vvEPA
United States
Environmental Protection
Agency
2001 National Sewage Sludge Survey
Report
September 2007
Cl
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U.S. Environmental Protection Agency
Office of Water (4303T)
1200 Pennsylvania Avenue, NW
Washington, DC 20460
EPA-822-R-07-006
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ACKNOWLEDGMENTS
This report was prepared by Computer Sciences Corporation (CSC) under the direction of Rick
Stevens of the Office of Science and Technology's Health and Ecological Criteria Division, within the
U.S. Environmental Protection Agency (EPA's) Office of Water. This report is based on a report initially
prepared by CSC (formerly DynCorp Systems & Solutions LLC) and submitted to EPA under the terms
of a task order under MOBIS contract GS-23F-9820H. The efforts of the CSC staff who contributed to
this study and the initial report are gratefully acknowledged, as are the contributions of the staff of Axys
Analytical Laboratories, which provided analytical services for the study through a subcontract with CSC.
DISCLAIMER
This EPA report was prepared by CSC under EPA direction. Questions regarding the 2001
National Sewage Sludge Survey, the survey results, or future plans may be directed to the EPA Biosolids
Coordinator:
Rick Stevens
U.S. Environmental Protection Agency
Office of Water
Office of Science and Technology
Health and Ecological Criteria Division
Ecological and Health Protection Branch
1200 Pennsylvania Avenue, NW
Mail Code: 4304T
Washington, DC 20460
202-566-1135
Stevens .rick@epa.gov
2007 National Sewage Sludge Survey Report Hi September 2007
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TABLE OF CONTENTS
Page
Acknowledgments iii
Disclaimer iii
Executive Summary v
Section 1.0 Introduction 1
Section 2.0 Study Management and Implementation 2
Section 3.0 Study Objectives and Selection of Facilities 3
3.1 Study Objectives 3
3.2 Selection of Facilities 3
Section 4.0 Sample Collection and Analysis 5
4.1 Sample Collection 5
4.2 Analytes of Interest 5
4.3 Methods Modifications 6
Section 5.0 Data Reporting and Validation 8
Section 6.0 Results, Data Analysis, and Discussion 9
6.1 Toxic Equivalent Concentration 9
6.2 Summary Results 10
6.3 Frequency Distributions 12
6.4 Field Duplicate Results 13
Section 7.0 Conclusions 16
Section 8.0 References 16
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EXECUTIVE SUMMARY
This report presents the results of the U.S. Environmental Protection Agency's (EPA's) 2001
National Sewage Sludge Survey (NSSS). The survey was conducted jointly by the Health and Ecological
Criteria Division (HECD) and the Engineering and Analysis Division (EAD) within the EPA Office of
Water's Office of Science and Technology. The objective of the survey was to obtain unbiased national
estimates of dioxin and dioxin-like compounds in sewage sludge to enable EPA to perform a multi-
pathway exposure assessment and risk assessment of the disposal of sewage sludge through land
application.
A total of 113 samples of sludge were collected from 94 publicly owned treatment works
(POTWs) in 32 states and the District of Columbia during a seven-week period in February and March
2001. Eighty-nine of these POTWs had a single system for treating and processing their sludge material.
Therefore, one final sludge product sample was collected from each of these POTWs. Five of the
POTWs had two systems for treating their sludge material; therefore, two final sludge product samples
were collected from each of these five facilities (one sample per treatment process). For quality control
purposes, field duplicate samples were collected from 15% of the facilities (14 POTWs) sampled. All
113 samples were analyzed for a suite of poly chlorinated dibenzo-p-dioxins (PCDDs), polychlorinated
dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) using state-of-the-art EPA analytical
methods and project-specific modifications to ensure that the lowest consistent practical sensitivity was
achieved. The suite of analytes included the seventeen 2,3,7,8-substituted PCDDs/PCDFs of
toxicological concern and the twelve PCB congeners identified as "toxic" by the World Health
Organization. The analytical results were reviewed to verify completeness and compliance with the
method specifications and study requirements.
The results for each sludge sample were calculated in terms of the toxic equivalents of 2,3,7,8-
tetrachlorodibenzo-/?-dioxin (TCDD or "dioxin") represented by the various substituted chlorinated
dioxins, furans, and PCBs that were present. For the purposes of this calculation, the concentration of any
congener that was not detected in the sample was set to one-half the quantitation limit for that congener.
This commonly used substitution scheme is conservative relative to protection of the environment, as it
assumes that there may be some of the contaminant present below the level at which quantitative
measurements can be made. Using this scheme, every sample will have a TEQ value, even if no
contaminants were detected in the sample. The lowest possible TEQ value in this study would be 1.6
ng/kg of TCDD on a dry-weight basis.
Sample results ranged from 3 ng/kg to 718 ng/kg of TCDD. The vast majority of the samples had
TEQ values in the range of 7 to 55 ng/kg. Only seven results over 100 ng/kg TEQ were reported, and two
of those were for field duplicate samples collected as part of the quality assurance program for the survey.
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SECTION 1.0 INTRODUCTION
Section 405(d) of the Clean Water Act (CWA) requires that the U.S. Environmental Protection
Agency (EPA) propose, solicit public comments, and promulgate standards for the use or disposal of
sewage sludge. These standards are codified at 40 CFR Part 503 (Part 503 Standards). To date, EPA has
accomplished this rulemaking activity in phases referred to as "rounds."
Round One of the Part 503 Standards was promulgated on February 19, 1993 (58 FR 9248). The
Round One standards established numerical limits for 10 metals in sewage sludge produced at publicly
owned treatment works (POTWs) and managed through land application, surface disposal, and
incineration. This rule also established an operational standard for sewage sludge incinerator emissions.
These standards were based on a National Sewage Sludge Survey conducted by EPA in 1988-1989
(1989 NSSS) to obtain unbiased national estimates of the concentrations of more than 400 pollutants in
sewage sludge collected from 174 wastewater treatment plants that practiced at least secondary
wastewater treatment.
On December 23, 1999, EPA proposed Round Two of the Part 503 Standards (64 FR 72045).
