40 CFR 437.21 - Effluent limitations attainable by the application of the best practicable control technology currently available (BPT).

Regulations last checked for updates: Feb 06, 2026

Title 40 - Protection of Environment last revised: Dec 22, 2026

View all text of Subpart B [§ 437.20 - § 437.26]

§ 437.21 - Effluent limitations attainable by the application of the best practicable control technology currently available (BPT).

Except as provided in 40 CFR 125.30 through 125.32 or § 437.20(b), any existing point source subject to this subpart must achieve the following effluent limitations representing the application of BPT:

BPT Limitations

Regulated parameter	Maximum daily ¹	Maximum monthly avg. ¹
Conventional Parameters
O&G	127	38.0
pH	( ²)	( ²)
TSS	74.1	30.6
Metal Parameters
Arsenic	2.95	1.33
Cadmium	0.0172	0.0102
Chromium	0.746	0.323
Cobalt	56.4	18.8
Copper	0.500	0.242
Lead	0.350	0.160
Mercury	0.0172	0.00647
Tin	0.335	0.165
Zinc	8.26	4.50
Organic Parameters
Bis(2-ethylhexyl) phthalate	0.215	0.101
Butylbenzyl phthalate	0.188	0.0887
Carbazole	0.598	0.276
n-Decane	0.948	0.437
Fluoranthene	0.0537	0.0268
n-Octadecane	0.589	0.302

¹ mg/L (ppm).

² Within the range 6 to 9.

[65 FR 81300, Dec. 22, 2000, as amended at 68 FR 71023, Dec. 22, 2003]

authority: 33 U.S.C. 1311,1314,1316,1317,1318,1342,and

source: 65 FR 81300, Dec. 22, 2000, unless otherwise noted.

cite as: 40 CFR 437.21