c/EPA
        United States
        Environmental Protection
        Agency
           Municipal Environmental Research EPA-600/2 79 098
           Laboratory         August 1979
           Cincinnati OH 45268
        Research and Development
Comparison of
Ozone
Contactors for
Municipal
Wastewater Effluent
Disinfection
         Packed Column
         Versus Jet Scrubber

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Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology.  Elimination  of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in  related fields.
The nine series  are:

      1   Environmental  Health Effects Research
      2   Environmental  Protection Technology
      3   Ecological Research
      4.  Environmental  Monitoring
      5.  Socioeconomic Environmental Studies
      6.  Scientific and Technical Assessment Reports (STAR)
      7.  Interagency  Energy-Environment Research and Development
      8.  "Special" Reports
      9.  Miscellaneous Reports

This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution-sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                      EPA-600/2-79-098
                                      August 1979
    COMPARISON OF OZONE CONTACTORS FOR
MUNICIPAL WASTEWATER EFFLUENT DISINFECTION

     Packed Column Versus Jet Scrubber
                    by

    Albert D. Venosa, Edward J. Opatken
            and Mark C.  Meckes
       Wastewater Research Division
Municipal Environmental Research Laboratory
          Cincinnati, Ohio  45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
    OFFICE OF RESEARCH AND DEVELOPMENT
   U.S. ENVIRONMENTAL PROTECTION AGENCY
          CINCINNATI, OHIO  45268

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                                 DISCLAIMER

     This report has been reviewed by the Municipal Environmental  Research
Laboratory, U. S. Environmental Protection Agency,  and approved for publi-
cation.  Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
                                      11

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                                  FOREWORD
     The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people.  Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.

     Research and development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and
searching for solutions.  The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention, treat-
ment, and management of wastewater and solid and hazardous waste pollutant
discharges from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize the adverse
economic, social, health, and aesthetic effects of pollution.  This publica-
tion is one of the products of that research; a most vital communications
link between the researcher and the user community.

     As part of these activities, this report was prepared for use by design
engineers whose responsibility is to design the most efficient, cost-
effective ozone contacting system for achieving a specified bacteriological
quality of wastewater effluent.
                                       Francis T. Mayo
                                       Director
                                       Municipal Environmental
                                        Research Laboratory
                                     111

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                                   PREFACE

     In January 1974,  a U.  S.  Environmental Protection Agency (USEPA)  Task
Force was formed to review USEPA policy on  wastewater disinfection and the
use of chlorine.  The Task Force recognized that chlorine and chlorine-based
compounds were being used almost exclusively for the disinfection of waste-
water.  While chlorine was considered an effective disinfectant with respect
to meeting bacteriological standards and was adequately protecting public
health, there were potential dangers associated with the use of chlorine.
Disinfection of wastewater with chlorine could result in the formation of
halogenated organic compounds which have been identified as potential
carcinogens.  Considerable data also existed that chlorination of wastewater
could result in residual chlorine or chloramine levels that could be toxic
to aquatic life.  The Task Force concluded that, in view of the fact that
existing regulations inadvertently encouraged the use of chlorine, a
national regulation requiring disinfection would further compound the
potential problems associated with the chlorination of wastewater.

     The Agency recognized that protection of public health from disease
continues to be the primary objective under the present system of regulation
of disinfection of municipal wastewater by means of State standards.  It
also recognized that continuous disinfection in some localities was not
necessary to insure public health protection.  The exclusive use of chlorine
for disinfection should not be continued where protection of aquatic life
is of primary consideration.  Alternate means of disinfection or disinfectant
control  (i.e., dechlorination) must be considered where public health hazards
and potential adverse impact on the aquatic or human environments exist.

     Consequently, on July 26, 1976, USEPA amended the Secondary Treatment
Information regulation contained in 40 CFR Part 133^ Section 304(d)(l) of the
Federal Water Pollution Control Act Amendments of 1972.  The amendment
deleted the fecal coliform bacteria limitation from the definition of
secondary treatment.  Reliance on water quality standards for establishment
of disinfection requirements for publicly owned treatment works was selected
by the Agency.to replace the limitations in 40 CFR Part 133.

     The USEPA Municipal Wastewater Disinfection Program is intensively
pursuing development of alternative disinfection technology which could
reliably achieve any specified bacteriological limitation without adversely
affecting the environment.  Ozonation appears to be the most promising
alternative process presently under investigation.  However, ozone is both
cost and energy sensitive.  Generation of ozone by corona discharge is only
about 10 percent efficient from a power consumption standpoint.  Thus, it
becomes imperative that all or most of the ozone produced on-site must be
utilized in the most efficient manner to prevent needless loss of energy and
resources.

                                       iv

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     An in-house research program was initiated at USEPA-Cineinnati's
experimental pilot plant located in the Robert A.  Taft Laboratory building.
The purpose of the project is to compare and evaluate various types of gas-
liquid contacting devices in parallel on the same wastewater effluent so
that the conditions necessary for microorgansim reduction efficiency and
mass transfer efficiency can be properly defined and quantified.  The
ultimate goal is to optimize ozone contacting to achieve the desired bac-
teriological quality and reduce operational costs of ozonation by eliminating
excessive loss.

     This report is the first of a series on the comparative performance of
ozone contactors.  It discusses the results of a study comparing a packed
column with a jet scrubber operating in parallel on conventional activated
sludge effluent.

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                                  ABSTRACT

     This research effort was initiated with the overall objective of deter-
mining which engineering and microbial operating parameters must be controlled
with respect to municipal effluent disinfection and ozone utilization for
various generic contactors.

     Pilot scale investigations were made comparing two ozone contactors, a
jet scrubber and a packed column, for ozone utilization and coliform reduction
efficiency.  These investigations were conducted in three phases:  (1) batch
operation phase - both contactors were operated separately under identical
conditions using a batch sample of activated sludge effluent; (2) parallel
operational phase   both contactors were operated in parallel on the same
activated sludge effluent; and (3) continuous operational phase - both
contactors were operated in parallel to achieve a three log reduction of
coliform bacteria on the same activated sludge effluent.  The effluent was
characterizied by determining COD, TOC, SS, NH4~N, N03-N, N02-N, pH and
turbidity.

     Bacterial enumerations included total and fecal coliforms, fecal
streptococci, and Salmonella spp.  Ozone gas concentrations, before and
after contacting, were determined iodometrically, and ozone residual was
determined by amperometric techniques.

     Results showed that the packed column significantly outperformed the
jet scrubber with respect to microorganism reduction and efficiency of ozone
utilization.  Wastewater effluent quality interfered with disinfection in
both contactors, the most important variables being chemical oxygen demand
(total and soluble) and organic carbon.  Initial bacterial density and ozone
residual were also important factors affecting log reduction of coliforms
and fecal streptococci in both contactors.
                                     VI

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                                  CONTENTS
                                                                        Page


Foreword	   iii


Preface	    iv


Abstract	    vi


Figures	    ix


Tables	    xi


Abbreviations and Symbols  	   xiv


Acknowledgements 	   xvi


     1.  Introduction  	    1


     2.  Conclusions	,	    3


     3.  Recommendations 	    5


     4.  Materials and Methods


          Sources of wastewater effluent 	    6


          Description of equipment  	    7


          Sample collection   	   11


          Ozone concentration	12


          Chemical and physical characterization of wastes 	   13


          Bacteriological methods   	   13


          Statistical data handling and experimental design  	   13


     5.  Results and Discussion


          Ozone generator output	   16
                                     vn

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                            CONTENTS (Continued)


          Phase 1 - batch operational mode	18

               Wastewater effluent characteristics  	   19

               Determination of mass transfer coefficients  	   19

               Ozone utilization	23

               Effect of packing size on packed column
                performance	24

               Contactor performance  	   25

               Regression analysis  	   31

          Phase 2 - parallel operational mode-factorial
           experiment	38

               Characteristics of wastewater effluent 	   38

               Total coliform log reduction	38

               Fecal coliform log reduction	41

               Percent ozone utilization  	   43

               Actual ozone utilization 	   43

               Ozone residual	47

               Ozone consumption	50

               Linear regression analysis of data from factorial
                experiment	54

          Phase 3   continuous operation-pilot plant effluent 	   65

References	67

Appendices

     A.  The Modified Kenner-Clark Procedure for Enumerating
          Salmonella spp	69

     B.  Mass transfer calculations	   71

     C.  Safety precautions used in the ozone test facility	75
                                     Vlll

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                                   FIGURES


1.   Flow schematic of ozone pilot plant system 	    7

2.   Mass balance on ozone pilot plant  	    8

3.   View of packed column	10

4.   View of jet scrubber .	10

5.   Jet action of scrubber (removed from contactor)   .  .  .  .  	   11

6.   View of ozone gas decomposer	11

7.   View of gas analysis work station	12

8.   Relationship between power consumption and ozone
      concentration 	   17

9.   Effect of gas flow rate on ozone production	17

10.  Effect of gas flow rate on power consumption	18

11.  Variation of Henry's Constant with temperature 	   20

12.  Effect of gas flow rate on mass transfer coefficient	22

13.  Effect of ozone dosage on percent ozone utilization  	   23

14.  Effect of G/L ratio on percent ozone utilization at a
      constant dosage of 8.0 mg/	24

15.  Total coliform log reduction as a function of ozone
      dosage in the packed column and jet scrubber	40

16.  Total coliform log reduction at all dosage levels as  a
      function of effluent total chemical oxygen demand in the
      packed column and jet scrubber	41

17.  Percent ozone utilization as a function of ozone dosage
      in the packed column and jet scrubber	45

18.  Percent ozone utilization as a function of effluent
      total chemical oxygen demand in the packed column and
      jet scrubber	45

                                     ix

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                             FIGURES (Continued)
19.  Ozone utilization as a function of ozone dosage in the
      packed column and jet scrubber	   48

20.  Ozone utilization at all  dosage levels  as a function of
      effluent total chemical  oxygen demand  in the packed
      column and jet scrubber	   48

21.  Ozone residual as a function of ozone dosage in the
      packed column and jet scrubber	   51

22.  Ozone residual as a function of effluent total chemical
      oxygen demand in the packed column and jet scrubber 	   51

23.  Ozone consumption as a function of ozone dosage in the
      packed column and jet scrubber	   53

24.  Ozone consumption as a function of effluent total chemical
      oxygen demand in the packed column and jet scrubber 	   53

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                                   TABLES


1.   List of Equipment and Specifications	    9

2.   Summary of Muddy Creek Effluent Characteristics  	   19

3.   Effect of Packing Size on Overall Mass Transfer
      Coefficients (kgVa) of the Packed Column at
      Various Gas Flow Rates	25

4.   Difference in Total Coliform Log Reduction (TCLR)
      Between the Packed Column and Jet Scrubber as a
      Function of Applied Dosage (MCWTP Effluent) 	   26

5.   Difference in Fecal Coliform Log Reduction (FCLR)
      Between the Packed Column and Jet Scrubber as a
      Function of Applied Dosage (MCWTP Effluent) 	   27

6.   Difference in Fecal Streptococcus Log Reduction  (FSLR)
      Between the Packed Column and Jet Scrubber as
      a Function of Applied Dosage (MCWTP Effluent) 	   28

7.   Densities of Salmonella spp. Before and After the
      Ozone Contactors (MCWTP Effluent) 	   29

8.   Difference in Ozone Utilization Between the Packed
      Column and Jet Scrubber as a Function of Applied
      Dosage (MCWTP Effluent) 	   30

9.   Difference in Ozone Consumption Between the Packed
      Column and Jet Scrubber as a Function of Applied
      Dosage (MCWTP Effluent) 	   30

10.  Difference in Ozone Residual Between the Packed Column
      and Jet Scrubber as a Function of Applied Dosage
      (MCWTP Effluent)	31

11.  Correlation of Total Coliform Log Reduction (TCLR) in
      the Packed Column with Ozone Dosage, Utilization,
      Consumption, Residual, and Initial Total Coliform
      Density (MCWTP Effluent)  	   33
                                     XI

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                             TABLES (Continued)


12.    Correlation of Fecal Coliform Log Reduction (FCLR)
       in the Packed Column With Ozone Dosage, Utilization,
       Consumption, Residual, and Initial Fecal Coliform
       Density (MCWTP Effluent)  	    33

13.    Correlation of Fecal Strep Log Reduction (FSLR) in the
       Packed Column with Ozone Dosage, Utilization, Consump-
       tion, Residual, and Initial Fecal Strep Density (MCWTP
       Effluent)	    34

14.    Correlation of Total Coliform Log Reduction (TCLR) in
       the Jet Scrubber with Ozone Dosage, Utilization, Con-
       sumption,  Residual, and Initial Total Coliform Density
       (MCWTP) Effluent) 	    34

15.    Correlation of Fecal Coliform Log Reduction (FCLR) in
       the Jet Scrubber with Ozone Dosage, Utilization, Con-
       sumption,  Residual, and Initial Fecal Coliform
       Density (MCWTP Effluent)  	    34

16.    Correlation of Fecal Strep Log Reduction (FSLR) in the
       Jet Scrubber with Ozone Dosage, Utilization,  Consumption,
       Residual,  and Initial Fecal Strep Density (MCWTP
       Effluent)	    35

17.    Characteristics of the Pilot Plant Effluent Prior
       to Ozonation	    38

18.    Split-Split-Plot Layout for Total Coliform Log
       Reduction Data	    39

19.    ANOVA for Total Coliform Log Reduction 	    39

20.    Split-Split-Plot Layout for Fecal Coliform Log
       Reduction Data	    42

21.    ANOVA for Fecal Coliform Log Reduction Data	    42

22.    Split-Split-Plot Layout for Percent Ozone Utilization Data  ...    44

23.    ANOVA for Percent Ozone Utilization Data 	    44

24.    Split-Split-Plot Layout for Ozone Utilization Data 	    46

25.    ANOVA for Actual Ozone Utilization Data  	    46

26.    Split-Split-Plot Layout for Ozone Residual Data  	    49

27.    ANOVA for Ozone Residual Data	    49
                                    XII

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                            TABLES (Continued)


28.  Split-Split-Plot  Layout  for  Ozone Consumption Data  	    52

29,  ANOVA for Ozone Consumption  Data	    52

30.  Correlation  of Total Coliform Log Reduction  (TCLR)
       in the Packed Column  at  Different Applied Ozone
       Dosage Levels with Effluent Quality  Parameters   	    56

31.  Correlation  of Fecal Coliform Log Reduction  (FCLR)
       in the Packed Column  at  Different Applied Ozone
       Dosage Levels with Effluent Quality  Parameters   	    58

32.  Correlation of Total Coliform Log Reduction (TCLR) in
      the Jet Scrubber at Different Applied Ozone Dosage
      Levels with Effluent Quality Parameters 	  58

33.  Correlation of Fecal Coliform Log Reduction (FCLR) in
      the Jet Scrubber at Different Applied Ozone Dosage
      Levels with Effluent Quality Parameters 	  59

34.  Correlation of Ozone Utilization in the Packed Column
      at Different Applied Ozone  Dosage Levels with
      Effluent Quality Parameters 	 .   	  59

35.  Correlation of Ozone Utilization in the Jet Scrubber
      at Different Applied Ozone  Dosage Levels with
      Effluent Quality Parameters 	  62

36.  Correlation of Ozone Residual in the Packed Column
      at Different Applied Ozone  Dosage Levels with
      Effluent Quality Parameters 	  62

37.  Correlation of Ozone Residual in the Jet Scrubber
      at Different Applied Ozone  Dosage Levels with
      Effluent Quality Parameters 	 .  	  63

38.  Correlation of Ozone Consumption in the Packed Column
      at Different Applied Ozone  Dosage Levels with
      Effluent Quality Parameters  	   63

39.  Correlation of Ozone Consumption in the Jet Scrubber
      at Different Applied Ozone  Dosage Levels with
      Effluent Quality. Parameters	64

40.  Continuous Operation of Packed Column and Jet Scrubber
      for the 100-hour Period of  February 28, 1977 to
      March 3, 1977	64
                                    Xlll

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                      LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS

ANOVA
COD
df
F
FC
FCLR
FS
FSLR
kg
kg/d
kg/h
kPa
kW
kWh/kg
m3/d
MCWTP
mgA
mg/min
mm Hg
MS
n
r
T2
SCOD
S.D.
t
TC
TCLR
TKN
TOC
TSS
VSS
   analysis of variance
   chemical oxygen demand
   degree of freedom
   F-statistic
   fecal coliform
   fecal coliform log reduction
   fecal streptococci
   fecal streptococci log reduction
   kilogram
   kilogram per day
   kilogram per hour
   kilopascals pressure
   kilowatt
   kilowatt hour per kilogram
   litre per minute
   cubic meter per day
   Muddy Creek Wastewater Treatment Plant
   milligram per litre
   milligram per minute
   millimeter mercury
   mean square
   number of observations
   correlation coefficient
   coefficient of determination
   soluble chemical oxygen demand
   standard deviation
   "t"-statistic
   total coliform
   total coliform log reduction
   total Kjeldahl nitrogen
   total organic carbon
   total suspended solids
   volatile suspended solids
SYMBOLS
a
Ck
Co
-- probability of error
-- contactor designation (i.e., packed column or jet scrubber)
-- ozone consumption (U    R0J
                                   xiv

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                LIST OF ABBREVIATIONS AMD SYMBOLS (Continued)
C        -- degree centigrade
D.J        -- dosage level
D0        -- applied ozone dosage
AY,       -- log mean concentration difference of ozone in the gas phase in
              equilibrium with ozone in the liquid phase
Fe        -- iron
G         -- gas flow rate
G/L       -- ratio of gas flow rate to liquid flow rate
H         -- Henry's Constant
HC1       -- hydrochloric acid
H2S04     -- sulfuric acid
KgV       -- mass transfer coefficient
KgVa      -- overall mass transfer coefficient
KI         potassium iodide
L         -- liquid flow rate
Mn         manganese
N         -- ozone transferred from the gas phase into the liquid
Na2S203   -- sodium thiosulfate
NH.+-N    -- ammonium nitrogen
NO--N     -- nitrite nitrogen
NO_-N     -- nitrate nitrogen
ORG-N     -- organic nitrogen
03         ozone
R^        -- replicate
RQ        -- ozone residual
Sj        -- standard deviation of the difference
U0        -- ozone utilization
X         -- total coliform density after ozonation  (no./100 m)
X         -- initial total coliform density (no./lOO m)
X         -- mean
X,        -- difference between means
x         -- ozone concentration in the effluent (mols 0_/mol liq)
Y         -- fecal coliform density after ozonation  (no./lOO m)
Yo        -- initial fecal coliform density (no./lOO m)
Y,        -- ozone concentration in the inlet gas (mg/)
Y2        -- ozone concentration in the exhaust gas  (mg/)
y*        -- partial pressure of ozone gas in equilibrium with dissolved ozone
Z         -- fecal streptococci density after ozonation (no./lOO m&)
Z         -- initial fecal streptococci density (no./lOO mJl)
                                      xv

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                             ACKNOWLEDGEMENTS
     The able efforts of Messrs.  Glenn Gruber,  Leo Fichter, and Burney
Jackson in constructing the ozone disinfection system are gratefully
acknowledged.

     Messrs. Richard Butler and William McErlane and Ms.  Karen Hoskins
conducted the sampling and assisted in the performance of the ozone mass
balances.  Assays of the samples for pathogenic microorganisms were per-
formed by Messrs. Harold Clark and Harold Sparks.  Chemical analyses
were performed by the Waste Identification and Analysis Section, Wastewater
Research Division, Municipal Environmental Research Laboratory, USEPA,
Cincinnati, Ohio.

     We are indebted to Mr. Joseph Santner for his invaluable guidance in
planning the factorial experiments.  The above assistance of Mr. E. J.
Madison in computer data handling is gratefully acknowledged.
                                    xvi

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                                  SECTION 1

                                INTRODUCTION


     Ozonation is rapidly gaining ground in the U.S. as a viable wastewater
disinfection process alternative to chlorination.  However, the relatively
high capital and operating costs of ozone generating equipment, as compared
to chlorination, have hampered progress in attainment of widespread accepta-
bility.  Any process development which offers promise in reducing the overall
costs of ozonation will accelarate that acceptability.

     Ozone is a potent oxidizing agent and its reaction with oxidizable
materials is non-selective.  The demand exerted by organic matter in effluents
can have a marked influence on the disinfection efficiency and reliability
of ozone.  Care must be exercised in making certain that the ozone produced
is utilized in the most efficient manner; otherwise, the operating costs of
ozonation may be needlessly high due to excessive use of energy resources.
Detailed evaluations on gas-liquid contacting devices are needed so that ozone
utilization can be optimized, reliability established, and operating costs
identified.

     Several studies are reported in the literature describing either the
disinfection performance or the mass transfer capability of different con-
tacting devices (8,14,15,18,19).  Ghan et al. (8) evaluated three commercially
available contacting devices: a bubble diffuser, a positive pressure injector,
and a multi-stage mixing pump.  The authors based their evaluation on ozone
utilization, defined as the difference in the ozone concentration between the
feed gas and exhaust gas.  Ozone utilization was converted to a percent by
dividing the difference by the inlet gas concentration and multiplying by 100.
Percent ozone utilized in each contactor was plotted as a function of applied
ozone dosage.  Results indicated 90 percent ozone utilization in the mixing
pump up to 50 mg/ applied ozone, while the percent utilization in the other
two contactors decreased markedly with increasing dosage.  They concluded that
the higher utilization in the mixing pump was due to the splitting of the
ozone gas stream into four injection points, thus maintaining a low ozone
dosage at each addition point.  Later studies with a multi-stage,sparged system
confirmed that a 90 percent utilization efficiency could be readily achieved.

