This means that the deiment is washed off giving the filter a longer life. This is only practical for filters over 5 microns. This system will also remove organics, herbacids, pesticides, some viruses and detergents. The granular carbon filters usually have a micron rating of 25, are now less popular simce the advent of corbon block cartridges. Carbon block cartridges let water flow through faster and can have micron ratings as low as one.
Carbon filters are the most widely advertised.
KDF has a brown metallic substance, that when water passes through it, creates an electro-chemical reaction. It crates a current of 0.4 volts that should change clorine into chloride etc, which is less harmful and is easier to filter. KDF coupled with carbon produces a filter with a longer life than carbon alone. KDF will remove a small quantity of some heavy metals. They are usually combined with carbon and sediment filters so as to catch chlorine and particulates as well.