y>EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-155 Sept. 1981
Project Summary
Parallel Evaluation of Air- and
Oxygen-Activated Sludge
Scott Austin, Fred Yunt, and Donald Wuerdeman
To provide data on the relative
merits of air and of oxygen in the
activated sludge process, two 1,900-
mVday (0.5-mgd) activated sludge
pilot plants, one air and one oxygen
system, were operated side-by-side at
the Joint Water Pollution Control
Plant, Carson, California. Although
both pilot plants met the applicable
discharge limitations for everything
but three trace metals, the oxygen
system provided a more stable opera-
tion.
Primary differences in performance
concerned ammonia nitrogen removals.
Calculated differences in energy
consumption indicate a savings might
be expected with the oxygen system.
Differences in sludge production were
not significant.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory. Cincin-
nati, OH, to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Since the introduction of high-purity,
oxygen-activated sludge, a controversy
has existed concerning the relative
merits of air and of oxygen in the
activated sludge process. Very little
data, however, were available on side-
by-side operation of relatively large-
scale systems with comparable engi-
neering.
As part of the research effort involved
with federally-mandated secondary
treatment at the Joint Water Pollution
Control Plant (JWPCP) in Carson,
California, the County Sanitation Dis-
tricts of Los Angeles County constructed
two 1,900-m3/day (0.5-mgd) activated
sludge demonstration plants. One
incorporated the UNOX high-purity
oxygen process, and one used an air-
sparged mechanical aerator. The primary
purpose of the study was to obtain data
pertinent to the selection and design of
an activated sludge system at the
JWPCP, but the nature of the research
facilities allowed a direct comparison of
the two activated sludge processes. The
pilot plants were operated on identical
feed. Equal engineering care was taken
in the design of the aeration system, and
identical clarifiers were used. The
research motivations in establishing the
operating parameters for the two plants
were different: the oxygen system was
operated to refine specified design
parameters, whereas the air system
was operated to determine its capabili-
ties and limitations.
The JWPCP is a 15-mVsec (350-
mgd) primary treatment plant treating a
mixture of domestic and industrial
wastes. This facility allowed a good'
comparison of the two activated sludge
alternatives for treating relatively
concentrated municipal wastewater.
Selection and Description of
the Pilot Plants
Air-Sparged Turbine System
Locating the Districts' JWPCP in an
urban area placed a definite land
constraint on the proposed secondary
-------
treatment system for that plant. When
preliminary site layouts were made for a
conventional activated sludge system
with the standard 4.6-m (15-ft) deep
aeratiorrtanks and an optimistic 6-hr
aeration period, no excess land was
available for waste activated sludge
processing. Because of this land con-
straint, the Sanitation Districts proceeded
to evaluate activated sludge systems
that could reduce the land area required
for secondary treatment. One of those
alternatives was the deep tank sub-
merged turbine (DTST) system. The
DTST system was selected not only
because of the land savings from the
deeper tank (7.6 m or 26 ft) but also
because the submerged turbine is a
more efficient oxygen transfer device
than the conventional coarse bubble air
diffusers. The land savings from the
deeper tank and the possibility of
reducing the aeration period made the
DTST system a realistic candidate
system for secondary treatment at the
JWPCP.
High-Purity Oxygen System
One of the major advantages offered
by the pure oxygen biological treatment
process is the ability to reduce the
period of time required for treatment of
wastewater by increasing the rate at
which oxygen can be dissolved into the
mixed liquor within the biological
reactor. The results of preliminary
studies using Union Carbide's 0.6-
L/sec (10-gpm) mobile pilot plant
verified this claim since acceptable
effluent quality was achieved at aeration
periods as short as 1.5 hr (V/Q).
As a result of competitive bidding.
Union Carbide Corporation* constructed
the pure oxygen biological reactor,
which was to utilize the existing pilot
plant influent pumping station and final
clarifier system. The reactor was
designed to incorporate a submerged
turbine/gas recirculation compressor
arrangement for oxygen dissolution in
each reactor stage.
Table 1 compares the design criteria
for the air-sparged system and the high-
purity oxygen system as well as the
associated final clarifiers. Tables 2 and
3 summarize the operational parameters
for the air and oxygen systems, respec-
tively.
