Freshwater from salt water using only solar energy
news.rice.edu
news.rice.edu
We require 130 litres / person per day in Europe. A town of 10,000 people would require 1,300,000 litres / day = ~54,000 litres / hour = 9000 metres-squared.
A facility of 100 x 100 x 1 m seems feasible. Based on those calculations, this all seems quite practical. I do wonder how frequently the filters need to be changed, though.
Of course, I you have saltwater and no freshwater, you would probably use saltwater in your toilets, so that could reduce the daily usage of at least 20 litres. But then, if you consider agriculture and manufacturing, I guess that the number of 130litres/person would blow up completely.
I couldn't find anything against showering with saltwater by skimming the results of a naive google search.
I imagine the biggest strike against showering with salt water is that you'd need treatment, supply and heating dedicated to the salt tap. And then the salt water is busy corroding all the infrastructure devoted to it.
Also related, a chemical engineer from MIT started a company[0] back in 2013 purporting that showering kills our healthy bacteria. Supposedly he hasn't showered in 13 years, although their latest product recommends "rinsing in the shower for 3 minutes" followed by spraying their product on your body.
As someone who spends ~3 hours a day doing vigorous exercise, there is no way this is true. I smell awful afterwards.
Nope, I sweat pretty profusely throughout the day. Antiperspirant keeps me a part of civilization. FWIW I'm at a healthy weight and in good shape, just genetics.
I should have also noted that I haven't used deodorant in at least 10 years.
Maybe I just got lucky and won the genetic lottery in regards to smelly bacteria.
Not a fun experience the first few times though.
And lukewarm is exactly the same problem; 5 minutes to get that temperature, and some minutes to get it back if you leave the water off.
I am looking for a solution, not for someone to try convincing my entire family that we should prefer the problem. :-P
On-demand water heaters, or electric pre-pumps, or a needle valve with continuous return, are the three viable solutions, period.
Ask me how I know, go on...
Saltwater saturating our soils, water table or even being too concentrated in a bay would affect the ecosystem negatively.
Source: Someone who isn't an expert in waste management or ecology.
Similarly multiple out-going pipes to split off various levels of grey waste (some direct to garden, others, to soakways, or to septic processing systems).
Capex for these kinds of systems is ultimately dwarfed by savings on opex - just like we find with mandatory double-glazing & other insulation regulations.
Regulations lag behind optimum configuration, though parts of EU, especially in the north, legislated triple-glazing (f.e.) quite a few years ago (can't find a cost analysis of break-even points, unfortunately). I'm sure there's plenty of assumptions wrapped up in these regulations around estimated abode longevity, energy pricing over that period, etc. But as to multiple water sources into abodes, I haven't seen much formal work on it. I think the idea gets touted in London periodically - it'd be a nice solution to the dual problems of high water table and (surprisingly) occasional potable water shortages. But retrofitting this to an existing, massive, badly planned metropolis would be a nightmare.
now what should be more easily done is require building codes to insure large complexes have separate gray and black water pipes so that easier to treat water is routed better.
Are there examples of this done on a larger scale? I know facilities processing their waste-water onsite sometimes have this, but has it been done on a town/city level?
If your target it a farmer in the middle of nowhere you have twice as many pipes, twice as many pumps and no real ways to leverage economies of scale. Thus farmers typically have their own private well: they can drill a new well every 10 years for less than the cost of putting a pipe from the nearest city to their house. (wells generally last more than 10 years, but you have to replace the pump once in a while)
If you are targeting a downtown then there are high rises all over which increases the population density. The cost of putting in two sets of pipes is not much more than one larger pipe, and the pipes are amortized over everyone in the building on both sides of the roads - figure and extra $.50/month to have the second set of pipes: cheap enough that nobody will care.
The above are two different extremes, the only question is where along the spectrum is your question asked?
I looked up liters to gallons since I'm backwards and - in case anyone else is too - 10 liters is ~2.5 gallons. I replaced three toilest in my home that were flushing ~4 gallons with each flush with ones that flush with 1.28 gallons now. They are much more powerful than the previous ones I had, and use (liter-wise) less than half of the 10-liter mark.
Do your efficient toilets overseas not get down to the 4-6 liter range per flush?
The switch to more efficient toilets really made a big impact on my water bill for barely a dent to the wallet.
That doesn't include things like delivery fees, sewer charges, etc.
http://www.hcsa.us/files/What-does-my-toilet-really-cost-me....
Regulating the volume of the tank is useless unless you also define a test standard for functionality.
It's like saying that cars have to meet a minimum mileage standard without also specifying that they have to be able to maintain 60 mph while going up a 10% grade. Except in that situation, cars that do not meet the implicit minimum consumer standard don't get purchased off the lot. In houses, the person who buys the toilet is more likely planning to repackage it into an entire house and resell it to someone else than use it personally. So your toilet might look like a full-sized sedan, but have a go-kart engine under the hood. They just bolted a smaller tank onto a base that was designed for a larger flush volume.
So what those toilets are allowed de jure is not necessarily lowering de facto water use.