This proposal sought to establish a numerical standard for 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin)
and dioxin-like compounds (furans) applicable to sewage sludge managed through land application (under
Subpart B of the Part 503 rule). In addition, this proposed rule found that numerical standards or
management practices were not necessary to protect public health from the presence of dioxins in sewage
sludge managed by surface disposal or incineration. The proposal solicited public comments.
The list of pollutants in the 1989 NSSS included the seventeen 2,3,7,8-substituted congeners of
chlorinated dibenzo-^-dioxins and chlorinated dibenzofurans. PCBs were determined as Aroclors, but no
attempt was made to measure the concentrations of the 12 coplanar PCB congeners identified as "toxic"
by the World Health Organization. In developing the Round Two rule, EPA relied on estimates of the
concentrations of the dioxins and dibenzofurans in sewage sludge from the 1989 NSSS and a national
estimate of the 12 coplanar PCB congeners concentrations obtained from a 1995 survey commissioned by
the Association of Metropolitan Sewerage Agencies. These estimated concentrations were used as a
source term in the risk assessment as the technical basis of the proposed numerical standard and in the
proposed rule's regulatory impact analysis to estimate the costs to the regulated community of complying
with the rule. Following proposal of the Round Two rule, EPA received and considered a number of
public comments, including comments that strongly urged EPA to conduct a new survey of dioxin and
furan concentrations in sewage sludge. Commenters suggested that given the extensive efforts to reduce
the sources of dioxins and furans from specific industries, the concentrations of dioxins and furans in
sewage sludge at the start of the 21st century were likely to be lower than those concentrations found in
sewage sludge in the 1989 NSSS. To address these comments, EPA conducted a second NSSS in 2001.
The purpose of the 2001 NSSS was to obtain updated, unbiased national estimates of dioxins and dioxin-
like compounds in sewage sludge managed by land application. This report describes the sampling and
analysis aspects of EPA's 2001 NSSS and summarizes the analytical results.
EPA developed two documents in preparation for this study: Sampling Procedures for the 2001
National Sewage Sludge Survey (Reference 8.1), which contains the study sampling protocol, and Quality
Assurance Project Plan for the 2001 National Sewage Sludge Survey (Reference 8.2), which identifies
study objectives and measurement quality objectives established for the collection and analysis of
environmental samples during the study and serves as the study plan. These documents are available
separately from EPA.
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SECTION 2.0 STUDY MANAGEMENT AND IMPLEMENTATION
The EPA Office of Science and Technology (OST) is responsible for proposal and promulgation
of the Part 503 Standards and for overall management of the 2001 NSSS. Day-to-day responsibility for
managing various aspects of the Round Two rulemaking was delegated to the Health and Ecological
Criteria Division (HECD) and the Engineering and Analysis Division (EAD) within OST. EAD was
responsible for managing all sample collection, laboratory analysis, data verification (data review), and
database development activities. Both EAD and HECD were responsible for day-to-day interaction with
contractors and with personnel at the POTW facilities visited. HECD was responsible for conducting the
data analysis, risk assessment, and environmental assessments necessary to support the rulemaking. The
EPA Sample Control Center, operated by CSC (then known as DynCorp) provided cradle-to-grave study
support under EAD's direction.
To minimize analytical variability, EAD used a single contract laboratory (Axys Analytical
Services) to perform all study analyses. The laboratory has extensive experience in dioxin/furan and PCB
analyses and, prior to participation in the study, demonstrated that it could produce data of the quality
required for regulatory purposes. CSC facilitated effective communication among all parties involved in
the shipment and analysis of samples under this study. CSC's responsibilities also included:
Drafting the sampling procedures document
Developing the draft QAPP
Preparing and distributing field sampling kits
Participating in sample collection
Documenting all sample shipments
Resolving any shipping and analytical problems that arose
Reviewing laboratory data
Working with the laboratory and EPA to correct quality control failures, where possible
Documenting the extent to which data submissions met method acceptance criteria
Developing a database of study results
Drafting the study report.
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SECTION 3.0 STUDY OBJECTIVES AND SELECTION OF FACILITIES
3.1 STUDY OBJECTIVES
The objective of the survey was to obtain unbiased national estimates of dioxin and dioxin-like
compounds in sewage sludge to enable EPA to perform a multi-pathway exposure assessment and risk
assessment of the disposal of sewage sludge through land application. Data collected in the study also
were to be used in assessing risks associated with surface disposal and incineration of sewage sludges.
These risk assessments would serve as the technical basis for determining whether numerical standards
for dioxins for these sewage sludge management practices are warranted in the final Part 503 rule.
3.2 SELECTION OF FACILITIES
To ensure that EPA obtained a representative sampling of POTW facilities and that data collected
could be compared with data from the 1989 NSSS, a total of 101 facilities throughout the contiguous
United States were randomly selected from the pool of 174 facilities in the 1989 NSSS for participation in
the 2001 NSSS. Seven of the selected facilities were either closed or no longer treated their own sewage
sludge and, therefore, were not eligible for sampling. As a result, only 94 facilities were sampled. These
94 facilities were located in 32 states and the District of Columbia and are listed in Table 1, in
alphabetical order by state, then city.