Table 1. Design Criteria for Pilot Plants
Item
Air
System
Oxygen
System
Biological Reactors:
Average flow, m3/day (mgd) 1900 (0.5) 1900 (0.5)
Length, m (ft) 6.1 (20) 7.3 (24)
Width, m (ft) 6.1 (20) 7.3 (24)
A verage water depth, m (ft) 7.6 (25) 3.7 (12)
No. of stages 1 4
Detention time (V/Q), hr 3.5 2.5
Oxygen Storage Tank:
Number — 1
Volume, m3 (ft3) NTP — 3900
(350.000)
Capacity, m3/hr (ft3/hr) — 740
(4940)
Standard Large
Final Clarifiers:
Number 2 1
Length, m (ft) 22 (72) 34 (111)
Width, m (ft) 3.0 (10) 3.0 (10)
Average water depth, m (ft) 3.0(10) 3.0(10)
Overflow rate. m3/m2/day (gpd/.f?) 28.5 (700) 18.3 (450)
Detention time
(Q x 1/3 return), hr 2.0 3.0
Weir loading rate. m3/m/day (gpd/ft) 62.1 (5000) 62.1 (5000)
Flowthrough velocity
(Q x 1/3 return), mm/sec (ft/min) 3.2 (0.6) 3.2 (0.6)
'Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use by the U.S. Environmental Protection
Agency.
Discussion of Results
Effluent Quality
Activated sludge systems consist of
two component units—the reactor and
the final clarifier. The quality of the final
effluent is related to the interaction of
the component parts, and poor effluent
quality may be caused by an inadequacy
of only one part. The effluent quality of
the air and oxygen systems is described
in Tables 4 and 5.
Soluble BOD
A primary indicator of the adequacy of
the reactor in terms of oxygen transfer
and treating the wastewater is the
removal of soluble organics. In all
phases, for both pilot plants, the soluble
BOD5 concentrations were 6 mg/L or
less. These BOD measurements are low
enough that 'differences between the
two systems are not considered signifi-
cant.
Suspended Solids
Secondary effluent solids concentra-
tions depend on the effectiveness of the
final clarifier. High effluent suspended
solids, however, may be an indication of
poor clarifier design, poor aerator
design, or poor plant operation. During
startup, both 1,900-m /day <0.5-mgd)
pilot plants experienced periods of high
effluent suspended solids and turbidity,
which were alleviated by reducing the
power input to the final stages of the
reactors.
Sludge Production
One of the most important claims
made on behalf of pure oxygen is thai
the net growth of solids in these
systems will be less than a similar air
system when operated at the same
mean cell residence time (MCRT). Since
a large portion of the cost of wastewater
treatment is usually associated with
solids processing and sludge handling,
this claim would represent a significant
savings in both capital and operating
costs. The claim is based on a comparison
between the two systems that shows
the net sludge production of air systems
to be greater for any given organic
loading rate than a similarly operated
oxygen system.
From an analysis of the data collected
both from this and an earlier, smaller-
scale study, the Districts have concluded
there is little difference between the an
-------
Table. 2. Summary of Operational Parameters—Air-Sparged Turbine System
Parameter . Phase
DATES:
Start
End
Duration, days
Flow Pattern
REACTOR:
Influent Flow, m3/day (mgd)
Recycle. %
Hydraulic Detention Time:
V/Q, hr
V/(QxR). hr
MLSS, mg/L
Volatility. %
Mean Cell Residence Time:
Reactor So/ids, days
Total System Solids, days
Organic Loading Rate:
BODR/MLVSS. kg/ kg/ day
BODn/TPVSS. kg/kg/day
CODR/MLVSS, kg/kg/day
CODn/TPVSS, kg/kg/day
flODA. kg/ m3/ day fib/ ft3 /day)
Sludge Production:
VSS/BOD*. kg/ kg
VSS/CODn, kg/ kg
CLARIFIER:
Overflow Rate, m3/m2/day (gpd/ff)
Dentention Time:
V/Q, hr
