40 CFR 471.22 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT).

Regulations last checked for updates: May 01, 2025

Title 40 - Protection of Environment last revised: Nov 01, 2025

Collapse to view only § 471.22 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT).

Table of Contents

§ 471.20 - Applicability; description of the magnesium forming subcategory.

§ 471.21 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT).

§ 471.22 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT).

§ 471.23 - New source performance standards (NSPS).

§ 471.24 - Pretreatment standards for existing sources (PSES).

§ 471.25 - Pretreatment standards for new sources (PSNS).

§ 471.26 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best conventional pollutant control technology (BCT). [Reserved]

§ 471.20 - Applicability; description of the magnesium forming subcategory.

This subpart applies to discharges of pollutants to waters of the United States, and introductions of pollutants into publicly owned treatment works from the process operations of the magnesium forming subcategory.

§ 471.21 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT).

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):

(a) Rolling spent emulsions.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium rolled with emulsions
Chromiun	0.033	0.014
Zinc	0.109	0.046
Ammonia	9.95	4.37
Fluoride	4.440	1.97
Oil and grease	1.49	0.895
TSS	3.06	1.46
pH		( ¹)

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

(b) Forging spent lubricants—subpart B—BPT. There shall be no discharge of process wastewater pollutants.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of forged magnesium cooled with water
Chromium	1.27	0.520
Zinc	4.22	1.77
Ammonia	385	170
Fluoride	172	76.3
Oil and grease	57.8	34.7
TSS	119	56.4
pH		( ¹)

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

(d) Forging equipment cleaning wastewater.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium forged
Chromium	0.018	0.007
Zinc	0.059	0.025
Ammonia	5.32	2.34
Fluoride	2.38	1.06
Oil and grease	0.798	0.479
TSS	1.64	0.778
pH		( ¹)

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

(e) Direct chill casting contact cooling water.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods
Chromium	1.74	0.711
Zinc	5.77	2.41
Ammonia	527	232
Fluoride	235	105
Oil and grease	79.0	47.4
TSS	162	77.1
pH		( ¹)

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

(f) Surface treatment spent baths.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	0.205	0.084
Zinc	0.681	0.285
Ammonia	62.1	27.3
Fluoride	27.8	12.3
Oil and grease	9.32	5.59
TSS	19.1	9.09
pH		( ¹)

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

(g) Surface treatment rinse.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	8.32	3.4
Zinc	27.6	11.5
Ammonia	2520	1110
Fluoride	1130	499
Oil and grease	378	227
TSS	775	369
pH		( ¹)

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

(h) Sawing or grinding spent emulsions.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sawed or ground
Chromium	0.009	0.004
Zinc	0.029	0.012
Ammonia	2.60	1.15
Fluoride	1.16	0.515
Oil and grease	0.390	0.234
TSS	0.800	0.381
pH		( ¹)

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

(i) Degreasing spent solvents—subpart B—BPT. There shall be no discharge of process wastewater pollutants.

(j) Wet air pollution control scrubber blowdown.

Subpart B—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged
Chromium	0.273	0.112
Zinc	0.904	0.378
Ammonia	82.5	36.3
Fluoride	36.9	16.4
Oil and grease	12.4	7.43
TSS	25.4	12.1
pH		( ¹)

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

§ 471.22 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT).

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 representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT):

(a) Rolling spent emulsions.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium rolled with emulsions
Chromium	0.033	0.014
Zinc	0.109	0.046
Ammonia	9.95	4.37
Fluoride	4.44	1.97

(b) Forging spent lubricants—subpart B—BAT. There shall be no discharge of process wastewater pollutants.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of forged magnesium cooled with water
Chromium	0.127	0.052
Zinc	0.422	0.177
Ammonia	38.5	17.0
Fluoride	17.2	7.63

(d) Forging equipment cleaning wastewater.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium forged
Chromium	0.002	0.0007
Zinc	0.006	0.003
Ammonia	0.532	0.234
Fluoride	0.238	0.106

(e) Direct chill casting contact cooling water.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods
Chromium	1.74	0.711
Zinc	5.77	2.41
Ammonia	527	232
Fluoride	235	105

(f) Surface treatment spent baths.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	0.205	0.084
Zinc	0.681	0.285
Ammonia	62.1	27.3
Fluoride	27.8	12.3

(g) Surface treatment rinse.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	0.832	0.340
Zinc	2.76	1.16
Ammonia	252	111
Fluoride	113	49.9

(h) Sawing or grinding spent emulsions.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sawed or ground
Chromium	0.009	0.004
Zinc	0.029	0.012
Ammonia	2.60	1.15
Fluoride	1.16	0.515

(i) Degreasing spent solvents—subpart B—BAT. There shall be no discharge of process wastewater pollutants.

