





          piping.   Special attention shall be paid to piping containing





          material which has a tendency to plug, such as  scum lines,





          drain lines, and lime  sludge lines.  System design shall





          be such that the mechanical cleaning can be accomplished





          without violation of effluent limitations.





132.    Provisions  for Draining Pipes





       Where practicable,  all piping shall be sloped and/or have





       drains (drain plug or valve) at the  low points to permit com-





       plete draining.  Piping shall be installed with no isolated





       pockets which cannot be drained.





133.    Maintenance and Repair of Feed Lines





       Lines feeding chemicals  or process air to basins,  wetwells,





       and tanks shall be designed to enable repair  or replacement





       without drainage of the basins, wetwells  or  tanks.
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                                                  Works Design Criteria


140.    COMPONENT MAINTENANCE AND REPAIR REQUIREMENTS

   141.    Component Repair

          Every vital mechanical component (mechanical components

          include such items as pumps,  bar screens, instrumentation

          and valves, but not piping,  tanks,  basins,  channels, or wells)

          in the works shall be designed to enable repair or replace-

          ment without violating the effluent limitations or causing a

          controlled diversion.  To comply with this requirement, it

          is permissible to use the collection system storage capacity

          or holding basins and to perform maintenance during the low

          influent flow periods.  This requirement applies to shutoff

          and isolation valves.  Provisions shall be made in the  initial

          works  design to permit repair and replacement of these types

          of valves.

          Example:  This criterion applies to the isolation valves of
          main wastewater  pumps.  The following are examples  of ways
          these valves could be maintained.  Pump suction  isolation
          valves can be maintained if the works has a two compartment
          main pump wetwell and if the works  can continue  operation
          (during the diurnal low flow period,  for example) with  one
          part of the wetwell isolated.  Pump discharge isolation valves
          connected to a  pressurized outlet header can be maintained
          if the collection system storage capacity is sufficiently large
          to permit all main wastewater pumps to be stopped (collection
          system storage capacity  is used) while the valve in question
          is removed and blind flanges  installed.
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                                               Works Design Criteria


142.   Component Access Space

       Adequate access and removal space  shall be provided around

       all components to permit easy maintenance and/or removal

       and replacement without interfering  with the operation of

       other equipment.  Components located inside buildings  or

       other structures shall be removable  without affecting the

       structural integrity of the building or creating a safety hazard.

       Normal disassembly of the component is permissible for

       removal and replacement.  This criterion is not intended to

       be applicable to the removal or replacement of large tanks,

       basins,  channels, or wells.

       Note: This criterion requires that consideration be given to
       the sizing  of doors, stairways,  hallways, hatches, elevators
       and other access ways in the initial works  design.  It also
       requires that special thought be given to the physical layout
       of piping systems and components in the initial design,
       especially to components located above  and below  the ground
       level  of buildings and to unusually large components.  The
       complete path of removal from in-plant location,  through
       hatches, doors and passageways,  to  a truck or other service
       vehicle  should be checked and defined for each component.

143.   Component Handling

       The works shall have lifting and handling equipment available

       to aid in the maintenance and replacement  of all components.

       In addition, the  placement of structures and other devices,

       such as pad-eyes and hooks, to aid component handling  shall

       be considered in the initial design.   This is particularly
                              -12-

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                                                  Works Design Criteria









          important for large and/or heavy components which require





          special handling and lifting equipment.  Means shall be





          provided for removal of components located above and below





          the ground level of buildings and other structures.  This





          criterion is not intended to be applicable to the removal or





          replacement of large tanks,  basins,  channels,  or wells.





   144.    Essential Services





          Essential services, such as water, compressed air,   and





          electricity,  shall be made available throughout the works





          where required for  cleaning,  maintenance, and repair work.





          To facilitate cleaning wetwells, tanks, basins and beds, water





          (supplied from a non-potable  water system or the works'





          effluent) shall be supplied at these points by means of a





          pressurized water  system with  hydrants or hose  bibs  having





          minimum outlet diameters of one inch.








150.    ISOLATION OF HAZARDOUS EQUIPMENT





       Equipment whose  failure could be hazardous to personnel or to





       other equipment shall have means  for isolation, such as  shutoff





       valves, or shutoff switches and controls located away from the





       equipment to permit safe shutdown during emergency conditions.
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                                               System Design Criteria
                200.	SYSTEM DESIGN CRITERIA

                                                             Page


210.   Wastewater Treatment System                           15

   211.    System Requirements                                15

   212.    Component Backup Requirements                     18

   213.    Component Design Features and Maintenance          25
             Requirements


220.   Sludge Handling and Disposal System                    30

   221.    System Requirements                                30

   222.    Component Backup Requirements                     31

   223.    Component Design Features and Maintenance          35
             Requirements


230.   Electric Power System                                 38

240.   Instrumentation and Control Systems                    47

250.   Auxiliary Systems                                      49
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                                               System Design Criteria
             200.	SYSTEM DESIGN CRITERIA








210.   WASTEWATER TREATMENT SYSTEM





       The wastewater treatment system includes all components from





       and including the bar screens and wastewater pumps to and





       including the works outfall.





   211.   System Requirements





           The wastewater treatment system shall be designed to





          include the following:





   211.1     Trash Removal or Comminution





             The system shall  contain components to remove and/or





             comminute trash and all other large solids contained in





             the wastewater.





