WATER POLLUTION CONTROL RESEARCH SERIES • 11020 FDC 01/72
    SCREENING/FLOTATION TREATMENT
     OF COMBINED SEWER OVERFLOWS
U.S. ENVIRONMENTAL PROTECTION AGENCY

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

Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Waterj, Research Information Division, R&M, Environmental
Protection Agency, Washington, D. C.  20460

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                 SCREENING/FLOTATION TREATMENT

                               OF

                    COMBINED  SEWER OVERFLOWS


                               by

                     The Ecology Division
                      Rex  Chainbelt Inc.
                     Milwaukee, Wisconsin
                              for the

               Office of Research and Monitoring
                 Environmental  Protection  Agency
                        Contract 14-12-40
                        Project 11020 FDC

                          January  1972
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.50

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                   Kr'A  Review Notice
This  rej.ort has been  reviewed by the Environmental Protection
Agency and ar :,rcv-jl  for publication.  Approval does not
signify that'tao ci.r^-;:,ts  necessarily reflect the views and
policies of the ;•_•:-/:ror-.-ntal Protection Agency nor does
mention of trade i.•_;•..;.•::  or  corrraercial products constitute
endorsement or rucG::;::.-jndation for use.

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                               ABSTRACT
This report documents a study to develop a treatment system for combined
sewer overflows.  The processes of chemical oxidation, screening,
dissolved-air flotation and disinfection were evaluated in the laboratory.
It was determined that chemical oxidation was not feasible.  The majority
of the pollutants were of a particulate nature, which indicated solids/
liquid separation processes could possibly provide effective treatment.
A 5 MGD combination screening and dissolved-air flotation demonstration
system was designed, installed and evaluated.

The system was utilized to treat 55 combined sewer overflows.  The
drainage area served by the facility was a completely developed 500 acre
residential area of Milwaukee, Wisconsin.  Suspended solids and volatile
suspended solids removal in the range of 65-80% were consistently obtained
at influent concentrations of 150 to 600 rag/1.  BOD and COD removals were
slightly lower at 55 to 65% for influent concentrations of 50 to 500 mg/1.
Addition of chemical flocculents (ferric chloride and a cationic poly-
electrolyte) was necessary to obtain these removals.  Without the use of
chemical flocculents, removal of BOD, COD, suspended solids, and volatile
suspended solids were all in the range of 40-50%.  The screening/flotation
system provided sufficient detention time (^15 minutes) for adequate
disinfection with hypochlorite salts.  Cost estimates indicate a capital
cost of $21,056 per MGD capacity or $3,828 per acre for a 90 MGD screening/
flotation system.  Operating costs were estimated at $3.09c/1000 gallons of
treated overflow, including chemical flocculent addition.

This report was submitted as partial fulfillment of contract number 14-12-40
under the sponsorship of the Water Quality Office Environmental Protection
Agency.
                                   iii

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                             TABLE OF CONTENTS
SECTION I

SECTION II

SECTION III

SECTION IV
SECTION V
SECTION VI
SECTION VII
CONCLUSIONS

RECOMMENDATIONS

INTRODUCTION

LITERATURE SEARCH

   Characteristics of Combined Sewer Overflows
   Removal of Solids by Screening
   Dissolved-Air Flotation
   Disinfection of Combined Sewer Overflows
      Ultraviolet Light Disinfection
      Disinfection by Chemicals
   Summary Remarks

SITE SELECTION AND PRELIMINARY INVESTIGATIONS

   Site Selection
   Preliminary Investigations
   Conclusions — Preliminary Investigations

DESIGN AND CONSTRUCTION OF DEMONSTRATION FACILITY

   Design of Screen
   Flotation System Design
   Design of Supporting System
   Operation Methods and Test Plan
      Methods and Operational Procedures
      Sampling Procedures
      Test Plan

OPERATING RESULTS AND DISCUSSION

   Characterization of Raw Waste
   Results of the Screening Operation
   Operation of the Flotation System
   Disinfection of Combined Overflows
   Conceptual Design
      Pumping System
      Screening System
      Flotation System
   Economic Considerations
PAGE

  1

  5

  7

  9
 13
 15
 18
 18
 18
 20

 23

 23
 27
 36

 39

 39
 44
 45
 48
 48
 51
 51

 53

 53
 59
 61
 72
 72
 74
 75
 78
 81
SECTION VIII   ACKNOWLEDGEMENTS
                                                      87

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                      TABLE OF CONTENTS (CONTINUED)
SECTION IX

SECTION X

APPENDIX I
APPENDIX II
APPENDIX III

APPENDIX IV
BIBLIOGRAPHY

PUBLICATIONS

CHEMICAL OXIDATION

   LITERATURE SEARCH
      Hydrogen Peroxide
      Ozone
      Oxidation by Chlorine
      Oxidation by Oxy-Acids and Their Salts
      Electro-Chemical Oxidation
      Combination of Oxidants

   LABORATORY INVESTIGATIONS
      General Test Procedures
      Special Test Procedures with Various
         Chemical Oxidants
      Ozone Oxidation System

   RESULTS AND DISCUSSION
      Oxidation x^ith Hydrogen Peroxide
      Oxidation with Chlorine
      Oxidation with Combined System of Hydrogen
         Peroxide and Chlorine
      Oxidation with Ozone
      Oxidation with Gamma Radiation

   SUMMARY AND CONCLUSIONS

   BIBLIOGRAPHY - APPENDIX I, CHEMICAL OXIDATION

ANALYTICAL PROCEDURES

   Analytical Instruments and Apparatus
   Analytical Procedures and Analyses
   Dissolved - Air Flotation Test
      Procedure

DEMONSTRATION SYSTEM COSTS

OPERATING DATA AND STATISTICAL PROCEDURES

   OPERATING DATA
   STATISTICAL PROCEDURES
PAGE

  89

  93

  95

  96
  97
  99
 102
 104
 105
 105

 106
 106
 106

 111

 111
 111
 116

 116
 120
 122

 125

 127

 131

 132
 133

 135

 139

 143

 144
 170
                                vi

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                        LIST OF TABLES

TABLE                                                               PAGE

1      QUALITY OF COMBINED SEWER OVERFLOWS                            12
2      CHARACTERISTICS OF COMBINED OVERFLOW                           30
3      SUMMARY OF PRELIMINARY SCREENING DATA                          32
4      SUMMARY PRELIMINARY FLOTATION DATA                             34
5      PRELIMINARY SCREENING/FLOTATION DATA                           35
6      PRELIMINARY DISINFECTION DATA                          '        37
7      VARIABLE COMBINATIONS UTILIZED FOR TESTING                     40
8      SUMMARY FIRST FLUSH DATA                                       54
9      SUMMARY OF DATA - AT INTERVALS OF GREATER THAN 4 DAYS
          BETWEEN OVERFLOWS                                           55
10     SUMMARY OF EXTENDED OVERFLOW DATA                              58
11     PARTICULATE & DISSOLVED RELATIONSHIPS                          58
12     POLLUTANT REMOVALS BY SCREENING                                60
13     POLLUTANT REMOVALS BY SCREENING/FLOTATION                      62
14     SUMMARY PARTICULATE AND DISSOLVED ORGANIC REMOVAL EFFICIENCIES 65
15     COMPARISON OF PRESSURIZED FLOW RATES                           67
16     COMPARISON OF THE EFFECT OF OVERFLOW RATE ON REMOVAL           70
          EFFICIENCIES
17     SUMMARY OF DISINFECTION DATA                                   73
18     OPERATING COST ESTIMATES                                       86
1-1    LABORATORY ANALYSIS OF COMBINED SEWER SAMPLES UTILIZED
          FOR CHEMICAL OXIDATION STUDY                               107
1-2    RESULTS OF CHEMICAL OXIDATION WITH HYDROGEN PEROXIDE          113
1-3    EFFECT OF UV LIGHT AND COBALT ON HYDROGEN PEROXIDE OXIDATION  114
1-4    CHLORINE OXIDATION TESTS                                      117
1-5    LIGHT CATALYZED CHLORINE OXIDATION                            118
1-6    OXIDATION WITH COMBINED HYDROGEN PEROXIDE AND CHLORINE        119
1-7    SUMMARY 03 OXIDATION TESTS                                    121
1-8    SUMMARY 03 OXIDATION AND AIR FLOTATION TESTS                  123
1-9    SUMMARY DISINFECTION DATA - ALL SPRING STORMS                 124
I-10   SUMMARY OF OXIDATION OF COMBINED OVERFLOWS WITH VARIOUS
          OXIDANTS AND COMBINATIONS                                  126
IV-1   OPERATIONAL DATA                                              144
IV-2   RAW WASTE CHARACTERISTICS - FIRST FLUSHES                     148
IV-3   RAW WASTE CHARACTERISTICS - EXTENDED OVERFLOWS                149
IV-4   SCREENED WATER QUALITY - FIRST FLUSHES                        15]
IV-5   SCREENED WATER QUALITY - EXTENDED OVERFLOW                    152
IV-6   EFFLUENT WATER QUALITY - FIRST FLUSHES                        154
IV-7   EFFLUENT WATER QUALITY - EXTENDED OVERFLOW                    155
IV-8   DISSOLVED COD AND TOG DATA                                    158
IV-9   SCREEN BACKWASH & FLOATED SCUM QUALITY 1969 DATA              159
IV-10  SCREEN BACKWASH & FLOATED SCUM QUALITY 1970 DATA              161
IV-11  FIRST FLUSH EVALUATIONS                                       162
IV-12   ...RST FLUSH REMOVALS IN PERCENT                               164
IV-13  EXTENDED OVERFLOW REMOVALS IN PERCENT                         165
IV-14  SUSPENDED SOLIDS MASS BALANCE                                 168
                             vii

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                        LIST OF FIGURES
FIGURE                                                             PAGE

1      RELATIONSHIP OF FREQUENCY OF COMBINED SEWER OVERFLOWS
          TO INTERCEPTOR CAPACITY                                    11
2      PROJECT DRAINAGE AREA                                         25
3      RELATIONSHIP OF RUNOFF COEFFICIENT TO PERVIOUSNESS            26
4      RELATION BETWEEN WATER DEPTH AND FLOW IN HAWLEY ROAD SEWER    28
5      TYPICAL INTERCEPTOR DEVICE                                    29
6      COMPARISON TYLER MESH TO SIZE OF OPENING                      33
7      SCALE DRAWING OF DEMONSTRATION SYSTEM                         40
8      DEMONSTRATION SYSTEM                                          41
9      SCREENING SYSTEM                                              42
10     SCREENING SYSTEM                                              43
11     FLOTATION SYSTEM                                              46
12     FLOTATION TANK                                                47
13     HAWLEY ROAD OUTFALL                                           49
14     INTERIOR VIEWS OF THE CONTROL SHACK                           50
15     RELATIONSHIP BETWEEN FLOW IN SEWER AND SUSPENDED SOLIDS       57
16     SUSPENDED SOLIDS REMOVAL-SCREENING/FLOTATION                  63
17     BAFFLE ARRANGEMENT FOR OVERFLOW RATE TESTS                    68
18     RECOMMENDED SCREEN ARRANGEMENT                                79
19     RECOMMENDED SCREENING/FLOTATION ARRANGEMENT                   82
20     OVERALL SYSTEM CONFIGURATION                                  83
1-1    HUMAN TOLERANCE FOR OZONE                                   100
1-2    OZONE ABSORPTION SYSTEMS                                    103
1-3    APPARATUS FOR ULTRA VIOLET LIGHT OXIDATIONS                 108
1-4    APPARATUS FOR OZONE OXIDATIONS                              108
1-5    SCHEMATIC OF OZONE TEST APPARATUS                           112
                              vili

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                            SECTION I

                           CONCLUSIONS
The following conclusions can be made based on the data obtained during
this study.
1.  A screening/flotation treatment system is an effective method of
reducing the pollution caused by combined sewer overflows.

2.  The combined sewer overflows monitored during this study had the
following characteristics in mg/1 at the 95% confidence level.

     BOD                            49110
     COD                           161±19
     Suspended Solids              166±26
     Volatile Suspended Solids      90114
     Total Nitrogen                5.510.8

3.  Approximately 20% of the overflows monitored exhibited first flushes
of the following characteristics in mg/1 at the 95% confidence level.

     BOD                           186140
     COD                           581+92
     Suspended Solids              522±150
     Volatile Suspended Solids     308183
     Total Nitrogen               17.613.1
                                                               i
When present these first flushes persisted for 20 to 70 minutes.

4.  All first flushes occurred at a time interval of greater than 4 days
between overflows.

5.  It was demonstrated that a screening/flotation system could achieve
the following percent removal efficiencies based on the raw waste
characteristics encountered(Hydraulic Loading:Screen 40 gpm/sq ft,Flotation
2.75 gpm/sq ft).
                                 Without Chemical         With Chemical
                                Flocculant Addition    Flocculant Addition

     BOD                             3518                    60111
     COD                             4118                    57111
     Suspended Solids                4317                    7119
     Volatile Suspended Solids       48111                   7119
     Nitrogen                        29H4                   2419

6.  The chemical flocculant addition required to achieve the above stated
removals was 20 mg/1 ferric chloride and 4 mg/1 of a cationic polyelec-
trolyte.

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7.  An operating pressure of 50 psig and a pressurized flow rate of 20%
of the raw waste flow provided sufficient air bubbles for proper
flotation tank operation.

8.  The average volume of waste residual solids (i.«e^ screen backwash
and floated scum) was 1.75% of the raw flow.

9.  The average removal efficiencies for the screening/flotation svstem
decreased (as shown below in percent removals) when the hydraulic over-
flow rate was increased from ^2.75 to 3.75 gpm/sq ft.

                                 Low Overflow Rate   High Overflow Rate

     BOD                                 59                 52
     COD                                 57                 54
     Suspended Solids                    70                 61
     Volatile Suspended Solids           71                 64

10.  Utilizing a 50 mesh  (297 y) screen at a hydraulic loading of 40 gpm
per sq ft of screen.  The percent removal efficiencies for screening alone
were observed to be:

     BOD                                 27 ± 5
     COD                                 26 ± 5
     Suspended Solids                    27 ± 5
     Volatile Suspended Solids           34 ± 5

 11.  Capital cost  estimated for a full scale screening/flotation system
completely  installed was  $21,056 per MOD capacity or $3,828 per acre
for a  plant capacity of 90 MGD.  These costs were distributed as
follows:    screening/flotation modules and accessories 71%; sewers and
outfall  4%, land costs 9%, engineering and related costs 16%.

 12.  The  operating costs  for a screening/flotation system were estimated
 at 3.09C/1000 gallons of  treated overflow.  These costs include chemical
 flocculant  addition.  These costs were distributed as follows:  chemicals
 81%, power  17%, maintenance 2%.

 13.  The  screening/flotation system provides sufficient detention  time
 (^ 15  min.) for  effective chlorination.

 14.   Because of  the intermittent operation and remote location of
 combined  sewer overflow  treatment systems, completely automated opera-
 tion  is  required.

 15.  The  use of  a  50 mesh (297 y) screen eliminated  the need  for bottom
 sludge scrapers.

 16.   It  was not  always possible  to obtain optimum chemical  flocculant
 addition due  to  widely varying raw waste characteristics.

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1.7.  The following conclusions were made from the chemical oxidation
study:
        a.  Chemical oxidation of combined sewer overflow is not
        technically or economically feasible.
        b.  Ozone was the best oxidant evaluated.
        c.  Chlorine and hydrogen peroxide are not effective oxidants.
        d.  Particulate organic matter is very difficult to oxidize.
        e.  Ozone disinfection was found to be less reliable than
        chlorine for combined sewer overflows.

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                          SECTION II

                        RECOMMENDATIONS
It is recommended:

     1.  that screening/flotation be utilized to reduce the
     pollution from combined sewer overflows where treatment is the
     preferred alternative.

     2.  that the design and operating procedures outlined in the
     conceptual design section of this report be utilized for screening/
     flotation systems treating combined sewer overflow.

     3.  to investigate the effects of the unit process of flocculation
     on flotation removal, efficiencies.          |

     4.  to investigate methods of control of chemical addition as
     waste strength varies.
                                                 •»
     5.  to evaluate the dewatering characteristics of the sludges
     produced and various sludge disposal alternatives.

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                             SECTION III

                             INTRODUCTION
During recent years combined sewer overflow has been recognized as a
significant pollution problem.  Immediate reaction was to separate the
sewer systems.  It was found, however, that this solution was expensive
and sometimes impossible.  Furthermore, it has also been shown that
stormwater could carry a large pollutional load, therefore, tending to
reduce the effectiveness of sewer separation.  As research to find a
solution to the combined sewer problem began, it became apparent that
no one solution would solve all the problems associated with combined
overflows.  The ultimate solution depends upon successful application
of many different approaches which may include separation of sewers,
holding tanks, and treatment systems.

The objective of EPA/WQO Contract Number 14-12-40 is to develop and
demonstrate a method of treating combined sewer overflows.  It is
envisioned that the system or systems developed during this project will
be utilized to provide effective and economic treatment for those
combined sewer overflows where treatment is the best alternative.

Initially, the technical approach in this project was screening and
chemical oxidation of combined overflows.  Early during the study it
was determined that chemical oxidation was not feasible and this approach
was abandoned.  A summary of the work done on chemical oxidation may be
seen in Appendix I.  During the investigation of chemical oxidation,
however, a promising alternative was uncovered.  It was discovered that
the pollutants in combined sewer overflow consisted mainly of particulate
matter.  This clearly indicated that an efficient solids/liquid separa-
tion process should provide a high degree of treatment for combined
overflows.  The work scope of the existing contract was modified to allow
study of a screening/dissolved-air flotation system.  Later, after
evaluating the system for a short time, it became apparent that a more
detailed study of the screening process could provide important addi-
tional information and the contract was amended to include these studies.

The amended contract is divided into the following phases.

     I.  Literature search, site arrangements, preliminary investiga-
         tions
    II.  Design and construction of a 5 MGD screening/flotation system
   III.  Operation of the screening/flotation system
    IV.  Design and construction of a 5 MGD series screening system
     V.  Operation of the screening/flotation and series screening
         systems in various combinations
    VI.  Final report, system disassembly and restoration of demonstra-
         tion site

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This report summarizes the work done to date on the above mentioned
phases I, II, and III.  Work on phases IV, V and VI is now underway
and completion is expected by March of 1972.

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                              SECTION IV

                           LITERATURE SEARCH
 It  is  assumed that the following process  elements  will  be  utilized  to
 accomplish the treatment of combined sewer overflows.

     A.   Solids/liquid separation

          1.   Screening
          2.   Dissolved-Air flotation

     B.   Disinfection of the waste flow

 A search of  the existing literature was made  to determine  the
 characteristics of combined sewer overflow, and to obtain  pertinent
 information on the above mentioned process elements.

 Characteristics Of Combined Sewer Overflows

 More than 1400 U.S.  communities serving 50 million people  have what is
 known  as combined sewer systems which provide one collection system
 for both sanitary sewage and stormwater runoff (1).  During dry weather
 the flow in such a system consists mainly of  sanitary sewage and is
 normally intercepted by the interceptor systems before  it  reaches the
 outfall, where it otherwise would be discharged to a lake  or river.  As
 long as  the  capacity of the interceptor system exceeds  the flow in the
 combined sewer, the flow is directed to the sewage treatment plant for
 purification.

 During a storm, the flow in the combined  sewer can increase from 50 to
 100 times the normal dry weather flow (2).  Normal interceptor capaci-
 ties are between 1.5 and 5.0 times the dry weather flow (hereafter
 abbreviated  DWF)(2)(3)(4).   This would mean that at normal interceptor
 capacities,  the interceptors would be from 97.3 to 99.0% efficient in
 collecting and transporting the sanitary  sewage to the  treatment plant.
 These  efficiencies are very misleading, since during periods of high
 stormwater runoff, it is possible to have up  to 96% of  the sanitary
 sewage bypassing the interceptor system and being  discharged untreated
 into the receiving waters (5).   This discharge of  untreated combined
 overflows could cause severe pollution problems if the  water is reused
 a relatively short distance downstream as a water  supply or for
 recreational activities.

 The  pollution  caused by combined sewer discharge is directly related to
 the  frequency  of storm runoff exceeding the interceptor capacity.
 Three  independent  investigators (5) (6) (7)  report that the  normal dry
weather  flow is approximately equivalent  to a rainfall  intensity of
about  0.01 inch per  hour.   With interceptor capacities  of  1.5 to 5 times
the  dry  weather flow,  rainfall  intensities greater than 0.015 to 0.05

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inches per hour would be necessary to cause combined overflow which
would go untreated.  Palmer (6), Johnson (7),  and McKee  (5) studied
the  rainfall records of Detroit, Washington, D.C.,  and Boston.  The
results of their findings showing the number of  combined overflows per
month for given interceptor capacities may be  seen  in Figure 1.  with
an  interceptor capacity of 5 times (DWF),  the  number of overflows per
month was between four (4) and six (6).   This  indicates the extent ot
possible pollution of the receiving body of water.

The  pollutional effect of combined sewer overflows  will, of course, be
determined not only by the frequency of  overflows,  but also by the quality
of  the overflow.  The most important and commonly discussed pollutional
parameters associated with combined sewer  overflows are suspended solids,
BOD, and coliform count.   To establish a basis for  comparison, the
average raw  (primarily domestic) sewage  contains 200 to 300 mg/1 suspended
solids (1)(8)(9), (50 to 60% of these suspended  solids are settleabje),
100  to 300 mg/1 BOD (1)(8)(9)  and coliform counts of 43 to 150 x 10
per  ml (9)(10).

Assuming pure stormwater to be essentially unpolluted, it would be
expected that the BOD, suspended solids, and coliform counts of
combined sewer overflow to be  substantially lower than those of raw
sewage.  This assumption could result in considerable error when
estimating the quality of combined sewer overflows.  A limited amount
of  data has been obtained which indicates  the quality of pure storm
runoff is highly variable and  can be quite polluted (4)(6)(11)(12)(13)
(14).  BOD's ranging from 6 to 600 mg/1, suspended  solids ranging from
100  to 2000 mg/1, and coliform counts as high as 200,000 per ml have
been reported.

Another factor which can greatly influence the quality of combined
sewer overflow is the amount of solids which settle in the sewer system
during periods of low flow.  Since combined sewer systems must be
designed for a wide range of flow, the amount of solids which are
deposited during periods of dry weather  can be significant (15)(16)(17).
Hopefully, these solids will be resuspended during  the first flushes of
the  storm and be intercepted before combined overflow begins.   Published
data has shown, however,  that  with an interceptor capacity of only 1.5
to  5 times the dry weather flow and a sewer system  designed to take 50
to  100 times the dry weather flow, most  of  the solids which have settled
are  not resuspended until after the capacity of the interceptors has
been exceeded (11) (14) (15) (16) (17).   Hence, these solids can contribute
greatly to the pollutional load in the stormwater overflow.

The  above discussion has  illustrated that  combined  sewer overflows can
contribute a significant  pollutional load  to receiving streams or lakes.
Table 1 summarizes data reported by others  on the quality of combined
sewer overflows.  It is obvious that the quality of combined overflows
is highly variable.   Of the three pollutional parameters most  mentioned,
i.e., BOD, suspended solids and coliform count, the coliform count,
a measure of pathogenic bacteria contamination (8), appears to be
the  most significant (10) (13).   In a recent study (13), a survey was
made to indicate what water uses were most  affected by combined

                                 in

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246
  Interceptor Capacity (times DWF)

              FIGURE 1

  RELATIONSHIP OF FREQUENCY OF
  COMBINED SEWER OVERFLOWS TO
     INTERCEPTOR CAPACITY
10
            J.1

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TABLE 1

Source
Reference iiUU
; < urn b e r mg / 1
(b; ^o
(14) 100
(13) 59
(13) 92
(13) 121
(12)
(11) 40-260
(11) 220-614
QUALITY OF
Suspended
Solids
mg/1
250
544
203
129
436
150
130-930
168-426
COMBINED SEWER
E. Coli
Density
per ml.
43,000
—
300,000
500
—
180,000
2300-24000
2,100
OVERFLOWS
Discussion
Detroit, Michigan
Average Estimated Values
Buffalo, New York (Bird Avenue)
1 Sample
San Francisco, California
(Average Value 14 Samples)
Chicago, -Illinois
Average 31 Overflows (1962
Buffalo, New York (Bailey Avenue)
Average Values, 43 Samples
1964 Data
Toronto, Ontario, Canada
(Eglinton Avenue)
Welland, Ontario, Canada
                (Burgar Street)

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overflows.  The survey indicated those uses most affected were commercial
(fishing), recreational  (swimming), and public health  (water supplies).
The main pollutant affecting these water uses is pathogenic bacterial
contamination  (measured by coliform density)  (1)(5)(15)(16).  Table 1
shows the range of coliform counts to vary from 0.5 x  10' to 300 x
10 /ml in combined sewer overflows.  (A review of disinfection starts
page 170

The suspended solids concentration of combined overflow can be quite
large.  Table 1 shows a range of suspended solids in combined overflows
of 129 to 390 mg/1.  The values shown in Table 1 are averages.  The
initial peak of suspended solids can be higher (11) (15)(14).  Romer and
Klashman (16) presented graphs which illustrate how suspended solids in
combined overflows vary as the flow increases.  They reported that, in
general, the svispended solids concentration and the flow reach a maxi-
mum value at approximately the same time.  The suspended solids then
begin to fall off rapidly.  Stegmaier (17) has shown that the main
increase in solids is of inorganic nature.  Initially, the BOD exerted
by the solids will probably be quite large, since the  settled organic
material will be resuspended before the inorganics.  Hence, the BOD of
combined sewer overflows will initially be quite high with a large
portion of the BOD in the particulate form.  This would seem to indicate
some sort of mechanical separation may be very effective in removing
BOD during the first flushes of a storm.  Later, as the storm progresses
the BOD would be expected to decrease to levels much lower than those
of raw sewage.  The ratio of dissolved to particulate  BOD will increase
and mechanical separation will probably become less efficient in removing
BOD.

Removal of Solids by Screening

Bar screens with openings of 1/2 to 1-1/2 inches are used extensively
in sewage treatment plants throughout the United States (18),  The
amount of solids removed by these coarse type screens  ranges from 0.5
to 6 cubic feet of wet solids per million gallons of sewage (19) (20).
On a dry weight basis, this represents 9 to 48 pounds  of dry solids per
million gallons of sewage (19)(20) or a removal of about 1 to 6 ppm
from the sewage flow.  Since raw sewage contains 200 to 300 ppm (1)(8)
(9) suspended s-lids, bar screens remove only a small  fraction of the
solids, i.e., 0.5 go 2%.  This fact is not surprising, since the primary
purpose of bar screens is to remove large and/or floating solids to
protect pumps and other treatment devices downstream of the bar screens
(8)(18).

In general, the approach velocity in the screening channel should not
fall below a self-cleaning value (about 1.25 fps) or should it rise to
values high enough to force the screenings through the bars (about 3
fps) (8)(18).  Headlosses through bar racks can be formulated as an
orifice loss (8).
               4/3
     h = B(w/b)   h  sine
                              13

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where

     h = loss of head in feet
     w = maximum width of the bars facing the flow
     b = minimum width of the clear openings between pairs of bars
    hy = velocity head (in feet) of the water as it approached the rack
     6 = the angle of the rack with the horizontal
     6 = bar shape factor

Values for 3 are 2.42 for sharp-edged rectangular bars, 1.79 for
circular bars, and 0.76 for tear-drop shaped bars (8).  Headless
through bar racks is generally held below one foot by periodic
cleaning of the bars.  This cleaning can be accomplished manually or
mechanically (8).

Fine screens 1/16 inch to 1/32 inch openings have been used in a
number of locations  (19)(20)(21)(22) to treat municipal wastes.  This
size of screen will remove 2 to 20% of the suspended solids in raw
sewage (8)(18)(19)(20)(21)(22).  Openings of 1/16 inch, correspond to
a sieve size (Tyler series) of 12 to 20 mesh.  Use of standard wire
sizes finer than these meshes tend to blind because of the build-up of
animal fats and greases on the screen (23).  It has been reported by
Peterson (23), however, that the use of new synthetic materials for
screens has greatly reduced the blinding tendency and allows greases to
be discharged from the top of the screens.  He also reports meshes as
fine as 300 have been used when filtering raw sewage.  The allowable
rates of filtration, with these extremely fine mesh screens, however,
were not reported.  The results of screening raw sewage through a 300
mesh screen showed a reduction in suspended solids from 196 to
101 mg/1 or a 48.5% removal (23).  This removal rate is approximately
equal to the rates obtained by primary sedimentation of raw sewage (8)
(18).

As the openings in the screen are reduced, the headloss increases and
screen blinding becomes very important.  This necessitates automatic
mechanical cleaning, which is generally accomplished by backwashlng
the screen with jets of water and/or air.  Headlosses through fine
screens can be calculated from an orifice type equation.
where:

     Q = flow  (cfs)
     A = area  (sq ft)(actual open area)
     g = gravity constant (32 ft/sec2)
     C = screen coefficient
     h = headloss through the screen (feet)

Screen coefficients  (C) vary with the size of the screen openings
Values are generally between 0.3 to 0.6 for 2 to 60 mesh screens.
                                14

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Headlosses through fine mesh screens are generally held below 2.5 feet
(8) by varying the frequency of cleaning.

There is a very limited mention found in the literature on screening of
combined sewer overflows.  Stegmaier (17) and Romer and Klashman (16),
however, have shown that a large portion of the suspended solids in
combined sewer overflows can be attributed to inorganic materials.
This tends to indicate that fine screening of combined sewer overflows
may show a higher percentage removal of suspended solids than is
obtainable when screening raw sewage.  Boucher and Evans (24) have
discussed the microstraining process and its applications in removal of
suspended material.  They have indicated that microstraining can be
effectively and economically used in polishing of sewage effluents.
Metropolitan Sanitary District of Chicago is reported to be utilizing
microstrainers for its Hanover Water Reclamation Facility (25).  In a
recently reported study by Keilbaugh es£ aJL (26), up to 98% of suspended
solids were removed from a combined sewer overflow by using a nominal
23 micron aperture microstrainer screen.  However, most of the data
published towards the use of microstrainers in waste treatment has been
of investigational nature only, and significantly more data is needed to
substantiate such findings.

Dissolved-Air Flotation

An active use of dissolved-air flotation (DAF) in the waste treatment
area has only been made in the last two decades, but the use of air-
bubbles to change the apparent specific gravity of suspended matter in
water has been practiced for nearly a century in the mining industry
for the beneficiation of ores.  Selective adsorption was accomplished
by the use of flotation agents.  Chase (27) and Rohlich (28) have
discussed the developmental background of dissolved-air flotation.   The
process as it is used now is an outgrowth of air flotation methods used
in the recovery of paper fibers.  The fiber recovery was achieved by
the adsorption of an air bubble on the fiber.  The floated material
formed a scum and was collected by a suitable mechanism.  The presence
of alum and addition of glues aided the separation of fiber by the
flotation process.  Dissolved-air flotation utilizes a much smaller
diameter bubble (less than 100 microns) than that used in the mining
industry.  It is clear from the above discussion that the removal of
suspended matter is accomplished when there exists sufficient ad-
sorption forces between the air bubble and solid particle.

Geinopolos and Katz (29) have discussed solids-liquid separation by
dissolved-air flotation as compared to sedimentation and have indicated
that a waste could be treatable by either sedimentation or flotation,
but higher separation rates and solids concentration may be possible by
dissolved-air flotation.  This results in smaller basins, smaller
sludge volumes and higher water recoveries for treatment by flotation
processes as compared to sedimentation.  The mechanism and driving
forces involved in the flotation process is similar to those
encountered in sedimentation. Stoke"s Law illustrates the mechanism
                               15

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by the following equation:

                V = gD2(Ys-Yi) / 18y

Where:

     V = Particle separation velocity, ft/sec
     g = Gravity constant, ft/sec2
     D = Diameter of particle, ft
    Ys = Density of particle, Ib/cu ft
    YI = Density of liquid, Ib/cu ft
     V = Viscosity of liquid, Ib/ft/sec

In the flotation process, the density of the air-solid combination is
less than the suspending medium and value of V becomes negative, caus-
ing an upward particle velocity.  Also, the effect of the air-bubble is
to increase the difference in densities between the particle and
suspended medium, which in turn increases the solids separation rate.

