The design is simple and relatively inexpensive: a clay flowerpot-shaped filter through which water seeps at a rate of 1 to 3 liters an hour, dripping into a receptacle below.
But these filters, which are being produced at three factories in Cambodia, make a big difference. According to one study, they remove up to 99.99 percent of E coli bacteria from water and reduce by about half instances of diarrhea in people who drink the filtered water.
That’s in a country where, according to statistics from the World Health Organization, diarrhea is the second biggest cause of death in children younger than 5, after respiratory infections. But diarrhea has another cost: lost time.
“It’s debilitating in the sense that it keeps people from school and working,” said Michael Roberts, country director for International Development Interprises Cambodia, which runs a factory making the filters in Kompong Chhnang province. Roberts estimated that about 250,000 filters have been distributed by the three filter factories in Cambodia since IDE Cambodia opened the first one in 2001.
“Between the three organizations we’re getting close to about the 10 percent market penetration,” he said.
IDE Cambodia’s factory sells the filters to non-governmental organizations and distributors, Roberts said, adding that a filter’s retail price is in the $8.50 to $10 range, although some NGOs give the filters away for free.
IDE Cambodia helped set up another factory run by the Cambodian Red Cross in Prey Veng province, he said, while the organization Resource Development International runs a third in Kandal province.
The filter’s design originated outside Cambodia; it was honed by the NGO Potters For Peace in Nicaragua in the late 1990s after a hurricane hit the region, Roberts said.
“They adopted it, improved it and popularized it,” he said.
The manufacturing process varies at the three factories, but at RDI’s compound in Kandal province, the pot-like filter is made from a fired mixture of clay, rice husks and laterite, RDI Country Director Mickey Sampson said.
According to Sampson, organisms have a hard time getting through the filter because the “pores are so small and they’re so convoluted,” he said, but the filter is also painted with a silver solution that inhibits microbial growth.
The water seeps through and collects in a plastic container that, in the case of RDI, has room for about 25 liters of water.
Research showing how well the filters worked won an award from the International Water Association in 2008.
The research, conducted by the University of North Carolina, was supported by UNICEF and the World Bank’s Water and Sanitation Program, and looked at about 500 families that were using RDI and IDE filters in Cambodia between 2002 and 2006. The filter reduced E coli in water by as much as 99.99 percent and led to about half as many reported cases of diarrhea, the study found.
“The filter’s demonstrated effectiveness in improving water quality and health, over a wide range of conditions, makes it an attractive option for household water treatment in Cambodia,” a presentation of the results stated.
But the researchers cautioned that the pots could be contaminated through misuse.
So why aren’t they used more? Roberts explained: “For very poor, rural people, cost remains an obstacle,” he said. “And many people are happy with their existing source. Whether it’s clean or not, it’s perceived to be clean.”