V-/EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-196 Dec. 1981
Project Summary
Evaluation of a Treatment
Lagoon for Combined
Sewer Overflow
Daniel J. Connick, William C. Pisano, and Gerald L. Aronson
Results are summarized of a 2-year
study to assess the effectiveness of
the world's largest facultative lagoon
for treating combined sewer overflow
and the polishing effluent from a
secondary wastewater treatment
plant. The project was divided into five
different activities, each of which
evaluated a different aspect of the
overall treatment scheme.
The first activity was to determine
the physical characteristics of the
lagoon (size, aerator locations, and
influent and effluent discharge levels).
Second, lagoon performance was
evaluated for changes in the degree of
aeration, which has the dual function
of mixing the lagoon and increasing
the oxygen levels above those provided
by natural reaeration. Third, the
pollutant removal performance of the
lagoon was evaluated for different
discharge levels and detention periods.
Removal efficiencies were determined
by daily sampling of the influent and
effluent and of water at several
locations within the lagoon. Fourth,
the effects of the stormwater loadings
on lagoon performance were assessed
to determine the buffering capacity of
the lagoon for treating volumes of
highly polluted, intermittent flow.
Fifth, full-scale application of sequen-
tial chlorine and chlorine dioxide
disinfection was evaluated.
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
The East Chicago Sanitary District
(ECSD) operates a wastewater treatment
plant that handles about 19 mgd* of dry
weather municipal wastewater from
the city of East Chicago, Indiana. This
wastewater includes industrial dis-
charges. Secondary treatment consists
of a conventional activated sludge
process. The East Chicago sewerage
system has combined sewers with
overflows containing both direct indus-
trial discharges and runoff from indus-
trial areas. Bacterial contamination of
the Grand Calumet River has occurred
in the past as a result of combined
sewer overflows (CSO).
In the late 1960's, the ECSD received
a demonstration grant to construct and
evaluate the world's largest facultative
lagoon. The facility was intended to
polish the secondary effluent from the
wastewater treatment plant (WWTP)
and to provide preliminary treatment
with disinfection to the combined sewer
overflows. The project was to demon-
strate the feasibility of this technique for
dual CSO treatment and secondary
effluent polishing at an industrial urban
area.
The city's objective was to meet the
state, regional, and federal water
*To convert mgd to mVs, multiply by 0.044.
-------
quality requirements for the Grand
Calumet River by improving the quality
of effluent from the East Chicago
wastewater treatment plant and over-
flows from the Magoun Avenue pump-
ing station. Interception of the combined
sewer overflows prevents discharge of
raw wastewater into the Grand Calumet
River, thus eliminating excessive bac-
terial levels after storms and providing
improvement in other respects. The
improved quality of the Grand Calumet
River Basin and of the lower reaches of
Lake Michigan will enable increased
industrial and recreational use of these
waters. The value of the project to the
federal water program was to demon-
strate a proven wastewater treatment
approach for handling combined sewer
overflows.
Physical Characteristics of the
Lagoon and Related
Appurtenances
Construction of the East Chicago
treatment lagoon began in 1969 and
was completed in 1971. During con-
struction, several actions were under-
taken that resulted in substantial
changes from the original design. The
original lagoon design specified a 700-
by 900-ft basin with levee sides and a
maximum water depth of 40 ft. Field
surveys indicated that the post-con-
struction lagoon surface area remained
unchanged, but that the water depth
was considerably less than that originally
planned. Depth readings were measured
throughout the lagoon. Readings within
15 m (50 ft) of the shore on any side
reflected the 2 to 1 slope of the levee
sides. Depths throughout the remainder
of the basin ranged from 7.62 to 9.75 m
(25 to 32 ft), with an overall average of
9.1 m (30.1 ft). Volume of the post-
construction lagoon is estimated to be
142.2 million gal.
Final construction of the influent
system included a 9-ft-wide by 8-ft-high
concrete channel along the north side,
with final discharge through a 48-in.
conduit. Original intentions were that
the influent be controlled by means of
four outlets from the influent channel,
with a combined capability of handling
the entire Magoun Avenue Pumping
Station flow of 178 mgd. The capacity of
the single 48-in. conduit is insufficient
to handle the combined sewer overflow
(CSO) and overflow of the influent
spillway during major storms.
