WATER POLLUTION CONTROL RESEARCH SERIES  •  17O9ODOY12/7O
FEASIBILITY  OF COMPUTER CONTROL
                 OF
     WASTEWATER TREATMENT
 ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE

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      WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes
the results and progress in the control and abatement
of pollution in our Nation's waters.  They provide a
central source of information on the research, develop-
ment, and demonstration activities in the Water Quality
Office, Environmental Protection Agency, through inhouse
research and grants and contracts with Federal, State,
and local agencies, research institutions, and industrial
organizations.

Inquiries pertaining to WateJr Pollution Control Research
Reports should be directed to the Head, Project Reports
System, Office of Research and Development, Water Quality
Office, Environmental Protection Agency, Room 1108,
Washington, B.C.  20242.

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     FEASIBILITY OF COMPUTER CONTROL
          OF WASTEWATER TREATMENT
                     by
    American Public Works Association
         Chicago, Illinois  60637
                  for  the

    ENVIRONMENTAL  PROTECTION AGENCY

          WATER QUALITY OFFICE
            Project #17090 DOY
            Contract #14-12-580
              December,  1970
For sale by the Superintendent of Documents, U.S. Government Printing Office
            Washington, D.C. 20402 - Price $1.00
                Stock Number 5501-0145

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        SUPPORTING AGENCIES
        City of Tempe, Arizona
        City of Kelowna, British Columbia
        City of San Jose, California
        City of Los Angeles, California
        City of Marietta,  Georgia
        City and County  of Honolulu
        City of Peoria, Illinois
        City of Wichita, Kansas
        City of Bloomington, Minnesota
        City of New York, New  York
        City of Toronto,  Ontario
        City of Philadelphia, Pennsylvania
        City of Pittsburgh, Pennsylvania
        City of Oak Ridge, Tennessee
        City of Fort Worth, Texas
        City of Richmond, Virginia
        Municipality of Metropolitan
          Seattle, Washington
        City of Seattle, Washington
        City of Madison,  Wisconsin
              EPA Review Notice

This report has been reviewed by the Environmental
Protection  Agency and  approved for  publication.
Approval  does  not  signify  that  the contents
necessarily  reflect  the views  and policies  of the
Environmental Protection Agency.

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                                   STEERING COMMITTEE

    Joseph V. Radziul (Chairman), Chief of Research and Development, Philadelphia Water Department
Waddy M. Allnut, Chief of Bureau of Business Management, Department of Public Works, Richmond, Virginia
       Ben Cramer, Director, Organization and Methods Division, Fiance Department, City of Toronto
          Harry Fite, Chief of Information Systems Division, U. S. Department of Transportation
                Charles V. Gibbs, Executive Director, Municipality of Metropolitan Seattle
                     Sam Hobbs, Director of Public Works, Bloomington, Minnesota
            E. Steve Savas, Deputy City Administrator, Office of the Mayor, City of New York
                                           Project Director
                                         Richard H. Sullivan
                                        Principal Investigator
                                          Harold D. Oilman
                                   ADVISORY COMMITTEE

 Waddy M. Allnut, Chief of Bureau of Business Management, Department of Public Works, Richmond, Virginia
                      Peter G. BardezBanian, City Finance Director, Peoria, Illinois
                 R. R. Blackburn, Assistant Director of Public Works, San Jose, California
                           Walter J. Brown, City Manager, Marietta, Georgia
      Ben Cramer, Director, Organization and Methods Division, Finance Department, City of Toronto
           C. W. Dotts, Administrative Supervisor, Department of Public Works, Wichita, Kansas
                Charles V. Gibbs, Executive Director, Municipality of Metropolitan Seattle
                       Jack M. Graham, Public Works Director, Fort Worth, Texas
             Herbert J. Hellen, Civil Engineer IV, City Engineering Division, Madison, Wisconsin
                     Sam Hobbs, Director of Public Works, Bloomington, Minnesota
                      Douglas L. Jonas, Management Engineer, Seattle, Washington
                          Yoshio Kunimoto, Chief Engineer, Honolulu, Hawaii
     Otto V. Kendzior, Administrative Assistant, Department of Public Works, Pittsburgh, Pennsylvania
                       E. P. Lawrence, City Engineer, Kelowna, British Columbia
          Joseph V. Radziul, Chief of Research and Development, Philadelphia Water Department
                      O. K. Rickman, Public Works Director, Oak Ridge, Tennessee
             E. Steve Savas, Deputy City Administrator, Office of the Mayor, City of New York
                      Robert J. Snyder, Director of Public Works, Tempe, Arizona
                 Donald C. Tillman, Chief Deputy City Engineer, Los Angeles, California

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        AMERICAN PUBLIC WORKS ASSOCIATION
                    Board of Directors

               Myron D. Calkins, President
             William W. Pagan, Vice President
               Ross L. Clark, Past President
Ray W. Burgess                             Erwin F. Hensch
Lt. Gen. Frederick J. Clarke                  Leo L. Johnson
Harmer E. Davis                            Timothy J. O'Leary
Donald S. Frady                            Lyall A. Pardee
Wesley E. Gilbertson                        Frederick R. Rundle
Herbert Goetsch                            Gilbert M. Schuster
         Robert D.  Bugher, Executive Director
             APWA RESEARCH FOUNDATION
                      Board of Trustees
                 Samuel S. Baxter, Chairman
                 W. D. Hurst, Vice Chairman
         Fred J. Benson              William S. Foster
         John F. Collins              D. Grant Mickle
         James V. Fitzpatrick         Milton Offner
                       Milton Pikarsky
            Robert D. Bugher, Secretary-Treasurer
             Richard H. Sullivan, General Manager

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                                 ABSTRACT

     This  report  contains the results  of  an investigation  into the use of digital
computers  for management  and  control  of wastewater treatment facilities. The
objectives of the study included the generation of guidelines for implementation of
digital  computers  for these  purposes  and recommendations for further  relevant
research.
     For the purpose of gathering information, visits were made to plants and the
literature was searched. A survey was conducted of current practices and problems in
the operation of wastewater treatment plants. Emphasis was placed on the processes of
secondary  treatment  with  regard  to management and control  of unit  processes,
continuous monitoring needs, the influences of regulatory agencies, and certain local
conditions. A set of guidelines  and steps for computer control implementation and
peripheral applications were evolved.
     It was concluded that both off-line computer applications and on-line computer
control in wastewater treatment  are feasible and should be implemented.
     This  Report  was submitted in  fulfillment of Contract  14-12-580 between the
Environmental Protection  Agency,  the American Public Works  Association and
nineteen cost sharing local governmental  agencies.

KEY WORDS: Computers, Wastewater Treatment, Monitoring, Control

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                                 CONTENTS

                                                                         Page

SECTION 1
   SUMMARY AND RECOMMENDATIONS
   Objectives   	1
   Conclusions	1
   Recommendations	2

SECTION 2
   WASTEWATER TREATMENT PROCESSES AND CONTROL APPLICATIONS
   Wastewater Treatment System	3
   Process Control Computer System   	3
   Common Treatment Processes, Variables and Instrumentation	4
   Continuous Monitoring and Control   	13

SECTION 3
   SOME ASPECTS OF HIGHER ORDER TREATMENT
   Introduction  	23
   Microstraining	23
   Chemical Coagulation   	23
   Filtration	24
   Activated Carbon  	25
   Ammonia Removal by Air Stripping   	26
   Ion Exchange	26

SECTION 4
   SURVEY OF WASTEWATER TREATMENT PLANTS  	29

SECTION 5
   DATA NEEDS OF REGULATORY AGENCIES
   Introduction  	31
   Regulatory Agency Data Requirements	31
   Automatic Control and Regulatory Agency Data   	32

SECTION 6
   GUIDELINES FOR COMPUTER IMPLEMENTATION
   Introduction  	35
   Technical Justification for Computer Control   	35
   Sources of Economic Justification for Computer Control   	40
   Preliminary Information Needs for Computer Control	42
   Mathematical Modeling Applications   	43

SECTION 7
   MEASURED STEPS TOWARD PLANT AUTOMATION
   Introduction  	47
   Design of Plant Management Information Reporting System   	47
                                     Vll

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                              CONTENTS (Continued)

   Design of Computerized Equipment Maintenance File	49
   Computer Programs for Reporting, PM Files, and Other Off-line Uses   	49
   Plant Instrumentation Review and Upgrading   	50
   Preliminary Automation Study and Computer System Specification	50
   Implementing Plant Automation	51

SECTION 8
   LOCAL INFLUENCES ON PLANT AUTOMATION
   Public Concern  	53
   Water Quality as a Resource	53
   Regional Water Pollution Control Systems	53
   Controlled Plant Influent	54

SECTION 9
   ADVANCED RESEARCH ON CONTROL SYSTEMS	57

SECTION 10
   RECOMMENDED RESEARCH
   Development of a Suspended Solids Probe	59
   Development of Instrument for Rapid Determination of Biological Oxygen Demand   . .   59
   Development of Instrument for Rapid Fecal Coliform Counting	59
   User's Experience Instrumentation Study for Wastewater Treatment Processes	60
   Analyses and Procedures for Computer Control of Wastewater Treatment Processes  ...   60
   Augmented Instrument Study   	61
   Computer Implementation for Monitoring and Control of a Wastewater Treatment Plant    62
   feasibility Study for Rapid Mercury Analysis	62
   Development of an On-line Phenol Sensor Probe   	63
   Development of an On-line Trace Oil Monitor Instrument	63

SECTION 11
   ACKNOWLEDGEMENTS	65

SECTION 12
   GLOSSARY   	67

SECTION 13
   REFERENCES  	69

SECTION 14 - APPENDIX
   CONTINUOUS MONITORING INSTRUMENTATION SURVEY
   Method    	71
   Results and Uses	71
                                     Vlll

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                                ILLUSTRATIONS

Figure

  1     Northeast Water Pollution Control Plant,
       Philadelphia, Pa	       3
  2     Process Computer, Peripheral Equipment and
       Industrial Tie-ins  	       4
  3     Common Processes in Secondary Wastewater Treatment	°. .  .       5
  4     Monitoring and Control of Common Wastewater
       Treatment Processes   	       14
  5     Map of Metro Seattle Wastewater Collection System	       16
  6     Filter Backwash Monitor	       25
  7     Example of a Data Logger   	       33
  8     Excerpt from the Computer Generated NELOG Summary
       Report  	       37
  9     Off-Line vs. On-Line Computer Control  	       44
 10     Computer Assisted Straight-Line Regression Analyses  	       45
 11     Automatic Plot of Two Variables vs. Time	       46
 12     Off-Line Computer Generated Excerpts from Wastewater
       Treatment Plant Reports	       48
 13     Using the Time-Sharing System	       50
 14     Whittier Narrows Water Reclamation Plant	       55

                                     TABLES
Table

 1      Common Wastewater Treatment Processes	       6
 2      Loose Treatment Control of BOD   	      4Q
 3      Improved Treatment Control (With Computer) of BOD   	      40
 4      Measurements for Wastewater Treatment Processes	      72
 5      Automatic Monitoring Instrumentation for Wastewater
       Treatment Processes	      73
 6      Symbols and Abbreviations	      75
 7      Manufacturers of Automatic Samplers	•      76
 8      Manufacturers' Addresses	      77
                                         IX

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                                      FOREWORD
     The completion of this report, Feasibility of Computer Control of Wastewater Treatment,
marks the completion of the second phase of APWA Research Foundation Project 66-6 which
was designed to investigate  the feasibility of computer control of public works processes. The
first  report, Public  Works Computer Applications, was published as APWA Special Report No.
38. The Special Report provides  a plan of action  for public works officials to computerize
information and control systems — or to extend the use of computer systems now in use. The
report  called attention to the  expanding role  of the computer for traffic and transportation
systems, water  supply and distribution, environmental management, and waste collection and
disposal. The report offered guidelines on feasibility studies, selecting equipment, preparing staff
and space, and beginning operations.
     This report is a detailed examination  of the  use  of process  computers in wastewater
management. The need for this detailed investigation was apparent upon investigation of the uses
which have been reported have been primarily for data logging.
     In contrast, considerable use of computer process control was found in industrial treatment
facilities.  Thus, this  project was  initiated to  determine  the  feasibility  of computer  process
control.  The initial report was prepared by the General Electric  Re-entry and Environmental
Systems Division. General Electric  worked closely with the Steering Committee to prepare the
final report. Additional input data  were provided by the APWA staff. Throughout the study it
was  pointed out by treatment plant personnel that  sensors are not generally available for
wastewater treatment  plant  processes. Sensors that  are  available have not been designed or
constructed  for use  in  this field. Devices which have  been installed,  generally have been
extensively modified.
     Manufacturers should  work towards the development of requisite sensors suitable for the
adverse  environment in which they  must be used as a design consideration. It is readily apparent
that  the use of  process  computers  for  the control  of  wastewater treatment plants  would
materially improve  efficiency of plants and plant management and perhaps reduce treatment
costs.
                                                              Joseph V. Radziul, Chairman
                                                                      Steering Committee
                                             XI

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                                         SECTION 1
                            SUMMARY AND RECOMMENDATIONS
     The summary of this study is reported in
the following paragraphs under the headings of
Objectives  and  Conclusions. Considerations for
further  action  are  included  in  the
Recommendations part of this section.

OBJECTIVES
     The threefold objectives of this wastewater
treatment study were as follows:
     1.   To   .analyze   the   advantages  and
limitations  associated with the use of computers
in the management and  control of wastewater
treatment facilities,
     2.   To document  potential  applications
and utilization procedures, and
     3.   To recommend further  research  to
achieve  full   computer  implementation  for
wa&tewater treatment operations and associated
management functions.
     The  following  tasks  were completed  in
support of the above objectives:
     1.   A survey of wastewater plants was
made  to  determine the  critical  problems  in
treatment and  whether  continuous monitoring
and  computer  control could  help solve these
problems.
     2.   Visits were made to wastewater plants
utilizing computer applications and automation
at Seattle, Washington; Hyperion (Los Angeles),
California;   Whittier-Narrows,   California  and
Philadelphia,   Pennsylvania   to  assess  these
applications.
     3.   Documentation   of   treatment
processes and operational reports were  received
from  the  surveyed  plants   and   studied  to
determine their feasibility for automation.
     4.   Information   on  continuous
monitoring  instrumentation  for   wastewater
treatment was acquired from manufacturers for
use in the instrumentation survey.
     5.   Numerous  documents  covering
automation and treatment were investigated in a
literature survey.
     6.   Meetings and  discussions were  held
with  plant  management,  consultants,
government regulatory agencies and the Project
Steering Committee.
CONCLUSIONS
     Resulting  from the above  tasks are the
following conclusions:
     1.   While conventional treatment systems
do have serious disadvantages and limitations,
they  will  continue  to  be the  most broadly
applied for the next 20 years.
     2.   While no new large scale innovation
threatens  to replace conventional  treatment,
modifications  to  the  processes  and
supplementary processes are being implemented.
Examples  are  chemical  coagulation  and
oxygenation.
     3.   Personnel pose a real problem  in the
operation   of  plants.   Difficulties  arise  in
obtaining  qualified  personnel,  in  training
operators and maintenance  men  and in reliable
follow-through of operational instructions.
     4.   Interest in  computer applications and
automatic control is widespread among plant
management.
     5.   A  recognition of the  advantages of
off-line  computer uses was  unanimous  with
general appreciation of automated management
reporting,  maintenance  scheduling, inventory
control, payroll and accounting.
     6.   Skepticism was apparent among plant
management regarding on-line computer control
of plant processes.
     7.   Computer  hardware  and
communication equipment are  available  and
reliable for use in industrial process control and
are  suitable  for  application to wastewater
treatment as well.
     8.   Off-line computer implementation for
plant  data  handling  and  management
information reporting is  being  successfully
practiced; it can serve a wide range of beneficial
applications and is fully feasible today.
     9.   On-line  instruments to  sense some of
the variables  considered essential to .continuous
monitoring and control of wastewater treatment
(such as BOD, bacteria and volatile acids) are
not on the market.
     10.  Computer control of the more critical
treatment  processes,  activated  sludge  and
anaerobic digestion is possible in  a limited sense

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based upon experienced operator control, and
will  require further  study  before optimization
via computer control is achieved.

RECOMMENDATIONS
     The  actions  indicated  from  the  above
conclusions are as follows:
     1.   Plant   management  should  consider
using off-line computer data processing for all
areas  of  plant  data handling:   reports,
maintenance  files  and  scheduling,  inventory
control,  and  business   areas.  Computer
availability for off-line applications may exist via
a  municipal facility,  a  nearby service bureau,
time-sharing or the  plant's computer.
     2.   Studies are  recommended to develop
the  mathematical-logical relationships of the
plant physical processes, notably the  activated
sludge and  anaerobic digestion processes. The
studies  should   result in the development  of
control  strategies for supervisory or closed-loop
control.

     3.   Further  work  must be done in the
development   of  reliable,  maintenance-free,
on-line  sensors.  An  in-depth  survey  of  users'
experience with  analytical instrumentation and
sensors in wastewater treatment plants should be
conducted. The survey would provide guidelines
 for improvement and innovative  approaches to
 solving the problems of continuous monitoring
 of wastewater treatment processes.
     4.   Plant management should give serious
 consideration to  computer  control of  plant
 processes, despite the lack of both knowledge
 and  sensors in  some  areas of  wastewater
 treatment. Today's impetus in plant controls is
 toward increased  application  of local  closed
 loops  with  advanced  instrumentation.  Some
 examples  are return sludge  on  the  basis of
 blanket level,  aeration  rate  to  maintain a
 dissolved oxygen  level  and variable  speed
 pumping  for  uniform plant  flow.  These local
 processes  can be integrated to achieve greater
 operational and economic benefits via computer
 control  of  centralized plant  monitoring,
 automatic  analyses,   timely  reporting  and
 improved  plant controls. Only by application of
 computer control can the wastewater treatment
 process be  optimized  as a  total integrated
 system.
     5.  Design of new plants or modification of
medium size (15  to 50  mgd) existing plants
should incorporate automatic  controls  of the
highest degree  available.  This  should  yield
economies of scale, operation  and management
and prepare the  plant for future  conversion to
full computer control.

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                                        SECTION 2
           WASTEWATER TREATMENT PROCESSES AND CONTROL APPLICATIONS
WASTEWATER TREATMENT SYSTEM
    The  w-astewater treatment  system
comprises  wastewater collection, treatment and
disposal. All three aspects must be considered in
the application of  computer monitoring and
control. The main emphasis of the study is on
the conventional  wastewater  plant,  such as
typically shown in Figure 1, through secondary
treatment and sludge disposal, and on the role of
the computer  to  upgrade  the  system.  The
processes,  operational  variables  and
instrumentation for  sensing  and control  are
examined  from phase  to  phase with a view
toward the feasibility of automatic monitoring
and control.
    The tertiary and advanced waste treatment
(AWT) processes are still relatively new and in
the demonstration stage. Although not included
in the processes listed in Table 1, some of the
techniques are covered briefly in Section 3.

PROCESS CONTROL COMPUTER SYSTEM
    The process control computer is the key to
automatic monitoring and control of wastewater
treatment. This digital computer control system
includes:
     1.   Central  processor  to  perform
computations and logic,
     2.   Core storage to retain both data and
instructions  for immediate  access to  central
processor,
     3.   Auxiliary storage, such as disk, drum
and tape to retain data and instructions, and
     4.   Peripheral  equipment  such  as  card
reader and card punch, input-output keyboard,
printer and cathode ray tube for communication
with a user.
     The process  computer  has  all  the
capabilities  of  a  purely  digital machine.  In
addition,  it  has an added  set  of peripheral
components  to  accommodate  the direct
monitoring and  control of industrial processes,
as  illustrated  in  Figure  2. .Such computer
applications are  commonplace in the  chemical,
petroleum  and  steel industries  among many
others.
                Figure 1. Northeast Water Pollution Control Plant, Philadelphia, Pa.
                    (This plant uses activated sludge and anaerobic digestion.)

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                                                                       PROCESS ACTUATORS &MNTROLURS
  PROCESS SENSORS & TRANSDUCERS
                                    INPUT / OUTPUT & CENTRAL PROCESSOR
              Figure 2. Process Computer, Peripheral Equipment and Industrial Tie-ins
     The following is a summary of computer
 capabilities  that suggest  a  more  efficient
 operation  than  by  manual control.  The
 computer can:
     1.  Monitor  operations  and  provide
 accurate,  useful  information — periodically  or
 on demand,
     2.  Generate  alarms  for  off-normal
 conditions,
     3.  Perform  conventional  controller
 functions with greater ease and flexibility,
     4.  Duplicate consistently the best-known
 control strategies on a continuous basis,
     5.  Make programmed decisions on more
 variables and data than a human — more rapidly,
 more usefully, and
     6.  Maintain   operating  levels   among
 diverse processes within limiting constraints.

 COMMON  TREATMENT  PROCESSES,
 VARIABLES AND INSTRUMENTATION
     Identified  in Table  1   are  the  physical
 processes  prevalent  in  a  large  number  of
 treatment plants.  Automation  of most  existing
 wastewater   treatment  plants  requires   an
examination  of  these  phases of  treatment.
Briefly delineated in Table 1 are each function,
the  role  of  management,  and  effectiveness
measures for operation.  Consideration  is also
accorded to  the existing status  of pertinent
analytical instrumentation.  In  Figure 3  is
depicted a  schematic flow  diagram  of the
common wastewater  treatment processes that
appear in Table 1.
     Computer implementation  for control in a
wastewater  treatment plant necessitates the
availability  of process monitoring  signals on a
continuous or sampled data basis. There are two
types of instrumentation for acquiring process
information:
     1.   In-stream   probe  or  sensor  which
generates  an  analog  signal of  the variable
measured, and
     2.   Automated  analytical procedure  (or
automated  wet chemistry) which samples a
quantity from the flow and subjects the  sample
to an automatic laboratory procedure, requiring
reagents. Although the procedure may be rapid,
a certain amount of time must elapse before a
variable is measured.
     Certain wastewater characteristics must be
measured   to  achieve  efficient treatment.

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COLLECTION SYSTEM
    REGULATOR
    (COMBINED
      SEWER)
  PLANT INFLUENT
      GATES
   MECHANICAL
     SCREENS
       GRIT
     REMOVAL
       RAW
   WASTE WATER
      PUMPS
                        EFFLUENT RECIRCULATION
                                        SLUDGE
                                       DISPOSAL
                                        SLUDGE
                                      DEWATERING
                                                                                  T
                                      ANAEROBIC
                                       DIGESTION
                                                                       SLUDGE
   PRIMARY
SEDIMENTATION
  SLUDGE
THICKENING
                                                                                LIQUID RETURNS
                                                        WASTE WATER

                                                        SLUDGE
                  Figure 3. Common Processes in Secondary Wastewater Treatment

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                                                 TABLE 1.  COMMON WASTEWATER TREATMENT PROCESSES (1 of 6)
Function
Operational management
Effectiveness measures
Monitored variables and use
Available
on-line
instruments
On-line
instrument needs
Divert excess wet weather
flow to receiving waters (in
combined sewer systems or
systems subjected to exces-
sive infiltration and inflow).
Prevent dry weather
overflow.
Investigate pollution
overflows.
Repair malfunctions.
Regulator monitoring and control

  No dry weather overflows.
  Reduced stream pollution.
  Reduced surveillance costs.
Depth to detect outfall sewer
overflows.
Flow to outfall sewer (in dry
weather).
Depth          Flow measurement Im-
               provement, since Venturl
               meters  and Parshall  flumes
               are.  difficult to  Install and
               expensive. Given sewer
               cross-section, slope and
               roughness, the depth
               measurement could  yield
               a more accurate, com-
               puted flow (via computer).
Regulate raw sewage flow
into plant.
Allow plant maintenance.
Capture and prevent coarse
material from entering
plant, thereby protecting
piping and equipment.
Screened material shredded
and returned to wastewater
or trucked away for disposal.
Regulate influent flow to help
maintain steady state flow
through treatment processes.
Optimize screen-cleaning
activity.
Too  little causes excessive
back-up; too much leads to
high  maintenance costs and
operational costs.
      Plant influent gates

   Prevention of plant influent
   surges.
   Preservation of steady plant
   flow.

      Mechanical screens

   Minimized influent back-up.
   Reduced screen cleaning
   costs.
   Minimal coarse solids to
   plant.
Depth to prevent flood levels    Depth
in adjacent residential areas.     Flow
Influent flow to approach
steady state design range.
Liquid level to detect high        Depth
head-loss across screen and to     Flow
initiate cleaning cycle.
               Adequate (see section 13,
               Instrument survey).
               Adequate (see section 13,
               Instrument survey).
Raise the level of influent
wastewater for continu-
ation through plant
Maintain steady-state design
range flows through plant.
Wet well level maintained
above minimum level for
suction, and below maximum
level to prevent flooding.
Best control of steady-state
design flow through plant.
   Raw wastewater pumping

  Control pumping for maxi-
  mum efficiency and life.
  Steady plant flow.
Depth of wet well kept          Depth
within normal limits.            Flow
Flow to approach steady-        Power
state.                          Current
Electrical power for opera-       Voltage
tion and determination of        Bearing
pump efficiency.                temperature
Bearing temperature to
protect pump.
Elapsed time meter to
monitor pump life and
maintenance requirements.
                Adequate (see section 13,
                Instrument survey).

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                                                 TABLE 1.  COMMON WASTE WATER TREATMENT PROCESSES (2 of 6)
Function
Operational management
Effectiveness measures
Monitored variables and use
Available
on-line
instruments
On-line
instrument needs
To remove abrasive, chiefly
inorganic materials, thereby
minimizing pump wear, pre-
venting clogging, and simpli-
fying sludge handling and
disposal.
Removed grit is disposed of
by incinerator, burial, dump,
or landfill.
 Maintain optimal, steady
 channel velocity to settle
 high density grit and to pass
 low density organics.
 Analyze grit for organic
 matter to determine grit
 channel efficiency.
 Maintain mechanical grit
 removal equipment.
       Grit channel

Minimal appearance of grit in
primary settling and sub-
sequent plant equipment,
especially in digesters.
Minimal organic settling in
grit channel.
 Channel flow and depth to
 determine velocity.
 Grit channel entry as moni-
 toring point for wastewater
 characteristics (pH, temper-
 ature, BOD, COD, DO, TOC,
 SS, percent volatile matter,
 phosphates, nitrogen, ORP,
 toxic metals, and toxic
 compounds).
Depth          BOD
Flow          Phenol
pH            Toxic material detector.
Temper-        On-line instrumentation
 ature          for phosphates and nitro-
COD          gens, COD and TOC com-
TOC           prises automated analytical
Phosphates     procedures (automated
Nitrogens       wet chemistry). Detec-
ORP           tion by probe or sensor
Chromium     in the stream flow would
Copper         be more direct and would
DO            yield a real-time measure-
               ment.
               Although a suspended
               solids on-line instrument
               is available for the high
               ranges, none exists that is
               suitable  for less than 500 mg/1,
               the level of suspended solids
               for influent wastewater.
Remove settlable and
floatable solids (and as-
sociated BOD).
Ascertain removal of sludge,
scum, grease and oil.
Minimize downtime of skim-
ming, sludge collecting, and
pumping equipment.
Maintain proper sludge density
for  pumping.
Determine pollutant removal
efficiencies.
 Primary sedimentation

Maximum  removal  of
suspended  solids in the
primary effluent and
floatable material.
Removals include scum,
grease and oil.
Influent and effluent            COD
measurements of BOD (or       TOC
COD or TOC), SS, percent       pH
volatile matter to evaluate       DO
efficiency of removals.           Sludge
pH and DO in effluent are        density
important to further treat-       Flow
ment.
Flow over weir controlled
and steady to promote sedi-
mentation.
Sludge density to control
pumping for sludge removal.
              BOD to measure removal
              efficiency.
              SS to measure removal
              efficiency.
              No on-line device has yet
              proved reliable for primary
              tank use to measure sus-
              pended solids or BOD.

