EPA-670/2-73-075
September 1973
Environmental Protection Technology Series
Laboratory Ozonation of
Municipal Wastewaters
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Monitoring, Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and appli-
cation of environmental technology. Elimination of traditional grouping
was consciously planned to foster technology transfer and a maximum
interface in related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the Environmental Protection Technology
Series. This series describes research performed to develop and demon-
strate instrumentation, equipment and methodology to repair or prevent
environmental 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.
EPA REVIEW NOTICE
This report has been reviewed by the Office of Research and Monitoring,
EPA, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
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EPA-670/2-73-075
September 1973
LABORATORY OZONATION OF MUNICIPAL WASTEWATERS
by
Stephanie G. Roan
Dolloff F. Bishop
Thomas A. Pressley
Contract No. 14-12-818
Project 11010 EYM
Program Element 1B2033
Project Officer
Dolloff F. Bishop
Advanced Waste Treatment Research Laboratory
National Environmental Research Center
Cincinnati, Ohio 45268
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
For sate by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 8fi cents
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ABSTRACT
Rau wastewater, secondary effluent, lime clarified and filtered raw and
secondary wastewaters, carbon treated wasteuaters, and breakpoint
chlorinated plus carbon treated wastewaters were ozonated at pH 7.0 over
a range of 5-90 minutes contact time. Ozonation of the raw wastewater,
with high solids and COD content required impractical ozone dosages for
appreciable COO removal. In all effluents, except raw wastewater, 100
mg/1 of ozone produced at least a 70$ COD removal. Organic oxidation
efficiencies in the raw and secondary uasteuiaters, based upon one atom
of available oxygen per molecule of ozone, exceeded 100$ indicating that
one or more atoms of the ozone molecule or molecular oxygen participated
in the organic oxidation mechanism.
Variable amounts of organic nitrogen and ammonia were oxidized at pH 7.0
by ozone to nitrate. Organic nitrogen and ammonia oxidation to nitrate
increased with increased pretreatment (lower initial COD in the waste-
water) and increased pH. Nitrate residuals formed by the oxidation of
ammonia and or organic nitrogen at the 70$ COD removal level were less
than 3 mg/1. The ozone distribution ratio between oxidation of the NOD
and COD, and the COD removals as a function of ozone dose suggested that
the relative order of oxidation was; easily oxidizable organic material,
NH3, TKN, and slowly oxidizable (nearly refractory) organic material.
This report was submitted in fullfillment of Project Number 11010 EYPI,
Contract Number 14-12-818 by the Department of Environmental Services
Government of the District of Columbia under the sponsorship of the
Environmental Protection Agency. Work was completed September 1971.
ii
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CONTENTS
Page
Abstract ii
Table of Contents iii
List of Figures iv
List of Tables v
Acknowledgments v/i
Sections
I Conclusions 1
II Recommendations 4
III Introduction 5
IV Experimental 7
V Organic Oxidation 11
VI Nitrogen Oxidation 23
VII pH Effects 35
VIII References 37
iii
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FIGURES
No. Page
1 Ozonation System 9
2 Ozonation of Rau Uasteuater 12
3 Ozonation of Secondary Effluent 14
4 Ozonation of Lime Clarified and Filtered Secondary 15
Effluent
5 Ozonation of Lime Clarified and Filtered Rau UJasteuater 16
6 Ozonation of Effluent from Carbon Column Physical- 18
Chemical Treatment of Rau Uasteuater
7 Organic Oxidation Efficiency in Raw and Secondary 20
Ulasteuaters
8 Organic Oxidation Efficiency in Lime Clarified and 22
Filtered Secondary Effluents, Lime Clarified and
Filtered Rau Uasteuater and Carbon Column Effluents
9 Oxidation of Nitrogen in Rau Uasteuater 24
10 Oxidation of Nitrogen in Lime Clarified and Filtered 25
Rau Uasteuater
11 Oxidation of Nitrogen in Secondary Effluent 26
12 Oxidation of Nitrogen in Lime Clarified and Filtered 27
Secondary Effluent
13 Oxidation of Nitrogen in Carbon Effluents from 28
Physical-Chemical Treatment
14 Oxidation of Nitrogen in Carbon Column Effluents 32
Before and After Ammonia Removal
15 Ozonation of Carbon Column Effluents Before and After 33
Ammonia Removal
IV
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TABLES
Page
1 Ozone Organic Oxidation Efficiencies in Various 19
Uasteuaters
2 Typical Nitrogen Concentration Before and After 29
Ozonation of Various Uastewaters
3 Total and Organic Oxidation Efficiencies After 30
70% COD Reduction of Various Uasteuaters
4 Ozonation and pH 36
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ACKNOWLEDGEMENTS
The authors greatfully acknowledge the assistance of Miss Natalie 3.
Taylor, Chemist, Department of Environmental Services, Government of the
District of Columbia with the experimental work.