The lagoon effluent mechanism was
to have incorporated four controlled
outlets feeding a concrete channel
within the south levee. A concrete
apron corner with a dry weather flow
channel was substituted for the original
system. Currently, no means exist for
directly controlling lagoon inflow and
outflow. Influent enters the lagoon at a
single point source and is directly
related to pump rates. Effluent rates are
directly related to lagoon water surface
levels and discharges from a single
point.
Aerators
Depth of the detention basin was
designed to allow partial oxygen deple-
tion, yielding aerobic surface treatment
with anaerobic bottom waters. The
depth of the aerobic layer is controlled
by eight surface aerators. The aerators
are single speed, 50-hp, electically
driven units with waterproof cables
connecting the units to onshore power
transformers. No guards are provided to
protect the upper section from induced
spray, nor is there any mechanism to
manipulate the area of inflow to limit
deep water draw.
Pumping Stations
During rainly periods, CSO from 20
percent of East Chicago reaches the
Magoun Avenue Pumping Station and
is pumped into the lagoon. Before
lagoon construction, CSO from this
station was pumped directly to the
Grand Calumet River.
A dry-weather flow lift station was
incorporated into the original facility
design to pump all the wastewater
treated at the East Chicago secondary
plant to the lagoon. Three fixed-speed
pumps were installed within the lift
station. Two were capable of pumping 8
mgd each to the lagoon, and the third
unit had the capacity to pump 3 mgd.
Dry-Weather Lagoon
Performance
The lagoon evaluation period of 56
weeks was divided into several phases
based on prevalent influent rates to the
lagoon. Six weeks were without any
inflow. The influent rate was 3 mgd for
33 weeks. Fifteen weeks of evaluation
were conducted at an influent rate of
18.8 mgd, which isthe maximum inflow
rate provided by all three pumps. The
final 2 weeks of the evaluation program
were conducted at a reduced flow rate
of 11.3 mgd. Flows were reduced during
this period to help evaluate the effects of
detention time on lagoon performance.
Pollutant loadings into the lagoon
were a function of the East Chicago
WWTP flow rate and the concentrations
of individual constituents within the
treatment plant effluent. Influent to the
lagoon was controlled on a volume basis
by the operation of the lift pumps.
Concentrations of wastewater constit-
uents were mainly a function of the
degree of treatment provided by the
secondary plant. Because of the com-
bined effects of erratic influent pollu-
tional loads and variable treatment
efficiency, the treatment plant effluent
concentrations varied widely.
Statistical reduction of the lagoon
performance data are shown in Tables
1, 2, and 3 for the three evaluation
periods. Except for organic pollutants,
the influent concentrations were rea-
sonably consistent over the three
evaluation periods. The organic con-
taminant increases during the low-flow
period could have been due to seasonal
changes, since the cold weather may
have reduced treatment plant effec-
tiveness.
The average pollutant removals for
the three flow rates are summarized in
Table 4. Effluent concentrations are
listed as averages of the flow period.
Percentage removals for each flow rate
were determined using the average
influent and effluent concentrations.
Also listed are the overall removal
efficiencies considered bypasses when
the secondary effluent exceeds the
pumpage rate of 11.3 mgd. No flows are
bypassed at a pumpage rate of 18.8
mgd.
The results listed in Table 4 were
expected, considering the nature of
difficulties encountered with the lagoon's
operation. Little aeration was provided
during most of the 3-mgd flow period.
Although long detention periods were
theoretically possible during this period,
severe short-circuiting of influent flow
effectively minimized the actual treat-
ment time. Lagoon removal efficiencies
for the 11.3 mgd flow rate were higher
than those computed at the higher rate
of 18.8 mgd.) This result was expected,
since a theoretical detention time of 12
days is possible at 11.3 mgd, but only 7
days of detention are provided at 18.8
mgd. Aeration/dye tracer studies
-------
Table 1.
Para-
meter
BODe
BODs
COD
TOC
TSS
VSS
TS
NOs
TP
Turbidity]
Summary of lagoon
Mean
cone.
(mg/l)
36
44
155
47
168
75
1585
...
1.30
80
performance
Influent
No. of
samples
1
28
60
81
71
68
52
...
52
78
* Test period covered August 1978 to April
t Turbidity values in JTU.
>
Table 2.
Para-
meter
BODe
BODs
COD
TOC
TSS
VSS
TS
NOs
TP
Turbidity]
Summary of lagoon
Mean
cone.
(mg/l)
21.
23.
117.
39.
230.
68.
1639.
6.3
1.13
113.
performance
Influent
No. of
Samples
12
12
14
12
15
15
15
15
14
13
at an influent
Std.
dev.
