United States
            Environmental Protection
            Agency
             Municipal Operations Branch    EPA/430/9-79-010
             Office of Water Program Operations  April 1979
             Washington DC 20460
?/EPA
            Water
Inspectors Guide
for Evaluation
of  Municipal Wastewater
Treatment Plants

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                                 INSPECTOR'S GUIDE:
                             TO BE USED  IN THE EVALUATION
                      OP MUNICIPAL WASTEWATER TREATMENT PLANTS
                                           by
                                  Daniel J.  Hinrichs
                                   Culp/Wesner/Culp
                                     P.O. Box  40
                             El  Dorado Hills,  CA 95630
                            EPA Contract No.  68-01-4727
                                      April  1979
                                    Prepared for
                            Municipal Operations Branch
                        Office of Water  Program Operations
                       U.S.  Environmental  Protection  Agency
                              Washington, D.C.   20460
I
                    For sale by the Superintendent of Documents, U.S. Government Printing Office
                                    Washington, D.C. 20402
                                  Stock Number 055-002-00169-6

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                                  DISCLAIMER
     This report has been reviewed by the Municipal Operations Branch,
     Environmental Protection Agency, and approved for publication -
U.S.
Approval does not
and policies of the U.S
of trade names or
recommendation for use.
signify that the contents necessarily reflect the views
e U.S. Environmental Protection Agency, nor does mention
commercial products constitute endorsement or

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                                ACKNOWLEDGEMENTS

    Contributors to the various unit process sections within this manual
includes the following Culp/Wesner/Culp staff members:

                          Justine Faisst
                          Bruce Winsor
                          Bruce Burr is
                          Tom Lineck
                          Rob Williams
                          Sig Hansen
                          William Ettlich (principal)

    The advice and encouragement of Lehn J.  Potter, Municipal Operations
Branch of the EPA is greatly appreciated.

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                                    PREFACE

    This inspectors guide  is designed to provide state and EPA  inspectors with
the background necessary to evaluate the operation and maintenance of waste-
water treatment plants.  This guide also provides the information necessary to
make subjective judgements required for plant evaluation.  The  guide includes
checklists for individual unit processes.

    This guide has been developed simultaneously with a new EPA O&M inspection
form.  In addition to being a training tool the guide provides  a reference
source for inspectors.  To provide a complete O&M reference file, there are
several other EPA manuals that should be used in conjunction with this guide.
They are:
    1.
    2.
Field Manual  for Performance Evaluation  and Troubleshooting  at
Municipal Wastewater Treatment 'Facilities. U.S.E.P.A., Municipal
Operations Branch, Office of Water Program Operations, Washington,
D.C. 20460, EPA-430/9-78-001.

Operations Manual, Sludge Handling and Conditioning, U.S.E.P.A.,
Municipal Operations Branch, Office of Water Program Operations,
Washington, D.C. 20460, EPA-430/9-78-002.
    3-    Operations Manual.  Stabilization Ponds.  U.S.E.P.A.,  Municipal
    4.
Operations Branch, Office of Water Program Operations, Washington,
D.C. 20460, EPA/430-9-77-012.

Operations Manual, Anaerobic Sludge Digestion, U.S.E.P.A., Municipal
Operations Branch, Office of Water Program Operations, Washington,
D.C. 20460, EPA-430/9-76-001.

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                                    CONTENTS
  I.  OVERALL PLANT MANAGEMENT
       Staffing and Training
       Revenue Program
       Budgeting
       Maintenance Management
       Records Keeping
       Sampling and Laboratory Testing

 II.  SAFETY
       General
       Chlorination
       Ozonation
       Activated Carbon Columns
       Recarbonation
       Ferric Chloride Feeding
       Lime Feeding
       Other Chemical Feeding
       Furnaces and Incinerators
       Heat Treatment
       Anaerobic Digesters
       Pressure Filtration

III.   PLANT HYDRAULICS

 IV.   COMPATIBILITY OF UNIT PROCESSES

  V.   UNIT PROCESS EVALUATION SECTIONS
     Section

        1
        2
        3
        4
        5
        6
        7
        8
        9
       10
       11
Unit Process

Raw Sewage Pumping Stations
Screening
Shredding
Grit Removal
Primary Sedimentation
Activated Sludge
Trickling Filters
Activated Bio Filters (ABF)
Lagoons
Rotating Biological Contactors  (RBC)
Secondary Sedimentation
                                          Page

                                            1
                                            2
                                            2
                                            3
                                            5
                                            6
                                            7
                                            9
                                           10
                                           13
                                           13
                                           13
                                           14
                                           15
                                           16
                                           16
                                           17
                                           18

                                           19

                                           20
Pages
1-1
2-1
3-1
4-1
5-1
6-1
7-1
8-1
9-1
10-1
11-1
- 1-8
- 2-5
- 3-5
- 4-8
- 5-9
- 6-11
- 7-8
- 8-10
- 9-12
- 10-8
- 11-7

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CONTENTS (Continued)
     Section

       12
       13
       14
       15
       16
       17
       18
       19
       20
       21

       22
       23
       24
       25
       26
       27  ,.
       28
       29
       30
       31
       32
       33
       34
       35
       36
       37
       38
       39
       40
       41
       42
Unit Process

Chlorination
Ozonation
Filtration
Microscreen ing
Carbon Adsorption
Nitrification
Denitrification
Ammonia Stripping
Chemical Feeding
Rapid Mixing, Flocculation  and
Chemical Clarification
Recarbonation
Land Application of Wastewaters
Flow Measurement
Sludge Pumping
Chemical Conditioning
Thermal Treatment
Gravity Thickening
Flotation  Thickening
Anaerobic  Digestion
Aerobic Digestion
Centr ifugation
Vacuum Filtration
Pressure Filtration
Drying Beds
Drying Lagoons
 Incineration-Multiple Hearth
 Incineration-Fluidized Bed
 Lime Recalcining
 Carbon Regeneration
 Land Application  of  Sludges
 Landfill
                                                                     Pages
12-1
13-1
14-1
15-1
16-1
17-1
18-1
19-1
20-1
21-1
22-1
23-1
24-1
25-1
26-1
27-1
28-1
29-1
30-1
31-1
32-1
33-1
34-1
35-1
36-1
37-1
38-1
39-1
40-1
41-1
42-1
- 12-7
- 13-8
- 14-9
- 15-6
- 16-9
- 17-18
- 18-7
- 19-7
- 20-8
- 21-15
- 22-8
- 23-10
- 24-4
- 25-4
- 26-5
- 27-6
- 28-7
- 29-8
- 30-9
- 31-9
- 32-7
- 33-7
- 34-7
- 35-7
- 36-5
- 37-7
- 38-8
- 39-6
- 40-5
- 41-7
- 42-7
                                        VI

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                                    FIGURES
Number

   1   Ozone toxicity
  1-1  System-head pump curves
  4-1  Estimated unit process sampling and testing needs - pretreatment
  4-2  Estimated unit process sampling and testing needs - pretreatment
  5-1  Estimated removals of suspended solids and BOD in primary
         basins at various hydraulic loadings
  5-2  Estimated unit process sampling and testing needs - primary
         clarification
  6-1  Activated sludge flow diagram
  6-2  Estimated unit process sampling and testing needs - secondary
         treatment
  7-1  Estimated unit process sampling and testing needs - secondary
         treatment
  8-1  Estimated unit process sampling and testing needs - activated
         biofilter process
  9-1  Estimated unit process sampling and testing needs - secondary
         treatment
  9-2  Estimated unit process sampling and testing needs - secondary
         treatment
 10-1  Rotating biological media for secondary treatment
 10-2  Estimated unit process sampling and testing needs
         treatment
 11-1  Estimated unit process sampling and testing needs
         treatment
 12-1  Estimated unit process sampling and testing needs - disinfection
 13-1  Basic ozonator configuration
 13-2  Estimated unit process sampling and testing needs
 14-1  Estimated unit process sampling and testing needs
 15-1  Estimated unit process sampling and testing needs -
         microscreening
 16-1  Expansion of carbon bed at various flow rates
 16-2  Estimated unit process sampling and testing needs -
         activated carbon adsorption
 17-1  Effect of BOD5 concentration and hydraulic load on
         nitrification in the RBC process
 17-2  Design relationships for  a 4-stage RBC process treating
         secondary effluent
 17-3  Estimated unit process sampling and testing needs -
         nitrification
secondary

secondary
ozonation
filtration
  1.1
 1-2
 4-4
 4-5

 5-3

 5-6
 6-2

 6-8

 7-5

 8-6

 9-7

 9-8
10-2

10-5

11-4
12-5
13-2
13-5
14-6

15-3
16-3

16-7

17-5

17-6

17-8
                                      vii

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FIGURES  (Continued)

Number

 17-4  Estimated unit process sampling and testing needs
         nitrification
 17-5  Estimated unit process sampling and testing needs
         nitrification
 17-6  Estimated unit process sampling and testing needs
         nitrification
 18-1  Estimated unit process sampling and testing needs
         denitr ification
 19-1  Estimated unit process sampling and testing needs
         nitrogen removal
 21-1  Power requirements for rapid mix and flocculation
 21-2  Estimated unit process sampling and testing needs
         chemical treatment
 22-1  Estimated unit process sampling and testing needs
         two stage recarbonation
 23-1  Estimated unit process sampling and testing needs
         land treatment
 27-1  Estimated unit process sampling and testing needs
         solids reduction
 28-1  Estimated unit process sampling and testing needs
         sludge concentration
 29-1  Estimated unit process sampling and testing needs
         sludge concentration
 30-1  Estimated unit process sampling and testing needs
         solids reduction
 30-2  Estimated unit process sampling and testing needs
         solids reduction
 31-1  Estimated unit process sampling and testing needs
         solids reduction
 32-1  Estimated unit process sampling and testing needs
         sludge concentration
 33-1  Estimated unit process sampling and testing needs
         sludge concentration
 34-1  Estimated unit process sampling and testing needs
         sludge concentration
 35-1  Estimated unit process sampling and testing needs
         drying beds
 37-1  Estimated unit process sampling and testing needs
         incineration
 38-1  Fluidized bed  furnace system monitoring  points
 39-1  Estimated unit process sampling and testing needs
         recalcination
  40-1  Estimated unit process sampling and testing needs -
          carbon regeneration
  41-1  Estimated unit process sampling and testing needs -
          land application of sludges
  42-1  Estimated unit process sampling and testing needs -
          landfill
 17-9

17-10

17-11

 18-4

 19-4
 21-6

21-11

 22-5

 23-7

 27-3

 28-4

 29-4

 30-4

 30-5

 31-5

 32-5

 33-4

 34-4

 35-4

 37-5
 38-5

 39-3

 40-3

 41-3

 42-4
                                       viii

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                                     TABLES
Number
   1   Minimum Recommended Safety Equipment for Wastewater Works
         Personnel                                                           8
  6-1  Typical Activated Sludge Design Parameters                          6-3
  6-2  Summary of Operating Data - Activated Sludge Plants                 6-5
  7-1  Trickling Filter Classification                                     7-1
  8-1  Typical Activated Biofilter Design Criteria                         8-2
  9-1  Empirical Design Criteria for Waste Stabilization Lagoons           9-2
  9-2  Alternative Operational Strategies for Unaerated Aerobic
         and Facultative Lagoons                                           9-5
 11-1  Typical Loading Rates for Secondary Sedimentation Basins           11-2
 12-1  Estimate of Chlorine Demand for Various Wastewaters                12-1
 14-1  Design Criteria for Orange County Water District Open
         Gravity, Mixed Media Filter System                               14-4
 15-1  Microscreen Design Parameters                                      15-2
 17-1  Design Parameters for Typical Suspended Growth
         Nitrification Systems                                            17-2
 17-2  Hydraulic Loading for Two-Stage Nitrifying Trickling Filter        17-3
 17-3  General Design Parameters for Nitrification of Domestic
         Wastewater with ABF Process                                      17-4
 17-4  Substances Toxic to Nitrifying Organisms                           17-7
 20-1  Some Chemicals and Their Principal Uses in Wastewater Treatment    20-2
 21-1  Velocity Gradients (G)  for Rapid Mix                               21-2
 21-2  Typical Design for 10 MGD Rapid Mixer                              21-2
 21-3  Typical Design for 10 MGD Flocculator                              21-3
 21-4  Velocity Gradients (G)  for Flocculation Basins                     21-3
 21-5  Typical Design for 10 MGD Clarifiers                               21-4
 21-6  Typical Phosphorus Removal Efficiencies                            21-4
 21-7  Equations Used to Evaluate Rapid Mix and Flocculation Systems      21-5
 21-8  Temperature Corrections                                            21-7
 23-1  Typical Design Criteria for Irrigation, Infiltration-Percolation,
         and Overland Flow Systems for Municipal Wastewater               23-3
 28-1  Gravity Thickener Typical Loadings and Performance                 28-2
 29-1  Flotation Thickener Operation and Performance                      29-2
 30-1  Digester Supernatant Quality                                       30-6
 31-1  Aerobic Digestion Design Parameters                                31-2
 32-1  Expected Centrifuge Performance                                    32-3
 33-1  Vacuum Filtration Typical Loadings and Performance                 33-2
 34-1  Typical Results Pressure Filtration                                34-2
.37-1  Multiple Hearth Furnace Loading Rates                              37-1
 37-2  Stack Sampling Results, Multiple Hearth Incinerator with
         Combination Lime-Organic Solids Feed                             37-3
 38-1  Loading Rates                                                      38-1
                                       IX

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TABLES  (Continued)
Number

 38-2
 41-1
 42-1
 42-2
 42-3
Monitoring
Rate Determination  (tons/acre)
Design Criteria
Well Analysis
Drainage Ditch Analysis

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 I.  OVERALL  PLANT MANAGEMENT

    Proper operation  and maintenance of  a wastewater  treatment plant  requires
 qualified staff  and a certain degree of  effort on  the part of the operating
 agency.  This effort  can be expressed  in terms of  budgets, industrial waste
 ordinances,  and  willingness to hire and  maintain qualified personnel.   The
 overall plant management review should include budgets,  user .charges, indus-
 trial waste  ordinances and enforcement,  staff numbers and qualification (cer-
 tification) , salary levels, promotion opportunity, maintenance management, and
 more.  To simplify, the overall plant management can  be  divided  into  the  fol-
 lowing areas:

         Staffing and training
         Revenue program
         Budgeting
         Maintenance  management
         Records keeping
         Sampling and laboratory testing

 Staffing and Training

    A major part of evaluating the staffing and training at a wastewater
 treatment plant  requires some subjective judgement by the inspector.  Subjec-
 tive judgements  are difficult to make without several years of experience.
 These evaluations are often complicated by special circumstances found  within
 local or. regional areas.  However, after reviewing several plants subjective
 judgements should be  easy to make.  The  first step is to review  the staff
 numbers and certification level.  Staffing levels for different  types of
plants and unit  processes are published  in two EPA publications, "Estimating
 Staffing for Municipal Wastewater Treatment Facilities", 68-01-0328, March,
 1973(1), ancj "Estimating Costs and Manpower Requirements for Conventional
Waste Treatment  Facilities", 17090 DAN 10/71, October, 197l(2).  These  are
 for guidance only.   Local conditions, number of shifts, and days per week of
operator coverage will determine the right staffing level for each plant.  If
 the staffing numbers  are close to that recommended by the publications, then
 the numbers should be adequate.   Certification requirements are different for
each state.  Some are mandatory and some are voluntary.  The operations staff
certification levels  should be compared to the applicable state recommenda-
 tions.
    The staff training opportunities should be reviewed for availability of
courses and operating authority policies for providing expenses and time off
from work.  The training program should be available to all personnel rather
than supervisory staff only.  The agency budgets funds for training but there
is no guidance as to the proper amount, due to area constraints and cost vari-
ations.  There should be some planned training effort by the agency for train-
ing new operators and keeping trained operators up to date with new processes/
and operations techniques.

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      The roost difficult analysis to make is that regarding operator compe-
  tency.   Unfortunately, many courses and certification exams neglect areas of
  process control.   Many operators are well trained in the mechanics of treat-
  ment plant operation but have no knowledge as to proper  control techniques to
  optimize unit process performance.   The only way to judge operator competency
  is  to compare treatment results with other agencies having similar systems and
  waste characteristics.

      Other  areas to review include the O&M staff salary schedule and promotion
  potential.   A national salary survey of treatment plants and collection  sys-
  tems was published by the Water Pollution Control Federation in their  May 1977
  issue of "Deeds and  Data".   This survey result  provides  some guidance  as  to
  average  salaries being  paid  to  O&M personnel.   Promotion potential is  impor-
 tant for minimizing  staff turnover,  which  in  turn minimizes  training
  requirements.

 Revenue Program

     A well designed revenue program will not  insure good  operation and mainte-
 nance but will provide  the funds necessary to operate and maintain the facil-
 ity as wen as money for  future replacement of equipment.  All  facilities that
 receive federal grant funds after 1974  should have approved  revenue programs.

     There can be many variations in revenue programs.  Generally, the revenues
 should equal costs (including buildup and maintenance of a reserve fund)    The
 revenues should  be obtained by a system of equitable user charges.  Equitable
 user charges are determined depending on local constraints.  For example, if
 the  system receives only domestic waste, the users would pay based on a flat
 rate per hookup  for each family,  if there is an industrial user, then the
 user charge should be based on the contribution in terms  of flow and strength
 of wastewaters.   If the wastewater strength is basically  equivalent to domes-
 tic  waste,  then  the user charge should be based on flow only.  Three example
 models are shown  in Appendix B to federal regulations, "Construction Grants
 for  Waste Treatment Works", found in the Federal Register dated February  11,
 1974 

     Usually,  if the operating authority has a revenue program in effect,  it
 will be  acceptable.   This information is normally not available at the  plant
 and  must  be obtained  at the authority's main  office.

 Budgeting

    One of  the most neglected areas with small treatment  plants is  the
 budget.  Often workers  are divided between  operating  a wastewater  treatment
plant and other duties  (e.g.  water plant,  sewer  lines,  street-repair, etc.)
Chemicals may be purchased  for use at  several  places.   The net  result is that
no one really knows the  cost  of  operating  the  wastewater  treatment plant
References 1, 2,  and 3 can provide information as  to  the  cost for operating
and maintaining most unit processes.  There are many publications available on

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costs but those showing total plant cost should be avoided.  Instead, the cost
for individual unit processes should be determined and the total plant O&M
cost determined by adding the individual unit costs.

    The correct budgeting procedures should include allowances for emergency
repairs, special expenses such as operator training and schools, and the
planned expenses for salaries, utilities, and bond repayment.  As with revenue
programs there are no one or two "correct" methods for budgeting.  A budget
should be prepared so that the actual costs of operation and maintenance can
be reviewed in several categories such as salaries, electricity, chemicals,
fuel, laboratory cost, and training.

Maintenance Management

    The publication, Maintenance Management Systems for Municipal Wastewater
Facilities provides an excellent guide -for determining adequacy of maintenance
systems.  A simplified version of their evaluation guidelines follows:

     1.  Is there an equipment numbering or other  identification system to aid
         in locating and identifying all major items of equipment?

     2.  Is there a system for maintaining nameplate data and other essential
         information on all major equipment items within the treatment system?

     3.  Does the maintenance record system provide for listing preventive
         maintenance  (PM) tasks, giving their frequency and recording the PM
         work performed?

     4.  Does the maintenance record system provide for recording corrective
         maintenance work performed?

     5.  Does the maintenance record system provide for recording such infor-
         mation as maintenance manhours, spare parts or components used in
         repair and name of individual performing each job?

     6.  Does the maintenance record system provide for recording all mainte-
         nance related costs and can these costs be readily compiled for use
         in maintenance budget preparation?

     7.  Are miscellaneous maintenance related documents such as as-built
         drawings, construction specifications and photos, shop drawings and
         manufacturers' literature properly filed and indexed and readily
         available to maintenance staff?

     8.  Is some form of schedule chart or priority list provided to assist
         maintenance supervisors in controlling maintenance tasks?

     9.  Are there planned and scheduled preventive maintenance  (PM) tasks for
         all major equipment items within the treatment system?

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      a.    Are  PM frequencies  based upon manufacturers'  recommendations and
           by  inspection?

      b.    Does the  existing maintenance organization permit  the proper
           scheduling of required PM and take  into  account the  corrective
           maintenance manhour requirements?

 10.   Are potential  corrective maintenance  tasks  adequately considered  in
      maintenance planning?

 11.   Is there  a work order system that  satisfies the treatment system's
      maintenance requirements?

 12.   Are manpower management  techniques used  effectively  to  obtain maximum
      utilization?                         .
                                          t
 13.   Is there  some  form of labor  standards to assist in preparing accurate
      work  estimates for repetitive  maintenance jobs?

 14.   Are contracting services utilized  for maintenance tasks beyond  staff
      capability.

 15.   Is there  a storeroom or  storage area to  assist  in controlling the
      flow  of spare  parts, components and maintenance supplies?

 16.   Have  manufacturers' recommendations been reviewed and each  major
      equipment item's maintenance requirements been  studied  to determine
      what  maintenance items should  be maintained?

      a.    Has  a system been developed to monitor qualities of all mainte-
           nance items kept in  stock?

      b.    Have  minimum and maximum quantities been established for all
          maintenance items kept in stock?

      c.    Is there  a purchase  order system that  adequately controls  the
          procuring of maintenance  items?

17.   Is there  a catalog or index system to assist in  identifying and lo-
     cating a  given item in the storeroom?

18.   Is there  a storeroom ticket or withdrawal slip  to use when mainte-
     nance items are taken from stock?

19.  Is there a maintenance organization chart that satisfies treatment
     system requirements?

20.  Is the maintenance organization chart reviewed and updated as
     required?

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    21.  Are there job descriptions for each job title within your maintenance
         organization?

    22.  Are job descriptions kept up to date and made available to mainte-
         nance personnel as required?

    23.  Prior to initiating any program to correct deficiencies in a mainte-
         nance job, is a thorough analysis of this job performed?

    24.  Is there a maintenance training program that satisfies the mainte-
         nance objectives of the treatment system?

    25.  Are maintenance costs broken down by maintenance categories such as
         preventive maintenance, corrective maintenance and major repairs or
         alterations?

    26.  Is there a system of cost codes or charge numbers for allocating
         labor and materials to specific maintenance jobs?

    27.  Is there a system for recording the maintenance cost history of all
         major equipment items?

    28.  Is there a system for compiling cost information for use in budget
         preparation and maintenance cost studies.

    29.  Is there a system for recording contract maintenance costs so they
         can be used in preparing maintenance budgets?

    The above evaluation would apply mainly to large, complex systems.
Although all the details would not be necessary for a small system, the prin-
ciples would be applicable.  Basically, any system should provide information
as to costs and materials necessary for maintenance of all items in the plant.

Records Keeping

    The three major areas of record keeping are maintenance, laboratory (unit
process and plant performance), and cost accounts.  Maintenance records were
discussed in the previous section.  Laboratory records can be divided into two
areas.  One area is that.required for NPDES permits reporting.  Preprinted
forms are usually provided by the enforcement agency.  The other area is indi-
vidual unit process control test results.  Historical record keeping of indi-
vidual unit processes is extremely important for process problem solving or
troubleshooting.  Often process upsets occur during certain seasons of the
year or during certain unusual events such as weather extremes or specially
planned social activities where large numbers of people visit from outside the
service area (e.g. small tourist towns).  Records of process performance will
show when the previous problems occurred and when corrections were made.  The
corrections made should be noted in the record or in an operators diary.  This
way previously attempted corrective action can be reviewed to see how effec-
tive it was.  This procedure can be accomplished very simply through the use
of trend charts.  When a trend is reversed the probable reason should be
written down.

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     Regardless  of the procedure  used there  should be a means of identifying
 and recording periods when process  upsets occurred.

     Cost  accounts are the  most often neglected  area  in small wastewater  treat-
 ment plants.  When good  records  are kept, the operating agency  is  more  likely
 to  be  aware of  the need  for replacing high  maintenance equipment.   For exam-
 ple, a pump requiring frequent costly repair should  be replaced.   This deci-
 sion is a judgement decision which  can only be  made  if accurate records  have
 been kept.  General utilities can be a major cost factor  in  a treatment
 plant.  If fuel costs increase at a faster  rate  than the  unit cost then  there
 is  a chance that  fuel is being wasted or a  unit  being  operated  improperly
 (e.g.  incinerator  temperature too high).  There  is no  one correct  system,  but
 the system used should provide the  information  necessary  to  determine a  de-
 tailed breakdown  of all expenditures required to operate  and maintain the
 wastewater treatment  system.

     Often, these  records will be kept at the agency's  main office  or the city
 hall.  The inspector  should either  request  in advance  that the  records be
 available at the  treatment  plant or  be prepared  to visit  the agency's main
office.
Sampling and Laboratory Testing

    Proper procedures and techniques for laboratory analyses are presented in
references 4, 5, and 6.  A facilities inspector should be sure that laboratory
personnel are aware of the proper techniques.  He should also observe a sam-
pling procedure and one analysis to see if the staff personnel are conscien-
tious in doing their work.

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II.  SAFETY

General

    Management has the primary responsibility for safety.  The inspector
should examine the plant safety program and verify that a complete and effec-
tive program has been established.  He should also observe plant personnel to
verify that they actually perform their duties in a safe manner.

    Certain process units involve particular hazards, and these will be dis-
cussed in greater detail later in this section.  The requirements of an effec-
tive overall plant safety program are discussed here.  Reference 8 provided
much of the background for development of this section.

    Management's responsibility for safety consists of four major areas:

    1.   Providing a safe place to work.
    2.   Providing safe equipment and tools.
    3.   Hiring only qualified personnel or personnel with the aptitude to be
         trained.
    4.   Training workers for job skills as well as safety precautions.

    The first two areas are self-explanatory.  The plant has to be designed
and constructed so that unsafe conditions can be avoided.  Then the facility
must be maintained to prevent unsafe conditions from developing.  Some of the
features of plant design and maintenance relating to safety which the inspec-
tor should check include:

    Handrails should be provided around all basins and openings.

    All stairs, walkways, and platforms should be free of grease, oil, and
    debris, and should be well lighted.

    Adequate ventilation systems should be provided for all enclosed spaces.

    Life preservers and throwlines should be provided adjacent to all basins,
    ponds, and lagoons.

    Protective guards should be provided on all rotating machinery.

    Protective guards and handrails which can be removed for maintenance
    should be in place.

    Where flammable gases may be present, explosion-proof electrical equipment
    should be provided and all bolts, gaskets, globes and guards should be
    intact.

    Carbon dioxide fire extinguishers should be provided adjacent to motor
    control centers and automatic control systems.

    Signs should be provided at the entrances of all wetwells and rooms in
    which toxic or flammable gases may be present.

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     Signs should be provided at the entrance to all rooms in which high volt-
     age electrical equipment is located.

     Instrumentation for the detection of toxic and flammable gases and low
     oxygen levels should be provided and should be operational.

     All boats at lagoons should be provided with at least two life jackets.

     All vehicles should be equipped with appropriate safety equipment,
     including lights,  horns, windshield washers and fire extinguishers.

     Pressure vessels should be operating within their design rating and should
     have a pressure relief, where appropriate.

     A list of minimum recommended safety equipment is shown on Table l(&).


 TABLE 1.   MINIMUM RECOMMENDED SAFETY EQUIPMENT  FOR WASTEWATBR WORKS PERSONNEL
                 Equipment
     Portable air  blower  (gas motor  or
     electric motor  operated)

     Electric explosion-proof lantern
     Safety  harness
    Hose mask with  hand blower and
    50-ft hose
    Self contained breathing
    apparatus for plants using
    chlorine

    Explosion and oxygen meters
               Use
Ventilating manholes and other
enclosed  subterraneous  structures

Illumination  in  tanks or sewers
where gas may be present

For workers entering deep manholes
or tanks

Respiratory protection  in all gas
and vapor atmospheres including
oxygen deficiency

Respiratory protection  against
chlorine gas leaks
Monitor air around pure oxygen
processes
    The third area is difficult when hiring new employees.  New employees may
not be qualified for their new job but may be trained.  Those that do not have
the physical or mental capability to do the work or do not possess the neces-
sary aptitude to perform certain tasks will be more susceptible to accidents.
It is therefore, important to see that new employees were properly evaluated
before hiring them and time was spent with them to see that they are given
proper instructions on both job skills and safety training.

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    The fourth area is an extension of the third  in that a program should be
provided for all employees to continually be given skill and safety  training
so that chances for accidents are minimized.

    Each safety program should include a list of  safety rules for all
employees to learn and use.  An inspector cannot  enforce safety rules but a
written set of safety rules should be available to all employees.

    The safety rules should include the following areas(9).
     1.  Personal hygiene
     2.  Fire protection
     3.  Protection around openings
     4.  Tools & safety equipment
     5.  Accidents & first aid
     6.  Safety drill procedures
     7.  Gases
     8.  Created hazards
     9.  Accident preventation
    10.  Driving safety
11.  In-plant traffic
12.  Machinery guards
13.  Ventilation
14.  Gas utilization
15.  Structures
16.  Housekeeping
17.  Safe operation
18.  Electrical equipment
19.  Procedures for one-man shifts
20.  Laboratory
    A detailed, well-written safety manual should include the above plus spe-
cific rules for individual unit processes.

Chlorination
    Chlorine is a highly toxic gas which may be fatal if inhaled in sufficient
quantity.  The presence of chlorine is easily detected however.  A concentra-
tion of 3.5 parts per million of chlorine by volume is detectable.  At concen-
trations between 15 and 30 parts per million significant irritation of the
mucus membranes and nasal linings will occur.  Exposure to chlorine at a con-
centration of 1,000 parts per million will result in fatalities in a very
short exposure time.  Most chlorination facilities using gaseous or liquid
chlorine are designed to rigorous safety standards presenting minimum hazards
to operating personnel.  An adequately designed facility will have contin-
uously monitoring chlorine leak detectors which sound an alarm in the event of
a leak.  The following safety requirements should be met for any chlorine
application facility.

     1.  Chlorination equipment should always be placed in an adequately ven-
         tilated room and isolated from other working areas.  Ventilation
         should be provided with fan at floor level since chlorine is heavier
         than air.  Access should be from an outside door.

     2.  Provisions should be made to continuously ventilate the area sur-
         rounding the chlorine cylinders and the chlorination equipment.

     3.  Equipment should be provided for continuous monitoring of the air in
         chlorine storage and application area.

     4.  Proper instructions and supervision to workers charged with responsi-
         bility of chlorination equipment should be provided.

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      5.   Proper  and  approved  self-contained breathing  apparatus for  persons
          working where  there  is  a possibility  of exposure  to chlorine  gas
          fumes should be provided,  should  be stored  outside  the area of
          danger, and should be quickly  accessible.

      6.   Combustible or inflammable materials  should never be stored near
          chlorine containers  or  application equipment.

      7.   Heat should never be applied to any chlorine  container.

      8.   A water supply to keep  chlorine containers  cool in  case of  fire
          should be provided.

      9.   Several appropriate  emergency  container  leak  repair  kits  should  be
          stored near the chlorine application  facility.

    10.   Plant safety rules should  require  that  any  leak in  storage  cylinders
          or application equipment be attended  by  at  least two persons  wearing
          self-contained breathing apparatus.

    11.   Emergency shower and eye wash  facilities should be provided adjacent
          to entry doors into  chlorine storage  or  application  facility.

    12.   First aid procedures should be developed and  all personnel  handling
          chlorine should be familiar with  their  application.   These  procedures
          should be posted in  the chlorine area.

    14.   Fire protection should be provided  by class C fire extinguishers  (for
          energized electrical equipment) and located in the area immediately
          adjacent to the chlorination room.

    15.   Procedures  should be developed to handle chlorine leaks from  storage
          cylinders or application equipment.  Periodically operating personnel
          should review these procedures in a hypothetical emergency  situation.

Ozonation

    Ozone is a highly toxic gas which may be fatal if  inhaled  in sufficient
quantity.  The maximum acceptable limit for personnel exposed  to ozone  is 0.1
ppm by volume.   Exposure to 100 ppm  by volume  for a period of  1 minute will
cause significant nasal and mucous membrane  irritation.  However, since ozone
has a very noticeable odor at concentrations far below harmful or toxic
levels, it is immediately detected.   Concentrations up to 20 or 30 times
higher than this and prolonged exposure over many hours are required before
the gas can be harmful.   See Figure  1.   The hazards to operating personnel by
ozone exposure is minimized because  any escape of ozone from a treatment sys-
tem can be quickly stopped by turning off the electric supply.  Furthermore,
equipment used to generate ozone is protected by  fail safe devices which uti-
lize continuous ozone sensors.
                                       10

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  10,000
   1,000
o
>
o
t-

oc
t-

ui
o

o
o

UJ


N
O
                                              PERMANENT

                                              TOXIC

                                              BEGION
                                                          TEMPORARY

                                                          TOXIC

                                                          REGION
           NON-SYMPTOMATIC REGION
    0.1
                   1            10          100



                         EXPOSURE TIME IN MINUTES
                                                        1,000
10,000
               Figure 1.   Ozone toxicity.
                                    11

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    The following safety requirements should be met for any ozone application
system.

     1.  An ozone generator should never be operated in a closed, environment
         where there are no provisions for destruction of the ozone gas or a
         safety venting arrangement to dispose of any excess ozone produced.

     2.  Ozone generators should be installed in an enclosed room.  Provisions
         should be made to continuously ventilate the air space surrounding
         the operating ozone generator.

     3.  Facilities should be provided for continuous monitoring of ozone con-
         centration in the air surrounding the operating ozone generator.  If
         ozone concentration exceeds 0.1 ppm by volume, an alarm-should be
         initiated.

     4.  Remote means for shutting down ozone generator in the event of a leak
         should be provided.

     5.  Self-contained breathing apparatus should be provided in area imme-
         diately outside of ozone room for respiratory protection of any per-
         son who must enter an area where ozone is present.

     6.  A high voltage supply is required for all ozone generators.  Electri-
         cal safety criteria must be followed.  All equipment should be pro-
         vided with electrical lockout safety switches which prevent danger of
         electrical shock.

         Combustible mixtures should never be allowed  to enter the ozone gen-
         erator either as a part of the feed gas or as flow back  from the
         ozone use point downstream.

         Equipment should be operating between the maximum  internal pressure
         limitation of the equipment and  the minimum pressure rating.

         Provisions should be made to  insure that the  ozone distribution sys-
         tem will  not allow liquid or  moisture to back flow into  the generator,

         Safety  signs should be placed outside each door  leading  to the ozone
         generator room.   The signs should  (a) restrict  entry to  authorized
         personnel only  (b) prohibit smoking or open  flames in the generator
         room  (c)  warn of  the existence of ozone equipment  and the possible
         presence  of ozone gas and  (d)  advise personnel  to  leave  the room
         immediately  if  the odor of ozone is detected.

     11.  When performing  service work  on  ozone generators,  plant  rules should
         require that at  least 2 persons  be present.

     12.  Plant  rules  should require  that  only  experienced  maintenance  techni-
         cians  familiar with  the construction  and operation of the apparatus
         should be allowed to open  cabinet  doors,  remove side panels and
         otherwise service the equipment.
 7.
 8.
 9.
10.
                                        12

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    13.  Fire protection should be provided by Class C fire extinguishers  (for
         energized electrical equipment) and located in the area immediately
         adjacent to the ozone generator room.

    14.  If pure oxygen is generated on-site and used to supply the ozone gen-
         eration equipment all appropriate safety standards associated with
         the handling and use of pure oxygen must be observed.

Activated Carbon Columns

    Activated Carbon can adsorb oxygen  from the environment.  Forced air ven-
tilation or respiratory protective equipment should be provided for entry  into
carbon columns, wash tanks, and carbon  regeneration furnaces.  Other safety
precautions pertaining to furnaces should also be observed.

Recarbonation

    Under certain conditions, carbon dioxide can be dangerous, and special
safety precautions should be observed.  Prolonged exposure to concentrations
of 5 percent or more CC>2 in air may cause unconsciousness and death.  Self-
contained breathing apparatus or hose masks should be stored near basins and
worn when working in the area.

    Recarbonation basins must be located out-of-doors, and enclosed structures
must not be constructed above the basins because of the danger of excessive
amounts of CC>2 accumulating within the  structures.

    There are many other detailed safety considerations associated with liquid
CO2 handling and use.  These should be  obtained from the supplier.

Ferric Chloride Feeding

    Dust from ferric chloride can be damaging to the respiratory system if
inhaled.  In plant areas where the dust may be present, such as bag handling
areas, unloading areas, or around open  feeders, lightweight filter masks and
tight fitting safety glasses with side  shields should be available and worn by
workers.

    Great care should be taken to AVOID THE CONTACT OF ANHYDROUS FERRIC CHLO-
RIDE WITH ANY PART OF THE BODY, and especially with the eyes.  The moisture
present in the eyes or on the skin can  cause sufficient heat to burn the
skin.  Ferric chloride solutions should be handled with the same care as acid
solutions, since they can cause burns similar to those caused by acids.  They
are also injurious to clothing and cause difficult-to-remove stains.  Person-
nel handling anhydrous ferric chloride  or ferric chloride solutions should
wear overalls, rubber apron, rubber gloves and chemical goggles.  Floors,
walls and equipment which are subject to splashing should be protected with
corrosion-resistant paint or rubber mats.
                                       13

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   Plant operators should be instructed in proper procedures for handling fer-
ric chloride and these procedures should be posted wherever it is stored, han-
dled, or fed.  These instructions should include:

         If anhydrous ferric chloride comes in contact with the skin or cloth-
    ing, DO NOT WASH IMMEDIATELY WITH WATER.  Severe burns can result from the
    high heat produced when anhydrous ferric chloride is dissolved.  Wipe off
    the excess ferric chloride first with a cloth, and then flood rapidly with
    large amounts of water.

         If liquid ferric chloride comes in contact with the skin or clothing,
    wash it off immediately and throughly with water.

    The following additional safety features should be checked to ensure
proper operational conditions:

     1.  The chemical storage tanks should be specifically designed to handle
         the particular chemical.  These considerations include air-tight for
         hygroscopic chemicals and rubber lined or similar for ferric chloride.

     2.  Storage bins should be large enough to avoid continuous filling which
         requires the presence of an operator all the time.

     3.  The chemical storage and feed rooms should be well ventilated and
         should include special dust collectors when handling fine powdered
         chemicals.

Lime Feeding

    Dust from lime can be irritating to the respiratory system if inhaled.  In
plant areas where the dust may be present, such as bag handling areas, unload^
ing areas, or around open feeders, lightweight filter masks and tight fitting
safety glasses with side shields should be available and worn by workers.

    The problem of protection from quicklime burns is serious, particularly in
hot weather when workers are perspiring freely.  Besides using eye protection
and respirators workers exposed to quicklime dust should also wear proper
clothing, including long-sleeved shirt with sleeves and collar buttoned,
trousers with legs down over tops of shoes or boots, head protection, and
gloves.  Clothing should not bind too tightly around neck, wrists, or ankles.
Protective cream should also be available for application to exposed parts of
the body, particularly neck, face, and wrists.

    Freshly slaked lime in stiff putty or milk form can produce burns when
hot.  After slurry is cool, contact with skin is virtually harmless, the prin-
cipal effect being removal of natural skin oils.  Therefore, workers who
frequently handle lime slurry should oil their skin, where exposed, daily.
Something similar to a petroleum jelly should be available for this use to
help prevent chapping and thus reduce danger from burns or infection.
                                       14

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    Workers inspecting or cleaning slakers  should have  safety  goggles  avail-
able and should wear them.

    Showers should be provided to permit workers to shower  after  handling  lime.

    Instructions should be posted wherever  lime is handled  for  the  treatment
of lime handling accidents.

    An efficient dust collecting and removal system should  be  provided wher-
ever lime is handled.  An industrial vacuum should be provided  for  cleaning  up
lime dust around and on equipment.

    Quicklime bags should be stored in a clean, dry place to avoid  moisture
pickup.  Otherwise the intense heat generated from accidental  contact  with
water, may be enough to start a fire in nearby flammable materials.

    An important slaker safety measure is the installation  of  a thermostatic .
valve to prevent overheating and possible explosion.  This  could  occur if  the
water supply fails and the lime feed continues, allowing the lime to overheat
and produce excessive steam.  The safety valve delivers a supply  of cold water
as soon as maximum safe slaker temperature  is exceeded.  An added safety
feature is a high temperature alarm device.

Other Chemical Feeding

    Dust from any dry chemical can be irritating to the eyes and  respiratory
system.  In plant areas where the chemical dusts may be present lightweight
filter masks and tight fitting safety glasses with side shields should be
available and worn by workers.

    Dry polymer powder can be extremely irritating to eyes.  Eye  protection
should be available and worn when handling powder.  Instructions  should be
posted to flush with water if powder gets in the eyes.  The major hazard with
polymer handling is powder spilled on the floor which becomes wet,  causing
extremely slippery surfaces.  This powder remains slippery  until  washed down
with large volumes of water.

    The following safety features should be checked to ensure proper opera-
tional conditions:

     1.  The chemical storage tanks should be specifically designed to handle
         the particular chemical.  These considerations include air-tight for
         hygroscopic chemicals.

     2.  Storage bins should be provided with dust collectors and vents.

     3.  Storage bins should be large enough to avoid continuous  filling which
         requires the presence of an operator all the time.
                                       15

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     4.  The chemical storage and feed rooms should be well ventilated and
         should include special dust collectors when handling fine powdered
         chemicals.

     5.  Operators should be instructed to avoid using the same conveyor
         mechanism for more than one chemical.  This is especially important
         with quicklime and chemicals containing moisture as fire and
         explosions could occur.

Furnaces and Incinerators

    Safety measures for furnaces and incinerators should be observed at all
sludge heat treatment and wet air oxidation steam generators, multiple hearth
incinerators, fluidized bed incinerators, lime recalcining furnaces, and car-
bon regeneration furnaces.  The protective measures listed should be provided
wherever appropriate and the procedural measures should be posted in a prom-
inent place:

     1.  No smoking should be allowed around natural gas lines or when
         checking the system for leaks.  No smoking signs should be posted.

     2.  Protective clothing and face shield should be worn when repairing or
         lighting furnaces and incinerators.

     3.  A colored plate should be provided for use when looking into an oper-
         ating hearth to protect the eyes from the bright flame.

     4.  A sign should be posted introducing operators to open hearth access
         doors with caution, to not stand in front of them when they are
         initially opened, and to close them as soon as possible.

     5.  Flame safety devices should be fully operational.

    The appropriate procedures for hauling of lime and activated carbon should
be observed for recalcining and regeneration furnaces.

Heat Treatment

    The proper safety procedures for furnaces and incinerators should be
observed for heat treatment steam generators.

    The following safety features of the heat treatment process should be
checked:

     1.  Operators should be instructed that if at any time during operation
         the system temperatures are abnormally high, the air compressor
         should be stopped and the system switched from sludge to water.
         Abnormally high temperatures are shown in the manufacturer's manuals
         and should be posted.
                                       16

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     2.   Any inspection'or clean ing"'should be done with that section of the
         system completely depressurized.   Liquids under pressure can cause
         serious harm to personnel'if suddenly discharged.

     3.   Proper protective equipment should be available and worn during
         inspection and cleaning per manufacturer's recommendations.

     4.   Observe proper handling procedures when using acid solutions for
         cleaning.   Recommended safety procedures should be obtained from the
         supplier,  implemented, and posted prior to handling of any acid in
         the plant.

     5.   Operators should be instructed that vessels should be well ventilated
         and completely isolated before entering.  A vessel should never be
         entered without a lift line held by someone outside the vessel and a
         reliable source of air inside the tank.

     6.   Carbon coatings on high pressure air compressor discharge valves
         indicate too much oil is being used to lubricate the cylinder.  Fail-
         ure to correct this could result in fires at the discharge of these
         cylinders.

     7.   Proper masks should be available when working around the supernatant
         and liquor because of the gases and odors.

Anaerobic Digesters

    The following safety features should be checked in anaerobic digesters,
around digester gas-fired boilers and engines, wherever anaerobic sludge is
discharged, such as at drying bed and lagoons, and any other locations where
digester gas or anaerobic sludge may be present.

     1.   Since digester gas is explosive when in contact with air,  there
         should be no smoking, open  fires or flame wherever gas may be
         present.  No smoking  signs  should be posted.

     2.   Operators should be instructed to observe the following when entering
         a digester:

         (a)  Provide adequate ventilation - be sure exhaust fan is on.
         (b)  Always have two persons present.
         (c)  Use  safety harness equipment with safety line.
         (d)  Check for gases with  explosimeter.
         (e)  Be careful of footing.
         (f)  Use  bucket  and rope to lower tools and equipment.
                                        17

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      3.   Positive pressures should be maintained in all gas collection systems.

      4.   Digesters accidentally drained below'the operating range of the
          floating cover  introduce air into  the digester causing  an explosion
          hazard.   In this  case  all personnel  should be  familiar  with pro-
          cedures  for constant purging with  a  noncombustible gas.

      5.   Periodic checks should.be made of  the gas collection/storage system
          for  leaks.

      6.   Regular  checks should  be made on the operation of  the following
          equipment:

          (a)  pressure regulators
          (b)  pressure relief valves
          (c)  flame  arresters
          (d)  waste  gas burners
          (e)  gas engines
          (f)  boilers
          (g)  automatic gas and pilot valves
          (h)  gas condensate traps
          (i)  explosive atmosphere  detectors

     7.   If it is  necessary to enter  a  sludge pumping station:

          (a)  A blower should be provided and used  for  ventilation because
              toxic  gases can accumulate in low places.  A  sign warning  of
              possible toxic gases  should be present.

          (b)  Safety harnesses should be available and be worn.

          (c)  At  least two persons  should remain at the surface in case  of an
              injury or accident.

Pressure Filtration

     1.  For safety, filter press installations are usually equipped with a
         photo-electric light that surrounds the press and  stops the closing
         mechanism if the light beam is interrupted.  This  system must be
         checked for proper operation:
         (a)

         (b)
Check that the light curtain is illuminated after switching it
on.
Check that the closing motor stops when the light beam is
blocked.
     2.   Face shields and rubber gloves should be worn during acid cleaning of
         media.

     3.   The feed pumps develop high pressures and the press should not be
         opened  until these pressures are relieved.
                                       18

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 II.   PLANT HYDRAULICS

     Plant hydraulics includes  liquid  flow through the plant as well as sludge
 flow to processing  units  and/or  disposal  areas.   The  objectives of analyzing
 the  hydraulics  of a system are to  insure  that  raw sewage is not backed up into
 the  collection  system  or  bypassed  around  the plant and that there  are  no flow
 restrictions  that could  inhibit  unit  process performance.

     The first area  to  inspect  is the  raw  sewage pumping  station and nearby
 (upstream)  manhole  covets.  Visual inspection  should  be  adequate to determine
 if the  wet well flooded or  if  sewage  spilled out  through the  manhole.   Usu-
 ally, an overflow will leave a stain  or deposit and is obvious.  The individ-
 ual  and total station pumping capacities  should be noted.   Standby pumps
 should  be adequately sized  to maintain pumping station capacity with the
 largest pump  out of service.

     Inadequate  hydraulic  capacity  in  the  unit processes  will  often be  obvious
 from old high water lines or open  tanks or  flooded weirs on clarifier
 launderers.   If only a portion of  the weirs on one tank  are flooded,  then the
 weirs are improperly leveled and should be  adjusted.   If there are multiple
 units and only  one  unit has flooded weirs,  then the problem is unequal flow
 distribution.   Unequal flow distribution  is a common  problem  when  taking flow
 from multiple units through a common  distribution  channel  leading  to other
 multiple  units.  This problem  is compounded during extremely  high  or low flow
 periods.   Inspection of a facility  in the morning  hours  will  generally reveal
 if there  are  distribution problems with the morning's peak  flow.

     Recycle flow pumping  and piping are critical to most secondary treatment
 processes.  The problems  most commonly found are insufficient capacity and
 uneven  sludge withdrawal  from clarifiers.  Insufficient  capacity is  difficult
 to determine  without a detailed  analysis, but will usually  result  in less  than
 expected  treatment  efficiency.   (Proper metering would make this a simple
 analysis  but  meters are not always installed or properly calibrated).   Uneven
 withdrawal from clarifiers results from pumping sludge from two or more  clar-
 ifiers  simultaneously through a  common header pipe.   This  is  more  critical
 with unequal  pipe lengths from the clarifiers to the  pump.  If  two  identical
 clarifiers receiving the  same amount of influent have different appearances
 (e.g. one  - clear,  one -  cloudy),  then unequal drawoff of sludge is possible.

     Inadequate sludge pumping capacity or pipeline size  can result  in  sludge
 being stored  in unit processes which were not intended for  storage.  This
 results in poor performance of sludge treatment processes.  Unit process per-
 formance  records should be reviewed and if less than  optimum performance  is
 achieved  the  one possible cause could be lack of hydraulic capacity  in  the
 system pumping  sludge to  the next unit process.

    Hydraulic capacity  of sludge pumping systems will appear  to be lacking if
dewatering units are not performing properly.   A system may have been designed
 for a dewatering sludge to 15% solids.  If the dewatering process performance
provides a sludge with  10% solids then the sludge pumping system may not be
sufficient to pump  the  additional water.  The dewatering system design per-
formance should be compared with the actual performance before making con-
clusions on the hydraulics of the sludge transfer system.
                                       19

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IV.  COMPATIBILITY OF UNIT PROCESSES

    In the following sections and in referenced design or operation manuals
anticipated unit process performance is discussed.  The individual plant being
reviewed was designed with certain process performance standards in mind.
Occasionally a system will be reviewed where a unit process is not performing
as expected.  The unit may be properly designed and operated but the perform-
ance is still not acceptable.  One possible cause is that the unit is not com-
patible with the waste stream being treated.  An example of this situation is
gravity thickening of waste activated sludge.  A gravity thickener will usu-
ally not effectively thicken waste activated sludge.  Another example is con-
ventional filtration of lagoon effluent without chemical pretreatment.  Pri-
mary sedimentation of waste activated sludge, although a common practice, can
hinder primary treatment performance.   Microscreening of chemical sedimenta-
tion effluent is generally not effective.  Pumps designed for general water
pumping are not effective with sludge pumping (e.g.  closed impeller pump).
Certain chemical sludges can only be pumped by systems constructed with spe-
cial materials.

    Related to unit process compatibility is individual unit process com-
patibility with the waste being treated.  Process designs should be carefully
reviewed to see that the application was properly determined.  For example, a
filtration process was designed to obtain a suspended solids effluent of less
than 5 mg/1.  This was also based on a secondary (activated sludge)  effluent
of less than 30 mg/1.  If the secondary treatment system is changed to aerated
ponds then the filtration system will not operate as designed.
                                       20

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References

 1. CH2M Hill, "Estimating Staffing for Municipal Wastewater Treatment
    Facilities",  U.S.E.P.A. Office of Water Program Operations, Washington,
    D.C.,  March,  1973.

 2. Black  & Veatch, "Estimating Costs and Manpower Requirements for Conven-
    tional Wastewater Treatment Facilities", U.S.E.P.A. Office of Research and
    Monitoring, October, 1971.

 3. Water  Pollution Control Federation, "WPCF Salary Survey of Treatment
    Plants and Collection Systems", Deeds and Data, W.P.C.F., Washington,
    D.C.,  May, 1977.

 4. Standard Methods for the Examination of Water and Wastewater, American
    Public Health Association, Washington, D.C.,  14th Edition,  1975.

 5. U.S.E.P.A., Methods for Chemical Analysis of  Water and Wastes, Office of
    Technology Transfer, Washington, D.C., 1974.

 6. U.S.E.P.A., Analytical Quality Control in Water and Wastewater
    Laboratories, Office of Technology Transfer,  Washington,  D.C., 1972.

 7. Wiley  & Wilson, Inc.,  Maintenance Management  Systems for  Municipal Waste-
    water  Facilities,  U.S.E.P.A.,  Municipal Operations Branch,  Washington,
    D.C. 20460, October, 1973.

 8. Wirts,  J.J.,  et al,  Safety in  Wastewater Works Manual of  Practice No. 1,
    Water  Pollution Control Federation,  Washington, D.C.,  1967.

 9. California Water Pollution Control Association Safety Manual,  Pasadena,  CA
    91101,  1973.
                                      21

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V.  UNIT PROCESS EVALUATION SECTIONS
     The following chapters consist of a brief discussion
of each unit process followed by a suggested checklist.
These checklists are provided to aid the inspector and
should not be considered as required for each inspection.
They are intended mainly for new inspectors or experienced
inspectors who are reviewing a process which they have not
previously inspected.

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1. RAW SEWAGE PUMPING STATIONS

Process Description

    Raw sewage pumping stations are used to lift or pump the raw sewage  into a
treatment facility when the influent sewers or interceptors are at too low an
elevation to allow the sewage to flow by gravity into the treatment facility.

    The pumps most commonly used for pumping raw sewage include centrifugal
pumps, screw lift pumps and air lift ejectors.  Each of these systems is
described in detail in Reference 1.

Typical Design Considerations

    The basic criteria by which pumping stations are rated are their capacity
(gpm or mgd) and pumping head (feet) capability.  Because of the many kinds of
pump designs and capacities, the manufacturers performance curves should be
used to provide the required information on discharge, power requirements, and
head characteristics for a specific pump.  Every pumping system should have
been analyzed in detail and a "system-head" curve developed which describes
the operation of the system.  An example of such a curve is shown in Figure
1-1, and shows the static head, frictional head and total dynamic head for the
system.  The point of crossover of  the pump curves and the pipe system curve
represents the operational point.   This point delineates the capacity of the
pumping system and the total dynamic head.  Also shown in Figure 1-1 are
curves for, the horsepower required  and the net positive suction head  (NPSH)
for varying flow rates.  Depending  on the type of pump, the number of pumps
operating, and the discharge pipe diameter and length, the shape of the  curves
could be altered considerably.

Typical Performance Evaluation

    A pumping system is normally evaluated by checking the operating point in
the "system-head" curve, similar to the one shown in Figure 1-1.  The evalua-
tion requires the following procedure:

    1.   Determine the physical conditions that affect the pumping operation:
         Height of sewage above pump impeller in wet well
            (suction head)                                       =  6 ft
         Height of sewage at pump discharge point above
           impeller (discharge head)                            = 30 ft
         Frictional losses in suction and discharge piping
            (based on diameter, length, bends & valves in lines) =
         Pump efficiency
         Motor efficiency
         Voltage to motor
         Plant flow (mgd)
               from influent flume
gallons/minute = mgd x 1,000,000/(24x60)
 5 ft
85%
90%
460 volts
 5 mgd
3472 gpm
                                      1-1

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                          OPERATING
                          POINT - 2
                          PUMPS
  _TOTAJ__HEAD_ I	
   1 PUMP
                                      OPERATING
                                      POINT - 1    /
                                      PUMP       /
 U PUMP
 /    EFFICIENCY
'    CURVES

       DYNAMIC
       HEAD OR
     X FRICTIONAL
       LOSS
                                                             '-STATIC HEAD
tr
UJ
o
Q.
Ill
tn
cc
o

UJ
m
    -HP REQ'D
         FLOW RATE
O
HI
DC
     'NPSH REQ'D
                                FLOW RATE
                               FLOW RATE
         FLOW RATE
            Figure 1-1.    System-head pump curves.
                            1-2

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 Determine  the  head characteristics against which the pump is
 operating:
 Static  head  (ft)   =  Difference in elevation between discharge and
                      suction (or  difference in elevation between
                      water  surface in wet well and water surface at
                      discharge  point)
                   =  30-6 = 24  feet
 Total Dynamic  head (ft)  = Static  head + frictional losses
                         = 24 +  5  = 29 feet
 Determine  the  horsepower characteristics of the pump and motor:
 Required pump  HP   = (flow in gal/min  x (total head in ft)
                                    3960                         ,*
                   = (3472)   (29)
                         3960
Required motor HP =
 25.4 HP
	(pump HP)	
(pump efficiency)
 25.4
                     (0.85)
                     29.9 HP
Consumed HP
     (motor HP)
                     (motor efficiency)
                  =  29.9
                     0.90
                  =  33.2 HP
Compare the above computed head  and power  characteristics  of the pump
with those provided  by the manufacturer.   Check  to  ensure  that the
pump is not being forced to operate under  conditions  outside its
rated design range.
Check motor horsepower by measuring current  draw or amperage through
each of the three phases of electrical  supply  to the  motor  using a
"clamp around" current meter on  each  lead  wire.   The  reading from
each phase should be within 10 to  15  percent of  each  other,  and
should not be more than the amount listed  on the nameplate  of the
motor.
Determine the horsepower of the  pump  and motor from the  current read-
ings taken above.
Current (amps)   =  (amps in phase  1 + phase  2  +  phase 3)
                                      3
                  = use 40 amps
Motor HP          =  (Amps) x (volts)  x  (1.9)/(1000)
                  =  (40.0) x (460) x  (1.9)/(1000)
                  =  36.0 HP

These values of amperage were selected  to  give the  correct  horse-
power.  It is only an approximate  method,  and  should  only be used as
a rough check.
                            1-3

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Control Considerations

    A raw sewage pumping system essentially has no method of controlling its
operation, because the system is designed to pump to the treatment facility
headworks the volume of raw sewage that enters the wet well.  The only control
the operator has is the selection of the lead and lag pumps and manipulation
of the automatic controls from the water level in the wet well that starts and
stops the pumps.  Frequently, especially in larger treatment facilities, the
raw sewage pumping station has a variable pumping rate controller.  This de-
vice, which can be anything from a special type of motor to varying the fre-
quency of the current to some type of mechanical device, operates the pumps by
sensing the level of the water in the wet well.  Conditions that could affect
the efficient operation of the pumping station should be monitored carefully.
An example of this could be the build-up of debris on an influent screen or
rack, which might cause surges of sewage into the wet well, with the resulting
impact on the level sensors, which in turn causes the pumps to start and stop
intermittently.  Influent screens are recommended in raw sewage pumping sta-
tions to protect the pumps from abrasive materials and objects that could plug
the suction line to the pumps.  These screens should be cleaned regularly as
is discussed in the next section.

    Pumping stations have an important effect on the overall performance of
the treatment plant, since the flow through the plant depends on the pump
capacity.  Intermittent pumping during periods of low flow and frequent
changes in pumping rates can cause process upsets.  As a result, it is desir-
able for the pump capacity and storage capacity to be designed so that fre-
quent stops and starts of the lead pump are avoided, and changes in pumping
rates are minimal.

Maintenance Considerations

    In addition to the maintenance management program described in the Overall
Plant Management Section, the following list covers maintenance items specific
to pumping stations.

     1.  The spare parts inventory should include at least the following
         items:  one set of each type of bearing, grease seals, all necessary
         gaskets for replacement of parts, one set of mechanical seals if used
         on the pump, and the washers for adjusting the position of the
         impeller.

     2.  Deteriorated concrete or expansion joints should be repaired.

     3.  Measures for control of sewer gas (hydrogen sulfide) odors in the wet
         well should be provided.

     4.  Wet well ventilation and odor control systems should be checked reg-
         ularly for correct operation.

     5.  All pumps should be visually checked for misalignment of the drive
         shaft, for constant rotation speeds, and for any excessive vibrations.
                                     1-4

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     6.  Pumps should be checked for unusual operating sounds such as screech-
         ing which could indicate lack of lubrication, thumping which could
         indicate broken or loose components or sharp, quick pinging sounds
         (like gravel hitting a metalic surface) accompanied by pump vibration
         which could indicate cavitation.

     7.  Daily, readings of pumping times should be recorded from elapsed time
         meters.   This can be used as a check on the plant flow and also for
         scheduling maintenance work.

Records

    There are no recommended sampling or laboratory tests on a pumping station
unless the station includes a screening device.  In this case, required pro-
cedures would be as described in the next section.

    Daily operating records at the raw sewage pumping station should include:

    1.   The length of time that each pump operates, as recorded by the
         elapsed time meters.

    2.   The total energy (electrical power) consumed.

    3.   The total pumpage through the station as measured by a flow meter
         with a flow-indicator-recorder unit and chart drive, (frequently a
         totalizer is also included which simplifies pumpage computations).

    4.   A determination of the sewage pumped by each pump.

    5.   An estimate of the rate of wastewater pumped per kilowatt.

Laboratory Equipment

    There is no specific laboratory equipment required for this unit operation.

Sampling Procedures

    Wastewater sampling is not required at this location in a treatment facil-
ity.  If screening devices are included as an integral part of the pumping
station, then the sampling procedures and requirements are as described for
the next section.

Sidestreams

    There are no sidestreams associated with raw sewage pumping stations.
                                     1-5

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Process Checklist - Raw Sewage Pumping Stations

 1. Name of pumping station	
 2. Location of pumping station (if not on plant site)
 3. What are the design flows?
 4. What are the actual flows?
 5. Are all pumps operable?  (
    why not
                            )  Yes  (  )
    gpm average;  	 gpm peak?
    gpm average;  	 gpm peak?
    No.   If no,  describe reason
 6. Are all control systems, ventilation fans and miscellaneous equipment
    operable?  (  )   Yes  (  )  No.  If no, explain 	
 7.
 8.
 9.
10.



11.



12.



13.

14.

15.

16.

17.
18.

19.
20.


21.

22.
23.
24.
25.
Is the pump control system  (  )  variable speed,
If variable speed, type of controller
             (   )   constant speed?
In multiple pumping unit systems, is each unit operated  (  )   about
15-20% apart,   (  )  equally   (  )  not alternated?  Remotely monitored?
(  )  Yes  (  )  No
Does the facility have an alarm system?   (  )  Yes  (  )   No.
Is it working?  (  )  Yes  (   )  No.  Points monitored:  wet well
high water	, power failure 	,  aux.  power
running 	, pump  failure 	.
Does the pumping station have  a portable generator connection (for small
systems)? (  )  Yes  (  )  No.
Is the portable generator operable? (  )  Yes  (  )  No.
Does it have sufficient capacity? (  )   Yes  (  )  No
Does the pumping station have  a portable pump connection (for  small
systems)? (  )  Yes  (  )  No.
Is the portable pump operable? (  )  Yes  (  )  No
Does it have sufficient capacity? (  )   Yes  (  )  No
Does the pumping station have  a bypass? (  )  Yes  (  )  No
If yes, can the bypass flow be disinfected? (  )   Yes  (   )   No
Can the wet well be isolated into a minimum of two separate basins for
maintenance?  (  )   Yes  (  )   No
If one wet well basin is down  for maintenance, how many pumping units are
operable? 	
Does the wet well design provide for equal division of flow to each of the
pumping units?  (  )  Yes  (  )  No
Condition of the sump pump  (  )   good  (  )  fair  (  )   poor  (  )  N/A
Condition of the water seal system  (  )  good  (  )   fair  (   )   poor
(  )  N/A
Does the station have an adequate spare parts inventory?  (  )  Yes  (  )   No
Does the station have proper ventilation  (both for safety and  cooling of
motors and motor control center)? (  )   Yes  (  )  No. If no,  what is the
problem? 	
Are there adequate safety provisions?
the problem?	
(   )   Yes  (   )   No.  If  no,  what  is
How often is the pumping station checked? (  )   Daily  (  )   Other
What is the downtime of the pumping units? 	
What is frequency of scheduled maintenance?	
Is the maintenance program adequate? (  )   Yes  (  )   No.  If no,
explain 	
                         /year
                                     1-6

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26. If constant speed station, does it affect the operation of the treatment
    facility through sudden surges as each pumping unit is activated?
    (  )   Yes  (   )   No
27. What is general condition of station (housekeeping)?
    (  )   good  (   )   fair  (  )   poor
28. What are the  most common problems the operator has had with the pumping
    station?  If  problem with screens, use next section.
                                     1-7

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References           '-                     >:

 1. Culpr G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11,  Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.
                                     1-8

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2.  RAW SEWAGE SCREENING

Process Description

    The principal purpose of screening raw sewage flows is to remove large
solids and trash, such as rags, sticks, lumber and other debris that could
clog pumps and piping, and interfere with the proper operation of the treat-
ment facility.  Also, screens are sometimes used to provide some degree of
wastewater treatment by incorporating significantly smaller openings for the
passage of the sewage, thereby capturing larger volumes of influent solids.
Screens are described in detail in Reference 1.

Typical Design Considerations

    The bar screens are usually sized according to the velocity of the water
passing through the screen, which has a recommended maximum velocity in the
range of 2 to 2.5 fps for the maximum day flow.  This value is related to two
factors, the first being the significant headless caused by higher velocities,
especially if the bar screen is partially clogged.  The second factor is the
more practical aspect of raking the solids from the bars, which is made more
difficult at higher velocities.  Both these factors are less important when
considering mechanical screens, although the recommended velocities still hold.

    The fine screening devices, with openings less than 0.75 inches, are
usually sized from manufacturers' literature and then provided with additional
units for standby capacity.  The standby units are put in service to allow
cleaning of plugged screens.  Typically, smaller openings allow less water
through and require more width of screen.  For example, the rotating screen
allows only 12.25 gpm/inch width of screen through the .01 inch opening, but
80 gpm/inch width through the 0.1 inch openings.

Typical Performance Evaluation

    The performance of the bar screens can be evaluated as described in Ref-
erence 1.  A simple performance evaluation consists of visual inspection to
see that debris has been cleared.:

Process Control

    The only control that an operator has over a bar screen, or trash rack, is
the frequency of removal of screenings trapped by the screen.  If screenings
are not removed sufficiently frequently, water in the approach channel will
back up resulting in surges of high flow after the screen has been cleaned.
These conditions potentially could cause problems in following unit processes
such as the grit chamber, primary clarifier and aeration basin.

