Regulations last checked for updates: May 19, 2024

Title 40 - Protection of Environment last revised: May 16, 2024
All TitlesTitle 40Chapter IPart 421Subpart W - Subpart W—Primary Precious Metals and Mercury Subcategory
View all text of Subpart W [§ 421.250 - § 421.257]
§ 421.252 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available.

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:

(a) Smelter wet air pollution control.

BPT 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
Lead0.5460.260
Mercury0.3250.130
Silver0.5330.221
Zinc1.8980.793
Gold0.130
Oil and grease26.00015.600
Total suspended solids53.30025.350
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(b) Silver chloride reduction spent solution.

BPT Limitations for the Primary Precious Metals and Mercury Subcategory

Pollutant of pollutant property Maximum for any 1 day Maximum for monthly average
mg/troy ounce of silver reduced in solution
Lead0.1680.080
Mercury0.1000.040
Silver0.1640.068
Zinc0.5840.244
Gold0.040
Oil and grease8.0004.800
Total suspended solids16.4007.800
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(c) Electrolytic cells wet air pollution control.

BPT 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
Lead83.16039.600
Mercury49.50019.800
Silver81.18033.660
Zinc289.100120.800
Gold19.800
Oil and grease3,960.0002,376.000
Total suspended solids8,118.0003,861.000
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(d) Electrolyte preparation wet air pollution control.

BPT 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
Lead0.0210.010
Mercury0.0130.005
Silver0.0210.009
Zinc0.0730.031
Gold0.005
Oil and Grease1.0000.600
Total suspended solids2.0500.975
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(e) Calciner wet air pollution control.

BPT 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
Lead78.20037.240
Mercury46.55018.620
Silver76.34031.650
Zinc271.900113.600
Gold18.600
Oil and Grease3,724.0002,234.000
Total suspended solids7,634.0003,631.000
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(f) Calcine quench water.

BPT 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
Lead7.3923.520
Mercury4.4001.760
Silver7.2162.992
Zinc25.70010.740
Gold1.760
Oil and Grease352.000211.200
Total suspended solids721.600343.200
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(g) Calciner stack gas contact cooling water.

BPT 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
Lead1.7430.830
Mercury1.0380.415
Silver1.7020.706
Zinc6.0592.532
Gold0.415
Oil and Grease83.00049.800
Total suspended solids170.20080.930
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(h) Condenser blowdown.

BPT 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
Lead5.7962.760
Mercury3.4501.380
Silver5.6582.346
Zinc20.1508.418
Gold1.380
Oil and Grease276.000165.600
Total suspended solids565.800269.100
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

(i) Mercury cleaning bath water.

BPT 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
Lead0.5880.280
Mercury0.3500.140
Silver0.5740.238
Zinc2.0440.854
Gold0.140
Oil and Grease28.00016.800
Total suspended solids57.40027.300
pH( 1)( 1)

1 Within the range of 7.5 to 10.0 at all times.

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,c,e,and, 1316 (b) andc, 1317 (b) andc,1318; 86 Stat. 816, Pub. L. 92-500; 91 Stat. 1567, Pub. L. 95-217; 101 Stat. 7, Pub. L. 100-4
source: 49 FR 8790, Mar. 8, 1984, unless otherwise noted.
cite as: 40 CFR 421.252
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