Section 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) . 65 FR 81300 , Dec. 22, 2000, as amended at 68 FR 71023 , Dec. 22, 2003