Our waterways are becoming more and more polluted due to PFAS, plastics, medicines, drugs, and new chemicals made by companies that just hand over the responsibility of cleaning to plants paid for by public moneys. Detecting the different chemicals and filtering them out if getting harder and harder. Could the simple solution of heating up past a point where even PFAS/forever chemicals decomposes (400C for PFAS, 500C to be more sure about other stuff) be alright?
Let’s assume that heating water to 500C does what you want it to do. Even then, the sheer amount of energy required to do this would be massive. It would just be incredibly uneconomical to do this, when other cheaper solutions (like not polluting in the first place) exist.
Not only that, but given that heating up volumes of water is basically the metric around which energy units and calculations are all derived, it’s easy to determine just how much energy.
Assuming an inlet temperature of a fairly optimistic 60°F or 15.56°C, it takes 12,934,470.48 joules to heat one US gallon of water to 500°C. Or if you prefer, possibly because you’re an American used to reading your electricity bill, 3.59 kWh to heat that gallon. Just one.
The EPA estimates that just in the US alone, wastewater plants treat 34 billion, with a B, gallons of water per day. No need to get out your calculator, that’s 122,060,000,000 kWh or if you prefer, just under 11.5 times the existing average daily power production of the entire country (10,640,243 MWh, if you’re wondering).
So, uh. Yeah. Probably not feasible.
You’d have heat exchangers, like a desalination plant
https://en.m.wikipedia.org/wiki/Multi-stage_flash_distillation
Such plants can operate at 23–27 kWh/m3 (appr. 90 MJ/m3) of distilled water.[5]
So still impossible, but not unfathomable
when other cheaper solutions (like not polluting in the first place) exist
That involves convincing your polluting cousin, who doesn’t believes climate change doesn’t exist, not to buy non-stick pans or not to dump their pills into the toilet.
Edit:
Let’s assume that heating water to 500C does what you want it to do.
That’s the question I’m asking btw.
You could always regulate and ban toxics at the point of production or sale, before they get into the waste stream
You realise water boils at 100°C, right?
Edit: yes, I know it boils a different temperatures, but we’re talking about 500°C for a practical use case at scale here…
You can still heat it up past 100 once it’s turned to vapor. However, it requires a ton of energy to convert it to vapor in the first place.
At standard pressure. high pressures can make it liquid. I can’t find charts that go high enough with a simple search but it looks like you need to get to 4000-5000psi. industry does go that high for some operations. It needs special design to toeit safely though.
Right… Have you considered that a basic order-of-magnitude estimate of scale of water, energy, and pressure requirements make the idea wildly infeasible in practice?
A lot is all I need to know. Since others have allready pointed out we have ways that work that use much less energy I don’t feel a need to estimate deeper.
Bit pendantic but I think its interesting: no, water doesn’t always boil at 100 °C. It can boil anywhere between -50 °C and 317 °C, depending on pressure.
On top of Mt. Everest you cannot cook potatoes because the water boils at 71 °C. On the other hand, with enough pressure water does not boil at all, instead becoming a supercritical fluid - a different phase from gas or liquid.
I think at this point, it would be more economical to distill the water than to burn up contaminants.
Now explain making steel.
There isn’t a steel supply tap to every house is it? I don’t think I’ve had to replace or buy any steel pieces over the last two months or so. Different story with water.
Why would you need to purify the water locally at everyone’s individual house? Your logic makes me chuckle. Just wait untill you find out about a steam engine.
Unfortunately, even if we stopped using PFAS entirely it will remain a legacy problem in wastewater and landfills because so many consumer products contain PFAS. That said, some places are working towards banning PFAS in new products and some of the really nasty ones are already banned in many countries. Here is Canada’s plan to phase PFAS out of industrial and consumer goods:
Heat exchangers are extremely efficient. You use the 500C water to heat 400C water, then use your 400C water to heat 300C water etc etc. It still takes energy, but you recover over 90% of it.
Stopping pollution is difficult, and filtering water is expensive, but boilers are well established technology.
Yes; this is something that has been studied. However as other commenters have said it requires a lot of energy, and is better suited for processing smaller quantities of water with a high level of PFAS contamination than massive quantities of water with an extremely low level of PFAS. It’s also not a standalone solution, as plenty of harmful chemicals survive heating past 400/500C (heavy metals like cadmium, lead, and mercury do not break down at any temperature).
In a practical sense, making lead hot won’t break it down. But I wonder if there is any temperature where lead would stop being lead and continue to not be lead after the results cool down again?
Alchemy! Now this is the out-of-the-box thinking that I like!
In all seriousness, lead is lead because it’s made of lead atoms. It can’t not be lead. (The reference to alchemy was because before we knew about atoms, many alchemists tried their hand at turning low-value metals like lead into high-value metals like gold).
To answer your question in a silly but scientifically accurate way, there is a temperature to which lead can be heated to become something else, but these are nuclear fusion temperatures, like you get in the Sun.
Much higher than the sun, unless you’re also adding the pressure of a star.
Magnetic fields should be able to extract lead.
Lead being an element means you would either need to make it radioactively decay somehow(which I’m not sure any form of lead is want to do) or perform some kind of alchemy.
Well… The Large Hadron Collider can smash lead nuclei together at nearly the speed of light, which turns them into something that is definitely no longer lead.
Thank you for the only response that actually answers the main question and linking to a scientific paper. Much appreciated.
