{"data":{"id":"us/40-cfr-421.122","jurisdiction":"us","citation":"40 CFR 421.122","heading":"Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available.","body":"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 practicable technology currently available:\n(a) Subpart L—Film Stripping.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver from film stripping\nCopper 95.670 50.350\nZinc 73.510 30.720\nAmmonia (as N) 6,712.000 2,951.000\nTotal suspended solids 2,065.000 981.800\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(b) Subpart L—Film Stripping Wet Air Pollution Control and Precipitation and Filtration of Film Stripping Solutions Wet Air Pollution Control.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver from precipitation and filtration of film stripping solutions\nCopper 1.843 .970\nZinc 1.416 .592\nAmmonia (as N) 129.300 56.840\nTotal suspended solids 39.770 18.920\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(c) Subpart L—Precipitation and Filtration of Film Stripping Solutions.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver precipitated\nCopper 109.400 57.570\nZinc 84.050 35.120\nAmmonia (as N) 7,674.000 3,374.000\nTotal suspended solids 2,361.000 1,123.000\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(d) Subpart L—Precipitation and Filtration of Photographic Solutions.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver precipitated\nCopper 50.540 26.600\nZinc 38.836 16.226\nAmmonia (as N) 3,545.000 1,559.000\nTotal suspended solids 1,090.600 518.700\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(e) Subpart L—Precipitation and Filtration of Photographic Solutions Wet Air Pollution Control.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver from precipitation and filtration of photographic solutions\nCopper 23.070 12.140\nZinc 17.730 7.406\nAmmonia (as N) 1,618.000 711.400\nTotal suspended solids 497.800 236.800\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(f) Subpart L—Electrolytic Refining.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver from electrolytic refining\nCopper 1.444 .760\nZinc 1.110 .464\nAmmonia (as N) 101.300 44.540\nTotal suspended solids 31.160 14.820\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(g) Subpart L—Furnace Wet Air Pollution Control.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver roasted, smelted, or dried\nCopper 1.273 .670\nZinc .978 .409\nAmmonia (as N) 89.310 39.260\nTotal suspended solids 27.470 13.070\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(h) Subpart L—Leaching.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver produced from leaching\nCopper .164 .086\nZinc .126 .053\nAmmonia (as N) 11.470 5.040\nTotal suspended solids 3.526 1.677\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(i) Subpart L—Leaching Wet Air Pollution Control and Precipitation of Nonphotographic Solutions Wet Air Pollution Control.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver produced from leaching or silver precipitated\nCopper 8.417 4.430\nZinc 6.468 2.703\nAmmonia (as N) 590.500 259.600\nTotal suspended solids 181.700 86.390\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(j) Subpart L—Precipitation and Filtration of Nonphotographic Solutions.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver precipitated\nCopper 5.833 3.070\nZinc 4.482 1.873\nAmmonia (as N) 409.300 179.900\nTotal suspended solids 125.900 59.870\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(k) Subpart L—Floor and Equipment Washdown.\nBPT Effluent Limitations\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver production\nCopper .000 .000\nZinc .000 .000\nAmmonia (as N) .000 .000\nTotal suspended solids .000 .000\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER N—EFFLUENT GUIDELINES AND STANDARDS","PART 421—NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY","Subpart L—Secondary Silver Subcategory"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"3ba616ba54eb3ffac0ff0fd6ef7b067c182b14e4db6db6d9fc548b29cf4aeaa2","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-421.121","next":"us/40-cfr-421.123"},"notice":"GroundRules: Original legal text. Not legal advice."}