Table 1. Facilities Sampled in 2001 NSSS
Facility Name
Sacramento Regional
VWVTP
Fallbrook Public Utility
District
Manteca WQCF
Central Contra Costa
Sanitary District
Fairfield - Suisun Sewer
District
Boulder - 75th St VWVTP
Steamboat Springs
Rocky Hill WPCP
Waterbury WPCF
DC WASA (Blue Plains)
Mulberry STP
Escambia County - Main
Street WTP
St. Petersburg SW
Treatment Plant
Sunrise Sewage
Treatment Plant No.1
R. M. Clayton WPCP
Buford Westside WPCP
Cartersville WPCP
City
Elk Grove
Fallbrook
Manteca
Martinez
Suisun City
Boulder
Steamboat Springs
Hartford
Waterbury
Washington
Mulberry
Pensacola
St. Petersburg
Sunrise
Atlanta
Buford
Cartersville
State
CA
CA
CA
CA
CA
CO
CO
CT
CT
DC
FL
FL
FL
FL
GA
GA
GA
Facility Name
Metropolitan Council - Metro
Crocker WWTP
Mason Farm WTP
Whiteville WWTP
BurwellWWTF
Middletown Sewerage Authority
Joint Meeting Sewage Treatment
Passaic Valley Sewerage
Commission
Bowery Bay WPC
Hunt's Point WPC
Cayuga Heights WWTP
BrewsterWWTP
NEORSD - Southerly
Brentwood Estates STP #24
Delphos
Massillon
North Olmsted
City
Saint Paul
Crocker
Carrboro
Whiteville
Burwell
Belford
Elizabeth
Newark
Corona Queens
Corona Queens
Ithaca
Mahopac
Cleveland
Cuyahoga Falls
Delphos
Massillon
North Olmsted
State
MN
MO
NC
NC
NE
NJ
NJ
NJ
NY
NY
NY
NY
OH
OH
OH
OH
OH
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Table 1. Facilities Sampled in 2001 NSSS
Facility Name
Dekalb Co - Snapfinger Cr
WPCP
Garden City WPCP
Gwinnett Co Jackson Cr
Ocmulgee WPCP
Boise
Belleville STP #1
MWRDGC Stickney STP
Jacksonville STP
Morris STP
Tolono STP
Evansville STP - Westside
Frankton Municipal STP
Hammond Municipal STP
Muncie Sanitary District
Terre Haute Municipal
STP
Union City Municipal STP
Oakland STP
Shepherdsville STP
Billerica WWTP
Fall River WWTF
Medfield WWTP
Pittsfield WWTP
Patapsco WWTP
South Portland WPCF
DowagiacWWTP
Iron Mountain - Kingsford
WWTP
Genesee County -
Ragnone WWTP
Port Huron WWTP
Wyandotte WWTP
Western Lake SSD
City
Decatur
Garden City
Lilburn
Warner Robins
Boise
Belleville
Cicero
Jacksonville
Morris
Westville
Evansville
Frankton
Hammond
Muncie
Terre Haute
Union City
Topeka
Shepherdsville
Billerica
Fall River
Medfield
Pittsfield
Baltimore
South Portland
Dowagiac
Kingsford
Montrose
Port Huron
Wyandotte
Duluth
State
GA
GA
GA
GA
ID
IL
IL
IL
IL
IL
IN
IN
IN
IN
IN
IN
KS
KY
MA
MA
MA
MA
MD
ME
Ml
Ml
Ml
Ml
Ml
MN
Facility Name
Port Clinton
Twin Lakes WWTP
Thornville
West Carrollton
Blackwell
Lebanon
Portland
Burnham STP
Downingtown Area Regional
Authority
Girard Boro
Kiski Valley Water Pollution Control
Philadelphia Water Dept (SW)
Philadelphia Water Dept (NE)
Allegheny County Sanitary Authority
Narragansett Bay Commission -
Bucklin
Florence - Pee Dee River Plant
WCRSA/Pelham WWTF
Brooking
Sioux Falls
Andrews STP
Del Rio -San Felipe
Navasota, Grimes Co. STP
Orange, Jackson St WWTP
Brazos River Authority (Waco)
Fredericksburg City STP
Augusta County Service Authority
HRSD - James River STP
HRSD - Chesapeake/Elizabeth STP
Metropolitan King County
Greenbrier County PSD No 2
City
Port Clinton
Ravenna
Thornville
West Carrollton
Blackwell
Lebanon
Portland
Burnham
Downingtown
Girard
Leechburg
Philadelphia
Philadelphia
Pittsburgh
Providence
Florence
Greenville
Brookings
Sioux Falls
Andrews
Del Rio
Navasota
Orange
Waco
Fredericksburg
Verona
Virginia Beach
Virginia Beach
Renton
Rainelle
State
OH
OH
OH
OH
OK
OR
OR
PA
PA
PA
PA
PA
PA
PA
Rl
SC
SC
SD
SD
TX
TX
TX
TX
TX
VA
VA
VA
VA
WA
WV
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SECTION 4.0 SAMPLE COLLECTION AND ANALYSIS
4.1 SAMPLE COLLECTION
Samples were collected from all 94 facilities between February 5, 2001 and March 20, 2001, by
two EPA personnel in the Health and Ecological Criteria Division (HECD) and Engineering and Analysis
Division (EAD), and by six CSC Sample Control Center staff. All samples were collected according to
the Sampling Procedures for the 2001 National Sewage Sludge Survey (Reference 8.1).
Eighty-nine of the sampled POTWs had a single system for treating and processing their sludge
material. Therefore, one sample of the final sludge product was collected from each of these facilities.
Five of the POTWs had two systems for treating sludge. Therefore, two final sludge product samples
were collected from each of these five facilities (one sample from each treatment process). A total of 99
final product samples were collected from the 94 facilities.
A second aliquot of each sample was collected and archived at EAD's chemical repository,
operated by Gascoyne Laboratories, for possible future analysis. Split samples were collected for the
facility at their request.
EPA's study design called for the collection of a field duplicate sample from 15% of the facilities.
A field duplicate sample is a second sample collected at the facility using similar procedures and
equipment as the original sample. The results of the field duplicate sample can be compared to the results
of the original sample as a means of assessing the overall precision of the sampling and analysis
processes.
EPA randomly selected 15 of the original pool of 101 POTWs for collection of field duplicates.
Those 15 POTWs are identified in the sampling procedures document (Reference 8.1). However, once
the study began, field duplicates were not collected at three of those facilities for various reasons.
Therefore, EPA selected 2 more facilities from those that remained to be sampled, such that a total of 14
field duplicate samples ultimately were collected from the pool of 94 POTWs sampled (a 14.9%
frequency for field duplicates). The 14 facilities are listed in Table 2, below. The results of the field
duplicate samples are discussed in Section 6.4.