Yes, there are toilets out there that were redesigned for low flush volumes, and they do save water, but they have not displaced the letter-of-the-law, flush-it-twice toilets in the construction of cut-every-possible-corner suburban subdivisions.
I don't usually have to use a plunger (thankfully, since I don't live there and only shit there as a guest). But I've learned through hard experience: the Americans basically gave up on the toilet 100+ years ago.
Cold as fuck porcelain, rarely a slow-seat-lowering mechanism, no stain-resistant adherence-resistant polymers, no way you're getting any heated seats or odor-suppressing intake fans than vent air through filters, and, for whatever reason (asshole/vagina-squeamish culture?) there are virtually no spraywash/bidet type features...and to add insult to injury they can't even reliably flush a man-size shit down !!! :-O
I mean, they usually do, but any failure rate above 0.01% will make you quickly learn that you should just flush, then wipe, and if you feel like you need to wipe a bit extra this time, just flush again mid-wipe, and once more at the end.
logfromblammo I am so utterly with you: flush-test the toilets (and fuck it, if we ban toilets that use too much water, we should ban toilets that can't reliably flush a heavy load).
P.S. Yes, I live in Japan, the world's only toilet-superpower, and yes, I've ranted on this topic before on HN (https://news.ycombinator.com/item?id=4787587).
The lack of water in the bowl concerned me, but the "flushing power" makes up for it. I've had them installed for about two years now and the kids' toilets hasn't had anything that couldn't be flushed.
But, as you mention, these aren't contractor-grade toilets. Indeed, those do suck. I've used plenty.
Think of it like this. Lets say there were 10 toilet usages in a day, 8 urination and 2 defecation. If a flush takes 5 units of water, and works for either situation, that is 50 units of water a day.
Now you replace the toilet with one that uses 2 units of water but takes 3 flushes to clear defecation. 8 of your uses take 2 units, 2 of your uses take 6 units (3 flushes) total units of water 16 + 12 or 28 units. You save 22 units of water a day.
But no matter what you do regarding toilet laws, the benefit simply vanishes in the noise when you also consider agricultural/industrial water use. It is pissing into a hurricane-force wind.
Domestic use in the US is 40.5 km^3/year, of which maybe 4.1 km^3/year is used in toilets (both for intentional flushes and leaks). Total freshwater use in the US is 483 km^3/year. A 50% reduction in water use for toilets would amount to a 0.5% reduction in total water use. For comparison purposes, 23.5 km^3/year of domestic water is used outdoors, for watering lawns and gardens or for filling swimming pools.
From a purely legislative perspective, it makes more sense to mandate leak-resistant flush valves than the size of the tank. It makes even more sense to strike down at a federal level all local zoning laws and HOA covenants that mandate a certain appearance for lawns, to explicitly allow alternate yard arrangments, such as xeriscaping and no-mow approaches, on residential properties. That would save more water in total than you could even by mandating that toilets could not use any water at all. And even that would pale in comparison to laws requiring just a 4% reduction in water use in steam-turbine power plants or in agricultural irrigation.
If you do the math, the burden of regulating toilet flush volume far outweighs the benefits from doing so. While you were counting flushes, one leak in one pivot irrigation rig just wasted more water than you will ever save in your entire lifetime of flushing toilets. This is my problem with individual environmentalism. An individual human already wastes so little that sacrificing just a bit more for the sake of the planet is easily flushed away by industry that has zero incentive--economic or regulatory--to conserve limited resources. You can drive a zero-emissions vehicle for an entire lifetime of commuting, and that benefit is more than erased by just one container ship burning bunker oil to ship consumer goods from Shanghai to Long Beach one time.
I pay by the cubic foot for municipal water, and I pay again for the municipal sewers and water treatment. For what I pay, I expect to be able to actually get my solid waste into the sewers without some jackass telling me how much water I can use to do it without also telling the toilet vendor that their product has to be able to do the job with that volume. Regulation for the public good is fine. Idiotic regulation, that does not accomplish the intended purpose, is not okay.
> I pay by the cubic foot for municipal water, and I pay
> again for the municipal sewers and water treatment. For
> what I pay, I expect to be able to actually get my
> solid waste into the sewers without some jackass
> telling me how much water I can use to do it ...
And yes, it is true that agricultural use dwarfs urban use. But the same logic applies. Someone trying to grow almonds in the desert should pay more than someone trying to grow beans.
You don't even need to have bracketed, progressively higher rates for water use. It would be enough to just stop subsidizing those who use the most.
Less than 1% of human-used freshwater in the US goes through toilets.
Personally, I don't bother to optimize code unless the profiler says it is heavily used. I am probably not going to mess with a routine that only accounts for 1% of execution until well after I have optimized the hell out of the two functions that collectively account for 80% of CPU time. (Analogy-wise, that's power plants and irrigation.)
Of course, given enough developers, someone will eventually have to optimize out at the edges. There's no reason to say we can't tackle toilets at the same time as pivot irrigators; it's just that any work done on them will be inherently less valuable. You're not going to need your best people on it. And any gains will be small.
