A PLANNING AND DESIGN GUIDEBOOK FOR
COMBINED SEWER OVERFLOW CONTROL AND TREATMENT
by
Dulcie A. Weisman
Richard Field
Storm and Combined Sewer Section
Wastewater Research Division
Municipal Environmental Research Laboratory (Cincinnati)
Edison, New Jersey 08837
September, 1981
-------
INTRODUCTION
This report is a survey of control and treatment of combined sewer
overflows (CSO), encompassing the Storm and Combined Sewer Section's
research efforts over the last fifteen years.
The survey was prepared to assist Federal, state, and municipal agencies,
and private consultants, in 201 Facilities Planning and Design, Steps 1 and 2,
respectively.
The discussions of control/treatment technologies which consist, mostly,
of downstream treatment, have been divided into seven chapters:
(1) Source Control
(2) Collection System Control
(3) Storage
(4) Physical with/without Chemical Treatment
(5) Biological Treatment
(6) Advanced Treatment
(7) Disinfection
Storage is the best documented CSO abatement measure currently
practiced, and it must be considered at all times in system planning, because
it allows for maximum use of existing dry-weather facilities. Physical
with/without chemical treatment will generally be the minimum required to
meet discharge or receiving water quality goals. If a higher degree of
organics removal is needed, biological treatment should be examined. If
maintaining a viable microorganism population is not feasible, but removal of
dissolved and colloidal organics is desired, advanced treatment may be
attractive.
General discussions of CSO control/treatment can be found in the
following documents, which also served as principal references for this report:
EPA-670/2-74-040
Urban Storm water Management and Technology: An Assessment
EPA-600/8-77-014
Urban Storm water Management and Technology: Update and
User's Guide
EPA-6QO/2-7S-286
Cost^EstimatingManual—Combined Sewer Overflow Storage and
Treatment
-------
EPA-600/8-80-035
Urban Stormwater Management and Technology: Case Histories
Field, R., and E. J. Struzeski, Jr. Management and Control
of Combined Sewer Overflows. J. Water Pollution Control
Federation, Vol. 44, No. 7, July, 1972.
Field, R., and J.A. Lager. Urban Runoff Pollution Control
State-of-the-Art. J. Environmental Engineering Division, ASCE,
Vol. 101, No. EE1, February, 1975.
A comprehensive list of references appears at the end of each chapter.
-------
SOURCE CONTROL
Street Sweeping
Street sweeping, to remove accumulated dust, dirt, and litter, has been
shown to be an effective, but limited method of attacking the source of storm-
water-related pollution problems. Street cleaning effectiveness is a function of
(1) pavement type and condition, (2) cleaning frequency, (3) number of passes, (4)
equipment speed, (5) sweeper efficiency and, (6) equipment type. Pavement type
and condition affect performance more than differences in equipment, and in
general, smooth asphalt streets are easier to keep clean than those in poor con-
dition, or streets with oil and screens surfaces (pavement type consisting of
loosely bound aggregate in a very thick, oily matrix).
The most important measure of street cleaning effectiveness is "pounds per
curb-mile removed" for a specific program condition. This removal value, in
conjunction with the unit curb-mile costs, allows the cost for removing a pound
of pollutant for a specific street cleaning program to be calculated.
In the San Jose, CA, street sweeping project (EPA-600/2-79-161), experi-
mental design and sampling procedures were developed that can be used in
different cities to obtain specific information about street dirt characteristics
and its effects on air and water quality. At the test site in San Jose, it was
determined that frequent street cleaning on smooth asphalt streets (once or
twice per day) can remove up to 50 percent of the total solids and heavy metal
mass yields of urban runoff, whereas, typical street cleaning programs (once or
twice per month) remove less than 5 percent of the total solids and heavy metals
in the runoff.
It was also determined that removal per unit effort decreased with
increasing numbers of passes per year. This is shown in Figure 1, which relates
the annual total solids removed to the street cleaning frequency, for different
street surface conditions in San Jose.
Street sweeping results are highly variable. Therefore, a street sweeping
program for one city cannot be applied to other cities, unless the program is
shown to be applicable through experimental testing. This may be seen when
comparing street sweeping test results from San Jose, and an ongoing project in
Bellevue, WA. In Bellevue, it was demonstrated that additional cleaning, after
a certain level of effort, is not productive, and that the additional street
cleaning effort would be better applied to other areas. For the study area in
Bellevue, it is estimated that_street cleaning operations of about two or three
passes per week would remove up to about 68 kg of solids per curb-km (150
lb/curb-mi), or up to 25 percent of the initial street surface load. Increased
utilization of street cleaning equipment would result in very little additional
-------
•o
o
o —
d £
2 '5
50.000-
40.006
30.000-
20.000
10.000-
Oil and screens surfaced /
streets or asphalt streets /
in poor condition /
X
Asphalt streets in
good condition
1O
100
1.000
Number of Passes Per Yr
ID per curb-mi x 3.55 * kg per curb-tan
Figure 1. Anr.ual Amount Removed as a Function
of the Number of Passes per yr at San Jose Test Site
(EPA-600/2-79-161)
benefit. This is illustrated, for total solids and COD removals, in Figures 2, and
3, respectively. Increased street cleaning operations beyond two or three times
per week are likely to increase the street surface loadings, due to erosion of the
street surface. Increasing the"".cleaning frequency from once per week to two or
more times per week, will have only a very small additional benefit. Cleaning
very infrequently (once every two months) may not be beneficial at all, except
in cities where it may be possible to schedule street cleaning so that it is
coordinated with rainfall events.
Street cleaning not only affects water quality, but has multiple benefits,
including improving air quality, aesthetic conditions, and public health. Since
street cleaning alone will probably not ensure that water quality objectives are
met, a street cleaning program would have to be incorporated into a larger
program of "best management practices," and/or downstream treatment.
Costs of street cleaning have been reported to range from ($3.40 to
$13.14/curb-km) ($5.47 to S21.13/curb-mi) swept (ENR = 3452). The wide
variation in these costs was attributed to differences in labor rates, and
equipment costs.
-------
700 •
g 600 -
i
S3 SOD -1
"•o 400 H
300
200
100
TOTAL SOLIDS
50
100
200
300
lb per curb-ffli x 3.55 - kg .per curb-km Numb€f °f PaSSeS Per Yr
Figure 2. Street Cleaner Productivity
(Bellevue, WA)
I
V
01
Q
O
O-
90
80
70
60
50
40
30
20
10
0
CHEMICAL OXYGEN DEMAND
50 100 200 300
Number of Passes Per Yr
Figure 3. Street Cleaner Productivity
(Bellevue, WA)
-------
References
Bellevue (WA) Street Sweeping Demonstration Project-First Annual Report,
Cooperative Agreement S CR-805929, U.S. Environmental Protection Agency,
January, 1981.
EPA-600/8-80-035 -
EPA-600/2-79-161 -
Urban Stormwater Management and Technology: Case
Histories: by W.G. Lynard et aL, Metcalf & Eddy, Inc.,
Palo Alto, CA, August, 1980.
NTIS PB 81 107153
Demonstration of Nonpoint Pollution Abatement Through
Improved Street Cleaning Practices; by R. E. Pitt,
Woodward-Clyde Consultants, San Francisco, CA,
August, 1979.
NTIS PB 80-108988
EPA-600/2-75-004 -
EPA-R2-73-283
EPA-R2-72-081
Contributions of Urban Roadway Usage to Water
Pollution: by D.G. Shaheen, Biospherics Inc.,
Rockville, MD, March, 1975.
NTIS PB 245 854
Toxic Materials Analysis of Street Surface Con-
taminants: by R.E. Pitt, and G. Amy, URS Re-
search Co., San Mateo, CA, August, 1973.
NTIS PB 224 677
Water Pollution Aspects of Street Surface Con-
taminants: by J.D. Sartor and G.B. Boyd, URS
Research Co., San Mateo, CA, November, 1972.
NTIS PB 214 408
-------
COLLECTION SYSTEM CONTROL
Catchbasins/Catchbasin Cleaning
A catchbasin is defined as a chamber or well, usually built at the curbline
of a street, for the admission of surface water to a sewer or subdrain, having
at its base a sediment sump designed to retain grit and detritus below the point
of overflow. It should be noted that a catchbasin is designed to trap sediment,
while an inlet is not. Historically, the role of catchbasins has been to minimize
sewer clogging, by trapping coarse debris (from unpaved streets) and to reduce
odor emanations from low-velocity sewers, by providing a water seal.
In a project conducted in the West Roxbury section of Boston, three
catchbasins were cleaned, and subsequently, four runoff events were monitored
at each catchbasin. Average pollutant removals per storm are shown in Table 1.
Table 1. Pollutants Retained in Catchbasins
Constituent % Retained
SS 60-97
Volatile SS 48-97
COD 10-56
BOD5 54-88
Catchbasins must be cleaned often enough to prevent sediment and debris
from accumulating to such a depth that the outlet to the sewer might become
blocked. The sump must be kept clean to provide storage capacity for sediment,
and to prevent resuspension of sediment. Since the volume of stormwater
detained in a catchbasin will reduce the amount of overflow by that amount (it
eventually leaks out or evaporates), it is also important to clean catchbasins to
provide liquid storage capacity.
To maintain the effectiveness of catchbasins for pollutant removal will
require a cleaning frequency of at least twice per year, depending upon
conditions. The increased cost of cleaning must be considered in assessing the
practicality of catchbasins for pollution control.
Typical cost data for catchbasins are presented in Table 2. The reported
costs will vary, depending on the size of the catchbasin used by a particular city.
Catchbasin cost multiplication factors, as a function of sump storage capacity,
are shown in Figure 4.
-------
Table 2. Catchbasin Costs
Range Avg
Total
Installed
Cost, $ 700-1,700 1,400
ENR = 3452
(EPA-600/2-77-051)
U
1.0 2.0
Storage Capacity (Sump), yd3
3.0
yd3 x 0.765 • ra3
•The standard basin Is basically a barrel 133 ca (6 ft) deep and
122 cm (4 ft) In dianetsr with an open tap covered by a grating and an outlet
pip? mounted at ths side approximately 107 ca (3.5 ft) above the bottom.
Figure 4. Catchbasin Cost Factors vs Storage Capacity
(EPA-600/2-77-051)
Estimated national average costs for three catchbasin cleaning methods are
presented in Table 3.
8
-------
Table 3. Catchbasin Cleaning Costs
Manual Eductor
S/catchbasin S/m3 S/yd3
13.20 32.5025.00
S/catchba^n S/m*
10.20 9.2S 7.00
Vacuum
S/catchbas1n 5/m3 S/yd3
13.80 19.40 14.80
ENR» 3452
(EPA-600/2-77-051)
References:
EPA-600/2-77-051
- Catchbasin Technology Overview and
Assessment: by J. Lager et al.,
Metcalf & Eddy. Inc., Palo Alto, CA,
in association with Hydro-Research-
Science, Santa Clara, CA, May, 1977.
NTIS PB 270 092
Evaluation of Catchbasin Monitoring- Draft Final Report, by G.L. Aronson et
al., Environmental Design & Planning, Inc., Allston, MA, Grant No. R-804578.
-------
Sewer Flushing
The deposition of sewage solids in combined sewer systems during dry
weather has long been recognized as a major contributor to "first-flush"
phenomena occurring during wet weather runoff periods. The magnitude of
these loadings during runoff periods has been estimated to range up to 30
percent of the total annual dry weather sewage loadings.
Sewer flushing during dry weather is designed to remove the material,
periodically, as it accumulates, and hydraulically convey it to the treatment
facilities, thus, preventing resuspension and overflow of a portion of the solids
during storm events, and lessening the need for CSO treatment. Flushing is
particularly beneficial for sewers with grades too flat to be self-cleansing, and
also helps ensure that sewers can carry their design flow capacities. Sewer
flushing requires cooperation between the authorities with jurisdiction over
collection system maintenance and wastewater treatment.
For developing sewer flushing programs, it is necessary to be able to
estimate deposition build-up. Predictive equations have been developed, based
on field studies in Boston, to relate the total daily mass of pollutant deposition
in a collection system to collection system characteristics, such as per capita
waste production rate, service area, total pipe length, average pipe slope, and
average pipe diameter. A simple model is given by the equation:
TS = 0.0076(L')1-063(S)-°-4375(q)-0-51 (R2=0.845)
where TS = deposited solids loading, Ib/d
§ = mean pipe slope, ft/ft
L' = total length of sewer system, ft
q = per capita waste rate* (plus allowance for
infiltration), gpcd
(EPA-600/2-79-133)
*U.S. Public Health Service has indicated a national average of 150 gpcd
(Wastewater Treatment Plant Design- WPCF and ASCE, 1977).