--
33.4
49.5
45.
267.
110.
757.
...
1.49
51
1979.
at an influent
Std.
dev.
11.
17.3
112
10.7
407.
79.
370.
3.7
.67
61.
rate of 0.13
Coeff.
var.
(%>
--
76
32
96
159
147
48
...
115
64
rate of 0.49
Coeff.
var.
(%)
92
75
96
27
177
116
23
59
59
54
m3/s 13 mgd)*
Mean
cone.
(mg/l)
17
30
83
28
35
24
1365
...
.57
40
m3/s (11.3 mgd)
Mean
cone.
(mg/l)
22.
13.
57.
26
16.
9.
1323.
6.1
.23
21.
Effluent
No. of
samples
69
28
60
81
71
68
62
...
62
78
*
Effluent
No. of
Samples
12
12
14
12
15
15
15
15
14
13
Std.
dev.
13.9
29.5
30.1
10.9
23.
20
579
—
.80
10.
Std.
dev.
8.5
8.3
19.
5.7
6.6
5.3
201.0
4.7
.12
10.7
Coeff.
var.
(%)
82
105
36
39
66
83
50
...
140
25
Coeff.
var.
(%)
37
64
33
22
41
59
15
77
52
51
Test period covered August to September 1979.
\Turbidity values in JTU.
-------
Table 3. Summary of lagoon performance at an influent
Influent
Mean
Para- cone. No. of Std.
meter (mg/l) samples dev.
50De 18. 17 8.8
BODs 22. 17 10.3
COD 120. 1
TOC 40. 23 17.0
TSS 144. 25 147.
VSS 60. 25 51.
TS 1626. 25 333.
NOs 5.5 1
TP 1.24 23 .72
Turbidity^ 83. 22 54.
* Test period covered May to August 1979.
t Turbidity values in JTU.
rate of 0.82 m3/s (18.8 mgd)*
Effluent
Coeff.
var.
(%)
49
47
-
42
102
85
20
-
58
65
Mean
cone. No. of Std.
(mg/l) samples dev.
26. 19 18.5
21. 19 18.5
79. 23 34.7
28. 23 9.6
32. 25 11.4
21. 25 9.0
1571. 1
5.5 1
.34 23 .22
21. 23 9.6
Coeff.
var.
(%)
71
88
44
34
36
43
-
-
65
42
Table 4. Summary of average pollutant removal efficiencies for three influent flow rates
0. 13 m3/s (3 mgd) 0.49
Influent* Effluent* Removal Influent*
Parameter (mg/l) (mg/l) (%) (mg/l)
fiODe 36. 17. 53 21.
BODs 44. 30. 32 23.
COD 155. 83. 46 117.
TOC 47. 28. 42 38.6
TSS 168. 35. 79 230.
VSS 75. 24. 68 68.
TS 1585. 1365. 14 1639.
NOs - - - 6.3
TP 1.3 .57 56 1.13
Turbidity 80. 40. 49 113.
m3/s(11.3
Effluent*
(mg/l)
22.
12.7
57.
25.9
16.
9.
1323.
6.1
.23
21.
mgd) 0. 82 m3/s (18.8 mgd)
Removal Influent Effluent* Removal
(%) (mg/l) (mg/l) (%)
18. 26.
45 22. 21. 4
51 120. 79. 34
33 40. 28. 31
93 144. 32. 78
86 60. 21. 65
19 1626. 1571. 3
3 5.5 5.5 0
80 1.24 .34 73
91 83. 21. 75
Overall
Removal^
(%)
--
27
31
20
56
52
11
2
48
55
* Mean concentrations.
t Overall removal at 0.49 m3/s (11.3 mgd) rate, considering untreated bypassed flows.
4
-------
shown that even with the limited
aeration provided during evaluation at
these flow rates, nearly complete
lagoon mixing occurred. Influent pol-
lutant concentrations were quite similar
and temperature variations were min-
imal, thereby eliminating the possible
effects of these variables.
Based on the overall removal rate
(including bypasses), the higher inflow
rate of 18.8 mgd is considered optimum.
At the 11.3 mgd pumping rate, excess
secondary treatment plant effluent is
discharged to the river without further
treatment. The removal rates at the
11,3-mgd flow rate are less than those
at the 18.8-mgd rate, with the exceptions
of BOD, total solids (TS), and N03. The
NO3 removals are low in both situations.
