5-Stage Drinking Water Purification Filters Out Contaminants
The Oasis-3 water purification system uses filters and ultraviolet light to remove biological, inorganic and chemical contaminants from dirty water making it safe to drink.
Water is passed through a series of filters which progressively removes larger then smaller material. The chart below shows how different water-borne threats are eliminated turning polluted water into clean, potable water safe for human consumption.
- Filter #1 - 80-mesh (177 micron) screen removes heavy solids such as sand and organic material.
- Filter #2 - 50-micron sediment filter removes sediment including sand, mud and other suspended solids.
- Filter #3 - A choice of 0.2, 0.45, or 1-micron "absolute" rated membrane filter removes fine sediment including hair, dust, protozoa, viruses, bacteria and cysts.
- Filter #4 - 10-micron activated carbon filter removes chemicals, tastes and odors.
- Filter #5 - Intense exposure to ultraviolet (UV) light scrambles the DNA of bacteria and viruses rendering 99.99% of them sterile.
|Water enters the filter...||Polluted||Dirty||Clear||Clean|
#1 & #2
|Gastroenteritis causative (rotavirus, norovirus, adenovirus, astrovirus)|
|Giarda lamblia cysts|
|Rust / Sand / Sediment / Silt|
|Solvents / Trihalomethanes|
|Volatile Organic Compounds|
|Water exits the filter...||Dirty||Clear||Clean||Safe
Membrane filtration removes various sized contaminants from water by passage through a microporous membrane. A typical micro-filtration membrane pore size range is 0.1 to 10 microns (µm). The larger the pore size, the greater the flow of water (and contaminants!) through the filter. Membrane filtration is fundamentally different from reverse osmosis and nanofiltration because those technologies use pressure as a means of forcing water to go from low pressure to high pressure. Read a useful guide on membrane filtration published by The National Environmental Services Center.
Activated carbon filtration uses activated carbon to remove contaminants and impurities, utilizing chemical adsorption. Each piece of carbon is designed to provide a large section of surface area, in order to allow contaminants the most possible exposure to the filter media. For example, 1lb (450 g) of activated carbon contains a surface area of approximately 100 acres (40 hectares). This type of carbon is activated with a positive charge and is designed to attract negatively charged water contaminants. Carbon filters are most effective at removing chlorine, sediment, and volatile organic compounds (VOCs) from water. However, they are not effective at removing minerals, salts, and dissolved inorganic compounds. Read more about carbon adsorption.
Ultraviolet (UV) filtration uses low-pressure mercury-vapor lamps to emit about 86% of their light at 254 nanometers (nm), which causes adjacent thymine molecules on DNA to dimerize (combine with similar molecules). If enough of these defects accumulate on a microorganism's DNA, its replication is inhibited, thereby rendering it harmless (even though the organism may not be killed outright). However, since microorganisms can be shielded from ultraviolet light in small cracks and other shaded areas, UV lamps are used only as a supplement to other filtration techniques (in this case the membrane and carbon filters). The UV lamps must be replaced after 9,000 of use or annually (whichever comes first) because their germicidal effectiveness diminishes over time. You can read a more in-depth explanation of ultraviolet disinfection for potable water.