[Foreignborn]

For anyone wondering if this works, the EPA seems to think it does:

>>> High-pressure membranes, such as nanofiltration or reverse osmosis, have been extremely effective at removing PFAS. Reverse osmosis membranes are tighter than nanofiltration membranes. This technology depends on membrane permeability. A standard difference between the two is that a nanofiltration membrane will reject hardness to a high degree, but pass sodium chloride; whereas reverse osmosis membrane will reject all salts to a high degree. This also allows nanofiltration to remove particles while retaining minerals that reverse osmosis would likely remove.

>>> Research shows that these types of membranes are typically more than 90 percent effective at removing a wide range of PFAS, including shorter chain PFAS.

https://www.epa.gov/sciencematters/reducing-pfas-drinking-wa...

[axus]

Was curious, where does all the stuff that's filtered out go? And then industry sites like https://americanhomewater.com/the-truth-about-reverse-osmosi... raise more questions which probably have better answers.

[yojo]

RO systems use a lot of waste water. So the contaminants get concentrated into that and go out the sewer.

I’ve got one set up for my drinking water and it’s 1:1, so a gallon of waste water for every useful gallon. Others use even more.

[joenathanone]

You can dramatically increase efficiency by adding a permeate pump, search Amazon, they can be had very cheaply, they recycle the concentrate, increasing recovery and filter effectiveness.

[permo-w]

so you go through all the effort of removing them, then release them straight back into the water supply?

[yojo]

That’s… not how it works. The RO membrane keeps contaminants on one side of the barrier, but it requires that they still be in solution. It’s not like you isolate all the bad stuff then mix it back in, you’re just siphoning off some clean water from the rest of the mix.

Obviously I don’t feel great about the waste, but I’ve got two kids under 6 and I’m trying to do what I can to avoid dosing them with this crap.

I do my best to make up for it in other ways - not watering any landscaping, scraping but not rinsing dishes, water off while brushing teeth/lathering hands, low flow shower heads and toilets, etc. But I'm not aware of another way to get sufficiently clean water.

[sokoloff]

What else would you have them do? They are roughly only doubled in concentration and still mixed into hundreds of gallons of water per year.

[yojo]

The average 4 person house uses 190 gallons per day. About 4 of that is drinking water. So my wastewater contains about 2% more PFAS than a household not using an RO system. Assuming that all of it ends up in my body and not in the toilet.

[sokoloff]

Yes, I'm agreeing with you that you're doing the only remotely sensible thing. My calculation was considering only alternative disposal options for the RO wastewater, not your entire household water usage. (1 gallon of drinking water per person seems like an over-estimate as well, making your point ever so slightly stronger.)

[abduhl]

Good point. Knowingly, too. How much do you think we should fine these people?