     Masschelein et al'. (13,14) examined the ozone utilization efficiency of
various contacting devices.  Systems studied included:  (1) a multi-stage,
porous-pipe diffuser system operating in a countercurrent flow configuration;
(2) an injection system, similar in principle to a commercially available
positive pressure injection system; and (3) different types of single-stage
or multi-stage stirred turbine reactors.  Comparisons were made on ozone
utilization in water and on total energy consumption.  No bacteriological data

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were gathered,  nor were parallel studies performed.

     Nebel et al.  (18)  evaluated the rate of phenol  oxidation in various ozone
mixing devices.  They found that an important consideration in determining
the economic feasibility of a given mixer was whether extensive pumping of
the liquid to be treated is necessary.   Parallel studies were not performed.

     In 1974, Rosen et  al.  (19)  postulated a conceptual model for ozone dis-
infection.  Their model assumes  that the rate of reaction of ozone with
bacteria is virtually instantaneous and that ozone disinfection occurs by
direct cell lysis.  It  was  further assumed that lysis would result from
direct contact of a microorganism and an ozone gas bubble.  Thus, they sug-
gested that disinfection is  independent of dissolved  ozone concentration and
that the rate of disinfection is not limited by the  bulk mass transfer rate
of ozone into solution.  This concept formed the basis for design of the
positive pressure injection system.

     Recently, Farooq et al. (7) tested this hypothesis by observing the
different responses of yeasts and acid-fast bacteria to ozone under different
experimental conditions: (1) in  the presence of both ozone bubbles and ozone
residual; (2) in the presence of ozone residual alone; and (3) in the presence
of ozone bubbles alone.  They found that the primary microbicidal effect
occurred as a result of dissolved ozone.  The presence of bubbles enhanced
microorganism reduction  slightly, but the enhancement was not of such a
magnitude to affirm the validity of the bubble hypothesis.  Since the primary
effect was due to dissolved ozone, disinfection efficiency would not be
independent of dissolved ozone concentration.

     The project reported herein was initiated to evaluate various types of
ozone contacting devices operating in parallel on the same wastewater effluent,
so that the disinfection efficiency of ozone can be  optimized and operating
costs evaluated.  The types of contactors to be used in the study were
selected as representative  of a  variety of standard  gas-liquid mixing
principles in the chemical  engineering field and were not necessarily the most
efficient for wastewater effluent disinfection.  The thrust of the study was
not achievement of a specified microbial density in  the effluent, but rather
comparative log reductions  under controlled conditions with definition of the
process variables most  effectively influencing disinfection.  The total waste-
water flow available at the experimental pilot facility (described in the
next section) is approximately 150 /min.  Thus, only two contactors, each
with a design capacity of 75 /min, can be evaluated at any one given time.
A packed column is serving  as the base unit, the performance of which will be
compared individually with  all other contacting units.  Other contacting
systems to be investigated  in the future include: (1) a positive pressure
injector, (2) a bubble  diffuser, and (3) a stirred turbine reactor.  This
report concerns the comparison of the packed column with the jet scrubber.

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                                  SECTION 2

                                 CONCLUSIONS
     Results of this ozone contactor evaluation have indicated that a jet
scrubber type contactor is not efficient for effluent disinfection with ozone.
The most important factor affecting microorganism reduction in the jet
scrubber was ozone residual.  As the ozone residual levels increased, the
exhaust gas concentrations, by necessity, increased.  Maintenance of an ozone
residual in the jet scrubber, which operated in a concurrent flow configur-
ation, was predicated upon maintenance of a high concentration of ozone in
the gas phase in equilibrium with the liquid phase.  Performance of the jet
scrubber was further hampered by the exceedingly short residence time
(<3 seconds at 75 /min liquid flow rate).  Thus, microorganism reduction in
in the jet scrubber was poor.

     The packed column, which was operated in a countercurrent mode, exhibited
a higher mass transfer driving force.  Consequently, more ozone was utilized,
higher residuals were achieved, and microorganism reduction was better.

     The packed column significantly outperformed the jet scrubber with
respect to microorganism reduction and efficiency of ozone utilization.
Wastewater effluent quality interfered with disinfection in both contactors,
the most important variable being chemical oxygen demand (total and soluble)
and organic carbon.  Initial bacterial density was also an important factor
affecting log reduction of coliforms and fecal streptococci in both contactors.

     The packed column was superior to the jet scrubber with respect to percent
ozone utilization, regardless of effluent quality and the magnitude  of
applied dosage.  This superiority was significant at all dosage levels
employed.  With respect to actual ozone utilized, the packed column was
superior to the jet scrubber regardless of effluent quality, but the
difference between the contactors increased with increasing dosage.

     An analysis of variance of the ozone utilization data from a factorial
experiment indicated that effluent quality did not significantly affect
overall ozone utilization in both contactors.  However, linear regression
analyses of the data from each contactor at each individual dosage level
revealed that organic demand measured by TCOD, SCOD, and TOC significantly
affected ozone utilization in both contactors at high but not at low dosage
levels.  Coliform reduction was adversely affected in both contactors by
TCOD, SCOD, and TOC at applied ozone dosage levels <13.1 mg/Ji and by TKN and
organic-N at 19.5 mg/ applied ozone.  It was concluded that at low doses
(i.e., 4.9 and 9.7 mg/& ozone), ozone utilization was mass transfer limited,

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while at higher dosages (i.e.  >9.7 ing/5, ozone) it was reaction rate limited.
Coliform reduction was reaction-rate limited at all dosage levels.

     Ozone residual and ozone consumption (i.e., the difference between ozone
utilization and residual)  were significantly affected by effluent quality in
both contactors.

     Coliform reductions in the pilot plant effluent to levels less than
100 total coliform/100 mi  were achieved in the packed column only at an
applied dosage of 19.5 mg/&.   Fecal coliform levels less than 200/100 m were
approached in the packed column at 19.5 mg/Ji applied ozone, but not in the
jet scrubber at any dosage.

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                             SECTION 3

                          RECOMMENDATIONS
(1)  Studies with other contactors should be conducted in a manner
similar to that described in this report.  It is essential that gas-
liquid contacting be optimized to eliminate inefficient utilization of
the ozone generated.

(2)  Since ozone residuals are so transient and short-lived, more
accurate methods of measurement of such residuals should be devised so
that disinfection control by residual monitoring can be made possible.

(3)  In this study, applied dosage was varied by maintaining a constant
ozone gas concentration and varying the gas flow rate.  In subsequent
studies, dosage should also be varied by changing the ozone gas concen-
tration and maintaining a constant gas flow rate.  This will enable a
better determination of the optimum operating conditions for a specific
contactor.

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                                  SECTION 4

                            MATERIALS AND METHODS


SOURCES OF WASTEWATER EFFLUENT

Muddy Creek Wastewater Treatment Plant Effluent

     During the first few months of the project, secondary effluent from the
Muddy Creek Wastewater Treatment Plant served as the wastewater source for
the ozone disinfection studies.   This plant,  operated by the Metropolitan
Sewer Board of Greater Cincinnati, is a conventional activated sludge system
treating approximately 57,000 m^/day of domestic wastewater.

     On the day of an experiment, 20 m3 of Muddy Creek effluent were drawn
into a tank truck and transported to the experimental pilot plant located at
the Robert A.  Taft Laboratory building.  The  effluent was pumped from the tank
truck through a magnetic flow meter and split into two lines.  Both lines
were suitably valved to allow for any desired flow configuration.  One line
passed through a rotameter and control valve  and finally into the top of the
packed column.  The second line was fed into  a pump, where the pressure was
boosted to 380 kPa.  The wastewater then flowed through a rotameter into the
jet scrubber.

     Using the above mode of operation, an entire series of experiments was
performed on each contactor separately.  This experimental arrangement, which
was essentially a batch operation, permitted  the same effluent to be pumped
to each ozone contactor without the need for  parallel, simultaneous operation.

Pilot Plant Effluent at Robert A. Taft Laboratory

     Secondary effluent was also obtained from the conventional activated
sludge pilot plant located at the Robert A. Taft Laboratory building.  The
raw wastewater entering the plant was of mixed industrial and domestic origin.
Effluent from the final clarifier was pumped  through a magnetic flow meter,
and the flow split between the two contactors.  An optional mixed media
pressure filter was available for removing suspended solids from the effluent
prior to splitting the flow.  Data obtained under this arrangement were
collected with both contactors operating in parallel.

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 DESCRIPTION OF EQUIPMENT

 General

      All experimental work was performed  at  the  USEPA pilot plant facility
 located  at the Robert A. Taft Laboratory  building,  Cincinnati, Ohio.  The
 ozonation system consisted of ozone generation equipment and two generic
 type  contactors.  A flow schematic of  the ozone  pilot system is shown in
 Figure 1.   A block diagram is presented in Figure  2 showing a mass balance
 for ozone and effluent during a typical pilot run.

      Nominal design flow capacity for  each ozone contactor was 75 /min of
 secondary effluent.  The ozone generator  was capable of producing ozone at
 a. maximum rate of 3500 mg/min.  Since  the pilot  facilities were designed
 for evaluating two contactors in parallel, the maximum applied dosage per
 contactor was approximately 23 mg/.
        oo o
     TANK TRUCK
   FROM MUDDY CREEK
   TREATMENT PLANT
   PILOT PLANT
    CLARIFIERS
Ozone Generation
                                                     	AIR, OZONE

                        FLOW SCHEMATIC   OZONE CONTACTORS 	 SECONDARY EFFLUENT
                       Figure 1.  Schematic of Ozone Pilot Plant System
     Service  air  from the Robert A. Taft Laboratory building,  supplied at a
pressure of 600 kPa,  served as the source of air for ozone  generation.   A
standby 4 kW  compressor was available for air supply in the event  of failure
in the service air  system.

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                      SERVICE AIR
                                           Q,i  flow rate of air

                                           QSE = flow rate of secondary effluent

                                           DP   Dew Point
                         Q,=76 l/min
                         T=23C
                         P=0.5tPo
                         Ol=745mg/min
                                                  QsE=76 l/min
                                                  T=20C
                                                  Oj-lSmg/min
                        Figure 2.  Mass Balance on Ozone Pilot Plant

     The air was  filtered for removal  of particulates and  lubricants, then
dried by adsorption of water vapor on  activated alumina.   The  dryer con-
sisted of two parallel dryer beds, each containing 7.7  kg  of activated alumina.
The process air was passed through one of  the dryer beds,  where the dew point
was lowered to -78  C.  Approximately  15 percent of the dried  air was returned
for regenerating  the alumina in the  other  dryer bed.  The  dryers then auto-
matically reversed  their function, placing the regenerated bed on line for
drying air while  the other bed underwent regeneration.  The dried air was then
filtered for removal of any carry-over adsorbant and  continuously monitored  by
an in-line dew-point meter.

     The dried air  was reduced in pressure from 600 kPa to 55  kPa and then
split into two lines, each equipped  with  a rotameter  and valve for flow con-
trol between 75 and 500 /min.  The  gas then entered  the dual  ozonator, which

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was air-cooled and  contained six plates per unit.  Power was applied  between
200 and 2000 watts, depending upon the ozone concentration and  air  flow
desired for the particular experimental run.  The temperature of  both ozone-
enriched gas streams  was  measured upon exiting the ozonator.  The two streams
were recombined to  obtain a homogeneous mixture and then split before entering
rotameters with a range between 20 and 130 A/min.  After the rotameters,
seperate gas lines  fed  the packed column and the jet scrubber.  An  equipment
description for pilot items is shown in Table 1.
                     TABLE 1.  LIST OF EQUIPMENT AND SPECIFICATIONS
     Description
                        Manufacturer
                             Model no.
                                              Capacity
Prefilter
Dryer
Afterfilter
Dew point monitor
Ozonator
Pall Trinity Micro Corp.
Pall Trinity Micro Corp.
Pall Trinity Micro Corp.
Shaw
Computerized Pollution
MCC1001SV160
25HA1
MCC1101EC12
Mini Hygrometer
OZ-180-G
-
700 I/rain 6 -40
-
-20 C to -80 C
4 kg 0,/d

C



   Packed column
Abatement Corp.

Corning Glass
                                               230 mm D X 3.1 m
                                                              Intalox Packing, Size:
                                                              13 ram 5 25 mm
Jet scrubber
Decomposer
Multi-media filter
Ozone gas analyzer
Ozone residual
analyzer
R. P. Industries
Chromalox
Baker Filtration Co.
Dasibi Environmental Corp.
Fischer f, Porter
Dynactor Model
DY 12-10
GCII330
HRC-30D
1003-AH
17L2112A1
76 1/min
100-350 C
370 1/min
-
0 - 2.5 rag 03/1

Packed Column

     The packed  column was a 230 mm diameter glass column  3.1  m in length.
The packing  consisted of either 13 mm or 25 mm ceramic  intalox saddles.   A
teflonredistrubutor plate was located midway in the column to  redirect the
liquid towards the  center of the column.  The packing rested on a  ceramic
support plate at  the bottom of the column.  Secondary effluent entered the
top of the column (Figure 3)  and exited at the bottom.  The residence time
of the secondary  effluent was 20 seconds at a flow rate of 75  /min.   Ozone
was injected at the bottom of the column, flowed upward and countercurrent
to the secondary  effluent, and exited at the top.  Pressure taps were located
in the gas lines  at the bottom and top of the column for determining  the
differential gas  pressure during an experimental run.  A photograph of the
entire packed column is shown in Figure 3.

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  Figure 3.  View of Packed Column
Figure 4.  View of Jet Scrubber
Jet Scrubber Contactor

     The jet scrubber was a stainless steel liquid-gas contactor in which
secondary effluent was pumped at a pressure of 280 kPa through an orifice
into a 300 mm diameter chamber.   The resulting pressure drop caused minute
droplets to form.   The ozone entered near the orifice and both components
(secondary effluent and ozone) flowed concurrently down the chamber.  The
combined stream then flowed to a bottom outlet where the contacting gas was
separated from the effluent.  A portion of the gas was aspirated back into
the upper chamber by the liquid flowing through the orifice and recycled to
the inlet area.  A photograph of this contactor is shown in Figure 4.
Figure 5 shows the action of the jet orifice producing droplets.

Ozone Decomposer

     The exhaust gas from each of the contactors was directed to an ozone
decomposer.  An electric heater was used to increase the exit gas temperature
to between 260 C  and 290 C to insure destruction of the ozone in the off-
gases.  Figure 6 is a photograph of the decomposer.
                                      10

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              Figure 5.                                 Figure 6.
        Jet  Action of Scrubber               View of Ozone Gas Decomposer
      (removed from contactor)

SAMPLE COLLECTION

Gas Samples

     Ozone gas sampling ports were located at the outlet of the ozone
generator, the exhaust gas line from each contactor, and the exit gas line
following the ozone decomposer.  Prior to sample collection the gas line was
purged for approximately one minute to insure equilibrium conditions.

     All gas samples were analyzed for ozone by the standard iodometric
method, based on the report of Birdsall, Jenkins, and Spadinger (6).  A
specified dosage condition was set by collecting a grab inlet gas sample
and measuring  the ozone concentration iodometrically.  Continuous measurement
of ozone in the gas stream was made subsequent to the grab analysis to provide
assurance of a steady state ozone concentration.  The continuous monitoring
for operating control was accomplished by a Dasibi Environmental Corporation
(Glendale, California) ozone analyzer.  Recalibration of the latter instrument
was performed at the start of each day.

     Exhaust gas samples from the ozone contactors were collected and analyzed
iodometrically immediately after collection of ah effluent wastewater sample.
Wastewater  Effluent  Samples

     Valved sampling ports were  located on the  influent and  effluent  lines
of both ozone contactors.  Prior to actual sample  collection,  the  sample
                                       11

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lines were flushed for approximately 30 seconds to make certain that any
build-up of solid materials or microorganisms would be eliminated.

     All samples were grab samples.   Coliform MPN tubes were inoculated and
ozone residuals were measured immediately after sample collection.  Samples
taken for physical-chemical characterization and for pathogen enumeration
were preserved by refrigeration for no more than one hour, according to
Standard Methods (1).   Samples for chemical oxygen demand (COD) and total
organic carbon(TOC) analyses were preserved by acidification with sulfuric
acid and hydrocloric acid, respectively.

     Samples were collected approximately 30 minutes after start-up or a
change in experimental conditions.  The sampling schedule was based on the
flow rate such that sample collection followed the flow of a single slug of
liquid through the treatment process.

OZONE CONCENTRATION

Ozone Gas Analysis

     Ozone concentration in the inlet and exhaust gas was determined
iodometrically (6).  The ozone-air lines were first purged by allowing the
gas to flow into a solution of approximately 1 N potassium iodide (KI).
Following purging, the gas stream was then directed through a series of
two 500 ml gas washing bottles, each containing approximately 400 ml of a
1 percent KI solution.  The exit gas from the second gas washing bottle passed
through a wet test meter for determination of the gas sample volume (Figure 7),
The solutions in the gas washing bottles were transferred to a 1500 ml beaker
and acidified to a pH of less than 2 by the addition of 20 percent sulfuric
acid.  This solution was titrated to the starch end point with 0.050 N sodium
thiosulfate (Na2S203).  The titrant was standardized daily against
potassium dichromate (6).
                Figure 7.   View of Gas Analysis Work Station
                                     12

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Ozone  Residual  Analysis

     A modification  of the amperometric  titration  method  for  total  residual
chlorine  (1)  was  used for determination  of effluent  residual  ozone.   Samples
were collected  at the effluent lines  of  both contactors in  a  200 ml sample
bottle containing 1  ml of a 1 percent KI solution  and  4 ml  of pH 4  acetic
acid-sodium acetate  buffer.   The sample  was immediately transferred to  the
titration cup and titrated with 0.0050 N Na2S203 to the amperometric end point.
The titrant was standardized daily against a standard  iodine  solution.
CHEMICAL AND PHYSICAL CHARACTERIZATION OF WASTES

     Total  chemical oxygen demand  (TCOD), soluble chemical oxygen demand (SCOD)
after  filtration  through  a Whatman glass  fiber filter,  total organic carbon
(TOC),  total  suspended solids  (TSS), volatile suspended solids (VSS), ammonia
nitrogen  (NHj-N), total Kjeldahl nitrogen  (TKN), manganese  (Mn) , iron (Fe)  ,
pH, and turbidity were determined according to the USEPA Methods Manual  (15).
Nitrate nitrogen  (N03-N)  and nitrite nitrogen (NC^-N) were determined by the
automated hydrazine reduction  method  (10).

BACTERIOLOGICAL METHODS
     Samples  collected for bacteriological  analysis,  both before and after
ozonation,  were mixed with sodium thiosulfate (1) .  Total and fecal  coliforms
were enumerated by the 5-tube,  4-dilution most probable number (MPN) technique
(1).   Presumptive medium  was  lactose broth  (Difco), and confirmatory medium
for total coliforms was brilliant green  bile broth (Difco).  EC broth was used
as confirmatory medium for fecal coliforms.  Fecal streptococci were enumerated
by the membrane filter technique  (1) using  KF streptococcus agar (Difco).
Isolation and enumeration of  Salmonella  spp. were performed using a  modifi-
cation of the Kenner  and  Clark Method  (11)  (see Appendix A  for a detailed
description of  the method.)

STATISTICAL DATA  HANDLING AND  EXPERIMENTAL  DESIGN

     Testing  of the pilot plant ozonation process  was  performed according  to
predetermined factorial arrangement.   The arrangement, called a split-split-
plot design,  was  modelled according to Anderson and McLean  (4).

     Secondary  effluent was  pumped to  each ozone contactor  at a rate of
75 J?,/min, while ozone gas,  generated  from air at a constant concentration  of
9.7 mg ozone/  air, was fed  to both contactors at  various gas flow  rates.
Dosage was determined by multiplying  the concentration of  ozone in the inlet
gas by the  ratio  of the gas  to liquid  flow rates.  Four different pre-selected
dosage levels were used,  and grab  samples of ozonated  effluent from both con-
tactors were  taken for bacteriological and chemical  analysis.  Both contactors
received  the  same dosage  at  any given  time,  but the  order in  which  the  four
dosage levels were applied in any  given  experiment was randomized by referring
to a random number table.   Each entire experiment  was  considered a  "whole
plot"  and was replicated  on  six different days  (R^).   The "split-plot"
consisted of  four dosage  levels (D-)within a replicate experiment,  and  the
"split-split-plot" consisted of the two  contactors (C^) compared at each
dosage level  within  each  replicate experiment.

                                       13

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     Separate analysis of variance (ANOVA) were performed to compare the two
contactors on the basis of six dependent variables (performance criteria) as
a function of one independent variable (applied ozone dosage) .

     The performance criteria were log total coliform reduction, log fecal
coliform reduction (log Ng/N, where NQ = the initial number of coliform
bacteria and N = the number remaining after treatment) , percent ozone
utilization, total ozone utilized  (mg/#), ozone residual  (mg/), and ozone
consumtion  (mg/).

     Applied ozone dosage was defined as  follows:

          D0 = y^/L                                                       (1)

where     DQ = applied dosage  (mg  OT/^
          y, = ozone concentration  in  the  inlet  gas  (mg  0,/jl   )
            i                                              j   gas
          G  = gas flow rate  (&   /min)
                               gas

          L  = liquid  flow rate  (jL . /min).

     Percent ozone utilization was  defined as  follows:

             y - y
                     (100)
where y2 = ozone  concentration  in  the  exhaust  gas  (mg 0 / g   ) .
     Total ozone utilization was  defined  as  follows:                       (3)
                                                     ^1  "  y2
          U  = Dosage x  fraction  utilized =  y  (G/L)  - = G/L (y1  - y-) ,
                                                        y~i
where U  = total ozone utilized  (mg/&).


