Clay Water Filter Turn Sea Water to Fresh Water

I"Di had a post with links to a cottage type industry in Africa for a water filter. I'm good at mechanical things, and have done pottery, but I can't figure out that contraption. The principle is easy.

I read long ago about the ancient Greeks, referring to the then ancient Phoenecians, throwing a corked empty jug over the side when at sea, and the next morning hauling in fresh water in the jug. I've puzzled over that for decades and still hadn't figured it out. That mentioned post solved that. If the mix for a vessle is 30% fine wheat flour and 60% ultra fine potter's clay, when it is fired, the flour burns out and leaves a filter mechanism in the 1 to 2 micron variety! Colloidal silver was used in the liquid because silver inhibits or kills bacteria etc. within the vessel. Supposedly it must be semi dry, the wet mix for throwing a vase is supposedly too wet. Who knows? Might a friendly potter be willing to experiment?"

Clay Water Filters are a Simple Solution for Clean Water

I did a search on clay filters and found the following story:

Diseases caused by dirty drinking water kill 6,000 children a day around the world. But millions have benefited from a simple solution using clay filters invented and pioneered in Central America, and now manufactured by 28 small factories in 23 countries - the largest in Ghana and Cambodia. Each factory makes up to several thousand filters a day. They offer an ingenious solution that also creates local jobs and skills.

Looking like 30 centimetre-high flowerpots, the filters designed by Guatemalan chemist Fernando Mazariegos blend local clay and plant husks to create a filter capable of killing 98 percent of the contaminants that cause diarrhoea. The husks are burnt away when the filters are fired in a kiln, creating tiny holes that filter out harmful organisms. A coating of colloidal silver is painted on the filters after they have been fired in the kiln.

“Each filter can support a family of six,” said Kaira Wagoner, Coordinator of Ceramic Water Filter Projects with the NGO Potters for Peace (www.pottersforpeace.org). Founded in Nicaragua but now US-based, Potters for Peace has popularized the filters and helps with all the training and support required to establish the workshops and market the filters.

The first filter-making workshop was set up in Managua, Nicaragua after Hurricane Mitch in 1999 (http://en.wikipedia.org/wiki/Hurricane_Mitch). That workshop has made and distributed 40,000 filters through the Red Cross and NGOs such as Medecins Sans Frontieres/Doctors Without Borders. Potters for Peace has now stopped running workshops and factories themselves, and provides others with the training and advice necessary to produce clay filters.

To work, the filters are placed in a plastic bucket, a spigot added, and a cover put on top to prevent contamination. The filters are capable of filtering four litres of water an hour.

The genius behind the filters is the fact they can be made by small, local workshops - making access to clean water available anywhere, and creating jobs. Just three to four people can produce up to 50 filters a day. According to tests by the Family Foundation of the Americas, a Guatemalan NGO, the filters halve the incidence of diarrhoea in households that use them.

“The cost of establishing a workshop varies largely,” said Wagoner, “depending on the factory’s location, desired production - from 50 per day to 1000 per day - and on the equipment already available in the potter’s workshop. Potters for Peace generally tries to work with potters who already have some of the needed equipment, such as a hammer mill and clay mixer.

“Filters are distributed hand in hand with health and sanitation information which highlights practices such as hand washing,” said Wagoner. “Since many individuals would otherwise boil their water, the filter significantly reduces the time many women would spend gathering firewood. This gives them time for other things such as school and income generating activities, and is better for the environment, especially in locations where problems with deforestation are significant.”

Experience has found marketing is key to the successful adoption of the filters by communities.

“It is very difficult to create a market in a region of poverty,” said Beverly Pillars, also from Potters for Peace, “and to gain acceptance of a new product that the community will want to purchase to keep a workshop sustainable. NGOs may distribute the ceramic water filters, but for the community to fully accept the idea of seeking out clean, safe drinking water on their own, we urge the local owners of the factory to be innovative in marketing.

