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Ask the Expert Question-and-Answer Archive
(Wastewater Treatment)

by Mike McGinness, EcoShield Environmental Systems, Inc.
May, 2008

433.10 Metal Finishing Subcategory

Q. 1) Would dipping of parts in diluted (alkaline) aqueous cleaners to remove cutting oils constitute chemical etching/milling? Is this a subjective interpretation by the oversight agency?

Q 2)re: the 40 process operations - is there a definition of "process operations" as cleaning or machining are so broad they could encompass virtually anything...  Again, is this a subjective interpretation by the oversight agency?

This is relevant as to what/how much must be pre-treated prior to discharge.

A. The way it works, if you have anything that meets the EPA 40 CFR definition of Electroplating, then and only then do the 40 Metal Finishing processes get added to the list of regulated items, and the category becomes Metal Finishing instead of just Electroplating. Alkaline cleaning is included in the 40 Metal Finishing processes included in the  Metal Finishing category. BUT, if you do not do any electroplating (which as you asked, or noted includes chemical milling, etching, phosphating, & coloring) then the 40 listed Metal Finishing processes are not regulated under Metal Finishing or Electroplating. So far I have not seen anyone try to call alkaline soap cleaning an electroplating process, but it is considered a Metal Finishing process in that list of 40 processes. Note that the metal finishing processes are not regulated under the electroplating rule, UNLESS there is electroplating (as defined in the electroplating rule) on the site first.

If there is no electroplating on site, there is a new category with tougher limits that covers water contact with metals in ANY washing process where metal is involved. It is called the Metal Products and Machinery category, or MP & M rule. If one rule does not cover you, then the other does, unless it is covered by another category already (the term is "not elsewhere regulated"), like metal vat or tank washing in a synthetic chemicals manufacturing  plant. They have their own category already.


Mike McGinness



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