Water in the oceans may become fresh water available to humans through the processes of

Water in the oceans may become fresh water available to humans through the processes of evaporation, condensation and precipitation.

In these processes, water is heated to a very high temperature until it evaporates in order to kill the germs and remove the salts which remains after water evaporation. The next step in condensing the water vapor (which is now fresh) and precipitating this vapor to be used by humans.