United States
Environmental Protection
Agency
Municipal Environmental Research *
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-094 Jan. 1983
Project Summary
Characteristics and
Treatability of Urban
Runoff Residuals
Donald J. Carr, Anthony Geinopolos, and A. E. Zanoni
This study was undertaken to
determine the characteristics of urban
stormwater runoff residuals as well as
their handling and disposal
techniques. Residuals were obtained
from a field-assembled sedimentation
basin in Racine, Wisconsin; from swirl
and helical bend solids separators in
Boston, Massachusetts; and from an
in-line upsized storm conduit in
Lansing, Michigan. The drainage
basins at each site were primarily
residential land use areas. The charac-
terization study included analyses for
nine metals, eight pesticides and
PCB's, solids, nutrients, andorganics.
The treatability study was based on
bench scale sedimentation,
centrifugation, lime stabilization, and
capillary suction time tests.
The total solids concentration of the
residual samples from Racine ranged
from 233 to 793 mg/L. Total solids in
the Boston sample ranged from 344 to
1,140 mg/L, and the residuals from
Lansing had a solids concentration of
161,000 mg/L. Individual nutrients
(P, TKN, NH3, NO2, and NO3) in the
Boston and Racine samples never
exceeded 5 mg/L, while the concen-
trations in the Lansing sample varied
between 0.3 and 2,250 mg/L. Anal-
yses for metals showed iron to be
present in the highest concentration in
all the samples (6.1 to 2,790 mg/L),
with lead and zinc ranking second and
third, respectively. PCB's ranged in
measurable concentrations from 0.19
to 24.6 fjg/l. Of the eight pesticides
surveyed, only three (DDT, DDD, and
Dieldrin) were observed in measurable
concentrations. The pesticides were
primarily soluble, whereas the PCB's
were more related to the suspended
solids. _
Based on the results of this study,
the most cost-effective treatment for
handling and disposal of urban
stormwater runoff residuals is gravity
thickening followed by lime stabili-
zation and landspreading, or direct
landfilling. Total annual cost estimates
for landfilling and landspreading of
residuals generated from a hypothet-
ical 50 hectare site ranged from $360
to $470 per hectare.
This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory. Cincinnati, OH.
to announce key findings of the
research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Controlling stormwater runoff from
urban areas is a problem for some cities
and towns. Studies have shown that
biochemical oxygen demand (BODs) and
suspended solids (SS) in the runoff
represents 20 and 85 percent,
respectively, of the total input to the
receiving streams; and for 20 percent of
the year (during runoff events),
receiving stream quality may be
-------
governed by stormwater. A number of
communities have already undertaken
projects to mitigate the impact of urban
runoff on rivers and lakes in their areas.
Relatively little is known, however, of the
characteristics and disposal of storm-
water residuals removed in these facil-
ities. The objective of this study was to
provide that data.
Approach
The project objective was achieved
through the performance of a program
consisting of the following:
1. Identifying and selecting sites
using promising methods to treat
urban runoff.
2. Characterizing the residuals
generated from this treatment.
3. Determining the most feasible
handling processes for the
residuals.
4. Evaluating the costs for handling
and disposal of the residuals.
Urban Runoff Pollution
Control Techniques
Solutions to the urban runoff
pollution problem can be divided into
source control and treatment
categories. Source control techniques
involve nonstructural approaches and
include land use restrictions, erosion
control practices, and catch basin and
sewer cleaning. Evaluation of these
techniques was not an objective of this
study. Treatment techniques include
the following processes:
1. storage/sedimentation;
2. sedimentation/chemical
clarification;
3. microscreening;
4. screening/dissolved-air
flotation;
5. filtration;
6. swirl solids separation; and
7. helical bend solids separation.
Processes 2, 3, 4, and 5, above,
require some type of preliminary
storage/sedimentation to dampen the
shock loads associated with the runoff.
Therefore, these processes were
deemed to be relatively costly,
sophisticated polishing steps following
storage/sedimentation that would not
likely find widespread use. In view of
this, the residuals investigated in this
project were limited to those produced
by high flow rate treatment methods
such as 1, 6, and 7, above.
