U.S. Code of Federal Regulations
Regulations most recently checked for updates: Mar 27, 2023
§ 425.01 - Applicability.
This part applies to any leather tanning and finishing facility which discharges or may discharge process wastewater pollutants to the waters of the United States, or which introduces or may introduce process wastewater pollutants into a publicly owned treatment works.
§ 425.02 - General definitions.
In addition to the definitions set forth in 40 CFR part 401, the following definitions apply to this part:
(a) “Sulfide” shall mean total sulfide as measured by the potassium ferricyanide titration method described in appendix A or the modified Monier-Williams method described in appendix B.
(b) “Hide” means any animal pelt or skin as received by a tannery as raw material to be processed.
(c) “Retan-wet finish” means the final processing steps performed on a tanned hide including, but not limited to, the following wet processes: retan, bleach, color, and fatliquor.
(d) “Hair pulp” means the removal of hair by chemical dissolution.
(e) “Hair save” means the physical or mechanical removal of hair which has not been chemically dissolved, and either selling the hair as a by-product or disposing of it as a solid waste.
(f) “Chrome tan” means the process of converting hide into leather using a form of chromium.
(g) “Vegetable tan” means the process of converting hides into leather using chemicals either derived from vegetable matter or synthesized to produce effects similar to those chemicals.
(h) “Raw material” means the hides received by the tannery except for facilities covered by subpart D and subpart I where “raw material” means the hide or split in the condition in which it is first placed into a wet process.
(i) “Monthly average” means the arithmetic average of eight (8) individual data points from effluent sampling and analysis during any calendar month.
(j) “Interference” means the discharge of sulfides in quantities which can result in human health hazards and/or risks to human life, and an inhibition or disruption of POTW as defined in 40 CFR 403.3(i).
§ 425.03 - Sulfide analytical methods and applicability.
(a) The potassium ferricyanide titration method described in appendix A to part 425 shall be used whenever practicable for the determination of sulfide in wastewaters discharged by plants operating in all subcategories except the hair save or pulp, non-chrome tan, retan-wet finish subcategory (subpart C, see § 425.30). In all other cases, the modified Monier-Williams method as described in appendix B to part 425 shall be used as an alternative to the potassium ferricyanide titration method for the determination of sulfide in wastewaters discharged by plants operating in all subcategories except subpart C.
(b) The modified Monier-Williams method as described in appendix B to part 425 shall be used for the determination of sulfide in wastewaters discharged by plants operating in the hair save or pulp, non-chrome tan, retan-wet finish subcategory (subpart C, see § 425.30).
§ 425.04 - Applicability of sulfide pretreatment standards.
(a) A POTW receiving wastewater from a facility subject to this part may require more stringent pretreatment standards for sulfide than those established by this part without EPA approval.
(b) The pretreatment standards for sulfide established by this part will not apply if the POTW receiving wastewater from a facility subject to this part certifies in writing with explanation of relevant factors considered, in accordance with the provisions of paragraph (c) of this section, that the discharge of sulfide from the facility does not interfere with the operation of the POTW. In making this determination, the POTW shall consider all relevant factors including but not limited to the following:
(1) The presence and characteristics, of other industrial wastewaters which can increase or decrease sulfide concentrations, pH, or both.
(2) The characteristics of the sewer/interceptor collection system which either minimize or enhance opportunities for release of hydrogen sulfide gas.
(3) The characteristics of the receiving POTWs headworks, preliminary and primary treatment systems, and sludge holding and dewatering facilities which either minimize or enhance opportunities for release of hydrogen sulfide gas.
(4) The occurrence of any prior sulfide related interference as defined in § 425.02(j).
(c)(1) On October 13, 1983, a POTW which intends to certify that the sulfide pretreatment standard should not apply must publish, in a local newspaper with the largest circulation, a notice that presents the findings supporting this determination consistent with paragraph (a) of this section. Allowance for public hearing of these findings also must be provided. The POTW shall identify all existing facilities to which the sulfide pretreatment standard otherwise established by this part would not apply.
(2) On January 11, 1984, a POTW which intends to certify that the sulfide pretreatment standard should not apply must file a written certification with the Regional Water Management Division Director, Environmental Protection Agency, in the appropriate Regional Office. This certification shall include the findings supporting this determination and the results of public comments, and public hearing(s) if held.
(3) On February 10, 1984, EPA shall acknowledge to the POTW receipt of any certification submitted under paragraphs (c) (1) and (2) of this section, and shall indicate to the POTW the adequacy of the submission based upon a review of the factors set forth in paragraph (b) of this section.
(4) Within 30 days of the date of receipt of adequate submissions under paragraphs (c) (1), (2), and (3) of this section, EPA shall publish a notice in the
(5) A POTW may certify that the sulfide pretreatment standards of this part should not apply to a new source planning to discharge into the POTW. This certification must be submitted prior to the commencement of discharge, and must conform at a minimum with criteria in paragraph (b) of this section and the general procedures and intervals of time contained in paragraphs (c) (1), (2), (3), and (4) of this section.
(d)(1) If, after EPA and the POTW have determined in accordance with this section that the sulfide pretreatment standards of this part are not applicable to specified facilities, a POTW then determines that there have been changed circumstances (including but not limited to changes in the factors specified in paragraph (b) of this section) which justify application of the sulfide pretreatment standards, the POTW shall revoke the certification submitted under paragraph (c) of this section. The POTW and EPA shall then adhere to the general procedures and time intervals contained in paragraph (c) of this section in order to determine whether the sulfide pretreatment standards contained in this part are applicable.
(2) If pursuant to paragraph (d)(1) of this section, the sulfide pretreatment standards of this part are applicable to a specified facility, the indirect discharger shall comply with the sulfide pretreatment standards no later than 18 months from the date of publication of the
(e) At any time after October 13, 1983, if a POTW determines that there have been changed circumstances (including but not limited to changes in the factors specified in paragraph (b) of this section), it may initiate proceedings contained in paragraph (c) of this section to determine that the sulfide pretreatment standards of this part shall not be applicable. The POTW and EPA shall follow the procedures and time intervals contained in paragraph (c) of this section to make this determination. A final determination that the sulfide pretreatment standards are not applicable must be made prior to the discharge of sulfide not in accordance with the standards set forth in this part.
§ 425.05 - Compliance dates.
The compliance date for new source performance standards (NSPS) and pretreatment standards for new sources (PSES) is the date the new source commences discharge. The compliance date for BPT effluent limitations and guidelines and pretreatment standards for existing sources to no later than March 31, 1989.
§ 425.06 - Monitoring requirements.
Compliance with monthly average discharge limitations is required regardless of the number of samples analyzed and averaged.