The total pipe length of the system, L', is generally assumed to be known. In
cases where this information is not known, and where crude estimates will suf-
fice, the total pipe length can be estimated from the total basin area, A
(acres) _ using the expressions:
For low population density (10-20 people/acre)
L' = 168.95 (A)0-928 (R2 = 0.821)
For moderate-high population density (30-60 people/acre)
L' = 239.41 (A)0-928 (R2 = 0.821)
If data on pipe slope is not available, the mean pipe slope can be estimated
using the following equation:
10
-------
3 = 0.348(Sg) (R2 = 0.96)
where S = mean ground slope, ft/ft
It has been found that cleansing efficiency of periodic flush waves is
dependent upon flush volume, flush discharge rate, sewer slope, sewer length,
sewer flow rate, sewer diameter, and is also dependent upon population
density. Maximum flushing rates at the downstream point are limited to the
regulator/interceptor capacities prior to overflow.
Internal automatic flushing* devices have been developed for sewer sys-
tems. An inflatable bag is used to stop flow in upstream reaches until a
volume capable of generating a flushing wave is accumulated. When the
appropriate volume is reached, the bag is deflated, with the assistance of a
vacuum pump, releasing impounded sewage, and resulting in the cleaning of
the sewer segment. Field experience has indicated that sewer flushing by
manual means (water tank truck) is a simple, reliable method for CSO solids
removal in smaller diameter laterals and trunk sewers.
Pollutant removals as a function of length of pipe flushed, (Dorchester,
MA - EPA-600/2-79-133) are presented in Table 4. The relationship between
cleaning efficiency and pipe length is important, since an aim of flushing is
to wash the resuspended sediment to strategic locations, such as a point where
sewage is flowing, to another point where flushing will be initiated, or to the
sewage treatment plant.
Table 4. Pollutant Removals by Sewer Flushing as a Function of
Length of Segment Flushed (254-381 mm (10-15 in.) pipe)
% Removals, % Removals,
Organics and Dry-weather
Nutrients grit/inorganic
material
Manhole to Manhole 75-95 75
Segments
Serial Segments up to 55-75 55-65
213 m (700 ft)
Segment lengths greater 35-45 1&-25
than 305 m (1000 ft)
Flushing is also an effective means for suspending and transporting heavy
metals associated with light colloidal solids particles. Approximately 20-40
percent of heavy metals contained within sewage sediment, including cad-
mium, chromium, copper, lead, nickel and zinc, have been found to be
transported at least 305 m (1000 ft) by flush waves.
11
-------
Estimated costs of sewer flushing methods are shown in Table 5.
Table 5. Estimated Costs of Sewer Flushing Methods
Based on Daily Flushing Program
Number of Segments: 46 (254-457 mm (10-18 in) pipe)
Automatic Flushing Module Operation (one module/segment)
Capital Cost* $15,QOO/segment
Annual O&M Cost $138,000
Manual Flushing Mode
Capital Costt $95,000
Annual O&M Cost $164,100
"includes site preparation, and fabrication and installation of air-
operated module
fincludes 3 outfitted water tankers
ENR = 3452 (EPA-6QO/2-79-133)
References:
EPA-600/2-80-118 - Review of Alternatives for Evaluation of
Sewer Flushing-Dorchester Area-Boston:
by H.L. Kaufman and F. Lai, Clinton Bogert
Associates, Ft. Lee, NJ, August, 1980.
NTIS No. Pending
EPA-600/2-79-133 -
EPA-6 00/2-77-120 -
Dry-Weather Deposition and Flushing for
Combined Sewer Overflow Pollution Control:
by W. Pisano, Northeastern University,
Boston, MA, August, 1979.
NTIS PB 80-118524
Procedures for Estimating Dry-Weather Pollutant
Deposition in Sewerage Systems: by W. Pisano
and C.S. Queriroz, Energy and Environmental
Analysis, Inc., Boston, MA, July, 1977.
NTIS PB 270 695
11020DNO03/72
A Flushing System for Combined Sewer Cleansing:
by Central Engineering Laboratories, FMC Corp.,
Santa Clara, CA, March, 1972.
NTIS PB 210 858
12
-------
11020DNO08/67 - Feasibility of a Periodic Flushing System for
Combined Sewer Cleansing: by FMC Corp., Santa
Clara, CA, August. 1967.
NTIS Only PB 195 223
13
-------
Regulator/Concentrators
Swirl Regulator/Concentrator —
The dual-functioning swirl regulator/concentrator can achieve both flow
control and good removals (90-100 percent, laboratory determined) of inert
settleable solids (effective diameter 0.3 mm, s.g. 2.65) and organics (effec-
tive diameter 1.0 mm, s.g. 1.2). It should be noted that the laboratory test
solids represent only the heavier fraction of solids found in CSO. Actual CSO
contains a wider range of solids, so removals in field operations are closer to 40-
50 percent.
Swirls have no moving parts. Flow is regulated by a central circular weir
spillway, while simultaneously, solid/liquid separation occurs by way of flowpath
induced inertial separation, and gravity settling. Dry-weather flows are diverted
through the foul sewer outlet, to the intercepting sewer for subsequent
treatment at the municipal plant. During higher flow storm conditions, 3-10
percent of the total flow, which includes sanitary sewage, storm runoff, and
solids concentrated by swirl action, is diverted by way of the foul sewer outlet
to the interceptor. The relatively clear, high-volume supernatant overflows the
central circular weir, and can be stored, further treated, or discharged to a
stream.
The swirl is capable of functioning efficiently over a wide range of CSO
rates and has the ability to separate settleable light weight solids and floatable
solids at a small fraction of the detention time normally required for
sedimentation. A swirl unit is illustrated in Figure 5.
Suspended solids removals for the Syracuse, NY, prototype unit, as
compared to hypothetical removals in a conventional regulator, are shown in
Table 6. BOD$ removals for the Syracuse unit are shown in Table 7 .(see EPA-
600/2-79-134), Disinfection/Treatment of Combined Sewer Overflows).
Helical Bend Regulator/Concentrator —
The helical bend flow regulator is based on the concept of using the helical
motion imparted to fluids at bends when a total angle of approximately 60
degrees and a radius of curvature equal to 16 times the inlet pipe diameter (D)
are employed.
Figure 6 illustrates the device. The basic structural features of the helical
bend are: the transition section from the inlet to the expanded straight section
before the bend, the overflow side weir and scum baffle, and the foul outlet for
concentrated solids removal, and controlling the amount of underflow going to
the treatment works.
Dry-weather flow goes through the lower portion of the device, and to the
intercepting sewer. As the liquid level increases during wet-weather, helical
motion begins and the solids are drawn to the inner wall and drop to the lower
14
-------
inn*.
overflow
Inlet Ramp
How Deflector
Scum Hint,
Overflow Wsir and Weir Hat*
Spoikn
. FloiubtaTnp
Foul Sewer Outlet
Floor Gutters
Figure 5. Isometric View of Swirl Regulator/Concentrator
(EPA-670/2-73-059)
15
-------
Table 6. SS Removal
SVKRL REGUlATOR/CCr.C£HTRATOR
Average SS Kass Loading.
ner stona. BO/!
**-..,-« *
2- 1974
3-1374
7-1974
10-1974
14-1974
-1-1975
2-1975
6-1975
12-1975
14-1975
15-1975
Inf.
535
182
110
230
159
374
342
342
291
121
115
Eff.
345
141
90
164
123
167
202
259
232
81
55
Ren*
36
23
18
29
23
55
41
24
20
33
52
Inf.
374
69
93
255
99
103
463
112
250
83
117
ko
Eff.
179
34
61
134
57
24
167
62'
168
48
21
Rsn.a
52
51
34
48
42
77
64
45
33
42
82
CONVEHTIOHAk REGULATOR
(hypothetical)
Mass Loading Swirl Net Removal
Inf.
374
69
93
256
99
103
463
112
250
83
117
ka
Underflow
101
33
20
49
26
66
170
31
48
14
72
&
27
48
22
19
26
64
37
28
19
17
62
Benefit (Z\c
25
3
12
29
16
13
27
17
14
25
20
Data reflecting negative 35 renavais ac tail ena or
storss not included.
b For the conventional regulator removal calculation, it is assumed that the
SS concentration of the foul under flaw equals the SS concentration of the
inflow.
c Calculated by subtracting .the hypothetical percent SS removals in a conventional
regulator, from the percent SS removals in a swirl regulator/concentrator.
(EPA-600/2-79-134; EPA-625/2-77-012)
Table 7. Swirl Regulator/Concentrator BODs Removal
Mass Loading, kq
Average BODs
per storm, mo/1
Storm £
7-1974
1-1975
2-1975
Inf.
26,545
3,565
12,329
Eff.
4,644
1,040
6,154
(%)
Rem.
82
71
50
Inf.
314
165
99
Eff.
65
112
70
(at)
Rem.
79"
32
29
(EPA-6QO/2-79-134; EPA-625/2-77-012)
16
-------
INLET
CHANNEL FOR
OVERFLOW
WEIR
OUTLET TO
STREAM
TRANSITION SECTION
15D
STRAIGHT
SECTION
50
BENO 60
R-16D
NOTES:
1. Scum baffle is not shown.
2. Dry-weather flow shown in channel
OUTLET TO PLANT
Figure 6. Isometric View Of Helical Bend Regulator/Concentrator
(EPA-600/2-75-062)
level of the channel leading to the treatment plant. When the storm subsides,
the velocity of flow increases, due to the constricted channel. This helps
prevent the settling of solids. As with the swirl, the proportion of concentrated
discharge will depend on the particular design. The relatively clean CSO passes
over a side weir, and is discharged to the receiving water, or storage and/or
treatment facilities. Floatables are prevented from overflowing by a scum
baffle along the side weir, and collect at the end of the chamber. They are
conveyed to the treatment plant when .the storm flow and liquid level subside.
Based on laboratory tests, pollutant removals in a helical bend unit are
comparable to those in a swirl (a full scale helical bend is currently being
demonstrated in Boston, MA). Helicals and swirls are, in effect, upstream
treatment devices for the removal of relatively heavy, coarse material, but they
cannot be used to substitute for primary clarification.
A comparison of construction costs for helical bend and swirl regulator/
concentrators is presented in Table 8.
17
-------
Table 8. Comparison of Construction Costs-Helical
Bend and Swirl Regulator/Concentrators
Capacity
1.42 m3/s (50 ft3/s)
2.83 m3/s (100 ft3/s)
4.67 m3/s (165 ft3/s)
Swirl
$182,463
295,886
410,952
Note: Land Costs not included
ENR = 3452
Helical
445,472
835,055
1,176,908
It should be noted that these costs do not reflect the real cost-effective-
ness of swirls and helicals, since these units actually serve dual functions, i.e.,
flow control, and waste water treatment. Even though the construction cost for
the helical bend is higher than for the swirl, the helical may be more appropriate
for a particular site, based on space availability and elevation difference
between the interceptor and the incoming combined sewer (the helical requires
a smaller elevation difference than the swirl). If there is not sufficient hydraulic
head to allow dry-weather flow to pass through the facility, an economic
evaluation would be necessay to determine the value of either pumping the foul
sewer flow continuously, pumping the foul flow during storm conditions, or
bypassing the facility during dry-weather conditions.
References
EPA-625/2-77-Q12 -
EPA-670/2-74-039 -
Swirl Device for Regulating and Treating
Combined Sewer Overflows: EPA Technology
Transfer Capsule Report, Prepared by R.
Field and H. Masters, USEPA, Edison, NJ
ERIC 2012 (Cincinnati), 1977.
Relationship between Diameter and Height
for Design of a Swirl Concentrator as a Com-
bined Sewer Overflow Regulator: by R.H.
Sullivan et al., American Public Works Assoc.,
Chicago, IL, July, 1974.
NTTS PB 234 646
EPA-670/2-73-059 -
The Dual-Functioning Swirl Combined Sewer
Overflow Regulator/Concentrator; by R. Field,
USEPA, Edison, NJ, September, 1973.
NTIS PB 227 182/3
18
-------
EPA-R2-72-008 - The Swirl Concentrator ar a Combined Sewer
Overflow Regulator Facility: by R. Sullivan,
American Public Works Association, Chicago, IL,
September, 1972.
NTIS PB 214 687
EPA-600/2-75-062 - The Helical Bend Combined Sewer Overflow
Regulator: by R.H. Sullivan et al., American
Public Works Association, Chicago, IL,
December, 1975.
