U.S. Code of Federal Regulations
Regulations most recently checked for updates: Aug 27, 2025
§ 437.10 - Applicability.
(a) Except as provided in § 437.1(b), (c), or (d) or in paragraph (b) of this section, this subpart applies to that portion of the discharge of wastewater from a CWT facility that results from the treatment of, or recovery of metals from, both metal-bearing wastes received from off-site and other CWT wastewater associated with the treatment of, or recovery of metal-bearing wastes.
(b) In order to ensure appropriate treatment rather than dilution of dissimilar wastes, an NPDES permit writer or control authority may require a new source or an existing facility subject to this subpart to achieve alternative effluent limitations and standards as defined in § 437.2(b) in the following circumstances:
(1) The facility receives, on a continuing basis, flows of process wastewater from five or fewer facilities subject to 40 CFR subchapter N limitations and standards; and
(2) The process wastewater flows received for treatment at the facility have relatively consistent pollutant profiles.
§ 437.11 - Effluent limitations attainable by the application of the best practicable control technology currently available (BPT).
(a) Except as provided in 40 CFR 125.30 through 125.32 or § 437.10(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 |
|---|---|---|
| O&G | 205 | 50.2 |
| pH | ( 2) | ( 2) |
| TSS | 60.0 | 31.0 |
| Antimony | 0.249 | 0.206 |
| Arsenic | 0.162 | 0.104 |
| Cadmium | 0.474 | 0.0962 |
| Chromium | 15.5 | 3.07 |
| Cobalt | 0.192 | 0.124 |
| Copper | 4.14 | 1.06 |
| Lead | 1.32 | 0.283 |
| Mercury | 0.00234 | 0.000739 |
| Nickel | 3.95 | 1.45 |
| Silver | 0.120 | 0.0351 |
| Tin | 0.409 | 0.120 |
| Titanium | 0.0947 | 0.0618 |
| Vanadium | 0.218 | 0.0662 |
| Zinc | 2.87 | 0.641 |
1 mg/L (ppm).
2 Within the range 6 to 9.
(b) The following in-plant limitations apply to metal-bearing wastewater containing cyanide:
In-Plant Limitations
| Regulated
parameter | Maximum daily 1 | Maximum monthly avg. 1 |
|---|---|---|
| Cyanide | 500 | 178 |
1 mg/L (ppm).
§ 437.12 - Effluent limitations attainable by the application of the best conventional pollutant control technology (BCT).
Except as provided in 40 CFR 125.30 through 125.32 or § 437.10(b), any existing point source subject to this subpart must achieve the following effluent limitations representing the application of BCT: Limitations for oil and grease, pH, and TSS are the same as the corresponding limitation specified in § 437.11(a).
§ 437.13 - Effluent limitations attainable by the application of the best available technology economically achievable (BAT).
(a) Except as provided in 40 CFR 125.30 through 125.32 or § 437.10(b), any existing point source subject to this subpart must achieve the following effluent limitations representing the application of BAT: Limitations for antimony, arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, tin, titanium, vanadium, and zinc are the same as the corresponding limitation specified in § 437.11(a).
(b) In-plant standards for cyanide are the same as the limitations specified in § 437.11(b).
§ 437.14 - New source performance standards (NSPS).
(a) Except as provided in § 437.10(b), any new source subject to this subpart must achieve the following performance standards:
Performance Standards
| Regulated
parameter | Maximum daily 1 | Maximum monthly avg. 1 |
|---|---|---|
| O&G | 205 | 50.2 |
| pH | ( 2) | ( 2) |
| TSS | 29.6 | 11.3 |
| Antimony | 0.111 | 0.0312 |
| Arsenic | 0.0993 | 0.0199 |
| Cadmium | 0.782 | 0.163 |
| Chromium | 0.167 | 0.0522 |
| Cobalt | 0.182 | 0.0703 |
| Copper | 0.659 | 0.216 |
| Lead | 1.32 | 0.283 |
| Mercury | 0.000641 | 0.000246 |
| Nickel | 0.794 | 0.309 |
| Selenium | 0.176 | 0.0698 |
| Silver | 0.0318 | 0.0122 |
| Tin | 0.0955 | 0.0367 |
| Titanium | 0.0159 | 0.00612 |
| Vanadium | 0.0628 | 0.0518 |
| Zinc | 0.657 | 0.252 |
1 mg/L (ppm).
2 Within the range 6 to 9.
(b) In-plant standards for cyanide are the same as the limitations specified in § 437.11(b).
§ 437.15 - Pretreatment standards for existing sources (PSES).
(a) Except as provided in 40 CFR 403.7, 403.13 or § 437.10(b), and no later than December 22, 2003, any existing source subject to this subpart must achieve the following pretreatment standards: Standards for antimony, arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, tin, titanium, vanadium, and zinc are the same as the corresponding limitation specified in § 437.11(a).
(b) In-plant standards for cyanide are the same as the limitations specified in § 437.11(b).
§ 437.16 - Pretreatment standards for new sources (PSNS).
(a) Except as provided in 40 CFR 403.7 or § 437.10(b), any new source subject to this subpart must achieve the following pretreatment standards: Standards for antimony, arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, tin, titanium, vanadium, and zinc are the same as the corresponding limitation specified in § 437.11(a)
(b) In-plant standards for cyanide are the same as the limitations specified in § 437.11(b).
