TECHNICAL SUPPORT DOCUMENT
rOk
THE SURFACE DISPOSAL OF SEWAGE SLUDGE
Prepared for
Office of Water
U.S. Environmental Protection Agency
401 M Street SW
Washington, DC 20460
Prepared by
Eastern Research Group
110 Hartwell Avenue
Lexington, MA 02173
and
Abt Associates
55 Wheeler Street
Cambridge, MA 02138
November 1992
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ACKNOWLEDGMENTS
The technical writing, editing, and production of this document was managed by Eastern
Research Group, Inc. (ERG). Abt Associates Inc. prepared the risk assessment (Section Five) and
a large portion of Section Three. This work was performed for the U.S. Environmental Protection
Agency's Health and Ecological Criteria Division of the Office of Water. The following personnel
from ERG and Abt Associates contributed to this document.
Eastern Research Group
Anne Jones Project Manager
Scott Cassel Task Manager/Writer
Linda Stein Writer
John Bergin Copyeditor/Production Coordinator
,»
Abt Associates
Kirkman O'Neal Principal Investigator
Vicki Hutson Project Manager
Daniel McMartin Environmental Scientist
Elizabeth Fechner Levy Environmental Scientist
ERG and Abt Associates staff would like to thank Dr. Alan Rubin for his guidance and support as
EPA Project Manager. We would also like to thank Robert Southworth, Mark Morris, arid Norma
Whetzel of the Office of Water for their useful comments and valuable insights on various aspects
of this study.
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PREFACE
On November 25, 1992, pursuant to Section 405(d) of the Clean Water Act, the
Administrator of the U.S Environmental Protection Agency signed a notice for publication in the
Federal Register taking final action with respect to a regulation establishing use or disposal
standards, including numerical pollutant limits, for sewage sludge. This regulation was published
in the Federal Register on February 19, 1993 (58 Fed. Reg. 9248, et seq.).
The information included in this Technical Support Document provides further
explanation of the regulation. It describes in detail the risk assessment methodology the Agency
used in evaluating pollutants to determine whether they posed a risk to public health and the
environment as well as the approach used to derive the risk-based numerical pollutant limits.
t *
+
This document is substantially similar to the Technical Support Document that is
included in the evidentiary record considered by the Administrator when promulgating the
sewage sludge use or disposal regulation. However, typographical and technical errors found in
the November 25, 1992, signature version relied on by the Administrator have been corrected in
this Technical Support Document. A copy of an errata sheet showing where changes have been .
made is enclosed with this copy. The November 25, 1992, signature version of this Technical
Support Document is available for .review and copying at EPA's Water Docket, Room L-102, 401
M Street, S.W., Washington, D.C. 20460. For access to this and other docket materials, call
(202) 260-1306.
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CONTENTS
LIST OF UNITS AND ACRONYMS
LIST OF TABLES
SECTION ONE INTRODUCTION ................................... 1-1
1.1 Background .................... « ................. ........... 1"!
1.2 Description of Part 503 .............................. "•" ........... I'3
1.2.1 General Provisions ........................... • ............ 1-3
1.2.1.1 Purpose and Applicability ............................. 1-3
1.2.1.2 Compliance Period .................................. 1-4
1.2.1.3 Permits and Direct Enforceability ....................... 1-5
1.2.1.4 Relationship to Other Regulations ...................... 1-5,
1.2.1.5 Additional or More Stringent Requirements ............... 1-6*,
1.2.1.6 Exclusions ......................................... I-6
1.2.1.7 Requirement for a Person Who Prepares Sewage Sludge ....... 1-7
1.2.1.8 Sampling and Analysis . . . : ....................... ..... 1-7
1.2.1.9 General and Special Definitions ...................... ... 1-7
1.2.2 Subpart C — 503 Standard and Other Requirements ............... 1-8
1.2.2.1 General Requirements ... ............................. 1-8
1.2.2.2 Pollutant Limits .................................... I'9
1.2.2.3 Operational Standard ........ ........ ................. 1-10
1.2.2.4 Management Practices ............. .... .............. 1-10
1.2.2.5 Other Requirements (Frequency of Monitoring, Recordkeeping,
and Reporting) ..................................... 1-H
J.3 Scope of the Sewage Sludge Surface Disposal Technical Support Document . . . 1-13
SECTION TWO SURFACE DISPOSAL OF SEWAGE SLUDGE ............. 2-1
2.1 Introduction ................................................. 2-1
2.2 Exclusions ............................. :..... .............. 2-1
2.3 Types of Surface Disposal Sites ............. . ....... . .............. 2-2
2.3.1 Monofills , ............................... ................ 2-2
2.3.2 Surface Impoundments . . .................... . .............. 2-4
• 2.3.3 Dedicated Sites .......................................... 2-4
SECTION THREE RISK ASSESSMENT METHODOLOGY 3-1
3.1 Hazard Identification 3-1
3.2 Dose-Response Evaluation 3-5
3.3 Exposure Evaluation 3-7
3.3.1 Monitoring 3-7
3.3.2 Modeling , • • 3-8
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CONTENTS (cont.)
PAGE
3.3.3 Population Analysis 3.9
3.4 Risk Characterization 3.9
SECTION FOUR POLLUTANTS AND PATHWAYS OF CONCERN FOR
PART 503 RISK ASSESSMENT FOR THE SURFACE
DISPOSAL OF SEWAGE SLUDGE 4-1
4.1 Initial List of Pollutants 4.!
4.2 Environmental Profiles and Hazard Indices 4.3
SECTION FIVE PART 503 RISK ASSESSMENT METHODOLOGY •'
FOR THE SURFACE DISPOSAL OF SEWAGE
SLUDGE 5.1
5.1 Description of Two Model Prototypes of Surface Disposal Sites—Monofill
and Surface Impoundment 5-1
5.2 General Approach Used to Derive Risk-Based Pollutant Criteria 5-3
5.2.1 Mass Balance 5.4
5.2.2 Modeling of Ground-Water Contamination 5-4
5.2.3 Modeling the Contamination of Ambient Air 5-5
5.2.4 Exposure Scenarios 5.5
5.2.5 Uncertainties and Limitations . . . 5.7
5.3 Risk Assessment Methodology for Monofill Prototype 5-7
5.3.1 Methodology for Mass Balance 5.3
5.3.1.1 Pollutant Losses through Leaching . 5-8
5.3.1.2 Pollutant Losses to Volatilization 5-9
5.3.2 Methodology for Ground Water Pathway 5-15
5.3.2.1 Simulating Flow and Pollutant Transport through Unsaturated
and Saturated Soil Zones 5-16
5.3.3 Methodology for Vapor Pathway 5-21
5.3.4 Monofill Prototype Sample. Calculations for Pollutant Criteria 5-26
5.3.4.1 Mass Balance Calculations 5-26
5.3.4.1.1 Pollutant Losses through Leaching 5-26
5.3.4.1.2 Pollutant Losses through Volatilization 5-27
5.3.4.2 Pollutant Criteria Calculations for Ground-Water Pathway 5-35
5.3.4.3 Pollutant Criteria Calculations for Vapor Pathway 5-39
5.4 Risk Assessment Methodology for.Surface Impoundment Prototype 5-42
5.4.1 Methodology for Mass Balance 5-42
5.4.1.1 Pollutant Losses from Liquid Layer 5.44
5.4.1.2 Pollutant Losses from Sediment Layer . 5-51
5.4.2 Methodology for the Ground-Water Pathway 5-54
5.4.3 Methodology for Vapor Pathway : 5-60
5.4.4 Surface Impoundment Prototype Sample Calculations for
Pollutant Criteria 5_63
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CONTENTS (cont.)
5.4.4.1 Mass Balance Calculations 5-63
5.4.4.2 Pollutant Criteria Calculations for Ground-Water Pathway 5-73
5.4.4.3 Pollutant Criteria Calculations for Vapor Pathway 5-76
5.5 Results of Part 503 Risk Assessment • 5-79
5.6 Factors Related to Risk Assessment • 5-79
5.6.1 The Highly Exposed Individual 5-88
5.6.2 Factors Related to Calculating the Human Dose 5-89
5.6.2.1 Maximum Pollutant Level 5-89
5.6.2.2 Cancer Potency • • 5-89.
5.6.2.3 Risk Level • ^-90
5.6.2.4 Relative Effectiveness of Exposure . 5-91
5.6.2.5 Duration of Exposure • 5-91
5.6.2.6 Body Weight - J-9J.-
5.6.2.7 Inhalation Rate • 5-92 -
5.7 Technical Parameters Used to Derive Risk-Based Pollutant Criteria—Tables . . 5-92
5."g Technical Parameters Used to Derive Risk^Based Pollutant Criteria-
Discussion • ' ft
5.8.1 Site Parameters -. ™
5.8.1.1 Area of the Disposal Site 5-98
5.8.1.2 Depth of Disposal Facility • 5-98
5.8.1.3 Distance to Well 5-99
5.8.1.4 Thickness of Cover • 5-99
5.8.1.5 Numbers of Days Average Cell Uncovered 5-99
5.8.1.6 Inflow Rate J-lOO
5.8.1.7 Ratio of Sludge Volume to Total Volume 5-1UU
5.8.1.8 Site Life J-lO.l-
5.8.1.9 Wind Velocity 5-101
5.8.1.10 Air Temperature 5-101
5.8.2 Sludge Parameters • 5-102
5.8.2.1 Solids Contact 5-10Z
5.8.2.2 Particle Density of Sludge • 5-103
5.8.3 Soil Parameters ™;J
5.8.3.1 Soil Type J-103
5.8.3.2 Porosity of Sludge/Soil 5-104
5.8.3.3 Bulk Density of Soil 5-105
5.8.3.4 Porosity of Cover So.l , 5-105
5.8.3.5 Saturated Hydraulic Conductivity of Soil 5-105
5.8.3.6 Unsaturated Hydraulic Conductivity of Soil • • • 5-106
5.8.3.7 Fraction of Organic Carbon in Soil or Sludge 5-106
5.8.3.8 Depth to Ground Water 5-107
5.8.4 Hydrologjc Parameters 5-107
5.8.4.1 Net Recharge or Seepage 5-108
5.8.4.2 Thickness of Aquifer 5-108
5.8.4.3 Hydraulic Gradient 5-110
' 5.8.5 Chemical-Specific Parameters 5-110
5.8.5.1 Distribution Coefficients : , • • • 5-110
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CONTENTS (cont.)
5.8.5.2 Decay Rates ;... 5.114
5.8.5.3 Molecular Weight 5-117
5.8.5.4 Henry's Law Constants 5-117
5.8.5.5 Diffusion Coefficients 5-121
5.8.5.6 Reference Water Concentration 5-121
5.8.5.7 Reference Air Concentration 5-123
SECTION SIX POLLUTANT LIMITS FOR SEWAGE SLUDGE
PLACED ON A SURFACE DISPOSAL SITE 6-1
6.1 Pollutant Selection Process 6-1
6.2 Derivation of Pollutant Concentration Limits 6-2
SECTION SEVEN MANAGEMENT PRACTICES . 7-1
7.1 Protection of Threatened or Endangered Species 7-1
7.2 Restriction of Base Flood Flow 7-1
7.3 Geological Stability , 7-1
7.3.1 Seismic Impact Zones 7-2
7.3.2 Fault Areas 7-2
7.3.3 Unstable Areas 7-2
7:4 Protection of Wetlands 7.3
7.5 Collection of Runoff 7.3
7.6 Collection of Leachate 7.3
7.7 Limitations on Methane Gas Concentrations 7.4
7.8 Prohibition on Crop Production 7.5
7.9 Prohibition on Grazing 7.5
7.10 Restriction of Public. Access 7-6
7.11 Protection of Ground Water 7-6
SECTION EIGHT PATHOGEN AND VECTOR ATTRACTION REDUCTION
REQUIREMENTS 8-1
8.1 Pathogen Requirements ; 8-1
8.2 Vector Attraction Reduction 8-2
IV
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CONTENTS (cont.)
PAGE
SECTION NINE FREQUENCY OF MONITORING, RECORDKEEPING,
AND REPORTING REQUIREMENTS 9-1.
9.1 Frequency of Monitoring • % • • • 9-1,
9.1.1 Sewage Sludge (Other Than Domestic Septage) 9-1
9.1.2 Domestic Septage • 9-3
9.1.3 Air Monitoring for Methane Gas 9-3
9.2 Recordkeeping • 9-3
9.2.1 Sewage Sludge (Other Than Domestic Septage) 9-4
9.2.2 Domestic Septage 9-4
9.3 Reporting Requirements , 9-5
SECTION TEN REFERENCES 10-1;
APPENDIX A STANDARDS FOR THE USE OR DISPOSAL OF
SEWAGE SLUDGE A-l
Subpart A—General Provisions
Subpart C—Surface Disposal
Subpart D—Pathogens and Vector Attraction Reduction
APPENDIX B PARTITIONING OF CONTAMINANT AMONG AIR, WATER,
AND SOLIDS IN SOIL B-l
APPENDIX C DERIVATION OF FIRST-ORDER COEFFICIENT FOR
LOSSES TO LEACHING C-l
APPENDIX D DERIVING A "SQUARE WAVE" FOR THE
MONOFILL PROTOTYPE D-l
APPENDIX E JUSTIFICATION FOR THE DELETION OF POLLUTANTS
FROM THE FINAL STANDARDS FOR THE USE OR
DISPOSAL OF SEWAGE SLUDGE E-l
APPENDIX F CALCULATION OF THE AMOUNT OF SEWAGE SLUDGE
USED OR DISPOSED FOR THE PART 503 FREQUENCY OF
MONITORING REQUIREMENTS F-l
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LIST OF UNITS AND ACRONYMS
a = van Genuchten water retention parameter
at; = intermediate variable used to calculate emissions from contaminated soil
<*! = longitudinal dispersivity (m)
ft = van Genuchten water retention parameter soil
9 = angle subtended by width of disposal site at distance equal to estimated
virtual distance from site (degrees)
0» = air-filled porosity (dimensionless)
0 = effective porosity (dimensionless)
V = pressure head (m)
Va = air pressure head (m)
a = first coefficient for calculating at
A = surface area of surface disposal facility (m2)
ADF . = anti-dilution factor (dimensionless)
ADLE = average daily lifetime exposure
AF = absorption factor
AL == annual loading of pollutant to monofill facility (kg/ha-yr)
b = second coefficient for calculating al
BD = bulk density of sludge/soil mix (kg/m3)
BIj = background intake of pollutant; (mg/kg/day)
BW as average body weight (kg)
C — concentration of contaminant in sludge (mg/kg)
G! = concentration of contaminant in liquid layer of surface impoundment
(kg/m3)
GZ = concentration of contaminant in sediment layer of surface impoundment
(kg/m3)
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List of Units and Acronyms (cent.)
concentration of contaminant in air-filled pore space of sludge/soil mixture
C . = average concentration of contaminant in ambient air at the receptor
location (ug/m3)
Cb = background concentration of contaminant in groundwater (mg//)
C. = concentration of contaminant in inflow to surface impoundment (kg/m3)
C = concentration of contaminant; in sludge (g/DMT)
C^ = concentration of contaminant in water leaching from site (kg/m3)
C = concentration of contaminant in outflow from surface impoundment
(kg/m3)
Cf = concentration of contaminant adsorbed to solids (kg/kg)
C^ = dry weight concentration of contaminant in eroded soil (mg/kg)
G = concentration of contaminant in seepage from surface impoundment (mg//)
C^ = the concentration of contaminant in soil eroding from the sluge
management area (mg/kg) ,.«•
Ct = total concentration of contaminant in sludge/soil mixture (kg/m3)
C = concentration of contaminant in unsaturated zone (g/m3)
cl = concentration of contaminant in water-filled pore space of sludge/soil
mixture (kg/m3)
Cwe, = concentration of contaminant in well-water (mg/L)
cF = incremental cancer risk for exposed individual (incremental risk of
developing cancer per lifetime of exposure)
CL = incremental cancer risk from contaminant; for exposed individual
(incremental risk of developing cancer per lifetime of exposure)
CWA = Clean Water Act
CR = contact rate
d, = depth of liquid layer in surface impoundment (m)
d, = depth of sediment layer in surface impoundment (m)
d[ = depth of aquifer (m)
dc = depth of soil cover (m)
d^, = depth of monofill (m)
d^, = total depth of surface impoundment (m)
D ' = lifetime dose (mg)
Dj = lifetime dose to exposure group i (mg)
D'° =• effective molecular diffusion coefficient (m2/sec)
D,, = anti-dilution factor (unitless)
D = diffusivity of contaminant in air (cm2/sec)
D = diffusivity of contaminant in water (cm2/sec)
D^ = diffusivity of diethly ether in water (cmr/sec)
D' = dispersion coefficient tor cell / from facility/? (ug/m3 per g/sec)
DF = dilution factor (dimensioniess)
DV = rate of change of volume, positive for sediment layer in surface
impoundment, negative for liquid layer (m3/sec)
ED = exposure duration
EPA = Environmental Protection Agency
f = fraction of total contaminant loading lost during active operation of
monofill facility (dimensioniess)
VII
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List of Units and Acronyms (cont)
'-- ' ' -•-->,---', ' ' " •-•.:. •;•'. . _ r_ir
f,a = fraction of contaminant lost during surface impoundment's active phase
(dimensionless)
fa, = fraction of facility's active lifetime that typical cell contains sludge and
temporaiy soil cover (dimensionless)
fdi - fraction of contaminant in the liquid layer of surface impoundment that is
dissolved (dimensionless)
f,a = fraction of contaminant in the sediment layer of surface impoundment that
is dissolved (dimensionless)
fc = organic carbon as fraction of soil mass (dimensionless)
f0u. = fraction of total contaminant loss attributable to effluent (dimensionless)
fouti = fraction of contaminant loss from a surface impoundment that is lost to
outflow (dimensionless)
fpi = fraction of contaminant in liquid layer of surface irapounmdment adhering
to solid particles (dimensionless)
fpz r fraction of contaminant in sediment layer of surface impoundment
adhering to solid particles (dimensionless)
f«p = fraction of total contaminant loss attributable to seepage (dimensionless)
f^,i = fraction of mass lost from the liquid layer of surface impoundment that is
lost to seepage (dimensionless)
f«p2 = fraction of mass entering the sediment layer of surface impoundment that
is lost to seepage (dimensionless)
f*i = fraction of monofill's total volume containing pure sludge (m3/m3 or
dimensionless)
f*>i ' = fraction of solids in sludge (kg/kg or dimensionless)
^n = fraction of monofill's active lifetime that typical cell contains uncovered
sludge (dimensionless)
Vlll
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List of Units and Acronyms (cont.)
f = fraction of contaminant loss during monofill's active lifetime that is lost to
volatilization (dimensionless)
f\ = fraction of contaminant loss from inactive monofill that is lost to
volatilization (dimensionless)
£h = fraction of total contaminant loading to monofill that is lost to
volatilization during a time interval equivalent to the life expectancy of
the highly exposed individual (dimensionless)
f^ = fraction of total, contaminant loss caused by volatilization (dimensionless)
£oll = fraction of contaminant leaving the liquid layer that leaves through
volatilization (dimensionless)
f^e, = ratio of contaminant concentration in well-water to concentration in
seepage beneath the surface disposal facility (dimensionless)
F = volume of fluid passing through a vertical cross section of the aquifer
oriented perpendicular to the direction of flow, and having a width equal
to the source width and a depth equal to the saturated thickness of the
aquifer (m3/sec) „
FA, = annual flux of contaminant leaching from monofill (kg/ha-yr) ''
FD = ratio of effective diameter to depth of surface impoundment
(dimensionless)
H = Henry's Law constant (m3-atm/mol)
H * Henry's Law constant (dimensionless at specified temperature)
i » index for crops
I.. = inhalation volume (m^/day)
I,, = rate of water ingestion (//day)
IRIS = Integrated Risk Information System
j = index for contaminants
k,, = . effective permeability (dimensionless)
K = saturated hydraulic conductivity (m/sec)
= degradation rate coefficient for monofill (yr~l)
= degradation rate coefficient for liquid layer of surface impoundment
(m3/sec)
= degradation rate coefficient for sediment layer of surface impoundment
(m3/sec)
= degradation rate coefficient for unsaturated soil zone (s"1)
= rate coefficient for loss of contaminant from liquid layer as result of
decreasing volume (m3/sec)
— rate coefficient for dissolved contaminant gained in sediment layer as
result of increasing volume (m3/sec)
= mass transfer coefficient for liquid layer (m/sec)
'= mass transfer coefficient for liquid layer (m/sec)
= rate coefficient for loss of contaminant to leaching from monofill (yr"1)
= rate coefficient for loss of contaminant from liquid layer through outflow
(m3/sec)
=* rate coefficient for loss of contaminant through seepage from the liquid
layer (m3/sec)
= rate coefficient for loss of contaminant through seepage from the
sediment layer (m3/sec)
ix
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List of Units and Acronyms (conk)
KD
KOC
KOW
LF
LOAEL
LOEL
LS
M,
MOD
MO-
MS
MTD
MW
n
NAS
NOAEL
NR
rate coefficient for total loss of contaminant during monofill's active lifetime
(yO
rate coefficient for total loss of contaminant from inactive monofill (yr"1)
lumped rate coefficient for contaminant loss from treated land (yr"1)
lumped rate coefficient for contaminant loss from the liquid layer of
surface impoundment (m3/sec)
lumped rate coefficient for contaminant loss from the sediment layer of
surface impoundment (m3/sec)
rate coefficient for loss of contaminant to volatilization from active
monofill (yr"1)
rate coefficient for loss of contaminant to volatilization from inactive
monofill (yr"1)
rate coefficient for loss of contaminant to volatilization from treated land
(y^1)
rate coefficient for loss of contaminant to volatilization from the liquid
layer of surface impoundment (m/sec) , *
equilibrium partition coefficient for contaminant (m3/kg)
organic carbon partition coefficient (m3/kg)
octanol-water partition coefficient for contaminant
lethal dose, the average inhalation dose at which 50 percent of the
animals exposed died; also used for aquatic toxicity tests, refers to the
concentration of the test substance in the water that results in 50 percent
mortality in the test species
lethal dose, the average dose level that is lethal to 50 percent of the test
animals, refers to oral doses
active lifetime of monofili facility: the period in which the facility accepts
sludge (yr)
Lowest Observed Adverse Effect Level
Lowest Observed Effect Level .
lifespan of average individual (yr)
mass of air per volume of soil
,mass of gaseous contaminant per volume of soil
mass of adsorbed contaminant per volume of soil
total mass of contaminant per volume of soil
mass of dissolved contaminant per volume of soil
mass of solids per volume of soil
mass of liquid per volume of soil
million gallons per day
Maximum Contaminant Level for drinking water (rhg/7)
mass of solids in one m3 of pure sludge (kg/m3)
Maximum Tolerated Doxe, largest dose a test animal can receive for most
of its lifetime without demonstrating adverse effects other than cancer
molecular weight of contaminant
empirically derived exponent (dimensionless)
National Academy of Sciences
No Observed Adverse Effect Level
net recharge (m/yr)
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List of Units and Acronyms (cent)
NSSS
OST
OWRS
PI
PI
P.
PCB
PFRP
POTW
PSRP
r'
R
fiep
RC..C
RC,
**!>
RCRA
RCS
RE .
RfC
R£D
RF
National Sewage Sludge Survey
Office of Science and Technology (EPA)
Office of Water Regulations and Standards (EPA)
percent solids in liquid layer of surface impoundment (kg/kg)
percent solids in sediment layer of surface impoundment (kg/kg)
ratio of contaminant concentration in fillet to whole fish (unitless)
number of persons in cell i exceeding RfD for pollutant/ (persons)
percent liquid in the water column of surface water body (kg/kg, or
dimensionless) -
percent solids in the water "column (kg/kg or dimensionless)
polychlorinated biphenyl
Process to Further Reduce Pathogens
publicly owned treatment works
Process to Significantly Reduce Pathogens
human cancer potency for pollutant j (rag/kg/day)"1
human cancer potency (mg/kg-day)'1 ,:
time-weighted average rate of contaminant volatilization from a monofill
(g/m2-sec)
rate of contaminant volatilization from a covered monofill cell (g/m-sec)
rate of contaminant volatilization from an uncovered monofill cell
(g/m2/sec)
rate of inflow for sludge into a surface impoundment (m3/sec)
rate of outflow from a surface impoundment (mVsec)
seepage rate for both liquid and sediment layers (m/sec)
distance from center of sludge disposal facility to HEI's location (m)
universal gas constant (m3-atm/mol-K)
combined removal efficiency for pollutant/ for furnace and controlp
expressed as fraction of original contaminant remaining in emissions
(dimensionless)
reference concentration for pollutant in air (ug/m3)
reference concentration for pollutant in groundwater (kg/m3)
reference concentration for pollutant in leachate from sludge monofill
(kg/m3)
reference concentration for pollutant in seepage from surface
impoundment (kg/ra3)
Resource Conservation and Recovery Act
reference concentration of pollutant in sewage sludge (mg/kg dry weight)
relative effectiveness of exposure (dimensionless)
Reference Concentration (inhalation exposure), threshold level for critical
noncancer effects below which a significant risk of adverse effects is not
expected
Reference Dose (oral Exposure), threshold level for critical noncancer
effects below which a significant risk of adverse effects is not expected
retardation factor (dimensionless)
reference annual flux of contamiant to air above the site (kg/ha-yr)
reference annual flux of pollutant to the unsaturated soil zone beneath
the surface disposal facility (kg/ha-yr) '•
XI
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List of Units and Acronyms (cont.)
RfDj
RL
RWC
S
s,
S2
s,
s,
sc
SOUR
SRAB
SRR
t
tu.
T
TF
TP
TSCA
TSS
TWTDS
v
v,
vv
x
z
Risk Reference Dose for pollutant/ (mg/kg/day)
risk level (incremental risk of cancer per lifetime)
reference water concentration (mg/L)
intermediate variable used to calculate volatile emissions from soil
solids concentration in the liquid layer of a surface impoundment (kg/m3)
solids concentration in the sediment layer of a surface impoundment
(kg/m3)
effective water saturation (dimensionless)
specific storage (mf1)
water saturation (dimensionless)
residual water saturation (dimensionless)
Schmidt number on gas side (dimensionless)
Schmidt number on liquid side (dimensionless)
mass of sludge contained in one hectare of surface disposal facility (kg/ha)
specific oxygen uptake rate
Sludge Risk Assessment Branch (EPA)
source-receptor ratio (s/m) , •
time (sec)
time that typical monofill cell contains sludge without soil cover (yr)
temperature (K)
active lifetime of surface disposal facility (sec)
length of "square wave" in which maximum total loss rate of contaminant
depletes total mass of contaminant at site (sec or yr)
Toxic Substances Control Act
total suspended solids content of the stream (mg/L)
treatment works treating domestic sewage
vertical term for dispersion of contaminant in air (dimensionless)
darcy velocity (m/s)
regional velocity of horizontal groundwater flow (m/sec)
superimposed radial velocity from water seeping from the impoundment
(m/sec)
vertical velocity due to the source (m/sec)
volume of air in soil (rn3)
total volume of soil (m3)
volume of void space in soil (m3)
volume of water in soil (m3)
distance from surface disposal facility to receptor (km)
lateral virtual distance to receptor location (m)
vertical coordinate in unsaturated zone (m)
XII
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LIST OF TABLES
Page
4-1 Pollutants Selected for Environmental Profiles/
Hazard Indices 4-4
4-2 Pollutants Excluded or Deferred from Regulatory
Consideration for the Surface Disposal of Sewage Sludge 4-8
4-3 Pollutants Evaluated for Surface Disposal of Sewage
Sludge for the Proposed Part 503 Risk Assessment 4-9
5-1 Parameters Used to Calculate 5-24
5-2 Pollutant Loading Criteria for Sewage Sludge Disposal
in Unlined Monofill Over Class I Ground Water 5-80^
< *
5-3 Pollutant Loading Criteria for Sewage Sludge Disposal
in Unlined Surface Impoundment Over Class I Ground Water 5-81
5-4 Pollutant Loading Criteria for Sewage Sludge Disposal
in Lined Monofill Over Class 1 Ground Water 5-82
5-5 Pollutant Loading Criteria for Sewage Sludge Disposal
in Lined Surface Impoundment Over Class 1 Ground Water 5-83
5-6 Pollutant Loading Criteria for Sewage Sludge Disposal
in Unlined Monofill Over Class II/ni Ground Water 5-84
5-7 Pollutant Loading Criteria for Sewage Sludge Disposal
in Unlined Surface Impoundment Over Class ll/QI
Ground Water 5-85
5-8 Pollutant Loading Criteria for Sewage Sludge Disposal
in Lined Monofill Over Class II/III Ground Water 5-86
5-9 Pollutant Loading Criteria for Sewage Sludge Disposal
in Lined Surface Impoundment Over Class II/ni
Ground Water 5-87
5-10 Site and Sewage Sludge Parameters for Monofill and Surface
Impoundment Prototypes 5-93
5-11 Soil and Hydrologic Parameters for Monofill and Surface
Impoundment Prototypes 5-94
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LIST OF TABLES (cont)
5-12 Input Parameters for Vadoft Simulation of Flow and
Pollutant Transport Through the Unsaturated Zone for
Monofill and Surface Impoundment Prototypes 5-95
5-13 Input Parameters for AT123D Simulation of Flow and
Pollutant Transport Through the Saturated Zone for
Monofill Prototype 5-96
5-14 Input Parameters for AT123D Simulation of Flow and
Pollutant Transport Through the Saturated Zone for
the Surface Impoundment Prototype 5-97
»*
5-15 Summary of Measured Seepage Rate from Municipal
Lagoon Systems 5-109
5-16 Distribution Coefficients for Organic and
Inorganic Contaminants 5-111
5-17 Octanol-Water and Organic Carbon Partition
Coefficients for Organic Contaminants 5-113
5-18 Octanol-Water Partition Coefficients for PCBS 5-114
5-19 Degradation Rates 5-116
5-20 Molecular Weights for Organic Contaminants 5-118
5-21 Henry's Law Constants 5-120
5-22 Diffusion Coefficients for Organic Contaminants 5-122
5-23 Adjusted Reference Water Concentration 5-124
5-24 Human Cancer Potencies and Reference Air Concentrations 5-125
6-1 Pollutants Deleted from Regulatory Consideration-for
the Surface Disposal of Sewage Sludge (Meet Two of
Three Deletion Criteria) 6-3
6-2 Pollutants Deleted from Regulatory Consideration for
the Surface Disposal of Sewage Sludge (Meet Two of
Three Deletion Criteria) 6-4
xiv
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LIST OF TABLES (cont.)
6-3 Pollutants Regulated by the Part 503 Regulation for the
Surface Disposal of Sewage Sludge 6-5
6-4 Summary of Risk Assessment Results for Arsenic, Chromium
and Nickel for Sewage Sludge Disposal in a Lined and
Unlined Monofill and Surface Impoundment Over Class Il/ni
Ground Water • 6-7
6-5 Pollutant Concentrations - Active Sewage Sludge Unit
Without a Liner and Leachate Collection System that
Has a Unit Boundary to Property Line Distance Less
. Than 150 Meters 6-8
9-1 Minimum Frequency of Monitoring for Surface Disposal of
Sewage Sludge 9'2
XV
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SECTION ONE
INTRODUCTION
1.1 BACKGROUND
I
Sewage treatment works generate sewage sludge from raw sewage in the process of
maintaining the quality of our water resources. The sewage sludge must then be disposed or
used in a manner that does not adversely affect public health or the environment. Sewage sludge
is used or disposed in a number of ways, including land application, surface disposal,
incineration, and codisposal with municipal solid waste. This document discusses the surface
disposal of sewage sludge.
EPA's role is to control the potential adverse effects to public health and the
environment that any use or disposal of sewage sludge may cause. Existing federal regulations
are authorized under several legislative mandates and have been developed independently along
media-specific concerns to regulate sewage sludge use and disposal. Section 405(d) of the Clean
Water Act (CWA), as amended (33 U.S.C. 1345), directed the Agency to develop, propose, and
promulgate regulations establishing standards for the use and disposal of sewage sludge.
Additional authorizing legislation includes sections of the Clean Air Act, the Resource
Conservation and Recovery Act (RCRA), and the Toxic Substances Control Act (TSCA).
In 1979, EPA responded to these mandates and promulgated criteria for using
nonhazardous solid waste including sewage sludge when it is applied to land or disposed in
landfills. These criteria were incorporated into 40 CFR Part 257, Criteria for Classification of
Solid Waste Disposal Facilities and Practices, which contained specific requirements for
managing sewage sludge. Any use or disposal of sewage sludge that caused the concentration of
10 heavy metals and 6 organic chemicals in an underground drinking water source to exceed
specified maximum contaminant levels (MCLs) was prohibited. Management standards for using
or disposing sewage sludge were set so that surface waters, flood plains, and endangered species
were protected. Part 257 also established annual and cumulative application rates for cadmium,
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a numerical concentration of polychlorinated biphenyls (PCBs) in sewage sludge, and pathogen
requirements for sewage sludge applied to land used for the production of animal feed or food-
chain crops. (Part 257 has been modified and now excludes from coverage sewage sludge applied
to land.)
In 1982, the EPA established an Intra-Agency Sludge Task Force to recommend
procedures for putting into effect a comprehensive regulatory program for sewage sludge
management. The task force recommended that such a regulatory program be developed using
the combined authorities of Section 405 of the CWA and other existing regulations so that
comprehensive coverage could be provided. Accordingly, a regulation was recommended that
would provide technical criteria for the use or disposal of sewage sludge.
*
The Office of Water Enforcement and Compliance proposed State Sludge Management
Program Regulations (U.S. EPA, 1986a). These regulations proposed that states develop
management programs that comply with existing federal criteria for the use or disposal of sewage
sludge. The proposed State Sludge Management Program Regulations focused on the
procedural requirements for submittal, review, and approval of state sewage sludge management
programs. On March 9,1988, these regulations were proposed again to reflect changes in
requirements for sewage sludge management programs imposed by the 1987 Water Quality Act.
After public comment, these regulations were promulgated under 40 CFR Part 501 on May 2,
1989.
Although EPA's Office of Solid Waste began the task of preparing a comprehensive
sewage sludge regulation in 1979 with the promulgation of 40 CFR Part 257, the overall task of
completing the comprehensive sewage sludge regulation was transferred to the Office of Water in
1984. A Wastewater Solids Criteria Branch was established under the Office of Water
Regulations and Standards (OWRS) within the Office of Water to develop the risk assessment to
support the rule. After the Office of Water was reorganized, the OWRS was renamed the Office
of Science and Technology (OST), and the Wastewater Solids Criteria Branch was renamed the
Sludge Risk Assessment Branch (SRAB). The SRAB developed the final Part 503 regulation.
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1.2 DESCRIPTION OF PART 503
The Part 503 standard consists of five subparts. Subpart A contains general provisions
that apply to each of the three sewage sludge use or disposal practices. Subparts B and C
pertain to specific requirements for land application and surface disposal of sewage sludge,
respectively, while Subpart D, Pathogens and Vector Attraction, specifies requirements to control
pathogens and other organisms, such as rodents, flies, and mosquitoes, that are capable of [
transporting infectious agents. Subpart E contains the provisions for sewage sludge incineration.
This section (Section One) provides an overview, of Subpart A, General Provisions, and
Subpart C, Surface Disposal, as well as a brief introduction to the applicable requirements in
Subpart D. The text of all three subparts appears in full as Appendix A. Although much ofahe
General Provisions section is relevant to all the regulated use or disposal practices, it also
contains references that are specific to each practice. This discussion will focus on the general
and specific requirements affecting the surface disposal of sewage sludge. Where there is overlap
between the requirements of Subparts A and C, the information will be presented in the General
Provisions section.
1.2.1 General Provisions
Subpart A of Part 503, General Provisions, consists of nine parts: the purpose and
applicability of the regulation; the compliance period; permits and direct enforceability; the
relationship to other regulations; additional or more stringent requirements; exclusions; the
requirement for-a person who prepares sewage sludge; sampling and analysis; and general
definitions.
12.1.1 Purpose and Applicability \
Part 503 establishes standards for the final use or disposal of sewage sludge generated
during the treatment of domestic sewage in a treatment works. For sewage sludge placed on a
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sewage sludge unit, the standard contains general requirements, pollutant limits, and
management practices that protect public health from the reasonably anticipated adverse effects
of pollutants in sewage sludge.1 These elements of the standard are discussed in Subpart C,
which includes pollutant limits for arsenic, chromium, and nickel. Subpart C also includes
operational standards for pathogens and vector attraction reduction, and requirements for
frequency of monitoring and recordkeeping. In addition, Subpart C includes reporting
requirements for Class I sludge management facilities, treatment works with flow rates equal to
or greater than 1 million gallons per day, and treatment works that serve a population of 10,000
people or greater that practice surface disposal of sewage sludge.
Subpart C applies to a person who prepares sewage sludge for placement on a surface
disposal site; to owners/operators of a surface disposal site; to the surface disposal site; and to
sewage sludge placed on a surface disposal site.
Subpart C does not apply to either sewage sludge being stored or treated or to land on
which sewage sludge is placed for storage or treatment It also does not apply to sewage sludge
that remains on the land for longer than two years when the person who prepares the sewage
sludge demonstrates that the land on which the sewage sludge remains is not an active sewage
sludge unit. (See the rule in Appendix A (Part 503.20) for information needed for the
demonstration.)
1.2.12 Compliance Period
Compliance with the Part 503 standard for the surface disposal of sewage sludge is to be
achieved as expeditiously as practicable, but in no case later than one year from the date of
publication in the Federal Register. If compliance with the standards requires construction of new
pollution control facilities, compliance is to be achieved by two years from the date of
publication in the Federal Register, or sooner if practicable.
'One or more sewage sludge units constitute a surface disposal site.
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Compliance with the frequency of monitoring, recordkeeping, and reporting requirements
for all pollutants regulated under Subpart C is to begin. 120 days after the effective date of tiie
regulation.
Permits and Direct EnforccabiUty
A permit is not a prerequisite for enforcement actions to be taken against any person
i
who violates applicable Part 503 standards. However, the Part 503 standards for the surface
disposal of sewage sludge and the requirements pertaining to frequency of monitoring,
recordkeeping, and reporting may be put into effect through a permit under the following two
conditions: , ;
I *
• A permit issued to a "treatment works treating domestic sewage" (TWTDS), as
defined in 40 CFR Section 122.2 and in accordance with 40 CFR Parts 122 and
124, either by EPA or by a state that has a state sludge management program
approved by EPA in accordance with 40 CFR Part 123 or 40 CFR Part 501.
• A permit issued under Subtitle C of the Solid Waste Disposal Act; Part C of the
Safe Drinking Water Act; the Marine Protection, Research, and Sanctuaries Act
of 1972; or the Clean Air Act.
A TWTDS is required to submit a permit application in accordance with either 40 CFR Section
122.21 or an approved state program. The standards and requirements in Subpart C are
enforceable directly against any person who places sewage sludge on a surface disposal site, i
1.2.1.4 Relationship to Other Regulations
Disposal of sewage sludge in a municipal solid waste landfill unit (as defined in
40 CFR 258.2) that complies with the requirements in 40 CFR Part 258 constitutes compliance
with Section 405(d) of the CWA. Any person who prepares sewage s'.udge that is disposed in a
municipal solid waste landfill unit must ensure that the sewage sludge meets the requirements in
40 CFR Part 258 concerning the quality of materials disposed.
1-5.
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/J JJ Additional or More Stringent Requirements
On a case-by-case basis, the permitting authority (either EPA or a state with an EPA-
approved sludge management program) may impose more stringent or additional requirements
for the use or disposal of sewage sludge if necessary to protect public health and the
environment from adverse effects of pollutants in sewage sludge. A state, a political subdivision,
or an interstate agency also can impose requirements for the use or disposal of sewage sludge
that either are more stringent than, or are in addition to, the requirements of Part 503.
1.2.1.6 Exclusions
Eight exclusions to the Part 503 rule apply to all three use or disposal practices:
• Treatment processes—processes used to treat domestic sewage or processes used
to treat sewage sludge prior to final use or disposal, except as provided in 503.32
and. 503.33, are not covered by Part 503.
• Selection of a use or disposal practice—The manner in which sewage sludge is
used or disposed is a local determination and is not specified by Part 503.
• Sludge generated at an industrial facility—sludge generated in industrial
wastewater treatment works that treat either industrial wastewater or industrial
wastewater combined with domestic sewage generated at the industrial facility is
not covered by Part 503. This exemption does not apply to sewage sludge treated
separately from industrial waste at an industrial facility.
• Hazardous sewage sludge—sewage sludge determined to be hazardous in
accordance with 40 CFR Part 261 is not covered by Part 503.
• Sewage sludge with high PCB concentration—sewage sludge that has a
concentration of polychlorinated biphenyls (PCBs) equal to or greater than 50
milligrams per kilogram of total solids (dry weight basis) is not covered by Part
. 503.
• Grit and screenings—grit (e.g., sand, gravel, cinders, or other materials with a
high specific gravity) or screenings (e.g., relatively large materials such as rags)
generated during preliminary treatment of domestic sewage in a treatment works
are not covered by Part 503.
• Drinking water treatment sludge—sludge generated during the treatment of either
surface water or ground water used for drinking water is not covered by Part 503.
.1-6 •
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Commercial and industrial septage—commercial septage or industrial septage^
even if mixed with domestic septage, is not covered by Part 503.
13.1.7 Requirement for a Person Who Prepares Sewage Sludge
A person who prepares sewage sludge that is either fired in a sewage sludge incinerator,
applied to the land, or placed on a surface disposal site must meet the applicable requirements
of the Part 503 rule.
.1.2.1.8 Sampling and Analysis
, »
1^
Representative samples of sewage sludge placed on an active sewage sludge unit must be
collected and analyzed. Samples of sewage sludge (other than domestic septage) are to be ,
analyzed for the regulated inorganic pollutants and pathogens according to methods specified in
the Part 503 rule (see Appendix A, Part 503.8).
1.2.1.9 General and Special Definitions
The following words, phrases, acronyms, and concepts apply to information provided in
this technical support document for the surface disposal of sewage sludge and are defined in
Appendix A. These terms can be found either under the General Provisions subpart (Subpart A,
503.9) or the Surface Disposal subpart (Subpart C, 503.20). ;
General Definitions f503.9^
Base flood
Class I sludge management facility
CWA
Domestic septage
Domestic sewage
Dry weight basis
EPA
Feed crops
Fiber crops
Food crops
Special Definitions (503.20^
Active sewage sludge unit
Aquifer
Contaminate an aquifer
Cover
Displacement
Fault
Final cover
Holocene time
Leachate collection system
Liner
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General Definitions (503.9) fcont.) Special Definitions (503.20') (cont.^
Ground water Lower explosive limit for methane gas
Industrial wastewater Qualified ground water scientist
Municipality Seismic impact zone
Permitting authority Sewage sludge unit
Person who prepares sewage sludge Sewage sludge unit boundary
Place sewage sludge Surface disposal site
Pollutant Unstable area
Pollutant limit
Runoff
Sewage sludge
State
Storage of sewage sludge
Treatment of sewage sludge
Treatment works
Wetland
1.2.2 Subpart C—Part 503 Standard and Other Requirements
For each sewage sludge use or disposal practice, a person to whom the rule applies must
comply with general requirements, pollutant limits, management practices, and operational
standard(s), as well as other requirements related to frequency of monitoring, recordkeeping, and
reporting. The overview presented below discusses Subpart C which, in addition to Subpart A,
regulates the surface disposal of sewage sludge. Section 1.3 below outlines the sections of this
Technical Support Document where more detailed discussion of the Subpart C standard takes
place.
1.2.2.1 General Requirements
The general requirements of the Part 503 regulation state that no person is permitted to
place sewage sludge on an active sewage sludge unit unless the-requirements of Subpart C are
met. In addition, the general requirements include notification and closure requirements', as
follows:
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Notification to the subsequent owner—The owner of a surface disposal site must
provide the subsequent owner with written notification that sewage sludge was
placed on the land.. _
Closure—If an active sewage sludge unit is located within 60 meters of a fault, in
an unstable area, or in a wetland, the unit must close by one year after the
effective date of the regulation unless, in the case of a unit near a fault, the
permitting authority specifies otherwise, or if the unit is in a wetland and the
permit was issued under the Clean Water Act.
In addition, the owner/operator of an active sewage sludge unit must submit a
written closure and post-closure plan to the permitting authority 180 days prior to
closure explaining how the unit will be closed (e.g., how the leachate collection
system will be operated and maintained for three years; a description of the
system used to monitor methane gas; how public access will be restricted for three
years). ;
Pollutant Limits
Subpart C of Part 503 establishes limits for three inorganic pollutants — arsenic, !
chromium, and nickel — for active sewage sludge units that do not contain a liner and leachate
collection system. The pollutant limits do not apply to sewage sludge units with a liner and
leachate collection system. In addition, these limits do not apply to domestic septage.
Stricter pollutant limits are set for active sewage sludge units whose boundaries are less
than 150 meters from the property line. Alternatively, site-specific pollutant limits may be
developed if requested by the owner/operator of a surface disposal site at the time of permit
application. Site-specific pollutant limits can be used if the existing values for site parameters
specified by the permitting authority are different from the values for those parameters used to
develop the pollutant limits in Table 1 of Part 503.23 (see Appendix A) and if the permitting
authority determines that site-specific pollutant limits are appropriate for the unit.
If site-specific pollutant limits are used, the concentration of each of the three inorganic
pollutants covered in Subpart C may not exceed either: (a) the concentration of the pollutant
determined during a site-specific assessment, or (b) the existing concentration of the pollutant in
the sewage sludge, whichever is lower.
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Operational Standard
Subpart C also includes operational standards to control pathogens and vectors (e.g.,
insects, rodents, birds) that are capable of transporting infectious agents. These requirements for
pathogens and vector attraction reduction are detailed in Subpart D of the Part 503 rule. The
pathogen requirements in Subpart D apply to sewage sludge (excluding domestic septage) placed
on an active sewage sludge unit unless a specific soil cover requirement is met
(50333[b][llJ). For domestic septage, pathogens are controlled through management practices
as specified in Subpart C of Part 503 and 40 CFR Part 257 (see Section 8.1). The vector
attraction reduction requirements apply to sewage sludge (including domestic septage) that is
placed on an active sewage sludge unit.
122.4 Management Practices
Subpart C includes several management practices that are required for the surface
disposal of sewage sludge, including:
• Threatened or endangered species—Sewage sludge cannot be placed on an active
sewage sludge unit if it is likely to adversely affect a threatened or endangered
species listed under Section 4 of the Endangered Species Act or its designated
critical habitat. EPA will develop guidance to carry out this provision, consistent
with the Endangered Species Act.
• Base flood—An active sewage sludge unit may not restrict the flow of a base
flood.
• Geological stability—Three management practices state that an active sewage
sludge unit must: (a) be located at least 60 meters from a fault (unless otherwise
specified by the permitting authority); (b) not be located in an unstable area; and
(c) if located in a seismic impact zone, withstand certain ground movements.
• Wetlands—An active sewage sludge unit may not be located in a wetland (unless
a permit was issued under Section 402 or 404 of the Clean Water Act).
• Runoff—Two management practices specify that: (a) runoff from an active sewage
sludge unit must be collected and disposed according to requirements of the
National Pollutant Discharge Elimination System and any other applicable
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requirements; and (b) the runoff collection system must have the capacity to
handle runoff from a 24-hour, 25-year storm event.
Leachate—Two management practices require that for active sewage sludge units
with a liner and leachate collection system: (a) the leachate collection system must
be operated and maintained; and (b) leachate must be collected and disposed
according to applicable requirements. Both of these management practices must
be conducted while the unit is active and for three years after the unit closes.
Methane gas concentrations—For an active sewage sludge unit that receives a
cover material, limits are established on the concentration of methane gas (based
on its lower explosive limit) both within structures (i.e., buildings) on the surface
disposal site and in air at the property line of the site. For a unit that receives a
final cover at closure, the same concentration limits apply for three years after the
unit closes, unless the permitting authority specifies otherwise.
Crops—Food, feed, or fiber crops may not be grown on an active sewage sludge
unit unless the owner/operator of the site demonstrates to the permitting authority
that, through management practices, public health and the environment can be
protected from reasonably anticipated adverse effects of pollutants in sewage
sludge when the crops are grown.
Grazing—Animals may not graze on an active sewage sludge unit unless the
owner/operator of the site demonstrates to the permitting authority that public
health and the environment can be protected from reasonably anticipated adverse
effects of pollutants in sewage sludge when the animals are grazed.
Public access—Public access to a surface disposal site must be restricted while the
site contains an active sewage sludge unit and for three years after the last active
sewage sludge unit closes. ;
Ground water—Sewage sludge placed on an active sewage sludge unit may not
contaminate an aquifer. This demonstration must be confirmed by the results of a
ground water monitoring program developed by a qualified ground water scientist
or a certification by a qualified ground water scientist.
1.233 Other Requirements (Frequency of Monitoring, Recordkeeping, and Reporting) '
For sewage sludge placed on an active sewage sludge unit, there are additional
requirements related to the Part 503 standard, including frequency of monitoring, recordkeeping,
and reporting. The frequency of monitoring for arsenic, chromium, nickel, pathogens, and
selected vector attraction reduction requirements ranges from once per year to once per month,
depending on the amount of sewage sludge placed on an active sewage sludge unit. The
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regulation allows the permitting authority to modify the frequency of monitoring for the three
pollutants and for pathogens after the sewage sludge has been monitored for a period of two
years in accordance with Subpart C, as long as the frequency of monitoring is at least once per
year. In addition, continuous monitoring for methane gas is required within structures on the
surface disposal site and in air at the property line while the site contains an active sewage sludge
unit that is covered, and for three years after the unit closes if a Gnal cover is placed on the
sewage sludge. If the vector attraction reduction requirements are met for domestic septage
placed on an active sewage sludge unit, each container of domestic septage must be monitored
for compliance with those requirements.
Any person who prepares sewage sludge for placement on an active sewage sludge unit
must retain certain data for a period of five years. These data include the concentrations of
arsenic, chromium, and nickel in the sewage sludge,-as well as certification that the requirements
for pathogens and vector attraction reduction (if achieved through a preparation process) have
been met, along with a description of how these requirements have been met. In addition, the
owner/operator of a surface disposal site must retain pollutant concentration data and must
identify and describe how required management practices have been met. Additionally, the
owner/operator must certify and describe vector attraction reduction requirements achieved
through a management-type practice (e.g., daily cover). Persons placing domestic septage on a
surface disposal site must retain information certifying that vector attraction reduction
requirements have been met, along with a description of how these requirements have been met.
The reporting requirements under Subpart C pertain to Class I sludge management
facilities and treatment works with a flow rate equal to or greater than one million gallons per
day (MOD) or that serve a population of 10,000 people or greater. These specified facilities
where sewage sludge is placed on a surface disposal site are required to report yearly to the
permitting authority.
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1.3 SCOPE OF THE TECHNICAL SUPPORT DOCUMENT FOR THE SURFACE
DISPOSAL OF SEWAGE SLUDGE
This document consists of 10 sections, including this introduction. The next section,
Section Two, provides an overview of the different types of surface disposal sites, such as
monofills and surface impoundments. Section Three is a general discussion of EPA risk
assessment methodology, while Section Four discusses, the process by which EPA selected the
pollutants for which the risk assessment was conducted.
Section Five provides a detailed discussion of the risk assessment methodology
established for the surface disposal of sewage sludge, which is the basis for developing pollutant
limits on the concentration of the three inorganic pollutants in sewage sludge. This section also
. tf
contains sample calculations deriving the pollutant criteria used to develop the pollutant limifc.
In addition, it explains the rationale for using the numerous technical and risk-based factors in
the risk assessment equations. Section Six presents the pollutant limits for the surface disposal
of sewage sludge and explains their derivation from the risk assessment results. Section Seven
provides more detail on the management practices required under Subpart C, while Section
Eight presents the operational standards for pathogens and vector attraction reduction. Section
Nine describes the frequency of monitoring, recordkeeping, and reporting requirements.
References appear in Section Ten, and six appendices are provided as supporting material.
Appendix A consists of the text of Part 503, Subpart A, Subpart C, and Subpart D.
Appendix B, Appendix C, and Appendix D all pertain to aspects of the detailed risk assessment
presented in Section Five. Appendix B relates to the partitioning of the evaluated contaminants
among air, water, and solids in the soil. Appendix C presents the derivation of the first-order
coefficient for losses from leaching. Appendix D derives a "square wave" function for the
monofill prototype. In Appendix E, a detailed explanation is given for the deletion of pollutants
from the Part 503 regulation based on the results of the risk assessment. Appendix F provides
the calculation of the amount of sewage sludge used or disposed, which is used to determine the
Part 503 frequency of monitoring requirements.
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SECTION TWO
SURFACE DISPOSAL OF SEWAGE SLUDGE
2.1 INTRODUCTION
Surface disposal is defined in the Part 503 regulation as an area of land that contains one
or more active sewage sludge units. A sewage sludge unit is an area of land on which only
sewage sludge is placed for final disposal. Various types of surface disposal sites exist, including
monofills (landfills containing only sewage sludge), surface impoundments, lagoons, waste jJiles,
and dedicated sites. The Part 503 regulation does not require sewage sludge units to have a^daily
t *
or final cover, as is required of some other types of solid waste disposal practices (e.g., municipal
landfills). However, cover material, usually soil, is sometimes used at surface disposal sites to
minimize odors and help prevent vectors (e.g., insects, rodents, birds) from contacting the sewage
sludge and spreading contaminants. Some of the different types of surface disposal sites !
regulated by the Part 503 rule are discussed in more detail later in this section.
2.2 EXCLUSIONS
The Part 503 regulation applies only to surface disposal sites used for final disposal of
sewage sludge and not to sites on which sewage sludge is treated or on which sewage sludge is
stored for less than 2 years. Treatment is the preparation of sewage sludge for final use or
disposal. Examples of treatment processes include thickening, stabilizing, and dewatering.
Storage is the placement,of sewage sludge on an area of land (except for treatment) on which
the sewage sludge remains for 2 years or less. Therefore, sites such as aeration lagoons that are
used for treatment of sewage sludge are not regulated by the Part 503 rules, and sites such as
storage piles are not covered for 2 years, unless the treatment works can justify a longer storage
period. The Part 503 regulation also does not apply to sites where sewage sludge is codisposed
with refuse (e.g., municipal solid waste landfills).
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2-3 TYPES OF SURFACE DISPOSAL SITES
2.3.1 Monofills
Monofills are landfiUs that contain only dewatered sewage sludge. Types of monofills
include trenches and area-fills (mounds, layers, and diked containments). Monofill trenches can
be wide or narrow, with each size requiring different sewage sludge characteristics. Trenches
range from 1 to 15 meters (m) (3-50 feet [ft]) wide. In narrow trenches (1-3 m [3-10 ft] wide),
dewatered sewage sludge is usually deposited in the trench from a haul vehicle alongside the
ditch. To ensure that the sewage sludge will spread evenly throughout a narrow trench, sewage
sludge should be less than 30 percent solids and the trench floor-should be nearly level.
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A wide trench (3-15 m [10-50 ft] wide) allows a vehicle to work within the trench itself.
