We start our purification process  with a charcoal filter to remove organic compounds, large sediment and chlorine. A water softener is used next to remove the  calcium and magnesium that is present and then through a 20 Micron and a 5 Micron filter. At this point our water could be sold as filtered but we are going for purified so on to the pressurized reverse osmosis cylinders to remove 99.8% of anything that is not water, including dead bacteria that was killed by the chlorine we removed in the first step. Once our water is down to 10ppm TDS (total dissolved solids) we can put "purified" on our label, but since we're overachievers we guarantee our water to be 4ppm TDS or less.