V/(Q+R), hr
Solids Loading Rate, kg/ m3/ day
(Ib/ft3/day)
Return Sludge Concentration, %
SVI. ml/g
1
2/9/75
3/1/75
21
Steady
1200
(0.32)
90
5.6
2.9
3100
72
5.1
6.8
0.34
0.26
0.80
0.60
0.75
(12.0)
0.51
0.22
18.3
1450)
4.0
2.1
107
(1714)
0.7
252
II
3/9/75
3/29/75
21
Steady
1700
(0.45)
65
4.0
2.4
3400
73
3.7
5.4
0.38
0.27
1.07
0.74
1.00
(16.0)
0.64
0.27
21.3
(523)
2.8
1.7
117
(1874)
0.9
183
III
4/6/75
5/3/75
29
Steady
1700
(0.45)
45
4.0
2.8
2600
74
2.2
3.3
0.49
0.33
1.30
0.87
1.03
(16.5)
0.79
0.34
16.9
(415)
4.3
3.0
63
(1009)
0.9
163
IV
5/11/75
6/21/75
42
Steady
1900
(0.50)
40
3.5
2.5
4000
73
3.7
5.5
0.30
0.23
0.90
0.60
1.15
(18.4)
0.73
0.30
18.3
J450)
4.1
2.9
103
(1650)
0.9
165
V
7/20/75
8/30/75
42
Steady
1700
(0.45)
44
4.0
2.8
2300
73
1.8
2.8
0.70
0.47
1.61
1.06
1.34
121.5)
0.70
0.35
16.1
(395)
4.5
3.1
54
(865)
0.9
227
VI
9/28/75
10/25/75
28
Steady
1500
(0.40)
29
4.5
3.5
3300
70
3.0
4.3 .
0.49
0.33
1.16
0.82
1.24
(19.9)
0.56
0.26
14.7
(361)
5.0
3.9
63
(1009)
1.2
200
VII
10/26/75
11/20/75
26
Steady
1500
(0.40)
38
4.5
3.3
3300
71
3.2
4.3
0.44
0.30
1.00
0.75
1.12
(17.9)
0.63
0.31
14.7
1361)
5.0
3.6
68
(1089)
1.1
160
VIII
11/27/75
12/25/75
29
Steady
1500
(0.40)
50
4.5
3.0
3600
70
3.4
4.5
0.44
0.30
1.00
0.75
1.20
(19.2)
0.63
0.30
14.7
(361)
5.0
3.3
83
(1329)
1.1
173
IX
3/4/76
3/25/76
22
Steady
1300
(0.34)
47
5.3
3.6
2900
70
3.6
5.9
0.45
0.29
1.10
0.68
0.97
(15.5)
0.60
0.27
19.4
(476)
3.6
2.5
83
(1329)
0.9
146
and oxygen systems in terms of sludge
production. When an analysis of the
system is made based on the mass of
micrporganisms contained within the
biological reactor (which is the method
used by proponents of pure oxygen), the
data do indeed indicate that the oxygen
systems produces less sludge. The
authors believe, however, that the mass
of solids within the entire biological
system must be considered to obtain a
true indication of the level of sludge
production. This means that the solids
present in the final clarifiers must be
included when the total system solids
are calculated. When the data are
reexamined in this way, the oxygen
system will no longer demonstrate an
advantage over air systems in terms of
sludge production. This reversal is
because a greater portion of the total
system solids will be contained within
le clarifiers of an oxygen system than
is typically encountered in air-activated
sludge systems. Improved sludge settling
and oxygen transfer capability allows
the oxygen system to be operated as a
high-rate system. As a result, as much
as 50% of the total system solids will be
carried in the final clarifiers. If the
comparison of air and oxygen systems is
based on reactor solids only, then a
significant portion of the oxygen solid
will be eliminated from the analysis,
thus falsely indicating a higher organic
loading rate than that imposed on the air
system.
Sludge Settleability
Two parameters are commonly used
to indicate sludge settleability. The
sludge volume index (SVI) is the inverse
of the settled sludge concentration
expressed in ml/g, and the initial
settling rate (ISR) is the maximum rate
at which the sludge interface drops
during the test.
ISR data are reported from one series
of tests conducted during a period when
the performance of both pilot plants was
characterized as "good." In this series
of tests, the oxygen sludge settled about
three times as fast as the air sludge.
Although these results are the product
of limited testing, they are in qualitative
agreement with the general operating
experience of the JWPCP pilot plants.