TheTS and BOD removals were impaired
by four storm events during the higher
flow period. These occurrences caused
pollutant washout from the WWTP that
resulted in high residual loadings to the
lagoon.
Limited removal of TS during both
flow periods resulted from the poor
settling of fine particles. Although
suspended solids (SS) removals were
high, these loadings represent only a
small fraction of the TS load. The results
suggest that the settling velocities of the
fine solid participates are insufficient to
overcome lagoon currents and scouring
near aerators. This problem was further
complicated by the high occurrence of
aerator failures. Quiescent settling
zones near nonoperational units devel-
oped, and upon restart, bottom scouring
occurred often, and to the extent that
the surrounding surface waters became
visually black.
Wet-Weather Lagoon
Performance
Assessment of lagoon performance
for storm events is extremely difficult.
First, the pumped effluent from the
wastewater treatment plant varied so
much that any estimate of dry-weather
loadings would have been subject to
considerable error. Second, the auto-
matic samplers monitoring both the
influent and effluent were prone to
mechanical malfunctions, resulting in
incomplete representations of storm
events. Third, the wet-weather events
were never totally monitored, since the
washout period was always substantially
longer than the period during which the
samplers were in operation. The average
removals for the three storm events
approximated the removal rates during
dry-weather flow.
Aeration Studies
Lagoon Mixing and Flow
Characteristics for Various
Aeration Schemes
Lagoon flow patterns are determined
by the rate of inflow into the lagoon and
by the number and locations of aerators
in operation. The lagoon was originally
designed to contain nine equally spaced
aerators. The current configuration
includes eight irregularly spaced units.
Random down time of the units resulted
in numerous combinations of aerators
in operation during the lagoon evaluation
period. Lagoon flow and mixing patterns
could not be directly assessed for all
such combinations. Several studies
were performed to ascertain the effects
of aeration on lagoon flow patterns.
Documentation of short-circuiting and
limited detention times was needed for
data reduction and analysis.
Dye studies performed under several
of these conditions demonstrated the
general trend of induced low patterns.
Influent discharge from the 48-in. feed
line tended to flow directly across the
lagoon. The extent of the immediate
flow across the lagoon was a function of
initial influent momentum and thus
flow rate. As expected, higherf low rates
extended the flows further across the
lagoon. Without aeration, lagoon flow
patterns allowed limited mixing of the
interlagoon waters, with most of the
inflow rising to the surface and flowing
to the effluent spillway with minimal
detention time and limited treatment.
Evaluation of the mixing character-
istics of a single aerator indicated that
each unit was capable of influencing
lagoon water flow patterns to a distance
of more than 100 ft. Aerators create
flow patterns that extend to the lagoon
bottom near the units. Flow patterns
generally moved toward the aerators at
depths below 10 ft and away from the
aerators above this depth. Water
velocity generally decreased with
distance from the aerator and with
depth.
With the aerators in operation, the
lagoon waters were adequately mixed
with the influent. Operation of all eight
aerators mixed the lagoon completely,
producing high removal rates at optimum
detention times. Analysis later indicated
that only four aerators were required to
mix the lagoon completely. Each 50-hp
surface aerator effectively mixed 35 mil
gal indicating a requirement of 1.3
hp/mil gal in a water body approximately
30 ft deep.
Lagoon Performance With and
Without Aeration
Several days after the startup of the
rehabilitated lift pumps, oxygen levels
stabilized at low levels. A period with
high flow and no aeration began at this
time and was characterized by oxygen
levels below 0.5 mg/l and temperatures
near 20°C. Removal efficiencies for this
period are listed in Table 5. Average
influent concentrations of most constit-
uents were similar during periods of
aeration and no aeration. Analyses of
aeration effects were made after
suficient aeration occurred to replenish
Table 5. Mean pollutant removal rates
under different aeration
schemes at a flow rate of
0.82 m3/s (18.8 mgd)
Parameter
No aeration:}
BODel
BODs
COD
TOC
TSS
VSS
TS
NOs
TP
Turbidity§
Influent Effluent
mean* mean* Removal
(mg/l) (mg/l) (%)
21
25
139
40
192
76
1782
2.21
1.42
97
34
23
91
27
32
23
1607
.94
.26
17
.-
6
35
32
83
69
10
57
82
83
Aeration:*
BODs
COD
TOC
TSS
VSS
TS
NOs
TP
Turbidity§
16
20
93
41
89
42
3.40
0.92
17
18
58
31
34
19
3.54
0.33
11
37
24
62
54
63
* Mean concentrations.
t 5/26/79 to 6/25/79.
j BOD analysis using elecrolytic BOD
respirometer.
