For centuries water has been boiled to render it free of Biological Pathogens. Yet this technique is only a half measure as it still leaves most of the chemical contaminants intact. Chemical disinfectants, like chlorine and iodine, have the same limitation. Some of these chemical disinfectants are now suspected to be cancer-causing carcinogens. Distilled Water is safe, but time and resource consuming to produce.
Many peoples lack both the time and resources to distill drinking water to render it safe to drink.
Additionally, the distillation process is a low yield affair and also removes the beneficial minerals from water. To be truly effective, a water purification system would have to have met certain criteria. Effectively remove from the water, both chemical and biological contaminants. Able to produce an appropriate amount of purified drinking water to meet the daily needs of an individual or a group. Portable, so it can be transported easily to the water source, or easily taken with the user as they move from one location to another.