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Manz BioSand Filters


EWB-Hope was partnered with the NGO Life and Water Development Group Cameroon (LWGDC) to find a solution to the water issues in Nkuv, Cameroon. The first problem that was addressed was the issue of lack of water quality. Nkuv is located in a valley and the surrounding hills are dedicated to livestock. When it rains, the surface water becomes highly contaminated with the runoff from the animal feces, resulting in high levels of bacteria in the water. A standard sample of the raw river water contains approximately 680 E. Coli counts; safe swimming water in America must contain less than 300 counts. Human activity is another source of bacterial contamination. After looking at several options, it was decided to use Manz BioSand filters to address the quality issue. There are now approximately 138 filters in the village. 

Manz BioSand filters

The Manz BioSand filter is a point of use, slow sand filtration system. It uses a concrete body, which can be built out of locally available resources; including cement, sand, gravel, and water; and costs approximately $12 per unit. The filter uses fine sand to mechanically remove the parasites found in the water and some of the bacteria. More bacteria are removed by a biolayer, which is a layer of “good” bacteria that kills the harmful bacteria. Overall, a filter used in the right conditions can remove all of the parasites and most of the bacteria found in the surface water.  

Distribution of Filters

One of the questions that had to be addressed was how to distribute the filters to the individual homes. Models from other organizations showed building a central “filter factory” and then transporting the built filters to the home. Due to the lack of infrastructure, this model could not be applied in Nkuv. Instead, local filter technicians were trained in filter production and would then build the filters at the homes with materials that the families helped gather. This model required that both the technicians and the community were trained in filter construction and maintenance. External funding, from Thirst Relief Intentional, was vital in providing the resources for LWDGC to provide the filters to all the families. The NGO and filter technicians have also taken the distribution model and the filters and begun building them in the surrounding area, mostly at hospitals and schools. There have been a total of 656 filters built in the area.  

Analyzing Filters

A quantitative way of determining if the filters are working was the next important part of the project. It was important to make sure that the families knew how to properly use and maintain the filters and that the filters were performing as expected. Teams of students did house-to-house visits and surveyed the filters over several consecutive years. The visits included questions of user perception as well as looking for proper filter use and microbiology testing on samples taken from both the filters and the raw water source. The results were mostly positive, with families using the filters correctly and seeing health benefits from them. The average bacterial removal rate of the filters as of May, 2008 was 90.2%. This increased to 92.4% in 2009, which points to the fact that the filters are being maintained and cleaned by the community. A last step, disinfection by chlorination, is in the process of being introduced to the community as a means of removing the remaining bacteria which is not removed by the filters.