When I wrote "Britain and the World in 2050" I forecast that despite UN talk of water shortages and some alarmist predictions of "Water Wars" by mid-century, the most likely outcome would be that access to very cheap energy would enable osmotic desalination to solve the problem.
The problem with current membranes used to turn seawater into drinkable quality water is that it is very energy intensive and requires high maintenance to clean the salt sludge from the membranes. The first of these will be solved by the abundance of low cost gas from fracking, and a continuing steep decline in the cost of photovoltaic energy.
Now a major breakthrough in membrane technology has been announced. Graphene-oxide membranes have had the problem that because they swell slightly in water, smaller salts flow through them with the water, even though they block the larger molecules. A University of Manchester group has just revealed in the journal Nature Nanotechnology that it has developed a way to avoid the membrane becoming swollen in water, and to precisely control the its pore size. This enables the unwanted salts to be sieved out at speed, leaving clean, drinkable water.
The drive now is to scale up the technology so it is capable of large-scale, cost-effective production. In addition it is hoped that smaller-scale versions can be developed for countries lacking the finance to fund large-scale plants. As with so many anticipated problems, human creativity and resourcefulness seem capable of stepping up to the plate with technological solutions to them.