     Ozone consumption was  defined  as  follows:

        '  Co = Uo  -  Ro>                                                    C4)

where Co = consumption  (mg/A) ,  and  R0  = ozone  residual  (mg/) .


     In each analysis of variance (ANOVA) there  were three "main effects"
 (i.e., Cj. D . , and R.) under  investigation,  and  two  "interaction effects"
 (i.e., R^C^ and DjC^J.   The contactor  main effect (C^)  tested the difference
 in  performance  (i.e., total or  fecal coliform  log reduction  (TCLR or FCLR)
 ozone utilization, etc.)  between  the two  contactors.  The dose main effect
 (Dj) tested the effect of ozone dosage on the  performance of both contactors.
                                      14

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The replication main  effect  (RjJ  tested  the  effect of different days on the
performance  of both contactors.   Since the only variable which was not
controlled from day to  day was  effluent  quality,  R^ actually tested the effect
of effluent  quality on  contactor  performance.  The contactor-dosage
interaction  effect  (CkDj) tested  whether the difference in performance
between the  two contactors was  consistent or changed at each dosage level.
Finally, the contactor-replication  interaction effect  (C^R^ tested whether
the difference in performance between the two contactors was consistent or
changed from day to day.

     In addition to the ANOVA's described above,  data were subjected to
linear and stepwise multiple regression  analyses to evaluate the effects of
different wastewater parameters individually or in concert on the selected
performance  criteria.   Data analyses were facilitated by an IBM 370 computer,
using Biomedical Computer Programs  BMD02V (Analyses of Variance for Factorial
Design) and  BMD02R ( Stepwise  Regression) (5).
                                      15

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                                  SECTION 5

                          RESULTS AND DISCUSSIONS

OZONE GENERATOR OUTPUT

     The ozone generator was designed to deliver 4 kg 0,,/d.   Initial evalu-
ation of ozone output revealed that less than 2 kg/d were being generated.
A dew point monitor was inserted into the conditioned air line following the
dryer and indicated that the dew point of the air was above -20  C.  The
purge rate to the dryer was increased and the dew point subsequently fell
below -40 C.  This caused the ozone output from the generator to rise to the
specified 4 kg/d level.  No further problems were experienced in either main-
taining a dew point below -40  C or achieving the desired ozone output.

Mapping of Ozone Generator

     Before initiating the contactor evaluation phase of the investigation,
it was necessary to establish the relationship between electrical power, gas
flow rate, and ozone concentration in the gas to permit evaluation of the
ozone generation efficiency of the CPAC ozone generator under various experi-
mental conditions.   This was accomplished by mapping the ozone generator,
using only one module of the dual unit to insure accurate gas flow control.

     Ozone concentration in the gas was measured as a function of electrical
power at various gas flow rates.  Power was ajusted from 0.25 to 2.0 kw at
0.25 kw increments.  Results are shown in Figure 8.  At a constant gas flow
rate, ozone concentration increased with power until a plateau was reached.
After this point, further increase in power actually resulted in a reduction
in ozone concentration.

     The data from Figure 8 were rearranged to illustrate ozone production,
in terms of kg/h, as a function of gas flow at various power levels.  Results
are shown in Figure 9. It is evident that ozone production increased with
gas flow rate, followed by a declining production as optimum gas flows were
exceeded, except at the 0.25 kw power level.

     The data were again rearranged to demonstrate the power requirements
necessary to produce a unit weight of ozone as a function of gas flow rate
at specified power levels.  Results are presented in Figure 10.  It is clear
that, at low gas flow rates, considerably more energy was required to
generate a unit weight of ozone than at higher flow rates.

     The above mapping experiment can provide useful information to the
                                     16

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                                                   G = GAS FLOW (l/min)
01
E
<

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        50
       40
        30
       20
        10
                                          0.25 ft*
                                         I
                                        I
                 20
40
                        60       80       100     120       140
                          GAS FLOW (l/min)

Figure 10.   Effect of Gas Flow Rate on Power Consumption
design engineer in sizing ozone generator equipment and to the plant operator
in selecting an operating condition that would deliver the required ozone
capacity at the minimum power requirement per unit weight of ozone.  Thus,
to maximize ozone production (kg per unit time) higher gas flows are needed
(Figure 9), resulting in improved power efficiency (Figure 10).  However,
higher power levels are also needed (Figure 9), thereby offsetting the
improved production efficiency by a greater energy usage per kg ozone  (Figure
10).   Conversely, to maximize the ozone concentration, lower gas flows  are
needed (Figure 8), resulting in increased power per kg ozone produced  (Figure
10) and lower ozone production in terms of kg per unit time (Figure 9).

PHASE 1   BATCH OPERATIONAL MODE

     In this phase of the investigation, experiments were performed on  waste-
water effluent which was transported by truck from the Muddy Creek Wastewater
Treatment Plant (MCWTP).   Since the effluent was a batch source not subject
to continual change in quality, experiments were conducted on each contactor
separately rather than in parallel.
                                      18

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Wastewater Effluent  Characteristics
     Table 2  summarizes  the  mean,  standard deviation,  and range of the efflu-
ent characteristics  of the Muddy Creek effluent from August 2,  1976,  to Novem-
ber 2, 1978,  the experimental  period for this  phase of the study.

     It is evident that  the  levels of TSS, turbidity,  and TOC were low, and
there was very  little difference between TCOD  and SCOD.   Most of the TKN
was composed  at NH^-N.   In general,  the MCWTP  effluent quality was excellent.

                      TABLE 2.  SUMMARY OF MUDDY CREEK EFFLUENT CHARACTERISTICS
Parameter
Temperature (C)
TCOD, mg/
SCOD, mg/
TOC, mg/
TSS, mg/
TURB, JTU
TKN, mg/J,
NHj-N, mg/H
ORG-N, mg/Jl
Log total coliform
density
Log fecal coliform
density
Log fecal streptococci
density
Mean
21
30
24
10.3
6.7
3.8
8.3
7.2
1.6
5.77
5.38
4.19
Standard
Deviation
3
10
9
5.2
3.8
1.5
8.2
7.6
1.0
0.51
0.64
0.71
Range
14-24
18-56
15-49
4.4-25.5
2.4-20
2.3-7.6
1.9-37.8
0.1-34
0.2-3.8
4.90-6.73
4.36-6.54
2.70-5.23
Determination of Mass  Transfer  Coefficients

     Mass transfer  coefficients in the packed column and jet scrubber were
determined using MCWTP effluent.   Gas  flow rates were varied between
35 and 150 Vmin.   Ozone  was  measured  in the inlet and exhaust gases and in
the liquid emerging from  the  contactors.

     The quantity of ozone  that could  be absorbed by the secondary effluent
was limited by  the  inlet  ozone  gas concentration as related to Henry's law.
This relationship is described  by the  following equation:
     y* = Hx

where y* = partial  pressure  of ozone in the gas in equilibrium with the
           dissolved  ozone  in the liquid (mm Hq)
(5)
                                      19

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      H  = Henry's  constant  (mm Hg/mol fraction of ozone in the liquid)

      m  = mol  fraction  of ozone in the secondary effluent
            (moIs  03/mol  liquid).

     Henry's  constant  defining the relationship between the partial pressure
 of  ozone and  the  concentration of ozone in the liquid can be obtained  from
the International Critical Tables  (16).  Since  the units  of the terms in
equation 5 were tedious to manipulate,  they were  converted to the following
more useful terms by incorporating  relationships  defined  in the gas laws:

     y* = concentration of ozone  in the gas in  equilibrium with ozone in
          the liquid (rag Gig/litre  gas),

     H  = litres of liquid/litre  of gas,

     x  = concentration of ozone  in the liquid  (mg Oy'litre liquid).


     The magnitude of Henry's  constant  is  substantially affected by temper-
ature, as shown in Figure  11.   As  temperature  increases,  the value of
Henry's constant increases.
                         8.0,	
                         7.0
                         6.0
                         5.0
                         4.0
                      c/>  3.0
                         2.0
                         1.0
                                              I
                                 10     20      30     40
                                      TEMPERATURE (C)
            Figure 11.  Variation of Henry's Constant  with Temperature
                                      20

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     The mass transfer coefficients for the packed column were determined
using the following equation:

     N = G  (7l   y2)  - KgVa  (A ylm)                                         (6)

where N = ozone transferred  from the  gas phase  into the secondary
          effluent  (mg/min) ,

     G = gas flow rate  (litres gas/rain) ,

     y1= ozone concentration in the inlet  gas  (mg/),

     y2= ozone concentration in the exhaust gas  (mg/) ,

     KgVa = overall mass  transfer  coefficient  (litres  gas/minj ,

     A/-,  = log mean  concentration difference  of ozone in the  gas phase
            across  the entire column  (mg/)
The term Ay1  is defined by the following equation:

            (71 - 71*) - (72 - 72*)
          = -
       1m
           = -                                       (7)
              In
                 (72  -  72*)
where y, *  =  ozone  concentration (mg/ )  in the  gas  phase  in  equilibrium with
             the  ozone residual  in the liquid at  the  bottom  of  the  column,  as
             defined by Henry's  Law (equation 5),

and y2*  =  ozone  concentration (mg/&)  in the gas  phase  in equilibrium with
           the  ozone residual  in the liquid at  the  top  of the column.

     In the packed  column, y->*  -  0  because  there was no  ozone residual  in  the
liquid entering the  top of the  column.   Thus,  equation 7  simplifies to:

             (/! -  7!*)   72
      7lm  = - (       *5                                                (8)
               In
                    72

     The mass transfer coefficients  for  the  jet  scrubber were computed  in  the
same manner.  However, since  the  flow  configuration  in  the  jet  scrubber was
concurrent rather than countercurrent, yj* = 0 because  the  liquid  entering
the contactor contained no  ozone  residual.   Thus,  for the jet scrubber,
equation 7 simplifies to  :

            y-,-  (77   y/)
     A/lrn = - ~ -                                                  (9)

            111   (72 - 72*)

                                       21

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     Detailed results from these experiments are given  in Appendix  B.   The
mass transfer coefficients for both contactors at various flow rates  are
illustrated in Figure 12.  The data indicate that the mass transfer coeffi-
cients for the packed column were more than twice the value determined for
the jet scrubber at the gas flow rates studies.

     Henry's Law states, by definition, that as ozone residual increases,
ozone concentration in the gas phase in equilibrium with the  residual  also
increases.  This means that transfer is inhibited by high ozone  residuals.
A countercurrent flow configuration, such as in the packed column,  has the
advantage not only of contacting the liquid containing  the highest  ozone
residual with the gas containing the highest ozone concentration (i.e.,  at
the bottom of the column), but also of contacting the liquid  containing the
least ozone residual with the gas containing the lowest concentration  of
ozone (i.e., at the top of the column).  This tends to  equalize  the concen-
tration driving force and mass transfer rate across the entire length  of the
column.
                 200
                 150
                 100
                 50
                                              PACKED COLUMN
                               I
     Figure 12.
              50           100           150
                 GAS FLOW RATE (l/minj

Effect of Gas Flow Rate on Mass Transfer Coefficient
     In contrast, the jet scrubber, which operates in a concurrent  flow
configuration, maintains a high concentration gradient at the  inlet end.   As
the residual increases, the exit gas concentration, which must be  in equi
librium with the residual, also increases.  This substantially limits the
concentration driving force in the jet scrubber and explains the lower mass
transfer coefficients relative to those of the packed column.
                                      22

-------
     Both contactors had relatively  short  contact  times  (approximately
20 seconds for the packed  column  and 3  seconds  for the jet  scrubber,  at  a
liquid flow rate of 75  /min).  This tended  to  hinder both  mass  transfer and
ozone utilization.  Longer contact times would  permit the dissolved  ozone to
react with oxidizable constituents in the  secondary effluent,  lowering the
ozone residual and increasing  the overall  ozone concentration  driving force.

Ozone Utilization

     Ozone utilization, as  defined earlier,  was  evaluated in both contactors
from the same data base used to compute the  mass transfer coefficients.

     The quantity of ozone  that can  be absorbed  by water is limited by the
temperature of the water and the  concentration  of  the ozone in the gas stream.
Thus, the maximum ozone residual  that can  be obtained in water is fixed  by
Henry's Law (equation 5).   However,  the results  from experiments with secon-
dary effluent revealed  that ozone transfer was  greater than could be  predicted
by Henry's Law.  The demand of the secondary effluent created  by the  presence
of oxidizable organic and  inorganic  compounds enabled more  ozone to be
transferred to the wastewater.

     Figure 13 summarizes  the  percent ozone  utilization data in both
contactors as a function of applied  ozone  dose.  Results indicate that the
percent ozone utilized  by  the  packed column  was  substantially  greater than
the jet scrubber.  Thus, the packed  column was  superior to  the jet scrubber
from the standpoint of  mass transfer efficiency and percent ozone utilization
efficiency.
                      80
                    -  60
                      20
                                                PACKED COLUMN
                                                  JET SCRUBBER
                              4       8      12      16
                                  OZONE DOSAGE (mg/I)
        Figure 13.  Effect of Ozone Dosage on Percent Ozone Utilization
                                      23

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Ozone Dosage

     Dosage was defined earlier in equation  (1):  DQ = y1G/L.

     There are two ways to vary ozone dosage:  (1) change  the  G/L  ratio while
maintaining a constant gas concentration, or  (2)  change the ozone gas
concentration while maintaining a constant G/L ratio.  However, utilization
can be changed by maintaining dosage constant and increasing  the  concentra-
tion of ozone in the gas  (i.e., increase y^  and decrease  G/L).  Figure 14
illustrates the change in percent ozone utilization in both contactors as
a function of G/L at a constant dosage level.  It is clear that as G/L
increased  (or y  decreased), percent ozone utilization decreased, even though
the applied dosage was constant.  Caution must be exercised in using these
data, because increased y-, values require increased power input per unit
weight of ozone when the dosage is constant  (see  Figures  8 and 9).  Thus,
power must be factored into any evaluation to establish optimum performance
criteria.  The most cost-effective operating condition for ozone  disinfection
does not necessarily comprise the lowest ozone dosage.
               100
                80
               BO
             LU 40
               20
          Figure 14,
    0.5         1.0         1.5        2.0
   RATIO OF GAS FLOW RATE TO LIQUID FLOW RATE (G/L|

Effect of G/L Ratio on Percent Ozone Utilization
   at a Constant Dosage of 8.0 mg/
 Effect  of  Packing  Size  on  Packed  Column Performance

      After completing Phase  I  of  the investigation, it was necessary to switch
 from the MCWTP  effluent to the R.A.  Taft Laboratory building pilot plant
 effluent so that both contactors  could be operated in parallel.  The overall
 quality of the  latter effluent was inferior to the MCWTP effluent.  This
 factor  resulted in excessive pressure drops in the packed column when the
 system  was operated at  a liquid flow rate of 75/min.
                                      24

-------
      To compensate for the increased pressure drops in the packed column, it
 was necessary to increase the packing size from 13 mm to 25 mm ceramic inta-
 lox saddles.  This modification, in effect, lowered the surface area of the
 packing and consequently enabled operation of the column at more reasonable
 pressure drops (i.e.,  <300 mm H20).   However,  this also affected the mass
 transfer efficiency of the column.   Table 3 demonstrates the effect of packing
 size on the overall mass transfer coefficients of the packed column at.various
 gas flow rates.

      The overall  mass  transfer coefficient (KgVa)  consists of the product of
 the mass transfer coefficient (KgV)  and the surface area per unit volume
 of packing (a).   Although the KgVa did not substantially change with packing
 size,  the total .mass transfer of ozone into the liquid over the entire column
 decreased as a direct  result  of the  decrease in surface area of the packing.
           TABLE 3.   EFFECT OF PACKING SIZE ON OVERALL MASS TRANSFER
      COEFFICIENTS (Kg Va) OF THE PACKED COLUMN AT VARIOUS GAS FLOW RATES
 Gas flow
rate, /min
                                           Kg Va, & gas/min
13 mm packing
(KgV, /min/m)
25 mm packing
(KgV, fc/min/m)
     37
     74
    110
    147
      84
   (0.135)

     163
   (0.261)

     175
   (0.280)

     205
   (0.329)
      46
   (0.180)

      66
   (0.258)

      73
   (0.285)

      86
   (0.336)
Contactor  Performance

Total  Coliform Reduction--

     During the three month period  between August  2,  1976,  to  November 2,  1976,
a  total  of 40  experiments were  performed with  MCWTP  effluent to  evaluate  the
total  coliform reduction efficiency of the packed  column  and the jet  scrubber.
The  data were  grouped into three  segments according  to  the  magnitude  of the
applied  ozone  dosage  (i.e.,  low,  moderate, and high).   All  observations were
taken  in matched pairs  to facilitate direct comparison  between the  two
contactors.  The t-test for matched pairs was  performed according to  Natrella
 (17) after confirming that the  data were normally  distributed.   A significance
level  (2)  of 0.05 was chosen  for  all tests.  The data are summarized  in
Table  4.
                                      25

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                           TABLE 4.  DIFFERENCE  IN TOTAL COLIFORM LOG  REDUCTION (TCLR)
                                 BETWEEN THE PACKED COLUMN AND JET SCRUBBER  AS  A
                                   FUNCTION OF APPLIED DOSAGE  (MCWTP EFFLUENT)
NJ
CT)

Ozone
Level
Low
Mod-
erate
High
All
dosage, mg/
Range Mean
2.4- 4.6 3.6
5.9-10.0 7.5
11.8-18.6 13.9
2.4-18.6 7.4
Number of
data points
(n)
14
18
8
40
Mean TCLR
(Std. dev.)
Packed column Jet
1.99
[0. 63)
2.77
CO. 59)
2.41
CO. 96)
2.43
CO. 76)
scrubber
1.36
CO. 87)
2.32
CO. 64)
2.21
CO. 92)
1.96
(0.89)
Mean
difference
(Std. dev.)
0.63
(0.77)
0.45
CO. 52)
0.21
CO. 53)
0.46
CO. 62)
t
t (a=0,05)
3.06 2.16
3.67 2.11
1.12 2.36
4.69 2.02

-------
     The t-statistics  in Table 4 and subsequent tables were calculated  from
the following equation (17):
     t = xd"
(10)
where x, = mean difference  in  TCLR between contactors, S, = standard deviation
of the difference, and n  =  number of data points.  It is clear that total
coliform reduction was significantly greater in the packed column than  in  the
jet scrubber at the  low and moderate dosage levels but not at the high  dosage
level.  When considering  all dosage levels combined (n = 40), TCLR in the
packed column was significantly greater than that in the jet scrubber.

Fecal Coliform Reduction--

     The fecal coliform data were analyzed similarly and summarized in  Table 5,
The fecal coliform data reflect the same trends as the total coliform data.
The packed column significantly outperformed the jet scrubber with respect to
fecal coliform reduction  at low and intermediate dosage levels but not  at  the
high dosage level.   When  considering all dosage levels, the packed column  was
significantly better than the  jet scrubber with respect to FCLR.
                 TABLE 5. DIFFERENCE IN FECAL COLIFORM LOG REDUCTION (FCLR)
                     BETWEEN THE PACKED COLUMN .AND JET SCRUBBER AS A
                      FUNCTION OF APPLIED DOSAGE (MCWTP EFFLUENT)
Number of
Ozone dosage, mg/l data points
Level Range Mean (n)
Low 2.6- 4.6 3.6 13

Mod- 5.9-10.0 7.5 17
erate
High 11.8-18.6 14.0 8
All 2.6-18.6 7.5 38

Mean FCLR
(Std.
Packed column
2.28
(1.27)
3.27
(1.12)
3.09
(1.33)
2.89
(1.27)
dev. )
Jet scrubber
1.42
(1.15)
2.76
(1.09)
2.53
(0.90)
2.25
(1.21)
Mean
difference
(Std. dev/
0.86
(1.10)
0.51
(0.86)
0.56
(0.98)
0.64
(0.98)

t
) t (o=0.05)
2.82 2.18

2.45 2.12

1.62 2.36
4.02 2.03

Fecal Streptococcus  Reduction--

     The difference  in  efficiency between the two ozone contactors with
respect to fecal  streptococcus reduction are presented in Table 6.   It is
clear that the packed column significantly outperformed the jet scrubber with
respect to fecal  streptococcus reduction at all dosage levels studied.
                                      27

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               TABLE 6.  DIFFERENCE IN FECAL STREPTOCOCCUS LOG REDUCTION (FSLR)
                       BETWEEN THE PACKED COLUMN AND JET SCRUBBER
                     AS A FUNCTION OF APPLIED DOSAGE (MCWRTP EFFLUENT)
Number of
O'one dosage, m/i data points
Level Range Mean (.n)
Low 2.6- 5.S 3.4 10

Mod- 6.0-8.6 ".3 13
erate
High 10.0-14.6 12.7 6

All 2.4-14.6 7.1 29

Mean FSLR
(Std. dev.)
Packed column
1.
to.
->
10.
3 .
(.0.
T
10.
63
40)
65
67)
12
48)
.39
.SO)
Jet scrubber
1.
(0.
-)
to.
-1
to.
1 .
to.
36
S7)
,28
86)
.17
65)
.94
S3)
Mean
difference t
(Std.
0.
(0.
0.
to.
0.
to.
0.
to.
dev.) t (a=0.05)
27 3.05 2.26
28)
.37 4.04 2.18
33)
95 3.S8 2.57
60)
.45 5.39 2.05
.45)
Salmonella Reduction--

     Attempts were made to quantify the density of Salmonella spp. before and
after the ozone contactors to evaluate the  disinfection efficiency of both
contactors with respect to enteric pathogens.   The method involves a 3-tube
MPN procedure (see Appendix A) and is limited  in precision and accuracy.  A
total of 20 samples were analyzed for Salmonella spp.  in the MCWTP effluent
entering the ozone contactors, plus an additional 39 matched pair samples
exiting the contactors.  The geometric mean Salmonella density in the 20 samples
of MCWTP effluent entering the' contactors was  only 180 organisms/10 liters.
Many of the samples from the ozone contactors  contained too few numbers to
measure.  The data are summarized in Table  7.

