In an emergency situation it ...

In an emergency situation it will still depend whether there is any access to water and of what source. Usually I would recommend a point of use system such as a water filter. We work with a company called basic water needs: basicwaterneeds.com . You can also do this in combination with drilling a borehole/ setting up a waterpump for example. Again, I do not know what the exact situation or the region or country is. Good luck. Mark