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                                                              TABLE 1. COMMON WASTEWATER TREATMENT PROCESSES (3 of 6)
oo
Function
Operational management
	 	 	
Effectiveness measures
Monitored variables and use
Available-
on-line
instruments
On-line
instrument needs
           Remove BOD and SS by means
           of biological activity and
           subsequent settling.
 Maintain healthy, active
 organisms through the bal-
 ance of influent, effluent,
 and sludge-return flows.
 Maintain proper loading rates,
 satisfactory DO level and
 good mixing throughout tank.
 Provide sufficient sampling
 of variables.
 Control applied air to
 maintain aerobic conditions
Activated sludge (aeration tank)

  Maximized BOD removals and
  sludge density index.
  Minimized need for applied
  air with resultant power
  savings.
BOD (influent and effluent)
to determine removal ef-
ficiencies.
DO to maintain optimum
level in aeration tank for ap-
plied air flow.
Mixed liquor suspended solids
(MLSS) to determine return
sludge needs.
ORP to indicate the state of
oxidation and oxygen utili-
zation.
Flow to approach steady-state
design range.
Return sludge flow to verify
required  rate.
pH as alarm indicator if too far
from normal.
Temperature  for record pur-
poses and correlation studies.
DO
MLSS
ORP
Flow
PH
Temperature
               BOD to oplinn/c return
               sludge  mix.
          Remove solids settling
          in effluent from secondary
          treatment units (aeration
          tanks or trickling filters).
          Provide activated sludge
          return to the aeration tank.
Maintain timely removal of
properly concentrated set-
tled solids for fresh return
activated sludge.
Maintain proper level of
sludge blanket.
Maintain design value of
surface application rate.
           1 Activated Sludge Process Automated. Water and Sewage Works.
            May 1970.

           2Stack,  V.T.  Continuous Monitoring  Devices  -  Treatment
            Plants.  Proceedings  Ninth   Engineering   Conference,
            Instrumentation, Control  and Automation For Water Supply
            and  Wastewater  Treatment Systems.  University  of Illinois,
            College of Fngmccrmp  1967.
   Secondary clarification

 High removals in effluent of
 BOD, COD, SS.
Rate of liquid overflow from
clarifier to indicate effluent
flow.
Sludge blanket level in tank
to determine start of sludge
removal.
ORP to indicate condition of
sludge.
BOD (or COD or TOC) and SS
in effluent to indicate removal
efficiency.
Nitrogens and phosphates to
indicate removals of respective
nutrients.
Temperature for record pur-
poses and correlation studies.
DO in effluent to indicate
effect on receiving waters.
pH as alarm indicator when
outside normal range.
PH
DO
SS
Sludge
 blanket
Flow
ORP
COD
                                                                                                                                      Nitrogens
                                                                                                                                      Phosphates
                BOD
                No on-line instrumentation is
                available to directly indicate
                biological characteristics,
                such as the status of the
                bacterial culture in the return
                sludge.

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                                                  TABLE 1.  COMMON WASTEWATER TREATMENT PROCESSES (4 of 6)
Function
Operational management
Effectiveness measures
Monitored variables and use
Available
on-line
instruments
On-line
instrument needs
Remove BOD and SS by
means of biological activity
in stone or plastic media
followed by settling.
Destroy bacteria prior to
discharge of effluent
into receiving waters.
Concentrate a dilute
sludge, maintaining a
pumpable viscosity.
Maintain well distributed,
unclogged flow, proper
loading rates, effluent re-
cycling, and adequate air
circulation.
Check influent and effluent
for removal efficiencies.
Prevent toxic or high pH
materials from entering.
          Trickling filter

     Steady, continuous flow.
     High percent BOD and SS
     removals.
Maintain satisfactory
operational chlorination
equipment.
Observe safety regula-
tions.
Maintain satisfactory
chlorine residual.
Control rate of feed.
Maintain satisfactory
pumping operations.
Check sludge blanket
density.
Monitor flow rates.
Extract samples for
testing.
Control flow of dilution
water (when required).
Flow of influent and re-
cycling to retain steady-state
design range.
BOD to determine removal
efficiency.
pH as alarm indicator when
outside normal range.
Temperature for record
purposes.
Chlorination (disinfection of effluent)

     Overall bacterial kill or
     bacterial concentration with
     minimum chlorine application.
Flow to pace chlorine
application.
Chlorine residual to determine
         Sludge thickening

     Maximized increase of total
     solids.
                                                                                           BOD (or COD or TOC), SS,
                                                                                           turbidity to determine re-
                                                                                           moval efficiencies and load to
                                                                                           receiving waters.
                                                                                           Nitrogens and phosphates to
                                                                                           indicate nutrient load to re-
                                                                                           ceiving waters.
                                                                                           Bacterial content to determine
                                                                                           effectiveness of disinfection
                                                                                           and load to receiving waters.
Total solids of influent vs
underflow to evaluate thicken-
ing efficiency.
Percent of volatile matter in
influent and underflow to
indicate organic loading.
Flow and SS content of
dilution water to balance
influent, effluent
measurements.
Flow rate of influent, under-
flow, and overflow to measure
loading.
BOD (or COD or TOC) and SS
of overflow to indicate loading
of return to primary sedimenta-
tion tank.
Flow
pH
Temperature
                                                                                                                                         BOD
Flow
Turbidity
COD
TOC
Chlorine
residual
Nitrogens
Phosphates
BOD
SSbelow500mg/l
Bacteria sensor
Chlorine demand would generate
direct determination of required
dosage.
Flow
SS (high)
COD
TOC
Sludge-
 density
BOD
SS (below 500 mg/1)
Total solids
Percent volatile matter

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                                                     TABLE 1.  COMMON WASTEWATER TREATMENT PROCESSES (5 of 6)
Function
Operational management
Effectiveness measures
Monitored variables and use
Available
on-line
instruments
On-line
instrument need1.
 Decompose organic
 matter in a controlled
 environment devoid of
 free oxygen.
 Good digestion yields:
    1) An innocuous
 sludge that de-waters with
 mechanical filtration.
    2) A gas, approximately
 65 percent methane, useable
 for general heating purposes,
 to heat sludge, or in engines
• to generate power. Excess
 is burned.
    3) A supernatant liquid
 of low solids concentration.
Maintain:
   1) Safety code
   2) Temperature control
   3) Continuous feed rate.
   4) High solids in feed
   5) Complete digester
mixing
   6) Monitoring of volatile
solids loadings
   7) Monitoring of digester
detention  time
   8) Minimal pH variation
   9) Alkalinity to assure
proper buffering capacity
  10) Monitoring of volatile
acids as digestion indicator
  I 1) Lime feed for pH
adjustment
  12) Gas burner
Sludge digestion (anaerobic)

 Rate and composition of gas
 formation are reliable in-
 dicators of the speed and
 success of digestion.
 Volatile solids reduction
 indicates effective digestion.
1) Raw sludge feed:
   Total solids
(above minimum percent
volatile matter) to indicate
organic load.
pH for preferred range is
6.8 to 7.4.
2) Digester contents:
   pH for optimal operation
range.
ORP to indicate oxidation
activity.
Alkalinity for buffering.
Volatile acids to prevent high
concentrations.
Temperature for optimal value.
Total solids to indicate loading.
Percent volatile matter to in-
dicate digestible solids.
Level indication to keep below
maximum, especially  with
floating covers.
3) Gas produced:
   Percent CO2 indicates
digester activity.
Rising percent CO2 indicates
process unbalance.
High  methane percent in-
dicates good digester  activity.
Volume  indicates total gas
production.
4) Digested sludge:
    pHof 6.8 to 7.4 is pre-
ferred range for digestion.
Total solids to indicate good
digestion.
Alkalinity to check proper
buffering.
Temperature for optimal
digester  range.
Flow to  indicate withdrawal
rate.
PH
ORP
Alkalinity
Temperature
Level
Carbon
 dioxide
Methane
How
Total solids
Percent volatile mallei
Volatile acids

-------
                                              TABLE 1. COMMON WASTEWATER TREATMENT PROCESSES (6 of 6)
Function
Operational management
Effectiveness measures
Monitored variables and use
Available
on-line
instruments
On-line
instrument needs
Reduce the moisture content
of sludge to a cake form suit-
able for disposal by inciner-
ation or landfill.
Continuous process coats
liquid sludge on a porous
medium drum through which
liquid is drawn by vacuum,
leaving the solid to form a
cake which is removed.
The drum is coated by sludge
while rotating partially sub-
merged in a vat.
During rotation the coating
is vacuum dried, then re-
moved just before that
portion submerges again
in the sludge.
Dispose of sludge at sea by
barge or pipeline.
Digested sludge is preferred
because it should be innocuous,
of low volatile content, less
likely to create nusiance con-
ditions, and more  conducive
to mixing and dispersion.
Maintain:
   1) Equipment
   2) Proper sludge
condition
   3) Operating vacuum
   4) Drum submergence,
speed, and feed rate.
   5) Maximum solids
concentration in feed.
   6) Functioning filter
(change if necessary).
   7) Sampling for per-
formance evaluation.
Maximize solids con-
centration in a pumpable
sludge:
Prevent nusiances from
odors, floating material,
bottom deposits, and
toxic matter.
Locate discharge point to
prevent beach pollution.
Control transport in pipe-
lines to utilize tides for
carrying solids away.
aiudge dewatering vacuum filtration)

     Minimal moisture content of
     removed filter cake.
     Maximum rate of dry solids
     cake produced (Ibs/sq ft/hr).
      Sludge disposal (at sea)

     Minimal local beach pollution
     and nusiance at discharge
     point.
1) Sludge feed:                 Flow
   Total solids above            Weight
minimum value.
Percent volatile matter
indicates organic load.
Flow to determine feed
rate.
Chemical demand to in-
dicate conditioning needs.
2) Cake:
   Total solids should be of
high concentration.
Percent volatile solids to in-
dicate organic content.
Total weight for total cake
production rate.
3) Filtrate:
   Total solids should be of
low concentration.
Percent volatile matter to in-
dicate organic content.
Flow to indicate rate of
liquid separation.
Flow (pipeline) to record        Flow
disposal rate.                   Density
Bacterial sampling (pipe-          (solids)
line) to monitor area
surrounding outfall.
Solids content for concen-
tration efficiency.
Volume loading (barge) for
records.
Solids loading (barge) for
concentration efficiency.
Total solids
Percent volatile matter
                                                                                                             Bacteria detection

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Measurements  are taken  at  a  plant influent
point, at  certain  locations  in  the  treatment
processes  and  at the  plant effluent.  Those
recommended for monitoring at  the entrance to
the grit  channel  (as a plant influent  point) are
shoun  in  Table  1   They  include  pH,
temperature,   biochemical  oxygen demand
(BOD)  or chemical oxygen demand  (COD)  or
total  organic carbon  (TOQ,  suspended  solids
(SS), dissolved  oxygen (DO), percent volatile
matter,  phosphates,  nitrogen.
oxidation-reduction potential  (ORP)  and toxic
metals  and  compounds. While  not  necessarily
involved  in  direct control  of the  grit channel,
these  measurements  indicate  the  chemical,
physical  and  biological nature of  the  flow
entering the plant. Plant efficiency is determined
by the removals of pollutants, such as BOD, SS,
phosphates, nitrogen and the toxic matter. Some
items such as pH, temperature,  and  ORP must
be within  specified  normal  ranges  to  allow
satisfactory treatment in other plant operations
(sedimentation,  digestion  and  the  activated
sludge process).  The variables are discussed  in
the following paragraphs.
pH
     pH  indicates the  acid-base condition  of
sewage  flow. Fresh sewage  is slightly alkaline;
stale  sewage is  acid.  pH  is  important for
anaerobic  digestion   and  can  be   detected
automatically with a probe. '
Temperature
     Temperature is  important  to  certain
treatment processes, especially digestion, and is
automatically measured with a sensor.
BOD
      BOD indicates the oxygen requirements of
the organic and chemical matter. BOD removal
is a  prime  function  of treatment.  No  fully
acceptable  direct  BOD  measuring  device or
methodology exists.
COD and TOC
     COD  and  TOC are frequently suggested  as
substitutes for BOD. Data correlations are being
tested  at some  plants (Philadelphia,  Pa.3 and
'Guarino, OF. and G.W. Carpentar. Philadelphia's Plans Toward
Instrumentation and Automation of the Wastewater Treatment
Process.  5th  International Water  Pollution  Research
Conference San 1 ranciseo, California. July  29, 1970.
 Seattle,  Washington)  with  varying degrees  ot
 success.  The  following  methods of  predicting
 BOD from TC and COD resulted from studies at
 the   Philadelphia  Northeast  Water  Pollution
 Control  Plant, and any  correlation, however, is
 generally characteristic of the plant and its own
 data  and  is  not usually  applicable to  other
 plants.
            Method I

                                Method II
      Simultaneous equations  I  Linear Regression

     BOD = 0.82 COD - 0.98 TC |  BOD = 43 + 0.66 COD
                         ,        -0.88TC
       Deviation breakdown
                             Deviation breakdown
Deviation of
estimate
from actual
(percent)
Percent of
time


0-10 50
0-20 67
0-30 83
Deviation of
estimate
from actual
(percent)
Percent of
time


0-10 33
0-20 92
0-30 100
COD
     COD measures the total oxygen consuming
capacity of the wastewater and can indicate the
chemical  loading on a plant.  While COD can be
measured quickly by automated wet chemistry4,
there is no continuous monitoring sensor.
TOC
      TOC  yields an indication  of the organic
carbon in the wastewater. Through an automated
analytical procedure, TOC  has demonstrated its
applicability in wastewater  monitoring2. A TOC
determination  specifically  represents oxidation
of only carbonaceous  materials. While inorganic
carbon may cause interference, it is removed by
acid treatment  of the sample or by a separate
determination  and subtraction of the inorganic
carbon from the total sample reading (TC).
SS
     SS  solids  floating  or  in  suspension,
determined according  to  "Standard Methods",
indicate the suspended solids concentration  in
4Milbury,  W.F.,  V.  Stack, N.S.  Zaleiko,  F.L. Doll.  A
 Comprehensive  Instrumentation  System for Simultaneous
 Monitoring for Multiple Chemical Parameters in  a Municipal
 Activated  Sludge  Plant. Preprints 16tn  Annual Analysis
 Instrumentation Symposium, ISA. Pittsburgh, Pa. May 25-27,
 1970.

-------
the wastewater. A continuous monitoring sensor
is on the  market (Keene) for  the  500 to 5000
mg/1  range. Higher ranges can be  measured via
dilution,  but  no  continuous monitoring
instrument is  available for direct  measurement
of suspended solids concentrations of less than
500 mg/1.
DO
     DO indicates the oxygen dissolved in the
liqwid and is essential for bacterial activity. DO
is measurable by on-line probe.

Percent Volatile Matter
     This is a measure of the organic content in
suspended solids in a sampling of sewage. The
volatile content is determined  by ignition of the
suspended solids with   a weight loss  due  to
burning  of the volatile  matter. The inorganic
solids remain.

Phosphates
     These constitute a  nutrient in wastewater.
Orthophosphates and total phosphorous can be
detected by automated wet chemistry2
Nitrogen
     Nitrogen indicates the nitrogenous nutrient
presence  in  the wastewater. Automated wet
chemistry systems  can be  used  for total
Kjekdahl  nitrogen, ammonia  nitrogen, nitrites
and  nitrates2.  The   relative  quantities  of
ammonia  nitrogen,   nitrite  and  nitrate
compounds indicate the degree  to which  the
nitrogen compounds are  oxidized (nitrification).
ORP
     ORP  is the potential required to  transfer
electrons  from the oxidant to the reductant and
presents a qualitative measure of the  state of
oxidation  in  the treatment processes.  Sensors
permit continuous monitoring.
Toxic Compounds and Metals
     These may be present in sewage, especially
industrial  wastes. These include  phenols and
aldehydes  as  well  as   hexavalent chromium,
copper, cadmium, zinc and nickel. Above certain
thresholds, they are toxic to bacteria, especially
in  the  digestion process  and  can  cause a
significant reduction in treatment efficiency.

2Ibid.
 CONTINUOUS  MONITORING   AND
 CONTROL
      For years analyses in wastewater treatment
 have depended upon elaborate, time-consuming
 chemical procedures which yield results too late
 to  exert  direct  control.  While  many tests
 continue  to be made  on  samples in  the
 laboratory, notably BOC, the tests  for  solids
 content, bacterial analyses and others are being
 replaced with the on-line sensors or automated
 analytical  procedures.  These new  continuous
 monitoring devices yield rapid intelligence  of
 plant operations and enable- the application of
 timely, corrective measures as off-normal trends
 appear.   The  applications  of  the  measured
 variables in control loops are described chiefly to
 introduce  some broad approaches  to  the logic
 and computations suitable for process computer
 control. Monitoring and control of the common
 wastewater treatment processes are illustrated in
 Figure 4.
      While many loops can be currently closed
 via  local analog  controls, the central computer
 can simplify the local equipment, accommodate
 all  plant  closed  loop controls and generate
 integrated logging and reporting.  The general
 control  sequence  can   be  divided  into  the
 elements of 1) Monitoring, 2) Data gathering, 3)
 Status  determination, 4) Data processing,  5)
 Decision  making,  6)  Control  execution,   7)
 Verification, and 8) Evaluation.


 ENVIRONMENTAL FACTORS
      The measurement and recording of rainfall
 and other  meteorological  data  can add to the
 total  information delivered  to  the  central
 computer.  Such  information  can  be used  to
 relate environmental  factors  to the treatment
 plant influent. A specific case is the prediction of
 flow patterns in the collection system to control
 routing  and storage of  such  flows  in  order to
 prevent  hydraulic overloading  of a collection
 system or the treatment plant.
REGULATOR MONITORING AND CONTROL
     Centralized  monitoring  and  control  of
regulators can result in  significant reduction of
                                               13

-------
 o
 a
 o
 a.
 9
 a
a
2
o
a
f
1
(5
I
a
••»
?
                      CA
                      CPR
                      CR
                      D
                      DO
                      OS
                      F
                      G
                      MLSS
                      Nit
                      OD

                      ORP
                      Phoi
                      SB
                      SO
                      Sit Sol
                      ss
                      T
                      TD
                      To»
                      Turb
                      V
                      VA
                      {%>  VM
                         O
 -  Alkalinity
 -  Chlorine application
 —  Cake production rate
 -  Chlorine residual
 -  Depth
 -  Dliiolvtd
 —  Drum ipeed
 -  Flow
 -  Gate
 -  Mixed liquir cuipended solids
 -  Nitrogens
 -  Oxygen demand IBOD or TOC or
    COD I
 -  Oxidation reduction potential
 -  Photphatet
 -  Sludge blanket
 -  Sludge density
 -  Settletble tolidt
 —  Suipended solids
 -  Temperature
 -  Tub depth
 -  Toxic mated or compoundi
 -  Turbidity
 -  Vacuum
 -  Volatile ac»di
 -  Percent volatile matter
Sampling point* and computer logging
Waitewater
Sludge
                       (J   Monitor and computer logging
                       t^
                       ff^  Computer control
                      O

-------
                                              Variable
Sampling
point
SS
OD
Phos
Nit
PH
ORP
T
Set
Sol
Do
%VM
Turb
V.A.
Alk
Tox.
Grit channel,
M1 XXXXXXXXX X
Primary
sedimentation,
M2

Aeration, M3

Trickling
filter, M4

Secondary
clarification,
M5

Plant effluent,
M6

Digester, M7
X     X

      X
X

X
X     X     X    X
                              XXX
X     X

X
       PLANT EFFICIENCY MONITORING
      Besides  the  variables monitored  (see
diagram) others  may be applied at key points in
the  plant for  determining plant  efficiencies,
logging, historical records, and correlation studies.
They  are not  all automatic,  and not all need be
measured.
      X     X    X    X    X
                        XXX
                                                                   X     X
                                                                       DIAGRAM NOTATIONS
Aeration:       DO  monitored to  determine
                aeration rate. MLSS monitored to
                determine return sludge flow. M3
                monitoring.

Chlorination:    Chlorine  residual monitored  to
                determine chlorine  application.
                M6 monitoring.

Clarification:    Flow monitored  for optimal set-
                tling.  Sludge   blanket   level
                monitored to determine sludge re-
                moval flow. M5 monitoring.
Digester:        Temperature  determines sludge
                circulation for heating. Gas analy-
                sis and  other variables determine
                sludge loading  as well as liquor
                and sludge withdrawals. M7 moni-
                toring.
                                         Grit channel:    Flow  and  depth monitored to
                                                        achieve optimal grit settling. Peri-
                                                        odic  (time-  controlled)  grit
                                                        removal. M1 monitoring.

                                         Mechanical     Cleaner  mechanism  actuated by
                                         screens:        differential level across screen.
                                         Plant influent   Gate position determined by flow
                                         gate:           and sewer backup depth.
                                         Primary        Compute total flow for optimal
                                         sedimentation:  settling. Sludge  density dictates
                                                        sludge pumpage rate. M2 monitor-
                                                        ing.
                                         Pumping:       Approach steady state plant flow.
                                                                           Regulator:      Overflow determined by flow and
                                                                                          depth of collection system.
                                                                           Thickener:      Sludge density determines sludge
                                                                                          pumping rate. Liquid overflow re-
                                                                                          turn monitored.
                                                                           Trickling       Flow  and  wastewater  variables
                                                                           filter:          monitored to determine recircula-
                                                                                          tion rate. M4 monitoring.
                                                                           Vacuum        Operation monitored by tub level,
                                                                           filtration:      drum speed, vacuum,  incoming
                                                                                          sludge density  and rate of cake
                                                                                          production.

-------
                         5. Map of Metro Seattle Wastewater Collection System
combined sewer overflow to receiving waters. To
achieve the objective of using available storage
within  the  existing combined   sewers  for
regulating stormwater flows, the Municipality of
Metropolitan Seattle, as indicated by the map in
Figure 5, is installing a "Computer  Augmented
Treatment . and  Disposal  System  (CATAD)".
Reduction of both the  frequency and magnitude
of  wastewater  overflow   is part of Seattle's
objective. It is further anticipated that flow to
the treatment plant will be kept under control
within specified limits.  When  overflows cannot
be avoided, the system will control discharges at
selected stations to minimize harmful effects on
marine life or  public beaches. Monitoring within
the system includes:
     1.    Level of trunk lines, interceptors and,
in some cases,  tide,
     2.    Regulator and outfall gate positions,
     3.    Influent level  and  pump speeds  at
pump stations, and
     4.    As  many  as  23  separate  alarm and
control contact status points.
     Implementation of the system over the area
indicated  in Figure 5 is based upon centralized
computer control operating in conjunction with
automatic  local  station  controls  to  utilize
storage  in  the  trunk  sewers.  Within  the
permissible limits for back-up of wastewater, the
computer will control5:
     I.    The  position  of the  regulator gate
which diverts flow from the trunk sewer into the
interceptor sewer,
     2.    The position of the outfall gate which
allows flow to the receiving waters, and
     3.    The number of  operating pumps and
the  pump   speed to  build  up  storage  of
wastewater  in the interceptor and trunk sewers
upstream  of pumping stations.
 5Metropolitan Engineers. Municipality of Metropolitan Seattle
  Sewage Disposal Project Contract No. 68-1 for Computer
  Augmented Treatment and Ditpoal System. March 1968.
                                              16

-------
     Within  the  collection  system aside from
the hydraulic variables, such variables as DO, pH,
toxic compounds and metals, gaseous hydrogen
sulfide and combustible gas detectors  can  be
monitored  from various  points to provide useful
information  for  operation  of  the  collection
system and the treatment  plant,  the data can
provide early warnings  of future  maintenance
problems and hazardous conditions  within the
collection  system. The  data may  also help in
locating sources of undesirable industrial waste
dumps or spills.

GATES
     Gate  control  is utilized  to  prevent flow
surges  into  the  plant while  simultaneously
avoiding nearby  residential  flooding  due to
excessive back-up.

     Under computer control, internally stored
reference flows and depths for the  sewer system
can  be compared  with measured  flows  and
depths to determine the desired gate setting and
to deliver the adjustment signal as necessary.
     On-line monitoring is  especially applicable
to a multiple influent gate system where two or
more gates are regulating raw sewage flow to the
plant, and  the problem  of simultaneous  control
is  more   complex.  With  computer  stored
intelligence of system  capacity,  programmed
schemes can control emergencies  in combined
sewer collection systems (such as local storms).
The high flow from one part of the system may
be permitted to enter the plant while a low flow
component is further reduced via  gate control,
utilizing the permissible back-up in  the sewer.
Where  the  situation approaches the  allowable
system capacity constraints, an alarm can signal
off-normal  conditions.

MECHANICAL SCREENS
     Removal of coarse material from the plant
influent causes an accumulation of debris on the
upstream side  of the  screen.  This  creates a
sufficiently large difference in water level across
the screen  for automatic control to initiate the
scaper  activity thereby removing the  coarse
material' for disposal. The time interval between
checks should not exceed 1/2 hour.
     Should the scraper malfunction, an alarm
can  be  triggered  on  the  basis of no  scraper
 activity, excessive influent main depth, excessive
 head-loss  across screens,  and  excessive  flow
 reduction.
     To prevent scraper breakdown, a  counter
 for  the number of cleaning operations or an
 elapsed  time meter  could  signal the  optimal
 period  to  apply preventive maintenance to the
 equipment.

 GRIT CHANNEL
     The effectiveness of grit channel operation
 is based  upon  differential sedimentation.  The
 flow velocity  through  the  channel is  slow
 enough to allow the  high density grit to settle,
 while the lower density organic solids remain in
 the effluent. Flow and depth in the grit channel
 should be monitored so that  the velocity can be
 kept  constant  despite   wastewater  flow
 variations.
     Through use of multiple, parallel channels,
 continuous monitoring and control can regulate
 the division of total flow among the channels.
 The number  in use  as  well  as the optimal
 velocity of  the  channels  can be  determined
 according to total plant influent flow.
     Grit removal by mechanical devices such as
 scrapers,  conveyors  and  screws  should be
 monitored  for  operation every  half hour to
 prevent possibility  of miring under  too heavy
 grit deposits.

 RAW WASTEWATER PUMPING
     Monitoring   of pump  operation  can
 accommodate the following functions:
     1.   Maintaining steady state plant flow,
     2.   Prevention of flooding condition,
     3.   Pump  cycling and  speed  changes to
 accommodate flow changes  and to increase
 pump life,
     4.    Pump operation  at peak efficiency,
      5.    Prevention  of  excessive  power
demand factor,
      6.    Alarms for off-normal flow and level
 conditions,
      7.   Alarms for pump malfunction, and
      8.   Alarms for bearing temperature.
      With  the   above  conditions  under
 continuous  monitoring, a  computerized
 mathematical model  can be developed from the
 pump  requirements  for  control  of raw
 wastewater pumping. Control of flow  into the
                                               17

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 plant via variable speed pumping  can minimize
 hydraulic transients. Complex multiple  influent
 channels and pumping requirements are feasible
 for computer control.

 PRIMARY SEDIMENTATION
      The  requirements  of  primary  settling
 include a  steady, optimal  surface application
 rate and overflow weir rate to promote solids
 settling,  and  sludge  density  monitoring  for
 control of solids removal. Floating debris is
 removed by a skimming device for discharge into
 a scum sump and subsequent disp&sal.
      Monitoring of  the  surface application  or
 overflow weir rate can exert control on the rate
 of flow to the primary tank to maintain design
 flow rates.
       Sludge removal can  be based upon sludge
 density.  Under  density  monitoring,  a  thick
 sludge is preferred for efficiency of removal and
 for subsequent treatment. The upper limit on
 sludge  density  is  based upon the  pump
 capability.  Control of  the mechanical collectors
 also contributes to sludge density. Time intervals
 between  sludge removal cycles should  be
 adjusted  to  maintain  aerobic  conditions
 throughout the sedimentation tanks.

