Maji Safi International LLC, which means clean water in Swahili, was founded by John Maiyo, a doctoral student in Purdue’s College of Engineering. Chad Jafvert, professor of civil engineering and environmental and ecological engineering; and John Howarter, associate professor of materials engineering and environmental and ecological engineering, are company advisers. The company installs groundwater wells, and provides ceramic filters and slow sand filters, in western Kenya where safe water is not readily accessible.

“Access to clean water is a huge problem that many countries and communities face around the world, especially developing countries,” Maiyo says. “Around the globe, twice the population of the United States lives without access to safe drinking water, and globally one-third of all schools lack access to safe water and adequate sanitation.”

The unique Purdue technology used by Maji Safi is a slow sand filter that utilizes containers filled with sand and water. At the bottom of the container is a water collection plate, designed at Purdue. The sand provides a large surface area on which microbial growth occurs that metabolizes the dissolved and particulate organic material in the water. The point-of-use slow sand filters are made from readily available five-gallon plastic pails or 55-gallon drums.

“Typical slow sand filters use gravel layers at the bottom of the filter as the water collection zone, however, our filters do not use gravel. Instead we use a porous plastic plate enclosed within a mesh bag,” Jafvert says. “We’ve found this method to be much simpler to use and maintain. There is only the sand to sieve and rinse, instead of sand and different gravel sizes. It provides easier maintenance and makes for easier filter transportation and final assembly.”

Once water is treated by a filter, a small amount of chlorine is added to the water for final disinfection, producing clear, colorless, drinkable water.

Maiyo says that after 30 minutes of contact with the chlorine, the water is ready to drink. “People and children in schools come up to the filter systems with a cup to get a drink, and the schools are able to use the water in their kitchens or for cleaning,” he says. “Because the filters are operated in ‘batch’ mode, water is generally added three times each day, providing for an eight-hour contact time between the water and microorganisms in the filter. Each 55-gallon drum filter can process 200 liters of water each day. With five filters installed at one school, this meets the needs of over 400 children and teachers at the school every day.”

Howarter says the filters are ideal for rural communities. “The materials needed for these filters are very basic and can be found in the countries we aim to serve. The idea is that the microorganisms do the work to remove organic materials from the water so the only energy demand is pouring water into the filter.

“Our particular design allows for the filters to be easily transported, and does not require any particular expertise for final construction at the point-of-use,” he says. “As a disinfectant chlorine is very inexpensive in the countries where we have installed filters, so there is no huge investment required by the communities to use the technology.”

Maji Safi has installed 10 large slow sand filters in rural schools in Kenya, and Jafvert and Howarter have installed similar filters in Colombia, Tanzania and China.

“Our team, as well as many of our undergraduate and graduate students, have traveled to these countries to install the filters, and we’ve been able to see that the children and teachers use the filters every day,” Jafvert says. “The first filters we installed in Colombia in 2011 are still being used today, so that’s a good sign.”

Maji Safi founder John Maiyo, at right, advises Kenyans on the use of slow sand filters that the company is developing to provide clean and safe drinking water to schools and communities in developing countries. The technology, which can be used in plastic pails or 55-gallon drums, utilizes sand and water to better disinfect the contaminated water. At the bottom of the container is a porous plastic water collection plate, designed at Purdue

Kenyan school children display clean, safe drinking water that has been filtered using slow sand water filter technology.