It would seem that removing the salt and other minerals froom seawater would be the preferred method, not only because of the magnesium recovered, but because sea water is an easy to get resource that we won't be in any danger of running out of. If the berries are different after a few years it is probably because of cost being taken out of the growing process, not because of the water. What quality reduction has been implemented to increase profits?
Of course desalination does need a lot of energy, I don't know any way around that, one other option is for people to not live in that area that has no water. Did anybody ever stop and consider that some places that seem uninhabitable ARE UNINHABITABLE? Even if some developer puts houses there?
REmember the Bob Dylan quote: "One should never be where one does not belong"? It is also appropriate for areas without water.
The problem is that while we can make potable water out of seawater, we can't make the energy to do the process.
Desalinization isn't a good long term solution. It's been used in Israel for years for crop irrigation. The strawberries in Israel today aren't nearly as delicious or nutritious as they were decades ago. I think the berries are telling us something. Legalizing and building infrastructure to utilize grey water would offer a longer solution for potable water shortages.
This may be easily used for manufacturing and energy creation. Many newer processes seem to involve massive amounts of fresh water.
Reverse osmosis and other membrane technologies are the methods I'm more familiar with and have heard mentioned more often, so I was surprised to discover that thermal distillation is the technology used in the majority of installations. Although RO presumably uses somewhat less energy, both processes are quite intensive energy users. Re temperatures, thermal distillation is a form of vacuum distillation, which allows water to boil at a lower than normal temperature due to lower pressure. The Wikipedia article on desal is helpful.
When reading of flash-tube boilers I envisioned tubes heated to several hundred or more degrees, not 70-130. The concept of having water spray and evaporated steam in close proximity without excessive mixing is interesting. I wonder if flash-tube could be economically superior to Reverse Osmosis? Certainly the next 30 or so years will see the need for many more water purification methods.
Very interesting development, Ann. Providing a more economical way to attack the desalination process could really make a big difference in pushing more of these projects to the fore and help them gain a foothold in developing areas that are really desparate for fresh water sources.
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