Van Vuuren e_t^ £d (30) has reported the use of oxygen produced by algal
photosynthesis to accomplish flotation.  He also cites the applicabil-
ity of dispersed air flotation in conjunction with chemical precipita-
tion in advanced treatment of wastes (31).  Chase (27) has described
the types of dissolved-air flotation processes used for waste treatment.
These include pressure and vacuum types.  However, pressure type appli-
cations in waste handling fer outnumber those for vacuum flotation,
primarily because of inherent flexibility in a pressurized system.
The vacuum process is limited by the amount of reduced pressure that
can be effectively used.  Geinopolos and Katz (29) state that the
process elements of dissolved-air flotation are:

      (1)  Flow pressurization
      (2)  Air Introduction
      (3)  Air Solution
      (4)  Pressure reduction and bubble formation
      (5)  Bubble/solids attachment
      (6)  Solids/liquid separation
      (7)  Separated solids removal

The literature describes variations in the flow pressurizing process
(27)(28)(32)(33).  These include:  total pressurization, in which the
entire volume of raw waste is pressurized, split flow, in which a
portion of the raw waste is pressurized and later blended with the
remaining raw waste stream; and effluent pressurization, in which a
portion of basin effluent is pressurized and later blended with the
entire volume of raw waste.

The dissolved-air flotation process has been applied to remove
suspended matter from many industrial wastes such as:  paper wastes
(35), refinery wastes (28) (36), laundry wastes (37), soap wastes (38),
machine shop wastes (39), automobile wastes (40), and others (27)(28)
                               16

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prior to discharge in a receiving body of water or reuse.   Vrablic
(34) in his discussion of the fundamental principles of dissolved-air
flotation mentions that hydrophobic solids will float much more easily
than will hydrophilic ones.  In an investigation of the kinetics of
removal of organic matter by activated sludge, Rohlich and Katz (4)
demonstrated that activated sludge floe can be separated from water by
dissolved-air flotation.  Ettelt (42) has also shown that dissolved-
air flotation can be successfully employed for activated sludge
thickening.  There have been several other reports on the use of
dissolved-air flotation for dewatering of aerobic biological solids
(43)(44)(45)(46).

Proper performance of a flotation unit is dependent upon sufficient
air bubble/solids attachment to effect good flotation.  Batch
laboratory flotation tests as described by Eckenfelder (47) have been
used to estimate the flotation characteristics of wastes for the
purposes of  design.  Howe  (48), in a mathematical derivation of flota-
tion cell design also recommended that considerable experimentation
with each different waste precede the use of his equations in determin-
ing the exact criteria for flotation cells.  For sludge thickening
application, air/solids ratio has been used to relate laboratory data
to prototype facilities.  A ratio of 0.03 to 0.1 is considered
optimum for  most sludges  (34)(49).  However, air/solids ratio for
clarification alone is generally not critical.  Truck mounted
continuous flow, pilot scale units are used widely for obtaining
design information.  The primary variables for flotation design are
operating pressure, ratio  of pressurized flow to raw waste flow,
retention period, and the  combined particle/air bubble rise rate.
Generally, the  effluent suspended solids decrease and the concentra-
tion of solids  in the floated sludge increase with increasing reten-
tion period. For clarification, a detention period of 15 to 30 minutes
is  normally  considered adequate  in the flotation zone.  Rise rates of
1.0 to 3.0 gpm/sq ft  (0.13-0.39  feet per minute) are commonly
employed.  The  amount of pressurized flow usually varies  from 15  to
50% of raw waste flow for  separation.  The recycle amount and
detention period are higher  for  thickening application depending
upon feed solids concentration.  The process  pressure may vary  from
30  to  70 psig,  with 40  psig  considered normal.  Air requirements
range  from 0.5  to  1.0 cu  ft  of  standard  air per one hundred  gallons
of  pressurized  flow  (32).  The  air and liquid  are mixed under
pressure  in  a  retention tank with a  detention time  of  1 to  3 minutes.

Addition  of  chemicals may  be employed depending upon  the  nature of
the waste and  the degree  of  treatment required.   Chemicals  such as
alum,  lime and  ferric  chloride  are usually used  in the  chemical
treatment of a wastewater.  The purpose  of chemical treatment  is to
precipitate  and coagulate  colloidal  and  finely suspended  particles to
form large  suspended  floe  particles.  This increases  the  separation
rate of  the  solids by  flotation.  Recent efforts  to improve flotation
efficiency by  chemical  addition have involved use of  synthetic  organic
polyelectrolytes.  Generally,  these  polymers  have been found to
                               17

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improve solids capture (clarification), to increase the concentra-
tion of solids in the float and to increase the capacity of flotation
equipment (50)(51)(52) .  An apparent advantage of polyelectrolytes
is the elimination of a separate flocculation tank, since the floe
particles are formed in an extremely short period of time.  Cationic
polyelectrolytes have been successfully employed as flotation aids
for thickening applications (46) (53).  The results indicate that
desired float concentrations may be achieved with high solids
loadings when polymers are utilized.  Bench scale procedures are
normally employed for determining the dosage and effectiveness of a
particular polymer application in dissolved-air flotation.

Disinfection Of Combined Sewer Overflows

Disinfection may be defined as destroying those bacteria that cause
infection or disease.  Sterilization is defined as the destruction of
all living organisms (54).  Methods commonly used for disinfection
include heat, ultraviolet light, and chemical addition.  Chemicals
which have been used include chlorine, bromine, iodine, potassium
permanganate and ozone (8).  The various methods and chemicals used
for disinfection which appear to be applicable to this project will
be discussed below.

Ultraviolet Light Disinfection

The effect of radiation on bacteria has been studied in detail, and
the relationship between wave length and germicidal effect is well
known.  The optimum wave length is 2600 angstrom, hence, low
pressure mercury vapor lamps with their high output at 2537 angstrom
are effective bactericidal  agents (55).  Light of this wave length
falls in the ultraviolet section of the light spectrum.  To insure
disinfection, the water should be relatively free of suspended
matter which might shade the organisms against the light (8).  Time
and exposure intensity must also be adequate to insure disinfection.
One hundred microwatts per square centimeter of 2537 angstrom light
will produce high bacteria kills at contact times of less than one
minute (55)(56).

Use of ultraviolet light for disinfection has found limited appli-
cation, probably because other methods of disinfection are more
economical (8).

Disinfection Bv Chemicals

Chlorine and chlorine compounds have proven so economical and effi-
cient that they are widely employed for their bactericidal action.
The chlorination of wastes may be regulated to accomplish various
degrees of bactericidal action.  Chlorine is a bacteriostatic agent
when applied in small concentrations, to prevent an increase in the
bacterial population.  Chlorine is a disinfecting agent when
applied in larger amounts to destroy those bacteria that cause
                              18

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infection or disease.  Chlorine may be, but seldom is, applied in
amounts so large as to be a sterilizing agent, i.e., to destroy all
living organisms (54).

Forms of chlorine which may be used for disinfection and other purposes
include gaseous or liquid chlorine, chlorinated lime, calcium hypo-
chlorite, sodium hypochlorite, chlorinated copperas, and chloramines.
Chloramines, however, are a slower acting and less active form of
disinfectant.  Liquid or gaseous chlorine is the most commonly
utilized form.

The efficiency of disinfection using chlorine or other disinfecting
agents is dependent on (a) the contact time, (b) the type and
concentration of microorganisms, (c) the pH and temperature of the
water, (d) the presence of interfering substances, (e) and the degree
of protection afforded organisms from the disinfecting solution by
materials in which they may be imbedded.

Generally, a chlorine dosage, sufficient to give a 0.5 ppm residual
after a 15 minute contact time, is considered adequate for disinfec-
tion  (54).  The actual amount of chlorine added to obtain this
residual will vary with the waste being chlorinated.  Fair and Geyer
(8) give values of 6 to 24 mg/1 for raw sewage.

Camp  (10) indicates screening and chlorination of combined sewer
overflows would be an effective and inexpensive way of treating
these flows.  Chlorine dosages were estimated to range from 1.6 to
8.5 ppm.

Symons (57) found the chlorine demand for Buffalo sewage during
periods of combined overflow to range from 6 to 7 mg/1.  Considering
the possible quantities of combined sewer overflow, this represents
quite a substantial chlorine dosage, and will require chlorine
feeders operating over a very wide range of flows.

Iodine and bromine were also found to be effective in disinfecting
sewage, but required higher dosages compared to chlorine (58).
Fluorine was found to be so reactive that it was difficult to store
and apply (58).

Potassium permanganate has been used to disinfect water supplies (59)
(60), and is an effective disinfectant at relatively low dosages (59).
Use of potassium permanganate has not been widespread.  This is
probably due to one or more of the following disadvantages of
potassium permanganate disinfection when compared to chlorine dis-
infection.

     1.  KMNO, imparts a color to the water which must be removed
         before use (62).
                                19

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     2.  Most effective pH for KMNO^ is 5.9 which is below the pH of
         many water sources.

     3.  Potassium permanganate is not a good post-treatment
         disinfectant because of the color and pH criteria.

Ozone  is a very effective disinfectant.  This fact is well known and
has been proven over a period of 60 to 80 years (35)(46)(61)(62) (63) .
Ozone  is used extensively in Europe, especially in France (62).
Disinfection by ozone follows a slightly different pattern when
compared to chlorine.  Generally, with increasing chlorine dosage the
number of bacteria progressively decrease, while with ozone little
reduction is noticed until a critical dosage is reached.  At this
critical value, the bacterial population is rapidly reduced (35).

Unlike chlorine,  the disinfecting action of ozone is little affected
by changes in temperature or pH.  Ozone acts rapidly and is almost
instantaneous, where chlorine needs time to be effective (35) (61).

The reason ozone  is not utilized to the same extent as chlorine is
probably twofold,  i.e., cost and inability to carry an ozone residual
for any length of  time.  Hann  (62)  states that, in general, if
disinfection is the sole objective, ozone is more expensive than
chlorine.  When using ozone as a disinfectant, it is not possible to
carry  an ozone residual for a  significant period of time (35), and
this is sometimes  cited as  a disadvantage when using ozone.

When using ozone  proper precautions must be  taken in applying  the
ozone  to insure disinfection  (62).  The water should be low in
turbidity, the ozone demand must be satisfied, and there must  be a
residual of  free  ozone  in the  water for a definite period  of  time.
This usually is from 0.1 to 0.2  ppm ozone residual for  1 to 5
minutes  (35)(62).

Summary  Remarks

The material contained  in this literature  search was compiled  in an
effort to  uncover the  known process elements applicable to  the
treatment  of wastes  similar to combined sewer overflows.   The informa-
tion gained  from  this  literature search will be used as a  guideline
for  laboratory  and bench  scale tests  to determine what  combination(s)
of the various  process  elements is  (are)  best  suited to the design,
fabrication, and  operation  of  a prototype  combined  sewer overflow
treatment  unit.

Although a literature  search  is technically  concerned only with the
reporting  of data found in  published  form,  some  of  this data   for
one  reason or  another,  can  be  eliminated  from further consideration
without  the  benefit of  laboratory testing.   As a  result,  this report
comprises  a  certain number  of  engineering judgments and/or eval-
uations.   Such judgments, however,  have been made only  where  the
                                20

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material available or the investigator's experience have justified
making them.  That data which appeared to have genuine value to the
completion of this project has been carried forward to the
laboratory studies portion of the project.

Significant observations from the literature search are summarized below:

     1.  The flox<7 in combined sewers can Increase 50 to 100 times the
     dry weather flow,

     2.  Normal interceptor capacities are between 1.5 and 5.0 times
     the dry weather flow.

     3.  Up to 96% of the sanitary sewage can bypass the interceptor
     system during heavy storms.

     A.  Rainfall intensity greater than 0.015 to 0.05 inches per hour
     is generally sufficient to cause combined sewer overflow.

     5.  Limited data indicate pure storm water can be quite polluted.

     6,  The ma-jority of the solids settled in the sewer svstem during
     dry weather are not resuspended until the capacity of the intercep-
     tor system is exceeded.

     7.  It was indicated that the main water usages effected by combined
     sewer overflow were commercial fishing, swimming, and public
     water supply due to bacterial contamination.

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                             SECTION V

            SITE SELECTION AND PRELIMINARY INVESTIGATIONS
Site Selection

A search was conducted to select a suitable demonstration site for
the installation and operation of a demonstration treatment unit.
The City of Milwaukee, as an available source of combined sewer
overflow, was solicited in regard to participating in the demon-
stration of the proposed treatment system.  The City of Milwaukee
responded favorably by offering both access to a combined sewer as
well as providing sufficient land to install the demonstration
equipment.  In addition, the City Engineer's Office was made
available for consultation and aid in selecting the most beneficial
demonstration site.

Six potential sites were investigated.  These sites were located
in the City of Milwaukee as follows:

     1.  The Edgewood Avenue site, consisting of a 72 inch combined
         dewer discharging into the Milwaukee River.

     2.  The 27th Street site (south end of viaduct), consisting of a
         48 inch combined sewer discharging into the Menomonee River.

     3.  The East Kane Place site, consisting of a 72 inch combined
         sewer discharging into the Milwaukee River.

     4.  The Bay Street site, consisting of a 90 inch diameter
         combined sewer discharging into Lake Michigan.

     5.  The Russell Avenue site, consisting of a 120 inch diameter
         combined sewer discharging into Lake Michigan.

     6.  The Hawley Road site, consisting of an 8'6" by 5'0" combined
         box sewer discharging into the Menomonee River.

The potential sites were appraised and evaluated from the standpoint
of availability for project duration, access to sewer flow, access to
utility sources, space limitations, extent of structural and/or
topographical modifications, proximity to residential or developed
areas, drainage area covered, and the socio-economic nature of the
drainage area.

By inspection, the Edgewood Avenue, 27th Street, and East Kane Place
locations were eliminated as potential demonstration sites.  The
Edgewood Avenue and 27th Street sites were inaccessible and were
limited in space.  The East Kane Place site was located in a residen-
tial and developed area.  In fact, the site consisted of a city-owned
                                23

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lot, located between two residences, which were about thirty feet
apart.

The Bay Street, Russell Avenue, and Hawley Road locations were
further investigated as potential demonstration sites.  Maps of the
respective combined sewer areas were obtained from the City
Engineer's Office in which the drainage area covered and the socio-
economic nature of the drainage area were delineated.  The areas
drained by each of these three sites is predominantly residential
with some local business and industrial activity.  The drainage areas
covered by the three potential sites were as follows:

                    Bay Street           385 acres
                    Russell Avenue       465 acres
                    Hawley Road          495 acres

The Bay Street location was eliminated because an investigation
revealed that it would be difficult and impractical to impound the
flow in the sewer to provide the necessary raw sewage pump suction
conditions.

The Russell Avenue site was eliminated because of a restrictive time
limit placed by Milwaukee County authorities upon the use of the site
for project purposes.  It was felt that the site may not be available
for the full duration of the project.

Since the Hawley Road site appeared to be the most desirable .locatation
for a demonstration unit, additional information was obtained on this
sewer and the area served.

As mentioned above, the total area served by this sewer is 495 acres.
The area is located on the western edge of the Milwaukee City limits.
Figure 2 presents a street map of the City of Milwaukee.  The outlined
portion depicts the drainage area served by the Hawley Road sewer.  The
drainage area was studied using recent (1970) aerial photographs.  It
was determined that approximately 42% of the area was impervious, i.e.,
roof tops, streets and parking lots.  This value is within the range
presented in the literature (8) for North American cities in areas of
1 and 2 family dwellings.  The relationship between runoff coefficient
and perviousness is presented in Figure 3.  The data in Figure 3 is
based on the City of Milwaukee runoff curves.  It may be seen from
Figure 3 that the runoff coefficient for the Hawley Road drainage area
is  0.40.  While it is recognized that the runoff coefficient can vary
as  the storm progresses  (8), no attempt was made to refine the runoff
coefficient, since an exact number was not critical to this project.
The aerial photograph indicated that the area is a completely
developed residential area of one of the older sections of the city.
There is very little open area present such as parks or fields.  All
dwellings are of the one and two family variety.  Population density
based on number of dwellings per acre and assuming four persons per
family was estimated at 35 persons per acre.  There are some small

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                        STADIUM
                          F R w r
                    WASHINGTON
                      location
                         0^*
                        unit
      FIGURE 2
PROJECT  DRAINAGE AREA
         25

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  100.
   8(
         Based on City of Milwaukee, Wisconsin
                      Runoff Curves
 CO
 o 60
O-

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 shops such as jewelry,  hardware,  etc.   No industrial manufacturing
 facilities are located  within the drainage area  served by  the
 Hawley Road sewer.   The one industry which is  within the drainage
 area is Topp Oil and Supply Company.  They are involved with blending
 various oils and apparently do not actually process any oil at  this
 site.   A discussion with personnel at  the Milwaukee Sewage Treatment
 Plant revealed that Topp Oil did  not discharge any significant
 pollutional load into the sewage  system.

 The  combined sewer  outfall serving the Hawley  Road drainage area is
 rectangular in cross section 8.5  feet  wide and 5 feet high.  The
 relationship between water depth  and flow rate is shown in Figure 4.
 It may be seen from the figure that the sewer  has a capacity well in
 excess of 100 MGD.   Because of the location of the sewer and the
 rectangular shape,  a retaining structure  was easily added  to impound
 the  flow.  This allowed long test runs even during periods of low
 rainfall intensity.  Calculations show that if a 3 foot high retaining
 structure is placed at  the combined sewer outfall to retain the flow,
 a volume of about 100,000 gallons can  be  retained for evaluation
 after normal overflow has stopped.   The retaining structure is a
 movable dam which tips  up as a result  of  water pressure if the sewer
 begins to surcharge. In the normal untipped position the  dam does not
 seal the sewer completely and this insures that the sewer  will always
 be dry prior to any overflow.  At a treatment  rate of 5 MGD, this
 reservoir would allow an additional one half hour operation of the
 demonstration system.  In actual  operation,  an additional  operating
 time of only 15-20  minutes has been realized.  It should be noted
 that the length of  operation reported  herein includes this 15-20
 minute storage factor and hence the duration of overflow is shorter
 than the length of  run  by this time period.  The Hawley Road Sewer
 is fed by two interceptor devices.   These interceptor devices are of
 the  sump type.   A sketch of the interceptor device utilized is shown
 in Figure 5.

 Since the Hawley Road Sewer and adjacent  land  met all the  requirements
 necessary to successfully complete the demonstration phase of this
 contract, arrangements  were completed  with the City of Milwaukee in
 February of 1968 to allow use of  the sewer and land for this project.

 Preliminary Investigations

 After  the site  selection was finalized, 14 overflows were  monitored to
 obtain information  on overflow characteristics, and to provide  raw
 overflow for subsequent laboratory testing.  Results of the laboratory
 testing  program were then utilized to  design the demonstration  system.
 Table  2  presents a  summary of the data collected prior to  system
 design.   As  was expected,  the range of values  is quite large.
 Suspended  solids  values from 2158 to 65 mg/1 were observed, while COD
values ranged between 1410 and 52 mg/1.  The dissolved organic  fraction
of the overflows  as measured by COD was only 4 to 25% of the total
organic  load present  in the  combined overflow.  This indicated  that an
                                27

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      100



       80




       60


       50



       40



       30






       20
    •o
    60
    e
    01
    in

    •O
    OJ
    c
    •H
    JD
    E
    o
       10


































/
f














/
/














/
f













j
/
f














/
f
















/

















/

























7

/























Combined Overflow SeweF—
(8'-6" x 5'-0")
Haw ley Road Outfall
Based on Manning _
Formula
1 1
Water Depth - Feet
FIGURE 4
.0
RELATION  BETWEEN WATER DEPTH AND  FLOW IN HAWLEY ROAD SEWER

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NJ
o
                                          Combined  Sewer
                                                    Man Hole
                                                 Interceptor  Sewer
                                                      FIGURE 5
                                             TYPICAL INTERCEPTOR DEVICE

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                                         TABLE 2

                           CHARACTERISTICS OF COMBINED OVERFLOW
                                (Fall 1967 - Spring 1968)

Date
of
Overflow
09/27/67
11/02/67
11/10/67
Il/16/b7
11/25/67
12/07/67
12/21/67
01/29/68
04/03/68
04/03/68
04/17/68
04/20/68
04/23/68
04/28/68
04/28/68
05/20/68

Total
Solids
mg/1
388
	
651
664
649
	
	
	
	
	
	
	
	
	
	
	

Suspended
Solids
mg/1
65
	
418
	
138
232
242
2158
808
194
228
70
137
461
248
194
Volatile
Suspended
Solids
mg/1
__.
	
	
	
	
113
	
	
	
	
	
	
	
	
	
	

Total
COD
mg/1
91
65
520
210
159
298
150
1410
889
188
178
52
134
476
311
251

Dissolved
COD(1)
mg/1

	
110
	
	
50
30
60
95
48
	
	
	
	
	
	


BOD (5)
mg/1

	
	
	
59
— — _
17
	
	
	
47
13
26
111
65
54


Coliform
///ml
440
5000
	
	
4260
2151
1860
5730
1388
421
1280
1850
6000
32000
26000
25600
                                                                                 Remarks

                                                                             Extended Rain
                                                                             Extended Rain—
                                                                                4 Days
                                                                             First Flushes

                                                                             First Flushes—
                                                                                L. Rain
                                                                             End of Overflow
                                                                             First Flushes
                                                                             Extended Overflow
                                                                             First Flushes
                                                                             Extended Overflow
(1)   See Appendix II Analytical Procedures

-------
efficient solids/liquid separation system  should provide high removals
of  pollutants from the raw waste.   Coliform density also varied
widely from 440 to 26,000 per milliliter.

Laboratory testing which was performed included screening, chemical
oxidation, flotation and disinfection.  Chemical oxidation proved
impractical for use in treating combined sewer overflow.  Complete
details of oxidants utilized, reaction times and efficiency may be
seen in Appendix I.

A summary of the preliminary screening data is presented in Table 3.
Various mesh sizes from 50 to 400 (297-37  \i openings) were investi-
gated.  The majority of the tests were run on a 50 mesh-297 y opening
screen.  The laboratory screen test consisted of pouring the sample
through the screen into a beaker.  The sample was poured gently to
avoid breakup of any particles, and in all tests a mat of solids was
not allowed to  form on the screen.  This eliminated the filtering action
which could have resulted if a layer of solids was allowed to form on
the screen.  It was anticipated that in actual field operation the
screens would operate partially blinded and, hence the removal rates
would probably  be higher  in the field when compared to the laboratory
analysis  shown  in Table 3.  All screen mesh sizes mentioned in this
report are Tyler series mesh.  Relationship of opening size to mesh
size  is presented  in  Figure 6.

Based on  the data  of  Table 3, average removal of suspended solids was
18.6% for a  50  mesh screen, 32% for 100 to 200 mesh screen, and 51% for
a  400 mesh screen.  An exception  to these  figures may be seen in the
data  from 12/21/67  in Table  3.  For this test a  120 mesh screen was
utilized  and  the  raw  waste was flocculated with  1 mg/1 of Reten A-l
polyelectrolyte.   Removals of COD and suspended  solids from this test
were  56%  and  55%  respectively.  These removals were significantly
higher than  those  obtained on the same waste  (12/21/67) using a 200
mesh  screen,  i.e. ,  22% COD removal and 26% suspended solids removal
 (Table 3).   These  results indicate that flocculation prior to screening
can improve  the efficiency of  the screens. More detailed data,
however,  is  needed to verify  these results.

The results  of  the laboratory  flotation testing  is  presented in Tables
4  and 5.   Table 4  indicates  those flotation tests which were run on the
raw overflow and  Table  5  those tests  run on screened overflow.  The
results  shown in  Table  4  indicated extremely high  removals of COD  and
suspended solids  may  be  obtained  using  flotation alone  in conjunction
with  polyelectrolyte  addition.   The bench scale  flotation testing  was
performed using a standard  procedure  which is detailed  in Appendix II.
Removals  of  73  to 95% COD and  88  to 97% suspended  solids  were  obtained.
In Table  5  data on screening/flotation  are presented.   All  the
experiments  except 5/20/68  were  performed without  the  addition of
flocculating chemicals.   Based on the data presented  in Table  5,
suspended solids  removals of  41% to 72%,  BOD removals  of  40% to*62%
and COD  removals  of 42%  to  72% were predicted at the  90% confidence
level.   By  comparing  the two experiments  on the overflow of  5/20/68
                                  31

-------
                                             TABLE 3
                               SUMMARY OF PRELIMINARY SCREENING DATA
                                        COD Data
Suspended Solids
Date
of
Overflow
11/10/67
11/16/70
12/07/67
12/21/67
01/29/68
04/03/68
04/03/68
04/17/68
04/20/68
04/23/68
04/28/68
04/28/68
05/20/68
01/29/68
12/21/67
11/10/67
12/07/67
12/21/67
01/29/68
12/07/67
01/29/68
Screen
Size
Mesh
50
50
50
50
50
50
50
50
50
50
50
50
50
100
120
170
200
200
200
400
400
Screen
Opening
Microns
297
297
297
297
297
297
297
297
297
297
297
297
297
145
122
87
74
74
74
37
37

Raw
mg/1
520
210
298
150
1410
889
188
178
52
134
476
311
251
1410
150
520
298
150
1410
298
1410

Dissolved
mg/1
110
— _
50
30
60
95
	
	
	
. 	
	
	
	
60
30
110
50
30
60
50
60
After
Screening
mg/1
407
182
247
121
922
559
121
134
51
99
331
199
188
899
66
340
233
117
	
200
	

Removal
%
22
13
17
19
35
37
36
25
2
26
30
36
25
36
56
35
22
22
—
33
—

Raw
mg/1
418
	
232
242
2158
808
194
228
70
137
461
248
194
2158
242
418
180
242
2158
180
2158
After
Screening
mg/1
270
	
	
195
1526
707
183
207
67
122
331
177
153
1504
68
210
150
178
1368
100
900

Removal
%
35
__
—
19
29
13
6
9
4
11
28
29
21
30
55*
50
17
26
37
44
58
* Flocculated with 1 mg/1 Reten A-l (Hercules, Inc.)

-------
   500


   400



   300





   200
CO
ID

-------
                                                       TABLE 4
UJ
c-
SUMMARY PRELIMINARY FLOTATION DATA
Deten Chemical COD Data Suspended Solids
Date of Pressurized Time Dosage Raw Effluent
Overflow Flow - % Min. Type mg/1 mg/1 mg/1
12/21/67 15 3 Reten A-l(1) 1 150 37
12/21/67 8 3 Reten A-l(i) 1 150 40
1/29/68 15 5 C-31m 10 1410 98
Removal Raw Effluent Removal
% mg/1 mg/1 %
75 242 17 93
73 242 28 88
93 2524 75 97
              NOTES:  1.  Anionic polyelectrolyte-Hercules,  Inc.
                      2.  Cationic polyelectrolyte-Dow Chemical

-------
                                              TABLE 5
                               PRELIMINARY SCREENING/FLOTATION DATA
                    4/3/68
SUSPENDED SOLIDS
Raw mg/1
After Screen mg/1
Screen & flota-
tion mg/1
Overall Removal %
COD
Raw mg/1
After Screen mg/1
Screen Flota-
tion mg/1
Overall Removal %

808
707

279
65

889
559

	
	

194
183

114
41

188
121

	
	

228
207

73
68

178
134

69
61

70
67

55
21

52
51

44
15

137
122

65
53

134
99

64
52

461
331

65
86

476
331

119
75

248
	

	
— — —

311
199

93
70

194
153

68
65

251
188

114
56

194
153

36
81

251
188

92
63
BOD
Raw mg/1
After Screen mg/1
Screen & flota-
tion mg/1
Overall Removal %
181
148

85
53
36
33

12
67
47
33

21
55
13
10

10
23
26
20

12
54
111
92

36
68
65
58

27
58
54
49

39
28
54
49

29
46
       (1)  10 mg/1 C-31 added to flotation test - all other runs without chemicals
  pressurized flow - 20%;  pressure 50 psig;  detention time - 5 minutes

-------
the effect of chemical flocculant addition may be seen.  Addition of
10 mg/1 C-31, a cationic polyelectrolyte, caused and increase in
suspended solids removal from 61 to 81%, while the BOD and COD removals
increased from 56 and 28% to 63 and 46% respectively.

A summary of the preliminary disinfection data collected during the
preliminary sampling period is presented in Table 6.  Data from ozone
and chlorine disinfection are shown.  In general, ozone disinfection was
not as reliable as chlorine.  Ozone demand for these waters was quite
high, and since ozone is extremely reactive, a residual ozone
concentration could not be obtained except at extremely high dosages
(approximately 60 mg/1 or greater).  Inability to obtain small
residual ozone concentrations for a short period of time resulted in
the relatively poor E. Coli removals.

Chlorine disinfection on the other hand provided improved disinfection
at a dosage of 10 mg/1.  Since chlorine is less reactive compared to
ozone, some chlorine residual could generally be attained.  Disinfection
efficiency was better than ozone, but  in some tests (April 28, 1968)
with high coliform densities, the effluent had significant coliform
indicating incomplete disinfection.  It appears from this data, as the
coliform density increases, higher chlorine dosages will be required.

Conclusions — Preliminary Investigations

The following conclusions can be made  based on the data taken during the
preliminary investigations.

     1.  Combined Sewer overflow from  the Hawley Road sewer contains
         primarily particulate pollution.

     2.  Chemical oxidation is not technically feasible for combined
         overflows.

     3.  Screening/dissolved-air flotation is a relatively effective
         method for treating combined  overflow.

     4.  Addition of chemical flocculents greatly increases the removal
         efficiency of dissolved-air flotation.

     5.  Uisinfection with chlorine was found to be more reliable than
         with ozone.
                                36

-------
           TABLE 6
PRELIMINARY DISINFECTION DATA
E. Coli.


3
3
17
20
23
28
28

Date
April
April
April
April
April
April
April


1968
1968
1968
1968
1968
1968
1968

Type
FF
EO
EO
EO
EO
FF
EO

Ozone
E. Coli. Dosage
per ml rog/1
1

1
1
6
32
26
,388 80
421 59
,280 40
,850 ^30
,000 <10
,000 <10
,000 <10
in
Effluent
per ml
21
4
74
17
3,200
9,500
13,700
Chlorine
Dosage
mg/1
—
—
10
10
10
10
10
E. Coli
in
Effluent
per ml
—
—
0.
1
2
20
8


5




FF - First Flush
EO - Extended Overflow

-------
                            SECTION VI

          DESIGN  AND  CONSTRUCTION OF DEMONSTRATION  FACILITY


The  results  of the preliminary  sampling  and  laboratory analysis were
utilized  in  the  design of  a 5 MGD demonstration  treatment facility in-
corporating  screening  and  dissolved-air  flotation.  This section of
the  report describes the design criteria utilized, and the features of
the  demonstration system.   A flow sheet  for  the  system is shown in
Figure  7  and a photograph  of the overall system  is shown in Figure 8.

