There are two general of contamination: organic (bacteria, parasites, viruses) and chemical (farm, industrial, mining, etc). There is a third contaminant, radiation, but that is beyond the scope of most people.
And there are two kinds of water treatments: filtering and purification. Filtering sifts out the lumps (debris, parasite eggs and most bacteria) but most can't handle viruses (too small). The exception to the viruses is the Sawyer PointZeroTWO.
If you want a filter that does it all and is cheap, there isn't one.
Boiling and iodine kills organic contaminants. Distillation (condensation) works fine for some things, unless the water vapor can carry the chemical contaminant with it.
Heavy metals, lead, arsenic, copper, mercury, chromium 6 (did you see movie 'Erin Brockovich'?) are difficult to impossible to remove because they bind to the water or the molecules are too small. Boiling has no effect on this stuff, it just concentrates the toxins.
ZeroWater brand filter will filter out lead and chromium.
Granular Activated Carbon (GAC) filters will to bind to harmful contaminants, especially Volatile Organic Compounds (VOCs), from water. They can also be used to remove chemicals that give objectionable odors or tastes to water such as hydrogen sulfide (rotten eggs odor) or chlorine.
If you have a filter that will remove chemical contaminants, it won't filter organic contaminants, so after filtering the chemicals, you will still need to boil the water afterward.
Brita filters only cleanse regular tap water of chlorine and odors, nothing more dangerous, and certainly NOT 'wild water'.
Collecting rainwater for drinking is another option. Texas A&M University has collected a lot of info on rainwater harvesting. "Harvesting, Storing, and Treating Rainwater for Domestic Indoor Use" at
http://rainwaterharvesting.tamu.edu/files/2011/05/gi-366_2021994.pdf
Before the Acid Rain Fearmongers (ARF) jump all over me, YES, there is such a thing as acid rain. Acid rain comes from industrial pollution, usually in the form of sulfur dioxide and nitrogen oxides. Looking at this map, you'll see that the pH of the worst areas is about 4.3 in the NE part of the country:
h
ttps://water.usgs.gov/edu/graphics/phmap2002.gif You'll also notice that the acidity of the rain in the western half of this country ranges from 5.3 to 6.0.
Many people seem to think that acid rain is approximately as strong as battery acid, which simply isn't the case. The lowest pH of 4.3 is LESS ACIDIC than orange and grapefruit juices, sodas and tomato juice. ISN'T THAT AWFUL? I'll bet none of you drink that dangerous stuff! The western states range from strength of coffee to coffee with some milk in it. HORRORS! Why aren't we all DEAD?
pH of common liquids:
http://www.discountfilterstore.com/media/wysiwyg/fridgepedia/fridgepedia-ph-scale-02.jpg
The next argument of the ARFs is organic contamination, like bacteria. Stop and think for a few seconds, and ask yourself this: Do You Think There Is More Bacteria In the Air Or In The Soil? About 43 million people (15% of the U.S. population) rely on drinking water from home wells. I would guess that most of those wells haven't been tested for any kind of contamination for at least ten years.
HOW CAN WELL WATER BE CLEANER THAN RAINWATER? Answer: It can't, and it isn't.