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SECTION I
CONCLUSIONS
Ozonation at pH 7.0 of raw wastewater with high solids and high COD
content required impractical ozone dosages ( 300 mg/l) for COD removals.
Ozonation at pH 7.0 of wastewater effluents from the EPA-DC Pilot Plant
(secondary, lime clarified and filtered secondary, lime clarified and
filtered raw wastewater, and carbon column effluent from the physical-
chemical treatment system) reveal that reacting 100 mg/l or less of ozone
with waters of low initial COD ( 50 mg/l) produced at least 70% COD
removal in all effluents.
The addition of ozone beyond the 70$ COD removal level produced only a
very gradual COD decrease. In all tests, the COD never decreased to zero
even at high ozone doses (200-300 mg/l 0™) and indicated the presence of
ozone-oxidation resistant organic materials. It is not known if these
oxidation resistant organic materials remaining in the wastewater were
originally present or if they were a byproduct of ozonation.
Typical residual COD's at 70$ removal for secondary, lime clarified and
filtered secondary, lime clarified and filtered raw wastewater, and carbon
column effluents from physical-chemical treatment of raw wastewater were
10.5 mg/l, 13.5 mg/l, 14.2 mg/l and 3.6 mg/l, respectively.
In ozonation of raw wastewater and secondary effluent the organic oxida-
tion efficiency, based upon one atom of oxygen available per molecule of
ozone, and for COD reduction of 70$, exceeded 100$ of the available
"active" oxygen in the ozone. The organic oxidation efficiencies in
chemically clarified effluents avereaged 100$ for the COD reduction of
70$. In the carbon column effluent with a low initial COD of 13 mg/l, the
organic oxidation efficiency at the 70$ COD reduction was 55$.
-------
The observed organic oxidation efficiencies above 100$ indicated that
either molecular oxygen or the oxygen in the entire ozone molecule
contributed to the oxidation mechanism.
Portions of the total organic carbon (TOC), mere oxidized to carbon
dioxide. Typically, the TOC removal was about one half of the COD
removal.
Organic nitrogen and ammonia were also oxidized at pH 7.0 by ozone to
nitrate. For any given ozone dosage the ozone consumed by the nitrogen
oxygen demand (NOD) increased with increasing wastewater pretreatment.
The total organic carbon and nitrogen oxidation efficiencies in all
effluents except raw wastewater exceeded 100$ at the 70% COD removal
level. This confirmed that either molecular oxygen or the entire ozone
molecule participated in the oxidation mechanism. The total oxidation
efficiencies and ratios of ozone used for nitrogen oxidation to organic
carbon oxidation indicated that the oxidation sequence, in the order of
reactivity, was easily oxidized organic material, ammonia nitrogen,
organic nitrogen and slowly oxidizable (nearly refractory) organic
material.
Ozonation of carbon column effluents of low initial COD, containing
ammonia and organic nitrogen, required greater amounts of ozone for the
removal of COD and TOC than were required for the same carbon column
effluent without ammonia. For example, in the non-chlorinated carbon
column effluent (with ammonia) a COD removal of 40$ was achieved with a
residual COD of 6.7 mg/1 at an applied ozone dose of 50 mg/1. In the
breakpoint chlorinated carbon column effluent (without ammonia) a 55$ COD
removal was attained with a residual COD of 5.0 mg/1 at the same applied
dosage. The TOC removals similarly required less ozone in the absence of
ammonia. In all cases, however, the removal of ammonia before ozonation
did not permit complete oxidation of the COD.
-------
Increasing the pH from pH 5 to 11 increased the transfer of ozone to the
effluent. Above pH 9, COD removal was similar to that at lower pH's and
additional ozone was used in ammonia and organic nitrogen oxidation.
-------
SECTION II
RECOMMENDATIONS
Pilot studies of ozone transfer are needed to determine realistic transfer
efficiencies and process costs.
Laboratory studies are needed to determine the types of residual organics
remaining after ozonation.
Disinfection studies are needed to evaluate the removal of bacteria and
virus.
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SECTION III
INTRODUCTION
Ozone has been used for nearly a century in wastewater treatment primarily
as a disinfectant (l, 2, 3, 4, 5,6).Ozone inactivates E. Coli, Poli virus,
cysts of histolytica, spores, algae, and protozoa more rapidly than
chlorine (7). Ozone exhibits an "all or nothing" action on bacteria in
contrast to the linear relationship between chlorine and bacteria kill (2).
More recently, ozone has been used to control odor, taste and color in
wastewater (2, 5, 6, 7, 8, 9, 10, 11, 12).
Ozone has also been successfully used to treat waters polluted by phenols
and cyanides from industrial wastes (7, 13, 14, 15).