Design  of Screen

The  design of the demonstration unit involved three basic areas, i.e.,
screen  design, flotation tank design and integration of all system
components.   Based on  removal efficiencies obtained in the preliminary
sampling  phase,  a screen mesh of 50 (297y openings) was selected.
This mesh gave fairly  good removal of  pollutants  (20-30%) and allowed
high flow rates  (50  gpm/sq ft)  at reasonable headlosses.  The screen
is an open ended drum  into which the raw waste flows after passing a
1/2" bar  rack.   The  purpose of  the bar rack  is to  remove large
objects which may clog the screened solids removal system or damage
the  screen material, which is 306 stainless  steel.  The water passes
through the  screen media and into a screened water chamber directly
below the drum.   The drum  rotates and  carries the  removed solids to
the  spray water  cleaning system where  they are flushed from the
screen.   Those solids  which will not adhere  to the screen media are
picked  up by 4 angle iron  sections which act similar to a roto-dip
feeder  and are thus  removed from the flow.   Screened water is used
for  backflushing the screen.  The drum rotation  and spray water
cleaning  are controlled by liquid level  switches located in the
screen  chamber.   The switches are set  to actuate at a headloss of 6"
of water  through the screen.  The solids which are flushed from the
screen  along with the  spray water are  collected  in a hopper inside
the  drum.  This  hopper is  connected to a drain pipe which forms the
main axis of the drum.  The slurry is  then routed  to waste.  Detailed
photographs  of the screening system are  shown in Figures 9 and 10.
These photographs show the screen, internal  hopper, float switches,
and  drive system.  The basic screen is fabricated  from mild carbon
steel.  The  screen backing material (Figure  9) is  a perforated metal
plate which  has  proved to  be adequate  support for  the screen.  Hole
size for  the backing material is 3/4"  x  3/4" on  7/8" centers.  This
provides  73% open area and only a minimum of flow  restriction.
Rotation  speed is controlled by a variable speed drive, which is
positioned manually.   Rotation  speed range is 0.5  - 5 rpm.  The
screened water is sealed from the raw  waste  by compressing a tube
between the  end  of the drum and a stationary ring.  The sealing
arrangement  allows operation at a maximum headloss of about 12".
Any  excess headloss  will allow  some unscreened water to enter the
screened water chamber  and a possible  raw waste  overflow from the
bar  screen chamber.   During some runs  with extremely heavy solids
loads,  the headloss  capacity of the screen has been exceeded.  These
                                39

-------
                                               ;f f i"<>nr
                                                Wo 1 r
S'fR-\TION SYS

-------
      FIGURE 8
DEMONSTRATION SYSTEM

-------
     FIGURE 9
SCREENING SYSTEM
      42

-------
••
              FIGURE 10
          SCREENING SYSTEM

-------
instances will be discussed in a later section of this report.

The drum screen as installed is an 8 sided drum with an effective
diameter of 7*5 feet.  The length of the drum is 6 feet.  The 8 panels
have dimensions of 3' wide by 61 long.  Total screen area is 144 sq ft.
The wetted screen area was a minimum of 72 sq ft and a maximum of
90 sq ft depending upon the head loss across the screen.
Flotation System Design

The dissolved air flotation basin design was based on the criteria
utilized by the American Petroleum Institute (API)(64).  The major design
parameters are overflow rate, detention time, horizontal velocity and
depth to width ratio.  The design procedures were modified slightly to
allow the high flexibility required in a project of this nature.

The basic principle of dissolved air flotation (DAF) is to produce
extremely small air bubbles (<100u) which can be attached to the partic-
ulate matter in a wastewater and cause flotation and removal of the
particulate matter.  To provide these fine air bubbles a liquid stream
is mixed with air under pressure.  The pressure is then released through
a weir type diaphragm valve to form the bubbles.  The bubble laden
stream is then mixed with the remaining wastewater to be clarified in a
contained mixing zone within the DAF tank.  This mixing zone has a
detention time of approximately 60 seconds.  The bubbles attach to the
solids in this mixing zone.  The bubble formation system is termed the
pressurized flow system.  Generally, the source of pressurized flow is
the process effluent or another relatively solids free stream.  In this
project the screened water was used as the source of pressurized flow.
The advantages to this approach eliminate an increase in hydraulic
loading on the DAF tank and provides a simplified plumbing system.
Because of the possible presence of a significant amount of solids in
the pressurized flow stream, a pressure tank without packing material
was utilized.  This avoided the potential clogging problems associated
with a pressure tank packed with some furm of tower packing to increase
the air water interface.  The type of pressurization utilized in this
project has been termed sidestream-pressurization.

The following discussion will delineate the process steps occurring
in the flotation tank.  Screened water is pumped into the pressure
tank.  Air is mixed with the water at the inlet to the pressure tank.
Water level in the tank is controlled by a liquid level float switch.
A slight excess of air is always added.  If the water level becomes
too low the air stream is vented to atmosphere to allow the water level
to rise.  Hence, the water level in the pressure tank is positively
controlled.  There is a deflector baffle in the tank which spreads the
incoming water and promotes a large air water interface for good air
solution.  The pressure in the tank is controlled by an air operated
weir valve; this valve provides the proper back pressure as well as the
required shearing action to form the small bubbles.  This valve is
                                44

-------
controlled by a pneumatic controller.  Once the pressure has been
released and the bubbles formed, the bubble laden stream is mixed with
the remainder of the screened water flow.  A 60 second mixing chamber
is provided in the tank prior to entering the flotation zone.  This
allows time for bubble/solid attachment.  When flocculating chemicals
are utilized they may be added either to the raw flow or to the pressur-
ized flow after the pressure has been reduced.  Generally polyelectrolyte
type flocculants, which require little or no flocculation period are
added in the pressurized flow stream.  Once the pressurized stream and
remaining raw waste have been mixed, they enter the flotation zone of
the tank where separation occurs.  A skimming system skims the floated
scum into three separate scum troughs, which convey the scum to ultimate
disposal.  Generally the solids concentration of the scum is 1-2% solids
on a dry weight basis.  This concentration flows easily by gravity and
does not require screw conveying.  Figures 11 and 12 show various details
of the flotation system.

The design of the DAF system was such that a wide range of selected
variables could be evaluated in order to be able to recommend design
procedures specific to combined sewer overflow.  The following range of
variables is possible with the demonstration system.


                      Flow rate               1500 - 4400 gpm
                      Surface loading         2-10 gpm/sq ft
                      Horizontal velocity     1.30 - 3.75 ft/min
                      Pressurized flow rate   300 - 1100 gpm
                      Operating pressure      40 - 70 psig
                      Detention time          7-44 minutes
In addition to the above flexibility, the flotation tank can be divided
down the center.  This in effect forms two separate flotation tanks.
The lengths of these tanks can be controlled by appropriate baffels.
This then allows the evaluation of two separate overflow rates on the
same storm,  thus allowing direct comparison of the overflow rate variable
and elimination of all other possible interacting variables.  The tank
was divided as described above at the start of the 1970 storm period
(April, 1970).  The final as-built dimensions of the flotation tank were
18 feet wide, 8% feet water depth, and a 65' long flotation zone.
Design of. Supporting Systems

The appurtenant equipment and tasks necessary to provide a functional
demonstration system included site preparation, construction of a manhole
and pumping sump, selection of the necessary flow metering equipment, and
design of suitable electrical and pneumatic control systems.
                                45

-------
PRESSURE TANK,  CONTROL  SHACK,  AND  SCREEN SYSTEM
              1

  PRESSURE TANK AND PRESSURE REDUCTION VALVE


                   FIGURE 11


               FLOTATION SYSTEM (See also Figure 7)
                                                    '
                                                   »'
                                                    •

-------
      HEAD END OF FLOTATION TANK
OVERHEAD COLLECTOR AND EFFLUENT STRUCTURE
                 FIGURE 12
              FLOTATION TANK
                   47

-------
As may be seen In Figure 8, the system was located under an existing
highway bridge which provided overhead protection.  Site preparation
involved laying a concrete slab to provide support for the system
tankage.  A manhole was constructed as well as a pumping sump, directly
in the combined sewer.  A dam was also provided in the sewer to allow
impoundment of a limited quantity of overflow for subsequent treatment.
This dam was designed to tip under the hydraulic pressure of the overflow
to prevent surcharging the sewer.  A photograph of the outfall is shown
in Figure 13.

Flow metering equipment is provided to measure the influent flow rate,
the volume of screen backwash water and the volume of floated scum.
All other process flows could be obtained by adding or subtracting the
proper measured values.  The raw flow and screen backwash are measured
via venturi meters connected to differential pressure gauges which both
record and totalize the flows.  The floated scum is measured with an
open channel float type meter, which records and totalizes the flow of
floated scum.

The electrical control panel provides all necessary controls for 100%
automatic operation with manual overrides on all systems.  Operational
modes will be discussed in a later section of this report.  A Merchants
Police alarm is connected to the system so that personnel will be alerted
when the system goes into operation.  The system is always (24 hours per
day, 7 days per week) ready to operate, and hence, the maximum possible
number of overflows can be monitored.  Photographs of the control shack
are shown in figure 14.  Demonstration system costs are presented in
Appendix III.
Operation Methods and Test Plan

Methods and Operational Procedures

The demonstration system previously described was put into operation
in May of 1969.  Data reported herein represent data taken during the
period May, 1969 through November, 1970.  During this period 55 over-
flows were treated with the demonstration system.  The system is put
into operation automatically when a float switch in the sewer senses
an overflow.  The pressurized flow system is immediately put into
operation and the raw feed pump begins to prime.  All runs were started
with the tank approximately 80% full of water.  The water in the tank
was that left from the previous run.  The raw feed pump generally
primed in about 12-15 minutes.  When primed the raw pump is activated,
and the flow meters, chemical feeder  (if utilized), skimmers and all
other auxiliary equipment are put into operation.   At the end of the
run the system shuts down automatically.  All variables are then
selected for the next run and the controls positioned.  Variables
associated with tank operation include pressurized flow rate, operat-
ing pressure, scum removal cycle, raw flow rate, and chemical dosage.
                                 48

-------
     FIGURE 13
HAWLEY ROAD OUTFALL

-------
             FIGURE 14
INTERIOR VIEWS OF THE CONTROL SHACK

-------
Sampling Procedures

Sampling began when the raw pump primed.  Raw waste and screened water
sample collection was started immediately.  Effluent sample collection
was delayed for 15 minutes to allow purging of the water in the tank
from the previous run.  This procedure insured collection of represen-
tative effluent samples.  Screen backwash and floated scum samples were
taken during screen backwash and scum removal periods.

Sampling during 1969 runs was manual.  Equal volumes of raw waste were
taken every ten minutes.  Screened water and effluent samples were
taken continuously at a rate producing about 2.5 gallons of sample per
hour.  Screen backwash and floated scum were composited in equal volumes.

An automatic sampling system was put into operation for all 1970 runs.
The system consists of two timers connected through the proper valving,
to automatically composite the raw waste, screen water and effluent
samples.  The first timer controls the sample taking frequency (0-30
minutes).  The second timer controls the duration of sampling time (0-60
seconds).  The sampling valves are air operated weir valves.  The
automatic system has proved much superior to the manual methods, since
the chance for human error has been eliminated and the operator is free
to monitor the remainder of the system.  In general samples were compos-
ited every 5 minutes with the automatic system.  Floated scum and screen
backwash sample taking was not automated due to the problems associated
with intermittent flows and heavy solids concentrations in these process
streams.  The samples were refrigerated immediately after the run.
Analysis were then started within 0-8 hours.  Sample analysis procedures
are discussed in Appendix II.
Test Plan

Variables associated with the operation of the demonstration system
include hydraulic overflow rate  (gpm/sq ft of tank area), pressurized
flow rate, operating pressure, addition of chemical flocculants, and
the floated scum removal cycle.  During the first few runs it was
determined that values for operating pressure and the removal cycle
for floated scum were not critical.  A test plan was then initiated
with pressurized flow rate, hydraulic overflow rate, and addition of
chemical flocculants as the three variables.  Eight possible combinations
of these variables are shown in Table 7-  It was planned to obtain 7 to
8 runs for each variable combination requiring 56 to 64 separate runs.
The demonstration system was operated on 55 combined sewer overflows.
All variable combinations of Table 7 were fully evaluated except
Numbers 3 and 4.  These combinations were abandoned based on the results
obtained from combinations 1 and 2 which indicated higher overflow rates
without chemicals was not feasible.
                                 51

-------
                             TABLE 7

          VARIABLE COMBINATIONS UTILIZED FOR TESTING


                     Pressurized
                      Flow as
                     % of Total          Overflow Rate         Chemical
Combination             Flow               gpm/sq ft          Flocculants

     1                 14-20                  2.5                No

     2                 21-30                  2.5                No

     3                 14-20                  3.8                No

     4                 21-30                  3.8                No

     5                 14-20                  2.5                Yes

     6                 21-30                  2.5                Yes

     7                 14-20                  3.8                Yes

     8                 21-30                  3.8                Yes
                                52

-------
                             SECTION VII

                  OPERATING RESULTS AND DISCUSSION


  Characterization of Raw Waste

  As  was expected, the quality of  the combined  sewer overflow  from  the
  Hawley sewer varied widely.   In  12 of the  55  overflows reported herein,
  extremely high pollutional  values were observed.  These first flushes
  persisted for 20 to 70 minutes.   A summary of the first flush data
  may be seen in Table 8.   The range of the  data presented is at the 95%
  confidence level.   First  flush occurrence  appears to be associated with
  the length of time  between  overflows  and the intensity of the overflow.
  The suspended solids concentration for those overflows occurring within
  4 days of a previous overflow were calculated to be 151± 29 mg/1 while
  the suspended solids for  those overflows occurring at an interval larger
  than 4 days were found to be 349  ± 80 mg/1.  Comparison of the COD data
  at  intervals shorter than 4  days  and  longer than 4 days produced CODs
  of  144 ±  21 and  394  ±  72  mg/1 respectively.  These values are at the
  95% confidence level.  All  the data was tabulated as  a function of the
  interval  between overflows.   (Table IV-10,  Appendix IV-11.)  This data
  indicates  that essentially all overflows which exhibited  the  first
  flush  phenomenon occurred at intervals of  4 days or  longer between
 overflows.   However, all  overflows occurring at  an interval of greater
 than 4 days  did  not  exhibit  the first flush phenomenon.   Table 9
 illustrates  this point.  All overflows which occurred  at  intervals of
 greater than 4 days  are presented in Table  9 along with data  on rain-
 fall intensity and total rainfall.   A total of  23 overflows  occurred  at
 intervals of  greater than 4 days  between overflows.  Of these 23 over-
 flows only  12  exhibited the first flush phenomenon.  It may be concluded
 from this data that  the length of time between overflows  is related  to
 the occurrence of first flushes and there are  obviously other  variables
 which strongly influence this phenomenon.   These  variables  could  include:
 the dry weather flow variation, the intensity  of  rainfall and  runoff
 and the sewer system interceptor  capacity.   Furthermore the data presented
 herein may be biased by the  12-15 minutes which was required  to prime  the
 raw pump for the treatment system in that extremely short first  flushes
 would not  have been detected.

 A satisfactory method for  measuring the rate of flow in the sewer  has
 not  been developed.   Development  of a  method has  been complicated  due
 to  the presence of  the dam,  which  was  placed in the sewer to impound the
 flow.   This dam backs water  up past one of  the two interceptor devices
 feeding the Hawley Road sewer.  This makes  single point gauging impossible.
Another complication  which arises  is the fact that the dam is not  station-
ary. As  the flow increases  the dam  tips  to prevent sewer surcharge.  This
causes  large fluctuations  in  water level.   Down stream of the dam  the
sewer has  a  dog leg and extreme turbulence  has been observed at the mouth
of the  sewer.   Because  of  the  above discussed difficulties reliable data
on the  total flow rate  in  the  sewer was not obtained.   However, lack of
total flow data does  not in any way influence the operation of the demon-
stration system.

                                53

-------
                         TABLE 8

                SUMMARY FIRST FLUSH DATA



Analysis	                    Concentration mg/1

COD                                           581 ± 92

BOD                                           186 * 40

Total Solids                                  861 - 117

Total Volatile  Solids                         489 ± 83

Suspended  Solids                              522 - 150

Volatile Suspended Solids                     308 - 83

Total Nitrogen                                17.6 * 3.1

Ortho Phosphate                              2.7 - 1.0

PH                                            7.0 ± 0.1

Coliform Density                              142 i 108 x 10^
                                                        per ml
                  Data  Represents 12 Overflows
                  (J5/o  Confidence Level Range

-------
                          TABLE 9

                      SUMMARY OF DATA

   AT  INTERVALS  OF  GREATER THAN 4 DAYS BETWEEN OVERFLOWS
 Run
 No.

 691
 695
6911
6912
6914
6916
6919
 702
 708
7011
7013
7022

6918
6922
6923
6925
6928
 707
 7010
 7014
 7017
 7019
 7020

Days
Between
Overflows
18
15
8
5
6
12
24
26
9
14
12
19
11
17
6
11
19
7
11
6
8
18
15

First
Flush
Occurrence
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
Average
Rainfall
Intensity
in/hr
0.13
0.32
0.40
0.70
0.35
0.40
1.2
0.17
0.84
0.17
0.80
0.10
1.6
0.3
0.5
	
0.1
0.4
0.11
0.18
0.36
0.15
0.24

Total
Rainfall
(inches)
0.42
0.25
0.50
1.00
0.17
0.10
0.10
0.3
0.14
0.25
0.20
0.15
0.45
0.10
0.5
0.17
0.12
0.30
0.33
0.22
0.30
0.23
0.25
                               55

-------
 Data on rainfall was obtained routinely and runoff rate estimates were
 made using the rational method.  These runoff rates were then plotted
 against the suspended solids in the overflow.  A result of this plot
 is presented in Figure 15.   It appears from Figure 15 that there was
 no relationship between flow rate in the sewer and the suspended solids
 in the overflow.  This is as expected, since once the sewer system and
 drainage basin has been thoroughly flushes, the rate of low flow should
 not have a significant effect on overflow quality.  However, since actual
 sewer flow rates were not obtained, a positive conclusion cannot be made.

 After the flushes had passed (if they were present), the characteristics
 of the overflow became remarkably stable,  considering the large variations
 present in the first flushes.  The end of  the first flushes was determined
 by visual observation of the raw combined  overflow.  The screen backwash
 ran continuously during periods when high  suspended solids were present
 in the raw feed.  Thus when the screen backwash pump began cycling the
 end of the first flushes was indicated.  The exact length of the first
 flushes was not recorded.  A summary of  all data other than first flushes
 (termed extended overflows) is presented in Table 10.   The data of Table 10
 show a relatively small range of values  at the 95% confidence level.   The
 data compared well to data  from other research on combined sewer overflow
 (6)(11)(12)(13)(14)(65)(66).   The pollutant levels in the extended over-
 flow are about what  is expected from a very weak domestic sewage.   One
 major difference is  the BOD value of 49  mg/1.   This is  quite low compared
 to the COD value of  161 mg/1.   Generally,  the  BODrCOD  ratio of  domestic
 sewage is in the range of 0.6 (67).   The dissolved solids in combined
 overflow is also quite low.   Total dissolved solids (TDS)  based on the
 data of Table 10, is 212 mg/1.   Milwaukee  tap  water is  about 160 mg/1.
 This represents only about  42 mg/1 TDS increase as compared to  'WOO mg/1
 usually added when water is used and discarded as  domestic  sewage (8).

 Of particular Interest ot this  project is  the  amount of  organic  material
 present in the dissolved state.   Table 11  presents data  on  this  relation-
 ship.   The amount of dissolved  COD ranges  from 30  to  38%  of  the total  COD.
 The dissolved TOC ranges from 26 to  42%  of  the total TOC.   These values
 are somewhat  higher  than those  obtained  in  the preliminary  sampling phase
 of 4-25%.   The cause of this  difference  is  not known.  The  dissolved
 portion of the overflow will  not be  removed  in the screening/flotation
 system,  unless it is chemically  precipitated.   Hence, lower  removal
 efficiencies  will be expected as the  dissolved fraction of  the waste
 increases.

 A  discussion  of  the  results of  the operation of  the demonstration  unit
 follows.   A discussion is divided  into three phases:  screening
 operation,  flotation tank operation  and  disinfection.   Because  of  the
wide range of  pollutional values obtained in the raw waste,  the  removals
 through various  processing  steps are  presented  as  percentage removals.
Absolute effuent water  quality data may  be  seen  in Appendix  TV,
Tables IV-6 and  IV-7.   Absolute  effluent quality can also be estimated
by applying the  observed percentage  removal  figures  (Table  12 and  13)
to the raw overflow water quality presented  in Tables 9 and  10.
                               56

-------
800
600
r-l
to
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M 400
T3
0
41
(X
00
W
iAn
ZOO

0

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            x            f.            -J           y            -»
                                Flow  in Sewer  (10*  gpm)

                                  FIGURE 15

          RELATIONSHIP BETWEEN FLOW IN SEWER AND SUSPENDED SOLIDS

-------
                        TABLE 10

            SUMMARY OF EXTENDED OVERFLOW DATA


Analysis                                 Concentration mg/1

COD                                      161 ± 19

BOD                                      49 ± 10

Total Solids                             378 ± 46

Total Volatile Solids                    185 ± 23

Suspended Solids                         166 ± 26

Volatile Suspended Solids                90 ± 14

Total Nitrogen                           5.5 ± 0.8

pH                                       7.2 ± 0.1

Coliform Density per ml                  62.5 ± 27 x iti3

        Data represents 44 overflows
          at 95% confidence level range
                        TABLE 11
PARTICULATE & DISSOLVED RELATIONSHIPS
Relationship
Dissolved COD/Total COD
Dissolved TOC/Total TOC
Dissolved TOC/Dissolved COD
Total TOC/Total COD
No. of
Samples
34
13
14
17
95% Confidence Level
0.34 ± 0.04
0.34 ± 0.08
0.36 ± 0.02
0.33 i 0.05
               Range at the 95% confidence level
                          58

-------
Results of the Screening Operation

Table 12 presents a summary of the data on removal of pollutants by
screening alone.  A listing of all data collected is presented in
Appendix IV.  Generally, the percent removals during the first flush
were in the range of 30 to 40%.  The confidence ban is wide due to the
relatively small number of first flush overflow occurrences.  During
the first flushes a mat of solids sometimes covered the entire screen.
This mat acted as a fine filter medium and undoubtedly, increased the
removal efficiencies as compared to a clean screen.  Unfortunately
the headloss increased greatly as the mat formed and in runs 695, 6911,
6912, 6914, 6916 and 702, the headloss capacity of the screen was exceeded
for brief periods of time.  Examination of these runs indicated that the
screen was removing about 200 mg/1 of suspended solids which was equiva-
lent to 4.9 pounds of dry solids per minute.  Based on screen rotation
speed and area, this amounts to a solids loading of approximately 1.2
pounds of dry solids removed per 100 sq ft of screen area.  This number
represents the critical level of solids loading at which a headloss of
14 inches will be exceeded.

This value of solids loading is specific for a 14 inch headloss across
the screen.  The loading could possibly be increased by increasing the
allowable headloss differential.  This could, however, cause a decrease
in removal efficiencies by forcing more solids through the screen and/or
cause a break up of solids which could affect the efficiency of the
flotation process.

The hydraulic flow rate was in the range of 40-45 gpm/sq ft.  This rate
depending upon solids loading, could probably be increased.

The design of the screening system should be based on both hydraulic
flow rate and solids loading rate.  Either of these variables could
control screen design depending upon waste characteristics.  It is
obvious that proper screen design requires additional study.  All facets
of screening combined sewer overflows will be studied in Phase VI of
this project which is scheduled for completion in March of 1972.

During the extended overflows and after the first flushes had passed,
removal efficiencies dropped to the 20 to 30 percent levels (Table 12).
The probable cause of this decrease is that essentially no solids mat
formed during extended overflows, and hence, no added filtering action
was obtained.

The screen was backwashed with water from the screened water chamber via
a pressurizing pump.  Spray nozzles with 1/4" diameter orifices were
used to effectively distribute the water over the screen media.  Washing
was performed from outside the screen drum.  Some problems were encountered
with nozzle plugging due to an inefficient seal on the drum screen.  The
seal has been improved significantly, but it is still recommended that
an inline small hydraulic cyclone be utilized on future designs to
eliminate any operational problems.  The volume of screen water required
                                59

-------
                            TABLE 12
                 POLLUTANT REMOVALS BY SCREENING
                               Removal During         Removal During   _
       Pollutant               First Flushes %     Extended Overflows %
COD                                39 ± 15                26 ± 5

BOD                                33 ± 17                27 ± 5

Suspended Solids                   36 ± 16                27 ± 5

Volatile Suspended Solids          37 ± 18                34 ± 5



        1.   Represents 8 overflows  (see page 53 to 5fi for discussion)

        2.   Represents 46 overflows

        Data at 95% confidence level
                                60

-------
is approximately  100 gallons per minute.   Continuous  washing of the screen
would  therefore require about  3% of  the raw waste  flow.   Actual spray
wash requirements were in  the  range  of 0.7 to  1.0  percent of the raw flow,
since  the screen wash did  not  run continuously during operation.   Screen
wash quality was  in the range  of 500 to 3000 mg/1  suspended  solids.
(Appendix IV - Table IV-9.)  Good media cleaning was  always  obtained and
no permanent media blinding was experienced.   In general  operation  of the
screen was very satisfactory.  Tentative design criteria  for  the  screen
system will be presented in a  later  section of this report and  final
specifications at the completion of  the project.
Operation  of  the Flotation System

Overall  contaminant removals using the screening and flotation systems
are presented in Table  13.  A listing of all data is presented in
Appendix IV.   During  the  first flushes removals of BOD and COD were
in the range  of 55 to 65  percent, while suspended solids removals were 70
to 75 percent.  Removals  of nitrogen were significantly lower at about
46 percent.   In those first flush runs where flocculating chemicals were
added the  optimum chemical dosage was generally not obtained, since the
pollutant  levels were significantly higher compared to extended overflows.
This difficulty illustrates the need for some type of control system
which would automatically adjust the chemical dosage depending upon the
raw feed water quality.

Removals during extended  overflows were generally lower than during first
flushes.   Removals also varied widely depending upon whether flocculating
chemicals  were utilized.  Table 13 presents various pollutant removal
efficiencies  for three  different categories, i.e., without chemical
flocculant addition,  with polyelectrolyte (Dow C-31) and clay addition,
and with polyelectrolyte  (Dow C-31) and ferric chloride addition.

Figure 16  presents a  probability plot of suspended solids removal for
the 1969 data.  The slope of the probability line shows a distinct change
at about 50%  removal.   This change in slope indicates some operating
variable was  affecting  the removal rates and caused a change in the normal
distribution  of the data.  This change was chemical flocculant addition.
Examination of the data more closely indicated 10 of 14 runs without
chemical addition were  below 52% suspended solids removal, while 10 of
13 runs  with  chemical addition were above 52% removal.  Removals of
volatile suspended solids show trends similar to suspended solids removals.

The effect of  optimizing  the chemical treatment scheme is clearly illus-
trated in  Table 13.   Suspended solids and volatile suspended solids
removals increased significantly by varying the chemical addition from
polyelectrolyte and clay  (1969 data) to polyelectrolyte and ferric chloride
(1970 data).   The chemical dosage required to provide consistent removals
was found  to  be 20 mg/1 ferric chloride and 4 mg/1 polyelectrolyte.  The
ferric chloride is added  to the raw waste water flow prior to screening
                                61

-------
                                     TABLE 13
                     POLLUTANT REMOVALS BY SCREENING/FLOTATION
                                            Remova1 During Extended Overflows - %
                                                                                 (2)
Pollutant
COD
BOD
Suspended Solids
Volatile Suspended
Solids
Total Nitrogen
During First
Flushes %(!'
64 ±
55 ±
72 ±
75 ±
46 t
6
8
6
6
7
Without Chemical
Flocculants
(1969-1970 Data)
41 ±
35 ±
43 ±
48 ±
29 ±
8
8
7
11
14
With Chemical
Flocculants
(1969 Datap)
40 ±
46 ±
59 ±
58 ±
19 ±
14
17
11
10
11
With Chemical
Flocculants
(1970 Data)(4
57
60
71
71
24
± 11
± 11
± 9
± 9
± 9
All Data at 95% confidence level
Overflow Rate ^2.5 gpm/sq ft

(1)  Represents 12 overflows
(2)  Represents 38 overflows
(3)  2.5 - 3.5 mg/1 C31, 6 mg/1 Clay
(4)  3-6 mg/1 C31, 20-25 mg/1 FeCl_

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-------
and the polyelectrolyte is added  to  the pressurized  flow stream prior  to
mixing with  the remainder of  the  screened waste  flow.

The BOD ana  COD data also indicate increased removals when chemical
flocculants  were  added.  An exception  to this observation is  the COD
removal data with and without chemicals for the  1969 overflows (Table  13)-
It is felt that the small decrease in  COD removals was due to an increase
in the dissolved  organic fraction of the raw combined overflow.  During
late summer  and fall leaves and other  decaying organic material can cause
a substantial  amount of organic material to be converted to the dissolved
state.  This was  very evident in  run number 6919 as  the appearance of  raw
waste after  filtering was quite yellow.  Run numbers 6928, 6929, and 6930
also had  a very high dissolved fraction.  This increase in dissolved organics
resulted  in  the small decrease noted when chemical flocculants were
added, since dissolved organic removals can be accomplished only by precip-
itation.  Apparently, the dissolved organic material was not exerted as
BOD  (5) possibly  due to unacclimated organisms and BOD removals were
therefore not  affected to the same degree as COD removals.

A summary of removal efficiencies for  particulate organic material is
presented in Table 14.  It may be seen that during the 1969 runs,
numbers 6923 through 6929, particulate COD removal ranged from a high
of 96% to a  low of 34%.  It is obvious from the spread of the data that
effective coagulation was not always being achieved.  During the 1970
runs (700 Series) particulate COD removals were much more consistent
reflecting the improved chemical  treatment system, i.e., ferric chloride
and polyelectrolyte addition.  The average particulate COD removal
efficiency for the 1970 data  was  76±8% at the 95% confidence level.  This
value compared closely to the suspended solids removals for the 1970 data
of 71±9%  (Table 13) thus indicating that effective chemical treatment
was generally  obtained during the 1970 overflows.  There are,  however,
some overflows (7012, 7014, 7015, 7023) where the particulate COD removals
were below the 95% confidence range.   This further illustrates the need
for some  type  control system  for metering the chemical addition.

Removal of dissolved organic  compounds can only be obtained by precipitation
of the material or adsorption on the flocculated particles obtained when
polyelectrolyte or other flocculating  chemicals were added to the raw
waste stream.  Removal of dissolved COD for those runs,  where data is
available, is  presented in Table 14.  As expected removal of dissolved COD
was erratic  and ranged from no removal to a high of 43% removal.   Generally,
the removals were in the range of 20 to 25%.   Other chemical flocculants
may give  slightly improved removals, but 20-30% removal  of dissolved
organics  is  all that can be expected in a screening/flotation system.

It has been  determined from laboratory studies that a flocculation period
may further  improve the removal efficiency of the flotation process.
Research  is  now underway to substantiate these laboratory results at
demonstration  svstem scale.
                                      64

-------
                            TABLE 14

  SUMMARY PARTICULATE AND DISSOLVED ORGANIC REMOVAL EFFICIENCIES
                      Chemical Dosage
Run
till

6923
6924
6925
6926
6927
6928
6929
 704
 705
 706
 707
 708
 709
7011
7012
7013
7014
7015
7016
7018
7019
7020
7021
7022
7023
7024
7025
C-31
mg/1
6.0
0
0
2.7
0
3.0
3.0
6.0
6.0
6.0
6.0
6.0
4.2
5.3
3.9
4.6
3.5
4.5
4.5
4.5
4.5
3.8
3.8
0.5
0.5
0.5
4.0
1.
2.
FeCl3
mg/1
0
0
0
0
0
0
0
0
0
0
0
0
30
17
16
16
21
21
21
21
21
18
18
(2) 15
(2) 15
(2) 25
25
Overflow Rate ^2.5
Herco Floe 810 used
Clav
mg/1
6
0
6
0
0
0
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
gpm/sq
for t
Particulate
COD
Removal
54
34
86
83
73
57
39
63
95
95
74
85
88
87
53
80
42
50
93
87
77
81
91
88
48
78
69
Dissolved
COD
Removal
+2
+14
+25
+22
+23
+23
+23
+11
0
-2
+10
-3
+20
+27
-19
+30
+31
+29
+4
+8
+33
+40
+24
+43
+21
-3
+22

-------
An important variable in the operation of a dissolved-air flotation system
is the volume of pressurized flow required to supply sufficient air bubbles
for proper process operation.   For a given volume of liquid, the number
of bubbles and their size will be a function of the operating pressure.
Generally the greater the pressure, the larger the volumes of air dissolved
and the smaller the size of the bubbles.  There is of course a limit to
the benefit to be gained by increasing operating pressure.  Pressurized
flow volumes generally utilized are in the range of 15-50% of the raw
waste flow.  Table 14 presents a comparison of pressurized flow ratios
utilized.  Rates from 13 to 22% of the raw flow were considered low values
while rates from 23 to 44% were considered high values.  The data is
further segregated into those runs with and without chemical flocculant
addition.  A comparison of means test (68) was performed on the high and
low pressurized flow values of Table 15.  The procedure for performing
this test may be seen in Appendix IV.  The results of this comparison
indicated there was no statistically significant difference between sus-
pended solids removals for low or high pressurized flow whether or not
chemical flocculants were utilized.