ACTIVATED SLUDGE (AERATION TANK)
     Aeration tank control involves:
     1.    Flow rate of influent (from primary),
     2.    Flow rate of return sludge,
     3.    Flow rate of effluent,
     4.    Flow  of air to  maintain dissolved
oxygeri (DO) levels, and
     5.   Sampling  and   measurement of
wastewater  and mixed liquor characteristics to
determine operating levels.
     A real  time BOD  reading could optimize
our mix on a minute-to-minute basis6 a quote
from  one  plant operator. Since  there  is no
acceptable  continuous  BOD  monitoring
instrument,  other properties of wastewater must
be used for control of the aeration tank mix.
     One  alternative  is  to  measure the
concentration of mixed liquor suspended  solids
 (MLSS)7 which can be  used to  determine the
 return sludge flow. However, the concentration
 of solids in the aeration tank liquor is strongly
 dependent  upon the nature of the wastewater8.
 This would require therefore a local adjustment
 of the MLSS — return sludge relationship based
 upon the operator's experience.
      Aeration may be applied by diffused air
 generated by blowers or mechanical agitation.
 Control is expedited via the quantity of diffused
 air or  power to the mechanical aerators. The
 loop  is  closed by signals  from  strategically
 located DO probes in  the tank to maintain an
 optimal DO level  consistent  with the needs of
 bacterial activity and  economy  (prevention of
 excessive  power  usage). Monitoring  can be
 continuous  with  DO  probes,  but an  outage
 should not exceed a half hour.
      Biological  systems  are  sensitive  to  step
 changes9  in  the  wastewater  characteristics.
 Sudden temperature  changes  can  increase
effluent turbidity of the clarifier,  and sudden
changes in  BOD or pH  can cause the  sludge
blanket  to  deflocculate.  Maintaining  constant
conditions tends  to stabilize  the  process,
however,  plant  influent  characteristics  are
subject to sudden  changes in chemical nature.
Continuous monitoring  and computer data
logging  can  alert  operators   to indications of
changing characteristics.
     Optimal  control of  aeration tank activity
must  be integrated with clarifier control, since
they  are sequential  processes with controlled
feedback.
     The direct use of oxygen for aeration from
on-site  oxygen generators or  sale of the  gas is
currently being tested and proving economically
feasible.  The  supply  of oxygen  can  be
automatically controlled in direct proportion to
the BOD of the influent wastewater1 °
^Crises in the Megalopolis Demand New Electronics. Electronic
 Design 1 January 4, 1968.
1 Mixed Liquor Suspended Solids Analyzer/Controller, Bulletin
 No. 8200. Keene Corporation Water Pollution Control Division,
 Aurora, Illinois.

8Cosens, K.W., The Operation of Sewage  Treatment Plants.
 Public Work Publication.

9Knowles, C.L., Improving Biological Processes.  Chemical
 Engineering/Desk Book Issue. April 27, 1970.

10Oxygen Can Replace Aeration. The American City June
  1970.
                                              18

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TRICKLING FILTER
     Control of trickling filter operation is again
a matter of maintaining a steady state influent in
both  flow and wastewater characteristics  with
no material  in the flow toxic to bacteria. Forced
air draft may be added  to improve aeration in
the filter.
     With little  to  control,  good continuous
monitoring  and logging  of the variables which
can affect operation such as  pH, temperature,
influent  flow return  (where  used),  flow and
toxicity, can help improve operations.

SECONDARY CLARIFICATION
     Control  in  secondary   clarification
comprises:
     1.    The maintaining of the proper sludge
blanket level,
     2.    The removal of as  concentrated a
sludge as  possible  within the  constraint of
pumpability,
     3.    The  removal  of settled sludge as
quickly as possible to prevent septicity, and
     4.    The setting of the proper fraction of
sludge removal for return to the aeration tanks
as seeding.
     Since the purpose of the return sludge is to
provide thriving bacteria  to meet the aeration
tank influent, the wastewater  characteristics of
that influent are also important. Optimal control
of return sludge flow should be  based  upon
flow,  temperature,  pH and DO, as well as on
BOD. Of  further importance is the population
and health of the bacteria. No sensor exists to
identify either the  species or  condition  of the
bacteria.
     In one article  a  successful application of
sludge removal on  the  basis  of blanket  level
control is described.1  A sensing head probe is
located at a preset level in the settling tank and
detects  the  sludge  blanket level via the gap
between  an infrared source and  a photocell.
When the  blanket reaches the specified level, the
light  source is  cut off, initiating the  sludge
draw-off  mechanism from the  tank.- As the
sludge blanket drops below the desired level, the
sensing head probe halts sludge draw-off. While
sensing can be continuous, the interval between
checks should not exceed five minutes.
     Nevertheless,  to accommodate the  factors
relating to the return sludge flow would require
a comprehensive study to determine the nature
of the relationships among the variables from
which the control model could evolve.

CHLORINATION
     The  chief function to control is chlorine
dosage which can be  done automatically  as a
combination of pacing with flow and adjusting
the rate by the chlorine residual measurement.
The  residual recorders measure the free chlorine
remaining in the flow after a specified contact
period and yield a dosage verification which is
converted to a dosage adjustment for subsequent
flow.  Close  control  is  important  since
insufficient  feed  rate will not  fully  destroy
bacteria, and too much is wasteful.  The interval
between checks should not exceed five minutes.
A chlorine demand instrument would determine
the dosage directly.11

MONITORING OF RECEIVING WATER
     Monitoring of receiving water is certainly a
part  of the  total wastewater treatment system.
Besides chlorine residual of the plant effluent,
such variables  as  DO,  pH,  turbidity  and
conductivity  are   monitored   in  the receiving
water. Other variables are cited for measurement
in Table  4,  Measurements for  Wastewater
Treatment Processes. Aside from plant effluent
area, water quality stations may be located both
upstream and downstream of the plant.
     In most areas, regulatory agencies collect
this  information.  Hence  this topic is  further
covered   under Section  5,  "Data  Needs  of
Regulatory Agencies."

SLUDGE THICKENING (GRAVITY)
     Sludge thickening by gravity is  similar to
    Water and Sewage Works, op. cit.
     s, A., and H.F. Hanson. Water, Water Everywhere, But-
   Control Engineering. May, 1970.
                                               19

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primary  sedimentation  where  solids  are
concentrated to form a sludge blanket. The chief
control operation  is  proper  removal of  the
thickened  sludge.  Through  utilization  of  a
nuclear radiation  or sonic device, the density of
the  thickened  sludge  can  be  continuously
monitored to initiate  intervals of removal by
pumping.
SLUDGE DIGESTION (ANAEROBIC)
     Anaerobic digestion is a critical operation
easily  subject to  instability. In  the process
bacteria groups work simultaneously to consume
organic  matter.  One  group  breaks  down the
material to  the  acid  stage,  while  another
continues the conversion to methane and carbon
dioxide.  In a favorable environment, a balance is
maintained  among  the  different  groups; the
acids are consumed as they are formed, and the
pH remains in a  suitable range for the methane
bacteria.
     Instability  is  a problem because  of the
generally greater prevalence of acid producing
bacteria  over methane bacteria. Thus, unless a
digester  has been  sufficiently  seeded  and
properly fed,  the smaller population of methane
bacteria  may  be  unable to keep pace with the
acid forming bacteria. As the production of acid
lowers the  pH,  the  methane bacteria become
seriously inhibited.
     The variables involved in digester operation
include  temperature,  pH,  alkalinity,  carbon
dioxide,  methane, volatile acids, percent volatile
matter, rate of raw solids feed, rate of digested
sludge removal and rate of supernatant  liquor
removal.
     Volatile acid  determinations  provide
valuable  information concerning the anaerobic
degradation of raw organic solids  as well as the
environmental  conditions  for  methane
production.12While the value of the volatile acid
test is recognized, it is a laboratory procedure.
     Gas analysis is another indicator of digester
activity  and  can be performed   on-line. The
 proportion of  methane  and  carbon  dioxide
 remains fairly constant during normal operation.
 However, at the onset of disestion troubles, the
 carbon dioxide  content of  the gas increases.
 Continuous gas analysis can indicate satisfactory
 or off-normal operation and is  useful to control
 digester activity  (with  volatile acid testing to
 confirm conditions).
      Temperature is essential to  satisfactory
 digester activity "and should be kept around 95
 deg F. Heat application can be  controlled by the
 digester temperature.
      pH  can indicate the  presence of excess
 volatile acids.  Below a  pH  of 6.5, methane
 producing  activity becomes  inhibited.  An acid
 neutralizing agent,  such as lime,  will raise the
 alkalinity and  bring  back  more favorable
 conditions of  pH  (around  7.2)  for methane
 production. Thus pH or alkalinity monitoring
 can control lime feed.
      The  addition  of  raw  solids  and sludge
 removals must  not  disturb the desired  delicate
 volatile acids — methane balance.
      Sludge density or solids content of the feed
 should also  be  monitored  to  assure  proper
 loading to the  digester  tanks. Pumping a thin
 sludge may wash out the alkalinity and upset
 digester balance.
      There are  many  factors  involved  in
 monitoring and controlling digester activity, and
 they  can  be synthesized into  a  mathematical
 model. In its simplest sense, (using continuous
 monitoring variables) pH  can  determine  lime
 feed;  gas analysis  and  sludge   density  can
 determine raw solids feed and sludge removal.
      A mathematical model  was  developed  to
 study anaerobic digestion,  13 and  its problems
 of failure and start-up. The quantities  cited as
 effective  in  decreasing  start-up  time  and
 preventing  digester failure were seed sludge, pH
 and digester loading. To study the problems of
 digester start-up and failure, which are transients
 rather than steady state  operation, necessitated
 use of a dynamic (time-varying) model. In this
 case  a steady state model would be ineffective.
 12Sawyer, C.N. and P.L. McCarty.  Chemistry for Sanitary
  Engineers. McGraw-Hill Book Company. 1967.
^Andrews, John F., Dynamic Model of the Anaerobic Digestion
 Process. Proc. Paper 6418. Journal of the Sanitary Engineering
 Division, ASCE, pp 95-116. Feb., 1969.
                                                20

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SLUDGE  DEWATERING  (VACUUM
FILTRATION)

     Although  sludge  is  most  frequently
dewatered  in  open  or covered  drying  beds,
controls  are  minimal.  The vacuum  filtration
technique was selected for discussion because it
can  save  labor, is rapid  and is  suitable  for
automated control.
     In this process a thickened and conditioned
sludge coats a filter on a rotating drum through
which a vacuum extracts the liquid. Continuous
monitoring should include  flow, density and
chemical conditioning of influent sludge, level of
drum submergence, effectiveness of the vacuum,
effectiveness  of the  filter, drum  rotation and
rate  of  sludge cake  produced.   Information
brought to  the computer  can be logged and
checked for  values outside normal  ranges  to
trigger alarms.
     Equipment control is chiefly maintenance
of the proper level of drum submergence in the
sludge tub to keep up with removal by coating
of the  rotating  drum.  Closed loop  control
operates the sludge flow to the tub to retain the
set point level.
                                             21

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                                          SECTION 3
                      SOME ASPECTS OF HIGHER ORDER TREATMENT
INTRODUCTION
     Continued refinement and higher removals
beyond secondary  standards are becoming a
necessity in the search for quality effluent from
wastewater  treatment plants. Thus,  secondary
effluents  are  being  subjected  to  further
processing  involving  chemical  application,
settling, filtration and mechanical separation.
     Those briefly considered here are described
with  respect  to  the  process, its removal
capability and requirements for monitoring and
control. They include microstraining, chemical
coagulation  and  settling,  filtration,  carbon
columns,  ammonia  stripping, and ion exchange.
     The  examples  of higher order  treatment
cover  tertiary for increased removals of BOD
and  suspended solids  and advanced waste
treatment (AWT)  for special removals  such as
phosphorus, nitrogen  or  minerals. Refined
removals  of  suspended solids, organics,
inorganics and nutrients are covered.

MICROSTRAINING
     Microstraining  removes  suspended solids
and the  associated  BOD.   The microstrainer14
equipment consists of a  rotating drum  covered
with a very fine  stainless steel woven fabric
through  which  wastewater is strained.  As  the
drum  revolves, wastewater  enters through one
end under gravity and strains out through  the
drum  wall,  leaving suspended material  trapped
on  the inner  surface.  Meanwhile  above and
outside the drum, jets of water strike through
the  mesh and force the  trapped material into a
trough just inside the drum to be carried away as
waste washings to the primary settling tank.
     The  microstrainer  performs  mechanical
separation  of solids.  Therefore   any  BOD
removals  are associated with  the   suspended
solids. Results from different operational studies
showed varying degrees of removals:
          SS:   50-89 percent of influent
          BOD:  30-81 percent of influent
     Supervision  is minimal with an intelligent
operator checking equipment once a shift.
     Continuous  automatic  monitoring could
detect local  electric power, water  level, drum
rotation, raw water influent flow, strained water
effluent  flow, washwater  flow, and wastewater
flow. The  information  could be  logged
periodically with allowance for an  alarm upon
detection of an off-normal value.
     Continuous  turbidity measurement could
monitor  the  improvement  of clarity. Samplings
would be required  for laboratory tests of BOD
and  suspended solids. It  is also important to
continuously  monitor  head  loss  across  the
microstrainer to indicate blockage.

CHEMICAL COAGULATION
     The addition of chemical coagulants such
as alum and lime to  secondary effluent in a rapid
mixing basin initiates the  chemical  coagulation
process.15  This flash mixing is followed  by
gentle agitation by rotating paddles to form
large  size  floe  which   traps  solid  particles
including organic matter and bacteria. The solids
are then settled  in a basin and  removed  by
sludge scrapers, while the effluent flows over
weirs into collecting troughs. Coagulant aids
such as activated silica, clay and polyelectrolytes
are also  used to enhance floe  formation and
improve settling.
     In  a  feasibility study at  Dayton, Ohio,
where chemical coagulation  and settling were
applied  to  secondary effluent,16 the following
conclusions were drawn:
     1.   Overall  phosphate  removal  was  89
percent  with alum,  89 percent with lime at pH
of 9.5 and up to 97 percent with lime at pH of
11+.
     2.   At  a pH of 11 the chemical treatment
phase was  capable  of reducing the phosphate
14Dixon, R.M. and G.R. Evans. Experiences with Microstraining
  on Trickling Filter Effluents in Texas. 48th Texas Water and
  Sewage Works Associations Short School. March, 1966.
15Marks, R. H. Wastewater Treatment. A Special Report, Power.
  June, 1967.

16Tossey, D.F., P.J.  Fleming, and  R.F. Scott.  Tertiary
  Treatment by  Flocculation and Filtration.  Journal of the
  Sanitary Engineering Division, Proceedings of the American
  Society of Civil Engineers, 7106 SA1. Feb., 1970.
                                               23

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content from 28 mg/1 to 1.5 mg/1, a greater than
94 percent removal.
     3.   Chemical settling  significantly
improved effluent quality over plain settling.
     4.   Overall BOD removal up to 97 percent
was achieved.
     5.   With  alum  and silica the  chemical
treatment phase  was  capable of  reducing  the
BOD content  from 26  mg/1  to 4  mg/1, an 84
percent removal.
     6.   Overall suspended  solids  removals
were 89 percent with indications, however, that
a  portion of the suspended  matter may have
been chemical coagulant.
     7.   With  alum  and silica the  chemical
treatment phase  was  capable of  reducing  the
suspended solids content from  127 mg/1  to 21
mg/1, an 83 percent removal.
     Clarification efficiency can be continuously
monitored  via  turbidity measurements,  while
BOD and suspended solids tests are performed in
the  laboratory. Continuous monitoring should
include  analyses  of the  wastewater
characteristics,  such as  pH,  temperature, and
DO.
     Choice of coagulant and  coagulant aid will
depend upon the results of experimentation at
the  plant.  With a choice  selected, the dosage
must also depend upon experimentation such as
the jar test.
     It  is possible to relate coagulant dosages to
plant   variables  suitable  for  continuous
monitoring such  as pH, temperature,  turbidity
and wastewater characteristics  of  influent and
effluent   flow.  Other  variables  relating  to
coagulation  are zeta  potential and  streaming
current,   which have  possibilities  for
development  into  continuous,  on-line
instruments.  Where these measurements  are
feasible,  an  empirical relationship  can   be
developed  suitable for  implementation  in  a
process computer to control dosage application.

FILTRATION
     Filtration  is generally used on the effluent
from chemical  coagulation  and  settling. The
filter media is usually sand and other media such
as anthracite. As the wastewater flows through
the  filter bed, suspended particles are captured,
thereby  effecting  a  reduction  in  turbidity.
However,  through continued use of the filter,
the  trapped particles  build  up  head  loss,
necessitating  removal  of the material by filter
washing.
     In the City of Dayton study16 referred to
under  Chemical Coagulation, rapid  sand
filtration was used to  polish the effluent of the
wastewater treatment  plant.  Some of the results
of filtration usage were:
     1.   With  no prior chemical treatment,
filtration  of settled  trickling  filter  effluent
produced  overall removals  of  91  percent
suspended solids  and  80 percent BOD during
poor trickling filter performance. When trickling
filter  operation  improved,  the corresponding
figures for sand filtration resulted in an overall
removal rise for BOD to 95 percent.
     2.   Following chemical treatment it was
also stated, "It was possible to polish effluents
to a higher degree than plain settling alone".
     3.   When   preceded  by  chemical
coagulation,  the  filtration phase  of treatment
removed 30 percent to 70 percent of the applied
phosphate load.
     Steady  flow  and  gradual flow changes are
essentials  for filtration control  since transients
cause  increases  in  effluent  turbidity  or
breakthrough. Flow and limitations on  the rate
of change of  flow  can be  monitored and
controlled via computer.  In open tank filters,
continuous monitoring  is  also  important  for
tank level to prevent  flooding, head-loss  to
initiate backwash  and  level of water storage (for
backwashing). Pumps  for feed and  backwash
should also be monitored.
     To measure filter efficiency, turbidity can
be  monitored  automatically,  but suspended
solids (low levels) and  BOD analyses must  be
performed on samples  in the  laboratory. All
continuously  monitored data can be computer
stored for logging, off-normal checking to alarm
and management reporting.
     The initiation of backwash as well as the
backwash  cycle can be controlled  by computer.
A simple routine  can  examine  information
acquired  from the  filter, and on the basis  of
response to a few questions,  determine whether
16Tossey. D.F., et. al., op.cit.
                                             24

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                                  Figure 6. Filter Backwash Monitor
 to start the cycle. Information is examined on
 v/hether the filter is in operation, the head loss is
 too high, the washwater tank is sufficiently full,
 and  another filter is operating.  If  the proper
 responses  are received the filter is submitted to
 the backwash cycle. The monitoring scheme is
 flow-charted in Figure 6.

 ACTIVATED CARBON
      Filtering  wastewater  through  granular
activated  carbon  results  in   adsorption  and
absorption  of  biodegradable   and
non-biodegradable organic matter. Turbidity and
color are also significantly reduced. Batch mixing
of carbon is commonly used in  municipal water
treatment to remove tastes  and  odors. However
in wastewater  treatment, columns of granular
activated carbon are considered more practical to
use because separation and regeneration of spent
carbon  for reuse present less difficulty than the
batch  process.17   The  carbon  is  periodically
rejuvenated by draining to concentrate the slurry
and  by high temperature  furnace heating to
 remove the adsorbed organic matter.  The cycle
 of use and reactivation results in a 5 percent loss
 of granular carbon.15
     In operations at the South Tahoe Public
 Utility  District "over 80 percent of all organic
 material  found  in the  secondary  effluent was
 removed by carbon treatment".18
     At a Pomona pilot  treatment  plant19 ' a
 carbon  adsorption system was operated for over
 a  year  with  achievement of over 90 percent
17Burleson, N.K., W.W. Eckenfelder, and J.F. Malina. Tertiary
  Treatment of Secondary Industrial Effluents by Activated
  Carbon, 23rd Industrial Waste Conference, Purdue University.
  Lafayette, Indiana.
15Marks, R.H.,op. cit.

18Slechta, A.F. and G.L. Culp. Water Reclamation Studies at the
  South Tahoe Public Utility District. Journal Water Pollution
  Control Federation. May, 1967.

19FWPCA U.S. Dept. of Interior. Summary Report Advanced
  Waste Treatment. Publication WP-20-AWTR-19.
                                                 25

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suspended  solids and  80  percent  total COD
removals (77 percent dissolved COD removal).
At the same time regeneration losses averaged 10
percent.
     Some  absolute  figures  on carbon column
removals in the Pomona study included:
         SS (mg/1):   from  10 to less than 1,
         COD (mg/1): from 47 to 9.5,
         TOC(mg/l): from 13 to 2.5,
         Nitrate, as  N (mg/1): from 6.7 to 3.7,
         Turbidity (JTU): from  10.3 to 1.6.
     The   sizeable  nitrate reduction was
attributed  to  biological  activity  within  the
carbon column.
     In  the  Pomona  operation  continuous
carbon  column monitoring  for  efficiency
included COD, TOC, ammonia  and ultraviolet
absorbance (2537 Angstrom). It was found that
ultraviolet  absorbance  correlated well enough
with TOC to be considered as a possible control
variable for operation.
     One of the most important functions of
monitoring is  to determine  when  the carbon
adsorptive  capability is  spent.  At  the  South
Tahoe installation where COD  and TOC  are
continuously monitored, carbon is withdrawn
for reactivation  when COD  reaches  20 mg/1 or
TOC reaches 7.5 mg/1.

AMMONIA REMOVAL BY AIR STRIPPING
     Ammonia  stripping  is  a  technique  for
removing volatile NH3- Ammonia may exist in
water as volatile NH3 or ionized  ammonium,
NH4+. When the pH  is raised to  10 or above in
the   wastewater,  the  predominant  form  of
ammonia is the NH3-  Being volatile it can be
driven off as  a gas by air-contact.  This is
accomplished in towers where the liquid flows
steadily downward as air is blown across.19
     Experimentation to seek economically high
removals continues with variation in tower size,
configuration,  internal  structure, pH and flow
rate of wastewater, flow rate and direction of air,
and recycling. Removals of ammonia from 85 to
95  percent  were   achieved  under  different
conditions.  Greater  air circulation  can  boost
removal to 98 percent.18
     Some advantages of  nitrogen removal by
ammonia stripping include:
     1.   Gaseous form removal, requiring no
extra handling,
     2.   No  requirement  for  nitrogen
conversion to nitrate, and
     3.   Increase of the pH to a range suitable
for  ammonia   stripping  by  previous  lime
coagulation  for  phosphate  and  turbidity
removal.
     Some of the problems which  arise  with
ammonia stripping include: 1) poor efficiency in
winter  due to  freezing  of  water  and  high
solubility  of ammonia,  and 2)  formation  of
calcium carbonate scale in the tower from the
lime application of earlier treatment phases.20
     Continuous  monitoring  must  include
wastewater flow,  pH, and air  flow  to assure
proper  conditions  for  the  design  removals.
Ammonia NH3  influent, effluent monitoring is
required to determine removal efficiency.

ION EXCHANGE
     Ion  exchange  presents a method  for
wastewater demineralization by the removal of
undesirable cations and anions.  Certain resins
have  the ability  to  exchange   ions  from  a
solution. Under proper conditions the polluting
cations  are  exchanged for  hydrogen and the
polluting anions for hydroxyl ions.
     During treatment,21  wastewater  flows
through  the  resin until it begins to reach its
exchange capacity.  This  is  evidenced by
breakthrough or reappearance of the undesirable
ions in the effluent. Once the exchange bed  loses
its ion removal effectiveness, treatment is halted
while the bed is backwashed to remove dirt, and
regenerated. The operational cycle then resumes.
     Since  ion   exchange  materials  may be
contaminated by  solids  and  organics in the
wastewater, some prior  tertiary removals are
recommended.
19,
 'ibid.
18
  Slcchta, A.F. op. cit.
20FWQA., U.S. Dept. of Interior. Current Status of Advanced
  Waste Treatment Processes.  Advanced Waste  Treatment
  Research Laboratory, Division of Process Research and
  Development. July, 1970.

21Eckenfelder,  W.W. Industrial Water Pollution Control.
  McGraw-Hill Book Company. 1966.
                                             26

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     Studies on the removal of ammonia at the
South Tahoe Public Utility District18 were very
encouraging. With an influent of 18 to 28 mg/1,
the ion  exchange resin showed the capability of
treating an average of 400 bed volumes before
breakthrough  reached  1 mg/1  of  ammonia
nitrogen. With  successive  regeneration  and
operation the resin lost little exchange capacity
and exhibited no significant organic fouling.
     It has been suggested that demineralization
is so  effective that only a portion of the total
wastewater flow need be treated.19
18Slechta, A.F.,op. cit.

