{"data":{"id":"us/40-cfr-421.253","jurisdiction":"us","citation":"40 CFR 421.253","heading":"Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable.","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 available technology economically achievable:\n(a) Smelter wet air pollution control.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of gold and silver smelted\nLead 0.364 0.169\nMercury 0.195 0.078\nSilver 0.377 0.156\nZinc 1.326 0.546\nGold 0.130\n(b) Silver chloride reduction spent solution.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver reduced in solution\nLead 0.112 0.052\nMercury 0.060 0.024\nSilver 0.116 0.048\nZinc 0.408 0.168\nGold 0.040\n(c) Electrolytic cells wet air pollution control.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of gold refined electrolytically\nLead 5.544 2.574\nMercury 2.970 1.188\nSilver 5.742 2.376\nZinc 20.200 8.316\nGold 1.980\n(d) Electrolyte preparation wet air pollution control.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver in electrolyte produced\nLead 0.014 0.007\nMercury 0.008 0.003\nSilver 0.015 0.006\nZinc 0.051 0.021\nGold 0.005\n(e) Calciner Wet Air Pollution Control.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 6.160 2.860\nMercury 3.300 1.320\nSilver 6.380 2.640\nZinc 22.440 9.240\nGold 2.200\n(f) Calcine quench water.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 4.928 2.288\nMercury 2.640 1.056\nSilver 5.104 2.112\nZinc 17.950 7.392\nGold 1.760\n(g) Calciner stack gas contact cooling water.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 1.162 0.540\nMercury 0.623 0.249\nSilver 1.204 0.498\nZinc 4.233 1.743\nGold 0.415\n(h) Condenser blowdown.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 3.864 1.794\nMercury 2.070 0.828\nSilver 4.002 1.656\nZinc 14.080 5.796\nGold 1.380\n(i) Mercury cleaning bath water.\nBAT Limitations for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 0.392 0.182\nMercury 0.210 0.084\nSilver 0.406 0.168\nZinc 1.428 0.588\nGold 0.140","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 W—Primary Precious Metals and Mercury 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":"1bd095458a6e06fe6dc5e2d90fb26998c3970a9591acff7ddde1683efb9dc398","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-421.252","next":"us/40-cfr-421.254"},"notice":"GroundRules: Original legal text. Not legal advice."}