PB91-921364
The findings of a recent study conducted by EPA indicate that discharge of CERCLA wastewater to a POTW can be
a feasible and effective part of a Superfund response action, and that currently, the option of discharging to a POTW is
under-utilized. This guide provides quick reference to the statutory, policy, administrative, and technical factors
involved in discharging aqueous wastes generated during Superfund response actions to a POTW. Additional
guidance on evaluating the use of POTWs can be found in three documents: "CERCLA Site Discharges to POTWs~Guidance
Manual' (EPA/540/G-90/005, August 1990), "Treatability Manual' (EPA/540/2-90/007, August 1990), and "CERCLA Site
Sampling Program Detailed Data Report" (EPA/540/2-90/008, August 1990).
United States	Office of
Environmental Protection	Solid Waste and	9330.2-13FS
Agency	Emergency Response	March 1991
<*e:pa Guide to Discharging CERCLA
Aqueous Wastes to Publicly
Owned Treatment Works
(POTWs)
Office of Emergency and Remedial Response
Hazardous Site Control Division 0S-220W	Quick Reference Fact Sheet
The discharge of aqueous wastes to a publicly-owned
treatment works (POTW) as part of a Superfund response
action generally is considered to be an off-site activity,
even if a CERCLA waste is first pretreated in a
wastewater facility located on site. Consequently, all
discharges to a POTW still have to be in compliance with
the off-site policy, i.e., any facility accepting the waste
must have no relevant violations, uncontrolled releases, or
other environmental conditions that pose a significant threat
to human health, welfare, or the environment, or otherwise
affect the satisfactory operation of the facility. In addition,
site managers must comply with both substantive and
administrative requirements (e.g., permits) of Federal,
State, and local laws and regulations.
EVALUATING THE POTW OPTION
Determining the feasibility of utilizing a POTW as a
discharge option should begin as early in the remedial
process as possible, i.e., once it is known that wastewater
streams generated during site characterization, treatability
studies, and/or response actions-will require treatment.
Wastewater streams at CERCLA sites that may be
suitable for treatment in a POTW include ground water,
leachate, surface runoff, or process streams generated by
remedial activities (e.g., wastewaters from treatment
processes). The necessary steps involved in evaluating the
POTW option are outlined below.
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1. Identify and Characterize CERCLA Wastewater
Discharge
In order for a POTW to accept a CERCLA discharge,
it will require data on the nature of the discharge, including
the constituents within the wastestream. Therefore, data
necessary to characterize wastestreams and determine
whether a POTW can receive the discharge should be
identified and collected as early in the remedial process as
possible (e.g., during the sampling phase(s) of the
Remedial Investigation/Feasibility Study).
A POTW generally will require sampling information on
all Target Compound List (TCL) constituents before it can
accept a waste. [The TCL is a list of 152 volatile and
semi-volatile organic compounds, pesticides,
poly chlorinated biphenyls (PCBs), and inorganics used in
the contract laboratory program (CLP) under CERCLA.]
In addition, POTWs usually require information about
conventional pollutants in the wastestream, such as the
five-day suspended solids, nitrite-nitrate, total Kjeldahl
nitrogen, total phosphorus, oil and grease, total dissolved
solids, color, total sulfides, and pH. The wastestream to be
discharged also should be characterized in terms of
quantity, i.e., as a function of time or expressed in terms of
daily average and daily maximum flows and size and
frequency of batch discharges.

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Lastly, because of the potential applicability of RCRA
requirements to a POTW and the waste management
requirements that may be triggered during transportation
and storage of the wastes, site managers should determine
whether a CERCLA wastewater is a RCRA hazardous
waste.
If the CERCLA wastestrearn is considered a RCRA
hazardous waste, site managers need to determine whether
the Domestic Sewage Exclusion (DSE) applies to the
discharge of that waste to a POTW. The RCRA DSE
exempts domestic sewage, any mixture of domestic
sewage, and other wastes, that pass through a sewer
system to a POTW for treatment from classification as a
solid waste and, therefore as a RCRA hazardous waste.
[The Domestic Sewage Exclusion applies only to the actual
point discharge; it does not exclude industrial wastewaters
while they are being collected, stored, or treated before
discharge; sludges that are generated by industrial
wastewater treatment; or wastes received within the
POT'W's property boundary by truck, rail, or dedicated
pipe.]
