40 CFR § 425.21 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT).

---
identifier: "/us/cfr/t40/s425.21"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 425.21 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT)."
title_number: 40
title_name: "Protection of Environment"
section_number: "425.21"
section_name: "Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT)."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "N"
subchapter_name: "EFFLUENT GUIDELINES AND STANDARDS"
part_number: "425"
part_name: "LEATHER TANNING AND FINISHING POINT SOURCE CATEGORY"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "33 U.S.C. 1311, 1314 (b), (c), (e) and (g), 1316 (b) and (c), 1317 (b) and (c), 1318 and 1361."
regulatory_source: "47 FR 52870, Nov. 23, 1982, unless otherwise noted."
cfr_part: "425"
---


# 425.21 Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT).

Except as provided in 40 CFR 125.30 through 125.32, any existing point source subject to this subpart must achieve the following effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT):

|  |  |  |
| --- | --- | --- |
|  | Kg/kkg (or pound per 1,000 lb) of raw material |  |
| BOD | 8.2 | 3.7 |
| TSS | 11.8 | 5.4 |
| Oil and grease | 3.4 | 1.5 |
| Total chromium | 0.21 | 0.08 |
| pH | () | () |
| Within the range 6.0 to 9.0. |  |  |