[aerio]

I don't think the article dodges the question at all. Did you properly read it or just skim it? It goes over multiple ways of desalinating water, distillation and osmosis - as you also cover. The most relevant paragraph to the question and a bit of a conclusion seems to be:

>And that’s the problem with desalination. It’s kind of like the nuclear power of water supply. It seems so simple on the surface, but when you add up all the practical costs and complexities, it gets really hard to justify over other alternatives. It’s also harder to compare costs between those alternatives because of desal’s unique problems. It’s just a newer technology, so it’s harder to predict hidden technical, legal, political, and environmental challenges. For example, because of the high energy demands, desalination can strongly couple water costs with electricity costs. During a drought, the cost of hydropower goes up because there’s less water available, increasing overall energy costs and thus making desalination less viable right when you need it most.

[nardi]

The article talks about why it's maybe politically or economically difficult, but not why it's physically difficult.

[101011]

Subtracting economics from the equation, aren't there a very limited number of physically difficult problems?