Although ozone reacts with dissolved organics in uiastewaters to yield high
quality water, it has not been used extensively in municipal wastewater
treatment because of the relatively high cost of ozone, the lack of
residual ozone in the wastewater (2), and a lack of knowledge of the
effectiveness of ozone treatment. A recent study (16) of ozone treatment
of clarified secondary wastewater revealed an average COD removal of 57^
and an ozone oxidation efficiency, based on one atom of available oxygen
per molecule of ozone, of B0%. For a 10 mgd plant, the treatment cost
was estimated at 7.7 cents per 1,000 gallons.
The study described herein was undertaken to determine the dissolved
organic removals and ozone oxidation efficiencies for ozonation of various
municipal wastewaters and to evaluate the effect of ozone on the nitorgen
content of these wastewaters.
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The municipal uasteuaters treated with ozone were raui uiasteuater, secondary
effluent, lime clarified and filtered raw uasteuater, lime clarified and
filtered secondary effluent, carbon column effluents, and breakpoint
chlorinated and carbon treated effluents. These effluents were obtained
from the EPA-DC Pilot Plant in Washington, D.C.
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SECTION IV
EXPERIMENTAL
The effluents were collected in eight liter batches. The wastewater pH
was adjusted with H2SO, or NaOH to 7.0 before ozonation at various
contact times. Secondary effluents were also ozonated at pH's of 5, 9,
and 11.
Ozone was generated by passing pure dry oxygen at a flow rate of 1.2 1/min
through a silent discharge ozonator. Line voltage to the ozonator was
kept constant to minimize variations in ozone production. A portion of
the ozone-oxygen from the ozonator was continuously fed through two KI
traps and a wet test meter to determine inlet ozone concentrations. The
flow rate through the reactor averaged 0.65 liters per minute at 8 psi and
25°C. The ozone concentration in the gas fed into the system averaged
21.5 mg/1.
The oxygen-ozone mixture was introduced to the sample in a baffled reactor
beneath turbine blades mixing at 500 rpm, to ensure complete dispersion of
the gas throughout the sample. One liter aliquots of the eight liter grab
samples were ozonated in the reactor for 5, 15, 30, 45, 60 and 90 minutes,
respectively. Thus ozone transferred to the sample was a function of both
the wastewater content, and the ozone contact time. Unreacted ozone and
oxygen carrier gas passed from the reactor through two KI traps and a wet
test meter. After ozonation, the system was flushed with helium for ten
minutes to remove ozone and oxygen from the lines and sample. Samples of
the ozonated wastewater in the reactor were then titrated for residual
ozone to confirm complete ozone removal.
Variables used to evaluate ozone treatment of the wastewaters were COD,
TOC, BODg, NH,, TKN., (NO, + N0«), and ozone reacted. Organic oxidation
efficiencies were calculated from the ratio of the change in COD in mg/1
-------
to the amount of ozone reacted. The organic oxidation efficiencies (OOE)
were calculated assuming that in each of the reacting ozone molecules,
only one oxygen atom uas available for the oxidation.
COD m1 (IDD) _
OOE-
°'U-L' "
reacted (1/3) mg/1
COD mg/1 + NOD mq/1 (lOO) . *
IU " 0 reacted (1/3) mg/1 v ;
O
As organic nitrogen may also be oxidized in the COD analysis, total
oxidation efficiencies were only approximate.
The experimental system consisted of a Uelsbach Laboratory Ozonator
Model T-408, a Sola constant voltage transformer, a two-liter glass
reaction kettle with a one inch double grid baffle attached to the side.
The kettle top uas welded to the kettle to prevent gas leakage. Mixing
was achieved by an inverted turbine inserted in the bottom of the kettle,
propelled by a heavy duty Waring commercial blender (Model CB-5) with a
rheostat to control blender speed. Two wet test meters and four 500 ml
gas washing tubes were used in the ozone analysis. All connecting lines
were 1/4 inch OD aluminum or teflon tubing (Figure l).
Ozone was produced from dry zero grade oxygen containing less than 1 molar
ppm mg/1 hydrocarbon. Helium used in flushing ozone from the reactor was
also zero grade. Nitrogen used in stripping TOC samples was ultra high
purity. All other chemicals were ACS reagent grade.
Analytical equipment included a Corning pH meter (Model 12), a Beckman
DU-2 spectrophotometer, a Technicon Autoanalyzer, and a Beckman
Carbonaceous analyzer, Model 915. Gas volume measurements were read on
wet test meters from Precision Scientific Company. Ozone concentrations
were determined by the iodometric method (17). Because of the high con-
centrations of ozone, the ozonated KI solution was diluted to three
8
-------
O3 ANALYSIS
REACTOR
WET TEST
METER
MOTOR
Figure 1. Ozonation System
-------
fourths of a known volume, acidified with IN HLSCL and brought to volume.
An aliquot of the diluted KI solution uias theft titrated with 0.1N sodium
thiosulfate.
Ammonia (18) and nitrate + nitrite (19) were determined on a Technicon
Auto Analyzer. Total Organic Carbon (TOC) was measured on a Beckman
Carbonaceous Analyzer (20). The COD, BOD, and TKN analyses employed
Standard Methods (21).
