WATER FOR HUMANITY APPROPRIATE TECHNOLOGY:

CERAMIC WATER FILTERS

by Steven G. Herbert

According to a United Nations report, 1.2 billion people in the world (one fifth the world population) lack access to safe drinking water. Twice that number lack proper sanitation facilities. To address this issue, in the year 2000 the UN established among its Millennium Development Goals the objective to cut these numbers in half by the year 2015. The American Society of Dowsers Water for Humanity Fund is proud to be a part of helping to reach this goal.

            Water for Humanity’s stated mission is to fund water resources development globally, in areas of critical need. However, it is unique among water resources development organizations in adding the aspect of dowsing, to locate water resources in a more efficient manner. Thus it improves water resources in terms of quantity, quality and accessibility while also accomplishing its second goal of demonstrating the practicality of dowsing and developing credibility for the art.

            The kinds of projects which the WFH Fund may fund include dug or drilled wells, rainwater harvesting systems, spring capitation projects, distribution of water filters, and building of composting latrines which conserve and protect ground water. WFH operates under the philosophy that all its projects must demonstrate that they are environmentally sustainable, technologically appropriate and culturally sensitive and respectful. Appropriate technology means that the technology proposed must be simple enough to be understandable to the beneficiaries, accepted by the community, repairable by locally trained appointed individuals, made of parts which are locally available or accessible, easy to use and maintain, and be affordable.

            In searching for appropriate technologies involving water purification, WFH came to focus on two in particular, the slow-sand bio-filter and the ceramic water filter. Both of these have the advantages of not involving chemical treatment, which can expose the user to carcinogens, nor needing firewood to boil, which adds the work of gathering and contributes to deforestation. In this article, we will focus on the ceramic water filter.

            The ceramic water filter was the concept of Ron Rivera and a group of potters which formed the organization Potters for Peace (www.pottersforpeace.com).

Image left: The type of clay used to make the filters. At center, a hammer mill used to pound the clay into fine grains. Image right: A screen is used to sieve the clay particles to a certain maximum size.

This filter consists of a large “flower pot” shaped clay filter element which sits in a five-gallon bucket fitted with a spout. In 2007, I had the honor of meeting with Ron in Managua, Nicaragua, and having a tour of the filter manufacturing facilities there. Once clay is locally mined and transported to the factory, the dry clumps are pounded into tiny particles by a hammer mill and sieved so that only uniform fine grains are used. Sawdust is also sieved and dry-mixed with the clay to a certain pre-determined proportion (60 pounds clay to 7.5 pounds sawdust). Eight to ten liters of water are then added to wet mix. This one batch will make five and a half filter elements.

In photo left, sawdust is also screened to be dry-mixed with the clay. At center, both clay and sawdust are weighed mixed in a predetermined proportion. On right, clay, sawdust and water are mixed in an electric mixer.

            Besides sawdust, the organic material can also be rice husks, paper pulp, coffee husks, etc, anything which is combustable. The object is when the firing process reaches and surpasses 400 degrees C, this “burn-out material” burns away to leave the fine pore spaces. The filter elements are “low-fired”, meaning the temperature reaches at least 750 but no more than 1000 so that the porosity is maintained. An assortment of pyrometric cones are used to help the potter gauge the temperature. The pore spaces will be about one micron in size.

            For one filter element, a ball of clay is weighed out to 15 lbs., then put into the press with aluminum mold, which forms it into the "flower pot" shape. After a bit of touchup with a wet sponge, it is set on a shelf to dry, covered, for a day, then up to two weeks uncovered. The kiln used is a "flat-topped Mani kiln." The firing is an 8-hour process, and afterwards the pots are soaked for four hours. Then they are ready for a flow-rate test. The acceptable range is between one and two-and-a-half liters per hour. If the filter element passes the flow-rate test, then it is coated inside and out with a 300cc solution of colloidal silver at a precise concentration, which further inhibits harmful bacteria.

Left photo shows amount of mixture to make one filter element. At center, the mixture is pressed hydraulically in an aluminum mold into a "flower pot" shape. At right, the freshly pressed filter element is wiped with a sponge to smooth out cracks and imperfections.

The finished filter element sits in a 5-gallon bucket fitted with a spout and a cover. One such unit is generally available for purchase at $20 to $40. For maintenance, a brushing of the filter element may be needed about once a month, or never depending on the water, and replacement is recommended about every two years. The price of a liter of filtered water may be as low as 1/100 cent, but never higher than 1/10 cent, far less expensive than bottled water and there is none of the plastic waste. Here, on a sticker attached to the outside of the filter, was a quote, "Cuida tu Vida - Cuida tu Agua" (Take care of your Life - Take care of your Water).

Right photo shows the Flat-topped Mani Kiln used to fire the elements. At center, pyrometric cones aid the potter in judging temperature. On left, after firing, the filter elements go into a four-hour water bath.

There are four main pathogens that are targeted by the filter are worms and protozoa (and their cysts and eggs) with a size of approximately 30 microns, and bacteria and viruses with a size range of two microns and smaller. With a pore space of one micron, the mechanical filtration of the filter element removes 100% of worms and protozoa and 99% of bacteria and viruses. The coating of colloidal silver further acts as a bacteriacide to add another layer of protection. It is not practical or realistic to expect any purification method to remove 100% of everything. Rather, the goal is to remove as much as possible to bring the residual pathogen level down below the “minimum effective dose”. In other words, we seek to bring the level down far below the level in which it could make a person sick.

On the left, if the filter element passes the flow rate test, it gets fitted into a plastic bucket with spout. Center photo shows the container can be either plastic or ceramic. Right photos shows Potters for Peace founder Ron Rivera (right) with apprentices Reynaldo Diaz (left) and Kaira Wagoner (center).

One ceramic water filter is normally enough to serve a single household. It has been proven to be appropriate technology in that it is valued by the beneficiaries, simple to maintain, the filter element is replaceable locally, and the unit is of low cost. Its price is usually within reach of a typical household, and much more so when subsidized by an aid project. Previous WFH projects distributing such filters in El Salvador have demonstrated significant improvements to the health of family members. With appreciation to the late Ron Rivera and Potters for Peace, WFH seeks to see more families benefit on a more global scale.