Oh dear. After reading the notes in the study itself about the scale this was done at, scaling up might be an issue:
> A typical H₂O₂ synthesis reaction was carried out using 120 mg of 1% AuPd/TiO₂ [...] The reactor system was then pressurized, typically to 10 bar. The reactor was then cooled by a water bath to 2 °C. When the reactor had reached the required pressure and the flow through the system had stabilized, the solvent (H²O, HPLC grade), typically at a flow of 0.2 ml min¯¹, was introduced into the system.
Oh hey, 0.2 mL/min of water. In Virginia, the lowest flow cutoff for waterworks is 0.5 MGD (or 5000 people), the border between Class 3 and Class 4. That flow rate is 6.5 million times that done in the tests here. The large water treatment plant I worked at is another 400 times that, and there are plants that would be another 5 or 6 times that. So the necessary scaling factor is going to be measured in the billions.
So what about those reagants? This uses about 0.6 mg of gold to process 0.2 mL/min of water (if I'm reading the notation of 1% AuPd/TiO₂ correctly). Scale that to our small plant, and that's about $225,000 of gold and $350,000 of palladium. Go to the scale I worked at, and that's $190 million of catalyst in terms of raw metal worth alone. That's comparable to the cost of a regular treatment plant of that scale--just on the catalyst. This assumes that there's a neat linear scaling, which I doubt is going to be the case (square-cube law!).
Thanks for the insights, though let's remember that research is just a first step. This isn't a product being announced for the market. If we looked at the original research behind a lot of mature technology, we'd find the state of the technology to be similarly far from from production.
Now others can try to reproduce it, refine it, find other methods of producing the same reactive oxygen species, find substitutes that are more effective or cheaper, etc.
It doesn't have to be panacea either. Maybe it will fill a niche. It could save some lives.
“When the reactor had reached the required pressure and the flow through the system had stabilized, the solvent (H²O, HPLC grade), typically at a flow of 0.2 ml min¯¹, was introduced into the system.“
You’re making such a big deal of the 0.2 ml/min that you didn’t stop to read that it’s talking about the amount of solvent… you’re just stirring up drama for the sake of drama
If its effectiveness is as good as they say, seems like you could just use 1,000,000x less catalyst and end up with something as effective as current technology.
$190 million -> 190 bucks ;)
Seriously though, couldn't they just use far less catalyst and not have to deal with the prices you've calculated?
What does MGD mean, and what is it in SI units? Million gallons per day? US gal or Imperial ones? (I'm not being facetious -- I genuinely don't know and it's my understanding that the US mix parts of the old British Imperial system, e.g. BTU, together with their own)
(I should preface this by saying that, unlike you, I have no real water disinfection expertise, so I may be overlooking significant fundamentals in what follows.)
Those costs sound reasonable for niche uses (though I do think they would prevent it from "revolutionizing water disinfection technologies" as they claim in the Conclusions), and being able to operate in practical terms at a very small scale seems to me like an advantage rather than a disadvantage. It clearly is more expensive than conventional water treatment and would have difficulty scaling to replace it for reasons of material availability. Other alternative very-small-scale disinfection approaches are probably cheaper than their process in its current form; they mention ozonation, UV irradiation with germicidal lamps, photocatalytic disinfection, and the Fenton process in the paper and supplement.
I don't see how the square-cube law plays into it; the reason they're supporting the catalyst on rutile (anatase?) instead of just using solid bars of metal alloy is precisely to ensure neat linear scaling, and the reason it's 1% metal instead of 0.1% or 0.001% is that the rutile is in the form of 1–100 nm particles. (See p. 8/12 in the article and Fig. 4 on p. 7/12). The only square-cube thing that occurs to me is that a large ice bath requires much less ice input than a small ice bath, but that favors scaling the process up, not down.
A couple of other points:
⓪ Your calculations seem to be correct.
① People's drinking water needs are lower than you suggest by a factor of about 65, although conventional surface-water treatment plants cannot take advantage of this.
② You're not taking into account the supply-chain issues that plague smaller-scale treatment facilities.
③ The cost of consumables that this process would eliminate would still be lower than the cost of the catalyst.
④ There are plausible ways the process might be improved that could make it economic.
Here are the calculations in more detail, since I misread yours badly at least twice.
You say 0.5 MGD is 6.5 million times higher than the 0.2 mℓ/min (3.3 μℓ/s) in the experiment. 0.5 MGD is 21.9 ℓ/s, which is 6.6 million times higher than 3.3 μℓ/s.
