Rural Water Problems Cleared Up With Students’ Filter

Forty dollars is a small price to pay for good health, and it’s all two Phnom Penh high students say they need to build an effective water purifier for household use in the countryside.

The students, Khieu Sambath and Him Sam Nang, and their teachers at Beng Trabek High School recently developed the device as a project for a regional science congress in Malaysia. Their process reduces the risk of water-borne illnesses such as cholera, which killed more than 95 people in Ratanakkiri province earlier this year.

“We wanted to solve the problem in the countryside, because people there often use the Mekong River water,” Him Sam Nang said. The students gave the system to a family in Kandal province, which used it for four months and were pleased with the results.

“Neighbors were interested in getting one,” said Susan Smith of Cooperative Services Interna­tional, one of the students’ advisers.

The project took the students and their advisers to Penang, Malay­sia, earlier this month for a science fair for young scientists. The fair, sponsored by the Southeast Asian Ministers of Education Orga­ni­za­tion, included projects from students in seven countries. Khieu Sambath and Him Sam Nang, the only Cambo­dians, posted one of the four highest overall scores.

Mark Sampson, a former chemistry professor from the US who now works for Cooperative Services Interna­tional, originally came up with the idea of developing a small-scale water purification system. The device made by the students works like this: The river water runs through a 10-cm layer of sand, fine gravel, and charcoal, which filter out the lumps of dirt and grime, but not the microorganisms that cause illness. The charcoal makes the water taste and smell better.

The water, now clear of its chunkiest filth, then is piped into another container, where it is exposed to ultraviolet, or UV, light. The UV light kills the bacteria and critters that passed the first purification gauntlet. After a couple minutes of exposure to the light, the water is ready to drink, and can be stored safely in bottles or jars.

The process is identical to the one used to filter the water sold in bottles available all over Phnom Penh, the advisers said but the students’ project carries out the process on a smaller scale.

Currently, the most common way water is purified in rural homes is by boiling. But boiling requires fuel, usually wood, and that contributes to the depletion of Cambodia’s forests.

The process is also much cheaper, Him Sam Nang said. The two students estimate that boiling water costs a family 400 riel a day, while a functioning UV system needs only electricity for a UV light, at an expense of about 1,000 riel every week or two.

The start-up expense for fitting pipes, buying a UV light bulb, and getting charcoal and gravel is about $40. A light bulb lasts about three years.

“I want to use it in my own house, buy one, or make one myself,” said their teacher, So Chanvary.

Smith noted that the students’ device doesn’t cleanse the water of mercury, arsenic or heavy metals, and that an improved version might address that problem.

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