   211.2     Grit Removal





             The system shall  contain components to remove grit and





             other heavy inorganic solids from the wastewater.  This





             requirement shall not apply to types of treatment works





             which do not pump or dewater sludge,  such as waste





             stabilization ponds.
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                                             System Design Criteria







211.3     Provisions for Removal of Settled Solids





          All components, channels, pump wells and piping prior to





          the degritting facility or primary sedimentation basin





          shall be accessible for cleaning out settled solids.  The





          provisions  shall enable manual or mechanical cleaning of





          equipment on a periodic basis without causing a controlled





          diversion or causing violation of effluent limitations.





211.4     Treatment  Works Controlled Diversion





          Wastewater treatment works shall be provided with a





          controlled diversion channel or  pipe sized to handle peak





          wastewater flow.  Actuation of the controlled diversion





          shall be by use of a gravity overflow.  The overflow





          elevation shall be such that the maximum feasible  storage





          capacity of the wastewater collection system will be utilized





          before the controlled diversion will be initiated.   The





          controlled diversion flow shall be screened to remove





          large solids unless  the wastewater  flow  has  been previously





          screened.   The actuation of a controlled diversion shall be





          alarmed and annunciated (see Paragraph 243 of this





          Technical Bulletin), and the flow shall be measured and





          recorded.
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                                             System Design Criteria







          All Reliability Class I wastewater treatment works shall





          have a holding basin to augment the storage capacity of





          the collection system.  The controlled diversion system





          and the holding basin shall be designed to permit the





          wastewater retained by  the holding basin to be fully treated





          in the wastewater treatment works.  The capacity of the





          holding basin shall be sized by the Grant Applicant based





          on the constraints and conditions applicable to that specific





          treatment works.





2' 11. 5     Unit Operation  Bypassing





          The design of the wastewater  treatment system  shall





          include provisions for bypassing around each unit opera-





          tion,  except as follows.  The  term unit operation does not





          apply to pumps in the context  of this criterion.   Unit





          operations with two or more units and involving open basins,





          such as  sedimentation basins,  aeration basins, disinfectant





          contact basins, shall not be required to have provisions





          for bypassing if the peak wastewater flow can be handled





          hydraulically with the largest flow capacity unit out of





          service.   All other  unit operations with three or more





          units shall not be required to  have provisions for bypassing





          if the peak wastewater flow can be handled hydraulically





          with the two largest flow capacity units out of service.





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                                             System Design Criteria






          The comminution facility shall be provided with a means





          for bypassing regardless of the number and flow capacity





          of the comminutors.






          The bypassing system for each unit operation shall be





          designed to provide control of the diverted flow such that





          only that portion of the flow in excess of the hydraulic





          capacity of the units in service need be bypassed.  With





          the exception of the comminution facility, which shall have





          a gravity overflow, the actuation of all  other unit operation





          bypasses shall require manual action by operating personnel.





          All power  actuated bypass valve operators  shall be designed





          to enable actuation with loss of power and shall be designed





          so that the valve will fail as is,  upon failure of the power





          operator.  A disinfection facility having a bypass shall





          contain emergency provisions for disinfection  of the  bypassed





          flow.






212.   Component  Backup Requirements





       Requirements for backup components for the main wastewater





       treatment system are specified below for Reliability Class I,





       II, and III works.






       Except as modified below,  unit operations in the main waste-





       water  treatment system shall be designed  such that, with the





       largest flow capacity unit out of service, the hydraulic





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                                             System Design Criteria






       capacity (not necessarily the design-rated capacity) of the





       remaining units shall be sufficient to handle the peak  waste-





       water flow.  There shall be system flexibility to enable the





       wastewater flow to any unit out of service to be distributed





       to the remaining units in service.






       Equalization basins or tanks  shall not be  considered a substi-





       tute for component backup  requirements.





212. 1     Reliability Class I





          For components included in the design of Reliability Class I





          works,  the following backup requirements apply.





212. 1. 1      Mechanically-Cleaned Bar  Screens or Equivalent Devices





             A backup  bar screen shall be provided.  It is permissible





             for the backup bar screen to be designed for manual





             cleaning only.   Works with only two bar screens shall





             have at least one bar screen designed to permit manual





             cleaning.





212. 1. 2      Pumps





             A backup  pump shall be provided for  each set of pumps





             which performs the same function.   The capacity of the





             pumps shall be such  that with any one pump out of





             service, the remaining pumps will  have capacity  to





             handle the peak flow.  It  is permissible for one pump





             to  serve as  backup to more than one set of pumps.






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                                              System Design Criteria


212.1.3      Comminution Facility

              If comminution of the total wastewater flow is provided,

              then an overflow  bypass with an installed manually- or

              mechanically-cleaned bar screen shall be provided.

              The hydraulic capacity  of the  comminutor overflow

              bypass shall be sufficient to pass the peak  flow with all

              comminution units out of service.

212.1.4      Primary Sedimentation Basins

              There shall be a  sufficient number of units of a size,

              such that with the largest flow capacity  unit out of

              service,  the remaining units shall have a design flow

              capacity of at least 50 percent of the total design flow

              to that unit operation.

2 12o 1. 5      Final and Chemical Sedimentation Basins,  Trickling
              Filters,  Filters and Activated Carbon Columns

              There shall be a  sufficient number of units of a  size,

              such that with the largest flow capcity unit out of

              service,  the remaining units shall have a design flow

              capacity of at least 75 percent of the total design flow

              to that unit operation.

212.1.6      Activated Sludge  Process Components

212.1.6.1      Aeration Basin

                A backup basin shall not  be required; however, at
                               -20-

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                                             System Design Criteria






                least two equal volume basins shall be provided.





