My initial statement did not presume that the water disappeared, but water processed through biological systems pick up contaminants.
Also, I'm uncertain whether Omestes' original calculation was based only on consumption of drinking water per individual and was ignoring the obvious externalities of manufacturing usage of water per annum. I imagine if we included all manufacturing and industrial useages of water, the number is likely to be higher.
I am, of course, assuming that Omestes' was not including these latter factors.
Multiplying the Daily water useage into a year, then multiplying it out to an average 70 year lifespan gives 0.000007665
Which is still only 7/1,000,000 of a change in value, but that's assuming consumption and useage levels remain the same and Jevon's Paradox doesn't have a significant rebound from the drop in cost of desalinization.
And what about when the world is consuming trillions of gallons of Water from the oceans? I'm sure the oceans becoming saltier over time (As a result of removal of clean water from the system as well as salts/other chemicals being added from all the pissing people, cows and pigs will be doing with all the readily available water) isn't going to cause any problems.
Oh, wait, no, I mean the other thing.
Systems are not closed, coming up with a solution that makes consumption easier doesn't actually solve problems down the road.