For the purpose of this subpart:

(a) Total Toxic Organics (TTO). TTO is a regulated parameter under PSES (§464.35) and PSNS (§464.36) for the ferrous subcategory and is comprised of a discrete list of toxic organic pollutants for each process segment where it is regulated, as follows:

(1) Casting Quench (§464.35(b) and §464.36(b)):

(2) Dust Collection Scrubber (§464.35(c) and §464.36(b)):

(3) Investment Casting (§464.35(e) and §464.36(e)):

(4) Melting Furnace Scrubber (§464.35(f) and §464.36(f)):

(5) Mold Cooling (§464.35(g) and §464.36(g)):

(6) Slag Quench (§464.35(h) and §464.36(h)):

(7) Wet Sand Reclamation (§464.35(i) and §464.36(i)):

(b) Cast Iron. An iron containing carbon in excess of the solubility in the austentite that exists in the alloy at the eutectic temperature. Cast iron also is defined here to include any iron-carbon alloys containing 1.2 percent or more carbon by weight.

(c) Ductile Iron. A cast iron that has been treated while molten with a master alloy containing an element such as magnesium or cerium to induce the formation of free graphite as nodules or spherules, which imparts a measurable degree of ductility to the cast metal.

(d) Gray Iron. A cast iron that gives a gray fracture due to the presence of flake graphite.

(e) Malleable Iron. A cast iron made by a prolonged anneal of white cast iron in which decarburization or graphitization, or both, take place to eliminate some or all of the cementite. Graphite is present in the form of temper carbon.

(f) Steel. An iron-base alloy containing carbon, manganese, and often other alloying elements. Steel is defined here to include only those iron-carbon alloys containing less than 1.2 percent carbon by weight.

(g) The “primary metal cast” shall mean the metal that is poured in the greatest quantity at an individual plant.

(h) Multiple Ferrous Melting Furnace Scrubber Configuration. A multiple ferrous melting furnace scrubber configuration is a configuration where two or more discrete wet scrubbing devices are employed in series in a single melting furnace exhaust gas stream. The ferrous melting furnace scrubber mass allowance shall be given to each discrete wet scrubbing device that has an associated wastewater discharge in a multiple ferrous melting furnace scrubber configuration. The mass allowance for each discrete wet scrubber shall be identical and based on the air flow of the exhaust gas stream that passes through the multiple scrubber configuration.

(i) Discrete Wet Scrubbing Device. A discrete wet scrubbing device is a distinct, stand-alone device that removes particulates and fumes from a contaminated gas stream by bringing the gas stream into contact with a scrubber liquor, usually water, and from which there is a wastewater discharge. Examples of discrete wet scrubbing devices are: Spray towers and chambers, venturi scrubbers (fixed and variable), wet caps, packed bed scrubbers, quenchers, and orifice scrubbers. Semi-wet scrubbing devices where water is added and totally evaporates prior to dry air pollution control are not considered to be discrete wet scrubbing devices. Ancillary scrubber operations such as fan washes and backwashes are not considered to be discrete wet scrubber devices. These ancillary operations are covered by the mass limitations of the associated scrubber. Aftercoolers are not considered to be discrete wet scrubbing devices, and water discharges from aftercooling are not regulated as a process wastewater in this category.