                (For the purpose of this criterion,  the two zones of





                a contact stabilization process are  considered as





                only one basin. )





212. 1.6.2      Aeration Blowers or  Mechanical Aerators





                There shall be a  sufficient number  of blowers  or





                mechanical aerators  to enable the design oxygen





                transfer to be maintained  with the largest capacity





                unit out of service.  It is permissible for the backup





                unit to be an uninstalled unit, provided that the





                installed unit can be easily removed and replaced.





                However, at least two units shall be installed.





212.1.6.3      Air Diffusers





                The air diffusion system for each aeration basin





                shall be  designed such that the largest section of





                diffusers can be  isolated without measurably





                impairing the oxygen transfer capability of  the





                system,,





212.1.7      Chemical Flash Mixer





             At least two mixing  basins  or a backup means  for





             adding arid mixing chemicals, separate from the basin,





             shall be provided.   If only one basin is provided,  at





             least two mixing devices and a bypass around the basin






                             -21-

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                                             System Design Criteria


             shall be provided.  It is permissible for one of the

             mixing devices to be uninstalled, provided that the

             installed unit can be easily removed and replaced.

212.1.8     Flocculation Basins

             At least two flocculation basins shall be provided.

212.1.9     Disinfectant Contact Basins

             There shall be a  sufficient number of units of a  size,

             such that with the largest flow capacity  unit out  of

             service,  the remaining units shall have a design flow

             capacity of at least 50 percent of the total design flow

             to that unit operation.

212.2     Reliability Class II

          The Reliability Class I requirements shall apply except

          as modified below.

212.2.1     Primary and Final  Sedimentation Basins and Trickling
             Filters

             There shall be a  sufficient number of units of a  size

             such that, with the  largest flow capacity unit out of

             service,  the remaining units shall have a design flow

             capacity of at least 50 percent of the design basis flow

             to that unit operation.
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                                             System Design Criteria








212.2.2      Components Not Requiring Backup





             Requirements for backup components in the wastewater





             treatment system shall not be mandatory for  components





             which are used  to provide treatment in excess of typical





             biological (L e. , activated  sludge or trickling filter),





             or equivalent physical/chemical treatment, and disin-





             fection.   This may include such components as:





                Chemical Flash Mixer





                Flocculation Basin





                Chemical Sedimentation Basin





                Filter





                Activated Carbon Column





212.3     Reliability Class III





          The Reliability Class I requirements shall apply except





          as modified  below.





212.3.1      Primary  and Final Sedimentation Basins





             There shall be at least two sedimentation basins.





21203.2      Activated Sludge Process  Components





2 120 3. 2, I      Aeration Basin





                A  single basin is permissible.
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                                             System Design Criteria








212.3.2.2      Aeration Blowers or Mechanical Aerators





                There shall be at least two blowers or mechanical





                aerators available for service.  It is permissible





                for one of the units to be uninstalled, provided that





                the installed unit can be easily removed and replaced.





212.3.2.3      Air Diffusers





                The Reliability Class I requirements shall apply.





212.3.3      Components Not Requiring  Backup





             Requirements for backup components in the wastewater





             treatment  system shall not be mandatory for components





             which are  used to provide treatment in  excess of primary





             sedimentation and disinfection, except as modified





             above.  This may include such components as:





                Trickling Filter





                Chemical Flash Mixer





                Flocculation Basin





                Chemical Sedimentation Basin





                Filter





                Activated Carbon Column
                              -24-

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                                             System Design Criteria


213.   Component Design Features and Maintenance Requirements

213. 1     Provisions for Isolating Components

          Each component shall have provisions to enable it to be

          isolated from the flow stream to permit maintenance and

          repair of the component without interruption of the works'

          operation.  Where practicable, simple shutoff devices,

          such as  stop logs and slide gates,  shall be used.

213. 1. 1      Main Wastewater System Pump Isolation

             The use of in-line valves to isolate the main wastewater

             pumps shall be minimized.  It is permissible to place

             shutoff valves  on the suction and discharge lines of

             each  pump.  However,  in  such a case,  alternate means

             shall be provided for stopping flow through the  pump

             suction or  discharge lines to permit maintenance on the

             valves.

                Example:  Pump discharge isolation and check
                valves are not needed if the pumps have a free
                discharge into an open  channel  rather than dis-
                charging into a pressurized discharge header.
                Pump suction isolation valves can be maintained
                if  the plant has a two compartment wetwell  design
                and if the plant can continue operation (during the
                diurnal  low-flow period,  for  example) with  one
                part of the wetwell isolated.
                               -25-

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                                             System Design Criteria







213.2     Component Protection





213.2.1      Protection from Overload





             Components or parts of components subject to clogging,





             blockage, binding or other overloads shall be protected





             from damage due  to the overload.   Examples of com-





             ponents requiring protection include the rake mechanism





             of bar screens, comminuting equipment,  the grit-





             removal mechanism in degritting facilities,  and sludge





             and scum arms of sedimentation basins.





213. 2,2      Protection from Freezing





             Components or parts of components which are wetted





             and subject to freezing shall be designed to ensure





             that the components will be operable during winter





             climatic conditions anticipated at the works.  Examples





             of components or  parts  of components which may  require





             protection include bar screens, comminuting equipment,





             the grit-removal mechanism in degritting facilities,





             mechanical aerators and the scum arm of sedimentation





             basins.





213.2.3      Protection from Up-Lift Due to Ground Water





             In-ground tanks and basins  shall be protected from





             up-lift due to ground water.  If sufficient ballast is not





             provided in  each tank or basin,  other means for ground





             water relief shall be provided.



                               -26-

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                                             System Design Criteria







213.3     Slide Gates





          Consideration shall be given to providing mechanical





          operators  or other mechanical assistance for slide gates





          which,  due to their  size or infrequent use, may not be





          easily removable by manual means alone.





