Resource Development Partners International

The Ceramic Water Filter - Background

Why Ceramic Water Filters?

While a few areas in China have drinking water contaminated with heavy metals or have too high concentrations of fluoride, fecal contamination of source waters is almost universal. If the source water is not contaminated, then water often becomes contaminated in transport or storage. In fact, according to the experience of experts at RDPI, greater than 90% of all rural drinking water is contaminated with fecal contamination.

While boiling is one method to reduce biological contamination problems in water, it does not remove all problems, and most rural people do not often drink fully boiled water. They prefer fresh, cool water. On top of that boiling requires a fuel source which in rural areas is almost surely wood. This requires felling of trees, carrying the wood to homes typically by the elderly or by girls who should be in school, and increasing the carbon footprint of each family.

A recent review of literature sponsored by the World Health Organization* concluded that simple, socially acceptable, and low-cost interventions in homes (point-of-use) have the potential to significantly improve the microbial quality of household water and reduce the risk of diarrheal disease, dehydration, and death particularly among children. Studies in Cambodia showed with a ceramic water filter like the one manufactured by RDPI, diarrhea rates decreased by 46% A similar study carried out in Guatemala showed a decrease in diarrhea rates of approximately 50% with the use of a ceramic water filter.

A Very Brief History

Ceramic water filters were first used by the Chinese who developed them over a thousand years ago. Pots were made of high quality, thin clay which slowly seeped water. While a great improvement over directly drinking contaminated water, they were relatively expensive, fragile, and had low flow rates which made them impractical for most people. In the 1980's Potters for Peace developed on the Chinese method by adding organic material, called burnout material, such as rice husks or saw dust to the clay. Once fired in the kiln the organic material is burned away leaving small pores for the water to seep through. Potters for Peace also thickened the wall of the filter making it both stronger and more consistent in removing microorganisms. Later colloidal silver was applied to the filter itself. Silver has been used for centuries to keep water clean or for medicinal purposes. Adding silver to ceramic water filters improves their biological removal efficiencies.

What is a Ceramic Water Filter

The filters RDPI manufactures is a simple, flower pot shape about 33 cm in diameter and 24 cm tall. It is made with a mixture of high quality clay from a nearby ceramics factory and the burnout material is rice husks. It comes with a lid to keep dusk and bugs out, a receptacle that holds about 25 liters of purified water, and a water faucet. Just pour water in to the filter, which itself holds about 10 liters of water, and wait until the water comes through. Depending on the individual filter, water flows through at a rate of between 2 to 3 liters per hour. This provides more than enough water for drinking and cooking for a typical day in a rural village. With a useful life of 5 years, the ceramic water filter can provide clean, safe water for the whole family for years.

How does the Ceramic Water Filter purify the water?

As we mentioned above, the biggest problem in most areas is the abundance of microorganisms in the water. For microorganism removal the filter has two mechanisms: size exclusion and biocide effect. The filters are designed to have pours so small that microorganisms can not pass. Tests done on filters at RDIC in Cambodia and other facilities show that pores in ceramic water filters are typically less than 1 micron -- smaller than the smallest microorganism. So the filter acts as a barrier, not allowing microorganism to pass.

However, just in case a few pores in the filter are too large, RDPI filters all come with a coating of silver. Silver is a known biocide. If any microorganisms come in contact with silver it will die. However, silver is not harmful to people. That is why we have "silverware" and silver cups. Over the centuries people realized using silver decreases their chances of getting sick. So for an added dose of protection, RDPI adds a silver lining to everyone of its filters. It is safe and effective. To find out more about the use of colloidal silver. Please visit: Wikipedia:Colloidal Silver and frequencyrising.com: Colloidal Silver.

How do we know the filters are effective?

RDPI is following the methods of RDIC. They have extensively studied these filters in both the lab and field. Also, before RDPI sold any filters technicians have tested random samples of filters coming out of our factory here in Kunming to verify quality. Also, every filter is individually flow tested to make sure that each one flows at just the right flow rate. Too slow and it won't produce enough water. Too fast means the pores are too large and microorganisms might pass. Studies have shown that the ideal is 2-3 liters/hour. Also, technicians at RDPI will continue to randomly sample filters to verify that filters continue to meet quality standards of greater than 99% removal of all microorganisms. Presently typical bacterial removal efficiencies are on the order of 99.5% or greater.

Other Organizations Making Ceramic Water Filters