19FWPCA U.S. Dept. of Interior, op. cit.
     Continuous  monitoring  is  important to
both  the  operational  and  the  regeneration
cycles.  Monitoring  influent  and  effluent
presence of the undesirable ion during operation
yields  both the efficiency of removal and the
onset   of  breakthrough.  Through repeated
cycling, sufficient data may be accumulated to
prepare a  curve of ion removal  efficiency vs.
cumulative  volume  of  flow  as  treatment
progresses toward breakthrough. The curve can
be used to determine optimum operational cycle
time.
     The  regeneration  cycle requires clean
rinsing  water  and  chemicals  which may  be
costly.  Monitoring  the  application  of
regenerative materials and  duration of the cycle
can lead to optimal economic operation.
                                              27

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                                           SECTION 4
                       SURVEY OF WASTEWATER TREATMENT PLANTS
     Survey  forms  were  sent  to  the  larger
wastewater treatment plants across the country.
Information  was  requested on plant processes,
the problems of plant operational management
and  process  control,  and  experience and
opinions  regarding computer applications. Of
the 40 forms sent, 22 returns were received.
     The survey attempted to determine:
     1.   Where  are  the most critical problems
in wastewater treatment?
     2.   Could  continuous monitoring of the
problem processes help? and
     3.   Consequently, could digital computer
control solve the problem!
     Among the survey forms received, nineteen
contained  information  on  the  type  of
wastewater treatment distributed as follows:
No.
7
1
9
2
1 Type
primary
intermediate
secondary
tertiary
     Plant-flow capacity was reported in million
 gallon per day (mgd) on 21 forms, as follows:
Number
3
4
4
7
1
1
1
| Capacity (mgd)
< 10
11-50
51 - 100
101 - 200
300
343
750
      In  response to  the  question,  What plant
 processes  require close control  and could be
 improved by continuous monitoring? one-half of
 the returns stated  All. While this  answer has
 merit, it does not convey any sense  of priority.
 Those processes selected are listed in descending
 order of frequency of appearance  on the returns,
 as follows:
Process |
sludge digestion
activated sludge
chlorination
vacuum filtration
incineration
sludge pumping
Percent cited
26
19
18
14
13
10
     The  question,  What  is  the most critical
problem  in  plant  operational  management?
 received  almost   unanimous  response  on
 problems with plant personnel. The complaints
 in descending order were as follows:
        Complaint
   Percent cited
     Unreliability of follow-through          44
     Obtaining qualified men               19
     Communications                    13
     Training                          12
     Lack of process feel; sensing changes      12

     The  question,  What is  the  most  critical
problem  in  plant process  control? received
answers   attributing the  problems  to  the
following:
          Causes
|   Percent cited
     External	17
       Excess and peak flows
       Industrial spills
       Harmful material entering system
       Variations in influent sewage
        strength
     Operations	60
       Monitoring, but no control
       Lack of timely recognition
        of malfunctions
       Lack of process flexibility
       Lack of timely data to maintain
        balance in:
          digesters
          aeration tanks
       Handling and disposal of sludge
       Safe disposal in oceans
     Equipment	23
       Pumping
       Density meter calibrations
       Incinerator operation and
        maintenance	

      The question, Do you use  a  computer to
assist plant operations and management?  was
positively answered  by  ten  returns,  which  is
about  40 percent of those received.  Only one
respondent  was applying  the computer to an
on-line,  plant-control  operation,  influent
pumping. The device, used at the headworks of
the Deer Island Treatment Plant, Boston, is not a
digital computer but a pneumatic controller that
continuously  monitors  flow  and  elevations  at
three  he ad works:  Pumping  is  adjusted to
maintain  predetermined  levels in the shafts of
the  headworks  in accordance with the signals
                                               29

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received.  The  remaining  applications "/ere
related to plant operations and business services,
as follows:
         Event
  No. of
Applications
     Operations
       Plant periodic reporting
       Maintenance planning and
          reporting
       Chemical results
       Engineering research
     Services
       Payroll and personnel
          accounting
       Cost accounting and billing
       Requisitioning
     8
     4
     2

     1
     1
     8
     5

     2
     1
     The question, Are you contemplating use
 of the computer? was answered  positively  by
 twelve respondents, of which four are currently
 using some computational facility.
       No.  and  contemplated  uses  (with
       overlap):
                  5 automation
                  1 accounting
                 10 undesignated
     The question,  What  are the benefits and
 disadvantages  of computer  applications  in
 sewage   treatment?  received  answers  which
 indicated recognition  of the benefits from the
 following:
            Benefit
      • Data logging
       Long term data storage
       Process monitoring and alarms
       Operational maintenance scheduling
       Summary and exception reporting
       Inventory control
       Quality control analyses
       Reduced labor costs
       Studies and operational evaluations
     Suggested  disadvantages  included  the
following:
       	Disadvantages	
       Cost
       Additional justification
       Loss of personalized process fee!
       Too great reliance on sensors (distrust
          of instruments)
       Manual inputs from laboratory testing
          are  too  late  for  control
          (instrumentation disadvantage)
       Need for measurement standards of
          input variables
     A question was posed requesting comment
on  any  special local  conditions which would
influence computer applications  in wastewater
treatment. Although the responses varied, some
significant opinions appeared in more than one
of the returns, as follows:
      1.   Local  regulatory  agencies  stipulate
specific and consistent plant effluent quality. To
minimize plant process fluctuations and produce
consistent  effluent  load,  process  computer
control may be necessary.
     2.    To upgrade the waterway system into
which the  plant  discharges,  it  is  felt  that
computer  control  offers  an  opportunity  for
closer control of treatment processes by timely
adjustments to  influent flow rates and sewage
composition. This  should aid  in producing  a
more satisfactory overall discharge.
     3.    Lower   hardware  costs,  packaged
software at reasonable prices, higher labor costs,
and  regulatory  agency  demands for  more
information all will contribute  to a greater use
of computers.

     4.    Increasing costs of operation may lead
to automation (forcing function).
      5.    Cost may be prohibitive  to  the  local
administration which sanctions expenditures.
     There  is  no  question  that  computer
applications for wastewater treatment processes
are receiving a  great deal of attention. Among
some  larger  plants,  off-line  applications are
already commonplace, and management is giving
strong  consideration  to   computer
implementation for continuous monitoring and
control.  The survey has indicated the pressures
on plant management to  upgrade effluents and
to  reduce  costs.   The  returns  cited  that 60
percent  of the most critical problems in plant
process  control  were  attributable to  internal
plant   operations   involving  manpower.
Improvements  can be realized  through higher
quality   labor,  training programs,  and better
tools,   such  as  continuous  monitoring
instrumentation and computer controls.
                                               30

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                                          SECTION 5
                         DATA NEEDS OF REGULATORY AGENCIES
INTRODUCTION
     Throughout the  country  state  agencies
acquire data on the operation of wastewater
treatment plants, chiefly to document effluent
characteristics and  to  tabulate statistics.  Most
regulatory  agencies  investigate the pollution of
streams  and  its  causes.  They  foster the
promulgation  of regulations  to establish water
quality standards. Whenever a pollution problem
is  evident,  new  treatment  facilities  or
improvement  of  older  plants  are   often
prescribed  by the regulatory agency.  Lack of
compliance with regulatory orders may result in
rejection of local building permits, suspension of
treatment  permits,  adverse publicity,  fines or
imprisonment. The  Federal Water Quality Acts
have  engendered the recent  adoption  of  more
stringent standards by  the states.  They  have
effectively  required the upgrading of practically
all wastewater treatment plants. Inherent in the
new  regulations  are construction time tables,
stream and effluent standards, monitoring  and a
rigorous program of enforcement.
     Industrial waste discharges are subjected to
similar abatement regulations. The  FWQA
estimated that over half the load on public waste
treatment  facilities  originates from  industry.
Pending Federal guidelines   for construction
grants  stipulate  pre-treatment  of industrial
wastes  before  acceptance into  a  municipal
sewerage  system and   the  establishment  of
industrial waste surcharges.
     The Federal construction grants  program
further encourages  the   development  of
comprehensive  river basin-wide  programs for
pollution  abatement22.  The percentage  of
awards for  grants are determined to some extent
on the degree that new treatment works as well
as Metropolitan  and  regional plans fit into a
basin-wide approach.
     The requirements of both the Federal and
State regulatory  agencies can  be summarized as:
     1.   High  water  quality  standards for
receiving waters,  necessitating greater pollutant
removals than currently practiced.
^•Federal Register. Volume 35, Number 128. July 2,1970.
     2.   Strong  encouragement  of
regionalization  approaches to  implement  the
new removal standards.
     3.   Rig i d   enforcement  of  discharge
regulations.
     4.   Pre-treatment  of  industrial  wastes
financed by the industry itself.
     5.   Increased  surveillance  with  more
sophisticated  instrumentation  and  analyses to
assure compliance.

REGULATORY  AGENCY  DATA
REQUIREMENTS
     The  prime concern  of  the regulatory
agencies is the effect of wastewater effluent on
the local receiving waters. Stream surveillance is
usually  accomplished  indirectly  through the
medium  of  operational reports from the
regulated facilities. Report requirements may be
comprehensive or  minimal in  nature.  A
comprehensive report may include  operational
data and removal efficiencies from all phases of
plant processing as well  as  information  on
bypasses and  conditions of receiving waters.  A
minimal report  may address itself directly to
effluent characteristics. Information is reported
on  total daily  flow, raw influent and final
effluent values of pH, settlable solids, suspended
solids,  BOD,  and effluent  data  on  bacterial
analysis and chlorine residual.
     In  many cases  the  criticism  is that very
little is  done  with these reports beyond storage
for historical  record purposes,  especially where
state-wide reporting brings in huge quantities of
information. The data should be used to observe
trends  and  present information for local plant
construction.
     Each state  has its own reporting system,
although  data  requirements  are somewhat
similar.  It  would also  appear that  standard
reporting formats for all plants have  not been
established for any state.
     Samples  of  reports  and  forms examined
include the following:
     1.   New  York  State  Department of
Health  Report  on  Operation  of Sewage
Treatment Plant  (Form San. 46  10M 2-10-68
                                             31
                                                     AWBLRC  LIBRARY U.S.

-------
(7D232)).  The  form  is rigidly defined, very
comprehensive  and  states:  "These  reports
should  present  a  representative  picture  of
operating conditions at the plant  so that this
Department may be informed  and be  able to
advise  and  assist  the  operator in  correcting
difficulties  and  maintaining  the  maximum
efficiency of the treatment plant at all  times."
     2.   New  Jersey State  Department  of
Health  Monthly Operating Report of  Sewage
Treatment  Plant (Form WP-5 Jan 68). This is a
basic flexible form with allowance for specifying
variables to be measured and laboratory tests.
     3.   Renton  Treatment Plant,  State  of
Washington,  report  for the  state  agency is
essentially the plant's own monthly report.
     4.   Hyperion  Treatment   Plant,  Los
Angeles, California, report on analyses of plant
effluent and  digested sludge  is tailored to the
plant and is  comprehensive with emphasis  on
monitoring  of  ocean   waters   and   beach
conditions.
     5.   The Pennsylvania State Department of
Health  has  adopted  minimum  information
requirements  to  evaluate  state-wide plant
efficiencies. With  few  exceptions  the  report
requires raw and final effluent values of settlable
solids, suspended solids, BOD, and pH, as well as
daily flow, population served, relative stability,
and chlorine residual.
     The new regulations of the Department of
Interior published  March 31,1970 require data
for evaluating new treatment works construction
applications.  The FWQA may demand detailed
data on the sources of pollution for the entire
river basin, the volume of discharge from each
source,  the character  of effluent, the  present
treatment,  the water quality  effect, and so on.
These  requirements may include  not  only
measurement of variables, but extensive analyses
as well. It appears that the  geographic  and
physical situation  may  be  the  determinant of
some of the requirements.

AUTOMATIC   CONTROL  AND
REGULATORY AGENCY DATA
     Automatic  control  and  monitoring  of
wastewater treatment and water quality are fully
compatible with the data needs of regulatory
 agencies. The goals of automated control include
 both improved data and an improved and more
 timely reporting process.
     A  second aspect is that the regulatory
 agency  report can be  a  direct fall-out of the
 plant management information system. It can be
 assumed that any data requested by the state is
 already  a segment of plant reporting or will have
 to be  incorporated  into it. Under computer
 implementation an internal data bank of plant
 operational information is stored as the basis of
 automatic control and information processing.
 Where a computer program system is written to
 process  plant data into a management hierarchy
 of periodically generated reports, the regulatory
 agency report is just a part of the system.
     Another consideration is the action  taken
 by the  regulatory agency upon  receipt of the
 report.  The assumption  that a great store of
 state-wide environmental control data is arriving
 at a central location presents an opportunity for
 statistical  studies and  analyses on a large  scale
 basis.  The  data  can  be processed  into  an
 overview of the status of water pollution control
 throughout  an entire region.  Plant  effluent
 variables can be processed into long term trend
 plots for observation as well  as indications for
 action.
     The total approach  presented here for a
regulatory  agency  could  not  readily  be
accomplished on a purely  manual basis because
of the volume of information qcquired, and the
sophistipated statistical nature of the processing.
The increased scope  of regulatory agency data
processing  can  be  directly  compatible  with
computer  implementation  in  wastewater
treatment.
     The  Municipality  of Metropolitan Seattle
 uses a basic data logger device (See Figure  7) to
 monitor the Green and Duwanish  Rivers.  The
 system  automatically  samples measurements
 from five water quality analyzers on the rivers in
 a  cycled sequence,  usually hourly, and prints
 them on the typewriter. Some of the variables
 measured  are  dissolved  oxygen, conductivity,
 pH,  and  turbidity.  The   logger  concurrently
 punches  data onto a paper  tape which is later fed
 to offline computers for statistical analysis and
 reporting purposes.
                                              32

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      Figure 7.  Example of a Data Logger
   (Water Quality Monitoring at Metropolitan
              Seattle, Washington)
     Another  water  resource  management
approach being given serious consideration is the
establishment  of  basin-wide water quality
monitoring systems. 'The use of electronic data
processing  techniques as  a management tool
becomes necessary for  the control  of  water
pollution because the magnitude of the problem
is too great to be controlled manually".23 Such
a monitoring system should  be  designed  to
provide immediate, accurate information on the
extent,  nature  and movement of pollutants at
remote  stations.  Its  objectives should include
provisions for:
     1.   Constant  surveillance  of  water
pollution and its sources
     2.   Warning networks
     3.   Information on fishkills
     4.   Assistance in  further development of
water quality standards and regulations
     5.   Exploitation of the water resource
     6.   Means for analyzing  special problems
     7.   Aid in evaluating local water pollution
control problems

     The physical system includes a network of
remote  stations containing automatic sampling
and  continuous water   quality monitoring
equipment.  Data  are transmitted  to a central
station  which will  receive and  process  the
signals, and may  then calculate and display the
results. The fundamental premise of the system
is continuous monitoring with direct connection
to an electronic computer.24 In this manner the
system  may  track  the hydraulic flow  of  a
pollutant  as  well  as  its  identity.  Pollution
sources can  result from continuous flow, diurnal
patterns, seasonal variations and instantaneous
releases such  as  storm  overflows or industrial
spills. Continuous monitoring may identify the
temporal nature of the flow. An  alarm system
associated  with  continuous  monitoring  can
signal an operator's attention at the central site
or at some watchdog headquarters, should the
presence of a toxic substance or abnormally high
pollutant appear.
 23Ellis, Eddie E. The Application of Electronic Data Processing
  Techniques to Water Pollution Control. Florida Ail and Water
  Pollution Control Commission.
 24Schieber,  John  R.  Continuous Monitoring.  Chemical
  Engineering. Deskbook Issue. April 27,1970.
                                              33

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                                         SECTION 6
                      GUIDELINES FOR COMPUTER IMPLEMENTATION
INTRODUCTION
     Implementing a digital computer into  an
operational  plant  presents a  challenge to  all
disciplines  involved in plant  management and
operation.  The  decision  to  investigate  the
possibilities of automation is to embark on long
range, dedicated planning by management. What
are the considerations? First,  you must know
your plant and its system, where administration
and  communication begin and  end, the physical
boundary,  the  technology   operations and
control. These  form  the  basis  for the technical
justification of computerized  process control.
Equally important are the economics relevant to
computer implementation. Can   sufficient
sources and amounts of cost  improvement  be
found  to  pay  for the automation  system for
either  existing plants  or those in  the design
stage?  Can  economies  of design,  scale and
operation be effectuated? What are the tradeoffs
of computer costs versus savings in manpower,
materials and plant space?
     Improvement of product  quality cannot be
discounted.   Greater  percentage  removals
through better process control via computer can
be  translated  into  capital  costs  for  newly
designed or existing  plants. A small guaranteed
increase  in   percent  removal  accomplished
through automation  will more than justify the
expenditures for the control system.

TECHNICAL   JUSTIFICATION  FOR
COMPUTER CONTROL
     Recent technical  literature proliferates in
discussions of  computer control of  industrial
processes. Some criteria2 5  have been suggested
as comprising  a basis for technical feasibility of
computer control. While they  are considered in
context to industrial, profit-making operations,
these  criteria  are applicable to  waste water
treatment. The -status of  the process and  its
suitability  with regard to automated operation
are examined.  Questions are asked whether it is
worth  the expense,  time  and  manpower  to
•^Scrimgeour, J.H. How to Assess the Economic Justification
  for Process Computer Control  Canadian Controls and
  Instrumentation. Canadian General Electric. April, 1968.
 implement a computer. In essence, automation
 should  not be considered where production is
 smooth,  steady-state,  free  of  disturbances,
 relatively simple  and  operating  at high
 efficiency. This is  not  the case  in wastewater
 treatment. Influents  are  variable in  flow and
 quality. Process stages are not optimized, so that
 greater  percentage  removals are  possible with
 proper  control.  Effluent improvement  and
 overall  efficiency  can  be enhanced. Process
 disturbances do occur and can have dire effects.
     With  population and industrial  growth,
 regulatory  agency requirements  are becoming
 more stringent to' preserve  the quality of our
 environment.   These  increasing  removals  are
 taxing the capability of present day plants both
 in   capacity  and  controllability.  New
 sophisticated controls and treatment procedures
 must be  implemented  to  accommodate  the
 demands of an affluent  society  with a high
 standard of living. Computer control can offer
 an upgrading of operations.
      Once  the basic  premise of automated
 process  control is accepted, then the feasibility
 of computer implementation can be considered.
 Can  the  process  be  automated?  Can the
 computer  communicate with the  process? Are
 models  or systems  for  this  process  control
application available, or can they be developed?
What is the  cost?  What  is the  degree of
improvement?

 Process Improvement
     One benefit to be expected from computer
 control  is some improvement in the quality of
 the throughput and management of the process.
 The survey of plant management in Section 4
 disclosed  the   need for improvement in  the
 following general areas:
     1.   Balance  in the critical  treatment
 phases of:
         a)   Activated sludge,
         b)   Anaerobic digestion, and
         c)   Sludge conditioning,
     2.   Accurate  plant  data and its timely
 implementation, and
                                              35

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     3.   Plant  operational and  maintenance
personnel.
     As an  example of  improvement  in  plant
 management,  the City of Philadelphia can be
 cited for an effective, well maintained computer
 program for information reduction. Implementa-
 tion of the NELOG2 6  program, a management
 information  system for the  Northeast  Water
 Pollution Control Plant, has:
     1.  Reduced the tune required for record
 keeping,
     2.  Minimized human errors,
     3.  Eliminated  long,  cumbersome  data
 sheets,
     4.  Eliminated tedious hand calculations,
     5.  Permitted detection  of out-of-spec
 input data,
     6.  Permitted   standard deviation
 computations for all data on a daily basis,
     7.  Added more  calculated parameters
 than the manual version of the original report,
     8.  Reduced  manual processing needs by
 almost  a half man-year per  year for original
 report,
     9.  Standardized  procedures  for  data
 acquisition,
     10. Initiated  a  data  bank for model
 building,
     11. Initiated  simulation and engineering
 studies, and
     12. Established a basis for and major step
 toward closed loop control.
     The computerized version  of NELOG, of
 which an  excerpt  is shown   in  Figure 8, has
 permitted  more  calculations   and data checks
 which   were not  possible with  the  original
 manual  version. The  additional  features are
 valued at approximately three  man years.
     Another example of process  improvement
 via computer implementation is the electronic
 data logger monitoring  system  at  the  Los
 Angeles Hyperion Wastewater  Treatment Plant.
 This system monitors operation of ten electric
 power generators which supply the plant and air
 blowers. The engines are fueled almost entirely
 (94  percent) by gas from  the digester system.
 The logger generates operational parameters on
 26Guarino,  C.F  and J.V. Radziul. Data Processing  in
  Philadelphia. Journal Water Pollution Control Federation.
  August, 1968.
two typewriters periodically  with out-of-spec
values  printed in red to alert the operator. There
are output and data controls such as frequency
of  printing,  arbitrary  selection,  and output
hold except for the alarm condition. Currently
there  is  no   feedback  control  to engine
operation.  The  logger  has eliminated manual
monitoring,  thereby   yielding  a  manpower
saving  of three men, their overhead and backup
and "does a better job".

Disturbances in Processing
     If  all  processes are  steady-state  and
function smoothly  over long  periods  of  time,
then computer control  may be unnecessary. If
computer assistance is desired, off-line computer
calculations  may be  generally  sufficient to
define  the  control requirements. However, in a
secondary  sewage treatment  plant, operations
are generally  vulnerable to disturbances  with
regard  to:
     1.  The unpredictable nature of the plant
influent in both quality and quantity, and
     2.  The critical  problem of maintaining
healthy  hordes  of  hungry  organisms  for
biological treatment.
     Some  specific plant disturbances are cited:
     1.  Storms can raise the influent flow well
beyond plant capacity
     2.  A toxic spill entering the plant can kill
the bacteria and upset the biological activity
     3.  A power  failure will cease pumping,
aeration, clarification, etc.
     4.  Digesters  are  frequently reported as
going sour, or failing, and it can take weeks for
the unit to return to normal.
     With continuous monitoring of the influent
flow  and  critical  plant processes, imminent
changes can be recognized, and corrective action
taken  before  the  disturbances cause critical
conditions.

Process Complexity
     Secondary treatment   is  complex.  A
well-monitored  plant requires' continuous
measurement of variables during each  stage of
the  treatment  process.  The  Northeast Water
Pollution Control Plant  at Philadelphia with a
design  capacity of 175 mgd, lop approximately
400 measurements  per day, which aid in  the
operation and maintenance of this plant.
                                             36

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3/19/70
     PHILADELPHIA WATER DEPARTMENT
NORTHEAST  WATER POLLUTION  CONTROL PLANT
         JANUARY-OECEMBEFU  1969

     ***OVERALL PLANT SUMMARY***
PAGE
01







02








03













. _ -








._


SEWAGE FLOW 	
FHL
DLL "~
TOTAL - 	 ,
PRIMARY BY-PASS
PRIMARY TREATMENT
SECONDARY BY-PASS 	 -
SECONDARY TREATMENT
KG
1775.91
3154.74
4930.65
0.04
4929.38
0.40
4928.98
SEWAGE ANALYSIS COM3 — RAW-- -SETTLED-
RAW FHL
PH 6.7 7.3
SETTLEABLE SOLIDS
(MG/L) 6.6 4.2
SUSPENDED SOLIDS 	
(MG/L) 317.5 191.6
PCT. VOLATILE 71.7 80.8
5 DAY BOD(MG/L) 231.8 146.1
PLANT EFFICIENCIES
. 	 	 	 .... . _ - 	 	 	 	
PRIMARY TANKS (LOAD TO PLANT)
(SEPARATE INFLUENT SAMPLES)
MA (PRIMARIES IE 2)
CS (PRIMARIES 3£4)
COMB " "
PRIMARY TANKS (LOAD
TO PRIMARY TANKS)
(fQMRIMFD INFLUENT SAMPLES! -
IVrUflty-livLL/ A IT| I l_ Vs I— 1 « • -«Jr*liri«l_OJ-
MA (PRIMARIES l£2)
CS (PRIMARIES 3£4)
COMB - 	 	 - 	 - - -
SECONDARY PROCESS "
MA - - 	 -
CS
COMB
PLANT LOAD TO FINAL EFFLUENT
MA
-- CS 	 - .- - 	 — - 	
COMB
PRIMARY TANK LOAD TO
FINAL EFFLUENT
"MA
re 	 .. 	
oo - - -
COMB
. DLL MA CS
7.2 7.3 7.3

8.1 0.2 0.0

379.9 185.0 131.0
77.9 79.9 79.6
275.6 191.6 126.5
MGD
58.34
103.69
162.03
1.27
161.99
0.01
161.98
PCT
36.02
63.98
	 	 	 	 _. ..

" ~
.. - .. - _.. __

-FINAL- COMB
MA
7.3

0.0

82.9
84.8
95.9
SUS.SOL. BOD
PCT. REMOVAL PCT


28.31
52,22
44.59

-

43.46
49.61
46.68

51.43
49.14
51.25

65.99
77.49
74.18
, . , _ 	 __ . . .....

73.74
75.35
74.76
.REMOVAL


4.64
39.50
27.20



22.02
34.43
27.92


47.51
56.35
50.44

49.85
74.48
64.24
	 . ._.. ..

59.96
72.08
64.54
CS FINAL
7.4 7.3

0.0 0.0

60.8 77.3
85.7 83.1
54.1 79.3
DELTA PSI
(1000 LBS
REM/KG)

	 0.37
0.66
0.53



0.51
0.60
0.57


0.78
0.60
0.71

0.74
1.50
1.23


1.29
1.20
1.27
          Figure 8. Excerpt From the Computer Generated NELOG Summary
             Report (Northeast Water Pollution Control Plant, Phila., Pa.)
                                    37

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    The  degree  of  complexity  in  both
monitoring and control  is  too great  for one
operator to respond to all plant conditions. As a
tool to tie  into monitoring and control, the
computer  can process data, make decisions and
generate commands well within the sensitivity of
the wastewater treatment  process.  Complex
systems with multiple stations for sampling and
feedback of  data  are  well  within the
state-of-the-art  of  process  computer
applications.  The lack of automated wastewater
treatment plants must be attributed to  other
reasons. The  control capability of computers has
been  demonstrated  in other  bulk  processing
industries such as petroleum  refineries, steel
refineries and chemical plants.

Automatic Operation
     The  questions  of  process  improvement,
disturbances  and  complexity  have  been
discussed. The system now must be examined
for suitability to computerized operation. One
important conversion to computer operations is
data  logging  and  management reporting, the
improvement of data  collection  and recording
for better operator control.
     Many   analog  loops exist in  sewage
treatment27. Some are:

     1.   Air  flow  regulated  by  dissolved
oxygen measurements,
     2.   Return sludge  proportioned  back to
the  aeration  tanks  to maintain  a  desired
mass-to-food ratio,
     3.   Pos t-chl orin a t ion  regulated
automatically on the basis of flow and residual
chlorine control,
     4.   Variable speed wastewater pumping to
maintain  more  Uniform  flow to  the treatment
process,
     5.   Bar screen  clearing on the  basis of
increased head loss
     6.   Level  sensor to  determine  rate of
pumping into primary tank,
     7.   Sludge density to determine when to
pump from primary tank, and
     8.   Pumping station control of number of
pumps stepped  on or  off  according  to flow
requirements.
     The  existence  of local  analog loops
indicates  that  local  hardware  can  be made
compatible with digital  computer closed loop
control.
     Despite   the  potential  of  closed loop
control, the human factor is still very strongly
present in the wastewater treatment plant, and
the operator is still the most important monitor
and decisionmaker.

Computer-Process Communication
     Computer  control  requires  considerable
communication equipment to tie the computer
to the process for both monitoring and feedback
control.  Internally  the   computer  central
processor  looks  to core memory for its stored
data.  If  a  routine  is  called to operate  on
information  sampled  from  the  plant  process,
then  that information will have been sampled,
brought to the  computer, converted to input
data, read in and stored for digital processing.
     Communication equipment is reliable and
converters, remote scanners, recorders, telemetry
and telephone lines.  Any variable that can be
measured can be incorporated into  a centralized
control system. But, not every pertinent variable
can be automatically and continuously sensed as
cited in Section 1.
continuously sensed as cited in Section 1.
     Sensors  as  probes or  electrodes  used in
wastewater treatment are subjected to  a hostile
environment. They get coated and attacked by
the materials in the stream  flow. Satisfactory
operation  of  sensors,  however,   can  be
maintained by adequate preventive maintenance
measures2 8.
Process Models
     Closing control  loops  or replacing analog
with  digital loops  requires a computer stored
process model to interpret the sampled variable
and to generate a control signal response.
 27
   Ryder, Robert S. Automatic Control for Smaller Water and
   Wastewater Facilities. Proceedings, Ninth Sanitary Engineering
   Conference.  University  of Illinois College of Engineering.
   February 7-8. 1967.
28Puzniak, T.J., W.F. Benusa, and J.A. Condron. Mobile Water
  Conservation Laboratory. Preprints, 16th Annual Analysis
  Instrumentation Symposium. May 25-27, 1970
                                              38

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     The relationships among the variables in
each treatment  process  must be  defined  and
implemented into  the  computer  software as
control  algorithms.  They  may  result from
mathematical  models  based upon  scientific
theory  of  treatment,  from  empirical
relationships based upon regression analysis of
plant data, or from both.
     The Federal Water Quality Administration
is sponsoring a study of mathematical modeling
of wastewater treatment processes29. Virtually
all phases of conventional secondary treatment
are being modeled with further work continuing
into advanced and tertiary treatment.
     At  some   treatment  plants  correlation
studies  are  being  performed  to  statistically
uncover  relationships among variables  of
sufficient  significance to be suitable as  control
algorithms. However, the predictive capability of
a statistical  relationship for one plant may be of
little value  to  another plant treating different
waste. Each plant  should make its own study
based upon its  own data to evolve its  specific
empirical relationship for a particular control.