For wide monofill trenches, the sewage sludge should be at least 30 percent solids (which may
include bulking material, such as fine sand) to ensure that it will stay in piles and not slump.
The addition of a bulking agent is generally not cost-effective if the sewage sludge solids content
is less than about 20 percent. If the sewage sludge solids content is too low, the sewage sludge
should undergo additional dewatering at the treatment plant before being transported to the
monofill.
Sewage sludge in monofill trenches is often covered with soil the same day it is deposited
to minimize odors and to prevent insects, birds, and other vectors from contacting the sewage •
sludge and spreading contaminants. As each new trench is dug, the excavated soil is used to
cover the sewage sludge in a nearby trench. If the sewage sludge is solid enough to support a
vehicle (greater than about 30 percent solids), a soil cover can be applied by a vehicle within the
trench. For sewage sludge containing less than 30 percent solids, the cover should be applied by
a front-end loader or dragline next to the ditch.
Sewage sludge applications for narrow trenches range from about 460 to 2,120 dry metric
tons per hectare (dry mt/ha) (200 to 940 tons per acre [tons/ac]), including areas between
trenches. Wide trench operations can accommodate larger sewage sludge applications than
narrow trenches, ranging from about 1,200 to 5,430 dry mt/ha (530-2,440 tons/ac).
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If covers are used for monofill trenches, the sewage sludge generally should contain at
least 20 percent solids to support the cover material. Narrow trenches can handle sewage sludge
with as low as 15 percent solids because the ground on either side helps support the cover.
At area fills, another type of monofill, sewage sludge is placed on the original ground
surface. Excavation is not required (as it is with trenches) because sewage sludge is not placed
below the ground surface. Area fills'are often used at sites with shallow depths to bedrock or
ground water. There are three types of area-fill -applications: area-fill mounds, area-fill layers,
and diked containment. These are discussed below.
In area-fill mounds, the sewage sludge solids content should be no more than 20 percent.
Sewage sludge is mixed with a soil-bulking agent to produce a mixture that is physically mcjiy
stable and has greater weight-bearing capacity. The sewage sludge is usually mixed at one
location and then hauled to the filling area. At the filling area, the mixture is stacked into:
mounds approximately 2 m (6 ft) high, and 1 m (3 ft) of cover material is applied. ;
In area-fill layer applications, sewage sludge is received at the site and mixed with a soil-
bulking agent The mixture is spread evenly in layers from 0.2 to 1 m (0.5 to 3 ft) thick in a
number of applications. An interim soil cover is applied between consecutive layers in 0.2 to
0.3 m (0.5 to 1 ft) thick applications. The final soil cover is from 0.6 to 1 m (2 to 3 ft) thick.
In diked containment applications, dikes are constructed on level ground around all four
sides of a containment area. Access is provided to the top of the dike so that haul vehicles can
dump sewage sludge directly into the containment area. Usually, diked containment operations
are conducted without adding soil-bulking agents. Diked containments are relatively large, with
typical dimensions of 3 to 152 m (10 to 500 ft) wide, 30 to 61 m (100 to 200 ft) long, and 0:3 to
9 m (1 to 30 ft) deep.
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2.3.2. Surface Impoundments
Surface impoundments are surface disposal sites for sewage sludge generally containing
more liquid than sewage sludge placed in monofills. The solids content of sewage sludge in
surface impoundments is usually between 2 and 5 percent. The water level in the impoundment
is maintained at a constant height by using an outflow pipe. Liquid usually leaves the
impoundment through both the outflow pipe and seepage through the base of the impoundment.
Settling of paniculate matter occurs over time,-and a layer of sediment accumulates on the floor
of the impoundment. Eventually, the sediment layer reaches the top of the impoundment and no
further inflow is possible. The impoundment is then either covered and closed or the sewage
sludge can be dredged and disposed in another manner.
2.3.3 Dedicated Sites
Dedicated sites are surface disposal sites on which sewage sludge is spread at greater than
agronomic rates. Thus, the sites do not qualify as land application sites under Subpart B of Part
503.2 These sites are often located onsite at the treatment works and receive multiple
applications of sewage sludge each year for a number of years, usually for the sole purpose of
final disposal. Dedicated sites range in size from less than 10 acres to greater than 10,000 acres.
Public access to dedicated sites is strictly controlled to protect public health.
Very few dedicated sites are used to grow food, feed, and/or fiber crops or vegetative
cover. These are known as dedicated beneficial use sites. The sewage sludge increases the soil's
productivity and can reduce soil erosion and acidity. The high application rates of sewage sludge
placed on these sites can reclaim and restore marginal and disturbed soils, such as strip mines, by
supplying nutrients that act as fertilizers, as well as organic matter that conditions the soil.
2An agronomic rate is the whole sludge application rate (dry weight basis) designed to: (1)
provide the amount of nitrogen needed by the food crop, feed crop, fiber crop, cover crop, or
vegetation grown on the land and (2) minimize the amount of nitrogen in the sewage sludge that
passes below the root zone of the crop or vegetation grown on the land to the ground water.
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SECTION THREE
RISK ASSESSMENT METHODOLOGY
This chapter discusses current EPA methods and established Agency policy for
performing a risk assessment. This process was outlined originally by the National Academy of
Sciences (NAS, 1983) and was established as final Risk Assessment Guidelines in the Federal I
Register (U.S. EPA, 1986b). Five types of guidelines were issued:
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• Guidelines for Carcinogen Assessment
• Guidelines for Estimating Exposure
• Guidelines for Mutagenicity Risk Assessment
• Guidelines for Health Effects of Suspect Developmental Toxicants
• Guidelines for Health Risk Assessment of Chemical Mixtures.
The Risk Assessment Methodology consists of four distinct steps: hazard identification;
dose-response evaluation, exposure evaluation, and characterization of risks. |
3.1 HAZARD IDENTIFICATION
The primary purposes of hazard identification are to determine whether the chemical
poses a hazard and whether there is sufficient information, to perform a quantitative risk
assessment. Hazard identification consists of gathering and evaluating all relevant data that help
determine whether a chemical poses a specific hazard, then qualitatively evaluating those data;on
the basis of the type of health effect produced, the conditions of exposure, and the metabolic
processes that govern chemical behavior within the body. Thus, the goals of hazard identification
are to determine whether it is appropriate scientifically to infer that effects observed under onb
set of conditions (e.g., in experimental animals) are likely to occur in other settings (e.g., in
human beings), and whether data are adequate to support a quantitative risk assessment.
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The first 'step in hazard identification is gathering information on the toxic properties of
chemical substances. The principal methods are animal studies and controlled epidemiological
investigations of exposed human populations.
The use of animal toxicity studies is based on the longstanding assumption that effects in
human beings can be inferred from effects in animals. There are three categories of animal
bioassays: acute exposure tests, subchronic tests, and chronic tests. The usual starting point for
such investigations is the study of acute toxicity in. experimental animals. Acute exposure tests
expose animals to high doses for short periods of time, usually 24 hours or less. The most
common measure of acute toxicity is the lethal dose (LDJO), the average dose level that is lethal
to 50 percent of the test animals. LD;,, refers to oral doses. LCSO designates the inhalation dose
at which 50 percent of the animals exposed died. LC50 is also used for aquatic toxicity tests apd
'••
refers to the concentration of the test substance in the water that results in 50 percent mortality
in the test species. Substances exhibiting a low LD^ (e.g., for sodium cyanide, 6.4 mg/kg) are
more acutely toxic than those with higher values (e.g., for sodium chloride, 3,000 mg/kg)
(NIOSH, 1979).
Subchronic tests for chemicals involve repeated exposures of test animals for 5 to 90 days,
depending on the animal, by exposure routes corresponding to human exposures. These tests are
used to determine the No Observed Adverse Effect Level (NOAEL), the Lowest Observed
Adverse Effect Level (LOAEL), and the Maximum Tolerated Dose (MTD). The MTD is the
largest dose a test animal can receive for most of its lifetime without demonstrating adverse
effects other than cancer. In studies of chronic effects of chemicals, test animals receive daily
doses of the test agent for approximately 2 to 3 years. The doses are lower than those used in
acute and subchronic studies, and the number of animals is larger because these tests are trying
to detect effects that will be observed in only a small percentage of animals.
The second method of evaluating health effects uses epidemiology—the study of patterns
of disease in human populations and the factors that influence these patterns. In general,
scientists view well-conducted epidemiological studies as the most valuable information from
which to draw inferences about human health risks. Unlike the other approaches used to
evaluate health effects, epidemiological methods evaluate the direct effects of hazardous
substances on human beings. These studies also help identify human health hazards without
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requiring prior knowledge of disease causation, and they complement the information gaineti
from animal studies.
Epidemiological studies compare the health status of a group of persons who have been
exposed to a suspected causal agent with that of a comparable nonesposed group. Most
epiderniological studies are either case-control studies or cohort studies. In case-control studies,
a group of individuals with specific disease is identified (cases) and compared with individuals
not having the disease (controls) in an attempt to-ascertain commonalities in exposures they may
t
have experienced in the past. Cohort studies start with a group of people (a cohort) considered
free of the disease under investigation. The health status of the cohort known to have a
common exposure is examined over time to determine whether any specific condition or cause of
death occurs more frequently than might be expected from other causes. ,;
i •*
Epidemiological studies are well suited to situations in which exposure to the risk agent is
relatively high; the adverse health effects are unusual (e.g., rare forms of cancer); the symptoms
of exposure are known; the exposed population is clearly defined; the link between the causal
risk agent and adverse effects in the affected population is direct and clear; the risk agent is;
present in the bodies of the affected population; and high levels of the risk agent are present in
the environment.
I
The next step in hazard identification is to combine the pertinent data to ascertain the
degree of hazard associated with each chemical. In general, EPA uses different approaches for
qualitatively assessing the risk or hazard associated with carcinogenic versus noncarcinogenic
effects. For noncarcinogenic health effects (e.g., systemic toxicity), the Agency's hazard
identification/weight-of-evidence determination has not been formalized and is based only on a
qualitative assessment. •
EPA's guidelines for carcinogenic risk assessment (U.S. EPA, 1986b) group all human
and animal data reviewed into the following categories based on .degree of evidence of '
carcinogenicity:
• Sufficient evidence
• Limited evidence (e.g., in animals, an increased incidence of benign tumors only)
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• Inadequate evidence
• No data available
• No evidence of carcinogenicity.
Human and animal evidence of carcinogenicity in these categories is combined into the
following weight-of-evidence classification scheme:
• Group A—Human carcinogen
• Group B—Probable human carcinogen
Bl—Higher degree of evidence
B2—Lower degree of evidence
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• Group C—Possible human carcinogen
• Group D—Not classifiable as to human carcinogenicity
• Group E—Evidence of noncarcinogenicity
Group B, probable human carcinogens, is usually divided into two subgroups: Bl,
chemicals for which there is some limited evidence of carcinogenicity from epidemiology studies;
and B2, chemicals for which there is sufficient evidence from animal studies but inadequate
evidence from epidemiology studies. EPA treats chemicals classified in categories A and B as
suitable for quantitative risk assessment. Chemicals classified as Category C receive varying
treatment with respect to dose-response assessment, and they are determined on a case-by-case
basis. Chemicals in Groups D and E do not have sufficient evidence to support a quantitative
dose-response assessment.
The following factors are evaluated by judging the relevance of the data for a particular
chemical:
• Quality of data.
• Resolving power of the studies (significance of the studies as a function of the
number of animals or subjects).
• Relevance of route and timing of exposure.
• Appropriateness of dose selection.
• ' 3-4 . • ' ' . '
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' • Replication of effects.
• Number of species examined. :
• Availability of human epidemiologic study data.
• Relevance of tumors observed (e.g., forestomach, mouse liver, male rat kidney)
Although the information gathered during the course of identifying each chemical hazard
is not used to estimate risk quantitatively, hazard identification enables researchers to
characterize the body of scientific data in such a way that two questions can be answered:
(1) Is a chemical a hazard? and (2) Is a quantitative assessment appropriate? The following two
sections discuss how such quantitative assessments are conducted.
3.2 DOSE-RESPONSE EVALUATION
Estimating the dose-response relationships for the chemical under review is the second
step in the risk assessment methodology. Evaluating dose-response data involves quantitatively
characterizing the connection between exposure to a chemical (measured in terms of quantity
and duration) and the extent of toxic injury or disease. Most dose-response relationships are
estimated based on results of animal studies, because even good epidemiological studies rarely
have reliable information on exposure. Therefore, this discussion focuses primarily on dose-
response evaluations based on animal data.
There are two general approaches to dose-response evaluation, depending on whether the
health effects are based on threshold or nonthreshold characteristics of the chemical. In this
context, thresholds refer to exposure levels below which no adverse health effects are assumed to
occur. For effects that involve altering genetic material (including carcinogenicity and
mutagenicity), the Agency's position is that effects may take place at very low doses, and
therefore, they are modeled with no thresholds. For most other biological effects, it is usually
(but not always) assumed that "threshold" levels exist.
For nonthreshold effects, the key assumption is that the dose-response curve for such
chemicals exhibiting these effects in the human population achieves zero risk only at zero dose.
A mathematical model is used to extrapolate response data from doses in the observed ;
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(experimental) range to response estimates in the low-dose ranges. Scientists have developed
several mathematical models to estimate low-dose risks from high-dose experimental risks. Each
model is based on general theories of carcinogenesis rather than on data for specific chemicals.
The choice of extrapolation model can have a significant impact on the dose-response estimate.
For this reason, the Agency's cancer assessment guidelines recommend the use of the multistage
model, which yields estimates of risk that are conservative, representing a plausible upper limit of
risk. With this approach, the estimate of risk is not likely to be lower than the true risk (U.S.
EPA, 1986b).
The potency value, referred to by the Carcinogenic Assessment Group as qt*, is the
quantitative expression derived from the linearized multistage model that gives a plausible upper-
bound estimate to the slope of the dose-response curve in the low-dose range. The q/is ,;
expressed in terms of risk-per-dose, and has units of (mg/kg'day)"1. These values should be used
only in dose ranges for which the statistical dose-response extrapolation is appropriate. EPA's
qt" values can be found in the Integrated Risk Information System (IRIS), accessible through the
National Library of Medicine.
Dose-response relationships are assumed to exhibit threshold effects for systemic
toxicants or other compounds exhibiting noncarcinogenic, nonmutagenic health effects. Dose-
response evaluations for substances exhibiting threshold responses involve calculating what is
known as the Reference Dose (oral exposure) or Reference Concentration (inhalation exposure),
abbreviated to RfD and RfC, respectively. This measure is used as a threshold level for critical
noncancer effects below which a significant risk of adverse effects is not expected. The RfDs and
RfCs developed by EPA can be found in IRIS.
The RfD/RfC methodology uses four experimental levels: No Observed Effect Level
(NOEL), No Observed Adverse Effect Level (NOAEL), Lowest Observed Effect Level (LOEL),
or Lowest Observed Adverse Effect Level (LOAEL). Each level is stated in rag/kg-day, and all
the levels are derived from laboratory animal and/or human epidemiology data. When the
appropriate level is determined, it is then divided by an appropriate uncertainty (safety) factor.
The magnitude of safety factors varies according to the nature and quality of the data from
which the NOAEL or LOAEL is derived. The safety factors, ranging from 1 to 10,000, are used
to .extrapolate from acute to chronic effects, interspecies sensitivity, and variation in sensitivity in
human populations. They are also used to extrapolate from a LOAEL to a NOAEL. Ideally, for
' ' . . 3-6 . •
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all threshold effects, a set of route-specific and effect-specific thresholds should be developed. If
information is available for only one.route of exposure, this value is used in a route-to-route
extrapolation to estimate the appropriate threshold. Once these values are derived, the next step
is to estimate actual human (or animal) exposure.
3.3 EXPOSURE EVALUATION
Exposure evaluation uses data concerning the nature and size of the population exposed
to a substance, the route of exposure (i.e., oral, inhalation, dermal), the extent of exposure
(concentration times time), and the circumstances of exposure.
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There are two ways of estimating environmental concentrations:
• Directly measuring levels of chemicals (monitoring)
• Using mathematical models to predict concentrations (modeling)
In addition, an analysis of population exposure is necessary. :
3.3.1 Monitoring
Monitoring involves collecting and analyzing environmental samples. These data provide
the most accurate information about exposure. The two kinds of exposure monitoring are
personal monitoring and ambient (or site and location) monitoring.
Most exposure assessments are complicated by the fact that human beings move from
place to place and are therefore exposed to different risk agents throughout the day. Some
exposure assessments attempt to compensate for this variability by personal monitoring. Personal
monitoring uses one or more techniques to measure the actual concentrations of hazardous
substances to which individuals are exposed. One technique is sampling air and water. The
amount of time spent in various microenvironments (i.e., home, car, or office), may be combined
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with data on environmental concentrations of risk agents in those microenvironments to estimate
exposure.
Personal monitoring may also include the sampling of human body fluids (e.g., blood,
urine, or semen). This type of monitoring is often referred to as biological monitoring or
biomonitoring. Biological markers (also called biomarkers) can be classified as markers of
exposure, of effect, and of susceptibility. Biological markers of exposure measure exposure either
to the exogenous material, its metabolite(s), or to the interaction of the xenobiotic agent with the
target cell within an organism. An example of a biomarker of exposure is lead concentration in
blood. In contrast, biologic markers of effect measure some biochemical, physiologic, or other
alteration within the organism that points to impaired health. (Sometimes the term
biomonitoring is also used to refer to the regular sampling of animals, plants, or microorganisms
in an ecosystem to determine the presence and accumulation of pollutants, as well as their effects
on ecosystem components.)
Ambient monitoring (or site or location monitoring) involves collecting samples from the
air, water, soil, or sediments at fixed locations, then analyzing the samples to determine
environmental concentrations of hazardous substances at the locations. Exposures can be further
evaluated by modeling the fate and transport of the pollutants.
3.3.2 Modeling
Measurements are a direct and preferred source of information for exposure analysis.
However, such measurements are expensive and are often limited geographically. The best use
of such data is to calibrate mathematical models that can be more widely applied. Estimating
concentrations using mathematical models must account not only for physical and chemical
properties related to fate and transport, but must also document mathematical properties (e.g.,
analytical integration vs. statistical approach), spatial properties (e.g., one, two, or three
dimensions), and time properties (steady-state vs. nonsteady-state).
Hundreds of models for fate, transport, and dispersion from the source are available for
all media. Models can be divided into five general types by media: atmospheric models, surface-
water models, ground-water and unsaturated-zone models, multimedia models, and food-chain
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models. These five types of models are primarily applicable to chemicals or to radioactive
materials associated with dusts and other particles.
Selecting a model for a given situation depends on the following criteria: capability of
the model to account for important transport, transformation, and transfer mechanisms; fit of
model to site-specific and substance-specific parameters; data requirements of the model,
compared to availability and reliability of off-site information; and the form and content of the
model output that allow it to address important questions regarding human exposures.
To the extent possible, selection of the appropriate fate and transport model should
follow guidelines specified for particular media where available; for example, the Guidelines on
Air Quality Models (U.S. EPA, 1986c).
3-3.3 Population Analysis
Population analysis involves describing the size and characteristics (e.g., age/sex
distribution), location (e.g., workplace), and habits (e.g., food consumption) of potentially
exposed human and nonhuman populations. Census and other survey data often are useful in
identifying and describing populations exposed to a chemical.
Integrated exposure analysis involves calculating exposure levels, along with describing the
exposed populations. An integrated exposure analysis quantifies the contact of an exposed
population to each chemical under investigation via all routes of exposure and all pathways from
the sources to the exposed individuals. Finally, uncertainty should be described and quantified to
the extent possible.
3.4 RISK CHARACTERIZATION
This final step in the risk assessment methodology involves integrating the information;
developed in hazard identification, dose-response assessment, and exposure assessment to derive
quantitative estimates of risk. Qualitative information should also accompany the numerical risk
estimates, including a discussion of uncertainties, limitations, and assumptions. It is. useful to
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distinguish methods used for chemicals exhibiting threshold effects (i.e., most noncarcinogens)
from those believed to lack a response threshold (i.e., carcinogens).
For carcinogens, individual risks are generally represented as the probability that an
individual will contract cancer in a lifetime as a result of exposure to a particular chemical or
group of chemicals. Population risks are usually estimated based on expected or average
exposure scenarios (unless information on distributions of exposure is available). The number of
persons above a certain risk level, such as 10^, or above a series of risk levels (10"s, 10"4, etc.), is
another useful descriptor of population risks. Thus, individual risks also may be presented using
cumulative frequency distributions, where the total number of people exceeding a given risk level
is plotted against the individual risk level.
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For noncarcinogens, dose-response data above the threshold are usually lacking.
Therefore, risks are characterized by comparing the dose or concentration to the threshold level,
using a ratio in which the dose is placed in the numerator and the threshold in the denominator.
Aggregate population risks for noncarcinogens can be characterized by the number of people
exposed above the RfD or RfC. Recall that the hazard identification step for threshold
chemicals is addressed qualitatively because no formal Agency weight-of-evidence evaluation is
currently available for noncarcinogenic chemicals. The same approach can be used to assess
both acute and chronic hazards. For assessing acute effects, the toxitity data and exposure
assessment methods must account for the appropriate duration of exposure.
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SECTION FOUR
POLLUTANTS AND PATHWAYS OF CONCERN FOR PART 503
RISK ASSESSMENT FOR THE SURFACE DISPOSAL OF SEWAGE SLUDGE
Which pollutants are regulated under the Part 503 regulation depends on the sewage
sludge use or disposal practice—surface disposal, land application, or incineration. Subpart C,
Surface Disposal, establishes limits for three pollutant; for sewage sludge placed on a surface
disposal site. This section describes how EPA selected the 17 pollutants for which the Agency
conducted detailed risk assessments and discusses the data bases used to collect information
about the pollutants. Following a detailed explanation of the risk assessment methodology in
Section Five, Section Six explains how EPA used the risk assessment results to select the three
pollutants and establish limits for these pollutants in the final Part 503 regulation for sewage
sludge placed on a surface disposal site.
Since the pollutants to be regulated under all sewage sludge use or disposal practices
were selected concurrently, this section discusses the selection process broadly and, where !
appropriate, focuses on the pollutants of concern in sewage sludge placed on a surface disposal
site. Those interested in greater detail on the pollutant evaluation process are encouraged to
refer to the following documents: The Record of Proceedings on the OWRS Municipal Sewage
Sludge Committees and Summary of the Environmental Profiles and Hazard Indices for Constituents
of Municipal Sludge (U.S. EPA, 1983a; 1985a).
4.1 INITIAL LIST OF POLLUTANTS
In the Spring of 1984, EPA enlisted the assistance of federal, state, academic, and private
sector experts to determine which pollutants likely to be found in sewage sludge should be
further examined as possible candidates for regulation under the Part 503 standard. These
experts screened a list of approximately 200 pollutants in sewage sludge that, when sewage sludge
is used or disposed, could cause adverse human health or environmental effects. Many of the
pollutants placed on the initial list for consideration came from the Clean Water Act's list of
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Priority Pollutants and Appendix Vm of the Resource Conservation and Recovery Act, and were
based on available information such as human health effects, domestic and wildlife effects,
aquatic toxicity, plant uptake, phytotoxicity, and frequency of occurrence. The experts were
requested to review and revise the list, adding or deleting pollutants, based on the following
criteria:
• Pollutants in sewage sludge for which an adequate database existed to indicate the
hazard posed to human health and/or the environment (i.e., potential health
hazards);
• Pollutants in sewage sludge for which sufficient data existed to exclude them as
hazards to human health and/or the environment; or
• Pollutants in sewage sludge for which insufficient data were available to determine
if they posed a human health and/or environmental problem. ,;
^
Based on qualitative assessments of each of the approximately 200 initial pollutants, the
committee of experts recommended that the Agency gather additional environmental information
on 50 pollutants (see Table 4-1) and 7 pathogens. The other 150 pollutants were not included
on the list because the committee judged them not likely to cause adverse human health or
environmental effects if disposed properly. EPA developed an environmental profile for each of
the 50 pollutants and 7 pathogens selected for further evaluation. Each profile consisted of a
compilation of data on toxicity, occurrence, and fate and effects of the pollutant, and a "hazard
index" to rank the degree of hazard each of the 50 pollutants posed for the major exposure
pathway(s) for each use or disposal practice (U.S. EPA, 1985a,b,c,d)
Environmental profiles, including hazard indices, were developed for pollutants likely to
be found when-sewage sludge is applied to land, incinerated, disposed in the ocean, or placed in
a landfill (raonofill). Ocean disposal of sewage sludge has since been prohibited. At the time
the environmental profiles were developed, types of surface disposal practices other than
placement in landfills/raonofills were not included as part of the regulatory development effort
because they were considered isolated practices that would not be expected to pose significant
risks. Later in the development of the Part 503 regulation, however, the Agency concluded that
the proposed rule should cover disposal of sewage sludge in other types of surface disposal sites,
including surface impoundments, lagoons, waste piles, and dedicated sites. EPA determined that
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the pollutants of concern for regulating all types of surface disposal sites were the same as those
for landfilling (monofilling), since the most critical pathway of exposure for all types of surface
disposal sites is through potential ground water contamination. In addition, the hazard indices
developed for landfilling were based on worst-case assumptions and, therefore, would adequately
identify pollutants of concern for other types of surface disposal sites. ,
Of the 50 pollutants selected for further consideration through development of i
environmental profiles and hazard indices, the OWRS expert committee identified 28 as
potentially of concern for landfilling (see Table 4-1). Not every pollutant was considered a
potential risk under each use or disposal practice because different use or disposal practices can
result in different exposure levels for the same pollutant A summaiy of the results of the
environmental profiles and hazard indices for pollutants in landfilled sewage sludge is included in
-*
the Summary of the Environmental Profiles and Hazard Indices for Constituents of Municipal
Sludge (U.S. EPA, 1985a). Although cadmium and chromium initially were not identified in the
hazard profile as posing a potential ground-water risk for landfilling, they were later added to the
risk assessment analysis for consistency with calculations for land application.
4.2 ENVIRONMENTAL PROFILES AND HAZARD INDICES
During 1984 and 1985, the Agency collected data from published scientific papers onithe
list of 50 pollutants of concern, including information on toxicity and persistence; pathways by
which the pollutants travel through the environment to a receptor organism (plant, animal, or
human); mechanisms that transport or bind the pollutants; and the effects of the pollutants on
the target organism. EPA also analyzed data on the relative frequencies and concentrations of
sewage sludge pollutants as part of an Agency study of 45 POTWs in 40 cities. The study was
officially called the "Fate of Priority Pollutants in Publicly Owned Treatment Works," but was
better known as the "40-City Study" (U.S. EPA. 1982a). The 40-City Study contained data on the
concentrations of 40 pollutants in sewage sludge (12 metals, 6 base neutral organic compounds, 6
volatile organic compounds, 9 pesticides, and 7 polychlorinated biphenyls [PCBs]).
4-3
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TABLE 4-1
POLLUTANTS SELECTED FOR
ENVIRONMENTAL PROFILES/HAZARD INDICES*
Pollutants
Aldrin/Dieldrin
Arsenic
Benzene
Benzo(a)anthracene
Benzo(a)pyrene
Beryllium
Bis (2-ethylhexyl) phthalate
Cadmium
Carbon tetrachloride
Chlordane
Chlorinated dibenzodioxins
Chlorinated dibenzofurans
Chloroform
Chromium
Cobalt
Copper
Cv snide
DDT/DDD/DDE
2,4-Dichlorophenoxy-acetic acid
• Fluoride
Heptachlor
Hexachlorobenzene
_
Hexachlorobutadiene •
Iron
Lead
Land
Application
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Surface Disposal Site
(formerly Landfill)
X
X
X
X
X
X
X
X
X
X
X
X
X
Incineration
X
X
X
X
X
X
X
X
X
X
X
X
X
X
.
X
X
•
X
X
4-4
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TABLE 4-1 (continued)
Pollutants
Lindane
Malathion
Mercury
Methylene bis (2-chloroaniline)
Methylene chloride
Methylethyl ketone
Molybdenum
Nickel
n-Nitrosodimethylamine
PCBs
Pentachlorophenol
Phenanthrene
Phenol
Selenium
Tetrachloroethylene
Toxaphene
Trichloroethylene
Tricresol phosphate
Vinyl chloride
Zinc
Land
Application
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Surface Disposal Site
(formerly Landfill)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Incineration
x:
X
X
X-
X
X
X
x;
X
X
X
•Excludes pollutants selected for environmental profiles and hazard indices for the ocean
disposal of sewage sludge.
4-5
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For surface disposal of sewage sludge, drinking contaminated ground water initially was
"determined to be the only critical pathway. A second pathway, inhaling pollutants that volatilize
from a surface disposal site, was not considered at this early stage because EPA assumed that
good management practices were in place at sewage sludge landfills and that the volatilization of
pollutants was not a likely route of exposure. The volatilization pathway, however, was
considered in the later, more detailed risk assessment conducted for the final Part 503 regulation.
EPA used the data collected on the 50 .pollutants to assess the likelihood of each
pollutant affecting human health or the environment adversely. For this analysis, EPA relied on
rudimentary risk assessments to predict at what concentration a pollutant would occur in surface
or ground water, soil, air, or food. EPA then compared the predicted pollutant concentration
with an Agency human health criterion to determine whether, at that concentration, the pgllutant
could be expected to have an adverse effect.
For carcinogens, if the calculated risk using the predicted concentration was lower than
an allowable cancer risk level of 1 x 10"6 (1 person hvl,000,000),1 the pollutant was not
considered to have an adverse effect. For noncarcinogens, adverse impact hinged on whether the
pollutant concentration exceeded an existing standard. To determine the human health impact
of the pollutants of concern, EPA assumed worst-case Conditions that would maximize the
pollutant exposure.
The Agency used the rudimentary risk assessments to score and rank each pollutant
according to its "hazard index," screening out those pollutants not expected to have an adverse
human health impact before proceeding with more thorough, detailed modeling for pollutants
considered to be of concern. Two hazard indices were developed for landfilling: (1) an index
indicating effects of a pollutant on ground water; and (2) an index of human toxicity/cancer risk
'In the initial phase of the pollutant selection process, EPA chose the 1 x lO"6 risk level as
. being protective of human health for a most sensitive individual exposed under a hypothetical
worst-case scenario. Later EPA analyses for the proposed Part 503 rule used a 1 x 10'5 risk level
for sewage sludge incineration and a 1 x 10"4 risk level for the other use or disposal practices,
while the final rule uses a risk level of 1 x 10"4 for all use or disposal practices. The 1 x 10^ risk
level used at the outset of the pollution selection process allowed more pollutants to be
evaluated than those later selected for further, more extensive analysis under a 1 x 10"* risk level.
. 4-6
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resulting from ground water contamination. The ground water contamination index was based
on the EPA Exposure Assessment Group's model, "Rapid Assessment of Potential Ground
Water Contamination Under Emergency Response Conditions" (U.S. EPA, 1983b). The ground
water index estimated the pollutant transport through the soil to the water table beneath the
landfill and through the aquifer to a nearby well. The human toxicity/cancer risk index for
noncarcinogens was determined by comparing the estimated exposure from drinking ground
water beneath a sewage sludge landfill with available acceptable daily intake values for the '
pollutants of concern. For carcinogens, the humanAoxidty cancer risk index was based on
comparing estimated exposure to a particular pollutant of concern from drinking from a wejl
supplied by ground water beneath a landfill to the intake level of that pollutant at the 10"* cancer
risk level.
i. if
t *
EPA excluded two categories of pollutants from further evaluation. First, EPA excluded
pollutants that, when compared to the hazard index, presented no risk to human health at the
highest concentration found in the 40-City Study or in other available data bases for each
particular use or disposal practice. The hazard index developed for each pollutant and for 6ach
use or disposal practice was used to compare a pollutant's risk to the 1 x 10"6 risk level for
carcinogens or to a threshold level index for noncarcinogens. Second, EPA deferred from
consideration those pollutants for which there were insufficient data to conduct a risk assessment.
Table 4-2 identifies the pollutants excluded or deferred under these two categories. Table 4-3
presents the 16 pollutants that remained for regulatory consideration for the surface disposal of
sewage sludge at the time the proposed Part 503 rule was published on February 6,1989.
Following publication of the proposed rule, additional data available on the toxicity and
environmental properties of chromium subsequent to its exclusion warranted that it be further
evaluated. EPA conducted a more detailed risk assessment, therefore, on 17 pollutants (see
Section Five), forming the basis for the limits for the three pollutants (arsenic, chromium, and
nickel) in Part 503, Subpart C.
Although EPA believed that the 40-City Study data were the appropriate data on which
to base the February 6,1989, proposed Part 503 regulation, the Agency later concluded thatthe
data needed to be replaced or, at a minimum, supplemented to support the final regulation.'
4-7
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TABLE 4-2
POLLUTANTS EXCLUDED OR DEFERRED
FROM REGULATORY CONSIDERATION
FOR THE SURFACE DISPOSAL OF SEWAGE SLUDGE
Pollutant
Chromium*
Cobalt
Cyanide
2,4-DichIorophenoxy-acetic acid
Malathion
Methylene chloride
Methylene ketone
Molybdenum
Phenanthrene
Phenol
Selenium
Zinc
Reason
Excluded — no adverse
Deferred — insufficient
Excluded — no adverse
Excluded — no adverse
Excluded — no adverse
Deferred — insufficient
Deferred — insufficient
Excluded — no adverse
Deferred — insufficient
Excluded — no adverse
Excluded — no adverse
Excluded — no adverse
effect on human health
data for risk assessment
effect on human health
effect on human health
effect on human health
data for risk assessment » '
data for risk assessment
effect on human health
data for risk assessmenl:
effect on human health
effect on human health
effect on human health
•Additional data available on the toxicity and environmental properties of chromium subsequent
to this exclusion warranted that a risk assessment be performed and that a pollutant limit be
developed.
4-X
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TABLE 4-3
POLLUTANTS EVALUATED FOR
SURFACE DISPOSAL OF SEWAGE SLUDGE
FOR THE PROPOSED PART 503 RISK ASSESSMENT
.Arsenic
Benzene
Benzo(a)pyrene
Bis (2-ethylhexyl) phthalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nitrosodimethylamine
PCBs
Toxaphene
Trichloroethylene
4-9
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EPA therefore undertook the National Sewage Sludge Survey (NSSS)2 to obtain a current and
reliable data base for developing the final Part 503 regulation. The NSSS data base was used to
develop the regulatory impact of the Part 503 regulation on existing sewage sludge use or
disposal practices, to delete pollutants from regulation under Part 503, and to derive the nickel
pollutant limit in Subpart C.
National Sewage Sludge Survey data collection effort began in August 1988 and was
completed in September 1989. EPA collected sewage sludge samples at 180 publicly owned
treatment works (POTWs) with either secondary or advanced treatment processes and analyzed
them for more than 400 pollutants. In addition, through the use of detailed questionnaires, the
survey collected information on sewage sludge use or disposal practices from 475 POTWs with at
least secondary treatment of wastewater.
4-10
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-------
SECTION FIVE
PART 503 RISK ASSESSMENT METHODOLOGY FOR THE
SURFACE DISPOSAL OF SEWAGE SLUDGE
This section describes the risk assessment methodology EPA used to further evaluate the
17 pollutants of concern discussed in Section Four to determine whether they posed a risk to
human health and the environment and should be regulated under Part-503. Section 5.1
describes why EPA chose two prototype surface disposal units—a monofill and a surface
impoundment—on which to conduct the risk assessment. Section 5.2 presents the general
approach that EPA took to derive the risk-based pollutant criteria. The next two sections
explain the methodology by which EPA conducted the risk assessment for the monofill prototype
(Section 5.3) and the surface impoundment prototype (Section 5.4). Each section contains
sample calculations for the pollutant criteria. The results of the risk assessment appear in
Section 5.5. The risk assessment methodology is based on numerous references, some of which
relate to technical criteria of ground water and air modeling and others relating directly to risk-
based factors. The factors regarding risk methodology are discussed in Section 5.6, while
technical parameters are summarized in tables in Section 5.7 and discussed fully in Section 5.8.
5.1 DESCRIPTION OF TWO MODEL PROTOTYPES OF SURFACE DISPOSAL SITES—
MONOFILL AND SURFACE IMPOUNDMENT
The surface disposal of sewage sludge potentially can cause pollution of ground water and
subsequent health risks to humans who use the ground water for drinking. It can also lead to
the emission of volatile organic pollutants and result in risks to humans who are exposed to the
pollutants and who inhale the contaminated air. The risk assessment conducted for the surface
disposal of sewage sludge evaluates risk to a highly exposed individual (HEI) via these two
pathways. Potential exposure of an HEI to pollution from nearby surface water bodies is not
considered in this analysis because responsible management practices are assumed to control
runoff.
5-1
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EPA defines the term "surface disposal" broadly to include the disposal of sewage sludge
in surface impoundments, waste piles, lagoons, sludge-only landfills (monofills), and dedicated
sites (see Section Two). Within each category, surface disposal sites may differ further by site
design and management practices. To account for the risk posed by sewage sludge placed in any
one of these surface disposal sites, EPA calculated the risk from disposal of. sewage sludge in two
common surface disposal units—a surface impoundment and a monofill—and generalized the I
conditions at these sites. Two idealized prototypes, therefore, have been defined to represent
this wide mix of surface disposal practices: a trench monofill and a surface impoundment with
continuous inflow.
The monofill prototype is represented by a sewage sludge-only trench fill. Disposal
involves the excavation of trenches so that dewatered sewage sludge may be directly deposited* Z
•»
from a haul vehicle. Sewage sludge is entirely buried below the original ground surface. Only
dewatered sewage sludges with solids contents greater than or equal to 20 percent are assumed
to be suitable for disposal and the sewage sludge is often mixed with a bulking agent (e.g., soil)
to increase solids content. Normal operating procedures require that the monofill be covered
daily to reduce odors and provide vector (pest) control. In addition, a final cover is assumed to
be placed on the monofill after closure. ;
The surface impoundment prototype is assumed to receive a continuous inflow of
wastewater. A vertical outflow pipe maintains the surface level at a constant height and liquid is
assumed to leave the impoundment both in the outflow and in seepage through the floor of the
impoundment. Sewage sludge entering the impoundment is assumed to have a low solids content
(between 2 and 5 percent). Over time, paniculate settling occurs and a denser layer of sediment
accumulates on the floor of the lagoon. Eventually, this layer of sediment extends to the top of
the impoundment and no further inflow is possible. Upon closure, the sewage sludge is left
permanently in place and remains uncovered.
•
One key difference between the surface impoundment and monofill prototypes is that the
active surface impoundment is assumed to contain significantly more liquid than the active
monofill. Seepage through the floor of the facility is therefore expected to be greater for a
surface impoundment and may be sufficient to sustain a local "mounding" of the underlying water
5-2
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table. The surface layer of the impoundment is also assumed to be in a liquid state over the
active lifetime of the facility. The volatilization of organic pollutants from this liquid layer is
therefore expected to differ from volatilization predicted for a monofill since the monofill is
assumed to contain a higher percentage of solids and to receive a daily and eventually a
permanent soil cover.
5.2 GENERAL APPROACH USED TO DERIVE RISK-BASED POLLUTANT CRITERIA
For each surface disposal prototype (monofill and surface impoundment), risk-based
pollutant criteria are derived separately for the vapor and ground-water pathways of exposure.
. Calculations, however, have been integrated so that pollutant mass is conserved, meaning that^
'?
the total mass of pollutant loss is equal to the sum of losses to ground water, vapor, degradation,
and, for surface impoundments, outflow. The ground-water pathway criteria are limited to a 300-
year time horizon; pollutant concentrations that may occur in well water after 300 years are
ignored. For organic pollutants, the maximum predicted 70-year average ambient air
concentration is used to derive criteria for the vapor pathway. EPA derived the risk-based
pollutant criteria by following four steps:
1) prepare a "mass balance" of pollutant loss by calculating the relative rates at which
the pollutant is removed from the site by leaching to ground water, volatilization
to air, degradation, and, for surface impoundments, outflow; .
2) determine the reference concentration of the pollutant in ground water or air;
3) determine the pollutant concentration in each medium resulting from a unit
concentration (rag/kg dry weight) in sewage sludge at the site; and
4) derive the .reference concentration of the pollutant in sewage sludge (e.g., the
pollutant criteria) by dividing the reference concentration of the pollutant in
ground water or air by the pollutant concentration predicted per unit
concentration in sewage sludge.
5-3
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5.2.1 Mass Balance
l
EPA developed the risk assessment methodology to account for the multiple partitioning
of each pollutant concentration. All losses are treated as first-order and a rate-loss coefficient is
calculated for each scenario. Calculations for the raonofilling of sewage sludge account for
l
leaching to ground water, volatilization, and pollutant degradation. For surface impoundments,
pollutant losses include leaching to ground water, volatilisation, pollutant degration, and effluent
or water discharge.
5.22 Modeling of Ground-Water Contamination
•r
'<
The risk assessment methodology for the surface disposal of sewage, sludge evaluated the
risk from drinking contaminated water from different classes of ground water (Class I, II, or IE)
according to EPA's ground-water classification system. Risk-based criteria (see Section 5.6) were
developed for both Class I and Class U/UI ground water. However, after completing the risk
assessment, EPA determined that it would be more appropriate to treat all ground water as
drinkable in accordance with EPA's Class II designation in the development of pollutant limits
for the final Part 503 regulation.
For the risk assessment, EPA modeled ground-water pollution near surface disposal sites
using a computer code consisting of linked versions of VADOFT and AT123D. The VADOFT
module simulates the flow of both water and pollutants through the unsaturated soil zone. The
AT123D component simulates the lateral movement of pollutants through the saturated soil
zone. For surface-disposal facilities, EPA assumed that no individual on-site drank well water
and that the property boundary (fenceline) extended 150 meters (m) beyond the edge of the
surface disposal site. For all sites, the depth to ground water is conservatively assumed to be one
meter,' although typical depths for actual sites are much greater. EPA calculated the maximum
pollutant concentrations estimated within the first 300 years at 150 m in the downgradient
direction from each surface disposal prototype facility and used these concentrations to derive
criteria based on the reference drinking water concentration. The pollutant criteria correspond
to the concentration of a given pollutant received by an HEI who consumes two liters of
' 5-4
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contaminated ground water per day at a cancer risk level of 10"*. Every HEI exposed to this
concentration of pollutant faces a one in 10,000 lifetime risk of contracting cancer as a result.
EPA derived separate pollutant criteria for lined and unlined monofills and surface
impoundments for a Class I aquifer and a Class n or HI aquifer. To derive pollutant limits for
lined and unlined surface disposal sites, EPA used similar models, although some of the
modeling assumptions are different. The main difference is that, for lined units, EPA assumed
that an additional three foot clay layer is located between the facility bottom and the unsaturated
zone. The effect of the liner on pollutant transport into ground water is a function of the
hydraulic conductivity of the liner, which is expected to reduce the net recharge to the aquifer,
and the additional vertical distance between the facility bottom and the water table. These
factors tend to reduce pollutant flux to ground water and increase volatilization.
5.2.3 Modeling the Contamination of Ambient Air
The volatile emission of pollutants from surface disposal facilities differs according to the
type of facility being considered. For the surface impoundment prototype, emissions can occur
from the impoundment's liquid surface, which remains uncovered throughout the life of the
facility. For the monofill prototype, volatile emissions occur from a mixture of sewage sludge
and soil and are limited by the application of a daily and, ultimately, a permanent layer of soil
cover. Volatile emissions from the liquid surface of the surface impoundment prototype are
modeled with a two-film resistance model (Thomann and Mueller, 1987). Emissions from the
monofill prototype are estimated with a model described in U.S. EPA (1986d), which calculates
these emissions for both uncovered monofill cells and for those protected by daily and permanent
cover. A weighted average of these estimates is used to predict total average volatile emissions
to which an HEI would be exposed.
After estimating the emissions, EPA calculates the expected concentrations of pollutants
in ambient air based on a conservative simplification of the ISCLT model (Bowers et al., 1980)
as discussed in Environmental Science and Engineering (1985) and U.S. EPA (1986d).
Concentrations are estimated at the property boundary (150 m from the edge of the site) and are
5-5 .
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used to derive pollutant limits for an HEI who inhales contaminated air at a rate of 20 cubic
meters per day with a lifetime exposure based on a risk level of 10~*.
5.2.4 Exposure Scenarios :
To derive the risk-based pollutant criteria for the surface disposal of sewage sludge \
established in the Part 503 regulation, EPA evaluated 10 exposure scenarios. These scenarios
account for exposure to pollutants from sewage sludge placed in lined orunlined surface ;
impoundments or monofills. In addition, these scenarios are all based on one of the two
pathways: inhalation of volatile emissions or ingestion of contaminated ground water (Class I or
Class II/ni). These exposure scenarios are listed below: ,;
Scenario 1: Sludge-soil-air-human (fumes from volatile pollutants in raonofilled sewage
sludge)
Scenario 2: Sludge-soil-air-human (fumes from volatile pollutants in sewage sludge placed in a
surface impoundment)
Scenario 3: Sludge-soil-ground water (water from wells near a monofill without a liner and
leachate collection system: Class I aquifer)
-1
Scenario 4: Sludge-soil-ground water (water from wells near a surface impoundment without a
liner and leachate collection system: Class I aquifer) i
Scenario 5: Sludge-soil-ground water (water from wells near a monofill with a liner and
leachate collection system: Class I aquifer)
Scenario 6: Sludge-soil-ground water (water from wells near a surface impoundment with a
liner and leachate collection system: Class I aquifer)
Scenario 7: Sludge-soil-ground water (water from wells near a surface impoundment without a
liner and leachate collection system: Class II or ffl aquifer) :
Scenario 8: Sludge-soil-ground water (water from wells near a surface impoundment without a
liner and leachate collection system: Class II or in aquifer)
Scenario 9: Sludge-soil-ground water (water from wells near a raonofill with a liner and
' leachate collection system: Class II or in aquifer) ;
5-6
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Scenario 10: Sludge-soil-ground water (water from wells near a surface impoundment with
liner and leachate collection system: Class II or HI aquifer)
5.2.5 Uncertainties and Limitations
To obtain an estimate of risk from placing sewage sludge on a surface disposal site, EPA
simplified calculations by deciding on numerous assumptions, almost all of which are
conservative. True exposure and risk will differ from the estimates provided here depending on
the extent to which actual conditions at each site differ from those that are assumed in the
models. For example, if the local depth to ground water exceeds I m or if the hydraulic
conductivity of the local soil medium is less than that of sand, actual pollution of ground water
*
beneath the surface disposal site is likely to be lower than that calculated for this risk asses'sment.
Similarly, concentrations in ground water at distances greater than 150 m and in directions other
than downgradient are likely to be lower than those calculated for this analysis. On the other
hand, a nonhomogeneous or fractured medium beneath a surface disposal facility might lead to
the pollution of ground water at higher concentrations than those predicted by the VADOFT
and AT123D models.
5 J RISK ASSESSMENT METHODOLOGY FOR MONOFILL PROTOTYPE
EPA derived the risk-based pollutant criteria for sewage sludge placed in a monofill
prototype according to the following four basic steps:
1) prepare a "mass balance".of pollutant loss, which involves calculating the
individual and combined rates at which the pollutant is removed from the site by
competing loss processes;
2) determine the reference concentration of pollutant in the medium of concern for
each exposure pathway;
3) determine the relationship between the pollutant concentrations in the
environmental media and the pollutant concentrations in the sewage sludge
deposited in the monofill; and
5-7
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4) combine the results from Steps (1) through (3) to calculate the pollutant criteria.
5.3.1 Methodology for Mass Balance
EPA assumed that pollutants enter the monofill facility through daily deposits of sewage
sludge and are removed through degradation, leaching, and volatilization. Rates of pollutant loss
are assumed to be proportional to the residual concentration of pollutants in the monofill, and
mass balance calculations begin by estimating first-order loss coefficients for each competing loss
process.
5.3.1.1 Pollutant Losses Through Leaching
EPA calculated a coefficient for the rate of pollutant loss to leaching by assuming that
pollutant mass in a filled raonofill cell is partitioned between dissolved and adsorbed phases and
that this partition is at equilibrium. Based on mathematical relationships discussed in
Appendix B, the concentration of pollutants dissolved in water within the monofill can be
estimated from the total concentration of pollutants within the facility:
• —— • (1)
" BDKD+ew+H8,
where:
H = JL ' . (2)
RT
and:
Cfe,. = concentration of pollutants in water-filled pore space of soil (kg/m3)
C, = total concentration of pollutants in soil (kg/m3)
BD = bulk density of sewage sludge/soil mature (kg/m3)
KD = equilibrium partition coefficient for the pollutant" (m3/kg)
• &„ — water-filled porosity of sewage sludge/soil mixture (unitless)
H = nondimensional Henry's Law constant for the pollutant
0, = air-filled porosity of sludge/soil (unitless)
H = Henry's Law constant for the pollutant (atra»m3/raol)
R = ideal gas constant (8_21xlO'$ rn3'atm/mol«K)
T = temperature (K).
5-8
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As discussed in Appendix C, the flux of pollutant mass leaching from treated soil can be
calculated as the product of net ground-water recharge times the estimated concentration of
*
pollutant in leachate. This flux can then be divided by total pollutant mass per unit area to
obtain the first-order loss coefficient for leaching as follows:
„ = NR
where:
Kfc. = loss rate coefficient for leaching (yr1)
NR = annual recharge to ground water beneath the monofill (ra/yr)
BD = bulk density of sewage sludge/soil mixture (kg/ra3)
KD = equilibrium partition coefficient for the pollutant (m3/kg)
Qy, = water-filled porosity of sewage sludge/soil mixture (unitless)
H = nondimensional Henry's Law constant for the pollutant
0, = air-filled porosity of sewage sludge/soil mixture (unitless)
df = depth of a monofill cell (m)
5.3.1.2 Pollutant Losses to Volatilization
Rates of volatilization from a filled cell in a sewage sludge monofill will vary according to
whether a cover layer of soil has been applied. EPA assumed that each cell in the monofUl
contains uncovered sewage sludge for a few hours on each of the days it receives sewage sludge.
Following each deposit, a temporary cover layer of soil is applied. Once the monofUPs capacity
is exhausted, a thicker permanent cover of soil is applied to the entire facility (U.S. EPA, 1986d).
A time-weighted average of emission rates with and without cover is, therefore, used to describe
the average rate of volatile emissions for an individual cell in the monofill. The fraction of the
facility's active lifetime that a typical cell will be uncovered is calculated as:
f,» = — (4)
m LF
where:
fan = fraction of facility's active lifetime that a typical cell contains sewage.
sludge without soil cover (unitless)
t^ = time that each individual monofill cell contains uncovered sewage sludge
(yr)
LF = active lifetime of monofill (yr)
5-9
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Some monofill cells will be filled early in the facility's operation, while others become
filled closer to facility closure. The average monofill cell will contain sewage sludge for half the
active lifetime of the facility. The fraction of the facility's active lifetime that such a cell will
contain sewage sludge protected by temporary cover is:
where: ;
f^ = fraction of facility's active lifetime that typical cell contains sewage sludge
with temporary soil cover
f^, = fraction of facility's active lifetime that a typical cell contains sewage
sludge without soil cover (yr)
EPA calculated a time-weighted average rate of emissions for a typical monofill cell us-ifig
•»
equations describing emissions from cells with and without soil cover. Equations describing rates
of volatile emissions from covered and uncovered landfill cells were estimated by Environmental
Science and Engineering (1985) as discussed in U.S. EPA (1986d). Within each of these '.
equations, presented below, there are unitless numerical constants which resulted from the initial
estimation process. It must be noted that such constants in these and other equations from this
source (used further below) cannot be given any precise definitions. :
The equation estimating the rate of emissions from an uncovered landfill cell is:
0.17 o> 0.994(r-293> C,
qm =
~U&
where:
qUB . = emission rate from treated soil for uncovered period (kg/m2«sec)
0.17 . = empirical constant transferred from the literature source of the equation
-------
9.2xlO-5 0^ l.OOe^-293) C,
fl = — (7)
where:
^oo = emission rate from treated soil for covered period (kg/m2*sec)
9.2xlO's = numerical constant
0a = air-filled porosity in cover layer of soil (unitless)
1.006 = numerical constant
T = temperature (K) .
293 = 15°C (converted to K)
C, = concentration of pollutant fn air-filled pore space of sewage sludge/soil
mixture (kg/m3)
MW = molecular weight of pollutant (g/mole)
dc = depth of cover (m)
&a = total porosity of cover layer (unitless)
Equations 6 and 7 are based on the concentration of the pollutant in air-filled pore-space
within the monofill. As explained in Appendix B, this concentration can be related to the total
concentration of pollutant in the sewage sludge/soil mixture as:
Ct
BDKD ew fl w
H H *
where:
C, = concentration of pollutant in air-filled pore space of sewage sludge/soil
mixture (kg/m3)
C, = total concentration of pollutant in sewage sludge/soil mixture (kg/m3)
BD = bulk density of sewage sludge/soil mix (kg/m3)
KD = equilibrium partition coefficient for pollutant (m3/kg)
H . = Henry's Law constant (unitless at specified temperature)
0W = water-filled porosity in sewages sludge/soil mixture (unitless)
0, = air-filled porosity in sewage sludge/soil mixture .(unitless)
EPA combined estimated emissions from both an uncovered and a temporarily covered
raonofill cell to derive a time-weighted average rate of emissions from a monofill cell during the
facility's active lifetime:
5-11
-------
^ ^n -m + q» fco (9)
where: >
q^ = time-weighted average rate of emissions from typical raonofill cell over the
• active lifetime of the monofill (kg/in2*sec).
qua = rate of pollutant volatilization from an uncovered monofill cell !
(Kg/m2«sec)
futt = fraction of monofiU's active lifetime that typical cell contains uncovered
sewage sludge ;
q^ = emission rate from treated soil for covered period (kg/m2-sec)
fj = fraction of facility's active lifetime that typical cell contains sewage sludge
with temporary soil cover
By dividing the above estimated loss rate for volatile emissions by total pollutant mass;per
unit area in the filled monofill, EPA obtained a first-order loss rate coefficient:
f +
3.16xl07
A r<
df Ct
where:
3.16xl07
df
C
first-order loss rate coefficient for volatilization during facility's
active operation (yr"1) ;
time-weighted average rate of emissions from typical monofill cell
over the active lifetime of the monofill (kg/m2»sec)
conversion factor (sec) (yry1 ]
depth of a monofill cell (m) :
total concentration of pollutant in sewage sludge/soil mixture i
(kgAn3) !
In this equation, total pollutant mass is calculated by multiplying the depth of the monofill cell
by the total pollutant concentration.
