If you look, or google, you can find that one of the traditional uses of NaCl (salt) is as a food preservative agent. It has been used for thousands of years.

In your case, it looks like you could consider NaCl to be a preservative for water.

Pray tell, what biological or bacteriological food can be found in pure water or pure NaCl/KCl crystals?

Even sugars have been used for thousands of years as food preservatives, under the right conditions.