Description of Selected
Study Sites
In contrast to the treatment of
combined sewer overflow (CSO) where
full-scale operating control facilities
exist, a paucity of information was
available regarding full-scale operating
stormwater control facilities at which
residue samples could be obtained for
characterization and study for
treatment and disposal. Although this
made it difficult to obtain potential
candidate sites for the study, an
extensive investigation uncovered the
following site locations considered
suitable for obtaining stormwater runoff
residuals from the selected treatment
options, namely, storage/sedimentation,
swirl solids separation, and helical bend
solids separation.
Storage/Sedimentation
Two sites were selected, one in
Racine, Wisconsin, and the other in
Lansing, Michigan. A description of the
storage/sedimentation facilities used
at these sites is presented below.
Racine, Wisconsin, Site
A dry retention pond that serves a
29.3-hectare (72.3-acre) drainage area
located on Bird Avenue was selected for
this study. The pond receives runoff
from single family and general
residential as well as office/institu-
tional land use areas, and the runoff is
carried to the pond by a 1.22- by 1.52-m
(48- by 60-in.) storm sewer. A 6.1- x
24.4-m (20- by 80-ft.) sedimentation
basin was constructed in the detention
pond to facilitate the collection of the
residuals from a storm event and to
prevent the adverse effect on residuals
quality that may have been brought
about by percolation into the site soil
and by overland passage through high
grass. The basin was constructed with
10-mil polypropylene sheeting, sand-
bags, and 2- by 4-in. lumber. Storm-
water entered the south end of the basin
and then overflowed at the north end.
After the runoff from a storm event
decreased significantly, the inlet to the
basin was blocked, and the runoff that
was contained was allowed to settle for
1 hour. At the end of the settling phase,
the level of the runoff in the basin was
gradually reduced by draining the
supernatant. The remaining residuals
were then collected and returned to the
laboratory in Milwaukee for
characterization analyses and
treatability studies.
Lansing, Michigan, Site
In Lansing an assessment of urban
stormwater best management practices
(BMP's), including an in-line wet
retention basin and two in-line upsized
pipes, is being undertaken pursuant to
the goals of the U.S. Environmental
Protection Agency (USEPA) Nationwide
Urban Runoff Program (NURP). The
study is being conducted to determine
the operational costs and effectiveness
of the two types of BMP's in the
enhancement of the quality of storm
generated runoff. The site was of
interest to this study because in-line
BMP's within a drainage network may
provide a cost effective technique to
reduce the velocity of stormwater
thereby allowing for disposal of solids
and subsequent periodic removal.
Samples of the residuals from one of
the in-line upsized pipes were obtained
for characterization and treatability
studies. The upsized pipe receives
drainage from 31.6 hectares (78.0
acres) of mixed, residential (50percent),
industrial (20 percent), and public (30
percent) land uses. The pipe is 2.4 m
(96 in.)in diameter, made of reinforced
concrete, and has crown elevations the
same as the inlet and outlet pipes. The
inlet and outlet pipe diameters are 1.2 and
1.4 m. (48 and 54 in.), respectively. The
pipe has a length of 43.9 m (144 ft) at a 0.8
percent slope, which provided an average
standing water depth of 1.1 m (42 in.) and
a capacity of 70.8 m3 (2,500 ft3).
Samples of settled solids from the
upsized storm sewer were collected
after the system had been in operation
for approximately 6 months during
1980 and represented residuals deposits
by several storms. Five-gallon containers
were used to scoop up equal volumes of
runoff residuals along the length of the
conduit. The samples were then
transported to Milwaukee for
-------
characterization analyses and
treatability studies.
Swirl and Helical Bend
Solids Separators
The Boston, Massachusetts, site was
constructed as part of a USEPA pilot
project for the swirl and helical bend
solids separators. The total area drained
is 84 hectares (60 acres) with
essentially all of it having, low density
residential land use.
The swirl solids separator uses a high
rate swirl action to separate grit,
settleable matter, and floatable solids.
