At one time, impregnated silver was the main element in water filtration systems. However, in recent years it has been replaced by KDF (for more information on KDF view our blog entry What is KDF?).
Silver in Water Filtration:
(1) Silver inhibits the growth of bacteria within the water filter unit
(2) Designed to remove objectionable taste, odors, and color from municipally treated tap water.
KDF in Water Filtration:
(1) KDF Process Media enhance the performance, extend the life, reduce the maintenance and lower the total cost of many available carbon-based systems.
(2) KDF Process Media help control microorganisms by creating an environment that's deadly to some microorganisms and that interferes with the ability of many other microorganisms to function.
With both elements having similar effects within water filtration systems, why the sudden shift from using silver to KDF?
Beginning in 1991, silver had to be registered with the EPA as TOXIC because:
(1) In humans, silver can be absorbed from the lungs and gastrointestinal tract. When an excessive amount of silver is absorbed, tissues become impregnated with silver sulfite, which forms a complex in elastic fibers. Large amounts of this complex under the skin will give it bluish, grey-blue, or in extreme cases a black color. This condition is called argyria. Although it is not a toxic effect, argyria is undesirable and usually permanent. Excessive exposure to silver can also cause lung and kidney lesions and skin contact can cause mild allergic reactions such as rashes, swelling, and inflammation.
(2) Silver is highly toxic to fish, aquatic invertebrates, and estuarine organisms.
KDF Process Media vs. Silver-Impregnated Carbon