KDF Filters

KDF filters employ a matrix (generally small granules) of a zinc/copper alloy, which eliminates contaminants from water by utilizing electrochemical oxidation reduction. Chemical properties of KDF include its ability to remove chlorine (actually changes free chlorine to a less active form), Kill algae and fungi, control bacterial growth in the filter.
Remove hydrogen sulfide, iron, lead, cadmium, aluminum, mercury, arsenic and other inorganic compounds, partially reduce hardness.

Zinc and copper are the preferred metals used in the KDF alloy since both are relatively good reducing agents with respect to common inorganic contaminants (such as chlorine), and both can be tolerated in solution in moderate concentrations without adverse side effects.

 The advantages of KDF filters include:

KDF is the only filter that allegedly removes contaminants from running hot water (unlike carbon filters where hot water can release trapped contaminants into the water stream).  This makes them ideal for use in the shower. 
The filters change the free chlorine some people are allergic to into a form (zinc chloride) that is much more easily tolerated.

 The disadvantages of KDF filters include:

KDF filters do not remove organic chemicals (pesticides, disinfection byproducts, etc.), or parasitic cysts (giardia and cryptosporidium), KDF filters need to be backwashed periodically with water to remove the insoluble contaminants.