2.	Identify Local POTWs
Once CERCLA wastestreams have been
characterized, site managers should identify existing
POTWs within a delineated geographic area in which it is
technically feasible to transport the CERCLA
wastestrearn. Factors for evaluating the feasibility of
transport to a POTW include:
•	The distance to the POTW or its existing sewer
lines;
•	The volume of the wastewater;
•	The viscosity or percent solids of the wastewater;
•	Topography of the area;
•	The need to obtain right-of-way permits; and
•	Cost of transportation.
3.	Evaluate Regulatory Status
If the determination is made that the discharge of
CERCLA aqueous wastes to a POTW is technically
feasible, site managers should begin evaluating the
regulatory status of the POTW potentially receiving the
wastes. One important source of information about the
regulatory status and facility-specific acceptance
requirements are the municipal authorities responsible for
technical and administrative oversight of each POTW. The
NationalPollutant Discharge Elimination System (NPDES)
authority (State or Regional Office of Water) can provide
additional information concerning the level of treatment,
capacity, operating history, and collection system that will
be helpful for screening POTWs.
If the CERCLA waste stream is considered a RCRA
hazardous waste and the DSE does not apply, site
managers should determine whether the POTW meets
RCRA Permit-bv-Rule requirements. POTWs operating
under an NPDES permit issued before November 8,1984
currently must be operating under a valid permit and be in
compliance with the permit, including RCRA manifesting
and reporting requirements. [In addition, the waste must
meet all Federal, State, and local pretreatment
requirements that would apply to the waste if it were
discharged through a sewer, pipe, or similar conveyance.
The necessary "POTW-specific" analyses of pretreatment
requirements are discussed later under step 5.] If the
POTW is operating under a permit issued or renewed after
November 8, 1984, it also must comply with RCRA
correrative action requirements under 40 CFR 264.101.
Site managers should identify the operations and
responsibilities of the POTW and the regulations that apply
to these activities to ensure compliance with RCRA
permit-by-rule requirements. It is important to involve
POTW personnel to ensure that accurate and complete
information is received and evaluated. As an additional
check, site managers can review EPA's Quarterly
Noncompliance Report that includes a listing of all POTW
facilities that are in significant non-compliance.
4. Evaluate Technical/Administrative Feasibility
If a POTW is determined to be in compliance with its
NPDES permit and is technically capable of accepting the
waste (see Highlight 1), it should be determined whether
acceptance of the CERCLA waste is administratively
feasible. Negotiations between EPA and the POTW
authority concerning administrative feasibility should
consider the permitting process and effects of existing local
ordinances.
If pollutants exist in the CERCLA wastewater that the
POTW did not previously handle, the NPDES permit may
require modifications, or the pretreatment program may
require revisions to regulate the new pollutant or increased
discharges. In such cases, the POTW may be unwilling to
have the changes made, or the required changes may not
be feasible in a timely manner. Similarly, local ordinances
may include prohibitions that make it illegal for the POTW
to
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Highlight 1
TECHNICAL FACTORS AFFECTING
THE FEASIBILITY OF DISCHARGING
TO A POTW
•	The POTW's hydraulic and organic load
capacity;
•	The suitability of the POTW's unit operations
for treatment of contaminants;
•	If the CERCLA wastestream will be
discharged to a sewage collection system,
whether that system is separate from or
combined with the storm drain system, and the
capacity of that system to provide proper
containment of the wastestream;
•	Whether there are combined sewer overflows
between the site and the POTW;
•	The adequacy of the capacity and age of the
sewer piping system for the CERCLA
discharge flow rate;
•	The sludge disposal processes currently
employed by the POTW; and
•	The likelihood that the POTW could treat the
CERCLA wastestream for the duration
required.
accept the CERCLA wastes, (e.g., restrictions on
accepting only domestic discharges). Consequently, it is
necessary to ensure compliance with these laws and
regulations or to see if the possibility of obtaining variances
exists.
There also may be liability issues associated with a
POTW's accepting Superfund wastes. Section 107 of
CERCLA states that whenever there is a release or a
threatened release of a hazardous substance, the
responsible parties can be held liable for the costs of
cleanup of that release. Potentially responsible parties
(PRPs) include current owners and operators of the
facility, those who owned and operated the facility at the
time of the release, persons who transported the
substances and selected the disposal facility, the generators
of the waste, and the persons who arranged for disposal or
treatment of the hazardous substances.