10
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SECTION V
ORGANIC OXIDATION
Repetitive ozonation of the various uastewaters revealed that variable
ozone transfer occurred in the laboratory tests for the same contact time,
ozone dosage, and experimental conditions. The ozone transfer varied with
the organic content of the water, not only in wastewaters of different
types, but with different samples of the same wastewaters. Thus, the
maximum applied ozone dose at the maximum experimental contact time of
90 minutes varied not only with type of wastewater but also uiithin
different samples of the same type. The organic removals (TOC and COD)
presented, however, were typical of wastewater types.
When unfiltered raw wastewater containing high suspended solids and
dissolved organic material urns treated with increasing ozone doses, the
total COD gradually decreased by 50$ to a residual of 159 mg/1 at the
maximum (90 minute contact time) applied ozone dose of 325 mg/1
(Figure 2). Ozonation at the maximum dose removed 73% of the BOD,_
(Figure 2). At the maximum ozone dose, the removal of total organic
carbon (TOC) in the raw wastewater was 36^ with a residual of 60 mg/1
TOC (Figure 2). As the end product of organic carbon oxidation is CO^,
the removal of TOC indicated that portions of the organics were oxidized
to C02.
In the raw wastewater, COD, BOD5 and TOC residuals continued to decrease
sharply with increasing ozone doses (and contact time) revealing that
additional easily oxidizable organic compounds remained in the wastewater
at the maximum applied ozone dose.
In contrast to raw wastewater, oxidation of the organics in treated
wastewaters required much lower and potentially practical ozone dosages.
Ozonation of a high quality secondary effluent at the maximum applied
11
-------
300 _
250
200 .
O)
E
150 _
100
50
100 150 200
mg/l OZONE REACTED
250
300
Figurs 2. Ozonation of Ram Wasteuater
-------
ozone dose (90 minutes of contact) of 258 mg/1 ozone reduced the COD by
81% to a residual COD of 7 mg/1 (Figure 3). An ozone dose of approximately
60 mg/1, however, reduced the residual COD to less than 10 mg/1 for about
70% removal.
The rate of COD removal occurred rapidly only at low ozone doses
( 60 mg/1). At higher ozone doses in the secondary effluent (60-258 mg/l)
the slow decrease in COD per unit of added ozone (or time) indicated the
presence of organic material that was difficult to oxidize.
Ozonation completely removed the BOD- from the secondary effluent
(Figure 3)^ but required an ozone dose of 210 mg/1. At the 60 mg/1
ozone dose, the BOD- was reduced by 58% to 5 mg/1. The TOC decreased by
60% to a residual of 6 mg/1 (Figure 3) at the maximum ozone dose. At the
60 mg/1 ozone dose, the residual TOC was reduced by 36% to 13 mg/1.
Ozonation of typical lime clarified and filtered secondary effluents
exhibited similar COD removals as the secondary effluent (Figure 4). The
COD removed from the lime clarified and filtered secondary effluent
exceeded 93% with a residual COD of 3.4 mg/1 at maximum applied ozone dose
of 307 mg/1 (Figure 4). An ozone dosage of 100 mg/1, however, reduced
the COD from 45 mg/1 to 12 mg/1 (approximately 70% removal). Above 70%
of COD removal, the rate of COD reduction per unit ozone began to decrease
sharply. Ozonation completely removed the BOD5 from the lime clarified
and filtered secondary effluent at the maximum applied ozone dosage of
397 mg/1 and reduced the BOD to approximately 4 mg/1 at the 100 mg/1
ozone dosage (Figure 4). The TOC at the 100 mg/1 ozone dosage (70% COD
reduction) was reduced from 21 mg/1 to less than 10 mg/1.
In typical lime clarified and filtered D.C. raw wastewater, the COD
removal was 73% with a residual COD of 13 mg/1 at a maximum applied ozone
dose of 104 mg/1 (Figure 5). The BOD was completely removed at the
13
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O)
E
15
10 -
5 -
• COD
A BOD
• TOC
50
100 150 200
mg/l OZONEREACTED
250
Figure 3. Ozonation of Secondary Effluent
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U1
0)
E
• COD
• TOC
A BOD
50
250
100 150 200
mg/l OZONE REACTED
Figure 4. Ozonation of Lime Clarified and Filtered Secondary Effluent
300
-------
O>
E
10
50 75
mg/l OZONE REACTED
Figure 5. Ozonation of Lime Clarified and Filtered Raw Wastewater
100
-------
maximum applied ozone dose of 104 mg/1. TOC removals gradually increased
to 58$ removal at the maximum applied ozone dose to a residual of 10 mg/1
(Figure 5).