It appears considering all data, that a pressurized flow value of 20%
of the raw flow will be sufficient for dissolved-air flotation operation
on combined sewer overflow.  A slight increase in pressurized flow may
be required if the improved efficiencies predicted in the laboratorv are
obtained in the field, since a larger volume of solids will require
floating.  Air requirements based on a 20% pressurized flow system would
be 1.4 SCFM per million gallons per day of raw flow capacity.  An oper-
ating pressure of 50 psig provides sufficient air solution and a small
enough bubble size to be effective without requiring excessive pressure
drops at the pressure reduction value.

Another variable which can significantly affect the removal efficiencies
of a dissolved air flotation system is the overflow rate, i.e., gpm/ sq ft
of tank area.  Removal data presented in Table 13 were all at the over-
flow rate of approximately 2.5 gpm/sq ft.

To allow for a study of higher overflow rates, the flotation tank of the
demonstration system was partitioned as shown in Figure 17 for all 1970
runs.  All process elements up to the point of entering the flotation
zone were identical to the 1969 runs.  A longitudinal baffle was placed
the entire length of the tank.  This had the effect of producing two
separate flotation zones.  Lateral baffles were then placed at one-half
the length of the tank on side one and at two-thirds the length of the
tank on side two.  Effluent samples were taken just as the water flowed
under these baffles to insure collection of a sample representative of
the portion of the tank being utilized.  The unshaded area of Figure 17
represents the unused portion of the tank.  The raw flow as it enters
the flotation zone is split into equal volumes.  Since the effective
length of each side of the tank is different, two overflow rates are thus
obtained on the same storm.  This completely eliminates the effect of any
interacting variables like pressurized flow, chemical addition, and the
                               66

-------
TABLE 15
COMPARISON OF PRESSURIZED FLOW RATES
Low Pressurized Flow

Run
#
6911
6912
6914
6915
6917
6924
6927
7012


Average
6920
6921
6922
6923
6928
6930
707
708
7015
7016
7018
7019
7020
7022
Average
Pressur-
ized
Flow-%
17
21
13
16
16
16
18
17


16.8
21
17
16
20
19
19
22
22
19
20
20
20
19
19
19.5
Chemical
Flocculents
Utilized
No
No
No
No
No
No
No
No


—
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
—
NOTE: Overflow Rate @ ^2
Suspended
Solids
Removal-%
30
55
80
53
64
48
61
52


55
70
57
66
52
49
40
68
76
37
85
86
71
85
85
66
.5 gptn/sq ft

Run
#
692
693
695
696
697
699
6910
6913
6917
6925
Average
6919
6926
6929
704
705
706
709
7011
7013
7014
7021
7023
7024

Average

High Pressurized Flow
Pressur-
ized
Flow-%
24
29
34
29
31
23
23
33
23
29
27.8
28
31
27
37
44
40
28
24
23
28
23
25
27

29.6

Chemical
Flocculents
Utilized
No
No
No
No
No
No
No
No
No
No
—
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes

—

Suspended
Solids
Removal-%
40
65
44
34
28
40
32
63
64
46
46
65
75
45
77
79
80
82
69
72
68
72
49
66

69


-------
                 Pressurized
                 Flow System
Oi
x
         Bar
        Screen
                    Drum
                    Screen
          M
           I
          x
           I
          n
          g

          Z
          0
          n
          e

                                   Effluent  Sample
                                  Collection Point
                                            30'
                                                                 Sidewater Depth 8.5'

                                                     40'
                                                               Effluent Sample
                                                              Collection Point
                                            FIGURE 17
                                                                                              V
                                                                                              9'
                             BAFFLE ARRANGEMENT FOR OVERFLOW RATE TESTS

-------
differences inherent in any two combined overflows, allowing direct
determination of the effect of overflow rate.

Data taken on direct comparison of overflow rates are presented in Table 16,
The data indicates removal efficiencies decrease as the overflow rate is
increased.  Data from each run is presented, as well as average values
for low and high overflow rates along with the 95% confidence range.
By comparing the mean values, removal efficiency decreased approximately
5-14% as the overflow rate increases from ^2.5 to 3.75 gpm/sq ft.
A paired comparison test (Appendix IV) was also run on the data of Table 16.
The results of this test indicated that there was a difference in the low
and high overflow rate data.  Confidence levels at which the difference
was significant are as follows:  COD - 90%, BOD - 95%, suspended solids -
99% and volatile suspended solids - 95%.  It is anticipated that at
higher overflow rates the decrease in removal efficiencies will be even
greater.  However, higher rates will be evaluated during this study.
Based on the data of Table 16 an overflow rate of 3.3 gpm/sq ft is recom-
mended as the basic design value.

Of considerable importance in the operation of a screening-flotation
system is the volume of residual solids produced during operation.
Volumes of floated scum generated during operation of the demonstration
unit ranged from 0.75 to 1.41 percent of the raw flow at the 95%
confidence level.  Scum concentration was generally in the range of 1 to
2% solids on a dry weight basis (Appendix IV, Table IV-9).  The floated
scum and screen washwater from this project are disposed of via an inter-
ception sewer which directs them to the sewage treatment plant for
ultimate disposal.  Since gravity flow is utilized it is desirable to
limit the sludge concentration to about 2% as this concentration easily
flows by gravity.  Higher concentrations can be obtained by skimming the
floated scum blanket at less frequent intervals.  Sludge concentrations
as high as 4% solids have been obtained in this manner.  Obviously the
higher the concentrations, the smaller the volume of sludge produced
for ultimate disposal.  For this reason it is felt that in full scale
operations sludge volumes will be somewhat less than those obtained
during this study.  Another factor, which will offset this reduction in
scum volume, is the addition of more effective chemical flocculants.
As the chemical flocculant addition is optimized, the volume of scum
will increase due to the additional chemicals added and the higher
efficiency of solids capture.

Ultimate solids disposal will dictate the desired solids concentration
in the floated scum and, hence, the volume of scum which requires disposal.
If scum is disposed of by way of an interceptor  sewer  a  solids content  in
the range of 1-2% will be desirable.  This should result in an average
scum plus screen wash volume of 1.75 percent of the raw flow.  If disposal
is by tanker truck or solids dewatering at the site, a high solids
concentration is desired (4%), and the volume should be less than 1 percent
of the raw flow.  Additional discussion on solids handling is presented
in the full scale design consideration section of this report.

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                                TABLE 16

    COMPARISON OF THE EFFECT OF OVERFLOW RATE ON REMOVAL EFFICIENCIES
Run
II
704
705
706
707
708
709
7011
7012
7013
7014
7015
7016
7020
7021
7023
7024
7025
Average
95%
Confidence
Limits

COD
35
72
76
52
67
66
63
41
56
36
43
74
74
58
37
61
50
56.5

49-64

Low Overflow
BOD
69
69
75
61
59
51
60
36
55-
—
37
—
77
7e>
51
52
62
59.3

52-66

Rate -\-2.51
SS
77
79
81
68
76
82 -
70
" 52
72
68
52
85
85
72
49
66
59
70.2

64-76


vss
90
79
73
72
77
76
76
58
80
68
47
84
86
70
49
61
61
70.7

64-77

High
COD
28
74
72
43
62
61
60
36
48
29
39
71
68
67
46
51
60
53.8

46-62

Overflow
BOD
55
69
54
58
36
51
64
31
46
—
40
—
45
80
46
46
64
52.3

45-60

Rate ^3.7
SS
33
79
66
50
66
76
74
36
66
66
48
83
63
67
35
56
68
60.7

53-69

5^
VSS
51
80
64
62
71
73
79
56
69
68
27
82
69
68
36
70
70
64.4

57-72

1.  Actual Range 2.43 - 3.1 gpm/sq ft
2.  Actual Range 3.4 - 4.5
3.  Removal in %
           NOTE:   chemical flocculants added for all runs

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During the operation of the demonstration system some settled sludge
was noticed.  The amounts of settled sludge were, however, extremely
small, with one exception.  Runs number 691 and 692 were made without
using the^drum screen.  Upon draining the tank after run number 692,
about 4-6" of settled material was discovered.  This consisted of grit,
twigs and other material which could not be floated.  Later in the year
the tank was again drained after 13 additional runs which were all made
with the screen in service.  Settled sludge volume amounted to only
2-3 inches at this draining.  This clearly demonstrates the value of
the screen in removing heavy particulate matter which cannot be floated
in the flotation  tank.  The tank was again drained at the end of the
1969 season and sludge volumes were again only 2-3 inches.  It may be
concluded that bottom skimming systems are not required when screening
precedes flotation.  If, however, applications arise where flotation is
used alone, it is imperative that some type of bottom skimming be provided
or large sludge blankets will form which will eventually scour into the
effluent.

Material balances for suspended  solids were made for almost all runs.
The tabulated  data may be  seen  in Table IV-14, Appendix IV.  The balance
of solids  in and  solids  out of  the system generally totaled within about
25%.   In some  cases, however, the error was higher.  The probable
reasons for the material balance errors are believed to result from scum
sampling and collection  procedures.  At the end  of a run,  the floated
scum blanket which  remained on  the tank was lost with respect to material
balances.   Generally this  scum  was skimmed off after the  run when the
scum meter was not  totalizing.   It was also difficult to  obtain a
representative sample  of scum,  since scum was  scraped intermittently
and the  solids concentration  could vary widely from  the beginning to the
end of the skimming cycle.  Scum samples were  taken manually and if other
operating  problems  arose,  a scum sample  from  every  skimming  cycle may
not have been obtained.   Because of  the  sampling procedures  it is felt
that  scum  suspended solids concentrations were not  representative.   Since
suspended  solids in the scum could account  for a significant portion of
the  solids balances, it is felt that these  errors  contributed  to a  large
extent in  the  material balance discrepancies.

Difficulties  were also experienced with the raw flow meter totalizer.
The  units  on the totalizer were 30,000 gallons per count  and thus  could
not  be read accurately.   The totalizer has  subsequently been changed and
 thus  this  problem eliminated.   Another possible source of material  balance
error is the fluctuating concentration of the raw overflow.   Limited data
has  been collected to indicate that the pollutant  concentration  can vary
 significantly  during an overflow.   This variation could introduce
 errors in the material balance.

The  maintenance of the demonstration system has been limited to lubrica-
 tion of moving components.  The following discussion will be limited to
 those problems which were encountered and the method of solution.   Some
 difficulties were encountered with the float switches utilized in the
 system.   These switches are the reed type which are activated by a sliding
                                  71

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 float.  They  required frequent cleaning, once per week, as sand would
 work its way  between the float and the shaft and caused the float to
 become inoperable.  Replacement of this type switch with a conductivity
 type should solve this problem.

 Difficulties  were also encountered with the back pressure control valve
 on  the pressurized flow system.  This problem resulted from excess
 moisture in the compressed air.  The valve positioner apparently could
 not tolerate  the moisture level encountered.  All problems were in the
 positioner for the valve which accepts  a 0-20 psi control pressure and
 positions the valve accordingly.  The positioner was utilized only because
 of  the design flexibility required in a demonstration system.  In the full
 scale applications when the pressurized flow rates are known, valve posi-
 tioners will  not be required and the problems incurred will be eliminated.

 A minimum amount of difficulty was experienced with the chemical metering
 pump, but this was a result of improper materials selection and the
 difficulties  were easily eliminated.  As may be concluded from the above
 discussion, the operation problems encountered were minimal and this
 attests to the soundness of the system design.

 Disinfection  of Combined Overflows

 Another important aspect in the treatment of combined sewer overflows
 is  adequate disinfection.  The screening/flotation system provides
 sufficient detention time (12-20 minutes) to obtain the necessary chlorine
 contact time.  The system also is flexible in that various points of
 chlorine addition are available depending upon process needs.  A summary
 of  the disinfection data taken during the project is presented in Table 17.
 Hypochlorite  salts were utilized as a source of chlorine.  Dosage was
 held essentially constant at 10 mg/1.  It was noticed, however, that the
 strength of the chlorine stock solution could decrease rapidly depending
 upon environmental conditions.  Therefore, some of the storms could have
 had dosages less than 10 mg/1.  In general, relatively good disinfection
 was obtained.  A trend seems to exist in Table 17 which indicates that
 as  the coliform density increases the absolute coliform density in the
 effluent also increases.  Nevertheless good disinfection can be obtained
 in  conjunction with the operation of a screening/flotation system.

 Conceptual Design

 This section of the report deals with the design concepts necessary to
 utilize a screening/flotation system on a full scale basis for treating
 combined sewer overflow.  It is not the intention of this discussion to
 provide specific answere to all design details.  Sufficient information
will be presented to form a basis for process design.  Various engineering
 considerations and/or judgements must be provided to produce the final
overall system design.   It should also be recognized that this project
is still underway and that later data may indicate changes in design
philosophy.
                               72

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                            TABLE  17
SUMMARY OF DISINFECTION DATA
Run
No.
695
696
697
698
699
6910
6911
6912
6913
6919
6920
6921
6922
703
704
706
707
708
PF
EFF
INF
Chlorine
Dosage
tng/1
10
10
10
8
10
10
10
10
10
10
10
10
10
10
10
10
10
10
= Chlorine added
» Chlorine added
» Chlorine added
Point
of
Addition
PF
PF
PF
PF
PF
PF
PF
PF
PF
EFF
EFF
EFF
EFF
INF
INF
INF
INF
INF
Detention
Time
min
20
20
20
20
20
20
20
20
20
10
10
10
10
21
21
21
21
21
in pressurized flow line
to effluent from flotation
to raw waste prior to bar
Influent
Coliform per
100 ml x 105
36
5.7
1.3
7.8
6.2
19
20
65
38
310
160
55
82
270
12.2
0.7
340
110
basin
screen
Effluent
Coliform
per 100 ml
<100
<4
<4
<4
2
<2
10
<5000
<5000
60,000
40,000
<7
15000
<1000
<100
200
3800
18000

Note:  Samples were dechlorinated  when necessary using  Na2S03<
                               73

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The overall system can be divided into various subsystems and these
subsystems are listed and discussed below:

     1.  Pumping system
         a.  Self cleaning bar screen
        - b.  Pump pit
         c.  Variable rate pumping system

     2.  Screening/flotation system
         a.  Drum screens
         b.  Pressurized flow system
         c.  Sludge collection
         d.  System tankage
         e.  Flocculators

     3.  Solids slurry storage
         a.  Mixers
         b.  Transfer system
         c.  Dewatering  (if required)

     4.  Chemical Addition
         a.  Chemical storage
         b.  Mixing system
         c.  Metering pumps
         d.  Disinfection

     5.  Control Systems
 Pumping  System
 I
 The pumping system is obviously a vital subsystem in the overall treat-
 ment concept.  It is envisioned that a sump will be utilized to provide
 the necessary pump suction conditions.  A self cleaning bar screen will
 be utilized just up stream of the sump to remove large objects which will
 not pass the pumps and/or could cause problems down stream in the treat-
 ment system in such areas as the drum screens or sludge removal systems.
 Bar spacing is recommended at 1/2" as this value proved adequate in the
 demonstration system.  A medium duty bar screen will have sufficient
 strength to handle the imposed solids loadings.

 The pumping system must be able to handle the variable rates whi,ch wij.1
 be encountered during operation.  The pumps therefore must be controlled
 automatically to vary tne pumpage as the raw flow varies.  There are
 numerous pumping system configurations of this type which have been
 employed in the past for storm water pumping, municipal waste treatment
 and industrial processing.  Many pump manufacturers offer package pumping
 systems  (69) which would meet the required design consideratins.  There-
 fore no detailed information on pump station design will be presented  herein.

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It should be noted however that open type screw pumps seem to be ideally
suited to combined sewer overflow treatment systems,  since they can
provide variable flow rate from a constant speed motor.  Since any system
must be designed for a specific hydraulic flow rate, an overflow structure
should be provided for the pumping system.  Considerations involved in
overflow design should include utilization of the sewer system for maximum
storage of raw overflow.  This will provide a damping effect on the raw
flow rate, and minimize control problems in the treatment system.  Proper
design of the overflow will provide satisfactory treatment system operation
with a minimum of excess overflows.  Provisions should also be made for
sump cleaning, since large volumes of gravel and grit are anticipated.
Overall pump system design should provide for ease of cleaning and maintain-
ing the pumps.  No problems were encountered during operation of the demon-
stration syste, with regard to feed pumps.  The demonstration system,
however, had only a single feed pump and the flow rate did not vary during
operation.  Since the screening flotation system can function at overflow
rates higher than the design value, the pumping system should be designed
with this fact in mind and sufficient capacity should be provided.  A
pumping capacity of one and one-half the flotation design capacity should
be provided, since the flotation unit can handle this additional volume
for short periods with only moderate decrease in removal efficiencies.

It may be possible in some applications to utilize gravity flow.  In this
case only sluice gates will be required to direct the raw flow to the
various screening/flotation modules.  The gates should be automatically
positioned to provide proper control.  Consideration of head loss across
the screen becomes more critical when contemplating a gravity feed design.
It may also be possible in some applications to utilize gravity feed and
effluent pumping.  This approach should provide the most maintenance free
pumping system since the effluent water will be low in suspended solids.
When gravity feed systems are utilized, a sump or stilling basin will
still be required to provide proper hydraulic control, and the bar screen
is also required for system protection.  Grit accumulations are expected
to be greater in the gravity flow systems, since turbulance from the pump
suction will not be present.
Screening System

The screening system consists of basically two sections, the drum screen
and the backwashing system.  The critical design parameters associated
with the drum screen include hydraulic loading, solids loading, and head
loss capability.  The hydraulic loading is a function of the wetted screen
area.  •'fhis area varies only slightly as the head loss across the screen
increases during operation.  The hydraulic loading is not affected by
rotation speed.  Generally a drum screen can operate with up to 70% of
the screen surface submerged.  Higher submergence is not recommended due
to possible flooding of the backwash water removal hopper.  Hydraulic
loading in the range of 25-45 gpm/sq ft of screen area was utilized in
the demonstration system for a 50 mesh, 297y opening screen media.
                                75

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                                2
A hydraulic loading of 40 gpm/ft  and a screen size of 50 mesh are recom-
mended at this time.  Additional data on screen mesh size and hydraulic load-
ing are being obtained in Phase V of this project.  Upon completion of this
phase, extensive information on screen design will be available.

Drum rotation speed controls the solids loading on the screen.  It was
found during this study that a solids loading of 1.2 pounds of dry solids
removed per 100 sq ft of screen media produced a head loss of about 13 inches
of water.  Drum rotation speeds were in the range of 1 to 5 rpm.  Solids
loading may be calculated with the following equation:

                             Ls = FsR/rAD

     where:
             Ls = Solids loading per 100 sq ft

             R  = Screen removal efficiency (%)

             Fe = Feed solids into screen (Ibs per min)
              S

             r  = Drum rotation speed rpm

             AD = Total surface area of screen

As may be seen from the equation solids loading is directly proportional
to solids removal efficiency and inversely proportional to drum rotation
speed.  A removal efficiency (R) of 35% is recommended based on the results
obtained in the demonstration unit.  Drum rotation speeds of 2 to 12 rpm
are also recommended.

It is apparent that selection of drum area is controlled by two criteria;
hydraulic loading and solids loading.  Either of these two variables may
control the screen area requirements.  If a solids loading of 1.2 Ibs per
100 sq ft is utilized resulting head losses will be in the range of 12 to
14 inches of water.  Higher head losses and subsequently higher solids
loadings may be possible without a significant effect on process efficiency.
Data  to support this statement are now being obtained.  The inside of the
drum  should be fitted with an angle iron system (similar to a roto-dip
feeder), which will pick up any solids which will not adhere to the screen
media and would not be carried up to the spray washing system.

The screen cleaning system consists of a pump, a header system and spray
nozzles.  A hopper  inside the drum collects the material as it is flushed
from  the screen.  Required screen wash water rates amount  to  15 gpm per
foot  of drum length.  This volume is sufficient to clean a completely
blinded screen.  The spray nozzles utilized should provide a  low mechanical
pressure on the screen media, but still provide good washing  capability.
The nozzles should have as large an opening as possible consistant with
a good spray pattern.  The nozzles utilized on the demonstration unit had

-------
egg shaped openings with  the smallest dimensions being 1/4 of an  inch.
They were positioned about  12"  from  the drum  surface and provided
excellent cleaning capability.  They exerted  an average pressure  of
less than  1 psi on the media.

Some problems were encountered with  nozzle plugging due to an inefficient
seal between the raw and  screened water.  Plugging occurred mostly from
gravel or grit with some  plugging due to string and twigs.  The drum seal
has subsequently been improved, but  to eliminate a possible plugging problem,
a small wet cyclone (six  inch diameter) should be utilized to trap any
material which could cause  plugging.  The dirty water discharge from the
cyclone should be routed  back through the screen.

It is recommended that screen rotation be continuous.  This eliminates
rapid change in head loss when  the clean screen enters the water, which
could result in an incomplete washing cycle.  If the drum were stationary,
the portion of media not  in contact  with the  flow would initially be clean.
As the head loss reached  the limit of the backwash actuating system and
the drum was activated, it  would rotate only  until sufficient clean screen
area was wetted to reduce the head loss to normal values and the washing
system would then be deactivated,  this could leave portions of the screen
unwashed and cause rapid  head loss flocutations.  When the rotation is contin-
uous, a solids layer gradually builds up over the entire drum surface.
The back wash system is then activated and cleans the entire screen before
deactivating.  It is recommended that the spray water cleaning system be
activated by monitoring differential pressure, i.e. head loss across the
screen.  Conductivity probes can be  utilized, and there are a number of
commercially available, inexpensive  units on  the market.   The system
consists of two probes and  an electrical circuit board with relays.  The
probes are mounted in the tank at the desired differential elevation.
When the water contacts both probes, a relay  is tripped which can be used
to activate the backwash  pump.  The  relay remains closed until the water
level is below the lower  probe.  The differential chosen should be about
50-60% of the expected head loss across the screen, i.e.  for a 2' head loss
the spray system should activate at  1 to 1.2 foot of head loss.  This
prevents the screen from  becoming completely blinded prior to activation
of the back wash system.  The lower  probe should be set two to three inches
higher than the head loss level when the screen is completely clean.  This
will prevent unnecessarily  long back wash cycles.

The media utilized in the demonstration system was type 304 stainless steel.
This media proved adequate.  Because of the near neutral pH encountered in
the demonstration runs (6.8 - 7.5), brass screen which is considerably less
expensive could be utilized.  During the two years of operation reported
herein some bacterial growth on the  screen has been experienced.  It was
found that a rinsing with chlorine solution would remove these growths.

The control of the feed water flow into the drum screen is extremely
important.  Since the possibility exists, with this highly variable raw
waste, that the head loss capacity of the screen may be exceeded during
the heavy solids loading peaks.   The system should therefore have an automa-
tic by-pass feature, which will allow relief of the screen if the head loss


                                 77

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capacity is exceeded.  The water which is bypassed during these times can
be routed to the flotation zone.  It is also recommended that a head loss
capacity of 24 inches of water be provided.

Figure 18 presents a sketch of the recommended screen configuration.  This
sketch illustrates the important features of the screen installation which
have been discussed above.
Flotation  System

The design of the flotation system requires the consideration of the follow-
ing components:  pressurized flow system, flotation basin and scum removal
system.  Details on design recommendations will be discussed in this section
along with a proposed system arrangement.

The pressurized flow system is the heart of the dissolved air flotation
process.   It includes a pump, air solution tank, pressure reduction valve,
source  of  compressed air and suitable control systems.

The pressurized flow system should be designed to provide a volume equal
to 30%  of  the raw flow rate into the system.  This should provide an
adequate margin of safety since testing at the demonstration site indicated
20% was sufficient.  The recommended design operating pressure is 50 psig.
The air solution tank should provide maximum air water interface to obtain
high air solution.  Some air solution tanks are packed with a tower packing
to provide this interface.  For treatment of combined overflows, however,
a packless tank is recommended.  A packed tank would be very susceptible
to plugging  due to the solids present in the waste stream.  Packless tanks
are generally  fitted with an internal baffle to promote air water interface.
Nominal detention time in the tank is generally in the range of one minute.
The tank should also have some method of controlling the water level,  since
only about 20% of the tank volume is filled during operation.

The pressure in the system is controlled via an adjustable valve.  Weir
type valves  have been utilized successfully.  The valve is positioned  by
way of  a pneumatic controller which allows automatic control of the system
pressure.   The valve besides providing pressure control, provides the
necessary  shear forces to promote proper bubble formation.

The sizing of  the flotation basin is based mainly on the American Petroleum
Institute  (API) standards (64).  Based on operation of the demonstration
system, some modifications have been made to this procedure.  The API  design
criteria are listed below as follows:

                          L - 1.2 FVhd/Vt

     where:  L  = effective tank length  (ft)

             Vt = rate of rise of particles  (fpra)
                                 78

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                                      Backwash
                                      Header
                                   Lifting Flights for
                              Solids Not Adhering to Screen
Backwash
Actuators
  Feed
Channel
                     Screen Backwash Header


                                      A
A
                           Screened
                           Solids
                           Hopper
                     Screened Solids Discharge
                         Screened Water
                         FIGURE 18
              RECOMMENDED SCREEN ARRANGEMENT

-------
           V^  =  horizontal velocity in tank (fpm)

           d   =  effective tank depth (ft)

           F   =  (0.026  Vh/Vt)  + 0.995

     Vjj maximum =  15 Vfc  or 3  fpm

     tD  (tank detention) = 10 minutes minimum

     d  (depth of tank) = 0.3  to 0.5 of tank width

           minimum  depth  = 3'


     The particle  rise rate can also be expressed as a  surface  loading
     rate, i.e.,

           SL  "  (Vt)7.48

     where SL = surface  loading gpm/sq ft  and Vfc is in  fpm


The demonstration  system design was based  on  the API procedures listed
above.  A  particle rise  rate  of 0.4 fpm (SL = 3 gpm/sq  ft) was utilized
based on laboratory tests.  The tank was also designed  to allow changing
the overflow  rate.  It is obvious  from the above discussion that the
particle rate of rise  is critical  in the flotation basin sizing.  It may
also be seen  that  the horizontal velocity  will be at the maximum value
(3 fpm) for all rise rates  in excess of 0.2 fpm.  The particle rise rate
is dependent  upon  particle  diameter to the second power and the apparent
difference in density of the  particle bubble combination and suspending
fluid to the  first  power.   Little  can be done to control the latter, but
the particle  size  can be significantly affected by proper chemical addition
and flocculating procedures.   Rise  rates as great as 5  fpm have been
obtained in the  laboratory, indicating large floe particles can be
developed.

It is recommended  that the  above discussed procedures be utilized to size
the flotation basin.  A  particle rise rate of 0.45 (SL =3.3 gpm/sq ft)
should be utilized.  This recommendation may be modified, depending upon
results obtained during  the remainder  of the project.

Overhead skimmers are provided  to remove the floated scum.  Bottom skim-
mers are sometimes utilized on  flotation systems to remove any sludge
which may possibly settle.  If  screening (50 mesh or finer) is utilized
in the system, bottom skimming  is not  recommended since the small amount
of settled sludge expected  can  be removed while draining the tank between
storms.   If,  however,  flotation  is  utilized without screening, bottom
skimming will be required.  Removal  of  scum should be controlled by a
                                80

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timed cycle or the sensing of a sludge blanket.  This will allow sludge
to be removed only when required and hold to a minimum the volume of
floated scum which will require ultimated disposal.

The recommended general arrangement for the screening/flotation system
is presented in Figure 19.  It is felt that this configuration will
meet all process requirements and be the most economical system.

The additional subsystems required to complete the treatment system are
sludge storage and the chemical storage and feeder units.  A possible
overall site arrangement including these subsystems is shown in Figure 20.
Sludge storage should be sufficient to handle 2% of the raw flow for the
design storm period.  This should provide sufficient storage volume,
however, the ultimate sludge disposal method may dictate the desired
storage volume.  Sludge disposal alternatives available include tanker
trucking, providing a truck mounted vacuum filter to reduce the slurry
to a cake for hauling, or disposal by pumping to an interceptor sewer
for transporting to the sewage treatment plant.  If the latter method is
used, the interceptor obviously must not have possible overflow points
in its course to the sewage treatment plant.  If disposal via interceptor
is utilized a sludge pump will be required and essentially no solids
storage pit will be necessary.  On the other hand, if it is not feasible
to pump solids into the interceptor during a storm, they may be stored
at the site and pumped to the interceptor after the storm has passed.
Regardless of which method is selected, proper attention should be given
to the problems associated with handling sewage solids slurries.

The chemical treatment module (Figure 20) should provide for storage of
flocculating chemicals (ferric chloride and a polyelectrolyte) as well
as chlorine.  A sufficient supply of chemicals consistent with the require-
ments of the system should be provided.  Estimated chemical dosages are:
ferric chloride - 20-25 mg/1, polyelectrolyte - 5 mg/1, and chlorine -
10-15 mg/1.  The chemical treatment module also houses the proper feeder
systems to accurately dispense the chemicals into the wastewater flow.

The entire system detailed in Figure 20 should be automated 100%.  This
will allow remote monitoring and control of the treatment facility at a
central location.   However, the maintenance involved with automatic
systems which are used intermittently will have to be tolerated.  It
is felt that this maintenance will not be of such a magnitude to negate
the advantages of automation.

Economic Considerations

There are many factors which must be considered when estimating the
capital costs of a combined sewer treatment facility.  The basic areas
of consideration for a screening/flotation system are listed below:

     1.  Screening/flotation system including
              self cleaning bar screen
              variable rate pumping system
                              81

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                        Screw Convenor
         Drum Screen
  Feed
Channel
                                                Scum Collector
                                                                    Z=±£
                              Mixing
                               Zone
Flotation Zone
                           o
                            Pressurized  Flow Header
                                Effluent
                                Weir

                                         FIGURE  19
                        RECOMMENDED  SCREENING/FLOTATION ARRANGEMENT

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   Automatically Cleaned
         Bar Screen \^
                                        Influent
                                         Sewers
                           Pumping System
                            Flotation Tanks
w
£

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              solids storage and disposal
              instrumentation
              control building
              erection costs
     2.  Sewer interconnection (i.e.  combining a number of overflow
         points to reduce the number of treatment sites) and outfall
         facilities
     3.  Land costs
     4.  Special design problems
              foundations (soil problems)
              ground water
              special construction techniques
              freezing problems
     5.  Engineering costs and fees
Generalized cost estimates for Item 1 can be made since these costs are
now known.  Cost estimates for Items 2, 3, 4, and 5 are highly specific
for the selected treatment sites,  and cannot be generalized.  Total
installed costs for the screening/flotation system is estimated at
$19POO per MGD capacity for 10 MGD plants and $15,000 per MGD for 45
MGD and larger plants.  This price includes system tankage in concrete,
all necessary hardware, pressurized flow system, variable rate pumping
system and scum collection and storage.  The foundation is assumed to be
a simple slab, and solids disposal by gravity drainage into an intercep-
tor sewer.

The total installed cost for the demonstration facility was approximately
$90,000 or $18,000 per MGD capacity for the 5 MGD plant.  It should be
noted that the demonstration system did not have a self cleaning bar
screen, a variable rate pumping system, or solids storage facilities
which would increase the cost per MGD capacity.  On the other hand the
demonstration system was of all steel construction and only 5 MGD
capacity, larger capacity and concrete construction are expected to
decrease the cost per MGD capacity.