(j) Wet air pollution control scrubber blowdown.

Subpart B—BAT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged
Chromium	0.273	0.112
Zinc	0.904	0.378
Ammonia	82.5	36.3
Fluoride	36.9	16.4

§ 471.23 - New source performance standards (NSPS).

Any new source subject to this subpart must achieve the following new source performance standards. The mass of pollutants in the magnesium forming process wastewater shall not exceed the following values:

(a) Rolling spent emulsions.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off/kg (pounds per million off-pounds) of magnesium rolled with emulsions
Chromium	0.028	0.011
Zinc	0.076	0.032
Ammonia	9.95	4.37
Fluoride	4.44	1.97
Oil and grease	0.746	0.746
TSS	1.12	0.895
pH	( ¹)	( ¹)

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

(b) Forging spent lubricants—subpart B—NSPS. There shall be no discharge of process wastewater pollutants.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off/kg (pounds per million off-pounds) of forged magnesium cooled with water
Chromium	0.107	0.044
Zinc	0.295	0.122
Ammonia	38.5	17.0
Fluoride	17.2	7.63
Oil and grease	2.89	2.89
TSS	4.34	3.47
pH	( ¹)	( ¹)

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

(d) Forging equipment cleaning wastewater.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off/kg (pounds per million off-pounds) of magnesium forged
Chromium	0.002	0.0006
Zinc	0.004	0.002
Ammonia	0.532	0.234
Fluoride	0.238	0.106
Oil and grease	0.040	0.040
TSS	0.060	0.048
pH	( ¹)	( ¹)

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

(e) Direct chill casting contact cooling water.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods
Chromium	1.46	0.593
Zinc	4.03	1.66
Ammonia	527	232
Fluoride	235	105
Oil and grease	39.5	39.5
TSS	59.3	47.4
pH	( ¹)	( ¹)

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

(f) Surface treatment spent baths.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	0.173	0.070
Zinc	0.476	0.196
Ammonia	62.1	27.3
Fluoride	27.8	12.3
Oil and grease	4.66	4.66
TSS	6.99	5.60
pH	( ¹)	( ¹)

¹ Within the range of 7.5 to 10.0 at all times

(g) Surface treatment rinse.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pound pers million off-pounds) of magnesium surface treated
Chromium	0.700	0.284
Zinc	1.93	0.794
Ammonia	252	111
Fluoride	113	49
Oil and grease	18.9	18.9
TSS	28.4	22.7
pH	( ¹)	( ¹)

¹ Within the range of 7.5 to 10.0 at all times

(h) Sawing or grinding spent emulsions.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sawed or ground
Chromium	0.007	0.003
Zinc	0.020	0.008
Ammonia	2.60	1.15
Fluoride	1.16	0.515
Oil and grease	0.195	0.195
TSS	0.293	0.234
pH	( ¹)	( ¹)

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

(i) Degreasing spent Solvents—subpart B—NSPS. There shall be no discharge of process wastewater pollutants.

(j) Wet air pollution control scrubber blowdown.

Subpart B—NSPS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged
Chromium	0.229	0.093
Zinc	0.632	0.260
Ammonia	82.5	36.3
Fluoride	36.9	16.4
Oil and grease	6.19	6.19
TSS	9.29	7.43
pH	( ¹)	( ¹)

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

[50 FR 34270, Aug. 23, 1985; 51 FR 2884, Jan. 22, 1986]

§ 471.24 - Pretreatment standards for existing sources (PSES).