The oxygen sludge definitely settled
and gravity thickened better than the air
sludge during this project. At this time,
however, it's impossible to determine
the extent to which this is an innate
property of oxygen-activated sludge or a
function of the reactor design.
One factor that affected the sludge
settleability in both of these systems
was power input. To produce an
acceptable eff I uent during the startup of
-------
Table 3. Summary of Operational Parameters—Oxygen System
Parameter
Phase
I
II
III
IV
VI
VII
VIII
IX
XI
DATES'
Start
End
Duration, days
Flow Pattern
REACTOR:
Influent Flow, rrf/day fmgd)
Recycle. %
Hydraulic Detention Time-
V/Q, hr
V/(Q+R), hr
MLSS. mg/L
Volatility. %
Mean Cell Residence Time:
Reactor Solids, days
Total System Solids, days
Organic Loading Rate:
BODH/MLVSS. kg/kg/day
BODn/TPVSS. kg/kg/day
CODR/MLVSS. kg/kg/day
CODR/TPVSS, kg/kg/day
BODA, kg/m3/day (Ib/ft3/day)
Oxygen Utilization.
02/BODK, kg/kg
Oi/CODn, kg/kg
Sludge Production:
VSS/BODR, kg/kg
VSS/COD*. kg/kg
CLARIFIER:
9/22/75 10/27/75 12/1/75 2/1/76 2/18/76 3/31/76 6/21/76 9/30/76 10/28/76 11/9/75 12/10/71
9/25/75 11/10/75 12/30/75 2/17/76 2/29/76 5/20/76 9/14/76 10/13/76 11/7/76 11/24/76 12/23/71
4 15 30 17 12 51 85 14 11 16 14
Diurnal Steady Steady Steady Steady Steady Steady Steady Dirunal Dirunal Diurnal
1900
(0.511
40
2.5
1.8
3800
75
1.8
3.4
0.70
0.31
1.67
0.89
2.15
134.4)
1.36
0.71
0.97
0.48
1500
(0.40)
40
31
2.2
2800
73
2.5
5.9
074
0.31
1.52
0.64
1.73
127.7)
0.60
0.29
1400
fO 37)
44
3.4
2.3
4200
74
3.4
6.8
1700
(0.45)
44
2.8
1.9
4600
72
1.9
5.6
1900
(0.51)
42
2.5
1.6
3300
75
1.7
34
1900
(0.51)
40
2.5
1.8
3900
74
1.9
4.4
1800
(0.48)
38
2.6
1.9
4100
77
2.7
4.8
1900
(0.51)
40
2.5
1.8
4420
75
2.1
3.8
0.52
0.26
1.14
0.56
1.62
(25.9)
0.60
0.20
1.31
045
2.03
(32.5)
0.83
042
1.61
0.81
2.05
132.8)
0.69
0.29
1.54
0.64
2.00
(32.0)
0.57 '
0.33
1.15
0.66
1.76
(282)
0.48
0.27
0.95
0.54
1.63
(26.1)
0.64
0.28
0.63
0.29
0.78
0.40
0.80
0.36
0.69
0.33
1.52
0.81
0.84
0.42
1900
(0.51)
39
2.5
1.8
3700
70
2.0
4.2
0.67
0.32
1.46
0.69
1.94
(31.0)
1.24
0.69
0.98
0.38
1600
(0.43)
47
3.1
2.1
3990
70
3.0
6.6
0.55
0.24
1.07
0.47
1.54
(24.6)
1.48
0.71
0.74
0.38
1600
(0.43)
39
3.0
2.2
3840
77
2.8
5.4
0.51
0.27
1.05
0.55
1.44
(23.0)
1.49
070
0.66
0.37
Overflow Rate, m3/ rrf/day (gpd/ff)
Detention Time:
V/Q, hr
V/IQ+R). hr
Weir Loading Rate, m3/m/day
(ff/ft/day)
Solids Loading Rate, kg/ m3/ day
(Ib/ff/day)
Return Sludge Concentration, %
SVI, ml/g
18.7
(459)
3.7
2.8
79.1
(852)
98
(1568)
1.05
78
23.2
(570)
3.0
2.2
62.6
(674)
90
(1440)
1.06
153
21.2
(521)
3.3
2.3
52.2
(562)
127
(2032)
1.40
99
25.4
(625)
.