    The only control of the fine screening units is the frequency of cleaning
and the number of individual units that are operational at one time.  As more
units are put into service, the individual loading rates will reduce and the
removal efficiency will increase.  The more units in service will also result
in fewer surges of water to downstream processes.
                                      2-1

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Maintenance Considerations

    In additibn to the general maintenance management section presented in the
overall plant management program the following items should be included for
screen maintenance:
     1.
     2.
     3.
Spare parts inventory should include the following:  one set of each
type of bearings, seals and gaskets, one set of chain drives or
cables for the mechanical bar screen or rotating drum, shear pins,
and a spare set of rake teeth.

There should be a daily inspection of the screening assemblies to
visually inspect the equipment for misalignment, excessive noise,
excessive vibrations, unequal loading of equipment.

Daily readings of screening volumes from each screening device should
be recorded.  These can be used to check for unbalanced loadings on
the screens, which could cause undue stress, requiring more frequent
maintenance.
Records
    There are no recommended sampling or laboratory tests required specifi-
cally for the screening devices.  However, the channel in which the screen is
located is normally the location of sample collection for influent data.  This
location is usually upstream of any recycle flows that may influence the con-
centrations of the various parameters measured.

    Other operating records should include:

    1.   Volume of screenings captured per day on each screen.

    2.   An estimate of the unit volume of screenings captured per million
         gallons of flow.

Laboratory Equipment

    There is no specific laboratory equipment required for this unit opera-
tion.  The raw sewage is not normally sampled upstream of the screening device
in order to avoid damage to the sampling mechanisms.  However, "grab" samples
are sometimes taken in order to correlate the volume of screenings captured to
the percent reduction in total solids concentration across the screen.  The
following items could be used to determine solids content:

    1.   Balance
    2.   Drying Oven
    3.   Dessicator

Sampling Procedures

    Although wastewater sampling is not routinely done on both sides of the
screening device, "grab" samples should be taken occasionally to correlate the
                                     2-2

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reduction in total solids concentration across the screen with the volume of
screenings captured.  The grab sample should be taken at the center of the
channel, where the wastewater is normally homogeneous, and channel velocities
are high.

    Also, the screenings captured should be sampled occasionally to determine
the volatile content and the moisture content.  The volume of screenings cap-
tured can be determined by computing the volume of the containers into which
they are placed and counting the number of containers filled each day.

Sidestreams   .

    The only sidestream from the screening assemblies is the volume of screen-
ings captured.  The estimated unit volumes of screenings as a function of
screen openings have already been shown.  Generally screenings are incinerated
or hauled to a landfill for disposal.
                                     2-3

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Process Checklist - Raw Sewage Screening
 1.
 2.
 3.

 4.

 5.
 6.
 7.
 8.
 9.
10.

11.
12.

13.

14.
15.
16.
17.
18.

19.
What are design flows	
What are actual plant flows
Type of screen
           mgd.
	 Number
 Size of opening
                                         mgd avg.
                                          mgd peak?
                                          mgd peak?
                                           Capacity of each unit
Are the bar screens and associated equipment operable?(  )
If no, what is reason
                                                           Yes  (  )No
                                                                	 cu ft
                                                                 cu feet/mg
What are dimensions of channels?
What is total daily volume of screenings?	
What is unit volume of screenings?	
Is screening  (  )  manual  (  )  mechanical?
Is there a bypass channel? (  )   with screen  (  )   without screen.
Does influent channel design provide equal division of flow to each screen?
(  )  Yes  (  )   No
Do mechanical screens have adequate spare parts inventory? (  )  Yes (  )  No
If enclosed, is building properly ventilated? (  )   Yes  (  )   No
If no, what is problem?
Are there adequate safety provisions? (
If no, what is problem?
                                         )   Yes  (  )  No
                                  )  Daily  (  )   Other
                                                                      /Year
How often are screens checked? (
What is downtime of the screens?	
What is frequency of scheduled maintenance?	
Is the maintenance program adequate?  (  )  Yes   (  )  No
What is general condition of the screening system?
(  )  Good   (  )  Fair  (  )  Poor  (  )  N/A
What are the most common problems the operator has had with the screening
system?	______	
                                     2-4

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References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).
 3.  CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.
                                     2-5

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3.  RAW SEWAGE SHREDDING AND GRINDING

Process Description

    Raw sewage shredding and grinding devices are used to reduce the particle
size of objects or debris in the influent wastewater.  These devices may be
installed with a screen directly in the wastewater flow or separately out of
the wastewater flow, with the shredded particles returned to the flow down-
stream of the screen.

    The shredding and grinding devices that are installed directly  in the in-
fluent channel are termed comminutors or macerators and barminutors.  The com-
minutor or macerator are similar devices that screen and grind simultane-
ously.  The influent flow is channeled to and through these units.  The debris
collects against the screen, or outside drum, and the teeth which penetrate
this screen cut up the solids.  When the solids are reduced to the  size of the
screen or drum openings they pass through and on for additional treatment.
The barminutor, is a comminuting device that incorporates revolving cutters
that move up and down the upstream face of a bar screen, shredding  and cutting
whatever debris has accumulated against the screen.  The shredding  and grind-
ing devices that are placed outside the wastewater flow receive debris from a
mechanically cleaned bar screen.  The screenings are transported to the cut-
ting device, shredded and then allowed to fall back into the influent channel
downstream of the bar screen.  Detailed description of these devices are  in
Reference 1.

Typical Design Considerations

    In-channel shredding and grinding devices are normally sized in terms of
the flow rate that can pass through the unit.  The greater the diameter of the
unit, the greater the capacity.  In addition, the velocity of approach of the
wastewater should be limited to a range of 2 to 5 fps.  Individual  units have
capacities ranging from 0.35 to 25.0 mgd and are capable of processing 650 to
5,200 Ibs of solids, or debris, per hour.

Typical Peformance Evaluation

    The inspector can evaluate the performance of shredders and grinders by
observing or checking the following:

    1.   Observe the flow and build-up of debris against the screen and the
         cutting action of the unit.  Plugging may occur if the debris are not
         properly cut up and flushed through the unit for further  treatment
         downstream.

    2.   Check maintenance records for regular sharpening and adjustment  of
         cutting edges or teeth.

    3.   Check the records for the frequency of maintenance as an  indication
         of the amount or abrasive quality of debris being processed.
                                       3-1

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     If the shredding and grinding units are located upstream of the grit cham-
 ber, abrasive action on the units would be more severe due to the presence of
 grit.

 Process Control

     Control of this unit operation is simply one of ensuring smooth function-
 ing equipment and not permitting an accumulation of debris against the
 screens.   If debris are not properly cut up, serious problems could poten-
 tially occur in downstream processes.  For example, grit chambers could become
 clogged or subject to odors as a result of submerged debris and rags that
 escaped shredding.  In addition, pumps and pipelines,  especially suction
 lines, could become plugged and pump impellers damaged by poorly shredded
 material.   Another example might be mechanical surface aerators becoming en-
 tangled with the rags and debris if not preceded by primary sedimentation.
 These problems can be essentially eliminated by proper maintenance of
 equipment.

 Maintenance Considerations

     In addition to the maintenance management programs discussed in the Over-
 all Plant  Management Section,  shredding and grinding operations should include
 the following maintenance items.

      1.  Channel stop-logs checked for  warping and  possible replacement.

      2.  Channel sluice gates  checked for  operability.

      3.  Scheduled replacement of barminutor  cables or  chains.

      4.  Scheduled maintenance and sharpening  of cutter  teeth.

      5.  Spare parts should include  the following:  cutting  teeth,  shear bars,
         cables,  rotative  barminutor  cutting  edge,  shear pins and  drive chains.

Records

    Operating  records  should include:

    1.   Raw  sewage  flow per influent channel.
    2.   Energy  usage  for  each  unit.

Laboratory Equipment

    There  are no specific  laboratory  equipment  items required for  this  unit
process.
                                      3-2

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Sampling Procedures

    It is sometimes desirable to determine the total solids content of waste-
water after shredding and grinding.  These tests are usually accomplished on
grab samples.  The sample should be collected from a point in the channel
where the wastewater is well mixed and relatively homogeneous and the veloci-
ties are high.

Sidestrearns

    There are no sidestreams associated with raw sewage shredding and grinding.
                                     3-3

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Process Checklist - Raw Sewage Shredding and Grinding
 1.
 2.

 3.
 4.

 5.
 6.
 7.
 8.

 9.

10.
11.

12.
13.
14.
15.
16.
17.
18.
What  is  the  actual  flow
mgd average,
How many  shredding and grinding units are  there
make?
	 mgd peak?
 What type or
What is the capacity of each unit
           mgd?
 If multiple units are used,  is the  flow evenly distributed?
 (  ) Yes  (  ) No
 Is shredding and grinding unit operable?  (   )  Yes   (   )  No
 What are dimensions of channels?	
 Is there a bypass channel?   (  )  Yes  (  )  No
 If units enclosed, is ventilation system operable?  (  )  Yes
 If no, what is the problem? 	
                         (   )   No
What is general condition of the shredding and grinding facilities?
(  )  Good   (  )  Fair   (  )  Poor
Are proper safety precautions used?   (  )  Yes   (  )  No
Is there an alarm system for equipment failures or overloads?
(  )  Yes  (  )  No
How often are units checked?	
What is downtime of the units?
Does the sampling program meet the recommendations?
Are the operating records adequate?  (  )   Yes  (  )
What is frequency of scheduled maintenance? 	
Is maintenance program adequate?	
What spare parts are stocked? ____^______	
                (   )  Yes
                No
      (   ) No
19. What are the most common problems the operator has had with the process?
                                      3-4

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References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities/ US EPA
    Report 430/9-78-001 (Jan.  1978).

 2. Guarino,  C.F.,  et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice  No.  11,  Water Pollution Control Federation (1976).
 3.  CH2M-Hill,  Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4.  Wirts,  J.J.,  et al,  Safety in Wastewater Works,  Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5.  Miorin,  A.F.,  et al, Wastewater Treatment Plant  Design,  Manual of Practice
    No.  8,  Water  Pollution Control Federation (1977).

 6.  State of Virginia O&M inspection form.
                                     3-5

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  4.  GRIT REMOVAL

  Process Description

      Grit removal facilities are designed to allow the settling out of this
  material.   Grit includes sand and gravel,  cinders,  coffee grounds, small
  stones,  cigarette filter tips and other large-sized materials.  Grit removal
  is an important process for several reasons:  (1)  To prevent cementing effects
  at the bottom of sludge digesters and primary sedimentation tanks; (2)  to
  reduce the potential for clogging of pipes and sludge hoppers; (3) to protect
  moving mechanical equipment and pumps from unnecessary wear and abrasion; (4)
  to reduce  accumulations of  materials in aeration  tanks and sludge digesters
  which would result in a loss of usable volume;  and  (5)  to reduce accumulations
  at the bases of mechanical  screens.

      Grit removal equipment  can be velocity controlled,  aerated,  or of the con-
  stant head type,  and the tanks can be rectangular,  square or  round in shape.
  Details  of these  systems can be found in Reference  1.

      Grit handling  facilities normally include  facilities  to wash or classify
  the  grit in order  to reduce the organic content in  the grit.   The grit washer
  consists of screw  or rake mechanisms.   To  ensure  a  low volatile  content  in the
  grit,  sufficient wash or  dilution water is  required.   Grit washing is per-
  formed at  the  lower  end  of  a grit classifier, which  is  a  device  that  separates
  the  organic material from the grit by a upflow  water movement.   The dewatered
  grit falls  into containers  for  removal  to a sanitary  landfill  for  disposal.

      For  installations having  a  large percentage of organic  material,  a cyclone
  type grit classifier  is used  ahead of  the grit  washer.  Cyclone  degritters use
  centrifugal force  to  separate  the  grit  from the wastewater  in  conically  shaped
  units.

 Typical Design Considerations

     The velocity controlled  systems limit the velocity  in the  rectangular
 channels to a maximum of 1 foot per second  (fps).   This velocity  is low enough
 to allow the grit to settle but fast enough to maintain a majority of the
 organic material in suspension.  The aerated grit chambers are normally sized
 on the basis of both detention time and volume of air.  Typically, the deten-
 tion time is in the range of 2 to 5 minutes and the air flow is in the range
-of 0.04 to 0.06 cu ft/gallon of wastewater.  The constant head type of system
  is normally designed using an overflow rate of 15,000 gallons per day per
 square foot and a 1 minute detention time at peak  day flows.

 Typical Performance Evaluation

     Grit removal facilities  can be evaluated by comparing  the amount of grit
 captured to typical values that have been recorded at other facilities.   The
 volume of grit capture is directly related  to  whether the  collection system is
 combined or separate or some combination of these.  If the system is combined
 or partially combined, the amount of grit collected  would  be greater than for
 separate systems.
                                       4-1

-------
    The performance of  the grit washer or classifying  system can be evaluated
 against the volatile content of the grit.  The volatile content of grit meas-
 ured prior to classification would be in the range of  10  to 70 percent, with a
 predominant range in values close to 30 to 50 percent.  However, after washing
 and classifying  the grit, the organic content should be less than 5 percent
 for the majority of the time and always less than 10 percent.

 Process Control

    The only control considerations for velocity-controlled grit systems are
 the speed of the scraper mechanism, and the frequency  of  operation of the
 scrapers.  The scrapers should operate at a slow speed to minimize turbulent
 conditions and at frequent intervals to avoid excessive grit accumulations in
 the channel.  The grit conveyance system to the grit classifier should have
 sufficient capacity to remove the grit from the collecting hopper.  Improper
 speed control could result in damage to equipment due  to grit packing in the
 basin if the speed is too slow, or too much water pumped  and turbulent con-
 ditions if the speed is too fast.

    In the aerated grit removal systems, the operator  controls the air supply
 to the tank.  The air rate must be adjusted so that the spiral roll velocity
 is low enough for grit to settle out of suspension but fast enough to maintain
 organics in suspension.

    The constant head grit removal system requires that the influent flow be
 evenly distributed across the inlet side of the unit,  and flow with equal
 velocity to the outlet weir.  The grit collected by the scraper mechanism must
be removed at a rate that will avoid build-up of grit  in  the basin.

    The grit washer or classifier mechanisms should be operated so as to re-
move all the organic material as measured by the volatile content of the ma-
 terial.  The control feature in the washer is the adjustable weir and rate of
 flow of the wash water.  The efficiency of the cyclone device, as described,
can be altered by changing the inlet and outlet orifices of the unit.   Poorly
washed grit removal can result in a high volatile solids content and severe
odor nuisances can then develop.

Maintenance Considerations

    Maintenance programs for grit removal systems should  include the following
 items:

     1.  Spare parts inventory should include the following: flights and drive
         chains, turntable gears, and motors, wear shoes,  sprockets,  wall
         brackets,  chain pins,  shear pins,  bearings, seals and gaskets,
         buckets, screw conveyor, impellers, air diffusers.

     2.  Record of broken or damaged guide vanes replaced in the case of a
         detritor.

     3.  Replacement of damaged scraper flights.
                                      4-2

-------
      4.   Replacement of broken,  loose or damaged air piping or diffusers.

      5.   Chain tensions adjusted regularly on equipment using chains.

      6.   Daily inspection of the grit to check for odor which would indicate
          high organic content in the grit.

      7.   Daily readings of grit  quantities from each grit chamber are re-
          corded.   These can be used to check  for unbalanced loadings which
          might cause more frequent maintenance.

 Records

     The  recommended  sampling and laboratory tests are shown in Figure 4-1 for
 the  grit removal  system and in Figure 4-2  for  the grit washer or  classifier.
 Similar  tests could  be performed on the cyclone  grit concentrator.

     Other operating  records should include  the following:

     1.   Raw  sewage  influent flow.

     2.   Amount of grit collected per  day.

     3.   Volatile content of grit.

     4.   Moisture content of grit.

     5.   Frequency and  duration  of grit  raking mechanism  for  velocity  con-
         trolled facilities.

     6.   Air  flow per million gallons  for the aerated grit  chamber.

Laboratory Equipment

    The  laboratory should  include  the  following minimum equipment in order to
monitor  the grit removal  system:

    1.   Analytical balance

    2.   Clinical centrifuge with graduated tubes

    3.   Drying oven

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chem-
icals, miscellaneous furniture, etc., and should be referred to for any de-
tailed questions.
                                      4-3

-------






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       ESTIMATED UNIT PROCESS SAMPLING AND
                  TESTING NEEDS
         PRETREATMENT
                     GRIT REMOVAL
      INFLUENT
                                        EFFLUENT TO NEXT
                                        MAINFLOW
                                        TREATMENT PROCESS
                                      RC
                                      REMOVED GRIT TO
                                      CLASSIFIER WASHER
                                      OR FINAL DISPOSAL
        A. TEST FREQUENCY
             H = HOUR      M  - MONTH
             D= DAY       R  - RECORD CONTINUOUSLY
             w- WEEK      Mn= MONITOR CONTINUOUSLY

        B.  LOCATION OF SAMPLE

            RG= REMOVED GRIT




        C.  METHOD OF SAMPLE
            24C-24 HOUR COMPOSITE
            G  GRAB SAMPLE
            R - RECORD CONTINUOUSLY
            Mn- MONITOR CONTINUOUSLY

        D.  REASON FOR TEST
            H - HISTORICAL KNOWLEDGE
            P  PROCESS CONTROL
            C - COST CONTROL

       E.  FOOTNOTES:

             1. AERATED TYPE  ONLY
Figure 4-1

     4-4

-------






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LOCATION OF
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       ESTIMATED UNIT PROCESS SAMPLING AND
                  TESTING NEEDS
         PRETREATMEMT
                     GRIT CLASSIFIER
         RECYCLE TO
         MAIN PROCESS
         FLOW
REMOVED GRIT
 FROM GRIT
 REMOVAL
 PROCESS
                                       GRIT PRODUCT
                                       TO WASHER OR
                                       DISPOSAL
        A.  TEST FREQUENCY
            H HOUR     M- MONTH
            D - DAY       R m RECORD CONTINUOUSLY
            w- WEEK     M- MONITOR CONTINUOUSLY

       B.  LOCATION OF SAMPLE

            GP  =CRIT PRODUCT




       C. METHOD OF SAMPLE
           24C-24 HOUR COMPOSITE
           G"  GRAB SAMPLE
           R   RECORD CONTINUOUSLY
           Mr,- MONITOR CONTINUOUSLY

       D. REASON FOR TEST
           H -  HISTORICAL KNOWLEDGE
           P -  PROCESS CONTROL
           C -  COST CONTROL

       E.  FOOTNOTES:
Figure 4-2

     4-5

-------
Sampling Procedures

    Samples should be collected from the grit container after washing and de-
watering of the captured grit.  The samples are normally grab samples, but
should be representative of the grit collected and not taken at times of peak
flows or low flows.  The sample container should be clean to avoid incorrect
results.

Sidestreams

    The only sidestream from the grit removal facility is the volume of grit
removed from the wastewater.  The unit volumes (cu ft/mil, gal.) should be
estimated and the volatile and moisture content of the grit should be deter-
mined for historical reasons, as already described.
                                      4-6

-------
Process Checklist - Grit Removal
 1.
 2.
 3.

 4.

 5.
 6.
 7.
 8.

 9.
10.

11.

12.

13.

14.
15.
16.
17.
What is design flow 	mgd avg. 	mgd peak?
What is actual plant flow 	mgd avg?
Type of grit removal system	, Number 	
each unit 	mgd, based on what criteria 	
Is all equipment operable? (  ) Yes     (  ) No
If no, what is reason 	
                                                          and capacity of
What are the dimensions of unit?_
What is daily volume of grit?	
What is unit volume of grit?	
                                              	 cu feet
                                              	 cu feet/mg
                                              ) Manual,  (
                                                            )  time clock
Is operation of grit collection equipment? (
(  )  continuous duty.
Is there a bypass channel? (  )  Yes  (  )  No
Does influent channel design provide equal division of flows to each grit
unit? (  )  Yes  (  )  No
Do grit collection mechanisms have adequate spare parts inventory?
(  }  Yes  (  )   No
Is the grit washer housing properly ventilated? (  )  Yes  (  )   No.  If
no, what is problem? 	
Are there adequate safety provisions? (  )  Yes
p roblem?               	
                                                (  )   No.  If no, what is
                                                                      /Year
How often are grit facilities checked? (  )  Daily  (  )  Other 	
What is frequency of scheduled maintenance?	
Is the maintenance program adequate? (  )   Yes  (  )   No
What are the most common problems the operator has had with the grit
removal facility?  	
                                      4-7

-------
References                                       ;

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et alf  Operation of Wastewater Treatment Plants, Manual of
    Practice No.  11, Water Pollution Control Federation (1976).
 3.  CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4.  Wirts,  J.J.,  et al,  Safety in Wastewater Works,  Manual of Practice No.  1,
    Water Pollution Control Federation (1959).

 5.  Miorin,  A.F.,  et al, Wastewater Treatment Plant  Design, Manual of Practice
    No.  8,  Water  Pollution Control Federation (1977).

 6.  State of Virginia O&M inspection form.

 7.  Okun, D.A., et al, Sewage Treatment Plant Design,  ASCE Manual of
    Engineering Practice,  No.  36, 1959.
                                     4-8

-------
5.  PRIMARY SEDIMENTATION

Process Description

    Primary sedimentation basins or clarifiers are tanks used to remove  sus-
pended solids (SS) which will settle from the wastewater.

    The main objectives of primary sedimentation basins are:

    1.   Remove settleable solids.
    2.   Remove floatable solids.
    Sedimentation basins may be square, rectangular or circular in shape.   In
rectangular tanks, the wastewater flows from one end to the other and  the
settled sludge is moved to a hopper at one end, either by scrapers called
"flights" set on parallel chains, or by a single bottom scraper set on a trav-
eling bridge.  Floating materials, such as grease and oil, are collected by a
surface skimmer and then removed from the tank.

    In circular tanks, the wastewater usually enters in the middle and flows
toward the outside edge.  Settled sludge is pushed to a hopper that is in  the
middle of the tank bottom.  Floating material is removed by a surface  skimmer
connected to the sludge collector.  Square sedimentation basins are basically
the same as circular except corner mechanisms are added to sludge collectors
and skimmers.

Typical Design Considerations

    The most important loading factor is the rate of flow through the  sedimen-
tation basin.  This factor is expressed in terms of gallons per day per square
Soot of surface area of the tank.  The factor is called the "surface overflow
rate" or "hydraulic loading rate."  It is calculated as shown in the following
example.

    1.   Determine basin shape and dimensions.  The plant construction draw-
         ings and specifications include this information.
         Shape
         Diameter, dia.
         Depth, D
         Basin area, A = (TT/4)
         Basin volume, gallons
           V = A x D x 7.48
                                        = circular
                                        = 100 ft
                                        =  12 ft
                                        = 7,850 sq ft
                                        = 704,616 gal

Determine total basin flow from plant records.*

Daily Average: 6 mgd
Peak Hour:  9.5 mgd
*If sidestreams (e.g. digester supernatant) are returned to the headworks then
they should be added to the influent flow.
                                      5-1

-------
     3.    Calculate  hydraulic  surface  loading  rate  (both  daily  average  and  peak
          hour)  for  clarifier.

          Hydraulic  Surface  Loading  Rate =     flow  in gal/day
                                           surface  area in  sq ft
                                        =  6,000,000   =  764 gpd/sq  ft
Daily Average Loading Rate

Peak Hour Loading Rate
                                            7,850
                                        = 9,500,000   =  1,210 gpd/sq  ft
                                            7,850
    The detention time of sedimentation basins  is also often calculated.  An
example calculation for the same clarifier  follows:
         Detention Time
               =  (volume in gal) x 24 hr/day x 60 min/hr
                               flow in gal/day
               =  704,616 x 24 x 60
                       6,000,000
                        =  169 minutes
    Typical design criteria are:

    'Average daily hydraulic loading,
      gpd/sq ft
    Peak hour hydraulic loading,
      gpd/sq ft
    Detention Time, min

Typical Performance Evaluation
                                        Typical Design
                                          600 - 1,000

                                        1,200 - 2,500

                                           90 -   150
    Primary sedimentation basins are designed to remove 100% of the settleable
solids.  In most wastewaters, this corresponds to about 65% removal of the raw
wastewater suspended solids.

    A number of factors affect the performance of primary sedimentation basin,
including the following:

    1.   The surface overflow rate.

    2.   Wastewater characteristics (wastewater strength, freshness, and
         temperature; types and amount of industrial waste; and the density,
         shapes, and sizes of particles).

    3.   Pretreatment operations (carryover of grit and screenings).

    4.   Nature and amount of any in-plant wastes recycled ahead of the pri-
         mary clarifier.

    Figure 5-1 shows how much BOD and suspended solids are typically removed
from wastewater in a primary sedimentation basin using the ratio of actual to
design flow.  The figure shows a design overflow rate of 800 gpd/sq ft.  Be-
cause of the fixed size of the tank, the overflow flow rate and detention time
will change with flow, resulting in different removal efficiencies.
                                      5-2

-------
I
   100  *
    90  
    80  
70 
                                Overload
=   60  
(ft

2

E
    50  
oc
a
s   40 
5
o

3   30
OC
    20  
    10
                                               Range ot basin performance,

                                               SS removal
                                nge of ba*ln performance

                              BQD removal
                0.5
                         1.0
                                  1.5
                                           2.0
                                                    2.5
                                                             3 .0
                                                                              4.0
                               Hydraulic Loading Factor
                                                  Actual Plant Loading



                                                     Design Loading
              Figure 5-1.     Estimated removals of  suspended solids and BOD

                               in primary basins  at various  hydraulic loadings.
                                          5-3

-------
     Using  the same example sedimentation basin and Figure 5-1,  the expected
 performance would be:
     Loading  factor

     Average  conditions

     Peak conditions
= actual loading
  design loading
= 764  =  0.96
  800
= 1,210  =  1.5
   800
    Referring  to Figure  5-1,  a  loading  factor of  0.96  (average  condition)
 should  result  in 50  to 65%  SS removal and  25  to 35%  BOD  removal.   Under  peak
 loading conditions,  a factor  of 1.5  should provide 40  to 50%  SS removal,  and
 20  to 30% BOD  removal.

 Process Control

    The major  factor which  the  operator can easily control  is the  rate at
 which sludge is pumped out  of the primary  sedimentation  basin.   How often and
 how long sludge is pumped determines the solids concentration in the  sludge.
 This, in turn, has a major  effect on downstream sludge thickening  and dewater-
 ing processes.  Pumping  too often or too long will cause thin sludge  which
 lowers plant digester capacity;  causes  hydraulic  overloads  to sludge  thicken-
 ing processes; and uses  too much fuel for  sludge  heating.

    If sludge  is not pumped often enough or long  enough,  it can go septic,
 causing odors, and may float  to  the  surface of the sedimentation basin.   Some
 of  the floating sludge may  go into the  sedimentation basin effluent causing a
 reduction in sedimentation  basin efficiency.  Laboratory "spin"  tests (small
 centrifuge)  are often used  by operators to determine when it  is  time  to pump
 out the sludge.  Primary sludge  concentrations of 5-7% are often found with
proper operation of the sludge pumping  system.  By frequent checks, the opera-
 tor can determine the relation between volume of  sludge  in the  test tube  at
 the end of the spin test and  the solids concentrations.

    Sludge pumping may be continuous or operated  on  a timer.  When several
pumps are used, one pump may  withdraw sludge from one hopper while another
pump withdraws from another.  However,  a single pump should not withdraw
sludge from more than one hopper at  any one time  since differences in piping
 friction and sludge characteristics  can cause more sludge to be withdrawn  from
one hopper than from the other.   Pumping should be done  often and  for short
periods rather than less often for longer periods.

    In very small treatment plants with operating personnel on duty only part
of the time, sludge is sometimes pumped only once or twice a day.

    A properly operated primary  sedimentation basin will do much to provide
smooth and efficient operation of downstream unit processes.  For example,
improper control of primary tank operations may cause solids and BOD overload-
ing problems and result in poor  effluent quality.
                                      5-4

-------
    For good operation, sedimentation basin flows must be distributed evenly
among all available tanks.  Uneven flows to the various tanks result in a poor
overall reduction of SS and BOD.

    As with npst unit processes, primary sedimentation is related to other
plant processes.  Some of the factors that will affect settling tank operation
include recycling of waste sludge and supernatant, and carryover of grit and
screenings from pretreatment.

Maintenance Considerations

    Maintenance considerations in addition to those discussed for Overall
Plant Management ares

     1.  Scraper flight inspection and maintenance schedule.

     2.  Periodic chain tension adjustment (in rectangular basins) so that
         there is no chattering sound.

     3.  Spare parts inventory should contain the following:  flights and
         drive chains for rectangular basins, turntable gears and motors for
         circular basins, wear shoes, sprockets, wall brackets, chain pins,
         and shear pins.

Records

    Recommended sampling and laboratory tests are shown in Figure 5-2.

    Other operating records should include:

    1.   Raw sewage influent flow.
    2.   Volume of recycle flows to primary clarifier.
    3.   Amount of sludge and scum pumped per day.
    4.   Frequency and duration of operation of sludge pumps.

Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor primary sedimentation:

    1.   Analytical balance
    2.   Clinical centrifuge with graduated tubes
    3.   BOD incubator
    4.   Drying oven
    5.   Imhoff Cones

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be referred to for any de-
tailed questions.
                                      5-5

-------

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                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS
                                                     PRIMARY CLARIFICATION
                                                                                       EFFLUENT TO
                                                                                       NEXT MAIN
                                                                                       FLOW TREAT-
                                                                                       MENT PROCESS
                                                      INFLUENT FROM
                                                      PREVIOUS MAIN
                                                      FLOW TREATMENT
                                                      PROCESS. OR RAW
                                                      SEWAGE
                      SLUDGE UNDERFLOW
                      TO SLUDGE TREATMENT
                      PROCESS
                                                   A.  TEST FREQUENCY

                                                        H m HOUR     M - MONTH
                                                        0- DAY      R - RECORD CONTINUOUSLY
                                                        W- WEEK     Mn- MONITOR CONTINUOUSLY

                                                   B. LOCATION OF SAMPLE

                                                        I - INFLUENT
                                                        E  EFFLUENT
                                                        $   SLUDGE UNDERFLOW
C. METHOD OP SAMPLE

     24C*24 HOUR COMPOSITE
     G - GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     MB. MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL


E. FOOTNOTES:
                                                   Figure 5-2

                                                  5-6

-------
Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
such as at the center of the channel of flow where velocities are high.  Raw
wastewater samples should be collected after screening and grit removal.  The
sample collector and containers should be clean.  A wide mouth sample collec-r
tor of at least 2 inches should be used.  Samples collected in the effluent
channel should be collected near the discharge point so that any isolated
areas of short circuiting do not influence the results.  Where automatic sam-
plers are used, it is important to keep the sampler tubes clean.

Sidestrearns

    The only sidestream from the primary sedimentation process is the sludge
pumped from the sedimentation basin.  When pumping 5 to 7% sludge, the volume
of sludge pumped for most wastewaters from municipalities will be about 1,500
- 2,000 gallons per day per million gallons treated.  If 3% solids are pumped,
the volume would jump to 3,300 gallons.  This shows the importance of not
pumping thin sludges.
                                      5-7

-------
 Process Checklist - Primary Sedimentation
 1.
 2.

 3.
 4.
 5.
 6.
 7.
 8.
 9.
10.
11.
12.
13.

14.

15.
16.

17.
18.
19.

20.
21.

22.

23.
24.
25.
26.
    What  is  the volume of  influent  flow
    What  is  the design flow 	
dimensions of the sedimentation basin
How much sludge is pumped 	
                                                     gallons/day average?
                                   gallons/day average?  What are the
                                            _gallons/day?
What is the solids concentration in the sludge  	
Are there settleable solids in the effluent              ml/liter?
Is sludge pumping  (  )   manual  (  )   automatic?
How often do sludge pumps run 	minutes/hour?
Frequency of maintenance inspections by plant personnel
Is maintenance program adequate?  (  )   Yes  (  )  No
Does the influent baffle system accomplish its purpose?
Is the scum collection system operating properly?  (  )
Is the sludge collection system operating properly?  (
                                                                      /year.
                                                                          )  No
                                                          (  ) Yes   (
                                                        Yes   (  )  No
                                                        ) Yes   (  )  No
Does the sludge collection system show any signs of mechanical  failure?
(  ) Yes   (  )  No
Does the tank surface indicate improper sludge withdrawal?  (i.e. excessive
floating solids, gas. . .)   (  ) Yes  (  )  No
Is there an excessive accumulation of scum?   (  ) Yes   (  )  No
Does the effluent baffle system accomplish its purpose?
(  )  Yes  (  )  No
Are the effluent weirs level?  (  )  Yes  (  )  No
Are the effluent weirs kept clean? (  )   Yes  (  )  No
If multiple units are used, is the flow distributed evenly?
(  )  Yes  (  )  No
Are proper safety precautions used?  (  )  Yes  (  )  No
Does the unit show signs of short circuiting and/or overloads?
(  )  Yes  (  )  No
Is there an alarm system for equipment failures or overloads?
(  )  Yes  (  }  No
Does the sampling program meet the recommendations?  (  )  Yes  (  )  No
Are operating records adequate?   (  )   Yes  (  )   No
Is the laboratory equipped for the necessary analyses?  (  )   Yes  (  )   No
What spare parts are stocked? 	
27. What are the most common problems the operator has had with the process?
                                      5-8

-------
References

 1. Gulp, G.L., and Polks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.
                                      5-9

-------

-------
6.  ACTIVATED SLUDGE

Process Description

    The activated sludge treatment process is used to convert nonsettleable
and dissolved organic contaminants, such as BOD, into biological floe, which
can then be removed from the wastewater by settling.  Conversion of organics
into biological solids for easier removal is the prime reason for using the
activated sludge process and forms the basis for an understanding of the
process.

    The activated sludge process is a treatment system in which the incoming
wastewater is mixed with existing biological floe (microorganisms or activated
sludge) in an aeration basin.  The bio logical,;-floe is separated from the
liquid in a sedimentation tank which follows Mhe aeration basin.  Part of the
separated biological floe is returned to the aeration basin to provide good
treatment of the wastewater and part is waste|t  (see flow diagram on Figure
6-1).  A detailed description of the activated sludge process can be found in
Reference 1.

Typical Design Considerations

    Typical design criteria for variations of the activated sludge process are
presented in Reference 1 and repeated in Table 6-1.  The values represent the
ranges that are normally found in operating systems.  Many design methods and
considerations have been proposed over the years.  Descriptions of these
methods are not repeated here.

Typical Performance Evaluation

    The activated sludge process can convert nearly all influent soluble or-
ganic matter into solids.  Good treatment includes removing these solids in a
secondary clarifier.  The performance of plain sedimentation of biological
sludge is not easily predicted.  When there are large amounts of solids there
can be poor settling and solids carryover.  When properly designed and oper-
ated, an activated sludge plant should consistently produce effluent suspended
solids and BOD of 20-30 mg/1 or less.

    Many small extended aeration plants do not have good sludge wasting prac-
tices and frequently discharge effluent with high solids concentrations.  The
oxidation ditch extended aeration process has performed well and reliably when
solids are managed properly.

    The activated sludge process can be evaluated by using plant operational
data to check the operating conditions against values given in the previous
section.  For a better understanding of how to evaluate plant performance,
certain terms are defined in Reference 1.  Additional information can be found
in the references listed at the end of the chapter.
                                      6-1

-------
Primary
Effluent
AERATION
  BASIN
 	./SECONDARY \
P^"""1^  SEDIMEN.  T
                    Return activated sludge
                                                 Waste
                                              activated sludge
                                                                    Effluent
            Figure  6-1.   Activated  sludge  flow  diagram.
                                     6-2

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     Based on operating data from plants in the United States,  Table 6-2 has
 been developed.   This table shows several values that are actually being used
 in the operation of the plants and the range of effluent qualities obtained.
 Note that the average aeration time of 3.3 hours is lower than the currently
 accepted values  presented in Table 6-1.

 Process Control

     The activated sludge process has many controls that can be used to change
 the operation of the system.   A brief description of the major control vari-
 ables is given here.

 Dissolved Oxygen in Aeration Tank
     With conventional aeration systems, dissolved oxygen (DO)  in the mixed
 liquor should be maintained in the 1-3 mg/1 range with 2 mg/1  being the desir-
 able minimum.  With pure oxygen systems,  higher levels of DO are maintained,
 with minimum levels being 2-3 mg/1.

 Return Activated Sludge Flow Rate
     To properly  operate the activated sludge process,  a good settling mixed
 liquor must  be achieved and maintained.  The MLSS are  settled  in a clarifier,
 and then returned to  the aeration tank as the Return Activated Sludge (RAS).
 The RAS makes  it possible for the microorganisms to be in the  treatment system
 longer than  the  flowing wastewater.   For  conventional  activated sludge opera-
 tions,  the RAS flow is .generally about 25 to 75% of the incoming wastewater
 flow.   Changes in the activated sludge quality will require  different RAS flow
 rates due to settling characteristics of  the sludge.

 Sludge Blanket Depth  in Secondary Clarifier
     Checking  the depth of the sludge  blanket in the clarifier  is the  most di-
 rect method  for  determining the RAS flow  rate.   The depth of the sludge blan-
 ket may be found by  several types of  devices.   Some are commercially  available
 while others must be  made by  the operator.

 Waste Activated  Sludge Flow Rate
     The objective of  wasting  activated sludge is  to maintain a balance between
 the  microorganisms and the amount of  BOD.  When the microorganisms  remove BOD
 from wastewater,  the  amount of activated  sludge increases.   The rate  at which
 these  microorganisms  grow is  called  the "growth rate"  and is defined  as the
 increase  in  the  amount of activated  sludge that takes  place  in one  day.   The
 objective of sludge wasting, is  to remove  just that  amount of microorganisms
 that grow each day.   This  allows the  total amount of activated sludge in the
process  to remain nearly  constant.  This  condition  is  called "steady-state"
which  is  a desirable  condition  for operation.

    Wasting of the  activated  sludge  is  normally done by  removing  a portion of
 the  RAS  flow.  The waste  activated  sludge is  either pumped to  thickening
 facilities and then to  a digester, or  to  the primary clarifiers  where  it is
pumped  to a digester  with  the raw sludge.
                                      6-4

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     An alternate method for wasting sludge is from the mixed liquor in the
 aeration tank.   There is much higher concentration of suspended matter in the
 HAS than there  is in the mixed liquor.   When wasting from the mixed liquor is
 practiced,  larger sludge handling facilities may be required because of the
 greater liquid  volumes involved.

 Microscopic Examination
     Microscopic examination of the MLSS can be used to evaluate the activated
 sludge process.  The presence of  various microorganisms within the sludge floe
 can rapidly indicate good or poor treatment.   Protozoa play an important role
 in clarifying the wastewater and  act as indicators of the degree of treat-
 ment.   The  protozoa  eat the bacteria and help produce a clear effluent.   The
 presence of rotifers is also an indicator of effluent stability.   The presence
 of filamentous  organisms and a limited  number of protozoa is characteristic of
 a  poor quality  activated sludge.   This  condition is commonly associated with a
 sludge that settles  poorly.

 Process Control References
     There have  been  many publications on the control of activated sludge sys-
 tems.   It is not practical to summarize all of this information in this  manu-
 al.  The evaluator should read the following  references (from which portions
 of this section were drawn)  for detailed information on process control:

          "Process  Control Manual  for  Aerobic  Biological Wastewater Treatment
          Facilities",  U.S.  EPA, Municipal Operations Branch,  Office of Water
          Programs, Washington,  D.C.  20460 (March,  1977)

          "Design Procedures  for Dissolved Oxygen  Control of  Activated Sludge
          Processes",  U.S.  EPA, Office of Research  and  Development,  Cincinnati,
          Ohio 45268

         West, Alfred W.,  Operational Control  Procedures  for  the Activated
          Sludge Process, Parts I,  II, IIIA,  IIIB,  IV and V,  U.S. EPA Office  of
         Enforcement and General Counsel,  1975.

Maintenance Considerations

    Maintenance considerations specific  to activated sludge  systems  are  listed
below.  The general maintenance management discussion  in  the Overall  Plant
Management Section also should be reviewed.

     1.  The spare parts inventory should contain at least the  following
         parts:   one set of each type of bearing, V-belt or chain drives for
         each system, grease seals, all necessary gaskets for replacement of
         parts,  one set each of mechanical seals, washers or sheaves  to allow
         for adjustment of impellers.
                                      6-6

-------
     2.  Inspection each shift of the aeration basin  and oxygen  transfer  fa-
         cilities  (blowers, mechanical aerators, oxygen generation equipment)
         for signs of equipment misalignment, constant rotative  speeds, any
         excessive vibrations, excessive noise from the blowers  or compressors.

     3.  Schedule rotation of mechanical equipment to ensure even wear.

     4.  Mechanical aerators regularly overhauled and the floats and  steel
         parts painted and adjusted as necessary to achieve the  correct oxy-
         genation rate.

     5.  Daily readings of pumping times (RAS and WAS) recorded  from  elapsed
         time meters.  This can be used as a check on plant operations and
         also for scheduling maintenance work.

     6.  Daily readings of blower operating times and/or air flow rates re-
         corded.  These can be used for plant operations and also for sched-
         uling regular maintenance work.  Similar procedures should be follow-
         ed for mechanical aerators and air compressors for the  oxygen gen-
         erating system.

     7.  Utilization rate of oxygen monitored in order to optimize treatment
         efficiency and minimize energy consumption.  Also check the  cfm of
         air per Ib of BOD removed to ensure it is within recommended ranges.

     8.  Motor operating times scheduled so that maintenance downtimes do not
         occur simultaneously.

     9.  Flow rate per kilowatt hour determined for the blowers, mechanical
         aerators or oxygen system.  A deviation from an average value is a
         good indication of efficiency and changing conditions that might re-
         quire maintenance.

    10.  Periodic tests run on each pump or blower to ensure that it operates
         at the same conditions as when it was supplied.

    11.  All non-operating equipment, such as basin dewatering pumps, sluice
         gates and weir gates or standby electric generators, tested at least
         once per month.

    12.  All underwater instrumentation checked and cleaned weekly.   An
         example would be the DO probes or MLSS analyzers.

    13.  All scum and sludge lines flushed regularly.

Records

    Recommended sampling and laboratory tests are shown on Figure 6-2.
                                      6-7

-------
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                                                     ESTIMATED UNIT PROCESS SAMPLING AND
                                                                TESTING NEEDS
                                                     SECONDARY TREATMENT
                                                                    ACTIVATED SLUDGE
                                                INFLUENT FROM
                                                PREVIOUS MAIN
                                                FLOW TREATMENT
                                                PROCESS
                         AERATION DEVICES

                                   E
                                                                 AERATION BASIN
                                                      RECYCLE
                                                      SLUDGE
                                  EFFLUENT TO
                                  SECONDARY
                                  CLARIFIER
 A.  TEST FREQUENCY
     H a HOUR      M  MONTH
     D- DAY       R - RECORD CONTINUOUSLY
     W- WEEK      Mn- MONITOR CONTINUOUSLY

 B.  LOCATION OF SAMPLE

      I = INFLUENT
     E- EFFLUENT
     P= PROCESS
     B= BLOWER (INCLUDE WITH PROCESS TESTING)
     RS =RECYCLE SLUDGE

 C. METHOD OF SAMPLE
     24C-J4 HOUR COMPOSITE
     G - GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     Mn- MONITOR CONTINUOUSLY

 D. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P - PROCESS CONTROL
     C - COST CONTROL

E. FOOTNOTES:

     1. DIFFUSED AIR ONLY
     2. TO BE RUN IF PROCESS IS DESIGNED TO
       CONTROL THIS PARAMETER
     3. MAYBE RUN ON PLANT INFLUENT IF THIS
       IS INITIAL UNIT PROCESS FOLLOWING
       PRETREATMENT
                                             Figure 6-2

                                                  6-8

-------
     Other operating records should include:

     1.    Raw sewage influent flow.

     2.    Return and waste activated sludge flows.

     3.    MLSS and MLVSS in the aeration basin and the return sludge line.

     4.    The unit volume of air or pure oxygen supplied per Ib of BOD removed.

     5.    Frequency and duration of operation of the RAS and WAS pumps.

     6.    The total energy (electricity)  consumed.

 Laboratory Equipment

     The  laboratory should include  the  following minimum equipment in order to
 monitor  the  activated  sludge process.
     1.
     2.
     3.
     4.
     5.
     6.
Analytical balance
Clinical centrifuge with graduated tubes
BOD incubator
Drying oven
Oxygen analyzer or titration equipment
Wet chemistry equipment for monitoring ammonia conversion  (nitrifica-
tion)  if this is required.
    The EPA report  "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc. and should be referred to for any detailed
questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
and homogeneous such as in the aeration basin close to the mixing device or
air diffusers, or from the sludge lines after the sludge has been flowing for
about a minute.  The sample collector and containers should be clean.  A wide
mouth sample collector of at least 2 inches should be used.  Samples collected
in the effluent channel should be collected near the discharge point so that
any isolated areas of short circuiting do not influence the results.  Where
automatic samplers are used, it is important to keep the sampler tubes clean.

Sidestreams

    There are no sidestreams associated with the aeration basin of the acti-
vated sludge process.   The RAS and WAS are discussed in conjunction with the
secondary sedimentation basin.
                                      6-9

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Process Checklist - Aeration Basin
 1.
 2.
 3.

 4.
 5.
 6.

 7.
 8.
 9.
10.

11.

12.

13.

14.

15.

16.

17.
18.
19.

20.

21.
22.
What is actual plant flow
                                      mgd avg.
Type of activated sludge system (flow regime e.g. conventional)
Type of aeration system                        Number of units
                                                               mgd peak?
                                                      (  ) Other
and capacity of each unit 	    _
Color  (  ) Black  (  ) Dark Brown  (  ) Light Brown
Odor  (  ) septic  (  ) Earthy  (  ) None  (  )  Other 	
Foam  (  ) light, crisp    (  ) thick, dark    (  ) heavy white
(  )  Other 	
Are tank contents mixed thoroughly?   (  )  Yes  (  )  No
Are all diffusers or mech. aerators operating properly? (  )  Yes (  )No
Does mixing appear excessive?  (  )  Yes  (  )  No
Do there appear to be dead spots in aeration tank? (  ) Yes (  )  No
If yes, at what location?
Is the process operating in its design mode? (
no, explain
                                                )   Yes  (  )  No  If
Are RAS pumps operating? (
reason?            	
                            )   Yes  (  )  No.  If no, what is the
Are there flow measurement devices for the RAS and WAS systems?
(  )  Yes   (  )  No.  Are they operable  (  )  Yes   (  )  No
Does the aeration basin have a foam control system?  (  ) Yes   (  ) No
Is it operable?  (  )  Yes  (  )  No.  Is it operating:   (  )  Yes  (  )  No
Is the aeration  tank area provided with adequate safety  features (guard-
rails, nonskid surfaces, life preservers, lights)?  (  )  Yes   (  )  No
If multiple basins are operating, is the flow distributed equally?
(  )  Yes   (  )  No  How is it distributed?	
Are the characteristics of the basin contents different  in the various
units? (  )  Yes  (  )  No,
 If yes, describe	
What are the tank dimensions?	
Is operation of  the system  (
(  )  Automatic  (  )
Do mechanical equipment  (blowers, air diffusers, mech. aerators, oxygen
system, etc.) have adequate spare parts inventory?  (  )  Yes   (  )  No
Is the pump station housing adequately ventilated?  (  )  Yes   (  )  No
How often are facilities checked? (  ) once per shift   (  )  daily
(  )  Other 	
                               )  Manual   (  )  Semi-Automatic
                       Computer controlled  (  )  Other 	
23. What is frequency of scheduled maintenance?_
24.
25.
26,
Is the maintenance program adequate?
If no, explain
                                      (  )  Yes
(   )   No
What is general condition of the activated sludge facilities?
(  )  good   (  )  fair   (  )  poor
What are the most common problems the operator has had with the activated
sludge system? 	
                                      6-10

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA.
    Report 430/9-78-001 (Jan.  1978).                   -?-*

 2. Guarino,  C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice  No.  11,  Water Pollution Control Federation (1976).

 3. CH2M-Hill,  Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4.  Wirts,  J.J.,  et al,  Safety in Wastewater Works,  Manual of Practice No.  1,
    Water Pollution Control Federation (1959).

 5.  Miorin,  A.F.,  et al,  Wastewater  Treatment Plant  Design,  Manual of Practice
    No.  8,  Water  Pollution Control Federation (1977).

 6.  State of Virginia O&M inspection form.

 7.  Tsugita,  R.A.,  et al,  Process Control Manual  for Aerobic 'Biological
    Wastewater  Treatment  Facilities,  US  EPA, Municipal Operation Branch,  March
    1977.

 8.  Flanagan, M.J.  and Braken,  B.D.,  Design  Procedures for Dissolved Oxygen
    Control  of  Activated  Sludges,  US  EPA, EPA 600/2-77-032,  Office of Research
    and  Development,  June  1977.

 9.  Ettlich,  W.F.,  A Comparison of Oxidation Ditch Plants  to Competing
    Processes for Secondary and Advanced Treatment of  Municipal  Wastes, US
    EPA,  600/2-78-051, March 1978.
                                     6-11

-------

-------
 7.   TRICKLING FILTERS

 Process  Description

     Trickling filters consist of a bed of coarse material,  either natural or
 synthetic,  over  which primary effluent is uniformly distributed.   As the
 wastewater  trickles through the media,  dissolved organics and finely divided
 organic  solids are  oxidized.   The effluent is collected in an underdrain sys-
 tem  and  either recycled  through the filter or diverted to a secondary
 clarifier.

     As the  microorganisms utilize the  organics and  nutrients provided by the
 wastewater,  the  slime coating on the media thickens.   This  periodically
 sloughs  (falls)  off.   Secondary sedimentation tanks are used to remove it
 from the wastewater  flow.   This sloughing activity  removes  stabilized mate-
 rial from the trickling  filter and prevents clogging  of the void  spaces in
 the  filter  media.

 Typical  Design Considerations

    Trickling  filters are classified according to hydraulic and organic load-
 ings given  in  Table  7-1.  The low rate  filter  is generally  a single  stage
 system without recirculation.   Intermediate rate  filters  are generally single
 stage with  some  recirculation.   High rate  filters generally have  a two stage
 system with  recycle  to provide a relatively constant  hydraulic  loading.   The
 super-high  rate  trickling filter  uses plastic  media.   Plastic media  is rela-
 tively light  so  it can be used for  deep media  beds.   Higher hydraulic loading
 rates can be used with deep beds.   The  flow configurations  suitable  for
 super-high rate  filters are similar to  those  for high rate  units.  There  are
many flow configurations for  trickling  filters.  Details  of these design  con-
 siderations can be found in Reference 1.
                 TABLE 7-1.  TRICKLING FILTER CLASSIFICATION
    Trickling filter
    classification
 Hydraulic loading,
	mgd/ac	
   Organic loading,
Ib BOD/1000 cu ft/day
    Low rate
    Intermediate rate
    High rate
    Super-high rate
       1-4
       4  -  10*
      10  -  40*
       150*
       5-25
      15 - 30
      25 -300
      up to 300
* including recirculation
                                     7-1

-------
Typical Performance Evaluation

    Typical overall efficiency of a trickling filter treatment plant  is about
80 to 85 percent removal of BOD and suspended solids for municipal waste-
waters, or a concentration of about 30 mg/1 of suspended solids and BOD in the
final effluent.  The actual effectiveness of the trickling filter process,
however, depends on the following factors:

        Growth of biological organisms
        Raw wastewater concentration
        Dissolved oxygen
        Temperature
        pH and/or toxic conditions

    The following will serve as an example of step-by-step procedures for
evaluating the performance of trickling filters:

    1.   Define the design and operating mode of the trickling filter.
         Intermediate Rate Rock Media
         Depth, D
         Diameter, dia
         Surface Area, A = (IT /4) dia2
         Volume, V = A x D
         Flow
             Raw wastewater
             Recirculated
             Total, Raw + Recirculated
         BOD, influent to trickling filter
         BOD, clarifier effluent
         Temperature
                                         8
                                         200 ft
                                         31,400 ft2
                                         251,200 ft3

                                         3.5 mgd
                                         3.5 mgd
                                         7.0 mgd
                                         170 mg/1
                                         30 rag/1
                                         20C
    2.
Determine the combined efficiency of BOD removal for the trickling
filter and secondary clarifier.
% BOD    BOD (primary effluent) - BOD  (clarifier effluent) x 100
removal                       BOD (primary effluent)
       =  (170-30)  x 100
           170
       =  82%
    3.   Determine the hydraulic loading rate for the filter.
         Hydraulic load  =
                   Total Flow in gpd
                   Surface Area in ft2
                         =  7.0 x 106 gpd
                            31,400 ft2
                         =  223 gpd/ft2  (9.71 mgd/ac)
    As given in Table 7-1, this is within the typical range given for inter-
    mediate rate filters.
                                     7-2

-------
    4.   Determine the organic  loading  rate  for  the  filter.
         Organic Load  =   (Flow in mgd) x  (BOD mg/1)  x  (8.34  Ib/gal)
                          3.5 x
 (Vol in ft3) - 1000
170 x 8.34 x 1000
                                  251,200
                       =  20  Ib BOD/1000 cu  ft
    This value falls within the range  for organic  loading of  15  to 30  Ib
    BOD/1000 cu ft also given in Table 7-1.

    5.   Calculate the recirculation ratio for  the trickling  filter.
         Recirculation ratio   =  Recirculated flow, mgd
                                 Raw wastewater  flow, mgd
                               =  3.5
                                 3.5
                               =  1/1

    The recirculation ratio is important to  the  control and proper operation
of a trickling filter.  Although they  are designed for a theoretical recircu-
lation ratio, the actual day-to-day recycling of trickling filter  effluent
will depend on field conditions.

Process Control

    The efficiency of treatment attained by  trickling filter  plants depends on
the operation of the final settling tanks.   It  is  essential that sludge  be
removed from the final settling tank before  it rises to the surface and  is
carried out with the final effluent.   The operation of final  settling  tanks is
especially important in the case of high rate trickling filters.   In this
case, sludge becomes septic much faster than the sludge from  standard  rate
filters; consequently, it should be removed  more rapidly.

    In intermediate and high  rate trickling  filters, recirculation ratios usu-
ally range from 0.5 to 4.0 with higher ratios considered to be economically
unjustifiable.  Common engineering practice  is  to  design for  ratios of 0.5 to
2.0.  Trickling filters with  synthetic media use recirculation as  a means of
maintaining a hydraulic loading (gpra/sq ft)  which  will maintain biological
growth throughout the media depth.

    For more detailed information on process control, the evaluator should
read:

         "Process Control Manual for Aerobic Biological Wastewater Treatment
         Facilities", U.S. EPA, Municipal Operations Branch,  Office of Water
         Programs, Washington, D.C. 20460  (March,  1977)

Maintenance Considerations

    In addition to the maintenance program discussion in the  Overall Plant
Management section, there are  several maintenance  considerations for trickling
filters listed below.
                                     7-3

-------
     1.  The spare parts inventory should contain at least the following
         parts:  one set of each type of bearing,  grease seals, all necessary
         gaskets for replacement of parts, one set each of mechanical seals,
         washers or sheaves to allow for adjustment of impellers.  Extra flow
         distribution nozzles should also be in stock.

     2.  Periodic check for deterioration of filter media or housing.

     3.  Inspect the towers and appurtenant facilities each shift.  Recycle
         pumping and flow distributors should be checked daily and cleaned
         bi-annually.

     4.  Schedule overhaul of flow distributors with steel parts painted and
         adjusted as necessary to achieve the desired application rate.

     5.  Motor operating times scheduled so that maintenance downtimes do not
         occur simultaneously.

     6.  Periodic tests run on each pump to ensure that it operates at the
         same conditions as when it was supplied.

     7.  All non-operating equipment, such as standby electric generators,
         tested at least once per month.

     8.  Instrumentation immersed in water checked and cleaned weekly.

     9.  Regular cleaning of underflow and recycle lines.

Records

    Recommended sampling and laboratory tests are shown in Figure 7-1.

    Other operating records should include:

    1.   Raw sewage influent flow.

         Recirculation flow and recirculation ratio.
2.

3.
         DO should be analyzed periodically to verify adequate ventilation of
         the filter.
    4.   The total energy (electricity) consumed.

Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor the trickling filter process.

    1.   Analytical balance
    2.   Clinical centrifuge with graduated tubes
                                     7-4

-------
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H






   ESTIMATED UNIT PROCESS SAMPLING AND
              TESTING NEEDS
   SECONDARY TREATMENT
              TRICKLING FILTER

                               "EFFLUENT TO
                                SECONDARY
                                CLARIFIER
            LINFLUENT FROM
              PREVIOUS MAIN FLOW
             TREATMENT PROCESS
   A. TEST FREQUENCY
       H = HOUR      M - MONTH
       0 DAY       R - RECORD CONTINUOUSLY
       w WEEK      MO- MONITOR CONTINUOUSLY

  B.  LOCATION OF SAMPLE
       I = INFLUENT
  C. METHOD OF SAMPLE
      24C-24 HOUR COMPOSITE
      G - GRAB SAMPLE
      R - RECORD CONTINUOUSLY
      Mn- MONITOR CONTINUOUSLY

  D. REASON FOR TEST
      H - HISTORICAL KNOWLEDGE
      P - PROCESS CONTROL
      C - COST CONTROL

  E.  FOOTNOTES:
 Figure  7-1
7-5

-------
    3.   BOD incubator
    4.   Drying oven
    5.   Oxygen analyzer or titration equipment

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc. and should be consulted for any detailed
questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
and homogeneous such as in the distribution line or from the sludge lines
after the sludge has been flowing for about a minute.  The sample collector
and containers should be clean.  A wide mouth sample collector of at least 2
inches should be used.  Samples collected in the effluent channel should be
collected near the discharge point so that underflow from all areas of the
filter is thoroughly mixed.  Where automatic samplers are used, it is impor-
tant to keep the sampler tubes clean.

Sidestrearns

    There are no sidestreams associated with the trickling filter process it-
self.  Solids production and disposal are discussed in Section 11.
                                     7-6

-------
Process Checklist - Trickling Filters
 1.
 2.
 4.
 5.
 6.
 7.
 8.
 9.

10.

11.

12.

13.

14.


15.

16.

17.


18.

19.

20.
21.
What is actual plant flow
What is recycle flew 	
                                  	 mgd, average;
                                  mgd?   Is  it 	
_mgd,  peak?
  constant,
               intermittent?
 3. What is filter classification
               high,
                                         low,
                                                          intermediate,
                            super-high?
What type of media is used?
What is the depth of media?
Number of units 	
Color (  ) Black  (
Odor  (  )  Septic  (  ) Earthy   (  )
                                            feet
                     	; Diameter of units 	
                     ) Dark Brown   (  ) Light Brown   (  ) Other_
                                       None  (  )  Other 	
                                                 (  )  Yes   (  )  No
Is there evidence of uneven flow distribution?
Are any nozzles clogged?   (  )  Yes   (  )  No
Is there evidence of filter clogging  such as ponding?   (  )  Yes
(  )  No.  Icing?   (  )  Yes   (  )  No  Other 	
Is there evidence of filter flies?  (  )  Yes   (  )  No,  Snails
(  )  Yes  (  )  No.  Roaches   (  )   Yes  (  )  No.  Other 	
Is there grass or other vegetative material growing on the filter?
(  )  Yes  (  )  No  Other 	
Are there flow measurement devices for the recirculation flow?
(  )  Yes  {  )  No.  Are they operable?  (  )  Yes   (  )  No
Are the recirculation pumps operating? (  )   Yes  (   )  No.  If no,
why?	

Is the trickling filter area provided with adequate safety features
(guardrails, nonskid surfaces, life lines, lights)? (  }   Yes  (  )  No
If multiple filters are operating, is the flow distributed equally?
(  )  Yes  (  )  No. How is it distributed?
Are the characteristics of the filter contents different in the various
units? (  )   Yes  (  )   No.  If yes, describe 	
                                                semi-automatic
                                               )   other 	
Is operation of the system  (  )   manual  (  )
(  )   automatic  (  )   computer controlled  (           	
Does mechanical equipment (flow distributors, pumps, etc) have adequate
spare parts inventory? (  )   Yes  (  )   No
Is the pump station housing adequately ventilated?  (  )  Yes  (  )  No
How often are facilities checked? (  )   once per shift   (  )  daily
(  )   other
22. What is frequency of scheduled maintenance?
23. Is the maintenance program adequate? (  )   Yes  (  )   No.  If no,
    explain	
24. what is general condition of the trickling filter facilities?
    (  )   good  (   )   fair  (  )   poor
25. What are the most common problems the operator has had with the trickling
    filter system?
                                     7-7

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al.  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.
 7. Benjes, H.H., Jr., Attached Growth Biological Wastewater Treatment
    Estimating Performance and Construction Costs and Operating and
    Maintenance Requirements, EPA Contract 68-03-2186 (January, 1977).

 8. Battelle Pacific Northwest Laboratories, Evaluation of Municipal Sewage
    Treatment Alternatives, Council on Environmental Quality, Contract EQC316
    (February, 1974).
                                     7-8

-------
8.  ACTIVATED BIOFILTER PROCESS

Process Description

    The activated biofilter  (ABF)  is the proprietary name  for  a  treatment
process combining a trickling filter with an activated sludge  system.  After
primary sedimentation, wastewater  flows to the filter  (bio-cell)  lift  station
where  it  is mixed with filter underflow and return activated sludge  from the
secondary sedimentation basins.  This mixed liquor is distributed over the
redwood slat trickling filter media and the organic matter in  the waste is
oxidized by the attached microbes growing on the media as  well as the  sus-
pended microorganisms present in the return sludge.  As the wastewater
trickles through the media,  it is naturally aerated.  The  underflow  from the
filter is split, with the majority going to the aeration basin and the
remainder being recycled.  The activated sludge system is  generally  equipped
with mechanical surface aerators.  This additional aeration provides sup-
plemental BOD removal while producing a well-settling sludge.  Final sedi-
mentation is basically the same as that following standard activated sludge,
except solids are recycled to the bio-cell rather than the aeration basin.

Typical Design Considerations

    Although the design of an ABF system is not as simple  as merely adding a
trickling filter to an activated sludge system or vice-versa,  the basic
design theories of the individual systems are applicable.  Generally,  the
trickling filter is designed to remove about 65 percent of the influent
(primary effluent)  BOD and the aeration basin is designed  to remove the
remainder.  Table 8-1 presents the basic design criteria.

Typical Performance Evaluation

    The performance of ABF systems has been evaluated in both  pilot and full-
scale applications.  Overall, an ABF system can be expected to produce
secondary effluent quality (20 to 30 mg/1 BOD and SS) from domestic waste-
water.  By reducing the design loadings, it can produce roughly  the same
quality effluent from municipal wastewater with a significant  industrial
(particularly food processing)  waste contribution.
                                     8-1

-------
          TABLE 8-1.  TYPICAL ACTIVATED BIOFILTER DESIGN CRITERIA

EFFLUENT CRITERIA
BOD5
Suspended solids
BIO-CELL PARAMETERS
Organic load Ib
Media depth
BOD removal
HYDRAULIC PARAMETERS
Bio-cell recycle
Sludge recycle
Bio-cell flow
Bio-cell hydraulic load
AERATION PARAMETERS**
Detention time*
Organic load Ib
F/M Ib
MLVSS
MLSS
SLUDGE PRODUCTION Ib
Units

mg/1
mg/1

BOD/1000 cu ft/day
ft
%

*
*
*
gpm/sq ft

hrs
BOD/1000 cu ft/day
BOD/MLVSS/day
mg/1
mg/1
VS/lb BOD removed
Typical Value

20
20

200
14
65

0.4Q
0.5Q
1.9Q
3.5

0.8
95
0.5
3000
4000
0.65
Range

10-30
10-30

100-350
5-22
55-85

0-2. OQ
0.3-l.OQ
1.5-4.0Q
1.5-5.5

0.5-2.0
50-225
0.2-0.9
1500-4000
2000-5000
0.55-0.75

*Based on design average flow and secondary influent BOD=150 mg/1
**Based on aeration BOD_ loading after bio-cell removal
                                    8-2

-------
    The following example demonstrates the steps to be taken to evaluate ABF
performance.
    1.   Determine operating conditions
         Flow
              Influent to bio-cell
              Bip-cell recycle
              Sludge recycle
              Total to bio-cell
         Bio-cell characteristics
              Media depth
              Surface area
              Media volume
         Aeration basin characteristics
              Volume
              Hydraulic detention
         BOD
              Influent to bio-cell
              Influent to aeration basin
              Effluent from final clarifier
  3 mgd
1.5 mgd
1.5 mgd
  6 mgd

    14 ft
 2,000 sq ft
28,000 cu ft

17,000 cu ft
 1 hr

150 mg/1
 72 mg/1
 30 mg/1
         Determine hydraulic loading rate on the bio-cell
         Hydraulic Loading  =  Total flow in gpd
                               Surface area in ft^
                            =  6 mgd x 694  gpm/mgd  =  2.08 gpra/sq ft
                               2000 sq ft
         This value is within the range presented in Table 8-1.

         Determine organic loading rate on the bio-cell.
         Organic Loading  =  (Flow, mgd)  x (BOD, mg/1) x (8.34 Ib/gal)
                                        (Vol, cu ft) - 1000
                          = 3.0 x 150 x 8.34 x 1000 = 134 Ib BOD/1000 cu ft/day
                                  28,000
         This, too, is within the prescribed loading rate given in typical
         design criteria.