     Of the 39 total samples from each contactor analyzed for Salmonella spp.,
28 from the packed column and 24 from the jet  scrubber contained insufficient
numbers to quantify as signified by the "<" symbol.  Thus, it is virtually
impossible to quantitatively assess the Salmonella reduction efficiency of
either contactor.
Ozone Utilization--

     Ozone utilization data were analyzed  in  the same manner as the bacteri-
ological data.  Results are summarized  in  Table 8.

     It is clear from Table 8 that  ozone utilization in the packed column was
significantly higher than the jet scrubber at all dosage levels studied.  In
addition, the difference in utilization appeared to increase with increasing
dosage.  Thus, the packed column was  a  more efficient ozone contactor than
the jet scrubber with respect to total  ozone  utilized, and the relative
efficiency increased with increasing  dosage.
                                      28

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TABLE 7.  DENSITIES OF SALMONELLA SPP.  BEFORE AND AFTER
               THE OZONE CONTACTORS  (MCWTP EFFLUENT)
03 Dose,
mg/&
2.5
2.8
3.0
3.6
3.6
3.6
3.6
3.8
3.8
6.0
6.0
6.4
6.9
7.2
7.4
7.4
7.5
7.5
7.6
7.8
7.9
7.9
7.9
8.0
8.6
10.0
11.2
12.0
12.0
12.4
13.2
13.5
14.2
14.2
14.2
14.5
14.5
14.8
17.7
Influent
No./lO liters
18.2
280
280
7.2
7.2
7.2
2300
86
18.2
7.2
86
1900
780
2300
730
15000
7.2
1280
7.2
480
480
1280
1900
480
480
780
360
2300
15000
42
920
42
7.0
46
150
7.0
46
150
920
Effluent
No./lO liters
Packed
column
<6
7.2
<6
<6
<6
<6
<300
7.2
<6
<6
<6
18.2
6
<300
<300
360
<6
7
<6
<6
46
<4
<6
7.2
<6
<6
<300
<300
<300
<3.6
920
<3.6
<6
<6
<6
<6
<6
72
186
Jet
scrubber
7.2
7.2
480
<6
<6
<6
360
<6
7.2
<6
<6
18.2
18.2
<300
<300
<300
<6
18
<6
<6
<6
7
86
7.2
<6
18.2
<300
<300
<300
7.2
2200
18
<6
<6
<6
<6
<6
<6
420
                            29

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                TABLE 8.  DIFFERENCE  IN OZONE UTILIZATION BETWEEN THE PACKED COLUMN AND
                    JET SCRUBBER AS  A FUNCTION OF APPLIED DOSAGE (MCWTP EFFLUENT)
Number of Mean ozone utilization, mg/
Ozone dosage, mg/J. data points (Std
Level Range Mean (n)
Low 2.4- 4.6 3.6 14

Mod- 5.9-10.0 7.5 18
erate
High 11.9-18.6 13.9 8

All 2.4-18.6 7.4 40

Packed column
2.9
(0.6)
5.3
(1.0)
7.4
(1.6)
4.9
(2.0)
. dev.)
Jet scrubber
1.7
(0.3)
3.1
(1.0)
4.0
(1.2)
2.8
(1.2)
Mean
difference
(Std. dev.)
1.2
(0.6)
2.2
(1-1)
3.4
(1-8)
2.1
(1.4)

t
t (a=0.05)
8.1 2.16

8.3 2.11

5.2 2.36

9.6 2.02

Ozone Consumption--

     The  contactors were  also evaluated with respect to ozone  consumption
(i.e., utilization minus  residual).   Table 9 summarizes these  data.

     It is  evident that ozone consumption in the  packed column was signifi-
cantly higher than in  the jet scrubber at all dosage levels  studied.  Also,
the difference in consumption between the contactors increased with dosage,
just as did the difference in utilization (Table  8).  The pattern expressed
by the change in ozone utilization and consumption  as a function of dosage
was consistent.
            TABLE 9.  DIFFERENCE IN OZONE CONSUMPTION BETWEEN THE PACKED COLUMN AND
                JET SCRUBBER AS A FUNCTION OF APPLIED DOSAGE (MCWTP EFFLUENT)
Number of
Ozone dosage, mg/5, data points
Level Range Mean (n)
Low 2.4- 4.6 3.6 14
Mod- 5.9-10.0 7.5 18
erate
High 11.8-18.6 13.9 8
All 2.4-18.6 7.4 40
Mean ozone consumption, mg/(t
(Std. dev.)
Packed column Jet scrubber
2.0
(0.5)
3.6
(0.9)
5.2
(1.4)
3.4
(1.5)
1.3
(0.4)
2.3
(1.0)
3.0
(1.3)
2.1
(1.1)
Mean
difference
(Std. dev.
0.7
(0.7)
1.4
(1.4)
2.2
(1.9)
1.3
(1.4)
t
) t (a=0.05)
3.8 2.16
4.2 2.11
3.3 2.36
6.0 2.03
                                        30

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Ozone Residual--


     Table 10  summarizes the differences between  the two contactors with
respect to ozone  residual as a function of dosage.   Not only was the ozone
residual in the packed column significantly higher  than the corresponding
residual in the jet scrubber at each dosage level,  but also the difference  in
residual between  the two contactors increased  with  higher dosages.


                  TABLE 10. DIFFERENCE IN OZONE RESIDUAL BETWEEN THE PACKED COLUMN AND
                     JET SCRUBBER AS A FUNCTION OF APPLIED DOSAGE (MCWTP EFFLUENT)


                           Numer of    Mean ozone residual, mg/      Mean
          Ozone dosage, mg/      data points        (Std. dev.)       difference        t
        Level	Range	Mean	(n)	Packed column  Jet scrubber	(Std. dev.)  t  (q=Q.Q5)
"Low 2.4- 4.6 3.6 14

Mod- 5.9-10.0 7.5 18
erate
High 11.8-18.6 13.9 8

All 2.4-18.6 7.4 40

0.8
(0.4)
1.7
(0.5)
2.2
(0.6)
1.5
(0.7)
0.3
(0.2)
0.8
(0.6)
1.0
CO. 5)
0.7
(0.5)
0.5
(0.3)
0.8
(0.6)
1.2
(0.3)
0.8
(0.5)
6.4 2.16

5.8 2.11

11.4 2.36

9.6 2.02

Summary of Contactor Performance--

     From the foregoing data analyses, it is clear  that the packed column
significantly outperformed the jet scrubber with  respect to coliform
reduction efficiency and mass transfer efficiency.   Total coliform density,
fecal coliform density, and fecal streptococcus density were all reduced to  a
significantly greater extent in the packed column than in the jet scrubber.
When considering  each individual dosage level, the  packed column was superior
to the jet scrubber with respect to total and  fecal coliform reduction at  low
and intermediate  dosages but not at the high dosage.   However, fecal strep-
tococcus reductions were significantly higher  in  the packed column at each
dosage level studied.

     Ozone utilization, consumption, and residual were significantly higher
in the packed column than in the jet scrubber  at  all dosage levels studied,
and these differences increased in magnitude with increasing dosage.

Regression Analyses

     The data from the above experiments were  subjected to linear regression
analyses to determine which factors in the effluent contributed to the varia-
tion in the microorganism reduction efficiency data and mass transfer ef-
ficiency data.  One parameter, such as log total  coliform reduction, was
chosen as a dependent variable and regressed individually against a number
of independent variables (i.e., TCOD, SCOD, TOG,  TSS,  turbidity, TKN, NH -N,
and organic-N).   This was also done for log fecal coliform reduction, log
fecal streptococcus reduction, ozone utilization, ozone consumption, and ozone
residual as the dependent variables.  No correlations were found between the


                                       31

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dependent variables and any of the independent variables mentioned.  It was
concluded that the effluent quality was sufficiently constant that the
variation observed in any of the dependent variables could not be accounted
for by the variation of the individual physical-chemical characteristics
of the wastewater effluent.

     Attempts were then made to determine whether bacterial reduction  (TCLR,
FCLR, and FSLR) could be correlated with ozone dosage, utilization, consump-
tion, and/or residual in each contactor.  A fifth variable, initial bacterial
density, was also included as an independent variable.  Tables 11 to 16
summarize the correlation matrices resulting from these analyses.

     Tables 11 to 13 summarize the correlation between total coliform  log
reduction (TCLR), fecal coliform log reduction (FCLR), and fecal strep log
reduction (FSLR), respectively, in the packed column and the various indepen-
dent variables mentioned above.  Correlations among the variables themselves
are also presented.

     In Tables 11,  12,  14,  and 15,  a correlation  coefficient greater than
0.275 or less than  -0.275 is significantly different from zero at the
95 percent confidence level (as determined by the t-test).   In tables 13 and
16, an r-value greater than 0.33 or less than-0.33 is significantly different
from zero.

     As expected,  significant positive correlations existed among the four
ozone variables.   Weak but  statistically significant correlations existed
between TCLR, FCLR,  or FSLR and ozone dosage,  residual consumption,  and
utilization.   Thus,  as any  one of the latter variables increased in magnitude,
there was a corresponding increase in bacterial reduction.   Finally, there
was statistically significant correlations between TCLR and initial total
coliform density,  FCLR and  initial fecal coliform density,  and FSLR and initial
fecal streptococcus  density.  Thus, the higher the initial  bacterial density,
the higher was the  resulting log reduction.

     Several regression equations for the packed  column were derived from the
data used to construct Tables 11 to 13 and are given as follows:

               CQ =  0.3 DQ  + 1.1                                         (11)

               U0 =  0.4 D0  + 1.7                                         (12)

               R0 =  0.1 Do  + 0.5                                         (13)

where C  = ozone consumption (mg/), Uo= ozone utilization (mg/), R = ozone
residual (mg/),  and D  = ozone dosage (mg/).

     Tables 14 to 16 summarize the correlations between TCLR, FCLR, and FSLR,
respectively, in the jet scrubber and the various selected independent
variables.

     The most significant trends observable in the jet scrubber are quite
different from those seen in the packed column.  For example, among the ozone

                                      32

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variables,  residual  did not correlate at  all with  consumption.  This was
because the residual was very low  most of the time and thus most  of the ozone
utilized in the jet  scrubber was consumed by the effluent.   The strongest
correlations with  bacterial reductions were initial bacterial densities and
ozone residuals.   Ozone dosage weakly correlated with microorganism reduction,
but  neither ozone  consumption nor  ozone utilization correlated at all.  Thus,
it appears  that the  only time significant microorganism  reduction occurred in
the  jet scrubber was when  an ozone residual was present.

      A relationship  derived from the data used to  construct Tables 14 to  16 is
given as follows:
                 R0  = 0.07  DQ + 0.1
(14)
                        TABLE 11.  CORRELATION OF TOTAL COLIFORM LOG REDUCTION (TCLR)
                   IN THE PACKED COLUMN WITH OZONE DOSAGE, UTILIZATION, CONSUMPTION, RESIDUAL,
                            AND INITIAL TOTAL COLIFORM DENSITY (MCWTP EFFLUENT)
Correlation coefficient (r)*
0^ Dose Residual Utilization Consumption
Dose 1,000 0.725 0.869 0.823
Residual 1.000 0.806 0.608
Utilization 1.000 0.960
Consumption 1.000
Initial TC
density
TCLR
Initial TC
density
0.299
0.22S
0.380
0.403
1.000

TCLR
0.319
0.339
0.519
0.535
0.541
1.000
                 40 data points used to derive each r-value
                    TABLE 12.  CORRELATION OF FECAL COLIFORM LOG REDUCTION (FCLR)
               IN THE PACKED COLUMN WITH OZONE DOSAGE, UTILIZATION, CONSUMPTION, RESIDUAL, AND
                         INITIAL FECAL COLIFORM DENSITY (MCWTP EFFLUENT)

Dose
Residual
Utilization
Consumption
Initial FC
density
FCLR
Correlation coefficients (r)*
Dose Residual Utilization Consumption
1.000 0.718 0.866 0.821
1.000 0.800 0.603
1.000 0.961
1 000



Initial FC
density
0.322
0.302
0.476
0 . 494
1.000


TCLR
0.326
0.414
0.543
0.531
0.596
1 .000
        *3S data points used to derive each r-value
                                           33

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        TABLE 13.   CORRELATION OF FECAL STREr LOG REDUCTION (FSLR)  IN THE PACKED COLUMN
           WITH OZONE DOSAGE,  UTILIZATION,  CONSUMPTION,  RESIDUAL,  AND INITIAL FECAL
                                 STREP DENSITY (MCWTP EFFLUENT)

Dose
Residual
Utilization
Consumption
Initial FS
density
FSLR
Correlation coefficients (r)*
Dose Residual Utilization Consumption
1.000 0.763 0.888 0.827
1.000 0.817 0.605
1.000 0.953
1.000


Initial TC
density
0.374
0.286
0.332
0.309
1.000

FSLR
0.713
0.597
0.706
0.664
0.845
1.000
29 data points used to derive each r-value
        TABLE  14.   CORRELATION OF TOTAL COLIFORM LOG REDUCTION  (TCLR)  IN THE JET SCRUBBER
            WITH  OZONE  DOSAGE, UTILIZATION, CONSUMPTION, RESIDUAL, AND INITIAL TOTAL
                                COLIFORM  DENSITY  (MCWTP EFFLUENT)


Dose
Residual
Utilization
Consumption
Initial TC
density
TCLR
Correlation coefficients {r)*
Dose Residual Utilization Consumption
1.000 0.5S3 0.732 0.54S
1.000 0.440 0.007
1.000 0.901
1.000



Initial TC
density
0.297
0.549
0.108
-0.146
1.000


TCLR
0
0
0
-0
0

1
360
519
212
015
649

000
  40 data points  used  to  derive  each  r-value
                    TABLE 15.  CORRELATION OF FECAL COLIFORM LOG REDUCTION (FCLR)
                   IN THE JET SCRUBBER WITH OZONE DOSAGE, UTILIZATION, CONSUMPTION,
                    RESIDUAL, AND INITIAL FECAL COLIFORM DENSITY (MCWTP EFFLUENT)


Dose
Residual
Utilization
Consumption
Initial FC
density
FCLR
Correlation coefficients (r)*
Dose Residual Utilization Consumption
1.000 0.543 0.728 0.546
1.000 0.432 -0.001
1.000 0.901
1.000


Initial FC
density
0.316
0.608
0.232
-0.035
1.000

FCLR
0.418
0.620
0.254
-0.016
0.708
1.000
 *38 data points used to derive each r-value
                                                   34

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        TABLE 16.   CORRELATION OF FECAL STREP LOG REDUCTION (FSLR)  IN THE JET SCRUBBER
           WITH OZONE DOSAGE,  UTILIZATION,  CONSUMPTION, RESIDUAL,  AND INITIAL FECAL
                                STREP DENSITY (MCWTP EFFLUENT)

Dose
Residual
Utilization
Consumption
Initial FS
density
FSLR
Correlation coefficients (r) *
Dose Residual Utilization Consumption
1.000 0.568 0.672 0.483
1.000 0.525 0.080
1.000 0.890
1.000

_ _ 	 	 _ _  _ _ _ __ _ __ _ _  	 _ . _. _  _ _ 	 
Initial FS
density
0.370
0.605
0.054
-0.261
1.000

FSLR
0.332
0.707
0.268
-0.065
0.851
1.000
29 data points used to derive each r-value

-------
Stepwise Multiple Regression--

     The linear regression analyses discussed above provided insight in
determining which factors were responsible for the variation observed in the
data.  Further refinement in quantifying these effects was possible by
performing stepwise multiple regression analyses in which ordered, linear
models were developed to predict the overall net effect of all variables
on  contactor performance.

     The procedure involves re-examination, at every stage of the regression,
of  the variables incorporated into the model in previous stages.  A variable
which may have been the best single variable to enter at an early stage may,
at  a later stage, be superfluous because of the relationships between it and
other variables not in the regression.  A judgement on the contribution of
each variable is made after each step of the analysis, as though it had been
the most recent variable entered, irrespective of its actual point of entry
into the model.  Any variable which provides a nonsignificant contribution
is  removed from the model.  This process is continued until no more variables
will be admitted to the equation and no more are rejected.  The  final result
is  a multiple regression equation including all variables contributing to the
effect under examination.

     A total of six equations resulted from this analysis, three for the
packed column and  three for the jet scrubber.  The dependent variables under
examination were TCLR, FCLR, and FSLR.  The independent variables were
initial TC, FC, or FS density, ozone dosage, utilization, consumption, and
residual.  The three equations for the packed column are given as follows:

                XG
          Log  x	  =  0.61  Log X0 + 0.34C0 - 1,77  (r =  0.671)         (15)

where X0 = initial  total  coliform density,  X = total coliform density.after
ozonation,  C0 = ozone consumption (mg/),  and DQ = ozone dosage  (mg/).

                 Yo
          Log    y       =0.82  Log Y0 + 0.47U0 - 0.14DO - 2076 (r =  0.698)(16)

where YQ = initial  fecal  coliform density,  Y = fecal coliform density after
ozonation,  and UQ = ozone utilization (mg/).

                 Z0
          Log  	  = 0.78  Log Z0 + 0.21U0 - 1.76 (r =  0.958)         (17)

where ZQ = initial  fecal  strep  density and  Z = fecal strep  density after
ozonation.

     The multiple correlation coefficients  (r)  were significant at the
cKO.05 level.
                                      36

-------
    It is clear from these equations that initial bacterial density was an
important contributing factor to the variation in the data.  Thus, when
predicting the effect of ozone on the microorganism reduction efficiency of
a packed column, one must account for the initial bacterial numbers in the
overall model.

    It was previously shown that ozone utilization, consumption, and residual
in the packed column were mathematically related to applied dosage (equations
11 to 13).  If these relationships are substituted into equations 15 to 17
so that log microorganism reduction is expressed in terms of initial bac-
terial density and dosage alone, the latter equations simplify to:

         TCLR = 0.04 DQ + 0.6 log Xo - 1.4                                (18)

         FCLR = 0.06 DQ + 0.8 log Y  - 2.0                                (19)

         FSLR = 0.09 D0 + 0.8 log Zo - 1.4                                (20)

Thus, if the initial total coliform density were 10^/100 ml, the ozone dosage
needed to achieve a 3 log reduction in the packed column would be 20 mg/fc.

    The equations for the jet scrubber are given as follows:

         TCLR = Log -^-  = 0.39RQ + 0.99 Log XQ - 4.01 (r = 0.678)       (21)


         FCLR = Log -^  = 0.68R0 + 1.07 Log YQ   3.95 (r = 0.747)       (22)


         FSLR = Log -|  = 0.46RQ + 0.79 Log YQ - 1.55 (r = 0.884)       (23)

The multiple r-values were significant at the a<0.05 level.

    It is clear that, aside from initial bacterial density, the only factor
significantly affecting microorganism reduction efficiency in the jet scrubber
was ozone residual.  Substituting equation 14 into equations 21 to 23 so that
microorganism reduction is given in terms of initial bacterial numbers and
applied dosage, the relationships become:

         TCLR = 0.03D + log XQ   4.0                                      (24)

         FCLR - 0.05D + 1.1 log YQ - 3.9                                  (25)

         FSLR = 0.03D + 0.8 log ZQ - 1.5                                  (26)

Thus, to achieve a 3 log reduction of total coliforms in the jet  scrubber,
assuming an initial density of  106/100 ml, the applied ozone dosage would be
33 mg/&.  This  is considerably  higher than in the packed column.

    It should be pointed out that the above data were obtained  at a constant
ozone gas concentration of 10 mg/ and varying gas flow rates.  According to
Henry's Law, mass transfer depends on the difference between the  ozone
concentration in the gas and in the liquid.  Increasing the concentration of

                                      37

-------
ozone in the gas stream would enable operation  of  the  contactors at lower gas
flow rates and thus improve mass transfer  efficiency.   This  would presumably
improve microorganism reduction efficiency as well,  since more ozone would be
added to the liquid.  Work is presently underway to  verify this hypothesis
experimentally.

PHASE 2 - PARALLEL OPERATIONAL MODE - FACTORIAL EXPERIMENT

   During this phase of the investigation,  both contactors were operated in
parallel on effluent from the Robert A. Taft Laboratory pilot plant facility.

   The experimental arrangement described  in Section 4 enables the investi-
gator to test the significant differences  in performance between the two
ozone contactors with minimum bias.  Moreover,  if  the  resulting analyses of
variance (ANOVA) indicate significant interactions between the various levels
of one factor and those of another, the data can be  easily subjected to linear
and stepwise multiple regression analyses  to determine which physical-
chemical characteristics of the effluent contribute  to such  interactions and
to quantify the extent to which each parameter  is  involved.

Characteristics of the Wastewater Effluent

   Table 17 summarizes the mean, standard  deviation, and range of the physical-
chemical characteristics of the filtered pilot  plant effluent used in this
phase of the study.  Effluent was generally poorer than that of the MCWTP
effluent (Table 2).

                     TABLE 17. CHARACTERISTICS OF THE PILOT PLANT
                          EFFLUENT PRIOR TO OZONATION
Parameter
Temperature (C)
TCOD
SCOD
TOC
TSS
TURB (JTU)
TKN
" NH4-N
ORG-N
Mean*
mg/l
14
76
65
19.9
6
11.3
16.1
8.6
7.4
Standard deviation
mg/l
0.5
20
23
6.3
3
12.4
7.9
3.0
6.9
Range
mg/l.
13
41
34
8.2 -
2
1.6 -
6.5 -
3.6 -
2.2 -
14
106
105
30.
11
40
27
14.
30.