Under CERCLA Section 1070, federally permitted
releases as defined in Section 101 (10) are not subject to
such liabilities. These releases include discharges covered
by an NPDES permit, permit application, or permit
administrative record. These releases also include the
introduction of any pollutant into a POTW when such
pollutant is specified in (and in compliance with)
pretreatment standards, and a pretreatment program has
been submitted to EPA for approval. Therefore, local limits
should be established for all of the pollutants that exist in
the CERCLA wastewater to eliminate the possibility of the
POTW's being held liable for the release of hazardous
wastes.
Section 119 of CERCLA does not authorize
indemnification from liability to facilities regulated under
RCRA, including RCRA Permit-By-Rule POTWs. At this
time, EPA believes that an extension of indemnification to
POTWs, even those not subject to RCRA regulations,
would be inconsistent with Congressional intent.
5. Evaluate POTW Pretreatment Requirements
Once the best candidate(s) for receiving the discharge
has been determined using the four steps outlined above, a
POTW-specific analysis of pretreatment requirements
designed to prevent pass through, inhibition, and sludge
contamination at a POTW should be conducted to ensure
that CERCLA discharges are in compliance. Section
307(b) of the CWA established the National Pretreatment
Program, which specifies three types of pretreatment
standards: general prohibitions, national categorical
standards, and local limits (see Highlight 2).
General prohibitions are intended to address site-
specific problems at POTWs and to apply a broad baseline
level of control to all industrial users discharging to any
POTW. National categorical standards are
technologically-based effluent limits that must be achieved
prior to introduction into a POTW of wastes generated by
particular categories of industry, such as leather tanning
and metal finishing. [EPA however, has not promulgated
specific national categorical pretreatment standards that
govern the discharge of CERCLA wastes to a POTW. As
a result, CERCLA wastes are treated as non-domestic
wastestreams, and are subject to the general pretreatment
regulations.] Local limits are specific requirements
developed and enforced by individual POTWs to
implement the national general prohibitions and categorical
standards.
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Highlight 2
PRETREATMENT STANDARDS SPECIFIED
UNDER THE CWA
•	General Prohibitions - National prohibitions that are
applicable to nondomestic uses that control the
introduction of contaminants into POTWs to:
(a)	prevent interference (i.e., a discharge that inhibits or
disrupts a POTW causing a violation of its NPDES
permit or other requirements) with the operations of a
POTW; and
(b)	prevent pass through (i.e., any discharge to a POTW in
concentrations that cause a violation of any
requirement of the POTW's NPDES permit) of
contaminants through the POTW.
•	National Categorical Standards - National prohibitions
that apply to all non-domestic users and protect
against:
(a)	fire or explosion hazard in Elie sewers or POTWs:
(b)	corrosive structural damage to the POTW;
(c)	obstruction of flow in the sewer system;
•	interference due to the pollutants high concentration
or flow rate; or
•	an increase in temperature of Wastewater entering the
POTW that inhibits biological activity resulting in
interference.
•	Local Limits - Specific requirements that are developed
and enforced by individual POTWs to implement the
national general and specific prohibitions. States and
localities also may impose more stringent requirements
than the national limits on dischargers to their
regulated facilities.
POTWs also may have a State-approved pretreatment
program and be required to have mechanisms in place to
ensure that dischargers comply with applicable
pretreatment standards and requirements. Most POTWs
likely will require some type of self-monitoring program
and submission of monitoring results to the POTW on a
periodic basis.
An approved pretreatment program for a POTW may
not address all of the constituents of the CERCLA
discharge, in which case the site manager must proceed as
though an approved pretreatment program did not exist,
i.e., site managers must determine whether sufficient
mechanisms exist to enable the POTW to ensure
compliance with appropriate pretreatment requirements.
Whether an approved pretreatment program exists
or not, compliance with applicable regulations must be
achieved. If an approved program exists, the
evaluation of a POTW's pretreatment requirements
consists of obtaining the local limits enforced by the
POTW to prevent pass through, inhibition, and sludge
contamination. If an approved program does not exist or if
the pretreatment program does not address all of the
components of the CERCLA waste, local limits must be
estimated by calculating the mass balances of the
wastestrearn to be disposed.