I think you are reading it correctly; they do say their catalyst is 0.5% Au and 0.5% Pd on a TiO₂ support: 0.6 mg of gold and 0.6 mg of palladium to process 0.2 mℓ/min of water. The supplementary material has a plot of different catalyst mixes they tried (Sup. Fig. 14, p. 12, 13/32).
If we normalize that amount of catalyst metal to SI units, that's 180 gram seconds per liter (g·s/ℓ) each of gold and palladium. Your 0.5 MGD (22 ℓ/s) for 5000 people is 4.4 mℓ/s per person, which works out to 790 mg per person each of gold and palladium. Palladium at US$2800 per troy ounce (https://www.kitco.com/charts/livepalladium.html — that is per troy ounce, isn't it?) is US$90/g. Gold at US$1800 per troy ounce is US$58/g. Multiplying it out, that's US$71 of palladium per person and US$46 of gold per person, for a total of US$117 of catalyst metals per person. This seems likely to be the dominant cost of the whole shebang at anything larger than laboratory scale; the actual preparation of the catalyst with these metals by the process they reported in the paper might be even more expensive, but presumably cheaper methods are possible.
The 5000-person 0.5 mgd plant you cite as an example would need 3.9 kg of gold (US$230k) and of palladium (US$350k) for its catalysts, a total of US$580k, which is the number you gave for "our small plant".
790 mg of gold per person, times 7.7 billion people, would be about 6100 tonnes, about 3% of all the 200 000 tonnes of gold that has been mined so far. However, the corresponding 6100 tonnes of palladium would vastly exceed the above-ground stocks of palladium, estimated at 4.5 "moz", which I think means "million troy ounces", or 140 tonnes.
However, they also tried 1% gold without any palladium, and although this produced lower H₂O₂ concentrations, they were still high enough to be somewhat effective (≈80 ppm rather than 220 ppm, resulting in a 1.6 log₁₀ reduction rather than the 8.1 they were so satisfied with). So in the face of resource limits you could trade off a larger amount of gold and a longer residence time against scarce palladium.
① Potable water needs are 5.7 ℓ/day/person, not 380.
Your figure of 4.4 mℓ/s/person is 380 liters per day per person (100 gallons per day per person), but Burning Man recommends 1.5 gallons per day per person (5.7 liters/day/person, 0.066 mℓ/s/person), which includes water for showers, for cooking, and for drinking in a very dry environment with extensive physical exertion, though not for bidets. My experience at Burning Man is that you can get by on less.
That's 67 times less water than your figure.
Maybe your waterworks is supplying not only drinking water but also toilet-flushing water and lawn-irrigating water? Those don't normally need antibacterial treatment. Even the 0.2 mℓ/min benchtop catalyst they used in the paper (containing 5.4¢ of palladium and 3.5¢ of gold) would supply 0.29 liters per day; it would only need to be scaled up by a factor of 20 (to 12 mg gold (US$0.69) 12 mg palladium (US$1.10), 2.4 g rutile) to supply the requisite 5.7 liters per day per person.
Anytime you read things like 100,000,000 times more effective - you should be asking, what was the numerator or denominator in this. Or are they just describing some tiny part of the system.
For example, normally you need to filter, do settling for sediment etc - how did they solve all this?
Given the orders of magnitude involved here a 5 MGD plant could produce 500 trillion gallons per day of "commercial approach" water cleaning. The water handling issues alone in doing 500 trillion GPD seem large. Am I missing something?
If I've understood correctly, the denominator being compared against isn't a "best available alternative" treatment solution of H2O2. It's against the concentration that's an "equivalent amount"-- which is actually a pretty dilute concentration (for H2O2), that *isn't* effectively bactericidal.
>"...are over 10^7 times more potent than an equivalent amount of preformed hydrogen peroxide..."
Per fig. 2(c,d), the "commercial H2O2" items are solutions of 100 and 200 ppm (0.01% / 0.02%), and have nearly zero effect (less than 1 order-of-magnitude reduction in bacterial/viral viability).
([edit]: or quoting the paper itself: "These standardized preformed H2O2 samples, produced either commercially or catalytically (100–200ppm), exhibited limited bactericidal activity [my emphasis] against...")
Their actual point is that this H2O2+ROS is highly effective at a concentration at which H2O2 alone is not effective.
[edit]: In attempt to find further context, here's some data about disinfection with H2O2 solutions (in entirely different experimental setups which probably have important caveats I don't know):
>"...organisms with high cellular catalase activity (e.g., S. aureus, S. marcescens, and Proteus mirabilis) required 30–60 minutes of exposure to 0.6% hydrogen peroxide for a 10^8 reduction in cell counts, whereas organisms with lower catalase activity (e.g., E. coli, Streptococcus species, and Pseudomonas species) required only 15 minutes’ exposure [657]..."