NTIS PB 250 619
EPA-600/2-79-134 - Disinfection/Treatment of Combined Sewer Over-
flows, Syracuse, New York:" by F. Drehwing et al.,
O'Brien 4 Gere Engineers, Inc., Syracuse, NY,
August, 1979.
NTIS PB 80-113459
Design Manual-Secondary Flow Pollution Control Devices:
al., APWA, Grant No. R-803157, (Publication Pending).
by R.H. Sullivan et
19
-------
STORAGE
Because of the high volume and variability associated with CSO, storage
is considered a necessary control alternative. Storage is also the best
documented abatement measure currently practiced. Storage facilities are
frequently used to attenuate peak flows associated with CSO. Storage must be
considered, at all times, in system planning, because it allows for maximum
use of existing dry-weather treatment plant facilities, and results in the
lowest cost system in terms of treatment. The CSO is stored until the
treatment plant can accept the extra volume. At that time, the CSO is
dischared.
Storage facilities can provide the following advantages: (1) they respond
without difficulty to intermittent and random storm behavior, and (2) they are
not upset by water quality changes.
Figure 7 shows that there is an increase in BOD and SS percent removals,
with an increase in tank volume per drainage area. Figure 8, however,
demonstrates decreasing removal efficiencies per unit volume, as tank size
increases. Also, beyond an optimum tank volume, the rate of cost increase
for retaining the extra flow increases, therefore, it is not economical to
design storage facilities for the infrequent storm. During periods when the
tank is filled to capacity, the excess which overflows to the receiving water
will have had a degree of primary treatment, by way of sedimentation.
Storage facilities can Declassified as either in-line or off-line. The basic
difference between the two is that in-line storage has no pumping require-
ments. In-line storage can consist of either storage within the sewer pipes
("in-pipe"), or storage in in-line basins. Off-line storage requires detention
facilities (basins or tunnels), and facilities for pumping CSO to storage, or
pumping the CSO to the sewer system.
Examination of storage options should begin with in-pipe storage. If
this is not suitable, the use of in-line storage tanks should be considered,
however, head allowances must be sufficient since no pumps will be used.
Off-line storage should be considered last, since this will require power for
pumping. Since the idea of storage is to lower the cost of the total treatment
system, the storage capacity must be evaluated simultaneously with down-
stream treatment capacity so that the least cost combination for meeting
water/CSO quality goals can be implemented. If additional treatment capacity
is needed, a parallel facility can be built at the existing plant, or a satellite
facility can be built at the point of storage.
20
-------
1
"3
Tank Volume, Mgal/mi2
*48.5 cm (19.1 in.) rainfall
t!03.4 cm (40.7 in.) rainfall
runoff coefficient (C) = 0.5
Figure 7. Pollution and Volumetric Retention
vs. Storage Tank Volume for Wet- and Dry-Years
(EPA-600/8-77-014)
be
iu
Tank Size, Mgal/mi2
Figure 8. Unit Removal Efficiencies for
CSO Detention Tanks
21
(EPA-600/8-77-014)
-------
In-Pipe Storage
Because combined sewers are designed to carry maximum flows occur-
ring, say, once in 5 years (50 to 100 times the average dry-weather flow),
during most storms, there will be considerable unused • volume within the
conduits. In-pipe storage is provided by damming, gating, or otherwise re-
stricting flow passage causing sewage to back-up in the upstream lines. The
usual location to create the back-up is at the regulator, or overflow point, but
the restrictions can also be located upstream.
For utilization of this concept, some or all of the following may be
desirable: sewers with flat grades in the vicinity of the interceptor, high
interceptor capacity, and extensive control and monitoring networks. This
includes installation of effective regulators, level sensors, tide gates, rain
gage networks, sewage and receiving water quality monitors, overflow
detectors and flowmeters. Most of the systems are computerized, and to be
safe, the restrictions must be easily and automatically removed from the flow
stream when critical flow levels are approached or exceeded. Such systems
have been successfully implemented in Seattle, and Detroit. In-pipe storage
was also demonstrated in Minneapolis-St. Paul.
Costs associated with in-pipe storage systems are summarized in Table
9. Costs include regulator stations, central monitoring and control systems,
and miscellaneous hardware.
Table 9. Summary of In-Pipe Storage Costs
Location
Storage
capaci ty.
Mgal
Drainage
area,
acres
Capital
cost, S
Storage
cost,
$/gal
Cost per
acre,
$/acre
Annual operation
and eaintenance
$/yr
Seattle, Washington
Control and
monitoring system - 6,040,000 126,000
Automated
regulator stations 6,730,000 330,000
17.8 13,120 12.770,000 T73 974~~ 505.000
Hinneapolis-St. Paul,
Minnesota
Detroit. Michigan
KA
140
64.000
89.600
5,200,000
4.850,000
.04
81
54
., 2.47 • S/ha
NA - not available. s/gal x 0.264 - S/I
EKR- 3452 «gai ,3 78S » n»3
(EPA-600/8-77-014)
Off-line Storage
Off-line storage facilities can be located at overflow points, or near dry
weather treatment plants. Typical storage facilities include lagoons, and
covered, or uncovered concrete tanks. Tunnels are also used where land is not
available.
22
-------
Costs for basin storage facilities are presented in Table 10, and
construction cost curves are shown in Figure 9. Note that these curves do not
include pumping facilities, so these curves are applicable to in-line basins.
The costs for earthen basins include liners.
Innovative Storage. Technology
Lake-Flow Balance System—
Karl Bunkers, an independent research engineer from Sweden, has
developed, under the auspices of the Swedish EPA counterparts, an approach
to lake protection against pollution from storm water runoff. Instead of using
conventional systems for equalization, i-e., concrete tanks or lined ponds,
which are relatively expensive and require a lot of land area, the flow balance
method uses a wooden pontoon tank system in the lake, which performs in
accordance with the plug flow principle. This system is illustrated in Figure
10. The tank bottom is the lake bottom itself. The tank volume is always
filled up, either with polluted stormwater runoff or with lake water. When it
is raining, the stormwater_runoff will "push" the lake water from one
compartment to another. ~The "compartment walls are of flexible PVC
fiberglass cloth. When not receiving runoff, the system reverses by pump back
and the lake water fills up the system. Thus, the lake water is utilized as a
flow balance medium.
Sweden has invested in three of these installations so far. Two have
been in operation for one to two years and a third was recently constructed.
The systems seem to withstand wave-action up to .9m (3 ft) as well as severe
icing conditions. If a wall .is punctured, patching is easily accomplished.
Maintenance has been found to be inexpensive.
So far, the lake-flow balance system has been demonstrated with urban
runoff only. If used with CSO, consideration would have to be given to sludge
handling and disposal. The Storm and Combined Sewer Section hopes to
demonstrate this unique system with CSO in New York City, and at other
locations in the United States. The estimated cost of this system is
$52S/linear meter ($160Ainear foot) (ENR = 3452).
Self-Cleaning Storage/Sedimentation Basin—-
In the city of Zurich, Switzerland, an in-line sedimentation-storage tank
•was designed to prevent solids shoaling after a storm, and provide for solids
transport to the interceptor. The floor of the tank contains a continuous dry-
weather channel, which is an extension of the tank's combined sewer inlet,
that meanders from side to side (see Figure 11) through the tank. This
channelized floor arrangement allows for complete sediment transport to the
interceptor during both dry weather, and upon draw down after a. storm event.
The dry-weather flow comes through the meandering bottom channel.
During wet weather flows, the water level in the tank rises above the channel.
If the storm intensity is low enough, there is complete capture, and if the
storm intensity continues to rise, an overflow occurs through a weir at the tail
23
-------
Table 10 . Summary of Basin Storage Costsa
s
Location ca
Akron, Ohio ( 1)
Milwaukee, Wisconsin
Humboldt Avenue
Boston. Massachusetts
Cottage Farm
Detention and
Chi ori nation,.
Station °
Charles River Marginal
Conduit Project ( 2)
New York City.
New York
Spring Creek Auxiliary
Water Pollution Control
Plant
Storage
Sewer
Chippewa Falls,
Wisconsin
Storage
Treatment
Chicago, Illinois (3)
Phase I Tunnels
Under constr. or
completed, and
pumping stations
Phase I Tunnels
Remaining
Phase II Tunnels
and Reservoirs
Sandusky. Ohio (4 }
Washington, O.C.(S)
Columbus. Ohio(6)
Whittier Street
Cambridge,
Maryland ( 7)
i to rage
paci ty ,
Mgal
1.1
3.9
1.3
1.2
12.39
13.00
25.39
2.82
liaT
1.016
1,033
2,049
42.325
44.374
0.36
0.20
3.75
0.25
Drainage Storage
area, Capital cost, cost,
acres S S/ 1.04
2,265,000.000 1.11
1.4CO.OOO.OOo(3c) 0.03
240.000 3,666.000,000 O5
14.86 900,000 2.49
30.0 1,500,000 7.61
29,250C 10.600,000 2.83
20 550,000 2.21
Cost per ;
acre. e
S/acre
4,180
5,370
720
5.500
6.300
tttuu"
14,300
3.700
18,000
15.275
60,400
50,800
360
28.C1CO
tnnual operation
ind maintenance
cost, ?/yr
5,000
88,000
140,000
170.000
173,000
iJi',666
4,700
13.800
TSTfuO
(Id
7,800,000*
17,700.000
10.700
5.800
25,000
(Continued)
24
-------
Table 10 (Concluded)
a. ENR = 3452, except as noted
b. Estimated values
c. Estimated area.
(U EPA-600/2-76-272 (media-void space storage)
(2) Environmental Assessment Statement for Charles River Marginal Conduit Project
in the Cities of Boston and Cartridge. HA. Commonwealth of Massachusetts. Metropolitan
District Coimrission. September, 1974
(3) The Metropolitan Sanitary District of Greater Chicago, Personal Cofnnunicaflon
from Mr. Forrest Neil, Chief Engineer. September, 1931
(3a) Actual award TARP Status Report July 1, 1981 (July 1981 dollars}
(3b) Estimate as of January 1. 1981. TARP Status Report July 1. 1931
(January 1981 dollars)
(3c) TARP Phase II estimate as of July 31, 1931. ENR = 3574
(3d) Estimate (May 1980 dollars)
(4) EPA 11022ECV09/71 (underwater)
(5) EPA 110200WF12/69(underwater)
.(6) EPA-600/2-77-064
EPA 11020FAL03/7I
(7) EPA 110220PP10/ 70(underwater)
S/«re x 2.47 • S/ha
S/sil x O.Z64 • S/|
Kga) i 3785 - a3
(EPA-600/8-77-014)
end of the tank. A scum baffle prevents solids from overflowing. This
arrangement allows for sedimentation to take place during a tank overflow
condition and at the same time transport of solids that settle, by way of the
bottom channel.
25
-------
10 038
1-4 I C53
8
u
o
— •
c;
O
O
10
1 1 1
1 1
CONCRf lt-e«HUJ— -^_ /
\
s
,22
s
X
'' \,< I
>x^ 1
S
^i-
I
flif
• t
I i
1 t !
1
II
Hi
I ! 1
1 t t
X
X
7
•
s
Jr
X
J
-^.
*—
2
-I
xf
.c
1
t»
±::
x
_ *
X
a»c«i
-v
XL
-
II
[N
~S^
f
rt-ttucavi
X
±=
-------
Figure 10. Lake-Flow Balance System
27
-------
BY-PAS?
"
JL WITH
SLUICE- GATE
WF CHANNEL
;ge~*~. ' .;./_J.. ":.:.~T —>TO
CSC
RIVER
Figure 11. Self-Cleaning Storage/Sedimentation Basin
(Source: Trip Report, R. Field, Chief, Storm and Combined Sewer Section,
USEPA-MERL, October, 1978).
References:
EPA-600/2-77-046 - Cottage Farm Combined Sewer Detention
and Chlorination Station, Cambridge, MA:
by Commonwealth of MA Metropolitan Dis-
trict Commission, MA, November, 1977.
NTIS ONLY PB 263 292
EPA-600/2-76-222a Wastewater Management Program, Jamaica Bay-
Vol I. Summary Report: by D.L. Feurstein and
W.O. Maddaus, City of New York, NY, September, 1976.
NTIS PB 260 887
EPA-600/2-76-222b Wastewater Management Program, Jamaica Bay-
Vol II, Supplemental Data, NYC Spring Creek:
by D.L. Feurstein and W.O. Maddaus, City of
New York, NY, 1976.
NTIS ONLY PB 258 308
EPA-670/2-74-075 - Surge Facility for Wet- and Dry-Weather Flow
Control: by H.L. Welborn, City of Rohnert Park, CA,
November, 1974.