213.4     Bar Screens or Equivalent Devices





213.4. 1      Provisions for Manual  Cleaning





             Manually-cleaned bar screens or mechanically-cleaned





             bar  screens which can  be manually cleaned shall have





             accessible platforms above the bar screen from which





             the operator can rake screenings easily and safely when





             the screens are in operation.





213.4.2      Provisions for Lifting and Handling Equipment





             The  design of the equipment and the works shall contain





             provisions for easily and safely lifting and handling all





             parts of a mechanically-cleaned bar screen.  Special





             attention shall be given to the proper  location of eyes,





             rails, and hooks located above  the equipment  to facilitate





             lifting and handling.





213.5     Comminution Equipment and Degritting Facility





          All mechanical components shall be easily removable for





          maintenance and repair.
                              -27-

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                                             System Design Criteria







213.6     Sedimentation Basins





          The main drive mechanism and reducing gears shall be





          maintainable and repairable without draining the basin.





          The number of other operating parts which require draining





          the basin for repair and maintenance shall be minimized.





Z1307     Aeration Equipment





2 130 1, 1      Component Maintenance





             Mechanical aerators or air diffusers shall be easily





             removable from the aeration tank to permit  maintenance





             and repair without interrupting operation of  the aeration





             tank or inhibiting  operation of the other aeration  equip-





             ment.





Z13.7.2      Filtration of Air





             If air is supplied to fine bubble diffusers,  air filters





             shall be provided  in numbers, arrangement  and capac-





             ities  to furnish at all times an air supply sufficiently





             free from dust to  minimize clogging of the diffusers.





213.8     Chemical Mixing  Basin and Flocculation Basin





213. 8. 1      Component Maintenance





             The mixing and flocculating devices shall  be completely





             removable from the basin to allow maintenance and





             repair of the device, preferably without draining  the





             basin.






                              -28-

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                                             System Design Criteria







213. 8. 2      Chemical Feed Line Cleaning





             Chemical feed lines shall be designed to permit their





             being cleaned or replaced without draining the mixing





             basin or interrupting the normal  flow through the basin.





213. 8. 3      Provisions for Isolation





             Isolation valves or gates for the mixing or flocculation





             basin shall be designed to minimize the problems





             associated with operation of these devices after long





             periods of idleness and the resulting buildup of chemical





             deposits.  Access and capability  for cleaning debris





             and deposits which interfere with valve or gate closure





             shall be provided.





213.9     Filters and Activated Carbon Columns





          There shall be easy access to the interior of carbon





          columns and filters to permit maintenance and repair of





          internal mechanisms.
                              -29-

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                                               System Design Criteria


220.   SLUDGE HANDLING AND DISPOSAL SYSTEM

       This system includes all components and unit processes from

       the sludge pumps servicing the sedimentation basins to the

       final disposal of waste  products, including ancillary components.

       Sludge disposal includes the special handling and treatment of

       sludge bypassing a normal stage of treatment. In some treatment

       works  the  system may  also include processes such as recalci-

       nation  of lime or regeneration of activated carbon.

   221.    System Requirements

          The sludge handling and disposal system shall be designed

          to include the following:

   221. 1    Alternate Methods of Sludge  Disposal and/or Treatment

            Alternate methods of sludge  disposal and/or treatment

            shall be provided for each sludge treatment  unit operation

            without installed backup capability.

   221.2    Provisions for Preventing Contamination of  Treated
            Wastewater

            All connections (sludge, scum, filtrate, supernatant, or

            other contaminated water flows), direct or indirect, from

            the sludge handling system to the wastewater treatment

            system shall be at a point in the wastewater treatment

            system that will ensure adequate treatment.
                                 -30-

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                                             System Design Criteria







222.   Component Backup Requirements





       For components included in the design of the sludge handling





       and disposal system of Reliability Class I, II,  or III works





       the following backup requirements apply.





222. 1      Sludge Holding Tanks





          Holding tanks are permissible as an alternative to com-





           ponent or system backup capability for components down-





           stream of the tank, provided the following requirements




           are met.  The volume of the holding tank shall be based





           on the expected time necessary to perform maintenance





           and repair of the  component in question.  If a holding tank





           is used as an alternative to backup capability in a sludge





           treatment system which is designed for continuous operation,





           the excess capacity in all components downstream of the





          holding tanks shall be provided to enable processing  the





           sludge which was retained together with the normal sludge





           flow.





222. 2      Pumps





          A backup pump shall be provided for each set of pumps





           which performs the same function.  The capacity of  the





           pumps shall be such that with  any one pump out of service,





           the remaining pumps will have capacity to handle the peak





           flow.  It is  permissible for one pump to serve as backup






                               -31-

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                                             System Design Criteria






          to more than one set of pumps.  It is also permissible





          for the backup pump to be uninstalled, provided that the





          installed pump can be easily removed and replaced.





          However,  at least two pumps shall be installed.





222. 3     Anaerobic Sludge Digestion





222. 3. 1      Digestion Tanks





             At least two digestion tanks  shall be provided.  At least





             two of the digestion tanks provided shall be designed to





             permit  processing all types  of  sludges normally digested.





222.302      Mixing  Equipment





             If mixing is required as part of the digestion process,





             then each tank requiring mixing shall have sufficient





             mixing  equipment or  flexibility in  system design to





             ensure  that the total capability  for mixing is not lost





             when any one  piece of mechanical mixing equipment is





             taken out of service.   It is permissible for the backup





             equipment not to be installed (eģ g, , a  spare  uninstalled





             digester gas compressor is  permissible if gas mixing





             is used); not be normally used for  sludge mixing (e. g. ,





             sedimentation basin sludge pumps  may be used); or not





             be full capacity (e. g. , two 50 percent-capacity recircu-





             lation pumps would comply with this requirement).
                             -32-

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                                             System Design Criteria


222.4     Aerobic Sludge Digestion

222. 4. 1      Aeration Basin

             A backup basin is not required.