§ Values in JTU.
**7/7/79 to 8/7/79.
-------
the dissolved oxygen levels in the
lagoon. Removal efficiencies for the
period with high oxygen and complete
mixing are also listed in Table 5.
Comparison of the removal rates
indicates that each treatment scheme
provided superior removal for certain
parameters.
As shown throughout the study, the
electrolytic method of BOD analysis
using a respirometer (BODe) failed to
indicate any reduction of BODe in the
lagoon. BOD and COD showed slightly
better removal rates with aeration, but
removal efficiencies for all other
parameters tended to be better when
aerators were not operating. Without
aeration, improved nitrate removal
results from denitrification within zones
of depleted oxygen. With aeration,
induced currents limit the settling of
solids, as reflected in the decreased
removals.
The disadvantage of reduced deten-
tion time appears to be more than
compensated by the lower degree of
flow turbulence. Parameters that re-
quire lengthy reaction times and rea-
sonable oxygen levels (such as BOD and
COD) receive a greater degree of
treatment under conditions conducive
to complete mixing and reoxygenation.
Suspended solids and the large mass of
fine solids require quiescent conditions
for optimal removal, as provided in the
lagoon without aeration. Those param-
eters that are typically tied up in the
solid particulates—total particulates
(TP), for example—indicate similar
removal rates and are therefore primarily
removed by settling. Reductions in
parameters such as BOD and COD,
which are impeded by decreased oxygen
levels, are also related to the solids
fraction and thus undergo some removal
by this mechanism. The data indicate
that this mechanism is less effective.
Optimum treatment conditions, then,
would consist of a water body high in
oxygen content and sufficiently quies-
cent to promote particulate settling. In
the case of a treatment lagoon, these
conditions could be achieved by using
initial aeration to levels beyond the
depletion capability of the wastewater
and following it with a zone of quiescent
flow toward the effluent to maximize
settling conditions.
Removal of Heavy Metals
The inflow of heavy metals and their
presence throughout the lagoon was
monitored. Approximately 75 samples
were evaluated for iron, cadmium,
chromium, copper, lead, zinc, and
mercury (Table 6). Influent lead and zinc
concentrations appear to have been
reduced as a result of treatment in the
lagoon.
Disinfection Studies
Review of Disinfection at
ECSD Facility
The original disinfection design
specified chlorine as the disinfecting
agent and the construction of a chlorine
contact chamber at the lagoon effluent.
The latter was omitted, however, and
limited contact time was developed by
installation of a steel weir in the effluent
chamber. A high-rate chlorine/chlorine
dioxide system was installed to disinfect
lagoon effluent waters.
In a previously published bench-scale
study,* high-rate disinfection of com-
bined sewer overflows with chlorine
and chlorine dioxide was evaluated to
aid in the design and operation of full-
scale treatment facilities. The report
concluded that a four-logarithm reduc-
tion in indicator bacteria was obtained
with dosages of 25 mg chlorine/I or 12
mg chlorine dioxide/I and a 2-minute
contact time. Disinfection was enhanced
beyond the expected additive effect by
using sequential addition of chlorine
followed by chlorine dioxide in 15 to 30
seconds. Addition of 8 mg chlorine/I
followed by 2 mg chlorine dioxide/I
provided reductions similar to the single
dosages noted above. The ECSD disin-
fection system was designed on this
basis.
Disinfection Program Results
The disinfection evaluation program
was divided into three phases. The first
phase dealt with routine bacterial
monitoring of the lagoon disinfection
system for dosage rates established and
maintained by ECSD to meet permit
requirements for the National Pollutant
Discharge Elimination System (NPDES).
The data collected during this period
have limited practical value because of
continuous malfunction of the disin-
fection system. The second phase
consisted of a controlled set of varied
*Moffa, P.E., et al. Bench-Scale High-Rate
Disinfection of Combined Sewer Overflows with
Chlorine and Chlorine Dioxide, EPA-670/2-75-
021, April 1975.
chlorine/chlorine dioxide dosage ex-
periments. This program was aimed at
developing various equivalent dosage
combinations for comparable fecal
coliform kill effectiveness. The final
phase of work was a special bench-
scale study using chlorine and chlorine
dioxide to augment the data deficiencies
of the second phase.