NTIS PB 238 905
EPA-600/2-75-071 - Detention Tank for Combined Sewer Overflow -
Milwuakee, WI Demonstration Project: by Consoer,
Townsend and Associates, Chicago, IL, December,
1975.
NTIS PB 250 427
28
-------
11023—08/70
11020FAQ03/71
EPA-R2-72-070
11022ELK12/71
- Retention Basin Control of Combined Sewer
Overflows; by Springfield Sanitary District,
Springfield, IL, August, 1970.
NTIS PB 200 828
- Dispatching Systems for Control of Combined
Sewer Losses: By Metro. Sewer Board, St. Paul, MN,
March, 1971.
NTIS PB 203 678
- Storage and Treatment of Combined Sewer
Overflows: by the City of Chippewa Falls, WI,
October, 1972.
NTIS PB 214 106
- Maximizing Storage in Combined Sewer Systems:
by Municipality of Metropolitan Seattle, WA,
December, 1971.
NTIS ONLY PB 209 861
EPA-670/2-75-020 - Sewerage System Monitoring and Remote Control:
by T.R. Watt et al., Detroit Metro Water Dept.,
Detroit, MI, May, 1975.
NTIS PB 242 107
EPA-670/2-74-022 - Computer Management of a Combined Sewer
System: by C.P. Leiser, Municipality of Metro-
politan Seattle, Seattle, WA, July, 1974.
NTIS PB 235 717
EPA-670/2-75-010 - Multi-Purpose Combined Sewer Overflow Treatment
Facility, Mount Clemens, Michigan: by V.U. Mahida
et ah, Spalding, DeDecker & Associates, Inc., Madison
Heights, MI, May, 1975.
NTIS PB 242 914
29
-------
TREATMENT
PHYSICAL WITH/WITHOUT CHEMICAL
Physical-chemical processes are of particular importance in CSO treatment
because of their adaptability to automatic operation (including almost instantaneous
startup and shutdown), excellent resistance to shockloads, and ability to consistently
produce a low SS effluent.
In this paper, physical-chemical systems will be limited to screening, filtration,
chemical clarification, and dissolved air flotation.
Screening
Screens have been used to achieve various levels of SS removal contingent with
three modes of screening process applications.
• Main treatment - screening is used as the primary treatment process.
• Pretreatment - screening is used to remove suspended and coarse
solids prior to further treatment to enhance the treatment process
or to protect downstream equipment.
• Dual use - screening provides either main treatment or pretreatment
of stormwater and is used as an effluent polisher during periods of
dry weather.
Screens can be divided into four categories: (1) bar screens (>25.4 mm (>in.)
openings), (2) coarse screens (25.4-4.S mm (1-3/16 in.)), fine screens (4.8-0.1 mm
(3/16-1/250 in.)), and (4) microscreens (<0.1 mm (<1/250 in.)). No special studies
have been made to evaluate bar and coarse screens in relation to CSO, so the basis
for design should be the same as for their uses in dry-weather treatment facilities.
Because CSO contains a significant amount of coarse debris, which is aesthetically
undesirable, providing coarse screening as-the minimum CSO treatment may be
useful. Fine screens and microscreens are discussed, together because in most cases,
they operate in a similar manner.
Several distinct types of screening devices have been developed and used for SS
removal from CSO, and are described in Table 11.
Design parameters for static screens, microstrainers, drum screens, disc
screens, and rotary screens are presented in Tables 12, 13, and 14.
Removal efficiency of screening devices is adjustable by changing the aperture
size of the screen placed on the unit, making these devices very versatile. Solids
30
-------
removal efficiencies are affected by two mechanisms: (1) straining by the screen,
and (2) filtering of smaller particles by the mat (schmutzdeeke) deposited by the
initial straining. The efficiencies of screens treating a waste with a typical
distribution of particle sizes will increase as the size of screen opening decreases.
Table 11. Description of Screening Devices Used
in CSO Treatment
Type of screen
General description
Process
application
Comments
Drum screen
Microstrainers
Rotastrainer
Disc strainer
Rotary screen
Static screen
Horizontally mounted cylinder with
screen fabric aperture in the range
of 100 to 841 microns. Operates at
2 to 7 r/min.
Pre treatment
Horizontally mounted cylinder with Main treatment
screen fabric aperture in the range
of 23 to 100 microns. Operates at
2 to 7 r/min.
Horizontally nouned cylinder made
of parallel bars perpendicular to
axis of drum. Slot spacing in the
range of 250 to 2500 aicrons.
Operates at 1 to 10 r/oin.
Series of horizontally mounted
woven wire discs mounted on a
center shaft. Scrsan aperture in
the range of 45 to SCO microns.
Operates at 5 to 15 r/atn.
Vertically aligned iron with
screen fabric aperture in the
range of 74 to 1S7 cicrons.
Operates at 30 to 65 r/min.
Stationary Inclined screening
surface with slat spacing in.the
range of 250 to 1500 aicrons.
Pretreatment
Pretreatment, main
treatment, or post
treatment of concen-
trated effluents
Main treatment
Pretreatment
Solids are trapped an
Inside of drum and
are backwashed to a
collection trough.
Solids are trapped on
Inside of drum and are
backwashed to a collec-
tion trough.
Solids are retained on
surface of drum and are
removed by a scraper
blade.
Unit achieves a 12 to
151 solids cake.
Splits flow into tvo
distinct streams: unit
effluent and concentrate
flow, in the proportion of
approximately 85:15.
No moving parts. Used for
removal of large suspended
and sett!cable solids.
a A vertically mounted microstrainer is available, which operates totally submerged and operates at
approximately 65 r/nin. Aperture range 10 to 70 microns. Solids are moved from the screen by a
sonic cleaning device.
(EPA-600/8-77-014)
The second most important condition affecting removal efficiencies, especially for
microstrainers, is the thickness of filtered material on the screen. Whenever the.
thickness of this filter mat is increased, the suspended matter removal will also
increase because of the decrease in effective pore size and the filtering action of
the filtered mat. This will also increase head loss across the screen.
It was found, during experimental microstrainer operation in Philadelphia, that
because of extreme variation of the influent SS concentration of CSO, removal
efficiency would also vary, while effluent concentration remained relatively
31
-------
constant. For example, an effluent concentration of 10 mg/l SS would yield a
reduction of 99.0 percent for an influent concentration of 1,000 mg/l (representative
of "first-flush")*whereas, the S3 reduction would be only 50 percent if the influent
concentration were 20 mg/l (representative of tail end of storm). This phenomenon
is apt to recur in other physical-chemical storm water treatment operations. (R.
Field and E. Struzeski, JWPCF, Vol. 44, No. 7, July, 1972).
Table 12. Design Parameters for Static Screens
Hydraulic loadinq. gal/min per
ft of width 100-180
Incline of screens, degrees
frora vertical 35*
Slot space, microns 250-1 600
Automatic controls Hone
a. Bauar Hydrasieves (TM) have 3-stage
slopes on each screen: 25°. 35°,
and 45°.
gal/oin-ft x 0.207 - 1/a-s
(EPA-600/8-77-014)
Table 13. Design Parameters for Microstrainers,
Drum Screens, and Disc Screens
Paraceter Hicrostrainers Drum screen Disc screens
Screen aperture, microns 23-ICO 100-420 45-500
Screen caterial Stainless steel or plastic Stainless steel or plastic wire cloth
Orcsi speed* r/oin
Speed range 2-7 2-7 5-15
Reconnended speed 5 5 ....
Submergence of drum, I 60-80 60-70 SO
Flux rate, gal/rain per
ftZ of submerged screen 10-45 20-50 20-25
Headless, in. 10-24 6-24 18-24
Backwash
Volume, X of inflow 0.5-3 0.5-3 ...a
Pressure. Ib/in? 30-50 30-50
a. Unit's waste product is a solids cike of 12 to 15t solids content.
gal/inin-ft2 x 2.445 - n3/h-n»2
in. x 2.54 - ca
ft x 0.305 « cm
lb/in.2 x 0.0703 - kg/cm?
(EPA-600/8-77-014)
32
-------
Table 14. Design Parameters for Rotary Screens
Screen aperture, nicrcns
Range 74-167
Recomnended aparture 105
Screen material Stainless steel or plastic
Peripheral speed of screen, ft/s 14-16
(TruD speed, r/nrin
Range 30-65
Reconnended speed 55
Flux rate. gal/ft2
-------
o
e
a
:V "ICDOSTRkIKCR
CORRIUTION C0t« = 0.71
2 3« H1C«QST»»IHE«
II IN CMEMI :i L 1001 Tl ON
33^ MICR03TRAIMR
CORRCLATIOM tills 0.49
MICIOSTIAINIR WITH CMCHICAL 10DITION
0 - 23,. Ml CtOSTIAINCI
9 - 20.* KICHOSIK* tNtI
T - 33/% MICXOSTRAIIIII
100 200 300 4QB JOO (00 700 100 900 1000
Influent SS Concentration, mg/1
Figure 12. Microstrainer Performance as a Function of SS Concentration
(EPA-600/8-77-014)
CORIKLtTtOII COIF. =1 0. SO
O(«M seiitcii
- 397^. OI»M SCKEtN
ICHEIS
I 100 200 100 tOO JOO 898 700 SOO 900 (000
Influent SS Concentration, mgfl
Figure 13. Drum Screen Performance as a Function of SS Concentration
(EPA-600/8-77-014)
34
-------
100
la
10
. 70
"3
O 10
E
o
£ 30
09
W 40
IB
20
10
I
Figure
- ROTARY :c»IE»
- HQTJUT SCREENS 10 3^
- ROTJUY SCREEN JOS,*
CURRtliTION COEf.= 0.30
0 tOO 200 300 400 300 tOO 700 100 900 1,800
Influent SS Concentration, mgA
14. Static Screen Performance as a Function of SS Concentration
(EPA-600/8-77-014)
loo r-
10
10
70
a 10
30
O
O
-1,32V XTOMSIEVS
HTORASIEYE
OSM SCREEN
- 781^ HTOXiSICYI
CORRELATION COEF-=0.3S
CO «»
«
30
20
10
0
0 100 200 300 tOO 300 100 700 800 SOO I. 000
Influent SS Concentration, mg/1
Figure 15- Rotary Screen Performance as a Function of SS Concentration
(EPA-600/8-77-014)
35
-------
Table 15. Cost Summary of Selected Screening Alternatives3
Project location
Belleville.
Ontario (1)
Cleveland,
Onio(2Xb.c
Ft. Wayne.
Indiana
Ht. Clemens,
Hiehigan(3)
Philadelphia.
Pennsylvania
Racine,
Wisconsin
Seattle,
Hashing ton(*).b
Syracuse,
New York (Sfcc
Type of screen
Rotary screen
Static screen
Drum screen
Static screen
Drum Screen
Rotary screen
Hicrostrainer
Hi eras trainer with
chemical addition
Hicrostrainer
without
chemical addition
Drum Screen
Rotary screen
.Rotary Screen
Drum screen
Screening
capaci ty.
Kgal/d
1.8
5.4
7.2
0.75
5.3
7.5
25
50
100
200
18
18
38
1.0
7.4
7.4
3.9
25
5
10
Capital
cost, $
57.800
168.600
221,600
25,700
165,000
225,600
1.050,300
1.532.300
3,012,200
5.765,400
470,200
438,500
1.009.200
45,200
156.700
255.300
39.000
1.035.600
223.500
443,600
Cost,
$/Mgal/d
3.. 100
30.900
30,700
34,300
31.400
30,000
42.000
30,600
30.100
28,800
26.100
24,300
26.600
45,200
21,200
34,500
10,000
41.400
44,700
44.400
Annual operation
and maintenance
cost, S/1COO gal
0.143
0.143
0.143
0.073
0.073
0.073
• ••••>
• *•*•
0.03S
0.067
0.079
• •••*
0.083
0.085
0.169
a. EKR»3452.
b. Estimated costs for several sizes of facilities.
c. Estimates include supplemental pumping stations and appurtenances
(l)Operational Data for the Belleville Screening Project. Ontario Ministry of
the Environment. August 6. 1976.
12) EPA 11023EY104/72
3)EPA-670/2-75-010
;4)EPA 11023FDD03/70
;S)EPA-600/2- 76-286
Hgal/d x 0.0438 » «3/s
J/1000 gal x 0.264 - S/«*
(EPA-600/8-77-014)
36
-------
References
EPA-600/2-79-031b
EPA-67 0/2-74-049
U023EY006/70
EPA-R2-73-124
EPA-600/2-79-106a
EPA-600/2-77-069a
EPA-600/2-79-085
11020FDC01/72
Combined Sewer Overflow Abatement Program,
Rochester, NY - Volume II - Pilot Plant Evalua-
tions: by F. Drehwing et al., O'Brien & Gere
Engineers, Inc., Syracuse, NY, July, 1979.
