V-/EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-045 August 1982
Project Summary
Evaluation of Secondary
Environmental Impacts of
Urban Runoff Pollution Control
Kathryn R. Huibregtse and Anthony Geinopolos
The full report presents a generalized
evaluation of the impacts associated
with different urban stormwater run-
off (UR) treatment techniques. The
report addresses the definition of the
problem, estimates the volume and
characteristics of the UR and the
sludges expected, evaluates six meth-
ods of UR sludge treatment, and
examines alternatives and impacts for
UR treatment sludge handling such as
bleed/pump-back to the dry-weather
plant, and land disposal.
Regarding bleed/pump-back of UR
sludges, solids deposition in sewers
and overload to the dry-weather facil-
ities are anticipated to cause problems.
The most cost-effective sludge treat-
ment alternative appeared to be lime
stabilization followed by thickening,
pressure filter dewatering, and landfill
disposal. Secondary impacts included
costs, water quality, noise, energy
consumption, air pollution, and land
area requirements.
This Project Summary was devel-
opedby EPA's Municipal Environmen-
tal Research Laboratory. Cincinnati.
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Urban stormwater management is a
major problem in the field of water
quality management. As a result, much
research, development, and demonstra-
tion of techniques for controlling and/or
treating this source of pollution have
been implemented. Moreover, great
emphasis has been placed on the pri-
mary impacts from urban runoff pollu-
tion control, and the secondary impacts
have generally been neglected.
This study is concerned with the
secondary environmental impacts of
urban runoff pollution control tech-
niques. The project report summarized
here presents an overview of the prob-
lems associated with handling residuals
from treating urban stormwater runoff
(UR) or from various housekeeping
practices. The evaluation is performed
for typical national areas as well as for a
well-defined drainage basin.
The study's major objectives were to:
1. Provide a general definition of the
sludge handling program if UR
treatment is implemented on a
nationwide basis.
2. Evaluate feasibility of various UR
sludge handling options on a
technical and/or economic basis.
3. Establish the land area require-
ments anticipated for implement-
ing UR treatment and associated
sludge handling.
The overall purpose of the study is,
therefore, to roughly quantify the sec-
ondary impacts associated with UR
management options in the United
States.
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Project Approach
The study's main emphasis was to
evaluate impacts associated with hand-
ling the sludges generated from pro-
posed UR treatment. Because of the
difficulty in defining UR quality on a
national basis, a dual approach was
used: (1) National UR sludges were
characterized based on published aver-
age data. (2) These were compared with
sludges associated with a specific moni-
tored urban drainage area to illustrate
the differences in impacts and to em-
phasize the need to define each site
individually.
The various methods for handling
sludges from UR treatment were then
investigated. Since satellite treatment
of the sludges is most feasible on a
generalized basis, this alternative was
given the most emphasis. The high costs
associated with the sludge handling, as
well as the area needs for the treatment
processes, indicated, however, that use
of other control alternatives, such as
streetsweeping, might be beneficial.
Throughout the evaluation, both pri-
mary and secondary environmental
impacts were considered. Primary im-
pacts are those that can be attributed
directly to the proposed action. In this
report they are considered to be water
quality, cost, and land area require-
ments. Secondary impacts are more
difficult to quantify since they are con-
sidered indirect or direct changes. The
general approach was that the environ-
mental effects can be related to induced
changes in the pattern of land use,
population density, and related effects
on airandwaterquality or other natural
resources. Since these criteria are most
directly related to facilities construction,
the main secondary impacts for this
report are those effects on air and water
quality. Energy consumption was also
considered in this category. Costs reflect
June 1977 dollars.
Limitations of the Study
This evaluation was performed to
provide a generalized quantification of
the problems associated with handling
UR treatment residuals. Sludge quantity
and quality were not obtained from
studies but were extrapolated from
available data for combined sewer over-
flow (CSO) sludges. The project effort
was limited tothis approach since it was
believed that the extreme variabilities of
UR quality would preclude an accurate
nationwide assessment. It is anticipated
that UR sludges must be evaluated on a
site-specific basis for accurate quantifi-
cations, so a detailed national review is
not required. The data are intended to
alert the reader to the magnitude of the
potential problems associated with UR
sludge handling and should not be used
for design.