Estimated coefficients for losses to volatilization and leaching are combined with an
assumed coefficient for losses to degradation (obtained from scientific literature) to yield a
"lumped" coefficient describing pollutant loss through all three pathways during the facility's
active lifetime:
where:
K,,
K,,
coefficient for total rate of pollutant loss through leaching, volatilization,
and degradation during facility's active operation (yr'1)
5-12
-------
K,.,. =
rate coefficient for loss of pollutant to leaching from monofill (yr1)
rate coefficient for loss of pollutant to volatilization from active raonofill
(yr1)
degradation rate coefficient for raonofill (yr'1)
The fraction of the total rate of pollutant loss attributable to each individual process
during the facility's active lifetime is then:
.-
KV,
K.
where:
K,,
fraction of total pollutant loss during facility's active operation attributable
to leaching (unitless)
rate coefficient for loss of pollutant to leaching from monofill (yr"1)
coefficient for total rate of pollutant loss through leaching, volatilization,
and degradation during facility's active operation (yr"1)
fraction of total pollutant loss during facility's active operation attributable
to volatilization (unitless)
rate coefficient for loss of pollutant to volatilization from active monofill
(yr-1)
fraction of total pollutant loss during facility's active operation attributable
to degradation (unitless)
rate coefficient for loss of pollutant to degradation from monofill (yr"1)
The fraction of total pollutant loading lost over the facility's active lifetime is calculated
as follows:
where:
f,c = fraction of total pollutant lost during monofill's active lifetime (unitless),
MU = mass of pollutant in soil at end of active lifetime of monofill (kg/ha)
LF = active lifetime of mono fill facility: the period in which the facility accepts
sewage sludge (yr)
5-13
-------
The variable M^ is a function of the lumped rate of pollutant loss and is evaluated as:
= 0
(t=0)
(lit^LF)
(14)
where:
Mt =
LF =
K,, =
mass of pollutant in soil at end of year t (kg/ha)
active lifetime of monofill facility: the period in which the facility accepts
sewage sludge (yr)
coefficient for total rate of pollutant loss through leaching, volatilization
and degradation during facility's active operation (yr"1) i
Once the facility's capacity is exhausted, a permanent cover layer of soil is applied to its
surface. This permanent cover reduces the rate of volatilization, changing both the total rate of
• pollutant loss and the fraction of that loss attributable to volatilization, leaching, or degradation^
Based on the increased thickness of cover, EPA calculated an estimated rate of volatilization
from the inactive monofill (K^) with Equations 9 and 10 by setting £„„ to zero. Rate coefficients
for loss to leaching and degradation were assumed to be unaffected by soil cover, so the lumped
rate of loss for the inactive monofill is described by:
where:
Kfee =
(15)
coefficient for total rate of pollutant: loss from inactive monofill (yr"x)
coefficient for.rate of pollutant loss through leaching from monofill (yr"1)
coefficient for rate of pollutant loss through volatilization from inactive
monofill (yr"1).
coefficient for rate of pollutant loss through degradation from monofill
The fraction of loss attributable to each individual process is calculated as:
5-14
-------
Kvi
(16)
where:
fii = fraction of total pollutant loss from inactive monoffll attributable to
leaching (unitless)
= rate coefficient for loss of pollutant to leaching from monofill (yr"1)
= coefficient for total rate of pollutant loss from inactive monofill (yr"1)
= fraction of total pollutant loss from inactive monofill attributable to
volatilization (unitless) „
= coefficient for rate of pollutant loss through volatilization from inactive,
monofill (yr'1)
= fraction of pollutant loss from inactive monofill that is lost to degradation
(unitless)
= coefficient for rate of pollutant loss through degradation from monofill
As discussed below, EPA used these fractions and the lumped rate coefficients for pollutant loss
to derive criteria for the vapor and ground-water pathways.
5.3.2. Methodology for Ground-Water Pathway
Derivations of pollutant limits for the ground-water pathway began with the calculation of
an adjusted reference water concentration for each pollutant of concern. EPA calculated this
value from the maximum- pollutant level (MCL) by subtracting an estimated background
concentration of the pollutant in ground water:
q, (17)
where:
RCp, = adjusted reference water concentration (mg/1)
MCL = maximum pollutant level (mg/1)
5-15
-------
Q, = average background concentration of pollutant in drinking water from
wells (mg/1)
Alternatively, if no MCL is available, the adjusted reference water concentration is
calculated (for carcinogenic pollutants) from a selected risk level and a human cancer potency:
(18)
qi RE
where:
= reference concentration for pollutant in ground water (mg/1)
RL = risk level (incremental risk of cancer per lifetime, unitless)
BW = human body weight (kg)
q," = human cancer potency (mg/kg-dayy1 or (kg -day/rag)
RE = relative effectiveness of exposure through ingestion (unitless)
!„ = total water ingestion rate (I/day) .
5.32.1 Simulating Flow and Pollutant Transport Through Unsaturated and Saturated Soil
Zones
In the next step, EPA used the reference water concentration of pollutant in well water
to calculate a reference concentration'of pollutant in seepage beneath the facility. Two
mathematical models were combined to calculate an expected ratio between these two ;
concentrations. The Vadose Zone Flow and Transport finite element module (VADOFT) from
the RUSTIC model (U.S. EPA, 1989a,b) was used to estimate flow, and transport through the
unsaturated zone, and the AT123D analytical model (Yeh, 1981) was used to estimate flow and
transport through the saturated zone.
VADOFT allows consideration of multiple soil layers, each with homogeneous soil
characteristics. Within the unsaturated zone, the attenuation of organic pollutants is predicted
based on longitudinal dispersion, an estimated retardation coefficient derived from an
equilibrium partition coefficient, and a first-order rate of pollutant degradation. The model is
executed in two steps; results from the unsaturated zone flow and transport module are passed as
input to the saturated zone module. The input requirements for the unsaturated zone module
include various site-specific and geologic parameters and the leaching rate from the bottom of
5-16 '
-------
the raonofill. It is assumed that the flux of pollutant mass into the top of the unsaturated zone
beneath a facility can be represented by results from the mass-balance calculations described
above. Results from analysis of the unsaturated zone give the flow velocity and concentration
profiles for each pollutant of interest. These velocities and concentrations are evaluated at the
water table, converted to mass fluxes for each pollutant, and then these fluxes are used as input
to the saturated zone module.
The flow system in the vertical column is solved with VADOFT, which is based on an
overlapping representation of the unsaturated and saturated zones. The water flux at the
soil/liquid interface is specified for the bottom of the impoundment, which defines the top of the
unsaturated zone in the model. In addition, a constant pressure-he'ad boundary condition is
specified for the bottom of the unsaturated zone beneath the lagoon. This pressure-head is
chosen to be consistent with the expected pressure head at the bottom of the saturated zone, * *
without consideration of the added flux leaching from sewage sludge in the monofill. Transport
in the unsaturated zone is determined using the Darcy velocity (Vj) and saturation profiles from
the flow simulation. From these, the transport velocity profile can be determined.
Although limited to one-dimensional flow and transport, the use of a rigorous finite-
element model in the unsaturated zone allows consideration of depth-variant physical and
chemical processes that would influence the mass flux entering the saturated zone. Among the
more important of these processes are advection (which is a function of the Darcy velocity,
saturation and porosity), mass dispersion, adsorption of the leachate onto solids, and both
chemical and biological degradation.
To represent the variably saturated soil column beneath the floor of the monofill, the
model discretizes the column into a finite-element grid consisting of a series of one-dimensional
elements connected at nodal points. Elements can be assigned different properties for the
simulation of flow in a heterogeneous system. The model generates the grid from user-defined
zones; the user defines the homogeneous properties of each zone, the zone thickness and the
number of elements per zone, and the code automatically divides each zone into a series of
elements of equal length. The governing equation is approximated using the Galerkin finite
element method and then solved iteratively for the dependent variable (pressure-head) subject to
5-17
-------
the chosen initial and boundary conditions. Solution of the series of nonlinear simultaneous
equations generated by the Galerkin scheme is accomplished by either Picard iteration, a |
Newton-Raphson algorithm or a modified Newton-Raphson algorithm. Once the finite-element
calculation converges, the model yields estimated values for all the variables at each of the
discrete nodal points. A detailed description of the solution scheme is found in U.S. EPA
(1989a).
One-dimensional advective-dispersive transport is estimated with VADOFT based on the
estimated mass flux of pollutant into the top of the soil column, and a zero concentration
boundary condition at the bottom of the saturated zone. Sewage sludge is assumed to be
deposited in the monofill for 20 years, followed by an inactive period in which pollutant is
tf
depleted from the monofill by leaching and volatilization. To simulate potential pollution of'^
ground water, the loading of pollutant into the unsaturated zone beneath the monofill is ;
"linearized" into a pulse of constant magnitude to represent the maximum annual loss of ;
pollutant (kg/ha-yr) occurring over the 300-year simulation period modeled. The duration of that
pulse is calculated so that pollutant mass is conserved. For monofills, the rate of maximum total
pollutant loss (kg/yr) will occur in the year immediately following the last deposit of sewage \
sludge since the total mass of pollutant at the site reaches its peak at that time. As explained in
Appendix C, this peak rate of loss could be maintained for a maximum length of time described
by: '
where:
TP = . length of "square wave" in which maximum total loss rate of pollutant
depletes total mass of pollutant applied to site (yr)
LF = active lifetime of raonofill facility: the period in which the facility accepts
sewage sludge (yr)
K^ = rate coefficient for total loss of pollutant during monofill's active lifetime
This result is used to prepare inputs for VADOFT, which predicts the concentration of
pollutant at the water table. The mass flux of pollutant into the saturated zone is evaluated at
the water table based on the derived concentration distribution and the Darcy velocity. The
5-18
-------
resulting mass flux from the VADOFT simulation is used as input for the AT123D model, which
simulates pollutant transport through the saturated zone. It is represented as a mass flux
boundary condition applied over a rectangular area representative of the facility's air-exposed
surface. The transient nature of the flux is represented by time-dependent levels interpolated
from the results generated by the VADOFT simulation of the unsaturated zone.
AT123D estimates the transport of pollutant through the saturated soil zone. As in
calculations for the unsaturated zone, degradation of organic pollutants is assumed to be first-
order during transport through the aquifer. Speciation and complexation reactions are ignored
for metals, leading to the possible over- or underestimation of expected concentrations of metals
in ground water at the location of a receptor well. Detailed descriptions of the AT123D model
are provided by Yeh (1981) and will not be repeated here. In general, the model provides an
analytical solution to the basic advective-dispersive transport equation. One advantage of .;
AT123D is its flexibility: the model allows the user up to 450 options and is capable of simulating
a wide variety of configurations of source release and boundary conditions.
For the current application, AT123D uses the source term and other input parameters to
predict concentrations of pollutant within 300 years in a receptor well at the downgradient edge
of the site (based on a unit concentration of 1 mg/1 in leachate from the monofill). The ratio of
these two concentrations is then:
fwel = qf (20)
where:
fwei = ratio of predicted concentration in well to concentration in leachate
(unitless)
Cw«i =' predicted concentration of the pollutant in well (mg/1)
Cfce = unit concentration of the pollutant in leachate (1 mg/1)
Because calculations in both the VADOFT and AT123D components of the ground-water
pathway model are linear with respect to the pollutant concentration in leachate beneath the site,
this ratio can be used to back-calculate a reference concentration of pollutant in leachate:
5-19
-------
where:
(21)
reference concentration of pollutant in leachate from the sewage sludge
monofill (rag/1)
reference concentration for pollutant in ground water (mg/1)
ratio of predicted concentration in well to concentration in leachate .
(unitless)
Next, multiplying this reference concentration (in mg/1) oy the assumed net recharge (in
m/yr) and adjusting units yields the reference flux of pollutant mass from the site.
10 RC. MR (22)
RF.
gv
where:
10
NR =
reference annual flux of pollutant to the unsaturated soil zone beneath the
surface disposal facility (kg/ha »yr)
conversion factor (kg/ha) ([mg-ra]/!)'1 ;
reference concentration for pollutant in leachate from sewage sludge
monofill (mg/1)
net recharge (m/yr)
This allowable flux must be related to the pollutant dry-weight concentration in sewage
sludge deposited in the monofill. Using the variables fu (which describes the maximum fraction
of total pollutant mass lost from the monofill through leaching) and TP (which provides an
estimate for the minimum amount of time required to release all significant pollutant), the
reference flux can be converted to an equivalent dry-weight concentration in sewage sludge:
RCS =
TPRF
where:
RCS
TP
10
:« =
(23)
f,,sc
reference dry-weight concentration of pollutant in sewage sludge (mg/kg)
length of "square wave" in which maximum total loss rate of pollutant
depletes total mass of pollutant at site (yr)
reference annual flux of pollutant to the unsaturated soil zone beneath the
surface disposal facility (kg/ha»yr)
conversion factor (kg)(rag)''
fraction of pollutant loss during monofilPs active lifetime that is lost to
leaching (unitless)
5-20
-------
SC = estimated dry mass of sewage sludge contained in one hectare of
completed monofill (kg/ha)
The diy mass of sewage sludge contained in one hectare of completed monofiH is
calculated by multiplying the facility's depth by the fraction of its volume containing pure sewage
sludge and the mass of solids per cubic meter of sewage sludge:
SC =
where:
SC =
MS =
104 =
and:
MS 104
(24)
_
estimated mass of dry sewage sludge contained in one hectare of
completed monofill (kg/ha)
depth of a monofill cell (m)
fraction of monofill's total volume containing pure sewage sludge (m3/m3
or unitless)
mass of solids in 1 rn3 of pure sewage sludge (kg/m3)
conversion factor (m2) (hay1 '
MS =
where:
MS =
pw
(25)
mass of solids in 1 m3 of pure sewage sludge (kg/m3),
fraction of solids in sewage sludge (kg/kg)
particle density of sewage sludge (kg/m3)
density of water (kg/m3)
5.3.3 Methodology for Vapor Pathway
Calculations of pollutant criteria for the vapor pathway begin with derivations of
reference air concentrations for each pollutant. Because all the pollutants under consideration
for this pathway are considered carcinogenic, the reference air concentration is calculated as:
where:
RClir =
RL =
RL BW 1000
'. ii'
reference air concentration for pollutant (/ig/m3)
risk level (incremental risk of cancer per lifetime)
5-21
(26)
-------
BW - average body weight (kg)
1000 = conversion factor (jig) (mg)-1
In - inhalation volume (m3/day)
qt" = human cancer potency (mg/kg'day)'1
The next step is to relate releases of volatilized pollutant to expected concentrations in
ambient air. The model used to simulate transport of volatilized pollutant from a surface :
disposal site is described by U.S. EPA (1986d) and is based on equations provided by
Environmental Science and Engineering (1985). The highly exposed individual (HEI) is assumed
to live at the downwind property boundary of the monofill site. A source-receptor ratio is
calculated to relate the concentration of pollutant in ambient air at the HEFs location (g/m3) to
the rate at which that pollutant is emitted from the facility (g/m2-sec).
SRR = 2.032 — (27)
/ / \
(r + *y) U °z
where: !
SRR = source-receptor ratio (sec/m)
2.032 = empirical constant transferred from the literature source of the equation
A = area of monofill (m2) i
v = vertical term (unitless)
r' = distance from the center of monofill to receptor (m) >
x, = lateral virtual distance (m) |
a) = wind speed (m/sec)
<7Z = standard deviation of the vertical distribution of concentration (m) !
The vertical term (v) is a function of source height, the mixing layer height, and az.
Under stable conditions the mixing layer height is assumed infinite, and for a pollutant release
height of zero, v=l. The lateral virtual distance is the distance from a virtual point source tb the
monofill such that-the angle 0 subtended by the monofill's width is 22.5°. This distance is
calculated as:
* - FA cot e (28)
^'Nl* 2
where:
Xy = lateral virtual distance to receptor location (m)
A • = surface area of surface disposal facility (rn2)
6 = angle subtended by width of disposal site at distance equal to estimated
virtual distance from site (degrees)
I
5-22 :
-------
The standard deviation of the vertical distribution of concentration (aj is defined by an
atmospheric stability class and the distance from the center of the monofill to the receptor.
Based on values for parameters a and b listed for stable atmospheric conditions in Table 5-1,
-------
TABLE 5-1
PARAMETERS USED TO CALCULATE tr*
Pasquill Stability Category x (km)
Stable 0.10 - 0.20
0.21 - 0.70
0.71-1.00
1.01 - 2.00
2.01 - 3.00
3.01 - 7.00
7.01 - 15.00
15.01 - 30.00
30.01 - 60.00
> 60.00
a
15.209
14.457
13.953
13.953
14.823
16.187
17.836
22.651
27.084
34.219
b 1
0.81558 :
0.78407 :
0.68465 :
0.63227
0.54503
0.46490
0.41507 : „
t *
0.32681 -
0.27436 ;
0.21716
* at calculated as crI=axb where x is distance in km.
Source: Environmental Science and Engineering (IS'85).
5-24
-------
* VI-
where:
f^ = fraction of pollutant mass which volatilizes over a human lifetime
(unitless)
^ = fraction of pollutant loss during monofilPs active lifetime that is lost to
volatilization (unitless)
f,c = fraction of total pollutant loading lost during active operation of monofill
facility (unitless)
fvi = fraction of total pollutant loss from inactive monofill attributable to
volatilization (unitless)
K,j = rate coefficient for total loss of pollutant from inactive monofill (yr"1)
LS = lifespan of average individual (yr)
LF = active lifetime of monofill facility: the period in which the facility accepts
sewage sludge (yr)
This result is combined with the reference annual flux of pollutant (Equation 31) and the
estimated mass of dry sewage sludge per hectare of monofill (Equation 24) to calculate a
reference concentration of pollutant in monofilled sewage sludge:
RCS . "* " 10< (33,
• <*sc
where:
RCS = reference concentration of pollutant in sewage sludge for the volatilization
pathway (mg/kg dry weight)
. RF.J, = reference annual flux of pollutant to air above the site (kg/ha »yr)
LS = lifespan of average individual (yr)
10* = conversion factor (rag) (kg)*1
fv,, = fraction of pollutant mass which volatilizes over a human lifetime
(unitless)
SC = mass of sewage sludge contained in one hectare of surface disposal facility
(kg/ha)
5-25
-------
534 Monofill Prototype Sample Calculations for Pollutant Criteria
53.4.1 Mass Balance Calculations
The methodology described above is illustrated with sample calculations for benzene.
Sample calculations are described to two significant figures, except in cases where additional
precision further clarifies the methodology. Actual calculations are performed with eight-byte
"double" precision, leading to occasional discrepancies between actual results and the calculations
described here. ;
5-3.4.1.1 Pollutant Losses Through Leaching ,:
A coefficient for the rate at which benzene is lost to leaching is calculated as:
„ NR(m/yr) ;
[BD(kg/m3) KD(m3/kg)+6w+H 6,] df(m)
(0.5)
[(1400) (0.033) + (0.2) + (0.23) (0.2) ] (3.46)
= 0.0031 (yr'1)
where:
Kfce = loss rate coefficient for leaching (yr1)
NR = annual recharge to ground water beneath the monofill (m/yr)
BD = bulk density of sewage sludge/soil mixture (kg/m2)
KD = equilibrium partition coefficient for the pollutant (m3/kg)
0w = water-filled porosity of sewage sludge/soil mixture (unitless)
H = - nondimensional Henry's Law constant for the pollutant
0t ~ air-filled porosity of sewage sludge/soil mixture (unitless)
df = depth of a raonofill cell (m)
In this equation, the non-dimensional Henry's Law constant is calculated as:
5-26
-------
H(atm«m3/inol)
H = -
R(atm«m3/mol»°K)
= (0.0054) (35)
(8.21xlO-5)(288)
= 0.23
where:
H = nondimensional Henry's Law constant for the pollutant
H = Henry's Law constant for the pollutant (atm»m3/mol)
R = ideal gas constant (821xlQ's m3»atra/mol»K)
T = temperature (K)
5.3.4.1.2 Pollutant Losses Through Volatilization
'-
It is assumed that each monofill cell receives deposits of sewage sludge on each of three
consecutive days. Each deposit is uncovered for a total of four hours before application of a
daily cover of soil. The time that an individual cell is uncovered (in years) is then:
_ _J4+4+4)(hr)
8.776 x ^(hr/yr) (36)
= 1.4xlO-3(vr)
where:
t^ = time that each individual monofill cell contains uncovered sewage sludge
(yr)
The fraction of the facility's active lifetime that a typical cell will be uncovered is
calculated as:
5-27
-------
_ (1.4xlQ-3)
(20)
= 6.8xl
f~-f-c '•
. I - 6.8x10- <38>
2
= 0.49993
I
where: '
fa, = fraction of facility's active lifetime that typical cell contains sewage sludge
with temporary soil cover (unitless)
faa • = fraction of facility's active lifetime that a typical cell contains sewage
sludge without soil cover (unitless)
Equations 7 and 8 (reproduced in these sample calculations as equations 40 and 41) are
based on the concentration of pollutant in air-filled pore space within the monofill. This '
concentration can be related to the total concentration of pollutant in sewage sludge/soil
(arbitrarily set to 1 kg/m3) as:
5-28
-------
Ct(kg/m3)
BD(kg/m3)KD(m3/ig) , 6w , g
H H '
(1) (39)
(1400) (0.033) , (0.2) ^
(0.23) (0.23)
= 0.0050(kg/m3)
where:
Ca = vapor concentration of pollutant in air-filled pore space, of treated soil
(kg/m3)
C, = total concentration of pollutant in sewage sludge/soil mixture (kg/ra3)
BD = bulk density of sewage sludge/soil mixture (kg/m2)
KD = equilibrium partition coefficient for the pollutant (m3/kg)
H = nondimensional Henry's Law constant for the pollutant
0W = water-filled porosity of sewage sludge/soil mixture (unitless)
0, = air-filled porosity of sewage sludge/soil mixture (unitless)
Emissions from an uncovered landfill cell are described by:
_ 0.17 co(m/sec) (p.994)V™-2 (0.0050)
= 4.4xlO~4(kg/m2»sec)
where:
qoa = emission rate from treated soil during uncovered period
(kg/m2 • sec)
0.17 = empirical constant transferred from literature source of equation
a = wind speed (m/sec)
0.994 = empirical constant transferred from literature source of equation
. T = temperature (K)
293 = 15°C (converted to K)
C, = concentration of pollutant in air-filled pore space of sewage sludge/soil
mixture (kg/ra3)
MW = molecular weight of pollutant (g/mole)
For a cell with soil cover:
5-29
-------
9.2xl(T5 e^ l.&XF™-*3* Ca(kg/m3)
dc(m) 6*
= 4.9xlO~9(kg/m2«sec) !
where:
q,.,, = emission rate from treated soil for covered period (kg/m2«sec)
9.2xlO's = empirical constant transferred from literature source of equation
0a = air-filled porosity of cover layer (unitless)
1.006 = empirical constant transferred from literature source of equation
C, = concentration of pollutant in air-filled pore space of sewage sludge/soil
mixture (kg/ra3) „
MW = molecular weight of pollutant (g/mole)
dc = depth of cover (m)
6a = total porosity of cover layer (unitless)
Estimated emissions from uncovered and temporarily covered mono fill, cells are combined
to derive a time-weighted average rate of emissions from a monofill cell during the facility's
active lifetime: :
= (4.4xlO-4)(6.8xlO-5) f (4.9xlO-9)(0.50)
where: . . ,
q,c — time-weighted average rate of emissions from typical landfill cell over the
active lifetime of the monofill (kg/ra2* sec)
qM s - rate of pollutant volatilization from an uncovered monofill cell (g/m2»sec)
f,, = fraction of monofuTs active lifetime that typical cell contains uncovered
sewage sludge (unitless)
Qo, = emission rate from treated soil for covered period (kg/mz»sec)
fa, = fraction of facility's active lifetime that typical cell contains sewage sludge
and temporary soil cover (unitless)
The estimated loss rate is converted to a first-order loss coefficient as:
5-30
-------
_ q«.(kg/m3-sec) 3.16xl07
= d^rnX:,
_ (3.3xlQ-8) 3.16xl07 (43)
where:
K,, = first-order loss rate coefficient for volatilization during facility's
active operation (yr"1) -
q^ = time-weighted average rate of pollutant volatilization from a
rnonofill (g/ra2«sec)
3.16xl07 = conversion factor (sec'1) (yr'1)
d{ = depth of a monofill cell (m)
. C, = total concentration of pollutant in sewage sludge/soil mixture
(assumed to be 1 kg/m3) ^
Estimated coefficients for losses to volatilization and leaching are combined with an
assumed rate of degradation to yield a "lumped" coefficient describing the total rate of pollutant
loss through all three pathways during the facility's active lifetime:
= (0.0031) + (0.300) + (0) (44)
= 0.303 (yr-1)
where:
K,, = coefficient for total rate of pollutant loss through leaching, volatilization,
and degradation during facility's active operation (yr'1)
= rate coefficient for loss of pollutant to leaching from monofill (yr"1)
= rate coefficient for loss of pollutant to volatilization from active monofill
degradation rate coefficient for monofill (yr"1)
The fraction of total pollutant loss attributable to each individual process during the
facility's active phase is then:
5-31
-------
(0.303)
0.01
= ^0300) = (45
(0-303)
= ^ = __
dt -) (0.303)
where:
fh = fraction of total pollutant loss during facility's active operation attributable
to leaching (unitless) I
» rate coefficient for loss of pollutant to leaching from monofill (yr1)
= rate coefficient for total loss of pollutant during monofilPs active lifetime
(yr-1)
= fraction of total pollutant loss during facility's active operation attributable
to volatilization (unitless)
= rate coefficient for loss of pollutant to volatilization from active monofill
= fraction of total pollutant loss during facility's active operation attributable
. to degradation (unitless)
= degradation rate coefficient for monofill (yr"1) '
The fraction of total pollutant loading lost during the facility's active lifetime is calculated
as follows: [
LF
(20)
= 0.86
where: !
f^ = fraction of total pollutant lost during facility's active lifetime (unitless)
MJJ, = mass of pollutant in soil at end of rnonofill's active lifetime of operation
(kg/ha)
LF = number of years sewage sludge is deposited in monofill (yr) ;
The variable MID is evaluated as follows:
5-32
-------
= 0
M,
where:
M,
K,,
LF =
to yield:
where: •
^ + 1] e
"*"
(t=0)
(UtsLF)
(47>
mass of pollutant in soil at end of year t (kg/ha)
coefficient for total rate of pollutant loss during monofiU's active lifetime
of operation (yr"1)
active lifetime of monofill facility: the period in which the facility accepts
sewage sludge (yr)
= 2.8
(48>
mass of pollutant in soil at end of monofiU's active lifetime of operation*
(kg/ha)
Thus, Equation 46 shows that about 86 percent of the mass of benzene in sewage sludge
disposed of in the monofill is expected to be lost during the 20 years the facility receives sewage
sludge.
Upon closure of the monofill, a permanent soil cover one meter deep is applied. The
emission rate after closure is therefore reduced as follows:
9.2xlO
-5
C,(g/m3)
9.2x lQ-5-(0.2)(UV3) 1.006g88"293) (0.0050)
V/(7O)(1)(0.4)2
(49}
v '
= 1.5x10-* (kg^m2- sec)
where:
q,,,
9.2X10"6
6a
1.006
T
293
emission rate from treated soil for covered period (kg/m2»sec)
empirical constant transferred from literature source of equation
air-filled porosity of cover layer (unitless)
empirical constant transferred from literature source of equation
temperature (K)
15°C (convened to K)
5-33
-------
C.
MW
d,.
0
concentration of pollutant in air-filled pore space of sewage
sludge/soil mixture (kg/m3)
molecular weight of polluitant (g/raole)
depth of cover (m)
total porosity of cover layer (unitless)
This rate of emissions is converted to a first-order loss coefficient as:
qco(kg/m2-sec)3.16x!07
where:
(l-5xl(T9)3.16xl07
(3.46)
= 0.013 (yr-
3.16xl07
d,
rate coefficient for loss of pollutant to volatilization from inactive
rnonofill (yr'1)
emission rate from treated, soil for covered period (kg/m2 • sec)
conversion factor (sec'1) (yr1)'1
depth of a monofill cell (m)
Rate coefficients for losses to leaching and degradation are assumed to be unaffected by
soil cover. The lumped rate of loss for the inactive monofill is therefore described by:
K,.
= (0.0031) + (0.013) + (0)
= 0.017 (yr-1)
(51)
where:
coefficient for total rate of pollutant loss from inactive monofill (yr"1)
rate" coefficient for loss of pollutant to leaching from monofill (yr"1)
coefficient for rate of pollutant loss through volatilization from inactive
monofill (yr"1)
degradation rate coefficient for monofill (yr"1) !
The fraction of loss from an inactive monofill attributable to each individual process is
calculated as:
5-34
-------
f
11 -) (0.016)
(0.016)
f -5^2 - (Q)
(52)
) (0.016)
where:
fu = fraction of total pollutant loss from inactive monofill attributable to
leaching (unitless)
Kfa. = rate coefficient for loss of pollutant to leaching from monofill (yr"1)
Ktf = coefficient for total rate of pollutant loss from inactive raonofill (yr"1)
f^ = fraction of total pollutant loss from inactive raonofill attributable to
volatilization (unitless)
K^ = coefficient for rate of pollutant loss through volatilization from inactive
monofill (yr'1)
fa = fraction of total pollutant loss from inactive monofill attributable to
degradation (unitless)
degradation rate coefficient for monofill (yr"1)
5.3.4.2 Pollutant Criteria Calculations for Ground-Water Pathway
Derivation of criteria for the ground-water pathway begins with the calculation of an
adjusted reference water concentration. For benzene, this value is calculated from the pollutant
level by subtracting an estimated background concentration of the pollutant in ground water
(assumed to be zero):
=MCL(mg/l)-Cb(mgyi)
= (0.005) -'(0) (53)
= 0.005 (mg/1)
where:
RC^ = reference concentration for pollutant in ground water (mg/1)
MCL = maximum pollutant level for drinking water (rag/1)
Q, = average background concentration of pollutant in drinking water from
wells (mg/1)
5-35
-------
The next step is to use the adjusted reference water concentration of pollutant in well
water to calculate a reference concentration of pollutant: in leachate beneath the facility. The
maximum rate of pollutant loss for a monofill (kgtyr) will occur in the year immediately following
the last deposit of sewage sludge, since the total mass of pollutant at the site reaches its peak at
that time. For benzene, this peak rate of loss could be maintained for a maximum length of time
described by:
r
TT , LFfri)
(20) <54>
1 _e-
-------
where:
fwel
_ (0.005)
(0.31)
= 0.016 (mg/1)
(56)
reference concentration of pollutant in water leaching from the monofill
reference concentration for pollutant in ground water (kg/nr)
ratio of pollutant concentration in well-water to concentration in leachate
beneath the surface disposal facility (unitless)
Next, multiplying this reference concentration (in mg/1) by the assumed net recharge (in
i
m/yr) and adjusting units yields, the reference flux of pollutant mass from the site can be ' '
calculated:
where:
10
(57)
NR =
10 RC^mg/l) NR(m/yr)
10 (0.016) (0.5)
0.08 (kg/ha- yr)
reference annual flux of pollutant beneath the site (kg/ha»yr)
conversion factor ([mg»m]/l) (kg/ha)'1
reference concentration for pollutant in leachate from sewage sludge
monofill (kg/m3)
net recharge (m/yr)
The mass of solids contained in 1 ra3 of pure sewage sludge is calculated as:
MS =
(0^) (1200) (1000)
(58)
(0^)(1000) + (1-0.2) (1200)
= 210(kg/m3)
5-37
-------
where:
MS s mass of solids in one m3 of pure sewage sludge (kg/m3)
4,, = fraction of solids, in sewage sludge (by mass, kg/kg)
pA = particle density of sewage sludge (kg/m3)
pw = density of water (kg/m3)
The mass of sewage sludge in one hectare of landfill is:
SC - df fd MS 10*
=(3.46) (0.64) (210) 104
= 4.6xl06(kg/ha)
where: ,
SC = estimated mass of sewage sludge contained in one hectare of completed
monofill (kg/ha)
df = depth of a raonofill cell (m)
fj = fraction of raonofill's volume containing sewage sludge (unitless)
MS = mass of solids in one m3 of pure sewage sludge (kg/m3)
104 » conversion factor (1/m2) (1/ha)'1
The reference flux is converted to an equivalent concentration in sewage sludge by: i
TP(yr) RF^Qcg/ha-yr) 10*
fuSC(kg/faa)
= (20.0) (0.08) 106 (60)
(0.01)(4.6xl06)
= 34(mg/kg)
where:
RCS = __ reference dry-weight concentration of pollutant in sewage sludge (mg/kg)
TP = length of "square wave" in which maximum total loss rate of pollutant
depletes total mass of pollutant at site (sec or yr) i
RFp, = reference annual flux of pollutant to the unsaturated soil zone beneath the
surface disposal facility (kg/ha«yr)
10s = conversion factor (kg) (mg)~l
fh = fraction of pollutant loss during monofilPs active lifetime that is lost to
leaching (unitless)
SC = mass of sewage sludge contained in one hectare of surface disposal facility
(kg/ha)
5-38
-------
5J.4J Pollutant Criteria Calculations for Vapor Pathway
Calculation of numerical criteria for the vapor pathway begins with the derivation of a
reference air concentration for benzene:
RC = RL BWQcg) 1000
I,(m3/day) q^mg/kg-day)
= (1Q-4) (70) 1000 (61)
(20) (0.029)
= 12(ug/m3)
where:
RCJir = reference air concentration for pollutant (ng/m3)
RL = risk level (incremental risk of cancer per lifetime)
BW = body weight (kg) - .-*
I, = inhalation volume (m3/day)
q/ = human cancer potency (kg»day»mg)
1000 = conversion factor (mg)
The next step is to relate releases of volatilized benzene to the expected concentration in
ambient air, based on a source-receptor ratio calculated to relate the concentration of pollutant
in ambient air at the HEI's location to the rate that pollutant is emitted from the facility. The
appropriate value for the standard deviation of the vertical distribution of pollutant concentration
is calculated as:
x = 0.001 r'(m) = 0.001(50) = 0.05 (km) (62)
where:
x = intermediate variable for Equation 63
r' = . distance from the monofill center to the receptor (m)
and:
oz = a xb = 15.209(0.05)(081538) = 1.3(km) (63)
where:'
oz = standard deviation of the vertical concentration distribution (m)
a,b = empirical constants
x = intermediate variable
5-39
-------
The vertical term v is a function of source height, the mixing layer height, and yf Under
stable conditions the mixing layer height is assumed infinite and for a pollutant release height of
zero, v equals one. The lateral virtual distance is the distance from a virtual point source to the
monofill, such that the angle 9 subtended by the monofill's width, is 22.5°. This distance is
calculated as:
^ 3.14 ( 2
= 284(m)
(64)
-cot - ^
where:
Xy = lateral virtual distance to receptor location (m)
A = surface area of surface disposal facility (m2)
0 = angle subtended by width of disposal site at distance equal to estimated
virtual distance from site (degrees)
The source-receptor ratio is calculated as:
A(m2) Q(m/sec)
SKR = 2.032
. 2.032 (^OQOKD
o> oz(m)
(65)
[(50)+(284)](4.5)(1.3)
= 10(sec/m)
where:
SRR ss " source-receptor ratio (sec/rn)
2.032 = empirical constant transferred from literature source of equation
A = area of monofill (ra2)
v = vertical term (unitless)
r' = distance from the monofill center to the receptor (m)
x^ = lateral virtual distance (ra)
w = wind speed (m/sec)
az = standard deviation of the vertical concentration distribution (m)
5-40
-------
The source-receptor ratio is combined with the reference air concentration to calculate a
reference annual flux of pollutant:
316
SRR(sec/m)
= 316(12) (66)
(10)
= 370(kg/ha-yr)
where:
RFair = reference annual flux of pollutant emitted from the site (kg/ha »yr)
316 = conversion factor (;tg/m2»sec) (kg/ha'yr)"1
RCair = reference air concentration for pollutant (/tg/m3)
SRR = source-receptor ratio (sec/m)
•»
The reference annual flux of pollutant is calculated by considering the maximum fractio'n
of total pollutant mass expected to be lost during the equivalent of a human lifetime, as well as
the fraction of that loss attributable to volatilization:
= (0.99X0.86) --^01^0-20' (67)
= 0.91
where:
fvb = fraction of pollutant mass which volatilizes over a human lifetime
(unitless)
t, = fraction of pollutant loss during monofiU's active lifetime that is lost to
volatilization (unitless)
fac = . fraction of total pollutant loading lost during active operation of monofill
facility (unitless)
IQ = - rate coefficient for total loss of pollutant from inactive monofill (yr'1)
LS = lifespan of average individual (yr)
LF = active lifetime of monofill facility: the period in which the facility accepts
sewage sludge (yr)
This result is combined with the reference annual flux of pollutant and the estimated
mass of sewage sludge in one hectare of monofill (Equation 59) to calculate a reference
concentration of pollutant in monofilled sewage sludge:
5-41
-------
RCS
where:
RF^Qcg/ha-yr) LS(yr) 106(mg/kg)
(370) (70) 10*
(0.91) (4.6x10*)
6100(mg/kg)
1(68)
RCS =
LS
106
sc
reference concentration of pollutant in sewage sludge for volatilization
pathway (rag/kg dry weight)
reference annual flux of pollutant to air above the site (kg/ha »yr)
lifespan of average individual (yr)
conversion factor (kg) (rag)'1 I
fraction of pollutant mass which volatilizes over a human lifetime
(unitless) . ,.:
mass of sewage sludge contained in one hectare of surface disposal facility
(kg/ha) ;
5.4 RISK ASSESSMENT METHODOLOGY FOR SURFACE IMPOUNDMENT
PROTOTYPE
Algorithms for deriving pollutant criteria for sewage sludge placed in a prototype surface
impoundment are based on methods described in U.S. EPA (1990a), to which the reader is
referred for a more detailed discussion. The present methodology refines that earlier work with
its inclusion of "mass balance" calculations to partition pollutant losses among competing loss
processes within the impoundment.
5.4.1 Methodology for Mass Balance
Pollutants in sewage sludge are assumed to enter the surface impoundment facility
through continuous inflow and to be removed through four general processes:
1) pollutant is lost to degradation within the unit (e.g., by photolysis, hydrolysis, or
microbial decay),
5-42
-------
2) pollutant is transported out of the unit by seeping through the floor of the
impoundment,
3) pollutant is lost through outflow (possibly for return to the treatment works), and
4) pollutant volatilizes from the liquid surface of the impoundment.
A mathematical model for describing these four processes has been adapted from a two-
layer model by Thomann and Mueller (1987) initially developed for modeling toxic substances in
a lake. For the water column of a lake, those authors consider the inflow and outflow of
pollutant, diffusive exchange between the sediment layer and the water column, degradation,
volatilization, settling of particulate toxicant from the water column to the sediment, and re-
suspension of particulate from the sediment layer to the water column. For the sediment layer,
they consider diffusive exchange with the water column, decay processes, particulate settling from
<*
the overlying water column, re-suspension flux from the sediment because of water column, and-
loss of toxicant from the sediment due to net sedimentation or burial.
The methodology for deriving pollutant limits for sewage sludge uses a similar two-layer '
model. The "liquid" layer begins at the surface and has the same average solids content as inflow
to the facility. The "sediment" layer beneath has a higher solids content. Although a gradient of
solids concentrations is likely to form in an actual impoundment, the two-layer model assumes
each layer is horagenous with respect to both solids .and pollutant concentrations.
Thomann and Mueller provide explicit equations for predicting settling velocities for
particulate and rates of diffusive exchange between the two layers. The present methodology
derives simpler equations by making a number of simplifying assumptions: First, it is assumed
that the sediment "layer will eventually reach the surface of the impoundment. Second, it is
assumed that outflow contains negligible concentrations of suspended solids. Third, all loss
processes are approximated as proportional to pollutant concentration. In other words, the loss
rate at any given time is assumed to be proportional to the pollutant concentration in the
impoundment at that time. Fourth, concentrations of pollutant within each layer are assumed to
have reached steady-state and to be partitioned at equilibrium between adsorbed and dissolved
phases. And finally, rates of pollutant transfer and loss at the time that impoundment is half
5-43 '
-------
filled with sediment are assumed to be typical of the facility both before and after it fills witij
sewage sludge solids. ;
If rates of loss to effluent, volatilization, seepage, and degradation are all proportional to
pollutant concentration, the maximum total rate of loss will occur should equilibrium
concentrations be attained. Moreover, after the continuous deposition of sewage sludge to the
facility is terminated, the rates at which pollutant is lost to seepage and volatilization should
decline. By assuming that equilibrium conditions are representative of the entire (active and
inactive) lifetime of the surface impoundment facility prototype, this methodology probably
overestimates rates of pollutant loss through seepage and volatilization, leading to conservative
criteria for this prototype.
5.4.1.1 Pollutant Losses from Liquid Layer
The concentration of pollutant in the inflow of the impoundment (Q) and in the liquid
layer (Ct) are assumed to remain constant throughout the facility's active lifetime. The
partitioning of pollutant in the liquid layer is described as:
. + DVq (69)
where:
Q; = rate at which sewage sludge enters the impoundment (m3/sec)
Q = concentration of pollutant in inflow to the impoundment (kg/m3)
Q0 = rate at which outflow leaves the impoundment (m3/sec)
fd! — fraction of total pollutant in liquid layer that is dissolved (unitless)
GI = total concentration of pollutant (adsorbed and dissolved) in liquid layer
= rate of pollutant degradation in liquid layer (sec'1)
A as surface area of impoundment (m2)
dt = depth of liquid layer (ra)
KTOU = rate of pollutant volatilization from liquid layer (m/sec) ;
Qiee = rate of seepage beneath the impoundment (m/sec)
DV — rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (m3/sec) I
Because the total depth of the impoundment (including both liquid and sediment layers) is
assumed constant, the depth of the liquid layer is reduced as more sewage; sludge accumulates in
5-44
-------
the sediment layer. If the rate at which the sediment accumulates is constant over the active
lifetime of the facility, the rate of accumulation can be determined by dividing the total volume
of the impoundment by its expected active lifetime:
DV = -2S2 (70)
TF
where:
DV = rate at which sediment accumulates (ra3/sec)
d,,,, = total depth of impoundment (m)
A = surface area of impoundment (m2)
TF = estimated active lifetime of facility (sec)
The active lifetime of the facility is calculated as:
TF = ^SL^l <7f)
where:
TF = estimated active lifetime of facility (sec)
dto, = total depth of impoundment (ra)
A = surface area of impoundment (m2)
S2 = concentration of solids in sediment layer (kg/m3)
Qi = rate at which sewage sludge enters the impoundment (m3/sec)
St = concentration of solids in liquid layer (kg/m3)
For the first term on the right of Equation 69 [Q^C^], the volume of outflow from the
facility (Q0) is calculated to be consistent with assumptions about rates of inflow, seepage, and
accumulation of the sediment layer as follows:
l--^-) (72)
•( PslJ "" I PdJ .
where:
Q0 = rate at which outflow leaves the impoundment (m3/sec)
Qi — rate at which sewage sludge enters the impoundment (m3/sec)
St = concentration of solids in liquid layer (kg/ra3)
p,, = particle density of sewage sludge (kg/m3)
Q^P = seepage rate for both liquid and sediment layers (m/sec)
A = surface area of impoundment (m2)
DV = rate at which sediment accumulates (m3/sec)
S2 = concentration of solids in sediment layer (kg/m3)
5-45
-------
Hie concentration of solids in the liquid and sediment layers is calculated from
parameters describing the percent solids (by mass) in each layer:
s,-
where:
PA
Pw
PI
concentration of solids in liquid layer (kg/m3)
particle density of sewage sludge (kg/m3)
density of water (kg/m3)
percent solids (by mass) in liquid layer (kg/kg)
concentration of solids in sediment layer (kg/m3)
percent solids (by mass) in sediment layer (kg/kg)
(73)
In each layer pollutant is partitioned between adsorbed and dissolved phases. As
discussed earlier, the partitioning depends on both the pollutant-specific partition coefficient and
the concentration of solids in the layer:
fdl
fpl
1 -«• KD S,
(74)
1-f
dl
where:
KD
Si
fraction of pollutant dissolved in the liquid layer i
pollutant-specific partition coefficient (m3/kg)
concentration of solids in liquid layer (kg/m3)
fraction of pollutant in liquid layer of surface impoundment adhering to
solid particles (unitless) \
The second term on the right side of Equation 69 [K^Ad^J describes the rate of
degradation of the pollutant in the liquid layer (through photolysis, hydrolysis, microbial decay,
and other processes). Values for K^^ are taken from studies of anaerobic microbial degradation
and are applied to pollutant in both dissolved and adsorbed phases.
The third terra on the right side of Equation 69 [K^f^AQ] describes pollutant loss from
the liquid layer through volatilization. This terra is the only part of Equation 69 that is directly
5-46
-------
linked with human exposure. The overall mass transfer coefficient for volatilization (K^j) is
calculated with a two-film resistance model (Thoraann and Mueller, 1987) in which the overall
resistance equals the sum of the liquid and gas phase resistances:
_L. = -I *
Kvoll Kl
where:
Kl HKg
KVOU — overall mass transfer coefficient for volatilization (m/sec)
K, = mass transfer coefficient for (the liquid later (m/sec)
R = ideal gas constant (821xlO'satm»m3/K»mol)
T = temperature (K)
H = Henry's Law constant for pollutant (atm»m3/mol)
Kg = mass transfer coefficient for gas layer (m/sec)
Numerous methods for calculating K, and Kg for water surfaces have been proposed (see,
e.g., Hwang, 1982; Hwang and Thibodeaux, 1982; MacKay and Leinohen, 1975; MacKay and *•
Yeun, 1983; Shen, 1982; Springer et al., 1984; U.S. EPA, 1987a; U.S. EPA, 1989c). This
methodology follows an approach described in U.S. EPA (1987a, 1989c) for estimating
volatilization from surface impoundments. The selection of appropriate equations for calculating
mass transfer coefficients depends on two characteristics of the site: (1) the ratio of the
impoundment's effective diameter (or "fetch") to its depth and (2) the local average wind speed.
Effective diameter (in meters) is defined as the diameter of a circle with area equal to that of the
impoundment. Depth is defined as that of the liquid layer. For the purpose of this calculation it
is assumed to average half of the impoundment's total depth. The ratio of fetch to depth is
therefore calculated as:
4.---
FD = -1
where:
de = effective diameter (or fetch) of site (m)
" A = surface area of impoundment (m2)
FD = ratio of fetch to depth (unitless)
d! = depth of liquid layer (rn)
5-47
-------
For fadlities where the average wind speed 10 m above the liquid surface is greater than 3.25
ra/sec and FD s 512 (as in the scenario used for the surface impoundment prototype): \
„ /n \2P . :
K, = 2.611xlO-7 Uj, -Z (77)
\D«*/
where:
K! = mass transfer coefficient for the liquid layer (m/sec)
U10 = average wind speed 10 m above surface (m/sec) :
Dw = diffusivity of pollutant in water (cmz/sec)
Detk = diffusivity of diethyl ether in water (cmz/sec)
Calculation of the mass transfer coefficient for the gas phase is based on Hwang (1985).
For all values of FD and U10, K, (m/sec) is calculated from:
Kg = LSxlO-Xo78 Sc,-0'67 de-*11 (78)
where:
K, = mass transfer coefficient for gas layer (m/sec)
UK, = average wind speed 10 m above surface (m/sec)
Sc8 = Schmidt number on gas side (unitless) '••
where Sct equals the Schmidt number on the gas side, defined as: >
Sc, = -^- (79)
8 P.D.
and where:
SCj = Schmidt number on gas side (unitless)
/^ = viscosity of air (g/cm" sec)
p, = density of air (g/cm3)
• D,., = diffusivity of pollutant in air (cm2/sec)
Equations 75 through 78 are sufficient to estimate K^, the overall mass transfer coefficient for
the volatilization of the poilutant. \
The fourth term on the right side of Equation 69 [QjecfdtACJ describes losses of dissolved
pollutant (p. 5-49) from the liquid layer as a result of the seeping through the sediment layer and
the floor of the impoundment. The rate of leachate (Q^p) is based on measured values from
sewage sludge lagoons. Only dissolved pollutant is included in this term. The fifth term of the
5-48
-------
equation [DVCj] describes loss of adsorbed pollutants from the liquid layer as a result of the
diminishing volume of that layer.
All terms on the right side of Equation 69 are proportional to the concentration of
pollutant in the liquid layer. A coefficient for the total rate at which pollutant mass is lost from
the liquid layer (K^, in m3/sec) can be defined as:
+ DV
(80)
where:
Q0
fdl
DV =
so that:
where:
QA -
lumped rate coefficient for pollutant loss from the liquid layer of surface
impoundment (m3/sec)
rate at which outflow leaves the impoundment (m3/sec)
fraction of total pollutant in liquid layer that is dissolved (unitless)
rate of pollutant degradation in liquid layer (sec'1)
depth of liquid layer (m) ( »
surface area of impoundment (m2) "
rate of pollutant volatilization from liquid layer (m/sec)
rate of seepage beneath the impoundment (m/sec)
rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (ra3/sec)
(81)
Q; = rate of inflow for sludge into a surface impoundment (m3/sec)
Q = concentration of pollutant in inflow to surface impoundment (kg/m3)
K,,,,! = lumped rate coefficient for pollutant loss from the liquid layer of surface
impoundment (m3/sec)
C, = concentration of pollutant in liquid layer of surface impoundment (kg/m3)
Because all estimated rates of pollutant loss from the liquid layer are proportional to the
concentration of pollutants in this layer, total losses can be partitioned among competing loss
processes according to fixed ratios. Of the total mass of pollutant lost from the liquid layer, the
fraction lost to each process is:
-------
82>
where: '< "
4«ti = fraction of total pollutant lost from liquid layer that is lost in outflow from
the impoundment (unitless)
Q0 = rate at which outflow leaves the impoundment (mVsec)
fdl = fraction of total pollutant in liquid layer that is dissolved (unitless)
Ktou = lumped rate coefficient for pollutant loss from the liquid layer of surface
impoundment (ra3/sec)
f^n = fraction of total pollutant lost from liquid layer that is lost to degradation
(unitless)
= rate of pollutant degradation in liquid layer (sec"1)
= surface area of impoundment (ra2) >
= fraction of total pollutant lost from liquid layer that is lost to volatilization
(unitless)
= fraction of total pollutant lost from liquid layer that is lost to seepage
(unitless)
= rate of seepage beneath the impoundment (m/sec) •
• = fraction of total pollutant lost from the liquid layer as a result of the
diminishing volume of the liquid layer (unitless)
DV = - rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (ra3/sec) <
5-50
-------
5.4.12 Pollutant Losses from Sediment Layer
Pollutant mass accumulates in the sediment layer as the depth of this layer increases
eventually reaching the surface of the impoundment If the only source of pollutant mass for the
sediment layer is the losses estimated for the liquid layer:
where:
fdl
A
G!
DV
C2
DV
A C2 * DV C2
(83)
seepage rate for both liquid and sediment layers (m/sec)
fraction of pollutant in the liquid layer of surface impoundment that is
dissolved (unitless)
surface area of surface disposal facility (m2)
concentration of pollutant in liquid layer of surface impoundment (kg/m3)
rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (m3/sec)
rate of pollutant degradation in sediment layer (sec'1) ,*
depth of sediment layer (m)
total concentration of pollutant in sediment layer (kg/m3)
fraction of pollutant in the sediment layer of surface impoundment that is
dissolved (unitless)
and:
1 + KD S
where:
KD
S,
fraction of pollutant in the sediment layer of surface impoundment that is
dissolved (unitless)
equilibrium partition coefficient for pollutant (m3/kg)
solids concentration in the sediment layer of a surface impoundment
(kg/m3)
A coefficient for the total loss or storage of pollutant in the sediment layer (K,^ m3/sec) can be
defined as:
where:
Q^f^
DV
(85)
lumped rate coefficient for pollutant loss from the sediment layer of
surface impoundment (mVsec)
rate of pollutant degradation in sediment layer (sec'1)
depth of sediment layer (m)
surface area of surface disposal facility (m2)
seepage rate for both liquid and sediment layers (m/sec)
5-51
-------
fc = fraction of pollutant in the sediment layer of surface impoundment that is
dissolved (unitless)
DV = rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (m3/sec)
As with the liquid layer, this coefficient can be partitioned into its individual components:
f _ DV
•NfclZ ~ ~£ - ,
KWC
where:
f^ = fraction of pollutant reaching the sediment layer that is lost to degradation
(unitless)
Kjj^ = rate of pollutant degradation in sediment layer (sec"1)
dj = depth of sediment layer (ra)
A = surface area of surface disposal facility (m2) i
K^Q = lumped rate coefficient for pollutant loss from the sediment layer of
surface impoundment (m3/sec)
f«p2 = fraction of pollutant reaching the sediment layer that is lost to seepage;
(unitless)
Q,q, = seepage rate for both liquid and sediment layers (m/sec)
fd2 = fraction of pollutant in the sediment layer of surface impoundment that is
dissolved (unitless) I
f
-------
= fraction of total pollutant lost from liquid layer that is lost to volatilization
(unitless)
= fraction of total pollutant lost from liquid layer that is lost to degradation
(unitless)
outl = fraction of total pollutant lost from liquid layer that is lost in outflow from
the impoundment (unitless)
^p! = fraction of total pollutant lost from liquid layer that is lost to seepage
(unitless)
deii = fraction of pollutant loss from the liquid layer that is displaced by the
accumulating sediment layer (unitless)
^ = fraction of pollutant reaching the sediment layer that is lost to degradation
(unitless)
= fraction of pollutant reaching the sediment layer that is lost to seepage
(unitless)
Finally, if all pollutant is eventually lost from the impoundment and the partitioning of
pollutant mass halfway through the facility's lifetime is generalized for the entire mass of '
pollutant, the fraction of pollutant mass lost through each pathway can be calculated as:
f = SCI
-------
= fraction of total pollutant lost from the impoundment through degradation
(unitless)
s fraction of total pollutant lost from liquid layer that is lost to degradation
(unitless)
W = fraction of pollutant reaching the sediment layer that is lost to degradation
(unitless)
f«t = fraction of total pollutant lost from the impoundment through outflow
(unitless)
These results are used to calculate pollutant limits for the ground water and vapor pathways.
5.4.2 Methodology for the Ground-Water Pathway
tf
i *
Derivations of pollutant criteria for the ground-water pathway begin with the calculation"
of an adjusted reference water concentration (RC,.,) for each pollutant of concern. This value is
calculated from the maximum pollutant level (MCL) by subtracting an estimated background
concentration of the pollutant in ground water:
= MCL -
where:
= adjusted reference water concentration (rag/1)
MCL = maximum pollutant level (mg/1)
Cb = average background concentration of pollutant in drinking water from
wells (mg/1)
Alternatively, if no MCL is available, the reference water concentration is calculated for
carcinogenic pollutants from a selected risk level and a human cancer potency.
-------
The next step is to use the reference concentration for the pollutant in well water to
calculate a reference concentration of pollutant in leachate beneath the facility. As discussed in
Section 5.32 for the monofill prototype, two mathematical models are combined to calculate an
expected ratio between these two concentrations. The VADOFT component of the RUSTIC
model (U.S. EPA, 1989a,b) estimates flow and transport through the unsaturated zone, and the
AT123D model (Yeh, 1981) estimates pollutant transport through the saturated zone.
Minor adjustments have been made to the linked models to represent a phenomenon
unique to this prototype: seepage from a surface impoundment can cause local elevation of the
water table if rates of seepage exceed natural rates of aquifer recharge in the surrounding area.
Such elevation, or mounding, of the water table has two implications for the expected
•concentrations of pollutants at a receptor well. The first is that the reduced vertical distance
•»
between the impoundment and the local water table will result in a shorter timespan for seepage
from the impoundment to reach the saturated zone. The second is that an increased hydraulic
gradient will form in the aquifer between the impoundment and the downgradient receptor well.