NTIS PB 80-159262
Microstraining and Disinfection of Combined
Sewer Overflows- Phase JHT by M.B. Maher,
Crane Co., King of Prussia^ PA, August,
1974.
NTIS PB 235 771
Microstraining and Disinfection of Combined
Sewer Overflows: by Cocnrane Div., Crane
Co., King Of Prussia, PA, June, 1970.
NTIS PB 195 67
Microstraining and Disinfection of Combined
Sewer Overflows-Phase II: by G.E. Glover, and G.R.
Herbert, Crane Co., King of Prussia, PA,
January, 1973.
NTIS PB 219 879
Screening/Flotation Treatment of Combined
Sewer Overflows: Volume II: Full-Scale Opera-
tion, Racine, WI:by T.L. Meinholz, Envirex, Inc.,
Milwaukee, \VI, August, 1979.
NTIS PB 80-130693
Screening/Flotation Treatment of Combined
Sewer Overflows, Volume I - Bench-Scale and
Pilot Plant Investigations: by M.K. Gupta
et al., Envirex, Environmental Science Div.,
Milwaukee, WI, August, 1977.
NTIS PB 272 834
Combined Sewer Overflow Treatment by
Screening and Terminal Ponding - Fort
Wayne, IN: 'by D.H. Prah and P.T. Brun-
ner, City of Fort Wayne, IN, August, 1979.
NTIS PB 80-119399
Screening/Flotation Treatment of Combined
Sewer Overt lows: by the Ecology Division,
Rex Chainbelt, Inc., January, 1972.
No NTIS Number
37
-------
11023FDD07/71 " Demonstration of Rotary Screening for Com-
bined Sewer Overflows: by City of Portland,
Dept. of Public Works, Portland, OR, July,
1971.
NTIS PB 206 814
11023FDD03/70 - Rotary Vibratory Fine Screening of Combined
Sewer Overflows: by Cornell, Rowland, Hayes
and Merryfield, Corvallis, OR, March, 1970.
NTIS PB 195 168
11020EXV07/69 - Strainer/Filter Treatment of Combined
Sewer Overflows: by Fram Corporation,
East Providence, RI, July, 1969.
NTIS ONLY PB 185 949
38
-------
Screening/Dual Media High-Rate Filtration
Dual Media high-rate filtration (DMHRF) (>20m3/m2-h l>8 gal/ft2-min))
removes small size particulates that remain after screening, and floe remaining
after polyelectrolyte and/or coagulant addition. Principal advantages of the
proposed system are: high treatment efficiencies, automated operation, and limited
space requirements.
To be most effective, filtration through media that are graded from coarse to
fine in the direction of filtration is desirable. A uniform size, single specific
gravity medium filter cannot conform to this principle since backwashing of the bed
automatically grades the bed from coarse to fine in the direction of washing;
however, the concept can be approached by using a two layer bed. A typical case
is the use of coarse anthracite particles on top of less coarse sand. Since anthracite
is less dense than sand, it can be coarse and still remain on top of the bed after
the backwash operation. Another alternative would be an upflow filter, but these
units have limitations in that they cannot accept high filtration rates.
The principal parameters to be evaluated in selecting a DMHRF system are
media size, media depth and filtration rate. Since much of the removal of solids
from the water takes place within filter media, their structure and composition is
of major importance. Too fine a medium may produce a high quality effluent but
also may cause excessive head losses and extremely short filter runs. On the other
hand, media that is too coarse may fail to produce the desired clarity of the
effluent. Therefore, the selection of media for DMHRF should be made by pilot
testing using various materials in different proportions and at different flow rates.
Depth of media is limited by head loss and backwash considerations. The deeper
the bed, the greater the head loss and the harder it is to clean. On the other hand,
the media should be of sufficient depth so as to be able to retain the removed solids
within the depth of the media for the duration of the filter run at the design flux
rate without permitting breakthrough. The design filtration flux must be such that
the effluent will be of a desired quality without causing excessive head loss through
the filter, which in turn requires frequent backwashing. At high flux, shear forces
seem to have significant effect on solids retention and removal.
Several DMHRF pilot study installations have been demonstrated for control of
CSO pollution. These facilities have used 15.2, 30.5, and 76.2 cm (6, 12, and 30 in.)
diameter filter columns with anthracite and sand media, together with various
dosages, of coagulants and/or polyelectrolytes. Descriptions of the DMHRF
facilities are summarized in Table -16.
Suspended solids removal by DMHRF was found to vary directly with influent
SS concentrations and inversely with flux or hydraulic loading rate. Experimental
results have shown that SS removals from CSO increase appreciably with
appropriate chemical additions (New York City; Cleveland).
DMHRF treatment of CSO at New York City's dual-use facility, (40 m3/m2-h
(16 gal/ft2 -min) constant flux) provided overall average SS removals of 61 percent
across the filter and 66 percent across the system with an average influent SS
concentration of 182 mg/1. Average SS removals for the three testing modes (no
chemicals, polymer only, polymer and alum) and test ranges are shown in Table 17.
39
-------
Table 16. Description of CSO-DMHRF Pilot Plant Demonstration Facilities"
Project
Location Process description
Cleveland, Pilot deep bed, dual media
Ohio high rate filtration, with
chemical addition. Facilities
Include pretreatment, storage,
and filtration.
New York City, Pilot deep bed, dual media high
New York, rate filtration, with polyelec-
Ncwtown Creek trolyte addition. Facilities
include pretreatment, storage,
and filtration. Dry-weather
and combined sewer flow Is
pumped from grit chamber of
Newtown Creek plant.
No. of
filter
columns
3
1
Diameter of
columns, In.
6
12
Pretreatment
facilities
420 micron
drum screen
Filter media*
5 ft of No. 3
anthracite
over 3 ft of
No. 612 sand
30 420 micron 5 ft of No. 3
6 rotostralner anthracite
later replaced over 2 ft of
with a 420 No. G12 sand
micron disc
strainer
Period of
operation
1970 to 1971
1975 to
present
Rochester, Pilot deep bed, dual
New Vork high rate filtration
chemical addition.
«. System oper«u at flu* ritet ranging
Effective Size
*Med1a (mm)
No. 3 Anthracite 4.0
No. 2 Anthracite 1.78
No. l"j Anthracite 0.98
No. 612 Sand 2.0
Ho. 1220 Sand 0.95
media 3 6 swirl
with separator
frea 20 to 73 mW-h (B to 30 gal/ftZ-mtn).
Uniformity Coefficient
1.5
1.63
1.73
1.32
1.41
5 ft of No. 1- 1975 to 1976
1/2 or No. 2
Anthracite
over 3 ft of
No. 1220 sand
In. x 2.54 • cm
ft * 0.30} • 01
(EPA-600/8-77-014)
-------
Table 17. CSO-DMHRF Average SS Removals (New York City)
Plant Filter Filter Filter System
Influent Influent Effluent Removals Removals
(mq/1) (mq/1) (mq/1) (%) (%)
No chemicals 175 150 67 55 62
Poly only 209 183 68 63 67
Poly & alum 152 143 47 67 69
(EPA-600/2-79-015)
A measure of the capability or' a filter to remove SS, which is useful for
predicting removals and filter-run cycle, is the specific capture, or mass cap-
ture. This can be expressed as pounds of solids removed per filter surface, or
pounds of solids removed per media volume. Table 18 presents average SS mass
captures obtained across the filter (New York City) during CSO tests of at least
3 hours duration, and the average for tests S-13, 14 and 16 which used more
optimal chemical feeds and occurred during the storms of greatest intensity. It
should be noted that these mass capture values are specific to the Newtown
Creek filter and the test conditions.
Table 18. DMHRF Average Mass Capture Of CSO (New York City)
Capture per Filter Surface Capture per Media Volume
CSO Test Nos. Ih/ft2/run* Ib/ft2/hr Ib/ft3/run** Ib/ft3/hr
S4B, S9-16 3.7 0.76 0.54 0.11
S-13, 14, 16 5.2 1.2 0.76 0.17
* 1 lb/ft2 = 4.88 kg/m2
** 1 lb/ft3 = 16.02 kg/m3
(EPA-600/2-79-015)
BOD removals (New York City) from CSO averaged 32 percent across the filter
and 41 percent across the system with an average influent BODs of 136 mg/i. The
removals improved with chemical additions. Average BODs removals for the three
testing modes and test ranges are shown in Table 19.
41
-------
Table 19. CSO-DMHRF Average BODs Removals (New York City)
No chemicals
Poly only
Poly & alum
Plant
Influent
(mq/1)
164
143
92
Filter
Influent
(mg/1)
131
129
85
Filter
Effluent
(mg/1)
96
84
53
Filter
Removals
tt)
27
35
38
System
Removals
41
41
43
(EPA-600/2-79-015)
It should be noted that the nature of the CSO tested (for example, the presence
of dissolved industrial organic contaminants), may account for variable BOD5
removals.
Limited tests were also run (New York City) to determine heavy metals
reduction. These results, shown in Table 20, represent composite samples.
Table 20. Removal Of Heavy Metals by
DMHRF
Cadmium Chromium Copper Mercury Nickel Lead Zinc
Average
removal, %a 56 SO 39 0 13 65 48
a. Concentration basis
(EPA-600/2-79-015)
Design parameters for DMHRF are shown in Table 21.
Costs of DMHRF facilities are summarized in Table 22. These costs are based
on facilities similarly designed to that of the Cleveland demonstration project.
Comparison with alternate treatment systems show that DMHRF is cost-
competitive with conventional sedimentation facilities for dual process (sanitary and
CSO), or CSO treatment, yet DMHRF has only 5-7 percent the area requirements.
For strict CSO treatment, DMHRF is competitive with dissolved air flotation and
microstraining processess.
42
-------
Table 21. Design Parameters for DMHRF
Filter icedia depth, ft
No. 3 anthracite 4-S
No. 612 sand 2-3
Effective size, ma
Anthracite 4
Sand 2
Flux rate, gal/ft2-Bin
Range 8-40
Design 24
Headless, ft 5-30
Backwash
Volume. Z of inflow 4-TO
Alr
Rate, standard ft3/nin-ft2 10
Tioe. Pin 10
Water
Rate. gal/ft2-ain 60
Tine, oin 15-20
ft x 0.305 - a
gal/ft2.nin x 2.445 - n3/m2-h
standard ft3/ain.ftZ x 0.305 » tfl/a^-mn
(EPA-600/8-77-014)
Table 22. Summary of Costsa for DMHRF Facilities
Operation and maintenance
Plant Construction costs. Sa Construction costs. S/Kgal-d costs.
bapaEi ty
Kgal/d
25
50
100
200
24 gal/ft2:n1n
2.485.000
3.745.000
6.870.000
11.668.000
16 gal/ft2-aii
2.900.000
4.522.000
8.388.000
13.843.000
t 24 gal/ftZ-nin
99.400
74.900
68.700
58.300
16 gal/ft2-min
116.000
90.400
83.900
69.200
24 gal/ftz-Diin
76.000
95.000
169.000
223.000
16 gal/ft2;nin
78,000
98.000
176.000
231.000
a. EOT -3452
b. Includes low lift punping station, prescreening. and chemical addition facilities; and excludes
engineering and adniniscration.
Hgal/d x 0.0438 » m3/*
gal/ft2-cin x 2.445 • sH/aZ-min
(EPA-600/8-77-014)
43
-------
References
EPA-600/2-79-015
11023EYI04/72
- Dual Process High-Rate Filtration of Raw
Sanitary Sewage And Combined Sewer Overflows:
(Newtown Creek) by H. Inherfeld etal., New
York City Dept. of Water Resources, New York,
NY, April, 1979.
NTIS PB 296 626/AS
. High-Rate Filtration of Combined Sewer Over-
flows:(Cleveland), by R. Nebolsine et al.,
Hydrotechnic Corp., New York, NY, April,
1972.
NTIS PB 211 144
EPA-600/2-79-031b - Combined Sewer Overflow Abatement Program,
Rochester, NY - Volume II: Pilot Plant Evalua-
tions:by F.J. Drehwing et al., O'Brien & Gere
Engineers, Inc., Syracuse, NY, July, 1979.
NTIS PB 80-159262
EPA-R2-73-222
Ultra High-Rate Filtration of Activated Sludge
Plant Effluent: by R. Nebolsine et al., Hydro-
technic Corp., New York, NY, April, 1973.
