Rainwater has been collected and used as drinking water for centuries around the globe. Here in the US, all drinking water rainwater harvesting systems must meet or exceed EPA standards for potable water. This is accomplished by installing a secondary water treatment and filtration system after the water exists the pillow. System options on the market include ultraviolet light purification, reverse osmosis, chlorination, and ozone.
Minimum requirements for a Potable Rainwater System:
1. Pre filters need to be of high quality and remove fine debris before the water is stored in the pillow.
2. First flush diverters should be used to further remove debris. This removes the first 10% or so of rainfall, which contains the highest amount of debris from entering the pillow.
3. The water stored in the pillow should be aerated to reduce the amount of anaerobic decomposition.
4. Once the water exits the pillow, it is time for the secondary filtration and treatment. One option is a four stage filtration system. The first stage is to filter the water to 20-25 microns. This first stage of pressurized filtration is an important component in lengthening the use-full life of the smaller filters.
5. Next the water will flow though a 5 micron filter for further cleaning.
6. The third stage of filtration is with a .5-5 Micron Charcoal Block. This removes debris from the water through a combination of filtration and absorption.
7. Lastly the water is treated with UV Light. This light sterilizes any organisms that could have passed through the filtration stages. For the UV Light to be effective, the water must be filtered to at least 5 Microns. The size of the UV Light is determined by water flow requirements.
The result is water that if most often cleaner than any other water source.
This is an example of a potable water system that is designed to provide 14 gallons of water per minute.