So, as a hand-waving non-expert: it looks like you can get the same order of magnitude of effect (factor of 10^8 bacterial reduction) as the stuff in the OP paper, at a hydrogen peroxide concentration that's ~60 times higher than what OP uses (0.6% = 6000 ppm). (?)
"millions of times more effective at killing viruses and bacteria than traditional commercial methods.." "..revolutionise water disinfection technologies"
I don't think this is comparable to a water treatment plant. No sediment settling, biofiltration etc. It's comparable to sterilising water using hydrogen peroxide or boiling it, in a camping context.
> For example, normally you need to filter, do settling for sediment etc - how did they solve all this?
The key sentence should be this:
> In their study, the team tested the disinfection efficacy of commercially available hydrogen peroxide and chlorine compared to their new catalytic method.
In other words, no, this doesn't replace coagulation+flocculation, sedimentation, and filtration; it's only replacing the specific disinfectant in use.
The specific measure appears to be in CFU/mL of E. Coli in their test sample before and after. As you suspected, this does not include filtering or settling, just clearing out bacterial contamination.
I haven't read the paper yet (paywall)- just looked at their supplementary data.
The increased effectiveness appears (guessing here a bit) to be in terms of bacteria load reduction given similar concentration of bacteriacidal agents in same volume of liquid.
Yeah, the use of "millions of times better" just doesn't pass the sniff test. Given that current commercial methods kill 90%+ bacteria in water, thus, nothing can be even 2x better...and makes me suspicious of any claim in the article. Hopefully it can help people in areas that are currently without clean water, but I'm not holding my breath.
If you take your 90%+ as a baseline (ie zero) then you can fiddle with the stats to get a massive number.
Let's say the best effort is 91.001% and our smart new process is 92.001%. Now set the baseline at 91.000% This is the sleight of hand bit: If we say that "normal" is 91.000, we now set the best effort as 0.001 and our effort as 1.001. That can seem quite reasonable when trotted out by a news reader or reporter.
So we are (1.001/0.001) x 100 = 100,100% better than the previous best!
The real improvement is more like: 92.001/91.001 x 100 = 101.098% which is a bit obvious when you look at the numbers involved.
With a single quite clumsy move and a bit of misdirection you can turn 101 into 100,100 and sound quite convincing. Now that's only using the very basic arithmetic operations and a bit of bullshit. The clever kids can really go to town.
We need some sort of laws about the presentation of statistics because it really is getting out of hand. The nonsense I've just presented isn't fiction. I saw something similar recently, can't remember what for but it took a while for me to calm down afterwards 8)
> Given that current commercial methods kill 90%+ bacteria in water, thus, nothing can be even 2x better
That depends how you look at it. Is it 90% killed, or is it 10% survived? If it's 10% survived, then 100m times better is a system where 10/100m % survived instead.
(CFU/mL of E. Coli with stored H2O2) / (CFU/mL of E. Coli with catalysts) = 10M
With that in mind "millions of times better" isn't necessarily a disingenuous description. Though you might say it's somewhat misleading, since as the denominator goes to zero, the fraction goes to infinity :)
It's the equivalent of saying 99.99999999% uptime is "ten million times more available" than 99.9% uptime - um, just give me the number of nines please!
this is poor logic. imagine two disinfectants, A and B, both kill 90%+ of known bacteria. imagine that you need 1 part per billion for A to be effective and 10 million parts per billion for B to be effective.
“Better” does not necessarily mean “kills a higher percentage of bacteria”
By the way, this isn’t a comment on the article itself in any way, simply a comment on the logic of your comment
If you're measuring in (1-n) terms, you can be 2x better. 95% is 2x as good as 90% and 99.9% is 100x better. Not at all clear at first glance or sure that it's what they're doing here, but just something to keep in mind.
Wow, that’s incredible. Since it uses electricity for it’s energy input, this could be readily adapted for use in remote areas powered by solar plus battery. Even in Western nations this is a boon to treat well water sources instead of shock chlorination.
This combined with GAC filtration can produce very clean water anywhere you can get sunlight.
It needs gold and platinum catalyst. The trouble would be there would be no catalyst in the plant to process water, the day after it is deployed in a remote area.
The amount of electricity required wasn't mentioned, so while I'm hopeful that you're right I'm worried that the energy requirements will be prohibitive to adoption in many areas.
> The team showed that as the catalyst brought the hydrogen and oxygen together to form hydrogen peroxide, it simultaneously produced a number of highly reactive compounds, known as reactive oxygen species (ROS), which the team demonstrated were responsible for the antibacterial and antiviral effect, and not the hydrogen peroxide itself.