The helical bend separator uses the
same mechanism of solids/fluid sep-
aration as the swirl device; however, the
effectiveness of the helical bend is a
result of helical motion developed in
fluids at bends when a total angle of 60
degrees and a radius of curvature equal
to 16 times the inlet pipe diameter is
used. The characteristics of the swirl
and helical bend systems used in the
Boston demonstration project are given
below:
1. Swirl solids separator
a. Design flow - 0.17 cms
(6 cfs)
b. Peak flow - 0.34 cms (12
cfs)
c. Diameter-3.20m (10 ft-6
in.)
d. Depth - 1.83 m (6ft)
2. Helical bend solids separator
a. Design flow - 0.17 cms (6
cfs)
b. Peak flow - 0.34 cms (12
cfs)
c. Length - 19.83 m (65 ft)
d. Depth - 1.22 m (4ft)
Samples of the underflows from each
process were taken during two storm
events and shipped by air express to
Milwaukee for analyses.
Summary of Findings
Characteristics of the
Residuals
Data for the storm events investigated
in this study (Table 1) include th^
drainage basin areas and runoff coeffi-
cients, rainfall, runoff volume sampled,
and volume of residuals obtained from
the control techniques. Volumes of
residuals varied from less than 1 to 12.6
percent of the volume of runoff treated
and sampled.
Table 2 summarizes the chemical and
biological characteristics of the
residuals obtained from each of the
three sites. The conclusions drawn from
the data include the following:
1. The residuals collected from the
stormwater controls in Racine
and Boston were relatively thin
and dilute as evidenced from the
total solids content that varied
from 233 to 1,140 mg/L On the
other hand, residuals collected
were relatively concentrated as
evidenced by the total solids
content of 160,865 mg/L. The
wide range of residuals solids
characteristics observed is attrib-
uted to the design and operation
of the control method utilized.
2. The total volatile solids content of
the stormwater runoff residuals
varied from 11 to 43 percent.
These results indicate that storm-
water residuals are more inert
than municipal primary and activ-
ated sludges, whose volatile solids
contents may vary from 70 to 85
percent.
These results indicate that storm-
water residuals are more inert
than municipal primary and activ-
ated sludges, whose volatile solids
contents may vary from 70 to 85
percent.
3. Pesticide and PCB materials were
present in the residuals and
generally, the PCB concentrations
were appreciably higher than
those for the pesticides. More-
over, it was generally observed
that the PCB's were insoluble,
Whereas the pesticides were pre-
dominately soluble in nature.
4. Iron wasbyfarthe mostabundant
metal observed in the residuals
analyzed, followed in the ranking
by lead and zinc, respectively.
Table 1.
Stormwater Runoff from Monitored Storms and the Volume of Residuals from Each Site Studied
Site
Racine. Wl
Lansing, Ml
Boston. MA
Treatment
Settling basin
Upsized storm sewer
Swirl
Helical Bend
Swirl
Helical Bend
Drainage
Basin
Area,
hectares
29.3
32.4
64.9
64.9
Estimated
Runoff
Coefficient
0.5
0.5
0.5
0.5
Date
of
Event
6/28/80
9/9/80
10/25/80
6/23/81
Rainfall,
cm
1.2
1.3
2.5
1.0
Antecedent
Dry Days
7
3
7
Runoff
Volume
Sampled,
m3
1460
1230
319
119
130
424
Volume
Stormwater
Runoff
Residuals,
m3
6b
14"
103C
33
15
5
30
Volume
Settleable
Solids a
L/m*
2
6
590
0.6
0.3
3.5
22
" Volume settleable solids per m3 stormwater runoff residuals,
b Volume retained for one hour settling in field basin.
0 Volume is fixed by storm sewer pump.
Conversions: 2.47 acres = 1 hectare
264.2 gal. = 1 m3
0 26 gal. = 7 L
-------
Table 2. Characteristics of the Residuals Obtained from the Stormwater Runoff Control Technologies Investigated
Parameter
Total solids
Volatile total solids
Suspended solids
Volatile suspended solids
BOD.,
Total organic carbon
Total phosphorus (as P)
Total Kjeldahl nitrogen (as N)
NH3
N02 + NO3 {as N)'
pH
Total conforms, no. /WO mL
Fecal coliforms, no. /WO mL
PCB
DDT
ODD
DDE
Aldnn
Endrin
Lmdane
Methoxychlor
Dieldrin
Mercury
Arsenic
Lead
Zinc
Iron
Copper
Nickel
Chromium
Cadmium
Units
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
V9/L
ug/L
V9/L
(tg/L
M9/L
U9/L
V9/L
U9/<-
V9/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
Racine
6-2-80
233
155
149
122
11
29
0.42
3.48
0.52
0.70
8.1
87,000
2,200
0.19
<0.003
<0.005
<0.008
<0.002
<0.005
<0.004
<0.01
<0.005
<0 0003
<0.01
0.25
0.14
6.6
0.105
0.12
0.025
0.01
9-9-80
793
104
723
90
15
23
0.68
3.5
-
0.41
7.5
74,000
71,000
0.32
<0.004
<0.008
-------
bench scale tests showed that the
residuals from Racine and Boston
could be concentrated up to 14
percent solids. The residual from
Lansing was thickened by centri-
fugation to cake solids concentra-
tions as high as 55 percent.