Based on the above generalized information, the cost of providing a
screening/flotation system to treat the entire Hawley Road drainage area
(^500 acres) is presented below.  It was assumed that the design storm
was the once in 5 year storm.  From Milwaukee rainfall records this
intensity is approximately 1.0 inch per hour for the estimated time of
concentration of the drainage area of 100 to 110 minutes.  This amounts
to an overflow rate of approximately 120 MGD.  Allowing a 33% surge
factor for this peak storm results In a design capacity of 90 MGD.
The following costs are estimated for this system capacity.

     1.  Screening/flotation system                     $1,350,000
     2.  Sewer interconnection and outfall facilities   $   65,000.
     3.  Land costs (1.5 acres @ 100,000/acre)          $  150,000
     4.  Special design problems                        $   90,000
                                84

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     5.  Engineering costs and fees                     $  240,000
                                 Total                  $1,895,000
                                 Cost/MGD               $   21,056
                                 Cost/acre              $    3,828

A detailed design and cost estimate for a midwest city indicated a
system cost of $22,000 per MGD capacity which compares favorably with
the above estimate for the Hawley Road drainage basin.

The operating costs for a screening flotation system include power,
chemicals, and maintenance.  Table 18 presents a summary of the estimate
operating costs.  The total operating cost is 3.09C/1000 gallons of
treated overflow.  The majority of this cost is for chemical addition,
i.e. 2.51C/1000 gallons.  These costs are based on operation of the
demonstration system at Hawley Road and are not expected to vary signif-
icantly with plant size.
                                85

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                           TABLE 18
                   OPERATING COST ESTIMATES
      Item
Power

FeCl3(1)

Polyelectrolyte Q\

Chlorine

Labor^2\

Parts/2)
                                                           Cost
                                                         C/1000
Quantity
15 KW/MGD
20 mg/1
4 mg/1
15 mg/1
30 hr/mo
$300/mo
Unit Cost
1.5C/KWH
4.5C/lb
35C/lb
4.7C/lb
$10/hr
	
gallons
0.54
0.75
, 1.17
t
0.59
0.02
0.02
              TOTAL COST = 3.09C/1000 gal

       (1)  Based on carload prices

       (2)  Based on 90 MGD system 40 hours per month operation
                               86

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                          SECTION VIII

                       ACKNOWLEDGEMENTS
The cooperation of the City of Milwaukee on this project is deeply
appreciated.  Messrs. Herbert A. McCullough, City Engineer, and
Gilbert Vosswinkel's assistance in site selection and review of
construction plans allowed timely completion of the construction of
the demonstration facility.

Many people at the Rex Ecology Division contributed to the success of
this project.  Design of the demonstration system was made by J. E.
Milanowski.  Operation of the unit at any time day or night was performed
by M. K. Gupta, F. Toman, and D. G. Mason.  Excellent cooperation was
provided by the process equipment laboratory, headed by R. W. Wullschleger,
with regard to timely completion of the large numbers of analyses which
were required.

The principal author of the report is Donald G. Mason.  Valuable assis-
tance in preparation of the literature search and the chemical oxidation
studies sections of the report was provided by M. K. Gupta.

Encouragement and assistance from EPA personnel, i.e. Messrs. William A.
Rosenkranz, Frank Condon, Ralph Christensen and Clifford Risley is also
deeply appreciated.
                                 87

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                           SECTION IX

                           REFERENCES


 (1)  Romer, H. and Klashman, L., Public Works 94:3:100 (1963).

 (2)  Camp, T.R., Sewage and Industrial Wastes 31:4:381 (1957).

 (3)  Benjes, H.H., WPCF Journal 33:12:1252 (1961).

 (4)  Palmer, C.L., WPCF Journal 35:2:162 (1963).

 (5)  McKee, J.E., Journal Boston Society Civil Engineering 34:2:55 (1947).

 (6)  Palmer, C.L., Sewage and Industrial Wastes 22:2:154 (1950).

 (7)  Johnson, C.F., Civil Engineering 28:2:56 (1958).

 (8)  Fair, G. and Geyer, J., Water Supply and Waste Disposal, John
      Wiley & Sons, Inc., New York, 1961.

 (9)  Eckenfelder, R.B. and O'Conner, D., Biological Waste Treatment,
      Pergamon Press, 1961.

(10)  Camp, T., Journal ASCE. Sanitary Engineering Division 87:SA1:1 (1961)

(11)  Dunbar, D. and Henry, J.,  WPCF Journal 38:1:9 (1966).

(12)  Benzie, W. and Courchaine, R., WPCF Journal 38:3:410 (1966).

(13)  U.S. Department of Health, Education and Welfare, "Pollutional
      Effects of Stormwater and  Overflows from Combined Sewer Systems",
      November, 1964.

(14)  Riis-Carsten, E., Sewage and Industrial Wastes 27:10:1115 (1955).

(15)  Romer, H.  and  Klashman, L., Public Works 94:4:88 (1963).

(16)  Romer, H. and Klashman, L., Public Works 92:10:129 (1961).

(17)  Stegmaier, R.B., Sewage Works Journal 14:6:1264 (1942).

(18)  Steel, E.W., Water Supply  and Sewerage, McGraw-Hill, 1960.

(19)  Boruff, C.S. and Buswell,  A.M., Sewage Works Journal 4:6:973 (1932).

(20)  Flood, F.L., Sewage Works  Journal 3:4:223 (1932).

(21)  Rudolfs, W. and Hesig, H., Sewage Works Journal 1:5:519 (1929).

(22)  Muldoon, J.A., Sewage Works Journal 11:6:1054 (1939).
                               89

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(23)   Peterson,  K.,  "Sludge Thickening by  Screens", Presented  at  the
      California Water  Pollution  Control Federation Conference,
      April 28,  1966.

(24)   Boucher, P.L.  and Evans,  G.R., Water and  Sewage Works  109:11:R184
      (1962).

(25)   Lynam,  B.T.,  Ettlet,  G.,  Me Aloon, T.,  WPCF  Journal 41:2:247 (1969).

(26)   Keilbough, W.A.  , et  al., "Microstraining with Ozonation or
      Chlorination  of Combined  Sewer Overflows", Preliminary Report by
      Cochrane Division,  Crane  Company for presentation at FWPCA
      Seminar, Edison,  New  Jersey,  1970.

(27)   Chase,  E.S.,  Sewage and Industrial Wastes 30:6:783 (1958).

(28)   Rohlich, G.A., Industrial and Engineering Chemistry 46:2:83 (1954).

(29)   Geinopolos, A. and  Katz,  W.J., Chemical Engineering 75:20:78 (1968).

(30)   Van Vuuren, L.R.J., et al., International Journal of Air and
      Water Pollution 9:823 (1965).

(31)   Van Vuuren, L.R.J., e^ al., Water Research 1:463  (1967).

(32)   Katz, W.J., "Principles of  Flotation Design", part of  a  panel
      panel discussion  on flotation, presented  at  the Fall Meeting of  the
      Committee  on  Waste &  Disposal of the American Petroleum  Institute,
      Denver, Colorado, September 15, 1954.

(33)   Katz, W.J., "Solids Separation Using Dissolved Air Flotation",
      presented  at  the  Air  Utilization Institute,  University of
      Wisconsin, April  15,  1958.

(34)   Vrablic, E.R., "Fundamental Principles  of Dissolved Air
      Flotation  of  Industrail Wastes", Proceedings of the 14th
      Industrial Waste  Conference,  Purdue  University, 1959.

(35)   Berraan, R.I.  and  Osterman,  J., "Dissolved Air Flotation  for White
      Water Recovery",  Proceedings  of the  10th  Industrial Waste
      Conference, Purdue University, May,  1955.

(36)   Katz, W.J., Petroleum Refining 37:5:32  (1958).

(37)   Wollner, H.J., et al.,  Sewage and Industrial Wastes ,  26:4:309
      (1954).

(38)   Sessler, R.E., "Wastewater  Use in a  Soap  and Edible Oil  Plant",
      Sewage and Industrial Wastes  27:10:1178 (1955).
                               90

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(39)   Osterman,  J.,  Waste Engineering 26:2:37 (1955).

(40)   Balden, A.R.,  WPCF Journal 41:11:1912 (1969).

(41)   Katz,  W.J.,  and Rohlich, G.A.,  "A Study of the Equilibria and
      Kinetics of  Adsorption by Activated Sludge",  Biological Treatment
      of Sewage and  Industrial Wastes by McCabe, J.  and Eckenfelder,
      W.W.,  Volumn I, p 66, Reinhold, New York,  1956.

(42)   Ettelt, G.A.,  "Activated Sludge Thickening by  Dissolved-Air
      Flotation",  Proceedings 19th Purdue Industrial Wastes  Conference,
     ' p 210-244, 1964.

(43)   Katz,  W.J.,  Public Works 89:12:114 (1958).

(44)   Hurwitz, E.  and Katz, W.J.,  Wastes Engineering 30:12:730 (1959).

(45)   Ettelt, G.A.  and Kennedy, T.J., WPCF Journal  38:2:248  (1966).

(46)   Katz,  W.J.,  and Geinopolos,  A., WPCF Journal  39:6:946  (1967)-

(47)   Eckenfelder,  W.W., Jr., Industrial Water Pollution Control,
      McGraw-Hill,  New York, p 275,  1966.

(48)   Howe,  R.H.L.,  "Mathematical  Interpretation of  Flotation for Solid-
      Liquid Separation", Biological  Treatment of Sewerage and Industrial
      Wastes, Reinhold Publishing  Company, 2nd Edition, 1958.

(49)   Eckenfelder,  W.W., Jr., et al., "Dissolved-Air Flotation of
      Biological Sludges", Biological Treatment  of  Sewage and Industrial
      Wastes, Reinhold, New York,  p 251-248,  1958.

(50)   Garwood, J.,  Effluent and Water Treatment  Journal 7:380 (1967)

(51)   Mogelnicki,  S.J., "Experiences  in Polymer  Application  to Several
      Solids-Liquid Separation Processes", Proceedings 10th  Sanitary
      Engineering  Conference, University of Illinois,  Bulletin 65,
      115:47 (1968).

(52)   "The Use of Organic Polyelectrolyte for Operational Improvement
      of Waste Treatment Processes",  Report prepared by City of
      Cleveland, Ohio, for FWPCA,  Grant No. WPRD 102-01-68,  May,  1969.

(53)   Braithwaite,  R.L., Water and Sewage Works  111:12:547 (1964).

(54)   "Chlorination of Sewage and  Industrial Wastes",  Manual of Practice
      No.  4, Federation of Sewage  and Industrial Wastes Association,
      1951.
                              91

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(55)   Koller,  L.R.,  Ultraviolet  Radiation,  John Wiley  &  Sons,  Inc.,
      New York,  1952.

(56)   Kelly, C.B., American Journal  of  Public Health 51:11:1670 (1961).

(57)   Symons,  R.S.,  Sewage  Works Journal  13:2:249  (1941).

(58)   McKee, J.E., £t  al^,  WPCF  Journal 32:8:795 (1960).

(59)   Cleasby, J.L., et^ al^,  Journal AWWA 56:4:466  (1964).

(60)   Cherry,  A.K.,  Journal AWWA 54:5:417 (1962).

(61)   Hann, V.A., Journal AWWA 48:10:1316 (1956).

(62)   Hann, V.A., Journal AWWA 35:5:585 (1943).

(63)   Powell,  M.P.,  et al._, Journal  AWWA  44:12:1144  (1952).

(64)   Manual on  Disposal of Refinery Wastes,  Chapter 5,  Copyright
      American Petroleum Institute,  1969.

(65)   Christensen, Ralph, Private communication, EPA Project No.  11030
      FOB, Detroit,  Michigan, FWQA Chicago, Illinois,  1969.

(66)   Gannon J.  and  Stueck, L.,  "Current  Developments  in Separate vs.
      Combined Storm and Sanitary Sewage  Collection  and  Treatment",
      presented  42nd Michigan WPCF Conference,  June, 1967.

(67)   Eckenfelder, W.W.  Jr.,  Principles of  Biological  Oxidation,
      Pergamon Press,  New York,  1966.

(68)   Bennett, C.A.  and Franklin, N.L.,  Statistical Analysis  in
      Chemistry  and  the Chemical Industry , John Wiley and  Sons,
      London,  1954.

(69)   Bulletin_720B  "Variable Capacity  Pumping Systems",  Aurora Pump
      Company, Aurora, Illinois.

(70)   Albrecht,  A.E.. Turbine Flocculators.  Rex Chainbelt Inc.  Research
      Report 3W-40 //I, December, 1969.
                               92

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                           SECTION X

                          PUBLICATIONS
The data reported in this report have been utilized as a basis for three
technical papers:

1.  Mason, D.G., "The Use of Screening/Dissolved-Air Flotation for
    Treating Combined Sewer Overflows," Presented at the Seminar on
    Storm and Combined Sewer Pollution Problems, Edison, New Jersey,
    November 4-5, 1969.

2.  Mason, D.G., "Screening/Dissolved-Air Flotation for Treating
    Combined Overflows," Presented at the Seminar on Combined Sewer
    Overflow Abatement Technology, Chicago, Illinois, June, 1970.

3.  Mason, D.G., "Treatment of Combined Sewer Overflows Utilizing
    Screening/Dissolved Air Flotation", Presented at the WPCF
    Conference  October 3-8, 1971, San Francisco, California
                                93

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       APPENDIX I
CHEMICAL OXIDATION STUDY

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                        LITERATURE SEARCH


Removal of organic contaminants from combined sewer overflows cannot be
effectively and economically accomplished by conventional biological
oxidation methods (1)(2) for the following reasons:

     A.  Large and highly variable flows
     B.  Intermittent operation would be required because of the nature
         of the flows,  and this has a very detrimental effect on
         biological oxidation systems (3)(4) (5).
     C.  Removal of the solids produced would require a large number of
         sedimentation tanks (because of high flows) which would be used
         only periodically.

Use of chemical oxidation on combined overflows has the potential
advantage of effective destruction of biological organisms and the
removal of organic contaminants without the production of residual waste
concentrates.  Some of the technical difficulties connected with the
successful treatment of wastes by chemical oxidation include the rela-
tively dilute concentrations of organic materials present, the unknown
composition of a wide range of possible organic compounds present, and
the continually changing concentrations and compositions present in a
combined wastewater flow such as the one with this project is concerned.

These difficulties necessitate the use of gross parameters in evaluating
the effectiveness of a given chemical oxidant.  Such parameters would
include knowing the chemical oxygen demand of the waste (COD) and the
concentration of the oxidizing properties in the chemical being utilized.
Having this information, the oxidation efficiency (6) can be calculated
as shown below:

  Oxidation Efficiency =  	ACOD	
                          Available Oxidation Equivalents x 100 (6)

  Where:  ACOD = change in COD brought about by the oxidation process
           (in milligrams of Q£ per liter)

  And:    Available Oxidation Equivalents = amount of chemical oxidation
          equivalents available from the oxidant used (in milligrams of
          02 per liter)

Taking into account the variation in organic concentration and volume
of the waste flow to be treated under this contract, the "ideal" oxidant
should have the following characteristics:

     A.  It must be nonspecific in its attack on organic materials.
     B.  Its required contact and retention time should not be excessive
         (30 minutes or less).
     C.  It should be easy to handle and dispense.
     D.  It should effectively oxidize the organic materials at the
         prevailing pH of the waste
     E.  It should not  produce any secondary pollutants which are
         difficult to remove from the waste flow.

                               96

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From the literature  (6) it was found that six  types of oxidation  systems
offer various degrees of potential for  the  treatment of organic impuri-
ties in wastewater.  These systems are:

     A.  Oxidation by oxidants containing active oxygen
     B.  Accelerated molecular oxygen oxidation
     C.  Catalytic oxidation of adsorbed organics
     D.  Oxidation by chlorine and its  derivatives
     E.  Oxidation by oxy-acids and their salts
     F.  Electrochemical oxidation

Of the six oxidation systems mentioned, only systems A, D, E, and F appear
to have potential for treating combined sewer  overflows.  These systems
will be discussed in detail below.
Hydrogen Peroxide

Considerable work has been done regarding the application of hydrogen
peroxide (H202) as an oxidizing agent in the treatment of wastewater
containing organic impurities  (6)(7)(8)(9)(10)(11)(12).

In aqueous media, hydrogen peroxide  decomposes to  form the  'OH radical.
This radical is one of the strongest oxidants known in aqueous systems.
However, hydrogen peroxide does not, when used alone, oxidize organic
materials within a practical reaction time.  The system requires a multi-
valent iron salt as a catalyst.

The principle reactions involved  in  a hydrogen peroxide iron salt
system are as follows (11)(12):
     1.  Fe   + H202 +Fe    + H02 + H'

     2.  Pe4* + H202 ->Fe'f++ + OH~ + *OH

Considering reactions I and 2, above, the iron salt acts truly as a
catalyst i.e., is not utilized during the reactions.  Reaction 1 is the
rate limiting reaction.  Once the ferrous ion is formed, reaction 2 is
extremely rapid (11)(12).  The production of 'OH radicals via reactions
1 and 2 using ferric salts requires two to three hours at 65°C (6).  By
using ferrous salts, the production of "OH radicals is essentially
immediate, but the iron salt no longer performs as a true catalyst, since
it is not reproduced at the same rate at which it is being utilized.
There are other reactions associated with the H-jO,—iron salt system
which compete with the organic material being oxidized for the 'OH
radical.  The following reactions illustrate the competition for 'OH
radicals (11)(12).
     3.  Fe   + 'OH -»-Fe    + OH
                                97

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     4.  HO  +tO
           £-      £.
     5.  Fe    + 02~ -> Fe^ + 02

     6.  H202 + 'OH -»• H02 + H20

Hence, only an unknown portion of the *OH radicals produced are available
to oxidize the organic substrate.

The efficient production of 'OH radicals requires a specific pH range
of 3 to 5 (6)(7;(10)(11).  Above or below this specific pH range,
production of 'OH radicals is greatly reduced.  During the reactions,
an excess of H+ ions are formed (9) so the pH will normally stabilize
in the optimum range.  Eisenhauer  (7) found that the initial pH of an
ABS solution could be as high as 11, before it would significantly affect
pH stabilization in the 3 to 4 pH range.  The pH of the system can also
be lowered to the specific range by use of acid (11).

The reactions between "OH radicals and specific organic substrates were
summarized by Busch (12) after review of a number of papers on the
subject.  Since the waste to be oxidized under this contract contains
many different types of organic substrates in unknown proportions, these
specific equations were not directly applicable and hence were not repro-
duced herein.

Use of the hydrogen peroxide method of oxidizing organic wastes has
been experimentally evaluated.  Davidson found that phenols could be
chemically oxidized (90% complete) to carbon dioxide and water in ten
minutes (9).  Eisenhauer demonstrated that in dilute aqueous solutions
of phenol, the reaction efficiency was considerably increased in the
presence of air-available oxygen (7).

Eisenhauer also found that the reaction between a hydrogen peroxide-
ferrous salt combination and ABS was rapid and 80 to 90% of the ABS was
destroyed in the first ten minutes.  Further ABS removals were obtained
at slower reaction rates, with a 99% ABS removal effected after fifteen
to twenty hours.  The optimum reaction pH level was found to be from
3.0 to 3.5.  The optimum concentrations of the reactants were six moles
of ferrous salt per mole of ABS, and nine moles of EjQ^ per mole of ABS.
Multiple incremental additions of the ferrous salt will decrease the
reaction time required (11).

Applying this information to a treatment of laundry wastes containing
ABS, Eisenhauer obtained ABS reductions in excess of 90%, both with the
raw waste and with effluent from a pretreatment process in which the
detergent builders were precipitated.  For a laundry waste containing
50 to 80 parts per million ABS, it was found that chemical costs ranged
from $0.45 to $0.70 per 1,000 gallons for the raw waste treatment and
$0.15 to $0.25 per 1,000 gallons for the effluent pretreated with
ferric sulfate.  This includes the cost of ferrous sulfate, ferric
sulfate, sulfuric acid, and hydrogen peroxide (7).
                                98

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Bishop et al (11) used hydrogen peroxide-iron salt systems to oxidize
refractory organics in municipal wastewaters previously subjected to
secondary biological treatment.  Significant conclusions from this paper
(11) are presented below.

     1.  The hydrogen peroxide-iron salt systems in various wastewaters
         oxidize a significant portion  (-70%) of the organics refractory
         to biological oxidation.

     2.  The oxidation process involves free radical ('OH) oxidation and
         auto-oxidation and is effective only in the pH range of 3 to A.

     3.  Oxidation efficiencies of 60%  for the ferric ion systems and 30
         to 51% for the ferrous systems were reported.

No data were found in the existing literature where hydrogen peroxide
was used to oxidize raw sewage or combined sewer overflow.  Since the
H202 systems did oxidize the refractory organics present in sewage,
there should be no problem oxidizing  the organics in combined sewer
overflow.  The important problems associated with the use of this
oxidation system for combined sewer overflow include:

     1.  The restricted pH range will require lowering of the pH of the
         combined sewer flow.

     2.  Materials used for construction will have to be able to withstand
         the pH of the system.  This  will require the use of stainless
         steel, or rubber coated mild carbon steel.

     3.  Removal of the ferric hydroxide formed during the reaction will
         require a flocculation and settling period.

     4.  The pH will have to be readjusted to near neutral before the
         effluent is discharged.
Ozone

The use of ozone as an oxidant  for water and waste  treatment is described
in the literature  (6)(13)(14)(15)(16)(17)(18)(19)(20)(21).  Ozone is a
blue gas under normal conditions.  It contains  three  atoms of oxygen (0.,)
and is heavier than air or oxygen.  Ozone  is one  of the most powerful
oxidants known (13).  The oxidizing power  of ozone  is exceeded only by
fluorine and compounds such as  oxygen difluoride, atomic  oxygen, and
the hydroxyl radical  (22).  In  high concentrations, ozone is toxic  (13)
(14).  Figure 1-1  shows the human tolerance for ozone at  various concen-
trations and exposure times.

The area between the symptomatic line and  irritant  line of Figure 1-1
is a nontoxic region.  The threshold odor  level of  ozone  is 0.01 to
0.02 ppm (V) which is well below the toxic region as  shown in Figure 1-1
(13).  Exposed persons are thus given a warning of  ozone's presence.

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        Source:  Prolonged Ozone  Inhalation  8,  Its  Effects  on
                Visual Parameters, J.M. Langewerf,  Aerospace
                Medicine, 36, June 1963
                          Permanent
                            Toxic
                              Region
                             Temporary
                               Toxic
                                 Regidn
   Non Sympton
        Regioi
0.1
     10          100        1000

Exposure Time in Minutes
                                                          10,000
                          FIGURE 1-1

                    HUMAN TOLERANCE FOR OZONE
                           100

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Ozone can be produced in a number of ways.  Among these are silent elec-
tric discharge, electrochemically, and chemically (22).  Use of silent
electric discharge is the principal upon which most laboratory and
large scale ozonizers depend  (13)(22).  Production of ozone by this method
requires the use of cold, clean air or oxygen.  Basic equipment necessary
include an air fan, equipment for filtering and drying the air and an
ozonizer (14).  When applying the ozone to water, some type of diffuser
system and a contact tank will also be needed  (14).  Ozonizers produce
ozone.by passing the dried air between two concentric electrodes separated
by a dielectric.  High frequencies (500 cps to 1000 cps) and high voltages
(4000 to 30,000 volts)are utilized.  Some oxygen in the air passing through
the ozonizer is broken into charged oxygen atoms, which recombine to form
03.  Ozonizers operating on air under pressure produce far greater quan-
tities of ozone in higher concentrations than  those operating in air -it
atmospheric pressures (13)(17).  Commercial ozonators produce ozone
concentrations of 1 to 4 percent by weight in  air (17)(23).  Power consump-
tion is 9.5 to 11.5 KWH per pound of ozone produced (23).

Ozone is very corrosive and hence the materials used in the piping system
carrying ozonated air must be carefully chosen.  Porcelain has been used
with success, as have aluminum, stainless steel, pressboard, oak, vinyl
plastic and glass  (14)(24).  Polyvinyl chloride (PVC) has been used but
there is a possibility that this material decomposes ozone (14).

The exact oxidation mechanism of ozone on organic materials is not
thoroughly understood.  Ozone decomposition may be a source of 'OH radicals
or the 03 itself may be the actual oxidant (6)(21).  Ozone is known, how-
ever, to be an effective oxidant (17)(18)(21).  The exact oxidation
products and intermediates resulting from ozone oxidation have not been
defined.  Evans and Ryckman (18) when ozonating secondary sewage treat-
ment plant effluents have found that ozone readily oxidized ABS to inter-
mediate compounds which were not detected by an ABS analysis.  These
intermediates actually caused an increase in BOD and COD values of the
partially ozonated waste, and in fact destroyed the biological inertness
of the ABS.  Increased ozonation of this partially ozonated waste then
caused a decrease in BOD and COD of the waste, apparently due to oxidation
of some of the organic carbon to C02 and l^O.

Andrews (16) was recently granted a patent on  a new method of treating
raw sewage.  The method involves removal of the solids from raw sewage
by a combination of settling, screening, and centrifuging.  The resulting
liquor, esentially free of solids and containing the soluble BOD fraction
of the raw sewage, is ozonated to oxidize the  BOD.  The effluent from
ozone treatment is filtered before discharging into the receiving stream.

The patent claims this method of treatment produces an effluent which is
dear, colorless, free from bacteria and contains a high quantity of
dissolved oxygen.  No reference is made, however, as to dosages of ozone
required and BOD content of the effluent.

Miller (21) reports use of ozone to control sewer odors at sewage lift
stations.  He states ozone addition reduced the raw sewage BOD from
                                 101

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120 to 32-39 mg/1.  Septic conditions in flat sewers disappeared and
the plant influent contained 2 to A mg/1 of dissolved oxygen.  No mention
was made of the quantities of ozone added.  The ozone was injected
directly into the pump wet wells for conventional lift stations and into
the air compressors supplying air for the pneumatic-ejector type lift
stations.

March and Panula  (15) reported on a study where raw sewage was ozonated.
They report that the BOD of the sewage which was ozonated decreased from
400 to 300 mg/1.  Application rate was 6 mg/1 of ozone actually absorbed
by the sewage.  This indicates that 1 mg of 03 will oxidize about 16 mg
of BOD which seems quite high.  The amount of 03 applied during this
study was greater than the amount actually utilized.  Absorption effi-
ciencies averaged 22.6%.  Hence, the actual ozone dosage was about 26 mg/1.
March and Panula  (15) indicate that the biggest problem in full-scale
ozone treatment is efficient use of the ozone being produced.  They
suggest collecting the unabsorbed ozone and reapplying it to the sewage
to obtain better absorption efficiencies.  It should be noted that a
simple diffusion system was used during this -study with a 3% foot depth
of liquid over the diff users.  Bubble size was on the order of 0.01 inches
in diameter.

O'Donovan (14) stresses the importance of mixing techniques when intro-
ducing ozone into water.  He stresses small bubble diameter and turbulence
to be important in obtaining good 0^ adsorption efficiencies.  Two types
of adsorption systems which have been used are illustrated in Figure 1-2
(14) (25).  Campbell (25) reports 90% utilization of ozone when using a
partial-ejection system.

The use of ozone to oxidize combined sewer overflow appears to hold
considerable promise.  Ozone has many of the characteristics of the
"ideal oxidant" as previously discussed.  It is apparently nonspecific
in its oxidation of organic material (21) , the necessary contact time
is less than 30 minutes (14) (25), it oxidizes at the prevailing pH of
the waste (25), and is not difficult to dispense (14) .  Some disadvantages
involved with the use of ozone include precipitation of iron and manganese
when present in concentrations greater than 0.2 mg/1 Fe and 0.1 mg/1 Mn,
and inability to store ozone requires ozonators at each application site.
Recently, however,  Matheson Inc. has announced it has a process which
will allow storage of ozone which could eliminate i this latter disadvantage.


Oxidation by Chlorine
Chlorine or its derivatives are added to most municipal water supplied
in the United States to kill micro-organisms.   Green and Stumpf (26)
have shown that chlorine compounds react with certain enzymes which are
essential to the metabolic process of living cells and that death results
from the inactivation of these enzymes.  Dosages required for disinfection
are low, 0.2 to 2 mg/1 (1).  At these dosages, probably little, if any,
oxidation of organic material is occurring.

Use of chlorine to reduce the BOD of sewage has been practiced.  Four
kinds of reactions could be involved in reducing BOD by chlorination
                                102

-------
                                     Injector
         Ozonized Air
                                                 Pump
Contact Tank


1

I
1
JL
— • " O-^-Main F

/
J

*"^"" O >> Ozonized Water

                    Partial-Injection
                            (A)
         Mixer
                                Ozonized Air
 Raw Water-
Turbulence s
Chamber
                      Kerag System
                           (B)
                           FIGURE 1-2
                     OZONE ABSORPTION SYSTEMS
                                                  Ozonized Water
                                103

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     1.  Direct oxidation of organic materials.

     2.  Substitution of chlorine for hydrogen which produces compounds
         which have a bactericidal power.

     3.  Substitution of chlorine for hydrogen which produces compounds
         which are no longer biologically degradable.

     4.  Addition of chlorine to unsaturated compounds forming nonbio-
         degradable substances.

Griffin and Chamberlin (28) have shown that chlorination of sewage does
result in a reduction of BOD.  After an 18 hour contact period, about
35% of the BOD had been removed from screened raw sewage at a 200 mg/1
chlorine dosage.  Increasing the dosage had little effect on further
removals.

Although chlorine and its derivatives do oxidize many of the organic
chemicals contained in municipal wastewaters, they do not usually convert
them to the readily acceptable forms of carbon dioxide and water (6).
Instead, the reaction of chlorine with organics may produce molecules
having considerable taste and odor, and complex compounds which serve
as secondary pollutants may also be formed.  The addition of stoichio-
raetric amounts of chlorine will not effect oxidation of the organics,
and a large chlorine residual may remain in the treated waste (6)(28).
Since oxidation by chlorine is far less effective than by active-oxygen
elements and since the unknown by-products of chlorine oxidation may be
toxic, chlorine and its derivatives are not considered to be good
prospects for removal of large amounts of organic pollutants from waste-
waters by oxidation (6).

A method of making chlorine more reactive could, however, make the use
of chlorine more attractive.  Use of ultraviolet radiation to catalyze
the oxidation of organic material by chlorine has been suggested (29).
No specific data on such a process was found in the literature, but
the process will be investigated during the laboratory phase of this study.
Oxidation by Oxy-Acids and Their Salts

The oxy-acid oxidants are usually added to aqueous systems as the salt
of the oxy-acid.  Important oxy-acid salts with high oxidation potentials
include potassium permanganate (KMNO^), sodium ferrate (NaFeO^) and
potassium ferrate (I^FeO^).  The oxidation potentials of the oxy-acids
are strongly dependent upon the acidity of the aqueous system, with the
potential increasing as the acidity increases (6).

Potassium permanganate (KMNO,) is used as an oxidant to disinfect water
supplies (1)(30) and as an oxidizing agent in the permangate oxygen
demand test (31).  However, references in the literature report only
limited oxidation of organics with KMNO^, and a residual permanganate
persists in the water for more than twenty-four hours (30)(31).  Vosloo
                                104

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 (32)  reports  that  the  permanganate concentration necessary for  maximum
 oxidation should be  about  twice the concentration of  permanganate which
 will  be  utilized.  The use of potassium permanganate  would therefore
 require  removal of the excess MNC^-ion as  a part of the  treatment process,
 and this would greatly increase the salt load in the  aqueous  system  (6).
 The potential for  using KMNO^ as an oxidant in this project is  not. at
 all promising, and hence,  KMN04 oxidation  will not be considered.

 Although ferrate salts such as potassium ferrate (l^FeO*)  are not
 commercially  produced, their high oxidation potentials (33) and the
 coagulating properties of  their oxidation  products, a highly  insoluble
 ferric hydroxide,  make the ferrates a  potentially attractive  group of
 oxidants for  treatment of  wastewaters  (6).