Summary of Findings
Definition of the Problem
An average volume of UR on a nation-
wide basis was calculated to be 2.9 x
109 mVyear (7.7 x 105 M gal/yr). The
associated sludge volumes were as-
sumed or calculated to range from 0.3 to
6.0 percent of the influent flow depend-
ing upon the treatment used and the
sludge handling techniques employed.
The UR quality directly impacted the
associated sludge characteristics. The
selected national average for suspended
solids concentration (415 mg/L) greatly
exceeded a previously verified STORM
model predicted value for a part of the
Milwaukee River Basin area in Wiscon-
sin (156 mg/L). As a result, sludge
quantities and qualities for the two were
extremely different.
Storage volume requirements were
evaluated for 5-yr and 1-yr design
storms at 1 -hour and 24-hour durations.
Total pumpout times of 24 and 48 hours
were considered. The type and duration
of the design storm, pumpout rates, and
rainfall significantly affected the storage
required. The nationwide evaluation
indicated that storage volumes of 81 to
224 mVha (1,160 to 3,200 ftVacre)
were needed compared with 67 to 197
mVha (954 to 2,820 ftVacre) for the
Milwaukee River Basin.
Land area needs depend on the type
of storage technique employed, the
basin volume and depth, and the pump-
out rate. Assuming a 4.8 m (15 ft) basin
depth, national storage area require-
ments ranged from 0.2 to 0.6 percent of
the area served by storm sewers and 0.3
to 0.4 percent for the Milwaukee River
Basin.
Sludge quantities and qualities were
extrapolated based on published remov-
al efficiencies and similarities to CSO
sludges. Percent solids in the UR sludges
were calculated to range from 0.5 to 12
percent depending upon the treatment
used and the sludge handling tech-
niques employed.
Since storage/sedimentation was
evaluated for total capture and 24-hour
detention, solids removal efficiencies
were high (87 percent). A flow-through
mode of operation would significantly
reduce the effectiveness of the treat-
ment methods.
The quality of sludges generated by
UR treatment varied significantly for the
national and for the Milwaukee River
Basin areas. The greatest differences
were present in the sludge solids con-
centrations—the national values were
approximately three times greater than
those calculated for Milwaukee. Con-
versely, BOD5 concentrations were
greater in the Milwaukee UR sludges.
These differences and others reflect the
variation in UR qualities used in the
calculations.
Nationwide, UR sludge volumes
ranged from 8.8 x 106 to 175 x 106 mVyr
(2.3 x 103 to 46.2 x 103 M gal/yr)
compared with 156 x 106 mVyr (41.2 x
103 M gal/yr)for CSO sludge and 60.9 x
106m3/yr(16.1 x 103 M gal/yr) for raw
primary sludge. Annual dry solids
weights for UR sludges [7.5 x 106 metric
tons (8.2 x 106 tons)] also exceeded
calculated amounts for CSO sludge [1.7
x 108 metric tons (1.8 x 106 tons)] and
raw primary sludges [2.9 x 10B metric
tons (3.2 x 106 tons)].
UR sludge nutrient concentrations
ranged from 502 to 1,270 mg/kg total
phosphorus as P and 1,140 to 3,370
mg/kg total Kjeldahl nitrogen (TKN).
These amounts were consistently lower
than nutrients found in CSO sludges
(2,800 to 7,400 mg/kg as P and 1,100 to
13,000 mg/kg TKN) and raw primary
sludges (3,500 to 12,200 mg/kg - P and
15,000 to 40,000 mg/kg TKN).
Differences in other parameters in-
cluding metals and BOD5 were incon-
clusive, given the range of removal
efficiencies and source variations.
Because of the intermittent nature of
UR sludge generation and the sources
of the runoff, grit concentrations would
be expected to be high and volatile
solids concentrations, low. These char-
acteristics would probably adversely
affect operation of many treatment
processes.
Impacts of Bleed/Pump-Back
of Urban Runoff Sludges
The problems associated with bleed/
pump-back of UR sludges are similar to
those evaluated with regard to CSO
sludges. It is anticipated that bleed/ j
pump-back of UR sludges may adversely
affect operation of a dry-weather plant
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due to sludge age, high grit, and low
volatile solids content.