222.4.2      Aeration Blowers or Mechanical Aerators

             At least two blowers or mechanical aerators shall be

             provided.  It is  permissible for less than design oxygen

             transfer capability to be provided with one unit out of

             service.  It is permissible for  the backup unit to be an

             uninstalled unit,  provided that the installed unit can be

             easily removed  and replaced.

222.4.3      Air Diffusers

             The  air diffusion system for each aeration basin shall

             be designed  such that the largest section  of diffusers

             can be isolated without measurably impairing the oxygen

             transfer capability of the system.

222. 5     Vacuum Filter

          There shall be a sufficient number of vacuum filters to

          enable the design sludge flow to be dewatered with the

          largest capacity vacuum filter out of service.

          Note:  Since the design basis of sludge dewatering equip-
          ment is  often not continuous operation, this  criterion does
          not necessarily require additional vacuum filter capacity
          if the installed  equipment  is operated on less than a 24
          hour-per-day basis and if the normal operating hours can
          be extended on the  remaining units to make up the capacity
          lost in the unit out  of service.

                              -33-

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                                             System Design Criteria


222. 5. 1      Auxiliary Equipment

             Each vacuum filter shall be serviced by two vacuum

             pumps and two filtrate pumps.  It is permissible for

             the backup to the normal vacuum or filtrate pump to be

             an uninstalled unit,  provided that the installed  unit can

             be easily removed and replaced; or to be a cross -

             connect line  to the appropriate system of another

             vacuum filter.

222.6     Centrifuges

          There shall be a sufficient  number  of centrifuges  to enable

          the design sludge flow to be dewatered with the largest

          capacity centrifuge out of service.  It is permissible for

          the backup unit  to be an uninstalled unit, provided that the

          installed unit can be easily  removed and replaced.

          Note:  Since the design basis of sludge dewatering equip-
          ment is  often not continuous operation,  this criterion  does
          not necessarily require additional equipment if the installed
          equipment is operated on less than  a 24 hour-per-day basis
          and if the normal operating hours can be extended on the
          remaining units to make up the capacity lost in the unit
          out of service.

222. 7     Incinerators

          A backup incinerator is not required (see Paragraph 221. 1

          for requirements for alternate sludge disposal capability).

          Auxiliary incinerator equipment  whose failure during

          incinerator operation could result in damage to the

                              -34-

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                                             System Design Criteria








          incinerator shall be provided with backups (e. g. ,  failure





          of a center shaft cooling fan could result in damage to the





          center shaft of a multi-hearth incinerator).  In such cases,





          automatic  actuation of the backup auxiliary equipment





          shall be provided.





223.   Component Design Features and Maintenance Requirements





223. 1     Provisions for Isolating Components





          Each component shall have provisions to enable it to be





          isolated from the flow stream to permit maintenance and





          repair of the component without interruption of the works'





          operation.   Where  practicable, simple shutoff devices,





          such as  stop logs and slide gates,  shall be used.





223.2     Component Protection





223.2. 1      Protection from Overload





             Components  or  parts of components subject to clogging,





             blockage, binding or other  overloads shall be protected





             from damage due  to the overload.





223. 2. 2      Protection from Freezing





             Components  or  parts of components which are wetted





             and subject to freezing shall be designed to ensure that





             components will be operable during  winter climatic





             conditions anticipated at the works.
                              -35-

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                                             System  Design Criteria








223.2.3     Protection from Up-Lift Due to Ground Water





             In-ground tanks and basins shall be protected from





             up-lift due to ground water.  If sufficient ballast is not





             provided in each tank or basin,  other means for ground





             water relief shall be provided.





223.3     Slide Gates





          Consideration  shall be given to providing mechanical





          operators or other mechanical assistance for  slide gates





          which,  due  to their  size or infrequent use,  may  not be





          easily removable by manual means alone.





223.4     Aeration Equipment





223.4. 1     Component  Maintenance





             Mechanical aerators or air diffusers shall  be easily





             removable from the aeration tank to permit maintenance





             and repair without interrupting operation of the aeration





             tank or inhibiting operation of the other  aeration equip-





             ment.





223.4.2     Filtration of Air





             If air is  supplied to fine bubble diffusers, air filters





             shall be  provided in numbers, arrangement and capa-





             cities to furnish at all times an air supply sufficiently





             free from dust to minimize clogging of the  diffusers.
                              -36-

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                                            System Design Criteria








223. 5     Anaerobic Sludge Digester





          At Least three access manholes shall be provided in the





          top of the tank.  One opening shall be  large enough to





          permit  the use of mechanical equipment to remove grit





          and sand.  A separate side wall manhole shall also be





          provided,





223.6     Incinerators





          There  shall be easy access to the interior of incinerators





          to permit maintenance and repair of internal mechanisms.





          Multi-hearth incinerators  shall have a manhole on each





          hearth level.
                              -37-

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                                                System Design Criteria


230.   ELECTRIC POWER SYSTEM

       The following criteria shall apply only to those portions of the

       system supplying power to vital components.

   23 10   Power Sources

          Two separate and independent sources of electric power shall

          be provided to the works from either  two separate utility

          substations or from a single substation and a works based

          generator.  If available from the electric utility,  at least one

          of  the works'  power sources shall be  a preferred source

          (i. e. , a utility source which is one  of the last to lose power

          from the utility grid due to loss of power generating capacity).