 Exploratory laboratory tests using K2FeO^  to treat filtered municipal
 secondary effluents  in dosages supplying approximately 100 milligrams
 per liter of  available oxygen showed the combination  of  ferrate oxida-
 tion  and coagulation to be nearly as effective as the previously
 discussed ^C^ - iron  salt system for  removing organic materials from
 wastewaters  (5).   The  ferrate salts, however,  also possess the  same
 disadvantages as the l^C^  iron salt system,  (see previous  discussion
 on hydrogen peroxide oxidation)  and these  disadvantages  must  be consid-
 ered  when attempting to use the ferrate salts  as oxidants  in  this
 project.
Electro-Chemical  Oxidation

Any material  that increases  the  electrical  conductivity of an aqueous solu-
tion may  enter  into  a  chemical reaction  at  the  surface of electrodes placed
in the  solution (27).   Interest  in  electrochemistry as a possible technique
for purifying municipal wastewaters is based on the fact that many organic
chemicals take  part in such electrode reactions, often  resulting in the
complete  degradation of complex  organic  molecules to carbon dioxide,
water and other oxides.  After reviewing a  recent study on electrochemi-
cal oxidation (34),  it  was concluded that electrochemical oxidation did
not hold  potential for  treating  combined sewer  overflows for the following
reasons:

     1.   High operating and maintenance  costs.

     2.   Formation of precipitates  which would have to be removed from
          the waste flow.

     3.   Long reaction  times are necessary —2  to 5 hours.


Combination of  Oxidants

Although  no specific data were found  in  the literature about combining
various oxidants, a combination of  ozone and H^Oj or other oxidant
combinations may  produce an effective oxidation system.  For this reason,
                                105

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various combinations of oxidants will be evaluated during the laboratory
phase of this project.

                   LABORATORY INVESTIGATIONS

General Test Procedures

The literature search indicated that the oxiaants with the highest poten-
tial success were ozone, hydrogen peroxide, and chlorine.  During the
laboratory investigation phase the above mentioned oxidants as well as
various oxidant combinations were evaluated.

Samples of seven separate combined sewer overflows from the demonstration
site at Hawley Road were collected during the Fall of 1967.  These samples
were analyzed in the laboratory within twenty-four hours of their collec-
tion for BOD, COD, dissolved COD, total solids, suspended solids, volatile
suspended solids, coliform density and pH.  The data from these analyses
has been reported and discussed in the main body of this report.  Since
the likelihood of getting sufficient and frequent combined overflows
during the fall and winter seasons in Milwaukee is small, it was decided
to freeze some combined overflow samples and use them for chemical
oxidation evaluation during dry weather.  Therefore, about twenty liters
of combined overflow samples from three separate storms was frozen in
individual containers having volumes of from 100 to 200 milliliters.
The laboratory analysis of the three storm samples frozen for chemical
oxidation studies is shown in Table 1-1.  During dry periods, samples
were thawed as needed.  Samples were mixed thoroughly in a Waring blinder
after thawing to provide a colloidal system characteristic of the
original unfrozen raw sample.  Whenever a sample without the particulate
matter was needed for oxidation of the dissolved organic matter, the
thawed sample was not mixed.  Instead, the supernatant was filtered
through a SS-597 filter paper and millipore filter discs to obtain a
dissolved sample.  Standard Method (35) procedures were employed for
various analysis in the laboratory and are discussed in Appendix II.

Special Test Procedures with Various Chemical Oxidants

Chlorine and Hydrogen peroxide oxidations were performed with and without
ultra-violet (UV) light.  Chlorine was applied in the form of calcium
hypochloride solution (HTH) and a 0.75% stock solution was utilized for
hydrogen peroxide oxidation.  Procedures for determination of oxidant
dosages and residuals are discussed in Appendix II.  Cobalt in the form
of CoCl2-6 HpO was utilized in a number of tests to determine if it
helped to c^f-.aZyze oxidation reactions of 1^02 and chlorine.  The
apparatus consisted of an eight inch diameter flat bottomed dish on a
magnetic stirrer under a protective hood cover.  A 300 ml aliquot of raw
waste was used.  For tests  performed with ultra-violet light, the UV
lamp was suspended above the water surface with ring stands at three and
six inch heights.  The two UV lamps utilized were a single bulb Sperti
sunlamp and a double bulb G.E. germicidal lamp.  Figure 1-3 shows a
photograph of the apparatus utilized for these tests.  Samples were
taken at various intervals during the oxidation period for COD analysis.

                                106

-------
TABLE 1-1
LABORATORY ANALYSIS OF COMBINED SEWER SAMPLES UTILIZED FOR
CHEMICAL OXIDATION STUDY
Date pH
11/25/67 7.4
12/07/67 6.6
01/29/68 7.1
Total
Solids
mg/1
649
—
—
Suspended
Solids
mg/1
138
232
2158
Volatile
Suspended
Solids COD
mg/1 mg/1
- — 159
113 298
1410
Dissolved
COD BOD
mg/1 mg/1
59
50
60
Coliforms
per ml
4260
2151
5730

-------
I '/AW&




                 FIGURE 1-3




    APPARATUS FOR ULTRA VIOLET LIGHT OXIDATIONS
 S  I
                FIGURE 1-4
      APPARATUS FOR C7ONE OXIDATIONS
                     108

-------
Some difficulty was encountered in measuring the COD after oxidation
with various oxidants.  Contrary to expectations, some samples
exhibited an increase in COD after oxidation.  This observation could
have been caused by the break down of organic material which prior
to oxidation was not measured by the COD tests.  The increase may also
have been caused by the excess oxidant remaining (the reaction kinetics
were not known and exact amounts of oxidants could not be utilized).
Since it was desirable to know if the COD was increasing due to
partial oxidation, the excess oxidants were removed prior to analyzing
for COD.  Several trial and error procedures were investigated for the
removal of these excess oxidants.  It was planned that excess oxidant
would be removed after oxidation tests by adding a small excess of
sodium sulfite.  After the addition of sodium sulfite, the sample was
aerated until a galvanic cell oxygen analyzer indicated the presence
of dissolved oxygen in the sample.  Also investigations were undertaken
to study the effect of excess oxidants and chemicals on the COD test
results.  Theoretically, the reaction between hydrogen peroxide and
hexavalent chromium in a COD test may proceed as follows:

3H202 + K2Cr207 + 8H+ = 302 + 2Cr+3 + 7H202 + 2K+ [ORP = +0.65] ---- EQ

Then 1 mg H202 = 0.47 mg COD

Similarly, the reaction between sodium sulfite and dichromate may
proceed as follows :

   3Na2S03 + K2Cr20? + 8H+ = 3Na2S04 + 2Cr+3 + 4H20  + 2K+ .....  EQ II
Then  1 mg Na2S03 =  0.127 mg/COD
                               109

-------
Experimentally it was found that the COD exerted by hydrogen peroxide
solution decreased with increasing strength of H202 solution as follows:

              Concentration of
                H202 Solution            Ratio of mg COD/mg H202

                     50                            0.42
                    100                            0.41
                    150                            0.39
                    200                            0.38
                    250                            0.37

The reason for such observation can be attributed to the redox relation-
ships of hydrogen peroxide, since H202 can also react with the trivalent
chromium produced as follows:

3H202 + 2Cr+3 + 6H+ + 7H20 = 6H20 + Cr207= + 14H+ [ORP = +.44]	 EQ III
Thus hydrogen peroxide solution was found to exert a significant COD
value and this was a factor in the increased COD results of hydrogen
peroxide treated samples.

Also, sodium sulfite was experimentally found to have a chemical oxygen
demand of 0.09 mg per mg of Na2S03.  This is approximately 70% of the
theoretically calculated value of 0.127 and is not significant in light
of the small amounts of sodium sulfite utilized in these studies.

When calcium hypochlorite was used as an oxidant, the sulfite was added
in increments until a spot test with ortho-tolidine indicated that
there was no more free chlorine.  The sample was then aerated until a
galvanic cell oxygen analyzer indicated the presence of dissolved
oxygen in the sample.  Experimentally it had been found that a 715 mg/1
calcium hypochlorite solution exerted a nominal COD of 9 mg/1 which
could possibly be the result of experimental errors.  This experimental
observation is also supported by possible theoretical reaction between
chlorine and hexavalent chromium, as:

3C12 + 5Cr207= + 34H+ = 6C103- + 10Cr+3 + 17H20 [ORP = -.14]	 Eq IV
The negative oxidation reduction potential indicates that the above
reaction should proceed to the left and therefore, theoretically the
reaction should not take place.  This leads to the conclusion that no
COD should be exerted by the chlorine solution.

Somewhat contradictory results were obtained when COD tests were
performed on samples from stormwater oxidation tests, whereas the COD
of calcium hypochlorite solution was negligible and the COD of oxidized
sodium sulfite was very small, in most cases the COD values of
                               110

-------
chlorinated waste samples which were dechlorinated with sodium sulfite
and aerated were 5 to 35% higher than the samples which were not dechlor-
inated.  Because of this difference, an alternate method of dechlorination
was also used:  the sample was acidified to a pH of one and stripped
of chlorine by aeration.  Unfortunately, the stripping process was
extremely slow, often requiring several hours.  In some cases, not all
the chlorine was removed by the time the COD analyses were performed.
In general, the COD values obtained by acidification and stripping
were lower than the values obtained by sulfite treatment.  The exact
cause of this difference in values is not known.


Ozone Oxidation System

Ozone was purchased by the bottle and used in a pressure tank system.
A photograph of the apparatus utilized is shown in Figure 1-4 and a
schematic is shown in Figure 1-5.  Ozone was supplied dissolved in
'Freon 13' under high pressure in stainless steel cylinders.  Since
ozone has a half life of approximately three days at room temperature
it was necessary to keep the ozone cylinder packed in dry ice.  A
three mole-percent vapor phase concentration was utilized for oxidation
studies.  To maintain a constant ozone concentration supply, ozone was
utilized in the vapor phase.  This was achieved by inverting the ozone
bottle and converting the liquid ozone to vapor phase by passing it
through a vaporizing coil.

Ozone was mixed with the waste at elevated pressures in the range of
40 to 80 psig.  This pressure charged stream was then placed in a
graduated cylinder for the required reaction time.  Samples were air-
stripped to remove excess ozone remaining after the reaction time.
Pressurization of waste could be total or partial.  When the entire
waste was pressurized, it was called total pressurization.  If only a
portion of the waste was pressurized, the amount was calculated as a
percentage of the nonpressurized portion, and was called a recycle
system.  Use of a pressure tank system enabled large amounts of ozone
to be dissolved and when the pressure was released the extremely small
air-ozone bubbles stayed in contact with the liquid much longer than
the coarse bubbles produced from diffuser type systems.  Such a system
was utilized because the literature search indicated that the ozone
contact time is critical and greatly affects efficient use of ozone.
Titrations for ozone determination were performed in accordance with
Standard Methods(35).

                      RESULTS AND DISCUSSION

Oxidation with Hydrogen Peroxide

Results of chemical oxidation with hydrogen peroxide are presented in
Tables 1-2 and 1-3.  Hydrogen peroxide requires a catalyst to oxidize
effectively within reaction times of one hour or less.  Table 1-2
shows the results of the tests performed using iron as a catalyst.
Oxidation tests were run on the dissolved fraction of the overflov
                                 111

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Gas Collection
For Analysis
                                                                                     Ozone  Supply
                                                                                        (Cylinder)
       Gas Sampling
       Access Ports
              Pressure Vessel
              for Dissolving
              O-j in Waste
                 Sample
 Sampling
   Port
            -X-
                                                    Vaporizing Coil
                                          egulator
Reaction Vessel for
Non-pressurized Oxidation
                                         FIGURE 1-5
                               SCHEMATIC  OF  OZONE TEST APPARATUS

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                              TABLE 1-2
Test
 No.

1

2

3

4

5

6(3)

7(4)

8

9


NOTES:
Available
   02

   50

  100

  100

  100

  100

  100

  100

  150

  300
,TS OF CHEMICAL OXIDATION OF
'ER OVERFLOW WITH HYDROGEN P:
COD
Initial
54
67
54
54
65
65
65
216
216

Final
50
30
41
33
37
42
31
186
185
Percent
Reduction
7
55
24
39
43
35
52
14
14
Oxidation    Filtered
Efficiency   Prior to
  Percent    Analysis
     8

    37

    13

    21

    28

    23

    34

    20

    10
No

Yes

No

Yes

Yes

Yes

Yes

No

No
 1.  In Tests 1  through  7 only the dissolved COD was oxidized, i.e,
     all solids  removed  prior to oxidation.  Tests 8 and 9 were
     run on combined overflow after screening through a 50 mesh
     screen.

 2.  All oxidations were for 15 minutes at room temperature.

 3.  Aerated during the  oxidation.

 4.  Cobalt added during the oxidation.
                              113

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                                             TABLE 1-3

                    EFFECT OF UV LIGHT AND COiiALT ON HYDROGEN PEROXIDE OXIDATION
Test
 No.
 Type of
  Sample

Filtered
      Filtered
 H202
Dosage
mg/1 as
  02

 110
            110
     H202
   Remaining
after Oxidation
  mg/1 as 02
Catalyst Used
                                           None
                          UV Light
                                                   1
                                                                            COD, mg/1
Reaction              After      % COD
  Time    Influent  Oxidation  Reduction
                                     15
                                     30
                                     90

                                     15
                                     30
                                     90
                              92
                              92
                       62
                       75
                      175

                      149
                      161
                      138
           33.0
           19.0
  5
  6
  7
  8
  9

 10

 11
 12
 13
 14
      Filtered
Filtered

Filtered
Filtered
Filtered
Filtered
Distilled
  Water
Distilled
  Water
Filtered
Filtered
Filtered
Filtered
            110
 110

 110
 110
 110
 110
 110

 110

 110
 110
 110
 110
              29
     15

     66
     54
     60
     62
     93

    106

     78
     66
     79
     68
UV Light &
10 mg/1 Cobalt

UV Light &
100 mg/1 Cobalt
10 mg/1 Cobalt
100 mg/1 Cobalt
UV Light
UV Light &
UV Light

UV Light &
5 mg/1 Cobalt
UV Light
UV Light
UV Light
UV Light
                                     30
                                                               30
   30
            106
            106
100
 98
30
30
30
30
30
106
106
58
58
—
119
114
34
39
80
 81
5.6
7.5
                                 41.0
                                 33.0
15
30
15
30
114
114
112
112
76
107
59
80
34.0
6.0
47.0
29.0
 NOTES:
         1.  Ultra-violet light wave length 2800 to 3200 A.

-------
(Tests 1 through 7) as well as the overflow after screening through a
50 mesh screen (Tests 8 and 9).

Test 1 through 7 (Table 1-2) indicated that a substantial portion of the
 dissolved  COD can be oxidized in 15 minutes and the oxidation
efficiencies were in the range of those reported in the literature.
When the effluent from the 50 mesh screen (Tests 8 and 9) was oxidized
with the hydrogen peroxide - iron salt system, the oxidation
efficiencies were lower than those obtained when oxidizing only dissolved
COD.  This indicated the importance of removing a major portion of the
solids prior to oxidation, since particulate matter is more difficult
to oxidize than dissolved organic matter.

Use of hydrogen peroxide-iron salt system does not appear feasible.
Ferrous iron seems to work well, but relatively large concentrations
are required (on the order of 60 to 100 mg/1 as Fe  ).  This system
requires strict pH control (3 to 4) and a neutralization and settling
period to remove the iron precipitate which is formed.  Organic
removal efficiencies are in the 30 to 50% range for dissolved organics
and were reduced to about 14% when  particulate organics were present.
In an attempt to more efficiently utilize the hydrogen peroxide,
other catalysts were evaluated which would not be as restrictive as
ferrous salts.

The literature indicated that hydrogen peroxide is decomposed by
ultra-violet light.  Also Test 7 (Table 1-2) indicated that cobalt
may help catalyze a hydrogen peroxide system.  Therefore, tests were
run with both these catalysts to study any improvements in the
efficiency of hydrogen peroxide oxidation system.  The results of
these tests are shown in Table 1-3.  It is seen that the use of either
or both cobalt and ultra-violet light along with hydrogen peroxide
did not produce consistent results.  From Tests 1 and 2 (Table 1-3)
it is clear that reaction time has an important bearing on COD reduc-
tions in the treatment of storm waters with hydrogen peroxide.  In
Test 1, when a hydrogen peroxide dosage of 110 mg/1 as 02 was utilized,
a 33% reduction in COD was obtained in 15 minutes; the COD reduction
reduced to 19% in 30 minutes and even became negative at the end of
the 90 minute reaction time.  A possible explanation for the increase
in COD in a certain initial reaction time may be the partial oxidation
of large molecular weight organic compounds in the raw storm samples
to smaller intermediate compounds which exhibited an increase in COD.
Increased oxidation at a higher reaction time may then cause a decrease
in COD of these samples, apparently, due to the oxidation of some of
the organic carbon to C02 and F^O.  Similar explanations have been
mentioned in literature for ozone oxidation(18).  When UV light was used
as a catalyst, results were contradictory as shown in Tests 2, 7, 11, 12,
13 and 14 (Table 1-3).  Test 2 showed negative COD reductions for all
reaction times between 15 to 90 minutes while Tests 7 and 11 to 14 showed
COD reduction between 6 to 47% for reaction times of 15 and 30 minutes.
Similar contradictions in results were shown when cobalt was used as a
catalyst either independently or in combination with UV light (Tests 3
to 6, Table 1-3).
                                115

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The results presented in Tables 1-2 and 1-3 clearly indicated that a
Hydrogen Peroxide Reaction System was not technically feasible for treat-
ing combined sewer overflows.  Thus work on such a system was abandoned.
Oxidation with Chlorine

Results of chlorine oxidation with and without ultra-violet light are
presented in Tables 1-4 and 1-5.  Oxidation with chlorine and no ultra-
violet light resulted in a reduction of COD of about 20 to 25% at
available chlorine dosages of 280 to 560 mg/1 (Table 1-4).  The amount
of chlorine destroyed was about 25% and hence a large chlorine residual
remained after the oxidation.  Reducing the chlorine dosage of 56 mg/1,
reduced the percent COD oxidized to only 8% (Test 3, Table 1-4).  These
results indicate that chlorine is not an effective oxidant for combined
sewer overflows.  This conclusion is supported by the literature search.

Oxidation with chlorine and ultra-violet light in the 2800 to 3200 X
range was not significantly different from those oxidations where ultra-
violet light was not used (Table 1-4).  The reason for these low oxida-
tion efficiencies may have been due to the long wave length light which
was used i.e. 2800 to 3200°A or the low ultra-violet output of the lamp
which was used for the reactions.  A review of the research conducted by
Midwest Research Institute (36) indicated that lower wave lengths were
more effective.  Therefore, a lower UV light wave length of 2587 A was
used for further experiments.  This wave length would also provide good
disinfection.  The results of these experiments are shown in Table 1-5.
It should be noted that for light catalyzed oxidations to be effective,
relatively clear solutions were required.  Therefore, the results of
the screening step could have a pronounced influence on the efficiency
of light catalyzed oxidations.

From the results shown in Table 1-5, it is seen that COD reductions
of 10% to 50% can be expected depending upon light intensity, chlorine
dosage and reaction time.  The amount of chlorine required is extremely
large.  Approximately 7 to 10 mg of chlorine is required per mg of COD
oxidized.  Hence, for a 200 mg/1 COD waste, 1400 to 2000 mg/1 of chlorine
would be consumed.  This also results in high chlorine residuals in the
effluent.  With the use of an ultra-violet light catalyst, organic
removal does increase to the 25 to 50% level compared to 10-25% level
without the catalyst, but large chlorine residuals are still present in
the reactor effluent.  This fact, coupled with relatively long reaction
times (30 to 60 minutes) and poor light penetration when the waste is
turbid appear to eliminate the possibility of using light catalyzed
chlorine to oxidize combined sewer overflows.
Oxidation with Combined System of Hydrogen Peroxide and Chlorine

Results of oxidation with the combined system of hydrogen peroxide and
chlorine with and without ultra-violet light catalyst are shown in
Table 1-6.  The results of these tests were extremely discouraging as

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                                             TABLE 1-4
CHLORINE OXIDATION TESTS
Test
No.
I1
2
3
4
5
Chlorine
Concentration
mg/1
280
560
56
276
284
Reaction
Time
Min.
15
15
15
15
15

Raw
65
259
177
198
205
COD mg/1
After
W/UV
211
167
169
151

Oxidation
No Light
51
194
163
164
161
% COD
Reduction
W/UV2 No
	
19
6
15
26

UV
21
25
8
17
21
Chlorine
Remaining
W/UV No UV
	
	
	
160 202
145 216
NOTES:  1.  Sample filtered prior to oxidation
        2.  Ultra-violet wave length 2800 to 3200 A.
        3.  Ca (OC1)2 used as source of chlorine.

-------
                                                  TABLE  1-5
                                      LIGHT  CATALYZED  CHLORINE OXIDATION
00
               Reaction
Date  Type of    Time
1969  Sample     Min.

2/2   Filtered    15
2/2   Filtered    30
2/2   Filtered    60

2/2   Filtered    15
2/2   Filtered    30
2/2   Filtered    60

2/8   Filtered    15
2/8   Filtered    30
2/8   Filtered    60

2/9   Raw         15
2/9   Raw         30
2/9   Raw         60

2/13  Filtered    15
2/13  Filtered    30
2/13  Filtered    60

2/16  Filtered    30
2/16  Filtered    30

2/16  Raw         30
2/16  Raw         30

2/26  Filtered    30
                                     COD mg/1
Influent
105
105
105
105
105
105
71
71
71
147
147
147
97
97
97
108
108
167
167
After
Oxidation
94
86
77
91
89
96
43
44
37
121
111
102
81
77
77
76
60
118
68
COD
Reduction
11
18
27
13
15
9
39
38
48
18
25
31
17
21
21
30
44
29
59
Dosage
mg/1
280
280
280
280
280
280
600
600
600
600
600
600
600
600
600
900
900
900
900
       Percent  Chlorine   Chlorine  U.V.  Light  Chloride  Cl/COD
                          Remaining  Intensity     Cone.    Ratio
                                   93
72
23
300
mg/1

 115
  70
  42

 185
 182
 182

 401
 309
 204

 384
 283
 286

 497
 497
 497

 576
 541

 576
 497

  84
Watts

 2.9
 2.9
 2.9

 0
 0
 0

 2.9
 2.9
 2.9

 2.9
 2.9
 2.9

 0
 0
 0

 2.9
 5.8

 2.9
 5.8

 5.8
                                                                                          r
                                                                                                mg/1
                                                                                                  45
                                                                                                  82
                                                                                                 253
 37

382
502

397
487

352
15
11
 8.5

 6.
 6.1
10.9

 7.1
10.8
11.6

 8.3
 8.8
 7.0

 6.6
 5.7
 5.7

10.
 7.5

 6.6
 4.1

10.3
           NOTES:  1) U.V. Light Wave Length  2587 A -  2.9 watts  intensity  (bulb  output).
                   2) Ratio is mg Cl utilized per mg COD oxidized.

-------
                                              TABLE 1-6
OXIDATION WITH COMBINED
Chlorine 1^02
Test Type Dosage Dosage
No. of Sample nig/1 mg/1 as Op
I Filtered2 no 100

2 Filtered 110 100

3 Filtered no 100



4 Filtered 110 _ 100

SYSTEM OF HYDROGEN PEROXIDE
Reaction
Catalyst Used Time
15
None 30
60
2 15
UV Light 30
60
Instant
15
UV Light 30
45
60
Instant
15
UV Light 30
45
60
AND CHLORINE
COD, mg/1
After1
Influent Oxidation
81
93 95
122
115
93 117
127
80
104
86 108
104
85
82
99
86 106
100
113

% COD
Reduction
13.0
	
—
7.0
	

4.8
	
	
	
NOTES:
        1.  After stripping of the excess oxidant .
        2.  Ultra-violet light wave length 2587 A.

-------
inconsistent and negative reductions in COD were observed.  The importance
of reaction time was again demonstrated (Tests 1 to 4, Table 1-6) in  the
use of the combination of these oxidants for the treatment of storm wastes.
These results were similar to the ones discussed earlier for oxidation by
hydrogen peroxide alone.  A small positive COD reduction was shown when
reaction time was very small (instantaneous sample, Tests 3 and 4,
Table 1-6).  For higher reaction times up to 60 minutes negative COD
reductions were obtained.  Also the use of U.V. light as a catalyst did
not show any improvement in results (Tests 2, 3 and 4 compared to 1,
Table 1-6).  Hence, investigations in this area were terminated.

Oxidation with Ozone

The result of the ozone oxidations are shown in Table 1-7.  Using total
pressurization at 40 psig Tests 1 and 2 show the difference in COD
reductions for raw and filtered storm water samples.  The higher COD
reduction of 46% exhibited for raw waste sample (Test 2, Table 1-7) was
probably due to the flotation of some of the suspended matter as well
as the higher solids content of the raw waste sample.  When a 20% recycle
system was used with the 10 mg/1 dosage of polymer C-31 on raw sample
(Test 4) the COD reduction was extremely high at 96%.  The reason for
such a high reduction was probably the flocculation of the suspended
matter with the C-31 flocculant and the flotation of floe on the surface.
Tests 5 and 6 (Table 1-7) show the effect of reaction time of ozone at
two different operating pressures of 40 and 70 psig.  It was shown that
COD reductions increased from 27 to 52% when the reaction time was
increased from 1 to 20 minutes at 40 psig.  There was no significant
improvement in COD reductions when the operating pressure was increased
to 70 psig.  Therefore, a pressure of 40 psig was utilized for all
future tests.  The ozone dosage utilized for all the tests discussed
above was 40 mg/1.  When a 30 mg/1 ozone dosage was utilized the COD
reduction was 32% (Test 1-7) for a reaction time of five minutes as
compared to 43% COD reduction shown for 40 mg/1 for corresponding
conditions (Test 1-5).  This means that higher ozone dosages result in
improved COD reductions.  When ozone was applied in combination with
other oxidants (such as C12 and E^Q^) or catalysts (such as Co and Ni)
(Tests 8 through 18), no significant improvement in COD reductions
could be obtained in most cases either with dissolved or raw storm water
samples.  However, in one case where ozone was used with both chlorine
and hydrogen peroxide (Test 10), the COD reductions were observed to
be significantly improved at 70%.  However, this efficiency was only  for
the dissolved organic fraction and would be reduced significantly if
particulate organic materials are present.  The use of all three oxidants
at their respective dosages (Test 10, Table 1-7) would result in extremely
high(>$l.00/1000 gal) operating costs.

Two benefits which are possible when using a pressure tank system are
the possibility of floating some of the lighter organic solids, and the
probability that the heavier grit particles will settle.  These benefits
can greatly increase the removal efficiencies of the treatment system.
From the results shown in Table 1-7, ozone appears to be the best oxidant
among the ones evaluated in this study because it:
                                 120

-------
                                             TABLE 1-7
SUMMARY 03 OXIDATION TESTS







Reaction
Test
No.
1
2
3
4
5
5
5
5
6
6
6
6
7
8
9
10
11
12
13
14
15
16
17
18
Type
Sample
Filtered
Raw
Filtered
Raw
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Filtered
Raw
Raw
Raw
Raw
Raw
Raw
Time
Miri.
3
3
3
3
1
5
10
20
1
5
10
20
5
5
5
5
8
8
8
8
8
8
8
8

Raw
74
1680
73
1680
69
69
69
69
69
69
69
69
69
69
69
69
84
84
189
189
189
189
189
189
After
Oxidation
55
959
49
61
50
43
40
33
51
42
36
31
46
46
- 45
21
61
62
92
154
114
120
1414
116
% COD
Removed
26
43
33
96
27
38
42
52
26
39
48
55
32
33
35
70
27
26
51
19
40
37
25
39
Type
Recycle
Total
Total
Total
20%
Total
Total
Total
Total
Total
Total
Total
Total
Total
Total
Total
Total
Total
Total
Total
20%
Total
Total
20%
Total
°3
Dissolving
Pressure
psig
40
40
40
40
40
40
40
40
70
70
70
70
40
40
40
40
40
40
40
40
40
40
40
40

Approx .
03 Dosage
mg/1
40
—
40
—
40
40
40
40
—
—
—
—
30
30
30
30
30
30
—
10
. —
36
8
67
                                                                                 	Remarks	

                                                                                 Excess 03
                                                                                 No Excess 03
                                                                                 Excess 03
                                                                                 10 mg/1 C-31
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 Excess 03
                                                                                 50 mg/1 H202
                                                                                 50 mg/1 Cl
                                                                                 50 mg/1 Cl and H202

                                                                                 5  mg/1 Co added
                                                                                 25 mg/1 H202 and Cl
                                                                                 Actual measurement

                                                                                 3 mg/1 Ni added actual
NOTE:  Samples collected fall of 1967 and frozen for subsequent  use.

-------
     1.   Provides the best oxidation
     2.   Requires reasonable reaction time
     3.   Can be used in a pressure system allowing effective introduction
         of ozone

It should be noted that all the tests shown in Table 1-7 were obtained
with overflow samples which had earlier been collected and frozen.
Therefore, it was not possible to run disinfection tests because of the
adverse effect that freezing has on the coliform organisms.  Hence,
further experiments were planned to study disinfection efficiency and
BOD and COD removals using ozone treatment and fresh overflows.

The results of these experiments are shown in Tables 1-8 and 1-9.  A
recycle system was utilized and a value of 10% recycle was used to keep
the ozone dosage in 10 to 40 mg/1 range on all overflows except the
April 3 overflow (Tables 1-8 and 1-9).  Since some flotation and/or
sedimentation occurs, air flotation tests were run as a control to
determine how much removal was due to oxidation and how much to
sedimentation and/or flotation.

Comparing the suspended solids removals (Table 1-8) indicates little
difference between ozone treatment and air flotation.  This points out
that little if any particulate matter is oxidized.  These results are
consistent with the oxidation results obtained with the frozen overflows.
The BOD removal was generally better with the ozone treatment compared
to air flotation (Table 1-8).  The COD removals, however, followed the
opposite trend.  Overall removal rates with screening and ozone treatment
or flotation are in the range of 50 to 80% for the first flushes and
45-65% for the normal overflows providing means are available to remove
settled and floated solids.

The amount of disinfection obtained with ozone and chlorine is shown in
Table 1-9.  At relatively high ozone dosages good disinfection is obtained.
When the dosage is dropped below 10 mg/1 disinfection becomes very poor.
Chlorine, however, will give good disinfection at a 10 mg/1 dosage
over a wide range of coliform concentrations.  These results indicate
that ozone may not be satisfactory for disinfection because of its high
costs and nonattainment of residual ozone for a sufficient period.
Oxidation With Gamma Radiation

Use of gamma radiation for oxidizing organics was indicated in the
literature (38)(39).  Tests were run on gamma irradiation of combined
overflow using a cobalt source.  The results of preliminary tests on
these were discouraging and investigations into this area were terminated.
                                 122

-------
                                                   TABLE 1-8
to
LO
SUMMARY 03 OXIDATION AND AIR FLOTATION
Date
4/3
4/3
4/17
4/20
4/23
4/28
4/28
Type
FF
EO
EO
EO
EO
FF
EO
SS
After
Screening
707
183
207
67
122
331
177
SS
After
Oxidation
279
114
106
48
86
102
109
SS
After
Air Flo-
tation
	
	
73
55
65 "
65
61
BOD
After
Screening
148
33
33
13
21
92
58
BOD
After
Oxidation
85
12
17
10
20
36
27-
TESTS
BOD
After
Air Flo-
tation
	
	
21
10
12
42
27
COD.
After
Screening
559
121
134
51
99
331
199
COD
After
Oxidation
	
	
79
36
83
159
143
COD
Air Flo-
tation
	
	
69
44
64
119
93
       NOTES:  FF - First Flush
               EO - Extended Overflow
               all values in mg/1

-------
Date

 4/3

 4/3

 4/17

 4/20

 4/23

 4/28

 4/28
                             TABLE 1-9
           SUMMARY DISINFECTION DATA - ALL SPRING STORMS

Type
FF
EO
EO
EO
EO
FF
EO

E. Coli
per ml
1388
421
1280
1850
6000
32000
26000

°3
Dosage
mg/1
80
59
40
•v30
<10
<10
<10
E. Coli
in
Effluent
per ml
21
4
74
17
3200
9500
13700

Cl
Dosage
mg/1
—
—
10
10
10
10
10
 E. Coli
   in
Effluent
 per ml
   0.5

   1

   2

  20

   8
 NOTES:  FF - First Flush
         EO - Extended Overflow
                                 124

-------
                     SUMMARY AND CONCLUSIONS

Table 1-10 presents a summary of the various oxidants and oxidation
systems utilized.  Hydrogen peroxide, chlorine, and ozone were evaluated
both alone and in combination.  Various catalysts were also utilized
including ferrous iron, nickle and cobalt.  The best system was a
mixture of all three oxidants, which provided up to 70% oxidation of the
dissolved   fraction of a combined sewer overflow.  Any single oxidant
did not produce greater than 50% oxidation of the dissolved fraction.
When screened overflow was utilized, the highest oxidation percentage
was 40%, hence particulate matter was oxidized only to a very limited
extent.  This indicates that an efficient solids/liquid separation system
must be utilized prior to chemical oxidation.  Even if this is done a
removal efficiency of only about 40% in the chemical oxidation stage
could be economically realized.  Therefore chemical oxidation of combined
sewer overflows cannot be justified.