Interesting. I hope those aren't harmful to humans (or plants, or other animals). Also, from the high reactivity I suppose they might not stick around very long, which could be a good thing or a bad thing depending. It might be useful to be able to treat a large amount of water without leaving any long-lasting impurities, but on the other hand you might have to treat the water again if you want to store it any length of time... On the other hand, if a reactive thing doesn't have anything to react with, maybe it does persist for a long while?
Funny, there was a report on Swiss TV[1] just yesterday where they were talking about how concentrating water cleaning systems is more effective. The went from 11 to 2 large water cleaning facilities in the Kanton of Uri as it is a lot easier to keep those using the latest standard than to maintain 11 separate facilities. They now pump the dirty water at hight pressure to the 2 facilities because of the large altitude drop the the pressure needs to be reduced so electricity is also generated from the waste water. The pipeline last around 70 years while a cleaning facility needs an overhaul every 25 years.
This got me thinking about what we could and could not do if we had a magical a energy-unbottlenecker, say an infinite capacity battery with arbitrary power output.
These become much cheaper:
- Transport: synthesise fuel from CO2 + seawater. Or charge a battery.
- Water: electrolysis of seawater.
- Food grown anywhere: Light + water + fertiliser can be made from commonly available materials. Soil is a bit trickier, but I think you could bootstrap up with composting.
- Global warming: pull CO2 out of the air.
- Raw materials (concrete, metals): all cheaper to extract with free energy.
- producing medicine
Still really hard:
- making new treatments
- inflation of housing prices
- escaping earth's gravity (need bounce per ounce)
- world peace
- writing books
- politics
I don't think its fair to say they are "energy" issues, or that they are bottlenecked by a lack of energy.
When building the desalination plant, we can build a solar farm right next door.
The problems are political. Nobody is willing to go out and spend the money.
My hope is that when automation starts taking peoples jobs, governments will employ and train people to build these big infrastructure projects. Desalination, Green Energy, Reforestation, better Agriculture and Land Management.
I feel that, once you have reduced the consumables of something to energy, that doesn't tend to make it energy limited. Instead, it becomes capital limited. You need to be able to pay for the upfront capital costs of installing the thing.
Add to that the fact that, once these developments have happened, they tend to improve a lot, quickly. That means anything you build will, soon, be outdated and stop producing as much yield. Hence, you don't want to invest too much.
Nice, but it seems the method is not exactly new. Here's a short nature article from the 2nd of March 2016 talking about the same research programme on catalysts at Cardiff University.
How much gold and palladium are required? Those are massively expensive catalysts and it feels borderline disingenuous to talk about how this will bring clean drinking water to the masses without so much as mentioning cost.
Imagine some kind of Ice9 scenario but instead with a catalytic everlasting ultra-disinfectant released into the water cycle. Could it be stopped? Do we live with it? Does everything die and the world enters a new age of archae supremacy?
What if it didn’t evaporate so it was oceans only — is the plot about mankind living without fish suppers or is there more to it? The oceans effectively become poisonous to humans too of course. Any city with brackish tidal rivers becomes affected. Does the disinfectant work immediately — do salmon carry it up river? Salmon ladders get blown up by desperate citizens who inadvertently destroy the dams to which the ladders are attached etc.
I like hard scifi plots. I am not suggesting this is an actual risk. Time to re-read some classics.
Though I wish this article addressed some of the questions I had around commercialization, namely the cost of the gold + palladium, the expected lifecycle, and the expected maintenance routine (e.g. do they have to be regularly removed and cleaned?).
The article makes great arguments for why this should work (i.e. hydrogen peroxide is already being used, this just short-circuits how we get a known effective cleaning agent, reducing/removing logistics inefficiencies). So a lot of the question is: Is this cheaper/less hassle than buying stabilized hydrogen peroxide commercially?
A lot of these fantastic advances often end up in the black hole, wherein they work as advertised, but the financials/logistics never line up and therefore nobody uses them in anger.
> So a lot of the question is: Is this cheaper/less hassle than buying stabilized hydrogen peroxide commercially?
From the article: "The team showed that as the catalyst brought the hydrogen and oxygen together to form hydrogen peroxide, it simultaneously produced a number of highly reactive compounds, known as reactive oxygen species (ROS), which the team demonstrated were responsible for the antibacterial and antiviral effect, and not the hydrogen peroxide itself."
I used to have a camping water purifier from MSR that they developed with a company called MIOX. It ran on batteries and had a little catalyst and you put salt solution in and it fizzed and produced chlorine that you poured into your water bottles. It smelled like a pool. As long as you had batteries and salt you could make an infinite amount of chlorine.
