I’m a water engineer with a PhD, so not a tech nerd but definitely a nerd :) I came here mostly because I find the Reddit app annoying and the app I was using came here.

The Romans used lead as a sweetener…

I don’t know the details about alum production (assuming that is what you are referring to), but there are many alternative coagulants available now. Sure the supply logistics would be incredibly challenging and many people would have to boil their water or use point-of-use filters, but this take is pretty doomer in my opinion. Most plants use alum because it’s cheap and easy, not because it’s their only option.

Systems that were already using activated carbon or ion exchange for organics removal may have some treatment capacity, but otherwise the first systems specifically for treating drinking water are being designed and constructed now. There are contaminated sites that already have treatment or containment in place.

This is very interesting. Currently, most ion exchange systems that remove PFAS have to dispose of their brine as hazardous waste, which is very costly and doesn’t necessarily destroy PFAS - in Florida, for example, they inject the brine into a deep aquifer.

A lot of novel technologies target PFAS destruction in these concentrated waste streams, but often further concentration is required before you can effectively destroy PFAS with advanced oxidation processes. If they could use low-UV to destroy it without further concentration or additional chemicals (beside the salt already used to regenerate the resin), ion exchange would become a much better solution for treated PFAS contaminated water.

It’s “forever” in the environmental sense that they don’t break down naturally (or at least very, very slowly). That said, “forever chemicals” is more of a media buzzword than a term that scientists use.

Exactly my workflow, but I used R Markdown!

I wrote about half of my thesis in R Markdown using Git to backup my work. It’s fantastic because you can have your plots and statistics integrated directly into your paper and formatting in Markdown is much easier than straight up latex.

There are lots of things dissolved in our water that give it “flavour”, but the goal of all utilities is to minimize this as much as possible. Some water objectively tastes better than others, and a common segment of local drinking water conferences is a taste test. That said, for normal people usually the water they prefer is what their palette is used to. Someone who grew up drinking groundwater with very high alkalinity and pH will prefer that over surface water that is actually more “pure”. Similarly, if you normally drink water from a private well that you don’t add chlorine to, you likely dislike the taste of “city water”.

The common offenders for bad tasting water are excessive chlorine and some specific organic compounds. Both of these flavours can be removed using a granular activated carbon filter (e.g., a Britta), but you can actually remove the chlorine by just letting your water sit in the fridge for a while.

Some facts:

Background info.

• PFAS is a class of chemical substances with varying properties, but in general act as surfactants.

• PFAS are considered carcinogenic and impact birth weight.

• PFAS contain a carbon-fluorine bond, which is a very strong bond that does not naturally degrade.

• Some PFAS will naturally decrease concentration over time, but only to be transformed into other compounds that will not (often PFOS).

Regulation.

• The US EPA has taken the approach of regulating a select few PFAS, generally based on their known toxicity. PFOA and PFOS will essentially be limited to a concentration of zero.

• The US EPA has been working on this for years. Mr. Biden did not snap his fingers and make a regulation. These things move much slower than that, and the industry generally feels that this process moved too quickly because there is limited understanding of how much PFAS exists in drinking water.

• Health Canada has proposed a guideline which limits PFAS to 30 ng/L (ppt) as a total sum of all compounds that can be accurately measured. Currently their guidelines limit PFOA to 200 ng/L and PFOS to 600 ng/L. Health Canada does not regulate your water provider through, that is up to your provincial/territorial government, which may have different guidelines than this.

PFAS in the environment.

• PFAS is ubiquitous in the environment due to its travel through the water cycle. It exists in Antarctic ice and on top of Mount Everest.

• Usually the largest sources of PFAS in drinking water are firefighting training areas that used PFAS containing foams (airports and military bases), landfills, certain manufacturers (metal plating, paper, semiconductors), and municipal wastewater. There are many more sources than this though.

• Landfills and municipal wastewater tend to be the highest mass loading of PFAS because of the ubiquity of PFAS in consumer products.

Treatment.

• PFAS can be destroyed using electrochemical and thermal methods, but these are not feasible for drinking water treatment.

• The current approach for drinking water treatment is adsorption to either granular activated carbon (GAC) or ion exchange resin.

• Treating PFAS at the source is always the goal instead of treating it at a water treatment plant.

Feel free to ask questions, I will do my best to answer them!

They have settled several lawsuits already and there are more to come. It will never be enough, but it is inaccurate to say that they haven’t paid.

Not not contaminants are anthropogenic. Decomposing organic matter, heavy metals from soil and rock erosion, microorganisms and microbial by-products all naturally occur in wetlands and are dangerous to us. There’s nothing wrong with that, just don’t drink it or get it in open wounds :)

Clean is relative, there are lots of contaminants in wetland water that make it unsafe. They are incredibly important and very useful for naturally cleaning water, but please don’t drink the swamp water.

It’s not nothing, it’s just below the freezing point of water. Zero energy is zero Kelvin. This is also a bad take because Fahrenheit also goes negative. I suppose you should just start using Kelvin if that is your opinion.