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Fluorides, POTW influent, & metal finishing



Greetings,

   I am searching for information on materials that are used in industry that contain fluoride.

   An Indiana POTW will have a fluoride limit (2 mg/L) imposed in its NPDES permit.  The POTW is concerned that it will not meet the limit due to the average concentration (~8 mg/L which is two times the MCL of 4 mg/L) of fluoride in the POTW influent.  Downstream of the POTW discharge is an intake for another city's drinking water.

   The POTW is aware of one industrial user that etches steel using Fluoboric acid (Tetrafluoroboric acid).  The POTW would like that user to explore other chemicals for use as an etchant whereas the industrial user does not believe its use is contributing to the POTW's problem with fluorides.

   As part of the Office of Pollution Prevention & Technical Assistance, I would like to assess other possible sources (contributions from certain industrial sources, etc.) of fluorides to the POTW influent.  Perhaps there are industrial sources/uses that would commonly use materials that might cause a fluoride discharge.  Once I can narrow down the types of fluoride compounds used and the types of sources using them, I want to find fluoride subsitutes that could be considered/tested or possible use.

   It would be great not only to help the POTW, but to help the POTW help their industrial users.

   Thanks for your input in this matter.

Mark C. Stoddard
IDEM
OPPTA
mstoddar@dem.state.in.us