It looks like MIOX is still around [0], they make portable units for the military and for temporary installation but I imagine this approach isn't cost effective for a permanent facility.
Considering that catalytic converters are routinely stolen from cars in car parks in places like the UK, I wouldn't feel confident installing expensive catalysts in the places where this would be needed.
A tangentially related development recently has been peroxide generators to put inside buildings to generate enough hydrogen peroxide to sterilize the air/surfaces without being a health hazard. I've recently had a local school district request that we analyze these devices as an option for COVID mitigation: https://synexis.com/science/reports-data/
yeah, we will take the catalysts that get donated and buy our way out of the third world!
"heres a solution for limitless free energy! step one, launch a bunch of solar reflectors into space to reflect solar energy at concentrated points on the surface of the earth. Step 2, wait, you don't have a scalable and advanced aerospace industry capable of launching thousands of collectors into orbit? I guess this won't work for you."
[edit: commenter is right, the paper abstract rendered as "107" not "10^7" in browser, will leave followup question]
Since it's a challenge to separate the products/byproducts in catalytic reactions that are homogenous/liquid phases, how would this setup achieve separation post reaction exactly? Anyone know?
[+] [-] jcranmer|4 years ago|reply
> A typical H₂O₂ synthesis reaction was carried out using 120 mg of 1% AuPd/TiO₂ [...] The reactor system was then pressurized, typically to 10 bar. The reactor was then cooled by a water bath to 2 °C. When the reactor had reached the required pressure and the flow through the system had stabilized, the solvent (H²O, HPLC grade), typically at a flow of 0.2 ml min¯¹, was introduced into the system.
Oh hey, 0.2 mL/min of water. In Virginia, the lowest flow cutoff for waterworks is 0.5 MGD (or 5000 people), the border between Class 3 and Class 4. That flow rate is 6.5 million times that done in the tests here. The large water treatment plant I worked at is another 400 times that, and there are plants that would be another 5 or 6 times that. So the necessary scaling factor is going to be measured in the billions.
So what about those reagants? This uses about 0.6 mg of gold to process 0.2 mL/min of water (if I'm reading the notation of 1% AuPd/TiO₂ correctly). Scale that to our small plant, and that's about $225,000 of gold and $350,000 of palladium. Go to the scale I worked at, and that's $190 million of catalyst in terms of raw metal worth alone. That's comparable to the cost of a regular treatment plant of that scale--just on the catalyst. This assumes that there's a neat linear scaling, which I doubt is going to be the case (square-cube law!).
[+] [-] wolverine876|4 years ago|reply
Now others can try to reproduce it, refine it, find other methods of producing the same reactive oxygen species, find substitutes that are more effective or cheaper, etc.
It doesn't have to be panacea either. Maybe it will fill a niche. It could save some lives.
[+] [-] aardvarkr|4 years ago|reply
You’re making such a big deal of the 0.2 ml/min that you didn’t stop to read that it’s talking about the amount of solvent… you’re just stirring up drama for the sake of drama
[+] [-] mmazing|4 years ago|reply
$190 million -> 190 bucks ;)
Seriously though, couldn't they just use far less catalyst and not have to deal with the prices you've calculated?
[+] [-] azalemeth|4 years ago|reply
[+] [-] yxhuvud|4 years ago|reply
[+] [-] kragen|4 years ago|reply
Those costs sound reasonable for niche uses (though I do think they would prevent it from "revolutionizing water disinfection technologies" as they claim in the Conclusions), and being able to operate in practical terms at a very small scale seems to me like an advantage rather than a disadvantage. It clearly is more expensive than conventional water treatment and would have difficulty scaling to replace it for reasons of material availability. Other alternative very-small-scale disinfection approaches are probably cheaper than their process in its current form; they mention ozonation, UV irradiation with germicidal lamps, photocatalytic disinfection, and the Fenton process in the paper and supplement.
I don't see how the square-cube law plays into it; the reason they're supporting the catalyst on rutile (anatase?) instead of just using solid bars of metal alloy is precisely to ensure neat linear scaling, and the reason it's 1% metal instead of 0.1% or 0.001% is that the rutile is in the form of 1–100 nm particles. (See p. 8/12 in the article and Fig. 4 on p. 7/12). The only square-cube thing that occurs to me is that a large ice bath requires much less ice input than a small ice bath, but that favors scaling the process up, not down.
A couple of other points:
⓪ Your calculations seem to be correct.
① People's drinking water needs are lower than you suggest by a factor of about 65, although conventional surface-water treatment plants cannot take advantage of this.
② You're not taking into account the supply-chain issues that plague smaller-scale treatment facilities.
③ The cost of consumables that this process would eliminate would still be lower than the cost of the catalyst.