2.8
1.9
68.9
(741)
168
(2688)
1 54
65
28.4
(698)
, 2.4
1.7
77.0
(829)
134
(2144)
1.18
83
27.9
(686)
2.5
1.8
101.2
(1089)
152
(2432)
1.36
77
27.5
(676)
2.5
1.8
99.4
(1070)
141
(2256)
1.22
83
18.1
(445)
3.8
2.7
101.5
(1092)
113
(1808)
1.34
113
28.4
(698)
25
1.8
102.3
(1101)
147
(2352)
0.88
124
23.3
(573)
2.9
2.0
84.2
(906)
141
(2256)
0.99
114
23.2
(570)
2.9
2.1
85.8
(923)
126
(2016)
094
101
each pilot plant, the mixer power had to
be reduced. Excessive power input
shears the floe, which can cause poor
settleability of the sludge and a turbid
effluent.
Power Consumption
In the present economic climate,
energy consumption is one of the most
important factors involved in comparing
the air and oxygen activated sludge
processes. Since power intensity prob-
lems in both pilot plants required the
aeration equipment to be operated at
speeds lower than design, a comparison
based on the pilot plant data is inappro-
priate. Additionally, because the effects
of scale would be difficult to predict,
estimates based on typical aerator
efficiencies produce more applicable
results.
The results of power consumption
estimates made usi ng the above ground
rules indicate that the oxygen systems
use substantially less energy. The
surface aerator oxygen system, in fact,
is estimated to require only 52% of the
energy used by the air system, and the
submerged turbine oxygen system,
62%. Because of land constraints at the
JWPCP, aeration tank depths greater
than 5 m (15 ft) would be required with
an air system, so surface air aeration
was not evaluated.
Conclusions
Both air- and oxygen-activated sludge
systems can produce effluents meeting
the JWPCP discharge limitations for
everything but certain trace metals,
which require source control. The
oxygen system is somewhat more
stable and flexible in its operation.
The two systems obtained good
removals of soluble organics, and
factors affecting solids separation in the
final clarifier are most significant ii
terms of their effects on effluent quality
The most notable detrimental factor
encountered in the study were excessiv
input of aerator power, which sheare
the floes in both systems, and nitrifica
tion-denitrification, which caused trv
settled sludge from the air system t
resuspend.
The major difference between the tw
systems in terms of pollutant removal
concerns ammonia nitrogen. The oxyge
system did not nitrify. At the JWPCF
where the ammonia discharge limitatio
is high enough to impose no constrain'
this characteristic is an advantage i
that it eliminates rising sludge resultin
from nitrification-denitrification.
Claims have been made that oxygen
activated sludge processes produce les
sludge than air-activated sludg
processes. In this study, the total plar
solids were compared and the different^
-------
Table 4. Summary of Effluent Quality— Air Stream
Parameters
Aeration Period (V/Qj. hr
MCRT (Total System), days
Flow Pattern
Suspended Solids:
Influent, mg/L
Effluent, mg/L
Removal, %
Total BODS:
Influent, mg/L
Effluent. mg/L
Removal. %
Soluble BODS:
Influent, mg/L
Effluent. mg/L
Removal, %
Total COD:
Influent, mg/L
Effluent, mg/L
Removal, %
Soluble COD:
Influent, mg/L
Effluent, mg/L
Removal. %
Grease (By Hexane Extraction}:
Influent, mg/L
Effluent, mg/L
Removal, %
Ammonia Nitrogen:
Influent, mg/L
Effluent, mg/L
Removal, %
1
5.6
6.8
Steady
167
89
47
178
75
92
118
2
98
458
118
74
262
49
81
51
8
84
35
14
6O
II
4.0
5.4
Steady
179
80
55
167
17
90
102
3
97
447
152
66
247
56
77
41
6
85
32
20
38
III
4.0
3.3
Steady
167
67
60
172
15
91
98
3
97
453
130
71
234
59
75
37
5
86
35
28
20
IV
3.5
5.6
Steady
170
22
87
171
8
95
101
4
96
460
77
83
241
56
7*7
38
1
97
35
32
9
Phase
V
4.0
2.8
Steady
204
110
46
224
16
93
126
5
96
513
191
63
265
72
73
—
—
—
31
28
10
VI
4.5
4.3
Steady
204
36
82
234
12
95
132
4
97
556
91
84
257
57
78
—
—
—
36
32
11
VII
4.5
4.3
Steady
165
37
78
212
12
94
129
2
98
483
92
81
270
55
80
—
—
—
33
28
15
VIII
4.5
4.5
Steady
216
54
75
226
13
94
109
2
98
515
111
78
256
48
81
—
—
—
34
32
6
IX
5.3
5.9
Steady
177
29
84
211
18
92
119
2
98
517
84
84
282
54
81
—
—
—
38
31
18
was found to be insignificant at the 90%
confidence level. The trend, however,
was for the oxygen system to produce
more sludge.