         Determine minimum efficiency of bio-cell.
         % BOD removal = BOD in - BOD out x 100
                             BOD in
                       = 150 - 72 x 100 = 52%
                           150
         This should be considered an absolute minimum removal efficiency from
         the bio-cell; generally the removal is around 65 percent.
                                     8-3

-------
     Determine the organic loading on the aeration basin.
     Organic loading = {Flow, mgd) x (BOD, mg/1)  x 8.34 Ib/gal
                                (Vol, cu ft)  T 1000
                      =  3.0 x 72 x 8.34 x 1000 = 106 Ib/BOD 1000 cu ft/day
                                  17000
     This value is again within the acceptable range for organic loadings
     on the aeration basin.

     Determine the removal efficiency in the aeration basin.  The value
     calculated will be a maximum for this example since that for the
     bio-cell was a minimum.
     % BOD removed  ~   72 - 30 x 100 = 58%
                           72

     Determine the overall process efficiency.
     % BOD removal   -   Bio-cell removal + aeration basin removal -
                         (Bio-cell removal x aeration basin removal)
                         0.52 + 0.58 - (0.52 x 0.58) = 0.80 (or 80%)
     Overall BOD removal efficiency can also be determined as follows:
     % BOD removal   =   BODin - BODout   x 100
8.
                         BODin

                    150 - 30  x 100  =  80%
                       150

Determine recirculation rates
Bio-cell recirculation   =  Bio-cell recycle
     Sludge recirculation
                            Influent to bio-cell
                            1.5 mgd  =  0.5
                            3.0 mgd
                            sludge recycle	
                            Influent to bio-cell
                                 1.5 mgd  =
                                 3.0 mgd
                                        0.5
     Both of these values are typical for the ABF process.  They can be
     varied over fairly wide ranges as indicated in Table 8-1 to provide a
     good deal of process flexibility and control.
                                 8-4

-------
 Process Control

     The control of the ABF process is much like the control of the activated
 sludge process, with the bio-cell serving as a mixed liquor aerator.  The
 activated sludge control considerations in Section 6 of this manual should be
 reviewed for information relevant to the ABF process.  Detailed trickling
 filter control considerations in Section 7 are generally applicable to ABF
 bio-cells.

     Return  sludge rates of 50 percent of the average flow rate and bio-cell
 recycle rates of 50 percent of the average flow rate are most often used.

 Maintenance Considerations

     Use maintenance information for  Sections 6 and 7, activated sludge and
 trickling filters.

 Records

     Recommended sampling and laboratory tests are  shown in Figure  8-1.

     Other operating records should include:

     1.    Raw sewage influent flow.
     2.    Recirculation  flow.
     3.    Return and waste activated  sludge flows.
     4.    MLSS  and MLVSS in the aeration basin and  the return  sludge line.
     5.    The unit volume of air  supplied per  Ib  of BOD  removed  in  the  aeration
          step.
          Frequency  and  duration  of operation  of  the RAS and WAS pumps.
6.
    7.   The total energy  (electricity) consumed.

Laboratory Equipment

    The laboratory should  include the following minimum equipment  in order  to
monitor the activated sludge process.

    1.   Analytical balance
    2.   Clinical centrifuge with graduated tubes
    3.   BOD incubator
    4.   Drying oven
    5.   Oxygen analyzer or titration equipment

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chem-
icals, miscellaneous furniture, etc. and should be referred to for any de-
tailed questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
and homogeneous such as at the bio-cell recirculation lift station or in the
                                     8-5

-------
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aeration basin close to the mixing device or from the sludge lines after  the
sludge has been flowing for about a minute.  The sample collector and con-
tainers should be clean.  A wide mouth sample collector of at least 2 inches
should be used.  Samples collected in the bio-cell underflow or aeration  basin
effluent channel should be collected near the discharge point so that any iso-
lated areas of short circuiting do not influence the results.  Where automatic
samplers are used, it is important to keep the sampler tubes clean.

Sidestreams

    The sidestreams from the ABF process are similar to those from activated
sludge and are discussed in the section regarding secondary sedimentation,  in
general, the recycling of sludge to the bio-cell and the accumulation of  sol-
ids (humus)  in that unit reduces the total solids production from the process.
                                    8-7

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 Process Checklist - ABF
  1.
  2.

  3.
  4.
  5.
  6.
  7.

  8.
 9.



10.

11.
12.

13.

14.

15.

16.

17.
 What is  actual plant flow?	 mgd,
 What is  underflow recycle rate	
 cycle rate  to  the bio-cell	
 What type of media is used in the  bio-cell?
 What is  the depth of media 	
 Number of bio-cell units
                                          average;
                                             mgd?
                                            mgd?
	mgd,  peak
 What is the solids re-
                                            feet?
                                       ; Size of bio-cell units
Type of aeration system (flow regime)
Type of aeration equipment 	
Capacity of each unit 	
                                             	; Number of units
                                             Tank dimensions
                                                   )  Yes   (  )  No.  Are
Color of bio-cell growth:
(  ) Black   (  ) Dark Brown   (  ) Light Brown   (  ) Other
Color of activated sludge:
(  ) Black   (  ) Dark Brown   (  ) Light Brown   (  ) Other
Odor of bio-cell growth:
(  )  Septic   (  ) Earthy   (  )  None  (  )  Other 	
Odor of activated sludge:
(  )  Septic   (  ) Earthy   (  )  None  (  )  Other 	
Is there evidence of uneven flow distribution?  (
any nozzles clogged?  (  )  Yes  (  )  No
Is there evidence of bio-cell clogging, such as ponding? (  ) Yes   (  ) No.
Is there evidence of filter flies?   (  )   Yes   (  )  No.  Snails?   (  ) Yes
(   )  No.  Roaches?  (  )  Yes  (  )  No.  Other 	
Is there grass or other vegetative material growing on bio-cell?  (  ) Yes
(   )  No.  Other	
Are there flow measurement devices for the recirculation and return sludge
flows?  (  )   Yes  (  )   No.  Are they operable?  (  )   Yes  (  )  No
Are recirculation lift station and RAS pumps operating? (  ) Yes  (  ) No.
If no, what is the reason?	
If multiple bio-cells are operating, is the flow distributed equally?
(   )   Yes  (   }  No. How is it distributed?
Are the characteristics of the bio-cell contents in each bio-cell
different?  (  )  Yes  (  )  No. If yes, describe 	
18.
19,
20.
21.

22.

23.

24.

25.

26.
Are aeration tank contents mixed thoroughly?  (  )   Yes
Are mechanical aerators operating properly?  (  ) Yes (
Does mixing appear excessive? (  )   Yes  (  }  No
Do there appear to be dead spots in the aeration tank? (
If yes, at what location? 	
                                                         (
                                                        )No
         )  No
                                                          )  Yes  (  )   No
Is the process operating in its design mode? (
no, explain 	
                                                )   Yes  (  )   No.  If
Does the aeration basin have a foam control system?(  )  Yes  (  )  No.
Is it operable? (  )   Yes  (  )   No
Is the aeration tank area provided with adequate safety features (guard-
rails, nonskid surfaces, life preservers, lights)? (  )  Yes  (  )   No
If multiple basins for each step are operating, is the flow distributed
equally?  (  )   Yes  (  )  No. How is it distributed?	
Is operation of the system  (  )   Manual  (  )   Semi-Automatic
(  )   Automatic  (  )   Computer  controlled  (   )   Other
                                     8-8

-------
27. Does mechanical equipment (flow distributors, pumps, mechanical aerators,
    etc) have adequate spare parts inventory?  {  )   Yes  (  )  No
28. Is the pump station housing adequately ventilated?  (  ) Yes  (  )   No
29. How often are facilities checked? (  )  once per shift  (  )   daily
    (  )  Other 	
30. What is frequency of scheduled maintenance?	
31.
32.
33,
Is the maintenance program adequate? (
If no, explain 	
)   Yes
(   )   No
What is general condition of the ABP facilities?
(  )   good  (  )   fair  (  )   poor
What are the most common problems the operator has had with the ABF system?
                                    8-9

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US >EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).

 3. CH2M-HI11, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water'Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.

 7. Benjes, H.H., Jr., Attached Growth Biological Wastewater Treatment
    Estimating Performance and Construction Costs and  Operating  and
    Maintenance Requirements, EPA Contract 68-03-2186  (January,  1977).

 8. Battelle Pacific Northwest Laboratories, Evaluation of Municipal Sewage
    Treatment Alternatives, Council on Environmental Quality, Contract EQC316
    (February, 1974).

 9. Dunnahoe, R.G., and Hemphill, B.W., The ABF Process, A Combined
    Fixed/Suspended Growth Biological Treatment System, AWWA-FACE Conference
    (September 1976).
                                     8-10

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 9.  LAGOONS

 Process Description

     Lagoons,  or stabilization ponds are commonly used in the U.S. to treat
 domestic wastewater from small communities (less than 10,000 people) and have
 some application in treating industrial wastes.   Lagoons are generally simple
 basins enclosed by earthen dikes.

     Lagoons can be classified by many characteristics including depth, rate
 of waste loading,  detention time,  source of oxygen or type of biological
 activity.   There are four principal types - aerobic,  anaerobic, facultative,
 and aerated.   Since anaerobic lagoons are rarely used for municipal waste-
 water treatment, this discussion will be limited to the other three lagoon
 systems.

     A simple  aerobic lagoon or oxidation pond is a shallow pond in which
 organic materials  are degraded by  aerobic bacteria.  The dissolved oxygen
 (DO)  is supplied by oxygen transfer between the  air and water surface and by
 algae growth.   The amount of oxygen supplied by  natural surface aeration is
 not dependable,  therefore the oxygen supplied by algae photosynthesis is
 considered  limiting in design.

     Facultative lagoons provide a  more  complex environment in which waste
 stabilization  occurs.   The surface of a facultative lagoon is similar to that
 of  an aerobic  lagoon in that bacteria and algae  provide organic stabiliza-
 tion.   Solids  settle to the  lower  depths of the  lagoon and are anaerobically
 decomposed.  In  the intermediate zone,  facultative bacteria,  oxidize the
 dissolved solids in the  influent wastewater.   Mechanical aeration equipment
 is  sometimes provided  for  mixing the upper  zone  of a  facultative lagoon  and
 to  augment  natural aeration.

    Aerated lagoons do not depend  on algae  and sunlight supplying the neces-
 sary  DO for bacteria but  diffusers  or mechanical aerators  are  used to supply
 oxygen  and  suspend  the solids by mixing  action in  the  wastewater.   A separate
 sedimentation  step  is  required.  Aerated lagoons are commonly  arranged in
 series  for  improved  BOD removal and  can  be  followed by an  aerobic lagoon
 acting  as a polishing  pond or sedimentation step for suspended  solids  removal.

 Typical Design Considerations

    Properly designed  and operated  lagoon systems  are  capable of producing
high  removals of organic materials,  solids, and  bacteria.  Design  criteria
 for the three  lagoon types described  in  this chapter are given  in  Table 9-1.

Typical Performance Evaluation

    In evaluating the performance of a lagoon, the  evaluator should  check the
system records to see  that effluent BOD5 and SS  concentrations are gener-
ally within the expected ranges presented in Table  9-1.  The following step-
by-step procedure shows how to evaluate  lagoons:
                                     9-1

-------

















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-------
    1.   Determine the design criteria  for  the pond  system.

         Type of Pond - Facultative
         Pond Dimensions
              Area, A                   =  872,356  ft2 or  20  acres
              Depth, D                  =  3  ft
              Volume, V = A x D = 60 acre-ft
         Flow                           =1.0 mgd
         Influent BOD                   =  300 mg/1

    2.   Determine the detention time of  the wastewater  within  the  pond.

         Detention Time =  (V in acre-ft)  (7.48 gal/ft3)  (43,560 ft2/ac)
                                        (Flow in gpd)
                        =  (60) (7.48)  (43,560)
                                (1 x 106)
                        =  20 days
         For a facultative lagoon, Table  9-1 shows that  a 20-day detention
         time is within the acceptable  7- to 30-day  range.

    3.   Determine the organic loading  for  the pond.

         Organic Loading  =  (Flow in mgd)  (BOD,  mg/1)  (8.34  Ib/gal)
                                        (Area in Acres)
                          =  (1) (300)  (8.34)
                                    (20)
                          =  125 Ibs BOD/day/acre

         By checking Table 9-1 the organic  loading of the lagoon is higher
         than normally expected.  If the  pond is  not performing  as  desired,
         the referenced design shortcomings and troubleshooting  guide  should
         be consulted for possible solutions to remedy this problem.

    To achieve best results,  lagoons must be operated to provide enough mixing
to distribute the influent and settleable solids  throughout the  pond.  In
unaerated ponds, mixing is provided by  wind and wave turbulence,  as well as at
inlets and outlets.

    For the light to moderately loaded  lagoon, sludge usually does  not accum-
ulate in large quantities, although there may be  small deposits  near the inlet
and in cold weather over wider areas.    For moderate  to heavily  loaded  lagoons,
sludge accumulation may be more significant and it may need to be removed  and
disposed of.  The accumulation of sludge  must be  carefully controlled  since
the performance of the pond will be reduced, as measured by the  SS content of
the effluent.
                                     9-3

-------
    There are four operation strategies presented in Table 9-2.  Aerated
lagoon process control strategy consists mainly in aeration control.  Aerators
are usually constant speed so variation is accomplished by time-clock-con-
trolled operation.  By this procedure those aerators that are unnecessary
during warm summer afternoons (high algae concentration) can be turned off.
During early morning hours or during peak conditions more aerators can be
turned on.

Maintenance Considerations

    The features of a good maintenance program that the inspector should look
for are listed below.  General features for both unaerated and aerated ponds
are followed by those relating specifically to systems with mechanical
equipment.  These should be used in conjunction with general maintenance
management guidelines.

     1.  Scheduled inspection of the pond linings and/or levees.

     2.  Weed control program.

     3.  Insect control in the vicinity of the lagoons.

     4.  Burrowing animals control.

     5.  Regular inspection of the lagoon site for visible signs of process
         upset or vandalism of the facilities.  Mechanical equipment, such as
         automatic effluent level controls, should also be routinely checked
         and tested to insure proper operation.

     6.  Regular inspection of aerated lagoons and oxygen transfer facilities
         (i.e.,  mechanical aerators,)  to visibly inspect the equipment for
         abnormalities.

     7.  Spare part inventory should contain at least the following parts:
         one set of each type of bearing,   grease seals, all necessary gasket
         for replacement of parts, one set each of mechanical seals,  washers
         or sheaves to allow for adjustment of impellers.

     8.  Daily readings of mechanical aerators operating times.   These can be
         used for plant operations and also for scheduling regular maintenance
         work.

     9.  Periodic tests run on each aerator to ensure that it operates at the
         same conditions as when it was supplied.

    10.  All non-operating equipment,  such as basin dewatering pumps, sluice
         gates and weir gates or standby electric generators,  should be tested
         at least once per month.
                                     9-4

-------
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Records

    Recommended sampling and laboratory tests for aerated and unaerated
lagoons are shown in Figures 9-1 and 9-2.

    Other operating records should include:

    1.   Raw sewage influent flow.

    2.   Return and waste activated sludge flows  (for aerated systems with
         solids recycle).

    3.   MLSS and MLVSS in the aeration basin and the return sludge  line  (for
         aerated systems with solids recycle).

    4.   The unit volume of air supplied per Ib of BOD removed  (for  aerated
         systems).

    5.   Frequency and duration of operation of the RAS and WAS pumps (for
         aerated systems with solids recycle).

    6.   The total energy (electricity) consumed  (for aerated systems).

    7.   Graphical plots of pH and DO  to characterize diurnal and seasonal
         variations in lagoon operation.

Laboratory Equipment

    The laboratory should include the  following minimum equipment in order to
monitor the lagoon treatment process.

    1.   Analytical balance
    2.   Clinical centrifuge with graduated tubes
    3.   BOD incubator
    4.   Drying oven
    5.   Oxygen analyzer or titration  equipment
    6.   pH meter

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc. and should be referred to for any detailed
questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
and homogeneous such as in aerated lagoons close to the mixers. Samples ob-
tained from naturally aerated systems  should be from a location in the center
of the pond.  The sample collector and containers should be clean.  A wide
mouth sample collector of at least 2 inches should be used.  Samples collected
in the effluent channel should be collected near the discharge point so that
                                     9-6

-------
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                                                    PREVIOUS MAIN
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                                                        H  HOUR     M - MONTH
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                                                        w- WEEK     Mn- MONITOR CONTINUOUSLY

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                                                   C. METHOD OF SAMPLE

                                                       24C-2* HOUR COMPOSITE
                                                       C - CRAB SAMPLE
                                                       R - RECORD CONTINUOUSLY
                                                       Mn MONITOR CONTINUOUSLY

                                                   D. REASON FOR TEST

                                                       H - HISTORICAL KNOWLEDGE
                                                       P - PROCESS CONTROL
                                                       C - COST CONTROL

                                                  E. FOOTNOTES:

                                                       1. PROCESS NOT LIKELY FOR FLOWS
                                                         GREATER THAN S MGD
                                                   Figure 9-1
                                               9-7

-------








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Figure 9-2
9-8

-------
any isolated areas of short circuiting do not influence the results.  Where
automatic samplers are used,, it is important to keep the sampler tubes clean.

Sidestreams

    Although many such ponds have functioned for years with little amounts of
sludge build-up, there are exceptions to the rule.  Any accumulated solids
should be well digested and can be dewatered in sand beds and buried on site
or at a sanitary landfill.  This will only be required every few years.
                                     9-9

-------
 Process  Checklist - Aerated  Lagoons
  1.
  2.
  3,

  4.
  5.
  6.
  7.

  8.

  9.
10.
11.

12.

13.

14.
15.
     What is  actual plant flow 	 mgd avg. 	 mgd peak?
     Type of  lagoon system 	
     Type of  aeration  system	Number  of units 	
     and  capacity of each unit  '	               .
     What "are the lagoon  dimensions?	'' ;	      '
     Color   (  ) Green (   )  Dark Brown   (   )  Light Brown1 (   )  Other_	
     Odor   (   ) Septic  ( ) Earthy   (   )  None   (   )  Other  -''.     .-
     Foam  (   ) light,  crisp    (  ) thick,  dark    (   )  heavy white
     (  )   Other 	
     Are  lagoon contents  mixed thoroughly?  (   )   Yes  (  )   No
     (Aerobic lagoons  should be, facultative  lagoons  should  not)
     Are  all  mechanical aerators operating properly?  (   ) Yes {   )No
     Does mixing appear excessive? (  )  Yes   (  )  No
     Do there appear to be dead  spots in lagoon? (  )  Yes  (   )   No
     If yes,  at what location? 	
    Is the process operating  in  its design mode?
    no, explain	
(   )   Yes  (   )   No  If
    Does the lagoon basin have a foam or scum control system?  (   ) Yes  (   )
    Is it operable? (  )  Yes  (  )  No.  Is it operating?   (  )  Yes   (   )
    If multiple lagoons are operating, is the flow distributed equally?
    (  )  Yes  (  )  No  How is it distributed?	
    Are they operated in  (  )  series,  (  )  parallel?
    Are the characteristics of the lagoon contents different in the various
    units (  )  Yes  (  )  No. If yes, describe 	
                           No
                            No
16. Is there vegetation growing in the lagoon or on the dikes?  (  ) Yes  (  ) No
17. Is there evidence of rodent burrowing on the dikes?   (  )  Yes  (.  )  No
18. Is there an excessive insect population in the vicinity of the lagoon?
    (  )   Yes  (  )  No
19. Does mechanical equipment (motors, mechanical aerators, etc.) have
    adequate spare parts inventory? (  )   Yes(  )   No
20. Is the pump station housing adequately ventilated? (  ) Yes  (  )   No
21. How often are facilities checked? (  )  once per shift  (  )   daily
    (  )   Other 	
22. What is frequency of scheduled maintenance?
24.
25
    Is the maintenance program adequate?
    If no, explain ^	
                                         (  )   Yes
     (  )  No
    What is general condition of the lagoon facilities?
    (  )   good  (  )   fair  (  )   poor
26. What are the most common problems the operator has had with the lagoon
    system? 	
                                     9-10

-------
Process Checklist - Unaerated Lagoons
 1.
 2.
 3.
 4.
 5.
 6,
 7.
10
11.
12.
13.

14.
What is actual plant flow
Type of lagoon system
mgd avg.
mgd peak?
What are the lagoon dimensions? 	;	;	
Color  (  )  Green (  ) Light Brown  (  ) Grey   (  ) Other_
Odor  (  ) Septic  (  ) Earthy  (  ) None  (  ) Other 	
Are lagoon contents properly mixed?  (  )  Yes  (
Is the process operating in its' design mode? (  )
no, explain
             )  No
             Yes  (
)   No  If
    Does the lagoon basin have a foam or scum control system?
    (  ) Yes  (  )  No  Is it operable?  (  )  Yes  (  )  No.  Is it operating?
    (  )  Yes  (  )  No
    If multiple lagoons are operating,  is the flow distributed equally?
    (  )  Yes  (  )  No. How is it distributed
Are the characteristics of the lagoon contents different in the various
units (  )   Yes  {  )   No, If yes, describe
Is there vegetation growing in the lagoon or on the dikes?  (  ) Yes  (   ) No
Is there evidence of rodents burrowing on the dikes?  (  )   Yes  {  )  No
Is there an excessive insect population in the vicinity of  the lagoon?
(  )   Yes  (  )   No
How often are facilities checked?(  ) once per shift   (  )  daily
(  )   Other	
15. What is frequency of scheduled maintenance?_
16. Is the maintenance program adequate?  (
    If no, explain 	
                                        )  Yes
            (  )  No
17. What is general condition of the lagoon facilities?
    (  )   good  (  )   fair  (  )  poor
18. What are the most common problems the operator has had with the lagoon
    system? 	
                                     9-11

-------
References

 1. Gulp, G.L.r and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No.  11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts,  J.J.,  et al. Safety in Wastewater Works,  Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.P., et al, Wastewater Treatment Plant  Design, Manual of Practice
    No.  8,  Water  Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.

 7,, URS  Research  Company,  Procedural Manual for Evaluating the  Performance of
    Wastewater Treatment Plants,  EPA contract No.  68-01-0107.

 8. Metcalf & Eddy, Inc.,  Wastewater Engineering;  Collection, Treatment,
    Disposal, McGraw Hill  Book Company (1972).
                                    9-12

-------
10.  ROTATING BIOLOGICAL CONTACTORS

Process Description

    Rotating biological contactors  (RBC's) consist of large discs mounted on
horizontal shafts in concrete tanks.  Organisms attach and grow on  the surface
of the media forming a 1- to 4-mm thick layer of biomass for organic removal.
The rotation of the reactor provides a source of oxygen for microbial growth
and promotes mixing, keeping the wastewater solids in suspension.   Shearing
forces on the biomass as it passes through the liquid cause the excess growth
to be stripped from the media surface.  Sedimentation basins downstream of the
RBC's are used to remove the excess growth from the waste stream.   There is
neither solids recycle nor liquid recirculation with RBC's.

    Shafts of discs are arranged in stages.  The first stages are provided
with media having a specific unit surface area of 30 to 35 sq ft/cu ft, while
the latter stages have a higher value - 45 to 50 sq ft/cu ft.  The  media
shafts are generally designed with covers or in enclosures to provide effi-
cient operation in low-temperature climates and to protect the biological
surfaces against direct sunlight and rainfall which could affect growth.

Typical Design Considerations

    The design of RBC treatment systems has been based on a graphical approach
relating hydraulic loading to BOD removal.  Figure 10-1 presents one manu-
facturer's design approach.

    An alternative method of sizing RBC systems^)  is to use the equation

         Le  =  e-s
-------
en
111
_I
m
o
to
I-
z
HI
D
_l
U.
u.
Ill
        30
        25
        20
        15
        10 -
        5 
                                                  INFLUENT SOLUBLE BOD, mg/l

                                                    150     120     100
                BIO-SURF PROCESS DESIGN CRITERIA
                DOMESTIC WASTEWATER TREATMENT

               Wastewater Temperature * 13*C

               4Stage Operation
                                                                             60
                                                                            50
                                                                            40
30
                                                                            20
                 0.5      1.0     1.5     2.0     2.5     3.0     3.5     4.0     4.5
                              HYDRAULIC LOADING, gpd/sq it
Figure 10-1.   Rotating biological media for secondary treatment.
                                     10-2

-------
     The following  example is an evaluation of the performance of an RBC system.

     1.    Define the design and operating data for the system
          4-stage system;  24 shafts,  100,000 sq ft of effective surface area on
          each  shaft.
          Effective surface area
               Each stage                  =  600,000  sq ft
               Total                      =  2,400,000 sq ft
          Flow                             =3.5 mgd
          BOD
               Influent, total            =150 rag/1
                       , soluble (assume  65% of total)   =  98 mg/1
               Effluent, total            =30 mg/1
                       , soluble (assume  50% of total)   =  15 mg/1
          Temperature                      =  20C

     2.    Determine the hydraulic  loading for the RBC system
          Hydraulic Loading  =  Total  flow in gpd
                                Total  surface area
                             =  3,500,000
                                2,400,000
                             =  1.46 gpd/sq ft

     3.    Determine the efficiency of  the RBC system
          % BOD  removal  =   BODin - BODout  x 100
                                 BODin
                           150 - 30  x 100
                             150
                        =  80%
Process Control
    The only operating variable with RBC's is the speed at which the shafts
rotate.  Generally, the units are equipped with mechanical drives to rotate
the media at 1 to 3 rpm.  This can be adjusted to compensate for changes in
the wastewater characteristics and flow.  Other areas that should be reviewed
are sludge pumping and flow distribution.  Sludge pumping schedules should be
set so that septic sludge is avoided but dilute sludge is not pumping.  Inade-
quate pumping results in septic sludge.  Excessive pumping results in a thin
sludge which causes inefficient dewatering performance and increases pumping
costs.  Poor flow distribution between units can cause overloading on one and
a decrease in treatment efficiency.

Maintenance Considerations

    The features of a good maintenance program are listed below.  They should
be used in addition to the general maintenance management program presented
earlier.
                                     10-3

-------
1.
2.
3.
      4.
          Spare part inventory should contain at least the following parts:
          one set of each type of bearing, V-belt or chain drives for each
          system, and grease seals.

          Inspection each shift of the discs and appurtenant facilities to
          visibly inspect the equipment for misalignment,  constant rotative
          speeds, any excessive vibrations.

          Record flow rate per kilowatt hour is determined for  the mechanical
          drives. A deviation from an average value is  a  good  indication of
          efficiency and changing conditions that might  require maintenance.
    All non-operating equipment, such as standby electric generators
    tested at least once per month.
                                                                            is
      5.   Immersed  instrumentation  checked  and  cleaned  weekly.

Records

    Recommended  sampling and  laboratory  tests  are  shown  in Figure  10-2.

    Other operating  records should include:

      1.  Raw sewage  influent  flow.
      2.  The total energy  (electricity)  consumed.

Laboratory Equipment

    The laboratory should  include  the  following minimum equipment  in order  to
monitor the RBC process.

    1.   Analytical balance
    2.   Clinical centriguge with graduated tubes
    3.   BOD incubator
    4.   Drying oven
    5.   Oxygen analyzer or titration equipment

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware,
chemicals, miscellaneous furniture, etc. and should be referred to for any
detailed questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
and homogeneous such as in the influent and effluent lines.  The sample col-
lector and containers should be clean.   A wide mouth sample collector of at
                                     10-4

-------
a
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a
Q
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UI
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a
 o
a
o

BOD
DO













COD






UJ
N
V)
Z Q
n
ALL
ALL













75






TEST
FREQUENCY |
2/W
5/W













2/W






LOCATION OF
SAMPLE
I
I
E













I






METHOD OF
SAMPLE
24C
G













24C






1 REASON
FOR TEST
H
H













H






                                                    ESTIMATED UNIT PROCESS SAMPLING AND
                                                               TESTING NEEDS
                                                     SECONDARY TREATMENT
                                                                  ROTATING BIOLOGICAL CONTACTOR
                                                        INFLUENT FROM
                                                         PREVIOUS MAIN
                                                         FLOW TREATMENT
                                                         PROCESS
                                   EFFLUENT TO]
                                   SECONDARY J
                                   CLARIFIER S
                                                     A. TEST FREQUENCY
                                                          H m HOUR      M  MONTH
                                                          D - DAY       R - RECORD CONTINUOUSLY
                                                          w- WEEK      M,,- MONITOR CONTINUOUSLY

                                                     B.  LOCATION  OF SAMPLE

                                                          I = INFLUENT
                                                          E = EFFLUENT
C. METHOD OF SAMPLE

     24C~24 HOUR COMPOSITE
     G - GRAB SAMPLE
     R " RECORD CONTINUOUSLY
     Mn- MONITOR CONTINUOUSLY

D. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P  PROCESS CONTROL
     C =- COST CONTROL

E. FOOTNOTES:
      1. THESE TESTS SHOULD ALSO  BE RUN ON RECEIVING
        WATER. ABOVE AND BELOW OUTFALL, ON A
        PERIODIC BASIS, DEPENDING ON LOCAL CONDITIONS.
                                                          2.
                                                            FOR PLANTS DESIGNED TO CONTROL THIS
                                                            PARAMETER.
                                            Figure  10-2

                                                     10-5

-------
least 2 inches should be used.  Samples collected in the effluent channel
should be collected near the discharge point so that any isolated areas of
short circuiting do not influence the results.  Where automatic samplers are
used, it is important to keep the sampler tubes clean.

Sidestreams

    There are no sidestreams associated with the RBC process.
                                     10-6

-------
Process Checklist - Rotating Biological Contactors
 1.
 2.
 3.
What is actual plant flow
Type of RBC media 	
Type of RBC drive
10.
11.
12.
mgd avg.
mgd peak?
    Number of units (shafts)
and surface area of each unit
Color of biomass   (  )   Black
(  )   Other 	
Odor
                                    (  )   Dark Brown  (  )   Light Brown
 5. Odor  (  )   Septic  (   )   Earthy  (  )   None  (  )   Other
 6. Are all mechanical drives and motors operating properly?  {
 7. Is rotation of media uniform?  (  )   Yes  (  )  No
 8. Is the flow distributed equally to parallel shafts?  (  )  Yes
    How is it distributed?       	
                                                             ) Yes (  )  No
                                                               (  )  No
 9. Are the characteristics of the tank contents different in the various
    units?  (  )   Yes  (  )   No.  If yes, describe 	
Do mechanical equipment (mechanical drives, motors, etc.) have adequate
spare parts inventory? (  )   Yes  (  )   No
Is the RBC housing adequately ventilated?  (  )   Yes  (  )  No
Is RBC housed in a building?  (  )  Yes  (  )   No, or is each unit
equipped with a cover?  (  )   Yes  (  )   No
How often are facilities checked? (  )   once per shift   (  )   daily
(  )   other 	
13. What is frequency of scheduled maintenance?_
14. Is the maintenance program adequate? (  )   Yes  (  )   No
    If no, explain	
15. What is general condition of the RBC facilities? (  )   good  (  )  fair
    (  )   poor
16. What are the most common problems the operator has had with the RBC
    system? 	
                                     10-7

-------
References

 1. Gulp/ G.L., and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation  (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328  (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.

 7. Benjes, H.H., Jr., Attached Growth Biological Wastewater Treatment
    Estimating Performance and Construction Costs and Operating and
    Maintenance Requirements, EPA Contract 68-03-2186 (January, 1977).

 8. Battelle Pacific Northwest Laboratories, Evaluation of Municipal Sewage
    Treatment Alternatives, Council on Environmental Quality,  Contract EQC316
    (February, 1974).

 9. Benjes, H.H., Jr., Small Community Wastewater Treatment Facilities,  U.S.
    EPA Technology Transfer National Seminar on Small Wastewater Treatment
    Systems (January,  1978).

10. Antonie, R.L., Fixed Biological Surfaces - Wastewater Treatment, CRC
    Press, Cleveland,  Ohio (1976).
                                     10-8

-------
 11.   SECONDARY SEDIMENTATION

 Process Description

     Secondary sedimentation basins are  very similar in structure  to primary
 sedimentation basins,  but are  used to remove biological solids from the waste
 stream.  In the case  of activated sludge systems  they also provide a source of
 concentrated return sludge for return to the aeration basin.   Secondary sedi-
 mentation basins can  be circular, square,  or rectangular.   They are equipped
 with scrapers or suction type  sludge removal units.  The scrapers are gen-
 erally  used for light sludges  in smaller diameter tanks (less than 50 feet)
 while the suction mechanisms are installed in larger tanks.  Surface skimming
 is also necessary to  prevent the escape of floating materials in  the ef-
 fluent.  A radial scum arm with a blade moves the scum to the periphery of the
 clarifier and deposits it in a disposal trough.

 Typical Design Considerations

     The design of the secondary sedimentation basins is critical  to the over-
 all  performance of a  treatment facility and is dependent upon the upstream
 biplogical process.   Table 11-1 summarizes loading rates for  these basins.

     Sedimentation basins are ordinarily sized using a surface overflow rate as
 described previously  in Section 5.  The example given in Section  5 applies
 equally to secondary  sedimentation basins as to primary sedimentation basins,
 however,  the loading  rates are different.   Providing adequate surface area for
 peak flows is also critical since the overall plant performance is directly
 related to the sedimentation basin performance.

     In  the case of sedimentation following activated sludge,  additional design
 criteria must be considered.  Because large solids concentrations limit set-
 tling rates,   the surface area requirement may be governed by the solids load-
 ing  rate; this is particularly true when the mixed liquor suspended solids
 (MLSS)  is greater than 2,000 to 3,000 rag/1.  The  criteria providing the larg-
 est  surface area should be used to insure adequate liquid-solids separation at
 all  times.

 Typical Performance Evaluation

     The performance of secondary wastewater treatment systems is  determined by
 comparing the quality of the overflow from the secondary clarifiers to that of
 the  incoming wastewater.  Typical removals for secondary treatment facilities
 are  given in the previous sections dealing with biological treatment processes.

 Process Control

     There are different operational considerations depending  on the nature of
 the  upstream processes.  Sedimentation following  trickling filters or other
 attached growth processes is similar to primary sedimentation in that there is
.no solids recycle. Trickling  filter humus typically has a solids concentra-
 tion of 5 to 10 percent and can be pumped as described for primary sludge.
                                      11-1

-------
      TABLE 11-1.  TYPICAL LOADING RATES FOR SECONDARY SEDIMENTATION BASINS
   Type of treatment
  Overflow rate
Average      Peak
    gpd/sq ft
               Solids loading
               Average    Peak    Depth
             Ib solids/day/sq ft    ft
 Settling following
   trickling filtration

 Settling following
   activated sludge

 Settling following
   oxygen-activated
   sludge with primary
   settling
400-600    1,000-1,200     	


400-800    1,000-1,200    20-30
400-800
1,000-1,200    25-35
                                  10-12
                          < 50     12-15
<50     12-15
 Allowable solids loadings are governed by sludge settling characteristics.


     On the other hand,  the controls of secondary sedimentation systems are
 part of the activated slu'dge process.   The secondary sedimentation basins
 should not be used as a storage basin  for activated sludge;  the sludge should
 be removed and a portion of it returned to the aeration tanks as quickly as
 possible.   Best return  rates are often in the range of 20 to 50 percent of  the
 secondary inflow rate for most systems.   The sludge level in each basin should
 not be greater than one-quarter the total basin depth.   The  sludge level is
 controlled by the sludge removal rate.   Some of the removed  solids are wasted
 from the system and the remainder returned to the aeration basins.   Excessive
 sludge inventory in the secondary sedimentation basins can lead to loss of
 sludge over the basin effluent weirs,  causing high effluent  solids.

     Scum should be properly removed from the secondary basins.   Excessive
 skimming will result in too much water being carried over with  the scum.  If
 insufficient scum is removed,  it will  flow around or under the  baffle  and
 leave  the  tank in the effluent.

     Equal  flow distribution should  be provided  among all  available  secondary
 settling tanks.   Even with  equal distribution of  flow,  some   differences  in
 efficiencies may  be found between two or  more" units.  With unequal  flow,  how-
 ever,  less  SS and BOD will  be  removed overall.

Maintenance  Considerations

    The  features  of  a good  maintenance program  that  the  inspector should  note
 include  the  items  listed below.   These should be  used  in  addition to general
maintenance  management consideration presented  earlier.
                                     11-2

-------
      1.  Scheduled  inspection and maintenance of baffle boards and  scraper.

      2.  Inspection of  scum  removal equipment.

      3.  Spare part inventory should contain the following:   turntable gears
         and motors for circular basins, wear shoes, sprockets, wall brackets,
         chain pins and flights, shear pins, and cable for  travelling bridges.

Records

    Recommended sampling and laboratory  tests are shown on  Figure 11-1.

    Other operating records are directly related to the biological  treatment
process preceding secondary sedimentation.  The appropriate section of this
report should be consulted for additional information.

Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor secondary sedimentation.  In addition, the equipment  required to mon-
itor  the biological process will be needed.

    1.   Analytical balance
    2.   Clinical centrifuge with graduated tubes.
    3.   BOD incubator
    4.   Drying oven
    5.   Imhoff Cones

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chem-
icals, miscellaneous furniture, etc. and should be referred to for any
detailed questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
such as at the center of the channel of flow where velocities are high.  The
sample collector and containers should be clean.  A wide mouth sample collec-
tor of at least 2 inches should be used.  Samples collected in the effluent
channel should be collected near the discharge point so that  any isolated
areas of short circuiting do not influence the results.  Where automatic
samplers are used, it is important to keep the sampler tubes  clean.

Sidestrearns

    The only sidestream from secondary sedimentation is the sludge pumped from
the basin.   The solids from an activated sludge plant are either returned to
the aeration tank (RAS)  or wasted (WAS)  to the primary sedimentation tank,
thickeners, or digester.  Generally, 85 to 95 percent of the  settled sludge is
returned to the process.  The actual amount must be determined by the plant
control considerations as discussed in Section 6.  Trickling  filter sludge is
                                     11-3

-------
a
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ui
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<9
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 Q.
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SUSPENDED
SOLIDS
BOD
SETTLEABLE
SOLIDS
TOTAL
SOLIDS
NHv-N1
ORG-N1
NOy-M1
TOTAL-P
ORTHO-P
PLOW
SLUDGE VOLUMB
LAB CENTRIFUC
TOTAL SOLIDS



ALKALINITY
pH
TURBIDITY




UJ
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ALL
ALL
ALL
<1
ALL
ALL
ALL
ALL
ALL
ALL
>1
p
>1



ALL
ALL
>15




TEST
FREQUENCY |
3^W
2/W
1/D
3/W
1/D
1/W
VP
VD
1/D
R
3/D
1/W



1/W
1/D
Mn




LOCATION OF
SAMPLE
I
B
E
I
E
S
E
E
E
E
E
WS
RS
S
S



1
1
E




METHOD OF
SAMPLE
24<;
24C
G
G
24C
24Q
24C
24C
24C
R
G
G



24C
G
Mn




1 REASON
FOR TEST
P
H
P
P
H
H-
9
H
H
P
P
P



P
H
P




                                                ESTIMATED UNIT PROCESS SAMPLING AND
                                                           TESTING NEEDS
                                                 SECONDARY TREATMENT

                                                        SECONDARY CLARIFIES
                          tiy
                                                                                    EFFLUENT TO
                                                                                    NEXT MAIN
                                                                                    TREATMENT
                                                                                    PROCESS
                                                                                   SLUDGE UNDERFLOW
                                                   INFLUENT FROM
                                                   SECONDARY
                                                   TREATMENT
                                                   PROCESS
                      RECYCLE SLUDGE
                      TO AERATION BASIN
                     (FOR ACTIVATED
                     SLUDGE)
A. TEST FREQUENCY
     H - HOUR     M - MONTH
     D- DAY      R - RECORD CONTINUOUSLY
     W- WEEK     Mn- MONITOR CONTINUOUSLY

8. LOCATION OF SAMPLE

     I - INFLUENT
     6 - EFFLUENT
     S= SLUDGE UNDERFLOW
     WS =WASTE SLUDGE
     RS=RECYCLESLUDGE

C. METHOD OF SAMPLE

    24C-24 HOUR COMPOSITE
    G" GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn= MONITOR CONTINUOUSLY

0. REASON FOR TEST

    H "HISTORICAL KNOWLEDGE
    P -PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
     1.  TO BE RUN IF PROCESS IS DESIGNED TO
        CONTROL THIS PARAMETER
                                          Figure 11-1
                                                11-4

-------
not recycled back to the process.  Generally,"it is pumped back  to  the  head  of
the plant upstream of the primary sedimentation basins,  to thickening tanks,
or directly to digesters.

    Regardless of the type of secondary sludge or where  it is being pumped,
pumping should be on a continuous basis.   Standby units or adequate pumping
flexibility should be provided to avoid interrupted or intermittent operation.
                                     11-5

-------
 Process Checklist - Secondary Sedimentation
  1.

  2.

  3.
  5.
  6.
  7.

  8.
  9.
10.
11.
12.
13.
14.

15.

16.
17.
18.
19.
20.

21.

22.

23.
24.
25.
26.
What  is the  total flow  to the sedimentation basins
	 gpd peak.
What  is the  design flow	 gpd average,
                                                               gpd average,
                                                            gpd peak?
What are the dimensions of the sedimentation basin?	
Is chemical addition used to improve settling?  If so, what chemical(s)
are added?	
                         , and for what reason?
                                         gpd total,
What are the dose rate(s)	
How much sludge is pumped
	 gpd WAS?
What is the solids concentration in the sludge?
Are there settleable solids in the effluent 	
Is sludge pumping 	
continuous
                                                           gpd RAS,
                                manual
                                                                 mg/liter?
automatic
                               intermittent?
                                                            other?
How often do sludge pumps run
                                                 minutes/hour?
Frequency of maintenance inspections by plant personnel
Is maintenance program adequate?  {  )   Yes  (  )   No
Does the influent baffle system accomplish its purpose?
Is the scum collection system operating properly?   (  )
Is the sludge collection system operating properly? (  )
                                                                    /year.
                                                            (i.e.  exces-
                                                              No
                                                              Yes
                                                          (   )  Yes  (   )
                                                          Yes  (   )  No
                                                          Yes  (   )  No
Does  the sludge collection system show any signs of mechanical failure?
(  )  Yes   (  )  No
Does  the tank surface indicate  improper sludge withdrawal?
sive  floating solids, gas...) {  )  Yes   (  )  No
Is there an excessive accumulation of scum?   (  )  Yes   (  )
Does  the effluent baffle system accomplish its purpose?  (  )
Are the effluent weirs level?   (  )  Yes  (   )  No
Are the effluent weirs kept clean?  (  )   Yes  (  )  No
If multiple units are used, is the flow distributed evenly?
(  )  Yes   (  )  No
Does  the unit show signs of short circuiting and/or overloads?
(  )  Yes   (  }  No
Is there an alarm system for equipment failures or overloads?
(  )  Yes   (  )  No
Does  the sampling program meet the recommendations?  (  ) Yes  (  )  No
Are operating records adequate?  (  )   Yes  (  )   No
Is the laboratory equipped for the necessary analyses? (  )Yes (  )  No
What spare parts are stocked?
                    No
              (   )   No
27. What are the most common problems the operator had had with the process?
                                     11-6

-------
References

 1. Gulp, G.L., and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation  (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

6.  State of Virginia O&M inspection form.
                                     11-7

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12.  CHLORINATION

Process Description

    The most common method of wastewater disinfection is by chlorination.
Chlorine is added to the treated effluent to destroy any bacteria, pathogens
or viruses.  Other principal uses of chlorine are for odor control, and often
times for control of bulking activated sludge.  Chlorine application systems
are described in Reference 1 and 2.

Typical Design Considerations

    The design criteria and related performance of a chlorination system
depends upon whether the chlorine is being applied strictly for disinfection
purposes or, in the case of advanced waste treatment, for removal of nitro-
gen.  Chlorine dosages vary for the two different applications.

    The destruction of pathogens by chlorination is dependent upon water
temperature, pH, time of contact, degree of mixing, turbidity, presence of
interfering substances, and the concentration of chlorine available.   Table
12-1 provides a general indication of chlorine dosage ranges for disinfecting
wastewater after various degrees of pretreatment.

	TABLE 12-1.  ESTIMATE OF CHLORINE DEMAND FOR VARIOUS WASTEWATERS
    Raw fresh domestic waste
    Raw septic domestic waste
    Primary sedimentation effluent
    Recirculated biofilter effluent
    Biofilter effluent (secondary)
    Trickling filter effluent
    Activated sludge effluent
    Sand filtered effluent
    Septic tank effluent
8-15 ppra
15-30 ppm
8-15 ppm
5-8 ppm
3-8 ppm
3-10 ppm
2-8 ppra
1-5 ppm
30-45 ppm
    Breakpoint chlorination is also used in advanced wastewater treatment
facilities for nitrogen removal.  Chlorine is added to convert ammonia nitro-
gen to nitrogen gas.  With the exception of the chlorine dosages, which may be
anywhere from 40 to 50 times greater than that required for disinfection pur-
poses only, the nitrogen removal process involves essentially the same equip-
ment.  Wastewater (after secondary or tertiary treatment)  enters the chlorine
contact chamber at which point chlorine is added and completely dispersed with
incoming flow.  In the breakpoint chlorination process about 10 mg/1 of chlo-
rine must be added for each 1 rag/1 of ammonia nitrogen present in the waste-
water.  A more highly treated wastewater requires less chlorine to reach
breakpoint.  The breakpoint process can result in 99% plus percent removal of
ammonia nitrogen, reducing concentrations to less than 0.1 mg/1 (as N).
                                     12-1

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Typical Performance Evaluation

    To determine the adequacy of the chlorination system to accomplish dis-
infection or other objectives the evaluator should examine the chlorine con-
tact basin detention time, the chlorine residual in the basin effluent, and
the MPN count of coliform organisms after chlorination.  This evaluation can
be performed very easily in the following steps:
    1.
    2.
         Obtain design and typical operating data for the chlorination system
         being studied.
         Example:
         Type of Effluent
         Peak plant flow
         Volume of chlorine contact tank, V
         Chlorine dosage
         Chlorine residual
         Determine the contact time for the chlorine contact tank based on
         peak flow.
         Contact time, hrs - V in cu ft x 7.48 gal/cu ft x 24 hrs/day
                                                 Activated Sludge
                                                 5.0 mgd
                                                 13,926 cu ft
                                                 6.0 mg/1
                                                 1.0 rag/1
                           = (13,926)
                                   5
                                             Flow in gpd
                                       (7.48)  (24)
                                     x 106
    3.
                           =0.50 hrs or 30 min

         Examine the daily disinfection log sheet for chlorine feed rates and
         chlorine residual patterns.  Compare calculated contact time and
         measured chlorine residuals with the values for these parameters
         established by the proper regulatory agency.  As a general rule, if
         the residual falls between 0.2 mg/1 and 1.0 mg/1 and there is 15 to
         30 minutes of contact time there should be reasonable assurances of
         good disinfection.  In the above example the 30 minutes of contact
         time with a 1.0 mg/1 of chlorine residual effluent should indicate
         that the plant is meeting appropriate standards.

Process Control

    In general the better the treatment plant is operated the easier it will
be to disinfect the effluent.  A poorly treated effluent will contain high
levels of bacteria and higher concentrations of suspended solids which will
increase the chlorine requirement.  Effective disinfection of chlorine is
dependent upon the combined effect of chlorine dosage, mixing and contact time
with the wastewater.  Overall process control is accomplished by measurement
of the effluent chlorine residual.  Maintenance of the proper chlorine resi-
dual is dependent upon the adequacy of the chlorination system to respond to
changes in chlorine demand.

    Applying chlorine to wastewater in a well mixed system produces a much
higher degree of disinfection than when chlorine is fed without mixing, even
though the contact time and residual are adequate.   Longer contact times are
more important than higher chlorine dosages or residuals in wastewater
disinfection.
                                     12-2

-------
    In breakpoint chlorination for nitrogen removal the system must be able to
respond quickly to changes in ammonia nitrogen concentration, chlorine demand,
pH, alkalinity and flow.  Failure to closely match chlorine dosage to ammonia
concentration can result in incomplete nitrogen removal or chlorine over-
doses.  A control system for nitrogen removal by breakpoint chlorination
should include automatic analyzers to control chlorine dosage within a narrow
range around the required values.  Direct measurement of residual chlorine or
indirect measurement of pH can be used to control breakpoint chlorination.

Maintenance Considerations

    The features of a good maintenance program that the inspector should look
for are:
     1.  Established schedules for checking all connections for chlorine gas
         leaks.  The piping system can be checked for chlorine leaks by using
         an ammonia solution or checking for the appearance of green copper
         scum around the edges of corroded metal at the joints.

     2.  Atmospheric chlorine leak detection equipment checked out and peri-
         odically calibrated.

     3.  Evaporator periodically checked for corrosion.

     4.  Inspect chlorine gas filter at 6 months intervals.

     5.  Chlorine pressure reducing valve regularly inspected.  Every 2 to 3
         years the spring opposing the silver diaphram will suffer fatigue and
         should be replaced.  Every 5 years the entire assembly should be dis-
         mantled and the diaphram inspected for fatigue.

     6.  Chlorination system regularly inspected for restrictions between the
         cylinder and the chlorinator caused by impurities.
     9.
    10.
    11.
         Chlorine Institute Emergency Kit to seal off leaking cylinders.
         eral units should be provided near the feed facility.
                                                                 Sev-
Gas diffusion devices in the contact basins periodically inspected to
ensure that they are not clogged.

Bulk liquid chlorine storage tanks flow control valves in the dome of
the tank inspected regularly.  Provisions made to hydrostatically
test the bulk liquid chlorine storage tank at 2 years intervals.

Rotameter tube and chlorine metering orifice removed from the chlori-
nator and cleaned at least once every 6 months.

Chlorine residual analyzer calibrated and maintained on a regular
basis.  In order for this equipment to perform effectively it must
receive daily, weekly, and quarterly inspections.
                                     12-3

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Process Checklist - Chlorination
 3,
 4.
 5.
 6.
 7.
 8.

 9.

10.

11.


12.

13.

14.

15.

16.

17.
    What is the flow to the chlorine contact basin?_
    	" -   mgd.peak
    What are contact basin dimensions? 	
             	width/feet,	
                                                                   jngd avg.
                                                          length/feet,
    What is contact basin detention time?_
    What is applied chlorine dosage?_
                                              	 depth/feet.
                                              	min. (at peak flow)
                                               mg/1
                                                     )
                                                          	 mg/1
                                                         )   No
                                                        chlorine cylinders
                                                        sodium hypochlorite

                                                       	Ibs/pe r/day
What is normal chlorine residual in basin effluent?
Are disinfection standards being met?  (  )   Yes  (
What type of chlorination system is being used?(
(  )   on-site sodium hypochlorite generation  (
solution  (  )  calcium hypochlorite solution?
What is the chlorination system design capacity?
maximum capacity?	 Ibs/per/day
What is the configuration of the chlorine contact basin? (  )   round
(  )   rectangular  (  )  other 	
Is contact basin adequately baffled to minimize shortcircuiting?
(  )   Yes  (  )  No
How is chlorine introduced into the wastewater entering contact basin?
(  )   perforated diffusers  (  )  injector with single entry point
(  )   other 	  *
Are mechanical mixing provisions incorporated in the chlorine contact
basin design?  (  }   Yes  (  )  No
Is plant equipped with automatic chlorine leak detectors with alarms in
critical areas?  (  )  Yes  (  )  No
Is' the ventilation system for chlorine cylinders storage and chlorination
equipment rooms adequate?  (  ) Yes  (  ) No
How often are facilities checked?  (  )   once per shift  (  )   daily
(  )   other 	
Does the treatment plant maintain an adequate spare parts inventory?
(  )   Yes  (  )  No
What is the frequency of scheduled maintenance?  Describe 	"
18. Is the maintenance program adequate?
    the problem? 	
                                          (  )   Yes  (  )   No.  If no, what is
                                                              )  Yes {   )   No
19. Are proper safety precautions used?  {  )   Yes  (  )   No
20. Does the sampling program satisfy the recommendations? (
21. Are operating records adequate?  (  )   Yes  (  )   No
22. Is the laboratory equipped to perform the necessary analyses?
    (  )   Yes  (  )   No
23. What is the general condition of the chlorination facilities?
    (  )   good  {  )   fair  .(  )   poor
24. What are the most common problems the operator has had with the chlorina-
    tion process?	
                                     12-6

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References

 1. Gulp, G.L., and Polks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, EPA
    Report 430/9-78-001.

 2. George Clifford White, Handbooks of Chlorination, Nostrand Reinhold Co.
    1972.

 3. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation, 1977.

 4. Gulp, Gordon L., and Gulp, Russell L., Handbook of Advanced Wastewater
    Treatment, Van Nostrand Reinhold, 1977.
 5. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-02-0328, June 1973.
 6. Rand, M.C. et al, Standards Methods for the Examination of Water and
    Wastewater, American Public Health Association 14th edition, 1975.
                                     12-7

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-------
 13.  OZONATION

 Process Description

     Ozone is an extremely powerful oxidizing agent which has been used princi-
 pally in Europe for the disinfection of water supplies.  When applied to
 wastewaters, ozone will oxidize many residual organic compounds, reducing the
 effluent BOD, COD, and color and adding dissolved oxygen to the final ef-
 fluent.   Unlike chlorine, ozone produces no residual materials which are toxic
 to aquatic life in the receiving stream and adds no dissolved solids.

     Ozone is produced by passing air, oxygen enriched air,  or pure oxygen be-
 tween two electrodes across which an alternating high voltage potential is
 maintained.   Figure 13-1 illustrates a basic configuration  of an element com-
 mon to the various types of ozone generators commercially available.  This
 method of ozone production is inefficient.   Only about 10%  of the energy sup-
 plied is used to produce ozone.  The remainder  is lost as light, sound and
 heat.   Ozone gas is unstable and within a very  short time period decomposes to
 oxygen.   The inability to store ozone requires  that it must be produced at its
 point of use.

     There are three basic types of commercially available ozone generators:
 the  Otto plate,  the tube and the Lowther plate.   These are  described in
 Reference 1.

 Typical  Design Considerations and Performance Evaluation

     The  design criteria  and related ozone dosages for  an ozonation system de-
 pends  upon whether the ozone is to be applied for disinfection or  as a ter-
 tiary  treatment process  for effluent polishing.   Ozone dosages and required
 contact  times  are  different for the two  requirements.

     A  value of 200 fecal coliform/100 ml can  usually be attained in  secondary
 effluents using  an ozone dosage of about 5 mg/1.   Contact times  may  range  from
 as little as  2 minutes to as much  as 15  minutes.   Five  minutes appears  to  be
 adequate  with  proper dosages and with efficient contactor design.  Standards
 calling  for almost complete  coliform removal  (to  2  fecal  coliform  per  100  ml)
 may  require dosages of 15 mg/1  or  more.   For  most cases,  an ozone  residual of
 0.1  mg/1  for 5 minutes is adequate to disinfect waters  low  in  organics and
 free of  suspended  materials.  The  degree  of pretreatment  has a significant
 impact upon the effectiveness of ozone for disinfection.  The  presence of
 organic material exerts  an  ozone demand which can prevent maintenance of a
 killing  residual.  Also  the presence of particulate material can shield organ-
 isms from the germicidal  effects of ozone.

    As a  tertiary  treatment process, ozone can reduce BOD, COD, color, turbid-
 ity and odor.  Ozone dosages are widely variable  depending upon particular
 treatment  requirements.  Contact times tend to be  in a  range similar to disin-
 fection. With good mixing, a contact time of 5-10 minutes will achieve maximum
oxidation of organics.  Theoretically 3 mg/1 of ozone will destroy about 1
mg/1 of COD.  Experimentally, it has been observed when applying ozone to alum
coagulated and filtered secondary effluent that the COD was  reduced from 36-41
                                      13-1

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                         HEAT
                    DISCHARGE GAP
ELECTRODE



DIELECTRIC






03







ELECTRODE
                        HEAT

Figure 13-1.  Basic  ozonator configuration.
                        13-2

-------
 mg/1 to 15-17 mg/1 with 63-89 mg/1 ozone.  These data exhibit a COD to ozone
 ratio ranging from 2.6-3.7 which corresponds reasonably to the predicted
 ratio.  Considering that a well treated secondary effluent has a COD range of
 25-35 mg/1, a 50% reduction would require an ozone dosage ranging from 36 to
 50 mg/1.  For general design purposes the ozone system for polishing secondary
 efflue.it to the above standards should be capable of providing ozone dosages
 in excess of 50 mg/1.

     The following example is for calculating ozone requirements.
          Desired Dosage in contact basin
          Wastewater flow
          Ozone concentration (%/wt)
          Peed gas
                                                5  mg/1
                                                10 mgd
                                                3%
                                                Oxygen
     Determine required ozone production,  Ibs/day
          Ibs/day ozone = Dosage,  mg/1 x flow mgd x 8.33 Ibs/gal
                        = 5 mg/1 x 10 mgd x 8.33 Ibs/gal
                        = 417 Ibs/day 03
     Determine  feed gas (oxygen)  flow,  SCFM
          @  3%  O3,  Ibs of 02 required per day
                                                 417 Ibs/day 03
                                                0-03 Ibs O3/lbs 02

                                               * 13,900 Ibs 02/day
At 70F and 14.7 psia, 1 Ib O2 has volume of 12.08 ft3
    Volume SCFM  =  13,900 Ibs O? x 12.08 ft3 x 1 day  x
                                       Ib       24 hrs  60 min
                                                          1 hr
                = *117  scfm oxygen  flow

*Changes in temperature, pressure or  feed gas oxygen  concentration  affect
required generator feed gas flow.   Appropriate correction  factors must be
applied to determine correct values.  Refer  to manufacturer's  instruction
manuals.

Process Control

    The application of  ozone to a wastewater, whether it be for disinfection
or for effluent polishing, requires close control to ensure effective perform-
ance.  Production of ozone which is related  to the flow of water under treat-
ment and its dosage requirements may be controlled manually or automatically
by probe and relay.  The automatic dosage control loop system  is preferred
since it compensates for changes in flow and ozone demand to provide a preset
ozone residual.  Starting up sequences are important and require establishment
of exact procedures and timing.  A centralized control panel containing all
initiating controls,  process performance indicators,  inner locks and other
safeguards are generally incorporated in any ozone system.
                                      13-3

-------
Maintenance Considerations

    The features of a good maintenance program that the inspector should look
for are:

     1.  Schedules established for checking electrical and gas connections for
         tightness.  The piping system can be checked for ozone leaks by hold-
         ing paper towels soaked in potassium iodide solution to the connec-
         tors or by applying an approved leak detection material.

     2.  Atmospheric ozone leak detection equipment check-out and calibra-
         tion. Has a specific schedule for this attention been established?

     3.  Ozone cells checked for accumulations of grease and dirt.

     4.  Gas diffusion devices in the contact basins regularly inspected to
         ensure that they are performing properly.  Porous diffusers may
         become clogged with materials percipitated from solution requiring
         acid or caustic cleaning to remove.

     5.  Basin covers periodically checked for gas leaks.

     6.  Ozone destruction devices (single pass systems)  checked for effective
         functioning.
     7.
Instrumentation for measuring ozone concentrations of ozonator output
and the dew point analyzer on the feed gas supply periodically
calibrated.

Spare parts inventory should include:  SCR rectifier and control cir-
cuit fuses, fan belt set, fan bearing, fan belt grease, fan starter,
thermal overloads, various relays for key electrical components,
replacement cell module, high temperature alarms, and spare parts for
ozone leak detection instrumentation and for other monitoring instru-
mentation.  Some variation will occur with the different styles of
generators.
Records
    Recommended sampling locations and laboratory tests are shown in Figure
13-2.  Other operating records should include:

     1.  Ozone contact basin influent flow
     2.  Ozonizied gas flow to contact basin
     3.  Flow rate of off-gas from contact basin

Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor the performance of the ozonation process:
                                      13-4

-------
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Q
UJ
t-
tn
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OZONE
RESIDUAL
OZONE
CONCENTRATION
OZONE
CONCENTRATION
CONFORM
FECAL
COLIFORM










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TEMP
DO
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:OD
TURBIDITY

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TEST
FREQUENCY
R
Mn
Mn
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1/W










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1/D
/W
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/W
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LOCATION OF
SAMPLE
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METHOD OF
SAMPLE
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Mn
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G
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G
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REASON
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P/L
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P,C
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H
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                                                     ESTIMATED UNIT PROCESS SAMPLING AND
                                                                TESTING NEEDS
                                                     OZONATION
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                                                                                          EFFLUENT
                                                                                          TO RECEIVING
                                                                                          WATER
                                                  INFLUENT FROM PREVIOUS
                                                   MAIN FLOW TREATMENT
                                                   PROCESS
                                                     A. TEST FREQUENCY
                                                          H m HOUR
                                                          D - DAY
                                                          w- WEEK
                   M - MONTH
                   R - RECORD CONTINUOUSLY
                   Mn- MONITOR CONTINUOUSLY
                                                     B.  LOCATION OF SAMPLE

                                                         O3= OZONE GAS FLOW
                                                         OG= CONTACT BASIN OFF GAS
C. METHOD OF SAMPLE

     24C-24 HOUR COMPOSITE
     G-  GRAB SAMPLE
     R -  RECORD CONTINUOUSLY
     Mn= MONITOR CONTINUOUSLY

D. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P - PROCESS CONTROL
     C - COST CONTROL

E. FOOTNOTES:
      1. THESE TESTS SHOULD ALSO  BE RUN ON RECEIVING
        WATER. ABOVE AND BELOW OUTFALL, ON A
        PERIODIC BASIS. DEPENDING ON LOCAL CONDITION*.
      2. FOR PLANTS DESIGNED TO CONTROL THIS
        PARAMETER.
                                           Figure 13-2

                                                 13-5

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    1.   Analytical balance
    2.   Wet test drum meter with associated barometer and thermometer
    3.   Gas washing bottles (2)
    4.   Dewpoint meter for monitoring moisture content of feed gas
    5.   General laboratory glassware including volumetric flasks, graduated
         cylinders, burets, beakers, pipettes, etc.
    6.   Tygon tubing
    7.   Test reagents including potassium iodide solution, sulfuric acid,
         sodium thiosulfate, starch indicator solution, potassium dichromate
    8.   Ozone residual colormetric test kit

    The EPA report entitled "Estimating Laboratory Needs for Municipal Waste-
water Treatment Facilities" provides a detailed listing of glassware, chemi-
cals, miscellaneous furniture,  etc., and should be referred to for any
detailed questions.

Sampling Procedures

    Effluent residual ozone determinations must be performed immediately
because samples can not be preserved or stored due to the instability of the
residual.  Samples should be collected in a manner so as to minimize aera-
tion.  There are three testing methods described in Standard Methods.

Sidestreams

    The off-gas from the ozone contact basin can be considered a sidestream.
In a single pass, once-through system, the ozone in the waste gas is destroyed
by heat or chemicals, or catalyic decomposition prior to venting to atmos-
phere.  In the closed loop system, the off-gas is recycled back to the ozone
generation equipment and reused.

    In some applications, the introduction of ozone produces foam and scum
which collects on the contact basin and must be removed.  The quantity of this
material is, however, very small and the removal requirements are minimal. The
best way of controlling of foam on contact basins is to reduce it with water
sprays.
                                      13-6

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Process Checklist - Ozonation
 1.

 2.

 3.
 4.
 5.
 6.
 7.

 8.

 9.

10.

11.
12.

13.

14.

15.
16.

17.

18.
What is flow through ozone contact basin
	.        mgd peak?
What are contact basin dimensions? length_
feet, depth	 feet
What is contact detention time? 	
What is applied ozone dosage
                     mgd avg?
         feet,   width
   minutes  at
mgd?
in mg/1?
What is normal ozone residual in basin effluent 	   mg/1?
Are disinfection standards being met?  (  )  Yes  (  )  No
What type of ozone generation equipment?  (  )  plate style  (  )  tube
style  (  )   other 	
What is ozone generator design capacity 	_lbs/day, maximum
capacity 	 Ibs/day?
Ozone generation equipment uses (  ) air, oxygen enriched air  (  )  pure
oxygen (  )  as feed gas?
What type ozone contactor? (  ) gravity feed covered basin
(  )  packed tower  (  )  Other 	
Is ozonation system {  ) Once through  (  )  closed loop?
How is ozone introduced into contactor? {  )  porous diffusers
(  )   injectors  (  )  turbine aerators   (  )  other?
Are residual ozone determinations made with (  )  continuous analyzers or
by (   )  laboratory tests?
Is plant equipped with automatic ozone leak detectors with alarm in crit-
ical areas? (  )   Yes  {  )   No
Is ozone generator room adequately ventilated?  (  )   Yes  (  )  No
How often are facilities checked?  (  )  once per shift  (  )   daily
(  )   other 	
Does the mechanical equipment have an adequate spare parts inventory?
(  )   Yes  (  )  No
What is the frequency of scheduled maintenance?
Describe
19. Is the maintenance program adequate?  (  )   Yes  (  )   No.
    the problem?
                                                            If no, what is
20. Are proper safety precautions used?  (  )   Yes  (  )   No
21. Does the sampling program satisfy the recommendations? (  )Yes  ( )  No
22. Are operating records adequate?  (  )Yes  (  )   No
23. Is the laboratory equipped for the necessary analyses? (  )Yes  ( )  No
24. What is the general condition of the ozonation process?  (  )   good
    (   )   fair  (  )   poor
25. What are the most common problems the operator  has had with the process?
                                      13-7

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References

 1. Gulp, G.L. and Folks Heim, N., Field Manual for Peformance Evaluation and
    Troubleshooting at Municipal Wastewater Treatment Facilities, EPA Report
    430/9-78-001.

 2. Rosen, H.M., "Ozone Generation and It's Relationship to the Economical
    Applications of Ozone and Wastewater Treatment", Chapter VI, Ozone in
    Water and Wastewater Treatment, Ann Arbor Science Publishers Incorporated
    1972.