5



1
5
            * 24 data points
Total Coliform Log Reduction  (TCLR)

   Table 18 illustrates the split-split  plot  layout as described in Section 4
and summarizes the data for log total  coliform reduction in both contactors.
Analysis of the data from Table 18  is  shown in Table 19.  Examination of the
geometric mean total coliform densities  (after ozonation)  in Table 18 reveals
                                      38

-------
that a coliform reduction to a level less than 1000 TC/100 ml was achieved
in the packed column  only at a dosage of 19.5 mg/.  Such a level of disin-
fection was not achieved  in the jet scrubber.

   If the computed  F-statistic in Table 19 with the appropriate degrees of
freedom is greater  than the corresponding F-value from the F-distribution
table (5 percent  significance level), the effect under examination is signi-
ficant.  The various  F-statistics were computed as follows: (1) Dose main
effect (Dp -- the  Mean Square (MS) for doses was ratiod against the MS for
the I^Dj interaction;  (2)  Replication main effect (R-jJ -- the MS for
replication was ratiod against the MS for the ^D- interaction; (3) CkD.=
interaction effect  --  the MS for the CkD- was ratiod against the MS for the
RiDiCk interaction;  (4) C^ interaction effect -- the MS for the C,R.
interaction was ratiod against the MS for the R-D-Ck interaction.   To1test
for a significant difference between the two contactors (contactor main
effect), a Pseudo-F test  was performed in which the mean square (MS) for
contactors (Ck) was ratiod against the MS for the R^ interaction plus the
MS for  theD-Ck interaction minus the mean square for the R^D-C^ interaction.
                     TABLE 18. SPLIT-SPLIT-PLOT LAYOUT FOR TOTAL COLIFORM LOG REDUCTION DATA
Replicates
1
2
3
4
5
6
Mean
Standard
deviation
Effluent geometric
mean, TC/100 mfc

Source
of variation
Contactors (C, )
Doses (D.)
Replicates (R. )
CkD.
CkRi
R.D.
l J
RiDjCk
Total
Packed column ,_ TCLR
0- dose, mg/
4.9 9.7 13.1 19.5
2.03 3.09 4.15 3.14
1.00 2.15 2.22 2.00
2.00 2.46 3.35 2.86
1.00 3.02 3.22 3.31
0.03 0.85 1.35 4.02
0.24 1.16 1.27 3.43
1.05 2.12 2.59 3.13
0.84 0.94 1.17 0.67

9.9.X104 8.7xl()J 2.2xlOJ 5.5x10"
TABLE 19. ANOVA OF TOTAL COLIFORM
Degrees of Sums of
freedom squares
1 16.70
3 19.14
5 17.92
3 1.20
5 0.79
15 12.07
15 3.54
47 71.36

4.9
1.00
1.00
0.14
0.16
0.00
0.07
0.40
0.47

4.7x10
LOG REDUCTION
Mean
squares
16.70
6.38
3.58
0.40
0.16
0.80
0.24
Jet scrubber, TCLR
0 dose, mg/
9.7 13.1 19.5
1.86 3.00 2.52
0.30 0.07 0.31
1.79 2.54 2.27
0.81 0.91 2.16
0.03 0.00 2.48
0.43 0.03 1.16
0.87 1.09 1.82
0.78 1.35 0.89
)
5 1.6xl05 8.9xl04 1.6xl04
DATA
F
F (a = 0.05)
51.80 37.0
7.90 3.29
4.45 2.90
1.70 3.29
0.67 2.90


                                     39

-------
     Results from Table 19 indicate that the difference between the two ozone
contactors (C, ) with respect to TCLR was significant at the 5 percent signifi-
cance level.   It can also be seen that the dosage effect  (D.) on the combined
TCLR in both contactors was significant at the 5 percent  significance level*
This is not unexpected, since an increase in ozone dosage should cause a
corresponding increase in coliform reduction.  Significant differences in
TCLR for both contactors were observed among replicate experiments  (R^),
indicating that effluent quality varied from day to day and that these
variations affected coliform reduction efficiency in both contactors.

     The interaction between contactor and dosage (C,D.)  was not significant
(Table 19).  This means that the difference between the two contactors with
respect to TCLR was consistent at all dosage levels studied.  The interaction
between contactors and replication (C^R.) was also not significant.  This
indicates that the differences in TCLR observed between the two contactors
were the same regardless of effluent quality.

     The relationship between TCLR and applied ozone dose in each contactor
is depicted graphically in Figure 15.  Each point is the  mean of the six
replicate experiments.  It can be seen that TCLR was better in the  packed
column than in the jet scrubber  (significant contactor main effect) and that
TCLR was directly proportional to dosage  (significant dosage main effect).
The fact that the two lines are nearly parallel illustrates the lack of a
significant contactor-dosage (C.D^) interaction.  The replication main effect
(i.e. effect of effluent quality) is illustrated in Figure 16, where the
average TCLR in each contactor at all dosage levels is plotted against total
chemical oxygen demand in the pilot plant effluent.  Each point is  the mean
TCLR at the four dosage levels.  It is evident that an increase in  TCOD  (a
variable representative of effluent quality) corresponded to a decrease in
TCLR in both contactors.  Moreover, the lack of a significant contactor-
replication interaction (Ci,R-) is evidenced by the parallel nature  of the two
lines.  Thus, effluent quality adversely  affected overall TCLR efficiency in
both contactors.  The packed column significantly and consistently  outper-
formed the jet scrubber with respect to total coliform reduction at all dosage
levels s'tudied and under varying conditions of effluent quality.
                    s
                                                    PACKED COLUMN

                                                   - IET SCRUBBER
                                    OZONE DOSE , mg/l
        Figure 15.  Total Coliform  Log Reduction  as  a  Function  of  Ozone
                 Dosage in the Packed Column and  Jet Scrubber
                                      40

-------
            S: 4
                          
                                                  A
                                                       -PACKED COLUMN

                                                        IET SCRUBBER
                              I
                                   I
                                            I
               "40    50    60   70    80    90    100
                           EFFLUENT TOTAL CHEMICAL OXYGEN DEMAND , mg/l

      Figure  16.   Total  Coliform  Log Reduction at all Dosage Levels
         as a Function  of Effluent Total Chemical Oxygen Demand
                   in the Packed Column and Jet Scrubber

Fecal Coliform Log Reduction (FCLR)

     Table 20 summarizes the data for log fecal coliform reduction in both
contactors.   Analysis of the data from Table 20 is presented in Table 21.

     Results  from  Table  21 are  similar to those depicted in Table 19.   All
main effects  were  significant,  and both interactions were not significant.
Thus, as with total coliform reduction, the packed column outperformed  the
jet scrubber  with  respect to fecal coliform reduction at all dosage  levels
studied and at all conditions of  effluent quality.

     Examination of the  geometric mean fecal coliform densities  (after
ozonation) in Table 20  reveals  that a mean FC reduction to a level of less
than 200/100  ml was almost achieved in the peaked column at the highest
dosage level  but not even approached in the jet scrubber.  These results  are
comparable to the  total  coliform  data.
                                      41

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TABLE 20.  SPLIT-SPLIT-PLOT LAYOUT FOR
  FECAL COLIFORM LOG REDUCTION DATA



Replicates 4.9
1 2.35
2 0.49
3 1.29
4 0.15
5 0.0
6 0.31
Mean 0.76
S.D. 0.90
Effluent 4.6x10
geometric
mean,
FC/100 ml
Packed column
FCLR
Dose, mg/5,
9.9 13.1
3.15 5.33
2.17 1.27
3.00 1.52
2.95 3.93
0.31 2.65
0.66 3.15
2.04 2.64
1.26 l.OS
3.6xl03 5.7x10



Jet scrubber
FCLR

19.5
3.21
2.71
3.00
3.02
3.33
3.52
3.13
0.28
2 2.2xl02



Dose, Mg/l
4.9 9.7 13.1 19.5
1.07 2.06 2.54 2.60
0.50 0.84 0.14 0.00
0.29 2.81 1.87 2.00
0.15 1.15 1.35 1.43
0.18 0.0 0.0 2.17
0.14 0.14 0.0 0.66
0.39 1.17 0.98 1.48
0.36 1.10 1.09 0.99
1.2xl05 2.9xl04 3.7xl04 7.3xl03




TABLE
Source of
variation
Contactors (C . )
J
Doses (D.)
Reps (Ri)
C. D.
k 3
C. R.
k i
R.D.
i j
R.D.C.
Total
21. ANOVA FOR FECAL COLIFORM LOG REDUCTION DATA
Degrees of
freedom
1

3
5
3
5
15

15
47
Sums of Mean F
squares squares F (a=0.05)
15.62 15.62 13.93 13.50

19.03 6.34 8.46 3.29
15.48 3.10 4.13 2.90
3.56 1.19 2.64 3.29
1.92 0.38 0.85 2.90
11.25 0.75

6.75 0.45
73.60
             42

-------
Percent Ozone Utilization

     Table 22 illustrates the split-split-plot layout and summarizes the data
for percent ozone utilization as a function of ozone dosage.  Analysis of the
data from Table 22 is given in Table 23.

     Results indicate that the difference between the two ozone contactors
(C^) with respect to percent ozone utilization was significant.  In addition,
percent ozone utilization in both contactors was significantly different at
all dosage levels studied (D-).  Replication (R.^ did not significantly affect
percent ozone utilization in either contactor.  Thus, variation in effluent
quality did not bring about a corresponding variation in percent ozone utili-
zation at the four dosage levels studied.

     Neither the contactor-dosage (C,D.) interaction nor the contactor-
replication (C, R,) interaction with respect to percent ozone utilization were
significant in this experiment.  This means that the differences observed
between the contactors were consistent at all dosage levels studied and at
all conditions of effluent quality experienced.

     The relationship between percent ozone utilization and applied ozone
dose in each contactor is depicted graphically in Figure 17.  Each point is
the mean of six replicate experiments.  It can be seen that percent ozone
utilization was better in the packed column than in the jet scrubber (signifi
cant contactor main effect) and that percent ozone utilization was inversely
proportional to dosage (significant dosage main effect).   The fact that the
lines are parallel illustrates the  lack of significant contactor-dosage
(CiD-) interaction.  The lack of a significant replication main effect (i.e.,
effect of effluent quality) is illustrated in Figure 18 where the average
percent ozone utilization in each contactor at all dosage levels is plotted
against TCOD in the influent wastewater.  Each point is the mean percent ozone
utilization at the four dosage levels.  It is evident that an increase in
TCOD was not accompanied by any significant overall change in percent ozone
utilization in both contactors.  In addition, the lack of a significant con-
tactor-replication interaction (C, R-^) is evidenced by the nearly parallel
nature of the two lines.   The packed column significantly and consistently
outperformed the jet scrubber with respect to percent ozone utilization at all
dosage levels studied and under varying conditions of effluent quality.  How-
ever, effluent quality did not significantly affect overall percent utili-
zation in either contactor.

Actual Ozone Utilization

     Table 24 illustrates the split-split-plot layout and summarizes the data
for ozone utilization.  Analysis of the data from Table 24 is given in
Table 25.

     Results indicate that the difference between the two ozone contactors
(Cv) with respect to ozone utilization was significant.  In addition, ozone
utilization in both contactors combined was significantly different at each
dosage level (D:) studied.  The replication main effect (R^ was not signifi-
cant.  This means that overall ozone utilization in both contactors was not

                                      43

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TABLE 22.  SPLIT-SPLIT-PLOT LAYOUT FOR
    PERCENT OZONE UTILIZATION DATA

Replicates
1
2
3
4
5
6
Mean
S.D.
Packed column,
ozone utilized, percent

4.9 9.
78 57
67 49
78 52
73 56
61 58
68 63
71 56
6.7 4.
Dose mg/Ji
7 13.1
42
49
46
43
49
53
47
9 4,1

19.5
34
49
40
35
43
43
41
5.6
ozone

4,9
45
57
52
53
61
65
56
7,1
Jet scrubber
utilized, percent
Dose
9.7
32
32
26
34
41
43
35
6.3
rag/Jl
13.1
23
32
25
27
32
35
29
4.7

19.5
20
37
25
21
27
27
27
6,1
    TABLE 23.  ANOVA FOR PERCENT
     OZONE UTILIZATION DATA
Source of Degrees of Suras of
variation freedom squares
Contactors (C, )
Doses (D.)
Reps (R^
C, D.
k J
C. R.
k i
R.D.
i 3
R.D.C,
i j k
Total
1
3
5
3
5
15
15
47
3570,
6159.
384,
81,
191
467
291
11,145
,75
.08
,67
,42
.00
.17
.76
.84
Mean
squares F
3570.
2053.
76.
27.
38.
31.
19
75 77.81
03 65.92
93 2.47
.14 1.40
,20 1.96
.14
.45
F
(a=0.05)
7.60
3.29
2.90
3.29
2.90


             44

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     70
     60
      50
   - 40
      30
  S  20
      10
                                          I
I
                                                                   PACKED COLUMN

                                                                   JET SCRUBBER
                                   8      10      12

                                  OZONE  DOSAGE mg/l
      14
16
18
20
   Figure 17.   Percent  Ozone Utilization as  a Function of Ozone  Dosage
                    in the Packed  Column and Jet Scrubber
             3.0
             2.0
                                                       0	PACKED COLUMN

                                                       A	  -JET SCRUBBER
                                                             A A
                   _J	|	|	|	|	|	|	|	|	|_
                   10     20    30     40    50    60     70    80     90    100
                         EFFLUENT TOTAL CHEMICAL OXYGEN DEMAND , mg/l

Figure  18.  Percent Ozone  Utilization as  a  Function  of Effluent Total
    Chemical Oxygen Demand in the  Packed  Column and  Jet Scrubber
                                        45

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  TABLE  24.  SPLIT-SPLIT-PLOT  LAYOUT FOR
          OZONE UTILIZATION DATA



Packed
column
ozone utilized,


Replicates






1
2
3
4
5
6
Mean
S
D.

4.9
3.8
3.2
3.7
3.5
2.9
3.3
3.4
0.3
dose
9.
5.
4.
S.
S.
5.
6.
5.
0.
mg/
7
5
8
0
5
6
1
4
5

mg/

13.1 19.5
5
6
5
5
6
6
6
0
.5 6.6
.4 9.6
.9 7.8
.7 6.9
.5 8.4
.9 8.4
.2 8.0
.6 1.1

Jet
scrubber
ozone utilized
mgA

dose mg/
4.9
2.2
2.7
2.5
2.5
2.9
3.1
2.7
0.3
9
3
3
2
3
3
4
3
0
.7
.1
.1
.5
.3
.9
.2
.4
.6
13.1
3.0
4.2
3.2
3.6
4.2
4.6
3.8
0.6
19.5
3.9
7.2
4.8
4.2
5.3
5.3
5.1
1.2
TABLE 25.   ANOVA FOR OZONE UTILIZATION DATA
Source of
variation
Contactors (C, )
Doses (D.)
Reps (R..)
C D.
k ]
CkRi
R.D.
i ]
R.D.C,
1 J k
Total
Degrees of Sums of
freedom squares
1
3
5
3
5
15
15
47
47
75
7,
7
0.
11.
0.
151.
.9
.7
.8
.3
.8
,2
.9
5
Mean
squares
47
25
1
Z 
0.
0.
0,
.9
.2
.6
.4
.2
.7
.1
F F
(a=0. OS)
19.0 9.1
33.8 3.3
2.1 2.9
38.9 3.3
2.5 2.9


                   46

-------
significantly affected by changes in effluent quality.

     The contactor-dosage (CjD.) interaction with respect to ozone utilization
was significant at the 5 percent level  (Table 25) .  This contrasts with the
lack of interaction between  contactor and dosage with respect to  log total and
fecal coliform reduction (Tables 19  and  21) and percent ozone utilization
(Table 23) .  This means that the difference in actual ozone utilization be-
tween the  packed column and  the jet scrubber at some dosage levels was not the
same at other dosage  levels.
     Finally, the contactor-replication  (C^R^)  interaction with respect to
ozone utilization was not  significant.   This means that the difference in
performance of the two  contactors with respect  to ozone utilized was the same
regardless of effluent  quality.  This effect was also observed for  log total
and fecal coliform reduction  and percent ozone  utilization.

     These effects are  clearly visualized by examining Figures 19 and 20.
The relationship between ozone utilization and  applied ozone dose in each
contactor is depicted graphically in Figure 19.  Each point is the  mean of
six replicate experiments.  It can be seen that  ozone utilization in the packed
column was better than  in  the jet scrubber  (significant contactor main effect)
and that ozone utilization in both  contactors was proportional to dosage
(significant dosage main effect) .   The fact that the two  lines are  not par-
allel illustrates the significant contactor -dosage interaction (CkD.).  As
dosage increased, the increase in ozone  utilization in the packed column was
greater than in the jet scrubber.   The lack of  a significant replication main
effect is illustrated in Figure  20, where the average ozone utilization in
each contactor at all dosage  levels is plotted  against TCOD in the  pilot plant
effluent.  Each point is the  mean ozone  utilization at the four dosage levels.
It is evident that an increase in TCOD was not  accompanied by any significant
overall change in ozone utilization in either contactor.  Moreover, the lack
of significant contactor-replication interaction  (C^R.:) is evidenced by the
nearly parallel nature  of  the two lines.  Thus, the packed column significantly
outperformed the jet scrubber with  respect to actual utilization.   Effluent
quality did not significantly affect overall ozone utilization in both con-
tactors; however, it will  be  seen later  that ozone utilization in each con-
tactor was affected by  effluent  quality  at certain individual dosage levels.

Ozone Residual

     Table 26 illustrate the  split-split-plot layout and summarizes the data
for ozone residual.   Analysis of the data from Table 26 is given in Table 27.

     Results indicate that the difference between the two ozone contactors
(C, ) with respect to ozone residual was  significant at the 5 percent level.
In addition, ozone residual was significantly different at each dosage level
(D.) studied.  This is  expected, since ozone residual should increase with
increasing dosage.  Finally,  Table  27 indicates that effluent quality (rep-
lication) significantly affected the magnitude  of ozone residual in the
effluent from both contactors.  Thus,  as effluent quality deteriorated, ozone
residual decreased at the  same applied dosage level.
                                      47

-------
                                                	PACKED COLUMN

                                                A	JET SCRUBBER
                                                15
                                                             20
                              OZONE DOSE , nig/1
    Figure 19.   Ozone Utilization  as a Function of Ozone Dosage
                in the Packed Column and Jet Scrubber
                                    I
                                                	PACKED COLUMN

                                                A	JET SCRUBBER
                                                    I
                                                         I
               10    20    30    40    50     60    70    80

                      EFFLUENT TOTAL CHEMICAL OXYGEN DEMAND . mg/l
90    100
Figure  20.  Ozone Utilization at  all Dosage Levels  as a Function
      of Effluent  Total  Chemical Oxygen Demand in  the Packed
                       Column and Jet Scrubber
                                   48

-------
   TABLE 26.   SPLIT-SPLIT-PLOT LAYOUT
         FOR  OZONE RESIDUAL DATA
Packed column
ozone residual,
rag/
Jet scrubber
ozone residual,
dose, mg/
Replicates
1
2
3
4
5
6
Mean
S.D.
4.
0.
0.
0.
0.
0.
0.
0.
0.
9
9
1
6
.2
0
0
.3
4
9.
0.
0.
1.
0,
0,
0,
0,
0,
.7
.9
.3
.4
.4
.2
.1
.6
.5
13
1.
0.
1.
1.
0.
0.
0.
0.
.1
7
4
6
1
4
2
9
7
19
1.
0.
1.
0.
0.
0.
1.
0.
.5
9
9
6
9
2
4
0
7
4.
0.
0.
0.
0.
0.
0.
0.
0.
9
2
0
1
0
0
0
05
08
dose, mg/
9.
0.
0.
0.
0.
0,
0.
0.
0,
.7
.3
.2
.4
.2
.0
.0
, 2
,2
13
0.
0.
0.
0.
0.
0.
0.
0.
rag/H

.1
8
2
5
3
0
1
3
3


19.5
0.7
0.2
0.4
0.4
0.0
0.0
0.3
0.3
TABLE 27   ANOVA FOR OZONE RESIDUAL DATA
Source of
variation
Contactors (C )
i\
Doses (D.)
Reps (Ri)
CkD.
C, R.
k i
R.D.
R.D.C.
i ] k
Total
Degrees of
freedom
1
3
5
3
5
15
15
47
Sums of
squares
2
1
5
0
1.
0
0
12
.71
.69
.10
.37
.18
.75
.21
.02
Mean
squares F
2
0
1,
0
0
0
0
.71 7.80
.56 11.24
.02 20.32
.12 8.98
.24 16.99
.05
.01
F
(a=O.OS)
5.60
3.29
2.90
3.29
2.90


                 49

-------
     The contactor-dosage (Cj,D.) interaction with respect to ozone residual
was also significant.  This means that the difference in ozone residual be-
tween the contactors was not consistent with effluent quality.

