Source: Wikipedia and Doulton
Ceramic water filters are an inexpensive and effective type of water filter, that rely on the small pore size of ceramic material to filter dirt, debris, and bacteria out of water.
Doulton ceramic cartridges filter particles from the water but leaves oxygen and mineral contents unchanged, which gives water it's spring-like freshness and taste (not "pure" but wholesome). Pathogens of the most varied diseases which are reliably filtered from the water include; cholera, typhus, cryptosporidium, amoebic dysentery, ecoli, colibacillose or bilharzia, anthrax spores among others.
Doulton Ceramic Filter Elements have been trusted by relief organizations around the globe for over 150 years. These filters were developed in the 1850's to remove disease causing bacteria from London's Thames River.