Ozonation of carbon column effluents from physical-chemical treatment of
raw wastewater with low initial COD's exhibited a COD removal of 90$ with
a residual COD of 1.3 mg/1 at a maximum applied ozone dose of 151 mg/1
(Figure 6). A COD residual of 3.7 mg/1, however, was achieved with a
50 mg/1 ozone dose. The BOD,, was also essentially removed at the 50 mg/1
ozone dose (Figure 6). The TOC removal was 44$ at a 50 mg/1 ozone dose
with a residual TOC of 3.8 mg/1. The TOC residual decreased very little
with increasing ozone doses above the 50 mg/1 ozone dose.
While repetitive tests on the lime clarified and filtered effluents
revealed that variable ozone transfer occurred with time for the same
type of effluent and experimental conditions, more ozone was generally
transferred in a given time to secondary and to lime clarified and
filtered secondary effluents than to lime clarified and filtered raw
wastewater or to carbon column effluents from physical-chemical treatment
of raw wastewater (Table l). The reason for the difference in transfer
efficiency between the biologically treated and physical-chemical
effluents was not determined.
The effectiveness of ozone for removing COD was described using the
organic oxidation efficiencies (equation l). The organic oxidation
efficiencies based upon 1 available oxygen atom per molecule of ozone for
COD removal in raw wastewater and in secondary effluents (Figure 7)
exceeded 100$ (356$ for raw wastewater and 280$ for secondary effluent).
The high organic oxidation efficiencies observed in raw wastewaters and
secondary effluents at high COD/0- ratios revealed that either molecular
oxygen or the entire ozone molecule was involved in the initial oxidation
of the organics. The efficiencies, however, decreased as the ozone dose
17
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CD
O)
50 100
mg/l OZONE REACTED
150
Figure 6. Ozonation of Effluent from Carbon Column Physical-Chemical Treatment of
Raw Wastetuater
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TABLE 1
OZONE ORGANIC OXIDATION EFFICIENCIES
IN
VARIOUS UASTEUATERS
EFFLUENT
RAW
70$ REMOVAL OF COD
RESIDUAL COD
mg/1
97
mg/1 of OZONE
TRANSFERRED
510*
OZONE TRANSFERRED
IN 90 MINUTES
0.0. E.
130*
mg/1
325
SECONDARY
10.6
60
124
285
RAW LIME
13
104
102
104
LIME SECONDARY 13
95
101
300
CARBON COLUMN 3.7
47
55
150
* Extrapolated value (0 required to achieve 1Q% reduction in COD
«J
within the 90 minutes of contact time employed in the study).
19
-------
fO
o
300
200 ~
o
•
o
100 -
• RAW WASTEWATER
^SECONDARY
50
100 150 200
mg/l OZONE REACTED
250
300
Figure 7. Organic Oxidation Efficiency in Raw and Secondary Wasteiuaters
-------
increased and at the maximum applied ozone dose, the efficiencies were
approximately 150% in raw wastewater and 33$ in the secondary effluent.
Ozonation of other raw wastewaters produced organic oxidation
efficiencies at low ozone dosages (high COD to applied ozone) exceeding
700$. In contrast to the raw wastewater and secondary effluent,
organic oxidation efficiencies for COD removal in lime clarified and
filtered raw and secondary effluents (Figure 8) initially varied little
with ozone dosage, averaging approximately 100$ until the COD removal
increased above 70% ( 100 mg/1 ozone). Then the organic oxidation
efficiencies gradually began to decrease and indicated the presence or
formation of an oxidation resistant residual organic material.
Organic oxidation efficiencies of carbon column effluent from physical-
chemical treated raw wastewater (Figure 8) were lower than those in
clarified effluents. With low initial COD's of the carbon column
effluent, the organic oxidation efficiencies averaged approximately 50%
until the COD removal increased above 70% (50 mg/1 ozone dose). Then the
efficiencies gradually decreased to approximately 20% at the maximum
applied ozone dose.
With the 90 minute contact time system previously described, 70% COD
removal could not be achieved in the raw wastewater samples. The organic
oxidation efficiencies (Table 1) at 70% COD removal were approximately
130$ in the raw wastewater (extrapolated), 124$ in secondary, 101$ in
lime clarified and filtered secondary effluent, 102$ in lime clarified
and filtered raw wasteuater, and 55$ in the carbon column effluent. In
all effluents, further addition of ozone beyond 70$ COD removal produced
inefficient COD reduction with a sharp decrease in organic oxidation
efficiency, and therefore, further ozonation after 70$ COD removal was
not practical for COD reduction.
21
-------
150
• RAW LIME
A LIME SECONDARY
• CARBON
100
S)
N3
LU
•
o
•
o
50
0
Figure 8.