Estimating Local Limits to Meet Standards
Ideally, the POTW will have existing local limitations
for all of the contaminants present in the CERCLA
discharge. However, in many cases, the POTW will not
have local limitations for all of the contaminants in the
CERCLA discharge or existing limits may need to be
changed as a result of the discharge. In this case, the limits
must be developed by the POTW or estimated by the site
managers so that pretreatment alternatives may be
evaluated. Promulgated national categorical pretreatment
standards can be used in calculating local limits for the
CERCLA wastewater constituents where limits do not
already exist.
When the estimation of local limitations is necessary,
the following measures may be taken:
•	Obtain Pertinent Regulatory Criteria to Ensure
Compliance of Estimated Limits With the Criteria: In
estimating local limits it is necessary to comply with
limits that have been established on the Federal and
State levels. Furthermore, consulting these limits can
give necessary guidance for establishing limits on the
local level.
•	Calculate a mass balance for each compound detected
in the CERCLA waste using treatability data: The
purpose of the mass balance is to calculate the general
treatment efficiency of the POTW and identify which
POTW removal mechanisms will be impacted by the
removal of each constituent from the CERCLA
wastestrearn. There are several options for calculating
the mass balance of a particular contaminant, including
the use of POTW-specific or published treatability data
and the use of computer models.
•	Evaluate the impact of each contaminant on air
emissions, treatment plant operations, sludge disposal.
and effluent air quality: Data exists (for most
contaminants) that makes it possible to calculate the
concentration of those contaminants in air emissions,
sludge, and also the amount that will be biodegraded by
certain operations.
•	Estimate local limits and the expected level of
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pretreatment necessary to ensure continued
compliance with NPDES permit limits and applicable
air emission standards, avoiding any exceedance of
State water quality standards and maintaining
acceptable levels of sludge quality. Using the local
limits and the composition of the CERCLA
wastewater, determine if and when additional
pretreatment is necessary to ensure compliance with
the POTW's pretreatment requirements.
(Eventually, the estimated limits must be transferred by the
POTW into enforceable limits. Because this process may
take time and cause a delay in the evaluation process, site
managers should begin this evaluation as early as possible).
Determining Pretreatment Options
Generally, site managers will have several pretreatment
options to achieve the identified limits in effect at a POTW:
• Treatment technologies~(e.g., aerobic biological
treatment, precipitation, and oxidation);
•	Separation technologies --(e.g., clarification, filtration,
and oil and grease separation);
•	Polishing technologies-(e. g., carbon adsorption and ion
exchange).
[Note: in many cases, these technologies may have
already been evaluated as part of other alternatives not
involving discharge to a POTW.]
Once possible treatment technologies are identified
based on the nature of the CERCLA wastes and the
pretreatment requirements of the POTW, it is necessary to
develop a pretreatment program that will result in
CERCLA wastewater that complies with the POTW's
pretreatment requirements.
The key steps in the process for evaluating the
feasibility of discharging CERCLA wastes to a POTW are
summarized in Highlight 3.
Identify and Characterize
CCRCtA
Waetewater Dtediarge
Identify the slte-specfflc CERCLA
wastewater discharges
Determine data requirements and collect
data to fulfill these requirements
Evaluate all available data to
characterize wastewater
Determine If the CERCLA wastewater
Is a RCRA hazardous waste
2.
MenMy Local POTWe
Determine geographic area to be
considered
Consider methods or transporting the
wastesteam to the POTW
Identify potential POTWs and gather
Information about each facility
4.
Evaluate Technical
and MRtMetraim
FeaeMRy
Contact the POTW to determine If they are
willing to accept a CERCLA wastettream
Evaluate the POTWs ability to handle and
property treaf the CERCLA wastestieam
Address and discuss the POTWs potential
liability associated wtth accepting a
CERCLA wastestream
Evaluate the current permits of the POTW
and determine changes required and other
permits needed
Evaluate
Regulatory Statue
•	Investigate the compliance status of
the POTW
•	If CERCLA wastestream Is a hazardous
waste, determine H Domestic Sewage
Exclusion Is applicable, if not. determine
Permit - by - Rule requirements
Evaluate PieUeatiiiei*
Requirement* ot
"Beet" CendkJate(s)
Obtain or estimate the local limits enforced by
the POTW to prevent pats through. Inhibition
and sludge contamination
Compare CERCLA discharge characteristics
to local limits to determine which
contaminants require pretreatment
Identify possible pretreatment technologies
Develop a pretreatment process train to property
pretrial the CERCLA wastestream
Highlight 3
PROCESS FOR EVALUATING CERCLA DISCHARGES TO POTWs
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