 3. Kinman, R.N., "Ozone and Water Disinfection" Chapter VII, Ozone in Water
    and Wastewater Treatment, Ann Arbor Science Publishers Incorporated 1972.

 4. Diaper, E.W.J., "Practical Aspects of Water and Wastewater Treatment by
    Ozone" Chapter VII, Ozone in Water and Wastewater Treatment, Ann Arbor
    Science Publishers Incorporated 1972.

 5. Gulp, R.L., Wesner, G.M., and Gulp, G.C., Handbook of Advanced Wastewater
    Treatment, Van Nostrand Reinhold (1978).

 6. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328, June 1973.

 7. Union Carbide Corporation, Linde Division, Operation and Maintenance of
    the Union Carbide LG-90 Ozone Generator Tonawanda, N.Y. 1977.

8.  Stopka, Karel, "Ozone Plant Improves Efficiency and Economy of Wastewater
    Treatment", Water and Sewage Works, April 1978.
                                      13-8

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 14.   FILTRATION

 Process  Description

     The  filtration process  is  used  to  remove or  reduce the suspended or col-
 loidal matter  from a  liquid stream  by  passing the water through a bed of
 graded granular material.   The granular  material can be sand,  gravel, coal,
 garnet or  similar materials.   The main purpose of filtration is meet more
 stringent  discharge standards  and improve  disinfection efficiency and
 reliability.   Filtration  is used  to remove BOD,  COD,  turbidity,  phosphorus,
 virus, asbestos, heavy metals  and others from secondary or tertiary effluent.
 It  is always used ahead of  granular activated carbon contactors to protect
 against  fouling and improve the adsorption efficiency.   Filtration is fre-
 quently  installed following chemical treatment processes to remove flocculant
 materials  not  removed in  the clarifiers.

     Filters are classified  in  many  ways.   They can be described according to
 the  direction  of flow through  the bed, that is,  downflow,  upflow,  biflow,
 radial flow, horizontal flow,  fine  to  coarse,  or  coarse to fine.   They may be
 classed  according to the  type  of filter  media used,  such as sand,  coal (or
 anthracite), coal-sand, multilayered,  mixed media, or diatomaceous earth.
 Filters  are also classed  by flow rate.   Slow sand filters operate  at rates of
 0.05-0.13  gpm/ft2, rapid  sand  filters  operate at  rates of 1-2  gpm/ft2 and
 high rate  filters operate at rates  of  3-15  gpm/ft2.   They can  also be
 classed  by the  flow characteristics of filters which  can be pressure or grav-
 ity  flow.  Filters used for wastewater treatment  are  predominantly downflow,
 multi-media, high rate filters  that can  have  either gravity of pressure flow
 characteristics.

     Because of  the high loading rates currently used  in filtration systems
 (about 30  times the rate of slow sand  filters) they capture more  solids in
 less  time  and must be cleaned more  often.   The filter is  cleaned by reversing
 the  flow through the media  ("backwashing").   The  upward backwash  rate must be
 high enough that the media particles are suspended and  the wastewater solids
 and  captured materials are washed from the  bed.   These  backwash wastewaters
 (usually less than 5% of  the wastewater  flow  treated)  are  stored  in an equal-
 ization  tank and then recycled  to the wastewater  treatment plant for
 processing.

 Typical Design Considerations

    The principal criteria by which  filters are sized are  related  to  the  flow
 characteristics, gravity or pressure, and the  type, size  and depth of the
 filtering  media.  Once these have been established, the loading, backwashing
 and  surface washing rates can be established.  These  items  are briefly dis-
 cussed in  the following paragraphs:

    Filter media designs are usually either dual media  filters which  consist
of 15 in. of coal (about 1.8 mm in diameter) and over  15  in. of sand  (0.55 mm)
or mixed media which consists of about 16 in.  of coal,  9  in. of sand,  and  4
 in.  of garnet.
                                      14-1

-------
    The most common filtration rates used in wastewater treatment range from 3
to 6 gpm/sq ft of filter area.  This range in loading rate is applicable to
both the dual media and mixed media configurations.

    Backwash systems for filters usually are operated at rates in the range of
15 to 20 gpm/sq ft for 5-10 min.  The backwash water is returned to the
headworks for treatment.

Typical Performance Evaluation

    The filtration process is evaluated by the quality of the filtered water
measured in terms of suspended solids or turbidity.  Other factors include:

         Rate of headless build-up, feet/hour
         Water application rate
         Influent characteristics
         Filtration media characteristics
         Filter backwash system
         Filter surface wash system

    Of these factors, the most important is the quality of the influent to the
filter.  When filtering secondary effluent, if the biological system always
operates well, good filter performance can be expected.  However, if the bio-
logical system is frequently upset, filtration will be much more difficult.
Performance evaluation may be conducted as described below.

    1.   Collect the required base information.
         Plant flow rate  =  15 mgd
         BOD in influent to filter  =  20 mg/1
         Suspended solids in influent to filter  =  25 mg/1
         BOD in filter effluent  =  10 mg/1
         Suspended solids in filter effluent  =  3 mg/1
         Filter size  =  22 ft x 24 ft
         Number of filters  =  4
         Backwash flow rate  =  7920 gpm
         Backwash duration  =  7 min
         Frequency of filter backwash  =  once each 12 hours
         Headloss to backwash (preset condition)  =  10 feet

    2.   Compute.the filter area and rate of filtration under normal conditions
         Plant flow rate
                           15 mgd x 106 =  10,417 gpm
                          1440 min/day
     Filter area  =  4 x 22 x 24  = 2,112 sq ft
     Filtration rate  =   10,417 gpm   =  4.93 gpm/sq ft
                          2,112 sq ft

This system is within the range of filtration rates normally used, which
is 3 to 6 gpm/ft2.
                                      14-2

-------
     3.    Compute the rate of backwash and the volume used.
          Rate of backwash  =   7920  =  15 gpm/sq ft per filter
                                2112/4 filters
          Flow through each filter  =   15 mgd x 106
                                                  2604 gpm
                                      4 x 1440 min/day
     Volume  of backwash water   =  7920 gpm x 7 min/backwash x 2 day x 4 filters
                          =  443,520  gallons/day
          Volume  of water  through filters  =  (1440 - 2 x 7). x 2604.x 4
                                                    10 6
          Percent backwash  water
                                  =  14.85 mgd
                             0.433   x 100  =  3%
                             14.85
     The  backwash  rate  of 15  gpm/sq  ft2  falls  at the lower end of the normal
 range  for backwashing  of 15  to  20 gpm/ft2.  The backwash percentage of 3% is
 within the  desirable range of backwash  usage  of 1  to 5%.

     4.   Compute  the percentage of  BOD  and  suspended solids removals.
         Percentage BOD  removal -    20 - 10    =  50%
                                        20
         Percentage suspended solids  removal   =   25 -  3   =  88%
                                                     25

     5.   Characterize  the influent  water to the filter  as being  activated
         sludge,  trickling filter,  chemical clarification or some other pro-
         cess effluent.  Using  the  average  values  developed above,  compare
         them to  the average values expected  values presented in Table 14-1.
         These values  are for mixed media filters  and were developed using
         data at  several operating  facilities.   When treating chemically
         coagulated and  settled effluent, the  filter  effluent should be less
         than 1 turbidity unit.

 Process Control

    The control considerations  for  the  filtration  process  depend almost total-
 ly on  the filter aid facilities provided.   These include polymer  and chemical
 conditioners to be added ahead of the filters.  Other controls include adjust-
ment of the headloss to backwash value  and  the  length of  the backwash  runs.
These are discussed in more detail  in Reference 1.

Maintenance Considerations

    The evaluator should study  the  maintenance program  to  determine  whether
 the following items are  included (in addition to general maintenance manage-
ment discussed earlier).
    1.
Spare parts inventory should include at least the following items:
one set of each type of bearing for pumps, grease seals, one set of
all gaskets, mechanical seals, washers or sheaves for adjusting pump
impellers, nozzles for surface wash system and underdrain system,
control solenoid and some volume of the filter media.
                                      14-3

-------
         TABLE 14-1.  DESIGN CRITERIA FOR ORANGE COUNTY WATER DISTRICT
                      OPEN GRAVITY, MIXED MEDIA FILTER SYSTEM
Dimensions:
      4 filters each
      22 ft x 24 ft (plan area)
      media depth = 30 in
Bed construction:
Media
Anthracite coal
Silica sand
Garnet sand
Garnet gravel
Garnet gravel
Silica gravel
Silica gravel
Silica gravel
Depth
(in)
16.5
9
4.5
1.5
1.5
2
2
2
Specific
gravity
1.6
2.6
4.0
4.0
4.0
2.6
2.6
2.6
Grain size
range (mm)
0.84-2.00
0.42-0.84
0.18-0.42
1
2.00-4.76
3.18-6.36
6.36-12.72
12.72-19.08
Surface hydraulic
  loading rate:

Max operating
  headless:
4.93 gpm-sq ft at 15 mgd (2604 gpm per filter)
10 ft
                                      14-4

-------
     2.
     3.
     4.
     5.
     6.
     7.
 Records
 Daily inspection of the rotary surface washers  to  insure  they  are
 free to rotate and the nozzles are not plugged?  In gravity  filters,
 the washing operation should be monitored for any  plugged orifices.

 Inspection in each shift to check the calibration  of the  effluent
 turbidimeters and any other remote recording or instrumentation.

 Recorder charts on flow, headless, and turbidity meters changed
 routinely and the recorder ink supply checked at each chart change-

 System is monitored routinely and that the filters are not operating
 out of their anticipated operating range.

.Regular  readings of backwash pumping times are recorded from elapsed
 time meters.   These can be used for  scheduling maintenance work and
 also to  insure that backwash cycles  are correct.

 Periodic performance tests run on each pumping unit to insure that it
 is operating  along  the same pump  curve as supplied  at the time of
 purchase of the pumping unit.
     The recommended sampling and laboratory tests are shown in Figure 14-1 for
 the filters.   The same tests are performed on all types of filters.
     Other  operating  records should include the following:
     1.
     2.
     3.
     4.
     5.
     6.
 Influent  flow  to  the  filters
 Backwash  flow  rate and duration
 Surface wash flow rate and duration
 Filter run time or frequency of backwash
 Headless  through  filter as a function of time
 Filter aid type and dosage
Laboratory Equipment

    The  laboratory should  include the following minimum equipment  in  order  to
monitor  the filtration system.
     1.
     2.
     3.
     4.
     5.
     6.
Analytical balance
Clinical centrifuge with graduated tubes
BOD incubator
Drying oven
Dessicator
Turbidimeter
    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be referred to for anv de-
tailed questions.                                                    y
                                      14-5

-------
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                                                    ESTIMATED UNIT PROCESS SAMPLING AND
                                                               TESTING NEEDS
                                                     FILTRATION
                                                              MIXED MEDIA OR SAND TYPE
                                                                                  (INFLUENT FROM
                                                                                  PREVIOUS MAIN
                                                                                  FLOW TREATMENT
                                                                                  PROCESS
                                                                                     II
                                                           EFFLUENT TO
                                                           NEXT MAIN FLOW
                                                           TREATMENT PROCESS
                                                   NOTE: PRESSURE TYPE SHOWN.
                                                        GRAVITY TYPE HAVE
                                                        SIMILAR FLOW STREAMS.
                              BACKWASH WASTE
                              RECYCLE TO PLANT
                              INFLUENT OR
                              CHEMICAL TREATMENT
                              INFLUENT-
                                                     A.  TEST FREQUENCY
                                                         H m HOUR      M - MONTH
                                                         D- DAY       R - RECORD CONTINUOUSLY
                                                         W- WEEK      Mr.- MONITOR CONTINUOUSLY

                                                    B.  LOCATION OF SAMPLE

                                                         I - INFLUENT
                                                         E - EFFLUENT
                                                         BW = BACKWASH
C. METHOD OF SAMPLE

    24C-24 HOUR COMPOSITE
    G - GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn= MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL
                                                    E.  FOOTNOTES:
                                                          1. WHEN BACKWASHING
                                                          2. FOR CONTROL OF PROCESS
                                                             RECEIVING THIS FLOW
                                                    Figure  14-1
                                                  14-6

-------
Sampling Procedures

    Samples should be collected from sampling taps in the  influent  and ef-
fluent lines for pressure filters and from the influent distribution  trough
and backwash storage well in the case of gravity filters.  The sample col-
lector and containers should be clean.  A wide mouth sample collector of at
least 2 inches should be used.  Samples collected in the effluent lines or
storage tank should be collected near the discharge point  so that any isolated
areas of short circuiting do not influence the results.  Where automatic
samplers are used, it is important to keep the sampler tubes clean.

Sidestrearns

    The only sidestream associated with the filtration process is the waste-
water associated with backwashing or cleaning the filters.  The volume of
water is normally in the range of 1 to 5 percent of the volume of water pass-
ing through the filter,  and is most frequently found to be,about 2  to 3 per-
cent of the throughput volume.

    The wastewater from backwashing the filters contains suspended  solids in
the range of 100 to 1000 mg/1, with an average value of about 300 mg/1.  The
water may be discharged to a settling tank where the settled solids are with-
drawn and pumped to the solids handling facility and the supernatant recycled
to the treatment plant.   In many cases, the backwash water is all recycled to
the treatment plant at a controlled rate from a storage tank.
                                      14-7

-------
Process Checklist - Filtration
 1.

 2.

 3.

 4.
 5.
 6.
 7.

 8.
 9.

10.

11.

12.
13.

14.

15.

16.
17.

18.
19.

20.

21.
What is flow through filters
	 mgd min?
Type of filters (  )  gravity
and capacity of each filter
           mgd avg.
                                                                  mgd max.
  (   )   pressure,  number  of  units
What is type of filter media? (  )   sand  (  )   dual media  (  )  mixed
media  (  )   multi-media  (  )   diatomaceous earth  (  )   other 	
What is surface loading rate?	 gpm/ft2
What is backwash rate?	gpm/ft2
What is surface wash rate?	
Type of control system? (  )
(  )  turbidity of effluent
	 gpm/ft2  and  pressure  	
 constant  flow  (  )   headless
                                                                     psi
                                                             (   )   time
                             (  )   total gallons filtered  (  )   other
Are all automatic valves operating correctly? (  )   Yes  (  )   No
Are the valves sequencing (opening and closing in order)  correctly?
(  )   Yes  (  )   No
Is there a coagulant aid (filtration aid) system? (  )   Yes  (   )   No
If yes, what type
Is the chemical aid system operating? (
If no, explain
            )   Yes  (   )   No
What are the dimensions of the filter?	
Operation of the system is? (  )   Automatic  (  )   Manual
(  )  semi-automatic  (  )  Other ______	
Are all pumps operating? (  )   Yes  (  )   No.  If no, what is the
problem? 	;	
Does the mechanical equipment have an adequate spare parts inventory?
(  )  Yes  (  )  No
Is the filter building adequately ventilated? (  )   Yes  (  )  No
How often are facilities checked? (  )  Once per shift  (  )   Daily
(  )  Other 	
What is frequency of scheduled maintenance?	
Is the maintenance program adequate?  (  )  Yes  (  )  No
If no, what is problem _____________	
What is the general condition of the filtration process? (  )   good
 (  )fair  (  )  poor
What are the most common problems the operator has had with the filtration
systems?	
                                      14-8

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4.  Wirts,  J.J.,  et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5.  Miorin,  A.F.,  et al, Wastewater Treatment Plant Design, Manual of Practice
    No.  8,  Water  Pollution Control Federation (1977).

 6.  State of Virginia O&M inspection form.

 7.  Gulp, Gordon  L.,  and Gulp,  Russell L.,  New Concepts in Water Purification,
    Van  Nostrand  Reinhold,  1974.

 8.  Gulp, Russell  L., Wesner,  G.  M., and  Gulp, Gordon  L.,  Handbook of Advanced
    Wastewater  Treatment,-Van  Nostrand Reinhold,  1978.
                                     14-9

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-------
 15.   MICROSCREENING

 Process  Description

     A microscreen  is  a mechanical filter, process used to remove suspended
 solids from secondary effluent.   The equipment consists of cylindrical drums
 horizontally mounted  in a two-compartment concrete tank.   Each drum is covered
 with a woven fabric which serves  to trap the solids as the wastewater flows
 through  it.   The drum is usually  submerged about two-thirds underwater, with
 solids being retained on the  inside surface as it slowly rotates.   The screen
 is equipped with a backwashing unit to  remove the accumulated solids.  Wash-
 water is collected in a hopper or trough mounted inside the screen and is re-
 cycled to another  process.  The water used for backwashing is recycled
 screened effluent,  constituting about 3  to 5 percent of the total  screened
 flow.

     Table 15-1 shows  typical  values for  microscreen and backwash design para-
 meters for  solids  removal from secondary effluents.   Similar values would
 apply to direct microscreening of good quality effluent from trickling filters
 or rotating  biological contactors where  the microscreens  replace secondary
 settling tanks.

 Typical  Performance Evaluation

     Microscreens with  23-y apertures can be expected to remove 70  to 80 per-
 cent of  the  suspended  solids  in activated sludge  effluent  and 60 to 70 percent
 of the BOD.  With  a larger aperture  (35  y)  50  to  60  percent of the suspended
 solids and  40-50 percent of the BOD would be  removed.   Detailed performance
 factors  are  given  in Reference 1.

 Process  Control

     Except for drum speed there is  little  the  operator  can control with the
 microscreening process.   If the drum travels  too  fast,  it  will not do an ef-
 fective  screening  job  and may cause  excess  wear on  the  mechanical  parts.   If
 it runs  too  slowly, the  fabric will  become  clogged and  the head between the
 influent and the effluent may become  so  great  that  the  fabric  breaks.   A
 clogged  screen may cause the  influent to bypass the  microscreen.

Maintenance Considerations

    The  features of a good maintenance program that  the inspector  should look
 for are:
     1.

     2.

     3.
Tears in screen are repaired or replaced as soon as possible.

Backwash nozzles cleaned on a regular basis.

Drum is periodically cleaned of accumulated grease and oil and algae
or slime growths.
                                      15-1

-------
                    TABLE  15-1.   MICROSCREEN DESIGN PARAMETERS
    Item
Typical Value
Remarks
 Screen mesh

 Submergence
Hydraulic
  Loading
Headless  (HL)
  through screen
Peripheral
  Drum Speed
Typical Diameter
  of Drum
Backwash Flow
  and Pressure
20-25 microns

75 percent of height
66 percent of area

5-10 gpm/sq ft
of submerged drum
square area

3-6 in.
Range 15-60 microns
15 fpm at 3 in.(HL)
125-150 fpm at
6 in. (HL)

10 ft
2 percent of throughput
at 50 psi
5 percent of throughput
at 15 psi
Maximum under extreme condition
12-18 in. Typical designs pro-
vide for overflow weirs to
bypass part of flow when head
exceeds 6-8 in.

Speed varied to control
extreme maximum speed
150 fpm.

Use of wider drums
increases backwash
requirements.
     4.  Spare parts inventory should contain the following:  replacement mesh
         for rotating drum, gears and motors for rotating drives, backwash
         nozzles, etc.

Records

    Recommended sampling and laboratory tests are shown on Figure 15-1.

    Other operating records should include:

    1.    Backwash flow rate.
    2.    Percent of throughput used for backwash.
                                      15-2

-------
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                                                     ESTIMATED UN4T PROCESS SAMPLING AND
                                                                TESTING NEEDS
                                                     M1CROSCREEN1NG
                                                                   BACKWASH -.RECYCLED
                                                                   MICROSCREJEN EFFLUENT
                                                                               BW
                                                     INFLUENT FROM
                                                     PREVIOUS MAIN
                                                     FLOW TREAT-
                                                     MENT PROCESS
                                                                                       ^BACKWASH WAST.E
                                                                                         RECYCLE TO PLANT
                                                                                         INFLUENT
                                                                                            E
                                     EFFLUENT TO
                                     NEXT MAIN FLOW
                                     TREATMENT
                                     PROCESS
                                                     A.  TEST FREQUENCY

                                                          H  HOUR      M  MONTH
                                                          0- DAY       R - RECORD CONTINUOUSLY
                                                          W- WEEK      Mn- MONITOR CONTINUOUSLY

                                                     B.  LOCATION Of SAMPLE

                                                          I  = INFLUENT
                                                          E- EFFLUENT
                                                         BW =BACKWASH
C. METHOD OF SAMPLE

     24C-24 HOUR COMPOSITE
     G - GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     Mn = MONITOR CONTINUOUSLY

0. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P - PROCESS CONTROL
     C - COST CONTROL

E. FOOTNOTES:
      1. WHEN BACKWASHING
      2. FOR CONTROL OF PROCESS
        RECEIVING THIS FLOW
                                                     Figure 15-1
                                                   15-3

-------
Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor the microscreening.

     1.  Analytical balance
     2.  Clinical centrifuge with graduated tubes
     3.  BOD incubator
     4.  Drying oven

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be consulted for any detailed
questions.

Sampling Procedures

    Samples should be collected at points where the wastewater is well mixed
such as at the center point of the channel of flow where velocities are high.
The sample collector and containers should be clean.  A wide mouth sample col-
lector of at least 2 inches should be used.  Samples collected in the effluent
channels should be collected near the discharge point to insure well mixed
specimens.  Where automatic samplers are used, it is important to keep the
sampler tubes clean.

Sidestreams

    The backwash from microscreening constitutes about 2 to 3 percent of the
through-put and has a suspended solids concentration of 700 to 1000 mg/1.  It
is ordinarily returned to the headworks of the plant and does not present any
particular operating problems.  Because there is a certain amount of grease
and oil mixed in this flow, keeping the return lines clear is important to
proper plant operations.
                                      15-4

-------
Process Checklist - Microscreens
 2.
 3.

 4.

 5.

 6.

 7.


 8.
 9,

10.

11.

12.
13,

14.
15.
    What is the volume of flow to the microscreens
      .       mgd peak?.
                                                    _mgd average;
Type of filter fabric
Number of microscreens
operating loading rate
Backwash rate
    ;  mesh aperture
     capacity of each unit
    .       gpm/ft2.
Frequency of backwashing
Location of backwash recycle 	.
Are all microscreen and. backwash units operating properly?
(  )  Yes  (  )  No                     .;,..,
Does filter mesh appear to be clogged in one particular spot?
(  ) Yes(  )  No. Are all backwash nozzles spraying properly?(  ) Yes  (  )No
Is backwash collection trough adequate to collect solids and backwash
flow  (  )   Yes  (  )  No. If not, would adjusting it's position result in 
proper collection.   (  )  Yes  (  )  No.  Other    ,	. .   .
Does backwash water flow freely to recycle point?   (  )  Yes
Does filter fabric show signs of wear?   (  )  Yes   (  )  No.
unrepaired tears in it?  (  )  .Yes  {  )  No
Is there a accumulation of slime or algae on filter mesh?
 Grease or oil?  (  )   Yes  (  )  No
If multiple units are used, is flow distributed evenly?
(  )   Yes  (  )  No
Is all mechanical equipment operating properly? (   )  Yes
How often is facility checked? (  )  Once per shift   (  )
(  )   Other 	
Frequency of maintenance inspections by plant personnel _
Is the maintenance program adequate? (  )  Yes  (   )  No
If no, explain	
                              (  )   No
                              Are there
                           (  )  Yes (  )  No
                           (  )  No
                           Daily
                                  /year.
16. Does the sampling program meet the recommendations?   (
17. Are operating records adequate?  (  )  Yes   (  )  No
18. Is the laboratory equipped for the necessary analyses?
    (  )   Yes  (  )   No
19. What is the general condition of the microscreening facilities?
    (  )   Good  (  )   Fair  (  )  Poor
20. What spare parts are stocked?	
                                                        )  Yes  (  ) No
21. What are the most common problems the operator has had with the filtration
    systems? 	
                                      15-5

-------
References

 1. Gulp/ G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. CH2M-H111, Estimating Laboratory Heeds for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 3. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 4. State of Virginia O&M inspection form.

 5. Hazen and Sourfer Inc., Process Design for Suspended Solids Removal, EPA
    Technology Transfer (January 1975).

 6. Gulp, Russell L., Wesner, G. M., and Gulp, Gordon L., Handbook of Advanced
    Wastewater Treatment,  Van Nostrand Reinhold, 1978.
                                      15-6

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 16.  ACTIVATED CARBON ADSORPTION

 Process Description

     The activated carbon adsorption process is used to reduce the concentra-
 tion of the soluble or dissolved organic matter in the wastewater.  This
 process is normally used in one of two treatment schemes: (1) As an advanced
 wastewater treatment (AWT)  process following a conventional biological treat-
 ment system; or (2) in conjunction with independent physical-chemical (IPC)
 treatment processes.

     When used as an AWT process, the activated carbon process follows biologi-
 cal treatment, or sometimes chemical coagulation and sedimentation.  Filtra-
 tion normally precedes the activated carbon process to protect the system from
 fouling with suspended matter in the water.  Biological systems can remove the
 majority of organic materials,  but not the more complex soluble organic mate-
 rial.   These organics can be removed by the activated carbon.

     When the activated carbon adsorption process is used as an IPC process, it
 provides the only method for organic removal.  In an IPC treatment system, the
 raw wastewater undergoes preliminary treatment,  chemical coagulation and clar-
 ification,  and filtration before carbon treatment.   This treatment scheme
 removes a greater  percentage of organics than  biological secondary treatment
 alone,  but not as  much  as when  used as an AWT  process.

     Wastewater treatment with activated carbon involves two process opera-
 tions,  a  contact  system,  and a  carbon regeneration  system.   Th water passes
 through a container  filled  with carbon granules  or  a carbon slurry.   Organic
 impurities  are removed  from the water by adsorption onto the carbon.   The con-
 tactors are either open  concrete gravity-type  systems,  or steel pressure con-
 tainers suitable for either upflow  or downflow operation.   Upflow operation
 occurs  when the water enters the bottom of the pressure contactor and flows
 upwards through the carbon  to exit  at the top.   Downflow is  sinply the reverse
 operation.

     After  the  water has passed  through the carbon beds  for  a period of time,
 it  loses  its capacity to  adsorb the organics and must then be regenerated.
 The regeneration system  is  a furnace  in which  the carbon  is  placed and
 heated.  The regeneration process is  described in detail  in  Section 40 of this
 manual.  The heat  drives  off the organic material that  was adsorbed onto  the
 carbon, and "reactivates" the carbon  for continued  use  in the treatment  sys-
 tem.  About 5  to 10 percent of  the  carbon  is lost during  regeneration  and must
 be  replaced with new, fresh carbon.

     The activated  carbon  that is used  for  wastewater treatment  is  either  gran-
 ular or powdered.

Typical Design Considerations

    Activated carbon adsorption  systems are chosen based on  their  location  in
 an overall  treatment system and  on  the  estimated organic removal efficiency
                                      16-1

-------
that is required.  The type of carbon system used depends on the other treat-
ment processes and the topography of the plant site.

    Sizing of the unit is based on four factors: the contact time, the hydrau-
lic loading rate, the carbon depth, and the number of contactors.  Typical
contact times range from 15 to 40 min, depending on the strength of the waste-
water and the required effluent quality, and are normally selected after pilot
plant testing.
                                                      *
    Hydraulic loading rates vary from 3 to 12 gpm/ft2 of cross-sectional
carbon area for upflow contactors and from 2 to 5 gpm/ft^ for downflow con-
tactors.  The upflow contactors must also include an allowance for the carbon
bed expansion during operation.  Typical expansion percentages for upflow
contactors are given in Figure 16-1.

    The depth of the carbon contactors ranges from 10 to 30 feet.  The bed
depth is normally determined from the surface area and the contact time.

    The number of contactors depends on the treatment processes preceding
them.  The system must produce the required effluent quality with one unit out
of operation.  There should always be a minimum of two contactors.

Typical Performance Evaluation

    Activated carbon contactors can' be evaluated by using plant operational
data and contactor characteristics.  The following is an example of the step-
by-step procedures for evaluating the performance of an activated carbon
adsorption system:

    1.    Define the dimensions and design data for the carbon system.

         Upflow Contactor
         Pretreatment:  Filtered Secondary Effluent
         Column Flow Hate              =  650 gpm
      .   Column Diameter, D              12 ft
         Column Area, A - (Tr/^D2     -  113 sq ft
         Carbon Depth                  -  26 ft 2 in. (312 in.)
         Carbon Volume, V-A x Depth    =  22,140 gal

    2.    Determine the contact time of the carbon column.
         Contact time (min)
Volume occupied by carbon in gal
       Flow rate in gpm
22,140
 650
34 min
                                      16-2

-------
    80,
    70
    SO
1
'S
#
X

Ul
                                10
                                              15
                                                           20
25
                               FLOW RATE, gpm/sq ft


              CARBON:  12 x 40, 8 x 30


              LIQUID:   WATER AT 22 C
   Figure l&r-l.   Expansion of carbon bed at various flow  rates.
                                    16-3

-------
    3.   Determine the hydraulic loading rate.

         Hydraulic loading rate        =  Flow rate in gpm
                                          Surface area of column
                                       -  650
                                          113
                                       =  5.75 gpm/sq ft

         Numerous tests have shown that the efficiency of the carbon is not
         affected by hydraulic loading rate (at a given contact time) for
         rates in the range of 2 to 8 gpm/sq ft.

    The container should be checked to see if it is large enough for the car-
bon expansion.  From Figure 16-1, the expansion would be about 3% of the bed
depth.
         Bed expansion
3   3   x 312 in.
   100
=  10  x 312 in.
   100
9.4 in. for 8 x 30 mesh

31 in. for 12 x 40 mesh
         If the bed is constrained from expanding, suspended matter could be
         trapped in the bed and the effectiveness of the filter will be
         reduced.

         Review available effluent quality data and, if needed, collect
         samples from the carbon column influent and effluent, and analyze the
         samples for the following:

              TOG,
              Soluble Organic Carbon
              SS
              BOD
              COD
              Color
              Turbidity

         The results should be compared to those shown in the following table.
         Filtered Secondary
         Description

         TOC Removed, percent
         Soluble Organic Carbon
           Removal, %
          Unfiltered Secondary
              Effluent	

               45 - 55

               40 - 45
                   Effluent
                  50 - 60

                  45 - 50
         Review the carbon dosage and carbon losses to see if the fall within
         typical design ranges.  The importance of carbon dosage is described
         in the section on carbon regeneration  (Section 40) and is not dis-
         cussed here.
                                      16-4

-------
Process Control

    The major control variations relate to the rate of flow through the con-
tactors, the contact time, and the number of contactors in operation.  These
are interrelated, because adjustment of one of these control options changes
the other two.  It is important to avoid excessive contact times to prevent
excessive biological growth which fouls the bed and results in a strong odor.
This often occurs at the startup of a new plant when the flows are low.  Main-
taining the contact time and rate of flow through the bed within the typical
ranges should result in efficient operation of the system.

    The carbon dosage can be adjusted either upwards or downwards to optimize
treatment efficiency-  The upper limit is governed by the capacity of the re-
generation system.  If lower carbon doses can be used to achieve the desired
effluent quality, the operating costs for regeneration will be less.

    The rate of adsorption of organics found in municipal wastewater usually
increases as the pH of the water decreases.  Adsorption is very poor at pH
values above 9.0.  High pH wastewaters should be neutralized before carbon
adsorption, and the influent pH should be kept fairly constant.  A sudden,
upward shift in pH can lead to desorption of organics and an increase in ef-
fluent COD.

    Treating water that has high turbidity will plug carbon pores and result
in the loss of carbon capacity.  Thus, special attention should be given to
the control of processes upstream of the carbon columns.  The adsorptive ca-
pacity and service life of the carbon can be maximized by applying to the car-
bon water that has been carefully pretreated to the highest practical clarity.

Maintenance Considerations

    Proper maintenance of a facility is an important function to insuring ef-
ficient, troublefree operation.  The features of a good maintenance program
are listed below.  These considerations are to be used in conjunction with
general maintenance management discussed earlier.

     1.  Spare parts inventory should include at least one set of each type of
         bearing, grease and water seals, all necessary gaskets.for replace-
         ment of parts, influent and effluent strainers or underdrain systems.

     2.  Visual inspection each shift of the activated carbon process equip-
         ment to check the equipment for misalignment, excessive noise, un-
         equal loading of the contactors, excessive pressures in pressure con-
         tactors.

     3.  Pressurized containers checked regularly to insure their integrity
         against failure.

     4.  All non-operating equipment, such as by-pass valves, being operated
         every month to test for operability.
                                      16-5

-------
       5.  Saiqple lines flushed regularly to flush out material, such as carbon
           fines, that may have entered the lines.

  Records


  ,  The.recommended sampling and laboratory tests are shown in Figure 16-2 for
  the activated carbon adsorption system.


      Other operating records should include the following:

      1.    Influent  flow rate
      2.    Carbon dosage in Ibs per  million  gallons.
      3.    The  amount of COD removed per pound of carbon
      4.    The  contact time
      5.    Frequency  of backwashing, if also used as  a  filter

 Laboratory Equipment
 mnnir           .       inlude the followin9 "inimum equipment in order to
 monitor the activated carbon adsorption system.
     1.   Reflux apparatus to perform COD tests
     2.   Colorimeter
     3.   Turbidimeter

 TreaSenf MiS "I8""*"1* ^oratory Needs for Municipal Wastewater
               uties" contains very detailed information on glassware, chemi-

                     furniture- etc-' and shouid b
 Sampling Procedures
                       C0llected frffl ** influent and effluent channels of

ha   tein         "p"*11 aS *" Clear "" r effluent channe1'  w
has  the  combined flows.   For  pressure contactors,  the samples are taken

                                                                     '
           ai                                             cm
          line.  The  sample  container  should  be clean to  avoid bad results   if

  ildof^f111  " Td'  the  lineS  ShUld  be  flushed regularly to avoid
build-up  of solids or other deposits.

Sidestreams
hn       f 6 normallv " * sidestreams associated with an activated car-
bon contacb system.  However, when the system also acts as a filter, t^ere

                 "^ ^^^^ with <*e backwashing cycle as described for the
           Process.  When the carbon has not been washed well, carbon fines

                       Can be fUnd in the eff luent-  C"^ ^nes in the ef-
                 erroneous ^emical oxygen demand tests as well as greater
                 co"centrati0^ and higher turbidities.  To avoid these prob-
                Carbn SyStemS are often Provided with the necessary piping to
                  fiW thrUgh the C0lumns b* returning it to the the p?ant
                 Sldestreams "e very small and do not^dd a significant Joad
                                      16-6

-------
s
o
a
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COD
PH
MBAS



















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AT,T.



















TEST
FREQUENCY
3/W
Mn
V"



















LOCATION OF
SAMPLE
I
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METHOD OF
SAMPLE
24C
Mn
?-W



















REASON
FOR TEST

H
P
._P_



















                                                  ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS


                                                  ACTIVATED CARBON ADSORPTION
                                                                        'ACTIVATED
                                                                        CARBON IN
                                                 /

f^"1 ^>v
C, EFFLUENT TO
NEXT MAIN FLOW
TREATMENT PROCESS
                                                V-
               - SPENT CARBON TO
                REGENERATION OR
                FINAL DISPOSAL
 INFLUENT FROM
 PREVIOUS MAIN
 FLOW TREATMENT
 PROCESS
                                                   A.  TEST FREQUENCY

                                                       H . HOUR     M - MONTH
                                                       D - DAY      R - RECORD CONTINUOUSLY
                                                       w- WEEK     MK- MONITOR CONTINUOUSLY

                                                   B.  LOCATION OF SAMPLE

                                                       I  INFLUENT
                                                       E- EFFLUENT
C. METHOD OF SAMPLE
    24C24  HOUR COMPOSITE
    G - GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn- MONITOR CONTINUOUSLY

D. REASON  FOR  TEST

    H - HISTORICAL KNOWLEDGE
    P  PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:

     1. PROCESS CONTROL ON EFFLUENT
     2. PROCESS CONTROL FOR SYSTEM
       EQUIPMENT FOR pH ADJUSTMENT
                                                 Figure 16-2
                                               16-7

-------
Process Checklist - Activated Carbon Adsorption
 1. What is actual plant flow?	mgd avg.
 2. What is total flow through the carbon system?_
 3. How many contactors? 	
 4
 6
 7
 8
 9
10
                                                            mgd.
    What is flow through each contactor
    	mgd 	mgd
             mgd
mgd
                                       gravity  (
                                       )   series
    What type of carbon system?  (
    (  )   downflow  (  )   parallel
    (  )  Other	
    What are contactor dimensions? 	
    What is the COO removal per Ib of carbon? 	
    What is the Ibs carbon used per million gallons?
    What is contact time?                min
        )   pressure  (   )   Upflow
                              Ibs/lb
                              Ibs/MG
    Does the system have pH adjustment as part of the carbon process?
    (  ) Yes  (  )  No. If yes, what type and dose?	
11. Is the flow measured through each contactor?  (  )  Yes  (  )   No
12. For pressure systems, are the influent pumps operating properly?
    (  )  Yes  (  )  No.  If no, what is problem?	
13. If have pumps in the system, are they operating? (  }   Yes  (  )   No
    If no, what is problem?
                                                                 What are the
    pumps used for?
14. Do mechanical equipment have adequate spare parts inventory?  {  )  Yes
    (  )  No.  If no, what is problem?	
15. Is the carbon building adequately ventilated? (  )   Yes  (  )   No
16. How often are the facilities checked? (  )   once per shift  (   )  daily
    (  )  other	
17. What is frequency of scheduled maintenace? 	
18.
25.
20,
    Is the maintenance program adequate?(
    explain
)   Yes  (  )   No. If no,
    What is the general condition of the carbon system?  (  )   good
    (  )  fair  (  )  poor
    What are the most common problems the operator has had with the activated
    carbon system?	
                                      16-8

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants/ Manual of
    Practice No. 11, Water Pollution Control Federation  (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.
                    0

 7. Gulp, Gordon L., and Gulp, Russell L., New Concepts in Water Purification,
    Van Nostrand Reinhold, 1974.                                         r

 8. Gulp, Russell L.,  Wesner, G. M., and Gulp, Gordon L., Handbook of Advanced
    Wastewater Treatment, Van Nostrand Reinhold, 1978.

 9. CH2M-Hill, Process Design Manual for Carbon Adsorption, USEPA, Technology
    Transfer, April 1976.

10. Shuckrow, A.M. and Gulp, G.L., "Appraisal of Powdered Activated Carbon
    Processes for Municipal Wastewater Treatment," USEPA Report EPA-600/
    2-77-156, September 1977.
                                      16-9

-------

-------
17.  NITRIFICATION

Process Description

    Nitrification is a biological process in which specific organisms convert
ammonia-nitrogen (NH3-N) to nitrate-nitrogen (NO-N).  Nitrification
can be accomplished by a two-stage process with separate oxidation of carbon-
aceous material (BOD) and nitrogen or single-stage schemes in which both BOD
and NH3-N are removed in the same basin.  All nitrification systems are
sensitive to low temperatures.

    Extended aeration activated sludge systems have long aeration times (24
hours) and high solids retention times  (20 to 30 days).  This process is good
for maintaining a large population of nitrifying bacteria in a single treat-
ment unit.

    Attached growth biological treatment systems, when properly designed and
operated can also produce nitrified effluent.  A single-stage trickling filter
system designed for a very low organic loading in a warm climate can produce
nitrified effluent.  Synthetic media has been found more effective than rock  .
media because it provides a greater, more uniform surface area.  In two-stage
trickling filter systems, the first filter is designed as a roughing filter to
remove BOD and the second is designed for nitrification.  In this case, the
contact time (wetting rate) rather than the organic loading determines process
performance.  Trickling filters can also be used in a two-stage system follow-
ing secondary treatment by activated sludge.  The influent to the filter must
have a low BOD concentration  (less than 20 rag/1) to provide effective
nitrification.

    The ABP system can be designed to provide almost complete nitrification.
The tower or bio-cell is designed for BOD removal and the aeration basin for
additional BOD removal and complete ammonia conversion.

    Rotating biological contactors  (RBC's) are an effective means of single or
two-stage nitrification.  The first series of discs  in the system provides BOD
removal, while the downstream units provide nitrification.

    The reader should refer to Reference 1 and other  sections of this manual
to obtain more specific process information.

Typical Design Considerations

    The basic design procedures for nitrification follow  the same steps as for
conventional secondary  treatment, but the criteria  for process  sizing and  the
selection of equipment  are different.   Table 17-1 summarizes the basic design
criteria  for suspended  growth systems.  The oxygen  requirement  for nitrifica-
tion  is about 4.6  Ib 02/lb NH3 removed; this amount must  be supplied over
and above the carbonaceous oxygen demand of about 1.4  Ib  O2/lb  BOD removed.
If  the dissolved oxygen (DO)  drops  below 1 mg/1, nitrification  will be re-
duced.  In  the activated  sludge process, the degree of nitrification depends
on  the sludge retention time  (SRT).  Nitrification  normally requires an SRT of
about 10-12  days.
                                      17-1

-------
                 TABLE 17-1.  DESIGN PARAMETERS FOR TYPICAL
                  SUSPENDED GROWTH NITRIFICATION SYSTEMS
Single-stage Nitrification
   Loading
   F/M
   SRT
   Aeration time
   Solids recirculation
   MLSS
Ib BOD /1000 cu ft/day
Ib BODV1000 ib MLSS/day
       days
       hrs
        %Q
       mg/1
  10-30
0.05-0.15
  10-15
   6-12
  30-100
3000-6000
Extended Aeration
   Loading
   F/M
   SRT
   Aeration time
   Solids recirculation
   MLSS
Ib BOD /1000 cu ft/day
Ib BODg/1000 Ib MLSS/day
       days
       hrs
        %Q
       mg/1
  10-15
 , <0.05
  > 30
  16-24
 100-300
2000-6000
Two-Stage Nitrification
Carbonaceous removal by high-rate activated sludge
   Loading
   F/M
   SRT
   Aeration time
   Solids recirculation
   MLSS
Ib BOD /1000 cu ft/day
Ib BODVlb MLSS/day
       days
       hrs
        %Q
       mg/1
Nitrogen removal by conventional plug-flow, aeration
   Loading
   SRT
   Aeration time
   Solids recirculation
   MLSS
Ib NH3-N/1000 cu ft/day
       days
       hrs
        %Q
       mg/1
  70-180
  0.4-1.0
   2-4
   2-4
  30-100
3000-5000
  10-20
  10-20
    3
  30-100
1000-2000
                                     17-2

-------
    Nitrification will generally not occur in trickling filters loaded at
greater than 12 Ib BOD/1000 cu ft/day.  For good nitrification to occur the
loading should be less than 5 Ib BOD/1000 cu ft/day.  As indicated previously
in Table 17-1, this value is the minimum loading for a low rate filter.
Plants which include recirculation generally produce a greater degree of nit-
rification.  Synthetic media trickling filters tend to be more effective for
nitrification since they have a greater specific surface area on which nitri-
fying organism can grow.  For two-stage trickling filters, nitrification is
limited by the contact time.  Typical values for a 21.5-foot deep synthetic
media filter are given in Table 17-2.
       *

    TABLE 17-2.  HYDRAULIC LOADING FOR TWO-STAGE NITRIFYING TRICKLING FILTER
Nitrification
performance, ?
 Wetting Rate, gpm/sg ft
18C                7C
90
85
80
75
0.5
0.75
1.0
1.5
0.50
0.65
0.75
0.85

    The design criteria for the biofilter  is the same as that  for the standard
ABF system; it is designed to remove only BOD and not ammonia  from the waste-
water.  Nitrification as well as additional BOD removal occurs in the aeration
basin.  The design parameters for ABF nitrification are summarized in Table
17-3.  The aeration detention time is about four times that  for regular oxida-
tion and the organic loading about one-third.

    The design relationship for single-stage nitrifying RBC's  is given on Fig-
ure 17-1.  The hydraulic loadings for various influent BOD and ammonia concen-
trations are presented.  When used following secondary treatment, RBC's should
be designed according to the relationship given on Figure 17-2.  The basic
curves are for a four-stage system achieving 90 to 95 percent  nitrification.

Typical Performance Evaluation

    Virtually any level of nitrification can be achieved with  any of the proc-
esses described herein if the design parameters are selected according to the
treatment conditions.  The most common cause of systems not  meeting design
standards are cold weather and peak flows.  These factors should be considered
when evaluating processes.
                                      17-3

-------
           TABLE 17-3.
GENERAL DESIGN PARAMETERS FOR NITRIFICATION OF
DOMESTIC WASTEWATER WITH ABF PROCESS

Parameter
Units
Typical
value
Range
Effluent criteria
  5-day BOD
  Suspended  solids
  NH3-N

Bio-cell parameters
  Organic  load
  Media depth
  BOD5 removal

Hydraulic parameters
  Bio-cell recycle
  Sludge recycle
  Bio-cell flow
  Bio-cell hydraulic
    load

Aeration parameters**
  Detention time*
  Organic load
  Ammonia load
  F/M
  MLVSS concentration
  MLSS concentration
Carbonaceous oxygen***

Sludge production
             rag/1
             rag/1
             rag/1
     Ib BOD5/day/1000 cu ft
            ft
           gpra/sq ft
              hr
     Ib BOD5/day/1000 cu ft
     Ib NH3-N/day/1000 cu ft
     Ib BOD5/day/lb MLVSS
           mg/1
           rag/1
     Ib 02/lb BOD5

     Ib VS/lb BOD5 removed .
 15
 20
1.0
200
 14
 65
1.5 Q
0.5 Q
3.0 Q
3.5
3.5
 25
 10
0.13
3000
4000
1.4

0.45
  5-30
 15-30
0.5-2.5
100-350
  5-22
 55-85
0.5-2.0 Q
0.3-1.0 Q
2.3-4.0 Q
1.5-5.5
2.5-5.0
 20-40
5.0-15.0
0.1-0.2
1500-4000
2000-5000
1.2-1.5

0.30-0.55
  * Based on design average flow and secondary influent BOD5  =  150 mg/1.

 ** Based on aeration BOD5 loading after bio-cell removal.

*** Total oxygen utilization  carbonaceous oxygen + 4.6 Ib 02/lb NH3-N
    oxidized.
                                     17-4

-------
     100
i

ui
x
UJ
o
o
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     90
     83
     80
     75
      70
            2501-150
          r120-100-T80
                             INLET BO05 CONCENTRATION,

                                                mg/l


                                    MAXIMUM AMMONIA

                                    NITROGEN CONCENTRA-

                                    TION, mg/l
gpd/tq
        REGION OF

        UNSTABLE

        NITRIFICATION
                          /m2/day)
                0.5
         1.0
1.5
2.0
                                               2.5
                                                       3.0
                                                3.5
4.0
                           HYDRAULIC LOADING, gpd/*q ft
           TEMPERATURE > 13* C
 Figure 17-1.  Effect of BOD  concentration and  hydraulic load

                 on nitrification  in the  RBC process.
                                 17-5

-------
c
i
Ul
a
i

   100.
    95
    90
    85
    80
    75
    70
    85
          INLET AMMONIA NITROGEN
             CONCENTRATION, mg/1
           1 gpd/sq It =* 41
                                HYDRAULIC LOADING, gpd/sq ft
          RELATIVE CAPACITIES
          FOR STAGED OPERATION
          (80-S5S Nitrification)

          No. Stage*  Relative Capacity
             1            0.60
             2            0.80
             3            0.90
             4            1.00
             6            1.07
Condition*
     Temperature >
                                                                  13* C
                                                      BODg < 20 mg/l
       Figure 17-2.
                        Design relationships for  a 4-stage RBC process
                        treating secondary  effluent.
                                        17-6

-------
 Process Control

     Because nitrifying bacteria are slow-growing  and sensitive to environmen-
 tal conditions,  close process monitoring and specific control features must be
 followed.   Loss of nitrifying bacteria can mean inadequate treatment for  many
 months while they re-establish themselves.  There are several key factors in-
 fluencing  the nitrification process.

     The concentration of dissolved oxygen (DO)  has a significant effect on the
 rate of nitrification in biological wastewater  treatment systems.  Although
 nitrification can be achieved at DO levels of 0.5 rag/1,  it is at a very low
 rate.   The  DO of the wastewater should be kept  at 1 to 3 mg/1 for consistent
 nitrification.   Air  can be supplied by additional aeration of suspended growth
 systems and by increased ventilation of attached  growth  units.

     Certain heavy metals,  complex anions,  and organic compounds which are
 toxic  to nitzifiers  are listed in Table 17-4.  The amounts of these substances
 necessary to effect  nitrifiers depend  on the overall environment of a partic-
 ular system.   A good source control program should be established to prevent
 harmful concentrations of toxic materials from  entering  the treatment stream.
             TABLE 17-4.  SUBSTANCES TOXIC TO NITRIFYING  ORGANISMS
         Organics
Inorganics
         Thiourea
         Ally1-thiourea
         8-hydroxyquinoline
         Salicyladoxine
         Histidine
         Amino acids
         Mercaptobenzth iazole
         Perchloroethylene
         Tr ich lor oe thy lene
         Abietec acid
    Zn
    octr1
    CIO"1
    Cu
    Hg
    Cr
    Ni
Maintenance Considerations

    Maintenance considerations for the specific facility used apply here also.

Records

    Recommended sampling and laboratory tests are shown in Figure 17-3  through
17-6, depending on the basic process being examined.
                                     17-7

-------
o
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BOD
SUSPENDED
SOLIDS
SETTLEABILITY
pH
DO
MR INPUT1
ra3-N
3RG-N
I03-N
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HCROSOPie
ANALYSIS
XWAL SOLIDS
TOTAL
VOLATILE
SOLIDS
COD



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!!

ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL





ILL
>1
>1
>5



EST
:REQUENCY

2/W
5/W
5/W
5/W
5/W
R
L/D
L/D
L/D
R





/W
3/W
/W
2/W



.OCATION OF
AMPLE

I
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P
P
B
J

J
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>
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I



METHOD OF
AMPLE

24C
24C
G
G
G
R
24C
24C
24C
R





G
24C
24C
24C



i-
z
S"
< a
UJ O

P
p
P
P
P
H
P
H
H
P





H
H
H
H



                                                    ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS

                                                    NITRIFICATION
                                                          2 - STAGE ACTIVATED SLUDGE
                                                         OXIDATION
                                                                                    NITRIFICATION
                                                          1 - STAGE ACTIVATED SLUDGE
                                                        OXIDATION-NITRIFICATION
 1
'2
                                                     INFLUENT FROM PREVIOUS MAIN FLOW TltCATMENT PROCESS
                                                     EFFLUENT FROM 1ST STAGE
                                                 E = EFFLUENT TO DOWNSTREAM PROCESS
                                                 RS= RECYCLE SLUDGE

                                                    A.  TEST FREQUENCY
                                                        H m HOUR      M - MONTH
                                                        D-DAY       R . RECORD CONTINUOUSLY
                                                        W- WEEK      MK- MONITOR CONTINUOUSLY

                                                   B.  LOCATION  OP SAMPLE

                                                        I - INFLUENT
                                                        E  EFFLUENT
                                                        RS= RECYCLE SLUDGE
                                                        B = BLOWER
  C. METHOD OF SAMPLE
      24C-24 HOUR COMPOSITE
      G - GRAB SAMPLE
      R - RECORD CONTINUOUSLY
      MB- MONITOR CONTINUOUSLY

  D REASON FOR TEST
      H - HISTORICAL KNOWLEDGE
      P - PROCESS CONTROL
      C  COST CONTROL
                                                  E. FOOTNOTES:
                                                        1. DIFFUSED AIR ONLY
                                                        i MAYBE RUN ON PLANT INFLUENT IF THIS
                                                          IS INITIAL UNIT PROCESS FOLLOWING
                                                          PRETREATMENT
                                                  Figure  17-3
                                                17-8

-------
a.
o

BOD
NH,-N
ORG-N
NO~-N
W
DO










COD






PLANT SIZE 1
(MOD) 1
ALL
ALL
ALL
ALL
ALL










>5






TEST
FREQUENCY |
2/W
1/D
1/D
1/D
5/W










2/W






LOCATION OF
SAMPLE |
I
I
B
I
E
I
E
I
E










I






METHOD OF
SAMPLE
24C
24C
24C
24C
6










24C






zS
< a
Ul O
a: u.
P
P
H
H
P










H






                                                 ESTIMATED UNIT PROCESS SAMPLING AND
                                                            TESTING NEEDS
                                                  NITRIFICATION
                                                        OXIDATION
                                                                             NITRIF.
                                                               2 . STAGE TRICKLING FILTER
f1 \
h ... T
OXIDATION -
NITRIFICATION
^


^ \
J


1 M
EFFLUENT TO
SECONDARY
SEDIMENTATION
                                               k INFLUENT FROM
                                                PREVIOUS MAIN
                                                FLOW PROCESS
                                                               1 - STAGE TRICKLING FILTER
                                                  A. TEST FREQUENCY
                                                      H m HOUR     M - MONTH
                                                      D - DAY      R - RECORD CONTINUOUSLY
                                                      W- WEEK     Mn" MONITOR CONTINUOUSLY

                                                  B.  LOCATION OP SAMPLE

                                                      I m INFLUENT
                                                      6 - EFFLUENT
C. METHOD OP SAMPLE
    24C-24 HOUR COMPOSITE
    G * GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
                                                  Figure 17-4
                                             17-9

-------
a
o
UJ
i
a
a
o

BOD
DO
NH..-N
ORG-N
NO,-N










COD






PLANT SIZE 1
(MCD)
ALL
ALL
ALL
ALL
ALL










>5






TEST
FREQUENCY
2/W
5/W
1/D
1/D
1/D










/w






LOCATION OF
SAMPLE
I
I
E
I
E
I
E
I
E










I






METHOD OF
SAMPLE
24C
G
24C
24C
24C










24C






s^
2>-
< oc
UJ O
a: u.
H
H
P
H
H










H






                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS
                                                    NITRIFICATION
                                                               ROTATING BIOLOGICAL CONTACTOR
* INFLUENT FROM
 PREVIOUS MAIN
 FLOW TREATMENT
 PROCESS
EFFLUENT TO
SECONDARY
CLARIFIER
                                                   A. TEST FREQUENCY

                                                        H . HOUR      M - MONTH
                                                        0 - DAY       R  RECORD CONTINUOUSLY
                                                        W- WEEKS      Mn- MONITOR CONTINUOUSLY

                                                   8.  LOCATION OF SAMPLE

                                                        I - INFLUENT
                                                        E= EFFLUENT
  C. METHOD OP SAMPLE

      24C-24 HOUR COMPOSITE
      G- GRAB SAMPLE
      H - RECORD CONTINUOUSLY
      Mn MONITOR CONTINUOUSLY

  0. REASON FOR TEST

      H - HISTORICAL KNOWLEDGE
      P - PROCESS CONTROL
      C - COST CONTROL

 E. FOOTNOTES:

       1. THESE TESTS SHOULD ALSO  BE RUN ON RECEIVING
         WATER, ABOVE AND BELOW OUTFALL, ON A
         PERIODIC BASIS, DEPENDING ON LOCAL CONDITIONS.

       3. FOR  PLANTS DESIGNED TO CONTROL THIS
         PARAMETER.

 Figure 17-5
                                            17-10

-------
Q
U
 I
 a
 o

BOO
SUSPENDED
SOLIDS
SETTLEABILITY
pH
DO
PLOW
NH,-N
ORG-N







COD
TOTAL SOLIDS
TOTAL VOLATILI
SOLIDS
MICROSCOPIC
ANALYSES



PLANT SIZE
(MGO) |
ALL
ATiTi
ALL
ALL
ATTi
ALL
ALL
ALL







>5
>1
>1
ALL



TEST
FREQUENCY |
2/W
i/W
5/W
5/W
VW
R
1/D
1/D







2/W
3/W
J/W
>/w



LOCATION OF
SAMPLE
xl
In
K
z
En
?
s
Ilsj,
R,,*
^
^







^
E
E
*



METHOD OF
SAMPLE
24C
24n
G
G
G
R
24C
24C







24C
24C
24C
G



REASON
FOR TEST
P
J?
P
P
P ,
P
P
H







H
H
H
H



                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS
                                                   NITRIFICATION

                                                            ACTIVATED BIOFILTER PROCESS
R2_
INFLUENT PROM
PREVIOUS MAIN
FLOW TREATMENT <
PROCESS j
'' / 1
j-Ln
I
BIO-CELL
1 + . 1
| ^ .,_., L.,^. 1 	 > | ^
ft! ' (<- EFFLUENT TO
~^ Ri 12 1 SECONDARY
- -WET WELL 8. AERATION BAS.N
P,, ,
PUMP STATION
RECYCLED SLUDGE
A. TEST FREQUENCY
H a HOUR M - MONTH
D- DAY R - RECORD CONTINUOUSLY
W- WEEK Mn- MONITOR CONTINUOUSLY
B. LOCATION OF SAMPLE
    'l  INFLUENT  TO WETWELL
    I2 = INFLUENT TO AERATION BASIN
    E = EFFLUENT FROM AERATION BASIN
    RS = RECYCLED SLUDGE
    R! = BIO-CELL RECYCLE    R2 = BIO-CELL RECIRCULATION

C. METHOD OF SAMPLE
    24C-24 HOUR COMPOSITE
    G - GRAB SAMPLE
    R " RECORD CONTINUOUSLY
    Mn- MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
                                                   Figure  17-6
                                               17-11

-------
     Other  operating  records should include:

     1.   Raw sewage  influent flow.
     2.   Total electrical energy  consumed.
     3.   Recirculation  flows -  liquid  and  solids.
     4.   MLSS and MLVSS in any  aeration basins  and  return  sludge  lines.
     5.   The unit volume of air supplied per  Ib BOD and ammonia removed by any
         aeration equipment.
     6.   Quantity and location  of lime or  caustic added to buffer wastewater.

Laboratory Equipment

     The  laboratory should include the  following minimum equipment in order to
monitor  the  activated sludge process.

     1.   Analytical  balance
     2.   Clinical centrifuge with graduated tubes
     3.   BOD incubator
     4.   Drying oven
     5.   Oxygen analyzer or  titration  equipment
     6.   Wet chemistry  equipment  for monitoring ammonia conversion

     The EPA  report "Estimating  Laboratory Needs for Municipal Wastewater
Treatment  Facilities" contains  very detailed  information on glassware, chemi-
cals, miscellaneous  furniture,  etc., and should be  referred to for any
detailed questions.

Sampling Procedures

     Samples  should be collected at points  in  the process where the wastewater
is well mixed and homogeneous.  The sample collector and containers should be
clean.  A wide mouth sample  collector  of at least 2 inches should be used.
Samples collected in the effluent channel should be collected near the dis-
charge point so that any isolated (area's of short circuiting do not influence
the  results.  Where  automatic samplers are used, it is important  to keep the
sampler tubes clean.

Sidestreams

    The sidestreams associated  with nitrification are the  same as those
associated with carbonaceous oxidation.  There  is little wasting  of solids
from the nitrification step of  two-stage processes and reduced wasting from
single-stage process.  Refer  to the secondary sedimentation section for addit-
ional information on sidestreams.
                                    17-12

-------
 Process Checklist - Suspended Growth Nitrification
 . 1.  What is the actual plant flow?	
     	mgd,  peak.
  2.  How many stages does the nitrification system have?
                                               mgd,  average;
     type of aeration system (flow regime)  does each have?
                                                                       What
  3.  What type of aeration equipment does each have?
     Number  of units
  4.  What are  the aeration basin(s)  dimensions?
                                    Capacity of each unit
 7.
 8.
 9.
10.

11.

12.

13.

14.

15.

16.
17,

18,

19.

20.
21.
                                                       Color  (   )   Black
                                                        Other
                                                        heavy white

                                                      {   )   Black
Basin  characteristics - Carbonaceous oxidations
 (   )   Dark  Brown   (   )   Light  Brown  (   )   Other
Odor  (   ).  Septic   (   )   Earthy   (   )   None  (   )"
Foam   (   )   Light, crisp  (  )   Dark,  thick  (   )
 {   )   Other	
Basin  characteristics -  Nitrification:Color
 (   )   Dark  Brown   (   )   Light  Brown  (   )   Other
Odor  (   )   Septic   (   )   Earthy   (   )   None  (   )
Foam   (   )   Light, crisp  (  )   Dark,  thick  (   )
(   )   Other
Are tank(s)  contents  mixed thoroughly?   (   )  Yes   (   )   No
Are all diffusers or  mech. aerators operating properly?  (   )  Yes (   )No
Does mixing  appear excessive?  (   )   Yes  (   )  No
Do  there appear to be dead spots in tank(s)   (  )  Yes   (   )   No
If yes, at what location?
                                                        Other 	
                                                        heavy white
Is the process operating  in  its design mode?
no, explain
                                              (  )  Yes   (   )  No   If
Are HAS pumps operating?
reason?
                          (  )  Yes   {  )  No.   if no, what  is  the
Are there flow measurement devices for the RAS and WAS  systems
(  )  Yes   (  )  No.  Are they operable?  (  )  Yes   (   )  No
Does the aeration basin(s) have a foam control system?   (   )  Yes
Is it operable?  (  )  Yes  (  )  No.  Is  it operating?
                                                             Yes
If multiple basins for each step are operating,  is  the  flow distributed
equally?  (  )  Yes   (  )  No  How is it distributed	
Are the characteristics of the basin contents for each  step different?
(  )  Yes  (  )  No. If yes, describe	
                     No
                      No
                                     (  )  Yes
Is there an alkaline buffer added?
it?       	.  Dose 	
Is operation of the system  (  )  Manual  (  )
(   )   Automatic  (  )   Computer controlled  (
Is there an adequate spare parts inventory? (
it contain?
)   No.  If yes, what is
                                                Semi-Automatic
                                               )  Other 	
                                               )  Yes(  )  No.  What does
Is the pump station housing adequately ventilated?  (  ) Yes
How often are facilities checked? (  ) Once per shift   (  )
{  )   Other
                                                              (  )  No
                                                             Daily
22. What is frequency of scheduled maintenance?
                                    17-13

-------
23. Is the maintenance program adequate? {
    If no, explain
                                             )   Yes
                                                       (   )   No
 24.  What is general condition of the nitrification facilities?
          (   )   good  (   )   fair  (   )   poor
 25.  What are the most common problems  the operator has had with the nitrifica-
     tion system? 	^	
 Process  Checklist -  Nitrifying  Trickling  Filters
  1. What  is  actual plant  flow?_
  2. How many stages? 	
                                        mgd,  average;
                                                               jngd,  peak
 4.
 5.
    What  is  recycle  flow  to  each -stage?
    	  intermittent?
    What  type of media  is used?	
    What  is  the depth of media?	
                                          Is  it
                                                              constant,
 6. Number of units  in each  stage
                                                feet
                                                 ;  Size  of  units
10.
11.
12.
13
    Characteristics of Oxidation  Tower:
    Color  (   ) Black   (   ) Dark Brown   (   ) Light Brown   (   )
    Odor   (   )  Septic   (  ) Earthy   (  )  None   (   )  Other
    Characteristics of Nitrification Tower:
    Color  (   ) Black   (   ) Dark Brown   (   ) Light Brown   (   )
    Odor   (   )  Septic   (  ) Earthy   (  )  None   (   )  Other
                                                              Other
                                                              Other
    Is there evidence of uneven flow distribution in each stage?   (  )  Yes
    (  )  No.  Are any nozzles clogged?   (  )  Yes   (  )  No
    Is there evidence of filter clogging  such as ponding?   (  )  Yes
    (  )  No.  Icing?  (  )  Yes   (  )  No  Other 	
    Is there evidence of filter flies?  (  )  Yes   ( . )  No.  Snails
    (  )  Yes  (  )  No.   Roaches   (. )   Yes  (  )  No.  Other 	
    Is there grass or other vegetative material growing on the filter?
    (  )  Yes  (  )  No  Other 	.
    Are there flow measurement devices for the recirculation flow?
    (  )  Yes  (  )  No.  Are they operable?   (  )  Yes  (  )  No
14. Are the recirculation pumps operating? (  )  Yes  (  )   No.  If no,
    why? 	;	

15. If multiple filters are operating for each stage, is the flow distributed
    equally?(  )   Yes  (  )  No  How is it distributed? 	
16. Are the characteristics of the filter contents different in the various
    units of each stage? (  )   Yes  (  )   No.  If yes, describe 	,
17. Is operation of the system  (  )  manual  (  )   semi-automatic
    (  )   automatic  (  )   computer controlled  (  )   other 	
18. Is there an alkaline buffer added?  (  }   Yes  (   )   No.  If yes, what is
    it?	.  Dose
                                    17-14

-------
19. Does mechanical equipment (flow distributors, pumps, etc)  have adequate
    spare parts inventory? (  )   Yes  (  )   No.  What does it contain?