④ There are plausible ways the process might be improved that could make it economic.
Thanks to mkr-hn I found the paper at https://www.researchgate.net/publication/352882305_A_residue... the canonical paper link (unforgivably missing from the original press release) is https://www.nature.com/articles/s41929-021-00642-w, and the supplementary material is at https://static-content.springer.com/esm/art%3A10.1038%2Fs419....
— ⁂ —
⓪ Scaling calculations.
Here are the calculations in more detail, since I misread yours badly at least twice.
You say 0.5 MGD is 6.5 million times higher than the 0.2 mℓ/min (3.3 μℓ/s) in the experiment. 0.5 MGD is 21.9 ℓ/s, which is 6.6 million times higher than 3.3 μℓ/s.
I think you are reading it correctly; they do say their catalyst is 0.5% Au and 0.5% Pd on a TiO₂ support: 0.6 mg of gold and 0.6 mg of palladium to process 0.2 mℓ/min of water. The supplementary material has a plot of different catalyst mixes they tried (Sup. Fig. 14, p. 12, 13/32).
If we normalize that amount of catalyst metal to SI units, that's 180 gram seconds per liter (g·s/ℓ) each of gold and palladium. Your 0.5 MGD (22 ℓ/s) for 5000 people is 4.4 mℓ/s per person, which works out to 790 mg per person each of gold and palladium. Palladium at US$2800 per troy ounce (https://www.kitco.com/charts/livepalladium.html — that is per troy ounce, isn't it?) is US$90/g. Gold at US$1800 per troy ounce is US$58/g. Multiplying it out, that's US$71 of palladium per person and US$46 of gold per person, for a total of US$117 of catalyst metals per person. This seems likely to be the dominant cost of the whole shebang at anything larger than laboratory scale; the actual preparation of the catalyst with these metals by the process they reported in the paper might be even more expensive, but presumably cheaper methods are possible.
The 5000-person 0.5 mgd plant you cite as an example would need 3.9 kg of gold (US$230k) and of palladium (US$350k) for its catalysts, a total of US$580k, which is the number you gave for "our small plant".
790 mg of gold per person, times 7.7 billion people, would be about 6100 tonnes, about 3% of all the 200 000 tonnes of gold that has been mined so far. However, the corresponding 6100 tonnes of palladium would vastly exceed the above-ground stocks of palladium, estimated at 4.5 "moz", which I think means "million troy ounces", or 140 tonnes.
However, they also tried 1% gold without any palladium, and although this produced lower H₂O₂ concentrations, they were still high enough to be somewhat effective (≈80 ppm rather than 220 ppm, resulting in a 1.6 log₁₀ reduction rather than the 8.1 they were so satisfied with). So in the face of resource limits you could trade off a larger amount of gold and a longer residence time against scarce palladium.
① Potable water needs are 5.7 ℓ/day/person, not 380.
Your figure of 4.4 mℓ/s/person is 380 liters per day per person (100 gallons per day per person), but Burning Man recommends 1.5 gallons per day per person (5.7 liters/day/person, 0.066 mℓ/s/person), which includes water for showers, for cooking, and for drinking in a very dry environment with extensive physical exertion, though not for bidets. My experience at Burning Man is that you can get by on less.
That's 67 times less water than your figure.
Maybe your waterworks is supplying not only drinking water but also toilet-flushing water and lawn-irrigating water? Those don't normally need antibacterial treatment. Even the 0.2 mℓ/min benchtop catalyst they used in the paper (containing 5.4¢ of palladium and 3.5¢ of gold) would supply 0.29 liters per day; it would only need to be scaled up by a factor of 20 (to 12 mg gold (US$0.69) 12 mg palladium (US$1.10), 2.4 g rutile) to supply the requisite 5.7 liters per day per person.
(continued below)
[+] [-] slownews45|4 years ago|reply
For example, normally you need to filter, do settling for sediment etc - how did they solve all this?
Given the orders of magnitude involved here a 5 MGD plant could produce 500 trillion gallons per day of "commercial approach" water cleaning. The water handling issues alone in doing 500 trillion GPD seem large. Am I missing something?
[+] [-] perihelions|4 years ago|reply
>"...are over 10^7 times more potent than an equivalent amount of preformed hydrogen peroxide..."
Per fig. 2(c,d), the "commercial H2O2" items are solutions of 100 and 200 ppm (0.01% / 0.02%), and have nearly zero effect (less than 1 order-of-magnitude reduction in bacterial/viral viability).
([edit]: or quoting the paper itself: "These standardized preformed H2O2 samples, produced either commercially or catalytically (100–200ppm), exhibited limited bactericidal activity [my emphasis] against...")