     The relationship between ozone residual and applied ozone dosage in each
contactor is depicted graphically in Figure 21.  Each point is the mean of six
replicate experiments.  It can be seen that ozone residual in the packed column
was higher than in the jet scrubber (significant contactor main effect) and
that ozone residual in both contactors was proportional to dosage (significant
dosage main effect).  The fact that the two lines are not parallel illustrates
the significant contactor-dosage interaction (CD.).  As dosage increased,
the increase in ozone residual in the packed column was greater than in the
jet scrubber.  The significant replication main effect is illustrated in
Figure 22, where average ozone residual in each contactor at all dosage levels
is plotted against TCOD of the effluent.  Each point is the mean ozone resi-
dual at the four dosage levels.  It is evident that an increase in TCOD
corresponds to a decrease in ozone residual in both contactors.  Moreover, the
significant contactor-replication interaction(C^R^) is evidenced by the fact
that the two lines intersect.  Thus, the magnitude of the ozone residual in
the packed column appeared to be more sensitive to changes in applied ozone
dosage (Figure 21) and shift in ozone demand (Figure 22) than in the jet
scrubber.  This is most likely because the packed column was a better overall
ozone contactor than the jet scrubber.

Ozone Consumption

     Table 28 illustrates the split-split-plot layout and summarizes 'the data
for ozone consumption (i.e., the difference between actual ozone utilization
and ozone residual).  Analysis of the data from Table 28 is given in Table 29.

     Results indicate that all main effects were significant and both inter-
actions were significant.  This is similar to the ozone residual data analysis
presented in Table 27.  Thus, consumption in both contactors was significantly
different; dosage and wastewater quality significantly affected consumption in
both contactors; and the significant differences in consumption between the
contactors were not consistent over all levels of dosage and under different
conditions of wastewater quality.

     The relationship between ozone consumption and applied ozone dose in each
contactor is depicted graphically in Figure 23''.  Each point is the mean of
six replicate experiments.   It can be seen that more ozone was consumed in the
packed column than in the jet scrubber (significant contactor main effect) and
that ozone consumption was proportional to dosage  (significant dosage main
effect).. The fact that the  two lines intersect illustrates the significant
contactor-dosage interaction  (C,D.)-  The replication main effect is illus-
trated in Figure 24, where the average ozone consumption in each contactor
at all dosage levels is plotted against total chemical oxygen demand in the
pilot plant effluent.  Each point is the mean ozone consumption at the four
dosage levels.  It is evident that an increase in TCOD corresponded to an
increase in ozone consumed in both contactor.  However, the TCOD effect on
ozone consumption in both contactors, although statistically significant, was
for all practical purposes negligible, as a 60 mg/J, increase in TCOD

                                      50

-------
                      PACKED COLUMN

                     -JET SCRUBBER
   Figure 21
                                       10    12    14

                                 OZONE DOSAGE , mg/l
Ozone  Residual  as  a Function of Ozone  Dosage  in  the
    Packed Column  and Jet  Scrubber
                                                -
                                                A-
                                                 
                                      PACKED COLUMN

                                       -JET SCRUBBER
            40     50    60    70     80     90     100

                      EFFLUENT TOTAL CHEMICAL OXYGEN DEMAND , mg/I
Figure  22.  Ozone Residual  as a Function of  Effluent  Total Chemical
         Oxygen  Demand in  the Packed Column and Jet Scrubber
                                     51

-------
   TABLE  28.  SPLIT-SPLIT-PLOT  LAYOUT  FOR
          OZONE CONSUMPTION  DATA
Packed column
ozone consumption,

Replicates
1
2
3
4
5
6
Mean
S.D.

4.
2.
2.
3.
3.
2.
3.
3.
0.

9
9
6
6
3
9
3
1
4
mg/
Jet scrubber
ozone consumption
dose, mg/
9.
4.
3.
4.
5.
5.
6.
4.
0.
7
6
,4
.7
1
4
.0
9
9
13
3.
4.
5.
4.
6.
6.
5.
1.
.1
8
8
5
6
1
7
3
1
19
4.
8.
6.
6.
8.
8.
7.
1.
.5
7
0
9
0
2
0
0
4
4.
2.
2.
2.
2,
2'.
3,
2,
0.
.9
.0
.6
.5
,5
9
.1
,6
4
, mg/1
dose, mg/i
9.
2.
3.
2,
3.
3.
4.
3.
0,
.7
.8
.1
.3
.1
.9
.2
.2
.7
13
2.
3.
3.
3.
4.
4.
3.
0.
.1
2
7
0
3
2
5
5
8
19
3.
6.
4.
3.
5.
5.
4.
1.
.5
2
8
6
8
3
3
8
3
TABLE 29.  ANOVA FOR OZONE CONSUMPTION DATA
Source of
variation
Contactors (C, )
Doses (D.)
Reps (R.)
C, D.
k j
C, R.
k i
R.D.
i ]
R.D.C,
ilk
Total
Degrees of
freedom
1
3
5
3
5
15
il
47
Sums of
squares
27
56
17
4
2
13
1
123
.26
.44
.87
.56
.28
.52
.60
.53
Mean
squares F
27.
18
3.
1.
0.
0.
0.

.26 14.60
.81 20.87
.57 3.96
.52 14.20
.46 4.26
.90
.11

F
(a=0.05)
7.71
3.29
2.90
3:29
2.90



                   52

-------
                                                             PACKED COLUMN

                                                      A	JET SCRUBBER
                                         10     12    H    IB
18     20
                                  OZONE DOSAGE , mg/l
  Figure 23.   Ozone  Consumption as a  Function  of Ozone  Dosage  in the
                       Packed Column and Jet Scrubber
             70
             60
              50
             40
          ^ 30
          5
          LU
          S 20
              10
                                
                                           0
                                           A
                                               "A
                                                     0-
                                                     A-
                                                            -PACKED COLUMN
                                                            -IET SCRUBBER
               40    50     60    70     80     90    100
                          EFFLUENT TOTAL CHEMICAL OXYGEN DEMAND  , mg/l
Figure 24.   Ozone Consumption  as a  Function  of Effluent Total  Chemical
           Oxygen Demand in the Packed Column and Jet  Scrubber
                                       53

-------
corresponded to less than 2 rag/5, increase in ozone consumption.  The daily
variation of the difference in ozone comsumption between contactors
(contactor-replication interaction) was also satistically significant.  Hence,
the two lines in Figure 24, although appearing parallel, have significantly
different slopes, but from a practical standpoint the difference is considered
negligible.   Thus, it appears that ozone consumption in both contactors was
more dependent on applied ozone dosage (Figure 23) than on the demand of the
effluent being treated (Figure 24).  More ozone was consumed in the packed
column than in the jet scrubber, and the increase in consumption as a
function of dosage was greater in the packed column.

Summary of the Factorial Experiment--

       On the basis of total and fecal coliform log reduction, it is clear
that the packed column contactor was superior to the jet scrubber, at least
within the limits of effluent quality encountered and ozone dosages used
(5 - 20 rag/).  Effluent quality significantly affected microorgani'sm
reduction efficiency in both contactors.

       On the basis of ozone utilization efficiency, several conclusions can
be made.  First, the packed column was superior to the jet scrubber with
respect to percent ozone utilization, regardless of effluent quality and the
magnitude of applied dosage.  This superiority was significant and consistent
at all dosage levels employed.  Percent utilization in both contactors was
inversely proportional to dosage.  Since dosage was increased by maintaining
the ozone concentration in the gas stream constant and varying the gas flow
rate, this result is not unexpected.  Second, the packed column was superior
to the jet scrubber with respect to actual ozone utilization regardless of
effluent quality.  The magnitude of this difference in performance actually
increased with increasing dosage (significant C,D. interaction).  Ozone
utilization in both contactors increased with increasing dosage, as expected.
Third, both ozone residual and ozone consumption in each contactor increased
with increasing dosage.  Effluent quality had a greater effect on the magni-
tude of ozone residual in both contactors than on the amount of ozone
consumed.  Thus, since TCLR, FCLR, and ozone residual were significantly
affected by effluent quality while overall ozone utilization and ozone
consumption were less significantly affected, it follows that organism
reduction was not mass transfer limited, but overall ozone utilization and
consumption were.  However, it should be emphasized that these were overall
effects and no account has yet been made of the effect of effluent quality
at each individual dosage level.  This will be discussed in the following
section.

Linear Regression Analysis of Data from the Factorial Experiment

       The foregoing analyses of variance (ANOVA) were useful in enabling
conclusions on the overall comparative disinfection and mass transfer
efficiencies of the packed column and jet scrubber contactors.  However, the
ANOVA1s do not reveal which factors in the effluent contributed to the
variation in the data.  Information of this kind would provide invaluable
                                     54

-------
assistance in designing or upgrading ozone contactors.

     The factorial arrangement used in this study facilitates performance of
other statistical tests to furnish the desired information, because both
contactors were treated in parallel under identical conditions at four sepa-
rate and distinct applied dosage levels.  Thus, if it is desired to test the
effect of chemical oxygen demand, for example, on coliform reduction in each
contactor, there exists six data points at each dosage level to establish a
correlation.  Tests performed were linear regression analysis.

Total Coliform Reduction   Packed Column--

     Table 30 summarizes the correlation between total coliform log reduction
(TCLR) in the packed column and each effluent quality variable at different
applied ozone dosage levels.

     A correlation coefficient greater than 0.73 or less than -0.73 in
Table 30 is significantly different from zero at the 95 percent confidence
level.

      It is clear from Table 30 that chemical oxygen demand (total and soluble)
and total organic carbon significantly interfered with TCLR in the packed
column at dosage levels ranging  from 4.9 to 13.1 mg/.  At 19.5 mg/ ozone
dosage, TKN and organic-N significantly interfered with TCLR, but not TCOD,
SCOD, or TOG.  Thus, at all dosage levels TCLR appears to have been rate
limited since the magnitude of TC reduction was affected by the effluent
quality.

      It appears that a strong negative correlation was associated with total
suspended solids and TCLR at 4.9 mg/ ozone dosage but not at the higher
dosages.  Although it is possible that TSS exerted an ozone demand at low
applied ozone levels, it is likely that this observation was an experimental
artifact, because the variation in TSS from day-to-day was not high enough
to warrant such a conclusion.  Data on unfiltered effluent are needed to
better quantify this relationshiip.

      It appears that a strong positive correlation existed between ammonium-N
and TCLR at 4.9, 9.7, and 13.1 mg/ applied ozone but not at 19.5 mg/.  This
compares with the substantial negative correlation observed for TCOD, SCOD,
and TOC at the same dosage levels and the lack of correlation at 19.5 mg/fc
applied ozone.  Since NH^-N was inversely related to TCOD, SCOD, and TOC in
this effluent (Table 17), it is likely that the above observation merely
reflects the effect of COD and TOC on TCLR.

     Total Kjeldahl nitrogen and organic nitrogen did not appear to affect
disinfection efficiency until 19.5 mg/ ozone was applied.  This suggests that
the organic demand exerted by COD and TOC in this effluent significantly
affected TCLR in the packed column at lower ozone dosages but the demand
exerted by nitrogenous compounds became significant at higher dosages.  This
conclusion would not be inconsistent with the observation that TKN and ORG-N
did not correlate with COD or TOC.
                                     55

-------
 TABLE 30.  CORRELATION OF TOTAL COLIFORM LOG REDUCTION  (TCLR)
 IN THE PACKED COLUMN AT DIFFERENT APPLIED OZONE DOSAGE  LEVELS
                WITH EFFLUENT QUALITY PARAMETERS
Parameter
TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N

4.9
-0.96
-0.96
-0.90
-0.83
0.76
-0.10
0.87
0.38
TCLR Correlation
Dose mg/
9.7
-0.84
-0.91
-0.68
0.10
0.44
0.03
0.72
0.13
Coefficient (r)*
13.1
-0.98
-0.97
-0.94
-0.29
0.16
-0.11
0.82
-0.08

19.5
0.22
0.14
0.18
0.64
-0.88
-0.71
-0.25
-0.88
6 data points used to derive each r-value
                               56

-------
Fecal Coliform Reduction - Packed Column--

     Table 31 summarizes the correlation between fecal coliform log reduction
(FCLR) in the packed column and each effluent quality variable at different
applied ozone dosage levels.

     Results from the FCLR data are similar to the TCLR data at 4.9 and 9.7
mg/ applied ozone dosage.  However, at 13.1 mg/, COD and TOG no longer
affected FCLR, while TKN and ORG-N significantly interfered with FCLR.  At
19.5 mg/ ozone, the only variable adversely affecting FCLR was TCOD.   No
explanation can be offered for the latter observation except to suggest the
observation may be artifactual.  The demand exerted by nitrogenous material
with respect to FCLR in the packed column became significant between 9.7 and
13.1 mg/ applied ozone, while the same demand with respect to TCLR became
significant at dosages greater than 13.1 mg/.

Total Coliform Reduction - Jet Scrubber--

     Table 32 summarizes the correlation between total coliform log reduction
(TCLR) in the jet scrubber and each effluent quality variable at different
applied ozone dosage levels.

     Results from Table 32 indicate that TCLR in the jet scrubber was not
affected by any of the measured effluent parameters at 4.9 mg/ applied ozone.
The reason for this is that little microorganism reduction occurred at this
dosage level  (Table 18) to permit correlations to occur.

     At 9.7 and 13.1 mg/, the same trend in TCLR noted in the packed column
was observed in the jet scrubber.  Thus, TCOD, SCOD, and TOC adversely
affected TCLR, while NHt-N showed a positive correlation.  At 19.5 mg/
ozone, the adverse affect of COD and TOC disappeared, but, in contrast to the
packed column, TKN and ORG-N did not correlate with TCLR. Hence, TCLR in the
jet scrubber was reaction rate limited at lower dosage levels but became mass
transfer limited at a dosage somewhere between 13.1 and 19.5 mg/.

Fecal Coliform Reduction - Jet Scrubber--

     Table 33 summarizes the correlation between fecal coliform log reduction
(FCLR) in the jet scrubber and each effluent quality variable at different
applied ozone dosage levels.

     Results from Table 33 are similar to those in Table 32.  The only
difference is the significant negative correlation of FCLR with TOC at 4.9
mg/ ozone.  Thus, in general, FCLR was affected by the same parameters as
TCLR in the jet scrubber.

Ozone Utilization - Packed Column--

     Table 34 summarizes the correlation between ozone utilization in the
packed column and each effluent quality variable at different applied ozone
dosage levels.
                                      57

-------
    TABLE 31.   CORRELATION-OF FECAL COLIFORM LOG REDUCTION (FCLR)
       IN THE  PACKED COLUMN AT DIFFERENT APPLIED OZONE DOSAGE
                LEVELS WITH EFFLUENT QUALITY PARAMETERS
Parameter
TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N

4.
-0
-0
p
.9
.87
.82
-0.91
-0.
0.
-0.
0.
0.
,86
,44
,27
,66
,09
CLR Correlation Coefficient (r)*
Dose mg/J,
9,
-0,
-0,
-0.
-0.
0.
0.
0.
0.
.7
.84
.92
,72
07
61
03
80
28
13.1
-0
-0
0,
0
-0.
-0,
-0.
-0.
.25
.29
,08
.63
.82
,40
,28
84
19
-0.
-0.
-0.
-0.
0.
0.
0.
-0.
.5
77
41
64
72
21
07
56
02
  6  data points  used  to  derive  each  r-value
   TABLE 32.   CORRELATION OF TOTAL COLIFORM LOG REDUCTION (TCLR)
   IN THE JET SCRUBBER AT DIFFERENT APPLIED OZONE DOSAGE LEVELS
                 WITH EFFLUENT QUALITY PARAMETERS
                          TCLR Correlation Coefficients (r)J
Parameter                           Dose mg/

TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N
4
-0
-0
-0
-0,
0
0.
0.
0.
.9
.40
.36
.67
.74
.38
,57
,27
,32
9
-0.
-0,
-0.
0,
0.
-0.
0.
0.
.7
.94
.93
.86
.12
,41
46
88
02
13
-0.
-0.
-0.
-0.
0.
-0.
0.
-0.
.1
94
92
87
40
06
44
82
20
19
-0.
-0.
-0.
0.
-0.
-0.
0.
-0.
.5
39
51
55
19
40
70
39
64
  6  data points  used to derive each r-value
                               58

-------
    TABLE 33.  CORRELATION OF FECAL COLIFORM LOG REDUCTION  (FCLR)
    IN THE JET SCRUBBER AT DIFFERENT APPLIED OZONE DOSAGE LEVELS
                  WITH EFFLUENT QUALITY PARAMETERS
Parameter
TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N

4.9
-0.64
-0.60
-0.83
-0.78
0.24
0.07
0.38
0.04
FCLR Correlation
Dose
9.7
-0.83
-0.88
-0.78
-0.19
0.68
-0.25
0.90
0.32
Coefficient (r)*
mg/l
13.1
-0.99
-0.99
-0.90
-0.26
-0.01
-0.37
0.80
-0.26

19.5
-0.48
-0.51
-0.64
-0.02
-0.30
-0.69
-0.47
-0.57
  6 data points used to derive each r-value
    TABLE 34.  CORRELATION OF OZONE UTILIZATION IN THE F-ACKED COLUMN
AT DIFFERENT APPLIED OZONE DOSAGE LEVELS WITH EFFLUENT QUALITY PARAMETERS
Parameter
TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N
Ozone Utilization Correlation Coefficients (r)*
Dose rag/?,
4.
-0.
-0,
-0.
-0.
0,
-0.
0.
0.
.9
.96
.96
.69
.69
,58
,32
96
05
9,
0
0
0
0
-0,
-0.
-0.
-0.
,7
.18
.23
.30
.78
.89
.59
,26
,90
13
0.
0.
0.
0.
-0.
0.
-0.
0.
.1
93
94
93
24
01
13
67
20
19
0.
0.
0.
0.
0.
0.
-0.
0.
.5
77
80
71
03
25
47
67
60
    6 data points used to derive each value
                                 59

-------
     At an ozone dosage of 4.9  mg/  there appears to be a significant negative
correlation between ozone utilization and COD (total and soluble), while at
9.7 mg/ no correlation exists,  and  at higher levels there is a positive
correlation.   This  observation  can be explained as follows.   According to the
International Critical  Tables  (16),  the magnitude of Henry's Constant (H)
increases as the temperature of the  liquid increases.  The mean temperature of
the effluent in the six replicate experiments was 14 C.  At that temperature
and an ozone concentration in the gas of 9.7 mg/ the highest possible con-
centration of ozone which can exist  in the liquid, regardless of the gas/liquid
flow ratio, is 4.8  mg/.   Thus,  when the dosage is 4.9 mg/, (gas/liquid ratio
= 0.5), it is theoretically possible for the liquid itself in the contactor to
absorb 4.8 mg/ regardless of the organic demand of the liquid.  The driving
force at any point  in the column for mass transfer of ozone from the gas phase
to the liquid phase is  determined primarily by the difference in concentration
of ozone in the gas stream and  dissolved ozone.   This difference in concentration
diminishes as the gas rises through  the column.   At low dosage levels, most of
the driving force occurs at the bottom of the column, and ozone will be absorbed
into the water with or  without  the presence of organic demand.   Therefore, it
is reasonable to conclude that  the significant negative correlation between
ozone utilization and COD observed at 4.9 mg/ dosage was coincidental.

     At 9.7 mg/ dosage (gas/liquid  ratio  = 1), the exhaust gas concentration
was higher, and consequently a  greater mass transfer driving force was available
at the top of the column.  This means not only that ozone absorption occurred
more evenly through the length  of the column but also that more ozone was
available to react  with organic demand.   An average of 5.4 mg/ ozone was
utilized at that dosage, or 0.6 mg/ more than the theoretical maximum
allowable concentration.   Since only 0.6 mg/ of the 5.4 mg/ ozone utilized
can be attributed to the organic demand, no correlation was found between
TCOD or SCOD and ozone  utilization at 9.7 mg/ dosage.

     At dosage levels greater than 9.7 mg/, the dosage was sufficiently above
the ozone solubility at that temperature and the driving force at the top of
the column was sufficiently high relative to the TCOD and SCOD concentration
that a change in TCOD and SCOD  caused a corresponding change in ozone utili-
zation.  Hence, at  13.1 mg/ applied ozone, an average of 6.2 mg/ was utilized
(1.4 mg/ greater than  the theoretical maximum), while at 19.5 mg/ applied
ozone, an average of 8.0 mg/ was utilized (3.2 mg/ greater than the theoretical
maximum).  This explains the high positive correlation between ozone utilization
and TCOD, SCOD, and TOC at the  high  dosage levels.

     The observations appear to contrast with the ANOVA for the ozone
utilization data (Table 25), which indicated no significant effect of effluent
quality on the amount of ozone  utilized.  However, the ANOVA averaged the data
for both contactors over all dosage  levels, while the regression analyses
isolated and examined the effects of effluent quality at each individual dosage
level for each contactor.  These individual effects cancelled each other when
averaged together in the ANOVA.

     It is concluded that, at  low doses (i.e., 4.9 and 9.7 mg/), ozone
utilization was mass transfer  limited, while at high dosages (i.e., >9.7 mg/)
reaction kinetics influenced mass transfer.  This contrasts with the


                                     60

-------
conclusions made for TCLR and FCLR.  It means that, as ozone absorption by
the effluent proceeded at low dosage levels, the ozone which had been trans-
ferred at those dosage levels was rapidly consumed in chemical reactions with
oxidizable materials, the concentrations of which far exceeded the concen-
trations of microorganisms.  Thus, coliform reduction at dosages >9.7 mg/
was essentially reaction rate limited while utilization was mass transfer
limited.  At higher dosage levels, utilization exceeded that which would be
predicted by Henry's Law, due to the effect of COD and TOG.  However, the
ozone which was transferred was immediately consumed by the organic demand
causing the excessive absorption.  Hence, at the high dosage levels, coliform
reduction was again reaction rate limited, as was ozone utilization.

Ozone Utilization - Jet Scrubber--

     Table 35 summarizes the correlation between ozone utilization in the jet
scrubber and each effluent quality variable at different applied ozone dosage
levels.