 LABOR ALLOCATION AND MAINTENANCE
      One of the most critical problem  areas in
 wastewater treatment is the cost and quality of
 labor. Competent personnel are difficult to find,
 and labor costs keep rising. In a sewage plant
 labor is stigmatized, and few care to work there.
 Some proponents say that those that do should
 be  paid  premium wages.  The reduction  of
 manual  labor  requirements  in  a  wastewater
 treatment  plant  via  automation  can yield
 economic  significance and  add prestige to this
 industry.
     Those areas which  are designated as under
 computer  responsibility  will become tied  into
 the system for  automatic monitoring, reporting
 and  control. The respective changes  will be
 reflected throughout the system as reductions in
 operational.labor requirements in such functions
 as  equipment  adjustments,  monitoring,  data
 logging and report preparation.
 29Srnith, R.,  R.G. Eilers, and E.P. Hall. Executive Digital
   Computer Program for Preliminary Design of Wastewater
   Treatment Systems. Water Pollution Control Research Series
   Publication No. WP-20-14. Cincinnati, Ohio. August, 1968.
     Under automated operations, the emphasis
of labor applications will shift from equipment
operation to  equipment  maintenance,  thus
requiring a higher quality worker.
     The response  from  the  APWA  survey
(Section 4) includes direct  references  to the
labor and maintenance areas as sorely in need of
improvement.  Specific  recommendations  were
noted  with   regard  to  standardized,  well
documented maintenance procedures assisted by
computer stored records.
     An available  computer  presents the
opportunity   for  automatic  storage  and
processing  of  the  files  for equipment
maintenance. Such computer stored  files can
aptly supplement  a  plant-wide  comprehensive
program  of  preventive  maintenance.
Management can establish  a new program  of
maintenance records on all  major equipment
with  designated functions to be performed at
specified  intervals for optimum operational
performance and life. Some of the operations of
computer stored  preventive  maintenance  files
may include:
     1.   Daily listing of required maintenance
work,
     2.   Daily   file  updating  of  work
performed,
     3.   Reminders for work falling behind,
and
     4.    Special  studies on  maintenance cost
and equipment depreciation.
     In  short,  computer  control  offers  a
potential three part economic advantage in:
     1.   The  elimination  of  some  labor
operations,
     2.   The  improvement  of  equipment
maintenance via better labor utilization, and
     3.   Centralized,  computer  processed
preventive maintenance files.
     The presence of a  sophisticated computer
complex and its associated controls will demand
higher  calibre plant personnel  to operate and
maintain the equipment. Labor standards and
grading will correspondingly have to be modified
upwards.  It will  be necessary  to  train  plant
operators and maintenance  personnel to  work
with the computer controlled  system.  This
training period  is usually  of  short  duration,
relatively inexpensive  and   provided  by  the
equipment manufacturer.
                                             39

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     As  the  system  evolves,   some
reprogramming  may  also  be necessary to
optimize computer operations. This should be
performed   in-house  or  by  the   original
programmers  and  should  be economically
feasible, yielding improved operation at reduced
costs.

SOURCES  OF ECONOMIC  JUSTIFICATION
FOR COMPUTER CONTROL
     Implementation of computer  control  can
be   a  costly,  time-consuming  and   critical
undertaking.  Economic justification must be
sought to determine how  automation costs can
be self-liquidating, if they are to be borne by the
general  public. Under commercial production,
the  improvement of a few percent in  product
output and a more efficient use of raw materials
and  power are expected to pay for the computer
complex and the systems engineering costs. In
wastewater treatment the product is not an item
to   be   marketed,  unless  direct  reuse is
contemplated.  The  pay-off  can  be  a  social
investment in effluent quality improvement and
the  associated  abatement in  pollution of the
receiving  waters.  Internal factors should be
examined for an economic return, such as labor
savings,  improved maintenance, reductions in
power and material usage, and less costly control
equipment.
     Many areas of plant processing can be cited
 as capable of  yielding economic  return under
 computer control. A true economic evaluation
 can  only be  resolved by plant management and
 supervisory personnel  because they are familiar
 with  and  responsible  for the day-to-day
 operation, the changes to  be put into effect
 under   computer  implementation  and the
 associated influences on operational costs.
     In  general, for existing  plants automation
 can  defer expansion and the  consequent capital
 costs.   For new   plants,  automation  offers
 increased processing capability for the same size
 or  allows smaller  plant  construction,  thereby
 permitting  savings  in  land  needs and  capital
 costs.

 Higher Quality Product
      The  ultimate  goal  of any wastewater
 treatment plant is to produce the highest quality
 effluent achievable, consistent  with  its design
and  good  operating  procedure.  Where plant
removals have been significantly upgraded, the
surrounding area  can  realize some economic
returns  from  the correspondingly upgraded
quality of the local receiving waters. These may
be in the form of renewed recreational activity
such as fishing and boating, improved  influent
for a water treatment  plant  downstream  and
new lands for development. The state and local
governments  could realize  a sizeable income
from increased  taxables of the land around the
streams.

Operational Efficiency
     Computer  assisted  plant  control  should
permit  plant  operation  at higher  removal
efficiencies  with   less  variations.  Consider  a
hypothetical case  of a  plant  operating in the
percent BOD removal range of 75 to 90 with an
average  of 85.  If the percent BOD removals
could be raised to a range  of 90 to 95 with an
average  of  92.5,  the  BOD  loading  to  the
receiving water would be halved3 °. Consider the
BOD  reduction and stream loading per 1000
pounds BOD influent in Tables 2 and 3.

       TABLE 2.  LOOSE TREATMENT CONTROL
                     OF BOD
BOD
Percent
removal
Pounds
removed
Pounds
to stream
min. 75 750 250
max. 95 950 50
ave. 85 850 150
      TABLE 3.  IMPROVED TREATMENT CONTROL
             (WITH COMPUTER) OF BOD
BOD
Percent
removal
Pounds
removed
Pounds
to stream
min. 90 900 100
max. 95 950 50
ave. 92.5 925 75
     Although  a  plant  may  be  deliberately
designed  for a  higher  capacity  than normal
design to  accommodate wide  variations  of
influent quality and quantity,  the capability of
closer automated  control may  deem  the added
capital costs unnecessary.  As cited  above, it
should be possible to operate the plant closer to
its designed maximum efficiency with a lesser
degree of variation.
^Andrews, John F. Dynamic Modeling and Simulation of
  Biological Processes Used for Waste Treatment. Environmental
  Systems Engineering Dept., Clemson University.  June 30,
  1969.
                                              40

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     More  efficient plant control should  lead
to reduced usage  of  input materials  such  as
compressed  air,   chemicals   and  fuels  and
consequent reduced  in-process  inventory  and
warehouse  space.
     Improved plant  control  should  result  in
more efficient usage  of electrical energy. For
instance, automatic monitoring  of total power
usage  can  cause  an   alarm  whenever  power
consumption  is approaching that peak demand
which raises the power rate for the month.  At
the  warning  alarm,  steps  can be  taken,  if
possible, to prevent  the  peak  from  occurring
by   shutting   down   some   less   essential
equipment.  On  the  other hand,  should the
peak have  occurred,  then during the  ensuing
period  of  high rate charges, the computer can
generate control rules  to make  the best use  of
the extra power charge.


Digital  Versus Analog Loops
     Closing  control loops  via  the  digital
computer can yield a saving through elimination
of the  hardware associated with analog  devices,
such as the analog-controller,  its panel set-up
and  alarm  equipment.   It  has  been
suggested:  "the economic  crossover  point
between conventional  analog  instrumentation
(both   electronic   and  pneumatic)  and direct
digital  control  lies  somewhere around  100
loops".3 1  Yet, cost alone is an insufficient  basis
for comparison. Consideration must be  allotted
to some of the  benefits of digital  over analog
control to which  it  is difficult to assign  an
economic value, such as:
     1.   Operational  improvement,
     2.   More easily   implemented changes  in
control conditions,
     3.   Sampling, storage and computational
operations  with the control data, and
     4.   Remote availability of data.
     It  is possible  with a digital, closed  loop  to
make subtle custom changes to  the system via
changes in  the program. The control strategy can
be arbitrarily modified almost at will without
requiring equipment additions or changes. The
control engineer is not constrained  to  working
^Forecast, Evolutionary and Revolutionary Trends in Process
  Control. Chemical Engineering. January 13, 1969.
out the best trade-off with the available analog
products.

By-Products
      As  stated  previously  plant  effluent  is
 usually not  a  product for sale. High quality is
 sought to  prevent pollution of the receiving
 waters. With sufficiently high removals,  it also
 has been possible to  find  some economically
 useful  applications of the  water  other than
 merely losing it to  the local  streams.  Some
 examples of such  water  reclamation32  from
 wastewater treatment plants are cited:
     1.   Washing tanks and watering the  plant
lawns and shrubbery,
     2.   Ground water recharging or control of
salt water intrusion,
     3.   Industrial use notably for cooling,
     4.   Agricultural  use  in irrigation and
watering of golf courses, and
     5.   Recreational  use  through  a series of
treatment ponds.
     Water reclamation is a growing economic
consideration in  water resources  management.
With  increased water  needs in the  future the
importance of  water reclaimed  from municipal
return flows must begin to  look more like  a
resource rather than a waste.
    Other  by-product  yields  from  wastewater
treatment which may b epossible sources of
ieconomic return are:
     1.   Digester gas to heat the plant, to heat
sludge entering the digesters  and to fuel the
power generator engines,
     2.   Dried sludge  for sale as fertilizer, and
     3.   Composting of sludge for use as a soil
conditioner.33

Intangible Benefits
     The availability  of the computer offers a
tool  for  engineering  studies  and  research.
Monitoring  and  control  data  retained  in
computer storage can  be periodically  processed
to  generate  new parameters for the  on-line
32McGaughey, P.H. Engineering Management of Water Quality.
  McGraw Hill Book Company. 1968.

33Clark, J.W. and W. Viessman. Water Supply and Pollution
  Control, p. 453. International Textbook Company. Scranton,
  Pa. 1965.
                                               41

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control  functions. New approaches to system
operation  can be  tested in simulation studies
with the computer. The day-to-day operation is
its   own   evaluation  of  effectiveness.  The
computer simultaneously yields information and
avails itself for modifications of its programmed
routines where  the functions show a  need for
improvement.
     In  these   days  of  great  concern  over
pollution abatement, a  plant that does its job
well becomes  an acclaimed  asset  to  the
community.
     Via improved,  more  efficient operation,
monitoring  and  maintenance under computer
control, equipment  can be expected to last
longer, thereby allaying capital expenditures.
      The revived importance and recognition of
the critical  nature of pollution control has served
to attract additional capable engineers into plant
operation.  These  progressive  engineers  are
already  applying  experimental  approaches to
treatment  and are eager to investigate computer
control. This  next dimension in treatment
practices will increase  the  challenge of a new,
sophisticated technology and further  enhance
the attraction of highly capable engineers.

PRELIMINARY INFORMATION NEEDS FOR
COMPUTER CONTROL
     Some  assessment of the operational load on
the  computer occasioned by process control as
well  as desired  off-line operations should be
sought.

The Plant System and Computer Responsibility
     An evaluation   requires  a  thorough
knowledge  of the total plant,  identified  as a
system.  Management must define the boundary
of the treatment system, which  may go beyond
the physical plant  to include the sewer network
lines or portions of them and  the  receiving
waters, to whatever vicinity  they are affected by
the effluent. Where gaseous effluents and odors
are  a possibility, the  surrounding air should
come within the system boundary.
     Once  the  treatment system  and its
boundaries  are  defined,  the  overall  area of
computer  implementation  and  responsibility
within  that system  can then  be  determined.
Management must judge the extent of functional
responsibility  and  area  of  control  to  be
encompassed  by  the computer, or  left  to
supervisory control by humans.

System Inputs and Outputs
     The boundary of computer responsibility is
delineated for inputs and outputs of material,
energy and  manpower. These  variables  relate
directly  to  the  objective  of  highest quality
effluent  at  minimum  consumption of energy,
material and manpower within the constraints of
the wide variations in quality and quantity of
influent.
     In the  wastewater treatment plant, inputs
have the following influent identification:  flow
(mgd),  temperature,  suspended solids
concentration, biochemical oxygen demand and
concentrations  of other  contaminants. As the
major stream flow, the influent  identifies the
sewage strength  to be  processed,  and therefore
determines  the  requirements on  other inputs
which  are  utilized in the treatment  process.
These minor stream flow inputs may include
power,  chemicals,  water,  air  flow  and  gas.
Outputs from the plant can include the effluent
to  the receiving waters  characterized by the
same stream flow parameters as well as chlorine
residual.  Other outputs include sludge and gas
generated.
     A clearly delineated definition of system
inputs  and  outputs  under jurisdiction of the
computer helps to determine the goals necessary
to optimize  operations and the functions to be
performed.

Operation Review
     The approach to plant process automation
must be  accompanied by an investigation of all
facets  of  operational  management  and
processing functions; All too  often reporting
forms become  obsolete; the report hierarchy
changes; new hand-made forms are invented, and
standardization collapses.   A  modernized,
up-to-date standardization and  streamlining of
information  processing must be established.
     Each process  should  be  investigated  to
develop a logical control procedure based  upon
experience  and  quality  engineering practices.
Measurements, 'decisions,   computations,
whenever involved should be entered as steps in
                                             42

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an operational control procedure. Such activities
when documented become an empirical basis for
a standardized approach to computer control.
     A  complete   review  of  maintenance
procedures should be performed to establish a
schedule of  preventive maintenance  functions
and a standardized log for the work.
     A preliminary  order must be achieved and
documented, guided by economy and efficiency
before  steps  can be  taken  toward computer
implementation. This approach  leads  to  a
studied  awareness  of  plant functions  by
management and allows a better communication
with the automation engineers.

MATHEMATICAL  MODELING
APPLICATIONS

Mathematical Modeling and Simulation
     In the  application of computers to  control
of a physical  process, the  loop is  eventually
closed through use  of a mathematical model of
the  process. The mathematical model  can be
defined as a logical-mathematical representation
of a concept, system or operation. The model
operates  on  the  measured variables  and
calculates   the  proper  values of  adjustable
variables to actuate the required control. As an
abstraction  from a  real  world situation, the
mathematical model is an attempt to simplify
the  existing  complexities   for  each  of the
control  computations,  while  simultaneously
generating  data of  sufficient  accuracy  to
represent    the   real  system   in   required
applications.
     The  word simulation  occurs in association
with  mathematical modeling.  There is  a
distinction in definitions although the two terms
complement each  other.  The  mathematical
model  is  the  tool,  the  actual
mathematical-logical system, the program built
for  a digital computer.  The  applications to
which the  model  is   subjected  comprise
simulation.  This is particularly true  in digital
computer programmed models where the test
cases  operate the  mathematical  model under
varying simulation conditions.
     Mathematical  models  can  be  used  off-line
in  a strictly  digital  simulation atmosphere to
study  a physical system. The constants  can be
changed to represent different  versions of the
system, and the variables can be incremented to
modify the operating conditions.  For example,
in a wastewater collection system some of the
constants  are  shape  of conduit,   length  of
conduit, slope of conduit and friction factor. If
any of these factors are changed, the represented
physical system, i.e.,  the mathematical model, is
changed.  On  the  other hand, flow supplies,
branch  inputs  and pump  operations,  are
variables. When these values are  changed, and in
a real hydraulic system they change continually,
the original system remains the same, but it has
been subjected to different operating conditions.
So,  in  a programmed  hydraulic  collection
system, a given model is entered once into the
computer,   while   test cases  or  simulation
conditions  on the  model  may  be  run  ad
infinitum.
     The value of digital simulation  lies in the
flexibility of  operation. A simulated system can
be put through its paces and operated under all
variations  of  normal and extreme  conditions.
The system can be checked  out and evaluated,
and never leave the  computer. Many questions
can  be asked during  simulation. The validity of
the answers is a function of how well the model
represents  the  true  system  or  prototype.
Information  that  can  be acquired  during
operation  of  the mathematical model includes:
     1.   Sensitivity   and range of  adjustable
variables,
     2.   Variables most suitable for control,
     3.    Interactions   among   variables,
beneficial or  detrimental,
     4.   Variable combinations  applicable to
control,
     5.   Sources  of disturbances  and  their
corrective action,
     6.   Operational  effectiveness   and
improvement,
     7.   Required variables  and accuracy,
     8.   Superfluous variables,
     9.   Potential for model improvement, and
    10.   Response to simulated emergencies.
     The  information acquired  during the
simulation  runs may  be used  to  design  new
systems or  to develop  models for automatic
control.
                                              43

-------
    With  plant  operations  simulated,  the
computer will allow an engineer to experiment
beyond anything that would be  tolerated  by
management in the real plant. Each subsystem
can be exercised through the widest variations of
its parameters to determine the best operational
range.  Furthermore,  the  opportunity  exists
through  modeling  to  apply   optimization
techniques to an objective function, such as cost
minimization, and its constraints.
     Once  a  fully  off-line  digital  simulation
model has been checked out,  it is adaptable  for
use in a process control, on-line loop. Figure 9
illustrates the relationship of the computer to a
control process  on an off-line and an  on-line
basis. Note that the loop can  be closed without
the man when the computer is on-line.
                                  Delay
t

Off -Line
Computer
1

          a.  Process Operation
             Assisted by Off-Line Computer

L_»
i
Records

On-Line
Computer
\
,- •
                   Process
           b. Process Operation
             Assisted by On-Line Computer

Figure 9. Off-Line vs. On-Line Computer Control

Mathematical  Modeling for  Wastewater
Treatment Processes
     One of the areas  cited as needing  further
development in computer control of wastewater
treatment is mathematical modeling. Interest is
strong,  and much work is being done from at
least  two  directions,  the  empirical  (often
referred  to as practical)  and the  theoretical
approach.
     The empirical approach is being taken by
many  researchers  in  wastewater  treatment
plants.  In a  well-monitored plant, data  are
available for a great variety of variables, many of
which are directly  related to process control.
With  statistical  analysis  and  the  digital
computer, these can be subjected to  correlation
studies. Where indications of high  correlation
appear, the data can be processed by a regression
analysis,  such  as least squares,  to  generate a
functional  relationship. This new function can
serve as  the   approximate  or   empirical  law
governing the variations of a dependent variable
with one or more independent variables and can
therefore  be  considered  a mathematical  model
for the particular plant process. Where empirical
relations are used, they are properly referenced
as backed by experimental verification.
     In this method it is also very useful to plot,
if possible on an automatic plotter tied  into a
digital computer, all the original  data points as
well  as  the  generated  curve. The picture
enhances  the  feel  for the  new function.  In
Figure 10 are shown cases of data points plotted
along with the  computer generated straight line
function. In Figure 11  two variables are plotted
versus   time  to  demonstrate   their
interdependence.
     While the above empirical approach seeks a
relationship among  data purely for data's sake
with  no  guidance except what is extracted  by
the   statistics,  the  alternate  approach  to
mathematical  modeling seeks  a   theoretical
foundation to  the relationship.  All parameters
involved  are identified and assigned dimensions.
Physical and chemical laws are cited as the basis
for formulas among the variables.
     The Federal Water Quality Administration
has   been  sponsoring   the  development  of
mathematical  models   for  wastewater
treatment28  U»  fit  a  system   approach
framework.  The  models  are  for specific
treatment processes, such as a primary settler,
digester,  trickling filter, etc. The models operate
on  a stream  vector  of wastewater flow
 28Smith, R., et. al. op. cit.
                                              44

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M

§
i
o
CD
00
100
 50
                     COR.COEF.
                     NUM. SAMP.
                     X AVERAGE
                     YAVERAGE
                     STD. ERR.
                     "T"VALUE
 16
 165.
 56.47
 0.57
 51.28
 2.054
      0.1  0.3  0.5 0.7 0.9
         PERCENT ONA
  2000
  i
  a
  u
                       COR.COEF
                       NUM. SAMP.
                       X AVERAGE
                       YAVERAGE
                       STD. ERR.
                         " VALUE
= 19
= 293.
= 399.58
= 40.60
= 140.38
= 3.310
          LB BOD/CU. FT.
                                   100.
  Figure 10. Computer-Assisted Straight-Line
  Regression Analyses at Metropolitan Seattle,
     Washington, Basis for Development of
    Empirical Laws Relating Plant Variables.
 descriptive  parameters, such  as  volume  flow,
 solid  BOD,  dissolved  BOD,  total suspended
 solids, volatile suspended solids, etc. For a given
 process a stream vector is numerically defined,
enters  the treatment component, is processed
through  the  model equations and is converted
for  exit  from  the   treatment   component
according   to  the  calculated  removals.  By
associating a sequence of treatment  component
models, with travel and conversion of the stream
vector tying the  processes together,  the unit
process models can be assembled into simulated
plants. The  computer program system operated
under  control  of an  executive routine also
computes   the  cost  of  operation   and  an
evaluation of performance.
     Thus,  an  arbitrary  assemblage  of
wastewater   treatment  unit  processes  can  be
fabricated into  a  plant model.  The model can
then  be  subjected  to   a series of simulated
wastewater  conditions with variations  in flow,
contaminants and  relative strength  of
contaminants. Each  case  will generate  an
evaluation with respect  to cost and contaminant
removal effectiveness of the individual processes
and  the system as a whole.  Costing  refers to
computation of capital costs, debt amortization,
plant operation and maintenance  ". . . with a
fair degree of reliability".34 While the emphasis
is on  design analysis in  these  FWQA studies,
further  investigation  could reveal  their
applicability to plant control as well.
                                                 34Smith,  Robert. Preliminary  Design and Simulation of
                                                   Conventional Wastewater Renovation Systems  Using the
                                                   Digital Computer. U.S. Department of Interior, FWPCA No.
                                                   WP-20-9.
                                                45

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    -UCI.- !-*•
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    -OCT.-10-69
    -OCT.-11-69
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                                                                           ••••••«•*•*«»«»•««•••***•*••*•••*•
    -OCT.-12-69
    -OCT.-1J-69
      PLOt             DESCRIPTION OF                   SMALLEST  LARGEST    SCALE
      CHAR                VARIABLE                      VALUE    VALUE    1 INCH -
        I   LOS dOO REMOVtD/LBS SOLIDS UNDER AER.    OCT.     0.00      0.06      O.OO
        i_    L*S BOD APPLIED/IBS SOLIDS UNDER AER.   OCT.     0.01      0.10      0.00
                 CS — ABBREVIATION FOR CONTACT STABILIZATION
Figure 11.  Automatic Plot of Two  Variables vs. Time. (Generated From a Computer Stored Data Bank
        Indicates Correlation of BOD Removal vs. BOD Input of Contact Stabilization System
                                            at Philadelphia.)
                                                     46

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                                         SECTION 7
                      MEASURED STEPS TOWARD PLANT AUTOMATION
INTRODUCTION
     The  approach  to  wastewater treatment
plant automation is seen as a coordinated effort
to  establish  computer  control  of plant
processing  and  management  information.
Careful  planning  and  study are required to
incorporate into a functioning plant as powerful
and  critical a tool  as the digital computer.  The
technologies required necessitate a team of plant
management  associated with  expertise in
wastewater  treatment  processes,
instrumentation,  plant  hardware,
communications  and  process  computer
application.
     Computer implementation can be designed
into new plants,  existing plants or expanding
plants  (such  as  primary to  secondary). A
preliminary  automation study can  develop the
required automation steps  for compatibility
with the particular situation.
     Despite  the  lack  of  both treatment
knowledge and adequate  instrumentation in
some   areas,  there  are  sufficient  workable
applications to  encourage  automation.  The
challenge can be met and solved once the effort
is made. A series of measured steps are presented
toward  the goal  of automated  plant control.
Each is  designed to yield new confidence in the
system  while setting  the stage for the next step.
These  steps  are  briefly  introduced  in  the
following four paragraphs.

Systemize Plant Data Handling
     Allow a digital computer to process all the
manual work  for  plant  reporting and  the
retention of records for equipment maintanance.
Other  areas  of off-line  computer application
include  engineering  design  and  analysis,
inventory control, payroll and accounting.

Improve Instrumentation  and  Supervisory
Control
     Where  possible, implement improved,
automatic  monitoring  instrumentation
compatible  with  computer  inputs. Centralize
plant  communications,  reporting  and
supervisory  control  at a  conveniently  located
supervisory  panel  and  associated  computer
console.

Convert to Automated Operation
    Allow  the  computer to  assist  in
decision-making by  implementing some of the
basic operator logic of supervisory control into
the computer. Initiate a study (based upon the
improved  data  collection)  to  develop
mathematical  relationships  among  the
measurements  involved  in closed  loop  control.
Test the control methods off-line (modeled in a
computer) to prove them out.

Closed Loop Control
    Program the checked-out  off-line  control
models into the  on-line (tied into equipment)
system and retain those  that continue to prove
feasible. At  this  stage the digital computer is
implemented  into  the  dynamics  of the plant
operational system for both  closed loop control
and the processing of management information.
    The following  procedure is  designed  to
gradually evolve a beneficial computer presence
in the plant. While instrumentation is improved
and supervisory  control  is  centralized,  the
computer  operations initially are  non-critical,
non-control  applications. They are  relatively
simple, based upon current plant procedures and
involve no real time closed loops. Computerizing
plant information and maintenance records can
serve a useful purpose  for  plant  management,
while  personnel  gain experience working  in a
computer  environment.  By  the  time
programming is  initiated for real time plant
control, the computer presence and its operation
will have become a familiar and dependable ally
of plant processing.