          In  geographical areas where it is projected that sometime

          during the design period of the works, the  electric utility may

          reduce the rated line voltage (i. e. ,  "brown out") during peak

          utility system load demands,  a works based generator  shall

          be provided as an  alternate power source,  where practicable.

          As a minimum, the capacity of the backup  power source for

          each class of  treatment works shall be:

          Reliability
          Class I        Sufficient to operate all vital components,
                        during peak wastewater flow conditions,
                        together with critical lighting and ventilation.
                                 -38-

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                                             System Design Criteria
       Reliability
       Class II       Same as Reliability Class I, except that vital
                      components used to support the secondary
                      processes (i. e. ,  mechanical aerators or
                      aeration basin air compressors) need not be
                      included as  long as treatment equivalent to
                      sedimentation and disinfection is provided.

       Reliability
       Class III      Sufficient to operate the screening or
                      comminution facilities, the main wastewater
                      pumps, the  primary sedimentation basins,
                      and the disinfection facility during peak
                      wastewater  flow condition,  together with
                      critical lighting and ventilation.

       Note:  This requirement concerning  rated capacity of electric
       power sources is not intended to prohibit other forms of
       emergency power, such as diesel driven main wastewater
       pumps.

232.   Power Distribution External to the Works
       The independent sources of power shall be distributed to the

       works' transformers in a way to minimize common mode

       failures  from affecting both sources.

          Example:  The two sets  of distribution lines should not be
          located in the same conduit or supported from the  same
          utility pole.  The two sets of overhead distribution lines,
          if used,  should not cross nor be located in an area where
          a single plausible occurrence (e. g. , fallen  tree) could
          disrupt both lines.  Devices should be used to  protect the
          system from lightning.

233.   Transformers
       Each utility source of power to the works shall be transformed

       to usable voltage with a separate transformer.   The trans-

       formers shall be protected from common mode failure by

       physical separation or other means.

                             -39-

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                                             System Design Criteria







234.   Power Distribution Within the Works





234. 1     Service to Motor Control Centers





          The internal power distribution system shall be designed





          such that no single fault or loss of a power source will





          result in disruption (i. e. ,  extended, not momentary) of





          electric service to more than one motor control center





          associated with the Reliability Class I,  II, or III vital





          components requiring backup power per Paragraph 231,





          above.





234.2     Division of Loads at Motor Control Centers





          Vital components of the same type and serving the same





          function shall be divided as equally as possible between





          at least two motor control centers. Nonvital components





          shall be divided in a similar manner,  where practicable.





234. 3     Power Transfer





          Where power feeder or branch circuits  can be transferred





          from one power source to  another,  a mechanical or





          electrical safety device shall be provided to assure that





          the two power'sources cannot be cross-connected, if





          unsynchronized.  Automatic transfer shall be provided in





          those cases when the time delay required to manually





          transfer power could result in a failure to meet effluent





          limitations, a failure to process peak influent flow,  or






                             -40-

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                                             System Design Criteria


          cause damage to equipment.  Where automatic pump

          control is used, the control panel power source and pump

          power source shall be similarly transferred.   The

          actuation of an automatic transfer  switch shall be alarmed

          and annunciated.

             Example: An example for feeder distribution and bus
             transfer which meets these criteria is shown in Figure 1.
             The  two  power sources from  utility substations are
             connected to the motor control centers through circuit
             breakers.  A circuit breaker is  provided to cross-
             connect the  two motor control centers in the event  one
             of the two normally energized power feeders fail.
             Additional backup capability has been achieved for  the
             main pump by connecting one of  the three pumps to the
             motor control center cross-connect.  This assures
             that  two  out of  three pumps will  be available in the
             event of  a panel fire or panel bus short circuit.

235.   Breaker Settings or Fuse Ratings

       Breaker settings or fuse ratings shall be coordinated to effect

       sequential tripping such that the breaker or fuse nearest the

       fault will clear the fault prior to activation of other breakers

       or fuses to the degree practicable.

236.   Equipment Type and  Location

       Failures resulting from plausible causes,  such as fire or

       flooding,  shall be minimized by equipment design and location.

       The following requirements  apply:
                              -41-

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                                               System Design Criteria
                FROM
                POWER
                sounet
                NO. 1
         FROM
         POWER
         SOURCE
          NO. 2
               S~Y-V-Y~Y-Y-\

                  )
                     TRANSFORMER
                                          TRANSFORMER
                                                   rYYVWI
                   SOURCE NO. 1 BUS
                                          SOURCE NO. 2 BUS
             I MOTOR CONTROL CENTER;
                                   BUS
                                 TIE BREAKER
                                 NORMALLY
                                  OPEN
                                           j MOTOR CONTROL CENTERJ
                               MOTOR CONTROL
                                  CENTER
                                TIE BREAKER
               BLOWER  SLUDGE SLOWED
                no. i   PUMP  wo. s
                     NO. 1
BLOWER SLUDGE
 NO. 1    PUMP
       NO. 2
FEEDER  DISTRIBUTION AND  POWER  TRANSFER

                          FIGURE  1
                              -42-

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                                             System Design Criteria







236. 1     Switchgear Location





          Electric switchgear and motor control centers shall be





          protected from  sprays or moisture from liquid processing





          equipm ent and from breaks in liquid handling piping.,





          Where practicable, the electric  equipment shall be  located





          in a separate room from the liquid processing equipment.





          Liquid handling piping shall not be run through this  room.





          The electric switchgear and motor control centers shall





          be located above ground and above the one hundred (100)





          year flood (or wave action) elevation.