This change in gradient will increase the expected rate of horizontal transport of the pollutant
through the saturated zone.
To accommodate these two effects in the model calculations, this methodology modifies
an approach used in the RUSTIC model. The first component of the model (VADOFT)
performs calculations for a vertical column containing both unsaturated and saturated zones and
predicts the extent to which the elevation of the water table will be increased by the flux of water
seeping from the impoundment. Once the vertical column problem has been solved for mass and
water fluxes at the water table elevation, the second model component (AT123D) simulates the
movement of pollutants through the saturated zone, with adjustments to represent increased
elevation of the water table. Unlike RUSTIC, however, the present methodology does not allow
for partial feedback between the unsaturated and saturated zone components of the model; the
saturated zone is' represented separately by an analytical transport model.
The AT123D model accepts as input the flux of pure pollutant mass entering the top of
the saturated zone and does not consider the extent of the pollutant's dilution by water from the
source area or the impact of that water on ground-water flow within the saturated zone.. When
5-55
-------
the vertical movement of pollutant through the unsaturated zone is due only to natural recharge
throughout the area, the gradient within the aquifer is a function of the water entering the
saturated zone. Under these conditions, neglect of pollutant dilution in the source area may be
valid. With a surface impoundment, however, neglect of the extent of the pollutant's initial
dilution could result in nontrivial overestimation of the source concentration leading to
overestiraation of pollutant concentrations at the receptor well. Furthermore, neglect of
mounding effects could lead to incorrect assumptions about the velocity of ground water flow
near the site.
These concerns are addressed with three simple adjustments to the execution of the
AT123D model. First, to correct for AT123D's potential overestimation of the original
concentration of pollutant at the aquifer's boundary, the mass flux estimated from VADOFT
results is adjusted by a dilution factor (DF) as follows:
i
Df ?5 (91)
(ACLp+F.) i
where: - ;
DF =* dilution factor (unitless)
F, = the volume of fluid passing through a vertical cross section of the aquifer
oriented perpendicular to the direction of flow, and having a width equal
to the source width and a depth equal to the saturated thickness of :the
aquifer (m3/sec)
A = surface area of surface disposal facility (m2) •
Q«P = seepage rate for both liquid and sediment layers (m/sec)
In cases where seepage from the impoundment is not significant compared with the
natural, regional rate of aquifer recharge, this dilution adjustment is inappropriate and can be
left out of program execution.
The excess water released by seepage from a surface impoundment can also result in a
superimposed radial velocity field on the background or regional velocity field of ground-water
flow. In other words, the horizontal velocity of water within the aquifer can be slowed up-
gradient of the lagoon, and accelerated downgradient of the impoundment. This change in the
velocity field might result in reduced time of travel for pollutants moving to receptor wells
downgradient of the impoundment site, which could in turn lead to reductions in pollutant
5-56
-------
degradation prior to human exposure. Accurate accounting of the influence of mixing and
degradation would require a fully three-dimensional flow and transport model. This
methodology uses a simpler approach to estimate a conservative limit to pollutant decay within
the system. The limit is estimated by increasing the estimated velocity of ground water flow to
account for the maximum downgradient increase in velocity due to the source so that velocity
increase can be approximated by idealizing the lagoon as a circular source, so that the rate at
which seepage passes outward through a cylinder beneath the perimeter of the impoundment's
floor to be expressed as:
(92)
where:
V; = superimposed radial velocity from water seeping from impoundment
(m/sec), and t;
Q^ = seepage rate for both liquid and sediment layers (m/sec)
da = depth of aquifer (m)
In addition to increasing the expected velocity of pollutant transport through the aquifer,
this superimposed velocity would also have the effect of increasing AT123D's estimate of
pollutant dilution within the aquifer. This additional dilution effect must be subtracted back out
of the model calculations since the true dilution is explicitly included in the factor introduced by
Equation 91. The model performs this calculation automatically based on the following equation
for the anti-dilution factor:
Dtf. K_p) (93)
where:
Dmf <= anti-dilution factor (unitless)
vv = the vertical velocity due to the source (m/sec)
vh = the regional velocity of horizontal ground water flow (m/sec)
It should be noted that the above methodology is conservative since it overestimates the
velocity beneath the source and does not allow for decreases in the superimposed velocity beyond
the source. As a result, the methodology is more conservative than a three-dimensional model.
In comparison with a two-dimensional cross-sectional flow and transport model, the methodology
is more conservative beneath the source but less conservative beyond :he source.
5-57
-------
By combining the VADOFT module with AT123D and adjusting calculations in AT123D
to accommodate the dilution and superimposed velocity described above, concentrations of a
pollutant in ground water at a receptor well can be predicted as a function of the following
factors: the liquid concentration of pollutants near the floor of the impoundment; the rate of
seepage from the facility; and hydrogeological characteristics of the area. It should be noted: that
all of the calculations described above are linear with respect to pollutant concentrations in
liquid seeping from the impoundment. It is convenient to perform the calculations based on the
assumption of a "unit" concentration of dissolved pollutant in seepage beneath the facility.
For the solute transport component of model execution, the flux of pollutant into the top
of the unsaturated zone is represented as a pulse of constant magnitude or (e.g., square wave).
'"
The duration of this pulse is calculated so that the entire mass of pollutant will be depleted at*,
the equilibrium rates calculated for the active impoundment:
TP = - 3.2xl
-------
f»ei = ratio of predicted concentration in well to assumed concentation in
seepage (unitless)
Cml - predicted concentration of pollutant in well (mg/1)
C^ = assumed concentration of pollutant in seepage (mg/1)
Since calculations in both the VADOFT and AT123D components of the ground-water
pathway model are linear with respect to pollutant concentration in seepage beneath the site.
The above ratio can be used to back-calculate a reference concentration of pollutant in seepage:
RC_
RC^ = -y-^ " <96)
where:
, = reference concentration of pollutant in water seeping from the bottom of
the surface impoundment (mg/1)
^ = reference concentration for pollutant in groundwater (kg/m3)
fwei = ratio of predicted concentration in well to assumed concentation in ' -
seepage (unitless)
Next, multiplying this reference concentration (mg/1) by the weighted average estimate of
fluid flux (m/sec) and adjusting units yields the reference flux of pollutant mass from the site:
RF^ = 3.2X108 RC^ Q^ (97)
where:
RFg,, = reference, annual flux of pollutant beneath the site
(kg/ha »yr)
3.2xl08 = .conversion factor (kg/ha«yr) [(rag•m)/(l»sec)]'1
RC^ = reference concentration of pollutant in water seeping from the
bottom of the surface impoundment (mg/1)
Qsep = seepage rate for both liquid and sediment layers (m/sec)
This allowable flux must be related to the dry-weight concentration of sewage sludge
entering the impoundment. Because f^ describes the fraction of total pollutant mass seeping
from the impoundment and'TP provides a !ov-er-bound estimate for the amount of time required
to release all significant pollutant from the facility, the reference flux can be converted to an
equivalent concentration in sewage sludge by
RCS . *• (98)
fsepS2dUX
where:
RCS = reference dry-weight concentration of pollutant in sewage sludge (mg/kg)
5-5*
-------
TP '= length of "square wave" in which maximum total loss rate of pollutant
depletes total mass of pollutant at site (yr)
RF^ as reference annual flux of pollutant beneath the site
(kg/ha«yr) i
100 = conversion factor (mg/m2) (kg/ha)
fjq, = fraction of total pollutant loss attributable to seepage (unitless)
S2 = solids concentration in the sediment layer of a surface impoundment
(kg/m3) ;
^ = total depth of surface impoundment (m)
5.43 Methodology for Vapor Pathway
l
The vapor pathway of potential exposure is considered for organic pollutants only. The
first step is to determine a reference air concentration for each pollutant of concern: **
(99)
i.qi
where:
RCi£r = reference air concentration for pollutant (jig/m3)
1000 = conversion factor (jig) (rag)'1
RL = risk level (incremental risk of cancer per lifetime) i
BW = body weight (kg)
I, = . inhalation volume (m3/day)
q/ = human cancer potency (kg 'day/rag)
The next step is to relate releases of volatilized pollutant from the site to the expected
concentration in ambient air. The model used to describe transport of pollutant from a monofill
is described in '(U.S. EPA, 1986d) and is based on equations described in Environmental Science
and Engineering.(1985). The highly exposed individual (HEI) is assumed to live at the
downwind property boundary of the surface impoundment. A source-receptor ratio is calculated
to relate the concentration of pollutant in ambient air at the HEI's location (g/ra3) to the rate
that. pollutant is emitted from the treated soil (g/ra2* sec).
SRR = 2.032 - — - (100)
(r7 + x CD o
z
5-60
-------
where:
SRR = source-receptor ratio (sec/m)
2.032 = empirical constant
A = area of surface impoundment (m2)
v = vertical term (unitless)
r' = distance from the impoundment center to the receptor (m)
Xy = lateral virtual distance (m)
co = wind speed (m/sec)
crz = standard deviation of the vertical concentration distribution (m)
The vertical term (v) is a function of source height, the mixing layer height and az.
Under stable conditions the mixing layer height is assumed infinite. Thus, given also a pollutant
release height of zero, v=l.
The lateral virtual distance is the distance from a virtual point source to the surface
impoundment, such that the angle 0 subtended by the surface impoundment's width is 22.5°. ' *
This distance is calculated as:
where:
Xy = lateral virtual distance (m)
A = area of surface impoundment (m2)
The standard deviation of the vertical distribution of concentration (<7Z) is defined by an
atmospheric stability class and the distance from the center of the impoundment to the receptor.
Parameter values for a and b are listed in Table 5-1 of Section 5.3. Using values from this table
for stable atmospheric conditions an appropriate value of
-------
Dividing the reference air concentration by this source-receptor ratio and adjusting units
E
yields a reference annual flux of emitted pollutant: :
_ 3M
SRR
where: '
RF.^ - reference annual flux of pollutant to air to the site (kg/ha »yr)
316 = conversion factor (ug/m2»sec) (kjj/ha'yr)*1 ;
RClir = reference concentration for pollutant in air (jig/m3)
SRR = source-receptor ratio (s/m)* .... ;
Pollutant limits for the vapor pathway are based on the highest average concentrations of
pollutants to be encountered over an expected human lifetime. At the rate at which pollutant is
• lost during the facility's active operation, the fraction that would be lost to all processes over^a
period equivalent to the life expectancy is:
f = LS (105)
u TP
where:
fj, = fraction of total pollutant lost during human lifetime (unitless)
LS = life expectancy (yr)
TP = length of "square wave" in which maximum total loss rate of pollutant
depletes total mass of pollutant at site (sec or yr)
The reference annual flux multiplied by the human life expectancy yields the total
reference mass of pollutant emitted from one hectare of surface impoundment during the period
of concern. That mass can be divided by the fraction of pollutant mass volatilized during that
period and the dry mass of sewage sludge in one hectare of impoundment to yield (after
adjusting units) a reference dry-weight concentration of pollutant in sewage sludge: |
RCS S._«- (106)
ffclOOS,^
where: :
RCS = reference dry-weight concentration of pollutant in sewage sludge (rag/kg)
RFiir = reference annual flux of pollutant to air above the site (kg/ha-yr) • !
LS = life expectancy (yr)
fb = fraction of total pollutant lost during human lifetime (unitless)
5-62
-------
100 = conversion factor (kg/ha) (mg/m2)'1
S2 = solids concentration in the sediment layer of a surface impoundment
(kg/m3)
d^j = total depth of surface impoundment (m)
5.4.4 Surface Impoundment Prototype Sample Calculations for Pollutant Criteria
5.4.4.1 Mass Balance Calculations
Algorithms for deriving pollutant limits for the surface impoundment prototype will be
illustrated with sample calculations for PCBs using parameter values discussed in Section 5.8 and
listed in Tables 5-10 through 5-14 (Section 5.7). The first step in mass balance calculations for
this prototype is to estimate the concentration of solids in the liquid and sediment layers:
Psl(kg/m3)pw(kg/m3)P1 (kg/kg)
Pw(kg/m3)P1 (kg/kg) + [l-P1(kg/kg)]Psl(kg/m3)
= (1200) (1000) (0.03)
(1000) (0.03) + (1-0.03) (1200)
= 30 (kg/m3)
and:
S = Pd(kg/m3)pw(kg/m3)P2 (kg/kg)
2 " Pw(kg/m3)P2(kg/kg) + [1-P2 (kg/kg)] Psl(kg/m3)
= (1200) (1000) (0.175)
(1000) (0.175) + (1-0.175) (1200)
= I80(kg/m3)
where:
3j = concentration of solids in liquid layer (kg/m3)
psl '=• particle density of sewage sludge (kg/m3)
pw =. density of water (kg, m!)
PI = fraction solids in liquid layer (kg/kg)
S2 = concentration of solids in sediment layer (kg/m3)
P2 = fraction solids in sediment layer (kg/kg)
5-63
-------
The volume of outflow from the fadlity (Q0) is calculated as:
Q,, - Qi(m3/sec)
where:
i —.
- DV(m3/sec)
1-
S,(kg/m3)
(109)
Q0
Q.
Sj
pu
Q^p
DV
S2
= (0.0022)[l—^U-(7.9xlO-8)(20,236) -(3.
= 2.3xlO~4(m3fsec)
rate at which outflow leaves the impoundment (m2/sec)
rate of inflow for sludge into a surface impoundment (m3/sec) ^ »
concentration of solids in liquid layer (kg/m3)
particle density of sewage sludge (kg/m3)
rate of seepage beneath the impoundment (m3/sec)
rate of change in the volume of the layer, positive for the sediment layer
negative for the liquid layer (ra3/sec)
concentration of solids in sediment layer (kg/m3)
In each layer, pollutant is partitioned between adsorbed and dissolved phases according
to the pollutant-specific partition coefficient and the concentration of solids in the layer:
Su
1 +
j (kg/to3)
1 + (468) (30)
7.ixi
-------
(HI)
and:
FD = ratio of effective diameter to depth of surface impoundment (unitless)
de = effective diameter, or "fetch" (m)
d, = depth of liquid layer in surface impoundment (m)
d =2 =2
3.14
(112)
de
A
effective diameter, or "fetch" (m)
surface area of surface disposal facility (m2)
Because the assumed wind speed is greater than 3.25 m/sec and the ratio of fetch to
depth is greater than 51.2, the mass transfer coefficient for liquid is calculated as in equation 77:
where:
K,
D,.,
D
K^m/sec) = 2.611X10'7 o>J0
= 2.611xlO-7(4.5)2
3
"
4.2x10
-1*
eth
8.5x10"
mass transfer coefficient for liquid layer (ra/sec)
wind velocity at 10 meters altitude (m/sec)
diffusivity of pollutant in water (cm2/sec)
diffusivity of diethly ether in water (cm2/sec)
The mass transfer, coefficient for gas requires the Schmidt number, defined as:
Sc.
(0.0012) (0.057)
2.63
where:
Sc
Schmidt number on gas side (unitless)
5-65
-------
Pa
viscosity of air (g/cm-sec)
density of air (g/cm3)
diffusivity of constituent in air (cra2/sec)
where:
o>
10
Sc
From Hwang (1985), the mass transfer coefficient for the gas phase is then:
Kf = l.SxlO-^tOy^m/sec)]0-78 Sc^0'67 [de(m)]~°-u
= (l.SxlO-3) (4.50-78) (5.23) (161 -0-11)
. = 1.74xlO'3 (m/sec)
mass transfer coefficient for liquid layer (m/sec)
wind velocity at 10 meters altitude (m/sec)
Schmidt number on gas side (unitless)
effective diameter, or "fetch" (m)
(115)
The overall mass transfer coefficient is calculated as:
Kvoll (m/sec) =
J ^ R(m3«atm/°K«mol) T(°K)
K,(m/sec) H(m3» atm/mol) Kg (m/sec)
1 ^ (8.21 xlO"5) (288) I"1
(3.2x10^) (0.0017) j
-i
where:
R
T
H
3.3x10-*
= 2.9X10"6
overall mass transfer coefficient for volatilization (m/sec)
mass transfer coefficient for the liquid layer (m/sec)
ideal gas constant (821xlO'J atm«m3/K*mol)
temperature (K)
Henry's Law constant for pollutant (atm«m3/niol)
mass transfer coefficient for gas layer (m/sec)
The "active" period in which the impoundment receives sewage sludge (TF, seconds) !is
calculated from the mass of solids in the filled impoundment divided by the rate at which solid
mass enters the impoundment:
5-66
-------
) A(m2) S2(kg/m3)
Qi(m3/sec) S1(kg/m3)
_ (4) (20,236) (180) , (117)
(0.0022) (30)
= 2.2xl08(sec)
where:
TF = duration of facility's active lifetime (sec)
d,,,, = total depth of surface impoundment (m)
A = surface area of surface disposal facility (m2)
S2 = solids concentration in the sediment layer of a surface impoundment
(kg/m3)
Qj = rate of inflow for sludge into a surface impoundment (nr/sec)
St = concentration of solids in liquid layer (kg/m3)
The rate of accumulation can be determined by dividing the total depth of the
impoundment by its expected active lifetime:
) A(m2)
DV = _ - _ -
TF(sec)
= (4) (20,236)
(2.2xl08)
where:
DV - = rate at which sediment layer accumulates (m3/sec)
d^ = total depth of impoundment (m).
A = surface area of surface disposal facility (ra2)
TF =" duration of facility's active lifetime (sec)
A coefficient for the total rate at which pollutant mass is lost from the liquid layer
mVsec) is calculated as:
5-67
-------
where:
d,
A
DV =
= Q^m'/sec) fc
fdl ACm2)
dl
DVCm3/sec)
C0.00023)C7.1 x ID'5) + (2.0 x 10-n)(2) (20,236)
+ (2.9 x io-*)(7.i x i
-------
. _ ^ fdl Afrn2) _ (2.9x10^) (7.0xlQ-*) (20,236)
" " (3.9xlO-<)
fdl Adn2) _ (7.9xlO-8) (7.0xlQ-5) (20,236) . A in
- — j.UXlU
, — — — - •
' (3.9X10-4)
f = DV(m3/sec) . (3.8x10-*) =
(3.9X1Q-4)
where:
fouti = fraction of total pollutant lost from liquid layer that is lost in outflow from
the impoundment (unitless)
Q; = rate of inflow for sludge into a surface impoundment (nvYsec)
fdl = fraction of total pollutant in liquid layer that is dissolved (unitless)
K^ = lumped rate coefficient for pollutant loss from the liquid layer of surface
impoundment (ra3/sec) ^ „
fdegi = fraction of total pollutant lost from liquid layer that is lost to degradation
(unitless)
Kjegj = rate of pollutant degradation in liquid layer (sec"1)
dt = depth of liquid layer (m)
A = surface area of impoundment (m2)
t,oll = fraction of total pollutant lost from liquid layer that is lost to volatilization
- (unitless)
KVOU = overall mass transfer coefficient for volatilization from the liquid layer of
surface impoundment (m/sec)
fy.p! = fraction of total pollutant lost from liquid layer that is lost to seepage
(unitless)
Q«P = rate of seepage beneath the impoundment (m/sec)
f^u = fraction of total pollutant lost from the liquid layer as a result of the
diminishing volume of the liquid layer (unitless)
DV = rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (mVsec)
For the sediment layer, the fraction of pollutant that is dissolved is first calculated as: .
f = - L__ (122)
- c 1 + KD S2 - '
where:
fjc = fraction of pollutant in the sediment layer of surface impoundment that is
dissolved (unitless)
KD = equilibrium partition coefficient for pollutant (m3/kg)
S2 = solids concentration in the sediment layer of a surface impoundment'
(kg/m3)
5-69
-------
A coefficient for the total loss or storage of pollutant (K^ in raVsec) is then calculated
as: . [
A(m2) + Q^Cm/sec) fo ACm2) + DV(m3/sec)
= (2.0xl(Tu) (2) (20,236) + (7.9xlO-*X1.2xlO-*)<2Q£36) + (S.Txlp-4)
= 3.7xlO-*(m3/sec)
where:
K^a = lumped rate coefficient foT pollutant loss from the sediment layer of
surface impoundment (m3/sec)
K^^ = rate of pollutant degradation in sediment layer (sec'1)
dz = depth of sediment layer (m) |
A = surface area of surface disposal facility (m2) i
Q^P = seepage rate for both liquid and sediment layers (m/sec) ,
fd2 = fraction of pollutant in the sediment layer of surface impoundment th£t is
dissolved (unitless) i -
DV = rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (ra3/sec)
As with the liquid layer, this coefficient is partitioned into its individual
components:
= (2.0xlO-u)(2)(20^36) = 2^xlo_3
(3.8x10-*)
i
A(m2) = (7.9xlQ-8)(1.2xlQ-5) (20^36) = 52xlo-5 (124)
"** "
= DV(m3/sec)
where:
fraction of pollutant reaching the sediment layer that is lost to degradation
(unitless) ;
rate of pollutant degradation in sediment layer (sec'1)
depth of sediment layer (ra)
surface area of surface disposal facility (m2)
lumped rate coefficient for pollutant loss from the sediment layer of
surface impoundment (m'/sec) ;
fraction of pollutant reaching the sediment layer that is lost to seepage
(unitless)
seepage rate for both liquid and sediment layers (m/sec) i
fraction of pollutant in the sediment layer of surface impoundment that is
dissolved (unitless)
5-70
-------
fdeE = fraction of pollutant reaching the sediment layer that is stored in the
accumulating depth of this layer (unitless)
DV = rate of change in the volume of the layer, positive for sediment layer,
negative for liquid layer (m3/sec)
These results are combined to calculate the fraction of yearly loading of pollutant mass
lost during each year of the active phase of the impoundment's operation:
= (0.011) + (0.0022) + (4.3 xlO'5) -. '
+ [(S.OxlO-4) + (0.986)][(0.0022) + (5.2xlO'5)]
= 0.015
where:
fact = fraction of pollutant lost during surface impoundment's active phase , *
(unitless)
fvoll = fraction of total pollutant lost from liquid layer that is lost to volatilization
(unitless)
fdegi = fraction of total pollutant lost from liquid layer that is lost to degradation
(unitless)
foutl = fraction of total pollutant lost from liquid layer that is lost in outflow from
the impoundment (unitless)
f^! = fraction of total pollutant lost from liquid layer that is lost to seepage
(unitless)
fd*u = fraction of pollutant loss from the liquid layer that is displaced by the
accumulating sediment layer (unitless)
fdegz = fraction of pollutant reaching the sediment layer that is lost to degradation
(unitless)
f^2 s= fraction of pollutant reaching the sediment layer that is lost to seepage
(unitless)
Finally, the fraction of pollutant mass lost through each pathway is calculated, based on
the simplifying assumption that the partitioning of pollutant mass during the facility's active
operation can be used to represent the partitioning of the entire mass of pollutant in the facility.
For losses to seepage:
5-71
-------
[(3.0x10-*) * (0.986)] (5.2xlO'5)
(0.016)
= 0.0033
where:
fraction of total pollutant lost from the impoundment through seepage
(unitless)
fraction of total pollutant lost from liquid layer that is lost to seepage
(unitless)
fraction of pollutant loss from the liquid layer that is displaced by the
accumulating sediment layer (unitless)
fraction of pollutant reaching the sediment layer that is lost to seepagd?
(unitless) *
fraction of pollutant lost during surface impoundment's active phase ;
(unitless)
For losses to volatilization:
(0JOU)= (127)
(0.015)
where:
^o, = fraction of total pollutant lost from the impoundment through
volatilization (unitless)
^u = fraction of total pollutant lost from liquid layer that is lost to volatilization
(unitless)
f,,, = fraction of pollutant lost during surface impoundment's active phase
(unitless) .
f
For losses to degradation:
•et
= (0-0022) •»• [(S.OxlQ-4) * (0.986)1(0.0022)
(0.016) _ i
= 0.28
where:
ffcg = fraction of total pollutant lost from the impoundment through degradation
(unitless) '
-------
f
-------
where:
IP
TF
3.2XKT8
duration of square wave for approximating the loading of pollutant
into the, top of the unsaturated soil zone (yr)
duration of facility's active lifetime (sec)
conversion factor (yr) (sec)'1
fraction of pollutant lost during surface impoundment's active
phase (unitless)
This value is used to prepare input for the VADOFT model.
The VADOFT and AT123D models are executed with adjustments for local elevation of
the water table. With input values provided in Tables 5-12 through 5-14 (see Sections 5.7 and
5.8), the linked models provide an estimate of 0.478 mg/1 for the maximum pollutant
concentration in ground water within the 300 years simulated. This estimate is divided by the
assumed concentration of pollutant in seepage from the facility (1 mg/1) to estimate a ratio
between these two concentrations:
where:
Cw.(mg/l)
_ (0.478)
(1.0)
= 0.478
(131)
ratio of predicted pollutant concentration in well to assumed concentration
in seepage (unitless)
predicted concentration in well (mg/1)
assumed concentration in seepage (1 mg/1)
A reference concentration of pollutant in seepage is calculated as:
RC fmg/1)
RC = *•* *'
(4-SxlQ-4)
, (0.478)
9.5xlO-4(mg/l)
(132)
5-74
-------
where:
RC^j, = reference concentration of pollutant in water seeping from the bottom of
the surface impoundment (mg/1)
RC,, = reference concentration for pollutant in groundwater (kg/m3)
f,,el = ratio of predicted pollutant concentration in well to assumed concentration
in seepage (unitless)
Next, multiplying this reference concentration (mg/1) by the fluid flux (in m/sec) and
adjusting units yields the reference flux of pollutant mass from the site:
3.2x10*
= (9.5xlO-4)(7.9xlO-8)(3.2xl08) (133)
= 2.4xlO~2(kg/ha-yr)
where: „
RF^ = reference annual flux of pollutant beneath the site (kg/ha »yr)
RC^ = reference concentration of pollutant in water seeping from the bottom of
the surface impoundment (mg/1)
Q«P = seepage rate for both liquid and sediment layers (m/sec)
3.2xl08 = constant to convert units ([rag«m]/[l»sec]) to (kg/ha»yr)
This reference flux is related to the dry-weight concentration of sewage sludge entering
the impoundment by:
RF^qcg/ha'vr) 100
f^ S2(kg/m3)
= (450) (2.4xlQ-2) 100
(0.0033) (180) (4)
= 451(mg/kg)
where:
RCS = reference dry-weight concentration of pollutant in sewage sludge (mg/kg)
TP = length of "square wave" in which maximum total loss rate of pollutant
depletes total mass of pollutant at site (yr)
RFp, = reference annual flux of pollutant beneath the site (kg/ha»yr)
100 = conversion factor (mg/nr) (kg/ha)
fjep = fraction of total pollutant loss attributable to seepage (unitless)
S2 = solids concentration in the sediment layer of a surface impoundment
(kg/m3)
d^, = total depth of surface impoundment (m)
5-75
-------
5.4 JJ Pollutant Criteria Calculations for Vapor Pathway
Pollutant limit criteria for the air pathway are derived for organic pollutants only. For
each pollutant, a reference air concentration is first established based on cancer potency:
where:
RL
BW
1000
I,
RL BW(kg) 1000(ug/m3)
I.(m3/day) qi*(kg-day/mg)
(IP"4) (70) 1000
(20) (7/7)
0.045 (u-g/m3)
= reference air concentration for pollutant (pg/m3)
= risk level (incremental risk of cancer per lifetime)
= body weight (kg)
= conversion factor (jig) (rag)'1
» inhalation volume (m3/day)
= human cancer potency (kg-day/rag)
(135)
To relate this reference concentration to a rate of volatile emissions from treated land, a
source-receptor ratio is calculated from a vertical term, a lateral virtual distance, and the
standard deviation of the vertical distribution of concentrations.
The vertical term (v) is a function of source height, the mixing layer height and az.
Under stable conditions the miring layer height is assumed infinite, and for a pollutant release
height of zero, v=l. ;
The lateral virtual distance is the distance from a virtual point source to the
impoundment, such that the angle B subtended by the impoundment's width is 22.5°. This
distance is calculated as:
5-76
-------
(136)
and:
x = 0.001 (rO . • (137)
r'-71 •
where:
Xy = lateral virtual distance (ra)
A = area of surface impoundment (m2)
r' = distance from the impoundment center to the receptor (m)
An appropriate value of az is calculated as:
°z = a*b
= 15.209 (0.071)0'81558 (138)
= 1.8 (ra)
where:
az =. standard deviation of the distribution of vertical concentrations (m)
a = . first coefficient for calculating az
b = second coefficient for calculating az
Using these results, a source-receptor ratio (SRR) is calculated to relate the
concentration of pollutant in ambient air at the HEI's location (g/m3) to the rate that pollutant is
emitted from the treated soil (g/m2«sec):
SRR = 2.032 A(m2)v
|r(in) + Xy(m)] u(m/sec) az(m)
_. 2.032 (20^36) (1) (139)
" [(71)-H(403)](4.5)(1.8)
= ll(sec/m)
where:
SRR = source-receptor ratio (sec/m)
2.032 , = empirical constant
A = area of impoundment (m:)
5-77
-------
v = vertical terra (unitless)
r* = distance from the impoundment's center to the receptor (m)
Xy = lateral virtual distance (m)
W = wind speed (m/sec) ;
az = standard deviation of the distribution of vertical concentrations (m)
i
Dividing the reference air concentration by this source-receptor ratio (and adjusting
units) yields a reference annual flux of emitted pollutant:
316 RC . (|jig/m3)
RF . = - S2LZL -
"* SRR(sec/m)
= 316(0.045) (140)
(11) i.
i *
= 1.3(kg/ha«yr)
where:
RFiir = reference annual flux of pollutant emitted from the site (kg/ha «yr) |
316 = conversion factor (/tg/ra2»sec) (kg/ha'yr)'1
RC,j, = reference concentration for pollutant in air Gtg/ra3)
SRR = source-receptor ratio (s/m)
The fraction of total pollutant lost during a human lifetime is:
(141)
TP ;
where: i
fb = fraction of total pollutant lost during human lifetime (unitless)
LS = life expectancy (yr)
TP = duration of "square wave" for approximating the loading of pollutant into
the top of the unsaturated soil zoine (yr)
Finally, the reference dry-weight concentration of pollutant in sewage sludge is calculated
as:
5-78
-------
LS(yr) (100)
b S2(kg/m3)
- (1.3)(70)(100) (142)
" (0.72)(0.16)(180)(4)
= 110(mg/kg)
where:
RCS = reference dry-weight concentration of pollutant in sewage sludge (mg/kg)
RFlir = reference annual flux of pollutant to air above the site (kg/ha-yr)
LS = life expectancy (yr)
fb = fraction of total pollutant lost during human lifetime (unitless)
100 = conversion factor (kg/ha) (mg/m2)"1
S2 = solids concentration in the sediment layer of- a surface impoundment
(kg/m3)
d,,,, = total depth of surface impoundment (m)
5.5 RESULTS OF PART 503 RISK ASSESSMENT
This section presents the results of the risk assessment for the monofill and surface
impoundment prototypes modelled in support of the Part 503 regulation for surface disposal.
Tables 5-2 and 5-3 give the pollutant loading criteria for sewage sludge placed in an unlined
monofill and surface impoundment, respectively, located over Class I ground water. The
pollutant loading criteria for sewage sludge placed in a lined monofill and surface impoundment
located over Class I ground water are shown in Tables 5-4 and 5-5, respectively. Tables 5-6
through 5-9 present the pollutant criteria for sewage sludge placed in unlined and lined monofills
and surface improvements located over Class II/UI ground water.
5.6 FACTORS RELATED TO RISK ASSESSMENT
This section discusses the risk-based factors related to the risk assessment performed for
the surface disposal of sewage sludge. It also explains the concept of the highly exposed
individual (HEI) that EPA used as a means to limit human exposure to ground water and vapor
potentially containing pollutants resulting from the surface disposal of sewage sludge. In
5-79
-------
TABLES-?,
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN UNLINED MONOFILL
OVER CLASS I GROUND WATER
Contaminants
Groundwater
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ethylhexyl)phthalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nhrosodimethylamine
PCBs
Toxaphene
Trichlorocthylene
17
33
78,00
44,00
360
unlimited
140
4,800
unlimited
2,300
9,200
99
150
0.022
23,000
unlimited
1,500
#N/A
6,100
imlimitpH
unlimft/eH
#N/A I
unlinyted
#N/A ",
#N/A
unlimited
#N/A :
unlimited
#N/A
#N/A
3,000
unlimited
unlimited
unlimited
Note: Criteria are expressed in mg per kg.
5-80
-------
TABLE 5-3
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN UNLINED SURFACE IMPOUNDMENT
OVER CLASS I GROUND WATER
Contaminant
Groundwater
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ethylhexyl)phthalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nitrosodimethylamine
PCBs
Toxaphene
Tricbloroethylene
8.8
19
950
550
20
unlimited
57
1,200
unlimited
95
660
7.4
62
0.01
450
unlimited
340
#N/A
3,300
unlimited
w^fJTn*t?d
#N/A
nnjjpifrftd
#N/A
#N/A
unlimited
#N/A
28,000
#N/A
#N/A
15
110
26,000
10,000
Note: Criteria are expressed in mg per kg.
5-81
-------
TABLE 5-4
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN LINED MONOFILL
OVER CLASS I GROUND WATER
Contaminant
Giroundwtter
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ctnylhexyl)phmalate
Cadmium
. Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nrtrosodimethylamine
PCBs
Toxaphene
Trichloroethylene
13,000
unlimited
unlimited
unlimited
unlimited
iinjiimitgd
W^I'mitcd
unlimited
20
unliiTiitfld
unlimited
6,000
unlimited
unlimited
L '
unlimited
#N/A
#N/A
unlimited
#N/A
v
#N/A
#N/A
2,3000
unlimited
unlimited
unlimited
Note: Criteria are expressed in mg per kg
-------
TABLE 5-5
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN LINED SURFACE IMPOUNDMENT
OVER CLASS I GROUND WATER
Contaminant
Groundwater
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ethylhexyl)phthalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Ntaosodimethylamine
PCBs
Toxaphene
Trichloroethylene
35,00
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
92
unlimited
unlimited
#N/A
3,400
unlimited
iTnlitnffftH
#N/A
unlimited
#N/A
unlimited
28,000
#N/A
#N/A
16
110
26,000
10,000
Note: Criteria are expessed in mg per kg.
5-83
-------
TABLE 5-6
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN UNLINED MONOFILL
OVER CLASS n/m GROUND WATER
Contaminant
Giroundwater
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ethylhexyl)phthalate
Cadmium
Chlordane
Chronuum
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nitrosodimethylamine
PCBs
Toxaphene
Trichloroethylene
140
1,200
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
' unlimited
unlimited
unlimited
0.47
unlimited
unlimited
#N/A
6,100
unlimited
unlimited
#N/A >l\
#N/A :
unlimited
#N/A \
unlimited
#N/A
#N/A
3,000
unlimited
unlimited
unlimited
Note: criteria are expressed in mg per kg.
5-84
-------
TABLE 5-7
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN UNLINED SURFACE IMPOUNDMENT
OVER CLASS n/m GROUND WATER
Contaminant
Groundwater
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ethylhexyl)phthalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
73
140
unlimited
unlimited
unlimited
#N/A
600
46,000
3,300
unlimited
unlimited
I
unlimited
#N/A
#N/A
u
#N/A
28,000
Mercury
Nickel
n-Nitrosodimethylamine
PCBs
Toxaphene
Trichloroethylene
unlimited
690
0.88
unlimited
unlimited
9,500
#N/A
15
110
26,000
10,000
Note: Criteria are expressed in mg per kg.
5-85
-------
TABLE 541
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN LINED MONOFELL
OVER CLASS n/IH GROUND WATER
Contaminant
Groundwater
Pathway
Vapor
Pathway
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-emylhexyl)phtnalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nitrosodimethylamine
PCBs
Toxapbene
Trichloroethylene
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
790
unlimited
unlimited
unlimited
#N/A
6,000
unlimited
unlimited
#N/A ;
iifllitpitml
#N/A V,
#N/A ;
unlimited
#N/A ;
unlimited
#N/A' I
#N/A ;
2,300
unlimited
unlimited
iinlimit^rj
Note: Criteria are expressed in mg per kg.
5-86
-------
TABLE 5-9
POLLUTANT LOADING CRITERIA
FOR SEWAGE SLUDGE DISPOSAL IN LINED SURFACE IMPOUNDMENT
OVER CLASS n/ffl GROUND WATER
Contaminant
Arsenic
Benzene
Benzo(a)Pyrene
Bis(2-ethylhexyl)phtbalate
Cadmium
Chlordane
Chromium
Copper
DDT/DDD/DDE
Lead
Lindane
Mercury
Nickel
n-Nitrosodimethylamine
PCBs
Toxaphene
Trichloroethylene
Groundwater
Pathway
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
unlimited
"nlimitgd
3,400
unlimited
unlimited
unlimited
Vapor
Pathway
#N/A
3,400
unlimited
unlimited
#N/A
unlimjtej
#N/A
#N/A
unlimited'
#N/A
28,000
#N/A
#N/A
16
100
26,000
10,000
Note: Criteria are expressd in mg per kg.
5-87
-------
addition, this section explains the way in which EPA applied its risk assessment methodology to
' the development of pollutant limits fbr-Subpaft C of the sewage sludge regulation.
5.6.1 The Highly Exposed Individual
The risk-based equations developed for the Part 503 regulation were designed to limit
potential exposure of an HEI to the pollutants of concern. The HEI is an individual who ;
remains for an extended period of time at the point of maximum ambient ground-level pollutant
concentration. For sewage sludge placed on a surface disposal site, total concentration is limited
so that the increased risk attributable to each carcinogenic pollutant being regulated does not,
^ *
exceed an additional lifetime risk (70 years) of 1 x 10"* (1 in 10,000) to the HEI.
The 1989 proposed Part 503 rule considered the exposed individual to be a "most exposed
individual11 (MEI). EPA changed the terminology to an HEI for the final rule based on a revised
exposure assessment analysis. The assessment for the final Part 503 regulation incorporates !
assumptions that the Agency has concluded present a more realistic characterization of the
potential for adverse effects on public health and the environment. These exposure assumptions
are designed to limit the potential exposure to an HEI rather than an MEI. i
EPA's HEI exposure assessment analysis and the numerical pollutant limits developed
from that analysis are designed to address the risk to individuals and populations which may face
a greater risk than the general population from exposure to pollutants in sewage sludge. The
analysis attempts to evaluate realistic risk by using variables that are reflective of likely
experience. This approach does not evaluate the risk associated with a combination of ;
improbable occurrences, as did the MEI approach. EPA concluded that the HEI approach is;
consistent with its statutory duty to develop regulations that are "adequate to protect public ;
health and the environment from any reasonably anticipated adverse effects." In the case of the
surface disposal of sewage sludge, the assumptions used in the risk assessment methodology did
not change as a result of the change in terminology from the MEI to the HEI.
5-6
-------
In developing Subpart C of the rule, EPA used two variations of the HEI in evaluating
each pathway of potential exposure to the toxic effects of pollutants in sewage sludge placed on a
surface disposal site. For the vapor pathway, the HEI is assumed to live at or beyond the
property boundary of the surface disposal site and inhale 20 m3/day for 70 years. The air
dispersion was modeled by an ISCLT plume model or box model. For the ground water
pathway, the HEI is assumed to drink 2 liters/day of water containing the pollutant for 70 years.
If the surface disposal unit is greater than 150 meters from the property boundary, the HEI is
assumed to draw water from a well that is 150 meters from the surface disposal site. If the unit
is less than 150 meters from the property boundary, the HEI is assumed to draw water from a
well that is whatever distance that unit is from the surface disposal site.
5.6.2 Factors Related to Calculating the Human Dose
5.62.1 Maximum Pollutant Level
The maximum pollutant level is the "maximum permissible level of a pollutant in water,
which is delivered to the free-flowing outlet of the ultimate user of the public water system,
except in the case of turbidity where the maximum permissible level is measured at the point of
entry to the distribution system. Pollutants added to the water under circumstances controlled by
the user, except those resulting from corrosion of piping and plumbing caused by water quality,
are excluded from this definition (40 CFR Part 141)."
5.62.2 Cancer Potency
•£',-•-.''.:*'
'. '.'.y.~j. .-•
The cancer potency value (q,*) represents the relationship between a specified
carcinogenic dose and its associated degree of risk. The q," is based on continual exposure of an
individual to a specified concentration over a period of 70 years. Established EPA methodology
for determining cancer potency values assumes that any degree of exposure to a carcinogen
produces a measurable risk. The q,' value is expressed in terms of risk per dose and is measured
5-89
-------
in reciprocal units of milligrams of pollutant per kilogram of body weight and per day of
exposure (rag/kg-day)'1. I
EPA previously has calculated cancer potency estimates for arsenic, cadmium, and
chromium, which appear in the Agency's Integrated Risk Information System (IRIS) database
(U.S. EPA, 1992a). EPA also compiles scientific data on the observed health effects from
exposure to a large number of pollutants in its IRIS database. The "most sensitive endpoint" for
humans exposed to the three carcinogens regulated in Subpart G are listed in IRIS as follows:
arsenic (lung, skin, and gastrointestinal cancers); hexavalent chromium (lung cancer and cancers
in other organs); and nickel subsulfide (lung and nasal carter) (U.S. EPA, 1992a). ;
5.623 Risk Level
EPA's regulations are designed to achieve risk levels of between IxlO"4 and IxlO'7 in a '
number of regulatory applications, depending on the statute, surrounding issues, uncertainties,
and available data bases. In the case of sewage sludge placed in a surface disposal site, EPA
chose the 1x10"* risk level, or the probability of 1 cancer case in 10,000 individuals, as a
conservative public health goal. This target was selected because the aggregate effects
assessment for the final rule, which considers the health effects to the HEI and the population as
a whole, showed minimal risk from current sewage sludge surface disposal management practices,
even in the absence of regulation.
i
i
In determining the appropriate doses to use in the exposure assessment models for ;
carcinogenic pollutants, EPA used the quotient of an incremental risk and the potency value, qj.
The incremental risk is defined as the probability of an individual contracting cancer following a
i
lifetime of exposure to the maximum modeled long-term ambient concentration! The
incremental risk cannot be construed as an absolute measure of the risk to the exposed i
population because of the uncertainties inherent in determining the cancer potency for each
chemical. Furthermore, a case does not indicate the severity of the outcome. An additional
cancer case does not necessarily mean a mortality. Therefore, such estimates are best reviewed^
as relative estimates of the likelihood of cancer.
5-90
-------
To reduce this aggregate carcinogenic risk, the Agency chose to regulate sewage sludge
surface disposal practices such that each carcinogen present in sewage sludge does not exceed an
incremental unit risk of 1 x 10~* to the HEI. The incremental risk for this practice only
considered the surface disposal of sewage shidge and does not consider exposure from other
sources, natural or man-made.
5.62.4 Relative Effectiveness of Exposure
The relative effectiveness (RE) of exposure value as used in the surface disposal risk
assessment is a unitless factor that shows the relative lexicological effectiveness of an exposure by
a given route when compared with another route. In addition to route differences, RE can ateo
reflect differences in the exposure conditions. For example, absorption of nickel ingested in
water has been estimated to be five times greater than when ingested in food.
5.6.2.5 Duration of Exposure
For each pathway, the exposure was assumed to occur for 70 years based on the Agency-
approved estimated 70-year lifespan for adults (U.S. EPA, 1990b).
5.62.6 Body Weight
As defined by EPA, lifetime inhalation exposures are estimated for a 70 kg man (154
pounds), which is considered the standard body weight of an adult male (U.S. EPA, 1990b).
5-91
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5.62.7 Inhalation Kate
EPA uses 20 m3/day as the amount of air inhaled long-term by the HEI. The Agency
regards this value as the standard inhalation rate of an adult male during a normal day (U.S.
EPA, 1990b).
5.7 TECHNICAL PARAMETERS USED TO DERIVE RISK-BASED POLLUTANT
CRITERIA—TABLES
This section provides the technical parameters used in the risk assessment to derive the
pollutant criteria for the surface disposal of sewage sludge. Tables 5-10 through 5-14 provide ,$e
inputs and sources used for each parameter. A more detailed discussion of each parameter value
is provided in Section 5.8. ;
Site and sewage sludge parameters for the monoffll and surface disposal prototypes are
given in Table 5-10. Table 5-11 provides the soil and hydrologic parameters. Input parameters
for VADOFT simulation of flow and pollutant transport through the unsaturated zone are given
in Table 5-12. The inputs used in the AT123D simulation, of flow and pollutant transport
through the saturated zone are given in Tables 5-13 and 5-14 for raonofills and surface
impoundments, respectively.
5.8 TECHNICAL PARAMETERS USED TO DERIVE RISK-BASED POLLUTANT
CRITERIA—DISCUSSION
. This section discusses values of the technical input parameters used to derive pollutant
criteria for surface disposal. Many input parameters are the same for modeling the monofill and
surface impoundment prototypes; where differences occur, separate discussion^ are provided for
each prototype.
5-92
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TABLE 5-10
SITE AND SEWAGE SLUDGE PARAMETERS
FOR MONOFILL AND SURFACE IMPOUNDMENT PROTOTYPES
Parameter
Value
Source
MONOFILL PROTOTYPE
Area (m2)
Depth of Facility (m)
Active Lifetime (yr)
Thickness of Daily Cover (m)
Thickness of Permanent Cover (m)
Time Each Cell Uncovered (hr)
Time Average Cell Contains Sewage sludge (hr)
Sewage sludge as Fraction of Monofill's Content
(kg/kg)
Distance to Well
Class I Aquifer (m)
Class II Aquifer (m)
Solids Content o£ Sludge
10,000
3.46
20
03
1
12
87,660
0.63
0
150
020
U.S. EPA (1986e)
U.S. EPA (1986d)
U.S. EPA (1986d)
U.S. EPA (1978)
U.S. EPA (1978)
U.S. EPA (1986d)
U.S. EPA (19864)
'«
U.S. EPA (1978)
U.S. EPA Policy
U.S. EPA (1978)
SURFACE IMPOUNDMENT PROTOTYPE
Area (m2)
Depth of Facility (m)
Active Lifetime (yr)
Rate of Inflow (mVsec)
Solids Content of Inflow (kg/kg)
Solids Content of "Liquid" Layer (kg/kg)
Solids Content of "Sediment" Layer (kg/kg)
-•Tf-;.!,:
Particle Density of Sewage sludge (kg/m3)
Distance to Well
Class I Aquifer (m)
Class II Aquifer (m)
BOTH PROTOTYPES
Wind Velocity (m/sec)
Average Air Temperature (K)
20,236 U.S. EPA (1986f)
4 Abt Associates Inc. (1989)
7 Calculated
0.0022 . U.S. EPA (1986f)
0.03 U.S. EPA (1978)
0.03 U.S. EPA (1978)
0.175 Abt Associates Inc. (1989)
Chancy (1992)
1200 Calculated
0
150 U.S. EPA Policy
4.5 U.S. EPA (1990a)
288 U.S. EPA (1986e)
5-93
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TABLE 5-11
SOIL AND HYDROLOGIC PARAMETERS
FOR MONOFILL AND SURFACE IMPOUNDMENT PROTOTYPES
Parameter
Value
Source
Sofl Type
Bulk Density of Sewage sludge/Soil
Bulk, Density for Pure Sofl (kg/taj)b
Porosity of Sewage Sludge/Soil
Porosity of Soil Cover (monoffll only)
Saturated Hydraulic Conductivity of Soil (m/hr)
Water Retention Parameters
0,
a (m'1)
p
Fraction of Organic Carbon in Sofl or Sewage sludge
Sewage sludge
Unsaturated Zone
Saturated Zone
Depth 'to Groundwater
Class I Aquifer (m)
Class n Aquifer (m)
Net Recharge or Seepage
Monoffll Prototype (mfyr)
Surface Impoundtnent Prototype (rn/yr)
Thickness of Aquifer
Gass I Aquifer (m)
Class II/III Aquifer (m)
Hydraulic Gradient
Sand Policy
WOO Chancy (1992)
1600 Freeze and Cherry (1979)
0.4 Todd (1980)
Carsel and Fairish (1988)
0.4 . Todd (1980)
Carsel and Parrish (1988)
0.61 Carsel and Parrish (1988^
0.045 Carsel and Parrish (1988)
14.5 Carsel and Parrish (1988)
2.68 Carsel and Parrish (1988)
0.31 U.S. EPA (1983c)
10-3 U.S. EPA (1986e) i
Iff4 U.S. EPA (1986e)
0 Poh'cy ;
1 Policy
0.5 U.S. EPA (1986e)
2.5 U.S. EPA (1987b)
1 Policy
5 Policy
0.005 U.S. EPA (1986e) j
'Assumed for this analysis to be comparable to soil treated with land-applied sludge.
""Calculated from porosity and particle density of 2.650 (kg/Hi5) from Freeze and Cherry (1979).
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TABLE 5-12
INPUT PARAMETERS FOR VADOFT SIMULATION OF FLOW AND POLLUTANT
TRANSPORT THROUGH THE UNSATURATED ZONE
FOR MONOFILL AND SURFACE IMPOUNDMENT PROTOTYPES
Parameter
Value
Source
Source Area (ha)
Monofill
Surface Impoundment
Distance to Bottom of Saturated Zone (m)
Class I, Class U
Input Parameters for Flow Calculations
Eux at Top Node (m/yr)
Monofill
Surface Impoundment
Head at the Bottom Node (m)
Class I, Class n
Saturated Hydraulic Conductivity (m/yr)
Effective Porosity (unitless)
Specific Storage (unitless)
Residual Water Saturation (unitless)
Power Index - N
Leading Coefficient - a (m'1)
Power Index - ft
Power Index - y
Input Parameters for Transport Calculations
Longitudinal Dispersivity
Effective Porosity
Default Darcy Velocity
Default Water Saturation
Soil-Water Partition Coefficients
Unsaturated Zone Decay Rates
Molecular Diffusion Coefficients
1 U.S. EPA (1986e)
2.0236 . U.S. EPA (1986f)
1,6 Policy
0.5 U.S. EPA (1986e)
25 U.S. EPA (1987b)
1,5 Policy
0.61 Carsel and Parrish (1988)
0.4 Carsel and Parrish (1988)
0 U.S. EPA (1989b)
0.045 Carsel and Parrish (1988)
-1.0 Carsel and Parrish (1988)
14.5 Carsel and Parrish (1988)
2.68 Carsel and Parrish (1988)
0.62 Carsel and Parrish (1988)
1.0 U.S. EPA (1989b)
0.4 Carsel and Parrish (1988)
0 Carsel and Parrish (1988)
1.0 Carsel and Parrish (1988)
Table 5-15 - See Table 5-15
Table 5-18 See Table 5-18
Table 5-21 See Table 5-21
5-95
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TABLE 5-13
INPUT PARAMETERS FOR AT123D SIMULATION OF FLOW AND POLLUTANT
TRANSPORT THROUGH THE SATURATED ZONE
FOR MONOFILL PROTOTYPE
Parameter
Source Area (ha)
Distance to receptor well (m)
Q ass I
Class n
Aquifer width
Aquifer depth (m)
Q ass I
Class n
Begin point of x-source location (m)
End point of x-source location (m)
Begin point of y-source location (m)
End point of y-source location (m)
Effective porosity '
Hydraulic conductivity (m/yr)
Hydraulic gradient (m/m)
Longitudinal dispersivity (m)
Lateral dispersivity (m)
Vertical dispersivity (m)
Distribution coefficient
Decay rate
Bulk density of soil (kg/m3)
Density of water (kg/m3)
Value
1
0
150
infinite
1
5
0
100
50
50
0.4
0.61
0.005
153
5.1
1.0
Table 5-15
Table 5-19
1600
1000
Source
U.S. EPA (1986e)
Policy
Policy
AT123D
.„
Policy
Policy j
Based on source Area
Based on source area
Based on source area
Based on source area
i
Carsel and Parrish {1988)
Carsel and Parrish (1988)
US. EPA (1986e)
I
U.S. EPA (19860 '
U.S. EPA (19860
U.S. EPA (19860
See Table 5-15
See Table 5-19 '• .
Based on particle density of
2.65 and model porosity;
i
5-96
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TABLE 5-14
INPUT PARAMETERS FOR AT123D SIMULATION OF FLOW AND POLLUTANT
TRANSPORT THROUGH THE SATURATED ZONE
FOR THE SURFACE IMPOUNDMENT PROTOTYPE
Parameter
Value
Source
Source Area (m2)
Distance to receptor well (m)
Class I
Class II
Aquifer width
Aquifer depth (m)
Class I
Class II
Begin point of x-source location (ra)
End point of x-source location (m)
Begin point of y-source location (ra)
End point of y-source location (m)
Effective porosity
Hydraulic conductivity (ra/yr)
Hydraulic gradient (ra/ra)
Longitudinal dispersivity (m)
Lateral dispersivity (m)
Vertical dispers'ivity (m)
Distribiitic^vcbefficient
, .~;; iif :,ii-,v • : -
Decay rate "
Bulk density of soil (kg/m3)
Density of water (kg/m3)
20,236
0
150
Infinite'
1
5
0
142
71
71
0.4
0.61
0.005
15.3
5.1
1.0
Table 5-15
Table 5-19
1600
1000
U.S. EPA (1986f)
Policy
Policy
AT123D
Policy
Policy
Based on source area
Based on source area
Based on source area
Based on source area
Carsel and Parrish
(1988)
Carsel and Parrish
(1988)
U.S. EPA (1986e)
U.S. EPA (1986f)
U.S. EPA (1986f)
U.S. EPA (1986f)
See Table 5-15
See Table 5-19
Based on particle
density of 2.65 and
model porosity
5-97
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5.8.1 Site Parameters
For both monofills and surface impoundments, EPA assumed that the sludge is placed
entirely beneath the ground surface, requiring subsurface excavation. For monofills, the ;
excavated soil is typically piled next to the trench and used for cover. For simplicity, it is
assumed that the geometry of the site is square for both prototypes: the length of each side is i
equal to the square root of the site's surface area. Values for input parameters used to
characterize surface disposal facilities are listed in fable 5-10 for the raondfill and surface '
impoundment prototypes. i
5.8.1.1 Area of the Disposal Site
The area for the monofill prototype is set to 1 hectare (10,000 m2), based on a design
scenario described in U.S. EPA (1986e). The model area of a surface impoundment is set to
20,236 m2. This value represents the 98th percentile of areas for surface impoundments, as
reported in the RCPvA Subtitle D survey (U.S. EPA, 1986f).
5.8.12 Depth of Disposal Facility
i
The depth of a monofill determines the total quantity of sludge contained in the site. ;
The assumed depth of 3.46 m (10 ft) is based on a design sicenario described in U.S. EPA
(1986d). The depth of the surface impoundment is assumed to be 4 m. This value represents
the average of data collected from an informal survey of municipal sewage sludge practices by:
Abt Associates Inc. (1989). Based on analysis of data from the 1988 NEEDS Survey, Abt
Associates contacted sewage sludge coordinators in the nine states with the largest number of
surface impoundments.
