40 CFR § 471.21 - 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/s471.21"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 471.21 - 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: "471.21"
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: "471"
part_name: "NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "Secs. 301, 304(b), (c), (e), and (g), 306(b) and (c), 307, 308, and 501 of the Clean Water Act (the Federal Water Pollution Control Act Amendments of 1972 as amended by the Clean Water Act of 1977) (the “Act”); 33 U.S.C. 1311, 1314(b), (c), (e), and (g), 1316(b) and (c), and 1361; 86 Stat. 816, Pub. L. 92-500; 91 Stat. 1567, Pub. L. 95-217."
regulatory_source: "50 FR 34270, Aug. 23, 1985, unless otherwise noted."
cfr_part: "471"
---
# 471.21 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 for the process operations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT):
(a) *Rolling spent emulsions.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium rolled with emulsions | |
| Chromiun | 0.033 | 0.014 |
| Zinc | 0.109 | 0.046 |
| Ammonia | 9.95 | 4.37 |
| Fluoride | 4.440 | 1.97 |
| Oil and grease | 1.49 | 0.895 |
| TSS | 3.06 | 1.46 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(b) *Forging spent lubricants—subpart B—BPT.* There shall be no discharge of process wastewater pollutants.
(c) *Forging contact cooling water.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of forged magnesium cooled with water | |
| Chromium | 1.27 | 0.520 |
| Zinc | 4.22 | 1.77 |
| Ammonia | 385 | 170 |
| Fluoride | 172 | 76.3 |
| Oil and grease | 57.8 | 34.7 |
| TSS | 119 | 56.4 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(d) *Forging equipment cleaning wastewater.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium forged | |
| Chromium | 0.018 | 0.007 |
| Zinc | 0.059 | 0.025 |
| Ammonia | 5.32 | 2.34 |
| Fluoride | 2.38 | 1.06 |
| Oil and grease | 0.798 | 0.479 |
| TSS | 1.64 | 0.778 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(e) *Direct chill casting contact cooling water.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods | |
| Chromium | 1.74 | 0.711 |
| Zinc | 5.77 | 2.41 |
| Ammonia | 527 | 232 |
| Fluoride | 235 | 105 |
| Oil and grease | 79.0 | 47.4 |
| TSS | 162 | 77.1 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(f) *Surface treatment spent baths.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium surface treated | |
| Chromium | 0.205 | 0.084 |
| Zinc | 0.681 | 0.285 |
| Ammonia | 62.1 | 27.3 |
| Fluoride | 27.8 | 12.3 |
| Oil and grease | 9.32 | 5.59 |
| TSS | 19.1 | 9.09 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(g) *Surface treatment rinse.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium surface treated | |
| Chromium | 8.32 | 3.4 |
| Zinc | 27.6 | 11.5 |
| Ammonia | 2520 | 1110 |
| Fluoride | 1130 | 499 |
| Oil and grease | 378 | 227 |
| TSS | 775 | 369 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(h) *Sawing or grinding spent emulsions.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium sawed or ground | |
| Chromium | 0.009 | 0.004 |
| Zinc | 0.029 | 0.012 |
| Ammonia | 2.60 | 1.15 |
| Fluoride | 1.16 | 0.515 |
| Oil and grease | 0.390 | 0.234 |
| TSS | 0.800 | 0.381 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |
(i) *Degreasing spent solvents—subpart B—BPT.* There shall be no discharge of process wastewater pollutants.
(j) *Wet air pollution control scrubber blowdown.*
Subpart B—BPT
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged | |
| Chromium | 0.273 | 0.112 |
| Zinc | 0.904 | 0.378 |
| Ammonia | 82.5 | 36.3 |
| Fluoride | 36.9 | 16.4 |
| Oil and grease | 12.4 | 7.43 |
| TSS | 25.4 | 12.1 |
| pH | | () |
| Within the range of 7.5 to 10.0 at all times. | | |