236.2     Conductor Insulation





          Wires in underground conduits or  in conduits that can be





          flooded shall have moisture resistant insulation as identified





          in the National Electric Code.





236. 3     Motor Protection from Moisture





          All outdoor motors shall be adequately protected from the





          weather.  Water-proof, totally enclosed or weather-protected,




          open motor enclosures shall be used for exposed outdoor





          motors.   Motors located indoors and near liquid handling





          piping or  equipment shall be, at least,  splash-proof design.




          Consideration shall be given to providing heaters in motors





          located outdoors or in areas where condensation may
          occur.
                               -43-

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                                             System Design Criteria







           The following criteria shall apply to motors (and their





           local controls) associated with vital components.  All





           outdoor motors, all large indoor motors (i. e. , those not





           readily available as stock items from motor  suppliers),





           and, where practicable,  all other indoor motors  shall be





           located at an elevation to preclude flooding from  the one





           hundred (100) year  flood (or wave action), or from clogged





           floor drains. Indoor motors located at or below  the one





           hundred year flood  (or wave action) elevation shall be





           housed in a room or building which is protected from





           flooding  during the  one hundred year  flood (or wave action).





           The building protection shall include  measures such as





           no openings  (e.g.,  doors, windows,  hatches) to the outside





           below  the flood  elevation and a drain  sump pumped to an





           elevation above the  flood elevation.





236.4      Explosion Proof Equipment





           Explosion proof motors,  conduit  systems,  switches and





           other electrical equipment shall be used in areas where





           flammable liquid, gas or dust is  likely to be present.





236. 5      Routing of Cabling





           To avoid a common mode failure, conductors to components





           which  perform the same function in parallel shall not be





           routed in the same  conduit or  cable tray.  Conduits housing







                               -44-

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                                             System Design Criteria









          such cables shall not be routed in the same underground





          conduit bank unless the conduits are protected from





          common mode failures (such as by encasing the conduit





          bank in a protective layer of concrete).





236.6     Motor Protection





          Three phase motors and their starters  shall be protected





          from electric overload and short circuits on all three





          phases.








          Large motors  shall have a low voltage protection device





          which  on the reduction or  failure of voltage will cause and





          maintain the interruption  of power to that motor.








          Consideration  shall be given to the installation of tempera-





          ture detectors in the stator and bearings of large motors





          in order to give  an indication of overheating problems.





237.   Provisions for Equipment Testing





       Provisions shall be included in the design of equipment





       requiring periodic testing, to enable the tests to  be accom-





       plished while maintaining electric power to all vital components.





       This  requires being able to  conduct tests,  such as actuating





       and resetting automatic transfer switches,  and starting and





       loading emergency  generating equipment.
                               -45-

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                                             System Design Criteria







238.   Maintainability





       The electric distribution system and equipment shall be





       designed to permit inspection and maintenance of individual





       items without causing a controlled diversion  or causing





       violation of the effluent limitations.





239.   Emergency Power Generator  Starting





       The means for  starting a works based emergency power





       generator shall be completely independent of the normal





       electric power  source.  Air starting systems shall have an





       accumulator tank(s) with a volume sufficient  to furnish air





       for starting the generator engine a minimum of three (3)





       times without recharging.  Batteries used for starting  shall





       have  a sufficient charge to permit starting the generator





       engine a minimum of three (3) times without  recharging.





       The starting system shall be appropriately alarmed and





       instrumented to indicate loss  of readiness (e. g. ,  loss of





       charge on batteries, loss  of pressure in air accumulators,





       etc. ).
                               -46-

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                                                 System Design Criteria







240.   INSTRUMENTATION AND CONTROL SYSTEMS





       These criteria cover the requirements for the instrumentation





       and control systems:





   241.    Automatic Control





           Automatic control systems  whose failure could  result in a





           controlled diversion or a violation of the effluent limitations





           shall be provided with a manual override.   Those automatic





           controls shall have alarms  and annunciators to  indicate





           malfunctions which require use of the manual override.  The





           means for detecting the malfunction shall be independent of





           the automatic control system,  such that no single failure





           will result  in disabling both the automatic  controls and the





           alarm and annunciator.





   242.    Instrumentation





           Instrumentation whose failure  could result in a  controlled





           diversion or  a violation of the  effluent limitations shall be





           provided with an installed backup sensor and readout.  The





           backup equipment may be of a  different type and located  at





           a different  point, provided that the same function is  performed.





           No single failure shall result in disabling both sets  of parallel





           instrumentation.
                                  -47-

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                                             System Design Criteria
243.   Alarms and Annunciators
       Alarms and annunciators shall be provided to monitor the





       condition of equipment whose failure could result in a





       controlled  diversion or a violation of the effluent limitations.





       Alarms and annunciators shall also be  provided to  monitor





       conditions which could result in damage to vital equipment





       or hazards to personnel.   The alarms shall sound in areas





       normally manned and also in areas near the equipment.





       Treatment works not continuously manned shall have the





       alarm signals transmitted to a point (e. g. , fire station,





       police station, etc. ) which is  continuously manned.   The





       combination of alarms and annunciators shall be such that





       each announced condition is uniquely identified.  Test circuits





       shall be provided to  enable the alarms  and annunciators to





       be tested and verified to be in working  order.





