40 CFR 471.81 - Effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT).

Regulations last checked for updates: Feb 16, 2025

Title 40 - Protection of Environment last revised: Nov 16, 2025

View all text of Subpart H [§ 471.80 - § 471.86]

§ 471.81 - 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 neat oils—subpart H—BPT. There shall be no discharge of process wastewater pollutants.

(b) Rolling spent emulsions.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc rolled with emulsions
Chromium	0.0006	0.0003
Copper	0.003	0.002
Cyanide	0.0004	0.0002
Zinc	0.002	0.0009
Oil and grease	0.028	0.017
TSS	0.057	0.027
pH	( ¹)	( ¹)

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

(c) Rolling contact cooling water.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc rolled with contact cooling water
Chromium	0.236	0.0097
Copper	1.02	0.536
Cyanide	0.156	0.065
Zinc	0.783	0.327
Oil and grease	10.7	6.43
TSS	22.0	10.5
pH	( ¹)	( ¹)

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

(d) Drawing spent emulsions.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc drawn with emulsions
Chromium	0.003	0.001
Copper	0.011	0.006
Cyanide	0.002	0.0007
Zinc	0.009	0.004
Oil and grease	0.116	0.070
TSS	0.238	0.113
pH	( ¹)	( ¹)

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

(e) Direct chill casting contact cooling water.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc cast by the direct chill method
Chromium	0.222	0.091
Copper	0.960	0.505
Cyanide	0.147	0.061
Zinc	0.738	0.308
Oil and grease	10.1	6.06
TSS	20.7	9.85
pH	( ¹)	( ¹)

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

(f) Stationary casting contact cooling water—subpart H—BPT. There shall be no discharge of process wastewater pollutants.

(g) Heat treatment contact cooling water.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc heat treated
Chromium	0.336	0.138
Copper	1.45	0.763
Cyanide	0.221	0.092
Zinc	1.12	0.466
Oil and grease	15.3	9.16
TSS	31.3	14.9
pH	( ¹)	( ¹)

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

(h) Surface treatment spent baths.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc surface treated
Chromium	0.039	0.016
Copper	0.169	0.089
Cyanide	0.026	0.011
Zinc	0.130	0.054
Oil and grease	1.78	1.07
TSS	3.64	1.73
pH	( ¹)	( ¹)

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

(i) Surface treatment rinse.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc surface treated
Chromium	1.58	0.645
Copper	6.80	3.58
Cyanide	1.04	0.430
Zinc	5.23	2.19
Oil and grease	71.6	43.0
TSS	147	69.8
pH	( ¹)	( ¹)

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

(j) Alkaline cleaning spent baths.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc alkaline cleaned
Chromium	0.002	0.0007
Copper	0.007	0.004
Cyanide	0.001	0.0004
Zinc	0.005	0.002
Oil and grease	0.071	0.043
TSS	0.146	0.069
pH	( ¹)	( ¹)

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

(k) Alkaline cleaning rinse.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc alkaline cleaned
Chromium	0.744	0.304
Copper	3.21	1.69
Cyanide	0.490	0.203
Zinc	2.47	1.03
Oil and grease	33.8	20.3
TSS	69.3	33.0
pH	( ¹)	( ¹)

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

(l) Sawing or grinding spent emulsions.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc sawed or ground with emulsions
Chromium	0.011	0.005
Copper	0.045	0.024
Cyanide	0.007	0.003
Zinc	0.035	0.015
Oil and grease	0.476	0.286
TSS	0.976	0.464
pH	( ¹)	( ¹)

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

(m) Electrocoating rinse.

Subpart H—BPT

Pollutant or pollutant property	Maximum for any 1 day	Maximum for monthly average
	mg/off-kg (pounds per million off-pounds) of zinc electrocoated
Chromium	1.01	0.412
Copper	4.35	2.29
Cyanide	0.664	0.275
Zinc	3.35	1.40
Oil and grease	45.8	27.5
TSS	93.9	44.7
pH	( ¹)	( ¹)

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

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

[50 FR 34270, Aug. 23, 1985; 51 FR 2888, Jan. 22, 1986]

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 471.81

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