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National Pretreatment
Program
(40 CFR 403)
Pretreatment Streamlining Rule
Fact Sheet 3.0: Equivalent Mass Limits for
Concentration Limits
Summary
Who might be
affected by this
provision?
In the Pretreatment Streamlining Rule of October 14,
2006, EPA finalized a provision that allows, in limited
circumstances, the conditional use of equivalent mass
limits in lieu of concentration-based limits to facilitate
adoption of water-saving technologies. Industrial users
whose wastewater discharges are controlled by
equivalent mass limits have more flexibility to
implement water conservation, as they may elect to
control their wastewater discharges through more
efficient wastewater control technologies and pollution
prevention practices (i.e., resulting in lower pollutant
concentrations in the discharged wastewater) or more
efficient water conservation practices (e.g., resulting in
less wastewater volume discharged from an industrial
operation) or both.
This provision affects Pretreatment Programs that
accept wastes from qualifying indirect dischargers in
certain industrial categories and that want the
discretion to express Categorical Industrial Users'
(Gills') concentration-based categorical Pretreatment
Standards as equivalent mass limits. The affected
industrial categories are those that have Pretreatment
Standards expressed as concentration limits alone.
Currently, this includes 14 industrial categories:
Inorganic Chemicals (40 CFR 415)
Fertilizer Manufacturing (40 CFR 418)
Petroleum Refining (40 CFR 419)
Steam Electric Power Generating (40 CFR 423)
Leather Tanning (40 CFR 425)
Glass Manufacturing (40 CFR 426)
Rubber Manufacturing (40 CFR 428)
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December 2006
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How can a CIU
qualify for an
equivalent mass
limit?
• Metal Finishing (40 CFR 433)
• Pharmaceutical Manufacturing (40 CFR 439)
• Transportation Equipment Cleaning (40 CFR 442)
• Paving and Roofing Materials (40 CFR 443)
• Commercial Hazardous Waste Combustors
Subcategory of the Waste Combustors Point Source
Category (40 CFR 444)
• Carbon Black Manufacturing (40 CFR 458)
• Electrical and Electronic Components (40 CFR 469).
The provision also affects states that plan to amend
state law to allow POTW Pretreatment Programs the
discretion to set equivalent mass limits.
To qualify for an equivalent mass limit, a CIU must:
* Implement or demonstrate that it will implement
water conservation measures that "substantially
reduce" water use. This is intended to encourage
prospective innovation in water conservation
methods; there is no precondition that Industrial
Users have already employed water conservation
measures.
* Use control and treatment technologies adequate to
achieve compliance with categorical Pretreatment
Standards, and demonstrate that it has not used
dilution as a substitute for treatment. (There are a
number of ways the Control Authority may evaluate
whether the CIU is diluting its flows. This evaluation
can be made by comparing the CIU's product to flow
ratio relative to that of other facilities within its
industry, reviewing historical monitoring reports, or
comparing current flows to the flows that are
assumed as part of the model technology for the
standard in the Technical Development Document for
the Effluent Guideline for that industry.)
* Provide monitoring data to establish its actual
average daily flow rate and its baseline long-term
average production rate.
t Demonstrate that it does not have daily flow
rates, production rates, or pollutant levels that
fluctuate so significantly that establishing
equivalent mass limits would not be appropriate.
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December 2006
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What constitutes
a substantial
reduction in
water use?
* Have consistently complied with the applicable
Categorical Pretreatment Standards. While the
regulations do not define a set period of
consistent compliance, the Control Authority
should evaluate a period of time that is long
enough to ensure that seasonal violations do not
occur. The regulations in 40 CFR403.12(o)
require that Industrial Users maintain records of
all information from any monitoring activities for a
minimum of three years; EPA recommends that
these records should be reviewed and considered
to the extent that they reflect compliance with
current conditions. It is also important to note
that "consistent compliance" is a more restrictive
requirement than "not in SNC," and that EPA
expects that no Industrial User found to have
been in SNC at any time during the previous two
years would be considered to have achieved
consistent historical compliance.
The Streamlining Rule does not specify the amount of
water conservation that should be achieved or that
constitutes a substantial reduction in water use. EPA
notes that several existing programs define thresholds
that the Control Authority may consider for use in this
context. For example:
* The final rule for the Pretreatment Community XL
(XLC) Site-Specific Rulemaking for Steele County, MN
indicates that the participating Industrial Users
committed as a group reduce water usage by 10
percent over the initial 5 year project period.
* The National Metal Finishing Strategic Goals Program
promotes a 50 percent water reduction from each
participating industrial facility's baseline 1992 water
usage.
