this post was submitted on 10 Oct 2024
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collapse of the old society
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Is reverse osmosis enough or do I need a fancy PFAS filter too?
Reverse osmosis manages to remove about 90% of PFAS.
But I'm assuming it's with that weird effect where it gets 90% the first time but then that remaining 10% needs to be done like 40 times before it's "100%"
No clue, but I wouldn't even be surprised if parts of filtration systems use PFAS themselves as coatings or similar, to reduce friction in pumps, for water proofing etc.
If you already have reverse osmosis, you're probably good.
As a long cost option for others reading this, apparently the activated charcoal Berkey filters remove 100% of PFAS, and due to the filters being rated to last 8 years of continuous use, are exceptionally affordable.
To bring the costs even lower, you can just buy the filters and not the expensive stainless steel containers by drilling some holes in a 5gal plastic bucket for the filters (it's gravity fed) and place another bucket below to collect it.
To bring the cost even lower, you can make your own activated charcoal filters. Theyre very simple.
Thanks for the recommendation. They had to change the name after a Stop Sale order from the EPA for claims about filtering microbes. They're now Boroux filters.
One caution I have about carbon filters is regarding breakthrough. Activated carbon works through the contaminants "sticking" to it. Some contaminats are stickier than others. If a really sticky something comes along, it will knock off the less sticky thing that was already there. Hopefully this less sticky thing will restick further down the column, but there's a possibility for it to breakthrough into the filtered water. Imagine you're at a party with a friend and someone they like better shows up. The new person is stickier so you get knocked off. Now you can find someone else to hang out with, or just leave the party.
The particles like PFAS and microplastics are likely getting trapped in the pore space rather than being stuck to the carbon. This means that they won't come unstuck, but they will decrease the flow rate through the filter. Like having a car break down and block a lane of traffic.
@I_am_10_squirrels @ProdigalFrog There is more to it than just molecules getting "trapped in pore spaces" and it's a little complicated.
Activated carbon (and its more affordable, carbon-sequestering cousin #biochar) has functional attachment points on the edges of ring and plate molecular structures. These can attract and retain some substances from solution.
But the real fun happens when we add dopants. Other molecules present in the carbon matrix supercharge the chemical potential.
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@I_am_10_squirrels @ProdigalFrog The most exciting announcement I've seen in a long time is this one:
https://www.nature.com/articles/s44172-024-00267-4
Adding iron to biochar gives it the ability to adsorb *and* destroy PFAS in contaminated water. This is a product that can be produced relatively cheaply and contribute to drawdown of atmospheric CO2, and effectively degrades hazardous fluorocarbon pollutants with minimal disposal headaches after the fact.
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