     The correlation of ozone utilization with TCOD, SCOD, and TOC was
significant at 4.7 and 13.1 mg/ applied ozone, but,not at 9.7 and 19.5 mg/&.
Perhaps more data points would have provided the necessary information to
establish the correlation, since the r-values were near the critical value
(i.e., 0.73) to be considered significant.  The fact that the gas-liquid
contact time in the jet scrubber was so low (3 sec at 75 /min liquid flow
rate) may have been a significant factor affecting absorption in this
contactor and/or reaction of ozone with organic matter.

Ozone Residual - Packed Column--

     Table 36 summarizes the correlation between ozone residual in the
packed column and each effluent quality variable at different applied ozone
dosage levels.

     It is clear from Table 36 that the magnitude of ozone residual in the
effluent from the packed column was significantly affected by the presence
of soluble organic material at all dosage levels studied.  Thus, if the COD
(total and soluble) or TOC was high, the ozone residual was low and vice
versa.  This would at least partially explain why coliform reduction in the
packed column was significantly affected by replication, i.e., effluent
quality (Tables 19 and 21).

Ozone Residual - Jet Scrubber--

     Table 37 summarizes the correlation between ozone residual in the jet
scrubber and each effluent quality variable at different applied ozone dosage
levels.

     It is evident from Table 37 that, as COD  (total and soluble) and TOC
increased, ozone residual  in the effluent from the jet scrubber decreased at
all dosage levels.  Thus,  the results from the jet scrubber are comparable to
those from the' packed column and the same conclusions apply.
                                      61

-------
     TABLE 35.  CORRELATION OF OZONE UTILIZATION IN THE JET SCRUBBER
AT DIFFERENT APPLIED OZONE DOSAGE LEVELS WITH EFFLUENT QUALITY PARAMETERS
Ozone Utilization
Parameter
4.9
TCOD 0.91
SCOD 0.91
TOC 0.81
TSS 0.60
TKN -0.48
TURB 0,05
NH4-N -0.69
ORG-N -0.12

9.7
0.63
0.71
0.62
0.48
-0.87
-0.12
-0.74
-0.62
Correlation Coefficients
Dose mg/X,
13.1
0.96
0.95
0.95
0.38
-0.06
0.31
-0.79
0.19
(r)*

19.5
0.62
0.70
0.61
-0.08
0.38
0.66
-0.58
0.71
* 6 data points used to derive each r-value
TABLE 36. CORRELATION OF OZONE RESIDUAL IN THE PACKED COLUMN
AT DIFFERENT APPLIED OZONE DOSAGE LEVELS WITH EFFLUENT QUALITY PARAMETERS
Ozone
Parameter
4.9
TCOD -0.96
SCOD -0.93
TOC -0.90
TSS -0.77
TKN 0.48
TURB -0.35
ORG-N 0.08
Residual Correlation Coefficients

9.7
-0.74
-0.77
-0.71
-0.21
0.64
-0.37
0.29
Dose mg/i
13.1
-0.97
-0.97
-0.91
-0.31
0.04
-0.38
-0.22
(r)*

19.5
-0.90
-0.86
-0.96
-0.78
0.58
-0.09
0.22
   * 6 data points used to derive each r-value
                                62

-------
                   TABLE 37.  CORRELATION OF OZONE RESIDUAL IN THE JET SCRUBBER
             AT DIFFERENT APPLIED OZONE DOSAGE LEVELS WITH EFFLUENT QUALITY PARAMETERS
Ozone Residual
Parameter

TCOD
SCOD
TOC
TSS
TKN
TURR
NH4-N
ORG--N
4.9
-0.88
-0.83
-0.88
-0.77
0.34
-0.40
0.61
-0.01
9
-0
-0
-0
-0
0
-0
0
0
Correlation Coefficients (r)*
Dose rag/Jl
.7
.80
.85
.76
.30
.78
.04
.84
.46
13
-0.
-0.
-0.
-0.
0.
-0.
0.
-0.
.1
96
92
88
41
14
24
79
10
19
-0.
-0.
-0.
-0.
0.
-0.
0.
-0.
.5
98
90
94
56
35
02
87
01
               * 6 data points used to derive each r-value

Ozone Consumption  -  Packed Column--

      Table  38 summarizes  the correlation between ozone consumption  in the
packed column and  each effluent quality variable at  different applied ozone
dosage levels.

      Data from Table 38 parallel the trends  noted  in the ozone utilization
data  (Table  34), namely,  that at higher dosage levels, ozone consumption
                  TABLE 38.  CORRELATION OF OZONE CONSUMPTION IN THE PACKED COLUMN
             AT DIFFERENT APPLIED OZONE DOSAGE LEVELS WITH EFFLUENT  QUALITY PARAMETERS
Parameter
TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N
Ozone Consumption Correlation Coeff icie'nts (r)*
Dose mg/5.
4.9
-0.
-0.
0.
0.
0.
-0.
0.
-0.
.34
.37
.06
.07
.27
.68
52
04
9
0
0
0.
0
-0.
-0.
-0.
-0.
.7
.23
.21
.40
.61
.71
.78
.03
.82
13
0.
0.
0.
0.
-0.
-0.
-0.
-0.
.1
76
73
85
39
24
29
50
10
19
0.
0.
0.
0.
-0.
0.
-0.
0.
.5
98
87
86
38
07
16
81
30
              * 6 data points used to derive each r-value

                                          63

-------
increased as carbonaceous demand increased.   Thus,  at dosage levels greater
than 9.7 mg/, the dosage was sufficiently high relative to COD and TOG  that
a change in COD or TOC caused a concomitant change  in ozone consumption.   At
lower dosage levels, mass transfer was  determined primarily by the concen-
tration of ozone in the inlet gas and secondarily by organic demand.

Ozone Consumption - Jet Scrubber--

     Table 39 summarizes the correlation between ozone consumption in the  jet
scrubber and each effluent quality variable at different applied ozone dosage
levels.

     A significant positive correlation is noted in Table 39 between ozone
consumption and TCOD, SCOD, and TOC  at  all dosage levels.  This contrasts
with the data observed in the packed column in which positive correlations
were observed only at dosage levels  greater than 9.7 mg/.

Summary of Regression Analyses--

     This section attempted to  explain  the variation observed in the micro-
organism reduction and ozone utilization  data from the factorial experiments
by quantitatively examining the effect  of each effluent constituent on


                TABLE 39.  CORRELATION OF OZONE  CONSUMPTION IN THE JET SCRUBBER
            AT DIFFERENT APPLIED OZONE DOSAGE LEVELS UTTH EFFLUENT QUALITY PARAMETERS
Parameter
TCOD
SCOD
TOC
TSS
TKN
TURB
NH4-N
ORG-N
0:
4.
0.
0.
0.
0.
-0
0,
-0
-0
:one Consumption Correlation Coefficients (r)*
Dose mg/S,
9
90
89
.86
.69
.45
.02
.66
.11
9.
0.
0.
0.
0.
-0,
-0.
-0
-0
7
74
SO
71
.35
.SO
.04
.79
.52
13
0.
0.
0.
0.
-0.
0.
-0.
0.
.1
96
94
97
43
16
12
77
06
19
0.
0.
0.
0.
0.
0.
-0.
0.
.5
76
78
71
05
27
53
67
63
              * 6 data points used to derive each r-value


coliform reduction and  ozone  utilization, consumption, and residual  at
each dosage  level studied.  Results indicated that TCLR in the  packed column
was significantly and adversely  affected by COD and TOC at ozone  dosages less
than 13.1 mg/, while at higher  dosages  demand exerted by nitrogenous mate-
rials became significant.   In the jet scrubber, the same trends were noted

                                      64

-------
except that no  correlations were found at 4.9 mg/X, ozone dose, where very
little coliform reduction occurred anyway.  Variations in the levels of
nitrogenous materials did not significantly affect coliform reduction in
the jet scrubber at any dosage level, presumably because of the exceedingly
short reaction time available.

     Ozone utilization and consumption in the packed column were significantly
affected by COD and TOC at dosage levels greater than 9.7 mg/.  At lower
dosage levels absorption was governed primarily by Henry's Law.  In the jet
scrubber, ozone consumption and utilization were significantly affected by
COD and TOC at essentially all dosage levels studied.

     Ozone residual in both contactors was significantly affected by COD and
TOC at all dosage levels.
PHASE 3 - CONTINUOUS OPERATION - PILOT PLANT EFFLUENT

     During this phase of the investigation, an attempt was made to evaluate
the reliability of each contactor in achieving a consistent 3-log reduction
in coliform numbers, and to determine if the ozonation system (generator,
drier, contactors, and analyzer equipment) could be operated for 100 contin-
uous hours without major breakdowns.  Ozone gas concentrations and flow rates
were varied to maintain the highest possible ozone residuals in both con-
tactors.  This necessitated the use of high gas/liquid flow ratios in the
jet scrubber, which in turn caused a reduction in percent ozone utilization.
Ozone gas concentrations were monitored continuously by a Fisher and Porter
Residual Ozone Analyzer.  Grab samples of inlet and exhaust gas and ozonated
effluent from each contactor were also taken manually for measurement.  All
bacteriological and physical-chemical analyses were performed on grab
samples collected at 10-hour intervals.  The experiment commenced at 7:00 AM
on February 28, 1977, and terminated at 1:00 AM on March 3, 1977.  The
wastewater effluent was filtered prior to ozonation.

     All systems operated satisfactorily for the entire 100 hours.  Results
are presented in Table 40.  A 3-log reduction in total coliforms was
achieved in 5 out of 10 samples in the packed column and only 1 out of 10
in the jet scrubber.  A 3-log reduction in fecal coliforms was achieved in
4 out of 10 samples in the packed column and only 2 out of 10 in the jet
scrubber.  Thus, neither contactor gave reliable results in this particular
wastewater.  Short contact times (20 seconds in the packed column and 3
seconds in the jet scrubber) may partially explain the low microorganism
reduction efficiencies observed.  Wastewater quality may have played a key
role in affecting the reliability of ozone disinfection in both contactors
during these tests.  The ranges of TCOD and TSS were 51 to 91 mg/Jl (mean of
66 mg/) and 4 to 30 mg/ (mean of 20 rag/A), respectively.  The TSS levels
were considerably higher than in the prior testing period.  Thus, it appears
that additional wastewater treatment beyond secondary may be needed to
achieve a reliable, and consistent microorganism reduction by ozone, generated
from air and applied in a packed column or a jet scrubber.
                                     65

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                  TABLE 40.   CONTINUOUS OPERATION OF PACKED COLUMN AND JET SCRUBBER
                    FOR THE  100-HOUR PERIOD OF FEBRUARY 28, 1977 TO MARCH 3,  1977
Date
             Time
                       Contactor
                             G/L
                            Inlet
                            ozone,
                            nig/ft gas
                                                               Exhaust
                                                               ozone,
                                 Ozone
                                 residual
                                 mg/8. liq.
                                                                                       TCLR
                                                                                                 FCLR
2/28/77


2/28/77


3/01/77

3/01/77

3.01/77


3/02/77

5/02/77

3/03/77

3/03/77

3/04/77
0700

1700


0300

1300


2300

0900

1900

0500

1500

0100
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
Packed column
Jet scrubber
1.2
2.0
1.3
2.0
1.0
2.0
0.6
2.0
0.6
2.0
1.2
2.0
1.1
2.0
1.8
2.0
13.4
13.4
13.2
13.2
         14.
         14.
14.5
14.5
17.0
17.0
14.2
14.2

14.3
14.3
11.9
11.9
11.5
11.5
10.9
10.9
 5.7
10.0

 6.1
10.0

 3.9
 5.9

 6.3
11.2

 5.5
13.4

 3.5
12.7

 6.4
10.8

 2.4
 6.1

 4.8
 9.2

 6.4
0.7
0.3
0.6
0.3
0.5
0.7

1.1
1.0
0.4
0.3
0.5
0.4
1.0
0.9
 3.22
 2.22
 1.92
 1.08
 1.42
<1.00
 2.66
 2.52

 3.00
 2.54
 2.86
 2.28
 2.85
 3.04
 1.48
 3.48
 1.18
 3.38
 3.33
 2.69
 2.38

 1.76
 1.62
 1.46
<0.31
 3.00
 3.17

 2.23
 2.75
 3.15
 3.00
 2.71
 1.50
 3.42
 1.69
 3.38
 1.50
 2.50
 2.65
                                                 66

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                                 REFERENCES
1.   American Public Health Association.  1975.  Standard Methods for the
     Examination of Water and Wastewater, 14th ed. American Public Health
     Association, Inc., New York.

2.   American Standards for Testing and Materials.  1974.  Interfacial
     Tension of Oil Against Water by Ring Method.  ASTM D-071, p. 576.

3.   American Standards for Testing and Materials.  1974.  Kinematic
     Viscosity of Transparent and Opaque Liquids.  ASTM D-445, p. 355.

4.   Anderson, Virgil L., and Robert A. McLean.  1974.  Design of Experiments
     A Realistic Approach.  Marcel Dekker, Inc., New York, N. Y., 418 pp.

5.   Dixon, W. J. (Ed.).  1973.  Biomedical Computer Programs.  University of
     California Press, Berkeley; California, 773 pp.

6.   Birdsall, C. M., A. C. Jenkins, and Edward Spadinger.  1952.  lodometric
     Determination of Ozone.  Anal. Chem. 24:662.

7.   Farooq, S., R.  S. Engelbrecht, and E. S.  K. Chian.  1977.  The Effect of
     Ozone Bubbles on Disinfection.  Progress in Water Technology, 7_:233.

8.   Chan, H. B., C. L. Chen, R. P. Miele, and I. J. Kugelman.  1975.
     Wastewater Disinfection With Ozone.  California Water Pollution Control
     Association Bulletin 12(2):47.

9.   Hicks, Charles R.  1964.  Fundamental Concepts in the Design of
     Experiments.  Holt, Rinehart, and Winston, Inc., New York, N. Y.,
     293 pp.

10.  Kamphake, L. J., S. A. Hannah, and J. M.  Cohen.  1967.  Automated
     Analysis for Nitrate by Hydrazine Reduction.  Water Research 1_:205.

11.  Kenner, Bernard A., and Harold P. Clark.   1974.  Detection and
     Enumeration of Salmonella and Pseudomonas aeruginosa.  J. Water Poll.
     Con. Fed. 46_:2163^

12.  Marks, Henry C., and G. L. Banister.  1974.  Amperometric Methods in
     the Control of Water Chlorination.  Anal. Chem. 19:200.
                                      67

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13.  Masschelein,  W.,  G. Fransolet, and J. Genot.  1975.  Techniques for
     Dispersing and Dissolving Ozone in Water.  Part 1.  Water and Sewage
     Works, L22_(12) :57.

14.  Masschelein,  W.,  G. Fransolet, and J. Genot.  1976.  Techniques for
     Dispersing and Dissolving Ozone in Water.  Part 2.  Water and Sewage
     Works, 125(1):34.

15.  Methods Development and Quality Assurance Research Laboratory.  1975.
     Methods for Chemical Analysis of Water and Wastes.  EPA-625/6-74-003,
     U.  S.  Environmental Protection Agency, Cincinnati, Ohio, 298 pp.

16.  National Research Council.   1928.   International Critical Tables of
     Numerical Data,  Physics,  Chemistry, and Technology.  McGraw-Hill Book
     Co.,  Inc., New York, N. Y.,  _3, p.  255.

17.  Natrella, M.  G..   1966.  Experimental Statistics.   U. S. Government
     Printing Office,  Washington, D.  C., 485 pp.

18.  Nebel, C., P. C.  Unangst,  and R.  D. Gottschling.  1973.  An Evaluation
     of Various Mixing Devices  for Dispersing Ozone in Water.  Water and
     Sewage Works, 120:R6.

19.  Rosen, H. M., F.  E. Lowther, and R. G. Clark.   1974.   Get Ready For
     Ozone.  Water and Wastes  Eng. 11(7):25.
                                     68

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                                 APPENDIX A

                     THE MODIFIED KENNER-CLARK PROCEDURE
                       FOR ENUMERATING SALMONELLA SPP.
     The following describes the quantitative method used for enumerating
Salmonella spp. from ozonated and unozonated activated sludge effluents. It
is based on the original technique developed by Kenner and Clark (11) but with
certain modifications.

SAMPLE TREATMENT

     Concentration of organisms is attained by filtration through either
membrane filters  (0.45 ym) or glass fiber filters  (Reeve Angel 984H ultra
glass fiber filter).  To obtain MPN results in the per 10 liter range, three
1000 ml samples are filtered through three membranes or glass fiber filters
and the filters placed into enrichment tubes containing single strength
enrichment broth  (first row).  Three 100 ml samples are filtered through three
membrane or glass fiber filters and the filters placed into enrichment tubes
containing single strength enrichment broth (second row).   Three 10 ml samples
are pipetted into three tubes with double strength enrichment broth (third row),
row).  Finally, three 1.0 ml samples are delivered into three tubes containing
9 ml of single strength enrichment broth (fourth row).

CONFIRMATION OF SALMONELLA SPP.

     Primary enrichment medium is Dulcitol Selenite Enrichment (DSE) broth
(Difco) and incubation is for 24 to 48 hours at 40 C + 0.2 C.

     After incubation for 24 hours a loopful is removed from each culture tube,
streaked onto Xylose Lysine Desoxycholate (SLD) agar (Difco) plates, and
incubated at 35 C for 24 hours.  The DSE tubes are placed back into the 40 C
incubator, incubated for an additional 24 hours, and the isolation procedure
on XLD plates is repeated as above.  This allows an additional 24 hours of
enrichment for any salmonellas which may have been originally present but had
not yet grown to sufficient numbers to be detectable.

     After the XLD plates have incubated 24 hours, they are examined for
appearance of Salmonella-type colonies.  Typical Salmonella colonies appear
clear and pink-edges with black centers.  The presumptive Salmonella colonies
(at least 2 per plate and well isolated) are picked to Triple Sugar Iron Agar
(TSIA) or Kligler's Iron Agar (KIA) slants (Difco) and Lysine Iron Agar (LIA)
slants (Difco) for biochemical identification.  Slants are incubated 24 hours


                                      69

-------
at 35 C.  If the black -centered colonies on the XLD plates are not well-
isolated, another XLD plate must be streaked from the poorly isolated colony
to purify the culture for subsequent biochemical identification.  The typical
reactions of Salmonella spp. on TSIA are alkaline slant, acid stab, and I^S
production.  The reactions on LIA are alkaline slant and stab (i.e., positive
for lysine decarboxylase) and F^S production.
     Confirmation is achieved in a very short time.  The agglutination
reaction, performed on the culture from the TSIA slant, using Salmonella
0 Antiserum Poly A-l, will confirm the presence of Salmonella spp. in a
few minutes.  Thus, the serological agglutination reaction will confirm or
deny the presence of Salmonella.

     If the TSIA and LIA reactions are not typical for Salmonella, repurifi-
cation from the TSIA on XLD followed by picking subsequent black colonies (if
any) back to TSIA and LIA is necessary before concluding that Salmonella are
not present.  This adds an additional two days of work to the test.  Thus
the time span for the entire method will produce results in as little as
three to four days and as many as six days.

