Potable Water Sources (continued - p2 of 2)

Harvesting Water From Air

As with de-humidification, humidity and fog collection is accomplished by condensing moisture from the air. Rather than wasting the water collected however, it is saved, filtered, purified (usually by distillation), stored and continually re-circulated and re-purified to maintain purity and quality. Non-toxic hygroscopic materials such as calcium chloride can also be used to absorb water from air. Using calcium chloride in a solar distillation system (with a few slight modifications), it is possible to collect, filter, purify and store water from air without electricity or chemicals. Vapor collection is possible at 5-100% humidity, but the larger the volume of air and the more difference in temperatures between incoming air and the condenser or condensation surface there is, the more efficient the process will be.

Other methods of harvesting water from the air include fog fences, air wells, earth tubes, dew condensers, dew ponds or reservoirs. All such forms of atmospheric de-humidification collect and condense water from air. Fog fences can collect up to 5 gallons of water per square foot of collection space, while air wells, earth tubes and dew condensers collect up to one quart per square foot. Dew ponds and reservoirs can collect up to 1.5 gallons per day in the winter and up to 4 gallons per day in the summer per square foot.

Drilling a Well

Sometimes drilling a well is a viable option, although it may be expensive depending on how deep you have to drill. Wells can dry up, so the reliability of this water source depends primarily on available groundwater, the total amount of water needed and storage space (i.e., how much water can be stored at one time).

Water Filtration and Purification

These days even sewer water is filtered, disinfected (most often using chemicals such as chlorine and epichlorohydrin) and reused, although I wouldn't consider this a potable water source, and certainly not suitable for drinking water, no matter what has been done to it. Chemicals used for disinfecting water are made to kill organisms, and in case we have forgotten, we are organisms! Fortunately there are better ways to filter, disinfect and purify water however, ways which are natural, earth friendly and non-toxic. Simple filtration with a mesh screen should remove particles and debris, but generally not pathogens, poisons, toxins, heavy metals or VOCs (volatile organic compounds). Natural ceramic or activated carbon water filters will remove nearly if not all of these impurities but must be replaced every ten years or so, depending on the filter and the amount of water to be filtered and purified. UV light is an effective alternative to the use of chemicals for water disinfection, and distillation is one of the best, safest, most reliable methods of water purification there is. Distillation involves boiling water, condensing and storing the vapors which rise from the steam. One simple way to distill water at home is to place a bowl of water inside a cooking pot or wok, cover the pot with a lid and top the lid with a bag of ice. If brought to a boil, steam will rise from water inside the bowl and condense on the bottom of the lid. Purified water then runs down the insides of the pot, leaving up to 99% of all impurities (except VOCs) behind in the bowl. When there is no water remaining in the bowl, remove the pot and bowl from heat, then remove the bowl from inside of the pot and remove lid from the pot of distilled water (to allow evaporation of VOCs); let cool, bottle the water and store.