» In Agency guidance for the Use of Production Based
Pretreatment Standards and the Combined
Wastestream Formula (1985), EPA considers a 20
percent change in flow rate to be a significant change
in flow rate.
Office of Water
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December 2006
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How are
equivalent mass
limits put in
place?
Once a POTW revises its approved pretreatment
program to allow for mass-based limits, EPA anticipates
that Industrial Users will initiate the process by
requesting that their concentration-based limits be
converted to equivalent mass limits and demonstrating
that they meet the qualifications. Although a CIU may
request an equivalent limit, the Pretreatment Control
Authority has the discretion to decide whether an
equivalent mass limit is appropriate. To approve the
request, the Control Authority must:
t Work with the EPA or state Approval Authority to
review, and revise as necessary, its Sewer Use
Ordinance (or equivalent authority), program
procedures, Enforcement Response Plan, and local
limits to determine whether changes are needed. (In
most cases, the legal authority will require revision.)
* Determine the CIU's actual average daily flow rate.
Equivalent mass limits must be based on the CIU's
actual average daily flow rate from the regulated
processes at the designated sampling location. If
necessary, the combined wastestream formula must
be used to account for any flows not regulated by the
standard. The flow rate used must be representative
of current operating conditions, and the flows must
be measured using a continuous effluent flow
monitor.
* Calculate the equivalent mass limit by multiplying the
Pretreatment Standard in the regulations (expressed
as concentration) by the Industrial User's actual
average daily flow rate for the regulated processes
and the appropriate unit conversion factor. For
example, the unit conversion factor is 8.34 when
multiplying a concentration limit (expressed as
milligrams/liter) by flow (expressed as millions of
gallons per day). It is important to note that the
same flow value (the CIU's actual long-term average
daily flow rate) is used in the calculation of both the
daily maximum and monthly average equivalent
mass limits.
t Document how the mass limit calculations were
derived and make the documents publicly available.
Office of Water
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December 2006
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What is required
after mass limits
are in place?
Can local limits be
expressed as mass
based limits?
* Incorporate the equivalent mass limits into the CIU's
permit (or other equivalent control mechanism). The
Control Authority should include the four conditions
listed below in the CIU's permit to clarify the
requirements for continued use of the equivalent
mass limits.
After the Control Authority issues a permit (or control
mechanism) with equivalent mass limits, the continued
applicability of the equivalent mass limit depends on the
CIU's continued compliance with certain requirements.
The CIU must:
* Maintain and effectively operate control and
treatment technologies adequate to achieve
compliance with the equivalent mass limits;
* Record the facility's flow rates through the use of a
continuous effluent flow monitoring device;
* Continue to record the facility's production rates and
notify the Control Authority if the rates vary by more
than 20 percent from the production rates used as
the basis for the equivalent mass limits; and
* Continue to employ the same or comparable water
conservation measures which made the facility
eligible for receiving the equivalent mass limits.
If the CIU does not meet these requirements, the CIU's
permit would have to be revised to require compliance
with the pre-existing concentration-based Pretreatment
Standard.
The ability to establish mass-based local limits was not
affected by the Pretreatment Streamlining rule. The
POTW chooses its local limits implementation method
(concentration, mass, or a combination) during the local
limits determination process and adopts the limits into
its program. For more information on developing local
limits, see Local Limits Development Guidance (July
2004), available at EPA's Pretreatment Web site,
http://www.epa.aov/npdes/pubs/final local limits quid
ance.pdf
A POTW can allocate and apply its Maximum Allowable
Industrial Loading (MAIL) to its controllable sources as
mass-based limits. If a POTW allocates its MAILs on a
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December 2006
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Where can I get
more information?
case-by-case basis, it may be easier to apply mass-
based limits to Industrial Users that have the capability
to accurately measure their flows at the designated
sample points. If approved local limits are currently
expressed as concentration-based limits, the POTW
cannot convert the local limits to mass limits without
modifying the approved program, which under certain
circumstances would be a substantial modification (see
40 CFR 403.18(b)(2)). Specific circumstances under
which the reallocation of a MAIL would be a substantial
program modification are discussed in a 1997 Federal
Register (see 62 FR 38409 and also 40 CFR
403.18(b)(2)).
The regulations covering equivalent mass for
concentration limits are found in 40 CFR 403.6(c)(5),
which was published in the Federal Register on October
15, 2005 (70 FR 60134). You can get a copy of the rule
at EPA's Pretreatment Web site,
http://cfpub.epa.gov/npdes/home.cfm7proqram id = 3
Additional information is also available from your state
or from EPA.
Office of Water
EPA-833-F-06-008
December 2006
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