DESIGN   OF   PLANT  MANAGEMENT
INFORMATION  REPORTING SYSTEM
    An initial  approach  to  the wastewater
treatment  plant  reporting system is  to review
thoroughly and update  current procedures for
direct  compatibility  with the  needs  of
operational management and  the requirements
of  computer  implementation.  The  revisions
                                             47

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should  be  implemented  manually  as soon as
possible so that operational personnel' can gain
experience  with the new requirements prior to
computer  implementation. This  will facilitate
verification  of  the  automated  version. Three
excerpts from automated municipal wastewater
plant reports are shown in Figure 12.
     Consider, for example, a plant preparing to
expand from primary to secondary treatment.
Minimal primary  reporting will be expanded to
secondary where  the amount of information to
report  as  well   as  the  justification   for  the
computer  will increase considerably. An  early
adjustment to computer reporting on the smaller




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                                                 48

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 scale of primary treatment information can serve
 to  familiarize  personnel  with  computer
 applications and  ease  the  expansion  into
 secondary treatment reporting.
     Furthermore, where  plant  automation is
 the eventual goal, the reporting system is the
 basis  of operational information for  studies of
 control by process  computer.  The reports
 become a comprehensive  source of  the entire
 scope  of  plant operational data. With both a
 store  of conveniently  tabulated data and  the
 digital computer (as the tool) available, control
 guideline studies can be made without disturbing
 plant operation. An  essential  point  previously
 mentioned is the necessity for each plant to base
 its approach to control on information gathered
 from its own operations.
 DESIGN  OF  COMPUTERIZED EQUIPMENT
 MAINTENANCE FILE
     A  major  computer  application  in  a
 wastewater treatment plant is the design of a file
 for equipment maintenance records.
     To continue with the example of a plant
 augmenting  to  secondary  treatment,  the
 preventive maintenance (PM) file is designed at
 an  early stage for  the primary  treatment plant
 with  its lower equipment complement. In this
 manner the small  scale  system can  be  more
 easily  implemented  and  operated before  the
 plant grows into secondary treatment.  Once the
 file is in operation, new equipment data can be
 incorporated at any time.
     The file itself should  retain information on
 equipment identification, PM  schedules,  PM
 work monitor, and breakdown repairs. Some of
 the applications can be:
     1.   Scheduling and monitoring PM work,
     2.   Reporting on PM status,
     3.   Reminder of backlogged maintenance,
         and
     4.   Special studies on maintenance.
     The basis for a PM  file system should be
implemented  manually as soon as possible to
accustom  plant   personnel   to the   concept,
thereby facilitating eventual computer operation
of the system.
COMPUTER  PROGRAMS FOR  REPORTING,
PM FILES, AND OTHER OFF-LINE USES
     The preparation of the computer programs
is  based  upon the revised manual systems for
plant reporting, preventive maintenance records,
and other applications such as inventory control,
payroll and accounting. The key to a successful
computer program  is  a clear,  well-delineated
program  design  document  which  can serve
simultaneously as:
     1.   The description of an  operational
system procedure understood by the user  and
meeting his needs and
     2.   A guide to  the programmer  as  he
writes instructions for the computer.
     The transition  toward  computerized
reporting  extends  through  manual
implementation of the reporting revisions  and
adoption  of  preventive  maintenance
record-keeping.  Operating manually  with  the
system will allow it to check itself out as a viable
plant information exchange and communication
procedure.
     An   inexpensive approach  to gain
experience and know-how in these early stages is
to  write  the  programs  for  a  time-sharing,
desk-side computer installation, such as is shown
in  Figure 13.  The time-sharing approach ties the
user into a modern,  large-scale digital computer
at   modest rentals.   Other  facilities  may   be
available, such  as  a  municipal finance
department or  service  bureau.  They may  be
suitable and economic, but do not give the user
immediate access to the computer.
     The programs are written to  implement the
revised  manual  reporting  procedures.
Automating a functioning manual system should
allow very little change in the basic information
interfaces for users even as reports come to be
generated by the computer.
     Automated  information  systems   are  a
reality  and can  be achieved. The  success  of the
system  requires  a  coordinated  team  effort,
dedicated  and  committed   to  a completed
product and backed by management.35
35Sullivan, J.L. What to do Until the Computer Comes (Part I
 and II). Willing Water, AWWA. Dec. 15, 1969 and Dec. 31,
  1969.
                                             49

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   Figure 13. Using the Time-Sharing System

PLANT INSTRUMENTATION  REVIEW AND
UPGRADING
     Simultaneous  with  the information and
maintenance studies, a survey of all plant sensors
and instrumentation should be  performed. The
emphasis should  be on  the  replacement of
laboratory procedures with on-line probes, solid
state instrumentation and automated analytical
procedures, suitable for continuous or sampled
data monitoring and  compatible with digital
computer  input.  It  should  be  noted  that
automation depends upon  a  sampled  signal
available from the controlled process. Upgrading
the sensors improves plant process surveillance
and the quality of plant reporting, and puts the
plant  into  a   more  suitable  status  for
implementation of closed loop control.
PRELIMINARY AUTOMATION STUDY AND
COMPUTER SYSTEM SPECIFICATION
    The initial phases of this plant automation
approach introduce and make use of off-line
computer work through a time-sharing system or
other off-line computer arrangements. For plant
control  the  process  computer,  which has the
capability of tying directly into the plant system
and doing on-line work, must be considered. The
process  computer is the tool  to improve plant
operations  immediately,  and  more  so in the
future, as familiarity with its capabilities  grows,
and  management  acquires confidence  in its
application.
     Because  process computer  hardware must
be assembled and software  programmed  for its
own special  use, namely,  the  tie-in with the
wastewater treatment plant, a study should be
made prior to implementation to define its role.
Unlike  the  time-sharing or other off-line  digital
computer into which any problem can be  fed,
the  process  computer  is a dedicated, special
purpose tool, programmed, in  this  case, to serve
the improvement of wastewater treatment in its
many complex facets  of plant operation. To
determine  the computer functions, it is essential
to  study   the  plant  by  a  team  of plant
management, wastewater treatment experts and
computer  application  consultants.  The
preliminary automation study should review all
plant operations and controls, both present and
planned, to determine where  the computer can
be  used to enhance  the  work of management
and  to  improve treatment. The study should
define the changes  in operational procedure, the
hardware and computer software requirements,
the plant monitoring and control equipment, a
schedule for  implementation and  budgetary
costs.
     The study results  in a document to assist
plant management in  arriving at  agreed upon
procedures  for  continuation  into  the
development  of  the  system and specifications
for the process computer.
     The computer system specifications should
establish the operational requirements of the
process  computer,  its equipment  complement.
such as quantity of immediate  access memory
(core),  auxiliary  memory  (disks,  drum or
magnetic  tape),  input-output  and  peripheral
devices. The  requirements for control  displays.
coordinated with plant  management,  can also be
established.  Consideration j^hould  be  given to
requirements  for the plant controller console.
displays and alarms.
                                            50

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IMPLEMENTING PLANT AUTOMATION
     The previous steps in the progress toward
automation are planned to include a sufficient
elapse of time for smooth operation to develop
between the off-line digital computer and daily
plant  procedures.  Upgraded  instrumentation
should also be operating reliably. The goals to
accomplish include:
     1.   Development  of  a  reliable,  digital
computer presence at the plant,
     2.   Management  recognition  of  the
advantages  of digital  computer applications in
wastewater treatment,
     3.   Management  desire  to  increase
implementation of the computer beyond off-line
informauon processing  into plant  monitoring
and operational control, and
     4.   Implementation  of  continuous
monitoring  instrumentation  to  allow  the
broadest range  of  computer  monitoring  and
control.

     A  satisfactory experience with  a  rented
computer will help  ease phasing of the process
computer into plant operations.
     Implementation of plant  automation  will
put the computer into the heart of plant control
and  operation,  on-line  a  24-hour  day.  The
approach   is  to  initiate  automated  plant
operation  primarily  with  data  logging,
monitoring for  alarms  and  information
reporting. System hardware can be checked out
in conjunction with less critical plant functions,
and  prior  to  the  initiation  of closed loop
control.
     As  the  system  is  checked out  and
confidence  grows, the  more  readily defined
loops for operation control which may be direct
conversions  of  manual control can be  closed
through  the computer.  The  more complex
control functions will continue to be studied via
statistical  and correlation  analyses of the
relevant  collected  and  processed   data  until
satisfactory control algorithms are evolved.
     The initially implemented computer system
is  finally promoted to satisfactory operation of
feasible  closed  loops,  but  not  without
overcoming  great and frequently discouraging
obstacles which  should be anticipated. At this
stage,  study continues  toward  closing  other
loops as well as  seeking  improvement of those
already operational. Further investigation should
be  directed  toward  developing optimization
techniques  to  minimize  cost,  maximize
contaminant   removals,  stabilize   plant
throughput, etc.
     Seeking improvement  is  a  never-ending
cycle.
                                              51

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                                          SECTION  8
                        LOCAL INFLUENCES ON PLANT AUTOMATION
    During preparation of  this report  certain
situations were observed which related directly
to automation of wastewater treatment plants
and  yet could  not  be  categorized in  the
preceding sections.  They  do  relate to  local
conditions however. The subjects considered are
public concern over local water pollution, water
quality  as a  resource and  regionalization, all
affecting  operation  of the local  wastewater
treatment plants. A  discussion is also included
on the  unique  Whittier  Narrows  Water
Reclamation Plant at Los Angeles, California.
PUBLIC CONCERN
     Where  the  local  populace  has  become
aroused  over  the problems of pollution, or
where the receiving waters are  heavily used for
recreation, the wastewater plants are sensitive to
criticism.  If occurrences of polluted outfalls are
aired via the news media, plant management will
attempt  to  upgrade  the  effluent and prevent
overflows.  Seeking approaches to  improve
operations and to tighten controls, management
will consider automation.
     On the other hand, where  there appears to
be  no problem and no local complaint about the
effluent, there is  a  reluctance to  change
anything.
     However, the state regulatory agencies and
the Federal  government are exerting pressure to
upgrade  effluents regardless of any apparent
local indifference.  As  the  pollution control
agencies   enforce  their requirements  through
both funding assistance and fines, the plants will
have to respond.
WATER QUALITY AS A RESOURCE
     Concern is growing for the preservation of
local  bodies  of water  as resources to  be
protected from deterioration.  Whether it  is a
stream,  river,  estuary,  lake  or  ocean,  the
regulatory agencies are seeking to determine the
quality status of the waters. There is widespread
interest  in  monitoring, prediction of future
conditions and pollution control measures.
     Automation  techniques  suitable  for
continuous  monitoring are  available.  When
associated with a careful maintenance program,
a network of water quality analyzers located at
key points can yield reliable in-stream data. The
information can  be transmitted  to a  central
computer to be logged, analyzed  and reported
with  alarms  for  off-normal or  emergency
conditions.
     Once   the  monitoring intelligence  is
converted to a set of properties of the body of
water,  quality status can be determined relative
to what is desired. Where the status falls short,
management  of the water resource  must  be
established to  improve  quality.  As  a
consequence  regulatory  agencies  impose
restrictions upon the outfalls of municipal and
industrial water pollution control plants.
     Automation and digital computers can play
an  even  larger   role as  further  steps  in
sophistication are implemented. These include
mathematical models of the diffusion and decay
of pollutants and the variations in water quality
variables through the body Of water.
     As a direct result  of comprehensive water
resources management,  regulatory  agencies have
begun to stipulate specific upper limit quantities
on  effluent  loadings to  receiving  waters.
Constant BOD and suspended solids loadings in
plant  effluents  are  more difficult to  maintain
than percentage  removals. Hence  the use of a
process control  computer may be necessary  to
minimize plant process fluctuations and produce
a more consistent effluent load.
REGIONAL WATER POLLUTION CONTROL
SYSTEMS
     One  approach to  improvement of local
water resources is through a regional authority
to manage  water pollution control. Because  of
their geographic association in a natural drainage
area,  several  communities,   crossing political
boundaries,  can join to build  a comprehensive
treatment  facility  and  a common  collection
system. The regional facility  offers economic as
well as practical benefits over separate, smaller
                                              53

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plants.36 Some of these are:
     1.   Scale  of economy  for capital  and
operating budgets,
     2.   Reduced cost per community,
     3.   More  available  revenue  to attract
higher calibre personnel,
     4.   Improved   operation  and  control
through greater available skills,
     5.   More efficient inventory,
     6.   More  efficient overall  regional
planning for improvement and expansion, and
     7.   More  effective  compliance  with
regulatory agencies.

     Furthermore, although  the bypassing of
raw  sewage to the local  receiving waters is far
more detrimental from a large centralized plant,
such a likelihood is greatly reduced. With proper
contingency  provisions,  the  large  plant  can
divert flow among its  units when one  is out of
service.   On  the other  hand,  a small plant
generally has only one unit.
     A   large   scale  regional  water  pollution
control  plant  with quality personnel  is better
equipped technically and economically to move
into higher degrees of treatment and computer
control.  A large secondary  treatment plant
already  has the skills,  while small, local plants
generally cannot  afford them. Another incentive
for the  adoption of basin-wide pollution control
systems is the Federal  Government's  promotion
of such approaches to  plant improvements in its
grants program.22
     Despite  the  advantages  and  Federal
encouragement of the basin-wide approach to
water pollution control, some  words of caution
are  suggested. The  central  location of a
treatment  facility  requires  a  comprehensive
collection  system  of  very long sewer lines.
Effluents which would normally flow into local
tributaries  and  augment  the  stream  flow  are
carried away to be treated and disposed of at the
central  plant. Thus  an area-wide depletion of
stream flow is possible.
     Simultaneously  all the   wastewater  is
focused  to  the  regional  plant  and  creates an
  Oluv*.-n. N.W.. B.C. Scalf, and J.B. Copcland Jr. Economics of
  Regional Sewerage Systems. Public Works. April 1970.

—Federal Register, op. cil.
inordinately large outfall at one location. The
long lines transporting raw sewage to the central
plant could be subject  to  septicity and odor
problems.
     It  is generally felt  that the advantages of
regionalization  outweigh  the  disadvantages.
Nevertheless, each such plan should be carefully
reviewed. With so much emphasis on centralized
treatment  systems,  some  studies  should  be
undertaken to assess the real value of these plans
on   a   geographic basis to  arrive  at either
modifications  to the  plan or recommendations
for the preferred geographic regions.

CONTROLLED PLANT INFLUENT
     One of  the requirements  for optimum
wastewater  treatment is the  attainment of a
steady  flow.  Since  raw  wastewater  flow is
characteristically  not steady,  some  influent
control  to allow constant flow  would aid  the
cause of improved treatment and  automation. A
basin for raw  wastewater storage prior to plant
entry could  prove useful for  equalizing flow,
especially during storms.
     The  Whittier Narrows  Water Reclamation
Plant,  shown  in  Figure   14,  uses  another
approach. The plant  itself  is superimposed  on
the  existing sewerage system.  A  steady rate of
15  mgd is pumped  from a large trunk sewer
passing  through the plant site. The large sewer
carries 50 mgd of principally domestic sewage.
Inlet pumps from Whittier Narrows are set for a
constant rate  and "maintain a  steady hydraulic
loading  24 hours a day".3 7
     All  sewage  solids   upon separation  are
returned  to   the  trunk  sewer  for  transport
downstream to another plant. Water reclamation
is executed by channeling effluent to spreading
basins   for  percolation  into  the ground  and
subsequent  use  in water supply. Hence  the
favorable flows situation  extends to steady plant
effluents as well as influent.
     Primarily  an activated sludge  treatment
plant with  well  controlled steady  flows,  the
Whittier Narrows  plant  is ideally amenable to
closed  loop control  and  makes  use  of a  high
degree   of  instrumentation.  Variable speed
37Parkhurst. J.D. and W.E.  Garrison. Wliitlier Narrows Water
 Reclamation  Plant     Two Years  of Operation.  Civil
 Lnginecring. Sept.. 1964.
                                              54

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                      Figure 14.  Whittier Narrows Water Reclamation Plant
wastewater pumps automatically maintain flow
to the primary tank. In the  final  clarifier, the
sludge blanket level is continuously sensed by a
Hach  falling-stream  turbidity meter which
determines the rate of sludge withdrawal for
return to aeration. The  blowers supplying air
operate virtually unattended. Chlorine residual is
continuously  monitored,  and  chlorine
automatically fed to the effluent. These controls
permit minimal use of manpower, two operators
and  one laboratory technician  on a six day,
48-hour week.
     The Whittier Narrows plant is a unique and
advantageous system of operating a wastewater
treatment plant where flow can be regulated to
meet plant requirements. Its success has resulted
in future  planning  in Los  Angeles County for
other  such  plants  to  be superimposed on
existing sewerage  networks, and can serve as a
model for other communities.
                                             55

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                                          SECTION 9
                       ADVANCED RESEARCH ON CONTROL SYSTEMS
      The  need  for  sensing  for  mounting
 operations which  are primarily  organic rather
 than  chemical  in  nature was  recognized
 throughout the project.  Information concerning
 rapid  BOD determination artd control of the
 activated  sludge  process was obtained and  is
 presented  here to  give  an indication of how
 control may be achieved.

 RAPID BOD DETERMINATION
      The BOD  test,  which  defines  the
 pollutional strength of wastewater, is one of the
 most important variables in plant monitoring and
 control. However, the industry standard for BOD
 is based  upon a  five-day incubation  period to
 generate  a value.  This eliminates the possibility
 of using  BOD for real-time operational control.
 There have been studies, notably by R.A. Arthur
 •of Rose Polytechnic Institute  and R.S. Ingols of
 Georgia Institute  of Technology  to determine
 BOD in much shorter time.
 r     Professor  Arthur  makes  use  of  an
 automatic respirometer to determine the oxygen
 uptake of bacteria cultures.38 The instrument
 manometically senses  the reduction in partial
 pressure of the oxygen as it is consumed by the
 wastewater sample,  converts it to an electrical
 signal and continuously records the value. The
 result is a graph of  oxygen consumption versus
 time.  The  immediate  advantages  are  an
 elimination of tedious data  taking  and curve
 plotting.
     A series of oxygen uptake curves generated
 by the system were investigated  to determine
 whether they could serve to predict the five-day
 BOD from  a  much  shorter period of  plotted
 data.3 9 The comparison with a standard five-day
 BOD dilution test of a- series of oxygen uptakes
through a  four-hour period yielded an  average
error of  21.3  percent. A similar  seven-hour
 38Arthur, R.M., An Automated BOD Respirometer, Proceed-
   ing of the Nineteenth Industrial Waste Conference, May
   5, 6,  7, 1964, Purdue University

 39Arthur, R.M. and Hursta, W.N., Short Term BOD Using the
   Automatic Respirometer, Proceedings of the 23rd Industrial
   Waste Conference, May 7, 8, 9,  1968, Purdue University
period test yielded an  average error of  1'5.8
percent.  These errors are not  considered large
when it  is  recalled that the  five-day BOD is
reported  to have an accuracy of plus'or minus 20
percent.
      Further  study  involved the  fitting of
quadratic functions to  the  uptake data  of 48
plots. For each run the standard deviation of the
computed  curve  from the actual  uptake curve
was computed yielding  the  following table of
results:
   Hours of
Demand Curve

       7
       4
       3
 Percent Deviation
From Quadratic Fit

        2.1
        5.0
        7.5
      The reference concludes that the five-day
BOD can be predicted with reasonable accuracy
using  four  hours  of  uptake data  from  the
automatic respirometer.
      Through  continued research  Professor
Arthur has  evolved an automatic respirometer
capable  of  yielding  an  oxygen  demand
measurement within fifteen to thirty minutes.
Although   the  reading  is not  the  standard
BOD5 Professor Arthur claims it  is suitable for
monitoring and control.
      Professor Ingols performs a repetitive short
term BOD  Test40 utilizing a dissolved oxygen
electrode unit. A measured sample is aerated for
a nine minute period in a chamber while the DO
reduction is recorded. The device can generate
information every ten minutes on the rate of
oxygen depletion at the selected sampling point.
The author states that  the  dissolved oxygen
during each period is recorded, and the records
"compared  to indicate what BOD load exists."
Analytical relationships are not discussed.
      The purpose of the  "repetitive, short term
BOD  test" is to  generate information  for
 40Ingols, R.S., Short Term BOD, Water & Sewage Works, April
   1968
                                               57

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optimum monitoring and control of an activated
sludge plant. Automatic sampling, recording and
analysis is clearly stated as necessary to provide
the operator with frequent and sufficient current
information  to promote better decisions and to
reduce  periods  of  uneconomic or inefficient
operations.
     Recent improvements  in  the short  term
BOD  detector permit  a one minute detection
time, allowing for a permissable minimum period
of five  minutes  between readings.  The oxygen
uptake is computed  by an automatic subtraction
of initial DO from final DO.

CONTROL  OF  THE  ACTIVATED  SLUDGE
PROCESS
     P. Brouzes of Omnium d'assainissement,
France, has  installed control  systems  for the
activated  sludge process which  can  control
aeration and excess sludge removal continuously
according  to  the  pollution  load.41   At  least
twenty  of  these  systems  are  currently
operational in France at a cost of about $20,000
to install. Practically automatic operation of the
   Brouzes, P., Automated Activated  Sludge Plants with
   Respiratory Metabolism Control, Advances in Water Pollu-
   tion Research, Proceedings of the 4th International Confer-
   ence, Prague, 1969
 plant  is  assured  with controls varying  in
 complexity  from  the  simple  regulator to  the
 analog  computer.  The  instantaneous pollution
 load  and specified operating conditions define
 the  automatic  removal  of  excess  sludge.
 Maintaining  a  constant  dissolved  oxygen
 concentration determines the air input.
      The  method avoids "empirical"  control
 practices  of constant  air input  and periodic
sludge removals based on volume, or weight. The
empirical  approaches   lead  to  uneconomical
safety margins and uncontrolled variations hi the
growth rate of microorganism cultures.
      Inherent  in  the  Brouzes process  is
intelligence of the growth rate of an activated
sludge culture. The author demonstrates through
a  mathematical  derivation  (in  the
aforementioned reference) that  the growth rate
can   be  defined,  instantaneously  detected,
controlled and regulated.
      The derivations relate the energy required
for oxygenation to the pollution load.  Since the
excess sludge removal  is also  related  to the
pollution  load,  the  power  consumed by the
blowers  can be used to  control the removal of
waste activated sludge.
      The simplicity and advantages of economy
in the Brouzes method offer more promise than
other  methods  dependent  upon  online
measurement of organics.
                                              58

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                                        SECTION 10
                               RECOMMENDED RESEARCH
    As a consequence of the work performed on
 the  study  Feasibility of Computer Control of
 Waste-water Treatment, recommendations for con-
 tinued research have evolved. These  are listed
 and  described.  For each project, the  need, ob-
 jective,  and time required are stated.

 DEVELOPMENT OF A SUSPENDED SOLIDS
 PROBE

 Introduction
      A  probe-type  instrument  could be
 developed to measure the concentrations and
 densities of various size particles in water, using
 an  electrolytic  (Coulter-type) counter. These
 counters  are  commercially   available,
 batch-measuring  instruments  which  size  and
 count particles  in an aqueous medium, with a
 sensitivity of one micron or less.
     By  developing:   l)a  continuous-flow
 sampling probe and 2) automatic data processing
 of the output pulses, the counter could be used
 to  give  a  continuous measurement of the
 number of particles  in  any desired size range.
 Furthermore the  size range could  be adjusted
 electronically without modifying the probe.
 Objectives
     The objectives  of the proposed program
are:   1)  to  evaluate  several  flow-through
sampling  concepts which have been developed,
2) to develop the electronic logic  circuitry to
pulse-height  analyze   the  resulting  pulses  and
3) to categorize and enumerate them according
to particle size.

 Time Estimate
    The time will require a fifteen-month effort.

 DEVELOPMENT OF  AN  INSTRUMENT FOR
 RAPID   DETERMINATION   OF
 BIOCHEMICAL OXYGEN DEMAND

Introduction
   It  may be  possible  to  develop  a  near
real-time instrument to measure oxygen demand
which would correlate with the 5 day BOD test.
     Because  the rate   of  oxidation of  a
substrate is  a function  of its  concentration  in
most  enzyme   reactions,  controlled  constant
 addition of oxygen should result in maintaining
 the oxygen tension of an  oxidizing wastewater
 sample at a level which is dependent  on "the
 rate   of   oxidation  and   therefore   on  the
 concentration  of  oxidizable  materials.  The
 resulting  QI  tension should  therefore be  a
 measure of short term BOD.

 Objectives
     The  objectives of the research include the
 design and verification of a device employing a
 controlled oxygen addition method  of BOD
 analysis. Design parameters must be established
 for O2 diffusion rate, 02 demand  rate, and ©2
 tension which will determine pumping rate and
 coil dimensions. A laboratory breadboard must
 be designed, constructed,  and tested and the
 results compared to Standard Methods for BOD
 analysis, using a variety of sample sources.
     The  correlation  between  the  proposed
 short term BOD and the standard 5  day BOD
 must be  evaluated  to  determine  quantitative
 relationships. These relationships will depend on
 supplementary characterization of the sample by
 other rapid chemical analysis means.

 Time Estimate
    It  is  anticipated that this program  will
 require a two-year schedule.

DEVELOPMENT OF AN INSTRUMENT FOR-
RAPID FECAL COLIFORM COUNTING
Introduction
     A  technique is under development  at
General Electric  by  which  the   24-48  hour
coliform test can be performed in approximately
4  hours.  This  is  based  upon metabolizing a
labeled nutrient to produce radioactively labeled
metabolic  products.   These products can  be
conclusively identified and measured long before
measurable colonies have formed. The heart of
this method is the GE silicon avalanche  diode
which can detect very low concentrations of the
radioactive metabolic effluents.
Objectives
     In the proposed study, this technique is to
be  extended  to  very short culture periods,
                                              59

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providing  near real-time  analysis  of coliform
counts. Microorganisms in a water sample are to
be concentrated  on  the  membrane filter and
exposed  to Endo  broth MF  enriched  with
14C-lactosc. ' 4CO2evolved by lactose fermenters
will be captured  by a getter and the radiation
monitored by   a  GE   avalanche  detector.
Read-out is contemplated  on a digital printer or
strip clnirt recorder.
     The feasibility study will correlate the level
of radiation monitored with the actual number
of viable fecal coliforms in the original sample.

Time Estimate
      The  feasibility study for near real-time
 fecal  coliform counting will require a fifteen-
 month program.
      An  instrument  to  perform  this analysis
 might  be  developed  by adapting the liquid-
 liquid extractor of the General Electric phenol
 analyzer to separate the mercury  ions  from
 interfering cations.


ANALYSES  AND  PROCEDURES  FOR
COMPUTER CONTROL  OF WASTEWATER
TREATMENT  PROCESSES

Introduction
    With   nationwide  concern  for  upgrading
secondary treatment and seeking .higher quality
effluents  via tertiary  treatment,  computer
control can help.  There is a need for analyses of
wastewater treatment  processes with regard  to
computer  control,  since  most  current studies
and computer simulations examine optimization
of process design.
    Before consideration can be  given to the
computer, management  must  thoroughly
analyze  plant  operational control, process  by
process. This  can  be done in  a  general way
among different  plants  to accommodate the
most common treatment  phases as well as the
new advanced types.
    One   of  the  major  considerations  in
computer control of wastewater treatment is the
list of tasks to  be assigned to the process control
computer.  For each treatment  facility to  be
associated  with  automatic  monitoring and
control, the information entering the computer,
the logic and computations relevant to reporting
and  control, and the information leaving the
computer  must  be  defined.  The  logic  and
computation  procedures  are  written  in flow
chart  form  to  serve two  documentation
purposes:
     1.   A  record of the process requirements
for monitoring and control identifiable to plant
management, and
     2.   Guidelines   for  computer
programming.
     The document will also serve to determine
hardware and software requirements for plant
automation.
Objectives
     The objectives of the proposed project are
to develop and document the computer-stored
procedures  for  continuous  monitoring and
control of wastewater treatment. The steps are
to be prepared for existing wastewater treatment
plants encompassing processes through tertiary
and  advanced  treatment, and  will reflect the
most advanced  thinking and good practices of
engineering management.
Time Estimate
    To perform an analysis  and  to develop flow
charts for monitoring and control of wastewater
treatment  processes will require a fifteen-month
schedule.

USERS' EXPERIENCE  INSTRUMENTATION
STUDY  FOR  WASTEWATER TREATMENT
PROCESSES

Introduction
     Among   the  major  impediments  to  the
achievement  of full  computer  control  of
wastewater treatment  is the lack of satisfactory
sensors  for  continuous   process monitoring.
Some  sensors  do not coyer  a  wide  enough
range;  others  are  unreliable;  and  for some
wastewater  treatment processes, no continuous
monitoring  instrumentation is  available. Thus,
there is a need for a comprehensive field study
of  users'  experiences   with  installed and
operating  on-line instrumentation to learn their
recommendations  for  improvements  and  to
define bases for new  instrumentation.  Such a
study  would provide a base-line  and  direction
                                             60

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from  which  manufacturers  could proceed  to
fulfill this need.

Background
     As  a  result  of  the  survey  relating  to
Computer  Control of  Wastewater  Treatment
(SECTION  4) and recent contacts with managers
of treatment facilities, it has become apparent
that there  are fundamental gaps in continuous
monitoring  technology  for   wastewater
treatment.  It is still impossible to react quickly
enough to  variations  in  plant influent, and in
certain  treatment  processes,  to  minimize
undesirable  effluent  characteristics.  It  is,
therefore,  equally impossible  to  implement
continuous computer  control on those variables.
Inefficiencies and attendant uneconomical plant
operations  still occur, and  the  quality of the
effluent  may not   always  meet  or  exceed
established criteria.
     While  industry is continuing to improve
monitoring  devices with  better packaging and
solid state circuitry, plant management still finds
them  requiring  too  much  attention  for
satisfactory operation.

Objectives
     The objectives of this study will be  to
determine,  on a  nationwide  basis,  for  each
process within primary, secondary, and tertiary
wastewater treatment plants:
     1.   The  effectiveness of  installed and
operating on-line sensors,
     2.   The  effectiveness of  installed and
operating automated  analysis  instrumentation,
     3.   Present   needs  for  improvement  in
existing instrumentation, and
     4.   Present  needs  for  new
instrumentation.
     The effectiveness of installed and operating
instrumentation will be gauged by considering
such  characteristics  as  its  performance (e.g.,
range,  accuracy,  response time,  etc.)  with
relation to the variable being measured; costs
(•procurement,   installation,  operation and
maintenance), and simplicity of connection to
the process. Present and  future needs must not
only be expressed  in general terms, but must be
quantified into specifications which can be used
to develop the needed  instrumentation.
Time Estimate
    To perform the survey of users' experience
in  wastewater  treatment  instrumentation will
require a fifteen-month schedule.

