Could wastewater plant simply heat up water past 500C to decompose all chemicals and output clean water?

Submitted ⁨⁨3⁩ ⁨weeks⁩ ago⁩ by ⁨atro_city@fedia.io⁩ to ⁨nostupidquestions@lemmy.world⁩

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?

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Brainsploosh@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
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.

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- Redex68@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
  How the hell do people use that much water? Are they including water consumption needed for the products we use or? Let’s say a flush is 8L and the average person flushes 5 times a day, that’s 40L. The average person needs about 2L of water a day. Let’s say an average shower is 100L. Cleaning dishes at worst is probably like 20L per person without a dishwasher. That’s like 160L of water per day and I feel like most of those were over-estimates. How did they get to that number?
  
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  - jerkface@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
    They eat meat.
    
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  - Initiateofthevoid@lemmy.dbzer0.com ⁨3⁩ ⁨weeks⁩ ago
    Dishwashing is a significant underestimate here, and don’t forget hand-washing (before/after bathroom, food, cleaning…).
    
    Plus you missed outdoor and gardening, which would help explain why the Land of the ~~Free~~ Lawns uses more than anybody else.
    
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TerranFenrir@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
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.

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- dual_sport_dork@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
  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.
  
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  - lemming741@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
    You’d have heat exchangers, like a desalination plant
    
    …wikipedia.org/…/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
    
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- al_Kaholic@lemmynsfw.com ⁨3⁩ ⁨weeks⁩ ago
  Now explain making steel.
  
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  - Mothra@mander.xyz ⁨3⁩ ⁨weeks⁩ ago
    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.
    
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- Waterdoc@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
  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:
  
  canada.ca/…/per-polyfluoroalkyl-substances.html#a…
  
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- deegeese@sopuli.xyz ⁨3⁩ ⁨weeks⁩ ago
  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.
  
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ptc075@lemmy.zip ⁨3⁩ ⁨weeks⁩ ago
At the risk of sounding silly - Instead of focusing on burning the solids, boil the water. Water boils at 100C, at which point the water vapor should separate and leave all the solids behind. Then capture the vapors and condense it back down into clean water. Now, if you later want to incinerate the leftover solids, sure, go for it, fire’s always cool in my book.

I’ll add, simply boiling water is energy intensive. What you are proposing probably won’t work at any scale.

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- MajorMajormajormajor@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
  
  fire’s always cool in my book.
  
  I think you’re doing fire wrong, friendo.
  
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- I_Has_A_Hat@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
  Golly gee, if only there were some form of energy generation that required boiling vast amounts of water to turn into steam. But no, that would be silly.
  
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  - neukenindekeuken@sh.itjust.works ⁨3⁩ ⁨weeks⁩ ago
    You definitely wouldn’t want to drink the water from any of those systems you’re describing though :)
    
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- x00z@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
  I thought about this too for a while but I learned that even rain contains microplastics.
  
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- sploosh@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
  Yeah, turning wastewater plants into sewage distilleries doesn’t seem like a public health win.
  
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  - GreyEyedGhost@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
    What exactly do you think evaporation ponds are doing, then?
    
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specialseaweed@sh.itjust.works ⁨3⁩ ⁨weeks⁩ ago
No. The far more likely way to handle it is with flocculation/coagulation since plants are already set up to support this.

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- Waterdoc@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
  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.
  
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  - specialseaweed@sh.itjust.works ⁨3⁩ ⁨weeks⁩ ago
    Yes, that’s why I said my explanation was quick and dirty.
    
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Brkdncr@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
Where does the energy to do that come from.

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zxqwas@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
That sounds expensive.

And the chemicals decompose into what? How do you get whatever they decompose into out of the water?

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- Tja@programming.dev ⁨3⁩ ⁨weeks⁩ ago
  At 500C there’s not much water to speak of… And if they decompose enough it would be a bunch of carbon a hydrogen mainly, so a bit of CO2 and more water.
  
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pineapplelover@lemm.ee ⁨3⁩ ⁨weeks⁩ ago
This would be carcinogenic beyond imagination

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AstralPath@lemmy.ca ⁨3⁩ ⁨weeks⁩ ago
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?

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- bob_omb_battlefield@sh.itjust.works ⁨3⁩ ⁨weeks⁩ ago
  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.
  
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- truthfultemporarily@feddit.org ⁨3⁩ ⁨weeks⁩ ago
  Its above the critical point, so water will be a supercritical fluid. 370 C already requires 217 atm of pressure.
  
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YiddishMcSquidish@lemmy.today ⁨3⁩ ⁨weeks⁩ ago
The temperature will be impossible to maintain at any scale. Why do you think our high end computers use “water cooling”?

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robato@lemmy.world ⁨3⁩ ⁨weeks⁩ ago
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.

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Ledericas@lemm.ee ⁨2⁩ ⁨weeks⁩ ago
sounds expensive, you need alot of electricity to do that, its like desalination, its not cheap. heat my not dissociate chemical compounds.

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