50
100 150 200
mg/l OZONE REACTED
250
300
Organic Oxidation Efficiency in Lime Clarified and Filtered Secondary
Effluents, Lime Clarified and Filtered Raw Uasteuater and Carbon Column
Effluents
-------
SECTION VI
NITROGEN OXIDATION
The literature (22) indicated that ozone reacted with organic nitrogen
(amino acids and proteins) to liberate ammonia. In this study, the
ozonation of uasteumters oxidized the total kjeldahl nitrogen (TKN)
(Figures 9, 10, 11,. 12, and 13) including both organic nitrogen and free
ammonia. The liberated ammonia from the organic nitrogen and original
dissolved ammonia reacted with ozone to form NO -N.
-------
IS3
o
o
oc
25
TKN
NH4+-N
(NO3+ NO2)-N
100 150 200
mg/l OZONE REACTED
250
300
Figure 9. Oxidation nf IM.itrngen in Raw Uastewater
-------
ro
en
o
o
O)
E
10
25
TKN
Figure 10,
50 - 75
mg/l OZONE REACTED
Oxidation of Nitrogen in Lime Clarified and Filtered Raw Uasteuater
100
-------
cn
o
o
O)
E
50
100 150 200
mg/l OZONE REACTED
250
Figure 11. Oxidation of Nitrogen in Secondary Effluent
-------
o
o
O)
20
50
TKN
NH4 + -N
NO2)-N
300
100 150 200 250
mg/l OZONE REACTED
Figure 12. Oxidation of Nitrogen in Lime Clarified and Filtered Secondary Effluent
-------
K>
(X
CD
O
ex.
10
• TKN
• NH4+-N
MNO3+NO2)-N
3 50 100 150
mg/l OZONE REACTED
Figure 13. Oxidation of Nitrogen in Carbon Effluents from Physical-Chemical Treatment
-------
TABLE 2
TYPICAL NITROGEN CONCENTRATIONS
Rau Uasteuater
mq/1 ozone reacted TKN mq/1 NHt mq/1 (NOZ + ND^) mq/1
•™~~~ 4 o Z
0 21.5 14.0 0
100 18.0 13.0 1
Secondary
0 14.4 12.0 0
100 9.6 9.4 3.8
Lime Clarified and Filtered Secondary
0 15.2 12.6 0
100 12.9 11.6 2.6
Carbon Column
0 11.0 10.9 0
100 5.3 5.08 5.4
29
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TABLE 3
TOTAL AND ORGANIC OXIDATION EFFICIENCIES
EFFLUENT OXYGEN DISTRIBUTION 70% COD REMOVAL
RATIO
- ORGANIC O.E.J6 TOTAL O.E.
L» ULJ
RAW .07 150 162*
SECONDARY .27 124 151
RAW LIME .34 ' 102 140
LIME SECONDARY .27 101 129
CARBON 1.68 55 155
* Extrapolated value (ozone required to achieve 70$ COD reduction
could not be applied within the 90 minute maximum contact time
employed in the study).
30
-------
distribution ratio between NOD and COD during ozonation and the COD
removals as a function of ozone dose suggested that the relative order
of oxidation was; easily oxidizable organic material, TKN, and slowly
oxidizable (nearly refractory) organic material.
Ozonation of carbon column effluents from physical-chemical treatment of
raw wastewater which had been breakpoint chlorinated (and dechlorinated)
for ammonia removal, and ozonation of the carbon column effluents with
the ammonia revealed the oxidation of ammonia nitrogen before the
organic nitrogen (Figure 14). For example, in the non-chlorinated
carbon column effluent, NH, -N removals corresponded to approximate
stoichiometric increases in N0_ -N, while the organic nitrogen concentra-
«J
tion remained constant. In the chlorinated waters (without NH. -N) , the
organic nitrogen was oxidized to N0~ -N (Figure 14). Thus, the complete
relative order of oxidation was easily oxidizable organics (COD),
ammonia, organic nitrogen, and slowly oxidizable (nearly refractory)
organic material.
In the studies on physical-chemical treatment effluents, ozonation of
carbon column effluents of low initial COD required greater amounts of
ozone for the removal of COD and TOC than was required in the same
waters without ammonia (Figure 15). For example, in non-chlorinated
carbon column effluent (with ammonia), a COD removal of 40$ was achieved
with a residual COD of 6.7 mg/1 at an applied ozone dose of 50 mg/1. In
the same carbon column effluent, after breakpoint chlorination (ammonia
free), a 55$ COD removal was attained with a residual COD of 5.0 mg/1 at
the same applied ozone dosage. The TOC removals also required less ozone
in the absence of ammonia (Figure 15). For example, in the breakpoint
chlorinated carbon column effluent, an applied ozone dose of 40 mg/1 was
required for a 60$ TOC removal to a residual of 2.5 mg/1 TOC. The same
non-chlorinated effluent (with ammonia) required an applied ozone dosage
of 90 mg/1 to achieve the 2.5 mg/1 TOC residual. It should be noted,
31
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O
O
OL
15
- 10
o>
E
NOo)-N
AMMONIA
FREE
50
100 150 200
mg/l OZONE REACTED
250
Figure 14. Oxidation of Nitrogen in Carbon Column Effluents Before and After Ammonia
Removal
-------
O)
E
• COD
• TOC
AMMONIA
FREE
100 150
mg/l OZONE REACTED
200
250
Figure 15. Ozcnation of Carbon Column Effluents Before and After Ammonia Removal
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however, that even with the ammonia and organic nitrogen essentially
removed, the residual COD mas only very slouly oxidized after appreciable
exposure to additional ozone. The removal of the nitrogen did not
permit complete oxidation of the residual organics.