NTIS ONLY
44
-------
Screening/Dissolved Air Flotation
Dissolved air flotation (DAF) is a unit operation used to separate solid particles
or liquid droplets from a liquid phase. Separation is brought about by introducing
fine air bubbles into the liquid phase. As the bubbles attach to the solid particles
or liquid droplets, the buoyant force of the combined particle and air bubble is great
enough to cause the particle to rise. Once the particles have floated to the surface,
they°are removed by skimming. The most common process for forming the air
bubbles is to dissolve air into the waste stream under pressure, then releasing the
pressure to allow the air to come out of solution. The pressurized flow carrying
the dissolved air to the flotation tank is either (1) the entire stormwater flow, (2)
a portion of the stormwater flow (split flow pressurization), or (3) recycled DAF
effluent.
Higher overflow rates 3.2-25 m3/m2-h (1.3-10.0 gal/ft2-min) and shorter de-
tention times (0.2-1.0 h) can be used for DAF than for conventional settling (1.7
m3/m2
-------
The percent removals (concentration basis) are presented in Table 24.
Table 24. Percent Removals Achieved with Screening/DAF (Racine)
BOD
TOC
Suspended Solids
Volatile Suspended Solids
Total Phosphorus
Percent Removal
Site I
57.5
51.2
62.2
66.8
49.3
Site II
65.4
64.7
73.3
70.9
70.0
(EPA-6QO/2-79-106a)
The results from Site II are better than Site I because the hydraulic loading was
usually lower at Site II than at Site I, resulting in lower overflow rates and longer
tank detention times at Site n.
Typical design parameters for DAF facilities are presented in Table 25.
Table 25. DAF Design Parameters
Overflow rat», gal/ft^-min
'Low rate 1.3-4.0
High rate 4.0-10.0
• Horizontal velocity, ft/rain 1.3-3.8
Detention tins, nln
Flotation cell range 10-60
" Flotation call average 25
Saturation tank 1.3
nixing chamber |
Pressurized flow, X of total flow
Split flow pressurlzatlon 20-30
Effluent recycle pressurlzatlon 25-45
Air to pressurized flow ratio.
Standard ftVnin.lCO gal J.Q
Air to solids ratio 0.05-0.35
Pressure In saturation tank, Ib/inZ 40-70
Moat
Yolure, t of total flow 0.75-1.4
Solids concentration. I dry weight basis 1-2
x 2.445
ft/min x 0.00:03 - m/s
Standard ftVnin-100 gal x 0.00747
Ia/in2 x 0.0703 - kg/ra?
stf/min-IOOT
(EPA-600/8-77-014)
-------
For the two full scale CSO test sites in Racine, WI, capital costs (including
land) were $763,882 and $1,472,165 for 54,126 and 168,054 m3/d (14.3 and 44.4
Mgal/d) facilities, respectively (ENR = 3452). Construction cost curves (ENR = 2000)
for DAF facilities, based on the experienced cost of the demonstration facilities,
are presented in Figure 16.
The operation and maintenance cost (ENR = 3452) for the systems was $0.117
cu m ($0.40/1,000 gal). It was thought that these costs would be reduced to $0.067
cu m ($0.21/1,000 gal) by process and procedural modifications as described in EPA-
600/2-79-106a. The major reason for the high operation and maintenance cost is the
cost of labor for maintenance of the sites and cleanup of the sites after a system
operation. These costs were $0.07/cu m ($0.26/1,000 gal), or 65 percent of the
totaL Therefore, maintenance becomes the major cost item in the full-scale
application of screening/DAF for the treatment of CSO.
10 000
I 000
t-
o
0
100
1
1
— i
SAN FRANCISCO.
ESTIMATED 90 tt|>l/d FIAMT.
MILWAUKEE (ISC. £ b ]
^
r-
*
^-
r'
A
s'
/
^
s •
\^
t S
"2
_y
^
st
1 X
•X
/•'f
X
w
J.
/
CA
«»
_.<
^J
y1
A
RACI
IHCLI
a ] — -
*1
ri^*
\d
' *- 1
!
x'
ACJb
^/. Scrtcninj/flautlon; EPA-600/2-77-059i.
C. Don not Include scrccfling; EPA-600/2-75-2ES
4. ScrcMtng/HoUtlon; EPA-500/2-79-i
ft2 x 0.0929 « m2
Mgal/d x 0.0433 - i
Figure 16. DAF Construction Costs (ENR = 2000)
(EPA-600/8-77-014)
47
-------
References
EPA-600/2-79-106a -
Screening/Flotation Treatment of Combined
Sewer Overflows: Volume II: Fuil-Scale Opera-
tion, Racine, WI: by T.L. Meinholz, Envirex, Inc.,
Milwaukee, WI, August, 1979.
NTIS PB 80-130693
EPA-600/2-77-069a -
EPA-600/2-75-033 -
Screening/Flotation Treatment of Combined
Sewer Overflows, Volume I - Bench-Scale~and
Pilot Plant Investigations: by M.K. Gupta et aL,
Envirex, Environmental Science Division, Milwaukee,
WI, August, 1977.
NTIS PB 272 834
Treatment of Combined Sewer Overflows by
Dissolved Air Flotation: by T.A. Bursztynsky
et ah, Engineering Science, Inc., Berkeley, CA,
September, 1975.
NTIS PB 248 186
11020FDC01/72
Screening/Flotation Treatment of Combined Sewer
Overflows: Rex Chainbelt, Inc., Milwaukee, WI,
January, 1972.
No NTIS Number
48
-------
BIOLOGICAL TREATMENT
Biological treatment is a means for stabilizing dissolved organic matter,
and removing nonsettleable colloidal solids. This can be accomplished either
aerobically, or anaerobically. Several biological processes have been applied
to CSO treatment. These include: contact stabilization, trickling filters, ro-
tating biological contactors (RBC), and treatment lagoons. Descriptions of
these processes and typical combined sewage treatment installations are pro-
vided in Tables 26 and 27.
Biological treatment processes are generally classified as secondary
treatment processes, capable of removing between 70 and 95 percent of the
BODs and SS from waste flows at dry-weather design flowrates and loadings.
When biological treatment processes are used for combined sewage treatment,
removal efficiencies are lower (the percent organic matter is smaller for CSO
solids than for dry-weather solids), and are controlled to a large degree by
hydraulic and organic loading rates. Most biological systems are susceptible
to overloading conditions and shock loads as compared to physical treatment
processes. However, RBC's have achieved high removals at flows 8 to 10
times dry-weather design flows.
Typical pollutant removals for contact stabilization, trickling filters, and
RBC's (wet-weather loading conditions), are presented in Table 28. These
processes include primary (except contact stabilization) and final clarification.
Final clarification greatly influences the overall performance of the system by
preventing the carryover of biological solids produced by the processes. Pol-
lutant removal efficiencies by treatment lagoons have varied from highs of 85
to 95 percent to negative values, due to excessive algae production and
carryover. In addition to the type of lagoon and the number of cells in series
(stages), several major factors that influence removal efficiencies include: (1)
detention time, (2) source of oxygen supply, (3) mixing, (4) organic and
hydraulic loading rates, and (5) algae removal mechanisms. A single cell
storage/oxidation lagoon in Springfield, IL, averaged 27 percent BOD$ removal
and 20 percent SS removal; however, fish kills in the receiving water were
greatly reduced as compared to that prior to the construction of the facility.
Multiple cell facilities with algae control systems constructed at Mount
Clemens, MI, and Shelbyville, IL, provide 75 to 90 percent SS and BOD5
removal efficiencies during wet-weather conditions.
An operational problem common to all storm water biological systems is
that of maintaining a viable biomass to treat flows during wet-weather con-
ditions. At New Providence, NJ, trickling filters are operated in series during
dry weather, and in parallel during wet weather. This type of operation
maintains a viable microorganism population during dry weather and also
provides greater capacity for the wet-weather flows. For processes that
borrow biomass from dry-weather facilities or allow the biomass to develop,
a lag in process efficiency may be experienced as the biomass becomes ac-
climated to the changing waste strength and flowrate. Also, because of the
limited ability of biological systems to handle fluctuating and high hydraulic
shock loads, storage/detention facilities preceding the biological processes
may be required.
49
-------
Table 26. Description of. Biological Processes Used in CSO Treatment
en
O
Biological
praccit
Contact
tiabl llmlon
Trickling
filters
Routing
biological
conuctors
Treatment
lagoons
Oxidation
ponds
Aerated
lagooni
Facultative
lagoon t
Process description
Process Is « modified activated sludge process In
which the absorption phase, or contact, ind Ilia
oxidation phase (lUbllliatlon) takes place In
two separate tanks. Sludge Is waited "from tho
itabllliatlon tank to maintain constant blomais
concentrations.
Standard trickling (11 tor process In which t bio-
logical growth Is supported on a stationary
•tedium and the ttoniujtur .distributed over the
surface and allowed to Mow through the media.
Process can Include Standard rate or ddOp bed
plastic eedla deitgns.
Process operates on the same principle as trick-
ling filters! however, the biological growth It
supported on large diameter, closely spaced disks
which art partially submerged and rotate at slow
speeds.
Shallow aerobic ponds which rely on surface
reaeratlon for oxygen supply to maintain blolgl-
cal uptake of organic*. Sedimentation also
occurs In oxidation ponds.
Similar to oxidation pondi except they, are deeper
and rely on artificial means of oxygen supply
such as surface aerators or diffused air systems.
System operates under aerobic conditions.
facultative lagoons are the deepest of the
lagoons and rely on surface reaeratlon. The
lagoons have three distinct layers: aerobic near
the surface due to algae and rea oration, a tran-
sition tone, and an anaerobic lone near the ,
bo t ton sludge deposits. The biological oxidation
and anaerobic stabllliatlon occur simultaneously.
additional
Source of Blonass treatment
From conventional activated yes
sludge treatment facility.
Must be continuously nafn- yes
talned with a source of
food.
Must be continuously main- Yes
talned with a source of
food.
Allowed to generate for Optional
each storm.
Allowed to generate for Optional
each storm.
Allowed to generate for Optional
each tiara.
additional
treatment
Secondary
clarification
Secondary
clarification
Secondary
clarification
Final clarifi-
cation, screen-
Ing, or sand
filtration
Final clarifi-
cation, screen-
Ing, or sand
filtration
Final clarifi-
cation, screen-
Ing, or sand
filtration
(EPA-600/8-77-014)
-------
Table 27. Summary of Typical Biological CSO Treatment Installations
Project location
Xcnoshii
Wisconsin
Milwaukee.
Wisconsin
Ml. Clemens,
Michigan
Demons tritlon
system
CILvwIrfi full
scale system
Him Providence,
HUM Jersey
Shelby* (He,
nifnol*
Sprlngflold,
Illinois
Type of Tributary Design
biological area. capacity
trcatwnl *crot Hgal/d
Contact 1,200 20
stauillHtlon
Rotating 35 0.05*
biological
contactors
Treatment lagoons 212 1.0b
In series with
reel rcul atton
between storms
SluMgR/lrttdtmcnt 1 ,471 4.0b
lagoons In series
Mltb wclrculj-
clim beUatn
storms
TrtckUng flllors ..... 6.0
Trcatunt lagoons i
Southern site 44 2B6
Southwest site. 450 110
Treatment lagoon 2,208 67
No.
, Major of
process components units ' lolil stie
Contact tank 2 32,700 ft1
Stabilization tank 2 97,900 ft'
3 rt diameter 24 28,300. ft2
ROC units
Storage/aerated lagoon
Oxidation lagoon
Aerated lagoon
Aerated storage basin
Aerated lagoon
Oxidation laooaa
Acra tod/oxidation lagoon
High- ran plastic awdU
High-rate rock ncdlt
Oxidation Ugoon
Detention lagoon plus
2- cell ftcultattvQ lagoon
750,000 ft1
1,100,000 ft>
910.000 ft'
4,440.000 ft3
too ,000 ft1
1,100,000 ft3
922,000 ft'
36 ft diameter
65 ft diameter
255.600 ft3
2,702,700 ft!
