Boiling is sufficient to purify the water. I do take exception to your statement that you will hydrate from the food. I don't think there is any food that will hydrate you, as it all takes water from you body to digest. Some foods, just less than others. But I believe that the best rule of thumb is if you don't have enogh water to digest the food you plan to eat, then don't eat. Think of a scale water intake must at least equal water output. If your urine isn't nearly clear then you are a bit dehydrated.