Regulations last checked for updates: May 24, 2025

Title 40 - Protection of Environment last revised: Apr 24, 2028
All TitlesTitle 40Chapter IPart 421Subpart AA - Subpart AA—Secondary Tin Subcategory
View all text of Subpart AA [§ 421.290 - § 421.297]
§ 421.294 - Standards of performance for new sources.

Any new source subject to this subpart shall achieve the following new source performance standards:

(a) Tin smelter SO2 scrubber.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of crude tapped tin produced
Arsenic12.7905.703
Lead2.5751.196
Iron11.0405.611
Tin3.4952.024
Total suspended solids138.000110.400
pH( 1)( 1)

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

(b) Dealuminizing rinse.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of dealuminized scrap produced
Lead0.0100.005
Cyanide (total)0.0070.003
Fluoride1.2250.697
Tin0.0130.008
Total suspended solids0.5250.420
pH( 1)( 1)

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

(c) Tin mud acid neutralization filtrate.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of neutralized dewatered tin mud produced
Lead1.4130.656
Cyanide (total)1.0090.404
Fluoride176.600100.400
Tin1.9181.110
Total suspended solids75.71060.560
pH( 1)( 1)

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

(d) Tin hydroxide wash.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of tin hydroxide washed
Lead3.3471.554
Cyanide (total)2.3910.956
Fluoride418.400237.900
Tin4.5422.630
Total suspended solids179.300143.400
pH( 1)( 1)

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

(e) Spent electrowinning solution from new scrap.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of cathode tin produced
Lead4.7042.184
Cyanide (total)3.3601.344
Fluoride588.000334.300
Tin6.3843.696
Total suspended solids252.000201.600
pH( 1)( 1)

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

(f) Spent electrowinning solution from municipal solid waste.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of MSW scrap used as raw material
Lead0.0330.015
Cyanide (total)0.0240.010
Fluoride4.1652.368
Tin0.0450.026
Total suspended solids1.7851.428
pH( 1)( 1)

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

(g) Tin hydroxide supernatant from scrap.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of tin metal recovered from scrap
Lead15.5807.233
Cyanide (total)11.1304.451
Fluoride1,947.0001,107.000
Tin21.14012.240
Total suspended solids834.600667.700
pH( 1)( 1)

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

(h) Tin hydroxide supernatant from plating solutions and sludges.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of tin metal recovered from plating solutions and sludges
Lead32.2014.95
Cyanide (total)23.009.20
Fluoride4,025.002,289.00
Tin43.7025.30
Total suspended solids1,725.001,380.00
pH( 1)( 1)

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

(i) Tin hydroxide filtrate.

NSPS for the Secondary Tin Subcategory

Pollutant or pollutant property Maximum for any 1 day Maximum for monthly average
mg/kg (pounds per million pounds) of tin metal produced
Lead7.0123.256
Cyanide (total)5.0092.004
Fluoride876.500498.400
Tin9.5175.510
Total suspended solids375.700300.500
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
cite as: 40 CFR 421.294
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