is^,
I
I
UJ
CJ
National Pretreatment
Program
(40 CFR 403)
Pretreatment Streamlining Rule
Fact Sheet 4.0: Equivalent Concentration-Based
Limits for Flow-Based Standards
Summary
Who might be
affected by this
provision?
As part of the 2005 Pretreatment Streamlining Rule,
EPA created new flexibility for Control Authorities and
Industrial Users by providing Control Authorities the
discretion to control pollutant discharges through
equivalent concentration-based limits in lieu of flow-
based mass limits for certain industrial categories.
EPA established this flexibility because flow-based
mass limits can be difficult for the Control Authority to
implement and enforce. For example, flow-based
mass limits may be difficult to develop and enforce in
situations where the facility has highly variable
production with flows that often vary week-to-week or
day-to-day.
This provision affects Control Authorities that want the
discretion to replace Categorical Industrial Users'
(CIUs') flow-based mass limits with equivalent
concentration-based limits. The affected industrial
categories are:
• Organic Chemicals, Plastics, and Synthetic
Fibers (OCPSF), 40 CFR 414;
• Petroleum Refining, 40 CFR 419; and
• Pesticide Chemicals, 40 CFR 455.
The standards for these three industry categories
require the Control Authority to develop a flow-based
mass limit by identifying the average daily flow rate of
the Industrial User's regulated process wastewater
and then multiplying that value by the appropriate
promulgated concentration-based Categorical
Standard (e.g., see 40 CFR 414.111(a)).
The provision also affects states that plan to amend
state law to allow Control Authorities the discretion to
set equivalent concentration-based limits.
National Pretreatment Program - 40 CFR 403
-------
Who qualifies for
equivalent
concentration-based
limits?
How are equivalent
concentration-based
limits put in place?
Control Authorities can use equivalent concentration-
based limits instead of flow-based mass limits for
three industry categories identified above. EPA notes
that the decision to use equivalent concentration-
based limits for flow-based mass limits is at the
discretion of the Control Authority and not the CIU.
Once a POTW revises its approved pretreatment
program to allow for equivalent concentration-based
limits, Industrial Users may initiate the process by
submitting an application to the Control Authority
requesting replacement of their flow-based mass
limits with the equivalent concentration-based limits.
This application should detail the CIU's eligibility for
equivalent concentration-based limits using the
following criteria:
• Equivalent concentration-based limits are not
currently being or will not subsequently be met
through the use of dilution or by-pass as a
substitute for treatment (see 40 CFR 403.6(d))
and 40 CFR 403.17). (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 or requesting an
explanation of why it uses the level of process
water that it uses.)
• CIUs that mix their process effluent prior to
treatment with wastewaters other than those
generated by the regulated process must
provide information regarding the pollutant
concentrations at the sample point that need
adjustment using the combined wastestream
formula. See 40 CFR 403.6(e) for more details.
The Control Authority will approve or reject the CIU
application. The Control Authority will also verify and
document that the CIU meets the above eligibility
requirements before incorporating the equivalent
concentration-based limits into the CIU's permit (or
other equivalent control mechanism). The Control
Authority will document how the equivalent
concentration-based limits were derived and make the
documents publicly available.
National Pretreatment Program - 40 CFR 403
-------
What is required
after equivalent
concentration-based
limits are in place?
Once the Control Authority has properly authorized
the use of an equivalent concentration limit and has
incorporated that limit into the Industrial User's
control mechanism, the concentration limit replaces
the mass limit. For example, Control Authorities may
use this new flexibility to control pollutant discharges
from OCPSF facilities by using the concentration-
based standards in 40 CFR 414.111(b). The final rule
requires that an Industrial User must comply with the
equivalent limit in lieu of the promulgated categorical
Pretreatment Standard once the limit is incorporated
into its control mechanism. The Control Authority may
also determine that an Industrial User should be
subject to both the flow-based mass limit as well as
the concentration-based limit. When incorporated into
the issued control mechanism, the Industrial User
would have to comply with both limits.
After the Control Authority issues a permit (or control
mechanism) with equivalent concentration-based
limits, the continued applicability of the equivalent
concentration-based limits depends on the CIU's
continued compliance with certain requirements. EPA
recommends that Control Authorities consider
specifying appropriate flow monitoring requirements
and including evaluation of flow data in the review of
periodic reports for Industrial Users subject to
equivalent concentration standards. This will enable
Control Authorities to determine if there have been
changes in flows that may indicate dilution, such as
increases in process, non-process or overall flows,
especially those not accompanied by production
increases. (The Control Authority should note that 40
CFR 403.12(e)(l) already requires CIUs to provide
information regarding maximum and average daily
flows in their periodic reports, and to require more
detailed flow data as necessary.)
If the CIU subsequently fails to comply with these
requirements, the Control Authority must revise the
CIU's permit (or control mechanism) to require the
CIU to comply with flow-based mass limits derived
from the Categorical Pretreatment Standards (e.g.,
see 40 CFR 414.111(a)).
National Pretreatment Program - 40 CFR 403
-------
When are the
equivalent
concentration-based
limits effective?
Where can I get
more information?
Equivalent concentration-based limits are effective
when the Control Authority issues a permit (or control
mechanism) that establishes equivalent
concentration-based limits under 403 CFR
403.6(c)(6). These equivalent concentration-based
limits are federally enforceable. If the Control
Authority has not issued a control mechanism that
establishes the equivalent concentration-based limits
for facilities in these three categories, the IU must
comply with the default flow-based mass limits as
established in the applicable Pretreatment Standards
(e.g., see 40 CFR 414.111(a)).
EPA notes that, for the Pesticides Chemicals category
(40 CFR 455), in certain circumstances, an Industrial
User may already be subject to concentration based
limits rather than the otherwise required mass limits.
Where the Control Authority has not established flow-
based mass limits as required, 40 CFR 455.26 and
455.27 provide that Industrial User must comply with
the default concentration-based limits as established
in the categorical Pretreatment Standard.
The equivalent concentration-based limits provision is
found in 40 CFR 403.6(c)(6), 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.QOv/npdes/home.cfm7program id=3.
Additional information is also available from your state
or from EPA.
Office of Water
EPA-833-F-08-002
March 2008
------- |