Solids deposition in gravity flow
sewers is anticipated to be a severe
problem with regard to bleed/pump-
back of UR sludges. Depending on the
degree of capacity available at the dry-
weather plant, bleed/pump-back can
cause overloads with respect to solids
loadings. Specifically, the solids over-
load caused by bleed/pump-back to the
dry-weather plant detrimentally affects
the primary and final clarifiers as well as
those sludge handling facilities whose
design is based on solids loading such
as thickeners, digesters, filters, centri-
fuges, etc. The weight of solids associ-
ated with bleed/pump-back can be
shown using population equivalents to
represent service to an additional
224,000 to 316,000 people in a dry-
weather plant area serving 340,000
persons. The increased solids from
bleed/pump-back of UR sludges will
substantially overload sludge handling
processes based on solids loading and
require 1.5 to 4.5 times additional
capacity.
There does not appear to be any
toxicity impact on the dry-weather plant
due to bleed/pump-back of UR sludges
when the sludge is mixed with dry-
weather influent flow. Secondary im-
pacts from bleed/pump-back are asso-
ciated with transportation to a dry-
weather plant or to the disposal site.
Nuisance problems, air and noise
pollution, and increased energy consump-
tion are anticipated. Disposal secondary
impacts involve all those associated with
any dry-weather plant disposal tech-
nique with increases proportional to
increases in sludge volumes (18 to 25
percent). Bleed/pump-back of the de-
watering residuals generated from satel-
lite treatment plant dewatering does not
appear to cause significant overloading
to a dry-weather or associated sludge
handling facilities.
Impacts Associated with Urban
Runoff Sludge Handling at
Satellite Treatment Facilities
Review of available sludge handling
processes indicated that the most appli-
cable processes for UR sludge handling
are: gravity thickening, lime stabilization
and vacuum filter, or filter press de-
watering. Truck transport followed by
., landfill or landspreading disposal were
considered appropriate.
Because of the low nutrient content
anticipated in UR sludges, landspread-
ing is considered a disposal option,
rather than a resource recovery method.
Landspreading rates are limited by the
cadmium content in sludges. Sludge
loading rates range from 26.9 metric
ton/ha/yr(12ton/acre/yr)ona nation-
al basis to 33.6 to 62.7 metric ton/ha/yr
(15 to 28 ton/acre/yr) for the Milwaukee
River Basin sludge. Site life is 40yrs. Of
the six UR treatment sludge handling
schemes evaluated for three national
UR areas and for the Milwaukee River
Basin area, the sludge scheme involving
lime stabilization, gravity thickening,
pressure filtration dewatering, and land-
fill disposal was most cost-effective.
Capital and annual costs associated
with disposal of sludges from the Mil-
waukee area were less than those
calculated for national areas because of
the lesser weight of solids generated
per unit area in Milwaukee. Annual
costs, including operating costs and
amortized capital costs, range from
$126to$251/ha($51 to$102/acre)on
the national level and $52 to $113/ha
($21 to $46/acre) for Milwaukee. The
only UR and sludge handling alternative
found to be completely inappropriate on
a cost basis was swirl concentration
treatment without sludge thickening
followed by landspreading disposal.
Total capital costs for sludge handling
methods ranged from $365 to $1,3907
ha ($148 to $563/acre) on a national
level. Milwaukee River Basin capital
costs were again substantially lower,
ranging from $168 to $743/ha ($68 to
$301/acre).
Land area needs for sludge handling
were quite small. If storage sedimenta-
tion is involved, the processes can be
located above the covered basin, elimi-
nating the need for additional area.
Swirl concentration land area needs
involve only sludge handling and range
from 0.4 to 0.5 mVha (1.8 to 2.1
ftVacre) on a national basis; 0.2 to 0.5
mVha (0.9 to 2.0 ftVacre) for Milwau-
kee.
Secondary impacts can be associated
with the treatment system, transporta-
tion mode, and the disposal site. Evalu-
ation of these must be performed on a
site-specific basis. The potential impacts
can only be identified on a general level.
Treatment system impacts include nui-
sance associated with odor from stored
sludge, reduction in area availability,
increases in noise levels, and energy
consumption. Transportation causes
increase in noise and air pollution from
travel over dusty roads and emissions.
