40 CFR § 421.123 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable.
---
identifier: "/us/cfr/t40/s421.123"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 421.123 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable."
title_number: 40
title_name: "Protection of Environment"
section_number: "421.123"
section_name: "Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "N"
subchapter_name: "EFFLUENT GUIDELINES AND STANDARDS"
part_number: "421"
part_name: "NONFERROUS METALS MANUFACTURING 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 (b) and (c), 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) and the Water Quality Act of 1987 (the “Act”); 33 U.S.C. 1311, 1314 (b), (c), (e), and (g), 1316 (b) and (c), 1317 (b) and (c), 1318 and 1361; 86 Stat. 816, Pub. L. 92-500; 91 Stat. 1567, Pub. L. 95-217; 101 Stat. 7, Pub. L. 100-4."
regulatory_source: "49 FR 8790, Mar. 8, 1984, unless otherwise noted."
cfr_part: "421"
---
# 421.123 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable.
Except as provided in 40 CFR 125.30 through 125.32, any existing point source subject to this subpart shall achieve the following effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable:
(a) Subpart L—Film Stripping.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver from film stripping | |
| Copper | 64.450 | 30.720 |
| Zinc | 51.360 | 21.150 |
| Ammonia (as N) | 6,712.000 | 2,951.000 |
(b) Subpart L—Film Stripping Wet Air Pollution Control and Precipitation and Filtration of Film Stripping Solutions Wet Air Pollution Control.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver from precipitation and filtration of film stripping solutions | |
| Copper | 1.242 | .592 |
| Zinc | .990 | .408 |
| Ammonia (as N) | 129.300 | 56.840 |
(c) Subpart L—Precipitation and Filtration of Film Stripping Solutions.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver precipitated | |
| Copper | 73.690 | 35.120 |
| Zinc | 58.720 | 24.180 |
| Ammonia (as N) | 7,674.000 | 3,374.000 |
(d) Subpart L—Precipitation and Filtration of Photographic Solutions.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver precipitated | |
| Copper | 34.048 | 16.226 |
| Zinc | 27.132 | 11.172 |
| Ammonia (as N) | 3,545.000 | 1,559.000 |
(e) Subpart L—Precipitation and Filtration of Photographic Solutions Wet Air Pollution Control.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver from precipitation and filtration of photographic solutions | |
| Copper | 15.540 | 7.406 |
| Zinc | 12.380 | 5.099 |
| Ammonia (as N) | 1,618.000 | 711.400 |
(f) Subpart L—Electrolytic Refining.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver from electrolytic refining | |
| Copper | .973 | .464 |
| Zinc | .775 | .319 |
| Ammonia (as N) | 101.300 | 44.540 |
(g) Subpart L—Furnace Wet Air Pollution Control.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver roasted, smelted, or dried | |
| Copper | .000 | .000 |
| Zinc | .000 | .000 |
| Ammonia (as N) | .000 | .000 |
(h) Subpart L—Leaching.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver produced from leaching | |
| Copper | .110 | .053 |
| Zinc | .088 | .036 |
| Ammonia (as N) | 11.470 | 5.040 |
(i) Subpart L—Leaching Wet Air Pollution Control and Precipitation of Nonphotographic Solutions Wet Air Pollution Control.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver produced from leaching or silver precipitated | |
| Copper | 5.671 | 2.703 |
| Zinc | 4.519 | 1.861 |
| Ammonia (as N) | 590.500 | 259.600 |
(j) Subpart L—Precipitation and Filtration of Nonphotographic Solutions.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver precipitated | |
| Copper | 3.930 | 1.873 |
| Zinc | 3.132 | 1.290 |
| Ammonia (as N) | 409.300 | 179.900 |
(k) Subpart L—Floor and Equipment Washdown.
BAT Effluent Limitations
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver production | |
| Copper | .000 | .000 |
| Zinc | .000 | .000 |
| Ammonia (as N) | .000 | .000 |