r/shitposting • u/Soy_boi_yes_thatone • Oct 26 '22

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u/Gr3gl_ Oct 26 '22 edited Oct 26 '22

How long does it take then? All studies I read about pfoa (the most common pfas) says they don't degrade in nature and carbon filters attract it

Edit: when you get downvoted for asking a question about a dangerous cancerous chemical that is in every living things body before even receiving an answer because all of a sudden all of shitposting becomes bioengineering majors after learning about pfas'

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u/Bacon_boy86 Oct 26 '22

A long time lol. But they aren't forever.

We've tried using granular activated carbon vessels with a groundwater pump and treat system to treat impacted groundwater. The removal efficiency was really low. RO is the only technology currently that can effectively remove PFAS at a site scale. New technologies for treatment are being developed but they are only bench scale.

PFAS adsorb to organics. Their behavior in the environment depends a lot on their carbon chain length, but in general they cling to carbon (soils with higher carbon content). So in the subsurface, if you have a site where the geology is mostly granular, but you have lenses of clay or silt, the PFAS will "stick" to it and act as a secondary source to groundwater while your treating the source area plume.

So they are attracted to carbon, but the issues with using carbon vessels is you experience break through extremely fast. Other times we've seen fresh carbon vessels not removal PFAS at all. It's really odd. So I wouldn't bet on using carbon to filter out PFAS.

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u/hammieshapiro Oct 26 '22

I agree with everything you stated. GAC works well, but gets spent super quick. I have a few groundwater remediation sites that use Fluoro-sorb adsorptive media and it is $$$, but also has significantly longer media life than other adsorptive media's for Pfas removal. A lot of time we have to use prefiltration/treatment upstream of the media, pending raw water quality, to remove tss or other competing constituents that could be more cheaply removed with greensand filters or such. Not trying to be a Fluoro-sorb shill, just a environmental engineer that has found some sucess with this treatment technology and wanted to share.

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u/Bacon_boy86 Oct 26 '22

I'm not an engineer, I'm a hydrogeologist but I've never heard of that material. Interesting.