Energy uses are also greater. Disposal
secondary impacts are most significant.
They include those associated with
surface or groundwater contamination,
increased use of available disposal area,
higher instances of vectors, noise and
air pollution, or impact on sensitive/
unique areas. Proper operation of dis-
posal sites should minimize these prob-
lems.
Land Disposal of Storm
Generated Sludges
It is believed that wet-weather flow
sludges can be incorporated into EPA
sludge land disposal programs. The
problems associated with this incorpor-
ation are not insurmountable.
The quantity of UR and CSO sludges
requiring disposal is about the same
magnitude as that of dry-weather
sludge. Therefore, a significant amount
of additional land will be required for
land utilization of wet-weather sludges
(CSO and UR) over that needed for dry-
weather sludge (see Table on following
page).
Dry-weather and UR sludges are
distributed relatively uniformly over the
United States. In contrast, CSO sludges
are concentrated in the Northeast and
Great Lakes regions of the country.
Therefore, separate or codisposal of dry-
and wet-weather sludges will be a more
formidable problem in the Northeast
and Great Lakes region. Dry-weather
sludge is considered a low grade fertil-
izer based on nutrient content. UR and
CSO sludges, in comparison, may be
considered lower grade fertilizers. Wet-
weather sludges may be disposed of by
landfilling or may be applied on land.
Design criteria are available for each
method. Sludge application rates are
appreciably greater for landfilling dis-
posal than for land application. Disposal
of liquid wet-weather sludges on land
will see limited use because the rela-
tively low «15%) solids concentration
is not applicable to wet soils during or
immediately after heavy rainfall and is
cost-effective only for short distances [8
to 16 km (5 to 10 miles) ] from the
treatment site. Therefore, wet-weather
sludges will have to be pretreated before
being applied on land.
The most applicable pretreatment
processes for handling wet-weather
sludges for land disposal are storage,
thickening, lime stabilization, and filtra-
tion dewatering.
« U.S. GOVERNMENT PRINTING OFFICE. 1H2 -559-017/0770
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Sludge
Annual
Sludge Volume
106m3 103gal
A verage
Percentage
Solids
Dry weather
CSO
UR
125.0
157.0
8.8-175.0
33.0
41.5
2.3-45.5
2.3
0.3-6
0.5-12
Although costs for land use of wet-
weather sludges have been estimated,
these costs should be used only for
preliminary work as actual costs may
vary considerably with specific local
conditions.
Recommendations for Future
Research
• The quantity of UR sludges should
be defined through on-site testing
to determine if the actual quanti-
ties are similar to those predicted
in this report.
• Associated water quality impacts
after streetsweeping and UR treat-
ment should be evaluated in more
detail to provide needed justifica-
tion for implementing manage-
ment procedures.
• Actual removal efficiencies for
storage/sedimentation treatment
over extended treatment periods
should be verified on a large scale.
• Swirl concentration treatment re-
moval efficiencies for nitrogen and
phosphorus should be established
by on-site testing.
• Secondary impacts associated
with disposal techniques should
be evaluated. Leachate qualities
f rom U R si udge or streetsweepi ngs
should be established by lysimeter
or other appropriate testing.
• A nationwide survey should be
made of land area availability in
densely populated city areas.
• A user's manual or handbook
should be prepared, which is
similar in nature to those prepared
for land utilization of domestic
sludges, but specific to land utili-
zation of wet-weather sludges (UR
and CSO).
The full report was submitted in partial
fulfillment of Contract No. 68-03-2574
by the Environmental Research Center
of Rexnord, Inc., under the sponsorship
of the U.S. Environmental Protection
Agency.
Kathryn R. Huibregtse and Anthony Geinopolos are with Rexnord, Inc.. Environ-
mental Research Center. Milwaukee. WI53214.
Anthony N. Tafuri and Richard Field are the EPA Project Officers (see below).
The complete report, entitled "Evaluation of Secondary Environmental Impacts
of Urban Runoff Pollution Control." (Order No. PB 82-230319; Cost: $12.00.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
For information contact Richard Field at:
Storm and Combined Sewer Section
Municipal Environmental Research Laboratory-Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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