Complete evaluation of the oxidation capabilities of ozone must account
for ozone consumed in nitrogen oxidation* Total oxidation efficiencies
(equation 2) after five minutes of ozonation did not significantly differ
from the organic oxidation efficiencies, because in all wasteuaters, less
than 1 mg/1 of nitrate uas produced with high COD/0- ratios.
«J
After removal of 70% of the COD, total oxidation efficiencies for
organic and ammonia oxidation (Table 3) in all treated effluents were
significantly higher than oxidation efficiencies based on COD removal
alone, and were greater than 100$. As an example, the organic oxidation
efficiency for carbon treated effluents at 70j£ COD removal uas 55JK,
while the total oxidation efficiency was 155JC. These total oxidation
efficiencies confirm-that either oxygen from molecular oxygen or the
entire ozone molecule uas involved in the oxidation mechanism, and
strongly suggested that contributions -to the oxidation process include
an autoxidation (molecular oxygen) mechanism.
34
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SECTION Mil
pH EFFECTS
Aliquots of secondary effluent were ozonated at pH 5, 9 and 11 for 60
minutes. The ozone transferred at pH 5 was 38 mg/1, at pH 9, 160 mg/1
and at pH 11, 256 mg/1. Thus, the transfer of ozone increased with
increasing pH.
At pH 5, a 14% COD removal occurred with a 50$ organic oxidation
efficiency (Table 4). At pH 9, the COD removal was 57% with a
organic oxidation efficiency, and at pH 11, the COD removal was 60$ with
a 34$ organic oxidation efficiency. Similarly the TKN at pH 5, 9 and 11
were reduced by 1%, 52% and 90$ with residuals of 16.6 mg/1, 8.8 mg/1
and 0.5 mg/1, respectively. Total oxidation efficiencies (organic and
nitrate) were: 58.8$ at pH 5, 93.3$ at pH 9 and 82.1$ at pH 11 (Table 4),
At pH's 5 and 9, TKN removals correspond to an approximate stoichiometric
increase in NO™. The TKN removed at pH 11 was 15.4 mg/1 but only 11.9
mg/1 NO, -N was detected. The difference between the NHL removed and the
*j O
nitrate produced was likely caused by oxygen stripping of ammonia from
the wastewater at pH 11.
Thus, the study revealed the pH range for optimum COD removal was
between 7 and 9. The literature indicated that ozone in acid solution
is more stable with slower decomposition rates. In this study, the ozone
produced the least COD oxidation at pH 5. At pH's above 9, the nitrogen
oxidation increased. For example, at the maximum applied ozone dose,
the nitrogen oxygen demand for ozone in secondary effluent was 7.7 mg/1
ozone at pH 9, and 13.6 mg/1 ozone at pH 11 (Table 4).
35
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TABLE 4
OZONATION AND pH
pH mg/1 of OZDNE
REACTED IN 60
MINUTES
Q.E.% % REP10UAL
COD
TKN NH
'4
N02) -N
mg/1
38
50 14
0.35
160
50 57
52 55
6.75
11
256
34 60
90 97
11.90
36
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SECTION IX
REFERENCES
1. Hann, V.A., "Disinfection of Drinking Uater with Ozone", Jour. AWWA,
1316 (1956).
2. O'Donovan, D.C., "Treatment with Ozone", Jour. AWWA, 57, 1167,
September 1965.
3. Ozonation treatment shown. Water and Wastes Engineering, 8, 8
January 1971.
4. Stumm, Werner, "Ozone as a Disinfectant for Water and Sewage."
Boston Society of Civil Engineers, 6B, October 1957.
5. Diaper, E.W.J., "Microstraining and Ozonation of Water and Waste-
water." Water and Wastes Engineering, J5, 56, February 1968.
6. Campbell, R.M., and M.B. Pescad, "Ozonation of Turret and other
Scottish Waters", Water and Sewage Works, 113, 268, July 1966.
7. Thirumurthi, D., "Ozone in Water Treatment and Wastewater Renova-
tion", Water and Sewage Works, 115;R. 106, November 29, 1968.
8. Palin, A.T., "The Ozonation of Water with Special Reference to Color
Removal", Water and Wastes Engineering, 56, 271 (1953).
9. Masse, A.E., "Successful Odor Control at Michigan Wastewater Treat-
ment Plant", Water and Sewage Works, 114, 322, September 1967.