Regarding harmful chemicals that do not decompose beyond 500C, could it be more likely that the number of such chemicals/materials (known and unknown) is much lower than the number of chemicals/materials at the temperatures used for current clarification processes?
No. The far more likely way to handle it is with flocculation/coagulation since plants are already set up to support this.
Edit: the quick and dirty overview: shit water comes in. Chlorine and other chemicals are added to the water which kills the bad stuff. Polymers are added to the water which binds to the chlorine, causing chunks. Chunks removed. Water discharged. You can change the polymers used to bind specifically to which pollutant is coming in.
That part of the process is called flocculation. Using it to add polymers that have additional capability (like removing microplastic) is where you’d want to do it. The cost is the polymer which would be some sort of reasonable, not rebuilding every plant that exists to boil water.
Check out the video on the flocculation page. Does a great job of showing how floc works.
https://en.m.wikipedia.org/wiki/Flocculation
https://en.m.wikipedia.org/w/index.php?title=Wastewater_treatment&wprov=rarw1
The difficulty is that you need to target all the pollutants and you can’t know of all the pollutants. There are new ones constantly entering the market and being discovered years, maybe even decades later.
Correct. Samples are taken regularly in order to determine if there’s something in there that’s not in the models or polymer table.
I can’t name names but there was a plant in Houston, TX that would have incoming water that would glow when a local very large company would illegally dump. I witnessed it personally after I overheard plant operators talking about it and I asked them to show me. Samples of the water would be taken and passed up to state authorities.
That was back when Texas had state authorities that sort of gave a shit about pollution.
They’re all gone now.
You COULD name names… Perhaps via Tor to a journalist
bruh it’s houston literally everyone is polluting on the east side of the city. the only people that don’t know are the people that don’t wanna know. honestly the fact that their plant never exploded killing people and belching nightmarish shit into the air made them good guys
For simplicity, this process is called clarification.
Unfortunately, coagulants are not effective at removing PFAS. The only effective methods for PFAS removal are adsorption (using granular activated carbon or ion exchange resins) or reverse osmosis filtration. These approaches are not used in traditional wastewater treatment because they are very expensive and are not required to meet registrations. However, potable reuse facilities will use these approaches to further treat wastewater effluent to drinking water standards. This is the future of water supply for arid areas like the southwest USA.
Also PS, the most commonly used coagulants are aluminum sulphate (alum) and ferric sulphate, which are not polymers. Polymers definitely are used (especially where I live) but they are more expensive and thus avoided when not needed.
Yes, that’s why I said my explanation was quick and dirty. Regular people don’t know what a plant does.
Where does the energy to do that come from.
Same place as nearly everything else, the Sun.
I’m not a scientist but wouldn’t the atmospheric pressure need to be insane to bring the boiling point of water to 500°C? Is that even possible?
500C is above the critical temperature for water. So it would probably be a supercritical fluid. Unless the pressure was above 10 GPa or so in which case it would be solid.
Its above the critical point, so water will be a supercritical fluid. 370 C already requires 217 atm of pressure.
Lava is 800 to 1200C and regularly comes in contact with water, which turns into vapor in our atmosphere.
It’s not about bringing the boiling point to 500C, but getting the water (vapor at that point) to 500C.
Raising water temperature from 10 to 500 degrees requires about 500 calories/mm3. That’s 2 MJ/litre, meaning if you want to heat 1 liter/second you need 2 MW with perfect insulation, so a power plant of say 10 MW.
A post industrial world citizen could probably get by on 200 l/day (US averages about 300/day). That needs 2 kW/person/day.
Total global energy production is about 630 EJ which averages out at about 12 TW.
Meaning if the whole global energy production went to treat water in that way, we have enough clean water for about 6 million people.
sounds expensive, you need alot of electricity to do that, its like desalination, its not cheap. heat my not dissociate chemical compounds. that high temp would probably degrade whatever container its in overtime. you’re better of using wastewater treatment and filtration systems.
Molten Salt Nuclear Reactors (like the one China’s making with thorium) operate at something like 700* C to generate electricity. With the waste heat, we could desalinate water. Instead of Yucca Mountain as a nuclear waste repository, it becomes Yucca Mountain Molten Salt Nuclear Reactor and brackish groundwater distillation for Las Vegas.
This, I like. The water would be radioactive though, wouldn’t it? I wonder if “exchanging” the unknown toxins for radioactivity in the dispelled water would be better or worse. But, it could maybe help decompose some of the toxic chemicals during in the process.
No. Radioactivity isn’t like a disease. Specific particles are radioactive. If you remove it prevent contamination form the first place, there is no reason the water would become radioactive. Heat is just heat.
That made no sense at all. Do you think toxic water is 100 toxins or that when somebody is sick they become one big walking disease?
And “water can’t become irradiated” is a great take. So radioactive radiation has no effect on water whatsoever? “High energy particles don’t exist and they can’t hurt you🧠”
This would be carcinogenic beyond imagination
Please explain.
Because you’re essentially cooking a cocktail of complex chemicals, many of which were never designed to be heated, and the result is often airborne toxins and volatile organic compounds (VOCs) that are far worse than drinking trace amounts of the original chemicals.the chemicals dont vanish or turn into pure air when vaporized. they degrade into other more harmful chemicals. which are carcinogenic and more toxic.
Can the degraded chemicals withstand sustained exposure to 500C?
The chemicals don’t just disappear, whatever they’ve degraded into will still remain.
Yes, but will they all be harmful?
they can get even worse than previous forms, so yes.
Got an example?
