{"data":{"id":"us/40-cfr-421.256","jurisdiction":"us","citation":"40 CFR 421.256","heading":"Pretreatment standards for new sources.","body":"Except as provided in 40 CFR 403.7, any new source subject to this subpart which introduces pollutants into a publicly owned treatment works must comply with 40 CFR part 403 and achieve the following pretreatment standards for new sources. The mass of wastewater pollutants in primary precious metals and mercury process wastewater introduced into a POTW shall not exceed the following values:\n(a) Smelter wet air pollution control.\nPSNS 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.\nPSNS 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.\nPSNS 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.\nPSNS 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.\nPSNS 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.\nPSNS 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.\nPSNS 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.\nPSNS 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 5.656\nGold 1.380\n(i) Mercury cleaning bath water.\nPSNS 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":"d68504648f62a73ae1cbb73a83ffa29ca9aa1995d94fa1ccd3087e2f4ee18367","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-421.255","next":"us/40-cfr-421.257"},"notice":"GroundRules: Original legal text. Not legal advice."}