3. The concentration of lime required
to stabilize thickened residuals
was up to five times greater than
that for unthickened residuals.
The quantity of lime based on
volume treated, however is signifi-
cantly less for the thickened
residuals because of separation of
water and its associated lime
demand.
Handling and Disposal Costs
for Urban Runoff Residuals
Based on the results of the thickening
tests, two residuals handling and
disposal options were evaluated. These
were: (1) storage/sedimentation and
landfilling; and (2) storage/sedimenta-
tion, lime stabilization, and land-
spreading. Storage/sedimentation for
thickening is common to both options,
and the two sludge disposal alternatives
selected, landfilling and landspreading,
appear to be the most efficient and cost-
effective manner for disposing of the
thickened residuals. Lime stabilization
was included in Option No. 2, above,
because of the requirement for destroy-
ing pathogens in the residuals before
surface land application.
For purposes of calculating costs, the
residuals were assumed to be generated
from a hypothetical drainage basin
covering 50 hectares (124 acres) and
collected and thickened by a storage/
sedimentation facility designed for a 1-
in 10-year storm of 60 minutes. For the
Milwaukee area, this would amount to a
5-cm (2-in.) rainfall.
No specific land use was designated
for the hypothetical drainage basin, and
it was assumed that the stormwater
runoff residuals were similar to those
from the Racine and Boston sites. Using
a runoff coefficient of 0.5, the volume of
runoff from the area would be 12,700
m3 (3.4 million gal) for the 1 - in 10-year
storm of 1-hour duration. For the
purposes of this analysis, it was
estimated that such a storm would
generate 30,000 kg (66,000 Ib) of wet
residuals with a solids concentration of
10 percent.
Shown in Table 4 are cost summaries
for the management of residuals for
Table 4.
Summary of Cost* Data (Cost of Residuals Management for
Hypothetical SO Hectare Sitel
Item
Option 1
Landfill
Option 2
L andspreading
Total capital costs $12.500
Amortized capital cost (20 years/8% interest) 1,270
Annual operation and maintenance cost 16,750
Total annual cost 18,020
Annual cost per hectare 360
Annual cost per metric ton dry residuals 400
Annual cost per m3 of wet residuals 40
$41,300
4,200
19,200
23,400
470
520
52
*Cost data are in 1981 dollars.
Options 1 and 2, respectively. It maybe
concluded from a comparison of the
costs in this table that the more
cost-effective means for handling and
disposal of urban stormwater runoff
residuals is gravity thickening followed
by landfilling. It must be kept in mind
that the costs for both options are very
much influenced by hauling distances
and tipping fees.
The full report was submitted in
fulfillment of Research Grant No. R-
806785 by Marquette University,
Milwaukee, Wisconsin, under the
cosponsorship of the U.S. Environ-
mental Protection Agency.
Donald J. Carr and Anthony Geinopolos are with Rexnord, Inc., Milwaukee, Wl
53214; A. E. Zanoni is with Marquette University, Milwaukee, Wl 53233.
John N. English is the EPA Project Officer (see below).
The complete report, entitled "Characteristics and Treatability of Urban Runoff
Residuals," (Order No. PB 83-133 561; Cost: $11.50, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U. S. GOVERNMENT PRINTING OFFICE: 1983/659 -095/574
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED
Third-Class
Bulk Rate
MERL0063240
LOU « TILLEY
REGION V EPA
LIBRARIAN
230 S DEARBORN ST
CHICAGO IL 60604
------- |