Table 2. Facilities at which Field Duplicates were Collected
Manteca WQCF, Manteca, CA
Buford Westside WPCP, Buford, GA
Garden City WPCP, Garden City, GA
Boise STP, Boise, ID
Hammond Municipal STP, Hammond, IN
Oakland STP, Topeka, KS
Shepherdsville STP, Shepherdsville, KY
Metropolitan Council - Metro, Saint Paul
MN
Crocker WWTP, Crocker, MO
Mason Farm WTP, Carrboro, NC
Portland STP, Portland, OR
Pee Dee River Plant, Florence, SC
Metropolitan King County, Renton, WA
Greenbrier County PSD No 2, Rainelle, WV
Field duplicates were not identified as such in the traffic reports sent to the laboratory. Therefore,
the laboratory was not aware of which samples were field duplicates.
4.2 ANALYTES OF INTEREST
Samples were analyzed by Axys Analytical Services (2045 Mills Road West, Sydney, British
Columbia, Canada V8L 3S8), using the methods and modifications specified by EPA and described in
Section 4.3.
Samples were analyzed for the seven 2,3,7,8-substituted polychlorinated dibenzo-/?-dioxin
congeners, the ten 2,3,7,8-substituted polychlorinated dibenzofuran congeners, and the full set of 209
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coplanar polychlorinated biphenyls (PCBs) congeners. EPA Method 1613B was used to analyze the 17
dioxin and furan compounds and EPA Method 1668A was used for PCB analysis, as shown in Table 3.
Method modifications were used to achieve better sensitivity, as described in Section 4.3. Analytical
results were reported in the units of nanograms of congener per kilogram of sewage sludge (ng/kg) on a
dry-weight basis (100% solids) for all samples.
Table 3. Analytical Methods and Target Analytes
Method
Analytes
Method 1613B, Dioxins and Furans by Isotope
Dilution High-Resolution Gas
Chromatography/Mass Spectrometry
2,3,7,8-TCDD
1,2,3,7,8-PeCDD
1,2,3,4,7,8-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,7,8,9-HxCDD
1,2,3,4,6,7,8-HpCDD
OCDD
2,3,7,8-
1,2,3,7,
2,3,4,7,
1,2,3,4,
1,2,3,6,
1,2,3,7,
2,3,4,6,
1,2,3,4,
1,2,3,4,
OCDF
-TCDF
8-PeCDF
8-PeCDF
7,8-HxCDF
7,8-HxCDF
8,9-HxCDF
7,8-HxCDF
6,7,8-HpCDF
7,8,9-HpCDF
Method 1668A, Polychlorinated Biphenyls by
Isotope Dilution High-Resolution Gas
Chromatography/Mass Spectrometry*
209 congeners**, including the following 12 congeners identified
as toxic by the World Health Organization:
Method 1668A includes all 209 PCB congeners in
its list of target analytes. The method is capable of
separating 167 individual congeners, including the
12 toxic congeners; the remaining 42 congeners are
identified in pairs or groups and reported together.
Congeners in each pair or group have the same
TEFs.
3,3',4,4'-TeCB (PCB 77)
3,4,4',5-TeCB(PCB81)
2,3,3',4,4'-PeCB(PCB105)
2,3,4,4,5-PeCB (PCB 114)
2,3',4,4',5-PeCB(PCB118)
2',3,4,4',5-PeCB(PCB123)
3,3',4,4',5-PeCB (PCB 126)
2,3,3',4,4',5-HxCB (PCB 156)
2,3,3',4,4',5'-HxCB (PCB 157)
2,3',4,4',5,5'-HxCB (PCB 167)
3,3',4,4',5,5'-HxCB(PCB169)
2,3,3',4,4',5,5'-HpCB (PCB 189)
"All 209 congeners are listed in Table 1 of Methodl 668A.
TCDD Tetrachlorodibenzo-p-dioxin
PeCDD Pentachlorodibenzo-p-dioxin
HxCDD Hexachlorodibenzo-p-dioxin
HpCDD Heptachlorodibenzo-p-dioxin
OCDD Octachlorodibenzo-p-dioxin
TCDF Tetrachlorodibenzofuran
PeCDF Pentachlorodibenzofuran
HxCDF Hexachlorodibenzofuran
HpCDF Heptachlorodibenzofuran
OCDF Octachlorodibenzofuran
TeCB Tetrachlorobiphenyl
PeCB Pentachlorobiphenyl
HxCB Hexachlorobiphenyl
HpCB Heptachlorobiphenyl
4.3 METHODS MODIFICATIONS
Axys Analytical Services performed analyses for dioxins/furans using Method 1613, Revision B,
and for PCB congeners using Method 1668, Revision A, with the modifications listed below:
Method 1613B: Axys achieved MDLs and MLs that were 5 times lower than those specified in
Method 1613B. This was accomplished by using a sixth calibration solution, CSO, that contained all
method-specified analytes at levels 5 times lower than the levels specified in Table 4 of the method.
All other method requirements, including QC acceptance criteria for calibration linearity and
laboratory blanks, were met using the modified method.
Method 1668A: Axys employed the 6-point calibration option that encompassed the high sensitivity
low calibration point CS-0.2 specified in Table 5 of the method. If interferences were encountered
with coplanar congeners 77, 126, or 169, the charcoal column clean-up or DB-1 (or equivalent) GC
column was used to resolve interferences.
To achieve the lowest reasonable quantitation limits and to provide relatively consistent
quantitation limits across all the sludge samples, the laboratory determined the solids content (e.g.,
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percent solids) of an aliquot of each sample prior to taking an aliquot for the analysis of either the
dioxins/furans or the PCBs. For all field samples, the laboratory used the protocol specified in Section
11.2.2 of Methods 1613B and 1668A for the determination of percent solids (i.e., the laboratory
determined percent solids, as opposed to total suspended solids). The laboratory used the data on the
solids content of each sample to determine the appropriate size aliquot that resulted in the extraction and
analysis of 10 g of dry solids for each sample (e.g., a liquid sample with 3% solids required the use of a
334-mL aliquot to obtain 10 g of dry solids). Samples that contained 5% solids or greater were prepared
and extracted as solid samples, in accordance with the procedures delineated in Sections 11.1.3, 11.5, and
12.3 of Methods 1613B and 1668A.