Their actual point is that this H2O2+ROS is highly effective at a concentration at which H2O2 alone is not effective.
https://www.researchgate.net/publication/352882305_A_residue...
~~~~~
[edit]: In attempt to find further context, here's some data about disinfection with H2O2 solutions (in entirely different experimental setups which probably have important caveats I don't know):
>"...organisms with high cellular catalase activity (e.g., S. aureus, S. marcescens, and Proteus mirabilis) required 30–60 minutes of exposure to 0.6% hydrogen peroxide for a 10^8 reduction in cell counts, whereas organisms with lower catalase activity (e.g., E. coli, Streptococcus species, and Pseudomonas species) required only 15 minutes’ exposure [657]..."
https://www.cdc.gov/infectioncontrol/pdf/guidelines/disinfec... (page 47)
So, as a hand-waving non-expert: it looks like you can get the same order of magnitude of effect (factor of 10^8 bacterial reduction) as the stuff in the OP paper, at a hydrogen peroxide concentration that's ~60 times higher than what OP uses (0.6% = 6000 ppm). (?)
[+] [-] dalbasal|4 years ago|reply
I don't think this is comparable to a water treatment plant. No sediment settling, biofiltration etc. It's comparable to sterilising water using hydrogen peroxide or boiling it, in a camping context.
Not sure what the "millions of times" measures.
[+] [-] jcranmer|4 years ago|reply
The key sentence should be this:
> In their study, the team tested the disinfection efficacy of commercially available hydrogen peroxide and chlorine compared to their new catalytic method.
In other words, no, this doesn't replace coagulation+flocculation, sedimentation, and filtration; it's only replacing the specific disinfectant in use.
[+] [-] icegreentea2|4 years ago|reply
I haven't read the paper yet (paywall)- just looked at their supplementary data.
The increased effectiveness appears (guessing here a bit) to be in terms of bacteria load reduction given similar concentration of bacteriacidal agents in same volume of liquid.
[+] [-] mkr-hn|4 years ago|reply
[+] [-] unknown|4 years ago|reply
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[+] [-] rmah|4 years ago|reply
[+] [-] gerdesj|4 years ago|reply
Let's say the best effort is 91.001% and our smart new process is 92.001%. Now set the baseline at 91.000% This is the sleight of hand bit: If we say that "normal" is 91.000, we now set the best effort as 0.001 and our effort as 1.001. That can seem quite reasonable when trotted out by a news reader or reporter.
So we are (1.001/0.001) x 100 = 100,100% better than the previous best!
The real improvement is more like: 92.001/91.001 x 100 = 101.098% which is a bit obvious when you look at the numbers involved.
With a single quite clumsy move and a bit of misdirection you can turn 101 into 100,100 and sound quite convincing. Now that's only using the very basic arithmetic operations and a bit of bullshit. The clever kids can really go to town.
We need some sort of laws about the presentation of statistics because it really is getting out of hand. The nonsense I've just presented isn't fiction. I saw something similar recently, can't remember what for but it took a while for me to calm down afterwards 8)
[+] [-] mabbo|4 years ago|reply
That depends how you look at it. Is it 90% killed, or is it 10% survived? If it's 10% survived, then 100m times better is a system where 10/100m % survived instead.
[+] [-] gus_massa|4 years ago|reply
[+] [-] TimTheTinker|4 years ago|reply
With that in mind "millions of times better" isn't necessarily a disingenuous description. Though you might say it's somewhat misleading, since as the denominator goes to zero, the fraction goes to infinity :)
It's the equivalent of saying 99.99999999% uptime is "ten million times more available" than 99.9% uptime - um, just give me the number of nines please!
[+] [-] permo-w|4 years ago|reply
“Better” does not necessarily mean “kills a higher percentage of bacteria”
By the way, this isn’t a comment on the article itself in any way, simply a comment on the logic of your comment
[+] [-] mathstuf|4 years ago|reply
[+] [-] sp332|4 years ago|reply
[+] [-] tristor|4 years ago|reply
This combined with GAC filtration can produce very clean water anywhere you can get sunlight.
[+] [-] wanderingmind|4 years ago|reply
[+] [-] riknos314|4 years ago|reply
[+] [-] jimmaswell|4 years ago|reply
[+] [-] elihu|4 years ago|reply
Interesting. I hope those aren't harmful to humans (or plants, or other animals). Also, from the high reactivity I suppose they might not stick around very long, which could be a good thing or a bad thing depending. It might be useful to be able to treat a large amount of water without leaving any long-lasting impurities, but on the other hand you might have to treat the water again if you want to store it any length of time... On the other hand, if a reactive thing doesn't have anything to react with, maybe it does persist for a long while?