“Our best approach has been to select partners in developing areas that have some experience such as a potter or brick maker, and help them to find methods that work in their communities to distribute as many of the ceramic water filters as possible, such as a distribution link through local health centres and small corner markets, adds in Yellow Pages, road signs.”

To get a workshop up and running, they need to have a machine to press the clay filters, a kiln to fire them, and a pyrometer (http://en.wikipedia.org/wiki/Pyrometer) to measure the temperature of the kiln. It usually takes between three and six weeks of training to become proficient at making the filters. Trainers help with acquiring the proper equipment, building the kiln, the clay filter formula, quality control procedures, and marketing techniques and materials.

“My advice to people wanting to start making filters is to look for local craftspeople to partner with,” said Pillars. “Look at local access to brick, clay and sawdust. Be prepared for hard and rewarding work to bring safe, clean drinking water to developing populations.

“Every location is a best location, because the demand for safe, clean drinking water worldwide is so great. The beauty of the ceramic water filter technology is that it uses very few resources: clay, sawdust or other burnout material available and bricks for a kiln. We have found these resources to be present worldwide.”

The filter has been cited by the United Nations’ Appropriate Technology Handbook, and is used by the International Red Cross and the Nobel Prize winning medical relief organization Doctors Without Borders. There are plans to start more filter factories in Cote d’Ivoire, Bolivia and Somaliland.


I asked the engineers at www.WaterAid.org what they thought about the water filter. I believe that they are the experts in bringing clean water to people as cheaply as possible. Here was their reply:

Stephanie, Thanks for your message.

We do not use ceramic water filters Stephanie.We are aware of Potters for Peace.They work in Africa as well as South and Central America.

The filters do work but produce small amounts of water per day. Several filters are required to meet the daily need of 25 to 30 litres per person. If they are used to treat turbid water the filter needs to be frequently scrubbed clean to remove the retained material This abrasive treatment rapidly wears away the ceramic.Care has to be taken to prevent cracking of the ceramic as short circuiting of the filter by pathogens can occur.

There is one advantage in that the filters are low cost but if the surface water that they are treating is highly turbid the filters may have a relatively short life.

Some Thoughts on Water Treatment in Developing Countries

In projects adopting low cost appropriate technologies for water supply and sanitation it is essential in terms of their long-term sustainability that they are within the technical and financial capacity of the benefiting community to be able to operate and maintain them.

Consequently it is usually cheaper and more sustainable for communities to prevent pollution and preserve the quality of their water resources than it is to treat polluted water. For example a community can fence off the catchment area of a small upland stream or spring to keep animals and children away from the site or keep the area clear of decaying vegetable matter to reduce potential taste problems and coloration. Alternatively the water from the source would have to be settled or put through a sedimentation process using a chemical coagulant and subsequently filtered and disinfected. The energy and chemicals required would be beyond the financial capacity of poor communities to procure them. Whereas the simple water quality conservation activities would be very easily achieved at little or no cost, although the community would have to devote their time to the tasks.

The exceptions to the foregoing are one or two instances where slow sand filtration is adopted when there is no alternative to a surface water source such as a river, stream, lake or pond being used as no alternative is feasible, other than perhaps rainwater harvesting.

Any source that is highly turbid with high suspended solids must be filtered before disinfection with chlorine etc. This is because particulate matter left in suspension may contain encapsulated pathogens that if chlorinated would escape oxidation. Subsequently this encapsulation could break down when ingested and carried into the gut of the drinker and thereby infecting that person.

These principles hold true for the hand dug wells, tubewells, rainwater harvesting, spring protection etc. that form the basic resources which we adopt.

Ceramic filters like solar disinfection (SOLDIS) do work but have the drawback of relatively low output, and for solar disinfection, doesn't work effectively in overcast weather.They also involve time consuming filter and bottle charging.activities.

Thanks for your interest in and support of WaterAid.

Best wishes,

Ray Heslop
Engineering Adviser


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