Some samples were pourable liquids with solids contents that ranged from <1% to as high as 5%.
For these samples, the laboratory centrifuged the sample to separate the solids from the aqueous portion
of the sample. The treatment of the sample phases after centrifugation depended on the analysis to be
conducted. Samples for dioxins/furans were treated differently than those for PCBs, as follows.
Preparation of 'Samples for Dioxin/Furan Analyses: For dioxin/furan analyses using Method 1613B,
the supernatant liquid that resulted from centrifugation was filtered as described in Section 11.4.3 of
the method. The filtrate (i.e., liquid phase) was then subjected to separatory funnel extraction as
specified in Section 12.1, and the filter and particles were extracted by the Soxhlet-Dean Stark
(SDS) extraction procedure specified in Section 12.3. The separatory funnel and SDS extracts were
combined, processed, and analyzed as a single extract using the procedures specified in Method
1613B
Preparation of Samples for PCB Analyses: To minimize the risk of losing some low-molecular
weight PCB congeners, the supernatant that resulted from the centrifugation step was not filtered as
described in Section 11.4.3 of Method 1613B, since that step involved a vacuum filtration. Instead,
the supernatant liquid was extracted using a separatory funnel procedure as described in Section 12.1
of Method 1613B, and the extract was combined with the extract from the centrifuged solids,
processed, and analyzed as a single extract using the procedures specified in Method 1668A.
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SECTION 5.0 DATA REPORTING AND VALIDATION
Each laboratory data package submitted under this study was reviewed for completeness and
compliance with method specifications and subcontract requirements to ensure that the data met the
measurement quality objectives of the study. These data reviews were performed by CSC Sample
Control Center data review staff trained in procedures for reviewing dioxins/furans and PCB results
produced by Method 1613B and 1668A, respectively. Data reviews were performed using a multi-stage
review process designed to identify and correct data deficiencies as early as possible, to maximize the
amount of usable data generated during the study. This data review process included the following
elements.
Data Completeness Check in which all elements in the laboratory submission were evaluated to verify
that results for all specified samples were provided, that data were reported in the correct format, and
that all relevant information, such as preparation and analysis logs, were included in the data package.
Instrument Performance Check in which the data reviewers verified that calibrations, calibration
verifications, standards, and calibration blanks were analyzed at the appropriate frequency and met
method or study performance specifications.
Laboratory Performance Check in which the reviewers verified that the laboratory correctly
performed the required analytical procedures and was able to demonstrate a high level of precision
and accuracy. This check included evaluation of QC elements such as the initial precision and
recovery (IPR) and ongoing precision and recovery (OPR) tests, field blanks, method blanks, and
reference standards.
Method/matrix Performance Check to discern whether any QC failures were a result of laboratory
performance or difficulties with the method or sample matrix. Data evaluated in this stage included
labeled compound results. The data reviewers also verified that proper sample dilutions were
performed and that necessary sample cleanup steps were taken.
If errors were noted during any of these checks, corrective actions were initiated with the
laboratory to resolve the deficiencies identified. After reviewing each data package, the CSC data
reviewers prepared written reports in narrative format that described data quality limitations and
recommendations concerning data use. These narrative data reports were provided to the EPA Study
Manager.
Upon completion of data review, CSC created an analytical database that contained all field
sample results from the 2001 NSSS. This database was prepared using Statistical Analysis Software
(SAS) and was designed to be consistent with the database format used in EPA's 1989 NSSS. At
intervals during database production and again upon completion of the study, CSC ran queries to verify
the accuracy of the database. Upon database completion, CSC prepared a Microsoft Access report that
contained all data from the 2001 NSSS database in tabular format. This report was provided to the EPA
Study Manager.
At EPA's direction, CSC prepared individual reports of facility data and distributed these reports
to the participating facilities. The reports contained the results for the seventeen 2,3,7,8-substituted
dioxins and furans and the 209 PCB congeners for each sample collected at a given facility, and the EPA
sample number(s) associated with the sample(s) collected at that facility. In addition, each facility
received a summary of the results across all facilities. The summary report listed each EPA sample
number with the Total TEQ for that sample, but did not identify any of the facilities by name. The
information in the facility-specific report made it possible for each facility to compare its own results to
those of all the other facilities in the survey.
2001 National Sewage Sludge Survey Report 8 September 2007
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SECTION 6.0 RESULTS, DATA ANALYSIS, AND DISCUSSION
6.1 Toxic EQUIVALENT CONCENTRATION
Historically, 2,3,7,8-TCDD has exhibited the greatest toxicity in animal studies and therefore has
been considered the most toxic of the 210 dioxin and furan compounds. The toxicity of a mixture of
dioxin-like compounds is often reported in terms of the toxic equivalents of 2,3,7,8-TCDD, or the TEQ
(for the Toxic Equivalent concentration). The toxicity equivalency factor (TEF) is the scaling factor that
relates the toxicity of a concentration of a specific dioxin, furan, or PCB compound to a concentration of
2,3,7,8-TCDD. The TEF represents an order of magnitude estimate of the toxicity of the compound of
interest, based on a consensus of current research results on these compounds.
The TEQ is calculated as the sums of the products of each PCDD, PCDF, and PCB congener and
its respective TEF, as follows:
10
Total TEQ = £ [PCDDX x TEFX ] + £ [PCDFX x TEFX ] + £ [PCBX x TEFX ]
The results from the 2001 NSSS were reported in terms of the total TEQ.
The TEF values used for the 2001 NSSS are shown in Table 4. These values were developed by
the World Health Organization (WHO) in 1998 (Reference 8.3) and include non-zero TEFs for the
seventeen 2,3,7,8-substituted PCDDs/PCDFs and twelve non-ortho-substituted and mono-ortho-
substituted (coplanar) PCBs. The 1998 WHO TEF for 1,2,3,7,8-pentachlorodibenzo-^-dioxin (PeCDD) is
1, indicating the current consensus that this compound is as toxic as 2,3,7,8-TCDD. The TEFs for PCBs
156 and 157 are equal, however, these two congeners cannot be completely separated from one another
and are reported as the sum of the two congeners in Method 1668A.
