Water Filters

Time:2017/4/28 13:44:55

 The topic of water filters is complicated because there are so many models available, and because there are so many types of filtration strategies and combinations of strategies used.

The basic concept behind nearly all filters, however, is fairly simple. They work by physically preventing contaminants from moving through the filter. There are 4 main types of filters:

1. Sediment Filters - trap contaminants by screening them out with very small pores.

2. Carbon Filters - trap contaminants by attracting them (through the process of adsorption) to the surface of carbon particles.

3. Reverse Osmosis Filters - use water pressure to force water molecules through a membrane that has extremely tiny pores, leaving the larger contaminants behind.

4. KDF Filters - use electrochemical oxidation and reduction to eliminate contaminants from water.

Filter performance is often rated in terms of micron or sub micron filtration. This is a measure of how good the filter is at removing particles from the water - smaller is better. A micron is a unit of measure - one micron is about 1/100 the diameter of a human hair. 
A filter that removes particles down to 5 microns will produce fairly clean-looking water, but most of the water parasites, bacteria, cryptosporidia, giardia, etc. will pass through the pores.

A filter must trap particles one micron or smaller to be effective at removing cryptosporidia or giardia cysts. Viruses can not be effectively removed by most filtration methods. In theory, reverse osmosis will remove viruses, however, just a small flaw in the membranes would allow viruses to pass undetected into the ’filtered’ water. UltraFiltraton (UF) membranes are the only filter systems that can reliably remove viruses.

A benefit of most home filtration systems is that they are passive. That is, they require no electricity to filter the water. The only routine maintenance required is periodic replacement of the filtration element.