PureMadi - A Ceramic Filter For Purifying Drinking Water

Interview conducted by G.P. Thomas

James Smith is a Professor in the Civil and Environmental Engineering Department at the University of Virginia and also the founder of PureMadi. In this Iinterview he talks about the unique properties of their ceramic filters and why water filtration so important for the health of many countries. 

GT: What issues still surround the availability of clean drinking water in some areas of the world and what problems do these cause?

JS: Here in the US, we have great centralized water treatment plants that are highly regulated, can supply high-quality water 24/7, and that provide a chlorine residual throughout the distribution system. In many parts of the developing world, there are not sufficient resources to provide this level of service.

As a result, a decentralized approach, wherein water is treated in the home right before consumption, offers great promise to improve global water quality. When people drink untreated water, the may consume waterborne pathogens like Vibrio cholerae, pathogenic strains of E. coli, or protozoan pathogens like Cryptosporidium parvum.

These pathogens cause gastrointestinal infections that cause diarrhoea, stomach pain, vomiting, and dehydration. Symptoms can be particularly severe in children. About 2 million children die each year from drinking contaminated water, and many more are subject to cognitive impairment and growth stunting.

Due to insufficient resources clean water is a still a luxury in many parts of the world. Image credit: PureMadi.

GT: What are the most common methods currently employed to make clean water available in impoverished countries? Are there any shortfalls associated with these methods?

JS: Unfortunately, several billion people drink contaminated water at least some of the time. There has been an increased interest in the development and testing of point-of-use water treatment technologies, including the Pur Sachet from Proctor and Gamble, solar disinfection, silver-impregnated ceramic water filters, and our invention, the MadiDrop (a ceramic water purification tablet).

GT: Could you give a brief history of ceramic water filters and how these have developed?

JS: Ceramic filters for developing world communities have been developed over many years and lots of people have contributed to their manufacturing and dissemination. Most notably, Ron Rivera of the organization Potters for Peace helped to establish a few dozen ceramic filter factories around the world.

GT: How do ceramic filters help to purify water and how are these manufactured?

JS: The filters are made from clay, water, and sawdust. These ingredients are mixed in the proper proportions and pressed into the shape of a pot with a filter press. The pot is then fired in a kiln at 900 ˚C. At these high temperatures, the clay hardens into a ceramic and the sawdust combusts, leaving behind a porous ceramic matrix.

The finished ceramic filters. Image credit: PureMadi

After cooling, an aqueous suspension of silver nanoparticles is painted on the inside and outside of the filter. The silver nanoparticles lodge in the pore space of the filter. When water passes through the filter, particles and microorganisms are removed by both physical filtration and chemical disinfection, as the silver is a very effective antimicrobial agent.

The filters are designed to fit into common 5-gallon plastic buckets, and by attaching a spigot, the bucket becomes a safe storage reservoir for the treated water. The filters can treat 1-3 Liters per hour of water.

Applying colloidal silver to the filters. Image credit: PureMadi

GT: How did you become interested in ceramic filters and how did PureMadi get started?

Organizations like Potters for Peace did a great job of teaching communities how to make ceramic filters. However, they were potters, not water quality specialists. So in many respects, they did not fully understand how the filters worked or even IF they worked. When I heard about their work, I was skeptical but intrigued.

Under a grant from the National Science Foundation, I began to test the performance of the filters. They worked great in the laboratory! Then we tested them in Guatemala and they continued to work well. Then we tested them to see if they could improve human health in S. Africa, and they did! So, we decided to create our own production facility that built upon the expertise developed by organizations like Potters for Peace and also our strong understanding of fluid flow in porous media, water chemistry, and environmental microbiology and health.

GT: What are the economic benefits of using ceramic filters?

JS: They are low cost and highly effective, so it offers a path for even relatively poor communities to improve their water quality and health. Even better, revenue from filter sales remains in the community, creating jobs and economic development.

GT: Could you briefly explain the ‘MadiDrop’ and how this is used?

JS: The MadiDrop is an entirely new point-of-use water treatment technology developed here at the University of Virginia. It is a silver-impregnated porous ceramic “tablet”. To use it, you simply drop it into a water storage container, fill up the container with water before bedtime, and the next morning, the water will be safe to drink. Just fill it up again each night at bedtime. We believe the MadiDrop will last for 6 months or more. It is lighter and less fragile than the ceramic filters, so it can easily be transported long distances. And it likely will have a retail price about one fifth of the ceramic filter.

GT: What does the future hold for PureMadi?

JS: Over the next 10 years or so, we hope to create 10-12 ceramic filter factories around the world. Our first factory in Limpopo Province is complete thanks to help from our partners at the University of Venda and Rotary International. We are already making plans for a second factory in South Africa.

We are also working in collaboration with the University of Venda to test the performance of MadiDrops in the field in South Africa and we have created a trial production facility here in Charlottesville for MadiDrops. We are very excited about the future!

It is hoped that PureMadi will continue to expand and provide drinkable water far into the future.  

About James Smith

James Smith is a Professor in the Civil and Environmental Engineering Department at the University of Virginia.  He is the founder of PureMadi (www.puremadi.org), and organization dedicated to disseminating metal-ceramic technologies for household-level water treat throughout the developing world.

PureMadi is composed of an interdisciplinary team of students, faculty, and staff from the University of Virginia.  They have partnered with students and faculty at the University of Venda in Thohoyandou, South Africa and Rotary International to create the first ceramic filter factory in South Africa.  

Professor Smith has BS and MS degrees in Civil Engineering from Virginia Tech and a PhD in Civil Engineering from Princeton University.  He has bee on the faculty at the University of Virginia since 1992.


Date Added: Aug 27, 2013 | Updated: Jan 18, 2014
  1. Ramkumar Narendran Ramkumar Narendran India says:

    It is great for the needy. There is enough for every body's need not greed. Also an effective way to live with that need and don't destroy nature. This ais a good first step.

  2. Ssali Gadafih Ssali Gadafih ug says:

    Hello Smith, thanks for the great work u did. my question is about the silver application, how do u mix/ know the concentration of silver to be applied to a filter? expect a quick response, thanks.

  3. Ssali Gadafih Ssali Gadafih ug says:

    Also would like to access your detailed design analysis the one u used to know the internal/external diameters, expected pore size, thickness of the filter, height/ vertical length, and flow rate. thanks once again

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