In calculating the TEQ for samples in the 2001 NSSS, EPA handled the results for all of the toxic
PCDDs, PCDFs, and PCBs that were "not detected" by substituting one-half of the quantitation limit
(called the "Minimum Level," or ML, in Methods 1613B and 1668A) reported by the laboratory for the
concentration of that analyte. This commonly used substitution scheme is conservative relative to
protection of the environment, in that it assumes that there may be some of the analyte present below the
laboratory's reported quantitation limit. Other common substitution schemes include setting all non-
detects to zero or using the quantitation limit (rather than one-half the limit). The use of any non-zero
substitution scheme means that every sample will have a non-zero TEQ, regardless of whether or not any
analytes were detected. Using the WHO TEF values and one-half of the quantitation limits in Table 4, the
lowest possible TEQ for a sample in this study would be 1.6 ng/kg (rounded to one decimal place).
Table 4. Minimum Levels, Toxicity Equivalency Factors for Dioxins, Furans, and PCBs
Analyte
ML (ng/kg)
1/2 ML
(ng/kg)
WHO TEF
TEQ Using ML
(ng/kg)
TEQ Using 1/2 ML
(ng/kg)
Dioxins
2,3,7,8-TCDD
1,2,3,7,8-PeCDD
1,2,3,4,7,8-HxCDD
1,2,3,6,7,8-HxCDD
1,2,3,7,8,9-HxCDD
1,2,3,4,6,7,8-HpCDD
OCDD
0.1
0.5
0.5
0.5
0.5
0.5
1
0.05
0.25
0.25
0.25
0.25
0.25
0.5
1
1
0.1
0.1
0.1
0.01
0.0001
0.1
0.5
0.05
0.05
0.05
0.005
0.0001
0.05
0.25
0.025
0.025
0.025
0.0025
0.00005
2007 National Sewage Sludge Survey Report
September 2007
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Table 4. Minimum Levels, Toxicity Equivalency Factors for Dioxins, Furans, and PCBs
Analyte
ML (ng/kg)
1/2 ML
(ng/kg)
WHOTEF
TEQ Using ML
(ng/kg)
TEQ Using 1/2 ML
(ng/kg)
Furans
2,3,7,8-TCDF
1,2,3,7,8-PeCDF
2,3,4,7,8-PeCDF
1,2,3,4,7,8-HxCDF
1,2,3,6,7,8-HxCDF
1,2,3,7,8,9-HxCDF
2,3,4,6,7,8-HxCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,4,7,8,9-HpCDF
OCDF
0.1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1
0.05
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.5
0.1
0.05
0.5
0.1
0.1
0.1
0.1
0.01
0.01
0.0001
0.01
0.025
0.25
0.05
0.05
0.05
0.05
0.005
0.005
0.0001
0.005
0.0125
0.125
0.025
0.025
0.025
0.025
0.0025
0.0025
0.00005
PCBs
PCB-77
PCB-81
PCB-105
PCB-114
PCB-118
PCB-123
PCB-126
PCB-156+PCB-157
PCB-167
PCB-169
PCB-189
20.0
2.0
20.0
1.0
20.0
2.0
20.0
2.0
1.0
1.0
1.0
10.0
1.0
10.0
0.5
10.0
1.0
10.0
1.0
0.5
0.5
0.5
0.0001
0.0001
0.0001
0.0005
0.0001
0.0001
0.1
0.0005
0.00001
0.01
0.0001
Lowest Possible Toxic Equivalent Concentration (TEQ)
0.002
0.0002
0.002
0.0005
0.002
0.0002
2
0.001
0.00001
0.01
0.0001
3.26821
0.001
0.0001
0.001
0.00025
0.001
0.0001
1
0.0005
0.000005
0.005
0.00005
1.634105
6.2 SUMMARY RESULTS
Table 5 presents the total TEQ and the portions of the TEQ due to the dioxins, furans, and PCBs,
for the 113 samples analyzed during the survey, rounded to the nearest whole number. The total TEQ
values range from 3 to 718 ng/kg for the samples in this study. Keep in mind that substituting one-half of
the quantitation limit for each analyte means that no sample can have a total TEQ less than 1.6 ng/kg (see
Table 4 above).
Note: Fourteen of the results in Table 5 are for the field duplicate samples collected as part of the
quality assurance effort for the survey. The field duplicates are discussed in detail in Section 6.4.
