In polluted or even unfiltered mountain water there are many parasitic organisms and inorganic chemicals that are dangerous to humans.

Common organisms:

• giardia, which causes gastroenteritis
• cryptosporidium, which causes gastroenteritis

Common Chemicals:

• Lead
• Arsenic
• Mercury

Reverse osmosis

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A reverse osmosis filter is larger and requires more energy than a pressure-gradient design that fits on a water faucet.

Atmospheric water generator

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Atmospheric water generator (AWG), WaterMaker (WM), Air to Water Harvest (A2WH) and Water Air Extraction Devices (WAED) are machines that produce pure drinking water from the air we breathe, in other words from atmospheric moisture. An AWG operates in a manner very similar to that of a refrigerative dehumidifer: air is passed through a cooled coil, causing water to condense. The amount of water that can be produced depends on the humidity, the volume of air passing through the coils, and the size of the machine.

Handheld filters

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In the handheld sizes, there are gravity based filters like Brita and handheld pumps. These are usually based on active carbon filtration.

No energy filters

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For minimal energy, "chlorine" tablets can be used to kill off organisms. However, these chlorine tablets should be used within 6 months or they lose their effectiveness. Care should be taken in keeping the container tightly sealed, because air quickens the tablet's deterioration.

See also

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• Atmospheric water generator
• Water purification
• Sewage treatment

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