Ceramic Filters: The Fight Against Bacteria, Viruses and Protozoa

Until recently, the United States was essentially a carbon filter market, in that chlorine, dirt, foul taste and odor were thought to be the only problems with drinking water. With the advent of the Cryptosporidium parvum outbreak in Milwaukee in 1993, the general public and water treatment dealers started to question the quality of municipally treated water and private wells.

The quality of drinking water is no longer taken for granted and has been the subject of tremendous attention from various pressure groups and the media during recent years and with good reason—many of the older treatment plants are incapable of effectively reducing Cryptosporidium to safe levels.

There are various definitions of "safe." The U.S. government considers that 10 or less viable Cryptosporidium oocysts are an infective dose, while the British government believes that one viable oocyst is an infective dose. It really depends how old, how fit and how healthy you are at the time you consume contaminated water.

How can someone protect himself from consuming water contaminated with Cryptosporidium or other microorganisms? One durable and competitively priced option is ceramic filters.

Ceramics origins easily can be traced to the early 1800s when bacteriological studies by Louis Pasteur and others led people such as Henry Doulton to devise a ceramic filter for drinking water when safe drinkable water was scarce. Pasteur’s problems in the 19th century were a combination of disbelief in his ideals of microbiology and solutions to the bacterial problems during that time. Unknowingly, he devised the first filtration device that opened the door to what is now a widely diverse industry.

Today’s ceramic filters have come a long way from the basic designs of the past. One method used today is a filter element that incorporates oligodynamic silver that is impregnated into a porous ceramic outer shell (80 million pores) that can trap bacteria down to as low as .22 of a micron in particle size (1/100,000 of an inch).

Laboratories consider a filtering medium with an effective pore size of .01 micron to .45 micron to be bacteriologically "sterile" and .45 micron to 1.0 micron to be bacteriologically "safe." Re-growth of the bacteria that becomes trapped on the outside of the element or in the ceramic’s pores is controlled by the silver that, on contact with water, releases small quantities of positively charged metal ions. These ions are taken into the enzyme system of the bacteria’s cell and are neutralized. The flow of a ceramic is renewed by brushing the outer surface—the top layer of ceramic and contaminants—allowing a new layer to be available. This process can be repeated several dozen times before the ceramic material is exhausted.

What does a ceramic filter offer the end consumer in terms of effectiveness? Although only a small proportion of the myriad of microorganisms that abound in nature are disease producing or pathogenic to man, the ones that are should be discussed to explain a ceramic’s effectiveness. Three basic groups affect North America: bacteria, protozoa and viruses.

Bacteria, in most cases, have rigid cell walls that maintain their characteristic shape (spherical, rod-shaped, comma-shaped and spiral). Harmful bacteria, better described as disease causing enteric pathogenic bacteria, thankfully, are few in number (cholera, shigella and salmonella) and therefore, reliance is placed on relatively simple and more rapid bacteriological tests for the detection of certain commensal intestinal bacteria such as Esherichia coli (E. coli).

E. coli and other coliform bacteria are easy to isolate and characterize because they always are present in the feces of humans and warm-blooded animals; therefore, they have a large presence in sewage. Very few harmful bacteria are smaller than
1 micron in size and are easily removed by ceramic filtration.

Viruses are the smallest and simplest infectious microorganisms known and can be up to 1,000 times smaller than some bacteria. They have no ability to travel independently, requiring adherence to other particles to "hitch a ride." Viruses can be removed through adsorption by filtering out a particle from which the virus is attached.

The best known of the protozoa, often referred to as bacteria, is Cryptosporidium. This organism, together with Giardia lamblia, causes a greater health threat than most other microorganisms. Protozoan organisms are chlorine resistant in their cyst form, and are resistant to freezing, heating, abrasion and ultraviolet light. However, due to their size (2 to 6 microns), both Cryptosporidium and Giardia can be removed by the ceramic filter.

A ceramic element may contain additional filtration media within the shell of the structure, whereby it can process from the water additional contaminants such as lead, organic and inorganic chemicals, foul tastes and odors. Once the water passes through the ceramic shell, the particulate-free water then can be processed via the additional media.

A ceramic filter element offers a simple, effective and often economical means of producing safe, clean, potable water fit for human consumption.

About the Author
David Webb is president of Ceramic Filters Co., which has distributed Doulton and British Berkefeld products in North America for more than 10 years. His experience within the field of water filtration spans almost 30 years. David and his staff can be reached at 517-467-4788; e-mail [email protected]; www.doultonwaterfilters.com.

What Is a Ceramic Filter Element?

A ceramic filter element is manufactured primarily of diatomaceous "earth." This earth is a fossil substance made up of tiny silicon shells left by trillions of microscopic, one-celled algae called diatoms that have inhabited the waters of the earth for the last 150 million years. Unlike other algae, diatoms weave shells, microscopic in size, which they use for protection and locomotion.

These shells are covered with a pattern of tiny holes so regular that the slightest change in design usually signifies a different species. As these diatoms died, their shells remained, piling up as deposits that are known as "diatomaceous earth." There are now more than 1,500 uses for this earth, ranging from abrasives for toothpaste, filtering agents for water and milk and insulators for kilns.

ceramic filters

Can you list what ceramic filters filter out and the appoximate%?


About the author