AUGMENTED INSTRUMENT SURVEY

Proposed  Future  Work  on  the  Instrument
Survey
     The usefulnes and value  of the instrument
survey included in this document (Section 13)
can  be  increased  by: l)expanding  the
information content, 2) enlisting  the  aid  of
equipment  manufacturers,   3)building  a
computerized data  bank, and 4)making  the
information readily available.

Expand Information Content
     The introductory nature  of the information
contained in the present survey necessarily limits
the amount  of  useful   data  which  can  be
presented.   To • help  a user more effectively
narrow  down  his  search  for  candidate
instruments, it  is recommended that the survey
be expanded. This would provide room for such
potentially  useful information  as: cost, power
requirements,  maintenance  requirements
(recalibration,  duration  for  unattended
operation — some analyzers require reagents to
be  replenished  and/or  their  sensors  to  be
cleaned);  optimal  equipment  for  readout,
recording,  transmission and telemetry;  more
detail on ranges of measurement; information on
specific applications and limitations; and so on.

Enlist Aid of Equipment Manufacturers
     To  facilitate the gathering of information
and to  ensure that  all  applicable equipment
offered by  a manufacturer is  included in the
survey, it is proposed that the manufacturers
themselves generate the information. This would
eliminate  the need to glean  information  from
catalogs, and would ensure that all information
is  current.  By  going directly   to   the
manufacturers,  information  could   also  be
requested which might not normally be included
in  their  catalogs  (e.g.,  price,  maintenance
requirements,  specific  applications  or
limitations).
     Because information of this type is subject
                                              61

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to  frequent  changes, especially pricing,  a
procedure  for periodic  updating would be
provided. The ultimate situation would be one
in which  the manufacturers  would keep the
survey  alive,  once  it  gained  acceptance, by
deeming it essential to their product's visibility.

Build a Computerized Data Bank
     As the  survey grows in size, it would
eventually become more  efficient  to  build  a
computerized data  bank to  eliminate the
handling of unwieldly card decks.  This would
also provide a degree of flexibility that would be
difficult to achieve with the present system.
     When generating the software for the data
bank,  special attention would be given to
facilitating  its  use  by  personnel   without
programming skills.  The  software  can be
designed to lead  the  user through all of the
operating steps in response to his initial typing
in of key request words. Provisions can be made
for detecting input errors and  allowing  the user
to  see  changes  before  they are  finalized
(especially important when  deleting data).

Make the Information Readily Available
     The success of the survey will ultimately
depend upon its acceptance as a useful source of
accurate data for wastewater  instrumentation
and  equipment.  In   order to promote  and
encourage   its use,  the  survey  should be
published  in technical  journals  and  trade
magazines as well  as a separate technical paper.
Publishers should be informed  of the potential
value that a survey of this type could have, that
is, its periodic publication as a special feature of
a journal.would not only add to the value of the
sponsoring publication, but could also boost its
circulation.

Time Estimate
     To build  the  data bank and its associated
computer program for information on available
continuous  monitoring instrumentation would
require a fifteen-month schedule to  completion
COMPUTER  IMPLEMENTATION  FOR
MONITORING  AND  CONTROL  OF  A
WASTEWATER TREATMENT PLANT

Introduction
     The  study.  Computer  Control of
Wastewater  Treatment,  has  evolved   a
documented  Guidelines for Computer
Implementation. It is recommended that they be
put to practice.  There are  sufficient  workable
applications to encourage an approach toward
automation, despite the lack of both treatment
knowledge  and  adequate  instrumentation  in
some areas. To achieve a computer controlled
wastewater treatment plant  is the ultimate goal
of this study.
     The  requirements of  a   project of this
magnitude can only be briefly  outlined  in this
document. The  text  contains  two  sections
suitable  as a guide to computer applications.
These are:
     •   SECTION  6     Guidelines for
Computer Implementation
     •   SECTION  7     Measured  Steps
Toward Plant Automation
Objective
     To  automate a medium  sized (10  to 50
mgd) secondary wastewater treatment plant by
process  computer  implementation.

FEASIBILITY STUDY FOR RAPID MERCURY
ANALYSIS

Introduction
     The recent public concern  with mercury
pollution  indicates  that  analysis  for mercury
content, however  inconvenient, will increasingly
be  required.  Neutron activation  analysis  is
beyond the resources of  most laboratories.  In
order to achieve the sensitivity  required, atomic
absorption  spectroscopy  requires  sample
concentration  and  liquid-liquid extraction.
Neither of these methods are readily  adaptable
to field laboratory operations. There is a definite
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need  for  a  low-cost method  for  simplifying
and/or automating the assay technique.
     An  instrument  to perform this  analysis
could be developed by adapting the liquid-liquid
extractor  of  the  General Electric  phenol
analyzer  to  separate the mercury  ions  from
interfering cations.
Objectives
     The  objective  of this program is to
ascertain and optimize  the technical  details
involved  in adapting  the  semi-automatic
liquid-liquid extraction  capabilities  of  the
GE-developed phenol analyzer to  colorimetric
mercury  determination.  Work  could be
performed  to  determine  the  nature  of  the
necessary modifications, and then to obtain'the
optimal  conditions,  reagent  concentrations,
reaction duration and procedure.

 Time Estimate
    This   feasibility  study  will  require  a
 fifteen-month effort.
DEVELOPMENT OF
SENSOR PROBE
AN ON-LINE PHENOL
Introduction
     A  probe-type  sensor  for phenol  and
phenolic derivates could be developed, based on
the  General  Electric  phenol  analyzer.  This
batch-type analyzer uses liquid-liquid extraction
to separate  phenolics from a wide variety of
interfering substances. The extracted phenolics
are reacted by standard methods to produce a
characteristic absorption line at 457  m/z, and
their  concentration  is  measured
spectrophotometrically.  The  current General
Electric  analyzer will detect phenolics in water
with a sensitivity of 0.1 to 1.0 part per billion.
     A probe-type sensor could be developed by
1) partitioning the  phenolics with  a  selective
membrane rather than a liquid-liquid extractor
and 2) measuring their concentration directly by
fluorescent  spectroscopy,  thereby eliminating
                             the  colorimetric  reactions  and
                             spectrophotometry.

                             Objectives
                                 The objectives of the proposed  research
                             are: 1) to evaluate the partition coefficients for
                             various membrane materials, some of which have
                             been developed  for specific-ion probes, 2) to
                             measure  the  fluorescent  efficiency  of  the
                             partitioned  phenolics,  and  3) to design  a
                             prototype sensor for  continuously measuring
                             phenolics in water.

                             Time Estimate
                                 The  feasibility  evaluation  and prototype
                             fabrication  of a continuous probe-type phenol
                             analyzer will require an eighteen-month schedule.
                             DEVELOPMENT OF  AN ON-LINE
                             OIL MONITOR INSTRUMENT
                                    TRACE
Introduction
     There is an urgent need for an instrument
to make real-time in-situ measurements of trace
oil in water, including thin films and dispersed
and/or emulsified oil. The present method is to
take a sample  to  a laboratory, concentrate the
oils and then measure them by solubility tests,
by  chemical reactions, or by IR absorption or
spectroscopy.
     A  concept  has  been  evolved for  an
instrument which would continuously draw a
sample of the oil/water, extract and concentrate
the oils, and measure them by IR absorption at a
critical wavelength.
     A  continuously  sampling,  real-time
technique  capable of making  quantitative
measurements  in the  low  ppm. range must
perform two functions: It must first concentrate
the  oil,   and  second,  it  must 'analyze  the
concentrated sample. The  proposed method is
to:
     1.   Concentrate  the   oils  by
countercurrent solvent extraction and
                                              63

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     2.   Measure  them  by  IR transmission
spectroscopy.

This lends itself to a continuous monitor which
draws a sample  through  an extractor into  the
flow-through  absorption cell. The key to this
technique  is  the  countercurrent liquid-liquid
extractor  developed at  the  General Electric
Company  and  which  can   partition  and
concentrate the oils in real-time.

Objectives
     The  objectives  are  to investigate the
extraction  efficiencies  and  IR  transmission
windows  of  various solvents, provide  a
laboratory  feasibility  demonstration of  the
concept, and establish an engineering prototype
design. Test results can be presented in terms of
IR  spectrometer  absorption  curves,
nephelometric scattering,  and photographs  of
the state of emulsification of the oil used in each
test.
Time Estimate
    The task will require a fifteen-month effort
                                             64

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                                                  SECTION 11
                                            ACKNOWLEDGEMENTS
      The American  Public  Works  Association is deeply indebted to  the following persons and  their
organizations for the services they rendered to the APWA Research Foundation in carrying out this study
for  the  25  local  governmental  jurisdictions and the  Federal  Water  Quality Administration  who
co-sponsored  the  study.  Without  their  cooperation and assistance  the  study  would  not have  been
possible.
                  Steering Committee

 Joseph  V.  Radziul  (Chairman), Chief  of  Research  and
 Development, Philadelphia Water Department

 Waddy  Allnut, Chief  of  Bureau of  Business Management,
 Department of Public Works, Richmond, Va.

 Ben  Cramer,  Director, Organization  and Methods  Division,
 Finance Department of the City of Toronto

 Charles  V.   Gibbs,  Executive  Director, Municipality of
 Metropolitan Seattle

 Sam Hobbs, Director of Public Works, Bloomington, Minn.

 E. Steve Savas, Deputy City Administrator, Office of the Mayor
 of the City of New York

 Harry File,  Chief  of Information  Systems  Division,  U.S.
 Department of Transportation

                      Consultants

 Carmen  Guarino,  Deputy  Commissioner,  Water  Pollution
 Control, Philadelphia Water Department

 Morris H. Klegerman,  Alexander Potter Associates, Consulting
 Engineers

 Anton Sparr,  Alexander Potter Associates, Consulting Engineers

          Wastewater Treatment Plant Management

Robert  Bargman,  Director, City  of  Los Angeles, Bureau of
Sanitation
Jack Betz, Assistant Director, City of Los Angeles Bureau of
Sanitation

Walter  E. Garrison, Assistant Chief Engineer, County Sanitary
District of Los Angeles County

Gabriel  Lapidus, PhD,  Chief,  Lab  Branch, Water Pollution
Control Division, Washington, D.C.

Charles  V.  Gibbs,  Executive  Director,  Municipality  of
Metropolitan Seattle

Carmen  Guarino, Deputy  Commissioner,  Water Pollution
Control, Philadelphia Water Department
                  Regulatory Agencies

Larry  Miller ,  Assistant  Director, Division  of  Sanitary
Engineering, Pennsylvania Department of Health

Christian Beechwood,  Regional  Sanitary Engineer, Bureau of
Sanitary Engineering, State of Pennsylvania.
                  General Electric Staff
M.Y. Goodman, Computer Applications Engineer, Re-entry and
Environmental Systems Division
F.W.  Morris,  Water  Resources Analyst,  Re-entry  and
Environmental Systems Division
E.O. Potthoff, Applications Engineer, Industrial Sales Division

W.E. Sauer, PhD, Environmental Sciences Laboratory, Re-entry
and Environmental Systems Division
                                                        65

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                                              SECTION 12
                                              GLOSSARY
ACTIVATED  CARBON.  Carbon  particles  usually
obtained by carbonization of cellulosic material in
the absence of air  and possesing a high absorptive
capacity.
ABSORPTION. The taking up or into a solid, gas,
liquid or dissolved material.
ADSORPTION. The adherence of a gas, liquid, or
dissolved material on the surface of a solid.
AEROBIC. Requiring the  presence of free elemental
oxygen.
ALGORITHM.  A fixed step-by-step procedure for
accomplishing a given result.
ANAEROBIC. Requiring the absence of air or free
elemental oxygen.
AN I ON. A negatively charged ion in an electrolyte
solution, attracted to the  anode under the influence
of electric potential.
BREAKTHROUGH.  The  point where  an  ion
exchange  column  begins  to  lose  its  ion  removal
capability.
BUFFERING.  The  use  of certain combinations of
chemicals to stabilize the pH values of solutions.
CATION. The  ion in an electrolyte which carries the
positive  charge  and  which  migrates  toward  the
cathode under the influence of a potential difference.
CHLORINE DEMAND.  The difference  between the
amount of chlorine added to water or wastewater and
the amount of residual chlorine remaining at the end
of a specified contact period. The demand for any
given water varies  with  the amount  of  chlorine
applied, time of contact, and temperature.
CLARIFICATION.  Any process or combination of
processes the primary purpose of which is to reduce
the concentration of suspended matter in a liquid.
CLARIFIER. A unit the primary purpose of which is
to  secure  clarification.  Usually   applied  to
sedimentation tanks  or basins.
COMPUTER   MEMORY.  A device   for  storing
information  and instructions  in a digital computer.
Examples of memory include magnetic core, disks,
drums, and tape.
DIGESTERS.  Tanks in which sludge  is placed to
permit digestion to occur. Also called sludge digestion
tank.
EMPIRICAL  FORMULA.  A  formula  developed to
describe a relationship on the basis of experience and
data gathered from actual operations.
FEEDBACK (CONTROL). An automatic furnishing
of data concerning  the output of a machine to an
automatic control  device  so that  errors  may be
corrected.
FILTRATE. The liquid which has passed through a
filter.
FLOW  CHART.  An orderly  representation  of a
process. A graphic illustration in which activities are
defined and their interrelationships are illustrated.
INFILTRATION. The discharge of groundwater into
sewers, through defects in pipelines, joints, manholes
or other sewer structures.
INFLOW. The discharge of any kind of water into
sewer lines from such sources as roof leaders,  cellar
and yard area drains, foundation drains, commercial
and industrial so-called clean water discharges, drain
from springs and swampy areas, etc.
INPUT-OUTPUT DEVICES. Devices for entering and
extracting information from-computers: card readers,
card punch,  typers,  printers, cathode ray tubes, etc.
INTERMEDIATE TREATMENT. The removal of a
high percentage of suspended solids and a substantial
percentage  of coloidal matter,  but little dissolved
matter.
KJELDAHL. The Kjeldahl method employs sulfuric
acid as  the oxidizing agent  to  free  nitrogen as
ammonia .from  organic compounds in the  standard
nitrogen testing procedure.
MATHEMATICAL  MODEL. The mathematical
representation of a  process or operation for which
solutions can be obtained for a set of input variables.
MIXED LIQUOR. A mixture of activated sludge and
organic matter undergoing activated sludge treatment
in the aeration tank.
MODELING. A simulation technique for the analysis
of operations and systems.
NITRIFACATION.  The conversion  of nitrogenous
matter into nitrates by bacteria.
OFF-LINE   COMPUTER.  A  free  standing  digital
computer not tied into an industrial process.
ON-LINE.   Tied  into  a  process   and  operating
continuously.
ON-LINE   COMPUTER.  A  computer  which  is
integrated into the  dynamics of a process; a process
control computer.
OUTFALL.   1)  The point,  location, or structure
where  wastewater  or  drainage discharges  from a
sewer, drain, or other conduit. 2) The conduit leading
to the ultimate disposal area.
PARSHALL  FLUME. A calibrated device developed
by Parshall  for measuring the flow of liquid  in an
open circuit.
PATHOGENIC. A  description of  organisms  which
may cause  disease  in  the  host  organism  by their
parasitic growth.
PERCOLATION.  The  movement  or  flow  of  water
through the  interstices or the pores of a soil or other
porous medium.
                                                 67

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PERIPHERAL  DEVICES. Input/output equipment
used to make hard copies or to read in data from hard
copies (typer,  punch,  tape reader, Line  printer,
cathode ray tube, plotter).
PRIMARY SETTLER. The first settling tank for the
removal of settleable solids through which wastewater
is passed in a treatment works.
PROCESS  COMPUTER. A digital computer having
direct  communication capability with an industrial
process for data sampling and equipment control.
REGENERATION.  The process of restoring an-ion
exchange  material  to   the  state  employed  for
adsorption (in ion exchange).
REGRESSION  ANALYSIS.  The  analysis  of  the
association among several variables.
SCANNER,  REMOTE. A device  which will, upon
command,  connect  a  specified  sensor to measuring
equipment and  cause  the generation  of  a  signal
suitable for input to a computer.
SIMULATION. Operating  a  logical-mathematical
representation of a concept, system or operation.
SLUDGE.  1) The accumulated solids  separated from
liquids,  such  as  water or  wastewater,  during
processing, or deposits  on bottoms of streams or
other bodies of water. 2) The precipitate resulting
from  chemical  treatment,  coagulation,  or
sedimentation of water or wastewater.
SLUDGE   BLANKET.   Accumulation  of sludge
hydrodynamically   suspended  within an  enclosed
body of water or wastewater.
STEADY-STATE  PROCESS.  A process which has
reached  a  relatively  stable  operation, no longer
changing with time.
STREAM  VECTOR.  An  identification  of  the
variables comprising wastewater characteristics which
are changed by treatment processes.
STREAMING POTENTIAL - The  difference of elec-
trical potential between a porous diaphram, or other
permeable solid, and a liquid which is passing through
it. This arises from an imposed movement of solvent
through capilaries.
SUBSTRATE. 1) The substances used by organisms
in liquid suspension. 2) The liquor in which activated
sludge or other matter is kept in suspension.
SUPERNATANT.  The  liquid  standing above  a
sediment or precipitate.
SUSPENDED SOLIDS. 1) Solids that either float on
the  surface  of,  or  are in  suspension  in,  water,
wastewater, or  other  liquids, and which  are largely
removable by laboratory filtering. 2) The quantity of
material removed from  wastewater  in a  laboratory
test,  as  prescribed in Standard  Methods  for the
Examination of Water and Wastewater and  referred to
as nonfilterable residue.
TELEMETRY. The system of measuring, transmitting
and  receiving apparatus for indicating, recording or
integrating  at a  distance, by electrical  translating
means, the value of a quantity.
TIME-SHARING.  The simultaneous  use  of  a
computer system from multiple terminals; provides
economics through cost-sharing.
TOTAL  SOLIDS.  The  sum  of  dissolved  and
undissolved  constituents  in  water,  or  wastewater,
usually stated in milligrams per liter.
TOXIC. Usually referred to in this document as fatal
to the aerobic and anaerobic organisms.
TRICKLING  FILTER.  A  filter  consisting of  an
artificial bed of coarse  material, such as broken  stone,
clinkers, slate, slats, brush, or plastic materials, over
which wastewater is distributed or applied in drops,
films,  or  spray  from  troughs,  drippers,  moving
distributors, or  fixed nozzles, and through which it-
trickles  to the underdrains, giving opportunity for the
formation  of  zoogleal  slimes  which  clarify  and
oxidize the wastewater.
VARIABLE.  A  quantity to  which an  unlimited
number of values can be assigned in an investigation.
ZETA  POTENTIAL.  An  electrical charge at  the
boundary  between particles  and   the  suspending
medium that is related to repelling forces between
floccules.
                                                  68

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                                                       SECTION 13
                                                     REFERENCES
   1.  Guarino,  C.F. and  G.W.  Carpentar. Philadelphia's Plans
      Toward  Instrumentation  and  Automation  of  the
      Waste-water  Treatment Process.  5th International  Water
      Pollution  Research Conference. San Francisco, California.
      July 29,1970.

   2.  Milbury,  W.F.,  V.  Stack,  N.S.  Zaleiko,  F.L.  Doll. A
      Comprehensive Instrumentation System for Simultaneous
     Monitoring for Multiple Chemical Parameters in a Municipal
     Activated Sludge Plant.  Preprints 16th  Annual Analysis
      Instrumentation  Symposium,  ISA.  Pittsburgh,  Pa.  May
      25-27,1970.

   3. Activated Sludge Process  Automated.  Water and Sewage
     Works. May, 1970.

   4. Stack, V.T.,  Continuous Monitoring Devices - Treatment
     Plants.   Proceedings  Ninth  Engineering  Conference,
     Instrumentation,  Control  and  Automation  for  Water
     Supply and  Wastewater  Treatment Systems. University of
     Illinois, College of Engineering. 1967.

   5. Metropolitan  EngineeisMunicipality of Metropolitan
     Seattle  Sewage Disposal Project  Contract  No.  68-1  for
     Computer Augmented Treatment and Disposal System.
     March 1968.

  6.  Crises  in  the  Megalopolis Demand  New  Electronics.
     Electronic Design 1. January 4, 1968.

  7.  Mixed  Liquor  Suspended Solids  Analyzer/Controller,
     Bulletin  No.  8200.  Keene  Corporation  Water Pollution
     Control Division, Aurora, Illinois.

  8.  Cosens, K.W., The Operation of Sewage Treatment Plants.
     Public Works  Publication.

  9.  Knowles,  C.L., Improving Biological Processes. Chemical
     Engineering/Desk Book Issue. April 27, 1970.

 10.  Oxygen Can  Replace Aeration. The American City. June
     1970.

 11-  Hess, A., and H.F. Hanson."Watcr.Water Everywhere, But" -
     Control KnginceringMny 1970.

 12.  Sawyer, C.N.  and  P.L.  MeCarty. Chemistry for  Sanitary
     Engineers. McGraw-Hill Book Company. 1967.

 13.  Andrews,  John  !•".,  Dynamic Model  "f the Anaerobic
     Digestion  Process.  Proc.  Paper  6418  Journal  of  the
     Sanitary  Engineering  Division,  ASCE,  pp  95-116.  Feb.,
     1969.

14.  Di\on,  R.M.  and  G.R.  Evans.   Experiences with
    Micros!raining on Trickling Filter Effluents  in Texas. 48th
    Texas Water and Sewage Works Associations Short School.
     March, 1966.

15. Marks, R.H.,  Wastewater Treatment.  A special  Report,
    Power. June,  1967.
 16.  Tossey,  D.F.,  P.J.  Fleming,  and  R.F.  Scott.  Tertiary
     Treatment by Flocculation and Filtration. Journal of the
     Sanitary  Engineering Division, Proceedings of the American
     Society of Civil Engineers, 7106 SAL Feb.  1970.

 17.  Burleson, N.K., W.W. Eckenfelder, and J.F. Malina. Tertiary
     Treatment of Secondary Industrial Effluents by Activated
     Carbon.  23rd  Industrial  Waste  Conference,  Purdue
     University. Lafayette, Indiana.

 18.  Slechta, A.F. and G.L. Culp. Water Reclamation Studies at
     the South  Tahoe Public  Utility District.  Journal Water
     Pollution Control Federation. May, 1967.

 19.  FWPCA U.S. Dept. of Interior. Summary Report Advanced
     Waste Treatment. Publication WP-20-AWTR-19.

 20.  FWQA., U.S. Dept. of Interior. Current Status of Advanced
     Waste  Treatment Processes. Advanced  Waste Treatment
     Research Laboratory, Division of Process Research and
     Development. July, 1970.

 21.  Eckenfelder,  W.W.  Industrial  Water Pollution  Control.
     McGraw-Hill Book Company. 1966.

 22.  Federal Register.  Volume 35, Number 128. July 2, 1970.

23.  Ellis,  Eddie E.  The Application  of  Electronic Data
     Processing Techniques to Water Pollution Control.  Florida
     Air and Water Pollution Control Commission.

24.  Schieber, John  R. Continuous  Monitoring,  Chemical
     Engineering. Deskbook Issue. April 27, 1970.

25.  Scrimgeour, J.H. How to Assess the Economic Justification
     for Process  Computer Control. Canadian Controls  and
     Instrumentation. Canadian General Electric. April, 1968.

26.  Guarino,  C.F.  and  J.V.  Radziul.  Data  Processing in
     Philadelphia.  Journal Water Pollution Control Federation.
     August, 1968.

27.  Ryder,  Robert S. Automatic Control for Smaller Water and
     Wastewater  Facilities.  Proceedings,  Ninth Sanitary
     Engineering Conference.  University of Illinois College of
     Engineering. F'ebruary 7-8, 1967.

28.  Puzniak,  T.J., W.F.  Benusa, and  J.A.  Condron.  Mobile
     Water Conservation  Laboratory. Preprints,  16th  Annual
     Analysis Instrumentation Symposium.  May 25-27, 1970.

29.  Smith,  R., R.G.  Eilcrs, and  E.P. Hall.  Executive Digital
     Computer Program for Preliminary Design of Wastewater
     Treatment Systems.  Water  Pollution Control Research
     Scries Publication No. WP-20-14. Cincinnati, Ohio.  August,
     1968.

30.  Andrews,  John F. Dynamic Modeling and Simulation of
     Biological  Processes  Used  for   Waste  Treatment.
     Environmental  Systems   Engineering  Dept., Clemson
     University. June 30, 1969.
                                                            69

-------
31. Forecast,  Evolutionary and Revolutionary  Trends  in
    Process Control. Chemical Engineering. January 13, 1969.

32. McGaughey,  P.H.  Engineering  Management  of Water
    Quality. McGraw Hill Book Company. 1968.

33. Clark, J.W. and W. Viessman. Water Supply and Pollution
    Control,  p.   453.  International  Textbook   Company.
    Scranton.Pa. 1965.

34. Smith,  Robert. Preliminary Design and Simulation of
    Conventional  Wastewater Renovation Systems  Using the
    Digital  Computer. U.S. Department  of Interior, FWPCA
    No. WP-20-9.

35. Sullivan, J.L. What to do Until the Computer Comes (Part I
    and U). Willing Water, AWWA. Dec. 15, 1969 and Dec. 31,
     1969.

36. Classen, N.W., B.C. Scalf, and J.B. Copeland, Jr. Economics
    of Regional Sewerage Systems. Public Works. April 1970.
  37  Parkhurst, J.D. and W.E. Garrison. Whit tier Narrows Water
      Reclamation  Plant - Two  Years  of  Operation.  Civil
      Engineering. Sept., 1964.
 38.
39.
40.
41.
      Arthur, R.M., An Automated BOD Respirometer, Proceed-
      ing of the  Nineteenth  Industrial Waste  Conference,  Mav
      5, 6S 7, 1964, Purdue University
Arthur, R.M. and Hursta, W.N.,.Short Term BOD Using the
Automatic Respirometer, Proceedings of the 23rd Industrial
Waste Conference, May 7, 8, 9, 1968, Purdue University

Ingols, R.S., Short Term BOD, Water & Sewage Works, April
1968

Brouzes, P., Automated Activated Sludge Plants with Res-
piratory Metabolism  Control,  Advances in Water Pollution
Research,  Proceedings of the 4th INternational  Conference,
Prague,  1969
                                                                70-

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                                  SECTION 14 - APPENDIX
                 CONTINUOUS MONITORING INSTRUMENTATION SURVEY
METHOD
    The survey has compiled a list of automatic
monitoring instrumentation  on the  market for
continuous monitoring of wastewater treatment
processes and receiving waters.
    The   survey  'tabulated: an   instrument
listing,  manufacturers names  and  addresses,
abbreviations,  symbols  and  a  list  of  those
variables  which  are  usually  measured  for
monitoring a specific  treatment process. (Table
4). Excluded from this survey are portable and
laboratory  instruments,  and  those requiring
manual samples.
    The instrument listing has been subdivided
according to classification, i.e., water  quality,
flow,  level,  etc. This listing and  the  one of
measurements  vs.  wastewater  treatment
processes  can  guide  the  user in  instrument
selections.
    Data  were  obtained  from  manufacturers'
catalogs and from  those who advertise  in trade
journals, such  as: Public Works magazine,Water
and Wastes  Digest, Water and Sewage Works,
Pollution  Equipment  News,  and the American
City.

DESCRIPTION OF SURVEY DATA AMONG
THE LISTINGS
    A  format was selected  which utilizes two
standard 80-column  computer cards for each
instrument description. The  first card  contains
information about  the  instrument  itself. The
second card contains the manufacturer and some
additional information.  A description  of each
field heading follows (Table 5):
    1.    Variable.    This describes what  the
instrument  measures.  Where  H2O  QUAL
indicates  that   there  are   many  possible
measurements, the COMMENTS field should be
referred to for the specific variables  measured.