Storage/oxidation Ugoon 1 6, 330,000 ft3
Period
of operation
1971 to 197S
1969 to 1970
1972 to 1975
Under construction
1970 to present
1969 to present
1969 to present
1969 to present
a. Design based on average dry-weather flow) average wot-weather flov - 1 MgaT/d.
b. Dcslyn flwrale through Ifljoon system. Total flwrata to ftcllllles fs 64 MgaT/d for the deiranitratlon project and
260 Ngal/d forcllyMlde syslGiu.
c. Estluaivd using a SOI runoff coefficient it » wlnfal] rite of 1.95 fn./h.
acre} i 0.40S • ha
Hgal/d R 0.0438 •
fl3 k 0.020) * a>
ft' « 0.0929 • n*
rt * 0.305 • •
In./b » 2,S4 • cm/h
(EPA-600/8-77-014)
-------
Table 28. Typical Wet-Weather BOD and SS
Removals for Biological Treatment Processes
Expected range of
pol1utant removal, %
Biological treatment process BOD COD
Contact stabilization 70-90 75-95
Trickling filters 65-85 65-85
RBCa 40-80 40-80
al Removal reflects flow ranges from 30 to 10 times dry-weather
flow.
(EPA-600/8-77-014)
General maintenance problems experienced by wet-weather biological
facilities are similar to those experienced at conventional biological instal-
lations. Winter operation of mechanical surface aerators have had some
serious drawbacks, including icing, tipping, or sinking. Other methods of
providing the required oxygen that show promise and have been demonstrated
at many dry-weather facilities include diffused air systems and submerged
tube aerators.
A comparison of construction, and operation and maintenance costs for
biological treatment systems and treatment lagoons is presented in Table 29.
Costs of final clarification are included where control of solids and sludge pro-
duced by the biological treatment system are required. Costs also include
pumping, disinfection, and algae control systems, when applicable. Engineer-
ing, administration, and land costs are not included in the estimates; however,
land costs may be the controlling economic factor in the evaluation of lagoon
treatment systems and therefore must be evaluated for each specific location.
Biological CSO treatment systems are integrated with or are a part of dry-
weather treatment facilities. Cost estimates of the wet-weather portion of
these facilities were separated from total costs of the total treatment
systems. The cost of the in-line RBC at Milwaukee, WI, was used together
with an estimated cost for a final clarifier to develop an estimated cost of
a complete RBC treatment system. The final clarifier cost was based on one
19.8 m (65 ft) diameter clarifier with a surface loading rate of 2.04 m3/m2'h
(1,200J gal/ft2-d). Costs of lagoon treatment systems vary widely, and are
a function of the type of lagoon (oxidation, aerated, or facultative), the
number of cells, and the miscellaneous equipment requirements including:
aeration equipment, disinfection equipment, instrumentation, pumping, and
algae control provisions. Costs for many of these CSO facilities are based on
only one installation of each biological treatment process. Therefore, these
costs should be considered only coarse estimates and may be greatly
52
-------
influenced by the degree of integration with dry-weather treatment required
to produce a viable system. These costs can be used as a preliminary guide,
but detailed analyses should be performed to compare and evaluate biological
treatment alternatives with other methods of treatment and control.
Initial capital investments of integrated dual use facilities can be
reduced by apportioning part of the costs to the dry-weather facility. The cost
reduction is in proportion to the net benefit that the wet-weather facility
provides to the overall treatment efficiency during dry-weather periods. A
description of this evaluation is presented in Section 4 of EPA-600/8-77-014,
Urban Storm water Management and Technology; Update and User's Guide.
53
-------
Table 29 . Summary of' Capital and Operation and Maintenance
Costs for Biological Treatment Alternativesa
en
Project location
Kcnosha,
Wisconsin
Milwaukee,.
Wisconsin 6
Mount Clemens,
Michigan
Demonstration
system
City wide
system
New Providence,
New Jersey c
Shclbyvllle,
Illinois
Southeast
site
Southwest
site
Springfield,
Illinois'
Type of
biological
treatment
Contact
stabilization
Rotating
biological
contactor
Aerated
treatment lagoons
Storage/aerated
treatment lagoons
High-rate
trickling filter
Oxidation lagoon
Storage and facul-
tative lagoons
Oxidation lagoon
Peak
plant
capacity,
Mgal/d
20
4.3
64
260
6
28
110
67
Construction
cost, t
2,354,300
516,100
1,10*. 300
9,902,100
619,900
74,900
582.900
303,600
Cost/
capacf ty,
$/Mgal>d
117,700
119.400
17,300
30,000
136.600
2,680
5,300
4,500
Cost/
tributary
area,
I/acre
1.970
14,740
5,230
6,730
.....
1,730
1,300
140
Annual operation
and maintenance
cost, e/l,000 gal
(except as noted)
23.8
7.6
34.5
32. B
21.2
2.,640/yr"
9,980/yrd
3,630/yr
a. El«ls3452
b. Includes estimate of final clarifter.
c. Includes plastic media trickling filter, final claHfler. plus one-half of other costs.
d. Based on estimated man-day labor requirements.
Hgal/d x 0.0438 - D3/S
acres x 0.405 • ha
i/l.000 9&1 x 0.264 - t/m3
flEPA-600/8-77-014)
-------
EPA-67 0/2-75-019 -
EPA-670/2-7 3-071 -
References
EPA-670/2-74-050 - Combined Sewer Overflow Treatment by the
Rotating Biological Contactor Process: by F.L.
Welsh, and D.J. Stucky, Autotrol Corp., Milwaukee,
WU June, 1974.
NTIS PB 231 892
Biological Treatment of Combined Sewer Overflow
at Kenosha. WI: by R.W. Agnew et al., Envirex,
Milwaukee, WI, April 1975.
NTIS PB 242 126
Utilization of Trickling Filters for Dual-Treatment
of Dry and Wet-Weather Flows: by P. Homack
et al., E.T. Killam Assoc., Inc., MiUburn, NJ,
September, 1973.
NTIS PB 231 251
An Evaluation of Three Combined Sewer Overflow
Treatment Alternatives (Shelbyville, IL>:' by
J.W. Parks et ah, Urbana, IL, August, 1974.
NTIS ONLY PB 239 115
Retention Basin .Control of Combined Sewer Over~
flows: by Springfield Sanitary District, Springfield,
IL, August, 1970.
NTIS PB 200 828
Multi-Purpose Combined Sewer Overflow Treatment
Facility. Mount Clemens. Michigan: by V.U. Mahida
et al., Spalding, DeDecker & Associates, Inc.. Madison
Beifnts, MI, May, 1975.
NTIS PB 242 914
Post-Construction Evaluation of the East Chicago, Indiana CSO Treatment
Lagoon: by D.J. Connick et al., Environmental Design & Planning, Inc.,
Allston, MA, Grant No. 11023 FAY (Publication Pending).
EPA-670/2-74-079 -
11023—08/70
EPA-670/2-75-010 -
55
-------
ADVANCED TREATMENT
In this report, advanced treatment includes high gradient magnetic separation,
and powdered activated carbon-alum coagulation. The high pollutant removals
achievable with these processes may not always be necessary, or cost-effective for
CSO, but if a high degree of treatment is required, the processes may become more
attractive.
High Gradient Magnetic Separation
High gradient magnetic separation (HGMS) is a new treatment technology
applied to CSO management. In its simplest form, the high gradient magnetic
separator consists of a canister packed with a fibrous ferromagnetic material which
is magnetized by a strong external magnetic field (coils surround the canister). An
iron frame increases the efficiency of the electromagnetic coils. The device
operates in a sequence of feed and flush modes. The magnetic particles are trapped
on the edges of the magnetized fibers while the non-magnetic particles and slurry
fluid pass through the canister. The matrix offers only a small hydraulic resistance
to the feed flow, occupying less than 5 percent of the canister volume (95 percent
void volume). When the matrix has become loaded with magnetic particles, the
particles are easily washed from the matrix by reducing the magnetic field to zero
and opening valves and backflushing. High gradient magnetic separation may also
be used to remove non-magnetic contaminants from water. This is accomplished by
binding finely divided magnetic seed particles, such as magnetic iron oxide
(magnetite), to the non-magnetic contaminants, thus creating a "magnetic handle"
("indirect filtration*1 or "seeded water treatment"). Binding of the magnetic seed is
accomplished in two general ways: adsorption of the contaminant to magnetic seed
and chemical coagulation (alum). Particles ranging in size from soluble through
settleable (>Q.001u) may be removed with this process. Design parameters for HGMS
are presented in-Table 30.
Table 30. Preliminary Design Parameters for
High Gradient Magnetic Separators
Magnetic field strength, kGa 0.5-1.5
Maximum flux rate, gal/f t^-tain 100
Hinlnun detention tine, nin 3
Matrix loading, g solids/3 of
matrix fiber 0.1-0.5
Magnetite addition, og/1 100-500
Magnetite to suspended solids ratio 0.4-3.0
Alum addition, eg/1
Range 90-120
Average 100
Poljrelectrolyte addition, eg/) 0.5-1.0
a. kG • kilogauss
x 2.445 - n3/B2-h
(EPA-600/8-77-014)
56
-------
Magnetic separation can provide the rapid filtration of many pollutants from
water, with a small expenditure of energy. Removal is much more efficient than
with sedimentation because the magnetic forces on fine particles may be many
times greater than gravitational forces. To date, only bench scale tests and
a pilot plant scale system of 1 to 4 1/min (0.26 to 1.06 gal/min) have been op-
erated.
Typical pollutant removals are shown in Tables 31, 32, and 33.
Table 31. Removal of Solids by HGMS for CSO and Raw
Sewage Samples3
Removal,
Solids parameter
SS
Settleable solids
Apparent color, PCU
Turbidity, FTU
CSO
95
99+
87
93
Raw sewaqe
91
99+
82
88
a. All samples concentration basis except
as noted.
b. Operated at 1 to 4 1/min (0.26 to
1.06 gal/min), (3 to 12 min residence
ti mes). (EPA-600/8-77-014)
Table 32. Removal of Biological and Chemical Constituents
by HGMS
Pollutant parameter Avg. removal, %
BOO 92
COD 74
Total coliforms on
EMB agar at 37°C 99.3
Fecal coliforms on
EMB agar at 37°C 99.2
Algae 99.9
Virus, bacteriophage Tj 100
Virus* polio 99-100
(EPA-600/8-77-014)
57
-------
Table 33. Removal of Heavy Metals by HGMS
Heavy metal constituent
Cadmium Chromium Copper Mercury Nickel Lead Zinc
Average
removal, % 43 41 53 71 0-67 0-67 84
(EPA-600/8-77-014)
Costs of HGMS have been evaluated for a 94625 m3/d (25 Mgal/d) facility, and
are summarized in Table 34. Capital costs include pretreatment, chemical addition,
thickening and dewatering equipment, pumps, backflush system, instrumentation,
and disinfection system. Operation and maintenance costs include chemicals, labor,
electrical utilities, and maintenance.
Table 34. Construction and Operation and Maintenance
Costsa for a 25 Mgal/d HGMS Facility
Construction cost
Total, $ 3,647,000
$/Mgal-d 145,800
Operation and
maintenance cost
$/yr 938,900
$/l,000 gal treated 0.21
a. ENRa3452
Mgal/d x 0.0438 = m3/s
1,000 gal x 3.785 = m3
(EPA-600/8-77-014)
53
-------
Powdered Activated Carbon - Alum Coagulation
Several combined sewage treatment demonstration projects have evaluated
the benefits of chemical aids to process operations, but only one pilot operation
representing a complete physical chemical treatment system has been imple-
mented. It was demonstrated at a 379 m3/d (100,000 gal/d) pilot unit in Albany,
NY. In this project, raw municipal sewage and CSO were mixed with powdered
activated carbon, to remove dissolved organics. Alum was then added to aid in
subsequent clarification. Addition of polyelectrolyte was followed by a short
flocculation period. Solids were separated from the liquid stream by gravity
settling, and the effluent was then disinfected and discharged, or filtered (tri-
media), then disinfected prior to discharge. Carbon regeneration in a fluidized
bed furnace and alum recovery from the calcined sludge were also demonstrated,
as was reuse of the reclaimed chemicals. Average carbon losses per
regeneration cycle were 9.7 percent. Average removals in excess of 94 percent
COD, 94 percent BOD, and 99 percent SS were consistently achieved (without
filtration) in treating combined sewage.
Representative capital and operation and maintenance costs for a physical-
chemical treatment plant designed for raw storm water treatment, projected
from data developed during the Albany project, are summarized in Table 35.
Table 35. Estimated Capital and Operation and
Maintenance Costs for a Physical-Chemical Treatment Plant
. Operation and
Capital Costs. 5 Maintenance costs, t/1000 qal
-1 HqaVd 10 Mgat/d 25 Moal/d 100 Hqal/d ' 1 KqaV/d 10 Mqal/d 25 Hgal/d 100 Kqal/j
309.180 3.091,800 6.289.400 18.416,600 3.3 32.5 26.9 20.2
EMU • 3452
x 0.0438
4/1000 gat x 0.264 «
* Capital costs include screens, grit chambers, overflow facilities, pipe
reactor vessels, pumps, chemical storage, carbon slurry tanks, sludge storage,
agitators, flocculators, tube settlers, filtration, chlorination, carbon re-
generation/sludge incineration, fluidized bed furnace, chemical make-up
system, 10 percent contingencies, and land. Operation and maintenance
costs include all materials, power, and labor. Plant is designed for raw
stormwater treatment.