Table 5. Results for 2001 NSSS Samples, in order of increasing
EPA Sample Number
57631
58105
57948
57972
58026
57775
57900
57780
57691
57858
57859
Total TEQ
3
3
5
5
5
6
6
7
7
8
8
Dioxin TEQ
2
1
3
3
3
4
5
4
4
5
5
Furan TEQ
1
0
1
1
1
1
1
1
2
1
1
PCB TEQ
0
2
1
1
1
2
1
2
2
2
2
Total TEQ
2007 National Sewage Sludge Survey Report
10
September 2007
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Table 5. Results for 2001 NSSS Samples, in order of increasing
EPA Sample Number
57864
57738
58176
58069
57961
57841
57606
57798
57745
58104
57984
57930
57942
58032
58033
57804
57978
58038
58017
58014
58050
57810
57624
57684
57636
57601
57906
57918
57878
57660
57816
57828
57995
57834
57846
57763
57882
57943
57768
57786
58008
57839
57685
58122
57708
58164
57895
58110
58092
57757
57954
58134
57894
57936
57720
57678
57876
58147
57955
Total TEQ
8
9
10
10
10
11
11
12
12
12
12
12
13
13
13
13
13
14
14
14
15
15
16
16
16
16
17
17
17
17
17
18
18
18
18
19
19
19
20
20
20
20
20
21
22
23
23
24
24
24
24
24
24
25
26
26
27
27
27
Dioxin TEQ
5
5
1
6
8
8
7
6
7
8
7
7
10
6
7
7
9
9
7
8
10
11
8
12
13
7
13
7
14
10
15
14
9
7
9
11
14
14
16
15
15
7
12
17
16
12
15
12
17
12
14
19
15
19
13
23
22
21
16
Furan TEQ
1
1
1
2
2
3
2
1
2
2
3
1
2
4
4
3
4
4
2
2
2
4
2
2
2
3
2
8
2
4
3
4
3
1
4
3
3
3
3
3
4
2
3
4
5
4
3
3
5
5
5
5
3
4
4
3
2
4
6
Total TEQ
PCB TEQ
2
2
8
1
1
0
2
4
3
1
2
4
0
2
2
3
1
0
4
4
3
1
5
1
1
6
1
2
1
3
0
0
6
10
5
5
2
1
0
1
1
11
6
0
2
8
5
8
1
7
5
0
6
3
8
0
3
2
6
2007 National Sewage Sludge Survey Report
11
September 2007
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Table 5. Results for 2001 NSSS Samples, in order of increasing
EPA Sample Number
57924
57990
57852
57966
58116
57793
57912
58099
58044
57726
57655
58160
57613
57666
58020
58098
58074
58063
57751
58140
58062
57714
57702
58141
57696
58080
57673
58153
57870
57888
57996
57618
58128
57654
57732
57621
57648
57998
58170
57825
57824
57822
57642
Total TEQ
27
28
28
29
31
33
34
35
36
36
36
37
38
39
40
40
41
42
42
42
43
46
48
53
53
55
57
58
59
60
63
64
68
74
79
97
110
118
123
313
453
555
718
Dioxin TEQ
23
14
24
22
14
22
27
27
14
24
17
27
24
21
22
27
21
25
25
17
26
27
27
22
24
39
36
40
10
22
30
4
44
59
14
28
82
75
119
234
336
449
189
Furan TEQ
3
5
1
6
6
7
4
5
6
3
8
9
10
7
7
5
8
7
9
13
7
7
9
18
11
10
10
14
45
34
6
2
12
7
9
10
11
15
3
77
114
103
493
Total TEQ
PCB TEQ
1
9
2
1
11
4
3
2
15
9
11
0
4
11
10
8
12
9
7
13
9
13
12
13
18
5
11
4
4
3
27
58
12
8
56
58
17
28
1
1
3
3
36
*AII TEQ values were calculated using the WHO TEF values in Table 4. For analytes that were not
detected, the concentration of that analyte was set to one-half of the Minimum Level forthe analyte in
Table 4. All results are reported on a dry-weight basis.
6.3 FREQUENCY DISTRIBUTIONS
A frequency distribution of the total TEQ was plotted from the results for all the samples in Table
5 (including the 14 field duplicates). Because the data span a wide TEQ range and are not normally
distributed, the total TEQ data were log-transformed using the natural log (In, base e). The natural logs of
the TEQ results range from 1.07 to 6.58, and the span was divided into ranges, based on the first digit on
the natural log of the total TEQ. To emphasize the fact that no sample in this study can have a total TEQ
value less than 1.6 ng/kg because of the treatment of non-detect values, the first two ranges were
combined and the description of the bottom end of lowest range was raised from 0 to 1.6 ng/kg.
2007 National Sewage Sludge Survey Report
12
September 2007
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Figure 1 shows the frequency distribution based on the log-transformed TEQ data. The
concentration ranges used for the log-transformed frequency plot were:
1.6 to 7.4 ng/kg (encompassing In values from 0 to 2)
7.4 to 20.1 ng/kg (encompassing In values from 2 to 3)
20.1 to 54.6 ng/kg (encompassing In values from 3 to 4)
54.6 to 148.4 ng/kg (encompassing In values from 4 to 5)
148.4 to 403.4 ng/kg (encompassing In values from 5 to 6)
>404 ng/kg (all In values over 6)
50 -,
45
25
V)
10
16 to 7 4 7 4 to 30.1 20 t lo 54.6 54 6 to 148 4 148.4 to 403 4 >404
Ln Total TEQ (ng/kg)
Figure 1. Frequency of Log-Transformed Total TEQ Results for the 2001 NSSS
As can be seen, the vast majority of the survey samples have total TEQ values between 7.4 and
54.6 ng/kg. The data are approximately log-normally distributed, which is not unexpected, given the
small number of very high values.
A regression of total TEQ and percent solids was performed. The correlation coefficient (r) for
the regression was only 0.0608, indicating that there is no apparent relationship of total TEQ to percent
solids content of the sludge samples.
6.4 FIELD DUPLICATE RESULTS
Field duplicate samples were collected at 14 facilities. The results for the 14 field duplicate
samples and the associated original samples from each facility are shown in Table 6. For each pair of
samples, the total TEQ and percent solids results were compared using the relative percent difference
(RPD). The RPD is used as the measure of precision because both results from the pair are measured
concentrations and there is no "true" concentration to be used in the comparison. The formula for RPD is
shown below:
RPD
_ [Result 1-Result 2|x 100
(Result 1 + Result 2)
2007 National Sewage Sludge Survey Report
13
September 2007
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where Result 1 and Result 2 represent the concentrations reported in the two samples in each pair, the
vertical bars in the numerator indicate it is the absolute value of the difference, and the factor of 100
converts the value to a percent.
The pairs are presented in Table 6 in order of increasing RPD of the TEQ for each pair. The total
TEQ results in this table are expressed to two decimal places solely to illustrate some of the small
differences between the samples. However, the whole number TEQ values in Table 5 more appropriately
reflect the significant figures in the TEQ calculations.
