The best treatments for making natural drinking water safe are of course the natural ones. Funny that after 250 years of industrialization those wetlands prove to be the best natural filters for all types of water systems. Depending on where the natural drinking water is coming from additional filtration through activated carbon filters and treatment with chlorine dioxide may be necessary.
Even from glaciers, natural springs and deep water wells bacterial, viral and non-organic contaminants may occur. A recent report by the National Recourses Defense Council indicates that 22% of the bottled water they tested from 103 brands sold in the US did not pass California's tap water standards.
For in home methods of insuring the safety of natural drinking water a combination of carbon filtering and reverse osmosis is probably the best. Activated carbon filters remove most organics and some chemicals. Reverse osmosis removes salts and minerals such as mercury and lead. Distilling is the most efficient method for removing both organic and inorganic contaminants from drinking water but is not a practical option for most households.
When traversing the wilderness don't assume that that glacial stream is safe to drink from. Most experts recommend the use of activated chlorine dioxide to add to found water along with portable filtration systems available as drinking bottles or separate units. These are economical and easy to find from any outdoor outfitter.
Melbourne Water a company that specializes in water treatment has found that going natural is the best and most economically efficient addition to protecting natural drinking water supplies. Their belief is so strong that they spend 5.6 million a year to build or encourage wetlands management and restoration.
Wetlands pretty much run themselves once constructed they need little if any maintenance and act as the most efficient water filtration system in existence. They also give the added benefit of flood control and increased wildlife habitat. They act as giant carbon filters only there is no need to change them.
The mining industry has jumped on the bandwagon as illustrated in an October, 15 article for the Journal of Commerce by Jean Sorenson. He outlines the effort of the world's largest copper mine in the Tusceh Valley of Peru to build a series of the world's highest elevation wetlands to purify mine runoff before it enters the local water system.
More wetlands mean safer natural drinking water, better fishing and bird watching too.