10. Miller, F.J., "Upline Sewage Treatment Eliminates Odors, Reduces
BOD, Cuts Complaints", Water and Wastes Engineering, J5, 52,
December 1966.
11. Sewage Plant in Center of Town is Ozonized and Soundproofed,
Engineering News, 172, 34, June 11, 1964.
12. Pateman, S.G., "Oxnard Sewage Plant Solves Odor Control Problem",
Water and Sewage Works, 116, 352, September 1969.
13. Eisenhauer, H.R., "Oxidation of Phenolic Wastes", WPCF Jour., 36,
1116, September 28, 1964.
14. Cronan, C.S., Ozone Counters Waste Cyanides "Lethal-Punch", Chem.
Engineering, 65, 63, March 24, 1958.
37
-------
15. Labine, R.A., "Phenol-Free Wasteuater", Chemical Engineering, 66,
114, August 24, 1959.
16. "Ozone Treatment of Secondary Effluents from Wasteiuater Treatment
Plants", Huibers, A., R. McNabney, and A. Halfon, Report No.
TWRC-4, U.S. Department of the Interior, Federal Water Pollution
Control Administration, Cincinnati, Ohio, April 1969.
17. "Standard Methods for the Examination of Water and Wasteuater",
12 ed., American Public Health Association, New York, 1965.
18. "FWPCA Methods for Chemical Analysis of Water and Wastes", U.S.
Department of the Interior, Federal Water Poll. Control Adm.,
Cincinnati, Ohio, November 1969.
19. Kamphake, L. et al., "Automatic Analysis for Nitrate by Hydrazine
Reduction", Water Res., !_, 205, 1967.
20. Schaeffer, R.B., et al, "Application of a Carbon Analyzer in Waste
Treatment", Journal Water Poll. Control Fed., 37t 1545, 1965.
21. Ob. cit. (17)
22. Ptudd, 3.B., et al, "Reaction of Ozone with Amino Acids and Proteins",
Atmospheric Environment, ^5, 669, November 1969.
23. Bishop, D.F., et al, "Physical-Chemical Treatment of Municipal
Wasteuater", U.S. Dept. of the Interior, Fed. Water Quality Adm.,
Cincinnati, Ohio, October 1970.
38
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Report No.
N:'-
w
4. Tiiie
LABORATORY OZONATION OF MUNICIPAL WASTEWATERS
Roan, Stephanie G.. Bishop. Dolloff F., and Pressley, Thomas A
9, Otg miration
EPA-DC Pilot Plant
5000 Overlook Avenue S.W.
Washington, D.C. 20032
S.' Report Date
6. '
8. Performing Organisation
Report No,
11010 EYM
Envfronmentat Prdtefc'tftn Agency
14-12-818
13. Type of Repoi t and
Period Coveted
.,, ,........,, .....
Environmental Protection Agency report number EPA-670/2-73-075 ,
September 1973.
If. Ab^-act "
Raw wastewater, secondary effluent, lime clarified and filtered raw and secondary
wastewaters, carbon treated wastewaters, and breakpoint chlorinated plus carbon
treated wastewaters were ozonated at pH 7.0 over a range of 5-90 minutes contact
time. Ozonation of the raw wastewater, with high solids and COD content required
impractical ozone dosages for appreciable COD removal. In all effluents, except
raw wastewater, 100 mg/1 of ozone produced at least a 70% COD removal. Organic
oxidation efficiencies in the raw and secondary wastewaters, based upon one atom of
available oxygen per molecule of ozone, exceeded 100% indicating that one or more
atoms of the ozone molecule or molecular oxygen participated in the organic oxidation
mechanism.
Variable amounts of organic nitrogen and ammonia were oxidized at pH 7.0 by ozone
to nitrate. Organic nitrogen and ammonia oxidation to nitrate increased with
increased pretreatment (lower initial COD in the wastewater) and increased pH.
Nitrate residuals formed by the oxidation of ammonia and or organic nitrogen at
the 70% COD removal level were less than 3 mg/1. The ozone distribution ratio
between oxidation of the NOD and COD, and the COD removals as a function of ozone
dose suggested that the relative order of oxidation was; easily oxidizable organic
NH-. TKN, and slnwlv nxidiyahlp (npaHy rpfrartnry) nygarvir tnatoHal
17a. Descriptors
Oxidation Ammonia
* Ozone
Chemical Oxygen Demand
Tertiary Treatment
Sewage Treaetent
17b. Identifiers
* Wastewater"Ozonation
Oxi dati on E ffi ci en cy
Nitrogen Oxidation
Total Organic Carbon
17c. COWRR Field & Croup
'?. .4 v3/.'a?);'/;tv
*¥"'"'
(Report)
3Q. Sec trity Cl-ss.
(Page)
lit. ;
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. O. C. 2O24O
Stephanie G. Roan
Environmental Protection Agency
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