The following conclusions can be made based on the chemical oxidation
studies performed.

     1.  Chemical oxidation of combined sewer overflow is not technically
         feasible.

     2.  Ozone was the best oxidant evaluated in this study.

     3.  Oxidation with chlorine requires extremely high concentrations
         of chlorine and results in a high chlorine residual in the
         effluent.

     4.  Particulate matter is extremely difficult to oxidize.

     5.  A combination of oxidants can provide increased oxidation of
         organic material.
                                 125

-------
                 TABLE 1-10
SUMMARY OF OXIDATION OF COMBINED OVERFLOWS
WITH VARIOUS OXIDANTS AND COMBINATIONS
Residual
Line No
1
2
3
4
5
6
7
8
9
10
11
Required
. Oxidant Concentration
mg/mg(l)
H202
H2°2
Cl
Cl
Cl
Cl
°3
°3
H202
Cl &
°3
03
H202 &
Cl
3-5
5-10
17-20
30
17
17
1.2(2)
1.2(2)
1.0
1.0
0.6
1.1
30(3)
Contact Catalyst Oxidant
Times Used Remaining
(min) mg/1
15
15
15-60
15-60
15
15-30
5
5
5
8
60
Fe44"
Fe^
None
None
UV light
UV light
None
None
None
small
Large
180
500
400
300
Trace
None
Small
3 mg/1 Ni small
None
Large
Type of COD
Organics Removal
%
Dissolved
w/solids
Dissolved
Dissolved
Dissolved
w/solids
Dissolved
w/solids
Dissolved
w/solids
Dissolved
Dissolved
30-50
14
10-15
20
40
25-30
40
30-40
50-70
40
40
7-10
Other Limiting Criteria
Requires pH in 3-4 range
and removal of iron floe
formed during reaction.

Requires extremely high
chlorine dosages and
hence a dechlorinations
step would be required

03 equipment requires
extremely high capital
equipment costs at
these dosages


(1)   Milligrams oxidant per rag COD oxidized to obtain stated efficiencies
(2)   03 dosages are approximate
(3)   Equal amounts of Cl and

-------
BIBLIOGRAPHY - APPENDIX I, CHEMICAL OXIDATION

 1.  Fair, G. and Geyer, J., Water Supply and Waste Disposal, John Wiley
     and Sons, Inc., New York, 1961.

 2.  Eckenfelder, R.B. and O'Connor, D., Biological Waste Treatment,
     Pergamon Press, 1961.

 3.  Laboon, J.F., Sewage Works Journal 7:9:911 (1935).

 4.  Bolenius, R.M., Sexjage and Industrial Wastes 22:3:365 (1950).

 5.  Mills, E.V., et al._, The Surveyor 104:79 (1945).

 6.  Summary Report, Advanced Waste Treatment Research, U.S.  Department
     of Health, Education and Welfare, Public Health Service Publication
     No. 999-WP-24, o 69, 1965.

 7.  Eisenhauer, H.R., "The Chemical Removal of Aklylbenzenesulfonates
     from Wastewater Effluents", Presented before the Division of Water
     and Waste Chemistry, American Chemical Society, Los Angeles,
     California, 1963.

 8.  Busch, A.W., et al^, API Project for Research on Refinery Wastes
     (NonbiologicaT~Treatment) Progress Report No. 2, Rice University,
     p 11, 1963.

 9.  Davidson, C.A. and Busch, A.W., "Catalyzed Chemical Oxidation of
     Phenol in Aqueous Solution", Presented at 31st Midyear Meeting of
     API Division of Refining, Houston, Texas, 1966.

10.  Eisenhauer, H.R., WPCF Journal. 36:9:1116 (1964).

11.  Bishop, D.F., et al., "Hydrogen Peroxide Catalytic Oxidation of
     Refractory Organics  in Municipal Wastewaters", Presented at the 148th
     National Meeting of  the American Chemical Society, September 2,  1964.

12.  Busch, A.W., et al., API Project for Research on Refinery Wastes,
     Progress Report No.  3, Rice University, June 22, 1964.

13.  Connell, G.F., "Application of Ozone", Refrigeration Service Engineers
     Society, Chicago, Illinois, 1966.

14.  O'Donovan, D.C., Journal AWWA 57:9:1167  (1965).

15.  Marsh, G.R. and Panula, G.H., Water and Sewage Works 112:10:372  (1965),

16.  U.S. Patent No. 3,276,994, issued to C.W. Andrews.

17-  Sease, W.S. and Connell, G.F., Plant Engineering 20:11:486  (1966).
                                127

-------
18.  Evans, F.L.  and Ryckman, D.W.,  "Ozonated Treatment of Wastes
     Containing ABS", Proceedings 18th Industrial Waste Conference,
     Purdue University, p 141, 1963.

19.  Buecher, C.A.  and Ryckman, D.W.,  "Reduction of Foaming of ABS bv
     Ozonation",  Proceedings 18th Industrial Waste Conference. Purdue
     University,  p.  141, 1963.

20.  Tyler R.G.,_et_ai. , Sewage and  Industrial Wastes 23:9:1151 (1951).

21.  Miller, F.K.,  Water and Wastes  Engineering 3:12:52 (1966).

22.  Moeller, T., Inorganic Chemistry, John Wiley and Sons, Inc.,
     New York, p 485, 1957.

23.  "Welsback Ozone Equipment", Bulletin 109, September 1966.

24.  Schevchenko, E.T., "Tests of a  Semi-Industrial Apparatus for
     Ozonization for Dnieper Water",  Chemical Abstracts, Volume 65,
     5220, 1966,  Ozonirov.  Vody i Vybor Rajs, 1965, (Russian).

25.  Campbell, R.M., Journal of the  Institute of Water Engineers,
     17:333  (1963).

26.  Green, D.E.  and Stumpf, P.K., Journal AWWA 38:11:1301 (1946).

27.  Snow, W.B.,  Sewage and Industrial Wasjtes 24:6:689 (1952).

28.  Griffin, A.E.,  and Chamberlin,  N.S., Sewage Works Journal 17:4:730
     (1945).

29.  Private Communication, Mr. Carl Brunner, Taft Sanitarv Engineering
     Center, Cincinnati, Ohio, November 14, 1967.

30.  Spiker, R.G. and Skrinde, R.T.,  Journal AWWA. 57:4:472 (1965).

31.  Burtle, J. and  Buswell, A.M., Sewage Works Journal 7:9:839 (1935).

32.  Vosloo, P.B.,  Sewage Works Journal 20:1:171 (1948).

33.  Gould, E.S., Inorganic Reactions  and Structure, Henry Holt and
     Company, New York, 1956.

34.  Miller, H.C. and Knipe, W. , Report AWTR-U. U.S. Department of
     Health, Education and Welfare,  Public Health Service, 1965.

35.  American Public Health Association, Standard Methods for the
     Examination of  Water and Waste  Water - 12th Edition, APHA,
     New York, 1964.
                                128

-------
36.   Meiners,.A.F.,  et al.,  "An Investigation of Light Catalyzed
     Chlorine Oxidation for Treatment of Waste Water", Advanced
     Waste Treatment Research Laboratory, FW_QA,Report ffTWRC-3.

37.   Sawyer, C.M.,  Chemistry for Sanitary Engineers,  McGraw-Hill
     Publishing Comapny p 287, 1960.

38.   Touhell, C.J.,  et. al._, WPCF Journal 41:2LR44 (1969).

39.   Ballantine, L.A. , et al._, "The Practicality of Using Atomic
     "Radiation for Wastewater Treatment", WPCF Journal 41:3:447
     (March, 1969).
                                129

-------
     APPENDIX II




ANALYTICAL PROCEDURES
      131

-------
                  Analytical Instruments and Apparatus
pH Meter:  Beckman Model H-2
           Beckman Instruments Incorporated
           Fullerton, California

Incubator:  Model 1483
            Precision Scientific Company
            Chicago, Illinois

Conductivity Bridge:  Model RC16B2
                      Industrial Instruments Incorporated
                      Cedar Grove, New Jersey

BOD Incubator:  Labline No. 3554B Incubator
                Lab-Line Instruments, Incorporated
                Melrose Park, Illinois

Analytical Balance:  Type H5
                     Mettler Instruments Corporation
                     Hightstorm, New Jersey

Ozone Cylinder:  Vaporizing Coil and Regulator
                 Matheson Company, Inc.
                 East Rutherford, New Jersey

Spectrophotometer:  Coleman Model 14
                    Coleman Instrument Company
                    Maywood, Illinois
                                 132

-------
                   Analytical Procedures and Analyses


The following analyses were performed according to "Standard Methods
for the Examination of Water and Wastewater,"  (35)
The page numbers of the analytical procedures used and the modifications
to the listed procedures are noted:

     Total Solids - Method A, p. 423.  The amount of sample used
                was determined by weight rather than by volume;
                approximately 20 grams of sample was used for
                total solids.

     Suspended Solids - Method C, p. 424.  Reeve-Angel 934AH glass
                fiber discs were used in place of the mats prepared
                by using asbestos fibers.

     Chemical Oxygen Demand (COD) - p. 510.  The standard procedure
                was used for the analysis of the raw combined over-
                flow.  The alternate procedure for dilute samples
                (p. 513) was used to analyze the raw soluble and
                oxidized samples.

     Biochemical Oxygen (BOD) - p. 415.  The BOD tests were performed
                within several hours after collection.  Samples from
                laboratory oxidation tests were seeded.  The raw
                storm water was used as seed, with a volume of 1 ml
                of seed.  The azide modification of the iodometric
                method (Method A, p. 406) was used for the analysis
                of the dissolved oxygen content.

     Chloride - Method A, p. 86.    A 0.423N standard silver
                nitrate titrant was used instead of 0.0141N because
                of high chloride content in raw storm t^O, thus
                giving a more definite endpoint.

     Chlorine, Total Available - Method A, p. 91.

     Ozone Concentration - Method A, p. 220.  The titration procedure
                stated was followed, but the sample collection and
                ozone absorption techniques are those as specified
                by the Matheson Company (Matheson Gas Data Book).

     Nitrogen (Total Kjeldahl) - p. 44.

     Phosphates (ortho) - Method A, page 231.  Phosphate analyses
                were performed after removal of suspended solids
                by filtration.
                               133

-------
     pH - p. 226.   A Beckman Model H-2 meter was used.

The following analyses were performed according to the procedures
listed:

     Hydrogen peroxide - This was determined by the iodometric
                procedure described in Table 3-31 in Handbook of
                Analytical Chemistry, Edited bv Louis Meites,
                McGraw-Hill Book Company, New York, 1963, p, 3-69.
                                                           •» 'k .
     Coliform Bacteria Count - The millipore filter technique
                described in "Techniques for Microbiological Analysis,
                (ADM-40)", (Millipore Filter Corporation, Bedford,
                Mass., p. 22) was used.  Where necessary samples were
                dechlorinated using Na^SO.,.  (35)

     Conductivity - Measurements were made at 25°C using a conductivity
                cell having a cell constant of 2 cm  .  Measurements
                were made with a Model RC16B2 Conductivity Bridge
                made by Industrial Instruments, Inc. according to
                the procedure described by the manufacturer.
Analysis for Dissolved Matter

The analysis for dissolved matter(i.e.COD,  BOD,  TOG)  was obtained by
filtering the sample through a millipore filter  (O.A7)  and then per-
forming the appropriate analysis' (COD,  BOD,  TOC) on the filtrate.  If
the sample contained gross amounts  of solids which would rapidly blind
the millipore filter disc, the sample was r>refiltered through SS-597
filter paper.  The filtrate from this prefiItration was then filtered
through the millipore disc as described above.
                               134

-------
                 Dissolved-Air Flotation Test Procedure
A copy of the instructions for performing dissolved-air flotation
tests is attached.  This sheet described the test as normally used in
the REX Chainbelt Process Laboratory.  This procedure was modified at
times during the chemical oxidation tests by using different detention
times and by using ozone instead of normal air as the source of bubbles.

The rate of separation of the suspended solids from a waste is useful
in the design of industrial waste treatment equipment.  Rate of separation
data may be conveniently obtained in the laboratory from treatment tests
performed on the waste in question.  The treatment processes which will
be considered are dissolved-air flotation and sedimentation.  Generally,
the procedure used in obtaining rate-of-separation data is to observe
the solids-liquid interface and to reqord its travel with time.

     A.  Dissolved-Air Flotation
         In the tests using dissolved-air flotation, the rate of rise of
         the major portion of the solids is recorded.  At times the solids-
         liquid interface may be vague and good judgment may have to be
         exercised in following this interface.  Care should be taken
         to avoid following the interface formed ,by the air bubbles alone.
         In general, this interface lags behind the solids-liquid interface.

         A suggested procedure for the performance of laboratory flotation
         tests and the equipment needed is as follows:

         1.  Equipment
             a.  Flotation pressure cell
             b.  Graduated cylinder of one liter capacity containing
                 an effluent sampling arm
             c.  Tire pump or source of compressed air
             d.  Gooch crucibles for suspended solids determinations
             e.  Stop watch

         2.  Flotation Test Procedure
             a.  Record waste temperature, pH, operating pressure,
                 recycle rate, and flotation detention time
             b.  Record rate of separation data.  The form shown below is
                 suggested in obtaining the rate of separation data.

The ultimate data desired is the position of the interface at various?
intervals throughout the test.  The column below labeled "Volume" is
used as a convenient means of obtaining the position of the interface
at any given time.  For example, in the hypothetical case shown below, a
liter graduate was used in the test.  At the beginning of the test, the
solids-liquid interface is at the bottom of the graduate or at zero volume.
                                135

-------
As flotation progresses, the solids-liquid interface moves progressively
up the height of the graduate.   The position of the interface at any
given time may be conveniently obtained using the appropriate graduation
mark on the liter cylinder as a reference.  After the flotation test,
the graduation marks may be converted to the feed of height by actual
measurement.
            Time       Volume     POI (Position of Interface)
            (min)       (ml)      	(feet)	

              00                     0
              1         100                 0.115
              2         350                 0.411
              3         500                 0.589
              4         650                 0.766
              5         800                 0.946
              6         950                 1.122
              7         950                 1.122
              8         950                 1.122
The data obtained are plotted using Time as the abscissa and POI in feet
as the ordinate.
             POI
             (ft)
                    TIME (minutes)
                 The slope of the straight line portion of the curve
                 represents the rate of particle rise.

                 During flotation it should be noted whether settling
                 of solids took place.   Note observation.

             c.   Record the floated scum volume obtained immediately
                 before obtaining a sample of the effluent.

             d.   Obtain sample of effluent five minutes after flotation
                 is started for the appropriate analyses.   Repeat the
                 flotation and obtain another sample of effluent
                 for analysis after an eight minute detention period.
                                136

-------
If possible, a small portion of the floated scum
should be analyzed for total solids content.
               137

-------
       APPENDIX III
DEMONSTRATION SYSTEM COSTS
         139

-------
The following is a breakdown of the equipment and construction costs
incurred for completion of the demonstration facility.
RAW FLOW SYSTEM
             Primer System
             Pipe Fittings
                  Flanges
                  Elbows
                  Check Valve
                  Ballcentric  Valve
             Raw Feed Pump
PRESSURIZED FLOW SYSTEM
             Pressurized Flow Pump
             Air Compressor
             Pipe Fittings
                  Elbows
                  Flanges
                  Check Valve
                  8" Ballcentric  Valve
             Pressure Tank
             Grinnell Pressure Release Valve
             Air Control System, Complete
BACKWASH SYSTEM
             Nozzles
             Valve
             Backwash Pump
             Elbows
DRUM SCREEN ACCESSORIES

             Backing Plates
             Screen Mesh
             Drive Unit
             Chain, Sprockets
$1092
  125
  178
  250
  194
  236
 3482

$5557
$1080
  550

   70
  132
   93
  170
  945
  295
  950

$4285
                                                         $ 372
                                                         $1574
                                 140

-------
SKIMMER ASSEMBLY

             Drive Unit                                  $1300
             Chains & Flights, Sprockets                  1400

                                                         $2700

CHEMICAL SYSTEM

             Pump
             Tanks
             Mixer
             Hoses & Fittings

                                                         $1884

ELECTRICAL SYSTEM

             Float Switches                              $ 140
             Panel, Complete Prewired                     1710

                                                         $1850

FLOW METERS

             Raw Feed Venturi
             Raw Flow Meter  (Recorder)
             Pressurized Flow Venturi
             Pressurized Flow Meter
             Backwash Venturi
             Backwash Meter  (Recorder)
             Scum Recorder

                                                         $3462

PIPE FOR EFFLUENT AND SCUM

              6" Flanges                                 $ 115
              6" Elbows                                     60
             12" Flanges                                   125
             12" Elbows                                  	45

                                                         $ 345

MISCELLANEOUS

             Tank Fabrication                          $13,418
             Tank Erection                              20,225
             Tank Steel                                  4,830

                                                       $38,473
                                141

-------
MISCELLANEOUS (Continued)
             Electrical Power                          $   930
             Electrical Wiring Labor & Material          2,307

                                                       $ 3,237

             Piping Labor                              $ 5,862
             Manhole                                     2,015

                                                       $ 7,877

             Foundation                                $ 4,150

             Building                                  $   696

             Catwalks & Steps                          $1,400

             GRAND TOTAL                               $77,862

             Engineering                               $12,100
                               142

-------
        APPENDIX IV







      OPERATING DATA




AND STATISTICAL PROCEDURES
            143

-------
      TABLE IV-1
OPERATIONAL DATA - 1969

Run
No.
691
692
693
694
695
696
697
698
699
6910
6911
6912
6913
6914
6915
6916
6917
6918
6919
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930


Date
6/4/69
6/4/69
6/7/69
6/7/69
6/22/69
6/25/69
6/26/69
6/27/69
6/29/69
7/2/69
7/11/69
7/16/69
7/17/69
7/23/69
7/26/69
8/7/69
8/9/69
8/11/69
9/4/69
9/5/69
9/6/69
9/23/69
9/29/69
9/29/69
10/10/69
10/10/69
10/12/69
10/31/69
11/2/69
11/3/69

Duration
(min)
123
70
103
30
75
110
150
105
50
180
75
35
60
75
40
50
150
65
35
90
60
65
180
47
65
243
75
55
45
110
Raw
Waste
(sal)
378000
189000
302400
88200
201600
340200
441000
277200
151200
554400
226800
100800
163800
226800
100800
138600
395640
190680
100800
277200
176400
201600
453600
143640
176400
705600
226800
163800
113400
327600
Screen
Wash
(gal)
0
0
1600
800
2000
<600
600
600
<600
<600
800
3200
1200
5200
<600
4800
3600
<600
1200
600
<600
600
600
<600
<600
8400
1200
2400
1800
1800
Floated
Scum
(gal)
6200
3450
3400
900
1900
3500
6250
6700
850
4400
2100
400
700
1200
450
200
1700
460
450
1850
540
700
2200
310
3850
1700
750
600
250
1150
Overflow
Rate
gpm/sq ft
2.63
2.31
2.51
2.51
2.30
2.64
2.51
2.26
2.58
2.63
2.58
2.46
2.33
2.58
2.15
2.37
2.25
2.51
2.46
2.63
2.51
2.65
2.15
2.61
2.32
2.48
2.58
2.55
1.76
2.55
           144

-------
                     TABLE IV-1 (Continued)

                     OPERATIONAL DATA - 1969
 Run
 No.     Inches

 691      0.42
 692      0.17
 693      0.20
 694      0.10
 695      0.25
 696      0.50
 697      1.75
 698      0.50
 699      1.00
6910      1.50
6911      0.27
6912      0.12
6913      0.45
6914      0.17
6915      0.40
6916      0.10
6917      0.30
6918      0.45
6919      0.10
6920      0.05
6921      0.20
6922      0.14
6923
6924      0.70
6925      0.17
6926
6927      0.40
6928      0.12
6929      0.10
6930      0.50
Chemical

Inches
Hour
0.13
0.68
0.15
0.10
0.32
0.50
1.17
0.40
0.70
2.30
0.40
1.50
0.45
0.35
0.35
0.40
0.10
1.60
1.20
2.10
1.20
0.30


0.15

0.15
0.10

0.30
Operating
Pressure
scfm
50
40
50
50
50
50
50
50
60
60
60
55
50
60
60
60
60
60
60
60
50
50
50
50
50
60
50
50
50
50
Pressurized
Flow Rate
gpm
600
650
850
850
900
900
900
600
700
700
475
600
900
400
400
450
600
450
800
650
500
500
500
500
800
400
550
550
550
550
Addition
C-31
mg/1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5
0
3
3
3
3
3
5
0
0
3
0
2.5
2.5
5
Cl
mg/1
0
0
0
0
10
0
10
8
10
10
10
10
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
                               145

-------
TABLE IV-1 (Continued)




OPERATIONAL DATA - 1970

Run
No.
701
703
704
705
706
707
708
709
7010
7011
7012
7013
7014
7015
7016
7017
7018
7019
7020
7021
7022
7023
7024
7025


Date
4/13/70
4/9/60
5/11/70
5/12/70
5/15/70
5/22/70
5/31/70
6/1/70
6/12/70
6/26/70
6/26/70
7/8/70
7/14/70
7/15/70
7/19/70
7/27/70
7/31/70
8/18/70
9/2/70
9/3/70
10/23/70
10/26/70
10/27/70
10/31/70

Duration
Min.
90.7
47.6
49.7
138.6
52.3
73.7
90.1
90
44.1
75.1
68
49.5
40
49.8
97.2
66.6
34.1
36.4
51.8
95.6
38
64.5
149.1
95
Raw
Waste
Gal.
252000
126000
119700
286020
117180
153720
186480
178920
95760
142380
143640
131040
133560
118440
217980
147420
75600
10200
152700
229320
118440
153720
322560
241920
Screen
Wash
Gal.
1200
4800
360
60
0
1380
3960
420
120
3300
460
2820
1080
480
60
0
240
1740
0
0
2160
0
60
4260
Floated
Scum
Gal.
1050
500
300
500
250
350
1000
2050
1300
1900
1700
1000
1000
500
1600
1050
150
100
600
1150
200
500
750
600
Overflow
gpm/sq
High
4.75
4.52
4.16
3.53
3.83
3.56
3.54
3.40
3.71
3.24
3.61
4.52
5.71
4.06
3.83
3.79
3.79
4.79
5.08
4.10
5.33
4.07
3.75
4.35
Rate
ft
Low
3.56
3.39
3.09
2.65
2.87
2.67
2.65
2.55
2.78
2.43
2.71
3.39
4.28
3.05
2.88
2.84
2.84
3.59
3.81
3.08
4.00
3.06
2.81
3.27
           146

-------
             TABLE  IV-1  (Continued)




            OPERATIONAL  DATA -  1970

Run
No.
701
703
704
705
706
707
708
709
7010
7011
7012
7013
7014
7015
7016
7017
7018
7019
7020
7021
7022
7023
7024
7025


Rain
inches
0.7
0.3
0.07
0.57
0.25
0.28
0.14
0.5
0.33
0.25
0.10
0.20
0.22
0.10
0.25
0.30
0.45
0.23
0.25
0.35
0.15
0.70
0.40
0.32
in/hr

0.17
0.09
0.23
0.33
0.36
0.84
1.11
0.11
0.17
0.09
0.80
0.18
0.13
0.13
0.36
2.25
0.15
0.24
0.18
0.10
0.35
0.10
—
Operating
Pressure
psig
50
50
50
50
50
50
50
50
50
50
60
50
55
50
50
50
50
50
50
50
50
50
50
50
Pressurized Chemical Addition
Flow Rate
gpm
800
600
900
900
900
450
450
550
550
450
350
600
950
450
450
450
450
550
550
550
600
600
600
600

C-31
0
0
6
6
6
6
6
4.2
4.6
5.3
3.9
4.6
3.5
4.5
4.5
4.5
4.5
3.8
3.8
3.8
0.5*
0.5*
0.5*
4
(mg/1)
FeCl3
0
0
0
0
0
0
0
30
29
17
16
16
21
21
21
21
21
17.5
17.5
17.5
15
15
25
25

Cl
10
10
10
10
10
10
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
''Herco Floe 810 used for these runs.
                     147

-------
                                                    TABLE  IV-2
        Run
        No.
      COD   BOD
00
691   676
695   615
6911  920
6912  472
6914  574
6916  531
6919  642
702   617
708   512
7011  390
7013  649
7022  372
172
180
180

180
 89
170
224
160
212
330
145
RAW WASTE CHARACTERISTICS -

Suspended
Solids
642
538
1180
496
554
405
312
582
431
232
479
415
Volatile
Suspended
Solids
391
310
678
253
322
310
244
228
247
156
289
273

Total
Nitrogen
21.3
18.0
—
—
20.7
18.6
23.3
18.9
13.3
8.8
13.9
19.5


pH
7.20
7.08
6.80
7.2
6.7
6.9
7.0
6.90
7.1
7.1
7.0
7.35
FIRST F.

Total
Solids
815
798
1322
779
833
677
869
913
746
732
984
—
                                                       Total     Ortho
                                                      Volatile  Phosphate
                                                       Solids    as PC
431
480
780
300
488
443
536
494
387
433
604
                                                                                     3.92
                                                                                     2.47

                                                                                     4.24
2,
2,
5,
2.
 .88
 .24
 .96
 .00
2.15
0.68
1.06
2.46
                    Coliform
                     per ml
 62,000
110,000
 41,000
 65,000
 16,000
150,000
310,000
600,000
110,000
 16,650
  4,400
220,000
            NOTE:  All values  in mg/1  except  pH.

-------
                                            TABLE IV-3
Run
No.

 691
 692
 693
 694
 695
 696
 697
 698
 699
6910
6911
6913
6915
6917
6918
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
COD

108
220
241
173
207
 87
 66
 47
 59
 78
188
223
118
185
137
127
114
248
163
125
118
 95
 94
334
195
217
BOD

 38
 43
 65
 17
  7
  7

 12
 49
 37
 31
 25

 61
 31
 39
 29
 36
 124
 70
 65
NOTE:
Suspended
 Solids

   112
   365
   169
   158
   168
    88
   192
    57
   148
   208
   276
   176
   116
   104
   192
   114
   102
   165
   104
   129
    70
   141
    56
   180
    87
    87
All values
LARACTERISTICS - EXTENDED 0
Volatile
Suspended
Solids
58
145
117
80
102
46
55
29
43
66
105
120
62
78
82
62
64
117
68
66
22
65
45
138
63
66

Total
Nitrogen
4.1
8.1
—
—
6.4
2.3
2.0
1.4
—
3.1
—
—
—
7.6
4.8
4.3
4.6
8.1
8.4
3.8
8.8
3.3
—
10.2
9.1
7.0


jpH
7.10
6.80
7.60
7.60
7.10
6.80
7.20
7.45
7.00
7.10
6.40
7.45
7.30
7.10
7.00
6.85
6.80
7.20
7.18
7.18
7.60
7.10
7.20
6.90
7.30
7.40
         Total
Total   Volatile    Ortho
Solids   Solids   Phosphate
 244
 502
 560
 312
 302
 188
 157
 170
 208
 280
 384
 541
 197
 445
 278
 247
 226
 478
 279
 218
 478
 199
 269
 450
 457
 390
121
215
302
168
176
102
 90
 86
 70
102
162
250
118
222
170
160
108
296
152
105
225
 82
128
272
244
224
1.18
1.76
0.88
0.60
0.30
0.37

0.36

0.52
0.24
3.26
0.50
0.30
0.78
1.00
1.20
0.91
1.24
0.36
0.72
2.12
1.88
2.26
Coliform
 per ml

  9,500
 39,000
 36,000
  5,700
  1,300
  7,800
  6,200
 19,000
 20,000
 38,000
  1,300

  1,500
160,000
 55,000
 82,000
  1,400
    330
 55,000
 12,000
 78,000
200,000
180,000
110,000
                               in mg/1 except pH.

-------
                                      TABLE IV-3  (Continued)
Run
No.

 701
 703
 704
 705
 706
 707
 709
7012
7014
7015
7016
7018
7019
7020
7021
7023
7024
7025
COD

143
206
141
199
140
211
168
177
191
162
130
244
286
153
 90
169
178
139
BOD

 36
 91
 58
 35
 28
101
 37
 67
113
 53
 25
 67
 54
 66
RAW WASTE CHARACTERISTICS - EXTENDED OVERFLOWS

Suspended
Solids
151
218
109
316
149
228
148
119
232
140
135
337
264
466
118
107
171
123
Volatile
Suspended
Solids
75
88
39
193
75
146
86
81
139
85
95
183
164
204
63
73
125
103

Total
Nitrogen
2.9
7.4
5.4
6.3
3.7
7.5
4.4
6.3
5.55
4.9
—
—
6.95
3.4
2.4
8.7
4.9
6.4


PH
7.45
7.1
7.4
6.8
7.7
6.9
7.35
7.2
7.2
6.9
7.1
7.1
7.4
7.15
7.05
7.7
7.1
7.4

Total
Solids
295
412
676
511
466
533
343
577
441
415
304
566
574
673
266
—
—
—
- 1970 DATA
Total
Volatile
Solids
112
200
267
203
246
298
160
291
220
177
145
246
250
304
116
—
—
—
Ortho
Phosphate
as P04
0.83
1.34
1.08
1.1
0.5
1.17
0.92
0.96
0.06
.0.47
0.71
—
2.28
0.74
0.77
2.73
0.74
1.78

Colif orm
per ml
— —
270,000
12,200
—
700
340,000
73,000
12,000
35,500
118,800
7,660
—
3,800
160,000
4,800
55,000
26,000
117,000
     NOTE:  All values in mg/1 except pH.

-------
                                             TABLE IV-4
                              SCREENED WATER QUALITY - FIRST FLUSHES
Run
No.

 695
6912
6914
6916
6919
 702
 708
7011
7013
7022
COD

168
449
281
432
510
321
306
254
611
262
BOD

 51

120
 71
169
133
 93
141
295
113
Suspended
 Solids

   170
   424
   260
   290
   286
   306
   272
   180
   418
   331
Volatile
Suspended
 Solids

    91
   234
   150
   290
   236
   126
   128
   106
   231
   173


£l
7.75
7.0
7.0
6.9
6.8
7.30
7.3
6.8
6.8
7.4

Total
Solids
833
725
536
290
848
716
623
665
906
—
Total
Volatile
Solids
372
300
302
369
520
303
293
394
552
—
      NOTE:  All values in mg/1 except pH.