(EPA-670/2-74-040)
Reference
EPA-R2-73-149 - Physical-Chemical Treatment of Combined and
Municipal Sewage: by A.J. Shuckrow et al.,
Pacific NW Lab., Battelle Memorial Institute,
Richland, WA, February. 1973.
NTIS PB 219 668
. 60
-------
DISINFECTION
Conventional municipal sewage disinfection generally involves the use of
chlorine gas or sodium hypochlorite as the disinfectant. To be effective for
disinfection purposes, a contact time of not less than 15 minutes at peak flow
rate and a chlorine residual of 0.2 to 2.0 mg/1 are commonly recommended.
Disinfection of CSO is generally practiced at treatment facilities to
control the discharge of pathogens, and other microorganisms in receiving
waters. However, an approach other than that used for the conventional
municipal sewage is required, mainly because such flows have characteristics of
intermittent, high flow rate, high SS content, wide temperature variation, and
variable bacterial quality.
Several other aspects of disinfection practices require consideration for
CSO treatment applications:
• A residual disinfecting capability may not be feasible for CSO (and
all wastewater) discharges. Recent woik indicates that chlorine resi-
duals and compounds discharged to natural waters may be harmful
to aquatic life.
• The coliform count is increased by surface runoff in quantities un-
related to pathogenic organism concentration. Total coliform levels
may not be the most useful indication of disinfection requirements
and efficiencies.
• Discharge points requiring disinfection are often at outlying points
on the sewer system and require unmanned/automated installations.
The disinfectant used at a facility for treatment of CSO should be
adaptable to intermittent use. Other considerations include the disinfection
effectiveness, and the safety and ease of feeding. Table 36 shows disinfectants
that might be used for storm water disinfection. Chlorine and hypochlorite will
react with ammonia to form chloramines and with phenols to form chlorophenols.
These are toxic to aquatic life and the latter also produce taste and odor in the
water. Chlorine dioxide does not react with ammonia and completely oxidizes
phenols. Ozone is also effective in oxidizing phenols.
High-rate disinfection refers to achieving either a given percent or a given
bacterial count reduction through the use of (1) decreased disinfectant contact
time, (2) increased mixing intensity, (3) increased disinfectant concentration, (4)
chemicals having higher oxidizing rates, or (5) various combinations of these.
Where contact times are less than 10 minutes, usually in the range of 1 to 5
61
-------
Table 36. Characteristics of Principal
Slorrmvater Disinfection Agents
Chlorine
Characteristic
Chlorine
Hypochlorite
dioxide
Produces a residual Yes
Yes
a. Chlorine dioxide dissociates rapidly
Ozom
Stability
Reacts with ammonia
to form chloramines
Destroys phenols
Stable
Yes
At high
concentrations
6 month half-life
Yes
At high
concentrations
Unstable
Ha
Yes
Unstable
No
Yes
Short lived* Ho
Affected by pH
Hazards
More effective
at pH<7.5
Toxic
Kare effective
at pH<7.5
Slight
Slightly
Toxic,
explosive
Ho
Toxic
(EPA-6Q 0/8-77-014)
minutes, adequate mixing is a critical parameter, providing complete dispersion
of the disinfectant and forcing disinfectant contact with the maximum number
of microorganisms. The more physical collisions high-intensity mixing causes,
the lower the contact time requirements. Mixing can be accomplished by
mechanical flash mixers at the point of disinfectant addition and at intermittent
points, or by specially designed plug flow contact chambers containing closely
spaced, corregated parallel baffles which create a meandering path for the
wastewater (EPA-67Q/2-73-077).
High-rate disinfection was shown to be enhanced beyond the Expected
additive effect by sequential addition of Cl2 followed by CIO2 at intervals of 15
to 30 seconds (EPA-670-2-75-021; EPA-60Q/2-76-244). A minimum effective
combination of 8 mg/1 of Cl2 followed by 2 mg/1 of C102 was found as effective
in reducing total and fecal coliforms, fecal streptococci, and viruses to
acceptable target levels as adding 25 mg/1 Cl2 or 12 mg/1 C102 individually. It
was surmised that the presence of free Cl2 in solution with chlorite ions (ClO^),
(the reduced state of CIC^), may cause the oxidation of C102 back to its original
state. This process would prolong the existence of C102> the more potent
disinfectant.
Ozone has a more rapid disinfecting rate than chlorine and also has the
further advantage of supplying additional oxygen to the wastewater. The
increased disinfecting rate for ozone requires shorter contact times, and results
in a lower capital cost for a contactor, as compared to that for a chlorine
contact tank. Ozone does not produce chlorinated hydrocarbons or a long-lasting
residual as chlorine does, but it is unstable and must be generated on-site just
prior to application. Thus, unlike chlorine, no storage is required. In tests on
CSO in Philadelphia (see "microscreening and disinfection" reports listed at the
end of this Disinfection section), equivalent disinfection was obtained using
either 3.8 mg/1 of ozone or 5 mg/1 of chlorine.
62
-------
Because of the characteristic intermittent operation associated with
treatment of CSO, reduction of construction cost with a potential increase in
operating costs often results in overall minimum costs. In the case of
chlorination facilities, as applied to treatment of CSO, the construction costs
associated with contact basins having conventional contact time of 15 to 30
minutes are high and difficult to justify. Therefore, consideration should be
given to higher mixing intensities, to make better usage of the chlorine and/or
higher chlorine dosages and smaller, shorter detention time contact basins to
effect the same end results.
Disinfectant costs for CSO treatment are higher than those for sewage
treatment. This is the result of smaller total annual disinfectant volume
requirements, increased disinfectant concentration requirements, and higher unit
operation and maintenance costs for CSO treatment facilities. These costs could
be reduced by using the facilities in conjunction with dry-weather flow
treatment plants, whenever possible.
Curves comparing generation and feed costs for chlorine gas, chlorine
dioxide, and hypochlorite generation disinfection systems for CSO have been
developed and are presented in Figure 17. These costs (ENR = 2000) include
manufactured equipment, labor, piping, housing, electrical and instrumentation,
and miscellaneous items. No allowance for land was included.
Capital and operating costs for several CSO and stormwater disinfection
facilities are presented in Table 37.
As previously mentioned, conventionally long contact times may not be
economical. Short term contact times with more intense mixing, using a basin
and mixer similar to those used in coagulant mixing, can effect the same
disinfection results. Construction costs curves for high intensity mixing/chlorine
contact basins are presented in Figure 18. Power requirement curves, for high
intensity mixing, are presented in Figure 19.
The capital costs for different disinfection agents and methods resulting
from the Philadelphia study are shown in Table 38. The capital costs for ozone
generation are usually the highest of the most commonly used processes. Ozone
operation costs.are very dependent on the cost of electricity and the
source of the ozone, (air or pure oxygen).
63
-------
C/l
o
O
o
'•w
t)
L.
-w
s
I.000
I
I
100
10
III
1 •
1 1 1 II
HtHCHlOIIITE SEMII1TION
iNB run casts — ^
X
X
x
X
X
/
X
-H — V-
V
\
.X
^x
/CHLoTlNC DIOXI
StSE » IT 1 3X tfitt
FEED COSTS— pX
X
_x
,x
X
j ^
'!
^
"2.1
1 _x^
Tj
J
f
DTx
0
x
-CHLORINE CIS
FZEO COSTS
,
,'
*
3
X 3 * 9 « TIS I 3 4 S t 7St
toe i ooo ID ooo
Design Feed Rate, Ib/d
lb/d x 0.454 » kg/d
(EPA-600/8-77-014)
Figure 17. Chlorine Disinfection Feed Facilities Cost Curves (ENR = 2000}
64
-------
Table 37. Cost Data on Chlorine Gas
and Hypochlorite Disinfection3
Location, agent
and source
Capital Cost. J
Cost/to
Operating available
cost. S/yr Chlorine,
Akron. Ohio0
Sodium hypochlorite
Purchased
Caaarfdge, Massachusetts
aad Somerrille,
Massachusetts^
Sodiua hjpochlorite
Purchased
On-s1te generation
Hew Orleans, Lousianac
Sodiua hypochlorite
Do-sits generation
Saginaw. Michigan4
Chlorine gas
Sodiua hypochlorite
Purchased
Da-site generation
South Essex Sewerage
District. Massachusetts
Chlorine gas
Sodtin hvpochlorlte
Purchased
On-site generation
Sea water
Brine
76.2.000
1,000.000
280.000
34,000
165,000-273,000
1,151.000
728.000
2.900.0CO
2.900,000
40.200 0.26*0.46
0.67
0.35
500.000 0.21
4,000 0.60
11,000-20,000 0.31-.54
8,100-9.000 0.48-0.69
402.000
630.000
280,000
523.000
0.06
0.08
0.06
0.09
*. EMR - 3452
b. Coobined sewer overflow disinfection
e. Stora sewer discharge disinfection
d. Combined sewer overflow disinfection at use rate of 42,000 Ib/yr
of chlorine
e. Sewage treatment plant effluent disinfection at use rate of
24.000 Ib/dav of chlorine
S/lb x 2.2 - S/kg
(EPA-670/2-74-040)
65
-------
o
o
o
tn
O
O
o
4-1
CJ
h
4_l
01
O
O
10J
I
7
6
3 4 5 6789
10
3 4 5 6 789
100
Volume, 1,000 Cubic Feet
ft3 x 0.0283 -
Figure 18. High Intensity Mixing/
Chlorine Contact Basin Cost (ENR = 2000}
(EPA-600/2-76-286)
66
-------
s
o
o
-------
Table 38. Comparison of Estimated Capital Costs
for 3 Different Disinfection Methods*
Capital cost,
Disinfection method $/mgd
2-Minute ozone contact
(chamber with once-through b
oxygen-fed ozone generator) 22,460
2-Minute chlorine contact
(chamber with hypochlorite
feeder)0 2,625
5-10 Minute conventional
chlorine contact* 2,920
a. ENR'- 3452
b. Unit cost of ozone at $9.00/lb from oxygen @
$0.33/lb; dosage of 3.8 ppm; Otto plate type
generator.
c. Unit cost of hypochlorite at $0.73/lb
available chlorine; dosage of 15 ppm.'
d. Unit cost at $0.73/lb available chlorine;
dosage of 5 ppm.
$/mgd x 0.0228 = $/l/sec
$/lb x 2.2 * $/kg
(EPA-670/2-74-040)
68
-------
References
EPA-670/2-75-021 -
11023EVO06/70
EPA-R2-73-124
EPA-670/2-74-049
EPA-600/2-79-031b -
EPA-600/2-79-134 -
EPA-670/2-73-077 -
Bench-Scale High-Rate Disinfection of Com-
bined Sewer Overflows with Chlorine and
Chlorine Dioxide: by P.E. Moffa et al.,
O'Brien & Gere Engineers, Inc., Syracuse, NY,
April, 1975.
NTIS PB 242 296
Microstraining and Disinfection of Combined
Sewer Overflows: by Cochrane Div., Crane Co.,
King of Prussia, PA, June, 1970.
NTIS PB 195 67
Microstraining and Disinfection of Combined
Sewer Overflows-Phase II: by G.E. Glover, and G.R.
Herbert, Crane Company, King of Prussia, PA,
January, 1973.
NTIS PB 219 879
Microstraining and Disinfection of Combined
Sewer Overflows-Phase III: By M.B. Maher,
Crane Company, King of Prussia. PA,
August, 1974.
NTIS PB 235 771
Combined Sewer Overflow Abatement Program,
Rochester. NY - Volume II Pilot Plant Evaluations:
by F.J. Drehwing et al., O'Brien
& Gere Engineers, Inc., Syracuse, NY, July, 1979.
NTIS PB 80-159282
Disinfection/Treatment of Combined Sewer
Overflows, Syracuse, New York: by F. Drehwing
et aL, O'Brien & Gere Engineers, Inc., Syracuse, NY,
August, 1979.
NTIS PB 80-113459
Combined Sewer Overflow Seminar Papers
November, 1973.
U.S. EPA and N.Y.S. - DEC
NTIS PB 231 836
EPA-600/2-76-244 -
Proceedings of Workshop on Microorganisms in
Urban Stormwater: by R. Field et ah. Edison, NJ,
(March 24, 1975), November, 1976.
NTIS PB 263 030
69
------- |