[+] [-] sschueller|4 years ago|reply
[1] https://www.srf.ch/play/tv/sendung/schweiz-aktuell?id=cb28dd...
[+] [-] grenoire|4 years ago|reply
What are some other basic problems (food, water, temperature management, etc.) we're facing that are primarily energy-bottlenecked?
[+] [-] hazbot|4 years ago|reply
These become much cheaper:
- Transport: synthesise fuel from CO2 + seawater. Or charge a battery. - Water: electrolysis of seawater. - Food grown anywhere: Light + water + fertiliser can be made from commonly available materials. Soil is a bit trickier, but I think you could bootstrap up with composting. - Global warming: pull CO2 out of the air. - Raw materials (concrete, metals): all cheaper to extract with free energy. - producing medicine
Still really hard: - making new treatments - inflation of housing prices - escaping earth's gravity (need bounce per ounce) - world peace - writing books - politics
[+] [-] jay_kyburz|4 years ago|reply
When building the desalination plant, we can build a solar farm right next door.
The problems are political. Nobody is willing to go out and spend the money.
My hope is that when automation starts taking peoples jobs, governments will employ and train people to build these big infrastructure projects. Desalination, Green Energy, Reforestation, better Agriculture and Land Management.
[+] [-] rocqua|4 years ago|reply
Add to that the fact that, once these developments have happened, they tend to improve a lot, quickly. That means anything you build will, soon, be outdated and stop producing as much yield. Hence, you don't want to invest too much.
[+] [-] shados|4 years ago|reply
[+] [-] cpottamus|4 years ago|reply
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[+] [-] _0ffh|4 years ago|reply
https://www.nature.com/articles/531011b
[+] [-] sp332|4 years ago|reply
[+] [-] forgotmypw17|4 years ago|reply
"Cleaning" is much different from "disinfecting", sometimes the opposite.
[+] [-] xfour|4 years ago|reply
[+] [-] felixfurtak|4 years ago|reply
It's the same reason that we're not all driving around in hydrogen powered cars.
[+] [-] gundmc|4 years ago|reply
[+] [-] unknown|4 years ago|reply
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[+] [-] gorgoiler|4 years ago|reply
What if it didn’t evaporate so it was oceans only — is the plot about mankind living without fish suppers or is there more to it? The oceans effectively become poisonous to humans too of course. Any city with brackish tidal rivers becomes affected. Does the disinfectant work immediately — do salmon carry it up river? Salmon ladders get blown up by desperate citizens who inadvertently destroy the dams to which the ladders are attached etc.
I like hard scifi plots. I am not suggesting this is an actual risk. Time to re-read some classics.
[+] [-] Someone1234|4 years ago|reply
Though I wish this article addressed some of the questions I had around commercialization, namely the cost of the gold + palladium, the expected lifecycle, and the expected maintenance routine (e.g. do they have to be regularly removed and cleaned?).
The article makes great arguments for why this should work (i.e. hydrogen peroxide is already being used, this just short-circuits how we get a known effective cleaning agent, reducing/removing logistics inefficiencies). So a lot of the question is: Is this cheaper/less hassle than buying stabilized hydrogen peroxide commercially?
A lot of these fantastic advances often end up in the black hole, wherein they work as advertised, but the financials/logistics never line up and therefore nobody uses them in anger.
[+] [-] IncRnd|4 years ago|reply
From the article: "The team showed that as the catalyst brought the hydrogen and oxygen together to form hydrogen peroxide, it simultaneously produced a number of highly reactive compounds, known as reactive oxygen species (ROS), which the team demonstrated were responsible for the antibacterial and antiviral effect, and not the hydrogen peroxide itself."
[+] [-] mprovost|4 years ago|reply
It looks like MIOX is still around [0], they make portable units for the military and for temporary installation but I imagine this approach isn't cost effective for a permanent facility.
[0] https://www.miox.com/
[+] [-] globular-toast|4 years ago|reply
[+] [-] jhloa2|4 years ago|reply
[+] [-] foysaluix|4 years ago|reply
"heres a solution for limitless free energy! step one, launch a bunch of solar reflectors into space to reflect solar energy at concentrated points on the surface of the earth. Step 2, wait, you don't have a scalable and advanced aerospace industry capable of launching thousands of collectors into orbit? I guess this won't work for you."
[+] [-] poorjohnmacafee|4 years ago|reply
Since it's a challenge to separate the products/byproducts in catalytic reactions that are homogenous/liquid phases, how would this setup achieve separation post reaction exactly? Anyone know?
[+] [-] shkkmo|4 years ago|reply