20. Is the pump station housing adequately ventilated?()  Yes(jNo
21. How often are facilities checked? (  )   Once per shift  (  )  Daily
    (  )   other 	.
22. What is frequency of scheduled maintenance?	
23. Is the maintenance program adequate? (  )   Yes  (  )   No.  If no,
    explain 	.	.
24. What is general condition of the nitrification facilities?
    (  )   good  (  )   fair  (  )   poor
25. What are the most common problems the operator has had with the nitrifica-
    tion system?	
Process Checklist - Nitrifying Rotating Biological Contactors
 1. What is actual plant flow?_
 2. Number of stages 	
 3. Type of RBC media 	
 3. Type of RBC drive	
ragd, average;
mgd peak?
    ; Number of shafts
    and surface area of each unit
 4. Color of biomass   (  )   Black  (  )   Dark Brown  <  )   Light Brown
    (  )   Other 	.
 5. Odor   (  )  Septic  {  )   Earthy  (  )  None  (  )   Other 	,
 6. Are all drives operating properly?  (  )   Yes  (  )  No.  What type of
    drive is used  (  )   Mech.  (  )  Air?
 7. Is rotation of media uniform?  (  )   Yes  (  )   No
 8. Is the flow distributed equally to parallel shafts?  (  )  Yes (  ) No
    How is it distributed?
 9. Are the characteristics of the tank contents different in the various
    units?  {  )   Yes  (  )   No.  If yes, describe	'
10. Is there an alkaline buffer added?  (  )   Yes  (  )   No.  If yes, what is
    it? 	.  Dose 	.
11. Does mechanical equipment (mechanical drives, motors, etc.)  have an
    adequate spare parts inventory? (  )   Yes  (  )   No.  What does it
    contain?	
    Are the units housed in a building?  (  )   Yes  (  )  No, or does each
    unit have a cover?  (  )   Yes  (  )  No
12. Is the RBC housing adequately ventilated? (  )  Yes  (  )  No.
13. How often are facilities checked? (  )   once per shift  (  )  daily
    (  )  other 	.
14. What is frequency of scheduled maintenance?	
                                    17-15

-------
 15,
 16,
 17.
 Is the maintenance program adequate? (
 If no, explain
    )  Yes '(  )  No
 What is general condition of the nitrification facilities?
 (   )  good  (   )  fair(   )   poor
 What are the  most common  problems the operator has had with  the nitrifica-
 tion system?
 Process  Checklist - Nitrifying ABF
  1.
  2.

  3.
  4.
  5.
  6.
  7.

  8.
 What is  actual plant flow?
ragd,
                                         average;
                                         	ragd?
 What is  underflow recycle  rate 	
 recycle  rate  to  the bio-cell 	mgd?
 What type of  media is used in the biocell?	
 What is  the depth of media	 feet?
 Number of bio-cell units
	mgd,  peak
 What is the solids
  ; Size of bio-cell units
Type of aeration system (flow  regime)
Type of aeration equipment 	-
Capacity of each unit 	
              Number of units
         Tank dimensions
                                  (  ) Light Brown   (  ) Other
                                  (  ) Light Brown   (  ) Other
                                  )  None   (  )  Other
10.

11.
12.

13.

14.

15.

16.

17.
                                  )  None   (  )
                                             Other
                                                 (
               )   Yes  (   )   No.   Are
Color of bio-cell growth:
(  ) Black   (  ) Dark Brown
Color of activated sludge:
(  } Black   (  ) Dark Brown
Odor of bio-cell growth:
(  )  Septic   (  ) Earthy   (
Odor of activated sludge:
(  )  Septic   (  ) Earthy   (
Is there evidence of uneven flow distribution?
any nozzles clogged?   (  )  Yes  (  )  No
Is there evidence of filter clogging, such as ponding?  (
Is there evidence of filter flies?  {  )  Yes  (  )  No.
(  )  No.  Roaches?  (  )  Yes  (  )  No.  Other	
Is there grass or other vegetative material growing on filter?  (
(  )  No.  Other 	
Are there flow measurement devices for the recirculation and return sludge
flows?  (  )  Yes  (  )  No.  Are they operable?  (  )   Yes  (  )   No
Are recirculation left station and RAS pumps operating? (  ) Yes  (  )
No.  If no, what is the reason? 	
If multiple bio-cells are operating, is the flow distributed equally?
(   )  Yes  (  )  No  How is it distributed?	
                                                           ) Yes
                                                          Snails?
                              (   )  No
                               (   )  Yes
                                                                   )  Yes
Are the characteristics of the bio-cells contents for each step different?
{  )  Yes  (  )  No. If yes, describe	
18. Are aeration tank contents mixed thoroughly?  (
19. Are aerators operating properly? (  )  Yes (  )No
20. Does mixing appear excessive? {  )   Yes  (  )   No
                                                 )  Yes  (  )   No
                                    17-16

-------
21.

22.

23.

24.

25.

26.

27.

28.
29.
Do there appear to be dead spots in the aeration tank?  (  }
If yes, at what location?  .	_	
                    Yes  (  )   No
is the process operating in its design mode?  (
no, explain 	
        )   Yes  (  )   No  If
Does the aeration basin have a foam control system?(  ) Yes   (  ) No
Is it operable? (  )  Yes  (  )  No.  Is it operating?  (  )  Yes   (  )
If multiple basins for each step are operating, is the flow distributed
equally?  (  )  Yes  (  )  No  How is it distributed	
Is there an alkaline buffer added?  (  )  Yes   (  )  No.  If yes, what is
it?    	.  Dose 	.
Is operation of the system  (  )  Manual  (  )  Semi-Automatic
(  )   Automatic  (  )  Computer controlled  (  )  Other 	
                                 No
Does mechanical equipment (flow distributors, pumps, mechanical aerators,
etc) have adequate spare parts inventory?  (  )  Yes  (  )  No
Is the pump station housing adequately ventilated?  (  ) Yes  (  )  No
How often are facilities checked? (  ) Once per shift  (  )  Daily
(  )  Other 	
30. What is frequency of scheduled maintenance?
31.
32.
33.
Is the maintenance program adequate? (
If no, explain	
)   Yes
(   )   No
What is general condition of the nitrification facilities?
(  )   good  (  )  fair  (  )   poor
What are the most common problems the operator has had with the nitrifica-
tion system?
                                    17-17

-------
References

 1. Gulp, G.L., and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al/ Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirtsf J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.
 7. Benjes, H.H., Jr., Attached Growth Biological Wastewater Treatment
    Estimating Performance and Construction Costs and Operating and
    Maintenance Requirements, EPA Contract 68-03-2186 (January, 1977).

 8. Battelle Pacific Northwest Laboratories, Evaluation of Municipal Sewage
    Treatment Alternatives, Council on Environmental Quality, Contract EQC316
    (February, 1974).

 9. Sawyer, C.N., et al, Nitrification and Denitrification Facilities;
    Wastewater Treatment, EPA Technology Transfer (August 1973).

10. Gulp, Russell L., et al,  Handbook of Advanced Wastewater Treatment, Van
    Nostrand Reinhold Co., 1978.

11. Dunnahoe, R.G., and Hemphill, B.W., "The ABF Process, A Combined
    Fixed/Suspended Growth Biological Treatment System", AWWA-FACE Conference
    (September 1976).

12. Antonie, R.L., "Fixed Biological Surfaces-Wastewater Treatment," CRC
    Press, 1976.
                                    17-18

-------
 18.   DENITRIFICATION                         ;

 Process Description

     Denitrification is  the reaction in which  nitrate-nitrogen gas (N03~N)
 is converted  to  nitrogen  gas  (N2>.   It occurs when  nitrified wastewater
 comes in contact with certain  microorganisms  and there  is  no oxygen present.
 If low effluent  nitrogen  is desirable,  controlled denitrification is one way
 to meet treatment  standards.   Unaided  denitrification  is a slow, process, how-
 ever,  it can  be  speeded up if  an  oxygen-demanding food  source is added to  the
 wastewater.   Methanol is  commonly used,   industrial waste  which is low in
 nitrogen,  such as  that  from a  brewery,  can  also  be  used.

     Suspended growth denitrification requires a  gently  mixed,  plug-flow
 reactor  followed by solids separation.  Although a  tightly fitting cover may
 not  be needed, the  dissolved oxygen of  the  wastewater must be kept below 0.5
 rag/1.   Mixing is provided to keep solids  in suspension  without adding oxygen
 to the reactor.  In order to release the  nitrogen gas and  carbon dioxide pro-
 duced  in the  denitrification reaction,  short-term aeration must be provided
 before final  sedimentation.  This also  oxidizes  any methanol which might re-
 main in  the wastewater  after denitrification.

     The  alternative to  suspended  growth denitrification is an attached growth
 system.  Many types of  media have been  tested and used  including plastic,
 sand and activated  carbon.  In general, re-aeration is  not required following
 fixed  growth  denitrification,  but final sedimentation or filtration is needed
 to remove  solids from the effluent.  Depending on the mode of operation of
 the  denitrification system, backwashing may be required.

Typical  Design Considerations

     Suspended growth reactors  are usually designed  as plug-flow units to pre-
vent short circuiting.  Submerged mechanical  mixers (0.25-0.5  hp/1000 cu ft)
are  usually used for mixing.   Detention times range from 1 to  3  hours, de-
pending  upon  temperature  conditions  (longer detention times at lower  tempera-
tures) and nitrogen concentrations.  The mixed liquor volatile suspended
solids should be maintained at least 1500 to  2000 rag/1  and the sludge recycle
capacity should  be  50 to  100 percent of average  flow.

    About 3 mg/1 of methanol usually is fed per  rag/1 of nitrate-nitrogen.
Other organic materials also have been used,  but cause  increased sludge pro-
duction.  For example, about twice as much  sludge is produced  when saccharose
is used  instead of  methanol.   Low-nitrogen  industrial wastes (such as brewery
wastes) have also been used when  available.   Automatic  methanol  feed  systems
are recommended  since the organic source must be carefully controlled.

    Post-denitrification  aeration should only be  long enough for  facultative
bacteria to be mixed with  the waste  flow.  While  they oxidize  the  residual
methanol, the mixing action releases the nitrogen gas and  carbon dioxide
trapped  in the biological  floes.  This can generally be accomplished  in less
than one hour.
                                     18-1

-------
    The design of denitrificafcion columns depends on the configuration and
media used.  Examples of process sizing include using 6 feet of uniformly
graded 2- to 4- mm sand.  Filtration rates of 1.0 and 2.5 gpm/sq ft at 10C
and 21C, respectively, have removed 20 mg/1 N03-N from wastewater.
Mixed-media filters (coal, sand, garnet) have also been used as downflow,
packed beds for denitrification.  Using a 36-inch mixed-media filter (3
inches of 0.27 mm garnet, 9 inches of 0.5 mm sand, 8 inches of 1.05 mm coal,
and 16 inches of 1.75 mm coal), almost complete denitrification is possible
at 1.5 gpm/sq ft.at a temperature of 10c, and at 3 gpm/sq ft at a tempera-
ture of 20c.

Typical Performance Evaluation

    The overall effectiveness of nitrogen reduction by nitrification-denitri-
fication depends on the nitrification process.  Since denitrification is only
effective in reducing N03-N, a high level of nitrification is important.  A
good system can produce an effluent with a total nitrogen concentration of
about 2 to 3 mg/1.  About half of this would be organic-N and the remainder
ammonia and nitrate-N.  Data from actual operating plants is lacking since
there are no established, full-scale operations.  Pilot-scale test data in-
dicate that about 90 percent nitrogen removal can be achieved on a long-term
basis.

    The following exampleillustrates the evaluation of typical denitrifica-
tion process performance.
         Determine process characteristics
         Suspended growth denitrification
         Design flow, average
                    , peak
         N03-N concentration
              Influent
              Effluent
         MLVSS
         Minimum temperature
         Denitrification volume
         Determine process loading
         Total peak N03-N loading  =  Influent NO3-N concentration (mg/1) x
                                        peak flow (mgd) x 8.34 lb/mg/1
                                     -  20 x 15 x 8.34    2500 Ib/day
         Denitrification tank loading = Total peak N03-N  loading (Ib/day)
10 mgd
15 mgd

20 mg/1
1.5 mg/1
2000 mg/1
10C
120,000 cu ft
                                        Tank volume (cu ft) - 1000
                                  = 2500 x 1000  =  21 Ib N03/1000 cu ft/day
                                      120,000
         Determine efficiency of nitrate removal for the system.
         % N03-N removal =  (Influent N03-N - Effluent N03-N) x 100
                                            Influent N03-N
                           = 20 - 1.5 x 100 = 93%
                                20
                                     18-2

-------
  Process Control
      As with nitrification,  pH and  temperature  will affect the rate of denitr i
  fication.   Denitcification  rates are  much  lower  when the pH is below 6 0  or
  above 8.0.   The highest  rates occur around 7.0.   The denitr ification reaction
  produces bicarbonate while  reducing carbonic acid.   This tends to neutralize
  any  acid produced  during  nitrification  and reduces or  eliminates the need for
  chemical addition  to adjust the pH of the  wastewater.

      Temperature  has a significant  affect on the  rate of  denitr ification.
  There  1S a  marked  suppression of denitr ification below 15C.   To compensate
              denitr ification  in extremely cold climates,  covered  units can be
                                   f * few process <=n*ls available.  Gen-
             H   <                      Paced according to the nitrate concen-
            the nitrified effluent.  If for any reason there is a process up-
 set, methanol can be fed manually.  However, excess methanol can result in
 high effluent BOD and possible discharge violations.

     Fixed bed reactors must be backwashed periodically to prevent media clog-
 a~inndh nr?aSeS in h*adloss-  To prevent excessive accumulation of nitrogen
 gas in the columns,  a -bumping- procedure should be used after four to twelve
 hours of operation.   It consists of a short backwash cycle lasting ont o
                                                             effluents are
Maintenance  Considerations
K~ ~v w-   ^   .    f a  good  roaintenance program are  listed below.   These should
be combined with  sedimentation  and general  maintenance  management.

     1.  Spare parts inventory  should  contain  at least  the following parts:
         one  set  of each^type of bearing, V-belt or  chain drives  for each sys-
              *= ,,-,-   _-,-, necegsary gasket for  replacement  of parts, one
         ment of

     2.  Inspection each shift of the denitrification basin or  fixed growth
         column appurtenant facilities to visibly inspect  the equipment.
Records
    Recommended sampling and laboratory tests are shown in Figure 18-1.
                                     18-3

-------
o
ui
a
j
a
o

PH
DO
NH3-N
ORG-N
NO.,-N

















UJ
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V?
f-
z S
a
ALL
ALL
ALL
ALL
ALL

















TEST 1
FREQUENCY
5/W
5/W
1/D
1/D
1/D

















LOCATION OF 1
SAMPLE
I
I
I
I
I
E

















METHOD OF
SAMPLE
G
G
24C
24C
24C

















*
2-
< K
UJ O
cr u.
H
P
P
H
P

















                                                    ESTIMATED UNIT PROCESS SAMPLING AND
                                                               TESTING NEEDS
                                                    D6NITRIFICATION
                                                 INFLUENT FROM
                                                 NITRIFICATION
                                                 PROCESS-
                                                       S-,


                                                         i
                                                          R5 
                                                           RECYCLE SLUDGE
                                                           (SUSPENDED GROWTH
                                                          PROCESSES)
                                 ^DENITRIFIED EFFLUENT
                                 TO FINAL SEDIMENTATION
                                 OR NEXT MAIN FLOW
                                 TREATMENT PROCESS
                                                    A.  TEST FREQUENCY
                                                         H m HOUR     M - MONTH
                                                         0- DAY      R - RECORD CONTINUOUSLY
                                                         W- WEEK     M*- MONITOR CONTINUOUSLY

                                                    B.  LOCATION OF SAMPLE

                                                         I *= INFLUENT
                                                         E = EFFLUENT
C. METHOD OF SAMPLE

     24C-24 HOUR COMPOSITE
     G " GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     Mn- MONITOR CONTINUOUSLY

D. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P * PROCESS CONTROL
     C - COST CONTROL

E. FOOTNOTES:
      1. THIS PROCESS MUST FOLLOW BIOLOGICAL NITRIFICATION
                                                   Figure 18-1
                                                 18-4

-------
     Other  operating  records should include:
                                             i.    >   *'
     1.   Raw sewage  influent flow.

     2.   Return'sludge  flows for  suspended growth systems.

     3.   MLSS and MLVSS in  the  suspended growth  basin and  the return sludge
         line.

     4.   Hydraulic loading  and  backwash rate on  fixed film columns.

     5.   .The total energy  (electricity) consumed.

Laboratory Equipment

     The  laboratory should include the  following  minimum equipment  in order to
monitor  the  denitrification process.
    1.
    2.
    3.
    4.
Analytical balance
Clinical centrifuge with graduated tubes
Wet chemistry equipment for monitoring ammonia
Spectrophotometer
    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be referred to  for any
detailed questions.

Sampling Procedures

    Samples should be collected at points where the wastewater  is well mixed
and homogeneous such as in the denitrification basin close to the mixing de-
vice or from the sludge lines after the sludge has been flowing for about a
minute.  The sample collector and containers should be clean.  A wide mouth
sample collector of at least 2 inches should be used.  Samples collected in
the effluent channel should be collected near the discharge point so that any
isolated areas of short circuiting do not influence the results.  Where
automatic samplers are used, sampler tubes should be kept clean.

Sidestreams

    There are no significant sidestreams associated with the denitrification
processes.  Settled solids not recycled within the process are generally di-
verted to the primary treatment process.  The sludge quantity has been found
to be about 0.2 Ib/lb of methanol feed.
                                     18-5

-------
Process Checklist - Denitrification
1.
2.
3.

4.
5.
6.
7.
8.
                                          rogd avg.
    What is actual plant flow 	
    Type of denitrification system 	     	
    Type of mixing equipment or media	
    units 	  and capacity of each unit
    What are the tank  (or column) dimensions?
    Are tank contents mixed thoroughly?   (  )
                                                           ragd peak?
                                                            Number of
                                               Yes   (
                                                   )   No
Are all mechanical mixers operating properly? (  ) Yes (
Does mixing appear excessive so as to cause oxygenation?
Do there appear' to be dead spots in tank? (  )  Yes  (  )
If yes, at what location? 	'^
                                                              )No
                                                              (  ) Yes
                                                              No
                                                                       (  )  NO
    Is the process operating in its design mode?  (
    no, explain
                                                    )  Yes  (  )  No  If
10.
11.
12.
13.
Are the column pumping systems operating? ( )
Is the backwash system operating correctly? (
How often is it used?
Is operation of the system? ( ) Manual ( )
( ) Automatic ( ) Computer controlled ( ;
Is there an adequate spare parts inventory? ( ]
What does it contain?
Yes ( ) No.
) Yes ( ) No.
Semi- Automatic
) Other
1 Yes ( ) No
14. Is the pump station housing adequately ventilated? (  ) Yes
15. How often are facilities checked? (  ) Once per shift  (  )
    (  )  Other 	
16. What is frequency of scheduled maintenance?	
                                                                 (  >  No
                                                                 Daily
17,
18
    Is the maintenance program adequate? (
    If no, explain 	
                                        )   Yes
                                                     (   )
    What is general condition of the denitrification facilities?
    (  )  good  (  )  fair  (  )   poor
20. What are the most common problems the operator has had with the system?
                                     18-6

-------
References

 1. Gulp, G.L., and Polks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.

 7. Parker, D.S., et al, Process Design Manual for Nitrogen Control, EPA,
    Technology Transfer, (October 1975).

 8. Battelle Pacific Northwest Laboratories, Evaluation of Municipal Sewage
    Treatment Alternatives, Council on Environmental Quality, Contract EQC316
    (February, 1974).

 9. Gulp, Russell L., Wesner, G.M. and Gulp, G.L., Handbook of Advanced
    Wastewater Treatment,  Van Nostrand Reinhold Co., 1978.
                                     18-7

-------

-------
 19.   AMMONIA STRIPPING

 Process  Description

     Ammonia stripping  is  used to remove ammonia from water by passing high
 volumes  of  air  through an agitated water-gas mixture.   In wastewaters,  most of
 the  nitrogen is present in the form of ammonium ions (NH|)  and must be
 converted to ammonia gas  (NH3)  by raising  the pH of the wastewater to the
 range of 10.8 to 11.5.  At this high pH,  the nitrogen  is almost totally con-
 verted to the ammonia  form from the ammonium form.   Wastewater is pumped to
 the  top  of  a stripping  tower  and allowed to fall downwards through a series of
 splash bars.  At the same time,  high volumes of air are forced upwards through
 the  stripping tower by a  large fan.   Lime  is almost always used to raise the
 pH since it also removes  phosphorous and suspended  solids.

     The  two types of ammonia  stripping towers that  are  commonly used look much
 like cooling towers.   The towers differ in design only  in the location of the
 air  inlet louvers.   For the cross-flow tower, the air  is drawn through the
 sides for the total height of the packing.   The counter-current tower draws
 the  entire  air  flow through the bottom of  the tower.  The cross-flow towers
 have been found to  be  more susceptible to  scaling problems (build-up of cal-
 cium deposits)  and  are  less efficient than the counter-current towers.

 Typical  Design  Considerations

     The  major design considerations for ammonia stripping towers are pH, tem-
 perature, hydraulic loading,  tower packing,  air flow and scale deposit control.

     The  pH  of the water has a major  effect on the efficiency of the process.
 If the pH is  not raised to a  value at which all the ammonium ions are con-
 verted to ammonia gas,  ammonia removal is  not complete.

     As air  and  water temperatures decrease,  it it harder to strip the ammonia
 from the water.   To maintain  ammonia removal efficiencies at lower tempera-
 tures, the  air  volume  must be substantially increased.

     The  hydraulic-loading rate is expressed in terms of gallons per minute
 applied  to  each square  foot of the plan area of the tower packing.  The area
 is selected to  allow the  formation of water droplets which are needed for ef-
 ficient  ammonia removal.   If  the loading  rate is too high,  the efficiency is
 reduced  because the water does not form the droplets.   The normal range of
 loading  rate  is 1 to 3  gpra/ft2,  but mostly the rates are less than 2
 gpm/ft2.

     The  tower packing  depth,  material,  and shape all affect the ammonia re-
 moval efficiency.   The  greater  the depth  the better the performance,  up to a
 maximum  of  about 24  feet.   The packing material can be  either wood or plastic,
 with the plastic showing  more resistance  to scaling.  The shape refers to the
.shape of the  individual members  as well as how the  members are placed in the
 tower.   Packing should  be shaped to produce as many water droplets as possible
 as the water  cascades  down through the tower.
                                       19-1

-------
    Gas transfer relationships and practice show that the percentage ammonia
removal is increased with increasing air flow, for a given tower height.
There is a practical limit on the air flow rate which is related to the pres-
sure drop across the tower packing.  This maximum value is approximately 550
cfm/sq ft.  Typical air requirements are about 300 cfm/gal for 90 percent
removal and 500 cfm/gal for 95 percent removal.

    The scaling, or deposition of calcium carbonate, on the packing material
reduces the efficiency of the ammonia removal process.  The deposits are
caused by the unstable, high pH waters flowing through the tower.  To minimize
scaling, as much calcium carbonate as possible should be removed during the
chemical treatment step.  Scaling can also be controlled by eliminating carbon
dioxide from the air.

Typical Performance Evaluation

    The ammonia stripping process performance is judged on meeting discharge
standards.  The following steps can be used to check the performance of the
stripping process.

    1.   Obtain the tower dimensions and operating conditions and results.
         Wastewater flow to tower = 5200 gpm
         pH of wastewater  =10.9
         Ammonia concentration in influent and effluent of wastewater = 20 and
         2 mg/1, respectively.
         Air temperature s 65F

    2.   Check influent pH - it should be above 10.8

    3.   Check the tower hydraulic loading rate:
         Area covered by tower packing  =  4752 sq ft
         Plow to tower                  =  5200 gpm
         Hydraulic loading              -  5200 gpm      j^j. gpm/sq ft
                                           4752 sq ft
         Loadings should be less than 2 gpm/sq ft to keep water from moving
         through the tower in sheets rather than in drops.

    4.   Check the tower packing to make sure it is not coated with calcium
         carbonate.

    5.   Calculate the removal of ammonia in the tower and check the air
         temperature:
         Influent           20 mg/1
         Effluent         -   2 mg/1
         Removal          =  (20 - 2)  x IQO  =  90%
                                20
         Air Temperature  3  65P

    At 65F, 90 percent removal is good.  For every F decrease in
temperature, the efficiency will drop about 0.5%.
                                      19-2

-------
 Process Control

    The control options  for an  ammonia  stripping  facility  are  related  to  the
 influent pH,  the  rate of air flow, and  the  hydraulic  loading rate.   These
 items are discussed  in Reference 1.

Maintenance Considerations

    Proper maintenance of a facility will ensure  an efficient  and  trouble free
operating plant.  The features  of a maintenance program  to insure  these con-
ditions are listed below.  They do not  consider any other  process,  such as pH
adjustment, which are discussed under other process descriptions.

     1.  Spare parts inventory  should include at  least one set of  each type of
         bearing, grease and water seals, all necessary  gaskets  for  replace-
         ment of parts,  tower packing and spray nozzles.

     2.  Tower and appurtenant  equipment painted  regularly to  protect  against
         corrosion or weathering.

     3.  Scale (calcium  carbonate) formation regularly cleaned off.

     4.  Visual examination of  the stripping process  each  shift  to check  the
         equipment for misalignment, excessive noise, unequal  hydraulic load-
         ing or damage to the tower.

     5.  All wastewater  sampling lines  flushed out regularly to  insure no de-
         posits are formed.

Records

    The recommended sampling and laboratory tests are shown in Figure  19-1 for
the ammonia stripping process.

    Other operating records should include the following:

    1.   Influent flow rate
    2.   Air flow rate

Laboratory Equipment

    The laboratory should include the following list of  equipment  as a minimum
in order to monitor the  ammonia stripping process.

    1.   pH meter
    2.   Spectophotometer or filter photometer
    3.   Nessler Tubes
                                      19-3

-------
a
i
a
Ul
a
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1
0.
o

ORG-N
NOyN
NHyN
PH
TEMP
HARDNESS
















UJ
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t/t
t-
r S
n
ALL
ALL
ALL
ALL
ALL
ALL
















TEST
FREQUENCY
1/W
1/W
1/W
3/D
3/D
1/W
















LOCATION OF
SAMPLE
I
E
I
E
I
E
I
E
I
E
I
E

'














METHOD OF
SAMPLE
24C
24C
24C
G
G
24C
















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uj o
o: u.
H
H
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                                                  ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS


                                                   NITROGEN REMOVAL



                                                               AMMONIA STRIPPING
                                              tlNFLI
                                               'INFLUENT FROM
                                               PREVIOUS MAIN
                                               FLOW TREATMEN
                                               PROCESS
                                                             V
                                                                               EFFLUENT TO
                                                                               NEXT MAIN
                                                                               FLOW TREATMENT
                                                                               PROCESS
                                                   A. TEST FREQUENCY
                                                       H m HOUR     M - MONTH
                                                       0- DAY      R - RECORD CONTINUOUSLY
                                                       W- WEEK     MB- MONITOR CONTINUOUSLY

                                                   B.  LOCATION OF SAMPLE

                                                       I  INFLUENT
                                                       E - EFFLUENT
                                                  C. METHOD OF SAMPLE

                                                       24C-24 HOUR COMPOSITE
                                                       G- GRAB SAMPLE
                                                       R " RECORD CONTINUOUSLY
                                                       Mn MONITOR CONTINUOUSLY

                                                  D. REASON FOR TEST

                                                       H - HISTORICAL KNOWLEDGE
                                                       P - PROCESS CONTROL
                                                       C . COST CONTROL

                                                  E. FOOTNOTES:

                                                        I. PROCESS CONTROL ON EFFLUENT
                                                  Figure 19-1
                                              19-4

-------
    The EPA report  "Estimating Laboratory Needs  for Municipal Wastewater
Treatment Facilities" contains very detailed  information on glassware, chemi-
cals, miscellaneous furniture, etc., and should  be referred to  for any de-
tailed questions.

Sampling Procedures

    Samples should  be collected from the chemical clarifier effluent channel
or the influent pumping station wet well and  the effluent collection chan-
nels.  Samples should be taken from the center of the channels, where the
wastewater is normally homogeneous.

Sidestreams

    There are no sidestreams associated with  the ammonia stripping tower
process.
                                      19-5

-------
Process Checklist - Ammonia Stripping Tower
 1.
 2.
 3.
 4.
 6.
 7
 8.
 9
10.
11.

12.
13.
What is the actual plant flow	
What is total flow through the towers
How many towers?
                                            mgd avg
                                           	mgd
What is the flow through each tower 	
	mgd 	mgd
                                                     mgd
    What type of stripping tower?
    (  )   Other 	
                                (  )  counter current  (  )  cross flow
What are tower packing dimensions?
What is ammonia removal?     	
                                               JType of packing_
What is ammonia removal percentage?
What is the air flow? 	
                                         Ibs NH3
                                      cfm
Does previous process have automatic pH adjustment?  (
Are the influent pumps operating properly?  (  )  Yes
what is problem?
(
                                                          Yes  (
                                                          )  No.
                                                                  ) Mo
                                                                  If no,
Do the mechanical equipment have an adequate spare parts inventory?
(  )  Yes  (  )  No.  If no, what is problem?
How often are the facilities checked?
(  ) Daily  (  )  Other 	
                                       (  )  Once per shift
14. What is frequency of scheduled maintenance?
15,
16.
17.
Is the maintenance program adequate? (
explain 	
                                        )  Yes  (  )  No.  If no.
What is the general condition of the ammonia stripping system?
(  )  good  (  )  fair  (  )  poor
What are the most common problems the operator has had with the ammonia
stripping process?     	;	
                                      19-6

-------
References'

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.

 7. Gulp, Gordon L., and Gulp, Russell L., New Concepts in Water Purification,
    Van Nostrand Reinhold, 1974.

 8. Gulp, Russell L., Wesner, G. M., and Gulp, Gordon L., Handbook of Advanced
    Wastewater Treatment, Van Nostrand Reinhold, 1978.

 9. Parker, D.S., et al, Process Design Manual for Nitrogen Control, USEPA,
    Technology Transfer, October 1975.
                                      19-7

-------

-------
20.  CHEMICAL FEEDING AND CONDITIONING

Process Description

    Many different chemicals are used for the treatment of municipal waste-
waters as listed in Table 20-1.  However, many of these are for special condi-
tions and are not often used.  The chemicals that are used most frequently
include lime/ aluminum sulfate (alum), ferric chloride, and sodium hydroxide
(caustic soda).  Others used less frequently include ferric sulfate, ferrous
sulfate (copperas), and sodium aluminate.  The selection of which chemical to
use depends on the principal purpose of the chemical addition  (coagulant or
phosphorus removal), the quality of the wastewater, the type of handling and
feeding equipment available, and the chemical costs.  To minimize chemical
costs and to prevent excess use, it is very important that the system  include
good and reliable chemical feed equipment.

    Chemical feed systems are divided into two principal categories, dry feed-
ers and solution feeders.  Within each category there are several different
methods of feeding the chemical.  The most widely used equipment are the
volumetric, the belt gravimetric, and loss-in-weight gravimetric feeders, all
of which are of the dry feeder type.  Liquid feeders usually are metering
pumps or orifices.  These metering pumps usually are positive displacement,
plunger, or diaphragm type pumps.

    Lime can be added either before primary treatment or after secondary
treatment (as part of an AWT process).  As a coagulant used in primary treat-
ment, lime helps to remove SS, phosphorus, heavy metals, grease and viruses.
Lime also may be used to adjust the pH of the wastewater, or for sludge con-
ditioning.  Lime is never fed as a solution because of its low solubility in
water.

    Aluminum sulfate may be added to wastewater for coagulation or phosphorus
removal.  It may be used as the primary coagulant instead of lime, or  along
with lime.  Alum may be added as a filter aid to the influent of a mixed-media
filter.  It may also be added at several other points in the wastewater treat-
ment process including the primary influent, rapid mix basin, or first stage
recarbonation basin.  It is available in either dry or liquid  form.

    Polymers are used as an aid to flocculation, where a light or fine floe
settles too slowly.  They are also used as filter aids.  By adding the right
amount of polymer at the right point in treatment, both turdibity and  phos-
phorus removal can be improved.

    Like alum and lime, ferric chloride is an effective coagulant used to re-
move phosphorus and to lower suspended solids.  Ferric chloride also can be
used as an oxidant to control odor problems coming from hydrogen sulfide.
Since ferric chloride is always fed as a  liquid, it  is normally obtained as a
liquid and unloaded pneumatically.
                                       20-1

-------
TABLE 20-1.  SOME CHEMICALS AND THEIR PRINCIPAL JCJSES IN WASTEWATER TREATMENT
          Chemical
          Principal use
Activated, silica,
Aluminum ammonium sulfate,
  Al2(SOit) 3' (NHit ) 2SCV 12H20
Aluminum sulfate (alum) ,
Ammonia  (aqua or anhydrous)
      or NHi^C-H
Ammonium sulfate,
Bentonite clay
Calcium hydroxide, Ca(OH)2
   (hydrated lime) and calcium
  CaO  (quicklime)
Carbon dioxide, C02
Chlorinated ferrous sulfate
   (Chlorinated Copperas)
Ferric chloride, FeCla or
  Fed 3 6H20

Ferric sulfate,
  Fe2(SOt,.) 3XH2O
Hydrochlorie acid, HC1
Nitric acid, HNO3
Phosphoric acid,
Polyelectrolytes  (polymers)
Sodium aluminate, Na2M2Oit

Sodium carbonate, Na2Cos
Sodium hydroxide
   (Caustic Soda) , NaOH
Sulfuric acid
Coagulation aid
Coagulation

Coagulation, phosphorus precipitation

Nutrient addition

Activation of silica
Coagulant aid, weighting agent
Coagulation, neutralization,
  phosphorus precipitation

Recarbonation, neutralization
Coagulation


Coagulation, phosphorus precipitation


Coagulation, phosphorus precipitation

Neutralization, pH adjustment
Neutralization, pH adjustment,
  nutrient addition
Nutrient addition
Flocculation
Coagulation, phosphorus precipitation

pH adjustment
Neutralization, pH adjustment

Neutralization, pH adjustment,
  activation of silica
                                        20-2

-------
     In the biological nitrification-denitrification process,  an oxygen demand
 source such as methanol often is added to the wastewater in order to reduce
 the nitrates quickly.   Methanol may be used either in a column or in a 3-stage
 reaction basin as described in the Denitrification Section of this manual
 (Section 18).

     Sodium hydroxide (NaOH)  is a strong base used to neutralize an acidic
 wastewater.   Without proper neutralization, acid wastewaters can damage treat-
 ment facilities and  biological treatment processes.   Sodium hydroxide also is
 used for pH adjustment along with other chemicals used in the treatment
 process.

 Typical  Design Considerations

     The  chemical feed  systems are designed with  four factors  in mind:

         Location of chemical addition in the treatment system (whether
          primary sedimentation,  activated sludge,  rapid mix or other),

         Purpose of  chemical addition,

         Chemical dosage rates,  and

         Selection of  equipment  suitable  for  chemical used and feeding  rate..

     The  location of  the chemical coagulant addition  is related to the reason
 for  the addition.  Chemicals added  in  the primary  sedimentation basins,  acti-
 vated sludge aeration  tanks  or an advanced wastewater treatment chemical
 treatment system (Section  21)  are to remove phosphorus.   Chemicals added to
 the  secondary  sedimentation  basin and  ahead of filters are to improve removal
 of suspended solids.   Chemical addition  in a  tertiary step is generally con-
 sidered  to be  the  most reliable,  although it  is more expensive.

    The dose rate  of chemical  is  determined experimentally by either jar tests
 or zeta potential  tests.   Coagulant doses typically  are  in the following
 ranges: aluminum sulfate (alum),  75 to 250  mg/1; ferric  chloride,  45 to 90
 tog/1; and lime,  200  to 400 mg/1.

Typical Performance Evaluation

    The chemical  feed  system should be evaluated for  its ability to maintain
 the desired feed  rate per million gallons of  waste.   Chemical treatment  pro-
cess evaluation  is discussed  in Section 21  of this manual.

    The following  illustrates calculation of  lime  feed rates  for  a plant where
lime recovery by recalcining of lime sludges  is practiced:
                                      20-3

-------
Plant flow
Total CaO dosage
Ca(OH)2
380 rag/1 CaO
Makeup lime
Recalcined lime
Makeup lime dosage
Recalcined dosage

Makeup lime dosage

95 x 8.34
791 x 100
       92
860 x 15
12,900

Recalcined lime
  dosage

285 x 8.34
2,377 x 100
         70
3,396 x 15
50,940
         illustrates
   15 rogd
   380 mg/1
   1.32 x CaO; therefore
   1.32 x 380 = 500 mg/1 Ca(OH)2
   92% CaO                          ^
   70% CaO
   25% of total
   75% of total

   0.25 x 380 rag/1
   95 mg/1 as CaO
   791 Ib of CaO/mg
   860 Ib makeup lime at 92% purity/ing

   12,900 Ibs for 15 rag, Ib/day of makeup lime
   536 Ib/hr of makeup lime (makeup lime feeder
   setting)

   0.75 x 380 mg/1
   285 mg/1 CaO
   2,377 Ib of CaO/rag
   3,396'lb of recalcined lime at 70% purity/MG

   50,940 lb for 15 MG (Ib/day of recalcined lime)
   2,123 Ibs/hr of recalcined lime (recalcined
   lime feeder setting)
 the calculation of alum feed rates for a piston
    The following
feed pump system:
         Three alum feed pumps; two dual head and one single  head.
Dual head pumps
Single head pump
Plant flow
Liquid alum
  strength
Alum dosage
Alum dosage

lb/15 mgd

Ib/hr
gal/hr
One pump
  (2 heads)
0-50 gpm at 100% stroke/head
0-11.5 gph at 100% stroke
=  15 mgd

=  5.4 lb dry alum/gal
=  20 mg/1
=  (20 mg/1) x  (8.34 Ib/gal)
=  167 Ib/mg
=  (167 Ib/mg) x (15 rogd)
=  2,505 Ib/day
-  2,505 Ib/day
     24 hr/day
=  104 Ib/hr
=  104 Ib/hr
   5.4 Ib/gal
=  19 gal/hr
=  (19 gal/hr)   x 3.00
   (100 gal/hr)
=  19  (use 20% stroke :setting)
                              20-4

-------
Process Control

    Chemical feed systems can be operated either manually, semi-automatically
or fully automatically*  The method of control for the feed rate can be the pH
of the waste stream, in the case of lime addition or simply a dose rate or
concentration per million gallons of waste flow.  These control methods are
discussed in Reference 1.

Maintenance Consideration

    Proper and regular maintenance of the chemical feed system is critical to
the efficient and trouble free operation of the system.  The features of a
maintenance program that should insure these conditions are listed below.
They do not consider other processes such as recarbonation which are described
under separate sections.

     1.  Spare parts inventory should include at least one set of each type of
         bearing, grease and water s.eals, one each of all gaskets, drive
         belts, isolation pads and springs, one feed pump head.

     2.  Spilled material (chemicals) regularly cleaned off.

     3.  Visual inspection each shift of the chemical feeding equipment to
         check for excessive noise, unequal loading if there is more than one
         metering pump, chemical-leakage, damage to storage tanks, raw mate-
         rials, mixing .tanks or metering pumps.

     4.  Records to determine the dose rate to the wastewater and also eval-
         uate whether or not this value is changing with time.  If the waste-
         water characteristics remain the same, changing dosages could indi-
         cate a problem with the chemical feed equipment.

     5.  Storage bins and conveyance systems checked regularly to insure
         air-tightness.

     6.  Check the calibration of the pH probe each shift to insure the auto-
         matic control system is operating correctly.

     7.  Daily inspection to check for plugged feed lines.
     8,
Records
All chemical feed lines whether suction, discharge or  lines conveying
solid or powered materials, flushed or blown out regularly to  insure
against plugging and solids build-up.
    There are no recommended sampling or laboratory  tests  associated  specifi-
cally for the chemical feeding systems.  All  laboratory  testing  is performed
in connection with the process receiving the  chemical.
                                       20-5

-------
     Operating records should include the following:

     1.   Dose rate for each chemical.
     2.   Total volume or weight used per day of each chemical.
     3.   Dilution water volumes.
     4.   Remaining volumes or weight of chemicals in storage.

 Laboratory Equipment

     There is  no laboratory equipment required specifically for the chemical
 feed system.   However,  good plant operation dictates that the  composition and
 purity of the chemicals used should be checked occasionally.   Tests for  the
 various chemicals  are described in detail in Standard Methods.  Also,  the EPA
 report "Estimating Laboratory Needs for Municipal Wastewater Treatment Facil-
 ities" contains very detailed information on glassware, chemicals,  miscellane-
 ous  furniture,  etc.,  and should be referred to for any detailed questions.

 Sampling  Procedures

     Saicples are  not  usually taken from chemical feed systems because there  are
 no tests  done on a regular  basis.   However,  the dose rate  and  chemical concen-
 tration being added  to  the  wastewater  must  be checked at  regular intervals.
 Therefore, samples from the chemical  feed  lines should be  taken using  special
 sampling  taps.

Sidestreams

    There are no sidestreams  associated with  chemical storage  and feed systems.
                                      20-6

-------
 Process Checklist - Chemical Feeding and Conditioning

     This chemical feeding checklist relates to the liquid phase only.   For  the
 chemical feeds for sludge processing,  refer to the individual sludge processes.

  1.  What are actual plant flows?	 mgd avg.  	 rogd peak.
  2.  What chemicals are  used? (   )   lime   (   )   alum  (   )   ferric chloride
     (   )   sodium hydroxide  (   )   other
  3.  Where  is  chemical  added?()primary  se
-------
References

 1. Gulp, G.L., and Polks Heira, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et alf Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation  (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, US EPA Report 430/9-74-002 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation  (1959).

 5. Miorin, A.F., et al, Wastewater Treatment Plant Design,. Manual of Practice
    No. 8, Water Pollution Control Federation (1977).

 6. State of Virginia O&M inspection form.

 7. Gulp, Gordon L., and Gulp, Russell L., New Concepts in Water Purification,
    Van Nostrand Reinhold, 1974.

 8. Gulp, Russell L., Wesner, G. M., and Gulp, Gordon L., Handbook of Advanced
    Wastewater Treatment, Van Nostrand Reinhold, 1978.

 9. Black & Veatch, Process Design Manual for Phosphorus Removal, USEPA,
    Technology Transfer, April 1976.

10. Hudson, H.E., Jr., and Wolfner, J.P., "Design of Mixing and Flocculation
    Basins", Journal AWWA, Vol. 59, October 1967, p. 1257.

11. Evans, David R., "Mixing and Flocculation", unpublished paper.

12. Rich, Linvil G., Unit Operations of Sanitary Engineering, John Wiley &
    Sons, Inc., 1961.
                                      20-8

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21.  RAPID'MIXING, FLOCCULATION AND CLARIFICATION

Process Description

    Rapid mixing and flocculation are used in series to optimize chemical
treatment of wastewater.

    Rapid mixing is done in a small tank with a mechanical mixing device.
Sometimes the mixing is done with other equipment such as baffled channels,
hydraulic jump mixers, pneumatic (compressed air) mixing, or  in-line static
mixing devices.  The most common type of mixing device is the rotating  turbine
mixer; propellers are normally used for small volumes, such as the mixing
tanks in chemical feed systems discussed before  (Section 20);  and paddles are
usually used for flocculation agitation.

    Turbine mixers are like a centrifugal pump without the casing.  They force
the water outwards to the sides of the tank and create high turbulence  and
intense fluid shear.  The turbine mixer is usually located in the center of
the mixing tank and can have various shaped blades.  The diameter of the
impeller is usually 30 to 50 percent of the smallest dimension of the tank.
Baffles are located vertically to the wall of the tank to eliminate vortexing.

    Flocculation helps the suspended particles to stick  together  to make
larger clumps of particles (floes) which will settle out easily in clari-
fiers.  Flocculation  is done by controlled agitation or  slow  mixing of  the
coagulated wastewater in a tank which contains mechanical agitation devices
such as rotating paddles, vertical turbines,' or vertical reciprocating  mecha-
nisms.  The most common type used is the rotating paddle.  The paddle agitator
is sized so that the  sum of the width of each paddle on  a wheel equals  25 per-
cent of the water depth of the basin, or the total paddle area is  less  than  15
to 20 percent of the cross-sectional area of the water  (depth x width). The
range of speeds at the outside edge of  the paddles  (peripheral speed)  is 0.5
to 4 feet per second  (fps).  The vertical turbines operate at peripheral
speeds of 2 to 4 fps  and have a zone of influence of approximately  3  times  the
turbine diameter on the same plane as the turbine blades.  The vertical zone
of influence  is 4  to  5  times the diameter of the turbine.  The flocculation  of
the suspended particles is caused by the small eddy currents  that are  formed
at the trailing  (back)  edge of  the paddles, turbine blades or reciprocating
caps.

    Clarification  is  gravitational settling related  to  chemical processes.
Chemical clarification  almost always follows the rapid  mix-flocculation
steps.  It  is  similar  to sedimentation  which  is  described  in Sections 5 and  11
of this manual*.

Typical Design Considerations

    The principal criteria by which  the rapid  mixing  equipment is sized are
the velocity  gradient,  G,  and  the  detention time.   Once these have been
selected,  the type of mixer  and impeller  are  selected and the horsepower can
be computed.   Typical values  for  G and  the  detention times are given in Table
21-1.  For  these  values,  the  horsepower averages about 0.5 HP per mgd  for a
turbine.   The design  for  a 10  mgd rapid mixer  is shown in Table 21-2.

                                       21-1

-------
               TABLE 21-1.  VELOCITY GRADIENTS  (G) FOR RAPID MIX
            Application
fps/ft or sec"1
In-line, instantaneous blending

Rapid Mixing
    20 sec contact time
    30 sec contact time
    Longer contact time
3,000 to 4,000
  700 to 1,000
  650 to   900
  500 to   700
              TABLE 21-2.  TYPICAL DESIGN FOR 10 MGD RAPID MIXER

Detention time at maximum flow, in minutes
Width, in feet
Water depth, in feet
Volume, in cubic feet
Propeller diameter, in inches
Propeller capacity, in cubic feet per minute
Shaft speed, in revolutions per minute
Motor horsepower
Velocity gradient, G sec"1
1.1
11.0
8.5
1,030
38
2,060
100
5
360

    The principal criteria  for  the design of  the  flocculation  equipment  are
also the velocity gradient, G,  and the detention  time.  The  type of mixers
used will depend- upon the wastewater  and process  flexibility.   The  floccula-
tion basin is typically divided into  2 to 4 zones,  each with a different G
value.  Typical G values for  a  3  zoned system are 100, 60  and  20, with the
percentage volumes for the  respective zones of 30%,  30% and  40%. Velocities
through the flocculation basin  should range from  0.35  to 1 ft/sec.   Detention
times for flocculation typically  range from 20 to 40 minutes.   The  design cri-
teria for a 10 ragd plant flow are shown  in Table  21-3.  Flocculation velocity
gradients for various applications are shown  in Table  21-4.
                                       21-2

-------
              TABLE 21-3.  TYPICAL DESIGN FOR '10 MGD PLOCCULATOR
Detention period, in minutes
Width, in feet
Depth, in feet
Length, in feet
Volume of tank, in cubic feet
Mixing zones:  1 in cu ft
               2 in cu ft
               3 in cu ft
Velocity gradient, G zone 1 sec'1
                     zone 2 sec'1
                     zone 3 sec'1
    45
    30
    10
   140
41,778
12,500
12,500
16,788
   100
    60
    20
          TABLE 21-4.  VELOCITY GRADIENTS  (G)  FOR FLOCCULATION BASINS
         Application
 fps/ft or sec'1
Flocculation
    Tertiary wastewater

    Turb/color  removal - no solid recirc.

    Turb/color  removal - solids contact
       reactors  (5%  - vol in suspension)

    Softening - solids contact
       reactors  (10% - vol in suspension)

    Softening - ultra high solids
       contact  (20%  to 40% - vol in
       suspension)
  100* taper to 40

  100* taper to 40


  150* taper to 50


  200* taper to 100



  400* taper to 250
 * Drive layout should provide for alternate speeds, allowing selective down-
   ward variation from the maximum values shown.
                                       21-3

-------
    The  clarifiers  are  sized on  the basis  of  the overflow  rate  and detention
 time or  water  depth.  The overflow rate  for the clarifiers is based on  the
 chemical coagulant  used.  Typical  design values for clarification of a  lime
 treated  wastewater  for  a 10 rogd  plant  flow are shown  in Table 21-5.

	TABLE 21-5.  TYPICAL DESIGN  FOR 10 MGD  CLARIFIERS
    Type of coagulent
    Number of  tanks
    Overflow rate/ gpd/ft2
    Detention  time/ hrs
    Total surface area, ft2
    Diameter of tanks, ft
    Depth of tank, ft
Lime
   2
 903
   2
11,083
  84
  10
Typical Performance Evaluation

    The rapid mix, flocculation and clarification operations are typically
considered together and are ultimately judged on the suspended solids and
phosphorus removal efficiencies.  Typical removal efficiencies have been
determined and are shown in Table 21-6.

    To check these operations, the following simple computations can be made.
The equations used are shown in Table 21-7.  For easier solution, the power
equations have also been presented in graphical form on Figure 21-1.  Table
21-8 gives correction factors.

             TABLE 21-6.  TYPICAL PHOSPHORUS REMOVAL EFFICIENCIES

Range in percent removals
Chemical coagulant
Lime
Lime -f ferric
Alum
Ferric chloride
Ferric chloride
Ferric sulphate
Alum
Ferric chloride
Lime
Lime + ferric
Lime + ferric
Application location
Tertiary
Tertiary
Primary sed.
Primary sed.
Secondary sed.
Aeration basin
Aeration basin
Aeration basin
Primary sed.
Primary sed.
Trickling filter eff.
w/o filtration
95 to 97
96 to 98
75 to 90
70 to 90
83
91
75-85
75-85
75-90
90-95
93.5
w/filtration
97 to 99
98 to 99









                                      21-4

-------
   TABLE 21-7. EQUATIONS USED TO EVALUATE RAPID MIX AND PLOCCULATION SYSTEMS
Energy for Mixing by Mechanical Means

Water Power  P  G^V u     where


Brake Horsepower,
     PH -    P
           550 x ED x EB

Substituting for constants;
Velocity gradient  4589.4  P/S
Plocculator paddle area

    A *    2P
        CD   u3

      -  561.2 PH
    water power,  ft-lb/sec
    velocity gradient,
V =s volume of tank, cu  ft
u = absolute viscosity  of  liquid,
    Ib-sec/sq ft

  = 2.089 x 10~5 at 20C
ED= drive efficiency, %/100
EB= bearing efficiency, %/100
    brake horsepower, HP
A = paddle area, sq ft
P  water power, ft-lbf/sec
CD- drag coeff.
                  1.8
  3 mass density of liquid,
    Ib-sec2/ft4
   62.4
u  relative velocity of paddles, ft/sec
  = 0.75 V
v  velocity of paddle tip, fps
                                      21-5

-------
0.01
00.1
G
            1      10      100


       DETENTION TIME, sec
POWER REQUIRED FOR RAPID MIXING

            AT*C
  2     4   6 8 10    20    40  60 80100


       DETENTION TIME, mln



POWER REQUIRED FOR FLOCCULATION

             AT4C
  Figure  21-1.   Power requirements for  rapid mix and  flocculation.
                                      21-6

-------
TABLE 21-8.  TEMPERATURE CORRECTIONS

Multiply values obtained from accompanying graphs for



Water Temp.
C
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
4C by temperature correction factor stated
below to determine horsepower or velocity
gradient at any other temperature



Temperature Correction Factor
hp per mgd G,
1.14
1.11
1.07
1.03
1.00
0.981
0.940
0.914
0.889
0.863
0.838
0.811
0.794
0.774
0.748
0.729
0.716
0.696
0.678
0.669
0.646
0.629
0.615
0.600
0.586
0.572
0.559
0.547
0.535
0.523
0.512
sec"1
0.937
0.948
0.966
0.985
1.00
1.02
1.03
1.05
1.06
1.08
1.09
1.11
1.12
1.14
1.16
1.17
1.18
1.20
1.21
1.22
1.24
1.26
1.28
1.29
1.31
1.32
1.34
1.35
1.37
1.39
1.40
                 21-7

-------
3.
     Collect the  required base  information  for  the  rapid  mix,  floccula-
     tion,  and clarifiers.
     Plant  flow rate  =  5 rogd
     Phosphorus influent concentration  =   10 mg/1  as  P
     Phosphorus effluent concentration     0.6  mg/1 as P
     Rapid  mix tank dimensions  = 2  tanks at 6' x 6'
     Rapid  mixer  horsepower  =  1 HP per tank
     Flocculator  dimensions  =  2 tanks of  40'  x 20'
     Paddle area   47 sq ft
     Mixer  horsepower  s  1st stage    2 HP, 2nd stage   =   1/2 HP
     Clarifier diameter  =  60  ft
     Number of clarifiers  =  2
     Depth  of clarifier tank  =  12  ft
     Compute detention time and velocity gradient for  rapid  mix.
                                                 x 6'  water depth

                                                 x 10' water depth
     Volume  =  2x6'
     Detention time  =
     Water horsepower
                   x 6'  x 6'
     432 cu ft
                    432  x 7.48  x 24 x 60 x 60
                    56  sec
                       =  2
                                  5 ragd
x 0.8
1.6 HP
Velocity gradient,  G   =   4589.4  x P/V
                       =   4589.4  x 2/432
                       =   312  sec'1
Water HP/ragd    0.32
From curve, using 0.32 and  56 sec,  G = 260
Correction factor from Table  21-9 for 20C   =  1.24
G value  -  1.24 x  260 -  322 sec"1
Compute detention time, velocity gradient,  and  check paddle  area  for
flocculation.
     Total volume    2 x 40' x 20'x 10'
                                         16,000 cu  ft
            3  8000 cu ft per basin
     Detention time  =  16,000 x 7.48 x 24 x 60
                               5 ragd
                     =  34.5 rain
     Assumed two flocculation stages, using half volume of each tank.
     (From Table 21-7)
     1st stage G    4589.4    P/V
                    4589.4    2/4000
                  =  102.6 sec'1
     2nd stage G  =  4589.4    0.5/4000
                  -  51.3 sec"1
     Check value from graph.
     Ratio of water hp/mgd    2 x 0.8  *  0.64
                                 2.5
     Using 0.64 and detention time of 17 rain
     From graph, G
                  88 sec
                             -1
                                                   1.24
Correction factor to 20C from Table 21-8
            G  =  1.24 x 88  =  109 sec"1
Check paddle area using equations from Table 21-7.
Paddle area, A =  561.2 PH
                         V3
                   3  561.2 x 2
                         33
                     41.5 sq ft
                                  21-8

-------
      4.
           Determine overflow  rate  and detention  time  for  the  clarifier.

           Surface area  =  2  x   x D2
                               4
                        =  -L* _ x 60 x 60 =  5g55 ffc2
          Overflow rate =  5 x lp6  = 884 gp* maintenance progr^
                                     21-9

-------
     1.  Spare parts inventory should include at least one set of each type of
         bearing, grease and water seals, all necessary gaskets for replace-
         ment of parts, paddles and drive belts.

     2.  Visual inspection each shift of the rapid mix, flocculation and clar-
         ification equipment to check the equipment for misalignment, exces-
         sive noise, and unequal loading of each operation if there are two or
         more of each.

     3.  Regular checking and calibration of pH control equipment for lime
         systems.

     4.  All sample lines flushed regularly to flush out material, such as
         chemical floe, that may have entered the lines.

Records

    The recommended sampling and laboratory tests are shown in Figure 21-2 for
the rapid mix, flocculation, and clarification operations.

    Other operating records should include the following:

    1.   Influent flow to rapid mix
    2.   Chemical type and dosage
    3.   Estimated rotational speeds of mixers

Laboratory Equipment

    The laboratory should include the following minimum equipment to monitor
the chemical treatment system.

    1.   Clinical centrifuge
    2.   pH meter
    3.   Titration equipment

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains detailed  information on glassware, chemicals,
miscellaneous furniture, etc., and should be referred to  for any detailed
questions.

Sampling Procedures

    Samples should be taken from the center of  the influent and effluent chan-
nels where the wastewater is normally homogeneous and the channel velocities
are high.  If there are no channels, sample from the center of the flow dis-
tribution boxes.  The effectiveness of the chemical addition should be as
measured by the  suspended solids concentration  at the outfall from the floccu-
lation tank.  Samples of the chemical sludge should be  taken from special
sample taps in the pump discharge lines.  The solids concentration in the
sludge should be determined and recorded.
                                      21-10

-------
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pH
pH
ALKALINITY
SUSPENDED
SOLIDS
JAR TEST
HARDNESS
TURBIDITY
SLUDGE VOLUME
LAB CENTRIFUGI
TOTAL SOLIDS
TOTAL SOLIDS
FLOW
CALCIUM-
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CHLORIDES4
SULFATES
TOTAL-P6
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TEST
FREQUENCY
Mn
1/D
2/W
1/D
1
1/W
R
3/D
1/W
3/W
R
3
1/W
1/W
3/W
3/W






LOCATION OF
SAMPLE
FE
I
CE
I
PE
FE
CE
I
I
PE
I
CE
S'
S
S
S
LS
I
PE
I
PE
I
PE
I
PE






METHOD OF
SAMPLE
Mn
G
24C
24C
24C
24C
R
G
G
G
R
G
24C
24C
24C
24C






REASON
FOR TEST
P
H
H
H
P
C
H
P
p
P
P
P
C
H
H
H
H






                                                     ESTIMATED UNIT PROCESS SAMPLING AND
                                                                TESTING NEEDS
                                                     CHEMICAL TREATMENT
                                                      CHEMICAL
                                                      ADDITION
                                                            .FLASH MIX
                                    EFFLUENT TO
                                    NEXT MAIN FLOW
                                    TREATMENT.
                                    PROCESS
                               CLARIFIER-
                                                     INFLUENT FROM PREVIOUS
                                                     MAIN FLOW TREATMENT
                                                     PROCESS
                              SLUDGE UNDERFLOW TO
                              CHEMICAL SLUDGE
                              TREATMENT PROCESSES-
                                                 NOTE)  CONSIDER AS INDIVIDUAL UNIT PROCESSES
 A. TEST FREQUENCY

     H  HOUR      M  MONTH
     D-DAY       R - RECORD CONTINUOUSLY
     W- WEEK      Mn- MONITOR CONTINUOUSLY

 B.  LOCATION OF SAMPLE

      I = INFLUENT
     FE= FLOCCULATION EFFLUENT
     LS =LIME FROM SUPPLIER (INCLUDE W/FLASH MIX PROCESS
     CE=CLARIFIER EFFLUENT                   TESTING)
     PE= PLANT EFFLUENT     S  -SLUDGE UNDERFLOW

 C. METHOD OF SAMPLE

     24C-24 HOUR COMPOSITE
     G - GRAB SAMPLE
     R  RECORD CONTINUOUSLY
     Mn- MONITOR CONTINUOUSLY

 O. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P - PROCESS CONTROL
     C - COST CONTROL

E-. FOOTNOTES:
      1. SPOT CHECK
     2. IF LIME IS  USED
     3. WHEN LIME IS DELIVERED BY SUPPLIER
     4. IF FERRIC CHLORIDE IS USED
     S. IF ALUM OR FERRIC SULFATE IS USED
     6. IF PROCESS IS DESIGNED TO CONTROL THIS PARAMETER

 Figure  21-2
                                                  21-11

-------
Sidestteams

    The only sidestream from the chemical treatment system is the chemical
sludge or mud pumped from the clarifier.  The solids concentration is impor-
tant since it effects the volume of liquid to be pumped.  For example, in-
creasing the solids concentrations from 1% to 2% halves the volume of liquid
to be pumped.  The amount of chemical sludge produced is entirely dependent
upon the type of chemical used as the coagulant.  Typically/ the solids con-
centrations from the clarifier range between 1 and 2 percent-
                                      21-12

-------
Process Checklist - Rapid Mix, Flocculation and Clarification
 1. What is plant flow?
                                             mgd avg.
 2. What is total flow through chemical treatment system?
 3. How many units are there of each operation? 	
                                                                       mgd
 4.
 5.

 6.

 7.

 8.
 9.
10.
11.

12.
13.

14.
15.
16.
17.
                                                                 _mgd
What is the flow through of each unit? 	
If flow divided equally?   (  )  Yes   (  )  No.  If no, what is
problem?	
What type of rapid mixer?   (  )  turbine   (  )  propeller  (  )  air
(  )   other 	
What type of flocculator?   (  )  turbine   (  )  paddles   (  )  other

What are dimensions of rapid mix tank? 	
    What are dimensions of flocculation tank?
    What are dimensions of clarifier?
    What is chemical coagulant?  (  )  lime  (  )  alum   (  )  ferric
    chloride  (  )   ferric sulphate  {  )  other 	
    What is chemical dose?
    What are detention times?  Rapid mix
    	 rain., clarifier?
    What is clarifier overflow rate? 	
    What is volume of sludge pumped? 	
    What are solids concentration?
                                         mg/1
                                                       sec., flocculation
                                                       	hrs.
                                                       _ gpd/ft2
                                                       _ gallons/day
                                                    percent
    Are mixers operating properly?  (  )  Yes  (  )  No.  If no, explain
18. Are sludge pumps operating?  (  )  Yes  (  )  No.  If no, explain

19.    ~~~~~~~~

20.
    Is chemical feed system operating correctly?  {  )   Yes   (  )  No.  If
    no, explain 	
    Is there an automatic chemical feed control system? (  )  Yes   (  ) No
    If yes, what kind?	
    Is it operating?  (  )   Yes  (  )   No.  If no, explain 	
21.
22.
    Do mechanical equipment have adequate spare parts inventory?   (  ) Yes
    (  )   No.  If no, explain __________	
    Is the sludge pumping stations adequately ventilated and illuminated?
    (  )   Yes  (  )   No.  If no, explain	
    How often are the facilities checked?  (  )   Once per shift
    (  )  daily  (  )  other 	
23.

24. What is the frequency of scheduled maintenance?

25.
    Is the maintenance program adequate?  (  )  Yes  (  )  No.  If no,
    explain 	_________	
                                     21-13

-------
26. What is the general condition of the chemical treatment system?
    (  )  good  (  )   fair  (  )   poor
27. What are the most common problems the operator has had with the chemical
    treatment system?	
                                     21-14

-------
   References

   1. Gulp, G.L.,  and  Folks  Heim, N.,  Field Manual  for  Performance  Evaluation
      and Troubleshooting  at Municipal Wastewater Treatment Facilities,  US  EPA
      Report 430/9-78-001  (Jan.  1978).

   2. Guarino, C.F., et  al,  Operation  of Wastewater  Treatment Plants,  Manual of
      Practice No.  11, Water Pollution Control  Federation (1976).

   3. CH2M-Hill, Estimating  Laboratory Needs  for Municipal  Wastewater  Treatment
      Facilities,  EPA  Contract  68-01-0328  (June, 1973).

   4. Wirts, J.J.,  et  al,  Safety in Wastewater  Works, Manual of Practice No.  1,
      Water Pollution  Control Federation  (1959).

   5. Miorin, A.F., et al, Wastewater  Treatment Plant Design,  Manual of  Practice
      No. 8, Water  Pollution Control Federation (1977).

   6. State of Virginia  O&M  inspection form.

   7. Gulp, Gordon  L., and Gulp,  Russell L.,  New Concepts in Water  Purification,
      Van Nostrand  Reinhold, 1974..

   8. Gulp, Russell L.,  Wesner,  G. M., and Gulp, Gordon  L.,  Handbook of  Advanced
      Wastewater Treatment/  Van  Nostrand Reinhold, 1978.
   9. Gulp, Gordon L., and Hamann, Carl L.,  "Advanced Waste  Treatment  Process
      Selection", Public Works, March, April, May, 1974.

.  10. Hudson, H.E., Jr., and Wolfner, J.P.,  "Design of Mixing  and  Flocculation
      Basins", Journal AWWA, Vol. 59, October 1967, p. 1257.

  11. Evans, David R., "Mixing and Flocculation", unpublished  paper.

  12. Rich, Linvil G., Unit Operations of Sanitary Engineering, John Wiley  &
      Sons, Inc., 1961.
                                       21-15

-------

-------
 22.  RBCARBONATION

 Process Description

     Recarbonation is the process of lowering the pH of lime treated waste-
 waters to neutral (pH = 7)  conditions by the injection of carbon dioxide into
 the wastewater.  The process is used to prevent calcium problems on equipment
 and structures that follow either lime treatment or ammonia stripping.  Down-
 stream processes, such as filtration, carbon adsorption, reverse osmosis and
 others, operate most efficiently when the pH is at or slightly below neutral
 (pH = 7).

     Recarbonation can be carried out in either one or two stages.  In single-
 stage recarbonation, the pH of the water is reduced from a range of 10 to 11.5
 down to about 7 by applying the carbon dioxide to one recarbonation basin.
 This results in increased calcium hardness of the effluent.

     Two-stage recarbonation uses two contact basins for treating the waste-
 water with the carbon dioxide.   The two basins are separated by an intermedi-
 ate settling tank.   In the first-stage,  the pH of the wastewater is lowered to
 about 9.3.  At this  pH,  calcium carbonate is insoluble and a floe readily
 forms.   The wastewater then enters the settling basin in which the chemical
 reactions  continue and the  calcium carbonate floe settles out.  The effluent
 from the settling tank enters the second stage recarbonation basin where car-
 bon dioxide is added to  further reduce the pH.

     The two-stage recarbonation process  is normally used when  very low levels
 of  phosphorus are required  in the final  effluent.   The phosphorus is adsorbed
 on  the  calcium carbonate floe formed in  the first-stage basin  and removed in
 the settling basin.

     The usual source of  carbon  dioxide  for  recarbonation  is  the stack  gas from
 either  sludge incinerators  or lime  recalcination  furnaces.   When stack gas  is
 not available,  special carbon dioxide  (CO2)  generators,  underwater  natural
 gas burners,  or  liquid CO2  can  be used.
Typical Design Considerations
    The design criteria are related to the mode of operation,  the number of
stages, the basin sizes, and the carbon dioxide requirement and source.

    The mode of operation affects the basin sizing if an intermediate settling
tank is included.  For single-stage systems, the reaction or recarbonation
basin should have a detention time of 5 min with a minimum water depth of 8
feet.  If submerged burners or liquid C02 are used the water depth should be
10 to 12 feet.  The reaction basin should be followed by a basin having a de-
tention time of about 15 min to permit complete reactions.  The second basin
does not need settling or sludge collection equipment.
                                     22-1

-------
    Two-stage systems require the same 5 min detention  time  in  both  the  first
and second stage basins and  the same criteria  for  water  depth as  for  the sin-
gle stage.  The intermediate settling basin requires  a  detention  time in the
range of 30 to 40 min, and a maximum overflow  rate in the  range 2000  to  2400
gpd/ft2.