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5.8.1.3 Distance to Well
For both the raonofill and surface impoundment prototypes, the receptor well is
conservatively assumed to be located in the direction of ground water flow. For facilities located
above a Class I aquifer, it is conservatively assumed to be located at the edge of the site, or a
distance of 0 m downgradient from the monofill or surface impoundment. To determine an
appropriate distance for a Class II/III.aquifer, the Agency used results from a survey of 163
permit applications for land disposal of hazardous waste (U.S. EPA, 1986e) to conclude that 150
meters from the downgradient edge of the site is a reasonable assumption for the point of
effective potential human exposure.
5.8.1.4 Thickness of Cover
The thickness of the active cover is assumed to be 0.3 m and the thickness of the final
cover 1 meter. These values represent typical thicknesses for cover applied to an area-fill trench
(U.S. EPA, 1978).
5.8.15 Number of. Days Average Cell Uncovered
Total emissions from a monofill ceil depend on the length of time the cell is uncovered
or covered with a soil layer. For deriving criteria, it is assumed that a cell is open for 4 hours a
day for the 3 consecutive days it receives sludge (U.S. EPA,. 1986d). For the remaining 20 hours
of each of those. 3 days, and for the remainder of the active lifetime of the facility, the cell is
covered with a temporary layer of soil. During the 20-year active lifetime of the monofill,.half
the.cellswiU contain sewage sludge for more than 10 years and half for less than 10 years. A
typical cell isv therefore, uncovered for 3 x 4/24 or 0.5 days and covered for (20 x 365.25)/2 - 0.5,
or about 3,652 days. After the facility is filled to capacity, it is covered with a thicker, permanent
layer of soil for the remainder of the period simulated.
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5.8J.6 Inflow Eats
As explained in Section 5.2, the prototype facility for surface impoundments is assumed
to receive continuous inflow of sewage sludge throughout its active lifetime. The duration of
that active lifetime depends on the rate at which sludge enters the facility, the solids content of
that sludge, and the volume of the facility. According to the RCRA Subtitle D survey (U.S.
EPA, 1986f), almost 96 percent of the sludge lagoons surveyed received less than 50,000 gallons
per day (0.0022 m3/sec) of wastewater flow. This value is consistent with the mean inflow rate;
for surface impoundments, based on the data from the analytic survey of the NSSS, and is used
as the model inflow rate.
5.8.1.7 Ratio of Sludge Volume to Total Volume
A typical trench monofill is composed of numerous parallel trenches filled with sludge
and separated by soil, so that the entire monofill site contains both sludge and soil. To derive
criteria, these layers of sludge and soil are not modeled separately, but are instead idealized as a
homogeneous mixture. To calculate the total quantity of sewage sludge likely to be contained
within a monofill of specified dimensions, it is necessary to specify the fraction of the monofilPs
contents consisting of sludge. U.S. EPA (1978) describes several design scenarios for different
types of trench monofills and reports the approximate quantity of sludge that can be received per
acre for each scenario. The wide-trench monofill scenario (which receives the most sludge per
unit area) is reported to receive about 7,744 m3 of sludge per hectare and to have a depth of
about 1.22 m. Dividing this volume of sludge by the volume of facility per hectare (10,000 m2 x
1.22 m or 12,200 m3) yields the fraction of the monofill's volume that contains pure sludge (0.63).
For the surface impoundment prototype, the entire facility is assumed to be filled with
sludge, so that the volume of sludge contained by the facility is equal to the volume of the
impoundment. ;
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5JJ.8 Site Life
The site life for monofills is the length of time the monofill is receiving sewage sludge, up
until the time that a permanent cover is applied. 'The assumed site life of 20 years is based on
the design scenario described in U.S. EPA (1986d).
For surface impoundments, the site life is the time required to fill the impoundment with
sewage sludge solids, which is calculated from the inflow rate, the percent solids in the sludge,
and the dimensions of the facility. Using the inflow rate, percent solids, and site dimensions, the
expected lifetime is calculated to be about 7 years.
5.8.1.9 Wind Velocity
Wind velocity affects the transport of volatilized pollutant. As explained in Section 5.3,
the equations used to model emissions from monofills require an estimate of average wind
velocity at the ground level. For surface impoundments, wind velocity is specified at 10 m above
the surface. Although wind velocities at 10 m are likely to be somewhat higher than those at
ground level, a single value of 4.5 ra/sec (10 mph) has been assumed for both prototypes. This
value represents a typical yearly average wind speed in the United States (U.S. EPA, 1990a).
5.8.1.10 Air Temperature
The model air temperature of 15° C represents a typical annual average value for the
United States. This value is consistent with the range of temperatures presented in U.S. EPA
(1986e).
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5.8.2 Shidge Parameters
The physical characteristics of sewage sludge affect the fete and transport of pollutants.
In particular, the solids content and particle density of the sludge help determine how much
pollutant stays adsorbed to the sludge matrix, and how much is lost to various loss processes.
Values for these and other parameters are included in Table 5-10 and are discussed below.
5.82.1 Solids Content
The solids content of sewage sludge depends on the level of treatment (i.e., primary, J
: tr
secondary, advanced) and on the types of treatment processes used (e.g., stabilization, ' -
dewatering). Only dewatered sludges with solids contents greater than or equal to 15 percent kre
[
suitable for disposal in sludge-only monofills. Monofilled sludge is often mixed with a bulking;
agent (e.g., soil) to increase solids content. The solids content of sludge (20 percent) assumed
for deriving national criteria is based on the value reported for a typical wide-trench monofill
(U.S. EPA, 1978).
The solids content of sludge deposited in surface impoundments is typically lower than
that deposited in monofills. As described in Section 5.4.1, the solids content of sludges within a
surface impoundment is assumed to differ between two idealized layers: a "liquid" layer and
"sediment" layer. Sewage sludge entering the impoundment is assumed to contain 3 percent
solids by mass (0.03 kg/kg). This value falls within the range of concentrations reported for i
primary and secondary treated sludge (U.S. EPA, 1978). The solids content of the sediment
layer is assumed to be 17 J percent This value was obtained through a survey of municipal
sewage sludge disposal practices by Abt Associates Inc. (1989) and represents the midpoint of
solids contents found in surface impoundments after eight or more years. It is also consistent
with the range of solids concentrations (15-20 percent) typically encountered within ;
impoundments used to dewater sludge for land application (Chancy, 1992).
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5.823 Particle Density of Sludge
A particle density can be derived from the mass and solids content of a typical wet
sludge. According to Chancy (1992), a typical wet sludge in a surface impoundment has a
specific gravity of about 1.03, equivalent to a density of about 1030 kg/m3. If 17 _5 percent of the
mass of such sludge is solids and the remainder is water (with a density of 1000 kg/m3), the
particle density of pure sludge (p^) can be calculated as:
= (1030) (*g/*»3) - (1000)(*g/m3)(0.825)
5.8.3 Soil Parameters . "
The unsaturated zone is characterized by pore space containing both air and water,
whereas the pore space in the saturated zone contains water only. Because of differences in fluid
mechanics, these two zones require different equations and input parameters for tracking
pollutant transport. A simplifying assumption used for deriving criteria is that the basic soil
characteristics (including soil type, porosity, and bulk density) of the two zones are identical.
For both the monofill and surface impoundment prototypes, sewage sludge is assumed to
be placed entirely beneath the ground surface, requiring subsurface excavation. For raonofills,
the excavated soil is typically used for cover (U.S. EPA, 1978). Parameter values describing soil
and geo-hydrological characteristics for both raonofills and surface impoundments (previously
listed in Table 5-11 in Section 5.5) are discussed below.
5.83.1 Soil Type
The type of soil in the unsaturated and saturated zones affects the ability of a pollutant
to move vertically to the aquifer and laterally to a nearby well. In general, the pollution
potential of a soil is largely affected by the type of clay present, the shrink/swell potential of that
clay, and the grain size of the soil. For example, the less the clay shrinks and swells and the
5-103
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smaller the grain size of the soil, the less the pollution potential associated with that soil. Soil
types in the unsaturated zone in order of increasing pollution potential are: (1) nonshrinking
clay, (2) clay loam, (3) silty loam, (4) loam, (5) sandy loam, (6) shrinking clay, (7) sand^ (8)
gravel, and (9) thin or absent soil (U.S. EPA, 1985e). ;
Sand has been selected as a reasonable worst-case soil to use in model scenarios for
defining numerical criteria for sludge. Wherever possible, all values for parameters describing
soil characteristics for model simulations are based on values estimated for sand.
5.83.2 Porosity of Sludge/Soil
< *
Porosity is the ratio of the void volume of a given :soil or rock mass to the total volume of
that mass. If the total volume is represented by Vt and the volume of the voids by Vv, the ;
porosity can be defined as (?,=vyvr Porosity is usually rejportecl as a decimal fraction or
percentage, and ranges, from 0 (no pore space) to 1 (no solids). For soil types with small particle
sizes such as clay, porosity increases to a maximum of around 50 percent. Porosities of coarser
media like gravel decrease to a minimum of around 30 percent.
To derive pollutant criteria, a total porosity of 0.4 has been taken from Todd (1980).
This value is consistent with the average value for sand (0.43) reported in Carsel and Parrish
(1988). It is used to represent total porosity within a monofill, in the cover soil applied to a
monofill, and within the unsaturated and saturated soil zones beneath both monofill and surface
impoundment prototypes.
Effective porosity is calculated as the difference between the average saturated water
content and the approximate average residual water content, and refers to the amount of
interconnected pore space available for fluid flow. To derive the criteria, average residual water
content in the unsaturated zone is assumed to be less than 0.05, and effective porosity has been
approximated with the same value used for total porosity (0.4) in mass balance and ground water
transport calculations.
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5.8 JJ Bulk Density of Soil
The bulk density of soil is defined as the mass of dry soil divided by its total (or bulk)
volume. Bulk density directly influences the retardation of solutes and is related to soil
structure. In general, as soils become more compact, their bulk density increases. Bulk density
can be related to the particle density and porosity of a given soil as:
where:
BD = bulk density of soil (kg/m3),
/>„ = particle density of soil (kg/m3) and
0, = porosity of soil (dimensionless).
•»
» j
Typical mineral soils have particle densities of about 2,650 kg/m3 (Freeze and Cherry, *
1979). This value and a soil porosity of 0.4 suggest a bulk density of about 1,600 kg/m3 for pure
soil, which is somewhat higher than the 1,300 to 1,500 kg/ra3 range typically encountered for soil
mixed with sewage sludge (Chancy, 1992).
5,83.4 Porosity of Cover Soil
Because cover soil for a raonofiJl is typically excavated from the site, its total porosity is
assumed to be the same as for soil within or beneath the facility (0.4).
5.833 Saturated Hydraulic Conductivity of Soil
Saturated hydraulic conductivity refers to the ability of soil to transmit water, which is
governed by the. amount and interconnection of void spaces in the unsaturated or saturated
zones. These voids may occur as a consequence of inter-granular porosity, fracturing, or bedding
planes. In general, high hydraulic conductivities are associated with a high pollution potential.
The value for saturated hydraulic conductivity used for deriving criteria (0.61 m/hr) is the 95th
5-105
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perccntile of a probability distribution for hydraulic conductivity in sand derived by Carsel and
Parrish (1988). It thus represents a conservative or "reasonable worst case" value.
5.83.6 Unsaturated Hydraulic Conductivity of Soil
The hydraulic conductivity or effective permeability of soil in the unsaturated zone is a
function of its moisture content, which is, in turn, a function of the pressure head. These
relationships are central to the simulation of water flow through the unsaturated zone. The
VADOFT model, used to derive criteria, accepts as input sets of data points describing effective
permeability-saturation curves and the saturation-pressure head curves. Alternatively, it accepts
van Genuchten water retention parameters defining the curves (U.S. EPA, 1989b; Carsel and ,»
Parrish, 1988); this latter parameterization is used for deriving criteria.
Based on soils data from the Soil Conservation Survey (SCS), Carsel and Parrish derived
distributions for the three parameters required (0,, a, and 0) according to twelve SCS textural
classifications (Carsel and Parrish, 1988). Values used for deriving criteria (0.045,14.5 m'1, and
2.68 for 0t, a, and 0, respectively) correspond to the mean values reported for sand.
5.83.7 Fraction of Organic Carbon in Soil or Sludge
The model combines the fraction of organic carbon in the soil with each pollutant's
organic carbon partition coefficient to determine the partitioning of pollutant between soil and >
water. In general," a lower fraction of organic carbon implies greater mobility for organic
pollutants. The organic carbon content for sludge varies among sludge types, with mean values
for various types showing a relatively narrow range of 27.6 to 32.6 percent (U.S. EPA, 1983c).
Criteria for surface disposal are calculated based on the mean value of carbon reported for all
sludges combined (31 percent). A value of 10'1 has been selected tor the fraction of organic
carbon in the unsaturated zone because it is a typical value for sand, and falls at the lower end of
the range (0.001 - 0.01) reported for soil beneath hazardous waste disposal facilities (U.S. EPA,
1986e). The fraction of organic carbon in the saturated zone is expected to be lower than that of
5-106
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the unsaturated zone, and has been assigned a value of 10"4, or one tenth the fraction assumed
for the unsaturated zone.
5.83.8 Depth to Ground Water
The depth to ground water is defined as the distance from the lowest point of the surface
disposal facility to the water table. The water table is itself defined as the subsurface boundary
between the unsaturated zone (where the pore spaces contain both water and air) and the
saturated zone (where the pore spaces contain water only). It may be present in any type of
medium and may be either permanent or seasonal. The depth to ground water determines the
distance a pollutant must travel before reaching the aquifer and affects the attenuation of tl
*
pollutant concentration during vertical transport. As this depth increases, attenuation also tends
to increase, thus reducing potential pollution of the ground water.
For Class I aquifers, the model scenarios for both monofill and surface impoundment
prototypes are based on a worst-case condition, where the water table occasionally or regularly
rises above the bottom of the facility: a value of 0 m is chosen as the depth to ground water.
This conservative value has been selected to provide maximum protection for these most
sensitive aquifers.
For Class U/Ul aquifers, criteria are calculated based on a depth to ground water of 1 m.
This distance is shorter than is likely to be observed at most actual facilities, and represents a
conservative assumption designed to protect aquifers at relatively shallow depths.
5.8.4 Hydtoiogic Parameters
Key hydrologic parameters include net recharge or seepage, the thickness of the aquifer,
and the hydraulic gradient. Values used to derive criteria are included in Table 5-11 and
discussed below.
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5.8.4.1 Net Recharge or Seepage
The primary source of most ground water is precipitation, which passes through the
t
ground surface and percolates to the water table. Net recharge is the volume of water reaching
the water table per unit of land and determines the quantity of water available for transporting
pollutants vertically to the water table and laterally within the aquifer. The greater the recharge
rate, the greater the potential for pollution, up to the point at which the amount of recharge is
large enough to dilute the pollutant. Beyond that point, the pollution potential ceases to
increase and may actually decrease (U.S. EPA, 1985f).
For monofills, the selected recharge rate (0.5 ra/yr) represents the average of a range of^
«..
values presented in U.S. EPA (1986e). For surface impoundments, the relatively high water
content of sewage sludge can provide an additional source of recharge if water from the sludge.
seeps through the floor of the impoundment. In impoundments receiving continuous or periodic
deposits of sludge, this source may not be depleted during the active lifetime of the facility.
Table 5-15 lists seepage rates from municipal lagoons (U.S. EPA, 1987b). The value selected for
deriving criteria (2.5 ra/yr) represents the average seepage rate for lagoons over sandy soil. .
5.8.4.2 Thickness of Aquifer
Saturated zones are considered aquifers unless they lack the permeability to yield
sufficient water. Only true aquifers are considered when selecting input parameters for
calculating criteria. For deriving criteria, the thickness of the aquifer is assumed to be 1 m for
Class I aquifers and 5 m for. Class II/ni aquifers. These tliicknesses are assumed to represent
reasonable worst-case conditions and have been selected as a matter of policy to ensure that
criteria for sludge are sufficiently protective.
5-108
-------
TABLE 5-15
SUMMARY OF MEASURED SEEPAGE RATE FROM MUNICIPAL LAGOON SYSTEMS*
Water Depth
(ft) Lagoon Type
5
6
5
6
6
-
-
-
-
-
5
5
5
-
Facultative
Facultative
Facultative
Facultative
Facultative
_
Maturation
Facultative
Facultative6
Evaporation*1
Facultative
Underlying Soil
Heavy silty clay
Light jsilty clay
Alkaline silt
Fine sand
Gravel and silt
Sandy soil
Sand and gravel
Sandy soil
Clay loam and shale
Mica and schist
Silt, sand, marl
Sand, silt, marl
Sand, silt, marl
Sandy soil
Seepage Rate
(in/day)
0.3
0.29
0.65 '
1.2
1.3
0.35
0.61"
0.34
0.3
0.06 - 0.23
0.18
1.07
0.04 - 0.11
0.12
Seepage Rate
(L/m2-hour)
0.32
0.31
0.69
1.3
1.4
0.37 „
t *
0.65 *
0.36
0.32
0.06 - 0.24
0.19
1.13
0.04 - 0.12
0.13
1 Source: U.S. EPA (1987b).
b Includes net precipitation/evaporation.
c Used intermittently.
d Sealed with bentonite and soda ash.
5-109
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5.8.43 Hydraulic Gradient
The hydraulic gradient is a function of the local topography, ground-water recharge
volumes and locations, and the influence of withdrawals (e.g., well fields). It is also very likely to
be indirectly related to properties of porous media. Rarely are steep gradients associated with
very high conductivities. No functional relationship exists, however, to express this relationship.
The hydraulic gradient value selected for deriving criteria is 0.005 m/m or 0.5 percent,
and is based on an average value for ground waters surveyed for the Hazardous Waste '.
Management System Land Disposal Restrictions Regulation (U.S. EPA, 1986e).
5.8.5 Chemical-Specific Parameters |
5.83.2 Distribution Coefficients
Pollutant transport in soil systems is influenced by interactions between the pollutant and
soil. The affinity of pollutants for soil particles may result: from ion exchange on charged sites ior
adsorption due to surface forces. When the soil's capacity to attract pollutant is exceeded,
soluble pollutants will move through the soil at the same velocity as the bulk leachate. The
affinity between a soil and a pollutant is characterized by the distribution coefficient (KD).
Representative KD values (in L/kg or m3/kg) are defined as the equilibrium ratio of the pollutant
concentration in.soil (rag/kg) to that in associated water (rag/L or mg/m3). Values used for this
analysis are listed in Table 5-16, and discussed below.
For organic pollutants, KD is calculated from a pollutant's partition coefficient between
organic carbon and water
KD * KOCf^.
where:
KD = equilibrium partition coefficient for pollutant (nvVkg),
KOC = organic carbon partition coefficient (ra3/kg), and
fo,. = fraction of soil consisting of organic matter.
5-110
-------
TABLE 5-16
DISTRIBUTION COEFFICIENTS FOR ORGANIC AND INORGANIC CONTAMINANTS
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Benzene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT
Liridane
Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
Wiithin
Surface Disposal
Facility
(W
20
431
59
98
621
330
63
32.8
139,000
16,800
41,200
239,000
726
0.115
467,000
9,140
60.1
Unsatu rated
Zone
(«
20
431
59
98
621
330
63
0.106
448
54.1
133
772
2.34
0.000371
1,510
29.5
0.194
Saturated
Zone
(//kg)
20
431
59
98
621
• *
330
63
0.0106
44.8
5.41
13.3
77.2
0.234
0.0000371
151
2.95
0.0194
Notes: The distribution coefficient for organic pollutants (KD) is the product of the organic carbon
partition coefficient (KOC) and the fraction of organic carbon in the medium (fx). Assumes
/^ of 31% within the surface dipsosal facility and 0.1% and 0.01% in the unsaturated and
saturated soil zones, respectively. Distribution coefficients for metals are geometric means
of values reported for a "sandy loam' soil in Gerritse et al. (1982).
5-113
-------
As discussed in Section 5.83.7,/« values of 031,0.001 and 0.0001 are assumed for the sewage
sludge layer, unsaturated zone, and saturated zone, respectively.
The organic carbon partition coefficient for a pollutant can be estimated from its octanol-
water partition coefficient, which can be measured in laboratory experiments. Values of KOC \
used to determine criteria are shown in Table 5-17 and are calculated from the following
regression equation by Hassett et al. (1983):
Iog(£OC) = 0.0884 + 0.909log(KOW)
where:
KOW = octanol-water partition coefficient for pollutant
«:<
With the exception of PCBs, the KOW values used for this analysis have been obtained from the
CHEMEST procedures in the Graphical Exposure Modelling Systems (GEMS and PCGEMS), |
U.S. EPA (1988y, 1989d).
Polychlorinated biphenyls (PCBs) are a class of chemicals containing 209 possible
congeners. The most common constituent of PCB mixtures is Aroclor 1254, which is dominated
by penta-congeners, with about equal amounts of tetra- and hexa-congeners. In a well-aged soil
contaminated with PCBs, however, Aroclor 1260, which contains more penta- and hexa-
congeners than tetra-congeners, is more representative of Che PCBs found (O'Connor, 1992). Iri
order to determine a representative organic carbon partition coefficient for PCBs, an average has
been calculated from log KOW coefficients listed in Table 5-18 (from Anderson and Parker,
1990). The log KOW for the penta-congener has been estimated to be approximately 6.5 by
noting that the log KOW vajues are approximately linearly related to the number of chlorines in
the congener. Averaging that value with the hexa-congener value gives 6.7 for the log KOW. As
with other organic pollutants, the regression equation from Hassett et al., (1983) is used to
convert this K, value to an estimate of KOC. ;
For metals, values for KD are taken from Gerritse et al. (1982) and represent results of
laboratory tests with a sludge-amended sandy topsoil. The values used for each pollutant are
5-112
-------
r;; _ ' . •.:••- TABLE 5-17 .
OCtANOL-WATER AND ORGANIC CARBON PARTITION COEFFICIENTS
FOR ORGANIC CONTAMINANTS
Log of Octanol-
Watcr Partition
Coefficient*
Organic Carbon
Partition
Coefficient1*
Benzene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT
Lindane
Nitrosodimethylaraine
Polychlorinated biphenyls6
Toxaphene
Trichloroethylene
2.13
6.12
5.11
5.54
6.38
3.61
-0.57
6.70
4.82
2.42
106
448,000
54,100
133,000
772,000 t;
2,340
. 0.371
1,510,000
29,500
194
1 All values except for PCBs taken from the CHEMEST procedure of the Graphical Exposure
Modeling System (GEMS and PCGEMS), U.S. EPA (1988; 1989d).
b KOC for organic contaminants derived from KOWvnth Equation 6 from Chapter 15 of
Francis et al. (1983): log(KOQ= 0.0884 + Q.9Q9\og(KOW).
0 Based on aroclor 1254, the most common PCB in sewage sludge. Derived from O'Connor
(1991) and representative values from Anderson and Parker (1990)
5-113
-------
TABLE 5-18
OCTANOL-WATER PARTITION COEFFICIENTS
FOR PCBS'
Congener
2,4'
WAS*
All Penta
2,2',4,4'A5'
Average6
Number of Chlorines
2
- 4
5
6 ,
5.5
Log ROW
5.1
6.1
6.5" i
6.9
1
6.7 :
1 Source: Anderson and Parker (1990).
b Estimated based on apparent linear relationship between number of chlorines on congener
and log JCW. :
0 Log ROW values for penta- and hexa-congeners averaged for representative
logKOW. ',
5-114
-------
listed in Table 5-6, and are based on the geometric mean of the ranges provided by those
authors.
5,83.2 Decay Rates
Pollutant concentrations in the subsurface regime may be decreased by various
degradation processes, including abiotic hydrolysis and aerobic or anaerobic microbial
degradation. Although rates of hydrolysis are dependent only on pH and temperature (and can
be estimated with reasonable accuracy), estimates of rates for microbial degradation are fraught
with uncertainty. This uncertainty is due to many confounding influences in the field, such as
substrate availability (fraction of organic carbon present), temperature, the microbial consortium,
-i
and microbial acclimation to a given pollutant. Nevertheless, the range of microbial degradation
rates obtained in the laboratory by measuring the rate of disappearance of a pollutant in various
soil and water grab samples, soil column studies, etc., provides a rough estimate of the rate that
microbial activity is likely to degrade a particular pollutant in the field.
As shown in Table 5-19, this work utilizes several sources for representative microbial
degradation rates. Where a range of values is reported by these sources, values from the lower
end of the range have been selected to derive estimates most protective of public health. Studies
of biodegradation in soil have been favored over studies of biodegradation in aquatic
environments. If estimates of only aerobic biodegradation rates are available for a given
pollutant, a half-life for anaerobic biodegradation has been conservatively estimated to be four
times longer (Howard et al., 1991). However, if available data fail to show any indication that a
pollutant degrades in a particular regime, a value of 0 has been assumed for the degradation
rate.
For the sludge layer of a raonofill or surface impoundment, estimated rates of
degradation are based on studies of microbial degradation in anaerobic conditions. For the
unsaturated soil zone, aerobic microbial degradation and hydrolysis are assumed to be the two
dominant degradation processes. Lindane and trichloroethene are the only two compounds that
undergo hydrolysis. Since hydrolysis rates are far more accurately quantifiable than microbial
5-115 ,
-------
TABLE 5-19
DEGRADATION RATES
Benzene
Benzo(a)pyrene
BEHP
Chlordane
Lindane
DDT
Nitrosodimethylamine
PCBs
Toxaphene
Trichloroethene
Aerobic
Degradation
Rate (yr'1)'
16e
0.48«
11'
Ok
1.2m
0.04'
5.1°
0.063P
1.2"
0.78'
Anaerobic
Degradation
Rate (yr-1)*
; of
0.12k
oy
36'
8.3'
2.5k
1.3k
0.00063"
6r
3.3'
Unsaturated
Zone
Degradation
Rate (yr-1)0
1.6
0.048
1.1
0
1.2
0.004
OJ1
0.0063
0.12
0.78
Saturated
Zone!
Degradation
Rate (yr'1)'
0.8
0.084;
0.55
18
4.8 \:
1.3 \'
0.9
0.0035:
3.1
2.0 ;
* Based on microbial degradation rates, except for lindane and trichloroethene, where
hydrolysis rates are used.
b Based on microbial degradation rates.
c Estimated as 10% of aerobic biodegradation rates. Hydrolysis rates for lindane and
trichloroethene assumed same as aerobic rates.
d Estimated as the arithmetic average of the unsaturated zone degradation rates and the
anaerobic degradation rate.
e Vaishnav and Babeu. (1987).
' Horowitz et al. (1982).
* Coovcr and Sims. (1987).
k Anaerobic rate assumed to equal 25% of aerobic rate; see text for discussion.
1 Howard et al. (1991a).'
' Shelton et al. (1984).
" Castro and Yoshida (1971).
1 Stewart and Chisholm (1971).
" Ellington et al. (1988):
• Zhang et al. (1982).
0 Tate and Alexander (1975).
P Fries (1989)
q See text for discussion.
' Howard (1991b).
' Dilling et al. (1975).
1 Bouwer and McCarthy (1983).
-------
degradation rates, hydrolysis rates are used for these two chemicals. For the other eight organic
polhitarit^|||p^cent of the aerobic biodegradation decay rate is assumed to be appropriate for
the unsaturated zone. This decision is based on the scientific observation that/^ tends to
decrease with depth in the soil, thereby reducing the amount of suitable substrate for microbial
populations that might degrade these chemicals (O'Connor, 1992).
In the saturated zone, all three degradation processes can occur because some ground
*
water is anaerobic and some aerobic. To capture this mix of processes, an arithmetic mean has
been calculated from the aerobic and anaerobic biodegradation decay rates discussed above. For
lindane and TCE, the only two chemicals where hydrolysis is a significant degradation process,
estimated anaerobic decay rates are significantly higher than hydrolysis rates.
«r
t *
For PCBs, it is difficult to assign an anaerobic degradation rate. Highly chlorinated
congeners may be partially degraded very slowly in reducing conditions, but then oxidative
conditions must be established for further degradation to occur. Inadequate information on
anaerobic degradation rates exists in the scientific literature. We have conservatively assumed
that anaerobic degradation of PCBs occurs at 1 percent of the aerobic biodegradation rate.
5.83.3 Molecular Weight
The values presented in Table 5-20 are standard molecular weights for the pollutants of
concern. These weights are used in the vapor loss component of the mass balance program for
monofills.
5.83.4 Henry's Law Constants
&__
Henry's Law constants are used to calculate the rate at which organic pollutants volatilize
from sludge. Determining appropriate values for these constants is complicated by the wide
variation in estimates provided by various sources. Table 5-21 shows values taken from four
different sources, along with the value selected for this analysis. Whenever possible, values are
5-117
-------
TABLE 5-20
MOLECULAR WEIGHTS FOR ORGANIC CONTAMINANTS
Benzene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT
Lindane
Nitrosodimethylamine
Polychlorinated biphenyls (Aroclor 1254)
Toxaphene
Trichloroethylene
Molecular Weight
78.1
252.3
390.6
409.8
354.5
290.8
74.1
325.1
431.8
131.4
5-118
-------
taken from Lyraan et al. (1990); otherwise values are taken from the GEMS data base (U.S.
EPA, 1988), the PCGEMS data base (U.S. EPA, 1989d), or the Aquatic Fate Process Data for
Organic Priority Pollutants (U.S. EPA, 1982b). The decision process is as follows: if a value is
published in Lyman et al. (1990), it is used. If not, but if two values are similar, the mean of
those two values is used. If there is no value in Lyman et al. and no two values agree, a
measured value is chosen in preference to an estimated one. If only estimated, dissimilar values
are available, the value most conservative for ground water (i.e., the lowest Henry's Law
constant) is chosen. This last circumstance occurs only for nitrosodiraethylamine and bis(2-
ethylhexyl)phthalate.
The only exception to the decision process described above is for PCEs, which include a
variety of possible congeners with different chemical characteristics. Anderson and Parker (19§0)
provides a compilation of nondimensional Henry's Law constants for one penta-congener and
three hexa-congeners. To derive a representative Henry's Law Constant for PCBs, the three
values for hexa-congeners were averaged to a single value that was then averaged with the penta-
congener value to obtain the single constant reported in Table 5-21.
For all organic pollutants except PCBs, the dimensioned estimate of Henry's Law-
Constant reported in Table 5-21 has been convened to an equivalent nondimensional constant
based on an assumed temperature of 15 °C (288K) and the following equation:
R T
where:
T = " Temperature (assumed to be 288K),
R ==! Universal Gas Constant (m3-atm/mol-K),
H ,"'.=*., dimensional Henry's law constant (m-atm/mol), and
H =. non-dimensional Henry's Law constant.
Because Anderson and Parker (1990) report nondimensional values for PCBs at 25°C, the
average value derived from this source has been adjusted to an equivalent nondimensional value
at 15°C.
5-119
-------
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-------
5.833 Diffusion Coefficients
As discussed in Section 5.43, volatilization of pollutant from a surface impoundment is
modeled with a mass transfer coefficient derived with a two-layer resistance model. Because
pollutant must pass through both the liquid and air to be released into the atmosphere, the
overall resistance equals the sum of the liquid and gas phase resistances, which are described as
the inverse of mass transport coefficients for each phase. Methods for calculating these mass
transfer coefficients are selected according to two types of site characteristics: (1) the ratio of the
surface's effective diameter (or "fetch") to its depth and (2) the local average wind speed.
Effective diameter is defined as the diameter of a circle of area equal to the facility's. The
fetch:depth ratio for the model site is about 80 and is calculated using an effective diameter of
»
161 m (area = 20,236 m2), and a depth of 2 m (the depth of the liquid layer).
Mass transfer coefficients for the liquid and gas phases are calculated from effective
diameter, the fetch:depth ratio, wind velocity, the viscosity and density of air, and the estimated
diffusivity of each pollutant in water and air. Default values for the viscosity of air (1.8 x 10"4
g/cm-sec) and the density of air (1.2 x 10'3 g/cm3 at STP) have been taken from Incropera and
DeWitt (1985). Wilke and Lee's method provides estimates for the diffusivity of each pollutant
in air, and Hayduk and Laudie's method provides estimates for each pollutant's diffusivity in
water (Lyman et al., 1990). The resulting estimates, which are based on a temperature of 15"C,
are listed in Table 5-22.
5.83.6 Reference Water Concentration
The health effects level is defined as the concentration of pollutant in ground water or air
used to evaluate the potential for adverse effects on. human health as a result of sewage sludge
disposal. For the ground water pathway of human exposure, the health effects level is expressed
as a reference water concentration or adjusted reference water concentration (RWC, in mg/L),
and for the vapor pathway it is expressed as a reference air concentration (RAC, in ngfm3)-
Criteria for surface disposal, of sewage sludge are calculated to result in ground-water
5-121
-------
TABLE 5-22
DIFFUSION COEFFICIENTS FOR ORGANIC CONTAMINANTS
Benzene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT
Nitrosodimethylamine
Lindane
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
Difiusivity in Air
(cmiVsec)*
9.1 x lO'2
- 4.6 x 10-2
3.3 xlO"2
4.5 x 10-2
4.1 x 10-2
9.3 xlO-2
5.0 xlO"2
5.7 x 10'2
5.3 x 10-2
8.2 x lO'2
Difiusivity in Water
(cmVsec)"
7.8 x 10-« I
4.3 x 10-*
3.2 x 10-* \
3.7 xlO-« i
3.7x10^
8.5 x W* ,*
4.5 x 10-*
4.2x10^
3.6xlO-« !
7.3 x 1Q-* :
1 Calculated using the Wilke and Lee method from Chapiter 17-4 of Lyraan (1990), based on |
temperature of 15 °C.
b Calculated using the Hayduk and Laudie method from Chapter 17-7 of Lyman (1990), based
on temperature of 15 °C.
-------
concentrations equal to or less than the RWC, and air concentrations equal to or less than the
RAC at the point of compliance. Values for RWC are listed in Table 5-23.
For all pollutants except nitrosodimethylamine, the reference water concentration has
been calculated by adjusting the Maximum Pollutant Level (MCL) for background concentrations
of pollutant expected in ground water. For nitrosodimethylamine, the RWC has been derived
from the human cancer potency, with an equation provided in Section 5.32. It is assumed that
the highly exposed individual ingests 2 1 of water per day and weighs 70 kg. The RWC is
calculated based on a risk level of 10"*.
To ensure that well water does not exceed the MCL, any preexisting ground-water
concentrations must be considered in addition to pollutant contributions from the surface , l
disposal of sludge. Metals are ubiquitous in the environment and can be expected to occur
naturally in ground water; values for background concentrations of inorganic pollutants in ground
water are taken from the National Inorganic and Radionuclides Survey. These values (listed in
Table 5-23) represent average background levels observed in tap water, but have been used in
this analysis to approximate current background concentrations in ground water. Where
concentrations of a given metal in a particular sample fall beneath the limit of detection, a value
of 1/2 the detection limit has been assigned to the sample to derive these averages. These
estimated background concentrations are subtracted from the MCLs to determine the reference
water concentration for each pollutant in sludge. Organic pollutants are less likely to be found
in uncontaminated sources, so background concentrations are assumed to equal zero.
5.83.7 Reference Air Concentration
Values for the Reference Air Concentration of all organic pollutants are calculated from
the pollutants' estimated human cancer potencies, as discussed in Section 5.6.2.2. Estimates are
based on a risk level of 10"* and a body weight of 70 kg. The highly exposed individual is
assumed to inhale 20 m3 of contaminated air daily for his or her entire lifetime. Human cancer
potencies and reference air concentrations are listed in Table 5-24. •
5-123
-------
TABLE 5-23
ADJUSTED REFERENCE WATER CONCENTRATION
Background
Reference Water Concentration in
Concentration Groundwater
(ing//)' (rag//)
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Benzene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT
Lindane
Nitrosodimethylarninec
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
0.05
0.005
0.1
1.3
0.015
0.002
0.1
0.005
0.0002
0.004
0.002
0.0102
0.0002
0.00007
0.000454
0.003
0.005
0.0032
0.0011
0.0014
0.0499
0.0035
0.0001
0.0030
0
0
0
0
0
0
0
0
0
0
Adjusted
Reference Water
Concentration
(mg//)b |
0.0468 '
0.0039 ;
0.0986
1.2501
0.0115 ,:
0.0019 i*
0.097
0.005
0.0002 I
0.004
0.002 •
0.0102
0.0002 !
0.00007 !
0.000454 I
0.003
0.005
1 All values except those fdr DDT and nitrosodimethylarame are based on the Maximum
Contaminant Level (MCL) under the Safe Drinking Water Act (SDWA).
b Values represent the Reference Water Concentration less background concentrations (see
Sections 53 and 5.4)
0 Calculated from human cancer potency at the 10"1 risk level.
5-124
-------
TABLE 5-24
HUMAN CANCER POTENCIES AND REFERENCE AIR CONCENTRATIONS
Arsenic
Benzene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT
Lindane
'Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
Human Cancer
Potency
(mg/kg-day)-1
1.75
0.029
11.5
0.0141
1.3
0.34
51
1.33
7.7
1.1
0.011
Reference Air
Concentration
Otg/m3)
12.0
• 0.032
25.0
0.27
1.0
. 0.26
0.0071
0.045
' 0.32
32.0
Source: Human Cancer Potencies from the Integrated Risks Information System (IRIS).
Reference Air Concentrations derived as discussed in Sections 5.3 and 5.4.
5-125
-------
-------
SECTION SIX
POLLUTANT LIMITS FOR SEWAGE SLUDGE
PLACED ON A SURFACE DISPOSAL SITE
The Part 503 regulation pertaining to the surface disposal of sewage sludge contains
pollutant limits for three pollutants—arsenic, chromium, and nickel. This section explains why
EPA selected these three pollutants for regulation from the seventeen pollutants for which a risk
assessment was conducted. It also describes how Jhe concentration limits were established for
the three pollutants.
6.1 POLLUTANT SELECTION PROCESS
Based on the results of the risk assessment for the surface disposal of sewage sludge
(Section 5.5), EPA decided to delete from regulatory consideration those pollutants meeting one
of the following three criteria:
• EPA has banned the pollutant for use in the United States; EPA has restricted
the use of the pollutant in the United States; or the pollutant is neither
manufactured nor used to manufacture a product in the United States.
• Based on the results of the National Sewage Sludge Survey, the pollutant has a
low percentage of detection in sewage sludge.
• Based on data from the National Sewage Sludge Survey, the limit for an organic
pollutant in the Part 503 risk assessment by use or disposal practice is not
expected to be exceeded when sewage sludge is used or disposed.
For those pollutants meeting one of the above criteria, EPA believes, human health and
the environment still are protected from the reasonably anticipated adverse effects of placing
sewage sludge on a surface disposal site without establishing limits on those pollutants.
Therefore, limits are not established under Part 503 for pollutants deleted on this basis (see
Appendix E for additional discussion on the deletion of pollutants from the final Part 503'
6-1
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regulation). Table 6-1 lists the seven pollutants deleted from further regulatory consideration;
because they met two of the above criteria, while Table 6-2 lists seven additional pollutants ;
deleted because they met one of the criteria. The three pollutants for which pollutant, limits are
established under Part 503, Subpart C, are listed in Table 6-3, along with the allowable pollutant
concentration in sewage sludge that is placed on a surface disposal site.
6.2 DERIVATION OF POLLUTANT CONCENTRATION LIMITS [
The established limit on the concentration of arsenic, chromium, and nickel in sewage
sludge (other than domestic septage) placed on a surface disposal site depends on the distance
between the boundary of the active sewage sludge unit and the property line of the site. For '.-
active sewage sludge units without a liner and leachate collection system whose boundary is less
than 150 meters from the property line of the site, the pollutant concentration in the sewage ,
sludge cannot exceed the limit established in Table 6-3. (See Appendix E for a discussion about
why no pollutant limits are established for domestic septage.) ;
EPA derived the pollutant concentration limits in Table 6-3 by selecting either the lowest
risk-based criteria value from four tables from Section Five (Table 5-6 to 5-9) or the pollutant,
concentration representing the 99th percentile of sewage sludge samples analyzed for the
National Sewage Sludge Survey, whichever was more stringent. Tables 5-6 through 5-9 present
the results of the risk assessment for sewage sludge placed in both a lined or unlined monofill
and surface impoundment over Class II/III ground water. The risk assessment also developed
pollutant criteria for placement of sewage sludge in a lined or unlined monofill and surface
impoundment over Class I ground water. However, after additional consideration, EPA
determined that it would be more appropriate to treat all ground water as drinkable in
accordance with a Class II designation. For this reason, only the pollutant criteria developed
for sewage sludge placed on a surface disposal site over Class II/III ground water was
considered for the pollutant limits. All risk-based pollutant criteria were reported to two
significant figures and rounded down. For example, a pollutant criterion of 113 mg/kg was
rounded to 110 mg/kg.
6-2
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TABLE 6-1
POLLUTANTS DELETED FROM REGULATORY CONSIDERATION
FOR THE SURFACE DISPOSAL OF SEWAGE SLUDGE
(MEET TWO OF THREE DELETION CRITERIA)
Pollutant
Benzo(a)pyrene
Chlordane
DDT/DDD/DDE
Lindane
n-Nitrosodiraethylamine
PCBs
Toxaphene
Reason Deleted
,Met Criteria #1, 2 and 3
Met Criteria #1, 2 and 3
Met Criteria #1, 2 and 3
Met Criteria #1, 2 and 3
Met Criteria #1 and 2 , »
Met Criteria #1 and 2
Met Criteria #1, 2 and 3
6-3 .
-------
TABLE 6-2
POLLUTANTS DELETED FROM REGULATORY CONSIDERATION
FOR THE SURFACE DISPOSAL OF SEWAGE SLUDGE
(MEET ONE OF THREE DELETION CRITERIA)
Pollutant
Benzene
Bis (2-ethylhexyl) phthalate
Cadmium
Copper
Lead
Mercury
Trichloroethylene
Reason Deleted
Met Criterion #2 :
Met Criterion #3 .
Met Criterion #3
Met Criterion #3
Met Criterion #3
Met Criterion #3 '-
Met Criterion #2
' i
6-4
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TABLE 6-3
POLLUTANTS REGULATED BY THE PART 503 REGULATION
FOR THE SURFACE DISPOSAL OF SEWAGE SLUDGE
Pollutant
Arsenic
Chromium
Nickel
Concentration
(mg/kg)*
73
600
420
*Dry weight basis
6-5
-------
The risk assessment results presented in Tables 5-6 to 5-9 are summarized in Table
6-4. For arsenic and chromium, the pollutant limits established in Part 503, Subpart C, are the
lowest risk-based criteria from the table. The nickel limit, however, is taken to be the 99th
percentile value from the NSSS, since that value (420 rag/kg) is more stringent than the lowest
risk-based criterion derived from the risk assessment (690 mg/kg).
! -
Table 6-4 highlights two significant outcomes of the risk .assessment. First, none of the '
pollutant limits is derived from the risk-based criteria developed through the vapor pathway, >
since all three pollutants are inorganic compounds that do not tend to volatilize. Second, none
of the pollutant limits is derived from criteria developed through modeling a lined monofill or
surface impoundment for the ground-water pathway, since all the calculated risk-based pollutant
ir
loading criteria for lined units are unlimited values. Because the risk assessment showed that '*.
risks to human health from the placement of sewage sludge in lined sewage sludge units with -
leachate collection systems were negligible, pollutant limits under Part 503 only apply to unlined
i
sewage sludge units without leachate collection. Part 503 does, however, establish management'
practices for sites with.a liner and leachate collection system, as well as those without liners and
leachate collection systems (see Section Seven). ;
i
For active sewage sludge units without a liner and leachate collection system whose I
boundary is less than 150 meters from the property line of the site, the pollutant concentration in
the sewage sludge cannot exceed that shown in Table 6-5. These limits were derived based on
the same risk assessment models used to develop limits in Table 6-3. The difference between the
model assumptions used is that, for Table 6-3, exposure is modeled for an HEI who is 150
meters from the sewage sludge unit, whereas for Table 6-5, the HEI is located a distance less ;
than 150 meters from the unit. The owner/operator of the surface disposal site needs to ;
determine the actual distance between the unit and the property line of the site to derive the ;
pollutant concentration limits. ;
In addition to the pollutant concentration limits presented in Tables 6-3 and 6-5, an
owner/operator of a surface disposal site can, at the time of permit application, request that the
permitting authority develop site-specific limits, if appropriate, when the actual values for the site
parameters are different from the generic values used in the risk assessment to develop the
6-6
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TABLE 6-5
POLLUTANT CONCENTRATIONS FOR AN ACTIVE SEWAGE SLUDGE
UNIT WITHOUT A LINER AND LEACHATE COLLECTION
SYSTEM THAT HAS A UNIT BOUNDARY TO PROPERTY
LINE DISTANCE LESS THAN 150 METERS
Unit Boundary to Property
Line Distance (meters)
0 to less than 25
25 to less than 50
50 to less than 75
75 to less than 100
100 to less than 125
125 to less than 150
Pollultant Concentration*
Arsenic
(nag/kg)
30
34
39
46
53
62
Chromium
(nag/kg)
200
2210
2eiO
300
360
450 .
Nickel
(mg/kg) j
210
240
270
320
390 ;
420
*Dry weight basis
6-8
-------
pollutant limits in Table 6-3. The concentration of the three pollutants in sewage sludge placed
in an active sewage sludge unit without a liner or leachate collection system cannot exceed either
the concentration of the pollutant calculated based on site-specific parameters (as specified by
the permitting authority) or the existing concentration of the pollutant in the sewage sludge being
placed in the unit, whichever is lower.
6-9
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-------
SECTION SEVEN
MANAGEMENT PRACTICES
The Part 503 regulation, Subpart C, specifies management practices (Section 503.24) that
must be met if sewage sludge is prepared for, or placed on, a surface disposal site. These
management practices were established to ensure adequate protection of human health and the
environment by specifying requirements not addressed by the pollutant limits set forth in the Part
503 regulation. These management practices are discussed below.
7.1 PROTECTION OF THREATENED OR ENDANGERED SPECIES
Sewage sludge must not be placed on an active sewage sludge unit if it is likely to
adversely affect a threatened or endangered species listed under Section 4 of the Endangered
Species Act or its designated critical habitat. EPA will develop guidance to carry out this
provision consistent with the Endangered Species Act.
7.2 RESTRICTION OF BASE FLOOD FLOW
An active sewage sludge unit cannot restrict the flow of a base flood. This management
practice reduces the potential for a surface disposal site to disrupt an area that carries a 100-year
flood, limits the potential for sewage sludge to be swept up in surface water during a flood, and
also protects the surface disposal site from impacts of a base flood.
7.3 GEOLOGICAL STABILITY
Three of the management practices m Subpart C involve the location of active sewage
sludge units in relation to geologic formations. These management practices help ensure that
-------
[
active sewage sludge units are located in geologically stable areas and that the units can tolerate
certain ground movements. The intent of these management practices is to protect human
health and the environment by preventing uncontrolled releases of pollutants in sewage sludge
resulting from unstable geological conditions. Hie three types of management practices related
to geological stability are discussed below.
7.3.1 Seismic Impact Zones
When a surface disposal site is located in a seismic impact zone, an active sewage sludge
unit must be designed to withstand the maximum recorded horizontal ground-level acceleration.
This management practice helps ensure that the containment structures (e.g., slopes, liner aria
leachate collection system) of an active sewage sludge unit will remain intact (e.g., will not crack
or collapse) because of ground movement. Various seismic design methods are available to!
evaluate designs under seismic conditions (Lambe and Whitman, 1969; Hynes-Griffin and '
Franklin, 1984).
7.3.2 Fault Areas
An active sewage sludge unit must be located at least 60 meters from a fault that has
displacement in Holocene time, unless otherwise specified by the permitting authority. This
setback distance helps ensure that the structural integrity of an active sewage sludge unit will not
be affected should geologic movement occur in a fault area. Guidelines are available for
identifying fault-areas (State of California, 1975).
7.33 Unstable Areas
An active sewage sludge unit cannot be located in an unstable area, such as areas prpne
to landslides; areas with expansive soils; or subsidence areas (areas where the land surface is
lowered or has collapsed because of the dissolution of limestone or other soluble materials);
1-2
-------
This management practice helps to protect the structural components of an active sewage sludge
unit from damage by natural or human-induced forces. Owners/operators of surface disposal
sites may need to perform local geotechnical studies to determine that unstable conditions do not
exist at the site.
7.4 PROTECTION OF WETLANDS
Wetlands are known to provide important ecological functions such as holding flood
waters, retaining pollutants, serving as sources for food and habitat for numerous species,
reducing erosion, and acting as recharge areas for ground water (Office of Technology
Assessment, 1984). An active sewage sludge unit cannot be located in a wetland, unless a«permit
was issued under Sections 402 or 404 of the Clean Water Act. The risk assessment performed to
establish pollutant limits in Subpart C did not address wetlands protection. This management
practice provides wetlands protection from possible contamination from pollutants in sewage
sludge.
7.5 COLLECTION OF RUNOFF
Runoff from an active sewage sludge unit must be collected and disposed according to
the National Pollutant Discharge Elimination System and any other applicable requirements. In
addition, the runoff collection system of an active sewage sludge unit must have the capacity to
handle runoff from a 24-hour, 25-year storm event. The risk assessment for the Part 503
regulation and the pollutant limits do not evaluate risk from exposure to contaminated surface
water because these management practices controlling runoff are assumed to be in place.
7.6 COLLECTION OF LEACHATE
Leachate is fluid generated from excess moisture in the sewage sludge or from water
percolating through the site. Depending on the nature of the waste, leachate may contain
7-3
-------
metals, nutrients, and toxic organic chemicals. Two management practices in Subpart C address
collection of leachate from active sewage sludge units that have a liner and leachate collection
system. The first management practice requires that tlie leachate collection system be operated
and maintained while the unit is active and for three years after the unit closes. The second
management practice requires that leachate be collected and disposed in accordance with
applicable requirements while the unit is active and for three years after the unit closes. These
management practices seek to ensure that the liner is not damaged (e.g., by hydraulic pressure
from the leachate) and that pollutants in sewage, sludge are prevented from being released into
the environment. This management practice regulates only active sewage sludge, units with a
liner and leachate collection system. The Part 503 rule regulates active sewage sludge units
without liners and leachate collection systems through the pollutant limits in Section 50323 and
through other requirements in the regulation. „
7.7 LIMITATIONS ON METHANE GAS CONCENTRATIONS
The final Part 503 regulation contains a management practice that limits concentrations
of methane gas because of its explosive potential. Methane gas is generated and released from a
sewage sludge unit when the sewage sludge is covered ([because of anaerobic conditions). This
management practice requires that:
• If a cover is placed on an active sewage sludge unit, the concentration of methane
gas in air in any structure within the surface disposal site cannot exceed 25 ,
percent of the lower explosive limit for methane gas, and the concentration of
methane gas in the air at the property line of the surface disposal site cannot
exceed the lower explosive limit during the period that .the sewage sludge unit is
active.
• If a final cover is placed on a sewage sludge unit at closure, the concentration of
methane gas in air in any structure within the surface disposal site cannot exceed
25 percent of the lower explosive limit, and the concentration of methane gas in
the air at the property line of the surface disposal site cannot exceed the lower
explosive limit for 3 years after the sewage sludge unit closes, unless otherwise
specified by the permitting authority.
7-4
-------
Twenty-five percent of the lower explosive limit is the level used by other Federal
regulations, such as Occupational Safety and Health and National Fire Protection Code
regulations. Since the human health standard for methane is greater than the lower explosive
level, the EPA believes that the limits set forth hi this management practice provide an adequate
margin of safety to protect human health and {lie environment. Various methods are available to
control methane gas (U.S. EPA, 1977; Raymond Vail and Assoc., 1979).
7.8 PROHIBITION ON CROP PRODUCTION
Food, feed, or fiber crops cannot be grown on an active sewage sludge unit unless the
owner or operator of the surface disposal site can demonstrate to the permitting authority that
public health and the environment are protected, through management practices, from
reasonably anticipated adverse effects of pollutants in the sewage sludge when crops are grown.
This management practice is included because the risk assessment for the final Part 503
regulation and the pollutant limits in the regulation do not address crop production on active
sewage sludge units.
7.9 PROHIBITION ON GRAZING
. Animals cannot be allowed to graze on an active sewage sludge unit unless the
owner/operator of the surface disposal site can demonstrate to the permitting authority that
public health and the environment are protected, through management practices, from
reasonably anticipated adverse effects of pollutants in sewage sludge when animals are grazed
(e.g., through ingestion.of the sewage sludge/soil mixture). This management practice is included
because the risk assessment for the final Part 503 regulation and the pollutant limits in the
regulation do not address grazing of animals on active sewage sludge units.
7-5
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7.10 RESTRICTION OF PUBLIC ACCESS
Public access to a surface disposal site must be restricted while the site contains an active
sewage sludge unit and for three years after the last active sewage sludge unit in the surface
disposal site closes. This management practice is included because the risk assessment for the
final Fart 503 regulation and the pollutant limits in the regulation do not address the potential
for public contact with sewage sludge placed on an active sewage sludge unit (e.g., ingestion of
sewage sludge/soil, methane gas explosions). - i
7.11 PROTECTION OF GROUND WATER
if
>*
This management practice states that sewage sludge placed on an active sewage sludge
unit cannot contaminate an aquifer. This must be confirmed by the results of a ground-water
monitoring program developed by a qualified ground-water scientist or by certification by a
ground-water scientist. This management practice is included because the pollutant limits
established in Subpart C for surface disposal do not address potential nitrate contamination of
ground water, which can result from leachate percolating through the soil.
7-6
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SECTION EIGHT
PATHOGEN AND VECTOR ATTRACTION REDUCTION REQUIREMENTS
Subpart C specifies operational standards (Section 503.25) to control pathogen levels and
reduce the attraction of vectors (e.g., insects, rodents) in sewage sludge and domestic septage
placed on an active sewage sludge unit. Operational standards are set when, in the judgment of
the EPA Administrator, they fulfill regulatory requirements to protect human health and the
environment from reasonably anticipated adverse effects. The operational standards in Subpart
C refer to specific requirements in Part 503, Subpart D, entitled Pathogens and Vector
Attraction Reduction (Sections 503.32 and 503.33). Pathogen and vector attraction reduction
requirements as they apply to surface disposal of sewage sludge are discussed below. For'*
detailed information on these requirements, see Subpart D of the Part 503 regulation and the
Technical Support Document for Part 503 Pathogen and Vector Attraction Reduction Requirements
(U.S. EPA, 1992b).
8.1 PATHOGEN REQUIREMENTS
Sewage sludge, other than domestic septage, placed on an active sewage sludge unit must
meet either the Class A or Class B pathogen requirements (except site restrictions under Class B
requirements) specified in Subpart D (Section 50332), unless a cover is placed on the active
sewage sludge unit at the end of each operating day. Class A pathogen requirements are more
stringent, than Class B requirements and can be met by testing the sewage sludge for certain
pathogens of concern. If necessary, Class A requirements can also be met by treating the sewage
sludge with one of the Processes to Further Reduce Pathogens (PFRP) or by other methods
described in Subpart D. Class B pathogen requirements can be met by testing the sewage sludge
for certain pathogens of concern and, if necessary, treating the sewage sludge with one of the
Processes to Significantly Reduce Pathogens (PSRP) or by other methods described in
Subpart D.
