Filtration Background
As a member of the first MIT Masters of Engineering Nepal team, Junko Sagara `00 began study of filtration for appropriate point-of-use drinking water treatment in Nepal. She tested three filter/ purifier systems including a Nepalese ceramic candle filter (with and without colloidal silver[1] coating), an Indian ceramic candle filter, and the Gift of Water[2] purifier. While the Nepalese filter coated with colloidal silver was the only filter to successfully remove all hydrogen sulfide producing bacteria, no filters removed microbial contamination without the addition of chlorine. Additionally, Sagara recommended further study of the Biosand filter, a promising slow sand filtration technology developed by Dr. David Manz at the University of Calgary. The following year, Tse-Luen Lee `01 found that while the Biosand filter removed 99.5% of coliform bacteria in the laboratory, only 9 of 12 properly functioning Biosand filters currently used in Nepalese households removed total coliform. He noted the importance of a monitoring program to ensure the correct construction, operation, and maintenance of Biosand filters in order to increase the number of properly working filters.
Building on prior filtration studies, the filtration portion of the Nepal Project in 2002 aims to develop or discover a filtration system that successfully removes pathogens (bacteria, protozoan parasites, viruses), has an adequate flow rate, and is appropriate for point-of-use drinking water treatment in Nepal. An appropriate technology is simple, economically sustainable, socially acceptable, and uses local resources. Its function must be understood and accepted by community members, and its importance obvious (i.e. cleaner water). (Murcott, 1999) Specific Biosand filter variables will be examined in greater detail while preliminary studies of the Terafil Terracotta and Thimi Terracotta filters will be preformed in this new work to determine whether these filters should be recommended for widespread use in Nepal.
[1] Colloidal Silver is a disinfectant painted on ceramic filters made by Potters for Peace, an international aid organization based in Nicaragua directed by Ron Rivera.
[2] In 2000, this purifying system was known as the Industry for the Poor filter created for use in Haiti by Phil Warwick.