Emergency drinking water

Water filters are also used by recreational hikers, by aid organizations during humanitarian emergencies, and by the military. These filters are usually small, portable and light (1-2 pounds or less) and usually filter water by working a mechanical hand pump, although some use a siphon drip system to force water through. Dirty water is pumped via a screen-filtered flexible silicon tube through a specialized filter, ending up in a container. These types of filters work to remove bacteria, protozoa and microbial cysts, all of which can cause disease. Filters include fine meshes, which must be replaced, and ceramic filters which must have their outside abraded off when it becomes clogged with impurities.

 

These water filters should not be confused with devices or tablets that are water purifiers. Water purifiers satisfy higher EPA standards, and also remove or kill viruses such as hepatitis A and rotavirus. In a domestic emergency, where water needs will last beyond those of stored, bottled water, a device that is specifically certified as a water purifier, and not a water filter, is preferred.

 

The physics of filters is based on sieving, adsorption, ion exchanges and other processes. Unlike a sieve or screen, a filter can remove particles much smaller than the holes through which the water passes.

 

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