3-1
-------
As mentioned above, if a daily cover is used on an active sewage sludge unit, the
pathogen requirements do not have to be met because a daily cover isolates the sewage sludge
and reduces pathogen formation in sewage sludge. Site restrictions specified in Subpart D for
sewage sludge meeting Class B pathogen requirements do not need to be met for sewage sludge
placed on surface disposal sites because the management practices specified in Subpart C (see
Section Seven) already impose these site restrictions (e.g., restrictions on crop production, animal
grazing, and public contact). Similarly, .domestic septage placed on an active sewage sludge unit
does not have to meet the pathogen requirements of Subpart D because the management
practices in Subpart C already impose site restrictions on crop production, animal grazing, and
public contact for active sewage sludge units and because 40 CFR Part 257 already requires that
domestic septage applied to land on which food crops are grown be treated in a Process to
Significantly Reduce Pathogens (PSRP).
8.2 VECTOR ATTRACTION REDUCTION
Subpart D (Section 503.33) specifies vector attraction reduction requirements for sewage
sludge, including domestic septage, placed on an active sewage sludge unit. For sewage sludge
other than domestic septage, one of several vector attraction reduction requirements outlined in
Subpart D must be met, including using a daily cover to prevent access to sewage sludge by ,
vectors; reducing volatile solids content; meeting a specific, oxygen uptake rate (SOUR); treating
the sewage sludge in an aerobic process; raising the pH of the sewage sludge for a specified time;
meeting a minimum percent solids content; or injecting oir incorporating sewage sludge into the
soil. These practices must be conducted according to the requirements specified in Subpart D.
For domestic septage, vector attraction reduction requirements must be met by employing
one of the following practices: placing a daily cover on an active sewage sludge unit; injecting or
incorporating the domestic septage into the soil; or raising the pH of the domestic septage for a
specified time that is less than that required tor other types of sewage sludge. These practices
must be conducted according to the requirements specified in Subpart D.
S-2
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SECTION NINE
FREQUENCY OF MONITORING, RECORDKEEPING,
AND REPORTING REQUIREMENTS
The Part 503 regulation specifies monitoring, recordkeeping, and reporting requirements for
sewage sludge, including domestic septage, placed on a surface disposal site. These requirements
are discussed below.
9.1 FREQUENCY OF MONITORING
•»
*"
The Part 503 regulation requires that sewage sludge placed on an active sewage sludge unit
.be monitored for regulated pollutant concentrations (arsenic, chromium, and nickel), pathogen
requirements, and vector attraction reduction requirements. Domestic septage must be monitored
for pH under certain conditions. In addition, air at a surface disposal site must be monitored for
methane gas. These requirements are discussed in more detail below.
9.1.1 Sewage Sludge (Other Than Domestic Septage)
Sewage sludge other than domestic septage placed on an active sewage sludge unit must be
monitored for arsenic, chromium, and nickel; pathogen requirements (in Section 503.32(a) or
503.32(b) of the Part 503 regulation); and the applicable vector attraction reduction requirement
(Section 503.33(b)).
The minimum frequency of monitoring required by the regulation is based on the amount
of sewage sludge placed on an active sewage sludge unit annually and ranges from once per year to
once per month, as shown in Table 9-1. The calculations used to develop the different amounts of
sewage sludge on which the monitoring frequency is based are shown in Appendix F.
•9-1
-------
TABLE 9-1
MINIMUM FREQUENCY OF MONITORING
FOR SURFACE DISPOSAL OF SEWAGE SLUDGE
Amounts of Sewage Sludge*
(Metric Tons per 365-Day Period)
Greater than zero but less than 290
Equal to or greater than 290 but
less than 1,500
Equal to or greater than 1,500 but
less than 15,000
Equal to or greater than
15,000
Minimum Frequency
Once per year
Once per quarter
(four times per year)
Once per 60 days
(six times per year)
Once per month
(twelve times per yejar)
'Amount of sewage sludge (other than domestic septage) placed on an active sewage sludge unit
— dry weight basis.
9-2
-------
After the sewage sludge has been monitored for two years at the frequency specified in Table
9-1, the permitting authority may reduce the frequency of monitoring for arsenic, chromium, and
nickel, and for the pathogen requirements (which involve an analysis of sewage sludge prior to
treating it for pathogens to determine whether the sewage sludge contains enteric viruses or viable
helminth ova—see Appendix A, Subpart D). The frequency of monitoring cannot, however, be less
than once per year if sewage sludge is placed on an active sewage sludge unit.
9.1.2 Domestic Septage
If the vector attraction reduction requirement is met by raising the pH of domestic septage
as specified in Subpart D (Section 503.33(b)(12)), then each container of domestic septage placed
on an active sewage sludge unit must be monitored for pH to ensure compliance. ,»
*
9.1.3 Air Monitoring for Methane Gas
The Part 503 regulation also requires that air at a surface disposal site be monitored
continuously for methane gas. Air monitoring must be performed at the property line of the surface
disposal site and in all structures within a surface disposal site. Monitoring must occur while the site
contains an active sewage sludge unit that is covered and for three years after a sewage sludge unit.
closes when a final cover is placed on the sewage sludge. (See also Section 7.7.)
92 RECORDKEEPING
The Part 503 regulation requires that certain information be recorded and retained for 5
years whenever sewage sludge is placed on a surface disposal site. Different recordkeeping
requirements apply to: (a) a person who prepares sewage sludge for placement on an active sewage
sludge unit, and (b) the owner/operator of a surface disposal site. These records must be kept
whether or not a permit is required for certain activities. Different requirements exist for domestic
septage than for other types of sewage sludge. The recordkeeping requirements in the Part 503
regulation are discussed below.
9-3
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9.2.1 Sewage Sludge (Other Than Domestic Septage)
A person who prepares sewage sludge (other than domestic septage) for placement on an
active sewage sludge unit must develop and retain the following information for 5 years:
; I
• The concentrations of arsenic, chromium,, and nickel in sewage sludge meeting the
pollutant limits specified in Table 1 of Part 503.23.
• A certification statement, as worded in Part 503.27(a)(l)(ii) (see Appendix A).
• A description of how certain pathogen and vector attraction reduction requirements
in Subpart D are met.
An owner/operator of the surface disposal site on which sewage sludge (other than domestic
septage) is placed must develop and retain the following information for 5 years:
• The concentrations of arsenic, chromium, and nickel in sewage sludge meeting the
pollutant limits in Table 2 or site-specific pollutant limits as specified in Part 503.23.
• A certification statement, as worded in Part 503.27(a)(2)(ii) (see Appendix, A).
• A description of how the management practices in Subpart C are met. i
• A description of how certain vector attraction reduction requirements in Subpart D
are met.
. 9.2.2 Domestic Septage
A person who prepares domestic septage for placement on an active sewage sludge unit must
develop and retain the following information for 5 years when the vector attraction reduction
requirement is met by raising the pH of the domestic septage as specified in Subpart D,
503.33(b)(12): - \
• A certification statement, as worded in Part 503.27(b)(l)(i) (see Appendix A).
• A description of how the vector attraction reduction requirement in 503.33(b)(12)
(raising the pH of domestic septage) is met.
9-4
-------
An owner/operator of a surface disposal site on which domestic septage is placed must
develop and retain the following information for 5 years:
• A certification statement, as worded in Part 503.27(b)(2)(i) (see Appendix A).
• A description of how the management practices in Subpart C are met.
• A description of how certain vector attraction reduction requirements in Subpart D
are met.
9.3 REPORTING REQUIREMENTS
The Part 503 regulation specifies reporting requirements only for the following type,s of
» 4
facilities:
• Class I sludge management facilities.
• Publicly owned treatment works (POTWs) with a design flow rate equal to or greater
than 1 MOD.
• POTWs that serve 10,000 people or more.
These facilities must submit the information (except for data on domestic septage) they
developed in 503.27(a) (described above) annually to the permitting authority.
9-5
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SECTION TEN
REFERENCES
Abt Associates Inc. 1989. Characterization of Surface Disposal for Wastewater Sludge.
Memorandum to Alan Rubin, U.S. EPA Office of Water Regulations and Standards.
March 27.
Anderson, M.A. and J.C. Parker. 1990: "Sensitivity of Organic Contaminant Transport and
Persistence Models to Henry's Law Constants: Case of Polychlorinated Biphenyls."
Water, Air, and Soil Pollution, 50: 1-18. *
Bouwer, EJ. and P.L. McCarthy. 1983. Transformations of 1- and 2- Carbon Halogenated
Aliphatic Organic Compounds Under Methanogenic Conditions." Applied and
Environmental Microbiology, 45(4): 1286-1294.
Bowers, J.F. et al. 1980. Industrial Source Complex (ISC) Dispersion Model User's Guide ,?
(Vol 1). PB80-133044. U.S. EPA. Research Triangle Park. NC.
Carsel, R.F. and R.S. Parrish. 1988. "Developing Joint Probability Distributions of Soil Water
Retention Characteristics." Water Resources Research, 24(5): 755-769.
Castro, T.F. and T. Yoshida. 1971. "Degradation of Organochlorine Insecticides in Hooded Soils
in the Philippines." Journal of Agricultural Food Chemistry. 19(6): 1168-1170.
Chaney, R. 1992. U.S. Department of Agriculture. Personal Communication.
Coover, M.P. and R.C. Sims. 1987. The Effect of Temperature on Polycyclic Aromatic
Hydrocarbon Persistence in an Unacclimated Agricultural Soil." Hazardous Waste and
Hazardous Materials, 4(1): 69-82.
Dilling, W.L., N.B. Tefertiller, and G.J. Kallos. 1975. "Evaporation Rates and Reactivities of
Methylene Chloride, Chloroform. 1,1,1-Trichloroetnane, Trichloroethylene,
Tetrachloroethylene, and Other Chlorinated Compounds in Dilute Aqueous Solutions."
Environmental Science & Technology, 9(9): 833-838.
Ellington, J.J., F.E. Stancil, W.D. Payne. and.C.D. Trusty. 1988. Measurement of Hydrolysis Rate
Constants for Evaluation of Hazardous Waste Land Disposal: Volume 3. Data on 70
Chemicals. EPA-600/3-88-028. NTIS PB88-234 042/AS, as cited in Handbook of
Environmental Degradation Rate*.
Environmental Science and Engineering. 1^85. Exposure to Airborne Contaminants Released
from Land Disposal Facilities - A Proposed Methodology. Prepared by Environmental
Science and Engineering, Gainsvilie. FI_ for the U.S. EPA Office of Solid Wastes.
Washington DC.
10-1
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Freeze, R.A. and J.A. Cherry. 1979. Groundwater. Englewood Cliffs, NJ: Prentice-Hall. ;
Fries, G.F. 1989. "Potential Polychlorinated Biphenyl Residues in Animal Products from
Application of Contaminated Sewage Sludge to iLand." Journal of Environmental Quality.
11:14-20.
Gerritse, R.G., R. Vriesema, J.W. Dalenberg, and H.P. De Roos. 1982. "Effect of Sewage '.
Sludge on Trace Element Mobility in Soils." Journal of Environmental Quality, 11(3): 359-
364. i
Hasset, JJ, W.L. Banwart, and R.A. Griffin. 1983.^ Environment and Solid Wastes:
Characterization, Treatment, and Disposal. Edited by Francis, C.W., S.I. Auerbach, and
V.A. Jacobs. Butterworth Publishers, Woburn MA. pp. 161-175.
Horowitz, A., D.R. Shelton, C.P. Cornell, and J.M. Tiedjje. 1982. "Anaerobic Degradation of
Aromatic Compounds in Sediments and Digested Sludge." Developments in Industrial
Microbiology (Chapter 40). 23: 435-444.
•r
'i*
Howard, P.H., et al. 1991a. Handbook of Environmental Degradation Rates. Lewis Publishers,"
Inc. Chelsea, MI. '
i ' i
Howard, P.H. 1991b. Handbook of Environmental Fate and Exposure Data for Organic Chemicals.
Vol III, Pesticides. Lewis Publishers, Inc. Chelsea,, MI.
Hwang, S.T. 1985. "Model Prediction of Volatile Emissions." Environmental Progress, 4(2): 141-
144. I
i • l
Hwang, S.T. and LJ-. Thibodeaux. 1982. Toxic Emissions from Land Disposal Facilities." Enyir.
Prog. 1(1)46-52. \
Hynes-Griffin, M.A. and A.G. Franklin. 1984. Rationalizing the Seismic Coefficient Method.
Waterways Experiment Station, U.S. Army Corps of Engineers, Department of the Army,
Washington, DC. Miscellaneous paper GL-84-13.
Incropera, F.P. and D.P. DeWitt. 1985. Fundamentals of Heat and Mass Transfer. John Wiley
and Sons, Inc. New York.
Lambe, T.W. and R.V. Whitman. 1969. Soil Mechanics. John Wiley and Sons, Inc. New York.
Lyman, WJ., W.F. Reehl and D.H. Rosenblatt. 1990. Handbook of Chemical Property Estimation
Methods: Environmental Behavior of Organic Compounds, American Chemical Society.
Washington D.C.
MacKay, D. and PJ. Leinonen. 1975. "Rate of Evaporation of Low-Solubility Contaminants :
from Water Bodies to Atmosphere." Environmental Science & Technology, 9(13): 1178-
1180.
10-2
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MacKay, D; and A. Yeun. 1983. "Mass Transfer Coefficient Correlations for Volatilization of
Organic Solutes from Water." Environmental Science & Technology, 17(4): 423-429.
National Academy of Sciences (NAS). 1983. Risk Assessment and Management: Framework for
Decision Making. Washington, D.C.
National Institute of Occupational Safety and Health (NIOSH). 1979. Registry of Toxics Effects
of Chemical Substances.
O'Connor, G. 1992. Professor and Chairman, Soil and Water Science Dept., University of
Florida. Personal Communication.
Office of Technology Assessment. 1984. Wetlands: Their Use and Regulation. Washington, DC.
OTA-0-206.
Raymond Vail and Associates. 1979. State of Colorado Investigation of Methane Gas Problems at
High Priority Waste Disposal Sites. Vail and Associates, Wheat Ridge, CO.
l»
Shelton, D.R., S.A. Boyd, and J.M. Tiedje. 1984. "Anaerobic Biodegradation of Phthalic Acid
Esters in Sludge." Environmental Science & Technology, 18(2): 93-97.
Shen, T.T. 1982. "Estimation of Organic Compound Emissions from Waste Lagoons." Journal of
the Air Pollution Control Association, 32(1): 79-82.
Springer, C., P.D. Lunney and K.T. Valsaraj. 1984. Emission of Hazardous Chemicals from
Surface and Near Surface Impoundments to Air. U.S. EPA, Solid and Hazardous Waste
Research Division, Cincinnati, OH. Project Number 808161-02.
State of California, Division of Mines and Geology. 1975. Guidelines for Evaluating the Hazard of
Surface Fault Rupture. Department of Conservation, Sacramento, CA. CDMG Note
Number 49.
Stewart, D.K.R. and D. Chisholm. 1971. "Long-Term Persistence of BHC, DDT and Chlordane
in a Sandy Loam Clay." Canadian Journal of Soil Science, 61:379-83, as cited in Handbook
of Environmental Degradation Rates.
Tate III, R.L. and M. Alexander. 1975. "Stability of Nitrosamines in Samples of Lake Water,
Soil, and Sewage." /. National Cancer Inst., 54(2): 327-30.
Thomann, RJf., and Mueller, J.A. 1987. Principles of Surface Water Quality Modeling and
Control. Harper and Row. New York.
Todd, D.K. 1980. Groundwater Hydrology, Second Edition. John Wiley & Sons.
U.S. EPA. 1977. Environmental Assessment of Subsurface Disposal of Municipal Wastewater
Sludge. Interim Report. Municipal Environmental Research Laboratory, Cincinnati, OH.
EPA-530/SW-547.
.10-3
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U.S. EPA. 1978. Process Design Manual Municipal Sludge Landfills. Office of Solid Waste. EPA-
625/1-78-010/SW-705.
U.S. EPA. 1982a. Fate of Priority Pollutants in PubKcfy-Owned Treatment Works. Vol I. Effluent
Guidelines Division. Washington, DC. EPA 440/1-82-303.
U.S. EPA. 1982b. Aquatic Fate Process Data for Organic Priority Pollutants. Office of Water
Regulations and Standards, Washington D.C. EPA-440/4-81-014. !
U.S. EPA. 1983a. The Record of Proceedings on the OWRS Municipal Sewage Sludge Committee.
Washington, DC.
U.S. EPA. 1983b. Rapid Assessment of Potential Ground Water Contamination Under Emergency
Response Conditions. EPA 600/8-83-030.
U.S. EPA. 1983c. Process Design Manual: Land Application of Municipal Sludge. Office of
Research and Development, Municipal Environmental Research Laboratory, Cincinnati,
OH. EPA-625/1-83-016. t;
U.S. EPA. 1985a. Summary of the Environmental Profiles and Hazard Indices for Constituents of
Municipal Sludge: Methods and Results. Office of Water Regulations and Standards.
Washington, DC. \
U.S. EPA. 1985b. Environmental Profiles and Hazard Indices for Constituents of Municipal Sludge:
Arsenic. Office of Water Regulations and Standards. Washington, DC.
U.S. EPA. 1985c. Environmental Profiles and Hazard Indices for Constituents of Municipal Sludge:
Chromium. Office of Water Regulations and Standards. Washington, DC. \
U.S. EPA. 1985d. Environmental Profiles and Hazard Indices for Constituents of Municipal Sludge:
Nickel. Office of Water Regulations and Standards. Washington, DC. ;
U.S. EPA. 1985e. Technical Support Document for Development of Guidelines on Hydrologic
Criterion for Hazardous Waste Management Facility Location. Draft.
U.S. EPA. 1985f. DRASTIC: A Standardized System for Evaluating Groundwater Pollution
Potential.Using Hydrogeologic Settings. Report No. EPA-600/2-85/018. Ada, OK: EPA
U.S. EPA. 1986a. "State'Sludge Management Program Regulations." 51 FR 4458, February 4.
U.S. EPA. 1986b. "Guidelines for Carcinogen Assessment; Guidelines for Estimating Exposure;
Guidelines for Mutagenicity Risk A>scssmcnt; Guidelines for Health Assessment of
Suspect Developmental Toxicants. Guidelines for Health Risk Assessment of Chemical
Mixtures." Federal Register. Vol. 51. No. 185.
U.S. EPA. 1986c. Guidelines on Air Quality Models (Revised), EPA/OAQPS-450/2-78-027R. I
10-4
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U.S. EPA. 1986d. Research and Development: Development of Risk Assessment Methodology for
Municipal Sludge Landfilling. Prepared by Environmental Criteria and Assessment Office,
Cincinnati OH for the Office of Water Regulations and Standards. ECAO-CIN-485.
U.S. EPA. 1986e. "Hazardous Waste Management System Land Disposal Restrictions
Regulation." 51 FR 1602, January 14.
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Office of Solid Waste. EPA-530-SW-86-039.
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Emissions Models. Office of Air Quality Planning and Standards, Research Triangle Park,
NC. EPA-450/3-87-026.
U.S. EPA. 19875. Report to Congress: Municipal Wastertater Lagoon Study, Volumes I and II.
Office of Municipal Pollution Control. (Call No. 01A0005332)
U.S. EPA. 1988. Graphical Exposure Modeling System (GEMS) EPA Mainframe. User's Guide
prepared by General Sciences Corporation for the offices of Pesticides and Toxic
Substances. Contract No. 68-02-4281.
U.S. EPA. 1989a. Risk of UnsaturatedlSaturated Transport and Transformation Interactions for
Chemical Concentrations (RUSTIC), Volume I: Theory and Code Verification. Prepared
by Woodward Clyde Consultants, HydroGeologic, and AQUA TERRA Consultants for
the Office of Research and Development, Environmental Research Laboratory, Athens
GA. Contract No. 68-03-6304.
U.S. EPA. 1989b. Risk of Unsaturated/Saturated Transport and Transformation of Chemical
Concentrations (RUSTIC), Volume II: User's Guide. Environmental Research Laboratory
Athens GA. EPA/600/3-89/048b.
U.S. EPA. 1989c. Background Document for the Surface Impoundment Modeling System (SIMS).
Control Technology Center. Research Triangle Park, NC. EPA/600-6-89-001. NTIS
PB90-135740/A5.
U.S. EPA. 1989d. PCGEMS database. User's Guide, Release 1.0. Prepared by General Sciences
Corporation for the Office of Pesticides and Toxic Substances. Contract NO. 68024281.
U.S. EPA. 1990a. Development of Risk Assessment Methodology for Surface Disposal of Municipal
Sludge. Prepared by Abt Associates Inc. for the Environmental Criteria Assessment
Office, Office of Research and Development. Cincinnati. ECAO-CIN-750.
U.S. EPA. 1990b. Exposure Factors Handbook. Office of Health and Environmental Assessment.
Washington, DC. EPA/600/8-89/043.
U.S. EPA. 1992a. Integrated Risk. Information System (IRIS). [Current file; updated as
necessary.] Washington, DC. Available through the National Library of Medicine.
10-5
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U.S. EPA. 1992b. Technical Support Document for Part 503 Pathogen and Vector Attraction
Reduction Requirements. Office of Science and Technology. NTIS PB93-110609. ;
Vaishnav, D.D. and L. Babeu. 1987. "Comparison of Occurrence and Rates of Chemical
Biodegradation in Natural Waters." Bull Environ. Contam. TomcoL, 39: 237-44, as cited
in Handbook of Environmental Degradation Rates.
Yeh, G.T. 1981. AT123D: Analytical Transport One-, Two-, and Three Dimensional Simulation of
Waste Transport in the Aquifer System. Oak Ridge National Laboratory, Environmental.
Sciences Division. Publication No. 1439. March. ;
Zhang, S., Q. An, Z. Gu, and X. Ma. 1982. "Degradation of BHC in soil, Huanjing Kexue, 3:1-3,
as cited in Handbook of Environmental Degradation Rates.
10-6
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APPENDIX A
STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE
Subpart A—General Provisions
Subpart C—Surface Disposal
Subpart D—Pathogens and Vector Attraction Reduction
-------
-------
PwlftTaT VLeflAftier /* VhT ^fl Mn f? 7* TVTrl-nr VMWiii^i tn «n
' > Pofctant
C^hnvntmn ._,„,.., mtif Iiir ii<(
ODD. DOE. DDT (Town "" ~
2.4 Dt»"^^"^"* •**••—w*wiov» I^HH^HI, i—fncmerauon.
' fowage siudga unit without * Hoar and loachate collection system,
I Senaqt riudga untt wdh • Knar and tasctata cotectkjn system.
'Value axpnMod in grams per Wogiam—dn/ weight basis.
Subchapter O in chapter I of title 40
of the Code of Federal Regulations is
amended by adding part. 503, which
reads as follows:
SUBCHAPTER O—SEWAGE SLUDGE.
PART 503—STANDARDS FOR THE
USE OR DISPOSAL OF SEWAGE
SLUDGE
Subpart A—General Provtetons
Sec.
503.1
503.2
503.3
S03.4
503.5
Purpose and applicability.
Compliance period.
Permits and direct enforceabiliry
Relationship to other regulations.
Additional or more stringent
requirements.
503.6 Exclusions.
503.7 Requirement for a person who
prepares sewage sludge.
503.8 Sampling and analysis.
503.9 General definitions.
Subpart S-Lawi Application .
503.10 Appiicabilr^^l:
503.11 Special definitions.
503.12 General requirements.
503.13 Pollutant limits,
503.14 Managementpractics*.
503.15 Operational standards—pathogens
and vector attraction reduction.
503.16 Frequency of monitoring.
503.17 Recordkeeping.
503.18 Reporting.
Subpart C—Surfae* Diapoaal
503.20 Applicability.
503.21 Special definitions.
503.22 General requirements.
503.23 Pollutant limits (other than domestic
septage).
503.24 Management practices.
503.25 Operational standards—pathogens
and vector attraction reduction.
503.26 Frequency of monitoring.
503.27 Recordkeeping.
503.28 Reporting.
Subpart D—Pathogens and Vector
Attraction Reduction
503.30 Scope.
503.31 Special definitions.
503.32 Pathogens.
503.33 Vector attraction reduction.
Subpart E—tacinccatiian
503.40 Applicability.
503.41 Special definitions.
503.42. General requirements.
503.43 Pollutant limits.
503.44 Operational standard—total '
hydrocarbons. •
503.45 Management practices.
503.46 Frequency of monitoring.
503.47 Recordkeeping.
. 503:48 Reporting.
Appendix A to Part 503 Procedure to
Determine the Annual Whole Sludge
Application Rate for a Sewage Sludge
Appendix B to Part 1503—Pathogen
Treatment Processes
Authority: Sections 405 (d) and (e) of the
dean Water Act, as amended by Pub. L. 95-
217. Sec. 54(d). 91 Stat. 1591 (33 U.S.C 1345
(d) and (e)): and Pub. L. lOO-l. Title IV. Sec.
406 (a), (b). 101 Stat.. 71. 72 (33 U.S.C 1251
et seq.J.
Subpart A—General Provisions
S 503.1 PurpoM and uppHeabfltty.
(a) Purpose. (1) This part establishes
standards, which consist of general
requirements, pollutant limits.
management practices, and operational
standards, for the finql use or disposal
of sewage sludge generated during the
treatment of domestic sewage in a
treatment works. Standards are included
in this part for sewage sludge applied to
the land, placed on a surface disposal
site, or fired in a sewage sludge
incinerator. Also included in this part
are pathogen and alternative* vector
attraction reduction requirements for
sewage sludge applied to the land or
placed on a surface disposal site.
(2) In addition; the standards in this
part include the frequency of
monitoring and recordkeeping
requirements when sewage sludge is
applied to the land, placed on a surface
disposal site, or fired hi a sewaga sludge
incinerator. Also included in this part
are reporting requirements for Class I
sludge management facilities, publicly
owned treatment works (POTWs) with a
design flow rate-equal to or greater than
one million gallons per day, and POTWs
that serve 10.000 people or more.
(b) Applicability. (1) This part applies
to any person who prepares sewage
sludge, applies sewage sludge to the
land, or fires sewage sludge in a sewage
sludge incinerator and to the owner/
operator of a surface disposal site.
(2) This part applies to sewage sludge
applied to the land, placed on a surface
disposal site, or fired in a sewage sludge
incinerator.
(3) This part applies to the exit gas
from a sewage sludge incinerator stack.
-------
9388 Federal Register / Vol. 58. No. 32 / Friday, February 19, 1993 / Rules and Regulations
(4) This part applies to land where
sewage sludge is applied, to a surface -
disposal site, and to a sewage sludge
incinerator.
§50X2 Compliance period.
(a) Compliance with the standards'in
this part shall be achieved as
expeditiously as practicable, but in no
case later than February 19.1994. When
compliance with the standards requires
construction of new pollution control
facilities, compliance with the standards
shall be achieved as expeditiously as
practicable, but in no case later than
February 19,1995.
_ (b) The requirements for frequency of
monitoring, recordkeeping, and
reporting in this part for total
hydrocarbons in the exit gas from a
sewage sludge incinerator are effective
February 19,1994 or, if compliance
with the operational standard for total
hydrocarbons in this part requires the
construction of new pollution control
facilities. February 19,1995.
(c) All other requirements for
frequency of monitoring, recordkeeping,
and reporting in this part are effective
on July 20.1993.
S 503.3 Psrmltssnd direct •nforcssbUlty.
(a) Permits. The requirements in this
part may be implemented through a
permit:
(1) Issued to a "treatment works
treating domestic sewage", as defined in
40 CFR 122.2, in accordance with 40
CFR parts 122 and 124 by EPA or by a
State that has a State sludge
management program approved by EPA
in accordance with 40 CFR part 123 or
40 CFR part 501 or
(2) Issued under subtitle C of the
Solid Waste Disposal Act; part C of the
Safe Drinking Water Act; the Marine
Protection, Research, and Sanctuaries
Act of 1972; or the Clean Air Act.
"Treatment works treating domestic
sewage" shall submit a permit
application in accordance with either 40
CFR 122.21 or an approved State
program.
(b) Direct enforceability. No person.
shall use or dispose of sewage sludge
through any practice for which
requirements are established in this part
except in accordance with such
requirements.
S 503.4 Relationship to othsr regulations.
Disposal of sewage sludge in a
municipal solid waste landfill unit, as
defined in 40 CFR 258.2. that complies
with the requirements in 40 CFR part
258 constitutes compliance with section
405(d) of the CWA. Any person who
prepares sewage sludge that is disposed
in a municipal solid waste landfill unit
shall ensure that the sewage sludge
meets the requirements in 40 CFR part
258 concerning the quality of materials
disposed in a municipal solid waste
landfill unit.
9 50X5 Additional or more stringsnt
rsOjUlrenisnts.
(a) On a case-by-case basis, the
permitting authority may impose
requirements for the use or disposal of
sewage sludge in addition to or more
stringent than the requirement!! in this
part when necessary to protect public
health and the environment from any
adverse effect of a pollutant in the
sewage sludge.
(b) Nothing in this part precludes a
State or political subdivision thereof or
interstate agency from imposing
requirements for the use or disposal of
sewage sludge more stringent wan the
requirements in this part or from
imposing additional requirements for
the use or disposal of sewage shidge.
$503.6 Exclusions.
(a) Treatment processes. This part
does not establish requirements for
processes used to treat domestic sewage
or for processes used to treat sewage
sludge prior to final use or disposal,
except as provided in § 503.32 and
§503.33.
(b) Selection of a use or disposal
practice. This part does not require the
selection of a sewage sludge use or
disposal practice. The determination of
the manner in which sewage sludge is
used or disposed is a local
determination.
(c) Co-firing of sewage sludge. This
part does not establish requirements for
sewage sludge co-fired in an incinerator
with other wastes or for the incinerator
in which sewage sludge and other
wastes are co-fired. Other wastes do not
include auxiliary fuel, as defined in 40
CFR 503.41(b), fired in a sewage sludge
incinerator.
(d) Sludge generated at an industrial
facility. This part does not establish
requirements for the use or disposal of
sludge generated at an industrial facility
during the treatment of industrial
wastewater, including sewage sludge
generated during the treatment of
industrial wastewater combined with
domestic sewage.
(e) Hazardous sewage sludge. This
part does not establish requirements for
the use or disposal of sewage sludge
determined to be hazardous in
accordance with 40 CFR part 261.
(f) Sewage sludge with high PCB
concentration. This part does not
establish requirements for the use or
disposal of sewage sludge with a
concentration of polychlorinatffld
biphenyls (PCBs) equal to or greater
than 50 milligrams per kilogram of total
solids (dry weight basis).
• (g) Incinerator ash. This part does not
establish requirements for the use or
disposal of ash generated during the
firing of sewage sludge in a sewage
sludge incinerator.
(h) Grit and screenings. This part does
not establish requirements for the use or
disposal of grit (e.g., sand, gravel,
cinders, or other materials with a high
specific gravity) or screenings (e.g.,
relatively large materials such as rags)
generated during preliminary treatment
of domestic sewage hi a treatment
works.
(i) Drinking water treatment sludge.
This part does not establish
requirements for the use or disposal of
sludge generated during the treatment of
either surface water or ground water
used for drinking water.
(j) Commercial and industrial septage.
This part does not establish ,
requirements for the use or disposal of
commercial septage, industrial septage,
a mixture of domestic septage and
commercial septage, or a mixture of
domestic septage and industrial'septage.
§503.7 Rsquiracnsnt tors person who .
prepares sswags sludg*.
Any person who prepares sewage
sludge shall ensure that the applicable
requirements in this part are met when
the sewage sludge is applied to the land,
placed on a surface disposal site, or
fired in a sewage sludge incinerator.
§503.8 Sampling and analysis.
(a) Sampling. Representative samples
of sewage sludge that is applied to the
land, placed on a surface disposal site,
or fired in a sewage sludge incinerator
shall be collected and analyzed.
(b) Methods. The materials listed
below are incorporated by reference in
this part. These incorporations by
reference were approved by the Director
of the Federal Register in accordance
with 5 U.S.C 552(a) and 1 CFR part 51.
The materials are incorporated IBS they
exist on the date of approval, and notice
of any change in these materials will be
published in the Federal Register. They
are available for inspection at the Office
of the Federal Register, 7th Floor, suite
700. 800 North Capitol Street, NW..
Washington. DC, and at the Office of
Water Docket, room L-102. U.S.
Environmental Protection Agency, 401
M Street. SW., Washington, DC Copies
may be obtained from the standard
producer or publisher listed in the
regulation. Methods in the materials
listed below shall be used to analyze
samples of sewage sludge. <
A-2 .
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Federal Register / VoL 58. No. 32 / Friday, February 19, 1993 / Rules and Regulations 9388
(1) Enteric viruses. ASTM
Designation: D 4994-89. "Standard
Practice for Recovery of Viruses From
Wastewaier Sludges", 1992 Annual
Book of ASTM Standards: Section 11—
Water and Environmental Technology,
ASTM, 1916 Race Street, Philadelphia,
PA 19103-1187. ; 4>
(2) Fecal coliform. Part 9221E. or Part
9222 D., "Standard Methods for the.
Examination of Water and Waste water",
18th Edition, 1992, American Public
Health Association. 1015 15th Street,
NW., Washington, DC 20005.
(3) Helminth ova. Yanko, W.A..
"Occurrence of Pathogens in
Distribution and Marketing Municipal
Sludges", EPA 600/1-87-014,1987.
National Technical Information Service.
5285 Port Royal Road. Springfield,
Virginia 22161 {PB 88-154273/AS).
(4) Inorganic pollutants; "Test
Methods for Evaluating Solid Waste,
Physical/Chemical Methods", EPA
Publication SW-646, Second Edition •*
(1982) with Updates I (April 1984) and
II (April 1985) and Third Edition
(November 1986} with Revision I
(December 1987). Second Edition and
Updates I and U are available from the
National Technical Information Service,
5285 Port Royal Road, Springfield,
Virginia 22161 (PB-87-120-29*!). Third
Edition and Revision I are available
from Superintendent of Documents.
Government Printing Office, 941 North
Capitol Street. NE., Washington/DC
20002 (Document Number 955-001—
00000-1).
(5). Salmonella-sp. bacteria. Part 9260
D.. "Standard Methods for the
Examination of Water and Wastewater",
18th Edition. 1992, American Public
Health Association. 1015 15th Street.
NW.. Washington. DC 20005; or
Kenner, B.A. and H.P. Clark,
"Detection and enumeration of
Salmonella and Pseudomonas
aeruginosa", Journal of the Water
Pollution Control Federation, Vol. 46.
no. 9. September 1974, pp. 2163-2171.
Water Environment Federation, 601
Wythe Street. Alexandria, Virginia
22314.
(6) Specific oxygen uptake rate. Part
2710 B., "Standard Methods for the
Examination of Water and Wastewater",
18th Edition. 1992, American Public
Health Association. 1015 15th Street.
NW.. Washington, DC 20005.
(7) Total, fixed, and volatile solids.
Part 2540 G., "Standard Methods for the
Examination of Water and Wastewater",
18th Edition. 1992, American Public .
Health Association, 1015 15th Street,
NW., Washington, DC .20005.
§50X9 General iMMtlens.
(a) Apply sewage sludge or sewage
sludge applied to the land means land
application of sewage sludge. ,
(b) Base flood is& flood that has a one
percent chance of occurring in any
given year (i.e.. • flood with a
magnitude equalled oaca in 100 years).
(c) Class I sludge management facility
is any publicly owned! treatment works
(POTW), as denned in 40 CFR 501.2,
required to have an approved
pretreatment program under 40 CFR
403.8(a) (including any POTW located
in a State that has elected to assume
local program responsibilities pursuant
to 40 CFR 403.10(e)) and any treatment
works treating domestic sewage, as
defined in 40 CFR 1221.2. classified as. a
Class I sludge management facility by
the EPA Regional Administrator, or. in
.the case of approved State programs, the
Regional Administrator in conjunction
with the State Director, because of the
potential for its sewage sludge use or
disposal practice to affect public health
ana the environment adversely.
(d) Cover crop is a small grain crop;
such as oats, wheat, or barley, not grown
for harvest.
(e) CWA means the Clean Water Act
(formerly referred to as either the
Federal Water Pollution Act or the
Federal Water Pollution Control Act
Amendments of 1972), Public Law 92-
500, as amended by Public Law 95-217,
Public Law 95-576, Public Law 96^-483,
Public Law 97-117. and Public Law
100-4.
(!) Domestic septage is either liquid or
solid material removed from a septic
tank, cesspool, portable toilet. Type in'
marine sanitation device, or similar •
treatment works that receives only .
domestic sewage. Domestic septage does
not include liquid or solid material
removed from a septic tank, cesspool, or
similar treatment works that receives
either commercial Wastewater or
industrial wastewater and does not
include grease removed from a grease
trap at a restaurant.
(g) Domestic sewage is waste and
wastewater from h»imnng or household
operations that is1 discharged to or
otherwise enters a treatment works.
(h) Dry weight basis means calculated
on the basis of having been dried at 105
degrees Celsius until reaching a
constant mass (i.a., esitentially 100
percent solids content).
(i) EPA means the United States
Environmental Protection Agency.
(j) Feed crops are crops produced
primarily for consumption by animals.
(k) Fiber craps are crops such as flax
and cotton.
(1) Food crops are crops consumed by
humans. These include, but are not
limited to. fruits, vegetables, and
tobacco.
(m) Ground water i* water below the
land surface in the saturated zone.
(n) Industrial wastewater is
wastewater generated hi a commercial
or industrial process.
(o) Municipality means a city, town,
borough, county, parish, district,
association, or other public body
(including an intermunicipal Agency of
two or more of the foregoing entities)
created by or under State law; an Indian
tribe or an authorized Indian tribal
organization having jurisdiction over
sewage sludge management; or a
designated and approved management
Agency under section 208 of the CWA,
as amended. The definition includes a
special district created under State law,
such as a water district, sewer district,
sanitary district, utility district drainage
district, or similar entity, or an
integrated waste management facility as
defined hi section 201(e) of theJCWA, as
amended, that has as one of its principal
responsibilities the treatment, transport.
use, or disposal of sewage sludge.
(p) Permitting authority is either EPA
or a State with an EPA-approved sludge
management program.
(q) Person is an individual,
association, partnership, corporation,
municipality, State or Federal agency, or
an agent or employee thereof.
(r) Person who prepares sewage
sludge is either the person who
generates sewage sludge during the
treatment of domestic sewage in a
treatment works or the person who
derives a material from sewage sludge.
(s) Place sewage sludge or sewage
sludge placed means disposal of sewage
sludge on a surface disposal site.
(t) Pollutant is an organic substance',
an inorganic substance, a combination
of organic and inorganic substances, or
a pathogenic organism that, after
discharge and upon exposure, ingestion,
inhalation, or assimilation into an v
organism either directly from the
environment or indirectly by ingestion
through the food chain, could, on the
basis of information available to the
Administrator of EPA. cause death, __
disease, behavioral abnormalities,
cancer, genetic mutations, physiological
malfunctions (including malfunction in
reproduction), or physical deformations
in either organisms or offspring of the
organisms.
(u) Pollutant limit is a numerical
value that describes the amount of a
pollutant allowed per unit amount of
sewage sludge (e.g., milligrams per
kilogram of total solids); the amount of
a pollutant that can be applied to a unit
area of land (e.g.. kilograms per hectare); '
or the volume of a material that can be
-------
requirements in § 503.12 and the
management practices in § 503.14 do
not apply when sewage sludge is sold or
given away hi a bag or other container
for application to the land if the sewage
sludge sold or given away in a bag or
other container for application to the
land meets the pollutant concentrations
in $ 503.13(b)(3). the Class A pathogen
requirements in $ 503.32(a), and one of
the vector attraction reduction
requirements in § 503.33 (b)(l) through
939O Federal Register / Vol. 58, No. 32 / Friday, February 19, 1993 / Rules and Regulations
applied to a unit area of land (e.g.. .
gallons per acre).
(v) Runoff is rainwater, leachate, or
other liquid that drains overland on any
part of a land surface and runs off of the
land surface.
(w) Sewage sludge is solid, semi-solid,
or liquid residue generated during the
treatment of domestic sewage in a
treatment works. Sewage sludge
includes, but is not limited to, domestic
septage: scum or solids removed in
primary, secondary, or advanced
wastewater treatment processes; and a
material derived from sewage sludge.
Sewage sludge does not include ash
generated during the firing of sewage
sludge in a sewage sludge incinerator or
grit and screenings generated during
preliminary treatment of domestic
sewage in a treatment works.
(x) State is one of the United States of
America, the District of Columbia, the
Commonwealth of Puerto Rico, the
Virgin Islands, Guam, American Samoa,
the Trust Territory of the Pacific Islands,
the Commonwealth of the Northern
Mariana Islands, and an Indian Tribe
eligible for treatment as a State pursuant
to regulations promulgated under the
authority of section 518{e) of .the CWA.
(y) Store or storage of sewage sludge
is the placement of sewage sludge on
land on which the sewage sludge
remains for two years or less. This does
not include the placement of sewage
sludge on land for treatment.
(z) Trent or treatment of sewage
sludge is the preparation of sewage
sludge for final use or disposal. This
includes, but is not limited to.
thickening, stabilization, and
dewatering of sewage sludge. This does
not include storage of sewage sludge.
(aa) Treatment works is either a
federally owned, publicly owned, or
privately owned device or system used
to treat (including recycle and reclaim)
either domestic sewage or a
combination of domestic sewage and
industrial waste of a liquid nature.
(bb) Wetlands means those areas that
are inundated or saturated by surface
water or ground water at a frequency
and duratioA to support, and that under
normal circumstances do support, a
prevalence of vegetation typically
adapted for life in saturated soil
conditions. Wetlands generally include
swamps, marshes, bogs, and similar
areas.
Subpart B—Land Application
5503.10 Applicability.
(a) This subpart applies to any person
who prepares sewage sludge that is
applied to the land, to any person who
applies sewage sludge to the land, to
sewage sludge applied to the land, and
to the land on which sewage uludge is
applied.
(b)(l) Bulk sewage sludge. The general
requirements in $ 503.12 and the
management practices hi § 503.14 do
not apply when bulk sewage Kludge is
applied to the land if the bull: sewage
sludge meets the pollutant
concentrations in § 503.13(b)(3), the
Class A pathogen requirements in
§ 503.32(a). and one of the vector
attraction reduction requirements in
§ 503.33 (b)(l) through (b)(8).
(2) The Regional Administrator of
EPA or, in the case of a State with am
approved sludge management program,
the State Director, may apply any or all
of the general requirements in § 503.12
and the management practice!! in
§ 503.14 to the bulk sewage sludge in
§ 503.10(b)(l) on a case-by-case basis
after determining that the general
requirements or management practices
are needed to protect public health and
the environment from any reasonably
anticipated adverse effect that may
occur from any pollutant in the bulk
sewage sludge.
(c)fl) The general requirements in
§ 503.12 and the management practices
in § 503.14 do not apply when a bulk
material derived from sewage sludge is
applied to the land if the derived bulk
material meets the pollutant
concentrations in § 503.13(b)(3), the
Class A pathogen requirements in
§503.32(a), and one of the vector
attraction reduction requirements in
§503.33 (b)(l) through (b)(8).
(2) The Regional Administrator of
EPA or, in the case of a State with an
approved sludge management program,
the State Director, may apply any or all
of the general requirements in § 503.12
or the management practices in § 503.14
to the bulk material in § 503.10(c)(l) on
a case-by-case basis after determining
that the general requirements or
management practices are needed to
protect public health and the
environment from any reasonably
anticipated adverse effect that may
occur from any pollutant in the bulk
sewage sludge.
(d) The requirements in this subpart
do not apply when a bulk material
derived from sewage sludge is applied
to the land if the sewage sludge from
which the bulk material is derived
meets the pollutant concentrations hi
§ 503.13(b)(3), the Class A pathogen
requirements in § 503.32(a), and one of
the vector attraction reduction
requirements in § 503.33 (b)(l) through '
(e) Sewage sludge sold or given away
in a bag or other container for
application to the land. The general
(f) The general requirements in
§ 503.12 and the management practices
in § 503.14 do not apply when a
material derived from sewage sludge is
sold or given away in a bag or other
container for application to this land if
the derived material meets the pollutant
concentrations in § 503.13(b)(3), the
Class A pathogen requirements in
§ 503.32(a), and one of the vector
attraction reduction requirements in
§ 503.33 (b)(l) through fb)(8). « '
(g) The requirements in this snbpart
do not apply when a material derived
from sewage sludge is sold or given
away in a bag or other container for
application to the land if the sewage
sludge from which the material is
derived meets the pollutant
concentrations in § 503.13(b)(3), the
Class A pathogen requirements in
§ 503.32(a), and one of the vector
attraction reduction requirements in .
§503.33 (b)(l) through (b}(8).
$503.11 Special definition*.
(a) Agricultural land is land on which
a food crop, a feed crop, or a fiber crop
is grown. This includes range land and
land used as pasture.
(b) Agronomic rate is the whole
sludge application rate (dry weight
basis) designed: ;
(1) To provide the amount of nitrogen
needed by the food crop, feed crop, fiber
crop, cover crop, or vegetation grown on
the land; and
(2) To minimize the amount of
nitrogen in the sewage sludge that
passes below the root zone of the crop
or vegetation grown on the land to the
ground water.
(c) Annual pollutant loading rate is
the maximum amount of a pollutant that
can be applied to a unit area of land
during a 365 day period.
(d) Annual whole sludge application
rate is the maximum amount of sewage
sludge (dry weight basis) that can be
applied to a unit area of land during a
365 day period.
(e) Bulk sewage sludge is sewage
sludge that is not sold or given away in
a bag or other container for application
to the land.
A ,4
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Register / VoL 58. No. 32 / Friday. Fehraary 19,1993 / Rules and Regulations fl3SS
other container fat application te the
land, the person who ptepares the
sewage sludge that is sow or given away
in a bag or other container shafl develop
tin following information and shall
retain the information for five years:
(i) The auiiuai whulu sindgB
application rate for the sewage sludge
that does not causa the annual poifatant
loading rates in Table 4 of § 503,13 to
be exceeded.
(ii) The concentration of each
pollutant listed in Table 4 of §503.13 in
the sewage sludge.
(iii) The following certification
statement:
"I certify, under penalty of hnr, that tha
management practice in § 503.14(e), the Qass
A pathogen requirement in $ 503.32(aL and
the vector attraction reduction requirement
in [insert one of the vector attraction
reduction lequueuieiits ia $ S03.3
dinction aoa miMivuion in aooovoasoe with
too system QBngmd to^osoiv isat ijiiaUnKi
personnel properly gatliar mad avakiaU the
information used to determine that tha
pathogen requirements and vector attraction
reduction 4'&juii0uj0iibi nave oeen met* 2 axn
through (b)(8)] have been met This
determination has been made under my
direction and supervision in accordance with
the ay»tt3ui designed to ensure that qualified
personnel properly gather and evaluate the
information used to detennioe that the
manngnmont prar*iy«»
requirements, and vector attraction reduction
requirements have been met. I am aware that
there are significant penalties for false
certification including the possibility of fine
and imprisonment"
(iv) A description of how the Class A
pathogen requirements in § 503.32(a) are
met.
(v) A description of how one of the
vector attraction requirements hi
§ 503.33 (b)(l) through (b)(8) is met
(b) Domestic septage. When domestic
septage is applied to agricultural land,
forest, or a reclamation site, the person
who applies the domestic septage shall
develop the following information and
shall retain the information for five
years:
(1) The location, by either street
address or latitude and longitude, of
each site-on which domestic septage is
applied.
(2) The number of acres in each site
on which domestic septage is applied.
(3) The data and time domestic
septage is applied to each she. '
(4) The nitrogen requirement for the .
crop or vegetation grown on each site
during a 365 day period.
(5J The rate, in gallons per acre per
365 day period, at which domestic
septage is applied to each site.
(6) The fottowinf certification
statement:
"I certify, under penalty of law. that the
pathogen requirements in linsert either
S 503.32(cjn) or § S03.32tc)(2n and the vector
attraction reduction requirements in [insert
§ 503.33(bK»J. S S03.33(b]fM)J, or
$ 503 -33M1Z3) have keen met. This
determination hss been made miA»r my
aware that them «re «garfictnt panaMas lor
false certification iactadiag the possibility of
fine and imprisonment"
(7) A description of how the pathogen
requirement* in etthi»r § 50X33 tcj(l) or
(c)(2) are met.
(8) A description of how the vector
atUaclmrreductuui ^requirements In
§503.33 (bX9). (bMMU. or (b)(12) an .
met.
(Approved by the OffioB of Management and
Budget under control number 2G40-O357)
S 503.18 Reporting.
(a) Class I sludge management
facilities, POTYVs (as defined in -40 CFR
501.2} with a design flow rate equal to
or greater than one million gallons per
day. and POTWs that serve 10,000
people or more shall submit the
following infui iiiuliu n to the permitting
authority:
(1) The information in % 503.1 Tfe),
except the information in § 503.17
(a)(3j(ii). (a)(4)(ii) and in (aj(5)(ii). for
tfce appropriate requirements on
February 19 of each year.
(2) The informatioii in $ 503.17
(a)(5)(ii)(A) through (a)(5)(iiXG)on .
{insert the month and day fium the date
of publication of this rule] of each year
when 90 percent or more of any of the
cumulative pollutant loading rates in
Table 2 of § 503.13 is reached ata site.
{Approved by the Office of Management and
Budget nnrtnr control number 2040-41157)
Subpart C—Surface Disposal
§503.20 Applicability.
(a) This subpart applies to any person
who prepares sewage sludge that is
placed on a surface disposal site, to *t"»
owner/operator of a surface ftigp/""1!
site, to sewage sludge placed on a
surface disposal site, and to a surface
disposal site.
(b) This subpart does not apply to
sewage sludge stored on the land or to
the land on which sewage sludge is
stored. H also does not apply to sewage
sludge that remains OB the land for
longer than two years; when the person
who prepares the sewage sludge
demonstrates that the; land on which the
sewage sludge remains is not an active
sewage sludge unit. The demonstration
shall rncrade the following information,
which shall be retained by the person
who prepares the sewage sludge for the
period that the sewage sludge remains •
on the land:
(1) The name and address of the
person who prepares the sewage sludge.
(2) The name and address of the
person who either owns the land or
leases the land.
(3) The location, by either street
address or latitude and longitude, of the
land.
(4) -An explanation of why sewage
sludge needs to remain on the land far
. longer dun two yean prior to final UM
or disposal.
(5) The approximate time period
when the sewage sludge will be used or
disposed.
(c) This subpart does not apply to
s«wage sludge treated on the land or to
the land on which sewage sludge is
treated.
(a) Active sewage sludge unit is a
sewage sludge unit that has not dosed.
tb) Aquifer is a geologic formation.
group of geologic formations, or a
portion of a geologic formation capable
of yielding ground water to walls or
springs. r
{c) Contaminate aa aquifer means to
introduce a substance that causes the
maximum contaminant level for nitrate
in *o CFR 141.11 to be exceeded in
ground water or th«* causes the existing
concentration of nitrate in ground water
to increase when the existing
concentration of nitrate in the ground
water exceeds the maximum
contaminant level for nitrate in 40 CER
141.11.
(d) Cover is soil or other material used
to cover sewage sludge placed on an
active sewage sludge unit.
IB) Displacement is the relative
movement of any two sides of a fault
measured in any dimr-tin^
(f) Fault is a fracture or zone of
fractures in any materials alnng which
strata on one side are displaced with
respect to strata on the other side.
(g) Final cover is the last layer of soQ
or other material placed on a sewage
sludge unit at closure.
{hJHo/ocene time is the most recent
epoch of the Quaternary period,
extending from the end of the
Pleistocene epoch to the present.
(i) Leachate collection system a a
system or device installed immediately
above a liner that is designed,
constructed, maintained, and operated
to collect and remove ieachate from a
sewage sludge unit
(0 Liner is soil or synthetic material
that has a hydraulic conductirity of
1x10 ~' centimeters per second or less.
GO Lower explosive limit for methane
gas is the lowest percentage of methane
gas in air, by vorome, that propagates a
flame at 25 degrees Celsius and
atmospheric pressure.
(I) QuaJifieaffvuad-wateT scientist rs
an individual with a baccalaureate -or
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9396 Federal Register / VoL 58, No. 32 / Friday, February 19. 1993 / Rules and Regulations
post-graduate degree in the natural
science* or engineering who has .
sufficient training and experience in
ground-water hydrology and related
fields, as may be demonstrated by State
registration, professional certification.
or completion of accredited university
programs, to make sound professional
judgments regarding ground-water
monitoring, pollutant fete and transport.
and corrective action.
(m) Seismic impact zone is an area
that has a 10 percent or greater
probability that the horizontal ground
level acceleration of the rock hi the area
exceeds 0.10 gravity once in 250 years.
(n) Salvage sludge unit is land on
which only sewage sludge is placed for
final disposal. This does not include
land on which sewage sludge is either
stored or treated. Land does not include
waters of the United States, as defined
in 40 CFR 122.2.
(o) Sewage sludge unit boundary is
the outermost perimeter of an active
sewage sludge unit
(p) Surface disposal site is an area of
land that contains one or more active
sewage sludge units.
(q) Unstable
ile area is land subject to
natural or human-induced forces that
may damage the structural components
of an active sewage sludge unit This
includes, but is not limited to. land on
which the soils are subject to mass
movement
550X22 General requirement*.
(a) No person shall place sewage
sludge on an active sewage sludge unit
unless the requirements in this subpart
are met
(b) An active sewage sludge unit
located within 60 meters of a fault that
has displacement in Holocene time;
located in an unstable area: or located
in a wetland, except as provided hi a
permit issued pursuant to section 402 of
the CWA. shall close by (insert date one
year after the effective date of this Final.
rule], unless, in the case of an active
sewage sludge unit located within 60
meters of a fault that has displacement
in Holocene time, otherwise specified
by thepermitting authority.
(c) The owner/operator of an active
sewage sludge unit shall submit a
written closure and post closure plan to
the permitting authority180 days prior
to the date that the active sewage sludge
unit closes. The plan shall describe how
the sewage sludge unit will be closed
and, at a minimum, shall include:
(1) A discussion of how the leachate
collection system will be operated and
maintained for three years after the
sewage sludge unit closes if the sewage
sludge unit has a liner and leachate
collection system.
(2) A description of the system used
to monitor for methane gas in the air in
any structures within the surface
disposal site and in the air at the
property line of the surface disposal
site, as required in $ 503.2401 (2).
(3) A discussion of how public access
to the surface disposal site will be
restricted for three years after the last
sewage sludge unit in the surface
disposal site closes.
(d) The owner of a surface dispose!
site shall provide written notification to
the subsequent owner of the itite that
sewage sludge was placed on the land.
§5OX23 PoMutantllmfei (other than
domestic Mptage).
(a) Active sewage sludge unit without
a liner and leachate collection system.
(1) Except as provided in § 503.23
(a)(2) and (b), the concentration of each
pollutant listed in Table 1 of § 503.23 in
sewage sludge placed on an active
sewage sludge unit shall not oxceed the
concentration for the pollutant in Table
1 of §503.23.
