“Water, water everywhere, nor any drop to drink.”
Well, yes and no. But Coleridge did capture the essence our modern problem of a global freshwater crisis. Modern humans are not of course stranded on a becalmed ship on the ocean, but far too many of us are becalmed in our residencies where there was never much water to begin with.
It is our unthinking penchant for inhabiting such places as Saudi Arabia, Phoenix and Los Angeles, where there is insufficient fresh water to sustain us, and then building various expensive appliances to supply the water. Often, these devices not only cost prodigious sums to build and maintain (just one plant in California cost 1 billion dollars and provides only about 7% of drinking water to the City of San Diego), but also create monumental environmental degradations to boot. One of these is the now burgeoning desalination plant industry.
This technology is ancient but, historically, the facilities were smaller in both scale and numbers. It still consists of forcing large amounts of sea water through filters which soon accumulate huge blocks of salty, deadly gunk which is then deposited on shore or back into the ocean, along with highly concentrated poisons of every kind. This poses a threat to ocean biodiversity and marine habitats. Coral reefs require marine organisms to flourish. But as desalination takes place, numerous organisms, plankton and fish larvae are vacuumed up in the salt water that goes into the plant.
Moreover, most of the world’s 16,000 plants use either reverse osmosis (RO) or thermal processes which use fossil fuels as their energy source. It requires about 12kwh of electricity to produce a mere 1,000 gallons of fresh water. RO is the best of these two. Of course, it would be much better if the energy came from nuclear generation, wind generators or solar panels but that does not alleviate the problem of contamination.
As an Air Force pilot, I went through sea-survival training where I learned to make fresh water, in-exhaustively, from salt water, if downed at sea. This process consists of using clear bladders (on every inflatable life raft) which are partly filled with salt water and dragged behind the raft. When the sun heats the inflated bladder, fresh water condenses at the top. Voila! This process is scalable and should be pursued with all haste. A couple of prototypes are being tested but we need a large global project to succeed.