244.   Alignment and Calibration of Equipment





       Vital instrumentation and control equipment shall be designed





       to permit alignment  and  calibration without requiring a





       controlled diversion or a violation  of the effluent limitations.
                              -48-

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                                                System Design Criteria







250.   AUXILIARY SYSTEMS





       The auxiliary systems include typical systems such as:





       °  Drain system, for





             Components





             Systems





             Treatment works






          Compressed air system, for





             Pneumatic controls





             Pneumatic valve operators





             Hydropneumatic water systems





             Air lift pumps






       0  Service water systems, for





             High pressure  water





             Gland  seals





             General service






       0  Fuel supply system,  for





             Digester heaters





             Incinerators





             Building heat
                                 -49-

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                                        System Design Criteria


°  Lubrication oil system, for

   -  Pumps

      Blowers

      Motors

   Chemical supply and addition system, for

      Disinfection

      Sludge conditioning

      Chemical treatment of wastewater

The  reliability requirements of these systems are dependent on

the function of each system in the wastewater treatment works.

If a malfunction of the system can result in a controlled diversion

or a violation of the effluent limitations, and the required function

cannot be done by any other  means, then the system  shall have

backup capability  in the number of vital components (i. e. ,  pumps,

motors,  mechanical stirrers) required to  perform the system

function.  If the system performs functions which can be performed

manually or by  some other means,  then backup components shall

not be required.

   Example:  A compressed air system supplying air to air lift
   pumps, which are pumping return activated sludge from the
   secondary  sedimentation  basin to the aeration tanks, is an
   example of an auxiliary system whose failure could degrade
   effluent quality.  If no  other means for supplying  air or pump-
   ing sludge  were available, then this  system would be required
   to have backup vital components, such as compressors.
                         -50-

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                                             System Design Criteria


       Example:  If the compressed air system only supplied air to
       pneumatic controls which could not affect effluent quality,
       then the system would not require any backup components.

251.   Backup Components

       Auxiliary systems requiring backup components shall have

       a sufficient number of each  type of component such that the

       design function of the system can be fulfilled with any one

       component out of commission.   Systems having components

       of different capacities shall meet this  criterion with the

       largest capacity component  out of commission.  It is

       permissible for the backup component to be  uninstalled,

       provided that the installed component can be easily removed

       and replaced.  However, at least two components shall be

       installed.

          Example:  A chemical addition system supplying chlorinated
          water to the contact chamber and having six chlorinators
          and one water supply pump which just meets capacity
          requirements, would be required by this  criterion to have
          one additional chlorinator and one additional pump.

252.   Requirements for System,  Component and Treatment Works
       Drains  and Overflows

       All system,  component and  works drains and overflows shall

       discharge to an appropriate point in the main wastewater

       treatment process to ensure adequate  treatment.  Drains

       flowing to a two-compartment wetwell   shall be designed to

       discharge to either compartment of the wetwell.
                              -51-

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                                             System Design Criteria







252. 1     Works Drains





          The works  shall have sufficient drains to enable all spilled





          or leaked raw or partially treated wastewater,  sludge,





          chemicals or any other objectionable substance to freely





          drain out of the area of concern.  Special attention shall





          be given to specifying sufficient cleanouts  in drain lines





          which are  likely to clog (e.g. ,  drain  lines handling lime).





          All floors  within buildings and  structures shall be sloped





          to permit complete draining.





252.2     Sump Pumps





          Sump pumps shall be of a non-clog type.  Sump pumps are





          considered vital components and each sump shall be





          provided with two full capacity sump  pumps.





252. 3     Equipment Overflows





          All equipment located within buildings and which can





          overflow shall be equipped with an adequately sized





          overflow pipe.  The  overflow  shall be directed to a gravity





          drain.





252.4     Surface Water Drains





          The  works' grounds  shall be graded and drains provided





          in order to prohibit surface  water from draining into





          pump wells, tanks, basins,  beds, or buildings.  Drains
                             -52-

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                                             System Design Criteria







          which handle uncontaminated water  only shall not be





          connected to the contaminated drain system.





252,, 5     Component  Dewatering





          All pump wells,  tanks, basins and beds,  with  the exception





          of aeration  tanks,  shall be designed to enable  complete





          dewatering  in a reasonable length of time in order to





          minimize the component downtime for maintenance or





          repairs.  Where practicable,  these components shall have





          sloped bottoms to enable the units to be  completely drained,,





252, 6     Drain Backflow





          Drains  shall be designed to prevent backflow from other





          sources which would cause  flooding or violation of the





          effluent  limitations.  The drain  system shall be designed





          to prevent the  entrance of storm water during  the  one





          hundred year flood (or wave action) condition.





253.   Continuity of Operation





       The failure of  a mechanical component in an auxiliary system





       shall not result in disrupting the  operating  continuity of the





       wastewater treatment system or  sludge handling  and  disposal





       system to  the extent that flooding,  failure,  malfunctioning





       or damage to components in those  systems results.
                             -53-

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                                             System Design Criteria


          Example:  A seal water system with normal and backup
          water  supplies must transfer automatically to the backup
          upon failure of the normal supply in order to protect the
          equipment which needs the seal water to prevent damage.

254.   Emergency Fuel Storage

       If a vital  component  requires fuel for operation,  then the

       fuel supply system design shall include provisions for fuel

       storage or a standby fuel source.  The capacity of stored

       gaseous or liquid fuel shall be determined by the Grant

       Applicant based on the plausible downtime of the normal fuel

       supply and the expected consumption rate.  The emergency

       system shall be physically separate from the normal fuel

       supply up to its connection to the fuel distribution system

       within the works.

255.   Disinfectant Addition System

       The  capacity of the disinfectant addition system shall be

       designed with due consideration  of abnormal operating

       conditions, such as  having a disinfectant contact basin out

       of service. It is permissible for the additional  capacity

       required for abnormal conditions to be separate and

       independent from the normal disinfectant addition system.
                              -54-

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