    The amount of carbon dioxide required  to reduce the  pH from about 11 to 7
depends upon the alkalinity of the wastewater,  lime dose and the  ammonia
      concentration.
    The sources of carbon dioxide - stack gas, pressure generators,  submerged
underwater burners and liquid carbon dioxide - are discussed  in Reference 1.

Typical Performance Evaluation

    The effectiveness of a recarbonation systems is based on  its ability to
control and reduce the pH of the water to the desired value or range of val-
ues.  If the pH is within the limits of 9.2 to 9.5 and 6.5 to 7.5 for  the two-
stage system and 6.5 to 7.5 for the single-stage system, then the recarbona-
tion facility is operating correctly.

    Occasionally the C02 requirement or use should be checked and compared
to the theoretical requirements.

    1.   Collect plant information.
         Plant flow 5 mgd
         pH    11.7
         Alkalinity (mg/1 as CaC03)
              OHT    380
              CO2-  =  120
              HCO    0
         Ammonia  *  25 (mg/1 as N)
         CO2 content of stack gas  =  10%
         Blower capacity  *  1800
         Loss to atmosphere  =20%
         Temperature of cooled stack gas    110 F

    2.   Determine Ibs of CC>2 required to reduce pH to 7
         7.4 x 380    2812
         3.7 x 120  *   444
         25.4 x 25  *   635
                       3891 Ib /million gallons per day
         C02 requirement  =  5 x 3891  =  19,455 Ib/day
         Determine amount of stack gas that must be compressed to deliver
         19,455 Ibs/day.
         Stack gas  =  19,455 x 100
                                 10
iP-P-   3  194,550 Ib/day
                                     22-2

-------
    4.
    5.
Determine volume of stack gas,
60F (520K)
Stack gas flow  =    194,550
                           0.116 x 1440
in cfm,  required at 14.7 psia and
                                           1165 scfm
Convert stack gas flow to conditions at the plant site.
Temperature correction:  110 + 460  x  1165 _  1277 cfm
         Altitude correction:
                                                1618 cfm
    6.   Allowance for the C02 loss to atmosphere increases the required
         stack gas volume by 20%.
         Stack gas volume  =  1.2 x 1618  =  1941 cfm.

    7.   Based on these computations, the existing compressors do not have
         sufficient capacity.

Process Control

    Using pH measurements, control of CC>2 dosages may be determined by trial
and error.  In two-stage systems, the CC>2 flow should be set to reduce the
pH in the second-stage,recarbonation basin.  This flow should be split between
the two stages to get a pH of 10 in the center of the intermediate settling
basin.  Once the CC>2 valves are set for a proper split, they should need
very little other adjustment for changes in total C02 flow.  At average
wastewater temperatures, about 15 rain are needed for all C02 bubbles to
react completely to form calcium carbonate.  This is why pH is measured at the
middle of the settling basin rather than at the-entrance.

    The pH control can also be automatic.  Control on the output of the com-
pressors are sometimes used, but normally, surplus stack gas is vented to
atmosphere.

Maintenance Considerations

    The maintenance program should include the following items.

     1.  Spare parts inventory should include at least the following items:
         one set of each type of bearings, grease seals, water seal rings, one
         set of all gaskets, mechanical seals, nozzles for CC>2 dissolution,
         and items of the control system.

     2.  Daily inspection of the recarbonation basins to insure that the
         nozzles are not plugged.

     3.  Inspection each shift to check the calibration of the automatic pH
         control instrumentation.

     4.  Daily readings of compressor motor run times recorded from elapsed
         time meters.  These times can be used for scheduling maintenance work
                                     22-3

-------
     5.
Records
and to insure that the motors are used evenly.  Also, these run times
can be used to estimate the volume of stack gas compressed and re-
leased into the recarbonation basins.

Periodic performance tests run on the compressors to insure that they
are operating at the same capacity as they were when originally sup-
plied to the plant.
    The recommended sampling and  laboratory  tests are shown  in Figure 22-1 for
the recarbonation facilities.  The same  tests would be used  for a single-stage
recarbonation system.

    Other operating records should include the following:

    1.   Influent flow  to the recarbonation  basins
    2.   Calcium carbonate sludge volumes
    3.   Carbon dioxide useage

Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor the recarbonation system.

    1.   Analytical balance
    2.   Clinical centrifuge with graduated  tubes
    3.   Drying oven
    4.   Dessicator
    5.   pH meter

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be referred  to for any de-
tailed questions.

Sampling Procedures

    Samples should be collected from the center of the influent and effluent
channels where the wastewater is normally homogeneous and the channel veloci-
ties are sufficiently high to avoid solids deposition.  To check the effec-
tiveness of the first-stage recarbonation basin, grab samples from the center
of the settling basin should be measured for pH.

    Samples of the calcium carbonate sludge  should be taken  from sample taps
in the pump discharge lines.  The solids concentration in the sludge should be
determined.

Sidestreams

    The only sidestrearas from the recarbonation process is associated with the
two-stage process.  The intermediate clarifier captures calcium carbonate
                                     22-4

-------
z
a
o
o
Q.
O

3H
TOTAL SOLIDS
LAB CENTRIFUGE
TOTAL SOLIDS
DISSOLVED
SOLIDS

ALKALINITY
AMMONIA















PLANT SIZE
(MOD)
ALL
ALL
ALL
ALL

ALL
ALL















TEST
FREQUENCY
Mn
3/D
L/W
L/W

I/O
I/O









-





LOCATION OF
SAMPLE
PIS
P2S
s
P2S
P2S

PIS
P2S
PIS
P2S















METHOD OF 1
SAMPLE
Mn
G
24C
24C

24C
24C















REASON
FOR TEST
P
P
H
H

H
H















                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS
                                                    TWO STAGE RECARBONATION
 .INFLUENT FROM
  CHEMICAL TREATMENT
  OR CMMONIA STRIPPING
                                                                             /CARBON DIOXIDE
                                                                             ( DIFFUSERS,(TYPICAL)
                                                  1ST STAGE
                                                    SLUDGE UNDERFLOW
                                                    TO CHEMICAL SLUDGE
                                                    TREATMENT PROCESSES
                            EFFLUENT TO NEXT
                            MAIN FLOW TREATMENT
                            PROCESS
                                                   A. TEST FREQUENCY
                                                        H ~ HOUR      M - MONTH
                                                        D- DAY       R - RECORD CONTINUOUSLY
                                                        w- WEEK      MH- MONITOR CONTINUOUSLY

                                                   B. LOCATION OF SAMPLE

                                                       P1S= PROCESS FIRST STAGE
                                                       P2S= PROCESS SECOND STAGE
                                                        S = SLUDGE UNDERFLOW
C. METHOD OF SAMPLE
    24C-24 HOUR COMPOSITE
    G - GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn MONITOR CONTINUOUSLY

D. REASON FOR TEST
    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
                                                   Figure  22-1
                                               22-5

-------
sludge (sometimes termed mud) and returns this to the gravity  thickener and
then to the recalcination furnace where the lime  (CaO)  is produced.  The chem-
ical sludge has a concentration in the range of 1 to 2  percent.  The sludge
from this process is actually equivalent to the amount  of lime added in excess
of the amount required to react with the alkalinity of  the wastewater and
raise the pH to about 11.3 at the chemical clarification process.
                                     22-6

-------
Process Checklist - Recarbonation
 1.
 2.
 3.

 4.
 5.

 6.
 7.
 8.

 9.
10.
11.

12.
13.
14.
15.
    What is actual plant flow?
        mgd avg.
    What is total flow through recarbonation system?    '	 mgd
    What is flow through each unit? 	.	 mgd 	 mgd
    	mgd	 mgd
    What is type of system?  (  )   single-stage  (  )   two-stage
    What are basin dimensions? 	*	 1st stage 	2nd stage
    	 intermediate clarifier.
    What is (X>2 useage? 	 Ibs/day
    What are the concentrations of chemicals?
                          mg/1 C0|-; 	
                            mg/1 Off";
                   _mg/l HCO;
                         mg/1 NH3
    What type of C02 system?  (  )  stack gas  {  )   submerged burners
    (  )  pressure generators  (  )  liquid C02  (  )  other     -	
    What is estimated 0)3 loss to atmosphere? .  	percent
    What is C02 concentration in stack gas?	 percent
    What are detention times? 	rain., 1st stage;	 min.
    2nd stage;
min. clarifier
    What is clarifier overflow rate?
    What is volume of sludge pumped?
    What is sludge concentration?
                    _gpd/ft2
                    	galions/day
                     percent
    Are sludge pumps operating?  (  )   Yes  (  )  No.  If no, explain
16. Are C02 compressors operating?   (  j  Yes() No. If no, explain

17. Is C02 system working properly?  {)Yes() No. If no, explain

18. Do mechanical equipment have adequate spare parts inventory?   (  ) Yes
    {  )  No. If no, explain	
19. Are the housings associated with this system adequately ventilated?
     (  )  Yes   (  )  No.  If no, explain 	
20. How often are the facilities checked?   (  ) ' Once per shift
    (  )  daily   (  )  other     '	
21. What is frequency of scheduled maintenance? 	
22. Is the maintenance program adequate?   (  )  Yes   (  )  No.  If no,
    explain	:	
23. Are the recarbonation basins covered?   (   )  with air  tight structure
    (  )  with open  type structure   (  )   no covering
24. What  is the general condition of the recarbonation system?   (  )  good
    (  )  fair   (  )  poor
25. What  are  the most common problems  the  operator has had with the recarbona-
    tion  system? 	-    	;	.
                                      22-7

-------
 References

  1.  Gulp,  G.L.,  and Folks Heim,  N.,  Field Manual for Performance Evaluation
     and Troubleshooting at Municipal' Wastewater Treatment Facilities,  us EPA
     Report 430/9-78-001 (Jan.  1978).

  2.  Guarino,  C.F.,  et al,  Operation  of Wastewater Treatment Plants,  Manual of
     Practice  No.  11,  Water Pollution Control Federation (1976).
  3.  CH2M-Hill, Estimating Laboratory Needs for  Municipal Wastewater Treatment
     Facilities,  EPA Contract 68-01-0328  (June,  1973).
  4. Wirts, J.J.,  et  al,  Safety in Wastewater Works, Manual of Practice No.  1,
    Water Pollution  Control  Federation (1959).

  5. Miorin, A.F., et al, Wastewater Treatment Plant Design, Manual of Practice
    No. 8, Water  Pollution Control Federation  (1977).

  6. State of Virginia O&M inspection  form.

  7. Gulp, Gordon  L., and Gulp,  Russell L., New Concepts in Water Purification,
    Van Nostrand  Reinhold, 1974.

  8. Gulp, Russell L., Wesner, G. M.,  and  Gulp, Gordon L.,  Handbook of Advanced
    Wastewater Treatment, Van Nostrand Reinhold, 1978.
 9. CH2M Hill, Process Capacity and Ammonia Removal Study. South Tahoe Public
    Utility District, 1977.'	
10. Haney, P.O. and Hamann, C.L., "Recarbonation and Liquid Carbon Dioxide",
    Journal AWWA, Vol. 61, 1969, p. 512.
                                     22-8

-------
  23.  LAND  APPLICATION OP WASTEWATERS

  Process Description

     Land treatment systems are designed or operated for different reasons.
  The system can be used as a disposal area with no surface discharge.  The
  loading rate may be set at the maximum for soil infiltration rates, or lowered
  so that crop growth can be optimized.  Overland flow systems are designed for
  treatment  with surface discharge.  The different systems can be grouped into
  three categories as follows:

         Irr igation
         Overland Plow
         Infiltration-Percolation

     Irrigation systems are the most flexible.  These can be used for high or
 low rate application.   They can be used for disposal or treatment with dis-
 charge.   Irrigation systems operated for  crop growth can be used as high rate
 disposal systems during  the off-season.

     Irrigation is by sprinklers or surface spreading.   The sprinkler system
 may be  solid set with  underground piping,  hand movable  with light-weight
 piping  and  quick couplers,  or  mechanically moving  such  as center pivot,  trav-
 elling  gun, or side-wheel  roll.   Of the mechanical systems,  the center pivot
 system  is the  most widely  used for wastewater irrigation.

     Surface spreading may  be by  ridge  and  furrow,  border check, or  controlled
 flooding.   These  require runoff  control and recycling if no surface discharge
 is  allowed.

    Typical overall removals of pollutants by irrigation are:
         BOD
         COD
         Suspended  solids
         Nitrogen
         Phosphorus
         Metals
         Micro-organ isms
98%
80%
98%
85%
95%
95%
98%
    In an overland flow system, the wastewater  is sprayed over a hillside with
a 2-6% slope.  It flows slowly down the hill and through the vegetation.

    The primary filtering mechanism for overland flow systems is the plant
growth rather than the soil mantle.  Treatment efficiencies can vary consider-
ably but the following values can be attained with a properly designed, well
run system:
         BOD                        92%
         Suspended solids           92%
         Nitrogen                  70-90%
         Phosphorus                40-80%
         Metals                     50%
                                     23-1

-------
    Application of overland  flow systems  is  somewhat limited  in that a 2-9%
slope  is  required and  a clayey  soil  desirable.   These same  conditions are  very
poor sites  for irrigation  systems.

    In  infiltration-percolation systems,  the groundwater  is recharged by per-
colation of wastewater (after secondary treatment) using  spreading  basins.
This process is strictly for disposal with no surface runoff.   Wastewater
applied to  the land  for the purpose  of disposal  is also being  treated by
infiltration and percolation.   Removals by this  system are:
         BOD
         Suspended solids
         Nitrogen
         Phosphorus
         Metals
85-99%
 98%
 0-50%
60-95%
50-95%
    Infiltration-percolation  is mostly  a groundwater  recharge  system,  and does
not utilize nutrients  through crop growth.

    Land application systems  usually  include  the  following parts:

         Preapplication  treatment
         Transmission  to the  land treatment site
         Storage for the wastewater during the non-irrigation  season
         Distribution  over the irrigated area
         A system to recover  the renovated water
         The crop system

Typical Design Considerations and Performance Evaluation

    Loading rates are  highly  variable depending on climate, crop grown (if
any), soil type, and system objective.  Table 23-1 shows  typical design cri-
teria.  If crops are grown (low rate  irrigation)  and  the  soils, have a  high
infiltration capacity, then high rate irrigation  can.  be practiced  in the off
season.  There are other special situations where loading rates would  be ad-
justed; those shown cover the ranges  to be expected.

    The major concerns for operation of a land treatment  system are adequate
application area, adequate storage for periods when application is not possi-
ble, and adequate equipment to apply water during available time period. These
three concerns are more critical for crop irrigation  than the  other systems
due to the need to harvest and replant  the next crop.  Therefore,  the  follow-
ing example calculations are  set up for a crop growing system.   ' -
                                     23-2

-------
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23-3

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     1.    Application  area  requirement:
          Given:     a.    Location  - Minden,  Nevada
                    b.    Crop  -  alfalfa
                    c.    Crop  moisture requirement  -  4  ft/yr^1)  above  natural
                         precipitation
                    d.    Irrigation efficiency  -  80%(2)
                    e.    Effluent  quantity - 5  mgd

          Areaf acres  =   5  mgd x 365 days/yr x  3.07 ac.  ft./mil  gal  x  0.80
                                             4  ft/yr
                      =   1120  acres

     2.    Storage  requirement:
          Given:     a.    Growing season  - 180 days
          Storage, mil gal  - 365 - 180 daya/yr  x  5  mgd
                           = 925 mil gal

     3.    Application  equipment  capacity:
          Given:     a.    Maximum month - July
                    b.    Maximum water consumption  -  10  inches/month
                    c.    Irrigation efficiency  -  80%
                    d.    Acreage under irrigation - 1120 acres
                    e.    Percent operating time - 70%  (allowance for changing
                         fields)

Equipment capacity, gpm  s
	10 in./mo x 1120 acres x 10** gal/mil  gal	
 0.80 x 12 in/ft x  31 days/mo x 24 hr/day x 60 min/hr x 3.07 ac ft/mil gal
                         =  8513  gpm

    Once  the above  values  are determined, individual system limitations must
be applied to refine  the above  values.  For example, the application  area may
be adjusted if application can  continue after  the  growing season  is over.  If
effluent  application  is  continued then  less area will be necessary.   Also, the
system must be planned around crop planting and  harvesting periods, including
crop drying prior to  harvest.

    Other design criteria, in addition  to loading  rates are related to ef-
fluent qualities and precautions  necessary  to  prevent public health problems
or nuisance conditions from developing.  These criteria are applied to the
adjunct facilities  such  as pretreatment, storage,  and recovery  of renovated
water.  Pretreatment requirements vary  among the states and with  the  intended
use of the crop grown (if  any).   Most areas require at  least primary  treatment
or secondary treatment by  oxidation ponds or aerated lagoons.   Some areas re-
quire higher secondary effluent quality.
(1)Ft/yr is used by irrigators meaning acre-feet/acre-year.
(2)percent of applied water available for crop use.
                                     23-4

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    Storage ponds may be lined depending on the soil type and proximity of
groundwater aquifers.  Aeration systems should be provided.  The magnitude of
the aeration requirement depends on the amount of pretreatment provided.
Storage ponds or reservoirs should be inspected as treatment ponds.

    Recovery of renovated water is done by underdrains, recovery wells, and/or
tailwater return systems.  Irrigation efficiency used earlier to determine
area requirements would be increased depending on the degree of renovated
water recovery.  Irrigation efficiency is defined as the amount of water con-
sumed by the crop divided by the amount of water passing through the soil sur-
face.  Thus, if all water passing through the root zone is recovered and
returned then more application area will be necessary.

Process Control

    Operation of irrigation systems requires good crop management and proper
wastewater pretreatment.  Personnel must have a working knowledge of farming
practices, and principles of wastewater treatment.  Seasonal  (often weekly)
changes in operation must respond to changing crop requirements for nutrients
and water; monitoring must be done to determine removal efficiencies and to
forecast buildups of toxic compounds; and the system must be continuously
watched to avoid problems of ponding, runoff, or mechanical breakdowns.

    Close cooperation between the treatment system management and  the  farm
operation is always needed.  Irrigation must be scheduled with  farm operations
such as planting, tilling, spraying and harvesting, for successful operation.
Farm specialists can be helpful in setting up the management  of the crops,
soil, and irrigation portions of the operation.

    Proper cropping  is also  important for good nitrogen removal to prevent
pollution of groundwater.  Nitrate nitrogen can be removed by growing  and  re-
moving from the area a crop  which takes up nitrogen.  Nitrogen  removal by
crops  is dependent on the length of growing season, crop type,  and the avail-
ability of nitrogen.

    Operation  of  infiltration-percolation systems is much  simpler.  Process
control consists of  rotating areas  to allow drying and access for  discing
equipment.  Areas should be  allowed  to dry out annually so the  soil can be
broken up  to prevent clogging.

Maintenance Considerations

    Maintenance concerns mainly pumps and pipelines.   A good  maintenance pro-
gram  should  include  the  following:

     1.   Pre-startup inspection of  all equipment.

     2.    Schedules  set  up  to carry  out manufacturers'  recommendations  for
         maintenance of pumps, motors,  valves,  and  sprinklers (if used).
                                      23-5

-------
     3.   Lubrication program for regular oil changes, cleaning and flushing of
          gear housing, removal and cleaning of oil pump strainers, checking of
          oil seals for leaks.

     4.   Keeping maintenance records current.

     5.   Procedure for preparing equipment for winter shut down.

     6.   Farm equipment maintenance schedule.

     7.   Access road, dike, and/or levee maintenance program.

 Records

     Recommended sampling and laboratory tests are shown in Figure 23-1.

     Other operating records should include:

     1.   Influent flow quantity (from storage)
     2.   Volume of water recovery from wells or drainage system
     3.   Frequency and duration of operation of pumps

 Laboratory Equipment

     The laboratory should include the following minimum equipment in  order  to
 monitor land application:

     1.    Analytical balance
     2.    Blender
     3.    Fume hood
     4.    Incubator
     5.    Kjeldahl digesting and distilling  apparatus
     6.    Oven
     7.   .pH meter
     8.    Pump (vacuum-pressure)
     9.    Spectrophotometer
   10.    Sterilizer
   11.    Titrator-araperometric

Sampling  Procedures

     Samples  should be  collected at points where  the  wastewater  is well mixed
such as at the center  of channels of  flow where  velocities are  high.  The
storage pond  sampling  should be done  near the middle.  Soil samples should be
taken at  several  locations  so an average value may be determined and extremes
eliminated.   Sample collectors  and containers should be clean.

    A wide mouth  sample collector of  at least 2  inches should be used for
wastewater samples.  Where  automatic  samplers are used, it is important to
keep the  sampler  tubes clean.
                                     23-6

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O
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 a
 o


OH1
BOD1
SUSPENDED
SOLIDS
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K
SOIL
CONDUCTIVITY
COLIFORM



DISSOLVED
SOLIDS
ALKALINITY
HEAVY METALS
BORON



IU
M

-------
    Tensiometers or  lysimeters  are  used  to control application  rates.  Either
of  these can be used with  automatic controls  to  start or  stop sprinklers for
precise control of irrigation.

    Groundwater monitoring  is variable depending on the local health agency
requirements.  Generally speaking,  pathogen bacteria, nitrates, and metals are
measured.  Monitoring  is accomplished by small wells located around or thor-
oughout the application site.

Sidestreams

    The only sidestream with this process is  recovered tailwater or pumped
drainage.  This water can be discharged to surface streams if allowed or re-
cycled to the irrigation system.  The volume will be 10-14% of  the applied
effluent.  The quality of the renovated water will lower the constituent con-
centrations except total dissolved  solids.  Depending on the geology of the
area certain soluble metals concentrations may increase in pumped sub-surface
drainage water.
                                    23-8

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Process Checklist - Land Application
A.
B.
C.
D.
E.
P.
                                                    (  )   Yes  (  )   No
                                                     )   Yes  (' )   No
Pretreatment - see appropriate section elsewhere in this guide.
Storage
1.   Is scum controlled?  {  )  Yes  (  )   No
2.   Are odors present?  (  )   Yes  (  )   No
3.   Are levees free of excessive weed growth?
4.   Are there indications of levee erosion?  (
5.   Are there planned programs for rodent and insect control?
     {  )  Yes (  )  No
Pumping
1.   Frequency of maintenance 	/Year
2.   Is maintenance program adequate?  (  )   Yes  (  )   No
3.   Is standby pumping provided?  (  )   Yes  (  )   No
Irrigation System
1.   Do sprinklers clog frequently?  (  )   Yes  (  )  No
2.   Does distribution piping allow flexibility to maintain operation in
     one area while another is down?  (  )  Yes  (  )  No
3.   Are flood irrigation levees maintained?  (  )   Yes  (  )  No
4.   Are nuisance weed growths controlled?  (  )  Yes  (  )  No
5.   Is there a planned procedure for off season shut down and following
     season startup?   (  )  Yes  (  )  No
6.   Do any areas appear to lack moisture?  (  )  Yes  (  )  No.  Have
     excess moisture?  {  )  Yes  (  )  No
7.   Is a rotation plan in effect for changing infiltration-percolation
     cells?  (  )  Yes  (  )  No
Farming (If applicable)
         Is farming done by agency staff and equipment?
         (  )  Yes  (  )  No
    2.
    3.
    4.
    5.
    6.
     Is farming done by contract?
     What are crops grown?  	
(   )   Yes  (   )   No
     Are crops rotated periodically?   (  )  Yes  (
     Are soils tested to check nutrient balances?
                 )   No
                (   )   Yes
(   )   No
     Is fertilizer added?
     How much 	
Overall
  If  so,  what type
                                                         Yes   (  )  No
1.   Is a preventive maintenance plan in use?   (  )
2.   Is there a safety program?  (  )  Yes   (   )  No
3.   Is there an emergency plan for power outages or major equipment
     failure?  (  )  Yes  (  )  No
4.   Does the sampling program meet recommendations?   (  )  Yes   (  )
5.   Is an O&M manual available?  {  )  Yes  {  )  No
6.   Is O&M manual used?  (  )  Yes   (  }  No
7.   Is laboratory properly equipped?  (  )  Yes  {  )  No
8.   What spare parts are stocked? 	
                                                                           No
    9.   What are the most common problems the operator has had with the
         process ?	
                                     23-9

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References

 1. Gulp, G.L., and Polks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, us EPA
    Report 430/9-78-001 (Jan. 1978).  ,
 2.  CH2M-Hillf Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 3.  Pound,  C.E.,  et al, Costs of Wastewater Treatment by Land Application,  US
    EPA 430/9-75-003, June 1975.
                                   23-10

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24.  PLOW MEASUREMENT

Process Description

    Flow measurement is necessary for good operation and control of a waste-
water treatment plant.  Reasons for measuring flow of wastewater include:

    1.   To provide operating and performance data concerning the treatment
         plant.

    2.   To compute costs of treatment, where such costs are based on waste-
         water volume.

    3.   To obtain data for long term planning of treatment plant capacity
         versus actual capacity used.

    There are many methods of measuring flow, some for open channel flows and
others to measure flow in pipelines.  The most commonly used flow measurement
devices are the propeller meter, the magnetic flow meter, the Venturi tube,
the positive displacement diaphragm meter, weirs, the Parshall flume, the
parabolic nozzle and the rotameter.

Typical Performance Evaluation

    Since flow measuring devices are not for treating wastewater, this section
deals with performance in terms of accuracy of measurement.  The normal  accu-
racy for each meter previously described is shown below:
Type of flow meter
% Accuracy
Propeller meter
Magnetic meter
    Below 3 fps
    3 - 30 fps
Venturi tube
Plow tube
Positive displacement
    and diaphragm meter
Weirs
Parshall flume
Kennison or parabolic  nozzle

Rotameter
    of actual flow rate over a range
of 7:1 for small meters and up to
12:1 for large meters
2% of maximum scale reading
+1% of maximum scale reading
+3 to 4% of flow rate
+1% of flow rate

+1% of flow rate
4;5% of flow rate
HH5% of flow rate
+2% of flow rate over flow range of
10:1
+2% of maximum scale
                                      24-1

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Maintenance Considerations

    The features of a good maintenance program that the inspector should look
for are:

    1.   A thorough periodic inspection of the flow measuring device.

    2.   Floats and bubbler wells regularly checked for grease or debris build
         up.

    3.   Weir plates regularly cleaned of foreign matter.

    4.   Regular schedule for calibration of the flow meter.

    5.   Recording devices properly maintained.

Records

    Records should be kept for flows on a daily basis.  Many devices produce a
continuous flow chart for plant records.  Flow records should contain date,
flow/ time of reading and operator's name/ if applicable.  Inspection dates
and calibration data should also be recorded.
                                     24-2

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Process Checklist - Flow Measurement
1.
2.
    What type of flow meter is used
    What is the wastewater flow	
    What is the design flow
                                         jngd?
                                          mgd?
4. Frequency of routine inspection for proper operation
5.                          .......

6.
7.
8.
Frequency of maintenance inspections by plant personnel
Frequency of flow meter calibration 	/month?
Is maintenace program adequate?  (  )  Yes  (  )  No
                                                                       ./day?
                                                                        /yr?
    Are floats and bubbler wells clean and free of grease of debris?
    (  )  Yes  (  )  No
 9. Are weirs free of debris?  (  )   Yes  (  )  No
10. Are flow records properly kept? (  )  Yes  (  )  No
11. Are sharp drops or increases in flow records accounted for?
    (  )  Yes  (  )  No
12. Does the flow chart exhibit uniform flow? (  )  Yes  (  )  No
13. Do any plant return flows discharge upstream from the meter?
     (  )  Yes  (  )  No
14. Are recording devices properly maintained?  (  )  Yes  (  )  No
15. Does the meter show signs of oveload?  {  )   Yes  (  )  No
16. Are spare parts stocked, if applicable? (  )  Yes  (  )  No
17. What are the most common problems that the operator has had with the flow
    meter?     	;	
                                      24-3

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References

 1. Gulp, G.L., and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. State of Virginia O&M inspection form.
                                    24-4

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 25.  SLUDGE PUMPING

 Process Description

    Sludge pumps have many uses  in a municipal wastewater  treatment plant.
 Settled primary sludge must be moved regularly;  activated  sludge must be re-
 turned continuously  to aeration  tanks, with  the  excess  sludge wasted; scum
 must be pumped to digestion tanks; and sludge must be recirculated and trans-
 ferred within the plant in processes such as digestion,  trickling filter oper-
 ation, and final disposal. The type $f pumping station  used at  the plant de-
 pends on the characteristics of  the sludge itself.

    Pumps used for handling sludges may be centrifugal,  air lift and ejectors,
 grinding, Archimedes screw lift, and positive displacement types.

 Typical Performance Evaluation

    Below is a listing of various types of sludge pumps, their  capacities, and
 delivered pressure.  This table may be used  as a general guide  to evaluating
 the performance of sludge pumps at a treatment plant.  For a very precise
 evaluation, the actual operating characteristics of the  pump should be checked
 against manufacturers' design data for the pump.  Pumps  cannot  be expected to
 operate beyond their designed capacity.
Type of pump
Capacity (gpm)
   Delivered
pressure (psi)
Plunger pump

Rotary positive displacement
(progressing cavity pump)

Diaphragm

Sludge grinding pumps
(comminuting and pumping type)

Screw lift pump
up to 500


up to 400

up to 100


25 - 300

up to 80,000
 100 - 150


 up to 500

 up to 100
Process Control

    To be effective, sludge pumping systems must be flexible under different
plant operating conditions.  The overall piping, valves, and pumping system
must be set up to allow bypassing and provide standby pumping capacity when
problems occur.

    The most important control considerations are discussed in Reference 1.
                                      25-1

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Maintenance Considerations

    See Raw Sewage Pumping Stations and General Maintenance Management.

Records

    Recommended records include:

    1.   Amount of sludge and scum pumped per day.
    2.   Frequency and duration of operation of sludge pumps.
    3.   Maintenance charts including date, type of work and operator.
    4.   Inspection records including date/ type of inspection and operator.
                                      25-2

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Process Checklist - Sludge Pumping
 1.
 2.
 3.
 4.
 5.
 6.
 7.
 8.

 9.
10.
What is the volume of sludge pumped
What types of sludge are pumped? 	
gal/day?
What is the design sludge pumping rate 	gal/day?
Is sludge pumping  (  )  manual  (  }  automatic?
How often do sludge pumps run? ^	
Frequency of maintenance inspections by plant personnel	
Is maintenance program adequate?  {  )   Yes  {  )   No
Is there an alarm system for equipment failures or overloads?
(  )   Yes  (  )  No
Are operating records adequate?  (  )   Yes  (  )   No
What spare parts are stocked?	
                       year?
11.  What are the most common problems the operator has had with the system?
                                      25-3

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References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).
                                      25-4

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 26.  CHEMICAL CONDITIONING

 Process Description

    The most frequently encountered conditioning practice  is  the use of  ferric
 chloride either alone or  in combination with  lime, although the use of poly-
 mers is rapidly gaining widespread acceptance.  Ferric chloride and lime are
 normally used in combination, although it  is  not unusual for  them  to be  ap-
 plied  individually.  Lime alone  is a  fairly popular conditioner for raw  pri-
 mary sludge and ferric chloride  alone has  been used for conditioning activated
 sludges.  Lime treatment  to a pH of 10.4 or above has the  added advantage of
 providing a significant degree  (over  99 percent) of disinfection of the  sludge
 according to "Water Supply and Treatment", Bulletin 211, published by the
 National Lime Association.

    The popularity of polymers is primarily due to their ease  in handling,
 small  storage space requirements, and their effectiveness.  All of the inor-
 ganic  coagulants are difficult to handle and  their corrosive nature can  cause
 maintenance problems in the storing, handling, and feeding systems in addition
 to the safety hazards inherent in their handling.  Many plants in the U.S.
 have abandoned the use of inorganic coagulants in favor of polymers.

    The facilities for chemical  conditioning  are relatively simple and consist
of equipment to store the chemical(s), feed the chemical(s) at controlled
 dosages, place the chemical(s) in solution or slurry, and  feed the solution to
 the process.

    The equipment used for storing and handling these chemicals varies with
 the type of chemical used, liquid or dry form of the chemical, quantity  of
chemical used, and plant size.   Storage requirements vary, but typically may
be 15  to 30 days of use or 150 percent of  the bulk transport capacity, which-
ever is greater.

Typical Design Considerations

    Peed rates for chemical conditioning of sludges are extremely variable
depending on process used, nature of the sludge, and type of chemical.   Typi-
cal range of dosages are as follows:
Raw primary + waste
  activated sludge
Digested primary + waste
  activated sludge
Elutriated primary + waste
  activated sludge*
 FeCl3,
lb/solids

  40-50

 80-100

 40-125
  Lime,
lb CaO/solids

  110-300

  160-370
Polymer, solids

     15-20

     30-40

     20-30
*Elutriated sludge results from a process whereby the sludge  is washed with
either fresh water or plant effluent to reduce the demand for conditioning
chemicals and to improve settling of filtering characteristics.
                                     26-1

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Typical Performance Evaluation

    The primary benefits of chemical conditioning of sludge are improved de-
watering and thickening characteristics and higher loading rates and more ef-
fective solids capture in subsequent unit processes.  Because of vast differ-
ences in sludge characteristics, typical performance data varies widely from
plant to plant.

Process Control

    If the feeders are automatically paced to flow, feed rate adjustments are
required only to compensate for varying dosage requirements.  If the feeder is
not paced to flow the feed rate must be adjusted each time the plant flow rate
is changed.  The lime slaker requires occasional adjustment for variations in
lime quality.

Maintenance Considerations

    Proper and regular maintenance of the chemical feed system is critical to
the efficient and troublefree operation of the system. The features of a main-
tenance program that should insure these conditions are listed below.

    1.   Spare parts inventory should include at least one set of each type of
         bearing, grease and water seals, one each of all gaskets, drive     *
         belts, isolation pads and springs, one feed pump head.

    2.   Build-up or spilling of material (chemicals) regularly cleaned off.

    3.   Visual inspection each shift of the chemical feeding equipment to
         check for excessive noise, unequal loading if there is more than one
         metering pump, chemical leakage, damage to storage tanks, raw mate-
         rials, mixing tanks or metering pumps.

    4.   Records to determine the dose rate to the wastewater and also eval-
         uate whether or not this value is changing with time.  If the waste-
         water characteristics remain the same, changing dosages could indi-
         cate a problem with the chemical feed equipment.

    5.   Storage bins and conveyance systems checked regularly to insure
         air-tightness.

    6.   Check the calibration of the pH probe each shift to insure the auto-
         matic control system is operating correctly.

    7.   Daily inspection to check for plugged feed lines.

    8.   All chemical feed lines whether suction, discharge or lines conveying
         solid or powered materials, flushed or blown out regularly to insure
         against plugging and solids build-up.
                                      26-2

-------
 Records

     The. chemical dosage required for any sludge is determined in the labora-
 tory using the Buchner Funnel test,  filter leaf test,  or jar test.   Operating
 records should include:
     1.
     2.
     3.
     4.
     5.
     6.
Type of chemical used for conditioning.
Chemical dosage applied each day.
Type of sludge conditioned.
Sludge quantity conditioned each day.
Frequency and duration of operation of feed equipment or pumps.
Maintenance charts including date, type of work, and operator.
 Laboratory Equipment

     The laboratory  should  include  the following  minimum equipment in order  to
 monitor chemical sludge conditioning:

     1.   Analytical balance
     2.   Floe  stirrer
     3.   Buchner funnel

     The EPA report  "Estimating Laboratory Needs  for Municipal Wastewater
 Treatment  Facilities" contains very detailed  information on glassware,  chemi-
 cals, miscellaneous furniture, etc.,  and should  be referred to for  any
 detailed questions.

 Sampling Procedures

     Samples used to determine the  chemical dosage required for any  sludge
 should be  collected from valves provided in the  sludge  transfer piping.  The
 sample  collector and containers should be clean.  A wide mouth sample col-
 lector of  at least  2 inches should be used.

 Sidestrearns

     The  only sidestream from sludge conditioning is the  dust  associated with
 the  handling of bulk quantities of dry chemicals.  To control dust problems,
vapor and dust collection systems  are often used.
                                     26-3

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Process Checklist - Chemical Conditioning
 1.
 2.
 3.
 4.

 5.
 6.
 7.
 8.
 9.

10.
11.
12.

13.
14.

15.
16.
17.
  What is the volume of sludge conditioned
  What is the design sludge volume
                                                      _gallons/day average?
                                               gallons/day average?
  What typ of sludge is conditioned (primary, waste activated, combination,
  other, etc.)	         ?
  What type of chemical is used for conditioning (lime, ferric chloride,
  combination, polymer, etc.)	?
  What is the chemical dosage 	 Ib/ton dry solids average?
                                     or as a liquid_         ?
Are chemicals purchased dry
                                                       days?
                                               manual?
                                               )  volumetric
                                                            or
What chemical storage volume  is provided
Is chemical feed system  (  )  automatic  (
If dry feeders are used, are  the feeders
(  ) gravimetric?
Are chemical feeders automatically paced?   (   )  Yes   (  )  No
If lime is used, is lime purchased (  )  in bags   (  )  bulk quantities?
If lime feeding is used, is a vapor and dust collection system  installed?
(  )  Yes  (  )  No.  Operating?  (  )  Yes  (  )  No
Does the unit show signs of inadequate mixing?   (  )  Yes   (  )  No
Is there an alarm system for  equipment failures or overloads?
(  )  Yes  (  )  No
Are operating records adequate?  (  )  Yes  (  )  No
Is the laboratory equipped for. the necessary analyses?  (   )  Yes  (   )  No
What spare parts are stocked? 	
18
. What are the most common problems the operator has had with the process?
                                     26-4

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No.  11, Water Pollution Control Federation (1976).
 3.  CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4.  Wirts,  J.J.,  et al,  Safety in Wastewater Works,  Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5.  State of Virginia O&M inspection form.

 6.  National Lime Association, Lime Handling, Application, and Storage,
    Washington, D.C.  20016.
 7.  Ettlich,  W.F.,  et al,  Operations Manual - Sludge Handling and
    Conditioning, US EPA Report 430/9-78-002.
                                     26-5

-------

-------
 27.   THERMAL  TREATMENT

 Process Description

    There are two basic processes  for  thermal  treatment of  sludges.  One, wet
 air oxidation,  is the  flameless  oxidation of sludges at temperatures of 450  to
 550F and pressures of about 1200  psig.  The other  type,  heat  treatment,  is
 similar, but  carried out  at temperatures of 350  to  400F  and pressures of
 150 to 300 psig.  Wet  air oxidation  reduces the  sludge to an ash and heat
 treatment improves the dewaterability  of the sludge.  The lower temperature
 and pressure  heat treatment is more  widely used  than the  oxidation process.

    Thermal treatment  systems release  water that is bound within the cell
 structure of  the sludge and improves the dewatering and thickening character-
 istics of the sludge.  The oxidation process further reduces the sludge to ash
 by wet incineration (oxidation).   The  process  also provides effective disin-
 fection of the  sludge.

 Typical Design  Considerations

    The most  important parameter is  the influent sludge flow rate (gpm).  The
 flow  rate determines the detention time in the heat exchanger(s) which is
 typically 30  to 60 minutes.

    The influent solids concentration  is also  an important parameter.  Many
plants operating in the 350-400P  range use a  3  percent sludge, however, 6
percent is more desirable because  less steam is  needed.   An example calcula-
 tion  for percent solids is shown below:

    Percent solids concentration = weight of dry sludge   x 100
                                   weight of wet sludge
                                 =   0.6 Ib  x  100 = 6%
                                    10 Ib
Typical Performance Evaluation
    The reduction in chemical oxygen demand (COD) of the sludge depends on the
degree of wet oxidation achieved by the process.  The terms used to categorize
the degree of wet oxidation - low oxidation, intermediate oxidation, and high
oxidation - refer to the degree of reduction in the chemical oxidation demand
(COD) of the sludge.  Higher temperatures are required to effect higher de-
grees of oxidation, and the higher temperatures, in turn, require the use of
correspondingly higher pressures in order to prevent flashing to steam or
burning.

    The operating temperature, pressure ranges, and COD reduction for the
three oxidation categories are given below:
    Oxidation category
       Low
       Intermediate
       High
COD reduction, %
         5
        40
     92-98
Temp.,F
350-400
    450
    675
Pressure, psi
   300-500
       750
     1,650
                                     27-1

-------
 Process  Control

     The  extent and  rate  of sludge solids oxidation  are  determined  by  the re-
 actor pressure and  temperature.   These  and other process control considera-
 tions are  discussed in Reference  7.

 Maintenance Considerations

     The  features  of a  good maintenance  program for  both components and  system
 are  shown  below:

     1.  Schedule for  periodic cleaning of the heat treatment  system.

     2.  Routine  cleaning  procedures  available for  the  heat exchanger,  the
         reactorr and  the  oxidized sludge decant tank.

     3.  .Inspection schedule  for  piping to determine when a solvent wash is
         necessary.

     4.  Instructions  to the  operator to indicate if cleaning  is necessary be-
         fore  the scheduled time  period.   For  example,  the need for heat ex-
         changer  cleaning  is  indicated  by an increasing temperature differen-
         tial between  the  reactor inlet and outlet,  and an increasing pressure
         drop  through  the  system.

     5.  Provisions for  a  thorough check for scale  buildup inside  the reactor
         on an  annual  basis to determine if acid cleaning procedures are in-
         effective.

     6.  Provisions for mechanical removal of  the scale if acid cleaning pro-
         cedures  are ineffective  in the reactor.

     7.  Annual pressure check to insure  the integrity  of the pressure  piping
         and fittings.

Records

    Recommended sampling and  laboratory tests  are shown in Figure  27-1.

    Other  operating  records should include:

     1.  Influent sludge flow
     2.  Treated sludge flow
     3.  Frequency  and duration of system operation.
     4.  COD of oxidized sludge decant.

Laboratory Equipment

    The laboratory  should  include the following minimum equipment  in order to
monitor thermal treatment:
                                     27-2

-------
s
i
(9
_l
<
a
o

TOTAL SOLIDS
TEMPERATURE
pH
SUSPENDED
SOLIDS
BOD
FLOW














f

PLANT SIZE
(MGD)
ALL
ALL
ALL
ALL
ALL
ALL
















TEST
FREQUENCY
3/D
Mn
1/D
l/D
2/W
R








a







LOCATION OF
SAMPLE
I
DU
R
D
D
D
D
















METHOD OF
SAMPLE
G
Mn
G
G
G
R
















REASON
FOR TEST
P
P
H
H
P1
P1
















                                                  ESTIMATED UNIT PROCESS SAMPLING AND
                                                            TESTING NEEDS
                                                  SOLIDS REDUCTION

                                                          THERMAL TREATMENT
                                            (DEC,
HEAT
EXCHANGER-4
DECANT TANK-1
p
                                                                                       . .-REACTOR
                                             DECANT RECYCLE
                                             TO PLANT
                                             INFLUENT
                                                                     '
                                                                                     1C
                                                                                          STEAM
                     SLUDGE INFLUENT
                     FROM PREVIOUS
                     ORGANIC SLUDGE
                     TREATMENT PROCESS
                                                            UNDERFLOW SLUDGE
                                                            TO NEXT ORGANIC
                                                            SLUDGE TREATMENT
                                                            PROCESS
                                                  A. TEST FREQUENCY

                                                      H  HOUR     M - MONTH
                                                      D. DAY      R - RECORD CONTINUOUSLY
                                                      W- WEEK     Mn- MONITOR CONTINUOUSLY

                                                  B.  LOCATION OF SAMPLE

                                                       I - INFLUENT
                                                      D= DECANT
                                                       R= REACTOR (INCLUDE AS PROCESS TESTING)
                                                       DU= DECANT UNDERFLOW
C. METHOD OF SAMPLE

    24C-24 HOUR COMPOSITE
    G " GRAB SAMPLE
    R  RECORD CONTINUOUSLY
    MB- MONITOR CONTINUOUSLY

D. REASON FOB  TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
     1.  FOR CONTROL OF PROCESS RECEIVING THIS FLOW
                                                  Figure  27-1

                                              27-3

-------
    1.   Analytical balance
    2.   pH meter
    3.   BOD incubator
    4.   Drying oven
    5.   COD apparatus

Sampling Procedures

    The system should contain sample ports to aid in the collection process.
Before collecting the sample, the ports should be opened for several seconds
to purge the line.  The sample collector and containers should be clean.
Samples collected from the decant tank should be taken near the discharge
point so that any short circuiting does not influence the results.  Where
automatic samplers are used, it is important to keep the sampler tubes clean.

Sideatreams

    Two sidestreams, process off-gas and recycle liquor, require careful con-
sideration when operating heat treatment systems.  The system off-gas can
cause odor problems if not handled properly.  Treatment may include installa-
tion of deodorizing equipment, piping gases back to diffused system or piping
gases to an existing sludge incinerator.

    The recycle liquor can be very difficult to treat, offensive smelling, and
can upset plant treatment processes.  Typical recycle liquor characteristics
are as follows.
         Substances in
         strong liquor

            TSS
            COD
            BOD
          NH3-N
          Phosphorus
          Color
 Concentration range,
mg/1 (except as shown)

   100 - 20,000
   100 - 17,000
 3,000 - 15,000
   400 -  1,700
    20 -    150
 1,000 -  6,000 units
    These high concentrations illustrate the potential impact that recycle of
the liquor can have on the wastewater treatment processes.  It is important to
recognize the significance of the recycle load in the management of the over-
all plant operation.
                                     27-4

-------
Process Checklist - Thermal Treatment
 1.
What  is  the  influent sludge  flow
temperature 	
 3.
 4.
 5.
 6.
 7.
 8.
 9.
10.
11.
12.
13.
14.
15.
16.
17.
18.

19.
20.

21.
22.
23.
24.

25.
26.
27.
28.
    What  is the design sludge flow
    temperature 	
                                   	i	gpm? What is the operating
                       F? What is the operating pressure 	Ib/sq in?
                               	gpm? What  is  the design
                       P? What  is  the design pressure 	Ib/sq in?
                                                             _gal/day?
What is the influent sludge solids concentration
What is the volume of the treated sludge	
What is the recycle liquor flow	gal/day?
What is the solids concentration of the treated sludge 	
What is the BOD of the recycle liquor 	_mg/l?
What is the COD of the recycle liquor 	mg/1?
What is the suspended solids concentration of the recycle liquor?
How is the recycle or decant liquor treated 	
Does treatment of the recycle liquor upset  the plant?   {
How are the off-gases handled ^	
                                                          )  Yes   (  )  No
                                                           )  No
                                                                    _hr/day?
Are excessive odors present from off-gases?  (  )  Yes  (
What is the duration and frequency of system operation 	
Frequency of acid wash 	/year
Frequency of general maintenance inspections 	/year?
Frequency of scale buildup inspection:  Heat exchanger	/year
Reactor 	/year,  Piping     	/year, Oxidized sludge
    decant tank
                     _/year
                                _/year, Other component
Frequency of system pressure check to  insure  integrity of pressure piping
and fittings	/year
Is hhe maintenance program adequate?   {  )  Yes   (  )  No
If multiple units are used, is the flow distributed evenly?
 (  )   Yes  (  )  No
Are proper safety precautions used for handling acid?  (  )
                                                                Yes   (
Electrical (  )  Yes  {  )  No; Exposure to gases  (  )  Yes
High temperatures  (  )  Yes   (  )  No; High pressures  (   )
Mechanical equipment  (  )  Yes  (  )  No
Are State and Federal safety codes followed?  (  )  Yes  (
Does the unit show signs of overload?  (  )   Yes  (  )  No
Is there an alarm system for equipment failures or overloads?
(  )   Yes  (  )  No
Does the sampling program meet the recommendations? {
Are operating records adequate? (  )  Yes  (  )  No
Is the laboratory equipped for the necessary analyses?
What spare parts are stocked? 	
                                                                 Yes
                                                           )  No
                                                                    )
                                                                   No;
                                                                   (  )
No;

 No;
                                                       )  Yes   (  }  No

                                                        (  )  Yes  (  )  No
29. What are the most common problems the operator has had with the process?
                                     27-5

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities/ EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. Culp/Wesner/Culp Operation and Maintenance Manual, Water Factory 21,
    Orange County Water District,  (June,  1974).

 6. Gulp, R.L., et al, Effects of Thermal Treatment of Sludge on Municipal
    Wastewater Treatment Costs EPA Contract 68-03-2186.
 7. Ettlich, W.F., et al, Operations Manual - Sludge Handling and
    Conditioning, OS EPA Report 430/9-78-002.
                                     27-6

-------
28.  GRAVITY THICKENING

Process Description

    Gravity thickening is the most common sludge-concentration process used in
the United States.  Gravity thickening is a sedimentation process similar to
primary and secondary sedimentation.  The objective of sludge thickening is to
produce as thick a sludge as possible at minimum cost.  Chemicals may be used
to aid the gravity thickening process.

    Solids settle by gravity to the bottom of the basin forming a sludge
blanket with a clearer liquid (supernatant) above.  The supernatant is removed
from the basin over weirs located near the top of the tank at the outside
edge.  Thickening takes place as the sludge particles move to the bottom of
the tank and the water moves toward the top.  As the drive unit turns the
mechanism the blanket is gently stirred, which helps compact the sludge solids
and release water from the mass.  Sludge solids are scraped toward a center
well and withdrawn.

Typical Design Considerations

    Gravity thickeners are designed based on surface overflow rate  (hydraulic
loading)  and solids loadings.  The principles that apply are the same as those
used in designing sedimentation tanks. Typically, a proposed design is checked
for both overflow rate and solids loading and the final selection is based on
a thickener design that will meet both of the design considerations.

    The surface overflow rate is expressed in terms of gallons per day per
square foot of surface area of the tank.  The overflow rate is calculated as
shown in the following example.

    1.   Determine thickener shape and dimensions.  The plant construction
         drawings and specifications include this information.
         Shape                         =  circular
         Diameter, dia                 =30 ft
         Depth, D                      =  10 ft
         Thickener area, A = (ir/4)dia2   707 sq ft
    2.   Determine total sludge flow influent to thickener and influent sludge
         and thickened sludge solids concentrations and calculate total over-
         flow volume.
         Influent flow  =  700,000 gallons per day  (gpd)
         Influent solids, %  =  5
         Thickened solids, % = 10
         Overflow volume  =  Influent flow  ( 1 -  Influent solids   )
                                                  Thickened solids
                          =  700, 000. ( 1 - 5/10)
                          -  350,000 gpd
    3.   Calculate surface overflow rate for thickener.
         Overflow rate  =  flow in gal/day	
                           surface area in sq ft
                        =  350,000
                             707
                        =  495 gpd/sq ft

                                     28-1

-------
     The solids loading rate is expressed in terms of pounds per day of solids
 per square foot of surface area of the tank.  The solids loading rate is cal-
 culated as shown in the following example.

     1.    Thickener area  =  500 sq ft
     2.    Determine total pounds per day of solids applied to the thickener.
          Sludge flow  =  30,000 gpd
          Solids concentration  =  1.0 percent solids
          Total solids, Ib/day  -  30,000 gal/day x 8.34 Ib/gal x 0.01
                                =  2,502 Ib/day

     3.    Calculate solids loading rate for  thickener.
          Solids loading rate  =  2,502 Ib/day  =  5.0  Ib/sq ft/day
                                   500 sq ft

     Current practice in the United States calls for design overflow rates of
 400 to  800 gpd per square foot.  The design solids loadings will vary with the
 type of sludge and typical loadings are shown in Table 28-1.  This table was
 developed from information in "Process Design Manual for Sludge Treatment and
 Disposal",  EPA 625/1-74-006, October,  1974.

      TABLE 28-1.     GRAVITY THICKENER TYPICAL LOADINGS AND PERFORMANCE

Influent solids Typical solids Thickened sludge
concentration, loading rate, concentration,
Sludge type percent Ib/scr ft/dav percent
Raw primary
Raw primary + FeCl3
Raw primary + low lime
Raw primary + high lime
Raw primary -f WAS*
Raw primary + (WAS + FeCl3)
(Raw primary + FeCl3) + WAS
Digested primary
Digested primary + WAS
Digested primary + (WAS +
PeCl3)
WAS
Trickling filter
5.0
2.0
5.0
7.5
2.0
1.5
1.8
8.0
4.0

4.0
1.0
1.0
20-30
6
20
25
6-10
6
6
25
15

15
5-6
8-10
8.0-10
4.0
7.0
12.0
4.0
3.0
3.6
12.0
8.0

6.0
2-3
7-0

*WAS
Waste activated sludge
Typical Performance Evaluation

    Expected thickener performance, in terms of thickened sludge concentra-
tion, is also given in Table 28-1.  Gravity thickening should remove 90 per-
cent of the solids in the feed to the thickener as an average.
                                     28-2

-------
Process Control

    Typically the flow through the thickener is continuous and should be set
for as constant a rate as possible.

    The drive mechanism normally turns continuously and contains a torque mon-
itor which will shut down the drive and sound an alarm if the drive mechanism
is overloaded.

    A review of Table 28-2 will show that for many sludges the thickened
sludge is only 2 or 3 times the concentration of the influent sludge.  In
order to maintain the thickener solids balance, the thickened sludge flow rate
for these cases must be 30 to 50 percent of the influent flow.  In most cases
it will be advantageous to draw off thickened sludge continuously at a flow
rate approximately equal tos
Thickened sludge   =     Influent
  flow rate, gpm        flow, gpm
                                         Influent solids, %
                                         Thickened solids, %
    It is important to maintain an adequate thickened sludge flow rate or
sludge will accumulate very rapidly in the thickener.

Maintenance Considerations

    The features of a good maintenance program are the same as Sedimentation
Maintenance and as described for General Maintenance Management.

Records

    Recommended sampling and laboratory tests are shown in Figure 28-1.

    Other operating records should include:

     1.  Amount of sludge and scum pumped per day.
     2.  Amount of thickened sludge pumped per day.
     3.  Frequency and duration of operation of sludge pumps.

Laboratory Equipment

    The laboratory should include the following minimum equipment in order  to
monitor gravity thickenings

     1.  Analytical balance
     2.  Clinical centrifuge with graduated tubes
     3.  BOD  incubator
     4.  Drying oven
     5.  Imhoff Cones

    The EPA report "Estimating Laboratory Needs for  Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be referred to for  any de-
tailed questions.
                                      28-3

-------
O
o.
o

TOTAL SOLIDS
SUSPENDED
SOLIDS
BOD
FLOW


















u
N
Z?
31
o- C.
ALL
ALL
ALL
ALL


















TEST
FREQUENCY
VD
1/D
2/W
R


















LOCATION OF
SAMPLE
TS
SI
SO
su
su


















METHOD OF
SAMPLE
G
G
G
R


















H-
2s
s^-
< 0
UJ O
cc u.
p
c
p
P1
P1


















                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS
                                                    SLUDGE CONCENTRATION
                                                             GRAVITY THICKENER
                                                 SUPERNATANT RECYCLE
                                                 TO PLANT     	
                                                 INFLUENT 7 3
                                                    SU
F                                 SLUDGE INFLUENT
                                 FROM PREVIOUS
                                 SLUDGE TREATMENT
                                     PROCESS
                                                                                  THICKENED SLUDGE
                                                                                  TO NEXT SLUDGE
                                                                                  TREATMENT PROCESS
                                                   A. TEST FREQUENCY
                                                       H m HOUR
                                                       0- DAY
                                                       W- WBBK
                   M - MONTH
                   R - RECORD CONTINUOUSLY
                   MB- MONITOR CONTINUOUSLY
                                                  B.  LOCATION OF SAMPLE

                                                       SI =SLUDGE INFLUENT
                                                       TS = THICKENED SLUDGE
                                                       SU = SUPERNATANT
C. METHOD OF SAMPLE

     24C-24 HOUR COMPOSITE
     G - GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     Mn. MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
      1.   FOR CONTROL OF PROCESS RECEIVING THIS FLOW
                                                  Figure  28-1

                                               28-4

-------
Sampling Procedures

    Sampling should be performed as outlined under Records.  These samples may
be obtained through valves provided in the respective thickener piping.  If
sampling points are not provided, they should be installed to facilitiate
operation and control of the process.  Samples of the supernatant can be
obtained at the overflow weir.  The sample collector and containers should be
clean. A wide mouth sample collector of at least 2 inches should be used.
Where automatic samplers are used, it is important to keep the sampler tubes
clean.

Sidestreams

    The only sidestreara from the gravity thickening process is the thickener
supernatant.  Thickener supernatant is usually returned to either the primary
or the secondary treatment process and normally causes no problem to process
operation.  The respective treatment process must be sized to treat the super-
natant flow and organic loading in addition to normal plant flow.
                                     28-5

-------
 Process  Checklist -  Gravity Thickening
  1.

  2.
  3.
  4.
  5.
  6.
  7.
  8.
  9.

10.
11.
12.
13.
14.
15.
16.
17.
18.
19.

20.

21.
22.
23.
24.

25.

26.

27.
28.
29.
30.
     What type of sludges  ace  fed  to  the  thickener  (primacy, waste  activated,
     combination,  etc.)	?
    What  is  the  volume  of influent  sludge  flow
    What  is  the  design  influent  flow    	
                                                          _gal/day avg?
                                                          _gal/day avg?
What are the dimensions of the thickener	?
How much thickened sludge is pumped 	gal/day avg?
What is the solids concentration in the influent sludge	%?
What is the solids loading rate	 pounds/day/sq ft?
What is the solids concentration in the thickened sludge 	%?
What is the settleable solids concentration in the supernatant
	 ml/1?
Is influent sludge feeding intermittent or continuous 	
Is thickened sludge pumping (  )  manual  (  )  automatic?
How often do thickened sludge pumps run	minutes/hour?
Frequency of maintenance inspections by plant personnel 	/year?
Is maintenance program adequate?  (  )  Yes  (  )  No
How much downtime is there 	days/yeac?
What is the frequency of cleaning 	/year?
Does the influent baffle system accomplish its purpose? (" )  Yes
                                                        ) Yes  (
                                                                        (  )
                                                                      ) No
                                                            ) Yes  (  ) No
                                                                        No
                                                                ) Yes   (  ) No

                                                                (  )  No
Is the sludge collection system operating properly?   (
Does the sludge collection system show any signs of mechanical failure?
(  )  Yes   (  )  No
Does the tank surface  indicate improper sludge withdrawal?   (i.e.
excessive floating solids, gas. . .)
Does the effluent baffle system accomplish its purpose?   (
Ace the effluent weirs level?  (  )  Yes  (  ) _ No
Are surfaces and the effluent weirs kept clean?   (  )  Yes
If multiple units are used, is the flow distributed evenly?
(  )  Yes (  )  No
Does the unit show signs of short circuiting and/or overloads?
(  )  Yes   (  )  No
Is there an alarm system for equipment failures or overloads?
(  )  Yes   (  )  No
Does the sampling program meet the recommendations?   (
Are operating records adequate?  (  )  Yes  (  )  No
Is the laboratory equipped for the necessary analyses? (  ) Yes  (  )No
What spare parts are stocked? 	
31. What are the most common problems the operator has had with the process?
                                     28-6

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation  (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. State of Virginia O&M inspection form.

 6. Ettlich, W.F., et al, Operations Manual - Sludge Handling and
    Conditioning, US EPA Report 430/9-78-002.
                                     28-7

-------

-------
29.  FLOTATION THICKENING

Process Description

    Sludge thickening by flotation  is a process effective  for  light  sludges.
This process causes the sludge to float so  it can be  skimmed  from  the  surface
of the thickener.  Flotation  is especially  effective  on  activated  sludge  which
is difficult to thicken by gravity  because  of its low specific gravity.   Air
is injected into the incoming sludge under  pressure.   The  sludge then  flows
into an open tank where, at atmospheric pressure/ much of  the  air  comes out of
solution as minute air bubbles.  These bubbles attach to sludge particles,
floating them to the surface.  A sludge layer 8 to  24 inches  thick forms  on
the surface of the tank and can be  removed  by a skimming mechanism for  further
processing.  Flotation aids such as polymers can be used to increase perform-
ance.  If polymer is used the optimal chemical dosage for  the  feed sludge
should be determined at the start of each shift using jar  test procedures.

Typical Design Considerations

    Flotation thickeners are  typically designed based on solids loading,  over-
flow rate, and influent solids concentration.  Typical design  and  operating
parameters are given in Table 29-1.

    The solids loading rate is expressed in terms of  pounds per hour of dry
solids per square foot of surface area of the tank.   The solids loading rate
is calculated in the following example.

    1.   Determine the surface area of flotation thickener. The plant  con-
         struction drawings and specifications should include  this information.
              Area  -  168 sq ft

    2.   Determine total pounds per day of  solids applied  to  the thickener.
         Sludge flow  =  150,000 gallons/day
         Sludge concentration  =  1.0 percent solids
         Total solids, Ib/day  =  150,000 gal x 8.34  Ib  x  0.01
                                          day         gal
                               =  12,510 Ib/day

    3.   Calculate solids loading rate for  thickener.
         Total solids  =  12,510 Ib/day x 1 day/24  hours  =   521 Ib/hour
         Solids loading rate  =  521 Ib/hr  *  3.1  Ib/sq ft/hour
                                 168 sq ft

    Solids loading often is designed at 2 Ib/hr/sq  ft.   This  rate  is possible
using flotation aids, with or without auxiliary recycle.   Many flotation
thickeners are operated at 3.0 Ib/hr/sq ft, although  built-in  capacities  of
4.0-5.0 Ib/hr/sq ft are common and  provide  flexibility in  operation.  There
are times when flotation can be done without flotation aids,  and auxiliary
recycle is used instead.  Without flotation aids, loading  rates are  about 50
percent and solids removal may be less.
                                      29-1

-------
      TABLE  29-1.  FLOTATION THICKENER OPERATION AND PERFORMANCE
 Operation parameter
                                                Range
Typical
                                                                    2
                                                                    1

                                                               5,000 min

                                                                 0.03
 Solids loading,  Ib dry solids/hr/sq ft
  of  surface
  With chemicals                             2  to  5
  Without  chemicals                          1  to  2

 Influent solids  concentration,  mg/1          5,000 min

 Air to solids  ratio                          0.02-0.04

 Blanket thickenss,  in                           8-24

 Retention  tank pressure, psi                  60-70

 Recycle ration,  % of influent flow            30-150

 Expected Performance

Float solids concentration, %

Solids removal, %
  With flotation aid
  Without flotation aid
                                                                  3-7
                                                                   95
                                                                50-80
    Typical maximum hydraulic  loading  or  overflow rate  is  0.80  gpra/sq ft at
minimum solids concentration of  5,000  mg/1.   Lower solids  levels or  higher
hydraulic loadings  result  in lower  efficiencies  and/or  float solids
concentrations.

    Another operating parameter  included  in Table 29-1  is  the air  to solids
ratio.  The air  to  solids  ratio  is  the  ratio  of  air  feed to  dry Sludge  solids
feed by weight.  The weight of air  is  0.08 times the flow  rate  in  standard cu
ft per rain.

         Ratio   3   (0.08)  (Air flow, cfml
                    Influent dry  solids, Ib

Typical Performance Evaluation

    Expected thickener performance, in  terms  of  typical float solids concen-
tration and percent solids removal, is  shown  in  Table 29-1.

    A 4 percent minimum float solids concentration by weight  is  normally used
for design purposes.  However,  a 5-6 percent  float solids concentration can be
                                     29-2

-------
expected.  Flotation without chemical aids usually results in a solids concen-
tration that is about 1 percent less than with flotation aids.  Using flota-
tion, at least 95 percent of suspended solids can be removed with flotation
aids, and 50-80 percent without flotation aids.

Process Control

    Typically the flow through the thickener is continuous and should be set
for as constant a rate as possible.  Process controls are discussed in some
detail in References 1 and 6.

Maintenance Management

    The features of a good maintenance program are:

     1.  Major elements been inspected semi-annually for wear corrosion, and
         proper adjustment.
         a)   Drives and gear reducers
         b)   Chains and sprockets
         c)   Guide rails
         d)   Shaft bearings and bores
         e)   Bearing brackets
         f)   Baffle boards
         g)   Flights and skimming units

     2.  Mechanical check made on the following units at two hour intervals.
         a)   Pumps: chemical feed, recycle, reaeration, and sludge sumps
         b)   Air manometer operation
         c)   Retention tank pressure
         d)   Sludge pit mixers
     4.
     5.
Retention tank inspected on a regular basis for excessive corrosion.

Chain tension (in rectangular basins) been adjusted properly so that
there is no chattering sound.

Spare part inventory should contain the following:  flights and drive
chains for rectangular basins, turntable gears and motors for circu-
lar basins, wear shoes, sprockets, wall brackets, chain pins, and
shear pins.
Records
    Recommended sampling and laboratory  tests are shown  in  Figure  29-1.

    Other operating records should  include:

    1.   Amount of recycle flow pumped per day.
    2.   Amount of thickened sludge pumped per day.
    3.   Frequency and duration of operation of  sludge pumps.
    4.   Amount of polymer or other flotation aid fed each  day.
                                      29-3

-------
I
z
o
Ul
o


-------
Laboratory Equipment                        ..;   ,

    The laboratory should include the following minimum equipment in order to
monitor flotation thickening.

    1.   Analytical balance
    2.   BOD incubator
    3.   Drying oven

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chem-
icals, miscellaneous furniture, etc., and should be referred to for any de-
tailed questions.

Sampling Procedures

    Sampling should be performed as outlined under Records.  These samples may
be obtained through valves provided in the respective thickener piping.  If
sampling points are not provided, they should be installed to facilitate oper-
ation and control of the process.  Samples of the supernatant can be obtained
at the overflow weir.