Because of modifications made to the
pilot plant's aeration equipment to
prevent floe shear, an energy consump-
tion comparison was considered inap-
propriate. A paper study indicates that
substantial energy savings may be
expected with the oxygen system.
The full report was submitted in
partial fulfillment of Contract No. 14-
12-150 by Los Angeles County Sanita-
tion Districts under the sponsorship of
the U.S. Environmental Protection
Agency.
-------
Table 5. Summary of Effluent Quality—Oxygen System
Parameters
Aeration Period IV/Q). hr
MCRT (Total System), days
Flow Pattern
Suspended Solids:
Influent, mg/L
Effluent, mg/L
Removal, %
Total BOD:
Influent, mg/L
Effluent, mg/L
Removal, %
Soluble S005:
Influent, mg/L
Effluent, mg/L
Removal, %
Total COD:
Influent, mg/L
Effluent, mg/L
Removal, %
Soluble COD:
Influent, mg/L
Effluent, mg/L
Removal, %
Grease (By Hexane Extraction):
Influent, mg/L
Effluent, mg/L
Removal, %
Ammonia Nitrogen:
Influent, mg/L
Effluent, mg/L
Removal, %
1
2.5
3.4
• Diurnal
189
17
91
219
11
95
131
4
97
467
81
83
249
62
75
43
1
98
32
26
19
II
3 1
5.9
Steady
165
18
89
221
7
97
132
3
98
523
87
83
213
68
68
38
1
97
34
31
9
III
3.4
6.8
Steady
242
28
88
231
12
95
105
3
97
554
94
83
258
58
78
47
3
94
33
31
6
IV
2.8
5.6
Steady
201
54
73
238
20
92
122
5
96
561
122
78
279
59
79
56
4
93
32
31
3
V
2.5
34
Steady
172
28
84
219
21
90
121
6
95
486
100
79
283
67
76
42
3
93
36
31
14
Phase
VI
2.5
4.4
Steady
202
21
90
212
12
94
115
3
97
536
88
84
279
66
76
62
2
97
37
32
14
VII
26
4.8
Steady
142
17
88
187
8
96
93
2
98
438
82
81
255
64
75
64
2
97
32
30
6
VIII
2.5
38
Steady
140
14
90
176
5
97
90
1
99
400
71
82
260
58
78
46
1
98
34
29
15
IX
2.5
4.2
Diurnal
150
48
68
204
13
94
134
1
99
415
116
72
272
64
77
46
6
87
28
28
0
X
3.1
6.6
Diurnal
130
34
74
173
12
93
100
2
98
431
97
78
280
63
78
39
3
92
34
29
15
XI
3.0
5.4
Diurnal
120
20
83
185
6
97
124
2
98
446
83
81
305
65
79
41
2
95
37
34
8
Scott Austin and Fred Yunt are with, and Donald Wuerdeman was with, Los
Angeles County Sanitation Districts, Whittier, CA 90607.
Irwin J. Huge/man was the EPA Project Officer (see below).
The complete report, entitled "Parallel Evaluation of Air- and Oxygen-Activated
Sludge," fOrder No. PB 81-246 712; Cost: $8.00, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
Richard C. Brenner, the present contact, can be reached at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
ft US GOVERNMENT PRINTING OFFICE, 1981 — 757-012/7355
-------
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Agency Cincinnati OH 45268 Protection
Agency
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