Bioethics Institute Develops Sustainable Water Filter

Tuesday, August 7, 2012

PHILADELPHIA (Aug. 7, 2012) - The World Health Organization estimates that 1.1 billion people worldwide lack access to a safe and adequate water supply. To help address this public health crisis, a team of students, faculty and fellows associated with Saint Joseph’s University’s Institute of Catholic Bioethics has developed an inexpensive and sustainable slow-sand water filter for use by less-developed nations.

Bioethicist Peter Clark, S.J., professor of theology and health services and director of the Institute says he expects the filters to be available for use in September. “Everyone on the planet deserves access to clean water – it is a basic human right,” says Fr. Clark. “We are thrilled that this project has come to fruition, and that the filters will very shortly be contributing to a better quality of life for individuals living in vulnerable communities.”

A paper about the project titled “Slow-sand water filter: Design, implementation, accessibility and sustainability in developing countries,” coauthored by Fr. Clark; microbiologist Catalina Arango Pinedo, Ph.D., assistant professor of biology; and Institute fellows Mathew Fadus ’12 and Stephen Capuzzi ’12, was published recently in Medical Science Monitor, an international medical journal of experimental and clinical research.

“A group of us witnessed the need for clean water in Dar Es Salaam, Tanzania, in 2007, while working at St. John’s Parish Medical Center, where many people – children especially – were dying at a very high rate from water-borne illnesses like typhoid and bacterial diarrhea,” says Fr. Clark. “Realizing that a low-cost water filter could help lessen mortality from these diseases, we started working on several slow-sand water filter models when we returned to the U.S.”

The team spent the next four years experimenting until they optimized the current model, which meets the four criteria set for the project: the filter had to be cost-effective, reliable, sustainable and accessible. Comprised of two five-gallon plastic buckets, one spigot, gravel, a matrix of mesh and cheesecloth, and 50-lbs. of fine sand, the filter’s total cost is about $16 in the U.S., and under optimal conditions, removes bacteria from contaminated water with an efficiency of approximately 99 percent.

Slow-sand water filters are used in an estimated 500,000 homes around the world. The model developed by the Institute is easily constructed: one bucket with holes drilled in its bottom is nested inside another, which acts as the water collection site. The inside bucket contains the cheesecloth and mesh, two inches of gravel, and approximately 24 inches of sand. The spigot is installed in the collection bucket.

The filter was tested for four months last summer with water spiked with Escherichia coli, a bacterium that resembles Salmonella typhi, which causes typhoid fever. Slow-sand water filters develop a biofilm layer of bacteria, algae and other single and multiple cell organisms at the top few centimeters of sand as the treated water is poured through it, which traps the harmful bacteria, stopping them from passing through to the water collection bucket.

“The effectiveness of the slow-sand filter was evaluated using methods that are standard in water microbiology,” says Arango. “The students used a multiple tube fermentation technique that quantifies the presence of certain types of bacteria in the water that are indicative of contamination. By testing influent and effluent from the filters, they showed that under laboratory conditions, the filter can remove enough bacteria to render the water safe for drinking.”

The Institute of Catholic Bioethics has partnered with the Global Alliance for Africa (GAA), a non-profit that works with grassroots organizations to design and implement economic development programs that enable families living in sub-Saharan Africa to become self-sufficient. Through a gift made to the Institute by the Chair of its External Advisory Board, John J. Rangel, the GAA has developed a sustainable business model and is in the process of working with communities in Nairobi, Kenya, to construct and sell the filters – at a cost of 1,300 Kenyan shillings, or $12 – to families and individuals living in economically disadvantaged communities.


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