1. Introduction
When, in the spring of this year, I was invited to give the Opening Speech for this Congress in Cannes, I had just completed the writing of a history of a particular restricted area of desalination. I thought then it would be a pleasant change to do an essay on future prospects for desalination without having limitations to any particular aspects, and so I committed myself to the title 'The Distant Future'. I am afraid that in making such a choice I allowed the pendulum of my mind to swing too far, and I regret it. How long is a piece of string? How far is distant? Obviously for an audience of distinguished technologists I cannot go the distance of science fiction writers such as those who chart the travels of the Starship Enterprise. In it the good Captain Kirk, Mr. Spock, officers and crew, go about in an ambience where evidently the problems of recirculating the H20 substance necessary for their life support have been solved in an absolutely trouble-free plant. In many episodes you will hear the engineer officer, in his deplorable pseudo-Scottish accent, grumble about the state of his ion engines or other fancy propulsion equipment, but never about his water supply system. My imagination can go the length of those ecological writers who visualise our planet as starship Earth with its limited resources receiving no input except solar radiation and meteoric dust. I can see human life and destiny as conditioned by very many things, of which the technological manipulation of matter and energy is only one, but a very important one, and within that range the manipulation of H20 substance is a vital part. But the string of my imagination is finite in length and it is tethered to those twin sets of laws, the set of thermodynamics and the set of cussedness of things. In short whatever I say in this talk about future trends in desalination and water treatment affairs is limited by the extent of my technological knowledge and experience. All real futures must evolve from real pasts and presents.