    The sample collector and containers should be clean.  A wide mouth, sample
collector of at least 2- inches should be used.  Samples should be analyzed
according to procedures specified in Standard Methods and, in addition, should
be visually analyzed.

5idestrearns

    The only sidestream from flotation thickening process  is the thickener
subnatant. A portion of the subnatant flow is recycled back to the flotation
unit, while the remainder is usually returned to either the primary or the
secondary treatment process.
                                      29-5

-------
Process Checklist - Flotation Thickening
  1.
  2.
  3.
  4.

  5.
  6.
  7.
  8.
  9.
 10.
 11.
 12.
 13.
 14.
 15.
 16.
 17.
 18.
 19.
 20.

 21.
 22.
 23.
 24.
 25.
 26.
 27.
 28.

 29.

 30.

 31.
 32.
 33.
 34.

35.

36.

37.
38.
39.
    How many air flotation thickening units are there	?
    What are the dimensions of the thickener(s) 	?
    Are the flotation tanks  (  )   circular  (  )   rectangular?
    What type of sludge is fed to the thickener (waste activated, other bio-
    logical, etc.)	___?
                                                 	gal/day avg?
 What is the volume of influent sludge flow	
 What is the design influent flow	
 How much thickened sludge is pumped 	
 What is the solids concentration in the influent sludge 	
 What is the solids loading rate 	   Ib/hour/sq ft?
 What is the air to solids ratio                      ?
                                                                 _gal/day avg?
                                                          _gallons/day?
    What is the hydraulic loading or overflow rate 	
    What is the solids concentration in the thickened sludge 	
    What is the suspended solids concentration in the subnatant
    What is the solids removal efficiency	%?
    Are  flotation aids used?
                                                             jgpm/sq ft?
                                                                       rag/1?
                           (   )   Yes  (   )   No.
 What is the average dosage of flotation aid
                                                    What type
                                                             _lb/ton dry solids
                                                                       inches?
 What is the thickness of the floating sludge blanket	
 Is influent sludge feeding  (   )   intermittent  (   )   continuous?
 What is the effluent recycle ratio (percent of influent flow)  	?
 Are primary and secondary effluent readily available for auxiliary
 recycle?  (  )   Yes  (-  )   No
 Is thickened sludge pumping  (   )   manual  (  )  automatic?
 How often  do thickened sludge pumps run	minutes/hour?
 Frequency  of maintenance inspections by plant personnel 	/year?
 Is maintenance  program adequate?   (  )   Yes  (  )   No
 How much down time is there 	_days/year?
 What is the frequency of cleaning  	_/year?
 Does the influent  baffle system accomplish its purpose? (  )   Yes  (   )   No
 Is the  skimmer  blade sludge removal system operating properly?
 (   )  Yes   (  )  No
 Is the  bottom sludge collection system  operating properly?
 (   )  Yes   (  )  No
 Does the sludge collection system  show  any signs of mechanical failure?
 (   )  Yes   (  )  No
 Does the effluent  baffle system accomplish its purpose? (  )   Yes  (   )   No
 Are the effluent weirs level? (  )   Yes  (   )  No
Are  surfaces  and the effluent weirs kept clean?  (   )   Yes  (   )   No
 If  multiple units  are used,  is  the  flow distributed evenly?
 (   )  Yes   (  )  No
Does the unit show signs of short  circuiting and/or  overloads?
 (   )  Yes   (  )  No
Is  there an alarm  system for equipment  failures or  overloads?
 (   )  Yes   (  )  No
Does  the sampling program  meet  the  recommendations?  (   )  Yes   (   )  No
Are operating records adequate?  (   )   Yes   (  )  No
Is  the  laboratory equipped  for  the  necessary analyses?   (  )   Yes   (   )  No
                                    29-6

-------
40. What spare parts are stocked?
41. What are the most common problems the operator has had with the process?
                                     29-7

-------
References

 1. Gulp, G.L., and Polks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.P., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4.  Wirts,  J.J.,  et al,  Safety in Wastewater Works,  Manual of Practice Ho.  1,
    Water Pollution Control Federation (1959).

 5.  State of Virginia O&M inspection form.
 6.  Ettlich,  W.F.,  et al.  Operations Manual - Sludge Handling and
    Conditioning, US EPA Report 430/9-78-001.
7.  Harrison,  J.R.,  Goodson,  J.B.,  and Gulp,  G.L.,  Process  Design Manual for
    Sludge Treatment and Disposal.  US EPA 625/1-74/006.
                                    29-8

-------
30.  ANAEROBIC DIGESTION

Process Description

    EPA has published "Operations Manual - Anaerobic Sludge Digestion"  (EPA
430/9-76-001) which provides very detailed information on the process and
troubleshooting.  This manual should be read for more complete information
than given here.  In anaerobic digestion, the organic matter in the sludge is
broken down without oxygen.  In low rate digestion, one digester is used.
Fresh sludge is fed into it two or three times daily.  As decomposition
occurs, three separate layers form.  A scum layer is formed at the top of the
digester, and below it are supernatant and sludge layers.  The sludge zone has
an actively decomposing upper layer and a relatively stabilized bottom layer.
The stabilized sludge settles at the base of the digester and supernatant is
usually returned to the plant influent.  Most modern systems are "high rate"
systems utilizing one or two stages.  The sludge stabilizes in the first
stage, while the second stage provides settling and thickening.  In a single-
stage system, the secondary digester is replaced by some other thickening
process.

    The process converts about 50 percent of the organic solids to liquid and
gas, greatly reducing the amount of sludge to be disposed.  About two-thirds
of the gas produced in the process is methane.  Overall the gas has a heat
value of approximately 600 BTU/standard cubic foot (scf).  About 15 scf of gas
is formed per pound of volatile solids destroyed.  Anaerobic digester gas has
been used in wastewater treatment plants for many years to heat digesters and
buildings and as fuel for engines that drive pumps, air blowers and electrical
generators.

Typical Design Considerations

    The most important design factor is the organic loading rate, calculated
as the pounds of volatile solids fed per day per cubic foot of active digester
volume.  Sample calculations are as follows:
                                        =  8000 Ib/day
                                        =  70 percent
                                        =  50,000 cu ft
                                        =  50 feet
                                        *  8000 x .7
                                        =  5600 Ib/day
                                        5600   =  0.11 Ib VS/cu ft/day
1.   Raw sludge feed
     Volatile solids content
     Original digesters volume
     Diameter
2.   .Amount of volatile solids

3.   Original organic loading  =   	
                                   50,000
4.   Assume the digester has a scum blanket of 5 feet and a grit layer of
     3 feet.  This reduces the volume of the digester:
     Volume reduction              =  Depth x (Diameter)^ x 3.14
                                                  4
                                   =  8 x 2500 x 3.14
                                              4
                                   =  15,700 cu ft
                                     30-1

-------
          Usable  volume
         Actual  organic  loading
                                       =  Original volume - volume reduction
                                       -  50,000 - 15,700
                                         34,300 cu ft
                                       =  Amount of volatile solids
                                                Usable volume
                                       =  5600
                                          34,300
                                       =  0.16 Ib VS/cu ft/day

    The increase in the original organic loading of 0.11 Ib VS/cu ft/day to
0.16 Ib VS/cu ft/day due to a heavy scum layer and grit buildup may cause more
frequent upsets and make the digester harder to operate.

    Another important factor is the hydraulic loading rate.  This is the aver-
age time in days that the liquid stays in the digester and is related to di-
gester capacity.  This is calculated as follows:

    1.   Determine digester volume and feed volume
         Digester volume
         Feed volume              =
         Calculate hydraulic loading
         Hydraulic loading        
                                 50,000 cu ft x 7.48 gal
                                                cu ft
                                 374,000 gal
                                 19,100 gal/day

                                 Digester volume
                                 Feed volume
                              -  374,000
                                  19,100
                              =  19.6 days

Typical design criteria for loading rates are as follows:
      Parameter
Solids loading, Ib VS/cu ft/day
Hydraulic loading, days
                                     Low rate digester
                                          0.04-0.1
                                            30-60
                                                             High rate
                                                              0.15-0.40
                                                                10-20
Typical Performance Evaluation

    Digester performance is usually expressed as percent reduction  in volatile
solids or as volume of digester gas produced per pound of volatile  solids des-
troyed.  Typical values are shown below:
         Parameter
    Volatile solids, reduction %
    Digester gas production,
      cu ft/lb VS destroyed
                                            Performance Range
                                                  40-60%

                                                  13-18
                                     30-2

-------
Process Control

    Proper control of anaerobic sludge digestion is based on:

         Food supply
         Time and temperature
         Mixing
         pH and alkalinity
         Gas production

    These factors are discussed in Reference 1.

Maintenance Considerations

    The features of a good maintenance program are:

     1.  Daily check of the sludge pumping system including motors, pumps,
         packing, suction, meters and clocks.
     2.  Daily check of boiler and heat exchanger operation, temperature and
         pressures.
     3.  Daily check of digesters including mixing devices, covers, and gas
         collection devices.
     4.  Regular inspections of:
         (a)  gas safety devices
         (b)  gas piping system, compressors and scrubbers
         (c)  water seals
         (d)  manometers
         (e)  digester structure and heat transfer system
         (f)  scum blanket build-up
         (g)  equipment lubrication
     5.  Digester soundings performed semi-annually to determine volume reduc-
         tion from accumulation of solids and to determined temperature
         profile.
     6.  Safety equipment such as flame traps, vacuum breakers, waste gas
         burners, condensate traps, pressure relief valves, and combustible
         gas detection alarms properly maintained.
     7.  Instrumentation regularly inspected and calibrated.

Records
    Recommended sampling and laboratory  tests are shown on Figures 30-1 and
30-2.

    Other operating records should  include
    1.   Production rates of 014 and CC>2 gases
         Influent sludge flow
2.
3.
4.
         Grit depth
         Depth of scum layer
                                      30-3

-------
Q
tu
a
Q.
O

TEMPERATURE
PH
ALKALINITY
VOLATILE
ACIDS
TOTAL SOLIDS
jLUXALi
W&P*
rOTAJj
fflHH1"








3 AS
3REASE





UJ
Isl
/
(-
Z Q
21
ALL
ALL
ALL
ALL
ALL
ALL
ALL








>5
ALL





TEST
FREQUENCY
Mn
1/D
1/D
3/W
1/W
1/W
2 A?








1/W
1/M





LOCATION OF
SAMPLE
P
P
P
P
P
P
I








G
I
P





METHOD OF
SAMPLE
Mn
G
G
G
G
G
G








G
G





i-
Z"
8-
< a:
uj o
0 U.
P
P
P
P
P
P
P








P
P





                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS
                                                   SOLIDS REDUCTION
                                                            ANAEROBIC DIGESTION - PRIMARY
1
/
r ^^^^1


^-GAS TO
STORAGE OR
BURN
INFLUENT ~~**~*~~ 1
SLUDGE V. DIGESTED SLUDGE
TO SECONDARY
DIGESTER
                                                   A. TEST FREQUENCY
                                                        H m HOUR     M - MONTH
                                                        D-DAY       R - RECORD CONTINUOUSLY
                                                        w-WEEK     M- MONITOR CONTINUOUSLY

                                                   B. LOCATION OF SAMPLE

                                                        I =INFLUENT
                                                        P = PROCESS
                                                        G = GAS (INCLUDE WITH PROCESS TESTING)
C. METHOD OF SAMPLE

    24C-24 HOUR COMPOSITE
    G  GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn- MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
                                                   Figure 30-1
                                               30-4

-------
O
u
(9
ui
1
a
o


pH
TOTAL SOLIDS
TOTAL
VOLATILE
spr,ms
BOD
SUSPENDED
SOLIDS
FLOW
















UJ
N
7>
t-
z o
5?

ALL
ALL
ALL
ALL
ALL
ALL
















EST
=REQUENCY

Mn
2
2
1/W
1/W
R
















-OCATION OF
AMPLE

s1
u
n
S
S
s
















METHOD OF
AMPLE

Mn
G
a
G
G
R
















*
S1-
< a:
uj O

P
H
IT
P3
H
P3
















                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                              TESTING NEEDS
                                                    SOLIDS REDUCTION
r                                                  SUPERNATANT
                                                  RECYCLE TO
                                                  PLANT     -X
                                                  INFLUENT  J
                                                    rs
                                                               ANAEROBIC DIGESTION -SECONDARY
                             -GAS HOLDER
                               (FOR GAS STORAGE)
                                                 INFLUENT SLUDGE
                                                  FROM PRIMARY
                                                  DIGESTER
                             SLUDGE UNDERFLOW
                             TO NEXT ORGANIC  .
                             SLUDGE TREATMENT
                             PROCESS
                                                    A. TEST FREQUENCY
                                                         H m HOUR      M - MONTH
                                                         D-DAY       R - RECORD CONTINUOUSLY
                                                         W- WEEK      Mn- MONITOR CONTINUOUSLY

                                                    B.  LOCATION OF SAMPLE

                                                         U= UNDERFLOW
                                                         S = SUPERNATANT
C. METHOD OF SAMPLE

    24C- 24 HOUR COMPOSITE
    G - GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn. MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
      1. IN DIGESTER (INCLUDE WITH PROCESS TESTING)
      2. WHEN SLUDGE IS DRAWN OFF
      3. FOR CONTROL OF PROCESS RECEIVING THIS FLOW
                                                    Figure 30-2

                                                 30-5

-------
 Laboratory Equipment

     The laboratory should include  the following  minimum equipment  in  order  to
 monitor anaerobic  digestion:

      1.  Analytical balance
      2.  Clinical  centrifuge with  graduated  tubes
      3.  BOD  incubator
      4.  Drying  oven
      5.  Irahoff  cones
      6.  Graduated cylinders
      7.  Burettes
      8.  pH meter
      9.  Crucibles
     10.  Vacuum  source
     11.  Muffle  furnace,  550C
     12.  Evaporating dish
     13.  Bunsen  burner

 Sampling Procedures

     Samples should be collected at- points where  good mixing occurs.   Sample
 ports should be  allowed  to run for a  few moments to purge  the  line before
 sampling.   Always  run pH and temperature tests within 10 minutes to avoid
 deterioration.   The remainder of the  sample  should be refrigerated if the
 other tests are  not run  immediately,  when storing a sludge sample in a re-
 frigerator/ it is  a good idea to use  a plastic wrap over the jar with a rubber
 band to hold  it  in place.  This will  allow any gases that  might collect in the
 sample  to  expand without bursting  the jar.   The  sample  container should be
 cleaned thoroughly before and after each use.

 Sidestreams

     Supernatant  is  returned to the head of the plant; however, this recycle
 stream may greatly  increase the BOD,  SS, and ammonia nitrogen  loading  on the
 plant.  Table 30-1  presents typical digester supernatant quality data.

	TABLE  30-1.  DIGESTER SUPERNATANT QUALITY	
                      Primary plants
                           (mg/1)
Trickling filters*
     (mg/1)
  Activated
sludge plants*
    (rag/1)
Suspended solids
BOD
COD
Ammonia as NH_
Total phosphorus
200-1
500-3
1,000-5
300-
as P 50-
,000
,000
,000
400
200
500- 5
500- 5
2,000-10
400-
100-
,000
,000
,000
600
300
5,0000-15
1,000-10
3,000-30
500- 1
300- 1
,000
,000
,000
,000
,000
*  Includes primary sludge.
                                     30-6

-------
Process Checklist - Anaerobic Digesters
 1. What is the type of digester?
                                                       High rate
 2.
 3.
 4.
 5.
 6.
 7.
 8.
 9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.

23.
24.
25.
26.
27.
28.

29.

30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
Low rate	
secondary tanks 	
What type of sludge is digested?
What type of covers are  used?   (
What is the digester volume 	
                                primary tank
                                                             primary and
                                  )  fixed   (
                                               )  floating   (  )
                                              cu ft?
none
                                                     gal/day?
                                                       %?
What is the volume of the influent sludge 	
What is the design influent flow 	
What is the influent solids concentration 	
What is the volatile solids content of the influent sludge
What is the design volatile solids loading 	
What is the frequency and duration of the sludge feed pumping?
What is the depth of the scum blanket 	ft?
What is the depth of the grit layer 	
                                                               gal/day?
                                                              Ib/cu ft/day?
                                                 ft?
What is the active capacity of the digester 	
What is the actual volatile solids loading 	
What is the hydraulic loading 	days?
                                                          cu ft?
                                                          	 Ib/cu ft/day?
What is the gas production rate 	
What is the average C02 content of the gas 	
What is the average CH4 (methane) content of the gas_
What 'is the average reduction in volatile solids 	
What type of mixing .is used in the primary tank? 	
What are the heating provisions?	
                                            cu ft/lb VS destroyed?
What is the solids concentration of the sludge withdrawn from the
digester 	%?
What is the average pH of the digester 	?
What is the average temperature 	F?
What is the average alkalinity 	rag/1?
What is the average volatile acids content
                                                          mg/1?
At what point in the plant flow is the supernatant returned? 	
Is treatment of the supernatant provided before return to the plant?
(  )   Yes  (  )   No
Are there metering provisions for return of supernatant?
(  )   Yes  {  )   No
What is the average return flow of the supernatant 	gal/day?
What is the average BOD of the supernatant 	
                                                   	mg/1?
What is the average suspended solids content in the supernatant
Frequency of maintenance inspection by plant personnel for:
sludge pumping 	/year; digesters and mixing equipment 	
                                        /year; safety devices 	
                                                  No
                                                                       jng/1
gas collection/storage equipment
Is maintenance program adequate?
                                                                        _/year ;
                                                                        _/year
                                 (  )  Yes  (  )
Does the unit show signs of overload?
Is there an alarm system for hazardous equipment failures?
Frequency of tank cleaning 	?
Does the sampling program meet the recommendations?
Are operating records adequate?
Is the laboratory equipped for the necessary analyses?
                                     30-7

-------
41. What spare parts are stocked?-
42<
         are the most common problems the operator has had with the process?
                                   30-8

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No.  11, Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts,  J.J.,  et al,  Safety in Wastewater Works, Manual of Practice No.  1,
    Water Pollution Control Federation (1959).

 5. State of Virginia O&M inspection form.

 6. Operations Manual -  Anaerobic Sludge Digestion, EPA 430/9-75-001
                                     30-9

-------

-------
31.  AEROBIC DIGESTION

Process Digestion

    Aerobic digestion is the separate aeration of waste  sludge  in open  or
closed tanks.  The purpose  is  to  further  treat the sludge  so  it will  not cause
odors or other nuisances in final disposal.  Aerobic  digestion  also reduces
the volume of sludge solids.   Aerobic digestion  is used  commonly for  package
plants.  It is equally useful  for larger  plants  especially for  waste  biologi-
cal sludges.

    Aerobic digestion is a completely mixed activated sludge  system with
either batch or continuous flow input.  The contents  of  the digestor  are aer-
ated for a period of 12 to 22  days depending on  the type of sludge.   The
solids resulting from digestion are separated from the liquid.  They  dewater
easily and do not cause odor problems.

Typical Design Considerations

    Typical design criteria for aerobic digestion are shown in  Table  31-1,
which was adapted from "Process Design Manual for Sludge Treatment and  Dis-
posal", EPA 625/1-74-016.

    Solids Retention Time (SRT) is the average time that the  solids remain in
the process.  For continuous feed systems:

    SRT  total mass of solids in digester
             mass of solids wasted/day

For batch feed systems:
    SRT
    average mass of the solids in digester during batch
(mass of solids wasted from batch)  (number of days in batch
    As an example assume the following data:

    Continuous feed:

         Tank volume =  65,000 gal           Solids  =  2.5%
         Wasting rate  =  2000 gal/day       Solids  =  5.0%
         SRT  =  65,000 x 0.025  =  16.3 days
                  2,000 x 0.05
                                     31-1

-------
              TABLE 31-1.  AEROBIC DIGESTION DESIGN PARAMETERS
     Parameter
                         Value
Solids retention
 time, days
Solids retention
 time, days

Volume allowance,
 cu ft/capital

VSS loading,
 pcf/day
Air requirements
 Diffuser system
  cfm/1,000 cu ft

Diffuser system,
 cfm/1,000 cu ft

Mechanical system,
 hp/1,000 cu ft
   10-15


   15-20b


    3-4


0.024-0.14


   20-35a



  >60b


 1.0-1.25
 1.0-2.0
Minimum DO, mg/1
Temperature, C
VSS reduction, percent   35-50

Tank design
Power requirement,
 BHP/10,000
  Population Equivalent
    8-10
                              Remarks
Depending on temperature/
etc.
type of sludge,
Depending on temperature,
etc.
type of sludge,
Enough to keep the solids in suspension
and maintain a DO between 1-2 mg/1.
This level is governed by mixing require-
ments*  Most mechanical aerators in aero-
bic digesters require bottom mixers for
solids concentration greater than 8,000
mg/1, especially if deep tanks  (>12 feet)
are used.
             If sludge temperatures are lower than
             15C, additional detention time should be
             provided so that digestion will occur at
             the lower biological reaction rates.
             Aerobic digestion tanks are open and gen-
             erally require no special heat transfer
             equipment or insulation.  For small treat-
             ment systems (0.1 mgd), the tank design
             should be flexible enough so that the
             digester tank can also act as a sludge
             thickening unit.  If thickening is to be
             utilized in the aeration tank, sock type
             diffusers should be used to minimize
             clogging.
 Excess  activated sludge  alone.

 bPrimary and excess  activated sludge,  or primary  sludge  alone.
                                      31-2

-------
    Batch feed with sludge settling and drawoff once per week:
    Sludge volume in digester at beginning of week:
    Sludge volume in digester at end of week:
    Solids = 2.5%
    Total of supernatant and settled sludge drawoff:
    Number of days in batch  =  7
    Average volume of sludge in digester  =  40,000
                             40,000 gal
                             65,000 gal

                             25,000 gal

                        + 65,000  =  52,500
    SRT  =  52,500 x 0.025  x 7  =  15 days
            25,000 x 0.025

    The volatile suspended solids  (VSS) loading, expressed as pounds of VSS
per cubic foot of basin volume per day, is calculated as shown  in the follow-
ing example for a continuous feed digester.

    Tank volume  =  65,000 gal
    Wasting rate  =  2,000 gal/day @ solids  =  5.0%
    Waste activated sludge, volatile solids  =  80% of TSS
    Total VSS wasting rate  =  2,000 gal x 8.34 Ib x 0.05 x 0.80
                                     day     gal
                                        667 Ib VSS
                                              day
    VSS loading rate  =
667
            x 7.48 gal  = 0.077 Ib VSS/cu ft/day
65,000 gal     cu ft
Typical Performance Evaluation

    With aerobic digestion a 40 to 50 percent reduction in volatile suspended .
solids content is normally obtained.  The supernatant may contain as  little as
10 to 30 mg/1 BOD, 10 mg/1 ammonia nitrogen, and from 50 to 100 mg/1  nitrate
nitrogen.  When nitrification occurs, both pH and alkalinity are reduced.
                                     *               '              ~
Process Control

    In most plants the aerobic digester is operated as a self-regulating pro-
cess with very little process control needed.  That which is needed is dis-
cussed in Reference 6.

Maintenance Considerations

    The maintenance program for the aerobic digester is very similar  to the
program for the activated sludge process.  The features of a good maintenance
program that the inspector should look for are:

     1.  Air diffusers and tanks inspected at least once per year.
     2.  Mixing, pumping, and blower equipment inspected annually for worn
         blades and impellers.
     3.  Air filters serviced at regular intervals.
                                     31-3

-------
      4.
 Records
Digester inspected once per shift for proper operation of aeration
equipment and pumps.
     Recommended sampling and laboratory tests are shown in Figure 31-1.

     Other operating records should include:

     1.    Volume of sludge recycled to aerobic digester.
     2.    Frequency and duration of operation of sludge pumps.
     3.    Periods when a digester is not operated because of inspection and
          service.
     4.    Days when there are problems with mixing and/or odors.

 Laboratory Equipment

     The laboratory should include the following minimum equipment in  order to
 monitor aerobic digestion:

     1.    Thermometer
     2.    pH meter
     3.    Analytical balance
     4.    Clinical   centrifuge with graduated tubes
     5.    BOD  incubator
     6.    Drying oven
     7.    Muffler furnace
     8.    Oxygen gas analyzer (optional)

     The EPA report "Estimating  Laboratory  Needs for Municipal Wastewater
 Treatment Facilities" contains  very detailed information on glassware, chem-
 icals,  miscellaneous furniture,  etc.,  and  should be referred to  for any de-
 tailed  questions.

 Sampling Procedures

     Sampling  should be performed as outlined under Records.  These samples may
be obtained through valves  provided in the digester piping.  If  sampling
points  are  not  provided,  it may be necessary to obtain samples directly from
 the  digester  contents.

     The  sample  collector  and containers should  be clean.  A wide mouth sample
collector of  at least 2  inches  should  be used.   Samples  collected in  the ef-
 fluent channel  should be  collected near the  discharge point so that any iso-
 lated areas of  short circuiting  do not influence  the results.  Where  automatic
samplers are  used,  it is  important to  keep the  sampler tubes clean.

     Samples should be analyzed  according to procedures specified in Standard
Methods.
                                     31-4

-------
z
3
O
U
Ul
a
a
t-
Q.
o


TEMPERATURE
pH
TOTAL SOLIDS
TOTAL
VOLATILE
SOLIDS
DO
AIR INPUT
SETTLEABLE
SOLIDS
FLOW
PH
SUSPENDED
SOLIDS
BOD
PLOW



ALKALINITY






UJ
N
Co
1-
z a
28

ALL
ALL
ALL
1
ALL.
ALL
ALL
ALL
ALL
AT.T,
ALL
ALL



ALL






rEST
=REQUENCY

VD
1/D
2/W
2/W
3/W
R
3/W
R
2
2
2
R



/w






-OCATION OF 1
AMPLE

p
p
I
DS
I
DS
p
B
P
DS
S
s
S
S



P






METHOD OF
AMPLE

G
G
G
G
G
R
G
R
G
K
G
R



G






Z%
$>-
< 
                                                   INFLUENT
                                                    SLUDGE
                    AEROBIC DIGESTION
                  a
           i)  i   1   i
                                                                                 S


                                                                               DS
'SUPERNATANT
 RECYCLE TO
 PLANT INFLUENT
                                                                          DIGESTED SLUDGE
                                                                          TO NEXT ORGANIC
                                                                          SLUDGE TREATMENT
                                                                          PROCESS
                                                   A. TEST FREQUENCY
                                                       H  HOUR
                                                       0- DAY
                                                       w- WEEK
                   M - MONTH
                   R - RECORD CONTINUOUSLY
                   Mn- MONITOR CONTINUOUSLY
 B.  LOCATION OF SAMPLE

      I - INFLUENT
     DS= DIGESTED SLUDGE
     S = SUPERNATANT'
     P = PROCESS
     B = BLOWER {INCLUDE WITH PROCESS TESTING)

 C. METHOD OF SAMPLE
     24C-24 HOUR COMPOSITE
     G- GRAB SAMPLE
     R  RECORD CONTINUOUSLY
     MB. MONITOR CONTINUOUSLY

 D. REASON FOR TEST

     H - HISTORICAL KNOWLEDGE
     P - PROCESS CONTROL
     C - COST CONTROL

E. FOOTNOTES:
     1. DIFFUSED AIR ONLY
     2. WHEN DRAW OFF SUPERNATANT
     3. FOR CONTROL OF PROCESS RECEIVING
        THIS FLOW
                                                  Figure  31-1
                                               31-5

-------
Sidestreams

    The only sidestream from the aerobic digestion process is the super-
natant.  It is returned to either the primary or the secondary treatment
process and normally causes no problem to process operation.
                                     31-6

-------
Process Checklist - Aerobic Digestion
 1.
 2.
 3.
 4.

 5.
 6.
 7.
 8.
 9.
10.
11.
12.

13.

14.
15.
16.
17.

18.

19.

20.
21.
22.
23.
24.

25.

26.

27.
28.

29.

30.
31.
32.

33.

34.

35.
    How many aerobic digestion units are there 	___?
    What are the dimensions of each unit 	;	
    How many units are presently operating 	__?
    What type of sludge is treated in the aerobic digesters (waste activated,
    primary, primary + waste activated, etc.)                        ?
    What is the volume of influent sludge flow
    What is the design sludge flow
    How often is sludge applied to the digester	
    What is the total duration of influent pumping	
    Is influent sludge pumping  (  )   manual  (  )  automatic?
    What is the solids concentration in the influent sludge flow
    What is the solids concentration in the aerobic digesters 	
                                                          _gal/day average?
                                                           gal/day average?
                                                          	times.per day?
                                                             hours/day?
    What type of aeration equipment is used (diffused, mechanical,
    combination, etc.) 	j	?
    If diffused aeration is used, do air diffusers require frequent cleaning?
    (  )  Yes  (  )   No
    Are the aerobic digesters (  )  open  (  )   closed?
    Is the aeration (  )  conventional  (  )   pure oxygen?
    What is the sludge retention time (SET) 	days?
    What is the volatile suspended solids (VSS) loading 	lb
    VSS/cu ft/day?
    Is a separate sedimentation tank used or is it a batch-type
    system?	
    See Primary Clarification or Secondary Sedimentation for a checklist for
    sedimentation tanks.
    What is the solids concentration of the sludge following settling 	
    How much waste sludge is pumped 	 gallons/day?
    How often do waste sludge pumps run _
    Is waste sludge pumping  (  )   manual
                                                     minutes/hour?
                                       (  )  automatic?
How much sludge is recycled back to the aerobic digester	
gallons/day average?
What percentage of the influent sludge flow is the recycle sludge
flow	%?
Are .the contents of the tanks well mixed and relatively free of odors?
(  )  Yes  (  )  No
Is there a foaming problem?  (  )  Yes  (  )  No
What is the dissolved oxygen (DO) concentration in the aerobic digestion
units 	mg/1?
Are there provisions for pH adjustment by the addition of lime, sodium
hydroxide, or sodium bicarbonate?  (  )  Yes  (  )  No
What is the volume of supernatant flow 	gal/day average?
What is the BOD of the supernatant flow 	mg/1?
What is the suspended solids concentration of the supernatant 	
mg/1?
What is the nitrate nitrogen concentration of the supernatant 	
mg/1?
What is the ammonia nitrogen concentration of the supernatant 	
rag/1?
Frequency of maintenance inspections by plant personnel 	
                                                                       /year.
                                     31-7

-------
36,
37.

38.

39.

40.
41.
42.
43.
Is maintenance program adequate?   (   )  Yes   (  }  No
If multiple units are used,  is the flow distributed evenly?
(  )  Yes   (  )  No
Does the unit show signs of  short circuiting and/or overloads?
(  )  Yes   (  )  No
Is there an alarm system for equipment failures or overloads?
(  )  Yes   (  }  No
Does the sampling program meet the recommendations? (  )  Yes   (
Are operating records adequate?  (  )  Yes  (  )  No
Is the laboratory equipped for the necessary analyses? (  )  Yes
What spare parts are stocked? 	
)   No
(   )   No
44. What are the most common problems the operator has had with the process?
                                    31-8

-------
References

 1. Gulp, G.L., and Polks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution-Control Federation (1959).
                  \
 5. Harrison, J.R., Goodson, J.B., and Gulp, G.L., Process Design Manual for
    Sludge Treatment and Disposal, USEPA, 625/1-74-006.

 6. Ettlich, W.F., et al, Operations Manual - Sludge Handling and
    Conditioning, US EPA Report 430/9-78-002.
                                      31-9

-------

-------
32.  CENTRIFUGATION

Process Description

    The centrifuge is a sedimentation device  in which  the  solids-liquid  sepa-
ration is enhanced by rotating the liquid at  high speeds.  Centrifuges have
been used for both sludge thickening and dewataring especially  for waste acti-
vated sludge and digested sludges.  Both the  disc type and the  solid bowl
centrifuges are well suited to thickening operations.

    The solid bowl centrifuge is the most widely used  type for  dewatering of
sewage sludge.  It consists of a rotating bowl and conveyor.  Sludge enters
the rotating bowl through a stationary feed pipe ex-tending into the hallow
shaft of the rotating screw conveyor and is distributed through ports into a
pool within the rotating bowl.  The helical rotating conveyor moves the  sludge
solids across the bowl, up the beaching incline to outlet  ports and then to a
sludge cake discharge hopper.

    Water or centrate is discharged from the  bowl through  ports in the end
which maintain the pool in the bowl at the desired depth.

    The basket centrifuge is also referred to as the imperforate bowl, knife
discharge type and is a batch dewatering unit that rotates around the vertical
axis.  The sludge is charged into the basket  and forms an  annular ring as the
unit rotates.  The liquid (centrate) is displaced over a baffle or weir  at the
top of the unit.  When the solids concentration reaches the desired limit the
centrifuge is stopped.  A knife or skimmer displaces the cake from the verti-
cal wall and out the bottom openings.

    The disc centrifuge is continuous flow variation of the basket centri-
fuge.  It is prone to plugging and in some cases the sludge may have to be
screened prior to centrifugation.

Typical Design Considerations

    The most commonly used loading factor for centrifuges  is the sludge  feed
rate.  Single centrifuge capacities range from 4 gpm to about 250 gpm.  Feed
rates may also be given in pounds of dry solids per hour.  This is calculated
as shown on the following page.
                                     32-1

-------
     1.

     2.
    5.
 Determine wet sludge feed rate.
 Feed rate  =  150 gpm
 Determine solids concentration in the feed sludge.
 Concentration  -  weight of dry sludge solids x 100%
                     weight of wet sludge
                =  0.1 Ib  x 100 = 1%
                   10 Ib
 Calculate dry feed rate.
 Dry feed  rate  =  sludge wet feed rate x concentration
                =  150 x 0.01 x 8.34 Ib x 60 min
                                     gal      hr
                =  750 Ib dry solids/hr
 Typical feed rates for several sizes of solid bowl  centrifuges for
 typical municipal waste sludges  are:
                                             Feed rate
 Machine size,  in                         Ib dry solids/hr
      18                                     300 x 800
      24                                     700 to 2000
      36                                    1500 to 3500
 Solids recovery  is the ratio of  cake solids to feed solids  for equal
 sampling  times.   It can be calculated with suspended solids and flow
 data  or with only suspended solids  data.   The centrate solids must be
 corrected  if chemicals are fed to the centrifuge.
 Recovery    wet  cake  flow,  Ib    (cake solids,  %)   (100)
	                 hr
                      wet  feed flow,  Ib
                                     hr
                                     (feed  solids, %)
Recovery 
(cake solids, %)  (feed solids, % - centrate solids,  %)  (100)
(feed solids, %)  (cake solids, % - centrate solids,  %)
Centrate solids must be corrected if chemicals are added  to centri-
fuge.  Because  it is diluted by the extra water from the  chemical and
chemical dilution water feeds.  The measured centrate solids, there-
fore, are less  than the actual solids would be without  the added
water from the  chemical feed.

correction factor 
(feed rate, gpm) + (chemical flow, gpm) +  (dilution  water, gpm)
                        feed rate, gpm
         corrected centrate  solids  =
         (measured centrate  solids)  (correction  factor)

Typical Performance Evaluation

    Expected centrifuge performance is shown  in  Table  32-1  for  a  number  of
conditions.  These data were developed from "Process Design Manual  for Sludge
Treatment and Disposal", EPA 625/1-74-006 and actual plant  data.
                                     32-2

-------
                  TABLE 32-1. EXPECTED CENTRIFUGE PERFORMANCE

Sludge Cake Characteristics
Wastewater sludge type
Raw or digested primary
Raw or digested primary, plus
trickling filter humus
Raw or digested primary, plus
activated sludge
Activated sludge
Oxygen activated sludge
High-lime sludges
Lime classification
Heat treated sludge
Heat treated sludge
Solids ,
25-35
28-35
20-30
25-35
15-30
15-25
9-9
8-10
50-55
50
30-50
30-50
Solids
% recovery, %
90-95
70-90
80-95
60-75
80-95
50-65
80-85
80-85
90
75
85-90
92-99
Polymer-
addition
2-4 Ibs/ton
no
5-15 Ibs/ton
no
5-20 Ibs/ton
no
5-10 Ibs/ton
3-5 Ibs/ton
no
no
no
2-5 Ibs/ton
                         Typical Thickening Performance
                 (Based on limited plant operating experience)
                          Underflow                   Solids
Type of     Centrifuge     solids,    Feed solids,   recovery,
sludge	type	%            %             %
   Polymer
requirement,
WAS
EAS (after
roughing
filter)
EAS
EAS



Disc

Disc
Basket
Solid-bowl



4-5.5

5-7
9-10
5-13



0.75-1. a

0.7
0.7
0.4-1.5



80-90

80-97
90-70
70-90
85
90
95
None

None
None
None
5
5-10
10-15

WAS * waste activated sludge
EAS * extended aeration waste sludge
                                     32-3

-------
 Process  Control

     There  are  several variables  that  can be  controlled by  the operator to af-
 fect optimum centrifuge performance.   These  are presented  in Reference 6.

 Maintenance  Considerations

     The  features of a good maintenance program include general maintenance
 requirements as well  as the  following:

      1.  Conveyor belts properly checked for adjustment.

      2.  Spare part inventory contain the  following:  shear pins, main bear-
         ings, seals/  conveyor bushings, thrust bearing seal, feed and dis-
         charge ports.

 Records

     Recommended sampling and laboratory tests are shown in Figure 32-1.
     Other  operating records  should  include:
     1.   Frequency and duration of  centrifuge operating time.
     2.   Quantity of  sludge  cake produced.
     3.   Influent sludge flow.

 Laboratory Equipment

     The  laboratory should include the following equipment in order to monitor
 centrifugation:
     1.   Analytical balance
     2.   Clinical centrifuge with graduated  tubes
     3.   BOD incubator
     4.   Drying oven
     5.   Imhoff Cones
     The  EPA report "Estimating Laboratory Needs for Municipal Wastewater
 Treatment  Facilities* contains very detailed information on glassware, chemi-
 cals, miscellaneous furniture, etc.,  and should be referred to for any
 detailed questions.

Sampling Procedures

    Samples should be collected at  the points shown under the section Rec-
 ords.  The sample collector and containers should be clean.  A wide mouth
 sample collector of at least 2 inches should be used.  Where automatic
 samplers are used, it  is important  to keep the sampler tubes clean.

Sidestreams

    The  centrate is usually  returned  to the plant influent or some other ap-
propriate point in the main  treatment process.  Return of centrate to flota-
 tion thickeners has also proven satisfactory.
                                     32-4

-------
2
a
o

TOTAL SOLIDS
BOO
SUSPENDED
Qnr.Tns
SETTLEABLE
SOLIDS 
FLOW

















UJ
N
t/>
t-
z 5
< 0
Si *
ALL
ALL
ATiTi
ALL
ALL

















TEST
FREQUENCY
1/D
1/W
1/D
1/H
R

















LOCATION OF
SAMPLE
S
C
CE
CiS
CE
CE






.










1 METHOD OF 1
SAMPLE
G
G
G
G
R

















REASON
FOR TEST
P
P2
P
P
P1

















                                                  ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS
                                                  SLUDGE CONCENTRATION
                                                             CENTRIFUGATION
                                                                           (1)
rr
^ CENTRATE
TO PLANT
mm
RECYCLE 1
INFLUENT J (
*^**";
f SLUDGE FEED
1
S

iLUDGE CAKE
                                                  NOTE: SOLID BOWL TYPE SHOWN.
                                                       FLOW PATTERN IS SIMILAR
                                                       FOR OTHER MODELS.
                                                  A. TEST FREQUENCY
                                                       H - HOUR      M - MONTH
                                                       0 m DAY       R - RECORD CONTINUOUSLY
                                                       W- WEEK      M- MONITOR CONTINUOUSLY

                                                  B. LOCATION OF SAMPLE

                                                       S = SLUDCE FEED
                                                       C= SLUDGE CAKE
                                                       CE  =CENTRATE
C. METHOD Of SAMPLE
    24C-24  HOUR COMPOSITE
    G " GRAB SAMPLE
    R - RECORD CONTINUOUSLY
    Mn MONITOR CONTINUOUSLY

0. REASON  FOR  TEST
    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
     1.
     2.
                                                         DAILY OPERATION ASSUMED
                                                         FOR CONTROL OF PROCESS RECEIVING THIS FLOW.
                                                  Figure  32-1
                                              32-5

-------
Process Checklist - Centrifugation
 1.
 2.
 3.
 4.
 5.
 6.
 7.
 8.

 9.
10.
11.
12.

13.

14.

15.
16.
17.
18.
19.
20.
21.

22.
23.
24.
25.
What is the volume of influent sludge flow 	
What is the design flow 	gal/min?
How much cake is produced ?_
               gal/min?
_lb/day?
What is the solids concentration in the influent sludge? 	%
What type and size of centrifuges are used?	
What is the solids recovery 	%
What is the solids concentration in the discharge cake	%
Is operation of centrifuge, conveyors or sludge feed pumping  (  )  manual
(  )  automatic.
How often does the centrifuge run 	rain/hr?
Frequency of maintenance inspections by plant personnel	/yr
Is maintenance program adequate?  (  )  Yes  (  )  No
Are metering provisions available for return of the centrate?
(  )  Yes  (  )  No
If multiple units are used is the influent flow distributed evenly?
(  )  Yes  (  )  No
For multiple units are there provisions for equalization of centrate
flows?  (  )   Yes  (  )  No
What are the types of conditioning chemicals fed? 	'"'
What amounts of chemicals are fed	 Ib/day?
What are chemical feed cycle times 	
           minutes/hr?
           "  )   No
           )   No
           (   )  No
Is the general housekeeping satisfactory?  (  }  Yes
Does the unit show signs of overloading?   (  )  Yes  (
Does the unit show signs of excessive wear?  (  )  Yes
Is there an alarm system for equipment failures or overloads?
(  )   Yes  (  )  No
Does the sampling program meet the recommendations?  (  )  Yes
Are operating records adequate?  (  )  Yes  (  )  No
Is the laboratory equipped for the necessary analyses?   (  )  Yes
What spare parts are stocked? 	
                                                                 (  )  No

                                                                   (  )  No
27. What are the most common problems the operator has had with the process?
                                     32-6

-------
References

 1. Gulp, G.L., and Polks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).

 5. State of Virginia OSM inspection form.

 6. Harrison, J.R., Goodson, J.B., and Gulp, G.L., Process Design Manual for
    Sludge Treatment and Disposal, USEPA, 625/1-74-006.
 7. Ettlich, W.F., et al, Operations Manual - Sludge Handling and
    Conditioning, US EPA Report 430/9-78-002.
                                     32-7

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33.  VACUUM FILTRATION

Process Description

    A vacuum filter consists of a cylindrical drum which rotates partially
submerged in a vat of sludge.  The filter drum is divided into compartments by
partitions or seal strips.  A vacuum is applied between the drum deck and
filter medium causing filtrate to be removed and filter cake to be retained on
the medium during the pickup and cake drying cycle.  The filter medium may be
a cloth made of natural or synthetic fibers, stainless steel wire mesh or coil
springs.  Dewatered sludge is ordinarily removed by a fixed scraper blade.

Typical Design Considerations

    The most important loading factor is the amount of solids, on a dry basis,
applied to the filter per hour.  This is called the "solids loading rate" and
is expressed in pounds of solids per square foot of vacuum filter area per
hour.  This factor is calculated as shown in the following example.  Typical
values are shown in Table 33-1.

    1.   Determine effective surface area of vacuum filter.  The plant con-
         struction drawings or the vacuum filter O&M manual should contain the
         necessary information.
              Area = 75 sq ft
    2.   Determine sludge flow to vacuum filter from plant records  (must
         include chemical's).
              Sludge flow = 100,000 gal/hr
    3.   Determine the influent sludge concentration.
              Concentration = weight of dry sludge solids x 100%
                                  wet of wet sludge
                            =  1 Ib   x 100  = 10%
                              10 Ib
    4.   Determine the total dry weight of sludge  to the vacuum filter per
         hour.
         Dry weight  =  sludge flow x concentration - 8.34
                     =  100,000 x 0.1   -  12oo Ib/hr
                            8.34
    5.   Determine loading  rate.
         Loading rate  =  Dry weight
                            Area
                       =  1200   =  8  ib/sg  ft/hr
                          150

Typical Performance Evaluation

    The most common measure  of performance  for vacuum filters is  the  yield.
This  is expressed  in  terms  of pounds of  dry  total  solids  in  the cake  dis-
charged  from the  filter per  square  foot  of  effective  filter  area  per  hour.

    Performance of  the vacuum  filtration process can  vary  widely  depending  on
the sludge type,  sludge  characteristics,  conditioning,  type  of vacuum filter,
and loading  rates.   Typical applications are shown in Table  33-1.
                                      33-1

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         TABLE 33-1.  VACUUM FILTRATION TYPICAL LOADINGS AND PERFORMANCE



Sludge type
Primary

Primary + FeCl


Primary +
Low Lime

Primary +
High Lime

Feed
solids,
Design assumptions %
Thickened to 10% solids 10
polymer conditioned
85 mg/1 FeCl dose 2.5
Lime conditioning
Thickening to 2.5% solids
300 mg/1 lime dose 15
Polymer conditioned
Thickened to 15% solids
600 mg/1 lime dose 15
Polymer conditioned
Typical Performance
loading cake
rates , solids ,
psf/hr %
8-10 25-38

1.0-2.0 15-20


6 32-35


10 28-32

Primary H- WAS
Primary 4-
   (WAS 4- FeCl3)

(Primary  + FeCl )
  + WAS
Waste Activated
  Sludge  (WAS)'

WAS  FeCl..
Digested primary


Digested primary
  + WAS

Digested primary
  + (WAS + Fei

Tertiary alum
 Thickened to  15%  solids

 Thickened to  8% solids          8
 Polymer  conditioned

 Thickened to  8% solids          8
 FeCl,  &  lime  conditioned

 Thickened primary sludge      ~3.5
 to 2.5%
 Flotation thickened WAS
 to 5%
 Dewater blended sludges

 Thickened to  5% solids          5
 Polymer conditioned

 Thickened to  5% solids          5
 Lime + FeCl3  conditioned

 Thickened to  8-10%  solids   8-10
 Polymer conditioned

 Thickened to  6-8% solids    6-8
Polymer conditioned

Thickened  to  6-8% solids    6-8
FeCl_ + lime  conditioned

Diatomaceous  earth precoat 0.6-0.8
                                                              4-5
  1.5
2.5-3.5
1.5-2.0
                                                              7-8
                                                           3.5-6
                                                           2.5-3
                                                             0.4
             16-25
               20
                                                                         15-20
                                                                           15
                                                                          15
             25-38
             14-22
             16-18
             15-20
                                    33-2

-------
 Process Control

    Control of the  vacuum filter  systems  should be based on performance.  The
 performance of vacuum  filters may be measured by various criteria  such as the
 yield, the efficiency  of  solids removal,  and the cake  characteristics.  Each
 of  these criteria is of importance, but one or the other may be particularly
 significant in a given plant.  Control based on .these  criteria  is  discussed in
 Reference 7.

 Maintenance Considerations

    The maintenance program vacuum filters includes sludge pumping, chemical
 feed systems and the filter unit  itself.  Maintenance  items specific  to the
 filter unit are:

     1.  Daily inspection of filter media for excessive or unusual wear.

     2.  Daily checks  and lubrication of drive units.

     3.  Periodic cleaning of sludge lines and conveyor belts.

     4.  Spare parts inventory include the following: drive mechanism parts
         such as sprockets, chains, gears, motors, bearings, etc.  and vacuum
         mechanism  parts such as  hoses, fittings, pumps, gauges, etc.

Records

    Recommended sampling and laboratory tests are shown in Figure  33-1.

    Other records should include:

    1.    Influent sludge flow
    2.    Concentration of influent sludge and sludge cake
    3.    Frequency  and duration of operation

Laboratory Equipment

    1.    Analytical balance
    2.    Clinical centrifuge with graduated tubes
    3.    BOD incubator
    4.    Drying oven

    The EPA report  "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals,  miscellaneous furniture,  etc., and should be referred to for any de-
tailed questions.
                                     33-3

-------
Q.
O

TOTAL SOLIDS
BOD
SUSPENDED
SOLIDS
PLOW


















Ul
N
/
(-
Z Q
n
ALL
AH,
ALL
ALL


















TEST
FREQUENCY
1/D
?^f
1/D
R


















LOCATION OF
SAMPLE
S
C
F
P
F


















METHOD OF
SAMPLE
G
G.
G
R


















Z"
8>-
< 
-------
Sampling Procedures                            ,

    Sang?ling should be performed as outlined under Records.  These  samples may
be obtained through valves provided in the respective  thickener piping.   If
sampling points are not provided, they should  be  installed to  facilitate  oper-
ation and control of the process.  Samples of  the supernatant  can be obtained
at the overflow weir.

    Samples should be analyzed according to procedures  specified in Standard
Methods.

Sidestrearns

    The only sidestream is the filtrate which  is the liquid removed from  the
sludge during dewatering.  Filtrate is returned to a main plant treatment pro-
cess.  When filtrate quality is poor, it is possible to build  up a  large  pro-
portion of fine solids in the plant and reduce plant treatment efficiency.  In
an activated sludge process, the filtrate may be returned to a flotation  or
thickening process.
                                     33-5

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Process Checklist-Vacuum Filtration
 1.
 2.
 3.
 4.
 5.
 6.
 7.
 8.
 9.
10.
11.

12.
13.
14.

15.
16.
17.
18.
19.

20.

21.

22.
23.
24.
25.
What is the volume of the influent sludge flow 	
What is the percent solids of the influent sludge
What is the effective area of the vacuum filter 	
What is the design loading rate
                                                        _gal/day avg?
                                                          	sq ft?
                                                          Ib/sq ft/hr?
                                                            _rag/liter?
What is the percent solids in the discharge cake 	
Are there settleable solids in the filtrate 	
How often does vacuum filter run 	minutes/hour?
Frequency of maintenance inspections by plant personnel 	/year:
Is maintenance program adequate?  (  )  Yes  (  )  No
Is the vacuum system inspected regularly 	/year?
Frequency of maintenance inspections for chemical feed system
	/year
What type of conditioning chemicals are used	
What amount of conditioning chemicals are pumped 	Ib/day?
Are proper safety precautions used in handling these chemicals?
(  )  Yes  (  )  No.
Is sludge pumping   (  )  manual  {  )  automatic?
Is chemical feed  (  )  manual   (  )  automatic?
How often do sludge pumps run 	minutes/hour?
How often does conditioning equipment run 	minutes/hour?
If multiple units are used, is the flow distributed evenly?
(  )  Yes  (  )  No
Does the unit show signs of short circuiting and/or overloads?
(  )  Yes  (  )  No
Is there an alarm system for equipment failures or overloads?
(  )  Yes  (  )  No
Does the sampling program meet the recommendations? (  )  Yes   (  ) No
Are operating records adequate?  (  )  Yes   (  )  No
Is the laboratory equipped for the necessary analyses?  (  ) Yes  ( ) No
What spare parts are stocked? 	____^__
26. What are the most common problems the operator' has had with the process?
                                     33-6

-------
References

 1. Gulp, G.L., and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan.  1978)."

 2. Guarino,  C.F.,  et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice  No.  11,  Water Pollution Control Federation (1976).
 3.  CH2M-Hill,  Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June. 1973).~~~
 4.  Wirts,  J.J.,  et al,  Safety in Wastewater Works,  Manual of Practice No.  1,
    Water  Pollution Control Federation (1959).

 5.  State  of Virginia O&M inspection form.

 6.  Harrison, J.R.,  Goodson,  J.B.,  and Gulp, G.L., Process Design Manual for
    Sludge  Treatment and Disposal,  USEPA,  625/1-74-006.
 7.  Ettlich, W.F.,  et  al, Operations Manual  -  Sludge  Handling and
    Conditioning, US EPA Report 430/9-78-002.
                                    33-7

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-------
 34.  PRESSURE FILTRATION

 Process Description

     The filter press is a batch device used to dewater sludges.   There are
 several types of presses available but the most common consists  of vertical
 plates which are held in a frame and which are pressed together  between a
 fixed and moving end.  A cloth is mounted on the face of each individual
 plate.   Despite its name,  the filter press does not close to squeeze or press
 sludge.   Instead,  the press is closed and then sludge is pumped  into the press
 at pressures up to 225 psi and passes through feed holes in the  trays along
 the length of the press.   Filter presses usually require a precoat material
 (incinerator ash or diatomaceous earth are typically used)  to aid in solids
 retention on the cloth and release of the cake.

     The  water passes through the cloth,  while the solids are retained and form
 a  cake on the surface of  the cloth.   Sludge feeding is stopped when the cavi-
 ties or  chambers between  the trays are filled.   Drainage ports are provided at
 the bottom of each press  chamber.   The filtrate  is collected in  these,  taken
 to the end of the  press,  and discharged  to a common drain.

     The  pressures  which may be applied to a sludge for removal of water by
 filter presses now available range from  5,000 to 20,000 times the force by
 gravity.   In comparison,- a solid bowl centrifuge provides forces of 700 to
 3,500 times the force of gravity and  a vacuum filter,  1,000 times the force of
 gravity.   As a result of these greater pressures,  filter presses may provide
 higher cake solids concentrations  (30  to 50 percent solids)  at reduced  chemi-
 cal  dosage.   In some  cases,  ash from  a downstream incinerator is recycled as a
 sludge conditioner.

 Typical  Design Considerations

     Typical loading  rates  for  pressure filtration  of various sludges are  shown
 in Table 34-1.   This  data  was  developed  from "Process  Design Manual for  Sludge
 Treatment and  Disposal,"  (EPA  625/1-74-006).  Loading  rates depend on the
 length of  the  dewatering cycle described above.

Typical  Performance Evaluation

    Typical performance criteria for pressure filters  are the pressing  cycle
 length,  the  solids content of  the cake,  and the quality of  the filtrate.   Per-
 formance of filter press on various sludges will vary  widely,  but the data in
Table 34-1 are  typical.

Process Control

    Instrumentation is usually minimal,  however,  it is possible  to completely
automate  the operation of  the  filter press  if desired.  Pressure  gauges should
be provided to monitor the feed pressures and the  filtrate  flow must be moni-
 tored either visually or with  a flow  indicator.  Details of process control
are given  in Reference 7.
                                     34-1

-------
                  TABLE 34-1.  TYPICAL RESULTS PRESSURE FILTRATION

Sludge type
Primary
Primary + FeCl3
Primary + 2 stage
high lime
Primary + WAS
Primary + (WAS
PeCl3)
(Primary + FeCl3)
+ WAS
WAS
WAS -f FeCl3
Digested Primary
Digested Primary
f WAS
Digested Primay +
(WAS + FeCl3)
Tertiary Alum
Tertiary Low Lime
Conditioning
5% FeCl3, 10% Lime
100% Ash
10% Lime
None
5% FeCl3f 10% lime
150% Ash
5% FeCl3, 10% Lime
10% Lime
7.5% FeCl3, 15% Lime
250% Ash
5% FeCl3r 10% Lime
6% FeCl3, 30% Lime
5% FeCl3, 10% Lime
100% Ash
5% FeCl3, 10% Lime
10% Lime
None
Feed
solids, %
5
4*
7.5
8*
8*
3.5*
5*
5*
8
6-8*
6-8*
4*
8*
Typical
cycle
length, hr
2
1.5
4
1.5
2.5
2.0
3
4
2.5
2.0
3.5
2
2
1.5
3
6
1.5
% solids
filter cake
solids, %
45
50
40
50
45
50
45
40
45
50
45
40
45
50
40
35
55

* Thickening used to achieve this solids concentration
                                     34-2

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 Maintenance Considerations

     The features of a good maintenance program are:

      1.  A thorough semi-annual inspection of all equipment including the
          following.

          a)  Drive and gear reducers
          b)  Drive chains and sprockets
          c)  Closing mechanism
          d).  Bearing brackets
          e)  Electrical contacts in starters and relays

      2.  Filter  cloths or media washed in place.

      3.  Rubber  surfaces of the plates scraped only with  soft plastic or  wood
          to  avoid damage.

      4.  Spare part inventory should  contain the  following:   drives and gear
          reducers,  drive chains,  sprockets,  closing mechanism,  bearing
          brackets,  and electrical contacts.

Records

    Recommended  sampling and  laboratory tests are  shown in Figure  34-1.

    Other operating  records should  include:

      1.   Influent  sludge flow
      2.  Volume of  sludge  cake produced
      3.  Frequency  and  duration of operation

Laboratory Equipment

    The laboratory  should  include the  following minimum equipment  in  order to
monitor vacuum filtration:

      1.  Analytical balance
      2.  Clinical centrifuge with graduated  tubes
      3.  BOD incubator
      4.  Drying oven

    The EPA report  "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed  information on glassware, chemi-
cals,  miscellaneous furniture, etc., and should be referred to  for any de-
tailed questions.
                                     34-3

-------
o
u
8

0.
o

TOTAL SOLIDS
BOO
SUSPENDED
SOT.TDR
PLOW


















UJ
N
M
ll
ALL
ALL
AT.T
ALL


















TEST
FREQUENCY
VD
2/W
1/n
R


















LOCATION OF I
SAMPLE
S
C
P
P
P


















METHOD OF
SAMPLE
G
G
r:
R


















REASON
FOR TEST
P
P1
p
P1


















                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS
                                                   SLUDGE CONCENTRATION
                                                             PRESSURE FILTRATION
                                                                                       FILTRATE
                                                                                       RECYCLE TO
                                                                                       PLANT INFLUENT
                                                  A. TEST FREQUENCY
                                                       H * HOUR
                                                       0  DAY
                                                       W- WEEK
                  M - MONTH
                  R - RECORD CONTINUOUSLY
                  Mn- MONITOR CONTINUOUSLY
                                                  B. LOCATION OF SAMPLE

                                                       S= SLUDGE FEED
                                                       C= SLUDGE CAKE
                                                       F= FILTRATE
C. METHOD OF SAMPLE
     24C*24 HOUR COMPOSITE
     G- GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     MB- MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:

    1. FOR CONTROL OF PROCESS RECEIVING THIS FLOW.
                                                  Figure 34-1
                                               34-4

-------
Sampling Procedures

    Sampling should be performed as outlined under Records. These  samples may
be obtained through valves provided in the  respective piping or directly from
the process.  If sampling points are not provided, they  should be  installed  to
facilitate operation and control of the process.

    The sample collector and container should be clean.  Samples should be
analyzed according to procedures specified  in Standard Methods.

Sidestreams

    The only sidestream is the filtrate, which  is the liquid removed  from the
sludge during dewater ing.  Filtrate quality should be very good (less  than 100
mg/1 suspended solids)  if the system is properly operated.  During  the early
part of the cycle, the drainage from* a large press can be in the order of
2,000 to 3,000 gallons per hour.  This rate falls rapidly to about  500 gallons
per hour as the cake forms and at the end of the cycle the rate is  virtually
zero.  Filtrate is normally returned to the plant treatment process.
                                     34-5

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Process Checklist - Pressure Filtration
 1.
 2.
 3.
 4.
 5.
 6.
 7.
 8.
 9.
10.

11.
12.
13.

14.
15.
16.
17.
18.

19.

20.

21.
22.
23.
24.
    What is the volume of the influent sludge flow 	
    What is the percent solids of the influent sludge
    What is the filter press volume 	
                                                            gal/day avg.
                                                    cu ft?
    What is the percent solids in the discharge cake
    Are there settleable solids in the filtrate 	
    How often does pressure filter run 	
                                                          min/hr?
    Frequency of maintenance inspections by plant personnel 	
    Is maintenance program adequate?  (  )  Yes  (  )  Ho
    Frequency of maintenance inspections for chemical feed system	
    If acid washing is provided, is a recirculating system included?
    (  )  Yes  (  )  No
    What type of conditioning chemicals are used 	?
    What amount of conditioning chemicals are pumped _	Ib/day?
    Are proper safety precautions used in handling these chemicals?
    (  )  Yes  (  )  No
    Is sludge pumping (  )  manual  (  )   automatic?
    Is chemical feed (  )   manual  (  )   automatic?
    How often do sludge pumps run	minutes/hr?
    How often does conditioning equipment run 	minutes/hr?
    If multiple units are used, is the flow distributed evenly?
    (  )  Yes  (  )  No
    Does the unit show signs of short circuiting and/or  overloads?
    (  }  Yes  (  )  No
    Is there an alarm system for equipment failures or overloads?
    (  )  Yes  (  )  No
    Does the sampling program meet the recommendations? (  )   Yes  (
    Are operating records adequate? (  )   Yes  (  )   No
    Is the laboratory equipped for the necessary analyses? (   )  Yes
    What spare parts are stocked?	
                                                                    yyr?
                                                                       /yr?
                                                                  )   No

                                                                  (   )   No
25.
What are the most common problems the operator has had with the process?
                                     34-6

-------
References

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No.  11, Water Pollution Control Federation (1976).

 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328 (June, 1973).

 4. Wirts, J.J.,  et al, Safety in Wastewater Works,  Manual of Practice No.  1,
    Water Pollution Control Federation (1959).

 5. State of Virginia O&M inspection form.

 6. Harrison, J.R., Goodson, J.B., and Gulp, G.L., Process Design Manual for
    Sludge Treatment and Disposal, USEPA,  625/1-74-006.

 7. Ettlich, W.F., et al.  Operations Manual - Sludge Handling and
    Conditioning,  US EPA Report 430/9-78-002.
                                     34-7

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-------
 35.   DRYING BEDS                ;

 Process Description

     Drying  beds are generally used for  dewatering of well digested sludges.
 Attempts to air dry raw sludge usually  results in odor problems.

     Sludge  drying  beds consist of perforated or open joint drainage pipe laid
 within a gravel base.   The  gravel is covered with a layer of sand.  Partitions
 around and  between the drying beds may  be of concrete, wood or earthen embank-
 ment.   Drying beds are generally open to the weather but may be covered with
 ventilated  green-house type enclosures  in wet climates.

     Sand beds allow water  to drain from the  sludge mass  through the supporting
 sand to the drainage piping.   As the sludge  dries, cracks develop in the sur-
 face allowing natural  exaporation to occur from the lower layers.  This speeds
 the  drying  process.

 Typical Design  Considerations

     The most important loading factor is the solids loading rate  to the drying
 bed.   Solids loading rate  is the weight of solids on a dry weight basis ap-
 plied  yearly per square  foot of drying  bed area.   As an  example,  assume that
 10 inches of 5  percent solids anaerobically  digested sludge is applied to a
 drying  bed  five times  per year.   The weight  of solids will be calculated for
 one  square  foot of bed.
Solids Loading Rate "=
     dry weight of solids
            year

     cubic feed of sludge    Ibs
      square feet of bed
                                         square  feet of
                                           drying bed
                                        % solids
                                          100
Number of
applications
         1 x 1 x 10
         	12      62.4 Ibs       5        (5)
         sq ft of bed      ft^         ioo

         13 Ibs	
            year-sq ft

    Drying beds are usually sized based upon required square  feet of bed area
per capita (or per person) served by the treatment plant.  The area required
for drying beds depends on climate but typical criteria are given below for
several types of digested sludge and for whether the drying beds are open or
covered.
                                     35-1

-------
                                          Open beds
                                                     Covered beds
Bed sizing, sq ft/capita from WPCF, 1959:
    Primary digested sludge              1.0 - 1.5
    Primary and humus
      digested sludge                    1.25 - 1.75
    Primary and activated
      digested sludge                    1.75 - 2.5
    Primary and chemically
      precipitated digested sludge       2.0 - 2.5
                                                    0.75 - 1.0

                                                    1.0 - 1.25

                                                    1.25 - 1.5

                                                    1.25 - 1.5
    The population which can be adequately served by a set of existing drying
beds can be calculated, as shown in the following example.
    1.
    2.
Determine drying bed shape and dimensions.  The plant construction
drawings and specifications include this information.
Shape                        =  8 rectangular beds
Dimensions, each bed         =  20 ft x 40 ft
Single bed area  = 20 x 40   =  800 sq ft
Total Area  =  8 x 800       =  6,400 sq ft

Determine area required per capita.
Sludge type                  *  Digested primary and waste activated
Bed type                     =  Open beds
Area per capita              =  1.75 - 2.5 sq ft/capita
(from above summary)
Use 2.0 sq ft/capita
    3.
Calculate population which can be served.
Total Bed Area, Sq ft	  -  6,400
                                                     3,200 persons
         Area per capita, sq ft/capita

Typical Performance Evaluation
                                  2.0
    The performance of sludge drying beds is different from one location to
the next.  Sludge drying bed performance is affected by weather, sludge
characteristics, system design  (including depth of fill), chemical condition-
ing, and drying time.  Typical performance in terms of solids loading rate and
moisture content of dried sludge are as follows for open and covered beds.
    Solids Loading Rate,
      Ib/yr/sq ft

    Moisture content of dried
      sludge, percent

Process Control
                             Open beds

                             up to 25


                             50 - 60
Covered beds

up to 40


50 - 60
    Process control practices are described in detail  in Reference 4.
                                     35-2

-------
Maintenance Considerations

    The features of a good maintenance program are:

     1.  Drying beds inspected every few days with particular attention given
         to potential odor and insect problems.

     2.  Beds levelled and raked prior to each sludge application.

     3.  Sand depth checked regularly for losses of sand during sludge removal
         from beds.

     4.  Makeup sand added when sand depth decreases to 3 or 4 inches.

     5.  Weed growth on beds controlled by use of weed killer or hand pulling.

     6.  Fly control by destruction of breeding and use of traps and poisons.

     7.  Drainage system inspected and maintained on a routine basis.

     8.  Sludge lines drained after use in winter to prevent freezing.

     9.  If earth beds are used, grass and other vegetation cut regularly.

    10.  Stop logs kept well maintained to minimize leakage from vehicular
         access cutouts in drying bed walls.

Records

    Recommended sampling and laboratory tests are shown on Figure 35-1.

