Water Filters!

One day when Satan and God were having a weekly meeting (something Satan had started a few years previously. He got the idea from a new breed of residents called management consultants that had turned up in hell and told the most awful lies about how they had improved everything in their earthly life. In reality they had actually caused hell on earth), Satan started to boast that he was cleaning up the part of hell where he had to live. As a result of some engineering there was now clean water and no waste and corruption at all in his part of hell.

God got quite annoyed at this and said that all engineers belong in heaven not hell. Satan said, "Well some people who had once been engineers, had become managers instead and had slipped your net, but they still knew enough about engineering to do some good".

God - "Send them all back to me this instant"

Water Filter

An industrial water filter with geared motorA water filter is a device which removes impurities from water by means of a fine physical barrier, chemical processes and/or biological process. Filters are used to cleanse water for irrigation, drinking water, aquariums, and swimming pools.

Water filters are primarily used to soften water and remove chemicals such as chlorine. Some scientists believe that the contaminants found in drinking unfiltered drinking water can be harmful to your health, even increasing the risk of developing cancer. The most common problem with unfiltered water, however, is a bad taste or smell.

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 water bottle (or other container, such as a Camel Back). These types of filters work to remove bacteria, protozoa and cysts, all of which can cause disease. Popular and reliable makers of these small, portable water filters include General Ecology, Innova Pure Water, Katadyn,Mountain Safety Research, and Pure Water 2GO. 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 viruses, such as hepatitis A and rotavirus, among others.

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.

Water Filter Examples

Media filter

Screen filter

Disk filter

Slow sand filter bed

Rapid sand filter

Cloth filter