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
So still impossible, but not unfathomable
edit:
122,060,000,000 kWh becomes
003,500,000,000 kWh
About a third of the national capacity
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:
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
Yeah, sure, but regulation needs enforcement and countries are pretty lax on that. Just look at England that was dumping toxins into rivers for decades and recently raised the allowed levels in order to continue doing so. If there were a way to go “whatever, all you need to do is install this and you can dump as much as you like because it won’t end up in the water anyway” wouldn’t that be preferable?
Barring the fact that most pollutants aren’t that easy to deal with, I don’t think so. I think you’d suffer from a kind of Jevon’s Paradox of toxicity, where people would just dump more in, until whatever “ok” threshold previously existed would be breached, and you’d be left in the same situation, just systematically worse.
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…
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.
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.
I think at this point, it would be more economical to distill the water than to burn up contaminants.
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.
sorry, thought I was replying to OP
There’s no need to be condescending. You seem to have misunderstood the question. I’m not trying to keep water liquid at 500C and decompose other particles at that temperature. The state of the water isn’t mentioned anywhere in my post, just the temperature.
FYI, lava is 800-1000C and regularly comes in contact with water. The resulting vapor has a temperature way higher than 100C.
Fair enough, sorry. It’s just that your question (and some of your answers) don’t seem to be accounting for dealing with the volume change of steam, and how that would be managed.
Also the fact that if you’re evaporating the water off anyway, why not just let it escape and concentrate the chemicals, and then deal with them that way? I’d guess most of them would not be in the vapour anyway? (unless they’re volatile, in which case they’d probably boil off even earlier)
Re: Lava contact. I don’t think the resulting water vapour is much more than 100°C? The phase change takes a lot of energy to phase change, and is still at about 100°C after that, and then the steam would escape very quickly, and be displaced by more water, so it would not have much chance to heat up more. The lava-water interface would always be at about 100°C, give or take a few tens of degrees for the Leidenfrost effect, maybe? I might be wrong here, but I can’t see how it would get MUCH hotter than 100°C (assuming normal surface pressure).
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:
https://www.canada.ca/en/health-canada/services/chemicals-product-safety/per-polyfluoroalkyl-substances.html#a3
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.
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.
Their point, which you quite clearly missed, is that people don’t need a steady, reliable, high volume flow of steel delivered to every single home and business.
And maybe you should look into steam engines a little more and check out things like how hot that water actually gets. You’re gonna discover that for all the prodigious fuel use, the temperature is far below the goal of 500C and the flow rate far below requirements. But keep up the sass.
The point you missed and everyone’s autism is preventing y’all from seeing that the fact that we have water and elecricity flowing to most houses in the USA. Things which were deemed impossible back in the day. Imagine the energy cost of conditioning the air individually at everyone’s house let alone their moving car too. It would be iMpOsSiBlE.
It’s not 100 perfect so let’s do nothing.- great idea enjoy your day.
An idea that requires 11.5 times more energy production on a daily basis than the entire country’s output is a lot more than “Not perfect.” So maybe you pipe down before you go calling everyone who disagrees with you autistic, m’kay?
You’re right technology never improves. I loved you in that movie “Idiocracy” Red_october he’s got what plants crave! Enjoy your job at Costco.
Heating water is a matter of physics, not technology. The amount of energy used to increase the temperature of water is literally how the units are defined. Do feel free to make a breakthrough on Fusion power though, I hear it’s still only 20 years away.