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

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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

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 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

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 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

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      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

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Environmental Protection
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