While I love the idea of tapping the Mississippi River or the Pacific Ocean to slake the thirst of my family and neighbors living in Southern California, by installing costly desalination plants and further depleting our extensive, existing groundwater resources, the writing on the wall is water use restrictions, not more and better water resources.
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Of course there is one small nagging problem with desalination plants.
You pump water from your source (the ocean) then you extract the salt to produce drinkable water. The other byproduct is a hyper-salinated solution that must be returned to the source some distance away from the intake. And then you rely on ocean currents to disperse that. But it definitely has adverse effects on marine life in that dispersal region.
Otherwise, I suppose you could create massive salt ponds for the manufacture of table salt (?). Does it have any other use?
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And stillsuits.
Or more seriously, wastewater treatment and reuse.
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just put a roof over western Washington (WA) and route the drain to the south. Win-Win
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Indeed, I already studied the possibility of rainwater harvesting and re-use for a local demonstration project in San Diego. Due to the paltry amount of rain for that city, the resulting economics of harvesting it just do not pan out, unfortunately.
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That approach has several major advantages over desalination since it is more energy efficient (about a third the energy requirement), doesn’t produce huge amounts of hyper-salinated water as a byproduct and can be implemented anywhere instead of just coastal cities.
Besides, key parts of the required infrastructure are already in place in most cities anyway. The water you flush down the toilet or drain gets treated somewhere along its journey, so we might as well just go the extra step to make it fully drinkable again.
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That water is already essentially treated to drinking water standards for discharge to another water body. Reworking regulations, some minor technology, and getting past, “oh no I’m drinking pee!” is the next step.
A number of cities have developed pilot “purple pipe” systems, where treated wastewater is used for irrigation, etc. But that involves running a lot of additional infrastructure. Better uses will be aquifer recharge, surface water enhancement, or direct integration into overall water supply.
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A well-designed urban environment shouldn’t require a lot of irrigation anyway. Better to have native plants that can survive on local rainfall than to dedicate so much water toward sprawling grassy lawns.
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The technology is already there and from what I’ve seen it already meets drinking water standards 100%. It’s totally about getting public buy-in at this point.
The fact that some water districts have called the program “toilet to tap” doesn’t help make the marketing challenge easier though…
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Maybe they can brand it, “Peerrier.”
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This is indirect potable water re-use, treating wastewater to remove solids, organics, and targeted pollutants, which are essentially low-hanging fruit for contaminant removal systems, and then letting the treated water flow underground into an aquifer or the ocean. Down the street from where I live, an old classmate of mine is overseeing the construction of several groundwater recharge basins that will return treated wastewater to the water cycle. I mean, this has been known for some time now, but the major issue I see with Pure Water and One Water is the pollutants that slip through the cracks, such as emerging contaminants like microplastics, and ever present and unregulated pharmaceutical chemicals. Just use less water and then purifying and recycling water will not be as financially painful to water consumers.
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It was those environmentalists’ fault somehow
In the future a big strong man will make the lawsuits go away and build a brilliant new kind of reactor that won’t ever have any problems and it will all be ready to go by Tuesday 
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Definitely there are great prospects for, shall we say, secondhand water. There are golf courses, parks and horticultural uses - even in the manufacture of bioplastics. There are always byproducts, however, such as nitrates. Hence, saltpetre. Some interesting reading.
Then of course, there is always “Soylent Brown”. Here in Australia, at the domestic level we have a horticultural mulch called “Whoflungdung”. No points for guessing what it’s made of. Evidently it is hugely successful. Then, at an industrial level there are grazing properties that spread semi-trailer loads of dried human waste to revitalize their land and even with a single treatment at low rates the effect on improving the soil biome is dramatic and lasts for years.
Here are a couple of short preview vids and this.
That is just accounting for the human element. There is also the waste produced at feedlots. Urea can be produced from animal waste.
If it is aridification you face there is huge scope for diversification into suitable crops, one being Opuntia - otherwise known as “Prickly Pear”. There are non-prickly varieties and the healthful fruit can be grown at crop scale for fruit, for jam and for wine. The cladodes - the “ears” have been widely consumed in Mexico for centuries and also make very acceptable cattle feed. There are also cochineal resistant varieties to counter perhaps the plant’s only predator. Also think Pitaya or Dragonfruit.
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Singapore has the right idea.
And they’re just the latest to the “turning wastewater into beer” game…
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Someone could do a marketing tie-in with the Dune franchise…
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A huge win would be dual water systems. We waste a huge amount of resources, for example, flushing our toilets with perfectly purified drinking water.
Some model sustainable communities have been built with separate gray water systems plumbed into the houses, but it’s still very rare. There’s no need to, for example, purify water from dishwashers, sinks, and showers. That can go right back in to flush your toilets and water the plants (barring phosphates in the soaps and such). I lived in one community for a while that had a partial gray water system. The irrigation for road medians and such was all done with gray water. Of course, even better would be not irrigating grass on road medians at all, but it’s a start.
People fixate on sewer water all the time in conversations like this, but there’s a huge world of efficiency that we’re leaving in the table by not collecting and redistributing gray water. Purified fresh drinking water is a tiny fraction of our water use, and all the rest can be done with gray water. Furthermore sewer water is a tiny fraction of what treatment plants are purifying. Most of it is gray water that could be reused as-is with slightly better plumbing infrastructure.
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It has already started in the Southwest. The State of California just passed an emergency water conservation law that prohibits irrigating non-functional turf (NFT) like the landscaped medians and grass maintained around the expansive logistics centers and other industrial buildings. Ornamental, residential lawns, school ball fields, and parks are currently not considered NFT.
Regarding the great potential for recycling and reusing wastewater, recycled water projects I have designed and constructed were once at risk of running dry due to opposition from the US Fish and Wildlife Service. They prefer the return of treated wastewater to streams, creeks, canals, and rivers, where the recycled water can be of direct benefit to riparian habitat. And they make a really good point, one that the referenced article might have missed. Humans ought to have a right to water, sure, but then we need also to be sure we are not overlooking the prior rights of the flora and fauna that have thrived on the water of the Rio Grande for an unfathomable number years.
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Salt is actually a very good heat storage substance, not sure if sodium chloride has too high a melting temp to be useful (not my area of expertise for sure)?
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I built a molten salt heat treat furnace, sea salt melts at about 800C, and to contain it I followed the industry standard: heavy wall oil well casing, stainless and professionally welded (I don’t want 50lbs of molten salt spilling all over my shop, so I paid a pro to do the job right and provide xray proof.) So it can be used, but usually solar salt systems user lower temperature salts, such as various nitrates, or brines.
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Yeah, 800 C is like the Wu-Tang clan, nuthing to fuck wit.