    Other operating records should include:

    1.   Time and date sludge is applied to each drying bed.
    2.   Number of days before sludge is dry enough for removal.
    3.   Volume of sludge removed from beds.
    4.   Date makeup sand is required for each bed and quantity of makeup
         required.

Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor sludge drying beds:

    1.   Analytical balance
    2.   Clinical centrifuge with graduated tubes
    3.   BOD incubator
    4.   Drying oven
    5.   Imhoff Cones
                                     35-3

-------
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TOTAL SOLIDS
BOD
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TEST
FREQUENCY
W
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LOCATION OF
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METHOD OF
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H
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                                                   ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS
                                                    DRYING BEDS
                                                                                 DEWATERED SLUDGE
                                                                                  TO DISPOSAL
                                                  INFLUENT
                                                  SLUDGE
                                                                              DRAINAGE
                                                                                WATER
                                                   A.  TEST FREQUENCY
                                                       H, HOUR     M- MONTH
                                                       D - DAY       R - RECORD CONTINUOUSLY
                                                       W- WEEK     Mn- MONITOR CONTINUOUSLY

                                                  B.  LOCATION OF SAMPLE

                                                       I = INFLUENT SLUDGE
                                                       D= DEWATERED SLUDGE
                                                       Dr- DRAINAGE WATER
C. METHOD OF SAMPLE
     24C24 HOUR COMPOSITE
     G- GRAB SAMPLE
     R - RECORD CONTINUOUSLY
     MB- MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:
                                                 Figure 35-1

                                               35-4

-------
    The EPA report "Estimating Laboratory Heeds for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, miscellaneous furniture, etc., and should be referred to for any de-
tailed questions.

Sampling Procedures

    Samples of the influent sludge may be obtained through valves provided in
the sludge lines.  Samples of the dried sludge cake can be obtained directly
from the drying bed.  Samples of the drainage water should be collected from
valves in the drain lines or at the recycle pumping station.  The sample col-
lector and containers should be clean.  A wide mouth sample collector of at
least 2 inches should be used.

Sidestrearns

    The only sidestream is the drainage water.   This water is normally re-
turned to the raw sewage flow to the plant or to the plant headworks.

    The flow from the drainage piping consists primarily of the initial perco-
lation of water from the sludge plus some periodic percolation after rain
storms (assuming open beds).
                                     35-5

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Process Checklist-Drying Beds
1. What are the dimensions of the drying beds?

2.

3.

4.
    How many separate drying bed compartments are there?
    Are the sludges digested before they are applied to the drying bed?
    (   )   Yes  (  }  No
    What type of sludges are applied to the drying beds (digested primary,
    waste activated,  combination, etc. ) _                       ?
  5.
  6.

  7.
  8.
  9.
 10.
 11.
 12.
 13.
 14.
 15.
 16.

17.
18.

19.

20.

21.
    What is the volume of sludge flow applied to the drying beds
    _ gallons/day average?
    What is the design sludge flow _ _ gallons/day average?
    What is the solids concentration in the sludge applied to the drying
    beds? _ %
    What is the solids loading rate _____ _ ^^^ Ibs/yr/sq ft?
    What is the population served by the treatment plant? _
    What is the drying area provided,  based on sq ft/capita? _
    What is the solids concentration in the de watered sludge? _
    What is the typical drying time required?
    Are  there  odor problems?
                                                               days
                             (   )   Yes  (   )   No
   Are- there problems with flies or other  insects?  (  )   Yes  (  )   No-
   Are there problems with weed growth?  (  )   Yes  {  )   No
   Is there an underdrain system?  (  ) Yes  (  )   He-
   Are there provisions for the return of  drainage waters to the plant?
   {   )   Yes  (  )   No
   What is  the typical sand depth? 	 inches
   Are there any beds with sand depths less than 3 or 4 inches?
   (   )   Yes  (  )   No
   Are vehicles and equipment operated on  permanent vehicle treadways or  on
   planks or plywood laid on top of the beds?   (  )   Yes   (  )   No
   Are splash plates or diffusion devices  in place when sludge is applied to
   the beds?   (  )   Yes  (   )   No
   Are partitions between and around the bed tight so that sludge will not
   flow from one  compartment to another nor outside the beds?
   {   )   Yes  (  )   No
                                    35-6

-------
References'

 1. Gulp, G.L., and Folks Heim, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al,  Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control. Federation  (1976).

 3. State of Virginia O&M inspection form.
 4. Ettlich, W.F., et al, Operations Manual - Sludge Handling and
    Conditioning, US EPA Report 430/9-78-002.
                                     35-7

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36.  DRYING LAGOONS
Process Description

    Sludge lagoons are similar to sand beds in that sludge  is periodically
drawn from a digester, placed in the lagoon, removed after  a period of drying,
and the cycle repeated.  Drying lagoons do not have an underdrain system.
Most of the drying is by decanting supernatant liquor and by evaporation.
Plastic or rubber fabrics may be used as a bottom lining, or they may be natu-
ral earth basins.  Supernatant liquor and rainwater drain off points are usu-
ally provided, with the drain off liquid returned to the plant for further
processing.

Typical Design Considerations

    The loading rate to the lagoon is expressed as pounds of dry solids ap-
plied per year per cubic foot of lagoon capacity.  This is calculated as
follows:

    1.   Determine lagoon volume.   The plant construction drawings may contain
         this information or it may be possible to simply measure the lagoons.
         Length                    100 ft
                                  - 25 ft
                                  =  2 ft
                                  - 2
                                   Length x Width x Depth x Number of lagoons
                                   100 x 25 x 2  x 2
                                  - 10,000 cu ft
         Determine sludge flow to  lagoon from plant records.
     Width
     Depth
     Number of lagoons
     Total volume
         Daily flow
         Yearly flow
                              a 150 gal/day
                              * Daily flow x 365  (or weekly flow x 52)
                              - 55,000 gal/yr
3.   Determine sludge solids concentration
     Concentration             Weight of dry sludge
                                Weight of wet sludge
                              - 0.5 Ib  - 0.05 Ib    0.05
                                           10 Ib
4.   Determine weight of sludge applied to lagoon per year.
     Weight                   - yearly flow x concentration x 8.34
                              - 55,000 x 0.05 x 8.34
                              - 23,000 Ib/yr
5.   Calculate solids loading rate.
     Solids loading rate      - Weight of sludge applied per year
                                        Volume of lagoon
                              - 23,000 Ib/vr
                              - 10,000 cu ft
                              - 2.3 Ib/yr/cu ft
Typical design criteria are 2.2-2.4 Ib/yr/cu ft of lagoon capacity.
                                     36-1

-------
  Typical Performance Evaluations

      Drying  time  for sludge applied  to  a  depth  of 15  inches  or  less  is  3  to 5
  months.   This  figure is  highly  dependent on  weather  conditions.   The sludge  is
  usually dried  to 40 to 60  percent solids.

  Process  Control

      Sludge  depth should  not exceed  15  inches after excess supernatant  has been
  drawn off.  Unless  the lagoon is situated in an  arid climate,  depths of  over
  15 inches will require excessive drying  time.

      The operator  should promptly remove  supernatant liquor and rainwater so
  that the sludge  cake is  exposed to oxygen in the air and can dry  rapidly.
 Supernatant is normally  returned to the main plant treatment processes.

     Sludge will generally not dewater in any reasonable period of time.  Dried
 sludge may be removed with a front-end loader in 3 to 5 months.  When sludge
 is to be used for soil conditioning, it may be stored for added drying before
 use.   One operational approach uses a 3-year cycle in which the lagoon is
 loaded for 1 year, dries for 18 months, is cleaned,  and allowed to rest for 6
 months.

 Maintenance Considerations

    The  features  of a good maintenance program are:
     1.
     2.
     3.
     4.
     5.
     6.
Records
Broken dikes  repaired as  required.
Excess water  from rain or snow decanted  to  facilitate drying.
Weeds kept to a minimum.
Lagoons checked for odor  and  insect problems.
Lagoons leveled and weeds removed prior  to  each sludge application.
Sludge application lines and  valves regularly inspected and
maintained.
Sludge lines drainedto prevent breakage from freezing in winter.
    Monitoring of sludge  lagoons generally consists of visual  inspection by
the plant operator.  However,  records may be kept on  the sludge  loading,  per-
cent solids, quantity, depth,  date, drying time and weather conditions.   This
will provide the operator with the  information necessary to determine  the
optimal time of sludge removal from the  lagoon by comparing sludge moisture
content with time of drying for particular climatic'conditions.

Laboratory Equipment

   ,The laboratory should include the following equipment as a minimum to mon-
itor sludge drying lagoons.

    1.   Analytical balance
    2.   Drying oven
                                     36-2

-------
Sampling Procedures

    Samples of the influent sludge may be obtained through valves provided in
the sludge lines or directed from the lagoon.  Samples of dried sludge can be
obtained directly from the lagoon.  Samples of supernatant can be collected
from valves in the draw-off lines.  The sample collector and containers should
be clean.  A wide mouth sample collector of at least 2 inches should be used.

Sidestrearns

    The only sidestream is the supernatant or rainwater draw-off.  This water
is normally returned to the raw sewage flow for further processing.
                                      36-3

-------
Processing Checklist - Drying Lagoon

 1. What are the dimensions of the lagoon
    are there              ?
              _
    What is the volume of sludge applied to the lagoons
    What type of sludge is applied                  ?
    What is the design sludge application rate
    What is the solids loading rate
 2.
 3.
 4.
 5.                          _      	
 6. What is the typical drying time required
 7.
 8.
 9.
10.
                                                               How many  lagoons

                                                              	gal/day avg.
                                                 _
                                                 Ib/yr/cu ft?
                                                      months?
                                                             _gal/day avg.
                                             _
    What is the solids concentration in the dried sludge
    Are insects a problem?  (   )  Yes (   )   No
    Is weed growth a problem?   {   )   Yes  (  )   No
                                                                    %?
11.
12.
13.
14.
15.
    Are  partitions between and around the lagoons tight so that sludge will
    not  flow from one compartment to another?  (   )   Yes  (  )   No
    Are  there provisions for  supernatant draw-off?  (  )   Yes  (  )   No
    Are  there signs of overload?   (   )   Yes  (   )  No
    Does the sampling program meet the recommendations?  (  )   Yes  (  )   No
    Is the  laboratory equipped for the necessary  analyses?  (   )   Yes  (   )
    What are the  most common  problems the operator has had with the  process?
                                                                             No
                                    36-4

-------
References

 1. Gulp, G.t,., and Folks Helm, N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US EPA
    Report 430/9-78-001 (Jan. 1978).

 2. Guarino, C.F., et al, Operation of Wastewater Treatment Plants, Manual of
    Practice No. 11, Water Pollution Control Federation  (1976).
 3. CH2M-Hill, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328  (June, 1973).
 4. Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation (1959).
                                      36-5

-------

-------
37.  INCINERATION - MULTIPLE HEARTH

    A multiple hearth furnace consists of a circular steel shell surrounding a
number of solid refractory hearths and a central rotating shaft to which rab-
ble arms are attached.  The dewatered sludge enters at the top through a
flapgate and proceeds downward through the furnace from hearth to hearth,
moved by the rotary action of the rabble arms.  The hearths are constructed of
high heat duty fire brick and special fire brick shapes.  Since the furnace
may operate at temperatures up to 2,000F, the central shaft and rabble arms
are cooled by air supplied from a blower.  The hot air may be discharged to
atmosphere or returned to the bottom hearth of the furnace as preheated air
for combustion purposes.

    Periodically the ash produced by incineration must be removed from the
furnace.  There are two options for handling ash from the furnace.  One  is  to
provide a storage hopper and unload dry ash to trucks.  The other is  to add
water and handle ash as a slurry with the slurry being pumped to a  lagoon.

Typical Design Considerations

    Loading rates for several types of sludge are shown  in Table 37-1.

Solids/
Type of sludge %
1. Primary
2.
3.
4.
5.

6.

7.
8.
9.
Primary + FeCl.
Primary + low lime
Primary + WAS
Primary + (WAS +
FeCl3)
(Primary + Fed,
+ WAS
WAS
WAS + FeCl3
Digested primary
30
IS
35
16

20

16
16
16
30
Volatile Chemical
solids, concentration,*
% mg/1
60
47
45
69

54

53
80
50
43
N/A
20
298
N/A

20

20
N/A
20
N/A
Typical wet sludge
loading rate,**
Ib/hr/sq ft
7
6
8
6

6

6
6
6
7
.0-12.0
.0-10.0
.0-12.0
.0-10.0

.5-11.0

.0-10.0
.0-10.0
.0-10.0
.0-12.0

  * Assumes no dewatering chemicals.
 ** Low number is applicable to small plants, high number is applicable to large

    plants.
    The data in this table developed from manufacturers' information.
                                      37-1

-------
    The following sample calculations are examples of process control
equations.

    1.   Excess Air is the amount of air required beyond the theoretical air
         requirements for complete combustion.   This parameter is expressed as
         a percentage of the theoretical air required.
         Sample calculation for excess air:
              excess air = (actual air rate-theoretical rate)  x 100
                                 theoretical air rate
                         = (1,500 - 1,000) x 100
                                1,000
                         = 50%

    2-    Sludge loading  rate  is the weight of wet sludge  fed  to the reactor
         per  square  foot of reactor bed  area per  hour  (Ib/sq  ft/hr).
         Sample calculation for loading  rate:
              loading  rate =   Ib sludqe/hr           100
                                   TT/^2
                                             % moisture content
                                 440
                      	   100
                      3.14 (20)2    20
                          4
                    -  7.01 Ib/sq ft/hr

Solids  concentration is  the weight of solids per  unit  weight of
sludge.   It  is calculated aa follows:
concentration  =  weight of dry sludge solids x 100
                         weight  of wet sludge
               =  25 x 100
                     120
               =  20.8%

Moisture content is  the  amount  of  water per unit weight of sludge
The moisture content is  expressed  as a percentage of the total weight
of the wet sludge.   This parameter  is equal to 100 minus the percent
solids concentration  or  can be  computed as follows:
moisture content =  (weight of wet  solids - weight of dry solids) x 100
                                weight of wet solids
                 =   (120 - 25) x 100
                                  120
                            79.2%
                                   37-2

-------
 Typical Performance Evaluation

     Trie volume reduction by sludge incineration is  over  90  percent when  com-
 pared to the volume of  dewatered  sludge.   The  ash  from the  incineration  proc-
 ess  is free of pesticides,  viruses and  pathogens.   Metals will be converted  to
 the  less soluble  oxide  form or volatilized.  The ash  can be transported  in the
 dry  state  to appropriate landfill sites or used as  a  soil conditioner.

     The critical  sidestream treatment requirement  is  the flue gas treatment.
 The  scrubbed gases  should meet the most stringent air quality requirements.  A
 comparison of scrubbed  gas  quality with Southern California Air Pollution Con-
 trol District Rules is  shown  in Table 37-2.

       TABLE 37-2.   STACK SAMPLING RESULTS, MULTIPLE HEARTH  INCINERATOR
                    WITH COMBINATION LIME-ORGANIC SOLIDS  PEED

Test A Test B Test C SCAPCD rules
Combustion contaminants,
grains/SCFM at 12% CO2
Oxides of sulfur:
(as SO2), ppm
Oxides of nitrogen
(as ND2), ppm
.026 .016 .014 0.1
(Rule 473)
2.2 2.3 3.2 2000
(Rule 53)
52 65 - 300
(Rule 474)

Tests made at South Lake Tahoe Public Utility District, CA, on November  10,
1970.

Process Control

    Process control furnaces can be complex.  A complete discussion  is given
in Reference 3.

Maintenance Management

    A good preventive maintenance program will reduce breakdowns which could
be costly and dangerous for operating personnel.  A good preventative mainte-
nance program is very important for an incinerator because of the large  drives
and the need to minimize incinerator shutdowns.  The following are the major
elements which should receive regular attention.

     1.  Drives and gear reducers
     2.  Chains and sprockets
     3.  Burners
     4.  Air blowers
     5.  Sludge conveying equipment
     6.  Ash conveying equipment
                                     37-3

-------
      7.
      8.
      9.
     10.
     11.

 Records
Furnace seals
Draft controller
Temperature controllers
Any standby engine drives or generators
Scrubber
    Records  keeping  includes  the process  control  tests  shown  in  Figure  37-1
 and historical  data.   Historical data  include  the tons  of sludge incinerated
 each year/ the  fuel  consumed,  and  maintenance  records.  Maintenance  records
 are extremely important  since  equipment lives  with multiple hearth furnaces
 are accurately  predictable.  Knowing  the  last  date of equipment  replacement
 the operator can predict the next  time that  furnace will need  to be  shut down
 for equipment overhaul or  replacement.

 Laboratory Equipment

    Testing equipment  for  incineration monitoring  is quite simple.  Most con-
 tinuous monitoring is  accomplished by automatic equipment which  is part of the
 total system.  Additional  equipment items include a drying oven  and balance
 scales to determine solids contents.

Sampling Procedures

    Sampling for many parameters is automatic.  Sludge volatile  solids and
moisture contents o material  fed  to the  incinerator require a simple drawing
off of sludge from the feed line or from  the proceeding unit process (storage
or dewatering).   There are no  special sample preservation measures to be taken
other than capping the sample  to prevent a change in moisture content.
                                     37-4

-------
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TEMPERATURE
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TOTAL SOLIDS



















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TEST
FREQUENCY
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LOCATION OF
SAMPLE
A
F
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F
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-1
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                                                  ESTIMATED UNIT PROCESS SAMPLING AND

                                                             TESTING NEEDS
                                                   INCINERATION


                                                             (MULTIPLE HEARTH)



                                                   FEED    
                                                                             ^ ^HEARTHS
                                                                                        PRODUCT
                                                    A.  TEST FREQUENCY

                                                        H => HQUR     M  MONTH
                                                        0- DAY      R -. RECORD CONTINUOUSLY

                                                        W- WEEK     Mn" MONITOR CONTINUOUSLY


                                                    B.  LOCATION OF SAMPLE


                                                        F = FEED
                                                        f = PRODUCT
                                                        A = FURNACE ATMOSPHERE
                                                            (AT EACH HEARTH)
C. METHOD OF SAMPLE

    24C-24  HOUR COMPOSITE

    G " GRAB SAMPLE

    R - RECORD CONTINUOUSLY

    Mn MONITOR CONTINUOUSLY


D. REASON  FOR  TEST

    H - HISTORICAL KNOWLEDGE

    P m PROCESS CONTROL

    C - COST CONTROL


E. FOOTNOTES:

      1. WHEN FURNACE IS OPERATING
                                                    Figure 37-1



                                                 37-5

-------
Process Checklist - Multiple Hearth

 1. Are complete records kept on the following items?
4.
5,
6.
    a
    b.
    c.
    d.
    e.
    f.
    g.
      Hearth temperatures (each shift)   (   )   yes  (   )   NO
      Maintenance work  accomplished  (   )   Yes  (  )   No
      Schedule of upcoming  maintenance   (   )   Yes  (   )   No
      Fuel  consumption  (daily)   (   )  yes   (   )   NO
      Power consumption (daily)   (   )   yes  (   )  No
      Sludge moisture content  (each shift)   (   )  yes   (   )   No
      Sludge volatile solids content (daily)   (   )  yes   (   )   NO
Does  operator  have a planned procedure  for slowly  shutting  down the
process?   (  )   Yes  (   )  NO
Is there a plan  for emergency operation for:
a.   Power  outage?  (  )  Yes   (   )  NO
b.   Fuel  shortage?  (   )  Yes  (   )  NO
c.   Other  accidents?  (  )  Yes   (  )  NO
Is scum burned in the incinerator?   (  )  Yes  (   )  No
If scum is burned, is the feed rate regulated?   (  )   Yes   (   )  No
Is moisture content optimized for minimum total cost of dewatering and
fuel consumption in incinerator?   (  )   yes   (  )  No
                                   37-6

-------
References

1.  Standard Methods for the Examination of Water and Wastewater.  American
    Public Health Association, 14th Edition 1975, Washington, D.C. 20036.

2.  Unterberg, W., et al, Computerized Design and Cost Estimation for Multiple
    Hearth Sludge Incinerators US EPA, 17070 EBP 07/71.

 3. Ettlich, W.F. et al, Operations Manual Sludge Handling and Conditioning,
    U.S. EPA, Office of Water Program Operations, Washington, D.C.,
    430/9-78-002, February 1978.
                                     37-7

-------

-------
38.  INCINERATION - FLUIDIZED BED

    The fluidized bed incinerator is a vertical cylindrical  vessel with a
grid in the lower section to support a sand 6ed.  Dewatered sludge is injected
above the grid and combustion air flows upward to fluidize the mixture of hot
sand and sludge.  Supplemental fuel can be supplied by burners above or below
the grid.  In essence, the reactor is a single chamber unit were both moisture
evaporation and combustion occur.  Ash is carried out the top with combustion
exhaust and is removed by air pollution control devices.  A fluidized bed in-
cinerator does not need to be operated continuously since the sand bed stores
heat, thus reducing furnace reheating requirements.

Typical Design Considerations

    Typical loading rates for various types of sludge are shown on Table
38-1.  The loading rates are a function of the moisture content of the feed
sludge.

                     TABLE 38-1 LOADING RATES

Solids,
Type of sludge %
1.
2.
3.
4.
5.
6.
7.
8.
9.
Pr imary
Primary + FeCl_
Primary + low lime
Primary + WAS
Primary + (WAS +
PeCl3)
(Primary + FeCl
+ WAS
WAS
WAS + FeCl-
Digested primary
30
16
35
16
20
16
16
16
30
Volatile
solids,
%
60
47
45
69
54
53
80
50
43
Chemical
concentration,*
mg/1
N/A
20
298
N/A
20
20
N/A
20
N/A
Wet sludge
loading rate,
Ib/hr/sq ft
14
6.8
18
6.8
8.4
6.8
6.8
6.8
14

 * Assumes no dewatering chemicals.
                                      38-1

-------
 The following are sample design calculations.
 1.
3.
 Excess air  is  the amount of air  required beyond  the  theoretical air
 requirements for complete combustion.  This parameter  is expressed as
 a percentage of the  theoretical  air required.
 Sample calculation for excess air: Assume 1,200  SCFM actual, and
 1,000 SCFM  theoretical
           Excess  air
                    (actual air rate-theoretical rate) x
                       theoretical air rate
                    (1,200 - 1,000) x 100  =
                                                             100
                                                  20%
                             1,000
 Sludge loading rate is the weight of wet sludge fed to the reactor
 per square foot of reactor bed area per hour (Ib/sq ftAr).
 Sample loading rate: Assume 20 foot diameter reactor, 20 percent feed
 sludge moisture content and 440 pounds dry sludge per hour
      Loading rate  =    (Ib dry sludge/hr)  (100)
                       (% moisture content)  (area)
                    -    440 x 100
                      20% x 3.14 (20)2
                              4.
                    -  7.01 Ib/sq ft/hr

 Solids concentration is  the weight of solids  per  unit weight of
 sludge.   It is calculated  as follows:
 Assume 120  Ib  wet sludge with 25  Ib of dry  solids.
 Concentration   =   weight of dry sludge solids- x 100
                         weight of  wet  sludge
                -   25 x 100
                     120
                -   20.8%

Moisture  content  is  the  amount of  water per unit weight of sludge.
The moisture content is  expressed  as a percentage of  the  total  weight
of the wet  sludge.  This parameter  is  equal to 100 minus  the percent
solids concentration or can be computed as follows:
Same assumptions  as paragraph  3.
moisture content  =   (weight of wet solids)-(weight of dry  solids x 100
                                weight of wet solids
                 =   (120 - 25) x 100
                               120
                         79.2%
                                38-2

-------
Performance

    The measure of furnace performance is the stack gas quality.  The gas
quality is measured in terms of particulates, metals, gaseous pollutants, and
organic compounds.  The scrubber is designed to remove particulates with the
ash.  Most metals appear as oxides in the particulates removed by the scrub-
ber.  Lead and mercury vaporize and will appear in the stack gas.  Carbon
monoxide in the stack gas is a sign of improper design or operation.

Process Control

    The fluid bed furnace is furnished with a semi-automatic process control
system and a mechanical/electrical protection system, which free the operator
from continuous supervision.  The process is maintained in balance at the re-
quired excess air and operating temperatures by normal adjustments in air rate
and sludge feed rate, and automatic control of auxiliary fuel rate.  The proc-
ess parameters and physical conditions are kept in check by means of a multi-
point alarm system which warns the operator of impending imbalances in the
process or mechanical equipment.

    A variety of process controls are described in Reference 4.

Maintenance Considerations

    Sand from the reactor bed is gradually lost through the exhuast as indi-
vidual sand particles are gradually worn into finer and finer particles.  When
it has been determined that the bed level is getting low, proceed as follows:

    1.   Bed temperature should be at least 1,400F before any  sand is added
         to the reactor bed.  This is to avoid cooling the bed  below
         1,150P, and being forced to light the preheat burner.
         Be sure that the fluidizing blower  is completely  stopped.
    3.
    4.
Remove the blind flange on the sand feed nozzle.
chute.
Attach sand feed
Add sand in 10 bag batches.  If more than 10-100 Ib bags are re-
quired, replace the blind flange on the same feed nozzle and reheat
the bed to 1,400F before adding second 10 bag batch.
    There may be slight leakage of sand down  into  the windbox.  About  once  a
month  (when the reactor is not operating), open  the windbox  manhole  and  rake
out any accumulation.

    Occasionally a carbon deposit may  form near  the tip of  the  fuel  burner.
If this happens, fuel  flow to the bed  will be restricted.  When the  reactor  is
shutdown, clean the burner.  If available, a  slight flow of  compressed air
will aid inserting the gun back in the bed.
                                      38-3

-------
     From time to time,  check that the nut on the packing gland is  just tight
 enough to prevent loss  of cooling air.

     At times this pressure tap pipe may become partially plugged.   Refer  to
 manufacturer's manual for cleaning instructions.

     Keep gasketed surfaces on the reactor tight to avoid a fly ash nuisance.

 Records

     Records keeping includes the process control tests as well as  historical
 data and maintenance records.

     The analyses required for  furnace monitoring  and  their frequency  are  shown
 on Table 38-2 for each  monitoring point identified on Figure  38-1.

 	        TABLE 38-2.   MONITORING
Monitoring point
    Analysis
Frequency
        1
        2
        3
        3
        4
        5
        5
        5
        5
        5
        5
        5
        5
        6
        6
        7
        7
Solids content
Solids content
Solids content
Volatile solids
Fuel quantity
Oxygen content
Particulate concentration
Carbon monoxide
Lead
Mercury
Hydrogen chloride
Sulfur dioxide
Oxides of nitrogen
BOD5
Suspended solids
Metals content
Moisture content
Weekly
Weekly
Weekly
Weekly
Continuous
Continuous
Weekly
Monthly
Semiannual
Semiannual
Semiannual
Semiannual
Semiannual
Weekly
Weekly
Semiannual*
Weekly
* If ash used for soil conditioner.
Laboratory Equipment

    Testing equipment for incineration monitoring is quite simple.  Most con-
tinuous monitoring is accomplished by automatic equipment which is part of the
total system.  Additional equipment items include a drying oven and balance
scales to determine solids contents.
                                     38-4

-------








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Sampling Procedures

    Sampling for many parameters is automatic.  Sludge volatile solids and
moisture contents of material fed to the incinerator require a simple drawing
off of sludge from the feed line or from the preceeding unit process (storage
or dewatering).  There are no special sample preservation measures to be taken
other than capping the sample to prevent a change in moisture content.
                                    38-6

-------
Process Checklist - Multiple Hearth and Fluidized Bed Furnaces

 1. Are complete records kept on the following items?
    a.    Temperature (each shift)   (  )   Yes
    b.    Maintenance work accomplished  (  )
    c.    Schedule of upcoming maintenance  (
    d.    Fuel consumption (daily)   (  )   Yes
    e.    Power consumption (daily)   (  )   Yes
    f.    Sludge moisture content (each shift)
    g.    Sludge volatile solids content (daily)
 2. Does operator have a planned procedure for slowly shutting down the
    process?  (  )   Yes  (  )  No
 3. Is  there a plan for emergency operation for:
    a.    Power outage?  (  )   Yes  (  )   No
    b.    Fuel shortage?  (  )  Yes  (  )   No
    c.    Other accidents?  (   )   Yes  (   )   No
    Is  scum burned in the incinerator?  (  )   Yes  (   )   No
    If  scum is burned/  is the feed rate  regulated?  (  )   Yes  (  )   No
( ) No
Yes ( ) No
) Yes ( ) No
( ) No
( ) No
( ) Yes ( )
) ( ) Yes (
No
) No
4.
5.
6.
    Is moisture content optimized for minimum total cost of dewatering and
    fuel consumption in incinerator?  (   )   Yes  (   )   No
                                    38-7

-------
References

1.  Standard Methods for the Examination of Water and Wastewater.  American
    Public Health Association, 14th Edition, 1975, Washington, D.C.

2.  Dorr-Oliver FS Disposal System Operating Instructions.

3.  Copeland Systems Operating Instructions.

4.  Ettlich, W.F. et al, Operations Manual Sludge Handling and Conditioning,
    U.S. EPA, Office of Water Program Operations, Washington, D.C.,
    430/9-78-002, February 1978.
                                     38-8

-------
 39.  LIME RECALCINING

 Process Description

     Lime often is used as a coagulant either as a tertiary step or ahead of
 the primary clarifier for removal of phosphorus from wastewaters.  In recal-
 cining, the dewatered calcium-containing sludge is heated to about 1,850F.
 This drives off water and carbon dioxide leaving calcium oxide (or quicklime).

     In municipal wastewater treatment,  multiple hearth furnaces have been used
 for recalcining.  Although fluidized bed furnaces have been used for industri-
 al and water treatment purposes, these  furnaces have not been used for munici-
 pal wastewater recalcining.  Prior to the recalcining step centrifuges can be
 used to separate the phophate-rich lime from the inert solids also removed by
 the lime.

     The recalcined lime usually is discharged into a hammermi11 to break up
 any lumps  that have formed in the furnace.   The material is forced against a
 grinding plate by the rotating hammers.   The lumps are broken up until they
 are small  enough to fit through the openings in a metal screen.  The material
 then goes  to a thermal disc cooler.   When cool, the reclacined lime is stored
 and mixed  with fresh lime before reuse.

 Typical Design Considerations

     The capacity of a lime recalcining  multiple hearth furnace depends on
 solids  loading per  unit of hearth surface area.  Sizing also depends on the
 nature  of  the sludge cake,  including moisture,  volatile solids, inerts con-
 tent, and  heat value.   A  loading rate of 7  to 12 Ib wet sludge/hr/sq ft of
 hearth  is  common.   The feed sludge should have a moisture content of less than
 50 percent.

 Typical Performance Evaluation

     Proper operation of the recalcining  furnace .should produce a recalcined
 lime which will meet the  AWWA standard  for quicklime (CaO).   Typically,  the
 lime should  have  a  CaO content of at least 60 to 70 percent and should slake
 readily in standard slakers.   Typical loading rates are about 1 Ib dry solids <
per  square foot of  furnace hearth area.

Process Control

     There.are  two important characteristics  of  the  recalcined lime which must
be controlled.

     1.   Activity,  and
     2.   Slaking  characteristics

     Recalcined lime  must  be classified according  to the AWWA Standard  for
quicklime  (CaO) and  hydrated  lime  (Ca(OH)2)  (AWWA B202-65):
                                     39-1

-------
     High-reactive,
      soft burned lime

     Med ium-reac tive,
      medium burned lime

     Low-reactive,
      hard burned lime
Time for 40 rise
  in temp., (min)

   3 or less
   3-6
More than 6
Time for complete
  reaction (min)

        10
        20
 More than 20
     It is possible to produce quicklime with the same CaO content, but with
 very different slaking properties.

     The most important variables in the operation of the recalcining furnace
 are temperature and feed rate.  These are addressed in detail in Reference 1.
 The rabble arm rate in a multiple hearth furnace has little effect on recal-
 cined lime if it is within 1.5 to 2 rpra:

 Maintenance Considerations

     The features of a good maintenance program are:

      1.   Burner controls been checked and calibrated within a year.
      2.   Temperature controllers maintain the hearth temperatures near set
          point.
      3.   Refractory should be inspected on a regular basis.
      4.   Area housekeeping around the furnace or where there are spills of
          lime or buildups of  lime dust.
      5.   Interior of the scrubber been inspected within a year.
      6.   Check sand level in  the upper shaft seal.

Records

    Recommended  sampling and  laboratory  tests are shown in Figure 39-1.

    Operating  records  should  also include:

    1.   A method for  determining the feed  rate  to  the furnace.
    2.   Quantity of lime tecovered.

Laboratory Equipment

    The laboratory equipment  should  include the  following  minimum equipment:

    1.   Furnace  oxygen  analyzer
    2.   Equipment and procedures for  analyzing  CaO content
                                     39-2

-------
o
a
o

TEMPERATURE
CALCIUM
CONTENT (CaO)
MOISTURE
CONTENT



















UJ
(si
*/>
z S
1*
ALL
ALL
ALL



















TEST
FREQUENCY
Mri1
21
1/W



















LOCATION OF
SAMPLE
A
P
F



















METHOD OF
SAMPLE
Mn
G
G



















1 REASON
FOR TEST
P
P
C
P









'









   ESTIMATED UNIT PROCESS SAMPLING AND
              TESTING NEEDS
    RECALCINATION
                 {MULTIPLE HEARTH)
   FEED
                                   HEARTHS
                                   PRODUCT
    A. TEST FREQUENCY
        H m HOUR      M  MONTH
        D-DAY       R - RECORD CONTINUOUSLY
        W- WEEK      Mn- MONITOR CONTINUOUSLY

    B. LOCATION OF SAMPLE

        F = FEED
        P = PRODUCT
        A = FURNACE ATMOSPHERE
            (AT EACH HEARTH)
    C.  METHOD OF SAMPLE
        24C-Z4 HOUR COMPOSITE
        G - CRAB SAMPLE
        R - RECORD CONTINUOUSLY
        Mn MONITOR CONTINUOUSLY

    D.  REASON FOR TEST
        H - HISTORICAL KNOWLEDGE
        P m PROCESS CONTROL
        C - COST CONTROL

    E.  FOOTNOTES:
         1.  WHEN FURNACE IS OPERATING
         2.  SPOT CHECK
    Figure 39-1.
39-3

-------
    3.   Drying oven
    4.   Analytical balance
    5.   Normal glassware and accessories

    The EPA report "Estimating Laboratory Needs for Municipal Wastewater
Treatment Facilities" contains very detailed information on glassware, chemi-
cals, and miscellaneous furniture and should be referred to for any detailed
questions.

Sampling Procedures

    Samples should be taken at times and locations where representative
samples can be obtained.  Samples of hot materials should be handled carefully
and should be stored in metal containers.

Sidestrearns

    The major sidestream is the scrubber water which can be returned to the
liquid treatment process or to sludge thickeners.
                                    39-4

-------
Process Checklist - Lime Recalcining.
 1.

 2.
 3.

 4.
 5.
 6.

 7.

 8.
10.
11.
12.
13.

14.
15.

16.
What is required lime dosage in the liquid process
average?
What is average flow through lime treatment	
                                                             _lb/mg
                                                           rag/day?
Calculate approximate average lime recalciner feed rate,  item 1 x  item 2
                          Ib/day
                                                  Ib/day?
                                                  "	-Ib/hr.
What is rated capacity of furnace,
Check feed rate at the current setting, 	
Is the recalcined lime CaO content checked as a  regular process
control parameter?   (  )  Yes  (  )  No
Is feed sludge moisture content checked on a regular basis?
(  )  Yes  (  )  No          ;
Is there a method to selectively waste approximately 25% of  the  lighter
fractions of the feed sludge in order to control  inerts?
(  )  Yes  (  )  No
Are hearth temperatures logged and are they adequately controlled?
(  )  Yes  (  )  No
Is the lime grinder and cooler in operation?(  )  Yes   (   )  No
Is the maintenance program adequate?  (  )  Yes   (  )  No
Have the burners been calibrated within a year?   (  )  Yes  (  )  No
Are the alarms and shutdowns adequate?  (  )  Yes   (  )  No
Are they checked regularly?  (  )  Yes  (  )  No
Are operating records adequate?  (  )  Yes   (  )  No
Is the laboratory and operational office equipped for the  necessary
analyses?  (  )  Yes  (  )  No
What spare parts are stocked?	
17. What are the most common problems the operator has had with  the process?
                                     39-5

-------
 References

 1.  Gulp, G.L.  and  Polks  Heim, N., Field Manual  for  Performance Evaluation and
    Troubleshooting at Municipal Wastewater Treatment Facilities,  EPA
    430/9-78-001.~

 2.  Gulp, Russell It., and Gulp, Gordon  L., Advanced  Wastewater Treatment, Van
    Nostrand Reinhold Co., 1971.
3.  CH2M-H111, Estimating Laboratory Needs  for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328  (June, 1973).
4.  Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation  (1959).

5.  Culp/Wesner/Culp, Operation and Maintenance Manual, Water Factory 21,
    Orange County water District",  (June, 1974).
6.  CH2M-Hill, Operation and Maintenance Manual for Wastewater Reclamation
    Facility, South Tahoe PUD,  (1976).
7.  Gulp, R.L., et al, Advanced Wastewater Treatment as Practiced at South
    Tahoe, U.S. Environmental Protection Agency, Project 17010 ELQ  (WPRD
    52-01-67), August, 1971.
                                     39-6

-------
40.  GRANULAR CARBON REGENERATION

Process Description

    Granular activated carbon removes detergents, insecticides, herbicides,
and various organic substances which contribute to the taste, odor and color
of the wastewater.  The carbon eventually becomes saturated and loses its
ability to further adsorb organic materials.  The carbon nearest to the inlet
of the contactor becomes saturated or exhausted first.

    The purpose of the regeneration process is to restore the adsorptive
capacity of the granular carbon.  Regeneration is accomplished by heating  the
carbon to temperatures in excess of 1,500F.  The heat vaporizes and drives
off the adsorbed  impurities restoring the carbon essentially to its original
activity.  Regeneration is carried out most effectively in multiple hearth
furnaces.

    The carbon  is dewatered prior to feed to the furnace and the hot regen-
erated carbon cooled in a quench tank upon discharge  from the furnace.  The
regenerated carbon is then washed to remove fines.

Typical Design  Considerations

    Experience  has shown that carbon dewatering can be accomplished by gravity
in about 1 hour with properly designed dewatering bins.  The dewatered carbon
should have a moisture-content  of 40 to  45 percent.   The dewatering bin should
be sized for a  reasonable quantity of carbon,  typically, a days feed to the
furnace.

    Typically,  furnace  loadings are based on the hearth area, with an average
being  50 to 70  Ibs per  day of carbon per square  foot  of total hearth for  a 6
hearth furnace.   A 6-hearth, 54-inch inside diameter  furnace is rated for
approximately 6,000  Ib  of carbon per day.  A regeneration  furnace can be  oper-
ated over  a wide  range  of carbon feed, and can be  turned down  by  a ratio  of
6:1, however  it is usually better  to operate at  a constant  rate if possible.

Typical  Performance  Evaluation

    The  performance  of  the carbon regeneration process  is  best determined by
apparent density  (AD)  tests of  the  regenerated carbon.  The  AD of new carbon
is  about 0.48.  As carbon becomes saturated with adsorbed  organics,  the AD
increases  to  over 0.50.  If properly  regenerated,  the AD will return to 0.48.

     If the AD is  greater than 0.49,  the  carbon is not being heated enough to
volatilize a  sufficient quantity of organic material; conversely  if  the AD is
less  than  0.48, the  carbon  is being overheated and burned in the  furnace.

Process  Control

     The regeneration process  consists of several steps as the carbon passes
 through the furnace.
                                      40-1

-------
     1.   Drying
     2.   Decomposition or pyrolyzing of the adsorbed organic matter.
     3.   Gasification of the organics and reactivation of the carbon pore
          structure.
     These and other process considerations are discussed in Reference 1.

 Maintenance Considerations

     The features of a good maintenance program that the inspector should look
 for are:
      1.
      2.

      3.
      4.
      5.
      6.
      7.

 Records
Burner controls checked and calibrated within a year.
Temperature controllers maintain the hearth temperatures near set
point.
Refractory appears in good condition.
Dewatering screens cleaned regularly.
Area around the furnace cleaned.
Interior of the scrubber been inspected within a year.
Sand level in the upper shaft seal.
     Recommended sampling and laboratory tests are shown in Figure 40-1.

     (Derating  records should also include:
     1.    A written log of carbon movements  and regeneration scheduling.
     2.    A method to determine the carbon feed rate to the furnace.
     3.    A method to determine carbon losses and make-up carbon additions.

Laboratory Equipment

     The  laboratory equipment should include the following minimum equipment:

     1.    Graduated cylinder,  drying over, balance,  and shaker  for running
          apparent density test.
     2.    Carbon grinder  and  other equipment for  iodine number  test.
     3.    Furnace  oxygen  analyzer.

Sampling  Procedures

     Samples should be  taken  to assure  that  they  are  representative.  Most of
the  carbon  sampling  involves  dipping out  scoups  of  the material.   Hot carbon
should be handled with care  to avoid  injury and  should be stored  in metal
containers.

Sidestreams

    Sidestream flows consist  of carbon transport water,  dewatering tank drain-
age, defining water, quench  tank overflow,  and scrubber  water.  These side-
stream flows are a very  small  percent of  the  liquid process flow  and may be
returned  to the primary  or secondary treatment process.
                                     40-2

-------
a
s

8
(9
 t-
 a
 o

TEMPERATURE
OXYGEN
CONTENT
PERCENT ASH
APPARENT
DENSITY



IODINE
NUMBER
APPARENT
DENSITY













PLANT SIZE 1
(MGD) 1
ALL
ALL
ALL
ALL



ALL
ALL













ITEST
FREQUENCY |
Mn1
1/D1
1/D1
1/H1



1/D
VP1













1 LOCATION OF
SAMPLE |
A
A
P
P



F
P
F













METHOD OF
SAMPLE
Mn
G
G
G



G
G













1 REASON
FOR TEST 1
P
P
P
P



; H
H













                                                  ESTIMATED UNIT PROCESS SAMPLING AND
                                                             TESTING NEEDS
                                                   CARBON REGENERATION


                                                               (MULTIPLE HEARTH)


                                                    FEED
                                                                                 HEARTHS,
                                                                                        PRODUCT
                                                   A.  TEST FREQUENCY

                                                       H - HOUR     M - MONTH
                                                       0 - DAY       R - RECORD CONTINUOUSLY
                                                       W-~WEEK     MB- MONITOR CONTINUOUSLY

                                                   B.  LOCATION OF SAMPLE

                                                       F  =FEED
                                                       P  =PRODUCT
                                                       A  = FURNACE ATMOSPHERE
                                                           (AT  EACH HEARTH)
C. METHOD OF SAMPLE

    24C-24 HOUR COMPOSITE
    G - GRAB SAMPLE
    R " RECORD CONTINUOUSLY
    Mn MONITOR CONTINUOUSLY

D. REASON FOR TEST

    H - HISTORICAL KNOWLEDGE
    P - PROCESS CONTROL
    C - COST CONTROL

E. FOOTNOTES:

     1. WHEN FURNACE IS OPERATING
     2. SPOT CHECK
                                                  Figure 40-1

                                               40-3

-------
 Process Checklist - Granular Carbon Regeneration
  1.

  2.
  3.

  4.
  5.
  6.
  7.

  8.

  9.

10.

11.
12.
13.

14.
15.

16.
                                                               _lb/mg
 What is  required carbon dosage  in the  liquid process
 average?
 What is  average flow through carbon 	rag/day?
 Calculate  approximate average carbon regeneration  rate,  item 1  x  item 2
                           Ib/day
                                                                Ib/day?
                                                                Ib/hr.
What is rated regeneration capacity of furnace,
Check feed screw rate at the current setting,
Is carbon moved on a regular schedule?
                                         (   )   Yes   (   )   No
 Is carbon  dewatering  checked before  carbon  is  fed  to  furnace?
 (  )  Yes   (   )  No
 Are process control tests  (AD's)  run during  regeneration?
 (  }  Yes   (   )  No
 Are hearth temperatures  logged and are  they  adequately controlled?
 (  )  Yes   (   )  No
 Is the regenerated carbon washed  to  remove  fines prior to use?
 (  )  Yes   (   )  No
 Is the maintenance program adequate?  (  )   Yes  (  )  No
 Have the burners been calibrated within a year?  (  )  Yes   (  }  No
 Are the alarms and shutdowns adequate?   (  )   Yes   (  )   No
 Are they checked regularly?  (  )  Yes   (  )   No
 Are operating  records adequate?   (   )  Yes   (  )  No
 Is the laboratory and operational office equipped for the necessary
 analyses?   (   )  Yes  (  )  No
What spare parts are stocked? 	
17. What are the most common problems the operator has had with the process?
                                     40-4

-------
References

1.  Gulp, G.L. and Polks Heim, N., Field Manual for Performance Evaluation and
    Troubleshooting at Municipal Wastewater Treatment Facilities, EPA
    430/9-78-001.

2.  Gulp, Russell L., and Gulp, Gordon L., Advanced Wastewater Treatment, Van
    Nostrand Reinhold Co., 1971.
3.  CH2M-H111, Estimating Laboratory Needs for Municipal Wastewater Treatment
    Facilities, EPA Contract 68-01-0328  (June, 1973).

4.  Wirts, J.J., et al, Safety in Wastewater Works, Manual of Practice No. 1,
    Water Pollution Control Federation  (1959).

5.  Culp/Wesner/Culp, Operation and Maintenance Manual, Water Factory 21,
    Orange County water District",  (June, 1974).

6.  CH2M-Hill, Operation and Maintenance Manual for Wastewater Reclamation
    Facility, South Tahoe PUP,  (1976).

7.  Gulp, R.L., et al, Advanced Wastewater Treatment  as Practiced at South
    Tahoe, U.S. Environmental  Protection Agency,  Project  17010 ELQ (WPRD
    52-01-67), August, 1971.
                                       40-5

-------

-------
41.  LAND APPLICATION OF SLUDGES

    Sludge can be applied to land areas for disposal purposes, crop growing,
or to reclaim spoiled land.  Application for disposal purposes is identical in
concept to a landfill except only the top 1-2 feet of soil are used.  Sludge
application can be used for providing nutrients and organic matter to crop
lands.  These systems require careful controls to insure that crop nutrient
requirements are met and that no harmful elements such as cadmium are applied
in excessive amounts.  Reclamation of spoiled land, such as strip mined areas,
is a special case similar in scope to application to farm lands.  Due to the
specialized nature, reclamation will not be discussed.  The review procedures
would be very similar to those procedures used for crop use but loading rates
and use of other materials would be different.

    Sludge can be applied as a liquid, dewatered cake, dried matter, or ash.
For use with this section, the definitions of these forms are as follows:
         Form

         Liquid
         Dewatered cake
         Dried Matter
         Ash
Solids Concentration

      0-10%
     10-40%
     90-98%
      100%
    Application methods vary with  site  characteristics,  use  of site  and form
of  the sludge.

Typical Design Considerations,  Evaluation,  and Control

    The loading  rate  or application rate  is a function of the sludge and soil
characteristics  and crop  nutrient  requirements.  Sludge and  soil characteris-
tics  and  crop  requirements vary widely.

    The sludge application rate is primarily based on the sludge nitrogen con-
 tent  and  the nitrogen requirements of the crop.  Nitrogen in sludge  is avail-
able  for  immediate plant  use  in the ammonium (NH$)  or nitrate (NO)
 forms.  The availability  of organic nitrogen to the crop depends on  the miner-
alization rate which  can  be determined after several years of operation.

    The heavy  metal  application rate must also be checked so that recommended
maximum are not  exceeded.

    The procedure for determining  the application rate is described in Refer-
 ence  3.   To simplify this Table 41-1 is presented.  This table shows applica-
 tion  rates for various crops  based on the nitrogen requirements, and assuming
 70 Ib organic  nitrogen/ton of sludge, with a mineralization rate of 15-10-5,
 and an ammonium nitrogen content of 30 Ib/ton of sludge.

     The  monitoring program consists of the analyses shown in Figure 41-1.
 Sampling  and monitoring must be performed by qualified personnel or outside
 laboratories.
                                      41-1

-------

Crop
Alfalfa
Orchard grass
Corn (grain)
(stover)
Sorghum (grain)
(stover)
Corn silage
Oats (grain)
(straw)
Soybeans (grain)
(straw)
Wheat (grain)
(straw)
Barley (grain)
(straw)
Yield,
per acre
8
6
6
180
8,000
8,000
32
100
60
7,000
80
6,000
100

tons
tons
tons
bu
Ib
Ib
tons
bu
bu
Ib
bu
Ib
bu

Application yr
1
9.1
7.4
4.2
1.7
3.0
3.2
5.9
2.0
0
6
2
3
1
2
1
.86
.0
.1
.6
.0
.7
.0
234
Tons/acre of sludae
7.8
6.3
3.6
1.5
2.5
2.7
5.0
1.7
0
5
1
3
0
2
0
.74
.1
.8
.0
.89
.3
.84
7.4
6.0
3.4
1.4
2.4
2.6
4.8
1
0
4
1
2
0
0
.6
.70
.8
.7
.9
.84
.2
.80
7.0
5.6
3.2
1.3
2.2
2.4
4-5
1
0
4
1

0
0
2
.66
.6
.6
.7
.79
.1
.75
5
6.6
5.4
3.0
1.2
2.1
2.3
4.3
1.4
0.62
4.3
1 5
2.6
0.75
2.0
0.71

     Sensory observations can detect many problems before environmental mon-
 itoring tests.  When injecting sludge, the application rate should be such
 that sludge does not surface.  If sludge surfaces, the injector speed should
 be increased or the sludge flow decreased so that the quantity injected per
 unit area decreases.  If the injector travel speed is excessive, soil may be
 thrown away from the shank creating an open trench;

     If the sludge is spread on the surface, the rate should be low enough to
 prevent the excessive ponding or runoff.   Excessive ponding is when the liquid
 is still above the surface several hours  after application.  Either excessive
 ponding or runoff indicates excessive application rates for the soil.   This
 will vary widely from soil to soil.

 Maintenance Considerations

    Maintenance requirements  are  mainly cleaning  and  equipment service.   The
 cleaning operation  include daily  flushing of  the  injectors  (if used) and
 periodic flushing of the  tanks.   Truck, tractor,  and  equipment preventative
 maintenance schedules will be specified in  manufacturer's data.

 Records
                t0 the nrmal recrd kept  for *nitoring and process con-
where   L      Trat^S) mUSt keep a dail* log OE site maP  record *>
Where, when, and how much sludge has been  applied.
                                     41-2

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r






a
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COD
TKN
NH3-N
NO -N
P
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SALMONELLA
CYSTS
pH
Cl
AJjKATvTNTTY
1 'F&lB;
METALS NlJ
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1
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PKN
k-
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PLANT SIZE 1
(MOD) j
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
ALL
SJ,L_
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ALL
ATrT(
ALL
ALL
ALL
ALL
ALL
\LKALINITY |ALL
TEST 1
FREQUENCY j
w
w
w
w
w
w
M
M
M
M
D
M
W
M
M
W
M
A
A
A
A
A
[LOCATION OF
SAMPLE
SI
SI
SI
SI
SI
SI
SI
SI
SI
SI
SI
SI
R1
SI
SI
si
SI
So
So
So
So
So
[METHOD OF
SAMPLE
G
G
G
G
G
G
G
G
G
G
G
G
. G
G
G
G
G
G
G
G
G
G
H
Z%
S'1-
< o:
uj O
a u.
P
P
P
P
P
H
P
P
P
P
P
' P
c
P
P
P,,
P
P
P
P
P
P
ESTIMATED UNIT PROCESS SAMPLING AND
TESTING NEEDS
LAND APPLICATION OF SLUDGES
A. TEST FREQUENCY
H m HOUR M - MONTH
0 - DAY R - RECORD CONTINUOUSLY
W. WEEK Mn- MONITOR CONTINUOUSLY
B. LOCATION OF SAMPLE
SL =SLUDGE BEING APPLIED
SO =SOIL
M =MONITORING WELLS OR
NEARBY BY STREAMS
C. METHOD OF SAMPLE
24C-24 HOUR COMPOSITE
a - GRAB SAMPLE
R - RECORD CONTINUOUSLY
Mn- MONITOR CONTINUOUSLY
0. REASON FOR TEST
P - PROCESS CONTROL
C - COST CONTROL
E. FOOTNOTES:



Figure 41-1
41-3

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SUGGESTED MINIUUM
_J
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CONTROL EXCH.
CAPACITY
SALMONELLA
CYSTS
CHLORIDE
B
jpH
ICOLIFORM
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COLIFORM
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LOCATION OF
SAUPI f
So
So
So
So
So
So
M
M
M
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METHOD OF
SAMPLE
G
G
a
G
G
G
24C
24C
24C
G












REASON
FOR TEST
P
H

P
P
P
P
P
P
P












ESTIMATED UNIT PROCESS SAMPLING AND
TESTING NEEDS
LAND APPLICATION OF SLUDGES





A. TEST FREQUENCY
H m HOUR M - MONTH
D-DAY R - RECORD CONTINUOUSLY
W- WEEK Mn MONITOR CONTINUOUSLY
B. LOCATION OF SAMPLE
SL= SLUDGE BEING APPLIED
S0= SOIL
M = MONITORING WELLS OR
NEARBY BY STREAMS
C. METHOD OF SAMPLE
24C-24 HOUR COMPOSITE
G - GRAB SAMPLE
R " RECORD CONTINUOUSLY
Mn MONITOR CONTINUOUSLY
D. REASON FOR TEST
H - HISTORICAL KNOWLEDGE
P - PROCESS CONTROL
C - COST CONTROL
E. FOOTNOTES:
Figure 41-1  (cont'd)
          41-4

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Laboratory Equipment

    The laboratory should include the following minimum equipment in order to
monitor land application:

     1.  Analytical balance
     2.  Blender
     3.  Fume hood
     4.  Incubator
     5.  Kjeldahl digesting and distilling apparatus
     6.  Oven
     7.  pH meter
     8.  Pump (vacuum-pressure)
     9.  Spectrophotoraeter
    10.  Sterilizer
    11.  Titrator-araperometric

Sampling Procedures

    Sampling should be done on representative sludge and soil.  Sludge that
has been in storage for overnight should not be sampled for nitrogen forms or
pH.  "Fresh" sludge should be used  for samples to set  loading rates.

    Similarity,  soil samples should be taken from areas of the  field that pre-
dominate.  In other words if a field consists mainly of a clay-loam with  an
isolated area of sand, then the  samples should be taken from the  loam areas
and not in the  sandy area.  This does not mean the sandy area should be
ignored but rather  that  the overall loading rates should be based on results
from samples taken  in the loam soil.

Sidestrearns

    With a properly operated and maintained  land application system there
should be no sidestreams.  The land application system should b designed such
that accidental spills will be contained  and  sludge will not enter  surface
water.
                                      41-5

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Process Checklist - Land Application

A.  General
     1.  Is sludge application for disposal only, crop utilization, or recla-
         mation of spoiled area?  (circle one)
     2.  Does site visit reveal any areas of runoff or ponding?
         (   )   Yes  (   )  No
     3.  Is emergency  storage provided? (  )   yes  (  )   NO
     *    Are field records in order? (   )   Yes   (  )   No
         Is a  preventive maintenance plan in use? (  )   Yes  (   )   No
         Is there an emergency plan  for power outages or maior  equipment
         failures? (  )   Yes  (  )   NO
         Does  the sampling program meet recommendations? (
         Is an O&M manual available? (   )   Yes   (   )   No
         Is OSM manual used? (   )  Yes   (   )  No
         Is laboratory properly equipped?  (   )  Yes   (   )
        What  spare  parts are stocked?
 5,
 6.

 7.
 8.
 9,
10.
11.
                                                             )   Yes  (   )   NO
                                                            No
   12.
     What are the most common problems the operator has had with the
     process?
B.  Farming (if applicable)
     1.  la farming done by agency staff and equipment?   (
     2.  Is farming done by contract? (  )  yes  (  )  No
         What crops are grown? _^^_____^
         Are crops rotated?
                                                           )   Yes  (  ) NO
    3.
    4.
    5.
(   )   Yes  (   )
                                        NO  "
                                          and  are
                                   41-6

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References
3.
                     Research Publication  235,  Clumbus,
    nnirti. tTF  '-  -i. np>r,Mn, M.nual  Sludge  Haling and Conditioning.,
    U.S. EPA, Office  of Water  Program Operations,  Washington,  D.t. ,
    430/9-78-002, February  1978.   -
                                        41-7

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42. LANDFILL

Process Description

    Burying sludge to minimize nuisance conditions or public health problems
is called landfill.  Sludge is buried in layers which are covered with fill
material excavated at the site.  Landfills must be located where nearby wells
or groundwater supplies will not be contaminated by leachate from the fill
operation.  Sludge landfills are generally separate from refuse landfills.

Typical Design Considerations

    Loading rates for landfill operations and soil layer depths for a typical
site are given in Table 42-1.

                          TABLE 42-1.  DESIGN CRITERIA
    Trench width
         Bottom
         Top
    Trench length
    Sludge layer
    Intermediate fill  layer
    Top  fill  cover
    Distance  between
         trenches
    Distance  from property
         line
    Distance  from
         drainage ditch
12 ft
28 ft
50 ft
 2 ft
 1 ft
3-5 ft

15 ft

150 ft

30 ft
     The depths are required for safety (to prevent contamination of adjacent
 areas and to prevent cell or trench cave-ins)  and for ease of operations with
 conventional excavation equipment.  Variations deppend on special site
 characteristics.

 Typical Performance Evaluation

     Performance of a, landfill is measured as a function of disposal without
 harming the surrounding environment or producing nuisances.

     A landfill system can be operated such that no odors or vector habitats
 are produced.  There should be no runoff or change in natural drainage.
 Leachate is controlled by not trenching to an elevation less than 15 to 20
 feet above the impervious layer.  Leachate quantity can be minimized by pump-
 ing excess from the trench  to a tanker truck.  Unlike most other processes,
 this one either succeeds or fails with little margin for partial failure.
                                      42-1

-------
 Successful operation of a  landfill  system is measured by monitoring wells and
 nearby  surface  streams  and by  sensory observations.

     There should be several monitoring wells located just inside the site
 boundaries.  Well depths are variable.  The wells should consist of a 6-inch
 pipes fitted with a threaded cap on top and a well screen at the bottom  (or
 SkS^fS'a/flTi'i1?!11!*1?  nrmally placed in 16-inch borings, which are
 packed with 3/5 to 1-1/2-inch  gravel.  Sampling can be accomplished through
 hn^    13 Prtable PufflP and a 20-foot, 4-inch pipe with a foot valve at the
 bottom.   These wells and domestic wells within 1/4 mile of the landfill should
 be sampled prior to startup of the landfill.

     Table 42-2 shows a list of constituents to be included in the well
 monitoring.
                    TABLE 42-2.
WELL ANALYSIS
                    Boron
                    Cadmium
                    Copper
                    Iron
                    Lead
                    Mercury
                    Zinc
     TDS
     PH
     Chloride
     Phosphorus
     N02-N03
     Total coliforra
     Fecal coliform
     Fecal streptococcus
    The drainage ditch should be monitored during flow periods.  The ditch
           ^   ShOUid ^ 3t the tW PintS Where the ditch crosses toe
if *r  < difference between  upstream and downstream locations win show
if there is an increase due to the landfill operation.

    Table 42-3 shows the tests to be done on the drainage ditch flows.
          TABLE 42-3.     DRAINAGE DITCH ANALYSTS
                   Fecal coliform
                   Coliform
                   Suspended solids
                   BOD
    Phosphorus
    pH
                                    42-2

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    The monitoring wells are sampled monthly.  The drainage ditch is sampled
when rainfall occurs but no more than once per week.  The domestic wells are
sampled quarterly.

Process Control

    Landfill controls consist of surface runoff management to prevent runoff
from passing through the fill site.  The process is controlled by varying the
layers of sludge and/or fill material.  If the moisture content of the sludge
increases then smaller layers of sludge would be placed in the trench.

Maintenance Considerations

    Vehicle maintenance should  include preventative maintenance in accordance
with manufacturer's guidelines  and daily inspection.

    Daily inspection should  include the following:

    Fuel level
    Oil level
    Battery
    Tires (or tracks)
    Hydraulic systems  (where applicable)
    Grease crane  and crawler
    Turn signals  and brake  lights  on  trucks

    Completed landfill  areas should be  seeded and observed  to insure  that
grass  distribution  is  adequate  and that there are no  exposed soil areas.

Records

    Records  for  this process consist  of laboratory  analyses records of mon-
 itoring wells and nearby  drainage  areas,  notation of  visual or sensory obser-
vations, weather  records,  and maps showing areas filled and dates of filling.

    Sampling locations and frequencies  are shown on Figure 42-1.

Laboratory Equipment

    The following laboratory equipment items are required for monitoring a
 landfill  operation:

      1.   Analytical balance
      2.   Blender
      3.   Fume hood
      4.   Incubator
      5.   Kjeldahl digesting and distilling apparatus
      6.   Oven
      7.  pH meter
      8.  Pump (vacuum-pressure)
                                      42-3

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a
o
ui
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5?
I

BORON
CADMIUM
COPPER
IRON
LEAD
MERCURY
ZINC
IDS
pH
CHLORTDR
PHOSPHORUS
,-*>,
TOTAL
COLIFORM
FECAL
COLIFORM
PECAL
STRRPTornrpTT.c;
SUSPENDED
SOLIDS
BOD
SH,




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^1
OL i
ALL
ALL
ALT
ALL
ATT.
ALL
ALL
ALL
ALL
ftliTi
ALL
ALL
ALL
ALL
TiTi
ALL
\LL
\LL




TEST
FREQUENCY
S
S
S
S
S
S
S
S
M
M
M,A
M,A
Mrfl
M,A
M,A
S
A
A
A




LOCATION OF
SAMPLE
W
W
W
W
W
W
W
W
W,D
W
W,D
W,D
W.D
W,D
W.D
D
D
D




METHOD OF
SAMPLE






















REASON
FOR TEST






















                                                    ESTIMATED UNIT PROCESS SAMPLING AND
                                                               TESTING NEEDS


                                                     LANDFILL
                                                                                   DRAINAGE
                                                                                     DITCH
                                                                                   W]
                                                    A. TEST FREQUENCY

                                                  S= SEMI-ANNUAL      M - MONTH
                                                  A= AS REQUIRED-      R - RECORD CONTINUOUSLY
                                                      AFTER RAINFALL   Mn- MONITOR CONTINUOUSLY

                                                   B.  LOCATION OF SAMPLE

                                                        W=  WELL(  (w))
                                                        D=  DITCH  V^
   C. METHOD OF SAMPLE

       24C-24  HOUR COMPOSITE
       C- GRAB SAMPLE
       R - RECORD CONTINUOUSLY
       Mn. MONITOR CONTINUOUSLY

   D. REASON FOR TEST

       H - HISTORICAL KNOWLEDGE
       P - PROCESS CONTROL
       C - COST CONTROL

   E.  FOOTNOTES:

        1. THESE TESTS SHOULD ALSO BE RUN ON RECEIVING
          WATER, ABOVE AND BELOW OUTFALL. ON A
          PERIODIC BASIS. DEPENDING ON LOCAL CONDITIONS.

        2. FOR PLANTS DESIGNED TO CONTROL THIS
          PARAMETER.

   Figure 42-1

42-4

-------
     9.  Spec tropho borne ter
    10.  Sterilizer
    11.  Titrator-araperometric

Sidestreams

    The sidestream from a landfill operation  is the  leachate.  There  is very
little that can be done to control leachate from a landfill operation.  Gen-
erally, leachate is controlled by selecting a site with no underlying ground-
water or with an impermeable soil layer between the  fill bottom  and ground-
water.  Under certain conditions liners or clay soil layers are  allowed to
hold moisture and minimize leachate movement.
                                      42-5

-------
Process Checklist- - Landfill
 2,
 3,
 4.
 5,
 6.
 7.
 8.
 9.
              storage  available  for periods  of  rainy  weather
            .  Yes   (   )  No
Are trenches  dug in advance of  fill operation?  (  }  Yes   (
Do operators  maintain  safe distance from edge  of trench?  (
Are trenches  covered each night at end of shift?   (   )  Yes
Are odors present?  (  )  Yes   (  )  No
Are flies present?  {   )  Yes  (  )  No
Are rodents a problem?   (  )   Yes  (  )  NO
Are filled areas revegetated?   (  )   yes   (   )  NO
Is there a scheduled maintenance plan?  (  )  Yes  (  )   No
                                                                 (2 weeks or
 )   No
 Yes
(   )   No
                                  (   )  No
10. Are maintenance records current?
(   )
                                                (  )   NO
                                   42-6

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References

1.  Lukasik, G.D., and Cormack,  J.W.,  "Development and Operation of a Sanitary
    Landfill for Sludge Disposal",  paper presented at EPA 208 Seminar, Beston,
    Virginia, March 16, 1977.

2.  Standard Methods  for  the Examination of Water and Wastewater.  American
    Public Health Association,  14th Edition, 1975, Washington, D.C.

3.  Gulp, G.L., and Folks Heim,  N., Field Manual for Performance Evaluation
    and Troubleshooting at Municipal Wastewater Treatment Facilities, US  EPA
    Report 430/9-78-001  (Jan.  1978).
  U.S. GOVERNMENT PRINTING OFFICE: 1979-292-127
                                       42-7

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