Joint NRC/EPA
Sewage Sludge Radiological Survey:
Survey Design and Test Site Results: B. Background
Federal Regulations
Specific amounts and concentrations of radioactive material
are legally authorized to be disposed into the sanitary
sewage collection system by Federal and State regulations.
In 1991, NRC revised its sewer disposal criteria, partially
in response to evidence that certain radioactive materials
were reconcentrating in sewage sludge or incinerator ash.
The revised NRC regulations further limited the radioactive
materials that NRC licensees are allowed to discharge to
POTWs, which should preclude contamination at POTWs. The
current NRC regulations in 10 CFR 20.2003 permit disposal
of specific quantities of soluble material into a sanitary
sewer. NRC plans to use the survey information in assessing
whether to apply further restrictions to the licensed radioactive
material that is being discharged to sanitary sewage collection
systems.
The EPA standard for the use and disposal of sewage sludge
(biosolids) in 40 CFR Part 503 does not include limits for
radioactive material. POTW operators have requested that
EPA regulations address radioactive materials so POTWs would
have a basis to restrict discharges of radioactive materials
to the sewage collection system. EPA plans to use the survey
results to evaluate the need to include limits on radioactive
materials in biosolids standards.
Sources of Radioactive Materials
One possible source of radioactive material entering a
POTW involves naturally-occurring sources such as groundwater,
which can contain elevated levels of radioactive materials
in some parts of the U.S., as well as drinking water treatment
residuals disposed of into the sanitary sewage collection
system. Another possible source is the authorized disposal
by users of radioactive materials (such as NRC and Agreement
State licensees) of man-made radioactive materials into
the sanitary sewage collection system. The removal of contaminants
by various methods at POTWs, and the reduction of the volume
of solids that contains these contaminants (e.g. incineration
of sludge), can cause reconcentration of radioactive materials
in the treatment facility's sewage sludge or ash.
Background information on the nature of radioactivity in
sewage sludge can be found in reports published by NRC in
1992 and 1994 entitled "Evaluation of Exposure Pathways
to Man From Disposal of Radioactive Materials Into Sanitary
Sewer Systems" (NUREG/CR-5814) and "Reconcentration
of Radioactive Material Released to Sanitary Sewers in Accordance
with 10 CFR 20" (NUREG/CR-6289), respectively. Another
useful background document is a report entitled "Radioactivity
of Municipal Sludge" issued by EPA during the development
of the first round rulemaking of the 40 CFR Part 503 sewage
sludge technical rule.
Congressional Interest
This survey responds, in part, to a recommendation in the
General Accounting Office (GAO) report, "Actions Needed
to Control Radioactive Contamination at Sewage Treatment
Plants," published in May 1994. The GAO report recommended
that NRC determine the extent of elevated levels of radioactive
materials at POTWs and establish acceptable limits for radioactive
materials in sewage sludge and ash.
A joint House/Senate hearing was held in 1994 to officially
release and address questions raised in the GAO report.
The hearing was stimulated by concerns associated with elevated
levels of radioactive materials in incinerator ash at a
major sewage treatment plant in the Cleveland, Ohio, area.
The GAO stated that, over the past 20 years, NRC documented
about a dozen situations where elevated levels of radioactive
materials were identified in sewage sludge or sludge incinerator
ash; but, there has been no national survey of radiation
levels present in sewage sludge or sludge incinerator ash
to determine if this is a widespread problem.
At the time of the hearing, EPA was planning to conduct
a second National Sewage Sludge Survey (NSSS) to support
its efforts to develop the second round of the 40 CFR Part
503 sewage sludge technical regulations. EPA's planned survey
would have included the collection of data on concentrations
of radioactive materials in a representative sampling of
POTW sludges from across the country. (The first national
survey conducted in the late 1980s did not include analysis
of radioactive material.)
Testimony presented by both NRC and EPA during the 1994
hearing noted that there was no indication of a widespread
problem in this area and the Cleveland incident appeared
to be an isolated incident. Based on limited information
on radiation levels in sewage sludge and ash across the
country, it appeared that reconcentration of radioactive
materials may have been associated with authorized insoluble
industrial releases from both NRC and Agreement State licensees,
which was documented and used as a basis of the GAO report.
These problems occurred prior to the revision to NRC’s
regulations in 1991.
Industry Interest
In 1996, the Association of Metropolitan Sewerage Agencies
(AMSA) conducted a confidential voluntary survey of concentrations
of radioactive materials in some of its members' POTW sewage
sludges and ashes. The objective was to develop a better
estimate of the concentration of radioactive materials in
sewage sludges and sludge incinerator ashes. Samples from
55 wastewater plants in 17 States were supplied voluntarily
and analyzed for radioactive materials. These plants were
distributed across the country and ranged in size from small
to among the largest POTWs. The most significant levels
of radioactive material were the potassium and radium isotopes,
which are naturally-occurring radioactive materials. The
restricted nature of the AMSA survey limited its usefulness
in assessing regional background levels of radioactive materials
or the effects of licensees that dispose of radioactive
material into sanitary sewers.
Current Plans
EPA is not currently planning to move forward with a second
NSSS. Based on EPA’s plans and the limitations of the
AMSA survey, NRC and EPA decided to jointly fund a survey
of POTW sewage sludges and ash to assess the potential need
for NRC and/or EPA rulemaking. The survey information will
also be referenced in a joint NRC/EPA guidance document
for POTWs, which is currently under development by the ISCORS
Sewage Subcommittee. This guidance would provide information
to help POTW operators determine sources of radioactive
materials at POTWs, describe sampling and analysis procedures,
and advise whether a response is needed to the presence
of radioactive material in sludge.
