• A woman in Nepal cleans water for her family using a filter developed by MIT researchers.

    Photo / TOMMY NGAI

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MIT filter cleans Nepalese drinking water


An easy-to-use, inexpensive filter developed by MIT researchers for treating contaminated drinking water will be installed in 25 Nepalese villages this year, thanks to a $115,000 award from the World Bank Development Marketplace Global Competition.

Contaminated drinking water sickens or kills millions of people every year, mostly in developing countries. For several years, groups of MIT graduate students in the Department of Civil and Environmental Engineering (CEE), led by CEE lecturer and research engineer Susan Murcott, have studied ways to clean that water.

To be successful, a water filtration system must be affordable for some of the world's poorest people, easy to construct and operate and inexpensive to maintain. MIT's arsenic-biosand filter (ABF) meets those criteria. In addition, it removes not only arsenic but also the pathogens that cause childhood diarrhea, which leads to dehydration, malnutrition, stunted growth and sometimes death.

With their World Bank funding, the MIT team and Nepali partners "will set up an ABF technology center for enhanced research, and provide villagers with in-depth training and education about the ABF technology," said Tommy Ngai (M.Eng. 2002), a CEE lecturer who has been in Nepal for the last month and will be there another seven months to meet that goal. His teammates are Murcott and Sophie Walewijk, a Ph.D. student at Stanford who joined the MIT Nepal Water Project team a year ago.

"We will also be collecting useful information in one central database, such as how many filters have been distributed and how successful they have been," said Ngai, who earlier won a $5,000 IDEAS International Technology Innovation Award from the Lemelson-MIT Program for inventing the ABF system.

He wasn't alone in that work, however. "The ABF was developed based on five years of research at MIT involving a number of former Masters of Engineering Program students, lab and field work in Nepal, and assistance from our Nepali partners," Ngai said. Those partners are the Environment & Public Health Organization (ENPHO) in Kathmandu led by Roshan Shrestha, and the Rural Water Supply & Sanitation Support Programme (RWSSSP) in Butwal led by Heimo Ojanen.

The ABF filter shell or container, made of plastic or concrete, stands one meter high and is about 0.3 meters in length and width -- a little taller than a two-drawer filing cabinet. It's filled with gravel, coarse sand, fine sand and iron nails. Pathogens are removed from the water as it seeps through the sand and gravel; arsenic is removed as the iron nails rust, a process that attracts and binds the arsenic.

A pilot study with 15 filters in four villages over more than a year has found "that the technical performance is good," said Ngai. "Users like the filter very much because it's durable and offers a permanent solution to their water problem. Unlike other filters, there's nothing to break.

"People also like the very high flow rates. Other filters usually produce one to five liters of filtered water per hour as the water slowly passes through microscopic pores in clay or other media. The ABF can process 15 to 30 liters per hour," Ngai said.

ENPHO has a contract with the Nepal Red Cross Society to provide ABF filters, and they have already distributed 500 units. For the year ending this July, RWSSSP has already allocated funds to distribute more than 700 concrete filters, and has trained about 40 technicians from various villages in construction techniques.

Each village in the program receives two steel molds for making water filters, plus the necessary tools. Residents can then obtain their own ABF through the technicians.

Although capital costs are high by local standards -- $20 to $25 to produce filters in Kathmandu -- there are almost no maintenance costs aside from occasionally replacing the nails. Therefore, the long-term cost of the ABF is comparable to many other filters on the market. "In addition, we expect the manufacturing cost to drop as we train technicians from each village on filter construction," Ngai said.

Depending on the turbidity (sediment content) of the water supply, the ABF filter will clog between once a month and twice a year and need to be cleaned. That simple procedure takes about 15 minutes.

Ngai anticipates an active public education effort. "We'll set up health education workshops and filter demonstrations for all villagers. We'll also periodically evaluate the project, write up results, and publicize the efforts in conferences and journal articles for another form of public education," he said.

The team received support from M.Eng. program director Eric Adams and advice from Ede Ijjasz-Vasquez (S.M. 1990, Ph.D.) and Nat Paynter (M.Eng. 2001).


Topics: Civil and environmental engineering, Global, Environment and energy

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