TABLE 1 OF §503.23.—POUJJTANT CON-
CENTRATIONS—ACTIVE SEWAGE SLUDGE
UNIT WITHOUT A LINER AND LEACHATE
COLLECTION
TABLE 2 Of §503.23.—POLLUTANT CON-
CENTRATIONS—ACTIVE SEWAGE SLUDGE
UNIT WITHOUT A LINER AND LEACHATE
COLLECTION SYSTEM THAT HAS A UNIT
BOUNDARY TO PROPERTY UNE DIS-
TANCE LESS THAN ISO METERS
PoHuttrt
An*r4c --,
Mlrk^l ,.., ....
Conctnostion
(fnttiamrM p0r
Wloomrm1)
73
600
420
' Dry welgrt b««i».
(2) Except as provided hi § 503.23(b).
the concentration of each pollutant
listed in Table 1 of § 503.23 in sewage
sludge placed on an active sewage
sludge unit whose boundary Is less than
150 meters from the property line of the
surface disposal site shall not exceed
the concentration determined; using the
following procedure.
(i) The actual distance from the active
sewage sludge unit boundary to the
property line of the surface disposal site
shall be determined.
(ii) The concentration of each
pollutant listed in Table 2 of S 503.23 hi
the sewage sludge shall not exceed the
concentration in Table 2 of $ 503.23 that
corresponds to the actual distance in
§503.23(a)(2)(i).
Unttboundaiyto
proptny tint
Dfetanc* (RMtm)
0 to tot* than 25
25 to IMS Own 50
50 10 IMS man 75
7SioiaMttwn
100 , . .„.,..,.,.,..
100 to l«c« own
12S
125 to tott ten
ISO _____
PoMt
AiMric-
(110*0)
30
34
39
46
53
62
mt concentration '
Chro-
mium
(mgftg)
200
220
260
300
360
450
Nfcfeal
(mo*g)
210
240
270
320
300
420
i Dry weight taMl*.
(b) Active sewage sludge unit without
a liner and leachate collection system—
site-specific limits.
(1) At the time of permit application.
the owner/operator of a surface disposal
site may request site-specific gpllutant
limits in accordance with $ 503.23(b)(2)
for an active sewage sludge unit without
a liner and leachate collection system
when the existing values for site
parameters specified by the permitting
authority are different from the values
for those parameters used to develop the
pollutant limits hi Table 1 of § 503.23
and when the permitting authority
determines that site-specific pollutant
limits are appropriate for the active
sewage sludge unit
(2) The concentration of each
pollutant listed in Table 1 of § 503.23 hi
sewage sludge placed on an active
sewage sludge unit without a liner and
leachate collection system shall not
exceed either the concentration for the
pollutant determined during a site-
specific assessment, as specified by the
permitting authority, or the existing
concentration of the pollutant in the
sewage sludge, whichever is lower.
S 50X24 Management practice*.
(a) Sewage sludge shall not be placed
on an active sewage sludge unit if it is
likely to adversely affect a threatened or
endangered species listed under section
4 of the Endangered Species Act or its
designated critical habitat i
(b) An active sewage sludge unit shall
not restrict the flow of a base flood.
(c) When a surface disposal; site is
located in a seismic impact zone, an
active sewage sludge unit shall be
designed to withstand the maximum
recorded horizontal ground level
acceleration.
(d) An active sewage sludge unit shall
be located 60 meters or more from a
fault that has displacement in Holocene
A-6
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F»d«ri tegirter / VoL 51, No. 31 / ftinJrol imniber 3S4O-OTS7)
{503^7 Recordkeeping.
(a) Whan sewage sludge {other 4han
.domestic septage) is placed on an active
sewage .sludge unit
(1} The person who prepares the
sewage sludge shall develop the
following information end "*"Ti retain
the information for five years.
(i) The cflnfTftnt
pollutant listed in Table t of $ SOS.23 in
the -sewage sludge whea the pollutant
concentrations in Table 1 of $503-23 019
met.
M<)
when one of those requirements U met] and
the -vector attraction ieduutJunTBquIie>iient«
in linseit une of the mclui atlruLtiuu
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9398 Federal Register / VoL 58. No. 32 / Friday, February 19, 1993 / Rules and Regulations
reduction requirements in §S03J3(bXl)
through S 503.33(b}(8) whoa on* of them .
requirements Is met! have teen met This
dntorminition bu been made under my
direction and supervision in accordance with
the system designed to ensure tint qualified
personnel properly gather and evaluate the
information used to determine the (pathogen
requirements and vector attraction reduction
requirements .if appropriate] have been met
I am aware that there are significant penalties
for false certification including the
possibility of fine and imprisonment"
(Hi) A description of how the
pathogen requirements in § 503.32 (a),
(b)(2). (b)(3). or (b)(4) are met when one
of those requirements is met.
(iv) A description of how one of the
vector attraction reduction requirements
in § 503.33 (b)(l) through (b)(8) is met
when one of those requirements is met
(2) The owner/operator of the surface
disposal site, shall develop the
following information and shall retain
that information for five years."
(i) The concentration of each
pollutant listed in Table 2 of § 503.23 in
the sewage sludge when the pollutant
concentrations in Table 2 of § 503.23 are
met or when site-specific pollutant
limits in § 503.23(b) are met
(ii) The following certification
statement:
"I certify, under penalty of law, that the
management practices in § 503.24 and the
vector attraction reduction requirement in
(insert one of the requirements in § 503.33
(b)(9) through (b)(ll) if one of those
requirements is met! have been met This
determination has been made under my
direction and supervision in accordance with
the system designed to ensure that qualified
personnel properly gather and evaluate the
information used to determine that the
management practices (and the vector
attraction reduction requirements if
appropriate) have been met I am aware that
there are significant penalties for falsa
certification including the possibility of fine
and imprisonment'*
(iii) A description of how the
management practices in S 503.24 are
met.
(iv) A description of how the vector
attraction reduction requirements in .
§ 503.33 (b)(9) through (b)(ll) are met if
one of those requirements is met.
(b) When domestic septage is placed
on a surface disposal site: . . .
(1) If the vector attraction reduction
requirements in § 503.33(b)(12) are met,
the person who places the domestic
saptage on the surface disposal site shall
develop the following information and
shall retain the information for five .
years:
(i) The following certification
statement: •
"I certify, under penalty of law, that the
vector attraction reduction requirements in
§ 503.33(bHl2) have been met Thin
determination has been made under my
direction and supervision in accordance with
the system designed to ensure that qualified
personnel properly gather and evaluate the
information used to determine that the vector
Attraction requirements have been met I am
aware that there are significant penalties far
false certification including the possibility of
fine and imprisonment'*
(ii) A description of how the vector
attraction reduction requirements in
§ 503.33(b)(12) are met
(2) The owner/operator of th« surface
disposal site shall develop the following
information and shall retain that
information for five years:
(i) The following certification
statement:
"I certify, under penalty of law, that the
management practices in § 503.24 tnd the
vector attraction reduction requirements in
(insert § 503.33(b)(9) through § 503.33(bX«)
when one of those requirements is met] have
been met This determination has been made
under my direction and supervision in
accordance with the system designod to
ensure that qualified personnel properly
gather and evaluate the information used to
determine that the management practices
land the vector attraction reduction,
requirements if appropriate) have been met
I am aware that there are significant penalties
for falsa certification including the
possibility of fine or imprisonment"
(ii) A description of how the
management practices'in § 503.24 are
met
(iii) A description how the vector
attraction reduction requirements in
§ 503.33(b)(9) through § 503.33(b)(ll)
are met if one of those requirements is
met.
(Approved by the Office of Management and
Budget under control number 2040-0157)
S 503-28 Reporting,
Class I sludge management facilities,
POTWs (as defined in 40 CFR 501.2)
with a design flow rate equal to or
greater than one million gallons per day.
and POTWs that serve 10.000 poople or
more shall submit the information in
§ 503.27(a) to the permitting authority
on February 19 of each year.
(Approved by the Office of Management and
Budget under control number 2Q4O-0157)
Subpart D—Pathogens and Vector
Attraction Reduction
J5C3JO Scope.
(a) This subpart contains the
requirements for a sewage sludge to be
classified either Class A or Class B with
respect to pathogens.
(b) This subpart contains the site
restrictions for land on which a Class B
sewage sludge is applied.
(c) This subpart contains the pathogen
requirements for domestic septage
applied to agricultural land, forest, or a
reclamation site.
(d) This subpart contains alternative
vector attraction reduction requirements
for sewage sludge that is applied to the
land or placed on a surface disposal site.
J503J1 Special definition*.
(a) Aerobic digestion is the
biochemical decomposition of organic
matter in sewage sludge into carbon
dioxide and water by microorganisms in
the presence of air.
(b) Anaerobic digestion is the
biochemical decomposition of organic
matter in sewage sludge into methane
gas and carbon dioxide by
microorganisms in the absence of air.
(c) Density of microorganisms is the
number of microorganisms per unit
mass of total solids (dry weight) in the
sewage sludge.
(d) Land with a high potential for
public exposure is land that the public
uses frequently. This includes, bu^ is
not limited to. a public contact site and
a reclamation site located in a populated
area (e.g. a construction site located in
a city).
(e) Land with a low potential for
public exposure is land that the public
uses infrequently. This includes, but is
not limited to, agricultural land, forest,
and a reclamation site located in an
unpopulated area (e.g., a strip mine
located in a rural area).
(f) Pathogenic organisms are disease-
causing organisms. These include, but
are not limited to. certain bacteria,
protozoa, viruses, and viable helminth
ova.
(g) pH means the logarithm of the
reciprocal of the hydrogen ion
concentration.
(h) Specific oxygen uptak? rate
(SOUR) is the mass of oxygen consumed
per unit time per unit mass of total
solids (dry weight basis) in the sewage
sludge.
(i) Total solids are the materials in '
sewage sludge that remain as residue
when the sewage sludge is dried at 103
to 105 degrees Celsius.
(j) Unstabilized solids are organic
materials in sewage sludge that have not
been treated in either an aerobic or
anaerobic treatment process.
(k) Vector attraction is the
characteristic of sewage sludge that
attracts rodents, flies, mosquitos, or
other organisms capable of transporting
infectious agents.
(1) Volatile solids is the amount of the
total solids in sewage sludge lost when
the sewage sludge is combusted at 550
degrees Celsius in the presence of
excess air. >
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Federal Register / Vol 58. No. 32 / Friday. February'19. 1593'/ Hides and Regulations
§50132 Pt
(a) Sewage sludge—Class A. (1) The
requirement in § 503.32(a)(2) and the
requirements in either § 503.32(a)(3).
(a)(4). (a)(5). (a)(6), (a)(7). or (a)(8) shall
be met for a sewage sludge to be
classified Class A with respect to
pathogens.
(2) The Class A pathogen
requirements in § 503.32 (a)(3) through
(a)(8) shall be met either prior to.
meeting or at the same time the vector
attraction reduction requirements in
§ 503.33. except the vector attraction
reduction requirements in § 503.33
(b}(6) through (b)(8), are met.
(3) Class A—Alternative 1. (i) Either
the density of fecal coliform in the
sewage sludge shall be less than 1000
Most Probable Number per gram of total
solids (dry weight basis), or the density
of Salmonella sp. bacteria in the sewage
sludge shall be less than three Most
Probable Number per four grams of total
solids (dry weight basis) at the time the
sewage sludge is used or disposed; at
the time the sewage sludge is prepared
for sale or give away in a bag or other
container for application to the land; or
at the time the sewage sludge or
material derived from sewage sludge is
prepared to meet the requirements in
§ 503.10 (b). (c), (e), or(f).
(ii) The temperature of the sewage
sludge that is used or disposed shall be
maintained at a specific value for a
period of time.
(A) When the percent solids of the
sewage sludge is seven percent or
higher, the temperature of the sewage
sludge shall be 50 degrees Celsius or
higher; the time period shall be 20 •
minutes or longer; and the temperature
and time period shall be determined
using equation (2), except when small
particles of sewage sludge are heated by
either wanned gases or an immiscible .
liquid.
D=
131.700.000
HJO.HOJI ..
Eq. (2)
Where. vrrv?"'
D=tirae in days. ,. '
t=temperatur8 in degrees Celsius.
(B) When the percent solids of the
sewage sludge is seven percent or higher
and small particles of sewage sludge are
heated by either warmed gases or an
immiscible liquid, the temperature of
the sewage sludge shall be 50 degrees
Celsius or higher; the time period shall
be 15 seconds or longer and the
temperature and time period shall be
determined using equation (2).
(C) When the percent solids of the
sewage sludge is less than seven percent
and the time period is at least 15
seconds, but less than 30 minutes, the
temperature and time period shall be
determined using aquation (2).
(D) When the percent sou'ds of the
' sewage sludge is less than seven .
percent: the temperature of the sewage
sludge is 50 degrees; Celsius or higher;
and the time period is 30 minutes or
longer, the temperature and time period
shall be determined using equation (3).
50.070,000
Eq. (3)
Where,
D=time in days.
t=temperature in degntos Celsius.
(4) Class A—Alternative 2. (i) Either
the density of fecal coliform in the
sewage sludge shall be less than 1000
Most Probable Number per gram of total
solids (dry weight bajsis), or the density
of Salmonella sp. bacteria in the sewage
sludge shall be less than three Most
Probable Number par four grams of total
solids (dry weight basis) at the time die
sewage sludge is usod or disposed; at
the time the sewage sludge is prepared
for sale or give away in a bag or other
container for application to the land; or
at the time the sewage sludge or .
material derived from sewage sludge is
prepared to meet tho requirements in
§ 503.10 (b). (c). (e), or (f).
(ii) (A) The pH of the sewage sludge
that is used or disposed shall be raised
to above 12 and shall remain above 12
for 72 hours.
(B) The temperature of the sewage
sludge shall be above 52 degrees Celsius
for 12 hours or longer during the period
that the pH of the sewage sludge is
above 12.
(C} At the end of the 72 hour period
during which the pH of the sewage
sludge is above 12, the sewage sludge
shall be air dried to achieve a percent
solids in the sewage sludge greater than
50 percent.
(5) Class A—Alternative 3. (i) Either
the density of fecal coliform hi the
sewage sludge shall be less than 1000
Most Probable Number per gram of total
solids (dry weight basis), or the density
of Salmonella sp. bacteria in sewage
sludge shall be less than three Most
Probable Number per four grams of total •
solids (dry weight basis) at the time the
sewage sludge is used or disposed; at
the time the sewage sludge is prepared
for sale or give away in a bag or other
container for application to the land; or
at the time the sewage sludge or
material derived from sewage sludge is
prepared to meet the requirements in
§ 503.10 (b). (c). (e). or (f).
(ii) (A) The sewage sludge shall be
analyzed prior to pathogen treatment to
determine whether the sewage sludge
contains enteric viruses.
(B) When the density of enteric
viruses in the sewage sludge prior to
pathogen treatment is less than one
Plaque-forming Unit per four grams of
total solids (dry weight basis), the
sewage sludge is Class A with respect to
enteric viruses until the next monitoring
episode for the sewage sludge.
(C) When the density of enteric
viruses in the sewage sludge prior to
pathogen treatment is equal to or greater
than one Plaque-forming Unit per four
grams of total solids (dry weight basis),
the sewage sludge is Class A with
respect to enteric viruses when the
density of enteric viruses in the sewage
sludge after pathogen treatment is less
than one Plaque-forming Unit per four
grams of total solids (dry weight basis)
and when the values or ranges of values
for the operating parameters for the
pathogen treatment process that
produces the sewage sludge that meets
the enteric virus density requirement
are documented.
(D) After the enteric virus reduction
in paragraph (a)(5)(ii)(C) of this section
is demonstrated for the pathogen
treatment process, the sewage sludge
continues to be Class A with respect to
enteric viruses when the values for the
pathogen treatment process operating
parameters'are consistent with the
values or ranges of values documented
in paragraph (a)(5)(ii)(C) of this section.
(iii)(A) The sewage sludge shall be
analyzed prior to pathogen treatment to
determine whether the sewage sludge
contains viable helminth ova.
(B) When the density of viable
helminth ova in the sewage sludge prior
to pathogen treatment is less than one
per four grams of total solids (dry
weight basis), the sewage sludge is Class
A with respect to viable helminth ova
until the next monitoring episode for
the sewage sludge.
(C) When the density of viable
helminth ova in the sewage sludge prior
to pathogen treatment is equal to bt
greater than one per four grams of total
solids (dry weight basis), the sewage
sludge is Class A with respect to viable
helminth ova when the density of viable
helminth ova in the sewage sludge after
pathogen treatment is less than one per
four grams of total solids (dry weight
basis) and when the values or ranges of
values for the operating parameters for
the pathogen treatment process that
produces the sewage sludge-that meets
the viable helminth ova density
requirement are documented.
(D) After the viable helminth ova
reduction in paragraph {a)(5)(iii)(Q of
this section is demonstrated for the
pathogen treatment procbss. the sewage
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Federal Register / VoL 58; No. 32 / Friday. February 19. 1993 / Rides and Regulations
sludge continues to b* Class A with
respect to viable helminth ov» when the
values for the pathogen treatment
process operating parameters are
consistent with the values or ranges of
values documented in paragraph
(a)(5)(iii)(C) of this section.
(6) Class A—Alternative 4. (i) Either
the density of fecal coliform in the
sewage sludge shall be less than 1000
Most Probable Numbar per gram of total
solids (dry weight basis), or the density
of Salmonella sp. bacteria in the sewage
sludge shall be less than three Most
Probable Number per four grams of total
solids (dry weight basis) at the time the
sewage sludge is used or disposed; at
the time the sewage sludge is prepared
for sale or give away in a bag or other
container for application to the land: or
at the time the sewage sludge or
material derived from sewage sludge is
prepared to meet the requirements in
§ 503.10 (b). (c), (e). or(f).
(Si) The density of enteric viruses in
the sewage sludge shall be less than one
Plaque-forming Unit per four grams of
total solids (dry weight basis) at the time
the sewage sludge is used or disposed;
at the time the sewage sludge is
prepared for sale or give away in a bag
or other container for application to the
land: or at the time the sewage sludge
or material derived from sewage sludge
is prepared to meet the requirements in
§ 503.10 (b). (c). (e). or (f). unless .
otherwise specified by the permitting
authority.
(iii) The density of viable helminth
ova in the sewage sludge shnll be less
than one per four grams of total solids
(dry weight basis) at the time the sewage
sludge is used or disposed; at the time
the sewage sludge is prepared for sale or
give away in a bag or other container for
application to the land; or at the time
the sewage sludge or material derived
from sewage sludge is prepared to meet
the requirements in § 503.10 (b). (c). (el.
or (f). unless otherwise specified by the
permitting authority.
(7) doss A—Alternatives.® Either
the density of fecal coliform in the -
sewage sludge shall be less than 1000
Most Probable Number per gram of total
solids (dry weight basis), or the density
of Salmonella, sp. bacteria in the sewage
sludge shall be less than three Most
Probable Number per four grams of total
solids (dry weight basis) at the time the
sewage sludge is used or disposed; at
the time the sewage sludge is prepared
for salo or given away in a bag or other
container for application to the land; or
at the time the sewage sludge or
material derived from sewage sludge is
prupared to meet the requirements in
§ 503.10{b). (c). (e). or (f).
(ii) Sewage sludge that is used or
disposed shall be treated in one of the
Processes to Further Reduce Pathogens
described In appendix B of this part
(8) Class A—Alternative 6. (i) Either
the density of fecal conform hi Ihe
sewage sludge shall be less than 1000
Most Probable Number per gram of total
solids (dry weight basis), or the density
of Salmonella, sp. bacteria hi the sewage
sludge shall be less than three Most
Probable Number per four grams of total
solids (dry weight basis) at the time the
sewage sludge is used or disposed; at
the time the sewage sludge is prepared
for sale or given away in a bag or other
container for application to the land; at
at the time the sewage sludge or
material derived from sewage sludge is
prepared to meet the requirements in
" § 503.10(b). (c), (e), or (f).
(ii) Sewage sludge that is used or
disposed shall be treated in a process
that is equivalent to a Process tti Further
Reduce Pathogens, as determined by the
permitting authority.
(b) Sewage sludge—Class B. (l)(i) The
requirements in either § 503.32(b)(2),
(b)(3), or (b)(4) shall be met for n sewage
sludge to be classified Class B vrith
respect to pathogens.
(ii) The site restrictions in
§ 503.32(b)(5) shall be met when sewage
sludge that meets the Class B pathogen
requirements in § 503.32(b)(2). l[b)(3). or
(b)(4) is applied to the land.
(2) Class B—Alternative 1.
(i) Seven samples of the sewage
sludge shall be collected at the time the
sewage sludge is used or disposed.
(ii) The geometric mean of the density
of fecal coliform in the samples
collected in paragraph (b)(2){i) of this
section shall be less than either
2.000.000 Most Probable Number per
gram of total solids (dry weight basis) or
2.000.000 Colony Forming Units per
gram of total solids (dry weight basis).
(3) Class B—Alternative 2. Sewage
sludge that is used or disposed shall be
treated in one of the Processes Co
Significantly Reduce Pathogens
described in appendix B of this part.
(4) Class B—Alternative 3. Sewage
. sludge that is used or disposed shall be
treated in a process that is equivalent to
• Process to Significantly Reduce
Pathogens, as determined by the
permitting authority.
(5) Site Restrictions, (i) Food crops
with harvested parts that touch the
sewage sludge/soil mixture and are
totally above the land surface shall not
be harvested for 14 months after
application of sewage sludge.
(ii) Food crops with harvested parts
below the surface of the land shall not
be harvested for 20 months after
application of sewage sludge when the
sewage sludge remains on the land
surface for four months or longer prior
to incorporation into the soil
(iii) Food crops with harvested parts
below the surface of the land shall not
be harvested for 38 months after
application of sewage sludge when the
sewage sludge remains on the land
surface for less than four months prior
to incorporation into the soil
(iv) Food crops, feed crops, and fiber
crops shall not be harvested for 30 days
after application of sewage sludge.*
(v) Animals shall not be allowed to
graze on the land for 30 days after
application of sewage sludge.
(vi) Turf grown on land where sewage
sludge is applied shall not be harvested
for one year after application of the
sewage sludge when the harvested turf •
is placed on either land with a high
potential for public exposure or a lawn,
unless otherwise specified by the
permitting authority.
(vii) Public access to land with a high
potential for public exposure shall be
restricted for'one year after application
of sewage sludge.
(viii) Public access to land with a low
potential for public exposure shall be
restricted for 30 days after application of
sewage sludge.
(c) Domestic septage. (1) The site
restrictions in § 503.32(b)(5) shall be
met when domestic septage is applied to
agricultural land, forest, or a
reclamation site; or
(2) The pH of domestic septage
applied to agricultural land, forest, or a
reclamation site shall be raised to 12 or
higher by alkali addition and. without
the addition of more alkali, shall remain
at 12 or higher for 30 minutes and the
site restrictions in § 503.32 (b)(5)(i)
through (b)(5)(iv) shall be met.
S 503.33 Vector attraction reduction.
(a)(l) One of the vector attraction
reduction requirements in § 503:33
(b)(l) through (b)(10) «h"H be met when
bulk sewage sludge is applied to
agricultural land, forest, a public contact
site, or a reclamation site.
(2) One of the vector attraction
reduction requirements in § 503.33
(b)(l) through (b)(8) shall be mat when
bulk sewage sludge is applied to a lawn
or a home garden.
~ (3) One of the vector attraction
reduction requirements in § 503.33
(b)(l) through (b)(8) shall be met when
sewage sludge is sold or given away hi
a bag or other container for application
to the land.
(4) One of the vector attraction
reduction requirements in § 503.33
(b)(l) through (b)(ll) shall be met when
sewage sludge (other than domestic
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Federal Register / VoL 58. No. 32 / Friday. February 19. 1993 / Rules and Regulations S4O1
gas. from a sewage sludge Incinerator
stack.
(b) Auxiliary fuel is fuel used to
augment the fuel value of sewage
sludge. This includes, but is not limited
to, natural gas, fuel oil. coal, gas
generated during anaerobic digestion of
sewage sludge, and municipal solid
waste (not to exceed 30 percent of the
dry weight of sewage sludge and
auxiliary fuel together). Hazardous
wastes are not auxiliary fuel.
(c) Control efficiency is the mass of a
pollutant in the sewage sludge fed to an
incinerator minus the mass of that
pollutant in the exit gas from the
incinerator stack divided by the mass of
the pollutant in the sewage sludge fed
to the incinerator.
(d) Dispersion factor is the ratio of the
increase in the ground level ambient air
concentration for a pollutant at or
beyond the property line of the site
where the sewage sludge incinerator is
located to the mass emission jate for the
pollutant from the incinerator stack.
(e) Fluidized bed incinerator is an
enclosed device hi which organic matter
and inorganic matter in sewage sludge
are combusted in a bed of particles
suspended hi the combustion chamber
gas.
(f) Hourly average is the arithmetic
mean of all measurements, taken during
an hour. At least two measurements
must be taken during the hour.
(g) Incineration is the combustion of
organic matter and inorganic matter in
sewage sludge by high temperatures in
an enclosed .device.
•(h) Monthly average is the arithmetic
mean of the hourly averages for the
hours a sewage sludge incinerator
operates during the month.
(i) Risk specific concentration is the
allowable increase in the average daily
ground level ambient air concentration
for a pollutant from the incineration of
sewage sludge at or beyond the property
line of the site where the sewage sludge
incinerator is located.
(j) Sewage sludge feed rate is either
the average daily amount of sewage
sludge fired in all sewage sludge
incinerators within the property line of
the site where the sewage sludge
incinerators are located for the number
of days in a 36S day period that each
sewage sludge incinerator operates, or
the average daily design capacity for all
sewage sludge incinerators within the
property line of the site where the
sewage sludge incinerators are located.
(k) Sewage sludge incinerator is an
enclosed device in which only sewage
sludge and auxiliary fuel are fired.
(1) Stack height is the difference
between the elevation of the top of a
sewage sludge incinerator stack and the
septage) is placed on an active sewage
sludge unit : ' ,;-
(5) One of the vector attraction
reduction requirements in §503.33
(b)(9). (b){iO)rO|{bJ(i2J*&all ba met
when domestic septage is applied to
agricultural land; rarest, or a,
reclamation site and one of the vector
attraction reduction requirements in
§ 503.33 (b)(9) through (b)(12) shall be
met when domestic septage is placed on
an active sewage sludge unit
(b)(l) The mass of volatile solids in
the sewage sludge shell be reduced by
a minimum of 38 percent (see
calculation procedures in
"Environmental Regulations and
Technology—Control of Pathogens and
Vector Attraction in Sewage Sludge",
EPA-625/R-92/013. 1992, U.S.
Environmental Protection Agency,
Cincinnati, Ohio 45268).
(2) When the 38 percent volatile
solids reduction requirement in
§ 503.33(b)(l) cannot be met for an
anaerobically digested sewage sludge.
vector attraction reduction can be
demonstrated by digesting a portion of
the previously digested sewage sludge
anaerobically in the laboratory in a '
bench-scale unit for 40 additional days
at a temperature between 30 and 37
degrees Celsius. When at the end of the
40 days, the volatile solids in the
sewage sludge at the beginning of that
period is reduced by less than 17
percent, vector attraction reduction is
achieved.
(3) When the 38 percent volatile -
solids reduction requirement in
§ 503.33(bHD cannot be met for an
aerobically digested sewage sludge.
vector attraction reduction can be
demonstrated by digesting a portion of
the previously digested sewage sludge
that has a percent solids of two percent
or less aerobically in the laboratory in
a bench-scale unit for 30 additional days
at 20 degrees Celsius. When at the end
of the 30 days, the volatile solids in the .
sewage sludge at the beginning of that
period is reduced by less than I5f
percent, vector attraction reduction is
achieved. ^ "_
(4) The specific oxygen uptake rate
(SOUR) for sewage sludge treated in an
aerobic process shall be equal to or less
than 1.5 milligrams of oxygen per hour
per gram of total solids (dry weight
basis) at a temperature of 20 degrees
Celsius.
(5) Sewage sludge shall be treated in
an aerobic process for 14 days or longer.
During that time, the temperature of the
sewage sludge shall be higher than 40
degrees Celsius and the average
temperature of the sewage sludge shall
be higher than 45 degrees Celsius.
(6) The pH of sewage sludge shall be
raised to 12 or higher by alkali addition
and, without the addition of more alkali.
shall remain at 12 or higher for two - •
hours and then at 11.5 or higher for an
additional 22 hours.
(7) The percent solids of sewage
sludge that does not contain
unstabilized solids generated in a
primary wastewater treatment process
shall be equal to or greater than 75
percent based on the moisture content
and total solids prior to mixing with
other materials.
(8) The percent solids of sewage
sludge that contains unstabilized solids
generated in a primary wastewater
treatment process shall be equal to or
greater than 90 percent based on the
moisture content and total solids prior
to mixing with other materials.
(9)(i) Sewage sludge shall be injected
below the surface of the land.
(ii) No significant amount of the
sewage sludge shall be present on the
land surface within one hour after the
sewage sludge is injected.
(iii) When the sewage sludge that is
injected below the surface of the land is
Class A with respect to pathogens, the
sewage sludge shall be injected below
the land surface within eight hours after
being discharged from the pathogen
treatment process.
(10)(i) Sewage sludge applied to the
land surface or placed on a surface
disposal site shall be incorporated into
the soil within six hours after
application to or placement on die land.
(ii) When sewage sludge that is
incorporated into the soil is Class A
with respect to pathogens, the sewage
sludge shall be applied to or. placed on
the land within eight hours after being .
discharged from the pathogen treatment
process.
(11) Sewage sludge placed on an
active sewage sludga unit shall be
covered with soil or other material at
the end of each operating day.
(12) The pH of domestic septage shall
be raised to 12 or higher by alkali
addition and. without the addition of
more alkali, shall remain at 12 or higher
for 30 minutes.
Subpart E—Incineration
$503.40 Applicability.
(a) This subpart applies to a person
who fires sewage sludge in a sewage
sludge incinerator, to a sewage sludge
incinerator, and to sewage sludge fired
in a sewage sludge incinerator.
(b) This subpart applies to the exit gas
from a sewage sludge incinerator stack.
§503.41 Special definition*. '
(a) Air pollution control device is one
or more processes used to treat the exit
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APPENDIX B
PARTITIONING OF CONTAMINANT AMONG
AIR, WATER, AND SOLIDS IN SOIL
-------
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APPENDIX B
Partitioning of Contaminant Among Air, Water, and Solids in Soil
Calculations used to derive criteria for groundwater, surface water, and air pathways are
based on the assumption that equilibrium is maintained between concentrations of contaminant in
the air-filled pore space, the water-filled pore space, and the solid particles of soil. Equilibrium
partitioning between dissolved and gaseous phases is described by Henry's Law constants;
partitioning between adsorbed and dissolved phases is described by soil-water partition coefficients.
From these assumptions and the definitions of concentration are derived the equations used to
describe partitioning.
Define:
Cs
cw
c,
c,
concentration of adsorbed contaminant on soil particles (kg/kg),
concentration of dissolved contaminant in soil (kg/m3),
concentration of gaseous contaminant in soil (kg/m3), and
total concentration of contaminant in soil (kg/m3).
Mathematically:
r - ££ r = <¥. r - «
* M. w V V
and:
where:
Vw
mass of adsorbed contaminant (kg),
mass of soil (kg),
mass of dissolved contaminant (kg),
volume of water in soil (m3),
B-l
-------
= mass of gaseous contaminant (kg),
V, = volume of air in soil (m3),
M^ — total mass of contaminant in soil (leg),
V, = total volume of sofl (m3), and
V, = volume of solids in sofl (m3).
The equilibrium distribution coefficient (KD, in m3/kg) between adsorbed and dissolved phases can
be defined as: . : '
[MJMJ MaVw
~
The dimensionless Henry's Law constant (H) describing the partitioning between gaseous and
dissolved phases is defined as:
WctW _ MCA Vw
~
The bulk density of sofl (BD, in kg/m3) is defined as:
BD=MJVt
The air-filled porosity of sofl (0J is defined as:
*, = vjvt
water-filled porosity (0W) as:
OW = ^/F;
and the total porosity of sofl (0,) is defined as:
e, -
-------
j
and:
ew
and:
KD KD
tr
These relations are used throughout the calculations described in Sections 5.3 and 5.4. Where dry-
weight concentrations of contaminant in sludge or soil are involved, the equation are modified
slightly, based on the definition:
c -
*"
Ms Vt BD BD
where:
C^ = dry-weight concentration of contaminant in sludge/soil.
B-3
-------
-------
APPENDIX C
DERIVATION OF FIRST-ORDER COEFFICIENT
FOR LOSSES TO LEACHING
-------
-------
APPENDIX C
Derivation of First-Order Coefficient for Losses to Leaching
US EPA (1986d) provides an equation for computing a first-order loss rate to leaching for
contaminant in treated soil:
K =
kc
BD KD
where:
K,,.,. = first-order loss rate coefficient for leaching (yr'1),
NR = annual recharge rate (m/yr), ,
* *
BD = bulk density of soil (kg/m3), and
KD = soil-water distribution coefficient for contaminant (m3/kg).
This appendix describes a modified version of that equation.
The basic strategy for deriving a coefficient for first-order loss to leaching is to estimate the
mass of contaminant expected to be lost each year and divide by the available mass of contaminant.
The mass of contaminant that will be lost to leaching in any interval of time can be described by
the volume of water percolating through the treated soil multiplied by the average concentration of
contaminant in that water:
FA{ = NR CUc 1000
where:
FA, = flux.of leached contaminant from treated soil (kg/ha-yr),
NR = recharge to groundwater beneath the treated soil (m3/nr-yr, or m/yr),
Qec = concentration of contaminant in water infiltrating through the treated soil
(kg/m3), and
1000 = constant to convert units from (kg/nr-yr) to (kg/ha-yr).
C-l
-------
From Appendix B, the concentration of contaminant in leachate is related to the total concentration
(by volume) of contaminant in soil as:
cw = cti \BD-KD + ew -H #-ej I
where:
Ct = total concentration of contaminant in treated soil (kg/m3), j
0w = water-filled porosity of soil (dimensionless),
H = Henry's Law Constant for conjtaminant (dimensionless), and
0a = air-filled porosity of soil (dimensionless).
This flux of contaminant must be translated into a first-order loss coefficient so that:
d€< --K C '''
-' KC
where:
Kfc,. = first-order loss rate coefficient for leaching (yr1),
C, = total concentration of contaminant in soil at time t (g/m3), and
t = time (yr).
K,,.,. is estimated with the approximation: \
_ [dCJdt] _ [AC,/Af] _ [AMcf/Af]
lee C C M
<-f ^t a !
where:
i
Ma = mass of contaminant in soil, and
At = one year.
1
"The volume of treated soil beneath one square meter of soil surface (in m3/m2) is equal jto
the depth to which sludge has been incorporated into the soil (dt in m). The total mass ,of
contaminant beneath one square meter of surface can therefore be described by:
C-2
-------
Combining these equations with results" from Appendix B yields:
FA, 10-3 NR C^ NR
Mct Ct Vt
KD + 6W + H-QJ dt
C-3
-------
-------
APPENDIX D
DERIVING A "SQUARE WAVE" FOR THE MONOFILL PROTOTYPE
-------
-------
APPENDIX D
Deriving a "Square Wave" for the Monofill Prototype
Derivation of criteria for surface disposal includes the calculation of a "square wave" as a
conservative approximation of the loading of contaminant from the facility to the unsaturated soil
zone. This square wave is of magnitude equal to the maximum expected rate of loss of contaminant
from the facility (kg/ha-yr) and of a duration calculated to conserve contaminant mass. It is
assumed that all competing loss processes for contaminant in soil can be approximated as first-
order, and that coefficients describing the rate oi: loss to each process can be summed to yield a
total or "lumped" coefficient for first-order loss. ILosses at any time t can be described as:
dM.
where:
M, = mass of contaminant in treated soil at time t (kg/ha), and
K^, = lumped, first-order loss rate: for contaminant (yr"1).
If the rate of contaminant loss is proportional to the available mass of contaminant, the maximum
rate of loss will occur in the last year of the monofflrs operation. The mass of contaminant in the
facility after LF years of operation can be approximated by:
LF . •
M^* fAR <
o
where: ., . - - -. ,
AR _ = annual loading of contaminant to monofill facility (kg/ha-yr).
^ J&SP& •>
At that time, the rate of loss will be:
D-l
-------
At that rate, the total loading of contaminant to the facility would be depleted in:
- if I
*"-
D-2
-------
APPENDIX E
JUSTIFICATION FOR THE DELETION OF POLLUTANTS FROM THE
FINAL STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE
-------
-------
JUSTIFICATION FOR THE DELETION OF POLLUTANTS FROM THE
FINAL STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE
Office of Science and Technology
U.S. Environmental Protection Agency
401 M Street, S.W.
• Washington, D.c. 20460
November 16,, 1992
-------
-------
JUSTIFICATION FOR THE DELETION OF POLLUTANTS FROM THE
FINAL STANDARDS FOR THE USE OR DISPOSAL OF SEWAGE SLUDGE
TABLE OF CONTENTS
1. INTRODUCTION
E-.l
2. ORGANIC POLLUTANTS - LAND APPLICATION
AND SURFACE DISPOSAL
2.1 Criteria for the Deletion of An Organic Pollutant . E-2
2.2 Evaluation
2.2.1 Introduction . E-»2
2.2.2 Criterion 1 ". . » •] E_-3
2.2.3 Criterion 2 E_4
2.2.4 Criterion 3 ......... E_5
2.2.4.1 Land Application Comparison E-6
2.2.4.2 Surface Disposal Comparison E-ll
2.3 Evaluation results E-12
2.4 Conclusions
2.4.1 Land, application E-14
2.4.2 Surface disposal * E-16
3. INORGANIC POLLUTANTS - SURFACE DISPOSAL
3.1 Introduction E-17
3.2 Evaluation - Sewage Sludge E-17
3.3 Evaluation - Domestic Septage E-18
3.4 Conclusions
3.4.1 Sewage Sludge E-20
3;4.2 Domestic Septage . "'„_..
Jt*"""Z U
ATTACHMENTS
A - Revised Mean Application Rates for Land Application . E-21
B - Summary.Statistics for EPA's Study on the Quality
. of Domestic Septage E-25
-------
-------
SECTION ONE
INTRODUCTION
On February 6, 1989, the U.S. Environmental Protection Agency
(EPA) proposed Standards for the Use or Disposal of Sewage Sludge
(40 CPR Part 503) in the Federal Register (54 FR 5746). Included
in those standards were pollutant limits for different sewage
sludge use or disposal practices.
Several commenters on the proposed Standards for the Use or
Disposal of Sewage Sludge recommended that some of the organic
pollutants for which pollutant limits were proposed be deleted from
the final standards. The main reason for this recommendation was
that the pollutants are either banned or restricted for use in the
United States.
tf
'*
Because of the comments received on the proposal, EPA decided
to evaluate all of the organic pollutants in the proposed Part 503
standards for land application of sewage sludge and for placement
of sewage sludge on a surface disposal site to determine whether to
delete any of those pollutants from the final Part 503 standards.
This paper discusses the criteria the Agency used to evaluate each
organic pollutant; presents the' results of the evaluations; and
provides the Agency's conclusion about deleting organic pollutants
from the final Part 503 standards.
The Agency also evaluated the inorganic pollutants for surface
disposal for deletion from the final Part 503 regulation. This
paper presents the results of that evaluation and EPA's conclusions
about deleting inorganic pollutants from the surface disposal
subpart in the final Part 503 regulation.
-------
SECTION TWO
ORGANIC POLLUTANTS - LAND APPLICATION AND SURFACE DISPOSAL
2.1 Criteria for the Deletion of An Organic Pollutant. ;
The Agency used three criteria to evaluate whether to delete
an organic pollutant from the final Part 503 regulation. For an
organic pollutant to be deleted from the regulation for a
particular use or disposal practice,, one of the following three
criteria had to be satisfied.
1. The pollutant has been banned for use in the United
States; has restricted use in the United States; or is not
manufactured for use in the United States. ;
2. Based on the results of the National Sewage Sludge Survey...
(NSSS), the pollutant has a low percent detect in sewage.
sludge.
3. Based on data from the NSSS, the limit for an organic
pollutant in the Part 503 exposure assessment by use or
disposal practice is not expected to be exceeded in sewage
sludge that is used or disposed.
The evaluation for each of the organic pollutants for which
pollutant limits were published in the proposed Part 503 standards
using the above three criteria is presented below. ,
2.2 Evaluation \
2.2.1 Introduction ;
The first step in the evaluation of organic pollutants is to
identify the organic, pollutants for which limits were proposed in
the February 6, 1989, proposal (54 FR 5746) for land application of
sewage sludge and for placement of sewage sludge on a surface
disposal site* These pollutants are presented below in Table 1 by
use or disposal practice.
Limits' for organic pollutants also were proposed in Part 503
for distribution and marketing of sewage sludge and for _ sewage
sludge placed on a monofill. The requirements for land application
and distribution and marketing are combined in the final Part 503
regulation as are the requirements for placement of sewage sludge
on a monofill and placement of sewage sludge on a surface disposal
site. For this reason, the organic pollutants presented below for
land application include the organic pollutants in the proposal for
distribution and marketing and the organic pollutants for surface
disposal include the organic pollutants in the proposal for a
monofill.
-------
TABLE;!! - PART 503 ORGANIC POLLUTANTS BY USE OR DISPOSAL
PRACTICE
Use or Disposal Practice
Pollutant LA SD
Aldrin/dieldrin (total) x
Benzene x
Benzo(a)pyrene x x
Bis(2-ethylhexyl)phthalate x
Chlordane x x
DDT/DDE/DDD (total) . x x
Heptachlor x
Hexachlorobenzene x
Hexachlorobutadiene x
Lindane x x
N-Nitrosodimethylamine x x
Polychlorinated biphenyls x x
Toxaphene x x *•
Trichloroethylene x x
LA - land application
SD - surface disposal
The next step is to evaluate each of the organic pollutants
using the above three criteria.
2.2.2 Criterion 1
The organic pollutants listed in Table 2 have been banned for
use in the United States; have restricted uses in the United
States; or are not manufactured for use in the United States.
-------
TABLE 2 - ORGANIC POLLUTANTS THAT HAVE BEEN BANNED, HAVE
RESTRICTED USE/ OR ARE NOT MANUFACTURED
Pollutant
Reference
Aldrin/dieldrin (total)
Chlordane
DDT/DDE/DDD (total)
Heptachlor
Lindane
N-Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
*
*
**
40 CPR Part 761
* See "Suspended, Cancelled, and Restricted Pesticides, 20T-1002,
U.S. Environmental Protection Agency, February 1990. :
** See "1992 Directory of Chemical Producers", SRI International,
Menlo Par, California, 1992. ,j
These eight pollutants satisfy the first criterion for
deletion of an organic pollutant from the final Part 503 standards
for land application of sewage sludge and for placement of sewage
sludge on an active sewage sludge unit.
2.2.3 Criterion*2
The percent detect from the National Sewage Sludge Survey
(NSSS) for each of the organic pollutants in the proposed Part 503
standards for land application of sewage sludge and for placement
of sewage sludge on an active sewage' sludge unit is presented iri
Table 3.
-------
TABLE 3 - PERCENT DETECT FOR ORGANIC POLLUTANTS
Number of Percent
Pollutant POTWs Detect*
Aldrin/dieldrin (total) 177 8
Benzene 178 f 0
Benzo(a)pyrene 178 3
Bis(2-ethylhexyl)phthalate 178 63
Chlordane 177 0
DDT/DDE/DDD (total) 177 3
Heptachlor 177 •*• 0
Hexachlorobenzene 178 : 0
Hexachlorobutadiene 178 0
Lindane 177 0
N-Nitrosodimethylamine 178 0
Polychlorinated biphenyls 177 19
Toxaphene 177 0
Trichloroethylene 178 - 1 '*
* Estimated percent detect in sewage sludge used or disposed at
publicly owned treatment works nationwide. From "Statistical
Support Documentation for the 40 CFR Part 503 Final Standards for
the Use or Disposal of Sewage Sludge", Volume I, U.S. Environmental
Protection Agency, Washington, D.C., November 11, 1992.
A review of the above information indicates that .all of the
pollutants, except aldrin/dieldrin (total),
bis(2-ethylhexy1)phthalate, and polychlorinated biphenyls (PCBs),
satisfy Criteria 2 for the deletion of an organic pollutant from
the final Part 503 standards because the pollutants have a low
percentage of detection (i.e., five percent or less) nationwide.
Aldrin/dieldrin (total), bis(2-ethylhexyl)phthalate, and PCBs do
not satisfy this criterion because they have a percent detect
higher than five percent.
2.2.4 Criterion 3
For £he Criterion 3 evaluation, the 99th percentile.
concentrations (see Table 7-11 in the report referenced in Table 4)
from the v||s£S;: were» compared to the pollutant limits from the final
Part 503 §qcposure assessment by use or disposal practice. For land
application, the comparison was made by comparing annual pollutant
loading rates. For surface disposal, pollutant concentrations from
the final Part 503 exposure assessment were compared to the 99th
percentile pollutant concentrations.
The 99th percentile concentrations from the NSSS were
determined using the SM-ML procedure, except for
bis(2-ethylhexyl)phthalate. For bis(2-ethylhexyl)phthalate, the
MLE procedure was used to determine the 99th percentile
concentration because the data for that pollutant appeared to be
distributed log normally. The 99th percentile concentrations are
presented in Table 4 and the comparisons using those concentrations
-------
are presented below.
TABLE 4 - 99TH PERCENTILE CONCENTRATIONS
Pollutant
Aldrin/dieldrin (total) mg/kg
Benzene mg/kg
Benzo(a)pyrene mg/kg
Bis(2-ethylhexyl) phthalate mg/kg
Chlordane mg/kg
DDT/DDE/DDD (total) mg/kg
Heptachlor mg/kg
Hexachlorobenzene mg/kg
Hexachlorobutadiene mg/kg
Lindane mc«/kg
N-Nitrosodimethylamine me/kg
Polychlorinated biphenyls mg/kg
Toxaphene mg/kg
Trichloroethylene mg/kg
99th Percentile Concentration*
0.074
7.0
43
1000
1.8 [
0.14
0.14 ;
43
43
0.18 i '
210
9.1 '-
7.4 : "
7.0 '
* From "Statistical Support Documentation for the 40 CFR, Part 503
Standards for the Use or Disposal of Sewage", Volume I, U.S,
Environmental Protection Agency, Washington, D.C., November 11,
1992. Values are on dry weight 'basis and are reported in two
significant figures.
2.2.,4.1 Land Application Comparison
For the purpose of comparing annual pollutant loading rates
for land application, the annual whole sludge application rates in
Table 5, which are from the NSSS (see Attachment A), were used in
equation (1) below with the 99th percentile concentration from the
NSSS to determine the calculated annual pollutant loading rates.
The comparisons of the .calculated annual pollutant loading rates to
the annual pollutant loading rates from the Part 503 exposure
assessment are presented Tables 6 through 9. ;
TABLE 5 - ANNUAL WHOLE SLUDGE APPLICATION RATES
Tvne of 'Land Annual Whole Sludae Application Rate*
Agricultural
Forest
Public contact site
Reclamation site
7
26
18
74
* Metric tons per hectare per 365 day period (dry weight
basis) .
-------
APLR = C X AWSAR X 0.001
(1)
where,
==;,Annual pollutant loading rate in kilograms per hectare
per 365 day period.
C = pollutant concentration in milligrams per kilograms
(dry weight basis).
AWSAR = Annual whole sludge application rate in metric tons per
hectare per 365 day period (dry weight basis).
0.001 = A conversion factor.
Agricultural land:
TABLE 6 - COMPARISON OF ANNUAL LOADS FOR AGRICULTURAL LAND
Pollutant
Aldrin/dieldrin (total)
Benzo(a)pyrene
Chlordane
DDT/DDE/DDD (total)
Heptachlor
Hexachlorobenzene
Hexachlorobutadiene
Lindane
N-Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
APLR (Exposure)
ka/ha/365
0.027 •
0.15
0.86
1.2
0.074
0.29
6.0
0.84
0.021
0.046
0.10
1.00
APLR (NSSS)
ka/ha/365
0.00051
0.30
0.012
0.00098
0.00098
0.30
0.30
0.0012
1.4
0.063
0.049
0.05
The, annual pollutant loading rate for benzo(a)pyrene,
hexachlorgbenzene, N-Nitrosodimethylamine, and PCBs calculated
using the^9|»th percentile concentration for each pollutant from the
NSSS andgjajj* annual whole sludge application rate of seven metric
tons per,...hectare per 365 day period is greater than the annual
pollutant^loading rate for those pollutants from the Part 503
exposure* Assessment. For this reason, those pollutants do not
satisfy Criterion 3 for application of sewage sludge to
agricultural land.
-------
Forest:
TABLE 7 - COMPARISON OP ANNUAL LOADS FOR FORESTS
Pollutant
Aldrin/dieldrin (total)
Benzo(a)pyrene
Chlordane
DDT/DDE/DDD(total)
Heptachlor
Hexachlorobenzene
Hexachlorobutadiene
Lindane
N-Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
APLR (Exposure)
ka/ha/365
0.027
0.15
0.86
-. 1.2
0.074
0.29
6.0
0.84
0.021
, 0.046
0.10
100
APLR (NSSS)
ka/ha/365
0.0019
1.1
0.046
0.0036
0.0036
1.1
1.1
0.0046
5.4
0.23
0.19
0.18
The annual pollutant loading rate for benzo(a)pyrene,
hexachlorobenzene, N-Nitrosodimethylamine, PCBs, and toxaphene
calculated using the 99th percentile concentration from the NSSS
and an annual whole sludge application rate of 26 metric tons per
hectare per 365 day period is greater than the annual pollutant
loading rate for those pollutants from the Part 503 exposure
assessment. For this reason, those pollutants do not satisfy
Criterion 3 for application of sewage sludge to forests.
Public contact site;
TABLE 8 - COMPARISON OF ANNUAL LOADS FOR PUBLIC CONTACT SITES
Pollutant
APLR (exposure)
ka/ha/365
Aldrin/dieldrin (total) •
Benzo(a)pyrene
Chlordane
DDT/DDE/DDD(total)
Heptachlor
Hexachlorobenzene
Hexachlorobutadiene
Lindane
N-Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
0.027
0.15
0.86
1.2
0.074
0.29
6.0
0.84
0.021
0.046
0.10
APLR (NSSS)
ka/ha/365
100
0.0013
0.77
0.032
0.0025
0.0025
0.77
0.77
0.0032
3.7
0.16
0.12
0.13
-------
The annual pollutant loading rate for benzo(a)pyrene,
hexachlorpfienzene, N-Nitrosodimethylamine, PCBs, and toxaphene
calculated using the 99th percentile concentration from the NSSS
and an annual whole sludge application rate of 18 metric tons per
hectare per 365 day period exceeds the annual pollutant loading
rate for those pollutants from the Part 503 exposure assessment.
For this reason, those pollutants do not satisfy Criterion 3 for
application of sewage sludge to a public contact site.
Reclamation site;
TABLE 9 - COMPARISON OF ANNUAL LOADS FOR RECLAMATION SITES
Pollutant
Aldrin/dieldrin (total)
Benzo(a)pyrene
Chlordane
DDT/DDE/DDD(total)
Heptachlor
Hexachlorobenzene
Hexachlorobutad iene
Lindane
N-Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
APLR (Exposure)
kor/ha/365
0.027
0.15
0.86
1.2
0.074
0.29
6.0
0.84
0.021
0.046
0.10
100
APLR (NSSS)
kq/ha/365
0.0054
3.1
0.13
0.010
0.010
3.1
3.1
0.013
15
0.67
0.54
0.51
The annual pollutant loading rates for benzo(a)pyrene,
hexachlorobenzene, N-Nitrosodimethylamine, PCBs, and toxaphene
calculated using the 99th percentile concentration for each
pollutant from the NSSS and an annual whole sludge application rate
of 74 metric tons per hectare per 365 day period exceed th'~ annual
pollutant loading rates- for those pollutants from the Part 503
exposure assessment. For this reason, those pollutants do not
satisfy Criterion 3 for application of sewage sludge to a
reclamatipp site.
Annual pollutant loading rates for organic pollutants are
included In the final Part 503 exposure assessment only for land
application of sewage sludge. Those rates are the same for all
types of land on-which sewage sludge is applied. For this reason,
results of the above evaluation were combined to determine which
pollutants satisfy Criterion 3 for land application of sewage
sludge. When this is done, the pollutants that do not satisfy
Criterion 3 for land application of sewage sludge are
benzo(a)pyrene, hexachlorobenzene, N-Nitrosodimethylamine, PCBs,
and toxaphene.
-------
Sewage sludge sold or given-awav in a bag or other container for
application to the land (formerly distribution and marketing);
The Part 503 exposure assessment contains limits for organic
pollutants for sewage sludge sold or given-away in a bag or other-
container for application to the land. These limits are annual
pollutant loading rates. -
Sewage sludge sold or given-away in a bag or other container
for application to the land may be applied to all types of land.
For this reason, the annual whole sludge application rates used to
calculate the annual pollutant loading rates for the above land
application comparison also were used to calculate the annual
pollutant loading rates for sewage sludge sold or given-away in a
bag or other container for application to the land. i
For the purpose of comparing annual pollutant loading rates
for sewage sludge sold or given-away in a bag or other container^
for application to the land, the highest annual whole sludge?
application rate (i.e., 74 metric tons per hectare per 365 day*
period) from the land application comparison was used in equation
(2) below along with the 99th percentile concentrations from the
NSSS to calculate annual pollutant loading rates. Results of the
comparison of the calculated annual pollutant loading rates to the
annual pollutant loading rates for sewage, sludge sold or given-away
in a bag or other container for application to the land from the
Part 503 exposure assessment are presented in Table 10.
APLR = C X AWSAR X 0.001 (2)
where, ]
APLR = annual pollutant loading rate in kilograms per hectare
per 365 day period. i
C = pollutant concentration in milligrams per kilogram of
sewage sludge (dry weight basis). :
AWSAR = annual whole sludge application rate in metric tons per
hectare per 365 day period (dry weight basis). :
0.001 = a conversion factor.
-------
TABLE 10 - COMPARISON OF ANNUAL LOADS FOR SEWAGE SLUDGE SOLD
OR GIVEN AWAY IN A BAG OR OTHER CONTAINER FOR
APPLICATION TO THE
APLR (Exposure) APLR (NSSS)
Pollutant kg/hectare/365 kg/hectare/365
Aldrin/dieldrin (total) 0.027 0.0054
Benzo(a)pyrene 0.15 ' 3.1
Chlordane 0.86 , • "0.13
DDT/DDE/DDD (total) 1.2 0.010
Heptachlor 0.074 0.010
Hexachlorobenzene • 0.29 3.1
Hexachlorobutadiene 6.0 3.1
Lindane 0.84 . 0.013
Polychlorinated biphenyls 0.046 0.67
Toxaphene 0.10 0.54
The annual pollutant loading rate calculated using the 99th
percentile concentration for benzo(a)pyrene, hexachlorobenzene,
PCBs, and toxaphene from the NSSS and an annual whole application
rate of 74 metric tons per hectare per 365 day period exceeds the
annual pollutant loading rate for those pollutants from the Part
503 exposure assessment. For this reason, those pollutants do not
satisfy Criterion 3 for sewage sludge sold or given away in a bag
or other container for application to the land.
