Slow Sand Filters
The Challenge: Potable Water for Rural Communities
Clean, accessible water for all is an essential part of the world we want to live in. There is sufficient fresh water on the planet to achieve this. But due to bad economics or poor infrastructure, every year millions of people, most of them children, die from diseases associated with inadequate water supply, sanitation and hygiene. Water scarcity, poor water quality and inadequate sanitation negatively impact food security, livelihood choices and educational opportunities for poor families across the world. By 2050, at least one in four people is likely to live in a country affected by chronic or recurring shortages of fresh water. (https://www.un.org/sustainabledevelopment/water-and-sanitation/).
Water scarcity in Kenya has been an issue for decades, as only a small percentage of the country's land is optimal for agriculture, and the year-round climate is predominantly arid. A recent natural disaster also caused major soil degradation and refugee displacement throughout the country. Kenya's natural water resources also do not provide an equitable delivery of water to the various regions of the country and the country's water basins do not reach an equitable area of the country. This leaves most of the population without any fresh water. (https://thewaterproject.org/water-crisis/water-in-crisis-kenya)
In Colombia, a recent report shows that only 12.5% of the departments offer water safe for human consumption, with the Surveillance System for Potable Water Quality warning that 15% of departments have “high risk” water. On average, nationwide samples of water reveal contamination of residual chlorine, microorganisms, E. coli, and coliform bacteria. The main water sources for Colombians originate in the Colombian Andes, an area which is suffering contamination and at risk of drying up.
The Purdue Innovation: Rural Potable Water Systems
Professors Jafvert and Howarter have developed a cost-effective, low-maintenance point-of-use water treatment technology to meet local needs of people living in underserved communities. Point-of-use water filters were first designed and tested at Purdue, and then constructed in Colombia at three rural elementary schools near Barbosa, Antioquia Colombia in June 2011. Although these filters are very effective and still in use, their construction was labor intensive and needed to be performed by an experienced person (i.e., someone from Purdue). As a result of user feedback, a new design was developed that makes construction much easier and that requires no special skills for construction. This design allowed for delivery of an additional 30 SSF units to 15 elementary schools and community members during a following visit. Because of the success in Colombia, the effort has been expanded to Kenya, Tanzania, and Western China. Continuing partnerships exist at all four locations with over 50 Purdue undergraduate student participating in research and implementation activities.
The filters significantly improve water quality by removing particles and dissolved organic chemicals from the water, reducing turbidity below the U.S. drinking water standard of 1.0 NTU, and reducing taste and odor problems. Previous to our efforts, the school teachers in Colombia boiled the water to disinfect it prior to using it for cooking and drinking. Because turbidity is now removed from the water, alternative lower cost disinfection methods can now be used. Removal of the suspended particles is very important, as chemical disinfectants are much less efficient in inactivating micro-organisms that are encased within particle aggregates. The slow-sand-filters designed by Purdue University are made from readily available 5-gallon plastic pails. One slow-sand filter unit consists of a stack of two 5-gallon pails (two, for adequate total depth of filtration, with about 10 inches of sand in each pail). Typically 10 L can be poured in 1 unit (a 2-pail unit) every 8 hours, so that 30 Liters of water can be produced each day. Four pails, therefore can treat 60 L each day. A second design has recently been implemented for beta testing using a 55-gallon drum which is able to deliver 210 liters of clean water per day.
Key design drivers have been to minimize cost (including transportation costs) and construction time, and to keep operation and maintenance requirements to a minimum. As a result, while most NGOs that deliver water treatment units to developing areas either ship large containers to the site and/or design for 100% construction on-site, our approach has been “to design” using small, easily shipped components, for easy final construction at the point-of-use, using locally obtained 5 gallon pails and sand. We expect this approach to lead to an overall greater impact by reducing overall costs and construction time.
In the Spring of 2016, Jafvert Lab students designed a system to automate water treatment through five 55 gallon slow sand filters, with the intent of implementing this in rural schools in Kenya and Colombia. Single 55 gallon filters were installed with support from partners in Kenya at four schools. These filters were installed to test the filters' effectiveness, and because the results are positive, it is now time to provide these schools with sufficient filters for all their drinking water needs. Some students engaged in mechanical automation for disinfection, and others designed a simple water pumping system. This pumping system is being introduced to schools in Eldoret, Kenya.
Purdue University, Maji Safi (Kenya), AMPATH, Moi University, Tumaini Center, University of Cartagena
Chad Jafvert, Professor of Civil Engineering and Environmental & Ecological Engineering, firstname.lastname@example.org
John Howarter, Assistant Professor of Materials Science Engineering and Environmental & Ecological Engineering, email@example.com