CFR > Title 40 - Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER N—EFFLUENT GUIDELINES AND STANDARDS (Parts 400–471) > PART 421—NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY > SUBPART B—Primary Aluminum Smelting Subcategory (§421.20 to §421.27) > 421.20—Applicability: description of the primary aluminum smelting subcategory.

421.20—Applicability: description of the primary aluminum smelting subcategory.

The provisions of this subpart are applicable to discharges resulting from the production of aluminum from alumina in the Hall-Heroult process.