2.2.4.2 .Surface Disposal
For this disposal practice, the 99th percentile concentrations
from the NSSS were compared to the Part 503 pollutant
concentrations from the exposure assessment for an active sewage
sludge unit without 'a liner and leachate collection system. This
comparison is presented in Table 11.
-------
TABLE 11 - COMPARISON OF ORGANIC POLLUTANT CONCENTRATIONS FOR
SURFACE DISPOSAL
Concentration* Concentration
Pollutant Exposure - ma/kg NSSS - ma/kg
Benzene 140 7.0
Benzo(a)pyrene >100,000 43
Bis(2-ethylhexyl)phthalate >100,000 1000
Chlordane . >100,000 1.8
DDT/DDE/DDD (total) >100,000 0.14
Lindane 28,000 . 0.18
N-Nitrosodimethylamine 0.088 .210
Polychlorinated biphenyls 110 . 9.1
Toxaphene . 26,000 7.4
Trichloroethylene 9,500 ' 7.0
* Active sewage sludge unit without a liner arid leachate
collection system.
N-Nitrosodimethylamine does not satisfy Criterion 3- for
placement of sewage sludge on an active sewage sludge unit because
the 99th percentile concentration for that pollutant from the NSSS
exceeds the concentration for that pollutant from the Part 503
exposure assessment. All of the other organic pollutants for this
practice satisfy Criterion 3.
2.3 Evaluation results.
Following are the results of the evaluation of the organic
pollutants for which pollutant limits were published in the
proposed Part 503 standards to determine which of those pollutants,
if any, to delete from the final Part 503 standards:
»•«
o Eight of the organic pollutants for which pbllutant limits
were published in the proposed Part 503 regulation for land
application of sewage sludge and placement of sewage sludge on
a surface disposal site have been banned for use in the United
States; have been restricted for use in the United States; or
are not manufactured in the United States. They are:
aldrin/dieldrin (total), 'chlordane, DDT/DDE/DDD (total),
heptachlor, lindane, N-Nitrosodimethylamine, polychlorinated
biphenyls, and toxaphene. These pollutants satisfy Criterion
1.
o The percent detect from the NSSS for the organic pollutants
for which limits were proposed for land application of_sewage
sludge and placement of sewage sludge on a surface disposal
site are low (i.e., five percent or less), except for
aldrin/dieldrin (total), bis(2-ethylhexyl)phthalate, and
polychlorinated biphenyls. All of the other- organic
pollutants for which limits were proposed satisfy Criterion 2.
E-12
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o With the exception of benzo(a)pyrene, hexachlorobenzene, N-
Nitrosodimethylamine, PCBs, and toxaphene, the annual
pollutant loading rate for the organic pollutants calculated
using the 99th percentile concentration for each pollutant
from the NSSS and an annual whole application rate from the
NSSS is below the Part 503 exposure assessment annual
pollutant loading rate for each organic pollutant for sewage
sludge applied to agricultural land, forest, a public contact
site, or a reclamation site. For land application of sewage
sludge/ benzo(a)pyrene, , hexachlorobenzene, N-
Nitrosodimethylamine, PCBs, and toxaphene do .riot satisfy
Criterion 3. -•."•- :
o With the exception of benzo(a)pyrene, hexachlorobenzene,
PCBs, and toxaphene, the annual pollutant loading rate for the
organic pollutants calculated using the 99th percentile
concentration for each pollutant from the NSSS and an annual
whole sludge application rate from the NSSS is below the final
Part 503 exposure assessment annual.pollutant loading rate for
each organic pollutant for sewage sludge sold or given-away in
a bag or other container for application to the land (formerly
distribution and marketing). For sewage sludge sold or'given
away in a bag or other container, benzo(a)pyrene,
hexachlorobenzene, PCBs, and toxaphene do not satisfy
Criterion 3.
o With the exception of N-Nitrosodimethylamine, the 99th
percentile pollutant concentration from the NSSS is below the
Part 503 exposure' assessment concentration for each organic
pollutant in sewage sludge placed on an active sewage sludge
unit without a liner and leachate collection system. For this
practice, N-Nitrosodimethylamine does not satisfy Criterion 3.
Conclusions
«
Based on the results of the above evaluations, the Agency is
deleting organic pollutants from the final Part 503 regulation, as
indicated below, for the appropriate use or disposal practice. EPA
concluded that because those organic pollutants satisfy one of the
three criteria discussed above, public health and the environment
are protected from the reasonably anticipated adverse effects of
the organic pollutants in sewage sludge without establishing limits
for the pollutants in the final Part 503 regulation.
-------
2.4.1 Application to agricultural land, forest, a public
contact site, or a reclamation site - pollutants deleted;
Pollutant Criteria Met
Aldrin/dieldrin (total) 1 and 3
Benzo(a)pyrene 2
Chlordane 1, 2, and.3
DDT/DDE/DDD(total) 1/2, and 3
Heptachlor 1/2, and 3
Hexachlorobenzene 2
Hexachlorobutadiene • 2 and 3
Lindane 1, 2, and 3
'N-Nitrosodimethylamine 1 and 2
Polychlorinated biphenyls 1
Toxaphene ' 1 and 2
Trichloroethylene 2 and 3
Organic pollutant remaining: none.
Sewage sludge sold or given-awav in a bag or other container for
application to the land (formerly distribution and marketing) -
pollutants deleted;
Criteria Met
Aldrin/dieldrin (total)
Benzo (a) pyrene
Chlordane
DDT/DDE/DDE (total)
Heptachlor '
Hexachlorobenzene
Hexchlorobutadiene
Lifrdane
Polychlorinated biphenyls
Toxaphene
1 and '3
2
1, 2, and 3
1, 2, and 3
1, 2, and 3
2
2 and 3
1 , 2 , and 3
1
1 and 2
Organic pollutants remaining: none
As indicated above, PCBs were deleted from the final Part 503
regulation for land application because Criterion 1 is satisfied.
PCBs are restricted for use in the United States. They can be used
only in closed systems and the disposal of PCBs is closely
regulated under the Toxic Substances Control Act (40 CFR Part 761) .
Based on the results of the National Sewage Sludge Survey
(NSSS) , PCBs did not satisfy Criterion 2. PCBs are estimated to be
detected in sewage sludge that is used or.disposed at 19 percent of
the publicly owned treatment works nationwide. To satisfy
Criterion 2, the percent detect had to be five percent or less.
PCBs also did not satisfy Criterion 3 . If PCBs had been
E-14
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regulated, the pollutant limit for PCBs based on results of the
exposure assessment would be 0.046 kilograms per hectare per 365
day period. The annual pollutant loading rate (APLR) delivered to
each hectare of land assuming a concentration of PCBs in the sewage
sludge equal to the 99th percehtile concentration from the NSSS
(i.e., 9.1 milligrams per kilogram) and an annual whole sludge
application rate of 7, 18, 26, and 74 metric tons per hectare for
agricultural land, forest, a public contact site, and a reclamation
site, respectively, would be 0.063, 0.16, 0.23, and 0.67 kilograms
per hectare, respectively.
For application to agricultural land, which is by far the most
widely used land for application of sewage sludge, the above APLR
calculated using the 99th percentile PCB concentration is higher
than the pollutant limit for PCBs that would have been in the final
Part 503 regulation by only 37 percent. The APLRs for the other
types of land are higher than the potential Part 503 APLR by larger
factors. However, this is mitigated by the fact that sewage sludge
only is applied to forest, a public contact site, or a reclamation
site at most every three to five- years. in the case of a.
reclamation site, sewage sludge is applied to the site at most
three times during the period that the land is a reclamation site.
Another factor that mitigates the calculated APLRs is the use
of the 99th percentile concentration for PCBs from the NSSS to
calculate the APLRs. This concentration represents, to a large
extent, outlier values for PCBs and, therefore, "is conservative.
If the more reasonable worst case 90th percentile concentration for
PCBs (i.e., 1.9 milligrams per kilogram) is used to calculate the
APLRs, the annual amounts delivered to a hectare of land are 0.013,
0.034, 0.049, and 0.14 kilograms for agricultural land, forest, a
public contact site, and reclamation site, respectively. In this
case,the calculated APLRs for agricultural land and forest satisfy
Criterion 3, the APLR for a public contact site is only slightly
higher than the exposure assessment value for PCBs (i.e.,' 0.046
kilograms per hectare per 365 day period) , and the APLR for a
reclamation site does not satisfy Criterion 3.
EPA is committed to re-evaluate the decision not to regulate
PCBs in the final Part 503 regulation during the next review of the
regulation (i.e., Round II). EPA expects the concentration of PCBs
in sewage sludge to continue to decrease. In addition, EPA will
re-evaluate the toxicity of PCB congeners through use of a toxicity
equivalent factor system. Both of these factors will be considered
in Round II.
-------
2.4.2
Surface disposal - pollutant deleted;
Pollutant
Benzene
Benz o(a)pyrene
Bis(2-ethylhexyl)phthalate
Chlordane
DDT/DDE/DDD (total)
Lindane
N-Nitrosodimethylamine
Polychlorinated biphenyls
Toxaphene
Trichloroethylene
Organic pollutants remaining: none
Criteria Met
2 and
2 and
3
1, 2,
1, 2,
.1, 2,
1 and
1 and
1, 2,
2 and
3
3
and 3
and 3
and 3
2
3
and 3
3
E-16
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SECTION THREE
INORGANIC POLLUTANTS - SURFACE DISPOSAL
3.1 Introduction
After reviewing results of the exposure assessment for surface
disposal,, the Agency decided to evaluate the inorganic pollutants
to determine whether to include limits in. the final Part 503
regulation for all of the inorganic: pollutants for which limits
were included in the proposed Part 503 regulation. This evaluation
was done for both sewage sludge and domestic septage. Results the
evaluations and the Agency's conclusions based on those results are
presented below.
3.2 Evaluation - Sewage Sludge
The evaluation to determine whether to include limits for
inorganic pollutants in sewage sludge placed on an active sewage
sludge unit in the final Part 503 regulation consisted of comparing
the limits from the Part 503 exposure assessment to the 99th
percentile concentration for a pollutant from the NSSS. Results.of
this comparison are present in Table 12.
-------
TABLE 12 - COMPARISON OF INORGANIC POLLUTANT CONCENTRATIONS
FOR SEWAGE SLUDGE
Concentration Concentration Concentration
•- • f f mcr/kcn fma/kal
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
75
85
1200
4300
840
58
420
73
>100,000
600
46,000
>100,000
>100,000
690
>100,000
>100,000
>100,000
>100,000
>100,000
>100,000
' >100,000
1 - From "Statistical Support Documentation for the 40 CFR, Part
503 Final Standards for the Use 'or Disposal of Sewage Sludge,
Volume I, U.S. Environmental Protection Agency, Washington,
D.C., November 11,1992. Pollutant concentrations are dry
weight 99th percentile concentrations.
2 - From Part 503 exposure assessment for an active sewage sludge
unit without a liner and leachate collection system (dry
weight basis) - see technical support document for the Part
503 surface disposal requirements.
3 - From Part 503 exposure assessment for an active sewage sludge
unit with a liner and leachate collection system (dry weight
basis) - see technical support document for* the Part 503
surface disposal requirements.
Results of the above comparison indicate that the 99th
percentile pollutant concentrations are much lower than the Part
503 exposure assessment concentrations for an active sewage sludge
unit without a liner and leachate collection system, except_ for
arJBfenic, chromium, and nickel. In the case of arsenic, _chromium,
and nickel, the 99th percentile concentration is either higher than
or very close to the exposure assessment concentrations for those
pollutants.
The above results also indicate that the 99th percentile
pollutant concentrations are much lower than the Part 503_exposure
assessment concentrations for an active sewage sludge unit with a
liner and leachate collection system. In this case, all of the
99th percentile concentrations are at least an order of magnitude
lower than the exposure assessment concentrations.
3.3 Evaluation - Domestic Septage
The evaluation to determine whether to include limits in the
final Part 503 regulation for inorganic pollutants in domestic
septage placed on an active sewage sludge unit consisted of
comparing the limit from the Part 503 exposure assessment for
sewage sludge placed on an active sewage sludge unit to the 98th
percentile concentration for a pollutant in domestic septage (see
E-18
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Attachment B). Results of this comparison are presented in Table
13.
TABLE 13 - COMPARISON OP INORGANIC POLLUTANT CONCENTRATIONS FOR
DOMESTIC SEPTAGE
Concentration Concentration Concentration
Pollutant fmg/ka) (ma/kg) fma/kg1
Arsenic 304 73 ' >100,000
Cadmium . 25 >100,000 ' >100,000
Chromium 110 600 >100,000
Copper 2600 46,000 >100.,000
Lead . 100 >100,000 >100,000
Mercury 0.91 >100,000 >100,000
Nickel 50 690 >100,000
1 - Concentration on a dry weight basis (see page 26 in Attachment
B).
2 - From Part 503 exposure assessment for an active sewage sludge
unit without a liner and leachate collection system (dry
weight basis) - see the technical support document for the
Part 503 surface disposal requirements.
3 - From Part 503 exposure assessment for an active sewage sludge
unit with a liner and leachate collection system (dry weight
basis) - see the technical support document for the Part 503
surface disposal requirements.
4- - Concentration is the minimum level value (i.e., highest
I' detection limit value) because arsenic was not detected in any
of the collected domestic septage samples.
Results of the above comparison indicate that the 98th
percentile pollutant concentrations are lower than the Part 503
exposure assessment concentrations for sewage sludge placed on an
active sewage sludge unit both with and without a liner and
leachate collection system. The 98th percentile concentration that
is the closest to the Part 503 concentration is the value for
arsenic when compared to the Part 503 exposure assessment
concentration for an active sewage sludge unit without a liner and
leachate collection system. As indicated in a footnote above,
arsenic was not detected in any of the domestic septage samples
collected and analyzed. The concentration for arsenic in the table
is the minimum level value (i.e., the highest detection limit) for
arsenic in the domestic septage samples collected and analyzed.
-------
3.4 Conclusions :
3.4.1 Sewage Sludge i
• After comparing the 99th percentile concentrations to the Part
503 exposure assessment concentrations for an active sewage sludge i
unit without a liner and leachate collection system, the Agency
concluded that limits only should be included in the final Part 503 ;
regulation for arsenic, chromium, and nickel. Limits are not ;
needed in the final regulation to protect public health and the ;
environment from cadmium, copper, lead, and mercury in the sewage
sludge because the 99th percentile concentration is much lower than
the exposure assessment concentration for each of those pollutants.
In this case, the concentration of cadmium, copper, lead, and
mercury in the sewage sludge is not expected to exceed the exposure
assessment concentration for those pollutants. Consequently, there .
are no oollutant limits for cadmium, copper, lead, and mercury in
the final Part 503 regulation for an active sewage sludge without
a liner and leachate collection system.
The Agency also concluded that no limits are needed in the
final Part 503 regulation for inorganic pollutants in sewage sludge
placed on an active sewage sludge unit with a liner and leachate
collection system to protect public health and the environment
because the 99th percentile concentrations are much- lower than the
exposure assessment concentrations for the inorganic pollutants.
The concentration of each of the inorganic pollutants in sewage ;
sludge is not expected to exceed the exposure assessment :
concentration for the pollutant. Consequently, there are no
pollutant limits in the final Part 503 regulation for 'sewage sludge
placed on an active sewage sludge unit with a liner and leachate |
collection system. " ;
3.-4.2 Domestic Septage ;
After comparing the 98th percentile domestic septage
concentrations to the Part 503 exposure assessment concentrations
for an active sewage sludge unit both with and without a liner and
leachate collection, the Agency concluded that limits are not
needed in the final Part 503 regulation to protect public health ,
and the environment from the reasonably anticipated of arsenic,
cadmium, chromium, copper, lead', mercury, and nickel in domestic :
septage placed on an active sewage sludge unit because the 98th •
percentile concentrations are lower than the Part 503 exposure '•-
assessment concentrations for those pollutants. In this case, the
concentration of each of those pollutants is not expected to exceed ,
the exposure assessment concentration for each pollutant.
Consequently, there are no limits for inorganic pollutants in the ;
final Part 503 regulation for domestic septage placed on either an
active sewage sludge without a liner and leachate collection system
or an active sewage sludge unit with a liner and leachate (
collection system. [
-------
MEMORANDUM
Date: November 10,1992
To: Bob Southworth, EPA
From: Anne Jones and Matt Murphy, ERG
Re: Revised Mean Application Rates for land Application
We have calculated weighted mean application rates for agricultural land application,
land application to forest sites and public contact sites, and land reclamation. The following
methodology was used to derive these numbers.
First, we used the analytical survey rather than the -larger questionnaire survey for the
following reason. A question on numbers of applications was critical to the calculation of
application rates. However, respondents frequently, and fairly consistently, misinterpreted this
question. We made corrections (based on call backs) to the question on number of applications,
as well as to other questions that affected application rates, to many of the analytical survey
observations. Thus a larger proportion of the analytical survey had application rates based on
corrected data than the questionnaire survey. Because we had more confidence in a greater
proportion of data in the analytical questionnaire, we preferred to use this questionnaire.
Second, because of some remaining problems with the question on number of
applications we limited the number of applications to 10, that is, we allowed this number to
range up to 10, but where any number exceeded 10, it was set to 10. This was felt to be a very
conservatively high estimate of numbers of applications. We feel that, if anything, this
assumption would tend to somewhat overstate actual application rates in most cases.
Finally, we deleted one observation, which was a POTW practicing land reclamation.
This POTW was applying sewage sludge at over 1,600 dmt/ha. The sewage sludge fails ceiling
concentrations, but even if it passed, it is highly unlikely that this application rate would be
allowed under Subpart B. The mean application rate shown in the following tables reflects the
deletion of this observation.
=,n-4- A
-------
We then ran the Univariate Procedure in SAS to obtain the weighted means discussed
below and presented in the attached tables.
I
I
The results of this analysis are as follows: agricultural rates average about 7 drat/ha;
rates at forest sites average 26 dmt/ha; rates at public contact: sites average 19 dmt/ha; and rates
at reclamation sites average 74 dmt/ha, as shown in the attached tables.
E-22
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 210460
6 1952
OFF1CEOF
WATPP
MEMORANDUM
Subject: Summary Statistics for EPA's Study on the Quality of Domestic Septage
From: Charles E. White, Statistician/^
Statistical Analysis Section
To: Alan Rubin, Chief
Sludge Risk Assessment Branch
Through: Henry D. Kahn, Chief
Statistical Analysis Section
At your request, I will present and document summary statistics based on EPA's
Study on the Quality of Domestic Septage. These summary statistics wfll include basic
statistics on pollutants of concern, other requested pollutants, and the estimated relationship
between Total Kjeldahl Nitrogen and Ammonia. EFA's Study on the Quality of Domestic
Septage (1991) was conducted in order to support the development of hydraulic loading
rates for the land application of domestic septage und:er the 40 CFR Part 503 Final Rule for
Sewage Sludge Use or Disposal This loading rate is intended to be a protective and
affordable method for regulating the beneficial revise of septage. Development of the
loajiing rate itself will not be discussed in this memo.
Results
There are two basic results from these analyses. First, truckloads of domestic septage
are not expected to contain pollutant concentrations as high as could be found in sewage
sludge used or disposed from Publicly Owned Treatment Works that practice secondary or
better wastewater treatment Second, Total Kjeldahl Nitrogen is found to be approximately
43% Ammonia in wet domestic septage.
Data '
Nine trucks delivering domestic septage to the Madison Metropolitan Sewerage
District (MMSD) in Madison, Wisconsin were each sampled once. As septage was being
discharged, a grab sample was coDected and delivered to the MMSD lab for splitting,
labeling, icing, and snipping to appropriate labs tinder contract to the EPA. Each
E-25
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independent sample was physically analyzed for 324 pollutants. Only data regarding
pollutants of concern and some data for pollutants that are also micro-nutrients will be
considered in this report .
Physical Analytical Procedures
Physical analytical methods used here are the same as those used for the National
Sewage Sludge Survey (NSSS), though some pollutants are reported differently. Individual
PCB aroclors were reported in the NSSS; total PCB aroclors are reported here. Aldrin and
Dieldrin were reported separately in the NSSS; the totals for Aldrin and Dieldrin are
reported here. Total Chlordane is reported in the NSSS; the alpha and gamma portions of
chlordane are reported here. DDT, DDS, and DDD are reported separately in the NSSS;
totals for DDT, DDS, and DDD are reported here. LJndane is reported in the NSSS;
Lindane (Gamma-BHC) is reported here. •
Some pollutant concentrations were not measured above the Minimum Level for the
particular pollutant Minimum Levels are a form of "detection limit11 used in physical
analytical methods developed for the Office of Science and Technology. Under contract,
each contractor lab must demonstrate that it is able to achieve the Minimum Levels stated
for the particular EPA method to be used. In general, a Minimum Level is defined as the
lowest concentration at which the physical analytical process can be reliably calibrated.
Pollutant concentrations not measured above the Minimum Level for a particular pollutant
are not reported; the Minimum Level is reported instead.
Statistical Methods for Basic Summary Statistics
Statistical analysis methods were primarily selected to estimate a concentration level
for each pollutant such that, under certain assumptions, "most" septage concentrations for
a particular pollutant win be below it's respective level, i.e., we are primarily estimating
percehtiles. These methods will also be used to characterize both wet and dry weight
pollutant concentration measurements, mixed with "detection limits." Substitution and
Maximum Likelihood Methods wfll be used to estimate summary statistics. One overall
assumption of this study is that residential septage samples across the country follow
approximately the same probability distributions for pollutant concentrations as those
distributions found in the area around Madison, Wisconsin. Additional statistical
assumptions are discussed in the section on the Substitution Method, in the section on the
Maximum Likelihood Method for estimating summary statistics in the presence of censored,
or "non-detect," data and in the section on estimating the relationship between Ammonia
and Total Kjeldahl Nitrogen.
Drv Weight Conversion
Physical analyses were conducted on liquid septage samples. However, both because
pollutants are assumed to be concentrated in the solid phase of the septage sample and
E-26
-------
Because pollutants were reported this way in the NSSS, a dry weight conversion is also used
in presentation of these data. More detailed discussion of the reasons for dry weight
conversion and analyses in support of this practice are presented in the Statistical Support
Document for the 40 CFR Pan 503 Final Rule for Sewage Sludge Use or Disposal. Conversion
of a concentration reported in ug/1 is illustrated below:
Let PoUutant Concentration for Sample i = x, \igfl.
Solids Concentration for Sample i = v, mjg/1
Dry Weight PoUutant r^nr^tntion m ^g/kg = XP( 1,000,000
y
-------
size, measured pollutant concentrations, and the range of possible values for "detection limit11
data in order to pick optimum estimates for the log mean and log variance of a two
parameter lognormal distribution. If the assumption of a lognonnal distribution is not
closely approximated, this procedure is expected to produce good estimates for upper
percentiles while the mean and variance estimates may not be optimal.
The two parameter lognormal distribution is fully described by the log mean and log
variance, or the mean and standard deviation. Any desired summary statistic can be
calculated using an appropriate pair of sufficient statistics. More detailed discussion of this
method and the reasons why it was selected are presented, in Statistical Support Document
for the 40 CFR Pan 503 Final Rule for Sewage Sludge Use or Disposal (1992).
In order to assess-the quality of the MLEs, cumulative probability distributions were
plotted for both the wet and dry weight distributions. Each plot shows the estimated
cumulative distribution for all three estimation methods. The substitution methods are
illustrated with points for each observation. The probability plotting position for each point
is determined by a ranking procedure developed by Blom. The line indicating the estimated
lognonnal distribution is a plot of the 10th through 90th percentiles. These plots do not
indicate any obvious deviations from the assumption that the pollutant concentration data
are approximately lognormal in distribution. These plots are presented in the appendix,
Tables for wet weight summary statistics are presented on pages 10 through 12 and
tables for dry weight summary statistics are presented on pages 24 through 26. ^Pollutants
measured above their sample specific Minimum Level, or "(detection limit," one time or less
are not included in these tables as it is not possible to obtain MLEs under those conditions.
Note that truckloads of domestic septage are not: expected to contain pollutant
concentrations as high as could be found in sewage sludge used or disposed from Publicly
Owned Treatment Works that practice secondary or better wastewater treatment This
statement is based on the previously mentioned distributional assumptions of the MLE
estimation procedure and the additional assumption that domestic septage trucks across the
country have approximately the same probability distribution for pollutant concentrations as
domestic septage in trucks found in the area around Madison, Wisconsin. This result is
found by comparing the 98th percentfle estimates from the National Sewage Sludge Survey,
presented in Statistical Support Documentation for the 40 CFR, Part 503 Final Standards for
the Use or Disposal of Sewage Sludge (1992), to 98th percentfle estimates developed here for
dry weight concentrations of septage.
Statistical Methods for Estimating the Relationship Between Ammonia & TKN
Ammonia is the constituent of Total Kjeidahl Nitrogen (TKN) that is immediately
available for plant uptake. Over time, Total Kjeidahl Nitrogen is expected to completely
break down into Ammonia. The purpose of this analysis is to assist in determining an
E-28
-------
Relation of Total Kjeldahl Nitrogen to Ammonia:
80
70
SO
appropriate hydraulic loading rate, for
domestic septage that allows sufficient
nitrogen for crop growth while not allowing
for so much nitrogen that crop growth
would be adversely affected. The loading
rate itself will be estimated in another
document.
The observed relationship between
the Ammonia and the Total Kjeldahl
Nitrogen data indicates, as expected, that
both pollutants increase together. A
statistical model was fit "to these data that
assumes the concentration of Ammonia is
zero when the concentration of TKN is
zero, that the Ammonia concentration wfll
increase in a linear fashion as TKN
increases, that the Ammonia concentrations
about that line are approximately normal in
distribution, and that the deviations from
that line are independent and identically
distributed. Under these assumptions,
Total Kjeldahl Nitrogen is approximately 43% Ammonia in wet domestic septage.
30
20
SO 80 10O 120
Total KjddoM Nitrogen
of
Analytic of Variance
Source
OF
&• of
'Square*
Mean
Square
F Valu*
Prob>F
tfbbel
Error
C Total
Root USE
Dep Mean
C.V.
Variable DF
IMTERCEP 1
TO) 1
Variable DF
IKTE8CEP 1
TO* 1
1 3785.12042 3785.12042 9.806 0.0166
7 2702.12433 386.01777
8 6487.24480
19.64733 I-«quare 0.5835
42.72000 Adj K-*q ' 0.5240
45.99095
Piraaettr Estimates
Parameter Standard T for HO:
Estimate Error Para»t»r«0 Pirob > jTj
6.292426 13.34986889 0.471 0.6517
0.377705 0.12061931 3.131 0.0166
Variable
Label
Intercept
Total Kjeldahl nitrogen
Evaluation
Assumptions
For the
assumption that the
concentration of
Ammonia is zero
when the
concentration of TKN
is zero, a model was
fit that estimated a
non-zero constant
when TKN is zero and
a hypothesis test was
conducted that failed
to reject the
hypothesis that the
constant was
statistically different
than zero. The
E-29
-------
Source
OF
Analysis of Variance
SIB of
Squares
Square
f Value
Prob>F
Model
Error
U Total
Boot USE
Dep Mean
C.V.
Variable DF
TKX 1
Variable OF
TKN 1
1 20124.34510 20124.34510 57.748 0.0001
8 2787.88530 343.48566
9 22912.23040
18.66777
42.72000
43.69797
Para:
Parameter
Estimate
0.427247
Variable
Label
Total Kjeldaht
R-squiare 0.8783
Adj 8-sq 0.2631
•eter Estimates ,
Standard T for HO:
Error Para*eter=0 Prob > ,'TJ
0.05622261 7.599 0.0001
Hitrosen
Analysis of Variance
table for this model
indicates that the
intercept term is not
statistically significant
at the 0.05 level. The
significance test used
is robust to many
departures from
assumptions.
For the
assumption of
linearity, both the
Analysis of Variance
table for the model
with an intercept term
and for the model
without an intercept
term indicate that a ' ,
statistically significant linear relationship exists between Ammonia and TKN. Again, the
significance test used is robust to many
departures from assumptions.
Relation of Total Kjeldchl Nitrogen to Ammonia:
For . the assumption that,
Ammonia concentrations about that line
are approximately normal in
distribution, the Shapiro-Wflk test for;
the normal distribution fails to reject the
hypothesis that the residuals from the
fitted line come from a normal
distribution. Residuals are the
arithmetic difference between the
observed concentration of Ammonia at
a particular TKN concentration and the
Ammonia concentration predicted by
the statistical model Further evidence
is thai: the plot of the residuals versus
their expected position in a normal
distribution, a normal scores plot, is
approximately linear.
Normal Scorn Plot of Rmauan 'ram Regression
2 -!
-2
-1O
o to
Residual
20
40
Unrt3 ore mg/1
For the assumption that
deviations from the line are
E-30
-------
independent, the physical process of sampling from different truck loads of septage would
tend to make the sample results independent
For the assumption that deviations from the line are identically distributed, the plot
of residuals versus observed Ammonia values does not appear to .indicate strong deviation
from this assumption.
Rslotion of-Totol Kjeldohl Nitrogen to Ammonia:
rsui Oe»»v«d VOIUM
20-
10-
-30 •
0 102030«OSO«07080»O100
E-31
-------
References
Blom, G. (1958), Statistical Estimates and Transformed Beta Variables, New York: John
Wiley & Sons, Inc.
USEPA (1992), Statistical Support Documentation for the 40 CFR, Part 503 Final Standards
for the Use or Disposal of Sewage Sludge
E-32
-------
Appendix A
Summary Statistics
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Appendix B
Graphics
E-61
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Cumulative Frequency for Total/Udrin/Dieldrin (ug/I)
r.o
0.9
e -
u
m
0.7
0.6
0.4-1
0.2-
0.1 -I
SYMBOL
Concentration ( u g /1! )
•• 9 • SU-UL 000 SU-JQ
Cumulative Frequency for Total Aldrin/Dieidrin (ug/kg)
1.0
0.9
O.B:
J '.
n 0.7-
u
I
? 0.6-
v
'- o.s:
r ,
i 0.4-
o.3:
0.2:
o.i:
o.o;
100
SYMBOL
—i—i—i—<—i—i—'—' r—i ' ^^ ' i
200 300
Concentrot ion (ug/kg)
• • * SU-UL ooo SU-0
400
-------
r.o
0.9
0.8
0.7
0.6
0.5-
Cumulative Frequency for Ammonia (AS N) (mg/I)
0.3-;
0.2;
o.i-
O.o-L
1.0
0.9
0.8
0-7;
0.6 ;
0.5;
0.4 ;
0.3;
0.2;
o.i-
o.o-L
20 30 40 50 60 70
SYMBOL
80 90 100 110 120 130 140 150 160 170 180 190 200
Concentrotion (m g /1 }
MLE • • • SM-UL ooo SM-0
Cumulative Frequency for Ammonia (AS N) (mg/kg)
1 ' i
70000
1 ' i ' '
10000
20000
SYMBOL
30000 40000
Concentration (mg/kg)
MLE • • • • SM-HL
50000
ooo SU-0
60000
-------
1.0
0.9
0.8
a
t
0.6
r 0.5
e
q
« o.H
n
c
y 0.3-
0,2:
o. i-
Cumulative Frequency for Cadmium (ug/1)
SYUBOL
7 8 9 10 11 12 13 H- 15
Concentrotion (ug/l)
16 17 : 18 19
ULE
• • SM-UL ooo SM-0
Cumulative Frequency for Cadmium (mg/kg)
-f
2
SYMBOL
~r
3 4 5 '
Concent rot ion (ng/kg)
• • • SM-ML ooo
7
SM-0
-------
1 .0
0.9
0.8
0,5
Cumulative Frequency for Chromium (ug/1)
10
20
30
SYMBOL
50 60 70 80
Concentration (ug/l)
90
100
1 10
MLE ' • • • SU-ML ooo SU-0.
Cumulative Frequency for Chromium (mg/kg)
.1-20 13C
—'—i—'
10
SYMBOL
, : 1 1 1 1 1——< 1 1 1 1 1 I—1
20 , ' 30
Concen trot i on (ng/kg)
• • • SM-ML ooo SU-O
40
-------
Cumulative Frequency for Copper (ug/I)
'1.0
0.9
0.8
C
u
ffl 0.7-
u
I
f 0.6-1
i
v
« 0.5-1
F
r
e.0.4^
u
n 0.3
c
y
0.2-
0. 1 •
o.o-t
100 200 300 400 500 600 700 800 900 1000110012001300140015001600170018001900
Concent ro t i on (ug/I)
SYMBOL
• • SM-ML ooo SM'-O
Cumulative Frequency for Copper (mg/kg)
i.o-
0.9-
0.8-
0.7-
C
u
m
u
f 0.6
i
v
e 0.5
F
r
« 0.4
q
u
n 0.3
c
y
0.2
o.i:
o.oi
100
SYUBOL
200 300 400
Concen t r o t i on (mg/l:g)
ULE • • • SM-UL 060 SM-0
500
600
-------
Cumulative Frequency for Total DDT, DDE, and DDD (ug/l)
1.0
0.9
0.8
0.7
0.6-
: 0.5-
: 0.4-
0.3-
0.21
0. 1 -I
SYMBOL
Concentration (ug/l)
MLE • • • • SU-UL ooo SM-0
Cumulative Frequency for Total DDT, DDE, and DDD (ug/kg)
o.o-l
100
••—I—r
200
SYMBOL
300
Concen(ration (ug/kg)
UL£ • • • SM-ML
400
ooo SU-0
500
600
-------
Cumulative Frequency for Total Kjeldahl Nitrogen (mg/l)
1.0
o.9:
o.8:
c
u
« 0.7-j
u
I
f 0.6:
i
v
* 0.5-
3
j
1! 0.3:1
c
y
o.2H
0. 1
0.0
100
200
300
SYMBOL
Concent rot ion (rag/1)
M1_£ • • • SM-ML ooo SM-,0
Cumulative Frequency for Total Kjeldahl Nitrogen (mg/kg)
i.o:
o .9:
0.8-
i 0.6:
i
v
e 0.5d
F
r
e 0.4:
I 0.3^
c
y
0.2H
0. \;
0.0:
~r
-r
10000 20000 30000
SYMBOL
40000 50000 60000 70000
Concentrot ion (mg/kg)
ULE • • • SM-UL 000 SM-0
80000 90000 100000 110000
-------
"1.0
0.9
0.8
0.5-
0.4-
0.3'
0.2-
Cumulative Frequency for Lead (ug/I)
0.1 -L
T"1
90
1 . '
1 10
10
20
30
SYMBOL
40
50 60 70 80
Concentration (ug/I)
100
MLE
SM-UL ooo su-0
Cumulative Frequency for Lead (mg/kg)
120
130
SYMBOL
•I | . i . i ! i i i i . .... M
30 40 50 60
Concentration (rag/kg)
ULE • • • SU-UL o'o O SM-0
70
80
-------
Cumulative Frequency for Lindane (Gamma —BHC) (ug/I)
J.O
0.9
0.8
C
u
m 0.7
u
i 0.6:
i
v
e 0.5d
F
0.3d
0.2:
o. 1 -
o.o-l
0.00 0.02 0.0* 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26
Concentration(ug/il)
SYMBOL MLE • • • SU-UL o o o SU'-O
Cumulative Frequency for Lindane (Gamma—BHC) (ug/kg)
o. i-
O.OH
!
100
SYMBOL
200
Concentrotion (ug/kg)
• o • SU-ML ooo SM-0
300
-------
0. H
Cumulative Frequency for Mercury (ug/I)
1.0:
o.8
0.2
o. 1 -)
O.Oi
SYMBOL
2 3
Concentration ;(ug/l)
MLE ' • • • Swi-UL 000
Cumulative Frequency for Mercury (mg/kg)
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36
Concentration (ing/kg)
SYMB'OL ' MLE • • • SU-ML o o o su-o
-------
Cumulative Frequency for Nickel (ug/I)
J.O
0.9
C u*
u
m
y 0.7
a
t
! 0.6-
e
q
6 *
ft
y 0.3-1
0.2
o. i-L
—!—
70
0.0-i
10
20
'30
SYMBOL
—i—
50
60
80
90
Concentration (ug/I)
HLE . • • • SM-UL ooo SM-0
Cumulative Frequency for Nickel (mg/kg)
100
1 10
SYMBOL
30 40
Concentration (ng/k;|)
ULE • • • SM-ML
i i '
50
ooo SU-Q
60
70
-------
Cumulative Frequency for Nitrate 4- Nitrite (mg/I)
1.0
0.9
0.8
0.2-
0. 1 -
0.0
0.1 0.2 0.3 '0.4 0.5 0.6 0.7
Concentrot ion (ng/ I )
SYMBOL - MLE • • • SU-UL ' o o o SM-0
0.8
O.S
1 .0
Cumulative Frequency for Nitrate -K Nitrite (mg/kg)
o. i-
o.o-U
' I '
no
10 20 30 40
i i •••' i •''' i ••••'•••-"••--••
50 -60 70 80 • !JO 100
Concentration (aig/kg)
SYMBOL - ' WLE • • • SW--UL o o o SW-O
120 130 140 150 ISO
-------
Cumulative Frequency for Total Phosphorous (mg/1)
•1.0
0.9-
o.8:
c
u
m 0.7-
u
t 0.6:
I
V
e 0.5:1
F
r
e O.^-j
q
0.3
0.2
o. i-
o.o
10 20 30 40 50 60 . 70 80
Concentrot ion (mg/l)
SYMBOL MLE • • • «:S«-ML o o o SM-0
Cumulative Frequency for Total Phosphorous (mg/kg)
90
1.0
0.9
0.8
C
u
ra 0.7
u
I
f 0.6-
¥
e 0.5^
F
r
e 0.4-
q
u
„ 0.3d
c
y
0.2
o.i-
O.Oi
1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000.14000 15000
Concent rot ion (ng/k(|)
SYMBOL ULE * • • SM-ML • o o o SM-0
-------
Cumulative Frequency for Selenium (ug/I)
1 .0
0.9
0.8
0.5-
0.4-
0.3-
0.2:
0.1-
, , i , , •-••• . . 1 , , 1 , , , ; r ..,,,.,. | ,.,,,,,,.,...... . . ,
0 10 20 30 4050
Concent rot ion (ug/I)
SYMBOL
ULE •
SM-UL ooo SU-O
Cumulative Frequency for Selenium (mg/kg)
SYMBOL
i i . i i i ' ' ' ' i • • ' • i • '
4 5 6 7
Concentration (ng/kg)
ULE • • • SM-ML ooo
10
1 1
SU-O
-------
1.0
0.9
0.8
C
u
m 0.7-
u
e 0.5:
F
r
e 0
u
n 0.3d
c
0.2:
o, 1-
o.o:
Cumulative Frequency for Zinc (ug/I)
0.9-
0..8-
C
u
m 0.7-
u
I
? 0,6-
v
e 0.5-
F
r
« 0.4-
q
u
S 0.3-
e
y
0.2-
0.1-
o.o-
SYMBOL
10000 2QQOO
Concentration' (ug/I)
- «LE • • • SU-UL o o o SM-0
30000
Cumulative Frequency for Zinc (mg/kg)
1 i '
100
200
1 i ' • • ' i—
300 400
SYMBOL
• i i i i • i i ' ' ' —,i ' ' ' ' ~
500 600 700 800 900
Concentration (mg/kg)
MLE • • • SU-UL
1000 1100 1200 1300 HOO 1500
ooo SM-0
-------
Cumulative Frequency for Percent Solids (%)
i.o
0.9
0.8-
0.7-
0.6-
0.5-
0.4-
0.3 -
0,2 -
o.i-
o.o-
I I I 1 j I 1 I I [ I I I I I I I I I j 1 1 I I I .1 I I I [ I -I I ' I ' ' ' ' 1 ' ' ' ' ) ' ' ' ' I ' ' ' ' 1 ' '* ':' I ' -'. ' ' I ' ' ' ' I ' ' ' ' I
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
SYMBOL
Concentration (%)
MLE • • • SM-ML O O O SM-0
-------
Appendix C
Data Listing
-------
Wet Weight Concentrations of Pollutants in Septage
. Pollutant=ALDRIN/DIELDRIN (TOTAL)
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
2.50
0.75
Minimum
0.100
0.100
0.100
0.184
0.100
0.100
0.100
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Pollutant=ALPHA-CHLORDANE
Quantified
Amount
Minimum
Level
0.100
0.100
0.100
0.100
0.100
0.184
0.100
0.100
0.100
Units
UG/L
UG/L'
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
PollUtant=AMMONIA (AS N)
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
45.00
0.48
40.00
11.00
45.00
33.00
56.00
54.00
100.00
Minimum
Level
Units
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
-------
Wet Weight Concentrations of Pollutants in Septage
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
, ' 19981
19982
EPA
Sample
Number
19974
19977
19978
19979
' 19980
19981
19982
r t
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
• 19981
19982 "
Quantified Minimum
Amount Level
20.000
20.000
20.000
20.000
20.000
20.000
20.000
20.000
. - 20.000
•n*O 1 n^ai-i*- TJTTV7TTWT:1 ——•
Quantified Minimum
Amount Level
10.000
10.000
10.000
20.000
10.000
10.000
10.000
Pollutant— BENZO (A) PYRENE
Quantified Minimum
Amount Level
10.000
10.000
10.000
' . 10.000
10.000
20.000
10.000
10.000
10.000
Units-
UG/L
UG/L
•UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Units
UG/L
UG/L
• UG/L
UG/L
UG/L
UG/L
UG/L
Units
UG/L
UG/L
UG/L
, UG/L
UG/L
UG/L •
UG/L •
UG/L
UG/L
-------
Wet Weight Concentrations of Pollutants in Septage
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
• 19981
19982
Quantified
Amount
9
.
.
.
.
.
.
.
. •
EPA
Sample
Number
19974
19975
19976
19977
. 19978
19979
19980
19981
-' 19982
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
#
.
.
.
.
.
.
.
T^_^ 1 ••^••••M^**
Quantified
Amount
9.40
*
.
.
6.40
18.40
.
.
.
Minimum
I^evel
5.000
5.000
5.000
5.000
5.000
5.000
5.000
5.000
5.000
:LHEXYL) PHT
Minimum
Level
10.000
10.000
10.000
10.000
10.000
20.000
10.000
10.000
10.000
Minimum
Level
m
5.000
5.000
5.000
*
*
5 . 000
5.000
5.000
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Units
UG/L
. UG/L
UG/L -
UG/L
UG/L
UG/L
UG/L
UG/L :
UG/L ' :";: "£.
-------
Wet Weight Concentrations of Pollutants in Septage
— Pollutant=CHROMIUM • •—•
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
53.90
12.10
32.10
81.60
128.00
33.50
50.20
18.70
Minimum
Level
10.000
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
-UG/L
UG/L
UG/L
Pollutant=COPP£R
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
1340.00
77.10
80.30
115.00
758.00
174.00
1850.00
62.00
69.60
Minimum
Level
Units
UG/L
UG/L '
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Pollutant=DDT/DDE,ODD(TOTAL)
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
0.92
2.88
Minimum
Level
0.338
0.338
0.338
0.338
0.338
0.338
0.338
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
-------
Wet Weight Concentrations of Pollutants in Septage
EPA
Sample
Number
19974
19975
19976
19977
19978
19.979
. 19980
• 19981
19982
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
-' 19982
T\ —
— —• ——.—.—— pc
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Prt i I ^T^TSn i ^"^L^/V MJn A ***C ^H 1 J3fclJA.M
Quantified Minimum
Amount l^evel
0 . 113
0 . 113
0.113
0 . 113
0 . 113
0.207
0.113
0 . 113
0.113
TV..T 1 *v^->«+- tTWn f*VT /YD — .
• POJLJ.Uuan&— lit.r'lAtJlJJJit ~"
Quantified Minimum
Amount I^evel
0.25
0.063
0.063
0.063
0.063
0 . 115
0.063
0.063
0.063
*! T n4*aTi^ ffT*Y2kPTTT^^5OSElX2EI1i
Quantified Minimum
Amount ' Level
10.000
10.000
10.000
10.000
10.000
20.000
10.000
10.000
10.000
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Units
UG/L
UG/L'
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
• ill
Units
UG/L
, UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L £
UG/L
-------
Wet Weight Concentrations of Pollutants in Septage
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
. 19981
19982
EPA
Sample
Number
19974
19975
19976
19977
19978
' 19979
19980
:• 19981
19982
Po
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
XX U UOJ1 U— £LCtAAWUJ
Quantified
Amount
.
.
^
.
.
9
^
9
• •
Y\._. n 1 1,^-%^+*—
Quantified
Amount
121.00
.
.
,
*
70.30
79.30
9
•
m T ••JU**«fc^ T TIT^XUT
1 lutant— LIU UAH t
Quantified
Amount
.
.
0.13
m
^
0.25
.
.
Minimum
Levfitl
10.000
10.000
. 10.000
10.000
10.000
20.000
10.000
10.000
10.000
Minimum
Level
.
50.000
50.000
50.000
50.000
.
.
50.000
50.000
Minimum
Levesi
0.138
0.138
0.138
.
0.138
0,253
.
0.138
0.138
Units
UG/L
UG/L
-UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Units .
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
-y
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
-------
Wet Weight Concentrations of Pollutants in Septage
. Pollutant=MERCTOY
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981 .
19982
Quantified
Amount
0.30
1.30
0.45
0.50
4.05
Minimum
Level
0.200
0.200
0.200
0.200
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Pollutant=MOLYBD]SNUM
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
14.40
Minimum
Level
Units
.
10.000
10.000
10.000
10.000
10.000
10.000
10.000
10.000
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Pollutant=N-NITROSODIMETHYLAMINE
EPA
Sample
Number
19974
19975 '
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount •
Minimum
Level
50
50
50
50
50
100
50
50
50
.000
,000
,000
,000
,000
,000
,000
,000
,000
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
E-85
-------
Wet Weight Concentrations of Pollutants in Septage
Pollutant=NICKEL —
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
. Amount
79.80
61.80
105.00
41.90
•
41.60
Minimum
Level
40.000
40.000
40.000
40.000
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Pollutant=NITRATE+NITRIT£ (AS N)
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount
0.20
0.90
0.20
0.60
0.60
0.60
0.20
Minimum
Level
0.100
0.100
Units
MG/L
MG/L*
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
Pollutant=PCB(TOTAL)
EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
19981
19982
Quantified
Amount ,
Minimum
Level
1.750
1.750
.750
.750
,750
.218
1.750
1.750
1.750
1.
1.
1.
3.
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
F-Rfi
-------
Wet Weight Concentrations of Pollutants in Septage
—. . pollutant=SELENIUM
EPA
Sample Quantified Minimum
Number Amount level Units
19974 . 50.000 UG/L
19975 . 5.000 UG/L
19976 . 5.000 UG/L
19977 . 5.000 UG/L
19978 . 5.000 UG/L
19979 30.50 . UG/L
19980 . 5.000 UG/L
19981 . 50.000 UG/L
19982 32.00 . UG/L
Pollutant=TOTAL KJELDAHL NITROGEN
EPA
Sample Quantified Minimum
Number Amount Level Units
19974 142.00 . MG/L
19975 9.00 . MG/L-
19976 55.00 . MG/L
19977 31.00 . MG/L
19978 70.00 . MG/L
19979 119.00 . MG/L
19980 115.00 . MG/L
19981 175.00 . MG/L
19982 152.00 . MG/L
Pollutant=TOTAL PHOSPHOROUS
EPA
Sample Quantified Minimum
Number Amount . D»vel Units
19974 32.00 . MG/L
19975 1.70 . MG/L
19976 7.00 . MG/L
19977 25.00 . MG/L
19978 12.00 . MG/L
19979 48.00 . MG/L
19980 36.00 . MG/L
19981 46.00 . MG/L
19982 41.00 . MG/L
E-87
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Wet Weight Concentrations of Pollutants in Septage
" EPA
Sample
Number
19974
19975
19976
19977
19978
19979
19980
-. 19981
19982
EPA
Sample
Number
19974
19975
'19976
19977
19978
19979
•19980
19981
J' 19982
EPA
Sample
Number
19974
19977
19978
19979
19980
19981
19982
— Foj.iuranr=ro^
Quantified
Amount
4880.00
733.00
653.00
142000.00
2310.00
18500.00
11300.00
6580.00
11700.0.0
Quantified
Amount
•
•
•
•
*
•
•
•
•
Pollutant=TRX d
Quantified
Amount *
•
•
•
•
•
•
•
L'AL, 5O.LJLDS -
Minimum
Level
m
•
•
•
•
•
•
.
.
i/**v-» Taxrovrt?
Minimum
Level
11.375
11.375
0.9.10
11.375
11.375
20.920
11.375
11.735
11.375
'j f ^\*O^\T?^R\J t* MT?
U-iUrtUJL 1 Jl£*Tt CA
Minimum
Level
10.000
10.000
10.000
20.000
10.000
10.000
10.000
Units '
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Units
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
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Wet Weight Concentrations of Pollutants in Septage
Pollutant=ZINC
EPA
Sample Quantified Minimum
Number Amount l^evel Units
19974 5990.00 . UG/L
19975 182.00 . UG/L
19976 519.00 . UG/L
19977 6210.00 . UG/L
19978 . 1120.00 . . UG/L
19979 23800.00 . UG/L
19980 3810.00 . UG/L
19981 2850.00 . UG/L
19982 3190.0:0 . UG/L
E-89
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APPENDIX F
CALCULATION OF THE AMOUNT OF SEWAGE SLUDGE USED OR DISPOSED
FOR THE PART 503 FREQUENCY OF MONITORING REQUIREMENTS
-------
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j ,r • ^
CALCULATION' OP THE AMOUNT OP SEWAGE SLUDGE USED OP DISPOSED
POR TEE PART 503 FREQUENCY OP MONITORING REQUIREMENTS
Office of Science and Technology
U.S. Environmental Protection Agency
401 M Street, S.W. •
Washington, D.C. 20460
November 23, 1992
F-i
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CALCULATION OP THE AMOUNT OF SEWAGE SLUDGE USED OR DISPOSED
FOR THE PART 503 FREQUENCY OF MONITORING REQUIREMENTS
INTRODUCTION
The Standards for the Use or Disposal of Sewage Sludge in 40 :
CFR Part 503 contain frequency 'of monitoring requirements for land
application of sewage sludge, placement of sewage sludge on a ;
surface disposal site, and firing of sewage sludge in • a sewage
sludge incinerator. These requirements indicate how often sewage
sludge has to be monitored for pollutant concentrations, pathogen ,
densities, and vec-or attraction reduction. They are based on_the
amount of sewage sludge used or disposed during a 365 day period.
ind application, the frequency of monitoring requirements
iitheV or. the amount of bulk sewage sludge applied to the
For land
are based ei
land or the amount of sewage sludge received by a person who
prepares the sewage sludge for sale or give aw'ay in a bag or
similar enclosure for application to1the land. As those amounts
increase, the frequency of monitoring increases.
For surface disposal and firing of sewage sludge in a sewage •
sludge incinerator, the frequency of, monitoring requirements are
based on the amount of sewage sludge placed on a surface disposal ;
site and the amounr of sewage sludge fired in a 'sewage sludge
incinerator, respectively. For these two practices, the frequency
of monitoring also increases as the amount of sewage sludge used |
or disposed increases.
This document discusses calculation of the amounts of sewage -
sl>udge used or disposed for the Part. 503 frequency of monitoring
re&uirements. The assumptions on which those requirements are
based and the calculations for the amounts used or. disposed' are :
presented below. AJ.SO presented below are the Part 503 frequency
of monitoring requirements.
ASSUMPTIONS
o Wastewater is treated*in "typical" secondary wastewater
treatment plant (i.e., primary settling followed by
biological treatment followed by secondary settling).
•»
o Sewage sludge is stabilized in an anaerobic digester
prior to use or disposal.
o Influent wastewater BODS concentration = 200 mg/1.
o Effluent wastewater BODS concentration = 30 mg/1.
o Influent wastewater TSS concentration = 200 mg/1.
o Effluent wastewater TSS concentration =30 mg/1.
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o TSS percent removal in!primary treatment process = 60.
'o Percent volatile solids in the influent to digester =60,
o Percent volatile solids reduction in digester =38.
o Percent fixed solids ' in the influent to. digester - 40
o Solids concentration factor during -;
secondary settling ' • -
*=»-:fV- Q
#VV "*,'*
'
CALCULATIONS FOR TREATMENT WORXS WITH. A FLOW RATE Q-
-r:^^;-.Qef::fe.^ .
i ' • - -'vf^Ef ft --.s-y-v -•••;:"
o TSS removal in primary treatment process:
Influent TSS x Flow rate x Conversion factor x Percent -removal
200 mg/1 x 1 MGD x -8v34 x 0.6 = 1.000 pounds oer dav.
o BODS removal through secondary settling process;
Influent BODS - Effluent BODS = 200 - 30 = 170 .mg/1
Concentration removed x Flow rate x Conv. fact, x Cone. "fact.
170 mg/1 X 1 MGD x 8.34 x 0.9 = 1.276 pounds oer dav.
6 Sewage sludge to the digester:
Primary settling sludge + secondary settling sludge = total
1,000 4- 1,276 = 2.276 pounds per day.
jT* o Amount of sewage sludge used or; disposed:
Fixed solids = total amount x percent of total solids.
Fixed solids = 2,276 x 0.4 = 910 pounds per dav.
Volatile solids = total amount x percent of total solids x
percent remaining after digestion.
- Volatile solids = 2,276 x 0.6 x (1,0 - 0.38) = 847 pounds/day
Total amount used or disposed = Fixed solids + volatile
solids
910 -1- 847 = 1.757 pounds per dav
* ¥ *
H "
Total amount = 1,757 pounds x 365 days x 1 metric ton
days year 2,200 pounds
2 , J-***
Total amount for 1 MGD = 292 metric tons per year.
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Report amount in two significant fignores:
Use 290 metric tons per year for 1 MGD treatment works fdry
weight basis)
CALCULATION FOR A TREATMENT WORKS WITH A FLOW RATE OF FIVE MGD
Total amount = Amount for 1 MGD treatment works times 5
Total amount = 290 x 5 = 1.450 metric tons per year
Report amount in two significant figures:
Use 1,500 metric tons oer vear for five MGD treatment works :
fdrv weicht basis) • :
CALCULATION FOR A TREATMENT WORKS WITH A FLOW RATE OF 50 MGD
Total amount = Amount for 1 MGD treatment works x 50
Total'amount = 290 x 50 = 14,500 metric tons per vear . ;
Report amount in two significant figures:
Use 15,000 metric tons oer vear for 50 MGD treatment works
fdrv weight basis)
PaR? 503 FREQUENCY OF MONITORING REQUIREMENTS
Results of the above calculations ve::e used as the basis for
the frequency of monitoring requirements in Part 503. Those
frequencies are presented below.
*
* t
* • ;
FREQUENCY OF MONITORING
Amount of sewage sludge used or disposed ;
/metric tons per 365 dav period-dry weight) Frequency
Greater than zero but ^ once -per year
less than 290 * •
Eoual to or greater than once per quarter
29~0 but less than 1,500 (four times per year)
Ecrual to or greater than once per 60 days
1,~500 but less than 15,000 (six time per year)
Equal to or greater than once per month
15,000 (12 times per year)-
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