Debunking Misleading Connections Between PFAS and PVDF Membranes
There is confusion in parts of the U.S. water industry, possibly fueled by non-PVDF membrane suppliers, around the connection of PVDF membranes and new regulations for PFAS compounds in drinking water. PVDF (Polyvinylidene fluoride) is the most widely used material in the manufacture of MF and UF membranes.
The confusion stems from proposed regulations in Europe that
would broadly define PFAS as any substance that contains at least one fully
fluorinated methyl (CF3) or methylene (CF2) carbon atom (without any H/Cl/Br/I
attached to it). This definition would cover a wide variety of chemical
structures, including PVDF. In contrast, the current USEPA definitions of PFAS
exclude PVDF including the most recent update of the structural
definition of PFAS.
The American Membrane Technology Association (AMTA) has
stated that PVDF is considered to be part of a class of high molecular weight
fluoropolymers that are distinct from non-polymeric PFAS and have distinctly
different physiochemical, toxicological and environmental characteristics. AMTA
also states that suppliers of PVDF used for water treatment membranes have
certified that there is no use of PFAS as processing aids. See the full AMTA Fact Sheet here.
So, with all of this regulatory discussion there is an ‘opportunity’
to confuse those that are not conversant in polymer chemistry and the correct
definitions. I have heard concerns from some end users and engineers that PVDF
membranes may release PFAS compounds and may therefore be banned in the future.
Coincidentally, these rumors are strongest where ceramic membranes are being
considered… Ironically, when offered PES membranes as a non-PVDF polymeric
membrane alternative, one engineer said they did not want to consider
‘unproven’ membranes, implying that ceramic membranes were considered more
proven... I’d say there are orders of magnitude more PES membrane capacity
installed than ceramic membranes, also with a lot longer operating history.
If an engineer and owner want to install ceramic membranes,
that is their decision to make. I just want to make sure PVDF membranes are not
misrepresented and decisions and made based on facts. Firstly, the European
regulations are not being proposed due to any concern that PVDF membranes are
releasing PFAS into drinking water. They are just a broad regulation to ban
production of products using PFAS materials (like Teflon). Secondly, there is
no evidence that PFAS compounds are released into drinking water from PVDF
membranes after use for over 20 years. As part of the development of
regulations for PFAS in drinking water, the USEPA has required extensive
testing of drinking water supplies and no connection with systems using PVDF
membranes has been made. Thirdly, the USEPA has indicated it has no intention
of banning PVDF or classifying it is a PFAS compound, irrespective of what
happens in Europe.
I know some water systems will still lean towards using
ceramic membranes due to concerns about future regulations against PVDF even
though this is highly unlikely. If they are prepared to pay a high premium for membranes as
insurance against this low probability, sobeit. Maybe less expensive insurance
would be to install an open platform/universal polymeric membrane system now,
that can be converted to ceramic if needed in the future.
The comments and opinions in this post are my own and not those of my employer.