-------
                                      TABLE IV-5
Run
No.
693
694
695
696
697
698
699
6910
6911
6913
6915
6917
6918
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930

COD
132
165
159
49
26
51
49
60
144
163
89
141
103
76
91
184
138
105
122
73
78
260
171
200

BOD
_—
—
50
15
7
5
—
9
37
—
—
—
31
21
—
—
54
27
41
20
28
90
59
60
'ER QUALITY -

Suspended
Solids
123
124
148
68
152
40
132
156
249
111
67
62
139
45
88
99
95
124
79
96
47
105
72
71
EXTENDED OVER!
Volatile
Suspended
Solids
69
64
77
36
42
24
32
50
107
38
39
47
55
32
51
74
60
57
26
45
35
55
54
44
                                                           - 1969 DATA
                                                                       Total
                                                                       Solids
7.70
7.40
6.92
7.00
7.20
7.40
6.90
7.25
6.80
6.90
7.10
7.12
7.05
6.93
6.90
7.25
7.22
7.10
7.62
7.10
7.30
6.90
7.40
7.30
463
290
301
184
226
142
196
258
330
231
133
404
244
205
231
396
273
189
422
169
289
412
411
369
 Total
Volatile
 Solids

  234
  156
  165
   94
   84
   79
   77
  100
  173
  100
   70
  224
  147
  150
  105
  242
  125
   85
  194
   76
  129
  236
  226
  202
NOTE:  All values in mg/1 except pH.

-------
                                      TABLE IV-5  (Continued)
Run No.
COD
BOD
701
703
704
705
706
707
709
7012
7014
7015
7016
7018
7019
7020
7021
7023
7024
7025
133
183
126
121
90
156
84
123
183
137
80
169
201
122
57
136
82
132
35
75
15
26
18
51
18
49
—
—
—
—
71
35
13
58
29
47
ER QUALITY -

Suspended
Solids
138
180
52
198
86
126
55
104
226
132
98
272
202
252
131
99
85
161
EXTENDED OVERF!
Volatile
Suspended
Solids
66
95
16
122
44
61
39
53
114
63
56
125
108
86
156
73
64
101
 £H

7.5
7.2
7.6
7.2
7.6
7.2
6.6
7.1
6.8
6.7
6.6
6.8
7.4
7.1
6.9
7.6

6.6
Total
Solids

 294
 372
 635
 469
 410
 487
 344
 404
 441
 439
 281
 510
 543
 528
 298
  Total
Volatile
 Solids

  106
  193
  270
  174
  213
  207
  183
  189
  213
  205
  141
  214
  303
  192
  148
     NOTE:  All values in mg/1 except pH.

-------
                                     TABLE IV-6

                       EFFLUENT WATER QUALITY - FIRST FLUSHES
Volatile
Run
No.
691
6911
6912
6914
6916
6919
702
702(1)
708
708(i)
7011
7011(1)
7013
7013(1)
7022
7022(1)
Suspended Suspended Total
COD
177
137
245
179
173
263
64
63
168
197
143
157
285
337
73
68
BOD
74
39
—
64
51
94
24
21
66
103
85
76
149
178
18
22
Solids
166
130
224
109
89
108
102
84
105
145
70
60
135
165
65
59
Solids
92
62
102
57
64
96
61
51
57
73
38
33
58
90
47
48
Nitrogen
15.4
	
	
9.0
9.0
13.5
2.7
2.4
7.4
8.2
4.0
4.0
7.5
8.1
5.4
4.6
PH
7.50
7.00
8.00
7.10
7.12
7.53
7.7
7.6
7.2
7.2
6.8
6.8
7.0
7.1
7.6
7.6
Total
Solids
714
411
902
533
627
959
1251
1183
440
519
545
412
690
676
	
	
Total
Volatile
Solids
320
221
437
289
314
460
481
410
206
248
297
253
406
389
	
	
Ortho
Phosphate
as PO^
8.10
	
2.51
1.84
1.10
3.02
0.46
0.22
1.47
2.79
0.08
0.03
0.07
0.06
1.32
1.01

Coliform
per ml
26,000
40
	
16,000
80,000
8
1
1
180
1500
5700
5700
3150
500
	
1400
(1)  Overflow rate ^ 3.75 gpm/sq ft

All values in mg/1 except pH & coliform
Overflow Rate ^ 2.5 gpm/sq ft except where noted

-------
                                           TABLE IV-7
Run # COD  BOD
691
692
693
695
696
697
698
699
6910
6911
6913
6915
6917
6918
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
107
122
 60
105
 50
 25
 30
 34
 51
102
134
 69
122
 67
 57
 63
131
 99
 72
 54
 30
 45
189
149
207
36
25

52
13
 7
11

 6
25
22
15
 6

43
24
24
 8
17
73
48
54
EFFLUENT WATER QUALITY - EXTENDED I

Suspended
Solids
120
218
59
95
58
138
63
89
142
194
65
55
38
34
34
44
56
49
67
38
35
22
91
48
54
Volatile
Suspended
Solids
58
76
14
43
24
38
30
11
40
59
44
34
31
15
27
32
46
37 .
31
10
17
17
53
34
38

Total
Nitrogen
5.8
6.2
—
4.2
2.2
1.3
1.2
—
1.8



10.5
4.5
4.3
4.3
5.6
7.2
4.0
6.2
2.3
—
6^8
6.9
6.9


pH
7.25
6.60
8.15
7.60
7.10
7.20
7.45
7.10
7.25
7.10
7.70
7.90
7.20
7.10
6.98
7.00
7.50
7.32
7.20
7.85
7.00
7.10
7.00
7.30
7.30
                                                               Total
                                                       Total  Volatile
                                                      Solids   Solids
320
380
725
606
258
234
174
194
300
286
412
434
429
475
134
222
544
250
156
457
115
221
335
358
342
147
172
306
296
140
 84
 95
 77
125
206
220
203
240
185
 73
 98
282
109
 56
214
 46
100
184
176
182
  Ortho
Phosphate

   2.15
   1.76

   1.13
   0.90
   0.40
   0.40

   0.44

   1.77
   0.80
   2.
   3.
 ,82
 ,86
0.58
0.67
1.26
0.81
0.83
1.22
0.42
0.61
1.58
1.42
1.96
         Coliform
           per ml

            9,000
           61,000
  <0.04
  <0.04
  <0.04
   0.02
  <0.02
   0.1
    <50
 10,000

  1,000
   -400
     15
    150
      8
     30
 19,000
  8,200
 55,000
120,000
 69,000
110,000
     All values in mg/1 except pH and coliform

-------
                                              TABLE IV-7 CONTINUED
a\
Run
No.  COD

701   86
703  203
704  102
705   51
706   39
707  121
709   66
7012 113
7014 135
7015  99
7016  38
7018  67
7019  71
7020  56
7021  30
7023  92
7024  87
7025  57
                   BOD

                    24
                    74
                    26
                    11
                    13
                    42
                    18
                    46
                    23
                    29
                     5
                    36
                    29
                    24
           Volatile
Suspended Suspended
  Solids    Solids
   110
   161
    73
    65
    50
   114
    35
    76
    78
    84
    23
    47
    67
   172
    39
    70
    75
    39
49
89
37
38
27
56
23
36
45
44
17
39
35
63
20
47
38
31
TENDED OVERFLOW -

Total
Nitrogen
2.9
6.4
5.4
4.5
3.0
5.7
3.4
4.8
5.4
3.6
—
—
2.5
2
1.8
6.1
3.6
4


pH
7.7
7.6
7.6
7.6
7.6
7.3
6.8
6.8
6.9
6.6
6.6
6.8
8
7.4
7.0
7.6
7.3
6.6
1970 DATA

Total
Solids
519
541
702
341
390
385
279
465
421
349
184
295
751
683
184
	
	
	
HIGH OVERFLOW
Total
Volatile
Solids
168
236
290
127
194
189
139
234
199
168
91
137
305
297
108
	
	
	
RATES

Ortho
Phosphate
.58
1.9
1.5
1.4
0.6
1.38
0.09
0.01
0.03
0.03
0
	
0.28
0.06
0.12
0.31
0.43
0.06


Coliform
per ml
5,000
<1
<1
3
.06
33
> 10, 000
11,200
8,200
49,500
1,960
	
600
73,000
1,700
49,000
15,300
6,000
                 All values in mg/1 except pH and coliform

-------
                                TABLE IV-7 CONTINUED
EFFLUENT WATER QUALITY -
Volatile
Run
No.
701
703
704
705
706
707
709
7012
7014
7015
7016
7018
7019
7020
7021
7023
7024
7025

COD
98
184
92
55
33
102
57
104
122
92
34
61
102
49
38
107
69
69

BOD
23
72
18
11
7
39
18
43
	
	
	
	
34
12
6
33
26
25
Suspended
Solids
94
141
25
65
29
73
26
57
74
88
20
46
76
71
33
55
59
51
Suspended
Solids
40
79
4
40
20
41
21
34
44
41
15
30
37
29
19
37
49
40
EXTENDED OVERFLOW
Total
Nitrogen
2.9
2.7
5.3
4.5
2.9
5.2
3.4
4.4
3.9
2.6
—
	
3.1
1.9
1.8
5.3
3.8
3.9

PH
7.8
7.6
7.7
7.6
7.6
7.3
6.8
6.8
7.0
6.7
6.7
6.8
7.7
7.2
7.0
7.4
7.1
6.6
                                                              - LOW OVER RATES
                                                       Total
                                                       Solids

                                                         535
                                                         508
                                                         616
                                                         311
                                                         445
                                                         343
                                                         274
                                                         499
                                                         373
                                                         350
                                                         200
                                                         285
                                                         621
                                                         567
                                                         198
 Total
Volatile
 Solids

  174
  229
  241
  123
  237
  170
  152
  243
  183
  163
   91
  116
  274
  248
  116
  Ortho
Phosphate

   .37
  2.0
  1.1

  0.4
  1.29
  0.06
  0.05
  0.03
  0.03
  0

  0.95
  0.18
  0.09
  0.15
  0.43
  0.06
Coliform
 per ml

  5,800
      9
   .02
     38
> 10, 000
 14,200
  6,330
 28,000
  1,400

  2,100
 32,000
  1,400
 38,000
 14,400
 28,000
All values in mg/1 except pH and coliform

-------
                                                      TABLE IV-8
oo
 Run
 No.

 701
 702
 703
 704
 705
 706
 707
 708
 709
7011
7012
7013
7014
7015
7016
7018
7019
7020
7021
7022
7023
7024
7025
DISSOLVED COD AND TOC DATA
Raw Waste
Dissolved
COD
32
147
103
52
47
49
73
102
54
154
68
313
101
55
28
36
92
47
45
60
71
37
55
Total
TOC
35
237
75
42
71
41
—
—
—
—
—
249
—
—
—
79
139
38
—
—
—
—
57
Dissolved
TOC
12
57
39
18
16
17
—
—
—
—
—
128
—
—
—
—
36
13
17
—
—
—
25
Screened Effluent
Dissolved
COD
33
107
97
63
54
44
84
117
38
147
71
336
89
52
26
28
94
36
46
59
56
34
45
Total
TOC
31
121
53
38
36
29
—
—
—
—
—
235
—
—
—
61
91
27
—
—
—
—
49
Dissolved
TOC
12
41
37
20
15
14
—
—
—
—
—
137
—
—
—
—
31
12
17
—
—
—
18
System Effluent
nissolved
TOC
27
64
122
59
48
34
66
105
43
113
80
219
70
39
27
33
62
49
34
34
56
38
43
Total
TOC
24
23
74
31
16
18
—
—
—
—
—
117
—
—
—
21
44
7
—
—
—
_ _
27
Dl ssolved
TOC
8
18
48
20
15
12
—
—
—
—
—
86
—
—
_ —
—
24
9
13
—
—
__
14

-------
                    TABLE IV-9

     SCREEN BACK WASH & FLOATED SCUM QUALITY
                    1969 DATA
                  Screen Back Wash Quality
Run
 693
 694
 695
 696
 697
 698
 699
6910
6911
6912
6913
6914
6915
6916
6917
6918
6919
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
Pi
Total
Solids
Total
Volatile
Solids
Suspended
Solids1
6.8
6.8

7.8

7.1
6.5
7.0
7.2
7.0

6.9
6.6

6.8
7.1

7.1
7.2
7.4

6.8
7.2
7.3
1688
 643

 296

1443
2542
2192
1865
3638
1776

2303
2431

4185
 890
2901

1600
1623
1322
1388
 538

 220

1025
1814
1450
1100
2486
1406

1830
1813

2533
 694
 972

1236
1244
1048
1554
 543

 183

1371
2434
1909
1500
3366
1435

1746
2298

3872
 715
2843

1330
1253
1019
1.  Calculated based on dissolved solids in raw waste

           All values  in rag/1 except pH
                    159

-------
              TABLE IV-9 (Continued)

     SCREEN BACK WASH & FLOATED SCUM QUALITY
                    1969 DATA
          	Floated Scum Quality	
                                 Total
Run                Total       Volatile    Suspended
 f        £H       Solids       Solids       Solids1

 693      6.8       2395         1520        2004
 694
 695      7.2       4005         2390        3879
 696      7.1        584          330         484
 697      7.2        686          332         613
 698      7.5        385          202         272
 699
6910      7.3       1439          647        1367
6911      6.6      36860        19958       36720
6912      7.0      14282         7550       13999
6913      7.0      19081        10700       18716
6914      --       11131         6919       10852
6915      7.0       3705         2244        3624
6916      6.6      22627        13403       22355
6917      6.8       4687         3163        4346
6918      7.0       7694         3544        7608
6919      6.8      13650         8450       13093
6920      7.0      12168         6644       12035
6921      6.9       3111         1408        3087
6922      7.0       2291         1848        1978
6923      6.9      13228         8082       13053
6924      7.1       6699         3471        6610
6925      7.5       2508         1097        2100
6926      7.3      11361         5002       11303
6927      7.0       1705         1132        1492
6928      6.8       3268         2100        2998
6929      6.8       7027         5045        6657
6930      7.0       2804         2020        2501
1.  Calculated based on dissolved solids in raw waste

           All values in mg/1 except pH
                    160

-------
                                            TABLE IV-10
Run
No.

701
702
703
704
705
706
707
708
709
7011
7012
7013
7014
7015
7016
7018
7019
7020
7021
7022
7023
7024
7025
SCREEN BACKWASH AND
Screen Backwash
Screen
PH
7.7
7.2
6.9
7.1
6.6
6.7
6.9
6.7
7.1
7.1
Total
Solids
1655
3929
1891
3522
3976
3459
2817
1191
2945
2307
Total
Volatile
Solids
913
3017
1310
2723
3073
2387
2068
893
1987
1636
FLOATED SCUM
Suspended
Solids Q\
1435
3599
1697
3142
3781
2959
2312
1022
2716
1940
6.7
        (1) Calculated based on dissolved solids in raw waste
               All values in mg/1 except pH


pH

7 5
7.3
7.2
7.4
7.2
7.5
6.9
7.2
6.6
6.6
6.8
6.8
6.9
6.6
6.6
7.0
7.5
— ._
7.2
7.4
7.1
6.6
Floated

Total
Solids
2547
8044
4431
7374
34981
8399
11379
21201
27416
11601
15675
13427
6014
15452
13812
17062
3138
16300
24064
12709
3782
24026
Scum
Total
Volatile
Solids
1455
4549
2284
4408
9835
4484
5157
9074
10406
5618
7476
6829
2606
7005
5747
6249
1589
4360
9781
6024
1807
11683

Suspended
Solids Q\

2403
7713
4237
6807
34663
8082
11074
20866
27221
11101
15217
12922
5805
15177
13643
16836
2771
16152
	
	
	
	

-------
                           TABLE IV-11

                     FIRST FLUSH EVALUATIONS
              (RAW COMBINED SEWER OVERFLOW QUALITY)
Days Since
  Last
Overflow

0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
I
1
2
2
2
2
2
2
3
3
 Run
 No.

 703
 692
 694
6924
6930
 705
 709
7012
 697
 698
6913
6920
6921
6926
6927
7015
7021
7024
 699
6911
 706
 704
 706
7023
 693
 696
COD
mg/1

206
220
173
125
217
199
168
117
 66
 47
223
127
114
 95
 94
191
 90
178
 59
185
140
141
140
169
241
 87


BOD
mg/1
91
43
—
31
65
35
37
49
7
7
	
31
25
29
36
	
25
54
	
	
28
58
28
67
	
17

Suspended
Solids
mg/1
218
365
158
129
87
316
148
119
	
57
176
114
102
141
56
140
118
171
148
104
149
109
149
107
169
88
Volatile
Suspended
Solids
mg/1
88
145
80
66
66
193
86
81
26
29
120
62
64
65
45
85
63
125
43
78
75
39
75
73
117
46

-------
                      TABLE IV-11 CONTINUED

                     FIRST FLUSH EVALUATIONS
              (RAW COMBINED SEWER OVERFLOW QUALITY)
                                                                  Volatile
Days Since                                            Suspended   Suspended
  Last       Run            COD            BOD         Solids      Solids
Overflow     No.            mg/1           mg/1         mg/1	     mg/1

3            6915           118            	            116           62
3            6925           195             70            87           63
3            7016           130            	            135           95
3            7018           244            	            337          183
3            7025           139             66            123          103
4            6910             78             12            208           66
5            6912           472            	            496          253
5            7014           191            101            232          139
6            6914           574             18            554          322
6            6923           163             61            104           68
6              707           211            101            228          146
8            6911           920            180          1180          678
8              708           512            160            431          247
11           6918           137             37            192           82
11           6925           118             39            70           22
11           7013           649            330            479          289
12           6916           531             89            405          310
13           7011           390            212            232          156
14           7020           153             53            466          204
15             695           615            180            538          310
17           6922           248            	            165          117
17           7019           286            113            264          164
18             691           676            172            642          391
19           6928           334            124            180          138
19           7022            372            145            415          273
24           6919           642            170            312          244
26             702           617            224            582          228
                                  163

-------
                                           TABLE IV-12


Run //
691
695
6911
6912
6914
6916
6919
7021
702
708
70S1
711
7111
713
7131
722
7221


COD
__
72.7
—
4.9
51.1
18.6
20.6
—
48.0
40.2
—
34.9
—
5.9
—
29.6
—

Screen
BOD
„
71.7
—
—
33.3
20.2
0.6
—
40.6
41.9
—
33.5
—
10.6
—
22.1
—
FIRST
FLUSH REMOVALS IN PERCENT
Overall System
SS
__
68.4
—
14.5
53.1
28.4
8.3
—
47.4
36.9
—
22.4
—
12.7
—
20.2
—
VSS
__
70.6
—
7.5
53.4
17.1
3.3
—
44.7
48.2
—
32.1
—
20.1
—
29.3
—
COD
73.8
—
-85.1
48.1
68.8
67.4
59.0
89.7
89.6
67.2
61.5
63.3
59.7
56.1
48.1
80.4
81.7
BOD
57.0
—
78.3
—
64.4
42.7
44.7
90.6
89.2
58.8
35.6
59.9
64.2
54.9
46.1
87.6
84.8
SS
74.1
—
89.0
54.8
80.3
78.0
65.4
85.6
82.5
75.6
66.4
69.8
74.1
71.8
65.6
84.3
85.8
VSS
76.5
—
90.9
59.7
82.3
79.4
60.7
77.6
73.3
76.9
70.5
75.6
78.9
79.9
68.9
82.8
82.4
N
27.7
—
—
—
56.5
51.6
42.1
87.3
85.7
44.4
38.3
55.0
55.0
46.0
41.7
72.3
76.4
Overflow rate ^2.5 gpm/sq. ft. except where noted




1.  Overflow rate -v 3.75 gpm/sq. ft.

-------
                    TABLE IV-13
 EXTENDED OVERFLOW REMOVALS IN PERCENT - 1969  DATA
Screen
Overall System
Run //
69-2
69-3
69-4
69-5
69-6
69-7
69-8
69-9
69-10
69-11
69-13
69-15
69-17
69-18
69-20
69-21
69-22
69-23
69-24
69-25
69-26
69-27
69-28
69-29
69-30
COD

45.2
4.6
23.2
43.7
60.6
___
16.9
23.1
23.4
26.9
24.6
23.8
24.8
40.2
20.2
25.8
15.3
16.0
3.4
23.2
17.0
22.2
12.3
7.8
BOD

	
	
23.1
11.7
0
28.6
	
25.0
24.5
	
	
	
16.2
32.3
___
___
11.5
12.9
5.1
31.0
22.2
27.4
15.7
7.7
SS

27.2
21.5
11.9
22.7
20.8
29.8
10.8
25.0
9.8
36.9
42.2
40.4
27.6
60.5
13.7
40.0
8.6
3.8
12.9
31.9
16.1
41.7
17.2
18.4
VSS
___
41.0
20.0
24.5
21.7
23.6
17.2
25.6
24.2
43.8
68.3
37.1
39.7
32.9
48.4
20.3
36.8
11.7
13.6
18.2
30.7
22.2
60,1
14.3
33.3
COD
44.5
75.1
	
49.3
42.5
62.1
36.2
42.4
34.6
45.7
39.9
41.5
34.1
51.1
48.8
44.7
47.2
39.3
42.4
54.2
68.4
52.1
43.4
23.6
4.6
BOD
41.9
	
	
20.0
23.5
0
	
	
50.0
49.0
	
	
	
40.5
51.6
76.0
	
29.5
22.6
38.5
72.4
52.8
41.1
31.4
16.9
SS
40.3
65.1
	
43.5
34.1
28.1
10.5
39.9
31.7
29.7
63.1
52.6
63.5
82.3
70.2
56.9
66.1
52.9
48.1
45.7
75.2
60.7
49.4
44.8
37.9
VSS
47.6
88.0
	
57.8
47.8
30.9
3.4
74.4
39.4
43.8
63.3
45.2
60.3
81.7
56.5
50.0
60.7
45.6
53.0
54.5
73.8
62.2
61.6
46.0
42.4
N
23.5
	
	
34.4
4.3
35.0
14.3
	
41.9
	
	
	
	
6.2

6.8
30.9
14.3
	
29.5
30.3
— — —
33.3
24.2
1.4

-------
                                      TABLE IV-13 CONTINUED

               EXTENDED OVERFLOW REMOVALS IN PERCENT 1970 DATA - HIGH OVERFLOW RATES
Run
No.

701
703
704
705
706
707
709
7012
7014
7015
7016
7018
7019
7020
7021
7023
7024
7025
                                                  Overall System
COD
39.9
1.5
27.7
74.4
72.1
42.7
60.7
36.2
29.3
38.9
70.8
72.5
75.2
63.4
66.7
45.6
51.1
60.0
BOD
33.3
18.7
55.2
68.6
53.6
58.4
51.4
31.4
	
	
	
	
79.7
45.3
80.0
46.3
46.3
63.6
SS
27.2
26.7
33.0
79.4
66.4
50.0
76.4
36.1
66.4
40.0
83.0
86.1
74.6
63.1
67.0
34.6
56.1
68.3
VSS
34.7
1.1
51.2
80.3
64.0
61.6
73.3
55.6
67.6
48.2
82.1
78.7
78.7
69.1
68.3
35.6
69.6
69.9
N
0
13.5
0
27.7
23.0
24.0
22.7
23.8
3.6
26.5
	
	
64.0
41.2
25.0
29.9
26.5
37.5

-------
                         TABLE IV-13 CONTINUED




 EXTENDED OVERFLOW REMOVALS IN PERCENT 1970 DATA -  LOW OVERFLOW RATES







	Screen	       	Overall System	
Run
No.
701
703
704
705
706
707
709
7012
7014
7015
7016
7018
7019
7020
7021
7023
7024
7025

COD
7.0
11.2
10.6
39.2
35.7
26.1
50.0
30.5
4.2
15.4
38.0
31.0
30.0
20.0
37.0
19.5
53.9
5.0

BOD
2.8
17.6
74.1
25.7
35.7
49.5
51.4
26.9
10.6
	
	
	
37.0
34.0
48.0
13.4
46.3
28.8

SS
8.6
17.4
52.3
37.3
42.3
44.7
62.8
12.6
2.6
5.7
27.0
19.0
23.0
46.0
	
7.5
50.3
	

vss
12.0
	
59.0
36.8
41.3
58.2
54.7
34.6
18.0
25.9
32.0
32.0
34.0
58.0
11.0
	
-48.8
2.0

COD
31.5
10.7
34.8
72.4
74.6
51.7
66.1
41.2
36.1
43.2
73.8
75.1
64.3
68.0
57.8
36.7
62.1
50.4

BOD
36.1
20.9
69.0
68.6
75.0
61.4
51.4
35.8
	
	
	
	
69.9
77.4
76.0
50.7
51.9
62.1

SS
37.7
35.3
77.1
79.4
80.5
68.0
82.4
52.1
68.1
37.1
85.2
86.4
71.2
84.8
72.0
48.6
65.5
58.5

VSS
46.7
10.2
89.7
79.3
73.3
71.9
75.6
58.0
68.4
51.8
84.2
83.6
77.4
85.8
69.8
49.3
60.8
61.2

N
0
63.5
0
27.8
18.8
30.7
22.7
30.2
29.5
46.9
	
	
55.4
44.1
25.0
39.2
23,5
39.1

-------
                           TABLE IV-14
OLIDS MASS
Pounds
SS
Out
372
337
146
157
163
499
141
111
650
362
181
88
46
124
79
64
94
184
80
54
203
41
122
45
146
BALANCE -
Pounds
SS Left
in Tank
80
145
39
63
39
92
42
59
94
86
48
43
37
25
23
29
37
33
45
25
23
15
60
32
36
1969 DATA
Pounds
SS
Screen Wash
0
0
—
26
—
—
—
—
—
16
51
15
—
43
12
—
19
4
—
—
199
—
13
19
15

Pounds
SS
Scum
j_
	
58
63
14
31
15
—
50
84
47
109
15
62
191
13
12
239
17
68
160
11
15
17
25
           Pounds
Run         SS
No.         In

691         353
692         575
693         426
695         282
696         250
697         706
698         132
699         187
6910        961
6911        522
6912        417
6913        240
6915         97
6917        343
6920        263
6921        150
6922        277
6923        393
6924        154
6925        103
6926        829
6927        106
6928        246
6929         82
6930        238
     (1)  (+) Excess solids in;  (-)  Excess solids out
Balance
  -28
  +16
  +57
  - 9
  +14
  +12
  -50
  + 9
  +17
  _ c
  +22
  - 6
  - 1
  +26
  -16
  +29
  +41
  -17
  + 8
  -43
  +29
  +37
  +14
  -37
  + 7
                                168

-------
                      TABLE IV-14 CONTINUED
Run
No.

701
703
704
705
706
707
708
709
7011
7012
7013
7014
7015
7016
7018
7019
7021
7022
7023
7024
7025
Pounds
  SS
  In

  316
  228
  108
  750
  145
  291
  667
  220
  274
  142
  481
  257
  138
  244
  211
  224
  225
  408
  137
  458
  247
SOLIDS MASS
Pounds
SS
Out
211
151
48
154
38
120
181
44
74
76
158
83
84
40
29
60
68
60
80
179
89
BALANCE -
Pounds
SS Left
In Tank
68
100
33
43
26
63
80
20
43
43
100
50
57
15
31
48
24
41
42
44
30
1970 DATA
Pounds
SS
Screen Wash
14
67
__
—
—
36
,
38
81
—
54
—
—
5
54
28
—
—
—
—
—

Pounds
SS
Scum
21
18
17
144
17
32
173
463
175
215
107
48
63
181
21
2
154
40
53
24
120
                                                                   Balance
 + 1
 -47
 + 9
 +55
 +44
 +14
 +35
-157
 -36
-135
 +13
 +30
 -48
 + 1
 +36
 +35
 - 9
 +65
 -28
 +46
 + 3
      (1)  + Excess solids  in
          - Excess solids  out
                                  169

-------
                     STATISTICAL PROCEDURES






The following statistical procedures were utilized:






                       Estimate of a Mean Value



                          x = x ± ts
where: x - estimated mean value



       x = mean of n values



       t = student "t" value at n-1 degrees of freedom for some

           confidence level



       s = standard deviation of the data points


       n = number of pieces of data


                      Comparison of Means Test






1.  Perform "F" test
                             Fc = S?
                                  S2
    If: FC  < F  Go to Step 2



    If:  F  > F  Go to Step 3
          c    t          v


         Ffc = Table "F" value



         F  = calculated "F" value
          c


         s- = standard deviation of first set of data



         $  ~ standard deviation of second set of data
                                170

-------
2.   Comparison of means "t" test when:
                                            - ((Ex2)2/n)
                               nl
                        t =
     Degrees of freedom (DF) = n, 4- n2 - 2

     Read "t" table at t and DF to find confidence level at which a
     difference exists
3.  Comparison of means "t" test when
                    =  (S1)2/n1
                        2

     Complete DF  (v) from:
         = (l/V1)((S52)/(Sx2  + Sx2))2  +  (1/v   )((Sx?,)/(Sx2
     where: v-^ = N.. - 1

            v  = N  - 2

                              t =
                                      Sx2 + Sx2
     Read "t" table at t and DF to find confidence level at which a
     difference exists
                                 171

-------
                     Paired Comparison Test
1.   Calculate S,,
               di



         where S
                         n-1



         and d = x - y



             dj = x - y



             n = number of pairs of data



             x & y = data pair



             x & y = average of each set of data
2.  Calculate t;



         where t - d
    Compare calculated "t" to table "t" to determine if there is a

    significant difference in the two sets of data.
                        Confidence     _






The Confidence Rancre was calculated bv:




         = x ± ts/  \/n-l




        "here x = mean value




              t = value from "t" table at desired confidence

                  range and decrees of freedom




              s = standard deviation




              n = number of pieces of data
                                172

-------
1
Access/on Number
w
5
2

Subject Field &. Group
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Rex Cha-lnhpl t- Tnr . M-f luanlcop . U-iarnnc-tn
               Ecology Division
    Title
               SCREENING/FLOTATION TREATMENT  OF COMBINED SEWER OVERFLOWS
]Q Authors)
Mason,
Gupta,
Donald G.
Mahendra K.
16

21
Project Designation
EPA Contract
14-12-40, Project
11020 FDC
Note
 22
    Citation
 23
    Descriptors (Starred First)

          Sewage Treatment, Sewage Effluents, Sewage
 25
    Identifiers (Starred First)
      Combined Sewer Overflows, Treatment Screening/Dissolved Air
 27
    Abstract This report  documents a study to develop a treatment system  for  combined  sewer
    overflows.  The processes of chemical oxidation, screening, dissolved-air  flotation
and disinfection were  evaluated in the laboratory.  A 5 MGD demonstration  system was
designed, installed and  evaluated.

     The system was utilized to treat 55 combined sewer overflows.  The  drainage area
served by the system was a 500 acre completely developed residential area  of Milwaukee,
Wisconsin.  Suspended  solids and volatile suspended solids removal in  the  range of  65-80%
were consistently obtained at influent concentrations of 150 to 600 mg/1.   BOD and  COD
removals were slightly lower at 55 to 65% for influent concentrations  of 50 to 500  mg/1.
Addition of chemical flocculents (ferric chloride and a cationic polyelectrolyte) was
necessary to obtain these removals.  Without the use of chemical flocculents,  removal of
BOD, COD, suspended solids, and volatile suspended solids were all in  the  range of  40-50%.
The screening flotation  system provided sufficient detention time  (^15 minutes) for
adequate disinfection  with hypochlorite salts.  Cost estimates indicate  a  capital cost of
$21,056 per MGD capacity or $3,828 per acre for a 90 MGD screening/flotation system.
Operating costs were estimated at 3.09^/1000 gallons of teated overflow, including
chemical flocculent addition.
(Mason-Rex Chainbelt Inc.)
Abstractor
          Donald G. Mason
                              Institution
                                     Rex Chainbelt Inc., Ecology Division,  Milwaukee, Wis.
 WR:102 (REV. JULY 196
 WRSIC
                            SEND. WITH COPY OF DOCUMENT, TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
                                                      U.S. DEPARTMENT OF THE INTERIOR
                                                      WASHINGTON, D. C. 20240
                                                           OJ.S. GOVERNMENT PRINTING OFFICE: 1972  484-485/217 1-3

-------