40 CFR § 421.253 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable.
---
identifier: "/us/cfr/t40/s421.253"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 421.253 - 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: "421.253"
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: "2026-03-24"
last_updated: "2026-03-24"
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"
---
# 421.253 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) Smelter wet air pollution control.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of gold and silver smelted | |
| Lead | 0.364 | 0.169 |
| Mercury | 0.195 | 0.078 |
| Silver | 0.377 | 0.156 |
| Zinc | 1.326 | 0.546 |
| Gold | 0.130 | |
(b) Silver chloride reduction spent solution.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver reduced in solution | |
| Lead | 0.112 | 0.052 |
| Mercury | 0.060 | 0.024 |
| Silver | 0.116 | 0.048 |
| Zinc | 0.408 | 0.168 |
| Gold | 0.040 | |
(c) Electrolytic cells wet air pollution control.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of gold refined electrolytically | |
| Lead | 5.544 | 2.574 |
| Mercury | 2.970 | 1.188 |
| Silver | 5.742 | 2.376 |
| Zinc | 20.200 | 8.316 |
| Gold | 1.980 | |
(d) Electrolyte preparation wet air pollution control.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/troy ounce of silver in electrolyte produced | |
| Lead | 0.014 | 0.007 |
| Mercury | 0.008 | 0.003 |
| Silver | 0.015 | 0.006 |
| Zinc | 0.051 | 0.021 |
| Gold | 0.005 | |
(e) Calciner Wet Air Pollution Control.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/kg (pounds per million pounds) of mercury condensed | |
| Lead | 6.160 | 2.860 |
| Mercury | 3.300 | 1.320 |
| Silver | 6.380 | 2.640 |
| Zinc | 22.440 | 9.240 |
| Gold | 2.200 | |
(f) Calcine quench water.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/kg (pounds per million pounds) of mercury condensed | |
| Lead | 4.928 | 2.288 |
| Mercury | 2.640 | 1.056 |
| Silver | 5.104 | 2.112 |
| Zinc | 17.950 | 7.392 |
| Gold | 1.760 | |
(g) Calciner stack gas contact cooling water.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/kg (pounds per million pounds) of mercury condensed | |
| Lead | 1.162 | 0.540 |
| Mercury | 0.623 | 0.249 |
| Silver | 1.204 | 0.498 |
| Zinc | 4.233 | 1.743 |
| Gold | 0.415 | |
(h) Condenser blowdown.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/kg (pounds per million pounds) of mercury condensed | |
| Lead | 3.864 | 1.794 |
| Mercury | 2.070 | 0.828 |
| Silver | 4.002 | 1.656 |
| Zinc | 14.080 | 5.796 |
| Gold | 1.380 | |
(i) Mercury cleaning bath water.
BAT Limitations for the Primary Precious Metals and Mercury Subcategory
| Pollutant or pollutant property | Maximum for any 1 day | Maximum for monthly average |
| --- | --- | --- |
| | mg/kg (pounds per million pounds) of mercury condensed | |
| Lead | 0.392 | 0.182 |
| Mercury | 0.210 | 0.084 |
| Silver | 0.406 | 0.168 |
| Zinc | 1.428 | 0.588 |
| Gold | 0.140 | |