Bacterial analyses of the lagoon
effluent were conducted every other day
during the evaluation period. Bacterial
types monitored included total coliforms,
fecal coliforms, and fecal streptococci. A
statistical evaluation of the colony
counts for each bacteria type and
relationships among types was per-
formed. Residual bacteria counts fol-
lowing secondary and lagoon treatment
were roughly 1 percent of typical raw
wastewater values, as indicated by the
arithmetic and geometric means. The
linear correlations among bacteria
types were poor. Analysis of the t-
statistic implied no correlation among
the three types.
Chlorine/Chlorine Dioxide
Kill Studies
The dosage experiment program
began with chlorine only. Doses of 2.5
to 6.5 mg chlorine dioxide/I were added
to yield background data to determine
the actual chlorine dioxide efficiency
during detailed evaluation of the
disinfection system.
Effluent coliform levels varied widely
throughout the study period, with fecal
coliform colony counts ranging from
600 to 200,000 per 100 ml. This
variance created difficulty in the overall
evaluation, since equivalent kills, as
determined on a percentage or log
removal basis, would actually yield a
wide range of effluent levels.
Little difference in disinfection ef-
f icieny occurred with sequential chlorine
dioxide addition.
Bench-Scale Chlorine/
Chlorine Dioxide Experiments
The referenced bench-scale study
indicated optimum sequential dose
delays of 15 to 30 seconds. The full-
scale disinfection operation at East
Chicago could not be analyzed under
these conditions because of the fixed
locations of the diffusers and limited
lagoon effluent. After much data
analysis, little advantage was seen with
sequential chlorine dioxide addition
-------
after delays of 45 to 90 seconds. A
small-scale bench study was performed
for this project allowing the desired
sequential delay times of 15 to 30
seconds.
Chlorine was added in dosages of 1,2,
3, and 4 mg/l, with no sequential
chlorine dioxide addition. Next, sequen-
tial additions of chlorine dioxide in
doses of 0.5 to 3.0 mg/l were added
after 30-second delays to samples
prechlorinated with 1 and 2 mg chlorine
dioxide/I. Selected sequential dosage
combinations were also applied using a
15-second delay period. Disinfection
was greater with increased chlorine
dosage. The bench study data indicate
increased disinfection with sequential
chlorine dioxide addition and benefits
from reducing the delay period between
doses from 30 to 15 seconds.
Table 6. Heavy metal concentrations in the lagoon
Influent
Effluent
Metal
Fe
Cd
Cu
Pb
Zn
Cl
Hg
Mean
(W/n
38.3
5.9
186.5
200.2
603.5
107.7
2.52
Std.
dev.
198.0
6.3
220.
234.
1763.
191.
2.18
Mean
(ug/l)
5.3
6.9
53.5
79.4
120.3
90.6
2.45
Std.
deav.
12.2
22.0
81.0
123.0
261.0
160.5
5.0
Conclusions
Results of the East Chicago lagoon
evaluation clearly indicate that relatively
good treatment can be provided by a
deep stabilization pond. During dry
weather flow periods, the lagoon
provided removal capabilities of 30 to 70
percent for the secondary effluent,
depending on the parameter.
The reoxygenation function of the
aerators was found to be necessary.
Under most circumstances, four aerators
were adequate, but at times of high
organic loading, the use of all eight
appeared to be more advantageous. In
this study, surface aeration of 0.015 hp
per pound BOD applied to the lagoon per
day proved to be adequate.
Disinfection results indicated that
chlorination should be used until more
reliable chlorine dioxide equipment is
provided. The chlorine dioxide system
should be reconstructed to provide
extensive mixing upon initial disinfection
addition, and it should provide a 15- to
30-second delay time between doses.
This work was submitted in partial
fulfillment of Grant No. 11023FAV by
East Chicago Sanitary District under the
sponsorship of the U.S. Environemental
Protection Agency.
Daniel J. Connick, William C. Pisano, and Gerald L. Aronson are with Environ-
mental Design & Planning, Inc., Allston (Boston), MA 02134.
Richard P. Traver was the EPA Project Officer (for contact, see below).
The complete report, entitled "Evaluation of a Treatment Lagoon for Combined
Sewer Overflow," (Order No. PB 82-105 214; Cost: $11.00, subject to change}
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For information, contact Richard Field at:
Storm and Combined Sewer Section
Municipal Environmental Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
U.S. GOVERNMENT PRINTING OFFICE :1 981—559-09Z/3349
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