Illinois Administrative Code
Title 35 - ENVIRONMENTAL PROTECTION
Part 310 - PRETREATMENT PROGRAMS
Subpart B - PRETREATMENT STANDARDS
Section 310.230 - Concentration and Mass Limits
Current through Register Vol. 48, No. 38, September 20, 2024
a) Pollutant discharge limits in categorical pretreatment standards will be expressed either as concentration or mass limits. Limits in categorical pretreatment standards must apply to the discharge from the process regulated by the standard or as otherwise specified by the standard.
b) When the limits in a categorical pretreatment standard are expressed only in terms of mass of pollutant per unit of production, the Control Authority may convert the limits to equivalent limitations expressed either as mass of pollutant discharged per day or effluent concentration for calculating effluent limitations applicable to individual industrial users.
c) A Control Authority calculating equivalent mass-per-day limitations under subsection (b) must calculate such limitations by multiplying the limits in the standard by the industrial user's average rate of production. This average rate of production must be based not upon the designed production capacity, but rather upon a reasonable measure of the industrial user's actual long-term daily production during a representative year. For new sources, actual production must be estimated using projected production.
d) A Control Authority calculating equivalent concentration limitations under subsection (b) must calculate such limitations by dividing the mass limitations derived under subsection (c) by the average daily flow rate of the industrial user's regulated process wastewater. This average daily flow rate must be based upon a reasonable measure of the industrial user's actual long-term average flow rate, such as the average daily flow rate during the representative year.
e) When the limits in a categorical pretreatment standard are expressed only in terms of pollutant concentrations, an industrial user may request that the Control Authority convert the limits to equivalent mass limits. The determination to convert concentration limits to mass limits is within the discretion of the Control Authority. The Control Authority may establish equivalent mass limits only if the industrial user meets all the following conditions in subsections (e)(1)(A) through (e)(1)(E).
f) The Control Authority may convert the mass limits of the categorical pretreatment standards of Subparts O, T, and CD of 35 Ill. Adm. Code 307 to concentration limits for calculating limitations applicable to individual industrial users under the following conditions. When converting such limits to concentration limits, the Control Authority must use the concentrations listed in the applicable provisions of Subparts O, T, and CD of 35 Ill. Adm. Code 307 and document that dilution is not being substituted for treatment as prohibited by Section 310.232.
g) Equivalent limitations calculated in accordance with subsections (c) through (f) are deemed pretreatment standards. The Control Authority must document how the equivalent limits were derived and make this information publicly available. Once incorporated into its control mechanism, the industrial users must comply with the equivalent limitations instead of the promulgated categorical standards from which the equivalent limitations were derived.
h) Many categorical pretreatment standards specify one limit for calculating maximum daily discharge limitations and a second limit for calculating maximum monthly average or four-day average limitations. If such standards are being applied, the same production or flow figure must be used in calculating both the average and the maximum equivalent limitation.
i) Any industrial user operating under a control mechanism incorporating equivalent mass or concentration limits calculated from a production-based standard must notify the Control Authority within two business days after the user has a reasonable basis to know that the production level will significantly change within the next calendar month. Any user not notifying the Control Authority of such anticipated change will be required to meet the mass or concentration limits in its control mechanism that were based on the original estimate of the long-term average production rate.
BOARD NOTE: Derived from 40 CFR 403.6(c) (2005), as amended at 70 Fed. Reg. 60134 (Oct. 14, 2005).