The Botulinum toxins (two-chain polypeptide with a 100-kDa heavy chain joined by a disulphide bond to a 50-kDa light chain, which is an active enzyme) produced by Botulinum spores can be destroyed by boiling the water. The Botulium spores though can still present a danger as they are more heat tolerant. I would suggest the following procedure to deal with any contamination. Firstly filter the water with a suitable commercial ceramic based submicron filter such as Katadyn Pocket Water Microfilter (this will take care of most bacteria) then boil the water for 10 minutes, rolling boil or to be really sure, use an old fashioned pressure cooker (will raise water temperature higher than 100 degrees Celsius), allow to cool, then give it a blast with a Steripen (should deal with anything that has any DNA that has not already been destroyed by heat treatment). Then whisk the water thoroughly to add some oxygen to improve the taste. To improve the flavor of the water so that it is potable a chemical after taste tablet could also be added. This should deal with any non-chemical contamination.