Over the past 5 years, PureMadi, a non-profit organization composed of UVA faculty, students, and alumni, have created a ceramic water filter factory in Limpopo Province, South Africa. The factory is fully functioning and has produced and sold more than 1000 filter units. In 2015, PureMadi entered into a partnership with Khulisa Social Solutions, a 300-employee South African NGO. Last summer, a JPC team partnered with PureMadi and Khulisa to create the infrastructure for a second filter factory in Hammanskraal, South Africa. This includes a concrete open-air structure, a paved factory floor, a fence around the factory premises, a borehole for water supply, a hammer mill, a sieve table, and a filter drying rack.
This summer, we returned to the Hammanskraal factory with two primary objectives. First, we wanted to optimize the clay to sawdust ratio to achieve a flow rate of 1.5 – 3.0 L/hr (demonstrated in the literature to be an optimal range for disinfection via impregnated silver nanoparticles). Second, we wanted to teach local community members how to manufacture the filters.
Silver-impregnated clay-based ceramic water filters have been identified as an inexpensive, sustainable, and effective method of water purification. The method is simple – first, clay is mined from a dried riverbank and mixed with sawdust and water until the mixture is pliable enough to be molded into the shape of a flowerpot using a hydraulic press (pictured). The main mineral in clay, kaolinite, contains 1:1 silicon to aluminum oxides which form layers that hydrogen bond with each other. After molded filters are arranged in a kiln, they are heated up to 300 degrees Celsius, at which point the sawdust combusts, leaving behind micropores in the clay. The temperature is then ramped up to 500 degrees Celsius, at which point all water is driven off and the hydrogen bonds are replaced with shorter and stronger oxygen bridges which causes the clay to shrink down to 95% of its original volume. The temperature is then finally brought up to 1000 degrees Celsius to form any remaining oxygen bridges at which point it is considered ceramic.
The ceramic filters are then removed from the kiln and subjected to two tests – the pressure test and flow rate test (pictured) – which assure that there are no macroscale cracks in the ceramic and that the rate at which water flows through the pores is slow enough for the silver to act as a disinfectant. The filters that pass both of these tests are coated with a suspension of silver nanoparticles which embed themselves in the micropores left behind by the burnt sawdust. When water passes through the filter, any bacteria that contaminate the water ingest the silver which disrupts their metabolism. This method effectively kills most water-borne pathogens and there is enough silver to extend the lifespan of a single filter to two years if they are properly cleaned with boiling water every six months.
“Adapt” – that seemed to be the running theme of our mission here in South Africa. Our initial goals we set when we applied for the Center for Global Health Travel grant were the following: 1.) Establish positive relationships with people in the Hammanskraal area 2.) Find the optimal ratio of Clay/Sawdust for the ceramic filters created in the Hammanskraal area 3.) Teach the workers at the filter factory how to make filters. Prior to arriving, we were under the impression that the filter factory had electricity and ventilation for the kiln which, once we arrived, was not the case. We were first advised by our community supervisor that the electricity and ventilation would be installed within two weeks, but it turns out that contracting in South Africa is harder than it seems which brings us full circle to the main theme of our trip – “adapt”. We had to adapt the goals of our trip in order to suit the hand that we had been dealt.
We subsequently adapted our goals, with the permission of our wonderful faculty advisor Dr. Jim Smith, to the following: 1.) Build more filter drying racks for the factory since there will need to be significantly more once the factory is fully operational. 2.) Paint the exterior of the building to ensure that visitors and deliveries can spot it easily. 3.) Contract welders to weld bars to the doors and windows since the factory is in a high crime area 4.) Bolt the storage locker to the wall to ensure no one can take it in the middle of the night. 5.) Find and open up a clay deposit near the factory so that once the factory is operational, the workers can start extracting clay immediately. 6.) Hook up the factory to electricity to power the kiln, hammer – mill, and other necessary machinery. 7.) Contract someone to lay concrete for the factory floor so expensive machinery can be bolted down. While none of these are the goals we were initially looking to accomplish, all of these goals would help to accomplish the long – term sustainability of the filter factory for PureMadi. If there are any words of wisdom we can give to other CGH teams, it’s that if problems arise, don’t feel afraid to adapt your goals if need be.
Our next blog post will cover some more background on the accessibility of clean water throughout South Africa and the corresponding effects on public health. We will also discuss the art of tempering our desire for continual progress with the culture and resources available to us in a foreign country. Stay tuned!