     The method described is one of several methods in existence capable of
quantifying Salmonella in natural samples.  The limitations are indeed
recognized.  The precision of the 3-tube MPN is certainly inferior to the
5-tube procedure, but the trade-off in effort required in performing the
5-tube procedure for Salmonella enumeration does not justify its use at this
time.  It should be cautioned, however, that only an experienced micro-
biologist or microbiological technician should attempt the above procedure
for routine analysis, as the number of tubes, plates, slants, etc., could
overwhelm the investigator who has not been properly trained.
                                      70

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                                                             PACKED COLUMN MASS TRANSFER CALCULATIONS FOR PHASE  1
 DATE
               G

             i/min
               1
             rag/1
                 2
               mg/1
                                                  mg/min
                              Temp.
                               C
                              1
                           mg/1 ww
                                                                             H@T
                                             1
                                           mg/1
                                                                                                                                  mg/1
                                                                     KgVa

                                                                     iair/rain
     37
9-13
9-13
9-14
9-14
9-20
9-20
9-21
9-21
10-4
10-4
10-5
10-5
10-12
11-1
37
37
37
37
37
37
37
37
37
37
37
37
37
37
7.5
5.0
7.7
5.0
12.2
7.6
12.2
7.5
17.6
16.3
16.1
16.0
5.0
5.9
1.4
0.9
1.5
1.4
2.3
1.3
2.0
1.4
3.4
3.1
4.1
4.2
0.5
0.3
226
152
229
133
366
233
377
226
525
488
444
437
167
207
23
23
23.5
23.5
23
23
22
22
21
21
21
21
19
14.5
1.2
0.6
1.3
0.7
1.8
0.8
2.3
1.4
1.8
1.4
1.4
1.6
0.3
0.4
2.85
2.85
2.90
2.90
2.85
2.85
2.74
2.74
2.63
2.63
2.63
2.63
3.4
1.7
3.8
2.0
5.1
2.3
6.3
3.8
4.7
3.7
3.7
4.2
                                                                                           2.43
                                                                                           2.07
                                                                                           0.7
                                                                                           0.8
1.08
1.30
0.96
0.76
1.13
1.41
1.08
0.97
1.33
1.40
1.11
1.03
2.15
2.83
2.50
1.85
2.50
2.11
4.25
2.84
3.61
2.37
7.14
6.79
7.48
7.38
1.77
1.70
90
82
92
63
86
82
104
95
74
72
59
59
94
122
 G  73.6
7-26
7-27
8-2
8-2
8-2
8-3
8^9
8-9
8-10
8-10
73.6
73.6
73.6
73.6
73.6
73.6
73.6
73.6
73.6
73.6
11.5
7.6
3.7
7.4
11.9
11.9
3.8
7.7
3.7
7.6
3.4
1.7
0.7
2.1
3.8
3.9
0.8
2.3
0.8
2.5
596
434
221
390
596
589
221
397
213
375
                                                                 24
                                                                 24
                                                                 23
                                                                 23
                                                                 23
                                                                 23
                                                                 23
                                                                 21
                                                                 23
                                                               2.2
                                                               1.2
                                                               0.7
                                                               1.9
                                                               2.1
                                                               2.4
                                                               0.5
                                                               1.7
                                                               0.8
                                                               2.0
                                                                       97
                                                                       97
                                                                       85
                                                                       85
                                                                       85
                                                                       85
                                                                       85
                                                                     2.85
                                                                     2.85
                                                                     2.85
                                                                      6.5
                                                                      3.6
                                                                      2.0
                                                                      5.4
                                                                      6.0
                                                                      6.8
                                                                      1.4
                                                                      4.8
                                                                      2.3
                                                                      5.7
0.39
0.85
0.89
0.05
0.44
0.27
1.10
0.23
0.56
0.28
4.10
2.71
1.12
2.00
4.77
4.44
1.45
2.61
1.07
2.14
145
160
197
195
125
133
152
152
199
175
13
T)
Z
o
1 1
X
GO



    110
8-16
8-7
8-Z3
8-24
8-30
110
110
110
110
110
9.7
9.6
9.6
5.1
8.4
5.0
5.4
4.5
2.2
4.0
    147
8-16
8-23
8-24
8-30
147
147
147
147
 7.5
 7.5
 4.1
 7.0
4.6
4.0
2.1
4.0
                                                517
                                                462
                                                561
                                                319
                                                484
426
514
294
441
23
23
23
24
23
2.9
2.6
3.0
0.8
2.4
2.85
2.85
2. 85
2.97
2.85
8.3
7.4
8.6
2.4
6.8
 23
 23
 24
 23
2.3
2.0
0.8
2.1
2.85
2.85
2.97
2.85
6.6
5.7
2.4
6.0
                                                                                                     1.27
                                                                                                     0.90
                                                                                                     1.50
                                                                                                     0.21
                                                                                                     0.92
1.63
0.80
0.21
1.39
                                                                                                         2.83
                                                                                                         3.56
                                                                                                         2.33
                                                                                                         2.38
                                                                                                         2.61
2.27
2.75
1.90
2.16
                                                                                                         183
                                                                                                         130
                                                                                                         241
                                                                                                         134
                                                                                                         185
188
187
155
204
G = 55

10-18
10-18
11-1
55
55
57
13.8
 9.5
 5.9
4.4
2.8
1.3
517
368
262
 17
 17
14.5
2.1
2.1
0.9
2.25
2.25
2.06
4.7
4.7
1.9
0.73
0.54
1.12
6.47
3.71
2.40
 80
 99
109

-------
                                                             PACKED COLUMN MASS TRANSFER CALCULATIONS FOR PHASE 2


 DATE          G           Yj          Y2         ^VV     TeI"P'         H9T              Xl         Yl*    *"  Y1~Y1*        AYLM      KgVa
G = 37
             H/min        mg/1        mg/1        mg/min         C         J,ww/air        mg/1 ww       mg/1         Y           mg/i       J.air/min
 1-27-77       37         9.7          3.2           240          14            2.04             0.1         0.2          1.09          5.78       42
 1-31-77       37         9.6          2.1           278          14            2.04             0.6         1.2          1.39          4.53       61
 2-7-77        37         9.6          2.6           259          13            2.00             0.2         0.4          1.26          5.24       49
 2-8-77        37         9.6          3.7           218          14            2.04            <0.1         0.2          0.93          6.13       36
 2-8-77        37         9.5          3.0           240          14            2.04            <0.1         0.2          1.13          5.58       43
 1-24-77       37         9.9          2.2           285          13            2.00             0.9         1.8          1.30          4.54       63

G = 76

 1-27-77       76         9.7          4.9           365          14            2.04             0.3         0.6          0.62          6.78       54
 1-31-77       76         9.7          4.7           380          14            2.04             1.4         2.9          0.37          5.69       67
2-7-77        76         9.8          4.3           418          13            2.00             0.4         0.8          0.74          6.36       66
2-8-77        76         9.6          4.0           426          14            2.04             0.2         0.4          0.83          6.24       68
2-8-77        76         9.7          3.6           464          14            2.04             0.1         0.2          0.97          6.08       76
1-24-77       76         9.6          4.1           418          13            2.00             0.9         1.8          0.64          5.75       73

G = 101

1-27-77       101        9.8          5.0           485          14            2.04             0.4         0.8          0.59          6.81       71
1-31-77       101        9.7          5.2           455          14            2.04             1.6         3.3          0.21          5.78       79
2-7-77        101        9.9          5.6           434          13            2.00             1.1         2.2          0.32          6.52       67
2-8-77        101        9.9          5.0           495          14            2.04             0.4         0.8          0.60          6.85       72
2-8-77        101        9.8          4.6           525          14            2.04             0.2         0.4          0.71          6.72       78
1-24-77       101        9.9          5.7           424          13            2.00             1.7         3.4          0.13          6.10       70

G = 151
1-27-77       151        9.8          5.8           604          14            2.04             0.9         1.8          0.32          6.84       88
1-31-77       151        9.7          5.8           589          14            2.04             1.6         3.3          0.10          6.10       97
2-7-77        151        9.9          6.4           528          13            2.00             0.9         1.8          0.23          7.22       73
2-8-77        151        9.8          5.6           634          14            2.04             0.2         0.4          0.52          7.34       86
2-8-77        151        9.8          5.6           634          14            2.04             0.4         0.8          0.47          7.17       88
 1-24-77       151        9.7          6.4           498          13            2.00             1.9         3.8          0.08          6.17       81

-------
                                                            JET SCRUBBER MASS  TRANSFER CALCULATIONS  FOR PHASE 1
DATE
G = 37
              G

            H/min
            mg/1
              2
             mg/1
            mg/min
9-13
9-13
9-14
9-14
9-20
9-20
9-21
9-21
10-4
10-4
10-5
11-1
11-2
37
37
37
37
37
37
37
37
37
37
37
37
32
7.6
5.3
7.7
5.3
12.0
7.4
12.0
7.7
17.4
16.1
16.2
5.9
9.2
3.9
2.1
3.8
2.4
4.5
4.0
5.0
4.5
8.1
8.3
8.6
2.9
4.5
137
118
144
107
278
126
259
118
344
289
281
111
150
G = 55

10-18
10-18
H-l
    73.6
55
55
57
13.8
 9.5
 5.9
7.1
6.8
3.5
369
149
137
7-26
7-27
8-2
8-2
8-2
8-3
8-9
8-10
73.6
73.6
73.6
73.6
73.6
73.6
73.6
73.6
11.5
7.5
3.7
7.3
12.0
12.0
3.7
7.9
7.2
3.9
1.7
3.3
6.5
6.6
1.8
4.7
316
265
147
294
405
397
140
236
                                                   Temp.
                                                     C
                                                                 23
                                                                 23
                                                                 23.5
                                                                 23.5
                                                                 23
                                                                 23
                                                                 22
                                                                 22
                                                                 21
                                                                 21
                                                                 21
                                                                 14.5
                                                                 16
17
17
14.5
                                                                24
                                                                24
                                                                23
                                                                23
                                                                23
                                                                23
                                                                23
                                                                23
                            A2
                           rag/1
                                                     0.5
                                                     0.2
                                                     0.4
                                                    <0.1
                                                     0.5
                                                     0.2
                                                                0.6
                                                                0.3
                                                                1.2
                                                                0.6
                                                                1.0
                                                                0.3
                                                                0.5
2.7
1.3
0.3
                                                                0.9
                                                                0.5
                                                                0.0
                                                                0.3
                                                                0.7
                                                                0.7
                                                                0.2
                                                                0.7
                           H@T
                         fcww/fcair
                                                                               2.85
                                                                               2.85
                                                                               2.90
                                                                               2.90
                                                                               2.85
                                                                               2.85
                                                                               2.74
                                                                                                                      In Y-,-V
                                                                     74
                                                                     62
                                                                     62
                                                                     62
                                                                     06
                                                                                            2.18
2.25
2.25
2.06
                                                                                           2.97
                                                                                           2.85
                            mg/1
                                                                     1.4
                                                                     0.6
                                                                     1.2
                                                                     0.3
                                                                     1.4
                                                                     0.6
                                                                     1.6
                                                                     0.8
                                                                     3.1
                                                                     1.6
                                                                     2.6
                                                                     0.6
                                                                     1.1
6.1
2.9
0.6
                                                                                 2.7
                                                                                 1.5
                                                                                 0.0
                                                                                 0.9
                                                                                 2.0
                                                                                 2.0
                                                                                 0.6
                                                                                 2.0
                                                                                                  r'2
                                                                       1.11
                                                                       1.26
                                                                       1.09
                                                                       0.96
                                                                       1.35
                                                                       0.78
                                                                       1.26
                                                                       0.73
                                                                       1.25
                                                                       0.88
                                                                       0.99
                                                                       0.94
                                                                       1.00
2.62
0.89
0.71
                                                                                   0.94
                                                                                   1.14
                                                                                   0.78
                                                                                   1.11
                                                                                   0.98
                                                                                   0.96
                                                                                   0.90
                                                                                   1.07
AY
LM
rag/1
4.59
3.02
4.68
3.33
6.59
5.13
6.83
5.48
9.92
10.68
10.30
3.82
5.83
4.89
6.29
4.22
7.46
4.48
2.57
4.40
7.65
7.71
2.81
4.84
KgVa
iair/min
30
39
31
32
42
25
38
22
35
27
27
29
26
75
24
32
42
59
57
67
53
51
50
49
G = 110
8-16
8-17
8-23
8-24
8-30
110
110
110
110
110
9.6
9.8
9.8
5.3
8.5
7.5
6.2
6.8
3.4
7.0
231
396
330
209
165
                                                                  23
                                                                  23
                                                                  23
                                                                  24
                                                                  23
                                                                1.6
                                                                0.9
                                                                1.5
                                                                0.7
                                                                1.1
                                                                   2.85
                                                                   2.85
                                                                   2.85
                                                                   2.97
                                                                   2.85
                                                                    4.6
                                                                    2.6
                                                                    4.3
                                                                    2.1
                                                                    3.1
                                                                     1.20
                                                                     1.00
                                                                     1.37
                                                                     1.41
                                                                     0.78
                                                                   5.60
                                                                   6.19
                                                                   5.34
                                                                   2.85
                                                                   5.90
                                                                   41
                                                                   64
                                                                   62
                                                                   73
                                                                   28
G = 147
8-16
8-17
8-23
8-24
8-30
147
147
147
147
147
7.4
7.4
7.7
4.0
6.9
5.7
5.8
5.6
2.6
5.4
250
235
309
206
220
                                                                  23
                                                                  23
                                                                  23
                                                                  24
                                                                  23
                                                                1.2
                                                                0.7
                                                                0.6
                                                                0.4
                                                                0.7
                                                                   2.85
                                                                   2.85
                                                                   2.85
                                                                   2.97
                                                                   2.85
                                                                    3.4
                                                                    2.0
                                                                    1.7
                                                                    1.2
                                                                    2.0
                                                                     1.17
                                                                     0.67
                                                                     0.68
                                                                     1.05
                                                                     0.71
                                                                   4.36
                                                                   5.40
                                                                   5.59
                                                                   2.48
                                                                   4.95
                                                                   57
                                                                   44
                                                                   55
                                                                   83
                                                                   44

-------
                                                        JET SCRUBBER MASS TRANSFER CALCULATIONS FOR PHASE 2

DATE          G           Y           Y2         G(Y1-Y2)       Temp.         X2             H8T            Y2*         Hn  Y2 -Y2*      AY^      KgVa

            /min        mg/1        mg/1         mg/min          C         mg/1 ww        5,ww/J.air        mg/1             Y^      mg/1      t-air/min

G = 37

1-27-77      37           9.7        4.2            204            14           -?0.1           2.04           0.2          0.85          6.67        31
1-31-77      37           9.6        4.6            185            14            0.1           2.04           0.2          0.78          6.67        28
2-7-77       37           9.6        4.5            189            13           <0.1           2.00           0.2          0.80          6.60        29
2-8-77       37           9.6        3.7            218            14           <0.1           2.04           0.2          1.01          6.05        36
2-8-77       37           9.5        3.3            229            14           <0.1           2.04           0.2          1.12          5.71        40
1-24-77      37           9.9        5.4            166            13            0.2           2.00           0.4           .68          7.17        23

G = 76

1-27-77      76           9.7        6.6            236            14            0.2            2.04            0.4          0.45          7.82        30
1-31-77      76           9.7        7.2            190            14            0.4            2.04            0.8          0.42          7.94        24
2-7-77       76           9.8        6.5            251            13            0.2            2.00            0.4          0.47          7.80        32
2-8-77       76           9.6        5.7            296            14           <0.1            2.04            0.2          0.56          7.36        40
2-8-77       76           9.7        5.5            319            14           <0.1            2.04            0.2          0.60          7.28        44
1-24-77      76           9.6        6.5            236            13            0.3            2.00            0.6          0.49          7.60        31

G = 101

1-27-77     101           9.8        6.7            313            14            0.2            2.04            0.4          0.44          7.92        40
1-31-77     101           9.7        7.3            242            14            0.5            2.04            1.0          0.43          7.88        31
2-7-77      101           9.9        7.2            273            13            0.3            2.00            0.6          0.41          8.14        34
2-8-77      101           9.9        6.7            323            14           <0.1            2.04            0.2          0.42          8.08        40
2-8-77      101           9.8        6.4            343            14            0.1            2.04            0.2          0.46          7.86        44
1-24-77     101           9.9        7.6            232            13            0.8            2.00            1.6          0.50          7.80        30

G = 151

1-27-77     151           9.8        6.2            544            14            0.2            2.04            0.4          0.52          7.63        71
1-31-77     151           9.7        7.3            362            14            0.4            2.04            0.8          0.40          7.99        45
2-7-77      151           9.9        7.8            317            13            0.4            2.00            0.8          0.35          8.37        38
2-8-77      151           9.8        7.2            393            14           <0.1            2.04            0.2          0.34          8.32        47
2-8-77      151           9.8        7.2            393            14           <0.1            2.04            0.2          0.34          8.32        47
1-24-77     151           9.7        7.8            287            13            0.7            2.00            1.4          0.42          7.93        36

-------
                                 APPENDIX C

             SAFETY PRECAUTIONS USED IN THE OZONE TEST FACILITY


     A safety program was instituted for this research project based on the
draft report of "Technical Standards for Ozone" by the Occupational Safety
and Health Administration (OSHA).  The major thrust of the program was to
provide containment and destruction of residual ozone in and near the working
environment.

     The maximum permissable exposure concentration of ozone in air is less
than 0.1 part per million (ppm) on a volumetric basis.  The action level is
0.05 ppm ozone.  This low level of exposure was never exceeded during the
evaluation of the contactors.

     Four major areas of control in the research facility were established to
guard against the accidental release of ozone into the work area.

POTENTIALLY HIGH OZONE CONCENTRATION AREA

     The area between the generator and contactors was the most vulnerable
area to accidental ozone release because of the location of transmission
lines containing the highest levels of ozone in the facility (approximately
2,000 to 15,000 ppm).  The transmission lines were fabricated from aluminum
tubing and located underneath or alongside support beams to protect the lines
from accidental falling objects.

     If an accidental ozone release had occurred, the operators were
instructed to immediately vacate the area.  An electrical cut-off switch
was located in an adjacent room for de-energizing the ozonator.  A self-
contained breathing apparatus with a full facepiece and operated in a
pressure demand mode was located at an exit door from the building.  During
an emergency, re-entry would be permissable with this apparatus into an area
containing toxic levels of ozone.

POTENTIALLY MODERATE OZONE CONCENTRATION AREA

     The exhaust gases from the contactors contained ozone at concentrations
between 300 and 5000 ppm.  In this area, PVC pipe was used to convey the
ozone from the contactors to a thermal decomposer.  The decomposer was
controlled to maintain a temperature of 290 C to insure complete decom-
position of the ozone before discharge to the outside atmosphere.  A test was
conducted on the effect of temperature on ozone decomposition.  Results
showed that temperatures above 260 C were required to achieve a 90+% destruc-
tion of ozone.  The data from this test are shown in Table C-l.

                                      75

-------
          TABLE C-l.   EFFECT OF  TEMPERATURE  ON OZONE  GAS DECOMPOSITION
Temp.
C
90
150
200
260
Ozone
In
7.0
7.0
7.0
5.2
cone. , mg/
Out
6.8
2.3
0.8
0.1
Ozone decomposed
2
67
86
98
     A sample outlet was located in the line from the decomposer to the out-
side vent.   During normal operation gas samples from the decomposer were
checked by a Dasibi analyzer.   No evidence of ozone in the gas released to
the outside atmosphere was even indicated.

POTENTIALLY LOW OZONE CONCENTRATION AREA

     After ozone treatment,  the secondary effluent was discharged into an
open trench.  Residual ozone flashed (vaporized)  from solution and ozone
could be detected in the work area.  To remedy the situation,  a hood and
exhaust system were installed at the trench to collect the ozone gas and
vent it outside the building.   Following completion of the jet scrubber
evaluation, the scrubber was modified by installing a recirculating sodium
thiosulfate solution through the jet scrubber to  neutralize the ozone
escaping from the discharging effluent.  Ozone from the effluent was col-
lected by a fan and duct system and vented to the jet scrubber.

SAMPLING STATION

     A central gas sampling station containing gas outlets from all gas
transmission lines was located on a laboratory bench adjacent  to the ozone
contactors.  During wet gas analyses, the gas outlets required purging to
insure collection of a representative sample.  These ozone enriched gases
were decomposed by bubbling the purge gas through a concentrated solution of
potassium iodide.  This technique was effective for maintaining an ozone
free work area.

     A Dasibi analyzer was located at the central sampling station for
continuous monitoring of various ozone gas streams.  The exit  gas from the
Dasibi analyzer was vented into a line leading to the exhaust  system located
at the effluent discharge trench.

     In addition to the above preventive measures, all systems were tested
with air for leakage.  Joints were bubble checked with soap solution before
ozone was introduced into the system.
                                      76

-------
                                   TECHNICAL REPORT DATA
                            (Please rerd Instructions on the reverse before completing)
1. REPORT NO.
 EPA-600/2-79-098
                                                           3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
 COMPARISON OF OZONE  CONTACTORS FOR MUNICIPAL
 WASTEWATER EFFLUENT  DISINFECTION
 Packed Column Versus Jet Scrubber
              5. REPORT DATE
               August 1979 (Issuing Date)
              6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
 Albert D. Venosa,  Edward J.  Opatken and Mark C. Meckes
              8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Municipal Environmental  Research Laboratory--Cin.,OH
 Office of Research  and Development
 U.S. Environmental  Protection Agency
 Cincinnati, Ohio  45268
              10. PROGRAM ELEMENT NO.
               1BC611,  TOS #3,  Task A/02
              11. CONTRACT/GRANT NO.
               In-house  Report
12. SPONSORING AGENCY NAME AND ADDRESS

 Same as above
              13. TYPE OF REPORT AND PERIOD COVERED
               Interim Report 8/19/76-6/19/77
              14. SPONSORING AGENCY CODE
                                                                  EPA/600/14
15. SUPPLEMENTARY NOTES

 Contact:  Albert  D.  Venosa  (513) 684-7668
16. ABSTRACT pjQot  scaie  investigations were made comparing  two  ozone contactors, a jet
 scrubber and a packed  column, for ozone utilization  and effluent  coliform reduction
 efficiency.  The contactors were operated in three phases:   (1) Batch operational phase
 contactors were  operated separately under identical  conditions  on a batch sample of
 activated sludge effluent.   (2)  Parallel operational phase; both  contactors were
 operated in parallel on the same activated sludge effluent.   (3)  Continuous operational
 phase; both contactors were operated on the same activated  sludge effluent to achieve
 a specified coliform reduction.
      Results showed that the packed column significantly  outperformed the jet scrubber
 with respect to  microorganisms reduction.  Effluent  quality interfered with disin-
 fection in both  contactors, the  most important variables  being  chemical oxygen demand
 (total and soluble) and organic  carbon.  Initial bacterial  density and ozoen residual
 were also important factors affecting log reduction  of coliforms  and fecal streptococci
 in both contactors.
      The packed  column significantly outperformed the jet scrubber with respect to
 ozone utilization.  Organic demand measured as TCOD, SCOD,  and  TOC significantly
 affected ozone utilization  at high but not low ozone dosages.
      These results indicate that the use of a single stage  jet  scrubber type ozone
 contactor is not suitable for wastewater disinfection with  ozone.
17.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.IDENTIFIERS/OPEN ENDED TERMS
                              COS AT I Field/Group
 Wastewater, Disinfection,  Comparison, Ozone
 Contactors, Statistical  Analysis,  Micro-
 organism Control, Coliform Bacteria,
 Bactericides, Ozonization,  Utilization,
 Waste Treatment, Analysis  of Variance
  Parallel Streams
  Packed Column
  Jet Scrubber
  Cincinnati, Ohio
     43F
     68D
     91A
     57K
18. DISTRIBUTION STATEMENT
   RELEASE TO PUBLIC
 19. SECURITY CLASS (ThisReport)
    UNCLASSIFIED
21. NO. OF PAGES

     93
 20. SECURITY CLASS (This page)
     UNCLASSIFIED
                                                                         22. PRICE
EPA Form 2220-1 (Rev. 4-77)
77
                                                                     iUS GOVERNMENT POINTING OFFICE 1979 -657-146/5464

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