Table 6. Field Duplicate Comparisons
Sample
57858
57859
58032
58033
58014
58017
58062
58063
57834
57839
57954
57955
58098
58099
58140
58141
57824
57825
57990
57995
57942
57943
57876
57878
57996
57998
58104
58105
Total TEQ
8.08
8.14
12.80
12.96
14.09
13.91
43.01
41.94
18.36
20.14
24.04
27.41
40.49
34.56
42.30
52.74
453.41
312.68
27.58
18.36
12.57
19.10
26.56
16.91
63.30
118.04
11.77
3.32
RPD (%)
0.8
1.2
1.2
2.5
9.2
13.1
15.8
22.0
36.7
40.2
41.2
44.4
60.4
112
% Solids
17
17
29
29
14
15
67
68
14
14
81
83
0.60
0.62
18
17
16
15
11
16
1.7
1.5
12
13
15
16
14
14
RPD (%)
0.0
0.0
6.9
1.5
0.0
2.4
3.3
5.7
6.5
37.0
12.5
8.0
6.5
0.0
The field duplicate samples largely span the range of concentrations from all samples, with
concentrations ranging from 3 to 453 ng/kg. In general, the RPD values reflect those typically seen for
field duplicates, with nearly all RPDs < 40% and all but two RPDs < 45%. There is no apparent
relationship between the RPD of the TEQ in the field duplicates and the mean concentration of those
duplicates, since the two largest RPD values, 60.4% and 112%, occur at opposite ends of the
concentration range.
The 14 field duplicate pairs were collected by 8 different samplers, two from EPA and six from
CSC. There was no apparent effect of sampler experience on RPD values, because two of the pairs with
RPDs over 40% were collected by a sampler with over 30 years of experience, while field duplicates that
exhibited relatively little difference were collected by samplers with less than 5 years of sampling
experience.
The percent solids results for these field duplicates provide additional information. As described
in the sampling procedures document (Reference 8.1), most liquid sludge samples were collected directly
into the sample containers from a tap or valve in the sludge transfer plumbing. Other than asking the
facility staff to mix liquid sludge in any holding tanks and flushing the tap or valve before collecting the
2007 National Sewage Sludge Survey Report
14
September 2007
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sample, no other efforts were made to composite or homogenize the liquid sludge samples. The two pairs
of low-solids sludges (58098/58099 and 57942/57943) exhibited relatively similar percent solids results
within each pair, with RPD values of 3.3% and 12.5%, respectively. However the differences in the total
TEQ values were substantially greater, at 15.8% and 41.2%, respectively, and may be attributable to the
specific conditions of the sampling at each site, as discussed below.
Samples 58098 and 58099 (the field duplicate) were collected from a discharge hose on a storage
tank used to fill tankers for land application. The samples were collected immediately after the hose was
used to fill a tanker, thereby flushing the hose. However, because another tanker was not available to be
filled before the field duplicate sample was collected, the material in the hose was fairly similar to that
collected for the initial sample. In contrast, Samples 57942 and 57943 were collected from a large
anaerobic digester with an open top. The sampler had to lower a clean bucket into the digester from a
catwalk atop the tank to collect each sample. Although the digester had mixers, these results for TEQ and
percent solids suggest that the sludge in the tank was not completely homogeneous at the time that the
samples were collected.
The solid sludge samples presented more obvious sampling challenges. Many of the solid
samples were collected from dewatering devices such as belt presses, filter presses, or centrifuges. These
devices are run periodically as the facility removes sludge from the process. Samples collected even a
few minutes apart may contain different pollutants or different concentrations depending on the inputs to
the treatment plant at the time the sludge was produced, or based on variations in conditions at the time of
disposal.
In other cases, sludge is stockpiled at the facility and composted with wood chips, yard waste,
and other organic materials. The stockpiles vary greatly in size and complexity. Variations in both the
sludge removed from the treatment system and the nature of the amendments used for composting will
lead to differences in the pollutants and concentrations. Further, the size of some compost piles makes
collection of representative samples difficult. At least one field duplicate pair (57824/57825) was
collected at a facility that composted sludge in piles 10 to 12 feet tall, with steeply sloping sides. In this
case, small amounts of material were collected from multiple locations around the edges of the pile and
composited to form each sludge sample. The field duplicate sample was collected in a similar fashion,
but with materials from different locations around the pile. However, the materials that were accessible to
the sampler were only those within arm's reach of the sides of the pile and below shoulder height. Thus,
the RPD of 36.7% for the total TEQ values in these two samples may represent the variability in the
materials in that pile.
2001 National Sewage Sludge Survey Report 15 September 2007
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SECTION 7.0 CONCLUSIONS
EPA was successful in collecting and analyzing 113 sewage sludge samples from 94 POTWs for
the analysis of dioxins, furans, and PCBs during the 2001 NSSS. The selection of sites for sample
collection and the application of state-of-the-art analytical methods and project-specific analytical
modifications permitted EPA to develop unbiased national estimates of these pollutants in sewage sludge
at the lowest practical levels. These data are suitable for use in a multi-pathway exposure and risk
assessment of the land application of sludge that are part of EPA's review of regulations at 40 CFR Part
503.
Results from the survey were calculated in terms of the toxic equivalent concentration (TEQ) of
2,3,7,8-TCDD and ranged from 3 to 718 ng/kg (dry weight). The vast majority of the samples had TEQ
values in the range of 7 to 55 ng/kg. Only seven results over 100 ng/kg TEQ were reported, and two of
those were for a field duplicate pair collected as part of the quality assurance program for the survey.
SECTION 8.0 REFERENCES
8.1 Sampling Procedures for the 2001 National Sewage Sludge Survey, DynCorp, February 2001, 21
pages.
8.2 Quality Assurance Project Plan for the 2001 National Sewage Sludge Survey, DynCorp, March
2001, 57 pages.
8.3 Van den Berg, M, L. Birnbaum, A. T. C. Bosveld, B. Brunstrom, P. Cook, M. Feeley, J. P. Giesy,
A. Hanberg, R. Hasegawa, S. W. Kennedy, T. Kubiak, J. C. Larsen, F. X .R. van Leeuwen, A. K. D.
Liem, C. Nolt, R. E. Peterson, L. Poellinger, S. Safe, D. Schrenk, D. Tillitt, M. Tysklind, M.
Younes, F. Warn, and T. Zacharewski. 1998. Toxic Equivalency Factors (TEFs) for PCBs,
PCDDs, PCDFs for Humans and Wildlife. Environmental Health Perspectives. 106: 775-792.
2001 National Sewage Sludge Survey Report 16 September 2007
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