It isn't entirely about improving performance at that point. Anything I do to shave microseconds from that 1%-used function is likely to introduce additional bugs into the code--such as failures in one of the two major use cases for it. (Poop remains in the bowl after I flush.) That's not so bad if I set up unit tests beforehand, because I then know when I have broken something.
But where are your unit tests for toilet flushing, Mr. Legislator? Nowhere. They don't bother with the profiler or with unit tests. So they end up with shitty code.
"If it's yellow, let it mellow, if it's brown, flush it down".
If everyone acted like that, then toilets could have a good, decent flush, powerful enough to purge any normal mud dragon.
I guess you can produce constantly and store - a quick search suggests that 1.3M litres would barely be known to a reservoir but you wouldn’t have to worry about the seasonality of rainfall.
Yeah, seems feasible. Almost too good to be true…
> We require 130 litres / person
> per day in Europe
> For NEMD experiments with solar concentration, a 25.4 × 25.4 cm Fresnel lens was used to concentrate sunlight on the membrane surface by a factor of 25. The unconcentrated and concentrated solar intensities at the NESMD module surface were 0.7 and 17.5 kW·m−2, respectively.
A facility of 500x500 m^2 would probably still be feasible.
The link is to the university news department, the actual paper is here:
http://www.pnas.org/content/early/2017/06/14/1701835114.full
or here in PDF format:
http://www.pnas.org/content/early/2017/06/14/1701835114.full...
Amazing that that particular project got so much praise before the numbers were in.
I've played around with solar concentrators in the early 00's and realized very quickly that it wasn't worth my time due to all kinds of practical constraints, I always wondered why the companies and organizations that build these things don't do a scale model first. That way at least you get some real world data to plug into your spreadsheet before spending big $.
Our household solar power installation here in the very rainy Seattle area generates 98.15% of our electric power needs, including that for our electric car. I wish it were 100%, and if the sun shines for a few days in a row, sometimes it does generate 100% of our electric power needs for the last 365 days. It is, however, much better to meet 98% of our needs that to meet none of our needs.
In the context of grid power, that's an even bigger issue given cost and pollution from base load generators.
Because infrastructure should have redundancy.
Cairo has a population density of 18K people per km2, so this would mean covering 2% of the area. For contrast, streets and parking take up ~40% of most US cities.
This is the reverse - dispose of the residue, keep the water.
I'm not sure that increasing the complexity of the membrane substrate itself is a positive step here, or that a complex heating mechanism offers significant wins.
The alternative of more traditional membrane reverse-osmosis processing focusing on cheap substrates, whilst provisioning power separately (conventional solar PV would be suitable, and could be located on-site or remotely) seems rather more tractable.
Who wants to worry about wells and sump holes and and filters and bleach tabs when you can burn things?
Now that's a job for you to tell your kid's school class about on career day. A salt un-miner.
That's simply false. The amount of water that would need to be permanently removed from the ocean in order to measurably increase the salinity would be astounding. Let alone the amount that would need to be permanently removed to kill anything.
If local salinity was a problem (which it isn't) there's an extremely easy solution: Simply pump more water, remove less salt from it. Dump it in over a wider area of shore. Let mixing take care of the rest.
Actually most sewage systems output water that is safe to drink so we can put that water right back into our drinking water system and forget the whole problem over an over again. (If you ban lawns there might even be water left over as food is turned into water and the food probably isn't grown with city water). People generally don't like the idea of drinking sewage though so this will never happen.
The ships are probably full one direction (when traveling from countries that manufacture a lot) but relatively empty on the way back, so there's probably free space.
That's what's happening to the fresh water after it's used, it goes back to the ocean. It's a closed cycle.
The scale of human water consumption to the volume of the sea is miniscule.
Global fresh water consumption is a fraction of a percent of the volume of the ocean ( https://www.wolframalpha.com/input/?i=((total+water+consumpt... )
There's no reason why we couldn't ship it into the middle of a desert if for some reason it couldn't go back into the sea, it wouldn't go very far once it was dumped. Conveniently, the places that rely/will rely on desalination the most happen to be desert countries.
https://www.sciencetarget.com/Journal/index.php/IJES/article...
Locally high concentrations of salt are bad.
A little CO won't hurt you but it's not advisable to BBQ indoors.
Petrochem tech comes into play here, because in steam extraction of oil-sands, wastewater comes back up contaminated with silicates, and has to be treated before it can be reused. It turns out that similar processes can be used to further concentrate desalinator effluent above the 70 g/kg that regular RO tops out at, to about 130 g/kg. From there, any solar/thermal process equipment (i.e. flash distiller) can be made much smaller.
For reference, seawater is typically 35 g/kg, and the top stratum of the Dead Sea averages 315 g/kg (with significant fluctuation due to local weather history).
So Jordan and Israel can actually do RO on water from the Red Sea (40 g/kg), and pump the effluent to the Dead Sea. They don't have to worry about the hypersaline brine killing anything, because the Dead Sea is already dead (just like it says on the tin). And the pumping is easy, because the Dead Sea is below ocean level. A pair of siphoning aqueduct pipelines (40 g/kg and 70 g/kg) can supply a RO desalinator in every town from Aqaba to Potash City.