Except as provided in 40 CFR 403.7 and 403.13, any existing source subject to this subpart which introduces pollutants into a publicly owned treatment works must comply with 40 CFR part 403 and by August 23, 1988 achieve the following pretreatment standards for existing sources (PSES). The mass of wastewater pollutants in magnesium forming process wastewater introduced into a POTW shall not exceed the following values:

(a) Rolling spent emulsions.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium rolled with emulsions
Chromium	0.033	0.014
Zinc	0.109	0.046
Ammonia	9.95	4.37
Fluoride	4.44	1.97

(b) Forging spent lubricants—subpart B—PSE. There shall be no discharge of process wastewater pollutants.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium cooled with water
Chromium	0.127	0.052
Zinc	0.422	0.177
Ammonia	38.5	17.0
Fluoride	17.2	7.63

(d) Forging equipment cleaning wastewater.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium forged
Chromium	0.002	0.0007
Zinc	0.006	0.003
Ammonia	0.532	0.234
Fluoride	0.238	0.106

(e) Direct chill casting contact cooling water.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods
Chromiun	1.74	0.711
Zinc	5.77	2.41
Ammonia	527	232
Fluoride	235	105

(f) Surface treatment spent baths.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromiun	0.205	0.084
Zinc	0.681	0.285
Ammonia	62.1	27.3
Fluoride	27.8	12.3

(g) Surface treatment rinse.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromiun	0.832	0.340
Zinc	2.76	1.16
Ammonia	252	111
Fluoride	113	49.9

(h) Sawing or grinding spent emulsions.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sawed or ground
Chromiun	0.009	0.004
Zinc	0.029	0.012
Ammonia	2.60	1.15
Fluoride	1.16	0.515

(i) Degreasing Spent Solvents—subpart B—PSES. There shall be no discharge of process wastewater pollutants.

(j) Wet air pollution control scrubber blowdown.

Subpart B—PSES

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged
Chromium	0.273	0.112
Zinc	0.904	0.378
Ammonia	8.25	36.3
Fluoride	36.9	16.4

[50 FR 34270, Aug. 23, 1985; 51 FR 2884, Jan. 22, 1986]

§ 471.25 - Pretreatment standards for new sources (PSNS).

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 (PSNS). The mass of wastewater pollutants in magnesium forming process wastewater introduced into a POTW shall not exceed the following values:

(a) Rolling spent emulsions.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium rolled with emulsions
Chromium	0.028	0.011
Zinc	0.076	0.032
Ammonia	9.95	4.37
Fluoride	4.44	1.97

(b) Forging spent lubricants—subpart B—PSNS. There shall be no discharge of process wastewater pollutants.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of forged magnesium cooled with water
Chromium	0.107	0.044
Zinc	0.295	0.122
Ammonia	38.5	17.0
Fluoride	17.2	7.63

(d) Forging equipment cleaning wastewater.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium forged
Chromium	0.002	0.0006
Zinc	0.004	0.002
Ammonia	0.532	0.234
Fluoride	0.238	0.106

(e) Direct chill casting contact cooling water.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium cast with direct chill methods
Chromium	1.46	0.593
Zinc	4.03	1.66
Ammonia	527	232
Fluoride	235	105

(f) Surface treatment spent baths.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	0.173	0.070
Zinc	0.476	0.196
Ammonia	62.1	27.3
Fluoride	27.8	12.3

(g) Surface treatment rinse.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium surface treated
Chromium	0.700	0.284
Zinc	1.93	0.794
Ammonia	252	111
Fluoride	113	49.9

(h) Sawing or grinding spent emulsions.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sawed or ground
Chromium	0.007	0.003
Zinc	0.020	0.008
Ammonia	2.60	1.15
Fluoride	1.16	0.515

(i) Degreasing spent solvents—subpart B—PSNS. There shall be no discharge of process wastewater pollutants.

(j) Wet air pollution control scrubber blowdown.

Subpart B—PSNS

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of magnesium sanded and repaired or forged
Chromium	0.229	0.093
Zinc	0.632	0.260
Ammonia	82.5	36.3
Fluoride	36.9	16.4

[50 FR 34270, Aug. 23, 1985; 51 FR 2884, Jan. 22, 1986]

§ 471.26 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best conventional pollutant control technology (BCT). [Reserved]

authority: Secs. 301, 304(b), (c), (e), and (g), 306(b) and (c), 307, 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) (the “Act”); 33 U.S.C. 1311,1314,c,e,and, 1316(b) andc,and; 86 Stat. 816, Pub. L. 92-500; 91 Stat. 1567, Pub. L. 95-217

source: 50 FR 34270, Aug. 23, 1985, unless otherwise noted.

cite as: 40 CFR 471.22