Arsenic in water is invisible and has no taste or odor. Drinking enough of it leads to a range of health problems, including cancer. It's a common natural groundwater contaminant in much of Bangladesh.
Filters aren't cheap by local standards. Often the filtering material is several unwieldy pounds of specially prepared iron, a material that grabs arsenic out of water.
Pulak decided to find a better, cheaper system that would be easier to use.
He turned to the Internet, searching scientific papers about arsenic filtration. Eventually, he came across a paper about nanoparticles — incredibly small bits of things. A spoonful of nanoparticles can do the filtering work of many pounds of larger bits of iron. But nanoparticles generally aren't easy to make.
A researcher at Rice University, Cafer Yavuz, came up with a home-cooking recipe that started by making soap using drain cleaner, then heating it up after adding common rust. The result is a rough sort of nano-iron. Nano enough for possible use in arsenic filters, Yavuz wrote. The paper that described the process left the practical development to future researchers.
Pulak started by simplifying the recipe. Why play with toxic drain cleaner if off-the-shelf lye soap would work? It did. He tossed a handful of his nano-stuff into a homemade sand water filter of the sort often used in Bangladesh. The filter rendered arsenic-laced water safe for six months.
That was last year's science project. Pulak's awards included the EPA's Patrick H. Hurd Sustainability Award and a third prize at the Intel International Science Fair.
The next problem Pulak addressed was how to test water for arsenic. Standard tests aren't cheap and involve dangerous chemicals. Pulak reasoned that paper soaked in water with his nano-iron would conduct electricity differently if the paper was then dipped into arsenic-contaminated water.
It did. The result isn't as sensitive as the more expensive tests. But like the filter, it's easy to use.
Pulak added the test system to the filter for this year's science fairs. His awards this year included the grand prize at the Dallas Regional Science Fair, a second prize at the Intel fair and a gold medal at the International Sustainable World (Engineering, Energy & Environment) Project Olympiad.
Patricia Maurice is an environmental science professor at the University of Notre Dame and was one of the Intel judges this year. These days, it's unusual to find top-quality science projects that aren't connected with some formal laboratory, she said.
"His detection method is cheap and clever," she said.
Pulak has several families in Bangladesh that are using the filter and the test system and are reporting data back to him. But he is careful to note that his research is still more a proof of concept than a product ready for wide use.
His parents say they were surprised at their son's success last year with such an ambitious project, but that they've realized that he's onto something. Both parents were trained as engineers back home, and Mohammad Pulak works here as a software engineer.
When his son first told him what he wanted to do, Pulak said he wondered if the topic wasn't too complex.
"But these days, with the Internet, all things are there for him to read," he said.
Pulak hasn't quit experimenting. PVC pipes filled with sand are commonly used to filter out bacteria in Bangladesh, and that's what Pulak uses to test his work. Three of the filters still fill a corner of the kitchen, Pulak's mother said.
But Choudhuri Pulak doesn't mind. Even when her friends ask about the mess.
"They want to know what it is," she said proudly. "I feel good about it."
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