Evaluating Ceramic Water Filters

Protozoan cysts (i.e., Cryptosporidium parvum oocysts) in the water supply caused a number of deaths in Milwaukee, Wisconsin in 1993. As a result, many people are quite concerned about removing cysts from their water. This has resulted in ceramic filters becoming more and more common in the U.S.

Developed in Europe in the 1860s as a result of Louis Pasteur’s new germ theory (as a cause of illnesses), they were first popularly used by the military and by hospitals, then for domestic water supplies. Within two decades, ceramic water filters were being manufactured and promoted to combat highly infectious waterborne diseases such as typhoid fever, cholera and dysentery. Not surprisingly, the use of these life-saving filtering devices soon spread to other countries and colonies where conditions often favored the transmission of illnesses from polluted water.

What is a Ceramic Filter?

While the precise composition of various ceramic filters may vary, they’re generally are made of a high-temperature-fired type of diatomaceous earth (DE). DE is a fine silica powder made up of the cell walls of microscopic algae. It seems that the specific filtering ability of a ceramic filter depends on it’s pore size, and pore size is primarily determined by the ceramic base material used and the temperature at which it was kiln fired.

How do Ceramic Filters Work?

Very simply. Water just seeps through the tens of millions of pores in the ceramic material, which is usually in a cartridge form. In this process, solids (such as many kinds of sediment and organisms) accumulate on the ceramic surface — if they’re too large to pass through. For your information, most (some filters claim as high as 99.9%) of Cryptosporidium parvum oocysts are caught through this process.

You should be aware that sometimes a silver compound is incorporated into the ceramic itself to act as a bacteriostatic agent (to counter bacterial growth on, or in, the filter). These filters are manufactured in such a manner that the silver cannot migrate into the finished filtered water. However, the U.S Federal Trade Commission (FTC) reported that filters with bacteriostatic additives “have shown unpromising results.” In other words, silver does not meet the FTC’s anti-bacterial expectations of effectiveness.

Today, ceramic filters can be purchased as stand-alone, counter-top, gravity-feed models (no added water pressure is required to make the water pass through the filter) or combined with activated charcoal in some type of filtering cartridge. Often, manufacturers will suggest periodically washing the ceramic off. Depending on the kind of cartridge, it may last 6-12 months. (Read manufacturer’s product literature to be certain.)

The Downside

Drawbacks include the fact that volatile organic chemicals (VOCs), chlorine and other undesirable odor and taste compounds, wi...