{"data":{"id":"us/40-cfr-471.21","jurisdiction":"us","citation":"40 CFR 471.21","heading":"Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT).","body":"Except as provided in 40 CFR 125.30 through 125.32, any existing point source subject to this subpart must achieve the following effluent limitations for the process operations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT):\n(a) Rolling spent emulsions.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium rolled with emulsions\nChromiun 0.033 0.014\nZinc 0.109 0.046\nAmmonia 9.95 4.37\nFluoride 4.440 1.97\nOil and grease 1.49 0.895\nTSS 3.06 1.46\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(b) Forging spent lubricants—subpart B—BPT. There shall be no discharge of process wastewater pollutants.\n(c) Forging contact cooling water.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of forged magnesium cooled with water\nChromium 1.27 0.520\nZinc 4.22 1.77\nAmmonia 385 170\nFluoride 172 76.3\nOil and grease 57.8 34.7\nTSS 119 56.4\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(d) Forging equipment cleaning wastewater.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium forged\nChromium 0.018 0.007\nZinc 0.059 0.025\nAmmonia 5.32 2.34\nFluoride 2.38 1.06\nOil and grease 0.798 0.479\nTSS 1.64 0.778\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(e) Direct chill casting contact cooling water.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods\nChromium 1.74 0.711\nZinc 5.77 2.41\nAmmonia 527 232\nFluoride 235 105\nOil and grease 79.0 47.4\nTSS 162 77.1\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(f) Surface treatment spent baths.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium surface treated\nChromium 0.205 0.084\nZinc 0.681 0.285\nAmmonia 62.1 27.3\nFluoride 27.8 12.3\nOil and grease 9.32 5.59\nTSS 19.1 9.09\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(g) Surface treatment rinse.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium surface treated\nChromium 8.32 3.4\nZinc 27.6 11.5\nAmmonia 2520 1110\nFluoride 1130 499\nOil and grease 378 227\nTSS 775 369\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(h) Sawing or grinding spent emulsions.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium sawed or ground\nChromium 0.009 0.004\nZinc 0.029 0.012\nAmmonia 2.60 1.15\nFluoride 1.16 0.515\nOil and grease 0.390 0.234\nTSS 0.800 0.381\npH (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(i) Degreasing spent solvents—subpart B—BPT. There shall be no discharge of process wastewater pollutants.\n(j) Wet air pollution control scrubber blowdown.\nSubpart B—BPT\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged\nChromium 0.273 0.112\nZinc 0.904 0.378\nAmmonia 82.5 36.3\nFluoride 36.9 16.4\nOil and grease 12.4 7.43\nTSS 25.4 12.1\npH (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 471—NONFERROUS METALS FORMING AND METAL POWDERS POINT SOURCE CATEGORY","Subpart B—Magnesium Forming 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":"b81bcee4eda0e44f682f83d2c71673e3890e440e89be3917de8dfc7ee48297c2","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-471.20","next":"us/40-cfr-471.22"},"notice":"GroundRules: Original legal text. Not legal advice."}