    2.   Instrument.  Manufacturer's name for
his instrument. In many instances, a range of
model numbers is indicated, while in other cases,
only the name of the instrument line has been
given  (e.g.,  MAGNETIC  FLOWMETERS  and
 TURBINE  FLOWMETERS  have numerous
 models which depend upon pipe size).

     3.   Ranges.   Where an integer  or M (for
 multiple) appears within  the specified range
 limits,  or  that  the  number  of ranges  can be
 achieved  by virtue  of the  numerous  models
 available, each  of which may have one or more
 ranges.

     4.   Range  Limits.  This  indicates  the
 extreme ranges of measurement.

     5.  Method.    The  method  or basic
 principle  used  to  achieve the  measurement is
 cited.  For water quality monitor  packages,  this
 may be blank because of the numerous methods
 used to measure multiple parameters.

     6.  Outputs.   Standard  and  optional
 output signals are listed.

     7.  Manufacturer.    The name  may be
 shortened due to lack of  field space. However,
 the complete name  is given  under the  list of
 MANUFACTURERS  NATVIES and
 ADDRESSES.

     8.   Comments,  Other   Outputs,  Water
Quality Variables. This field is used to provide
other  useful information.  For water quality
instruments, this field will contain specific mea-
surements available.
    The symbols and  abbreviations for Table 5
are given in Table 6, and the manufacturers'
addresses are listed in Table 8. Table 7 contains
a  list  of  thirteen  manufacturers  of automatic
sampling equipment for one or more variables.
RESULTS AND USES
     A user of  the compilation will have at his
fingertips,  virtually  all potentially  useful
continuous  monitoring  instruments and their
manufacturers. Inquiries to a  manufacturer  will
be more direct  and the  time shortened,  since a
caller  will  already  have  basic details  about
specific instruments.
                                              71

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                                                              TABLE 4.  MEASUREMENTS FOR WASTEWATER TREATMENT PROCESSES
                                                                                       Measurements
-J
10
Process
pH
Temp
ORP
DO
BOD
COD
TOD
P04
. Toxic
metals
NO
CL
Alkal-
inity
Susp.
NHS
KJEL-
DAHL
N
Liquid
How
Level
Gas
volume
%
co2
%
Methane
Air
flow
Influent flow (at plant)

Bar screen

Raw wastewater pump

Grit channel

Primary sedimentation

Trickling filter

Aeration tanks

Secondary clarificrs

Oxidation pond

Chlorine contact chamber

Return sludge

Primary sludge

Waste activated sludge

Stodge thickening (gravity)

Sludge thickening (floatation)

Sludge digestion

Sludge dewatering

Ehitriation

Pipeline to sea

Incineration

Receiving water
X       X

X       X

X       X

X       X

        X
X

X       X



X       X

X

        X

X

X       X

X

X
                                                                                X

                                                                                X

                                                                                X

                                                                                X

                                                                                X
                                                                                X

                                                                                X
X

X
                 X

                 X
X

X
                                                                                                                                  X

                                                                                                                                  X
                                                                   X

                                                                   X
                                                                                                                                  X

                                                                                                                                  X
X

X
                 X

                 X
X

X
X

X

X



X

X

X

X
                                                                   X

                                                                   X

                                                                   X

                                                                   X

                                                                   X

                                                                   X

                                                                   X

                                                                   X

                                                                   X
                                                                                                                                                                   X

                                                                                                                                                                   X
                        Sludge
                        level
Sludge
level
                                                                                                   Sludge
                                                                                                   level
                                                      X

                                                      X

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                                                                                   TABLE 5

                              AUTOMATIC MONITORING INSTRUMENTATION FOR WASTEWATER TREATMENT PROCESSES (1 of 2)
         Variable        Instrument
         Flow     Series 600 magnetic mtrs
         Flow     Flumes, weirs, nozzles
         Flow     Magnetic resonance meter
         Flow     Universal'venturi
         Flow     Brooks-mag flowmeter
         Flow     Fullview,  armet rotameters
         Flow     Magnetic flowmeters
         Row     Turbine flowmeters
         Flow     Flumes and weirs
         Flow     All-metal  meters
         Flow     Orifices, nozzles, Venturis
         Flow     Swirlmeter
         Flow     Turbine flow transmitters
         Flow     Primary device flow mtrs
         Row     Magnetic flow transmitter
         Flow     Propeller type meters
         Flow     Stevens flow metrs (4 mdls)
         Flow     Mark V flow meter
         Flow     Varea-meter
         Flow     Le flowmeter
                                                    Range Limits
                                                                     Method
Manufacturer
FLOW MEASURING INSTRUMENTS

M
1
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M

M

.l-30Mgd
5-50 Gpm
To 16K Gpm
100K Gpm
1-2. 5K Gpm
To 100K Gpm
To 36K Gpm
To 90 mgd
To 320 gpm
To 20K gpm
-30K scfm
.2-30Kgpm


To 60K gpm
To SDK gpm
1.5-2K gpm

Unlimited

Primary
Mag res
Primary
Emf
Rotameter
Emf
Turbine
Primary
Rotameter
Primary
Vortex
Turbine
Primary
Emf
Turbine
Primary
Fluid Drag
Rotameter
Ultrasonic

V
V, A, dig
Press
V, A, Tm, R, rcdr
V, press, rly
A, press, tm
Vac, A, rcdr
Press, A, rcdr
A, press, rly
A, press, rcdr
Vac A, rcdr
Vac
Press, A, rly, tm
A, rcdr, rly, tm
Vac, tm, rly
Rcdr, dig, im
V, rcdr


American Meter
Badger Meter Mfg
Badger Meter Mfg
Bif
Brooks Instrument
Brooks Instrument
Fischer and Portei
Fischer and Porter
Fischer and Porter
Fischer and Porter
Fischer and Porter
Fischer and Porter
Foxboro
Foxboro
Foxboro
Hersey-Sparling
Leopold and Stevens
Ramapo
Wallace and Tiernan
Westinghouse
                     Comments, other Outputs, Water Quality Variables
                     Brochure not received
                     Uses Badger ML-MN trmtr to sense level (Flow)
                     Totalizer avail. Special fluid properties required
                     Pressure transmitter required. Available from Bif
                     Totalizer avail. Pneumatic output available
                     Totalizer avail. Also for metering gases
                     Rc'dr output also
                     Totalizer available
                     Uses Fischer and Porter float actuated transmitters
                     Rcdr output also. Also for metering gases
                     Uses DP transmitters
                     Gas flow only. Totalizer available
                     Brochure not received
                     Press and float types. Brochure not received

                     Rcdr output. Total flow output also
                     For weirs, flumes. Uses float or bblr. Total flow
                     Uses strain gage. Higher pipe flows available
                     Brochure not received. Also for metering gases
                     Single range per instrument. Pipe and open channels
OJ
                                                                   LEVEL MEASURING INSTRUMENTS
         Level     Model LM10A
         Level     Float-operated transducer    1     3.5-30 ft
         Level     Press-operated transducer    1     231 ft adj
         Level     ML-MN transmitter          1     32 inches
         Level     Series 200 liquilite           1     Fixed Ivl
         Level     Sonargage (3 mdls)          3     .5-150 ft
         Level     Super-sensor                2     Fixed Ivls
         Level     Float-actuated trmtrs        M    0-37 ft
         Level     Dp transmitters             M    0-2K inch
         Level     Liquid level instruments
         Level     Uni-sonic mdls 100, 200      1     0-200 ft
         Level     Stevens liquid Ivl instr       M
         Level     Level controls              1     Fixed Ivl
         Level     Metritape level sensor        M    2-500 ft
         Level     Interface/solids Ivl Ctrl       1     Fixed Ivl
         Level     Liquid level controller       2     Fixed Ivls
         Level     LSI27-1C Liqui   Ivl det    1     Fixed Ivl
         Level     P5200 series Ivl indie        1     2-150 ft
         Level     Zyrotron liq Ivl Ctrl sys      2     Fixed Ivls
         Sldglvl   Mdl 8100 sldg Ivl Ctrl        1     Fixed Ivl
Sonic
Float
Press
Float
Electronic
Sonar

Float
Press
Float, bblr
Sonic
Float, bblr
Float
R tape
Lite refl
Liq end
Thermal R
Press
Resistance
Photoel

R,V,A, rly, tm
V, Avrly, tm
V
Rly, tm
A, bed, rly, rcdr
Rly
Press, A, rcdr
A, nress, rcdr


Rcdr, dig, tm
Rly
V,A,R, rly, dig
Rly
Rly
Rly
V, rly
Rly
Rly
West Marine Elec
Autocon
Autocon
Badger Meter Mfg
Controlotron
C. W. Stevens
Farris Chemical
Fischer and Porter
Fischer and Porter
Foxboro
Inventron
Leopold and Stevens
Liq Lvl Lectronics
Metritape
Met-Pro Water Treatmt
Photronic
Trans-sonics
Trans-sonics
Zyrotron Industries
Keene
                     Rcdr output
                     Rcdr output, adjustable range
                     Use with primary devices—flumes, weirs, open nozzles

                     Models 3000, 3100, 3200
                     High and low level control applications
                     Used with Fischer and Porter flumes and weirs, also
                     Range suppression provided
                     Brochure not received
                     Also for sludge Ivl
                     4 models avail (3 with floats, 1 with bblr)

                     Rcdr output. Upper limit based on tape length
                     Mon and Ctrl liquid or solid particles level
                     High and low level control applications

                     V output assumed (To meter)
                     High and low level control applications
         Part size  Mdl 2150 cont part mon
                                                         PARTICLE SIZE MEASURING INSTRUMENTS

                                             2     2-100 mic          Lite scatr   Rcdr, rly          Particle Technology   Digital printer available

-------
                                                                     TABLE 5

                      AUTOMATIC MONITORING INSTRUMENTATION FOR WASTEWATER TREATMENT PROCESSES (2 of 2)
Variable
H20 qual
H20 qual
H20 quit
H20 qual
H20 qual
H20 qual
H20 qual
H20 qual
H20 qual
H20 qual
           Instrument
                                Range   Range Limits
CL
CL
CL
CL
CND
CND
CND
DO
DO
DO
F
F
ORP
ORP
ORP
        Mdl 880 resid anlzr-ctrlr
        CL resid anlzr and mon

        Resid CL anlzr mdl A-792
        Electrolytic CND cell
        CND monitor MDL 560B
        Mdls 101-11 5 CND sensors
        DO analyzer mdl 1101
        Dissolved oxygen anlzr
        Mdl 3000 DO analyzer
        Mdl 900F Fluoride anlzr
                                                       Method
                                                                    Outputs
                                                                                  Manufacturer
Comments, other outputs, water quality variables
        Mdls 1200,1250,1400,1500
        Mdl 9500 Water Qual Mon
        Series 8000 anlzrs/ctrlrs
        (Variable name) meas sys
        Series CR 2 & CR anlzrs
        H20 qual sys (4 mdls)
        Mdl 1-1000 Water qual mon
        Mdl 900
        CSM 6 Monitor
        Series 1600 H20 qual mon
                                 WATER QUALITY MEASURING INSTRUMENTS (MULTI-VARIABLE INSTRUMENTS)
        Mdls 330-331 ORP sensors
        Potential cell
02 Demand Oxymand
PH      Mdls RC, 1C, R4, 30
PH
PH      PH Electrode assembly
PH      Mdl 20 and cont rcdg mtr
PH      Mdls 320-323 PH sensors
Sludge Den Mdl 400
Susp slds Mdl ISO fluid anlzr
Susp slds Mdl 8200 anlzr/ctrlr
Susp slds W.P.R.L. Susp slds mon
TB      CR Turbidimeters (4 mdls)
TB      Turbidiphot
TC      Mdl 1610 TC analy zer
TC      TC analyzer Mdl 1212
TEMP
TEMP   Thermocouple and thermohm
TEMP   Temperature probe
TOC    Mdl 1600 TOC analyzer
TOD    Mdl 225 TOD analyzer
M
M
M
M
M
M
M

M
M








0-100 PPM

WATER QUALITY
6
5

5

M
M

2
2
3


M

1
1


1
M

3
1
3
M
1




1
2
1
0-20 PPM
0-10 PPM

0-20 PPM

0-1 OK PPM


0-25 PPM
0-1 S PPM
.1-100 PPM




0-100ML02
2-12 PH


0-14 PH

0-1
10-1 SOK PPM
500-SK PPM
0-SK MG/L
0-10KJTU
10 PPM Adj




0-50 C
0-4K MG/L
0-200 PPM
Color, othr

Color.othr

Color



Color

MEASURING
Amper
Amper

Amper
Electrode
Electrode
Electrode


Polar
Electrode


Electrode

Respir
Electrode

Electrode
Electrode
Electrode
Sonics
Back scatr
Electronic
Photoel
Nephel
Photoel


Liq tube
Thrmoc, R
Thermlster
Infrared
Combustion
V,AMdig, rly, tm
A, rcdr, tm
V, dig, tm, rly
A, rcdr, rly, tm
V, rly, rcdr
V, rly, rcdr, tm
V, rcdr, tm

V, rly, dig, tm
V, rcdr, dig, tm
INSTRUMENTS
V, rly, tm, press
A, rly, rcdr

A, V, rly, tm

V, rly
V


V, rcdr, rly
V,A


V
V
V, rly, rcdr
V, rly, rcdr, dig


V, rcdr
V

V, A, rly, rcdr
V, rcdr, rly
A, rcdr, rly
V, rly, rcdr
Rly, rcdr




V,
V,A, dig rly, tm
V, rcdr
AES
Beckman
Delta Scientific
Foxboro
Hach Chemical
Honeywell
KDI Poly-Technic
Robertshaw
Technicon
Union Carbide
(SINGLE VARIABLE
BIF
Capital Controls
Fischer and Porter
Wallace and Tiernan
Leeds and Northrup
Myron L
Universal Interloc
Union Carbide
Wallace and Tiernan
Weston and Stack
Beckman
Fischer and Porter
Fischer and Porter
Universal Interloc
Wallace and Tiernan
R.M.A. Development
Analytical Measuremts
Fischer and Porter
Leeds and Northrup
Limnetics
Universal Interloc
National Sonics Corp.
Gam Rad
Keene
Partech
Hach Chemical
Photronic
AES
Union Carbide
Fischer and Porter
Leeds and Northrup
Limnetics
AES
Ionics
Basic, NH3> BR, CA, CR, CU, F, HD, HY, I, FE, NO, PO4, SO, &
Basic &
Basic, NH3, BR, HD, CL, CM, CR, CU, CY, F, HY, FE, I, PO4, flow, &.
PH, CL, TB, ORP, CND
F, SI, PO^, CM, SO, HD, FE, CL, HY, CU, PE, PH, &.. Mon & Ctrl
Basic, &. Lvl and low velocity outputs also
Basic, CA, NO, F, DC, CU, PB, AG, SO, BR, CY, HD, I.PER. THI, &.
Brochure not received
NH,, NO, PO4, PH, HD, PN, SI, CU, F, FE, CR, DC, &,. Rcdr output
Basic (except SRI) &
INSTRUMENTS)


Brochure not received
Rcdr output avail
Brochure not received
5 CND cells avail depending on application
Flow, immersion types, Mdl 700 MA trmtr-anlzr avail
Brochure not received
Brochure not received
Uses mdl A-40 DO probe. For gas meas also

Brochure not received
Brochure 'not received
Flow, immersion types. Mdl 1021 trmtr-anlzr avail
Brochure not received
Automatic periodic sampling for monitoring and Ctrl

Brochure not received
Brochure not received
Range is adjustable
Flow, immersion, in-line types. Trmtr-anlzr avail

For meas susp slds and control of turbidity


Models 1031, 1720, 1861, 1889

Brochure not received. Mdl 1620 measures TOC and TC
Brochure not received
Brochure not received
Brochure not received
Range is adjustable
Mdl 1620 measures TOC and TC

Notes:
        (2)
             Symbols and abbreviations are given in Table 6
             Refer to Table 8 for addresses of manufacturers

-------
                                                         TABLE 6
                                           SYMBOLS AND ABBREVIATIONS
A        CURRENT  (AMPERAGE)
ACJ      AOJUSTABLEIRANGE  OR  SPREAD IS ADJ)
AG       SILVER
AMPER    AMPEROMETRIC
ANLZRIS) ANALYZER(S)
AVAIL    AVAILABLE
BASIC    BASIC WATER QUALITY  VARIABLES (TOTAL OF 8)
BBLR     BUBBLER
BCD      BINARY COOED  DECIMAL
BOO      BIOCHEMICAL OXYGEN DEMAND
BR       BROMIDE
C        CENTIGRADE
CA       CALCIUM
CC       CADMIUM
CL       CHLORINE
CM       CHROMATE
CND      CONDUCTIVITY  (BASIC  VARIABLE)
COD      CHEMICAL OXYGEN  DEMAND
CDLOR    COLORIMETRIC
CONT     CONTINUOUS
CR       CHROMIUM
CTRL     CONTROL
CTRLR(S) CONTROLLER(S)
CU       COPPER
CY       CYANIDE
OC       DISOLVED CHLORIDES  (BASIC VARIABLE)
DET      DETECTOR
DIG      DIGITAL
DO       DISOLVED OXYGEN  (BASIC VARIABLE)
EMF      ELECTROMOTIVE  FORCE
FE       IRON
F        FLUORIDE
FT       FEET
GPM      GALLONS  PER MINUTE
HO       HARDNESS
HY       HYDKAZINE
H20      HATtR
I        K1DIDF
INDIC    INDICATOR
JTU      JACKSON  TURBIC.ITY UNITS
K        1000  (FOR  EXAMPLE,  4K - 4Cm
LIO      LIUUID
LITE     LIGHT
LVL(S)   L6VELIS)
M        MULTIPLE RANGES  WITHIN MIM/MAX LIMITS
         PRCDUCED UY  SINGLfc/MULTIPLE MDOEL
MAG      MAGNETIC
MCL(S)   MODEL(S)
MFAS     "tASURINC
MGO      MILLION  GALLONS  PFR  DAY
MG/L     MILLIGRAMS/LITER
MIC      MICRONS
ML       WILLILITERS
MON      MONITOR,  MONITORING
MTR(S)   METER(S)
NEPHEL   NEPHELOMETRIC
NH3      AMMONIA
NO       NITRATE,  NITRITE
ORP      OXIDATION REDUCTION  POTENTIAL (BASIC VARIABLE)
OTHR     OTHER
02       OXYGfcN
PART     PARTICLE
PB       LEAD
PF       PERMANGANATE
PER      PERCHLORATE
PH       PH (BASIC VARIABLE)
PHOTOEL  PHOTOELECTRIC
PNL      PHENOLS
PO-4      PHOSPHATE
POLAR    POLAROGRAPHIC
PPM      PARTS PER MILLION
PRESS    PRESSURE
PRIMARY  PRIMARY FLOW MEASURING  DEV ICE(HEIR,VENTURI,£TC.I
OUAL     (JUALITY
R        RESISTANCE
RCDG     RECORDING
RCDR     RECORDER
REFL     REFLECTION
RES      RESONANCE
RESID    RESIDUAL
RESPIR   RESPIROMETRIC
RLY      RELAY
SCATR    SCATTER
SCFM     STANDARD  CUBIC  FEEI  PER  MINUTE
SI       SILICA
SLOG     SLUDGE
SLDS     SOLIDS
SO       SULFIOE,  SULFATE
SRI      SOLAK RADIATION  INTENSITY  (BASIC VARIABLE)
SUSP     SUSPENDER
SYS      SYSTEM
TP       TURBIDITY  (BASIC VARIABLE)
TC       TOTAL CARBON
TFMP     TEMPERATURE  (BASIC VARIABLE)
THI      THIOCYANATE
THRMOC   THERMOCOUPLE
TM       TELEMETRY
TCC      TOTAL ORGANIC CARHON
TOD      TOTAL OXYGEN DEMAND
TREATMT  TREATMENT
TRMTR(S) TRANSMITTERS)
V        VOLTAGE
VAC      A-C VOLTAGE
VARIOUS  VARIOUS MODELS  AVAILABLE
C        OTHFK VARIABLES AVAILABLE
                                                           75

-------
                                    TABLE 7

                              MANUFACTURERS OF
                             AUTOMATIC SAMPLERS
Brailsford & Company, Inc.
Milton Point
Rye, New York 10580

Instrument Specialties Company
4700 Superior
Lincoln, Nebraska 68504

Sirco Controls, Ltd.
8815 Silkirk Street
Vancouver 14, British  Columbia

Sanitary Engineering Research Company
4205 31st Avenue South
Minneapolis, Minnesota 55455

N-Con Systems, Inc.
410 Boston Post Road
Larchmont, New York 10538

Chicago Pump
622 Diversey Parkway
Chicago, Illinois 60614

Infilco Compnay
P.O. Box 5033
Tucson, Arizona 85703
Megator Corporation
136 Gamma Drive
Pittsburg, Pennsylvania 15238

Penberthy
P.O.Box 112
Prophetstown, Illinois 61277

Sigma Motor, Inc.
3 North Main Street
Middleport, New York 14105

Testing Machines, Inc.
6078 Sherbrooke Street
W. Montreal 28, Quebec

Calhoun & Sons Instruments
8227 Hampton
Gross  He, Michigan 48138

Pro-Tech, Inc. •
Lester Industrial Center
Lester, Pennsylvania 19113
                                      76

-------
                                                            TABLE 8
                                               MANUFACTURERS ADDRESSES
AES Automated Environmental Systems
135 Crossways Park Drive
Woodbury, New York 11797

American Meter Controls, Inc.
13500 Philmont Avenue
Philadelphia, Pennsylvania 19116

Analytical Measurements, Inc.
31 Willow Street
Chatham, New Jersey 07928

Autocon Industries, Inc.
995 University Avenue
St. Paul, Minnesota 55104

Badger Meter Manufacturing Co.
4545 West Brown Deer Road
Milwaukee, Wisconsin 53223

Beckman Instruments, Inc.
2500 Harbor Boulevard
Fullerton, California 92634

BIF
345 Harris Avenue
Providence, Rhode Island 02901

Brooks Instrument Div.
Emerson Electric Company
Hatfield, Pennsylvania 19440

Capital Controls Co., Inc.
Advance Lane
Colmar, Pennsylvania 18925
Controlotron Corporation
35 Central Avenue
Farmingdale, L. I. New York  11735

C. W. Stevens, Inc.
P.O. Box 619
Kennett Square, Pennsylvania 19348

Delta Scientific Corporation
120 East Hoffman Avenue
Lindenhurst, New York 11757

Farris Chemical Compnay, Inc.
P.O. Box 10126
Knoxville, Tennessee 37919

Fischer and Porter Company
Warminster, Pennsylvania

Foxboro Company
Neponset Avenue
Foxboro, Massachusetts 02035
Gam Rad, Inc.
16825 Wyoming Avenue
Detroit, Michigan 48221

Hach Chemical Company
Box 907
Ames, Iowa 50010
Hersey-Sparling Meter Company
4097 North Temple City Boulevard
El Monte, California 91730
Honeywell Industrial Div.
1100 Virginia Drive
Fort Washington, Pennsylvania 19034

Inventron Industries, Inc.
6508 South Arizona Avenue
Los Angeles, California 90045
Ionics, Inc.
65 Grove Street
Watertown, Massachusetts 02172

KDI Poly-Technic, Inc.
10540  Chester Road
Cincinnati, Ohio 45215

Keene Corporation
Water Pollution Control Div.
1740 Molitor Road
Aurora, Illinois 60507

Leeds and Northrup Company
Sumneytown Pike
North Wales, Pennsylvania 19454
Leopold and Stevens, Inc.
P.O. Box 25347
Portland, Oregon 97225
Limnetics, Inc.
6132 West Fond Du Lac Avenue
Milwaukee, Wisconsin 53218
Liquid Level Lectronics, Inc.
P.O. Box 1002
Richardson, Texas 75080

Met-Pro Water Treatment Corporation
5th Street and Mitchell Avenue
Lansdale, Pennsylvania 19446
Metritape Controls, Inc.
50 Commonwealth Avenue
West Concord, Massachusetts 01781
Myron L. Company
656 First Street
Encinitas, California 92024

National Sonics Corporation
43 Milbar Boulevard
Farmingdale, New York 11735
Partech, Ltd.
7 Broadwater Road, Welwyn Garden City
Hertfordshire, Great Britain

Particle Technology, Inc.
734 North Pastoria Avenue
Sunnyvale, California 94086

Photronic, Inc.
411 Cheltena Avenue
Jenkintown, Pennsylvania 19046

Ramapo Instrument Company, Inc.
Bloomingdale, New Jersey 07403

R.M.A. Development, Inc., Products Division
P.O. Box 1222
Fond Du Lac, Wisconsin 54935

Robertshaw Controls
P.O. Box 400
Knoxville, Tennessee 37901

Technicon Corporation
Tarrytown, New York 10591

Trans-Sonics, Inc.
P.O. Box 326
Lexington, Massachusetts 02173

Union Carbide Corporation
Instrument Department
5 New Street
White Plains, New York 10601

Universal Interloc, Inc.
17401 Armstrong Avenue
Santa Ana, California 92705

Wallace and Tiernan Div.
25 Main Street
Belleville, New Jersey 07109

Western Marine Electronics
509 Fairview Avenue North
Seattle, Washington 98109

Westinghouse Electric Corporation
P.O. Box 1488
Annapolis, Maryland 21401

Weston and Stack, Inc.
1426 Lewis Lane
West Chester, Pennsylvania 19380

Zyrotron Industries, Inc.
600 Huyler Street
South Hackensack, New Jersey 07606
                                                          77

-------
1
Accession Number
w
5
2

Subject Field & Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
       The  American  Public Works  Association,  Chicago,  Illinois 60637
    Title
       FEASIBILITY OF  COMPUTER CONTROL OF WASTEWATER TREATMENT
1 Q Authors)
American Public Works Association
16

21
Project Designation
EPA Contract
14-12-580; APWA 66-68
Note
22
     Citation
23
     Descriptors (Starred First)
                *Computers,  *Wastetfater  Treatment,  *Monitoring,  *Control
25
     Identifiers (Starred First)
27
     Abstract
                                    ABSTRACT:  This report  contains  the  results  of an
                                       investigation  into  the use  of  digital  computers  for
                                       management  and  control  of  wastewater  treatment
                                       facilities.  The  objectives  of the  study included  the
                                       generation of guidelines for implementation of digital
                                       computers for these purposes and recommendations for
                                       further relevant research.
                                       For the purpose of gathering information, visits were
                                       made to plants  and the literature  was searched. A survey
                                       was conducted  of current practices and problems in the
                                       operation of wastewater treatment plants. Emphasis was
                                       placed on the  processes of secondary treatment with
                                       regard to management and  control of  unit processes,
                                       continuous monitoring needs, the  influences of regulatory
                                       agencies, and  certain local conditions. A set of guidelines
                                       and steps for  computer control implementation  and
                                       peripheral applications were evolved.
                                       It was concluded that both off-line computer applications
                                       and on-line computer control in wastewater treatment are
                                       feasible and should be implemented.
                                       This Report  was submitted in fulfillment of_ Contract
                                        14-12-580 between the Environmental Protection Agency,
                                       the American Public Works Association and nineteen cost
                                       sharing local governmental agencies.
Abstractor
R.
H
WR.-102 (REV.
WRSIC
. Sul
JULY
.1
ivan
Institution
)969) SEND, WITH COPY
APWA
OF DOC
Research
UMENT. TO:
Foundation
WATER RESOURCE
U.S. DEPARTMENT
WASHINGTON. D. C


QF THE
. 20240

INTERIOR
                                                                                                            * CPO: 1970 — 389-930

-------