(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.